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Increasing the penetration and accumulation of antitumor drugs at the tumor site are crucial in chemotherapy. Smaller drug-loaded nanoparticles (NPs) typically exhibit increased tumor penetration and more effective permeation through the nuclear membrane, whereas larger drug-loaded NPs show extended retention at the tumor site. In addition, cancer stem cells (CSCs) have unlimited proliferative potential and are crucial for the onset, progression, and metastasis of cancer. Therefore, a drug-loaded amphiphilic peptide, DDP- and ATRA-loaded Pep1 (DA/Pep1), is designed that self-assembles into spherical NPs upon the encapsulation of cis-diamminedichloroplatinum (DDP) and all-trans retinoic acid (ATRA). In an acidic environment, DA/Pep1 transforms into aggregates containing sheet-like structures, which significantly increases drug accumulation at the tumor site, thereby increasing antitumor effects and inhibiting metastasis. Moreover, although DDP treatment can increase the number of CSCs present, ATRA can induce the differentiation of CSCs in breast cancer to increase the therapeutic effect of DDP. In conclusion, this peptide nanodelivery system that transforms in response to the acidic tumor microenvironment is an extremely promising nanoplatform that suggests a new idea for the combined treatment of tumors., (© 2024 Wiley‐VCH GmbH.)

Stemness and metastasis are the two main challenges in cancer therapy and are related to disease relapse post-treatment. They both have a strong correlation with chemoresistance and poor prognosis, ultimately leading to treatment failure. It has been reported that chemotherapy can induce stemness and metastasis in many cancer types, especially treatment with the chemotherapeutic agent doxorubicin (DOX) in breast cancer. A combination treatment is an efficient and elegant approach in cancer therapy through simultaneous delivery of two or more drugs with a delivery system for its synergistic effect, which is not an additive of two individual drugs. Herein, we report a combinatorial system with DOX and all-trans retinoic acid (ATRA) to address both of the above issues. As a common critical regulatory factor for oncogenic signal transduction pathways, Pin1 is a specific isomerase highly expressed within various tumor cells. ATRA, a newly identified Pin1 inhibitor, can abolish several oncogenic pathways by effectively inhibiting and degrading overexpressed Pin1. We successfully developed a folic acid (FA)-modified chitosan (CSO)-derived polymer (FA-CSOSA) and obtained FA-CSOSA/DOX and FA-CSOSA/ATRA drug-loaded micelles. FA modification can improve the uptake of the nanoparticles in tumor cells and tumor sites via folate receptor-mediated cell internalization. Compared to treatment with DOX alone, the combined treatment induced 4T1 cell apoptosis in a synergistic manner. Reduced stemness-related protein expression and inhibited metastasis were observed during treatment with FA-CSOSA/DOX and FA-CSOSA/ATRA and were found to be associated with Pin1. Further in vivo experiments showed that treatment with FA-CSOSA/DOX and FA-CSOSA/ATRA resulted in 85.5% tumor inhibition, which was 2.5-fold greater than that of cells treated with DOX·HCl alone. This work presents a new paradigm for addressing chemotherapy-induced side effects via degradation of Pin1 induced by tumor-targeted delivery of DOX and ATRA.

Despite recent advances in the treatment of human colon cancer, the chemotherapeutic efficacy against colon cancer is still unsatisfactory. The complexity in colorectal cancer treatment leads to new research in combination therapy to overcome multidrug resistance in cancer and increase apoptosis. The objective of the present research work was to develop polyplexes for co-delivery of plasmid DNA with retinoic acid against colorectal cancer cell line (HCT-15). Plain polyplexes were prepared using chitosan and hyaluronic acid solution (0.1% w/v), whereas retinoic acid polyplexes were prepared using ethanol: water (1:9 v/v) system. The particle size was observed in the order of chitosan solution > blank polyplex > retinoic acid-loaded polyplex. Encapsulation efficiency of retinoic acid was found to be 81.51 ± 4.33% for retinoic acid-loaded polyplex formulation. The drug release was observed to be in a controlled pattern with 72.23 ± 1.32% release of retenoic acid from polyplex formulation. Cell line studies of the formulation displayed better cell inhibition and low cytotoxicity for the retinoic acid-loaded polyplexes in comparison to pure retinoic acid, thus demonstrating better potential action against colorectal cancer cell line HCT-15. Retinoic acid-loaded polyplexes indicated higher potential for the delivery of the active whereas the cell line studies displayed the efficacy of the formulation against colorectal cancer cell line HCT-15., (© 2021. The Author(s).)

This paper reports a smart intracellular nanocarrier for sustainable and controlled drug release in non-invasive neuroregeneration. The nanocarrier is composed by superparamagnetic iron oxide-gold (SPIO-Au) core-shell nanoparticles (NPs) conjugated with porous coordination cages (PCCs) through the thiol-containing molecules as bridges. The negatively charged PCC-2 and positively charged PCC-3 are compared for intracellular targeting. Both types result in intracellular targeting via direct penetration across cellular membranes. However, the pyrene (Py)-PEG-SH bridge enabled functionalization of SPIO-Au NPs with PCC-3 exhibits higher interaction with PC-12 neuron-like cells, compared with the rhodamine B (RhB)-PEG-SH bridge enabled case and the stand-alone SPIO-Au NPs. With neglectable toxicities to PC-12 cells, the proposed SPIO-Au-RhB(Py)-PCC-2(3) nanocarriers exhibit effective drug loading capacity of retinoic acid (RA) at 13.505 μg/mg of RA/NPs within 24 h. A controlled release of RA is achieved by using a low-intensity 525 nm LED light (100% compared to 40% for control group within 96 h)., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Tumour heterogeneity remains a major challenge in cancer therapy owing to the different susceptibility of cells to chemotherapy within a solid tumour. Cancer stem-like cells (CSCs), which reside in hypoxic tumour regions, are characterized by high tumourigenicity and chemoresistance and are often responsible for tumour progression and recurrence. Here we report a nanotherapeutic strategy to kill CSCs in tumours using nanoparticles that are co-loaded with the differentiation-inducing agent, all-trans retinoic acid, and the chemotherapeutic drug, camptothecin. All-trans retinoic acid is released under hypoxic conditions, leading to CSC differentiation in the hypoxic niche. In differentiating CSC, the reactive oxygen species levels increase, which then causes the release of camptothecin and subsequent cell death. This dual strategy enables controlled drug release in CSCs and reduces stemness-related drug resistance, enhancing the chemotherapeutic response. In breast tumour mouse models, treatment with the nanoparticles suppresses tumour growth and prevents post-surgical tumour relapse and metastasis.

Pre-clinical models have shown that targeting pancreatic stellate cells with all-trans-retinoic-acid (ATRA) reprograms pancreatic stroma to suppress pancreatic ductal adenocarcinoma (PDAC) growth. Here, in a phase Ib, dose escalation and expansion, trial for patients with advanced, unresectable PDAC (n = 27), ATRA is re-purposed as a stromal-targeting agent in combination with gemcitabine-nab-paclitaxel chemotherapy using a two-step adaptive continual re-assessment method trial design. The maximum tolerated dose (MTD) and recommended phase 2 dose (RP2D, primary outcome) is the FDA/EMEA approved dose of gemcitabine-nab-paclitaxel along-with ATRA (45 mg/m 2 orally, days 1-15/cycle). Dose limiting toxicity (DLT) is grade 4 thrombocytopenia (n = 2). Secondary outcomes show no detriment to ATRA pharmacokinetics.. Median overall survival for RP2D treated evaluable population, is 11.7 months (95%CI 8.6-15.7 m, n = 15, locally advanced (2) and metastatic (13)). Exploratory pharmacodynamics studies including changes in diffusion-weighted (DW)-MRI measured apparent diffusion coefficient after one cycle, and, modulation of cycle-specific serum pentraxin 3 levels over various cycles indicate stromal modulation. Baseline stromal-specific retinoid transport protein (FABP5, CRABP2) expression may be predicitve of response. Re-purposing ATRA as a stromal-targeting agent with gemcitabine-nab-paclitaxel is safe and tolerable. This combination will be evaluated in a phase II randomized controlled trial for locally advanced PDAC. Clinical trial numbers: EudraCT: 2015-002662-23; NCT03307148. Trial acronym: STARPAC.

Recently, stromal targeting, by agents such as All trans retinoic acid (ATRA), has been regarded as a promising avenue for the treatment of pancreatic ductal adenocarcinoma (PDAC). The intra-cellular transportation of ATRA to the nuclear receptors is performed by either: fatty acid binding protein 5 (FABP5) or cellular retinoic acid binding protein 2 (CRABP2), dictating the transcription of downstream genes and, thus, eventual cell phenotype. Here, we explored the levels of each protein, in pancreatic tissues of patients presenting with a range of pancreatic diseases (pancreatic ductal adenocarcinoma (PDAC), chronic pancreatitis (CP), cholangiocarcinoma (CC)). We demonstrate that there is a significantly lower CRABP2 and FABP5 expression in activated fibroblasts or pancreatic stellate cells (PSC) in PDAC, as well as other diseased pancreas as in CC and CP, versus quiescent fibroblasts. The quiescent fibroblasts consistently show a pattern of high FABP5:CRABP2 ratio, whereas PSC in all non-PDAC tissues showed a low FABP5:CRABP2 ratio. PSC in PDAC patients had a range of FABP5:CRABP2 ratios (high, even and low). There was a lower CRABP2 expression in cancerous epithelial cells (PDAC) versus normal epithelial cells. This is also present in other disease states (CP, CC). Contrasting to the patterns seen for fibroblasts, the FABP5 expression in PDAC epithelial cells matched that of the normal epithelial cells. However, the normal epithelial cells had a high FABP5:CRABP2 ratio, compared to the PDAC epithelial cells. These ratios may have correlation with tumor progression, and overall survival. These findings could be confirmed in in vitro cell lysates. CRABP2 and FABP5 levels and ratios could serve as valuable biomarkers., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Psoriasis is a chronic immune-mediated inflammatory skin disease without effective treatment. The utilization of all trans-retinoic acid (TRA) and betamethasone (BT) for the treatment of psoriasis is still facing difficulties, due to their relatively poor stability, limited skin permeation, and systemic side effects. Flexible liposomes are excellent in deeper skin permeation and reducing the side effects of drugs, which is promising for effective treatment of skin disorders. This work aimed to establish dual-loaded flexible liposomal gel for enhanced therapeutic efficiency of psoriasis based on TRA and BT., Results: Flexible liposomes co-loaded with TRA and BT were successfully prepared in our study. The characterization examination revealed that flexible liposomes featured nano-sized particles (around 70 nm), high drug encapsulation efficiency (> 98%) and sustained drug release behaviors. Flexible liposomes remarkably increased the drug skin permeation and retention as compared with free drugs. Results on HaCaT cells suggested that flexible liposomes were nontoxic, and its cellular uptake has a time-dependent manner. In vivo studies suggested the topical application of TRA and BT dual-loaded liposomal gel had the best ability to reduce the thickness of epidermal and the level of cytokines (TNF-α and IL-6), largely alleviating the symptoms of psoriasis., Conclusions: Flexible liposomal gel dual-loaded with TRA and BT exerted a synergistic effect, which is a promising topical therapeutic for the treatment of psoriasis.

Purpose : Androgenic alopecia (AGA) is a condition of progressive hair loss and involves follicular miniaturization triggered mainly due to varying levels of androgen besides environmental and genetic factors, which may also play some role. Minoxidil (MXD) has been considered as most effective therapeutic moiety to treat this disorder. Another drug Tretinoin (TRET) is known for its comedolytic activity and is reported to enhance percutaneous absorption of MXD. Presently both these drugs are being utilized for treatment of androgenic alopecia (AGA) in solution form which poses several problems in terms of poor solubility of drug, frequency of application and side effects. Materials and methods: Current work investigates liposomal hydrogel system for simultaneous delivery of MXD and TRET to overcome the limitations of existing formulation. Successful development of liposomes was commenced by thin film hydration method and various parameters affecting desired characteristics like size, morphology, entrapment efficiency; stability and ex vivo permeation were optimized. The formulated liposomes were further characterized for various physicochemical properties and evaluated for in vivo irritancy study in animals. Results and discussion: Results suggested prepared liposomes to be stable, homogenous and capable to hold both the drugs within. Association with hydrogel enhanced the permeation of MXD through skin ex vivo but TRET retained on the skin. Liposome loaded hydrogel was found to be non-irritant to skin. Conclusion: Overall developed system showed potential for effective and simultaneous delivery of both the drugs.

Background: All-trans retinoic acid (ATRA) is widely employed in the treatment of various proliferative and inflammatory diseases. However, its therapeutic efficacy is imperiled due to its poor solubility and stability. Latter was surmounted by its incorporation into a solid matrix of lipidic nanoparticles (SLNs)., Methods: ATRA loaded SLNs (ATRA-SLNs) were prepared using a novel microemulsification technique (USPTO 9907758) and an optimal composition and were characterized in terms of morphology, differential scanning calorimetry (DSC), and powder X-ray diffraction studies (PXRD). In vitro release, oral plasma pharmacokinetics (in rats) and stability studies were also done., Results: Rod-shaped ATRA-SLNs could successfully incorporate 3.7 mg/mL of ATRA, increasing its solubility (from 4.7 μg/mL) by 787 times, having an average particle size of 131.30 ± 5.0 nm and polydispersibility of 0.283. PXRD, DSC, and FTIR studies confirmed the formation of SLNs. Assay/total drug content and entrapment efficiency of ATRA-SLNs was 92.50 ± 2.10% and 84.60 ± 3.20% (n=6), respectively, which was maintained even on storage for one year under refrigerated conditions as an aqueous dispersion. In vitro release in 0.01 M phosphate buffer (pH 7.4) with 3% tween 80 was extended 12 times from 2h for free ATRA to 24 h for ATRA-SLNs depicting Korsmeyer Peppas release. Oral administration in rats showed 35.03 times enhanced bioavailability for ATRA-SLNs., Conclusion: Present work reports preparation and evaluation of bioenhanced ATRA-SLNs containing a high concentration of ATRA (>15 times than that reported by others). Latter is attributed to the novel preparation process and intelligent selection of components. Lay Summary: All-trans retinoic acid (ATRA) shows an array of pharmacological activities but its efficacy is limited due to poor solubility, stability and side effects. In present study its solubility and efficacy is improved by 787 and 35.5 times, respectively upon incorporation into solid lipid nanoparticles (ATRA-SLNs). Latter extended its release by 12 times and provided stability for at least a year under refrigeration. A controlled and sustained release will reduce dose related side effects. ATRA-SLNs reported presently can thus be used in treatment /prophylaxis of disorders like cancers, tuberculosis, age related macular degeneration and acne and as an immune-booster., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Aim: Multicompartmental lipid-protein nanohybrids (MLPNs) were developed for combined delivery of the anticancer drugs tretinoin (TRE) and genistein (GEN) as synergistic therapy of lung cancer. Materials & methods: The GEN-loaded lipid core was first prepared and then coated with TRE-loaded zein shell via nanoprecipitation. Results: TRE/GEN-MLPNs demonstrated a size of 154.5 nm. In situ ion pair formation between anionic TRE and the cationic stearyl amine improved the drug encapsulation with enhanced stability of MLPNs. TRE/GEN-coloaded MLPNs were more cytotoxic against A549 cancer cells compared with combined free GEN/TRE. In vivo , lung cancer bearing mice treated with TRE/GEN-MLPNs displayed higher apoptotic caspase activation compared with mice-treated free combined GEN/TRE. Conclusion: TRE/GEN-MLPNs might serve as a promising parenteral nanovehicles for lung cancer therapy.

The all- trans -retinoic acid ( at RA) hydroxylase Cyp26a1 is essential for embryonic development and may play a key role in regulating at RA clearance also in adults. We hypothesized that loss of Cyp26a1 activity via inducible knockout in juvenile or adult mice would result in decreased at RA clearance and increased tissue at RA concentrations and at RA-related adverse effects. To test these hypotheses, Cyp26a1 was knocked out in juvenile and adult male and female Cyp26a1 floxed mice using standard Cre-Lox technology and tamoxifen injections. Biochemical and histological methods were used to study the effects of global Cyp26a1 knockout. The Cyp26a1 knockout did not result in consistent histopathological changes in any major organs. Cyp26a1 -/- mice gained weight normally and exhibited no adverse phenotypes for up to 1 year after loss of Cyp26a1 expression. Similarly, at RA concentrations were not increased in the liver, testes, spleen, or serum of these mice, and the Cyp26a1 knockout did not cause compensatory induction of lecithin:retinol acetyltransferase ( Lrat ) or retinol dehydrogenase 11 ( Rdh11 ) mRNA or a decrease in aldehyde dehydrogenase 1a1 ( Aldh1a1 ) mRNA in the liver compared with tamoxifen-treated controls. However, the Cyp26a1 -/- mice showed increased bone marrow cellularity and decreased frequency of erythroid progenitor cells in the bone marrow consistent with a retinoid-induced myeloid skewing of hematopoiesis. In addition, the Cyp26a1 knockout decreased clearance of exogenous at RA by 70% and increased at RA half-life 6-fold. These findings demonstrate that despite lacking a major impact on endogenous at RA signaling, Cyp26a1 critically contributes as a barrier for exogenous at RA exposure., (© 2019 Zhong et al.)

Fractional CO 2 laser treatment has been used in some clinical trials to promote topical drug delivery. Currently, there is no standard for laser settings to achieve a feasible therapy. The cutaneous recovery following laser treatment and its influence on drug absorption have not been well explored. This study evaluated the kinetics of laser-treated skin-barrier restoration and drug permeation in nude mice. The skin recovery and observation of the process were characterized by transdermal water loss (TEWL), erythema measurement, gross appearance, optical microscopy, and scanning electron microscopy (SEM). The skin absorption of a lipophilic small permeant (tretinoin), a hydrophilic small permeant (acyclovir), and a large molecule (fluorescein isothiocyanate dextran 4 kDa, FD4) was examined in vitro using Franz cell. TEWL suggested that the laser-treated skin restored its barrier function at 16 h after irradiation. The fractional laser produced microchannels of about 150 μm in diameter and 25 μm in depth that were surrounded with thermal coagulation. The bright-field imaging indicated that the micropores were progressively closed during the recovery period but had not completely closed even after a 16-h recovery. The laser treatment led to a rapid tretinoin penetration across the skin immediately after irradiation, with a 5-fold enhancement compared to intact skin. This enhancement was gradually reduced following the increase of recovery time. Conversely, the acyclovir and FD4 permeation peaked at 1-2 h post-irradiation. The FD4 flux was even elevated as the recovery time increased. The reasons for this could have been the subsequent inflammation after laser exposure and the deficient tight junction (TJ) barrier. The confocal imaging demonstrated the perpendicular diffusion of rhodamine B and FD4 through microchannels immediately after laser exposure. The lateral diffusion from the microchannels was observed at 2 h post-irradiation. Our results revealed a time-dependent recovery of skin permeation. The time frame for applying the drugs after laser irradiation was dependent upon the permeants and their various physicochemical properties., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Clinical studies have shown that all-trans retinoic acid (RA), which is often used in treatment of cancer patients, improves hemostatic parameters and bleeding complications such as disseminated intravascular coagulation (DIC). However, the mechanisms underlying this improvement have yet to be elucidated. In vitro studies have reported that RA upregulates thrombomodulin (TM) expression on the endothelial cell surface. The objective of this study was to investigate how and to what extent the TM concentration changes after RA treatment in cancer patients, and how this variation influences the blood coagulation cascade., Results: In this study, we introduced an ordinary differential equation (ODE) model of gene expression for the RA-induced upregulation of TM concentration. Coupling the gene expression model with a two-compartment pharmacokinetic model of RA, we obtained the time-dependent changes in TM and thrombomodulin-mRNA (TMR) concentrations following oral administration of RA. Our results indicated that the TM concentration reached its peak level almost 14 h after taking a single oral dose (110 [Formula: see text]) of RA. Continuous treatment with RA resulted in oscillatory expression of TM on the endothelial cell surface. We then coupled the gene expression model with a mechanistic model of the coagulation cascade, and showed that the elevated levels of TM over the course of RA therapy with a single daily oral dose (110 [Formula: see text]) of RA, reduced the peak thrombin levels and endogenous thrombin potential (ETP) up to 50 and 49%, respectively. We showed that progressive reductions in plasma levels of RA, observed in continuous RA therapy with a once-daily oral dose (110 [Formula: see text]) of RA, did not affect TM-mediated reduction of thrombin generation significantly. This finding prompts the hypothesis that continuous RA treatment has more consistent therapeutic effects on coagulation disorders than on cancer., Conclusions: Our results indicate that the oscillatory upregulation of TM expression on the endothelial cells over the course of RA therapy could potentially contribute to the treatment of coagulation abnormalities in cancer patients. Further studies on the impacts of RA therapy on the procoagulant activity of cancer cells are needed to better elucidate the mechanisms by which RA therapy improves hemostatic abnormalities in cancer.

Ending the tuberculosis (TB) epidemic by 2030 was recently listed in the United Nations (UN) Sustainable Development Goals alongside HIV/AIDS and malaria as it continues to be a major cause of death worldwide. With a significant proportion of TB cases caused by resistant strains of Mycobacterium tuberculosis (Mtb), there is an urgent need to develop new and innovative approaches to treatment. Since 1989, researchers have been assessing the anti-bacterial effects of the active metabolite of vitamin A, all trans-Retinoic acid (ATRA) solution, in Mtb models. More recently the antibacterial effect of ATRA has been shown to regulate the immune response to infection via critical gene expression, monocyte activation and the induction of autophagy leading to its application as a host-directed therapy (HDT). Inhalation is an attractive route for targeted treatment of TB, and therefore we have developed ATRA-loaded microparticles (ATRA-MP) within the inhalable size range (2.07 ± 0.5 µm) offering targeted delivery of the encapsulated cargo (70.5 ± 2.3%) to the site of action within the alveolar macrophage, which was confirmed by confocal microscopy. Efficient cellular delivery of ATRA was followed by a reduction in Mtb growth (H37Ra) in THP-1 derived macrophages evaluated by both the BACT/ALERT® system and enumeration of colony forming units (CFU). The antibacterial effect of ATRA-MP treatment was further assessed in BALB/c mice infected with the virulent strain of Mtb (H37Rv). ATRA-MP treatments significantly decreased the bacterial burden in the lungs alongside a reduction in pulmonary pathology following just three doses administered intratracheally. The immunomodulatory effects of targeted ATRA treatment in the lungs indicate a distinct yet effective mechanism of action amongst the formulations. This is the first study to-date of a controlled release ATRA treatment for TB suitable for inhalation that offers improved targeting of a HDT, retains antibacterial efficacy and improves pulmonary pathology compared to ATRA solution., (Copyright © 2018. Published by Elsevier B.V.)

Src family kinases (SFKs) are hyperactivated in acute myeloid leukemia (AML). SFKs impede the retinoic acid receptor, and SFK inhibitors enhance all-trans retinoic acid (ATRA)-mediated cellular differentiation in AML cell lines and primary blasts. To translate these findings into the clinic, we undertook a phase-I dose-escalation study of the combination of the SFK inhibitor dasatinib and ATRA in patients with high-risk myeloid neoplasms. Nine subjects were enrolled: six received 70 mg dasatinib plus 45 mg/m 2 ATRA daily, and three received 100 mg dasatinib plus 45 mg/m 2 ATRA daily for 28 days. Headache and QTc prolongations were the only two grade 3 adverse events observed. No significant clinical responses were observed. We conclude that the combination of 70 mg dasatinib and 45 mg/m 2 ATRA daily is safe with acceptable toxicity. Our results provide the safety profile for further investigations into the clinical efficacy of this combination therapy in myeloid malignancies.

The predominant function of the blood-retinal barrier (BRB) is to maintain retinal homeostasis by regulating the influx and efflux between the blood and retina. Breakdown of the BRB occurs in a number of ocular diseases that result in vision loss. Understanding the molecular and cellular pathways involved in the development and maintenance of the BRB is critical to developing therapeutics for these conditions. To visualize the BRB in vivo, we used the transgenic Tg(l-fabp:DBP-EGFP:flk1:mCherry) zebrafish model that expresses vitamin D binding protein (a member of the albumin gene family) tagged to green fluorescent protein. Retinoic acid (RA) plays a number of important roles in vertebrate development and has been shown to play a protective role during inflammation-induced blood-brain barrier disruption. The role of RA in BRB development and maintenance remains unknown. To disrupt RA signaling, Tg(l-fabp:DBP-EGFP:flk1:mCherry) zebrafish were treated with N, N-diethylaminobenzaldehyde and 4-[(1 E)-2-[5,6-dihydro-5,5-dimethyl-8-(2-phenylethynyl)-2-naphthalenyl]ethenyl]benzoic acid, which are antagonists of retinal dehydrogenase and the RA receptor, respectively. Treatment with either compound resulted in BRB disruption and reduced visual acuity, whereas cotreatment with all- trans RA effectively rescued BRB integrity. Additionally, transgenic overexpression of Cyp26a1, which catalyzes RA degradation, resulted in breakdown of the BRB. Our results demonstrate that RA signaling is critical for maintenance of the BRB and could play a role in diseases such as diabetic macular edema.-Pollock, L. M., Xie, J., Bell, B. A., Anand-Apte, B. Retinoic acid signaling is essential for maintenance of the blood-retinal barrier.

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

Pancreatic ductal adenocarcinoma is characterised by a dense desmoplastic stroma composed of stromal cells and extracellular matrix (ECM). This barrier severely impairs drug delivery and penetration. Activated pancreatic stellate cells (PSCs) play a key role in establishing this unique pathological obstacle, but also offer a potential target for anti-tumour therapy. Here, we construct a tumour microenvironment-responsive nanosystem, based on PEGylated polyethylenimine-coated gold nanoparticles, and utilise it to co-deliver all-trans retinoic acid (ATRA, an inducer of PSC quiescence) and siRNA targeting heat shock protein 47 (HSP47, a collagen-specific molecular chaperone) to re-educate PSCs. The nanosystem simultaneously induces PSC quiescence and inhibits ECM hyperplasia, thereby promoting drug delivery to pancreatic tumours and significantly enhancing the anti-tumour efficacy of chemotherapeutics. Our combination strategy to restore homoeostatic stromal function by targeting activated PSCs represents a promising approach to improving the efficacy of chemotherapy and other therapeutic modalities in a wide range of stroma-rich tumours.

All-trans-retinoic acid (ATRA) exhibits potent cytotoxicities against different cancer cells by binding to retinoic acid receptors (RARs), which is regarded as the first example of targeted therapy in acute promyelocytic leukemia (APL). However, its extensive clinical applications have been limited because of poor aqueous solubility, short half-life time and side effects. In this report, dimeric ATRA phosphorylcholine prodrug (Di-ATRA-PC) was designed and assembled into nanoliposomes to improve its pharmacokinetic properties. Di-ATRA-PC prodrug was synthesized by a facile esterification and characterized by mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). The Di-ATRA-PC assembled liposomes were prepared by thin film hydration method with ATRA loading efficiency up to 73wt%. The liposomes have a uniform particle size (73.1±3.6nm) with negatively charged surface (-20.5±2.5mV) and typical lipid bilayer structure as measured by dynamic light scattering (DLS), transmission electron microscope (TEM) and cryogenic transmission electron microscope (cryo-TEM). In vitro drug release study confirmed that Di-ATRA-PC liposomes could sustainedly release free ATRA in a weakly acidic condition. Furthermore, cellular uptake, MTT and cell apoptosis analysis demonstrated that the liposomes could be successfully internalized into tumor cells to induce apoptosis of MCF-7 and HL-60 cells. More importantly, in vivo pharmacokinetic assay indicated that Di-ATRA-PC liposomes had much longer retention time in comparison with ATRA. In conclusion, Di-ATRA-PC liposomal formulation could be a potential drug delivery system of ATRA with enhanced pharmacokinetic properties., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Hepatocellular carcinoma (HCC) is the second leading cause of cancer deaths worldwide largely due to lack of effective targeted drugs to simultaneously block multiple cancer-driving pathways. The identification of all-trans retinoic acid (ATRA) as a potent Pin1 inhibitor provides a promising candidate for HCC targeted therapy because Pin1 is overexpressed in most HCC and activates numerous cancer-driving pathways. However, the efficacy of ATRA against solid tumors is limited due to its short half-life of 45min in humans. A slow-releasing ATRA formulation inhibits solid tumors such as HCC, but can be used only in animals. Here, we developed a one-step, cost-effective route to produce a novel biocompatible, biodegradable, and non-toxic controlled release formulation of ATRA for effective HCC therapy. We used supercritical carbon dioxide process to encapsulate ATRA in largely uniform poly L-lactic acid (PLLA) microparticles, with the efficiency of 91.4% and yield of 68.3%, and ~4-fold higher C max and AUC over the slow-releasing ATRA formulation. ATRA-PLLA microparticles had good biocompatibility, and significantly enhanced the inhibitory potency of ATRA on HCC cell growth, improving IC 50 by over 3-fold. ATRA-PLLA microparticles exerted its efficacy likely through degrading Pin1 and inhibiting multiple Pin1-regulated cancer pathways and cell cycle progression. Indeed, Pin1 knock-down abolished ATRA inhibitory effects on HCC cells and ATRA-PLLA did not inhibit normal liver cells, as expected because ATRA selectively inhibits active Pin1 in cancer cells. Moreover ATRA-PLLA microparticles significantly enhanced the efficacy of ATRA against HCC tumor growth in mice through reducing Pin1, with a better potency than the slow-releasing ATRA formulation, consistent with its improved pharmacokinetic profiles. This study illustrates an effective platform to produce controlled release formulation of anti-cancer drugs, and ATRA-PLLA microparticles might be a promising targeted drug for HCC therapy as PLLA is biocompatible, biodegradable and nontoxic to humans., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: The current work was attempted to formulate and evaluate the topical sustained release delivery systems called cubosomes containing Tretinoin for the acne treatment. The recent patents on various formulations of tretinoin (EP0408370A2) helped in selecting a new formulation and evaluation., Methods: Tretinoin loaded cubosomes were prepared by bottom-up technique, using varying the concentration of lipid and surfactant and keeping the drug concentration constant, a total of nine formulations of tretinoin was developed. These preparations were evaluated for surface charge, particle size, particle morphology, encapsulation efficiency, in-vivo and in-vitro release studies of gel enriched with cubosome dispersion. Finally, the stability studies of cubosomal gel were performed on optimized formulations., Results: Significant result were obtained with tretinoin formulation as the drug is lipophilic, so it gives more depot effect on the epidermis and good retention property. The data obtained from the formulations showed that formulation TCF-5 was the optimized formulation which exhibited better drug release and entrapment efficiency., Conclusion: It can be concluded that cubosomes offer benefits of quick onset as well as the maximal release of drug with fewer side effects. Thus, cubosomes represent a capable transporter having the property to sustain the release of drug, potential to localize the drug in the skin with a possible clinical application for acne vulgaris treatment due to cubosome depot effect on the epidermis., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

All-trans retinoic acid (ATRA), a derivative of vitamin A, is a common component in cosmetics and commercial acne creams as well as being a first-line chemotherapeutic agent. Today, formulations for the topical application of ATRA rely on creams and emulsions to incorporate the highly hydrophobic ATRA drug. These strategies, when applied to the skin, deliver ATRA as a single bolus, which is immediately taken up into the skin and contributes to many of the known adverse side effects of ATRA treatment, including skin irritation and hair loss. Herein we present a new concept in topical delivery of retinoids by covalently bonding the drug through a hydrolytically degradable ester linkage to a common hydrophilic polymer, polyvinyl alcohol (PVA), creating an amphiphilic nanomaterial that is water-soluble. This PVA bound ATRA can then act as a pro-drug and accumulate within the skin to allow for the sustained controlled delivery of active ATRA. This approach was demonstrated to release active ATRA out to 10days in vitro while significantly enhancing dermal accumulation of the ATRA in explant pig skin. In vivo we demonstrate that the pro-drug formulation reduces application site inflammation compared to free ATRA and retains the drug at the application site at measurable quantities for up to six days., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Neurogenic niches constitute a powerful endogenous source of new neurons that can be used for brain repair strategies. Neuronal differentiation of these cells can be regulated by molecules such as retinoic acid (RA) or by mild levels of reactive oxygen species (ROS) that are also known to upregulate RA receptor alpha (RARα) levels. Data showed that neural stem cells from the subventricular zone (SVZ) exposed to blue light (405nm laser) transiently induced NADPH oxidase-dependent ROS, resulting in β-catenin activation and neuronal differentiation, and increased RARα levels. Additionally, the same blue light stimulation was capable of triggering the release of RA from light-responsive nanoparticles (LR-NP). The synergy between blue light and LR-NP led to amplified neurogenesis both in vitro and in vivo, while offering a temporal and spatial control of RA release. In conclusion, this combinatory treatment offers great advantages to potentiate neuronal differentiation, and provides an innovative and efficient application for brain regenerative therapies., Statement of Significance: Controlling the differentiation of stem cells would support the development of promising brain regenerative therapies. Blue light transiently increased reactive oxygen species, resulting in neuronal differentiation and increased retinoic acid receptor (RARα) levels. Additionally, the same blue light stimulation was capable of triggering the release of RA from light-responsive nanoparticles (LR-NP). The synergy between blue light and LR-NP led to amplified neurogenesis, while offering a temporal and spatial control of RA release. In this sense, our approach relying on the modulation of endogenous stem cells for the generation of new neurons may support the development of novel clinical therapies., (Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

This study was aimed to develop a novel microemulsion that contained oleth-5 as a surfactant to enhance the oral absorption of all-trans retinoic acid (ATRA). The prepared microemulsion was evaluated for its particle size, shape, zeta potential, in vitro release, in vitro intestinal absorption, intestinal membrane cytotoxicity and stability. The obtained microemulsion was spherical in shape with a particle size of <200 nm and a negative surface charge. The in vitro release of the ATRA-loaded microemulsion was best fit with the zero-order model. This microemulsion significantly improved the intestinal absorption of ATRA. Confocal laser scanning microscopy analysis using a fluorescent dye-loaded microemulsion also confirmed the intestinal absorption result. The intestinal membrane cytotoxicity of the ATRA-loaded microemulsion did not differ from an edible oil (fish oil). Stability testing showed that the ATRA-loaded microemulsion was more stable at 25°C than 40°C., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Retinoic acid (RA), an active metabolite of vitamin A, is a critical signaling molecule in various cell types. We found that RA depletion caused by expression of the RA-metabolizing enzyme CYP26A1 promotes carcinogenesis, implicating CYP26A1 as a candidate oncogene. Several studies of CYP26s have suggested that the biological effect of RA on target cells is primarily determined by "cellular RA bioavailability", which is defined as the RA level in an individual cell, rather than by the serum concentration of RA. Consistently, stellate cells store approximately 80% of vitamin A in the body, and the state of cellular RA bioavailability regulates their function. Based on the similarities between stellate cells and astrocytes, we demonstrated that retinal astrocytes regulate tight junction-based endothelial integrity in a paracrine manner. Since diabetic retinopathy is characterized by increased vascular permeability in its early pathogenesis, RA normalized retinal astrocytes that are compromised in diabetes, resulting in suppression of vascular leakiness. RA also attenuated the loss of the epithelial barrier in murine experimental colitis. The concept of "cellular RA bioavailability" in various diseases will be directed at understanding various pathologies caused by RA insufficiency, implying the potential feasibility of a therapeutic strategy targeting the stellate cell system., (© 2017 Japanese Society of Pathology and John Wiley & Sons Australia, Ltd.)

All- trans retinoic acid ( at RA) is a front-line treatment of acute promyelocytic leukemia (APL). Due to its activity in regulating the cell cycle, it has also been evaluated for the treatment of other cancers. However, the efficacy of at RA has been limited by at RA inducing its own metabolism during therapy, resulting in a decrease of at RA exposure during continuous dosing. Frequent relapse occurs in patients receiving at RA monotherapy. In an attempt to combat therapy resistance, inhibitors of at RA metabolism have been developed. Of these, ketoconazole and liarozole have shown some benefits, but their usage is limited by side effects and low potency toward the cytochrome P450 26A1 isoform (CYP26A1), the main at RA hydroxylase. We determined the pharmacokinetic basis of therapy resistance to at RA and tested whether the complex disposition kinetics of at RA could be predicted in healthy subjects and in cancer patients in the presence and absence of inhibitors of at RA metabolism using physiologically based pharmacokinetic (PBPK) modeling. A PBPK model of at RA disposition was developed and verified in healthy individuals and in cancer patients. The population-based PBPK model of at RA disposition incorporated saturable metabolic clearance of at RA, induction of CYP26A1 by at RA, and the absorption and distribution kinetics of at RA. It accurately predicted the changes in at RA exposure after continuous dosing and when coadministered with ketoconazole and liarozole. The developed model will be useful in interpretation of at RA disposition and efficacy, design of novel dosing strategies, and development of next-generation at RA metabolism inhibitors., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)

Retinoic acid is a physiological compound of human blood. Blood levels range from 1000 to 7000 pg/mL (usually 1500-5000 pg/mL). Results of studies on absorption of topical retinoic acid in laboratory animals, although rather conflicting, demonstrate that it induces plasma concentrations which are well below concentrations caused by non-teratogenic oral doses. In humans, minimal percutaneous absorption of tretinoin was observed after topical applications. Neither single dose nor long-term treatment with topical tretinoin affect the endogenous levels of retinoic acid or its metabolites. Topical application of tretinoin at doses used in acne unlikely induces systemic effects. Although some clinical cases of suspected tretinoin-related embryotoxicity have been described, three prospective cohort studies clearly demonstrated the safety of topical tretinoin as an embryotoxic agent.

In this paper, we describe the synthesis, physicochemical characterization, drug release kinetics and preliminary biological evaluation of several N-(2-hydroxypropyl)methacrylamide (HPMA)-based polymer-retinoid conjugates designed for solid tumor immunotherapy. The conjugates are supposed to inhibit the immunosuppressive activity of myeloid-derived suppressor cells (MDSC) accumulated in the solid tumor microenvironment. All-trans retinoic acid (ATRA) was derivatized to hydrazide (AtrHy) and then attached to the polymer backbone via a spacer that is stable at the normal pH of blood (7.4) and hydrolytically degradable in mildly acidic environments (e.g. in endosomes or lysosomes, pH~5.0-6.5). Polymer-AtrHy conjugates were designed to achieve prolonged blood circulation and release of the immunomodulator intracellularly or extracellularly in solid tumor tissue. Three types of polymer precursors, differing in the structure of the keto acid-containing side chains, were synthesized. A linkage susceptible to hydrolytic cleavage was formed by the conjugation reaction of the carbonyl group-terminated side chains of the polymer precursors with the hydrazide group of a drug derivative. In vitro incubation of the conjugates in buffers resulted in much faster release of the drugs or their derivatives from the polymer at pH 5.0 than at pH 7.4, with the rate depending on the detailed structure of the spacer. Both the AtrHy derivative and its polymer conjugates showed the ability to induce the differentiation of retinoid-responsive HL-60 cells, thus demonstrating the required biological activity.

Use of the ablative laser has been approved to enhance topical drug penetration. Investigation into the usefulness of the non-ablative laser for assisting drug delivery is very limited. In this study, we explored the safety and efficacy of the non-ablative fractional erbium:glass (Er:glass) laser as an enhancement approach to promote drug permeation. Both pig and nude mouse skins were employed as transport barriers. We histologically examined the skin structure after laser exposure. The permeants of 5-aminolevulinic acid (ALA), imiquimod, tretinoin, peptide, dextrans and quantum dots (QD) were used to evaluate in vitro and in vivo skin passage. The fractional laser selectively created an array of photothermal dots deep into the dermis with the preservation of the stratum corneum and epidermis. The barrier function of the skin could be recovered 8-60h post-irradiation depending on the laser spot densities. The application of the laser caused no local infection of Staphylococcus aureus and Pseudomonas aeruginosa. Compared to intact skin, ALA flux was enhanced up to 1200-fold after laser exposure. The penetration enhancement level by the laser was decreased following the increase of permeant lipophilicity. The skin accumulation of tretinoin, an extremely lipophilic drug, showed only a 2-fold elevation by laser irradiation. The laser promoted peptide penetration 10-fold compared to the control skin. Skin delivery of dextrans with a molecular weight (MW) of at least 40kDa could be achieved with the Er:glass laser. QD with a diameter of 20nm penetrated into the skin with the assistance of the non-ablative laser. The confocal microscopic images indicated the perpendicular and lateral diffusions of dextrans and nanoparticles via laser-created microscopic thermal zones. Controlled Er:glass laser irradiation offers a valid enhancement strategy to topically administer the permeants with a wide MW and lipophilicity range., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Objectives: All-trans-retinoic acid (ATRA), a naturally occurring metabolite of vitamin A, has been shown to have great potential as an antitumorigenic drug to treat acute leukaemia by promoting cancer cell differentiation. Cytochrome P450 oxidoreductase (POR) is the only obligate electron donor for all of the microsomal cytochrome P450 enzymes including CYP26A1 which is highly specific for ATRA metabolism and efficacy in human myeloid leukaemia cells. In this study, we aimed to investigate the effect of POR on ATRA efficacy and CYP26A1 expression in human myeloid leukaemia HL-60 cells., Methods: Stably expressed POR and POR-RNAi HL-60 cell lines were established by transfecting POR overexpression or RNAi (RNA interference) vectors mediated by lentivirus. The protein expression of POR and CYP26A1 was examined by Western blot. The potential roles of POR on ATRA efficacy in HL-60 cells were explored by cell viability assay, cell cycle distribution, cellular differentiation and apoptosis analysis., Key Findings: All-trans-retinoic acid treatment caused the expression of POR upregulation and CYP26A1 downregulation in dose- and time-dependent manners. POR overexpression decreased CYP26A1 expression in HL-60 cells. When POR gene was interfered, the downregulation of CYP26A1 expression by ATRA was abolished. In addition, POR overexpression in HL-60 cells significantly compromised ATRA-induced cell proliferation inhibition, cell cycle arrest, differentiation and apoptosis, whereas downregulation of POR significantly potentiated ATRA effects., Conclusions: Our study therefore suggested that POR played an important role in regulating ATRA efficacy and CYP26A1 expression in HL-60 cells., (© 2016 Royal Pharmaceutical Society.)

All-trans retinoic acid, a hydrophobic drug, has become one of the most successful examples of differentiation agents used for treatment of acute promyelocytic leukemia. On the other hand, histone deacetylase inhibitors, such as cholesteryl butyrate, present differentiating activity and.can potentiate action of drugs such as all-trans retinoic acid. Solid lipid nanoparticles represent a promising alternative for administration of hydrophobic drugs such as ATRA. This study aimed to develop, characterize, and evaluate the cytotoxicity of all-trans retinoic acid-loaded solid lipid nanoparticles for leukemia treatment. The influence of in situ formation of an ion pairing between all-trans retinoic acid and lipophilic amines on the characteristics of the particles (size, zeta potential, encapsulation efficiency) was evaluated. Cholesteryl butyrate, a butyric acid donor, was used as a component of the lipid matrix. In vitro activity on cell viability and distribution of cell cycle phases were evaluated for HL-60, Jurkat, and THP-1 cell lines. The encapsulation efficiency of all-trans retinoic acid in cholesteryl butyrate-solid lipid nanoparticles was significantly increased by the presence of the amine. Inhibition of cell viability by all-trans retinoic acid-loaded solid lipid nanoparticles was more pronounced than the free drug. Analysis of the distribution of cell cycle phases also showed increased activity for all-trans retinoic acid-loaded cholesteryl butyrate-solid lipid nanoparticles, with a clear increase in subdiploid DNA content. The ion pair formation in SLN containing cholesteryl butyrate can be explored as a simple and inexpensive strategy to improve the efficacy and bioavail-ability of ATRA in the treatment of the cancer and metabolic diseases in which this retinoid plays an important role.

During the past two decades, it has been reported that treatment with all-trans-retinoic acid (ATRA) induces alveolar regeneration in rodent emphysema models. In the present study, we investigated the regeneration by ATRA at various exposure conditions in two strains of mice with induced emphysema. The emphysema model was created by postnatal administration of dexamethasone to ICR and FVB mice, which were then treated with ATRA from postnatal day 42. The regeneration was observed in ICR mice but not in FVB mice given 10 and 40 mg/kg/d ATRA for 10 d. The concentration-time profiles of ATRA in plasma and lung were similar in both strains. These results suggest that the strain difference in the regeneration by ATRA was not caused by differences in the exposure to ATRA. On the other hand, the regeneration in ICR mice was enhanced by an increase of the intraperitoneal dose in the range of 10-40 mg/kg/d for 10 d. At an intraperitoneal dose of 40 mg/kg/d, the regeneration was observed after 10 and 20 d of treatment but not after 1 to 5 d of treatment. Meanwhile, the regeneration by intraperitoneal administration of ATRA was enhanced more than that by oral administration. Exposure to ATRA during repeated intraperitoneal administration to ICR mice was higher than that in oral administration. The results suggest that the regeneration in ICR mice requires at least 10 d of treatment with ATRA and its effects depend on the exposure to ATRA in plasma, which parallels that in lung.

The combined effects of iontophoresis and lipid nanoparticles on drug delivery across human epidermal membrane (HEM) were investigated. The delivery of lipophilic and hydrophilic drugs, all trans-retinoic acid (ATRA), salicylate (SA), and acyclovir (ACV), across HEM from lipid nanoparticles, solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), was compared in passive and iontophoresis experiments in vitro. Iontophoresis experiments were also performed with synthetic Nuclepore membrane for comparison. Drug distribution in the skin after iontophoretic delivery with the lipid nanoparticles was examined using a model probe rhodamine B base (RhoB). The drug-loaded lipid nanoparticles had average sizes of ∼ 118-169 nm and a negative zeta potential. Iontophoresis did not enhance the delivery of ATRA across HEM from SLN and NLC. However, HEM distribution study of RhoB suggested that lipophilic drugs could be delivered into the deeper layer of the skin following iontophoretic delivery of the drugs from the lipid nanoparticles. Iontophoresis enhanced the delivery of hydrophilic drug SA with the lipid nanoparticles. Similarly, iontophoresis enhanced the delivery of ACV when it was loaded in SLN. These results suggest that lipid nanoparticles are a promising drug delivery method that can be combined with iontophoresis to improve skin delivery of hydrophilic drugs., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Objective: Psoriasis is a chronic inflammatory skin disease and topical therapy remains a key role for treatment. The aim of this study is to evaluate the influence of psoriasis-like lesions on the cutaneous permeation of anti-psoriatic drugs., Methods: We first set up imiquimod-induced dermatitis in mice that closely resembles human psoriasis lesions. The development of the lesions is based on the IL-23/IL17A axis for phenotypical and histological characteristics. Four drugs, 5-aminolevulinic acid (ALA), tacrolimus, calcipotriol, and retinoic acid, were used to evaluate percutaneous absorption., Results: The most hydrophilic molecule, ALA, revealed the greatest enhancement on skin absorption after imiquimod treatment. Imiquimod increased the skin deposition and flux of ALA by 5.6 to 14.4-fold, respectively, compared to normal skin. The follicular accumulation of ALA was also increased 3.8-fold. The extremely lipophilic drug retinoic acid showed a 1.7- and 3.8-fold increase in skin deposition and flux, respectively. Tacrolimus flux was enhanced from 2 to 21 μg/cm2/h by imiquimod intervention. However, imiquimod did not promote skin deposition of this macrolide. The lipophilicity, but not the molecular size, dominated drug permeation enhancement by psoriatic lesions. The in vivo percutaneous absorption of ALA and rhodamine B examined by confocal microscopy confirmed the deficient resistance of epidermal barrier for facilitating cutaneous delivery of drugs via psoriasis-like skin., Conclusion: We established the topical delivery profiles of anti-psoriatic drugs via imiquimod-treated psoriasis-like skin.

The use of laboratory animals for toxicity testing in chemical safety assessment meets increasing ethical, economic and legislative constraints. The development, validation and application of reliable alternatives for in vivo toxicity testing are therefore urgently needed. In order to use toxicity data obtained from in vitro assays for risk assessment, in vitro concentration-response data need to be translated into in vivo dose-response data that are needed to obtain points of departure for risk assessment, like a benchmark dose (BMD). In the present study, we translated in vitro concentration-response data of the retinoid all-trans-retinoic acid (ATRA), obtained in the differentiation assay of the embryonic stem cell test, into in vivo dose-response data using a physiologically based kinetic model for rat and human that is mainly based on kinetic model parameter values derived using in vitro techniques. The predicted in vivo dose-response data were used for BMD modeling, and the obtained BMDL10 values [lower limit of the 95 % confidence interval on the BMD at which a benchmark response equivalent to a 10 % effect size (BMR10) is reached (BMD10)] for rat were compared with BMDL10 values derived from in vivo developmental toxicity data in rats reported in the literature. The results show that the BMDL10 values from predicted dose-response data differ about sixfold from the BMDL10 values obtained from in vivo data, pointing at the feasibility of using a combined in vitro-in silico approach for defining a point of departure for toxicological risk assessment.

All-trans retinoic acid (atRA) maintains physiological stability of the prostate, and we reported that ethanol intake increases atRA in the rat prostate; however the mechanisms underlying these changes are unknown. We evaluated the impact of a low- and high-dose ethanol intake (UChA and UChB strains) on atRA metabolism in the dorsal and lateral prostate. Aldehyde dehydrogenase (ALDH) subtype 1A3 was increased in the dorsal prostate of UChA animals while ALDH1A1 and ALDH1A2 decreased in the lateral prostate. In UChB animals, ALDH1A1, ALDH1A2, and ALDH1A3 increased in the dorsal prostate, and ALDH1A3 decreased in the lateral prostate. atRA levels increased with the low activity of CYP2E1 and decreased with high CYP26 activity in the UChB dorsal prostate. Conversely, atRA was found to decrease when the activity of total CYP was increased in the UChA lateral prostate. Ethanol modulates the synthesis and catabolism of atRA in the prostate in a concentration-dependent manner., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Pegylation method is widely used to prolong the blood circulation time of proteins and nanoparticles after intravenous administration, but the effect of surface poly (ethylene glycol) (PEG) chain length on oral absorption of the pegylated nanoparticles is poorly reported. The aim of our study was to investigate the influence of PEG corona chain length on membrane permeability and oral bioavailability of the amphiphilic pegylated prodrug-based nanomicelles, taking all trans-retinoic acid (ATRA) as a model drug. The amphiphilic ATRA-PEG conjugates were synthesized by esterification reaction between all trans-retinoic acid and mPEGs (mPEG500, mPEG1000, mPEG2000, and mPEG5000). The conjugates could self-assemble in aqueous medium to form nanomicelles by emulsion-solvent evaporation method. The resultant nanomicelles were in spherical shape with an average diameter of 13-20 nm. The drug loading efficiency of ATRA-PEG500, ATRA-PEG1000, ATRA-PEG2000, and ATRA-PEG5000 was about 38.4, 26.6, 13.1, and 5.68 wt%, respectively. With PEG chain length ranging from 500 to 5000, ATRA-PEG nanomicelles exhibited a bell shape of chemical stability in different pH buffers, intestinal homogenate and plasma. More importantly, they were all rapidly hydrolyzed into the parent drug in hepatic homogenate, with the half-time values being 0.3-0.4h. In comparison to ATRA solution and ATRA prodrug-based nanomicelles, ATRA-PEG1000 showed the highest intestinal permeability. After oral administration, ATRA-PEG2000 and ATRA-PEG5000 nanomicelles were not nearly absorbed, while the oral bioavailability of ATRA-PEG500 and ATRA-PEG1000 demonstrated about 1.2- and 2.0-fold higher than ATRA solution. Our results indicated that PEG1000 chain length of ATRA-PEG prodrug nanomicelles has the optimal oral bioavailability probably due to improved stability and balanced mucus penetration capability and cell binding, and that the PEG chain length on a surface of nanoparticles cannot exceed a key threshold with the purpose of enhancement in oral bioavailability., (Copyright © 2015. Published by Elsevier B.V.)

all-trans retinoic acid (atRA), the active metabolite of vitamin A, is an essential signaling molecule. Specifically the concentrations of atRA are spatiotemporally controlled in target tissues such as the liver and the testes. While the enzymes of the aldehyde dehydrogenase 1A family (ALDH1A) are believed to control the synthesis of atRA, a direct relationship between altered ALDH1A activity and tissue atRA concentrations has never been shown. To test whether inhibition of ALDH1A enzymes decreases atRA concentrations in a tissue specific manner, the potent ALDH1A inhibitor WIN 18,446 was used to inhibit ALDH1A activity in mice. The ALDH1A expression, atRA formation kinetics, ALDH1A inhibition by WIN 18,446 and WIN 18,446 disposition were used to predict the time course and extent of inhibition of atRA formation in the testis and liver. The effect of WIN 18,446 on atRA concentrations in testis, liver and serum were measured following single and multiple doses of WIN 18,446. ALDH1A1 and ALDH1A2 were responsible for the majority of atRA formation in the testis while ALDH1A1 and aldehyde oxidase contributed to atRA formation in the liver. Due to the different complement of enzymes contributing to atRA formation in different tissues and different inhibition of ALDH1A1 and ALDH1A2 by WIN 18,446, WIN 18,446 caused only a 50% decrease in liver atRA but testicular atRA decreased over 90%. Serum atRA concentrations were also reduced. These data demonstrate that inhibition of ALDH1A enzymes will decrease atRA concentrations in a tissue specific manner and selective ALDH1A inhibition could be used to alter atRA concentrations in select target tissues., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Background: Ambient particulate matters (PMs) are known as inducers that adversely affect a variety of human organs., Objectives: In this study, we aimed to evaluate the influence of PMs on the permeation of drugs and sunscreens via the skin. The role of skin-barrier properties such as the stratum corneum (SC) and tight junctions (TJs) during the delivery process was explored., Methods: This work was conducted using both in vitro and in vivo experiments in pigs to check the responses of the skin to PMs. PMs primarily containing heavy metals (1648a) and polycyclic aromatic hydrocarbons (PAHs, 1649b) were employed to treat the skin., Results: According to the transepidermal water loss (TEWL), 1649b but not 1648a significantly disrupted the SC integrity by 2-fold compared to the PBS control. The immunohistochemistry (IHC) of cytokeratin, filaggrin, and E-cadherin exhibited that 1649b mildly damaged TJs. The cytotoxicity of keratinocytes and skin fibroblasts caused by 1649b was stronger than that caused by 1648a. The 1649b elicited apoptosis via caspase-3 activation. The proteomic profiles showed that PMs upregulated Annexin A2 by >5-fold, which can be a biomarker of PM-induced barrier disruption. We found that the skin uptake of ascorbic acid, an extremely hydrophilic drug, was increased from 74 to 112 μg/g by 1649b treatment. The extremely lipophilic drug tretinoin also showed a 2.6-fold increase of skin accumulation. Oxybenzone and dextran absorption was not affected by PMs. The in vivo dye distribution visualized by fluorescence microscopy had indicated that 1649b intervention promoted permeant partitioning into SC., Conclusions: Caution should be taken in exposing the skin to airborne dust due to its ability to reduce barrier function and increase the risk of drug overabsorption, although this effect was not very marked., (Copyright © 2015 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.)

Unlabelled: This work describes innovative niosomes, composed of diolein alone or in association with the hydrophilic penetration enhancer Labrasol(®), as carriers for cutaneous drug delivery. The model drug was tretinoin and conventional, and Labrasol(®) containing liposomes was used as controls to evaluate the influence of vesicle composition and the role of Labrasol(®) on vesicle physico-chemical properties and performance as skin delivery system. Vesicles, prepared by the thin film hydration technique, were characterized in terms of size distribution, morphology, zeta potential, structure, incorporation efficiency, and rheological properties. The influence of carrier composition on tretinoin delivery to human skin was evaluated by in vitro percutaneous experiments, while formulation distribution on human skin and cellular uptake in human keratinocytes were studied using confocal laser scanning microscopy., Result: showed that tretinoin loaded diolein-niosomes formed unilamellar vesicles very similar in physico-chemical properties to liposomes. The role of Labrasol(®) was similar in niosomes and liposomes. Its addition affected vesicle structure and size, by formation of an interdigitate bilayer with higher curvature and larger vesicle size, and rheological properties. Indeed, the presence of Labrasol(®) allowed both niosomes and liposomes to shift from Newtonian to pseudo-plastic behavior. Confocal laser microscopy highlighted an important contemporaneous deposition of hydrophilic and lipophilic vesicle components in stratum corneum and a high vesicle affinity for skin appendages when Labrasol(®) was added to the diolein-niosomes. Moreover, all samples were internalized in human keratinocytes in vitro., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Little is known about the contribution of different tissues to whole-body vitamin A (VA) kinetics in neonates. Here, we have used model-based compartmental analysis of tissue tracer kinetic data from unsupplemented (control) and VA-retinoic acid (VARA)-supplemented neonatal rats to determine VA kinetics in specific tissues under control and supplemented conditions. First, compartmental models for retinol kinetics were developed for individual tissues, and then an integrated compartmental model incorporating all tissues was developed for both groups. The models predicted that 52% of chylomicron (CM) retinyl ester was cleared by liver in control pups versus 22% in VARA-treated pups, whereas about 51% of VA was predicted to be extrahepatic in 4- to 6-day-old unsupplemented neonatal rats. VARA increased CM retinyl ester uptake by lung, carcass, and intestine; decreased the release into plasma of retinol that had been cleared by liver and lung as CM retinyl esters; stimulated the uptake of retinol from plasma holo-retinol binding protein into carcass; and decreased the retinol turnover out of the liver. Overall, neonatal VA trafficking differed from that previously described for adult animals, with a larger contribution of extrahepatic tissues to CM clearance, especially after VA supplementation, and a significant amount of VA distributed in extrahepatic tissues., (Copyright © 2014 by the American Society for Biochemistry and Molecular Biology, Inc.)

Resistance to aromatase inhibitors is a major concern in the treatment of breast cancer. Long-term letrozole cultured (LTLC) cells represent a model of resistance to aromatase inhibitors. The LTLC cells were earlier generated by culturing MCF-7Ca, the MCF-7 human breast cancer cell line stably transfected with human placental aromatase gene for a prolonged period in the presence of letrozole. In the present study the effect of RAMBA, VN/14-1 on the sensitivity of LTLC cells upon multiple passaging and the mechanisms of action of VN/14-1 in such high passage LTLC (HP-LTLC) cells was investigated. We report that multiple passaging of LTLC cells (HP-LTLC cell clones) led to profound decrease in their sensitivity to VN/14-1. Additionally, microarray studies and protein analysis revealed that VN/14-1 induced marked endoplasmic reticulum (ER) stress and autophagy in HP-LTLC cells. We further report that VN/14-1 in combination with thapsigargin exhibited synergistic anti-cancer effect in HP-LTLC cells. Preliminary pharmacokinetics in rats revealed that VN/14-1 reached a peak plasma concentration (Cmax) within 0.17h after oral dosing. Its absolute oral bioavailability was >100%. Overall these results indicate potential of VN/14-1 for further clinical development as a potential oral agent for the treatment of breast cancer., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Vitamin A (VA) metabolism in neonates is virtually uncharacterized. Our objective was to develop a compartmental model of VA metabolism in unsupplemented and VA-supplemented neonatal rats. On postnatal day 4, pups (n = 3/time) received 11,12-[(3)H]retinol orally, in either oil (control) or VA combined with retinoic acid (VARA) [VA (∼6 mg/kg body weight) + 10% retinoic acid]. Plasma and tissues were collected at 14 time points up to 14 days after dose administration. VARA supplementation rapidly, but transiently, increased total retinol mass in plasma, liver, and lung. It decreased the peak fraction of the dose in plasma. A multi-compartmental model developed to fit plasma [(3)H]retinol data predicted more extensive recycling of retinol between plasma and tissues in neonates compared with that reported in adults (144 vs. 12-13 times). In VARA pups, the recycling number for retinol between plasma and tissues (100 times) and the time that retinol spent in plasma were both lower compared with controls; VARA also stimulated the uptake of plasma VA into extravascular tissues. A VARA perturbation model indicated that the effect of VARA in stimulating VA uptake into tissues in neonates is both dramatic and transient., (Copyright © 2014 by the American Society for Biochemistry and Molecular Biology, Inc.)

Tretinoin is a retinoid derivative that has an antiproliferative effect on several kinds of tumours. Human lung adenocarcinoma epithelial cell lines (A549) exhibit a profound resistance to the effects of tretinoin. Nanocarriers seem to be a good alternative to overcomecellular resistance to drugs. The aim of this study was to test whether tretinoin-loaded lipid-core nanocapsules exert anantitumor effect on A549 cells. A549 cells were incubated with free tretinoin (TTN), blank nanocapsules (LNC) and tretinoin-loaded lipid-core nanocapsules (TTN-LNC). Data from evaluation of DNA content and Annexin V binding assay by flow cytometry showed that TTN-LNC induced apoptosis and cell cycle arrest at the G1-phase while TTN did not. TTN-LNC showed higher cytotoxic effects than TTN on A549 cells evaluated by MTT and LIVE/DEAD cell viability assay. Gene expression profiling identified up-regulated expression of gene p21 by TTN-LNC, supporting the cell cycle arrest effect. These results showed for the first time that TTN-LNC are able to overcome the resistance of adenocarcinoma cell line A549 to treatment with TTN by inducing apoptosis and cell cycle arrest, providing support for their use in applications in lung cancer therapy., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The objective of this study was to investigate the effects of drug amounts (0.1%, 0.2% and 0.3% w/w), amounts of the oil (10%, 15% and 20% w/w of lipid matrix) and types of the oil (soybean oil (S), medium chain triglycerides (M), oleic acids (O) and linoleic acids (L)) in lipid matrix of all-trans retinoic acid (ATRA)-loaded nanostructured lipid carriers (NLCs) for transdermal drug delivery. The ATRA-loaded solid lipid nanoparticles (SLNs) were formulated with 30% w/w cetyl palmitate. All lipid nanoparticles had average sizes between 130 and 241 nm and had negative zeta potentials. The drug loading of all formulations was higher than 95%. The release of drug from all lipid nanoparticles followed zero-order kinetics. The amount of drug released from all the NLCs and SLNs was significantly greater than the drug released from the ATRA suspension. The ATRA flux of the SLNs was higher than the NLCs. The flux of the NLCs containing oleic acid was significantly higher than the other types of oils. The chemical stability at 4 °C, the percentage of ATRA remaining in all the lipid nanoparticles tested was higher than 80%. It can be concluded that both the SLNs and NLCs are promising dermal drug delivery systems for ATRA.

There is an urgent need to identify ways of enhancing the mucosal immune response to oral vaccines. Rotavirus vaccine protection is much lower in Africa and Asia than in industrialized countries, and no oral vaccine has efficacy approaching the best systemic vaccines. All-trans retinoic acid (ATRA) up-regulates expression of α4β7 integrin and CCR9 on lymphocytes in laboratory animals, increasing their gut tropism. The aim of this study was to establish the feasibility of using ATRA as an oral adjuvant for oral typhoid vaccination. In order to establish that standard doses of oral ATRA can achieve serum concentrations greater than 10 nmol/l, we measured ATRA, 9-cis and 13-cis retinoic acid in serum of 14 male volunteers before and 3 h after 10 mg ATRA. We then evaluated the effect of 10 mg ATRA given 1 h before, and for 7 days following, oral typhoid vaccine in eight men, and in 24 men given various control interventions. We measured immunoglobulin (Ig)A directed against lipopolysaccharide (LPS)and protein preparations of vaccine antigens in whole gut lavage fluid (WGLF) and both IgA and IgG in serum, 1 day prior to vaccination and on day 14. Median [interquartile range (IQR)] C(max) was 26·2 (11·7-39·5) nmol/l, with no evidence of cumulation over 8 days. No adverse events were observed. Specific IgA responses to LPS (P = 0·02) and protein (P = 0·04) were enhanced in WGLF, but no effect was seen on IgA or IgG in serum. ATRA was well absorbed, well tolerated and may be a promising candidate oral adjuvant., (© 2013 British Society for Immunology.)