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The most distinctive characteristic of podocytes in the kidney is the presence of interdigitating cell processes with nephrin and podocin that are concentrated at sites of cell-cell contact. Unfortunately, these defining features are easily lost in culture. We previously reported culture conditions that can restore the differentiated phenotypes in primary cultures of rat podocyte. Since then, some of the materials used have been discontinued or improved. In this chapter, we therefore provide our most recent protocol for the restoration of the podocyte phenotype in culture., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Multipotent neural stem cells (NSCs) are currently under investigation as a candidate treatment for central nervous system (CNS) injury because of their potential to compensate for neuronal damage and to reconstruct disrupted neuronal connections. To maximize the regenerative effect of the derived neurons and to minimize the side effects of the derived astrocytes, it is necessary to regulate the fate determination of NSCs to produce more neurons and fewer astrocytes. Both valproic acid (VPA) and all-trans-retinoic acid (ATRA), two clinically established drugs, induce neuronal differentiation and facilitate neurite outgrowth at the expense of astrocytic differentiation in NSCs. However, the time-dependent activities and the long-term treatment effects of these drugs have not been explored in NSCs. More importantly, the efficacies of VPA and ATRA in neuronal promotion and astrocytic suppression remain unclear. In this study, we compare the time-dependent characteristics of VPA and ATRA in NSC differentiation and neurite outgrowth in vitro and, for the first time, demonstrate the improved efficacy of their combined application in neuronal induction and astrocytic suppression. These significant effects are closely coupled to the altered expression of a neurogenic transcription factor, a Wnt signaling component, a cell cycle regulator and a neural growth factor, indicating an underlying cross-talk between the mechanisms of action of ATRA and VPA. These findings indicate that a novel strategy combining these two therapeutic drugs may improve the restorative effect of NSC transplantation by altering the expression of their interconnected targets for fate determination. [ABSTRACT FROM AUTHOR]

Combination treatment through simultaneous delivery of two or more drugs with nanoparticles has been demonstrated to be an elegant and efficient approach for cancer therapy. Herein, we employ a combination therapy for eliminating both the bulk tumor cells and the rare cancer stem cells (CSCs) that have a high self-renewal capacity and play a critical role in cancer treatment failure. All-trans-retinoic acid (ATRA), a powerful differentiation agent of cancer stem cells and the clinically widely used chemotherapy agent doxorubicin (DOX) are simultaneously encapsulated in the same nanoparticle by a single emulsion method. It is demonstrated that ATRA and DOX simultaneous delivery-based therapy can efficiently deliver the drugs to both non-CSCs and CSCs to differentiate and kill the cancer cells. Differentiation of CSCs into non-CSCs can reduce their self-renewal capacity and increase their sensitivity to chemotherapy; with the combined therapy, a significantly improved anti-cancer effect is demonstrated. Administration of this combinational drug delivery system can markedly augment the enrichment of drugs both in tumor tissues and cancer stem cells, prodigiously enhancing the suppression of tumor growth while reduce the incidence of CSC in a synergistic manner. [ABSTRACT FROM AUTHOR]

Vitamin A (VA) has a number of important biological functions in human growth and development. Previous studies by our group demonstrated that the normal VA levels improved recovery of learning and memory function and decreased apoptosis in rats with hypoxic-ischemic brain damage (HIBD). However, it has not been fully elucidated how VA regulates the apoptosis of neuronal cells. To investigate the anti-apoptotic effect of VA, an in vitro oxygen glucose deprivation (OGD) model in PC12 cells was treated with four concentrations of all-trans-retinoic acid (ATRA), an active in vivo product of VA. Following in vitro OGD injury in PC12 cells, the percentage of apoptosis and the fluorescence intensity of the mitochondrial membrane potential (MMP) were increased in the cells, and the expression levels of B-cell lymphoma-associated X (Bax) were enhanced. ATRA treatment at 2-4 μmol/l for 24 h decreased the percentage of apoptosis and the MMP of the PC12 cells injured by OGD. ATRA at 4 μmol/l also reduced the expression levels of Bax and enhanced the expression of B-cell lymphoma 2. Furthermore, RNA interference with retinoic acid receptor α (RARα) reversed the observed effect in PC12 cells following ATRA treatment at 4 μmol/l alone. In conclusion, the present study suggested that treatment with ATRA at 4 μmol/l suppressed apoptosis of PC12 cells following OGD injury, potentially through regulation of the RARα signaling pathway. [ABSTRACT FROM AUTHOR]

Human SPLUNC1 can suppress nasopharyngeal carcinoma ( NPC) tumor formation; however, the correlation between SPLUNC1expression and NPC patient prognosis has not been reported. In the present study, we used a large-scale sample of 1015 tissue cores to detect SPLUNC1 expression and its association with patient prognosis. SPLUNC1 expression was reduced in NPC samples compared to nontumor nasopharyngeal epithelium tissues. Positive expression of SPLUNC1 in NPC predicted a better prognosis (disease-free survival, P = 0.034; overall survival, P = 0.048). Cox's proportional hazards model revealed that SPLUNC1 could be a significant prognostic factor affecting disease-free survival ( P = 0.027). A c DNA micro-array analyzed by significant analysis of micro-array (SAM) and ingenuity pathway analysis (IPA) revealed that an indirect interaction existed between SPLUNC1 and retinoic acid (RA) in the cancer regulatory network. To further investigate the molecular mechanisms involved, we utilized several bioinformatics tools and identified 12 retinoid X receptors heterodimer binding sites in the promoter region of the SPLUNC1 gene. The transcriptional activity of the SPLUNC1 promoter was up-regulated significantly by all-trans-retinoic acid ( ATRA). SPLUNC1 and retinoic acid receptor expression were induced significantly by ATRA, and removal of ATRA led to a progressive loss of SPLUNC1 and retinoic acid receptor expression. ATRA inhibited proliferation and induced the differentiation of NPC cells. Interestingly, over-expression of SPLUNC1 sensitized NPC cells to ATRA, whereas knockdown of SPLUNC1 in HNE1 cells increased cell viability. Under SPLUNC1 knockdown conditions, differentiation was reversed by ATRA treatment. We concluded that SPLUNC1 could potentially predict prognosis for NPC patients and play an important role in ATRA-induced growth inhibition and differentiation in NPC cells. [ABSTRACT FROM AUTHOR]

Background and Aims Elevated levels of reactive carbonyl species such as methylglyoxal triggers carbonyl stress and activates a series of inflammatory responses leading to accelerated vascular damage. Carbonyl stress is implicated in conditions and diseases like aging, diabetes mellitus, Alzheimer's disease and cardiovascular diseases. Our aim was to examine the effects of methylglyoxal on human hCMEC/D3 brain endothelial cells and search for protective molecules to prevent endothelial damage. Methods Methylglyoxal-induced modification of albumin was tested in a cell-free assay. Endothelial cell viability was monitored by impedance measurement in real-time. The following compounds were tested in cell-free and viability assays: β-alanine, all-trans-retinoic acid, aminoguanidine, ascorbic acid, l -carnosine, GW-3333, indapamide, piracetam, γ-tocopherol, U0126, verapamil. Barrier function of brain endothelial monolayers was characterized by permeability measurements and visualized by immunohistochemistry for β-catenin. mRNA expression level of 60 selected blood–brain barrier-related genes in hCMEC/D3 cells was investigated by a custom Taqman gene array. Results Methylglyoxal treatment significantly elevated protein modification, exerted toxicity, reduced barrier integrity, increased permeability for markers FITC-dextran and albumin and caused higher production of reactive oxygen species in hCMEC/D3 endothelial cells. Changes in the mRNA expression of 30 genes coding tight junction proteins, transporters and enzymes were observed in methylglyoxal-treated hCMEC/D3 cells. From the tested 11 compounds only all-trans-retinoic acid, an antioxidant and antiglycation agent, U0126, a MAP/ERK kinase inhibitor and aminoguanidine attenuated methylglyoxal-induced damage in hCMEC/D3 cells. Conclusions All-trans-retinoic acid and inhibition of the MAP/ERK signaling pathway may be protective in carbonyl stress induced brain endothelial damage. [ABSTRACT FROM AUTHOR]

Our previous studies have shown that vitamin A (VA) status is associated with antiviral immunity and pathogenic conditions in enterovirus 71 (EV71)-infected children. In the present study, we established an in vitro model to investigate the effects and potential mechanism of the antiviral activity of VA. Human monocytic U937 cells were cultured in vitro and infected with EV71. All-trans-retinoic acid (ATRA), the active metabolite of VA, and Ro 41-5253, a retinoic acid receptor-α (RAR-α) antagonist, were used as the experimental treatment agents. The percentage of EV71-infected cells and apoptosis induced by EV71 were determined using flow cytometry. The level of interferon-α (IFN-α) in the supernatants of the cultures was detected using ELISA. The expression of retinoid-induced gene I (RIG-I) and its downstream genes was examined with real-time quantitative PCR. The results indicated that ATRA reduced the percentage of EV71-infected cells and protected cells against EV71-induced apoptosis. Correspondingly, ATRA increased the production of IFN-α one of the most important antiviral cytokines, at both mRNA and protein levels in EV71-infected cells. In addition, the expression of RIG-I mRNA and its downstream genes was up-regulated by ATRA in EV71-infected cells. Ro 41-5253 abrogated the inhibitory effects of ATRA on EV71. The present findings suggest that ATRA is an interferon-inducing agent with antiviral activity against EV71 in vitro and that its actions are mediated at least in part by RAR-α activity and the RIG-I signalling pathway. [ABSTRACT FROM PUBLISHER]

Abstract: Background: We previously demonstrated a stimulating effect of hepatectomy on residual tumor cells after resection of liver metastases. The aim of this study was to analyze the effect of all-trans-retinoic acid (ATRA) on the protumor effect of hepatectomy and survival of hepatectomized rats bearing liver metastases. We also explored whether ATRA interfered with the tumor promoting effect of hepatotropic growth factors (GFs). Methods: The in vitro effect of ATRA on proliferation of S4MH rhabdomyosarcoma tumor cells was assessed when cultured with laparotomized or hepatectomized rat serum (HRS), or in the presence of GFs (hepatocyte growth factor, insulin growth factor 2, Platelet Derived Growth Factor (PDGF)-BB, and vascular endothelial growth factor). For the in vivo studies, rats were partially hepatectomized on day 10 after metastasis induction, one group being treated with ATRA from day 7 to 14, and a second receiving cyclophosphamide (CY; on days 10 and 14) alone or with ATRA. We determined the size and number of liver and lung metastases. Finally, we analyzed the effect of treatments on rat survival. Results: Hepatotropic GFs increased cell proliferation in a similar manner to HRS. In vitro, ATRA blocked the protumor effect of both HRS and GFs. In vivo, ATRA reduced the size and number of liver and lung metastases, and significantly increased rat survival. Furthermore, adding ATRA to CY significantly increased survival compared with CY alone. Conclusions: In our model, ATRA minimizes the tumor-stimulating effect of hepatectomy, reducing the number and size of liver metastases and improving survival. The results suggest that the ATRA may be useful for blocking the growth-promoting effect of hepatotropic GFs released after liver metastasis resection. [Copyright &y& Elsevier]

The concept of differentiation therapy of cancer is ~40 years old. Despite many encour-aging results obtained in laboratories, both in vitro and in vivo studies, the only really successful clinical application of differentiation therapy was all-trans-retinoic acid (ATRA)-based therapy of acute promyelocytic leukemia (APL). ATRA, which induces granulocytic differentiation of APL leukemic blasts, has revolutionized the therapy of this disease by converting it from a fatal to a curable one. However, ATRA does not work for other acute myeloid leukemias (AMLs). Since 1,25-dihydroxyvitamin D3 (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs (VDAs) was widely accepted. Also, some types of solid cancers responded to in vitro applied VDAs, and hence it was postulated that VDAs can be used in many clinical applications. However, early clinical trials in which cancer patients were treated either with 1,25D or with VDAs, did not lead to conclusive results. In order to search for a molecular basis of such unpredictable responses of AML patients toward VDAs, we performed ex vivo experiments using patient's blast cells. Experiments were also performed using 1,25D-responsive and 1,25D-non-responsive cell lines, to study their mechanisms of resistance toward 1,25D-induced differentiation. We found that one of the possible reasons might be due to a very low expression level of vitamin D receptor (VDR) mRNA in resistant cells, which can be increased by exposing the cells to ATRA. Our considerations concerning the molecular mechanism behind the low VDR expression and its regulation by ATRA are reported in this paper. [ABSTRACT FROM AUTHOR]

In adult therapy, arsenic trioxide (ATO) and all-trans-retinoic acid (ATRA) are recognized as active treatment of relapsed acute promyelocytic leukemia (APL). The efficacy of this combination in pediatric APL has not yet been well established. We report the case of a 6-year-old girl with relapsed APL, with a PML-RARα mutation, treated with a combination of ATO and ATRA. Over a period of 5 months, she received in total, 75 doses of intravenous ATO and 40 doses of oral ATRA. Currently, 22 months after relapse, she is still in complete remission. Here, we describe treatment of a relapsed APL in a child with limited treatment of ATO and ATRA and review the literature. [ABSTRACT FROM AUTHOR]

Acute promyelocytic leukaemia (APL) in children and adolescents shares many features with APL in adults. There are important distinctions, however, between these age groups in the presentation, complications and treatment outcomes. Paediatric patients are more likely to present with high risk features including elevated WBC count or microgranular variant (M3v). Yet the early death rate is lower in paediatric patients compared to adult patients. Overall outcomes such as CR, OS and EFS appear similar in paediatric and adult patients treated on similar regimens except that very young children may have a higher risk of relapse. While contemporary studies have clearly demonstrated improved survival in adults receiving ATO therapy, currently there is more limited data on the role of ATO in paediatric patients. Here we highlight the similarities and important distinctions between paediatric and adult APL while reviewing available data on treatment of paediatric APL. [Copyright &y& Elsevier]

If looking for a mnemonic to remember the relevant facts about acute promyelocytic leukemia (APL), one just has to remember that APL is a disease of A's. It is acute and it is highly sensitive to treatment with anthracyclines, all-trans-retinoic acid (RA) and arsenic trioxide (ATO). The presence of fusions involving the retinoic acid receptor alpha (RARA) is without question the central player driving APL and dictating the response of this disease to these therapeutic agents. However, beyond this knowledge, the molecular mechanisms that contribute to the complicated pathogenesis and the response to treatment of APL are not completely defined. As more is understood about this hematological malignancy, there are more opportunities to refine and improve treatment based on this knowledge. In this review article, we discuss the response of APL to these “A” therapies. [Copyright &y& Elsevier]

Retinol-binding protein 2 (RBP2, also known as cellular retinol-binding protein 2 (CRBP2)) is a member of the fatty acid-binding protein family and has been extensively studied for its role in facilitating dietary vitamin A (retinol) uptake and metabolism within enterocytes of the small intestine. RBP2 is present in highest concentrations in the proximal small intestine where it constitutes approximately 0.1–0.5% of soluble protein. Recent reports have established that RBP2 binds monoacylglycerols (MAGs) with high affinity, including the canonical endocannabinoid 2-arachidonoylglycerol (2-AG). Crystallographic studies reveal that retinol, 2-AG, or other long-chain MAGs alternatively can bind in the retinol-binding pocket of RBP2. It also has been demonstrated recently that Rbp2 -deficient mice are more susceptible to developing obesity and associated metabolic phenotypes when exposed to a high fat diet, or as they age when fed a conventional chow diet. When subjected to an oral fat challenge, the Rbp2 -deficient mice release into the circulation significantly more, compared to littermate controls, of the intestinal hormone glucose-dependent insulinotropic polypeptide (GIP). These new findings regarding RBP2 structure and actions within the intestine are the focus of this review. • RBP2 binds 2-monoacylglycerols with very high affinity, equivalent to that of retinol binding. • 2-Monoacylglycerol and retinol bind in the same binding pocket of RBP2. • RBP2 modulates the intestinal release of glucose-dependent insulinotropic polypeptide (GIP) in response to a fat challenge. • The absence of RBP2 renders mice more prone to the development of obesity and associated metabolic diseases. [ABSTRACT FROM AUTHOR]

Conversion of dietary vitamin A (VA) into retinoic acid (RA) is essential for many biological processes and thus far studied largely in mammalian cells. Using targeted metabolomics, we found that commensal bacteria in the mouse gut lumen produced a high concentration of the active retinoids, all - trans -retinoic acid (at RA) and 13- cis -retinoic acid (13 cis RA), as well as the principal circulating retinoid, retinol. Ablation of anerobic bacteria significantly reduced retinol, at RA, and 13 cis RA, whereas introducing these bacteria into germ-free mice significantly enhanced retinoids. Remarkably, cecal bacterial supplemented with VA produced active retinoids in vitro , establishing that gut bacteria encode metabolic machinery necessary for multistep conversion of dietary VA into its active forms. Finally, gut bacteria Lactobacillus intestinalis metabolized VA and specifically restored RA levels in the gut of vancomycin-treated mice. Our work establishes vitamin A metabolism as an emergent property of the gut microbiome and lays the groundwork for developing probiotic-based retinoid therapy. [Display omitted] • Targeted metabolomics reveal that commensal bacteria produce retinoids in the gut • Vitamin A metabolism is a feature of symbiotic microbial community • Gut bacteria encode vitamin A metabolism machinery independent of the host • Lactobacillus spp isolated from murine gut restores at RA in vancomycin-treated mice Bonakdar, Czuba et al. show that commensal bacteria perform multistep conversion of dietary vitamin A into retinoic acid, significantly increasing the concentration of vitamin A metabolites in the gut lumen. Vitamin A metabolism is an emergent property of gut microbiome, pointing toward a mechanism by which gut microbes regulate host physiology. [ABSTRACT FROM AUTHOR]

Background: All-trans retinoic acid (ATRA), an active metabolite of vitamin A, is widely used for induction of differentiation, growth and proliferation of epithelial cells. Anticancer drug cisplatin induces apoptosis by cross-linking to DNA that it is commonly used for treatment of ovarian, head and neck, esophageal, and gastric cancers and melanoma. Previous studies on ovarian cancer and melanoma cell lines, suggesting additive effects of retinoic acid with cisplatin. The present study is the first study on simultaneous effects of all-trans retinoic acid and cisplatin on human esophageal cancer cell line KYSE-30. Material and Methods: In this experimental study, KYSE-30 cell line was cultured in presence of different concentration of ATRA alone and in combination with cisplatin. Then, cell death was investigated by clonogenic assay and acridine orange/ ethidium bromide staining. Results: The results showed that ATRA concentrations ≥15µM cause differentiation of KYSE30 to squamous cell morphology, while lower concentrations decreases the colony formation (p≤0.05). The best effects on cell death were observed in 10 µM of ATRA of combination with 5 and 10 µg/ml of cisplatin. Conclusions: Concomitant use of low concentrations of retinoic acid and cisplatin increases apoptosis and necrosis, thus reducing the number of cell line KYSE-30 colonies compared with cisplatin alone. [ABSTRACT FROM AUTHOR]

Retinoic acid (RA) plays an important role in the developing mammalian nervous system. Based on this concept, some studies have demonstrated the beneficial effects of RA administration on neurogenesis in neuropathological diseases. Some investigations have revealed the anti-inflammatory effects of RA treatment in multiple systems, in addition to its role in neurogenesis. To date, however, the neuroprotective efficacy of RA after cerebral ischemia, especially in the context of its anti-inflammatory effects, has been poorly demonstrated. Additionally, to the best of our knowledge, experiments of the therapeutic efficacy of RA treatment in a transient global ischemic model in the Mongolian gerbil have been lacking worldwide. Here, we studied the neuroprotective effects and neurobehavioral outcomes of intraperitoneally administered all- trans-RA (ATRA; a synthetic form of RA) on brains with transient global ischemia that was induced with the bilateral common carotid artery occlusion and reperfusion (BCCAO/R) model in the gerbil. In order to identify whether these neuroprotective mechanisms were due to the anti-inflammatory effects of ATRA, in vivo hippocampal expression of proinflammatory cytokines including tissue necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) after ATRA injection and in vitro levels of release of nitric oxide, TNF-α and IL-6 from lipopolysaccharide (LPS)-stimulated BV2 microglial cells after ATRA treatment were evaluated. The results showed that ATRA can protect pyramidal neurons in the hippocampal CA1 region against BCCAO-induced neuronal apoptosis and significantly reduce the extent of astrocytosis and microglial activation. In addition, the ischemia-induced neurobehavioral changes were normalized by ATRA injection. Consistent with these phenotypic data, we observed the diminishing effects of ATRA treatment on the production of proinflammatory mediators (e.g., TNF-α and IL-6) in hippocampal homogenates and LPS-stimulated BV2 cells, and these effects were dose-dependent. These results suggest a beneficial role of ATRA in the attenuation of global cerebral ischemia due to its anti-inflammatory properties, resulting in, at least partly, the inhibition of microglial secretion of variable proinflammatory cytokines. [ABSTRACT FROM AUTHOR]

Estrogen synthesis in adipose tissue is associated with the development of breast cancer. Tumors are preferentially found in breast quadrants with strongest expression of the cytochrome P450 aromatase (encoded by the gene CYP19A1). Several promoters regulated by various hormonal factors drive aromatase expression in human breast adipose fibroblasts (BAFs). As adipose tissue is a major source of retinoids, in this study, we investigated their role in the regulation of aromatase expression. The retinoids all-trans-retinoic acid (at-RA) and 9-cis-RA induce aromatase activity in human BAFs. In BAFs, at-RA induces aromatase gene expression via promoter I.4. In 3T3-L1 cells, both retinoids specifically drive luciferase reporter gene expression under the control of aromatase promoter I.4, whereas other promoters active in human adipose tissue are insensitive. Activation by retinoids depends on a 467 bp fragment (K256/C211) of promoter I.4 containing four putative retinoic acid response elements (RAREs). Site-directed mutagenesis revealed that only RARE2 (C91/C105) mediates the retinoid-dependent induction of reporter gene activity. In 3T3-L1 preadipocytes and human BAFs, RA receptor a (RARa (RARA)) expression is predominant, whereas RARb (RARB) or RARg (RARG) expression is low. Electrophoretic mobility shift assays with nuclear extracts obtained from human BAFs and 3T3-L1 cells identified a specific RARE2-binding complex. Retinoids enhanced complex formation, whereas pre-incubation with anti-RARa antibodies prohibited the binding of RARa to RARE2. Chromatin immunoprecipitation showed RA-dependent binding of RARa to the RARE2-containing promoter region in vivo. Furthermore, we provide evidence that RARE2 is also necessary for the basal activation of promoter I.4 in these cells. Taken together, these findings indicate a novel retinoid-dependent mechanism of aromatase activity induction in adipose tissue. [ABSTRACT FROM AUTHOR]

Polymeric biomaterials are being investigated for the last several years because of their controllable properties. In this study, it was aimed to prepare and evaluate the atRA carrying system using Poly(lactide-co-glycolide) (PLGA). Microparticles were characterized in terms of morphology and encapsulation efficiency. Release studies were performed for the evaluation of drug release rates. Cytotoxicity tests were implemented on MCF-7 Human breast cancer cell line for the investigation of drug and polymer toxicity. The microparticles were found smooth and spherical in shape. However, as the loaded drug amount increased, the sizes of microparticles also increased and the size distribution became less uniform. The sizes of atRA-loaded microparticles ranged between 1-10 µm. The encapsulation efficiency of atRetinoic acid (all- trans-Retinoic acid) was achieved approximately %90. Approximately, 45% of atRA was released from atRA-loaded microparticles by the end of 4-5 days. Cell growth inhibition was observed after 4 days of incubation of cells with PLGA microparticles. [ABSTRACT FROM AUTHOR]

Abstract: Melanoma incidence is dramatically increasing and the available treatments beyond partial efficacy have severe side effects. Retinoids are promising anticancer agents, but their clinical use has been limited by their toxicity, although a combination with other agents can possibly generate a therapeutic action at lower dosage. Thus, we investigated the effects of all-trans-retinoic acid combined with the antiestrogen endoxifen on melanoma cell proliferation and the effects were compared with its pro-drug tamoxifen. Moreover, we evaluated the effects of these combinations on non-neoplasic cells and assessed mitochondrial bioenergetic functions, to predict their potential toxicity. Individually, all-trans-retinoic acid and the antiestrogens endoxifen and tamoxifen decreased melanoma cell biomass, cell viability and DNA synthesis, without increased cell death, suggesting that the compounds inhibited cell proliferation. Noteworthy, endoxifen decreased cell proliferation more efficiently than tamoxifen. The combination of endoxifen with all-trans-retinoic acid enhanced the antiproliferative effects of the compounds individually more potently than tamoxifen, which did not enhance the effects induced by all-trans-retinoic acid alone, and blocked cell cycle progression in G1. Moreover, the combination of all-trans-retinoic acid with endoxifen significantly decreased melanoma cells migration, whereas the combination with tamoxifen did not present significant effects. At the concentrations used the compounds did not induce cytotoxicity in non-neoplasic cells and liver mitochondrial bioenergetic function was not affected. Altogether, our results show for the first time that a combined treatment of all-trans-retinoic acid with endoxifen may provide an anti-proliferative and anti-migration effect upon melanoma cells without major toxicity, offering a powerful therapeutic strategy for malignant melanoma. [Copyright &y& Elsevier]

Diabetes mellitus, a chronic disease with increasing prevalence worldwide, is known to be associated with thyroid disorders. Retinoic acid, a metabolite of vitamin A, is currently used for the treatment of diabetes and obesity.The present study aimed to evaluate the possibility of using all-trans-retinoic acid (atRA) in reducing the structural changes of the thyroid gland and pituitary thyrotrophs in streptozotocin-induced diabetic rats.Thirty adult male albino rats were divided into three equal groups: group I, control; group II, which included rats in which diabetes was induced by a single intraperitoneal injection of streptozotocin (100 mg/kg); and group III, which included rats in which diabetes was induced as in group II, followed by an intraperitoneal injection of atRA (2.5 mg/kg/day) from the third day. After 4 weeks, thyroid and pituitary specimens were processed for light and electron microscopic study.Most thyroid follicles of diabetic rats were distended with colloid and lined with flattened thyrocytes with hyperchromatic nuclei and vacuolated cytoplasm that contained dilated rough endoplasmic reticulum, few colloid droplets, and few lysosomes. Some exfoliated cells were observed in the lumen. C cells had rarefied cytoplasm containing a few secretory granules. The number of mast cells showed a nonsignificant change. Thyrotrophs showed dilated rough endoplasmic reticulum, destroyed mitochondria, and decreased secretory granules. The atRA-treated diabetic group showed almost the same structural alterations in the thyroid gland, with even more changes in thyrotrophs.Despite its current use as a novel therapy for diabetes, atRA exerted no ameliorating effect on diabetes-induced histological changes in the thyroid gland and, moreover, exacerbated the changes of pituitary thyrotrophs. [ABSTRACT FROM AUTHOR]

Objective: Brain is a very sensitive organ to oxidative stress due to its large amount of polyunsaturated fatty acid content and low antioxidant activity. In this study, effect of exogenous all-trans-retinoic acid (RA) on brain antioxidant activity was investigated in mice under hyperoxia-induced oxidative stress. Material and Method: Adult C57BL/6J mice were divided into 4 groups. Two groups were given daily either peanut oil/dimethylesulfoxide (PoDMSO) mixture or 50 mg/kg RA dissolved in PoDMSO (RA-PoDMSO). The remaining two groups were treated with PoDMSO or RAPoDMSO as described above, following hyperoxia (100% oxygen) for 72 h. The treatments were given daily 50 µl intraperitoneal injections for 12 days, with a 2 day interruption on days 6 and 7. Lipid peroxidation (LPO) and glutathione (GSH) levels as well as activities of several antioxidant enzymes were assayed in brain tissue to evaluate oxidative stress, biochemically. Results: Elevated LPO levels, increased catalase, superoxide dismutase, glutathione peroxidase and glutathione-S-transferase activities, and decreased GSH levels were observed in hyperoxic mice. RA administration to hyperoxic mice improved these biochemical alterations in favour of reduced oxidative stress. Conclusion: Exogenous RA, a small lipophilic molecule, is effective in reducing oxidative stress in the brain which can receive only small lipophilic molecules due to the presence of the blood-brain barrier. Also, RA exhibits an antioxidant effect by inhibiting the GSH depletion and increased LPO levels in brain of hyperoxic mice, directly. [ABSTRACT FROM AUTHOR]

Abstract: Aims: The clinical utilization of the combinations of all-trans-retinoic acid (RA) with antiestrogens, which present synergism of action in breast cancer, has been limited by RA adverse effects, including hepatotoxicity, which may be related with mitochondrial damage. This work evaluated the effects of RA alone and in combination with the antiestrogen endoxifen (EDX) on liver mitochondria. Main methods: Mitochondrial permeability transition (MPT) was assessed by using Calcium Green-5N fluorescence and a tetraphenylphosphonium selective electrode. Oxidative stress was evaluated by oxygen consumption and thiobarbituric acid method. Mitochondrial bioenergetic was monitored by measuring oxygen consumption and mitochondrial membrane potential (ΔΨ). Osmotic volume changes of mitochondria were followed at 540nm. Key findings: EDX prevents the MPT induced by RA, allowing mitochondria pre-incubated with RA to accumulate Ca2+ and inhibiting the depolarization of ΔΨ. RA above 10nmol/mg protein depresses the phosphorylation capacity of mitochondria, as shown by the increase in the time required for ADP phosphorylation as well as by the decrease in state 3 respiration. At 20nmol/mg protein, RA decreases the ΔΨ and increases the state 4 respiration, suggesting that high concentrations of RA permeabilize the membrane to protons, possibly due to a proton leak through the Fo fraction of complex V. Moreover, the effects of RA on mitochondrial bioenergetics are not changed by EDX. Significance: RA-induced hepatotoxicity may be related with induction of MPT and alterations in bioenergetic parameters; the combination with EDX, which reduces mitochondrial dysfunction and synergistically potentiates the anticancer activity, may provide a safer therapeutic strategy. [Copyright &y& Elsevier]

Alternative splicing is associated with human disease. In acute promyelocytic leukaemia ( APL) patients with the long ( L)-type promyelocytic leukaemia-retinoic acid receptor α fusion gene ( PML- RARA), three alternative splicing isoforms can be detected: E5(+) E6(+), E5(−) E6(+), and E5(−) E6(−). This study is the first to demonstrate that alternative splicing of L-type PML- RARA is associated with time to achieve complete remission ( CR) in APL. Higher expression of the E5(−) E6(−) isoform, the short isoform, was related to longer time to achieve CR. Each isoform was constructed into recombinant lentiviral vector and transfected into U937 cells. Compared with the E5(−) E6(+) and E5(+) E6(+) groups, the U937 cells with E5(−) E6(−) showed lower sensitivity to all-trans-retinoic acid treatment. [ABSTRACT FROM AUTHOR]

Background: Ischemia/reperfusion-induced intestinal injury is mediated by reactive oxygen species and inflammatory mediators. Objectives: This study was designed to evaluate whether all-trans-retinoic acid (ATRA) administration can attenuate intestinal injury and to analyze the antioxidant and anti-inflammatory effects of ATRA in a neonatal rat model of necrotizing enterocolitis (NEC). Methods: Twenty-nine Wistar albino rat pups were randomly divided into 3 groups: group 1 = control, group 2 = NEC and saline, and group 3 = NEC and ATRA treatment. NEC was induced by hyperosmolar enteral formula feeding and exposure to hypoxia after cold stress at +4°C and oxygen. Pups in group 3 were injected intraperitoneally with ATRA (0.5 mg/kg body weight) once a day prior to each NEC procedure, beginning on postnatal day 1 and daily through postnatal day 4. The pups were killed on the 4th day and their intestinal tissues were harvested for biochemical and histopathological analysis. Results: Mucosal injury scores and intestinal malondialdehyde levels in group 2 were found to be significantly higher than other groups (p < 0.05). Intestinal superoxide dismutase and glutathione peroxidase activities in group 3 were significantly higher than group 2 (p = 0.04 and p = 0.04, respectively). Intestinal tissue tumor necrosis factor-α levels were significantly reduced with ATRA treatment in group 3 compared to group 2 (p < 0.001). Conclusions: It is likely that oxidative stress and inflammatory mediators contributed to the pathogenesis of NEC and that ATRA had a protective effect on intestinal injury through its anti-inflammatory and antioxidant properties. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Purpose: Leukemic promyelocytes have the unique ability to undergo differentiation after exposure to retinoic acid and both differentiation and apoptosis after exposure to arsenic trioxide (ATO). Recent studies have shown that inhibition of Src family kinases (SFKs) resulted in enhancement of retinoic acid-induced myeloid differentiation. Materials and Methods: In this study, we investigated the question of whether the SFK inhibitor PP2 enhanced the differentiation of NB4 cells when combined with ATO as well as when combined with all-trans-retinoic acid (ATRA). In addition, we attempted to determine the difference in retinoic acid-induced gene expression between cells treated with PP2 in combination with ATRA and in combination with ATO. Results: SFK inhibitor PP2 induced significant enhancement of ATRA- or ATO-induced differentiation of NB4 cells. A significantly stronger synergistic effect was observed when PP2 was combined with ATRA than when combined with ATO. Flow cytometric analysis demonstrated a significant increase in CD11b-positive granulocytes up to 60.73% and 31.58%, respectively. These results were confirmed by nitroblue tetrazolium staining. These effects were not related to apoptosis. Results of Annexin-V-fluorescein staining revealed that PP2 combined with ATRA or PP2 combined with ATO did not induce apoptosis in NB4 cells. Retinoic acid-induced gene expression was different in both groups. Intercellular adhesion molecule-1 expression showed a significant increase in cells treated with PP2 in combination with ATRA, whereas cathepsin D expression showed a significant increase in cells treated with PP2 in combination with ATO. Conclusion: Our data showed that SFK inhibitor PP2 enhanced acute promyelocytic leukemia cell differentiation when combined with either ATRA or ATO with difference in activation of retinoic acid-induced genes. [ABSTRACT FROM AUTHOR]

Myeloid-derived suppressor cells (MDSC) are one of the major factors limiting the efficacy of immune therapy. In a clinical trial of patients with extensive stage small cell lung cancer (SCLC), we tested the possibility that targeting MDSC can improve the induction of immune responses by a cancer vaccine. Forty-one patients with extensive stage SCLC were randomized into three arms: arm A-control, arm B-vaccination with dendritic cells transduced with wild-type p53, and arm C-vaccination in combination with MDSC targeted therapy with all-trans-retinoic acid (ATRA). Interim results of the ongoing clinical trial are presented. Pre-treatment levels of MDSC populations in patients from all three arms were similar. Vaccine alone did not affect the proportion of MDSC, whereas in patients treated with ATRA, the MDSC decreased more than twofold ( p = 0.02). Before the start of treatment, no patients had detectable p53-specific responses in IFN-γ ELISPOT. Sequential measurements did not show positive p53 responses in any of the 14 patients from arm A. After immunization, only 3 out of 15 patients (20 %) from arm B developed a p53-specific response ( p = 0.22). In contrast, in arm C, 5 out of 12 patients (41.7 %) had detectable p53 responses ( p = 0.012). The proportion of granzyme B-positive CD8 T cells was increased only in patients from arm C but not in arm B. Depletion of MDSC substantially improved the immune response to vaccination, suggesting that this approach can be used to enhance the effect of immune interventions in cancer. [ABSTRACT FROM AUTHOR]

Summary: Adipose-derived adult stem (ADAS) cells can be easily obtained in large quantities. Previous studies have suggested that all-trans-retinoic acid (ATRA) plays an important role in the differentiation of mesenchymal stem cells toward an epithelial lineage. In order to verify that ADAS-cells can differentiate into an epithelial lineage retaining most of the characteristics of stem cells, ADAS-cells were isolated and cultured. They were induced to differentiate toward an epithelial lineage in vitro. Differentiated epithelial cells were assayed as to whether they retain characteristics of stem cells by RT-PCR and cell cycle stage analysis, and were further induced to differentiate toward an osteogenic lineage. RT-PCR analysis revealed that no CK5, CK10 or CK19 mRNA was detected in ADAS-cells, CK19 but not CK5 or CK10 mRNA was detected in differentiated cells at passage 1, CK10 and CK19 expression but not CK5 mRNA was detected in differentiated cells at passage 10. After induction, the expression of CK19 was observed by immunofluorescent staining. Positive staining with alkaline phosphatase (ALP) and Von Kossa staining verified that differentiated epithelial cells still had potential to further differentiate toward an osteogenic lineage. These experiments provide proof that ADAS-cells can differentiate into an epithelial lineage retaining most of the characteristics of stem cells. [Copyright &y& Elsevier]

Abstract: Retinoids constitute a family of organic compounds that are being used for the treatment of various diseases, ranging from acne vulgaris to acute promyelocytic leukemia. Their use however is limited due to serious adverse effects and there is a great need for analogues with better safety profile. In the present work, the effect of N 1,N 12-bis(all-trans-retinoyl)spermine (RASP), a conjugate of all-trans-retinoic acid (atRA) with spermine, on angiogenesis in vivo and viability of human endothelial and prostate cancer cells in vitro were studied. Both atRA and RASP dose-dependently inhibited angiogenesis in the chicken embryo chorioallantoic membrane model. RASP was more effective and could be used in a wider dose range due to lower toxicity compared with atRA. Both retinoids decreased the number of human umbilical vein endothelial and prostate cancer LNCaP and PC3 cells in a concentration-dependent manner. RASP was more effective and potent compared with atRA, spermine, their combination, or conjugates of spermine with other acidic retinoids and/or psoralens in prostate cancer cells. The inhibitory effect of both atRA and RASP seems to be related to an increase of the tumour repressing gene retinoic acid receptor beta mRNA, was mediated by retinoic acid receptor alpha, and was proportional to endogenous retinoic acid receptor beta expression. These data suggest that RASP is more effective than atRA in decreasing angiogenesis and prostate cancer cell growth and identify retinoic acid receptor alpha as the receptor through which it causes retinoic acid receptor beta up-regulation and decrease of prostate cancer cell growth. [Copyright &y& Elsevier]

00240.2012.-Intraperitoneal injection of all-trans-retinoic acid (ATRA) results in a reduction of blood pressure in spontaneously hypertensive rats. However, the mechanisms involved in this effect are not clear. We hypothesized that ATRA may relax resistance arteries. In this study, we found that ATRA relaxed phenylephrine-preconstricted mesenteric arterial rings, which were abrogated by the removal of the endothelium. Pretreatment of endothelium- intact arterial rings with an inhibitor of endothelial nitric oxide (NO) synthase, NG-nitro-L-arginine methyl ester (L-NAME), or soluble guanylyl cyclase, 1H-[1,2,4]-oxadiazole-[4,3-α]-quinoxaline-1- one, reduced the vasorelaxant effect of ATRA. Incubation of mesenteric arterial rings with ATRA increased the production of NO and cGMP, which were blocked by NG-nitro-L-arginine methyl ester. The vasorelaxant effect of ATRA was markedly attenuated in the presence of an inhibitor of big conductance calcium-activated potassium channels (charybdotoxin), but not with an inhibitor of voltage-dependent potassium channel (4-aminopyridine) or ATP-sensitive potassium channel (glibenclamide). Activation of retinoic acid receptors (RARs) with CH55 or retinoic X receptors (RXRs) with LGD1069 induced the vasorelaxation of phenylephrine-preconstricted mesenteric arterial rings. The RAR (BMS493) and RXR (UVI3003) antagonists blocked the ATRA-induced vasorelaxation. The vasorelaxant effect ATRA is physiologically relevant because the intravenous infusion of ATRA decreased blood pressure in normotensive rats. We conclude that ATRA relaxes resistance vessels via both RARs and RXRs receptors that are mediated by the endothelium-dependent NO-cGMP pathway, which may participate in the control of blood pressure. [ABSTRACT FROM AUTHOR]

Background Ethanol ( Et OH) alters the all -trans-retinoic acid ( ATRA) levels in some tissues. Retinol and ATRA are essential for cell proliferation, differentiation, and maintenance of prostate homeostasis. It has been suggested that disturbances in retinol/ ATRA concentration as well as in the expression of retinoic acid receptors ( RARs) contribute to benign prostate hyperplasia and prostate cancer. This study aimed to evaluate whether Et OH consumption is able to alter retinol and ATRA levels in the plasma and prostate tissue as well as the expression of RARs, cell proliferation, and apoptosis index. Methods All animals were divided into 4 groups ( n = 10/group). UCh A: rats fed 10% (v/v) Et OH ad libitum; UCh ACo: Et OH-naïve rats without access to Et OH; UCh B: rats fed 10% (v/v) Et OH ad libitum; UCh BCo: Et OH-naïve rats without access to Et OH. Animals were euthanized by decapitation after 60 days of Et OH consumption for high-performance liquid chromatography and light microscopy analysis. Results EtOH reduced plasma retinol concentration in both UCh A and UCh B groups, while the retinol concentration was not significantly different in prostate tissue. Conversely, plasma and prostate ATRA levels increased in UCh B group compared with controls, beyond the up-regulation of RARβ and -γ in dorsal prostate lobe. Additionally, no alteration was found in cell proliferation and apoptosis index involving dorsal and lateral prostate lobe. Conclusions We conclude that Et OH alters the plasma retinol concentrations proportionally to the amount of Et OH consumed. Moreover, high Et OH consumption increases the concentration of ATRA in plasma/prostate tissue and especially induces the RARβ and RARγ in the dorsal prostate lobe. Et OH consumption and increased ATRA levels were not associated with cell proliferation and apoptosis in the prostate. [ABSTRACT FROM AUTHOR]

Abstract: Various biochemical and physiological stimuli may interfere with endoplasmic reticulum (ER) homeostasis, causing aggregation and accumulation of unfolded or malfolded proteins in the ER and resulting in ER stress (ERS), and the ER attenuates ERS through unfolded protein response (UPR). All-trans-retinoic acid (ATRA) can enhance or attenuate some ERS-induced physiological or pathological changes. Our previous studies showed that there was UPR in short forelimbs induced by ATRA. Many kinds of malformations induced by ATRA may correlate with cell death, and knowing that UPR is closely associated with cell death, so we speculate that the short forelimbs may caused by UPR-induced cell death. To test this hypothesis, the present study investigated the expression of UPR-related genes and proteins in the same short forelimb malformation model to determine whether ATRA-induced short forelimb malformation occurred through UPR-induced cell death. Subsequently, we further observed the differentiation and proliferation of chondrocytes and the expression of related genes and/or proteins. It was found that ATRA evoked UPR in this short forelimb model, thus activating the anti-cell death pathway and inhibiting the cell death-promoting pathway. Cell death was not evident in short forelimb, and ATRA inhibited the expression of Ccnb1 and Ccna1, thus retarding chondrocyte maturation. As a result, the number of immature chondrocytes in short forelimb was greater than the normal level. We therefore believe that ATRA induces short forelimb malformation most likely by inhibiting chondrocyte maturation rather than by evoking excess cell death. [Copyright &y& Elsevier]

atRA (all-trans-retinoic acid) is known to induce the differentiation of mESCs (mouse embryonic stem cells) into PGCs (primordial germ cells) in vitro. However, it is not clear as to what changes occur in PGC differentiation-associated genes or what mechanisms are involved when EBs (embryoid bodies) derived from mESCs are induced by atRA. EBs derived from mESCs were treated with 1, 2 or 5 μM atRA for 16 h, 2 days or 5 days. Real-time PCR and Western blot analysis were performed to detect the relative levels of PGC differentiation-associated genes ( Lin28, Blimp1, Stra8 and Mvh) and the corresponding proteins respectively. Immunofluorescence was used to detect the protein location and distribution in EBs. The expression characteristics of genes could be divided into three categories: rapidly reached the peak value in 16 h and then decreased ( Stra8, Lin28), initially low and then increased to reach the peak value in 5 days ( Mvh) and relatively unchanged ( Blimp1). A low level of Lin28 was expressed in EBs treated with atRA for 2 days or 5 days. The variation in the level of Lin28 mRNA did not influence the change in the level of Blimp1 mRNA. The changes in Stra8/Lin28 were consistent with the corresponding changes in the levels of their respective mRNAs, but the changes for Mvh/Blimp1 were not consistent with the corresponding changes in the levels of their respective mRNAs. Blimp1 expression may be independent of the effect of atRA on PGC differentiation. atRA may promote the start of a period in which there is a low level of Lin28 expression during PGC differentiation. [ABSTRACT FROM AUTHOR]

Conazoles are fungicides used as agricultural pesticides and pharmaceutical products. We investigated whether a common core of toxicological and transcriptional responses underlies the observed carcinogenic effects of three conazoles: cyproconazole, epoxiconazole, and propiconazole. In studies where mice were fed diets of these conazoles for 30 days, we found a common set of toxicological effects altered by these conazoles: hepatomegaly, hepatocellular hypertrophy, decreased serum cholesterol, decreased hepatic levels of all-trans-retinoic acid, and increased hepatic cell proliferation. Microarray-based transcriptional analysis revealed 330 significantly altered probe sets common to these conazoles, many of which showed strong dose responses for cytochrome P450, glutathione S-transferase, and oxidative stress genes. More detailed analyses identified a subset of 80 altered genes common to the three conazoles that were associated with cancer. Pathways associated with these genes included xenobiotic metabolism, oxidative stress, cell signaling, and cell proliferation. A common TGFα-centric pathway was identified within the 80-gene set, which, in combination with the toxicological and other transcriptomic findings, provides a more refined toxicity profile for these carcinogenic conazoles. [ABSTRACT FROM PUBLISHER]

Background: Recent studies have demonstrated an essential role for IL-17 in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). Furthermore, it has been shown that FoxP3+Treg cells play an important role in the suppression of autoinflammatory reactions. Although, previous studies have determined the immunomodulatory potentials of all-trans-retinoic acid (ATRA), but these immunomodulations have been mostly justified by alteration in Th1/Th2 cytokines. The present study was carried out to investigate the therapeutic effects of ATRA on EAE and its effects on T-helper cells responses. Methods: EAE was induced by MOG35-55 peptide and complete Freund's adjuvant in female C57BL/6 mice. The mice were allocated to two therapeutic groups (n=7 per group). Treatment with ATRA (500 μg/mouse; every other day) was initiated in treatment group on day 12 when they developed a disability score. EAE controls received vehicle alone with the same schedule. Signs of disease were recorded daily until day 33 when the mice were sacrificed. Splenocytes were tested for proliferation by MTT test, cytokine production by ELISA and FoxP3+Treg cell frequency by flowcytometry. Results: ATRA significantly reduced the clinical signs of established EAE. Aside from decreasing lymphocytic proliferation (P<0.05), ATRA significantly inhibited the production of pro-inflammatory IL-17 (P<0.005) as well as IFN-γ (P<0.0005) upon antigen-specific restimulation of splenocytes. FoxP3+Treg cell frequency and IL-10 levels were not altered significantly. However, IFN-γ to IL-10 and IL-17 to IL-10 ratios decreased significantly (P<0.0005). Conclusion: Parallel to reducing autoreactive lymphocyte proliferation and cytokine production in favor of pro-inflammatory cytokines, all-trans-retinoic acid ameliorated established experimental autoimmune encephalomyelitis. [ABSTRACT FROM AUTHOR]

BACKGROUND: There are very limited data reported about acute promyelocytic leukemia (APL) from developing countries. We reviewed the clinical course and treatment outcome of APL patients treated at our center. MATERIALS AND METHODS: Between January 1997 and December 2007, 33 patients with APL received induction therapy using ATRA + daunorubicin (n = 26), As2O3 (n = 4) or daunorubicin + cytosar (n = 3). RESULTS: Median age was 30 years with a male to female ratio of 1.68. Twenty seven patients (82%) achieved CR. Complications during induction therapy were febrile neutropenia (33%), ATRA syndrome (30%), bleeding (58%), and diarrhea in (6%) patients. During induction and follow up, 8 (24.24%) patients died, 6 (18.18%) during induction, 1 (3%) during maintenance, and 1 (3%) after relapse. Median OS is 128 months while median EFS is 61 months. Four patients relapsed at a median time of 61 months. At the time of censoring, 25 patients were alive at a median follow up of 13 months (range 0.6 -127 months); 21 in CR1, 3 in CR2, 1 in CR3. Comparisons among the risk groups (CR and relapse rate and survival statistics) were not statistically significant. CONCLUSIONS: APL is a highly curable malignancy. Our results confirm the findings of the published literature from larger cooperative studies from the West. We may further improve outcome with quicker diagnosis and more efficient supportive care system. [ABSTRACT FROM AUTHOR]

The article presents information on a study which characterized clinical parameters and treatment outcomes of 29 patients with therapy-related acute promyelocytic leukemia (t-APL). Background on t-APL is given. Study subjects were randomly assiged to receive either with arsenic trioxide (ATO) and all-trans-retinoic acid (ATRA) or with standard ATRA plus anthracycline-based chemotherapy. A discussion on the research findings is detailed.

Interleukin 12 (IL-12) is a proinflammatory cytokine with antitumor activity. All-trans–retinoic acid (ATRA) exerts antitumor effects by regulating a variety of gene expressions, including tumor necrosis factor receptor 1 (TNFR1), increases the number of TNFR1 and potentiates TNF-α-induced apoptosis in cancer cells. In this study, ATRA-incorporated cationic liposome (ATRA-cationic liposome)/IL-12 plasmid DNA (pDNA) complexes were prepared to improve therapeutic efficacy of cationic liposome/IL-12 pDNA complexes in a mouse model of metastatic lung tumor after intravenous injection. IL-12 production in lungs by ATRA-cationic liposome/IL-12 pDNA complexes was comparable with that by cationic liposome/IL-12 pDNA complexes. The number of metastatic tumor cells (colon26/Luc) was quantitatively evaluated by measuring luciferase activity. ATRA-cationic liposome/IL-12 pDNA complexes reduced the number of colon26/Luc cells and tumor nodules in lungs. ATRA-cationic liposome/IL-12 pDNA complexes significantly prolonged the survival time of mice, whereas cationic liposome/IL-12 pDNA only slightly prolonged it. ATRA-cationic liposome/IL-12 pDNA complexes increased the TNFR1 mRNA upregulation and the number of apoptotic cells in the lung. Moreover, reduced serum alanine transaminase (ALT) and aspartate transaminase (AST) activities were observed in mice treated with ATRA-cationic liposome/IL-12 pDNA complexes. These results suggest that intravenous injection of ATRA-cationic liposome/IL-12 pDNA complexes is an effective method for the treatment of lung metastasis in mice. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) can differentiate into neurons in an appropriate cellular environment. Retinoid signaling pathway is required in neural development. However, the effect and mechanism through retinoid signaling regulates neuronal differentiation of MSCs are still poorly understood. Here, we report that all-trans-retinoic acid (ATRA) pre-induction improved neuronal differentiation of rat MSCs. We found that, when MSCs were exposed to different concentrations of ATRA (0.01–100 μmol/L) for 24 h and then cultured with modified neuronal induction medium (MNM), 1 μmol/L ATRA pre-induction significantly improved neuronal differentiation efficiency and neural-cell survival. Compared with MNM alone induced neural-like cells, ATRA/MNM induced cells expressed higher levels of Nestin, neuron specific enolase (NSE), microtubule-associated protein-2 (MAP-2), but lower levels of CD68, glial fibrillary acidic protein (GFAP), and glial cell line-derived neurotrophic factor(GDNF), also exhibited higher resting membrane potential and intracellular calcium concentration, supporting that ATRA pre-induction promotes maturation and function of derived neurons but not neuroglia cells from MSCs. Endogenous retinoid X receptors (RXR) RXRα and RXRγ (and to a lesser extent, RXRβ) were weakly expressed in MSCs. But the expression of RARα and RARγ was readily detectable, whereas RARβ was undetectable. However, at 24 h after ATRA treatment, the expression of RARβ, not RARα or RARγ, increased significantly. We further found the subnuclear redistribution of RARβ in differentiated neurons, suggesting that RARβ may function as a major mediator of retinoid signaling during neuronal differentiation from MSCs. ATRA treatment upregulated the expression of Vimentin and Stra13, while it downregulated the expression of Brachyury in MSCs. Thus, our results demonstrate that pre-activation of retinoid signaling by ATRA facilitates neuronal differentiation of MSCs. [ABSTRACT FROM AUTHOR]

Isochromosome of the long arm of the derivative chromosome 17, originating from the translocation t(15;17) [ider(17)(q10)t(15;17) or ider(17q)] in acute promyelocytic leukemia (APL), is a rare chromosome aberration which has been associated with a poor prognosis. In the present study, we report on 4 male APL patients with ider(17q) and review the clinical, cytogenetic and molecular characteristics of all previously reported APL patients with ider(17q) in order to clarify the clinical features and outcome of these patients. The data presented in this study demonstrated that ider(17q), which resulted in an extra RARA-PML fusion gene, was more frequent in males than females (male/female ratio of 2.12/1), was associated with a rather low initial white blood cell count and did not confer an adverse prognosis in APL patients treated with all-trans-retinoic acid and chemotherapy. The most frequent additional chromosome change to ider(17q) was trisomy 8. Ider(17q) was observed in all subtypes of the PML-RARA fusion gene, but the frequency of the bcr1 subtype was increased. Cases of overrepresentation of the RARA-PML fusion gene and ider(17q) cases may help in elucidating the role of RARA-PML in leukemogenesis. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Incorporation of all-trans-retinoic acid (ATRA) into the treatment of acute promyelocytic leukemia (APL), a type of acute myeloid leukemia (AML), revolutionized the therapy of cancer in the last decade and introduced the concept of differentiation therapy. ATRA, a physiological metabolite of vitamin A (retinol), induces complete clinical remissions (CRs) in about 90% of patients with APL. In contrast to the cytotoxic chemotherapeutics, ATRA can selectively induce terminal differentiation of promyelocytic leukemic cells into normal granulocytes without causing bone marrow hypoplasia or exacerbation of the frequently occurring fatal hemorrhagic syndromes in patients with APL. However, remissions induced by ATRA alone are transient and the patients commonly become resistant to the therapy, leading to relapses in most patients and thus limiting the use of ATRA as a single agent. Therefore, ATRA is currently combined with anthracycline-based chemotherapy, and this regimen dramatically improves patient survival compared to chemotherapy alone, curing about 70% of the patients. However, 30% of APL patients still relapse and die in five years. Recently, arsenic trioxide (As2O3) was proven to be highly effective in inducing CRs not only in APL patients relapsed after ATRA treatment and conventional chemotherapy but also in primary APL patients. Despite the well-documented clinical efficacy of ATRA, molecular mechanisms responsible for development of ATRA resistance are not well understood. Based on in vitro and clinical observations, several mechanisms, including induction of accelerated metabolism of ATRA, decreased bioavailability and plasma drug levels, point mutations in the ATRA-binding domain of promyelocytic leukemia (PML)-retinoic acid receptor-alpha (RARα) and other molecular events have been proposed to explain ATRA resistance. In this review, the molecular mechanisms of ATRA-induced myeloid cell differentiation and resistance are discussed, together with novel clinical approaches to overcome ATRA resistance in APL. [ABSTRACT FROM AUTHOR]

Abstract: Novel mono- and diacylated spermines, readily obtained using isolable succinimidyl active esters of acidic retinoids for the selective acylation of free spermine or in situ activated acidic retinoids for acylating selectively protected spermine followed by deprotection, were shown to inhibit the ribozyme ribonuclease P more strongly than the parent retinoids. [Copyright &y& Elsevier]

The Limb Morphogenetic Differentiation Scoring system introduced by Neubert and Barrach in 1977 has been used in drug testing as a measure of the degree of cartilage growth inhibition especially for forelimb in vitro. There is no scoring system to quantify the degree of hindlimb bud cartilage differentiation in vivo. A total of 60 female Sprague-Dawley rats weighing 220–250 g were assigned at random to six control groups and six experimental groups on day 0 of pregnancy. The experimental groups were treated with all-trans-retinoic acid (ATRA). A new limb morphogenetic differentiation scoring system was developed and used to quantify the degree of development of the hindlimb buds from the fetuses at embryonic days E13 to E18. The differentiation of cartilages assessed by the new scoring system showed a statistically significant difference between the experimental group and the control group from E13 to E18 ( T-test, p < 0.05). Cartilage growth (the proximodistal length) in the control group increased gradually from E14, reaching its peak at E17, but in the experimental group the growth at E13, E16, E17, and E18 was significantly shorter ( p < 0.05). In conclusion, the new limb morphogenetic differentiation scoring system described here can be used to quantify the degree of inhibition of the hindlimb bud development by teratogenic drugs or materials, and morphogenetic differentiation in vivo. [ABSTRACT FROM AUTHOR]

Using current treatment regimens, over 90% of patients with acute promyelocytic leukemia will achieve complete remission (CR). However, approximately 30% of these patients will relapse, including a small proportion who will develop extramedullary disease (EMD). In this study, we investigated the incidence of EMD in 263 patients with APL who were treated at our institution from January 1990 to May 2008. With a median follow-up of 31 months (range 2 days-203 months), 8 (3%) patients developed EMD. The most commonly affected site was the central nervous system (n = 7). Before developing EMD, one patient had achieved CR with a chemotherapy-only regimen, six patients had achieved CR with all-trans-retinoic acid (ATRA)-based regimens, and one patient had achieved CR with an ATRA plus arsenic trioxide (ATO)-based regimen. The EMD conferred a poor prognosis; five patients died within 4 months of developing EMD. The molecular status did not predict EMD; four patients had a negative PCR for the PML-RARA transcripts prior to relapse with EMD. In conclusion, the incidence of EMD is low. We were unable to identify any specific factors that could predict the development of EMD. [ABSTRACT FROM AUTHOR]

Ischemia-induced cerebral injury evolves over a longer period than previously believed through post-ischemic inflammation. Retinoic acid (RA) has been shown to exert cytoprotective effects on several cells, but its effects on ischemia-induced cerebral injury have been poorly characterized. The aim of the present study was to examine the effects of all- trans-RA on ischemia-induced cerebral injury and elucidate the underlying mechanism. All- trans-RA treatment reduced the size of the ischemia-induced cerebral infarct. To elucidate the underlying mechanism, ischemia-induced cerebral inflammation was studied by examination of expressions of interleukin 1β (IL-1β) and ED-1. RA treatment significantly reduced the cerebral inflammation. Moreover, cerebral ischemic induction of cyclooxygenase-2 (COX-2) and CCAAT/enhancer binding protein β (C/EBPβ), which binds to the COX-2 promoter, was also inhibited by RA. These results suggest that RA can reduce ischemia-induced cerebral injury by an anti-inflammatory action, which may be effected via inhibition of C/EBPβ-mediated COX-2 induction. [ABSTRACT FROM AUTHOR]