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Deficiency in vitamin A has been associated with adverse clinical outcomes1 in drug users with HIV-1 infection. Retinoids have been demonstrated to suppress proinflammatory cytokine production by immune cells in vitro. These effects are induced by ligand-mediated activation of the retinoid receptors—retinoic acid receptor (RAR) and retinoid X receptor (RXR). In these studies, the effects of all-trans-retinoid acid (ATRA, a RAR agonist), 9-cis-retinoic acid (9cis RA; RAR and RXR agonist), LG101305 (RXR agonist), LG100815 (RAR antagonist) and LG101208 (RXR antagonist) on TNF-α production by phytohemagglutanin-activated U937 cells and the modulation of these effects by morphine were examined. TNF-α production was suppressed in all cultures exposed to retinoid agonist and antagonist agents. For cells exposed to RXR agonists or RAR antagonist, incubation with morphine resulted in the reversal of TNF-α suppression and this effect was inhibited by naloxone. These data suggest that interactions between RXR and morphine are involved in the immune effects of retinoids on TNF-α production by activated U937 cells. Such information may be important for understanding interactions between drugs of abuse and immune function in individuals with chronic proinflammatory states such as HIV-1 infection. [Copyright &y& Elsevier]

9-cis-Retinoic acid (9CRA) and all-trans-retinoic acid (ATRA) are known to be involved in the regulation of glucose homeostasis in vertebrates by inducing insulin release and expression of glucose transporter proteins. In view of the fact that both 9CRA and ATRA are endogenous to the fiddler crab, Uca pugilator, that a retinoid X receptor exists in this fiddler crab and that activities of insulin-like and insulin-like growth factor-like peptides have been reported for crustaceans, we investigated whether 9CRA and ATRA also play a role in glucose homeostasis in U. pugilator. Neither 9CRA nor ATRA was found to produce hypoglycemic effects at a dose of 10 μg/g live mass. However, 9CRA, but not ATRA, induced hyperglycemia. Such 9CRA-induced hyperglycemia was apparently mediated by the eyestalk hormone CHH since injection of 9CRA into eyestalk-ablated crabs did not result in hyperglycemia. ATRA was found to have an inhibitory effect on the recovery of blood glucose concentration following ATRA administration. Discussion on the possible mechanisms for the actions of 9CRA and ATRA was presented. [Copyright &y& Elsevier]

The effect of ethanol (EtOH) exposure on extraembryonic vascular development was examined using the chick embryo area vasculosa (AV) in shell-less culture. Embryos were placed in cultures at Hamburger Hamilton (HH) stage 11/12 and a single dose of EtOH (10, 30 or 50%) was applied to the center of the blastodisc. Untreated/sodium-chloride-treated controls showed normal embryonic growth and well-developed extraembryonic vessels at 24/48 h of treatment. At doses of 30 and 50%, the mortality rate was significantly increased, and survivors demonstrated significant growth retardation and inhibition of normal vascular development in a dose-dependent manner. Immunostaining for vascular endothelial growth factor (VEGF) showed that mesenchymal cells continued to differentiate into angioblasts to form blood islands, but their assembly into primitive vessels was perturbed in a dose-dependent manner. Northern blot analyses of basic fibroblast growth factor, VEGF, Flt-1 and Flk-1 mRNA expression supported these findings and showed a dose-dependent decrease in EtOH-treated cultures compared to controls. Co-treatment with α-tocopherol (0.05 M) or all-trans-retinoic acid (10[sup –8] M) significantly decreased the mortality rate and improved both embryonic growth and extraembryonic vascular development in the cultures. On the other hand, almost all embryos treated with 10% EtOH survived the first 48 h after treatment. However, the complexity of the vascular tree measured as the relative vasculogenesis index, the surface area of the AV and the mRNA expression of vasculogenic molecules were increased during the first 24 h. This acute effect disappeared 48 h after treatment and the vascular tree continued to develop parallel to the controls. No significant growth retardation was observed in this group. These results suggest that, in terms of extraembryonic vascular development, an early, single, low-dose EtOH exposure may have an acute, short-term positive effect, whereas moderate- or high-dose EtOH exposure may severely perturb this process disabling the necessary absorption of the nutrients for the embryo to develop properly. The mechanisms of action of EtOH on extraembryonic vascular development may involve the establishment of reactive oxygen species, resulting in the initiation of oxidative stress and perturbation of retinoic acid signaling and alterations in the expression of growth-regulatory vasculogenic factors and their receptors.Copyright © 2003 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known to influence vitamin A homeostasis. In order to investigate the mechanism behind this retinoid disruption, male Sprague-Dawley rats were exposed to TCDD at doses ranging from 0.1 to 100 µg/kg body weight, and were killed 3 days after exposure. Additional groups of rats were killed 1 and 28 days after a single oral dose of 10 µg TCDD/kg body weight. Serum, kidney, and liver were investigated for retinoid levels, as well as gene expression and enzyme activities relevant for retinoid metabolism. Besides the well known effects of TCDD on apolar retinoids, i.e. decreased hepatic and increased renal retinyl ester (RE) levels, we have found dose-dependent elevation of all-trans-retinoic acid (all-trans-RA) levels in all investigated tissues. In the liver, 9-cis-4-oxo-13,14-dihydro-RA was drastically decreased by TCDD in a dose-dependent manner. In serum, cis-isomers of all-trans-RA, including 9,13-di-cis-RA, were significantly reduced already at the lowest dose level. Protein and mRNA levels of cellular retinol binding protein I (CRBP-I) in liver or kidneys were not significantly altered by TCDD exposure at doses at which retinoid levels were affected, making CRBP-I an unlikely candidate to account for the alterations in retinoid metabolism caused by TCDD. The expression and activities of relevant cytochrome P450 (CYP) enzymes with potential roles in all-trans-RA synthesis and/or degradation (CYP1A1, 1A2, and 2B1/2) were also monitored. A possible role of CYP1A1 in TCDD-induced all-trans-RA synthesis is suggested from the time-course relationship between CYP1A1 activity and all-trans-RA levels in liver and kidney. The significant alteration of the all-trans-RA metabolism has the potential to contribute significantly to the toxicity of TCDD. [ABSTRACT FROM AUTHOR]

Liver specific polymeric nanoparticles were designed and synthesized from biotinylated poly(ethylene glycol) conjugated with lactobionic acid containing a galactose moiety (abbreviated as BEL). Synthesized BEL conjugate was identified by Fourier transform-infrared (FT-IR) and 1H-nuclear magnetic resonance (NMR) spectroscopy. The fluorescence spectroscopy data showed that BEL conjugate was self-assembled in water to form core-shell structure nanoparticles, and the critical association concentration (CAC) value was estimated as 0.028 g/l. From the transmission electron microscope (TEM) observation, the BEL nanoparticles were spherically shaped and ranged in size between 30 and 60 nm. The particle size distribution was measured by photon correlation spectroscopy (PCS), and the result was 41.2±11.7 nm. Anti-cancer drug all-trans-retinoic acid (ATRA) was loaded into the BEL nanoparticles for evaluating its efficacy as a drug delivery carrier. The crystallinities of ATRA and ATRA-loaded nanoparticles were examined by X-ray diffraction (XRD) patterns. The ATRA release kinetics from the BEL nanoparticles showed a pseudo zero-order pattern during 1-month period. [Copyright &y& Elsevier]

The coactivators CBP and p300 are recruited by retinoic acid receptors (RARs) during retinoid mediated transcriptional regulation. To assess the role of CBP/p300 in all-trans-retinoic acid (ATRA)-mediated growth arrest in mammary epithelial cells, two systems were tested: (1) ATRA resistant MCF-7 cells were transduced with a functional RAR-β2; (2) normal human mammary epithelial cells (HMECs) were transduced with a pan-RAR dominant negative, RAR-α403. Expression of RAR-β2 in MCF-7 cells resulted in increased sensitivity to ATRA-induced growth arrest and correlated with induction of CBP/p300 mRNA and protein. Inhibition of RAR function in HMECs resulted in resistance to ATRA-induced growth arrest and loss of CBP/p300 induction. Antisense suppression of CBP/p300 in HMECs resulted in decreased retinoic acid response element reporter trans-activation and decreased ATRA-mediated growth arrest. Thus, in human mammary epithelial cells, CBP/p300 were both modulated by an ATRA signaling pathway and were required for a normal response to ATRA. [Copyright &y& Elsevier]

We previously reported that overexpression of the HER2/neu oncogene induces all-trans retinoic acid (ATRA) resistance in breast cancer cells. N-(4-hydroxyphenyl)-retinamide (4HPR), a synthetic analogue of ATRA, has been shown to repress the expression of HER2/neu and its family member, epidermal growth factor receptor (EGFR). We investigated whether 4HPR, by suppressing HER2/neu or EGFR expression, could sensitize breast cancer cells to ATRA. At 1.3 μM concentration (a clinically pharmacologically achievable dose), 4HPR increased ATRA sensitivity synergistically in HER2/neu-overexpressing BT-474, MDA-MB-453, and MCF-7/Her2 breast cancer cells. However, 4HPR did not sensitize EGFR-overexpressing MDA-MB-468, Hs578T, and MCF-7/EGFR breast cancer cells to ATRA. The increased inhibitory effects in HER2/neu-overexpressing cells were not correlated with increases in expression levels of p21WAF1/CIP1 or retinoblastoma protein. Combining 4HPR with ATRA may lead to a novel, selective therapeutic or chemopreventive strategy against HER2/neu-overexpressing breast tumors. Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

In this study we have demonstrated the potential of encapsulating all-trans-retinoic acid (ATRA) in niosomes and delivering it as an inhaled aerosol. Niosomes may provide a means to reduce the toxicity of ATRA and alter the pharmacokinetics in a manner similar to liposomes. In addition, the low cost of the surfactants used for preparing niosomes and their greater stability compared with liposomes makes them an attractive alternative. Various nonionic surfactants were used to achieve optimum encapsulation and nebulization efficiencies, and the best formulations were obtained with combinations of (Span 20+Tween 80) and (Span 60+Tween 80) using an ATRA concentration of 1 mg/ml. The aerosol produced with the selected niosomal formulations upon nebulization in PARI LC STAR nebulizers driven by a Pulmo-Aide compressor was subsequently analyzed for the determination of size distribution and entrapment efficiencies on each stage of an Anderson cascade impactor operated in a manner that avoids spurious sizing due to droplet evaporation. Mass median aerodynamic diameters (MMADs) of 3.7±0.3 and 3.58±0.03 μm, geometric standard deviation (GSD) values of 1.59±0.17 and 1.51±0.01 and entrapment efficiencies well above 50% were obtained for the optimized formulations. The results are very encouraging and offer an alternative approach to the respiratory delivery of ATRA by aerosolization. [Copyright &y& Elsevier]

Several acute-phase plasma proteins, including haptoglobin (Hp), are induced in the liver in response to inflammation. Recently, we found that Hp gene expression is up-regulated by all-trans-retinoic acid (ATRA) in the extrahepatic monocytic cell line, THP-1. To investigate the molecular mechanism underlying ATRA-induced Hp gene expression, we analyzed the induction of transcription factor CCAAT/enhancer-binding protein (C/EBP) isoforms in ATRA-stimulated THP-1 cells and their binding to the Hp promoter. Western blot analysis showed that treatment with ATRA increased C/EBPα and β expression, but decreased that of C/EBPδ. Electrophoretic mobility shift and supershift assays demonstrated that only C/EBPα of the C/EBP isoforms bound to the C/EBP DNA-binding sites in the Hp promoter. Furthermore, when ATRA-dependent Hp induction was inhibited by sodium butyrate or auranofin, induction of C/EBPα, but not C/EBPβ, was also diminished. These results suggest that C/EBPα is involved in the activation of Hp gene expression by ATRA in human monocytic cells. [Copyright &y& Elsevier]

Biocompatibility studies of all-trans-retinoic acid (RA)-loaded microspheres were carried out after they were subcutaneously injected into rats. To characterize the inflammatory response to these microspheres, tissue reactions at the implantation site and cell types in the interstices of the microspheres were evaluated for 180 days. On the 15th day, the cross-sectional area of the fibrous capsules surrounding the implantation site of the RA-loaded microspheres was four times larger than that of the control microspheres. The size of the fibrous capsules surrounding the implantation site of the RA-loaded microspheres decreased significantly over a period of 75 days, while the size of the fibrous capsules surrounding the implantation site of the control microspheres remained almost constant throughout the entire course of 180 days. The tissue response to the RA-loaded microspheres was more intensified by the increased extensive cellular infiltration of macrophages, granulation tissue, and fibrosis than that to the control microspheres. The difference in the inflammatory response between the RA-loaded microspheres and the control microspheres was significant for 75 days after implantation. It was suggested that the released RA from the microspheres stimulated inflammatory responses. However, no further enhanced inflammation reactions were detected after RA had been completely released from the microspheres. [ABSTRACT FROM AUTHOR]

Telomerase, a ribonucleoprotein complex of hTERT, hTR, and TP1, has been reported to be associated with carcinogenesis and multidrug resistance (MDR). This study used our in vitro human cervical multistep carcinogenesis/MDR model system in which normal human ectocervical and endocervical (HEN) cells were immortalized by HPV18 or 16, respectively, and subsequently transformed. The first evidence was found that immortalization and telomerase activation were correlated with increased expression specifically of two of the hTERT alternatively spliced mRNAs, one encoding wild-type protein containing the full-length functional reverse transcriptase (RT) region and one encoding a defective RT protein. Expression of neither hTERT mRNA containing full-length functional or defective RT motif was affected by transformation/MDR. All-trans-retinoic acid (ATRA) treatment of HPV-immortalized HEN-16-2 cells and transformed/MDR HEN-16-2/CDDP cells inhibited telomerase activity and downregulated expression of hTERT mRNAs containing full-length functional and a defective RT motif, but there were no changes in hTR and TP1 expression. Moreover, ATRA inhibited cell growth rate of HEN-16-2 and HEN-16-2/CDDP cells equally. These results provided the first evidence that ATRA equally in both immortalized and transformed/MDR cell lines inhibits telomerase activity and downregulates expression, but not splicing, of hTERT, and this is correlated with cell growth rate inhibition; the potential is implicated for applying ATRA to hTERT-targeted treatment of cervical cell carcinogenesis/MDR. [Copyright &y& Elsevier]

9-cis-Retinoic acid (9cRA), a geometric isomer of all-trans-retinoic acid (atRA), is an endogenous high-affinity ligand for retinoid X receptors and retinoic acid receptors activating them with high potency. 9,13-di-cis-Retinoic acid (9,13dcRA) has been described as a major plasma metabolite of 9cRA. In this study, the biological activity and the metabolism of 9cRA and 9,13dcRA were investigated and compared with those of atRA in a retinol-free culture system of HaCaT keratinocytes. 9cRA exhibited a slightly weaker activity overall than atRA in inhibiting cell proliferation, inducing cellular retinoic acid binding protein II (CRABP II) mRNA levels and upregulating cytokeratin 19 expression. 9,13dcRA regulated HaCaT keratinocyte activity only at the highest concentration tested (10–6M). In cultures of HaCaT keratinocytes with atRA and 9cRA, rapid intracellular accumulation of atRA was observed within 2 h, and atRA levels were higher with atRA treatment than with 9cRA treatment. 9,13dcRA remained relatively stable in the medium with intracellular 9,13dcRA levels below the level of detection. Taken together, 9cRA seems to be slightly less potent than atRA in regulating the biological activity of HaCaT keratinocytes, while its metabolite 9,13dcRA is effectively inactive at biologically relevant concentrations. Our data suggest a prodrug/drug relationship between 9cRA and atRA in human keratinocytes. 9,13dcRA seems to be a weaker prodrug of atRA or an inactive metabolic derivative. [ABSTRACT FROM AUTHOR]

Retinoids have shown promising activity for both cancer chemoprevention and as a treatment for emphysema. However, chronic oral administration of these drugs is limited by systemic side effects, including hepatic dysfunction, skeletal malformations, hyperlipidemia. hypercalcemia, and other reactions. In order to improve the pulmonary targeting of this potentially useful therapy, we developed a system for aerosolization of retinoids that substantially increased their local bioavailability. We compared the biodistribution and pharmacokinetics of an inhaled formulation of all-trans-retinoic acid (all-trans-RA), which was packaged in a metered dose inhaler, following both intratracheal (IT) and intravenous (IV) administration in male Sprague-Dawley rats. After drug administration, anesthetized animals were killed at 5 min, and at 1, 2, 4, 6 and 24 h. Plasma and emulsified samples of liver and lung tissues were dissected, extracted, and frozen prior to measurement of all-trans-RA concentration by high-performance liquid chromatography (HPLC). Aerosolization and IT injection of all-trans-RA resulted in a significantly longer pulmonary half-life of the drug (both 5-17 h), lower peak serum concentrations (aerosol 71 +/- 31 ng/ml, IT 68 +/- 50 ng/ml), and lower liver levels (aerosol 111 +/- 28 ng/g, IT 753 +/- 350 ng/g) than the same dose administered IV (2 h, 838 +/- 56 ng/ml, 4,258 +/- 1,006 ng/g, respectively; P < 0.05 for each comparison). Histologic examination of lungs and trachea showed no focal irritation attributable to the drug after single-dose administration. These results suggest that aerosolization of retinoids may offer a practical alternative to systemic oral administration for chemoprevention trials or treatment of lung diseases. This method may substantially increase the therapeutic index of these compounds by reducing systemic complications associated with long-term dosing. [ABSTRACT FROM AUTHOR]

Retinoids are involved in several physiological processes and are used in the treatment of various skin disorders. Therapy with retinoids during pregnancy may induce severe embryotoxic effects like craniofacial and cardiovascular malformations in the developing embryo. We investigated the effects of all-trans-retinoic acid (ATRA) and all-trans-retinoyl-β-D-glucuronide (ATRAG) in an amphibian embryotoxicity assay with Ambystoma mexicanum (axolotl) as an alternative in vitro method. Embryos were exposed to various concentrations of ATRA or ATRAG for 48 h beginning with the blastula stage. Kinetic investigations in the embryonic tissue were performed during the exposure period. Both retinoids interfered with the development of the axolotl embryos. Dose-dependent effects observed included growth retardation, craniofacial and cardiovascular malformations, as well as neural tube defects. In the axolotl, ATRA induced slightly more pronounced embryotoxic effects than ATRAG. All-trans-retinal was shown to be a major endogenous retinoid in this species. Endogenous levels of all-trans-retinaldehyde were increased during exposure to both ATRA and ATRAG. The glucuronide, however, was only detected in small amounts after ATRAG exposure. The embryotoxic potential of ATRAG could be explained by deglucuronidation to ATRA. [ABSTRACT FROM AUTHOR]

From January 1990 to August 1997, 29 consecutive patients were treated with newly diagnosed primary acute promyelocytic leukemia (APL) at the authors' Institution. Of these, 27 (16 boys and 11 girls) were evaluable. Median age at diagnosis was 6.3 (range: 1.9-15.7) years. This population was treated with two consecutive protocols: 13 patients were included in the AML-HPG90 protocol and 14 in the AML-HPG-95. The initial treatment was the same for both protocols: an induction 8-day phase with cytarabine, idarubicin, and etoposide was followed by a consolidation with cyclophosphamide, cytarabine, 6-mercaptopurine, vincristine, doxorubicin, and prednisone. Two courses of intensification with high-dose (HD) cytarabine and etoposide were given in the first study. Only one intensification course was administered in the second study, with HD cytarabine plus idarubicin or etoposide decided by randomization. Complete remission was achieved in 67% (18/27) of cases. Mortality on induction was quite high, 30% (8/27) mainly due to hemorrhages from disseminated intravascular coagulation (DIC). The event-free survival estimate for all patients was 0.47 (SE: 0.1). From April 1994, all-trans-retinoic acid (ATRA) was administered just during the first days of the induction phase (median: 9, range: 2-27) to stop or prevent DIC. Eighteen patients received ATRA and 9 did not. Three patients developed signs of ATRA syndrome during the first days of administration but no one died due to this toxicity. The impact of a short course of ATRA on early control of DIC was studied by analyzing the number of platelet, cryoprecipitate, and fresh frozen plasma transfusions during the induction phase in both groups. No statistical differences in complete remission rate, early mortality, need of transfusion of blood components for DIC, and survival estimates could be established between patients who received ATRA and those who did not. ATRA used in a short-course schedule during induction of APL did not stop early mortality due to DIC. Moreover, survival results did not improve with this method of ATRA usage. Longer periods of ATRA administration during APL therapy are strongly recommended. [ABSTRACT FROM AUTHOR]

ATRAGEN® is a liposome-encapsulated intravenous (IV) formulation of the anticancer drug all-trans-retinoic acid (tretinoin). Retinoids as a class of compounds produce a characteristic profile of toxicities collectively known as hypervitaminosis A. As part of the nonclinical regulatory submission, it was important to determine if liposome encapsulation of tretinoin would change the expected profile of toxicities. To this end, a single-dose study in rats and repeated-dose 28-day studies in rats and dogs were conducted. In the single-dose study, ATRAGEN was given as a single IV bolus via the tail vein at dosages of 5, 20, or 80 mg/kg. In the first repeated-dose studies in rats, ATRAGEN was given by tail vein infusion at dosages of 2.5, 15, or 25 mg/kg/day and in the second, at dosages of 1, 10 or 10 mg/kg/day. The second study in rats also included a group given free tretinoin at a dose of 10 mg/kg/day; lowered to 1 mg/kg/day. ATRAGEN was given to dogs as an IV infusion in the cephalic or saphenous vein at dosages of 2.5, 5, or 10 mg/kg/day. ATRAGEN was not acutely toxic in rats at doses of 5 or 20 mg/kg, whereas deaths were seen at 80 mg/kg. In contrast, free tretinoin at a dosage of 10 mg/kg caused the deaths of most male rats after the first dose in the repeated-dose study; consequently, the dose was lowered to 1 mg/kg/day for remaining males and all females in that study. In the 28-day repeated-dose studies, minimal toxicities were observed in either rats or dogs at ATRAGEN doses of 2.5 mg/kg/day or less. Both free tretinoin and ATRAGEN at 1 mg/kg/day were without signs of hypervitaminosis A in rats. Moderate to marked retinoid-associated hypervitaminosis A was observed in the 28-day rats studies in the dose range of 10 to 25 mg/kg/day. In dogs, repeated administration of ATRAGEN of 5 or 10 mg/kg/day also led to moderate to marked hypervitaminosis A. In both species, hypervitaminosis A was manifested primarily as bone and testicular toxicities. In bone, premature closure of epiphyseal growth plates and/or a decrease in the activity of cells in the growth plate were seen. Loss of the cartilaginous growth plate and replacement with less dense trabecular bone resulted in weakened bones, most evident in rats. Rats had increased levels of serum alkaline phosphatase (ALP) and bone fractures were common with ATRAGEN doses of 10 mg/kg/day and higher. In addition to effects on bone growth, endosteal fibroplasia, exostosis, and periosteal hemorrhages were observed in dogs. In both species, diffuse testicular atrophy, degenerative spermatic elements, and loss of seminiferous epithelium in the epididymis were observed microscopically. Hepatic enzyme levels were increased in rats, but no histopathological correlate was identified. Moderate to moderately severe nephrosis exemplified by a loss and/or degeneration of the kidney tubules was seen in dogs given 5 or 10 mg/kg/day. There was an increased weight of the spleens in rats receiving high dose volumes of liposomes; that is, control rats receiving empty liposomes and in rats receiving ATRAGEN in large dose volumes to provide tretinoin at dosages of 10 mg/kg/day and greater. Microscopically, there was an accumulation of macrophages with prominent vacuoles in the spleens of these rats. This effect on the spleen was not considered a pathological process but a clearance of liposomal material from the circulation by phagocytosis. No other toxicities were observed. Thus, these nonclinical safety studies of ATRAGEN conducted in rats or dogs found no unique toxicities from those observed previously in laboratory animals given tretinoin or other retinoids. [ABSTRACT FROM PUBLISHER]

All- trans-retinoic acid (RA) is a potent differentiating agent that is very effective in the treatment of patients with acute promyelocytic leukemia (APL). Since clinical response can be accompanied by extramedullary manifestations, we have investigated the influence of RA on cell adhesion to and migration through reconstituted basement membranes (Matrigel) in the APL cell line NB4. No apparent cellular differentiation was observed during a 24-h incubation with 1 μM RA, as indicated by the nitroblue tetrazolium reduction test. However, exposure to RA significantly enhanced NB4 cell adhesion to Matrigel and consecutive migration through Matrigel barriers in a dose-dependent manner. Several integrin molecules potentially involved in this process, i.e., CD29, CD18, CD11a, CD11b and CD11c, were therefore studied by fluorescence-activated cell sorting analysis. The expression of the β subunit of the β 2 integrins (CD18), but not that of β 1 integrins (CD29), was increased during 24-h RA treatment. Among the β 2 integrins, the expression of LFA-1 (CD11a) and of Mac-1 (CD11b), but not of p150,95 (CD11c), was induced by RA. When monoclonal antibodies that specifically block the interaction of these integrins with their ligands were used, we observed that CD29 is only involved in adhesion and CD11b only in migration, whereas CD11a participates in both processes. NB4 cells constitutively secreted the matrix metalloproteinases MMP-9 and MMP-2, which are known to promote cellular invasion processes by degradation of the extracellular matrix. RA treatment had no influence on the quantity of secreted MMP-9 or MMP-2 in these cells as determined by zymography. Addition of Batimastat (BB-94), a synthetic inhibitor of matrix metalloproteinases, blocked RA-induced cell migration without affecting cellular adhesion to Matrigel. These findings indicate that adhesion molecules as well as matrix metalloproteinases are involved in RA-stimulated migration of NB4 cells through Matrigel, possibly providing some explanation of tissue infiltration by leukemic cells as observed during treatment of APL patients with RA. [ABSTRACT FROM AUTHOR]

Acute myeloid leukemia (AML) is an aggressive and often fatal hematopoietic malignancy. A very attractive way to treat myeloid leukemia, called "differentiation therapy", was proposed when in vitro studies showed that some compounds are capable of inducing differentiation of AML cell lines. One of the differentiation-inducing agents, all- trans -retinoic acid (ATRA), which can induce granulocytic differentiation in AML cell lines, has been introduced into clinics to treat patients with acute promyelocytic leukemia (APL) in which a PML-RARA fusion protein is generated by a chromosomal translocation. ATRA has greatly improved the treatment of APL. Since 1,25-dihydroxyvitamin D (1,25D) is capable of inducing monocytic differentiation of leukemic cells, the idea of treating other AMLs with vitamin D analogs was widely accepted. However, early clinical trials in which cancer patients were treated either with 1,25D or with analogs did not lead to conclusive results. Recent results have shown that AML types with certain mutations, such as isocitrate dehydrogenase (IDH) mutations, may be the right targets for differentiation therapy using 1,25D, due to upregulation of vitamin D receptor (VDR) pathway.

All- trans -retinoic acid (ATRA) has been clinically used to treat acute promyelocytic leukemia and is being studied to treat other types of cancer; however, the therapeutic role and mechanism of ATRA against cholangiocarcinoma (CCA) remain unclear. The present study investigated the cytotoxic effect and underlying mechanisms of ATRA on CCA cell lines. Cell viability was evaluated by sulforhodamine B assay. Intracellular reactive oxygen species (ROS) levels were assessed by dihydroethidium assay. Apoptosis analysis was performed by flow cytometry. The pathways of apoptotic cell death induction were examined using enzymatic caspase activity assay. Proteins associated with apoptosis were evaluated by western blotting. The effects on gene expression were analyzed by reverse transcription-quantitative PCR analysis. ATRA induced a concentration- and time-dependent toxicity in CCA cells. Furthermore, when the cytotoxicity of ATRA against retinoic acid receptor (RAR)-deficient cells was assessed, it was revealed that ATRA cytotoxicity was RARB-dependent. Following ATRA treatment, there was a significant accumulation of cellular ROS and ATRA-induced ROS generation led to an increase in the expression levels of apoptosis-inducing proteins and intrinsic apoptosis. Pre-treatment with ROS scavengers could diminish the apoptotic effect of ATRA, suggesting that ROS and mitochondria may have an essential role in the induction of apoptosis. Furthermore, following ATRA treatment, an increase in cellular ROS content was associated with suppressing nuclear factor erythroid 2-related factor 2 (NFE2L2 or NRF2) and NRF2 -downstream active genes. ATRA also suppressed cisplatin-induced NRF2 expression, suggesting that the enhancement of cisplatin cytotoxicity by ATRA may be associated with the downregulation of NRF2 signaling. In conclusion, the results of the present study demonstrated that ATRA could be repurposed as an alternative drug for CCA therapy., Competing Interests: The authors declare that they have no competing interests., (Copyright: © Butsri et al.)

Background: Accumulation of evidence suggests that the gut microbiome, its specific metabolites, and differentially expressed proteins (DEPs) are related to non-small cell lung cancer (NSCLC) pathogenesis. We now report the influences of the gut microbiota, metabolites, and DEPs on the mediation of NSCLC's chronic inflammation and immune dysregulation., Methods: We conducted 16S ribosomal RNA sequencing for the gut microbiome in healthy volunteers and NSCLC patients. Liquid chromatography-mass spectrometry (LC-MS) analysis was employed to explore differences between metabolites and DEPs in serum samples. Additionally, LC-MS-based metabolomic analysis was conducted in 40 NSCLC tissues and 40 adjacent tissues. The omics data were separately analysed and integrated by using Spearman's correlation coefficient. Then, faecal microbiota transplantation (FMT) assay was used to assess the effects of the gut microbiome and specific metabolites in mice., Results: Faecal microbiome analysis revealed gut microflora dysbiosis in NSCLC patients with Prevotella, Gemmiger, and Roseburia significantly upregulated at the genus level. Then, we identified that nervonic acid/all-trans-retinoic acid level was negatively related to Prevotella. Additionally, a total of core 8 DEPs were selected in the proteome analysis, which mainly participated in the production of IL-8 and NF-κB pathways. CRP, LBP, and CD14 were identified as potential biomarkers for NSCLC. Transplantation of faecal microbiota from patients with NSCLC or Prevotella copri-colonized recipient in mice resulted in inflammation and immune dysregulation. In turn, nervonic acid/all-trans-retinoic acid treatment improved the phenotype of C57BL/6 mice bearing P. copri-treated Lewis lung cancer (LLC)., Conclusions: Overall, these results pointed out that P. copri-nervonic acid/all-trans-retinoic acid axis may contribute to the pathogenesis of NSCLC., (© 2022 The Authors. Clinical and Translational Medicine published by John Wiley & Sons Australia, Ltd on behalf of Shanghai Institute of Clinical Bioinformatics.)

The present study was undertaken to evaluate the systemic absorption and cervical tissue uptake of all-trans-retinoic acid (TRA), delivered via a collagen spongecervical cap delivery device in patients with intraepithelial cervical dysplasia. Ten patients with histologically proven mild or moderate cervical dysplasia were included in this pharmacologic study. The two TRA concentrations (0.05% and 0.372%) selected for study represent the starting and maximally tolerated doses used in phase I clinical trial. All-trans-retinoic-11-3H acid (3H-TRA, 500 mu Ci) was used to facilitate cervical tissue uptake studies. Cervical biopsies and post-treatment blood samples were obtained from each patient after TRA exposure. The uptake of TRA into cervical tissues four hours after drug administration was significantly increased at the maximally tolerated TRA dose. There was a rapid decrease in cervical tissue concentration of TRA at the 0.372% dose between 4 and 24 h after drug exposure, suggesting a relatively short elimination half-life of TRA in cervical tissues. HPLC analysis of post-treatment blood samples indicate that there was no systemic absorption of TRA after local cervical administration.

All-trans-retinoic acid (ATRA), the active metabolite of vitamin A, plays a pivotal role in cell differentiation, proliferation and embryonic development. It is an effective therapy for dermatological disorders and malignancies. ATRA is prone to isomerization and oxidation, which can affect its activity and selectivity. Novel diphenylacetylene-based ATRA analogues with increased stability can help to overcome these problems and may offer significant potential as therapeutics for a variety of cancers and neurodegenerative diseases, including amyotrophic lateral sclerosis. Here, we investigated the effects of these retinoids on cell viability and genotoxicity in the widely used model system of the rapidly proliferating Chinese hamster ovary cell line. DC360 is a fluorescent ATRA analogue and DC324 is a non-active derivative of DC360. EC23, DC525, DC540, DC645, and DC712 are promising analogues with increased bioactivity. The cytotoxic activity of the compounds was evaluated by ATP assay and DNA damage was tested by comet assay. No cytotoxicity was observed in the 10−6–10−5 M concentration range. All compounds induced DNA migration similar to ATRA, but DC324, DC360 and EC23 did so to a greater extent, particularly at higher concentrations. We believe that retinoid receptor-independent genotoxicity is a general characteristic of these compounds; however, further studies are needed to identify the molecular mechanisms and understand their complex biological functions. [ABSTRACT FROM AUTHOR]

Cellular retinoic acid binding proteins (CRABP1 and CRABP2) bind all-trans -retinoic acid ( at RA), the active metabolite of vitamin A, with high affinity. CRABP1 and CRABP2 have been shown to interact with the at RA-clearing cytochrome P450 enzymes CYP26B1 and CYP26C1 and with nuclear retinoic acid receptors (RARs). We hypothesized that CRABP1 and CRABP2 also alter at RA metabolism and clearance by CYP26A1, the third key at RA-metabolizing enzyme in the CYP26 family. Based on stopped-flow experiments, at RA bound CRABP1 and CRABP2 with K d values of 4.7 nM and 7.6 nM, respectively. The unbound at RA K m values for 4-OH- at RA formation by CYP26A1 were 4.7 ± 0.8 nM with at RA, 6.8 ± 1.7 nM with holo-CRABP1 and 6.1 ± 2.7 nM with holo-CRABP2 as a substrate. In comparison, the apparent k cat value was about 30% lower (0.71 ± 0.07 min -1 for holo-CRABP1 and 0.75 ± 0.09 min -1 for holo-CRABP2) in the presence of CRABPs than with free at RA (1.07 ± 0.08 min -1 ). In addition, increasing concentrations in apo-CRABPs decreased the 4-OH- at RA formation rates by CYP26A1. Kinetic analyses suggest that apo-CRABP1 and apo-CRABP2 inhibit CYP26A1 (K i = 0.39 nM and 0.53 nM, respectively) and holo-CRABPs channel at RA for metabolism by CYP26A1. These data suggest that CRABPs play a critical role in modulating at RA metabolism and cellular at RA concentrations.

Retinoids (vitamin A) have been reported extensively for anti-cancer properties due to their high receptor-binding affinities and gene regulation abilities. However, the anti-cancer potential of retinoids has not been reviewed in recent years. Thus, this review focused on the anti-cancer effects of retinoids and their synergistic effects with other drugs, together with their mechanisms of action in different types of cancers reported in the past five years. The retinoids were well studied in breast cancer, melanoma, and colorectal cancer. Synthetic retinoids have shown higher selectivity, stronger effectiveness, and lower toxicity than endogenous retinoids. Interestingly, the combination treatment of endogenous retinoids with chemotherapy drugs showed enhanced anti-cancer effects. The mechanisms of action reported for retinoids mainly involved the RAR/RXR signaling pathway. However, limited clinical studies were conducted in recent years. Thus, retinoids which are highly potential anti-cancer agents are worth further study in clinical, especially as a combination therapy with chemotherapy drugs., Competing Interests: None., (AJCR Copyright © 2022.)

Reduced or absent neutrophil alkaline phosphatase (NAP) activity is a common feature of neutrophilic granulocytes from patients with chronic myeloid leukemia (CML). In this study we examined whether NAP activity could be restored in vitro by stimulating CML cells with different promoters such as all-trans-retinoic acid (ATRA), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF). The results obtained indicated that ATRA and G-CSF, either alone or in combination, were effective in inducing NAP activity in CML cells, whereas GM-CSF was not. Further, NAP restoration in ATRA- and G-CSF-treated cultures was accompanied by increased morphologic differentiation of the CML clone. It might be concluded that the CML clone could be driven in vitro by ATRA and G-CSF both to achieve granulocytic maturation and to correct functional NAP-related defects. [ABSTRACT FROM AUTHOR]

The differential-display reverse transcription/polymerase chain reaction (DDRT-PCR) method was utilised to find genes differentially expressed at the messenger RNA level in SMMC-7721 human hepatocellular carcinoma cells treated and not treated with all- trans-retinoic acid, a differentiation inducer of the cell. Human transcription factor IIB (TFIIB) was discovered to be decreased on the 3rd day after the cells had been treated with retinoic acid and increased by phorbol 12-myristate 13-acetate, which stimulated the proliferation of human hepatocellular carcinoma cells. It was also found that the transcription of TFIIB in SMMC-7721 cell had no relationship to the cell cycle. [ABSTRACT FROM AUTHOR]

The effects of all-trans-retinoic acid (RA) (tretinoin) on the craniofacial development of mouse embryos were examined using whole embryo culture. In day 8 embryos cultured for 48 h, embryonic growth was inhibited concentration-dependently by all-trans-RA treatment. Most of the treated embryos exhibited hypoplasia of the primary palatal processes and a reduction in the development of the first viscreral arches. In day 10 embryos cultured for 48 h, although embryonic growth was not inhibited at any concentrations of all-trans-RA, median cleft lip (93%), hypoplasia of the primary palatal processes (37%) and limb reduction deformities (48%) occurred commonly. Furthermore, RA treatment greatly reduced the size of the secondary palatal processes. The incorporation ofH-thymidine in the treated maxillary processes was decreased to 65% of the control value at 1.0×10 M alltrans-RA. These findings indicate that all-trans-RA is teratogenic in mouse whole embryo culture. [ABSTRACT FROM AUTHOR]

Purpose: To optimize the delivery of all- trans-retinoic acid (ATRA) to lung tissue, we determined the potential of vehiculating the drug in liposomes (L-ATRA) and delivering it via aerosol. Liposomes may provide a means to prevent local irritation of lung tissue and reduce pulmonary toxicity, prolong therapeutic levels and generate high drug concentrations at the tumor sites. Cumulatively, this would result in reduced systemic toxicity and enhanced drug efficacy. Methods: Previous studies have shown that liposomes can serve as excellent carriers for otherwise poorly soluble ATRA. Delivery of ATRA to the lung tissue of mice was accomplished by nebulization of L-ATRA. The liposomes in the aerosol were relatively uniform (309 ± 138 nm), stable, and retained the drug well. Results: The drug was effectively delivered at high concentrations (10 ± 2 μg/g of tissue) to the lungs of mice and was retained for at least up to 96 h after a single exposure to L-ATRA aerosol. No appreciable levels of ATRA were detected in the blood or the liver of treated mice. The aerosol-delivered ATRA was biologically active as demonstrated by its ability to induce the expression of tissue-type transglutaminase. Conclusion: Aerosol delivery of L-ATRA offers an effective way to deliver high levels of ATRA to the lung without apparent pulmonary toxic effects. [ABSTRACT FROM AUTHOR]

Retinoids have been shown to have substantial anticancer activity in a number of preclinical and clinical situations. There are considerable epidemiologic, in vitro and in vivo data which indicate that retinoids may have a role in the prevention and therapy of human prostate cancer. Based on anecdotal evidence of response in one patient with hormone-refractory prostate cancer (HRPC), we conducted a phase II trial in HRPC during which we also examined changes in pharmacokinetics of all- trans-retinoic acid (ATRA) which occurred during therapy. Enrolled in the study were 17 patients with HRPC who received 50 mg/m2 ATRA three times daily orally on days 1–14, repeated every 22 days. The pharmacokinetics of ATRA were assessed with the first dose on day 1, again on day 14 and after a 7-day interruption in ATRA therapy on day 22. Patients were evaluable for response if they completed two 14-day courses of ATRA; among 13 such patients no responses were seen. Four patients were considered unevaluable for response owing to rapid disease progression in three and intercurrent illness in one. Apparent clearance of ATRA changed substantially during therapy: day 1 3779±4215 ml/min, day 14 7179±3197 ml/min, day 22 3213±2357 ml/min. Area under the curve was proportionately diminished on day 14 compared with day 1 and had returned to baseline by day 22. We conclude that ATRA is not active in HRPC. Failure of this agent in HRPC may be related to failure of drug delivery associated with enhanced mechanisms of ATRA clearance which occur within a few days of beginning ATRA treatment. [ABSTRACT FROM AUTHOR]

Malignant gliomas continue to be a significant sourceof mortality in young and middle aged adults.The introduction of new treatment strategies and multidisciplinaryapproaches has improved the outcome of patients withthese tumors only slightly. Because retinoic acid hasgrowth inhibitory activity against glioma and neuroblastoma cellsin cultures, we assessed the efficacy of all-trans-retinoicacid in the treatment of recurrent cerebral gliomas.Thirty-six patients with recurrent cerebral gliomas were enteredin the study and treated with 120 or150 mg/m2/day of all-trans-retinoic acid as a singleagent. The drug was given for 3 weeksfollowed with one week of rest. Two blocksof 4 weeks constituted one course of treatment.One (3%) of 34 evaluable patients had aminor response and 14 (41%) had stable disease.In the rest of the patients (56%), tumorscontinued to progress despite treatment. The median timeto progression of all evaluable patients was 8weeks, and for the responders was 17 weeks.The higher dose level (150 mg/m2) was associatedwith high incidence of headache, which responded todose reduction. The lower dose level was verywell tolerated, with mild, mainly dermatological toxicity.All-trans-retinoic acid as a single agent has nosignificant activity against recurrent cerebral gliomas. [ABSTRACT FROM AUTHOR]

Vitamin A, acting through its metabolite, all- trans -retinoic acid, is a potent transcriptional regulator affecting expression levels of hundreds of genes through retinoic acid response elements present within these genes. However, the literature is replete with claims that consider vitamin A to be an antioxidant vitamin, like vitamins C and E. This apparent contradiction in the understanding of how vitamin A acts mechanistically within the body is a major focus of this review. Vitamin E, which is generally understood to act as a lipophilic antioxidant protecting polyunsaturated fatty acids present in membranes, is often proposed to be a transcriptional regulator. The evaluation of this claim is another focus of the review. We conclude that vitamin A is an indirect antioxidant, whose indirect function is to transcriptionally regulate a number of genes involved in mediating the body's canonical antioxidant responses. Vitamin E, in addition to being a direct antioxidant, prevents the increase of peroxidized lipids that alter both metabolic pathways and gene expression profiles within tissues and cells. However, there is little compelling evidence that vitamin E has a direct transcriptional mechanism like that of vitamin A. Thus, we propose that the term antioxidant not be applied to vitamin A, and we discourage the use of the term transcriptional mediator when discussing vitamin E.

The article focuses on a research which examined the effects of all-trans-retinoic acid (ATRA) in the development of embryonic neural tissue of mice. The study involved pregnant mice that were treated with a single dose of 50 milligram ATRA by oral gavage on embryonic day. It is concluded that ATRA treatment increased expression of both Smad expression of p-Smad1 and total Smad1. Meanwhile, Smad6 was decreased in neural tissues of ATRA-exposed embryos in utero from embryonic day eight to 11, which a critical period for neural tube formation.