In Vitro Effects of Acitretin on Human Neuronal SH-SY5Y Cells.

Acitretin is an oral drug approved by the Food and Drug Administration that is commonly used to treat psoriasis. In recent years, acitretin has been identified as a candidate drug for the treatment of Alzheimer's disease, but its role in neuronal development is still unclear. In this study, the human neuroblastoma cell line SH-SY5Y was used as a model to study neuronal differentiation. We found that acitretin effectively promoted the differentiation of SH-SY5Y cells into neuronal cells and upregulated the expression of the neuronal marker ß-III tubulin and the mature neuronal marker NFH. Differentially expressed genes were identified by RNA sequencing and analyzed by bioinformatics approaches. The results showed that genes associated with neuron development-related pathways, such as SSPO and KCNT1, had significant changes in expression. Analysis showed that PRKCA and CAMK2B may play important roles in the process by which acitretin promotes neurodevelopment. Through whole-cell patch clamping and a microelectrode array assay, we found that acitretin-treated neurons generated electrical spikes similar to those generated by mature neurons. This study provided evidence to support an accessible and safe model of neuron-like cells and verified that acitretin can promote the differentiation of neurons and has the potential to treat brain tumors and neurodevelopmental and neurodegenerative diseases.

Acitretin and Retinoic Acid Derivatives Inhibit BK Polyomavirus Replication in Primary Human Proximal Renal Tubular Epithelial and Urothelial Cells.

Small-molecule drugs inhibiting BK polyomavirus (BKPyV) represent a significant unmet clinical need in view of polyomavirus-associated nephropathy or hemorrhagic cystitis, which complicate 5% to 25% of kidney and hematopoietic cell transplantations. We characterized the inhibitory activity of acitretin on BKPyV replication in primary human renal proximal tubular epithelial cells (RPTECs). Effective inhibitory concentrations of 50% (EC50) and 90% (EC90) were determined in dilution series measuring BKPyV loads, transcripts, and protein expression, using cell proliferation, metabolic activity, and viability to estimate cytotoxic concentrations and selectivity indices (SI). The acitretin EC50 and EC90 in RPTECs were 0.64 (SI50, 250) and 3.25 µM (SI90, 49.2), respectively. Acitretin effectively inhibited BKPyV replication until 72 h postinfection when added 24 h before infection until 12 h after infection, but decreased to <50% at later time points. Acitretin did not interfere with nuclear delivery of BKPyV genomes, but it decreased large T-antigen transcription and protein expression. Acitretin did not inhibit the initial round of BKPyV replication following transfection of full-length viral genomes, but it affected subsequent rounds of reinfection. Acitretin also inhibited BKPyV replication in human urothelial cells and in Vero cells, but not in COS-7 cells constitutively expressing Simian virus 40 (SV40) large T antigen. Retinoic acid agonists (all-trans retinoic acid, 9-cis retinoic acid [9-cis-RA], 13-cis-RA, bexarotene, and tamibarotene) and the RAR/RXR antagonist RO41-5253 also inhibited BKPyV replication, pointing to an as-yet-undefined mechanism. IMPORTANCE Acitretin selectively inhibits BKPyV replication in primary human cell culture models of nephropathy and hemorrhagic cystitis. Since acitretin is an approved drug in clinical use reaching BKPyV-inhibiting concentrations in systemically treated patients, further studies are warranted to provide data for clinical repurposing of retinoids for treatment and prevention of replicative BKPyV-diseases.

Mechanism of acitretin-induced relaxations in isolated rat thoracic aorta preparations.

Acitretin is a member of vitamin A-derived retinoids, and its effect on vascular smooth muscle had not yet been studied. The aim of this study is to investigate the effect of acitretin, a retinoid, on vascular smooth muscle contractility. Thoracic aorta preparations obtained from 34 male Sprague-Dawley rats (355 ± 15 g) were studied in isolated organ baths containing Krebs-Henseleit solution. The relaxation responses were obtained with acitretin (10-12-10-4 M) in endothelium-preserved and endothelium-denuded aorta preparations precontracted with submaximal concentration of phenylephrine (10-6 M). The role of retinoic acid receptors (RARs), nitric oxide, adenylyl, and guanylyl cyclase enzymes, and potassium channels in these relaxation responses were investigated. Acitretin produced concentration-dependent relaxations, which were independent of its solvent dimethylsulfoxide (DMSO), in endothelium-denuded phenylephrine-precontracted thoracic aorta preparations. While incubation with the RAR antagonist (AGN193109, 10-5 M) had no effect on these relaxations; nitric oxide synthase inhibitor (L-NG-Nitro arginine methyl ester (L-NAME), 10-4 M), adenylyl cyclase inhibitor (SQ2253, 10-5 M), guanylyl cyclase inhibitor (oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), 10-6 M), and potassium channel blocker (tetraethylammonium (TEA), 10-2 M) significantly eliminated the relaxation responses induced by acitretin. Acitretin induces relaxation in rat isolated thoracic aorta preparations without endothelium, which may be mediated by nitric oxide, cyclic adenosine monophosphate, and cyclic guanosine monophosphate-dependent kinases and potassium channels.

The Influence of Acitretin on Brain Lipidomics in Adolescent Mice-Implications for Pediatric and Adolescent Dermatological Therapy.

Administration of systemic retinoids such as acitretin has not been approved yet for pediatric patients. An adverse event of retinoid-therapy that occurs with lower prevalence in children than in adults is hyperlipidemia. This might be based on the lack of comorbidities in young patients, but must not be neglected. Especially for the development of the human brain up to young adulthood, dysbalance of lipids might be deleterious. Here, we provide for the first time an in-depth analysis of the influence of subchronic acitretin-administration on lipid composition of brain parenchyma of young wild type mice. For comparison and to evaluate the systemic effect of the treatment, liver lipids were analogously investigated. As expected, triglycerides increased in liver as well as in brain and a non-significant increase in cholesterol was observed. However, specifically brain showed an increase in lyso-phosphatidylcholine and carnitine as well as in sphingomyelin. Group analysis of lipid classes revealed no statistical effects, while single species were tissue-dependently changed: effects in brain were in general more subtly as compared to those in liver regarding the mere number of changed lipid species. Thus, while the overall impact of acitretin seems comparably small regarding brain, the change in individual species and their role in brain development and maturation has to be considered.

Repurposing Acitretin as an Antipseudomonal Agent Targeting the Pseudomonas aeruginosa Iron-Regulated Heme Oxygenase.

Iron is an essential micronutrient for the survival and virulence of the bacterial pathogen Pseudomonas aeruginosa. To overcome iron withholding and successfully colonize a host, P. aeruginosa uses a variety of mechanisms to acquire iron, including the secretion of high-affinity iron chelators (siderophores) or the uptake and utilization of heme. P. aeruginosa heme oxygenase (HemO) plays pivotal roles in heme sensing, uptake, and utilization and has emerged as a therapeutic target for the development of antipseudomonal agents. Using a high-throughput fluorescence quenching assay combined with minimum inhibitory concentration measurements, we screened the Selleck Bioactive collection of 2100 compounds and identified acitretin, a Food and Drug Administration-approved oral retinoid, as a potent and selective inhibitor of HemO. Acitretin binds to HemO with a KD value of 0.10 ± 0.02 µM and inhibits the growth of P. aeruginosa PAO1 with an IC50 of 70 ± 18 µg/mL. In addition, acitretin showed good selectivity for HemO, which uniquely generates BVIXß/δ, over human heme oxygenase (hHO1) and other BVIXα-producing homologues such as the heme oxygenases from Neisseria meningitidis (nmHO) and Acinetobacter baumannii (abHO). The binding of acitretin within the HemO active site was confirmed by 1H-15N heteronuclear single-quantum coherence nuclear magnetic resonance, and molecular modeling provided further insight into potential interactions of acitretin with residues specific for orienting heme in the ß/δ selective HemO. Moreover, at 20 µM, acitretin inhibited the enzymatic activity of HemO in P. aeruginosa cells by >60% and effectively blocked the ability of P. aeruginosa to sense and acquire heme as demonstrated in the ß-galactosidase transcriptional reporter assay.

Identification of Retinoic Acid Receptor Agonists as Potent Hepatitis B Virus Inhibitors via a Drug Repurposing Screen.

Currently available therapies for chronic hepatitis B virus (HBV) infection can efficiently reduce viremia but induce hepatitis B surface antigen (HBsAg) loss in very few patients; also, these therapies do not greatly affect the viral covalently closed circular DNA (cccDNA). To discover new agents with complementary anti-HBV effects, we performed a drug repurposing screen of 1,018 Food and Drug Administration (FDA)-approved compounds using HBV-infected primary human hepatocytes (PHH). Several compounds belonging to the family of retinoic acid receptor (RAR) agonists were identified that reduced HBsAg levels in a dose-dependent manner without significant cytotoxicity. Among them, tazarotene exhibited the most potent anti-HBV effect, with a half-maximal inhibitory concentration (IC50) for HBsAg of less than 30 nM in PHH. The inhibitory effect was also observed in HBV-infected differentiated HepaRG (dHepaRG) models, but not in HepG2.215 cells, and HBV genotypes A to D were similarly inhibited. Tazarotene was further demonstrated to repress HBV cccDNA transcription, as determined by the levels of HBV cccDNA and RNAs and the activation of HBV promoters. Moreover, RNA sequence analysis showed that tazarotene did not induce an interferon response but altered the expression of a number of genes associated with RAR and metabolic pathways. Inhibition of RARß, but not RARα, by a specific antagonist significantly attenuated the anti-HBV activity of tazarotene, suggesting that tazarotene inhibits HBV in part through RARß. Finally, a synergistic effect of tazarotene and entecavir on HBV DNA levels was observed. Therefore, RAR agonists as represented by tazarotene were identified as potential novel anti-HBV agents.

Evaluation of the Innate Immune Modulator Acitretin as a Strategy To Clear the HIV Reservoir.

The persistence of HIV despite suppressive antiretroviral therapy is a major roadblock to HIV eradication. Current strategies focused on inducing the expression of latent HIV fail to clear the persistent reservoir, prompting the development of new approaches for killing HIV-positive cells. Recently, acitretin was proposed as a pharmacological enhancer of the innate cellular defense network that led to virus reactivation and preferential death of infected cells. We evaluated the capacity of acitretin to reactivate and/or to facilitate immune-mediated clearance of HIV-positive cells. Acitretin did not induce HIV reactivation in latently infected cell lines (J-Lat and ACH-2). We could observe only modest induction of HIV reactivation by acitretin in latently green fluorescent protein-HIV-infected Jurkat cells, comparable to suboptimal concentrations of vorinostat, a known latency-reversing agent (LRA). Acitretin induction was insignificant, however, compared to optimal concentrations of LRAs. Acitretin failed to reactivate HIV in a model of latently infected primary CD4+ T cells but induced retinoic acid-inducible gene I (RIG-I) and mitochondrial antiviral signaling (MAVS) expression in infected and uninfected cells, confirming the role of acitretin as an innate immune modulator. However, this effect was not associated with selective killing of HIV-positive cells. In conclusion, acitretin-mediated stimulation of the RIG-I pathway for HIV reactivation is modest and thus may not meaningfully affect the HIV reservoir. Stimulation of the RIG-I-dependent interferon (IFN) cascade by acitretin may not significantly affect the selective destruction of latently infected HIV-positive cells.

Effect of retinoic acid on aquaporin 3 expression in keratinocytes.

To explore the possible mechanism of the third-generation retinoic acid drugs (isotretinoin, acitretin, adapalene) in inducing skin and mucosa dryness and rhagades; specifically, mechanism by which these drugs influence keratinocyte cell culture models in vitro (HaCaT) and aquaporin channel (AQP3) protein expression was investigated. Isotretinoin, acitretin, and adapalene were applied to human keratinocyte HaCaT cells. Immunohistochemistry, reverse transcriptase polymerase chain reaction, and western blotting were used to detect their effects on AQP3 expression in HaCaT cells at different concentrations (0.000, 0.001, 0.010, 0.060, and 0.100 mg/mL) or different at times (0, 6, 12, 24, and 48 h). At 0.010 mg/mL, maximal AQP3 expression was observed in HaCaT cells; this was significantly higher than the expressions at the other concentrations (P < 0.05). After treatment with isotretinoin, acitretin, or adapalene at 0.010 mg/mL for 12 h, the expression of AQP3 was the highest in the isotretinoin group, followed by the acitretin group, with the lowest expression in the adapalene group. However, the differences were not statistically significant (P > 0.05). Retinoic acid can increase AQP3 expression in HaCaT cells, with significant effects observed with 0.010 mg/mL isotretinoin treatment for 12 h. The side effects, namely skin and mucosa dryness caused by retinoic acid might be related to its effects on AQP3 expression.

Acitretin exhibits inhibitory effects towards UDP-glucuronosyltransferase (UGT)1A9-mediated 4-methylumbelliferone (4-MU) and propofol glucuronidation reaction.

The present study aimed to evaluate the potential risk of drug-drug interactions associated with acitretin which is a drug for therapy of psoriasis approved by the Food and Drug Administration (FDA). The initial screening of acitretin's inhibition towards 4-methylumbelliferone (4-MU) glucuronidation catalyzed by important UDP-glucuronosyltransferase (UGT) isoforms in the liver showed that UGT1A9 activity was strongly inhibited by acitretin with other UGT isoforms negligibly influenced. The inhibition type is best fit to competitive inhibition, and the inhibition kinetic parameter (K(i)) was determined to be 3.5 microM. The inhibition behaviour of acitretin towards UGT1A9 activity did not exhibit probe substrate-dependent behaviour when selecting human liver microsomes (HLMs)-catalyzed propofol-O-glucuronidation as probe reaction of UGT1A9. The same inhibition type and similar inhibition parameters (K(i) = 3.2 microM) were obtained. Using the maximum plasma exposure dose of acitretin (C(max)), the C(max)/K(i) values were calculated to be 0.23 and 0.25 when selecting 4-MU and propofol as probe substrates, respectively. All these results indicate a potential clinical drug-drug interaction between acitretin and 4-MU or propofol.

Therapeutic potential of stem cells and acitretin on inflammatory signaling pathway-associated genes regulated by miRNAs 146a and 155 in AD-like rats.

Alzheimer's disease (AD) is one of the most common causes of dementia. Several drugs are used to improve the symptoms, but do not stop AD progression. There are more promising treatments that may have a significant role in AD diagnosis and treatment such as miRNAs and stem cells. The present study aims to develop a new approach for AD treatment by mesenchymal stem cells (MSCs) and/or acitretin with special reference to inflammatory signaling pathway as NF-kB and its regulator miRNAs in AD-like rat model. Fourty-five male albino rats were allotted for the present study. The experimental periods were divided into induction, withdrawal, and therapeutic phases. Expression levels of miR-146a, miR-155, necrotic, growth and inflammatory genes were assessed using RT-qPCR. Histopathological examination of brain tissues was performed in different rat groups. The normal physiological, molecular, and histopathological levels were restored after treatment with MSCs and/or acitretin. The present study demonstrates that the miR-146a and miR-155 might be used as promising biomarkers for AD. MSCs and/or acitretin proved their therapeutic potential in restoring the expression levels of targeted miRNAs and their related genes concerning NF-kB signaling pathway.

miRNAs and Stem Cells as Promising Diagnostic and Therapeutic Targets for Alzheimer's Disease.

Alzheimer's disease (AD) is a cumulative progressive neurodegenerative disease characterized mainly by impairment in cognitive functions accompanied by memory loss, disturbance in behavior and personality, and difficulties in learning. Although the main causes of AD pathogenesis are not fully understood yet, amyloid-ß peptides and tau proteins are supposed to be responsible for AD onset and pathogenesis. Various demographic, genetic, and environmental risk factors are involved in AD onset and pathogenesis such as age, gender, several genes, lipids, malnutrition, and poor diet. Significant changes were observed in microRNA (miRNA) levels between normal and AD cases giving hope for a diagnostic procedure for AD through a simple blood test. As yet, only two classes of AD therapeutic drugs are approved by FDA. They are classified as acetylcholinesterase inhibitors and N-methyl-D-aspartate antagonists (NMDA). Unfortunately, they can only treat the symptoms but cannot cure AD or stop its progression. New therapeutic approaches were developed for AD treatment including acitretin due to its ability to cross blood-brain barrier in the brain of rats and mice and induce the expression of ADAM 10 gene, the α-secretase of human amyloid-ß protein precursor, stimulating the non-amyloidogenic pathway for amyloid-ß protein precursor processing resulting in amyloid-ß reduction. Also stem cells may have a crucial role in AD treatment as they can improve cognitive functions and memory in AD rats through regeneration of damaged neurons. This review spotlights on promising diagnostic techniques such as miRNAs and therapeutic approaches such as acitretin and/or stem cells keeping in consideration AD pathogenesis, stages, symptoms, and risk factors.

Etanercept downregulates the Th17 pathway and decreases the IL-17+/IL-10+ cell ratio in patients with psoriasis vulgaris.

PURPOSE: To evaluate circulating and lesional CD4(+) and CD8(+) cells belonging to Th1, Th2, and Th17 patterns as well as IL-10(+) cells before and after a 12-week lasting course with etanercept or acitretin in patients with psoriasis. METHODS: 15 patients were given etanercept 50 mg twice weekly and 15 patients acitretin 0,4 mg/kg/day, both for 12 weeks. At the baseline and at the end of the treatment, blood and skin samples were taken to investigate IL-4, IL-8, IL-10, IL-17, and IFN-γ-producing CD4(+) and CD8(+) cells. As controls, 10 healthy controls (HC) and 6 atopic dermatitis (AD) patients were included into the study. RESULTS: Psoriasis patients showed augmented IL-17- and IL-8-producing CD4(+) cells in the blood than HC and AD patients. In the skin lesions, IL-17(+) cells were more represented in psoriasis than in AD, while the number of IL-4-producing cells was reduced in psoriasis patients than in AD ones. Etanercept was able to significantly reduce the number of IL-17- and IL-8-producing CD4(+) and CD8(+) cells both in skin and blood, as well as to augment the proportion of IL-10-producing CD4(+) cells in the skin of psoriatic patients, while acitretin was not. CONCLUSIONS: Our results confirmed the role of Th17 cells in the pathogenesis of psoriasis. Etanercept, but not acitretin, was able to downregulate the Th17 pathway and to increase the percentages of IL-10-producing cells in the skin.

Acitretin, an enhancer of alpha-secretase expression, crosses the blood-brain barrier and is not eliminated by P-glycoprotein.

BACKGROUND: ADAM10 (a disintegrin and metalloproteinase 10) has been demonstrated to act as the main physiological α-secretase. Enzymatic activity of the α-secretase on the one hand prevents the formation of toxic Aß peptides and on the other hand promotes the secretion of a neurotrophic and neuroprotective amyloid precursor protein fragment (APPs-α) by cleaving the amyloid precursor protein within its Aß sequence. Enhancement of ADAM10's gene expression may therefore present a valuable therapeutic approach for the treatment of Alzheimer's disease (AD), where Aß peptides are severely involved in the pathogenesis. OBJECTIVE: In cell culture and in a transgenic mouse model of AD, retinoids led to increased ADAM10 expression and activity. We therefore endeavor to develop a clinical application of synthetic retinoids such as acitretin in AD. METHODS: The effect of synthetic retinoids on ADAM10 gene expression was analyzed by reporter gene assays in human neuroblastoma cell line SH-SY5Y. Penetrance of acitretin into the murine brain was analyzed by high-performance liquid chromatography. P-glycoprotein (P-gp) double-knockout mice with a deficiency in both isoforms, mdr1a and 1b, were used to analyze a possible role of P-gp-dependent efflux on acitretin distribution. RESULTS: Acitretin and tamibarotene are both potent activators of ADAM10 promoter activity. Acitretin crosses the murine blood-brain barrier and its level in the mouse brain is not reduced by P-gp. CONCLUSION: Synthetic retinoids and especially acitretin seem to be ideal candidates to establish an ADAM10-based AD treatment, and therefore have already entered first clinical trials.

Acitretin enhances the cytotoxic effect of 5-aminolevulinic acid photodynamic therapy on squamous cell carcinoma cells.

The efficacy of 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) on invasive cutaneous squamous cell carcinoma (cSCC) remains to be improved due to the limited penetration of this treatment. Previous study showed that acitretin and ALA-PDT had synergistic effect on cSCC, but whether acitretin can enhance the cytotoxic effect of ALA-PDT on cSCC is unclear. OBJECTIVE: To investigate whether acitretin can enhance the cytotoxic effect of ALA-PDT on SCL-1 cells, as well as the possible mechanism involved. METHODS: Inverted microscopy, trypan blue exclusion assay, and flow cytometry were used to studied the morphology, viability and apoptosis of SCL-1 cells treated with acitretin, ALA-PDT and acitretin followed by ALA-PDT treatment, respectively. Confocal microscopy was applied to detect the ROS formation of SCL-1 cells treated with acitretin of four different concentrations. The ROS formation of SCL-I cells treated with acitretin of four different concentrations followed by ALA-PDT treatment was detected using confocal microscopy and flow cytometry. RESULTS: SCL-1 cells exhibited a significant morphological alteration when treated with acitretin followed by ALA-PDT. The combination of acitretin and ALA-PDT induced a higher cell death rate and apoptosis than that with acitretin or ALA-PDT treatment alone. ROS could be induced when incubated with acitretin at a concentration of 6.4 × 10-4mg /mL or above. However, a higher level of ROS formation was observed when SCL-1 cells were treated with acitretin followed by ALA-PDT than that with ALA-PDT or acitretin alone. CONCLUSION: Acitretin can enhance the cytotoxic effect of ALA-PDT on SCL-1 cells, possibly via the ROS pathway.

Regulatory Effect of Adipose-Derived Mesenchymal Stem Cells and/ or Acitretin on Adam10 Gene in Alzheimer's Disease Rat Model.

BACKGROUND: Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by progressive cognitive deterioration. All recent therapeutic strategies tend to inhibit the generation of the Aß peptide. These approaches tend to mediate both α - and γ -secretases to undergo the nonamyloidogenic pathway. ADAM10 is the main α-secretase that cleaves APP, and it is regulated by the metabolic product of vitamin A (retinoic acid), which is being widely used recently in AD research as a target for treatment. Mesenchymal stem cells (MSCs) are also used recently as a promising regenerative therapy for AD. OBJECTIVES: The present study aimed to: (1) study the effect of MSCs with/without acitretin on the regulation of Adam10 gene expression in AlCl3-induced AD rat model, and (2) validate the hypothesis that AD is a time-dependent progressive disease that spreads spontaneously even after the stopping of exposure to AlCl3. METHODS: The experimental work has been designed to include three successive phases; AlCl3 induction phase (I), AlCl3 withdrawal phase (W), and therapeutic phase (T). Forty-five male albino Wistar rats were randomly divided into 2 main groups: the control (C) group (15 rats) and AD group (30 rats). The therapeutic potential of MSCs with/without acitretin has been evaluated at behavioral, physiological, molecular, and histopathological levels. RESULTS: Among the three therapeutic groups, combined administration of both MSC and acitretin showed the best compensatory effects on most of the measured parameters. CONCLUSION: The present study approved that AD is a time-dependent progressive disease which spreads spontaneously without more AlCl3 exposure.

IL-22 Downregulates Peptidylarginine Deiminase-1 in Human Keratinocytes: Adding Another Piece to the IL-22 Puzzle in Epidermal Barrier Formation.

Increased presence of IL-22+ cells in the skin is a characteristic finding in skin barrier defects, such as psoriasis and atopic dermatitis. However, mechanistic insight into effects of IL-22 on epidermal functioning is yet to be elucidated. One crucial step during epidermal differentiation is deimination or citrullination. Here, we show reduced levels of peptidylarginine deiminase 1, an enzyme that converts peptidylarginine into citrulline in lesional psoriatic skin. IL-22 signaling through the IL-22 receptor complex was found to suppress expression of peptidylarginine deiminase 1 in epidermal keratinocytes. Subsequently, total peptidylarginine deiminase activity and extent of protein deimination in keratinocytes treated with IL-22 were reduced together with a significant decrease in deimination of keratin 1 and FLG, both important for epidermal differentiation. Vitamin D and acitretin partly restored the peptidylarginine deiminase 1 defect caused by IL-22. Collectively, we show that IL-22 downregulates deimination, thus identifying a potential target for treatment of skin barrier defects.

Acitretin revisited.

Acitretin over the last 20 years has proven useful in a number of dermatologic diseases. Evidence of efficacy, side-effect profile, and approach to its use will be reviewed.