Experience With Bexarotene to Treat Cutaneous T-Cell Lymphomas: A Study of the Spanish Working Group of Cutaneous Lymphomas

BACKGROUND AND OBJECTIVES

Bexarotene has been approved to treat advanced stage cutaneous T-cell lymphomas (CTCL) since 1999. However, very few data have been published on its long-term safety and efficacy profile. The aim of this study is to determine the tolerability to bexarotene and outcomes by collecting the 2nd largest case series to date on its long-term use vs CTCL.

MATERIAL AND METHOD

This was a multicenter retrospective review of 216 patients with mycosis fungoides (174), or Sézary syndrome (42) on a 10-year course of bexarotene alone or in combinationwith other therapies at 19 tertiary referral teaching hospitals.

RESULTS

A total of 133 men (62%) and 83 women (38%) were included, with a mean age of 63.5 year (27-95). A total of 45% were on bexarotene monotherapy for the entire study period, 22% started on bexarotene but eventually received an additional therapy, 13% were on another treatment but eventually received bexarotene while the remaining 20% received a combination therapy since the beginning. The median course of treatment was 20.78 months (1-114); and the overall response rate, 70.3%. Complete and partial response rates were achieved in 26% and 45% of the patients, respectively. Treatment was well tolerated, being the most common toxicities hypertriglyceridemia (79%), hypercholesterolemia (71%), and hypothyroidism (52%). No treatment-related grade 5 adverse events were reported.

CONCLUSIONS

Our study confirms bexarotene is a safe and effective therapy for the long-term treatment of CTCL.

Experience With Bexarotene to Treat Cutaneous T-Cell Lymphomas: A Study of the Spanish Working Group of Cutaneous Lymphomas

BACKGROUND AND OBJECTIVES

Bexarotene has been approved to treat advanced stage cutaneous T-cell lymphomas (CTCL) since 1999. However, very few data have been published on its long-term safety and efficacy profile. The aim of this study is to determine the tolerability to bexarotene and outcomes by collecting the 2nd largest case series to date on its long-term use vs CTCL.

MATERIAL AND METHOD

This was a multicenter retrospective review of 216 patients with mycosis fungoides (174), or Sézary syndrome (42) on a 10-year course of bexarotene alone or in combination with other therapies at 19 tertiary referral teaching hospitals.

RESULTS

A total of 133 men (62%) and 83 women (38%) were included, with a mean age of 63.5 year (27-95). A total of 45% were on bexarotene monotherapy for the entire study period, 22% started on bexarotene but eventually received an additional therapy, 13% were on another treatment but eventually received bexarotene while the remaining 20% received a combination therapy since the beginning. The median course of treatment was 20.78 months (1-114); and the overall response rate, 70.3%. Complete and partial response rates were achieved in 26% and 45% of the patients, respectively. Treatment was well tolerated, being the most common toxicities hypertriglyceridemia (79%), hypercholesterolemia (71%), and hypothyroidism (52%). No treatment-related grade 5 adverse events were reported.

CONCLUSIONS

Our study confirms bexarotene is a safe and effective therapy for the long-term treatment of CTCL.

In silico bioavailability triggers applied to direct and indirect thyroid hormone disruptors

Among endocrine disruption, interference with the thyroid hormone (TH) regulation is of increasing concern. Respective compounds encode through their structural features both the potential for TH disruption, and the bioavailability mitigating the toxicological effect. The aim of this study is to provide a substructure-based screening-level QSAR (quantitative structure-activity relationship) that discriminates bioavailable TH disruptors from not bioavailable counterparts, covering both direct and indirect (retinoid- and AhR-mediated) modes of action. The QSAR has been derived from literature data for 1642 compounds, and takes into account Lipinski's rule-of-five and the brain/blood partition coefficient Kbrain/blood. For its validation, an external test set of 145 substances has been used. For 1787 compounds meeting the model application domain, the model yields only one false negative. The discussion addresses the mechanistic meaning of the bioavailability triggers molecular weight, H-bond donor and acceptor, hydrophobicity (log Kow), and the physicochemical properties underlying log Kbrain/blood. The model may serve as bioavailability-screening step within a decision support system for the predictive assessment of chemicals regarding their potential to disrupt thyroid hormone function in a direct or indirect manner.

Natural Retinol Analogs Potentiate the Effects of Retinal on Aged and Photodamaged Skin: Results from In Vitro to Clinical Studies

INTRODUCTION

Plants are a source of natural ingredients with retinol-like properties that can deliver anti-aging benefits without the side effects typically associated with retinoid use. We hypothesized that by combining two such analogs, bakuchiol (BAK) and Vigna aconitifolia extract (VAE), with the potent retinoid retinal (RAL), the anti-photoaging potential of RAL could be enhanced without compromising its skin irritation profile. The purpose of this study was to demonstrate that BAK and VAE potentiate the anti-photoaging activity of RAL.

METHODS

Gene expression profiling of full-thickness reconstructed skin was first used to examine the impact of BAK or VAE in combination with RAL on skin biology. Next, the irritative potential of this combination, and its capacity to reverse key signs of photoaging in an ex vivo model was assessed. Finally, a proof-of-concept open label clinical study was performed to evaluate the anti-photoaging capacity and skin compatibility of a cosmetic formulation (tri-retinoid complex; 3RC) containing this complex in combination with other well characterized anti-photoaging ingredients.

RESULTS

In vitro profiling suggested that combining 0.1% RAL with BAK or VAE potentiates the effect of RAL on keratinocyte differentiation and skin barrier function without affecting its skin irritation profile. When formulated with other anti-photoaging ingredients, such as niacinamide and melatonin, 3RC reversed ultraviolet radiation-induced deficits in structural components of the dermal extracellular matrix, including hyaluronic acid and collagen. In vivo, it led to a reversal of clinical signs of age and photodamage, with statistically significant improvement to skin firmness (+5.6%), skin elasticity (+13.9%), wrinkle count (-43.2%), and skin tone homogeneity (+7.0%), observed within 28 days of once nightly use. Notably, the number of crow's feet wrinkles was reduced in 100% of subjects. Furthermore, 3RC was very well tolerated.

CONCLUSION

These data suggest that 3RC is a highly effective and well-tolerated treatment for photoaging.

Prokaryotic expression and characterization of artificial self-sufficient CYP120A monooxygenases

Cytochrome P450 monooxygenases CYP120As are the unique non-membrane P450s, which are extensively involved in retinoid biodegradation. As the O-functionalized 1,3,3-trimethylcyclohex-1-ene moiety exists in many bioactive compounds which could only be catalyzed by Class II P450s, exploration of the catalytic repertoire of CYP120As is therefore highly attractive. However, up to date, only one bacteriogenic candidate (CYP120A1) was demonstrated for the hydroxylation of C16 and C17 of retinoic acid, by utilizing the integral membrane protein cytochrome P450 reductase redox partner for the electron transfer. Herein, we provided an efficient prokaryotic functional expression system of CYP120As in E. coli by expression of the CYP120A1 coupled with several reductase partners. Fusion redox partners to the C-terminal of the heme-domain are also working on other CYP120A members. Among them, the fusion protein of CYP120A29 and FAD/FMN reductase from Bacillus megaterium P450BM3 (CYP101A2) showed the highest expression level. Based on the available translational fusion systems, the regioselectivity and the substrate scope of the CYP120As have also been explored. This work represents a good starting point for further expanding the catalytic potential of CYP120 family. KEY POINTS: • Characterization of CYP120As in E. coli is firstly achieved by constructing fusion proteins. • The feasibility of three P450 reductase domains to CYP120As was evaluated. • Hydroxylated products of retinoic acid by six CYP120As were sorted and analyzed.

Influence of Season on Efficacy and Tolerability of Tazarotene 0.045% Lotion for the Treatment of Acne

Objective

The condition of the skin can vary due to weather fluctuations. Therefore, this post-hoc analysis evaluated efficacy and safety of tazarotene 0.045% lotion in warmer versus colder months.

Methods

In two Phase III, double-blind, 12-week studies, participants aged nine years or older with moderate-to-severe acne were randomized 1:1 to once-daily tazarotene or vehicle lotion. The pooled population (N=1,614) was stratified by randomization date (warmer=May to September; colder=October to April). Evaluations included inflammatory/noninflammatory lesion counts, treatment success, adverse events, and safety/tolerability.

Results

Tazarotene 0.045% lotion was similarly efficacious over colder and warmer months. Compared with vehicle, tazarotene demonstrated significantly greater least-squares mean absolute reductions from baseline to Week 12 in inflammatory (colder/warmer tazarotene vs. vehicle: -16.6/-15.8 vs. -13.2/-12.9) and noninflammatory lesions (-23.2/-22.6 vs. -17.5/-15.1); treatment success rates were also significantly higher (30.1/30.8% vs. 18.2/17.6%) (P<0.001, all). No strong seasonal trends in safety were observed, though tazarotene led to slightly more discontinuations (3.4% vs. 1.9%) and related adverse events (12.0% vs. 10.3%) in colder versus warmer months. Transient increases in scaling, erythema, and itching at Weeks 2 to 8 of tazarotene treatment were slightly higher in colder versus warmer months but returned to baseline/improved by Week 12.

Limitations

Geographical variation across study sites can lead to varying temperatures and humidity within the same months.

Conclusion

Tazarotene 0.045% lotion was efficacious and well tolerated for acne treatment, regardless of season. Year-round tolerability of tazarotene 0.045% lotion may be due to its lower tazarotene concentration and polymeric emulsion technology, which simultaneously delivers moisturizers/humectants/emollients to skin.

Phase I trial of intravenous fenretinide (4-HPR) plus safingol in advanced malignancies

PURPOSE

Fenretinide (4-HPR) is a synthetic retinoid that induces cytotoxicity through dihydroceramide production. Safingol, a stereochemical-variant dihydroceramide precursor, exhibits synergistic effects when administered with fenretinide in preclinical studies. We conducted a phase 1 dose-escalation clinical trial of this combination.

METHODS

Fenretinide was administered as a 600 mg/m2 24-h infusion on Day 1 of a 21-day cycle followed by 900 mg/m2/day on Days 2 and 3. Safingol was concurrently administered as a 48-h infusion on Day 1 and 2 using 3 + 3 dose escalation. Primary endpoints were safety and maximum tolerated dose (MTD). Secondary endpoints included pharmacokinetics and efficacy.

RESULTS

A total of 16 patients were enrolled (mean age 63 years, 50% female, median three prior lines of therapy), including 15 patients with refractory solid tumors and one with non-Hodgkin lymphoma. The median number of treatment cycles received was 2 (range 2-6). The most common adverse event (AE) was hypertriglyceridemia (88%; 38% ≥ Grade 3), attributed to the fenretinide intralipid infusion vehicle. Other treatment-related AEs occurring in ≥ 20% of patients included anemia, hypocalcemia, hypoalbuminemia, and hyponatremia. At safingol dose 420 mg/m2, one patient had a dose-limiting toxicity of grade 3 troponinemia and grade 4 myocarditis. Due to limited safingol supply, enrollment was halted at this dose level. Fenretinide and safingol pharmacokinetic profiles resembled those observed in monotherapy trials. Best radiographic response was stable disease (n = 2).

CONCLUSION

Combination fenretinide plus safingol commonly causes hypertriglyceridemia and may be associated with cardiac events at higher safingol levels. Minimal activity in refractory solid tumors was observed.

TRIAL REGISTRATION NUMBER

NCT01553071 (3.13.2012).

Retinoid-associated myopia in dermatologic patients: a systematic review

Systemic retinoids are among the most prescribed drugs in dermatology, thanks to their activity as proliferation modulators and keratinization normalizers. Common side effects such as blood lipid disorders, xerosis and photosensitivity are well established and usually dose dependent. Conversely, retinoid-associated ocular disturbances have been reported, yet with differences in terms of frequency and manifestations. As data regarding a potential correlation with refractive errors are heterogenous and have not been previously thoroughly addressed, we performed a systematic review of the literature with the aim of comprehensively evaluating the current evidence regarding retinoid-associated myopia in dermatologic patients.

Trifarotene 0.005% Cream in the Treatment of Facial and Truncal Acne Vulgaris in Patients with Skin of Color: a Case Series

The clinical appearance of acne vulgaris (AV) and the response to therapeutic agents may vary in people with skin of color (SoC) compared with those with lighter skin types. Given the heightened potential for postinflammatory hyperpigmentation and keloid development, effective and timely AV treatment in patients with SoC is especially important. However, these patients are frequently underrepresented in clinical trials, and SoC photographs are generally underrepresented in dermatology. Trifarotene 0.005% cream is a retinoid approved for the once-daily topical treatment of AV, and was studied in large-scale clinical trials that assessed the treatment of AV on both the face and trunk. For severe AV, a topical retinoid may be used in combination with an oral antibiotic, such as doxycycline. Five subjects covering Fitzpatrick skin phototypes III, IV, V, and VI were selected from two larger studies to visually demonstrate treatment of clinically diagnosed AV with trifarotene 0.005% cream. Two subjects received 24 weeks of treatment with trifarotene 0.005% cream for moderate AV on the face and trunk, while three subjects received 12 weeks of treatment with trifarotene 0.005% cream in association with 120 mg oral doxycycline with modified polymer coating for severe facial AV. This case series supports the favorable efficacy and safety of facial and truncal AV treatment with trifarotene 0.005% cream, with or without oral doxycycline, in subjects with SoC (phototypes III–VI).

Spatiotemporal variations of retinoic acids and their metabolites in the marine environment of Hong Kong

Excessive intake of retinoic acids (RAs) and the oxidative metabolites, 4-oxo-RAs, can lead to abnormal morphological development in animals. This study investigated spatiotemporal variations of concentrations and compositions of these compounds in Hong Kong's seawater and during algal blooms. Total concentrations of the studied compounds in seawater were up to 0.790 and 0.427 ng/L in dry and wet seasons, respectively, though no significant seasonal variation was observed. Spatially, the Deep Bay Water Control Zone was the most enriched area with the studied compounds owing to its semi-enclosed nature and influence from the Pearl River discharge. During algal blooms, the studied compounds were detected up to 4.74 ng/L. Based on calculated risk quotients, the ecological risk of the studied compounds to Hong Kong's marine ecosystems was low. Nevertheless, the occurrence and distribution of these chemicals in the marine environment should be closely monitored where algal blooms frequently occur.

Acneiform eruptions with combination targeted cancer therapy in colorectal cancer patients

PURPOSE

Epidermal growth factor receptor inhibitors (EGFRI) can be used with pathway inhibitors, including mitogen-activated protein kinase kinase inhibitors (MEKIs), BRAF inhibitors (BRAFIs), and checkpoint inhibitors such as programmed death-ligand 1 (PD-L1) and programmed cell death protein 1 (PD-1) to treat colorectal cancer. These can precipitate treatment-resistant acneiform eruptions, prompting dose modification or discontinuation. Predicting the likelihood of severe rash development and crafting effective treatments may promote adherence to life-saving chemotherapy.

METHODS

An Institutional Review Board-approved retrospective chart review of patients with colorectal cancer treated with EGFRI or MEKI in combination with HER2, BRAF, PI3K, or checkpoint inhibitors between January 1, 2016, and January 1, 2020, was performed. Surrogates for rash severity were investigated, including lower extremity involvement, utilization of oral steroids or retinoids, dose modification, and incidence of superinfection.

RESULTS

Of 122 patients treated with combination therapy, 105 developed a rash, and 87 developed an acneiform eruption. Common combinations included MEKI/PD-LI, EGFRI/MEKI, and MEKI/PD-1I. Patients treated with EGFRI/MEKI developed the most severe rashes (p = 0.02). Lower extremity involvement was more frequent with EGFRI/MEKI compared to alternative combinations (p = 0.05). Drug holiday correlated with all rash severity surrogates, including rash grade, lower extremity involvement, oral steroid or retinoid use, and incidence of superinfection. Use of oral steroids or retinoids was associated with development of superinfection (p = 0.002). Prophylactic tetracycline use did not impact rash severity or rash incidence.

CONCLUSION

This is the first descriptive analysis to characterize acneiform eruptions for patients with colorectal cancer on combination cancer therapy. Approximately 85% of patients developed a cutaneous toxicity with what appears to be synergistic effects of EGFRI and MEKI combination therapy causing the most severe eruptions. Superinfection rate correlated to systemic therapy use beyond oral tetracyclines. Further investigation into the utility of prophylactic oral tetracyclines in this population is needed.

Structural development of silicon-containing retinoids: structure-activity relationship study of the hydrophobic pharmacophore of retinobenzoic acids using silyl functionalities

We designed and synthesized a series of retinobenzoic acids bearing various silyl functionalities in order to explore in detail the structure-activity relationship (SAR) at the hydrophobic moiety of retinoids. Among the synthesized compounds, 24c bearing a t -butyldimethylsilyl (TBS) group at the hydrophobic site exhibited potent retinoid activity comparable to that of the lead compound Am555S ( 4 ). Compound 24c exhibited transcription-promoting activity towards all three subtypes of retinoic acid receptor (RAR), but showed the highest activity towards RARγ, in contrast to the high RARα-selectivity of Am80 ( 3 ) and Am555S ( 4 ). The SARs presented here should be helpful in the development of subtype-selective retinoids, and in particular 24c might be a promising lead compound for new RARγ ligands.

Rethinking Breast Cancer Chemoprevention: Technological Advantages and Enhanced Performance of a Nanoethosomal-Based Hydrogel for Topical Administration of Fenretinide

Herein, we developed an ethosomal hydrogel based on three types of ethosomes: simple, mixed (surfactant-based micelles and lipid vesicles) or binary (comprising two type of alcohols). Ethanol injection was employed for vesicles preparation, and sodium alginate, as gelling agent. We purposed the local-transdermal administration of the off-the-shelf retinoid fenretinide (FENR) for chemoprevention of breast cancer. Rheograms and flow index values for alginate dispersion (without ethosomes) and hydrogels containing simple, mixed or binary ethosomes suggested pseudoplastic behavior. An increase in the apparent viscosity was observed upon ethosome incorporation. The ethosomal hydrogel displayed increased bioadhesion compared to the alginate dispersion, suggesting that the lipid vesicles contribute to the gelling and bioadhesion processes. In the Hen's Egg Test-Chorioallantoic Membrane model, few spots of lysis and hemorrhage were observed for formulations containing simple (score of 2) and mixed vesicles (score 4), but not for the hydrogel based on the binary system, indicating its lower irritation potential. The binary ethosomal hydrogel provided a slower FENR in vitro release and delivered 2.6-fold less drug into viable skin layers compared to the ethosome dispersion, supporting the ability of the gel matrix to slow down drug release. The ethosomal hydrogel decreased by ~ five-fold the IC₅₀ values of FENR in MCF-7 cells. In conclusion, binary ethosomal gels presented technological advantages, provided sustained drug release and skin penetration, and did not preclude drug cytotoxic effects, supporting their potential applicability as topical chemopreventive systems.

A Bioluminescence Reporter Assay for Retinoic Acid Control of Translation of the GluR1 Subunit of the AMPA Glutamate Receptor

The present protocol describes a bioluminescence reporter assay developed to quantify the ability of synthetic agonists of retinoic acid receptors (RARs) to activate glutamate receptor subunit 1 (GluR1) translation. The reporter assay uses firefly luciferase under the control of the GluR1 5' untranslated region (5' UTR) which is bound by RARs to regulate its translation. This method is used to demonstrate the role of RARα in retinoic acid regulation of GluR1 translation. This method may also be used to screen drugs that influence RAR induction of GluR1 translation as an important mechanism controlling learning and memory in the brain.

The phosphorylated retinoid X receptor-α promotes diethylnitrosamine-induced hepatocarcinogenesis in mice through the activation of β-catenin signaling pathway

Previous studies have shown that phosphorylation of the retinoid X receptor-α (RXRα) is associated with the development of hepatocellular carcinoma (HCC). However, these findings were revealed using HCC cell lines that express phosphorylated-RXRα (p-RXRα) proteins; therefore, it remains unclear whether p-RXRα affects hepatocarcinogenesis in vivo. Therefore, to investigate the biological function of p-RXRα in vivo, we developed a doxycycline-inducible ES cell line and transgenic mouse, both of which overexpress the phosphomimetic mutant form of RXRα, T82D/S260D, in a doxycycline-dependent manner. We found that the development of liver tumors, especially high-grade adenoma and HCC, was enhanced in diethylnitrosamine (DEN)-induced T82D/S260D-inducible mice. Moreover, the increased incidence of liver tumors in the transgenic mice was attributable to the promotion of cell cycle progression. Interestingly, the expression of β-catenin protein and its target gene cyclin D1 was elevated in the liver tumors of DEN-treated T82D/S260D-inducible mice, concurrent with increased cytoplasmic and nuclear β-catenin protein expression, indicating its stabilization and transcriptional activation. These results indicate that p-RXRα promotes DEN-induced hepatocarcinogenesis in mice through the activation of the β-catenin signaling pathway, suggesting that p-RXRα may serve as a possible therapeutic target for HCC.

An investigation into the biological effects of indirect potable reuse water using zebrafish embryos

Advanced treatment technologies are being assessed as a proactive measure to assist with the transformation of treated wastewater into a source of water for potable water production. We investigated the biological effects along an advanced water treatment pilot plant, using zebrafish embryos throughout early development. The study compared phenotypic observations with global transcriptome responses, enabling us to keep an open mind about the chemicals that might influence the biological activity. There was no evidence of acute toxicity at any treatment stage, but skeletal, cardiovascular and pigmentation changes occurred in a small proportion of embryos along the treatment process, and in a tap water; not detected in the aquarium water control. Reverse osmosis (RO) reduced the concentration of measured chemical contaminants in the water the most, while eliminating the occurrence of abnormalities detected in fish embryos. Conversely, advanced oxidation reversed the benefits of RO treatment by increasing the frequency of teratogenic and sub-lethal abnormalities seen. Using the molecular responses of zebrafish embryos to different IPR water, we report the bioactivity within the water at different stages of advanced treatment and associate these to perturbed biological functions. Transcriptomic analysis revealed alterations to the retinoid system, which was consistent with the observed teratogenic effects. Changes to tryptophan metabolism (associated with the production of melatonin required for the control of normal circadian rhythms) and somatolactin-beta (associated with normal pigmentation in fish) were also found. We show that underexplored forms of biological activity occur in treated wastewater effluent, and/or may be created depending on the type of advanced treatment process used. By integrating the available analytical chemistry we highlight chemical groups associated to this response. Our study shows that more detailed and in-depth characterisation of chemicals and biological pathways associated with advanced treatment water systems are needed to mitigate possible risks to downstream organisms.

Sulfarotene, a synthetic retinoid, overcomes stemness and sorafenib resistance of hepatocellular carcinoma via suppressing SOS2-RAS pathway

BACKGROUND

Recurrent hepatocellular carcinoma (HCC) shows strong resistance to sorafenib, and the tumor-repopulating cells (TRCs) with cancer stem cell-like properties are considered a driver for its high recurrent rate and drug resistance.

METHODS

Suppression of TRCs may thus be an effective therapeutic strategy for treating this fatal disease. We evaluated the pharmacology and mechanism of sulfarotene, a new type of synthetic retinoid, on the cancer stem cell-like properties of HCC TRCs, and assessed its preclinical efficacy in models of HCC patient-derived xenografts (PDXs).

RESULTS

Sulfarotene selectively inhibited the growth of HCC TRCs in vitro and significantly deterred TRC-mediated tumor formation and lung metastasis in vivo without apparent toxicity, with an IC₅₀ superior to that of acyclic retinoid and sorafenib, to which the recurrent HCC exhibits significant resistance at advanced stage. Sulfarotene promoted the expression and activation of RARα, which down-regulated SOS2, a key signal mediator associated with RAS activation and signal transduction involved in multiple downstream pathways. Moreover, sulfarotene selectively inhibited tumorigenesis of HCC PDXs with high expression for SOS2.

CONCLUSIONS

Our study identified sulfarotene as a selective inhibitor for the TRCs of HCC, which targets a novel RARα-SOS2-RAS signal nexus, shedding light on a new, promising strategy of target therapy for advanced liver cancer.

Fixed-Combination Halobetasol Propionate and Tazarotene in the Treatment of Psoriasis: Narrative Review of Mechanisms of Action and Therapeutic Benefits

Psoriasis is a lifelong disease associated with cycles of remission and relapse. Topical treatments are the front line of psoriasis therapy for most patients and have antiproliferative, anti-inflammatory, and immunosuppressive mechanisms of action. Novel fixed-dose combinations of topical therapeutic agents are becoming increasingly available, leveraging multiple mechanisms of action to improve safety and efficacy with formulations that are easier to use and may allow for the use of lower doses of active ingredients. A fixed-combination lotion containing the potent-to-superpotent corticosteroid halobetasol propionate (HP) and the retinoid tazarotene (HP 0.01%/TAZ 0.045%) was recently developed using polymeric emulsion technology. This new formulation technology allows for more uniform and efficient delivery of the active ingredients at lower doses than conventional monotherapy formulations of either ingredient while providing enhanced hydration and moisturization. This review provides an up-to-date overview of the therapeutic mechanisms of action of HP and TAZ, the rationale behind the development of HP 0.01%/TAZ 0.045% lotion, and clinical trials data on the efficacy, safety and tolerability, and maintenance of therapeutic effect with HP 0.01%/TAZ 0.045% lotion in the treatment of moderate-to-severe plaque psoriasis.

Endocrine, metabolic and apical effects of in utero and lactational exposure to non-dioxin-like 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180): A postnatal follow-up study in rats

PCB 180 is a persistent and abundant non-dioxin-like PCB (NDL-PCB). We determined the developmental toxicity profile of ultrapure PCB 180 in developing offspring following in utero and lactational exposure with the focus on endocrine, metabolic and retinoid system alterations. Pregnant rats were given total doses of 0, 10, 30, 100, 300 or 1000 mg PCB 180/kg bw on gestational days 7-10 by oral gavage, and the offspring were sampled on postnatal days (PND) 7, 35 and 84. Decreased serum testosterone and triiodothyronine concentrations on PND 84, altered liver retinoid levels, increased liver weights and induced 7-pentoxyresorufin O-dealkylase (PROD) activity were the sensitive effects used for margin of exposure (MoE) calculations. Liver weights were increased together with induction of the metabolizing enzymes cytochrome P450 (CYP) 2B1, CYP3A1, and CYP1A1. Less sensitive effects included decreased serum estradiol and increased luteinizing hormone levels in females, decreased prostate and seminal vesicle weight and increased pituitary weight in males, increased cortical bone area and thickness of tibial diaphysis in females and decreased cortical bone mineral density in males. Developmental toxicity profiles were partly different in male and female offspring, males being more sensitive to increased liver weight, PROD induction and decreased thyroxine concentrations. MoE assessment indicated that the 95^th percentile of current maternal PCB 180 concentrations do not exceed the estimated tolerable human lipid-based PCB 180 concentration. Although PCB 180 is much less potent than dioxin-like compounds, it shares several toxicological targets suggesting a potential for interactions.

Tazarotene 0.045% Lotion for Moderate-to-Severe Acne in Male and Female Participants: A Phase II Post-hoc Analysis

CLINICAL TRIALS ID: NCT02938494 BACKGROUND: In a Phase II study, tazarotene 0.045% lotion was statistically superior to vehicle and comparable to tazarotene 0.1% cream in reducing acne lesions, with fewer treatment-related adverse events (TEAEs) than the cream. OBJECTIVE: We analyzed data from the aforementioned study post-hoc to evaluate the effects of sex on treatment outcomes. METHODS: Participants aged 12 years or older with moderate-to-severe acne were randomized to tazarotene (0.045% lotion or 0.1% cream) or vehicle (lotion or cream) for 12 weeks of double-blind treatment. Outcomes analyzed in male and female subgroups included changes from baseline in inflammatory/noninflammatory lesions and TEAEs. RESULTS: In the intent-to-treat population (94 males and 116 females), reductions in lesion count were greater with tazarotene (lotion or cream) than with vehicle. In participants receiving tazarotene 0.045% lotion, the least-squares mean percent changes from baseline to Week 12 were greater in females than males, but the differences were not statistically significant (inflammatory [-70.3% vs. -56.2%]; noninflammatory [-60.0% vs. -53.2%]). In both females and males, the TEAE incidence was lower with tazarotene 0.045% lotion than 0.1% cream. CONCLUSION: Tazarotene 0.045% lotion substantially reduced acne lesions in both female and male participants. This newest tazarotene formulation might benefit patients who cannot tolerate older formulations or other topical retinoids. Given the relatively small size of this study, however, the results of this post-hoc analysis are intended to be exploratory in nature.

SCF Improves In Vitro Differentiation of SSCs Through Transcriptionally Up-regulating PRTM1, STRA8, c-KIT, PIWIL2, and OCT4 Genes

Several lines of evidence strongly suggest that retinoic acid (RA) and stem cell factor (SCF)/c-Kit signal transduction pathways are involved in the differentiation of spermatogonial stem cells (SSCs). This study was aimed to investigate the effect of RA and SCF on in vitro differentiation of SSCs via evaluation of the mRNA expression of meiosis-specific genes in cultured testicular tissues. Testicular tissue samples were obtained from bilaterally vasectomized rats and also healthy adult rats and then were cultured for 25, 30, and 35 days on different conditions. The cultured testicular pieces were sectioned and stained with PAS to histological analysis. The total RNA was extracted from cultured testicular samples, and the expression of ACR, PRTM1, SYCP3, STRA8, c-KIT, PIWIL2, and OCT4 genes at mRNA level was quantified using real-time polymerase chain reaction (qPCR) procedure. After 1-month surgery, bilateral testicular weight showed a significant decrease in vasectomized adult rats compared with healthy adult rats (P < 0.05). Reduction in the diameter of the seminiferous tubules and depletion of advanced germinal elements in vasectomized rats compared with healthy adult rats were also observed. Our findings also demonstrated that the mRNA expression level of PRTM1, STRA8, c-KIT, PIWIL2, and OCT4 genes in cultured testicular tissues significantly up-regulated in experimental group II compared with the control group (P < 0.001). Our findings lead us to conclude that SCF improves in vitro differentiation of SSCs in the OA rats, at least partially, by transcriptionally upregulating PRTM1, STRA8, c-KIT, PIWIL2, and OCT4 genes.

A phase I study of intravenous fenretinide (4-HPR) for patients with malignant solid tumors

BACKGROUND

Fenretinide is a synthetic retinoid that can induce cytotoxicity by several mechanisms. Achieving effective systemic exposure with oral formulations has been challenging. An intravenous lipid emulsion fenretinide formulation was developed to overcome this barrier. We conducted a study to establish the maximum tolerated dose (MTD), preliminary efficacy, and pharmacokinetics of intravenous lipid emulsion fenretinide in patients with advanced solid tumors.

METHODS

Twenty-three patients with advanced solid tumors refractory to standard treatments received fenretinide as a continuous infusion for five consecutive days in 21-day cycles. Five different dose cohorts were evaluated between doses of 905 mg/m² and 1414 mg/m² per day using a 3 + 3 dose escalation design. A priming dose of 600 mg/m² on day 1 was introduced in an attempt to address the asymptomatic serum triglyceride elevations related to the lipid emulsion.

RESULTS

The treatment-related adverse events occurring in ≥ 20% of patients were anemia, hypertriglyceridemia, fatigue, aspartate aminotransferase (AST)/alanine aminotransferase (ALT) increase, thrombocytopenia, bilirubin increase, and dry skin. Five evaluable patients had stable disease as best response, and no patients had objective responses. Plasma steady-state concentrations of the active metabolite were significantly higher than with previous capsule formulations.

CONCLUSION

Fenretinide emulsion intravenous infusion had a manageable safety profile and achieved higher plasma steady-state concentrations of the active metabolite compared to previous capsule formulations. Single-agent activity was minimal but combinatorial approaches are under evaluation.

COVID-19: Endogenous Retinoic Acid Theory and Retinoic Acid Depletion Syndrome

This study presents two new concepts and definitions to the medical literature. One of those is "endogenous retinoic acid theory" and the other "retinoic acid depletion syndrome". A new classification will be provided for the immune system: "retinoic acid-dependent component" and "retinoic acid non-dependent component". If this theory is verified, all the diseases where the retinoic acid metabolism is defective and retinoic acid levels are low will be identified and new approaches will be developed fortreating such diseases. When the need for retinoic acids increases, such as acute infection, high fever, severe catabolic process, or chronic antigenic stimulation, cytochrome oxidase enzymes are inhibited by drugs or internal mechanisms. Metabolism and excretion of retinoic acids stored in the liver are prevented. In this way, retinoic acid levels in the blood are raised to therapeutic levels. This is called "Endogenous Retinoic Acid Theory". Retinoic acids also manage their metabolism through feedback mechanisms. Despite compensatory mechanisms, causes such as high fever, serious catabolic process and excessively large viral genome (SARS-CoV-2), excessive use of RIG-I and Type I interferon synthesis pathway using retinoic acid causes emptying of retinoic acid stores. As a result, the RIG-I pathway becomes ineffective, Type I IFN synthesis stops, and the congenital immune system collapses. Then the immune mechanism passes to TLR3, TLR7, TLR8, TLR9, MDA5 and UPS pathways in the monocyte, macrophage, neutrophil and dendritic cells of the adaptive immune defense system that do not require retinoic acid. This leads to excessive TNFα and cytokine discharge from the pathway. With the depletion of retinoic acid stores as a result of this overuse, the immune defense mechanism switches from the congenital immune system to the adaptive immune system, where retinoic acids cannot be used. As a result of this depletion of retinoic acids, the shift of the immune system to the NFκB arm, which causes excessive cytokine release, is called "retinoic acid depletion syndrome". COVID-19 and previously defined sepsis, SIRS and ARDS are each retinoic acid depletion syndrome. We claim that retinoic acid metabolism is defective in most inflammatory diseases, particularly COVID-19 (cytokine storm) sepsis, SIRS and ARDS. Finding a solution to this mechanism will bring a new perspective and treatment approach to such diseases.

Context-Dependent Role of miR-124 in Retinoic Acid-Induced Growth Cone Attraction of Regenerating Motorneurons

During development and regeneration, growth cones at the tips of extending axons navigate through a complex environment to establish accurate connections with appropriate targets. Growth cones can respond rapidly to classical and non-classical guidance cues in their environment, often requiring local protein synthesis. In vertebrate growth cones, local protein synthesis in response to classical cues can require regulation by microRNAs (miRNAs), a class of small, conserved, non-coding RNAs that post-transcriptionally regulate gene expression. However, less is known of how miRNAs mediate growth cone responses to non-classical cues (such as retinoic acid (RA)), specifically in invertebrates. Here, we utilized adult regenerating invertebrate motorneurons to study miRNA regulation of growth cone attraction to RA, shown to require local protein synthesis. In situ hybridization revealed the presence of miR-124 in growth cones of regenerating ciliary motorneurons of the mollusc Lymnaea stagnalis. Changes in the spatiotemporal distribution of miR-124 occurred following application of RA, and dysregulation of miR-124 (with mimic injection), disrupted RA-induced growth cone turning in a time-dependent manner. This behavioural regulation by miR-124 was altered when the neurite was transected, and the growth cone completely separated from the soma. miR-124 did not, however, appear to be involved in growth cone attraction to serotonin, a response independent of local protein synthesis. Finally, we provide evidence that a downstream effector of RhoGTPases, ROCK, is a potential target of miR-124 during RA-induced growth cone responses. These data advance our current understanding of how microRNAs might mediate cue- and context-dependent behaviours during axon guidance.

Development of Selective TGR5 Ligands Based on the 5,6,7,8-Tetrahydro-5,5,8,8-tetramethylnaphthalene Skeleton

TGR5, a G-protein-coupled receptor (GPCR), plays an important role in several physiological functions. TGR5 activation through bile acids induces an increase in energy expenditure. Therefore, synthetic TGR5 ligands could be useful for the treatment of obesity or dyslipidemia. In this study, we designed and synthesized a set of TGR5 ligands with a 5,6,7,8-tetrahydro-5,5,8,8-tetramethylnaphthalene (TMN) skeleton, and evaluated their TGR5 agonistic activity. We also investigated the selectivity of the synthesized compounds for TGR5 relative to the farnesoid X receptor (FXR) and retinoic acid receptor (RAR). Our results show that compound 4 b [N-(2-chlorophenyl)-5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenecarboxamide] exhibited potent TGR5 agonist activity with an IC₅₀ value of 8.4 nM without significant cytotoxicity. In addition, compound 4 b showed only slight agonistic activity toward FXR and RAR at 1 μM treatment. These data indicate that compound 4 b is a selective TGR5 agonist, and could be a promising therapeutic agent for dyslipidemia.

A Split-face, Controlled Study to Assess the Compatibility of Tretinoin 0.05% Acne Lotion with Facial Foundation Makeup

OBJECTIVE: This study was conducted to assess compatibility of tretinoin 0.05% acne lotion with foundation makeup. DESIGN: This was a single-center, evaluator-blinded, randomized, controlled clinical trial. Participants were randomized to apply tretinoin 0.05% lotion to either the right or left side of the face before applying full-face foundation makeup. SETTING: Participants were enrolled at a single center in the United States. PARTICIPANTS: Female individuals aged 18 to 50 years who used facial foundation makeup ≥5 days per week were included. MEASUREMENTS: Investigator-assessed grading for foundation coverage and participant evaluations of makeup appearance were conducted at post-makeup application (Post-Makeup) and Hour 6 (6H) timepoints. Antera 3D® images were taken for skin texture roughness analysis and tolerability evaluations were performed at baseline, post-tretinoin application, Post-Makeup, and 6H timepoints. RESULTS: A total of 30 participants were enrolled and 29 completed the study. There were no significant differences between tretinoin treated and untreated sides for any outcomes of investigator-assessed grading of foundation (percentage coverage, blotchiness, overall coverage, skin tone evenness, visual smoothness). There was a small but statistically significant worsening in percent coverage at 6H versus Post-Makeup on the untreated side, but not the treated side. As rated by participants, even/full coverage and skin smoothness were significantly better on the tretinoin-lotion treated versus the untreated side. Three-dimensional imaging showed there were no significant differences in skin roughness between the treated and untreated sides. Participants reported overall satisfaction with the tretinoin lotion-treated side. CONCLUSION: Tretinoin 0.05% lotion did not interfere with facial makeup application or wearability and was well tolerated.

The Need to Consider Context in the Evaluation of Anti-infectious and Immunomodulatory Effects of Vitamin A and its Derivatives

Vitamin A and its derivatives (retinoids) act as potent regulators in many aspects of mammalian reproduction, development, repair, and maintenance of differentiated tissue functioning. Unlike other vitamins, Vitamin A and retinoids, which have hormonal actions, present significant toxicity, which plays roles in clinically relevant situations, such as hypervitaminosis A and retinoic acid ("differentiation") syndrome. Although clinical presentation is conspicuous in states of insufficient or excessive Vitamin A and retinoid concentration, equally relevant effects on host resistance to specific infectious agents, and in the general maintenance of immune homeostasis, may go unnoticed, because their expression requires either pathogen exposure or the presence of inflammatory co-morbidities. There is a vast literature on the roles played by retinoids in the maintenance of a tolerogenic, noninflammatory environment in the gut mucosa, which is considered by many investigators representative of a general role played by retinoids as anti-inflammatory hormones elsewhere. However, in the gut mucosa itself, as well as in the bone marrow and inflammatory sites, context determines whether one observes an anti-inflammatory or proinflammatory action of retinoids. Both interactions between specialized cell populations, and interactions between retinoids and other classes of mediators/regulators, such as cytokines and glucocorticoid hormones, must be considered as important factors contributing to this overall context. We review evidence from recent studies on mucosal immunity, granulocyte biology and respiratory allergy models, highlighting the relevance of these variables as well as their possible contributions to the observed outcomes.

Subject Satisfaction with Trifarotene 50 μg/g Cream in the Treatment of Facial and Truncal Acne Vulgaris: A Case Series

There is a paucity of literature covering patient-reported outcomes of treatments for truncal acne. Trifarotene 50 μg/g cream is a novel retinoid molecule approved for once-daily topical treatment of facial and truncal acne vulgaris. As physicians are starting to gain real-world experience with this retinoid treatment, their access to reporting from the patient’s perspective provides a valuable adjunct to the pivotal studies. We report a case series of three subjects with moderate facial and truncal acne treated with trifarotene 50 μg/g cream on the face, shoulders, upper back and upper anterior chest for 12 weeks and evaluated by satisfaction questionnaires. This case series illustrating the treatment of facial and truncal acne with trifarotene 50 μg/g cream, in the form of real-world data, describes high overall satisfaction and excellent tolerability to support the use of this new retinoid molecule in the treatment of acne vulgaris on both the face and trunk.

Design of synthetic retinoids

This chapter has been conceived as an introductory text to aid in the understanding of the key design strategies for the development of synthetic analogs of endogenous retinoids as ligands for the retinoic acid receptors (RARs) and retinoid X receptors (RXRs). The structure and binding characteristics of the endogenous retinoids are first explained to put the main chemical design challenges in context. Existing biochemical and structural data is then used to describe the guiding principles used to develop agonists and antagonists of the RARs and RXRs. In light of the increasing proliferation of biophysical methods that employ fluorescence measurements or molecular tags, we also examine the application of retinoids as probes and the chemical principles required to develop these tools.

Analysis of vitamin A and retinoids in biological matrices

Vitamin A signaling pathways are predominantly driven by the cellular concentrations of all-trans-retinoic acid (atRA), as the main mechanism of retinoid signaling is via activation of retinoic acid receptors. atRA concentrations are in turn controlled by the storage of vitamin A and enzymatic processes that synthesize and clear atRA. This has resulted in the need for robust and highly specific analytical methods to accurately quantify retinoids in diverse biological matrices. Tissue-specific differences in both the quantity of retinoids and background matrix interferences can confound the quantification of retinoids, and the bioanalysis requires high performance instrumentation, such as liquid chromatography mass-spectrometry (LC-MS). Successful bioanalysis of retinoids is further complicated by the innate structural instability of retinoids and their relatively high lipophilicity. Further, in vitro experiments with retinoids require attention to experimental design and interpretation to account for the instability of retinoids due to isomerization and degradation, sequential metabolism to numerous structurally similar metabolites, and substrate depletion during experiments. In addition, in vitro biological activity is often confounded by residual presence of retinoids in common biological reagents such as cell culture media. This chapter identifies common biological and analytical complexities in retinoid bioanalysis in diverse biological matrices, and in the use of retinoids in cell culture and metabolic incubations. In addition, this chapter highlights best practices for the successful detection and quantification of the vitamin A metabolome in a wide range of biological matrices.

Addition of ethylamines to the phenols of bithionol and synthetic retinoids does not elicit activity in gram-negative bacteria

Our labs have demonstrated the activity of bithionol and synthetic retinoids against methicillin-resistant Staphylococcus aureus (MRSA), as well as their membrane-acting mechanism of action. However, the compounds lack activity in gram-negative species. Herein, we apply a known strategy for converting gram-positive agents into broad-spectrum therapies: addition of an alkylamine. By appending an alkylamine to the phenols of these known membrane disruptors, we test whether this approach is applicable to our compounds. Ultimately, biological testing in four MRSA strains and three gram-negative species showed abolished or diminished activity in all our analogs compared to their parent compounds and no gram-negative activity. Thus, we find that alkylamines would not elicit broad-spectrum activity from bithionol or CD437 derivatives.

Retinoic Acid Signaling and Development of the Respiratory System

Retinoic acid (RA), the bioactive metabolite of vitamin A (VA), has long been recognized as a critical regulator of the development of the respiratory system. During embryogenesis, RA signaling is involved in the development of the trachea, airways, lung, and diaphragm. During postnatal life, RA continues to impact respiratory health. Disruption of RA activity during embryonic development produces dramatic phenotypes in animal models and human diseases, including tracheoesophageal fistula, tracheomalacia, congenital diaphragmatic hernia (CDH), and lung agenesis or hypoplasia. Several experimental methods have been used to target RA pathways during the formation of the embryonic lung. These have been performed in different animal models using gain- and loss-of-function strategies and dietary, pharmacologic, and genetic approaches that deplete retinoid stores or disrupt retinoid signaling. Experiments utilizing these methods have led to a deeper understanding of RA's role as an important signaling molecule that influences all stages of lung development. Current research is uncovering RA cross talk interactions with other embryonic signaling factors, such as fibroblast growth factors, WNT, and transforming growth factor-beta.

Carotenoid metabolism at the intestinal barrier

Carotenoids exert a rich variety of physiological functions in mammals and are beneficial for human health. These lipids are acquired from the diet and metabolized to apocarotenoids, including retinoids (vitamin A and its metabolites). The small intestine is a major site for their absorption and bioconversion. From here, carotenoids and their metabolites are distributed within the body in triacylglycerol-rich lipoproteins to support retinoid signaling in peripheral tissues and photoreceptor function in the eyes. In recent years, much progress has been made in identifying carotenoid metabolizing enzymes, transporters, and binding proteins. A diet-responsive regulatory network controls the activity of these components and adapts carotenoid absorption and bioconversion to the bodily requirements of these lipids. Genetic variability in the genes encoding these components alters carotenoid homeostasis and is associated with pathologies. We here summarize the advanced state of knowledge about intestinal carotenoid metabolism and its impact on carotenoid and retinoid homeostasis of other organ systems, including the eyes, liver, and immune system. The implication of the findings for science-based intake recommendations for these essential dietary lipids is discussed. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Long-term dietary intake of excessive vitamin A impairs spermatogenesis in mice

Vitamin A and its derivatives contribute to many physiological processes, including vision, neural differentiation, and reproduction. Vitamin A deficiency causes early cessation of spermatogenesis, characterized by a marked depletion of germ cells. However, there has been no clear understanding about the role of chronic intake of vitamin A excess (VAE) in spermatogenesis. The objective of this study was to investigate whether chronic intake of VAE diet causes arrest of spermatogenesis. To examine the effects of VAE on spermatogenesis, we used ICR male mice fed with control (AIN-93G purified diet: 4 IU/g) diet or VAE (modified AIN-93G diet with VAE: 1,000 IU/g) diet for 7 weeks (from 3 to 10 weeks of age). At 10 weeks of age, the retinol concentration in the testes of VAE mice was significantly higher than that of control mice. Testicular cross sections from control mice contained a normal array of germ cells, while the seminiferous tubules from VAE mice exhibited varying degrees of testicular degeneration. Daily sperm production in VAE testes was dramatically decreased compared to that in control testes. Sperm viability, motility, and morphology were also impaired in VAE mice. Furthermore, we examined the effects of VAE on the expression of genes involved in retinoid signaling and spermatogenesis to determine the underlying molecular mechanisms. Therefore, we are the first to present results describing the long-term dietary intake of VAE impairs spermatogenesis using a mouse model.

What's New in Hair Loss

The treatment of hair loss is a challenge for all dermatologists. New medications are needed due to lack of efficacy of many treatments or their side-effect profile. This article discusses the most recent literature updates on the use of retinoids in frontal fibrosing alopecia, platelet-rich plasma in androgenetic alopecia, and JAK inhibitors in alopecia areata.

Vitamin A signaling and homeostasis in obesity, diabetes, and metabolic disorders

Much evidence has accumulated in the literature over the last fifteen years that indicates vitamin A has a role in metabolic disease prevention and causation. This literature proposes that vitamin A can affect obesity development and the development of obesity-related diseases including insulin resistance, type 2 diabetes, hepatic steatosis and steatohepatitis, and cardiovascular disease. Retinoic acid, the transcriptionally active form of vitamin A, accounts for many of the reported associations. However, a number of proteins involved in vitamin A metabolism, including retinol-binding protein 4 (RBP4) and aldehyde dehydrogenase 1A1 (ALDH1A1, alternatively known as retinaldehyde dehydrogenase 1 or RALDH1), have also been identified as being associated with metabolic disease. Some of the reported effects of these vitamin A-related proteins are proposed to be independent of their roles in assuring normal retinoic acid homeostasis. This review will consider both human observational data as well as published data from molecular studies undertaken in rodent models and in cells in culture. The primary focus of the review will be on the effects that vitamin A per se and proteins involved in vitamin A metabolism have on adipocytes, adipose tissue biology, and adipose-related disease, as well as on early stage liver disease, including non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH).

Insights into the role of bacteria in vitamin A biosynthesis: Future research opportunities

Significant efforts have been made to address the hidden hunger challenges due to iron, zinc, iodine, and vitamin A since the beginning of the 21st century. Prioritizing the vitamin A deficiency (VAD) disorders, many countries are looking for viable alternative strategies such as biofortification. One of the leading causes of VAD is the poor bioconversion of β-carotene into retinoids. This review is focused on the opportunities of bacterial biosynthesis of retinoids, in particular, through the gut microbiota. The proposed hypothesis starts with the premise that an animal can able to store and timely convert carotenoids into retinoids in the liver and intestinal tissues. This theory is experimental with many scientific insights. The syntrophic metabolism, potential crosstalk of bile acids, lipocalins and lipopolysaccharides of gut microbiota are reported to contribute significantly to the retinoid biosynthesis. The gut bacteria respond to these kinds of factors by genetic restructuring driven mainly by events like horizontal gene transfer. A phylogenetic analysis of β-carotene 15, 15'-mono (di) oxygenase enzymes among a selected group of prokaryotes and eukaryotes was carried out to validate the hypotheses. Shedding light on the probiotic strategies through non-genetically modified organism such as gut bacteria capable of synthesizing vitamin A would address the VAD disorders.

Analysis of Retinoic Acid Receptor Signaling in Colorectal Cancer

Retinoic acid receptor (RAR) signaling plays an important role in embryonic development and homeostasis of many tissues. At the cellular level, activation of RAR signaling often induces cell cycle arrest, differentiation, and apoptosis in many types of cells. Consequently, loss of normal RAR function in the presence of physiological levels of retinoic acid (RA) is often observed in cancers, and pharmacological reactivation of RAR signaling has been considered a promising strategy for cancer therapy and prevention. One of important mechanisms that regulate RAR activity in cancer cells is cross-talk with growth factor signaling, where activation of extracellular signal-regulated kinase (ERK) plays a major role in suppressing RAR transcriptional activity downstream of growth factor receptors. Conversely, strong activation of RAR can induce suppression of ERK activity by inducing expression of a phosphatase specific for ERK to exert tumor-suppressive activity in colorectal cancer. Here, we describe the basic methods to analyze interactions between RAR and ERK signaling in colorectal cancer cells.

Development of biotin-retinoid conjugates as chemical probes for analysis of retinoid function

Herein, we report the rational design, synthesis and biological evaluation of conjugates consisting of the synthetic retinoid Am580 and biotin connected via a linker moiety. We found that the linking substructure between the retinoid part and the biotin part is critical for retaining the biological activity. Conjugate 4 with a shorter linker showed similar potency to endogenous retinoid ATRA (1) and the parent compound Am580 (2) for neural differentiation of mouse embryotic carcinoma P19 cells, and showed the same pattern of induction of gene expression. It is expected to be useful as a probe for investigations of retinoid function. The design rationale and structure-activity relationship of the linker moiety are expected to be helpful for developing biotin conjugates of other nuclear receptor ligands.

A novel retinoid X receptor agonist, UAB30, inhibits rhabdomyosarcoma cells in vitro

BACKGROUND

While patients with early-stage rhabdomyosarcoma (RMS) have seen steady improvement in prognosis over the last 50 y, those with advanced-stage or high-grade disease continue to have a dismal prognosis. Retinoids have been shown to cause growth suppression and terminal differentiation in RMS cells, but the toxicities associated with retinoic acid limit its use. Rexinoids provide an alternative treatment approach to retinoic acid. Rexinoids primarily bind the retinoid X receptor with minimal retinoic acid receptor binding, the entity responsible for many of the toxicities of retinoid therapies. UAB30 is a novel rexinoid with limited toxicities. We hypothesized that UAB30 would lead to decreased cell survival in RMS.

MATERIALS AND METHODS

Two RMS cell lines, one embryonal (RD) subtype and one alveolar (St. Jude Cancer Research Hospital 30) subtype, were used. Cells were treated with UAB30, and cytotoxicity, proliferation, mobility, and apoptosis were evaluated.

RESULTS

UAB30 significantly decreased RMS tumor cell viability and proliferation. Invasion, migration, and attachment-independent growth were reduced following UAB30 treatment. UAB30 also resulted in apoptosis and G1 cell cycle arrest. UAB30 affected both the alveolar and embryonal RMS cell lines in a similar fashion.

CONCLUSIONS

The results of these studies suggest a potential therapeutic role for the low-toxicity synthetic retinoid X receptor selective agonist, UAB30, in RMS treatment.

Vitamin A deficiency induces endoplasmic reticulum stress and apoptosis in pancreatic islet cells: Implications of stearoyl-CoA desaturase 1-mediated oleic acid synthesis

Previously, we reported that vitamin A deficiency resulted in the reduction of stearoyl-CoA desaturase 1 (SCD1) and monounsaturated fatty acid (MUFA) levels, which corroborated with attenuation of high fructose-induced hepatic steatosis. Here, we aimed at assessing the effect of vitamin A deficiency on SCD1, MUFA levels and their impact on pancreas' structure and functions. Male weanling Wistar rats fed one of the four diets, namely control (Con), vitamin A-deficient (VAD), highfructose (HFr) and vitamin A-deficient diet with highfructose (VADHFr) for 16 weeks period. Compared to the control, feeding of VAD diet (alone or with HFr) resulted in pancreatic intra-islet vessel dilation and reduced plasma insulin, glucagon and C-peptide levels, however, glucose levels decreased only in VADHFr group. In line with plasma levels, VAD diet-fed animals displayed lower immunostaining for insulin and glucagon, which corroborated with increased apoptotic staining observed in the islet regions, possibly due to increased cellular stress, as indicated by high immunostaining for endothelial nitric oxide synthase (eNOS) and CCAAT/Enhancer-binding protein homologues protein (CHOP). On the other hand, it significantly decreased the SCD1 protein, which corroborated with reduced MUFA levels, particularly, oleic acid (C18:1), when compared to the control and HFr groups. In conclusion, chronic vitamin A deficiency altered the structure and functions of pancreas by diminishing the islet cells, possibly by inducing cellular stress-mediated apoptosis and decreasing SCD1-mediated oleic acid (C18:1) synthesis. Thus, the data suggest that unlike liver, the reduction in SCD1 and MUFA levels in the pancreas exerts deleterious effects on its functions and perturb the overall cellular metabolism.

Anticancer efficacy of p-dodecylaminophenol against high-risk and refractory neuroblastoma cells in vitro and in vivo

Neuroblastoma is an aggressive and drug-resistant refractory cancer. The human high-risk neuroblastoma cell line, SK-N-AS (non-amplified N-myc) is derived from stromal cells and it is resistant to treatment with retinoic acid (1, RA), which is a chemotherapeutic agent used to induce neuronal cellular differentiation of neuroblastomas. We have developed p-dodecylaminophenol (3, p-DDAP), based on N-(4-hydroxyphenyl)retinamide (2, 4-HPR), a synthetic amide of 1, since 1 and 2 are associated with the side-effect of nyctalopia. In order to evaluate the effects of 3 on high-risk neuroblastomas, we employed SK-N-AS cells as well asa second high-risk human neuroblastoma cell line, IMR-32, which is derived from neuronal cells (amplified N-myc, drug sensitive). Compound 3 suppressed cell growth of SK-N-AS and IMR-32 cells more effectively than 1, 2, p-decylaminophenol (4, p-DAP), N-(4-hydroxyphenyl)dodecananamide (5, 4-HPDD) or N-(4-hydroxyphenyl)decananamide (6, 4-HPD). In SK-N-AS cells, 3 induced G₀/G₁ arrest and apoptosis to a greater extent than 1 and 2. In IMR-32 cells, 3 induced apoptosis to a similar extent as 1 and 2, potentially by inhibiting N-myc expression. In addition, i.p. administration of 3 suppressed tumor growth in SK-N-AS-implanted mice in vivo. Since 3 showed no effects on blood retinol concentrations, in contrast to reductions following the administration of 2, it exhibited excellent anticancer efficacy against high-risk neuroblastoma SK-N-AS and IMR-32 expressing distinct levels of N-myc. Compound 3 may have potential for clinical use in the treatment of refractory neuroblastoma with reduced side effects.

Cigarette smoke condensate affects the retinoid pathway in human amnion

INTRODUCTION

The preterm premature rupture of membranes (PPROM) is a frequent pathology responsible of more than 30% of preterm births. Tobacco smoking is one of the most frequently described risk factors identified and contributes to the pre term weakening of fetal membranes. As previously demonstrated, all-trans retinoic acid (atRA) regulates several genes involved in the extracellular matrix dynamics, an essential actor in fetal membrane ruptures. We hypothesized that cigarette smoke may affect this pathway in human amnion.

METHODS

Amnion was obtained from full-term fetal membranes collected from non-smoking women after cesarean births and used either as explants or for the isolation of derived epithelial cells. The pro-healing and transcriptomic effects of atRA were studied by a scratch assay experiment and quantitative RT-PCR, respectively, after treatment with dimethyl sulfoxyde (DMSO), atRA, DMSO + cigarette smoke condensate (CSC), or atRA + CSC.

RESULTS

Our results show a strong alteration of the retinoid pathway after CSC treatment on amnion-derived epithelial cells and explants. We first demonstrated that CSC inhibits the activity of the RARE reporter gene in amnion-derived epithelial cells. Then, atRA's effects on both the transcription of its target genes and wound healing were demonstrated to be inhibited or at least decreased by the CSC in human amnion epithelial cells.

DISCUSSION

Here, we demonstrated that CSC altered the retinoid signal, already known to have roles in fetal membrane physiopathology. These results highlight a potential negative action of maternal smoking on the retinoid pathway in human amnion and more generally on pregnancy.

The age-old problem of acne

Acne vulgaris is one of the top three most commonly encountered dermatological problems worldwide in both primary and secondary care. Acne diagnosis and treatment date back to ancient Greek and Egyptian times. This article explores acne through the ages and discusses past theories on etiology and treatment with particular focus on the discovery of retinoids and their impact on women's health.

Carotenoid glycosides from cyanobacteria are teratogenic in the zebrafish (Danio rerio) embryo model

Toxigenicity of cyanobacteria is widely associated with production of several well-described toxins that pose recognized threats to human and ecosystem health as part of both freshwater eutrophication, and episodic blooms in freshwater and coastal habitats. However, a preponderance of evidence indicates contribution of additional bioactive, and potentially toxic, metabolites. In the present study, the zebrafish (Danio rerio) embryo was used as a model of vertebrate development to identify, and subsequently isolate and characterize, teratogenic metabolites from two representative strains of C. raciborskii. Using this approach, three chemically related carotenoids - and specifically the xanthophyll glycosides, myxol 2'-glycoside (1), 4-ketomyxol 2'-glycoside (2) and 4-hydroxymyxol 2'-glycoside (3) - which are, otherwise, well known pigment molecules from cyanobacteria were isolated as potently teratogenic compounds. Carotenoids are recognized "pro-retinoids" with retinoic acid, as a metabolic product of the oxidative cleavage of carotenoids, established as both key mediator of embryo development and, consequently, a potent teratogen. Accordingly, a comparative toxicological study of chemically diverse carotenoids, as well as apocarotenoids and retinoids, was undertaken. Based on this, a working model of the developmental toxicity of carotenoids as pro-retinoids is proposed, and the teratogenicity of these widespread metabolites is discussed in relation to possible impacts on aquatic vertebrate populations.

Roles of Retinoic Acid in Germ Cell Differentiation

The modalities of gametogenesis differ markedly between sexes. Female are born with a definitive reserve of oocytes whose size is crucial to ensure fertility. Male fertility, in contrast, relies on a tightly regulated balance between germ cell self-renewal and differentiation, which operates throughout life, according to recurring spatial and temporal patterns. Genetic and pharmacological studies conducted in the mouse and discussed in this review have revealed that all-trans retinoic acid and its nuclear receptors are major players of gametogenesis and are instrumental to fertility in both sexes.

Down-regulation of histone deacetylase 4, -5 and -6 as a mechanism of synergistic enhancement of apoptosis in human lung cancer cells treated with the combination of a synthetic retinoid, Am80 and green tea catechin

(-)-Epigallocatechin gallate (EGCG), a green tea catechin, acts as a synergist with various anticancer drugs, including retinoids. Am80 is a synthetic retinoid with a different structure from all-trans-retinoic acid: Am80 is now clinically utilized as a new drug for relapsed and intractable acute promyelocytic leukemia patients. Our experiments showed that the combination of EGCG and Am80 synergistically induced both apoptosis in human lung cancer cell line PC-9 and up-regulated expressions of growth arrest and DNA damage-inducible gene 153 (GADD153), death receptor 5, and p21^waf1 genes in the cells. To understand the mechanisms of synergistic anticancer activity of the combination, we gave special attention to the lysine acetylation of proteins. Proteomic analysis using nanoLC-ESI-MS/MS revealed that PC-9 cells treated with the combination contained 331 acetylated proteins, while nontreated cells contained 553 acetylated proteins, and 59 acetylated proteins were found in both groups. Among them, the combination increased acetylated-p53 and acetylated-α-tubulin through reduction of histone deacetylase (HDAC) activity in cytosol fraction, although the levels of acetylation in histones H3 or H4 did not change, and the combination reduced protein levels of HDAC4, -5 and -6 by 20% to 80%. Moreover, we found that a specific inhibitor of HDAC4 and -5 strongly induced p21^waf1 gene expression, and that of HDAC6 induced both GADD153 and p21^waf1 gene expression, which resulted in apoptosis. All results demonstrate that EGCG in combination with Am80 changes levels of acetylation in nonhistone proteins via down-regulation of HDAC4, -5 and -6 and stimulates apoptotic induction.

Combined Treatments with a Retinoid Receptor Agonist and Epigenetic Modulators in Human Neuroblastoma Cells

Neuroblastoma (NB) is the most common extracranial solid childhood tumor accounting for around 15% of pediatric cancer deaths and most probably originates from a failure in the development of embryonic neural crest cells. Retinoids can inhibit the proliferation and stimulate differentiation of NB cells. In addition, epigenetic events involving changes in chromatin structure and DNA methylation can mediate the effects of retinoids; hence, the scope of this study is to investigate the use of retinoids and epigenetic drugs in NB cell lines. Here, we demonstrate that the combination of retinoid all trans-retinoic acid (ATRA) with inhibitors of either histone deacetylases (HDACs) or DNA methyltransferase is more effective in impairing the proliferation of human SH-SY5Y and SK-N-BE(2) NB cells than any drug given alone. Treatments also induced differential changes on the messenger RNA (mRNA) expression of retinoid receptor subtypes and reduced the protein content of c-Myc, the neuronal markers NeuN and β-3 tubulin, and the oncoprotein Bmi1. These results suggest that the combination of retinoids with epigenetic modulators is more effective in reducing NB growth than treatment with single drugs.

Filling in Pediatric Acne Practice Gaps: A Prospective Multicenter Study of Case-Based Education

PURPOSE

Studies have documented practice gaps in acne management between pediatricians and dermatologists. Evidence-based recommendations for acne management were published by the American Acne and Rosacea Society and the American Academy of Pediatrics in 2013. We assess the impact of a case-based learning intervention on pediatrician knowledge and treatment of acne in accordance with published recommendations.

METHODS

Participants were recruited at four conferences for pediatric providers. Knowledge of the recommendations and confidence in utilizing them was assessed. Five case-based questions were presented, with providers choosing acne treatments before, immediately after, and 3 months after a case-based educational presentation. Answer selections consistent with the recommendations were scored as correct, and all responses were evaluated for patterns of medication selection.

RESULTS

A total of 150 individuals participated, most with over 10 years experience. Knowledge of the recommendations and confidence in prescribing acne therapy was poor. The average preintervention management selections were 70% correct, increasing significantly to 86% 3 months after intervention (p < .01). The most significant improvements were demonstrated in provider's ability to choose regimens for moderate acne consistent with published recommendations, and in recommendation-consistent usage of retinoids and benzoyl peroxide (p < .05). Persisting practice gaps included a reluctance to use topical retinoids in preadolescents and lack of initiating oral combination therapies in patients with severe acne.

CONCLUSIONS

A case-based educational intervention significantly increased providers choosing acne treatments in accordance with evidence-based recommendations in an examination setting. Limitations of the study include an inability to assess actual provider prescribing behavior through this methodology.