9-cis retinoic acid is the ALDH1A1 product that stimulates melanogenesis

The TRAF gene family in turbot (Scophthalmus maximus): Identification, characterization, molecular evolution and expression patterns analysis

Tumor necrosis factor receptor-associated factor (TRAF) is an important structural protein, which can bind to TNF receptors and participate in the regulation of TNF signaling pathway. Nonetheless, few studies have been conducted to investigate the systematic identification of TRAF gene family in teleost and role in innate immunity of turbot (Scophthalmus maximus). In this study, eight TRAF genes, namely SmTRAF2aa, SmTRAF2ab, SmTRAF2b, SmTRAF3, SmTRAF4a, SmTRAF5, SmTRAF6 and SmTRAF7, were identified and annotated in turbot by using bioinformatics methods. Analysis of the phylogenetic, syntenic and molecular evolution demonstrated that all SmTRAF members were evolutionarily conserved in teleost. Domain analysis showed all SmTRAF proteins contained a typical conserved N-terminal RING finger domain. Most SmTRAF proteins contained a MATH domain at the C-terminal, while SmTRAF7 contains seven duplicate WD40 domains. In addition, quantitative real-time PCR was performed to detect the expression patterns of SmTRAFs in tissues from healthy and Vibrio anguillarum infected turbots. The results indicated SmTRAFs had diverse tissue expression patterns and the expression of TRAF gene changed significantly after V. anguillarum infection. This study provided a basis for understanding the roles of TRAFs in the innate immune response of turbot.

TMT-Based Quantitative Proteomic and Physiological Analyses on Serums of Chinese Patients with Active Vitiligo

Purpose

Vitiligo is an acquired depigmented skin disorder. Though genetic background, autoimmune dysregulation, and oxidative stress were reported involved in the development of vitiligo, the exact pathogenesis remains largely unknown. This study aimed to investigate potential functional proteins, pathways, and serum biomarkers involved in active vitiligo.

Patients and Methods

Tandem Mass Tags (TMT) method was used to determine differentially expressed proteins (DEPs) in serum samples between 11 active vitiligo patients and 7 healthy controls of Chinese Han population.

Results

A total of 31 DEPs were identified (P < 0.05, fold change >1.2), with 21 proteins upregulated and 10 proteins downregulated in the vitiligo group. DEPs were enriched in GO terms such as "extracellular exosome" and "immunoglobulin receptor binding", as well as KEGG pathways including "cysteine and methionine metabolism" and other immune-related pathways. Furthermore, ALDH1A1 and EEF1G achieved areas under receiver-operating characteristic (ROC) curve of 0.9221 and 0.8571, respectively. The expression levels of these 2 proteins were validated in another active vitiligo patient group.

Conclusion

Our research provided novel insight into serum proteomic profile for vitiligo patients, detecting ALDH1A1 and EEF1G as potential biomarkers for active vitiligo and therapeutic intervention. Our work also detected several DEPs and associated pathways in the serum of active vitiligo patients, reinforcing the roles of retinoic acid and exosome processes in vitiligo pathogenesis.

Vitamin A in Skin and Hair: An Update

Vitamin A is a fat-soluble micronutrient necessary for the growth of healthy skin and hair. However, both too little and too much vitamin A has deleterious effects. Retinoic acid and retinal are the main active metabolites of vitamin A. Retinoic acid dose-dependently regulates hair follicle stem cells, influencing the functioning of the hair cycle, wound healing, and melanocyte stem cells. Retinoic acid also influences melanocyte differentiation and proliferation in a dose-dependent and temporal manner. Levels of retinoids decline when exposed to ultraviolet irradiation in the skin. Retinal is necessary for the phototransduction cascade that initiates melanogenesis but the source of that retinal is currently unknown. This review discusses new research on retinoids and their effects on the skin and hair.

Aldehyde Dehydrogenase 2 as a Therapeutic Target in Oxidative Stress-Related Diseases: Post-Translational Modifications Deserve More Attention

Aldehyde dehydrogenase 2 (ALDH2) has both dehydrogenase and esterase activity; its dehydrogenase activity is closely related to the metabolism of aldehydes produced under oxidative stress (OS). In this review, we recapitulate the enzyme activity of ALDH2 in combination with its protein structure, summarize and show the main mechanisms of ALDH2 participating in metabolism of aldehydes in vivo as comprehensively as possible; we also integrate the key regulatory mechanisms of ALDH2 participating in a variety of physiological and pathological processes related to OS, including tissue and organ fibrosis, apoptosis, aging, and nerve injury-related diseases. On this basis, the regulatory effects and application prospects of activators, inhibitors, and protein post-translational modifications (PTMs, such as phosphorylation, acetylation, S-nitrosylation, nitration, ubiquitination, and glycosylation) on ALDH2 are discussed and prospected. Herein, we aimed to lay a foundation for further research into the mechanism of ALDH2 in oxidative stress-related disease and provide a basis for better use of the ALDH2 function in research and the clinic.

Laser Treatment of Hypopigmentation in Scars: A Review

BACKGROUND

Despite history of multiple treatment modalities, repigmentation of hypopigmented scars remains a difficult clinical problem.

OBJECTIVE

The purpose of this review is to evaluate the literature on laser and combination laser plus adjunct topical therapy for hypopigmented burn and traumatic scars.

MATERIALS AND METHODS

A search on PubMed and on Oxford Academic was conducted with additional relevant literature obtained from reference lists.

RESULTS

Treatment regimens that address hypopigmentation within scars were reviewed. A combination of nonablative fractional or ablative fractional laser treatment with topical prostaglandin analogue with or without topical retinoid were found to result in superior repigmentation.

CONCLUSION

Reliable improvement of hypopigmentation in scars after laser treatment is challenging. Laser can achieve success in some cases. Ultraviolet laser can achieve modest repigmentation; however, results are short-lived and require continued re-treatment. Modest improvement in pigmentation is seen with nonablative fractional laser or ablative fractional laser alone and enhanced repigmentation is demonstrated when combining fractional laser resurfacing with topical application of synthetic prostaglandin analogues and other known modulators of melanogenesis.

Dysfunction of the limbal epithelial stem cell niche in aniridia-associated keratopathy

PURPOSE

Abnormalities in the limbal niche microenvironment have been suggested to be causally involved in aniridia-associated keratopathy (AAK), but histological analyses on the limbal structure and composition in AAK are lacking. Here, we investigated morphologic and molecular alterations of the limbal epithelial stem cell niche in human congenital aniridia.

METHODS

The blind, buphthalmic and painful left eye of a 16-year old girl with congenital aniridia and juvenile glaucoma had to be enucleated because of uncontrolled intraocular pressure. The diagnosis of AAK was based on classical clinical features and partial limbal stem cell deficiency in the superior half. Genetic analysis identified a large heterozygous PAX6 gene deletion encompassing exons 11-15 as well as exon 9 of the neighboring ELP4 gene. Three limbal biopsies were taken from the superior, nasal and temporal regions to isolate and cultivate limbal epithelial progenitor cells and subject them to mRNA expression analyses. The globe was vertically bisected and processed for light and transmission electron microscopy and immunohistochemistry.

RESULTS

Comparative analysis of the superior and inferior limbal zones showed a gradual degradation of palisade structures associated with the transition from a hyperplastic to an attenuated corneal epithelium, inflammatory cell infiltrations and basement membrane irregularities. The clinically unaffected inferior part revealed no distinct stem cell clusters in the preserved palisade region, but a uniform population of hyperproliferative, undifferentiated progenitor cells in the basal/suprabasal layers of limbal and corneal epithelia, which gave rise to maldifferentiated epithelial cells exhibiting a conjunctival/epidermal phenotype and nuclear-to-cytoplasmic translocation of Pax6. The structure of the limbal niche was fundamentally perturbed, showing marked alterations in extracellular matrix composition, dislocation of atypical melanocytes lacking melanosomes and melanin, aberrant Wnt/β-catenin and retinoic acid signaling, and massive immune cell infiltration.

CONCLUSIONS

Considering the limitations of a single Case study, the findings suggest that ocular surface alterations in AAK are caused by a primary dysfunction and gradual breakdown of the limbal stem cell niche through Pax6-related effects on both melanogenesis and epithelial differentiation.

Single-nucleotide polymorphisms responsible for pseudo-albinism and hypermelanosis in Japanese flounder (Paralichthys olivaceus) and reveal two genes related to malpigmentation

Paralichthys olivaceus is the kind of cold-water benthic marine fish. In the early stages of development, the symmetrical juveniles transform into an asymmetrical body shape through metamorphosis for adapting benthic life. After that, one side of the fish body is attached to the ground, and the eyes turn to the opposite side which is called ocular side. The body color also appears asymmetry. The skin on the ocular side is dark brown, and the skin on the blind side is white without pigmentation. Pseudo-albinism and hypermelanosis have been considered distinct body color disorders in flatfish. Pseudo-albinism and hypermelanosis in Paralichthys olivaceus are due to abnormal or uneven pigment distribution, due to the interaction of hereditary and environmental factors, rather than a single-nucleotide mutation of a specific gene. Here, we report three single-nucleotide polymorphisms (SNPs) responsible for both pseudo-albinism and hypermelanosis, which are located on two body color-related genes involved in melanogenesis-related pathways. c.2440C>A (P. V605I) and c.2271-96T>C are located on the Inositol 1,4,5-trisphosphate receptor type 2-like (ITPR2) (Gene ID: 109624047), they are located in exon 16 and the non-coding region, respectively, and c.2406C>A (P.H798N) is located in exon 13 of the adenylate cyclase type 6-like (AC6) gene(Gene ID: 109630770). ITPR2 and AC6 expression, which both participate in the thyroid hormone synthesis pathway associated with pseudo-albinism and hypermelanosis in P. olivaceus, were also investigated using qRT-PCR. In hypermelanotic fish, there were relatively higher levels of expression in ITPR2 and AC6 mRNA of hyper-pigmented skin of blind side than that of non-pigmented skin on the blind side and pigmented skin on the ocular side, while in pseudo-albino fish, expression level of ITPR2 and AC6 mRNA in pigmented skin of ocular side was significantly higher than that in non-pigmented skin both ocular and blind side. The results indicated that the expression of the two genes in abnormal parts of body color is positively correlated with pigmentation, suggesting that the influence of abnormal expression of two genes on the pigmentation in abnormal parts of body color deserves further study.

Boolean model for melanogenesis

Melanogenesis is a highly regulated process through which the pigment melanin is produced in skin cells. Irregularities in the molecular events that govern the process of skin pigmentation can cause disorders like vitiligo. In order to understand the biology of disease progression, it is important to have an in depth understanding of intracellular events. Mathematical models provide an integrated view of intracellular signalling. There are very few models to date that incorporate intracellular processes relevant to melanogenesis and only one to our knowledge that simulates the dynamics of response to varying levels of input. Here, we report the formulation of the largest Boolean model (265 nodes) for melanogenesis to date. The model was built on the basis of a detailed interaction network graph published by Raghunath et al. Through additional manual curation of the reported interactions, we converted the graph into a set of Boolean rules, following the procedure of the first Boolean model (62 nodes) for melanogenesis published by Lee et al. Simulations show that the predicted response to varying UV levels for most of the nodes is similar to the predictions of the existing model. The greater complexity allows investigation of the sensitivity of melanin to additional nodes. We carried out perturbation analysis of the network through node deletion and constitutive activation to identify sensitivity of outcomes, and compared the nodes identified as sensitive to previous reports.

The demethylase inhibitor GSK-J4 limits inflammatory colitis by promoting de novo synthesis of retinoic acid in dendritic cells

Dendritic cells (DCs) promote T-cell mediated tolerance to self-antigens and induce inflammation to innocuous-antigens. This dual potential makes DCs fundamental players in inflammatory disorders. Evidence from inflammatory colitis mouse models and inflammatory bowel diseases (IBD) patients indicated that gut inflammation in IBD is driven mainly by T-helper-1 (Th1) and Th17 cells, suggesting an essential role for DCs in the development of IBD. Here we show that GSK-J4, a selective inhibitor of the histone demethylase JMJD3/UTX, attenuated inflammatory colitis by reducing the inflammatory potential and increasing the tolerogenic features of DCs. Mechanistic analyses revealed that GSK-J4 increased activating epigenetic signals while reducing repressive marks in the promoter of retinaldehyde dehydrogenase isoforms 1 and 3 in DCs, enhancing the production of retinoic acid. This, in turn, has an impact on regulatory T cells (Treg) increasing their lineage stability and gut tropism as well as potentiating their suppressive activity. Our results open new avenues for the treatment of IBD patients.

Light-induced stress as a primary evolutionary driver of eye origins

Eyes are quintessential complex traits and our understanding of their evolution guides models of trait evolution in general. A long-standing account of eye evolution argues natural selection favors morphological variations that allow increased functionality for sensing light. While certainly true in part, this focus on visual performance does not entirely explain why diffuse photosensitivity persists even after eyes evolve, or why eyes evolved many times, each time using similar building blocks. Here, we briefly review a vast literature indicating most genetic components of eyes historically responded to stress caused directly by light, including ultraviolet damage of DNA, oxidative stress, and production of aldehydes. We propose light-induced stress had a direct and prominent role in the evolution of eyes by bringing together genes to repair and prevent damage from light-stress, both before and during the evolution of eyes themselves. Stress-repair and stress-prevention genes were perhaps originally deployed as plastic responses to light and/or as beneficial mutations genetically driving expression where light was prominent. These stress-response genes sense, shield, and refract light but only as reactions to ongoing light stress. Once under regulatory-genetic control, they could be expressed before light stress appeared, evolve as a module, and be influenced by natural selection to increase functionality for sensing light, ultimately leading to complex eyes and behaviors. Recognizing the potentially prominent role of stress in eye evolution invites discussions of plasticity and assimilation and provides a hypothesis for why similar genes are repeatedly used in convergent eyes. Broadening the drivers of eye evolution encourages consideration of multi-faceted mechanisms of plasticity/assimilation and mutation/selection for complex novelties and innovations in general.

Delineating the role of MITF isoforms in pigmentation and tissue homeostasis

MITF, a gene that is mutated in familial melanoma and Waardenburg syndrome, encodes multiple isoforms expressed from alternative promoters that share common coding exons but have unique amino termini. It is not completely understood how these isoforms influence pigmentation in different tissues and how the expression of these independent isoforms of MITF is regulated. Here, we show that melanocytes express two isoforms of MITF, MITF-A and MITF-M. The expression of MITF-A is partially regulated by a newly identified retinoid enhancer element located upstream of the MITF-A promoter. Mitf-A knockout mice have only subtle changes in melanin accumulation in the hair and reduced Tyr expression in the eye. In contrast, Mitf-M-null mice have enlarged kidneys, lack neural crest-derived melanocytes in the skin, choroid, and iris stroma, yet maintain pigmentation within the retinal pigment epithelium and iris pigment epithelium of the eye. Taken together, these studies identify a critical role for MITF-M in melanocytes, a minor role for MITF-A in regulating pigmentation in the hair and Tyr expression in the eye, and a novel role for MITF-M in size control of the kidney.

Retinoids Enhance the Expression of Cathelicidin Antimicrobial Peptide during Reactive Dermal Adipogenesis

A subset of dermal fibroblasts undergo rapid differentiation into adipocytes in response to infection and acutely produce the cathelicidin antimicrobial peptide gene Camp Vitamin A and other retinoids inhibit adipogenesis yet can show benefit to skin disorders, such as cystic acne, that are exacerbated by bacteria. We observed that retinoids potently increase and sustain the expression of Camp in preadipocytes undergoing adipogenesis despite inhibition of markers of adipogenesis, such as Adipoq, Fabp4, and Rstn Retinoids increase cathelicidin in both mouse and human preadipocytes, but this enhancement of antimicrobial peptide expression did not occur in keratinocytes or a sebocyte cell line. Preadipocytes undergoing adipogenesis more effectively inhibited growth of Staphylococcus aureus when exposed to retinoic acid. Whole transcriptome analysis identified hypoxia-inducible factor 1-α (HIF-1α) as a mechanism through which retinoids mediate this response. These observations uncouple the lipid accumulation element of adipogenesis from the innate immune response and uncover a mechanism, to our knowledge previously unsuspected, that may explain therapeutic benefits of retinoids in some skin disorders.

Role of ALDH1A1 and HTRA2 expression in CCL2/CCR2-mediated breast cancer cell growth and invasion

Chemokines mediate immune cell trafficking during tissue development, wound healing and infection. The chemokine CCL2 is best known to regulate macrophage recruitment during wound healing, infection and inflammatory diseases. While the importance of CCL2/CCR2 signaling in macrophages during cancer progression is well documented, we recently showed that CCL2-mediated breast cancer progression depends on CCR2 expression in carcinoma cells. Using 3D Matrigel: Collagen cultures of SUM225 and DCIS.com breast cancer cells, this study characterized the mechanisms of CCL2/CCR2 signaling in cell growth and invasion. SUM225 cells, which expressed lower levels of CCR2 than DCIS.com cells, formed symmetrical spheroids in Matrigel: Collagen, and were not responsive to CCL2 treatment. DCIS.com cells formed asymmetric cell clusters in Matrigel: Collagen. CCL2 treatment increased growth, decreased expression of E-cadherin and increased TWIST1 expression. CCR2 overexpression in SUM225 cells increased responsiveness to CCL2 treatment, enhancing growth and invasion. These phenotypes corresponded to increased expression of Aldehyde Dehydrogenase 1A1 (ALDH1A1) and decreased expression of the mitochondrial serine protease HTRA2. CCR2 deficiency in DCIS.com cells inhibited CCL2-mediated growth and invasion, corresponding to decreased ALDH1A1 expression and increased HTRA2 expression. ALDH1A1 and HTRA2 expression were modulated in CCR2-deficient and CCR2-overexpressing cell lines. We found that ALDH1A1 and HTRA2 regulates CCR2-mediated breast cancer cell growth and cellular invasion in a CCL2/CCR2 context-dependent manner. These data provide novel insight on the mechanisms of chemokine signaling in breast cancer cell growth and invasion, with important implications on targeted therapeutics for anti-cancer treatment.

This article has an associated First Person interview with the first author of the paper.

Summary: Chemokines are known to regulate immune cell recruitment during inflammation. This report characterizes novel molecular mechanisms through which CCL2/CCR2 chemokine signaling in breast cancer cells regulates growth and invasion.

Pigment Production Analysis in Human Melanoma Cells

The human epidermal melanocyte is a highly specialized pigmented cell that serves to protect the epidermis from ultraviolet (UV) damage through the production of melanin, or melanogenesis. Misregulation in melanogenesis leading to either hyper- or hypo-pigmentation is found in human diseases such as malasma and vitiligo. Current therapies for these diseases are largely unsuccessful and the need for new therapies is necessary. In order to identify genes and or compounds that can alter melanogenesis, methods are required that can detect changes in pigment production as well as expression of key melanogenesis transcription factors and enzymes. Here we describe methods to detect changes in melanogenesis in a human melanoma cell line, MNT-1, by (1) analyzing pigment production by measuring the absorbance of melanin present by spectrophotometry, (2) analyzing transcript expression of potent regulators of melanogenesis by qunatitative reverse-transcription (RT)PCR and (3) analyzing protein expression of potent regulators of melanogenesis by Western blot (WB).

Inhibition of Cell Proliferation in an NRAS Mutant Melanoma Cell Line by Combining Sorafenib and α-Mangostin

α-Mangostin is a natural product commonly used in Asia for cosmetic and medicinal applications including topical treatment of acne and skin cancer. Towards finding new pharmacological strategies that overcome NRAS mutant melanoma, we performed a cell proliferation-based combination screen using a collection of well-characterized small molecule kinase inhibitors and α-Mangostin. We found that α-Mangostin significantly enhances Sorafenib pharmacological efficacy against an NRAS mutant melanoma cell line. The synergistic effects of α-Mangostin and Sorafenib were associated with enhanced inhibition of activated AKT and ERK, induced ER stress, and reduced autophagy, eventually leading to apoptosis. The structure of α-Mangostin resembles several inhibitors of the Retinoid X receptor (RXR). MITF expression, which is regulated by RXR, was modulated by α-Mangostin. Molecular docking revealed that α-Mangostin can be accommodated by the ligand binding pocket of RXR and may thereby compete with RXR-mediated control of MITF expression. In summary, these data demonstrate an unanticipated synergy between α-Mangostin and sorafenib, with mechanistic actions that convert a known safe natural product to a candidate combinatorial therapeutic agent.

Tyrosinase Depletion Prevents the Maturation of Melanosomes in the Mouse Hair Follicle

The mechanisms that lead to variation in human skin and hair color are not fully understood. To better understand the molecular control of skin and hair color variation, we modulated the expression of Tyrosinase (Tyr), which controls the rate-limiting step of melanogenesis, by expressing a single-copy, tetracycline-inducible shRNA against Tyr in mice. Moderate depletion of TYR was sufficient to alter the appearance of the mouse coat in black, agouti, and yellow coat color backgrounds, even though TYR depletion did not significantly inhibit accumulation of melanin within the mouse hair. Ultra-structural studies revealed that the reduction of Tyr inhibited the accumulation of terminal melanosomes, and inhibited the expression of genes that regulate melanogenesis. These results indicate that color in skin and hair is determined not only by the total amount of melanin within the hair, but also by the relative accumulation of mature melanosomes.

Dioxin receptor regulates aldehyde dehydrogenase to block melanoma tumorigenesis and metastasis

Background

The dioxin (AhR) receptor can have oncogenic or tumor suppressor activities depending on the phenotype of the target cell. We have shown that AhR knockdown promotes melanoma primary tumorigenesis and lung metastasis in the mouse and that human metastatic melanomas had reduced AhR levels with respect to benign nevi.

Methods

Mouse melanoma B16F10 cells were engineered by retroviral transduction to stably downregulate AhR expression, Aldh1a1 expression or both. They were characterized for Aldh1a1 activity, stem cell markers and migration and invasion in vitro. Their tumorigenicity in vivo was analyzed using xenografts and lung metastasis assays as well as in vivo imaging.

Results

Depletion of aldehyde dehydrogenase 1a1 (Aldh1a1) impairs the pro-tumorigenic and pro-metastatic advantage of melanoma cells lacking AhR expression (sh-AhR). Thus, Aldh1a1 knockdown in sh-AhR cells (sh-AhR + sh-Aldh1a1) diminished their migration and invasion potentials and blocked tumor growth and metastasis to the lungs in immunocompetent AhR+/+ recipient mice. However, Aldh1a1 downmodulation in AhR-expressing B16F10 cells did not significantly affect tumor growth in vivo. Aldh1a1 knockdown reduced the high levels of CD133⁺/CD29⁺/CD44⁺ cells, melanosphere size and the expression of the pluripotency marker Sox2 in sh-AhR cells. Interestingly, Sox2 increased Aldh1a1 expression in sh-AhR but not in sh-AhR + sh-Aldh1a1 cells, suggesting that Aldh1a1 and Sox2 may be co-regulated in melanoma cells. In vivo imaging revealed that mice inoculated with AhR + Aldh1a1 knockdown cells had reduced tumor burden and enhanced survival than those receiving Aldh1a1-expressing sh-AhR cells.

Conclusions

Aldh1a1 overactivation in an AhR-deficient background enhances melanoma progression. Since AhR may antagonize the protumoral effects of Aldh1a1, the AhR^low-Aldh1a1^high phenotype could be indicative of bad outcome in melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0419-9) contains supplementary material, which is available to authorized users.

Knockdown of lecithin retinol acyltransferase increases all-trans retinoic acid levels and restores retinoid sensitivity in malignant melanoma cells

Retinoids such as all-trans retinoic acid (ATRA) influence cell growth, differentiation and apoptosis and may play decisive roles in tumor development and progression. An essential retinoid-metabolizing enzyme known as lecithin retinol acyltransferase (LRAT) is expressed in melanoma cells but not in melanocytes catalysing the esterification of all-trans retinol (ATRol). In this study, we show that a stable LRAT knockdown (KD) in the human melanoma cell line SkMel23 leads to significantly increased levels of the substrate ATRol and biologically active ATRA. LRAT KD restored cellular sensitivity to retinoids analysed in cell culture assays and melanoma 3D skin models. Furthermore, ATRA-induced gene regulatory mechanisms drive depletion of added ATRol in LRAT KD cells. PCR analysis revealed a significant upregulation of retinoid-regulated genes such as CYP26A1 and STRA6 in LRAT KD cells, suggesting their possible involvement in mediating retinoid resistance in melanoma cells. In conclusion, LRAT seems to be important for melanoma progression. We propose that reduction in ATRol levels in melanoma cells by LRAT leads to a disturbance in cellular retinoid level. Balanced LRAT expression and activity may provide protection against melanoma development and progression. Pharmacological inhibition of LRAT activity could be a promising strategy for overcoming retinoid insensitivity in human melanoma cells.

Targeting ALDH1A1 to treat pigmentary disorders

Clinical disorders related to skin pigmentation include hypo- or hyperpigmentation. Because they are difficult to treat, new approaches to develop safe pigment modulatory agents are needed. In the March issue of the journal, Paterson et al. (Exp Dermatol, 22, 2013) determined which aldehyde dehydrogenase 1A1 (ALDH1A1) substrates and products regulate melanogenesis. The authors demonstrated that ALDH1A1 substrate 9-cis retinal and its corresponding product 9-cis retinoic acid potently induced the accumulation of MITF mRNA, tyrosinase mRNA and melanin. Despite depletion of ALDH1A1, there was observed decreased ability of 9-cis retinal but not 9-cis retinoic acid to stimulate melanogenesis, indicating that ALDH1A1 regulates melanogenesis by catalysing the conversion of 9-cis retinal to 9-cis retinoic acid. Additionally, potent ALDH1A1 inhibitor such as cyanamide or Angeli's salt significantly suppressed pigmentation in human skin cells. These findings provide new candidate agents for the treatment of hypo- or hyperpigmentation disorders, using novel pigmentation-modulatory agents that target ALDH1A1.