👤 D Parsad

Recent studies have revealed critical roles that nuclear receptors like LXR-α (Liver X Receptor- alpha) plays as a class of post-transcriptional gene regulator in skin development and diseases. Keeping in view the fact that LXR-α plays crucial role in keratinocyte proliferation and differentiation, it becomes imperative to dissect the pathways and role of LXR-α genomics in the pathogenesis of psoriasis with ultimate aim to explore novel preventive/therapeutic strategies as treatment options. To explore the effects of agonists and activators of LXR-α on its own gene expression and the putative targets in psoriatic keratinocytes. Identification of promoter sequences for (vitamin D receptor) VDR and Catalase were done using in silico analysis followed by β-galactosidase (β-gal) reporter plasmid assay in keratinocytes from clinically heathy subjects. Determination of relative levels of LXR-α,VDR and catalase in control versus treated cells upon activation of LXR-α with Atorvastatin + 22R hydroxycholestrol and Ascorbic acid + 22R hydroxycholestrol was done by PCR and Cell Proliferation Assay. The cells transfected with the reporter plasmid element for VDR and catalase showed more than 5 and 4 fold increase respectively in the β-gal activity compared to the control. An increase of 55% in LXR-α gene expression at RNA level was observed in Atorvastatin + 22-R hydroxycholestrol compared to 24% in Ascorbic acid + 22-ROH cholesterol. The expression of the VDR and Catalase was significantly increased in both treated keratinocytes compared to its normal counterpart. Show less

In recent times, the role of LXRs in skin physiology and pathology has evolved rapidly because of their role in proliferation, carcinogenesis, differentiation and permeability barrier function. LXRs were identified as promising drug targets for the treatment of many skin diseases. For this study, skin biopsies were taken from 15 patients with vitiligo and six controls to culture melanocytes from clinically active perilesional and normal skin. Gene expression was examined by reverse transcriptase-polymerase chain reaction analysis. Role of LXR-α in regulating the expression of MMPs was checked by gene knock-down, and its role in vitiligo pathogenesis was checked by treatment with LXR-α agonist 22(R)-hydroxycholesterol. After treatment adhesion assay, annexin V staining and proliferation assay were performed. The expression of LXR-α was relatively more in perilesional skin melanocytes as compared to uninvolved skin melanocytes of non-segmental vitiligo patient, and controls on the other hand, perilesional melanocytes were more prone to apoptosis. LXR-α gene knock-down significantly increases the expression of MMPs. LXR-α agonist 22(R)-hydroxycholesterol treatment significantly decreases melanocyte adhesion, apoptosis and proliferation. Higher expression of LXR-α in perilesional skin melanocytes significantly decreases the adhesion, proliferation and matrix metalloproteinases and increases apoptosis. Show less

Liver X receptor-alpha (LXR-alpha), being a member of the nuclear receptor/transcription factor family, has been widely recognized to have a pleiotropic effect in the regulation of genes involved in innate immunity, inflammation and cholesterol homeostasis. Keeping in view the fact that psoriasis is a chronic, inflammatory and autoimmune disease with a high turnover of keratinocytes, this study was addressed to understand the functional RNomics of the LXR-alpha gene in cultured primary keratinocytes derived from skin biopsies of human psoriatic lesions, and from symptomless skin of psoriatic patients and clinically healthy subjects. The results of this study revealed for the first time that the LXR-alpha gene has an inherent capacity to regulate genes coding for inflammatory cytokines, cell cycle, immunomodulation and reactive oxygen species scavenging within human keratinocytes. Moreover, LXR-alpha gene knockdown within normal human keratinocytes simulated the genomic profile observed in psoriatic skin lesions. On the basis of our study, we propose that restoration of LXR-alpha expression/function within a psoriatic lesion may help to switch the transition from psoriatic to symptomless skin. Show less

Vitiligo is a common, non-contagious disorder. The basic pathogenesis of vitiligo generally, or for any of the putative subsets of vitiligo, remains unknown. The liver X receptors (LXRs), LXR-alpha and LXR-beta are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. Important genes involved in regulation of melanocytes are target genes of LXRs; it can be speculated that LXRs might be playing an important role in pathogenesis of pigmentary disorders. We have demonstrated in this study that there is expression of LXR-alpha/beta by human melanocytes at both transcriptional and translational levels. Our present data also revealed that the expression of LXR-alpha at both mRNA and protein level was significantly higher in perilesional skin as compared to the normal skin of vitiligo patient. Show less