👤 A J Kanwar

A substantial body of evidence has established the contributions of both mitochondrial dynamics and lipid metabolism to the pathogenesis of diabetic kidney disease (DKD). However, the precise interplay between these two key metabolic regulators of DKD is not fully understood. Here, we uncover a link between mitochondrial dynamics and lipid metabolism by investigating the role of carbohydrate-response element-binding protein (ChREBP), a glucose-responsive transcription factor and a master regulator of lipogenesis, in kidney podocytes. We find that inducible podocyte-specific knockdown of ChREBP in diabetic db/db mice improves key biochemical and histological features of DKD in addition to significantly reducing mitochondrial fragmentation. Because of the critical role of ChREBP in lipid metabolism, we interrogated whether and how mitochondrial lipidomes play a role in ChREBP-mediated mitochondrial fission. Our findings suggest a key role for a family of ether phospholipids in ChREBP-induced mitochondrial remodeling. We find that overexpression of glyceronephosphate O-acyltransferase, a critical enzyme in the biosynthesis of plasmalogens, reverses the protective phenotype of ChREBP deficiency on mitochondrial fragmentation. Finally, our data also points to Gnpat as a direct transcriptional target of ChREBP. Taken together, our results uncover a distinct mitochondrial lipid signature as the link between ChREBP-induced mitochondrial dynamics and progression of DKD. Show less

Long noncoding RNAs (lncRNAs) have been shown to play key roles in a variety of biological activities of the cell. However, less is known about how lncRNAs respond to environmental cues and what transcriptional mechanisms regulate their expression. Studies from our laboratory have shown that the lncRNA Tug1 (taurine upregulated gene 1) is crucial for the progression of diabetic kidney disease, a major microvascular complication of diabetes. Using a combination of proximity labeling with the engineered soybean ascorbate peroxidase (APEX2), ChIP-qPCR, biotin-labeled oligonucleotide pulldown, and classical promoter luciferase assays in kidney podocytes, we extend our initial observations in the current study and now provide a detailed analysis on a how high-glucose milieu downregulates Tug1 expression in podocytes. Our results revealed an essential role for the transcription factor carbohydrate response element binding protein (ChREBP) in controlling Tug1 transcription in the podocytes in response to increased glucose levels. Along with ChREBP, other coregulators, including MAX dimerization protein (MLX), MAX dimerization protein 1 (MXD1), and histone deacetylase 1 (HDAC1), were enriched at the Show less

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

Recent evidence suggests that epithelial cancers, including colorectal cancer are driven by a small sub-population of self-renewing, multi-potent cells termed cancer stem cells (CSCs) which are thought to be responsible for recurrence of cancer. One of the characteristics of CSCs is their ability to form floating spheroids under anchorage-independent conditions in a serum-free defined media. The current investigation was undertaken to examine the role of Wnt/beta-catenin pathway in regulating the growth and maintenance of colonospheres. Human colon cancer cells HCT-116 (p53 wild type; K-ras mutant), HCT-116 (p53 null; K-ras mutant) and HT-29 (p53 mutant) were used. Colonospheres formed in vitro exhibited higher expression of colon CSCs markers LGR5, CD44, CD166 and Musashi-1 along with putative CSC marker EpCAM, compared to the corresponding parental cancer cells and also exhibit the ability to form spheroids under extreme limiting dilution, indicating the predominance of CSCs in colonospheres. Colonospheres formed by HCT-116 cells show over 80% of the cells to be CD44 positive, compared to 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