Biology subjects

Sripathi, S. R.

Publications and source records attributed to Sripathi, S. R..

5 recordsLinked to original sources

bioRxiv2026

Gut-derived metabolic reprogramming drives immune aging and tissue degeneration

Aging is characterized by changes in gut microbiome, metabolic imbalance and chronic inflammation, yet how these processes integrate to drive tissue degeneration remains poorly defined. Using age-related macular degeneration (AMD) as a model of tissue aging, we identify a diet-induced metabolic-immune axis that promotes systemic and retinal degeneration. In mice, a high-fat, cholesterol-enriched (HFC) diet induced perturbations in the gut structural integrity and microbiome repertoire, as well as systemic metabolic aging signatures, prominently marked by reduced circulating histidine. Plasma histidine levels were similarly decreased in AMD patients and inversely correlated with body mass index (BMI) in control donors. These diet-induced gut microbiome changes and subsequent metabolic alterations promoted peripheral innate immune reprogramming, with expansion of inflammatory neutrophils and monocytes that infiltrated the outer retina in a mouse model. Mechanistically, the gut-derived IGF1R/AKT2 signaling acts as a central regulator of global epigenetic remodeling and systemic immune aging under high-fat conditions in C. elegans. In a mouse model with an age-dependent dry AMD-like pathology, distinct retinal pigment epithelium (RPE) subpopulations exhibited downregulation of the histidine transporter SLC7A5, linking metabolic stress to activation of MIF/CD74-dependent inflammatory signaling between RPE and infiltrating immune cells. Histidine supplementation or AKT2 phospho-state modulation attenuated systemic immune activation and rescued retinal degeneration. These findings identify histidine-axis dysregulation as a mechanistic bridge between diet-induced microbiome changes, metabolic stress, immune aging, and retinal degeneration.

cell biology↗

bioRxiv2020

Proteomic and phosphoproteomic analysis identifies novel liver-related signaling in retinal pigment epithelial cells during epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is associated with several potentially blinding retinal diseases. Proteomic and phosphoproteomic studies were performed on human pluripotent stem cell-derived RPE (hPSC-RPE) monolayers to better understand the pathways mediating RPE EMT. EMT was induced by enzymatic dissociation or by co-treatment with transforming growth factor beta (TGF{beta}) and tumor necrosis factor alpha (TNF; TGNF). The global and phosphoproteomes were analyzed at 1 hr post EMT induction to capture early events in kinase/phosphatase signaling cascades and at 12 hrs to define early changes in protein abundance. Pathway enrichment analysis revealed that TGNF and Dissociation rapidly perturbed signaling in many of the same pathways, with striking similarity in the phosphoproteome at 1 hr. Surprisingly, functions related to liver cell proliferation and hyperplasia were strongly enriched in the phosphosites altered by both treatments at 1 hr and in protein abundance changes at 12 hrs. Hepatocyte Growth Factor-cMET signaling exhibited the strongest overall enrichment in both treatments. These signaling pathways may serve as suitable targets for the development of therapeutic strategies for the inhibition of RPE EMT, and thus progression of several debilitating visual diseases.

cell biology↗

bioRxiv2018

Combinatorial library of biodegradable polyesters enables delivery of plasmid DNA to polarized human RPE monolayers for retinal gene therapy

AbstractEfficient gene delivery into hard-to-transfect cells is still a challenge despite significant progress in the development of various gene delivery tools. Non-viral and synthetic polymeric nanoparticles offer an array of advantages for gene delivery over the viral vectors and high in demand as they are safe to use, easy to synthesize and highly cell-type specific. Here we demonstrate the use of a high-throughput screening (HTS) platform to screen for biodegradable polymeric nanoparticles (NPs) that can transfect human retinal pigment epithelial (RPE) cells with high efficiency and low toxicity. These NPs can deliver plasmid DNA (pDNA) to RPE monolayers more efficiently compared to the commercially available transfection reagents without interfering the global gene expression profile of RPE cells. In this work, we have established an HTS platform and identified synthetic polymers that can be used for high efficacy non-viral gene delivery to human RPE monolayers, enabling gene loss- and gain-of-function studies of cell signaling and developmental pathways. This platform can be used to identify the optimum polymer, weight-to-weight ratio of polymer to DNA, and the dose of NP for various retinal cell types.

bioengineering↗

bioRxiv2018

A widespread decrease of chromatin accessibility in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the elderly. The extent to which epigenetic changes regulate AMD progression is unclear. Here we globally profiled chromatin accessibility in the retina and retinal pigmented epithelium (RPE) from AMD patients and controls. Global decreases in chromatin accessibility occurr in RPE in early AMD, and in the retina with advanced disease, suggesting that dysfunction in RPE cells drives disease progression. Footprints of photoreceptor and RPE-specific transcription factors are enriched in differentially accessible regions (DARs). Genes associated with DARs show altered expression in AMD. Cigarette smoke treatment of RPE cells recapitulates epigenomic changes seen in AMD, providing an epigenetic link between the known risk factors for AMD and AMD pathology. Finally, overexpression of HDAC11 is partially responsible for the reduction in chromatin accessibility, identifying potential new targets for treatment of AMD.

genomics↗

bioRxiv2018

Axon Guidance Signaling Modulates Epithelial to Mesenchymal Transition in Stem Cell-Derived Retinal Pigment Epithelium

The critical role of epithelial to mesenchymal transition (EMT) in embryonic development, malignant transformation, and tumor progression has been well studied in normal and cancerous tissues and cells. Interestingly, EMT has also been reported to play a key role in the early progression of several retinal degenerative diseases, including scarring associated proliferative vitro-retinopathy (PVR), choroidal neo-vascularization induced \"wet\" age-related macular degeneration (AMD) and diabetic retinopathy (DR). Despite these studies, many questions remain unexplored regarding EMT-associated retinal pigment epithelium (RPE) degeneration and dysfunction. We hypothesize that RPE cells undergo EMT prior to cell death during the progression of atrophic \"dry\" AMD. Utilizing human stem cell-derived RPE (hRPE) as a model to study RPE EMT, we optimized two independent but complementary RPE EMT induction systems: 1) enzymatic dissociation of hRPE monolayer cultures and 2) co-treatment of hRPE monolayer cultures with transforming growth factor beta (TGF-{beta}) and the inflammatory cytokine, tumor necrosis factor alpha (TNF-). To further understand the molecular mechanisms of RPE EMT regulation, we performed an RNA-Sequencing (RNA-Seq) time course examination across 48 hours beginning with EMT induction. Our transcriptome profiling provides a comprehensive quantification of dynamic signaling events and associated biological pathways underlying RPE EMT and reveals an intriguing significance for widespread dysregulation of multiple axon guidance molecules in this process.

genomics↗