Biology subjects

Veerareddy, V.

Publications and source records attributed to Veerareddy, V..

4 recordsLinked to original sources

bioRxiv2025

Molecular Mechanisms Underlying the Regulation of VCAM-1 Expression by the Short-Chain Fatty Acid Butyrate

Over the past decade, cerebrovascular inflammation has been increasingly recognized as a contributor to the progression of neurodegenerative diseases, particularly Alzheimers disease (AD). One of the molecular hallmarks of cerebrovascular inflammation is the increased expression of vascular cell adhesion molecule (VCAM)-1 on blood-brain barrier (BBB) endothelial cells. Exposure to amyloid beta (A{beta}) peptides, one of the primary hallmarks of AD, and pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-) induces VCAM-1 expression on the BBB endothelium, which facilitates extravasation of leukocytes into the brain thereby promoting an inflammatory response. Therefore, it is crucial to explore therapeutic agents that can inhibit VCAM-1 expression induced by A{beta} and TNF-. Short-chain fatty acids, such as butyrate, produced by the gut microbiota as byproducts of dietary fiber metabolism, are recognized for their anti-inflammatory properties. In this study, we successfully tested the hypothesis that butyrate mitigates A{beta} and TNF--induced VCAM-1 expression in polarized human cerebral microvascular endothelial cell monolayers, a widely used BBB in vitro model. Our findings indicated that pre-treatment with butyrate significantly reduced A{beta}42 and TNF- mediated upregulation of VCAM-1. Furthermore, we have shown STAT3/GATA6 axis as a key mediator of anti-inflammatory effects of butyrate. These findings provide mechanistic insight into butyrates protective role and highlight its potential to mitigate A{beta} and TNF--induced cerebrovascular inflammation in AD.

molecular biology↗

bioRxiv2025

Endothelial-pericyte interactions activate insulin signaling and its implications for blood-brain barrier dysfunction in Alzheimers disease

PurposeThis study aimed to investigate how pericyte degeneration contributes to BBB disruption in Alzheimers disease, focusing on the roles of insulin signaling and the imbalance between matrix metalloproteinases (MMPs) and endogenous tissue inhibitors of MMPs (TIMPs). MethodsWe employed an in vitro BBB model by co-culturing brain-specific microvascular endothelial-like cells (iBMECs) differentiated from human induced pluripotent stem cells (hiPSCs) and primary human brain vasculature pericytes (hBVPs). Protein expression under solo- versus co-culture conditions was assessed by western blot. MMP enzymatic activity in the culture media was measured by fluorometric assay. Exosomes were isolated from conditioned media and brain derived neurotrophic growth factor (BDNF) concentrations were determined using ELISA assays. ResultsTIMP1 and collagen-IV expression was significantly increased in co-cultured BBB endothelial cells and pericytes compared to solo-cultures. However, a greater effect was observed in cells co-cultured for 2 days than 7 days. Elevated TIMP1 in co-culture media significantly inhibited MMP activity. The AKT and ERK pathways were activated in both cell types after 7 days of co-culture, and the ERK signaling mediated TIMP1 upregulation in endothelial cells. BDNF was significantly enriched in exosomes isolated from co-culture media on the abluminal side compared to the solo-cultures. Endothelial cells also protected pericytes from accumulation of toxic amyloid-beta 42 by downregulating low density lipoprotein receptor-related protein 1 (LRP1) expression. ConclusionsThese findings provide mechanistic insights into BBB disruption due to pericyte degeneration and highlight the important role of BBB insulin resistance in causing cerebrovascular dysfunction in AD.

molecular biology↗

bioRxiv2025

Butyrate regulates the blood-brain barrier transport and intra-endothelial accumulation of Alzheimers disease Amyloid-beta peptides

Alzheimers disease (AD) is characterized by the pathological deposition of amyloid beta (A) proteins as amyloid plaques, tau aggregates, and cerebrovascular dysfunction that drive disease progression. Butyrate, a gut microbial metabolite, has been found to be reduced in AD patients; butyrate supplementation improved cognition and decreased amyloid burden in animal models. However, the precise underlying mechanisms are unclear. Our previous studies have demonstrated that insulin signaling impacts A transport kinetics at the blood-brain barrier (BBB). In this study, we investigated the effect of butyrate treatment on intra-endothelial A accumulation and BBB integrity by modulating the insulin signaling pathway. The effect of butyrate on A accumulation was assessed by flow cytometry in BBB cell culture models. Insulin signaling activation and the expression of various receptors and transporters at the BBB were evaluated by Western blots and confocal microscopy. The roles of various molecular mediators were confirmed using specific inhibitors (MK2206, Trametinib, Rapamycin, VX-745). The effect of butyrate on the expression of BBB receptors and transporters that play a critical role in A trafficking was examined in mouse brains colonized with butyrate-producing bacteria via immunohistochemistry. Butyrate significantly decreased A{beta}42 accumulation in endothelial cells. This effect was associated with insulin signaling pathway activation, particularly AKT and ERK phosphorylation. Inhibitor studies established the critical role of these specific arms, as co-incubation with MK2206 (AKT inhibitor) or Trametinib (ERK inhibitor) reversed the protective effect of butyrate and increased A{beta}42 accumulation. However, mTOR and p38 inhibitors did not show a similar effect. In addition, butyrate restored P-glycoprotein efflux transporter expression and claudin-5 tight junction protein levels that were reduced with A{beta} treatment. These effects were supported by in vivo work, which demonstrated the upregulation of Tissue Inhibitor of Metalloproteinases-2 (TIMP-2). This protein is associated with AKT activation and extracellular matrix stabilization in mice colonized with butyrate-producing bacteria. In conclusion, we have demonstrated that butyrate decreases A{beta}42 uptake at the BBB endothelium by activating the AKT and ERK arms of the insulin signaling pathway. These changes may also improve the integrity of BBB tight junctions by increasing claudin-5 expression and extracellular matrix, and by upregulating TIMP-2 expression. This study highlights butyrates potential as a therapeutic modulator of AD-related BBB dysfunction.

neuroscience↗

bioRxiv2025

Influence of Gut Microbiota on Oral Drug Absorption and Metabolism

Gut bacteria influence host intestinal phenotype in ways that impact drug absorption and metabolism. By comparing colonic tissue from germ-free mice to that of mice colonized with human microbiota, this study evaluates microbiota-driven differences in gene expression, mucosal permeability, and P-gp efflux capacity. Transcriptomic analysis revealed upregulation of genes coding ATP-binding cassette drug transporters P-gp (Abcb1a, Abcb1b), BCRP (Abcg2), and MRP3 (Abcc3), along with increased expression of solute carriers MCT1 (Slc16a1) and OCTN2 (Slc22a5). Immunohistochemistry indicated greater P-gp expression and apical localization in humanized mice. No relevant gene expression changes were observed in human homologs of drug-metabolizing cytochrome P450 enzymes, though cytochrome P450 oxidoreductase (Por) upregulation suggests increased cytochrome activity. Other phase I drug-metabolizing enzymes, including multiple homologs of human carboxylesterase 2 (CES2) and several reductases, were upregulated with high significance. Regarding phase II metabolism, genes encoding most UDP-glucuronosyltransferases and glutathione S-transferases were upregulated, along with the enzymes responsible for synthesizing their corresponding co-substrates, UDP-glucuronic acid and glutathione. Small intestinal mucosal explants demonstrated higher permeability to 14C-labeled polyethylene glycol 4000 (14C-PEG4000) in germ-free mice than in humanized mice. The 14C-PEG4000 permeability differences are in agreement with changes in paracellular tight junctional proteins such as claudins, zonula occludens, and myosin II-related genes. These results demonstrate the broader impact of gut microbiome on oral drug absorption and metabolism and implicate the contributions of gut microbiome to individual variations in drug efficacy and toxicity.

pharmacology and toxicology↗