Biology subjects

Gunasekaran, G.

Publications and source records attributed to Gunasekaran, G..

3 recordsLinked to original sources

bioRxiv2025

HIV-1 Amplifies IL-8 Response Of Human Stellate Cells To Gram-Positive Microbial Products Via H4K5 Histone Acetylation

BackgroundPatients living with human immunodeficiency virus 1 (PLWH) develop accelerated liver fibrosis, but the exact mechanism remains unknown. Activation of hepatic stellate cells (HSCs)--a cornerstone of fibrosis--is influenced by various factors, including viral infection, hepatocellular injury, chronic immune activation, gut barrier dysfunction, and microbial translocation. The role of gram-positive microbial products in human immunodeficiency virus 1 (HIV-1) infection-associated liver inflammation and fibrosis remains poorly understood. This study investigates the effect of lipoteichoic acid (LTA), a major gram-positive bacterial component, on HSCs in the context of HIV-1 infection. MethodsHuman HSCs were isolated from liver tissues of both HIV-1-infected and uninfected individuals undergoing hepatic resection. Inflammatory responses of HSCs to LTA stimulation were measured ex vivo via ELISA before and after HIV-1BaL exposure. Western blotting, ChIP-qPCR and RNA-seq were used to reveal the mechanisms contributing to the IL-8 response to LTA stimulation and HIV-1BaL exposure in HSCs. ResultsLTA modestly induced interleukin-8/CXCL8 (IL-8) production in HSCs, but this response was significantly heightened following HIV-1 exposure. Increased IL-8 levels were also observed in liver tissues from HIV-1-infected patients. In vitro, IL-8 treatment of HSCs elevated -SMA and COL1A1 expression, implicating IL-8 in fibrosis progression in HIV-1 infection. Transcriptomic analysis pointed to histone acetylation as a key regulator of the IL-8 response of HSCs to LTA during HIV-1 infection. Supporting this, the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA) further enhanced IL-8 expression in HIV-1-exposed HSCs. ChIP-qPCR confirmed that acetylation of histone H4K5 facilitated IL-8 promoter transactivation, sensitizing HSCs to LTA under HIV-1 influence. ConclusionsHIV-1 infection primes HSCs for an exaggerated response to LTA, driven by histone acetylation and resulting in elevated IL-8 production--potentially accelerating liver fibrosis in PLWH. Given the persistence of microbial translocation despite effective antiretroviral therapy, these findings highlight the need for targeted interventions to prevent or mitigate liver fibrosis in PLWH.

immunology↗

bioRxiv2024

Development and tissue specific expression of RAPGEF1 (C3G) transcripts having exons encoding disordered segments with predicted regulatory function.

The ubiquitously expressed RAPGEF1(C3G), regulates differentiation, and is essential for development of mouse embryos. While multiple transcripts have been predicted, evidence of their expression and function is scarce. We demonstrate tissue and development specific expression of novel transcripts with exons 12-14 in various combinations, in the mouse. These exons encode an intrinsically disordered serine-rich polypeptide, that undergoes phosphorylation. Isoform switching occurred during differentiation of myoblasts and mouse embryonic stem cells. In silico structure and docking studies indicated that the additional exons alter intra-molecular interactions keeping it in a closed confirmation, and interaction with its target, RAP1A. Our results demonstrate the expression of novel RAPGEF1 isoforms, and suggest cassette exon inclusion as an additional means of regulating RAPGEF1 activity during differentiation.

molecular biology↗

bioRxiv2023

TGF-β1 activates neutrophil signaling and gene expression but not migration

Tumor-associated neutrophils are found in many types of cancer and are often reported to contribute to negative outcomes. The presence of transforming growth factor-beta (TGF-{beta}) in the tumor microenvironment reportedly contributes to the skewing of neutrophils to a more pro-tumor phenotype. The effects of TGF-{beta} on neutrophil signaling and migration are, however, unclear. We sought to characterize TGF-{beta} signaling in both primary human neutrophils and the neutrophil-like cell line HL-60 and determine whether it directly induces neutrophil migration. We found that TGF-{beta}1 does not induce neutrophil chemotaxis in transwell or underagarose migration assays. TGF-{beta}1 does activate canonical signaling through SMAD3 and noncanonical signaling through ERK1/2 in neutrophils in a time-and dose-dependent manner. Additionally, TGF-{beta}1 present in the tumor-conditioned media (TCM) of invasive breast cancer cells results in SMAD3 activation. We discovered that TCM induces neutrophils to secrete leukotriene B4 (LTB4), which is a lipid mediator important for amplifying the range of neutrophil recruitment. However, TGF-{beta}1 alone does not induce secretion of LTB4. RNA-sequencing revealed that TGF-{beta}1 and TCM alter gene expression in HL-60 cells, including the mRNA levels of the pro-tumor oncostatin M (OSM) and vascular endothelial growth factor A (VEGFA). These new insights into the role and impact of TGF-{beta}1 on neutrophil signaling, migration, and gene expression have significant implications in the understanding of the changes in neutrophils that occur in the tumor microenvironment.

immunology↗