Valenzuela-Pérez, Lucía

Background and Aims: Unresolved inflammation and fibrosis are defining features of metabolic dysfunction–associated steatohepatitis (MASH), a progressive form of steatotic liver disease that can advance to cirrhosis and hepatocellular carcinoma. While innate immune mechanisms in MASH have been extensively characterized, the role of CD4 + T cells remains poorly understood despite their central function in orchestrating immune responses through effector and regulatory mechanisms. Approach and Results: Integrated single-cell proteomic, transcriptomic, and functional analyses were used to investigate the CD4 + T-cell landscape in murine and human MASH. We delineated a profound shift in the differentiation of intrahepatic and peripheral CD4 + T cells toward Th1, regulatory, and cytotoxic phenotypes in murine and human MASH. Notably, hepatic CD4 + T cells exhibited heightened effector activity and elevated secretion of proinflammatory cytokines, thus amplifying inflammatory signaling cascades. The CD4 + T-cell reprogramming in MASH also included the induction of the co-stimulatory receptor OX40. In parallel, OX40 ligand (OX40L)-expressing monocyte-derived macrophages and dendritic cells accumulated in MASH livers, establishing a feed-forward CD4 + T cell-myeloid activation loop. Therapeutic blockade of the OX40–OX40L axis, in turn, reversed liver pathology in mice with established MASH and reduced disease markers in an ex vivo human liver model. Furthermore, genetic depletion or functional inhibition of CD4 + T cells attenuated fibrosis, accompanied by decreased infiltration of monocyte-derived macrophages. Conclusions: These studies provide a comprehensive single-cell proteogenomic atlas of CD4 + T cells in MASH and identify an OX40-dependent CD4 + T cell-macrophage axis as a promising therapeutic target for the treatment of MASH and liver fibrosis.

Abstract Senescent cells secrete proinflammatory factors known as the senescence-associated secretory phenotype (SASP), contributing to tissue dysfunction and aging. Mitochondrial dysfunction is a key feature of senescence, influencing SASP via mitochondrial DNA (mtDNA) release and cGAS/STING pathway activation. Here, we demonstrate that mitochondrial RNA (mtRNA) also accumulates in the cytosol of senescent cells, activating RNA sensors RIG-I and MDA5, leading to MAVS aggregation and SASP induction. Inhibition of these RNA sensors significantly reduces SASP factors. Furthermore, BAX and BAK plays a key role in mtRNA leakage during senescence, and their deletion diminishes SASP expression in vitro and in a mouse model of Metabolic Dysfunction Associated Steatohepatitis (MASH). These findings highlight mtRNA's role in SASP regulation and its potential as a therapeutic target for mitigating age-related inflammation.

Abstract Background Inflammatory regulatory T cells (Tregs) are one of the hallmarks of therapy resistance. Yet mechanisms leading to inflammatory Treg development and its contribution to inflammatory bowel disease (IBD) are unexplored. Methods Tregs derived from healthy PBMCS were characterized by immune and mitochondrial phenotyping. Transcripts were validated in dataset from IBD intestinal lesions. Wildtype (WT) and IL21 receptor-deleted (Il21r−/−) Tregs were examined in murine models of CD4+ T cell-induced colitis. Results Through in vitro cytokine challenge of Tregs and subsequent analysis, we found that IL21 induces Tregs co-expressing TNF, IFNγ and IL17. Transcriptomic and metabolomic integration revealed upregulation of mRNA and metabolites associated with glycolysis, and amino acid, nucleotide and lipid metabolism. Moreover, IL21-induced metabolic transcripts were more enriched in Treg cluster within scRNA-seq dataset from intestinal lesions of anti-TNF non-responders vs. non-responders. Mechanistically, cell imaging and real-time bioenergetic analysis revealed disruption to mitochondria-ER ultrastructure and function, coinciding with glycogen synthase kinase 3β (GSK3β) activation and glycolytic switch rather than pyruvate-mediated oxidative phosphorylation. GSK3β inhibition or methyl pyruvate supplementation rescued IL21-induced metabolic and inflammatory phenotypes. In contrast to WT Tregs, murine Il21r−/− Treg transfer efficiently prevented and rescued CD4+CD45Rbhigh T cell-induced colitis. Conclusions IL21-induced metabolic dysfunction can incapacitate Treg immunosuppressive function. Desensitizing Tregs to IL21 through various therapeutic approaches can alleviate IBD. This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) K01DK124358, the Pilot & Feasibility Award by the Center for Cell Signaling in Gastroenterology (P30DK084567), and the Mayo Clinic Center for Biomedical Discovery Career Development Award, and David F. and Margaret T. Grohne Cancer Immunology and Immunotherapy (to AOB).

Background: NASH is the progressive form of NAFLD characterized by lipotoxicity, hepatocyte injury, tissue inflammation, and fibrosis. Previously, Rho-associated protein kinase (ROCK) 1 has been implicated in lipotoxic signaling in hepatocytes in vitro and high-fat diet-induced lipogenesis in vivo. However, whether ROCK1 plays a role in liver inflammation and fibrosis during NASH is unclear. Here, we hypothesized that pathogenic activation of ROCK1 promotes murine NASH pathogenesis. Methods and Results: Patients with NASH had increased hepatic ROCK1 expression compared with patients with fatty liver. Similarly, hepatic ROCK1 levels and activity were increased in mice with NASH induced by a western-like diet that is high in fat, fructose, and cholesterol (FFC). Hepatocyte-specific ROCK1 knockout mice on the FFC diet displayed a decrease in liver steatosis, hepatic cell death, liver inflammation, and fibrosis compared with littermate FFC-fed controls. Mechanistically, these effects were associated with a significant attenuation of myeloid cell recruitment. Interestingly, myeloid cell-specific ROCK1 deletion did not affect NASH development in FFC-fed mice. To explore the therapeutic opportunities, mice with established NASH received ROCKi, a novel small molecule kinase inhibitor of ROCK1/2, which preferentially accumulates in liver tissue. ROCK inhibitor treatment ameliorated insulin resistance and decreased liver injury, inflammation, and fibrosis. Conclusions: Genetic or pharmacologic inhibition of ROCK1 activity attenuates murine NASH, suggesting that ROCK1 may be a therapeutic target for treating human NASH.