# Loss of LXRβ Drives CD4+ T Cell Senescence and Exacerbates the Progression of Colitis

## TL;DR

Loss of LXRβ in CD4+ T cells increases inflammation and worsens colitis by promoting cell aging.

## Contribution

This study identifies LXRβ as a regulator of CD4+ T cell senescence and intestinal inflammation in colitis.

## Key findings

- LXRβ deficiency in mice worsens colitis and increases CD4+ T cell senescence.
- Senescent Lxrβ−/− CD4+ T cells produce more proinflammatory cytokines.
- LXRβ suppresses T cell senescence via the cGAS/STING pathway.

## Abstract

Background: Liver X receptors (LXRs) are critical regulators of cholesterol homeostasis that modulate T cell function with anti-inflammatory effects. LXR downregulation has been implicated in the pathogenesis of inflammatory bowel disease (IBD), although its underlying mechanisms remain to be fully elucidated. Recent evidence has confirmed the link between T cell senescence and autoimmune diseases. Here, we sought to investigate whether and how LXRs regulate T cell senescence in controlling intestinal inflammation. Methods and Results: We found that LXRβ expression was decreased in the colons of mice with experimental colitis, and LXRβ deficiency (Lxrβ−/−) significantly aggravated their colitis. Intriguingly, this finding was accompanied by enhanced CD4+ T cell senescence both in the colons and spleens of Lxrβ−/− mice, evidenced by upregulation of SA-β-gal levels and the remarkable expansion of effector memory subclusters in CD4+ T cells. Moreover, senescent Lxrβ−/− CD4+ T cells secreted elevated levels of proinflammatory cytokines, especially in effector memory populations, exhibiting a pronounced proinflammatory phenotype. RNA-sequencing further confirmed the role of LXRβ in restricting CD4+ T cell senescence. Mechanistically, the absence of LXRβ in CD4+ T cells directly enhanced senescence by promoting the cGAS/STING pathway. Blocking STING signaling with a targeted inhibitor significantly alleviated senescence in Lxrβ−/− CD4+ T cells. Conclusions: Our findings demonstrate the role of LXRβ in regulating intestinal CD4+ T cell senescence to inhibit colitis development, identifying LXRβ as a potential therapeutic target for treating IBD.