Macrophage TRIM21 lactylation exacerbates infection-induced orchitis through enhancing STAT1-mediated CXCL9 and CXCL10 production.

INTRODUCTION: Infection-induced orchitis, a leading cause of acquired male infertility affecting 8%-12% of couples globally, is driven by unresolved inflammatory responses following bacterial infection. METHODS: We employed uropathogenic Escherichia coli (UPEC)- and lipopolysaccharide (LPS)-induced orchitis models to define the mechanisms underlying testicular inflammation. We interrogated the cellular sources of CXCL9/CXCL10 and assessed macrophage-driven inflammatory cell recruitment and spermatogenic disruption. Mechanistic studies were focused on lysine lactylation, STAT1 protein stability, ubiquitin-proteasome-mediated degradation, and the role of the E3 ubiquitin ligase TRIM21. RESULTS: We demonstrate that macrophages are the predominant source of CXCL9 and CXCL10 responsible for recruiting inflammatory cells into the testis, thereby disrupting spermatogenesis. Mechanistically, the lysine lactylation in macrophages promotes STAT1-mediated CXCL9 and CXCL10 expression by inhibiting ubiquitin-proteasome pathway-mediated STAT1 degradation. Specifically, K345 lactylation of the E3 ubiquitin ligase TRIM21 attenuates ubiquitin-proteasome pathway-mediated STAT1 degradation in macrophages by preventing its interaction with STAT1. DISCUSSION: This study provides the first evidence that non-histone lactylation (TRIM21 K345) exacerbates inflammatory orchitis and highlights TRIM21 lactylation or CXCL9/10 as promising therapeutic targets for infection-associated male infertility.