Rosmarinic acid improves intestinal barrier integrity through PI3K/AKT/Nrf2-mediated regulation of tight junction protein expression

Rosmarinic acid (RA), a polyphenolic compound, exhibits diverse pharmacological activities, including anti-inflammatory, antioxidant, and antitumor effects. Despite its therapeutic potentials, the mechanisms underlying its efficacy in ulcerative colitis (UC), a chronic inflammatory bowel disease characterized by intestinal epithelial barrier dysfunction, remain incompletely elucidated. This study investigates RA's protective effects in UC using complementary in vivo and in vitro models. In a dextran sulfate sodium (DSS)-induced murine colitis model, RA administration significantly attenuated disease severity, mitigating weight loss, preventing colon shortening, and reducing histopathological inflammatory infiltration. RA restored intestinal barrier integrity via upregulation of key tight junction proteins such as ZO-1, occludin, claudin-1 in colonic tissues. Mechanistic analyses in lipopolysaccharide (LPS)-stimulated NCM460 human colonic epithelial cells revealed that RA inhibited phosphatidylinositol 3-kinase (PI3K)/AKT pathway activation, as evidenced by reducing AKT phosphorylation (p-AKT), while enhancing nuclear factor erythroid 2-related factor 2 (Nrf2) expression. Pharmacological PI3K inhibition with LY294002 abolished RA-induced upregulation of Nrf2 and TJPs, confirming the PI3K/AKT/Nrf2 axis as the central signaling cascade mediating RA's protective effects. Collectively, these findings elucidate a novel mechanism by which RA preserves intestinal barrier integrity through PI3K/AKT/Nrf2 axis modulation and propose a targeted therapeutic strategy for UC management.