MCT4 inhibition attenuates inflammatory response to Mycobacterium avium paratuberculosis infection and restores intestinal epithelial integrity in vitro

Ala' Alhendi Saleh A Naser ^*

• University of Central Florida, Orlando, United States

Mycobacterium avium paratuberculosis (MAP) plays a significant role in Crohn's disease (CD). Monocarboxylate transporter 4 (MCT4) is a proton-coupled symporter of lactate that facilitates the inflammatory shift in macrophages alongside an increased reliance on glycolysis. MCT4 is also involved in the negative regulation of intestinal epithelial barrier function. In this in vitro study, we examined the role of MCT4 in macrophages and its impact on intestinal epithelial homeostasis during MAP infection. Infection of THP-1 with MAP upregulated MCT4 expression (2 folds) and resulted in a significant increase in lactate export (1.3 folds), TNFα (13.8 folds), and IL-6 (1.3) via TLR2 activation. Consequently, intestinal damage markers were upregulated, including MUC2 (2.5 folds), NOX-1 (2 folds), SERPINE1 (2.1 folds), IL-6 (1.6 folds), and CLDN2 (1.4 folds). Inhibition of MCT4 during MAP infection using α-cyano-4-hydroxycinnamic acid (CHCα) significantly reduced TNFα and IL-6. This effect on macrophages restored baseline oxidative status and mucin production in HT-29 intestinal cells. Moreover, inhibition of MCT4 in a MAP-infected THP-1-Caco-2 co-culture system restored IL-6 and SERPINE1 to normal levels and enhanced tight junction protein TJP1 (ZO-1) expression. Collectively, the study revealed the significant role of MCT4 in CD pathophysiology during MAP infection and highlighted MCT4 as a potential therapeutic target for CD treatment.