Human epithelial cells stimulated with Vibrio cholerae produce thymic stromal lymphopoietin and promote dendritic cell-mediated inflammatory Th2 response

Vibrio cholerae induces acute inflammatory response at intestinal epithelial surface; the underlying cellular immune mechanisms for such effects are largely unexplored. Mucosal immune response is controlled by crosstalk between the intestinal epithelial cells (ECs) and dendritic cells (DCs). An EC-derived cytokine thymic stromal lymphopoietin (TSLP) has been found a critical regulator of several human inflammatory conditions. TSLP is highly elevated in ECs stimulated with V. cholerae and its recombinant flagellin (rFlaA). V. cholerae treated human ECs produce DC-attracting chemokine MIP-3α (CCL20). Flagellin, a potent V. cholerae factor was responsible for maximum stimulation of epithelial CCL20 production and subsequent DC activation. Activated DCs express high levels of costimulatory molecules and secrete inflammatory cytokines TNF-α, IL-6 and IL-1β. Bacteria stimulated ECs conditioned DCs to produce Th2 cell-attracting chemokines CCL17 and CCL22. TSLP and other mediators present in the V. cholerae stimulated EC-culture filtrate potently activated DCs, which subsequently primed CD4+T cells to differentiate into T helper type 2 (Th2) cells that produce high amounts of IL-4, IL-13 and TNF-α and low IFN-γ. TSLP-induced proinflammatory response in DCs involved the transcriptional mechanisms, MAPKs (ERK1/2, p38 and JNK) and STAT3 activation. This study suggests TSLP and other mediators released from ECs in response to V. cholerae colonization actively influence DCs in initiating inflammatory response.