Disruption of the TSLP-TSLPR-LAP signaling between epithelial and dendritic cells through hyperlipidemia contributes to regulatory T-Cell defects in atherosclerotic mice

Regulatory T-Cells (Tregs) play a protective role against the development of atherosclerosis. Moreover, thymic stromal lymphopoietin (TSLP)/thymic stromal lymphopoietin receptor (TSLPR) signaling in myeloid dendritic cells (DCs) promote Treg differentiation. Here, we examined the potential role of TSLP/TSLPR on Treg homeostasis in atherosclerosis. The frequencies of both latency-associated peptide (LAP)+ and Foxp3+ Tregs were reduced in the thymus and spleen of ApoE−/− mice compared with C57BL/6 mice, and this effect was associated with decreased thymic output. The tolerogenic function of DCs obtained from ApoE−/− mice was compromised compared with those from C57BL/6 mice. The expression of TSLP and TSLPR was also inhibited in ApoE−/− mice. In addition, we found that ox-LDL attenuated TSLP expression in cultured thymic epithelial cells (TECs) through the activation of retinoid X receptor alpha (RXRA) and IL-1β and decreased LAP and PD-L1 expression in oxLDL-activated DCs while both were up-regulated in TSLP-activated DCs. We also observed that the TSLP-DCs mediated differentiation of Tregs was abrogated through LAP neutralization. Furthermore, TSLP injection rescued Treg defects in ApoE−/− mice. These findings suggest that Treg defects in ApoE−/− mice might partially be attributed to the disruption of TSLP-TSLPR-LAP signaling in epithelial cells (ECs) and DCs.