High mobility group box 1 induces calcifcation of aortic valve interstitial cells via toll-like receptor 4

Abstract

Chronic inflammation and the calcifcation of aortic valve interstitial cells (AVICs) are the primary etiologies of calcifc aortic valve disease (CAVD). However, the underlying mechanism remains to be elucidated. The present study investigated the importance of high mobility group box 1 (HMGB1) via toll-like receptor 4 (TLR4) for the regulation of inflammation and calcifcation in AVICs. It was determined that the expression levels of HMGB1 and TLR4 were increased in the calcifc region of aortic valves with CAVD. In cultured primary AVICs from wild-type mice, HMGB1 treatment demonstrated a dose-dependent increase in mineralization levels and osteogenic gene expression. These effects were significantly reduced in AVICs obtained from TLR4 knockout mice (TLR4-/-). In addition, calcifcation was inhibited by TLR4-specifc antibodies in primary AVICs. HMGB1 induced the activation of p38 and nuclear factor-κB (NF-κB) in TLR4-/- primary AVICs, and inhibited p38 and NF-κB in wild-type AVICs treated with TLR4-specifc antibodies. The present study demonstrated that TLR4 may function as an essential mediator of HMGB1-induced calcifcation and in the activation of p38 and NF-κB.