Metformin mitigates inflammation and apoptosis in salivary gland epithelial cells via an AMPK-dependent mechanism in chronic obstructive sialadenitis.

Abstract

Chronic obstructive sialadenitis (COS) frequently results from apoptosis and inflammation in salivary gland epithelial cells, leading to salivary secretion dysfunction. Our previous research suggested that metformin (MET) might have a protective effect on salivary gland epithelial cells, but the underlying mechanism remains unclear. This study investigated the potential impact of MET on COS using human salivary gland tissues, an in vitro inflammatory cell model, and a Wharton's ductal ligation model. Western blot, immunohistochemistry, and immunofluorescence were employed to assess protein expression and phosphorylation. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining and Annexin V-FITC/PI double staining were used to assess cell apoptosis. Signaling pathways potentially affected by MET were assessed by RNA sequencing. The results showed that MET could attenuate LPS-induced cell apoptosis and inflammation in a dose-dependent manner, including increasing the Bcl-2/Bax ratio, inhibiting caspase-3 activation, reducing NF-κB p65 phosphorylation, and decreasing IL-1β and TNF-α levels. Moreover, we observed reduced AMPK phosphorylation in COS patient tissues, and AMPK inhibition reversed the regulation of MET's effect on NF-κB p65 phosphorylation and caspase-3. In the Wharton's ductal ligation model, MET mitigated ligation-induced cell apoptosis and inflammatory responses. These findings suggest that MET activates AMPK to attenuate apoptosis and inflammatory responses in salivary gland epithelial cells, offering a new therapeutic strategy for COS.