Vildagliptin, a DPP-4 inhibitor, attenuates carbon tetrachloride-induced liver fibrosis by targeting ERK1/2, p38α, and NF-κB signaling.

Mitogen-activated protein kinases (MAPKs) and nuclear factor (NF)-ĸB signaling have been recognized for their causal connection with liver fibrosis. Hence, it is encouraging to discover drugs that can modify the interactions between these signaling cascades. It has been suggested that glucagon-like peptide-1 receptors (GLP-1Rs) might have a role in the observed hepatoprotection of dipeptidyl peptidase-4 inhibitors other than vildagliptin (VLD). Consequently, we aimed to elucidate the mechanisms underlying its potential antifibrotic activity in a CCl4-intoxicated mouse model. VLD increased the percentage of viable CCl4-intoxicated primary rat hepatocytes in vitro. It also attenuated hepatic fibrosis, improved liver function, and prolonged survival of CCl4-intoxicated mice in a dose-dependent manner. This hepatoprotection might be mediated mainly through interference with extracellular signal-regulated protein kinase 1/2 phosphorylation, the most downstream signal of the MAPK pathway. In addition, VLD hepatoprotective activity could be partially mediated through inhibition of p38α phosphorylation and phosphorylation-induced NF-ĸB activation. As a result, VLD downregulated profibrogenic mediators, such as tumor necrosis factor α, transforming growth factor ß, tissue inhibitor of metalloproteinase 1 and platelet-derived growth factor BB. Consequently, decreased expression levels of fibrosis markers, such as hydroxyproline and α smooth muscle actin, were confirmed. VLD showed a strong trend toward increasing the antioxidant defense machinery of fibrotic tissue, and we confirmed that GLP-1Rs were not implicated in the observed hepatoprotection. Since VLD poses little risk of hypoglycemia and is a safe drug for patients with liver injury, it may be a hopeful candidate for adjuvant treatment of liver fibrosis in humans.

Celastrol augments sensitivity of NLRP3 to CP-456773 by modulating HSP-90 and inducing autophagy in dextran sodium sulphate-induced colitis in rats.

NLRP3, one of the HSP-90 clients, has been defined as a critical component of IBD. In a rat model of DSS-induced colitis, we investigated the anti-inflammatory potential of the combined therapy with CP-456773 (CP), an NLRP3 inhibitor, and celastrol (CSR), an NF-κB inhibitor. Our results revealed that the CSR/CP combined therapy (CCCT) attenuated colon shortening, DAI and MDI in addition to improvement of the colonic histological picture. Moreover, the CCCT increased the antioxidant defense machinery of the colonic tissue and decreased MPO activity. Furthermore, the inflammation markers such as TNF-α and IL-6 were downregulated. These effects might be attributed to the inhibitory effect of CSR on the priming step of the NLRP3 inflammasome activation by interrupting NF-κB signalling and inhibition of HSP-90 (at the protein and mRNA levels) along with inhibitory effect of CP on the expression of the NLRP3. These latter effects resulted in decreased tissue expression and activity of the caspase-1 and repressing the subsequent release of the active forms of IL-1ß and IL-18, hence, the pyroptosis process is restrained. Additionally, the CCCT resulted in inducing autophagy by AMPK/mTOR-dependent mechanisms leading to the accumulation of BECN1 protein and a significant decrease in the levels of p62 SQSTM1. The inhibitory effect on HSP-90 in conjunction with induction of autophagy suggest increased autophagic degradation of NLRP3. This novel approach provides a basis for the clinical application of this combination in IBD treatment and might also be promising for the pharmacological intervention of other NLRP3 inflammasome-dependent inflammatory conditions.