Lactic acid induces HSPA1A expression through ERK1/2 activation.

The article investigates how lactic acid (LA), the primary component of the traditional Japanese rice black vinegar Kurozu, induces the expression of heat shock protein A1A (HSPA1A) in rat liver RLN-10 cells. The study demonstrates that LA increases HSPA1A mRNA expression in a concentration-dependent manner through activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling, with this induction being inhibited by MEK1/2 and broad-spectrum protein kinase inhibitors. Additionally, 3,5-dihydroxybenzoic acid (DHBA), a ligand for G protein-coupled receptor 81 (GPR81), also induces HSPA1A expression at lower concentrations than LA, suggesting receptor-mediated involvement. The findings suggest that LA promotes HSPA1A expression via MEK-ERK pathway activation and potentially through GPR81, contributing to the understanding of molecular mechanisms underlying the health benefits associated with Kurozu.