Esculetin induces apoptosis and functional impairment in INS-1 pancreatic β-cells associated with ER stress and MAPK/JNK signaling.

Esculetin, a coumarin derivative, exhibits diverse biological activities; however, its impact on pancreatic β-cell stress responses and survival remains poorly defined. In this study, we investigated the effects of esculetin on cellular stress signaling, apoptosis, and functional gene expression in INS-1 pancreatic β-cells. Following treatment with 3000 µM esculetin for 6 h, cell viability, proliferation, apoptosis, oxidative stress, endoplasmic reticulum (ER) stress markers, MAPK signaling components, cell cycle distribution, and β-cell-specific gene expression were assessed. In silico molecular docking was performed to explore putative interactions between esculetin and proteins involved in ER stress, MAPK signaling, and apoptosis. Treatment with 3000 µM esculetin for 6 h increased apoptotic cell death by approximately 32-fold and elevated total oxidation status and oxidative stress index. Intracellular insulin, Ca²⁺, and CA19-9 levels were increased, accompanied by cell cycle arrest characterized by G0/G1 phase accumulation and a reduction in the G2/M population. Expression of ER stress sensors ATF6, IRE1α, and CHOP was upregulated, whereas PERK expression was reduced. In parallel, MAPK/JNK pathway activation was evidenced by increased levels of p-ATF2, p-c-Jun, and HSP90, along with decreased p-Elk1. Gene expression analysis revealed marked downregulation of β-cell functional and identity-associated genes, including Ins1, Ins2, IR, Akt, MafA, Nkx6.1, Pdx1, NeuroD1, and Pax6, while FoxO1 expression was upregulated. Collectively, these findings suggest the involvement of ER stress-associated MAPK/JNK signaling in esculetin-induced apoptosis and functional impairment in INS-1 pancreatic β-cells, providing mechanistic insight into stress-associated β-cell dysfunction.