Hydrostatic pressure induces mitochondrial oxidative stress and mtDNA-mediated cGAS-STING activation in acute pancreatitis.

Abstract

Increased mechanical pressure is a well-recognized feature of acute pancreatitis (AP), but its pathological mechanisms remain elusive. Although previous studies have emphasized shear stress-induced pancreatic injury, the effects of static hydrostatic pressure have been underappreciated. Mitochondria act as mechanosensitive organelles, and mechanical stimuli can induce mitochondrial oxidative stress. Release of mitochondrial DNA (mtDNA) could trigger activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway in immune cells. However, whether increased hydrostatic pressure can induce mtDNA-mediated cGAS-STING activation in pancreatic cells is unknown. In this study, we explored the mechanistic links between pressure-induced mitochondrial dysfunction, mtDNA release, and innate immune signaling activation in AP. Acute pancreatitis was induced in mice using two models: (1) intraperitoneal injection of caerulein combined with lipopolysaccharide (LPS), and (2) retrograde infusion of methylene blue-balanced salt solution through the pancreatic duct followed by briefly clamping to mimic elevated intrapancreatic hydrostatic pressure. AR42J cells, an immortalized pancreatic adenocarcinoma cell line exhibiting acinar-like characteristics, were cultured under controlled high hydrostatic pressure conditions to investigate pressure-induced cellular responses in vitro. Elevated hydrostatic pressure markedly aggravated mitochondrial dysfunction and induced mitochondrial permeability transition pore (MPTP) opening, accompanied by increased mitochondrial ROS production, leading to mtDNA leakage and cGAS-STING pathway activation, which exacerbated inflammatory responses and AP. Inhibition of MPTP suppressed mtDNA release, reduced STING activation, and ameliorated pancreatic injury. Collectively, our data show that increased hydrostatic pressure is a critical but underappreciated mechanical insult that causes mitochondrial dysfunction and mtDNA release in pancreatic cells through MPTP opening. The associated increase in mitochondrial oxidative stress may represent a key upstream trigger in this process, and cytosolic mtDNA could subsequently activate cGAS-STING signaling and exacerbate inflammatory responses in AP. These findings suggest that mitochondrial permeability transition is a potential therapeutic target in pressure-associated AP.