Molecular hydrogen accelerates the reversal of acute obstructive cholangitis-induced liver dysfunction by restoring gap and tight junctions

Introduction

The function of the ‘blood-biliary barrier’ is to ensure bile secretion without leakage from the centrizonal region to the periportal zone and then to bile ducts, in a highly ordered manner (1). Because gap junctions (GJs) regulate direct intercellular communication and tight junctions (TJs) completely seal the bile canaliculi, these are essential to maintain the function of the blood-biliary barrier (1). The most common GJ proteins in the liver, the connexins (Cx, also termed gap junction proteins) Cx26 (gap junction protein β2) and Cx32 (gap junction protein β1) have been found to be downregulated during obstructive cholestasis and lipopolysaccharide (LPS)-induced hepatocellular cholestasis (2). In addition, expression of TJ proteins, such as tight junction protein 1 (ZO1/TJP1), has also been reported to be influenced by LPS or liver injury (3,4). Alterations in GJ and TJ composition are associated with hepatic disease and lead to cholangiovenous reflux, liver injury, and even systemic disease (1). Acute obstructive cholangitis (AOC) is a bacterial infection caused by biliary obstruction, and it leads to systemic signs of infection (5). Due to the high biliary pressure and the presence of LPS, blood-biliary barrier disruption may occur in cases of AOC (5). In severe cases of AOC, LPS and cholochrome may be continuously released into the blood until functional restoration of the barrier occurs (5). Therefore, accelerating the restoration of hepatocyte GJs and TJs may improve patient prognosis and shorten the course of AOC.

Molecular hydrogen (H₂) is regarded as an important physiological regulatory factor with antioxidant effects, which protect cells and organs from injury caused by reactive oxygen species (ROS) and oxidative stress (6–8). Anti-inflammatory effects are another important physiological regulatory function of H₂ (6). H₂ may therefore be a promising therapeutic strategy to combat certain pathologies and sepsis (9–11). Given that H₂ serves important physiological functions, it is possible that H₂ may have a role in the process of AOC.

Therefore, the present study hypothesized that H₂ administration may help reverse the AOC-induced disruption of GJs and TJs in hepatocytes and accelerate the tissue recovery process.

Materials and methods

Experimental animals

Male Wistar rats, weighing 300–350 g (13–16 weeks old) were purchased from Shanghai SLAC Laboratory Animal Co., Ltd. All procedures were approved...