Cystathionine-gamma-lyase gene silencing with siRNA in monocytes/macrophages protects mice against acute pancreatitis

Hydrogen sulphide (H2S) is an endogenous inflammatory mediator produced by cystathionine-gamma-lyase (CSE) in monocytes/macrophages. To determine the role of H2S and macrophages in inflammation, we used small interference RNA (siRNA) to target the CSE gene and investigated its effect in a mouse model of acute pancreatitis. Acute pancreatitis is characterised by increased levels of plasma amylase, myeloperoxidase (MPO) activity and pro-inflammatory cytokines and chemokines in the pancreas and lung. SiRNA treatment attenuated inflammation in the pancreas and lungs of mice following caerulein-induced acute pancreatitis. MPO activity increased in caerulein-induced acute pancreatitis (16.21 +/- 3.571 SD fold increase over control) and treatment with siRNA significantly reduced this (mean 3.555 +/- 2.522 SD fold increase over control) (p < 0.0001). Similarly, lung MPO activity increased following treatment with caerulein (3.56 +/- 0.941 SD fold increase over control) while siRNA treatment significantly reduced MPO activity (0.8243 +/- 0.4353 SD fold increase over control) (p < 0.0001). Caerulein treatment increased plasma amylase activity (7094 +/- 207 U/l) and this significantly decreased following siRNA administration (5895 +/- 115 U/l) (p < 0.0001). Cytokine and chemokine levels in caerulein-induced acute pancreatitis reduced following treatment with siRNA. For example, siRNA treatment significantly decreased pancreatic and lung monocyte chemoattractant protein (MCP)-1 (169.8 +/- 59.75 SD; 90.01 +/- 46.97 SD pg/ml, respectively) compared to caerulein-treated mice (324.7 +/- 103.9 SD; 222.8 +/- 85.37 SD pg/ml, pancreas and lun,g respectively) (p < 0.0001). These findings show a crucial pro-inflammatory role for H2S synthesised by CSE in macrophages in acute pancreatitis and suggest CSE gene silencing with siRNA as a potential therapeutic approach for this condition.