Beneficial Effects of Trypsin Inhibitors Derived from a Spider Venom Peptide in L-Arginine-Induced Severe Acute Pancreatitis in Mice

HWTI is a 55-residue protein isolated from the venom of the spider Ornithoctonus huwena. It is a potent trypsin inhibitor and a moderate voltage-gated potassium channel blocker. Here, we designed and expressed two HWTI mutants, HWTI-mut1 and HWTI-mut2, in which the potassium channel inhibitory activity was reduced while the trypsin inhibitory activity of the wild type form (approximately 5 EPU/mg) was retained. Animal studies showed that these mutants were less toxic than HWTI. The effects of HWTI and HWTI-mut1 were examined in a mouse model of acute pancreatitis induced by intraperitoneal injection of a large dose of L-arginine (4 mg/kg, twice). Serum amylase and serum lipase activities were assessed, and pathological sections of the pancreas were examined. Treatment with HWTI and HWTI-mut1 significantly reduced serum amylase and lipase levels in a dose dependent manner. Compared with the control group, at 4 mg/kg, HWTI significantly reduced serum amylase level by 47% and serum lipase level by 73%, while HWTI-mut1 significantly reduced serum amylase level by 59% and serum lipase level by 72%. Moreover, HWTI and HWTI-mut1 effectively protected the pancreas from acinar cell damage and inflammatory cell infiltration. The trypsin inhibitory potency and lower neurotoxicity of HWTI-mut1 suggest that it could potentially be developed as a drug for the treatment of acute pancreatitis with few side effects.