Effects of melatonin on Trx-1 expression in the lungs of rats with acute necrotizing pancreatitis

AIM: To investigate the expression of thioredoxin-1 (Trx-1) in the lungs of rats with L-arginine (L-Arg)-induced acute necrotizing pancreatitis (ANP) and assess the effects of melatonin on Trx-1 expression.

METHODS: Seventy-two male Sprague-Dawley rats were randomly divided into three groups: normal control group, model control group and melatonin intervention group. The ANP model group was intraperitoneally injected three times with 6% L-Arg at a dose of 25 mL/kg body weight at an interval of 1 h to induce ANP. The normal control group was intraperitoneally injected with equal volumes of normal saline. The melatonin intervention group was injected intraperitoneally with 0.25% melatonin at a dose of 20 mL/kg body weight half an hour before ANP induction. Rats were executed at 6, 12 and 24 hours after last L-Arg injection. The expression of Trx-1 in the lungs was detected by immunohistochemistry. The pathological changes in the pancreas and lungs were analyzed and scored according to Kusser's and Lei's criteria, respectively. The contents of serum Trx-1 and amylase were measured.

RESULTS: At 6, 12 and 24 hours after last L-Arg injection, the pathological changes in the pancreas and lungs in the model control group were more severe than those in the normal control group (all P < 0.01). However, the pathological changes in the pancreas and lungs in the melatonin intervention group were milder than those in the model control group (P < 0.01 or 0.05). At 24 hours, the content of serum amylase in the model control group was significantly higher than that in the normal control group (4 598 U/L ± 2 274 U/L vs 2 033 U/L ± 863 U/L, P < 0.01). In contrast, the content of serum amylase in the melatonin intervention group was lower than that in the model control group (3 990 U/L ± 1 146 U/L vs 4 598 U/L ± 2 274 U/L, P < 0.05). Compared to the normal control group, serum Trx-1 contents in the model control group significantly decreased at 6 and 12 hours but significantly increased at 24 hours. The contents of serum Trx-1 in melatonin intervention group at 6 and 12 hours were significantly higher than those in the model control group.

CONCLUSION: Lung injury is closely related to pancreatic injury in ANP. The expression of Trx-1 in the lungs of rats with ANP increases significantly. Overexpression of Trx-1 in the lungs is closely associated with the development of ANP and acute pancreatitis-associated lung injury. Melatonin can, to a certain extent, alter the expression of Trx-1 and reduce pancreatic and pulmonary injury in ANP in rats.