Effects of pancreatic duct ligation and aging on acute taurocholate-induced pancreatitis. Experiments in the perfused pancreas in rats

Cannabinoid receptor 2 agonist attenuates pain related behavior in rats with chronic alcohol/high fat diet induced pancreatitis

Background

Chronic Pancreatitis (CP) is a complex and multifactorial syndrome. Many contributing factors result in development of dysfunctional pain in a significant number of patients. Drugs developed to treat a variety of pain states fall short of providing effective analgesia for patients with chronic pancreatitis, often providing minimal to partial pain relief over time with significant side effects. Recently, availability of selective pharmacological tools has enabled great advances in our knowledge of the role of the cannabinoid receptors in pathophysiology. In particular, cannabinoid receptor 2 (CB2) has emerged as an attractive target for management of chronic pain, as demonstrated in several studies with inflammatory and neuropathic preclinical pain models. In this study, the analgesic efficacy of a novel, highly selective CB2 receptor agonist, LY3038404 HCl, is investigated in a chronic pancreatitis pain model, induced with an alcohol/high fat (AHF) diet.

Results

Rats fed the AHF diet developed visceral pain-like behaviors detectable by week 3 and reached a maximum at week 5 that persists as long as the diet is maintained. Rats with AHF induced chronic pancreatitis were treated with LY3038404 HCl (10 mg/kg, orally, twice a day for 9 days). The treated animals demonstrated significantly alleviated pain related behaviors after 3 days of dosing, including increased paw withdrawal thresholds (PWT), prolonged abdominal withdrawal latencies (ABWL), and decreased nocifensive responses to noxious 44°C hotplate stimuli. Terminal histological analysis of pancreatic tissue sections from the AHF chronic pancreatitis animals demonstrated extensive injury, including a global pancreatic gland degeneration (cellular atrophy), vacuolization (fat deposition), and fibrosis. After the LY3038404 HCl treatment, pancreatic tissue was significantly protected from severe damage and fibrosis. LY3038404 HCl affected neither open field exploratory behaviors nor dark/light box preferences as measures of higher brain and motor functions.

Conclusion

LY3038404 HCl, a potent CB2 receptor agonist, possesses tissue protective and analgesic properties without effects on higher brain function. Thus, activation of CB2 receptors is suggested as a potential therapeutic target for visceral inflammation and pain management.

Age-dependent vulnerability to experimental acute pancreatitis is associated with increased systemic inflammation and thrombosis

The severity and mortality rates of acute pancreatitis (AP) are significantly elevated in the elderly population. However, due to a lack of appropriate animal models, the underlying mechanisms for this age-dependent vulnerability remain largely unknown. The purpose of this study was to characterize a murine model of AP, which displays age-associated severity, and to use this model to identify pathophysiologies that are distinctive of the aged with AP. AP was induced in young (4-5 months), middle-aged (12-13 months), and aged (23-25 months) C57BL/6 mice by repeated injection of caerulein, a homologue of the gastrointestinal hormone cholecystokinin. Approximately 10% of aged mice died during AP, while young and middle-aged mice showed no mortality. Although both young and aged mice exhibited early signs of edema and inflammation in the pancreas, kidney, and lung, young mice showed signs of recovery within 24 h, while aged mice exhibited increasingly severe tissue damage and cell death. There was a significant age-dependent increase in pancreatic neutrophil activation and systemic inflammation as assessed by pancreatic myeloperoxidase and plasma interleukin-6 (IL-6) concentration, respectively. Importantly, aged but not young mice with AP showed significantly elevated thrombosis in the lung and kidney as well as a marked increase in plasma concentration of plasminogen activator inhibitor-1 (PAI-1), a primary inhibitor of the fibrinolytic system. These results demonstrate that aging is associated with increased severity of AP characterized by augmented and prolonged pancreatic inflammation and the presence of multiple extra-pancreatic sequelae including thrombosis.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.

Melatonin modulates the severity of taurocholate-induced acute pancreatitis in the rat

The aim of this study was to investigate the effects of melatonin on serum amylase, tumor necrosis factor-alpha (TNF-alpha) and histological changes in rats with taurocholate-induced acute pancreatitis. Thirty male Wistar rats were randomly divided into three groups; group 1, group 2 and group 3 were enrolled as melatonin, control and sham groups, respectively (n = 10 per group). Acute pancreatitis was induced by 1 ml/kg body weight using 5% taurocholate injection into the biliopancreatic duct in groups 1 and 2 after clamping the hepatic duct. Those in group 1 received 50 mg/kg body weight melatonin by intraperitoneal (i.p.) injection. Group 2 received physiological saline i.p. at the same dose. Group 3 solely underwent laparotomy with cannulation of the biliopancreatic duct. Twenty-four hours after the intervention, the rats were killed, and serum samples were collected to measure amylase and TNF-alpha levels. Simultaneously, pancreatic tissues were removed, stained with hematoxylin-eosin and examined under a light microscope. Serum amylase and TNF-alpha levels were significantly lower in the melatonin group compared to the controls (P < 0.001). The total histological score, including edema, inflammation, perivascular infiltrate, acinar necrosis, fat necrosis and hemorrhage, was also significantly lower in the melatonin group as compared to the control (P < 0.0001). In conclusion, melatonin is potentially capable of reducing pancreatic damage by decreasing serum TNF-alpha levels in taurocholate-induced acute pancreatitis in rats. This result supports the idea that melatonin might be beneficial in ameliorating the severity of acute pancreatitis.