Mild hypothermia protects against sodium taurocholate (NaTc)-induced acute pancreatitis in rats with adverse effects on serum cytokines

Pathophysiologic Mechanisms of Hypothermia-Induced Pancreatic Injury in a Rat Model of Body Surface Cooling

OBJECTIVE

The mechanisms underlying hypothermia-induced pancreatic injury are unclear. Thus, we investigated the pathophysiology of hypothermia-induced pancreatic injury.

METHODS

We created a normal circulatory model with body surface cooling in rats. We divided the rats into control (36°C-38°C), mild hypothermia (33°C-35°C), moderate hypothermia (30°C-32°C), and severe hypothermia (27°C-29°C) (n = 5 per group) groups. Then, we induced circulatory failure with a cooling model using high-dose inhalation anesthesia and divided the rats into control (36°C-38°C) and severe hypothermia (27°C-29°C) (n = 5 per group) groups. Serum samples were collected before the introduction of hypothermia. Serum and pancreatic tissue were collected after maintaining the target body temperature for 1 hour.

RESULTS

Hematoxylin and eosin staining of the pancreas revealed vacuoles and edema in the hypothermia group. Serum amylase (P = 0.056), lactic acid (P < 0.05), interleukin 1β (P < 0.05), interleukin 6 (P < 0.05), and tumor necrosis factor α (P = 0.13) levels were suppressed by hypothermia. The circulatory failure model exhibited pancreatic injury.

CONCLUSIONS

Hypothermia induced bilateral effects on the pancreas. Morphologically, hypothermia induced pancreatic injury based on characteristic pathology typified by vacuoles. Serologically, hypothermia induced protective effects on the pancreas by suppressing amylase and inflammatory cytokine levels.

Multimodal Transgastric Local Pancreatic Hypothermia Reduces Severity of Acute Pancreatitis in Rats and Increases Survival

BACKGROUND & AIMS

Acute pancreatitis (AP) of different etiologies is associated with the activation of different signaling pathways in pancreatic cells, posing challenges to the development of targeted therapies. We investigated whether local pancreatic hypothermia, without systemic hypothermia, could lessen the severity of AP induced by different methods in rats.

METHODS

A urethane balloon with 2 polyurethane tubes was placed inside the stomach of rats. AP was induced in Wistar rats by the administration of cerulein or glyceryl tri-linoleate (GTL). Then, cold water was infused into the balloon to cool the pancreas. Pancreatic temperatures were selected based on those found to decrease acinar cell injury. An un-perfused balloon was used as a control. Pancreatic and rectal temperatures were monitored, and an infrared lamp or heating pad was used to avoid generalized hypothermia. We collected blood, pancreas, kidney, and lung tissues and analyzed them by histology, immunofluorescence, immunoblot, cytokine and chemokine magnetic bead, and DNA damage assays. The effect of hypothermia on signaling pathways initiated by cerulein and GTL was studied in acinar cells.

RESULTS

Rats with pancreatic cooling developed less severe GTL-induced AP compared with rats that received the control balloon. In acinar cells, cooling decreased the lipolysis induced by GTL, increased the micellar form of its fatty acid, lowered the increase in cytosolic calcium, prevented the loss of mitochondrial membrane potential (by 70%-80%), and resulted in a 40%-50% decrease in the uptake of a fatty acid tracer. In rats with AP, cooling decreased pancreatic necrosis by 48%, decreased serum levels of cytokines and markers of cell damage, and decreased markers of lung and renal damage. Pancreatic cooling increased the proportions of rats surviving 6 hours after induction of AP (to 90%, from <10% of rats that received the control balloon). In rats with cerulein-induced AP, pancreatic cooling decreased pancreatic markers of apoptosis and inflammation.

CONCLUSIONS

In rats with AP, transgastric local pancreatic hypothermia decreases pancreatic necrosis, apoptosis, inflammation, and markers of pancreatitis severity and increases survival.

The effects of profound hypothermia on pancreas ischemic injury: a new experimental model

OBJECTIVE

Pancreatic ischemia-reperfusion (IR) has a key role in pancreas surgery and transplantation. Most experimental models evaluate the normothermic phase of the IR. We proposed a hypothermic model of pancreas IR to evaluate the benefic effects of the cold ischemic phase.

METHODS

We performed a reproducible model of hypothermic pancreatic IR. The ischemia was induced in the pancreatic tail portion (1-hour ischemia, 4-hour reperfusion) in 36 Wistar rats. They are divided in 3 groups as follows: group 1 (control), sham; group 2, normothermic IR; and group 3, hypothermic IR. In group 3, the temperature was maintained as close to 4.5°C. After reperfusion, serum amylase and lipase levels, inflammatory mediators (tumor necrosis factor α, interleukin 6), and pancreas histology were evaluated.

RESULTS

In pancreatic IR groups, amylase, cytokines, and histological damage were significantly increased when compared with group 1. In the group 3, we observed a significant decrease in tumor necrosis factor α (P = 0.004) and interleukin 6 (P = 0.001) when compared with group 2. We did not observe significant difference in amylase (P = 0.867), lipase (P = 0.993), and histology (P = 0.201).

CONCLUSIONS

In our experimental model, we reproduced the cold phase of pancreas IR, and the pancreas hypothermia reduced the inflammatory mediators after reperfusion.

Hypothermia slows sequential and parallel steps initiated during caerulein pancreatitis

BACKGROUND AND OBJECTIVES

Multiple deleterious signaling cascades are simultaneously activated in acute pancreatitis (AP), which may limit the success of pharmacologic approaches targeting a single step. We explored whether cooling acinar cells slows distinct steps initiated from a stimulus causing pancreatitis simultaneously, and the temperature range over which inhibition of such deleterious signaling occurs.

METHODS

Caerulein (100 nM) induced trypsinogen activation (TGA), CXCL1, CXCL2 mRNA levels, cell injury were studied at 37 °C, 34 °C, 31 °C, 29 °C and 25 °C in acinar cells. Trypsin, cathepsin B activities and cathepsin B mediated TGA were studied at 37 °C, 23 °C and 4 °C.

RESULTS

There was >80% reduction in TGA, CXCL1 and CXCL2 mRNA levels at 29 °C, and in cell injury at 34 °C, compared to those at 37 °C. Trypsin activity, cathepsin B activity and cathepsin B mediated TGA at 23 °C were respectively, 53%, 64% and 26% of that at 37 °C. Acinar cooling to 31 °C reduced LDH leakage even when cooling was initiated an hour after caerulein stimulation at 37 °C.

CONCLUSIONS

Hypothermia synergistically and simultaneously slows parallel and distinct signaling steps initiated by caerulein, thereby reducing TGA, upregulation of inflammatory mediators and acinar injury.

Cerulein-induced acute pancreatitis in PACAP knockout mice

In our previous study, we reported that cerulein-induced acute pancreatitis is aggravated in pancreatic β-cell-specific pituitary adenylate cyclase-activating polypeptide (PACAP) transgenic mice, showing that an increase in pancreatic PACAP is a risk factor for progression of acute pancreatitis. Accordingly, in this study, we examined the progression of cerulein-induced acute pancreatitis in PACAP knockout (KO) mice. Unexpectedly, after cerulein, about 60% of the KO mice showed severe hypothermia below 30°C by 12 h and most of them died within 72 h. In contrast, the remaining KO and wild-type mice showed normothermia with no mortality. Thus, KO mice could be classified into two groups as hypothermic (HT-KO) and normothermic (NT-KO) to cerulein. Only HT-KO mice subsequently showed severe mortality, although both HT-KO and NT-KO mice exhibited similar susceptibility of lungs to cerulein toxicity, comparable to that in wild-type mice. Regarding pancreatitis, HT-KO mice showed ameliorated pancreatic damage without any rise in serum enzyme activities, whereas NT-KO mice exhibited a similar degree of pancreatitis to wild-type mice. Taken together, the present results indicate that lack of pancreatic PACAP did not aggravate, but rather ameliorated, cerulein-induced pancreatitis. In addition, about half of KO mice showed a novel phenotype in which cerulein caused rapid and severe hypothermia, followed by death.

Early induction of moderate hypothermia suppresses systemic inflammatory cytokines and intracellular adhesion molecule-1 in rats with caerulein-induced pancreatitis and endotoxemia

OBJECTIVES

To evaluate the systemic effects of moderate hypothermia (MH) and the timing of induction on acute pancreatitis (AP) and endotoxemia in rats.

METHODS

The effects of MH were compared in 4 groups, that is, sham group (38 degrees C), control group (38 degrees C), early MH group (32 degrees C on administration of lipopolysaccharide [LPS]), and delayed MH group (32 degrees C 1 hour after LPS). AP and endotoxemia were induced by intramuscular injection of caerulein and intraperitoneal injection of LPS.

RESULTS

Serum interleukin 6 (IL-6) in both MH groups was significantly lower than that in the control group at 3 hours. Serum interleukin 10 (IL-10) in the early MH group was significantly higher than those in the other 3 groups at 1 hour. IL-10/IL-6 ratios in both MH groups were significantly higher than that in the control group at 3 hours. Serum soluble intercellular adhesion molecule (sICAM-1) in both MH groups was significantly lower than that in the control group at 3 hours. Serum sICAM-1 in the early MH group was significantly lower than that in the delayed MH group. The tendency of pancreatic ICAM-1 was similar to that of serum sICAM-1.

CONCLUSIONS

Early induction of MH might be protective against pancreatic injury and systemic inflammation in AP and endotoxemia.

Preparation method of an ideal model of multiple organ injury of rat with severe acute pancreatitis

AIM: To establish an ideal model of multiple organ injury of rats with severe acute pancreatitis (SAP).

METHODS: SAP models were induced by retrograde injection of 0.1 mL/100 g 3.5% sodium taurocholate into the biliopancreatic duct of Sprague-Dawley rats. The plasma and samples of multiple organ tissues of rats were collected at 3, 6 and 12 h after modeling. The ascites volume, ascites/body weight ratio, and contents of amylase, endotoxin, endothelin-1 (ET-1), nitrogen monoxidum (NO), phospholipase A₂ (PLA₂), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) in plasma were determined. The histological changes of multiple organs were observed under light microscope.

RESULTS: The ascites volume, ascites/body weight ratio, and contents of various inflammatory mediators in blood were higher in the model group than in the sham operation group at all time points [2.38 (1.10), 2.58 (0.70), 2.54 (0.71) vs 0.20 (0.04), 0.30 (0.30), 0.22 (0.10) at 3, 6 and 12 h in ascites/body weight ratio; 1582 (284), 1769 (362), 1618 (302) (U/L) vs 5303 (1373), 6276 (1029), 7538 (2934) (U/L) at 3, 6 and 12 h in Amylase; 0.016 (0.005), 0.016 (0.010), 0.014 (0.015) (EU/mL) vs 0.053 (0.029), 0.059 (0.037), 0.060 (0.022) (EU/mL) at 3, 6 and 12 h in Endotoxin; 3.900 (3.200), 4.000 (1.700), 5.300 (3.000) (ng/L) vs 41.438 (37.721), 92.151 (23.119), 65.016 (26.806) (ng/L) at 3, 6 and 12 h in TNF-α, all P < 0.01]. Visible congestion, edema and lamellar necrosis and massive leukocytic infiltration were found in the pancreas of rats of model group. There were also pathological changes of lung, liver, kidney, ileum, lymphonode, thymus, myocardium and brain.

CONCLUSION: This rat model features reliability, convenience and a high achievement ratio. Complicated with multiple organ injury, it is an ideal animal model of SAP.

Oxidative stress is enhanced by hypothermia imposed on cerulein-induced pancreatitis in rats

BACKGROUND

Hypothermia is a frequent event in severe acute pancreatitis (AP) and its real effects on the normal pancreas have not been well demonstrated. Moreover, neither have its effects on the outcome of acute pancreatitis been fully investigated. One hypothesis is that oxidative stress may be implicated in lesions caused or treated by hypothermia.

AIM OF THE STUDY

To investigate the effect of hypothermia in cerulein-induced acute pancreatitis (CIAP) in rats and the role played by oxidative stress in this process.

METHODS

Male Wistar rats were divided into hypothermic and normothermic groups. Hypothermia was induced with a cold mattress and rectal temperature was kept at 30 masculineC for one hour. Acute pancreatitis was induced with 2 doses of cerulein (20 ìg/kg) administered at a one-hour interval. Serum amylase, pancreas vascular permeability by Evan's blue method, pancreas wet-to-dry weight ratio and histopathology were analyzed in each group.

RESULTS

When compared with normothermic rats, hypothermic animals, with cerulein-induced acute pancreatitis, showed higher levels of pancreatic vascular permeability (p < 0.05), pancreas wet-to-dry weight ratio (p = 0.03), and histologically verified edema (p < 0.05), but similar serum amylase levels. The hypothermic group showed a higher oxidized-reduced glutathione ratio than the normothermic group.

CONCLUSION

Moderate hypothermia produced a greater inflammatory response in established acute pancreatitis induced by cerulein in rats. Moreover, this study suggests that oxidative stress may be one of the mechanisms responsible for the worse outcome in hypothermic rats with cerulein-induced acute pancreatitis.

Moderate hypothermia therapy for acute liver failure in rats before liver transplantation

AIM: To observe the effect of moderate hypothermia on the donated livers in rats with acute liver failure (ALF) before liver transplantation.

METHODS: ALF rats model were established by hepatectomy and hepatic devascularization. In situ liver transplantations were carried out for hypothermia treated group (35.0ºC) and the control group (37.5ºC) 12 h after the transplantation. Blood and tissue samples were collected just before and 6 or 24 h after transplantation. The concentrations of TNF-α were compared before and after the transplantation. The content of malondialdehyde (MDA) and the apoptotic rate of hepatic cells after the transplantation were observed. The apoptotic rate and MDA contents in donated liver were also assayed. The morphological changes of liver tissues were observed under microscope.

RESULTS: In the hypothermia treated group, the concentrations of TNF-α before and after the transplantation were significantly lower than those in the control group (19.3±5.9 vs 43.4±9.0 µg/L, t= 5.008, P = 0.007; 6 h, 97.7±18.3 vs 137.1±23.3 µg/L, t = 9.471, P = 0.001); the MDA contents and apoptotic rate after transplantation were also significantly lower than those in the control group (407.1±49.4 vs 598.2±61.8 nmol/L, t = 34.46, P = 0.001; 18.3±3.9% vs 23.6±4.3%, t = 29.63, P = 0.001).

CONCLUSION: Moderate hypothermia can decrease TNF-α level and relieve the damages of the donated liver in rats with ALF.