M. P. N. Lewis

Interleukin-10 reduces the systemic inflammatory response in a murine model of intestinal ischemia/reperfusion

BACKGROUND Intestinal ischemia/reperfusion (I/R) is known to increase systemic cytokine levels, as well as to activate neutrophils in distant organs. This study was designed to investigate the effect of interleukin-10 (IL-10) on cytokine release, pulmonary neutrophil accumulation, and histologic changes in a murine model of I/R. METHODS Forty female Swiss-Webster mice were divided into four groups. Group 1 underwent 45 minutes of superior mesenteric artery occlusion followed by 3-hour reperfusion (I/R). Group 2 underwent laparotomy alone (Sham). Group 3 underwent I/R, but was treated with IL-10, 10,000 units IP every 2 hours, starting 1 hour before reperfusion (Pretreatment). Group 4 was treated with an equal dose of IL-10, starting 1 hour after reperfusion (Posttreatment). All animals were killed at 3 hours, standard assays were performed for serum cytokine levels, and lung myeloperoxidase activity and intestinal histology were scored. RESULTS Serum cytokines (TNF-alpha and IL-6), lung myeloperoxidase levels, and histologic score were significantly reduced when IL-10 was administered either before or after reperfusion. CONCLUSIONS IL-10 reduced the severity of local and systemic inflammation in a murine model of intestinal I/R when given before or after reperfusion injury. These observations suggest that IL-10 may exert its effect by blocking cytokine production and distant organ neutrophil accumulation.

Hepatic Kupffer cell blockade reduces mortality of acute hemorrhagic pancreatitis in mice

Inflammatory cytokines derived from the liver may cause distant organ failure and death m severe pancreatms To minmize hver cytokme release, we studied the effects of Kupffer cell blockade on the mortality rate and severity of mflammatlon m a model of that disease Thirty nuce were dlvlded mto three groups Group 1 received gadohmum chloride (1 mg/l00 g mtravenously), which blocks Kupffer cell acuvlty, and regular food Groups 2 and 3 were fed a chohne-deficient, etionine-supplemented diet and developed severe pancreatitls Group 2 (control) received intravenous sahne solution, and group 3 recewed gadohmum chlonde Animals were lulled at 72 hours Serum levels of tumor necrosis factor-a and mterlenkm-1p, mterleukmd, and mterlenkm-10 were determined by enzyme-hnked lmmunosorbent assay Lung neutrophll mfiltration was assessed by myeloperoxldase assay Pancreatic mflammauon was scored m a blinded manner In a separate experiment, mortahty rates were determmed m saline- and gadohnmm-treated animals (n = 100) Gadohmium reduced the levels of all the cytokmes and lung myeloperoxldase (P <0 0.5) Gadolmium also reduced the mortality rate (52% vs 86%,P<0 001) However, the degree of pancreatic mflammaaon was unchanged by gadohnmm treatment These data support the hypothesis that mortality m severe pancreauus may m part be related to the secondary release of hepauc cytokmes.

Ischaemia-reperfusion mechanisms in acute pancreatitis.

The role of ischaemia in the pathogenesis of acute pancreatitis is unknown. Some experimental studies have shown that ischaemia has little effect on the pancreas, while others have found an association with pancreatic injury. Ischaemia-reperfusion damage has been well documented in other sites such as the intestine, cardiac muscle, and skeletal muscle. However, in the pancreas, injury is usually seen only after complete ischaemia, which is uncommon clinically. Experimental chronic pancreatitis is characterized by low pancreatic blood flow, low interstitial pH, and impaired pancreatic tissue oxygenation, which are all findings consistent with the ischaemia-reperfusion mechanisms. Acute pancreatitis is also associated with a reduction in pancreatic blood flow and evidence of free radical generation, similarly suggesting the possibility of ischaemia-reperfusion injury. Ethanol ingestion, which is commonly associated clinically with both chronic and acute pancreatitis, may itself contribute to an ischaemic-reperfusion injury. We have shown that administration of ethanol to cats decreases pancreatic blood flow and may also directly activate neutrophils. Further investigation is needed to determine whether or not these findings are also associated with an ischaemia-reperfusion injury.

Endoscopic measurement of pancreatic tissue perfusion in patients with chronic pancreatitis and control patients

BACKGROUND Pancreatic blood flow is diminished in experimental models of acute and chronic pancreatitis. We attempted to develop a safe and reliable technique for its measurement in patients and to examine blood flow in patients with chronic pancreatitis and in control subjects. METHOD Pancreatic blood flow was measured using the hydrogen gas clearance technique and an endoscopically placed platinum ductal electrode. Pancreatic blood flow was measured in 12 patients with chronic pancreatitis diagnosed clinically and radiographically, and in 11 control patients undergoing endoscopic retrograde cholangiopancreatography (ERCP) for non-pancreatic pathology. RESULTS Patients with chronic pancreatitis had a significantly lower pancreatic blood flow compared with control patients (51.5 versus 91.7 mL/min/100 gm, p < 0.01). With secretin stimulation pancreatic blood flow increased in two control patients, whereas this notable rise was not seen in three patients with chronic pancreatitis. CONCLUSIONS Measurement of pancreatic blood flow with an endoscopically placed electrode is relatively safe and simple to perform. The scarring and vascular fibrosis associated histologically with chronic pancreatitis is reflected in lower pancreatic blood flow.

An ETa/ETb endothelin antagonist ameliorates systemic inflammation in a murine model of acute hemorrhagic pancreatitis

BACKGROUND Endothelin peptides are polykines with strong vasoconstrictor properties. We have previously shown that endothelin antagonism (PD145065) reduces the local severity of acute pancreatitis. We now investigated the effect of endothelin antagonism on systemic inflammation in a model of acute hemorrhagic pancreatitis. METHODS Forty-two mice were divided into four groups. Group 1 was fed standard food plus PD145065 every 8 hours. Group 2 was fed a choline-deficient ethionine (CDE) supplemented diet and given saline every 8 hours. Group 3 was fed a CDE diet and treated with PD145065 every 8 hours from initiation of diet. Group 4 was fed a CDE diet and given PD145065 from 48 hours after initiation of diet. Animals were killed at 70 hours. Serum was collected. Pancreata and lung tissue were harvested. RESULTS Histology score, serum amylase level, lung myeloperoxidase, and interleukin (IL)-10 were all significantly reduced in both treatment groups (groups 3 and 4) (p < 0.05). IL-6 levels were reduced in group 3 only (p < 0.05). The mortality rate did not differ among any of the groups. CONCLUSIONS Endothelin antagonism decreased the severity of acute pancreatitis and reduced markers of systemic inflammation. Late treatment at 48 hours failed to prevent the rise in IL-6. Mortality rates were unaffected by treatment.

Stenting does not decompress the pancreatic duct as effectively as surgery in experimental chronic pancreatitis

BACKGROUND In humans with chronic pancreatitis (CP), pancreatic interstitial pressure (IP) is elevated and pancreatic blood flow (PBF) is reduced. The efficacy of surgical decompression (SD) of the pancreatic duct (ie, pancreaticojejunostomy) is believed to be due to its ability to decrease IP and pancreatic vascular resistance (Rp), which increases PBF. Pancreatic duct stenting (STE) also probably reduces IP and Rp, which may explain its efficacy. The purpose of this study was to compare the efficacy of SD with STE. METHODS CP in cats was created by narrowing the main pancreatic duct. Six weeks later, CP and normal pancreata were isolated and perfused ex vivo under basal conditions and after secretin stimulation. In normal and CP glands, IP and perfusion pressure were measured and Rp (U) was calculated. In two additional groups, the pancreatic duct was decompressed, either by stenting or by complete transection of the duct with a longitudinal capsulotomy. RESULTS In CP glands, IP and Rp were increased and secretory output was markedly reduced compared with the normal (0.65 +/- 0.30 mm Hg and 0.46 +/- 0.04 U vs 3.90 +/- 0.80 mm Hg and 1.68 +/- 0.05 U; P < .05). Secretin administration (2 units) increased IP and Rp in CP glands (6.60 +/- 1.10 mm Hg and 2.87 +/- 0.07 U; P < .05), but these values did not chang in normal glands (0.81 +/- 0.20 and 0.53 +/- 0.03 U; NS). STE and SD decreased IP and Rp in CP glands (2.20 +/- 0.20 to 1.0 +/- 0.40 mm Hg and 1.20 +/- 0.015 to 0.90 +/- 0.01 U, respectively; P < .05). Both methods prevented an increase of IP and Rp after secretin administration. IP and Rp decreased to a greater degree following SD, compared with STE (P < .05). CONCLUSIONS Both STE and SD decreased IP and Rp in this experimental model of CP. However, SD was significantly more effective than STE.

Intragastric Alcohol Causes Endothelin Release from Feline Pancreas

The mechanism by which alcohol causes pancreaticdamage is still largely unknown. One importantcontributory factor may be the endothelins, potentvasoconstricting endothelialderived peptides. The aim of this study was to examine in vivo endothelinrelease from the pancreatic vascular endothelium afteralcohol ingestion. In anesthetized cats immunoreactiveendothelin was measured in serum after instillation of alcohol into the stomach (20 ml, 40%). Afterintragastric alcohol, a rise in endothelin was seen inpancreatic venous effluent (to a mean of 24.5 ±7.7 pg/ml at 60 min). Control serum from the femoral artery exhibited no rise in endothelin (2.11± 1.2 pg/ml). Pancreatic blood flow wassignificantly decreased in a further group to 93% basalafter intravenous infusion of 0.1 nmol/kg ET-1 and to61% after infusion of 1 nmol/kg ET-1. Portal serum levelsof endothelin were 105 pg/ml and 15 pg/ml, respectively,immediately following bolus infusion and decreased tonormal levels within 120 sec. We conclude that the serum endothelin rise after intragastricethanol may be a major factor behind the drop inpancreatic blood flow.

Ethanol-Mediated Neutrophil Extravasation in Feline Pancreas

Ethanol is a common cause of both acute andchronic pancreatitis. Studies in other organs suggestthat polymorphonuclear neutrophils activated by ethanolmay cause tissue injury in a variety of conditions. The aim of this study was to investigate theeffects of ethanol on neutrophil extravasation in thefeline pancreas. Pancreata were isolated and perfused atdifferent flow rates with varying concentrations of ethanol in either a physiological orneutrophil depleted perfusate. Neutrophil extravasationwas assessed by measuring pancreatic tissuemyeloperoxidase (MPO) activity. Ethanol at 2.5 (54.25mmol/liter) was the lowest concentration that still causedsignificant neutrophil extravasation (3.1 ± 0.8vs 1.9 ± 0.2 units, P < 0.05) and wasaccompanied by an increase in vascular resistance of15%. Reduction of pancreatic perfusion by 15% did notsignificantly increase neutrophil extravasation. (1.1± 0.3 vs 1.6 ± 0.2 units, NS) Perfusion ofthe pancreas with neutrophil-depleted blood containingeither ethanol or saline, followed by perfusion withan ethanol-free perfusate, showed an increase inneutrophil extravasation in the ethanol group comparedto the control group (3.2 ± 0.9 vs 1.9 ±0.2 units, P < 0.05). In conclusion, ethanol causesneutrophil extravasation in the feline pancreasindependent of blood flow changes and occurs despite theabsence of direct neutrophil exposure toethanol.