Michael H. Schoenberg

Reperfusion injury after intestinal ischemia

ObjectiveReview the histologic and pathophysiologic alterations seen after intestinal ischemia and reperfusion.Data SourceCurrent literature review.Study SelectionThe most pertinent, current, and representative articles describing results from both animal and human investigations are utilized and di

Combined Targeted Treatment to Eliminate Tumorigenic Cancer Stem Cells in Human Pancreatic Cancer

BACKGROUND & AIMS Pancreatic cancers contain exclusively tumorigenic cancer stem cells (CSCs), which are highly resistant to chemotherapy, resulting in a relative increase in CSC numbers during gemcitabine treatment. Signaling through sonic hedgehog and mammalian target of rapamycin (mTOR), respectively, may be essential for CSC self-renewal and could represent putative targets for novel treatment modalities. METHODS We used in vitro and in vivo models of pancreatic cancer to examine the effects of sonic hedgehog inhibition (cyclopamine/CUR199691) and mTOR blockade (rapamycin) on the tumorigenic CSC population. RESULTS Surprisingly, neither cyclopamine nor rapamycin alone or as supplements to chemotherapy were capable of effectively diminishing the CSC pool. Only the combined inhibition of both pathways together with chemotherapy reduced the number of CSCs to virtually undetectable levels in vitro and in vivo. Most importantly, in vivo administration of this triple combination in mice with established patient-derived pancreatic tumors was reasonably tolerated and translated into significantly prolonged long-term survival. CONCLUSIONS The combined blockade of sonic hedgehog and mTOR signaling together with standard chemotherapy is capable of eliminating pancreatic CSCs. Further preclinical investigation of this promising approach may lead to the development of a novel therapeutic strategy to improve the devastating prognosis of patients with pancreatic cancer.

Pathophysiologic role of oxygen free radicals in acute pancreatitis: initiating event or mediator of tissue damage?

BACKGROUND AND OBJECTIVE Oxidative stress is an important factor in the pathogenesis of acute pancreatitis, as shown in vivo by the beneficial effects of scavenger treatment and in vitro by the potential of free radicals to induce acinar cell damage. However, it is still unclear whether oxygen free radicals (OFR) act only as mediators of tissue damage or represent the initiating event in acute pancreatitis in vivo as well. In the present study the authors aimed to address this issue in an experimental set-up. MATERIALS AND METHODS Two hundred male Wistar rats were randomly assigned to one of the following experimental groups. In two groups, acute necrotizing pancreatitis was induced by retrograde intraductal infusion of 3% sodium taurocholate. Through the abdominal aorta, a catheter was advanced to the origin of the celiac artery for continuous regional arterial (CRA) pretreatment with isotonic saline (NP-S group) or superoxide dismutase/catalase (NP-SOD/CAT group). In another group, oxidative stress was generated by CRA administration of xanthine oxidase and intravenous administration of hypoxanthine (HX/XOD group). Sham-operated rats received isotonic saline both arterially and intraductally. After observation periods of 5 and 30 minutes and 3 and 6 hours, the pancreas was removed for light microscopy and determination of reduced glutathione (GSH), oxidized glutathione (GSSG), conjugated dienes (CD), and malondialdehyde as a marker for OFR-induced lipid peroxidation as well as myeloperoxidase as a parameter for polymorphonuclear leukocyte accumulation. RESULTS A significant decrease of GSH was paralleled by an increased ratio of GSSG per total glutathione and elevated CD levels after 5 minutes in the NP-S group versus the sham-operated group. Thereafter, the percentage of GSSG and GSH returned to normal levels until the 6-hour time point. After a temporary decrease after 30 minutes, CD levels increased again at 3 hours and were significantly higher at 6 hours in contrast to sham-operated rats. Myeloperoxidase levels were significantly elevated at 3 and 6 hours after pancreatitis induction. In contrast to NP-S rats, treatment with SOD/CAT significantly attenuated the changes in glutathione metabolism within the first 30 minutes and the increase of CDs after 6 hours. HX/XOD administration lead to changes in levels of GSH, GSSG, and CDs at 5 minutes as well as to increased myeloperoxidase levels at 3 hours; these changes were similar to those observed in NP-S rats. Acinar cell damage including necrosis was present after 5 minutes in both NP groups, but did not develop in HX/XOD rats. In addition, serum amylase and lipase levels did not increase in the latter group. SOD/CAT treatment significantly attenuated acinar cell damage and inflammatory infiltrate compared with NP-S animals during the later time intervals. CONCLUSION OFRs are important mediators of tissue damage. However, extracellular OFR generation alone does not induce the typical enzymatic and morphologic changes of acute pancreatitis. Factors other than OFRs must be involved for triggering acute pancreatitis in vivo.

Oxidative stress in acute and chronic pancreatitis.

Oxygen radicals mediate an important step in the initiation of acute pancreatitis. These reactive oxygen metabolites are generated at an early stage of the disease. The source of the enhanced production of oxygen radicals, however, still remains unclear. Experimentally, the effectiveness of antioxidant treatment varies from one model to the other, the differences depending on the experimental model and not on the form of pancreatitis that was induced. In most studies, the experimental animals were pretreated before acute pancreatitis was induced. This does not mirror clinical reality because patients are admitted to the hospital after the onset of the disease. It was shown in cerulein-induced pancreatitis, however, that scavenger treatment also mitigated the pancreatic tissue damage after induction of acute pancreatitis. Moreover, antioxidant treatment also attenuated the extrapancreatic complications, thus improving the final outcome of the disease. Initial indirect observations also suggest that in human acute, acute recurrent, and chronic pancreatitis, oxygen free radicals are generated and add to the damage. Concomitantly, these patients suffer from a severe depletion of oxidative stress. Whether or not this disbalance is instrumental in the development and course of disease remains unanswered. Supplementation with antioxidants that are deficient in patients with acute pancreatitis might be a feasible option to the present therapy to avoid extrapancreatic complications. Well-defined, controlled clinical trials involving patients suffering from acute pancreatitis are therefore needed to validate the role of oxygen radicals in this disease.

Free radicals and pathogenesis during ischemia and reperfusion of the cat small intestine

BACKGROUND/AIM In spite of the interest in free radicals as mediators of ischemic damage, most information on these species in biological systems is derived from indirect measurements. Our aim was to obtain more direct information concerning sources of free radical production during ischemia and reperfusion. METHODS We have performed simultaneous measurement of radical generation, purine metabolites, reduced glutathione, neutrophil infiltration and morphological appearance in the cat small intestine in vivo during 60 minutes of ischemia followed by 60 minutes of reperfusion. RESULTS Radical formation increased abruptly on reperfusion and remained elevated in untreated animals. Inhibition by a monoclonal antibody (IB4) against the neutrophil and by allopurinol treatment was paralleled by improvement of biochemical and morphological parameters. The radicals detected during reperfusion could be divided into one component arising directly from the neutrophils, one due to the xanthine oxidase reaction, and one unknown source. CONCLUSIONS Neutrophils are a major source of radical production during reperfusion after ischemia. Radicals formed in the xanthine oxidase reaction seem to function as a primer for the neutrophils. The nonsignificant linear correlation between radical formation and morphological appearance suggests that factors other than free radicals are important for the development of intestinal damage after a period of ischemia.

The role of polymorphonuclear leukocytes and oxygen-derived free radicals in experimental acute pancreatitis: mediators of local destruction and activators of inflammation

Using a retrograde infusion sodium taurocholate pancreatitis model in the rat treatment with oxygen radical scavengers or monoclonal anti‐ICAM‐1 antibody decreased tissue damage and polymorphonuclear leukocytes (PMN) infiltration. Scavengers or anti‐ICAM‐1 treatment attenuated the activating capacity of blood PMNs following zymosan stimulation. The local production of oxygen free radicals in the pancreas by systemic infusion of hypoxanthine and regional infusion of xanthine oxidase did not induce acute pancreatitis, although an increase of infiltrating PMNs was observed. Our data suggest that oxygen free radicals and infiltrating PMNs aggravate acute pancreatitis and that both are important mediators of local destruction and systemic activation of PMNs.

Lipid Peroxidation and Glutathione Metabolism in Chronic Pancreatitis

In experimental models of pancreatitis lipid peroxidation products are increased possibly because of an enhanced generation of oxygen radicals. The purpose of this study was to determine whether lipid peroxidation products are increased in pancreatic tissue and serum of patients suffering from chronic or acute pancreatitis. In 20 patients undergoing operative treatment for chronic (n = 11) and acute pancreatitis (n = 9) the levels of malondialdehyde, conjugated dienes, and reduced and oxidized glutathione were determined in resected tissue samples. The excised tissue was examined and evaluated by light microscopy. Shortly before operation the serum concentrations of malondialdehyde, α-amylase, and lipase were measured. Pancreatic tissue from eight organ donors who had no abdominal trauma or pancreatic disease served as control. In chronic pancreatitis, conjugated dienes as well as malondialdehyde concentrations in the tissue were significantly elevated. Reduced glutathione was significantly decreased, suggesting glutathione depletion due to oxida-tive stress. In acute pancreatitis only the tissue and serum malondialdehyde levels were significantly high, whereas conjugated dienes remained within the normal range. Serum malondialdehyde levels correlated significantly with tissue concentrations (r = 0.76; p < 0.05) but not with the clinical course or the enzyme levels. In chronic pancreatitis, the increased tissue levels of lipid peroxidation products and the changes in glutathione metabolism suggest ongoing peroxidation of lipids due to an enhanced generation of oxygen radicals. In hemorrhagic necrotizing pancreatitis, however, oxygen radical-induced lipid peroxidation cannot be proven. Apparently, other patho-mechanisms are involved in the development of the severe tissue damage.

Clinical course after total parathyroidectomy without autotransplantation in patients with end-stage renal failure

In patients with chronic renal failure, hyperparathyroidism is a common problem and surgical parathyroidectomy (PTX) is frequently required. The three different surgical approaches are subtotal PTX, total PTX with autotransplantation, and total PTX without autotransplantation. Recurrence of hyperparathyroidism varies from 5% to 80% in different studies for the first two surgical approaches. To minimize the risk for recurrence, and because we fear severe relapses with calciphylaxia, we perform total PTX without autotransplantation. From October 1993 to October 1997, 20 patients (9 men and 11 women) underwent total PTX without autotransplantation (median age, 52 years; range, 23 to 74 years; median dialysis time before PTX, 6.5 years; range, 1 to 22 years). All patients were supplemented with vitamin D analogues postoperatively. Patients were followed up for 1 to 48 months (median, 20 months). Bone pain, when present, disappeared within the first week after total PTX. Postoperatively, most patients had temporary hypocalcemia. In the long term, five patients had asymptomatic hypocalcemia. One patient, however, repeatedly had hypocalcemic seizures. Five patients developed asymptomatic hypercalcemia when supplemented with calcitriol. At the end of the individuals observation time, parathyroid hormone (PTH) levels were less than normal in six patients, normal in seven patients, and increased in seven patients despite total PTX. We conclude that total PTX should be reconsidered an option for the treatment of hyperparathyroidism secondary to renal failure. There was no evidence of clinical bone disease after total PTX. Apparently, remaining ectopic parathyroid tissue accounts for PTH levels after total PTX.

The induction of apoptosis in proliferating human fibroblasts by oxygen radicals is associated with a p53- and p21WAF1CIP1 induction

© 1997 Federation of European Biochemical Societies.

The role of oxygen radicals in experimental acute pancreatitis

Oxygen-derived free radicals mediate an important step in the initiation of experimental acute pancreatitis. Thereby, it seems that these reactive oxygen metabolites are generated at an early stage of disease. The source of the enhanced production of oxygen radicals still remains unclear. Experimentally, the efficiency of scavenger treatment varied between different models, whereby these differences depended on the experimental model and not on the form of pancreatitis which was induced. Most studies pretreated the experimental animals before inducing acute pancreatitis. This does not mirror the clinical reality, since patients are admitted to the hospital after onset of the disease. It was shown in Cerulein pancreatitis, however, that scavenger treatment also mitigated the pancreatic tissue damages after induction of acute pancreatitis. Moreover, antioxidant treatment also attenuated the extrapancreatic complications, thus improving the final outcome of the disease. The first indirect observations also suggest that in human acute recurrent and chronic pancreatitis, oxygen free radicals are generated and add to the damages seen. Therefore, well-defined controlled clinical studies with patients suffering from acute pancreatitis are needed to validate the role of oxygen radicals in this disease.