P S Haber

Periacinar stellate shaped cells in rat pancreas: identification, isolation, and culture

Background—The pathogenesis of pancreatic fibrosis is unknown. In the liver, stellate cells (vitamin A storing cells) play a significant role in the development of fibrosis. Aims—To determine whether cells resembling hepatic stellate cells are present in rat pancreas, and if so, to compare their number with the number of stellate cells in the liver, and isolate and culture these cells from rat pancreas. Methods—Liver and pancreatic sections from chow fed rats were immunostained for desmin, glial fibrillary acidic protein (GFAP), and α smooth muscle actin (α-SMA). Pancreatic stellate shaped cells were isolated using a Nycodenz gradient, cultured on plastic, and examined by phase contrast and fluorescence microscopy, and by immunostaining for desmin, GFAP, and α-SMA. Results—In both liver and pancreatic sections, stellate shaped cells were observed; these were positive for desmin and GFAP and negative for α-SMA. Pancreatic stellate shaped cells had a periacinar distribution. They comprised 3.99% of all pancreatic cells; hepatic stellate cells comprised 7.94% of all hepatic cells. The stellate shaped cells from rat pancreas grew readily in culture. Cells cultured for 24 hours had an angular appearance, contained lipid droplets manifesting positive vitamin A autofluorescence, and stained positively for desmin but negatively for α-SMA. At 48 hours, cells were positive for α-SMA. Conclusions—Cells resembling hepatic stellate cells are present in rat pancreas in a number comparable with that of stellate cells in the liver. These stellate shaped pancreatic cells can be isolated and cultured in vitro.

Pancreatic stellate cells are activated by proinflammatory cytokines: implications for pancreatic fibrogenesis

BACKGROUND The pathogenesis of pancreatic fibrosis is unknown. In the liver, stellate cells play a major role in fibrogenesis by synthesising increased amounts of collagen and other extracellular matrix (ECM) proteins when activated by profibrogenic mediators such as cytokines and oxidant stress. AIMS To determine whether cultured rat pancreatic stellate cells produce collagen and other ECM proteins, and exhibit signs of activation when exposed to the cytokines platelet derived growth factor (PDGF) or transforming growth factor β (TGF-β). METHODS Cultured pancreatic stellate cells were immunostained for the ECM proteins procollagen III, collagen I, laminin, and fibronectin using specific polyclonal antibodies. For cytokine studies, triplicate wells of cells were incubated with increasing concentrations of PDGF or TGF-β. RESULTS Cultured pancreatic stellate cells stained strongly positive for all ECM proteins tested. Incubation of cells with 1, 5, and 10 ng/ml PDGF led to a significant dose related increase in cell counts as well as in the incorporation of3H-thymidine into DNA. Stellate cells exposed to 0.25, 0.5, and 1 ng/ml TGF-β showed a dose dependent increase in α smooth muscle actin expression and increased collagen synthesis. In addition, TGF-β increased the expression of PDGF receptors on stellate cells. CONCLUSIONS Pancreatic stellate cells produce collagen and other extracellular matrix proteins, and respond to the cytokines PDGF and TGF-β by increased proliferation and increased collagen synthesis. These results suggest an important role for stellate cells in pancreatic fibrogenesis.

Expression of the Gene for Multidrug-Resistance–Associated Protein and Outcome in Patients with Neuroblastoma

BACKGROUND Overexpression of the gene for the multidrug-resistance-associated protein (MRP) has been linked with resistance to chemotherapeutic agents (multidrug resistance) in vitro. The expression of MRP by neuroblastoma cells correlates with N-myc oncogene amplification, a well-established prognostic indicator in patients with neuroblastoma. METHODS To relate MRP gene expression to established prognostic markers and the clinical outcome of neuroblastoma, we analyzed MRP expression in specimens of primary tumors from 60 patients with neuroblastoma. RESULTS Levels of MRP gene expression were significantly higher in tumors with N-myc amplification than in tumors without such amplification (P < 0.001). High levels of MRP expression were strongly associated with reductions in both survival and event-free survival (P < 0.001) in the overall study population and in subgroups of patients without N-myc amplification and patients with localized disease. For the overall study population, the five-year cumulative survival rates in the groups with high and low levels of MRP expression were 57 percent (95 percent confidence interval, 37 to 78 percent) and 94 percent (95 percent confidence interval, 86 to 100 percent), respectively. In contrast, expression of the MDR1 multi-drug-resistance gene was not predictive of survival or event-free survival. After adjustment by multivariate analysis for the effects of N-myc amplification and other prognostic indicators, high levels of MRP expression retained significant prognostic value for poor survival (relative hazard, 14.9; P = 0.01) and poor event-free survival (relative hazard, 9.7; P = 0.004), whereas N-myc amplification had no prognostic value. CONCLUSIONS High levels of MRP gene expression in patients with neuroblastoma correlate strongly with poor outcome. The findings suggest that expression of this multidrug-resistance gene accounts for the association between N-myc amplification and reduced survival.

Metabolism of ethanol by rat pancreatic acinar cells

It has been postulated that ethanol-induced pancreatic injury may be mediated by the oxidation of ethanol within the pancreas with secondary toxic metabolic changes, but there is little evidence of pancreatic ethanol oxidation. The aims of this study were to determine whether pancreatic acinar cells metabolize significant amounts of ethanol and, if so, to compare their rate of ethanol oxidation to that of hepatocytes. Cultured rat pancreatic acinar cells and hepatocytes were incubated with 5 to 50 mmol/L carbon 14-labeled ethanol (25 dpm/nmol). Ethanol oxidation was calculated from the production of 14C-labeled acetate that was isolated by Dowex ion-exchange chromatography. Ethanol oxidation by pancreatic acinar cells was demonstrable at all ethanol concentrations tested. At an intoxicating ethanol concentration (50 mmol/L), 14C-labeled acetate production (227+/-20 nmol/10(6) cells/h) approached that of hepatocytes (337+/-61 nmol/10(6) cells/h). Phenanthroline (an inhibitor of classes I through III isoenzymes of alcohol dehydrogenase (ADH)) inhibited pancreatic ethanol oxidation by 90%, but 4-methylpyrazole (a class I and II ADH inhibitor), carbon monoxide (a cytochrome P450 inhibitor), and sodium azide (a catalase inhibitor) had no effect. This study has shown that pancreatic acinar cells oxidize significant amounts of ethanol. At intoxicating concentrations of ethanol, pancreatic acinar cell ethanol oxidation may have the potential to contribute to pancreatic cellular injury. The mechanism appears to involve the class III isoenzyme of ADH.

Cytochrome P4502E1 is present in rat pancreas and is induced by chronic ethanol administration

Background—The mechanisms responsible for the initiation of alcoholic pancreatitis remain elusive. However, there is an increasing body of evidence that reactive oxygen species play a role in both acute and chronic pancreatitis. In the liver, cytochrome P4502E1 (CYP2E1, the inducible ethanol metabolising enzyme) is one of the proposed pathways by which ethanol induces oxidative stress. Aims—To determine whether CYP2E1 is present in the pancreas and, if so, whether it is inducible by chronic ethanol feeding. Methods—Eighteen male Sprague-Dawley rats were pair fed liquid diets with or without ethanol as 36% of energy for four weeks. CYP2E1 levels were determined by western blotting of microsomal protein from both pancreas and liver. Messenger RNA (mRNA) levels for CYP2E1 were quantified using dot blots of total pancreatic RNA. Results—CYP2E1 was found in the pancreas. Furthermore, the amount of CYP2E1 was greater in the pancreas of rats fed ethanol compared with controls (mean increase over controls 5.1-fold, 95% confidence intervals 2.4 to 7.7, p<0.02). In the liver, induction by ethanol of CYP2E1 was similar (mean increase over controls 7.9-fold, 95% confidence intervals 5.2 to 10.6, p<0.005). Pancreatic mRNA levels for CYP2E1 were similar in ethanol fed and control rats. Conclusions—CYP2E1 is present in the rat pancreas and is inducible by chronic ethanol administration. Induction of pancreatic CYP2E1 is not regulated at the mRNA level. The metabolism of ethanol via CYP2E1 may contribute to oxidative stress in the pancreas during chronic ethanol consumption.

Chronic ethanol administration causes oxidative stress in the rat pancreas.

There is increasing evidence implicating oxidative stress in the pathogenesis of both acute and chronic pancreatitis. Because ethanol is a major cause of pancreatitis in Western society, the aim of this study was to determine whether chronic ethanol administration results in oxidative stress in the pancreas. Twelve pairs of rats were fed a diet containing ethanol as 36% of calories or an isocaloric control diet for 4 weeks. Ethanol feeding resulted in a 46% increase in pancreatic malondialdehyde (p=0.006). In addition, total pancreatic glutathione was increased by 22% (p=0.005). These biochemical changes occurred in the absence of histologic evidence of inflammation or necrosis, implying that the observed oxidative stress is a primary phenomenon rather than part of an inflammatory response.

Evidence that the MYCN oncogene regulates MRP gene expression in neuroblastoma

We have recently shown that expression of the multidrug resistance-associated protein (MRP) gene is a powerful prognostic indicator in childhood neuroblastoma and have suggested that the MYCN oncogene may regulate MRP gene expression. To address this hypothesis, we have examined the relationship between MYCN and MRP gene expression in neuroblastoma tumours and cell lines. MYCN and MRP gene expression were highly correlated in 60 primary untreated tumours both with (P = 0.01) and without MYCN gene amplification (P < 0.0001). Like MRP, high MYCN gene expression was significantly associated with reduced survival, both in the overall study population and in older children without MYCN gene amplification (relative hazards = 13.33 and 19.61, respectively). Inhibition of MYCN, through the introduction of MYCN antisense RNA constructs into human neuroblastoma cells in vitro, resulted in decreased MRP gene expression, determined both by RNA-PCR and Western analysis. The data are consistent with MYCN influencing neuroblastoma outcome by regulating MRP gene expression.

Smoking and alcoholic pancreatitis.

Only a small minority of alcoholics develop clinical evidence of pancreatitis. The reasons for this variation in individual susceptibility have not yet been defined. Recent studies have suggested that smoking may be a risk factor for the development of pancreatitis. However, there have been methodological problems with these studies regarding choice of controls and assessment of tobacco consumption. The present study was designed to determine whether smoking is a risk factor for pancreatitis in alcoholics. Tobacco consumption in alcoholics with pancreatitis was compared to that of alcoholics without pancreatitis (controls). Of 52 subjects with alcoholic pancreatitis, 86.5% were smokers compared with 87.2% of 47 alcoholic controls. Both daily and lifetime tobacco consumption in subjects with pancreatitis were less than those of alcoholic controls. Thus, there was no association between smoking and pancreatitis in this study. The previously described association between smoking and pancreatitis may be related to the high prevalence of smoking among alcoholics.

The prognostic value of MDR1 gene expression in primary untreated neuroblastoma

The contribution of MDR1 gene expression to the biology of childhood neuroblastoma is unclear. To clarify the role of MDR1 in this malignancy, we examined the relationship between MDR1 expression and patient outcome in subsets of 60 primary untreated neuroblastomas for which MYCN gene copy number and expression of the multidrug resistance-associated-protein (MRP) gene had been previously characterised. In contrast to MRP gene expression, MDR1 expression was lower in tumours with MYCN gene amplification compared with those without amplification. Strong correlations between MDR1 and MRP gene expression, and between MDR1 and MYCN gene expression, were observed in tumours lacking MYCN gene amplification (P < 0.0005). In these single-copy tumours, very high MDR1 gene expression was significantly associated with poor outcome (P < 0.05). Very high MDR1 expression was also strongly predictive of poor outcome in older children (P < 0.0001), but not in infants. These findings suggest a clinical role for the MDR1 gene in specific subgroups of primary neuroblastoma.

Chronic ethanol consumption increases the fragility of rat pancreatic zymogen granules.

Intracellular activation of pancreatic digestive enzymes by lysosomal hydrolases is thought to be an early event in the pathogenesis of pancreatic injury. As ethanol excess is an important association of pancreatitis, experimental work has been directed towards exploring possible mechanisms whereby ethanol may facilitate contact between inactive digestive enzyme precursors and lysosomal enzymes. The aim of this study was to find out if chronic ethanol administration increases the fragility of rat pancreatic zymogen granules. Sixteen male Sprague-Dawley rats were pair fed ethanol and control liquid diets for four weeks. Zymogen granule fragility was then assessed in pancreatic homogenate by determination of (a) latency and (b) per cent supernatant enzyme after sedimentation of zymogen granules. Amylase was used as a zymogen granule marker enzyme. Latency was significantly reduced in pancreatic homogenates of ethanol fed animals suggesting increased zymogen granule fragility. In support of this finding, there was a trend towards increased supernatant enzyme after ethanol feeding. In conclusion, administration of ethanol increases the fragility of pancreatic zymogen granules in the absence of morphological evidence of pancreatic injury. It is proposed that zymogen granule fragility may play an early part in the pathogenesis of alcoholic pancreatitis by permitting contact between digestive and lysosomal enzymes.