Mark A. Korsten

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.

High blood acetaldehyde levels after ethanol administration. Difference between alcoholic and nonalcoholic subjects.

Blood actaldehyde and ethanol levels were measured in 11 subjects, six with chronic alcholoism and five nonalcholic controls, after alcohol had been given intravenously. Despite a progressive fall in blood ethanol over a range of 54 to 33 mM/acetaldehyde did not decrease in any of the 11 subjects. The mean acetaldehyde plateau level was significantly (p less than 0.001) higher in alcoholic (42.7 plus or minus 1.2 mum) than in nonalcoholic (26.5 plus or minus 1.5 mum) subjects. When the mean blood ethanol concentration reached 24 mM,the acetaldehyde plateau ended abruptly in each subject. The ethanol concentration at which this fall of blood acetaldehyde occurred suggests desaturation of an ethanol oxidizing system other than alcohol dehydrogenase and indicates that at high ethanol blood levels, such a system contributes to ethanol oxidation. The highet acetaldehyde levels in alcholism may result from both greater activity of this system and mitochondrial damage, and could contribut to the neurologic, hepatic and cardiac complications of alcoholism.

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.

Pancreatic stellate cells respond to inflammatory cytokines: potential role in chronic pancreatitis

Background: It is now generally accepted that chronic pancreatic injury and fibrosis may result from repeated episodes of acute pancreatic necroinflammation (the necrosis-fibrosis sequence). Recent studies suggest that pancreatic stellate cells (PSCs), when activated, may play an important role in the development of pancreatic fibrosis. Factors that may influence PSC activation during pancreatic necroinflammation include cytokines known to be important in the pathogenesis of acute pancreatitis, such as tumour necrosis factor α (TNF-α), and the interleukins 1, 6, and 10 (IL-1, IL-6, and IL-10). Aim: To determine the effects of these cytokines on PSC activation, as assessed by cell proliferation, α smooth muscle actin (α-SMA) expression, and collagen synthesis. Methods: Cultured rat PSCs were incubated with cytokines for 24 hours. Cell proliferation was assessed by measuring 3H thymidine incorporation into cellular DNA, α-SMA expression by western blotting, and collagen synthesis by incorporation of 14C proline into collagenase sensitive protein. mRNA levels for procollagen α1(1) in PSCs were determined by northern and dot blotting methods. Results: Expression of α-SMA by PSCs was increased on exposure to each of the cytokines used in the study. Stellate cell proliferation was stimulated by TNF-α but inhibited by IL-6, while IL-1 and IL-10 had no effect on PSC proliferation. Collagen synthesis by PSCs was stimulated by TNF-α and IL-10, inhibited in response to IL-6, and unaltered by IL-1. Changes in collagen protein synthesis in response to TNF-α, IL-10, and IL-6 were not regulated at the mRNA level in the cells. Conclusion: This study has demonstrated that PSCs have the capacity to respond to cytokines known to be upregulated during acute pancreatitis. Persistent activation of PSCs by cytokines during acute pancreatitis may be a factor involved in the progression from acute pancreatitis to chronic pancreatic injury and fibrosis.

Does alcohol directly stimulate pancreatic fibrogenesis? Studies with rat pancreatic stellate cells

BACKGROUND & AIMS Activated pancreatic stellate cells have recently been implicated in pancreatic fibrogenesis. This study examined the role of pancreatic stellate cells in alcoholic pancreatic fibrosis by determining whether these cells are activated by ethanol itself and, if so, whether such activation is caused by the metabolism of ethanol to acetaldehyde and/or the generation of oxidant stress within the cells. METHODS Cultured rat pancreatic stellate cells were incubated with ethanol or acetaldehyde. Activation was assessed by cell proliferation, alpha-smooth muscle actin expression, and collagen synthesis. Alcohol dehydrogenase (ADH) activity in stellate cells and the influence of the ADH inhibitor 4-methylpyrazole (4MP) on the response of these cells to ethanol was assessed. Malondialdehyde levels were determined as an indicator of lipid peroxidation. The effect of the antioxidant vitamin E on the response of stellate cells to ethanol or acetaldehyde was also examined. RESULTS Exposure to ethanol or acetaldehyde led to cell activation and intracellular lipid peroxidation. These changes were prevented by the antioxidant vitamin E. Stellate cells exhibited ethanol-inducible ADH activity. Inhibition of ADH by 4MP prevented ethanol-induced cell activation. CONCLUSIONS Pancreatic stellate cells are activated on exposure to ethanol. This effect of ethanol is most likely mediated by its metabolism (via ADH) to acetaldehyde and the generation of oxidant stress within the cells.

Rat pancreatic stellate cells secrete matrix metalloproteinases: implications for extracellular matrix turnover

Background: Pancreatic fibrosis is a characteristic feature of chronic pancreatic injury and is thought to result from a change in the balance between synthesis and degradation of extracellular matrix (ECM) proteins. Recent studies suggest that activated pancreatic stellate cells (PSCs) play a central role in pancreatic fibrogenesis via increased synthesis of ECM proteins. However, the role of these cells in ECM protein degradation has not been fully elucidated. Aims: To determine: (i) whether PSCs secrete matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) and, if so (ii) whether MMP and TIMP secretion by PSCs is altered in response to known PSC activating factors such as tumour necrosis factor α (TNF-α), transforming growth factor β1 (TGF-β1), interleukin 6 (IL-6), ethanol, and acetaldehyde. Methods: Cultured rat PSCs (n=3–5 separate cell preparations) were incubated at 37°C for 24 hours with serum free culture medium containing TNF-α (5–25 U/ml), TGF-β1 (0.5–1 ng/ml), IL-6 (0.001–10 ng/ml), ethanol (10–50 mM), or acetaldehyde (150–200 μM), or no additions (controls). Medium from control cells was examined for the presence of MMPs by zymography using a 10% polyacrylamide-0.1% gelatin gel. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to examine gene expression of MMP9 and the tissue inhibitors of metalloproteinases TIMP1 and TIMP2. Western blotting was used to identify a specific MMP, MMP2 (a gelatinase that digests basement membrane collagen and the dominant MMP observed on zymography) and a specific TIMP, TIMP2. Reverse zymography was used to examine functional TIMPs in PSC secretions. The effect of TNF-α, TGF-β1, and IL-6 on MMP2 secretion was assessed by densitometry of western blots. The effect of ethanol and acetaldehyde on MMP2 and TIMP2 secretion was also assessed by this method. Results: Zymography revealed that PSCs secrete a number of MMPs including proteinases with molecular weights consistent with MMP2, MMP9, and MMP13. RT-PCR demonstrated the presence of mRNA for metalloproteinase inhibitors TIMP1 and TIMP2 in PSCs while reverse zymography revealed the presence of functional TIMP2 in PSC secretions. MMP2 secretion by PSCs was significantly increased by TGF-β1 and IL-6, but was not affected by TNF-α. Ethanol and acetaldehyde induced secretion of both MMP2 and TIMP2 by PSCs. Conclusions: Pancreatic stellate cells have the capacity to synthesise a number of matrix metalloproteinases, including MMP2, MMP9, and MMP13 and their inhibitors TIMP1 and TIMP2. MMP2 secretion by PSCs is significantly increased on exposure to the proinflammatory cytokines TGF-β1 and IL-6. Both ethanol and its metabolite acetaldehyde increase MMP2 as well as TIMP2 secretion by PSCs. Implication: The role of pancreatic stellate cells in extracellular matrix formation and fibrogenesis may be related to their capacity to regulate the degradation as well as the synthesis of extracellular matrix proteins.

Bacteremia after endoscopic injection sclerosis

Endoscopic injection sclerosis is a therapeutic alternative in the management of esophageal varices. Complications of sclerotherapy have been minor, including fever, bacteremia, and abnormal chest x-ray. We performed a prospective study to evaluate the frequency of postsclerosis bacteremia. Bacteremia was detected in 14 procedures (50%). There were no cases of bacteremia in a group of control patients with esophageal varices undergoing upper gastrointestinal endoscopy without sclerosis (p less than 0.05). Bacteremia was transient and unrelated to the presence of fever or other clinical complications. The organism most commonly cultured from blood, alpha-hemolytic streptococcus, probably represents a contaminant from the oropharynx, introduced into the bloodstream during sclerosis. We conclude that injection sclerotherapy of esophageal varices is associated with a higher incidence of bacteremia than routine upper endoscopy and that selected patients may require antibiotic prophylaxis when undergoing this procedure.

Chronic xerostomia increases esophageal acid exposure and is associated with esophageal injury

OBJECTIVE To assess the effects of chronic xerostomia on parameters of gastroesophageal reflux and esophagitis. DESIGN Observational study of a cohort of male patients with xerostomia and age-matched control subjects. SETTING Tertiary-care Veterans Affairs Medical Center. SUBJECTS Sixteen male patients with chronic xerostomia secondary to radiation for head and neck cancers or medications. Nineteen age-matched male control subjects with comparable alcohol and smoking histories. MEASUREMENTS AND MAIN RESULTS Esophageal motility was similar in patients with xerostomia and controls. Clearance of acid from the esophagus and 24-hour intraesophageal pH were markedly abnormal in patients with xerostomia. Symptoms and signs of esophagitis were significantly more frequent in subjects with xerostomia. CONCLUSIONS Chronic xerostomia may predispose to esophageal injury, at least in part, by decreasing the clearance of acid from the esophagus and altering 24-hour intraesophageal pH. Esophageal injury is a previously unreported complication of long-term salivary deficiency.

The relationship of bacteremia to the length of injection needle in endoscopic variceal sclerotherapy

The authors evaluated whether depth of needle insertion as determined by needle length is an important factor in sclerotherapy-associated bacteremia. In 18 consecutive sclerotherapy sessions in which sodium morrhuate was used, blood cultures were positive in 11% when using an injector with only 3 to 4 mm of needle protruding beyond the sheath, compared with the 39% incidence of bacteremia previously observed when an injector was used which permitted 6 to 8 mm of needle to protrude (0.01 less than p less than 0.05). Twenty-five additional sclerotherapy sessions in which the shorter needle was used were performed with a different sclerosant, 1% sodium tetradecyl sulfate; only 8% of blood cultures were positive. No correlation was found between fever and bacteremia. The authors conclude that the exposed needle length of the injector must be specified in any report of endoscopic variceal sclerotherapy with the flexible endoscope since this length is critical in the incidence of associated bacteremia and possibly other complications.

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.