Response Of Pancreatic Acinar Cells Research Articles

Perfluorooctanoic acid activates the unfolded protein response in pancreatic acinar cells.

Perfluoroalkyl substances, such as perfluorooctanoic acid (PFOA), are widely used in consumer and industrial applications. Human epidemiologic and animal studies suggest that PFOA exposure elicits adverse effects on the pancreas; however, little is known about the biological effects of PFOA in this organ. In this study, we show that PFOA treatment of mouse pancreatic acinar cells results in endoplasmic reticulum (ER) stress and activation of the protein kinase-like endoplasmic reticulum kinase (PERK), inositol-requiring kinase/endonuclease 1α (IRE1α), and activating transcription factor 6 arms of the unfolded protein response (UPR) pathway. PFOA-stimulated activation of the UPR was blocked by pretreatment with specific PERK and IRE1α inhibitors and the chemical chaperone 4-phenyl butyrate, but not the antioxidants N-acetyl- l-cysteine and Tiron. PFOA treatment led to increased cytosolic Ca+2 levels and induction of the UPR was blocked by an inhibitor of the inositol 1,4,5-trisphosphate receptor. These findings indicate that PFOA-induced ER stress may be the mechanistic trigger leading to oxidative stress in the pancreas.

Dysregulation of miR-192-5p in acute pancreatitis patients with nonalcoholic fatty liver and its functional role in acute pancreatitis progression.

Background: Nonalcoholic fatty liver disease (NAFLD) is a frequent metabolic disease and has been demonstrated to contribute to the severity of acute pancreatitis (AP). The present study aimed to investigate the aberrant expression of microRNA-192-5p (miR-192-5p) in AP patients with NAFLD, and further analyze the clinical significance and biological function of miR-192-5p in AP progression.Methods: Expression of miR-192-5p was estimated using quantitative real-time PCR (qRT-PCR). Diagnostic value of miR-192-5p was evaluated by the receiver operating characteristic curve (ROC). The effects of miR-192-5p on cell proliferation, apoptosis and inflammatory response of pancreatic acinar cells were further assessed by CCK-8 assay, flow cytometry and enzyme-linked immunosorbent assay (ELISA).Results: Circulating miR-192-5p was decreased in AP patients with NAFLD compared with those patients without NAFLD and healthy controls (P<0.05). The down-regulated expression of miR-192-5p had a relative high diagnostic accuracy to distinguish the AP patients with NAFLD from the cases without NAFLD. Furthermore, the overexpression of miR-192-5p in pancreatic acinar cells led to the decreased cell proliferation, increased cell apoptosis and suppressed inflammatory reaction (all P<0.05).Conclusion: Collectively, all data indicated that serum expression of miR-192-5p in AP patients with NAFLD is significantly decreased and serves as a candidate diagnostic biomarker. The up-regulation of miR-192-5p in pancreatic acinar cell leads to increased cell apoptosis and decreased inflammatory response, suggesting the potential of miR-192-5p as a therapeutic target of AP.

Anisodamine alleviates lipopolysaccharide-induced pancreatic acinar cell injury through NLRP3 inflammasome and NF-κB signaling pathway

Purpose: Anisodamine (An) has anti-inflammatory effects, but its role in acute pancreatitis is still unknown. This study aimed to explore the action mechanism of An pretreatment in lipopolysaccharide (LPS)-induced pancreatic acinar cells, hoping to provide a research basis for the disease treatment.Materials and methods: Pancreatic acinar cells were pretreated with An at different concentrations and then induced by LPS. The viability and apoptosis of the treated cells were measured by Cell Counting Kit-8 and flow cytometry. The releases of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-18 were measured by enzyme-linked immunosorbent assay. The expressions of thioredoxin-interacting protein (TXNIP), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), NOD-like receptor protein 3 (NLRP3), Caspase-1, p65, and inhibitor of kappa B alpha (IκBα) in the treated cells were detected by Western blot and quantitative real-time polymerase chain reaction assay.Results: LPS promoted apoptosis of pancreatic acinar cells, suppressed cell viability, increased TNF-α, IL-1β, and IL-18 releases and the expression levels of TXNIP, ASC, NLRP3, Caspase-1, p-p65, and p-IκBα, however, such effects of LPS could be alleviated by An pretreatment with the strongest effect when the concentration of An was set at 100 μg/mL. Moreover, overexpressed NLRP3 aggravated the effects of LPS in pancreatic acinar cells, which could be reversed by pretreatment of 100 μg/mL An.Conclusion: An pretreatment attenuated LPS-induced apoptosis and inflammatory response of pancreatic acinar cells through suppressing NLRP3 and inactivating NF-κB signaling pathway, thus, it could be explored as a potential therapy for treating acute pancreatitis.

Effect of microRNA-27a-5p on apoptosis and inflammatory response of pancreatic acinar cells in acute pancreatitis by targeting PTEN.

To investigate the apoptosis and inflammatory response of microRNA-27a-5p (miR-27a-5p) in pancreatic acinar cells of acute pancreatitis (AP) and its related mechanisms. Rat pancreatic acinar cell line AR42J was treated with caerulein (10nmol/L) to construct an acute pancreatitis cell model. Quantitative real-time polymerase chain reaction was performed to measure the expression of miR-27a-5p; The miR-27a-5p mimic was transfected into cell, and the apoptosis rate of the cells was detected by flow cytometry; The levels of TNF-α, IL-1, and IL-6 in the culture supernatant were determined by enzyme-linked immunosorbent assay; TargetScans database predicted and dual luciferase reporter gene assay verified the relationship between miR-27a-5p and the phosphatase and tensin homolog deleted on chromosome 10 (PTEN); The recovery experiment explored the apoptosis and the effects of inflammatory responses. The expression of miR-27a-5p decreased gradually (P < 0.05) and the expression of PTEN increased gradually (P < 0.05) with the prolongation of acting time. Upregulation of miR-27a-5p significantly promoted cell apoptosis (P < 0.05) and inhibited inflammatory response (P < 0.05); The TargetScans database predicted that the 3'UTR of PTEN contains a base complementary to the miR-27a-5p seed region. Cotransfection of wild-type vector (PTEN-WT) with miR-27a-5p mimic or miR-27a-5p inhibitor significantly affected the relative activity of luciferase (P < 0.05), and no significant impact was observed in mutant PTEN-MUT. Compared with miR-27a-5p + pcDNA group, transfection of miR-27a-5p mimic and pcDNA-PTEN significantly increased the expression of PTEN (P < 0.05), decreased the apoptotic rate (P < 0.05), and increased the inflammatory response (P < 0.05). miR-27a-5p induced apoptosis and inhibited the inflammatory response of pancreatic acinar cells in AP by targeting PTEN.

ABT-199 (Venetoclax), a BH3-mimetic Bcl-2 inhibitor, does not cause Ca2+ -signalling dysregulation or toxicity in pancreatic acinar cells.

Background and PurposeMany cancer cells depend on anti‐apoptotic B‐cell lymphoma 2 (Bcl‐2) proteins for their survival. Bcl‐2 antagonism through Bcl‐2 homology 3 (BH3) mimetics has emerged as a novel anti‐cancer therapy. ABT‐199 (Venetoclax), a recently developed BH3 mimetic that selectively inhibits Bcl‐2, was introduced into the clinic for treatment of relapsed chronic lymphocytic leukaemia. Early generations of Bcl‐2 inhibitors evoked sustained Ca2+ responses in pancreatic acinar cells (PACs) inducing cell death. Therefore, BH3 mimetics could potentially be toxic for the pancreas when used to treat cancer. Although ABT‐199 was shown to kill Bcl‐2‐dependent cancer cells without affecting intracellular Ca2+ signalling, its effects on PACs have not yet been determined. Hence, it is essential and timely to assess whether this recently approved anti‐leukaemic drug might potentially have pancreatotoxic effects.Experimental ApproachSingle‐cell Ca2+ measurements and cell death analysis were performed on isolated mouse PACs.Key ResultsInhibition of Bcl‐2 via ABT‐199 did not elicit intracellular Ca2+ signalling on its own or potentiate Ca2+ signalling induced by physiological/pathophysiological stimuli in PACs. Although ABT‐199 did not affect cell death in PACs, under conditions that killed ABT‐199‐sensitive cancer cells, cytosolic Ca2+ extrusion was slightly enhanced in the presence of ABT‐199. In contrast, inhibition of Bcl‐xL potentiated pathophysiological Ca2+ responses in PACs, without exacerbating cell death.Conclusion and ImplicationsOur results demonstrate that apart from having a modest effect on cytosolic Ca2+ extrusion, ABT‐199 does not substantially alter intracellular Ca2+ homeostasis in normal PACs and should be safe for the pancreas during cancer treatment.Linked ArticlesThis article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc

Palmitic acid aggravates inflammation of pancreatic acinar cells by enhancing unfolded protein response induced CCAAT-enhancer-binding protein β–CCAAT-enhancer-binding protein α activation

Hypertriglyceridemia is an independent risk factor for acute pancreatitis, in which the pathological mechanisms are not fully illustrated. Intracellular inflammatory response is a key pathological response in acute pancreatitis and endoplasmic reticulum stress has been suggested to induce inflammation and CCAAT-enhancer-binding protein expression. Therefore, the current study aims to elucidate the possible relationship between endoplasmic reticulum stress and inflammation in hypertriglyceridemia associated pancreatitis and the possible involvement of CCAAT-enhancer-binding protein. In cholecystokinin-8 stimulated rat primary acinar cells, incubation with palmitic acid caused the activation of endoplasmic reticulum stress and inflammatory responses. Pre-incubation with the chemical chaperone 4-phenylbutyric acid inhibited inflammatory responses induced by palmitic acid, whereas stimulation with the endoplasmic reticulum stress inducer thapsigargin alone induced inflammatory responses. Meanwhile we found that the transcription factors CCAAT-enhancer-binding protein α and CCAAT-enhancer-binding protein β were also induced in the palmitic acid-stimulated pancreatic acinar cells, and were similarly inhibited by 4-phenylbutyric acid pre-incubation and induced by thapsigargin stimulation alone, indicating that endoplasmic reticulum stress was responsible for CCAAT-enhancer-binding protein α and CCAAT-enhancer-binding protein β induction in the pancreatic acinar cells. Knockdown of CCAAT-enhancer-binding protein β by siRNA transfection inhibited inflammatory responses and CCAAT-enhancer-binding protein α induction but did not affect endoplasmic reticulum stress. Our study provides strong evidence that in response to palmitic acid stimulation, endoplasmic reticulum stress induces inflammatory responses in pancreatic acinar cells through induction of the CCAAT-enhancer-binding protein family, wherein CCAAT-enhancer-binding protein β activation is responsible for CCAAT-enhancer-binding protein α activation.

Sa1786 Activation of the Inflammatory Response in Pancreatic Acinar Cells in Response to Tobacco Compared to Alcohol: An In Vitro Study

Sa1786 Activation of the Inflammatory Response in Pancreatic Acinar Cells in Response to Tobacco Compared to Alcohol: An In Vitro Study

Necro-inflammatory response of pancreatic acinar cells in the pathogenesis of acute alcoholic pancreatitis.

The role of pancreatic acinar cells in initiating necro-inflammatory responses during the early onset of alcoholic acute pancreatitis (AP) has not been fully evaluated. We investigated the ability of acinar cells to generate pro- and anti-inflammatory mediators, including inflammasome-associated IL-18/caspase-1, and evaluated acinar cell necrosis in an animal model of AP and human samples. Rats were fed either an ethanol-containing or control diet for 14 weeks and killed 3 or 24 h after a single lipopolysaccharide (LPS) injection. Inflammasome components and necro-inflammation were evaluated in acinar cells by immunofluorescence (IF), histology, and biochemical approaches. Alcohol exposure enhanced acinar cell-specific production of TNFα, IL-6, MCP-1 and IL-10, as early as 3 h after LPS, whereas IL-18 and caspase-1 were evident 24 h later. Alcohol enhanced LPS-induced TNFα expression, whereas blockade of LPS signaling diminished TNFα production in vitro, indicating that the response of pancreatic acinar cells to LPS is similar to that of immune cells. Similar results were observed from acinar cells in samples from patients with acute/recurrent pancreatitis. Although morphologic examination of sub-clinical AP showed no visible signs of necrosis, early loss of pancreatic HMGB1 and increased systemic levels of HMGB1 and LDH were observed, indicating that this strong systemic inflammatory response is associated with little pancreatic necrosis. These results suggest that TLR-4-positive acinar cells respond to LPS by activating the inflammasome and producing pro- and anti-inflammatory mediators during the development of mild, sub-clinical AP, and that these effects are exacerbated by alcohol injury.

Exocrine pancreas ER stress differentially induced by different fatty acids

Exocrine pancreas ER stress differentially induced by different fatty acids

Implication of PKCθ in the Activation of Several Kinases Important for Cell Activation, Secretion, Growth, Apoptosis and Inflammatory Responses in Pancreatic Acinar Cells

Implication of PKCθ in the Activation of Several Kinases Important for Cell Activation, Secretion, Growth, Apoptosis and Inflammatory Responses in Pancreatic Acinar Cells

Prevalence of stochasticity in experimentally observed responses of pancreatic acinar cells to acetylcholine

Calcium ions play an important role in both intra- and intercellular signaling. In pancreatic acinar cells intracellular Ca(2+) regulates exocytotic secretion and fluid secretion. In this paper we study the typical experimental traces of Ca(2+) responses in pancreatic acinar cells obtained in response to the physiological agonist acetylcholine. To determine whether they are stochastic or deterministic in nature, we analyze the traces with methods of nonlinear time series analysis. In particular, by performing surrogate data tests and employing a determinism test for short time series, we show that the responses of pancreatic acinar cells to acetylcholine are stochastic with only faintly expressed deterministic features. Presented results thus corroborate the notion that mathematical models should take stochasticity explicitly into account when describing intra- and intercellular processes, and that indeed further efforts should be directed toward this subject.

Corrigendum

CORRIGENDUMCorrigendumPublished Online:01 Jun 2007https://doi.org/10.1152/ajpgi.00000.2007Original articleMoreSectionsPDF (88 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Volume 292, March 2007 Volume 55, March 2007 Pages : L. Fischer, A. S. Gukovskaya, J. M. Penninger, O. A. Mareninova, H. Friess, I. Gukovsky, and S. J. Pandol, “Phophatidylinositol 3-kinase facilitates bile acid-induced Ca2+ responses in pancreatic acinar cells”Figure 6 was printed incorrectly; an extraneous trace was shown in panel A, right.The corrected figure is shown here. Fig. 6.Caffeine inhibits TLC-S induced [Ca2+]i responses in permeabilized pancreatic acinar cells. Rat pancreatic acini were resuspended in a permeabilization solution containing 10 μM digitonin. A: permeabilized acini were stimulated with 1 μM inositol (1,4,5)-trisphosphate (IP3). After [Ca2+]i reached a plateau, 20 mM caffeine was added. After 5 min of caffeine exposure (interrupted tracing), permeabilized acini were again stimulated with 1 μM IP3. B: permeabilized acini were incubated for 5 min with vehicle (top trace) or 20 mM caffeine and then stimulated with 180 μM TLC-S. Tracings are representative of 3 independent experiments. C: effect of 20 mM caffeine on the area under the curve of the [Ca2+]i response after stimulation of permeabilized acini with 180 μM TLC-S. The [Ca2+]i response to TLC-S in the absence of caffeine (i.e., in acini incubated with vehicle) was considered as 100%. Values are means ± SE from 3 tracings for the corresponding responses. *P < 0.05 compared with the [Ca2+]i response of acini stimulated by TLC-S in the absence of caffeine.Download figureDownload PowerPointThis article has no references to display. Download PDF Previous Back to Top FiguresReferencesRelatedInformationRelated articlesPhosphatidylinositol 3-kinase facilitates bile acid-induced Ca2+ responses in pancreatic acinar cells 01 Mar 2007American Journal of Physiology-Gastrointestinal and Liver Physiology More from this issue > Video Abstract Volume 292Issue 6June 2007Pages G1815-G1815 Copyright & PermissionsCopyright © 2007 the American Physiological Societyhttps://doi.org/10.1152/ajpgi.00000.2007PubMed17311895History Published online 1 June 2007 Published in print 1 June 2007 Metrics

Secretagogues differentially activate endoplasmic reticulum stress responses in pancreatic acinar cells

Endoplasmic reticulum (ER) stress leads to the accumulation of misfolded proteins in the ER lumen and initiates the unfolded protein response (UPR). Components of the UPR are important in pancreatic development, and recent studies have indicated that the UPR is activated in the arginine model of acute pancreatitis. However, the effects of secretagogues on UPR components in the pancreas are unknown. The present study aimed to examine the effects of different types and concentrations of secretagogues on acinar cell function and specific components of the UPR. Rat pancreatic acini were stimulated with the CCK analogs CCK8 (10 pM-10 nM) or JMV-180 (10 nM-10 microM) or with bombesin (1-100 nM). Components of the UPR, including chaperone BiP expression, PKR-like ER kinase (PERK) phosphorylation, X box-binding protein 1 (XBP1) splicing, and CCAAT/enhancer binding protein homologous protein (CHOP) expression, were measured, as were effects on amylase secretion and intracellular trypsin activation. CCK8 generated a biphasic secretion dose-response curve, and high concentrations increased intracellular active trypsin levels. In contrast, JMV-180 and bombesin secretion dose-response curves were monophasic, and high concentrations did not increase intracellular trypsin activity. All three secretagogues increased BiP levels and XBP1 splicing. However, only supraphysiological levels of CCK8 associated with inhibited amylase secretion and trypsin activation stimulated PERK phosphorylation and expression of CHOP. The effects of CCK8 on UPR components were rapid, occurring within 5-20 min. In conclusion, ER stress response mechanisms appear to be involved in both pancreatic physiology and pathophysiology, and future efforts should be directed at understanding the roles of these mechanisms in the pancreas.

STAT3 induction by LPS and TNFα in pancreatic acinar cells

Introduction. Inflammatory mediators have been implicated in the onset and progression of acute pancreatitis (AP). The signaling pathways affected by inflammation in pancreatic cells are still largely unknown. SOCS proteins are cytokine-induced cytokine signaling inhibitors that terminate the inflammatory response. Our previous studies show that SOCS-3 mRNA levels are up regulated in response to bacterial lipopolysaccharide (LPS) or inflammation (TNFα) in acinar cells. With the addition of IL-6 or IL-1β, SOCS-3 expression is down regulated. Since SOCS-3 proteins are known to affect the JAK/STAT pathway, we hypothesized that LPS and TNFα, in combination with the proinflammatory cytokines IL-6 and IL-1β, would mediate STAT3 mRNA expression in pancreatic acinar cells. Methods. Rat pancreatic acinar cells (AR42J) were treated with either LPS (10 μg/ml) or TNF-α (10, 100, or 200 ng/ml) in the presence or absence of IL-6 (20 ng/ml) or IL-1β (10 ng/ml) for 0, 15, 30, 45, 60, 180, or 360 min. Total RNA extracted at each time point was used in multiplex RT-PCR reactions to determine STAT3 mRNA expression. Values were standardized to 18S rRNA. Results. STAT3 mRNA expression was significantly ( P < 0.05) increased by 3 h in acinar cells treated with either LPS or TNFα. At the highest concentration of TNFα, the addition of IL-6 and IL-1β significantly ( P < 0.05) enhanced STAT3 mRNA expression. When added in combination with the proinflammatory cytokines IL-6 or IL-1β, LPS-induced STAT3 expression remained elevated without further change. Conclusions. STAT3 expression was increased in response to endotoxin and proinflammatory cytokines, suggesting that STAT3 plays a role in initiating the inflammatory response in pancreatic acinar cells. These results indicate that inhibition of pancreatic STAT3 expression is a potential therapeutic strategy during the onset of acute pancreatitis.

Suppression of Cerulein-Induced Cytokine Expression by Antioxidants in Pancreatic Acinar Cells

Reactive oxygen species (ROS) has been considered to be an important regulator in the development and pathogenesis of pancreatitis and an activator of the transcription factor, nuclear factor-κB (NF-κB), regulating inflammatory cytokine gene expression. NF-κB activation was demonstrated in cerulein pancreatitis, which rapidly induces an acute, edematous form of pancreatitis. This study aimed to investigate whether cerulein induced ROS generation, lipid peroxide and hydrogen peroxide production, NF-κB activation, and expression of cytokines (IL-1β, IL-6) in pancreatic acinar cells. An additional aim was to establish whether these alterations were inhibited by antioxidants such as glutathione, superoxide dismutase, and catalase and an inhibitor of NF-κB activation, pyrrolidine dithiocarbamate (PDTC). To determine the possible interactions of the antioxidants and PDTC with cerulein-induced signaling, Ca2+ signal and amylase release were monitored in the pancreatic acinar cells treated with cerulein in the presence or absence of either the antioxidants or PDTC. The results showed that cerulein generated ROS and increased lipid peroxide and hydrogen peroxide production in the acinar cells, as determined by dichlorofluorescein diacetate dye. This resulted in NF-κB activation and the induction of cytokine gene expression in the cells. The cerulein-induced NF-κB activation was in parallel to IκBα degradation. Cerulein also induced Ca2+ signals and amylase release in acinar cells. Both antioxidants (glutathione, superoxide dismutase, catalase) and PDTC inhibited the cerulein-induced, oxidant-mediated alterations but did not affect the cerulein-evoked Ca2+ signals and amylase release in acinar cells. In conclusion, ROS, generated by cerulein, activates NF-κB, resulting in the up-regulation of inflammatory cytokine gene expression in acinar cells. NF-κB inhibition by scavenging ROS might alleviate the inflammatory response in pancreatic acinar cells by suppressing cytokine gene expression.

Adenovirus-mediated gene transfer of RasN17 inhibits specific CCK actions on pancreatic acinar cells.

CCK stimulates pleiotrophic responses in pancreatic acinar cells; however, the intracellular signaling pathways involved are not well understood. To evaluate the role of the ras gene product in CCK actions, a strategy involving in vitro adenoviral-mediated gene delivery of a dominant-negative mutant Ras (RasN17) was utilized. Isolated acini were infected with various titers of either a control adenovirus or an adenoviral construct expressing RasN17 for 24 h before being treated with CCK. Titer-dependent expression of RasN17 in the acini was confirmed by Western blotting. Infection with control adenovirus [10(6)-10(9) plaque-forming units/mg acinar protein (multiplicity of infection of approximately 1-1,000)] had no effect on CCK stimulation of acinar cell amylase release, extracellular-regulated kinase (ERK) or c-Jun kinase (JNK) kinases, or DNA synthesis. In contrast, infection with adenovirus bearing rasN17 increased basal amylase release, inhibited CCK-mediated JNK activation, had no effect on CCK activation of ERK, and inhibited DNA synthesis. These data demonstrate important roles for Ras in specific actions of CCK on pancreatic acinar function.

Supramaximal secretagogue stimulation enhances heat shock protein expression in the rat pancreas.

Heat shock or stress proteins (HSPs) are synthesized by various cell types in response to different metabolic insults (e.g., hyperthermia). Although the function of HSPs is not fully understood, they are believed to be an evolutionary conserved intracellular defense mechanism. In an attempt to characterize the autoprotective potential of pancreatic acinar cells, we investigated the regulation of HSPs of the 70-kD family and the small HSP ubiquitin in vitro and in vivo during supramaximal cerulein stimulation. Infusion of the secretagogue cerulein induces a mild edematous form of pancreatitis in vivo and is characterized by a marked disturbance of the intracellular transport and segregation of enzymes. Synthesis of HSP70 mRNA is upregulated in isolated pancreatic lobules by either cerulein (100 nM) or hyperthermia (42 degrees C for 60 min). In contrast, expression of ubiquitin mRNA was not altered by either secretagogue treatment or hyperthermia. This heat shock-like response of pancreatic acinar cells could be reproduced in vivo: Pancreatitis was induced in male Wistar rats by intravenous infusion of supramaximal doses of cerulein (10 micrograms/kg/h). Analysis of mRNA expression revealed a significant upregulation of HSP70 RNA during supramaximal secretagogue stimulation. mRNA levels encoding for ubiquitin remained unchanged. Western blot analysis demonstrated that the transcriptional upregulation of HSP70 in vivo was reflected on the protein level. This study demonstrates that the marked intracellular disturbance observed in secretagogue-induced pancreatitis is associated with enhanced expression and synthesis of a major stress protein. Given the autoprotective potential of HSPs, this upregulation may indicate a self-defense mechanism of pancreatic acinar cells in experimental pancreatitis.

Identical regional mechanisms of intracellular free Ca2+ concentration increase during polarized agonist-evoked Ca2+ response in pancreatic acinar cells

The initial increase of intracellular free Ca2+ concentration ([Ca2+]i) following agonist stimulation is spatially restricted to one pole of the cell, from where a wave of [Ca2+]i spreads across the cytosol. In the present study we have investigated the dynamic properties of the agonist-activated Ca(2+)-release mechanisms in different regions of the acinar cell and show that, during maximal agonist stimulation, the rate of [Ca2+]i increase at the secretory pole is identical with that recorded at the basal pole. Furthermore, the relationship between [Ca2+]i and the apparent rate of [Ca2+]i increase is similar in both regions of the cell. The data show that whereas the sensitivity to the Ca(2+)-releasing agent is different in different regions of the cell, the process of [Ca2+]i increase, once triggered, will proceed in an identical fashion, irrespective of the area of the cell.

Metabolic and Pathologic Effects of Nicotine on Gastrointestinal Tract and Pancreas of Rats

We examined in male Sprague-Dawley rats the effects of nicotine at doses of 50 (0.31 mM) and 200 mg/L (1.23 mM) given for a period of 16 weeks on body weight gain, food and fluid intake, plasma CCK, glucose and insulin levels, amylase secretory responses of isolated pancreatic acinar cells to CCK-8 and carbachol, and histopathology (gross and light microscopy) of stomach and pancreas. These parameters were re-examined further in animals treated with nicotine at doses of 200 mg/L (1.23 mM) for 12 weeks and given tap water for an additional 4 weeks to evaluate the effects of nicotine withdrawal. Metabolic data suggest that decreases in body weight gain, food and fluid intake, and plasma levels of glucose and insulin by nicotine are dose dependent. Endocrinological studies showed that the plasma levels of CCK were significantly increased with nicotine but the amylase secretory response of pancreatic acinar cells was inhibited in response to CCK-8 and carbachol. Histopathologic data revealed that treatment of animals with a high dose of nicotine enhanced the appearance of numerous vacuoles in the pancreatic acinar cell cytoplasm. When the pancreatic acinar cell morphology was closely examined, it showed evidence of pyknotic nuclei and fusion of vacuoles. Prominent loss of gastric mucosal surface was found in nicotine-treated animals with gross microscopic evidence of bleeding ulcers. All of the metabolic parameters except body weight gain were reversed upon nicotine withdrawal. In addition, plasma CCK levels and pancreatic enzyme secretion were reversed upon nicotine withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium-calmodulin-stimulated protein kinase in developing pancreas.

To implicate the Ca2+-calmodulin-dependent protein kinase (CDPK) in the secretory response of pancreatic acinar cells to postnatal neurohumoral stimulation, we examined enzymatic protein kinase activity during pancreatic development. CDPK was investigated by measuring the phosphorylation of endogenous proteins and an exogenous substrate, synapsin I. Ca2+-calmodulin (CaM)-stimulated phosphorylation of endogenous proteins as well as synapsin I progressively increased in pancreatic supernatants from rats of increasing age. When compared with embryonic pancreas (1 day before birth), Ca2+-CaM-stimulated protein kinase activity increased two- and sixfold in neonatal (1 day after birth) and adult pancreas (60 days after birth), respectively, when normalized to protein content. To further characterize CDPK activity, soluble fractions prepared from embryonic, neonatal, and adult pancreas were separated by gel filtration chromatography. CDPK activities from embryonic and neonatal pancreas were contained in fractions of relative molecular weights (Mr) less than 200,000. In contrast, kinase activity from adult pancreas was predominantly comprised of a Mr approximately 550,000 species that coeluted with a type II CDPK. Increasing amounts of a Mr = 51,000 CaM-binding protein as a function of increasing age were consistent with the developmental appearance of the CaM-binding subunit of type II Ca2+-CaM-stimulated protein kinase. CaM levels increased in parallel with total Ca2+-CaM-stimulated protein kinase activity. Coordinate enhancement of type II CDPK activity and secretagogue responsiveness during pancreatic maturation may suggest a role for this enzyme in the secretory process.