Studies on the betacellulin receptor in pancreatic AR42J cells

Summary Betacellulin is a member of the epidermal growth factor family and converts pancreatic AR42J cells into insulin-producing cells. This study was conducted to characterise the receptor for betacellulin in AR42J cells. AR42J cells expressed two classes of binding sites for radioactive iodine labelled betacellulin, with Kd values of 4.6 × 10^{− 11} mol/l and 3.0 × 10^{− 10} mol/l. The binding of [¹²⁵I]betacellulin was inhibited by unlabelled betacellulin in a dose-dependent manner, but epidermal growth factor was 50 fold less effective than betacellulin. Affinity cross-linking showed a [¹²⁵I]betacellulin-binding protein with a molecular weight of approximately 180 KDa. When this protein was immunoprecipitated with antibody against epidermal growth factor receptors ErbB-1, ErbB-2, ErbB-3 or ErbB-4, it was immunoprecipitated only by the anti-ErbB-1 antibody. When the [¹²⁵I]betacellulin-labelled proteins were immunoprecipitated with a combination of the four ErbB antibodies, and the unprecipitated proteins were then immunoprecipitated with anti-phosphotyrosine antibody, a 190 KDa protein was observed. Betacellulin induced the tyrosine phosphorylation of ErbB-1, ErbB-2 and ErbB-4. Finally, while 100 pmol/l betacellulin converted all of the AR42J into insulin-producing cells in the presence of activin A, 10 nmol/l epidermal growth factor induced differentiation in only about 30 % of the cells. Higher concentrations of epidermal growth factor were less effective. Neu differentiation factor in the presence or absence of epidermal growth factor was ineffective. These results indicate that betacellulin binds to ErbB-1 and possibly another protein with a molecular weight of 190 KDa. The latter betacellulin-binding protein may be involved in the differentiation-inducing activity of betacellulin. Received: 15 October 1997 and in revised form: 5 February 1998     

miR-29a up-regulation in AR42J cells contributes to apoptosis via targeting TNFRSF1A gene

AIM: To investigate the expression of mi R-29 a in rat acute pancreatitis and its functional role in AR42 J cell apoptosis.METHODS: Twelve SD rats were divided into a control group and an acute edematous pancreatitis(AEP) group randomly. AEP was induced by intraperitoneal injection of L-arginine(150 mg/kg) in the AEP group and equal volume of 0.9% Na Cl was injected in the control group. The apoptosis of acinar cells in pancreatic tissue was determined by TUNEL assay. mi RNA chip assay was performed to examine the expression of mi RNAs in two groups. Besides, to further explore the role of mi R-29 a in apoptosis in vitro, recombinant rat TNF-α(50 ng/m L) was administered to treat the rat pancreatic acinar cell line AR42 J for inducing AR42 J cell apoptosis. Quantitative real-time PCR(q RT-PCR) was adopted to measure mi R-29 a expression. Then, mi RNA mimic, mi RNA antisense oligonucleotide(AMO) and control vector were used to transfect AR42 J cells. The expression of mi R-29 a was confirmed by q RT-PCR andthe apoptosis rate of AR42 J cells was detected by flow cytometry analysis. Western blot was used to detect the expression of activated caspase3. Moreover, we used bioinformatics software and luciferase assay to test whether TNFRSF1 A was the target gene of mi R-29 a. After transfection, q RT-PCR and Western blot was used to detect the expression of TNFRSF1 A in AR42 J cells after transfection.RESULTS: The expression of mi R-29 a was much higher in the AEP group compared with the control group as displayed by the mi RNA chip assay. After inducing apoptosis of AR42 J cells in vitro, the expression of mi R-29 a was significantly increased by 1.49 ± 0.04 times in comparison with the control group. As revealed by q RT-PCR assay, the expression of mi R-29 a was 2.68 ± 0.56 times higher in the mi R-29 a mimic group relative to the control vector group, accompanied with an obviously increased acinar cell apoptosis rate(42.83 ± 1.25 vs 24.97 ± 0.15, P 0.05). Moreover, the expression of mi R-29 a in the mi RNA AMO group was 0.46 ± 0.05 times lower than the control vector group, and the cell apoptosis rate was much lower accordingly(17.27 ± 1.36 vs 24.97 ± 0.15, P 0.05). The results of bioinformatics software and luciferase assay showed that TNFRSF1 A might be a target gene of mi R-29 a. TNFRSF1 A expression was up-regulated in the mi R-29 a mimic group, while the mi R-29 a AMO group showed the reverse trend.CONCLUSION: mi R-29 a might promote the apoptosis of AR42 J cells via up-regulating the expression of its target gene TNFRSF1 A.     

Pancreatic acinar AR42J cells express functional nerve growth factor receptors

The factors regulating the differentiation of the endocrine cells of the pancreas are still unknown. In previous studies, we have demonstrated that, like neurones, various beta-cell lines express functional neurotrophin receptors. Moreover, Trk-A, the nerve growth factor (NGF) high-affinity receptor, is expressed in vivo in mature rat islets and early during development in the pancreatic ductal network that represents the source of putative stem cells. Rat pancreatic AR42J cells possess both exocrine and neuroendocrine properties. Recent studies have shown that these cells can differentiate either into acinar cells or into insulin-expressing cells. In this study, we demonstrate that AR42J cells, in common with the embryonic ductal cells, do express Trk-A. Moreover, on treatment with NGF, Trk-A is phosphorylated and early responsive genes such as NGFI-A, c-fos and c-jun are induced. These results clearly show that the Trk-A receptor expressed in AR42J is functional. AR42J cells provide a model system with which to study the role of NGF in the development of the pancreatic cells.     

Expression of chromogranin A and somatostatin receptors in pancreatic AR42J cells

The exocrine pancreatic cell line AR42J is also known to display some neuroendocrine (NE) features. We have extended this fact by showing that AR42J cells express mRNA of chromogranin A (CgA), display immunoreactivity (IR) to CgA, and secrete its cleavage product pancreastatin. A sparse occurrence of typical NE secretion granules, together with only a faint IR to conventional NE markers, indicates that the NE cells are of a poorly differentiated type. CgA promoter reporter plasmid experiments showed that gastrin, epidermal growth factor, and phorbol 12-myristate 13-acetate, induce upregulation of CgA after 24 h. By RT-PCR, it was found that AR42J expresses all of the five subtypes of the somatostatin (SST) receptor (SSTR) family, except SSTR4. The existence of functional SSTRs was confirmed by showing that the SST analog octreotide could inhibit gastrin-induced proliferation. Thus, the AR42J cell line may function as a valuable experimental model to study the regulation of CgA and SSTRs in poorly differentiated NE tumor cells.     

Lysophosphatidylcholine induces apoptosis in human endothelial cells through a p38-mitogen-activated protein kinase-dependent mechanism

Lysophosphatidylcholine (lysoPC) is a component of oxidized low density lipoprotein (LDL) and is involved in the pathogenesis of atherosclerosis and inflammation. Previous studies demonstrated that lysoPC can induce various protein kinases including tyrosine kinases, protein kinase C (PKC), and mitogen-activated protein kinases (MAPK) in vascular endothelial cells. However, the role of lysoPC-activated kinases remains undefined. In this study, we examined the effect of lysoPC on apoptosis and investigated the role of lysoPC-activated protein kinases in human umbilical vein endothelial cells (HUVEC). The presence of apoptosis was evaluated by morphological criteria, MTT assay, and electrophoresis of DNA fragments showing the characteristic apoptotic ladder, TUNEL analysis, and quantified as the proportion of hypodiploid cells by flow cytometry. The lysoPC induced apoptosis in a time- and dose-dependent manner. It stimulated the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) and p38-MAPK in HUVEC. The use of specific pharmacologic inhibitors indicated that the p38-MAPK-signaling pathway (SB203580) is required for lysoPC-induced apoptotic signals. Furthermore, lysoPC-induced apoptosis was inhibited by DEVD-FMK (a caspas-3/CPP32 inhibitor), suggesting involvement of an important segment in the apoptosis. These results demonstrate that lysoPC induces apoptosis in human endothelial cells through a p38-MAPK-dependent pathway.     

不同胆汁酸诱导AR42J细胞凋亡与坏死的作用

目的:探讨7种不同胆汁酸对AR42J胰腺腺泡细胞的损伤作用,检测在各种胆汁酸作用下胰腺腺泡细胞的存活率和凋亡/坏死的改变.方法:以大鼠AR42J胰腺腺泡细胞系为研究对象,应用MTT法检测7种不同胆汁酸对细胞存活率的影响和剂量与时间依赖性,采用光学显微镜和荧光显微镜观察细胞形态学改变与凋亡/坏死的变化,流式细胞术AV/PI双染法检测细胞的凋亡/坏死卒.结果:CA,GCA和GDCA在0.1-1.0 mmol/L内对AR42J细胞不具有损伤作用;而DCA,CDCA和LCA分别从0.3 mmol/L开始,TDCA从0.4 mmol/L开始,呈剂量依赖性对AR42J细胞产生损伤作用.0.8 mmol/L CA组细胞凋亡率与坏死率同CON组无明显区别(1.2%VS'0.9%;1.0%VS 1.0%,均P>0.05);0.4 mmol/LDCA组细胞凋亡率和坏死率分别为45.2%和8.9%:0.8 mmol/L DCA组细胞凋亡率和坏死率分别为18.6%和45.4%.结论:7种胆汁酸对AR42J细胞的损伤作用不同,主要表现为凋亡或/和坏死,同剂量相关.     

Arginine induces apoptosis and gene expression of pancreatitis-associated protein (PAP) in rat pancreatic acinar AR4-2J cells

Arginine-induced pancreatic acinar cell injury has been reported in vivo, but the mechanism involved is unknown. In this study we investigated the effects of arginine on the cell morphology and pancreatitis-associated protein (PAP) gene expression in rat pancreatic acinar AR4-2J cells in vitro. Arginine inhibited the proliferation of AR4-2J cells in a dose-dependent manner. This decrease in proliferation was due to an increase in apoptosis, as assessed by cell morphology and DNA fragmentation. PAP messenger RNA (mRNA) was expressed at doses of 2.5 and 5.0 mg/ml of arginine, and a time-course study showed that the expression started 2 h after arginine addition and peaked at 6 h. Apoptosis was rarely seen when PAP mRNA was highly expressed, but occurred when PAP mRNA expression was decreased. These results suggest that arginine induces apoptosis and PAP gene expression in pancreatic acinar cells and that PAP might inhibit the induction of apoptosis.     

大黄素对脱氧胆酸诱导的AR42J细胞损伤的调节

目的:研究大黄素(Emodin)对脱氧胆酸(deoxy-cholicacid,DCA)诱导的胰腺腺泡细胞损伤的调节作用.方法:以大鼠AR42J胰腺腺泡系为研究对象,分为5组,分别为CON组、0.4mmol/LDCA刺激组、0.4mmol/LDCA刺激+Emodin(20mg/L)干预组、0.8mmol/LDCA刺激组、0.8mmol/LDCA刺激+Emodin(20mg/L)干预组.利用流式细胞术AV/PI双染法检测各组细胞凋亡/坏死率,提取细胞浆蛋白,并分别检测各组细胞培养液上清与细胞浆淀粉酶的活性.结果:0.4mmol/LDCA诱导AR42J胰腺腺泡细胞损伤以凋亡为主,0.8mmol/LDCA诱导AR42J细胞损伤则以坏死为主.20μmol/LEmodin可以明显减少0.4mmol/LDCA诱导的AR42J胰腺腺泡细胞的晚期凋亡(27.9%vs34.1%),并明显降低0.8mmol/LDCA诱导的AR42J细胞坏死(38.1%vs45.4%).大黄素对DCA诱导下AR42J胰腺腺泡细胞培养液上清及细胞浆淀粉酶活性均没有明显变化.结论:Emodin对胆汁酸诱导的胰腺腺泡细胞损伤有一定的保护性作用,对细胞淀粉酶的合成与分泌功能没有明显影响.     

Melatonin induces calcium release from CCK‐8‐ and thapsigargin‐sensitive cytosolic stores in pancreatic AR42J cells

Abstract: Melatonin is produced following circadian rhythm with high levels being released at night and has been implicated in the regulation of physiological processes in major tissues, including the pancreas. The aim of our study was to examine the effects of melatonin on intracellular free Ca²⁺ concentration ([Ca²⁺]_c) in AR42J pancreatic cells. Our results show that stimulation of cells with 1 nm cholecystokinin (CCK)‐8 led to a transient increase in [Ca²⁺]_c followed by a decrease towards a value close to the prestimulation level. Melatonin (at the concentrations 1, 10, 100 μm and 1 mm ) induced changes in [Ca²⁺]_c that consisted of single or short lasting spikes in the form of oscillations or slow transient increases followed by a slow reduction towards a value close to the resting level. Depletion of intracellular Ca²⁺ stores by stimulation of cells with 1 nm CCK‐8 or 1 μm thapsigargin (Tps) blocked Ca²⁺ responses evoked by melatonin in the majority of cells. Conversely, prior stimulation of cells with 1 mm melatonin in the absence of extracellular Ca²⁺ inhibited Ca²⁺ mobilization in response to a secondary application of CCK‐8 or Tps. In summary, our results show that melatonin releases Ca²⁺ from intracellular stores and can therefore modulate the responses of the pancreas to CCK‐8. The source for Ca²⁺ mobilization most probably is the endoplasmic reticulum. These data raise the possibility that melatonin also involves Ca²⁺ signalling, in addition to other intracellular messengers, to modulate cellular function.     

Growth and differentiation of pancreatic acinar cells: independent effects of glucocorticoids on AR42J cells.

Dexamethasone (DEX) inhibits growth and induces differentiation in rat pancreatic acinar AR42J cells. We wished to determine whether growth and differentiation are mutually exclusive in AR42J cells and whether DEX effects on growth and differentiation are mutually dependent or independent. Inhibition of DNA synthesis, assessed by [3H]thymidine incorporation, was detectable after 6 h, half-maximal after 12 h, and complete after 18-h DEX treatment, at which time incorporation was reduced to 9.0% of control. The half-maximal effective dose for inhibition of DNA synthesis was 0.5 nM, and maximal inhibition was achieved with 10 nM DEX. This dose-response was similar to that previously reported for DEX-induced parameters of differentiation. The rank order of potency for inhibition of DNA synthesis by various steroid hormones was DEX greater than corticosterone greater than aldosterone greater than progesterone. Hydroxyurea or serum starvation inhibited growth to the same extent as DEX but did not induce differentiation. Moreover, hydroxyurea or serum starvation did not block the ability of DEX to induce differentiation. Addition of either EGF or insulin significantly reversed the growth inhibitory effects of submaximal (1 nM) DEX. In cultures released from growth inhibition, 1 nM DEX increased cellular amylase content 5.9- to 6.5-fold, similar to the amylase increase in growth-inhibited cultures. Therefore, growth inhibition and differentiation are independent delayed events regulated by DEX in AR42J cells.     

Involvement of Smad proteins in the differentiation of pancreatic AR42J cells induced by activin A

Aims/hypothesis. Activin A induces differentiation of amylase-secreting pancreatic AR42J cells into endocrine cells. This study assesses the role of Smad proteins in the actions of activin A in AR42J cells. Methods. The expression of Smad proteins was determined by northern blotting. Phosphorylation and translocation of Smad2 was measured by transfecting flag-tagged Smad2. Involvement of Smad2 was examined by transfecting cDNA encoding N-terminal and C-terminal domains of Smad2. Results. The mRNAs for Smad2 and Smad4 were abundantly expressed whereas the expression of mRNA for Smad1 and Smad3 was very low. Activin A induced serine-phosphorylation and the subsequent accumulation of the Smad2 in nuclei. Transfection of the N-terminal domain of Smad2, which acts as a dominantly negative mutant (Smad2-N), blocked the morphological changes induced by activin A whereas the C-terminal domain of Smad2, which acts as a constitutively active mutant (Smad2-C), reproduced the activin-induced morphological changes. Similarly, Smad2-N blocked apoptosis induced by activin A and Smad2-C induced apoptosis. Activin A converted AR42J into insulin-secreting cells in the presence of hepatocyte growth factor and introduction of Smad2-N inhibited the differentiation. Smad2-C, however, did not induce differentiation in the presence of hepatocyte growth factor. Conclusions/interpretation. Activation of the Smad2 pathway is necessary and sufficient to induce apoptosis and morphological changes. Although activation of the Smad2 pathway is required, it is not solely sufficient for the differentiation of AR42J into endocrine cells. [Diabetologia (1999) 42: 719–727] Received: 15 October 1998 and in final revised form: 25 January 1999     

Early proteome analysis of rat pancreatic acinar AR42J cells treated with taurolithocholic acid 3-sulfate

BackgroundBile acids are the initiating factors of biliary acute pancreatitis. Bile acids can induce the activation of intracellular zymogen, thus leading injury in pancreatic acinar cells. Pathological zymogen activation in pancreatic acinar cells is a common feature of all types of acute pancreatitis. The proteins expressed in pancreatic acinar cells during the activation of zymogen may determine the severity of acute pancreatitis. The present study aims to determine the differentially expressed proteins in taurolithocholic acid 3-sulfate-stimulated pancreatic acinar cells as an in vitro model for acute pancreatitis.MethodsRat pancreatic acinar AR42J cells were treated with taurolithocholic acid 3-sulfate for 20 min. Laser confocal scanning microscopy and flow cytometry were used to detect activated trypsinogen in pancreatic acinar AR42J cells. After the determination of trypsinogen activation, proteome analysis was performed to identify the proteins differentially expressed in taurolithocholic acid 3-sulfate-treated cells and non-treated cells.ResultsAfter treatment with taurolithocholic acid 3-sulfate for 20 min, the activation of trypsinogen in AR42J cells was concurrent with changes in the protein expression profile. Thirty-nine differentially expressed proteins were detected; among these, 23 proteins were up-regulated and 16 proteins were down-regulated. KEGG analysis indicated that these proteins are involved in cellular metabolic pathways, cellular defensive mechanisms, intracellular calcium regulation and cytoskeletal changes.ConclusionThe expression of proteins in the pancreatic acinar cell changes at the early stage of biliary acute pancreatitis. These differentially expressed proteins will provide valuable information to understand the pathophysiologic mechanism biliary acute pancreatitis and may be useful for prognostic indices of acute pancreatitis.