Calcium signaling of pancreatic acinar cells in the pathogenesis of pancreatitis

Pancreatitis is an increasingly common and sometimes severe disease that lacks a specific therapy. The pathogenesis of pancreatitis is still not well understood. Calcium (Ca2+) is a versatile carrier of signals regulating many aspects of cellular activity and plays a central role in controlling digestive enzyme secretion in pancreatic acinar cells. Ca2+ overload is a key early event and is crucial in the pathogenesis of many diseases. In pancreatic acinar cells, pathological Ca2+ signaling (stimulated by bile, alcohol metabolites and other causes) is a key contributor to the initiation of cell injury due to prolonged and global Ca2+ elevation that results in trypsin activation, vacuolization and necrosis, all of which are crucial in the development of pancreatitis. Increased release of Ca2+ from stores in the intracellular endoplasmic reticulum and/or increased Ca2+ entry through the plasma membrane are causes of such cell damage. Failed mitochondrial adenosine triphosphate (ATP) production reduces re-uptake and extrusion of Ca2+ by the sarco/endoplasmic reticulum Ca2+-activated ATPase and plasma membrane Ca2+-ATPase pumps, which contribute to Ca2+ overload. Current findings have provided further insight into the roles and mechanisms of abnormal pancreatic acinar Ca2+ signals in pancreatitis. The lack of available specific treatments is therefore an objective of ongoing research. Research is currently underway to establish the mechanisms and interactions of Ca2+ signals in the pathogenesis of pancreatitis.

Effect of Tetrandrine on LPS-induced NF-κB activation in isolated pancreatic acinar cells of rat

AIM: To investigate the effect of Tetrandrine (Tet) on LPS-induced NF-κB activation and cell injury in pancreatic acinar cells and to explore the mechanism of Tetrandrine preventing LPS-induced acinar cell injury. METHODS: Male rat pancreatic acinar cells were isolated by collagenase digestion, then exposed to LPS (10 mg/L), Tet (50μmol/L, 100μmol/L) or normal media. At different time point (30 min, 1 h, 4 h, 10 h) after treatment with the agents, cell viability was determined by MTT, the product and nuclear translocation of subunit p65 of NF-κB was visualized by immunofluorescence staining and nuclear protein was extracted to perform EMSA which was used to assay the NF-κB binding activity. RESULTS: LPS induced cell damage directly in a time dependent manner and Tet attenuated LPS-induced cell damage (50μmol/L, P < 0.05; 100μmol/L, P < 0.01). NF-κB p65 immunofluorescence staining in cytoplasm increased and began showing its nuclear translocation within 30 min and the peak was shown at 1 h of LPS 10 mg/L treatment. NF-κB DNA binding activity showed the same alteration pattern as p65 immunofluorescence staining. In Tet group, the immunofluorescence staining in cytoplasm and nuclear translocation of NF-κB were inhibited significantly. CONCLUSION: NF-κB activation is an important early event that may contribute to inflammatory responses and cell injury in pancreatic acinar cells. Tet possesses the protective effect on LPS-induced acinar cell injury by inhibiting NF-κB activation.

Involvement of M3 Cholinergic Receptor Signal Transduction Pathway in Regulation of the Expression of Chemokine MOB-1, MCP-1 Genes in Pancreatic Acinar Cells

Whether M3 cholinergic receptor signal transduction pathway is involved in regulation of the activation of NF-κB and the expression of chemokine MOB-1, MCP-1genes in pancreatic acinar cells was investigated. Rat pancreatic acinar cells were isolated, cultured and treated with carbachol, atropine and PDTC in vitro. The MOB-1 and MCP-1 mRNA expression was detected by using RT-PCR. The activation of NF-κB was monitored by using electrophoretic mobility shift assay. The results showed that as compared with control group, M3 cholinergic receptor agonist (10 -3 mol/L, 10 -4 mol/L carbachol) could induce a concentration-dependent and time-dependent increase in the expression of MOB-1, MCP-1 mRNA in pancreatic acinar cells. After treatment with 10 -3 mol/L carbachol for 2 h, the expression of MOB-1, MCP-1 mRNA was strongest. The activity of NF-κB in pancreatic acinar cells was significantly increased (P<0.01) after treated with M3 cholinergic receptor agonist (10 -3 mol/L carbachol) in vitro for 30 min. Either M3 cholinergic receptor antagonist (10 -5 mol/L atropine) or NF-κB inhibitor (10 -2 mol/L PDTC) could obviously inhibit the activation of NF-κB and the chemokine MOB-1, MCP-1 mRNA expression induced by carbachol (P<0.05). This inhibitory effect was significantly increased by atropine plus PDTC (P<0.01). The results of these studies indicated that M3 cholinergic receptor signal transduction pathway was likely involved in regulation of the expression of chemokine MOB-1 and MCP-1genes in pancreatic acinar cells in vitro through the activation of NF-κB.

Ghrelin inhibits IKKβ/NF-κB activation and reduces pro-inflammatory cytokine production in pancreatic acinar AR42J cells treated with cerulein

Background: Previous studies have provided conflicting results regarding whether the serum ghrelin concentration can reflect the severity of acute pancreatitis(AP). The present study examined the correlation between the serum ghrelin concentration and AP severity in animal models and investigated whether altered ghrelin expression in pancreatic acinar cells influences IKK β/NF-κ B signaling and pro-inflammatory cytokine production. Methods: Mild or severe AP was induced in rats by intraperitoneal injection of cerulein or retrograde cholangiopancreatic duct injection of sodium taurocholate, respectively. After successful model induction, serum ghrelin, tumor necrosis factor-α(TNF-α), and interleukin-6(IL-6) concentrations were determined by enzyme-linked immunosorbent assay, and IKK β/NF-κ B activation was assessed by immunohistochemistry. Subsequently, stable overexpression or knockdown of ghrelin in AR42 J cells was achieved by lentiviral transfection. After transfected cells and control cells were treated with cerulein for 24 h, the TNF-αand IL-1 β levels in the supernatants were determined by enzyme-linked immunosorbent assay, and the expression levels of p-p65, IKK β, and p-IKK β were detected by Western blotting. Results: In rat AP models, AP severity was correlated with increased IKK β/NF-κ B activation, proinflammatory cytokine production, and ghrelin secretion. The levels of pro-inflammatory cytokines TNF-αand IL-1 β as well as IKK β/NF-κ B signaling activity were increased upon knockdown of ghrelin in the AP acinar cell model and decreased with ghrelin overexpression. Conclusions: Serum ghrelin is related to the severity of AP. Ghrelin may play a protective role in the pathogenesis of AP by inhibiting the pro-inflammatory cytokines and the activation of the IKK β/NF-κ B signaling pathway.

Inhibition of cathepsin B protects pancreatic acinar cells against apoptosis in early pancreatic trauma in rats

Objectives:To observe the protective effect of cathepsin B inhibition against apoptosis of acinar cells in the early management of pancreatic contusion and laceration in rats,which would provide evidence of a potential early therapeutic for pancreatic contusion and laceration.Methods:Twenty-four rats were assigned to 2 groups:1)Model(n=12)with an induced pancreatic injury of severity I-II and 2)CA074-V(n=12):an induced pancreatic injury,severity I-II treated with the cathepsin B inhibitor CA074-me(0.01mg/g)by intravenous administration through the caudal vein at 5minutes post model establishment.The mice in these two groups were further randomly divided into 4 subgroups containing 3 rats each that were sacrificed for quantitation of apoptosis,immunohistochemistry of cathepsin B,and serum amylase and lipase measurements at different time points after model establishment(0,3,6,and 12hours).Results:The percentage of apoptotic pancreatic acinar cells collected from the injured tissues were much lower in the CA074-V group than the Model group at 3hours[9.25±3.94%vs.64.76±26.47%,P<0.10]and 6hours[14.71±8.22%vs.66.60±13.54%,P<0.10]post model establishment.The percentage of cathepsin B-positive pancreatic acinar cells were much lower in the CA074-V group than in the Model group at 3hours[31.07±12.02%vs.69.16±5.71%,P<0.10],6hours[24.84±0.93%vs.47.06±0.91%,P<0.10],and 12hours[28.33±9.14%vs.52.72±1.25%,P<0.10]post model establishment.Conclusions:Early cathepsin B inhibition effectively blocked acinar cell apoptosis in an experimental rat model of pancreatic contusion and laceration.

Rare ROS1-CENPW gene in pancreatic acinar cell carcinoma and the effect of crizotinib plus AG chemotherapy:A case report

BACKGROUND This is the first report of an ROS1-CENPW fusion gene in pancreatic malignancies.CASE SUMMARY A 77-year-old woman with a pancreatic tumor and multiple liver metastases was admitted to our hospital.Genetic testing revealed the presence of the ROS1-CENPW fusion gene,a rare fusion gene that has not been previously reported in the field of pancreatic cancer.The patient received crizotinib plus AG(albumin paclitaxel plus gemcitabine)chemotherapy.After treatment,the patient’s condition stabilized,and her prognosis was good.CONCLUSION The ROS1-CENPW gene treatment regimen used in this case is an excellent treatment option that provides new hope for patients with advanced pancreatic cancer and similar genetic mutations.To date,owing to the rarity of the ROS1-CENPW fusion gene,our team has encountered only a single case.Therefore,the efficacy of crizotinib plus AG chemotherapy in patients with pancreatic acinar cell carcinoma harboring the ROS1-CENPW fusion gene requires further validation.

Functional Role of Micro RNA-19b in Acinar Cell Necrosis in Acute Necrotizing Pancreatitis

The expression of micro RNA-19b（mi R-19b） in acute necrotizing pancreatitis（ANP） and its functional role in acinar cell necrosis of SD rats were investigated. Twelve SD rats were divided into two groups randomly, including control group and ANP group. The rat ANP models were established by intraperitoneal injection of L-arginine（2400 mg/kg body weight）, and equal volume of 0.9% Na Cl was injected in the control group. Mi RNA chip assay was performed to examine the expression of mi RNAs in the pancreas in two different groups. Besides, to further explore the role of mi R-19 b in ANP in vitro, taurolithocholic acid 3-sulfate disodium salt（TLC-S）（200 μmol/L） was administrated to treat the rat pancreatic acinar cell line, AR42 J, for establishing the ANP cells model. The quantitative real-time PCR（q RT-PCR） was adopted to measure the mi R-19 b expression. Moreover, the mimic mi RNA, mi RNA antisense oligonucleotide（AMO） and control vector were used to transfect AR42 J cells, the expression of mi R-19 b was confirmed by q RT-PCR and the necrotizing rate of AR42 J cells was detected with AO/EB method. The expression of mi R-19 b was significantly higher in ANP group than in control group as displayed by the mi RNA chip assay. Furthermore, after inducing necrosis of AR42 J cells in vitro, the expression of mi R-19 b was significantly increased by 2.51±0.14 times in comparison with the control group. As revealed by q RT-PCR assay, the expression of mi R-19 b was 5.94±0.95 times higher in the mimic mi RNA group than in the control vector group, companied with an obviously increased acinar cell necrotizing rate（50.3%±1.5% vs. 39.6%±2.3%, P〈0.05）. Moreover, the expression of mi R-19 b in the mi RNA AMO group was 0.38±0.15 times lower than in the control vector group, and the cell necrosis rate was much lower accordingly（23.1%±3.3% vs. 39.6%±2.3%, P〈0.05）. Besides, there was no significant difference between the control vector cells and the cells without treatment（P〈0.05）. The expression of mi R-19 b was significantly induced in ANP. In addition, up-regulation of mi R-19 b could promote the necrosis of pancreatic acinar cells and mi R-19 b deficiency could decrease the rate of pancreatic acinar cell necrosis.

Nicotine as a mitogenic stimulus for pancreatic acinar cell proliferation

Cell proliferation is an important process in life for growth of normal and cancer cells. The signal transduction pathways activated during this process are strictly regulated. This editorial focuses on the role of nicotine, a mitogen, in the induction of signaling pathways resulting in proliferation of pancreatic tumor cells and compares these events with those in normal acinar cells isolated from the rat pancreas. The data shows striking similarities between these two cellular systems. In addition, the editorial reviews very recent literature of the contribution of MAPK signaling in cell lines associated with human diseases. A prospective cellular model of nicotine induced activation of MAPK cascade is presented.

Role of bone marrow-derived mesenchymal stem cells in a rat model of severe acute pancreatitis

AIM:To investigate the role and potential mechanisms of bone marrow mesenchymal stem cells(MSCs) in severe acute peritonitis(SAP).METHODS:Pancreatic acinar cells from Sprague Dawley rats were randomly divided into three groups:nonsodium deoxycholate(SDOC) group(non-SODC group),SDOC group,and a MSCs intervention group(i.e.,a co-culture system of MSCs and pancreatic acinar cells + SDOC).The cell survival rate,the concentration of malonaldehyde(MDA),the density of superoxide dismutase(SOD),serum amylase(AMS) secretion rate and lactate dehydrogenase(LDH) leakage rate were detected at various time points.In a separate study,Sprague Dawley rats were randomly divided into either an SAP group or an SAP + MSCs group.Serum AMS,MDA and SOD,interleukin(IL)-6,IL-10,and tumor necrosis factor(TNF)-α levels,intestinal mucosa injury scores and proliferating cells of small intestinal mucosa were measured at various time points after injecting either MSCs or saline into rats.In both studies,the protective effect of MSCs was evaluated.RESULTS:In vitro,The cell survival rate of pancreatic acinar cells and the density of SOD were significantly reduced,and the concentration of MDA,AMS secretion rate and LDH leakage rate were significantly increased in the SDOC group compared with the MSCs intervention group and the Non-SDOC group at each time point.In vivo,Serum AMS,IL-6,TNF-α and MAD level in the SAP + MSCs group were lower than the SAP group;however serum IL-10 level was higher than the SAP group.Serum SOD level was higher than the SAP group at each time point,whereas a significant betweengroup difference in SOD level was only noted after 24 h.Intestinal mucosa injury scores was significantly reduced and the proliferating cells of small intestinal mucosa became obvious after injecting MSCs.CONCLUSION:MSCs can effectively relieve injury to pancreatic acinar cells and small intestinal epithelium,promote the proliferation of enteric epithelium and repair of the mucosa,attenuate systemic inflammation in rats with SAP.

Trypsin in pancreatitis:The culprit,a mediator,or epiphenomenon?

Pancreatitis is a common,life-threatening inflammatory disease of the exocrine pancreas.Its pathogenesis remains obscure,and no specific or effective treatment is available.Gallstones and alcohol excess are major etiologies of pancreatitis;in a small portion of patients the disease is hereditary.Pancreatitis is believed to be initiated by injured acinar cells(the main exocrine pancreas cell type),leading to parenchymal necrosis and local and systemic inflammation.The primary function of these cells is to produce,store,and secrete a variety of enzymes that break down all categories of nutrients.Most digestive enzymes,including all proteases,are secreted by acinar cells as inactive proforms(zymogens)and in physiological conditions are only activated when reaching the intestine.The generation of trypsin from inactive trypsinogen in the intestine plays a critical role in physiological activation of other zymogens.It was proposed that pancreatitis results from proteolytic autodigestion of the gland,mediated by premature/inappropriate trypsinogen activation within acinar cells.The intra-acinar trypsinogen activation is observed in experimental models of acute and chronic pancreatitis,and in human disease.On the basis of these observations,it has been considered the central pathogenic mechanism of pancreatitis-a concept with a century-old history.This review summarizes the data on trypsinogen activation in experimental and genetic rodent models of pancreatitis,particularly the more recent genetically engineered mouse models that mimic mutations associated with hereditary pancreatitis;analyzes the mechanisms mediating trypsinogen activation and protecting the pancreas against its’damaging effects;discusses the gaps in our knowledge,potential therapeutic approaches,and directions for future research.We conclude that trypsin is not the culprit in the disease pathogenesis but,at most,a mediator of some pancreatitis responses.Therefore,the search for effective therapies should focus on approaches to prevent or normalize other intra-acinar pathologic processes,such as defective autophagy leading to parenchymal cell death and unrelenting inflammation.

Pancreatic acinar cell carcinoma: A review on molecular profiling of patient tumors

Pancreatic carcinomas with acinar differentiation are rare,accounting for 1%-2% of adult pancreatic tumors; they include pancreatic acinar cell carcinoma(PACC),pancreatoblastoma,and carcinomas of mixed differentiation. Patients with PACC have a prognosis better than pancreatic ductal adenocarcinomas but worse than pancreatic neuroendocrine tumors. Reports of overall survival range from 18 to 47 mo. A literature review on PACCs included comprehensive genomic profiling and whole exome sequencing on a series of more than 70 patients as well as other diagnostic studies including immunohistochemistry. Surgical resection of PACC is the preferred treatment for localized and resectable tumors. The efficacy of adjuvant treatment is unclear. Metastatic PACCs are generally not curable and treated with systemic chemotherapy. They are moderately responsive to chemotherapy with different regimens showing various degrees of response in case reports/series. Most of these regimens were developed to treat patients with pancreatic ductal adenocarcinomas or colorectal adenocarcinomas. Review of PACC's molecular profiling showed a number of gene alterations such as: SMAD4,BRAF,BRCA2,TP53,RB1,MEN1,JAK-1,BRCA-1,BRCA-2,and DNA mismatch repair abnormalities. PACCs had multiple somatic mutations with some targetable with available drugs. Therefore,molecular profiling of PACC should be an option for patients with refractory PACC.

Pancreatic acinar cell carcinoma:A comprehensive review

Acinar cell carcinoma(ACC)is a rare pancreatic malignancy with distinctive clinical,molecular,and morphological features.The long-term survival of ACC patients is substantially superior to that of pancreatic adenocarcinoma patients.As there are no significant patient series about ACCs,our understanding of this illness is mainly based on case reports and limited patient series.Surgical resection is the treatment of choice for patients with the disease restricted to one organ;however,with recent breakthroughs in precision medicine,medicines targeting the one-of-a-kind molecular profile of ACC are on the horizon.There are no standard treatment protocols available for people in which a total surgical resection to cure the condition is not possible.As a result of shared genetic alterations,ACCs are chemosensitive to agents with activity against pancreatic adenocarcinomas and colorectal carcinomas.The role of neoadjuvant or adjuvant chemoradiotherapy has not been established.This article aims to do a comprehensive literature study and present the most recent information on acinar cell cancer.

Acinar cell carcinoma of the pancreas in a young patient with chronic pancreatitis

BACKGROUND:Acinar cell carcinoma (ACC) is a rare malignancy of the pancreas arising from acinar cells.Unlike ductal adenocarcinoma,this tumor rarely presents with pancreatitis.METHODS:We present a case of ACC associated with chronic calcifying pancreatitis,and a review of the literature focusing on diagnosis and management.RESULTS:A 43-year-old man was proposed for Wirsungojejunal derivation for chronic pancreatitis.Histopathological examination of the tissue extracted revealed an ACC.Duodenopancreatectomy was performed.Six months postoperatively,the patient developed hepatic metastasis and was treated with gemcitabine as palliative chemotherapy.CONCLUSIONS:The clinical presentation of ACC of the pancreas is not specific and the tumor can be underdiagnosed when associated with chronic pancreatitis.Data regarding course,treatment,and prognosis of this tumor are generally lacking.

Acinar Cell Carcinoma of the Pancreas

Acinar cell carcinoma of the pancreas is a rare tumor which is defined as a carcinoma that exhibits pancreatic enzyme production by neoplastic cells.This review includes re- cent developments in our understanding of the epidemiology and pathogenesis of ACC,imaging and pathological diagnosis and ap- proaches to treatment with reference to the literature.

Relationship between Carbachol Hyperstimulation-Induced Pancreatic Acinar Cellular Injury and Trypsinogen or NF-κB Activation in Rats in vitro

The relationship between M3 cholinergic receptor agonist （carbachol） hyperstimulationinduced pancreatic acinar cellular injury and trypsinogen activation or NF-κB activation in rats was studied in vitro. Rat pancreatic acinar ceils were isolated, cultured and treated with carbachol, the active protease inhibitor （pefabloc）, and NF-κB inhibitor （PDTC） in vitro. Intracellular trypsin activity was measured by using a fluorogenic substrate. The cellular injury was evaluated by measuring the leakage of LDH from pancreatic acinar ceils. The results showed that as compared with control group, 10-3 mol/L carbachol induced a significant increase of the intracellular trypsin activity and the leakage of LDH from pancreatic acinar cells. Pretreatment with 2 mmol/L pefabloc could significantly decrease the activity of trypsin and the leakage of LDH from pancreatic acinar cells （P〈0. 01） following the treatment with a high concentration of carbachol （10^-3 mol/L） in vitro. The addition of 10^-2mol/L PDTC didn＇t result in a significant decrease in the activity of trypsin and the leakage of LDH from pancreatic acinar cells treated with a high concentration of carbachol （10^-3 mol/L） in vitro （P〉0. 05）. It was concluded that intracellular trypsinogen activation is likely involved in pancreatic acinar cellular injury induced by carbachol hyperstimulation in vitro. NF-κB activation may not be involved in pancreatic acinar cellular injury induced by carbachol hyperstimulation in vitro.

Primary extra-pancreatic pancreatic-type acinar cell carcinoma in the right perinephric space: A case report and review of literature

BACKGROUND Primary extra-pancreatic pancreatic-type acinar cell carcinoma(ACC)is a rare malignancy,and has only been reported in the gastrointestinal tract,liver,and lymph nodes until now.Extra-pancreatic pancreatic-type ACC in the perinephric space has not been reported.Herein,we report the first case of ACC in the perinephric space and describe its clinical and imaging features,which should be considered when differentiating perinephric space neoplasms.CASE SUMMARY A 48-year-old man with a 5-year history of hypertension was incidentally found to have an asymptomatic right retroperitoneal mass during a routine health check-up.Laboratory tests were normal.Abdominal computed tomography and magnetic resonance imaging showed an oval hypervascular mass with a central scar and enhanced capsule in the right perinephric space.After surgical resection of the neoplasm,the diagnosis was primary extra-pancreatic pancreatic-type ACC.The patient was alive without recurrence or metastasis during a 15-mo follow-up.CONCLUSION This is the first report of an extra-pancreatic ACC in right perinephric space,which should be considered as a possible diagnosis in perinephric tumors.

Synchronous concomitant pancreatic acinar cell carcin and gastric adenocarcinoma:A case report and review of literature

BACKGROUND Multiple primary malignant tumors are two or more malignancies in an individual without any relationship between the neoplasms.In recent years,an increasing number of cases have been reported.However,concomitant primary gastric and pancreatic cancer reported a relatively small incidence,involving no pancreatic acinar cell carcinoma reports.Here,we present the first case of concomitant pancreatic acinar cell carcinoma and gastric adenocarcinoma.CASE SUMMARY A 69-year-old male presented to our department with a history of vomiting,epigastric pain,and weight loss.Imaging revealed space-occupying lesions in the stomach and the tail of the pancreas,respectively.The patient underwent laparo-scopic radical gastrectomy and pancreatectomy simultaneously.The pathologies of surgical specimens were completely different:The resected gastric specimen was moderate to poorly differentiated adenocarcinoma,whereas the pancreatic tumor was consistent with acinar cell carcinoma.The patient was treated with six cycles of oxaliplatin and S-1 chemotherapy.As of March 2021,the patient was healthy without any recurrence or metastasis.After thoroughly reviewing the literature on simultaneous pancreatic and gastric cancers at home and abroad,we discussed the clinical characteristics of these rare synchronous double cancers.Most of the cases had undergone surgery and adjuvant chemotherapy,and all of the cases were pathologically confirmed by the postoperative specimen.CONCLUSION Synchronous pancreatic acinar cells and gastric adenocarcinoma can occur and should be considered when tumors are found in these organs.

Pancreatic panniculitis and elevated serum lipase in metastasized acinar cell carcinoma of the pancreas: A case report and review of literature

BACKGROUND Pancreatic panniculitis is an extremely rare condition associated with different underlying pancreatic disorders and characterized by subcutaneous fat necrosis induced by elevated serum lipase levels.These lesions usually affect the lower extremities and may precede abdominal symptoms of pancreatic disease.Acinar cell carcinoma(ACC)of the pancreas is a rare pancreatic neoplasm,accounting for only 1%-2%of pancreatic tumors in adults.We present the case of a 72-year-old man with ACC of the pancreatic head and synchronous liver metastases.Both the primary tumor and liver metastases were resected.Serum lipase was elevated before surgery and decreased to normal postoperatively.Rising serum lipase levels at follow-up led to the diagnosis of hepatic recurrence.This disease progression was then accompanied by pancreatic panniculitis,with subcutaneous fat necrosis and acute arthritis.To the best of our knowledge,only 4 cases have been reported in the literature and each showed a similar association of serum lipase levels with pancreatic panniculitis and progression of ACC.CONCLUSION Clinical symptoms and progression of ACC may correlate with serum lipase levels,suggesting potential usefulness as a follow-up biomarker.

Co-localization hypothesis:A mechanism for the intrapancreatic activation of digestive enzymes during the early phases of acute pancreatitis

Acute pancreatitis is generally believed to be a disease in which the pancreas is injured by digestive enzymes that it normally produces. Most of the potentially harmful digestive enzymes produced by pancreatic acinar cells are synthesized and secreted as inactive zymogens which are normally activated only upon entry into the duodenum but, during the early stages of acute pancreatitis, those zymogens become prematurely activated within the pancreas and, presumably, that activation occurs within pancreatic acinar cells. The mechanisms responsible for intracellular activation of digestive enzyme zymogens have not been elucidated with certainty but, according to one widely recognized theory （the ＂co-localization hypothesis＂）, digestive enzyme zymogens are activated by lysosomal hydrolases when the two types of enzymes become co-localized within the same intracellular compartment. This review focuses on the evidence supporting the validity of the m-localization hypothesis as an explanation for digestive enzyme activation during the early stages of pancreatitis. The findings, summarized in this review, support the conclusion that co-localization of lysosomal hydrolases with digestive enzyme zymogens plays a critical role in permitting the intracellular activation of digestive enzymes that leads to acinar cell injury and pancreatitis.

Types of voltage-dependent calcium channels involved in high potassium depolarization-induced amylase secretion in the exocrine pancreatic tumour cell line AR4-2J

In the perifused fura-2 loaded exocrine pancreatic acinar cell line AR4-2J pulses of high potassium induced repetitive increases in intracellular calcium. Attached cells when stimulated with high potassium secreted large amount of amylase. High potassium-induced secretion was dependent both on the concentration of potassium and duration of stimulation. High potassium induced increases in intracellular calcium were inhibited by voltage-dependent calcium channel antagonists with an order of potency as follows: nifedipine > ω-agatoxin IVA > ω-conotoxin GVIA. In contrast, the L-type calcium channel antagonist nifedipine almost completely inhibited potassium-induced amylase secretion, whereas the N-type channel antagonist ω-conotoxin GVIA was without effect. The P-type channel antagonist ω-agatoxin IVA had a small inhibitory effect, but this inhibition was not significant at the level of amylase secretion. In conclusion, the AR4-2J cell line possesses different voltage-dependent calcium channels (L, P,N) with the L-type predominantly involved in depolarization induced amylase secretion.