Deletion of myeloid-specific Orai1 calcium channel does not affect pancreatic tissue damage in experimental acute pancreatitis

BACKGROUND

Store-operated Ca2+ entry (SOCE) mediated by ORAI1 channel plays a crucial role in acute pancreatitis (AP). Macrophage is an important regulator in amplifying pancreatic tissue damage, but little is known about the role of ORAI1 in macrophages. In this study, we examined the effects of macrophage-specific ORAI1 on pancreatic tissue damage in AP.

METHOD

Myeloid-specific Orai1 deficient mice was generated by crossing a LysM-Cre mouse line with Orai1f/f mice. Bone marrow-derived macrophages (BMDMs) were isolated, cultured, and stimulated to induce M1 or M2 macrophage polarization. Intracellular Ca2+ signals were measured by time-lapse confocal microscope imaging, with a Ca2+ indicator (Fluo 4). Experimental AP was induced by hourly intraperitoneal injections of caerulein or retrograde biliopancreatic infusion of sodium taurocholate. Pancreatic tissue damage was assessed by histopathological scoring and immunostaining. Sepsis was induced by intraperitoneal injection of lipopolysaccharide; organ damage and serum pro-inflammatory cytokines were measured.

RESULT

Myeloid-specific Orai1 deletion exhibited minimal effect on SOCE in M0 macrophages and promoted M2 macrophage polarization ex vivo. Myeloid-specific Orai1 deletion did not affect pancreatic tissue damage, nor neutrophil or macrophage infiltration in two models of AP. Similarly, myeloid-specific Orai1 deletion did not influence overall survival rate in a model of sepsis, nor lung, kidney, and liver damage; while serum pro-inflammatory cytokines, including IL-6, TNF-α, and IL-1β were higher in Orai1ΔLysM mice, but were largely reduced in mice with Orai1 inhibitor.

CONCLUSION

Our data suggest that ORAI1 may not be a predominant SOCE channel in macrophages and play a limited role in mediating pancreatic tissue damage in AP.

Systemic Neutrophil Gelatinase-Associated Lipocalin Alterations in Chronic Pancreatitis: A Multicenter, Cross-Sectional Study

INTRODUCTION

Chronic pancreatitis (CP) is a progressive fibroinflammatory disorder lacking therapies and biomarkers. Neutrophil gelatinase-associated lipocalin (NGAL) is a proinflammatory cytokine elevated during inflammation that binds fatty acids (FAs) such as linoleic acid. We hypothesized that systemic NGAL could serve as a biomarker for CP and, with FAs, provide insights into inflammatory and metabolic alterations.

METHODS

NGAL was measured by immunoassay, and FA composition was measured by gas chromatography in plasma (n = 171) from a multicenter study, including controls (n = 50), acute and recurrent acute pancreatitis (AP/RAP) (n = 71), and CP (n = 50). Peripheral blood mononuclear cells (PBMCs) from controls (n = 16), AP/RAP (n = 17), and CP (n = 15) were measured by cytometry by time-of-flight.

RESULTS

Plasma NGAL was elevated in subjects with CP compared with controls (area under the curve [AUC] = 0.777) or AP/RAP (AUC = 0.754) in univariate and multivariate analyses with sex, age, body mass index, and smoking (control AUC = 0.874; AP/RAP AUC = 0.819). NGAL was elevated in CP and diabetes compared with CP without diabetes ( P < 0.001). NGAL + PBMC populations distinguished CP from controls (AUC = 0.950) or AP/RAP (AUC = 0.941). Linoleic acid was lower, whereas dihomo-γ-linolenic and adrenic acids were elevated in CP ( P < 0.05). Linoleic acid was elevated in CP with diabetes compared with CP subjects without diabetes ( P = 0.0471).

DISCUSSION

Elevated plasma NGAL and differences in NGAL + PBMCs indicate an immune response shift that may serve as biomarkers of CP. The potential interaction of FAs and NGAL levels provide insights into the metabolic pathophysiology and improve diagnostic classification of CP.

Interventions for Pancreatitis-New Approaches, Knowledge Gaps, and Research Opportunities: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

ABSTRACT

There exists no cure for acute, recurrent acute or chronic pancreatitis and treatments to date have been focused on managing symptoms. A recent workshop held by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) focused on interventions that might disrupt or perhaps even reverse the natural course of this heterogenous disease, aiming to identify knowledge gaps and research opportunities that might inform future funding initiatives for NIDDK. The breadth and variety of identified active or planned clinical trials traverses the spectrum of the disease and was conceptually grouped for the workshop into behavioral, nutritional, pharmacologic and biologic, and mechanical interventions. Cognitive and other behavioral therapies are proven interventions for pain and addiction, but barriers exist to their use. Whilst a disease specific instrument quantifying pain is now validated, an equivalent is lacking for nutrition - and both face challenges in ease and frequency of administration. Multiple pharmacologic agents hold promise. Ongoing development of Patient Reported Outcome (PRO) measurements can satisfy Investigative New Drug (IND) regulatory assessments. Despite multiple randomized clinical trials demonstrating benefit, great uncertainty remains regarding patient selection, timing of intervention, and type of mechanical intervention (endoscopic versus surgery). Challenges and opportunities to establish beneficial interventions for patients were identified.

Cancer-related cells and oncosomes in the liquid biopsy of pancreatic cancer patients undergoing surgery

Pancreatic ductal adenocarcinoma (PDAC) has a five-year survival rate of less than 10% due to its late diagnosis, rapid metastasis, and chemotherapeutic resistance. For a small proportion (10-20%) of early-stage patients however, surgical resection of the pancreatic tumor offers the best chance for survival but the effect of surgery on disease dissemination is unknown. The primary objective of this study was to characterize cellular and acellular blood-based analytes in portal and peripheral blood before pancreatic manipulation, during tumor dissection and immediately after surgical resection to determine the effects of the surgery. This study used the non-enriching third generation High-Definition Single Cell Assay (HDSCA3.0) workflow to investigate heterogeneous circulating rare cell population in the blood. Blood from both sites taken before surgical manipulation of the pancreas had significantly greater incidence of total rare cellular and acellular analytes than normal donor samples. Post-surgery portal and peripheral blood had significantly greater incidence of specific cellular and acellular subtypes compared to the matched pre- and during-surgery samples. Our results reveal that in patients with PDAC liquid biopsy analytes are increased in both the portal and peripheral blood; portal blood contains a higher frequency of analytes than in the peripheral blood; total analytes in the portal and peripheral blood samples were significantly associated with the tumor volume and pathological T stage; and the surgical procedure increased the blood levels of circulating cellular and acellular analytes, but not Epi.CTCs or Mes.CTCs. This study demonstrates liquid biopsy's utility in monitoring patients with PDAC with surgically resectable disease.

Role of YAP Signaling in Regulation of Programmed Cell Death and Drug Resistance in Cancer

Although recent advances in cancer treatment significantly improved the prognosis of patients, drug resistance remains a major challenge. Targeting programmed cell death is a major approach of antitumor drug development. Deregulation of programmed cell death (PCD) contributes to resistance to a variety of cancer therapeutics. Yes-associated protein (YAP) and its paralog TAZ, the main downstream effectors of the Hippo pathway, are aberrantly activated in a variety of human malignancies. The Hippo-YAP pathway, which was originally identified in Drosophila, is well conserved in humans and plays a defining role in regulation of cell fate, tissue growth and regeneration. Activation of YAP signaling has emerged as a key mechanism involved in promoting cancer cell proliferation, metastasis, and drug resistance. Understanding the role of YAP/TAZ signaling network in PCD and drug resistance could facilitate the development of effective strategies for cancer therapeutics.

Supraphysiological glutamine as a means of depleting intracellular amino acids to enhance pancreatic cancer chemosensitivity

Limited efficacy of systemic therapy for pancreatic ductal adenocarcinoma (PDAC) patients contributes to high mortality. Cancer cells develop strategies to secure nutrients in nutrient-deprived conditions and chemotherapy treatment. Despite the dependency of PDAC on glutamine (Gln) for growth and survival, strategies designed to suppress Gln metabolism have limited effects. Here, we demonstrated that supraphysiological concentrations of glutamine (SPG) could produce paradoxical responses leading to tumor growth inhibition alone and in combination with chemotherapy. Integrated metabolic and transcriptomic analysis revealed that the growth inhibitory effect of SPG was the result of a decrease in intracellular amino acid and nucleotide pools. Mechanistically, disruption of the sodium gradient, plasma membrane depolarization, and competitive inhibition of amino acid transport mediated amino acid deprivation. Among standard chemotherapies given to PDAC patients, gemcitabine treatment resulted in a significant enrichment of amino acid and nucleoside pools, exposing a metabolic vulnerability to SPG-induced metabolic alterations. Further analysis highlighted a superior anticancer effect of D-glutamine, a non-metabolizable enantiomer of the L-glutamine, by suppressing both amino acid uptake and glutaminolysis, in gemcitabine-treated preclinical models with no apparent toxicity. Our study suggests supraphysiological glutamine could be a means of inhibiting amino acid uptake and nucleotide biosynthesis, potentiating gemcitabine sensitivity in PDAC.

Neutrophil-specific ORAI1 Calcium Channel Inhibition Reduces Pancreatitis-associated Acute Lung Injury

Acute pancreatitis is initiated within pancreatic exocrine cells and sustained by dysregulated systemic inflammatory responses mediated by neutrophils. Store-operated Ca2+ entry (SOCE) through ORAI1 channels in pancreatic acinar cells triggers acute pancreatitis, and ORAI1 inhibitors ameliorate experimental acute pancreatitis, but the role of ORAI1 in pancreatitis-associated acute lung injury has not been determined. Here, we showed mice with pancreas-specific deletion of Orai1 (Orai1ΔPdx1, ∼70% reduction in the expression of Orai1) are protected against pancreatic tissue damage and immune cell infiltration, but not pancreatitis-associated acute lung injury, suggesting the involvement of unknown cells that may cause such injury through SOCE via ORAI1. Genetic (Orai1ΔMRP8) or pharmacological inhibition of ORAI1 in murine and human neutrophils decreased Ca2+ influx and impaired chemotaxis, reactive oxygen species production, and neutrophil extracellular trap formation. Unlike pancreas-specific Orai1 deletion, mice with neutrophil-specific deletion of Orai1 (Orai1ΔMRP8) were protected against pancreatitis- and sepsis-associated lung cytokine release and injury, but not pancreatic injury in experimental acute pancreatitis. These results define critical differences between contributions from different cell types to either pancreatic or systemic organ injury in acute pancreatitis. Our findings suggest that any therapy for acute pancreatitis that targets multiple rather than single cell types is more likely to be effective.

Retrospective quantification of clinical abdominal DCE-MRI using pharmacokinetics-informed deep learning: a proof-of-concept study

Introduction

Dynamic contrast-enhanced (DCE) MRI has important clinical value for early detection, accurate staging, and therapeutic monitoring of cancers. However, conventional multi-phasic abdominal DCE-MRI has limited temporal resolution and provides qualitative or semi-quantitative assessments of tissue vascularity. In this study, the feasibility of retrospectively quantifying multi-phasic abdominal DCE-MRI by using pharmacokinetics-informed deep learning to improve temporal resolution was investigated.

Method

Forty-five subjects consisting of healthy controls, pancreatic ductal adenocarcinoma (PDAC), and chronic pancreatitis (CP) were imaged with a 2-s temporal-resolution quantitative DCE sequence, from which 30-s temporal-resolution multi-phasic DCE-MRI was synthesized based on clinical protocol. A pharmacokinetics-informed neural network was trained to improve the temporal resolution of the multi-phasic DCE before the quantification of pharmacokinetic parameters. Through ten-fold cross-validation, the agreement between pharmacokinetic parameters estimated from synthesized multi-phasic DCE after deep learning inference was assessed against reference parameters from the corresponding quantitative DCE-MRI images. The ability of the deep learning estimated parameters to differentiate abnormal from normal tissues was assessed as well.

Results

The pharmacokinetic parameters estimated after deep learning have a high level of agreement with the reference values. In the cross-validation, all three pharmacokinetic parameters (transfer constant K trans , fractional extravascular extracellular volume v e , and rate constant k ep ) achieved intraclass correlation coefficient and R2 between 0.84-0.94, and low coefficients of variation (10.1%, 12.3%, and 5.6%, respectively) relative to the reference values. Significant differences were found between healthy pancreas, PDAC tumor and non-tumor, and CP pancreas.

Discussion

Retrospective quantification (RoQ) of clinical multi-phasic DCE-MRI is possible by deep learning. This technique has the potential to derive quantitative pharmacokinetic parameters from clinical multi-phasic DCE data for a more objective and precise assessment of cancer.

Abstract A037: Predicting pancreatic cancer using artificial intelligence analysis of pancreatic subregions using computed tomography images

Study background: Early detection of pancreatic ductal adenocarcinoma (PDAC) can elevate the current ~10% five-years survival rate of PDAC up to 50%. Accurate stratification of high-risk individuals for PDAC can improve early detection as follow-up screening may assist diagnosis at an early stage. Studies show that the pancreas adopts changes prior to or during the development of cancer due to the underlying biological variations. This study aimed to examine the precancerous changes that occurred within and across pancreatic subregions to help stratify individuals at high risk of developing PDAC. Dataset: In a multi-institute retrospective study, 108 contrast-enhanced CT abdominal scans were collected, consisting of 36 diagnostic scans with established PDAC and observable tumor, 36 pre-diagnostic scans of the same subjects as in the diagnostic group but were obtained up to 3 years before PDAC diagnosis and were deemed ‘normal’ by radiologists, and 36 healthy scans reported with no PDAC signs. Trained radiologists outlined 3 subregions (head, body, tail) in all scans. Also, the subregions in pre-diagnostic scans were classified into high-risk (with cancer underdevelopment) and low-risk (no cancer development) groups by exploring the tumor signs in their corresponding subregions in the diagnostic scans. Experiments and results: Radiomic analysis was performed on all 324 subregions by extracting and analyzing hundreds of morphological and textural features. In a pairwise feature analysis (i.e. between corresponding subregions), the texture of the high-risk subregions in pre-diagnostic scans was found significantly unique and statistically different than that of the low-risk subregions, supporting the study hypothesis. Such textural features are usually too minute and remain obscured when the pancreas is observed as a single structure. The analysis showed that AI can efficiently identify and quantify such predictors. A Naïve Bayes model was then trained using the same data to automatically predict PDAC using the textural features of the pancreatic subregions. In four-fold cross-validation, the model obtained prediction accuracy by correctly classifying pre-diagnostic and healthy CT scans by 88.2% on average, with sensitivity (true positive rate) and specificity (true negative rate) reaching 82.5% and 94.0%, respectively. The results of this preliminary study are promising and encouraging to further validate the model on a larger dataset. The model showed improved results over those produced in our recent study [1] in which the pancreas as a single structure was examined. The prediction based on the proposed model can potentially assist clinicians to undertake specialized screening, diagnosis, and treatment planning accordingly as the tumor structure, symptoms, and drug response for each pancreatic subregion differs a lot. 1. Qureshi et. al, Predicting pancreatic ductal adenocarcinoma using artificial intelligence analysis of pre-diagnostic computed tomography images. Cancer Biomarkers, 33(2), pp.211-217, 2022.

Citation Format: Sehrish Javed, Touseef Ahmad Qureshi, Srinivas Gaddam, Ashley Wachsman, Linda Azab, Vahid Asadpour, Wansu Chen, Bechien Wu, Yibin Xie, Stephen Pandol, Debiao Li. Predicting pancreatic cancer using artificial intelligence analysis of pancreatic subregions using computed tomography images [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A037.

High Prevalence of Osteopathy in Chronic Pancreatitis: A Cross-sectional Analysis From the PROCEED Study

BACKGROUND & AIMS

Chronic pancreatitis (CP) is associated with osteopathy (osteoporosis or osteopenia). However, existing literature is mostly limited to retrospective or administrative studies that have not clearly defined the prevalence and risk factors. Our aim was to identify patient- and disease-related associations with osteopathy in a prospective cohort study of CP.

METHODS

We studied 282 subjects with definitive CP enrolled in the PROCEED study who had a baseline dual-energy X-ray absorptiometry (DXA) scan. Osteopenia and osteoporosis were defined using the lowest T-scores. Clinical data were collected using standardized case report forms. Comparisons were performed with a multivariate logistic regression model with forward selection to identify risk factors for osteopathy.

RESULTS

The majority of subjects had osteopathy on DXA scan (56.0%; 17.0% osteoporosis; 39.0% osteopenia). Subjects with osteopathy had a higher prevalence of traumatic (40.0% vs 26.4%; P = .02) and spontaneous fractures (3.9% vs 0; P = .04). On multivariate analysis, older age (odds ratio [OR], 1.29 per 5 years; 95% confidence interval [CI], 1.15-1.45), female sex (OR, 3.08; 95% CI, 1.75-5.43), white race (OR, 2.68; 95% CI, 1.20-6.01), and underweight body mass index category (OR, 7.40; 95% CI, 1.56-34.99) were associated with higher probability of osteopathy. There were no significant associations between osteopathy and other patient and disease-related features of CP.

CONCLUSION

In the largest study of patients with CP who underwent DXA screening, the majority had osteopathy. There are overlapping risk factors with osteopathy in the general population, but the high prevalence in men and younger women supports the need for future investigations into the mechanisms of bone loss in CP.

CLINICALTRIALS

gov number, NCT03099850.

Uniting epidemiology and experimental models: pancreatic steatosis and pancreatic cancer

Research from epidemiologic studies and experimental animal models provide insights into the role of pancreatic steatosis in the development of pancreatic cancer. Epidemiologic data demonstrate that pancreatic steatosis is widely prevalent and significantly associated with both development and progression of pancreatic cancer. By focusing on current experimental models, this review elucidates potential cellular mechanisms underlying not only the pathophysiology of pancreatic steatosis itself, but also the pathogenesis behind pancreatic steatosis's role in changing the tumour microenvironment and accelerating the development of pancreatic cancer. This review further explores the impact of bariatric surgery on pancreatic steatosis and pancreatic cancer. Synthesizing knowledge from both epidemiologic studies and experimental animal models, this review identifies gaps in current knowledge regarding pancreatic steatosis and its role in carcinogenesis and proposes future research directions to elucidate the possible mechanisms underlying other obesity-associated cancers.

Hyaluronan heterogeneity in pancreatic ductal adenocarcinoma: Primary tumors compared to sites of metastasis

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers with poor survival. The dense desmoplastic stroma in PDAC contributes to treatment resistance. Among the components comprising the tumor stroma, hyaluronan (HA) has been demonstrated to play a critical role in tumor progression and survival. Previous preliminary studies have suggested differences in HA expression in primary and metastatic foci of PDAC. However, the effects of treatment and location of HA expression as a biomarker signature remain unknown; this study sought to compare HA expression in primary and metastatic sites of PDAC.

METHODS

Tissue from primary and metastatic PDACs were obtained from Cedars-Sinai Medical Center along with associated clinical data. Tissue slides were stained for H&E, HA, and CD44. Associations between HA levels and the evaluated variables were examined including progression free survival and overall survival.

RESULTS

HA score was significantly higher in primary PDACs compared to sites of metastases (p = 0.0148). Within the metastases, HA score was significantly higher in liver metastases compared to metastases at other sites (p = 0.0478). In the treatment-naive liver metastasis cohort, patients with HA high status had decreased progression free survival and overall survival compared to patients with HA low status (p = 0.0032 and p = 0.0478, respectively).

CONCLUSIONS

HA score is variable between primary PDAC, PDAC metastatic to the liver, and PDAC metastatic to other sites. Within liver metastases, patients with HA high status had decreased progression free survival and overall survival compared to patients with HA low status. HA levels can serve as a potential biomarker to guide pancreatic cancer treatments and trial design for agents targeting the stroma.

Loss of miR-29a/b1 promotes inflammation and fibrosis in acute pancreatitis

MicroRNA-29 (miR-29) is a critical regulator of fibroinflammatory processes in human diseases. In this study, we found a decrease in miR-29a in experimental and human chronic pancreatitis, leading us to investigate the regulatory role of the miR-29a/b1 cluster in acute pancreatitis (AP) utilizing a conditional miR-29a/b1-KO mouse model. miR-29a/b1-sufficient (WT) and -deficient (KO) mice were administered supramaximal caerulein to induce AP and characterized at different time points, utilizing an array of IHC and biochemical analyses for AP parameters. In caerulein-induced WT mice, miR-29a remained dramatically downregulated at injury. Despite high-inflammatory milieu, fibrosis, and parenchymal disarray in the WT mice during early AP, the pancreata fully restored during recovery. miR-29a/b1-KO mice showed significantly greater inflammation, lymphocyte infiltration, macrophage polarization, and ECM deposition, continuing until late recovery with persistent parenchymal disorganization. The increased pancreatic fibrosis was accompanied by enhanced TGFβ1 coupled with persistent αSMA+ PSC activation. Additionally, these mice exhibited higher circulating IL-6 and inflammation in lung parenchyma. Together, this collection of studies indicates that depletion of miR-29a/b1 cluster impacts the fibroinflammatory mechanisms of AP, resulting in (a) aggravated pathogenesis and (b) delayed recovery from the disease, suggesting a protective role of the molecule against AP.

Biomarkers of Chronic Pancreatitis: A systematic literature review

BACKGROUND

Chronic pancreatitis (CP) does not have diagnostic or prognostic biomarkers. CP is the end stage of a progressive inflammatory syndrome that is diagnosed at late stages by morphologic features. To diagnose earlier stages of the disease, a new mechanistic definition was established based on identifying underlying pathogenic processes and biomarker evidence of disease activity and stage. Although multiple risk factors are known, the corresponding biomarkers needed to make a highly accurate diagnosis of earlier disease stages have not been established. The goal of this study is to systematically analyze the literature to identify the most likely candidates for development into biomarkers of CP.

METHODS

We conducted a systematic review of candidate analytes from easily accessible biological fluids and identified 67 studies that compared CP to nonpancreatic-disease controls. We then ranked candidate biomarkers for sensitivity and specificity by area under the receiver operator curves (AUROCs).

RESULTS

Five biomarkers had a large effect size (an AUROC > 0.96), whereas 30 biomarkers had a moderate effect size (an AUROC between 0.96 and 0.83) for distinguishing CP cases from controls or other diseases. However, the studies reviewed had marked variability in design, enrollment criteria, and biospecimen sample handling and collection.

CONCLUSIONS

Several biomarkers have the potential for evaluation in prospective cohort studies and should be correlated with risk factors, clinical features, imaging studies and outcomes. The Consortium for the Study of Chronic Pancreatitis, Diabetes and Pancreas Cancer provides recommendations for avoiding design biases and heterogeneity in sample collection and handling in future studies.

Feasibility and safety study of 22-gauge endoscopic ultrasound (EUS) needles for portal vein sampling in a swine model

Background and study aims  Endoscopic ultrasound (EUS) has been used for portal vein sampling in patients with pancreaticobiliary cancers for enumerating circulating tumor cells but is not yet a standard procedure. Further evaluation is needed to refine the methodology. Therefore, we evaluated the feasibility and safety of 19-gauge (19G) versus a 22-gauge (22 G) EUS fine-needle aspiration needles for portal vein sampling in a swine model. Methods  Celiotomy was performed on two farm pigs. Portal vein sampling occurred transhepatically. We compared 19 G and 22 G needles coated interiorly with saline, heparin or ethylenediaminetetraacetic acid (EDTA). Small- (10 mL) and large- (25 mL) volume blood collections were evaluated. Two different collection methods were tested: direct-to-vial and suction syringe. A bleeding risk trial for saline-coated 19 G and 22 G needles was performed by puncturing the portal vein 20 times. Persistent bleeding after 3 minutes was considered significant. Results  All small-volume collection trials were successful except for 22 G saline-coated needles with direct-to-vial method. All large-volume collection trials were successful when using suction syringe; direct-to-vial method for both 19 G and 22 G needles were unsuccessful. Collection times were shorter for 19 G vs. 22 G needles for both small and large-volume collections ( P  < 0.05). Collection times for saline-coated 22 G needles were longer compared to heparin/EDTA-coated ( P  < 0.05). Bleeding occurred in 10 % punctures with 19 G needles compared to 0 % with 22 G needles. Conclusion  The results of this animal study demonstrate the feasibility and the safety of using 22 G needles for portal vein sampling and can form the basis for a pilot study in patients.

Abstract 6343: Mitochondrial bioenergetics mediate chemo-resistance of cancer cells

Background: Resistance to chemotherapy is a major cause of the failure of treatments in many cancers including pancreatic cancer. Accumulated evidence indicates that mitochondrial metabolic alterations are associated with cancer cells growth and proliferation. In this project, we investigated the role of mitochondrial bioenergetics in drug resistance.

Methods: Human pancreatic cancer cell lines MIA PaCa-2 and HPAF-II and mouse pancreatic cancer cell line UN-KPC-961 were treated with increased doses of chemotherapy drug Gemcitabine for 4 months until developing resistance. Mitochondrial proteins, cancer stemness markers and metabolic enzymes were measured by Western and RT-PCR. Cell survival was measured by MTT assay. Mitochondrial bioenergetics were measured by Seahorse Assay.

Results: We found that gemcitabine resistant (GR) cells grow at a much slower rate than wild type (WT) cancer cells; however, they express a significantly higher amount of cancer stemness markers such as Nanog, Oct4 and Sox2. They also expressed higher level of pro-cancer cytokines such as IL-6 and IL-4. Seahorse analysis showed a significantly lower oxygen consumption rate (OCR) in GR cells compared to WT cells. OCR did not change much in GR cells when applying inhibitors of the mitochondrial respiratory chain complex. GR cells produced lower level of ATP and lower spare respiratory capacity. However, GR cells expressed the same amount of mitochondrial proteins such as TOM40, TOM70 and COX4 suggesting the same mass of mitochondria. Pyruvate dehydrogenase-E1 Alpha1 (PDHA1) expression level was significantly lower in GR cells compared to WT cells. PDHA1 inhibition induced WT cells to develop a partial resistance to Gemcitabine; whereas, PDH1 overexpression in GR cells made these cells less resistant to Gemcitabine.

Conclusion: We showed for the first time the difference in mitochondrial bioenergetics between WT and GR cells and showed that GR cells grow independently of the mitochondrial energy production machinery. Furthermore, we identified PDHA1 as a critical mediator of cancer drug resistance.

Citation Format: Fouzia Zayou, Chintan Chheda, Stephen Pandol, Mouad Edderkaoui. Mitochondrial bioenergetics mediate chemo-resistance of cancer cells [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6343.

Abstract 2324: Replication and genetic risk score analysis for pancreatic cancer in a diverse multiethnic population

Background: Pancreatic cancer is one of the most fatal cancers, and it is projected to be the second leading cause of cancer-related death by 2030. Genome-wide association studies (GWAS) conducted in populations of European, Japanese, and Chinese-ancestry have identified several single nucleotide polymorphisms (SNPs) associated with pancreatic cancer risk. No studies yet have attempted to replicate these SNPs in African Americans, Latinos, or Native Hawaiians. In this study, we aimed to replicate the associations of 31 GWAS-identified SNPs with pancreatic cancer and build and test a polygenic risk score (PRS) for pancreatic cancer in an ethnically diverse population.

Methods: We evaluated 31 risk variants in a nested case control study within the Multiethnic Cohort (MEC) and the Southern Community Cohort Study (SCCS). We included 692 pancreatic ductal adenocarcinoma (PDAC) cases and 13,777 controls from African-American (230 cases/5,235 controls), white (132 cases/570 controls), Japanese-American (182 cases/3,284 controls), Latino (105 cases/ 2,935 controls), and Native Hawaiian (43 cases/1,753 controls) participants. We first tested the association between each SNP and PDAC in a combined sample and by race/ethnicity. We then established a PRS using the 31 SNPs and log-odds weights from the combined sample results and tested the association between the score and PDAC risk.

Results: Eleven of the 31 SNPs were replicated in the combined sample, ten initially discovered in GWAS of European ancestry and one in Japanese ancestry. Of these 11, three were also replicated in African Americans, two in whites, one in Japanese Americans, and one in Latinos at p&lt;0.05. Additionally, we observed directional consistency of associations for 26 of 29 SNPs with minor allele frequency &gt;0.05 in the multiethnic sample. The PRS showed strong performance in the multiethnic sample, with the top quintile (80%-100%) for the risk score associated with an odds ratio of 2.27 (95% CI: 1.73, 2.99) for PDAC compared with the middle quintile. Notably, the PRS was associated with PDAC risk within each racial/ethnic group (OR for continuous PRS ranged from 1.27 in Native Hawaiians to 1.97 in African Americans; P heterogeneity=0.16).

Conclusion: This is the first study to test GWAS-identified risk variants associated with pancreatic cancer in a multiethnic population including high-risk African Americans, Japanese Americans and Latinos. We successfully replicated 11 of the 31 risk variants in the combined sample. PRS performance was high in majority of racial/ethnic groups. Our results suggest a potential utility of PRS with GWAS-identified risk variants for the identification of individuals at increased risk for PDAC across multiple ethnic groups.

Citation Format: David Bogumil, David Conti, Xin Sheng, Lucy Xia, Xiao-ou Shu, Stephen Pandol, William Blot, Wei Zheng, Loic Le Marchand, Christopher Haiman, Veronica Wendy Setiawan. Replication and genetic risk score analysis for pancreatic cancer in a diverse multiethnic population [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2324.

Six-dimensional quantitative DCE MR Multitasking of the entire abdomen: Method and application to pancreatic ductal adenocarcinoma

PURPOSE

To develop a quantitative DCE MRI technique enabling entire-abdomen coverage, free-breathing acquisition, 1-second temporal resolution, and T₁ -based quantification of contrast agent concentration and kinetic modeling for the characterization of pancreatic ductal adenocarcinoma (PDAC).

METHODS

Segmented FLASH readouts following saturation-recovery preparation with randomized 3D Cartesian undersampling was used for incoherent data acquisition. MR Multitasking was used to reconstruct 6-dimensional images with 3 spatial dimensions, 1 T₁ recovery dimension for dynamic T₁ quantification, 1 respiratory dimension to resolve respiratory motion, and 1 DCE time dimension to capture the contrast kinetics. Sixteen healthy subjects and 14 patients with pathologically confirmed PDAC were recruited for the in vivo studies, and kinetic parameters v_p , K^trans , v_e , and K_ep were evaluated for each subject. Intersession repeatability of Multitasking DCE was assessed in 8 repeat healthy subjects. One-way unbalanced analysis of variance was performed between control and patient groups.

RESULTS

In vivo studies demonstrated that v_p , K^trans , and K_ep of PDAC were significantly lower compared with nontumoral regions in the patient group (P = .002, .003, .004, respectively) and normal pancreas in the control group (P = .011, <.001, <.001, respectively), while v_e was significantly higher than nontumoral regions (P < .001) and healthy pancreas (P < .001). The kinetic parameters showed good in vivo repeatability (interclass correlation coefficient: v_p , 0.95; K^trans , 0.98; v_e , 0.96; K_ep , 0.99).

CONCLUSION

The proposed Multitasking DCE is promising for the quantification of vascular properties of PDAC. Quantitative DCE parameters were repeatable in vivo and showed significant differences between normal pancreas and both tumor and nontumoral regions in patients with PDAC.

Chronic Pancreatitis: Current Status and Challenges for Prevention and Treatment

This paper reviews the current status of our understanding of the epidemiology, diagnosis, and management of the continuum of pancreatic diseases from acute and recurrent acute pancreatitis to chronic pancreatitis and the diseases that are often linked with pancreatitis including diabetes mellitus and pancreatic cancer. In addition to reviewing the current state of the field, we identify gaps in knowledge that are necessary to address to improve patient outcomes in these conditions.

The Potential for Circulating Tumor Cells in Pancreatic Cancer Management

Pancreatic cancer is one the most lethal malignancies. Only a small proportion of patients with this disease benefit from surgery. Chemotherapy provides only a transient benefit. Though much effort has gone into finding new ways for early diagnosis and treatment, average patient survival has only been improved in the order of months. Circulating tumor cells (CTCs) are shed from primary tumors, including pre-malignant phases. These cells possess information about the genomic characteristics of their tumor source in situ, and their detection and characterization holds potential in early cancer diagnosis, prognosis, and treatment. Liquid Biopsies present an alternative to tumor biopsy that are hard to sample. Below we summarize current methods of CTC detection, the current literature on CTCs in pancreatic cancer, and future perspectives.

Uniting Epidemiology and Experimental Disease Models for Alcohol-Related Pancreatic Disease

Findings from epidemiologic studies and research with experimental animal models provide insights into alcohol-related disease pathogeneses. Epidemiologic data indicate that heavy drinking and smoking are associated with high rates of pancreatic disease. Less clear is the association between lower levels of drinking and pancreatitis. Intriguingly, a very low percentage of drinkers develop clinical pancreatitis. Experimental models demonstrate that alcohol administration alone does not initiate pancreatitis but does sensitize the pancreas to disease. Understanding the effects of alcohol use on the pancreas may prove beneficial in the prevention of both pancreatitis and pancreatic cancer.

Academic Pancreas Centers of Excellence: Guidance from a multidisciplinary chronic pancreatitis working group at PancreasFest

Chronic pancreatitis (CP) is a progressive inflammatory disease, which leads to loss of pancreatic function and other disease-related morbidities. A group of academic physicians and scientists developed comprehensive guidance statements regarding the management of CP that include its epidemiology, diagnosis, medical treatment, surgical treatment, and screening. The statements were developed through literature review, deliberation, and consensus opinion. These statements were ultimately used to develop a conceptual framework for the multidisciplinary management of chronic pancreatitis referred to as an academic pancreas center of excellence (APCOE).

Abstract 4200: Novel treatment strategy for pancreatic cancer

Background: Solid association exists between high expression level of glycogen synthase kinase 3 beta (GSK-3β) and pancreatic cancer (PaCa) progression in humans. GSK-3β inhibition in a mouse orthotopic model of PaCa induced tumor shrinkage. However, GSK-3β inhibition stimulates pro-metastasis epithelial to mesenchymal transition (EMT). HDAC1/2 is involved in regulation of EMT in PaCa cells. We developed a novel strategy based on the combination of GSK-3β inhibition with inhibition of HDAC1 to prevent cancer cell survival, EMT and metastasis in vitro and in vivo. We designed, synthesized and tested a novel dual-inhibitor CSME-357 which inhibits both the proteins.

Methods: Pdx-Cre;LSL-Kras (KC) mice were ip injected with GSK-3β inhibitor TDZD-8 and/or HDAC1/2 inhibitor Saha. Pancreatic intraepithelial neoplasia (PanIN) lesions, fibrosis, and inflammation were measured by IHC. Pancreatic cancer cell lines MIA PaCa-2, BxPC3, AsPC1 were cultured in the presence of HDAC and/or GSK-3β inhibitors or with the novel compound CSME-357 which inhibits both proteins. Cell survival and apoptosis were measured by MTT assay and DNA fragmentation, respectively. EMT and cancer stemness markers, histone acetylation and GSK-3β level were measured by IHC and Western in tissue and cells. Invasion of the cells was measured by invasion assay. Ability of the cells to form metastatic niches in nude mice was measured by injecting PaCa cells in mice tails in the presence or absence of CSME-357 and live mice were analyzed by MRI and by tissue analysis after necropsy.

Results: Treatment of KC mice with Saha decreased the level of PanIN lesions, fibrosis, inflammation, and EMT. TDZD-8 potentiated the effect of Saha on PanIN prevention. Saha and TDZD-8 decreased EMT in KC mice. Pharmacological and molecular inhibitions of GSK-3β significantly, dose dependently, and synergistically decreased proliferation and at a lesser extent stimulated apoptosis in PaCa cell lines. GSK-3β inhibition stimulated EMT in PaCa cells; whereas, Saha reversed this effect. CSME-357 significantly and more potently (compared to the combination of two inhibitors) decreased proliferation, invasion and EMT and stimulated apoptosis in PaCa cells. Significance was achieved at 300nM. Toxicity assays showed no to very little toxicity of the novel compound. CSME-357 decreased the ability of cancer cells to form metastatic niches in nude mice.

Conclusion: Combination of HDAC1 and GSK-3β inhibitions induced a triple beneficial effect by decreasing proliferation, stimulating apoptosis and inhibiting EMT/metastasis. CSME-357 is a novel compound with promising anti-cancer properties. CSME-357 is a very potent inhibitor for both GSK-3β and HDAC1/2; in addition, CSME-357 prevents cancer cell growth, resistance to apoptosis, EMT, invasion and metastasis.

Note: This abstract was not presented at the meeting.

Citation Format: Chintan Chheda, Ramachandran Murali, Paul Grippo, Dale Uyeminami, Kent Pinkerton, Stephen Pandol, Mouad Edderkaoui. Novel treatment strategy for pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4200. doi:10.1158/1538-7445.AM2015-4200

Mouse models of pancreatic cancer induced by chronic pancreatitis and smoking

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Background: Chronic pancreatitis (CP) and smoking are two major risk factors for pancreatic cancer (PaCa). Here we developed mouse models of PaCa by exposing mice to CP and/or smoking. Methods: Wild type (WT) and Pdx1-Cre;LSL-Kras transgenic mice were subjected to 7-hourly cerulein injections (50µg/kg) twice a week for 3 weeks to induce CP. Another group of mice was exposed to tobacco smoke (80mg/m3) in chambers for 5days/week during 6 weeks. A third group was exposed to both treatments. Mice were then sacrificed and pancreatic tissue analyzed. Pancreatic lesions, proliferation, fibrosis, inflammation, EMT and stem cell markers were analyzed by immunohistochemistry and Western. Results: CP significantly increased the number and stage of pancreatic neoplastic (PanIN) lesions with fibrosis, stellate cell activation and inflammation in transgenic mice. These changes were significantly less in WT mice. EMT markers (decrease in E-Cadherin and increase in vimentin protein levels) were stimulated by CP in both WT and transgenic mice. Similarly, smoking stimulated PanIN lesion formation, fibrosis and inflammation in transgenic mice, but to a lesser extent than CP model. Expression of EMT and stem cell markers was greater in the smoking model compared to CP. Combination of CP and smoking induced greater stimulation of PanIN lesion formation, fibrosis and inflammation compared to either treatment alone in transgenic mice. Conclusions: The results indicate that both CP and tobacco smoke promote PaCa progression in transgenic mice. The combination of CP and smoking has greater effects than either treatment alone. EMT and stem cell markers developed in WT as well as in transgenic mice with smoking suggesting that smoking has effects independent of Kras on cell transformation.

Alterations in fecal Lactobacillus and Bifidobacterium species in type 2 diabetic patients in Southern China population

Background: The connection between gut microbiota and metabolism and its role in the pathogenesis of diabetes are increasingly recognized. The objective of this study was to quantitatively measure Bifidobacterium and Lactobacillus species, members of commensal bacteria found in human gut, in type 2 diabetic patients (T2D) patients from Southern China.

Methods: Fifty patients with T2D and thirty control individuals of similar body mass index (BMI) were recruited from Southern China. T2D and control subjects were confirmed with both oral glucose tolerance test (OGTT) and HbA_1c measurements. Bifidobacterium and Lactobacillus species in feces were measured by real-time quantitative PCR. Data were analyzed with STATA 11.0 statistical software.

Results: In comparison to control subjects T2D patients had significantly more total Lactobacillus (+18%), L. bugaricus (+13%), L. rhamnosum (+37%) and L. acidophilus (+48%) (P < 0.05). In contrast, T2D patients had less amounts of total Bifidobacteria (−7%) and B. adolescentis (−12%) (P < 0.05). Cluster analysis showed that gut microbiota pattern of T2D patients is characterized by greater numbers of L. rhamnosus and L. acidophillus, together with lesser numbers of B. adolescentis (P < 0.05).

Conclusion: The gut microflora in T2D patients is characterized by greater numbers of Lactobacillus and lesser numbers of Bifidobacterium species.

Apigenin inhibits NNK-induced focal adhesion kinase activation in pancreatic cancer cells

OBJECTIVES

Tobacco-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) activates β-adrenergic receptor (β-AR) signaling through Src/focal adhesion kinases (FAKs)/mitogen-activated protein kinase to modulate proliferation, migration, and survival. Apigenin (4', 5, 7-trihydroxyflavone) is reported to attenuate proliferation and migration of cancer cells. This study was designed to determine the effects of apigenin on NNK-induced procarcinogenesis using human pancreatic cancer cells BxPC-3 and MIA PaCa-2, which express β-AR.

METHODS

Proliferation and migration were assessed by standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and scratch assays. β-AR, FAK/mitogen-activated protein kinase and extracellular signal-regulated kinase (ERK) expression and activation were assessed by Western blotting and real-time polymerase chain reaction.

RESULTS

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone caused a dose- and time-dependent increase in BxPC-3 and MIA PaCa-2 cell proliferation that was inhibited by propranolol or apigenin. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone also stimulated a time-dependent increase in FAK and ERK activation that was suppressed by propranolol or apigenin. 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone-enhanced gap closure at 24 hours was prevented by either propranolol or apigenin.

CONCLUSION

Apigenin suppressed the effects of NNK on pancreatic cancer cell proliferation and migration that are mediated through the β-AR and its downstream signals FAK and ERK activation. These findings suggest a therapeutic role for this natural phytochemical in attenuating the procarcinogenic effects of NNK on pancreatic cancer proliferation and migration.

Epidemiology, risk factors, and the promotion of pancreatic cancer: role of the stellate cell

There are approximately 277,000 new cases of pancreatic cancer and 266,000 deaths from pancreatic cancer annually, indicating a mortality rate of 96% of the cases diagnosed. Because of the ineffectiveness of therapies, a major emphasis needs to be placed on prevention. This paper reviews the epidemiology and risk factors for pancreatic cancer, and uses this information to propose plausible research directions for determining the biological mechanisms mediating the effects of risk factors on the promotion of pancreatic cancer, with a focus on the pancreatic stellate cell.

The acinar-ductal tango in the pathogenesis of acute pancreatitis

There is an unacceptably high mortality in acute pancreatitis, which is due to the lack of specific treatments for the disease. A major reason stated to account for the inability to develop effective treatments is that there are multiple pathobiologic pathways activated in the acinar cell mediating pancreatitis making it difficult to choose molecular targets for therapeutic strategies. However, this reasoning limits opportunities for therapeutic development because it does include another important participant in pancreatitis - the pancreatic duct cells. The most recent advance in pancreatitis research is that depletion of both glycolytic and oxidative ATP synthesis is a common event in both acinar and ductal cells. Although ATP has a very short half-life in the blood and is hydrolysed to ADP, there is clear evidence that encapsulating ATP into liposomes can effectively drive ATP into the cells which can be effective in protecting them from necrosis. In this review, we will examine the effects of different insults associated with pancreatitis on both the acinar and ductal components of the exocrine pancreas pointing out the role of the ductal epithelial responses in both attenuating and increasing the severity of pancreatitis. In addition, we propose that exogenous ATP administration may restore ductal and acinar function providing therapeutic benefit.

Protein kinase C in the pancreatic acinar cell

Pathological activation of selective signaling molecules within the pancreatic acinar cell mediates the development of acute pancreatitis. Some of the key early acinar cell events include activation of proteases, inhibition of apical secretion, and elaboration of inflammatory mediators. Previous studies have shown that supraphysiological concentrations of cholecystokinin (CCK) that can cause pancreatitis in vivo, also initiate these pathological responses in dispersed groups of acinar cells (acini). Protein kinase C (PKC) regulates many cellular events and a role for this family of signaling molecules has been described in some of the pathological responses of pancreatitis. Notably, ethanol can activate specific PKC isoforms and sensitize the acinar cells to the pathological effects of CCK. Our preliminary studies in isolated pancreatic acini and a cell-free reconstitution system suggest that PKC can mediate protease activation in the acinar cell. These findings may be relevant to the pathogenesis of pancreatitis from alcohol and other etiologies.

Alcohol/cholecystokinin-evoked pancreatic acinar basolateral exocytosis is mediated by protein kinase C alpha phosphorylation of Munc18c

The pancreatic acinus is the functional unit of the exocrine pancreas whose role is to secrete zymogens into the gut lumen for food digestion via apical exocytosis. We previously reported that supramaximal CCK induced apical blockade and redirected exocytosis to ectopic sites on the basolateral plasma membrane (BPM) of this polarized cell, leading to pancreatitis. Basolateral exocytosis was mediated by protein kinase C phosphorylation of BPM Munc18c, causing its displacement into the cytosol and activation of BPM-bound Syntaxin-4 to form a SNARE complex. To mimic the conditions of alcoholic pancreatitis, we now examined whether 20 mm alcohol followed by submaximal CCK might mimic supramaximal CCK in inducing these pathologic exocytotic events. We show that a non-secretory but clinically relevant alcohol concentration (20 mm) inhibited submaximal CCK (50 pM)-stimulated amylase secretion by blocking apical exocytosis and redirecting exocytosis to less efficient BPM, indeed mimicking supramaximal CCK (10 nM) stimulation. We further demonstrate that basolateral exocytosis caused by both stimulation protocols is mediated by PKC alpha-induced phosphorylation of Munc18c: 1) PKC alpha is activated, which binds and induces phosphorylation of PM-Munc18c at a Thr site, and these events can be inhibited by PKC alpha blockade; 2) PKC alpha inhibition blocks Munc18c displacement from the BPM; 3) PKC alpha inhibition prevents basolateral exocytosis but does not rescue apical exocytosis. We conclude that 20 mm alcohol/submaximal CCK as well supramaximal CCK stimulation can trigger pathologic basolateral exocytosis in pancreatic acinar cells via PKC alpha-mediated activation of Munc18c, which enables Syntaxin-4 to become receptive in forming a SNARE complex in the BPM; and we further postulate this to be an underlying mechanism contributing to alcoholic pancreatitis.

Amelioration of rat cerulein pancreatitis by guamerin-derived peptide, a novel elastase inhibitor

Increased activity of various proteases is observed in both human and experimental pancreatitis; however, the information on the effects of specific protease inhibitors on the disease is limited. In this study we show that a novel elastase inhibitor, guamerin-derived synthetic peptide (GDSP), improves the parameters of cerulein-induced acute pancreatitis in the rat. The effects of GDSP on pancreatic weight, serum amylase and lipase, morphologic changes in the pancreas, neutrophil infiltration, and nuclear factor KB (NF-KB) activation were measured in rats infused with supramaximal dose of cerulein (5 (g/kg/h) for 6 h. The effects of GDSP were also measured on superoxide formation by activated human neutrophils. The effects of GDSP were compared with those of another elastase inhibitor, elastatinal. GDSP significantly inhibited edema formation, neutrophil infiltration, acinar cell damage, and plasma lipase and amylase increases caused by cerulein. GDSP also completely inhibited superoxide formation in the human neutrophils stimulated by N-formyl-methionine-leucine-phenyl-alanine (fMLP) or 12-O-tetradecanoylphorbol-13-acetate (TPA). Elastatinal had some of the same effects as GDSP but was less potent and effective. These results demonstrate a beneficial effect of GDSP, a novel specific elastase inhibitor, on the development of rat cerulein pancreatitis.

Disruption of Dictyostelium PI3K genes reduces [32P]phosphatidylinositol 3,4 bisphosphate and [32P]phosphatidylinositol trisphosphate levels, alters F-actin distribution and impairs pinocytosis

To understand how phosphatidylinositol 3-kinase (PI3K) modulates cell structure and function, we examined the molecular and cellular defects of a Dictyostelium mutant strain (pik1(Delta)2(Delta)) missing two (DdPIK1 and 2) of three PI3K genes, which are homologues of the mammalian p110 subunit. Levels of [32P]phosphatidylinositol 3, 4 bisphosphate (PI(3,4)P2) and [32P]phosphatidylinositol trisphosphate (PIP3) were reduced in pik1(Delta)2(Delta), which had major defects in morphological and functional correlates of macropinocytosis. This was accompanied by dramatic deficits in a subset of F-actin-enriched structures such as circular ruffles, actin crowns and pseudopodia. Although pik1(Delta)2(Delta) were mobile, they failed to aggregate into streams. Therefore we conclude that PIK1 and 2, possibly through modulation of the levels of PIP3 and PI(3,4)P2, regulate the organization of actin filaments necessary for circular ruffling during macropinocytosis, the extension of pseudopodia and the aggregation of cells into streams, but not the regulation of cell motility.

Nitric oxide production regulates cGMP formation and calcium influx in pancreatic acinar cells

Guanosine 3',5'-cyclic monophosphate (cGMP) rise is one of the early events in neurotransmitter or hormone-induced cascade of reactions in pancreatic acinar cells. The mechanism of agonist-stimulated guanylyl cyclase activation in these cells remains, however, unknown. In the present work, mechanisms of cGMP rise, as well as of Ca2+ influx, induced by carbachol were studied on acinar cells isolated from rat and guinea pig pancreas. In both types of acinar cells, blocking nitric oxide (NO) production by inhibitors of NO synthase, NG-monomethyl-L-arginine (L-NMMA) or NG-nitro-L-arginine, abolished carbachol-induced cGMP rise in a dose-dependent manner. The inhibition was reversed by addition of excess L-arginine. L-NMMA also caused inhibition of the basal cGMP level, suggesting a role for NO in cGMP homeostasis in resting cells. Carbachol was found to increase [3H]arginine conversion to [3H]citrulline. This conversion was inhibited by L-NMMA. By contrast, inhibition of carbon monoxide production by Zn-protoporphyrin did not affect carbachol-stimulated cellular cGMP levels. There was no increase in cellular cGMP levels in response to exogenous arachidonic acid (AA). Blocking of lipoxygenase oxidation of AA by nordihydroguaiaretic acid did not produce any changes in carbachol-induced cGMP rise. Indomethacin, a cyclooxygenase inhibitor, increased basal cGMP level through L-NMMA-sensitive mechanism. Blockade of NO production inhibited carbachol-induced increase in 45Ca2+ uptake in both guinea pig and rat acinar cells. The concentration-response curves for inhibition by L-NMMA of 45Ca2+ uptake and cGMP formation were superimposable. L-NMMA also suppressed stimulation of Mn2+ quenching by carbachol in fura 2-loaded acini.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbachol- and elevated Ca(2+)-induced translocation of functionally active protein kinase C to the brush border of rabbit ileal Na+ absorbing cells

Protein kinase C is involved in mediating the effects of elevated Ca2+ in ileal villus Na+ absorbing cells to inhibit NaCl absorption. The present studies were undertaken to understand the mechanism by which this occurs. The effects of carbachol and the calcium ionophore A23187, agents which elevate intracellular Ca2+ and inhibit NaCl absorption in ileal villus cells, were studied. Carbachol treatment of villus cells caused a rapid decrease in protein kinase C activity in cytosol, with an accompanying increase in microvillus membrane C kinase. Exposure of the villus cells to calcium ionophore also caused a quantitatively similar decrease in cytosol C kinase and increase in C kinase activity in the microvillus membrane. This increase caused by carbachol and Ca2+ ionophore was specific for the microvillus membrane. In fact, 30 s and 10 min after exposure of the cells to carbachol, basolateral membrane protein kinase C decreased, in a time-dependent manner; whereas 10 min of Ca2+ ionophore exposure did not alter basolateral C kinase. Exposure of villus cells to Ca2+ ionophore or carbachol caused similar increases in microvillus membrane diacylglycerol content. As judged by the ability to inhibit Na+/H+ exchange measured in ileal villus cell brush border membrane vesicles, the protein kinase C which translocated to the microvillus membrane was functionally significant. Inhibition of Na+/H+ exchange required ATP and was reversed by the protein kinase C antagonist H-7. In conclusion, the effect of carbachol and Ca2+ ionophore in regulation of ileal NaCl absorption is associated with an increase in microvillus membrane diacylglycerol content and functionally active protein kinase C. The effects of both carbachol and Ca2+ ionophore are different on brush border and basolateral membrane distribution of protein kinase C.

Inositol trisphosphate modification of ion transport in rough endoplasmic reticulum

The ion transport properties of the rough endoplasmic reticulum (RER) from liver have been defined by using measurements of active and potential gradient-driven transport. The Ca2+ pump is shown to be electrogenic, and both ATP and potential difference is able to drive vanadate-inhibitable Ca2+ uptake into the RER. ATP-dependent Ca2+ transport into the RER depends on the presence of tetraethylammonium-sensitive cation conductance and a furosemide-inhibited cation/chloride cotransport pathway. Inositol trisphosphate does not affect either of the monovalent ion translocation systems but activates a Ca2+ conductance in the RER, allowing efflux of RER Ca2+ stores into the cytosol in exchange for K+ uptake.