Dataset Information

Apoptosis signal regulating kinase-1 and NADPH oxidase mediate human amylin evoked redox stress and apoptosis in pancreatic beta-cells.

ABSTRACT: Misfolded toxic human islet amyloid polypeptide or amylin (hA) and plasma membrane-associated redox complex, NADPH oxidase (NOX), have been implicated in the islet ?-cell demise associated with type-2 diabetes mellitus (T2DM). Studies show that hA accumulation is stressful to ?-cells and that misfolding of human amylin evokes redox stress and activates mitogen activated protein (MAP) kinases, p38 MAPK and c-Jun N-terminal (JNK) kinase. However, the molecular link and causality between hA-evoked redox stress, NOX activity and MAP kinases signaling in pancreatic ?-cells is incompletely understood. Here, we show that in the process of activating JNK, aggregation prone hA also activates an upstream apoptosis signal regulating kinase-1 (ASK1) with concomitant decrease in intracellular levels of reduced glutathione. Inhibition of ASK1 kinase activity, either by specific ASK1 inhibitor, NQDI1 or by thiol antioxidants reduces human amylin-evoked ASK1 and JNK activation and consequently human amylin toxicity in rat insulinoma Rin-m5F cells and human islets. ?-cell specific overexpression of human amylin in mouse islets elicited ASK1 phosphorylation and activation in ?-cells but not in other rodent's islet or exocrine cells. This ASK1 activation strongly correlated with islet amyloidosis and diabetes progression. Cytotoxic human amylin additionally stimulated pro-oxidative activity and expressions of plasma membrane bound NADPH oxidase (NOX) and its regulatory subunits. siRNA mediated NOX1 knockdown and selective NOX inhibitors, ML171 and apocynin, significantly reduced hA-induced mitochondrial stress in insulinoma beta-cells. However, NOX inhibitors were largely ineffective against hA-evoked redox stress and activation of cytotoxic ASK1/JNK signaling complex. Thus, our studies suggest that NOX1 and ASK1 autonomously mediate human amylin-evoked redox and mitochondrial stress in pancreatic ?-cells.

SUBMITTER: Singh S

PROVIDER: S-EPMC6177334 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Apoptosis signal regulating kinase-1 and NADPH oxidase mediate human amylin evoked redox stress and apoptosis in pancreatic beta-cells.

Singh Sanghamitra S Bhowmick Diti Chatterjee DC Pany Satyabrata S Joe Myungkuk M Zaghlula Noor N Jeremic Aleksandar M AM

Biochimica et biophysica acta. Biomembranes 20180406 9

Misfolded toxic human islet amyloid polypeptide or amylin (hA) and plasma membrane-associated redox complex, NADPH oxidase (NOX), have been implicated in the islet β-cell demise associated with type-2 diabetes mellitus (T2DM). Studies show that hA accumulation is stressful to β-cells and that misfolding of human amylin evokes redox stress and activates mitogen activated protein (MAP) kinases, p38 MAPK and c-Jun N-terminal (JNK) kinase. However, the molecular link and causality between hA-evoked ...[more]

PMID: 29627323

Similar Datasets

Project description:The objective of these studies was to clarify the role of Ca(2+) in the mechanism of death evoked by human amylin (hA) in islet beta-cells. hA forms fibrils in vitro and islet amyloid in vivo. Here we show that pure synthetic hA aggregated in solution, formed fibrils and evoked death in cultured RINm5F islet beta-cells in a time-dependent (0-24 h) and concentration-dependent (0-20 microM) manner. Dying cells underwent shrinkage of the nucleus, with clumping and segregation of chromatin into masses that lay against the nuclear envelope, and internucleosomal DNA fragmentation. These cells therefore show many features of apoptosis, although aspects of the morphology might be characteristic of this particular cell type rather than of a general apoptotic nature. Aurintricarboxylic acid, an inhibitor of both Ca(2+)-dependent and Ca(2+)-independent nucleases, suppressed this DNA fragmentation and inhibited apoptosis at concentrations between 25 and 200 microM. Direct measurements of the cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) in fura-2 acetoxymethyl ester (AM)-loaded beta-cells showed that neither hA nor its non-cytotoxic homologue, rat amylin were effective in raising [Ca(2+)](i). Modulators of Ca(2+) regulation were tested for their effects on hA-induced beta-cell apoptosis. Ca(2+) ionophore (A23187) and thapsigargin (an inhibitor of endoplasmic reticular Ca(2+)-ATPase activity) by themselves evoked apoptosis accompanied by increased [Ca(2+)](i). Neither the Ca(2+) channel blocker verapamil, the extracellular Ca(2+) chelator EGTA nor the cytosolic Ca(2+) buffer bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid ('BAPTA')/AM protected beta-cells from hA-evoked apoptosis. Prolonged incubation of beta-cells with a lethal dose of hA altered neither the basal [Ca(2+)](i) nor the thapsigargin-induced release of Ca(2+) from intracellular stores. Furthermore, (45)CaCl(2) uptake by RINm5F cells did not differ in the presence or absence of hA. These results suggest that, whereas alterations in cytosolic Ca(2+) homoeostasis do have a significant role in certain forms of beta-cell death, they do not contribute to the pathway of apoptosis evoked by hA in islet beta-cells.

Project description:Neutrophils migrating from the blood (pH 7.35-7.45) into the surrounding tissues encounter changes in extracellular pH (pHe) conditions. Upon activation of NADPH oxidase 2 (Nox), neutrophils generate large amounts of H+ ions reducing the intracellular pH (pHi). Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET) formation (NETosis) is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS) and neutrophil protease activity, stimulating NETosis. Here, we found that raising pHe (ranging from 6.6 to 7.8; every 0.2 units) increased pHi of both activated and resting neutrophils within 10-20?min (Seminaphtharhodafluor dual fluorescence measurements). Since Nox activity generates H+ ions, pHi is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging) during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs). In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots) and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative)-, and Staphylococcus aureus (Gram-positive)-induced NETosis. Thus, higher pHe promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pHe-mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM) increases NETosis. Each Tris molecule can bind 3H+ ions, whereas each bicarbonate HCO3- ion binds 1H+ ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar bicarbonate solution. For that reason, regulating NETosis by pH with specific buffers such as THAM could be more effective than bicarbonate in managing NET-related diseases.

Dataset Information

Apoptosis signal regulating kinase-1 and NADPH oxidase mediate human amylin evoked redox stress and apoptosis in pancreatic beta-cells.

Publications

Apoptosis signal regulating kinase-1 and NADPH oxidase mediate human amylin evoked redox stress and apoptosis in pancreatic beta-cells.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets