Requirements of calcium fluxes and ERK kinase activation for glucose- and interleukin-1beta-induced beta-cell apoptosis.
Increasing evidence indicates that beta-cell apoptosis and impaired secretory function were partly mediated by interleukin (IL)-1beta and/or high-glucose-induced beta-cell production of IL-1beta. However, the specific signal transduction pathways and molecular events involved in beta-cell dysfunction remain largely unresolved. In this study, we investigated whether Ca(2+) and extracellular signal-regulated kinase (ERK) activation plays a role for IL-1beta action in rat islets. Exposure of rat islets for 4 days to 33.3 mM glucose and 140 ng/ml IL-1beta- induced beta-cell apoptosis and impaired glucose-stimulated insulin secretion. By Western blotting with phosphospecific antibodies, glucose and IL-1beta were shown to activate ERK. Ca(2+) channel blocker nimodipine or ERK inhibitor PD98059 prevented glucose- and IL-1beta-induced ERK activation, beta-cell apoptosis, and impaired function. Furthermore, treatment with Ca(2+) ionophore ionomycin, or exposure to thapsigargin, an inhibitor of sarco(endo)plasmic reticulum Ca(2+) ATPase, all caused an amplification of IL-1beta-induced ERK activation in rat islet. On the other hand, a chelator of intracellular free Ca(2+) [bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid-acetoxymethyl] (BAPTA/AM) and an inhibitor of calmodulin (W7) diminished IL-1beta-induced phosphorylation of ERK. Finally, islet release of IL-1beta in response to high glucose could be abrogated by nimodipine, mibefradil, or PD98059. Together, these data suggest that glucose- and IL-1beta-induced beta-cell secretory dysfunction and apoptosis are Ca(2+) influx and ERK dependent in rat islets.
Fei
Hongqiang
H
School of Life Science and Biotechnology, Key Laboratory of Microbial Metabolism, Ministry of Education, Shanghai Jiaotong University, 800 Dongchuan Road, Shanghai, People's Republic of China.
Zhao
Bin
B
Zhao
Shangang
S
Wang
Qin
Q
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D053583:Interleukin-1beta / Q000494:pharmacology*; D015640:Ion Channel Gating / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D020748:Mibefradil / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D007328:Insulin; D053583:Interleukin-1beta; D013449:Sulfonamides; D020748:Mibefradil; D004533:Egtazic Acid; D015759:Ionomycin; D009553:Nimodipine; C017967:W 7; D019284:Thapsigargin; D048049:Extracellular Signal-Regulated MAP Kinases; D005947:Glucose; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid