Exendin-4 Promotes Survival of Mouse Pancreatic β-Cell Line in Lipotoxic Conditions, through the Extracellular Signal-Related Kinase 1/2 Pathway

Figure 2

The antilipotoxic effects of exendin-4 on cell survival and apoptosis involve ERK1/2 pathway. MIN6 cells were preincubated overnight in serum-free DMEM and then incubated in serum-free DMEM containing 0.5% BSA (BSA) or 0.4 mM palmitate added 0.5% BSA (PA) for 24 h. Increasing concentrations (1–500 nM) of exendin-4 (Ex) were used to treat the cells for the indicated times. (a) Total ERK1/2 and p-ERK1/2 protein expression after 0–30 min of treatment with 100 nM Ex. Values are expressed as relative intensity ratio and represent the mean ± SE of three independent experiments. , , versus PA + Ex at 0 min. (b) Total ERK1/2 and p-ERK1/2 protein expression after 5 min of treatment with increasing concentrations (1–500 nM) of Ex. Values are expressed as relative intensity ratio and represent the mean ± SE of three independent experiments. , , versus PA group without Ex. (c) Total ERK1/2 and p-ERK1/2 protein expression after 5 min of treatment with 100 nM Ex, with or without inhibitor. Before Ex stimulation, cells with PA were pretreated for 30 min with ERK1/2 inhibitor, 50 μM PD98059 (PD). Values are expressed as relative intensity ratio and represent the mean ± SE of three independent experiments. , . (d) Cell survival was assessed by MTT assay. , . (e) apoptosis assessed by Hoechst33258 staining. MIN6 cells were incubated with BSA or PA, with or without PD, in the presence or absence of 100 nM Ex, in serum-free medium for 24 h. Values of survival are expressed as percentage of control (cells treated with BSA alone) and represent the mean ± SE of five independent experiments. Values of apoptosis are expressed as percentage of apoptotic cells and represent the mean ± SE of 10 random fields of vision of three independent experiments. , .

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