Lipotoxic Stress Induces Pancreatic β-Cell Apoptosis through Modulation of Bcl-2 Proteins by the Ubiquitin-Proteasome System

Figure 6

SFN protects β-cells from FFA-induced cell death. (a) MIN6 cells were treated with 10 μM MG132 and 2 mM SFN for 24 h and levels of ubiquitinated proteins were measured by Western blot. The result is representative of two independent experiments. (b) MIN6 cells were treated with SFN and palmitate as indicated and Western blot analysis was conducted to detect ubiquitinated proteins. β-actin levels were used as a loading control. The result is representative of two independent experiments. (c) MIN6 cells were treated for 24 h as indicated and viability was detected by HO/PI. Results are the means ± SEM of 4 independent experiments. . ((d)–(g)) MIN6 cells were treated with 0.5 mM palmitate and/or 2 mM SFN for 24 h and ER stress markers (ATF4, Chop, and Bip) and PUMA measured by qPCR as indicated. Results are the means ± SEM of 3-4 independent experiments. . ((h)–(j)) MIN6 cells were treated with 0.5 mM palmitate and/or 2 mM SFN for 24 h and expression of prosurvival Bcl-2 proteins was measured by Western blotting with antibodies detecting Bcl-2 (h), Bcl-XL (i), and Mcl-1 (j). Quantification of protein bands is indicated at the bottom as a ratio to β-actin loading control. The results are representative of two independent experiments.

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