Effects of caveolin-1 deficiency on palmitic acid-induced apoptosis of islet-β cells

Objective To investigate the role of caveolin-1 (Cav1) in palmitic acid-induced survival of pancreatic islet β-cell. Methods Cav1-deficient NIT-1 cells and mouse primary islets were constructed through lentiviral vector transfection. Control-shRNA was transfected as a control. After fatty-acid-free bovine serum albumin (BSA) and palmitic acid (0.5 mmol/L) incubation for 24 and 48 hours, cell viability and apoptosis werecalculated by methylcyclopentadienyl manganese tricarbonylassay and Hoechst33342/propidium iodide (PI) double staining.Real time PCR and Western blot were used to detect the expression of apoptosis-associated mRNA and protein. The t test and one-way ANOVA were used for statistical analysis. Results Compared with the control group, the cell survival rate of the palmitic acid treatment group was significantly decreased (0.89±0.10 vs 0.24±0.04, t=13.49, P<0.01), and mRNA and protein expressions of P18 and P19 were up-regulated (1.00±0.09 vs 1.30±0.04, 1.00±0.04 vs 1.37±0.13, t=5.28, 4.71, both P<0.05; 0.87±0.04, 1.48±0.05, 1.02±0.06 vs 1.41±0.07, t=16.50, 7.33, both P<0.01); mRNA expression levels of cysteine-containing aspartic proteolytic enzymes (Caspase-6, Caspase-9, and Caspase-12) were significantly up-regulated (1.00±0.04 vs 1.57±0.08, 1.01±0.15 vs 1.57±0.20, 1.02±0.19 vs 1.57±0.09, t=11.04,3.88, 4.53, all P<0.05), and protein expression of them were also significantly increased (0.86±0.10 vs 1.28±0.11, 0.69±0.01 vs 0.86±0.06, 0.70±0.02 vs 1.18±0.01, t=4.89,4.84, 37.18, all P<0.01). The cell survival rate of Cav1-shRNA+palmitic acid group was significantly higher than that of Ctrl-shRNA+palmitic acid group (0.53±0.10 vs 0.26±0.08, t=4.71, P<0.01). The mRNA and protein expression of P19 were all down-regulated (1.53±0.18 vs 0.66±0.04, 1.48±0.05 vs 0.70±0.02, t=8.17, 25.09, both P<0.01); mRNA expression levels of Caspase-6, Caspase-7, Caspase-9 and Caspase-12 were down-regulated (1.82±0.11 vs 1.03±0.07, 1.43±0.24 vs 0.42±0.15, 1.41±0.22 vs 0.51±0.18, 1.45±0.18 vs 0.42±0.13, t=5.48-10.49, all P<0.01), and protein expression of them were also down-regulated (0.99±0.14 vs 0.63±0.11, 0.90±0.14 vs 0.62±0.04, 0.90±0.02 vs 0.60±0.04, 1.30±0.01 vs 0.65±0.04, t=3.50-27.31, all P<0.01). Conclusion Cav1 deficiency inhibites palmitic acid-induced pancreatic β-cell apoptosis via regulating Caspase family, and ultimately protects β cell viability. Key words: Caveolin 1; Apoptosis; Cell proliferation; Islet-β cells