Barlow Jonathan, Hirschberg Jensen Verena, Affourtit Charles
School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK.
School of Biomedical and Healthcare Sciences, Plymouth University, Drake Circus, Plymouth PL4 8AA, UK.
Redox Biol. 2015;4:14-22. doi: 10.1016/j.redox.2014.11.009. Epub 2014 Nov 28.
High glucose and fatty acid levels impair pancreatic beta cell function. We have recently shown that palmitate-induced loss of INS-1E insulinoma cells is related to increased reactive oxygen species (ROS) production as both toxic effects are prevented by palmitoleate. Here we show that palmitate-induced ROS are mostly mitochondrial: oxidation of MitoSOX, a mitochondria-targeted superoxide probe, is increased by palmitate, whilst oxidation of the equivalent non-targeted probe is unaffected. Moreover, mitochondrial respiratory inhibition with antimycin A stimulates palmitate-induced MitoSOX oxidation. We also show that palmitate does not change the level of mitochondrial uncoupling protein-2 (UCP2) and that UCP2 knockdown does not affect palmitate-induced MitoSOX oxidation. Palmitoleate does not influence MitoSOX oxidation in INS-1E cells ±UCP2 and largely prevents the palmitate-induced effects. Importantly, UCP2 knockdown amplifies the preventive effect of palmitoleate on palmitate-induced ROS. Consistently, viability effects of palmitate and palmitoleate are similar between cells ±UCP2, but UCP2 knockdown significantly augments the palmitoleate protection against palmitate-induced cell loss at high glucose. We conclude that UCP2 neither mediates palmitate-induced mitochondrial ROS generation and the associated cell loss, nor protects against these deleterious effects. Instead, UCP2 dampens palmitoleate protection against palmitate toxicity.
高血糖和脂肪酸水平会损害胰腺β细胞功能。我们最近发现,棕榈酸诱导的INS - 1E胰岛素瘤细胞损失与活性氧(ROS)生成增加有关,因为棕榈油酸可预防这两种毒性作用。在此我们表明,棕榈酸诱导产生的ROS主要源自线粒体:棕榈酸可增加线粒体靶向超氧化物探针MitoSOX的氧化,而对等效的非靶向探针的氧化则无影响。此外,用抗霉素A抑制线粒体呼吸可刺激棕榈酸诱导的MitoSOX氧化。我们还表明,棕榈酸不会改变线粒体解偶联蛋白-2(UCP2)的水平,且UCP2基因敲低不影响棕榈酸诱导的MitoSOX氧化。棕榈油酸对±UCP2的INS - 1E细胞中的MitoSOX氧化无影响,并在很大程度上预防了棕榈酸诱导的效应。重要的是,UCP2基因敲低增强了棕榈油酸对棕榈酸诱导的ROS的预防作用。同样,在±UCP2的细胞中,棕榈酸和棕榈油酸对细胞活力的影响相似,但UCP2基因敲低显著增强了棕榈油酸对高糖条件下棕榈酸诱导的细胞损失的保护作用。我们得出结论,UCP2既不介导棕榈酸诱导的线粒体ROS生成及相关的细胞损失,也不预防这些有害效应。相反,UCP2会削弱棕榈油酸对棕榈酸毒性的保护作用。