Strelitz Diabetes Center, Department of Internal Medicine, Eastern Virginia Medical School, 825 Fairfax Avenue, Suite 410, Norfolk, Virginia 23507, USA.
J Clin Endocrinol Metab. 2010 Feb;95(2):887-93. doi: 10.1210/jc.2009-1102. Epub 2010 Jan 20.
Inflammation is increasingly recognized as an important contributing factor in diabetes mellitus. Lipoxygenases (LOs) produce active lipids that promote inflammatory damage by catalyzing the oxidation of linoleic and arachidonic acid, and LO is expressed in rodent and human islets. Little is known about the differential effect of the various hydroxyeicosatetraenoic acids (HETEs) that result from LO activity in human islets.
We compared the effects of 12-LO products on human islet viability and function.
Human islets were treated with stable compounds derived from LOs: 12(S)-HETE, 15HETE, 12HPETE, and 12RHETE and then examined for insulin secretion and islet viability. The p38-MAPK (p38) and JNK stress-activated pathways were investigated as mechanisms of 12-LO-mediated islet inhibition in rodent and human islets.
Insulin secretion was consistently reduced by 12(S)-HETE and 12HPETE. 12(S)-HETE at 1 nm reduced viability activity by 32% measured by MTT assay and increased cell death by 50% at 100 nm in human islets. These effects were partially reversed with lisofylline, a small-molecule antiinflammatory compound that protects mitochondrial function. 12(S)-HETE increased phosphorylated p38-MAPK (pp38) protein activity in human islets. Injecting 12-LO siRNA into C57BL/6 mice reduced 12-LO and pp38-MAPK protein levels in mouse islets. The addition of proinflammatory cytokines increased pp38 levels in normal mouse islets but not in siRNA-treated islets.
These data suggest that 12(S)-HETE reduces insulin secretion and increases cell death in human islets. The 12-LO pathway is present in human islets, and expression is up-regulated by inflammatory cytokines. Reduction of 12-LO activity could thus provide a new therapeutic approach to protect human beta-cells from inflammatory injury.
炎症越来越被认为是糖尿病的一个重要致病因素。脂氧合酶（LOs）通过催化亚油酸和花生四烯酸的氧化，产生促进炎症损伤的活性脂质，LO 在啮齿动物和人类胰岛中表达。关于 LO 活性在人类胰岛中产生的各种羟二十碳四烯酸（HETEs）的差异作用知之甚少。
我们比较了 12-LO 产物对人胰岛活力和功能的影响。
用 LO 的稳定化合物处理人胰岛：12(S)-HETE、15HETE、12HPETE 和 12RHETE，然后检查胰岛素分泌和胰岛活力。研究了 p38-MAPK（p38）和 JNK 应激激活途径作为 12-LO 介导的啮齿动物和人类胰岛抑制的机制。
胰岛素分泌始终被 12(S)-HETE 和 12HPETE 所抑制。12(S)-HETE 在 1nm 时通过 MTT 测定法将活力活性降低 32%，在 100nm 时将细胞死亡增加 50%在人类胰岛中。这些作用部分被小分子抗炎化合物 lisofylline 逆转，它可保护线粒体功能。12(S)-HETE 增加了人胰岛中磷酸化 p38-MAPK（pp38）蛋白的活性。向 C57BL/6 小鼠注射 12-LO siRNA 可降低小鼠胰岛中的 12-LO 和 pp38-MAPK 蛋白水平。炎性细胞因子的添加增加了正常小鼠胰岛中的 pp38 水平，但在 siRNA 处理的胰岛中没有增加。
这些数据表明，12(S)-HETE 可减少人胰岛中的胰岛素分泌并增加细胞死亡。12-LO 途径存在于人类胰岛中，其表达受炎性细胞因子上调。减少 12-LO 活性可能为保护人类β细胞免受炎症损伤提供新的治疗方法。
