Choi Sung-E, Min Se-Hee, Shin Ha-Chul, Kim Hyo-Eun, Jung Min Whan, Kang Yup
Institute for Medical Science, Ajou University School of Medicine,442-749, Suwon, Kyunggi-do, Republic of Korea.
Eur J Pharmacol. 2006 Oct 10;547(1-3):1-9. doi: 10.1016/j.ejphar.2006.06.016. Epub 2006 Jun 15.
Reactive oxygen species are believed to be the central mediators of beta-cell destruction that leads to type 1 and 2 diabetes, and calcium has been reported to be an important mediator of beta cell death. In the present study, the authors investigated whether Ca(2+) plays a role in hydrogen peroxide (H(2)O(2))-induced MIN6N8a mouse beta cell death. Treatment with low concentration H(2)O(2) (50 microM) was found to be sufficient to reduce MIN6N8a cell viability by 55%, largely via apoptosis. However, this H(2)O(2)-induced cell death was near completely blocked by pretreatment with BAPTA/AM (5 microM), a chelator of intracellular Ca(2+). Moreover, the intracellular calcium store channel blockers, such as, xestospongin c and ryanodine, significant protected cells from 50 microM H(2)O(2)-induced cell death and under extracellular Ca(2+)-free conditions, 50 microM H(2)O(2) elicited transient Ca(2+) increases. In addition, pharmacologic inhibitors of calpain, calcineurin, and calcium/calmodulin-dependent protein kinase II were found to have a protective effect on H(2)O(2)-induced death. Moreover, H(2)O(2)-induced apoptotic signals, such as c-JUN N-terminal kinase activation, cytochrome c release, caspase 3 activation, and poly (ADP-ribose) polymerase cleavage were all down-regulated by the intracellular Ca(2+) chelation. These findings show that Ca(2+) elevation, possibly due to release from intracellular calcium stores and the subsequent activation of Ca(2+)-mediated apoptotic signals, critically mediates low concentration H(2)O(2)-induced MIN6N8a cell death. These findings suggest that a breakdown of calcium homeostasis by low level of reactive oxygen species may be involved in beta cell destruction during diabetes development.
活性氧被认为是导致1型和2型糖尿病的β细胞破坏的核心介质，并且据报道钙是β细胞死亡的重要介质。在本研究中，作者研究了Ca(2+)是否在过氧化氢（H(2)O(2)）诱导的MIN6N8a小鼠β细胞死亡中起作用。发现用低浓度H(2)O(2)（50微摩尔）处理足以使MIN6N8a细胞活力降低55%，主要是通过凋亡。然而，这种H(2)O(2)诱导的细胞死亡几乎被用BAPTA/AM（5微摩尔）预处理完全阻断，BAPTA/AM是一种细胞内Ca(2+)螯合剂。此外，细胞内钙储存通道阻滞剂，如西司他汀c和ryanodine，显著保护细胞免受50微摩尔H(2)O(2)诱导的细胞死亡，并且在无细胞外Ca(2+)的条件下，50微摩尔H(2)O(2)引起瞬时Ca(2+)增加。此外，发现钙蛋白酶、钙调神经磷酸酶和钙/钙调蛋白依赖性蛋白激酶II的药理学抑制剂对H(2)O(2)诱导的死亡有保护作用。此外，细胞内Ca(2+)螯合下调了H(2)O(2)诱导的凋亡信号，如c-JUN N末端激酶激活、细胞色素c释放、半胱天冬酶3激活和聚（ADP-核糖）聚合酶裂解。这些发现表明，Ca(2+)升高，可能是由于细胞内钙储存释放以及随后Ca(2+)介导的凋亡信号的激活，关键地介导了低浓度H(2)O(2)诱导的MIN6N8a细胞死亡。这些发现表明，低水平活性氧导致的钙稳态破坏可能参与糖尿病发展过程中的β细胞破坏。
