Collier J Jason, Fueger Patrick T, Hohmeier Hans E, Newgard Christopher B
Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Duke Independence Park Facility, 4321 Medical Park Drive, Suite 200, Durham, NC 27704, USA.
Diabetes. 2006 May;55(5):1398-406. doi: 10.2337/db05-1000.
Type 1 diabetes results from islet beta-cell death and dysfunction induced by an autoimmune mechanism. Proinflammatory cytokines such as interleukin-1beta and gamma-interferon are mediators of this beta-cell cytotoxicity, but the mechanism by which damage occurs is not well understood. In the current study, we present multiple lines of evidence supporting the conclusion that cytokine-induced killing of rat beta-cells occurs predominantly by a nonapoptotic mechanism, including the following: 1) A rat beta-cell line selected for resistance to cytokine-induced cytotoxicity (833/15) is equally sensitive to killing by the apoptosis-inducing agents camptothecin and etoposide as a cytokine-sensitive cell line (832/13). 2) Overexpression of a constitutively active form of the antiapoptotic protein kinase Akt1 in 832/13 cells provides significant protection against cell killing induced by camptothecin and etoposide but no protection against cytokine-mediated damage. 3) Small interfering RNA-mediated suppression of the proapoptotic protein Bax enhances viability of 832/13 cells upon exposure to the known apoptosis-inducing drugs but not the inflammatory cytokines. 4) Exposure of primary rat islets or 832/13 cells to the inflammatory cytokines causes cell death as evidenced by the release of adenylate kinase activity into the cell medium, with no attendant increase in caspase 3 activation or annexin V staining. In contrast, camptothecin- and etoposide-induced killing is associated with robust increases in caspase 3 activation and annexin V staining. 5) Camptothecin increases cellular ATP levels, whereas inflammatory cytokines lower ATP levels in both beta-cell lines and primary islets. We conclude that proinflammatory cytokines cause beta-cell cytotoxicity primarily through a nonapoptotic mechanism linked to a decline in ATP levels.
1型糖尿病是由自身免疫机制诱导的胰岛β细胞死亡和功能障碍所致。白细胞介素-1β和γ干扰素等促炎细胞因子是这种β细胞细胞毒性的介质，但损伤发生的机制尚不清楚。在本研究中，我们提供了多条证据支持细胞因子诱导的大鼠β细胞杀伤主要通过非凋亡机制发生这一结论，包括以下几点：1）选择对细胞因子诱导的细胞毒性具有抗性的大鼠β细胞系（833/15），其对凋亡诱导剂喜树碱和依托泊苷的杀伤敏感性与细胞因子敏感细胞系（832/13）相同。2）在832/13细胞中过表达抗凋亡蛋白激酶Akt1的组成型活性形式，可显著保护细胞免受喜树碱和依托泊苷诱导地杀伤，但对细胞因子介导的损伤无保护作用。3）小干扰RNA介导的促凋亡蛋白Bax的抑制增强了832/13细胞在暴露于已知凋亡诱导药物时的活力，但对炎性细胞因子无增强作用。4）原代大鼠胰岛或832/13细胞暴露于炎性细胞因子会导致细胞死亡，这可通过腺苷酸激酶活性释放到细胞培养基中得到证明，同时半胱天冬酶3激活或膜联蛋白V染色无伴随增加。相比之下，喜树碱和依托泊苷诱导的杀伤与半胱天冬酶3激活和膜联蛋白V染色的显著增加有关。5）喜树碱增加细胞内ATP水平，而炎性细胞因子降低β细胞系和原代胰岛中的ATP水平。我们得出结论，促炎细胞因子主要通过与ATP水平下降相关的非凋亡机制导致β细胞细胞毒性。
