Welters H J, Smith S A, Tadayyon M, Scarpello J H B, Morgan N G
Institute of Biomedical and Clinical Science, Peninsula Medical School, Plymouth, Devon, PL6 8BX, UK.
J Mol Endocrinol. 2004 Feb;32(1):227-35. doi: 10.1677/jme.0.0320227.
Chronic exposure of pancreatic beta-cells to saturated fatty acids leads to loss of viability, an effect that has been implicated in the process of beta-cell 'lipotoxicity' associated with the progression of type 2 diabetes. The mechanisms involved are unknown but recent evidence has implicated the delta isoform of protein kinase C (PKCdelta) in mediating fatty acid toxicity. We have investigated this proposition in the clonal insulin-secreting cell line, BRIN-BD11. BRIN-BD11 cells were found to undergo apoptosis when exposed to palmitate and this response was attenuated by the purportedly selective inhibitor of PKCdelta, rottlerin. However, activation of PKCdelta with the phorbol ester, phorbol-12-myristate-13-acetate (PMA), failed to promote cell death and down-regulation of PKCdelta did not prevent the cytotoxic effects of palmitate. Moreover, rottlerin remained effective as a blocker of the palmitate response in cells depleted of PKCdelta. Since rottlerin can inhibit various other kinases in addition to PKCdelta, a range of additional kinase inhibitors was also tested. Of these, only the putative Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) inhibitor, KN-62, was found to inhibit palmitate-induced cell death. However, this effect was not reproduced by a more selective pseudo-substrate inhibitor of CaM kinase II. Therefore, the present results reveal that palmitate induces cell death in BRIN-BD11 cells and suggest that this may involve the activation of a rottlerin (and KN-62)-sensitive kinase. However, it is clear that PKCdelta is not required for this response.
胰腺β细胞长期暴露于饱和脂肪酸会导致细胞活力丧失，这一效应与2型糖尿病进展过程中的β细胞“脂毒性”有关。其涉及的机制尚不清楚，但最近有证据表明蛋白激酶C（PKCδ）的δ亚型介导脂肪酸毒性。我们在克隆胰岛素分泌细胞系BRIN - BD11中研究了这一观点。发现BRIN - BD11细胞暴露于棕榈酸时会发生凋亡，而这种反应会被据称是PKCδ选择性抑制剂的rottlerin减弱。然而，用佛波酯佛波醇-12-肉豆蔻酸酯-13-乙酸酯（PMA）激活PKCδ未能促进细胞死亡，PKCδ的下调也不能阻止棕榈酸的细胞毒性作用。此外，rottlerin在PKCδ缺失的细胞中作为棕榈酸反应的阻滞剂仍然有效。由于rottlerin除了能抑制PKCδ外，还能抑制其他多种激酶，因此还测试了一系列其他激酶抑制剂。其中，只有假定的钙/钙调蛋白依赖性蛋白激酶II（CaM激酶II）抑制剂KN - 62被发现能抑制棕榈酸诱导的细胞死亡。然而，这种效应并未被一种更具选择性的CaM激酶II假底物抑制剂重现。因此，目前的结果表明棕榈酸在BRIN - BD11细胞中诱导细胞死亡，并提示这可能涉及激活一种对rottlerin（和KN - 62）敏感的激酶。然而，很明显这种反应不需要PKCδ。
