Rho Mun-Chual, Ah Lee Kyeong, Mi Kim Sun, Sik Lee Chang, Jeong Jang Min, Kook Kim Young, Sun Lee Hyun, Hyun Choi Yung, Yong Rhim Byung, Kim Koanhoi
Natural Medicine Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejon, Republic of Korea.
Toxicol Appl Pharmacol. 2007 May 1;220(3):311-9. doi: 10.1016/j.taap.2007.02.008. Epub 2007 Feb 24.
Saturated free fatty acids (FFAs), including palmitate, can activate the intrinsic death pathway in cells. However, the relationship between FFAs and receptor-mediated death pathway is still unknown. In this study, we have investigated whether FFAs are able to trigger receptor-mediated death. In addition, to clarify the mechanisms responsible for the activation, we examined the biochemical changes in dying vascular smooth muscle cell (VSMC) and the effects of various molecules to the receptor-mediated VSMC death. Tumor necrosis factor (TNF)-alpha-mediated VSMC death occurred in the presence of sub-cytotoxic concentration of palmitate as determined by assessing viability and DNA degradation, while the cytokine did not influence VSMC viability in the presence of oleate. The VSMC death was inhibited by the gene transfer of a dominant-negative Fas-associated death domain-containing protein and the baculovirus p35, but not by the bcl-xL or the c-Jun N-terminal kinase (JNK) binding domain of JNK-interacting protein-1, in tests utilizing recombinant adenoviruses. The VSMC death was also inhibited by a neutralizing anti-TNF receptor 1 antibody, the caspase inhibitor z-VAD, and the cathepsin B inhibitor CA074, a finding indicative of the role of both caspases and cathepsin B in this process. Consistent with this finding, caspase-3 activation and an increase in cytosolic cathepsin B activity were detected in the dying VSMC. Palmitate inhibited an increase of TNF-alpha-mediated nuclear factor kappa B (NF-kappaB) activity, the survival pathway activated by the cytokine, by hindering the translocation of the NF-kappaB subunit of p65 from the cytosol into the nucleus. The gene transfer of inhibitor of NF-kappaB predisposed VSMC to palmitate-induced cell death. To the best of our knowledge, this study is the first report to demonstrate the activation of TNF-alpha-mediated cell death in the presence of palmitate. The current study proposes that FFAs would take part in deleterious vascular consequences of such patients with elevated levels of FFAs as diabetics and obese individuals via the triggering of receptor-mediated death pathways of VSMC.
饱和游离脂肪酸（FFA），包括棕榈酸，可激活细胞内的固有死亡途径。然而，FFA与受体介导的死亡途径之间的关系仍不清楚。在本研究中，我们调查了FFA是否能够触发受体介导的死亡。此外，为了阐明负责激活的机制，我们检查了垂死血管平滑肌细胞（VSMC）中的生化变化以及各种分子对受体介导的VSMC死亡的影响。通过评估活力和DNA降解确定，在亚细胞毒性浓度的棕榈酸存在下发生肿瘤坏死因子（TNF）-α介导的VSMC死亡，而在油酸存在下该细胞因子不影响VSMC活力。在利用重组腺病毒的试验中，VSMC死亡被显性阴性含Fas相关死亡结构域蛋白和杆状病毒p35的基因转移所抑制，但不被bcl-xL或JNK相互作用蛋白-1的JNK结合结构域所抑制。VSMC死亡也被中和性抗TNF受体1抗体、半胱天冬酶抑制剂z-VAD和组织蛋白酶B抑制剂CA074所抑制，这一发现表明半胱天冬酶和组织蛋白酶B在此过程中均起作用。与此发现一致，在垂死的VSMC中检测到半胱天冬酶-3激活和胞质组织蛋白酶B活性增加。棕榈酸通过阻碍p65的NF-κB亚基从胞质溶胶转运到细胞核，抑制TNF-α介导的核因子κB（NF-κB）活性增加，即细胞因子激活的存活途径。NF-κB抑制剂的基因转移使VSMC易受棕榈酸诱导的细胞死亡。据我们所知，本研究是首次报道在棕榈酸存在下TNF-α介导的细胞死亡被激活。当前研究提出，FFA可能通过触发VSMC的受体介导的死亡途径，参与糖尿病和肥胖个体等FFA水平升高患者的有害血管后果。
