Lee H S, Kim B C, Kim Y S, Choi K H, Chung H K
Department of Pathology, Seoul National University College of Medicine, Korea.
Kidney Int. 1996 Nov;50(5):1582-90. doi: 10.1038/ki.1996.474.
Oxidized low-density lipoprotein (Ox-LDL) is present in the lesions of focal segmental glomerulosclerosis (FSGS), but the role of Ox-LDL in the disease process is not clear. Recent studies have shown that LDL stimulates the type IV collagen mRNA expression in cultured mesangial cells. Thus, we examined whether oxidative stress is responsible for the stimulation of LDL-induced collagen gene expression in cultured human mesangial cells (HMCs). When quiescent HMCs were exposed to serum-free media containing LDL for 48 hours, peroxidation of LDL was induced as shown by the increased production of thiobarbituric acid-reactive substances (TBARS). LDL stimulated the alpha 1 (I), alpha 1 (III), and alpha 1 (IV) mRNA expression in a dose-dependent manner. At a concentration of 200 micrograms/ml, LDL enhanced the levels of alpha 1 (I), alpha 1 (III), and alpha 1 (IV) mRNA by 3.7-, 3.8- and 3.2-fold, respectively, over the levels in the control cells. These transcripts were further increased 5.4-, 6.7-, and 5.9-fold, respectively, by the addition of 500 micrograms/ml of LDL. Cu(2+)-catalyzed Ox-LDL at a concentration of 200 micrograms/ml also stimulated the alpha 1 (I), alpha 1 (III), and alpha 1 (IV) mRNA expression 4.4-, 5.9-, and 2.8-fold, respectively, compared with the control cells. The addition of monoclonal antibody (mAb) OL-10, which recognizes the malondialdehyde (MDA)-modified peptide epitope, or vitamin E (50 microM) to cultured HMC exposed to LDL markedly inhibited the stimulation of collagen gene expression. When HMCs were incubated with MDA (200 microM), alpha 1 (I), alpha 1 (III), and alpha 1 (IV) mRNA levels increased by two- to threefold compared to control cells. Immunohistochemical staining utilizing mAb OL-10 demonstrated the presence of MDA-modified proteins in the cytoplasm of HMC exposed to either LDL or MDA. These results suggest that peroxidative products of LDL stimulate collagen gene expression possibly via modification of proteins, which are responsible for the expression of collagen genes in cultured HMCs. Given that, lipid peroxidation of LDL may be implicated in the development of glomerulosclerosis by facilitating excessive mesangial matrix generation.
氧化型低密度脂蛋白（Ox-LDL）存在于局灶节段性肾小球硬化（FSGS）的病变中，但Ox-LDL在疾病过程中的作用尚不清楚。最近的研究表明，低密度脂蛋白（LDL）可刺激培养的系膜细胞中IV型胶原mRNA的表达。因此，我们研究了氧化应激是否是LDL诱导培养的人系膜细胞（HMCs）中胶原基因表达的原因。当静止的HMCs暴露于含LDL的无血清培养基中48小时时，LDL发生过氧化，硫代巴比妥酸反应性物质（TBARS）产量增加即表明了这一点。LDL以剂量依赖的方式刺激α1（I）、α1（III）和α1（IV）mRNA的表达。在浓度为200微克/毫升时，与对照细胞相比，LDL使α1（I）、α1（III）和α1（IV）mRNA水平分别提高了3.7倍、3.8倍和3.2倍。添加500微克/毫升的LDL后，这些转录本水平分别进一步提高了5.4倍、6.7倍和5.9倍。浓度为200微克/毫升的铜（2+）催化的Ox-LDL与对照细胞相比，也分别刺激α1（I）、α1（III）和α1（IV）mRNA表达4.4倍、5.9倍和2.8倍。向暴露于LDL的培养HMC中加入识别丙二醛（MDA）修饰肽表位的单克隆抗体（mAb）OL-10或维生素E（50微摩尔），可显著抑制胶原基因表达的刺激作用。当HMCs与MDA（200微摩尔）孵育时，与对照细胞相比，α1（I）、α1（III）和α1（IV）mRNA水平增加了2至3倍。利用mAb OL-10进行免疫组织化学染色显示，暴露于LDL或MDA的HMC细胞质中存在MDA修饰的蛋白质。这些结果表明，LDL的过氧化产物可能通过修饰蛋白质来刺激胶原基因表达，而这些蛋白质负责培养的HMC中胶原基因的表达。鉴于此，LDL的脂质过氧化可能通过促进系膜基质过度生成而与肾小球硬化的发展有关。
