Department of Internal Medicine III, University of Technology Dresden, Germany.
Am J Hypertens. 2010 Oct;23(10):1061-8. doi: 10.1038/ajh.2010.118. Epub 2010 Jun 17.
Serum aldosterone is a causative factor for various metabolic and cardiovascular disorders. Low-density lipoprotein (LDL) is a major cholesterol source for aldosterone steroidogenesis; however, the effect of oxidative modification of LDL on aldosterone release is not known. We studied the effect of hypochlorite-oxidized LDL (oxLDL) on adrenal aldosterone secretion.
LDL (native LDL (natLDL)) was obtained from healthy volunteers and oxidatively modified in vitro. NCI-H295R cells were stimulated with natLDL and oxLDL, and the aldosterone release was quantified by radioimmunoassay. Molecular changes were studied with western blot analysis and quantitative RT-PCR analysis.
NatLDL and oxLDL caused dose-dependent increase in aldosterone release up to threefold. However, the stimulatory effects of modified LDL on aldosterone secretion decreased with increasing degree of LDL oxidation. 24-h incubations with natLDL, mild- and medium-oxidized LDL sensitized the adrenocortical cells to subsequent angiotensin II (Ang II) stimulations by 2.9-, 2.8-, and 2.5-folds, respectively. Heavily oxidized LDL did not sensitize the cells to Ang II stimulations to a similar extent. At the molecular level, the ERK pathway was activated within a minute by both natLDL and oxLDL; however, oxLDL showed a stronger (2.75-fold at 1 and 15 min) and longer (15 min) activation of ERK than natLDL (twofold).
This study demonstrates the following: (i) both natLDL and hypochlorite-oxidized LDL utilize ERK pathway to mediate aldosterone release; (ii) mildly oxidized LDL sensitizes the adrenocortical cells to further stimulations by Ang II similar to natLDL that may have a role in pathological processes; (iii) extensive LDL oxidation counteracts adrenocortical aldosterone release.
血清醛固酮是各种代谢和心血管疾病的致病因素。低密度脂蛋白（LDL）是醛固酮类固醇生成的主要胆固醇来源；然而，LDL 氧化修饰对醛固酮释放的影响尚不清楚。我们研究了次氯酸氧化 LDL（oxLDL）对肾上腺醛固酮分泌的影响。
从健康志愿者中获取 LDL（天然 LDL（natLDL）），并在体外进行氧化修饰。用 natLDL 和 oxLDL 刺激 NCI-H295R 细胞，并通过放射免疫测定定量测定醛固酮释放。用 Western blot 分析和定量 RT-PCR 分析研究分子变化。
natLDL 和 oxLDL 引起醛固酮释放呈剂量依赖性增加，最高可达三倍。然而，修饰 LDL 对醛固酮分泌的刺激作用随着 LDL 氧化程度的增加而降低。24 小时孵育 natLDL、轻度和中度氧化 LDL 使肾上腺皮质细胞对随后的血管紧张素 II（Ang II）刺激分别敏感 2.9、2.8 和 2.5 倍。高度氧化的 LDL 不能使细胞对 Ang II 刺激产生类似程度的敏感。在分子水平上，ERK 通路在 1 分钟内被 natLDL 和 oxLDL 激活；然而，oxLDL 比 natLDL （1 和 15 分钟时分别为 2.75 倍和 15 分钟时为 2 倍）更强烈（1 和 15 分钟时为 2.75 倍）和更长时间（15 分钟）激活 ERK。
本研究表明：（i）natLDL 和次氯酸氧化 LDL 均利用 ERK 通路介导醛固酮释放；（ii）轻度氧化 LDL 使肾上腺皮质细胞对 Ang II 的进一步刺激敏感，类似于 natLDL，这可能在病理过程中起作用；（iii）广泛的 LDL 氧化会抵消肾上腺皮质醛固酮的释放。
