Vaddi K, Wei C T
Du Pont Merck Pharmaceutical Company, Wilmington, Delaware, USA.
J Toxicol Environ Health. 1996 Dec 27;49(6):631-45. doi: 10.1080/009841096160673.
The molecular basis of the immunotoxic effect of ammonium metavanadate on signal transduction involved in macrophage activation was studied in resident peritoneal macrophages (PEM) and a murine macrophage-like cell line, J774. A fourfold elevation in cytosolic free calcium levels was observed within 10 s following lipopolysaccharide (LPS) stimulation of the non-vanadate-exposed controls both in vitro and in vivo; the levels returned to prestimulation values within 70 s. Exposure to phorbol ester (PMA) did not result in any appreciable change in cytosolic free calcium levels. Compared to untreated controls, treatment with vanadate caused a significant elevation in basal cytosolic calcium levels. Such elevation was not enhanced further by LPS. LPS stimulation of macrophages also resulted in a significant elevation of membrane-associated protein kinase C (PKC) activity, which was, however, inhibited in a dose-dependent manner by vanadate in both in vitro and in vivo studies. Exposure to PMA also resulted in a significant elevation of membrane-associated PKC activity; vanadate treatment at lower levels did not cause downregulation, indicating that vanadate at these levels interfered with the receptor-mediated events rather than the enzyme directly. Vanadate at higher exposure levels inhibited the activity even in PMA-stimulated macrophages. No significant difference occurred in cytosolic PKC activities in control macrophages; vanadate treatment at lower levels resulted in a significant elevation of cytosolic PKC activities following stimulation with LPS or PMA, indicating that vanadate might be interfering with the translocation process.
研究了偏钒酸铵对巨噬细胞活化相关信号转导的免疫毒性作用的分子基础，实验对象为驻留腹腔巨噬细胞（PEM）和小鼠巨噬细胞样细胞系J774。在体外和体内实验中，未接触钒酸盐的对照组经脂多糖（LPS）刺激后10秒内，胞质游离钙水平升高了四倍；70秒内这些水平恢复到刺激前的值。暴露于佛波酯（PMA）并未导致胞质游离钙水平有任何明显变化。与未处理的对照组相比，钒酸盐处理导致基础胞质钙水平显著升高。LPS并未进一步增强这种升高。巨噬细胞经LPS刺激后，膜相关蛋白激酶C（PKC）活性也显著升高，然而，在体外和体内研究中，钒酸盐均以剂量依赖的方式抑制了该活性。暴露于PMA也导致膜相关PKC活性显著升高；较低水平的钒酸盐处理并未导致下调，这表明这些水平的钒酸盐干扰的是受体介导的事件而非直接作用于该酶。较高暴露水平的钒酸盐甚至抑制了PMA刺激的巨噬细胞中的活性。对照巨噬细胞的胞质PKC活性没有显著差异；较低水平的钒酸盐处理导致LPS或PMA刺激后胞质PKC活性显著升高，这表明钒酸盐可能干扰了转位过程。
