Kepka-Lenhart D, Mistry S K, Wu G, Morris S M
Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Am J Physiol Regul Integr Comp Physiol. 2000 Dec;279(6):R2237-42. doi: 10.1152/ajpregu.2000.279.6.R2237.
Because arginase hydrolyzes arginine to produce ornithine and urea, it has the potential to regulate nitric oxide (NO) and polyamine synthesis. We tested whether expression of the cytosolic isoform of arginase (arginase I) was limiting for NO or polyamine production by activated RAW 264.7 macrophage cells. RAW 264.7 cells, stably transfected to overexpress arginase I or beta-galactosidase, were treated with interferon-gamma to induce type 2 NO synthase or with lipopolysaccharide or 8-bromo-cAMP (8-BrcAMP) to induce ornithine decarboxylase. Overexpression of arginase I had no effect on NO synthesis. In contrast, cells overexpressing arginase I produced twice as much putrescine after activation than did cells expressing beta-galactosidase. Cells overexpressing arginase I also produced more spermidine after treatment with 8-BrcAMP than did cells expressing beta-galactosidase. Thus endogenous levels of arginase I are limiting for polyamine synthesis, but not for NO synthesis, by activated macrophage cells. This study also demonstrates that it is possible to alter arginase I levels sufficiently to affect polyamine synthesis without affecting induced NO synthesis.
由于精氨酸酶可将精氨酸水解生成鸟氨酸和尿素，因此它具有调节一氧化氮（NO）和多胺合成的潜力。我们测试了胞质型精氨酸酶（精氨酸酶I）的表达是否限制了活化的RAW 264.7巨噬细胞产生NO或多胺。将稳定转染以过表达精氨酸酶I或β-半乳糖苷酶的RAW 264.7细胞用γ-干扰素处理以诱导2型NO合酶，或用脂多糖或8-溴-cAMP（8-BrcAMP）处理以诱导鸟氨酸脱羧酶。精氨酸酶I的过表达对NO合成没有影响。相反，过表达精氨酸酶I的细胞在活化后产生的腐胺是表达β-半乳糖苷酶的细胞的两倍。用8-BrcAMP处理后，过表达精氨酸酶I的细胞也比表达β-半乳糖苷酶的细胞产生更多的亚精胺。因此，活化的巨噬细胞中精氨酸酶I的内源性水平限制了多胺的合成，但不限制NO的合成。这项研究还表明，有可能充分改变精氨酸酶I的水平，以影响多胺合成而不影响诱导的NO合成。
