Regunathan Soundar, Piletz John E
Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA.
Ann N Y Acad Sci. 2003 Dec;1009:20-9. doi: 10.1196/annals.1304.002.
Agmatine is a novel endogenous guanido amine synthesized from arginine by arginine decarboxylase. Among several biologic effects, the ability of agmatine to protect against ischemic injury and chronic neuropathic pain is particularly interesting. Because inflammation is a common contributor to these conditions, we sought to determine if agmatine acts by decreasing the production of proinflammatory molecules such as nitric oxide and if agmatine synthesis is regulated by inflammatory stimuli. We tested whether agmatine affects astroglial and macrophage (RAW 264.7 cell line) nitric oxide synthase-2 (NOS-2) expression. NOS-2 was induced in these cells by incubation with lipopolysaccharide (LPS) plus three cytokines for astrocytes and LPS alone for RAW 264.7 cells in the presence and absence of varying concentrations of agmatine. NOS-2 activity was assessed after 24 hours by nitrite accumulation in the culture media. Agmatine dose-dependently inhibited nitrite accumulation, and shorter incubation with agmatine (1 and 4 hours) also caused significant reduction. Agmatine decreased the expression of NOS-2 activity and NOS-2 protein as determined by immunoblot analysis. Incubation of astrocytes and RAW 264.7 cells with LPS/cytokines for 2 hours resulted in an increase in arginine decarboxylase (ADC) activity, whereas longer-term incubation (12-17 hours) lowered ADC activity. Agmatine levels in these cells are increased after 6-hour incubation with LPS/cytokines. These results show that agmatine inhibits the production of nitric oxide by decreasing the activity of NOS-2 in macrophages and astroglial cells by decreasing the levels of NOS-2 protein. These findings provide a molecular basis for the neuroprotective and anti-inflammatory actions of agmatine.
胍丁胺是一种由精氨酸脱羧酶从精氨酸合成的新型内源性胍基胺。在几种生物学效应中，胍丁胺预防缺血性损伤和慢性神经性疼痛的能力尤其令人关注。由于炎症是这些病症的常见促成因素，我们试图确定胍丁胺是否通过减少促炎分子如一氧化氮的产生起作用，以及胍丁胺的合成是否受炎症刺激调节。我们测试了胍丁胺是否影响星形胶质细胞和巨噬细胞（RAW 264.7细胞系）中一氧化氮合酶-2（NOS-2）的表达。在存在和不存在不同浓度胍丁胺的情况下，通过与脂多糖（LPS）加三种细胞因子孵育诱导星形胶质细胞中的NOS-2，对RAW 264.7细胞单独用LPS诱导NOS-2。24小时后通过培养基中亚硝酸盐积累评估NOS-2活性。胍丁胺剂量依赖性地抑制亚硝酸盐积累，并且与胍丁胺较短时间孵育（1和4小时）也导致显著降低。通过免疫印迹分析确定，胍丁胺降低了NOS-2活性和NOS-2蛋白的表达。星形胶质细胞和RAW 264.7细胞与LPS/细胞因子孵育2小时导致精氨酸脱羧酶（ADC）活性增加，而长期孵育（12 - 17小时）则降低ADC活性。与LPS/细胞因子孵育6小时后，这些细胞中的胍丁胺水平升高。这些结果表明，胍丁胺通过降低巨噬细胞和星形胶质细胞中NOS-2蛋白水平来降低NOS-2活性，从而抑制一氧化氮的产生。这些发现为胍丁胺的神经保护和抗炎作用提供了分子基础。
