Role of arginase in the negative feedback loop of the CpG-ODN-mediated nitric oxide secretion in murine macrophages

LISCOVSKY M,; MALETTO B,; ALIGNANI D,; RANOCCHIA R,; MORÓN G,; PISTORESI M.C .

Río de Janeiro, Brasil

Congreso; 13er Congreso Internacional de Inmunología; 2007

International Union of Immunological Societies

Macrophages respond to CpG secreting cytokines and nitric oxide (NO) that mediate an inflammatory response. The aim of this work was to investigate whether CpG modulate NO production. We focused on arginase, enzime which shares the L-arginine substrate with enzyme iNOS. Bone marrow-derived macrophages (BMM) were cultured with medium, CpG, IFNg or CpG+IFNg for 48h. Arginase activity (AA) was not induce by CpG alone but it was by CpG+IFNg (medium:78±13; CpG:83±7; IFNg:65±10; CpG+IFNg:187±5 mU/mg protein). This effect was correlated with increased expression of arginase II isoform. The use of specific inhibitors revealed that CpG+IFNg-mediated AA depended on p38 and ERK MAPK but it was independent of JNK. Since IL10 has been implied in AA regulation, we dosed IL10 in culture supernants. Contrarely to AA, IL10 dramatically diminished when IFNg was present (medium:272±113;CpG: 583±76;CpG+IFNg:70±30 pg/mL). Upon BMM preincubation with IFNg, washing and subsequent CpG stimulation, AA increased (medium: 56±2; CpG: 183±59 mU/mg protein). However, CpG preincubation and stimulation with IFNg did not exhibit this effect. Then an interesting observation of this study is that AA induced with CpG needs IFNg priming. Finally we investigated the relationship between AA and iNOS. Accumulation of NO in supernatant of BMM with CpG+IFNg peaked at 48h and remained stable while AA increased over 72h. The increasing AA in time might modulate NO secretion. In conclusion, CpG are able to regulate BMM NO production in the presence of IFNg through AA induction.