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, MC

Rio de Janeiro. Brasil

Congreso; 13 Congreso Internacional de Inmunología; 2007

Sociedad Internacional de Inmunología

Macrophages respond to CpG secreting cytokines and nitric oxide (NO) thatmediate an inflammatory response. The aim of this work was to investigatewhether CpG modulate NO production. We focused on arginase, enzime whichshares the L-arginine substrate with enzyme iNOS. Bone marrow-derivedmacrophages (BMMØ) were cultured with medium, CpG, IFNg or CpG+IFNg for48h. Arginase activity (AA) was not induce by CpG alone but it was byCpG+IFNg (medium:78±13; CpG:83±7; IFNg:65±10; CpG+IFNg:187±5 mU/mgprotein). This effect was correlated with increased expression of arginase IIisoform. The use of specific inhibitors revealed that CpG+IFNg-mediated AAdepended on p38 and ERK MAPK but it was independent of JNK. Since IL10 has been implied in AA regulation, we dosed IL10 in culturesupernants. Contrarely to AA, IL10 dramatically diminished when IFNg waspresent (medium:272±113;CpG: 583±76;CpG+IFNg:70±30 pg/mL). Upon BMMØ preincubation with IFNg, washing and subsequent CpGstimulation, AA increased (medium: 56±2; CpG: 183±59 mU/mg protein).However, CpG preincubation and stimulation with IFNg did not exhibit thiseffect. Then an interesting observation of this study is that AA induced with CpGneeds IFNg priming. Finally we investigated the relationship between AA andiNOS. Accumulation of NO in supernatant of BMMØ with CpG+IFNg peaked at48h and remained stable while AA increased over 72h. The increasing AA intime might modulate NO secretion. In conclusion, CpG are able to regulateBMMØ NO production in presence of IFNg as result of AA induction.