RhoA/ROCK downregulates FPR2-mediated NADPH oxidase activation in mouse bone marrow granulocytes.

Polymorphonuclear neutrophils (PMNs) express the high and low affinity receptors to formylated peptides (mFPR1 and mFPR2 in mice, accordingly). RhoA/ROCK (Rho activated kinase) pathway is crucial for cell motility and oxidase activity regulated via FPRs. There are contradictory data on RhoA-mediated regulation of NADPH oxidase activity in phagocytes. We have shown divergent Rho GTPases signaling via mFPR1 and mFPR2 to NADPH oxidase in PMNs from inflammatory site. The present study was aimed to find out the role of RhoA/ROCK in the respiratory burst activated via mFPR1 and mFPR2 in the bone marrow PMNs. Different kinetics of RhoA activation were detected with 0.1µM fMLF and 1µM WKYMVM operating via mFPR1 and mFPR2, accordingly. RhoA was translocated in fMLF-activated cells towards the cell center and juxtamembrane space versus uniform allocation in the resting cells. Specific inhibition of RhoA by CT04, Rho inhibitor I, weakly depressed the respiratory burst induced via mFPR1, but significantly increased the one induced via mFPR2. Inhibition of ROCK, the main effector of RhoA, by Y27632 led to the same effect on the respiratory burst. Regulation of mFPR2-induced respiratory response by ROCK was impossible under the cytoskeleton disruption by cytochalasin D, whereas it persisted in the case of mFPR1 activation. Thus we suggest RhoA to be one of the regulatory and signal transduction components in the respiratory burst through FPRs in the mouse bone marrow PMNs. Both mFPR1 and mFPR2 binding with a ligand trigger the activation of RhoA. FPR1 signaling through RhoA/ROCK increases NADPH-oxidase activity. But in FPR2 action RhoA/ROCK together with cytoskeleton-linked systems down-regulates NADPH-oxidase. This mechanism could restrain the reactive oxygen species dependent damage of own tissues during the chemotaxis of PMNs and in the resting cells.

Mononuclear Phagocytes in Rheumatoid Arthritis Patients and their Relatives - Family Similarity.

UNLABELLED: The aim of this work was to study the peripheral blood monocyte functions in patients with advanced RA and their predisposed to RA relatives in comparison with those in women, not hereditary tainted with autoimmune diseases (donors). In groups comprising 24 RA patients, 24 relatives, and 24 donors the following monocyte functions were assessed: engulfment and digestion (radioisotope method); release of lysosomal glucuronidase in response to opsonized zymosan (fluorescent method); reactive oxygen species (ROS) generation (chemiluminescence), and serum levels of proinflammatory cytokines (ELISA). The monocyte specific feature in patients and their relatives is chiefly extracellular digestion due to the delayed engulfment. The digestive activity, probably inhibited in relatives, is increased in advanced RA. ROS generation by the cells and serum levels of TNF-alpha and IL-1-beta are abundant both in the patients and their relatives. High levels of pro-inflammatory cytokines, presumably, of monocyte origin, and increased levels of stimulated ROS generation may be due to the priming and prolonged activation of monocytes in relatives. CONCLUSION: We show for the first time that the functioning of circulating mononuclear phagocytes in the assumed to be healthy predisposed to RA individuals differs from that in the healthy people not hereditary tainted with autoimmune diseases and in general resembles the functioning of the cells in the patients with advanced RA.