Increased expression of blood mononuclear cell nitric oxide synthase type 2 in rheumatoid arthritis patients.

Abstract

SummaryNitric oxide (NO) is an important inflammatory mediator in nonhuman animal models of rheumatoid arthritis (RA). The purpose of the present study was to determine whether blood mononuclear cells from patients with active RA (as compared to control subjects) have higher levels of NO synthase type 2 (NOS2) and produce more NO in vitro. Leukocytes from 25 RA patients and 20 normal subjects were examined. Arthritis activity was assessed by tender and swollen joint counts, duration of morning stiffness, patient assessment of pain, physician and patient global assessment of disease activity, the modified Stanford Health Assessment Questionnaire, and by blood levels of acute phase reactants. Blood mononuclear cell NOS enzyme activity/antigen content and nitrite/nitrate formation in vitro were measured. Blood mononuclear cells from RA patients had increased NOS activity and increased NOS2 antigen content as compared to those from normal subjects, and responded to interferon-'y with increased NOS expression and nitrite/nitrate production in vitro. NOS activity of freshly isolated blood mononuclear cells correlated significantly with disease activity, as assessed by tender and swollen joint counts. Our results demonstrate that patients with RA have systemic activation for NOS2 expression, and that the degree of activation correlates with disease activity. Increased NOS2 expression and NO generation may be important in the pathogenesis of RA.R heumatoid arthritis (RA) is a chronic systemic disease of unknown etiology that is characterized by joint inflammation and progressive loss of articular cartilage and subchondral bone (1). Prominent pathologic features of joint inflammation are synovial proliferation and mononuclear cell infiltration, which are believed to result from dysregulated production of cytokines, growth factors, cell adhesion molecules, and nonprotein mediators, such as arachidonic acid metabolites and reactive oxygen species (2-4).Nitric oxide (NO) may be a critical mediator in this inflammatory cascade (5, 6). NO is generated endogenously from L-arginine by oxidation to L-citrulline and NO. This reaction is catalyzed by a group of three related NO synthase (NOS) enzymes that are encoded by separate genes (neural NOS [NOS1], endothelial NOS [NOS3], and inducible NOS or NOS type 2 [NOS2]). Increased NOS2 expression and NO production have been noted in induced and spontaneous nonhuman animal models of arthritis, and inhibitors of NOS can reduce arthritis in these conditions (6-12). Moreover, serum and synovial fluid from humans with inflammatory arthritides have increased levels of NO catabolites (13-15). Also, synovial tissue from humans with inflammatory arthritis express NOS2 mRNA and protein, and generate NO in vitro (16).The purpose of the present study was to determine whether blood mononuclear cells from patients with active RA have enhanced expression of NOS2 and enhanced capability to produce NO in vitro. We report results of work that couples detailed clinical and laboratory rheumatological st...

Genetic determinants of rheumatoid arthritis: the inducible nitric oxide synthase (NOS2) gene promoter polymorphism

“…2,3 Studies in experimental animal models of arthritis have suggested that excessive levels of NO can promote tissue injury and contribute to progression of the disease. 3 Likewise, it has been shown that peripheral blood mononuclear cells (PBMC) from RA patients, have increased NOS2 expression and enhanced formation of NO that correlates with disease activity 4 and similarly, NO has been shown as a key mediator of apoptosis within the RA joints 5 as well as an important regulator of the Th1/Th2 balance in autoinmune diseases. 6 The final piece of evidence comes from the finding that administration of NOS2 inhibitors has provided beneficial effects on animal models of RA.…”

“…9 Tandem repeat variations within the promoter region may affect NOS2 transcription explaining the differences observed in NOS2 expression and NO formation between RA patients and control subjects. 4 With regard to this, variation in the number of CCTTT repeats has been shown to be functionally important in the regulation of NOS2 transcription. 10 The purpose of the present study was to address the possible contribution of the described polymorphism located within the NOS2 promoter region to the susceptibility and/or severity of RA.…”

The Anti-Inflammatory Effects of Persicaria thunbergii Extracts on Lipopolysaccharide-Stimulated RAW264.7 Cells

“…NO, as generated in activated macrophages by iNOS, is an important event in host defenses and it modulates the synthesis of prostaglandins, tormboxans and other inflammatory molecules [17]. Despite the beneficial roles of NO in host defense mechanism against tumor cells, viral replication and other factors, and over expression of NO can be harmful to the host, leading to rheumatoid arthritis [22], experimental allergic encephalomyelitis [4] and allograft rejection [27]. Thus, selective inhibition of iNOS can be beneficial to control the production of NO.…”

Mutations in the extracellular loop of α-rENaC alter sensitivity to amiloride and reactive species

“…In response to various inflammatory stimuli, lung endothelial, alveolar, and airway epithelial cells, as well as activated alveolar macrophages, produce both NO and O 2 Ϫ ⅐ (9, 13). Recent studies implicated NO and ONOO Ϫ in the pathogenesis of many diseases, such as septic shock, arthritis, acute lung injury, and atherosclerosis (19,28,30,33). Reactive oxygen-nitrogen intermediates (RONS) have also been demonstrated to have inhibitory effects on Na ϩ transport across epithelia (1,11,15,20).…”