Effect of hypoxia/reoxygenation on the cytokine-induced production of nitric oxide and superoxide anion in cultured osteoarthritic synoviocytes

SummaryObjectiveHypoxia/reoxygenation (H/R) is an important feature in the osteoarthritis (OA) physiopathology. Nitric oxide (NO) is a significant proinflammatory mediator in the inflamed synovium. The purpose of this study was to investigate the effects of H/R on inducible NO synthase (iNOS) activity and expression in OA synoviocytes. In addition we studied the relationship between nitrosative stress and NADPH oxidase (NOX) in such conditions.MethodsHuman cultured synoviocytes from OA patients were treated for 24 h with interleukin 1-β (IL-1β), tumour necrosis factor α (TNF-α) or neither; for the last 6 h, they were submitted to either normoxia or three periods of 1-h of hypoxia followed by 1-h of reoxygenation. NO metabolism (iNOS expression, nitrite and peroxynitrite measurements) was investigated. Furthermore, superoxide anion O2− production, NOX subunit expression and nitrosylation were also assessed.ResultsiNOS expression and nitrite (but not peroxynitrite) production were significantly increased under H/R conditions when compared with to normoxia (P < 0.05). H/R conditions decreased O2− production from ∼0.20 to ∼0.12 nmol min−1 mg proteins−1 (P < 0.05), while NOXs' subunit expression and p47-phox phosphorylation were increased. NOXs and p47-phox were dramatically nitrosylated under H/R conditions (P < 0.05 vs normoxia). Using NOS inhibitors under H/R conditions, p47-phox nitrosylation was prevented and O2− production was restored at normoxic levels (0.21 nmol min−1 mg of proteins−1).ConclusionsOur results provide evidence for an up-regulation of iNOS activity in OA synoviocytes under H/R conditions, associated to a down-regulation of NOX activity through nitrosylation. These findings highlight the importance of radical production to OA pathogenesis, and appraise the metabolic modifications of synovial cells under hypoxia

Lipocalin 2 as a potential systemic biomarker for central serous chorioretinopathy

No systemic biomarker of Central Serous Chorioretinopathy (CSCR) has been identified. Lipocalin 2 (LCN2 or NGAL), alone or complexed with MMP-9 (NGAL/MMP-9), is increased in several retinal disorders. Serum levels of LCN2 and NGAL/MMP-9 were measured in CSCR patients (n = 147) with chronic (n = 76) or acute/recurrent disease (n = 71) and in age- and sex-matched