Nitric oxide induced cell death in human osteoarthritic synoviocytes is mediated by tyrosine kinase activation and hydrogen peroxide and/or superoxide formation.
Bibliographic record
Abstract
OBJECTIVE: To investigate the regulation of osteoarthritis (OA) synovial fibroblast nitric oxide (NO) induced cell death. METHODS: Cultured synovial fibroblasts from human OA synovium were incubated with NO donor sodium nitroprusside (SNP) in the absence or presence of specific inhibitors of different protein kinases, cyclooxygenase-2 (COX-2), caspase-3 and caspase-9, inducible NO synthase, and in the absence or presence of prostaglandin E2 (PGE2). Experiments were also performed using scavengers of NO (carboxy-PXTO), peroxynitrite (uric acid), and superoxide (taxifolin). The level of cell death was measured by MTT and DNA fragmentation. RESULTS: Human OA synovial fibroblasts incubated with SNP decreased cell viability and increased DNA fragmentation in a dose dependent manner. This was associated with increased levels of both COX-2 and PGE2 production. Selective inhibition of COX-2 by NS-398 significantly inhibited SNP induced cell death, even in the presence of exogenously added PGE2. Experiments revealed that SNP treated cells expressed increased levels of active caspase-3 and caspase-9, while Bcl-2 was downregulated. Incubation of these treated cells with inhibitors of caspase-3 (Z-DEVD-FMK) or caspase-9 (Z-LEHD-FMK) protected viability of SNP treated OA synovial fibroblasts, indicating that NO mediated cell death was mainly related to apoptosis. This was also confirmed by measuring the DNA fragmentation (TUNEL method) and the level of active caspase-3 (immunocytochemistry) in these cells. Data also showed that SNP induces the activation of kinases MEK 1/2, p38, and tyrosine kinases. Specific inhibition of tyrosine kinases completely abrogated the SNP induced cell death. In turn, this cell death protection was associated with a marked inhibition of caspase-3 and caspase-9 activities, as well as COX-2/PGE2 production. Moreover, data showed that the NO donor SNP induced cell death was not solely related to the production of NO or peroxynitrite, but to the generation of reactive oxygen species (ROS) such as hydrogen peroxide and/or superoxide. CONCLUSION: Our results provided strong evidence of the role of tyrosine kinase and mitogen activated protein kinase activation, by upregulation of COX-2 expression, in NO induced OA synovial fibroblast death. The generation of ROS such as hydrogen peroxide and superoxide appeared to be a major factor in the death of these cells.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".