Nduction Of Acute And Chronic Articular Synovitis In Mice And Mechanism Underlying Anti-inflammation Of Artemisinin And Rapamycin

PurposeDue to unknown etiologica] cues, Rheumatoid arthritis (RA) is currently neither effectively prevented nor easily healed, thereby lunching the most critical challenge to the modernized medical science. Considering RA frequently occurring among elderly with compromised immunity, we suggest a proposition that RA may be originated from chronic pathogen infection. Based on our experimental results that bacterial infection in the gastrointestinal tract can trigger nitric oxide (NO) burst, we further envisage a scientific hypothesis that NO-driven hypoxia initiates synovial angiogenesis and hyperplasia.Material and MethodsTo verify such hypothesis practically, we conduct live bacterial feeding, collagen Il-complete Freund’s adjuvant (CII-CFA) inoculation, and CFA injection to allow the establishment of a bacteria-induced arthritis (BIA) model, a CII-CFA-or CFA-induced arthritis (CIA) model, and a BIA-CIA model in mice. During which a novel technique of rapid modeling of RA in mice has been invented by intra-articular injection of CII-CFA or CFA alone. Furthermore, comparison among different models on the inflammatory morphology, the histopathology, the immunohistochemistry, the expression profiles of pro-inflammatory cytokines, and hypoxia signaling pathways indicate. The efficacies combating the experimental arthritis of mice through anti-infection by cefotaxime and anti-inflammation and inhibition of NO production by artesunate and/or rapamycin has been evaluated using BIA, CIA, and BIA-CIA models. ResultBacterial infection as well as CII-CFA/CFA immunization can provoke NO burst by upregulation of pro-inflammatory cytokines. The dramatic elevation of serum NO level in a manner of CIA> BIA-CIA> BIA lead to metabolic hypoxia consequences, including significant decline of the saturated percentage of blood oxygen (SpO2) and simultaneous increase of the serum lactic acid (LA) content, hence initiating the overexpression of hypoxia-inducible factor1alpha (HIF-1α) and vascular epithelial growth factor (VEGF) genes in the synovium, and eventually renders tumor-like hyperplasia of the articular synovial tissue. This study has elucidated for the first time a molecular pathological mechanism underlying that gastrointestinal bacterial infection can elicit inflammatory alterations of the distal articulates through stimulating a systemic immune response and evoking inducible NO synthesis, and has addressed the pivotal role of high-level NO in RA pathogcnosis. This investigation has also revealed that articular injection of mice with the NO donor compound sodium nitroprusside (SNP) induces the incidence of acute synovitis symptoms (erythema and edema of paws) within hours, accompanying with the tremendous decrease of SpO2, thus demonstrating that NO i s an important initiator leading to RA. Consequently, downregulation of pro-inflammatory cytokines (IFNγ、TNFα、IL-1β), decline of serum NO and LA levels, and normalization of SpO2occur in the treatment group compared with the control group. Synchronous drug administration with modeling can effectively block the onset of synovitis, whereas drug administration after modeling shows no reversion of existed synovitis, but represses the aggravation of synovitis.ConclusionsOur studies have validated the accessibility of RA interventions via anti-arthritis drugs with such roles of anti-infection, anti-inflammation, and inhibition of NO production, which should pave a path towards clinic trials of those drugs and drug combinations for human RA treatment in the future.