The time course of the model. We also found that DRG
The time course of the model. We also found that DRG TNFR2 expression occurs PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28914615 exclusively on non-neuronal cells of the macrophage onocyte lineage, with cell numbers increasing in a TNF-dependent fashion during CFA arthritis. And, finally, we found a strong correlation between numbers of macrophage onocyte cells and development of mechanical hyperalgesia in CFA arthritis. CFA-induced arthritis has been used extensively in studies of PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/25636517 behavioural pain responses [29,30]. Three hours after induction of inflammation, TNF is significantly up-regulated in local tissues, with the rise being maintained for a minimum of 5 daysRAvailable online http://arthritis-research.com/content/7/4/RFigureMonitoring expression of TNFR2 with anti-TNFR2 single-chain variable fragment (ScFv). (a) Immunoprecipitation of His-tagged tumour necrosis fac(ScFv) tor types 1 and 2 (TNFR1 and TNFR2) with anti-His antibody (left panel), and anti-TNFR2 single-chain variable fragment (ScFv) (right panel). The ScFv precipitated TNFR2, at 75 KDa, but not TNFR1, at 55 KDa, while the anti-His antibody precipitated both receptors, indicating specificity of the ScFv. Double immunohistochemistry against TNFR2-transfected 293T cells with anti-His antibody (b), and ScFv plus anti-myc-CY-3 (c) indicates that the selected ScFv specifically binds toTNFR2. (d) Immunohistochemistry with anti-TNFR2 ScFv in the dorsal root ganglion 7 days after inflammation ipsilateral to injection. TNFR2 colocalisation was observed with the macrophage marker, ED1 (e) but not with glial fibrillary acidic protein (GFAP) (f), indicating expression of TNFR2 by macrophages following inflammation.observation that neuronal expression of neuronal TNFR1 increased with time confirms and extends previous observations made in neuropathic models [15,13]. It also accords with the time-dependent effects of etanercept, which was effective at reducing thermal hyperalgesia at 7 days but not at earlier time points of the experimental model, when TNFR1 expression was less apparent. This evolving pattern mirrors that observed after spinal ligation, which is associated with increasing sensitivity of both injured and noninjured neurons to TNF [34]. In contrast to TNFR1, we found no evidence for neuronal expression of TNFR2. Previously, TNFR2 has variously been reported either as being expressed on neuronal cells [11,12] or as not being expressed [13]. In our study, we used a highly specific antibody to TNFR2 protein, and although low-gradeneuronal TNFR2 expression may have been below the detection threshold for the immunocytochemical ZM241385 biological activity technique used, it seems unlikely that functionally important expression was present. TNFR2 was, however, shown to be expressed by non-neuronal cells of macrophage onocyte lineage. The expression of TNFR2 increased significantly during the time course of CFA arthritis as a result of increased numbers of ED1-positive cells in the DRG following inflammation. To our knowledge, macrophage invasion of the DRG has previously been reported only in association with nerve injury [28]. In neuropathic models, ATF-3, a member of the ATF/CREB family, is up-regulated in damaged neurons [35]. Although its role after nerve damage is not known, it is regarded as a unique neurochemical marker of nerve injury. Little or no ATF-3 DRG expression wasRArthritis Research TherapyVol 7 NoInglis et al.FigurePrearthritic treatment with etanercept reduces postarthritic macrophage accumulation in the dorsal root ganglion (DRG.