Elevated cytokine messenger RNA levels in the peripheral blood of patients with rheumatoid arthritis suggest different degrees of myeloid cell activation

Abstract

Objective. To determine whether monocytes in rheumatoid arthritis (RA) are activated to produce proinflammatory cytokines in the peripheral circulation before entering the synovium and whether the pattern of cytokines that is expressed correlates with disease activity. Methods. Cytokine messenger RNA (mRNA) levels were assessed in peripheral blood mononuclear cells (PBMC) from 14 RA patients and 14 healthy controls by semiquantitative reverse transcription–polymerase chain reaction technology. The method employed was sufficiently sensitive to assess cytokine mRNA levels in freshly isolated cells without the necessity of in vitro stimulation. Thus, an estimate of the in vivo state of activation could be obtained. Results. Interleukin‐8 (IL‐8) mRNA levels were elevated in all 14 RA patients compared with normal controls, whereas 7 of 14 RA patients had elevated levels of mRNA for IL‐6 or IL‐10. IL‐1B mRNA levels were below the normal range in 3 of 14 patients, within normal limits in 4 of 14, and elevated in 7 of 14. Tumor necrosis factor a mRNA levels were within the normal range in 9 of 14 patients and below normal in 5 of 14. There was a statistically significant difference between the mean IL‐10 (P < 0.05) and IL‐8 (P < 0.001) mRNA.levels in RA patients and normal controls. Of note, the 7 patients with elevated IL‐lβ mRNA levels also expressed the highest levels of IL‐8 mRNA. Whereas a strong correlation between the expression of IL‐lβ and IL‐8 mRNA (P < 0.001) was found, expression of all other mRNA occurred independently of each other. Levels of cyclooxygenase 2 (COX‐2) mRNA were also determined to evaluate the status of myeloid cell activation more completely. COX‐2 mRNA levels were within the normal range in 4 of 11 patients and below normal in 7 of 11, but did not correlate with the expression of any of the cytokine mRNA. Conclusion. Elevated levels of mRNA for selected cytokines that are predominantly produced by monocytes can be found in the PBMC of many RA patients. The data indicate that myeloid precursor cells become activated to produce cytokines before they enter the synovium, a finding which emphasizes the systemic nature of RA.

Effects of tripterygium wilfordii Hook F extracts on induction of cyclooxygenase 2 activity and prostaglandin E2 production

“…Primers specific for the control mRNA for G3PDH were purchased from Clontech Laboratories (Palo Alto, CA). Primers specific for COX-1 and COX-2 and the probes specific for the amplified sequences from G3PDH, COX-1, and COX-2 cDNA were generated as previously described (21). It has been demonstrated that the primers used for COX-1 and COX-2 were specific for the cDNA of the particular cyclooxygenase isoenzyme (20).…”

Systemic Macrophage Activation in Locally-induced Experimental Arthritis

“…Since the systemic signs appearing in acute AIA mostly exceed those observed upon systemic immunization, systemic MPS activation appears to be an integral pathogenetic feature of this local arthritis model, presumably driven by leakage of antigen and pro-inflammatory stimuli from the inflamed joints. This systemic feature of arthritis can clearly be observed also in human RA [27,48,49], and makes systemic counteraction of MPS activation an attractive target for therapeutic intervention [50,51].…”

The dynamics of macrophage lineage populations in inflammatory and autoimmune diseases

“…There are a number of reports describing changes in the properties of both peripheral blood mononuclear cells (31)(32)(33) and purified monocytes (34) in RA, suggestive of some form of activation. Whether these changes are dependent upon signals (for instance, from cytokines emanating from arthritic lesions) or whether the circulating cells are inherently different due to prior exposure to another stimulus, such as a microorganism or an endogenous pathogen-associated molecular pattern, is unknown.…”