Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
Age-Related Mitochondrial Dysfunction Sensitizes Human Synoviocytes to Inflammatory Response.
Valcarcel-Ares1, M. Noa, Riveiro-Naveira1, Romina R., Vaamonde-Garcia1, Carlos, Hermida-Carballo1, Laura, Blanco2, Francisco J., Lopez-Armada1, Maria J.
Rheumatoid arthritis (RA) is an age-related disease characterized by a marked inflammatory profile. Mitochondrial dysfunction has been widely related with aging and age-related diseases. Evidences support that RA synoviocytes present an increased mitochondrial genome mutagenesis, leading to mitochondrial alterations. However, its role in the inflammatory response of synoviocytes has not been investigated. The purpose of our study was to investigate the role of age-induced dysfunctional mitochondria in the inflammatory response of normal human cultured synovial cells.
The mitochondrial respiratory chain inhibitor oligomycin (OLI) was used to simulate the aging process in which ROS production is increased and mitochondrial bioenergetics is altered. The cytokines IL-1b and TNFa were employed as they constitute the major pro-inflammatory mediators in the diseased joint. The inflammatory response was measured by cyclooxygenase-2 (COX-2) protein (flow cytometry) and mRNA expression (RT-PCR), and prostaglandin E2 (PGE2) and interleukin-8 (IL-8) levels (ELISA). To identify possible pathways NF-kappaB activation was determined by EMSA and BAY was used as an inhibitor of NF-kappaB; also, N-acetylcysteine (NAC) was used as ROS scavenger. Cells were preincubated with the natural antioxidant resveratrol (RSV) to investigate its effect in our mitochondrial dysfunction model.
We found that oligomycin-induced mitochondrial dysfunction per se significantly stimulated the expression of slight levels of COX-2, PGE2 and IL-8. Oligomicyn-induced mitochondrial dysfunction synergistically intensifies the inflammatory response induced by low concentrations of cytokines. Pre-treatment of synoviocytes with 10mg/ml OLI for 30 minutes significantly increases the IL-1b (0.1ng/ml)-induced COX-2 protein expression (32.5±2.5 OLI+IL-1 vs. 6.5±2.4 IL-1 and 4.5±1.7 OLI, expressed as fluorescence intensity units, n=3, p<0.001) and COX-2 mRNA expression. Interestingly, the percentage of increase is higher with the lower dosage of cytokines (5ng/ml vs. 0.01ng/ml). When PGE2 production was assessed the synergistic effect was also found (277.0±67.6 OLI+IL-1 vs. 15.4±2.6 IL-1 and 97.5±45.6 OLI, expressed as pg/50,000cells, n=3 duplicate, p<0.005). Similar results were obtained when IL-8 production was measured (2887±272.6 OLI+IL-1 vs. 1313±201.2 IL-1 and 62.36±15.39 OLI expressed as pg/50,000cells, n=4 duplicate, p<0.005).
Finally, we demonstrated the involvement of NF-kB and ROS in this process since the inflammatory response was counteracted by the addition of BAY or NAC. NF-kB activation was also shown by EMSA assay. The natural antioxidant resveratrol also proved to significantly reduce inflammatory response.
The present study identifies for the first time mitochondria as organelles implicated in the proinflammatory response in human synoviocytes, since mitochondrial dysfunction sensitizes these cells amplifying the inflammatory response induced by cytokines. This effect is especially relevant in aging, in which a chronic low grade inflammatory state could act as a bridge between normal aging and age-related diseases.
To cite this abstract, please use the following information:
Valcarcel-Ares, M. Noa, Riveiro-Naveira, Romina R., Vaamonde-Garcia, Carlos, Hermida-Carballo, Laura, Blanco, Francisco J., Lopez-Armada, Maria J.; Age-Related Mitochondrial Dysfunction Sensitizes Human Synoviocytes to Inflammatory Response. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :48