Session Type: Abstract Submissions (ACR)
Background/Purpose: Tissues affected with inflammatory arthritis (IA) are subjected to great levels of oxidative stress. Synoviocytes from IA patients present a higher rate of mitochondrial DNA mutagenesis and mitochondrial dysfunction than those from healthy donors. In this work, we studied the role of mitochondrial dysfunction in the inflammatory, tissue-degrading and angiogenic response in human synoviocytes, as those are pivotal processes occurring in IA.
Methods: Mitochondrial dysfunction was induced in normal human synoviocytes with the ATPase inhibitor oligomycin (OLI). Antimycin (AA) and paraquat (PQ) were also used. Mitochondrial polarization was evaluated by TMRM staining; and cytosolic and mitochondrial superoxide production by DHE and mitoSOX staining, respectively. Cyclooxygenase-2 (COX-2), interleukin (IL)-8, metalloproteinase (MMP)-1, MMP-3 and vascular endothelial growth factor (VEGF) mRNA expression were evaluated by RT-PCR. COX-2 protein expression was tested by flow cytometry whereas prostaglandin E2 (PGE2), IL-8, and MMP-1/3 levels were assayed by ELISA. In order to establish the role of ROS production, the general and mitochondria-targeted ROS scavengers N-acetylcysteine (NAC) and mitoTEMPO, respectively, were employed. The involvement of NF-kappaB was evaluated by using the inhibitor BAY. Also p65 translocation to the nucleus and NF-kappaB binding activity were assayed by immunofluorescence and EMSA, respectively. The protecting effect of the natural antioxidant resveratrol (RSV) was tested.
Results: OLI induced mitochondrial depolarization and mitochondrial and cytosolic ROS production. OLI-treated synoviocytes showed an increased inflammatory response (as determined by COX-2, PGE2, and IL-8 expression) as well as a tissue-degrading phenotype confirmed by an increase in MMP-1/3 expression and an angiogenic potential (as evaluated by VEGF mRNA expression and tube formation assay). Besides, in the presence of IL-1β (one of the key pro-inflammatory mediators in IA affected tissues) synoviocytes with mitochondrial dysfunction exhibit a synergic effect regarding the expression of COX-2, PGE2, and IL-8, as well as MMP-1/3 as compared with healthy synoviocytes. When the role of ROS was investigated, we found that NAC and mitoTEMPO significantly reversed the inflammatory response. Involvement of NF-kappaB was confirmed when the inflammatory response was reduced after incubation with BAY; besides, p65 translocation to the nucleus and NF-kappaB binding activity were found in synoviocytes treated with OLI and IL-1β + OLI. AA and PQ showed a similar effect on the inflammatory response. Finally, RSV clearly prevented inflammation, MMP production and the angiogenic response.
Conclusion: The present study confirms the implication of mitochondria in the proinflammatory, tissue-degrading and angiogenic response in human synoviocytes. Also mitochondrial dysfunction sensitizes these cells amplifying the effect of IL-1β. The responses of synoviocytes with dysfunctional mitochondria are mediated at least in part by mitochondrial ROS production and NF-kappaB activation. RSV has proven to be effective in controlling the deleterious effect of mitochondrial dysfunction.
M. N. Valcárcel-Ares,
R. R. Riveiro-Naveira,
F. J. Blanco,
M. J. López-Armada,
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/mitochondrial-dysfunction-induces-an-inflammatory-tissue-degrading-and-angiogenic-response-in-normal-human-synoviocytes/