Mitophagy Defect in Fibroblast-like Synoviocytes of Rheumatoid Arthritis Is Improved By Pyruvate Treatment

Jeong Yeon Kim^1,2, ShinEui Kang^3,4, Hyun Jung Yoo^1,5, Ji Soo Park^1,2, Sehui Shon^1,2, Eun Young Lee², Eun Bong Lee⁵ and Yeong Wook Song^1,6, ¹Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea., Seoul, Korea, Republic of (South), ²Division of Rheumatology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea., Seoul, Korea, Republic of (South), ³Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea., seoul, Korea, Republic of (South), ⁴Division of Rheumatology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea., seoul, Korea, Republic of (South), ⁵Division of Rheumatology, Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea, Republic of (South), ⁶Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, and College of Medicine, Seoul National University, Seoul, Korea, Republic of (South)

Meeting: 2017 ACR/ARHP Annual Meeting

Date of first publication: September 18, 2017

Keywords: Fibroblasts, Inflammation, mitochondria and rheumatoid arthritis (RA)

Session Information

Date: Monday, November 6, 2017

Title: Rheumatoid Arthritis – Human Etiology and Pathogenesis Poster II

Session Type: ACR Poster Session B

Session Time: 9:00AM-11:00AM

Background/Purpose:

Fibroblast-like synoviocytes (FLS) in the synovial intimal lining produce pro-inflammatory cytokines resulting in increase of joint inflammation. Recent studies about the cellular metabolism in FLS offered novel approaches to understand the inflammation in rheumatoid arthritis (RA). However, it has been unknown about mitochondrial dysfunction and metabolic change in RA. Mitochondria are very dynamic organelle and dysfunctional mitochondria are removed by mitophagy for cellular homeostasis. In addition, it was reported that mitochondrial dysfunction may be induced by mitophagy defect and that treatment with pyruvate protects fibroblast senescence induced by mitochondrial dysfunction. In this study, we show that RA FLS has mitophagy defect which was improved by treatment with pyruvate.

Methods:

To analyze mitochondrial function in RA FLS, we determined mitochondria membrane potential by TMRM staining and FACS analysis. Mitochondrial respiration and glycolysis were measured using a Seahorse Bioscience Extracellular Flux Analyzer (XF24). Defective mitochondria are degraded by autophagy. We analyzed LC3b and p62 protein levels by Western-blotting. Cells were transfected with GFP-tagged LC3 expression vector. Mitochondria were stained by MitoTracker Deep Red and analyzed by confocal microscopy. Mitophagy was evaluated by transmission electron microscopy (TEM). The pyruvate effect on mitophagy process was analyzed by the change of fluorescence of mitochondria-targeted mKeima (mt-mKeima) using confocal microscopy. Pro-inflammatory cytokines were measured by qRT –PCR and ELISA.

Results:

Mitochondrial membrane potential (MMP), oxygen consumption rate (OCR) and the extracellular acidification rate (ECAR) were significantly increased in RA FLS compared with OA FLS. We also found that the abundance of LC3-b protein and p62 protein in RA FLS and the increase of colocalization of GFP-LC3 puncta with mitochondria in RA FLS. In addition, TEM and mt-mKeima confocal analysis revealed the accumulation of abnormal mitochondria and the dysregulation of mitophagy in RA FLS compared with OA FLS. Interestingly, these mitophagy defect and metabolic change such as increase of OCR, ECAR and MMP in RA FLS recovered by treatment with pyruvate. In addition, pyruvate decreased IL-6 and IL-8 production in RA-FLS.

Conclusion:

Pyruvate improved mitophagy defect and suppressed proinflammatory cytokine production in RA FLS.

Disclosure: J. Y. Kim, None; S. Kang, None; H. J. Yoo, None; J. S. Park, None; S. Shon, None; E. Y. Lee, None; E. B. Lee, None; Y. W. Song, None.

To cite this abstract in AMA style:

Kim JY, Kang S, Yoo HJ, Park JS, Shon S, Lee EY, Lee EB, Song YW. Mitophagy Defect in Fibroblast-like Synoviocytes of Rheumatoid Arthritis Is Improved By Pyruvate Treatment [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/mitophagy-defect-in-fibroblast-like-synoviocytes-of-rheumatoid-arthritis-is-improved-by-pyruvate-treatment/. Accessed .

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