Format

Send to

Choose Destination
Arthritis Res Ther. 2015 Mar 10;17:54. doi: 10.1186/s13075-015-0566-9.

Mitochondrial respiration and redox coupling in articular chondrocytes.

Lane RS1,2, Fu Y3,4, Matsuzaki S5, Kinter M6,7, Humphries KM8,9,10, Griffin TM11,12,13.

Author information

1
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. rachel-lane@ouhsc.edu.
2
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 853, Oklahoma City, OK, 73104, USA. rachel-lane@ouhsc.edu.
3
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. yao-fu@omrf.org.
4
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 853, Oklahoma City, OK, 73104, USA. yao-fu@omrf.org.
5
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. satoshi-matsuzaki@omrf.org.
6
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. michael-kinter@omrf.org.
7
Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC-1303, Oklahoma City, OK, 73104, USA. michael-kinter@omrf.org.
8
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. kenneth-humphries@omrf.org.
9
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 853, Oklahoma City, OK, 73104, USA. kenneth-humphries@omrf.org.
10
Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC-1303, Oklahoma City, OK, 73104, USA. kenneth-humphries@omrf.org.
11
Free Radical Biology and Aging Program, Oklahoma Medical Research Foundation, MS 21, 825 NE 13th Street, Oklahoma City, OK, 73104, USA. tim-griffin@omrf.org.
12
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, 940 Stanton L. Young Blvd., BMSB 853, Oklahoma City, OK, 73104, USA. tim-griffin@omrf.org.
13
Department of Geriatric Medicine, Reynolds Oklahoma Center on Aging, University of Oklahoma Health Sciences Center, 975 NE 10th Street, BRC-1303, Oklahoma City, OK, 73104, USA. tim-griffin@omrf.org.

Abstract

INTRODUCTION:

Chondrocytes rely primarily on glycolysis to meet cellular energy needs, but recent studies implicate impaired mitochondrial function in osteoarthritis (OA) pathogenesis. Our objectives were to investigate the ability of chondrocytes to upregulate mitochondrial respiration when challenged with a nutrient stress and determine the effect on mediators of chondrocyte oxidative homeostasis.

METHODS:

Primary bovine chondrocytes were isolated and cultured in alginate beads. Mitochondrial respiration was stimulated by culturing cells with galactose-supplemented media for a period of 1 or 5 days. Metabolic flexibility was assessed by measuring metabolite and enzymatic biomarkers of glycolytic and mitochondrial metabolism. Oxidative homeostasis was assessed by measuring (1) cellular glutathione content and redox homeostasis, (2) rates of nitric oxide and superoxide production, and (3) the abundance and activity of cellular anti-oxidant proteins, especially the mitochondrial isoform of superoxide dismutase (SOD2). The regulatory role of hypoxia-inducible factor 2α (HIF-2α) in mediating the metabolic and redox responses was evaluated by chemical stabilization with cobalt chloride (CoCl2).

RESULTS:

After 5 days of galactose culture, lactate production and lactate dehydrogenase activity were reduced by 92% (P<0.0001) and 28% (P=0.051), respectively. Conversely, basal oxygen consumption increased 35% (P=0.042) without increasing mitochondrial content. Glutathione redox homeostasis was unaffected by galactose culture. However, the production of nitric oxide and superoxide and the expression and activity of SOD2 were significantly reduced after 5 days in galactose culture. Nuclear protein expression and gene expression of HIF-2α, a transcription factor for SOD2, were significantly downregulated (more than twofold; P<0.05) with galactose culture. CoCl2-mediated stabilization of HIF-2α during the initial galactose response phase attenuated the reduction in SOD2 (P=0.028) and increased cell death (P=0.003).

CONCLUSIONS:

Chondrocyte metabolic flexibility promotes cell survival during a nutrient stress by upregulating mitochondrial respiration and reducing the rate of reactive nitrogen and oxygen species production. These changes are coupled to a substantial reduction in the expression and activity of the mitochondrial anti-oxidant SOD2 and its pro-catabolic transcription factor HIF-2α, suggesting that an improved understanding of physiologic triggers of chondrocyte metabolic flexibility may provide new insight into the etiology of OA.

PMID:
25889867
PMCID:
PMC4384316
DOI:
10.1186/s13075-015-0566-9
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for BioMed Central Icon for PubMed Central
Loading ...
Support Center