Regulation of autophagy in human and murine cartilage

Hypoxia-inducible factor 2 suppresses chondrocyte autophagy

Jolene Bohensky, Shawn P. Terkhorn, Theresa A. Freeman, Christopher S. Adams, Joseph A. Garcia, Irving M. Shapiro, Vickram Srinivas

Research output: Contribution to journalArticle

102 Citations (Scopus)

Abstract

Objective. We have previously demonstrated that the transcription factor hypoxia-inducible factor 1 (HIF-1) promotes the onset of autophagy in chondrocytes. The overall goal of this study was to test the hypothesis that another HIF family transcription factor, HIF-2, modulates the induction of autophagy by chondrocytes. Methods. Expression of HIF-1, HIF-2, and light chain 3 (LC3) in human and murine articular cartilage was visualized by immunohistochemistry. Suppression of HIF-2 was achieved using small interfering RNA technology. Assessments of autophagic flux and lysosomal activity, as well as ultrastructural analysis, were performed in chondrocytes in cell culture. Results. HIF-2 was expressed abundantly by cells in human and murine articular cartilage and in the cartilage of mineralizing vertebrae from neonatal mice. Protein levels were reduced in articular cartilage from older mice, in end-plate cartilage from mice, and in chondrocytes from human osteoarthritic (OA) cartilage. HIF-2 was robustly expressed in the prehypertrophic cells of mouse growth cartilage. When HIF-2α was silenced, the generation of reactive oxygen species was found to be elevated, with a concomitant decrease in catalase and superoxide dismutase activity. Suppression of HIF-2 was associated with decreased Akt-1 and mammalian target of rapamycin activities, reduced Bcl-xL expression, and a robust autophagic response, even under nutrient-replete conditions. In these silenced chondrocytes, HIF-1 expression was elevated. Decreased HIF-2 expression was associated with autophagy in OA tissues and aging cartilage samples. The autophagic response of chondrocytes in HIF-2α-knockout mouse growth plate showed an elevated autophagic response throughout the plate. Conclusion. Based on these observations, we conclude that HIF-2 is a potent regulator of autophagy in maturing chondrocytes. Our data suggest that this protein acts as a brake on the autophagy-accelerator function of HIF-1.

Original languageEnglish (US)
Pages (from-to)1406-1415
Number of pages10
JournalArthritis and Rheumatism
Volume60
Issue number5
DOIs
StatePublished - May 2009

Fingerprint

Autophagy
Chondrocytes
Cartilage
Hypoxia-Inducible Factor 1
Articular Cartilage
Transcription Factors
Growth Plate
Sirolimus
endothelial PAS domain-containing protein 1
Knockout Mice
Catalase
Small Interfering RNA
Superoxide Dismutase
Reactive Oxygen Species
Proteins
Spine
Cell Culture Techniques
Immunohistochemistry
Technology
Food

ASJC Scopus subject areas

  • Immunology
  • Immunology and Allergy
  • Rheumatology
  • Pharmacology (medical)

Cite this

Regulation of autophagy in human and murine cartilage : Hypoxia-inducible factor 2 suppresses chondrocyte autophagy. / Bohensky, Jolene; Terkhorn, Shawn P.; Freeman, Theresa A.; Adams, Christopher S.; Garcia, Joseph A.; Shapiro, Irving M.; Srinivas, Vickram.

In: Arthritis and Rheumatism, Vol. 60, No. 5, 05.2009, p. 1406-1415.

Research output: Contribution to journalArticle

Bohensky, Jolene ; Terkhorn, Shawn P. ; Freeman, Theresa A. ; Adams, Christopher S. ; Garcia, Joseph A. ; Shapiro, Irving M. ; Srinivas, Vickram. / Regulation of autophagy in human and murine cartilage : Hypoxia-inducible factor 2 suppresses chondrocyte autophagy. In: Arthritis and Rheumatism. 2009 ; Vol. 60, No. 5. pp. 1406-1415.
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