Influence of oxygen tension on interleukin 1-induced peroxynitrite formation and matrix turnover in articular cartilage.
OBJECTIVE
Osteoarthritis is characterized by the degradation of articular cartilage. The catabolic activity of chondrocytes is partly regulated by nitric oxide (NO), which with superoxide (O2-) leads to the formation of peroxynitrite (OONO-), a potentially damaging reactive species. Cartilage is avascular and functions at reduced oxygen tension. We investigated whether oxygen tension influences the effects of interleukin 1 (IL-1) on peroxynitrite formation and cartilage matrix metabolism.


METHODS
Porcine cartilage explants were incubated at either 1% O2 or 20% O2 with either 1 ng/ml IL-1alpha, 25 microM MnTE-2-PyP5+ [Mn porphyrin-based catalytic antioxidant, Mn(III) tetrakis(N-ethylpyridinium-2-yl)porphyrin], or 1 ng/ml IL-1 + 25 microM MnTE-2-PyP5+ to decrease peroxynitrite formation. Nitrotyrosine, formed by nitration of tyrosine by peroxynitrite, was measured by immunoblot. Proteoglycan and collagen synthesis and proteoglycan degradation were also determined.


RESULTS
IL-1-induced peroxynitrite formation was decreased in 1% O2 as compared to 20% O2. MnTE-2-PyP5+ inhibited IL-1-induced peroxynitrite formation in either 1% O2 or 20% O2. In 1% O2 (but not in 20% O2), Mn porphyrin significantly inhibited IL-1-induced proteoglycan degradation. IL-1 decreased both proteoglycan and collagen II synthesis in cartilage explants in 1% O2 or 20% O2, but MnTE-2-PyP5+ did not prevent these anti-anabolic effects. MnTE-2-PyP5+ alone caused a significant decrease in collagen synthesis at 20% O2 but not at 1% O2.


CONCLUSIONS
Our findings show that oxygen tension alters IL-1-induced peroxynitrite formation, which can influence proteoglycan degradation. Oxygen tension may influence the effects of reactive oxygen and nitrogen species on matrix homeostasis.
Cernanec
Julie M
JM
Department of Surgery, Division of Orthopaedic Surgery, Duke University Medical Center, Durham, North Carolina 27710, USA.
Weinberg
J Brice
JB
Batinic-Haberle
Ines
I
Guilak
Farshid
F
Fermor
Beverley
B
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002358:Cartilage, Articular / Q000187:drug effects* / Q000378:metabolism; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D003094:Collagen / Q000096:biosynthesis; D004338:Drug Combinations; D005109:Extracellular Matrix / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D053582:Interleukin-1alpha / Q000494:pharmacology*; D008665:Metalloporphyrins / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism; D013552:Swine; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000975:Antioxidants; D004338:Drug Combinations; D053582:Interleukin-1alpha; D008665:Metalloporphyrins; D011509:Proteoglycans; C431023:manganese (III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D003094:Collagen; D010100:Oxygen