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Neutrophil gelatinase-associated lipocalin is expressed in osteoarthritis and forms a complex with matrix

Kalpana Gupta1, Meenakshi Shukla, Jack B Cowland

  • 1Case Western Reserve University, and University Hospitals of Cleveland, Cleveland, Ohio 44106, USA.

Arthritis and Rheumatism
|October 2, 2007
PubMed
Abstract

Insights

High molecular weight gelatinase in osteoarthritis synovial fluid is a complex of neutrophil gelatinase-associated lipocalin (NGAL) and matrix metalloproteinase-9 (MMP-9). NGAL stabilizes MMP-9 activity, increasing cartilage matrix degradation in osteoarthritis.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Rheumatology

Background:

  • Matrix metalloproteinase 9 (MMP-9) expression is elevated in osteoarthritis (OA).
  • A high molecular weight (HMW) gelatinase band in OA synovial fluid (SF) remains uncharacterized.
  • Understanding MMP-9's role in OA pathogenesis is crucial.

Purpose of the Study:

  • To characterize the HMW gelatinase activity present in OA SF.
  • To investigate the composition and function of the HMW gelatinase complex.
  • To elucidate the role of neutrophil gelatinase-associated lipocalin (NGAL) in MMP-9 activity in OA.

Main Methods:

  • Gelatin zymography to assess MMP activity in OA SF.
  • Western immunoblotting and immunoprecipitation using specific antibodies for MMP-9 and NGAL.
  • In vitro reconstitution of the NGAL-MMP-9 complex.
  • Dimethylmethylene blue assay to measure cartilage matrix degradation.

Main Results:

  • Zymography and Western blot confirmed the HMW gelatinase is an MMP-9 and NGAL complex.
  • Immunoprecipitation verified that antibodies against NGAL or MMP-9 could isolate the HMW gelatinase.
  • In vitro studies showed NGAL stabilizes MMP-9 activity, preventing its rapid loss.
  • NGAL significantly enhanced MMP-9-mediated cartilage proteoglycan release.

Conclusions:

  • The HMW gelatinase activity in OA SF is a complex of NGAL and MMP-9.
  • NGAL plays a protective role in maintaining MMP-9 activity.
  • This NGAL-MMP-9 interaction is significant for cartilage matrix degradation in OA.

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