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Altered N-methyl D-aspartate receptor subunit expression causes changes to the circadian clock and cell phenotype in

M L Kalev-Zylinska1, J I Hearn1, J Rong2

  • 1Department of Molecular Medicine and Pathology, School of Medical Sciences, Auckland, New Zealand.

Osteoarthritis and Cartilage
|July 23, 2018
PubMed

Insights

N-methyl-D-aspartate receptors (NMDAR) regulate the chondrocyte circadian clock and phenotype in osteoarthritis. Targeting GluN2B subunits may restore normal clock function and reduce cartilage degradation.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Chronobiology

Background:

  • The circadian clock in chondrocytes is disrupted in osteoarthritis, contributing to cartilage loss.
  • N-methyl-D-aspartate receptors (NMDAR) are known regulators of the hypothalamic clock and are expressed in chondrocytes, with altered subunit expression in osteoarthritis.

Purpose of the Study:

  • To investigate the role of NMDAR in regulating the chondrocyte circadian clock and phenotype.
  • To determine if NMDAR activity influences osteoarthritis-associated changes in chondrocytes.

Main Methods:

  • Chondrocytes from normal and osteoarthritic human cartilage were treated with NMDAR antagonists or transfected with siRNAs targeting GRIN2A/GRIN2B.
  • Chondrocytes were also transfected with GluN2B-expression plasmids.
  • Expression of clock genes and chondrocyte phenotypic markers was analyzed using RT-qPCR.

Main Results:

  • Osteoarthritic chondrocytes exhibited altered PER2 and BMAL1 amplitudes compared to normal chondrocytes.
  • NMDAR inhibition in osteoarthritic chondrocytes normalized clock gene expression and reduced markers of cartilage degradation (MMP13, COL10A1).
  • Osteoarthritic chondrocytes uniquely expressed GluN2B subunits; GluN2B knockdown restored normal clock and phenotypic marker expression, while ectopic GluN2B expression disrupted them.

Conclusions:

  • NMDAR play a significant role in regulating the chondrocyte circadian clock and phenotype.
  • The expression of GluN2B in osteoarthritis may contribute to disease pathology by disrupting the chondrocyte clock.
  • These findings suggest NMDAR may also regulate circadian clocks in other peripheral tissues.
Keywords:
GluN2BNMDA receptorOsteoarthritisPeripheral clock

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