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Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms
13:40

Live Cell Calcium Imaging Combined with siRNA Mediated Gene Silencing Identifies Ca2+ Leak Channels in the ER Membrane and their Regulatory Mechanisms

Published on: July 7, 2011

Increased intracellular Ca2+ selectively suppresses IL-1-induced NO production by reducing iNOS mRNA stability

Y Geng1, M Lotz

  • 1Sam and Rose Stein Institute for Research on Aging, University of California, San Diego, La Jolla 92093-0663, USA.

The Journal of Cell Biology
|June 1, 1995
PubMed

Insights

Intracellular calcium (Ca2+) inhibits interleukin-1-induced nitric oxide (NO) release and inducible nitric oxide synthase (iNOS) expression in chondrocytes by reducing iNOS mRNA stability. Conversely, elevated Ca2+ enhances cyclooxygenase-2 (COXII) gene and protein expression.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Intracellular calcium (Ca2+) plays a critical role in cellular signaling pathways.
  • Interleukin-1 (IL-1) is a key mediator of inflammation in articular chondrocytes.
  • Inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COXII) are important inflammatory genes in chondrocytes.

Purpose of the Study:

  • To investigate the role of intracellular calcium (Ca2+) in regulating the expression of iNOS and COXII in human articular chondrocytes.
  • To determine the effect of Ca2+ modulation on IL-1-induced NO production and gene expression.

Main Methods:

  • Human articular chondrocytes were treated with calcium ionophores (A23187, ionomycin) and ER Ca2+ ATPase inhibitors (thapsigargin, cyclopiazonic acid) to modulate intracellular Ca2+ levels.
  • Nitric oxide (NO) release was measured.
  • Expression of iNOS and COXII at the mRNA and protein levels was assessed using various techniques.
  • iNOS mRNA stability was analyzed by measuring mRNA half-life.

Main Results:

  • Elevated intracellular Ca2+ inhibited IL-1-induced NO release and iNOS expression at both protein and mRNA levels.
  • Ca2+ modulating drugs reduced iNOS mRNA stability, suggesting a posttranscriptional inhibitory mechanism.
  • In contrast, these Ca2+ modulating drugs enhanced IL-1-induced COXII mRNA and protein expression.

Conclusions:

  • Intracellular calcium (Ca2+) negatively regulates IL-1-induced iNOS expression in human articular chondrocytes, primarily by decreasing iNOS mRNA stability.
  • Conversely, elevated intracellular Ca2+ positively regulates IL-1-induced COXII expression in these cells.
  • These findings highlight the complex and differential roles of intracellular calcium in regulating inflammatory gene expression in chondrocytes.

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