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Inducible NOS-induced chloride intracellular channel 4 (CLIC4) nuclear translocation regulates macrophage

Mariam Malik1, Kasey Jividen, V C Padmakumar

  • 1Laboratory of Cancer Biology and Genetics and Laboratory of Molecular Immunoregulation, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA.

Proceedings of the National Academy of Sciences of the United States of America
|April 5, 2012
PubMed

Insights

Nuclear translocation of CLIC4 in macrophages is regulated by inducible nitric oxide synthase (iNOS). This process is crucial for the macrophage deactivation program, influencing inflammatory responses and phagocytosis.

Area of Science:

  • Cell Biology
  • Immunology
  • Molecular Biology

Background:

  • Cytosolic CLIC4 (Chloride Intracellular Channel 4) undergoes nuclear translocation, which is vital for its proapoptotic and prodifferentiation roles.
  • Inflammatory responses in macrophages involve complex signaling pathways.

Purpose of the Study:

  • To investigate the role of inducible nitric oxide synthase (iNOS) in regulating CLIC4 nuclear translocation and its impact on macrophage inflammatory status.
  • To elucidate the function of iNOS-induced nuclear CLIC4 in the macrophage deactivation program.

Main Methods:

  • Utilized chemical inhibition and genetic ablation of iNOS in peritoneal macrophages.
  • Assessed CLIC4 S-nitrosylation and nuclear translocation.
  • Measured mRNA levels of inflammatory cytokines (IL-1β, CXCL1, TNFα) in wild-type, knockout, and inhibited macrophages.
  • Investigated the effect of nuclear-targeted CLIC4 overexpression.
  • Examined macrophage phagocytosis in CLIC4 knockout mice stimulated with LPS.

Main Results:

  • CLIC4 is induced and S-nitrosylated concurrently with iNOS in proinflammatory macrophages.
  • Inhibition or genetic deletion of iNOS abrogates CLIC4 S-nitrosylation and nuclear translocation.
  • iNOS-induced nuclear CLIC4 is associated with the transition from pro- to anti-inflammatory states in macrophages.
  • Elevated IL-1β and CXCL1 mRNA persist in CLIC4 and iNOS knockout macrophages, while TNFα is elevated only in iNOS knockout macrophages.
  • Overexpression of nuclear CLIC4 reduces IL-1β levels in stimulated macrophages.
  • CLIC4-deficient mice exhibit reduced LPS-stimulated macrophage phagocytosis.

Conclusions:

  • iNOS-induced nuclear translocation of CLIC4 is a critical component of the macrophage deactivation program.
  • Nuclear CLIC4 plays a role in modulating inflammatory cytokine production and maintaining macrophage homeostasis.
  • The iNOS-CLIC4 axis is essential for regulating macrophage inflammatory responses and phagocytic activity.

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