Calmodulin mediates DNA repair pathways involving H2AX in response to low-dose radiation exposure of RAW 264.7 macrophages

Heather Smallwood, Daniel Lopez-Ferrer, P. Elis Eberlein, David J. Watson, Thomas C. Squier

Research output: Contribution to journalArticle

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Abstract

Understanding the molecular mechanisms that modulate macrophage radioresistance is necessary for the development of effective radiation therapies, as tumor-associated macrophages promote both angiogenesis and matrix remodeling that, in turn, enhance tumor metastasis. In this respect, we have identified a dose-dependent increase in the abundance (i.e., expression level) of the calcium regulatory protein calmodulin (CaM) in RAW 264.7 macrophages upon irradiation. At low doses of irradiation there are minimal changes in the abundance of other cellular proteins detected using mass spectrometry, indicating that increases in CaM levels are part of a specific radiation-dependent cellular response. CaM overexpression results in increased macrophage survival following radiation exposure, acting to diminish the sensitivity to low-dose radiation exposures. Following macrophage irradiation, increases in CaM abundance also result in an increase in the number of phosphorylated histone H2AX foci, associated with DNA repair, with no change in the extent of double-stranded DNA damage. In comparison, when nuclear factor κB (NFκB)-dependent pathways are inhibited, through the expression of a dominantnegative IκB construct, there is no significant increase in phosphorylated histone H2AX foci upon irradiation. These results indicate that the molecular basis for the up-regulation of histone H2AX-mediated DNA repair pathways is not the result of nonspecific NFκB-dependent pathways or a specific threshold of DNA damage. Rather, increases in CaM abundance act to minimize the low-dose hypersensitivity to radiation by enhancing macrophage radioresistance through processes that include the up-regulation of DNA repair pathways involving histone H2AX phosphorylation.

Original languageEnglish (US)
Pages (from-to)460-470
Number of pages11
JournalChemical Research in Toxicology
Volume22
Issue number3
DOIs
StatePublished - Mar 16 2009

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Macrophages
Calmodulin
DNA Repair
Dosimetry
Repair
Histones
DNA
Irradiation
Radiation
DNA Damage
Tumors
Up-Regulation
Phosphorylation
Radiotherapy
Mass spectrometry
Radiation Exposure
Mass Spectrometry
Neoplasms
Hypersensitivity
Proteins

All Science Journal Classification (ASJC) codes

  • Toxicology

Cite this

Calmodulin mediates DNA repair pathways involving H2AX in response to low-dose radiation exposure of RAW 264.7 macrophages. / Smallwood, Heather; Lopez-Ferrer, Daniel; Eberlein, P. Elis; Watson, David J.; Squier, Thomas C.

In: Chemical Research in Toxicology, Vol. 22, No. 3, 16.03.2009, p. 460-470.

Research output: Contribution to journalArticle

Smallwood, Heather ; Lopez-Ferrer, Daniel ; Eberlein, P. Elis ; Watson, David J. ; Squier, Thomas C. / Calmodulin mediates DNA repair pathways involving H2AX in response to low-dose radiation exposure of RAW 264.7 macrophages. In: Chemical Research in Toxicology. 2009 ; Vol. 22, No. 3. pp. 460-470.
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