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Nuclear interaction between ADR-induced p65 and p53 mediates cardiac injury in iNOS (-/-) mice
Marsha P Cole1, Jitbanjong Tangpong2, Terry D Oberley3
1Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America.
Abstract:
Adriamycin (ADR) treatment causes an imbalance in the levels of nitric oxide ((•)NO) and superoxide (O2(•-)) production leading to cardiac injury. Previously we demonstrated that mice lacking inducible nitric oxide synthase (iNOS) have increased oxidative stress and mitochondrial injury. The molecular events leading to increased mitochondrial injury in iNOS deficient mice is unknown. ADR in the absence of iNOS preferentially activates a proapoptotic pathway without a concurrent increase in prosurvival pathways. Treatment with ADR leads to an increase in DNA binding activity of nuclear factor kappa B (NFκB) and p53 in wildtype mice. Following ADR treatment, p53, but not NFκB DNA binding activity, as well as the level of Bax, a p53 target gene, was increased in iNOS (-/-) mice. This apoptotic signaling effect in iNOS (-/-) is alleviated by overexpression of manganese superoxide dismutase (MnSOD). Increases in NFκB and p53 in ADR-treated wildtype mice did not lead to increases in target genes such as MnSOD, bcl-xL, or Bax. Moreover, co-immunoprecipitation analysis revealed that p65, a prominent member of the NFκB family, interacts with p53 in the nucleus. These results suggest that NFκB and p53 may counter act one another's actions in ADR-treated wildtype (WT) mice. Further, these results identify a novel mechanism by which oxidative stress may regulate transcription of proapoptotic genes.
Insights
Adriamycin (ADR) treatment induces cardiac injury by disrupting nitric oxide ((•)NO) and superoxide (O2(•-)) balance. In iNOS deficient mice, ADR activates apoptosis, a process mitigated by manganese superoxide dismutase (MnSOD).
Area of Science:
- Cardiovascular Toxicology
- Molecular Biology
- Biochemistry
Background:
- Adriamycin (ADR) treatment causes cardiac injury through nitric oxide ((•)NO) and superoxide (O2(•-)) imbalance.
- Mice lacking inducible nitric oxide synthase (iNOS) exhibit heightened oxidative stress and mitochondrial damage post-ADR treatment.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying increased mitochondrial injury in iNOS-deficient mice following ADR treatment.
- To investigate the interplay between oxidative stress, apoptosis, and transcription factors in ADR-induced cardiotoxicity.
Main Methods:
- Comparative analysis of wildtype (WT) and iNOS (-/-) mice treated with ADR.
- Assessment of DNA binding activity for nuclear factor kappa B (NFκB) and p53.
- Measurement of proapoptotic (Bax) and prosurvival (MnSOD, bcl-xL) gene expression.
- Co-immunoprecipitation to detect protein-protein interactions.
Main Results:
- ADR treatment in iNOS (-/-) mice preferentially activates a proapoptotic pathway, increasing p53 and Bax levels without activating prosurvival pathways.
- In WT mice, ADR increases NFκB and p53 DNA binding activity, but not their target genes, suggesting a counteracting effect.
- Overexpression of manganese superoxide dismutase (MnSOD) alleviates ADR-induced apoptosis in iNOS (-/-) mice.
- NFκB (p65) interacts with p53 in the nucleus of ADR-treated WT mice.
Conclusions:
- NFκB and p53 may antagonize each other's functions in ADR-treated WT mice.
- Oxidative stress regulates the transcription of proapoptotic genes via a novel mechanism involving NFκB and p53.
- Targeting MnSOD may offer a therapeutic strategy against ADR-induced cardiotoxicity.
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