Oxidative DNA damage and DNA mismatch repair pathway play an important role in failing human myocardium

Background

Heart failure is approaching epidemic proportions. However, DNA damage in the failing myocardium is not directly addressed yet. 8-Oxo-7,8-dihydrodeoxyguanine (8-oxoG) is a stable marker of DNA damage. The human Mut-Y homologue (hMYH) is a DNA mismatching repair enzyme promoting DNA reconstruction. The current study was designed to investigate whether DNA damage and repair as reflected in the levels of 8-oxoG and hMYH play an important role in the failing myocardium.

Methods

Donor and failing human myocardium were obtained from hearts of patients undergoing cardiac transplantation. DNA damage was determined by the presence of 8-oxoG. The protein level, activity, and expression of hMYH were determined by Western blot, the DNA gel-retardation binding assay and immunohistochemical staining (IHCS). The levels of apoptosis and apoptosis-related genes such as p53, p21-WAF, and caspase-3 were determined by TUNEL assay and IHCS.

Results

The levels of 8-oxoG indicating DNA damage significantly increased in the myocardium of failing hearts compared with donor subjects. On the other hand, the protein level and activity of the DNA repair enzyme, hMYH, was significantly decreased in CHF patients compared to donor subjects. Furthermore, apoptosis and apoptosis-related genes such as p53, p21-WAF, and caspase-3 were markedly increased in CHF myocardium.

Conclusion

Ongoing DNA damage is insufficiently repaired in the myocardium of failing hearts. This appears to be a major pathway responsible for myocardial failure in humans.