ABC | Volume 114, Nº2, February 2020

Original Article Stefani et al. DNA damage and heart failure Arq Bras Cardiol. 2020; 114(2):234-242 Table 2 – Mean, diastolic and systolic blood pressure, left ventricle end diastolic pressure, left ventricle systolic pressure and left ventricular maximum/minimum change over time of sham-operated rats and rats with left ventricular dysfunction Variables Sham CHF MBP (mmHg) 93.01 ± 14.70 76.78 ± 5.83* DBP (mmHg) 73.54 ± 16.28 67.54 ± 7.15 SBP (mmHg) 99.75 ± 20.91 85.93 ± 5.51 Heart Rate (bpm) 253.56 ± 70.84 245.19 ± 57.69 LVEDP (mmHg) 5.40 ± 2.26 32.55 ± 5.32* LVSP (mmHg) 104.24 ± 6.03 89.15 ± 3.15* + dP/dt max (mmHg/s) 6,264.33 ± 1,566.47 4,281.63 ± 708.75* - dP/dt max (mmHg/s) 5,209.63 ± 1,274.09 2,823.80 ± 540.65* Values are presented in mean ± SD; n = 6 for all groups. Sham, sham-operated rats; CHF: Chronic heart failure rats; MBP: Mean blood pressure; DBP: diastolic blood pressure; SBP: systolic blood pressure; LVEDP: left ventricular end-diastolic pressure; LVSP: left ventricular systolic pressure; +dP/dt max : Maximal positive derivative of ventricular pressure; -dP/dt max : maximal negative derivative of ventricular pressure. * p < 0.05 compared to the Sham group. Discussion Although there are some investigations using the comet assay in CHF, to the best of our knowledge, this is the first study to report the total extent of DNA damage in different tissues in an experimental model of CHF. The major finding of this investigation is the reproducibility and applicability of SCGE in the MI experimental model. Animals with CHF demonstrated higher extent of DNA damage than the control group in heart, lungs, diaphragm and skeletal muscles. This finding supports the main hypothesis that CHF affects the stability of DNA not locally, but systemically. Since CHF is a complex syndrome, it is essential to investigate the extent of damage that the hypoperfusion may promote. We showed an in vivo model of CHF whose damage was ranging from two- to six-fold higher than in the absence of heart failure. The animals of this study demonstrated traditional alterations observable in the ligation of the left coronary artery model of heart failure in rats. 22,23 Mean LVEDP above 30 mmHg was observed, which characterizes ventricular dysfunction. 14 Also, traditional hemodynamic alterations were observed in animals with CHF, such as lower LVSP, and maximum positive and negative derivatives of ventricular pressure. Morphological parameters also showed meaningful alterations in left and right ventricle hypertrophy, as well as pulmonary congestion. All these parameters (hemodynamic and morphological) characterize the presence of CHF. 12,24,25 The SCGE method performed in alkaline conditions allows the evaluation of global DNA damage. The damage observed in the comets is formed by single and double strand breaks that are unattached from the chromatin, in DNA fragments. 10 The evaluation of 8-OHdG in patients with CHF has been recently proposed. The 8-OHdG is an oxidized purine base, one of the most frequent oxidative products of DNA. 26 Most of the lesions in DNA may be manifested in single and double strand breaks, not only in oxidative by-products. Reactive oxygen species may damage DNA and form oxidative bases, such as 8-OHdG, 5-hydroxyuracil, 2-hydroxyadenine and 4,6-diamino-5-formamidopyridine. Some caveats should be made before comparing results measured by nuclear DNA damage, as in our study, to results obtained in concentrations of oxidized purine base. The DNA damage measured by the comet assay reflects the overall damage, other than the 8-OHdG measurement that cannot assert the same. 27 A recent meta-analysis demonstrated that eight studies evaluated the oxidative DNA damage to the specific DNA lesion of 8-OHdG. All investigations demonstrated higher Table 3 – DNA quantification in different tissues of sham-operated animals and rats with chronic heart failure Sham CHF % Tail DNA Tail Moment Olive Tail Moment % Tail DNA Tail Moment Olive Tail Moment Left Ventricle 7.65 ± 3.35 0.77 ± 0.44 1.37 ± 0.59 33.29 ± 7.70* 10.51 ± 3.31* 7.04 ± 1.71* Lungs 17.86 ± 3.93 6.76 ± 2.59 7.31 ± 2.15 36.20 ± 5.17* 23.30 ± 7.25* 19.10 ± 4.65* Diaphragm 6.86 ± 2.63 1.40 ± 0.93 1.82 ± 0.79 41.23 ± 13.86* 14.06 ± 6.51* 9.82 ± 3.03* Gastrocnemius 7.63 ± 4.66 1.04 ± 0.88 1.43 ± 0.70 28.07 ± 15.53* 8.69 ± 5.14* 6.17 ± 3.53* Soleus 11.54 ± 2.46 1.53 ± 0.96 1.84 ± 0.76 55.79 ± 11.53* 20.90 ± 5.32* 12.83 ± 3.68* Values are presented in mean ± SD; n = 6 for all groups. Sham, sham-operated rats; CHF: Chronic heart failure rats. * = p < 0.01 versus Sham in relation to the variable and its corresponding tissue. 237