Prolonged administration of a dithiol antioxidant protects against ventricular remodeling due to ischemia-reperfusion in mice

Abstract

The prolonged production of reactive oxygen species due to ischemia-reperfusion (I/R) is a potential cause of the pathological remodeling that frequently precedes heart failure. We tested the ability of a potent dithiol antioxidant, bucillamine, to protect against the long-term consequences of I/R injury in a murine model of myocardial infarction. After transiently occluding the left anterior descending coronary artery for 30 min, saline or bucillamine (10 microg/g body wt) was injected intravenously as a bolus within the first 5 min of reperfusion. The antioxidant treatment continued with daily subcutaneous injections for 4 wk. There were no differences in infarct sizes between bucillamine- and saline-treated animals. After 4 wk of reperfusion, cardiac hypertrophy was decreased by bucillamine treatment (ventricular weight-to-body weight ratios: I/R + saline, 4.5 +/- 0.2 mg/g vs. I/R + bucillamine, 4.2 +/- 0.1 mg/g; means +/- SE; P < 0.05). Additionally, the hearts of bucillamine-treated mice had improved contractile function (echocardiographic measurement of fractional shortening) relative to saline controls: I/R + saline, 32 +/- 3%, versus I/R + bucillamine, 41 +/- 4% (P < 0.05). Finally, I/R-induced injury in the saline-treated mice was accompanied by a fetal pattern of gene expression determined by ribonuclease protection assay that was consistent with pathological cardiac hypertrophy and remodeling [increased atrial natriuretic peptide, beta-myosin heavy chain (MHC), skeletal alpha-actin; decreased sarco(endo)plasmic reticulum Ca2+ ATPase 2a, and alpha-MHC-to-beta-MHC ratio]. These changes in gene expression were significantly attenuated by bucillamine. Therefore, treatment with a dithiol antioxidant for 4 wk after I/R preserved ventricular function and prevented the abnormal pattern of gene expression associated with pathological cardiac remodeling.

Fig. 1.

Infarct sizes in bucillamine-treated and control mice. Infarct size as a percentage of the left ventricle was measured after 48 h of reperfusion as described in materials and methods. Individual values for each mouse are represented by circles, and the mean value for each group is designated by a horizontal line.

Fig. 2.

Bucillamine protects against cardiac hypertrophy following ischemia-reperfusion (I/R) injury. A: body mass. Each mouse was weighed before surgery, weekly during the treatment interval, and just before death. Group averages are shown for the weights just before surgery (presurgery) and at the end of the experiment interval [28-day (28d) postsurgery]. B: cardiac mass (n, number of mice/group). Twenty-eight days after surgical induction of I/R injury, hearts were excised and trimmed of atria and major blood vessels. The ventricles were blotted dry before weighing. Ventricular weights were normalized to body weights for each mouse (heart weight-to-body weight ratio, in mg/g).

Fig. 3.

Representative echocardiographic M-mode tracings. Echocardiograms were obtained as detailed in materials and methods. M-mode echoes representative for each experimental group are shown.

Fig. 4.

Bucillamine protects against the loss of cardiac contractile function following I/R injury. Fractional shortening (FS) was measured as described in Table 1. The change in FS over the experimental interval in each individual animal was calculated as (FS_pre − FS_28d)/FS_pre × 100%, where FS_pre is FS before surgery and FS_28d is FS 28 days after surgery. The individual values were averaged to determine the means ± SE for each experimental group.

Fig. 5.

Bucillamine attenuates the expression of the pathological fetal gene program following I/R injury. Ventricular tissue was analyzed by ribonuclease protection assay for expression of pathological marker gene mRNAs as described in materials and methods. Individual values for each mRNA species were normalized to the mean sham value (saline or bucillamine, as appropriate) for the same mRNA. Each panel indicated the individual mRNA species measured, as follows: β-myosin heavy chain (β-MHC; A); atrial natriuretic peptide (ANP; B); skeletal α-actin (C); α-MHC (D); α-MHC-to-β-MHC ratio (E); and sarco(endo)plasmic reticulum Ca²⁺ ATPase 2a (SERCA2a; F).