Objectives: Second hand cigarette smoke is an independent risk factor for cardiovascular disease. Although a tie between smoking and cardiovascular disease is well established, the underlying mechanisms still remains elusive due to the lack of adequate animal models. This study was designed to use a mouse model of exposure to cigarette smoke, a surrogate of environmental tobacco smoke, to evaluate the impact of cardiac overexpression of heavy metal scavenger metallothionein on myocardial geometry, contractile and intracellular Ca(2+) properties and apoptosis following side-stream smoke exposure.
Methods: Adult male wild-type FVB and metallothionein transgenic mice were placed in a chamber exposed to cigarette smoke for 1 hour daily for 40 days. Echocardiographic, cardiomyocyte contractile and intracellular Ca(2+) properties, fibrosis, apoptosis and mitochondrial damage were examined.
Results: Our data revealed that smoke exposure enlarged ventricular end systolic and diastolic diameters, reduced myocardial and cardiomyocyte contractile function, disrupted intracellular Ca(2+) homeostasis, facilitated fibrosis, apoptosis and mitochondrial damage (cytochrome C release and aconitase activity), the effects of which were attenuated or mitigated by metallothionein. In addition, side-stream smoke expose enhanced phosphorylation of Akt and GSK3β without affecting pan protein expression in the heart, the effect of which was abolished or ameliorated by metallothionein. Cigarette smoke extract interrupted cardiomyocyte contractile function and intracellular Ca(2+) properties, the effect of which was mitigated by wortmannin and NAC.
Conclusions: These data suggest that side-stream smoke exposure led to myocardial dysfunction, intracellular Ca(2+) mishandling, apoptosis, fibrosis and mitochondrial damage, indicating the therapeutic potential of antioxidant against in second smoking-induced cardiac defects possibly via mitochondrial damage and apoptosis.