In utero exposure of female CD-1 mice to AZT and/or 3TC: II. Persistence of functional alterations in cardiac tissue

Abstract

To delineate temporal changes in the integrity and function of mitochondria/cardiomyocytes in hearts from mice exposed in utero to commonly used nucleoside analogs (NRTIs), CD-1 mice were exposed in utero to 80 mg AZT/kg, 40 mg 3TC/kg, 80 mg AZT/kg plus 40 mg 3TC/kg, or vehicle alone during days 12-18 of gestation and hearts from female mouse offspring were examined at 13 and 26 weeks postpartum. Alterations in cardiac mitochondrial DNA (mtDNA) content, oxidative phosphorylation (OXPHOS) enzyme activities, mtDNA mutations, and echocardiography of NRTI-exposed mice were assessed and compared with findings in vehicle-exposed control mice. A hybrid capture-chemiluminescence assay showed significant twofold increases in mtDNA levels in hearts from AZT- and AZT/3TC-exposed mice at 13 and 26 weeks postpartum, consistent with near doubling in mitochondrial numbers over time compared with vehicle-exposed mice. Echocardiographic measurements at 13 and 26 weeks postpartum indicated progressive thinning of the left ventricular posterior wall in NRTI-exposed mice, relative to controls, with differences becoming statistically significant by 26 weeks. Overall, progressive functional changes occurred in mouse mitochondria and cardiac tissue several months after in utero NRTI exposures; AZT and 3TC acted in concert to cause additive cardiotoxic effects of AZT/3TC compared with either drug alone.

Fig. 1

Diagram representing trimming of hearts from CD-1 female mice exposed transplacentally to AZT, 3TC, or AZT/3TC during the last 7 days of gestation. Each number designates the assay performed on the corresponding section of cardiac tissue. DGGE denaturing gradient gel electrophoresis, H&E hemotoxylin and eosin stain (as well as special stains), TEM transmission electron microscopy, IHC immunohistochemistry, DNA/RNA section preserved for DNA and/or RNA isolation for future studies

Fig. 2

mtDNA levels (LU/ng DNA ± SE) in heart tissue from 13 week (white bars) and 26 week (black bars) female CD-1 mice exposed transplacentally to vehicle, AZT, 3TC, or AZT/3TC. Asterisk indicates average values that are significantly greater than the average control value and significantly greater than the average 3TC value within each time point. (13 weeks: control vs. AZT, P < 0.001; control vs. AZT/3TC P < 0.001, AZT vs. 3TC P = 0.003, AZT/3TC vs. 3TC P < 0.001; 26 weeks: control vs. AZT P < 0.001, control vs. AZT/3TC P < 0.001, AZT vs. 3TC P = 0.004, AZT/3TC vs. 3TC P < 0.001)