8‐Oxoguanine DNA Glycosylase (OGG1) Deficiency Exacerbates Doxorubicin‐Induced Cardiac Dysfunction

Figure 1. Expression of Ogg1 in cardiomyocytes and cardiac fibroblasts at baseline. (a) Heat map showing the transcriptomic differences in the cardiomyocytes (CM) of wild-type (WT) mice compared to Ogg1-KO mice at baseline identified through RNA-sequencing analysis with a few genes highlighted. Z-scores are computed on a gene-by-gene basis and obtained by subtracting the mean and dividing by standard deviation. (b) qPCR validation of Ogg1 mRNA expression in wild-type (WT) and Ogg1-KO CMs. All values are mean ± SE. n = 3∗P < 0.05. (c) Expression of Ogg1 mRNA evaluated by qPCR in cardiomyocytes (CM) subjected to oxidative stress (Ox stress) and hypoxia (HYPOX), as well as cardiac fibroblasts (CF) in the heart treated with different stimuli. All values are mean ± SE. n = 3∗P < 0.05.

Figure 2. Heart morphology and function in aged WT and Ogg1-KO mice. (a) Ejection fraction, (b) left ventricular posterior wall, and (c) Left ventricle internal diameter measured monthly in both WT and Ogg1-KO mice from 7 months of age till 12 months. 3 mice per group. (d) Haematoxylin and Eosin staining of representative heart slices of WT and Ogg1-KO mice at 12 months of age.

Figure 3. Cardiac function after transverse aortic constriction in WT and Ogg1-KO mice. (a) Representative heart sections stained with haematoxylin and eosin in WT and Ogg1-KO mice hearts to show left ventricle wall thickness and fibrosis after TAC surgery. (b) Ejection fraction, (c) heart weight-to-body weight, (d) left ventricle internal diameter, (e) left ventricle posterior wall, and (f) fibrosis score were assessed presurgery and 6 weeks post-TAC in WT and Ogg1-KO mice. All values are mean ± SD. n = 3 − 5∗P < 0.05.

Figure 4. Cardiac function after doxorubicin treatment in WT and Ogg1-KO mice. (a) Survival plot 14 days after WT and KO mice were treated with 15 mg/kg doxorubicin. (b) Representative heart sections stained with haematoxylin and eosin 2 weeks after treatment with doxorubicin in both WT and Ogg1-KO mice. (c and d) Ejection fraction and left ventricle internal diameter measured at baseline, 1 and 2 weeks postdoxorubicin treatment. All values are mean ± SD. n = 3 − 7∗P < 0.05.

Figure 5. Mitochondrial DNA damage after doxorubicin treatment in WT and Ogg1-KO mice. (a) Mitochondrial DNA damage assessed after 2 weeks in doxorubicin-treated WT and Ogg1-KO mice. ∗P < 0.05. (b) qPCR of 2 mitochondrial genes quantified 2 weeks after treatment with doxorubicin. All values are mean ± SD. n = 3 − 7∗P < 0.05.

Figure 6. Transcriptomic profile after doxorubicin treatment in WT and Ogg1-KO mice. (a and b) Volcano plot showing genes that are changing after treatment with doxorubicin. The red dots are genes with fold change of log2 ≥ 0.5 and FDRvalue < 0.1. Some genes are highlighted. (c) qPCR of Col1a2, c-Myc, and Il-6 in cardiac fibroblasts in the heart after treatment with doxorubicin.