Impairment of the DNA damage response pathway as a potential contributor towards peripartum cardiomyopathy

Background and purpose

Peripartum cardiomyopathy (PPCM) affects prior heart-healthy women in the peripartum phase and is characterized by systolic heart failure (HF). Data from a German/ Swedish PPCM cohort revealed a 16-fold increased cancer prevalence. Several patients who were diagnosed with both, PPCM and cancer, carried gene variants located on DNA-damage-response (DDR) genes and/or received anthracycline based chemotherapies prior to their PPCM diagnosis. Here, we investigated juvenile anthracycline treatment prior to pregnancy as well as the effect of DDR impairment during the peripartum phase using mice heterozygous for Ataxia-Telangiectasia-Mutated (ATM), and determined the frequency of ATM gene variants and plasma levels of ATM-targeting miRNAs in PPCM patients.

Methods and results

Female C57BL/6N mice who received juvenile doxorubicin (DOX, 4x4mg/kgBW) treatment prior to pregnancy showed high mortality in the late peripartum phase. DOX-treated mice who survived two pregnancies and nursing periods exhibited reduced cardiac function compared to untreated (wildtype) WT mice (ctrl). RNAseq analysis of LV tissue from ctrl postpartum (PP) mice had shown peripartum induced upregulation of several DDR related transcripts compared with nulli-pari (NP) mice. This upregulation did not occur among PP mice who received juvenile DOX treatment.

Whole exome sequencing in 80 PPCM patients from the German PPCM registry identified 7 carriers of heterozygous ATM gene variants classified as variants of uncertain significance (VUS, n=6) or pathogenic (P, n=1). MiRNA-screening by using human TaqMan Array Cards identified elevated plasma levels of 5 miRNAs potentially targeting ATM in PPCM patients compared to heart-healthy PP-matched women. Overexpression of miRNA precursors of two of these miRNAs, miR-18a-5p and miR-18b-5p, resulted in the reduction of ATM protein levels in HL1 cardiomyocytes.

As proof-of-concept, we used a heterozygous ATM (ATM+/-) mouse model carrying a targeted mutation (Atmins5790neo) leading to a reduced protein expression. After 4 pregnancies and nursing periods (4xPP) ATM+/- mice showed systolic dysfunction and cardiac hypertrophy in contrast to WT 4xPP, ATM+/- NP and WT NP mice (FAC%: WT: 49±5 vs ATM+/-: 37±9; P<0.001). Moreover, mice with PPCM due to cardiac STAT3 deficiency (aMHCxCretg/+;STAT3flox/flox, CKO) and additional ATM heterozygosity showed an aggravated heart failure phenotype compared with CKO PP mice (FS%: CKO: 23.8±3 vs CKO/ATM+/-: 17.3±3.3; P<0.0005) associated with an induction of cell-cycle regulators p21 and Caspase 3.

In conclusion, our data suggests that the DDR pathway may be an important link between cancer and PPCM. Latent side effects of DOX therapy by DDR suppression as well as detrimental effects of DDR related gene variants are potential shared mechanisms. In line, reduced ATM expression induces cardiac dysfunction and hypertrophy in the ATM+/-PP mice and aggravates HF in CKO;ATM+/- PP mice.