Replication stress responses in human lymphocytes change sex-specifically during aging

The varying incidence of aging-related diseases and the gender gap in life expectancy suggest differences in the aging process between the sexes. Yet, little is known about sex-specific differences in genomic instability, a key factor in aging. Here, we analyzed DNA damage responses (DDRs) in cycling peripheral blood lymphocytes (PBL) and hematopoietic stem and progenitor cells (HSPC) from female and male donors of different age, focusing on replication stress. Transcriptomics revealed striking sex-dependent expression changes in DDR pathways during aging. Particularly, various DDR components, involved in DNA repair and replication fork remodeling, were upregulated with age in men. In older women, functional analysis indicated reduced activity of the Fanconi anemia pathway. Analyses of replication dynamics, PCNA ubiquitination, translesion synthesis (TLS)-polymerase signals, and sensitivities to TLS-polymerase inhibitors indicate a shift from fork remodeling to fast TLS inducing nonclassical replication stress. While replication dynamics were unaltered and replication stress rather reduced, PBL from older men were highly dependent on PARP activity. In conclusion, our findings revealed sex-specific strategies to cope with replication stress in PBL from older individuals, namely through DNA damage tolerance pathway switching in women and PARP activation in men, differentially contributing to the decline of genomic stability with age.