Cocaine alters mouse germ cells epigenome with direct impact on h4ac expression and dna methylation in the sperm

Abstract

Cocaine intake is associated with testicular toxicity and significantreproductive function impairment. There is accumulating evidencethat cocaine administration can trigger nongenetic inheritancethrough the male germ line affecting development and behavior ofthe offspring. The influence of environmental factors on the epigenomeof male germ cells appears to be most impactful if it happensduring a developmental phase when these cells are epigeneticallyreprogrammed. In the present study, we measured epigenetic marksin isolated germ cells of adult mice treated with cocaine (10 mg/kg) or vehicle, in an intermittent binge protocol (3 i.p. injections, 1h apart, one day on/off for 13 days). We found that chronic cocaineintake disrupts male germ cell epigenetic homeostasis, increasingglobal methylated citocine (5-mC) levels in DNA from germ cells andcauda epididymal sperm (germ cells: vehicle 13.15 ± 0.99 vs cocaine20.113 ± 2.28; sperm: vehicle 15.81 ± 1.08 vs cocaine 21.35± 1.52). Cocaine also increased acetylated histone 4 (H4ac) proteinlevels and decreased class I deacetylases HDAC1/2 mRNA andprotein expression (p<0.05). The mRNA expression levels of classIIa and IIb HDACs were also altered (p<0.05). Immunolocalizationstudies showed that HDAC1/2 were mainly expressed in primaryspermatocytes and H4ac was immunolocalized in late meiotic stagesin vehicle mice while it was detected in primary spermatocytesand in successive stages until round spermatid in cocaine-treatedmice. We observed altered mRNA expression of DNA methylationmarkers in isolated germ cells showing decreased levels of Dnmt3band Tet1 gene expression after cocaine treatment (p<0.05). TET1was mainly immunolocalized in primary spermatocytes in vehicleand cocaine-treated mice. The results presented here broaden thebasic knowledge of the impact of addictive stimulants on testicularpathophysiology, fertility and male reproductive health and implythat altered epigenetic homeostasis by cocaine may have potentialconsequences on future generations.