Monoethylhexyl phthalate (MEHP) alters steady‐state levels of mitochondrial proteins mediating oxidative stress responses in an immortalized male germ cell model.

Phthalates, used to soften polyvinylchloride, have deleterious affects on the male reproductive system, especially germ cells (GC), inducing oxidative stress, cytochrome c release and apoptosis. This study sought to further elucidate the molecular mechanisms involved by analyzing proteins associated with mitochondrial integrity and the oxidative stress response: peroxiredoxin 3 (Prx3), mitochondrial Hsp70 (mtHsp70), phosphorylation of protein kinase C (pPKC), and inducible cyclooxygenase-2 (Cox2). The SV-40 immortalized mouse spermatocyte-derived cell line, GC-2spd(ts), was used as a model system to determine effects of various doses of MEHP (24-h). MEHP increased mitochondrial Prx3 levels 2-fold, findings consistent with the protective role of Prx3 against pro-apoptotic effects of reactive oxygen species. MtHsp70 decreased (40%) whereas, at higher MEHP doses, cytoplasmic levels significantly increased (40%). Decreases in mitochondrial (45%) and nuclear pPKC levels (65%) were accompanied by increased cytoplasmic pPKC (1.7-fold). Cox2 was induced with increases in both nuclear (1.5-fold) and cytoplasmic (4-fold) levels observed. Additionally, higher doses of MEHP decreased cell proliferation (40%) without altering viability. In summary, these data indicate that male germ cell exposure to MEHP can alter levels and subcellular distribution of regulatory proteins involved in mitochondrial homeostasis and cellular stress response signaling. Studies supported by NIH grants HD-29428 and -039024 to PLM. TMO is a NIEHS Kirschstein-NRSA Postdoctoral Fellow.