Comparative Immunohistochemistry of Placental Corticotropin-Releasing Hormone and the Transcription Factor RelB-NFκB2 Between Humans and Nonhuman Primates

The transcription factor RelB-NF kappa B2, activated by the noncanonical NE kappa B pathway, positively regulates corticotropin-releasing hormone (CRH) and prostaglandin production in the term human placenta and may play an important role in the timing of human parturition. Here we explored whether RelB-NE kappa B2 signaling plays a role in parturition in nonhuman anthropoid primates. We performed immunohistochemical staining to assess the correlation between CRH and nuclear activity of RelB-NF kappa B2 heterodimers in term placentas from humans, 3 catarrhine primate species, and a single platyrrhine primate species. Consistent with our previous studies, the human placenta showed cytoplasmic staining for CRH and nuclear staining for RelB-NF kappa B2. Similar staining patterns were noted in the 3 catarrhine primates (chimpanzee, baboon, and rhesus macaque). The platyrrhine (marmoset) placentas stained positively for CRH and RelB but not for NF kappa B2. Catarrhine (but not platyrrhine) nonhuman primate term placentas demonstrate the same CRH staining and nuclear localization patterns of RelB and NE kappa B2 as does human placenta. These results suggest that catarrhine primates, particularly rhesus macaques, may serve as useful animal models to study the biologic significance of the noncanonical NE kappa B pathway in human pregnancy.