Changes in the Expression of Pituitary Adenylate Cyclase-Activating Polypeptide in the Human Placenta during Pregnancy and Its Effects on the Survival of JAR Choriocarcinoma Cells

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with survival-promoting actions, has been observed in endocrine organs and is thought to play a role in reproductive functions, including pregnancy. PACAP occurs in two forms, 27 and 38 amino acid residues, with PACAP38 being the predominant form in human tissues. In the present study, we determined the concentrations of PACAP38 and PACAP27 in first-trimester and full-term human placentas using radioimmunoassay. We found high levels of PACAP38 and lower levels of PACAP27 in different parts of the full-term human placenta. PACAP38 content increased in the placenta during pregnancy, both on the maternal side and on the fetal side. The effects of PACAP on the survival of JAR human choriocarcinoma cells were investigated using flow cytometry and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) cell viability assay in cells exposed to the widely used chemotherapeutic agent methotrexate (MTX). It was found that PACAP neither influenced the survival of JAR cytotrophoblast cells nor affected cellular response to the death-inducing effect of the chemotherapeutic agent MTX. The present observations further support the significance of PACAP in the human placenta. The observation that PACAP did not influence the effects of MTX may have future clinical importance, showing that PACAP does not decrease the effects of certain chemotherapeutic agents.

Occurrence and Functions of PACAP in the Placenta

“…These authors found no immunoreactive nerve fibers in the placenta or umbilical cord, immunoreactive nerve fibers were only present in the uterus, with isthmic region and nonpregnant myometrium showing stronger immunoreactivity than pregnant uterus. PACAP immunoreactivity by radioimmunoassay was confirmed later by Brubel et al [39]: both forms of the peptide could be detected with PACAP38 23 Occurrence and Functions of PACAP in the Placenta showing stronger immunoreactivity, in agreement with the above earlier observations. Furthermore, it was also found that different parts of the human placenta contained similar levels of PACAPs, such as central maternal, peripheral maternal, central fetal, and peripheral fetal parts.…”

“…A similar effect was observed in cells undergoing chemically induced hypoxia by CoCl 2 . No effects on survival were observed in cells exposed to lipopolysaccharide (LPS), methotrexate or ethanol [39,53]. These findings were contradicting the general survival-promoting effect of PACAP observed in many different cell lines and tissues both in vitro and in vivo [54].…”

“…The umbilical cord showed very weak immunoreactivity. In addition, Brubel et al [39] also compared the level of immunoreactivity in the 1st trimester samples and full-term placentas. Markedly stronger immunoreactivity for PACAP38 was found in full-term placentas on both the maternal and fetal sides.…”

Protective Effects of PACAP in the Retina

“…While in most cell types PACAP is protective, in some tumors it exerts toxic effects [ 111 ]. Furthermore, PACAP6-38 is in most cell types an antagonist, it can also behave as an agonist in some, tumorous and even non-tumorous, cells [ 112 , 113 ].…”

Examination of PACAP-Like Immunoreactivity in Urogenital Tumor Samples

“…The homogenate was centrifuged (12,000 rpm, 4°C, 30 min), and the supernatant was further processed for RIA analysis of PACAP38-LI and PACAP27-LI with a specific and sensitive RIA technique developed in our laboratory (Jakab et al 2004;Nemeth et al 2007;Borzsei et al 2009;Brubel et al 2010), and concentrations of the peptide were calculated with the help of a calibration curve. Briefly: Antiserum: PACAP38 B88111-3^(working dilution 1:10,000) and PACAP27 B88123^(dilution 1:45,000).…”