Effects of VIP in the female genital tract

VPAC1 and VPAC2 receptor deficiencies negatively influence pregnancy outcome through distinct and overlapping modulations of immune, trophoblast and vascular functions

Pregnancy outcome relies on the maintenance of immune and metabolic homeostasis at the maternal fetal interface. Maternal and perinatal morbidity and mortality is associated with impaired placental development. Multiple regulatory effects of the endogenous-produced vasoactive intestinal peptide (VIP) on vascular, metabolic and immune functions at the maternal-fetal interface have been reported. Here we studied the involvement of the two primary high affinity receptors for VIP (VPAC1 and VPAC2) on maternal immune response, placental homeostasis and pregnancy outcome. Targeted disruption of each receptor gene led to altered placental structure, vascular and trophoblast functional markers and shaped the functional profiles of macrophages and neutrophils towards a proinflammatory state. Several changes in pregnant mice were receptor specific: ROS production elicited by VIP on neutrophils was selectively dependent on the presence of VPAC1 whereas apoptosis rate was associated with the VPAC2 deletion. In peritoneal macrophages from pregnant mice, levels of MHC-II, TLR2, and IL-10 were selectively altered in VPAC2 receptor-deficient mice, whereas IL-6 gene expression was reduced only in mice lacking VPAC1 receptors. Additionally, MMP9 mRNA in isolated TGCs was reduced in VPAC2 receptor deleted mice, while the percentage of IL-12 cells in post-phagocytosis macrophage cultures was selectively reduced in VPAC2 receptor deficient mice. The results indicate that manipulation of VPAC1 and VPAC2 receptor affects immune, vascular and metabolic environment at the maternal fetal interface. These mouse models offer new approaches to study pregnancy complications adding new perspectives to the development of VPAC receptor-selective drugs.

Alterations in the relative abundance of the vasoactive intestinal peptide receptors (VPAC1 and VPAC2) and functions in uterine contractility during inflammation

Vasoactive intestinal peptide (VIP) receptor (VPAC1, VPAC2) abundances in the myometrium and functions in the regulation of inflamed uterine contractility in pigs were studied. In the CON group with gilts, only laparotomy was performed. The gilts of SAL- and E. coli-treated groups were administered saline or E. coli into the uterine horns, respectively. The E. coli-induced endometritis resulted in a lesser myometrial relative abundance of VPAC1 and VPAC2 receptor mRNA transcripts and larger abundance of protein for these receptors. In the myometrium, treatment with VIP resulted in a lesser contractility amplitude than in the tissues of the CON- and SAL- and E. coli-treated groups and in frequency in the CON- and E.coli-treated group compared to the period before VIP treatment. Compared to when there was VIP treatment alone, treatment with VPAC1 and VPAC2 receptor antagonists resulted in a lesser inhibitory effect of VIP on contractility amplitude in the myometrium of the CON and SAL-treated groups and there was complete abolishment of the inhibitory VIP effect on frequency of myometrial contractility of the CON group. In the myometrium of E. coli-treated group, treatment with VPAC1 and VPAC2 receptor antagonists resulted in a reversal of the inhibitory effect of VIP on contractility amplitude, while treatment with VPAC2 receptor antagonist resulted in elimination of contractility and a lesser endometrium/myometrium inhibitory effect of VIP on frequency of these contractions. Results indicate VIP functions to decrease myometrial contractility of the inflamed pig uterus by having functions at VPAC1 and VPAC2 receptors.

Peptidergic innervation of the human and guinea pig uterus

The peptidergic innervation of the human and guinea pig uterus was studied using immunohistochemical methods. Antibodies against several peptides were applied for the PAP-technique to stain peptidergic nerves specifically. These are located in the adventitia of large uterine vessels in the myometrium and smaller vessels of the myometrium and endometrium. A differential distribution of the individual peptides was observed for VIP-IR (vasoactive intestinal polypeptide immunoreactivity), NPY-IR (neuropeptide Y), SP-IR (substance P), SOM-IR (somatostatin) and NT-IR (neurotensin) nerve fibers. Specific functional implications for these neuropeptides can be derived from their histochemical location.

Neuropeptides in the female genital tract: effect on vascular and non-vascular smooth muscle

The presence of vasoactive intestinal polypeptide (VIP), substance P (SP), somatostatin, enkephalin, and avian pancreatic polypeptide (APP) in nerves in the female genital tract raises the question of their physiological significance as neurotransmitter substances. We have examined the effect of these peptides on non-vascular uterine smooth muscle in vivo as well as in vitro, and the effect on blood flow in the genital tract of rabbit and cat. SP caused a dose-dependent increase in mechanical and myoelectrical activity, an action which could be antagonized by VIP. Substance P, leu-enkephalin and VIP induced a concentration related increase in blood flow of the uterus, where VIP seems to be the most potent vasodilator. Neither the effects on vascular nor on non-vascular smooth muscle were inhibited by adrenergic nor cholinergic blocking agents. APP was able to inhibit the VIP-induced vasodilation in rabbits. These findings suggest that several peptides are involved in the local nervous control of both uterine contractions and haemodynamic events.

Effect of vasoactive intestinal polypeptide (VIP) on the in vitro and in vivo motility of the rabbit reproductive tract

Isolated segments of rabbit ampulla and isthmus and strips of uterus and cervix were spontaneously mechanically active in vitro, and this activity was inhibited in a dose-dependent manner by 2 to 200 ng/ml vasoactive intestinal polypeptide (VIP). The oviductal segments were the most inhibited, the uterine strips the least inhibited. These tissues were stimulated to contract in a dose-dependent manner by epinephrine (EPI), with the uterus and cervix being the more responsive. VIP (200 ng/ml) produced only a slight noncompetitive antagonism of this stimulation. Recordings made with miniature force transducers showed the isthmus, uterus, and cervix also to be spontaneously active in vivo. This activity was inhibited by injections (1, 10, and 20 micrograms) and infusions (1.0 and 2.5 micrograms/min) of VIP. The isthmus was the most inhibited, the cervix the least inhibited. Possible physiologic implications of these pharmacologic effects are discussed.