Interaction between norepinephrine, NPY and VIP in the ovarian artery

Enhanced neuropeptide Y synthesis during intermittent hypoxia in the rat adrenal medulla: role of reactive oxygen species-dependent alterations in precursor peptide processing

Intermittent hypoxia (IH) associated with recurrent apneas often leads to cardiovascular abnormalities. Previously, we showed that IH treatment elevates blood pressure and increases plasma catecholamines (CAs) in rats via reactive oxygen species (ROS)-dependent enhanced synthesis and secretion from the adrenal medulla (AM). Neuropeptide Y (NPY), a sympathetic neurotransmitter that colocalizes with CA in the AM, has been implicated in blood pressure regulation during persistent stress. Here, we investigated whether IH facilitates NPY synthesis in the rat AM and assessed the role of ROS signaling. IH increased NPY-like immunoreactivity in many dopamine-β-hydroxylase-expressing chromaffin cells with a parallel increase in preproNPY mRNA and protein. IH increased the activities of proNPY-processing enzymes, which were due, in part, to elevated protein expression and increased proteolytic processing. IH increased ROS generation, and antioxidants reversed IH-induced increases in ROS, preproNPY, and its processing to bioactive NPY in the AM. IH treatment increased blood pressure and antioxidants and inhibition of NPY amidation prevented this response. These findings suggest that IH-induced elevation in NPY expression in the rat AM is mediated by ROS-dependent augmentation of preproNPY mRNA expression and proNPY-processing enzyme activities and contributes to IH-induced elevation of blood pressure.

Neuropeptide Y receptor expression in human primary ovarian neoplasms

Peptide hormone receptors overexpressed in human malignant neoplasms are potential targets for diagnostic scintigraphy and radiotherapy. One such receptor is the neuropeptide Y (NPY) receptor, mediating primarily feeding behavior in the brain but shown recently to play a role in breast cancer. In this study, the presence of NPY receptors was evaluated in another group of gynecological tumors, namely ovarian tumors, using in vitro receptor autoradiography with (125)I-labeled peptide YY and receptor subtype selective analogs. Remarkably, all 10 investigated inhibin-expressing granulosa cell tumors, Leydig cell tumors, and Sertoli-Leydig cell tumors expressed NPY receptors. In contrast, receptors were found in only seven of 22 ovarian adenocarcinomas (32%). Pharmacological characterization of the expressed NPY receptor subtypes in the various tumors revealed the presence of Y1, Y2, or both. In addition, Y1 receptors were observed in intra- and peritumoral blood vessels as well. NPY receptors were not expressed in three ovarian adenomas, three borderline tumors, four fibromas and fibrothecomas, and one dysgerminoma. This is the first time that NPY receptors are described in human ovarian tissue. They may play a role in the pathogenesis and also in the pathophysiology of ovarian malignancies. Moreover, the high incidence and density of NPY receptors in sex cord-stromal tumors suggest that these receptors represent a new potential target for the diagnostic and therapeutic administration of NPY analogs in these tumors.

Local regulation of oviductal blood flow

1. Blood flow to the oviduct is implicated in the genesis and maintenance of oviductal fluid, in this way contributing to the creation of an adequate medium for ovum/embryo physiology. Therefore, factors controlling the tone of the vessels supplying the oviduct would be expected to affect its luminal environment. In addition, cyclic changes in oviductal blood flow have been suggested to have mechanical functions in the transport of the ovum/embryo. 2. The vascular supply to the oviduct has a prominent adrenergic vasomotor control. A dense adrenergic innervation, together with the presence of a predominant population of alpha(1)-adrenoceptors, provides a contractile regulatory mechanism of oviductal blood flow. No evidence is available on the presence of beta-adrenoceptors. The scanty cholinergic innervation of mammalian oviduct is mainly confined to the vessels, where acetylcholine (ACh) has a vasodilatory effect by releasing endothelium-derived relaxing factors. 3. The presence of nerves containing neuropeptides has been shown in the oviduct. Specifically, a high density of neuropeptide Y- and vasointestinal peptide-containing nerve fibers has been found in relation to blood vessels, but their role in the neutral control of the oviduct blood flow remains to be established. To date, it is not known whether or not oviductal blood vessels receive perivascular nitrergic nerves. 4. Relaxing and contracting factors derived from endothelium also seem to have a modulatory role on oviductal vascular tone. Neurotransmitters or autacoids, such as ACh and histamine, acting on endothelial receptors, release nitric oxide (NO), which relaxes oviductal arteries through guanylyl cyclase activation and accumulation of cyclic GMP. In addition, the release of an endothelium-derived hyperpolarizing factor (EDHF), distinct from NO, by ACh has been shown in oviductal arteries. It acts through the opening of low-conductance Ca(2+)-activated K+ channels leading to hyperpolarization and relaxation. Furthermore, potent and long-lasting contractions induced by the endothelium-derived contractile factor, endothelin (ET), points to its role in the long-term regulation of oviductal vascular tone. 5. A particularly high density of 5-hydroxytryptamine (5-HT) and histamine, present in mast cells clustered in the vicinity of blood vessels, has been described in the oviduct. It is known that histamine elicits a relaxation of oviductal arteries that is partially endothelium-dependent and mediated by the activation of H1-receptors. The implication of histamine in both the increase in blood flow and edema around ovulation, as well as the existence of a functional antagonism between histamine and 5-HT in the regulation of oviductal blood flow, await further investigation. 6. Other factors, such as relaxing and contracting cyclooxygenase-derived products, may also participate in the modulation of blood flow to the oviduct. 7. An overall endocrine regulation of the oviductal vascular supply exists, acting by both direct effects on smooth muscle and modulation of neural and autocrine factors. This control enables cyclic changes in blood flow to the oviduct that are tightly coupled to the reproductive functions of the tube.

Effects of noradrenaline and neuropeptide Y on rat mesenteric microvessel contraction

We have studied the contractile effects of the sympathetic transmitter noradrenaline and its cotransmitter neuropeptide Y (NPY) given alone and in combination on isolated rat mesenteric resistance vessels (200-300 microns diameter). Noradrenaline and NPY each concentration-dependently contracted rat mesenteric microvessels (EC50 approximately equal to 800 nM and 10 nM, respectively), but noradrenaline caused considerably greater maximal effects than NPY (14.3 mN vs. 3.5 mN). A low antagonistic potency of yohimbine indicated that the response to noradrenaline did not involve alpha 2-adrenoceptors, and the subtype-selective antagonists 5-methylurapidil, tamsulosin and chloroethylclonidine indicated mediation via an alpha 1A-adrenoceptor. Shallow Schild regressions for prazosin and 5-methylurapidil indicated that an alpha 1-adrenoceptor subtype with relatively low prazosin affinity might additionally be involved. Studies with the NPY analogues PYY, [Leu31, Pro34] NPY and NPY18-36 demonstrated that NPY acted via a Y1 NPY receptor. In addition to its direct vasoconstricting effects NPY also lowered the noradrenaline EC50 but did not appreciably affect maximal noradrenaline responses indicating possible potentiation. The potentiating NPY response occurred with similar agonist potency as the direct contractile NPY effects and also via a Y1 NPY receptor. The Ca2+ entry blocker nitrendipine (300 nM) reduced direct contractile responses to noradrenaline and NPY but did not affect the potentiation response to NPY.

Vascular effects and cyclic AMP production produced by VIP, PHM, PHV, PACAP-27, PACAP-38, and NPY on rabbit ovarian artery

The relationship between vessel tone and cAMP production induced by vasoactive intestinal polypeptide (VIP), peptide histidine methionine (PHM), peptide histidine valine (PHV), pituitary adenylate cyclase activating polypeptide (PACAP-27 and PACAP-38), and neuropeptide Y (NPY) was investigated in rabbit ovarian arteries in vitro. VIP, PHM, PHV, PACAP-27, and PACAP-38 added in single-dose experiments (10(-9), 10(-8), 10(-7), and 10(-6) M) induced all a significant dose-related relaxation of noradrenaline (NA)-precontracted vessels and displayed similar potencies. VIP, PHM, PHV, PACAP-27, and PACAP-38 all increased cyclic adenosine monophosphate (cAMP) accumulation. The cAMP accumulation induced by PACAP-27 and PACAP-38 was five times higher than the cAMP content induced by the other three peptides. The peptide-induced smooth muscle relaxation did not correlate to the cAMP accumulation. NPY (10(-7) M) markedly reversed the relaxations induced by VIP, PHM, PHV, PACAP-27, and PACAP-38, but did not influence the cAMP production induced by these peptides. In conclusion, the relaxation induced by VIP, PHM, PHV, PACAP-27, and PACAP-38 and the contraction induced by NPY are not solely related to the changes of cAMP contents. These findings indicate that in addition to cAMP, another intracellular signal transduction pathway may be involved in the relaxation and contraction induced by these peptides in rabbit ovarian artery.

Vasoactive intestinal polypeptide and other preprovasoactive intestinal polypeptide-derived peptides in the female and male genital tract: localization, biosynthesis, and functional and clinical significance

Vasoactive intestinal polypeptide, a neuropeptide with wide distribution in the central and peripheral nervous system, has a broad spectrum of biologic actions. The demonstration of vasoactive intestinal polypeptide containing nerve fibers within the female and male genital tract 17 years ago indicated a putative role for this peptide in the local nervous control of reproductive functions. The genes encoding the preprovasoactive intestinal polypeptide precursor molecule and the vasoactive intestinal polypeptide receptor have been identified. The gene expression has been studied by the use of specific antibodies against the functional domains of the vasoactive intestinal polypeptide precursor and the biologic action elucidated by both in vivo and in vitro methods. Evidence has been provided to support vasoactive intestinal polypeptide as a neurotransmitter in several physiologic events in the genital tracts (i.e., blood flow and nonvascular smooth muscle relaxation). In the ovary vasoactive intestinal polypeptide seems to play an important role as regulator and/or modulator of folliculogenesis and steroidogenesis. In the male genital tract vasoactive intestinal polypeptide seems to participate in the control of erection. Vasoactive intestinal polypeptide has been suggested as a causative factor in some diseases of the genital organs (e.g., it may play a pathophysiologic role in male impotence and the peptide is currently used in the treatment of this condition). Vasoactive intestinal polypeptide may be important for control of the low resistance in the fetomaternal vascular bed and is therefore a putative factor involved in the development of preeclampsia. The therapeutic potential of vasoactive intestinal polypeptide and future agonists and antagonists will be revealed by ongoing and forthcoming studies.

Pituitary adenylate cyclase activating polypeptide induces vascular relaxation and inhibits non-vascular smooth muscle activity in the rabbit female genital tract

In vitro effects of two bioactive forms of pituitary adenylate cyclase activating polypeptide (PACAP): PACAP-38 and PACAP-27 were studied on rabbit vascular and non-vascular smooth muscle. Segments of the ovarian artery and muscle strips from the fallopian tube were used. Two series of experiments were performed on vessels: the dose-response relationship of PACAP-38 (10(-10)-10(-7) M) was established on noradrenaline- (NA, 10(-6) M) contracted vessels. In the other set of experiments the contractile effect of 10(-8)-10(-4) M NA added cumulatively, was studied on arterial segments incubated with PACAP-38 (10(-7) M), PACAP-27 (10(-7) M) or VIP (10(-7) M). The effect of PACAP-38, PACAP-27 and VIP (10(-10)-10(-6) M) was investigated on spontaneously contracting smooth muscle of the fallopian tube. Longitudinally as well as transversally cut specimens were investigated. PACAP-38 produced a significant dose-related relaxation on the NA-precontracted vessels. However, pre-incubation of the vessels with 10(-7) M PACAP-38, PACAP-27 and vaso active intestinal polypeptide (VIP) did not induce a general rightward shift of the NA concentration-response curves, although a tendency to inhibition in the low-dose interval was observed. The peptides caused a significant, dose-dependent inhibition of both frequency and amplitude on the fallopian tube smooth muscle activity. The effects of the three peptides on longitudinally as well as transversally cut specimens were alike.