Stimulatory effect of a specific substance P antagonist (RPR 100893) of the human NK1 receptor on the estradiol-induced LH and FSH surges in the ovariectomized cynomolgus monkey

Substance P Mediates Estrogen Modulation Proinflammatory Cytokines Release in Intervertebral Disc

Intervertebral disc degeneration (IDD) is a main contributor to low back pain. A close relationship exists between inflammation and pain. Estrogen can affect inflammation and may play a crucial role in IDD and pain. Substance P (SP) can also regulate the expression of pro-inflammatory cytokines in intervertebral disc (IVD). This study aimed to investigate the potential role of SP in estrogen regulation of IDD. Nine-week-old C57BL/6 female mice were divided into four groups as follows: sham surgery (sham), ovariectomy (OVX), ovariectomy plus estrogen replacement therapy (ERT) group (OVX+E2), and ovariectomy, ERT plus neurokinin 1 receptor (NK1R) agonist (OVX+E2+G). Serum E2, body, and uterus weight were recorded. Immunohistochemistry study and quantitative real-time PCR were used for SP, NK1R, IL-1β, IL-6, and TNF-α examination and comparison in IVD at protein and gene levels. After OVX, the gene and protein expression of TNF-α, IL-1β, IL-6, SP, and NK1R in NP cells significantly increased compared with the sham group. ERT can reverse these impacts. ERT plays anti-inflammatory and anti-hyperalgesic roles in IDD of OVX mice. The estrogen-induced changes of the pro-inflammatory cytokines, TNF-α, IL-1β, and IL-6, are significantly inhibited by NK1R agonists. SP may be a mediator of estrogen regulating pro-inflammatory factors in IDD. Estrogen may affect IVD inflammation through two ways: one is to directly affect the level of pro-inflammatory cytokines and the other is by means of modulation of SP.

Substance P and fibrotic diseases

Substance P (SP) is an undecapeptide encoding the tachykinin 1 (TAC1) gene and belongs to the tachykinin family. SP is widely distributed in the central nervous system and the peripheral nervous system. SP is also produced by nonneuronal cells, such as inflammatory cells and endothelial cells. The biological activities of SP are mainly regulated through the high-affinity neurokinin 1 receptor (NK-1R). The SP/NK-1R system plays an important role in the molecular bases of many human pathophysiologic processes, such as pain, infectious and inflammatory diseases, and cancer. In addition, this system has been implicated in fibrotic diseases and processes such as wound healing, myocardial fibrosis, bowel fibrosis, myelofibrosis, renal fibrosis, and lung fibrosis. Recently, studies have shown that SP plays an important role in liver fibrosis and that NK-1R antagonists can inhibit the progression of fibrosis. NK-1R receptor antagonists could provide clinical solutions for fibrotic diseases. This review summarizes the structure and function of SP and its involvement in fibrotic diseases.

Do Substance P and Neurokinin A Play Important Roles in the Control of LH Secretion in Ewes?

There is now general agreement that neurokinin B (NKB) acts via neurokinin-3-receptor (NK3R) to stimulate secretion of GnRH and LH in several species, including rats, mice, sheep, and humans. However, the roles of two other tachykinins, substance P (SP) and neurokinin A, which act primarily via NK1R and NK2R, respectively, are less clear. In rodents, these signaling pathways can stimulate LH release and substitute for NKB signaling; in humans, SP is colocalized with kisspeptin and NKB in the mediobasal hypothalamus. In this study, we examined the possible role of these tachykinins in control of the reproductive axis in sheep. Immunohistochemistry was used to describe the expression of SP and NK1R in the ovine diencephalon and determine whether these proteins are colocalized in kisspeptin or GnRH neurons. SP-containing cell bodies were largely confined to the arcuate nucleus, but NK1R-immunoreactivity was more widespread. However, there was very low coexpression of SP or NK1R in kisspeptin cells and none in GnRH neurons. We next determined the minimal effective dose of these three tachykinins that would stimulate LH secretion when administered into the third ventricle of ovary-intact anestrous sheep. A much lower dose of NKB (0.2 nmol) than of neurokinin A (2 nmol) or SP (10 nmol) consistently stimulated LH secretion. Moreover, the relative potency of these three neuropeptides parallels the relative selectivity of NK3R. Based on these anatomical and pharmacological data, we conclude that NKB-NK3R signaling is the primary pathway for the control of GnRH secretion by tachykinins in ewes.

Expanding the Role of Tachykinins in the Neuroendocrine Control of Reproduction

Reproductive function is driven by the hormonal interplay between the gonads and brain-pituitary axis. Gonadotropin-releasing hormone (GnRH) is released in a pulsatile manner, which is critical for the attainment and maintenance of fertility, however, GnRH neurons lack the ability to directly respond to most regulatory factors, and a hierarchical upstream neuronal network governs its secretion. We and others proposed a model in which Kiss1 neurons in the arcuate nucleus (ARC), so called KNDy neurons, release kisspeptin (a potent GnRH secretagogue) in a pulsatile manner to drive GnRH pulses under the coordinated autosynaptic action of its cotransmitters, the tachykinin neurokinin B (NKB, stimulatory) and dynorphin (inhibitory). Numerous genetic and pharmacological studies support this model; however, additional regulatory mechanisms (upstream of KNDy neurons) and alternative pathways of GnRH secretion (kisspeptin-independent) exist, but remain ill defined. In this aspect, attention to other members of the tachykinin family, namely substance P (SP) and neurokinin A (NKA), has recently been rekindled. Even though there are still major gaps in our knowledge about the functional significance of these systems, substantial evidence, as discussed below, is placing tachykinin signaling as an important pathway for the awakening of the reproductive axis and the onset of puberty to physiological GnRH secretion and maintenance of fertility in adulthood.

Role of substance P in the cardiovascular system

This article provides an overview of the structure and function of substance P signalling system and its involvement in the cardiovascular regulation. Substance P is an undecapeptide originating from TAC1 gen and belonging to the tachykinin family. The biological actions of substance P are mainly mediated through neurokinin receptor 1 since substance P is the ligand with the highest affinity to neurokinin receptor 1. Substance P is widely distributed within the central and peripheral nervous systems as well as in the cardiovascular system. Substance P is involved in the regulation of heart frequency, blood pressure and in the stretching of vessels. Substance P plays an important role in ischemia and reperfusion and cardiovascular response to stress. Additionally, it has been also implicated in angiogenesis, pain transmission and inflammation. The substance P/neurokinin receptor 1 receptor system is involved in the molecular bases of many human pathological processes. Antagonists of neurokinin receptor 1 receptor could provide clinical solutions for a variety of diseases. Neurokinin receptor 1 antagonists are already used in the prevention of chemotherapy induced nausea and vomiting.

A randomised, placebo-controlled, double-blind study of aprepitant in nondrinking women younger than 70 years receiving moderately emetogenic chemotherapy

BACKGROUND

We evaluated the efficacy of aprepitant plus granisetron and an increased dose of dexamethasone in selected patients undergoing moderately emetogenic chemotherapy (MEC).

METHODS

Nondrinking women <70 years undergoing MEC were randomly assigned to aprepitant (day 1, 125 mg; days 2 and 3, 80 mg) or placebo. Dexamethasone on days 1-3 was 12, 4, and 4 mg with aprepitant and 20, 8, and 8 mg with placebo. The primary end point was complete response (CR; no emesis or rescue therapy) during 120 h of the first cycle. Logistic regression analysis was performed to identify predictors of overall CR.

RESULTS

Of the 94 patients enrolled, 91 were assessable. Most received carboplatin-based chemotherapy. In the aprepitant (n=45) and placebo (n=46) groups, the overall, acute (day 1), and delayed (days 2-5) CR rates were 62% and 52%, 98% and 96%, and 62% and 52%, respectively. Although not statistically significant, the overall CR rate was 10% higher in the aprepitant group. Both regimens were well tolerated. On multivariate analysis, advanced ovarian cancer (OR, 0.26 (0.10-0.72)) was independently associated with a lower CR.

CONCLUSION

Even with an increased dose of dexamethasone, aprepitant seemed more effective than placebo in these selected patients undergoing MEC; however, delayed phase management remains a significant problem.

Characteristics of substance P transport across the blood-brain barrier

PURPOSE

Substance P (SP; NH3(+)-Arg(+)-Pro-Lys(+)-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2) belongs to a group of neurokinins that are widely distributed in the central nervous system and peripheral nervous system. The biological effects mediated by SP in the central nervous system include regulation of affective behavior, emesis, and nociception. Many of these actions are believed to be the result of the binding of SP to the neurokinin-1 (NK-1) receptor and subsequent transport across the blood-brain barrier (BBB). The objective of the study was to investigate the involvement of the NK-1 receptor in the permeation of SP across the BBB.

METHODS

Transport of 3H SP (1-13 nM) was investigated using BBMEC monolayers grown on polycarbonate membranes mounted on a Side-bi-Side diffusion apparatus. 3H SP samples were analyzed by scintillation spectrometry. Liquid chromatography-tandem mass spectrometry was used to monitor the transport at higher concentrations (micromolar).

RESULTS

SP transport across BBMEC monolayers was found to be saturable (Km = 8.57 +/- 1.59 nM, Vmax = 0.017 +/- 0.005 pmol min(-1) mg(-1) protein) in the concentration range of 0-13 nM. Significant (p < 0.05) decline in 3H SP permeation was observed in the presence of unlabeled SP and at 4 degrees C, indicating that the transport process is carrier-mediated. High-performance liquid chromatography analysis showed no significant metabolism of 3H SP in either the donor or receiver chambers. 3H SP transport was inhibited by 2-11 SP (p < 0.05) but not by any other fragments, indicating that both the C- and N-terminal regions are essential for molecular recognition by the receptor. Endocytic inhibitors (chloroquine, phenylarsine oxide, monensin, and brefeldin) did not inhibit SP transport, suggesting the involvement of a nonendocytic mechanism in SP permeation. Pro(9) SP, a high-affinity substrate for the NK-1 major subtype receptor, significantly (p < 0.05) inhibited the transport of SP. However, Sar(9)Met(O2)(11) SP, a high-affinity substrate for the NK-1 minor subtype receptor, septide, and neurokinin A, inhibitors of NK-1 and neurokinin-2 (NK-2) receptors, respectively, did not produce any inhibition of SP transport. Western blot analysis confirmed the presence of the NK-1 receptor in BBMEC monolayers.

CONCLUSIONS

The above results provide functional and molecular evidence for the existence of a carrier-mediated mechanism in the transport of SP across the BBB. The effects of specific inhibitors and the results of Western blot analyses demonstrate the involvement of the NK-1 receptor in the transport of SP across the BBB.

Three-dimensional representation of the neurotransmitter systems of the human hypothalamus: inputs of the gonadotrophin hormone-releasing hormone neuronal system

The gonadotrophin-releasing hormone (GnRH) represents the final common pathway of a neuronal network that integrates multiple external and internal factors to control fertility. Among the many inputs GnRH neurones receive, oestrogens play the most important role. In females, oestrogen, in addition to the negative feedback, also exhibits a positive feedback influence upon the activity and output of GnRH neurones to generate the preovulatory luteinising hormone surge and ovulation. Until recently, the belief has been that the GnRH neurones do not contain oestrogen receptors and that the action of oestrogen upon GnRH neurones is indirect, involving several, oestrogen-sensitive neurotransmitter and neuromodulator systems that trans-synaptically regulate the activity of the GnRH neurones. Although this concept still holds for humans, recent studies indicate that oestrogen receptor-beta is expressed in GnRH neurones of the rat. This review provides three dimensional stereoscopic images of GnRH-immunoreactive (IR) and some peptidergic (neuropeptide Y-, substance P-, beta-endorphin-, leu-enkaphalin-, corticotrophin hormone-releasing- and galanin-IR) and catecholaminergic neurones and the communication of these potential oestrogen-sensitive neuronal systems with GnRH neurones in the human hypothalamus. Because the post-mortem human tissue does not allow the electron microscopic identification of synapses on GnRH neurones, the data presented here are based on light microscopic immunocytochemical experiments using high magnification with oil immersion, semithin sections or confocal microscopy.

Substance P: a new era, a new role

Substance P has been extensively studied and is considered the prototypic neuropeptide of the more than 50 known neuroactive molecules. The understanding of substance P has evolved beyond the original concept as the pain transmitter of the dorsal horn. Animal and genetic research, recent developments of nonpeptide substance P antagonists, and important changes in the understanding of neurotransmission have each contributed to the current understanding of substance P After 7 decades, the physiologic role of substance P is known as a modulator of nociception, involved in signaling the intensity of noxious or aversive stimuli. Genetic studies in mice and development of substance P antagonists provide more recent results that support the redefinition of the central role of substance P Evidence suggests that this neuropeptide is an integral part of central nervous system pathways involved in psychologic stress.

Substance P downregulates basal and gonadotropin-releasing hormone-induced gonadotropin in vitro secretion by pituitary gland of crested newt, Triturus carnifex

The possible role of Substance P (SP) was studied in the modulation of basal and gonadotopin-releasing hormone (GnRH)-induced gonadotropin secretion in the urodele crested newt, Triturus carnifex. During prereproduction, reproduction (noncourtship and courtship), refractory, recovery and aestivation, male and female pituitaries were incubated with medium-alone, GnRH, SP, GnRH receptor antagonist (antide), and SP receptor antagonist (L-703606). Since antisera raised against gonadotropins are not available for this species, we measured these hormones indirectly through their effects on the secretion of testicular androgens and ovarian progesterone from gonads superfused with the preincubated pituitaries. Pituitaries of both sexes preincubated with medium-alone, GnRH, GnRH plus L-703606, and GnRH plus SP plus L-703606 increased steroid secretion during prereproduction, noncourtship, courtship, and recovery; the increase induced by the pituitaries incubated with medium-alone was lower during prereproduction, noncourtship, and recovery. Pituitaries preincubated with SP, GnRH plus SP, GnRH plus SP plus antide, and SP plus antide did not change basal steroid secretion in any of the reproductive phases considered. Antide, L-703606, GnRH plus antide, GnRH plus SP plus antide plus L-703606, SP plus L-703606, and antide plus L-703606 experimental groups showed the same results as those with medium-alone. These results suggest that SP downregulates gonadotropin release in both Triturus carnifex sexes. In addition, an antagonist role, through receptor-independent mechanisms, exists between GnRH (upregulation) and SP (downregulation) in the modulation of pituitary.

Variations in plasma levels of substance P and effects of a specific substance P antagonist of the NK(1) receptor on preovulatory LH and FSH surges and progesterone secretion in the cycling cynomolgus monkey

These studies investigated the role of substance P (SP) in the regulation of the hypothalamic-pituitary-ovarian axis in cynomolgus monkeys with normal menstrual cycles. Plasma concentrations of SP were determined in blood samples taken every morning in normally menstruating cynomolgus monkeys throughout the menstrual cycle. There was a significant decreasing linear trend of SP during the follicular phase (cycle day -13 to day 0) and a significant inverse relationship between SP plasma values and plasma 17beta-estradiol (E(2)) values from day -13 to day 0 of the adjusted cycle. Correspondingly, SP area under the curve was significantly greater during the follicular phase than the luteal phase. In a second experiment, plasma concentrations of E(2), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and progesterone and length of cycles were measured after five daily intragastric administrations (10 mg/kg) of an NK(1) receptor (SP receptor) antagonist (RPR 100893; 10 mg/kg) initiated after serum E(2) concentrations had exceeded 125 pg/ml. There was a statistically significant reduction in the amplitude (41% of control) and the area under the curve (37% of control) of the preovulatory LH surge. In addition, there was a reduction of the duration of the LH surge (3 +/- 0.1 days in controls vs. 2.1 +/- 0.2 days in treated animals). The present results show for the first time that there are significant variations in plasma levels of SP, with a strong negative correlation with serum levels of E(2) during the follicular phase of the cynomolgus monkey, and that endogenous SP has a potentiating role in the interactive hypothalamo-anterior-pituitary mechanisms which lead to the preovulatory LH and FSH surges during the menstrual cycle in the monkey.