Differential action of anti-emetic drugs on defecation and emesis induced by prostaglandin E2 in the ferret

An assessment of the effects of neurokinin1 receptor antagonism against nausea and vomiting: Relative efficacy, sites of action and lessons for future drug development

A broad-spectrum anti-vomiting effect of neurokinin1 receptor antagonists (NK1 RA), shown in pre-clinical animal studies, has been supported by a more limited range of clinical studies in different indications. However, this review suggests that compared with vomiting, the self-reported sensation of nausea is less affected or possibly unaffected (depending on the stimulus) by NK1 receptor antagonism, a common finding for anti-emetics. The stimulus-independent effects of NK1 RAs against vomiting are explicable by actions within the central pattern generator (ventral brainstem) and the nucleus tractus solitarius (NTS; dorsal brainstem), with additional effects on vagal afferent activity for certain stimuli (e.g., highly emetogenic chemotherapy). The central pattern generator and NTS neurones are multifunctional so the notable lack of obvious effects of NK1 RAs on other reflexes mediated by the same neurones suggests that their anti-vomiting action is dependent on the activation state of the pathway leading to vomiting. Nausea requires activation of cerebral pathways by projection of information from the NTS. Although NK1 receptors are present in cerebral nuclei implicated in nausea, and imaging studies show very high receptor occupancy at clinically used doses, the variable or limited ability of NK1 RAs to inhibit nausea emphasizes: (i) our inadequate understanding of the mechanisms of nausea; and (ii) that classification of a drug as an anti-emetic may give a false impression of efficacy against nausea vs. vomiting. We discuss the potential mechanisms for the differential efficacy of NK1 RA and the implications for future development of drugs that can effectively treat nausea, an area of unmet clinical need.

The Contribution of Phospholipase C in Vomiting in the Least Shrew (Cryptotis Parva) Model of Emesis

Gq and Gβγ protein-dependent phospholipase C (PLC) activation is extensively involved in G protein-coupled receptor (GPCR)-mediated signaling pathways which are implicated in a wide range of physiological and pathological events. Stimulation of several GPCRs, such as substance P neurokinin 1-, dopamine D2/3-, histamine H1- and mu-opioid receptors, can lead to vomiting. The aim of this study was to investigate the role of PLC in vomiting through assessment of the emetic potential of a PLC activator (m-3M3FBS), and the antiemetic efficacy of a PLC inhibitor (U73122), in the least shrew model of vomiting. We find that a 50 mg/kg (i.p.) dose of m-3M3FBS induces vomiting in ∼90% of tested least shrews, which was accompanied by significant increases in c-Fos expression and ERK1/2 phosphorylation in the shrew brainstem dorsal vagal complex, indicating activation of brainstem emetic nuclei in m-3M3FBS-evoked emesis. The m-3M3FBS-evoked vomiting was reduced by pretreatment with diverse antiemetics including the antagonists/inhibitors of: PLC (U73122), L-type Ca2+ channel (nifedipine), IP3R (2-APB), RyR receptor (dantrolene), ERK1/2 (U0126), PKC (GF109203X), the serotoninergic type 3 receptor (palonosetron), and neurokinin 1 receptor (netupitant). In addition, the PLC inhibitor U73122 displayed broad-spectrum antiemetic effects against diverse emetogens, including the selective agonists of serotonin type 3 (2-Methyl-5-HT)-, neurokinin 1 receptor (GR73632), dopamine D2/3 (quinpirole)-, and muscarinic M1 (McN-A-343) receptors, the L-type Ca2+ channel (FPL64176), and the sarco/endoplasmic reticulum Ca2+-ATPase inhibitor thapsigargin. In sum, PLC activation contributes to emesis, whereas PLC inhibition suppresses vomiting evoked by diverse emetogens.

Mechanisms of Nausea and Vomiting: Current Knowledge and Recent Advances in Intracellular Emetic Signaling Systems

Nausea and vomiting are common gastrointestinal complaints that can be triggered by diverse emetic stimuli through central and/or peripheral nervous systems. Both nausea and vomiting are considered as defense mechanisms when threatening toxins/drugs/bacteria/viruses/fungi enter the body either via the enteral (e.g., the gastrointestinal tract) or parenteral routes, including the blood, skin, and respiratory systems. While vomiting is the act of forceful removal of gastrointestinal contents, nausea is believed to be a subjective sensation that is more difficult to study in nonhuman species. In this review, the authors discuss the anatomical structures, neurotransmitters/mediators, and corresponding receptors, as well as intracellular emetic signaling pathways involved in the processes of nausea and vomiting in diverse animal models as well as humans. While blockade of emetic receptors in the prevention of vomiting is fairly well understood, the potential of new classes of antiemetics altering postreceptor signal transduction mechanisms is currently evolving, which is also reviewed. Finally, future directions within the field will be discussed in terms of important questions that remain to be resolved and advances in technology that may help provide potential answers.

Anti-emetic Action of the Brain-Penetrating New Ghrelin Agonist, HM01, Alone and in Combination With the 5-HT3 Antagonist, Palonosetron and With the NK1 Antagonist, Netupitant, Against Cisplatin- and Motion-Induced Emesis in Suncus murinus (House Musk Shrew)

Ghrelin has well-known activity to stimulate appetite and weight gain. Evidence suggests that ghrelin may also have effects in reducing chemotherapy-induced emesis via growth hormone secretagogue receptors (GHS-R1A) in the brain. However, it is not known whether the stimulation of GHS-R1A has broad inhibitory anti-emetic effects. In the present studies, we used Suncus murinus to investigate the potential of the new and novel orally bioavailable brain-penetrating GHS-R1A mimetic, HM01 (1-[(1S)-1-(2,3-dichloro-4-methoxyphenyl)ethyl]-3-methyl-3-[(4R)-1-Methyl-3,3-dimethyl-4-piperidyl]urea), to reduce emesis induced by a variety of emetic challenges. HM01 (1 to 30 mg/kg, p.o.) antagonized emesis induced by cisplatin (30 mg/kg, i.p.) and by motion (4 cm horizontal displacement, 1 Hz) but was ineffective against emesis induced by nicotine (5 mg/kg, s.c.) and copper sulfate (120 mg/kg by intragastric gavage). In other experiments, HM01 (3 mg/kg, p.o.) enhanced the anti-emetic control of a regimen of palonosetron (0.01 mg/kg, p.o.) alone and palonosetron (0.01 mg/kg p.o.) plus netupitant (1 mg/kg, p.o.). HM01 (10 mg/kg, p.o.) also had positive effects in increasing feeding and drinking in nicotine-treated animals, and it shortened the latency to drink in animals treated with cisplatin. These data indicate that brain-penetrating GHS-R1A agonists may have use alone and/or in combination with standard anti-emetic regimens for the treatment of chemotherapy-induced nausea and vomiting and motion sickness.

Profile of Antiemetic Activity of Netupitant Alone or in Combination with Palonosetron and Dexamethasone in Ferrets and Suncus murinus (House Musk Shrew)

Background and Aims: Chemotherapy-induced acute and delayed emesis involves the activation of multiple pathways, with 5-hydroxytryptamine (5-HT; serotonin) playing a major role in the initial response. Substance P tachykinin NK₁ receptor antagonists can reduce emesis induced by disparate emetic challenges and therefore have a clinical utility as broad inhibitory anti-emetic drugs. In the present studies, we investigate the broad inhibitory anti-emetic profile of a relatively new NK₁ receptor antagonist, netupitant, alone or in combination with the long acting 5-HT₃ receptor antagonist, palonosetron, for a potential to reduce emesis in ferrets and shrews.

Materials and Methods: Ferrets were pretreated with netupitant and/or palonosetron, and then administered apomorphine (0.125 mg/kg, s.c.), morphine (0.5 mg/kg, s.c.), ipecacuanha (1.2 mg/kg, p.o.), copper sulfate (100 mg/kg, intragastric), or cisplatin (5–10 mg/kg, i.p.); in other studies netupitant was administered to Suncus murinus before motion (4 cm horizontal displacement, 2 Hz for 10 min).

Results: Netupitant (3 mg/kg, p.o.) abolished apomorphine-, morphine-, ipecacuanha- and copper sulfate-induced emesis. Lower doses of netupitant (0.03–0.3 mg/kg, p.o.) dose-dependently reduced cisplatin (10 mg/kg, i.p.)-induced emesis in an acute (8 h) model, and motion-induced emesis in S. murinus. In a ferret cisplatin (5 mg/kg, i.p.)-induced acute and delayed emesis model, netupitant administered once at 3 mg/kg, p.o., abolished the first 24 h response and reduced the 24–72 h response by 94.6%; the reduction was markedly superior to the effect of a three times per day administration of ondansetron (1 mg/kg, i.p.). A single administration of netupitant (1 mg/kg, p.o.) plus palonosetron (0.1 mg/kg, p.o.) combined with dexamethasone (1 mg/kg, i.p., once per day), also significantly antagonized cisplatin-induced acute and delayed emesis and was comparable with a once-daily regimen of ondansetron (1 mg/kg, p.o.) plus aprepitant (1 mg/kg, p.o.) in combination with dexamethasone (1 mg/kg, i.p.).

Conclusion: In conclusion, netupitant has potent and long lasting anti-emetic activity against a number of emetic challenges indicating broad inhibitory properties. The convenience of protection afforded by the single dosing of netupitant together with palonosetron was demonstrated and also is known to provide an advantage over other therapeutic strategies to control emesis in man.

Prostaglandin potentiates 5-HT responses in stomach and ileum innervating visceral afferent sensory neurons

Gastrointestinal disorder is a common symptom induced by diverse pathophysiological conditions that include food tolerance, chemotherapy, and irradiation for therapy. Prostaglandin E2 (PGE2) level increase was often reported during gastrointestinal disorder and prostaglandin synthetase inhibitors has been used for ameliorate the symptoms. Exogenous administration of PGE2 induces gastrointestinal disorder, however, the mechanism of action is not known. Therefore, we tested PGE2 effect on visceral afferent sensory neurons of the rat. Interestingly, PGE2 itself did not evoked any response but enhanced serotonin (5-HT)-evoked currents up to 167% of the control level. The augmented 5-HT responses were completely inhibited by a 5-HT type 3 receptor antagonist, ondansetron. The PGE2-induced potentiation were blocked by a selective E-prostanoid type 4 (EP4) receptors antagonist, L-161,982, but type 1 and 2 receptor antagonist AH6809 has no effect. A membrane permeable protein kinase A (PKA) inhibitor, KT5720 also inhibited PGE2 effects. PGE2 induced 5-HT current augmentation was observed on 15% and 21% of the stomach and ileum projecting neurons, respectively. Current results suggest a synergistic signaling in visceral afferent neurons underlying gastrointestinal disorder involving PGE2 potentiation of 5-HT currents. Our findings may open a possibility for screen a new type drugs with lower side effects than currently using steroidal prostaglandin synthetase inhibitors by selectively targeting EP4 receptor/PKA pathway without interrupt prostaglandin synthesis.

Pranlukast prevents cysteinyl leukotriene-induced emesis in the least shrew (Cryptotis parva)

Many chemotherapeutic agents activate multiple signaling systems, including potentially emetogenic arachidonic acid metabolites. Of these messengers, the emetic role of the leukotriene family has been neglected. The aims of this study were to test the emetic potential of key leukotrienes (LTA(4), LTB(4), LTF(4), and the cysteinyl leukotrienes LTC(4), LTD(4) and LTE(4)), and to investigate whether the leukotriene CysLT(1) receptor antagonist pranlukast or mixed leukotriene CysLT(1/2) receptor antagonist Bay u9773 can prevent the LTC(4)-induced emesis. Least shrews were injected with varying doses of one of the six tested leukotrienes and vomiting parameters were measured for 30min. LTC(4) and LTD(4) were most efficacious, and significantly increased both the frequency and percentage of animals vomiting at doses from 0.1 and 0.05mg/kg, respectively. The other tested leukotrienes were either weakly emetic or ineffective at doses up to 4mg/kg. The relative emetogenic activities of the cysteinyl leukotrienes (LTC(4)=LTD(4)>LTE(4)) suggest that leukotriene CysLT(2) receptors have a key role in emesis. However, pranlukast dose-dependently, and at 10mg/kg completely, blocked LTC(4)-induced vomiting, implicating a leukotriene CysLT(1) receptor-mediated emetic effect. Bay u9773 dose-dependently reduced the percentage of animals vomiting, but did not significantly reduce vomiting frequency. Fos immunoreactivity, measured subsequent to LTC(4)-induced vomiting to define its putative anatomical substrates, was significantly increased in the enteric nervous system and medullary dorsal vagal complex following LTC(4) (P<0.05) versus vehicle injections. This study is the first to show that some leukotrienes induce emesis, possibly involving both central and peripheral leukotriene CysLT(1) and/or leukotriene CysLT(2) receptors.

Mechanism of the prostanoid TP receptor agonist U46619 for inducing emesis in the ferret

U46619 is a potent thromboxane A(2) mimetic with emesis-inducing actions that are mediated via prostanoid TP receptors. We investigated its emetic mechanism of action in more detail using the ferret as model animal. The emesis induced by U46619 (30 microg/kg, intraperitoneal) was antagonized significantly by (+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine hydrochloride (CP-99,994; 1 and 10 mg/kg; P < 0.05) and metoclopramide (0.3 and 3 mg/kg), but not by domperidone (3 mg/kg), sulpiride (0.1 mg/kg), ondansetron (0.1 and 1 mg/kg) alone or combined with droperidol (3 mg/kg), GR125487 (1 mg/kg), promethazine (3 mg/kg), or scopolamine (3 mg/kg); GR 125487 (1 mg/kg) prevented the anti-emetic action of metoclopramide (3 mg/kg). U46619 0.3 microg administered into the fourth ventricle rapidly induced emesis. However, bilateral abdominal vagotomy was ineffective in reducing the emetic response (P > 0.05). Our data suggests that U46619 induces emesis via an extra-abdominal mechanism, probably within the brain. Metoclopramide probably has a mechanism of action to prevent U46619-induced emesis via 5-HT(4) receptor activation and NK(1) tachykinin receptor antagonists could be useful to prevent emesis induced by TP receptor activation in man.

Action of cyclooxygenase inhibitors and a leukotriene biosynthesis inhibitor on cisplatin-induced acute and delayed emesis in the ferret

Cisplatin at 5 mg/kg, i.p. induced an acute (day 1) and delayed (days 2 and 3) emetic response in the ferret that was used to investigate the anti-emetic activity of the non-selective cyclooxygenase inhibitor indomethacin (3 - 30 mg/kg, i.p., three times per day) and two cyclooxygenase-2 inhibitors, DFU [5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone; 1 - 10 mg/kg, i.p. administered at 40 and 48 h] and L-745,337 [5-methanesulphonamido-6-(2,4-diflurothiophenyl)-1-indanone; 10 mg/kg, i.p., administered at 40 and 48 h]. Only indomethacin potentiated significantly cisplatin-induced retching + vomiting (P<0.05); DFU antagonized delayed emesis (P<0.05) but the action was not dose-related and L-745,337 was inactive (P>0.05). However, indomethacin alone (30 mg/kg) also induced emesis (P<0.05). The leukotriene biosynthesis inhibitor, MK-886 {3-[1-(p-chlorobenzyl)-5-(isopropyl)-3-tert-butylthioindol-2-yl]-2,2-dimethylpropanoic acid; 1 - 10 mg/kg, i.p., three times per day} had no action to modify cisplatin-induced emesis (P>0.05). The combination treatment of indomethacin (10 mg/kg, i.p., three times per day) with MK-886 (10 mg/kg, i.p., three times per day) did not antagonize cisplatin-induced acute delayed retching + vomiting and had a different profile compared to the action of dexamethasone (1 mg/kg, i.p., three times per day; P<0.05). Inhibition of the cyclooxygenase and lipoxygenase pathways does not account for the anti-emetic of dexamethasone.