Involvement of tachykinin receptors in oedema formation and plasma extravasation induced by substance P, neurokinin A, and neurokinin B in mouse ear

Between two storms, vasoactive peptides or bradykinin underlie severity of COVID-19?

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to be a world-wide pandemic with overwhelming socioeconomic impact. Since inflammation is one of the major causes of COVID-19 complications, the associated molecular mechanisms have been the focus of many studies to better understand this disease and develop improved treatments for patients contracting SARS-CoV-2. Among these, strong emphasis has been placed on pro-inflammatory cytokines, associating severity of COVID-19 with so-called "cytokine storm." More recently, peptide bradykinin, its dysregulated signaling or "bradykinin storm," has emerged as a primary mechanism to explain COVID-19-related complications. Unfortunately, this important development may not fully capture the main molecular players that underlie the disease severity. To this end, in this focused review, several lines of evidence are provided to suggest that in addition to bradykinin, two closely related vasoactive peptides, substance P and neurotensin, are also likely to drive microvascular permeability and inflammation, and be responsible for development of COVID-19 pathology. Furthermore, based on published experimental observations, it is postulated that in addition to ACE and neprilysin, peptidase neurolysin (Nln) is also likely to contribute to accumulation of bradykinin, substance P and neurotensin, and progression of the disease. In conclusion, it is proposed that "vasoactive peptide storm" may underlie severity of COVID-19 and that simultaneous inhibition of all three peptidergic systems could be therapeutically more advantageous rather than modulation of any single mechanism alone.

Neurolysin substrates bradykinin, neurotensin and substance P enhance brain microvascular permeability in a human in vitro model

Increased brain microvascular permeability and disruption of blood-brain barrier (BBB) function are among hallmarks of several acute neurodegenerative disorders, including stroke. Numerous studies suggest the involvement of bradykinin (BK), neurotensin (NT) and substance P (SP) in BBB impairment and oedema formation after stroke; however, there is paucity of data in regard to the direct effects of these peptides on the brain microvascular endothelial cells (BMECs) and BBB. The present study aimed to evaluate the direct effects of BK, NT and SP on the permeability of BBB in an in vitro model based on human induced pluripotent stem cell (iPSC)-derived BMECs. Our data indicate that all three peptides increase BBB permeability in a concentration-dependent manner in an in vitro model formed from two different iPSC lines (CTR90F and CTR65M) and widely used hCMEC/D3 human BMECs. The combination of BK, NT and SP at a sub-effective concentration also resulted in increased BBB permeability in the iPSC-derived model indicating potentiation of their action. Furthermore, we observed abrogation of BK, NT and SP effects with pretreatment of pharmacological blockers targeting their specific receptors. Additional mechanistic studies indicate that the short-term effects of these peptides are not mediated through alteration of tight-junction proteins claudin-5 and occludin, but likely involve redistribution of F-actin and secretion of vascular endothelial growth factor. This is the first experimental study to document the increased permeability of the BBB in response to direct action of NT in an in vitro model. In addition, our study confirms the expected but not well-documented, direct effect of SP on BBB permeability and adds to the well-recognised actions of BK on BBB. Lastly, we demonstrate that peptidase neurolysin can neutralise the effects of these peptides on BBB, suggesting potential therapeutic implications.

Placental ischemia increases seizure susceptibility and cerebrospinal fluid cytokines

Eclampsia is diagnosed in preeclamptic patients who develop unexplained seizures and/or coma during pregnancy or postpartum. Eclampsia is one of the leading causes of maternal and infant morbidity and mortality, accounting for ∼13% of maternal deaths worldwide. Little is known about the mechanisms contributing to the pathophysiology of eclampsia, partly due to the lack of suitable animal models. This study tested the hypothesis that placental ischemia, induced by reducing utero-placental perfusion, increases susceptibility to seizures, cerebrospinal fluid (CSF) inflammation, and neurokinin B (NKB) expression in brain and plasma. Pentylenetetrazol (PTZ), a pro-convulsive drug, was injected into pregnant and placental ischemic rats (40 mg/kg, i.p.) on gestational day 19 followed by video monitoring for 30 min. Seizure scoring was blindly conducted. Placental ischemia hastened the onset of seizures compared to pregnant controls but had no effect on seizure duration. Placental ischemia increased CSF levels of IL-2, IL-17, IL-18 and eotaxin (CCL11), had no effect on plasma NKB; however, PTZ increased plasma NKB in both pregnant and placental ischemic rats. NKB was strongly correlated with latency to seizure in normal pregnant rats (R² = 0.88 vs. 0.02 in placental ischemic rats). Lastly, NKB decreased in the anterior cerebrum in response to placental ischemia and PTZ treatment but was unchanged in the posterior cerebrum. These data demonstrate that placental ischemia is associated with increased susceptibility to seizures and CSF inflammation; thus provides an excellent model for elucidating mechanisms of eclampsia-like symptoms. Further studies are required to determine the role of CSF cytokines/chemokines in mediating increased seizure susceptibility.

Microvascular dysfunction with increased vascular leakage response in mice systemically exposed to arsenic

The mechanisms underlying cardiovascular disease induced by arsenic exposure are not completely understood. The objectives of this study were to investigate whether arsenic-fed mice have an increased vascular leakage response to vasoactive agents and whether enhanced type-2 protein phosphatase (PP2A) activity is involved in mustard oil-induced leakage. ICR mice were fed water or sodium arsenite (20 mg/kg) for 4 or 8 weeks. The leakage response to vasoactive agents was quantified using the Evans blue (EB) technique or vascular labeling with carbon particles. Increased EB leakage and high density of carbon-labeled microvessels were detected in arsenic-fed mice treated with mustard oil. Histamine induced significantly higher vascular leakage in arsenic-fed mice than in water-fed mice. Pretreatment with the PP2A inhibitor okadaic acid or the neurokinin 1 receptor (NK1R) blocker RP67580 significantly reduced mustard oil-induced vascular leakage in arsenic-fed mice. The protein levels of PP2Ac and NK1R were similar in both groups. PP2A activity was significantly higher in the arsenic-fed mice compared with the control group. These findings indicate that microvessels generally respond to vasoactive agents, and that the increased PP2A activity is involved in mustard oil-induced vascular leakage in arsenic-fed mice. Arsenic may initiate endothelial dysfunction, resulting in vascular leakage in response to vasoactive agents.

Kinetics of neuronal contribution during the development of a contact allergic reaction

The nervous system contributes to allergic contact dermatitis (ACD). Elucidation of the implication of the nervous system during different stages of ACD could be of therapeutic value. Our aim was to study the kinetics and contribution of the nervous system to ACD by investigating innervation and expression of neuropeptides in skin biopsies obtained at 0, 6, 24, 48 and 72 h post-challenge. Biopsies were stained using antisera against protein gene product (PGP) 9.5, growth associated protein (GAP)-43, substance P and its receptor (R) neurokinin (NK)-1, NKA and NK-2R, and calcitonin gene-related peptide (CGRP). GAP-43-immunoreactive (ir) nerves revealed a time-dependent increase that was more pronounced at 48 and 72 h, while PGP 9.5-ir nerves remained unaltered. Substance P-, NKA- and CGRP-ir nerves at 0 and 6 h were significantly higher compared to later time points, whereas NKA-, NK-1R- and NK-2R-ir cells were lower. A dramatic rise in cell numbers was noted at 24 h. Our findings demonstrate the implication of nerves and sensory neuropeptides during the kinetics of ACD and suggest a possibility to target this system at an early time point for therapy.

Antioedematogenic effect of marrubiin obtained from Marrubium vulgare

This paper describes the antioedematogenic profile of marrubiin (1), the main constituent of Marrubium vulgare, a medicinal plant used in folk medicine of several countries to treat different pathologies. Compound (1) was analyzed in a model of microvascular leakage in mice ears. The results show that it exhibits significant and dose-related antioedematogenic effects. The results obtained for ID50 values (mg/kg, i.p.) and maximal inhibition (%) for the different phlogistic agents used were as follows: histamine (HIS, 13.84 mg/kg and 73.7%); (BK, 18.82 mg/kg and 70.0%); carrageenan (CAR, 13.61 mg/kg and 63.0%). The other phlogistic agonists, such as prostaglandin E2 (PGE2), caused inhibition of less than 50%. In addition, (1) (100 mg/kg) significantly inhibited the OVO-induced allergic edema in actively sensitized animals (maximal inhibition 67.6+/-4%). Our results demonstrate that the systemic administration of marrubiin exerts a non-specific inhibitory effect on pro-inflammatory agent-induced microvascular extravasation of Evans blue in mouse ear.

Involvement of substance P and neurogenic inflammation in arsenic-induced early vascular dysfunction

Vascular-related diseases, including Blackfoot Disease and atherosclerosis, are prominent clinical findings among populations residing in arseniasis areas. While oxidative stress provided a general but nonspecific mechanistic base for arsenic-induced endothelial cell damage in vitro, more specific mechanism is needed to explain the highly targeted vascular lesions induced by arsenic in vivo. Based on our previous studies, we hypothesized that arsenic exerted its action on blood vessels via the neurogenic inflammation process involving release of a neuropeptide (substance P) and activation of endothelial Neurokinin 1 (NK-1) receptor in vivo. Indeed, our present study demonstrated a significantly higher substance P levels in arsenic-treated tissues when compared to saline-treated controls indicating a rapid release of substance P under the influence of arsenic. Furthermore, the arsenic-induced vascular leakage could be significantly reduced when the neurogenic inflammation process was interrupted (via either disruption on the release of substance P, interference on the action of substance P, or blockage of endothelial NK-1 receptor) showing that the neurogenic inflammation process was indeed involved. Histamine release was not found to play a significant role in arsenic-induced vascular permeability change. Our present study affirmed a de novo concept that a pathophysiological mechanism involving the neurogenic release of substance P and activation of endothelial NK-1 receptor underlies the arsenic-induced vascular injury and dysfunction in vivo. This pathophysiological process constituted a two-tiered biological interaction between the nervous system and vascular system and therefore was not readily unveiled by traditional in vitro studies in the past. Our present finding unveiled an important de novo concept on arsenic vascular toxicity in vivo.

Inhibition of neutral endopeptidase (NEP) facilitates neurogenic inflammation

Neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE) are involved in neuropeptide degradation and may modulate neurogenic inflammation. We therefore explored the effect of specific blockers of NEP and ACE on the intensity of neurogenic inflammation. We investigated eight subjects on three occasions. Two pairs of microdialysis fibers equipped with intraluminal wires were inserted intracutaneously into the volar forearms and electrical stimuli were delivered via the intraluminal electrodes. The microdialysis fibers were perfused either with normal saline, phosphoramidon (NEP inhibitor), or captopril (ACE inhibitor). CGRP release was assessed in the microdialysis eluate via a specific EIA and by evaluating the extent and intensity of the neurogenic flare via a laser Doppler imager. The area of hyperalgesia and allodynia was assessed during electrical stimulation. Inhibition of NEP with phosphoramidon increased flare intensity (P < 0.002) and size (P < 0.01), while blocking ACE had no effect on neurogenic vasodilation. CGRP release could be measured in microdialysis samples after phosphoramidon perfusion only (P < 0.03), not in samples with captopril or saline perfusion. No effect on the areas of hyperalgesia and allodynia could be detected. Our findings suggest that NEP but not ACE is most important for CGRP degradation in human skin. This may be of particular importance for the understanding of pain disorders like migraine or complex regional pain syndrome.

Substance P does not play a critical role in neurogenic inflammation in the rat masseter muscle

In this study, we performed a series of experiments to investigate whether substance P (SP) contributes to neurogenic inflammation in the skeletal muscle tissue. Intramuscular injection of an inflammatory irritant, mustard oil (MO), induces significant edema formation in the rat masseter muscle. In order to study the contribution of endogenous SP in the MO-induced edema, groups of rats were pretreated with two different doses (100 nmol; 1 microl) of either peptidergic (Sendide) or non-peptidergic (L703, 606) neurokinin 1 (NK1) receptor antagonist in one masseter muscle 15 min prior to the MO injection in the same muscle. The extent of edema was assessed as the percent weight difference of the injected muscle compared to the non-injected muscle. Neither Sendide nor L703,606 pretreatment resulted in a significant inhibition of the MO-induced edema in the masseter muscle. Exogenous application of SP also produced a significant swelling of the muscle, which was blocked by L703,606 (1 microl) pretreatment, suggesting that evoked release of SP following MO injection is not sufficient to induce significant edema formation. Capsaicin (1% in 25 microl), which is known to cause neurogenic inflammation, failed to produce edema formation in the masseter muscle. The same concentration of capsaicin injected into the hindpaw produced significant swelling of the injected paw. Taken together, these results provide compelling evidence that, unlike cutaneous or joint tissue, SP does not play a critical role in inducing neurogenic inflammation in the skeletal muscle tissue.

Mechanisms underlying the inhibitory effects of tachykinin receptor antagonists on eosinophil recruitment in an allergic pleurisy model in mice

The activation of tachykinin NK receptors by neuropeptides may induce the recruitment of eosinophils in vivo. The aim of the present study was to investigate the effects and underlying mechanism(s) of the action of tachykinin receptor antagonists on eosinophil recruitment in a model of allergic pleurisy in mice. Pretreatment of immunized mice with capsaicin partially prevented the recruitment of eosinophils after antigen challenge, suggesting the potential contribution of sensory nerves for the recruitment of eosinophils Local (10-50 nmol per pleural cavity) or systemic (100-300 nmol per animal) pretreatment with the tachykinin NK1 receptor antagonist SR140333 prevented the recruitment of eosinophils induced by antigen challenge of immunized mice. Neither tachykinin NK2 nor NK3 receptor antagonists suppressed eosinophil recruitment. Pretreatment with SR140333 failed to prevent the antigen-induced increase of interleukin-5 concentrations in the pleural cavity. Similarly, SR140333 failed to affect the bone marrow eosinophilia observed at 48 h after antigen challenge of immunized mice. SR140333 induced a significant increase in the concentrations of antigen-induced eotaxin at 6 h after challenge. Antigen challenge of immunized mice induced a significant increase of Leucotriene B4 (LTB4) concentrations at 6 h after challenge. Pretreatment with SR140333 prevented the antigen-induced increase of LTB4 concentrations. Our data suggest an important role for NK1 receptor activation with consequent LTB4 release and eosinophil recruitment in a model of allergic pleurisy in the mouse. Tachykinins appear to be released mainly from peripheral endings of capsaicin-sensitive sensory neurons and may act on mast cells to facilitate antigen-driven release of LTB4.

Functional characterization of tachykinin NK1 receptors in the mouse uterus

1. Contractility studies were undertaken to determine the nature of the receptors mediating responses to tachykinins in uteri of oestrogen-treated mice. 2. In the presence of thiorphan (3 microM), captopril (10 microM), and bestatin (10 microM), substance P (SP), neurokinin A (NKA) and neurokinin B (NKB) produced concentration-related contractions of uterine preparations. The order of potency was SP > or =NKA>NKB. 3. Neither atropine (0.1 microM) nor l-NOLA (100 microM), nor indomethacin (10 microM) alone or in combination with either ranitidine (10 microM) or mepyramine (10 microM), affected responses to SP. These findings indicate that SP actions are not mediated or modulated through the release of acetylcholine, nitric oxide, prostanoids or histamine. 4. In the presence of peptidase inhibitors, the tachykinin NK(1) receptor-selective agonist [Sar(9)Met(O(2))(11)]SP, produced a concentration-dependent contractile effect. The tachykinin NK(2) and NK(3) receptor-selective agonists [Lys(5)MeLeu(9)Nle(10)]NKA(4-10) and [MePhe(7)]NKB were relatively inactive. The potencies of SP analogues in which Glu replaced Gln(5) and/or Gln(6) were similar to that of SP. 5. The tachykinin NK(1) receptor-selective antagonist, SR140333 (10 nM), alone or combined with the tachykinin NK(2) receptor-selective antagonist, SR48968 (10 nM), shifted log concentration curves to SP, NKA and NKB to the right. SR140333 (10 nM) reduced the effect of [Sar(9)Met(O(2))(11)]SP. SR48968 did not affect responses to SP or [Sar(9)Met(O(2))(11)]SP, but reduced the effect of higher concentrations of NKA and shifted the log concentration-response curve to NKB to the right. The tachykinin NK(3) receptor-selective antagonist, SR 142801 (0.3 microM), had little effect on responses to SP and NKB. 6. We conclude that the tachykinin NK(1) receptor mediates contractile effects of SP, NKA and NKB and [Sar(9)Met(O(2))(11)]SP in myometrium from the oestrogen-primed mouse. The tachykinin NK(2) receptor may also participate in the responses to NKA and NKB.

Neurokinin B induces oedema formation in mouse lung via tachykinin receptor-independent mechanisms

The tachykinin neurokinin B (NKB) has been implicated in the hypertension that characterises pre-eclampsia, a condition where tissue oedema is also observed. The ability of NKB, administered intradermally or intravenously, to induce oedema formation (assessed as plasma extravasation) was examined by extravascular accumulation of intravenously injected (125)I-albumin in wild-type and tachykinin NK(1) receptor knockout mice. Intradermal NKB (30-300 pmol) caused dose-dependent plasma extravasation in wild-type (P < 0.05) but not NK(1) knockout mice, indicating an essential role for the NK(1) receptor in mediating NKB-induced skin oedema. Intravenous administration of NKB to wild-type mice produced plasma extravasation in skin, uterus, liver (P < 0.05) and particularly in the lung (P < 0.01). Surprisingly, the same doses of NKB led to plasma extravasation in the lung and liver of NK(1) knockout mice. By comparison, the tachykinin substance P induced only minimal plasma extravasation in the lungs of wild-type mice. The plasma extravasation produced by NKB in the lungs of NK(1) receptor knockout mice was unaffected by treatment with the NK(2) receptor antagonist SR48968 (3 mg kg(-1)), by the NK(3) receptor antagonists SR142801 (3 mg kg(-1)) and SB-222200 (5 mg kg(-1)) or by the cyclo-oxygenase (COX) inhibitor indomethacin (20 mg kg(-1)). L-Nitro-arginine methyl ester (15 mg kg(-1)), an inhibitor of endothelial nitric oxide synthase (eNOS), produced only a partial inhibition. We conclude that NKB is a potent stimulator of plasma extravasation through two distinct pathways: via activation of NK(1) receptors, and via a novel neurokinin receptor-independent pathway specific to NKB that operates in the mouse lung. These findings are in keeping with a role for NKB in mediating plasma extravasation in diseases such as pre-eclampsia.

Effect of quercetin on plasma extravasation in rat CNS and dura mater by ACE and NEP inhibition

The effects of quercetin on substance P-induced plasma protein extravasation (PE) in the rat dura mater, cerebellum, olfactory bulb and cortex and also its modulation by endopeptidases, angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) were studied. PE was assessed by photometric measurement of extravasated Evans blue. Substance P (SP) and NEP or ACE inhibitors increased the PE in dura mater. Pretreatment with captopril or phosphoramidon potentiated PE induced by SP in the dura mater and cerebellum, respectively. Quercetin increased the PE in the dura mater, cerebellum and cortex. Further results suggested that the PE induced by SP in the dura mater was enhanced by pretreatment with quercetin, similar to that observed with selective peptidase inhibitors. Quercetin-stimulated extravasation in all tissues was abolished by NK-1 receptor blockade. These results suggest that quercetin increases PE in the dura mater and CNS tissues by inhibiting NEP and/or ACE, showing that the effect induced in the dura mater, cerebellum and cortex occurs through endogenous SP accumulation.

Effect of quercetin on tachykinin-induced plasma extravasation in rat urinary bladder

The effect of quercetin on substance P-induced plasma extravasation in rat urinary bladder and its modulation by endogenous peptidases in conscious rats was studied. Plasma protein extravasation (PE) was assayed by measurement of extravasated Evans blue dye (microg/g dry tissue). Intravenous injection of substance P (SP, 10 nmol/kg) significantly increased PE in the urinary bladder. PE evoked by SP was increased significantly by quercetin (20 mg/kg, p.o.) pretreatment in the urinary bladder (73.5 +/- 4.9 to 152.2 +/- 9.9). Pretreatment with captopril, an angiotensin-converting enzyme (ACE) inhibitor (10 nmol/kg, i.v.), or with phosphoramidon, a neutral endopeptidase (NEP) inhibitor (2.5 micromol/kg, i.v.) also potentiated the SP-induced PE in urinary bladder, 286.2 +/- 20.4 and 323.3 +/- 34.0, respectively. Quercetin did not show any effect on neurokinin-A (NKA, 10 nmol/kg, i.v.) -induced plasma extravasation. The present study demonstrates that quercetin potentiates the PE induced by substance P in the urinary bladder. These effects suggest that this flavonoid might cause inhibition of NEP and/or ACE.

Neurokinin mediation of edema and inflammation

The aim of this article is to furnish a brief review of the role played by neurokinins in the inflammatory process. Further attention is given to the mechanisms, as well as to the receptor subtypes involved in neurokinin-mediated inflammation, in an attempt to clarify the participation of neurokinins in different models of acute and chronic inflammation. The involvement of SP, NKA and NKB is also examined in relation to the major signs of inflammation, including edema formation, protein plasma extravasation and vasodilatation. Finally, we provide a general overview on the potential clinical applications of neurokinin antagonists, along with the involvement of neurokinins in human diseases.

Association between kinin B(1) receptor expression and leukocyte trafficking across mouse mesenteric postcapillary venules

Using intravital microscopy, we examined the role played by B(1) receptors in leukocyte trafficking across mouse mesenteric postcapillary venules in vivo. B(1) receptor blockade attenuated interleukin (IL)-1beta-induced (5 ng intraperitoneally, 2 h) leukocyte-endothelial cell interactions and leukocyte emigration ( approximately 50% reduction). The B(1) receptor agonist des-Arg(9)bradykinin (DABK), although inactive in saline- or IL-8-treated mice, caused marked neutrophil rolling, adhesion, and emigration 24 h after challenge with IL-1beta (when the cellular response to IL-1beta had subsided). Reverse transcriptase polymerase chain reaction and Western blot revealed a temporal association between the DABK-induced response and upregulation of mesenteric B(1) receptor mRNA and de novo protein expression after IL-1beta treatment. DABK-induced leukocyte trafficking was antagonized by the B(1) receptor antagonist des-arg(10)HOE 140 but not by the B(2) receptor antagonist HOE 140. Similarly, DABK effects were maintained in B(2) receptor knockout mice. The DABK-induced responses involved the release of neuropeptides from C fibers, as capsaicin treatment inhibited the responses. Treatment with the neurokinin (NK)(1) and NK(3) receptor antagonists attenuated the responses, whereas NK(2), calcitonin gene-related peptide, or platelet-activating factor receptor antagonists had no effect. Substance P caused leukocyte recruitment that, similar to DABK, was inhibited by NK(1) and NK(3) receptor blockade. Mast cell depletion using compound 48/80 reduced DABK-induced leukocyte trafficking, and DABK treatment was shown histologically to induce mast cell degranulation. DABK-induced trafficking was inhibited by histamine H(1) receptor blockade. Our findings provide clear evidence that B(1) receptors play an important role in the mediation of leukocyte-endothelial cell interactions in postcapillary venules, leading to leukocyte recruitment during an inflammatory response. This involves activation of C fibers and mast cells, release of substance P and histamine, and stimulation of NK(1), NK(3), and H(1) receptors.

Neurokinin B- and specific tachykinin NK(3) receptor agonists-induced airway hyperresponsiveness in the guinea-pig

1. The aim of this study was to determine whether neurokinin B (NKB) or specific agonists of tachykinin NK(3) receptors, [MePhe(7)]NKB and senktide, were able to induce airway hyperresponsiveness in guinea-pigs. The effects of these compounds were compared to those of substance P (SP), neurokinin A (NKA) and the preferential tachykinin NK(1) ([Sar(9), Met(0(2))(11)]SP) or NK(2) ([betaAla(8)]NKA (4-10)) receptor agonists. 2. In guinea-pigs pretreated with phosphoramidon (10(-4) M aerosol for 10 min) and salbutamol (8.7x10(-3) M for 10 min), all tachykinins administrated by aerosol (3x10(-7) to 10(-4) M) induced airway hyperresponsiveness 24 h later, displayed by an exaggerated response to the bronchoconstrictor effect of acetylcholine (i.v.). The rank order of potency was: [betaAla(8)]NKA (4-10)>NKA=NKB=senktide=[MePhe(7)]NKB=[Sar(9),Met(0(2))(11)]SP>SP. 3. Airway hyperresponsiveness induced by [MePhe(7)]NKB was prevented by the tachykinin NK(3) (SR 142801) and NK(2) (SR 48968) receptor antagonists. 4. Bronchoconstriction induced by tachykinins administered by aerosol was also determined. SP, NKA, NKB and the tachykinin NK(1) and NK(2) receptor agonist induced bronchoconstriction. The rank order of potency was: NKA=[betaAla(8)]NKA (4-10)>NKB=SP=[Sar(9), Met(0(2))(11)]SP. Under similar conditions, and for concentrations which induce airway hyperresponsiveness, senktide and [MePhe(7)]NKB failed to induce bronchoconstriction. 5. It is concluded that tachykinin NK(3)-receptor stimulation can induce airway hyperresponsiveness and that this effect is not related to the ability of tachykinins to induce bronchoconstriction.

Substance P dependence of endosomal fusion during bladder inflammation

Urinary bladder instillation of ovalbumin into presensitized guinea pigs stimulates rapid development of local bladder inflammation. Substance P is an important mediator of this inflammatory response, as substance P antagonists largely reverse the process. Vacuolization of the subapical endosomal compartment of the transitional epithelial cells lining the bladder suggests that changes in endosomal trafficking and fusion are also part of the inflammatory response. To test directly for substance P mediation of changes in endosomal fusion, we reconstituted fusion of transitional cell endosomes in vitro using both cuvette-based and flow cytometry energy transfer assays. Bladders were loaded with fluorescent dyes by a hypotonic withdrawal protocol before endosomal isolation by gradient centrifugation. Endosomal fusion assayed by energy transfer during in vitro reconstitution was both cytosol and ATP dependent. Fusion was confirmed by the increase in vesicle size on electron micrographs of fused endosomal preparations compared with controls. In inflamed bladders, dye uptake was inhibited 20% and endosomal fusion was inhibited 50%. These changes are partly mediated by the neurokinin-1 (NK1) receptor (NK1R), as 4 mg/kg of CP-96,345, a highly selective NK1 antagonist, increased fusion in inflamed bladders but had no effect on control bladders. The receptor-mediated nature of this effect was demonstrated by the expression of substance P receptor mRNA in rat bladder lumen scrapings and by the detection of the NK1R message in guinea pig subapical endosomes by Western blot analysis. The NK1Rs were significantly upregulated following induction of an inflammatory response in the bladder. These results demonstrate that 1) in ovalbumin-induced inflammation in the guinea pig bladder, in vitro fusion of apical endosomes is inhibited, showing endocytotic processes are altered in inflammation; 2) pretreatment in vivo with an NK1R antagonist blocks this inhibition of in vitro fusion, demonstrating a role for NK1R in this process; and 3) the NK1R is present in higher amounts in apical endosomes of inflamed bladder, suggesting changes in translation or trafficking of the NK1R during the inflammatory process. This suggests that NK1R can change the fusion properties of membranes in which it resides.

Release of substance P, calcitonin gene-related peptide and prostaglandin E2 from rat dura mater encephali following electrical and chemical stimulation in vitro

Neurogenic inflammation of the dura, expressed in plasma extravasation and vasodilatation, putatively contributes to different types of headache. A novel in vitro preparation of the fluid-filled skull cavities was developed to measure mediator release from dura mater encephali upon antidromic electrical stimulation of the trigeminal ganglion and after application of a mixture of inflammatory mediators (serotonin, histamine and bradykinin, 10(-5) M each, pH 6.1) to the arachnoid side of rat dura. The release of calcitonin gene-related peptide, substance P and prostaglandin E2 from dura mater was measured in 5-min samples of superfusates using enzyme immunoassays. Orthodromic chemical and antidromic electrical stimulation of dural afferents caused significant release of calcitonin gene-related peptide (2.8- and 4.5-fold of baseline). The neuropeptide was found to be increased during the 5-min stimulation period and returned to baseline (20.9 +/- 12 pg/ml) in the sampling period after stimulation. In contrast, release of substance P remained at baseline levels (19.3 +/- 11 pg/ml) throughout the experiment. Prostaglandin E2 release was elevated during chemical and significantly also after antidromic electrical stimulation (6- and 4.2-fold of baseline, which was 305 +/- 250 pg/ml). Prostaglandin E2 release outlasted the stimulation period for at least another 5 min. The data support the hypothesis of neurogenic inflammation being involved in headaches and provide new evidence for prostaglandin E2 possibly facilitating meningeal nociceptor excitation and, hence, pain.

Receptor subtypes involved in tachykinin-mediated edema formation

Intradermal (ID) injection of the natural tachykinins substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) (0.3-30 nmol) resulted in a marked and dose-related rat paw edema, with mean ED50 values of 2.68 nmol, 1.17 nmol, and 0.80 nmol, respectively. The ID injection of the selective NK1, SP methyl-ester (1-30 nmol), NK2, [beta-Ala8]-neurokinin A4-10) (beta-Ala, 0.3-30 nmol), or NK3, senktide (1-10 nmol) agonists, caused extensive edema formation with mean ED50s of 0.48 nmol, 0.41 nmol, and 0.18 nmol, respectively. The ID injection of the selective NK1 antagonist FK888 (0.1-3 nmol) produced marked inhibition (94%, 52%, and 66%, respectively) of rat paw edema induced by SP, NKA, or SP methyl-ester. The ID co-injection of the NK2 receptor antagonist SR 48968 elicited a graded inhibition (52%, 67%, and 35%, respectively) of rat paw edema induced by NKA, beta-Ala and, to a lesser extent, the edema caused by SP. Finally, the ID co-injection of the NK, receptor antagonist SR 142801 significantly inhibited (53%, 76%, 53%, and 100%, respectively) the edema formation caused by NKB and NKA or by SP and senktide. Together, the data of the present study suggest that tachykinin-mediated rat paw edema depends on the activation of NK1, NK2 and NK3 receptor subtypes, with apparent major involvement of NK1 receptors subtypes.

Involvement of tachykinin NK3 receptors in citric acid-induced cough and bronchial responses in guinea pigs

Aerosolized citric acid induces several pulmonary effects including bronchoconstriction, airway inflammation, and cough. Evidence from the use of tachykinin NK1 and NK2 receptor antagonists, as well as chronic treatment with high doses of capsaicin, have suggested that these effects are mediated through the release of tachykinins from sensory nerve endings. In the present study, we have investigated the effects of a tachykinin NK3 receptor antagonist, SR 142801 (osanetant), on cough, bronchoconstriction, and bronchial hyperresponsiveness induced by aerosolized citric acid (0.4 M) in guinea pigs. SR 142801, at 0.3 and 1 mg . kg-1 by intraperitoneal route, significantly inhibited cough in conscious guinea pigs by 57 +/- 3 and 62 +/- 10% (n = 8), respectively. In anaesthetized guinea pigs, it failed to inhibit the bronchoconstriction induced by citric acid when given alone but abolished it when combined with the tachykinin NK2 receptor antagonist, SR 48968 (saredutant). In guinea pigs pretreated with thiorphan (1 mg . kg-1), aerosolized citric acid (0.4 M, 1 h) induced airway hyperresponsiveness 24 h later, displayed by an exaggerated response to the bronchoconstrictor effect of acetylcholine. A microvascular leakage hypersensitivity also occurred and was demonstrated by a potentiation of the plasma protein extravasation from bronchial vessels induced by histamine. When given once intraperitoneally at 1 mg . kg-1 30 min before the citric acid exposure, SR 142801 inhibited both hyperresponsiveness to acetylcholine and the potentiation of histamine-induced increase in microvascular permeability. The results suggest that tachykinin NK3 receptors are involved in citric acid-induced effects on airways.

Mechanism of mustard oil-induced skin inflammation in mice

We examined the mechanism of the inflammatory response induced by topical application of mustard oil (0.5-20.0%/20 microliters per ear) to the mouse ear compared to that of the response to capsaicin. The dose-dependent increases in plasma extravasation and ear thickness reached a maximum at approximately 30 min after mustard oil application. Topical pretreatment of ears with capsaicin (250 micrograms/ear) diminished mustard oil-induced plasma extravasation for up to day 7 but not at day 14 after treatment. However, desensitization of the exudative response was not evoked by reapplication of mustard oil to ears. The inflammatory response to mustard oil did not differ between the ears of mast cell-deficient mice and those of the congenic normal mice. Mustard oil-induced plasma extravasation was unaffected by pretreatment with histamine H1 and 5-HT2 receptor antagonists and the capsaicin-functional inhibitor, ruthenium red, which inhibit capsaicin-induced ear oedema. The endopeptidase inhibitor, phosphoramidon, enhanced the ability of mustard oil to increase dye leakage. The tachykinin NK1 receptor antagonist, SR 140333 ((S)1-[2-[3-(3,4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)pi peridin-3-yl]ethyl]-4-phenyl-1-azoniabicyclo[2.2.2.]octane, chloride), not only inhibited mustard oil-induced plasma extravasation but also blocked the enhancement by phosphoramidon of the response to mustard oil. In contrast, the tachykinin NK2 receptor antagonist, SR 48968 ((S)-N-methyl-N[4-(4-acetylamino-4-phenylpiperidino)-2-(3,4,- dichlorophenyl)butyl]benzamide), and the tachykinin NK3 receptor antagonist, SR 142801 ((S)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl)pro pyl)-4- phenylpiperidin-4-yl)-N-methylacetamide), had no effect on plasma extravasation. The present results demonstrated that mustard oil induces mouse skin inflammation through a mechanism different from that for capsaicin. Mediators such as histamine and 5-HT from mast cells appear to be minor factors in the response to mustard oil. In addition, evidence supports the assumption that the tachykinin NK1 receptor is involved in this model.

Effect of the tachykinin receptor antagonists, SR 140333, FK 888, and SR 142801, on capsaicin-induced mouse ear oedema

We examined the effect of SR 140333, a nonpeptide NK1 receptor antagonist, FK 888, a peptide NK1 antagonist, and SR 142801, a non-peptide NK3 antagonist, on ear oedema induced by topical application of capsaicin (250 micrograms/ear) in mice. SR 140333 (ED50:39 micrograms/kg, i.v.) dose-dependently inhibited the oedema response to capsaicin, whereas FK 888 (1.0 mg/kg, i.v.) and SR 142801 (3.0 mg/kg, i.v.) had no effect. Furthermore, SR 140333 significantly (p < 0.001) suppressed ear oedema in response to intradermal injection of substance P (SP) (100 pmol/site) by i.v. administration (0.1 mg/kg,) and co-injection (50 pmol/site). In contrast, FK 888 (1.0 mg/kg, i.v. and 500 pmol/site) was ineffective in the response to SP. The present results suggest that the difference in effects of the two NK1 receptor antagonists on the oedema response to capsaicin is due to species differences in affinities for the NK1 receptor in the mouse skin. Moreover, it seems unlikely that the NK3 receptor is involved primarily in capsaicin-induced mouse ear oedema.