Effects of the tripeptide substance P antagonist, FR113680, on airway constriction and airway edema induced by neurokinins in guinea-pigs

TRPV1 and SP: key elements for sepsis outcome?

Sensory neurons play important roles in many disorders, including inflammatory diseases, such as sepsis. Sepsis is a potentially lethal systemic inflammatory reaction to a local bacterial infection, affecting thousands of patients annually. Although associated with a high mortality rate, sepsis outcome depends on the severity of systemic inflammation, which can be directly influenced by several factors, including the immune response of the patient. Currently, there is a lack of effective drugs to treat sepsis, and thus there is a need to develop new drugs to improve sepsis outcome. Several mediators involved in the formation of sepsis have now been identified, but the mechanisms underlying the pathology remain poorly understood. The transient receptor potential vanilloid 1 (TRPV1) receptor and the neuropeptide substance P (SP) have recently been demonstrated as important targets for sepsis and are located on sensory neurones and non-neuronal cells. Herein, we highlight and review the importance of sensory neurones for the modulation of sepsis, with specific focus on recent findings relating to TRPV1 and SP, with their distinct abilities to alter the transition from local to systemic inflammation and also modify the overall sepsis outcome. We also emphasize the protective role of TRPV1 in this context.

LINKED ARTICLES

This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.

A neuroactive steroid inhibits guinea pig airway sensory nerves via Maxi-K channel activation

BACKGROUND

Although neurogenic inflammation via the activation of C-fibers in the airway may have an important role in the pathogenesis of asthma, their regulatory mechanism remains uncertain.

OBJECTIVE

The pharmacological profiles of a neuroactive steroid, allotetrahydrocorticosterone, on the activation of C-fibers in airway tissues were investigated, and the mechanism how a neuroactive steroid regulates airway inflammatory reactions was clarified.

METHODS

The effects of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial smooth muscle contraction in guinea pig airway tissues were investigated. The influences of K+ channel blockers and intracellular protein inhibitors on the effects of allotetrahydrocorticosterone were examined.

RESULTS

Allotetrahydrocorticosterone dose-dependently inhibited electrical field stimulation-induced guinea pig bronchial smooth muscle contraction. The inhibitory effects of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial contraction were reduced by the pretreatment of Maxi-K+ channel blockers, iberiotoxin and charybdotoxin, but not other K+ channel blockers, dendrotoxin or glibenclamide. Pretreatment with pertussis toxin diminished the inhibitory effect of allotetrahydrocorticosterone, but not an adenylate cyclase inhibitor, SQ 22536, nor a specific inhibitor of mitogen-activated protein kinase kinase, PD 98059.

CONCLUSIONS

These findings suggest that allotetrahydrocorticosterone negatively modulates the activation of C-fibers in guinea pig airway tissues via the opening of Maxi-K+ channels and a pertussis toxin-sensitive G-protein-coupled mechanism.

A neuroactive steroid, allotetrahydrocorticosterone inhibits sensory nerves activation in guinea-pig airways

We examined the effects of a neuroactive steroid, allotetrahydrocorticosterone on the activation of capsaicin-sensitive afferent sensory nerves (C-fibers). Allotetrahydrocorticosterone (0.0001-1.0 microg/ml) dose-dependently inhibited electrical field stimulation-induced guinea-pig bronchial smooth muscle contraction, but not the substance P-induced contraction at 1.0 microg/ml. Allotetrahydrocorticosterone (0.01-1.0 microg/ml) also reduced the capsaicin-induced release of substance P-like immunoreactivity from guinea-pig airway tissues in a dose-dependent manner. The inhibitory effect of allotetrahydrocorticosterone on electrical field stimulation-induced bronchial contraction were reduced by the pretreatment of voltage-dependent K+ channel blockers, tetraethylammonium (1 mM). This evidence suggests that allotetrahydrocorticosterone negatively modulate the activation of C-fibers and substance P release from their endings in airway tissues via the opening of voltage-dependent K+ channels.

Endogenous cannabinoid receptor agonists inhibit neurogenic inflammations in guinea pig airways

BACKGROUND

Although neurogenic inflammation via the activation of C fibers in the airway must have an important role in the pathogenesis of asthma, their regulatory mechanism remains uncertain.

OBJECTIVE

The pharmacological profiles of endogenous cannabinoid receptor agonists on the activation of C fibers in airway tissues were investigated and the mechanisms how cannabinoids regulate airway inflammatory reactions were clarified.

METHODS

The effects of endogenous cannabinoid receptor agonists on electrical field stimulation-induced bronchial smooth muscle contraction, capsaicin-induced bronchoconstriction and capsaicin-induced substance P release in guinea pig airway tissues were investigated. The influences of cannabinoid receptor antagonists and K+ channel blockers to the effects of cannabinoid receptor agonists on these respiratory reactions were examined.

RESULTS

Both endogenous cannabinoid receptor agonists, anandamide and palmitoylethanolamide, inhibited electrical field stimulation-induced guinea pig bronchial smooth muscle contraction, but not neurokinin A-induced contraction. A cannabinoid CB2 antagonist, SR 144528, reduced the inhibitory effect of endogenous agonists, but not a cannabinoid CB1 antagonist, SR 141716A. Inhibitory effects of agonists were also reduced by the pretreatment of large conductance Ca2+ -activated K+ channel (maxi-K+ channel) blockers, iberiotoxin and charybdotoxin, but not by other K+ channel blockers, dendrotoxin or glibenclamide. Anandamide and palmitoylethanolamide blocked the capsaicin-induced release of substance P-like immunoreactivity from guinea pig airway tissues. Additionally, intravenous injection of palmitoylethanolamide dose-dependently inhibited capsaicin-induced guinea pig bronchoconstriction, but not neurokinin A-induced reaction. However, anandamide did not reduce capsaicin-induced guinea pig bronchoconstriction.

CONCLUSIONS

These findings suggest that endogenous cannabinoid receptor agonists inhibit the activation of C fibers via cannabinoid CB2 receptors and maxi-K+ channels in guinea pig airways.

The cannabinoid receptor agonist WIN 55212-2 inhibits neurogenic inflammations in airway tissues

We examined the effects of a cannabinoid receptor agonist, (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-merpholino)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthyl)methanone (WIN 55212-2), on various respiratory reactions induced by the activation of capsaicin-sensitive afferent sensory nerves (C-fibers). WIN 55212-2 significantly inhibited capsaicin-induced guinea pig bronchoconstriction, but not the neurokinin A-induced reaction. Intravenous injection of WIN 55212-2 also blocked cigarette smoke-induced rat tracheal plasma extravasation. However, substance P-induced rat tracheal plasma extravasation was not affected by the administration of WIN 55212-2. A cannabinoid CB(2) receptor antagonist, {N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide} (SR 144528) reduced the inhibitory effects of WIN 55212-2, but not a cannabinoid CB(1) antagonist, [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamidehydrochloride] (SR 141716A). A Maxi-K(+) channel opener, 1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3H)benzimidazolone (NS 1619), specifically inhibited capsaicin-induced guinea pig bronchoconstriction and cigarette smoke-induced rat tracheal plasma extravasation. These findings suggest that WIN 55212-2 inhibits the activation of C-fibers via cannabinoid CB(2) receptors and Maxi-K(+) channels and reduces airway neurogenic inflammatory reactions in vivo.

Cannabinoid receptor agonists inhibit sensory nerve activation in guinea pig airways

We examined the effects of cannabinoid receptor agonists on various respiratory reactions induced by the activation of capsaicin-sensitive afferent sensory nerves (C-fibers). (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-merpholino)methyl]pyrrolo-[1,2,3-de]-1,4-benzoxazin-6-yl](1-naphthyl)methanone (WIN 55212-2) dose-dependently inhibited electrical field stimulation- and capsaicin-induced guinea pig bronchial smooth muscle contraction, but not the neurokinin A-induced contraction. A cannabinoid CB2 receptor antagonist, [N-[(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide] (SR 144528), reduced the inhibitory effect of WIN 55212-2, but not a cannabinoid CB1 antagonist, [N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamidehydrochloride] (SR 141716A). A cannabinoid CB2 agonist, JWH 133, also inhibited electrical field stimulation-induced guinea pig bronchial smooth muscle contraction and its inhibitory effect was blocked by SR 144528. The inhibitory effect of WIN 55212-2 on electrical field stimulation-induced bronchial contraction was reduced by the pretreatment of large conductance Ca(2+)-activated K+ channel (Maxi-K+ channel) blockers, iberiotoxin and charybdotoxin, but not other K+ channel blockers, dendrotoxin or glibenclamide. A Maxi-K+ channel opener, 1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3H)benzimidazolone (NS1619), inhibited bronchial contraction induced by electrical field stimulation. WIN 55212-2 and JWH 133 blocked the capsaicin-induced release of substance P-like immunoreactivity from guinea pig airway tissues. These findings suggest that WIN 55212-2 inhibit the activation of C-fibers via cannabinoid CB2 receptors and Maxi-K+ channels in guinea pig airways.

Use of baclofen to suppress cough induced by angiotensin-converting enzyme inhibitors

OBJECTIVE

To determine whether baclofen can suppress the cough induced by angiotensin-converting enzyme (ACE) inhibitors.

DESIGN

Prospective, open-label, clinical trial of a 4-week course of low-dose oral baclofen (5 mg tid days 1-7, 10 mg tid days 8-28).

SUBJECTS

Seven patients with severe, persistent ACE inhibitor-induced cough.

SETTING

University-affiliated teaching hospital.

MAIN OUTCOME MEASURES

Study participants kept daily diaries monitoring the frequency of cough during and after completion of baclofen therapy.

RESULTS

All subjects demonstrated diminution of cough after initiation of baclofen. Initial improvement was noted by a mean of 4.0 days (range 3-6), and maximal improvement during treatment was achieved by a mean of 10.7 days (range 5-15). In addition, all subjects demonstrated persistent suppression of cough (range 25-74 d) after discontinuation of the study drug.

CONCLUSIONS

Low-dose oral baclofen therapy caused a prolonged antitussive effect in all subjects without inducing any adverse reactions. Baclofen may offer an alternative to the discontinuation of ACE inhibitor therapy in patients for whom these drugs are required.

Role of tachykinin and bradykinin receptors and mast cells in gaseous formaldehyde-induced airway microvascular leakage in rats

We have investigated the effects of CP-99,994 [(+)-(2s,3s)-3-(2-methoxybenzylamino)-2-phenylpiperidine], a tachykinin NK1 receptor antagonist, HOE 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]bradykinin), a bradykinin B2 receptor antagonist, and ketotifen (4-(1-methyl-4-piperidylidene)4 H-benzo[4,5]cycloheptal[1,2-b]thiophen-10(9H)-one hydrogen fumarate), a histamine H1 receptor antagonist with mast cell-stabilizing properties, on microvascular leakage induced by gaseous formaldehyde. Extravasation of Evans blue dye into airway tissues was used as an index of airway microvascular leakage. Leakage of dye in the trachea and main bronchi increased significantly in a concentration-dependent fashion after 10 min inhalation of formaldehyde (5-45 parts per million (ppm)). The airway response induced by 10 min inhalation of 15 ppm formaldehyde (trachea: 119.5 +/- 13.9 ng/mg, n = 7; main bronchi: 139.6 +/- 7.9 ng/mg, n = 7) was abolished by the administration of CP-99,994 (3 and 6 mg/kg i.v.), but not by the administration of HOE 140 (0.65 mg/kg i.v.) nor ketotifen (1 mg/kg i.v.). The increase in vascular permeability induced by formaldehyde in the rat airway was mediated predominantly by NK1 receptor stimulation. Activation of bradykinin receptors and mast cells did not appear to play an important role in this airway response.

Effects of omega-conotoxin GVIA on the activation of capsaicin-sensitive afferent sensory nerves in guinea pig airway tissues

We examined the effects of Ca2+ channel antagonists on various respiratory reactions induced by the activation of capsaicin-sensitive afferent sensory nerves. Intravenous (i.v.) injection of the N-type Ca2+ channel antagonist omega-conotoxin GVIA (CgTX) (1-20 micrograms/kg) dose-dependently inhibited capsaicin-induced guinea pig bronchoconstriction, whereas i.v. administration of the L-type antagonist nicardipine (100 micrograms/kg), the P-type antagonist omega-agatoxin IVA (AgaTX) (20 micrograms/kg) or the OPQ family-type antagonist omega-conotoxin MVIIC (CmTX) (20 micrograms/kg) had no effect. However, CgTX (20 micrograms/kg) failed to inhibit substance P-induced guinea pig bronchoconstriction. CgTX (20 micrograms/kg) significantly inhibited cigarette smoke-induced guinea pig tracheal plasma extravasation, but not the substance P-induced reaction. CgTX also reduced electrical field stimulation-induced guinea pig bronchial smooth muscle contraction (0.01-10 microM) and capsaicin-induced substance P-like immunoreactivity release from guinea pig lung (0.14 microM). This evidence suggests that N-type Ca2+ channels modulate tachykinin release from capsaicin-sensitive afferent sensory nerve endings in guinea pig airway tissue.

Pulmonary actions of the neurokinin1-specific agonist [Sar9,Met(O2)11]-substance P

We examined the relationship between airway obstruction and plasma extravasation produced by the intravenous administration of the selective NK1 receptor agonist [Sar9, Met(O2)11]-substance P(SP). Conscious guinea-pigs were injected with Evans' blue dye followed by intravenous [Sar9,Met(O2)11]-SP. Animals were killed 3 min later and airway obstruction, determined via excised lung gas volumes, and plasma extravasation in the trachea, mainstem bronchi and intrapulmonary airways quantitated. Maximal plasma protein extravasation occurred at a dose about 30 times less than that required to elicit airway obstruction. Neither the neutral endopeptidase (NEP) inhibitor, thiorphan, or the angiotensin-converting enzyme (ACE) inhibitor, captopril, altered the extravasation response to [Sar9,Met(O2)11]-SP. However, thiorphan alone or combined with captopril produced a small but significant potentiation of the airway obstructive response. The marked difference between pulmonary gas trapping and Evans' blue extravasation responses suggest that [Sar9,Met(O2)11]-SP-induced airway obstruction is not secondary to increased pulmonary edema.

Identification of both NK1 and NK2 receptors in guinea-pig airways

1. NK1 and NK2 receptors have been characterized in guinea-pig lung membrane preparations by use of [125I-Tyr8]-substance P and [125I]-neurokinin A binding assays in conjunction with tachykinin-receptor selective agonists ([Sar9Met(O2)11]substance P for NK1 and [beta Ala8]neurokinin A (4-10) for NK2) and antagonists (CP-99,994 for NK1 and SR48968 for NK2). 2. The presence of high affinity, G-protein-coupled NK1 receptors in guinea-pig lung parenchymal membranes has been confirmed. The rank order of affinity for competing tachykinins was as predicted for an NK1 receptor: substance P = [Sar9Met(O2)11]substance P > substance P-methyl ester = physalaemin > neurokinin A = neurokinin B >> [beta Ala8]neurokinin A (4-10). The novel NK1 antagonist CP-99,994 has a Ki of 0.4 nM at this NK1 site. 3. In order to characterize [125I]-neurokinin A binding to guinea-pig lung, the number of [125I]-neurokinin A specific binding sites was increased 3-4 fold by purification of the parenchymal membranes over discontinuous sucrose gradients. The rank order of affinity determined for NK1- and NK2-receptor agonists and antagonists in competition for these sites showed that the majority (80%) of [125I]-neurokinin A specific binding was also to the NK1 receptor. 4. Under conditions where the guinea-pig lung parenchymal NK1 receptor was fully occupied by a saturating concentration of either [Sar9Met(O2)11]substance P (1 microM) or CP-99,994 (2.7 microM), residual [125I]-neurokinin A specific binding was inhibited in a concentration-dependent manner by both [beta Ala8]neurokinin A and SR48968. This result shows that the NK2 receptor is also present in these preparations. 5. Similar studies using guinea-pig tracheal membranes demonstrated that [125I]-neurokinin A specific binding was composed of a NK1-receptor component (60%), inhibited by both [Sar9Met(02)11]substance P and CP-99,994, and a significant NK2-receptor component, inhibited by both [beta Ala 8]neurokinin A andSR48968.6. In summary, these data demonstrate that guinea-pig lung parenchyma and guinea-pig trachea express both NK1 and NK2 receptors.

Effects of adenosine A2 receptor agonists on the excitation of capsaicin-sensitive afferent sensory nerves in airway tissues

We examined the effects of adenosine analogues on the asthmatic reactions induced by the stimulation of capsaicin-sensitive afferent sensory nerves. Intravenous (i.v.) injection of adenosine A2 receptor agonists, 5'-(N-ethylcarboxamido)-adenosine (NECA) and 2-[p-(carboxyethyl)-phenylethylamino]-5'-N-ethylcarboxamido-adenos ine (CGS 21,680), dose dependently inhibited capsaicin-induced guinea-pig bronchoconstriction (1-1000 nmol kg-1), whereas i.v. administration of the adenosine A1 receptor agonist, N6-cyclo-hexyladenosine (CHA), did not affect it (1000 nmol kg-1). Intratracheal injection of NECA (0.05-5 nmol site-1) and CGS 21,680 (0.05-5 nmol site-1) also reduced capsaicin-induced constriction in a dose-dependent manner. However, NECA (1000 nmol kg-1) failed to inhibit substance P-induced guinea-pig bronchoconstriction. NECA (1-1000 nmol kg-1) dose-dependently inhibited cigarette smoke-induced rat tracheal plasma extravasation, but not substance P-induced reaction. NECA (0.1-10 microM) and CGS 21,680 (10 microM) significantly blocked the capsaicin-induced release of substance P-like immunoreactivity from guinea-pig lung, whereas CHA (10 microM) had no effect. This evidence suggests that adenosine A2 receptors modulate negatively the excitation of capsaicin-sensitive afferent sensory nerves and substance P release from their endings in airway tissues.

Effects of an NK1 receptor antagonist, FK888, on constriction and plasma extravasation induced in guinea pig airway by neurokinins and capsaicin

The effects of FK888, an NK1 receptor antagonist, on airway constriction and airway plasma extravasation induced by neurokinins and capsaicin were investigated in guinea pigs. FK888 inhibited substance P (10(-8) M)- and neurokinin A (10(-9) M)-induced contraction of isolated guinea pig trachea, with IC50 values of 3.2 x 10(-8) and 4.2 x 10(-6) M, respectively. FK888 given i.v. inhibited substance P (13.5 micrograms kg-1)-induced airway constriction with an ED50 value of 0.40 mg kg-1 but did not inhibit neurokinin A (1.1 micrograms kg-1)- and capsaicin (3.1 micrograms kg-1)-induced airway constriction at a dose of 1 mg kg-1. On the other hand, FK888 given i.v. inhibited airway plasma extravasation induced by substance P (1.3 micrograms kg-1), neurokinin A (11 micrograms kg-1) and capsaicin (100 micrograms kg-1) with equal potency and ED50 values of 0.011, 0.0063 and 0.019 mg kg-1, respectively. When FK888 was given locally (into the airway directly) inhibitory activities were more potent than following i.v. administration. In this case FK888 inhibited substance P-, neurokinin A- and capsaicin-induced airway constriction with ED50 values of 3.2, 190 and 550 micrograms kg-1, respectively, suggesting that an about 100 times higher dose is required to inhibit neurokinin A- and capsaicin-induced airway constriction than substance P-induced constriction. FK888 given orally was also effective in substance P-, neurokinin A- and capsaicin-induced airway plasma extravasation with ED50 values of 4.2, 5.9 and 9.5 mg kg-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of FR 113680 and FK 224, novel tachykinin receptor antagonists, on cigarette smoke-induced rat tracheal plasma extravasation

We examined the effects of novel tachykinin antagonists, FR 113680 (N alpha-[N alpha-(N alpha-acetyl-L-threonyl)-N1-formyl-D-tryptophyl]-N- methyl-N-phenylmethyl-L-phenylalaninamide) and FK 224 (N-[N2-[N-[N-[N-[2,3-didehydro-N-methyl-N-[N[3-(2-phenthylpheny l) - propionyl]-L-threonyl]-tyrosyl]-L-leucynyl]-D-phenylalanyl]-L-allo - threonyl]-L-asparaginyl]-L-serine nu-lactone) on rat tracheal plasma extravasation induced by cigarette smoke. Intravenous injection of FK 224 (0.032-3.2 mg kg-1) inhibited rat tracheal plasma extravasation induced by cigarette smoke and capsaicin. FR 113680 (32 mg kg-1 i.v.) also significantly inhibited cigarette smoke-induced plasma extravasation, whereas D-chlorpheniramine maleate, FPL 55712, atropine sulfate and indomethacin had no effect. Tracheal plasma extravasation induced by substance P (SP) and neurokinin A (NKA), but not histamine, was also reduced by intravenous administration of FR 113680 and FK 224. These findings suggest that cigarette smoke stimulates primary afferent sensory nerves, releases tachykinins and evokes plasma extravasation in rat trachea.