Pharmacological characterization of postjunctional alpha-adrenoceptors in human nasal mucosa.

BACKGROUND: Functional alpha1- and alpha2-adrenoreceptor subtype pharmacology was characterized in an in vitro human nasal mucosa contractile bioassay. METHODS: Nasal mucosa was obtained from 49 donor patients and mucosal strips were placed in chambers filled with Krebs-Ringer solution and attached to isometric force transducers. RESULTS: Nonselective a-adrenoreceptor agonists epinephrine, norepinephrine, and oxymetazoline produced concentration-dependent contractions of isolated human nasal mucosa (pD2 = 5.2, 4.9, and 6.5, respectively). The alpha2-adrenoreceptor agonist BHT-920 (10 microM)-induced contractions were blocked by yohimbine (0.01-1 microM) and prazosin (0.01-1 microM) inhibited the contractile response to the alpha1-adrenoreceptor agonist phenylephrine (10 microM). Histological analysis showed that phenylephrine and BHT-920 differentially contracted the arteries and veins of human nasal mucosa, respectively. CONCLUSION: Our results indicate that functional alpha1- and alpha2-adrenoceptors are present and functional in human nasal mucosa. The alpha2-adrenoceptors display a predominant role in contracting the veins and the alpha1-adrenoceptors appear to preferentially constrict the human nasal arteries.

Functional TRPV4 channels are expressed in human airway smooth muscle cells.

Hypotonic stimulation induces airway constriction in normal and asthmatic airways. However, the osmolarity sensor in the airway has not been characterized. TRPV4 (also known as VR-OAC, VRL-2, TRP12, OTRPC4), an osmotic-sensitive cation channel in the transient receptor potential (TRP) channel family, was recently cloned. In the present study, we show that TRPV4 mRNA was expressed in cultured human airway smooth muscle cells as analyzed by RT-PCR. Hypotonic stimulation induced Ca(2+) influx in human airway smooth muscle cells in an osmolarity-dependent manner, consistent with the reported biological activity of TRPV4 in transfected cells. In cultured muscle cells, 4alpha-phorbol 12,13-didecanoate (4-alphaPDD), a TRPV4 ligand, increased intracellular Ca(2+) level only when Ca(2+) was present in the extracellular solution. The 4-alphaPDD-induced Ca(2+) response was inhibited by ruthenium red (1 microM), a known TRPV4 inhibitor, but not by capsazepine (1 microM), a TRPV1 antagonist, indicating that 4-alphaPDD-induced Ca(2+) response is mediated by TRPV4. Verapamil (10 microM), an L-type voltage-gated Ca(2+) channel inhibitor, had no effect on the 4-alphaPDD-induced Ca(2+) response, excluding the involvement of L-type Ca(2+) channels. Furthermore, hypotonic stimulation elicited smooth muscle contraction through a mechanism dependent on membrane Ca(2+) channels in both isolated human and guinea pig airways. Hypotonicity-induced airway contraction was not inhibited by the L-type Ca(2+) channel inhibitor nifedipine (1 microM) or by the TRPV1 inhibitor capsazepine (1 microM). We conclude that functional TRPV4 is expressed in human airway smooth muscle cells and may act as an osmolarity sensor in the airway.

Development and potential utility of dual and triple NK receptor antagonists.

The mammalian tachykinin (TK) peptides and their three neurokinin (NK) receptors represent an effector system with wide-ranging actions on neuronal, airway smooth muscle, mucosal, endothelial, immune, inflammatory and remodeling cell function. Recent clinical and preclinical data suggests pathophysiological relevance for TKs in various diseases including asthma, emesis and depression. The promiscuous TK-NK receptor interactions and incompletely overlapping functions mediated by each NK receptor may indicate added therapeutic benefit of using multiple NK receptor blockade. Consequently, there has been substantial pharmaceutical effort in projects to develop nonpeptide dual and triple NK receptor antagonists. This review identifies the chemical and biological approach used to develop a TK antagonist active at the three NK receptors. Clinical activity has been observed using single and/or dual NK receptor antagonists in asthma, depression/anxiety and, most notably, emesis trials but no compound with mono or multiple NK receptor antagonist activities has cleared all the development and regulatory hurdles to commercialization. Current experience indicates that potent dual and triple NK receptor-selective antagonists possessing appropriate affinity and pharmacokinetic properties can be developed. As an example, the biological and pharmacokinetic profiles of a new representative of this class of agent, SCH 206272, is detailed in the present review. Whether such agents will fulfill researchers' expectations must await further clinical trials.

Coordination of histamine H3 receptor antagonists with human adrenal cytochrome P450 enzymes.

Optical difference spectroscopy was used to identify and quantify human adrenal microsomal and mitochondrial cytochrome P450 enzyme interactions with the histamine H(3) receptor antagonists thioperamide, clobenpropit and ciproxifan. Addition of these structurally diverse imidazole H(3) receptor antagonists to cytochrome-P450-containing human adrenal microsomal and mitochondrial preparations resulted in concentration-dependent type II optical difference spectra. Respective spectral dissociation constants (K(S)) for the drug interactions with human adrenal microsomal and mitochondrial cytochrome P450 were 1.5 and 1.6 micromol/l for thioperamide, 3.1 and 0.28 micromol/l for clobenpropit and 0.10 and 0.11 micromol/l for ciproxifan. The three compounds demonstrated a similar activity profile in cytochrome-P450-containing bovine adrenal microsomal and mitochondrial preparations. Findings indicate direct coordination of these imidazole-containing H(3) receptor antagonists with the heme moiety of human adrenal cytochrome P450 isozymes.

Identification of a novel 1'-[5-((3,5-dichlorobenzoyl)methylamino)-3-(3,4-dichlorophenyl)-4-(methoxyimino)pentyl]-2-oxo-(1,4'-bipiperidine) as a dual NK(1)/NK(2) antagonist.

A novel series of dual NK(1)/NK(2) receptor antagonists, based on the 2-oxo-(1,4'-bipiperidine) template, has been prepared. Compound 10R is a potent dual NK(1)/NK(2) antagonist and demonstrates excellent in vivo activity and good oral plasma levels in the dog.

Pharmacology of N-(3,5-dichloro-1-oxido-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 351591), a novel, orally active phosphodiesterase 4 inhibitor.

N-(3,5-Dichloro-1-oxido-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 351591) has been identified as a potent (IC(50) = 58 nM) and highly selective type 4 phosphodiesterase (PDE4) inhibitor with oral bioactivity in several animal models of lung inflammation. N-(3,5-Dichloro-4-pyridinyl)-8-methoxy-2-(trifluoromethyl)-5-quinoline carboxamide (SCH 365351), the only significant in vivo metabolite, is also a potent and highly selective PDE4 inhibitor (IC(50) = 20 nM). Both SCH 351591 and SCH 365351 inhibited cytokine production in human blood mononuclear cell preparations. Oral SCH 351591 significantly attenuated allergen-induced eosinophilia and airway hyperreactivity in allergic guinea pigs at doses as low as 1 mg/kg. In this model, oral SCH 365351 showed similar potency. When SCH 351591 was administered orally to allergic cynomolgus monkeys at 3 mg/kg, Ascaris suum-induced lung eosinophilia was blocked. Hyperventilation-induced bronchospasm in nonallergic guinea pigs, a model for exercise-induced asthma, was also suppressed significantly by oral SCH 351591 at 0.3 mg/kg. Cilomilast (SB 207499; Ariflo), a PDE4 inhibitor currently being developed for asthma and chronic obstructive pulmonary disease (COPD), was 10- to 30-fold less potent than SCH 351591 at inhibiting guinea pig lung eosinophilia and hyperventilation-induced bronchospasm. In a ferret model of emesis, maximum nonemetic oral doses of SCH 351591 and cilomilast were 5 and 1 mg/kg, respectively. Comparison of plasma levels at these nonemetic doses in ferrets to those at doses inhibiting hyperventilation-induced bronchospasm in guinea pigs gave a therapeutic ratio of 16 for SCH 351591 and 4 for cilomilast. Thus, SCH 351591 exhibits a promising preclinical profile as a treatment for asthma and COPD.

The IL-5 receptor on human bronchus selectively primes for hyperresponsiveness.

BACKGROUND: The role of IL-5-induced eosinophilia in airway hyperresponsiveness has been questioned. In addition, eosinophil-independent IL-5-induced airway hyperresponsiveness has been demonstrated in animals. OBJECTIVE: In this study, IL-5 was investigated for direct effects on human bronchial responsiveness. METHODS: Human muscle preparations were isolated from organ donor and surgical tissue. Bronchus, jejunum, and saphenous vein were incubated for 24 hours in vitro with recombinant human (rh) IL-5. Contractility to acetylcholine (bronchus, jejunum) and phenylephrine (saphenous vein) was then investigated. RT-PCR was used to evaluate IL-5 receptor alpha (IL-5R(alpha)) expression in various tissues and to assess bronchus and saphenous vein eosinophils through use of CCR3 expression. RESULTS: rhIL-5 primed bronchus for an exaggerated contraction to acetylcholine. The acetylcholine concentration that produced 50% of the control maximum response was reduced 17- to 20-fold in bronchus treated with 1 and 10 nmol/L rhIL-5. The lower concentration of 0.1 nmol/L rhIL-5 had no effect. The rhIL-5 effect on bronchial contractility was attenuated by antibodies to IL-5 (TRFK-5; 100 nmol/L) and human IL-5R(alpha) (100 nmol/L). rhIL-5 (10 nmol/L) did not enhance contractility of saphenous vein or jejunum. When RT-PCR was used, IL-5R(alpha) expression was strong in bronchus muscle, weak in trachealis, saphenous vein, and atrial muscle, and undetectable in jejunum, urinary bladder, and pulmonary and renal artery muscle. Comparable weak expression of CCR3 was identified in bronchus and saphenous vein. CONCLUSION: The findings are consistent with an airway tissue-selective expression of the IL-5 receptor that mediates IL-5-induced airway hyperresponsiveness independent of eosinophils. In asthma, in which IL-5 expression is elevated, IL-5 might directly induce bronchial hyperresponsiveness.

Nociceptin/orphanin FQ inhibits capsaicin-induced guinea-pig airway contraction through an inward-rectifier potassium channel.

Nociceptin/orphanin FQ (N/OFQ), an endogenous opioid-like orphan receptor (NOP receptor, previously termed ORL1 receptor) agonist, has been found to inhibit capsaicin-induced bronchoconstriction in isolated guinea-pig lungs and in vivo. The underlying mechanisms are not clear. In the present studies, we tested the effect of N/OFQ on VR1 channel function in isolated guinea-pig nodose ganglia cells. Capsaicin increased intracellular Ca(2+) concentration in these cells through activation of vanilloid receptors. Capsaicin-induced Ca(2+) responses were attenuated by pretreatment of nodose neurons with N/OFQ (1 microM). N/OFQ inhibitory effect on the Ca(2+) response in nodose ganglia cells was antagonized by tertiapin (0.5 microM), an inhibitor of inward-rectifier K(+) channels, but not by verapamil, a voltage gated Ca(2+) channel blocker, indicating that an inward-rectifier K(+) channel is involved in N/OFQ inhibitory effect. In isolated guinea-pig bronchus, N/OFQ (1 microM) inhibited capsaicin-induced airway contraction. Tertiapin (0.5 microM) abolished the N/OFQ inhibition of capsaicin-induced bronchial contraction. Capsaicin (10 microg) increased pulmonary inflation pressure in the isolated perfused guinea-pig lungs. This response was significantly attenuated by pretreatment with N/OFQ (1 microM). Tertiapin also abolished the N/OFQ inhibitory effect on capsaicin-induced bronchoconstriction in perfused lungs. Capsaicin increased the release of substance P and neurokinin A from isolated lungs. N/OFQ (1 microM) blocked the capsaicin-induced tachykinin release. These results indicate that N/OFQ-induced hyperpolarization of tachykinin containing airway sensory nerves, through an inward-rectifier K(+) channel activation, accounts for the inhibition of capsaicin-evoked broncoconstriction.