Emmanuel Naline

A potent and selective non-peptide antagonist of the neurokinin a (NK2) receptor

SR 48968 is a potent and selective non-peptide antagonist of the neurokinin A (NK2) receptor. SR 48968 selectively inhibited neurokinin A binding to its receptor and was a competitive antagonist of neurokinin A-mediated contraction of different isolated smooth muscle preparations from various species including human. In vivo, the compound inhibited the bronchoconstriction induced by neurokinin A in guinea pigs. SR 48968 can be used to study the physiological or pathological role of neurokinin A and may be useful in the treatment of neurokinin A-dependent pathology.

Neurokinin A (NK2) receptor revisited with SR 48968, a potent non-peptide antagonist

SR 48968, a new non-peptide antagonist of NK2 receptors, has been tested in a variety of isolated smooth muscle preparations from rats, guinea pigs, rabbits, hamsters and men, in order to assess its selectivity for NK2 receptors as well as its competitivity and specificity. The compound has been found to be inactive as a stimulant or relaxant in all preparations but to exert a potent, competitive antagonism, particularly in tissues obtained from rabbits (pA2 9.8-10.3), guinea pigs (10.5), rats (9.4-9.6), men (9.36-9.6) and hamsters (7.45-8.6). SR 48968 is therefore more active on the NK2A than on the NK2B receptor subtype and the human receptor is close to the NK2A subtype. SR 48968 exerts an antagonism of the competitive type and is therefore suitable for receptor classification despite its slow reversibility in vitro. The sensitivity of NK2A receptors to SR 48968 is at least 1000 times higher than those of NK1 and NK3 receptors. The compound does not affect the effects of bradykinin, angiotensin or bombesin. Because of its activity in human tissues, its potency and long duration of action, SR 48968 is a new promising pharmacologic and possibly therapeutic agent.

Relative potencies of neurokinins in guinea pig trachea and human bronchus.

The three endogenous neurokinins, substance P (SP), neurokinin A (NKA) and neurokinin B (NKB), as well as NKA-(4-10), carbachol, acetylcholine and histamine, were tested in guinea pig tracheae and human bronchi in order to compare the activities of peptides and non-peptide agents and to characterize the neurokinin receptors by means of agonists. Neurokinin A and NKA-(4-10) were potent stimulants of the two preparations: pD2 values for NKA-(4-10) averaged 8.62 in the guinea pig trachea and 7.50 in the human bronchus. The rank order of potency of neurokinins was NKA-(4-10) greater than NKA greater than SP greater than NKB in the human bronchus and NKA-(4-10) greater than NKA greater than NKB greater than SP in the guinea pig trachea. SP was 2-3 orders of magnitude less active than NKA and appears to be a partial agonist. NKB is inactive on the human bronchus. Compared to non-peptide agents, NKA had an affinity 2-3 orders of magnitude greater than acetylcholine and histamine but produced only 75-80% of the maximal effect of acetylcholine. The present results indicate that neurokinins contract the human bronchus by activating a NK-A receptor type which is more sensitive to NKA than to SP and is insensitive to NKB. The guinea pig trachea appears to be a complex preparation containing not only NK-A but also other neurokinin receptors.

Intranasal drug delivery: an efficient and non-invasive route for systemic administration: focus on opioids.

Intranasal administration is a non-invasive route for drug delivery, which is widely used for the local treatment of rhinitis or nasal polyposis. Since drugs can be absorbed into the systemic circulation through the nasal mucosa, this route may also be used in a range of acute or chronic conditions requiring considerable systemic exposure. Indeed, it offers advantages such as ease of administration, rapid onset of action, and avoidance of first-pass metabolism, which consequently offers for example an interesting alternative to intravenous, subcutaneous, oral transmucosal, oral or rectal administration in the management of pain with opioids. Given these indisputable interests, fentanyl-containing formulations have been recently approved and marketed for the treatment of breakthrough cancer pain. This review will outline the relevant aspects of the therapeutic interest and limits of intranasal delivery of drugs, with a special focus on opioids, together with an in-depth discussion of the physiological characteristics of the nasal cavity as well as physicochemical properties (lipophilicity, molecular weight, ionisation) and pharmaceutical factors (absorption enhancers, devices for application) that should be considered for the development of nasal drugs.

Contractile activity of three endothelins (ET-1, ET-2 and ET-3) on the human isolated bronchus.

1 The effects of three endothelins: (i) the classical or human/porcine endothelin (ET‐1); (ii) [Trp6, Leu7] endothelin (ET‐2) and (iii) [Thr2, Phe4, Thr5, Tyr6, Lys7, Tyr14] endothelin or rat endothelin (ET‐3) were tested on the human isolated bronchus. 2 ET‐1 produced a concentration‐dependent contraction of the human isolated bronchus that proceeded in two different steps. The first step was observed at very low concentrations (pD2 = 11.01 ± 0.17, n = 10) but corresponded to a low intrinsic activity (Emax = 15.6 ± 1.8% of Emax induced by acetylcholine (ACh) 3 × 10−3 m, n = 10). This effect was potentiated by Bay K 8644 10−7 m (Emax = 26.1 ± 2.9% of ACh 3 × 10−3 m, n = 5, P < 0.05), reduced by nicardipine 10−6 m (Emax = 6.0 ± 2.6% of ACh 3 × 10−3 m, n = 5, P < 0.05) and strongly inhibited in calcium‐free medium. The second step of the action of ET‐1 corresponded to a lesser potency (pD2 = 7.90 ± 0.17, n = 9) but a higher intrinsic activity (Emax = 82.5 ± 4.7% of ACh 3 × 10−3 m). This effect was not significantly modified by nicardipine 10−6 m or by Bay K 8644 10−7 m. Neither of the two effects was modified by indomethacin 3 × 10−6m. 3 The effects of ET‐2 and ET‐3 were qualitatively similar to those of ET‐1 but quantitatively different; for these two steps of contracting activity and for potency and efficacy the ranking was: ET‐1 > ET‐2 = ET‐3. 4 Thus, ET‐1 appears to be the most potent of these three substances in its effect on the human isolated bronchus. Its activity seems to involve the action of voltage‐dependent calcium channels at low concentrations (10−12 to 10−9 m), whereas other mechanisms are involved at higher concentrations (10−8 to 3 × 10−7 m).

Pharmacological Characterization of Olodaterol, a Novel Inhaled β2-Adrenoceptor Agonist exerting a 24-hour long Duration of Action in Preclinical Models

The preclinical pharmacological profile of 6-hydroxy-8-[(1R)-1-hydroxy-2-[[2-(4-methoxyphenyl)-1,1-dimethylethyl]amino]ethyl]-2H-1,4-benzoxazin-3(4H)-one monohydrochloride (olodaterol, previously known as BI 1744 CL), a novel, enantiomeric pure, inhaled human β2-adrenoceptor (hβ2-AR) agonist, was compared with marketed drugs, such as salmeterol and formoterol. In vitro, olodaterol showed a potent, nearly full agonistic response at the hβ2-AR (EC50 = 0.1 nM; intrinsic activity = 88% compared with isoprenaline) and a significant selectivity profile (241- and 2299-fold towards the hβ1- and hβ3-ARs, respectively). Likewise, olodaterol was able to potently reverse contraction induced by different stimuli in isolated human bronchi. In vivo, antagonistic effects of single doses of olodaterol and formoterol were measured against acetylcholine challenges in anesthetized guinea pigs and dogs for up to 24 h by using the Respimat Soft Mist inhaler. Heart rate and metabolic parameters (serum potassium, lactate, and glucose) were monitored to evaluate systemic pharmacodynamic effects in the dog model. In both models, olodaterol provided bronchoprotection over 24 h. Formoterol applied at an equally effective dose did not retain efficacy over 24 h. In both models olodaterol showed a rapid onset of action comparable with formoterol. Taken together, the preclinical behavior of olodaterol suggests that this novel β2-AR agonist has the profile for once-daily dosing in humans concomitant with a fast onset of action and a favorable systemic pharmacodynamic profile.

Effect of the two tachykinin antagonists, SR 48968 and SR 140333, on cough induced by citric acid in the unanaesthetized guinea pig

It is now well-established that sensory nerves stimulation in the airway induces bronchoconstriction and inflammation, but also protective reflexes, such as coughing. These effects are mediated through the release of tachykinins (substance P and neurokinin A) and we have recently shown that SR 48968, a tachykinin NK2-receptor antagonist, inhibited cough induced by citric acid. In this paper, we have studied the effects of SR 48968 administered by aerosol. We have also investigated the effects of SR 140333, a tachykinin NK1-receptor antagonist, and the combination of both SR 48968 and SR140333 to determine whether tachykinin NK1 receptors are involved in cough. Finally, we have studied the combined effects of SR 48968 and salbutamol to find out whether the antitussive effect of SR 48968 is a consequence of the inhibition of bronchoconstriction. Unanaesthetized guinea-pigs were placed in a transparent chamber and exposed to an aerosol of citric acid (0.4 M). The number of coughs was counted by visual inspection and by determination of sounds and pressure variations in the chamber. By the aerosol route, SR 48968 was an efficient antitussive and 16 times more potent than codeine. SR 140333 (0.1-1 mg.kg-1 i.p.) did not exert any antitussive effect but it potentiated the maximal effect induced by SR 48968. Finally, salbutamol, in a dose (0.3 mg.kg-1) which inhibits bronchoconstriction, but not cough induced by citric acid, did not modify the antitussive effect of SR 48968.(ABSTRACT TRUNCATED AT 250 WORDS)

Formoterol and salbutamol inhibit bradykinin- and histamine-induced airway microvascular leakage in guinea-pig.

1 The effects of the β2‐adrenoceptor agonists, salbutamol and formoterol, on the increase of microvascular permeability induced by histamine or bradykinin in guinea‐pig airways have been studied in vivo. Extravasation of intravenously injected Evans blue dye was used as an index of permeability. The effects of salbutamol and formoterol on the increase in pulmonary airway resistance induced by histamine or bradykinin have also been studied. 2 The increase in pulmonary airway resistance induced by histamine or bradykinin was totally inhibited by salbutamol and formoterol. The ED50 of the two mediators were 0.59 ± 0.21 (n = 5) and 0.20 ± 0.14 (n = 5) μg kg−1 respectively for salbutamol, and 0.13 ± 0.12 (n = 6) and 0.02 ± 0.01 (n = 6) μg kg−1 respectively for formoterol. 3 Salbutamol (10 and 30 μg kg−1) and formoterol (1 and 10 μg kg−1) inhibited the increase of microvascular permeability induced by histamine (30 μg kg−1) in the guinea‐pig airways. The inhibitory effect was predominant in the trachea and the main bronchi, with a maximum inhibition of 20 to 50%. The two drugs had little or no inhibitory effect on the other structures studied, viz. nasal mucosa, larynx, proximal and distal intrapulmonary airways. 4 Salbutamol and formoterol (1 and 10 μg kg−1) abolished the increase in microvascular permeability induced by bradykinin (0.3 μg kg−1). This inhibitory effect of two β‐adrenoceptor stimulants was predominant in the trachea and the nasal mucosa where it was observed with 1 μg kg−1 of the β‐adrenoceptor agonists. In the main bronchi, and in the proximal and distal intrapulmonary airways, the effects of bradykinin were abolished by 10 μg kg−1 of formoterol and salbutamol. 5 The effects of bradykinin, but not those of histamine, were significantly reduced (nasal mucosa, main bronchi and distal intrapulmonary airways) or abolished (trachea, proximal intrapulmonary airways) by morphine 10 mg kg−1, i.v. These results suggest that an indirect effect, through non‐adrenergic non‐cholinergic (NANC) nerves is involved in the action of bradykinin on the microvascular permeability. 6 In conclusion, intravenously injected β‐adrenoceptor stimulants can inhibit, partially or totally, the increase of airways microvascular permeability induced by intravenous histamine or bradykinin. However, these effects require doses that are higher than those that inhibit the increase in pulmonary airway resistance induced by these mediators. As suggested by the results obtained with morphine, the higher efficacy of β2‐adrenoceptor agonists versus bradykinin may occur through activation of presynaptic receptors of the non‐adrenergic non‐cholinergic (NANC) nerves preventing release of inflammatory neuropeptides such as substance P and neurokinin A.

Influence of (+/-)-CP-96,345 and SR 48968 on electrical field stimulation of the isolated guinea-pig main bronchus.

The aim of this study was to investigate the effects of (+/-)-CP-96,345 and SR 48968, two new nonpeptide antagonists of neurokinin NK1 and NK2 receptors, respectively, on the response of isolated guinea pig main bronchi to electrical field stimulation (EFS). Bronchi were stimulated transmurally with biphasic pulses (16 Hz, 1 ms, 320 mA for 10 s) in the presence of indomethacin (10(-6) M) and propranolol (10(-6) M). Two successive contractile responses were observed. Both responses were abolished by tetrodotoxin (10(-6) M) whereas only the first rapid phase was abolished by atropine (10(-6) M). The late and prolonged second phase was strongly reduced by the neurokinin A (NK2) receptor antagonist SR 48968 (10(-11) to 10(-8) M) with an EC50 of 0.056 nM and a maximal inhibition of 83.3 +/- 10.8% (10(-8) M, n = 4). This second response was partially inhibited by the substance P (NK1) receptors antagonist (+/-)-CP-96,345 (10(-8) to 10(-6) M). An incubation of 2 h was necessary for SR 48968 to inhibit the EFS-evoked noncholinergic contraction. These results confirm that EFS of guinea-pig bronchi involves stimulation of cholinergic and noncholinergic excitatory nerves and demonstrate that the new developed tachykinin receptors nonpeptide antagonists (+/-)-CP-96,345 and especially SR 48968 are potent inhibitors of the noncholinergic contraction induced by EFS of the isolated guinea-pig main bronchus.

Nerve growth factor is released by IL-1β and induces hyperresponsiveness of the human isolated bronchus

Nerve growth factor (NGF) is a neurotrophic factor essential for the development and survival of neurons, and is also an important mediator of inflammation. It is released by airway cells stimulated by interleukin (IL)-1β. As IL-1β induces airway hyperresponsiveness (AHR) to the tachykinin NK-1 receptor agonist [Sar9,Met(O2)11]-substance P in human isolated bronchi, the aim of this study was to determine whether IL-1β was able to induce NGF release from isolated bronchi, and whether NGF might participate into IL-1β-induced AHR. IL-1β (10 ng·mL−1; 21°C; 15 h) increased the release of NGF from human isolated bronchi in vitro, and, in organ bath studies, the response of human bronchi to [Sar9,Met(O2)11]-substance P (0.1 µm). A significant correlation was found between these responses. AHR induced by IL-1β was abolished by a blocking anti-human NGF antibody. Finally, NGF (1 ng·mL−1; 37°C; 0.5 h) by itself induced a significant increase in [Sar9,Met(O2)11]-substance P responsiveness. By contrast, it did not change the maximal contraction to acetylcholine. In conclusion, the present study clearly demonstrated that nerve growth factor may participate in the airway hyperresponsiveness induced by interleukin-1β, which supports the neuro-immune cross-talk that may be active in the development of hyperresponsiveness in the human airways, and suggests nerve growth factor is active in the airways in asthma.