Effect of antioxidants on airway smooth muscle contraction: action of lipoic acid and some of its novel derivatives on guinea pig tracheal smooth muscle

Objectives and design

The aim of this study was to investigate the ability of (a) antioxidants, some related to α-lipoic acid (LA), (b) histone deacetylase (HDAC) inhibitors, and (c) hybrid compounds possessing both α-lipoic acid-derived antioxidant properties and HDAC inhibitory activity to inhibit guinea pig smooth muscle contraction.

Materials and methods

Guinea pig isolated tracheal rings (GPTR) were prepared and their isometric tension measured using a transducer. Histamine, carbachol and 5-hydroxytryptamine (5-HT) served as agonists. Tests with antigen (ovalbumin) used GPTR from sensitised guinea pigs or rings from non-sensitised animals that had been incubated for at least 2 h with diluted serum from sensitised animals.

Results

All antioxidants tested showed a relaxant effect on resting tension and on tension induced by histamine or carbachol, with EC₅₀(s) of 0.2–5.0 mM and a rank order of potency: LA derivatives > glutathione (GSH) > ascorbic acid (AA). However, low concentrations (<50 μM) of GSH, AA and LA potentiated histamine-induced contractions. The benzamide HDAC inhibitor MGCD0103 inhibited mast cell activation and GPTR contraction produced by antigen and certain agonists, although a 2–6 h pre-incubation was required for those effects to be apparent. Two LA–benzamide HDAC hybrid compounds, UCL M084 and UCL M109 inhibited GPTR contraction after 30 min pre-incubation; however, even after long pre-incubation (up to 6 h) those hybrid compounds showed less potent inhibition of agonist-induced contraction than did MGCD0103.

Conclusions

The results showed that GSH more potently inhibited contraction induced by histamine than that induced by 5-HT or carbachol, whereas LA, and especially UCL M084 and UCL M109, more potently blocked contraction induced by carbachol and 5-HT than that induced by histamine. For GSH, and possibly also for LA-type compounds, the inhibition of agonist-induced tracheal smooth muscle contractions may be due to NO formation. This study did not detect a synergistic relaxant effect in two compounds incorporating the structural union of a benzamide HDAC inhibitor terminus with a LA-derived antioxidant moiety.

     

Quercetin inhibits anaphylactic contraction of guinea pig ileum smooth muscle

Certain flavonoids inhibit antigen-induced release of histamine from mast cells and basophils and also inhibit contraction of guinea pig ileum induced by histamine, acetylcholine, and PGE2. We examined the effect of one flavonoid, quercetin, on anaphylactic smooth muscle contraction of ileum from guinea pigs sensitized to egg albumin. Quercetin inhibited both the phasic and tonic components of anaphylactic contraction in a concentration-dependent fashion (IC50 approximately 10 microM). Whether this is primarily an effect on mast cell mediator release or inhibition of mediator effects on smooth muscle has not been established.     

Effect of genistein on agonist-induced airway smooth muscle contraction

Inflammation Research - .     

Influence of epithelium on beta-adrenoceptor desensitization of guinea pig tracheal smooth muscle

The effect of tissue incubation with a beta2-agonist of denuded and intact epithelium trachea on the responsiveness to isoprenaline and beta-receptor blocked by propranolol (CR-1) was examined in this study. We examined the effect of epithelium removal on the beta-adrenoceptor desensitization resulting from incubation of guinea pig trachea in the beta-adrenergic agonist isoprenaline (10 microM). Desensitization was measured as the change in EC50, the concentration of beta-agonist that produced 50% relaxation of tracheal rings contracted with methacholine. As a second measure of desensitization, we measured the shift in EC50 resulting from incubation of tracheal rings with the beta-adrenoceptor antagonist propranolol (20 nM), expressed as CR-1 ([post-propranolol EC50/baseline EC50]-1). Initially, we measured desensitization immediately after incubation in isoprenaline; subsequently, we repeated the protocol and allowed a 30 min rest between the end of incubation and the measurement. The sensitivity of denuded epithelium trachea to isoprenaline and (CR-1) was significantly higher than that of intact epithelium only in non-incubated preparations (p<0.05 to p<0.001). Incubation to isoprenaline caused a significant reduction in the tracheal response to isoprenaline in both the denuded groups (p<0.005 for both cases) and intact epithelium groups (p<0.05 for both cases). Incubation to isoprenaline also caused a significant reduction in (CR-1) value in both the denuded groups (p<0.005 for group 2 and p<0.001 for group 4) and intact epithelium only in group 1 (p<0.05). However, the changes in EC50 due to tissue incubation with isoprenaline were significantly greater in denuded than intact epithelium trachea (p<0.05 for all cases) and for CR-1 value only in groups 1 and 2 (p<0.05). These results indicate decrease in both tracheal response to beta-agonist (tolerance) and CR-1 (due to incubation of tissues with isoprenaline), which were greater in denuded epithelium groups.     

Role of amines in anaphylactic contraction of guinea pig isolated smooth muscle

The possible role of acetylcholine (ACh,) histamine (His), and 5-hydroxytryptamine (5-HT) in the contractile response to ovalbumin (Oval) of ileal and tracheal muscle from sensitized guinea pigs was examined. Antagonists to these agents (atropine, mepyramine and methysergide, 5-benzyloxygramine, or 5-HT tachyphylaxis, respectively) were employed singly or in combinations. Care was always taken to ensure specificity of blockade. Results indicate that about half of the peak magnitude of the oval-induced contraction is absent in the presence of a specific inhibitory concentration of mepyramine. This finding suggests that His plays a considerable role in the oval-induced contraction. Contrary to previous reports, similar evidence was not obtained of a role for ACh and 5-HT in the Oval-induced contraction. The source of the agonists released by Oval was also investigated. Pretreatment with compound48/80 almost completely eliminated the Oval-induced contraction of ileal muscle while reducing the tracheal contraction about one-half. It would appear that the Oval-induced ileal contraction involves primarily agonists released from mast cells in the preparation whereas tracheal contraction is only partly dependent on mediators from mast cells.     

Effect of some membrane stabilizing drugs on histamine-induced contraction of guinea pig ileum

The effect of disodium cromoglycate (DSCG), pyridoxine and procaine on histamine-induced contraction of isolated guinea pig ileum was investigated. The antiallergic drug DSCG exerted a protective action on ileum against histamine either when it was present or after it was washed out. Procaine, a local anesthetic exerted a similar pharmacological action on ileum to that of DSCG. On the other hand, pyridoxine protected guinea pig ileum against histamine only when it was present in the bath and this effect quickly disappeared after removing of pyridoxine. The mechanism of action of both DSCG and procaine is discussed in relation to their membrane stabilizing effect and inhibition of calcium transport, whereas effect of pyridoxine resembled to some extent, the action of theophylline.     

Effect of acute cold exposure on lung perfusion and tracheal smooth muscle contraction in rabbit

Acute exposure to cold temperature can affect the respiratory system of those exposed to extreme weather and induces asthma in asthmatic patients. However, the effect on lung perfusion and the pulmonary circulation was not addressed in any previous study. The present study investigates the effects of acute cold exposure on tracheal smooth muscle and lung perfusion. New Zealand White rabbits were used in these experiments. For in vitro experiments, isolated tracheal segments were suspended in organ baths containing Krebs?? solution for isometric tension recording. Tissue response to cooling from 37 to 4°C was examined. For in vivo experiments, the rabbits were kept in a cold room (4°C) for 1?h. Lung perfusion scintigraphy was performed at the end of this period. Each rabbit was injected with 74?MBq (2?mCi) technetium-99m macroaggregated (^99mTc MAA). Perfusion studies were done by using Gamma camera equipped with a low-energy, high-resolution, parallel-hole collimator interfaced with a computer. Static images were acquired 5?min after administration of the radiotracer. Cooling induced a rapid and reproducible contraction in the tracheal smooth muscle. Rabbits exposed to cold temperature had lesser lung perfusion than controls using radionuclide perfusion study. Our results highlight the response of tracheal muscle and pulmonary circulation to cold exposure. These results indicate that cooling induced contraction of the trachea and decreased pulmonary circulation and lung perfusion. This summation of acute cooling for tracheal smooth muscle and pulmonary circulation seems to be the reason for the severe cooling-induced contraction.     

Adenosine potentiates neurally- and histamine-induced contraction of canine airway smooth muscle

We studied the effect of adenosine on airway reactivity of isolated canine bronchial smooth muscle under isometric conditions in vitro. Administration of adenosine and its analogs increased the contractile responses of bronchial segments to electrical field stimulation in a dose-dependent fashion, where the rank order potency was N-ethylcarboxamideadenosine greater than adenosine greater than N-cyclohexyladenosine, but had no effect on those to exogenous acetylcholine. This potentiation was more pronounced at relatively low than at high stimulus frequencies, the maximal increase from the baseline responses being 56.3 +/- 9.6% at 1 Hz (mean +/- SE, p less than 0.01). Adenosine also increased the histamine-induced contraction causing a leftward shift of the histamine dose-response curves, an effect that was abolished in the presence of atropine. These results suggest that adenosine potentiates airway responsiveness to vagal stimulation and to histamine through the activation of prejunctional A2 receptor, probably involving the accelerated release of acetylcholine from the cholinergic nerve terminals.     

Action of ionophore A23187 on the strength of contraction and transmembrane action potential of guinea pig papillary muscle

The calcium ionophore A23187, in a concentration of 2.5 M, caused a two- to threefold increase in the strength of the contraction of the isolated papillary muscle of the guinea pig heart, stimulated at a frequency of 0.2 Hz. The ionophore A23187 reduced the resting voltage of the preparation in the intertrial interval and reduced the total duration of contraction. The increase in the strength of contraction was not accompanied by any change in the amplitude or duration of the transmembrane action potential. In the presence of the ionophore the ascending phase of a single contraction cycle showed a discontinuity separating the development of the twitch into two phases; differentiation of the twitch gave two positive maxima. The substance D-600, which blocks the calcium current, reduced the duration of the action potential and inhibited the second phase of twitch development, but caused no change in the magnitude or rate of the first phase of contraction. It is suggested that under the influence of the ionophore the component of the twitch which is not blocked by D-600 is caused by liberation of calcium from the sarcoplasmic reticulum.Laboratory of Electrophysiology of the Heart and Laboratory of Myocardial Metabolism, All-Union Cardiologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. Department of Pharmacology, Vanderbilt University, Nashville, USA. (Presented by Academician of the Academy of Medical Sciences of the USSR V. V. Zakusov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 6, pp. 690–693, June, 1978.     

Antigenic contraction of guinea pig tracheal preparations passively sensitized with monoclonal IgE: pharmacological modulation

Spirally cut guinea pig tracheal preparations were passively sensitized using a mouse monoclonal IgE antibody against dinitrophenol (DNP). Maximal contraction observed following challenge with DNP-bovine serum albumin (DNP-BSA, 5 micrograms/ml; n = 20) response was approximately 46% of the histamine response (0.52 +/- 0.09 g/mm2; n = 53). Indomethacin (1.7 microM) increased and PGE2 (1 microM) decreased the response to the antigen. FPL 55712 (10 microM), atropine (0.1 microM), L 651392 (5 microM) or tripelennamine (1 microM) always reduced the maximal DNP-BSA response, but not BN 52021 (100 microM). This model may be used for rapid detection of compounds with antiallergic properties on IgE-dependent lung pathological states.     

Innervation of tracheal epithelium and smooth muscle by neurons in airway ganglia

The neurochemical profiles of neurons in ferret tracheal ganglia has been characterized, but their projections to smooth muscle and epithelium in ferret trachea has not been examined. The purpose of this study is to determine the location of cell bodies that project VIP‐, SP‐, and NPY‐containing fibers to the ferret tracheal smooth muscle and epithelium. Segments of ferret trachea were cultured for 0, 1, 3, or 7 days, some in the presence of 3 μm capsaicin. VIP, SP, or NPY nerve fiber density was measured using morphometric procedures. A retrograde tracer, rhodamine‐labeled microspheres, identified neurons projecting to the epithelium. The density of SP fibers in the epithelium was reduced after culture, but VIP innervation was not different. In tracheal smooth muscle, the density of VIP‐ and SP‐IR fibers was not different during the culture period, but NPY fiber density was reduced at all culture times. Capsaicin treatment did not affect nerve fiber density in the tracheal smooth muscle but produced a significant reduction in the density of epithelial VIP‐ and SP‐IR nerve fibers after 1 day. Rhodamine‐labeled microspheres were identified in VIP‐containing nerve cell bodies of the ferret tracheal plexus. VIP innervation to the airway epithelium in ferret originates both from cell bodies in airway ganglia and cell bodies in sensory ganglia. The pathway from airway ganglia suggest the existence of a local reflex mechanisms initiated by epithelial irritation. Anat Rec 254:166–172, 1999. © 1999 Wiley‐Liss, Inc.     

聚乙二醇化重组人生长激素对离体豚鼠乳头肌细胞动作电位的影响

目的 探讨聚乙二醇化重组人生长激素(PEG-rhGH)对离体豚鼠乳头肌细胞动作电位的影响,并以重组人生长激素(rhGH)为阳性对照物比较二者的体外生物活性.方法 健康雄性DHP豚鼠12只,随机分为2组,PEG-rhGH干预组和rhGH干预组,每组6只.采用累计给药法和给药前后自身对照方法,分别观察不同质量浓度(1、5、...     

A comparison of the beta-blocking activities of practolol, sotalol, and propranolol in human and guinea pig tracheal smooth muscle

Beta adrenergic blockade was studied in vitro with hitman tracheal muscle strips and guinea pig tracheal chains. It was shown in isolated smooth muscle from both man and guinea pig that the order of potency for the three beta-blocking agents studied was: propranolol > sotalol > practolol. Under the conditions of this study, propranolol was about 30,000 times and sotalol about 30 times as potent as practolol. The order of potency suggests that the nature of adrenergic blockade induced by practolol on tracheal smooth muscle is only weakly beta₂-relative to the blocking effects of propranolol and sotalol. Beta adrenergic blockade by propranolol, sotalol, and practolol produced different degrees of increased histamine lethality in mice. Whereas both propranolol at 0.01 mg/kg and sotalol at 1.0 mg/kg resulted in 100% histamine-induced lethality, practolol at 50 mg/kg resulted in only 50% histamine-induced lethality. These data, when added to those from our previous studies, suggest that the mechanisms responsible for resistance to the effects of histamine in untreated mice are at least partially mediated by the beta₂-adrenergic system. Thus, in three different tissues, the blocking activity of practolol was shown to be less than that of sotalol or propranolol.     

Effect of papaverine on tone and contractions of the depolarized smooth muscle of the guinea pig taenia coli

Experiments were carried out on isolated strips of guinea pig taenia coli. The smooth muscle was depolarized in a solution with high potassium concentration (120 mM KCl). The effect of papaverine (in concentrations of 10^–5 to 3.10^–5 g/ml) on the tone and off-response to a prolonged and strong hyperpolarizing current was investigated on the denervated muscle. Papaverine was found: 1) to abolish contractile responses to application of histamine, bradykinin, and acetylcholine; 2) to reduce the tone of the depolarized muscle and abolish the effect of an increase in the Ca⁺⁺ concentration in the external medium on muscle tone; 3) to have no effect on the amplitude and velocity of the ascending phase of the off-response; 4) to accelerate the descending phase of the off-response. The following hypotheses are put forward to explain the result: 1) in the cell membrane there are chemically excitable calcium channels which are blocked by papaverine; 2) in the membrane there are calcium leakage channels responsible for the maintenance of tone and blocked by papaverine; 3) papaverine has negligible effect on electrically excitable calcium channels.A. V. Vishnevskii Institute of Surgery, Academy of Medical Sciences of the USSR, Moscow. Bio-Inorganic Chemicals BIKhS Research Institute, Kupavna, Moscow Region. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Fedorov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 2, pp. 177–180, February, 1978.