Interaction between -adrenergic stimulant and phosphodiesterase inhibiting drugs on the bronchial muscle

Antiallergic and antihistaminic actions of Ceasalpinia bonducella seeds: Possible role in treatment of asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Seed kernel of the plant Ceasalpinia bonducella Linn (Caesalpiniacaeae) are used for the treatment of asthma in folk medicine and ancient books.

AIM OF STUDY

To assess the pharmacological efficacy of the plant in asthma and to confine and describe the synthetic constituents from the seeds that are in charge of the action.

MATERIAL AND METHODS

The viability of petroleum ether, ethanol extract and ethyl acetate fraction from ethanol extract of C. bonducella seeds were screened for the treatment of asthma by various methods viz. effect of test drug on clonidine and haloperidol induced catalepsy, milk-induced leukocytosis and eosinophilia, mast cell stabilizing activity in mice and studies on smooth muscle preparation of guinea pig ileum (in-vitro). Column chromatography of active extract was done to pinpoint the active compound followed by structure elucidation by FTIR, GCMS and NMR spectroscopic methods.

RESULTS

Ethyl acetate fraction from ethanol extract of C. bonducella seeds exhibited antihistaminic activity at the dose of 50 and 100 mg/kg, inhibited clonidine-induced catalepsy but not haloperidol-induced catalepsy. Ethyl acetate fraction from ethanol extract significantly inhibited increased leukocyte and eosinophil count due to milk allergen and showed maximum protection against mast cell degranulation by clonidine. The results of guinea pig ileum indicated that the compound 2 methyl, 1 hexadecanol isolated from ethyl acetate fraction of ethanol extract relaxed significantly the ileum muscle strips pre-contracted by which suggests the involvement of β₂-agonists on the relaxation of the tissue. All the results are dose dependent. Active ethyl acetate fraction from ethanol extract showed presence of anti-asthmatic compound, 2-methyl, 1-hexadecanol.

CONCLUSION

The ethyl acetate fraction from ethanol extract of seeds of the plant C. bonducella can inhibit parameters linked to asthma disease.

Antihistaminic and antiallergic actions of extracts of Solanum nigrum berries: possible role in the treatment of asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Berries of the plant Solanum nigrum Linn (Solanaceae) are used for the treatment of asthma in folk medicine and ancient books.

AIM OF STUDY

To evaluate potential of the plant berries in the treatment of asthma.

MATERIALS AND METHODS

Petroleum ether, ethanol and aqueous extracts of S. nigrum berries (50, 100 and 200mg/kg, i.p.) were screened for the treatment of asthma by the various methods viz. effect on clonidine and haloperidol induced catalepsy, milk-induced leucocytosis and eosinophilia, mast cell stabilizing activity in mice and studies on smooth muscle preparation of guinea pig ileum (in vitro). Active petroleum ether extract was standardized by HPTLC.

RESULTS

The petroleum ether extract of S. nigrum berries inhibited clonidine-induced catalepsy significantly but not haloperidol-induced catalepsy. Petroleum ether extract significantly inhibited increased leukocyte and eosinophil count due to milk allergen and showed maximum protection against mast cell degranulation by clonidine. Petroleum ether extract resisted contraction induced by histamine better than other extracts. All the results are dose dependant. Active petroleum ether extract showed presence of antiasthmatic compound, β-sitosterol.

CONCLUSION

The petroleum ether extract of S. nigrum berries can inhibits parameters linked to the asthma disease.

The effect of smooth muscle relaxants working through different transduction mechanisms on the phorbol dibutyrate-induced contraction of the guinea-pig lung parenchymal strip: possible relevance for asthma

It has been suggested that protein kinase C activation may have a role in the maintained, 'latch-bridge' phase of smooth muscle contraction. We have examined the effects of a range of smooth muscle relaxants on the maintained contraction produced in the guinea-pig parenchymal lung strip by the protein kinase C activator, 4 beta-phorbol dibutyrate (4 beta-PDBu). The maximum histamine contraction (produced by 10 microM) was used as a standard and the effects of the smooth muscle relaxants were also studied on this histamine-induced contraction. After 4 beta-PDBu, 1 microM, had produced contraction, enprofylline, forskolin and papaverine caused concentration-dependent relaxation, producing total reversal of the contraction, while prostaglandin E2 and prostacyclin caused a concentration-dependent relaxation but less than total reversal. The concentrations required for the effects on the phorbol ester contraction were 10 to 100-fold higher than were necessary for relaxation of the maximum contraction produced by histamine. Isoprenaline, 1 microM, a concentration which caused total reversal of the histamine-induced contraction, caused only 22% decrease of the phorbol dibutyrate-induced contraction and no further relaxation occurred with higher concentrations. Cromakalim--a potassium channel activator proposed as a therapy for nocturnal asthma--had virtually no effect on preparations pre-contracted with 4 beta-PDBu, 1 microM, or histamine, 10 microM, but caused about 70% and 20% reversal of the contraction produced by 3 microM histamine and 100 nM 4 beta-PDBu respectively. When single doses of the relaxants were administered before a series of doses of 4 beta-PDBu given cumulatively, enprofylline, 1 microM, and aminophylline, 100 microM and 1 microM, caused a moderate right-shift of the phorbol dibutyrate concentration-response curve, but isoprenaline, 1 microM, was less effective, while cromakalim had no discernible effect. These results are discussed in the light of suggestions that inappropriate activation of protein kinase C in smooth muscle cells, may contribute to the pathogenesis of the late phase of asthma.

Inhibitory effects of a lipoxygenase inhibitor nordihydroguaiaretic acid on antagonism of leukotriene C4-induced contractions of isolated guinea-pig trachea

We have studied the effects of a lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) on antagonism of leukotriene (LT) C4-induced contractions of isolated guinea-pig trachea and the results were compared to that of a cyclooxygenase inhibitor indomethacin. NDGA (30 microM) as well as indomethacin (5 microM) inhibited LTC4-induced contractions. But, in the presence of indomethacin NDGA was ineffective to inhibit the LTC4 response, whereas two other lipoxygenase inhibitors, phenidone (3-30 microM) and 5,8,11,14-eicosatetraynoic acid (ETYA, 10 microM), markedly inhibited it. The antagonist action of an LTD4 receptor antagonist FPL55712 against LTC4-induced contractions was significantly reduced by NDGA (10-30 microM), but indomethacin had no effect on it. NDGA possessed the same inhibitory effect on the LTC4 antagonism in the presence of indomethacin, but 0.3 microM phenidone and 1 microM ETYA which did not inhibit the LTC4 response had no effect on it. NDGA also inhibited the relaxant response of isoproterenol on the contraction elicited by 30 nM LTC4, but did not affect those of forskolin and aminophylline. The relaxant response of isoproterenol on the LTC4 response was not inhibited by indomethacin, 0.3 microM phenidone and 1 microM ETYA. In the presence of a gamma-glutamyltranspeptidase inhibitor, L-serine borate (SB, 45 mM), NDGA had no effect on the LTC4 antagonism and the relaxant response of isoproterenol. In contrast, NDGA significantly inhibited the relaxant response of isoproterenol on 30 microM histamine- and 30 microM acetylcholine-induced contractions, but it did not affect the histamine antagonism by a histamine H1-blocker pyrilamine. These results suggest that some putative non-prostanoids are involved in LTC4-induced contractions of guinea-pig trachea and which regulate the effects of LTD4 antagonism and beta-adrenoceptor activation.

Bronchodilator and antiallergy activity of forskolin

Forskolin is a diterpene from the roots of Coleus forskohli which directly activates the adenylate cyclase and raises cyclic AMP levels in a variety of tissues. Forskolin was studied for its effects on the tone of airway smooth muscle and the immunologic release of leukotrienes and histamine. The bronchospasm induced by inhaled antigen in sensitized guinea pigs was prevented in a dose-related fashion by the intravenous (i.v.) or intratracheal administration of forskolin. Forskolin was more potent than aminophylline and less potent than salbutamol. There was no evidence that forskolin would potentiate the in vivo bronchodilator effects of either salbutamol or aminophylline. Forskolin was approximately 100 times more potent than aminophylline by the i.v. and intratracheal routes to reverse an established allergic bronchospasm. Forskolin given intratracheally also inhibited the bronchospasm to i.v. histamine, with a short duration of action. In vitro forskolin (less than 1 microM) inhibited contractions of lung parenchyma provoked by histamine, LTC4 or antigen. Forskolin (1 microM) also inhibited the immunologically stimulated release of LTD4 and histamine from sensitized guinea pig lung. These studies show that forskolin shares with other agents that elevate cyclic AMP levels the ability to relax airway smooth muscle and inhibit mediator release in vitro and elicit a bronchodilation in vivo.

Dissociation between the effects of some xanthine derivatives on the tracheal smooth muscle and on the skeletal muscle

The ability of some xanthine derivatives to relax the trachea, contracted by pilocarpine, and to increase the force of contraction of directly stimulated skeletal muscles from the guinea-pig was studied in vitro. No relationship was found between these two effects. Relaxation of the trachea occurred at lower concentrations and with a different order of potency as compared with the effects on the slow-contracting soleus muscle or on the fast-contracting extensor digitorum longus. One of the compounds, IBMX, 1-methyl-3-isobutyl-xanthine, showed an isoprenaline-like effect on the soleus muscle i.e. it depressed the force and fusion of subtetanic contractions. The relaxing effect of theophylline and IBMX on the trachea was additive to that of terbutaline but no clear potentiation was observed. The depression of the contraction of the soleus muscle elicited by terbutaline was reinforced by IBMX but not by theophylline. Theophylline in concentrations which used alone enhanced the contractions of the soleus muscle inhibited the effect of terbutaline. We conclude that the relative contribution of the various effects of xanthine derivatives differs from compound to compound.

Combination bronchodilators: antagonism of airway smooth muscle contractions in vitro

The component drugs of fixed-dose combination bronchodilators may interact in a synergistic manner to antagonize airway contractions. To examine this hypothesis, combinations of ephedrine (E) and theophylline (Th) or salbutamol (S) and theophylline were tested for their ability to relax contracted guinea-pig airway smooth muscle in vitro. The combination bronchodilator effect was compared to the summed effects of the component drugs given individually (i.e. a theoretical additive response, Ta). Relaxation responses to combination bronchodilators were considered less-than-additive if significantly less than Ta, additive if non-significant and greater-than-additive or synergistic if the values were significantly greater than Ta. It was found that the E-Th combinations interacted primarily in an additive fashion to relax contractions induced by histamine, acetylcholine and 5-hydroxytryptamine at concentrations that produced one-half maximal contractile response (ED50). Similarly S-Th combinations interacted in an additive manner to reverse histamine and acetylcholine contractions. In the case of both E-Th and S-Th combinations, the drugs were more effective in reducing the smooth muscle contractions when given during rather than prior to the response. It may be concluded that beta-sympathomimetics and methylxanthines when combined do not interact in a synergistic fashion to produce relaxation of contracted airway smooth muscle.