Current opinion of muco-active drug research: strategies and problems

The in-vivo effect of bakumondo-to (TJ-29), a traditional Japanese medicine used for treatment of chronic airway disease, on cytochrome P450 1A2, xanthine oxidase and N-acetyltransferase 2 activity in man

In Japan, patients with chronic airway disease are administered bakumondo-to (TJ-29), a mixture of six herbal components. We have assessed the effects of TJ-29 on the activities of cytochrome P450 (CYP) 1A2, xanthine oxidase and N-acetyltransferase 2 in 26 healthy subjects under a double-blind, randomized, placebo-controlled cross-over study design. The baseline activities of the three enzymes were assessed by the respective urinary metabolic ratios of an 8-h urine sample after an oral 150-mg dose of caffeine. Thereafter, the subjects received a thrice-daily 3.0-g dose of TJ-29 or placebo for seven days, and underwent the same caffeine test on the post-dose days 1 and 7. No statistically significant difference was observed in the activity of the three enzymes between those at baseline, and on day 1 after dosing with TJ-29 or placebo. The mean activity of CYP1A2, xanthine oxidase and N-acetyltransferase 2 tended to be lower on day 7 after dosing with TJ-29 compared with those at baseline and on day 7 after dosing with placebo. However, these changes were not statistically significant in CYP1A2 (P=0.120), xanthine oxidase (P=0.123) or N-acetyltransferase 2 (P=0.056). In conclusion, TJ-29 did not appear to substantially affect the activity of CYP1A2, xanthine oxidase or N-acetyltransferase 2 in man.

Eficácia antitussígena de duas formulações fitoterápicas

Avaliaram-se os efeitos antitussígenos-expectorantes de duas formulações fitoterápicas utilizando-se três modelos biológicos diferentes. Foram utilizados ratos Wistar no modelo da secreção das vias aéreas, cobaias no modelo de tosse induzido por ácido cítrico e codornas japonesas na determinação da velocidade de transporte mucociliar. Os animais foram distribuídos em grupos e tratados por via oral com as formulações, com doses equivalentes a 10 vezes a terapêutica recomendada, 9ml.kg-1. O grupo-controle negativo de cada espécie foi tratado com solução fisiológica, 10ml.kg-1. O grupo-controle positivo no modelo de tosse induzida pelo ácido cítrico foi tratado com morfina, 1mg.kg-1, por via subcutânea. No modelo em que foram utilizados ratos e codornas, o grupo-controle positivo recebeu erdosteína por via oral, 600mg.kg-1. Os resultados mostraram que as duas formulações fitoterápicas foram eficazes no reflexo da tosse em cobaias, causando 36,4% e 27,3%, respectivamente, de redução. Nos modelos de secreção das vias aéreas e determinação da velocidade de transporte mucociliar, ambas as formulações não apresentaram eficácia significativa.

Pharmacological Basis of Traditional Medicines and Health Supplements as Curatives

Traditional Oriental medicines and health supplements have been empirically used to treat various ailments but most of them have not been evaluated objectively to prove their efficacies. We have been investigating the medical benefits of traditional Oriental medicines and health supplements as alternatives and their varied actions and mechanisms by pharmacological approaches. The study on airway inflammation has shown that even a Kampo preparation, Bakumondo-to, has anti-inflammatory, anti-allergic, immunomodulatory, secretory-modulating, and metabolic regulatory actions. All of its actions are based on the restoration of normal molecular and cellular functions through DNA transcriptional regulation. In other previous studies, we showed that a health supplement, royal jelly (RJ) has weak estrogenic activity. RJ competes with 17beta-estradiol for binding to the human estrogen receptors alpha and beta, although it is much weaker than diethylstilbestrol in binding affinity. Treatment of MCF-7 cells with RJ enhances proliferation, and concomitant treatment with tamoxifen blocked this effect. A reporter gene assay showed that RJ enhanced transcription of the luciferase gene through the estrogen-responsive element in MCF-7 cells. Furthermore, subcutaneous injection of RJ restored the expression of vascular endothelial growth factor gene in the uteri of ovariectomized rats. We suggest that the diverse pharmacological functions of RJ can be ascribed, in part, to its estrogenic effects. We hypothesize that traditional medicine, which has multiple actions, may be better than Western medicine of a single component to treat various diseases including "Mibyou" (presymptomatic disease). Our findings provide new ideas about the nature of disorders nd disease-state development that involve complicated mechanisms and will contribute to novel principles to prevent diseases and establish new treatments. Adoption of the means of translational research should provide an objective background for efficacy and stimulate broader application and usage of traditional medicines and health supplements.

Effects of carbocisteine on altered activities of glycosidase and glycosyltransferase and expression of Muc5ac in SO2-exposed rats

Carbocisteine is a mucoregulatory drug regulating fucose and sialic acid contents in mucus glycoprotein. To investigate the mechanism of carbocisteine action, we evaluated the effects of carbocisteine on the activity of fucosidase, sialidase, fucosyltransferase and sialyltransferase, and on the expression of Muc5ac mRNA in the airway epithelium of SO(2)-exposed rats. Wistar rats were repeatedly exposed to a 300-ppm SO(2) gas for 44 days. Carbocisteine (125 and 250 mg/kg x2/day) was administered for 25 days after 20 days of SO(2) gas exposure. These enzyme activities were measured by fluorogenic substrate or glycoproteinic exogenous acceptor method. The expression levels of Muc5ac mRNA and protein were determined with real-time reverse transcriptase-polymerase chain reaction (real-time RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Carbocisteine (250 mg/kg x2/day) inhibited all the changes in these enzyme activities and the expressions of Muc5ac mRNA and protein in the lung after repeated SO(2) exposure. These findings suggest that carbocisteine may normalize fucose and sialic acid contents in mucin glycoprotein through regulation of these enzyme activities, and inhibition of both Muc5ac mRNA and protein expressions in SO(2)-exposed rats.

Novel Approach to Respiratory Pharmacology—Pharmacological Basis of Cough, Sputum and Airway Clearance

Disturbance of the normal mucociliary clearance due to hyperproduction of mucus and modification of its physicochemical characteristics is a common finding in airway diseases. Drugs that affect airway secretion have been developed and used to cleanse the respiratory tract for many centuries and in many countries. On the basis of the mechanism of their actions, the mucoactive drugs are classified into several groups. Some mucoactive drugs have direct effects on the production or composition of airway secretions, resulting in increased effectiveness of mucociliary clearance. Other mucoactive drugs do not have a specific action on mucus, but have beneficial effects on airway structure and function, which lead to correction of the pathophysiologic mechanisms that result in abnormal secretions. However, since many drugs have overlapping effects, it is difficult to classify these drugs into groups based on their major actions. Taken together with previous findings on mucoactive drugs, it appears that an antioxidant effect is a common property of mucoactive drugs and that it is a crucial action to exert their effects against airway diseases. In light of this idea, we must use specific experimental models to simulate pharmacologic events in airway inflammation. The development of new techniques has made it possible to identify and measure the mucus components, measure the rheologic parameters more accurately, and evaluate mucociliary clearance precisely in animals and humans. Therefore, with modifications of methods, we have investigated airway-cleansing drugs from various points of view to reflect actions in inflammatory states for more than two decades. Here, I introduce the methods we have used to study many of the parameters involved in airway clearance, including cough reflex, and describe some of the mucoactive-antitussive drugs that we have studied recently. There is an increasing usage of traditional Chinese herbal medicines in clinics and hospitals, because they tend to have moderate side effects and sometimes remarkable efficacy. To renormalize overall defects in airway disorders, Chinese medicines may be adequate, because they are composed of various herbs with weak but ubiquitous pharmacologic activities. We have been investigating Bakumondo-to. Bakumondo-to has been used for the treatment of bronchitis and pharyngitis accompanying severe dry cough. We found that unlike codeine Bakumondo-to had a notable antitussive activity against the cough associated with bronchitis and the cough increased by angiotensin-converting enzyme inhibitors. Recently, we have found that, in alveolar type II cells, Bakumondo-to attenuated phosphatidylcholine secretion increased by oxygen radicals from activated PMNLS. In addition, we found that Bakumondo-to itself stimulated phosphatidylcholine secretion and increased beta-adrenoceptor gene expression in rat alveolar type II cells. We studied the mechanism of action and clarified that Bakumondo-to increased glucocorticoid-sensitive promotor activity. The effect may contribute to its ubiquitous effectiveness in the treatment of airway diseases. Various parameters (chemical properties, physical properties, mucus production, surfactant phospholipid production, and mucociliary clearance) are considered to be important for the dynamics and mobilization of airway secretions. Pharmacologic investigation, with appropriate techniques, of the ability of an agent to modify these parameters can provide useful information about its mechanism of action. However, since these parameters are interconnected, it is very complicated to elucidate the precise mechanisms of action of mucoactive drugs. This means that the goal of treatment cannot always be achieved by the modification of a single parameter, but should, more realistically, be aimed at a renormalization of several parameters. On the basis of this idea, glucocorticoids are ideal mucoactive drugs because they exert various pharmacologic effects in the lung. From a polypharmacologic point of view, a traditional Chinese medicine can be classified as a glucocorticoid-like drug because Chinese medicines consist of many types of active components that have various pharmacologic effects. As one future course of research, we believe that efforts to seek compatible actions between glucocorticoids and Oriental medicines may lead to new opportunities for development of ideal airway-cleansing drugs with specific actions, i.e., suppression of gene expression.

Traditional oriental herbal medicine, Bakumondo-to, suppresses vagal neuro-effector transmission in guinea pig trachea

OBJECTIVE

Bakumondo-to (Maimendong tang) is a traditional oriental herbal medicine that has been used as an antitussive agent. We previously demonstrated that Bakumondo-to attenuates airway hyperresponsiveness induced by ozone. However, the mechanism(s) responsible for this effect remains unclear. In the present study, we examined the mechanism whereby Bakumondo-to inhibits ozone-induced airway hyperresponsiveness. First, we examined the effect of Bakumondo-to on prostanoids production, which are key mediators to airway hyperresponsiveness after ozone exposure. Second, we studied its effects on the vagal neuroeffector transmission, because vagal nerve is likely to play an important role in airway hyperresponsiveness after ozone.

METHODS

We measured the effects of Bakumondo-to on the concentrations of prostanoids in bronchoalveolar lavage fluid before and after ozone. We evaluated the effects of Bakumondo-to on the contraction of guinea pig tracheal smooth muscle evoked by electrical field stimulation (EFS) or the exogenous application of acetylcholine (ACh). Isometric tension of tracheal strips was measured in the presence of indomethacin (10(-6) M) and of guanethidine (10(-6) M).

RESULTS

Ozone caused significant increase in prostaglandin E2 (PGE2) and thromboxane B2 (TXB2); however, Bakumondo-to did not affect the increase in these prostanoids. Bakumondo-to (0.01 mg/mL-1 mg/mL) significantly suppressed the contraction evoked by EFS, but did not affect the ACh-evoked contraction, indicating that Bakumondo-to suppressed tracheal smooth muscle contraction pre-junctionally.

CONCLUSION

These results suggest that the mechanism by which Bakumondo-to inhibits airway hyperresponsiveness depends on inhibiting the release of acetylcholine from vagal nerve terminals.

Pharmacology of airway goblet cell mucin release

Airway mucus hypersecretion is one of the major clinical manifestations of patients suffering from various pulmonary diseases. However, no drugs are yet available to control airway mucus hypersecretion. For the past 15 years, a plethora of information has amassed with regard to the pharmacology of airway goblet cell mucin secretion using various primary cell culture systems. The recent discovery of various MUC genes has also greatly stimulated research in this field. Nevertheless, the heterogeneity of the oligosaccharide structure of mucin molecules makes it extremely difficult to assess the significance of the information derived from the pharmacological studies. Therefore, it seems crucially important to understand the roles of individual mucins in conjunction with normal airway physiology and pathology, which should be the future research directions necessary for studying airway goblet cell mucin pharmacology.

The effects of intravenously administered methylxanthine preparations on the glycoconjugate composition of goblet cells in rabbit tracheal epithelium

Effects of methylxanthine derivatives, which are inhibitors of phosphodiesterases I-IV used against bronchial asthma, on the composition of glycoconjugates in goblet cells were evaluated in tracheal epithelium of rabbits at 15 and 30 min after intravenous administration of aminophylline (Syntophyllin) and a mixture of etophylline and theophylline (Oxantil), respectively. Percentages of tracheal goblet cells containing neutral, total acidic, sulphated acidic, and sialylated acidic glycoconjugates were assessed using both conventional and lectin histochemistry. No significant changes were found in both experimental groups at 15 min after exposure. A significant decrease in percentage of alpha(2-3)-sialylated glycoconjugate-containing goblet cells occurred at 30 min after administration of Syntophyllin only. It is concluded that the mucus composition of tracheal goblet cells has been affected by the bronchospasmolytic drug Syntophyllin but not by the vasodilator drug Oxantil.

Protective effect of erdosteine against hypochlorous acid-induced acute lung injury and lipopolysaccharide-induced neutrophilic lung inflammation in mice

The effect of erdosteine, a mucoactive drug, on hypochlorous acid (HOCl)-induced lung injury, and the lipopolysaccharide (LPS)-induced increase in tumour necrosis factor-alpha (TNF-alpha) production and neutrophil recruitment into the airway, was investigated. Male BALB/c mice were orally administered erdosteine (3-100 mgkg(-1)), ambroxol hydrochloride (ambroxol) (3-30 mgkg(-1)), S-carboxymethyl-L-cysteine (S-CMC) (100-600 mgkg(-1)) or prednisolone (10 mgkg(-1)), 1 h before intratracheal injection of HOCl or LPS. In the HOCl-injected mice, erdosteine markedly suppressed increases in the ratios of lung wet weight to bodyweight and lung dry weight to bodyweight, whereas the other mucoactive drugs ambroxol and S-CMC had little effect. Erdosteine also inhibited the LPS-induced neutrophil influx, although it did not affect the increased level of TNF-alpha in the bronchoalveolar lavage fluid. The results suggest that attenuation of reactive oxygen species and neutrophil recruitment is involved in the clinical efficacy of erdosteine in the treatment of chronic bronchitis.

Effect of the Chinese herbal medicine, Bakumondo-to, on airway hyperresponsiveness induced by ozone exposure in guinea-pigs

OBJECTIVE

Bakumondo-to (Maimendong tang) is a Chinese herbal medicine that has been used as an anti-tussive agent. However, the effects of Bakumondo-to on airway hyperresponsiveness are unknown. We examine whether Bakumondo-to can inhibit airway hyperresponsiveness induced by ozone.

METHODOLOGY

Measurements of airway responsiveness and plasma extravasation and bronchoalveolar lavage (BAL) were performed before and after ozone exposure (3 p.p.m., 2 h). Guinea-pigs were anaesthetized with pentobarbital sodium and mechanically ventilated. Airway responsiveness was determined by an inhalation of doubling concentration of histamine, and the concentration of histamine required to produce a 200% increase in R(L) (PC200) was calculated by log-linear interpolation. Plasma extravasation was evaluated by measuring the extravasation of Evans blue dye in the airway.

RESULTS

Ozone produced significant airway hyperresponsiveness and plasma extravasation, with an influx of neutrophils in BAL fluid. Bakumondo-to (400 mg/kg p.o.) significantly inhibited airway hyperresponsiveness, but had no effect on neutrophil influx or plasma extravasation.

CONCLUSIONS

We demonstrated that Bakumondo-to can attenuate airway hyperresponsiveness induced by ozone without affecting airway inflammation, which suggests that Bakumondo-to may act on the subsequent mechanisms after the induction of inflammation, such as mediator release.

Mucolytic and antitussive effects of erdosteine

To investigate the influence of erdosteine, a new homocysteine-derived expectorant, on airway clearance we studied the effects of the drug on the viscosity of mucin, on the mucociliary transport rate in quails, on airway secretion in rats and on the cough reflex in guinea-pigs. The active metabolite of erdosteine, M1 (10 microM to 1 mM), significantly reduced the viscosity of porcine stomach mucin. Erdosteine by itself did not reduce viscosity. Erdosteine significantly promoted mucociliary transport in quails and increased airway secretion in rats. The effect was still apparent 24h after administration. Erdosteine significantly suppressed citric acid-induced cough reflexes in guinea-pigs but did not suppress mechanical stimuli-induced cough reflexes. Erdosteine suppressed the reduction of the recovery volume of bronchoalveolar lavage fluid and albumin leakage into the fluid in citric acid-exposed guinea-pigs. These results indicate that erdosteine removes sputum by reducing its viscosity, and by promoting mucociliary transport and sustained enhancement of airway secretion. It also suppressed the chemical stimulation-induced cough reflex and plasma leakage into the airway. These results suggest that erdosteine is an excellent expectorant with several modes of action.