The effects of Ma-Xing-Gan-Shi-Tang on respiratory resistance and airway leukocyte infiltration in asthmatic guinea pigs.

Ma-Xing-Gan-Shi-Tang (MXGST), a traditional Chinese medicine, has been used in treatment of the bronchial asthma for several centuries. However, the therapeutic mechanisms of this Chinese medicine are still far from clear. To understand the mechanism of anti-asthmatic property of MXGST, a guinea pig model of allergic asthma was used to investigate the effects of MXGST on Dermatophagoides pteronyssinus-induced early and late asthmatic responses and airway inflammation, and examine direct beta2-adrenoceptor agonist activity in guinea-pig isolated trachea. Administration of MXGST (10 g/kg) extracts significantly inhibited the antigen induced immediate asthmatic responses (IAR) in actively sensitized guinea pig. MXGST caused concentration-dependent relaxation in strips of guinea pig trachea contracted with carbachol, and ICI-118551, a selective beta2-adrenoceptor antagonist, significantly inhibit the relaxation caused by MXGST. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that MXGST significantly inhibited the increase in neutrophil in the airway at 1, 6 and 24 hr after antigen challenge. Histopathologic examination results showed that MXGST suppressed the neutrophil infiltration into lung tissue. In conclusion, we suggest that the anti-asthmatic effects of MXGST are mainly due to its stimulation of beta2-adrenoceptors on bronchial smooth muscle and its anti-inflammatory ability to inhibit the neutrophil into the airway. The precise mechanism of action of MXGST in asthma remains to be elucidated.

Luteolin-inhibited arylamine N-acetyltransferase activity and DNA-2-aminofluorene adduct in human and mouse leukemia cells.

N-Acetyltransferase enzyme is an important enzyme in the first step of arylamine compounds metabolism. Luteolin has been shown to exit antibacterial and antineoplastic activity. The purpose of this present study is to evaluate the question of whether luteolin could affect arylamine N-acetyltransferase (NAT) activity and DNA-2-aminofluorene adduct formation in human (HL-60) and mouse (L1210) leukemia cells. By using HPLC, N-acetylation of 2-aminofluorene was determined. Luteolin displayed a dose-dependent inhibition to cytosolic NAT activity and intact human and mice leukemia cells. Time-course experiments showed that N-acetylation of 2-aminofluorene measured from intact human and mice leukemia cells were inhibited by luteolin for up to 24 hours. Using standard steady-state kinetic analysis, it was demonstrated that luteolin was a possible uncompetitive inhibitor to NAT activity in cytosols. The DNA-2-aminofluorene adduct formation in human and mouse leukemia cells were inhibited by luteolin. This report is the first demonstration to show that luteolin affects human and mice leukemia cells NAT activity and DNA-2-aminofluorene on adduct formation.

Luteolin inhibits the growth and arylamine N-acetyl-transferase activity in Neisseria gonorrhoeae.

Growth inhibition and arylamine N-acetyltransferase (NAT) activity in Neisseria gonorrhoeae were inhibited by luteolin, a drug which originated from herbs. The growth inhibition was based on changes in optical density (OD) using a spectrophotometer, and arylamine NAT activity with 2-aminofluorene (2-AF) was determined using high pressure liquid chromatography. The inhibition of growth in N. gonorrhoeae demonstrated that luteolin elicited a dose-dependent growth inhibition in the N. gonorrhoeae cultures. Suspensions of N. gonorrhoeae with or without specific concentrations of luteolin cotreatment showed different percentages of 2-AF acetylation. The data indicated that there was reduced NAT activity associated with increased levels of luteolin in N. gonorrhoeae suspensions. Time-course experiments showed that NAT activity measured from intact N. gonorrhoeae cells was inhibited by luteolin for at least 4 h. Using standard steady-state kinetic analysis, it was demonstrated that luteolin was a possible uncompetitive inhibitor to NAT activity in N. gonorrhoeae. This report is the first to show that luteolin can inhibit N. gonorrhoeae NAT activity.

Anti-inflammatory and neuroprotective effects of magnolol in chemical hypoxia in rat cultured cortical cells in hypoglycemic media.

Our previous studies demonstrated that magnolol protects neurons against chemical hypoxia by KCN in cortical neuron-astrocyte mixed cultures (14). In the present study, we examined whether the neuroprotective effect of magnolol involve modulating inflammatory mediators, prostaglandin E2 (PGE2) and nitric oxide (NO), induced by KCN (hypoxia) or KCN plus lipopolysaccharide (LPS). In glucose-absent (hypoglycemia) media, KCN or KCN plus LPS induced increases in lactate dehydrogenase (LDH) activity by 32% and 34%, and PGE2 production by 12% and 32%, respectively. Both LDH and PGE2 increases were suppressed by 100 microM magnolol. In addition, although KCN or LPS alone did not increase NO generation, KCN plus LPS increased NO generation. This increase was reduced by 100 microM magnolol or 10 microM L-NAME, but the LDH increase and PGE2 production were not reduced by L-NAME. These findings suggest that the protective effects of magnolol against brain damage by KCN or KCN plus LPS in hypoglycemic media may involve inhibition of PGE2 production, but inhibition of NO generation may not be important.

Effect of San-Ao-Tang on immediate and late airway response and leukocyte infiltration in asthmatic guinea pigs.

San-Ao-Tang (SAT), a traditional Chinese medicines, has been used to treat patients with the bronchial asthma for several centuries. However, the therapeutic mechanisms of this Chinese medicine are still far from clear. To understand the mechanism of antiasthmatic property of SAT, a guinea pig model of allergic asthma was used to investigate the effects of SAT on Dermatophagoides pteronyssinus-induced immediate and late asthmatic responses and airway inflammation. Our results showed that administration of SAT (10 g/kg) extracts significantly inhibited the antigen induced immediate asthmatic responses (IAR) in actively sensitized guinea pig. Examination of bronchoalveolar lavage fluid (BALF) revealed that SAT significantly inhibited the increase in neutrophil in the airway at 1, 2, 4, 6, 8 hr after antigen challenge. Histopathologic examination showed SAT suppressed the neutrophil infiltration into lung tissue. These results suggest that the antiasthmatic effect of SAT be mainly due to its bronchodilator effect and its ability to inhibit the neutrophil into the airway. The precise mechanism of action of SAT in asthma remains to be elucidated.

Effects of aspirin on arylamine N -acetyltransferase activity and DNA adducts in human bladder tumour cells.

Aspirin (acetylsalicylic acid) was used to determine the inhibition of arylamine N-acetyltransferase (NAT) activity and DNA adduct formation in a human bladder tumour cell line (T24). The activity of NAT was measured by high-performance liquid chromatography, assaying for the amounts of N-acetyl-2-aminofluorene and N-acetyl-p-aminobenzoic acid and remaining 2-aminofluorene and p-aminobenzoic acid. Two assay systems were used: one with cytosol and the other with intact cells. High-performance liquid chromatography was also used to analyse for the 2-aminofluorene-DNA adducts. Intact bladder tumour cells were used. The results demonstrated that NAT activity and 2-aminofluorene-DNA adduct formation in human bladder tumour cells were inhibited by acetylsalicylic acid in a dose-dependent manner. The effects of acetylsalicylic acid on the values of the apparent K(m) and V(max) were also determined in both examined systems. The data also indicated that acetylsalicylic acid decreased the apparent values of K(m) and V(max) from human bladder tumour cells in both cytosol and intact cells.

Effects of ibuprofen on arylamine N-acetyltransferase activity in human colon tumor cells.

The inhibition of arylamine N-acetyltransferase (NAT) activity by ibuprofen was determined in a human colon tumour (adenocarcinoma) cell line. Two assay systems were employed, one with cellular cytosols (9000 g supernatant) and the other with intact colon tumour cell suspensions. The NAT activity in a human colon tumour cell line was inhibited by ibuprofen in a dose-dependent manner in both systems, i.e. the greater the concentration of ibuprofen in the reaction, the greater the inhibition of NAT activities in both systems. The data also indicated that ibuprofen decreases the apparent Km and Vmax of NAT enzyme from human colon tumour cells in both systems examined. This report is the first demonstration to show that ibuprofen affects human colon tumour cell NAT activity.

Magnolol protects cortical neuronal cells from chemical hypoxia in rats.

The protective effect of magnolol, a component of Magnolia officinalis, against hypoxia-induced cell injury in cortical neuron-astrocyte mixed cultures was examined. Exposure of the cells to chemical hypoxia (0.5 mM KCN) produced morphological changes in neurons but not in astrocytes. KCN induced dose- and time-dependent increases in release of LDH and decreases in viable cell number. Treatment with magnolol (10 and 100 microM) significantly reduced the KCN-induced LDH release in a concentration-dependent manner. A higher concentration (750 microM) magnolol was toxic. Nuclear condensation was not observed in KCN-treated cells, suggesting that chemical hypoxia-induced cell death was via necrosis, rather than via apoptosis. This is the first report demonstrating that magnolol protects neurons against chemical hypoxic damage or necrotic cell death in cortical neuron-astrocyte mixed cultures.

2-Phenyl-4-quinolone prevents serotonin-induced increases in endothelial permeability to albumin.

To investigate the role of 2-phenyl-4-quinolone in enhancing endothelial monolayer paracellular barrier function and preventing the disturbance of paracellular barrier function by vasoactive agents, the study examined the effect of 2-phenyl-4-quinolone on serotonin-mediated macromolecule transfer and microfilament changes in cultured rat heart endothelial cells. Serotonin-treated endothelial cells induced concentration-dependent increases in the passage of Evans blue dye-bound bovine serum albumin. Incubation of the endothelial monolayers with 2-phenyl-4-quinolone antagonized serotonin- and cytochalasin B-induced macromolecular permeability. 2-Phenyl-4-quinolone also opposed the effect of serotonin or cytochalasin B on the distribution and quantity of actin filaments in the endothelial cytoskeleton. Furthermore, 2-phenyl-4-quinolone alone led to an apparent quantitative increase in F actin fluorescence in endothelial cells. The addition of 10(-7) M 2-phenyl-4-quinolone had an effect on serotonin-induced changes in the myosin and distribution of myosin were comparable to that on serotonin monolayers. In conclusion, 2-phenyl-4-quinolone attenuated the serotonin-induced permeability of rat heart endothelial cells and this was associated with stabilization of F actin microfilaments and changes in the myosin organization. This result suggests that influences on cytoskeletal assembly may be involved in this process.

Decreased protein kinase C activation mediates inhibitory effect of norathyriol on serotonin-mediated endothelial permeability.

We examined the mechanisms of norathyriol on the serotonin-induced increased permeability of rat heart endothelial cell monolayers. The present study showed that the activation of rat heart endothelial cell protein kinase C by phorbol myristate acetate led to the dose-dependent increase in endothelial permeability to albumin, an effect that was inhibited by staurosporine (a protein kinase inhibitor). Staurosporine also attenuated the serotonin-induced increase in permeability. Norathyriol abolished both serotonin- and phorbol myristate acetate-induced permeability. We investigated whether norathyriol, by inhibiting protein kinase C activation, attenuated the serotonin-induced permeability. Immunofluorescence studies demonstrated that norathyriol prevented the redistribution of protein kinase C isozymes following stimulation with serotonin. Western blot analysis showed that norathyriol significantly inhibited the serotonin-induced translocation of the alpha protein kinase C isozyme from the cytosolic to the particulate fraction. In conclusion, norathyriol attenuates the serotonin-induced permeability of rat heart endothelial cells to macromolecules in association with inhibition of protein kinase C activation. This decrease in endothelial cell permeability may be one of the mechanisms for the protective effects of norathyriol against edema formation in response to inflammatory agonists in vivo.

Studies on the anticonvulsive, sedative and hypothermic effects of Periostracum Cicadae extracts.

The anticonvulsive, sedative and hypothermic effects of water and ethanol extracts of Periostracum Cicadae (PC), the cast off skin of Cryptotympana atrata were studied. The water-extract of whole Periostracum Cicadae (PCws) had anticonvulsive, sedative and hypothermic effects in rats. Orally, it decreased carrageenin-induced hyperthermia. The hypothermic effect of PCws was potentiated by 5-hydroxytryptophan and antagonized by p-chlorophenylalanine. PCws enhanced the decrease in locomotor activity induced by alpha-methyl-p-tyrosine or 5-hydroxytryptophan and reduced the increase in locomotor activity produced by levodopa plus benserazide or p-chlorophenylalanine. From these results, it was concluded that the sedative and hypothermic effect of PCws may be due to an increase in central serotonergic activity.

Effects of paweiwan on streptozotocin-induced hyperglycemia in rats.

The ancient Chinese remedy of Paweiwan was used by patients with polyuria, polydipsia, and polyphagia. The present study investigated the hypoglycemic effects of Paweiwan using streptozotocin-induced hyperglycemic rats. The effects on serum glucose in a 4-day course, in a 7-week course, on the standard oral glucose tolerance test, and on the liver glycogen content were studied. In the glucose tolerance test, chlorpropamide and insulin were used as the positive controls and 0.5% CMC (Carboxymethylcellulose) was used as the negative control. We found that Paweiwan decreased the baseline glucose concentration, ameliorated the blood glucose elevation after glucose challenge, and increased liver glycogen content. The results may imply that Paweiwan increases glucose entrance into cells.