Recent research and developmental strategy of anti-asthma drugs

Gut Microbiota-Derived Tryptophan Metabolites Alleviate Allergic Asthma Inflammation in Ovalbumin-Induced Mice

Asthma is a prevalent respiratory disease. The present study is designed to determine whether gut microbiota-derived tryptophan metabolites alleviate allergic asthma inflammation in ovalbumin (OVA)-induced mice and explore the effect and potential mechanism therein. Asthma model mice were constructed by OVA treatment, and kynurenine (KYN), indole-3-lactic acid (ILA), in-dole-3-carbaldehyde (I3C), and indole acetic acid (IAA) were administered by intraperitoneal injection. The percent survival, weight and asthma symptom score of mice were recorded. The total immunoglobulin E and OVA-specific (s)IgE in the serum and the inflammatory cytokines in the bronchoalveolar lavage fluid (BALF) were detected by the corresponding ELISA kits. The composition of the gut microbiota and tryptophan-targeted metabolism in mouse feces were analyzed using 16S rRNA gene sequencing and targeted metabolomics, respectively. The four tryptophan metabolites improved the percent survival, weight and asthma symptoms of mice, and reduced the inflammatory cells in lung tissues, especially I3C. I3C and IAA significantly (p < 0.05) downregulated the levels of OVA-IgE and inflammatory cytokines. KYN was observed to help restore gut microbiota diversity. Additionally, I3C, KYN, and ILA increased the relative abundance of Anaeroplasma, Akkermansia, and Ruminococcus_1, respectively, which were connected with tryptophan metabolic pathways. IAA also enhanced capability of tryptophan metabolism by the gut microbiota, restoring tryptophan metabolism and increasing production of other tryptophan metabolites. These findings suggest that tryptophan metabolites may modulate asthma through the gut microbiota, offering potential benefits for clinical asthma management.

Water extract of Pingchuan formula ameliorated murine asthma through modulating metabolites and gut microbiota

BACKGROUND

Pingchuan formula is a traditional Chinese herbal prescription for asthma, but its components and underlying mechanisms remain unclear. Here, we evaluated its anti-asthmatic actvity and regulatory effects on the gut microbiota in mice based on the traditional Chinese medicine Zang-Fu theory, which proposed the exterior-interior relationship between the lung and the large intestine.

METHODS

Mouse model withovalbumin (OVA)-induced asthma was used to assess the protective effect of the water extract of Pingchuan formula (PC). The chemical compounds of PC and mouse serum metabolites were identified by Ultraperformance liquid chromatography-Q Exactive HF-X spectrometry. Gut microbiota was evaluated by 16 S rRNA gene sequencing. The gut microbiota was depleted with a broad-spectrum antibiotic mixture (Abx) to explore whether it plays a role in the protective effects of PC.

RESULTS

PC mainly contains phenols, flavonoids, alkaloids, carboxylic acids, and their derivatives. PC attenuated OVA-induced asthma in mice by alleviating inflammatory infiltration, indicated by decreased levels of IL-18, IL-6, IL-4, and Eotaxin in lung tissues. PC treatment altered the serum metabolites and affected the pyrimidine pathway. In addition, our results showed that acacetin and abscisic acid were the key serum metabolites PC treatment changed the composition of gut microbiota by increasing the relative abundance of Clostridia_UCG_014 and Akkermansia while decreasing Blautia, Barnesiella, and Clostridium_Ⅲ at the genus level. Importantly, the Abx treatment partly abolished the anti-asthmatic effect of PC.

CONCLUSION

We demonstrated that PC could alleviate OVA-induced asthma in mice and protect against inflammatory infiltration in lungs via modulating the serum metabolites and gut microbiota, thereby providing a new reference for the therapeutic effect of PC.

Drug Development from Natural Products Based on the Pathogenic Mechanism of Asthma

Asthma is a chronic inflammatory disease of the pulmonary system associated with many wheeze-to-sleep apnea complications that may lead to death. In 2019, approximately 262 million patients suffered from asthma, and 455 thousand died from the disease worldwide. It is a more severe health problem in children and older adults, and as the aging of society intensifies, the problem will continue to worsen. Asthma inducers can be classified as indoor and outdoor allergens and can cause asthma due to their repeated invasion. There are several theories about asthma occurrence, such as the imbalance between Th1 and Th2, inflammation in the pulmonary system, and the abnormal apoptosis/cell proliferation of cells related to asthma. Although there are many medications for asthma, as it is an incurable disease, the purpose of the drugs is only to suppress the symptoms. The current drugs can be divided into relievers and controllers; however, as they have many adverse effects, such as immune suppression, growth retardation, promotion of cataracts, hyperactivity, and convulsions, developing new asthma drugs is necessary. Although natural products can have adverse effects, the development of asthma drugs from natural products may be beneficial, as some have anti-asthmatic effects such as immune modulation, anti-inflammation, and/or apoptosis modulation.

Codonopsis laceolata Water Extract Ameliorates Asthma Severity by Inducing Th2 Cells’ and Pulmonary Epithelial Cells’ Apoptosis via NF-κB/COX-2 Pathway

Asthma is an incurable pulmonary disease with several symptoms, including abnormal breathing, coughing, and sleep apnea, which can lead to death, and the population of asthma patients has been increasing worldwide. There are many adverse effects in current drugs, and thus, we have tried to develop anti-asthmatic agents from natural products such as Codonopsis laceolata. To define the anti-asthmatic effect and the mechanism of Codonopsis laceolata, an animal study was conducted considering different cell counts of BALF, serum IgE levels, morphological changes in the pulmonary system, the Th2 cell transcription factor (GATA-3), and the apoptotic pathway (NF-κB/COX-2). Codonopsis laceolata significantly suppressed the representative asthmatic changes, such as airway remodeling, mucous hypersecretion, epithelial hyperplasia, and inflammatory cell infiltration, in the respiratory system. It suppressed the levels of GATA-3, IL-4, and IL-13. The down-regulation of Th2-related factors, such as GATA-3, IL-4, and IL-13, results from the stimulated apoptosis of Th2 cells and epithelial cells via a decrease in the levels of NF-κB and COX-2. We concluded that Codonopsis laceolata might be a promising anti-asthmatic drug.

Discovery of potential asthma targets based on the clinical efficacy of Traditional Chinese Medicine formulas

ETHNOPHARMACOLOGICAL RELEVANCE

Standard therapy for asthma, a highly heterogeneous disease, is primarily based on bronchodilators and immunosuppressive drugs, which confer short-term symptomatic relief but not a cure. It is difficult to discover novel bronchodilators, although potential new targets are emerging. Traditional Chinese Medicine (TCM) formulas have been used to treat asthma for more than 2000 years, forming the basis for representative asthma treatments.

AIM OF THE STUDY

Based on the efficacy of TCM formulas, anti-asthmatic herbal compounds bind proteins are potential targets for asthma therapy. This analysis will provide new drug targets and discovery strategies for asthma therapy.

MATERIALS AND METHODS

A list of candidate herbs for asthma was selected from the classical formulas (CFs) of TCM for the treatment of wheezing or dyspnea recorded in Treatise on Cold Damage and Miscellaneous Diseases (TCDMD) and from modern herbal formulas identified in the SAPHRON TCM Database using the keywords "wheezing" or "dyspnea". Compounds in the selected herbs and compounds that directly bind target proteins were acquired by searching the Herbal Ingredients' Targets Database (HITD), TCM Data Bank (TCMDB) and TCM Integrated Database (TCMID). Therapeutic targets of conventional medicine (CM) for asthma were collected by searching Therapeutic Target Database (TTD), DrugBank and PubMed as supplements. Finally, the enriched gene ontology (GO) terms of the targets were obtained using the Database for Annotation Visualization and Integrated Discovery (DAVID) and protein-protein interactions (PPI) networks were constructed using Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). The effects of two selected TCM compounds, kaempferol and ginkgolide A, on cellular resistance in human airway smooth muscle cells (ASMCs) and pulmonary resistance in a mouse model were investigated.

RESULTS

The list of 32 candidate herbs for asthma was selected from 10 CFs for the treatment of wheezing or dyspnea recorded in TCDMD and 1037 modern herbal formulas obtained from the SAPHRON TCM Database. A total of 130 compounds from the 32 selected herbs and 68 herbal compounds directly bind target proteins were acquired from HITD and TCMDB. Eighty-eight therapeutic targets of CM for asthma were collected by searching TTD and PubMed as supplements. DAVID and STRING analyses showed targets of TCM formulas are primarily related to cytochrome P450 (CYP) family, transient receptor potential (TRP) channels, matrix metalloproteinases (MMPs) and ribosomal protein. Both TCM formulas and CM act on the same types of targets or signaling pathways, such as G protein-coupled receptors (GPCRs), steroid hormone receptors (SHRs), and JAK-STAT signaling pathway. The proteins directly targeted by herbal compounds, TRPM8, TRPA1, TRPV3, CYP1B1, CYP2B6, CYP1A2, CYP3A4, CYP1A1, PPARA, PPARD, NR1I2, MMP1, MMP2, ESR1, ESR2, RPLP0, RPLP1 and RPLP2, are potential targets for asthma therapy. In vitro results showed kaempferol (1 × 10^-2 mM) and ginkgolide A (1 × 10^-5 mM) significantly increased the cell index (P < 0.05 vs. histamine, n = 3) and therefore relaxed human ASMCs. In vivo results showed kaempferol (145 μg/kg) and ginkgolide A (205 μg/kg) significantly reduced pulmonary resistance (P < 0.05 vs. methacholine, n = 6).

CONCLUSION

Potential target discovery for asthma treatment based on the clinical effectiveness of TCM is a feasible strategy.

Fig (Ficus carica L.) leaf tea suppresses allergy by acceleration disassembly of IgE-receptor complexes

In this study, I investigated the allergy suppressive effect of tea made from fig (Ficus carica L.) leaves. In the rat basophil cell line RBL-2H3, degranulation was significantly suppressed by treatment with fig tea at the same time as addition of IgE antibodies (sensitization). IgE bound to the cell surface was liberated in the medium depending on the treatment time with fig tea. Therefore, it was suggested that the mechanism of action of fig tea is promotion of dissociation of IgE from FcεRI receptors. Such a mechanism is novel in food materials. On oral administration to mice, fig tea showed an inhibitory effect on allergic dermatitis. Furthermore, in tests using an atopic dermatitis model in NC/Nga mice, continued administration of fig tea suppressed symptom exacerbation after antigen administration.Abbreviations: AD: atopic dermatitis; β-Hex: β-hexosaminidase; FCM: flow cytometory; OA: oral administration; TA: transdermal administration.

Antiasthmatic Effects of Sanglong Pingchuan Decoction through Inducing a Balanced Th1/Th2 Immune Response

Objective

To investigate the antiasthmatic effects of Sanglong pingchuan decoction (SLPCD) and to explore its mechanisms of action.

Methods

The serum, bronchoalveolar lavage fluid (BALF), and lung tissues from OVA-induced allergic asthma mice were collected 24 h after the last administration. Lung pathological changes were observed by H&E staining. The inflammatory cells in BALF were counted by flow cytometry. The levels of total IgE in serum and cytokines in BALF were determined by ELISA. The expression levels of cytokine mRNA in lung were assayed by qRT-PCR.

Results

SLPCD significantly inhibited airway inflammation, reduced inflammatory cells in BALF, reduced the levels of total IgE in serum and Th2 cytokines (IL-10 and IL-13) in BALF, and downregulated the mRNA expression levels of Th2 cytokines (IL-4, IL-5, IL-10, and IL-13) in lung of asthmatic mice. However, SLPCD remarkably elevated the level of Th1 cytokine IFN-γ in BALF and upregulated the mRNA expression levels of Th1 cytokines (IL-2 and IFN-γ) in lung of asthmatic mice.

Conclusion

SLPCD could attenuate airway inflammation and alleviate the pathogenesis in asthma mice through inducing a balanced Th1/Th2 response and could act as an effective drug for treatment of asthma.

A Multicenter, Randomized, Double-Blind, Placebo-Controlled Study of the Effects of Loki zupa in Patients With Chronic Asthma

The purpose of this study was to evaluate the efficacy and safety of Uyghur medical formula Loki zupa in patients with chronic asthma. Adult patients with chronic asthma randomly received placebo or Loki zupa as add-on to inhaled corticosteroids (ICS) maintenance treatment. Loki zupa or mimics was administered orally 10 ml per time, three times a day for 8 weeks. The primary endpoints were asthma control test (ACT) score and peak expiratory flow (PEF). The secondary endpoints were acute exacerbation rate, lung function, night waking days, and symptom-free days in the near 2 weeks, Asthma Quality of Life Questionnaire (AQLQ) score and some inflammatory cytokines in peripheral blood. A total of 240 adult patients with chronic asthma were enrolled, and 218 patients were randomized to placebo (n = 109) or Loki zupa (n = 109) in addition to ICS for 8 weeks. Treatment with Loki zupa resulted in significant improvement in ACT score compared to the placebo group (p = 0.002). Furthermore, oral taken of Loki zupa increased the PEF obviously (p = 0.026). Loki zupa treatment did not improve the forced expiratory volume in 1 s (FEV₁, p = 0.131) and FEV₁/FVC compared to the placebo treatment (p = 0.805). The placebo group had higher rates of acute exacerbations than the Loki zupa group (6.3% vs. 0, p = 0.027). Subjects randomized to Loki zupa had increased daytime symptom-free days within 2 weeks than placebo (p = 0.016). However, Loki zupa had no effect on night waking days in the near 2 weeks (p = 0.369) and AQLQ score (p = 0.113). No significant effect was found on inflammatory cytokines (IL-2, IL-4, IL-5, IL-10, IL-13, IL-17, IL-33, IFN-γ, and TGF-β) between the two groups (p > 0.05). No adverse events and severe asthma exacerbations were recorded in the two groups (p > 0.05). Loki zupa add-on to standard ICS produced clinically significant improvements in ACT score, PEF, daytime symptom-free days and acute exacerbation in patients with chronic asthma.

Clinical trial: This study is registered at http://www.chictr.org.cn/ with identifier number ChiCTR-IPR-16008106.

Regulation of hypothalamic-pituitary-adrenal axis activity and immunologic function contributed to the anti-inflammatory effect of acupuncture in the OVA-induced murine asthma model

Asthma is a complex inflammatory disease of the airways and acupuncture is one of the effective therapies widely used to treat asthma in China. The aim of the study was to evaluate the regulatory role of acupuncture in airway inflammation and the hypothalamic-pituitary-adrenal (HPA) axis activity in OVA-induced murine asthma model. Our results demonstrated that acupuncture was effective in suppression of AHR, inhibition of total leukocyte, neutrophil, lymphocyte and eosinophil counts in BALF, attenuation of airway inflammation and TNF-α, IL-1β, IL-5 and eotaxin secretion. Furthermore, the HPA axis activity was also regulated by acupuncture, which included promotion of adrenocorticotropic hormone and cortisol secretion in the plasma. Our findings revealed that acupuncture could attenuate airway inflammation and regulate HPA axis and immunologic function in the OVA-induced murine asthma model, which may provide support to better understand the contribution of acupuncture to the regulation of airway inflammation and HPA axis activity in asthma.

Activation of angiotensin-converting enzyme 2 (ACE2) attenuates allergic airway inflammation in rat asthma model

Angiotensin-I converting enzyme (ACE) is positively correlated to asthma, chronic obstructive pulmonary disease (COPD), acute respiratory distress syndrome (ARDS) and is highly expressed in lungs. ACE2, the counteracting enzyme of ACE, was proven to be protective in pulmonary, cardiovascular diseases. In the present study we checked the effect of ACE2 activation in animal model of asthma. Asthma was induced in male wistar rats by sensitization and challenge with ovalbumin and then treated with ACE2 activator, diminazene aceturate (DIZE) for 2weeks. 48h after last allergen challenge, animals were anesthetized, blood, BALF, femoral bone marrow lavage were collected for leucocyte count; trachea for measuring airway responsiveness to carbachol; lungs and heart were isolated for histological studies and western blotting. In our animal model, the characteristic features of asthma such as altered airway responsiveness to carbachol, eosinophilia and neutrophilia were observed. Western blotting revealed the increased pulmonary expression of ACE1, IL-1β, IL-4, NF-κB, BCL2, p-AKT, p-p38 and decreased expression of ACE2 and IκB. DIZE treatment prevented these alterations. Intraalveolar interstitial thickening, inflammatory cell infiltration, interstitial fibrosis, oxidative stress and right ventricular hypertrophy in asthma control animals were also reversed by DIZE treatment. Activation of ACE2 by DIZE conferred protection against asthma as evident from biochemical, functional, histological and molecular parameters. To the best of our knowledge, we report for the first time that activation of ACE2 by DIZE prevents asthma progression by altering AKT, p38, NF-κB and other inflammatory markers.

Loki zupa (Luooukezupa) decoction reduced airway inflammation in an OVA-induced asthma mouse model

Background

Loki zupa (Luooukezupa) decoction, consisting of the roots of Hyssopuscuspidatus Boriss (Shenxiangcao) and Irishalophila Pall root (Yuanweigen), is commonly used in Uygur medicine to treat asthma. However, the mode of action of this material has yet to be elucidated. This study aims to investigate the effects of Loki zupa decoction on the airway inflammation of an ovalbumin (OVA)-induced asthma mouse model.

Methods

Mice were divided into normal control (NC), asthma (A), high, medium and low doses of Loki zupa decoction (L 14.0, L 7.0, L 3.5), water extract (LW), n-butanol extract (LN), ethyl acetate extract (LE) and dexamethasone (DEX) groups. Antiasthmatic model was induced by OVA sensitization and challenged using BALB/c mice. Airway hyperresponsiveness (AHR) toward methacholine (Mch) was assessed using Buxco equipment. Lung inflammation was measured by hematoxylin and eosin staining and bronchoalveolar lavage fluid (BALF) cell count and classification. Inflammatory cytokines in BALF and serum were analyzed by Bio-Plex assay, and mRNA levels were investigated by qPCR analysis. The roots of H. Boriss (250 g) and I. Pall (250 g) were decocted, concentrated and diluted to 14.0, 7.0 and 3.5 g crude herb/kg body weight. The LW, LN and LE of the Loki zupa decoction were prepared and diluted to a dose equivalent to 7 g of crude herb/kg body weight.

Results

Loki zupa decoction and its extracts significantly attenuated the AHR towards Mch (all P < 0.05). Treatment with Loki zupa decoction and its extracts relieved the infiltration of inflammatory cells in and around the airways, and reduced the total white blood cell (all P < 0.05), neutrophil (all P < 0.05), monocyte (all P < 0.05) and eosinophil (all P < 0.05) counts in the BALF. The BALF samples collected from the mice treated with the Loki zupa decoction and its extracts had lower levels of IL-1β (all P < 0.05), TNF-α (all P < 0.05), IL-2 (all P < 0.05), IL-4 (P = 0.047) and IL-5 (all P < 0.05). The serum samples of these mice also had lower IL-1β (all P < 0.05), TNF-α (all P < 0.05), IL-4 (all P < 0.05) and IL-5 (all P < 0.05) levels and higher levels of IFN-γ (P < 0.001) compared with the OVA-induced asthma mouse model. qPCR analysis revealed that Loki zupa decoction and its extracts inhibited mRNA expression of IL-4 (all P < 0.05), IL-5 (all P < 0.05) and IL-13 (all P < 0.05) and promoted mRNA expression of IFN-γ (all P < 0.05) in asthmatic mice.

Conclusion

Loki zupa decoction reduced AHR, attenuated airway inflammation, promoted Th1 and suppressed Th2 cell functions in an OVA-induced asthma mouse model.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-016-0094-9) contains supplementary material, which is available to authorized users.

Autotaxin production of lysophosphatidic acid mediates allergic asthmatic inflammation

RATIONALE

Bioactive lipid mediators, derived from membrane lipid precursors, are released into the airway and airspace where they bind high-affinity cognate receptors and may mediate asthma pathogenesis. Lysophosphatidic acid (LPA), a bioactive lipid mediator generated by the enzymatic activity of extracellular autotaxin (ATX), binds LPA receptors, resulting in an array of biological actions on cell proliferation, migration, survival, differentiation, and motility, and therefore could mediate asthma pathogenesis.

OBJECTIVES

To define a role for the ATX-LPA pathway in human asthma pathogenesis and a murine model of allergic lung inflammation.

METHODS

We investigated the profiles of LPA molecular species and the level of ATX exoenzyme in bronchoalveolar lavage fluids of human patients with asthma subjected to subsegmental bronchoprovocation with allergen. We interrogated the role of the ATX-LPA pathway in allergic lung inflammation using a murine allergic asthma model in ATX-LPA pathway-specific genetically modified mice.

MEASUREMENTS AND MAIN RESULTS

Subsegmental bronchoprovocation with allergen in patients with mild asthma resulted in a remarkable increase in bronchoalveolar lavage fluid levels of LPA enriched in polyunsaturated 22:5 and 22:6 fatty acids in association with increased concentrations of ATX protein. Using a triple-allergen mouse asthma model, we showed that ATX-overexpressing transgenic mice had a more severe asthmatic phenotype, whereas blocking ATX activity and knockdown of the LPA2 receptor in mice produced a marked attenuation of Th2 cytokines and allergic lung inflammation.

CONCLUSIONS

The ATX-LPA pathway plays a critical role in the pathogenesis of asthma. These preclinical data indicate that targeting the ATX-LPA pathway could be an effective antiasthma treatment strategy.

Accumulation of Mast Cells in the Lesions and Effects of Antiallergic Drugs on the Patients with Inflammatory Bowel Disease

The pathomechanism of inflammatory bowel disease (IBD) has not yet been fully demonstrated. However, it is well known that mast cells are present in the gastrointestinal tract, suggesting that mast cells may take part in it. So, we investigated the number of mast cells in IBD, such as ulcerative colitis (UC) and eosinophilic colitis, and showed that the number of mast cells was increased in the inflammatory lesions. We also presented a case of UC which was treated successfully with an antiallergic drug, tranilast. Furthermore, possible new approaches to treating the disease with immunomodulators including suplatast are introduced. However, our investigations were performed with a limited number of patients with IBD, and additional further studies are required to confirm the findings.

Insights into mast cell functions in asthma using mouse models

Therapeutics targeting specific mechanisms of asthma have shown promising results in mouse models of asthma. However, these successes have not transferred well to the clinic or to the treatment of asthma sufferers. We suggest a reason for this incongruity is that mast cell-dependent responses, which may play an important role in the pathogenesis of both atopic and non-atopic asthma, are not a key component in most of the current asthma mouse models. Two reasons for this are that wild type mice have, in contrast to humans, a negligible number of mast cells localized in the smaller airways and in the parenchyma, and that only specific protocols show mast cell-dependent reactions. The development of mast cell-deficient mice and the reconstitution of mast cells within these mice have opened up the possibility to generate mouse models of asthma with a marked role of mast cells. In addition, mast cell-deficient mice engrafted with mast cells have a distribution of mast cells more similar to humans. In this article we review and highlight the mast cell-dependent and -independent responses with respect to airway hyperresponsiveness and inflammation in asthma models using mast cell-deficient and mast cell-engrafted mice.

Should antihistamines be re-considered as antiasthmatic drugs as adjuvants to anti-leukotrienes?

In spite of histamine mimicking the symptoms of allergic bronchoconstriction and severe anaphylaxis, histamine antagonists most probably represent no effective treatment for these conditions. Anti-leukotrienes proved effective for preventing attacks of allergic asthma. In vitro evidence supports a supra-additive effect of histamine H1 receptor antagonists and anti-leukotrienes in vitro, in asthma models utilizing human bronchi. The same seems to hold true for human allergen provocation tests in vivo. We conclude that combinations of second-generation antihistamines and anti-leukotrienes deserve a large-scale clinical trial for preventing and/or treating attacks of allergic asthma. If useful, these drugs could provide a cost-effective alternative to some recent antiasthmatics. Given that redundant mechanisms may be included in asthma pathophysiology, other combinations (including thromboxane or platelet activating factor antagonists) could also be considered.

Simultaneous determination of montelukast as sparing therapy with some inhaled corticosteroids in plasma of asthmatic patients

Montelukast (MKST) is a leukotriene receptor antagonist that has been concomitantly used with inhaled corticosteroids (ICS) for its steroid-sparing effect in the long-term management of asthma. However, the simultaneous determination of MKST, when used as ICS tapering therapy, with ICS in human plasma has not yet been reported. A fast and efficient reversed phase monolith HPLC method was developed for simultaneous determination of MKST with some ICS in plasma of asthmatic patients. The separation was achieved on monolith reversed phase column by isocratic mode at a flow rate of 1.0 ml min(-1) using a mobile phase consisted of a mixture of acetonitrile and 10mM phosphate buffer adjusted to pH 3.5 (40:60, v/v) and detected at 240 nm. Betamethasone dipropionate (BDP) was used as the internal standard. All the studied ICS and MKST were efficiently separated within less than 6 min. The obtained linearity range for the developed HPLC method was 0.03-10 μg ml(-1) with correlation coefficients>0.9995 and the detection limits were 0.009-0.016 μg ml(-1) in plasma for all the studied drugs. The method was validated in agreement with the requirements of US-FDA guideline and was recommended for the target applications. The method is valuable for investigations concerned with the effective tapering of ICS therapy with MKST in patients with chronic asthma in clinical practice without loss of asthma control.