Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

P-Glycoprotein is a transmembrane efflux pump for different lipophilic drugs including glucocorticosteroids. Thus, upregulation of P-glycoprotein may provide a mechanism for reduced glucocorticosteroid responses as they occur in steroid-resistant asthma. To address this issue, we have examined freshly isolated peripheral blood mononuclear cells and granulocytes with regards to P-glycoprotein functional and surface expression. Using two-color immuno fluorescence techniques, we demonstrated a direct correlation between the efflux of the fluorescent dye Rh 123 and P-glycoprotein surface expression in lymphocytes, NK (natural killer) cells, monocytes and granulocytes. P-Glycoprotein levels varied widely between different leucocytes, with NK cells and CD8+ T cells having high, and granulocytes having no detectable levels. There was no evidence for upregulation of P-glycoprotein expression in any cell type from patients with steroid-resistant asthma compared to patients with steroid-sensitive or mild asthma. These results suggest that increased P-glycoprotein expression can be excluded as a mechanism for steroid resistance. Interestingly, a down regulation of P-glycoprotein expression in B cells was associated with systemic glucocorticosteroid treatment in vivo and in vitro. Whether this phenomenon may account for reduced immunoglobulin levels associated with oral glucocortico-steroid therapy remains to be determined.
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PMID:P-glycoprotein expression in circulating blood leukocytes of patients with steroid-resistant asthma. 883 64

Desloratadine is a new, selective, H(1)-receptor antagonist that also has anti-inflammatory activity. In vitro studies have shown that desloratadine inhibits the release or generation of multiple inflammatory mediators, including IL-4, IL-6, IL-8, IL-13, PGD(2), leukotriene C(4), tryptase, histamine, and the TNF-alpha-induced chemokine RANTES. Desloratadine also inhibits the induction of cell adhesion molecules, plateletactivating factor-induced eosinophil chemotaxis, TNF-alpha-induced eosinophil adhesion, and spontaneous and phorbol myristate acetate-induced superoxide generation in vitro. In animals desloratadine had no effect on the central nervous, cardiovascular, renal, or gastrointestinal systems. Desloratadine is rapidly absorbed, has dose-proportional pharmacokinetics, and has a half-life of 27 hours. The absorption of desloratadine is not affected by food, and the metabolism and elimination are not significantly affected by the subject's age, race, or sex. There are no clinically relevant interactions between desloratadine and erythromycin, ketoconazole, or grapefruit juice. Desloratadine is not a significant substrate of the P-glycoprotein transport system. Once daily administration of desloratadine rapidly reduces the nasal and nonnasal symptoms of seasonal allergic rhinitis, including congestion. In patients with seasonal allergic rhinitis and concomitant asthma, desloratadine treatment was also associated with significant reductions in total asthma symptom score and use of inhaled beta(2)-agonists. Use of desloratadine in patients with chronic idiopathic urticaria was associated with significant reductions in pruritus, number of hives, size of the largest hive, and interference with sleep and daily activities. Clinical experience in over 2300 patients has shown that the adverse event profile of desloratadine is similar to that of placebo; desloratadine has no clinically relevant effects on electrocardiographic parameters, does not impair wakefulness or psychomotor performance, and does not exacerbate the psychomotor impairment associated with alcohol use.
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PMID:Desloratadine: A new, nonsedating, oral antihistamine. 1129 78

Desloratadine is a biologically active metabolite of the second-generation antihistamine loratadine. Desloratadine is a highly selective peripheral H1 receptor antagonist that is significantly more potent than loratadine. Results of in vitro and in vivo studies have suggested that desloratadine has anti-allergic effects that are unrelated to its ability to antagonise the effects of histamine. Desloratadine inhibits the expression of cell adhesion molecules, inhibits the generation and release of inflammatory mediators and cytokines, attenuates eosinophil chemotaxis, adhesion and superoxide generation. Studies in animals indicate that desloratadine does not cross the blood-brain barrier and therefore does not cause sedation and does not impair cognition or psychomotor performance. Desloratadine has an excellent overall safety profile. It has no effect on QRS and QTc intervals and does not cause arrhythmias. Desloratadine is not associated with any significant changes in gastrointestinal function. In clinical studies, oral desloratadine is rapidly absorbed and bioavailability is not affected by ingestion with food or grapefruit juice. The half-life of desloratadine in humans is 27 h; the linear kinetic profile is unaltered by race or gender. Desloratadine is not a substrate for P-glycoprotein or organic anion transport polypeptide and the drug does not appear to be metabolised to a significant extent by the cytochrome P450 CYP3A4 pathway. It therefore may be safely administered with ketoconazole, erythromycin, fluoxetine, or azithromycin. Clinically, desloratadine effectively controls both nasal and non-nasal symptoms of seasonal allergic rhinitis (SAR), including nasal congestion. Desloratadine also provides significant relief of SAR symptoms in patients with co-existing asthma and is effective in the treatment of chronic idiopathic urticaria. Desloratadine improves quality of life and is well-tolerated.
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PMID:Pharmacology and clinical efficacy of desloratadine as an anti-allergic and anti-inflammatory drug. 1142 98

The cytokine interleukin-17 may play a role in the recruitment of airway neutrophils, and interleukin-17 protein is increased in the airways of patients with asthma. In this study, we characterised the effect of interleukin-17 on the release of the neutrophil-recruiting cytokines granulocyte chemotactic protein (GCP)-2, growth-related oncogene (GRO)-alpha and interleukin-8 in human bronchial epithelial (HBE) cells. We also characterised the involvement of mitogen-activated protein (MAP) kinases as well as the effect of beta-adrenoceptor and glucocorticoid receptor stimulation and calcineurin and P-glycoprotein inhibition on these epithelial responses to interleukin-17. We found that interleukin-17 (1-1000 ng/ml) increased the release of GCP-2, GRO-alpha and interleukin-8 in a concentration-dependent manner. This interleukin-17-induced release of C-X-C chemokines was sensitive to inhibition of the p38 MAP kinase pathway and to stimulation of glucocorticoid receptors. In contrast, stimulation of beta-adrenoceptors increased the release of interleukin-8 and did not markedly alter the release of GCP-2 and GRO-alpha. Inhibition of calcineurin and of P-glycoproteins did not exert any substantial effect on the release of C-X-C chemokines. In conclusion, interleukin-17 bears the potential to increase neutrophil recruitment into the airways by releasing several, different C-X-C chemokines, including GCP-2, GRO-alpha and interleukin-8 in human bronchial epithelial cells. Inhibition of the p38 MAP kinase pathway and glucocorticoid receptor stimulation constitute two credible therapeutic strategies against this interleukin-17-induced release of neutrophil-recruiting cytokines.
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PMID:Pharmacological modulation of interleukin-17-induced GCP-2-, GRO-alpha- and interleukin-8 release in human bronchial epithelial cells. 1259 Nov 13

Inhaled steroids are the most potent anti-inflammatory therapy commonly used in bronchial asthma. There are, however, a small number of asthmatic patients who do not respond to inhaled steroid-treatment. The stimulation of metabolism and excretion of inhaled drugs at bronchial tissues might lead to a decrease in the effect of the drugs, although the molecular mechanism of this resistance is unclear. In this study, we found that beclomethasone dipropionate (BDP) stimulated the expression of mRNAs for uridine 5'-diphosphate glucuronosyl transferase 2B4 and 2B11, and transporters such as multidrug resistance P-glycoprotein, multidrug resistance-associated protein 1 and 2 in cultured bronchial epithelial cells. It is possible that the individual differences of expression of drug metabolizing enzymes and transporters and their enhancement with BDP are implicated in the individual differences of reactivity over steroid medical treatment.
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PMID:Induction of drug-metabolizing enzymes and transporters in human bronchial epithelial cells by beclomethasone dipropionate. 1537 Aug 84

BMS-262084 is a potent and selective beta-lactam tryptase inhibitor with therapeutic potential for treating asthma. The oral bioavailability of BMS-262084 was low in rats (4% at a dose of 0.5 mg/kg) due to poor absorption. BMS-262084 was excreted mainly unchanged in the urine, suggesting minimal metabolism in rats. The objective of this study was to investigate the mechanisms of oral absorption of BMS-262084 in rats. Modulation of intestinal tight junctions, binding to trypsin, and involvement of the intestinal dipeptide transport system and P-glycoprotein (P-gp) in the absorption of BMS-262084 were examined. Coadministration of BMS-262084 with SQ-29852, a substrate of the intestinal dipeptide transport system, did not change the oral absorption of BMS-262084. An increase in the dose of BMS-262084 from 0.5 to 50 mg/kg resulted in a 3.7-fold increase in its oral absorption. Inulin absorption was enhanced upon coadministration with BMS-262084, suggesting the opening of tight junctions in the intestinal epithelium. Coadministration of aprotinin, a trypsin inhibitor, increased the oral absorption of BMS-262084 several fold. In vitro, using Caco-2 cells, BMS-262084 appeared to be a P-gp substrate, with an efflux ratio of 14. These results suggest that absorption of BMS-262084 is mediated by several concurrent mechanisms. At higher doses of BMS-262084, increased absorption may be primarily due to opening of tight junctions in the intestinal epithelium and consequent absorption via the paracellular pathway, while at lower doses, binding to trypsin may contribute to limiting its absorption. P-gp efflux may also play a role in influencing the absorption of BMS-262084. The intestinal dipeptide transporter system does not appear to be involved in the absorption of BMS-262084.
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PMID:Multiple pathways are involved in the oral absorption of BMS-262084, a tryptase inhibitor, in rats: role of paracellular transport, binding to trypsin, and P-glycoprotein efflux. 1579 9

ATP-binding cassette (ABC) transporters are a family of transmembrane proteins that can transport a wide variety of substrates across biological membranes in an energy-dependent manner. Many ABC transporters such as P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1) and breast cancer resistance protein (BCRP) are highly expressed in bronchial epithelium. This review aims to give new insights in the possible functions of ABC molecules in the lung in view of their expression in different cell types. Furthermore, their role in protection against noxious compounds, e.g. air pollutants and cigarette smoke components, will be discussed as well as the (mal)function in normal and pathological lung. Several pulmonary drugs are substrates for ABC transporters and therefore, the delivery of these drugs to the site of action may be highly dependent on the presence and activity of many ABC transporters in several cell types. Three ABC transporters are known to play an important role in lung functioning. Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene can cause cystic fibrosis, and mutations in ABCA1 and ABCA3 are responsible for respectively Tangier disease and fatal surfactant deficiency. The role of altered function of ABC transporters in highly prevalent pulmonary diseases such as asthma or chronic obstructive pulmonary disease (COPD) have hardly been investigated so far. We especially focused on polymorphisms, knock-out mice models and in vitro results of pulmonary research. Insight in the function of ABC transporters in the lung may open new ways to facilitate treatment of lung diseases.
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PMID:ATP-binding cassette (ABC) transporters in normal and pathological lung. 1596 26

Multi drug resistance(MDR) is a major problem in the treatment ofcancer and hematological malignancies. This resistance is multi factorial and is the result of decreased intra cellular drug accumulation. This is partly due to the presence of a 170KD intra membranous protein termed P-glycoprotein(P-gp) that is an energy- dependent efflux pump which has increased expression on drug-resistance cells. In this study we identified the presence of P-gp by staining with Fluorescent Iso Thio Cyanate (FITC) conjugated anti P-gp in acute leukemia patients and flow cytometry in addition to performing immunophenotype analysis and French, American British (FAB) classification. Results revealed that one fifth of leukemic patients expressed P-gp and this phenotype was more prevalent in Acute Undifferentiated Leukemia(AUL) and Acute Myelogenous Leukemia (AML) than in Acute Lymphoblastic Leukemia(ALL). Other findings showed a logical relationship between this phenotype and age groups. There was not any association between P-gp+ phenotype and FAB and Immunophenotyping sub classification, but there was a linear relationship between CD34 and CD7 expression and P-gp+ phenotype. The accumulation of P-gp molecule that was stated as Mean Fluorescence Intensity (MFI) on the blasts' membrane of AUL and AML patients showed marked increase in comparison to ALL. Furthermore MFI in P-gp+ relapsed patients was much more than P-gp+ pretreatment patients. Kepvords: Leukemia, Drug resistance, P-glycoprotein, Flowcytometry, FAB classification, Immunophenotyping, Mean Fluorescence Intensity.
Iran J Allergy Asthma Immunol 2003 Jun
PMID:P-glycoprotein quantitation in acute leukemia. 1730 57

Glucocorticoid resistance or insensitivity is a major barrier to the treatment of several common inflammatory diseases-including chronic obstructive pulmonary disease and acute respiratory distress syndrome; it is also an issue for some patients with asthma, rheumatoid arthritis, and inflammatory bowel disease. Several molecular mechanisms of glucocorticoid resistance have now been identified, including activation of mitogen-activated protein (MAP) kinase pathways by certain cytokines, excessive activation of the transcription factor activator protein 1, reduced histone deacetylase-2 (HDAC2) expression, raised macrophage migration inhibitory factor, and increased P-glycoprotein-mediated drug efflux. Patients with glucocorticoid resistance can be treated with alternative broad-spectrum anti-inflammatory treatments, such as calcineurin inhibitors and other immunomodulators, or novel anti-inflammatory treatments, such as inhibitors of phosphodiesterase 4 or nuclear factor kappaB, although these drugs are all likely to have major side-effects. An alternative treatment strategy is to reverse glucocorticoid resistance by blocking its underlying mechanisms. Some examples of this approach are inhibition of p38 MAP kinase, use of vitamin D to restore interleukin-10 response, activation of HDAC2 expression by use of theophylline, antioxidants, or phosphoinositide-3-kinase-delta inhibitors, and inhibition of macrophage migration inhibitory factor and P-glycoprotein.
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PMID:Glucocorticoid resistance in inflammatory diseases. 1948 16

Glucocorticoids are the mainstay of asthma management and effectively treat acute exacerbations of asthma. However, a small subset of asthmatics, usually with severe asthma, respond poorly even to systemic administration of high-dose glucocorticoids and this condition is termed "steroid-resistant asthma". This cohort, although small, accounts for approximately 50% of total health care cost for asthma. New investigations into the mechanisms of glucocorticoid action have broadened and deepened our understanding of glucocorticoid resistance. Here we review the importance and characteristics of steroid resistant asthma, the mechanisms that mediate the function of glucocorticoids and that lead to the development of this disease and potential therapies to reverse resistance to treatment. Cellular and molecular factors, receptors and complex signalling pathways have all been implicated. Indeed, based on molecular biological studies, excessive activation of intracellular transcription factors, impaired histone deacetylase, and epigenetic (such as miR-18 and miR-124a) as well as other factors (e.g. vitamin D, P-glycoprotein 170, and macrophage migration inhibitory factor and T helper 17 cells and factors related to innate immunity (such as IFN-gamma and LPS)) may result in glucocorticoid resistance. A thorough understanding of the pathogenesis of steroid resistant asthma will help to develop more efficacious agents for the treatment of the disease.
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PMID:Potential therapeutic targets for steroid-resistant asthma. 2041 45


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