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)

Melatonin has been reported to attenuate the oxidative damage caused by doxorubicin on kidney, brain, heart and bone marrow, whereas the in vivo antitumor effects of doxorubicin were not attenuated. The effects of melatonin on doxorubicin cytotoxicity have, therefore, been examined on human normal mammary epithelium HBL-100, on mammary adenocarcinoma MCF-7, on colon carcinoma LoVo, and on mouse P388 leukemia cell lines, and on tumor cell sublines pleiotropically resistant to anthracyclines. Melatonin in the concentration range 10-2000 pg/mL causes an inhibition of the growth of the human cell lines examined which is not clearly dose-dependent and less than 25% when significant. Melatonin similarly causes minor effects on doxorubicin cytotoxicity either on the parental human cell lines or on their resistant sublines. On the contrary, 200-1000 pg/mL melatonin cause a significant and dose-dependent partial sensitization to doxorubicin of resistant P388 mouse leukemia (P388/ADR), which occurs also in vivo, as indicated by a significant increase in survival time of the hosts. Doxorubicin intracellular concentrations in P388/ADR cells are increased by melatonin, suggesting that melatonin might inhibit P-glycoprotein-mediated doxorubicin efflux from the cells. These results indicate that the use of melatonin in clinical cancer treatment should not pose the risk of an attenuation of the effectiveness of doxorubicin, and encourage the further examination of the possible reduction by melatonin of the host toxicity of antitumor chemotherapy.
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PMID:Effects of melatonin on doxorubicin cytotoxicity in sensitive and pleiotropically resistant tumor cells. 1158 54

We examined how melatonin absorption was affected by pharmaceutical excipients using the Ussing chamber technique with mounted rat gastrointestinal (GI) segments. Melatonin absorption occurs throughout the GI tract, with the greatest absorption being in the rectum and ileum and the least in the stomach. Melatonin can be classified as a low permeability drug. P-glycoprotein (P-gp) does not affect melatonin absorption but transported rhodamine 123, a well-known P-gp substrate. The possibility of saturating P-gp by melatonin was excluded. Sodium cholate (0.5%) increased melatonin absorption, but decreased absorption at higher concentrations (1.0% and 5.0%). Sodium oleate (0.5% and 1.0%) consistently decreased melatonin absorption. Pharmaceutical excipients increased the absorption of Lucifer yellow (100 microg/mL), a paracellular probe but decreased the absorption of melatonin above the critical micelle concentration (cmc), suggesting that melatonin was transported mainly by transcellular pathway. Sodium cholate and sodium oleate, when above the cmc, resulted in micellar complexes as revealed by (1)H NMR spectra and particle size distribution. Histology tests showed mucosal damage of jejunum tissues in the presence of these excipients. The balance of tissue damage by the formation of micellar complexes could affect the melatonin absorption. This information on melatonin absorption behaviors and its modulation by pharmaceutical excipients can be used in further oral dosage formulations to affect circadian rhythm.
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PMID:New findings on melatonin absorption and alterations by pharmaceutical excipients using the Ussing chamber technique with mounted rat gastrointestinal segments. 1946 96

Melatonin has been known as a neuroprotective agent for the central nervous system (CNS) and the blood-brain barrier (BBB), which is the primary structure that comes into contact with several neurotoxins including methamphetamine (METH). Previous studies have reported that the activation of melatonin receptors (MT1/2) by melatonin could protect against METH-induced toxicity in brain endothelial cells via several mechanisms. However, its effects on the P-glycoprotein (P-gp) transporter, the active efflux pump involved in cell homeostasis, are still unclear. Thus, this study investigated the role of melatonin and its receptors on the METH-impaired P-gp transporter in primary rat brain microvascular endothelial cells (BMVECs). The results showed that METH impaired the function of the P-gp transporter, significantly decreasing the efflux of Rho123 and P-gp expression, which caused a significant increase in the intracellular accumulation of Rho123, and these responses were reversed by the interaction of melatonin with its receptors. Blockade of the P-gp transporter by verapamil caused oxidative stress, apoptosis, and cell integrity impairment after METH treatment, and these effects could be reversed by melatonin. Our results, together with previous findings, suggest that the interaction of melatonin with its receptors protects against the effects of the METH-impaired P-gp transporter and that the protective role in METH-induced toxicity was at least partially mediated by the regulation of the P-gp transporter. Thus, melatonin and its receptors (MT1/2) are essential for protecting against BBB impairment caused by METH.
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PMID:Activation of melatonin receptor (MT1/2) promotes P-gp transporter in methamphetamine-induced toxicity on primary rat brain microvascular endothelial cells. 2822 41