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

P-glycoprotein (PGP), an active efflux pump of antitumor agents in multidrug-resistant tumor cells, exists in brain capillary endothelium and could be functionally involved in the blood-brain barrier. To study the regulatory mechanism of PGP expression in brain capillary endothelium, various mouse tissue matrices were tested for their abilities to enhance the expression of PGP in mouse brain capillary endothelial cells (MBEC), which express relatively small amounts of PGP. Of the four tissue matrices we examined, PGP expression in MBEC cultured on the brain matrix increased 2.0-fold. The PGP-inducing activity was similarly detected in bovine brain matrix, and the activity was enriched in the fraction of pl 9.0 by isoelectric focusing. The fraction, named PIC-fraction (PGP-inducing component), increased the PGP expression in MBEC 3.5-fold. By Northern blot analysis, a 3.3-fold enhancement of mdr gene expression was observed in MBEC cultured on the PIC-fraction. The PGP-inducing activity of the PIC-fraction was reduced by the treatment with trypsin but not with collagenase, suggesting that a proteinaceous factor distinct from type I collagen might be responsible for the PGP-inducing activity of PIC-fraction. Although the PIC-fraction increased the PGP expression in other mouse brain capillary endothelial cells, the PIC-fraction did not increase PGP expression in mouse aortic endothelial cells and KB carcinoma cell lines expressing various amounts of PGP. These observations suggest that PGP expression in brain capillary endothelium is specifically regulated by a tissue-specific factor in the brain matrix.
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PMID:Enhanced expression by the brain matrix of P-glycoprotein in brain capillary endothelial cells. 784 16

Previous studies reported that, in the absence of drug exposure, multidrug resistance, including resistance to Adriamycin (ADR), could develop in primary rat hepatocyte cultures (B. Carr, Proc. Am. Assoc. Cancer Res., 29:1158, 1988). However, the hepatocytes in that report were cultured on plastic without the benefit of an extracellular matrix (ECM). Because the ECM regulates hepatic gene expression, we have critically evaluated in primary cultures of rat hepatocytes how the ECM affects hepatic ADR resistance, the level of the drug efflux transporter associated with MDR, P-glycoprotein (pgp), and transport of a prototypical pgp substrate, vincristine. Hepatocytes cultured on type I collagen (Vitrogen) had greater resistance to ADR toxicity accompanied by parallel increases in the level of pgp mRNA, decreased drug accumulation, and enhanced drug efflux when compared with the hepatocytes maintained on the basement membrane matrix Matrigel. The development of ADR resistance coincided with the time course of increased pgp mRNA but was not coincident with the time course of expression of either the placental isozyme of glutathione S-transferase or P-450 reductase, proteins associated with MDR in some resistance models. Southern blot analysis revealed neither gross changes in pgp gene structure or gene copy number to account for the increase in pgp RNA levels for hepatocytes cultured on Vitrogen. ECM also regulated xenobiotic-inducible expression of hepatic pgp, since chemotherapeutic agents, including vincristine and colchicine, induced pgp mRNA exclusively in hepatocytes cultured on Vitrogen. The critical matrix proteins in Matrigel responsible for regulation of pgp were determined by the selective addition of its components to the culture environment. The presentation of the individual matrix elements as a rigid substratum to the hepatocyte did not decrease pgp mRNA. In contrast, the presentation to the same hepatocytes of either laminin or type IV collagen in a nonrigid state (solubly in the medium) selectively decreased hepatocellular pgp mRNA. We conclude that primary rat hepatocytes develop ADR resistance with time in culture due to increased expression of pgp and that ECM proteins represent endogenous physiological modulators of both basal and chemotherapeutically inducible expression of hepatic P-glycoprotein.
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PMID:Extracellular matrix regulation of multidrug resistance in primary monolayer cultures of adult rat hepatocytes. 842 4

A human chondrosarcoma cell line, CS-1, was treated successively with increasing concentrations of the marine chemotherapeutic Ecteinascidin-743 (ET-743), yielding a variant cell line displaying a significant degree of resistance to the cytotoxic action of this drug. Various experiments were performed to discern molecular aberrations between the parent and resistant cell line, and also identify potential molecular markers indicative of drug resistance. Although no significant differences in the levels of membrane transporters such as P-glycoprotein or multidrug resistance protein 1 (MRP1) were detected, the cell migratory ability of the ET-743-resistant cell variant was reduced, as was its attachment capability to gelatin-coated cell culture dishes. Staining of the actin-containing cytoskeleton with fluorescent-labeled phalloidin revealed marked differences in the cytoskeleton architecture between the parent and ET-743-resistant CS-1 cell lines. Comparison of serum-free conditioned medium from both cell lines showed conspicuous differences in the levels of several proteins, including a quartet of high molecular weight proteins (> or =140 kDa). The protein sequences of two of these high molecular weight proteins, present at significantly higher concentrations in conditioned medium obtained from the parent cell line, corresponded to subunits of types I and IV collagen. Analysis of type I collagen alpha1 chain mRNA revealed a significantly lower level in the ET-743-resistant CS-1 cell line. Thus, prolonged exposure to ET-743 may cause changes in cell function through cytoskeleton rearrangement and/or modulation of collagen levels.
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PMID:Ecteinascidin-743 drug resistance in sarcoma cells: transcriptional and cellular alterations. 1463 96

We describe a method for generating primary cultures of human brain microvascular endothelial cells (HBMVECs). HBMVECs are derived from microvessels isolated from temporal tissue removed during operative treatment of epilepsy. The tissue is mechanically fragmented and size filtered using polyester meshes. The resulting microvessel fragments are placed onto type I collagen-coated flasks to allow HBMVECs to migrate and proliferate. The overall process takes less than 3 h and does not require specialized equipment or enzymatic processes. HBMVECs are typically cultured for approximately 1 month until confluent. Cultures are highly pure ( approximately 97% endothelial cells; approximately 3% pericytes), are reproducible, and show characteristic brain endothelial markers (von Willebrand factor, glucose transporter-1) and robust expression of tight and adherens junction proteins as well as caveolin-1 and efflux protein P-glycoprotein. Monolayers of HBMVECs show characteristically high transendothelial electric resistance and have proven useful in multiple functional studies for in vitro modeling of the human blood-brain barrier.
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PMID:Establishment of primary cultures of human brain microvascular endothelial cells to provide an in vitro cellular model of the blood-brain barrier. 2059 55