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      Comparative Study on the Effects of Cyclosporin A in Renal Cells in Culture

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          Background: Although cyclosporin A (CSA) inhibits P-glycoprotein (ABCB1), the relationship between this inhibition and CSA-induced nephrotoxicity is not established. Methods: Three renal cell lines were used to investigate the effects of CSA in cellular viability and accumulation of rhodamine 123 (Rho123): LLC-PK1, which does not express ABCB1 substantially; MDCK, expressing moderate amounts of this protein, and Ma104 cells, which express high amounts of ABCB1. Results: The viability was significantly reduced in the three cell lines after treatment with CSA concentrations >10 µ M. Ma104 was the more resistant and LLC-PK1 the more sensitive. CSA increased Rho123 accumulation in the three cell lines when incubated simultaneously, MDCK presenting the higher increase. However, different results were achieved when the periods of incubation with Rho123 and CSA were disconnected: a post-incubation with CSA was more effective in Ma104 cells, while MDCK and LLC-PK1 showed no difference between pre-, co- and post-incubation with CSA. Conclusions: Our results suggest that the effects of CSA may be divided into two groups: ABCB1-independent (direct injury), and ABCB1-dependent toxicity, due to modulation of its activity. This could result in increased accumulation of noxious ABCB1 substrates, contributing to CSA-induced nephrotoxicity. Furthermore, the mechanisms of ABCB1 modulation by CSA may be different for different cell lines.

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          Most cited references 22

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          Host Cell Invasion by TRYPANOSOMA cRUZI Is Potentiated by Activation of Bradykinin B2 Receptors

          The parasitic protozoan Trypanosoma cruzi employs multiple molecular strategies to invade a broad range of nonphagocytic cells. Here we demonstrate that the invasion of human primary umbilical vein endothelial cells (HUVECs) or Chinese hamster ovary (CHO) cells overexpressing the B2 type of bradykinin receptor (CHO-B2R) by tissue culture trypomastigotes is subtly modulated by the combined activities of kininogens, kininogenases, and kinin-degrading peptidases. The presence of captopril, an inhibitor of bradykinin degradation by kininase II, drastically potentiated parasitic invasion of HUVECs and CHO-B2R, but not of mock-transfected CHO cells, whereas the B2R antagonist HOE 140 or monoclonal antibody MBK3 to bradykinin blocked these effects. Invasion competence correlated with the parasites' ability to liberate the short-lived kinins from cell-bound kininogen and to elicit vigorous intracellular free calcium ([Ca2+]i) transients through B2R. Invasion was impaired by membrane-permeable cysteine proteinase inhibitors such as Z-(SBz)Cys-Phe-CHN2 but not by the hydrophilic inhibitor 1-trans-epoxysuccinyl-l-leucyl-amido-(4-guanidino) butane or cystatin C, suggesting that kinin release is confined to secluded spaces formed by juxtaposition of host cell and parasite plasma membranes. Analysis of trypomastigote transfectants expressing various cysteine proteinase isoforms showed that invasion competence is linked to the kinin releasing activity of cruzipain, herein proposed as a factor of virulence in Chagas' disease.
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            St John's wort (Hypericum perforatum): drug interactions and clinical outcomes.

            The aim of this work is to identify the medicines which interact with the herbal remedy St John's wort (SJW), and the mechanisms responsible. A systematic review of all the available evidence, including worldwide published literature and spontaneous case reports provided by healthcare professionals and regulatory authorities within Europe has been undertaken. A number of clinically significant interactions have been identified with prescribed medicines including warfarin, phenprocoumon, cyclosporin, HIV protease inhibitors, theophylline, digoxin and oral contraceptives resulting in a decrease in concentration or effect of the medicines. These interactions are probably due to the induction of cytochrome P450 isoenzymes CYP3A4, CYP2C9, CYP1A2 and the transport protein P-glycoprotein by constituent(s) in SJW. The degree of induction is unpredictable due to factors such as the variable quality and quantity of constituent(s) in SJW preparations. In addition, possible pharmacodynamic interactions with selective serotonin re-uptake inhibitors and serotonin (5-HT(1d)) receptor-agonists such as triptans used to treat migraine were identified. These interactions are associated with an increased risk of adverse reactions. In Sweden and the UK the potential risks to patients were judged to be significant and therefore information about the interactions was provided to health care professionals and patients. The product information of the licensed medicines involved has been amended to reflect these newly identified interactions and SJW preparations have been voluntarily labelled with appropriate warnings.
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              Intracellular mechanisms of cyclosporin A-induced tubular cell apoptosis.

              Tubular cell apoptosis contributes to the pathogenesis of renal injury. However, the intracellular pathways that are active in tubular epithelium are poorly understood. The lethal pathways activated by cyclosporin A (CsA), a nephrotoxin that induces caspase-dependent apoptosis in tubular epithelium, were explored. Fas expression, caspase activation, and mitochondrial injury were assessed by Western blot, flow cytometry, and microscopy in cultured murine tubular epithelial cells exposed to CsA. The influence of FasL antagonists, Bax antisense oligodeoxynucleotides, and caspase inhibitors on cell survival was explored. Tubular cells constitutively express FasL. CsA increased the expression of Fas. However, Fas had no role in CsA-induced apoptosis, as CsA did not sensitize to FasL-induced apoptosis, caspase-8 activity was not increased, and neither blocking anti-FasL antibodies nor caspase-8 inhibition prevented CsA-induced apoptosis. Apoptosis induced by CsA is associated with the translocation of Bax to the mitochondria and Bax antisense oligodeoxynucleotides protected from CsA-induced apoptosis. CsA promoted a caspase-independent release of cytochrome c and Smac/Diablo from mitochondria. CsA also led to a caspase-dependent loss of mitochondrial membrane potential. Caspase-2, caspase-3, and caspase-9 were activated, and specific caspase inhibitor prevented apoptosis and increased long-term survival. Evidence for endoplasmic reticulum stress, such as induction of GADD153, was also uncovered. However, endoplasmic reticulum-specific caspase-12 was not activated. CsA induces changes in several apoptotic pathways. However, the main lethal apoptotic pathway in CsA-exposed tubular epithelial cells involves mitochondrial injury.

                Author and article information

                Nephron Exp Nephrol
                Cardiorenal Medicine
                S. Karger AG
                March 2005
                20 January 2005
                : 99
                : 3
                : e77-e86
                aInstituto de Biofísica Carlos Chagas Filho, bDepartamento de Bioquímica Médica-ICB, UFRJ, cDepartamento de Clínica Médica, Universidade do Rio de Janeiro (UNI-RIO), RiodeJaneiro, Brazil
                83415 Nephron Exp Nephrol 2005;99:e77–e86
                © 2005 S. Karger AG, Basel

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                Figures: 7, References: 45, Pages: 1
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