| Multidrug resistance (MDR) is one of the most serious problems responsible for the failure of tumor chemotherapy. The most intensely studies are the P-glycoprotein encoded by the MDR1 gene and the multidrug-resistance associated protein (MRP). This two membrane proteins can extrude chemotherapeutic drugs from the cell under an ATP-dependent mechanism. At present, many efforts have been undertaken to identify a large group of agents (calcium channel blockers, steroid hormone, cyclosporine A, etc.) able to reverse MDR. But however, although immunohistochemistry or other molecular biological assays can be used to reflect drug sensitivity and resistance, or the effect of reversed agents, now it is still lacking reliable and sensitive assay on those issues. And the ultra-weak luminescence may provide a chance for solving this problem.All living systems exhibit a very weak photon emission of a few up to some hundred photons per second and square centimeter, ranging from ultravio- -let (up to about 200 nm) to infrared (at about 900 nm) of the wavelength. Its temperature dependence and the manifold correlations to physiological and biological functions, as, for instance, radical reactivity, oxygen consumption, stress, cell proliferation and differentiation, biological rhythms, even DNA conformations, point to a regulatory activity of these biological photons. Recently, the most modern aspects of this biological luminescence were extensively studied.In this study, the cyclosporine A (CSA) was used to reverse the MDR of the ADM refractory human leukemic cell line HL-60/ADM, the UPE intensity and the oxygen free radical (OFR) concentration changes were studied after the reversion, which might light on the mechanism of MDR and the clinical pratice.AIMS: To evaluate the reversed effects of CSA on HL-60/ADM cells, and to investigate the relationship of UPE intensity and the OFR changes before and after the reversion.METHODS: 1. The cytotoxicity and the reversed effects of CSA on multidrug resistance of human leukemic cell line HL-60/ADM were studied by MTT, Flow CytoMeter (FCM) and immunohistochemical assays; 2. IFFM-D chemiluminescence's instrument, which was made by Xi'an REMEX Analyse Instrment Corporation, was used to detect the intensity of UPE for HL-60/ADM and its reversed cell line HL-60/ADM+CSA; 3. the spectrophotometer was used to detect the SOD, MDA, and GSH concentration, which indirectly reflected the oxygen free radicals inside the HL-60/ADM and HL-60/ADM+CSA cell lines, by colorimetric method.RESULTS: 1. CSA more than 4μg/mL had significant cytotoxicity on HL-60/ADM, while the cytotoxicity was rised with CSA increasing; And CSA (4μg/mL) combined with ADM (1μg/mL) could obviously restrain the growth of HL-60/ADM cells (p<0.01). The P-gp expression of HL-60/ADM decreased clearly after 72 hours'exposure to CSA (4μg/mL) by immunohistochemical assays; 2. Under the same reactive systems (10-4mol/L luminol and 0.3% H2O2), also with a same volume and cells concentration, the intensity of ultraweak photon emission of HL-60/ADM cells was lower than that of HL-60/ADM+CSA cells (P<0.01); 3. At the same cell conditions, the MDA concentration of the reversed groups (HL-60/ADM+CSA cells) was higher than the control groups (HL-60/ADM cells) (p<0.05), while the antioxidants SOD and GSH has a significantly less level in the reversed groups than that in control groups (p<0.01).CONCLUSIONS: 1. The MDR of HL-60/ADM could be reversed by low dose of CSA effectively; 2. The decrease of the UPE intensity in HL-60/ADM+CSA cells, might be correlated with weaken of the oxidized metabolic reaction, the decreasing of cell-growth speed and DNA duplication inside the reversed cells. Another possible mechanism may relate to the variation of the oxygen radicals on reversed cells; 3. The MDR of HL-60/ADM could be reversed by low dose of CSA effectively. Free radicals may be involved in this reversed process, which can lead to the cell death. |
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