Mechanisms of muscular electrophysiological and mitochondrial dysfunction following exposure to malathion, an organophosphorus pesticide.

Muscle dysfunction in acute organophosphorus (OP) poisoning is a cause of death in human. The present study was conducted to identify the mechanism of action of OP in terms of muscle mitochondrial dysfunction. Electromyography (EMG) was conducted on rats exposed to the acute oral dose of malathion (400 mg/kg) that could inhibit acetylcholinesterase activity up to 70%. The function of mitochondrial respiratory chain and the rate of production of reactive oxygen species (ROS) from intact mitochondria were measured. The bioenergetic pathways were studied by measurement of adenosine triphosphate (ATP), lactate, and glycogen. To identify mitochondrial-dependent apoptotic pathways, the messenger RNA (mRNA) expression of bax and bcl-2, protein expression of caspase-9, mitochondrial cytochrome c release, and DNA damage were measured. The EMG confirmed muscle weakness. The reduction in activity of mitochondrial complexes and muscular glycogen with an elevation of lactate was in association with impairment of cellular respiration. The reduction in mitochondrial proapoptotic stimuli is indicative of autophagic process inducing cytoprotective effects in the early stage of stress. Downregulation of apoptotic signaling may be due to reduction in ATP and ROS, and genotoxic potential of malathion. The maintenance of mitochondrial integrity by means of artificial electron donors and increasing exogenous ATP might prevent toxicity of OPs.

In vitro study on the effect of doxorubicin on the proliferation markers MCM3 and Ki-67.

PURPOSE: Aberrant proliferation is an essential feature of cancer cells, which can be caused by alterations in components of the cell cycle, such as minichromosome maintenance protein-3 (MCM3) and Ki-67. Doxorubicin is a cytotoxic/cytostatic anticancer agent commonly used in chemotherapy. We investigated the effect of this drug on MCM3 and Ki-67 in the KB cell line, which is considered a subline of HeLa cell line. METHODS: KB cells were treated with doxorubicin and its effect on apoptosis, mRNA levels and protein expression of MCM3 and Ki-67 was determined by flow cytometry (annexin V-FITC/PI assay), quantitative real-time RT-PCR (qRT-PCR) and immunocytochemistry, respectively. Cytotoxicity was assessed using the MTT assay. One-way analysis of variance (ANOVA) was used for comparing groups and differences were assessed by a Tukey's post hoc test. RESULTS: Protein expression of both biomarkers and MCM3 mRNA were not affected by doxorubicin, but Ki-67 mRNA significantly increased after treatment (p=0.049). CONCLUSIONS: Considering that doxorubicin can influence certain biochemical events that lead to modifications in Ki- 67, this factor might be useful in evaluating the impact of anthracycline-based chemotherapeutic agents. Changes in MCM3 following doxorubicin treatment require further investigation.

Evaluation of anticancer effects of newly synthesized dihydropyridine derivatives in comparison to verapamil and doxorubicin on T47D parental and resistant cell lines in vitro.

Failure of current anticancer drugs mandates screening for new compounds of synthetic or biological origin to be used in cancer therapy. Multidrug resistance (MDR) is one of the main obstacles in the chemotherapy of cancer. Efflux of cytotoxic agents mediated by P-glycoprotein (P-gp or MDR1) is believed to be an important mechanism of multidrug resistance. Therefore, we decided to investigate the antiproliferative effects of seven newly synthesized 1,4-dihydropyridine (DHP) derivatives in comparison to verapamil (VP) and doxorubicin (DOX) on human breast cancer T47D cells and its MDR1 overexpressed and moderately resistant cells (RS cells) using MTT cytotoxicity assay. We also examined the effects of these compounds on cytotoxicity of DOX in these two cell types. The cytotoxicity assays using MTT showed that most of the tested new DHP derivatives and VP at 10 microM concentration had varying levels of toxicity on both T47D and RS cells. The toxicity was mostly in the range of 10-25%. However, the cytotoxicity of these DHP derivatives, similar to VP, was significantly less than DOX when comparing IC(50) values. Furthermore, these compounds in general had relatively more cytotoxicity on T47D vs RS cells at 10-microM concentration. Among new DHPs, compounds 7a (3,5-dibenzoyl-4-(2-methylthiazol-4-yl)-1,4-dihydro-2,6-dimethylpyridine) and 7d (3,5-diacetyl-4-[2-(2-chlorophenyl)thiazol-4-yl)]-1,4-dihydro-2,6-dimethylpyridine) showed noticeable potentiation of DOX cytotoxicity (reduction of DOX IC(50)) compared to DOX alone in both cells, particularly in RS cells. This effect was similar to that of VP, a known prototype of MDR1 reversal agent. In other words, compounds 7a and 7d resensitized RS cells to DOX or reversed their resistance. Results indicate that compound 7d exerts highest effect on RS cells. Therefore, these two newly synthesized DHP derivatives, compounds 7a and 7d, are promising as potential new MDR1 reversal agents and should be further studied on other highly resistant cells due to MDR1 overexpression and with further molecular investigation.