Triazole rizatriptan Induces Liver Toxicity through Lysosomal/Mitochondrial Dysfunction.

Background: Triptans are used as antimigraine agents. Some cases of hepatotoxicity by triptans have been reported. However, the exact mechanism of triptan-induced hepatotoxicity is not clear yet. Methods: In this study, the cytotoxic effects of rizatriptan were investigated in freshly isolated rat hepatocytes using accelerated cytotoxicity mechanism screening. We designed experiments to evaluate toxicity markers, such as cell death, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial membrane potential, lysosomal membrane integrity and the amount of reduced and oxidized glutathione in the rizatriptan-treated hepatocytes. Results: Cytotoxicity caused by rizatriptan in rat hepatocytes was concentration-dependent. An increase in ROS formation accompanied by a significant rise in lipid peroxidation, mitochondrial depolarization and loss of lysosomal membrane integrity was observed. Cellular glutathione reservoirs were decreased and a significant amount of oxidized glutathione was formed. All the aforementioned rizatriptan-induced cellular events were significantly (p<0.05) prevented by ROS scavengers, antioxidants, endocytosis inhibitors and adenosine triphosphate (ATP) generators. Also, the present results demonstrated that CYP450 is involved in rizatriptan-induced oxidative stress and cytotoxicity mechanism and different CYP450 inducers had different effects on the toxicity. Conclusion: It is suggested that the adverse effect of rizatriptan towards hepatocytes is mediated by oxidative stress and the hepatocytes lysosomes and mitochondria play an important role in rizatriptan-induced cell injury.

Carbenoxolone induces apoptosis and inhibits survivin and survivin-ΔEx3 genes expression in human leukemia K562 cells.

BACKGROUND AND THE PURPOSE OF THE STUDY: Leukemia is a malignant disorder of the blood progenitor/stem cells which is characterized by abnormal proliferation of white blood cells. Although anti-cancer drugs induce apoptosis in cancerous cells, drug resistance is the significant problem mainly due to over-expression of inhibitors of apoptosis proteins (IAPs) such as survivin. In this content, it has been reported that an anti-inflammatory drug, Carbenoxolone (CBX), could induce apoptosis and growth inhibition in several types of cancerous cells. In the present study, effects of CBX on apoptosis and level of the expression of survivin gene and its ΔEx3 splicing variant have were evaluated in K562 cells. METHODS: K562 cells were cultured and treated with different concentrations of CBX (50-300 µM) at different time intervals (12-48 hrs). Trypan blue exclusion test was used to evaluate cell viability. Fluorescent microscopy (Acridine Orange/Ethidium Bromide double staining) and DNA fragmentation assay were used to study apoptosis. The expression level of survivin and its ΔEx3 splice variant were studied by RT-PCR. RESULTS AND MAJOR CONCLUSION: It was found that both growth inhibition and apoptosis occurred in K562 cells. In addition, down-regulation of survivin and survin-ΔEx3 were observed, after 2-4 hrs treatment with 150 µM of CBX. However, the expression level of survivin and its ΔEx3 splice variant increased in subsequent time (6-12 hrs) nearly to the level of control cells. From the results of this study, it may be concluded that CBX can be considered as a candidate for further studies in CML treatment, especially in the case of drug-resistant leukemia cells.

The protective effects of garlic extract against acetaminophen-induced oxidative stress and glutathione depletion.

Acetaminophen, the most commonly sold over-the-counter antipyretic analgesic, is capable of causing severe and sometimes fatal hepatic damage in humans and experimental animals. The incidence of liver injury due to acetaminophen overdose, either with suicidal intent or by accident, is increasing. Garlic is among those medicinal plants famous for its different health protective effects. In this study, the protective effects of garlic extract on acute acetaminophen-induced liver injury were investigated using freshly isolated rat hepatocytes. The hepatocytes were isolated from Sprague-Dawley male rats by a two step collagenase model. Formation of Reactive Oxygen Species (ROS) and Glutathione (GSH) depletion were studied after addition of acetaminophen to cell suspensions. The effects of garlic extract on prevention of ROS formation as well as GSH depletion was investigated and compared with the effects of N-Acetyl Cysteine (NAC) as the standard treatment. Reactive oxygen species formation was assessed by a spectrofluorometry method and garlic extract was shown to be as effective as NAC in decreasing ROS formation induced by acetaminophen. Glutathione (GSH) levels of hepatocytes were determined using HPLC. Garlic extract was effective in preventing GSH depletion significantly (p < 0.05). It is concluded that garlic extract has an antioxidant effect and can protect hepatocytes from GSH depletion following NAPQI production.

Renin-angiotensin system polymorphisms and hemoglobin level in renal allografts: a comparative study between losartan and enalapril.

INTRODUCTION: In this study, hemoglobin (Hb) concentrations secondary to enalapril (E) or losartan (L) therapy were evaluated with respect to renin-angiotensin system (RAS) polymorphisms in renal transplant recipients. MATERIALS AND METHODS: After determination of RAS polymorphisms [angiotensin-converting enzyme (DD, non-DD), angiotensinogen (TT, non-TT), and angiotensin receptor type 1 (CC, non-CC)] by polymerase chain reaction, 70 renal transplant recipients were recruited to four groups randomly: first and second groups were treated with E (10 mg/d, 15 patients) and L (50 mg/d, 20 patients) alone, respectively. The third group received E+L (10 mg/d + 50 mg/d, 13 patients) and the fourth group (22 patients) received no medication. The treatment protocol was followed for 16 weeks. Complete blood counts were checked before treatment and every 2 months. P<.05 was considered to indicate statistical significance. RESULTS: Treatment for 4 months decreased the Hb level in the E+L (14.15 +/- 0.94 to 12.06 +/- 0.66 g/dL, P=.000), E (14.00 +/- 0.86 to 13.11 +/- 0.82 g/dL, P=.02), and L (14.12 +/- 0.90 to 12.10 +/- 2.35 g/dL, P=.01) groups, but not in the control group (13.55 +/- 0.70 to 13.36 +/- 0.69 g/dL, P>.05). None of these regimens showed greater Hb reduction than the others (P>.05). None of the RAS polymorphisms predicted the intensity of the reduced Hb according to the type of treatment (P>.05). Any other sets of RAS polymorphisms (alone or together) did not impact on Hb levels pre- or post-intervention (P>.05). CONCLUSION: Our findings suggest that low dosages of E and/or L decrease Hb levels regardless of the RAS polymorphisms.

Transcriptional regulation of cytochrome P4503A4 gene expression: effects of inherited mutations in the 5'-flanking region.

1. Understanding the genetic basis of interindividual variability in drug disposition and response is a fundamental focus for rational and individualized drug treatment. Cytochrome P4503A4 (CYP3A4) has a central role in human drug metabolism and polymorphic variation has been reported in this gene. 2. This study reports the in vitro functional analysis of inherited mutations in the 5' flanking region of the CYP3A4 gene using reporter constructs in which the 1141 bp proximal promoter region from the mutant alleles was inserted between a single copy of the CYP3A4 300 bp core distal enhancer (XREM) sequence and the cDNA for human secretory alkaline phosphatase. 3. Reporter constructs were co-transfected with an hPXR expression vector into human liver and intestinal cells in culture and xenobiotic modulation of CYP3A4 promoter activity determined by chemiluminescent secretory alkaline phosphatase assay. DNA-protein interactions were next examined using electrophoretic mobility shift assays. 4. The results demonstrated that inherited mutations in the CYP3A4 gene proximal promoter region could cause significant up-regulation of in vitro transcriptional activation by CYP3A4 xenobiotic inducers. In addition, the magnitude of the effect appeared to be dependent on the cell type used in the functional assays, possibly due to the differing availability of specific intracellular transcription factors or their activating ligands.