Genotoxic evaluation of chloroacetonitrile in murine marrow cells and effects on DNA damage repair gene expressions.

Although chloroacetonitrile (CAN), a disinfection by-product of chlorination of drinking water, is considered a rodent carcinogen that induces lung adenomas in mice, previous studies on its genotoxicity have yielded inconclusive results. Thus, its cancer mode of action has not been clearly defined. We evaluated CAN-induced genotoxicity in mice using mouse bone marrow micronucleus test, comet assays and expression of genes associated with DNA damage repair. Mice exposed to CAN at 8.75, 17.5, 35 and 52.5mg/kg for 7 days did not exhibit any significant increases in the incidence of micronuclei formation at 24 and 48h after last exposure. However, CAN caused significant suppressions of erythroblast proliferation at the highest dose. In the alkaline comet assay, there was a significant increase in the incidence of DNA strand breaks in mice killed after 3h of last treatment with 35 and 52.5mg/kg/day CAN, while no significant difference in the DNA strand breaks was found in mice killed after 24h of the last treatment. However, slight (but significant) CAN-induced oxidative DNA damage was detected following Fpg digestion at 3-h sampling time, digestion with EndoIII resulted in considerable increases in oxidative DNA damage at 3 and 24h after the last exposure to 35 and 52.5mg/kg/day CAN as detected by oxidative comet assays. The expression of DNA repair genes OGG1 , Apex1, PARP1 and p53 were up-regulated in mice given 35mg/kg/day CAN at 3h but not in 24h after the last treatment except OGG1 . However, the significant up-regulation of OGG1 at 24h after the last treatment further indicates the occurrence of oxidative DNA damage. Overall, CAN exposure is associated with up-regulation of DNA repair gene expression and the induction of oxidative DNA damage, which may be at least partially responsible for CAN-induced genotoxicity and eventually cause carcinogenicity.

Silencing of tissue factor by antisense deoxyoligonucleotide mitigates thioacetamide-induced liver injury.

BACKGROUND: Retinoid receptors (RRs), RAR-α and RXR-α, work as transcription factors that regulate cell growth, differentiation, survival, and death. Hepatic stellate cells (HSCs) store retinoid and release its RRs as lipid droplets upon their activation. PURPOSE: We test the hypothesis that loss of retinoid receptors RAR-α and RXR-α from HSCs is dependent on tissue factor (TF) during thioacetamide (TAA)-induced liver injury. METHODS: Liver toxicity markers, TF, fibrin, cleaved caspase-3, and cyclin D1 as well as histopathology were investigated. RESULTS: Increased TF, fibrin, cleaved caspase-3, and cyclin D1 protein expression is seen in zone of central vein after TAA injection compared with vehicle-treated mice. A strong downregulation of RAR-α and RXR-α is seen in TAA-induced liver injury. In addition, histopathological obliteration and pericentral expression of cleaved caspase 3 and cyclin D1 are observed after TAA injection compared with the normal vehicle-treated mice. No changes have been seen in TAA/TF-sense (SC) in whole parameters compared with TAA-treated animals. TAA/TF-antisense (AS)-treated mice show normal expression of all parameters and normal histopathological features when compared with the control mice. In conclusion, this study declares that the strong downregulation of RAR-α and RXR-α may cause liver injury and particularly activation of HSCs in TAA-induced toxicity. TF-AS treatment not only downregulates TF protein expression but also alleviates loss of liver RAR-α and RXR-α and suppresses the activated apoptosis signals in TAA-induced liver toxicity. Finally, TF and RAR-α/RXR-α are important regulatory molecules in TAA induced acute liver injury.

Carbon tetrachloride-induced liver injury in mice is tissue factor dependent.

Tissue factor (TF) is a membranous glycoprotein that activates the coagulation system when blood vessels or tissues are damaged. TF was up-regulated in monocrotaline (MCT)/lipopolysaccharide (LPS) hepatotoxicity model. The present study aimed to test the hypothesis that TF-dependent fibrin deposition occurs in liver toxicity induced by CCl4 in mice. Pericentral deposition of TF and fibrin is induced after CCl4-induced liver toxicity. The toxicity was evaluated by determination of serum activities of ALT, AST and ALP as well as GSH content and histopathological changes. The results showed that injection of mice with TF-antisense deoxyoligonucleotide (TF-AS) prevented the accumulation of TF and fibrin in the hepatic tissues. Furthermore, it significantly restored blood biochemical parameters, GSH content and distorted histopathological features caused by CCl4. The current study demonstrates that TF activation is associated with CCl4-induced liver injury. Furthermore, administration of TF-AS successfully prevented this type of liver injury.

Assessment of genomic instability in normal and diabetic rats treated with metformin.

To examine if a single or multiple oral administration of metformin, a member of the biguanide class of anti-diabetic agents, has any genotoxic and cytotoxic potential in normal and diabetic rats, a mammalian model, cytogenetic assays through several endpoints such as induction of micronuclei, chromosome aberrations, mitotic activity of bone marrow cells, sperm-head anomaly and assays of some oxidative stress markers have been conducted by the use of standard techniques. Diabetes was induced by streptozotocin injection. Metformin was administrated to both diabetic and non-diabetic rats in single doses of 100, 500 or 2500 mg/kg along with vehicle control groups for diabetic and non-diabetic rats. The animals were killed by cervical dislocation at 24h after treatment, and then bone marrow cells were sampled. Also, a multiple dose study has done in which diabetic and non-diabetic animals were treated with 100 or 500 mg/kg of metformin daily for 4 or 8 weeks after which the animals were killed by cervical dislocation, and then bone marrow and sperm cells were collected. Concurrent control groups were also included in each experiment. The obtained results revealed that metformin was neither genotoxic nor cytotoxic for the rats in all groups at all tested doses. Moreover, metformin significantly reduced the diabetes-induced genomic instability and cell proliferation changes in somatic and germinal cells in a dose-dependent manner (2500, 500, >100mg/kg). In addition, diabetes induced marked biochemical alterations characteristic of oxidative stress including, enhanced lipid peroxidation and reduction in the reduced glutathione level. Treatment with metformin ameliorated these biochemical markers. In conclusion, metformin is a non-genotoxic or cytotoxic compound and may protect from genomic instability induced by hyperglycemia. Apart from its well-known anti-diabetic effect, the antigenotoxic effect of metformin could be possibly ascribed to its radical scavenger effect that modulated the genomic instability responses and cell proliferation changes induced by hyperglycemia.

Influence of p-coumaric acid on doxorubicin-induced oxidative stress in rat's heart.

The therapeutic value of doxorubicin (DOX) as anticancer antibiotic is limited by its cardiotoxicity. The implication of natural phenolic acids in the prevention of many pathologic diseases has been reported. Herein, the ability of p-coumaric (PC) acid, a member of phenolic acids, to protect rat's heart against DOX-induced oxidative stress was investigated. Three main groups of albino rats were used; DOX, PC, and PC plus DOX-receiving animals. Corresponding control animals were also used. DOX was administered i.p. in a single dose of 15mgkg(-1). PC alone, in a dose of 100mgkg(-1), was orally administered for five consecutive days. In PC/DOX group, rats received PC 5 days prior to DOX. DOX-induced high serum levels of lactic dehydrogenase (LDH) and creatine phosphokinase (CPK), were reduced significantly by PC administration, compared to DOX-receiving rats. Pretreatment with PC ameliorated the cardiac content of glutathione (GSH), and superoxide dismutase (SOD) & catalase (CAT) activities, compared to DOX-receiving rats. On the other hand, accumulation of cardiac content of MDA significantly decreased following PC pretreatment, compared to DOX-treated rats. The data presented here indicate that PC protects rats hearts against DOX-induced oxidative stress in the heart. It may be worthy to consider the usefulness of PC as adjuvant therapy in cancer management.