Antioxidative effects of fluvastatin and its metabolites against DNA damage in streptozotocin-treated mice

Fluvastatin alleviates doxorubicin-induced cardiac and renal toxicity in rats via regulation of oxidative stress, inflammation, and apoptosis associated genes expressions

Doxorubicin (DOXO) is a cytostatic agent used in the chemotherapy protocol of several cancers for more than 40 years, but usage of this drug in cancer treatment has been limited due to severe renal and cardiac tissue toxicities that may result in death in patients. Fluvastatin (FV) is a fully synthetic hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitor used as a cholesterol-lowering agent in patients with hypercholesterolemia. Previous studies revealed that FV also exhibits antioxidant, anti-inflammatory, and antitumor activity. Additionally, our previous study indicated that FV exerts a prophylactic effect on DOXO-induced testicular toxicity by preventing lipid peroxidation, supporting the antioxidant system, and regulating the blood-testis barrier-associated genes expression. Herein, we purposed to evaluate the possible therapeutic and the protective effects of FV on the DOXO-induced cardiac and renal toxicitiy model by histochemical, immunohistochemical, biochemical, and real-time polymerase chain reaction (real-time PCR) analyses. Results point out protective use of FV exerts a beneficial effect by repressing lipid peroxidation and by regulating the inducible nitric oxide synthase (iNOS), nitric oxide synthase endothelial (eNOS), nuclear factor kappa-B (NF-κB), and Caspase-3 (Casp3) protein and mRNA expressions, which play an important role in mediating DOXO-induced renal and cardiac toxicity mechanisms. In conclusion, FV may be a candidate agent for the prevention of renal and cardiac toxicities in cancer patients receiving DOXO chemotherapy.

Fluvastatin attenuates doxorubicin-induced testicular toxicity in rats by reducing oxidative stress and regulating the blood–testis barrier via mTOR signaling pathway

Doxorubicin (DOX) is an anthracycline derivative antibiotic that still frequently used in the treatment of solid tumors and hematological malignancies. The clinical use of DOX is largely restricted due to acute and chronic renal, cardiac, hematological, and testicular toxicities. Previous studies have indicated that oxidative stress, lipid peroxidation, and apoptosis in germ cells are the main factors in DOX-induced testicular toxicity, but the entire molecular mechanisms that responsible for DOX-induced testicular damage are not yet fully understood. Fluvastatin is a cholesterol-lowering agent that acts by inhibiting hydroxylmethyl glutaryl coenzyme A, the key enzyme for cholesterol biosynthesis. In addition to its cholesterol-lowering effect, fluvastatin showed an antioxidant effect by cleaning hydroxyl and superoxide radicals and this drug could have a protective effect by acting on the mammalian target of rapamycin (mTOR) signal pathway in testicular damage caused by obesity. This study aimed to investigate the possible protective and therapeutic effects of fluvastatin on the DOX-induced testicular toxicity model by histochemical, immunohistochemical, biochemical, and real-time polymerase chain reaction analyses. The present study indicates that fluvastatin may have a protective and therapeutic effect by removing reactive oxygen species and by regulating the mTOR, connexin 43, and matrix metalloproteinase 9 protein and messenger ribonucleic acid expressions, which play an important role in regulating the blood–testis barrier. On the other hand, the use of fluvastatin as a protective/prophylactic agent was found to be more effective than the use of this drug for treatment. In light of this information, fluvastatin may be a candidate agent that can be used to prevent testicular toxicity observed in men receiving DOX treatment.

Protective effect of pomegranate seed oil against mercuric chloride-induced nephrotoxicity in rat

PURPOSE

Heavy metals such as mercury can induce the generation of free radicals and oxidative stress which are associated with tissue injury. The present study was designed to evaluate the protective effect of pomegranate seed oil against HgCl2-induced nephrotoxicity.

METHODS

Twenty-four W/A adult rats were randomly divided into four groups. Group I received corn oil (1 mL/kg). Group II received HgCl2 (5 mg/kg) for 3 days. Group III and IV received PSO 0.4 mL/kg and 0.8 mL/kg, respectively one hour before HgCl2 administration for 3 days. Blood samples were taken by cardiac puncture and used for the measurement of urea and creatinine concentration. Twenty-hour-hour urine samples were collected to measure protein and glucose. The right kidney was fixed in formalin for histological examination and the left kidney was homogenized for measuring malondialdehyde (MDA) and total sulfhydryl groups.

RESULTS

Significant elevation of serum creatinine and urea levels as well as urine glucose and protein concentrations, a significant decrease in total thiol content and a significant increase in MDA levels in kidney homogenate samples were observed after administration of HgCl2 as compared with control group. PSO pretreatment resulted in a significant decrease in serum creatinine and urea levels as well as urine glucose and protein concentrations when compared with HgCl2 treated (group II). PSO also significantly reversed the HgCl2-induced depletion in thiol content and elevation in MDA content. Histological studies revealed milder kidney lesions in PSO treated groups (groups III and IV) compared to HgCl2 treated group.

CONCLUSION

Our results suggest that PSO has a protective effect against HgCl2-induced nephrotoxicity in rats.

Myostatin induces DNA damage in skeletal muscle of streptozotocin-induced type 1 diabetic mice

One of the features of uncontrolled type 1 diabetes is oxidative stress that induces DNA damage and cell death. Skeletal muscle atrophy is also considerable in type 1 diabetes, however, the signaling mechanisms that induce oxidative stress culminating in muscle atrophy are not fully known. Here, we show that in Streptozotocin-induced diabetic wild type mice, hypo-phosphorylation of Akt, resulted in activation of Foxa2 transcription factor in the muscle. Foxa2 transcriptionally up-regulated Myostatin, contributing to exaggerated oxidative stress leading to DNA damage via p63/REDD1 pathway in skeletal muscle of Streptozotocin-treated wild type mice. In Myostatin(-/-) mice however, Streptozotocin treatment did not reduce Akt phosphorylation despite reduced IRS-1 signaling. Moreover, Foxa2 levels remained unaltered in Myostatin(-/-) mice, while levels of p63/REDD1 were higher compared with wild type mice. Consistent with these results, relatively less DNA damage and muscle atrophy was observed in Myostatin(-/-) muscle in response to Streptozotocin treatment. Taken together, our results for the first time show the role of Foxa2 in Myostatin regulation in skeletal muscle in diabetic mice. Altogether, these results demonstrate the mechanism by which Myostatin contributes to DNA damage in skeletal muscle of the diabetic mice that would lead to myofiber degeneration.

Alpha-lipoic acid upregulates antioxidant enzyme gene expression and enzymatic activity in diabetic rat kidneys through an O-GlcNAc-dependent mechanism

PURPOSE

The combined hyperglycemia lowering and antioxidant actions of α-lipoic acid (LA) contribute to its usefulness in preventing renal injury and other diabetic complications. The precise mechanisms by which LA alters diabetic oxidative renal injury are not known. We hypothesized that LA through its hypoglycemic effect lowers O-GlcNAcylation which influences the expression and activities of antioxidant enzymes which assume important roles in preventing diabetes-induced oxidative renal injury.

METHODS

An experimental model of diabetes was induced in rats by the administration of 40 mg/kg streptozotocin (STZ) intraperitoneally (i.p.) for five consecutive days. LA was applied at a dose of 10 mg/kg i.p. for 4 weeks, starting from the last day of STZ administration.

RESULTS

An improved glycemic status of LA-treated diabetic rats was accompanied by a significant suppression of oxidative stress and a reduction of oxidative damage of lipids, proteins and DNA. LA treatment normalized CuZn-superoxide dismutase (SOD) and catalase activities in renal tissue of diabetic rats. These changes were allied with upregulated gene expression and lower levels of O-GlcNA glycosylation. The accompanying increase in MnSOD activity was only linked with upregulated gene expression. The observed antioxidant enzyme gene regulation was accompanied by nuclear translocation of Nuclear factor-erythroid-2-related factor 2 (Nrf2), enhanced expression of heat shock proteins (HSPs) and by reduction in O-GlcNAcylation of HSP90, HSP70, and extracellular regulated kinase and p38.

CONCLUSION

α-Lipoic acid administration activates a coordinated cytoprotective response against diabetes-induced oxidative injury in kidney tissue through an O-GlcNAc-dependent mechanism.

Fermented garlic protects diabetic, obese mice when fed a high-fat diet by antioxidant effects

This study examined the bioactivity of yeast (Saccharomyces cerevisiae)-fermented aged black garlic (FBG) on obese mice supplied a high-fat diet (HFD) and its in vitro antioxidant activity. Aged black garlic (BG) exhibits potent antioxidative effects and has been subjected to extensive research. In addition, the bioactivity of some natural products is increased by fermentation. In a preliminary test, this study found that the antioxidant activity of FBG is stronger than that of BG. Therefore, it was hypothesized that the bioactivity of BG would be increased by yeast fermentation and would be a good candidate as a nutraceutical product for improving the oxidative defense systems in older patients or patients affected by various oxidative stresses, for example, diabetes and diabetic complications. To test this hypothesis, the bioactivities of FBG in diabetic and obese mice as well as the antioxidant activity in vitro were examined. After 91 days of continuous HFD supply, the mice showed marked obesity, hyperglycemia, hyperlipemia, and liver and kidney damages. Black garlic and all 3 different doses of FBG showed favorable hepatoprotective, nephroprotective, hypolipidemic, and antiobesity effects compared with the HFD control, but no hypoglycemic effects. In particular, more favorable bioactivity against all 4 HFD-induced diabetic complications was detected in the FBG-treated groups compared with the group given equivalent doses of BG. These findings suggest that the bioactivities of BG can be improved by yeast fermentation.

Protective Effects of Simvastatin, a Lipid Lowering Agent, against Oxidative Damage in Experimental Diabetic Rats

The present study was undertaken to evaluate the possible protective effects of simvastatin (SMV) against oxidative stress in streptozotocin- (STZ)-induced diabetic rats. Diabetes was induced experimentally in rats by i.p. injection of STZ in a dose of 60 mg/kg bwt. After 5 weeks of STZ injection, there were apparent reductions in the animal body weight and significant increase in blood glucose, HbA1(c), urea, creatinine, AST, ALT, and lipid profiles with a concomitant decrease in total hemoglobin, plasma glutathione and vitamin C as compared to the control group. The treatment with SMV at a dose (10 mg/kg, orally) normalized all the above-mentioned biochemical parameters in STZ-induced diabetic rats. In vitro studies confirmed the free radical scavenging and antioxidant activity of SMV. Therefore, the present results revealed that SMV has a protective effect against STZ-induced oxidative damage by scavenging the free radicals generation and restoring the enzymatic and nonenzymatic antioxidant systems.

Changes in prooxidant-antioxidant balance in tissues of rats following long-term hyperglycemic status

INTRODUCTION

Reactive oxygen species play an important role in the pathogenesis of organ damage in diabetes mellitus. Streptozotosin (STZ) is a commonly employed compound to produce diabetes mellitus and these animals exhibit most of diabetic complications.

METHODS

In our study, diabetes was induced by a single intraperitoneal injection of STZ at a dose of 50 mg/kg in rats and they were killed 12 weeks after STZ. Endogenous lipid peroxide levels, enzymatic and non-enzymatic antioxidants were measured in liver, heart, kidney, brain, and testis tissues to investigate the effect of long-term hyperglycemic state. The susceptibility of diabetic tissues to oxidative stress was also examined in in vitro oxidizing system containing ascorbic acid and iron.

RESULTS

We found that prooxidant and antioxidant balance has changed in favor of prooxidation in the tissues of diabetic rats. The susceptibility of liver to oxidative stress increased; however, this susceptibility did not change in heart, kidney, brain, and testis of diabetic rats.

CONCLUSION

Our results indicate that long-term hyperglycemic state disturbs hepatic prooxidant-antioxidant balance at an earlier period and more pronouncedly than other tissues.

Effect of long term, non cholesterol lowering dose of fluvastatin treatment on oxidative stress in brain and peripheral tissues of streptozotocin-diabetic rats

One of the main goals of treatment of diabetes mellitus is to prevent its complications. Oxidative stress is universal in diabetes, being ultimately involved with the development complications. As a result of hyperglycemia, reactive oxygen/nitrogen species are produced in various tissues that leads to tissue damage with lipid peroxidation and protein oxidation, along with disruption in cellular homeostasis and accumulation of damaged molecules. Hence, supplementation with antioxidant compounds may offer some protection against diabetic complications. The pleiotropic effects of statins, including antioxidant and anti-inflammatory properties, represent an area of great interest in prevention and therapy of cardiovascular and neurological disorders. Using biomarkers of oxidative stress, in this study we examined the effect of non cholesterol lowering dose, long term fluvastatin treatment on oxidative stress in streptozotocin-diabetic rats. Experiments were conducted in 24 Wistar adult male rats. Diabetic and non-diabetic rats were treated orally for 6 months with fluvastatin (2mg/kg/day, p.o) starting one week after streptozotocin injection (55 mg/kg, i.p.), (preventive study). In brain, heart, liver, pancreas and kidney homogenates malondialdehyde, lipid hydroperoxide, protein carbonyl content, advanced oxidation protein products, 3-nitrotyrosine levels and superoxide dismutase, catalase activities were measured. Hyperglycemia and dyslipidemia in diabetic groups remained unchanged after fluvastatin treatment. The drug act as antioxidant in the tissues. Hence, antioxidant property of fluvastatin, independent of cholesterol lowering effect, may play a role in prevention of diabetic complications. Clinical relevance of this effect of fluvastatin seems worthy of further studies.

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.

Effect of Picrorrhiza rhizoma extracts on early diabetic nephropathy in streptozotocin-induced diabetic rats

The hypoglycemic effect of an aqueous extract of Picrorrhiza Rhizoma (PR) was investigated on diabetic nephropathy. The body weight of each of eight rats per group was measured 7 days after streptozotocin (STZ) treatment. The blood glucose levels 3 days after STZ treatment and the changes in body weight, kidney weight, blood glucose levels, and serum blood urea nitrogen (BUN) were also measured, and the histopathology of the kidney was examined. Body weight decreases and increases of kidney weight, blood glucose levels, and serum BUN and creatinine levels were detected in the diabetic control with histopathological changes related to diabetic nephropathy in the kidney. However, the level of hyperglycemia was significantly lowered in all groups given the PR extract. In addition, the changes related to diabetic nephropathy with the body weight were also significantly lower in the captopril and all PR extract-dosing groups than in the diabetic control. In conclusion, an aqueous extract of PR has relatively good inhibitory effects on STZ-induced diabetes with early diabetic nephropathy with a similar efficacy to an equal dose of captopril.

In vivo Comet assay on isolated kidney cells to distinguish genotoxic carcinogens from epigenetic carcinogens or cytotoxic compounds

The objective of this study was to determine the ability of the alkaline in vivo Comet assay (pH>13) to distinguish genotoxic carcinogens from epigenetic carcinogens when performed on freshly isolated kidney cells and to determine the possible interference of cytotoxicity by assessing DNA damage induced by renal genotoxic, epigenetic or toxic compounds after enzymatic isolation of kidney cells from OFA Sprague-Dawley male rats. The ability of the Comet assay to distinguish (1) genotoxicity versus cytotoxicity and (2) genotoxic versus non-genotoxic (epigenetic) carcinogens, was thus investigated by studying five known genotoxic renal carcinogens acting through diverse mechanisms of action, i.e. streptozotocin, aristolochic acids, 2-nitroanisole, potassium bromate and cisplatin, two rodent renal epigenetic carcinogens: d-limonene and ciclosporine and two nephrotoxic compounds: streptomycin and indomethacin. Animals were treated once with the test compound by the appropriate route of administration and genotoxic effects were measured at the two sampling times of 3-6 and 22-26h after treatment. Regarding the tissue processing, the limited background level of DNA migration observed in the negative control groups throughout all experiments demonstrated that the enzymatic isolation method implemented in the current study is appropriate. On the other hand, streptozotocin, 20mg/kg, used as positive reference control concurrently to each assay, caused a clear increase in the mean Olive Tail Moment median value, which allows validating the current methodology. Under these experimental conditions, the in vivo rodent Comet assay demonstrated good sensitivity and good specificity: all the five renal genotoxic carcinogens were clearly detected in at least one expression period either directly or indirectly, as in the case of cisplatin: for this cross-linking agent, the significant decrease in DNA migration observed under standard electrophoresis conditions was clearly amplified when the duration of electrophoresis was increased up to 40min. In contrast, epigenetic and nephrotoxic compounds failed to induce any signifcant increase in DNA migration. In conclusion, the in vivo rodent Comet assay performed on isolated kidney cells could be used as a tool to investigate the genotoxic potential of a test compound if neoplasic/preneoplasic changes occur after subchronic or chronic treatments, in order to determine the role of genotoxicity in tumor induction. Moreover, the epigenetic carcinogens and cytotoxic compounds displayed clearly negative responses in this study. These results allow excluding a DNA direct-acting mechanism of action and can thus suggest that a threshold exists. Therefore, the current in vivo rodent Comet assay could contribute to elucidate an epigenetic mechanism and thus, to undertake a risk assessment associated with human use, depending on the exposure level.

Fluvastatin reduced liver injury in rat model of extrahepatic cholestasis

Inhibitors of 3-hydroxy-3methylglutarly coenzyme A, reductase, namely statins, exert pleiotropic actions beyond lipid-lowering effects. In ex vivo and in vitro studies, statins have antioxidative and antiinflammatory effects. Herein, we sought to determine whether treatment with fluvastatin (FV) would be beneficial in a rat model of common bile duct ligation (BDL)-induced liver injury. Female rats were subjected to a sham (n=10) or BDL (n=20). Obstructive jaundice was induced in rats by the ligation and division of the common bile duct. Three days after operation, rats subjected to CBDL were randomized to receive treatment with either FV (10 mg/kg) or saline every day over a 10 days experimental period. High levels of alanine aminotransferase, aspartate aminotransferase, and gamma glutamyltransferase decreased significantly (P<0.05) in animals treated with FV with compared to saline-administrated BDL animals. Compared with sham-operated rats, CBDL rats showed significantly higher levels of total nitrite and nitrate, malondihaldehyde, tumor necrosis factor alpha, myeloperoxidase, and lower concentrations of glutathione, superoxide dismutase, and catalase in the liver tissue (P<0.001). All of these changes were significantly attenuated (P<0.05) by treatment with FV after CBDL. CBDL was associated with increased apoptosis and nuclear factor kappa beta expression in saline-treated rats. Treatment with FV also decreased these parameters. These data support the view that FV ameliorates hepatic inflammation, lipid peroxidation, and tissue injury in rats subjected to CDBL. FV warrants further evaluation as an adjunctive treatment to ameliorate liver injury from extrahepatic biliary obstruction.

Chromosomal damage and atherosclerosis. A protective effect from simvastatin

In uremic patients, the frequency of sister chromatid exchanges appears markedly higher than in the general population. Statins are well known for their pleiotropic effects, which are independent of any reduction in cholesterol circulating levels. The aim of the present study was to determine the effects of exposure to escalating doses of simvastatin on the sister chromatid exchange rate in cultured lymphocytes in order to identify the influence of statin on genomic damage. Peripheral lymphocytic samples for culture were obtained from 25 healthy volunteers, 20 patients with documented carotid atherosclerosis and 30 atherosclerotic patients on maintenance regular acetate-free biofiltration. Hemodialyzed patients had a greater percentage of high frequency cells (50%) than healthy controls (3%) and a significantly higher average number of sister chromatid (9.82+/-2.1 vs. 4.65+/-2.18). The subgroup of hemodialyzed patients with high plaque score values was characterized by significantly greater values for both sister chromatid exchanges rate and high frequency cells percentage. Our findings demonstrate that there is an association between sister chromatid exchanges and high frequency cells rate and atherosclerosis in acetate-free biofiltration patients. In cultures with added simvastatin, high frequency cells percentages and mean sister chromatid exchanges levels were significantly lower than in cultures with an added vehicle alone, the reduction occurring in a dose-dependent fashion, above all in cultures from end stage renal disease patients. The findings, moreover, demonstrate new effects of simvastatin, which appeared to mitigate the expression of genomic damage in our model. However, it is not yet clear whether this effect is due to the prevention of genomic damage or to the potentiation of the DNA repair capacity. Statins may therefore have an anti-atherogenic action partly ascribable to their ability to provide protection against the development of atherosclerotic plaque.

Statins prevent dextrose-induced endothelial barrier dysfunction, possibly through inhibition of superoxide formation

Statins may have favorable effects on endothelial barrier function, possibly through reduction of oxidative stress and modulation of expression of vasoactive proteins. The permeability of human umbilical endothelial cells in culture to a group of fluorescein isothiocyanate dextrans of different molecular weights were studied under various experimental conditions. Superoxide anion production was measured with an ethidium bromide fluorescence method. Cellular endothelin 1 mRNA and endothelin 1 in culture media were measured with Northern blots and enzyme immunoassays, respectively. Rosuvastatin (10 nmol/l) normalized the 500 mg/dl dextrose-induced permeability changes. Superoxide anion production induced by 500 mg/dl dextrose was inhibited by therapeutic concentrations of rosuvastatin or simvastatin (10 nmol/l), whereas the increased levels of cellular endothelin 1 mRNA and endothelin 1 in culture media was inhibited by supratherapeutic concentrations of statins (> or =0.1 micromol/l). In conclusion, 1) endothelial cell barrier dysfunction occurs in cells treated with high concentrations of dextrose, 2) statin treatment of endothelial cells normalizes barrier permeability, and 3) the favorable effects of statins may be attributed to the inhibition of the dextrose-induced increase in superoxide anions, whereas inhibition of endothelin expression was observed only at supratherapeutic concentrations.

Multidose streptozotocin induction of diabetes in BALB/c mice induces a dominant oxidative macrophage and a conversion of TH1 to TH2 phenotypes during disease progression

Macrophages (Mp) are implicated in both early and late phases in type 1 diabetes development. Recent study has suggested that a balance between reductive Mp (RMp) and oxidative Mp (OMp) is possible to regulate T_H1/T_H2 balance. The aim of this study is to investigate the redox status of peritoneal Mp and its cytokine profile during the development of autoimmune diabetes induced by multiple low-dose streptozotocin in BALB/c mice. Meanwhile, the polarization of T_H1/T_H2 of splenocytes or thymocytes was also examined. We found that peritoneal Mp appeared as an “incomplete” OMp phenotype with decreased icGSH along with disease progression. The OMp showed reduced TNF-α, IL-12, and NO production as well as defective phagocytosis activity compared to nondiabetic controls; however, there was no significant difference with IL-6 production. On the other hand, the levels of IFN-γ or IL-4 of splenocytes in diabetic mice were significantly higher compared to the control mice. The ratio of IFN-γ to IL-4 was also higher at the early stage of diabetes and then declined several weeks later after the occurrence of diabetes, suggesting a pathogenetic T_H1 phenotype from the beginning gradually to a tendency of T_H2 during the development of diabetes. Our results implied that likely OMp may be relevant in the development of type 1 diabetes; however, it is not likely the only factor regulating the T_H1_H/T_H2 balance in MLD-STZ-induced diabetic mice.

Alleviation of Oxidative Damage in Multiple Tissues in Rats with Streptozotocin-Induced Diabetes by Rice Bran Oil Supplementation

The possibility of 8-hydroxy-2'-deoxyguanosine (8-OHdG) serving as a sensitive biomarker of oxidative DNA damage and oxidative stress was investigated. Reactive oxygen species (ROS) have been reported to be a cause of diabetes induced by chemicals such as streptozotocin (STZ) in experimental animals. In this study, we examined oxidative DNA damage in multiple tissues in rats with STZ-induced diabetes by measuring the levels of 8-OHdG in the liver, kidney, pancreas, brain, and heart. Levels of 8-OHdG in mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) were also determined in multiple tissues of rats treated with rice bran oil. Levels were 0.19 +/- 0.07, 0.88 +/- 0.30, 1.97 +/- 0.05, and 9.79 +/- 3.09 (1/10(5) dG) in the liver of nDNA of normal rats, nDNA of STZ-induced diabetic rats, mtDNA of normal rats, and mtDNA of STZ-induced diabetic rats, respectively. Levels of mtDNA of 8-OHdG were 10 times higher than those of nDNA in multiple tissues. Significant reductions in mtDNA 8-OHdG levels were seen in the liver, kidney, and pancreas of diabetic rats treated with rice bran oil compared with diabetic rats without intervention. Our study demonstrated that oxidative mtDNA damage may occur in multiple tissues of STZ-induced diabetics rats. Intervention with rice bran oil treatment may reverse the increase in the frequency of 8-OHdG.

Induction of micronuclei in CHO cells by bleomycin but not by X-irradiation is decreased by treatment with HMG-CoA reductase inhibitors

We investigated the effect of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, pravastatin and fluvastatin, on the induction of micronuclei by ionizing radiation or bleomycin in Chinese hamster ovary cells in order to assess the radical-scavenging ability of these inhibitors. The results indicated that both pravastatin and fluvastatin had no effect on the induction of micronuclei by X-irradiation when they were applied for either pre-treatment or post-treatment. In contrast, both drugs effectively reduced the frequency of bleomycin-induced micronuclei when they were applied for simultaneous treatment or post-treatment, but not for pre-treatment. This indicates that the radical-scavenging ability of these two HMG-CoA reductase inhibitors differs according to the origins of the radicals--e.g., X-rays or bleomycin--even when the two drugs are compared at an equivalent cytotoxic dose. Our results suggest that both pravastatin and fluvastatin have the ability to scavenge certain types of radicals and to protect cells against oxidative stress.

Hepatic changes in the acute phase of streptozotocin (SZ)-induced diabetes in mice

We have reported the streptozotocin (SZ)-induced hepatic lesions in the subacute phase (4 to 12 weeks after the treatment), which are characterized by appearance of oncocytic hepatocytes, cytomegalic hepatocytes and bile duct hyperplasia. In this study, we focused on the acute phase (6 to 48 hours after the treatment) of the SZ-induced hepatic lesions of mice to clarify the onset of the hepatic alterations, especially before the induction of hyperglycemia. Livers were taken from 8-week-old Crj:CD-1 (ICR) male mice at 6, 12, 24, 36 and 48 hours after the 200 mg/kg b.w. of SZ-injection. SZ-induced hyperglycemia was noted at 36 and 48 hours after the treatment, but the hepatic changes including lipid peroxidation, mitochondrial swelling, peroxisome proliferation and inhibition of hepatocyte proliferation occurred before the elevation of the serum glucose levels. The present findings indicate the direct effects of SZ on hepatocytes rather than the secondary effects of diabetes, and certain correlations between the hepatocytic changes in the acute phase and those in the subacute one. In addition, ulcer and submucosal edema of the gallbladder were observed at 36 or 48 hours after the SZ-treatment, which can be a novel finding in SZ-treated animal.

Effects of atorvastatin and pravastatin on glucose tolerance in diabetic rats mildly induced by streptozotocin

Effects of atorvastatin and pravastatin on glucose tolerance in mildly induced diabetic rats by streptozotocin at 24 mg/kg, i.v. were studied. Non-diabetic and diabetic rats were given orally 0.5% carboxymethylcellulose (control), 8 mg/kg atorvastatin or 8 mg/kg pravastatin once a day for 6 weeks. An oral glucose tolerance test (OGTT) was carried out 1, 2, 3, and 6 weeks after the administration. The blood glucose and plasma insulin levels measured before OGTT in the diabetic rats were not different from those in the non-diabetic rats. However, the hyperglycemic response to OGTT in the diabetic rats significantly exceeded that in the non-diabetic rats. The plasma insulin increased by OGTT in the diabetic rats appeared to be lower than that in the non-diabetic rats. Statin treatments for 1 week did not modify the OGTT-induced hyperglycemia appreciably, although there were some significant differences. More than 2 weeks after administration, the blood glucose levels at several time points after a glucose intake in the atorvastatin-treated diabetic rats were significantly higher than the respective levels in the control diabetic rats. Neither atorvastatin nor pravastatin modified the OGTT-induced insulin secretion. Statins, especially atorvastatin, may influence the glucose tolerance in mildly induced diabetic rats without alterations of insulin secretion.

Role of oxidative stress in age-associated chronic kidney pathologies

The kidneys exhibit age-associated deterioration in function via a loss of 20% to 25% kidney mass, particularly from the renal cortex and increased fibrosis. Oxidative stress has been found to mediate age-associated renal cell injury and cell death, particularly apoptosis. Oxidative stress results from an imbalance between the levels of free radicals generated during aerobic metabolism, inflammation, and infection and the safe breakdown of these species by endogenous and exogenous scavengers. Other factors may influence these pathologies. For example, growth hormone and caloric restriction have been shown to influence life span, although neither method of prolonging life is likely to find general acceptance in humans. Some genetic knockout models offer promise; for example, knockout of the p66 isoform of the Shc gene in mice increases life span by 30%, but appetite, size, and fertility are retained. Whether the increase in life span is via increased kidney health is not yet clear, but decreasing the age-related renal pathologies will no doubt aid in increasing life span and health in general. This review looks at the role and modulation of factors that influence life span, in particular modulation of oxidative stress, with particular relevance to age-related renal pathologies.

HMG-CoA Reductase Inhibitors Do Not Improve Glucose Intolerance in Spontaneously Diabetic Goto-Kakizaki Rats

We examined whether 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) improve glucose intolerance in spontaneously diabetic Goto-Kakizaki (GK) rats or not. The fasting blood glucose, plasma insulin, and serum cholesterol levels were significantly higher in GK rats than those in age-matched Wistar rats. All rats were given orally once a day 0.5% carboxymethylcellulose, pravastatin 8 mg/kg, simvastatin 8 mg/kg, or atorvastatin 8 mg/kg. An oral glucose tolerance test (OGTT) was performed before and 3, 6 and 12 weeks after statin treatments. The hyperglycemic response to OGTT in GK rats significantly exceeded that in Wistar rats. The plasma insulin level in GK rats increased with age until 14-week-old (treated for 6 weeks), and then decreased. Glucose intake significantly increased the plasma insulin in almost all rats. The increment of plasma insulin due to OGTT in GK rats appeared to be less than that in Wistar rats, because the basal level was already high in GK rats. Pravastatin, simvastatin, and atorvastatin did not modify changes in blood glucose and plasma insulin induced by glucose intake. In conclusion, long-term treatments of GK rats with statins did not improve glucose intolerance observed during OGTT.

Long-term effects of statins on arterial pressure and stiffness of hypertensives

Although lowering blood pressure (BP) reduces aortic stiffness, achieving the recommended BP goal can be difficult. Recent studies have shown that short-term use of statins can reduce BP significantly. To determine the long-term effects of statins on BP and aortic stiffness, a single-blind randomized prospective study was performed on 85 hyperlipidaemic hypertensive patients whose BP was insufficiently controlled by antihypertensive therapy. Every 3 months, aortic stiffness was assessed by measuring pulse wave velocity (PWV). Patients were randomly allocated to groups treated with pravastatin, simvastatin, fluvastatin, or a nonstatin antihyperlipidaemic drug. No significant differences in patient characteristics, kinds of antihypertensive drugs, BP, ankle brachial index, PWV, or serum lipid, creatinine, or C-reactive protein levels were found between the four groups at the start of the study. During the 12-month treatment period, PWV did not change in the pravastatin group or nonstatin group, but it was transiently reduced in the simvastatin group and significantly decreased in the fluvastatin group, even though the doses of the statins used in this study were lower than the usually prescribed dose. All four antihyperlipidaemic drugs significantly decreased serum cholesterol levels without affecting BP, ankle brachial index, or serum triglyceride levels. The C-reactive protein serum levels decreased significantly in the three statin groups but not in the nonstatin group. These results suggest that long-term use of fluvastatin by hyperlipidaemic hypertensive patients is associated with a significant reduction in aortic stiffness without any effect on BP.

Fluvastatin prevents nephropathy likely through suppression of connective tissue growth factor-mediated extracellular matrix accumulation

Diabetic nephropathy is related to glomerular extracellular matrix (ECM) accumulation that leads to glomerulosclerosis. Fluvastatin as a lipid-lowering medicine significantly prevents diabetic nephropathy, probably not only through its lipid-lowering action, but also mainly through its direct suppression of glomerular ECM accumulation. To test this hypothesis, in the present study, a five-sixths nephrectomized (5/6Nx) rat model to induce a renal ECM accumulation without coexistence of hyperlipidemia was used to investigate the effect of fluvastatin on renal function, glomerular ECM accumulation and expression of connective tissue growth factor (CTGF). 5/6Nx induced a significant nephropathy in rats at 13 weeks, indicated by renal dysfunction including increases in blood urine nitrogen, creatinine and urinary protein excretion, and renal histopathological changes. Administration of fluvastatin significantly prevented the renal dysfunction and histological abnormalities in the 5/6Nx rats. Furthermore, both significant suppression of matrix metalloproteinases (MMPs) activity such as MMP-2 and significant activation of tissue inhibitors of MMP (TIMPs) such as TIMP-2 observed in the 5/6Nx rats were almost completely prevented by fluvastatin, resulting in a significant prevention of glomerular ECM accumulation. For upstream mediator of ECM accumulation, 5/6Nx significantly up-regulated CTGF mRNA expression, but fluvastatin treatment prevented CTGF up-regulation. These results suggest that fluvastatin, as one of well-known lipid-lowering agents, plays an important role in the prevention of nephropathy, likely through suppression of CTGF-mediated ECM accumulation. Therefore, fluvastatin may be a potential candidate for developing a pharmaceutical approach to the prevention of diabetic nephropathy due to its both lipid-lowering and direct anti-renal ECM accumulation actions.

Protective effect of fluvastatin, an HMG-CoA reductase inhibitor, on the formation of 8-oxo-2'-deoxyguanosine in the nuclear DNA of hamster pancreas after a single administration of N-nitrosobis(2-oxopropyl)amine

We examined whether fluvastatin (FV), a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, has antioxidant activity against oxidative DNA damage to hamster pancreas induced by a chemical carcinogen, N-nitrosobis(2-oxopropyl)amine (BOP). Female Syrian golden hamsters were treated with FV by gastric intubation 30 min before BOP administration. Control animals were intubated with saline. Animals were injected subcutaneously with BOP (20 mg/kg body weight) or saline, and sacrificed 1 and 4 h later. The contents of 8-oxo-2'-deoxyguanosine (8-oxodG) in the nuclear DNA and thiobarbituric acid-reacting substances (TBARS) were measured in the pancreas and liver of hamsters. Treatment with more than 0.22 mg/kg body weight FV significantly inhibited the increase in 8-oxodG content induced by BOP treatment. The TBARS contents in pancreas changed similarly by intubation of FV. In the liver, the contents of 8-oxodG and TBARS were not affected by a single administration of BOP. The protective effect of FV was stronger than those of pravastatin and other antioxidants such as Trolox, ascorbic acid and green tea catechin. These results suggest that FV inhibits oxidative damage to DNA and lipids caused by reactive oxygen species formed through the metabolism of chemical carcinogens.