Enhancement of reactive oxygen species and induction of apoptosis in streptozotocin-induced diabetic rats under hyperbaric oxygen exposure

An important source of reactive oxygen species (ROS) production is nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which on activation induces superoxide production via oxidation in the mitochondria, inflammation and stress; such ROS are implicated in the pathogenesis of diabetic complications, including neuropathy. Hyperbaric oxygen (HBO) treatments are applied various diseases including diabetic patients with unhealing foot ulcers, however, and also increases the formation of ROS. In a previous study, we showed that a clinically recommended HBO treatment significantly enhanced oxidative stress of pancreatic tissue in the diabetic rats. However, no study has been undertaken with regard to the effects of HBO on the activity and gene expression of the NADPH oxidase complex and on apoptosis in the pancreas of diabetic animals. The purpose of this study was to investigate the effect of HBO exposure on gene expression of the NADPH complex, and pancreatic expression of genes related to apoptosis via the mitochondria, using the NADPH oxidase inhibitor apocynin. The mRNA expression of genes related to NADPH oxidase complex and apoptosis increased significantly (P < 0.05) in the pancreas of diabetic rats under HBO exposure. Similarly, activities of NADPH oxidase and caspase-3 changed in parallel with mRNA levels. These results suggest that oxidative stress caused by HBO exposure in diabetic animals induces further ROS production and apoptosis, potentially through the up-regulation of NADPH oxidase complex. Thus, this study can contribute to development of a better understanding of the molecular mechanisms of apoptosis via the mitochondria in diabetes, under HBO exposure.     

Inflammation,oxidative stress and apoptosis cascade implications in bisphenol A‐induced liver fibrosis in male rats

Bisphenol A (BPA) is a key monomer in the production of plastics. It has been shown to be hepatotoxic. Inflammation and oxidative stress are closely linked with liver fibrosis, the major contributing factor to hepatic failure. Therefore, the aim of this study was to evaluate the impact of chronic exposure to BPA on the development of hepatic fibrosis in male rats and to determine the cross‐talk between the hepatic cytokine network, oxidative stress and apoptosis. For this purpose, 30 male Wistar albino rats were divided into three equal groups as follows: the first group was given no treatment (normal control group); the second group was given corn oil once daily by oral gavage for 8 weeks (vehicle control group); and the third group received BPA (50 mg/kg body weight/day, p.o.) for 8 weeks. BPA administration induced liver fibrosis as reflected in an increase in serum hepatic enzymes activities, hepatic hydroxyproline content and histopathological changes particularly increased collagen fibre deposition around the portal tract. In addition, there was inflammation (as reflected in increase in interleukin‐1beta ‘IL‐1β’, decrease in interleukin‐10 ‘IL‐10′ serum levels and increase in IL‐1β/IL‐10 ratio), oxidative stress (as reflected in increase in malondialdehyde (MDA) level, reduction in reduced glutathione (GSH) content and inhibition of catalase (CAT) activity) and apoptosis [as reflected in an increase in caspase‐3 level and a decrease in numbers of B‐cell lymphoma 2 (BCL2)‐immunopositive hepatocytes]. Interestingly, BPA had an upregulating effect on an extracellular matrix turnover gene [as reflected in matrix metalloproteinase‐9 (MMP‐9)] and a downregulating effect on its inhibitor gene [as reflected in tissue inhibitor of matrix metalloproteinase‐2 (TIMP‐2)] expression. Thus, the mechanism by which BPA induced liver fibrosis seems to be related to stimulation of the inflammatory response, along with oxidative stress, the apoptotic pathway and activation of extracellular matrix turnover.     

Protective role of vitamins E and C against oxidative stress caused by intermittent cold exposure in aging rat's frontoparietal cortex

This study examined the role of vitamins E and C in combating oxidative stress (OS) caused by intermittent cold exposure (ICE) in the frontoparietal cortex (FPC) of adult (3 months), late-adult (12 months), middle-aged (18 months) and old (24 months) male Wistar rats. Each age group was divided into sub-groups, control (CON), cold-exposed at 5 °C (C5), control supplementees (CON + S) and cold-exposed supplementees (C5 + S). The supplement was a daily dose of 400 mg vitamin C and 50 I.U. of vitamin E/kg body weight. Cold exposure lasted 2 h/day for 4 weeks. All age groups except the old showed an increase in the final body mass in the cold-exposed. The feeding efficiency was higher in the cold-exposed irrespective of age. OS as reflected in age-related increased levels of hydrogen peroxide, protein carbonyl, advanced oxidation protein products and malondialdehyde showed further increase with ICE in the FPC. However, vitamins E and C supplementation attenuated the ICE-induced OS. ICE depleted the levels of tissue vitamins E and C while supplementation resulted in increased levels. Further age emerged as a significant factor in ICE-induced stress and also the response to vitamins E and C supplementation. Behavioral studies are underway to examine the findings on ICE-induced oxidative injury in the FPC, and the prospects for using vitamins E and C in cold exposures in the aged.     

Oxidative stress and nitric oxide synthase in skeletal muscles of rats with post‐infarction,compensated chronic heart failure

Aim: Involvement of oxidative stress and nitric oxide synthase (NOS) isoforms in skeletal muscle cellular adaptations to chronic heart failure (CHF) is controversial, and possible muscle fibre‐type heterogeneity in the oxidative stress and NOS responses to CHF have not been examined. Consequently, we hypothesized that the changes in determinants of elevated oxidative and nitrosylative stress associated with CHF would occur in skeletal muscle and would be similar in predominantly type I slow twitch muscle (soleus) and type II fast twitch muscle (plantaris) of rats. Methods: The purpose of this study was to measure NOS isoforms (endothelial, inducible and neuronal NOS) and antioxidant enzymes (SOD‐1, SOD‐2, catalase) by protein immunoblot as well as markers of oxidative stress by biochemical assays in soleus and plantaris muscle sections of the rat hind limb. This was performed for control and post‐infarction, compensated CHF rats. Results: Twelve weeks after coronary artery ligation‐induced moderate CHF, soleus exhibited decreased SOD‐1, SOD‐2 and eNOS, but increased iNOS and nNOS isoforms assessed by immunoblot. This was associated with elevated lipid and DNA oxidative damage assessed by biochemical assays. In contrast, plantaris muscle exhibited no changes in antioxidant enzymes or NOS isoforms, and had lower lipid and DNA oxidative damage. Conclusion: These observations suggest a heretofore unreported muscle fibre‐type‐specific response of oxidative stress and NOS isoforms to CHF is of importance in understanding the cellular mechanisms of skeletal muscle dysfunction in CHF.     

Protective effect of sesamin in lipopolysaccharide-induced mouse model of acute kidney injury via attenuation of oxidative stress,inflammation, and apoptosis

Abstract

Context: Acute kidney injury (AKI) is considered a major public health concern in today’s world. Sepsis‐induced AKI is large as a result of exposure to lipopolysaccharide (LPS) that is the major outer membrane component of Gram‐negative bacteria. Sesamin is the main lignan of sesame seeds with multiple protective effects.

Objective: In this research, we tried to demonstrate the protective effect of sesamin pretreatment in LPS-induced mouse model of AKI.

Methods: LPS was injected at a single dose of 10?mg/kg (i.p.) and sesamin was given p.o. at doses of 25, 50, or 100?mg/kg, one hour prior to LPS.

Results: Treatment of LPS-challenged mice with sesamin reduced serum level of creatinine and blood urea nitrogen (BUN) and returned back renal oxidative stress-related parameters including glutathione (GSH), malondialdehyde (MDA), and activity of catalase and superoxide dismutase (SOD). Moreover, sesamin alleviated inappropriate changes of renal nuclear factor-kappaB (NF-κB), toll-like receptor 4 (TLR4), cyclooxygenase-2 (COX2), tumor necrosis factor α (TNFα), interleukin-6, DNA fragmentation (an apoptotic index), and nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In addition, sesamin diminished magnitude of kidney tissue damage due to LPS.

Conclusion: In summary, sesamin could dose-dependently abrogate LPS-induced AKI via attenuation of renal oxidative stress, inflammation, and apoptosis.     

Epigallocatechin gallate inhibits oxidative stress-induced DNA damage and apoptosis in MRL-Faslpr mice with autoimmune sialadenitis via upregulation of heme oxygenase-1 and Bcl-2

Abstract

Pathogenic effects of reactive oxygen species (ROS) in the salivary glands of patients with Sjögren’s syndrome have been demonstrated. Epigallocatechin gallate (EGCG), which is a catechin derivative and exhibits potent antioxidant activity, has been reported to ameliorate autoimmune sialadenitis in a murine model, but the mechanism underlying its protective action remains to be investigated. Herein, we examined the effects of EGCG administration to MRL/MpJ-lpr/lpr (MRL-Fas^lpr) mice on disease severity of autoimmune sialadenitis and protein expression levels of 11 sialadenitis-related molecules – heme oxygenase-1 (HO-1) (antioxidant); thymidine glycol (marker of DNA damage); gp91phox/NADPH oxidase 2 (prooxidant); single-stranded DNA (ssDNA) and cleaved caspase 3 (apoptotic cell markers); p53 and Bax (proapoptotic molecules); Bcl-2 (antiapoptotic molecule); SSA/Ro, SSB/La, and Ifi202 (autoantigens). In EGCG-treated mice, the severity of sialadenitis was substantially decreased. Expression levels of thymidine glycol, gp91phox, ssDNA, cleaved caspase 3, p53, Bax, SSA/Ro, SSB/La, and Ifi202 in duct epithelial cells of salivary glands from EGCG-treated mice were reduced, whereas HO-1 and Bcl-2 were overexpressed. Results of correlation analysis among sialadenitis severity and 11 sialadenitis related-molecules, and those of partial correlation analysis between apoptotic related-molecules and sialadenitis severity or HO-1 suggested that the consecutive pathogenic cycle including activated autoimmune reactions, ROS synthesis, DNA damage and p53-dependent apoptosis was associated with the pathogenesis of autoimmune sialadenitis in MRL-Fas^lpr mice. Overexpression of HO-1 and Bcl-2 mediated by EGCG blocked this pathogenic cycle, subsequently resulting in the inhibition of ROS-mediated DNA damage and apoptosis, and protected salivary gland tissues from oxidative stress. Clinically, green tea catechin may have therapeutic efficacy for Sjögren’s syndrome.     

Increased oxidative stress is associated with balanced increases in hepatocyte apoptosis and proliferation in glycerol-3-phosphate acyltransferase-1 deficient mice

The absence of mouse mitochondrial glycerol-3-phosphate acyltransferase-1 (Gpat1-/-) increases the amount of arachidonate in liver phospholipids and increases beta-hydroxybutyrate and acyl-carnitines, suggesting an elevated rate of liver fatty acid oxidation. We asked whether these alterations might increase reactive oxygen species (ROS), apoptosis, or hepatocyte proliferation. Compared to wildtype controls, liver mitochondria from Gpat1-/- mice showed a 20% increase in the rate of ROS production and a markedly increased sensitivity to the induction of the mitochondrial permeability transition. Mitochondrial phosphatidylethanolamine and phosphatidylcholine from Gpat1-/- liver contained 21% and 67% more arachidonate, respectively, than wildtype controls, and higher amounts of 4-hydroxynonenal, a product of arachidonate peroxidation. Oxidative stress was associated with an increase in apoptosis, and with 3-fold and 15-fold higher TUNEL positive cells in liver from young and old Gpat1-/- mice, respectively, compared to age-matched controls. Compared to controls, bromodeoxyuridine labeling was 50% and 7-fold higher in livers from young and old Gpat1-/- mice, respectively, but fewer glutathione-S-transferase positive cells were present. Thus, Gpat1-/- liver exhibits increased oxidative stress and sensitivity of the mitochondrial permeability transition pore, and a balanced increase in apoptosis and proliferation.     

Regulation of oxidative stress and somatostatin,cholecystokinin, apelin gene expressions by ghrelin in stomach of newborn diabetic rats

The aim of the study was to determine whether ghrelin treatment has a protective effect on gene expression and biochemical changes in the stomach of newborn streptozotocin (STZ) induced diabetic rats. In this study, four groups of Wistar rats were used: control, ghrelin control, diabetic and diabetic + ghrelin. The rats were sacrificed after four weeks of treatment for diabetes. The gene expressions of: somatostatin, cholecystokinin, apelin and the altered active caspase-3, active caspase-8, proliferating cell nuclear antigen, were investigated in the pyloric region of the stomach and antioxidant parameters were measured in all the stomach. Although ghrelin treatment to diabetic rats lowered the stomach lipid peroxidation levels, the stomach glutathione levels were increased. Exogenous ghrelin caused an increased activities of stomach catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase in diabetic rats. Numbers of somatostatin, cholecystokinin and proliferating cell nuclear antigen immunoreactive cells decreased in the diabetic + ghrelin group compared to the diabetic group. Apelin mRNA expressions were remarkably less in the diabetic + ghrelin rats than in diabetic rats. The results may indicate that ghrelin treatment has a protective effect to some extent on the diabetic rats. This protection is possibly accomplished through the antioxidant activity of ghrelin observed in type 2 diabetes. Consequently exogenous ghrelin may be a candidate for therapeutic treatment of diabetes.     

Activation of the Hog1p kinase in Isc1p-deficient yeast cells is associated with mitochondrial dysfunction, oxidative stress sensitivity and premature aging

The Saccharomyces cerevisiae Isc1p, an orthologue of mammalian neutral sphingomyelinase 2, plays a key role in mitochondrial function, oxidative stress resistance and chronological lifespan. Isc1p functions upstream of the ceramide-activated protein phosphatase Sit4p through the modulation of ceramide levels. Here, we show that both ceramide and loss of Isc1p lead to the activation of Hog1p, the MAPK of the high osmolarity glycerol (HOG) pathway that is functionally related to mammalian p38 and JNK. The hydrogen peroxide sensitivity and premature aging of isc1Δ cells was partially suppressed by HOG1 deletion. Notably, Hog1p activation mediated the mitochondrial dysfunction and catalase A deficiency associated with oxidative stress sensitivity and premature aging of isc1Δ cells. Downstream of Hog1p, Isc1p deficiency activated the cell wall integrity (CWI) pathway. Deletion of the SLT2 gene, which encodes for the MAPK of the CWI pathway, was lethal in isc1Δ cells and this mutant strain was hypersensitive to cell wall stress. However, the phenotypes of isc1Δ cells were not associated with cell wall defects. Our findings support a role for Hog1p in the regulation of mitochondrial function and suggest that constitutive activation of Hog1p is deleterious for isc1Δ cells under oxidative stress conditions and during chronological aging.