Glycolaldehyde Induces Oxidative Stress in the Heart: A Clue to Diabetic Cardiomyopathy?

Cardiovascular complications account for 80% of the mortality related to diabetes mellitus. Hyperglycemia is believed to be the major culprit of angiopathy and cardiomyopathy. High glucose levels and oxidative stress cause elevation of Advanced Glycation End-products that are known to contribute to diabetic complications and correlate with many diseases. However, there are few reports describing the effects of glycating agents other than glucose. Here, we aimed to evaluate the effects of glycolaldehyde (GA) on oxidative stress parameters in the heart of Wistar rats. Male Wistar rats received a single injection of GA (10, 50 or 100 mg/Kg) and were sacrificed 6, 12 or 24 h after injection. As indexes of oxidative stress, we quantified protein carbonylation, lipid peroxidation and total reduced thiols. The activities of superoxide dismutase, catalase and glyoxalase I were assayed. Also, the content of N ^ɛ-(carboxymethyl)lysine (CML) was quantified. Glycolaldehyde induced an imbalance in the redox status, with increased protein carbonylation and lipoperoxidation. Catalase and glyoxalase I had a decrease in their activities. Despite the oxidative stress, we observed no increase in CML content. These results suggest that short-chain aldehydes such as GA might have a significant role in the development of diabetic cardiomyopathy.     

Hydrolysis of Conjugated Folic Acid by Pancreatic ‘Conjugase’

The present studies have shown that rat pancreatic juice is rich in conjugase, an enzyme which hydrolyzes the gamma-glutamyl peptide linkage in conjugated folic acid (pteroyl polyglutamate).

With pteroylpolyglutamate isolated from yeast as substrate, the products after hydrolysis are found to be pteroylmonoglutamate and an at present unknown product in equal amounts. The pH-optimum is found to be in the range of 5.5 to 6.0.

Preliminary estimation of the molecular weight gives a value of 60,000 for conjugase from rat pancreatic juice and 52,000 for conjugase from chicken pancreas.     

Hyperbaric Oxygen Enhances the Efficiency of 5-Aminosalicylic Acid in Acetic Acid–Induced Colitis in Rats

The aim of this study was to assess the efficienchyperbaric oxygen alone and in combination with 5-aminosalicylic acid in THE acetic acid–induced colitis model, a well-known experimental model of inflammatory bowel disease in rats. Rats were randomly divided into FIVE groups. In the noncolitis control group, rats were given isotonic saline, while in the other groups rats were treated by intracolonic administration of 4% acetic acid. In group 2, the untreated control group, no additional therapy was applied. In groups 3, 4, and 5 hyperbaric oxygen, 5-aminosalicylic acid. and 5-aminosalicylic acid + hyperbaric oxygen therapies were applied, respectively. Administration of acetic acid caused an inflammatory response in all animals. Histopathologic score was significantly higher in group 2 than in any other group. 5-Aminosalicylic acid and hyperbaric oxygen significantly decreased the histopathologic score (P < 0.05). Myeloperoxidase activity was also reduced significantly by 5-aminosalicylic acid (P < 0.05) but not by hyperbaric oxygen. The most prominent ameliorative effect, however, was seen in group 5 and the histopathologic score and myeloperoxidase activity were significantly lower than in groups 3 (P < 0.05) and 4 (P < 0.001). Hydroxyproline level also increased significantly in group 5, but not in groups 3 and 4 (P < 0.001). These findings indicate that hyperbaric oxygen therapy is effective in reducing the extent of colitis induced by acetic acid, although it is not as potent as 5-aminosalicylic acid. The combination of hyperbaric oxygen and 5-aminosalicylic acid, however, led to a much more prominent reduction in the severitcolitis. Hyperbaric oxygen may have a promising place in the treatment of inflammatory bowel disease.     

Antifibrotic Mechanism of Pinocembrin: Impact on Oxidative Stress,Inflammation and TGF-β /Smad Inhibition in Rats

Introduction. The present study aimed to elucidate the potential antifibrotic effects of pinocembrin (PIN), a flavanone found abundantly in honey and propolis, by studying its effect on different oxidative stress, inflammatory and fibrosis markers in an experimental model of CCl₄-induced liver fibrosis.Material and methods. PIN (20 mg/kg) was given orally 3 times/week for 6 consecutive weeks alternating with CCl₄ (0.5 mL/kg, 1:1 mixture with corn oil, i. p.) twice weekly. Different hepatotoxicity indices, oxidative stress, inflammatory and liver fibrosis markers were assessed.Results. PIN significantly restored liver transaminases and total cholesterol to normal levels. Also, PIN ameliorated oxidative stress injury evoked by CCl₄ as evidenced by inhibition of reduced glutathione depletion and lipid peroxidation as well as elevation of antioxidant enzyme superoxide dismutase (SOD). Further, PIN up-regulated the nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), thereby inducing the expression and activity of the cytoprotective enzyme hemeoxygenase-1 (HO-1). Moreover, PIN alleviated pro-inflammatory cytokines such as TNF-α via inhibiting nuclear factor-KB (nF-kB) activation. As markers of fibrosis, collagen and α-SMA expression increased markedly in the CCl₄ group and PIN prevented these alterations. In addition, PIN down-regulated TGFβ1 and p-Smad2/3, thereby inhibiting TGFβ1/Smad signaling pathway.Conclusion. These results suggest that PIN possess potent antifibrotic effects that can be explained on its antioxidant properties. It ameliorates oxidative stress and inflammation during induction of fibrogenesis via its ability to augment cellular antioxidant defenses, activating Nrf2-mediated HO-1 expression and modulating NF-KB and TGF-β1/Smad signaling pathway.     

Platelet Count Affects Efficacy of Folic Acid in Preventing First Stroke

Background

The role of platelets and important effect modifiers on the risk of first stroke is unknown.

Prevention by Intrarectal 5-Aminosalicylic Acid of <Emphasis Type="Italic">N</Emphasis>-Methylnitrosourea–Induced Colon Cancer in F344 Rats

PURPOSE: The protective effect of 5-aminosalicylic acid against colon carcinogenesis was investigated. METHODS: Eighty female F344 rats aged seven weeks received an intrarectal dose of 2 mg N-methylnitrosourea dissolved in 0.5 ml of water three times weekly for five weeks to induce colon cancer. Beginning at 6 weeks after the last dose of N-methylnitrosourea, the rats were treated with an intrarectal dose of 1 mg 5-aminosalicylic acid suspended in 0.5 ml of vehicle solution (0.3 percent water solution of methylcellulose) three times weekly for 15 weeks. RESULTS: Colon cancer incidence and mean number of tumors per rat at the end of the 15-week treatment period were significantly lower and smaller in the 5-aminosalicylic acid–treated group (10 percent and 0.2) than in the vehicle-treated (80 percent and 1.6) and untreated (68 percent and 1.1) control groups. However, the mean numbers of tumors per tumor-bearing rat were comparable: 1.5, 2, and 1.6. No distinct differences among the groups were observed in the tumor pathology with respect to their location (within 0–10 cm proximal to the anus), shape (plaque shaped or polypoid), size (<10 mm in diameter), invasion (restricted to the mucosa or submucosa), or histologic type (differentiated adenocarcinoma). CONCLUSION: Our results indicate that 5-aminosalicylic acid administered directly into the colonic lumen strongly suppresses the promotion stage of colon carcinogenesis.     

Interaction Between AT1 Receptor and NF-κB in Hypothalamic Paraventricular Nucleus Contributes to Oxidative Stress and Sympathoexcitation by Modulating Neurotransmitters in Heart Failure

Angiotensin II type 1 receptor (AT1-R) and nuclear factor-kappaB (NF-κB) in the paraventricular nucleus (PVN) play important roles in heart failure (HF); however, the central mechanisms by which AT1-R and NF-κB contribute to sympathoexcitation in HF are yet unclear. In this study, we determined whether interaction between AT1-R and NF-κB in the PVN modulates neurotransmitters and contributes to NAD(P)H oxidase-dependent oxidative stress and sympathoexcitation in HF. Rats were implanted with bilateral PVN cannulae and subjected to coronary artery ligation or sham surgery (SHAM). Subsequently, animals were treated for 4 weeks through bilateral PVN infusion with either vehicle or losartan (LOS, 10 μg/h), an AT1-R antagonist; or pyrrolidine dithiocarbamate (PDTC, 5 μg/h), a NF-κB inhibitor via osmotic minipump. Myocardial infarction (MI) rats had higher levels of glutamate (Glu), norepinephrine (NE) and NF-κB p65 activity, lower levels of gamma-aminobutyric acid (GABA), and more positive neurons for phosphorylated IKKβ and gp91^phox (a subunit of NAD(P)H oxidase) in the PVN when compared to SHAM rats. MI rats also had higher levels of renal sympathetic nerve activity (RSNA) and plasma proinflammatory cytokines (PICs), NE and epinephrine. PVN infusions of LOS or PDTC attenuated the decreases in GABA and the increases in gp91^phox, NF-κB activity, Glu and NE, in the PVN of HF rats. PVN infusions of LOS or PDTC also attenuated the increases in RSNA and plasma PICs, NE and epinephrine in MI rats. These findings suggest that interaction between AT1 receptor and NF-κB in the PVN contributes to oxidative stress and sympathoexcitation by modulating neurotransmitters in heart failure.     

Cardiac Peroxisome Proliferator-Activated Receptor-γ Expression is Modulated by Oxidative Stress in Acutely Infrasound-Exposed Cardiomyocytes

The aim of the present study was to examine the effects of acute infrasound exposure on oxidative damage and investigate the underlying mechanisms in rat cardiomyocytes. Neonatal rat cardiomyocytes were cultured and exposed to infrasound for several days. In the study, the expression of CAT, GPx, SOD1, and SOD2 and their activities in rat cardiomyocytes in infrasound exposure groups were significantly decreased compared to those in the various time controls, along with significantly higher levels of O₂ ^? and H₂O₂. Decreased cardiac cell viability was not observed in various time controls. A significant reduction in cardiac cell viability was observed in the infrasound group compared to the control, while significantly increased cardiac cell viability was observed in the infrasound exposure and rosiglitazone pretreatment group. Compared to the control, rosiglitazone significantly upregulated CAT, GPx, SOD1, and SOD2 expression and their activities in rat cardiomyocytes exposed to infrasound, while the levels of O₂ ^? or H₂O₂ were significantly decreased. A potential link between a significant downregulation of PPAR-γ expression in rat cardiomyocytes in the infrasound group was compared to the control and infrasound-induced oxidative stress. These findings indicate that infrasound can induce oxidative damage in rat cardiomyocytes by inactivating PPAR-γ.     

Elevated Oxidative Stress in the Brain of Senescence-accelerated Mice at 5 Months of Age

The senescence-accelerated mouse (SAM) is a useful animal model to study aging or age-associated disorder. In the present study, we have used a multidisciplinary approach to the characterization of changes that occur in aging and in the modelling of brain aging. The SAMP8 mouse at 5 months of age exhibited an increase in gliosis and molecular oxidative damage. Likewise, we found that superoxide dismutase activity decreased compared with age-matched SAMR1 while there were no differences in activity of catalase and glutathione reductase. These results indicate that the decrease of superoxide dismutase may be involved in the increase of oxidative stress in brain of SAMP8 at younger stages. This suggestion is supported by an increase in the expression of alpha-synuclein together with phosphorylated tau protein, which is concurrent with the decline of that antioxidant enzyme. Alpha-synuclein aggregates are invariably associated with tau pathologies and our results demonstrate that alpha-synuclein accumulation is a potent inducer of tau pathologies not only in neurodegenerative diseases but also in normal aging. These results also imply that SAMP8 are exposed to elevated levels of oxidative stress from an early age, and that could be a very important cause of the senescence-related impairments and degeneration in the brain seen in this strain. Mercè Pallàs, Ana Coto-Montes: Joint senior authorship.     

The Expression of β3-adrenoceptor of Left Ventricle and the Effect on Heart Function by Stimulating β3-AR in Rats With Experimental Heart Failure

Objectives To observe the expression of β3-adrenoceptor （β3-AR） of left ventricle and the effect on heart function by stimulating β3-AR in rats with experimental heart failure. Methods Rats were randomly divided into heart failure group and control group. Heart failure models were built up by ligating coronary artery in rats. The expression of β3-AR mRNA were detected with RT-PCR; The change of heart function were observed after administration of BRL37344 （β3-AR agonist） by measuring left ventricular end-systolic pressure （LVESP）, left ventricular end-diastolic pressure （LVEDP）, the maximum pressure ascending rate of left ventricle （＋dp/ dtmax） and the maximum pressure descending rate of left ventricle（-dp/dtmax）. Results The expression of β3-AR mRNA （β3/β-actin） was 0.028±0.005 and the proportion of β3-AR （β3/β1＋β2＋β3） was 5.4%±0.06% in failure rats while the expression of β3-AR mRNA was 0.011 ±0.004 and the proportion was 1.2%±0.04% in control rats; The descending percentage of LVESP, ＋ dp/dtmax and -dp/dtmax were 16.1%, 21.7% and 13.2% respectively with administration of BRL37344 in failure rats, while 12.2%, 15.8% and 11.5% in control rats. Conclusions Compared with control group the expression of β3-AR mRNA of left ventricle was obviously increased and the negative inotropic function with exciting β3-AR was obviously enhanced in failure groups.     

Metabolic complications of glucocorticoids – Prevention by metformin

Glucocorticoid treatment is prescribed in 2 to 3% of the population for various diseases. Chronic exposure to excess glucocorticoid can lead to iatrogenic Cushing's syndrome, which is associated with increased morbidity, especially from cardiovascular diseases and infections. While several ‘steroid-sparing’ drugs have been introduced, glucocorticoid treatment is still applied in a large number of patients. We have previously showed that the enzyme AMPK plays a key role in mediating the metabolic effects of glucocorticoids. While metformin is the most widely used drug for treatment of diabetes mellitus, its mechanism of effect is still debated. Among several effects, it stimulates AMPK in peripheral tissue, affects the mitochondrial electron chain, influences gut bacteria and stimulates GDF15. We have hypothesised that metformin will counteract the metabolic effects of glucocorticoids, even in patients without diabetes. Two double-blind placebo-controlled randomised clinical studies were conducted: in the first, glucocorticoid-naive patients started metformin treatment early together with the glucocorticoid treatment. While in placebo group glycaemic indices worsened, these sequelae were prevented in the metformin group, suggesting a beneficial effect of metformin on glycaemic control in non-diabetic patients receiving glucocorticoid treatment. In the second study, we treated patients already on established glucocorticoid therapy for a longer period with metformin or placebo. In addition to the beneficial effects on glucose metabolism, we observed significant improvement in lipid, liver, fibrinolysis, bone and inflammatory parameters, as well as fat tissue and carotid intima media thickness. Moreover, patients had a lower risk of developing pneumonia and a reduced number of admissions to hospital, representing financial advantage for the health service. We believe that the routine use of metformin for patients on glucocorticoid treatment would represent a key advantage in the care for this patient population.     

Oxidative Stress and Pathogenesis of Inflammatory Bowel Disease: An Epiphenomenon or the Cause?

Crohn’s disease (CD) and ulcerative colitis (UC), known as inflammatory bowel disease (IBD), are fairly common chronic inflammatory conditions of the gastrointestinal tract. Although the exact etiology of IBD remains uncertain, dysfunctional immunoregulation of the gut is believed to be the main culprit. Amongst the immunoregulatory factors, reactive oxygen species are produced in abnormally high levels in IBD. Their destructive effects may contribute to the initiation and/or propagation of the disease. We provided an extensive overview on the evidences from animal and human literature linking oxidative stress to IBD and its activity. Moreover, the effects of antioxidant therapy on IBD patients in randomized, controlled trials were reviewed and the need for further studies elaborated. We also summarized the evidence in support for causality of oxidative stress in IBD.