Dietary enrichment with omega-3 fatty acids partially protects against lipopolysaccharide-induced atrial depression in rats.

We tested the hypothesis that pretreatment with a diet enriched with omega-3 fatty acids can prevent lipopolysaccharide (LPS)-induced atrial dysfunction. Sprague-Dawley rats were fed a diet containing 20% safflower oil (control diet; CD) or 19.5% menhaden/0.5% safflower oil (experimental diet; ED). After 28 days, the animals were injected I.V. with LPS (20 mg/kg) or normal saline (S). Two hours later, the atria were harvested, connected to a force displacement transducer-amplifier-recorder system and maintained in vitro in oxygenated 37.5 degrees C Krebs-Henseleit buffer. Force of contraction indexed to body weight (FOCI; g/kg) and maximal rate of rise of contraction (dF/dt, g/sec) and relaxation (-dF/dt, g/sec) were similar in the CD-S (n = 6) and ED-S (n = 6) groups. FOCI, dF/dt, and -dF/dt were lower (P less than 0.05) in rats injected with LPS compared with rats injected with S irrespective of diet, but were significantly higher (P less than 0.05) in LPS-ED rats (n = 11) compared with LPS-CD rats (n = 11). Chronotropic and inotropic responses to graded doses (0.1, 0.5, 1.0, and 5.0 microM) of isoproterenol were not significantly different among groups. LPS-induced production of thromboxane B2 but not 6-keto-prostaglandin F1 alpha, was inhibited in ED fed rats. The ED did not enhance survival when rats were challenged with a 20 mg/kg I.V. dose of LPS. These results indicate that dietary enrichment with omega-3 fatty acids in rats partially protects against LPS-induced alterations in atrial function but does not change mortality after an LD100 dose of LPS.     

Dietary Dunaliella bardawil, a beta-carotene-rich alga, protects against acetic acid-induced small bowel inflammation in rats

BACKGROUND: Reactive oxygen species mediate tissue injury in inflammatory bowel disease. Beta-carotene is known as a potent free radical quencher and antioxidant. AIM: The authors evaluated the efficacy of prefeeding Dunaliella bardawil, rich in beta-carotene, to ameliorate acid-induced enteritis in a rat model. METHODS: Enteritis was induced in female Sprague-Dawley rats by injection of 2 mL acetic acid (0.67 mol/L) to a ligated duodenal loop following 10 weeks of feeding diets containing beta-carotene and compared with various controls. The effects of beta-carotene were evaluated by changes in myeloperoxidase activity, histology, and histomorphometry. RESULTS: Feeding beta-carotene resulted in suppressed mucosal myeloperoxidase activity, both basal and that induced by acetic acid injection. Acetic acid treatment induced major histopathologic changes in the duodenal mucosa, including small, irregular, and distorted villi; damage to the epithelium; edema of the lamina propria; accumulation of inflammatory cells; and hemorrhage. Beta-carotene treatment prevented these acid-induced histopathologic changes, and this was confirmed by histomorphometry of the villi. CONCLUSIONS: These results demonstrate the effectiveness of beta-carotene in a rat model as a prophylactic dietary measure in reducing the effects of acid-induced enteritis and raise the possibility that patients with Crohn's disease may benefit from the consumption of natural beta-carotene.     

Dietary modulation of colonic mucosal urokinase activity in rats

Abstract The amount and type of dietary fibre ingested influences colonic luminal characteristics, especially the concentration of carbohydrate fermentation products such as butyrate. This study aimed to assess whether diets supplemented with fibres of differing fermentability (delivering different amounts of butyrate to the colon) influence mucosal activities of urokinase and brush border hydrolases, and epithelial turnover. Groups of five rats were fed one of four diets containing low (2%), highly fermented (guar 10% or oat bran 10%) or slowly fermented fibre (wheat bran 10%) for 4 weeks. Activities of urokinase, alkaline phosphatase, dipeptidyl peptidase IV and maltase were measured in mucosal homogenates of proximal and distal colon and from rectum. Proliferative kinetics were assessed in distal and proximal colon by the metaphase arrest technique. Hydrolase activities were similar across all four dietary groups but a significant difference was found for urokinase ( P = 0.014). This was due to a reduction in urokinase activities of > 30% at the three sites in the wheat bran group compared with the other groups. Of proliferative indices, only crypt column height differed across the groups ( P = 0.038) and was highest in rats fed wheat bran and lowest in those fed the low fibre diet ( P = 0.047). The proportion of mitoses in the top one-fifth of the crypt also differed across groups ( P = 0.038) due to the high values in the distal colon of the low fibre group. Thus, addition of a slowly fermented (but not highly fermented) fibre to the diet of rats reduces net urokinase activity in large bowel mucosa and increases the life span of colonic epithelial cells without changing activities of brush border hydrolases.     

Simvastatin protects against the development of monocrotaline-induced pulmonary hypertension in rats via a heme oxygenase-1-dependent pathway

Heme oxygease-1 (HO-1) is the rate-limiting enzyme in heme catabolism. Induction of HO-1 has been shown to have vasodilatory, anti-inflammatory, and proapoptotic effects. More recently, experimental studies suggested the potential of simvastatin as a novel therapy for pulmonary hypertension (PH); however, the underlying mechanism remains to be investigated. The aim of this study was to evaluate whether HO-1 is required for the pulmonary vascular protective effects of simvastatin. Simvastatin (2 mg/kg/day) was administered once daily to rats for 4 weeks after monocrotaline (MCT) injection. Zn-protoporphyrin (Znpp), a potent inhibitor of HO, was used to confirm the role of HO-1. The hemodynamic changes, right heart hypertrophy, interleukin-6 (IL-6) level, and HO-1 protein expression in lungs were measured at day 28. Simvastatin significantly ameliorated mean pulmonary arterial hypertension (20.6 mm Hg). In addition, perivascular infiltration of inflammatory cells and the level of IL-6 were decreased in simvastatin treatment group. Simvastatin also increased significantly lung HO-1 protein expression. Inhibiting HO-1 using Znpp resulted in a loss of the effect of simvastatin in MCT rats. These results suggest that HO-1 expression is critical for the vascular protective effects of simvastatin in MCT-induced PH rats.     

Dietary fish oil protects against stretch-induced vulnerability to atrial fibrillation in a rabbit model

INTRODUCTION: Dietary fish oil is thought to reduce sudden cardiac death by suppressing ventricular arrhythmias but little is known about its impact on atrial arrhythmias. We examined the effect of dietary fish oil on the rabbit model of stretch-induced vulnerability to atrial fibrillation (AF). METHODS AND RESULTS: Six-week-old rabbits were fed standard rabbit pellets supplemented with 5% tuna fish oil (n = 6) or supplemented with 5% sunflower oil (n = 6) for 12 weeks. Six rabbits raised on the standard diet were used as controls. In Langendorff-perfused hearts intraatrial pressures were increased in a stepwise manner and rapid burst pacing applied to induce AF at increasing intraatrial pressures until AF was sustained (>1 minute). Atrial refractory periods were recorded at each pressure. Increased atrial pressure resulted in a reduction in atrial refractory period and a propensity for induction of sustained AF. Higher pressures were needed to induce and sustain AF in the fish oil group compared with the sunflower oil and control groups. The stretch-induced drop in refractory period was also less marked in the fish oil group. Red blood cell, atrial, and ventricular omega-3 fatty acid levels were significantly higher in the fish oil group. The ratio of atrial n-6/n-3 polyunsaturated fatty acids was 13 +/- 0.9 with sunflower oil and 1.5 +/- 0.01 with fish oil (P < 0.001). CONCLUSIONS: Incorporation of dietary omega-3 fatty acids into atrial tissue reduces stretch-induced susceptibility to AF.     

Lentiviral vector-mediated knockdown of SOCS3 in the hypothalamus protects against the development of diet-induced obesity in rats

Aim: Leptin resistance is a feature of most cases of obesity in both humans and rodents. The suppressor of cytokine signalling 3 (SOCS3) is a negative‐feedback regulator of leptin signalling involved in leptin resistance; therefore, the suppression of SOCS3 is a potential therapy for leptin resistance in obesity. In the studies, we investigated whether hypothalamic silencing of SOCS3 would attenuate diet‐induced obesity in rats. Methods: First we established hypothalamic SOCS3‐deficient rats through lentiviral vector (LV)‐mediated RNA interference (RNAi) technique, then provided a high‐fat diet or a chow diet to the rats. After 8 weeks of the diet, the serum leptin and insulin concentrations were measured by RIA, and the gene expressions of SOCS3 and the long form of leptin receptor in hypothalamus were detected by a real time RT‐PCR. The leptin‐induced Stat3 activation was examined by Western blot. Results: The RNAi protocol specifically knocked down the expression of SOCS3 mRNA by 50% approximately. The rats treated with LV‐SOCS3‐shRNA exhibited enhanced leptin‐induced Stat3 activation, decreased body weight gain and improved metabolic parameters when exposed to a high‐fat diet. Conclusion: Our results provide evidence that the rats treated with hypothalamic SOCS3 silencing are significantly protected against the development of diet‐induced obesity and SOCS3 is a potential target molecule for therapeutic intervention of obesity.     

Role of autologous lymphocyte cytotoxicity in colonic neoplasia.

The T-lymphocyte mediated killing of autologous carcinoma colon cells was investigated. There was no change in the incidence of activity with advanced disease, age, or nutritional status of the patient and no difference could be demonstrated in lymphocytes extracted from blood, draining lymph nodes, or the tumour itself. Nevertheless. T-lymphocyte activity did appear to be specific for the patients's own tumour, as it was rarely observed with allogeneic tumours. There was also no correlation with lymphocyte natural killer activity. The in vitro studies demonstrated patient specific T-lymphocyte activity in 23 of 47 patients with carcinoma of the colon, but the results do not correlate with clinical and pathological findings.     

Dietary xylitol protects against the imbalance in bone metabolism during the early phase of collagen type II-induced arthritis in dark agouti rats

The aim of the present study was to evaluate the changes in bone metabolism during the early phase of type II collagen–induced arthritis in rats and to evaluate whether a 10% dietary xylitol supplementation is able to protect against these changes. Arthritis was induced in female dark agouti rats by injections of type II homologous rat collagen emulsified with an equal volume of incomplete Freund adjuvant. In one group, the diet was supplemented with 10% xylitol. After 17 days, the rats were killed. Serum osteocalcin, as a marker of bone formation, and serum tartrate-resistant acid phosphatase, as a marker of bone resorption, were measured. Histologic measurements were made from Masson-Goldner trichrome–stained sections of distal tibiae. All the collagen-injected rats had arthritic symptoms at the end of the experiment. Serum osteocalcin was significantly higher in the collagen-injected rats fed a xylitol-supplemented diet (CI-X) than in the collagen-injected rats not fed xylitol (CI) and in the controls. Serum tartrate-resistant acid phosphatase was significantly higher in the CI and CI-X groups than in the controls. Trabecular bone volume was significantly lower in the CI group as compared with the CI-X and control groups. These results suggest that, at the time of the appearance of arthritic symptoms, bone resorption activity is high, but bone formation is not severely affected. Furthermore, dietary xylitol seems to protect against the imbalance of bone metabolism during the early phase of collagen type II–induced arthritis.     

Adiponectin protects against the development of systolic dysfunction following myocardial infarction

There is an association between obesity and heart failure associated with LV dysfunction. Adiponectin is an adipocyte-derived hormone that is downregulated in obesity. Here, we examined the role of adiponectin in cardiac remodeling after myocardial infarction with loss- and gain-of-function genetic manipulations in an experimental model. Myocardial infarction was created in adiponectin-deficient (APN-KO) and wild-type (WT) mice by the permanent ligation of the left anterior descending (LAD) artery. For some experiments, adenoviral vectors expressing adiponectin or beta-galactosidase were delivered systemically. Cardiac structure and function were assessed by echocardiographic and Millar catheter measurements. Myocardial capillary density was assessed by staining with anti-CD31 antibody. Myocyte apoptotic activity was determined by TUNEL-staining. Myocardial interstitial fibrosis was evaluated by Masson's trichrome staining. APN-KO mice showed exacerbated left ventricular (LV) dilation, myocyte hypertrophy and contractile dysfunction compared with WT mice at 4 weeks after LAD ligation. Impaired LV function in APN-KO mice was coupled to myocyte hypertrophy, increased apoptotic activity and interstitial fibrosis in the remote zone, and reduced capillary density in the infarct border zone. No difference in infarct size was observed between WT and APN-KO mice. Administration of adenovirus-mediated adiponectin in WT mice resulted in decreased LV dilatation and improved LV function that was associated with increased capillary density in the infarct border zone and decreased myocyte hypertrophy, diminished myocardial apoptosis and decreased interstitial fibrosis in the remote zone. These data suggest that adiponectin protects against the development of systolic dysfunction after myocardial infarction through its abilities to suppress cardiac hypertrophy and interstitial fibrosis, and protect against myocyte and capillary loss.     

The pituitary-adrenocortical system of neonatal rats is responsive to stress throughout development in a time-dependent and stressor-specific fashion.

The responsiveness of the neonatal hypothalamus-pituitary-adrenal (HPA) axis to stress has been thought to be impaired or diminished during the first 2 weeks of life. Although we previously found full responsiveness of the hypothalamus-pituitary unit to adrenalectomy in young rats [days (d) 5-10], we failed to measure a significant increase in ACTH 10 min after ether administration until d14 of age. These studies were, therefore, designed to test the functional activation of the HPA axis after a single or repeated exposures to stress. Both qualitative (time-course, stressor-specific, circadian) and quantitative changes in the ACTH and corticosterone (B) responses to various stressors were tested during the first 10 days of life. Exposure to 3 min of ether vapor increased ACTH and B secretion (P less than 0.05-0.01) in 1-, 5-, and 10-d-old rats, with an increasing amplitude of both ACTH and B responses as a function of age. Peak secretion of ACTH occurred 5 min after the onset of stress (122 +/- 3.8 to 359 +/- 54 pg/ml on d1-10), while the time of maximal B increased as a function of age. Other stressors, such as maternal separation (12 h), cold (4 C; 60 min), or histamine injection (4 mg/kg BW, ip), provoked significant and stressor-specific ACTH and B responses in 10-d old rats. Histamine administration increased ACTH secretion above that of vehicle-injected rats, with a peak of secretion 15 min after drug injection (272 +/- 29 vs. 127 +/- 8 pg/ml; P less than 0.01). Histamine-induced B secretion peaked at 60 min (3.7 +/- 0.5 micrograms/dl). In contrast to early responses observed after ether, separation, or histamine stress, cold stress in 10-d-old pups caused a large ACTH and B release 4 h after the onset of cold compared to that in maternally deprived pups [ACTH: cold, 457 +/- 61 pg/ml; separated, 150 +/- 14 (P less than 0.01); B: cold, 3.3 +/- 0.4 micrograms/dl; separated, 1.8 +/- 0.2 (P less than 0.05)]. We did not detect morning-evening (AM-PM) differences in either the pattern or the magnitude of the ACTH or B response to maternal separation or cold stress. Suppression of cold-induced ACTH release by B injection (1 mg/kg BW) 2 h before stress was observed until 4 h after stress in the AM and PM, whereas when given after cold, B was less effective in the PM than in the AM at preventing the rise in ACTH levels observed at 4 h.(ABSTRACT TRUNCATED AT 400 WORDS)     

Ritonavir protects against the development of atherosclerosis in APOE*3-Leiden mice

ObjectiveThe use of the HIV-protease inhibitor ritonavir (RTV) is associated with induction of hypertriglyceridemia, which is a cardiovascular risk factor. Therefore, we investigated the effect of RTV on atherosclerosis development in APOE*3-Leiden transgenic mice, a model for human-like lipoprotein metabolism and atherosclerosis.Methods and resultsAPOE*3-Leiden mice were fed a Western-type diet without or with RTV (35 mg/kg/day) for 19 weeks. RTV increased plasma TG levels throughout the study (～2-fold; P < 0.05). Despite these increased TG levels, RTV decreased the atherosclerotic lesion area in the aortic root (?57%; P < 0.05), concomitant with reduced macrophage area (?72%; P < 0.01) and decreased lesion severity. This could not be explained by reduced inflammatory markers in plasma (i.e. serum amyloid A, E-selectin and fibrinogen), nor by decreased lipid accumulation in macrophages or increased cholesterol efflux from macrophages, as assessed using peritoneal macrophages in vitro. Rather, whereas RTV did not affect plasma total cholesterol levels, RTV decreased (V)LDL-cholesterol and increased cholesterol in apoE-rich large HDL.ConclusionDespite inducing hypertriglyceridemia, RTV decreases atherosclerotic lesion area and severity, associated with decreased (V)LDL-cholesterol and increased atheroprotective apoE-rich large HDL.     

2-Mercaptoethane sulfonate (MESNA) protects against biliary obstruction-induced oxidative damage in rats.

The aim of this study was to assess the antioxidant and antifibrotic effects of chronic administration of 2-mercaptoethane sulfonate (MESNA) on oxidative liver damage and fibrosis induced by biliary obstruction in rats. Liver fibrosis was induced in male Wistar albino rats by bile duct ligation and scission (BDL). MESNA (150mg/kg, i.p.) or saline was administered for 28 days. At the end of the experiment, rats were killed by decapitation. Serum aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels were determined to assess liver function. Tumor necrosis factor-alpha (TNF-alpha) and lactate dehidrogenase (LDH) were also assayed in serum samples. Liver tissues were taken for determination of the free radicals, hepatic malondialdehyde (MDA) levels, an end product of lipid peroxidation; glutathione (GSH) levels, a key antioxidant; myeloperoxidase (MPO) activity, as an indirect index of neutrophil infiltration. Hepatic collagen content, as a fibrosis marker was also determined. Serum AST, ALT, LDH and TNF-alpha levels were elevated in the BDL group as compared to control group, while this increase was significantly decreased by MESNA treatment. BDL caused a significant (p<0.05-0.001) decrease in GSH levels while MDA levels and MPO activity were increased in the liver tissue. These changes were reversed by MESNA treatment. Collagen contents of the liver tissue was increased by BDL (p<0.001), and reversed back to the control levels with MESNA. Since MESNA administration alleviated the BDL-induced oxidative injury of the liver and improved the hepatic functions, it seems likely that MESNA with its antioxidant and antifibrotic properties, may be of potential therapeutic value in protecting the liver fibrosis and oxidative injury due to biliary obstruction.     

The lipoxygenase inhibitor phenidone protects against proteinuria and stroke in stroke-prone spontaneously hypertensive rats.

The present study examined whether the dual cyclooxygenase/lipoxygenase inhibitor phenidone would protect stroke-prone spontaneously hypertensive rats (SHRSP) from stroke and hypertensive renal disease. Vehicle-treated SHRSP (N = 6), fed stroke-prone rodent diet and 1% saline, exhibited severe systolic blood pressure elevation (261 +/- 10 mm Hg, mean +/- SEM), marked proteinuria (90 +/- 12 mg/day), and stroke, with an average age at death of 14 +/- 1 weeks. In a second group of six saline-loaded SHRSP, treatment with phenidone (60 mg/kg/day) was started at 8.4 weeks of age. Despite establishment of severe hypertension in this group (274 +/- 10 mm Hg), proteinuria remained at basal levels (28 +/- 13 mg/day), and signs of stroke were absent (P less than .01 v vehicle) through at least 16 weeks of age. Phenidone treatment also prevented the declines in body weight and food intake observed in vehicle-treated SHRSP, and maintained urine volume and saline intake. Serum 12-hydroxy-eicosatetraenoic acid (12-HETE) generation was significantly inhibited greater than 50% in incubates of whole blood from phenidone-treated SHRSP. We have previously shown that agents which interfere with the renin-angiotensin system afford protection from renal and cerebrovascular injury in saline-loaded SHRSP; cyclooxygenase inhibition alone will hasten the onset of these pathologic changes. Whether phenidone, which has been reported to attenuate angiotensin II-mediated effects, affords vascular protection by interference with a lipoxygenase-mediated action of angiotensin II remains to be elucidated.     

Dietary lipids and experimental colonic carcinogenesis. Critical review of the literature

Colon cancer is one of the most common tumours observed in the western population for which the relationship between epidemiological and laboratory findings and an overall assessment of the influence of diet on carcinogenesis is not straightforward. The aim of this review is to evaluate critically the experimental data which suggest a positive modulating effect of dietary lipids. Although a great number of data are available on the relation between the nature of fat in diet and colon cancer, no clear conclusions can be drawn from their analysis. The lack of consistent findings is due to the discrepancy of the results which may have arisen from methodological differences between the studies. Concerning the influence of the amount of dietary fat on colon cancer, it has been demonstrated that a high fat diet could increase the incidence and the number of colonic tumours in rats. Nevertheless, this positive modulating effect could be seen provided the fat amount in the diet was at least 20% (w/w). This observation is of first importance for colon cancer prevention and must be confirmed for fat of various nature. Systematic dose-effect studies are necessary. The question whether the effect of dietary fat on carcinogenesis is due to the specific action of fat or to an associated caloric effect has been raised several times. Although the previous studies concerned the role of caloric intake versus fat intake in carcinogenesis, the observed effects might have been due to a change in body weight or to changes in other dietary components such as non nutritive fibre, protein and micronutrients.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estrogen protects against the development of salt-induced cardiac hypertrophy in heterozygous proANP gene-disrupted mice

Cardiovascular disease is the leading cause of morbidity and mortality in both men and women, but the incidence for women rises sharply after menopause. This has been mainly attributed in the reduction of the female sex hormone estrogen during menopause, suggesting that estrogen may have cardioprotective effects, although how estrogen exerts its cardioprotective effects is not fully understood. Moreover, the beneficial effect of estrogen on end-organ damage such as cardiac hypertrophy (CH) remains unclear. The aim of the present study was to examine the interaction between estrogen and the natriuretic peptide system (NPS) and their possible roles during the development of CH by using the proANP heterozygous atrial natriuretic peptide (ANP +/-) mouse as a model of salt-sensitive CH. Male, female ANP +/- mice, and also ovariectomized (Ovx) female ANP +/- mice treated with oil or estrogen were fed either a normal or high salt (HS) diet. After a 5-week treatment period, marked CH was noted in the male and oil-injected Ovx female ANP +/- mice treated with HS. The cardiac NPS, i.e. ANP, B-type natriuretic peptide, and natriuretic peptide receptor-A, was activated in these ANP +/- mice. Interestingly, the female and estrogen-injected Ovx female ANP +/- mice did not exhibit CH, and the cardiac NPS remained unchanged. Collectively, we provide direct evidence that estrogen has the ability to resist the induction of salt-induced CH in ANP +/- mice. Furthermore, the development of hypertrophy may be activating the cardiac NPS in an attempt to blunt these structural changes.     

Heat-shock protein 72 protects against oxidant-induced injury of barrier function of human colonic epithelial Caco2/bbe cells.

BACKGROUND & AIMS: Barrier function of the inflamed intestinal mucosa can be compromised by reactive oxygen metabolites that increase mucosal permeability and disrupt the actin cytoskeleton, the integrity of which is important for maintaining tight epithelial junctions. Because heat-shock protein 72 (hsp72) protects intestinal epithelial cells against injury, we determined whether resistance of Caco2/bbe (C2) intestinal monolayer barrier function was related to their high endogenous hsp72 expression. METHODS: hsp72 anti-sense (C2/AS) and vector-only transfected C2 (C2/CEP4) clones, lines that exhibit low and high hsp72 expression, respectively, were studied. Permeability was assessed by measuring electrical resistance and mannitol fluxes and actin organization by confocal fluorescein isothiocyanate-phalloidin analysis. RESULTS: Basal transepithelial electrical resistance (TER) and mannitol fluxes were not significantly different between groups. However, the oxidant monochloramine rapidly decreased TER and increased mannitol permeability of C2/AS monolayers compared with C2/CEP4 (50% effective doses at 30 minutes were 0.53 +/- 0.11 and 2.06 +/- 0.34 mmol/L, respectively). Associated with these changes, decreased cell viability, dissociation and aggregation of perijunctional and stress actin filaments, loss of cell height, and increased intercellular separation were observed only in C2/AS cells treated with monochloramine. CONCLUSIONS: hsp72 protects intestinal epithelial barrier function against oxidant-induced stress, in part, by protecting the integrity of the actin cytoskeleton.