Pro-inflammatory cytokines of rat vasculature in DOCA-salt treatment

The purpose of this study was to ascertain the onset expression of pro-inflammatory cytokines in the aorta and kidney and establish their correlation with the increase in arterial blood pressure in rats subjected to DOCA-salt treatment. Male Sprague–Dawley rats underwent unilateral nephrectomy and received subcutaneous DOCA (20 mg/rat/week) as well as 1% NaCl and 0.2% KCl for drinking for 2 weeks. Blood pressure and expression of pro-inflammatory cytokines in aorta and kidney were studied weekly during the induction of hypertension. The treated rats exhibited a mild elevation of blood pressure at 1 week and a profound increase at 2 weeks. Quantitative RT-PCR demonstrated a 4.9-fold and a 3.6-fold enhancement in the expression of TNF-α and IL-6, respectively, in aorta as early as 1 week. The expression of IL-6 and TNF-α in the kidney remained almost unchanged at 1 week but mildly increased at 2 weeks DOCA-salt treatment. This study indicates a robust increase in the expression of IL-6 and TNF-α in aorta in DOCA-salt treated rats. This enhancement suggests that the activation of pro-inflammatory cytokines may contribute to onset of the elevation of blood pressure in DOCA-salt hypertension model.     

Water intake induced by isoprenaline in 2 models of experimental hypertension in rats

The drinking response to systemic injection of isoprenaline has been used to study the decreased beta-adrenergic reactivity in hypothyroid rats. Using the same test, the beta-adrenergic responsiveness has been investigated in two models of experimental hypertension (DOCA-salt and Goldblatt two kidney one clip rats). Three weeks after induction of hypertension, control and hypertensive rats were injected subcutaneously isoprenaline (0.1 mg/kg) and the accumulative water intake at 1st, 2nd and 3rd hours was recorded. Isoprenaline induced a smaller drinking response in DOCA-salt hypertensive (DS) and DOCA-normotensive (D) rats than in normotensive (age control, normal uninefrectomized-salt and sham operated) or hypertensive Goldblatt two kidney one clip rats. Isoprenaline induced a 50% mortality in the mineral-corticoid treated D and DS rats. The present study suggests that the reduced beta-adrenergic response (water intake) and the rate of mortality observed in DOCA treated rats may be due to the absence of renin release after isoprenaline injection, as previously reported by us.     

Mechanisms of cancer prevention by tea polyphenols based on inhibition of TNF-alpha expression

Among various biochemical and biological activities of tea polyphenols, we believe inhibition of the expression and release of tumor necrosis factor-alpha (TNF-alpha) is crucial, since our study with TNF-alpha-deficient mice has revealed that TNF-alpha is an essential factor in tumor promotion. We found that EGCG dose-dependently inhibited AP-1 and NF-kappaB activation in BALB/3T3 cells treated with okadaic acid, resulting in inhibition of TNF-alpha gene expression. Furthermore, treatment with 0.1% green tea extract in drinking water reduced TNF-alpha gene expression as well as TNF-alpha protein level in the lung of TNF-alpha transgenic mice; and IL-1beta and IL-10 gene expression in the lung was also inhibited by treatment with green tea extract, indicating that green tea inhibits both TNF-alpha and the cytokines induced by TNF-alpha in organs. We recently found synergistic effects of EGCG and cancer preventive agents such as tamoxifen and sulindac, on cancer preventive activity. Taken together, the results show that green tea is efficacious as a non-toxic cancer preventive for humans.     

Prevention of Dahl salt-induced hypertension by chronic dietary tryptophan

Four-week-old inbred Dahl salt-sensitive (DS/JR) and Dahl salt-resistant (DR/JR) rats were placed on an 8% salt diet with or without a supplemental 2.5% tryptophan (Trp). Blood pressures were monitored for the next 5 weeks. Urine volumes and ion concentrations were measured during the 6th week. Blood pressures of DS/JR rats on control diets elevated rapidly and markedly, whereas pressures of DS/JR rats on the Trp-supplemented diet were not significantly elevated over those of DR/JR rats. Pressures of DR/JR rats were unaffected by Trp supplementation. Urinary sodium was significantly greater in DR/JR rats compared with DS/JR rats and was unaffected by Trp supplementation. This suggests that the antihypertensive effect of Trp was not at the level of the kidney. We conclude that dietary Trp blocks the development of hypertension in DS/JR rats maintained on a high salt diet.     

Abnormal expression of ENaC and SGK1 mRNA induced by dietary sodium in Dahl salt-sensitively hypertensive rats

Epithelial sodium channel (ENaC) plays a crucial role in controlling sodium reabsorption in the kidney keeping the normal blood pressure. We previously reported that the expression of ENaC mRNA in the kidney of Dahl salt-sensitive (DS) rats was abnormally regulated by aldosterone, however it is unknown if dietary sodium affects the expression of ENaC and serum and glucocorticoid-regulated kinase 1 (SGK1), which plays an important role in ENaC activation, in DS rats. In the present study, we investigated whether dietary sodium abnormally affects the expression of ENaC and SGK1 mRNA in DS rats. DS and Dahl salt-resistant (DR) rats (8 weeks old) were divided into three different groups, respectively: (1) low sodium diet (0.005% NaCl), (2) normal sodium diet (0.3% NaCl), and (3) high sodium diet (8% NaCl). The high sodium diet for 4 weeks in DS rats elevated the systolic blood pressure, but did not in any other groups. The expression of alpha-ENaC mRNA in DS rats was abnormally increased by high sodium diet in contrast to DR rats, while it was normally increased by low sodium diet in DS rats similar to DR rats. The expression of beta- and gamma-ENaC mRNA in DS rats was also abnormally increased by high sodium diet unlike DR rats. The expression of SGK1 mRNA was elevated by high sodium diet in DS rats, but it was decreased in DR rats. These observations indicate that the expression of ENaC and SGK1 mRNA is abnormally regulated by dietary sodium in salt-sensitively hypertensive rats, and that this abnormal expression would be one of the factors causing salt-sensitive hypertension.     

Relationship between low magnesium status and TRPM6 expression in the kidney and large intestine

The body maintains Mg(2+) homeostasis by renal and intestinal (re)absorption. However, the molecular mechanisms that mediate transepithelial Mg(2+) transport are largely unknown. Transient receptor potential melastatin 6 (TRPM6) was recently identified and shown to function in active epithelial Mg(2+) transport in intestine and kidney. To define the relationship between Mg(2+) status and TRPM6 expression, we used two models of hypomagnesemia: 1) C57BL/6J mice fed a mildly or severely Mg(2+)-deficient diet, and 2) mice selected for either low (MgL) or high (MgH) erythrocyte and plasma Mg(2+) status. In addition, the mice were subjected to a severely Mg(2+)-deficient diet. Our results show that C57BL/6J mice fed a severely Mg(2+)-deficient diet developed hypomagnesemia and hypomagnesuria and showed increased TRPM6 expression in kidney and intestine. When fed a Mg(2+)-adequate diet, MgL mice presented hypomagnesemia and hypermagnesuria, and lower kidney and intestinal TRPM6 expression, compared with MgH mice. A severely Mg(2+)-deficient diet led to hypomagnesemia and hypomagnesuria in both strains. Furthermore, this diet induced kidney TRPM6 expression in MgL mice, but not in MgH mice. In conclusion, as shown in C57BL/6J mice, dietary Mg(2+)-restriction results in increased Mg(2+) (re)absorption, which is correlated with increased TRPM6 expression. In MgL and MgH mice, the inherited Mg(2+) status is linked to different TRPM6 expression. The MgL and MgH mice respond differently to a low-Mg(2+) diet with regard to TRPM6 expression in the kidney, consistent with genetic factors contributing to the regulation of cellular Mg(2+) levels. Further studies of these mice strains could improve our understanding of the genetics of Mg(2+) homeostasis.     

Zinc supplementation alleviates the progression of diabetic nephropathy by inhibiting the overexpression of oxidative-stress-mediated molecular markers in streptozotocin-induced experimental rats

Zinc deficiency during diabetes projects a role for zinc nutrition in the management of diabetic nephropathy. The current study explored whether zinc supplementation protects against diabetic nephropathy through modulation of kidney oxidative stress and stress-induced expression related to the inflammatory process in streptozotocin-induced diabetic rats. Groups of hyperglycemic rats were exposed to dietary interventions for 6 weeks with zinc supplementation (5 times and 10 times the normal level). Supplemental-zinc-fed diabetic groups showed a significant reversal of increased kidney weight and creatinine clearance. There was a significant reduction in hyperlipidemic condition along with improved PUFA:SFA ratio in the renal tissue. Expression of the lipid oxidative marker and expression of inflammatory markers, cytokines, fibrosis factors and apoptotic regulatory proteins observed in diabetic kidney were beneficially modulated by zinc supplementation, the ameliorative effect being concomitant with elevated antiapoptosis. There was a significant reduction in advanced glycation, expression of the receptor of the glycated products and oxidative stress markers. Zinc supplementation countered the higher activity and expression of polyol pathway enzymes in the kidney. Overexpression of the glucose transporters, as an adaptation to the increased need for glucose transport in diabetic condition, was minimized by zinc treatment. The pathological abnormalities in the renal architecture of diabetic animals were corrected by zinc intervention. Thus, dietary zinc supplementation has a significant beneficial effect in the control of diabetic nephropathy. This was exerted through a protective influence on oxidative-stress-induced cytokines, inflammatory proliferation and consequent renal injury.     

Rose hip exerts antidiabetic effects via a mechanism involving downregulation of the hepatic lipogenic program

The aim of this study was to investigate the metabolic effects of a dietary supplement of powdered rose hip to C57BL/6J mice fed a high-fat diet (HFD). Two different study protocols were used; rose hip was fed together with HFD to lean mice for 20 wk (prevention study) and to obese mice for 10 wk (intervention study). Parameters related to obesity and glucose tolerance were monitored, and livers were examined for lipids and expression of genes and proteins related to lipid metabolism and gluconeogenesis. A supplement of rose hip was capable of both preventing and reversing the increase in body weight and body fat mass imposed by a HFD in the C57BL/6J mouse. Oral and intravenous glucose tolerance tests together with lower basal levels of insulin and glucose showed improved glucose tolerance in mice fed a supplement of rose hip compared with control mice. Hepatic lipid accumulation was reduced in mice fed rose hip compared with control, and the expression of lipogenic proteins was downregulated, whereas AMP-activated protein kinase and other proteins involved in fatty acid oxidation were unaltered. Rose hip intake lowered total plasma cholesterol as well as the low-density lipoprotein-to-high-density lipoprotein ratio via a mechanism not involving altered gene expression of sterol regulatory element-binding protein 2 or 3-hydroxymethylglutaryl-CoA reductase. Taken together, these data show that a dietary supplement of rose hip prevents the development of a diabetic state in the C57BL/6J mouse and that downregulation of the hepatic lipogenic program appears to be at least one mechanism underlying the antidiabetic effect of rose hip.     

Epigallocatechin-3-gallate protects against cisplatin-induced nephrotoxicity by inhibiting endoplasmic reticulum stress-induced apoptosis

Cisplatin (CP)-induced nephrotoxicity hampers its application in clinic. Green tea, particularly its predominant polyphenolic constituent epigallocatechin-3-gallate (EGCG), possesses anti-inflammatory, antioxidant, and anti-apoptotic properties. The present study was designed to investigate the protective effects of EGCG against CP-induced nephrotoxicity in mice. Male C57/BL6 mice in different groups received single injection of CP (20 mg/kg) and EGCG (100 mg/kg) in various sets and kidney tissues and blood were collected after killing. Then, samples were used for biochemical and immunohistochemical assay. Our results showed EGCG decreased biochemical factors and immunohistochemical damage induced by CP. Besides, expression of phosphorylated-extracellular signal-regulated kinase (p-ERK), glucose-regulated protein 78 (GRP78), caspase-12, and apoptosis of kidney were decreased by EGCG via inhibition of endoplasmic reticulum (ER) stress-induced apoptosis.     

An analysis of the DOCA-salt model of hypertension in HO-1-/- mice and the Gunn rat

Heme oxygenase-1 (HO-1) is induced in the vasculature in the DOCA-salt model of hypertension in rats. Whereas the HO system and its products may exert vasodilator effects, recent studies have suggested that the HO system may predispose to hypertension. The present study examined the effects of selected components of the HO system, specifically, the HO-1 isozyme and the product bilirubin in the DOCA-salt model of systemic hypertension; the experimental approach employed mutant rodent models, namely, the HO-1(-/-) mouse and the hyperbilirubinemic Gunn rat. DOCA-salt induced HO-1 protein in the aorta in HO-1(+/+) mice and provoked a significant rise in systolic arterial pressure in HO-1(-/-) mice but not in HO-1(+/+) mice; this effect could not be ascribed to impaired urinary sodium excretion or impaired glomerular filtration rate in the DOCA-salt-treated HO-1(-/-) mice. The administration of DOCA salt to uninephrectomized rats significantly increased systolic arterial pressure in wild-type rats, an effect that was attenuated in the mutant Gunn rat; this reduction in systemic hypertension in the DOCA-salt-treated Gunn rat was not due to a greater induction of HO-1 in the vasculature or to a more avid urinary sodium excretion. DOCA-salt impaired endothelium-dependent and endothelium-independent vasorelaxation in wild-type rats but not in Gunn rats; prior exposure to bilirubin repaired the defect in endothelium-dependent vasorelaxation in aortic rings in DOCA-salt-treated rats. DOCA salt stimulated vascular production of superoxide anion in wild-type but not in Gunn rats. We suggest that HO-1 and the product bilirubin may exert a countervailing effect in the DOCA-salt model of systemic hypertension.     

Dietary red raspberries attenuate dextran sulfate sodium-induced acute colitis

Persistent intestinal inflammation severely impairs intestinal integrity resulting in inflammatory bowel disease. Red raspberries (RB) are a rich source of bioactive compounds; their beneficial effect on the colitis protection was evaluated in the current study using a dextran sulfate sodium (DSS)-induced acute colitis mouse model. Six-week-old mice were fed a standard rodent research diet supplemented with RB (0 or 5% w/w, n=20 each group) for 6 weeks. At the 4th week of dietary treatment, approximately half of mice in each dietary group (n=12 each group) were subjected to 2.5% DSS induction for 6 days, followed by 6 days of recovery, to induce colitis. RB supplementation decreased body weight loss (P≤.01), disease activity index (P≤.01), and colon shortening (P≤.05) in DSS-treated mice. In addition, RB supplementation protected the colonic structure (P≤.01), associated with suppressed NF-κB signaling and reduced expression of inflammatory interleukin (IL)-1β, IL-6, IL-17, cyclooxegenase-2, and tumor necrosis factor-α in DSS-treated mice. RB supplementation reduced neutrophil infiltration, monocyte chemoattractant protein-1 mRNA expression, and xanthine oxidase content, but enhanced catalase content in DSS-treated mice. Consistently, RB supplementation reduced pore forming tight junction protein claudin-2, increased barrier strengthening claudin-3, zonula occluden-1 protein content and mucin (MUC)-2 mRNA level, and activated AMP-activated protein kinase (AMPK) in DSS-treated mice. In conclusion, dietary RB protected against inflammation and colitis symptoms induced by DSS, providing a promising dietary approach for the management of colitis.     

Pharmacological studies of smooth muscle from Dahl salt-sensitive and salt-resistant rats

The pharmacological properties of various isolated smooth muscle preparations from the Dahl strain of hypertensive rats were studied. The Dahl salt-sensitive (DS) rat was allowed to develop hypertension by increasing the dietary sodium from 0.4 to 4.0 or 8.0%. The Dahl salt-resistant (DR) rat remained normotensive on the same diet. The preparations studied were the thoracic aorta, tail artery, portal vein, anococcygeus, and the perfused mesenteric bed. The noradrenaline mean effective doses (ED50) either in the absence or presence of cocaine, were similar for tissues obtained from hypertensive DS or normotensive DR. The reactivities of the isolated perfused mesenteric preparation to noradrenaline, serotonin, and phenylephrine were similar in DS and DR. The ED50 for the relaxing effects of papaverine in noradrenaline-precontracted aorta was similar for tissues from DS and DR and the profile for the washout of noradrenaline-precontracted aorta with Krebs (with or without papaverine) was also similar in DS and DR. The results of this study were compared with similar studies performed using other models of hypertension. It is concluded that vascular changes are unlikely to play a major role in the etiology of hypertension in the Dahl rat model of essential hypertension.     

Enalapril protects mice from pulmonary hypertension by inhibiting TNF-mediated activation of NF-kappaB and AP-1

The present study was undertaken to investigate the effects of treatment with the angiotensin-converting enzyme (ACE) inhibitor enalapril in a mouse model of pulmonary hypertension induced by bleomycin. Bleomycin-induced lung injury in mice is mediated by enhanced tumor necrosis factor-alpha (TNF) expression in the lung, which determines the murine strain sensitivity to bleomycin, and murine strains are sensitive (C57BL/6) or resistant (BALB/c). Bleomycin induced significant pulmonary hypertension in C57BL/6, but not in BALB/c, mice; average pulmonary arterial pressure (PAP) was 26.4 +/- 2.5 mmHg (P < 0.05) vs. 15.2 +/- 3 mmHg, respectively. Bleomycin treatment induced activation of nuclear factor (NF)-kappaB and activator protein (AP)-1 and enhanced collagen and TNF mRNA expression in the lung of C57BL/6 but not in BALB/c mice. Double TNF receptor-deficient mice (in a C57BL/6 background) that do not activate NF-kappaB or AP-1 in response to bleomycin did not develop bleomycin-induced pulmonary hypertension (PAP 14 +/- 3 mmHg). Treatment of C57BL/6 mice with enalapril significantly (P < 0.05) inhibited the development of pulmonary hypertension after bleomycin exposure. Enalapril treatment inhibited NF-kappaB and AP-1 activation, the enhanced TNF and collagen mRNA expression, and the deposition of collagen in bleomycin-exposed C57BL/6 mice. These results suggest that ACE inhibitor treatment decreases lung injury and the development of pulmonary hypertension in bleomycin-treated mice.     

Suppression of acute ethanol-induced hepatic steatosis by docosahexaenoic acid is associated with downregulation of stearoyl-CoA desaturase 1 and inflammatory cytokines

Excessive alcohol consumption can lead to hepatic steatosis. Omega-3 (n-3) polyunsaturated fatty acids (PUFA) have been shown to be effective in reducing hepatic accumulation of triglycerides (TG) by downregulation of TG biosynthesis in the liver. The aim of this study was to examine whether supplementation with the n-3 PUFA, docosahexaenoic acid (DHA), can effectively reduce acute alcohol-induced hepatic steatosis. Acute alcohol-induced hepatic steatosis was generated in 9-week-old male mice (C57BL/6J) by oral gavage of ethanol (4.7 g/kg BW) diluted in water (60%, v/v), with or without DHA (250 mg/kg BW), every 12 h for 3 administrations. Compared to the control (ethanol-alone) group, animals supplemented with DHA were protected against ethanol-induced TG accumulation in the liver. Accordingly, hepatic stearoyl-CoA desaturase-1 (SCD-1) expression, serum alanine aminotransferase (ALT) activity, and the levels of inflammatory cytokines (such as IL-6 and TNF-α) in the liver were significantly reduced, whereas the expression of heme oxygenase-1 (HO-1), an enzyme that can improve cell survival in liver tissue, was markedly increased in DHA-supplemented mice compared to the control animals. There were no differences in serum TG level and hepatic production of reactive oxygen species (ROS) between the two groups. Our findings demonstrate that DHA supplementation protects against acute ethanol-induced hepatic steatosis, which may be associated with reduced expression of SCD-1 and inflammatory cytokines.     

Attenuation by dietary taurine of dextran sulfate sodium-induced colitis in mice and of THP-1-induced damage to intestinal Caco-2 cell monolayers

The effects of dietary taurine on the experimental colitis induced by dextran sulfate sodium (DSS) in mice were evaluated. C57BL/6 female mice were given 3% DSS in drinking water for 5 d to induce acute colitis. Taurine at 2% was added to the drinking water 5 d before and during the DSS-treatment to investigate its preventive effect. Taurine supplementation significantly attenuated the weight decrease, diarrhea severity, colon shortening, and the increase in the colonic tissue myeloperoxidase activity induced by DSS. Taurine also significantly inhibited the increase in the expression of a pro-inflammatory chemokine, macrophage inflammatory protein 2 (MIP-2), but not of interleukin (IL)-1beta or tumor necrosis factor (TNF)-alpha mRNA. Furthermore, taurine significantly protected the intestinal Caco-2 cell monolayers from the damage by macrophage-like THP-1 cells in an in vitro coculture system. These results suggest that taurine prevented DSS-induced colitis partly in association with (1) its inhibitory effects on the secretion of MIP-2 from the intestinal epithelial cells and on the infiltration of such inflammatory cells as neutrophils and (2) its cytoprotective functions on the epithelial barrier from the direct toxicity of DSS and from the inflammatory cell-induced injury.