JAM-C induces endothelial cell permeability through its association and regulation of {beta}3 integrins.

OBJECTIVE: The molecular mechanisms regulating vascular permeability are only now being elucidated. The junctional adhesion molecule (JAM) JAM-C has been linked to the induction of vascular permeability. We sought to understand the mechanism whereby JAM-C may disrupt junctional integrity in endothelial cells (ECs). METHODS AND RESULTS: We show here that JAM-C alters permeability through modulation of integrin activity. JAM-C overexpression results in an increase in JAM-C at junctions and an increase in permeability. Conversely, knockdown of JAM-C by siRNA results in a reduction in permeability. JAM-C associates with alphavbeta3 integrin and regulates its localization and activity. JAM-C also inhibits the activation state of the beta(1) integrin although it does not associate with this integrin. These changes induced on the integrins are mediated through regulation of the small GTPase, Rap1b but not Rap1a. Thrombin, a powerful inductor of vascular leak, causes localization of JAM-C into the junctions, whereas angiopoietin-1, an inhibitor of permeability, prevents JAM-C translocation. CONCLUSIONS: The regulation of EC junctional integrity involves the coordinated and dynamic modification of localization and activity of junctional stabilizers such as the integrin beta(3) and the destabilizer, JAM-C.

A QSAR study of acute toxicity of N-substituted fluoroacetamides to rats.

Acute toxicity in vivo toward rats, of nineteen N-alkyl and N-cycloalkyl fluorocetamides [F-CH(2)-C(O)-NH-R] was correlated with their structure-dependent properties. Used descriptors are: molecular weights (M(w)) and heat of formation (DeltaH(f)) of compounds; molar refractivity (CMR), lipophilicity (ClogP), Broto lipol values, virtual logP, molecular lipophilic potential (MLP), Van der Waals surfaces (VdW SAS) and hydropathicity surface (ILM) of whole molecules; Taft steric parameters (E(s)); E(s) values with Hancock corrections (E(s)(CH)) and Verloop sterimol (B(5)) and (L) parameters of alkyl and cycloalkyl residues; superdelocalizabilities and electron densities on the [NH-C(O)-CH(2)-F] fragment. Strong quantitative structure-activity relationships were assessed. Obtained correlation suggested that lipophilicity, shape and bulkiness of the alkyl and cycloalkyl substituents, particular nearest vicinity of the amide nitrogen, as well charges on the amide moiety are the main factors that influence on the acute toxicity of studied compounds toward rats. Mechanism of toxic action was proposed.

The effects of α-lipoic acid on liver oxidative stress and free fatty acid composition in methionine-choline deficient diet-induced NAFLD.

Development of nonalcoholic fatty liver disease (NAFLD) occurs through initial steatosis and subsequent oxidative stress. The aim of this study was to examine the effects of α-lipoic acid (LA) on methionine-choline deficient (MCD) diet-induced NAFLD in mice. Male C57BL/6 mice (n=21) were divided into three groups (n=7 per group): (1) control fed with standard chow, (2) MCD2 group--fed with MCD diet for 2 weeks, and (3) MCD2+LA group--2 weeks on MCD receiving LA i.p. 100 mg/kg/day. After the treatment, liver samples were taken for pathohistology, oxidative stress parameters, antioxidative enzymes, and liver free fatty acid (FFA) composition. Mild microvesicular hepatic steatosis was found in MCD2 group, while it was reduced to single fat droplets evident in MCD2+LA group. Lipid peroxidation and nitrosative stress were increased by MCD diet, while LA administration induced a decrease in liver malondialdehyde and nitrates+nitrites level. Similary, LA improved liver antioxidative capacity by increasing total superoxide dismutase (tSOD), manganese SOD (MnSOD), and copper/zinc-SOD (Cu/ZnSOD) activity as well as glutathione (GSH) content. Liver FFA profile has shown a significant decrease in saturated acids, arachidonic, and docosahexaenoic acid (DHA), while LA treatment increased their proportions. It can be concluded that LA ameliorates lipid peroxidation and nitrosative stress in MCD diet-induced hepatic steatosis through an increase in SOD activity and GSH level. In addition, LA increases the proportion of palmitic, stearic, arachidonic, and DHA in the fatty liver. An increase in DHA may be a potential mechanism of anti-inflammatory and antioxidant effects of LA in MCD diet-induced NAFLD.

Time-dependent changes and association between liver free fatty acids, serum lipid profile and histological features in mice model of nonalcoholic fatty liver disease.

BACKGROUND AND AIMS: Methionine-choline deficient (MCD) diet duration necessary for development of non-alcoholic fatty liver disease (NAFLD) and the dynamic of lipid profile and fatty acids are not completely established. The study examined dynamics and association between liver free fatty acids (FFA), serum lipid profile and liver morphological changes on MCD diet-induced NAFLD in mice. METHODS: Male C57BL/6 mice (n = 28) were divided into four groups (n = 7 per group): control: fed with standard chow, MCD diet-fed groups: 2, 4 or 6 weeks. After treatment, liver and blood samples were taken for histopathology, serum lipid profile, and liver FFA composition. RESULTS: Hepatic FFA profile showed a decrease in saturated acids, arachidonic and docosahexaenoic acid, whereas proportions of docosapentaenoic, oleic and linoleic acid were increased. Total cholesterol, HDL and triglycerides progressively decreased, whereas LDL level progressively increased. Focal fatty change in the liver appeared after 2 weeks, whereas diffuse fatty change with severe inflammation and ballooned hepatocytes were evident after 6 weeks. CONCLUSIONS: Six-week diet model may be appropriate for investigation of the role of lipotoxicity in the progression of NAFLD. Therefore, supplementation with n-3 polyunsaturated acid like DHA, rather than DPA, especially in the initial stage of fatty liver disease, may potentially have preventive effects and alleviate development of NAFLD/NASH and may also potentially reduce cardiovascular risk by moderating dyslipidemia.

The effects of caloric restriction against ethanol-induced oxidative and nitrosative cardiotoxicity and plasma lipids in rats.

Caloric restriction (CR) prevents or delays a wide range of aging-related diseases possibly through alleviation of oxidative stress. The aim of our study was to examine the effect of CR on oxidative and nitrosative cardiac damage in rats, induced by acute ethanol intoxication. Male Wistar rats were divided into following groups: control; calorie-restricted groups with intake of 60-70% (CR60-70) and 40-50% of daily energy needs (CR40-50); ethanol-treated group (E); calorie-restricted, ethanol-treated groups (CR60-70 + E, CR40-50 + E). Ethanol was administered in five doses of 2 g/kg every 12 h, while the duration of CR was five weeks before ethanol treatment. Malondialdehyde level was significantly lower in CR60-70 + E and significantly higher in CR40-50 + E vs. control. Nitrite and nitrate level was significantly higher in CR40-50 + E compared to control group. Activity of total superoxide dismutase (SOD) and its isoenzyme, copper/zinc-SOD (Cu/ZnSOD), was significantly higher in CR60-70 + E and lower in CR40-50 + E vs. control. Activity of manganese-SOD (MnSOD), that is also SOD isoenzyme, was significantly lower in CR40-50 + E compared to control group. Plasma content of sulfhydryl (SH) groups was significantly higher in CR60-70 group vs. control. Plasma concentration of total cholesterol, triacylglycerol, low-density lipoproteins and high-density lipoproteins was significantly lower in CR60-70 group compared to control values. Food restriction to 60-70% of daily energy needs has a protective effect on acute ethanol-induced oxidative and nitrosative cardiac damage, at least partly due to alleviation of ethanol-induced decrease in SOD activity, while restriction to 40-50% of energy needs aggravates lipid peroxidation and nitrosative stress.

The effect of calorie restriction on acute ethanol-induced oxidative and nitrosative liver injury in rats.

The aim of our study was to examine the effect of calorie restriction (CR) on oxidative and nitrosative liver injury in rats, induced by acute ethanol intoxication. Male Wistar rats were divided into groups: (1) control; (2) calorie-restricted groups with intake of 60-70% (CR60-70) and 40-50% of daily energy needs (CR40-50); (3) ethanol-treated group (E); (4) calorie-restricted, ethanol-treated groups (E+CR60-70 and E+CR40-50). Ethanol was administered in 5 doses of 2g/kg every 12h, and duration of CR was 5 weeks before ethanol treatment. Malondialdehyde and nitrite and nitrate level were significantly lower in E+CR60-70 and higher in E+CR40-50 vs. E group. Liver reduced glutathione content and activity of both superoxide dismutase izoenzymes were significantly higher in E+CR60-70 and lower in E+CR40-50 vs. E group. Oxidative stress may be a potential mechanism of hormetic effects of CR on acute ethanol-induced liver injury.

Basal and angiopoietin-1-mediated endothelial permeability is regulated by sphingosine kinase-1.

Endothelial cells (ECs) regulate the barrier function of blood vessels. Here we show that basal and angiopoietin-1 (Ang-1)-regulated control of EC permeability is mediated by 2 different functional states of sphingosine kinase-1 (SK-1). Mice depleted of SK-1 have increased vascular leakiness, whereas mice transgenic for SK-1 in ECs show attenuation of leakiness. Furthermore, Ang-1 rapidly and transiently stimulates SK-1 activity and phosphorylation, and induces an increase in intracellular sphingosine-1-phosphate (S1P) concentration. Overexpression of SK-1 resulted in inhibition of permeability similar to that seen for Ang-1, whereas knockdown of SK-1 by small interfering RNA blocked Ang-1-mediated inhibition of permeability. Transfection with SKS225A, a nonphosphorylatable mutant of SK-1, inhibited basal leakiness, and both SKS225A and a dominant-negative SK-1 mutant removed the capacity of Ang-1 to inhibit permeability. These effects were independent of extracellular S1P as knockdown or inhibition of S1P1, S1P2, or S1P3, did not affect the Ang-1 response. Thus, SK-1 levels in ECs powerfully regulate basal permeability in vitro and in vivo. In addition, the Ang-1-induced inhibition of leakiness is mediated through activation of SK-1, defining a new signaling pathway in the Ang-1 regulation of permeability.