Mitogen-activated protein kinase (MAPK) phosphatase-1 and -4 attenuate p38 MAPK during dexamethasone-induced insulin resistance in 3T3-L1 adipocytes

Prolonged use of glucocorticoids induces pronounced insulin resistance in vivo. In vitro, treatment of 3T3-L1 adipocytes with dexamethasone for 48 h reduces the maximal level of insulin- and stress (arsenite)-induced glucose uptake by approximately 50%. Although phosphatidylinositol 3-kinase signaling was slightly attenuated, phosphorylation of its downstream effectors such as protein kinase B and protein kinase C-lambda remained intact. Nor was any effect of dexamethasone treatment observed on insulin- or arsenite-induced translocation of glucose transporter 4 (GLUT4) toward the plasma membrane. However, for a maximal response to either arsenite- or insulin-induced glucose uptake in these cells, functional p38 MAPK signaling is required. Dexamethasone treatment markedly attenuated p38 MAPK phosphorylation coincident with an up-regulation of the MAPK phosphatases MKP-1 and MKP-4. Employing lentivirus-mediated ectopic expression in fully differentiated 3T3-L1 adipocytes demonstrated a differential effect of these phosphatases: whereas MKP-1 was a more potent inhibitor of insulin-induced glucose uptake, MKP-4 more efficiently inhibited arsenite-induced glucose uptake. This coincided with the effects of these phosphatases on p38 MAPK phosphorylation, i.e. MKP-1 and MKP-4 attenuated p38 MAPK phosphorylation by insulin and arsenite, respectively. Taken together, these data provide evidence that in 3T3-L1 adipocytes dexamethasone inhibits the activation of the GLUT4 in the plasma membrane by a p38 MAPK-dependent process, rather than in a defect in GLUT4 translocation per se.     

Task-Specific and General Cognitive Effects in Chiari Malformation Type I

Objective

Our objective was to use episodic memory and executive function tests to determine whether or not Chiari Malformation Type I (CM) patients experience cognitive dysfunction.

Background

CM is a neurological syndrome in which the cerebellum descends into the cervical spine causing neural compression, severe headaches, neck pain, and number of other physical symptoms. While primarily a disorder of the cervico-medullary junction, both clinicians and researchers have suspected deficits in higher-level cognitive function.

Design and Methods

We tested 24 CM patients who had undergone decompression neurosurgery and 24 age- and education-matched controls on measures of immediate and delayed episodic memory, as well as three measures of executive function.

Results

The CM group showed performance decrements relative to the controls in response inhibition (Stroop interference), working memory computational speed (Ospan), and processing speed (automated digit symbol substitution task), but group differences in recall did not reach statistical significance. After statistical control for depression and anxiety scores, the group effects for working memory and processing speed were eliminated, but not for response inhibition. This response inhibition difference was not due to overall general slowing for the CM group, either, because when controls'' data were transformed using the linear function fit to all of the reaction time tasks, the interaction with group remained statistically significant. Furthermore, there was a multivariate group effect for all of the response time measures and immediate and delayed recall after statistical control of depression and anxiety scores.

Conclusion

These results suggest that CM patients with decompression surgery exhibit cognitive dysfunction compared to age- and education-matched controls. While some of these results may be related to anxiety and depression (likely proxies for chronic pain), response inhibition effects, in particular, as well as a general cognitive deficit persisted even after control for anxiety and decompression.     

Discovery of a series of novel 5H-pyrrolo[2,3-b]pyrazine-2-phenyl ethers,as potent JAK3 kinase inhibitors

We report the discovery of a novel series of ATP-competitive Janus kinase 3 (JAK3) inhibitors based on the 5H-pyrrolo[2,3-b]pyrazine scaffold. The initial leads in this series, compounds 1a and 1h, showed promising potencies, but a lack of selectivity against other isoforms in the JAK family. Computational and crystallographic analysis suggested that the phenyl ether moiety possessed a favorable vector to achieve selectivity. Exploration of this vector resulted in the identification of 12b and 12d, as potent JAK3 inhibitors, demonstrating improved JAK family and kinase selectivity.     

Anticancer potential of rhamnocitrin 4′-β-d-galactopyranoside against N-diethylnitrosamine-induced hepatocellular carcinoma in rats

The hepatoprotective activity of flavonoid rhamnocitrin 4′-β-d-galactopyranoside (RGP) obtained from leaves of Astragalus hamosus L. against N-diethylnitrosamine (DENA)-induced hepatic cancer in Wistar albino rats was evaluated. Hepatic cancer in rats was induced by single-dose intraperitoneal administration of DENA (200 mg/kg). Induction of hepatic cancer was confirmed after 7 days of DENA administration by measurement of elevated level of serum α-feto protein (AFP). Administration of DENA in a single dose lofted the levels of serum biochemical parameters like alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, total protein and AFP. Antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione-S-transferase (GST) and lipid per oxidation (LPO) were annealed significantly by administration of RGP in a dose-dependant manner. The histopathological examination of rat liver section was found to reinforce the biochemical observations significantly. It was observed that a substantial and dose-dependent reversal of DENA-diminished activity of antioxidant enzymes like SOD, CAT, GPx, GST and the reduced DENA-elevated level of LPO with a marked change. Any elevation in the levels of serum markers along with suppression of free radical formation by scavenging the hydroxyl radicals is significantly prevented by RGP. It also modulates the levels of LPO and perceptibly increases the endogenous antioxidant enzymes level in DENA-induced hepatocellular carcinogenesis. The findings suggest that RGP prevents hepatocellular carcinoma by suppressing the marked increase in the levels of serum marker enzymes, and suppresses the free radical by scavenging hydroxyl radicals.     

A new lectin from the tuberous rhizome of Kaempferia rotunda: isolation, characterization, antibacterial and antiproliferative activities

A lectin (designated as KRL) was purified from the extracts of Kaempferia rotunda Linn. tuberous rhizome by glucose-sepharose affinity chromatography. KRL was determined to be a 29.0 ± 1.0 kDa polypeptide by SDS-PAGE under both reducing and non-reducing conditions. KRL was a divalent ion dependent glycoprotein with 4% neutral sugar which agglutinated different groups of human blood cells. Methyl-α-D-mannopyranoside, D-mannose and methyl-α-D-glucopyranoside were the most potent inhibitors. N-terminal sequence of KRL showed similarity to some mannose/ glucose specific lectins but the main differences with their molecular masses and sugar content. KRL lost its activity markedly in the presence of denaturants and exhibited high agglutination activity from pH 6.0 to 8.2 and temperature 30 to 60° C. The lectin showed toxicity against brine shrimp nauplii with the LC50 value of 18 ± 6 μg/ml and strong agglutination activity against seven pathogenic bacteria. KRL inhibited the growth of six bacteria partially and did not show antifungal activity. In addition, antiproliferative activity against Ehrlich ascites carcinoma (EAC) cells showed 51% and 67% inhibition in vivo in mice administered 1.25 mg/kg/day and 2.5 mg/kg/day of KRL respectively by injection for five days.     

Effect of ischemia on fatty acid metabolism in fetal lung

The effects of ischemia on in vivo fatty acid metabolism in fetal lung were studied using rabbit fetuses of 25 to 28 gestational age. Ischemia was produced by inflating the aortic balloon thereby reducing the uterine blood flow. Ischemic insult resulted significant increase in lactate/pyruvate and NADH/NAD ratios and decrease in ATP/ADP ratio in fetal lung. Levels of CoA, acetyl CoA, carnitine and acetyl carnitine decreased while those of long chain acyl CoA and long chain acyl carnitine enhanced. Tissue content of these metabolites returned to normal after 2 hr stabilization following 20 min of ischemic insult. Ischemia also caused small increase in lipogenesis and neutral lipid content of fetal lungs. Our results thus suggest that β-oxidation in fetal lung is inhibited and becomes rate-limiting for fatty acid oxidation during ischemia.Sudden occurrence of hypoxia or ischemia in the fetus is a typical challenge for the obstetricians. The patients occasionally suffer from neurological injury following cerebral hypoxemia. The hypoxic insult may also affect the respiratory activity significantly. For example, acute alveolar hypoxia causes pulmonary vasoconstriction by damaging pulmonary vascular smooth muscle (1) and results in reduction of fatty acid oxidation by limiting the ATP supply required for metabolic processes (2). Hypoxia has also been shown to decrease the rate of palmitate incorporation into phospholipids (3), inhibit rate of fatty acid synthesis (3) and depress rate of incorporation of fatty acid and phosphatidic acid into lipids (4). Despite the fact that fatty acids represent a major substrate for energy metabolism in lung, no work has been done on the fatty acid metabolism in fetal lung. The present study was designed to determine the fate of fatty acid oxidation in fetal lung during ischemic challenge. The levels of acyl CoA and acylcarnitine intermediates were also measured in order to determine the rate-controlling steps of fatty acid metabolism in the fetal lung.     

Spontaneous insertion of lipopolysaccharide into lipid membranes from aqueous solution

Lipopolysaccharide (LPS), one of the main components of outer membranes of Gram-negative bacteria, consists of a hydrophobic lipid (lipid A) with six hydrocarbon chains and a large hydrophilic polysaccharide chain. LPS plays endotoxic roles and can stimulate macrophages and B cells. To elucidate the mechanism of the interaction of LPS with various cell membranes, it is important to investigate the interaction of wild type LPS in a buffer with lipid membranes. In this report we investigated the interaction of low concentrations of LPS in a buffer with giant unilamellar vesicles (GUVs) of dioleoylphosphatidylcholine (DOPC) membrane in the liquid-crystalline (L_α) phase and sphingomyelin (SM)/cholesterol(chol) (molar ration; 6/4) membrane in the liquid-ordered (lo) phase. We found that low concentrations (less than critical micelle concentration) of LPS in aqueous solution induced the shape changes such as the transformation from a prolate to a two-spheres-connected by a very narrow neck in the DOPC-GUVs and also in the SM/chol (6/4)-GUVs above their threshold concentrations. The analysis of the shape changes of the GUVs indicates that the monomers of LPS can insert spontaneously into the external monolayer of the lipid membranes of these GUVs from the aqueous solution. Moreover, higher concentrations of LPS induced the vesicle fission of SM/chol(6/4)-GUVs above its higher threshold concentration. The vesicle fission of GUVs is similar to those induced by single long chain amphiphiles such as lysophosphatidylcholine. On the basis of these results, we discuss the interaction of wild type LPS with lipid membranes and cell membranes. These results suggest that LPS molecules can insert spontaneously into the external monolayer of the plasma membranes composed of the L_α phase-membrane and the microdomain in the lo phase.     

Susceptibility of an organophosphate resistant strain of the two-spotted spider mite (<Emphasis Type="Italic">Tetranychus urticae</Emphasis>) to mixtures of bifenazate with organophosphate and carbamate insecticides

Bifenazate, a new and frequently used carbazate, is a pro-acaricide which needs to be activated by carboxylesterases. We evaluated the possible antagonism of organophosphate and carbamate insecticides on bifenazate toxicity in Tetranychus urticae applied in mixtures. Two organophosphate resistant strains were used (WI and MR-VL) and several organophosphate (chlorpyrifos, azinphosmethyl and phosmet) and carbamate (carbaryl and methomyl) insecticides were evaluated. Mixing chlorpyrifos with bifenazate decreased bifenazate toxicity in both tested strains. However, in the strain with a higher esterase activity, antagonism decreased after 2 days. Of all other tested chemicals, only methomyl displayed an antagonistic effect 1 day after treatment. These findings indicate that mixing organophosphate and carbamate insecticides with bifenazate may inhibit bifenazate efficacy under field conditions, especially when resistant strains are present.