SBION2: Analyses of Salt Bridges from Multiple Structure Files,Version 2

AvailabilitySBION2 is freely available at http://sourceforge.net/projects/sbion2/ for academic users     

Hydroxyxanthone as an inhibitor of cAMP-activated apical chloride channel in human intestinal epithelial cell

AimsPrevious investigation showed that polyphenols abundantly found in many plants could inhibit Cl^? secretion. The present study was aimed to investigate the effect of phenol containing xanthone derivatives on cAMP-activated intestinal Cl^? secretion and evaluate potential benefits of these compounds in the treatment of cholera.Main methodsFour hydroxy xanthones were synthesized via oxidative coupling reaction of the corresponding ortho-hydroxybenzoic acids and hydroxyphenols. Short-circuit current and apical Cl^? current measurements across monolayers of human intestinal epithelial (T84) cell and Fisher rat thyroid cells transfected with human CFTR (FRT-hCFTR cell) were performed to determine the effect of hydroxyxanthones on cAMP-activated Cl^? secretion. Intracellular cAMP was measured by immunoassay methods. Anti-diarrheal efficacy was evaluated using closed loop model of cholera.Key findingsAmong the tested xanthones, 1,3,6-trihydroxyxanthone (THX-001) was found to be the most potent derivative in the inhibition of cAMP-activated Cl^? secretion across T84 cell monolayers (IC₅₀ ~ 100 μM). Electrophysiological analysis of T84 cells and FRT-hCFTR cells revealed that THX-001 targeted two distinct cAMP-activated Cl^? channels in the apical membrane of T84 cells, namely, CFTR and inward rectifying Cl^? channel (IRC). In contrast, THX-001 had no effect on intracellular cAMP levels in these cells. Importantly, THX-001 completely abolished cholera toxin-induced Cl^? secretion across T84 cell monolayers and significantly inhibited cholera toxin-induced intestinal fluid secretion in mouse closed loop models.SignificanceThis study revealed that hydroxyxanthone represents another chemical class of polyphenolic compounds that may hold promise as anti-secretory therapy for cholera.     

Breakdown of the blood-brain barrier during tick-borne encephalitis in mice is not dependent on CD8+ T-cells

Tick-borne encephalitis (TBE) virus causes severe encephalitis with serious sequelae in humans. The disease is characterized by fever and debilitating encephalitis that can progress to chronic illness or fatal infection. In this study, changes in permeability of the blood-brain barrier (BBB) in two susceptible animal models (BALB/c, and C57Bl/6 mice) infected with TBE virus were investigated at various days after infection by measuring fluorescence in brain homogenates after intraperitoneal injection of sodium fluorescein, a compound that is normally excluded from the central nervous system. We demonstrate here that TBE virus infection, in addition to causing fatal encephalitis in mice, induces considerable breakdown of the BBB. The permeability of the BBB increased at later stages of TBE infection when high virus load was present in the brain (i.e., BBB breakdown was not necessary for TBE virus entry into the brain), and at the onset of the first severe clinical symptoms of the disease, which included neurological signs associated with sharp declines in body weight and temperature. The increased BBB permeability was in association with dramatic upregulation of proinflammatory cytokine/chemokine mRNA expression in the brain. Breakdown of the BBB was also observed in mice deficient in CD8(+) T-cells, indicating that these cells are not necessary for the increase in BBB permeability that occurs during TBE. These novel findings are highly relevant to the development of future therapies designed to control this important human infectious disease.     

Japanese encephalitis virus: from genome to infectome

Japanese encephalitis virus (JEV) is an arbovirus belonging to the family Flaviviridae. It is maintained in a zoonotic cycle involving pigs, ardeid birds and Culex species of mosquitoes. Humans are accidental/dead end hosts of JEV infection because they cannot sustain high viral titers. Factors affecting the clinical manifestations and pathogenesis of JEV infection are not well understood. Though, vaccines are currently available against JEV, it has to be further improved. Here we review the literature on the JEV life cycle, pathogenesis and host immune responses to JEV infection.     

Characterization of the Oligomerization and Aggregation of Human Serum Amyloid A

The fibrillation of Serum Amyloid A (SAA) – a major acute phase protein – is believed to play a role in the disease Amyloid A (AA) Amyloidosis. To better understand the amyloid formation pathway of SAA, we characterized the oligomerization, misfolding, and aggregation of a disease-associated isoform of human SAA – human SAA1.1 (hSAA1.1) – using techniques ranging from circular dichroism spectroscopy to atomic force microscopy, fluorescence spectroscopy, immunoblot studies, solubility measurements, and seeding experiments. We found that hSAA1.1 formed alpha helix-rich, marginally stable oligomers in vitro on refolding and cross-beta-rich aggregates following incubation at 37°C. Strikingly, while hSAA1.1 was not highly amyloidogenic in vitro, the addition of a single N-terminal methionine residue significantly enhanced the fibrillation propensity of hSAA1.1 and modulated its fibrillation pathway. A deeper understanding of the oligomerization and fibrillation pathway of hSAA1.1 may help elucidate its pathological role.     

Skin Colonization by Malassezia spp. in Hospitalized Neonates and Infants in a Tertiary Care Centre in North India

Malassezia, a skin colonizer, is associated with multiple skin disorders in adults, and cephalic pustulosis and folliculitis in children. It can cause fungemia in infants and neonates. The time and pattern of colonization, risk factors associated with colonization and causing fungemia in children, are not well understood. The prospective cohort study was conducted to determine the rate of Malassezia species colonization and associated factors in hospitalized neonates and infants. Consecutive 50 neonates and infants admitted in neonatal and pediatric intensive care units were studied. The skin swabs were collected on the day of admission and every fifth day, thereafter, till the patient was discharged or died. Putative risk factors for the colonization of Malassezia species were recorded. Isolates were identified by phenotypic methods and sequencing of the D1 and D2 region of rDNA. Neonates were not colonized at the time of entry in neonatal ICU or at birth. Nineteen (38 %) neonates were colonized with Malassezia species during their hospital stay. Among the infants, three (6 %) came to ICU with Malassezia colonization and 26 (52 %) acquired Malassezia during ICU stay. Mechanical ventilation, duration of hospital stay, central venous catheterization, and antifungal therapy were the significantly associated factors for colonization. Malassezia furfur was the most common species isolated from the skin of infants and neonates. Colonization by Malassezia species in infants and neonates in a hospital is not uncommon and can be a potential source of nosocomial infection.     

Antibacterial activity of berberine-NorA pump inhibitor hybrids with a methylene ether linking group

Conjugation of the NorA substrate berberine and the NorA inhibitor 5-nitro-2-phenyl-1H-indole via a methylene ether linking group gave the 13-substituted berberine-NorA inhibitor hybrid, 3. A series of simpler arylmethyl ether hybrid structures were also synthesized. The hybrid 3 showed excellent antibacterial activity (MIC Staphylococcus aureus, 1.7 μM), which was over 382-fold more active than the parent antibacterial berberine, against this bacterium. This compound was also shown to block the NorA efflux pump in S. aureus.     

Inhibitory effects of choleretic hydroxyacetophenones on ileal bile acid transport in rats

The effects of the choleretic and cholesterol lowering compound, 2,4,6-trihydroxyacetophenone (THA) and its analog, 2,6-dihydroxyacetophenone (DHA), on ileal bile acid absorption were investigated in rats. THA inhibited taurocholate (TC) uptake into ileal brush-border membrane vesicles (BBMV), showing a maximum inhibition of 50%, whereas DHA completely inhibited TC uptake into ileal BBMV. THA exhibited competitive inhibition with a Ki of 9.88 mM, while DHA showed non-competitive inhibition with a Ki of 7.65 mM. Both total and ouabain-sensitive basolateral membrane (BLM) Na+-K+-ATPase activities, which are essential for maintenance of the Na+-gradient for bile acid transport, were inhibited by THA and DHA in a dose-dependent manner. The inhibition of BLM ATPase was uncompetitive with a Ki of 10.1 and 5.0 mM for THA and DHA, respectively. Administration of THA or DHA (400 micromol/kg) twice a day, to hypercholesterolemic rats for 3 weeks caused similar and marked reductions in plasma cholesterol to 60% of the cholesterol-fed controls. The data suggest that the inhibitory actions of THA and DHA on two essential components of ileal bile acid recycling to liver could, in part, contribute to the cholesterol lowering effect of the hydroxyacetophenone compounds. These effects on decreasing bile acid recycling, in combination with their potent choleretic effect, accelerating biliary excretion of bile acids, are responsible for the effective cholesterol lowering capacities of these compounds.     

Biotransformations of 20-hydroxyecdysone and analogues by Curvularia lunata NRRL 2178

20-Hydroxyecdysone, the arthropod moulting hormone, was biotransformed by the fungus Curvularia lunata NRRL 2178 to the rare ecdysteroid, 2-dehydro-3-epi-20-hydroxyecdysone, and the novel 3alpha,9alpha-cyclo ecdysteroid analogue, (20R,22R)-3beta,14alpha,20,22,25-pentahydroxy-3alpha,9alpha-cyclo-5beta-cholest-7-en-2,6-dione in 14 and 44% yields, respectively. Ponasterone A and pterosterone were similarly biotransformed to the corresponding 2-dehydro-3-epi- and 3alpha,9alpha-cyclo-analogues.