Modulation of Pseudomonas aeruginosa lipopolysaccharide-induced lung inflammation by chronic iron overload in rat

Iron constitutes a critical nutrient source for bacterial growth, so iron overload is a risk factor for bacterial infections. This study aimed at investigating the role of iron overload in modulating bacterial endotoxin-induced lung inflammation. Weaning male Wistar rats were intraperitoneally injected with saline or iron sucrose [15 mg kg(-1) body weight (bw), 3 times per week, 4 weeks]. They were then intratracheally injected with Pseudomonas aeruginosa lipopolysaccharide (LPS) (5 μg kg(-1) bw) or saline. Inflammatory indices were evaluated 4 or 18 h post-LPS/saline injection. At 4 h, LPS-treated groups revealed significant increases in the majority of inflammatory parameters (LPS-binding protein (LBP), immune cell recruitment, inflammatory cytokine synthesis, myeloperoxidase activity, and alteration of alveolar-capillary permeability), as compared with control groups. At 18 h, these parameters reduced strongly with the exception for LBP content and interleukin (IL)-10. In parallel, iron acted as a modulator of immune cell recruitment; LBP, tumor necrosis factor-α, cytokine-induced neutrophil chemoattractant 3, and IL-10 synthesis; and alveolar-capillary permeability. Therefore, P. aeruginosa LPS may only act as an acute lung inflammatory molecule, and iron overload may modulate lung inflammation by enhancing different inflammatory parameters. Thus, therapy for iron overload may be a novel and efficacious approach for the prevention and treatment of bacterial lung inflammations.     

To bloom or not to bloom: contrasting responses of cyanobacteria to recent heat waves explained by critical thresholds of abiotic drivers

Past heat waves are considered harbingers of future climate change. In this study, we have evaluated the effects of two recent Central European summer heat waves (2003 and 2006) on cyanobacterial blooms in a eutrophic, shallow lake. While a bloom of cyanobacteria developed in 2006, consistent with our expectations, cyanobacterial biomass surprisingly remained at a record-low during the entire summer of 2003. Critical thresholds of abiotic drivers extracted from the long-term (1993–2007) data set of the studied lake using classification tree analysis (CTA) proved suitable to explain these observations. We found that cyanobacterial blooms were especially favoured in 2006 because thermal stratification was critically intense (Schmidt stability >44 g cm cm⁻²) and long-lasting (>3 weeks). Our results also suggest that some cyanobacterial species (Anabaena sp.) benefitted directly from the stable water column, whereas other species (Planktothrix sp.) took advantage of stratification-induced internal nutrient loading. In 2003, conditions were less favourable for cyanobacteria due to a spell of lower temperatures and stronger winds in mid-summer; as a result, the identified thresholds of thermal stratification were hardly ever reached. Overall, our study shows that extracting critical thresholds of environmental drivers from long-term records is a promising avenue for predicting ecosystem responses to future climate warming. Specifically, our results emphasize that not average temperature increase but changes in short-term meteorological variability will determine whether cyanobacteria will bloom more often in a warmer world.     

Stimulation of cytosolic and mitochondrial calcium mobilization by indomethacin in Caco-2 cells: Modulation by the polyphenols quercetin,resveratrol and rutin

Background

The effect of indomethacin (INDO) on Ca^2 + mobilization, cytotoxicity, apoptosis and caspase activation and the potential protective effect of quercetin (QUE), resveratrol (RES) and rutin (RUT) were determined in Caco-2 cells.

Methods

Caco-2 cells were incubated with INDO in the presence or absence of QUE, RES or RUT. The concentrations of Ca^2 + in the cytosol (Fluo-3 AM) and mitochondria (Rhod-2 AM) were determined as well as the cytotoxicity (MTT reduction and LDH leakage), apoptosis (TUNEL) and caspase-3 and 9 activities.

Results

INDO promoted Ca^2 + efflux from the endoplasmic reticulum (ER), resulting in an early, but transient, increment of cytosolic Ca^2 + at 3.5 min, followed by a subsequent increment of intra-mitochondrial Ca^2 + at 24 min. INDO also induced cytotoxicity, apoptosis, and increased caspase activities and cytochrome c release. All these alterations were prevented by the inhibitors of the IP3R and RyR receptors, 2-Aminoethoxydiphenyl borate (2-APB) and dantrolene. QUE was the most efficient polyphenol in preventing Ca^2 + mobilization induced by INDO and all of its consequences including cytotoxicity and apoptosis.

Conclusions

In Caco-2 cells, INDO stimulates ER Ca^2 + mobilization, probably through the activation of IP3R and RyR receptors, and the subsequent entry of Ca^2 + into the mitochondria. Polyphenols protected the cells against the Ca^2 + mobilization induced by INDO and its consequences on cytotoxicity and apoptosis.

General significance

These results confirm the possibility of using polyphenols and particularly QUE for the protection of the gastroduodenal mucosa in subjects consuming NSAIDs.     

Coordination of kinase and phosphatase activities by Lem4 enables nuclear envelope reassembly during mitosis

Mitosis in metazoa requires nuclear envelope (NE) disassembly and reassembly. NE disassembly is driven by multiple phosphorylation events. Mitotic phosphorylation of the protein BAF reduces its affinity for chromatin and the LEM family of inner nuclear membrane proteins; loss of this BAF-mediated chromatin-NE link contributes to NE disassembly. BAF must reassociate with chromatin and LEM proteins at mitotic exit to reform the NE; however, how its dephosphorylation is regulated is unknown. Here, we show that the C. elegans protein LEM-4L and its human ortholog Lem4 (also called ANKLE2) are both required for BAF dephosphorylation. They act in part by inhibiting BAF's mitotic kinase, VRK-1, in vivo and in vitro. In addition, Lem4/LEM-4L interacts with PP2A and is required for it to dephosphorylate BAF during mitotic exit. By coordinating VRK-1- and PP2A-mediated signaling on BAF, Lem4/LEM-4L controls postmitotic NE formation in a function conserved from worms to humans.     

Leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation is associated with cell-type-dependent splicing of mtAspRS mRNA

LBSL (leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation) is an autosomal recessive white matter disorder with slowly progressive cerebellar ataxia, spasticity and dorsal column dysfunction. Magnetic resonance imaging shows characteristic abnormalities in the cerebral white matter and specific brain stem and spinal cord tracts. LBSL is caused by mutations in the gene DARS2, which encodes mtAspRS (mitochondrial aspartyl-tRNA synthetase). The selective involvement of specific white matter tracts in LBSL is striking since this protein is ubiquitously expressed. Almost all LBSL patients have one mutation in intron 2 of DARS2, affecting the splicing of the third exon. Using a splicing reporter construct, we find cell-type-specific differences in the sensitivity to these mutations: the mutations have a larger effect on exon 3 exclusion in neural cell lines, especially neuronal cell lines, than in non-neural cell lines. Furthermore, correct inclusion of exon 3 in the normal mtAspRS mRNA occurs less efficiently in neural cells than in other cell types, and this effect is again most pronounced in neuronal cells. The combined result of these two effects may explain the selective vulnerability of specific white matter tracts in LBSL patients.     

Comprehensive analysis of TGF-β and BMP receptor interactomes

An immense number of cellular processes are initiated by cell surface serine/threonine kinase receptors belonging to the TGF-β/BMP family. Subsequent downstream signalling cascades, as well as their crosstalk results in enormous specificity in terms of phenotypic outcome, e.g. proliferation, differentiation, migration or apoptosis. Such signalling diversity is achieved by the ability of receptors to interact with distinct proteins in a spatio-temporal manner. Following the cloning of the TGF-β/BMP receptors a variety of different technologies were applied to identify such interacting proteins. Here we present a comprehensive survey of known interactome analyses, including our own data, on these receptors and discuss advantages and disadvantages of the applied technologies.     

Dextromethorphan-induced psychotoxic behaviors cause sexual dysfunction in male mice via stimulation of σ-1 receptors

Dextromethorphan (DM) is a well-known antitussive dextrorotatory morphinan. We and others have demonstrated that sigma (σ) receptors may be important for DM-mediated neuromodulation. Because an earlier report suggested that DM might affect sexual function and that σ receptor ligands affect signaling pathways in the periphery, we examined whether DM-induced psychotoxic burden affected male reproductive function. We observed that DM had a high affinity at σ-1 receptors in the brain and testis but relatively low affinity at σ-2 receptors. Prolonged treatment with DM resulted in conditioned place preference and hyperlocomotion, followed by an increase in Fos-related antigen expression in the nucleus accumbens in male mice. Simultaneously, DM induced significant reductions in gonadotropin-releasing-hormone immunoreactivity in the hypothalamus. Moreover, we observed that DM induced increased sperm abnormalities and decreased sperm viability and sexual behavior. These phenomena were significantly attenuated by combined treatment with BD1047, a σ-1 receptor antagonist, but not by SM-21, a σ-2 receptor antagonist. Thus, these results suggest that DM psychotoxicity might lead to reproductive stress in male mice by activating σ-1 receptors.     

IVUS-based computational modeling and planar biaxial artery material properties for human coronary plaque vulnerability assessment

Image-based computational modeling has been introduced for vulnerable atherosclerotic plaques to identify critical mechanical conditions which may be used for better plaque assessment and rupture predictions. In vivo patient-specific coronary plaque models are lagging due to limitations on non-invasive image resolution, flow data, and vessel material properties. A framework is proposed to combine intravascular ultrasound (IVUS) imaging, biaxial mechanical testing and computational modeling with fluid-structure interactions and anisotropic material properties to acquire better and more complete plaque data and make more accurate plaque vulnerability assessment and predictions. Impact of pre-shrink-stretch process, vessel curvature and high blood pressure on stress, strain, flow velocity and flow maximum principal shear stress was investigated.