ArfGAP1 restricts Mycobacterium tuberculosis entry by controlling the actin cytoskeleton

The interaction of Mycobacterium tuberculosis (Mtb) with pulmonary epithelial cells is critical for early stages of bacillus colonization and during the progression of tuberculosis. Entry of Mtb into epithelial cells has been shown to depend on F‐actin polymerization, though the molecular mechanisms are still unclear. Here, we demonstrate that mycobacterial uptake into epithelial cells requires rearrangements of the actin cytoskeleton, which are regulated by ADP‐ribosylation factor 1 (Arf1) and phospholipase D1 (PLD1), and is dependent on the M3 muscarinic receptor (M₃R). We show that this pathway is controlled by Arf GTPase‐activating protein 1 (ArfGAP1), as its silencing has an impact on actin cytoskeleton reorganization leading to uncontrolled uptake and replication of Mtb. Furthermore, we provide evidence that this pathway is critical for mycobacterial entry, while the cellular infection with other pathogens, such as Shigella flexneri and Yersinia pseudotuberculosis, is not affected. Altogether, these results reveal how cortical actin plays the role of a barrier to prevent mycobacterial entry into epithelial cells and indicate a novel role for ArfGAP1 as a restriction factor of host–pathogen interactions.     

Lactate dehydrogenase (LDH) gene duplication during chordate evolution: the cDNA sequence of the LDH of the tunicate Styela plicata

L-Lactate dehydrogenase (L-LDH, E.C. 1.1.1.27) is encoded by two or three loci in all vertebrates examined, with the exception of lampreys, which have a single LDH locus. Biochemical characterizations of LDH proteins have suggested that a gene duplication early in vertebrate evolution gave rise to Ldh-A and Ldh-B and that an additional locus, Ldh-C arose in a number of lineages more recently. Although some phylogenetic studies of LDH protein sequences have supported this pattern of gene duplication, others have contradicted it. In particular, a number of studies have suggested that Ldh-C represents the earliest divergence among vertebrate LDHs and that it may have diverged from the other loci well before the origin of vertebrates. Such hypotheses make explicit statements about the relationship of vertebrate and invertebrate LDHs, but to date, no closely related invertebrate LDH sequences have been available for comparison. We have attempted to provide further data on the timing of gene duplications leading to multiple vertebrate LDHs by determining the cDNA sequence of the LDH of the tunicate Styela plicata. Phylogenetic analyses of this and other LDH sequences provide strong support for the duplications giving rise to multiple vertebrate LDHs having occurred after vertebrates diverged from tunicates. The timing of these LDH duplications is consistent with data from a number of other gene families suggesting widespread gene duplication near the origin of vertebrates. With respect to the relationships among vertebrate LDHs, our data are not consistent with previous claims that Ldh-C represented the earliest divergence. However, the precise relationships among some of the main lineages of vertebrate LDHs were not resolved in our analyses.      

The Neuroprotective Effects of Justicidin A on Amyloid Beta25–35-Induced Neuronal Cell Death Through Inhibition of Tau Hyperphosphorylation and Induction of Autophagy in SH-SY5Y Cells

Justicidin A is a structurally defined arylnaphthalide lignan, which has been shown anti-cancer activity; however, the neuroprotective effect of justicidin A is still untested. In this study, we investigated the action of justicidin A on amyloid beta (Aβ)_25–35-induced neuronal cell death via inhibition of the hyperphosphorylation of tau and induction of autophagy in SH-SY5Y cells. Pretreatment with justicidin A significantly elevated cell viability in cells treated with Aβ_25–35. Western blot data demonstrated that justicidin A inhibited the Aβ_25–35-induced up-regulation the levels of hyperphosphorylation of tau in SH-SY5Y cells. In addition, treatment with justicidin A significantly induced autophagy as measured by the increasing LC3 II/I ratio, an important autophagy marker. These studies showed that justicidin A inhibited activity of glycogen synthase kinase-3beta (GSK-3β), which is an important kinase in up-stream signaling pathways; inhibited hyperphosphorylation of tau in AD; and enhanced activity of AMP-activated protein kinase (AMPK), which is the key molecule for both hyperphosphorylation of tau and induction of autophagy. These data provide the first evidence that justicidin A protects SH-SY5Y cells from Aβ_25–35-induced neuronal cell death through inhibition of hyperphosphorylation of tau and induction of autophagy via regulation the activity of GSK-3β and AMPK, and they also provide some insights into the relationship between tau protein hyperphosphorylation and autophagy. Thus, we conclude that justicidin A may have a potential role for neuroprotection and, therefore, may be used as a therapeutic agent for AD.

     

A new chemoheterotrophic bacterium catalyzing water-gas shift reaction

A new bacterium, Citrobacter sp. Y19, catalyzing the water-gas shift reaction was isolated from an anaerobic wastewater sludge digester. It grew aerobically with a high specific growth rate of 0.7 h^–1 in a mineral salt medium supplemented with yeast extract and Bacto-tryptone, and produced H₂ under anaerobic conditions after the cells were transferred to tryptone-deleted medium. The maximum H₂ production rate was 33 mmol H₂ g^–1 cell h, which was maintained for about 200 h. This is the first report on a chemoheterotrophic bacterium which utilizes CO with the production of H₂ and CO₂.     

Effect of increased pCO2 in seawater on survival rate of different developmental stages of the harpacticoid copepod Tigriopus japonicus

The rapid increase in carbon dioxide levels in seawater is causing ocean acidification and is expected to have significant effects on marine life. To explore the ability of the harpacticoid copepod Tigriopus japonicus to adapt to an increased concentration of dissolved carbon dioxide (CO₂) in seawater, we compared the survival rates of adult and nauplius stages at 400, 1000, and 1550?ppm pCO₂ over a 14-day period. The survival rate of T. japonicus dramatically decreased over time with increase in pCO₂ concentration. At 1550?ppm, the survival rate showed a decrease of more than 20% at the end of the experimental period over that at 400?ppm. Furthermore, the survival rate decreased by a greater amount at all concentrations in nauplii than in adults, with a greater effect in wild-collected specimens than in culture-derived individuals. The results suggest that future ocean acidification may negatively influence the sustainability of T. japonicus and thus may eventually influence benthic ecosystems.     

Lafutidine versus Lansoprazole in Combination with Clarithromycin and Amoxicillin for One versus Two Weeks for Helicobacter pylori Eradication in Korea

Background and Aims: Lafutidine is a novel H₂‐receptor antagonist with gastroprotective activity that includes enhancement of gastric mucosal blood flow. The aim of the present study was to test the efficacy of 7‐ or 14‐day lafutidine–clarithromycin–amoxicillin therapy versus a lansoprazole‐based regimen for Helicobacter pylori eradication. Methods: Four hundred and sixty‐three patients with H. pylori‐infected peptic ulcer disease were randomized to one of four regimens: (1) lafutidine (20 mg b.i.d.), clarithromycin (500 mg b.i.d.) and amoxicillin (1000 mg b.i.d.) for 7 days (the 7LFT group) or (2) for 14 days (the 14LFT group); (3) lansoprazole (30 mg b.i.d.), clarithromycin (500 mg b.i.d.), and amoxicillin (1000 mg b.i.d.) for 7 days (the 7LPZ group); or (4) for 14 days (the 14LPZ group). The eradication rates, drug compliance, and adverse effects among the four regimens were compared. Results: The eradication rates by the intention‐to‐treat and per‐protocol analyses in the 7LFT and 7LPZ groups were 76.5% and 81.6%, and 76.9% and 82.0% (p = .94 and .95), respectively. The eradication rates by intention‐to‐treat and per‐protocol analyses in the 14LFT and 14LPZ groups were 78.2% and 82.2%, and 80.4% and 85.9% (p = .70 and .49), respectively. The treatment duration for 7 days or 14 days did not affect the eradication rates. In addition, the adverse effect rates and discontinuation rates were similar among the four groups. Furthermore, the ulcer cure rate and symptom response rate were similar in the lafutidine and lansoprazole groups. Conclusion: The results of this study showed that lafutidine–clarithromycin–amoxicillin therapy was a safe and effective as lansoprazole‐based triple therapy for the eradication rate of H. pylori, and could be considered as an additional treatment option.     

Acetylcholine inhibits long-term hypoxia-induced apoptosis by suppressing the oxidative stress-mediated MAPKs activation as well as regulation of Bcl-2, c-IAPs,and caspase-3 in mouse embryonic stem cells

This study examined the effect of acetylcholine (ACh) on the hypoxia-induced apoptosis of mouse embryonic stem (ES) cells. Hypoxia (60 h) decreased both the cell viability and level of [³H] thymidine incorporation, which were prevented by a pretreatment with ACh. However, the atropine (ACh receptor [AChR] inhibitor) treatment blocked the protective effect of ACh. Hypoxia (90 min) increased the intracellular level of reactive oxygen species (ROS). On the other hand, ACh inhibited the hypoxia-induced increase in ROS, which was blocked by an atropine treatment. Subsequently, the hypoxia-induced ROS increased the level of p38 mitogen activated protein kinase (MAPK) and Jun-N-terminal kinase (JNK) phosphorylation, which were inhibited by the ACh pretreatment. Moreover, hypoxic exposure (90 min) increased the level of nuclear factor-κB (NF-κB) phosphorylation, which was blocked by a pretreatment with SB 203580 (p38 MAPK inhibitor) or SP 600125 (JNK inhibitor). However, hypoxia (60 h) decreased the protein levels of Bcl-2 and c-IAPs (cellular inhibitor of apoptosis proteins) but increased the level of caspase-3 activation. All these effects were inhibited by a pretreatment with ACh. In conclusion, ACh prevented the hypoxia-induced apoptosis of mouse ES cells by inhibiting the ROS-mediated p38 MAPK and JNK activation as well as the regulation of Bcl-2, c-IAPs, and caspase-3. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.