EscI: a crucial component of the type III secretion system forms the inner rod structure in enteropathogenic Escherichia coli

The T3SS (type III secretion system) is a multi-protein complex that plays a central role in the virulence of many gram-negative bacterial pathogens. This apparatus spans both bacterial membranes and transports virulence factors from the bacterial cytoplasm into eukaryotic host cells. The T3SS exports substrates in a hierarchical and temporal manner. The first secreted substrates are the rod/needle proteins which are incorporated into the T3SS apparatus and are required for the secretion of later substrates, the translocators and effectors. In the present study, we provide evidence that rOrf8/EscI, a poorly characterized locus of enterocyte effacement-encoded protein, functions as the inner rod protein of the T3SS of EPEC (enteropathogenic Escherichia coli). We demonstrate that EscI is essential for type III secretion and is also secreted as an early substrate of the T3SS. We found that EscI interacts with EscU, the integral membrane protein that is linked to substrate specificity switching, implicating EscI in the substrate-switching event. Furthermore, we showed that EscI self-associates and interacts with the outer membrane secretin EscC, further supporting its function as an inner rod protein. Overall, the results of the present study suggest that EscI is the YscI/PrgJ/MxiI homologue in the T3SS of attaching and effacing pathogens.     

Exenatide prevents high-glucose-induced damage of retinal ganglion cells through a mitochondrial mechanism

Exenatide (exendin-4 analogue) is widely used in clinics and shows a neuroprotective effect. The main objectives of the present study were to prove that retinal ganglion cells (RGC-5) express GLP-1R, to ascertain whether exenatide prevents a high-glucose-induced RGC-5 impairment, to determine the appropriate concentration of exenatide to protect RGC-5 cells, and to explore the neuroprotective mechanisms of exenatide. Immunofluorescence and Western blot analyses demonstrated that RGC-5 cells express GLP-1R. We incubated RGC-5 cells with 25 mM glucose prior to incubation with either 25 mM glucose, 55 mM glucose (high), high glucose plus exenatide or high glucose plus a GLP-1R antagonist. The survival rates of the cells were measured by CCK-8, and cellular injury was detected by electron microscopy. There were statistical differences between the high-glucose group and the control group (P<0.05). Exenatide improved the survival rate of the cells and suppressed changes in the mitochondrial morphology. The optimum concentration of exenatide to protect the RGC-5 cells from high-glucose-induced RGC injury was 0.5 μg/ml, and this protective effect could be inhibited by exendin (9-39). To further study the mechanism underlying the beneficial effects of exenatide, the expression levels of cytochrome c, Bcl-2, Bax and caspase-3 were analysed by Western blot. The present study showed that treatment with exenatide significantly inhibited cytochrome c release and decreased the intracellular expression levels of Bax and caspase-3, whereas Bcl-2 was increased (P<0.05). These results suggested that GLP-1R activation can inhibit the cellular damage that is induced by high glucose. A mitochondrial mechanism might play a key role in the protective effect of exenatide on the RGC-5 cells, and exenatide might be beneficial for patients with diabetic retinopathy.     

Overexpression of a short human seipin/BSCL2 isoform in mouse adipose tissue results in mild lipodystrophy

Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2) is a recessive disorder characterized by an almost complete loss of adipose tissue, insulin resistance, and fatty liver. BSCL2 is caused by loss-of-function mutations in the BSCL2/seipin gene, which encodes seipin. The essential role for seipin in adipogenesis has recently been established both in vitro and in vivo. However, seipin is highly upregulated at later stages of adipocyte development, and its role in mature adipocytes remains to be elucidated. We therefore generated transgenic mice overexpressing a short isoform of human BSCL2 gene (encoding 398 amino acids) using the adipocyte-specific aP2 promoter. The transgenic mice produced ～150% more seipin than littermate controls in white adipose tissue. Surprisingly, the increased expression of seipin markedly reduced the mass of white adipose tissue and the size of adipocytes and lipid droplets. This may be due in part to elevated lipolysis rates in the transgenic mice. Moreover, there was a nearly 50% increase in the triacylglycerol content of transgenic liver. These results suggest that seipin promotes the differentiation of preadipocytes but may inhibit lipid storage in mature adipocytes.     

Role of angiotensin-converting enzyme (ACE and ACE2) imbalance on tourniquet-induced remote kidney injury in a mouse hindlimb ischemia-reperfusion model

In this study, the relationship between the local imbalance of angiotensin converting enzymes ACE and ACE2 as well as Ang II and Ang (1-7) and renal injury was observed in the different genotypes mice subjected to tourniquet-induced ischemia-reperfusion on hind limbs. In wild-type mice, renal ACE expression increased while renal ACE2 expression decreased significantly after reperfusion, accompanied by elevated serum angiotensin II (Ang II) level and lowered serum angiotensin (1-7) (Ang (1-7)) level. However, renal Ang (1-7) also increased markedly while renal Ang II was elevated. Renal injury became evident after limb reperfusion, with increased malondialdehyde (MDA), decreased super-oxide dismutase (SOD) activity and increased serum blood urea nitrogen (BUN) and creatinine (Cr), compared to control mice. These mice also developed severe renal pathology including infiltration of inflammatory cells in the renal interstitium and degeneration of tubule epithelial cells. In ACE2 knock-out mice with ACE up-regulation, tourniquet-induced renal injury was significantly aggravated as shown by increased levels of MDA, BUN and Cr, decreased SOD activity, more severe renal pathology, and decreased survival rate, compared with tourniquet-treated wild-type mice. Conversely, ACE2 transgenic mice with normal ACE expression were more resistant to tourniquet challenge as evidenced by decreased levels of MDA, BUN and Cr, increased SOD activity, attenuated renal pathological changes and increased survival rate. Our results suggest that the deregulation of ACE and ACE2 plays an important role in tourniquet-induced renal injury and that ACE2 up-regulation to restore the proper ACE/ACE2 balance is a potential therapeutic strategy for kidney injury.     

Effect of intranasal arginine vasopressin on human headache

Arginine vasopressin (AVP), a nonapeptide hormone of posterior pituitary, reaches the central nervous system from systemic blood circulation with a difficulty because of the blood–brain barrier (BBB). The interest has been expressed in the use of the nasal route for delivery of AVP to the brain directly, exploiting the olfactory pathway. Our previous study has demonstrated that AVP in the brain rather than the spinal cord and blood circulation plays an important role in rat pain modulation. For understanding the role of AVP on pain modulation in human, the communication tried to investigate the effect of intranasal AVP on human headache. The results showed that (1) AVP concentration in both plasma and cerebrospinal fluid (CSF) increased significantly in headache patients, who related with the headache level; (2) there was a positive relationship between plasma and CSF AVP concentration in headache patients; and (3) intranasal AVP could relieve the human headache in a dose-dependent manner. The data suggested that intranasal AVP, which was delivered to the brain through olfactory region, could treat human headache and AVP might be a potential drug of pain relief by intranasal administration.     

High-throughput screening for Streptomyces antibiotic biosynthesis activators

A genomic cosmid library of Streptomyces clavuligerus was constructed and transferred efficiently by conjugation to Streptomyces lividans, and 12 distinct groups of overlapping cosmid clones that activated the silent actinorhodin biosynthesis gene cluster were identified. This generally applicable high-throughput screening procedure greatly facilitates the identification of antibiotic biosynthesis activators.     

Karyology of the genus Faberia (Cichorieae–Asteraceae) and its systematic implications

Faberia Hemsl., a small genus of six species in the tribe Cichorieae, Asteraceae, has been karyologically investigated for the first time. All four studied species were revealed to have the somatic chromosome number 2n = 34, and thus the basic number of the genus was assumed to be x = 17. This rather high basic number has been previously reported very rarely in the tribe, occurring otherwise only in Warionia Benth. & Coss., a monospecific genus endemic to northwestern Africa, and in the American species of Lactuca L. The chromosome morphology was very similar among the four species, with the majority being median centromeric (m) and a few submedian centromeric (sm). In all the karyotypes the chromosomes were medium‐sized (6.33–1.61 μm), and showed a steady gradation in length from the longest to the shortest, with no evidence of bimodality. Our results strongly support the recognition of Faberia as an independent genus and the inclusion of Faberiopsis Shih & Y. L. Chen in Faberia.     

An ATP signalling pathway in plant cells: extracellular ATP triggers programmed cell death in Populus euphratica

We elucidated the extracellular ATP (eATP) signalling cascade active in programmed cell death (PCD) using cell cultures of Populus euphratica. Millimolar amounts of eATP induced a dose‐ and time‐dependent reduction in viability, and the agonist‐treated cells displayed hallmark features of PCD. eATP caused an elevation of cytosolic Ca²⁺ levels, resulting in Ca²⁺ uptake by the mitochondria and subsequent H₂O₂ accumulation. P. euphratica exhibited an increased mitochondrial transmembrane potential, and cytochrome c was released without opening of the permeability transition pore over the period of ATP stimulation. Moreover, the eATP‐induced increase of intracellular ATP, essential for the activation of caspase‐like proteases and subsequent PCD, was found to be related to increased mitochondrial transmembrane potential. NO is implicated as a downstream component of the cytosolic Ca²⁺ concentration but plays a negligible role in eATP‐stimulated cell death. We speculate that ATP binds purinoceptors in the plasma membrane, leading to the induction of downstream intermediate signals, as the proposed sequence of events in PCD signalling was terminated by the animal P2 receptor antagonist suramin.     

Modification of hydroxypropyl guar gum with ethanolamine

A new guar gum derivative containing amino group was synthesized through nucleophilic substitution of p-toluenesulfonate activated hydroxypropyl guar gum with ethanolamine. For the preparation of p-toluenesulfonate esters hydroxypropyl guar gum, the results showed that the reaction rate was optimal at 25°C and the reaction could reach equilibrium state when it was carried out for 10h at 25°C. For the nucleophilic substitution of tosyl group with ethanolamine, the reaction was completed after 10h reaction at 50°C. The structures of products were characterized by NMR and FT-IR spectroscopy. The results showed that the p-toluenesulfonate esters can be effectively substituted by ethanolamine to form the hydroxyethyl amino hydroxypropyl guar gum (EAHPG). The content of nitrogen of EAHPG was determined by acid-base titration and element analysis.     

Carboxymethyl chitin/organic rectorite composites based nanofibrous mats and their cell compatibility

In this study, carboxymethyl chitin (CMC) - organic rectorite (OREC)/poly (vinyl alcohol) (PVA) composite nanofibrous mats were successfully prepared via electrospinning. SAXRD pattern showed that the interlayer distance of OREC was increased from 3.68 to 4.08nm, which verified that polymer chains were intercalated into the interlayer of OREC. Field emission scanning electron microscopy, Fourier transform infrared spectra and energy-dispersive X-ray spectroscopy were used to characterize the morphology and microcosmic structure of nanofibrous mats. Thermal properties of mats were determined by differential scanning calorimetry. To evaluate the cell compatibility of mats, mouse lung fibroblast (L929) was chosen for cell attachment and spreading assay. The results shows that nanofibrous mats contained OREC have better thermal properties. Besides, the addition of OREC has little effect on the cell compatibility of nanofibrous mats.