The influence of dietary lipid composition on liver mitochondria from mice following 1 month of calorie restriction

To investigate the role mitochondrial membrane lipids play in the actions of CR (calorie restriction), C57BL/6 mice were assigned to four groups (control and three 40% CR groups) and the CR groups were fed diets containing soya bean oil (also in the control diet), fish oil or lard. The fatty acid composition of the major mitochondrial phospholipid classes, proton leak and H₂O₂ production were measured in liver mitochondria following 1 month of CR. The results indicate that mitochondrial phospholipid fatty acids reflect the PUFA (polyunsaturated fatty acid) profile of the dietary lipid sources. CR significantly decreased the capacity of ROS (reactive oxygen species) production by Complex III but did not markedly alter proton leak and ETC (electron transport chain) enzyme activities. Within the CR regimens, the CR-fish group had decreased ROS production by both Complexes I and III, and increased proton leak when compared with the other CR groups. The CR-lard group showed the lowest proton leak compared with the other CR groups. The ETC enzyme activity measurements in the CR regimens showed that Complex I activity was decreased in both the CR-fish and CR-lard groups. Moreover, the CR-fish group also had lower Complex II activity compared with the other CR groups. These results indicate that dietary lipid composition does influence liver mitochondrial phospholipid composition, ROS production, proton leak and ETC enzyme activities in CR animals.     

Global Analysis of Transcriptional Regulation by Poly(ADP-ribose) Polymerase-1 and Poly(ADP-ribose) Glycohydrolase in MCF-7 Human Breast Cancer Cells

Poly(ADP-ribose) polymerase-1 (PARP-1) and poly(ADP-ribose) glycohydrolase (PARG) are enzymes that modify target proteins by the addition and removal, respectively, of ADP-ribose polymers. Although a role for PARP-1 in gene regulation has been well established, the role of PARG is less clear. To investigate how PARP-1 and PARG coordinately regulate global patterns of gene expression, we used short hairpin RNAs to stably knock down PARP-1 or PARG in MCF-7 cells followed by expression microarray analyses. Correlation analyses showed that the majority of genes affected by the knockdown of one factor were similarly affected by the knockdown of the other factor. The most robustly regulated common genes were enriched for stress-response and metabolic functions. In chromatin immunoprecipitation assays, PARP-1 and PARG localized to the promoters of positively and negatively regulated target genes. The levels of chromatin-bound PARG at a given promoter generally correlated with the levels of PARP-1 across the subset of promoters tested. For about half of the genes tested, the binding of PARP-1 at the promoter was dependent on the binding of PARG. Experiments using stable re-expression of short hairpin RNA-resistant catalytic mutants showed that PARP-1 and PARG enzymatic activities are required for some, but not all, target genes. Collectively, our results indicate that PARP-1 and PARG, nuclear enzymes with opposing enzymatic activities, localize to target promoters and act in a similar, rather than antagonistic, manner to regulate gene expression.     

Detectable levels of eHSP72 in plasma are associated with physical activity and antioxidant enzyme activity levels in hypertensive subjects

Previous studies reported that extracellular HSP72 (eHSP72) correlates with poor prognosis, markers of vascular dysfunction, and the severity of cardiovascular diseases, associated with a systemic oxidative and inflammatory profile. On the other hand, eHSP72 may represent immune-regulatory signaling that is related to exercise benefits, but the association between physical activity levels and eHSP72 levels is not established. Thus, since regular physical activity may avoid oxidative stress and inflammation, we investigate whether detectable levels of eHSP72 in plasma are associated with physical activity and antioxidant enzyme activity levels in hypertensive subjects. Physical activity levels of hypertensive subjects (n?=?140) were measured by tri-axial movement sensor pedometer for 24 h during 5 consecutive days. One day after, blood was collected into heparinized tubes for oxidative stress analyses (catalase—CAT and superoxide dismutase—SOD activities and malondialdehyde levels) or in disodium EDTA tubes for eHSP72 assays. Thus, hypertensive subjects were classified as physically inactive (<?10,000 footsteps/day) or active (>?than 10,000 footsteps/day) and according detectable or not detectable eHSP72 levels in plasma, performing the inactive/eHSP72^?, active/eHSP72^?, inactive/eHSP72⁺, and active/eHSP72⁺ groups. We found that detectable levels of eHSP72 in plasma were associated with physical activity levels and low oxidative stress profile (Higher CAT and SOD activities and low malondialdehyde levels). eHSP72 levels can be used as a biomarker of the amount of physical activity necessary to improve antioxidant defense and thus cardiovascular health in hypertensive subjects.     

肺炎支原体肺炎合并Epstein-Barr病毒感染患儿的血清因子及免疫分析

为了解肺炎支原体(Mycoplasma pneumoniae)合并Epstein-Barr 病毒(Epstein-Barr virus,EBV)感染患儿的血清因子水平和免疫功能,选取2016年9月-2017年3月于上海交通大学附属第六人民医院儿科住院的肺炎支原体肺炎(Mycoplasma pneumoniae pneumonia,MPP)合并EBV感染患儿(A组)、单纯MPP患儿(B组)和小儿骨科择期行六指切除手术的患儿(C组),采用酶联免疫吸附试验(enzyme-linked immunosorbent assay,ELISA)检测3组患儿血清白细胞介素6(interleukin 6,IL-6)、IL-4、γ干扰素(interferon γ,IFN-γ)、IL-10水平。结果显示,A和B组IL-6、IL-4、FIN-γ、IL-10水平高于C组(P＜0.05),A组IL-6、IL-10水平高于B组(P＜0.05),且A组中重症肺炎患儿血清IL-6、IL-10、IL-4水平较非重症肺炎患儿高(P＜0.05)。结果提示,MPP合并EBV感染患儿体内存在细胞免疫紊乱,MPP合并EBV感染后可通过诱导机体分泌 IL-6、IL-4、IFN-γ、IL-10而造成组织损伤。因此, IL-6、IL-4、IFN-γ、IL-10的检测对MPP合并EBV感染的诊断及评估病情具有重要意义。     

Bilayer Thickness and Curvature Influence Binding and Insertion of a pHLIP Peptide

The physical properties of lipid bilayers, such as curvature and fluidity, can affect the interactions of polypeptides with membranes, influencing biological events. Additionally, given the growing interest in peptide-based therapeutics, understanding the influence of membrane properties on membrane-associated peptides has potential utility. pH low insertion peptides (pHLIPs) are a family of water-soluble peptides that can insert across cell membranes in a pH-dependent manner, enabling the use of pH to follow peptide-lipid interactions. Here we study pHLIP interactions with liposomes varying in size and composition, to determine the influence of several key membrane physical properties. We find that pHLIP binding to bilayer surfaces at neutral pH is governed by the ease of access to the membrane’s hydrophobic core, which can be facilitated by membrane curvature, thickness, and the cholesterol content of the membrane. After surface binding, if the pH is lowered, the kinetics of pHLIP folding to form a helix and subsequent insertion across the membrane depends on the fluidity and energetic dynamics of the membrane. We showed that pHLIP is capable of forming a helix across lipid bilayers of different thicknesses at low pH. However, the kinetics of the slow phase of insertion corresponding to the translocation of C-terminal end of the peptide across lipid bilayer, vary approximately twofold, and correlate with bilayer thickness and fluidity. Although these influences are not large, local curvature variations in membranes of different fluidity could selectively influence surface binding in mixed cell populations.     

Triazavirine supramolecular complexes as modifiers of the peptide oligomeric structure

In this study, we present molecular dynamics simulations of the antiviral drug triazavirine, that affects formation of amyloid-like fibrils of the model peptide (SI). According to our simulations, triazavirine is able to form linear supramolecular structures which can act as shields and prevent interactions between SI monomers. This model, as validated by simulations, provides an adequate explanation of triazavirine’s mechanism of action as it pertains to SI peptide fibril formation.     

Priming of microbial microcystin degradation in biomass-fed gravity driven membrane filtration biofilms

Gravity-driven membrane (GDM) filtration is a promising tool for low-cost decentralized drinking water production. The biofilms in GDM systems are able of removing harmful chemical components, particularly toxic cyanobacterial metabolites such as microcystins (MCs). This is relevant for the application of GDM filtration because anthropogenic nutrient input and climate change have led to an increase of toxic cyanobacterial blooms. However, removal of MCs in newly developing GDM biofilms is only established after a prolonged period of time. Since cyanobacterial blooms are transient phenomena, it is important to understand MC removal in mature biofilms with or without prior toxin exposure. In this study, the microbial community composition of GDM biofilms was investigated in systems fed with water from a lake with periodic blooms of MC-producing cyanobacteria. Two out of three experimental treatments were supplemented with dead biomass of a MC-containing cyanobacterial strain, or of a non-toxic mutant, respectively. Analysis of bacterial rRNA genes revealed that both biomass-amended treatments were significantly more similar to each other than to a non-supplemented control. Therefore, it was hypothesized that biofilms could potentially be ‘primed’ for rapid MC removal by prior addition of non-toxic biomass. A subsequent experiment showed that MC removal developed significantly faster in mature biofilms that were pre-fed with biomass from the mutant strain than in unamended controls, indicating that MC degradation was a facultative trait of bacterial populations in GDM biofilms. The significant enrichment of bacteria related to both aerobic and anaerobic MC degraders suggested that this process might have occurred in parallel in different microniches.     

New Family of Ulvan Lyases Identified in Three Isolates from the Alteromonadales Order

Ulvan is the main polysaccharide component of the Ulvales (green seaweed) cell wall. It is composed of disaccharide building blocks comprising 3-sulfated rhamnose linked to d-glucuronic acid (GlcUA), l-iduronic acid (IdoUA), or d-xylose (Xyl). The degradation of ulvan requires ulvan lyase, which catalyzes the endolytic cleavage of the glycoside bond between 3-sulfated rhamnose and uronic acid according to a β-elimination mechanism. The first characterized ulvan lyase was identified in Nonlabens ulvanivorans, an ulvanolytic bacterial isolate. In the current study, we have identified and biochemically characterized novel ulvan lyases from three Alteromonadales isolated bacteria. Two homologous ulvan lyases (long and short) were found in each of the bacterial genomes. The protein sequences have no homology to the previously reported ulvan lyases and therefore are the first representatives of a new family of polysaccharide lyases. The enzymes were heterologously expressed in Escherichia coli to determine their mode of action. The heterologous expressed enzymes were secreted into the milieu subsequent to their signal sequence cleavage. An endolytic mode of action was observed and studied using gel permeation chromatography and ¹H NMR. In contrast to N. ulvanivorans ulvan lyase, cleavage occurred specifically at the GlcUA residues. In light of the genomic context and modular structure of the ulvan lyase families identified to date, we propose that two ulvan degradation pathways evolved independently.