Chitosan Oligosaccharides Attenuate Amyloid Formation of hIAPP and Protect Pancreatic ß-Cells from Cytotoxicity.

The deposition of aggregated human islet amyloid polypeptide (hIAPP) in the pancreas, that has been associated with ß-cell dysfunction, is one of the common pathological features of patients with type 2 diabetes (T2D). Therefore, hIAPP aggregation inhibitors hold a promising therapeutic schedule for T2D. Chitosan oligosaccharides (COS) have been reported to exhibit a potential antidiabetic effect, but the function of COS on hIAPP amyloid formation remains elusive. Here, we show that COS inhibited the aggregation of hIAPP and disassembled preformed hIAPP fibrils in a dose-dependent manner by thioflavin T fluorescence assay, circular dichroism spectroscopy, and transmission electron microscope. Furthermore, COS protected mouse ß-cells from cytotoxicity of amyloidogenic hIAPP, as well as apoptosis and cycle arrest. There was no direct binding of COS and hIAPP, as revealed by surface plasmon resonance analysis. In addition, both chitin-oligosaccharide and the acetylated monosaccharide of COS and glucosamine had no inhibition effect on hIAPP amyloid formation. It is presumed that, mechanistically, COS regulate hIAPP amyloid formation relating to the positive charge and degree of polymerization. These findings highlight the potential role of COS as inhibitors of hIAPP amyloid formation and provide a new insight into the mechanism of COS against diabetes.

Chitosan oligosaccharides alleviate macrophage pyroptosis and protect sepsis mice via activating the Nrf2/GPX4 pathway.

In the process of sepsis, excessive occurrence of pyroptosis, a form of programmed cell death acting as a defense mechanism against pathogens, can disrupt immune responses, thus leading to tissue damage and organ dysfunction. Chitosan oligosaccharide (COS), derived from chitosan degradation, has demonstrated diverse beneficial effects. However, its impact on sepsis-induced pyroptosis remains unexplored. In the present study, ATP/LPS was utilized to induce canonical-pyroptosis in THP-1 cells, while bacterial outer membrane vesicles (OMV) were employed to trigger non-canonical pyroptosis in RAW264.7 cells. Our results revealed a dose-dependent effect of COS on both types of pyroptosis. This was evidenced by a reduction in the expression of pro-inflammatory cytokines, as well as crucial regulatory proteins involved in pyroptosis. In addition, COS inhibited the cleavage of caspase-1 and GSDMD, and reduced ASC oligomerization. The underlying mechanism revealed that COS acts an antioxidant, reducing the release of pyroptosis-induced ROS and malondialdehyde (MDA) by upregulation the expression and promoting the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2), which led to an elevation of glutathione peroxidase 4 (GPX4) and superoxide dismutase (SOD). Notably, the actions of COS were completely reversed by the Nrf2 inhibitor. Consequently, COS intervention increased the survival rate of sepsis.

Comparative study of four flagellins of Vibrio anguillarum: vaccine potential and adjuvanticity.

Vibrio anguillarum is the etiological agent of vibriosis, an aquaculture disease that affects a wide range of farmed fish. The genome of V. anguillarum contains five flagellin genes, i.e. flaA, flaB, flaC, flaD, and flaE. In this study, we analyzed the vaccine potential and adjuvanticity of FlaA, FlaB, FlaD, and FlaE in a model of Japanese flounder (Paralichthys olivaceus). For this purpose, recombinant FlaA, FlaB, FlaD, and FlaE were expressed in and purified from Escherichia coli. In vivo immunogenicity analysis showed that antibodies against rFlaA, rFlaB, rFlaD, and rFlaE were detected in rat antiserum raised against live V. anguillarum, with the highest antibody level being that against rFlaB. When administered into flounder via intraperitoneal injection, rFlaA, rFlaD, and rFlaE induced comparable relative percent survival (RPS) rates, which were significantly lower than that induced by rFlaB. Specific serum antibodies were induced by all flagellins, however, the antibody level induced by rFlaB was significantly higher than those induced by other three flagellins. Compared to sera from fish vaccinated with rFlaA, rFlaD, and rFlaE, serum from fish vaccinated with rFlaB significantly reduced the infectivity of V. anguillarum against host cells. To examine the potential adjuvant effect of the flagellins, flounder were immunized with rEsa1, a D15-like surface antigen that induces protective immunity as a subunit vaccine, in the presence or absence of rFlaA, rFlaB, rFlaD, and rFlaE respectively. The results showed that rFlaE, but not other three flagellins, significantly increased the RPS of rEsa1. Compared to fish vaccinated with rEsa1, fish vaccinated with rEsa1 plus rFlaE exhibited a significantly higher level of serum antibodies and enhanced expression of the genes involved in innate and adaptive immunity. Taken together, these results indicate that FlaA, FlaB, FlaD, and FlaE have different immunological properties and, as a result, differ in vaccine and adjuvant potentials.

Purification and characterization of a new alginate lyase from a marine bacterium Vibrio sp.

An alginate lyase-producing bacterial strain, Vibrio sp. QY105, was isolated from sea mud of Qingdao. It secreted 90 % of total enzyme activity within the first 20 h of fermentation. An alginate lyase, AlyV5, with an apparent MW of 37 kDa and a specific activity of 2152 U/mg was purified from the culture supernatant. It was most active at 38 °C and pH 7.0 in 20 mM Tris/HCl. The enzyme was stable over a broad pH range (6.0-9.0) and retained ~40 % activity after holding at 90 °C for 10 min. AlyV5 showed activities towards both polyguluronate and polymannuronate, but degraded the former more efficiently. AlyV5 mainly produced disaccharide, trisaccharide and tetrasaccharide from polyguluronate, trisaccharide, tetrasaccharide and pentasaccharide from polymannuronate. PURPOSE OF WORK: The purpose of this study is to find a polyG-preference alginate lyase for the saccharification of alginate combined with our polyM-preference alginate lyases.

Cloning, expression and characterization of a new ι-carrageenase from marine bacterium, Cellulophaga sp.

PURPOSE OF WORK: The purpose of this study is to report a ι-carrageenase which degrades ι-carrageenan yielding neo-ι-carratetraose as the main product in the absence of NaCl. The gene for a new ι-carrageenase, CgiB_Ce, from Cellulophaga sp. QY3 was cloned and sequenced. It comprised an ORF of 1,386 bp encoding for a protein of 461 amino acid residues. From its sequence analysis, CgiB_Ce is a new member of GH family 82 and shared the highest identity of 32% in amino acids with ι-carrageenase CgiA2 from Zobellia galactanovorans indicating that it is a hitherto uncharacterized protein. The recombinant CgiB_Ce had maximum specific activity (1,870 U/mg) at 45 °C and pH 6.5. It was stable between pH 6.0-9.6 and below 40 °C. Although its activity was enhanced by NaCl, the enzyme was active in the absence of NaCl. CgiB_Ce is an endo-type ι-carrageenase that hydrolyzes ß-1,4-linkages of ι-carrageenan, yielding neo-ι-carratetraose as the main product (more than 80% of the total product).

Endotoxin accelerates insulin amyloid formation and inactivates insulin signal transduction.

AIMS AND OBJECTIVES: The aim of this study is to discuss the influence of endotoxin on insulin amyloid formation, to provide guidance for therapeutic insulin preparation and storage. MATERIALS AND METHODS: The ThT and ANS binding assays were applied to characterize the dynamics curve of insulin amyloid formation with the presence or absence of endotoxin. The morphological structures of intermediate and mature insulin fibrils were observed with SEM and TEM. Secondary structural changes of insulin during fibriliation were examined with CD, FTIR and Raman spectral analysis. The cytotoxic effects of oligomeric and amyloidogenic insulin aggregates were detected using a cck-8 cell viability assay kit. The influence of endotoxin on insulin efficacy was analyzed by monitoring the activation of insulin signal transduction. KEY FINDINGS: ThT analysis showed that endotoxin, regardless of species, accelerated insulin fibrils formation in a dose-dependent manner, as observed with a shorter lag phase. ANS binding assay demonstrated endotoxin provoked the exposure of insulin hydrophobic patches. The results of SEM and TEM data displayed that endotoxin drove insulin to cluster into dense and viscous form, with thicker and stronger filaments. Based on CD, FTIR and Raman spectra, endotoxin promoted the transition of α-helix to random coil and ß-strand secondary structures during insulin aggregation. Insulins in both oligomeric and amyloidogenic forms were cytotoxic to HepG2 cells, with the former being more severe. Finally, the efficacy of endotoxin treated insulin obviously decreased. SIGNIFICANCE: Our studies revealed that endotoxin disrupts the structural integrity of insulin and promotes its amyloidosis. These findings offered theoretical guidance for insulin storage and safe utilization, as well as pointing up a new direction for insulin resistance research.

[Research progress of new antibacterial drugs that target bacterial quorum sensing systems].

In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quorum sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo, recent research of quorum sensing inhibitors and so on.

[Model systems for bacterial biofilm research].

Contrast to planktonic cells, biofilms are complex communities of microorganisms that develop on biotic or abiotic surfaces. Most of bacteria can form biofilms under proper conditions. Once biofilm form, the inner bacteria cells often exhibit reduced antibiotic susceptibility than their free-floating counterparts, so conventional methods of killing bacteria, such as antibiotics and disinfections are often ineffective with them. Biofilms may cause huge economic loss in equipment damage, product contamination, energy losses and medical infections. Therefore, bacterial biofilm is evolving as a focal problem and an active area of research. As a relatively new area, the progress of biofilm science depends on the development of a satisfactory set of methods. But the classic methods to study planktonic bacteria cannot fulfill the biofilm research, one for which there are few widely accepted methodological standards. Even though biofilms are complicated physical-chemical-biological systems, experience demonstrates that accessible research methods are feasible. In this paper, the theories, principles, merits and limitations of some methods currently used in bacterial biofilm researches, involving artificial biofilm forming and biofilm measurement, were discussed.

A pivotal role for CC chemokine receptor 5 in T-cell migration to tumor sites induced by interleukin 12 treatment in tumor-bearing mice.

Interleukin (IL) 12 treatment in the CSA1M and OV-HM, but not in Meth A tumor models,induces tumor regression that is associated with T-cell migration to tumor sites.Here, we investigated the role of the CC chemokine receptor (CCR)5 in T-cell migration induced after IL-12 treatment. In the two IL-12-responsive tumor models (CSA1M and OV-HM), IL-12 treatment up-regulated the mRNA expression of CCR5 in splenic T cells as well as ligands for CCR5, such as macrophage inflammatory protein (MIP) 1alpha and MIP-1beta in tumor masses. In contrast, the expression of CCR5 in spleens and MIP-1alpha/MIP-1beta in tumor masses was marginally induced before and even after IL-12 treatment in the Meth A model in which T-cell migration is not observed. T cells infiltrating tumor masses in the former two IL-12-responsive models expressed CCR5. Administration of a synthetic CCR5 antagonist TAK-779 to tumor-bearing mice during IL-12 immunotherapy prevented T-cell migration and tumor regression. Furthermore, anti-CCR5 antibody was found to inhibit T-cell migration in the lymphoid cell migration assay. Namely, although splenic T cells prepared from IL-12-treated CSA1M or OV-HM-bearing mice migrated into the corresponding tumor masses in recipient mice, the migration was inhibited when donor T cells were treated with anti-CCR5 antibody before the injection. These results indicate a critical role for CCR5 in the induction of T-cell migration to tumor sites after IL-12 treatment.

[Purification and characterization of alginate lyase from marine bacterium Vibrio sp. QY101].

Extracellular alginate lyase secreted by Vibrio sp. QY101, which was isolated from brown algae, was purified to homogeneity by a combination of ammonium sulfate precipitation, DEAE-Sepharose Fast Flow anion-exchange chromatography and Superdex 75 gel filtration chromatography. Its molecular mass was 39 kD as determined by SDS-PAGE analysis. The enzyme had an optimal temperature of 30 degrees for its activity, and was most active at pH 7.5. The thermal and pH stability were 0-30 degrees, and pH 6.5-8.5, respectively. The enzyme activity was stimulated by 0.5 mol/L NaCl, 1.0 mmol/L Ca(2+) or 5.0 mmol/L (Mn(2+), and inhibited by 5.0 mmol/L Ni(2+), 1.0 mmol/L Fe2+) or 1.0 mmol/L EDTA. Preliminary analysis on substrate specificity showed that this alginate lyase had activity on both poly-alpha 1,4-L-guluronate and poly-beta1,4-D-mannuronate substrates.

Cloning, sequence analysis and expression of gene alyVI encoding alginate lyase from marine bacterium Vibrio sp. QY101.

The gene (alyVI) encoding an alginate lyase of marine bacterium Vibrio sp. QY101, which was isolated from a decaying thallus of Laminaria, was cloned using a strategy of combined degenerate PCR and long range-inverse PCR (LR-IPCR), then sequenced and expressed in Escherichia coli. Gene alyVI was composed of a 1014 bp open reading frame (ORF) encoding 338 amino acid residues. The calculated molecular mass of alyVI product is 38.4 kDa, but a signal peptide is cleaved off, leaving a mature protein of 34 kDa. AlyVI was purified from culture supernatants to electrophoretic homogeneity using affinity chromatography. AlyVI was most active at pH 7.5 and 40 degrees C in the presence of 1 mM ZnCl2. A nine-amino-acid consensus region (YXRESLREM), which was only found in polyguluronate lyases, was also observed in the amino-terminal region of AlyVI. However, AlyVI could degrade both M block and G block. These results indicate that a novel alginate lyase-encoding gene has been cloned.

[Inhibition of MCP-1 mRNA expression by propylene glycol mannate sulfate in hyperlipidemic rat aorta].

AIM: To study the effects of prophylene glycol mannate sulfate (PGMS) on monocyte chemoattractant protein-1 (MCP-1) mRNA expression in hyperlipidemic rat aorta and to clarify the molecular mechanism of PGMS for the prevention of atherosclerosis. METHODS: PGMS (37.8 and 75.6 mg.kg-1.d-1, ig) or PGMS (37.8 and 75.6 mg.kg-1.d-1, ig) combined with diethyldithiocarbamate (DDC, an inhibitor of SOD, 200 mg.kg-1 every three days, i.p.) were given to hyperlipidemic rats for three weeks. The MDA content and SOD activity were determined after 12 h of starvation, and MCP-1 mRNA expression in aorta was detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: There was significant decrease (29.46% or 58.40)% of MCP-1 mRNA expression in aortic after the therapy. The SOD activity increased markedly and the MDA content decreased at the same time. After treatment with DDC, the SOD activity was inhibited and the MDA content increased, but with no significant effect on MCP-1 mRNA expression. CONCLUSION: PGMS inhibited MCP-1 mRNA expression with no relation to its effect on decreasing MDA content.

[Molecular mechanisms of antioxidant effects of propylene glycol mannate sulfate].

AIM: To investigate the antioxidant mechanisms of propylene glycol mannate sulfate (PGMS) in hyperlipidemic rats. METHODS: Male Wistar rats were given high lipid emulsion diet to establish hyperlipidemic model. PGMS was given every day at different doses (37.8 and 75.6 mg.kg-1, ig) to hyperlipidemic rats for three weeks. In addition, diethyldithiocarbamate (DDC) was given 200 mg.kg-1.3 d-1 (i.p.) to inhibit SOD activity. Then, the MDA content was examined using TBA method to show the oxidation level, and the activities of SOD, GSH-Px and CAT were examined following the kit protocols to indicate the capability of eliminating OFR. RT-PCR was applied to study the expression of Cu, Zn-SOD mRNA in rat liver. RESULTS: The MDA content of PGMS treatment groups decreased markedly compared with hyperlipidemic group, and the activities of SOD, GSH-Px and CAT increased distinctly. Cu, Zn-SOD mRNA expression was significantly increased by PGMS treatment. Furthermore, the application of DDC(the SOD inhibitor) reduced total SOD activity and Cu, Zn-SOD mRNA expression induced by PGMS, and the content of MDA increased correspondingly. CONCLUSION: PGMS can induce the activities of antioxidant enzymes and the mRNA expression of Cu, Zn-SOD, which contribute to the elimination of oxygen free radical. This may explain the molecular mechanism of antioxidant effects of PGMS.

[Induction of CuZn-SOD mRNA expression and activity by PGMS in rat liver].

AIM: To study the effect of propylene glycol mannate sulfate (PGMS) on induction of CuZn-SOD. METHODS: Wistar rats were given PGMS p.o. at different doses (0, 18.9, 37.8 and 75.6 mg.kg-1.d) for ten days. Then the rats were sacrificed and the total RNA was extracted from the livers. The total RNA samples were loaded on a 1% agarose gel to detect the quality of total RNA. RT-PCR was applied to study the expression of CuZn-SOD mRNA in rat livers. The amplified products were detected by the 1.5% agarose gel electrophoresis. Simultaneously, the CuZn-SOD activities in rat liver were determined by nitrite method. RESULTS: The total RNA extracted from rat livers was integrated without being decomposed by RNase. The level of CuZn-SOD mRNA of the high-dosage group (75.6 mg.kg-1.d) was higher than that of the control group (0 mg.kg-1.d) (P < 0.01); the CuZn-SOD activities of the high-dosage group were significantly higher than those of the control group (P < 0.001) and the CuZn-SOD activities of the middle- (37.8 mg.kg-1.d) and low-dosage groups (18.9 mg.kg-1.d) were higher than those of the control group (P < 0.01). CONCLUSION: PGMS can increase the CuZn-SOD activities as well as CuZn-SOD on mRNA level. Therefore, it is possible for PGMS to counteract Atherosclerosis (AS) by inducing the expression of CuZn-SOD.

[Effect of propylene glycol mannate sulfate on blood lipids and lipoprotein lipase in hyperlipidemic rat].

AIM: To study the effect of propylene glycol mannate sulfate (PGMS) on blood lipids and lipoprotein lipase in hyperlipidemic rat, and its anti-hyperlipidemic mechanism. METHODS: PGMS was administered ig at different doses (37.8 mg.kg-1.d-1 and 75.6 mg.kg-1.d-1) to hyperlipidemic rats for three weeks and blood serum was obtained after starved 12 h. Total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) were examined. The mRNA expression of lipoprotein lipase (LPL) in liver, spleen and artery was detected by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: PGMS significantly decreased the levels of TC, TG and LDL-C and increased that of HDL-C in hyperlipidemic serum dose-dependently. PGMS was shown to increase the level of LPL mRNA expression, which is related directly to the controlling effects of PGMS on blood lipids. CONCLUSION: PGMS modulated blood lipids by promoting mRNA expression of LPL. This may be one important mechanism of PGMS to modulate blood lipids.

[Progress on gene targeting].

Gene targeting is a rising technology in molecular biology,which is defined as the introduction of exogeneous DNA to specific site in genome by homologous recombination,and consequently change the hereditary character of the cell. This technology provides a new and powerful means for research in developmental biology,molecular genetics,immunology and medicine. Progresses have been made in exploring gene structure and function,gene expression and regulation,transgene and gene therapy with the application of gene targeting. But there are some problems in gene targeting,especially for the low efficiency. This article just provided a review of the principle and program of gene targeting,and discussed the possible approaches to increase the efficiency of gene targeting.

[Molecular cloning and preliminary functional study of TRBP].

AIM: Construct prokaryotic expression vector carrying mouse TRBP (TAR RNA-binding protein) gene and test the double-stranded RNA binding ability of TRBP. METHODS: RT-PCR was used to obtain TRBP cDNA from mouse genomic DNA. Then, we built the His-tag fusion expression vector of TRBP and transformed it into E.coli BL21(DE3). Ni-NTA beads were used to isolate and purify the recombinant protein and vitro transcription was used to get Pre-miR-122. Finally, SDS-PAGE and ITC (isothermal titration calorimetry) assay were both used to validate TRBP's binding ability with Pre-miR-122. RESULTS: We purified the recombinant protein TRBP whose molecular weight is 32.4 kDa. The purified bioactive TRBP protein binding on NI-NTA beads showed that it had a strong binding capacity on Pre-miR-122. CONCLUSION: We constructed TRBP prokaryotic expression system successfully and studied the double-stranded RNA binding ability of TRBP preliminarily.

Purple sweet potato pigments protect murine thymocytes from 6°Co γ-ray-induced mitochondria-mediated apoptosis.

PURPOSE: Purple sweet potato (PSP) pigments have been widely accepted as antioxidants but their radioprotective effect still remains unclear. In this study we investigated the effect of PSP pigments on 6°Co γ-ray-induced mitochondria-mediated apoptosis in murine thymocytes. MATERIALS AND METHODS: The murine thymocytes were pretreated by PSP pigments before exposure to 4 Gy 6°Co γ-rays. Flow cytometry analysis was used to measure apoptotic cells and mitochondrial membrane potential. Reactive oxygen species (ROS) were detected using 2',7',-dichlorofluorescein diacetate (DCFH-DA) probe and the activity of antioxidant enzymes was tested by biochemical assay after irradiation. Cytochrome c, caspase-3 and poly ADP-ribose polymerase (PARP) were measured by Western blotting. RESULTS: After treatment with PSP pigments and exposure to 4 Gy radiation the apoptosis of thymocytes was reduced and the mitochondrial transmembrane potential was maintained compared to control cells. In the presence of PSP pigments, ROS were reduced and the activities of glutathione peroxidase (GSH-px) and superoxide dismutase (SOD) were protected and in some cases increased. All the pro-apoptotic proteins (cytochrome oxidase, caspase 3 and PARP) decreased in PSP pigments pretreated thymocytes compared to irradiated cells in the absence of PSP pigments. CONCLUSIONS: Pre-treatment with PSP pigments significantly inhibited 6°Co γ-ray-induced mitochondria-mediated apoptosis. This radioprotective effect might be related to ROS scavenging, the enhancement of the activity of antioxidant enzymes, the maintenance of mitochondrial transmembrane potential, and the sequential inhibition of cytochrome c release and downstream caspase and PARP cleavage.

Polypeptide from Chlamys farreri attenuates murine thymocytes damage induced by ultraviolet B.

AIM: Polypeptide from Chlamys farreri (PCF, molecular mass is 879) is a new marine polypeptide compound isolated from Chlamys farreri. This study investigates the possible protective roles and the mechanism of PCF against ultraviolet B (UVB)-induced apoptosis in murine thymocytes. METHODS: The rate of apoptosis and caspase-3 activation was measured by flow cytometry. The expression of stress-response genes c-fos and c-jun was observed by RT-PCR. Western blot analysis was performed to determine the release of cytochrome c. RESULTS: It was found that UVB induced murine thymocyte death. The cells treated with UVB showed an increase in cytochrome c release, caspase-3 activity, as well as in the expression of c-fos and c-jun. In addition, all were involved in UVB-induced cell apoptosis. CONCLUSION: Our present observations pointed to the ability of PCF to avert UVB-induced apoptosis in thymocytes by modulating c-fos and c-jun expression, cytochrome c release, and the consequent activation of caspase-3, which were essential components of the UV-induced cell apoptotic pathway. The results suggested that PCF is a promising protective substance against UV radiation.