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Objective:To investigate the possible mechanism of high mobility group box-1 (HMGB1) in amplifing inflammatory responses in Leptospira interrogans hemolysin Sph2-treated J774A.1 macrophages. Methods:Recombinant Sph2 was incubated with J774A.1 macrophages. The damage of cell membrane was detected by lactate dehydrogenase(LDH) determination; the changes of cell structure were observed by cryo-electron microscope; ELISA was used to determine the expression of HMGB1. After the commercial recombinant HMGB1 was incubated with mouse J774A.1 macrophages, the phosphorylation of NF-κB, p38-MAPK and JNK signaling pathway wsa detected by Western blot, and the expression of IL-1β, IL-6, and KC (IL-8) was detected by ELISA.Results:Recombinant hemolysin rSph2 induced significant changes in the structures of J774A.1 cells, including nucleus disappearance, cell membrane structure damage, cell lysis and membrane swelling. The yields of LDH and HMGB1 also increased significantly. Phosphorylated-NF-κB, -p38-MAPK and -JNK were increased by HMGB1. The expression of IL-1β, IL-6 and KC in J774A.1 cells was up-regulated by HMGB1 and inhibited via inhibitors of NF-κB, p38-MAPK and JNK signal pathways.Conclusions:Hemolysin rSph2 damaged the membrane of J774A.1 cells, and induced the secretion of HMGB1. Secreted-HMGB1 might induce the expression of IL-1β, IL-6 and KC in J774A.1 cells via NF-κB, p38-MAPK and JNK signal pathways, thus amplifying the inflammatory responses caused by Sph2.
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Objective:To investigate the role and mechanism of Leptospira interrogans ( L. interrogans) vWF-A gene products binding to human collagen proteins. Methods:Bioinformatic software was used to analyze the structure and function of the vWF-A genes (LA_0012, LA_0697 and LA_4207) of L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai. Prokaryotic expression systems for the vWF-A domain segments in the vWF-A genes were generated. The target recombinant proteins, rLep0012, rLep0697 and rLep4207, were purified by Ni-NTA affinity chromatography and analyzed by SDS-PAGE. ELISA and surface plasmon resonance (SPR) were performed to detect the binding ability of the target recombinant proteins to humanⅠ, Ⅲ, Ⅳ and Ⅵ types of collagen proteins (hCOL1/3/4/6). Expression of the vWF-A genes at mRNA and protein levels were detected by real-time fluorescent quantitative RT-PCT and Western blot during infection of human umbilical vein endothelial cells (HUVEC) and mouse hemangioendothelioma endothelial cells (EOMA). Results:The products of vWF-A genes were vWF-A superfamily domain-containing surface or transmembrane proteins, but LA_0697 and LA_4207 genes also contained metal ion-dependent adhesion sites (MIDAS). The established prokaryotic expression systems efficiently expressed the target recombinant proteins and each of the proteins extracted by Ni-NTA affinity chromatography showed a single band in SDS-PAGE. ELISA results showed the strong binding of rLep0697 to hCOL3/6 and rLep4207 to hCOL1/4. SPR results showed the rapid binding and dissociation of rLep0697 with hCOL3/6 ( KD values=5.71×10 -8 and 5.89×10 -8 mol/L) and the rapid and stable biding of rLep4207 with hCOL1/4 ( KD values=6.4×10 -9 and 3.2×10 -9 mol/L). Expression of the vWF-A genes at both mRNA and protein levels were significantly elevated ( P<0.05) during infection of HUVEC and EOMA cells. Conclusions:The products of LA_0697 and LA_4207 genes could act as the adherence factors of L. interrogans during infection.
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Objective:To investigate the influence of ferri ion on the growth, reproduction and energy metabolism of Leptospira interrogans ( L. interrogans), and to identify whether the LA_2690 and LA_3598 gene products functioned as ferritin and ferroxidase. Methods:Petroff-Hausser counting method was used to analyze the influence of ferri ion deficiency on the growth and reproduction of L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain 56601 in EMJH medium. Spectrophotometry and Chemiluminescence method was used to detect whether ferri ion deficiency inhibited the synthesis of DNA and ATP in L. interrogans. The structures and functions of L. interrogans LA_2690 and LA_3598 genes were analyzed using bioinformatic softwares. Prokaryotic expression systems for LA_2690 and LA_3598 genes were established and the target proteins, rLep2690 and rLep3598, were extracted by Ni-NTA affinity chromatography. The ferroxidase activity of rLep2690 and rLep3598 was detected by spectrophotometry. After L. interrogans strain 56601 was used to infect human umbilical vein endothelial cells (HUVEC) and monocytes (THP-1), changes in the expression of LA_2690 and LA_3598 genes at transcription level were detected using real-time fluorescence quantitative RT-PCR (qRT-PCR). Results:In the ferri ion-absent EMJH medium, the growth and reproduction of L. interrogans as well as the DNA and ATP synthesis levels were significantly decreased ( P<0.05). The products of LA_2690 and LA_3598 genes were predicted as bacterioferritin (Bfr) and DNA-binding ferritin containing ferroxidase diiron centers, but the latter lacked the heme-binding site and ferroxidase core. The prokaryotic expression systems for LA_2690 and LA_3598 genes could efficiently express the target recombinant proteins. Both the purified rLep2690 and rLep3598 showed a single band on SDS-PAGE. The ferroxidase activity of rLep2690 and rLep3598 was 1 238.619 U/L and 60.052 U/L, respectively. The expression of LA_2690 and LA_3598 genes of L. interrogans at mRNA level was significantly elevated during infection of the two types of cells ( P<0.05). Conclusions:Ferri ion participates in the growth and reproduction of L. interrogans as well as the synthesis of DNA and ATP. LA_2690 and LA_3598 genes were essential for L. interrogans to infect cells, and the product of LA_2690 gene possessed a stronger ferroxidase activity.
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Objective To analyze the enzymatic activity of Leptospira interrogans ( L. interrogans) LA_2144 gene product to hydrolyze platelet activating factor acetylhydrolase ( PAF-AH) and phosphatidase A2(PLA2). Methods Bioinformatic softwares were used to predict transmembrane regions, signal peptides and domains of the LA_2144 gene of L. interrogans strain Lai. A prokaryotic expression system for signal peptide-free LA_2144 gene was established. The expressed target recombinant protein rLep2144 was extrac-ted by Ni-NTA affinity chromatography and then renatured. Spectrometry was used to detect the activity of rLep2144 to hydrolyze PAF-AH substrate 2-thio PAF and the Km and Kcat values as well as the activity to hy-drolyze PLA2 substrate arachidonoyl 2-thio PC. Real-time fluorescence quantitative RT-PCR and Western blot were performed to detect the transcription, protein expression and secretion of LA_2144 gene during infection of human and mouse vascular endothelial cells ( HUVEC and EOMA) with L. interrogans. Results L. interrogans LA_2144 gene contained a signal peptide and a domain belonging to SGNH hydrolase super-family, but no transmembrane regions. The established prokaryotic expression system for signal peptide-free LA_2144 gene could efficiently express rLep2144. The extracted rLep2144 was shown as a single protein fragment in separation gel and then successfully renatured. rLep2144 had a stronger PAF-AH activity with the Km and Kcat values of 688. 235 μmol/L and 0. 976/s, but its PLA2 activity was relatively weak. Expres-sion of the LA_2144 gene at mRNA and protein levels in HUVEC and EOMA was rapidly increased after the cells were infected with L. interrogans (P<0. 05) and the secretion of LA_2144 gene product could be detec-ted. Conclusions L. interrogans LA_2144 gene product had a stronger PAF-AH and a certain PLA2 activi-ty, which might involve in the hemorrhage and inflammatory response in leptospirosis.
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Heme (heam) is a kind of iron porphyrin complexes. It is the most presence of iron in human bodies and also the main source of iron for pathogenic bacteria. Heme causes oxidative damage,cell death and organ failure and promotes inflammation in bacterial infection. This article will review the structure and sources of heme and its role in the process of bacterial growth and infection.
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Many bacterial pathogens can produce hemolysins to lyse erythrocytes,but recent studies revealed that bacterial hemolysins could cause injury and death of many nucleated cells and platelets.According to the difference of molecular structure,cell-binding manner and membrane pore-forming mechanism,most of bacterial hemolysins are classified into the toxins belonging to either repeats in toxin family (RTX) or cholesterol-dependent cytolysin family (CDC).Bacterial hemolysins play important pathogenic roles during infection of bacteria through membrane damage,cell lysis or disruption,ion disequilibriumassociated pathological changes,cell apoptosis or cell necroptosis as well as through TLR2/4-mediated NF-κB,p38MAPK,JNK signaling pathways and NLRs-mediated NLRP3 inflammasomes to cause powerful inflammatory reaction and inflammatory tissue injury.
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Objective To understand and determine the biological activity and pathogenicity of metalloendopeptidases encoded by LA2582 and LA2901 genes of Leptospira interrogans(L.interrogans) sero-group Icterohaemorrhagiaeserovar Lai strain Lai. Methods Structures and functions of LA2582 and LA2901 genes were analyzed by using bioinformatic software. Prokaryotic expression systems for expressing the extra-cellular regions of LA2582 and LA2901 genes were generated. The target recombinant expression products, rLA2582 and rLA2901,were extracted by Ni-NTA affinity chromatography. The Azo-casein-hydrolyzingactiv-ity of rLA2582 and rLA2901 was detected by spectrophotometry. Activities of rLA2582 and rLA2901 in the hydrolysis of Dabsyl-Leu-Gly-Gly-Gly-Ala-Edans, a fluorescence-labeling pentapeptide substrate, were de-tected by fluorospectrophotometry,and then the Km and Kcat values were determined. SDS-PAGE and spec-trophotometry were performed to detect the activities of rLA2582 and rLA2901 in hydrolyzing extracellular matrix molecules such as collagen type-Ⅰ (COL1), fibronectin (FN) and Congo red-labeling elastin (ELN). Real-time fluorescent quantitative RT-PCR(qRT-PCR) and Western blot were respectively used to measure the expression of LA2582 and LA2901 genes at mRNA and protein levels after infecting human um-bilical vein endothelial cells(HUVEC) with L. interrogans strain Lai. Results The gene products of LA2582 and LA2901 genes were identified as the signal peptide and matrix metalloproteinase motif HXH-containing Zn2+-dependent Gly-Gly metalloendopeptidases belonging to the M23 superfamily. rLA2582 and rLA2901 did not hydrolyze Azo-casein (Km=126.54 μmol/L, Kcat=4.67/s), but could hydrolyze the pentapeptide substrate (Km=190. 25 μmol/L, Kcat 4. 86/s). rLA2582 and rLA2901 could hydrolyze COL1, FN and ELN. Expression of LA2582 and LA2901 genes at both mRNA and protein levels was signifi-cantly increased after infection of HUVEC with L.interrogans strain Lai(P<0.05). Conclusion The prod-ucts of LA2582 and LA2901 genes of L.interrogans strain Lai are Zn2+-dependent M23 metalloendopeptidas-es, which can hydrolyze multiple ECM molecules and are closely associated with the leptospiral invasiveness.
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Bis-(3′,5′) cyclic di-guanylate (c-di-GMP) is an almost ubiquitous intracellular second messenger in bacteria.Now it is known to regulate complex physiological processes, including mobility, adhesion, virulence and biofilm formation.The level of c-di-GMP is regulated by diguanylate cyclases (DGCs) containing GGDEF domains and phosphodiesterases (PDEs) containing EAL or HD-GYP domains.Recent studies have demonstrated that HD-GYP domain protein is a novel phosphodiesterase, which is also involved in the regulation of c-di-GMP degradation.This review highlights recent advances in the structure and biochemical functions of HD-GYP domain proteins, which might help to further clarify the mechanism of c-di-GMP signal system.
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Objective To understand the differences in killing ability and mechanism of human mononuclear macrophages and neutrophils against Leptospira interrogans.Methods Human THP-1 and HL-60 cell lines were respectively pretreated with PMA (phorbol 12-myristate 13-acetate) and ATRA (all-trans retinoic acid) to induce their differentiation into macrophages and neutrophils.Confocal microscopy was used to detect the changes in total ROS (reactive oxygen species) and NO (nitric oxide) levels as well as free Ca2+ concentration ([Ca2+]i) in THP-1 monocyte-derived macrophages and HL-60 cell-derived neutrophils after infection with Leptospira interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai.Fluorospectrophotometry was applied to analyze the differences in killing ability between THP-1 monocyte-derived macrophages and HL-60 cell-derived neutrophils against intracellular leptospires before and after treatment with total ROS and NO inhibitors and intracellular free Ca2+ chelator.Results The total ROS and NO levels and [Ca2+]i in THP-1 monocyte-derived macrophages and HL-60 cell-derived neutrophils were significantly increased after infection with the spirochete (P<0.05).Moreover,the total ROS and NO levels and [Ca2+]i in the former were significantly higher than those in the latter (P<0.05).The THP-1 monocyte-derived macrophages had stronger killing ability against intracellular leptospires than the HL-60 cell-derived neutrophils (P<0.05).Inhibiting total intracellular ROS,NO or free Ca2+ could result in decreased killing ability of THP-1 monocyte-derived macrophages against intracellular leptospires,but not affect the killing ability of HL-60 cell-derived neutrophils.Conclusion Mononuclear macrophages rather than neutrophils act as the main phagocytes eliminating Leptospira interrogans.High levels of total intracellular ROS,NO and free Ca2+ are closely associated with the ability of mononuclear macrophages to kill Leptospira interrogans.
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Objective To investigate the regulatory effects of cyclic diguanylate (c-di-GMP) signaling on CheB and CheR, which were chemotaxis regulatory proteins relating to the motility of Leptospira interrogans.Methods Real-time PCR was used to determine the expression of cheB1, cheB2, cheB3, cheR1 and cheR2 genes at mRNA level during Leptospira interrogans infection.Fragments of these genes were amplified and cloned into the expression vector pET-28a, respectively, to construct the prokaryotic expression system for them.Colony morphologies of Escherichia coli (E.coli) strains that overexpressed the target genes were observed to determine the regulatory effects of c-di-GMP on CheB and CheR.Results The expression of cheB1 gene at mRNA level increased 60 min after infection and reached the peak at 90 min.Compared with the control group, the expression of cheB3 gene at mRNA level were up-regulated, while no significant difference in the expression of cheB2 and cheR genes was observed 60 min after infection.The prokaryotic expression system for the five genes was successfully constructed and the purified proteins were obtained.CheB1, CheB3 and CheR2 improved the motility of E.coli, but that was inhibited by the inhibitor of diguanylate cyclase (DGC) or phosphodiesterase (PDE).Conclusion CheB and CheR regulate the swarming motility of E.coli and are affected by intracellular c-di-GMP.
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Objective To analyze the platelet activating factor acetylhydrolase ( PAF-AH) activity of a gene product encoded by LA2144 gene of Leptospira interrogans ( L. interrogans) , to investigate the ex-pression and secretion of LA2144 protein in various cell cultures and to further understand its function in in-ducing internal hemorrhage in an animal model. Methods The DNA sample containing LA2144 gene was extracted from L. interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai and used as the template for gene cloning by PCR. The LA2144 gene without the signal sequence coding region was amplified by PCR and inserted into a prokaryotic expression construct for the protein expression. The expressed recombinant protein, rLep-PAF-AH, was purified by Ni-NTA affinity chromatography. Spectrophotometry was used to measure the hydrolytic activity, hydrolytic efficiency, Km and Kcat values of the rLep-PAF-AH protein in hydrolyzing PAF substrate. Real-time fluorescent quantitative RT-PCR ( qRT-PCR) and Western blot assay were performed to measure the expression of LA2144 gene at mRNA and protein levels in human umbilical vein endothelial cells (HUVEC), human monocytes (THP-1) and murine macrophages (J774A. 1) with L. interrogans strain Lai infection, respectively. Each syrian hamster was intravenously injected with 100 μg of LPS-free rLep-PAF-AH for two times. Hemorrhage in the lungs, livers and kidneys were observed in three days after the injection. Results The constructed prokaryotic expression system for LA2144 gene of L. inter-rogans strain Lai could highly express the rLep-PAF-AH upon the induction of IPTG. The purified rLep-PAF-AH showed high purity with a single protein band in gel as indicated by SDS-PAGE. The efficiency of 5 μg of rLep-PAF-AH in hydrolyzing PAF substrate was 26. 6 U/L with a Km value of 82. 79 μmol/L and a Kcat value of 0. 24 S-1 . The expression of Lep-PAF-AH at mRNA level in HUVEC, THP-1 and J774A. 1 cells were significantly elevated after co-culture with L. interrogans strain Lai for 1 or 2 hours (P<0. 05). A large amount of Lep-PAF-AH were detected in the supernatants from co-cultures of L. interrogans strain Lai with the three cell lines, but not from the culture of the spirochete in EMJH medium. The signs of hemor-rhage were observed in the lung of hamsters injected with rLep-PAF-AH, but not in tissue samples from liver and kidney. Conclusion The LA2144 gene product was characterized by a stronger PAF-AH activity. The expression of LA2144 gene at mRNA and protein levels in various cell lines were enhanced during L. interro-gans infection. Moreover, the rLep-PAF-AH could induce the pulmonary hemorrhage in hamsters. This stud-y indicated that the protein encoded by LA2144 gene was an important virulence factor causing hemorrhage in hosts during L. interrogans infection.
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Objective To construct a prokaryotic expression system for tlyA gene of Leptospira in-terrogans ( L.interrogans) strain and to investigate the effects of the expressed rTlyA protein on the hemolysis of sheep erythrocytes and the secretion of pro-inflammatory cytokines by human THP-1 cells and murine J774A.1 macrophages.Methods The fragment of tlyA gene of L.inetrrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai was amplified by PCR.The PCR product was sequenced after T-A cloning.A prokary-otic expression system for the tlyA gene was constructed by using pET-42a as the expression vector and E.coli BL21DE3 strain as the host strain.The expression of rTlyA protein was detected by SDS-PAGE.Ni-NTA af-finity chromatography was performed for purification.The lytic activity of the rTlyA protein on sheep erythro-cytes was determined by plate hemolytic test and spectrophotometry.Real-time fluorescence quantitative PCR and Western blot assay were performed to respectively detect the expression of tlyA gene in THP-1 and J774A.1 cells at mRNA and protein levels after infection with L.interrogans strain Lai.ELISA was per-formed to evaluate the effects of the rTlyA protein on the secretion of several pro-inflammatory cytokines ( IL-β, IL-6 and TNF-α) by THP-1 and J774A.1 cells.Results The nucleotide and amino acid sequences of the cloned tlyA gene were 99.2% and 99.8% identical to those corresponding sequences in GenBank, re-spectively.The constructed prokaryotic expression system for tlyA gene successfully expressed the rTlyA pro-tein.The rTlyA protein at the concentration of 10μg/ml showed stronger lytic activity on sheep erythrocytes. The transcription levels of tlyA gene (P<0.05) and the secretion of TlyA protein in THP-1 and J774A.1 cells were significantly increased after infecting with L.interrogans strain Lai for 1 to 8 hours.The rTlyA pro-tein at concentrations of 0.1, 1 and 10 μg/ml significantly enhanced the secretion of IL-1β, IL-6 and TNF-αby THP-1 and J774A.1 cells (P<0.05).Conclusion The TlyA protein, encoded by the tlyA gene of L.interrogans strain, was confirmed to be a hemolysin with the ability to induce macrophages to secret IL-1β, IL-6 and TNF-α.This study suggested that the TlyA protein played an important role in inflammatory responses during leptospirosis.
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Objective To construct a fusion gene (h1a-spaO) encoding H1a-SpaO protein of Sal-monella paratyphi A ( S.paratyphi A) and to express it in prokaryotic expression system , then to further ana-lyze the immunoprotective effects of the expressed protein rH 1a-SpaO.Methods The h1a-spaO fusion gene formed from separate h1a and spaO genes was amplified by PCR using flexible peptide sequence-containing linking primers and then sequenced after T-A cloning.A prokaryotic expression system for expressing h1a-spaO fusion gene was constructed by using the genetic engineering technique .The expressed protein rH1a-SpaO was examined by SDS-PAGE.The antigenicity and immunoreactivity of rH1a-SpaO protein were deter-mined by Western blot assay .The ability of rH1a-SpaO antiserum agglutinating S.paratyphi A strains was detected by micro-Widal′s test.The immunoprotective effects of rH 1a-SpaO against the lethal dose challenge of S.paratyphi A strains were analyzed in a mouse model and that were compared with those by using equal dose of individual recombinant protein H1a and SpaO (rH1a and rSpaO) as the immunogens, respectively. Results The h1a-spaO fusion gene was 100%identical with the individual h1a or spaO gene in nucleotide and amino acid sequences .The constructed prokaryotic expression system could express the recombinant pro-tein rH1a-SpaO with an advantage of high efficiency .rH1a-SpaO protein was able to react with rH 1a or rSpaO antiserum.Moreover, rH1a-SpaO antiserum also could efficiently recognize rH 1a and rSpaO as well as agglutinate Salmonella paratyphi A strains by binding with H-antigen.The immunoprotective rate (93.3%) in mice pre-immunized with 100 μg of rH1a-SpaO protein was significantly higher than that in those pre-immunized with equal dose of rH1a (60.0%) protein or rSpaO protein(53.3%) (P<0.05).Conclusion The recombinant fusion protein rH 1a-SpaO showed more stronger immunoprotective function than the individ-ual rH1a or rSpaO protein , which could be used as an effective antigen for the development of bi -valent para-typhoid A vaccine or typhoid/paratyphoid capsular polysaccharide-protein combined vaccine .
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<p><b>OBJECTIVE</b>To predict and screen the efficient antigenic epitopes in genus-specific envelope protein LipL41 of Leptospira interrogans and to determine the immunoreactive diversity of LipL41s from different genotypes.</p><p><b>METHODS</b>Bioinformatic methods were applied to predict the T/B combined epitope candidates in LipL41/1 and LipL41/2 molecules. The nucleotide fragments encoding epitopes were amplified by PCR. Phage display system with SDS-PAGE was performed to obtain the recombinant PIIIs containing different T/B combined epitopes. Western Blot assays were performed to determine the immunoreactivity of recombinant PIIIs to various antisera including antiserum against rLipL41/1, rLipL41/2 and whole cell of L.interrogans strain Lai, and serum from patients with leptospirosis.</p><p><b>RESULT</b>Based on the predicting data, eight common or differential combined epitopes in LipL41s were selected. The nucleotide fragments encoding the epitopes were obtained by PCR. All the T/B combined epitope fragments were correctly inserted into the N end of phage PIII protein and then successfully expressed. All the antisera were able to recognize each of the epitopes but the hybridization signal intensity was different. Among these epitopes, the common T/B combined epitopes LipL41/1-30 and LipL41/1-233 showed a stronger and stable hybridization signals.</p><p><b>CONCLUSION</b>All 8 selected T/B combined epitopes in the study are the efficient antigenic epitopes. The common T/B epitopes LipL41/1-30 and LipL41/1-233 can be first used in development of leptospiral MAP vaccine. The cross immunoreaction is between the differential T/B epitopes LipL41s-89,LipL41s-299 and the different antisera.</p>