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.

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.

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.