核糖核酸酶5在宿主防御中的作用及机制

抗菌肽是机体天然免疫的重要组成部分。核糖核酸酶5（ribonuclease5,RNASE5;又名angiogenin）属于核糖核酸酶A超家族,是一个分泌型小分子蛋白质,广泛分布于机体需要抵御外界病原微生物的组织中。RNASE5对病毒、细菌以及真菌都存在抑制效应,具有广谱抗菌特点,但其表达和活性受到宿主生理状态和外界环境多层次的调控。RNASE5存在多样的抗微生物作用机制,其带正电荷的理化特性破坏微生物细胞壁,而其核糖核酸酶活性则是杀伤真菌所必须的。除了直接作用于微生物外,RNASE5还可作为重要因子调节宿主免疫功能,参与多种病理过程。本文综述了RANSE5的结构、生物活性与功能、作用特点与机制,并讨论了在其研究中存在的问题,以期为今后的研究提供新思路和新方向。     

Role of Cathelicidin Peptides in Bovine Host Defense and Healing

The in vitro antimicrobial activities and biological effects on host cells were compared for the bovine cathelicidins BMAP-28, an alpha-helical AMP, and Bac5 and Bac7, proline-rich AMPs. Our results confirm that the broad-spectrum activity of BMAP-28 correlates with a high capacity to interact with and permeabilize bacterial membranes, whereas the proline-rich AMPs selectively internalize into the cytoplasm of susceptible Gram-negative bacteria with a non-lytic mechanism. All peptides efficiently translocated into mammalian fibroblastic cells, but while Bac5 and Bac7(1–35) localized to nuclear structures and induced cellular proliferation, BMAP-28 associated with mitochondria and did not induce proliferation. Moreover, BMAP-28 was considerably more cytotoxic than the proline-rich peptides due to cytolytic and pro-apoptotic effects. Our results highlight important functional differences among the bovine cathelicidins and suggest that they contribute to an integrated response of the host to infection, with distinct but complementary activities.     

A Novel Role for Pro-Coagulant Microvesicles in the Early Host Defense against Streptococcus pyogenes

Previous studies have shown that stimulation of whole blood or peripheral blood mononuclear cells with bacterial virulence factors results in the sequestration of pro-coagulant microvesicles (MVs). These particles explore their clotting activity via the extrinsic and intrinsic pathway of coagulation; however, their pathophysiological role in infectious diseases remains enigmatic. Here we describe that the interaction of pro-coagulant MVs with bacteria of the species Streptococcus pyogenes is part of the early immune response to the invading pathogen. As shown by negative staining electron microscopy and clotting assays, pro-coagulant MVs bind in the presence of plasma to the bacterial surface. Fibrinogen was identified as a linker that, through binding to the M1 protein of S. pyogenes, allows the opsonization of the bacteria by MVs. Surface plasmon resonance analysis revealed a strong interaction between pro-coagulant MVs and fibrinogen with a K_D value in the nanomolar range. When performing a mass-spectrometry-based strategy to determine the protein quantity, a significant up-regulation of the fibrinogen-binding integrins CD18 and CD11b on pro-coagulant MVs was recorded. Finally we show that plasma clots induced by pro-coagulant MVs are able to prevent bacterial dissemination and possess antimicrobial activity. These findings were confirmed by in vivo experiments, as local treatment with pro-coagulant MVs dampens bacterial spreading to other organs and improved survival in an invasive streptococcal mouse model of infection. Taken together, our data implicate that pro-coagulant MVs play an important role in the early response of the innate immune system in infectious diseases.     

Epithelial Pyroptosis in Host Defense

Pyroptosis is a lytic form of cell death that is executed by a family of pore-forming proteins called gasdermins (GSDMs). GSDMs are activated upon proteolysis by host proteases including the proinflammatory caspases downstream of inflammasome activation. In myeloid cells, GSDM pore formation serves two primary functions in host defense: the selective release of processed cytokines to initiate inflammatory responses, and cell death, which eliminates a replicative niche of the pathogen. Barrier epithelia also undergo pyroptosis. However, unique mechanisms are required for the removal of pyroptotic epithelial cells to maintain epithelial barrier integrity. In the following review, we discuss the role of epithelial inflammasomes and pyroptosis in host defense against pathogens. We use the well-established role of inflammasomes in intestinal epithelia to highlight principles of epithelial pyroptosis in host defense of barrier tissues, and discuss how these principles might be shared or distinctive across other epithelial sites.     

Processing of Doxorubicin-Containing Liposomes by Liver Macrophages in Vitro

Abstract

Previous results suggested that drug formation in macrophages is an important aspect of the mode of action of doxorubicin (DXR)-containing liposomes. Intracellular degradation of DXR-liposomes may result in the liberation of DXR molecules that subsequently are released from the macrophages. We investigated whether the rate of intracellular degradation of DXR-liposomes phagocytosed by rat liver macrophages (Kupffer's cells) in monolayer culture is dependent on the type of DXR-liposomes internalized and whether differences in degradation rate of DXR-liposomes are reflected in different DXR release profiles. Two DXR-liposome types that were previously shown to differ markedly both in antitumor activity and degradation rate in vivo were selected for this investigation: a liposome composed of egg-phosphatidylcholine (PC), phosphatidylserine (PS), and cholesterol (chol), and a liposome composed of distearoylphosphatidylcholine (DSPC), dipalmitoyl-phosphatidylglycerol (DPPG), and chol. To monitor the rate of intracellular degradation of DXR-liposomes, cholesterol-1-[¹⁴Cjoleate was used as marker of the liposomal lipid phase. DXR was monitored with the use of a high-performance liquid chromatography (HPLC) method capable of detecting not only intact DXR but also major metabolites.

Comparable amounts of both types of DXR-liposomes were taken up by in vitro cultured Kupffer's cells. Liposome-associated cholesteryloleate was metabolized by the cells in a liposome-type-dependent pattern. During the first 30 min after start of the incubation, degradation of cholesteryloleate occurred at a similar rate for both types of DXR-liposomes. During continued incubation, however, PC/PS/chol DXR-liposomes were degraded at a considerably higher rate than DSPC/DPPG/ chol DXR-liposomes. the difference in susceptibility to lysosomal degradation of the two liposome preparations was also demonstrated by incubating the DXR-liposomes with lysosomal fractions isolated from rat liver homogenates: PC/PS/chol DXR-liposomes were much more sensitive to lysosomal esterase than DSPC/DPPG/chol DXR-liposomes. DXR either free or in liposomal form was chemically stable for up to 26 hr during incubation with the lysosomal fractions. Following uptake of DXR-liposomes by the cells, DXR was released from the cells into the medium. the release of DXR from cells that internalized DSPC/DPPG/chol DXR-liposomes was significantly delayed compared to the release of DXR from cells that internalized PC/PS/chol DXR-liposomes. Correlation of the relatively slow intracellular degradation of the DSPC/DPPG/chol DXR-liposomes with the delayed release of DXR from the cells suggests that by varying the type of DXR-liposomes, the rate of intracellular degradation can be manipulated, which, in turn, determines the rate of extracellular DXR release and thereby the therapeutic availability of the drug.     

Arming Th17 Cells for Antifungal Host Defense

Interleukin 17 (IL-17)-mediated immunity has emerged as a crucial host defense mechanism against fungal infections. The family of IL-17 cytokines is phylogenetically ancient, but remains the least understood of all cytokine subclasses. The effects mediated by IL-17 are pleiotropic and include the induction of antimicrobial peptides as well as cytokines and chemokines that lead to the recruitment and activation of neutrophils. Neutrophils in turn are key effector cells of the antifungal defense. CD4⁺ T cells act as a major source of IL-17 and a lot has been learned about these cells since their discovery a decade ago. This review highlights key aspects of the underlying mechanisms regulating the development of Th17 responses during fungal infections. We discuss the impact of different subsets of antigen-presenting cells, innate cytokine signals and tissue-specific factors on Th17 differentiation, and we highlight the prerequisites for the mediation by Th17 cells of vaccine immunity against fungi.     

Role of Nucleotide-Binding Oligomerization Domain-Containing (NOD) 2 in Host Defense during Pneumococcal Pneumonia

Streptococcus (S.) pneumoniae is the most common causative pathogen in community-acquired pneumonia. Nucleotide-binding oligomerization domain-containing (NOD) 2 is a pattern recognition receptor located in the cytosol of myeloid cells that is able to detect peptidoglycan fragments of S. pneumoniae. We here aimed to investigate the role of NOD2 in the host response during pneumococcal pneumonia. Phagocytosis of S. pneumoniae was studied in NOD2 deficient (Nod2 ^-/-) and wild-type (Wt) alveolar macrophages and neutrophils in vitro. In subsequent in vivo experiments Nod2 ^-/- and Wt mice were inoculated with serotype 2 S. pneumoniae (D39), an isogenic capsule locus deletion mutant (D39Δcps) or serotype 3 S. pneumoniae (6303) via the airways, and bacterial growth and dissemination and the lung inflammatory response were evaluated. Nod2 ^-/- alveolar macrophages and blood neutrophils displayed a reduced capacity to internalize pneumococci in vitro. During pneumonia caused by S. pneumoniae D39 Nod2 ^-/- mice were indistinguishable from Wt mice with regard to bacterial loads in lungs and distant organs, lung pathology and neutrophil recruitment. While Nod2 ^-/- and Wt mice also had similar bacterial loads after infection with the more virulent S. pneumoniae 6303 strain, Nod2 ^-/- mice displayed a reduced bacterial clearance of the normally avirulent unencapsulated D39Δcps strain. These results suggest that NOD2 does not contribute to host defense during pneumococcal pneumonia and that the pneumococcal capsule impairs recognition of S. pneumoniae by NOD2.     

病毒的侵染策略和植物的防卫反策略

病毒对植物的侵染及植物对病毒侵染的抵抗实际上是病毒与寄主植物之间相互作用的结果,病毒和寄主植物共同参与调控植物的亲和反应及防卫反应。     

RNase A超家族多样性的产生及宿主防御

胰核糖核酸酶家族也被称为RNase A家族,包含了与牛胰核糖核酸酶同源的所有脊椎核糖核酸酶.从20世纪初.RNase A超家族就成为生物化学、结构生物学、酶学、进化学等领域的研究热点.最新的进化研究显示,脊椎动物RNase A家族起源于宿主防御功能,本文就RNaseA超家族多样性的产生及其宿主防御功能进行综述.     

Menacing Mold: Recent Advances in Aspergillus Pathogenesis and Host Defense

The genus Aspergillus is ubiquitous in the environment and contains a number of species, primarily A. fumigatus, that cause mold-associated disease in humans. Humans inhale several hundred to several thousand Aspergillus conidia (i.e., vegetative spores) daily and typically clear these in an asymptomatic manner. In immunocompromised individuals, Aspergillus conidia can germinate into tissue-invasive hyphae, disseminate, and cause invasive aspergillosis. In this review, we first discuss novel concepts in host defense against Aspergillus infections and emphasize new insights in fungal recognition and signaling, innate immune activation, and fungal killing. Second, the review focuses on novel concepts of Aspergillus pathogenesis and highlights emerging knowledge regarding fungal strain heterogeneity, stress responses, and metabolic adaptations on infectious outcomes. Mechanistic insight into the host–pathogen interplay is thus critical to define novel druggable fungal targets and to exploit novel immune-based strategies to improve clinical outcomes associated with aspergillosis in vulnerable patient populations.