Deficient IFN Signaling by Myeloid Cells Leads to MAVS-Dependent Virus-Induced Sepsis

The type I interferon (IFN) signaling response limits infection of many RNA and DNA viruses. To define key cell types that require type I IFN signaling to orchestrate immunity against West Nile virus (WNV), we infected mice with conditional deletions of the type I IFN receptor (IFNAR) gene. Deletion of the Ifnar gene in subsets of myeloid cells resulted in uncontrolled WNV replication, vasoactive cytokine production, sepsis, organ damage, and death that were remarkably similar to infection of Ifnar ^−/− mice completely lacking type I IFN signaling. In Mavs^−/−×Ifnar^−/− myeloid cells and mice lacking both Ifnar and the RIG-I-like receptor adaptor gene Mavs, cytokine production was muted despite high levels of WNV infection. Thus, in myeloid cells, viral infection triggers signaling through MAVS to induce proinflammatory cytokines that can result in sepsis and organ damage. Viral pathogenesis was caused in part by massive complement activation, as liver damage was minimized in animals lacking complement components C3 or factor B or treated with neutralizing anti-C5 antibodies. Disease in Ifnar ^−/− and CD11c Cre⁺ Ifnar ^f/f mice also was facilitated by the proinflammatory cytokine TNF-α, as blocking antibodies diminished complement activation and prolonged survival without altering viral burden. Collectively, our findings establish the dominant role of type I IFN signaling in myeloid cells in restricting virus infection and controlling pathological inflammation and tissue injury.     

Differential Susceptibility and Response of Primary Human Myeloid BDCA1+ Dendritic Cells to Infection with Different Enteroviruses

Coxsackie B viruses (CVBs) and echoviruses (EVs) form the Human Enterovirus-B (HEV-B) species within the family Picornaviridae. HEV-B infections are widespread and generally cause mild disease; however, severe infections occur and HEV-B are associated with various chronic diseases such as cardiomyopathy and type 1 diabetes. Dendritic cells (DCs) are the professional antigen-presenting cells of our immune system and initiate and control immune responses to invading pathogens, yet also maintain tolerance to self-antigens. We previously reported that EVs, but not CVBs, can productively infect in vitro generated monocyte-derived DCs. The interactions between HEV-B and human myeloid DCs (mDCs) freshly isolated from blood, however, remain unknown. Here, we studied the susceptibility and responses of BDCA1⁺ mDC to HEV-B species and found that these mDC are susceptible to EV, but not CVB infection. Productive EV7 infection resulted in massive, rapid cell death without DC activation. Contrary, EV1 infection, which resulted in lower virus input at the same MOI, resulted in DC activation as observed by production of type I interferon-stimulated genes (ISGs), upregulation of co-stimulatory and co-inhibitory molecules (CD80, CD86, PDL1) and production of IL-6 and TNF-α, with a relative moderate decrease in cell viability. EV1-induced ISG expression depended on virus replication. CVB infection did not affect DC viability and resulted in poor induction of ISGs and CD80 induction in part of the donors. These data show for the first time the interaction between HEV-B species and BDCA1⁺ mDCs isolated freshly from blood. Our data indicate that different HEV-B species can influence DC homeostasis in various ways, possibly contributing to HEV-B associated pathology.     

Interferon-Induced Ifit2/ISG54 Protects Mice from Lethal VSV Neuropathogenesis

Interferon protects mice from vesicular stomatitis virus (VSV) infection and pathogenesis; however, it is not known which of the numerous interferon-stimulated genes (ISG) mediate the antiviral effect. A prominent family of ISGs is the interferon-induced with tetratricopeptide repeats (Ifit) genes comprising three members in mice, Ifit1/ISG56, Ifit2/ISG54 and Ifit3/ISG49. Intranasal infection with a low dose of VSV is not lethal to wild-type mice and all three Ifit genes are induced in the central nervous system of the infected mice. We tested their potential contributions to the observed protection of wild-type mice from VSV pathogenesis, by taking advantage of the newly generated knockout mice lacking either Ifit2 or Ifit1. We observed that in Ifit2 knockout (Ifit2 ^−/−) mice, intranasal VSV infection was uniformly lethal and death was preceded by neurological signs, such as ataxia and hind limb paralysis. In contrast, wild-type and Ifit1 ^−/− mice were highly protected and survived without developing such disease. However, when VSV was injected intracranially, virus replication and survival were not significantly different between wild-type and Ifit2^−/− mice. When administered intranasally, VSV entered the central nervous system through the olfactory bulbs, where it replicated equivalently in wild-type and Ifit2 ^−/− mice and induced interferon-β. However, as the infection spread to other regions of the brain, VSV titers rose several hundred folds higher in Ifit2 ^−/− mice as compared to wild-type mice. This was not caused by a broadened cell tropism in the brains of Ifit2 ^−/− mice, where VSV still replicated selectively in neurons. Surprisingly, this advantage for VSV replication in the brains of Ifit2^−/− mice was not observed in other organs, such as lung and liver. Pathogenesis by another neurotropic RNA virus, encephalomyocarditis virus, was not enhanced in the brains of Ifit2 ^−/− mice. Our study provides a clear demonstration of tissue-, virus- and ISG-specific antiviral action of interferon.     

Use of IRF-3 and/or IRF-7 Knockout Mice To Study Viral Pathogenesis: Lessons from a Murine Retrovirus-Induced AIDS Model

Interferon regulatory factor (IRF) regulation of the type I interferon response has not been extensively explored in murine retroviral infections. IRF-3^−/− and select IRF-3/7^−/− mice were resistant to LP-BM5-induced pathogenesis. However, further analyses strongly suggested that resistance could be attributed to strain 129-specific contamination of the known retrovirus resistance gene Fv1. Therefore, caution should be taken when interpreting phenotypes observed in these knockout mice, as strain 129-derived genetic polymorphisms may explain observed differences.     

Fighting mycobacteria through ISGylation

The role of ISGylation in humans has been a long-standing question. A recent groundbreaking study by the Casanova group shows it is essential in the defence against mycobacterial disease but dispensable for other types of infection.Bogunovic et al. (2012). Science, Epub: Aug 2. DOI: 10.1126/science.1224026Our bodies use interferon (IFN) signalling as a central pathway to limit the spread of pathogens, such as viruses, bacteria and parasites. After pathogen exposure, IFN production leads to the activation of immune cells—such as natural killer cells, macrophages and T lymphocytes—which mediate pathogen clearance. There are two main types of IFN signalling, type I and II. In type I signalling, IFNs α and β—produced mainly by leukocytes and fibroblasts, respectively—stimulate macrophages and natural killer (NK) cells to initiate an antiviral response. In type II signalling, IFNγ from activated T cells and NK cells potentiate type I signalling and promote inflammation. During type I signalling IFNα and IFNβ bind to their cognate receptors, which results in the induction of IFN-stimulated genes (ISGs). A key function of ISGs is to interfere with viral replication, hence the name interferon. One of the most strongly induced ISGs is ISG15, a small protein consisting of two ubiquitin folds connected with a hinge spacer, thus resembling di-ubiquitin [1]. It has been proposed that ISGylation is antiviral in mice, but its effects on human virus infection or other functional roles have been a long-standing question in the field. A study by the Casanova group provides important new insights into the role of ISG15 in humans, showing it is essential in the defence against mycobacterial disease but dispensable for other types of infection [2].Similarly to ubiquitin, ISG15 can be conjugated to other proteins and several hundred targets have been suggested from proteomic studies [3]. However, few targets have been carefully evaluated, among them JAK1, STAT1, ERK1/2, PLCγ1, p63, PML-RARα, UBC13, filamin B and several viral proteins. In analogy to the ubiquitin system, ISG15 conjugation is mediated by an enzymatic cascade consisting of an E1 activating enzyme Ube1L, an E2 conjugating enzyme UbcH8 and a HECT-domain containing E3 ligase HERC5 (Fig 1A). Notably, both ISG15 and the E1/E2/E3 cascade are induced by type I IFN signalling.Open in a separate windowFigure 1ISGylation and its function in the antimycobacterial response. (A) The ISG15 conjugation system. ISG15 is activated by an E1 enzyme and conjugated to substrates (green) by the action of E2 and E3 enzymes. HERC5 (HERC6 in mice) is the main ISGylating E3. (B) Mycobacterial infection induces IFNα/β production, which stimulates ISG15 synthesis and secretion in granulocytes. Secreted ISG15 can then activate NK cells to produce IFNγ, which stimulates immune system cells. See text for details. (C) HERC5 has been described to bind to polysomes and to promote cotranslational ISGylation of newly synthesized proteins. EFP, oestrogen-responsive finger protein; HERC5/6, HECT and RLD domain containing E3 ubiquitin protein ligases 5/6; HHARI, human homologue of Drosophila ariadne; IFNα/β/γ;, interferon α/β/γ; IFNαR, interferon α receptor; IL-12, interleukin 12; ISG15, interferon-stimulated gene 15; Lys, lysine; mRNA, messenger RNA; NK, natural killer; TLR, Toll-like receptor; UbcH8, ubiquitin conjugating enzyme H8; Ube1L, ubiquitin activating enzyme E1-like.Knowledge of the biological functions of ISGylation comes mainly from the analysis of knockout mice for ISG15, Ube1L and from in vitro studies. ISG15^−/− mice are more prone to infection by certain viruses, such as Sindbis, influenza A/B and herpes simplex 1 [4]. Ube1L^−/− mice are also sensitized towards Sindbis and influenza infections [5]. Furthermore, ISG15 can inhibit the budding of certain viruses and modify viral proteins, and some viruses have developed strategies to inhibit ISGylation, underscoring the function of ISG15 and ISGylation in the antiviral response [6]. However, other viruses—such as vesicular stomatitis and lymphocytic choriomeningitis virus—have similar effects on ISG15^−/− and wild-type mice [7], suggesting specialized functions of ISGylation after viral infection. In addition, a closer look at the role of ISG15 in regulating human viruses complicates the picture further: ISG15 has been found to stimulate rather than inhibit hepatitis C virus production in vitro, probably by preventing the degradation of viral proteins through competition between ISGylation and ubiquitylation [8]. Considering the limited number of viral infections common to both mice and man, it has been difficult to extrapolate what the in vivo functions of ISGylation might be in humans.The Bogunovic et al [2] study is a clear step forward in our understanding of ISG15 function in infection biology. By analysing patients with the rare paediatric syndrome, Mendelian susceptibility to mycobacterial disease (MSMD), they identified mutations in ISG15 that lead to its loss of expression and suggest that these mutations cause the disease. Importantly, these patients do not suffer from increased sensitivity to viral infections but show severe clinical symptoms when exposed to weakly pathogenic mycobacteria, such as Mycobacterium bovis.As has been shown in ISG15^−/− and Ube1L^−/− mice, Bogunovic et al found that cells from MSMD patients lack ISG15 expression after IFNα/β stimulation, but other ISGs are induced normally, confirming that ISG15 is not essential to elicit an IFN response [2]. Furthermore, patient cell lines are not more susceptible to infection by viruses such as herpes simplex virus, Sindbis virus and vesicular stomatitis virus. Secretion of ISG15 by granulocytes from gelatinase and secretory granules is probably an important process in response to mycobacterial infection that cannot be triggered by, for example, bacterial lipopolysaccharides (Fig 1B). Monocytes and lymphocytes are known to secrete ISG15, and Casanova and colleagues show that even transfected HEK293T cells can do so—suggesting that ISG15 is both an intracellular and a secreted protein—independently of the cellular context. The main function of secreted ISG15 seems to be the triggering of IFNγ release, preferentially from NK cells, but also from T cells. Interestingly, IFNγ secretion is also stimulated by modified ISG15 that can no longer be conjugated to target proteins. This indicates that immune cells either have an ISG15 receptor or that secreted ISG15, which is endocytosed, can induce a response without being conjugated to an intracellular target. Importantly, ISG15 secretion is lost in cells from MSMD patients and, consistently, MSMD leukocytes stimulated with mycobacteria produce greatly reduced amounts of IFNγ, which can be restored by providing recombinant ISG15. In addition, the study also demonstrates that ISG15^−/− mice are more susceptible to mycobacterial infection than their wild-type littermates.Thus, the Bogunovic study identifies a common function of ISG15 in vertebrates: the ability to counteract mycobacterial infections by activating NK cells. The data also suggest that some viruses and bacteria must share pathogen-associated molecular patterns that resemble those of mycobacteria, thus initiating a similar response that involves IFNα/β, which is required for ISG15 induction. The initial activation of this mechanism by mycobacteria remains to be identified and seems to be complex, as treatment of macrophages with IFNα/β during mycobacterial infection has been shown to induce the loss of their mycobacteriostatic properties [9]; partly at odds with the conclusions from this study. These discrepancies notwithstanding, the new insights reveal an essential function for ISG15 in antimycobacterial signalling. Mycobacterial infections are hard to fight and thus the finding that ISG15 is a major effector between granulocytes and NK cells might help develop new treatment strategies. Other cellular mediators, such as the macrophage–T-cell pathway, are a crucial host defence against pathogenic (M. tuberculosis) and nonpathogenic mycobacteria (M. bovis), as well as salmonella, in other variants of MSMD. Hence, Casanova and colleagues speculate that the granulocyte–NK-cell pathway, which involves ISG15 and IFNγ, might constitute a more innate complement to the macrophage–T-cell pathway, which requires IL-12/IFNγ. However, they also report a synergistic effect of a combined treatment of cells with ISG15 and IL-12, which rather argues that the granulocyte–NK-cell and the macrophage–T-cell systems act together. Furthermore, both granulocytes and macrophages express Toll-like receptors (TLRs) that recognize mycobacterial structures—such as TLR2 for the lipomannan of M. tuberculosis.Finally, whether covalent modification of target proteins within cells by ISG15 is important during infection remains unclear. It is difficult to speculate what the main effects would be, as ISG15 modifies targets in diverse cellular pathways. Notably, the E3 ligase for ISG15 conjugation HERC5 has been shown to be associated physically with polysomes, leading to cotranslational ISGylation of newly synthesized proteins, which probably inhibits protein function in general (Fig 1C; [10]). Thus, ISG15 might have two roles in preparing cells to fight pathogens: intracellular proteome remodelling and initiating antimicrobial signalling pathways. It will be interesting to see if and how these functions intersect.     

Nox1 causes ileocolitis in mice deficient in glutathione peroxidase-1 and -2

We previously reported that mice deficient in two Se-dependent glutathione peroxidases, GPx1 and GPx2, have spontaneous ileocolitis. Disease severity depends on mouse genetic background. Whereas C57BL/6J (B6) GPx1/2-double-knockout (DKO) mice have moderate ileitis and mild colitis, 129S1Svlm/J (1 2 9) DKO mice have severe ileocolitis. Because GPx’s are antioxidant enzymes, we hypothesized that elevated reactive oxygen species trigger inflammation in these DKO mice. To test whether NADPH oxidase 1 (Nox1) contributes to colitis, we generated B6 triple-KO (TKO) mice to study their phenotype. Because the Nox1 gene is X-linked, we analyzed the effects of Nox1 on male B6 TKO mice and female B6 DKO mice with the Nox1^+/− (het-TKO) genotype. We found that the male TKO and female het-TKO mice are virtually disease-free when monitored from 8 through 50 days of age. Male TKO and female het-TKO mice have nearly no signs of disease (e.g., lethargy and perianal alopecia) that are often exhibited in the DKO mice; further, the slower growth rate of DKO mice is almost completely eliminated in male TKO and female het-TKO mice. Male TKO and female het-TKO mice no longer have the shortened small intestine present in the DKO mice. Finally, the pathological characteristics of the DKO ileum, including the high level of crypt apoptosis (analyzed by apoptotic figures, TUNEL, and cleaved caspase-3 immunohistochemical staining), high numbers of Ki-67-positive crypt epithelium cells, and elevated levels of monocytes expressing myeloperoxidase, are all significantly decreased in male TKO mice. The attenuated ileal and colonic pathology is also evident in female het-DKO mice. Furthermore, the male DKO ileum has eightfold higher TNF cytokine levels than TKO ileum. Nox1 mRNA is highly elevated in both B6 and 129 DKO ileum compared to wild-type mouse ileum. Taking these results together, we propose that ileocolitis in the DKO mice is caused by Nox1, which is induced by TNF. The milder disease in female het-TKO intestine is probably due to random or imprinted X-chromosome inactivation, which produces mosaic Nox1 expression.     

A Role for Ifit2 in Restricting West Nile Virus Infection in the Brain

Previous studies have demonstrated that type I interferon (IFN-I) restricts West Nile virus (WNV) replication and pathogenesis in peripheral and central nervous system (CNS) tissues. However, the in vivo role of specific antiviral genes that are induced by IFN-I against WNV infection remains less well characterized. Here, using Ifit2^−/− mice, we defined the antiviral function of the interferon-stimulated gene (ISG) Ifit2 in limiting infection and disease in vivo by a virulent North American strain of WNV. Compared to congenic wild-type controls, Ifit2^−/− mice showed enhanced WNV infection in a tissue-restricted manner, with preferential replication in the CNS of animals lacking Ifit2. Virological analysis of cultured macrophages, dendritic cells, fibroblasts, cerebellar granule cell neurons, and cortical neurons revealed cell type-specific antiviral functions of Ifit2 against WNV. In comparison, small effects of Ifit2 were observed on the induction or magnitude of innate or adaptive immune responses. Our results suggest that Ifit2 restricts WNV infection and pathogenesis in different tissues in a cell type-specific manner.     

Interferon Regulatory Factor-1 Protects from Fatal Neurotropic Infection with Vesicular Stomatitis Virus by Specific Inhibition of Viral Replication in Neurons

The innate immune system protects cells against invading viral pathogens by the auto- and paracrine action of type I interferon (IFN). In addition, the interferon regulatory factor (IRF)-1 can induce alternative intrinsic antiviral responses. Although both, type I IFN and IRF-1 mediate their antiviral action by inducing overlapping subsets of IFN stimulated genes, the functional role of this alternative antiviral action of IRF-1 in context of viral infections in vivo remains unknown. Here, we report that IRF-1 is essential to counteract the neuropathology of vesicular stomatitis virus (VSV). IFN- and IRF-1-dependent antiviral responses act sequentially to create a layered antiviral protection program against VSV infections. Upon intranasal infection, VSV is cleared in the presence or absence of IRF-1 in peripheral organs, but IRF-1^−/− mice continue to propagate the virus in the brain and succumb. Although rapid IFN induction leads to a decline in VSV titers early on, viral replication is re-enforced in the brains of IRF-1^−/− mice. While IFN provides short-term protection, IRF-1 is induced with delayed kinetics and controls viral replication at later stages of infection. IRF-1 has no influence on viral entry but inhibits viral replication in neurons and viral spread through the CNS, which leads to fatal inflammatory responses in the CNS. These data support a temporal, non-redundant antiviral function of type I IFN and IRF-1, the latter playing a crucial role in late time points of VSV infection in the brain.     

The Essential,Nonredundant Roles of RIG-I and MDA5 in Detecting and Controlling West Nile Virus Infection

Virus recognition and response by the innate immune system are critical components of host defense against infection. Activation of cell-intrinsic immunity and optimal priming of adaptive immunity against West Nile virus (WNV), an emerging vector-borne virus, depend on recognition by RIG-I and MDA5, two cytosolic pattern recognition receptors (PRRs) of the RIG-I-like receptor (RLR) protein family that recognize viral RNA and activate defense programs that suppress infection. We evaluated the individual functions of RIG-I and MDA5 both in vitro and in vivo in pathogen recognition and control of WNV. Lack of RIG-I or MDA5 alone results in decreased innate immune signaling and virus control in primary cells in vitro and increased mortality in mice. We also generated RIG-I^−/− × MDA5^−/− double-knockout mice and found that a lack of both RLRs results in a complete absence of innate immune gene induction in target cells of WNV infection and a severe pathogenesis during infection in vivo, similar to findings for animals lacking MAVS, the central adaptor molecule for RLR signaling. We also found that RNA products from WNV-infected cells but not incoming virion RNA display at least two distinct pathogen-associated molecular patterns (PAMPs) containing 5′ triphosphate and double-stranded RNA that are temporally distributed and sensed by RIG-I and MDA5 during infection. Thus, RIG-I and MDA5 are essential PRRs that recognize distinct PAMPs that accumulate during WNV replication. Collectively, these experiments highlight the necessity and function of multiple related, cytoplasmic host sensors in orchestrating an effective immune response against an acute viral infection.     

ISG15 is critical in the control of Chikungunya virus infection independent of UbE1L mediated conjugation

Chikungunya virus (CHIKV) is a re-emerging alphavirus that has caused significant disease in the Indian Ocean region since 2005. During this outbreak, in addition to fever, rash and arthritis, severe cases of CHIKV infection have been observed in infants. Challenging the notion that the innate immune response in infants is immature or defective, we demonstrate that both human infants and neonatal mice generate a robust type I interferon (IFN) response during CHIKV infection that contributes to, but is insufficient for, the complete control of infection. To characterize the mechanism by which type I IFNs control CHIKV infection, we evaluated the role of ISG15 and defined it as a central player in the host response, as neonatal mice lacking ISG15 were profoundly susceptible to CHIKV infection. Surprisingly, UbE1L^−/− mice, which lack the ISG15 E1 enzyme and therefore are unable to form ISG15 conjugates, displayed no increase in lethality following CHIKV infection, thus pointing to a non-classical role for ISG15. No differences in viral loads were observed between wild-type (WT) and ISG15^−/− mice, however, a dramatic increase in proinflammatory cytokines and chemokines was observed in ISG15^−/− mice, suggesting that the innate immune response to CHIKV contributes to their lethality. This study provides new insight into the control of CHIKV infection, and establishes a new model for how ISG15 functions as an immunomodulatory molecule in the blunting of potentially pathologic levels of innate effector molecules during the host response to viral infection.     

High Basal Expression of Interferon-Stimulated Genes in Human Bronchial Epithelial (BEAS-2B) Cells Contributes to Influenza A Virus Resistance

Respiratory epithelial cells play a key role in influenza A virus (IAV) pathogenesis and host innate response. Transformed human respiratory cell lines are widely used in the study of IAV−host interactions due to their relative convenience, and inherent difficulties in working with primary cells. Transformed cells, however, may have altered susceptibility to virus infection. Proper characterization of different respiratory cell types in their responses to IAV infection is therefore needed to ensure that the cell line chosen will provide results that are of relevance in vivo. We compared replication kinetics of human H1N1 (A/USSR/77) IAVs in normal primary human bronchial epithelial (NHBE) and two commonly used respiratory epithelial cell lines namely BEAS-2B and A549 cells. We found that IAV replication was distinctly poor in BEAS-2B cells in comparison with NHBE, A549 and Madin-Darby canine kidney (MDCK) cells. IAV resistance in BEAS-2B cells was accompanied by an activated antiviral state with high basal expression of interferon (IFN) regulatory factor-7 (IRF-7), stimulator of IFN genes (STING) and IFN stimulated genes (ISGs). Treatment of BEAS-2B cells with a pan-Janus-activated-kinase (JAK) inhibitor decreased IRF-7 and ISG expression and resulted in increased IAV replication. Therefore, the use of highly resistant BEAS-2B cells in IAV infection may not reflect the cytopathogenicity of IAV in human epithelial cells in vivo.     

Regulation of endothelial cell adhesion molecule expression by mast cells, macrophages, and neutrophils

Background

Leukocyte adhesion to the vascular endothelium and subsequent transendothelial migration play essential roles in the pathogenesis of cardiovascular diseases such as atherosclerosis. The leukocyte adhesion is mediated by localized activation of the endothelium through the action of inflammatory cytokines. The exact proinflammatory factors, however, that activate the endothelium and their cellular sources remain incompletely defined.

Methods and Results

Using bone marrow-derived mast cells from wild-type, Tnf^−/−, Ifng^−/−, Il6^−/− mice, we demonstrated that all three of these pro-inflammatory cytokines from mast cells induced the expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), P-selectin, and E-selectin in murine heart endothelial cells (MHEC) at both mRNA and protein levels. Compared with TNF-α and IL6, IFN-γ appeared weaker in the induction of the mRNA levels, but at protein levels, both IL6 and IFN-γ were weaker inducers than TNF-α. Under physiological shear flow conditions, mast cell-derived TNF-α and IL6 were more potent than IFN-γ in activating MHEC and in promoting neutrophil adhesion. Similar observations were made when neutrophils or macrophages were used. Neutrophils and macrophages produced the same sets of pro-inflammatory cytokines as did mast cells to induce MHEC adhesion molecule expression, with the exception that macrophage-derived IFN-γ showed negligible effect in inducing VCAM-1 expression in MHEC.

Conclusion

Mast cells, neutrophils, and macrophages release pro-inflammatory cytokines such as TNF-α, IFN-γ, and IL6 that induce expression of adhesion molecules in endothelium and recruit of leukocytes, which is essential to the pathogenesis of vascular inflammatory diseases.