Beschreibung: The Fas receptor/ligand system plays a prominent role in hepatic apoptosis and hepatocyte death. Although hepatitis B virus (HBV) surface Ag (HBsAg) is the most abundant HBV protein in the liver and peripheral blood of patients with chronic HBV infection, its role in Fas-mediated hepatocyte apoptosis has not been disclosed. In this study, we report that HBsAg sensitizes HepG2 cells to agonistic anti-Fas Ab CH11-induced apoptosis through increasing the formation of SDS-stable Fas aggregation and procaspase-8 cleavage but decreasing both the expression of cellular FLIP L/S and the recruitment of FLIP L/S at the death-inducing signaling complex (DISC). Notably, HBsAg increased endoplasmic reticulum stress and consequently reduced AKT phosphorylation by deactivation of phosphoinositide-dependent kinase-1 (PDPK1) and mechanistic target of rapamycin complex 2 (mTORC2), leading to enhancement of Fas-mediated apoptosis. In a mouse model, expression of HBsAg in mice injected with recombinant adenovirus-associated virus 8 aggravated Jo2-induced acute liver failure, which could be effectively attenuated by the AKT activator SC79. Based on these results, it is concluded that HBsAg predisposes hepatocytes to Fas-mediated apoptosis and mice to acute liver failure via suppression of AKT prosurviving activity, suggesting that interventions directed at enhancing the activation or functional activity of AKT may be of therapeutic value in Fas-mediated progressive liver cell injury and liver diseases.

Beschreibung: Enterovirus 71 (EV71) induces significantly elevated levels of cytokines and chemokines, leading to local or systemic inflammation and severe complications. As shown in our previous study, microRNA (miR) 302c regulates influenza A virus–induced IFN expression by targeting NF-B-inducing kinase. However, little is known about the role of the miR-302 cluster in EV71-mediated proinflammatory responses. In this study, we found that the miR-302 cluster controls EV71-induced cytokine expression. Further studies demonstrated that karyopherin α2 (KPNA2) is a direct target of the miR-302 cluster. Interestingly, we also found that EV71 infection upregulates KPNA2 expression by downregulating miR-302 cluster expression. Upon investigating the mechanisms behind this event, we found that KPNA2 intracellularly associates with JNK1/JNK2 and p38, leading to translocation of those transcription factors from the cytosol into the nucleus. In EV71-infected patients, miR-302 cluster expression was downregulated and KPNA2 expression was upregulated compared with controls, and their expression levels were closely correlated. Taken together, our work establishes a link between the miR-302/ KPNA2 axis and EV71-induced cytokine expression and represents a promising target for future antiviral therapy.

Beschreibung: Lymphatic vessels remove and transport excess interstitial fluid to lymph nodes (LNs) for fluid balance and immune protection. LNs are typically surrounded by perinodal adipose tissue (PAT). However, PAT is a blood vessel–rich but lymphatic-rare tissue; therefore, how excess fluid in PAT is removed remains unclear. Using C57BL/6 mice, fluorescent dye tracing and transmission electron microscopy results suggest that fluid in PAT can travel to the LN via collagen I + channels (PAT-LN conduits), merge into a collagen-rich space between the PAT and LN capsule (PAT-LN sinus), and may enter the LN via the LN capsule–associated conduits. This newly identified route of fluid flow allows fluid to enter the draining LN even when the afferent lymphatic vessels are blocked, indicating that fluid trafficking in PAT-LN conduits is not dependent on functional lymphatic vessels. Similar to lymphatic vessels, PAT-LN conduits can deliver Ags to the LN for immune protection. Additionally, Staphylococcus aureus from intradermal or i.v. infection may use PAT-LN conduits to infect PAT and stimulate PAT immune protection. Our studies revealed a new route of material exchange between PAT and the LN. Ag accumulation and bacterial infection in PAT demonstrate that PAT not only provides energy and regulatory factors, but can also directly participate in immune protection, indicating a new immune function of PAT for host immunity.

Beschreibung: Cytokine storm has been postulated as one of the major causes of mortality in patients with severe respiratory viral infections such as influenza. With the help of an influenza Ag- specific mouse experimental system, we report that CD4 + T cells contribute effector cytokines leading to lung inflammation in acute influenza. Although virus can no longer be detected from tissues 14 d postinfection, virus-derived Ag continues to drive a CD4 + T cell response after viral clearance. Ag-specific CD4 + T cells proliferate and evolve into memory CD4 + T cells efficiently, but the production of effector cytokines is seriously hampered during this phase. This decoupling of proliferation and effector cytokine production doesn’t appear in conjunction with increased suppression by regulatory T cells or decreased induction of transcription factors. Rather, GATA-3 and ROR-t levels are elevated when compared with cells that have effector cytokine production. T-bet dominance over GATA-3 and ROR-t decreases with the disarmament of effector cytokine production. Importantly, upon reinfection, these decoupled cells produce elevated levels of IFN- and were effective in virus eradication. These results provide a mechanism through altered T-bet dominance to dampen the cytokine storm without impeding the generation of memory T cells in influenza virus infection.

Beschreibung: The alveolar epithelium is characteristically abnormal in fibrotic lung disease, and we recently established a direct link between injury to the type II alveolar epithelial cell (AEC) and the accumulation of interstitial collagen. The mechanisms by which damage to the epithelium induces lung scarring remain poorly understood. It is particularly controversial whether an insult to the type II AEC initiates an inflammatory response that is required for the development of fibrosis. To explore whether local inflammation occurs following a targeted epithelial insult and contributes to lung fibrosis, we administered diphtheria toxin to transgenic mice with type II AEC–restricted expression of the diphtheria toxin receptor. We used immunophenotyping techniques and diphtheria toxin receptor–expressing, chemokine receptor-2–deficient (CCR2 –/– ) mice to determine the participation of lung leukocyte subsets in pulmonary fibrogenesis. Our results demonstrate that targeted type II AEC injury induces an inflammatory response that is enriched for CD11b + nonresident exudate macrophages (ExM) and their precursors, Ly-6C high monocytes. CCR2 deficiency abrogates the accumulation of both cell populations and protects mice from fibrosis, weight loss, and death. Further analyses revealed that the ExM are alternatively activated and that ExM and Ly-6C high monocytes express mRNA for IL-13, TGF-β, and the collagen genes, COL1A1 and COLIIIA1. Furthermore, the accumulated ExM and Ly-6C high monocytes contain intracellular collagen, as detected by immunostaining. Together, these results implicate CCR2 and the accumulation of ExM and Ly-6C high monocytes as critical determinants of pulmonary fibrosis induced by selective type II AEC injury.

Beschreibung: 3-Methyladenine (3-MA) is one of the most commonly used inhibitors in autophagy research today. However, rather than inhibiting class III PI3K that is involved in autophagy suppression, 3-MA might also interfere with class I PI3K and consequently augment autophagy flux. In this study, we aim to get a thorough understanding on the action mechanisms of 3-MA in TLR4-mediated inflammatory responses in RAW264.7 macrophages and, moreover, to decipher the action of 3-MA in modulation of autophagy. We found that 3-MA could enhance LPS-induced NF-B activation and production of TNF-α, inducible NO synthase (iNOS), cyclooxygenase-2, IL-1β, and IL-12. In contrast, 3-MA suppressed LPS-induced IFN-β production and STAT signaling. Studies revealed that 3-MA can, through inhibition of Akt as a result of class I PI3K interference, positively regulate p38, JNK, and p65, but negatively regulate TANK-binding kinase 1 and IFN regulatory factor 3 mediated by TLR4. As glycogen synthase kinase 3β (GSK3β) is an important Akt substrate, we further explored its involvement in the actions of 3-MA. 3-MA was found to enhance LPS-induced NF-B activation, iNOS, and pro–IL-1β expression, and these actions were reversed by either GSK3β inhibitors or small interfering GSK3β. Lastly, we demonstrated that 3-MA acts as an autophagy inducer in RAW264.7 macrophages, but the stimulating effects on NF-B activation and iNOS and cyclooxygenase-2 expression were not affected in LPS-stimulated macrophages with small interfering autophagy protein-5 treatment. These results not only shed new light on the action mechanisms of 3-MA to differentially regulate inflammatory outcomes derived from TLR4-mediated MyD88 and Toll/IL-1R domain-containing adapter inducing IFN-β pathways, but also highlight the necessity to check autophagy status upon taking 3-MA as a general autophagy inhibitor.

Beschreibung: Hemorrhagic manifestations occur frequently accompanying a wide range of dengue disease syndromes. Much work has focused on the contribution of immune factors to the pathogenesis of hemorrhage, but how dengue virus (DENV) participates in the pathogenic process has never been explored. Although there is no consensus that apoptosis is the basis of vascular permeability in human dengue infections, we showed in dengue hemorrhage mouse model that endothelial cell apoptosis is important to hemorrhage development in mice. To explore the molecular basis of the contribution of DENV to endothelial cell death, we show in this study that DENV protease interacts with cellular IBα and IBβ and cleaves them. By inducing IBα and IBβ cleavage and IB kinase activation, DENV protease activates NF-B, which results in endothelial cell death. Intradermal inoculation of DENV protease packaged in adenovirus-associated virus-9 induces endothelial cell death and dermal hemorrhage in mice. Although the H51 activity site is not involved in the interaction between DENV protease and IB-α/β, the enzymatic activity is critical to the ability of DENV protease to induce IBα and IBβ cleavage and trigger hemorrhage development. Moreover, overexpression of IBα or IBβ protects endothelial cells from DENV-induced apoptosis. In this study, we show that DENV protease participates in the pathogenesis of dengue hemorrhage and discover IBα and IBβ to be the new cellular targets that are cleaved by DENV protease.

Beschreibung: Dengue virus (DENV) is the causative agent of dengue fever, dengue hemorrhagic fever, and dengue shock syndrome and is endemic to tropical and subtropical regions of the world. Our previous studies showed the existence of epitopes in the C-terminal region of DENV nonstructural protein 1 (NS1) which are cross-reactive with host Ags and trigger anti–DENV NS1 Ab–mediated endothelial cell damage and platelet dysfunction. To circumvent these potentially harmful events, we replaced the C-terminal region of DENV NS1 with the corresponding region from Japanese encephalitis virus NS1 to create chimeric DJ NS1 protein. Passive immunization of DENV-infected mice with polyclonal anti–DJ NS1 Abs reduced viral Ag expression at skin inoculation sites and shortened DENV-induced prolonged bleeding time. We also investigated the therapeutic effects of anti-NS1 mAb. One mAb designated 2E8 does not recognize the C-terminal region of DENV NS1 in which host–cross-reactive epitopes reside. Moreover, mAb 2E8 recognizes NS1 of all four DENV serotypes. We also found that mAb 2E8 caused complement-mediated lysis in DENV-infected cells. In mouse model studies, treatment with mAb 2E8 shortened DENV-induced prolonged bleeding time and reduced viral Ag expression in the skin. Importantly, mAb 2E8 provided therapeutic effects against all four serotypes of DENV. We further found that mAb administration to mice as late as 1 d prior to severe bleeding still reduced prolonged bleeding time and hemorrhage. Therefore, administration with a single dose of mAb 2E8 can protect mice against DENV infection and pathological effects, suggesting that NS1-specific mAb may be a therapeutic option against dengue disease.

Beschreibung: Most knowledge on NK cells is based on studies of what are now known as conventional NK cells in the mouse spleen or human peripheral blood. However, recent studies in mice indicate the presence of tissue-resident NK cells in certain organs, such as the liver, that display different markers and transcription factor dependencies as compared with conventional NK cells. In this study, we provide evidence from cytometry by time-of-flight analysis and humanized mice indicating that human CD49e – NK cells are tissue resident in the liver. Thus, these studies indicate that tissue-resident NK cells are evolutionarily conserved in humans and mice, providing a foundation to explore their role in human disease.

Beschreibung: The spatial and temporal Ag distribution determines the subsequent T cell and B cell activation at the distinct anatomical locations in the lymph node (LN). It is well known that LN conduits facilitate small Ag distribution in the LN, but the mechanism of how Ags travel along LN conduits remains poorly understood. In C57BL/6J mice, using FITC as a fluorescent tracer to study lymph distribution in the LN, we found that FITC preferentially colocalized with LN capsule–associated (LNC) conduits. Images generated using a transmission electron microscope showed that LNC conduits are composed of solid collagen fibers and are wrapped with fibroblastic cells. Superresolution images revealed that high-intensity FITC is typically colocalized with elastin fibers inside the LNC conduits. Whereas tetramethylrhodamine isothiocyanate appears to enter LNC conduits as effectively as FITC, fluorescently-labeled Alexa-555–conjugated OVA labels significantly fewer LNC conduits. Importantly, injection of Alexa-555–conjugated OVA with LPS substantially increases OVA distribution along elastin fibers in LNC conduits, indicating immune stimulation is required for effective OVA traveling along elastin in LN conduits. Finally, elastin fibers preferentially surround lymphatic vessels in the skin and likely guide fluid flow to the lymphatic vessels. Our studies demonstrate that fluid or small molecules are preferentially colocalized with elastin fibers. Although the exact mechanism of how elastin fibers regulate Ag trafficking remains to be explored, our results suggest that elastin can be a potentially new target to direct Ag distribution in the LN during vaccine design.