E3 ubiquitin ligase NEDD4L negatively regulates inflammation by promoting ubiquitination of MEKK2.

Aberrant activation of inflammation signaling triggered by tumor necrosis factor α (TNF-α), interleukin-1 (IL-1), and interleukin-17 (IL-17) is associated with immunopathology. Here, we identify neural precursor cells expressed developmentally down-regulated gene 4-like (NEDD4L), a HECT type E3 ligase, as a common negative regulator of signaling induced by TNF-α, IL-1, and IL-17. NEDD4L modulates the degradation of mitogen-activated protein kinase kinase kinase 2 (MEKK2) via constitutively and directly binding to MEKK2 and promotes its poly-ubiquitination. In interleukin-17 receptor (IL-17R) signaling, Nedd4l knockdown or deficiency enhances IL-17-induced p38 and NF-κB activation and the production of proinflammatory cytokines and chemokines in a MEKK2-dependent manner. We further show that IL-17-induced MEKK2 Ser520 phosphorylation is required not only for downstream p38 and NF-κB activation but also for NEDD4L-mediated MEKK2 degradation and the subsequent shutdown of IL-17R signaling. Importantly, Nedd4l-deficient mice show increased susceptibility to IL-17-induced inflammation and aggravated symptoms of experimental autoimmune encephalomyelitis (EAE) in IL-17R signaling-dependent manner. These data suggest that NEDD4L acts as an inhibitor of IL-17R signaling, which ameliorates the pathogenesis of IL-17-mediated autoimmune diseases.

E3 ubiquitin ligase NEDD4L negatively regulates keratinocyte hyperplasia by promoting GP130 degradation.

Psoriasis is mainly characterized by abnormal hyperplasia of keratinocytes and immune cells infiltrating into the dermis and epidermis. Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is a highly conserved HECT type E3 ligase that plays an important role in regulating physiological and pathological processes. Here, we identify NEDD4L as a negative regulator of psoriasis. Nedd4l significantly inhibits imiquimod (IMQ)-induced skin hyperplasia, and this effect is attributed to the inhibitory effect of NEDD4L on IL-6/GP130 signaling in keratinocytes. Mechanistically, NEDD4L directly interacts with GP130 and mediates its Lys-27-linked ubiquitination and proteasomal degradation. Moreover, the expression of NEDD4L is downregulated in the epidermis from IMQ-treated mice and psoriasis patients and negatively correlates with the protein levels of GP130 and p-STAT3 in clinical samples. Collectively, we uncover an inhibitory role of NEDD4L in the pathogenesis of psoriasis and suggest a new therapeutic strategy for the treatment of psoriasis.

The cytosolic nucleic acid sensor LRRFIP1 mediates the production of type I interferon via a beta-catenin-dependent pathway.

Intracellular nucleic acid sensors detect microbial RNA and DNA and trigger the production of type I interferon. However, the cytosolic nucleic acid-sensing system remains to be fully identified. Here we show that the cytosolic nucleic acid-binding protein LRRFIP1 contributed to the production of interferon-beta (IFN-beta) induced by vesicular stomatitis virus (VSV) and Listeria monocytogenes in macrophages. LRRFIP1 bound exogenous nucleic acids and increased the expression of IFN-beta induced by both double-stranded RNA and double-stranded DNA. LRRFIP1 interacted with beta-catenin and promoted the activation of beta-catenin, which increased IFN-beta expression by binding to the C-terminal domain of the transcription factor IRF3 and recruiting the acetyltransferase p300 to the IFN-beta enhanceosome via IRF3. Therefore, LRRFIP1 and its downstream partner beta-catenin constitute another coactivator pathway for IRF3-mediated production of type I interferon.

A phase I/II clinical trial on the efficacy and safety of NKT cells combined with gefitinib for advanced EGFR-mutated non-small-cell lung cancer.

BACKGROUND: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib, have achieved good efficacy in EGFR mutation-positive non-small-cell lung cancer (NSCLC) patients, but eventual drug resistance is inevitable. Thus, new TKI-based combination therapies should be urgently explored to extend the overall survival time of these patients. CD8 + CD56+ natural killer T (NKT) cells are a natural and unique subset of lymphocytes in humans that present characteristics of T and NK cells and exert cytotoxicity on tumour cells in a granzyme B-dependent manner. The aim of this trial was to explore the efficacy and safety of CD8 + CD56+ NKT cell immunotherapy combined with gefitinib in patients with advanced EGFR-mutated NSCLC. METHODS: The study was designed as a prospective, randomized, controlled, open-label, phase I/II trial that includes 30 patients with EGFR mutation-positive stage III/IV NSCLC. All patients will be randomized in blocks at a 1:1 ratio and treated with gefitinib 250 mg/day monotherapy or combination therapy with allogeneic CD8 + CD56+ NKT cell infusions twice per month for 12 cycles or until disease progression occurs. The effectiveness of this treatment will be evaluated based on by progression-free survival (PFS), the time to progression (TTP), overall response rate (ORR), disease control rate (DCR) and overall survival (OS). The safety of the trail is being assessed based on adverse events (AEs). Recruitment and data collection, which started in December 2017, are ongoing. DISCUSSION: Although immunotherapy, including programmed death-1/programmed death-1 ligand (PD-1/PD-L1) immunotherapy, has been used for NSCLC treatment with or without EGFR-TKIs, its clear efficacy still has not been shown. Assessing the safety and therapeutic potential of allogeneic CD8 + CD56+ NKT killer cells in combination with EGFR-TKIs in NSCLC will be of great interest. TRIAL REGISTRATION: This trial (Phase I/II Trails of NKT Cell in Combination With Gefitinib For Non Small Cell Lung Cancer) was registered on 21 November 2017 with www.chictr.org.cn , ChiCTR-IIR-17013471 .

Phosphatase SHP-1 promotes TLR- and RIG-I-activated production of type I interferon by inhibiting the kinase IRAK1.

Unbalanced production of proinflammatory cytokines and type I interferons in immune responses may lead to immunopathology; thus, the mechanisms that ensure the beneficial production of proinflammatory cytokines and type I interferons are of particular importance. Here we demonstrate that the phosphatase SHP-1 negatively regulated Toll-like receptor-mediated production of proinflammatory cytokines by inhibiting activation of the transcription factor NF-kappaB and mitogen-activated protein kinase. Simultaneously, SHP-1 increased the production of type I interferon mediated by Toll-like receptors and the helicase RIG-I by directly binding to and inhibiting activation of the kinase IRAK1. Our data demonstrate that SHP-1 contributes to immune homeostasis by balancing the production of proinflammatory cytokines and type I interferons in the innate immune response.

Raf Kinase Inhibitor Protein Preferentially Promotes TLR3-Triggered Signaling and Inflammation.

Raf kinase inhibitor protein (RKIP) protects against host immunological responses in nematodes and Drosophila Whether RKIP functions in innate immune responses in mammals remains unknown. In this article, we report that RKIP preferentially regulates the TLR3-mediated immune response in macrophages. RKIP deficiency or silencing significantly decreases polyinosinic:polycytidylic acid [Poly(I:C)]-induced IFN-ß, IL-6, and TNF-α production without affecting the counterpart induced by LPS or CpG. Compared with their wild-type counterparts, RKIP-deficient mice produce less IFN-ß, IL-6, and TNF-α in serum and display decreased lethality upon peritoneal Poly(I:C) plus d-galactosamine injection. Mechanistically, RKIP interacts with TBK1 and promotes the Poly(I:C)-induced TANK-binding kinase 1/IRF3 activation. Simultaneously, RKIP enhances the Poly(I:C)-induced interaction between TGF-ß-activated kinase 1 and MAPK kinase 3 (MKK3), thus promoting MKK3/6 and p38 activation. We further demonstrated that Poly(I:C) treatment, but not LPS treatment, induces RKIP phosphorylation at S109. This action is required for RKIP to promote TANK-binding kinase 1 activation, as well as the interaction between TGF-ß-activated kinase 1 and MKK3, which lead to activation of the downstream IRF3 and p38, respectively. Therefore, RKIP acts as a positive-feedback regulator of the TLR3-induced inflammatory response and may be a potential therapeutic target for inflammatory disease.

Fas signal promotes the immunosuppressive function of regulatory dendritic cells via the ERK/ß-catenin pathway.

Dendritic cells (DCs) play important roles in the initiation of immune response and also in the maintenance of immune tolerance. Now, many kinds of regulatory DCs with different phenotypes have been identified to suppress immune response and contribute to the control of autoimmune diseases. However, the mechanisms by which regulatory DCs can be regulated to exert the immunosuppressive function in the immune microenvironment remain to be fully investigated. In addition, how T cells, once activated, can feedback affect the function of regulatory DCs during immune response needs to be further identified. We previously identified a unique subset of CD11b(hi)Ia(low) regulatory DCs, differentiated from mature DCs or hematopoietic stem cells under a stromal microenvironment in spleen and liver, which can negatively regulate immune response in a feedback way. Here, we show that CD11b(hi)Ia(low) regulatory DCs expressed high level of Fas, and endothelial stromal cell-derived TGF-ß could induce high expression of Fas on regulatory DCs via ERK activation. Fas ligation could promote regulatory DCs to inhibit CD4(+) T cell proliferation more significantly. Furthermore, Fas ligation preferentially induced regulatory DCs to produce IL-10 and IP-10 via ERK-mediated inactivation of GSK-3 and subsequent up-regulation of ß-catenin. Interestingly, activated T cells could promote regulatory DCs to secrete more IL-10 and IP-10 partially through FasL. Therefore, our results demonstrate that Fas signal, at least from the activated T cells, can promote the immunosuppressive function of Fas-expressing regulatory DCs, providing a new manner for the regulatory DCs to regulate adaptive immunity.

Fei-Yan-Qing-Hua decoction attenuates influenza virus infection by enhancing host antiviral response through microbiota-derived acetate.

Background: Fei-Yan-Qing-Hua decoction (FYQHD) is derived from the well-known Ma Xing Shi Gan decoction, which was documented in Zhang Zhong Jing's "Treatise on Exogenous Febrile Disease" during the Han Dynasty. Although FYQHD has been used in the treatment of pneumonia and has demonstrated clinical efficacy for decades, the underlying mechanism by which FYQHD protects against influenza virus infection through modulation of gut flora remains unclear. Here, we examined the regulatory impacts of FYQHD on an influenza virus-infected mouse model and explored the mechanisms involved. Methods: An infectious mouse model was created by intranasal instillation of influenza A virus (IAV). The effectiveness of FYQHD was assessed through various measures, including weight loss, lung wet/dry ratio, oxidative stress levels, viral load in lung tissues, and intestinal injuries. Changes in gut microbiota and SCFA production were also examined. Results: The results showed that FYQHD significantly reduced viral load, increased the production of type I interferon (IFN-I), and restored the integrity of the intestinal barrier following IAV challenge. Additionally, FYQHD significantly corrected the dysbiosis of gut microbiota induced by influenza virus infection, enhancing the abundance of SCFA-producing bacteria and acetate production. However, the depletion of gut microbiota significantly attenuated the protective effects of FYQHD against influenza virus infection. In vitro, the antiviral effect of acetate was demonstrated through the upregulation of concentrations of IFN-ß. Conclusion: FYQHD attenuates influenza virus-induced lung and intestinal injuries by boosting the host antiviral response through increasing the abundance of Lachnospiraceae_NK4A136 and Roseburia, along with elevated acetate levels. The study advances our understanding of the therapeutic mechanisms of FYQHD and provides a theoretical basis for the application of FYQHD in the treatment of influenza.

Ste20-Like Kinase TAOK1 Positively Regulates Antiviral Responses by Controlling the TBK1-IRF3 Signaling Axis.

The cytosolic viral nucleic acid-sensing pathways converge on the protein kinase TANK-binding kinase 1 (TBK1) and the transcription factor interferon (IFN)-regulatory factor 3 (IRF3) to induce type I IFN production and antiviral immune responses. However, the mechanism that triggers the binding of TBK1 and IRF3 after virus infection remains not fully understood. Here, we identified that thousand and one kinase 1 (TAOK1), a Ste20-like kinase, positively regulated virus-induced antiviral immune responses by controlling the TBK1-IRF3 signaling axis. Virus invasion downregulated the expression of TAOK1. TAOK1 deficiency resulted in decreased nucleic acid-mediated type I IFN production and increased susceptibility to virus infection. TAOK1 was constitutively associated with TBK1 independently of the mitochondrial antiviral signaling protein MAVS. TAOK1 promoted IRF3 activation by enhancing TBK1-IRF3 complex formation. TAOK1 enhanced virus-induced type I IFN production in a kinase activity-dependent manner. Viral infection induced TAOK1 to bind with dynein instead of microtubule-associated protein 4 (MAP4), leading to the trafficking of TBK1 to the perinuclear region to bind IRF3. Thus, the depolymerization of microtubule impaired virus-mediated IRF3 activation. Our results revealed that TAOK1 functioned as a new interaction partner and regulated antiviral signaling via trafficking TBK1 along microtubules to bind IRF3. These findings provided novel insights into the function of TAOK1 in the antiviral innate immune response and its related clinical significance.

ZDHHC9 promotes colon tumor growth by inhibiting effector T cells.

Zinc finger DHHC-type palmitoyltransferase 9 (ZDHHC9) has been reported to play an important role in the occurrence and development of several types of cancer. However, its effects on colon cancer growth remain unclear. Using Gene Expression Profiling Interactive Analysis and Tumor Immune Estimation Resource, data obtained from The Cancer Genome Atlas were analyzed, and the results showed that ZDHHC9 was highly expressed in colon cancer and that patients with higher ZDHHC9 expression levels had a worse prognosis. Inhibition of ZDHHC9 expression promoted the proliferation of colon cancer cells in vitro but decreased their growth in vivo. Additionally, inhibition of ZDHHC9 expression in cancer cells enhanced CD8+ T cell-mediated cytotoxicity in vitro and increased CD8+ T infiltration and activation in vivo. Furthermore, ZDHHC9 promoted IFN-γ-induced JAK/STAT1 activation and upregulated programmed death-ligand 1 (PD-L1) expression in colon cancer cells. In conclusion, the present findings showed that ZDHHC9 promoted colon cancer growth by upregulating the expression of PD-L1 and inhibiting the function of CD8+ T cells.

Dracorhodin targeting CMPK2 attenuates inflammation: A novel approach to sepsis therapy.

BACKGROUND: Despite all modern advances in medicine, an effective drug for treating sepsis has yet to be found. The discovery of CMPK2 spurred hopes for the treatment of sepsis. However, CMPK2-untapped target inhibitors are still an enormous obstacle that has hindered the CMPK2-centric treatment of sepsis. METHODS: Here, we found that the CMPK2 gene is highly expressed in the whole blood of sepsis patients by RNA-Seq. First, recombinant CMPK2 was purified by a eukaryotic expression purification system, and the activity of recombinant CMPK2 was detected by the ADP-GLO assay. Second, we developed an affinity MS strategy combined with quantitative lysine reactivity profiling to discover CMPK2 ligands from the active ingredients of Chinese herbs. In addition, the dissociation constant Kd of the ligand and the target protein CMPK2 was further detected by microscale thermophoresis technology. Third, we used this strategy to identify a naturally sourced small molecule, dracorhodin (DP). Using mass spectrometry-based quantitative lysine reactivity profiling combined with a series of mutant tests, the results show that K265 acts as a bright hotspot of DP inhibition of CMPK2. Fourth, immune-histochemical staining, ELISAs, RT-qPCR, flow cytometry and immunoblotting were used to illustrate the potential function and related mechanism of DP in regulating sepsis injury. RESULTS: Our results suggest that DP exerts powerful anti-inflammatory effects by regulating the NLRP3 inflammasome via the lipopolysaccharide (LPS)-induced CMPK2 pathway. Strikingly, DP significantly attenuated LPS-induced sepsis in a mouse model, but its effect was weakened in mice with myeloid-specific Cmpk2 ablation. CONCLUSION: We provide a new framework that provides more valuable information for new therapeutic approaches to sepsis, including the establishment of screening strategies and the development of target drugs to provide a theoretical basis for ultimately improving clinical outcomes for sepsis patients. Collectively, these findings reveal that DP is a promising CMPK2 inhibitor for the treatment of sepsis.

Scaffolding adaptor protein Gab1 is required for TLR3/4- and RIG-I-mediated production of proinflammatory cytokines and type I IFN in macrophages.

RIG-I-like helicases and TLRs are critical sensors in the induction of type I IFN and proinflammatory cytokines to initiate innate immunity against invading pathogens. However, the mechanisms for the full activation of TLR and RIG-I-triggered innate response remain to be fully investigated. Grb2-associated binder 1 (Gab1), a member of scaffolding/adaptor proteins, can mediate signal transduction from many receptors, however, whether and how Gab1 is required for TLR and RIG-I-triggered innate responses remain unknown. In this study, we demonstrated that Gab1 significantly enhances TLR4-, TLR3-, and RIG-I-triggered IL-6, IL-1beta, and IFN-alpha/beta production in macrophages. Gab1 knockdown in primary macrophages or Gab1 deficiency in mouse embryonic fibroblasts significantly suppresses TLR3/4- and RIG-I-triggered production of IL-6, IL-1beta, and IFN-alpha/beta. Consistently, Gab1 deficiency impairs vesicular stomatitis virus (VSV) infection-induced IFN-alpha/beta production. In addition to promoting both MyD88- and TLR/IL-1 receptor domain-containing adaptor protein inducing IFN-beta-dependent MAPKs and NF-kappaB activation, Gab1 enhances PI3K/Akt activation by directly binding p85 in TLR signaling and VSV infection. Accordingly, Gab1 inhibits VSV replication and VSV infection-induced cell damage by inducing type I IFNs and IFN-inducible gene expression via PI3K/Akt pathway. Therefore, Gab1 is needed for full activation of TLR3/4- and RIG-I-triggered innate responses by promoting activation of PI3K/Akt, MAPKs, and NF-kappaB pathways.

MEF2C promotes M1 macrophage polarization and Th1 responses.

The polarization of macrophages to the M1 or M2 phenotype has a pivotal role in inflammation and host defense; however, the underlying molecular mechanism remains unclear. Here, we show that myocyte enhancer factor 2 C (MEF2C) is essential for regulating M1 macrophage polarization in response to infection and inflammation. Global gene expression analysis demonstrated that MEF2C deficiency in macrophages downregulated the expression of M1 phenotypic markers and upregulated the expression of M2 phenotypic markers. MEF2C significantly promoted the expression of interleukin-12 p35 subunit (Il12a) and interleukin-12 p40 subunit (Il12b). Myeloid-specific Mef2c-knockout mice showed reduced IL-12 production and impaired Th1 responses, which led to susceptibility to Listeria monocytogenes infection and protected against DSS-induced IBD in vivo. Mechanistically, we showed that MEF2C directly activated the transcription of Il12a and Il12b. These findings reveal a new function of MEF2C in macrophage polarization and Th1 responses and identify MEF2C as a potential target for therapeutic intervention in inflammatory and autoimmune diseases.

MicroRNA-146a feedback inhibits RIG-I-dependent Type I IFN production in macrophages by targeting TRAF6, IRAK1, and IRAK2.

Upon recognition of viral components by pattern recognition receptors, including TLRs and retinoic acid-inducible gene I (RIG-I)- like helicases, cells are activated to produce type I IFN and proinflammatory cytokines. These pathways are tightly regulated by host to prevent inappropriate cellular response, but viruses can down-regulate these pathways for their survival. Recently, identification of negative regulators for cytoplasmic RNA-mediated antiviral signaling, especially the RIG-I pathway, attract much attention. However, there is no report about negative regulation of RIG-I antiviral pathway by microRNAs (miRNA) to date. We found that vesicular stomatitis virus (VSV) infection up-regulated miR-146a expression in mouse macrophages in TLR-myeloid differentiation factor 88-independent but RIG-I-NF-kappaB-dependent manner. In turn, miR-146a negatively regulated VSV-triggered type I IFN production, thus promoting VSV replication in macrophages. In addition to two known miR-146a targets, TRAF6 and IRAK1, we proved that IRAK2 was another target of miR-146a, which also participated in VSV-induced type I IFN production. Furthermore, IRAK1 and IRAK2 participated in VSV-induced type I IFN production by associating with Fas-associated death domain protein, an important adaptor in RIG-I signaling, in a VSV infection-inducible manner. Therefore, we demonstrate that miR-146a, up-regulated during viral infection, is a negative regulator of the RIG-I-dependent antiviral pathway by targeting TRAF6, IRAK1, and IRAK2.

Alveolar and lung interstitial macrophages: Definitions, functions, and roles in lung fibrosis.

Mϕs are the main innate immune cells in the lung at homeostasis, with important roles in host defence and immune modulation. Alveolar Mϕs (AMs) and interstitial Mϕs (IMs) are the two lung Mϕ subsets, so called according to the sites they reside in. These subsets are also defined by their origins and immunological microenvironment, which endow these cells with distinct features and plasticity. This review summarizes the latest definitions and functions of lung Mϕs during homeostasis and provides exemplar of their divergent roles in lung fibrosis.

E3 ligase Nedd4l promotes antiviral innate immunity by catalyzing K29-linked cysteine ubiquitination of TRAF3.

Ubiquitination is one of the most prevalent protein posttranslational modifications. Here, we show that E3 ligase Nedd4l positively regulates antiviral immunity by catalyzing K29-linked cysteine ubiquitination of TRAF3. Deficiency of Nedd4l significantly impairs type I interferon and proinflammatory cytokine production induced by virus infection both in vitro and in vivo. Nedd4l deficiency inhibits virus-induced ubiquitination of TRAF3, the binding between TRAF3 and TBK1, and subsequent phosphorylation of TBK1 and IRF3. Nedd4l directly interacts with TRAF3 and catalyzes K29-linked ubiquitination of Cys56 and Cys124, two cysteines that constitute zinc fingers, resulting in enhanced association between TRAF3 and E3 ligases, cIAP1/2 and HECTD3, and also increased K48/K63-linked ubiquitination of TRAF3. Mutation of Cys56 and Cys124 diminishes Nedd4l-catalyzed K29-linked ubiquitination, but enhances association between TRAF3 and the E3 ligases, supporting Nedd4l promotes type I interferon production in response to virus by catalyzing ubiquitination of the cysteines in TRAF3.

The Emerging Roles of NDR1/2 in Infection and Inflammation.

The nuclear Dbf2-related (NDR) kinases NDR1 and NDR2 belong to the NDR/LATS (large tumor suppressor) subfamily in the Hippo signaling pathway. They are highly conserved from yeast to humans. It is well-known that NDR1/2 control important cellular processes, such as morphological changes, centrosome duplication, cell proliferation, and apoptosis. Recent studies revealed that NDR1/2 also play important roles in the regulation of infection and inflammation. In this review, we summarized the roles of NDR1/2 in the modulation of inflammation induced by cytokines and innate immune response against the infection of bacteria and viruses, emphasizing on how NDR1/2 regulate signaling transduction through Hippo pathway-dependent and -independent manners.

TAOK1 positively regulates TLR4-induced inflammatory responses by promoting ERK1/2 activation in macrophages.

Thousand and one amino acid kinase 1 (TAOK1) is a member of Ste20-like kinases, but its function in regulating inflammatory responses remains largely unknown. In this study, we identify TAOK1 as a positive regulator of TLR4-triggered inflammatory responses in macrophages. TAOK1 increases LPS-induced production of pro-inflammatory cytokine such as IL-6, TNF-α and IL12p40 in macrophages. TAOK1 deficient mice showed decreased susceptibility to endotoxin shock, with less pro-inflammatory cytokine production than control mice. TAOK1 promotes LPS-induced activation of ERK1/2 by constitutively interacting with TRAF6 and TPL2. These finding unravel the important role of TAOK1 as a positive regulator of TLR4-induced inflammatory responses.

Xuebijing Injection Alleviates Pam3CSK4-Induced Inflammatory Response and Protects Mice From Sepsis Caused by Methicillin-Resistant Staphylococcus aureus.

A leading cause of death worldwide is sepsis that develops as a dysregulated immune response to infection. Serious infection caused by methicillin-resistant Staphylococcus aureus (MRSA) increases the difficulty of treatment in septic patients. Host-directed therapy (HDT) is an emerging approach to bacterial infections. Xuebijing injection (XBJ), a commercialized injectable prescription from traditional Chinese medicine, has been used as adjuvant therapy for sepsis with a history of 15 years. Whether it plays a protective role in severe infection caused by antibiotic-resistant bacteria is still unknown. In this study, XBJ significantly improved the survival of MRSA-induced sepsis mice. In MRSA-infected mouse model, XBJ down-regulated the expression of inflammatory cytokines interleukin (IL)-6, tumor necrosis factor (TNF)-α, MCP-1, MIP-2, and IL-10 in sera. Besides that, it decreased the bacterial load in spleens, livers, and alleviated tissue damage of lung, liver, and kidney. The combination of XBJ with vancomycin or dexamethasone exhibited a better down-regulatory role of the inflammatory response. Then, the protective mechanism of XBJ was further investigated. XBJ inhibited heat-killed MRSA-induced IL-6 and TNF-α production in mouse macrophages. XBJ also decreased Pam3CSK4 (a synthetic tripalmitoylated lipopeptide mimicking bacterial lipoproteins)-stimulated expression of IL-6, TNF-α, IL-1ß, IL-12, etc. in mouse macrophages. Furthermore, XBJ down-regulated the activation of NF-κB, MAPK, and PI3K/Akt pathways in Pam3CSK4-stimulated mouse macrophages. In conclusion, our findings demonstrated that XBJ played a protective role in MRSA-challenged mice and down-regulated the inflammatory response and the activation of signaling pathways initiated by Pam3CSK4. It enlarged the clinical application of XBJ in the treatment of severe bacterial infection, e.g. caused by MRSA.