Mouse macrophage specific knockout of SIRT1 influences macrophage polarization and promotes angiotensin Ⅱ-induced abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) is a vascular degenerative disease. Macrophage polarization and the balance between classically activated macrophages (M1) and alternatively activated macrophages (M2) are crucial for AAA pathogenesis. The present study aims to investigate the roles of macrophage SIRT1 in AAA formation and macrophage polarization. We found that in mouse peritoneal macrophages, SIRT1 expression was decreased after M1 stimulation, but was enhanced after M2 stimulation. Results from SIRT1^flox/flox mice and macrophage specific SIRT1 knockout mice with treatment of angiotensin II (Ang II) for 4 weeks showed that macrophage specific deficiency of SIRT1 increased the incidence of AAA and exacerbated the severity, including more severe aneurysm types, enlarged diameter of the aneurysm and increased degradation of elastin. In mouse aortas, SIRT1 deficiency increased the pro-inflammatory M1 molecule inducible nitric oxide synthase (iNOS), and decreased M2 molecules such as arginase 1 (Arg1) and mannose receptor (MR). Furthermore, in peritoneal macrophages, SIRT1 deficiency increased the expression of M1 inflammatory molecules, but decreased the expression of M2 molecules. Overexpression of SIRT1 had the opposite effects. Thus, macrophage specific knockout of SIRT1 influences macrophage polarization and accelerates Ang II-induced AAA formation.     

Probiotic Bacillus amyloliquefaciens mediate M1 macrophage polarization in mouse bone marrow-derived macrophages

Depending on the microenvironment, macrophages can acquire distinct functional phenotypes, referred to as classically activated M1 and M2. M1 macrophages are considered potent effector cells that kill intracellular pathogens, and M2 macrophages promote the resolution of wound healing. In this study, we are interested to know whether probiotic Bacillus amyloliquefaciens (Ba) can induce macrophages polarization. Real-time fluorescence PCR analysis demonstrated that the expression of IL-1β, iNOS, TNF-α and IL-6 genes for M1 macrophages was significantly increased at 1.5 h after probiotic Ba treatment compared to the probiotic Ba-free treatment (P < 0.01), whereas the expression of M2 macrophage marker genes (Arg1, Fizz1, MR, Ym1) was decreased (P < 0.05). Furthermore, the phagocytic activity was dramatically increased in the Ba-treated BMDMs using a FITC-dextran endocytosis assay. Together, these findings indicated that probiotic Ba facilitated polarization of M1 macrophages and enhanced its phagocytic capacity. The results expanded our knowledge about probiotic function-involved macrophage polarization.     

Functional delivery of lncRNA TUG1 by endothelial progenitor cells derived extracellular vesicles confers anti-inflammatory macrophage polarization in sepsis via impairing miR-9-5p-targeted SIRT1 inhibition

The delivery of biomolecules by extracellular vesicles (EVs) derived from endothelial progenitor cells (EPCs) has been proven to ameliorate sepsis, yet the therapeutic mechanism remains to be elucidated. Taurine upregulated gene 1 (TUG1) is a long noncoding RNA (lncRNA) that is downregulated in sepsis. The current study was designed to explore the role of EPCs derived EVs transmitting TUG1 in macrophage polarization and macrophage-mediated inflammation in a cecal ligation and puncture (CLP)-induced sepsis mouse model. TUG1 was underexpressed in CLP-induced sepsis, and its reexpression induced anti-inflammatory macrophage polarization and suppressed macrophage-medicated inflammatory injury to the pulmonary vascular endothelium. EPCs derived EVs transmitted TUG1 to promote M2 macrophage polarization. Luciferase, RIP, and RNA pull-down assays showed that TUG1 could competitively bind to microRNA-9-5p (miR-9-5p) to upregulate the expression of sirtuin 1 (SIRT1). Furthermore, EPCs derived EVs transmitted TUG1 to promote M2 macrophage polarization through the impairment of miR-9-5p-dependent SIRT1 inhibition. Finally, EPCs derived EVs carrying TUG1 were verified to ameliorate sepsis-induced organ damage in the murine model. In summary, EPCs derived EVs transmit TUG1 to attenuate sepsis via macrophage M2 polarization. This study also highlights the proinflammatory mechanism associated with miR-9-5p-mediated inhibition of SIRT1, which contributes to a more comprehensive understanding of the pathogenesis of sepsis.Subject terms: Cell biology, Diseases     

Impaired macrophage autophagy increases the immune response in obese mice by promoting proinflammatory macrophage polarization

Recent evidence that excessive lipid accumulation can decrease cellular levels of autophagy and that autophagy regulates immune responsiveness suggested that impaired macrophage autophagy may promote the increased innate immune activation that underlies obesity. Primary bone marrow-derived macrophages (BMDM) and peritoneal macrophages from high-fat diet (HFD)-fed mice had decreased levels of autophagic flux indicating a generalized impairment of macrophage autophagy in obese mice. To assess the effects of decreased macrophage autophagy on inflammation, mice with a Lyz2-Cre-mediated knockout of Atg5 in macrophages were fed a HFD and treated with low-dose lipopolysaccharide (LPS). Knockout mice developed systemic and hepatic inflammation with HFD feeding and LPS. This effect was liver specific as knockout mice did not have increased adipose tissue inflammation. The mechanism by which the loss of autophagy promoted inflammation was through the regulation of macrophage polarization. BMDM and Kupffer cells from knockout mice exhibited abnormalities in polarization with both increased proinflammatory M1 and decreased anti-inflammatory M2 polarization as determined by measures of genes and proteins. The heightened hepatic inflammatory response in HFD-fed, LPS-treated knockout mice led to liver injury without affecting steatosis. These findings demonstrate that autophagy has a critical regulatory function in macrophage polarization that downregulates inflammation. Defects in macrophage autophagy may underlie inflammatory disease states such as the decrease in macrophage autophagy with obesity that leads to hepatic inflammation and the progression to liver injury.     

M2-like macrophages polarized by Foxp3− Treg-of-B cells ameliorate imiquimod-induced psoriasis

Our group have demonstrated that splenic B cells contributed to the CD4⁺CD25⁻ naive T cells conversion into CD4⁺CD25⁺Foxp3⁻ regulatory T cells without adding appended cytokines, named Treg-of-B cells which were potent suppressors of adaptive immunity. We like to investigate whether Treg-of-B cells could promote alternatively activated macrophage (M2 macrophages) polarization and alleviate inflammatory disease, psoriasis. In this study, we co-cultured the bone marrow-derived macrophages (BMDMs) with Treg-of-B cells under LPS/IFN-γ stimulation and analyzed the M2-associated gene and protein using qPCR, western blotting, and immunofluorescence staining. We also examined the therapeutic effect of Treg-of-B cell-induced M2 macrophage for skin inflammation using imiquimod (IMQ)-induced psoriatic mouse model. Our results showed that BMDMs co-cultured with Treg-of-B cells upregulated typical M2-associated molecules, including Arg-1, IL-10, Pdcd1lg2, MGL-1, IL-4, YM1/2 and CD206. In an inflammatory environment, TNF-α and IL-6 production by macrophages co-cultured with Treg-of-B cells was decreased significantly. The molecular mechanism revealed that Treg-of-B cells promoted M2 macrophage polarization via STAT6 activation in a cell contact-dependent manner. Moreover, the treatment with Treg-of-B cell-induced M2 macrophages attenuated the clinical manifestations of psoriasis, such as scaling, erythema and thickening in the IMQ-induced psoriatic mouse model. T cell activation in draining lymph nodes was decreased in the Treg-of-B cell-induced M2 macrophage group after IMQ application. In conclusion, our findings suggested that Foxp3⁻ Treg-of-B cells could induce alternatively activated M2 macrophages through STAT6 activation, providing a cell-based therapeutic strategy for psoriasis.     

Lymphangiogenesis in renal fibrosis arises from macrophages via VEGF-C/VEGFR3-dependent autophagy and polarization

Inflammation plays a crucial role in the occurrence and development of renal fibrosis, which ultimately results in end-stage renal disease (ESRD). There is new focus on lymphangiogenesis in the field of inflammation. Recent studies have revealed the association between lymphangiogenesis and renal fibrosis, but the source of lymphatic endothelial cells (LECs) is not clear. It has also been reported that macrophages are involved in lymphangiogenesis through direct and indirect mechanisms in other tissues. We hypothesized that there was a close relationship between macrophages and lymphatic endothelial progenitor cells in renal fibrosis. In this study, we demonstrated that lymphangiogenesis occurred in a renal fibrosis model and was positively correlated with the degree of fibrosis and macrophage infiltration. Compared to resting (M0) macrophages and alternatively activated (M2) macrophages, classically activated (M1) macrophages predominantly transdifferentiated into LECs in vivo and in vitro. VEGF-C further increased M1 macrophage polarization and transdifferentiation into LECs by activating VEGFR3. It was suggested that VEGF-C/VEGFR3 pathway activation downregulated macrophage autophagy and subsequently regulated macrophage phenotype. The induction of autophagy in macrophages by rapamycin decreased M1 macrophage polarization and differentiation into LECs. These results suggested that M1 macrophages promoted lymphangiogenesis and contributed to newly formed lymphatic vessels in the renal fibrosis microenvironment, and VEGF-C/VEGFR3 signaling promoted macrophage M1 polarization by suppressing macrophage autophagy and then increased the transdifferentiation of M1 macrophages into LECs.Subject terms: Lymphangiogenesis, End-stage renal disease     

Mycobacterium tuberculosis-Induced Polarization of Human Macrophage Orchestrates the Formation and Development of Tuberculous Granulomas In Vitro

The tuberculous granuloma is an elaborately organized structure and one of the main histological hallmarks of tuberculosis. Macrophages, which are important immunologic effector and antigen-presenting cells, are the main cell type found in the tuberculous granuloma and have high plasticity. Macrophage polarization during bacterial infection has been elucidated in numerous recent studies; however, macrophage polarization during tuberculous granuloma formation and development has rarely been reported. It remains to be clarified whether differences in the activation status of macrophages affect granuloma formation. In this study, the variation in macrophage polarization during the formation and development of tuberculous granulomas was investigated in both sections of lung tissues from tuberculosis patients and an in vitro tuberculous granuloma model. The roles of macrophage polarization in this process were also investigated. Mycobacterium tuberculosis (M. tuberculosis) infection was found to induce monocyte-derived macrophage polarization. In the in vitro tuberculous granuloma model, macrophage transformation from M1 to M2 was observed over time following M. tuberculosis infection. M2 macrophages were found to predominate in both necrotic and non-necrotic granulomas from tuberculosis patients, while both M1 and M2 polarized macrophages were found in the non-granulomatous lung tissues. Furthermore, it was found that M1 macrophages promote granuloma formation and macrophage bactericidal activity in vitro, while M2 macrophages inhibit these effects. The findings of this study provide insights into the mechanism by which M. tuberculosis circumvents the host immune system as well as a theoretical foundation for the development of novel tuberculosis therapies based on reprogramming macrophage polarization.     

Chlamydia psittaci plasmid-encoded CPSIT_P7 induces macrophage polarization to enhance the antibacterial response through TLR4-mediated MAPK and NF-κB pathways

Although the protective effects of Chlamydia psittaci plasmid-encoded protein CPSIT_P7 as vaccine antigens to against chlamydial infection have been confirmed in our previous study, the function and mechanism of CPSIT_P7 inducing innate immunity in the antibacterial response remain unknown. Here, we found that plasmid protein CPSIT_P7 could induce M1 macrophage polarization upregulating the genes of the surface molecule CD86, proinflammatory cytokines (TNF-α, IL-6, and IL-1β), and antibacterial effector NO synthase 2 (iNOS). During M1 macrophage polarization, macrophages acquire phagocytic and microbicidal competence, which promotes the host antibacterial response. As we observed that CPSIT_P7-induced M1 macrophages could partially reduce the infected mice pulmonary Chlamydia psittaci load. Furthermore, CPSIT_P7 induced M1 macrophage polarization through the TLR4-mediated MAPK and NF-κB pathways. Collectively, our results highlight the effect of CPSIT_P7 on macrophage polarization and provide new insights into new prevention and treatment strategies for chlamydial infection.     

Dynamic expression of microRNAs in M2b polarized macrophages associated with systemic lupus erythematosus

Macrophage polarization contributes to the initiation and perpetuation of systemic lupus erythematosus (SLE). Our previous study demonstrated that M2b polarized macrophages induced by activated lymphocyte-derived DNA (ALD-DNA) have a crucial function in the initiation and progress of SLE disease. Accumulated data suggest that microRNAs (miRNAs) serve as critical regulators to control macrophage polarization. To investigate miRNA regulation during macrophage M2b polarization of SLE, miRNA microarrays of murine bone marrow derived macrophages (BMDMs) were performed following stimulation with ALD-DNA for 6 and 36 h. Over 11% of the 1111 analyzed miRNAs appeared differentially expressed during ALD-DNA triggered macrophage M2b polarization. Cluster analysis revealed certain patterns in miRNA expression that are closely linked to ALD-DNA induced macrophage M2b polarization. Analysis of the network structure showed that the predicted functions of the differentially regulated miRNAs at 6 h are significantly associated with inflammatory response and disease. Differentially regulated miRNAs identified at 36 h were determined to be significantly related to cell proliferation by biological network analysis. In this study, dynamic miRNA expression patterns and network analysis are described for the first time during ALD-DNA induced macrophage M2b polarization. The data not only provide a better understanding of miRNA-mediated macrophage polarization but also demonstrate the future therapeutic potential of targeting miRNAs in SLE patients.     

Crosstalk of renal cell carcinoma cells and tumor-associated macrophages aggravates tumor progression by modulating muscleblind-like protein 2/B-cell lymphoma 2/beclin 1-mediated autophagy

Background aimsM2-polarized tumor-associated macrophages contribute to the development of multiple human cancers, including renal cell carcinoma (RCC). However, the crosstalk mechanism between M2 macrophages and RCC remains unclear.MethodsThe authors constructed a co-culture system of M2 macrophages differentiated from THP-1 and RCC cells. Microscopic examination and quantitative real?time polymerase chain reaction (qRT-PCR) validated the morphology and types of macrophages. The proliferation, migration and invasion of RCC cells were assessed by Cell Counting Kit 8 (Dojindo Molecular Technologies, Inc, Santa Clara, CA, USA) and Transwell assay (Corning, Corning, NY, USA). Messenger RNA (mRNA) and protein expression of target molecules was detected by qRT?PCR and western blotting. Expression of Ki-67, E-cadherin and N-cadherin was measured by immunofluorescence staining or immunohistochemistry. Molecular interaction was evaluated by RNA pull-down, RNA immunoprecipitation and co-immunoprecipitation. A xenograft model was established to determine tumor growth in vivo.ResultsRCC cells triggered the activation of M2 macrophages. Functionally, M2-polarized macrophages facilitated the growth, migration, invasion and epithelial–mesenchymal transition of RCC cells by suppressing autophagy, whereas rapamycin, an activator of autophagy, significantly counteracted the tumor-promoting effects of M2 macrophages. Mechanistically, M2 macrophage-derived C-C motif chemokine 2 (CCL2) enhanced modulation of muscleblind-like protein 2 (MBNL2) expression. MBNL2 raised the stability of B-cell lymphoma 2 (Bcl-2) by directly binding to Bcl-2 mRNA, which endowed RCC cells with malignant properties via inhibition of beclin 1-dependent autophagy.ConclusionsRCC-induced M2-polarized macrophages secrete CCL2 to promote the growth and metastasis of RCC cells via inhibition of MBNL2/Bcl-2/beclin 1-mediated autophagy, which provide a novel perspective for the development of a therapeutic strategy for -RCC.     

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AimsDysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression.MethodsThis study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR.ResultsFACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003).ConclusionsIn DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.     

A comparative study on root and bark extracts of Eleutherococcus senticosus and their effects on human macrophages

BackgroundEleutherococcus senticosus or Siberian ginseng is a medicinal plant containing adaptogenic substances believed to regulate immune responses. Both, the root and stem bark are commonly used in traditional medicines.PurposeThe purpose of the present study is to chemically characterize E. senticosus root and bark extracts and to compare their effects on functions of human primary macrophages.Study design and methodsHPLC-DAD-MS analysis was used to characterize chemical constituents of alcoholic extracts from E. senticosus root and bark. The data obtained and available databases were combined for network pharmacology analysis. Involvement of predicted pathways was further functionally confirmed by using monocyte-derived human macrophages and endotoxin-free E. senticosus root and bark extracts.ResultsChemical analysis showed that the root extract contained more syringin, caffeic acid, and isofraxidin than the bark extract. At variance, bark extract contained more sesamin and oleanolic acid. Coniferyl aldehyde and afzelin were below the limit of quantification in both extracts. Network pharmacology analysis indicated that constituents of E. senticosus might affect the immune cell phenotype and signaling pathways involved in cell metabolism and cytoskeleton regulation. Indeed, both extracts promoted actin polymerization, migration, and phagocytosis of E. coli by macrophages pointing to macrophage polarization towards the M2 phenotype. In addition, treatment with E. senticosus root and bark extracts decreased phosphorylation of Akt on Ser473 and significantly reduced expression of the hemoglobin scavenger receptor CD163 by macrophages. Neither extract affected expression of CD11b, CD80, or CD64 by macrophages. In addition, macrophages treated with the bark extract, but not with the root extract, exhibited activated p38 MAPK and NF-κB and released increased, but still moderate, amounts of proinflammatory TNF-α and IL-6, anti-inflammatory IL-10, and chemotactic CCL1, which all together point to a M2b-like macrophage polarization. Differently, the root extract increased the IL-4-induced expression of anti-inflammatory CD200R. These changes in monocytes are in agreement with an increased M2a macrophage polarization.ConclusionThe ability of E. senticosus root and bark extracts to promote polarization of human macrophages towards anti-inflammatory M2a and M2b phenotypes, respectively, might underlay the immunoregulatory activities and point to potential wound healing promoting effects of this medicinal plant.     

Hypoxic glioma-derived exosomes promote M2-like macrophage polarization by enhancing autophagy induction

Exosomes participate in intercellular communication and glioma microenvironment modulation, but the exact mechanisms by which glioma-derived exosomes (GDEs) promote the generation of the immunosuppressive microenvironment are still unclear. Here, we investigated the effects of GDEs on autophagy, the polarization of tumor-associated macrophages (TAMs), and glioma progression. Compared with normoxic glioma-derived exosomes (N-GDEs), hypoxic glioma-derived exosomes (H-GDEs) markedly facilitated autophagy and M2-like macrophage polarization, which subsequently promoted glioma proliferation and migration in vitro and in vivo. Western blot and qRT-PCR analyses indicated that interleukin 6 (IL-6) and miR-155-3p were highly expressed in H-GDEs. Further experiments showed that IL-6 and miR-155-3p induced M2-like macrophage polarization via the IL-6-pSTAT3-miR-155-3p-autophagy-pSTAT3 positive feedback loop, which promotes glioma progression. Our study clarifies a mechanism by which hypoxia and glioma influence autophagy and M2-like macrophage polarization via exosomes, which could advance the formation of the immunosuppressive microenvironment. Our findings suggest that IL-6 and miR-155-3p may be novel biomarkers for diagnosing glioma and that treatments targeting autophagy and the STAT3 pathway may contribute to antitumor immunotherapy.Subject terms: Cancer microenvironment, Autophagy     

No evidence of altered alveolar macrophage polarization,but reduced expression of TLR2, in bronchoalveolar lavage cells in sarcoidosis

Background

Sarcoidosis is a granulomatous inflammatory disease, possibly of infectious aetiology. We aimed to investigate whether the degree of functional polarization of alveolar macrophages (AMs), or Toll-like receptor (TLR) expression, is associated with sarcoidosis or with distinct clinical manifestations of this disease.

Methods

Total BAL cells (cultured four or 24 h in medium, or stimulated 24 h with LPS) from 14 patients and six healthy subjects, sorted AMs from 22 patients (Löfgren''s syndrome n = 11) and 11 healthy subjects, and sorted CD4+ T cells from 26 patients (Löfgren''s syndrome n = 13) and seven healthy subjects, were included. Using real-time PCR, the relative gene expression of IL-10, IL-12p35, IL-12p40, IL-23p19, CCR2, CCR7, iNOS, CXCL10, CXCL11, CXCL16, CCL18, CCL20, CD80, and CD86, and innate immune receptors TLR2, TLR4, and TLR9, was quantified in sorted AMs, and for selected genes in total BAL cells, while IL-17A was quantified in T cells.

Results

We did not find evidence of a difference with regard to alveolar macrophage M1/M2 polarization between sarcoidosis patients and healthy controls. TLR2 gene expression was significantly lower in sorted AMs from patients, particular in Löfgren''s patients. CCL18 gene expression in AMs was significantly higher in patients compared to controls. Additionally, the IL-17A expression was lower in Löfgren''s patients'' CD4+ T cells.

Conclusions

Overall, there was no evidence for alveolar macrophage polarization in sarcoidosis. However, there was a reduced TLR2 mRNA expression in patients with Löfgren''s syndrome, which may be of relevance for macrophage interactions with a postulated sarcoidosis pathogen, and for the characteristics of the ensuing T cell response.     

Dioscin elicits anti‐tumour immunity by inhibiting macrophage M2 polarization via JNK and STAT3 pathways in lung cancer

Tumour‐associated macrophage (TAM) is an important component in tumour microenvironment. Generally, TAM exhibits the function of M2‐like macrophage, which was closely related to angiogenesis and tumour progression. Dioscin, a natural steroidal saponin, has shown its powerful anti‐tumour activity recently. However, the mechanism of dioscin involved in immune regulation is still obscure. Here, we observed dioscin induced macrophage M2‐to‐M1 phenotype transition in vitro and inhibited IL‐10 secretion. Meanwhile, the phagocytosis of macrophages was enhanced. In subcutaneous lung tumour models, dioscin inhibited the augmentation of M2 macrophage populations. Furthermore, dioscin down‐regulated STAT3 and JNK signalling pathways in macrophages in vitro. In BMDMs, activating JNK and inhibiting STAT3 induce macrophages to M1 polarization while inhibiting JNK and activating STAT3 to M2 polarization. Additionally, condition mediums from dioscin‐pre‐treated macrophages inhibited the migration of 3LL cells and the tube‐formation capacity of HUVECs. What's more, dioscin‐mediated macrophage polarization inhibited the in vivo metastasis of 3LL cells. In conclusion, dioscin may act as a new anti‐tumour agent by inhibiting TAMs via JNK and STAT3 pathways in lung cancer.     

Type I Interferon Induction Is Detrimental during Infection with the Whipple's Disease Bacterium,Tropheryma whipplei

Macrophages are the first line of defense against pathogens. Upon infection macrophages usually produce high levels of proinflammatory mediators. However, macrophages can undergo an alternate polarization leading to a permissive state. In assessing global macrophage responses to the bacterial agent of Whipple''s disease, Tropheryma whipplei, we found that T. whipplei induced M2 macrophage polarization which was compatible with bacterial replication. Surprisingly, this M2 polarization of infected macrophages was associated with apoptosis induction and a functional type I interferon (IFN) response, through IRF3 activation and STAT1 phosphorylation. Using macrophages from mice deficient for the type I IFN receptor, we found that this type I IFN response was required for T. whipplei-induced macrophage apoptosis in a JNK-dependent manner and was associated with the intracellular replication of T. whipplei independently of JNK. This study underscores the role of macrophage polarization in host responses and highlights the detrimental role of type I IFN during T. whipplei infection.