Rosalinda Sorrentino

The NOD/RIP2 Pathway Is Essential for Host Defenses Against Chlamydophila pneumoniae Lung Infection

Here we investigated the role of the Nod/Rip2 pathway in host responses to Chlamydophila pneumoniae–induced pneumonia in mice. Rip2−/− mice infected with C. pneumoniae exhibited impaired iNOS expression and NO production, and delayed neutrophil recruitment to the lungs. Levels of IL-6 and IFN-γ levels as well as KC and MIP-2 levels in bronchoalveolar lavage fluid (BALF) were significantly decreased in Rip2−/− mice compared to wild-type (WT) mice at day 3. Rip2−/− mice showed significant delay in bacterial clearance from the lungs and developed more severe and chronic lung inflammation that continued even on day 35 and led to increased mortality, whereas WT mice cleared the bacterial load, recovered from acute pneumonia, and survived. Both Nod1−/− and Nod2−/− mice also showed delayed bacterial clearance, suggesting that C. pneumoniae is recognized by both of these intracellular receptors. Bone marrow chimera experiments demonstrated that Rip2 in BM-derived cells rather than non-hematopoietic stromal cells played a key role in host responses in the lungs and clearance of C. pneumoniae. Furthermore, adoptive transfer of WT macrophages intratracheally was able to rescue the bacterial clearance defect in Rip2−/− mice. These results demonstrate that in addition to the TLR/MyD88 pathway, the Nod/Rip2 signaling pathway also plays a significant role in intracellular recognition, innate immune host responses, and ultimately has a decisive impact on clearance of C. pneumoniae from the lungs and survival of the infectious challenge.

TLR/MyD88 and liver X receptor alpha signaling pathways reciprocally control Chlamydia pneumoniae-induced acceleration of atherosclerosis.

Experimental and clinical studies link Chlamydia pneumoniae infection to atherogenesis and atherothrombotic events, but the underlying mechanisms are unclear. We tested the hypothesis that C. pneumoniae-induced acceleration of atherosclerosis in apolipoprotein E (ApoE)−/− mice is reciprocally modulated by activation of TLR-mediated innate immune and liver X receptor α (LXRα) signaling pathways. We infected ApoE−/− mice and ApoE−/− mice that also lacked TLR2, TLR4, MyD88, or LXRα intranasally with C. pneumoniae followed by feeding of a high fat diet for 4 mo. Mock-infected littermates served as controls. Atherosclerosis was assessed in aortic sinuses and in en face preparation of whole aorta. The numbers of activated dendritic cells (DCs) within plaques and the serum levels of cholesterol and proinflammatory cytokines were also measured. C. pneumoniae infection markedly accelerated atherosclerosis in ApoE-deficient mice that was associated with increased numbers of activated DCs in aortic sinus plaques and higher circulating levels of MCP-1, IL-12p40, IL-6, and TNF-α. In contrast, C. pneumoniae infection had only a minimal effect on atherosclerosis, accumulation of activated DCs in the sinus plaques, or circulating cytokine increases in ApoE−/− mice that were also deficient in TLR2, TLR4, or MyD88. However, C. pneumoniae-induced acceleration of atherosclerosis in ApoE−/− mice was further enhanced in ApoE−/−LXRα−/− double knockout mice and was accompanied by higher serum levels of IL-6 and TNF-α. We conclude that C. pneumoniae infection accelerates atherosclerosis in hypercholesterolemic mice predominantly through a TLR/MyD88-dependent mechanism and that LXRα appears to reciprocally modulate and reduce the proatherogenic effects of C. pneumoniae infection.

Chlamydia pneumoniae-Induced Foam Cell Formation Requires MyD88-Dependent and -Independent Signaling and Is Reciprocally Modulated by Liver X Receptor Activation

Chlamydia pneumoniae is detected by macrophages and other APCs via TLRs and can exacerbate developing atherosclerotic lesions, but how that occurs is not known. Liver X receptors (LXRs) centrally control reverse cholesterol transport, but also negatively modulate TLR-mediated inflammatory pathways. We isolated peritoneal macrophages from wild-type, TLR2, TLR3, TLR4, TLR2/4, MyD88, TRIF, MyD88/TRIF, and IFN regulatory factor 3 (IRF3) KO mice, treated them with live or UV-killed C. pneumoniae in the presence or absence of oxidized LDL, then measured foam cell formation. In some experiments, the synthetic LXR agonist GW3965 was added to macrophages infected with C. pneumoniae in the presence of oxidized LDL. Both live and UV-killed C. pneumoniae induced IRF3 activation and promoted foam cell formation in wild-type macrophages, whereas the genetic absence of TLR2, TLR4, MyD88, TRIF, or IRF3, but not TLR3, significantly reduced foam cell formation. C. pneumoniae-induced foam cell formation was significantly reduced by the LXR agonist GW3965, which in turn inhibited C. pneumoniae-induced IRF3 activation, suggesting a bidirectional cross-talk. We conclude that C. pneumoniae facilitates foam cell formation via activation of both MyD88-dependent and MyD88-independent (i.e., TRIF-dependent and IRF3-dependent) pathways downstream of TLR2 and TLR4 signaling and that TLR3 is not involved in this process. This mechanism could at least partly explain why infection with C. pneumoniae accelerates the development of atherosclerotic plaque and lends support to the proposal that LXR agonists might prove clinically useful in suppressing atherogenesis.

Involvement of Innate and Adaptive Immunity in a Murine Model of Coronary Arteritis Mimicking Kawasaki Disease

Kawasaki disease (KD) is the most common cause of acquired cardiac disease and acute vasculitis in children in the developed world. Injection of a cell wall extract isolated from Lactobacillus casei (LCCWE) into mice causes a focal coronary arteritis that histopathologically mimics the coronary lesions observed in KD patients. In this study we used this model to investigate the participation of T cells, B cells, and dendritic cells (DC) in the development of coronary arteritis. RAG1−/−, B cellnull, and wild-type (WT) mice were injected with a single dose of LCCWE (500 μg/mouse i.p.). None of the RAG1−/− mice developed coronary arteritis, whereas 70% of WT and 100% of B cellnull mice developed coronary lesions, indicating that T cells were required for lesion formation. When splenocytes isolated from LCCWE-treated mice were restimulated with LCCWE, we observed significant IFN-γ secretion in WT but not in RAG1−/− mice. Immunohistochemical staining showed F4/80+ macrophages, activated MIDC-8+ myeloid DCs (mDC), plasmacytoid DCs, and colocalization of CD3+ T cells with mDCs in coronary artery lesions, suggesting an Ag-driven process. T cells but not B cells are required for LCCWE-induced coronary arteritis. Similar to human lesions, the coronary lesions contain macrophages, activated mDCs, and plaslmacytoid DCs all in close proximity to T cells, further strengthening the relevance of this mouse model to the immunopathology of coronary disease in KD. These studies are consistent with the interpretation that macrophages and DCs may collaborate with T cells in the pathological mechanisms of coronary arteritis.

Inhibition of CD73 Improves B Cell-Mediated Anti-Tumor Immunity in a Mouse Model of Melanoma

CD73 is a cell surface enzyme that suppresses T cell-mediated immune responses by producing extracellular adenosine. Growing evidence suggests that targeting CD73 in cancer may be useful for an effective therapeutic outcome. In this study, we demonstrate that administration of a specific CD73 inhibitor, adenosine 5′-(α,β-methylene)diphosphate (APCP), to melanoma-bearing mice induced a significant tumor regression by promoting the release of Th1- and Th17-associated cytokines in the tumor microenvironment. CD8+ T cells were increased in melanoma tissue of APCP-treated mice. Accordingly, in nude mice APCP failed to reduce tumor growth. Importantly, we observed that after APCP administration, the presence of B cells in the melanoma tissue was greater than that observed in control mice. This was associated with production of IgG2b within the melanoma. Depletion of CD20+ B cells partially blocked the anti-tumor effect of APCP and significantly reduced the production of IgG2b induced by APCP, implying a critical role for B cells in the anti-tumor activity of APCP. Our results also suggest that APCP could influence B cell activity to produce IgG through IL-17A, which significantly increased in the tumor tissue of APCP-treated mice. In support of this, we found that in melanoma-bearing mice receiving anti–IL-17A mAb, the anti-tumor effect of APCP was ablated. This correlated with a reduced capacity of APCP-treated mice to mount an effective immune response against melanoma, as neutralization of this cytokine significantly affected both the CD8+ T cell- and B cell-mediated responses. In conclusion, we demonstrate that both T cells and B cells play a pivotal role in the APCP-induced anti-tumor immune response.

Lung cancer and Toll-like receptors

Lung carcinoma is one of the leading causes of death worldwide. It is a non-immunogenic cancer, resistant to immune surveillance. Toll-like receptors (TLRs) connect the innate to the adaptive immune system. Given that cancerous cells evade the immune system, the activation of TLRs could represent a potential target for cancer therapy. The induction of Th1-like and cytotoxic immunity by TLR signalling could lead to tumour cell death, resulting in tumour regression or arrest. However, basic research and clinical trials revealed that the activation of specific TLRs, such as TLR2, TLR4 and TLR9, do not have any anti-tumour activity in lung carcinoma. Increasing evidence suggests that TLRs are important regulators of tumour biology; however, little is known about their function in lung cancer. Thus, in order to develop new therapeutic approaches, further studies are needed to understand the connection between TLRs and lung cancer progression. This review focuses on the potential mechanisms by which TLR ligands can facilitate or not lung cancer and lung metastases establishment/progression.

The Uremic Toxin Indoxyl Sulphate Enhances Macrophage Response to LPS

Indoxyl sulphate (IS) is a protein-bound uremic toxin that results from the metabolism of dietary tryptophan normally excreted by kidney through the proximal tubules. Thus the toxin accumulates in the blood of patients with impaired renal function such as in chronic kidney disease (CKD). High IS serum levels in patients with CKD suggest its involvement in CKD progression and in the onset of complications. Its presence in plasma is also a powerful predictor of overall and cardiovascular morbidity/mortality. IS is a well known nephrovascular toxin but very little is known regarding its effects on the immune system and in particular during inflammation. In this study we examined the effect of IS on macrophage activation in response to lipopolysaccharide from E. coli (LPS), a gram negative bacterial endotoxin associated with inflammation and septic shock. To simulate the uremic condition, J774A.1 macrophages were incubated with IS at concentrations observed in uremic patients (1000–62.5 µM) both alone and during LPS challenge. IS alone induced release of reactive oxygen species (ROS), through a mechanism involving pro- and anti-oxidant systems, and alteration in intracellular calcium homeostasis. When added to J774A.1 macrophages in presence of LPS, IS significantly increased the nitric oxide (NO) release, inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX-2) expression. IS pre-treatment was also associated with an increase in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production by macrophages stimulated with LPS. Mechanistic studies revealed that IS increased LPS-induced NF-kB nuclear translocation, ROS release and altered calcium concentrations, mainly because of mitochondrial calcium overloading. Moreover also in primary mouse peritoneal macrophages IS enhances the inflammatory response to LPS increasing ROS, NO, iNOS, COX-2, TNF-α, IL-6 and NF-kB levels. This study provides evidences that IS stimulates macrophage function and enhances inflammatory reasponse associated with LPS, thus contributing to altered immune response dysfunctions observed in CKD.

Differential effects of Gram‐positive versus Gram‐negative bacteria on NOSII and TNFα in macrophages: role of TLRs in synergy between the two

1 Gram‐negative and Gram‐positive bacteria are sensed by Toll‐like receptor (TLR)4 and TLR2, respectively. TLR4 recruits MyD88 and TRIF, whereas TLR2 recruits MyD88 without TRIF. NOSII and TNFα are central genes in innate immunity and are thought to be differentially regulated by the MyD88 versus TRIF signalling pathways. Here, we have used Gram‐positive Staphylococcus aureus, Gram‐negative Escherichia coli and highly selective TLR ligands to establish the precise relationship between TLR2, TLR1, TLR6 and TLR4 for NOSII versus TNFα induction. 2 In murine macrophages at 24 h, E. coli or LPS (TLR4) induced NO and TNFα release. In contrast, S. aureus (TLR2/TLR1/TLR6) or Pam3CSK4 (TLR2/TLR1), or FSL‐1 and LTA (TLR2/TLR6) induced TNFα without an effect on NO. 3 At later time points (48–72 h), S. aureus induced NO release. The ability of S. aureus, but not E. coli or LPS, to induce NO release was inhibited by anti‐TNFα‐binding antibodies. 4 At 24 h, LPS synergised with TLR2 ligands to induce NO release and NOSII protein expression. LPS also induced the expression of TLR2 gene expression without affecting levels of TLR4. 5 Using cells from TLR2−/− or TLR4−/− mice, the ability of LPS to synergise with S. aureus or Pam3CSK4 was found to be dependent on both TLR2 and TLR4. 6 These observations are the first to clearly delineate the role of separately activating TLR2 and TLR4 in the induction of NOSII and TNFα genes compared with their coinduction when both receptor pathways are activated.

Polyinosinic-Polycytidylic Acid Limits Tumor Outgrowth in a Mouse Model of Metastatic Lung Cancer

Polyinosinic-polycytidylic acid (poly I:C), a TLR3 ligand, is currently being tested in human clinical trials as an adjuvant to anti-cancer vaccines and in combination with other therapies. However, little is known about its activity in established pulmonary metastasis. The aim of our study was to elucidate the effect of poly I:C (1, 10, or 100 μg/mouse) in a mouse model of B16-F10–induced metastatic lung cancer. Lung tumor growth was arrested after a single administration of poly I:C. This was associated with higher influx of mature dendritic cells (DCs), which drove toward a Th1-like, Th17-like, and cytotoxic immune environment. The interference with IFN type I receptor signaling by means of a specific mAb reversed poly I:C-mediated tumor regression due to lower presence of myeloid DCs, cytotoxic DCs (CD11c+CD8+), NKT cells, CD8+ T cells, and Th1-like cytokines. Moreover, the adoptive transfer of poly I:C-activated bone marrow-derived DCs into tumor-bearing mice resulted in activities similar to those of the systemic administration of poly I:C on lung tumor burden. In conclusion, our data prove that poly I:C has potential anti-tumor activity in a mouse model of established pulmonary metastasis. The activation of DCs and the production of IFN type I are responsible for an effective T cytotoxic immune response against metastatic lung cancer progression after poly I:C treatment.

B Cells Contribute to the Antitumor Activity of CpG-Oligodeoxynucleotide in a Mouse Model of Metastatic Lung Carcinoma

RATIONALE CpG-oligodeoxynucleotide (CpG-ODN; CpG), a Toll-like receptor-9 ligand, has been widely studied as a potential antitumor adjuvant. Toll-like receptor-9 is highly expressed on lung carcinoma tissues and some immune cells, such as plasmacytoid dendritic cells and B cells. OBJECTIVES The aim of our study was to elucidate the effect of CpG on B cells in a mouse model of lung carcinoma. METHODS C57Bl/6j, B cell-deficient, and Nude mice were intravenously implanted with the lung metastatic B16-F10 melanoma cells and killed 3 and 7 days after CpG administration. MEASUREMENTS AND MAIN RESULTS Administration of CpG increased lung tumor growth in B16-F10-implanted C57BL/6J mice. The genetic absence of B cells strongly facilitated CpG-induced tumor progression. In contrast, the adoptive transfer of CpG-activated B cells induced tumor arrest, associated with a reduced suppressive immune environment due to the lower recruitment of regulatory T cells, myeloid-derived suppressor cells, and CD8(+) regulatory T cells along with the reduced expression of suppressive cytokines such as IL-10 and transforming growth factor-β. Furthermore, concomitant with higher production of IFN-γ, the apoptosis rate in the lungs of mice adoptively transferred with CpG-activated B cells was increased. Depletion of mature CD20(+) B cells increased the lung tumor burden in CpG-treated C57BL/6J mice and nude mice. Moreover, nude mice had the same lung tumor burden as B cell-deficient mice when mature CD20(+) B cells were depleted. CONCLUSIONS Our data demonstrate the protective antitumor activity of CpG-activated B cells and shed light on CpG as an antitumor adjuvant for lung cancer therapy.