BACKGROUND:Colorectal cancer (CRC) progression is shaped by the tumor microenvironment, particularly tumor-associated macrophages (TAMs), which often adopt immunosuppressive functions. CD300e, a myeloid receptor involved in immune regulation, has an uncharacterized role in CRC. METHODS:Functional studies were conducted in azoxymethane/dextran sodium sulfate and MC38 murine CRC models using CD300e systemic and myeloid-specific CD300e knockout mice, and adoptive transfer experiments assessed macrophage-intrinsic effects. Human studies included analysis of CD300e expression in matched tumor and normal tissue from patients with CRC and in vitro co-culture of patient-derived colon tumor organoids with monocytes to study CD300e induction and TAM polarization. RESULTS:In vivo, CD300e deficiency led to reduced tumor burden, enhanced major histocompatibility complex expression on TAMs, and improved T-cell responses. CD300e-deficient macrophages exhibited increased phagocytic activity, antigen presentation, and support for T-cell proliferation and cytotoxicity. Adoptive transfer confirmed that macrophage-intrinsic CD300e expression is sufficient to suppress T-cell function and promote tumor growth. In patients with CRC, CD300e is selectively upregulated in tumor-infiltrating monocytes and macrophages, driving a suppressive phenotype marked by impaired antigen presentation. Tumor-derived signals in vitro induce CD300e expression and promote a protumorigenic macrophage profile. CONCLUSIONS:Our findings identify CD300e as a critical regulator of macrophage-mediated immune suppression in CRC and a potential target for reprogramming TAMs to enhance immunotherapy.

Microbial signals trigger the release of neutrophil extracellular traps (NETs) through peptidyl-arginine-deiminase-4 (PADI4). In turn, NETosis can propagate inflammation to distant tissues. We hypothesize that PADI4 mediates the interactions between diet-modified microbiota and host metabolism. We report that in the adipose tissue of individuals with obesity, NETosis was associated with dysglycemia. In mice, high-fat diet (HFD) induced not only dysmetabolism and meta-inflammation but also local and systemic signs of NETosis. Deleting Padi4 in hematopoietic cells (Padi4KO) blunted liver and adipose inflammation and improved metabolism under HFD. While NETs were able to disrupt gut epithelial integrity, abrogating NETosis preserved intestinal barrier function and mitigated metabolic endotoxemia due to HFD. Padi4 deletion did not prevent diet-induced dysbiosis, but Padi4KO mice were protected from intestinal hyper-permeability and metabolic impairment due to the transfer of HFD-modified microbiota. As Padi4KO did not blunt the dysmetabolic effects of LPS, we conclude that NETosis operates at the microbiota-intestinal interface, inducing hyperpermeability and the systemic spillover of bacterial-derived products, paving the way to the metabolic consequences of HFD. Finally, pharmacologic PADI4 inhibition recapitulated findings obtained in Padi4KO mice on metabolism and liver steatosis, thereby uncovering a druggable role for PADI4 in mediating the metabolic effects of unhealthy microbiota.

Several lines of evidence have linked the intestinal bacterium Helicobacter cinaedi with the pathogenesis of atherosclerosis, identifying the Cinaedi Antigen Inflammatory Protein (CAIP) as a key virulence factor. Oxidative stress and inflammation are crucial in sustaining the atherosclerotic process and oxidized LDL (oxLDL) uptake. Primary human macrophages and endothelial cells were pre-incubated with 10 µM diphenyl iodonium salt (DPI) and stimulated with 20 µg/mL CAIP. Lectin-like oxLDL receptor (LOX-1) expression was evaluated by FACS analysis, reactive oxygen species (ROS) production was measured using the fluorescent probe H2DCF-DA, and cytokine release was quantified by ELISA assay. Foam cells formation was assessed by Oil Red-O staining, and phosphorylation of p38 and ERK1/2 MAP kinases and NF-κB pathway activation were determined by Western blot. This study demonstrated that CAIP triggered LOX-1 over-expression and increased ROS production in both macrophages and endothelial cells. Blocking ROS abrogated LOX-1 expression and reduced LDL uptake and foam cells formation. Additionally, CAIP-mediated pro-inflammatory cytokine release was significantly affected by ROS inhibition. The signaling pathway induced by CAIP-induced oxidative stress led to p38 MAP kinase phosphorylation and NF-κB activation. These findings elucidate the mechanism of action of CAIP, which heightens oxidative stress and contributes to the atherosclerotic process in H. cinaedi-infected patients.

Tumor-associated macrophages (TAMs) are the predominant immune population within the tumor microenvironment (TME), playing a key role in promoting tumor growth and establishing an immunosuppressive environment that facilitate immune evasion. Here we report that the immune receptor CD300e is highly expressed by TAM in colorectal (CRC) and drives their immunosuppressive and pro-tumorigenic, correlating with reduced expression of MHC-II molecules, essential for antigen presentation. In vitro, CD300e-deficient macrophages exhibit enhanced pro-inflammatory activity and phagocytic capacity, coupled with reduced efferocytosis, suggesting a critical role for CD300e in promoting tumor progression. The depletion of CD300e, in vivo, results in a reduced tumor burden and enhanced survival in CRC mouse models, accompanied by a more robust anti-tumor immune response characterized by increased infiltration of activated CD4+ and CD8+ T cells producing IFN-γ. Our study provides comprehensive insights into the roles of CD300e in myeloid cells in CRC, highlighting its potential as a therapeutic target for reprogramming TAMs to support anti-tumor immunity. ### Competing Interest Statement The authors have declared no competing interest.

The Helicobacter pylori Neutrophil Activating Protein (HP-NAP) is endowed with immunomodulatory properties that make it a potential candidate for anticancer therapeutic applications. By activating cytotoxic Th1 responses, HP-NAP inhibits the growth of bladder cancer and enhances the anti-tumor activity of oncolytic viruses in the treatment of metastatic breast cancer and neuroendocrine tumors. The possibility that HP-NAP exerts its anti-tumor effect also by modulating the activity of innate immune cells has not yet been explored. Taking advantage of the zebrafish model, we examined the therapeutic efficacy of HP-NAP against metastatic human melanoma, limiting the observational window to 9 days post-fertilization, well before the maturation of the adaptive immunity. Human melanoma cells were xenotransplanted into zebrafish embryos and tracked in the presence or absence of HP-NAP. The behavior and phenotype of macrophages and the impact of their drug-induced depletion were analyzed exploiting macrophage-expressed transgenes. HP-NAP administration efficiently inhibited tumor growth and metastasis and this was accompanied by strong recruitment of macrophages with a pro-inflammatory profile at the tumor site. The depletion of macrophages almost completely abrogated the ability of HP-NAP to counteract tumor growth. Our findings highlight the pivotal role of activated macrophages in counteracting melanoma growth and support the notion that HP-NAP might become a new biological therapeutic agent for the treatment of metastatic melanomas.

The miniferritin HP-NAP of Helicobacter pylori was originally described as a neutrophil-activating protein because of the capacity to activate neutrophils to generate oxygen radicals and adhere to endothelia. Currently, the main feature for which HP-NAP is known is the ability to promote Th1 responses and revert the immune suppressive profile of macrophages. In this review, we discuss the immune modulating properties of the protein regarding the H. pylori infection and the evidence that support the potential clinical application of HP-NAP in allergy and cancer immunotherapy.

Tumor-associated macrophages (TAMs) are major components of the tumor microenvironment. In colorectal cancer (CRC), a strong infiltration of TAMs is accompanied by a decrease in effector T cells and an increase in the metastatic potential of CRC. We investigated the functional profile of TAMs infiltrating CRC tissue by immunohistochemistry, flow cytometry, ELISA, and qRT-PCR and their involvement in impairing the activation of effector T cells. In CRC biopsies, we evidenced a high percentage of macrophages with low expression of the antigen-presenting complex MHC-II and high expression of CD206. Monocytes co-cultured with tumor cells or a decellularized tumor matrix differentiated toward a pro-tumoral macrophage phenotype characterized by decreased expression of MHC-II and CD86 and increased expression of CD206 and an abundant release of pro-tumoral cytokines and chemokines. We demonstrated that the hampered expression of MHC-II in macrophages is due to the downregulation of the MHC-II transactivator CIITA and that this effect relies on increased expression of miRNAs targeting CIITA. As a result, macrophages become unable to present antigens to CD4 T lymphocytes. Our data suggest that the tumor microenvironment contributes to defining a pro-tumoral profile of macrophages infiltrating CRC tissue with impaired capacity to activate T cell effector functions.

CD300e is a surface receptor, expressed by myeloid cells, involved in the tuning of immune responses. CD300e engagement was reported to provide the cells with survival signals, to trigger the expression of activation markers and the release of pro-inflammatory cytokines. Hence, CD300e is considered an immune activating receptor. In this study, we demonstrate that the ligation of CD300e in monocytes hampers the expression of the human leukocyte antigen (HLA) class II, affecting its synthesis. This effect, which is associated with the transcription impairment of the signal transducer and activator of transcription 1 (STAT1), overcomes the capacity of interferon gamma (IFN-γ) to promote the expression of the antigen-presenting molecules. Importantly, the decreased expression of HLA-II on the surface of CD300e-activated monocytes negatively impacts their capacity to activate T cells in an antigen-specific manner. Notably, unlike in vitro- differentiated macrophages which do not express CD300e, the immune receptor is expressed by tissue macrophages. Taken together, our findings argue against the possibility that this molecule should be considered an activating immune receptor sensu stricto. Moreover, our results support the notion that CD300e might be a new player in the regulation of the expansion of T cell-mediated responses.

Macrophages have a major role in infectious and inflammatory diseases, and the available data suggest that Helicobacter pylori persistence can be explained in part by the failure of the bacterium to be killed by professional phagocytes. Macrophages are cells ready to kill the engulfed pathogen, through oxygen-dependent and -independent mechanisms; however, their killing potential can be further augmented by the intervention of T helper (Th) cells upon the specific recognition of human leukocyte antigen (HLA)-II–peptide complexes on the surface of the phagocytic cells. As it pertains to H. pylori, the bacterium is engulfed by macrophages, but it interferes with the phagosome maturation process leading to phagosomes with an altered degradative capacity, and to megasomes, wherein H. pylori resists killing. We recently showed that macrophages infected with H. pylori strongly reduce the expression of HLA-II molecules on the plasma membrane and this compromises the bacterial antigen presentation to Th lymphocytes. In this work, we demonstrate that H. pylori hampers HLA-II expression in macrophages, activated or non-activated by IFN-γ, by down-regulating the expression of the class II major histocompatibility complex transactivator (CIITA), the “master control factor” for the expression of HLA class II genes. We provided evidence that this effect relies on the up-regulation of let-7f-5p, let-7i-5p, miR-146b-5p, and -185-5p targeting CIITA. MiRNA expression analysis performed on biopsies from H. pylori-infected patients confirmed the up-regulation of let-7i-5p, miR-146b-5p, and -185-5p in gastritis, in pre-invasive lesions, and in gastric cancer. Taken together, our results suggest that specific miRNAs may be directly involved in the H. pylori infection persistence and may contribute to confer the risk of developing gastric neoplasia in infected patients.

Helicobacter pylori (HP) is a Gram-negative bacterium that chronically infects the stomach of more than 50% of human population and represents a major cause of gastric cancer, gastric lymphoma, gastric autoimmunity, and peptic ulcer. It still remains to be elucidated, which HP virulence factors are important in the development of gastric disorders. Here, we analysed the role of the HP protein HP1454 in the host-pathogen interaction. We found that a significant proportion of T cells isolated from HP patients with chronic gastritis and gastric adenocarcinoma proliferated in response to HP1454. Moreover, we demonstrated in vivo that HP1454 protein drives Th1/Th17 inflammatory responses. We further analysed the in vitro response of human T cells exposed either to an HP wild-type strain or to a strain with a deletion of the hp1454 gene, and we revealed that HP1454 triggers the T-cell antigen receptor-dependent signalling and lymphocyte proliferation, as well as the CXCL12-dependent cell adhesion and migration. Our study findings prove that HP1454 is a crucial bacterial factor that exerts its proinflammatory activity by directly modulating the T-cell response. The relevance of these results can be appreciated by considering that compelling evidence suggest that chronic gastric inflammation, a condition that paves the way to HP-associated diseases, is dependent on T cells.

Helicobacter pylori (HP) is a Gram-negative bacterium that chronically infects the stomach of more than 50% of human population and represents a major cause of gastric cancer, gastric lymphoma, gastric autoimmunity, and peptic ulcer. It still remains to be elucidated, which HP virulence factors are important in the development of gastric disorders. Here, we analysed the role of the HP protein HP1454 in the host–pathogen interaction. We found that a significant proportion of T cells isolated from HP patients with chronic gastritis and gastric adenocarcinoma proliferated in response to HP1454. Moreover, we demonstrated in vivo that HP1454 protein drives Th1/Th17 inflammatory responses. We further analysed the in vitro response of human T cells exposed either to an HP wild-type strain or to a strain with a deletion of the hp1454 gene, and we revealed that HP1454 triggers the T-cell antigen receptor-dependent signalling and lymphocyte proliferation, as well as the CXCL12-dependent cell adhesion and migration. Our study findings prove that HP1454 is a crucial bacterial factor that exerts its proinflammatory activity by directly modulating the T-cell response. The relevance of these results can be appreciated by considering that compelling evidence suggest that chronic gastric inflammation, a condition that paves the way to HP-associated diseases, is dependent on T cells.

Objective: To explore the effects of SERPINB3 administration in murine lupus models with a focus on lupus-like nephritis. Methods: 40 NZB/W F1 mice were subdivided into 4 groups and intraperitoneally injected with recombinant SERPINB3 (7.5 μg/0.1 mL or 15 μg/0.1 mL) or PBS (0.1 mL) before (group 1 and 2) or after (group 3 and 4) the development of proteinuria (≥100 mg/dl). Two additional mice groups were provided by including 20 MRL/lpr mice which were prophylactically injected with SERPINB3 (10 mice, group 5) or PBS (10 mice, group 6). Time of occurrence and levels of anti-dsDNA and anti-C1q antibodies, proteinuria and serum creatinine, overall- and proteinuria-free survival were assessed in mice followed up to natural death. Histological analysis was performed in kidneys of both lupus models. The Th17:Treg cell ratio was assessed by flow-cytometry in splenocytes of treated and untreated MRL/lpr mice. Statistical analysis was performed using non parametric tests and Kaplan-Meier curves, when indicated. Results: Autoantibody levels and proteinuria were significantly decreased and time of occurrence significantly delayed in SERPINB3-treated mice vs. controls. In agreement with these findings, proteinuria-free and overall survival were significantly improved in SERPINB3-treated groups vs. controls. Histological analysis demonstrated a lower prevalence of severe tubular lesions in kidneys of group 5 vs. group 6. SERPINB3-treated mice showed an overall trend toward a reduced prevalence of severe lesions in both strains. Th17:Treg ratio was significantly decreased in splenocytes of MRL/lpr mice treated with SERPINB3, compared to untreated control mice. Conclusions: SERPINB3 significantly improves disease course and delays the onset of severe glomerulonephritis in lupus-prone mice, possibly inducing a more tolerogenic immune phenotype.

Background Abnormal apoptosis and clearance of cellular debris concur to development of systemic lupus erythematosus (SLE). SERPINS (serin-protease inhibitors) are ancient molecules regulating immune homeostasis. SERPINB3 modulates apoptosis and is hypoexpressed on SLE B cells. Aim To explore the effects of SERPINB3 administration in murine lupus models, focusing on glomerulonephritis. Methods NZB/W F1 and MRL/lpr mice were used. 40 NZB/W F1 mice were divided into 4 groups of 10 mice each and intraperitoneally injected twice a week starting before occurrence of proteinuria traces (group 1 and 2, prophylactic approach) or after development of proteinuria 30 mg/dl (group 3 and 4, therapeutic approach) with hrSERPINB3 (7.5 µg/0.1 mL prophylactic approach, or 15 µg/0.1 mL therapeutic approach) or PBS (0.1 mL). 20 MRL/lpr mice were injected with hrSERPINB3 (group 5, n=10) or PBS (group 6, n=10) with a prophylactic approach. We assessed time of occurrence and titers of anti-dsDNA and anti-C1q antibodies by ELISA; proteinuria and serum creatinine; overall- and proteinuria-free survival. Six NZB/W F1 mice were sacrificed at week 27, while 10 MRL/lpr mice at week 13 and another 10 at 16/18 weeks for histological kidneys comparison. Flow-cytometry was performed on MRL/lpr splenocytes. Non parametric tests were performed for statistics; proteinuria-free (<300 mg/dl) and overall survival were evaluated by Kaplan-Meier method. Results Levels of autoantibodies were significantly decreased and delayed in group 1 vs group 2, group 3 vs group 4, and group 5 vs group 6 (p<0.0001 for all). Proteinuria levels were significantly reduced and proteinuria-free and overall survival were significantly improved in SERPINB3 groups vs controls (figure 1). No differences were found among creatinine serum levels. Histological analysis showed a lower prevalence of severe tubular lesions in group 5 vs group 6 MRL/lpr mice at week 16 (chi-squared p=0.014), and mice belonging to SERPINB3 groups showed a trend toward a reduced prevalence of severe glomerular and tubular lesions. Th17:Treg ratio significantly decreased due to a remarkable increase in Treg levels in MRL/lpr mice treated with SERPINB3. Conclusions Administration of SERPINB3 significantly improves disease and delays the onset of severe glomerulonephritis in lupus-prone mice. SERPINB3 may influence immune-cell function through immunoregulatory effects involving promotion of Treg.

Considerable progress has been made in the field of microfluidics to develop complex systems for modeling human skin and dermal wound healing processes. While microfluidic models have attempted to integrate multiple cell types and/or 3D culture systems, to date they have lacked some elements needed to fully represent dermal wound healing. This paper describes a cost-effective, multicellular microfluidic system that mimics the paracrine component of early inflammation close to normal wound healing. Collagen and Matrigel are tested as materials for coating and adhesion of dermal fibroblasts and human umbilical vein endothelial cells (HUVECs). The wound-on-chip model consists of three interconnecting channels and is able to simulate wound inflammation by adding tumor necrosis factor alpha (TNF-α) or by triculturing with macrophages. Both the approaches significantly increase IL-1β, IL-6, IL-8 in the supernatant (p < 0.05), and increases in cytokine levels are attenuated by cotreatment with an anti-inflammatory agent, Dexamethasone. Incorporation of M1 and M2 macrophages cocultured with fibroblasts and HUVECs leads to a stimulation of cytokine production as well as vascular structure formation, particularly with M2 macrophages. In summary, this wound-on-chip system can be used to model the paracrine component of the early inflammatory phase of wound healing and has the potential for the screening of anti-inflammatory compounds.