The nuclear receptor Nurr1 is preferentially expressed in human pro-inflammatory macrophages and limits their inflammatory profile.

Nurr1 is a member of the orphan nuclear receptor family NR4A (nuclear receptor subfamily 4 group A) that modulates inflammation in several cell lineages, both positively and negatively. Macrophages are key regulators of inflammatory responses, yet information about the role of Nurr1 in human macrophages is scarce. Here we examined Nurr1 expression and activity in steady state and activated human macrophages. Pro- and anti-inflammatory macrophages were generated in vitro by culture of blood monocytes with granulocyte/macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF), respectively. Nurr1 expression was predominant in macrophages with the pro-inflammatory phenotype. Nurr1 activation with the agonists 1,1-bis(3'-indolyl)-1-(p-chlorophenyl) methane (C-DIM12) or isoxazolo-pyridinone 7e (IP7e) did not globally modify the polarization status of pro-inflammatory macrophages, but they decreased their production of TNF, IL-1ß, IL-6, IL-8, IL-12 p40, CCL2, IFN-ß, and reactive oxygen species, with variable potencies. Conversely, Nurr1 deficient macrophages increased the expression of transcripts encoding inflammatory mediators, particularly that of IL6, IFNB1, and CCL2. Mechanistically, endogenous Nurr1 interacted with NF-κB p65 in basal conditions and upon lipopolysaccharide (LPS)-mediated activation. C-DIM12 stabilized those complexes in cells exposed to LPS and concurrently decreased NF-κB transcriptional activity and p65 nuclear translocation. Expression of high levels of Nurr1 was associated with a subset of dermal macrophages that display enhanced levels of TNF and lower expression of the anti-inflammatory marker CD163L1 in skin lesions from patients with bullous pemphigoid (BP), a chronic inflammatory autoimmune blistering disorder. These results suggest that Nurr1 expression is linked with the pro-inflammatory phenotype of human macrophages, both in vivo and in vitro, where it may constitute a brake to attenuate the synthesis of inflammatory mediators.

The Nurr7 agonist Cytosporone B differentially regulates inflammatory responses in human polarized macrophages.

The orphan nuclear receptor Nur77 is involved in diverse cellular processes such as inflammation, proliferation, differentiation and survival. Stimuli like lipopolysaccharide (LPS) and tumor necrosis factor (TNF) increase Nur77 expression in human and murine macrophages, and it has been proposed that Nur77 plays a major role in dampening the inflammatory response. Here, we evaluated the expression and function of Nur77 in human anti-inflammatory and pro-inflammatory macrophages derived from blood monocytes cultured with macrophage colony-stimulating factor (M-MDMs) or granulocyte/macrophage colony-stimulating factor (GM-MDMs), respectively. Nur77 mRNA expression was significantly enhanced in M-MDMs compared with GM-MDMs, both constitutively and upon exposure to Toll-like receptor (TLR)2, 3, and 4 ligands. Nur77 activation with the agonist Cytosporone B (CsnB) significantly suppressed the production of TNF, interleukin (IL)-1ß, IL-6, and IL-8 in GM-MDMs stimulated with LPS. In contrast, it tended to enhance the production of the anti-inflammatory cytokine IL-10. This effect was associated with reduced NF-κB p65 nuclear translocation. Similarly, Nur77 knockdown enhanced TNF production in GM-MDMs. CsnB effectively stimulated the transactivation activity of Nur77 in M-MDMs, but it did not alter cytokine synthesis or p65 nuclear translocation. However, Nur77 seemed to have a role in maintaining the anti-inflammatory profile of M-MDMs, since Nur77-deficient M-MDMs constitutively produced higher levels of TNF transcripts. Thus, in the absence of exogenous agonists, Nur77 activity favors the anti-inflammatory function of M-MDMs, whereas agonistic activation of this receptor preferentially drives attenuation of inflammation in inflammatory macrophages.

SORL1 Polymorphisms in Mexican Patients with Alzheimer's Disease.

The present study evaluated the risk effect of 12 Single Nucleotide Polymorphisms in the SORL1 gene in the Mexican population using Late-Onset Alzheimer's Disease (LOAD) and control subjects. Considering APOE as the strongest genetic risk factor for LOAD, we conducted interaction analyses between single nucleotide polymorphisms (SNPs) and the APOE genotype. METHODS: Patients were interviewed during their scheduled visits at neurologic and geriatric clinics from different institutions. The LOAD diagnosis included neurological, geriatric, and psychiatric examinations, as well as the medical history and neuroimaging. Polymorphisms in SORL1 were genotyped by real-time PCR in 156 subjects with LOAD and 221 controls. APOE genotype was determined in each study subject. Allelic, genotypic, and haplotypic frequencies were analyzed; an ancestry analysis was also performed. RESULTS: The A/A genotype in rs1784933 might be associated with an increased LOAD risk. Two blocks with high degree linkage disequilibrium (LD) were identified. The first block composed by the genetic variants rs668387, rs689021 and rs641120 showed a positive interaction (mainly the rs689021) with rs1784933 polymorphism. Moreover, we found a significant association between the APOE ε4 allele carriers and the variant rs2070045 located in the second LD block. CONCLUSION: The rs1784933 polymorphism is associated with LOAD in Mexican patients. In addition, the presence of APOE ε4 allele and SORL1 variants could represent a genetic interaction effect that favors LOAD risk in the Mexican population. SNPs have been proposed as genetic markers associated with the development of LOAD that can support the clinical diagnosis. Future molecular studies could help understand sporadic Alzheimer's Disease (AD) among the Mexican population, where currently there is a sub-estimate number in terms of disease frequency and incidence.

Host-Derived Lipids from Tuberculous Pleurisy Impair Macrophage Microbicidal-Associated Metabolic Activity.

Mycobacterium tuberculosis (Mtb) regulates the macrophage metabolic state to thrive in the host, yet the responsible mechanisms remain elusive. Macrophage activation toward the microbicidal (M1) program depends on the HIF-1α-mediated metabolic shift from oxidative phosphorylation (OXPHOS) toward glycolysis. Here, we ask whether a tuberculosis (TB) microenvironment changes the M1 macrophage metabolic state. We expose M1 macrophages to the acellular fraction of tuberculous pleural effusions (TB-PEs) and find lower glycolytic activity, accompanied by elevated levels of OXPHOS and bacillary load, compared to controls. The eicosanoid fraction of TB-PE drives these metabolic alterations. HIF-1α stabilization reverts the effect of TB-PE by restoring M1 metabolism. Furthermore, Mtb-infected mice with stabilized HIF-1α display lower bacillary loads and a pronounced M1-like metabolic profile in alveolar macrophages (AMs). Collectively, we demonstrate that lipids from a TB-associated microenvironment alter the M1 macrophage metabolic reprogramming by hampering HIF-1α functions, thereby impairing control of Mtb infection.

Specific macrophage subsets accumulate in human subcutaneous and omental fat depots during obesity.

Obesity is a chronic inflammatory disease associated with adipose tissue macrophage (ATM) activation. ATMs from lean mice contribute to tissue homeostasis by their M2-oriented polarization, whereas obesity leads to an increase of M1 inflammatory ATMs that underlies obesity-related metabolic disorders. In humans, studies characterizing ATMs and their functional status are limited. Here we investigated ATM phenotype in visceral (VAT) and subcutaneous (SAT) adipose tissue from healthy lean and obese individuals using two molecules previously identified as markers of M1-like and M2-like/tissue-resident macrophages, the C-type lectin CLEC5A and the scavenger receptor CD163L1, respectively. CD163L1 was expressed by the majority of ATMs, and CD163L1+ ATM density was greater with respect to cells expressing the pan-macrophage markers CD68 or CD11b. ATM counts in SAT, but not in VAT, increased in obese compared to lean individuals, measured with the three markers. Accordingly, CD163L1, CD68 and ITGAM gene expression was significantly enhanced in obese with respect to control individuals only in SAT. CLEC5A+ ATMs had a proinflammatory profile and were abundant in the lean VAT, but their density diminished in obesity. The only ATM subset that increased its counts in the obese VAT had a mixed M1-like (CD11c+ CD163- CD209- ) and M2-like (CLEC5A- CD206+ ) phenotype. ATM expansion was dominated by a subset of M2-like macrophages (CD11c- CLEC5A- CD163+ CD206+ CD209+ ) in the obese SAT, with a minor contribution of a CD11c+ CLEC5A- ATM subpopulation. Thus, both SAT and VAT seems to limit inflammation during obesity by differentially altering their ATM subset composition.

Regulatory T Cells Play a Role in a Subset of Idiopathic Preterm Labor/Birth and Adverse Neonatal Outcomes.

Regulatory T cells (Tregs) have been exhaustively investigated during early pregnancy; however, their role later in gestation is poorly understood. Herein, we report that functional Tregs are reduced at the maternal-fetal interface in a subset of women with idiopathic preterm labor/birth, which is accompanied by a concomitant increase in Tc17 cells. In mice, depletion of functional Tregs during late gestation induces preterm birth and adverse neonatal outcomes, which are rescued by the adoptive transfer of such cells. Treg depletion does not alter obstetrical parameters in the mother, yet it increases susceptibility to endotoxin-induced preterm birth. The mechanisms whereby depletion of Tregs induces adverse perinatal outcomes involve tissue-specific immune responses and mild systemic maternal inflammation, together with dysregulation of developmental and cellular processes in the placenta, in the absence of intra-amniotic inflammation. These findings provide mechanistic evidence supporting a role for Tregs in the pathophysiology of idiopathic preterm labor/birth and adverse neonatal outcomes.

Clinical Association of White Matter Hyperintensities Localization in a Mexican Family with Spastic Paraparesis Carrying the PSEN1 A431E Mutation.

Presenilin 1 gene (PSEN1) mutations are the most common cause of familial Alzheimer's disease (FAD). One of the most abundant FAD mutations, PSEN1 A431E, has been reported to be associated with spastic paraparesis in about half of its carriers, but the determining mechanisms of this phenotype are still unknown. In our study we characterized three A431E mutation carriers, one symptomatic and two asymptomatic, from a Mexican family with a history of spastic paraparesis in all of its affected members. At cognitive assessment and MRI, the symptomatic subject showed an atypical non-amnestic mild cognitive impairment with visuospatial deficits, olfactory dysfunction and significant parieto-occipital brain atrophy. Furthermore, we found several periventricular white matter hyperintensities whose progression pattern and localization correlated with their motor impairment, cognitive profile, and non-motor symptoms. Together, our data suggests that in this family the A431E mutation leads to a divergent neurological disorder in which cognitive deterioration was clinically exceeded by motor impairment and that it involves early glial and vascular pathological changes.

Effector and Activated T Cells Induce Preterm Labor and Birth That Is Prevented by Treatment with Progesterone.

Preterm labor commonly precedes preterm birth, the leading cause of perinatal morbidity and mortality worldwide. Most research has focused on establishing a causal link between innate immune activation and pathological inflammation leading to preterm labor and birth. However, the role of maternal effector/activated T cells in the pathogenesis of preterm labor/birth is poorly understood. In this study, we first demonstrated that effector memory and activated maternal T cells expressing granzyme B and perforin are enriched at the maternal-fetal interface (decidua) of women with spontaneous preterm labor. Next, using a murine model, we reported that prior to inducing preterm birth, in vivo T cell activation caused maternal hypothermia, bradycardia, systemic inflammation, cervical dilation, intra-amniotic inflammation, and fetal growth restriction, all of which are clinical signs associated with preterm labor. In vivo T cell activation also induced B cell cytokine responses, a proinflammatory macrophage polarization, and other inflammatory responses at the maternal-fetal interface and myometrium in the absence of an increased influx of neutrophils. Finally, we showed that treatment with progesterone can serve as a strategy to prevent preterm labor/birth and adverse neonatal outcomes by attenuating the proinflammatory responses at the maternal-fetal interface and cervix induced by T cell activation. Collectively, these findings provide mechanistic evidence showing that effector and activated T cells cause pathological inflammation at the maternal-fetal interface, in the mother, and in the fetus, inducing preterm labor and birth and adverse neonatal outcomes. Such adverse effects can be prevented by treatment with progesterone, a clinically approved strategy.

High prevalence of humoral autoimmunity in first-degree relatives of Mexican type 1 diabetes patients.

AIMS: To assess the prevalence of autoantibodies (Aab) to insulin (IAA), glutamic acid decarboxylase 65 (GADA) and insulinoma antigen 2 (IA-2A), as well as human leukocyte antigen (HLA) class II alleles, in first degree relatives (FDR) of Mexican patients with type 1 diabetes (T1D), and to explore whether these parameters mirror the low incidence of T1D in the Mexican population. METHODS: Aab titers were determined by ELISA in 425 FDR, 234 siblings, 40 offspring and 151 parents of 197 patients with T1D. Typing of HLA-DR and -DQ alleles was performed in 41 Aab-positive FDR using polymerase chain reaction with allele-specific oligotyping. RESULTS: Seventy FDR (16.47%) tested positive for Aab. The siblings (19.2%) and the offspring (25%) had significantly higher prevalence of Aab than the parents (9.9%). GADA was the most frequent Aab. Almost half of the Aab-positive FDR had two different Aab (45.7%), and none tested positive for three Aab. The highest prevalence of Aab was found among women in the 15-29 years age group. Moreover, the positivity for two Aab was significantly more frequent among females. A considerable number of FDR (48.8%) carried the susceptible HLA-DR3, -DR4, -DQB1*0201 or -DQB1*0302 alleles, but almost none had the high risk genotype HLA-DR3/DR4. CONCLUSIONS: FDR of Mexican T1D patients have high prevalence of islet Aab, comparable to countries with the highest incidence of T1D. However, Aab positivity does not seem to be associated with HLA risk genotypes, which may have an impact on the low incidence of T1D in Mexico.

Formation of Foamy Macrophages by Tuberculous Pleural Effusions Is Triggered by the Interleukin-10/Signal Transducer and Activator of Transcription 3 Axis through ACAT Upregulation.

The ability of Mycobacterium tuberculosis (Mtb) to persist in its human host relies on numerous immune evasion strategies, such as the deregulation of the lipid metabolism leading to the formation of foamy macrophages (FM). Yet, the specific host factors leading to the foamy phenotype of Mtb-infected macrophages remain unknown. Herein, we aimed to address whether host cytokines contribute to FM formation in the context of Mtb infection. Our approach is based on the use of an acellular fraction of tuberculous pleural effusions (TB-PE) as a physiological source of local factors released during Mtb infection. We found that TB-PE induced FM differentiation as observed by the increase in lipid bodies, intracellular cholesterol, and expression of the scavenger receptor CD36, as well as the enzyme acyl CoA:cholesterol acyl transferase (ACAT). Importantly, interleukin-10 (IL-10) depletion from TB-PE prevented the augmentation of all these parameters. Moreover, we observed a positive correlation between the levels of IL-10 and the number of lipid-laden CD14+ cells among the pleural cells in TB patients, demonstrating that FM differentiation occurs within the pleural environment. Downstream of IL-10 signaling, we noticed that the transcription factor signal transducer and activator of transcription 3 was activated by TB-PE, and its chemical inhibition prevented the accumulation of lipid bodies and ACAT expression in macrophages. In terms of the host immune response, TB-PE-treated macrophages displayed immunosuppressive properties and bore higher bacillary loads. Finally, we confirmed our results using bone marrow-derived macrophage from IL-10-/- mice demonstrating that IL-10 deficiency partially prevented foamy phenotype induction after Mtb lipids exposure. In conclusion, our results evidence a role of IL-10 in promoting the differentiation of FM in the context of Mtb infection, contributing to our understanding of how alterations of the host metabolic factors may favor pathogen persistence.

Soluble Factors from Human Olfactory Neural Stem/Progenitor Cells Influence the Fate Decisions of Hippocampal Neural Precursor Cells.

Neurogenesis plays a significant role during adulthood, and the observation that neural stem cells reside in the central nervous system and the olfactory epithelium has attracted attention due to their importance in neuronal regeneration. In addition, soluble factors (SFs) release by neural stem cells may modulate the neurogenic process. Thus, in this study, we identified the SFs released by olfactory human neural stem/progenitor cells (hNS/PCs-OE). These cells express Ki67, nestin, and ßIII-tubulin, indicating their neural lineage. The hNS/PCs-OE also express PSD95 and tau proteins during proliferation, but increased levels are observed after differentiation. Thus, we evaluated the effects of SFs from hNS/PCs-OE on the viability, proliferation, and differentiation potential of adult murine hippocampal neural precursor cells (AHPCs). SFs from hNS/PCs-OE maintain cells in the precursor and proliferative stages and mainly promote the astrocytic differentiation of AHPCs. These effects involved the activation, as measured by phosphorylation, of several proteins (Erk1/2; Akt/PRAS40/GSK3ß and JAK/STAT) involved in key events of the neurogenic process. Moreover, according to the results from the antibody-based microarray approach, among the soluble factors, hNS/PCs-OE produce interleukin-6 (IL-6) and neurotrophin 4 (NT4). However, residual epidermal growth factor (EGF) was also detected. These proteins partially reproduced the effects of SFs from hNS/PCs-OE on AHPCs, and the mechanism underlying these effects is mediated by Src proteins, which have been implicated in EGF-induced transactivation of TrkB receptor. The results of the present study suggest the potential use of SFs from hNS/PCs-OE in controlling the differentiation potential of AHPCs. Thus, the potential clinical relevance of hNS/PCs-OE is worth pursuing.

Metabolic Syndrome as a Risk Factor for Alzheimer's Disease: Is Aß a Crucial Factor in Both Pathologies?

SIGNIFICANCE: Recently, chronic degenerative diseases have become one of the main health problems worldwide. That is the case of Alzheimer's disease (AD) and metabolic syndrome (MetS), whose expression can be influenced by different risk factors. Recent Advances: In recent decades, it has been widely described that MetS increases the risk of cognitive impairment and dementia. MetS pathogenesis involves several vascular risk factors such as diabetes, dyslipidemia, hypertension, and insulin resistance (I/R). CRITICAL ISSUES: Reported evidence shows that vascular risk factors are associated with AD, particularly in the development of protein aggregation, inflammation, oxidative stress, neuronal dysfunction, and disturbances in signaling pathways, with insulin receptor signaling being a common alteration between MetS and AD. FUTURE DIRECTIONS: Insulin signaling has been involved in tau phosphorylation and amyloid ß (Aß) metabolism. However, it has also been demonstrated that Aß oligomers can bind to insulin receptors, triggering their internalization, decreasing neuron responsiveness to insulin, and promoting insulin I/R. Thus, it could be argued that Aß could be a convergent factor in the development of both pathologies. Antioxid. Redox Signal. 26, 542-560.

In vivo T-cell activation by a monoclonal αCD3ε antibody induces preterm labor and birth.

PROBLEM: Activated/effector T cells seem to play a role in the pathological inflammation associated with preterm labor. The aim of this study was to determine whether in vivo T-cell activation by a monoclonal αCD3ε antibody induces preterm labor and birth. METHOD OF STUDY: Pregnant B6 mice were intraperitoneally injected with a monoclonal αCD3ε antibody or its isotype control. The gestational age, the rates of preterm birth and pup mortality at birth as well as the fetal heart rate and umbilical artery pulsatility index were determined. RESULTS: Injection of a monoclonal αCD3ε antibody led to preterm labor/birth (αCD3ε 83 ± 16.97% [10/12] vs isotype 0% [0/8]) and increased the rate of pup mortality at birth (αCD3ε 87.30 ± 8.95% [77/85] vs isotype 4.91 ± 4.34% [3/59]). In addition, injection of a monoclonal αCD3ε antibody decreased the fetal heart rate and increased the umbilical artery pulsatility index when compared to the isotype control. CONCLUSION: In vivo T-cell activation by a monoclonal αCD3ε antibody in late gestation induces preterm labor and birth.

Calcium-sensing-receptor (CaSR) controls IL-6 secretion in metastatic breast cancer MDA-MB-231 cells by a dual mechanism revealed by agonist and inverse-agonist modulators.

IL-6 is a tightly controlled pleiotropic cytokine with hormone-like properties whose levels are frequently altered in cancer and inflammatory diseases. In highly invasive MDA-MB-231 breast cancer cells, basal activity of endogenously expressed calcium sensing receptor (CaSR) promotes IL-6 secretion. Interestingly, upon agonist stimulation, CaSR reduces IL-6 levels whereas it promotes secretion of various other cytokines and growth factors, raising intriguing questions about how CaSR signaling modulates IL-6 secretion. Here, using NPS-2143, which acted as an inverse agonist, we show that IL-6 secretion promoted by constitutive activity of CaSR is mechanistically linked to Gαs/PKC, MEK1/2 and mTORC1 signaling pathways, integrated by transactivated EGFR. On the other hand, agonist-stimulated CaSR engages in a Rab11a-dependent trafficking pathway critical to inhibit constitutive IL-6 secretion via the PI3K/AKT and PKC signaling pathways. These results support the emerging potential of CaSR as a therapeutic target in metastatic breast cancer whose pharmacological modulation would reduce IL-6.

Atypical Activin A and IL-10 Production Impairs Human CD16+ Monocyte Differentiation into Anti-Inflammatory Macrophages.

Human CD14(++)CD16(-) and CD14(+/lo)CD16(+) monocyte subsets comprise 85 and 15% of blood monocytes, respectively, and are thought to represent distinct stages in the monocyte differentiation pathway. However, the differentiation fates of both monocyte subsets along the macrophage (Mϕ) lineage have not yet been elucidated. We have now evaluated the potential of CD14(++) CD16(-) and CD16(+) monocytes to differentiate and to be primed toward pro- or anti-inflammatory Mϕs upon culture with GM-CSF or M-CSF, respectively (subsequently referred to as GM14, M14, GM16, or M16). Whereas GM16 and GM14 were phenotypic and functionally analogous, M16 displayed a more proinflammatory profile than did M14. Transcriptomic analyses evidenced that genes associated with M-CSF-driven Mϕ differentiation (including FOLR2, IL10, IGF1, and SERPINB2) are underrepresented in M16 with respect to M14. The preferential proinflammatory skewing of M16 relative to M14 was found to be mediated by the secretion of activin A and the low levels of IL-10 produced by M16. In fact, activin A receptor blockade during the M-CSF-driven differentiation of CD16(+) monocytes, or addition of IL-10-containing M14-conditioned medium, significantly enhanced their expression of anti-inflammatory-associated molecules while impairing their acquisition of proinflammatory-related markers. Thus, we propose that M-CSF drives CD14(++)CD16- monocyte differentiation into bona fide anti-inflammatory Mϕs in a self-autonomous manner, whereas M-CSF-treated CD16(+) monocytes generate Mϕs with a skewed proinflammatory profile by virtue of their high activin A expression unless additional anti-inflammatory stimuli such as IL-10 are provided.

CD163L1 and CLEC5A discriminate subsets of human resident and inflammatory macrophages in vivo.

Macrophages (Mϕ) can be differentiated and polarized in vitro from human CD14(+) monocytes under the influence of GM-CSF (GM-Mϕ) and M-CSF (M-Mϕ). GM-Mϕs are proinflammatory and M-Mϕs have an anti-inflammatory phenotype. We found selective expression of the lectin C-type lectin domain family 5 member A (CLEC5A) transcripts in GM-Mϕs and the scavenger receptor CD163 molecule-like 1 (CD163L1) in M-Mϕs by microarray assay. In vitro, CD163L1 expression was induced by IL-10 and M-CSF and CLEC5A by inflammatory cytokines and cell adherence. In secondary lymphoid organs, their respective expression was restricted to CD68(+)/CD163(+) Mϕs that preferentially produced either TNF (CLEC5A(+)) or IL-10 (CD163L1(+)). Mϕs from healthy liver and colon tissue were mostly CD163L1(+), and CLEC5A(+) cells were scarce. In contrast, CLEC5A(+) Mϕs were abundant in the intestinal lamina propria from patients with inflammatory bowel disease (IBD), with higher numbers of CLEC5A(+)CD163L1(+) found compared with those in secondary lymphoid organs. CLEC5A(+) cells were CD14(+)CD209(-)CD11b(+)CD11c(+)TNF(+)IL-10(+), and single positive CD163L1(+) cells were CD14(-)CD209(+)CD11b(-)CD11c(-)TNF(-)IL-10(+) in healthy donors and had lost the ability to produce IL-10 and to express CD209 in those with IBD. In melanomas, CLEC5A(+) tumor-associated Mϕs (TAMs) were not detected in 42% of the cases evaluated, but CD163L1(+) TAMs were found in 100%. Similar to IBD, CD163L1(+) TAMs expressed high levels of CD209 and produced significant amounts of IL-10, and CLEC5A(+) TAMs were CD14(hi) and produced enhanced levels of TNF in metastases. Overall, these results suggest that CD163L1 expression is associated with tissue-resident Mϕs with an anti-inflammatory or anergic phenotype and that CLEC5A(+) Mϕs exhibit TNF-producing ability and might display a proinflammatory effect.

Diverging biological roles among human monocyte subsets in the context of tuberculosis infection.

Circulating monocytes (Mo) play an essential role in the host immune response to chronic infections. We previously demonstrated that CD16(pos) Mo were expanded in TB (tuberculosis) patients, correlated with disease severity and were refractory to dendritic cell differentiation. In the present study, we investigated whether human Mo subsets (CD16(neg) and CD16(pos)) differed in their ability to influence the early inflammatory response against Mycobacterium tuberculosis. We first evaluated the capacity of the Mo subsets to migrate and engage a microbicidal response in vitro. Accordingly, CD16(neg) Mo were more prone to migrate in response to different mycobacteria-derived gradients, were more resistant to M. tuberculosis intracellular growth and produced higher reactive oxygen species than their CD16(pos) counterpart. To assess further the functional dichotomy among the human Mo subsets, we carried out an in vivo analysis by adapting a hybrid mouse model (SCID/Beige, where SCID is severe combined immunodeficient) to transfer each Mo subset, track their migratory fate during M. tuberculosis infection, and determine their impact on the host immune response. In M. tuberculosis-infected mice, the adoptively transferred CD16(neg) Mo displayed a higher lung migration index, induced a stronger pulmonary infiltration of murine leucocytes expressing pro- and anti-inflammatory cytokines, and significantly decreased the bacterial burden, in comparison with CD16(pos) Mo. Collectively, our results indicate that human Mo subsets display divergent biological roles in the context of M. tuberculosis infection, a scenario in which CD16(neg) Mo may contribute to the anti-mycobacterial immune response, whereas CD16(pos) Mo might promote microbial resilience, shedding light on a key aspect of the physiopathology of TB disease.

Intravenous immunoglobulin promotes antitumor responses by modulating macrophage polarization.

Intravenous Igs (IVIg) therapy is widely used as an immunomodulatory strategy in inflammatory pathologies and is suggested to promote cancer regression. Because progression of tumors depends on their ability to redirect the polarization state of tumor-associated macrophages (from M1/immunogenic/proinflammatory to M2/anti-inflammatory), we have evaluated whether IVIg limits tumor progression and dissemination through modulation of macrophage polarization. In vitro, IVIg inhibited proinflammatory cytokine production from M1 macrophages and induced a M2-to-M1 polarization switch on human and murine M2 macrophages. In vivo, IVIg modified the polarization of tumor-associated myeloid cells in a Fcεr1γ chain-dependent manner, modulated cytokine blood levels in tumor-bearing animals, and impaired tumor progression via FcγRIII (CD16), FcγRIV, and FcRγ engagement, the latter two effects being macrophage mediated. Therefore, IVIg immunomodulatory activity is dependent on the polarization state of the responding macrophages, and its ability to trigger a M2-to-M1 macrophage polarization switch might be therapeutically useful in cancer, in which proinflammatory or immunogenic functions should be promoted.

Tolerogenic dendritic cells induce antigen-specific hyporesponsiveness in insulin- and glutamic acid decarboxylase 65-autoreactive T lymphocytes from type 1 diabetic patients.

Tolerogenic dendritic cells (tDC) constitute a promising therapy for autoimmune diseases, since they can anergize T lymphocytes recognizing self-antigens. Patients with type 1 diabetes mellitus (T1D) have autoreactive T cells against pancreatic islet antigens (insulin, glutamic acid decarboxylase 65 -GAD65-). We aimed to determine the ability of tDC derived from T1D patients to inactivate their insulin- and GAD65-reactive T cells. CD14+ monocytes and CD4+CD45RA- effector/memory lymphocytes were isolated from 25 patients. Monocyte-derived DC were generated in the absence (control, cDC) or presence of IL-10 and TGF-ß1 (tDC), and loaded with insulin or GAD65. DC were cultured with T lymphocytes (primary culture), and cell proliferation and cytokine secretion were determined. These lymphocytes were rechallenged with insulin-, GAD65- or candidin-pulsed cDC (secondary culture) to assess whether tDC rendered T cells hyporesponsive to further stimulation. In the primary cultures, tDC induced significant lower lymphocyte proliferation and IL-2 and IFN-γ secretion than cDC; in contrast, tDC induced higher IL-10 production. Lymphocytes from 60% of patients proliferated specifically against insulin or GAD65 (group 1), whereas 40% did not (group 2). Most patients from group 1 had controlled glycemia. The secondary cultures showed tolerance induction to insulin or GAD65 in 14 and 10 patients, respectively. A high percentage of these patients (70-80%) belonged to group 1. Importantly, tDC induced antigen-specific T-cell hyporesponsiveness, since the responses against unrelated antigens were unaffected. These results suggest that tDC therapy against multiple antigens might be useful in a subset of T1D patients.

CCL2 shapes macrophage polarization by GM-CSF and M-CSF: identification of CCL2/CCR2-dependent gene expression profile.

The CCL2 chemokine mediates monocyte egress from bone marrow and recruitment into inflamed tissues through interaction with the CCR2 chemokine receptor, and its expression is upregulated by proinflammatory cytokines. Analysis of the gene expression profile in GM-CSF- and M-CSF-polarized macrophages revealed that a high CCL2 expression characterizes macrophages generated under the influence of M-CSF, whereas CCR2 is expressed only by GM-CSF-polarized macrophages. Analysis of the factors responsible for this differential expression identified activin A as a critical factor controlling the expression of the CCL2/CCR2 pair in macrophages, as activin A increased CCR2 expression but inhibited the acquisition of CCL2 expression by M-CSF-polarized macrophages. CCL2 and CCR2 were found to determine the extent of macrophage polarization because CCL2 enhances the LPS-induced production of IL-10, whereas CCL2 blockade leads to enhanced expression of M1 polarization-associated genes and cytokines, and diminished expression of M2-associated markers in human macrophages. Along the same line, Ccr2-deficient bone marrow-derived murine macrophages displayed an M1-skewed polarization profile at the transcriptomic level and exhibited a significantly higher expression of proinflammatory cytokines (TNF-α, IL-6) in response to LPS. Therefore, the CCL2-CCR2 axis regulates macrophage polarization by influencing the expression of functionally relevant and polarization-associated genes and downmodulating proinflammatory cytokine production.