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-1β, IL-6, IL-8, IL-12 p40, CCL2, IFN-β, 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.

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.

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.