The presence of both HLA-DRB1[*]04:01 and HLA-B[*]15:01 increases the susceptibility to cranial and extracranial giant cell arteritis.

Objectives: To determine if patients with the predominant extracranial large-vessel-vasculitis (LVV) pattern of giant cell arteritis (GCA) have a distinctive HLA-B association, different from that reported in biopsy-proven cranial GCA patients. In a further step we assessed if the combination of HLA-B and HLA-DRB1 alleles confers an increased risk for GCA susceptibility, either for the cranial and extracranial LVV phenotypes. Methods: A total of 184 patients with biopsy-proven cranial GCA, 105 with LVV-GCA and 486 healthy controls were included in our study. We compared HLA-B phenotype frequencies between the three groups. Results: HLA-B*15 phenotype was significantly increased in patients with classic cranial GCA compared to controls (14.7% versus 5.8%, respectively; p<0.01; OR [95% CI] =2.81 [1.54-5.11]). It was mainly due to the HLA-B*15:01 allele (12.5% versus 4.0%, respectively; p<0.01; OR [95% CI] =3.51 [1.77-6.99]) and remained statistically significant after Bonferroni correction. Similar HLA-B*15 association was observed in patients with the LVV-GCA (11.4% versus 5.8%, p=0.04, OR [95% CI] =2.11 [1.04-4.30]). This association was also mainly due to the HLA-B*15:01 allele (10.5% versus 4.0%, respectively; p=0.0054; OR [95% CI] =2.88 [1.19-6.59]). Noteworthy, the presence of HLA-B*15:01 together with HLA-DRB1*04:01 led to an increased risk of developing both cranial and extracranial LVV-GCA. Conclusions: Susceptibility to GCA is strongly related to the HLA region, regardless of the clinical phenotype of expression of the disease.This work was partially supported by RETICS Programs, RD08/0075 (RIER), RD12/0009/0013 and RD16/0012 from ‘‘Instituto de Salud Carlos III’’ (ISCIII) (Spain). However, this research did not receive any specific grant from funding agencies in the commercial or not-for-profit sectors

Lipin-2 inhibits inflammasome activation induced by palmitic acid in macrophages

Resumen del póster presentado presentado al CIBERDEM Annual Meeting, celebrado en Cerdanyola del Vallès, Barcelona (España) del 11 al 13 de mayo de 2016.It is well known that metabolic diseases are characterized by elevated concentrations of circulating free fatty acids (FFAs), especially saturated fatty acids (SFAs), which activate macrophages through Toll-like receptors (TLR2/4). Previous studies in our laboratory showed that depletion of lipin-2, a member of the phosphatidic acid phosphatase lipin family involved in de novo lipid biosynthesis, promotes increased an inflammatory response to SFAs such as palmitic acid. Further studies demonstrated that this inflammatory response also involves the increased expression and release of IL-1b, a pro-inflammatory cytokine produced by the activation of the NLRP3 (NLR pyrin domain containing 3) inflammasome. The aim of this study was to further investigate the mechanism by which the lack of lipin-2 increases the inflammasome-dependent response to palmitic acid. We produced a human macrophage cell line (THP1) knockout for lipin-2 using the CRISPR/Cas9 technology by lentiviral transfection. Palmitic acid has the capacity to act as the first and second signal needed to fully activate the NLRP3 inflammasome. During the priming signal (signal 1) palmitic acid induces proinflammatory gene expression (Il1b, Il6) by activating via ERK and NFKB, possibly through TLR2/4. As signal 2, the fatty acid induces the formation of the NLRP3 inflammasome complex and activation of caspase-1, with the consequent maturation of pro-IL-1b into IL-1b. Lipin-2 depletion has effects on the priming phase of the inflammasome activation, by increasing p65 NF-Kb translocation to the nucleus as well as activation of ERK. During the second phase, the absence of lipin-2 exacerbates palmitic acid-inflammasome activation, increasing expression of pro-IL-1b and components of the NLRP3 inflammasome complex. Collectively, these data suggest that lipin-2 participates as a mechanism to dampen inflammasome activation during palmitic acid treatment. We are currently working to characterize the molecular mechanisms that govern these effects.Peer reviewe

Lipin-2 regulates NLRP3 inflammasome by affecting P2X7 receptor activation

Mutations in human LPIN2 produce a disease known as Majeed syndrome, the clinical manifestations of which are ameliorated by strategies that block IL-1ß or its receptor. However the role of lipin-2 during IL-1ß production remains elusive. We show here that lipin-2 controls excessive IL-1ß formation in primary human and mouse macrophages by several mechanisms, including activation of the inflammasome NLRP3. Lipin-2 regulates MAPK activation, which mediates synthesis of pro-IL-1ß during inflammasome priming. Lipin-2 also inhibits the activation and sensitization of the purinergic receptor P2X7 and K+ efflux, apoptosis-associated speck-like protein with a CARD domain oligomerization, and caspase-1 processing, key events during inflammasome activation. Reduced levels of lipin-2 in macrophages lead to a decrease in cellular cholesterol levels. In fact, restoration of cholesterol concentrations in cells lacking lipin-2 decreases ion currents through the P2X7 receptor, and downstream events that drive IL-1ß production. Furthermore, lipin-2-deficient mice exhibit increased sensitivity to high lipopolysaccharide doses. Collectively, our results unveil lipin-2 as a critical player in the negative regulation of NLRP3 inflammasome.This work was supported by the Spanish Ministry of Economy and Competitiveness (grants SAF2013-48201-R and BFU2013-45867-R), Instituto de Salud Carlos III (RIC, RD12/0042/0006, Red Heracles), and the Regional Government of Castile and Leon (BIO/VA22/15). G. Lordén, I. Sanjuán-García, N. de Pablo, and I. Alvarez-Miguel were supported by predoctoral fellowships from the Spanish Ministry of Science and Innovation (FPU and FPI programs) and the Regional Government of Castile and Leon. Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas is an initiative of Instituto de Salud Carlos III.Peer Reviewe

The presence of both HLA-DRB1*04:01 and HLA-B*15:01 increases the susceptibility to cranial and extracranial giant cell arteritis.

Objective. To determine if patients with the predominant extracranial large-vessel vasculitis (LVV) pattern of giant cell arteritis (GCA) have a distinctive HLA-B association, different from that reported in biopsy-proven cranial GCA patients. In a further step we assessed if the combination of HLA-B and HLADRB1 alleles confers an increased risk for GCA susceptibility, both for the cranial and extracranial LVV phenotypes. Methods. A total of 184 patients with biopsy-proven cranial GCA, 105 with LVV-GCA and 486 healthy controls were included in our study. We compared HLA-B phenotype frequencies between the three groups. Results. HLA-B*15 phenotype was significantly increased in patients with classic cranial GCA compared to controls (14.7% vs. 5.8%, respectively; p<0.01; OR [95% CI]=2.81 [1.54-5.11]). It was mainly due to the HLA-B*15:01 allele (12.5% vs. 4.0%, respectively; p<0.01; OR [95% CI]=3.51 [1.77-6.99]) and remained statistically significant after Bonferroni correction. Similar HLA-B*15 association was observed in patients with the LVV-GCA (11.4% vs. 5.8%, p=0.04, OR [95% CI]=2.11 [1.04-4.30]). This association was also mainly due to the HLA-B*15:01 allele (10.5% vs. 4.0%, respectively; p=0.0054; OR [95% CI]=2.88 [1.19-6.59]). Noteworthy, the presence of HLA-B*15:01 together with HLA-DRB1*04:01 led to an increased risk of developing both cranial and extracranial LVV-GCA. Conclusion. Susceptibility to GCA is strongly related to the HLA region, regardless of the clinical phenotype of expression of the disease