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Gout is a chronic disease that is caused by an innate immune response to deposited monosodium urate crystals in the setting of hyperuricemia. Here, we provide insights into the molecular mechanism of the poorly understood inflammatory component of gout from a genome-wide association study (GWAS) of 2.6 million people, including 120,295 people with prevalent gout. We detected 377 loci and 410 genetically independent signals (149 previously unreported loci in urate and gout). An additional 65 loci with signals in urate (from a GWAS of 630,117 individuals) but not gout were identified. A prioritization scheme identified candidate genes in the inflammatory process of gout, including genes involved in epigenetic remodeling, cell osmolarity and regulation of NOD-like receptor protein 3 (NLRP3) inflammasome activity. Mendelian randomization analysis provided evidence for a causal role of clonal hematopoiesis of indeterminate potential in gout. Our study identifies candidate genes and molecular processes in the inflammatory pathogenesis of gout suitable for follow-up studies.

Ageing of the immune system, or immunosenescence, contributes to the morbidity and mortality of the elderly1,2. To define the contribution of immune system ageing to organism ageing, here we selectively deleted Ercc1, which encodes a crucial DNA repair protein3,4, in mouse haematopoietic cells to increase the burden of endogenous DNA damage and thereby senescence5–7in the immune system only. We show that Vav-iCre+/−;Ercc1−/flmice were healthy into adulthood, then displayed premature onset of immunosenescence characterized by attrition and senescence of specific immune cell populations and impaired immune function, similar to changes that occur during ageing in wild-type mice8–10. Notably, non-lymphoid organs also showed increased senescence and damage, which suggests that senescent, aged immune cells can promote systemic ageing. The transplantation of splenocytes from Vav-iCre+/−;Ercc1−/flor aged wild-type mice into young mice induced senescence intrans, whereas the transplantation of young immune cells attenuated senescence. The treatment of Vav-iCre+/−;Ercc1−/flmice with rapamycin reduced markers of senescence in immune cells and improved immune function11,12. These data demonstrate that an aged, senescent immune system has a causal role in driving systemic ageing and therefore represents a key therapeutic target to extend healthy ageing.

A plethora of vascular pathology is associated with inflammation, hypoxia and elevated rates of reactive species generation. A critical source of these reactive species is the purine catabolizing enzyme xanthine oxidoreductase (XOR) as numerous reports over the past 30 years have demonstrated XOR inhibition to be salutary. Despite this long standing association between increased vascular XOR activity and negative clinical outcomes, recent reports reveal a new paradigm whereby the enzymatic activity of XOR mediates beneficial outcomes by catalyzing the one electron reduction of nitrite (NO2−) to nitric oxide (NO) when NO2−and/or nitrate (NO3−) levels are enhanced either viadietary or pharmacologic means. These observations seemingly countervail numerous reports of improved outcomes in similar models upon XOR inhibition in the absence of NO2−treatment affirming the need for a more clear understanding of the mechanisms underpinning the product identity of XOR. To establish the micro-environmental conditions requisite for in vivoXOR-catalyzed oxidant and NO production, this review assesses the impact of pH, O2tension, enzyme–endothelial interactions, substrate concentrations and catalytic differences between xanthine oxidase (XO) and xanthine dehydrogenase (XDH). As such, it reveals critical information necessary to distinguish if pursuit of NO2−supplementation will afford greater benefit than inhibition strategies and thus enhance the efficacy of current approaches to treat vascular pathology.

A plethora of vascular pathology is associated with inflammation, hypoxia and elevated rates of reactive species generation. A critical source of these reactive species is the purine catabolizing enzyme xanthine oxidoreductase (XOR) as numerous reports over the past 30 years have demonstrated XOR inhibition to be salutary. Despite this long standing association between increased vascular XOR activity and negative clinical outcomes, recent reports reveal a new paradigm whereby the enzymatic activity of XOR mediates beneficial outcomes by catalyzing the one electron reduction of nitrite (NO2-) to nitric oxide (NO) when NO2-and/or nitrate (NO3-) levels are enhanced either viadietary or pharmacologic means. These observations seemingly countervail numerous reports of improved outcomes in similar models upon XOR inhibition in the absence of NO2-treatment affirming the need for a more clear understanding of the mechanisms underpinning the product identity of XOR. To establish the micro-environmental conditions requisite for in vivoXOR-catalyzed oxidant and NO production, this review assesses the impact of pH, O2tension, enzyme–endothelial interactions, substrate concentrations and catalytic differences between xanthine oxidase (XO) and xanthine dehydrogenase (XDH). As such, it reveals critical information necessary to distinguish if pursuit of NO2-supplementation will afford greater benefit than inhibition strategies and thus enhance the efficacy of current approaches to treat vascular pathology.

Extracellular superoxide dismutase (EC-SOD) is abundant in the lung and limits inflammation and injury in response to many pulmonary insults. To test the hypothesis that EC-SOD has an important role in bacterial infections, wild-type and EC-SOD knockout (KO) mice were infected with Escherichia colito induce pneumonia. Although mice in the EC-SOD KO group demonstrated greater pulmonary inflammation than did wild-type mice, there was less clearance of bacteria from their lungs after infection. Macrophages and neutrophils express EC-SOD; however, its function and subcellular localization in these inflammatory cells is unclear. In the present study, immunogold electron microscopy revealed EC-SOD in membrane-bound vesicles of phagocytes. These findings suggest that inflammatory cell EC-SOD may have a role in antibacterial defense. To test this hypothesis, phagocytes from wild-type and EC-SOD KO mice were evaluated. Although macrophages lacking EC-SOD produced more reactive oxygen species than did cells expressing EC-SOD after stimulation, they demonstrated significantly impaired phagocytosis and killing of bacteria. Overall, this suggests that EC-SOD facilitates clearance of bacteria and limits inflammation in response to infection by promoting bacterial phagocytosis.

Nitric oxide (•NO) can protect cells against the detrimental effects of reactive oxygen species. Using low-density lipoprotein as well as model systems, it has been demonstrated that •NO can serve as a chain-breaking antioxidant to blunt lipid peroxidation. To test the hypothesis that •NO can serve as a chain-breaking antioxidant in cell membranes, we examined the effect of •NO on iron-induced lipid peroxidation in human leukemia cells. We exposed HL-60 cells to an oxidative stress (20 μM Fe2+) and monitored the consumption of oxygen as a measure of lipid peroxidation. Oxygen consumption was arrested by the addition of •NO as a saturated aqueous solution. The duration of inhibition of oxygen consumption by •NO was concentration-dependent in the 0.4–1.8 μM range. The inhibition ended upon depletion of •NO. The addition of •NO prior to initiation of peroxidation delayed the onset of peroxidation; the nearer in time it was before Fe2+addition, the longer the inhibition. Depletion of cellular glutathione levels by d,l-buthionine-S,R-sulfoximine prior to Fe2+addition resulted in a more rapid initial rate of oxygen depletion and a shorter time for the •NO-induced inhibition of oxygen consumption. Complementary studies of this iron-induced lipid peroxidation, using thiobarbituric acid reactive substances as a marker, also demonstrated the protective effects of •NO. This protection of cells against lipid peroxidation also manifested itself as a reduction in trypan blue uptake, an observation demonstrating the protective effects of •NO on membrane integrity. We conclude that •NO protects HL-60 human leukemia cells from lipid peroxidation and that this protection ameliorates the toxicity of the oxidation processes initiated by Fe2+and dioxygen.

Pulmonary hypertension (PH) is emerging as a serious complication associated with hemolytic disorders, and plexiform lesions (PXL) have been reported in patients with sickle cell disease (SCD). We hypothesized that repetitive hemolysis per se induces PH and angioproliferative vasculopathy and evaluated a new mechanism for hemolysis-associated PH (HA-PH) that involves the release of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) from erythrocytes. In healthy rats, repetitive administration of hemolyzed autologous blood (HAB) for 10 days produced reversible pulmonary parenchymal injury and vascular remodeling and PH. Moreover, the combination of a single dose of Sugen-5416 (SU, 200 mg/kg) and 10-day HAB treatment resulted in severe and progressive obliterative PH and formation of PXL (Day 26, right ventricular peak systolic pressure (mmHg): 26.1 ± 1.1, 41.5 ± 0.5 and 85.1 ± 5.9 in untreated, HAB treated and SU+HAB treated rats, respectively). In rats, repetitive administration of HAB increased plasma ADA activity and reduced urinary adenosine levels. Similarly, SCD patients had higher plasma ADA and PNP activity and accelerated adenosine, inosine, and guanosine metabolism than healthy controls. Our study provides evidence that hemolysis per se leads to the development of angioproliferative PH. We also report the development of a rat model of HA-PH that closely mimics pulmonary vasculopathy seen in patients with HA-PH. Finally, this study suggests that in hemolytic diseases released ADA and PNP may increase the risk of PH, likely by abolishing the vasoprotective effects of adenosine, inosine and guanosine. Further characterization of this new rat model of hemolysis-induced angioproliferative PH and additional studies of the role of purines metabolism in HA-PH are warranted.

A plethora of disease processes are associated with elevated reactive species formation and allied reactions with biomolecules that alter cell signaling, induce overt damage, and promote dysfunction of tissues. Unfortunately, effective detection of reactive species in tissues is wrought with issues that significantly limit capacity for validating species identity, establishing accurate concentrations, and identifying anatomic sites of production. These shortcomings reveal the pressing need for new approaches to more precisely assess reactive species generation in vivo. Herein, we describe an in vivo immuno‐spin trapping method for indirectly assessing oxidant levels by detecting free radicals resulting from reaction of oxidants with biomolecules to form stable, immunologically detectable nitrone‐biomolecular adducts. This process couples the reactivity and sensitivity of an electron paramagnetic resonance spin trap with the resolution of confocal imaging to visualize the extent of cell and tissue oxidation and anatomic sites of production by detecting resultant free radical formation. © 2015 by John Wiley & Sons, Inc.