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Alarmins are classified by their release from damaged or ruptured cells. Many alarmins have been found to increase vascular tone and oppose endothelium‐dependent dilatation (EDD). Interleukin (IL)‐33 plays a prominent role in lung injury and can be released during vascular injury and in chronic studies found to be cardioprotective. Our recent work has implicated IL‐33 in acute vascular dysfunction following inhalation of engineered nanomaterials (ENM). However, the mechanisms linking IL‐33 to vascular tone have not been interrogated. We therefore aimed to determine whether IL‐33 directly influenced microvascular tone and endothelial function. Isolated feed arteries and in vivo arterioles from male and female Sprague–Dawley rats were used to determine direct vascular actions of IL‐33. Mesenteric feed arteries and arterioles demonstrated reduced intraluminal diameters when treated with increasing concentrations of recombinant IL‐33. IL‐33 activated extracellular signal regulated kinase (ERK)1/2 of rat aortic smooth muscle cells but not phosphorylation of myosin light chain kinase. This suggested IL‐33 may sensitize arterioles to Ca2+‐mediated responses. Indeed, IL‐33 augmented the myogenic‐ and phenylephrine‐induced vasoconstriction. Additionally, incubation of arterioles with 1 ng IL‐33 attenuated ACh‐mediated EDD. Mechanistically, in human aortic endothelial cells, we demonstrate that IL‐33‐mediated ERK1/2 activation leads to inhibitory phosphorylation of serine 602 on endothelial nitric oxide synthase. Finally, we demonstrate that IL‐33‐ERK1/2 contributes to vascular tone following two known inducers of IL‐33; ENM inhalation and the rupture endothelial cells. The present study provides novel evidence that IL‐33 increases vascular tone via canonical ERK1/2 activation in microvascular smooth muscle and endothelium. Altogether, it is suggested IL‐33 plays a critical role in microvascular homeostasis following barrier cell injury. Key points: Interleukin (IL)‐33 causes a concentration‐dependent reduction in feed artery diameter.IL‐33 acts on vascular smooth muscle cells to augment Ca2+‐mediated processes.IL‐33 causes inhibitory phosphorylation of endothelial nitric oxide synthase and opposes endothelium‐dependent dilatation.Engineered nanomaterial‐induced lung injury and endothelial cell rupture in part act through IL‐33 to mediate increased vascular tone. [ABSTRACT FROM AUTHOR]

Many preclinical reports have coalesced to identify a strong association between obesity and increased levels of uric acid (UA) in tissues and, importantly, in the circulation (hyperuricemia). Unfortunately, nearly all these studies were conducted with male mice or, in one case, female mice without a side-by-side male cohort. Therefore, the relationship between obesity and hyperuricemia in female mice remains undefined. This lack of clarity in the field has considerable impact as the downstream effects of obesity and allied hyperuricemia are extensive, resulting in many comorbidities including cardiovascular dysfunction, chronic kidney disease, and nonalcoholic fatty liver disease (NAFLD). Herein we begin to address this issue by revealing phenotypic and metabolic responses to diet-induced obesity (DIO) in a side-by-side male vs. female C57BL/6J study. Beginning at 6 weeks of age, mice were exposed to either an obesogenic diet (60% calories from fat) or control diet (10% calories from fat) for 19 weeks. Similar to numerous reported observations with the 60% diet, male mice experienced significant weight gain over time, elevated fasting blood glucose, impaired glucose tolerance and significantly elevated circulating uric acid levels (2.54 ± 0.33 mg/dL) compared to age-matched lean male controls (1.53 ± 0.19 mg/dL). As expected, the female mice experienced a slower rate of weight gain compared to the males; however, they also developed elevated fasting blood glucose and impaired glucose tolerance compared to age-matched lean controls. Countervailing our previous report whereby the control diet for the female-only study was vivarium standard chow (18% calories from fat), the obese female mice did demonstrate significantly elevated circulating UA levels (2.55 ± 0.15 mg/dL) compared to the proper control (1.68 ± 0.12 mg/dL). This affirms that the choice of control diet is crucial for reaching durable conclusions. In toto, these results, for the first time, reveal elevated circulating UA to be a similar long-term response to obesogenic feeding for both males and females and mirrors clinical observations demonstrating hyperuricemia in obesity for both sexes. [ABSTRACT FROM AUTHOR]

AimsRecent studies suggest that the molybdenum enzymes xanthine oxidase, aldehyde oxidase, and mARC exhibit nitrite reductase activity at low oxygen pressures. However, inhibition studies of xanthine oxidase in humans have failed to block nitrite-dependent changes in blood flow, leading to continued exploration for other candidate nitrite reductases. Another physiologically important molybdenum enzyme—sulfite oxidase (SO)—has not been extensively studied.ResultsUsing gas-phase nitric oxide (NO) detection and physiological concentrations of nitrite, SO functions as nitrite reductase in the presence of a one-electron donor, exhibiting redox coupling of substrate oxidation and nitrite reduction to form NO. With sulfite, the physiological substrate, SO only facilitates one turnover of nitrite reduction. Studies with recombinant heme and molybdenum domains of SO indicate that nitrite reduction occurs at the molybdenum center via coupled oxidation of Mo(IV) to Mo(V). Reaction rates of nitrite to NO decreased in the presence of a functional heme domain, mediated by steric and redox effects of this domain. Using knockdown of all molybdopterin enzymes and SO in fibroblasts isolated from patients with genetic deficiencies of molybdenum cofactor and SO, respectively, SO was found to significantly contribute to hypoxic nitrite signaling as demonstrated by activation of the canonical NO-sGC-cGMP pathway.InnovationNitrite binds to and is reduced at the molybdenum site of mammalian SO, which may be allosterically regulated by heme and molybdenum domain interactions, and contributes to the mammalian nitrate-nitrite-NO signaling pathway in human fibroblasts.ConclusionSO is a putative mammalian nitrite reductase, catalyzing nitrite reduction at the Mo(IV) center.

Air pollution accounts for more than 7 million premature deaths worldwide. Using ultrafine carbon black (CB) and ozone (O3) as a model for an environmental co-exposure scenario, the dose response relationships in acute pulmonary injury and inflammation were determined by generating, characterizing, and comparing stable concentrations of CB aerosols (2.5, 5.0, 10.0 mg/m3), O3 (0.5, 1.0, 2.0 ppm) with mixture CB + O3 (2.5 + 0.5, 5.0 + 1.0, 10.0 + 2.0). C57BL6 male mice were exposed for 3 h by whole body inhalation and acute toxicity determined after 24 h. CB itself did not cause any alteration, however, a dose response in pulmonary injury/inflammation was observed with O3 and CB + O3. This increase in response with mixtures was not dependent on the uptake but was due to enhanced reactivity of the particles. Benchmark dose modeling showed several-fold increase in potency with CB + O3 compared with CB or O3 alone. Principal component analysis provided insight into response relationships between various doses and treatments. There was a significant correlation in lung responses with charge-based size distribution, total/alveolar deposition, oxidant generation, and antioxidant depletion potential. Lung tissue gene/protein response demonstrated distinct patterns that are better predicted by either particle dose/aerosol responses (interleukin-1β, keratinocyte chemoattractant, transforming growth factor beta) or particle reactivity (thymic stromal lymphopoietin, interleukin-13, interleukin-6). Hierarchical clustering showed a distinct signature with high dose and a similarity in mRNA expression pattern of low and medium doses of CB + O3. In conclusion, we demonstrate that the biological outcomes from CB + O3 co-exposure are significantly greater than individual exposures over a range of aerosol concentrations and aerosol characteristics can predict biological outcome. [ABSTRACT FROM AUTHOR]

Vascular disease, a significant cause of morbidity and mortality in the developed world, results from vascular injury. Following vascular injury, damaged or dysfunctional endothelial cells and activated SMCs engage in vasoproliferative remodeling and the formation of flow-limiting intimal hyperplasia (IH). We hypothesized that vascular injury results in decreased bioavailability of NO secondary to dysregulated arginine-dependent NO generation. Furthermore, we postulated that nitrite-dependent NO generation is augmented as an adaptive response to limit vascular injury/proliferation and can be harnessed for its protective effects. Here we report that sodium nitrite (intraperitoneal, inhaled, or oral) limited the development of IH in a rat model of vascular injury. Additionally, nitrite led to the generation of NO in vessels and SMCs, as well as limited SMC proliferation via [p21.sup.Waf1/Cip1] signaling. These data demonstrate that IH is associated with increased arginase-1 levels, which leads to decreased NO production and bioavailability. Vascular injury also was associated with increased levels of xanthine oxidoreductase (XOR), a known nitrite reductase. Chronic inhibition of XOR and a diet deficient in nitrate/nitrite each exacerbated vascular injury. Moreover, established IH was reversed by dietary supplementation of nitrite. The vasoprotective effects of nitrite were counteracted by inhibition of XOR. These data illustrate the importance of nitrite-generated NO as an endogenous adaptive response and as a pathway that can be harnessed for therapeutic benefit., Introduction Vascular disease contributes significantly to morbidity and mortality in the developed world (1). Current treatments for this disease process, including surgical bypass and percutaneous interventions, are limited by the [...]