Differential HIF and NOS responses to acute anemia: defining organ-specific hemoglobin thresholds for tissue hypoxia.

Tissue hypoxia likely contributes to anemia-induced organ injury and mortality. Severe anemia activates hypoxia-inducible factor (HIF) signaling by hypoxic- and neuronal nitric oxide (NO) synthase- (nNOS) dependent mechanisms. However, organ-specific hemoglobin (Hb) thresholds for increased HIF expression have not been defined. To assess organ-specific Hb thresholds for tissue hypoxia, HIF-α (oxygen-dependent degradation domain, ODD) luciferase mice were hemodiluted to mild, moderate, or severe anemia corresponding to Hb levels of 90, 70, and 50 g/l, respectively. HIF luciferase reporter activity, HIF protein, and HIF-dependent RNA levels were assessed. In the brain, HIF-1α was paradoxically decreased at mild anemia, returned to baseline at moderate anemia, and then increased at severe anemia. Brain HIF-2α remained unchanged at all Hb levels. Both kidney HIF-1α and HIF-2α increased earlier (Hb ∼70-90 g/l) in response to anemia. Liver also exhibited an early HIF-α response. Carotid blood flow was increased early (Hb ∼70, g/l), but renal blood flow remained relatively constant, only increased at Hb of 50 g/l. Anemia increased nNOS (brain and kidney) and endothelia NOS (eNOS) (kidney) levels. Whereas anemia-induced increases in brain HIFα were nNOS-dependent, our current data demonstrate that increased renal HIFα was nNOS independent. HIF-dependent RNA levels increased linearly (∼10-fold) in the brain. However, renal HIF-RNA responses (MCT4, EPO) increased exponentially (∼100-fold). Plasma EPO levels increased near Hb threshold of 90 g/l, suggesting that the EPO response is sensitive. Collectively, these observations suggest that each organ expresses a different threshold for cellular HIF/NOS hypoxia responses. This knowledge may help define the mechanism(s) by which the brain and kidney maintain oxygen homeostasis during anemia.

Benefits and harms of aspirin desensitization for aspirin-exacerbated respiratory disease: a systematic review and meta-analysis.

BACKGROUND: Aspirin desensitization is increasingly recommended for the treatment of aspirin-exacerbated respiratory disease (AERD). The objective of this study is to systematically review the efficacy and safety of aspirin desensitization in patients with AERD. METHODS: We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, and World Health Organization (WHO) International Clinical Trials Registry Platform from inception to January 5, 2019. We included randomized trials and comparative observational studies in any language. Data extraction and risk of bias assessment were performed in duplicate independently. RESULTS: Five randomized controlled trials (RCTs) enrolled 233 patients with AERD. Compared to placebo, aspirin desensitization (mean daily dose 800 mg) improved quality of life (risk ratio [RR] 2.00; 95% confidence interval [CI], 1.31 to 3.06; heterogeneity measure [I2 ] = 0%; risk difference [RD] +24%; 22-item Sino-Nasal Outcome Test [SNOT-22] scale [0 to 110, higher worse]; mean difference [MD] -10.27 [95% CI, -6.39 to -14.15]; moderate-certainty); and respiratory symptoms (RR 2.20 [95% CI, 1.55 to 2.73], I2 = 34%, RD +36%; American Academy of Otolaryngology (AAO) scale [0 to 20, higher worse]; MD -2.56 [95% CI,-1.12 to -3.92]; high-certainty). Aspirin desensitization increased adverse events severe enough to cause treatment discontinuation (major bleeding, gastritis, asthma exacerbation, or rash causing drug discontinuation, RR 4.39 [95% CI, 1.43 to 13.50], I2 = 0%, RD +11%, moderate-certainty), and gastritis (RR 3.84 [95% CI, 1.12 to 13.19], I2 = 0%, RD +9%, low-certainty). Findings were robust to sensitivity analyses. Two available observational studies were not informative because they lacked adjustment for confounders and/or contemporaneous controls. CONCLUSION: In patients with AERD, moderate-certainty and high-certainty evidence shows that aspirin desensitization meaningfully reduces symptoms of rhinosinusitis and improves quality of life, but results in a significant increase in adverse events.

Age-associated metabolic dysregulation in bone marrow-derived macrophages stimulated with lipopolysaccharide.

Macrophages are major contributors to age-associated inflammation. Metabolic processes such as oxidative phosphorylation, glycolysis and the urea cycle regulate inflammatory responses by macrophages. Metabolic profiles changes with age; therefore, we hypothesized that dysregulation of metabolic processes could contribute to macrophage hyporesponsiveness to LPS. We examined the intracellular metabolome of bone marrow-derived macrophages from young (6-8 wk) and old (18-22 mo) mice following lipopolysaccharide (LPS) stimulation and tolerance. We discovered known and novel metabolites that were associated with the LPS response of macrophages from young mice, which were not inducible in macrophages from old mice. Macrophages from old mice were largely non-responsive towards LPS stimulation, and we did not observe a shift from oxidative phosphorylation to glycolysis. The critical regulatory metabolites succinate, γ-aminobutyric acid, arginine, ornithine and adenosine were increased in LPS-stimulated macrophages from young mice, but not macrophages from old mice. A shift between glycolysis and oxidative phosphorylation was not observed during LPS tolerance in macrophages from either young or old mice. Metabolic bottlenecks may be one of the mechanisms that contribute to the dysregulation of LPS responses with age.