Identifying secreted mediators driving the cognitive benefits of exercise holds great promise for the treatment of cognitive decline in aging or Alzheimer’s disease (AD). Here, we show that irisin, the cleaved and circulating form of the exercise-induced membrane protein FNDC5, is sufficient to confer the exercise benefits on cognitive function. Genetic deletion of FNDC5/irisin (global F5KO mice) impairs cognitive function in exercise, aging, and AD. Diminished pattern separation in F5KOs can be rescued by delivering irisin directly into the dentate gyrus, suggesting that irisin is the active moiety. In F5KO mice, adult-born neurons in the dentate gyrus are morphologically, transcriptionally, and functionally abnormal. Importantly, elevation of circulating irisin levels by peripheral delivery of irisin via adeno-associated viral overexpression in the liver, results in enrichment of central irisin and is sufficient to improve both the cognitive deficit and neuropathology in AD mouse models. Irisin is a crucial regulator of cognitive benefits of exercise and potential therapeutic for treating cognitive disorders including AD.

The beneficial effects of exercise on the brain are well known. However, the underlying molecular mechanisms are much less well understood. Interestingly, myokine, hormones secreted by muscle in response to exercise, gained attention as such beneficial mediators. In this review, we will focus on FNDC5 and its secreted form, the newly discovered myokine "irisin". We will discuss their role in the beneficial effects of exercise and its potential application in neurodegenerative disorders.

Cannabinoid receptor (CB) 2 is an immune cell–localized GPCR that has been hypothesized to regulate the magnitude of inflammatory responses. However, there is currently no consensus as to the mechanism by which CB 2 mediates its anti-inflammatory effects in vivo . To address this question, we employed a murine dorsal air pouch model with wild-type and CB 2 −/− 8–12-wk-old female and male C57BL/6 mice and found that acute neutrophil and lymphocyte antigen 6 complex, locus C hi monocyte recruitment in response to Zymosan was significantly enhanced in CB 2 −/− mice. Additionally, levels of matrix metalloproteinase 9 and the chemokines C-C motif chemokine ligand (CCL)2, CCL4, and C-X-C motif chemokine ligand 10 in CB 2 −/− pouch exudates were elevated at earlier time points. Importantly, using mixed bone marrow chimeras, we revealed that the proinflammatory phenotype in CB 2 −/− mice is neutrophil-intrinsic rather than stromal cell–dependent. Indeed, neutrophils isolated from CB 2 −/− mice exhibited an enhanced migration-related transcriptional profile and increased adhesive phenotype, and treatment of human neutrophils with a CB 2 agonist blocked their endothelial transmigration. Overall, we have demonstrated that CB 2 plays a nonredundant role during acute neutrophil mobilization to sites of inflammation and, as such, it could represent a therapeutic target for the development of novel anti-inflammatory compounds to treat inflammatory human diseases.—Kapellos, T. S., Taylor, L., Feuerborn, A., Valaris, S., Hussain, M. T., Rainger, G. E., Greaves, D. R., Iqbal, A. J. Cannabinoid receptor 2 deficiency exacerbates inflammation and neutrophil recruitment.

Chemerin is a chemotactic protein that induces migration of several immune cells including macrophages, immature dendritic cells, and NK cells. Chemerin binds to three G protein-coupled receptors (GPCRs), including CCRL2. The exact function of CCRL2 remains unclear. CCRL2 expression is rapidly upregulated during inflammation, but it lacks the intracellular DRYLAIV motif required for classical GPCR downstream signalling pathways, and it has not been reported to internalise chemerin upon binding. The aim of this study was to investigate what role if any CCRL2 plays during acute inflammation. Using the zymosan- and thioglycollate-induced murine models of acute inflammation, we report that mice deficient in the Ccrl2 gene display exaggerated local and systemic inflammatory responses, characterised by increased myeloid cell recruitment. This amplified myeloid cell recruitment was associated with increased chemerin and CXCL1 levels. Furthermore, we report that the inflammatory phenotype observed in these mice is dependent upon elevated levels of endogenous chemerin. Antibody neutralisation of chemerin activity in Ccrl2−/− mice abrogated the amplified inflammatory responses. Importantly, chemerin did not directly recruit myeloid cells but rather increased the production of other chemotactic proteins such as CXCL1. Administration of recombinant chemerin to wild-type mice before inflammatory challenge recapitulated the increased myeloid cell recruitment and inflammatory mediator production observed in Ccrl2−/− mice. We have demonstrated that the absence of CCRL2 results in increased levels of local and systemic chemerin levels and exacerbated inflammatory responses during acute inflammatory challenge. These results further highlight the importance of chemerin as a therapeutic target in inflammatory diseases.

Great attention has been placed on the link between metabolism and immune function giving rise to the term "immunometabolism." It is widely accepted that inflammation and oxidative stress are key processes that underlie metabolic complications during obesity, diabetes, and atherosclerosis. Therefore, identifying the mechanisms and mediators that are involved in the regulation of both inflammation and metabolic homeostasis is of high scientific and therapeutic interest. Recent Advances: G protein-coupled receptors (GPCRs) that signal in response to metabolites have emerged as attractive therapeutic targets in inflammatory disease. Critical Issues and Future Directions: In this review, we discuss recent findings about the physiological role of the main metabolite-sensing GPCRs, their implication in immunometabolic disorders, their principal endogenous and synthetic ligands, and their potential as drug targets in inflammation and metabolic disease. Antioxid. Redox Signal. 29, 237-256.

Background: Despite considerable research on exercise-induced neuroplasticity in the brain, a major ongoing challenge in translating findings from animal studies to humans is that clinical and preclinical settings employ very different techniques. Objective: Here we aim to bridge this divide by using diffusion tensor imaging MRI (DTI), an advanced imaging technique commonly applied in human studies, in a longitudinal exercise study with mice. Methods: Wild-type mice were exercised using voluntary free-wheel running, and MRI scans were at baseline and after four weeks and nine weeks of running. Results: Both hippocampal volume and fractional anisotropy, a surrogate for microstructural directionality, significantly increased with exercise. In addition, exercise levels correlated with effect size. Histological analysis showed more PDGFRα+ oligodendrocyte precursor cells in the corpus callosum of running mice. Conclusions: These results provide compelling in vivo support for the concept that similar adaptive changes occur in the brains of mice and humans in response to exercise.

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The first panellist will focus on the jurists view on the legislative proposal on DCC, discuss proportionality of measure, incl. key considerations for DCC and PLF data combinations. A basic overview on the differences between vaccination, certificates, immunity passports and other passes, and the key characteristics of the DCC will be provided. Feasibility in terms of implementing acts across EU Member-States will be elaborated upon, incl. both potential expiry and revocation, as well as potential remedies in case of emerging issues, i.e., right to DCC, but no vaccine, strong contraindication against vaccination, known issues of reduced immunity despite vaccination, etc. Critical aspects with relevance for both the European and the global dimensions, i.e., GDPR and data transfer agreements, secondary use of health data, human-rights' issues, implications for vulnerable groups, etc., will also be discussed.