Myokine irisin-induced protection against oxidative stress in vitro. Involvement of heme oxygenase-1 and antioxidazing enzymes superoxide dismutase-2 and glutathione peroxidase

Irisin is a recently discovered myokine reported as protective protein released from exercising skeletal muscles. Although myokines were recently reported to possess the antioxidizing properties, the impact of irisin on the functions of macrophages with respect to its anti-inflammatory potential has not been fully elucidated. Here, we determined the ability of irisin to interact with reactive oxygen species (ROS) in RAW 264.7 murine macrophages. The macrophages were pre-incubated with irisin (0 - 50 nM), some of which had undergone additional co-incubation with bacterial lipopolysaccharide (LPS) (100 ng/ml). Cell viability, the reactive oxygen species scavenging potential as well as the mRNA and protein expression of key oxidative stress factors such as superoxide dismutase 1 (SOD-1), superoxide dismutase 2 (SOD-2), glutathione peroxidase (GSH-Px), catalase 9 (Cat-9), nuclear factor (erythroid-derived 2)-like 2-related factor (Nrf2) and heme oxygenase-1 (HO-1) were evaluated. We found that irisin applied in a concentration of 50 nM significantly attenuated the production of harmful H₂O₂ and this effect appears to be mediated by a significant increase in the expression of key enzymes involved with antioxidative stress pathways including SOD, GSH-Px and Cat-9 predominantly observed after stimulation of these cells with LPS. We conclude that 1) irisin exhibits a potent antioxidant and anti-inflammatory activities in non-stimulated and LPS-stimulated isolated murine macrophages in vitro, and 2) this protective and antioxidative activity of irisin in vitro might be considered as an important component of protective action of this peptide in vivo, especially under condition of exercise.

New insight into the direct anti-inflammatory activity of a myokine irisin against proinflammatory activation of adipocytes. Implication for exercise in obesity

A biological activity of myokine irisin, has been intensively investigated in the context of a browning process occurring in white adipose tissue, but its role as a modulator of immune response has been little studied. The aim of our study was to determine the impact of irisin (0 - 100 nM) on pro-inflammatory activation of adipocyte 3T3 L1 cell line. Irisin reduced in a concentration-dependent manner the expression and activity of major proinflammatory cytokines, e.g. tumor necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6) expression and their secretion into cell medium. Moreover, irisin enhanced adiponectin synthesis reversing the effect of the lipopolysaccharide (LPS)-induced attenuation of this adipokine expression. The opposite effect was observed for leptin whose expression increased by LPS and this effect was suppressed by irisin application. A decreased phosphorylation and activation of nuclear factor kappa B (NFκB) in the presence of irisin suggests that mechanism of action irisin involves the inhibition of an inflammatory transcription factor. Irisin exerts also an inhibitory effect on macrophage migration toward chemoattractants present in adipocyte supernatants. Among the specific molecules secreted by adipocytes was monocyte chemotactic protein 1 (MCP-1) whose expression was suppressed by irisn. In majority of experiments irisin was effective in 100 nM concentration but in some of them the inhibitory effects occurred already in a concentration of 50 nM of this peptide. This study for the first time showed that adipocytes are directly affected by irisin and provides an evidence on anti-inflammatory action of irisin on fat cells.

Immunomodulatory effect of riboflavin deficiency and enrichment - reversible pathological response versus silencing of inflammatory activation

Ariboflavinosis, that is, vitamin B2 deficiency, is a common problem affecting the populations of both developing and affluent countries. Teenagers, elderly people, pregnant women, and alcohol abusers represent groups that are particularly susceptible to this condition. This study was aimed to determine the effect of different riboflavin concentrations (deficiency and supplementation) on macrophages response induced by bacteria or yeast-derived factors i.e. lipopolysaccharide (LPS) and zymosan, respectively. Mouse macrophage RAW 264.7 cells were cultured for 5 days in a medium with a riboflavin concentration corresponding to moderate riboflavin deficiency (3.1 nM), physiological state (10.4 nM), or vitamin pill supplementation (300 nM). On the third or fourth day of deprivation, the medium in some groups was supplemented with riboflavin (300 nM). Macrophages activation were assessed after LPS or zymosan stimulation. Short-term (5 days) riboflavin deprivation resulted in the pathological macrophages activation, manifested especially in a reduction of cell viability and excess release of tumor necrosis factor-α (TNF-α) and high-mobility group box 1 (HMGB1) protein. Moreover, the levels of inducible nitric oxide synthase (iNOS), nitric oxide (NO), heat shock protein (Hsp72), interleukin 1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and interleukin 10 (IL-10) decreased after riboflavin deprivation, but medium enrichment with riboflavin (300 nM) on the third or fourth day reversed this effect. In the riboflavin-supplemented group, LPS-stimulated macrophages showed lower mortality accompanied by higher Hsp72 expression, reduction of Toll-like receptor 4 (TLR4) and TNF-α, and elevation of NO, IL-6, and IL-10. Moreover, the TLR6, NO, iNOS, IL-1β, MCP-1, and the keratinocyte chemoattractant (KC) levels significantly decreased in the zymosan-stimulated groups maintained in riboflavin-enriched medium. We conclude that short-term riboflavin deficiency significantly impairs the ability of macrophages to induce proper immune response, while riboflavin enrichment decreases the proinflammatory activation of macrophages.

The impact of physical activity and nutrition on inflammatory bowel disease: the potential role of cross talk between adipose tissue and skeletal muscle

Crohn's disease and ulcerative colitis are both chronic inflammatory bowel diseases (IBDs) characterized by a cyclical nature, which alternates between active and quiescent states, ultimately impairing a patients' quality of life. The etiology of IBD is not known but it likely involves a combination of genetic predisposition and environmental risk factors. Physical exercise has been suggested to provide protection against the onset of IBD, but there are inconsistencies in the findings of the published literature. Current research recommends exercise to help counteract some IBD-specific complications and preliminary studies suggest that physical activity may be beneficial in reducing the symptoms of IBD. Obesity is becoming more prevalent in patients diagnosed with IBD and may be associated with higher disease activity. There is evidence that adipokines are involved in the inflammatory and metabolic pathways. Hypertrophy of the mesenteric white adipose tissue has been long recognized as a characteristic feature of Crohn's disease; however its importance is unknown. Recent data suggest that dysregulation of adipokine secretion by white adipose tissue is involved in the pathogenesis of Crohn's disease. Skeletal muscle was shown to produce biologically active myokines, which could be a important contributor to the beneficial effects of exercise. There is mounting evidence for the bi-directional endocrine cross talk between adipose tissue and skeletal muscle. The objective of the present review is to explore the role of exercise and its impact on IBD. Also, we discuss how current discoveries regarding the importance of adipokines and myokines and their cross talk expand our view of the pathological changes and the therapeutic options for IBD.