Switching off key signaling survival molecules to switch on the resolution of inflammation.

Inflammation is a physiological response of the immune system to injury or infection but may become chronic. In general, inflammation is self-limiting and resolves by activating a termination program named resolution of inflammation. It has been argued that unresolved inflammation may be the basis of a variety of chronic inflammatory diseases. Resolution of inflammation is an active process that is fine-tuned by the production of proresolving mediators and the shutdown of intracellular signaling molecules associated with cytokine production and leukocyte survival. Apoptosis of leukocytes (especially granulocytes) is a key element in the resolution of inflammation and several signaling molecules are thought to be involved in this process. Here, we explore key signaling molecules and some mediators that are crucial regulators of leukocyte survival in vivo and that may be targeted for therapeutic purposes in the context of chronic inflammatory diseases.

Dietary supplementation with omega-3-PUFA-rich fish oil reduces signs of food allergy in ovalbumin-sensitized mice.

We investigated the effect of dietary supplementation with n-3 PUFA (fish oil source) in an experimental model of food allergy. Mice were sensitized (allergic group) or not (nonallergic group) with OVA and were fed with OVA diet to induce allergy signals. Mice were fed with regular diet in which 7% of lipid content was provided by soybean (5% of n-3 PUFA) or fish (25% of n-3 PUFA) oil. Allergic group mice had increased serum levels of antiovalbumin IgE and IgG1 and changes in small intestine, characterized by an increased edema, number of rolling leukocytes in microcirculation, eosinophil infiltration, mucus production, and Paneth cell degranulation, in comparison to non-allergic group. All these inflammatory parameters were reduced in mice fed high-n-3-PUFA diet. Our data together suggest that diet supplementation with n-3 PUFA from fish oil may consist of a valid adjuvant in food allergy treatment.

Experimental food allergy leads to adipose tissue inflammation, systemic metabolic alterations and weight loss in mice.

To investigate the consequences of food allergy in adipose tissue and metabolism, we used a murine model in which mice have been sensitized subcutaneously with ovalbumin and further received antigen-containing diet. Allergic mice presented a significant weight loss 7 days after oral challenge with a concomitant decrease in epididymal adipose tissue mass. This decrease was associated with increased lipolysis and local inflammation. In adipose tissue of allergic mice there were increased leukocyte rolling and adhesion in the microvasculature, increased number of leukocytes in the tissue, especially macrophages (F4/80(+) cells) and increased pro-inflammatory cytokines levels, including TNF-α, IL-6 and CCL2. In addition, we observed low serum concentrations of triglyceride, glucose, total cholesterol and free fatty acids in the allergic mice. Our results suggest that the induction of food allergy in mice leads to adipose tissue inflammation and systemic metabolic alterations that contribute to the weight loss observed.

Inhibition of 5-lipoxygenase alleviates graft-versus-host disease.

Leukotriene B4 (LTB4), a proinflammatory mediator produced by the enzyme 5-lipoxygenase (5-LO), is associated with the development of many inflammatory diseases. In this study, we evaluated the participation of the 5-LO/LTB4 axis in graft-versus-host disease (GVHD) pathogenesis by transplanting 5-LO-deficient leukocytes and investigated the effect of pharmacologic 5-LO inhibition by zileuton and LTB4 inhibition by CP-105,696. Mice that received allogeneic transplant showed an increase in nuclear 5-LO expression in splenocytes, indicating enzyme activation after GVHD. Mice receiving 5-LO-deficient cell transplant or zileuton treatment had prolonged survival, reduced GVHD clinical scores, reduced intestinal and liver injury, and decreased levels of serum and hepatic LTB4 These results were associated with inhibition of leukocyte recruitment and decreased production of cytokines and chemokines. Treatment with CP-105,696 achieved similar effects. The chimerism or the beneficial graft-versus-leukemia response remained unaffected. Our data provide evidence that the 5-LO/LTB4 axis orchestrates GVHD development and suggest it could be a target for the development of novel therapeutic strategies for GVHD treatment.

Immunologic and metabolic effects of high-refined carbohydrate-containing diet in food allergic mice.

OBJECTIVE: Allergic mice show a reduction in body weight and adiposity with a higher inflammatory response in the adipose tissue similar to obese fat tissue. This study aimed to evaluate whether the low-grade inflammatory milieu of mice with diet-induced mild obesity interferes with the allergic response induced by ovalbumin (OVA). METHODS: BALB/c mice were divided into four groups: 1) non-allergic (OVA-) mice fed chow diet, 2) allergic (OVA+) mice fed chow diet, 3) OVA- mice fed high-refined carbohydrate-containing (HC) diet, and 4) OVA+ mice fed HC diet. After 5 wk, allergic groups were sensitized with OVA and received a booster 14 d later. All groups received an oral OVA challenge 7 d after the booster. RESULTS: Allergic groups showed increased serum levels of total IgE, anti-OVA IgE, and IgG1; a high disease activity index score; aversion to OVA; and increased intestinal eosinophil infiltration. Non-allergic mild-obese mice also showed aversion to OVA and an increased number of eosinophils in the proximal jejunum. After the allergic challenge, OVA+ mice fed chow diet showed weight loss and lower adiposity in several adipose tissue depots. OVA+ mice fed HC diet showed a loss of fat mass only in the mesenteric adipose tissue. Furthermore, increased levels of TNF, IL-6, and IL-10 were observed in this tissue. CONCLUSIONS: Our data show that mild-obese allergic mice do not present severe pathologic features of food allergy similar to those exhibited by lean allergic mice. Mild obesity promoted by HC diet ingestion causes important intestinal disorders that appear to modulate the inflammatory response during the antigen challenge.