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Investigation of the mechanisms activated by endogenous inhibitory pathways can lead to identification of novel targets for cardiovascular inflammatory pathologies. Here we exploited the potential protective role that melanocortin receptor type 3 (MC3-R) activation might play in a myocardial ischemia-reperfusion injury model. In resting conditions, mouse and rat heart extracts expressed MC3-R mRNA and protein, without changes following ischemia-reperfusion. At the cellular level heart macrophages, but not fibroblasts or cardiomyocytes, expressed this receptor, as demonstrated by immunogold labeling. In vivo, administration of the melanocortin agonist MTII (10 μg per mouse equivalent to 9.3 nmol) 30 min prior to ischemia (25 min) attenuated mouse heart 2 h reperfusion injury by ∼40%, an effect prevented by the mixed MC3/4-R antagonist SHU9119 but not by the selective MC4-R antagonist HS204. Similar results were obtained when the compound was given at the beginning of the reperfusion period. Importantly, delayed myocardial damage as measured 24 h post-reperfusion was equally protected by administration of 10 μg MTII. The focus on MC3-R was also substantiated by analysis of the recessive yellow (e/e) mouse, bearing a mutated (inactive) MC1-R, in which MTII was fully protective. Myocardial protection was associated with reduced markers of systemic and local inflammation, including cytokine contents (interleukin-1 and KC) and myeloperoxidase activity. In conclusion, this study has highlighted a previously unrecognized protective role for MC3-R activation on acute and delayed heart reperfusion injury. These data may open new avenues for therapeutic intervention against heart and possibly other organ ischemia-reperfusion injury.

Responses of human neutrophils to TNF‐α are complex and multifactorial. Exposure of human neutrophils to TNF‐α in vitro primes the respiratory burst, delays apoptosis and induces the expression of several genes including chemokines, and TNF‐α itself. This study aimed to determine the impact of TNF‐α exposure on the expression of neutrophil genes and proteins that regulate apoptosis. Quantitative PCR and RNA‐Seq, identified changes in expression of several apoptosis regulating genes in response to TNF‐α exposure. Up‐regulated genes included TNF‐α itself, and several anti‐apoptotic genes, including BCL2A1, CFLAR (cFLIP) and TNFAIP3, whose mRNA levels increased above control values by between 4‐20 fold (n = 3, P

The issue of which melanocortin receptor (MC-R) is responsible for the anti-inflammatory effects of melanocortin peptides is still a matter of debate. Here we have addressed this aspect using a dual pharmacological and genetic approach, taking advantage of the recent characterization of more selective agonists/antagonists at MC1 and MC3-R as well as of the existence of a naturally defective MC1-R mouse strain, the recessive yellow (e/e) mouse. RT-PCR and ultrastructural analyses showed the presence of MC3-R mRNA and protein in peritoneal macrophages (Mφ) collected from recessive yellow (e/e) mice and wild-type mice. This receptor was functional as Mφ incubation (30 min) with melanocortin peptides led to accumulation of cAMP, an effect abrogated by the MC3/4-R antagonist SHU9119, but not by the selective MC4-R antagonist HS024. In vitro Mφ activation, determined as release of the CXC chemokine KC and IL-1β, was inhibited by the more selective MC3-R agonist γ2-melanocyte stimulating hormone but not by the selective MC1-R agonist MS05. Systemic treatment of mice with a panel of melanocortin peptides inhibited IL-1β release and PMN accumulation elicited by urate crystals in the murine peritoneal cavity. MS05 failed to inhibit any of the inflammatory parameters either in wild-type or recessive yellow (e/e) mice. SHU9119 prevented the inhibitory actions of γ2-melanocyte stimulating hormone both in vitro and in vivo while HS024 was inactive in vivo. In conclusion, agonism at MC3-R expressed on peritoneal Mφ leads to inhibition of experimental nonimmune peritonitis in both wild-type and recessive yellow (e/e) mice.

RAW264.7 cell incubation with adrenocorticotrophin (ACTH) led to a time-dependent (4–24 h) and concentration-related (1–100 ng/ml) induction of heme oxygenase (HO)-1, and this was a specific effect, because the pattern of expression of other cellular proteins (HO-2, heat shock proteins 70 and 90) was not modified by ACTH. Combined RT-PCR and Western blot analyses revealed expression of the melanocortin receptor (MC-R) types 1 and 3, but not 4, in these cells. However, use of more selective agonists (including melanotan (MTII)) indicated a predominant role for MC3-R in the induction of HO-1 expression and activity. Relevantly, ACTH and MTII incubation with primary peritoneal macrophages (Mφ) also induced HO-1 expression. The potential link between MC3-R dependent cAMP formation and HO-1 induction was ascertained by the following: 1) ACTH and MTII produced a concentration-dependent accumulation of cAMP in RAW264.7 cells, and 2) whereas a selective inhibitor of cAMP-dependent protein kinase A abrogated ACTH- and MTII-induced HO-1 expression, a soluble cAMP derivative promoted HO-1 induction both in RAW264.7 cells and primary Mφ. HO-1 induction in peritoneal Mφ was also detected following in vivo administration of MTII, and appeared to be functionally related to the antimigratory effect of this melanocortin, as determined with a specific inhibitor (zinc protoporphyrin IX). In conclusion, this study highlights a biochemical link between MC-R activation and HO-1 induction in the Mφ, and proposes that this may be of functional relevance in determining MC-R-dependent control of the host inflammatory response.