The CD36 receptor plays an important role in facilitating fatty acid transport to the heart. The present study aimed to assess whether EP 80317, a selective synthetic peptide ligand of CD36, is cardioprotective in a murine model of myocardial ischaemia and reperfusion (MI/R) injury. Mice were pretreated with daily subcutaneous injections of EP 80317 for 14 days before being subjected to a 30 min ligation of the left anterior descending coronary artery. The treatment reduced the infarct area and improved myocardial haemodynamics and function, as shown by an increase in cardiac output, ejection fraction and stroke work, and a reduced total peripheral resistance. In contrast, administration of EP 51389, a tripeptide analogue devoid of binding affinity to CD36, did not protect against myocardial injury. Six hours after myocardial reperfusion, EP 80317-treated mice showed reduced myocardial fatty acid uptake, as assessed by micro-positron emission tomography, in agreement with reduced levels of circulating non-esterified fatty acids. Studies using [¹⁴C]-palmitate infusion revealed reduced lipolysis, although no significant change in insulin or catecholamine plasma levels were observed. Increased expression levels of adipogenic and anti-lipolytic genes further supported an effect of EP 80317 in preventing fatty acid mobilization from adipose tissue. No effect of the treatment was observed in CD36^−/− mice. Our results show that pretreatment with EP 80317 protected the heart against damage and dysfunction elicited by MI/R, along with a transient reduction in peripheral lipolysis. Our findings support CD36 as a novel target for the treatment of ischaemic cardiopathy.

CD36 has been shown to associate with non-receptor Src kinases to activate mitogen-activated protein kinases and trigger cytoskeletal remodelling, important events in foam cell formation and macrophage migration. Yet, its role in regulating circulating mononuclear phagocyte trafficking to atherosclerotic lesions has not been investigated. The aim of the present study was to investigate the role of CD36 in modulating the recruitment of mononuclear phagocytes to the arterial wall and the associated vascular inflammation, using both pharmacological and genetic approaches. Apolipoprotein E-deficient (apoE^−/−) mice fed a high-fat, high-cholesterol diet were treated daily with a CD36 ligand, EP 80317 (300 µg/kg), or 0.9% NaCl for 6 or 12 weeks. Forty-eight hours before sacrifice, mice were injected iv with ¹¹¹Indium-labelled macrophages. A 65% (P < 0.001) reduction of labelled macrophage accumulation at aortic lesions was observed in EP 80317-treated mice, mainly at the level of the aortic arch and iliac arteries, correlating with a 43% reduction of atherosclerotic lesion areas. This was associated with reduced phosphorylation of the focal adhesion kinase Pyk2 following stimulation with oxidized phospholipid in a Src kinase- and CD36-dependent manner. At the vascular level, EP 80317 treatment reduced the expression of pro-inflammatory proteins, including NADPH oxidase, inducible nitric oxide synthase, vascular endothelial cell adhesion molecule-1, and CCL2 chemokine. Plasma IL-6 levels were also reduced by 40% (P < 0.05). In contrast, none of these proteins was modulated in EP 80317-treated apoE/CD36 double knockout (apoE^−/−/CD36^−/−) mice. Our results support a role for CD36 signalling in the regulation of mononuclear phagocyte trafficking to atherosclerotic-prone sites and in the associated vascular wall inflammation.

Studies were undertaken to define the role of 5-lipoxygenase (5-LO) products and, in particular, of leukotriene (LT) B4 in the polymorphonuclear leukocyte (PMN) emigration process using a rabbit model of dermal inflammation. Our results show that i.v. administration to rabbits of MK-0591, a compound that inhibits LT biosynthesis in blood and tissues when administered in vivo, significantly reduced 51Cr-labeled PMN accumulation in response to intradermally injected chemotactic agonists, including IL-8, FMLP, C5a, and LTB4 itself. In addition, pretreatment of the labeled PMN with MK-0591 ex vivo before their injection in recipient animals was equally effective in reducing 51Cr-labeled PMN emigration to dermal inflammatory sites. These results support a role for de novo synthesis of 5-LO metabolites by PMN for their chemotactic response to inflammatory mediators. Other studies demonstrated that elevated intravascular concentration of LTB4 interferes with PMN extravasation inasmuch as a continuous i.v. infusion of LTB4, in the range of 5–300 ng/min/kg, dose-dependently inhibited extravascular PMN accumulation to acute inflammatory skin sites elicited by the chemoattractants LTB4, FMLP, C5a, and IL-8 and by TNF-α, IL-1β, and LPS; such phenomena may constitute a natural protective mechanism from massive tissue invasion by activated PMN in specific pathologic conditions such as ischemia (and reperfusion). These studies demonstrate additional functions of 5-LO products in the regulation of PMN trafficking, distinct from the well-characterized chemotactic activity of LTB4 present in the extravascular compartment.

Insufficient oxygen delivery to organs leads to tissue dysfunction and cell death. Reperfusion, although vital to organ survival, initiates an inflammatory response that may both aggravate local tissue injury and elicit remote organ damage. Polymorphonuclear neutrophil (PMN) trafficking to remote organs following ischaemia/reperfusion (I/R) is associated with the release of lipid mediators, including leucotriene (LT) B₄, cysteinyl‐LTs (CysLTs) and platelet‐activating factor (PAF). Yet, their potentially cooperative role in regulating I/R‐mediated inflammation has not been thoroughly assessed. The present study aimed to determine the cooperative role of lipid mediators in regulatingPMNmigration, tissue oedema and injury using selective receptor antagonists in selected models of I/R and dermal inflammation. Our results show that rabbits, pre‐treated orally withBIIL284 and/orWEB2086 andMK‐0571, were protected from remote tissue injury following I/R or dermal inflammation in an additive or synergistic manner when the animals were pre‐treated with two drugs concomitantly. The functional selectivity of the antagonists towards their respective agonists was assessedin vitro, showing that neitherBIIL284 norWEB2086 prevented the inflammatory response toIL‐8, C5a and zymosan‐activated plasma stimulation. However, these agonists elicitedLTB₄biosynthesis in isolated rabbitPMNs. Similarly, a cardioprotective effect ofPAFandLTB₄receptor antagonists was shown following myocardial I/R in mice. Taken together, these results underscore the intricate involvement ofLTB₄andPAFin each other's responses and provide further evidence that targeting bothLTs andPAFreceptors provides a much stronger anti‐inflammatory effect, regulatingPMNmigration and oedema formation.

CD36 is a multiligand receptor involved in lipid metabolism. We investigated the mechanisms underlying the cardioprotective effect of CP‐3(iv), an azapeptide belonging to a new class of selective CD36 ligands. The role of CP‐3(iv) in mediating cardioprotection was investigated because CD36 signaling leads to activation of peroxisome proliferator–activated receptor‐γ, a transcriptional regulator of adiponectin. CP‐3(iv) pretreatment reduced infarct size by 54% and preserved hemodynamics in C57BL/6 mice subjected to 30 min coronary ligation and reperfusion but had no effect in CD36‐deficient mice. The effects of CP‐3(iv) were associated with an increase in circulating adiponectin levels, epididymal fat adiponectin gene expression, and adiponectin transcriptional regulators ( Pparg, Cebpb, Sirt1 ) after 6 h of reperfusion. Reduced myocardial oxidative stress and apoptosis were observed along with an increase in expression of myocardial adiponectin target proteins, including cyclooxygenase‐2, phospho‐AMPK, and phospho‐Akt. Moreover, CP‐3(iv) increased myocardial performance in isolated hearts, whereas blockade of adiponectin with an anti‐adiponectin antibody abrogated it. CP‐3(iv) exerts cardioprotection against myocardial ischemia and reperfusion (MI/R) injury and dysfunction, at least in part, by increasing circulating and myocardial adiponectin levels. Hence, both paracrine and endocrine effects of adiponectin may contribute to reduced reactive oxygen species generation and apoptosis after MI/R, in a CD36‐dependent manner.—Huynh, D. N., Bessi, V. L., Ménard, L., Piquereau, J., Proulx, C., Febbraio, M., Lubell, W. D., Carpentier, A. C., Burelle, Y., Ong, H., Marleau, S. Adiponectin has a pivotal role in the cardioprotective effect of CP‐3(iv), a selective CD36 azapeptide ligand, after transient coronary artery occlusion in mice. FASEB J. 32, 807–818 (2018). www.fasebj.org

Diabetes is a conventional risk factor for atherosclerotic cardiovascular disease and myocardial infarction (MI) is the most common cause of death among these patients. Mesenchymal stromal cells (MSCs) in patients with type 2 diabetes mellitus (T2DM) and atherosclerosis have impaired ability to suppress activated T-cells (i.e. reduced immunopotency). This is mediated by an inflammatory shift in MSC-secreted soluble factors (i.e. pro-inflammatory secretome) and can contribute to the reduced therapeutic effects of autologous T2DM and atherosclerosis-MSC post-MI. The signalling pathways driving the altered secretome of atherosclerosis- and T2DM-MSC are unknown. Specifically, the effect of IκB kinase β (IKKβ) modulation, a key regulator of inflammatory responses, on the immunopotency of MSCs from T2DM patients with advanced atherosclerosis has not been studied. MSCs were isolated from adipose tissue obtained from patients with (i) atherosclerosis and T2DM (atherosclerosis+T2DM MSCs, n = 17) and (ii) atherosclerosis without T2DM (atherosclerosis MSCs, n = 17). MSCs from atherosclerosis+T2DM individuals displayed an inflammatory senescent phenotype and constitutively expressed active forms of effectors of the canonical IKKβ nuclear factor-κB transcription factors inflammatory pathway. Importantly, this constitutive pro-inflammatory IKKβ signature resulted in an altered secretome and impaired in vitro immunopotency and in vivo healing capacity in an acute MI model. Notably, treatment with a selective IKKβ inhibitor or IKKβ knockdown (KD) (clustered regularly interspaced short palindromic repeats/Cas9-mediated IKKβ KD) in atherosclerosis+T2DM MSCs reduced the production of pro-inflammatory secretome, increased survival, and rescued their immunopotency both in vitro and in vivo. Constitutively active IKKβ reduces the immunopotency of atherosclerosis+T2DM MSC by changing their secretome composition. Modulation of IKKβ in atherosclerosis+T2DM MSCs enhances their myocardial repair ability.