A Novel Cell-permeable Antioxidant Peptide, SS31, Attenuates Ischemic Brain Injury by Down-regulating CD36

Abstract

Oxidative stress is implicated in the pathogenesis of ischemia/ reperfusion injury. Recently, we demonstrated that activation of CD36, a class B scavenger receptor, mediates free radical production and tissue injury in cerebral ischemia (1). Oxidized low density lipoproteins (oxLDL) are among the ligands that bind to CD36 and are elevated in acute cerebral infarction. SS31 is a cell-permeable antioxidant peptide that reduces intracellular free radicals and inhibits LDL oxidation/lipid peroxidation (2). The current study was designed to investigate whether treatment with SS31 normalizes ischemia-induced redox changes and attenuates CD36-mediated tissue injury. C57BL/6 mice were subjected to transient middle cerebral artery occlusion (MCAO). Redox status and infarct volume were measured in animals treated with either saline or SS31. Oxidative stress induced by ischemia/reperfusion profoundly depleted glutathione (GSH) concentrations in the ipsilateral cortex and striatum. Treating mice with SS31 immediately after reperfusion significantly attenuated ischemia-induced GSH depletion in the cortex and reduced infarct size. By contrast, the protective effect of SS31 was absent in CD36 knock-out mice, indicating that SS31 is acting through inhibition of CD36. Treating C57BL/6 mice with SS31 reduced CD36 expression in postischemic brain and mouse peritoneal macrophages (MPM). Further in vitro studies revealed that SS31 attenuated oxLDL-induced CD36 expression and foam cell formation in MPM. These in vivo and in vitro studies indicate that the down-regulation of CD36 by novel class antioxidant peptides may be a useful strategy to treat ischemic stroke victims. Generation of reactive oxygen species (ROS)2 and depletion of intracellular antioxidants following cerebral ischemia/reperfusion are hallmarks of oxidative stress and lead to tissue injury. Glutathione and ascorbate are major endogenous cerebral antioxidants that serve as biochemical markers of intracellular redox status (3). It is generally accepted that these antioxidants are important for protection of brain during post-ischemic oxidative stress, although dynamic interactions among antioxidants in vivo are not entirely clear. Depletion of intracellular antioxidants has been associated with stroke pathology and repletion of antioxidant status has reduced neuronal damage but has produced inconsistent improvement in stroke outcome (4 -8). Ischemic injury also causes a local inflammatory reaction by activated microglia and infiltrated inflammatory cells that further release pro-inflammatory cytokines and ROS within the injured site.CD36, a glycosylated surface receptor, belongs to a class B scavenger receptor and is localized in lipid rafts of plasma membrane and in mitochondria (9 -11). It is expressed on microglia, macrophages, microvascular endothelium, cardiac and skeletal muscle, adipocytes, and platelets and recognizes a variety of ligands including oxidized low density lipoproteins (oxLDL), advanced glycation end products, long chain fatty acids, fibrillar ␤-a...

Hypoxia Up-regulates CD36 Expression and Function via Hypoxia-inducible Factor-1- and Phosphatidylinositol 3-Kinase-dependent Mechanisms

“…Consistent with this, we have reported that inflammatory corneal neovascularization induces elevated levels of CD36 (18), whereas others have documented an up-regulation of CD36 during cerebral ischemia (29) and an attenuation of its expression and activity following antioxidant treatment (30,31). Collectively, these studies led us to hypothesize that hypoxia modulates CD36 expression and function, with the objective of characterizing the mechanisms behind its regulation.…”

“…Transcripts-Studies have demonstrated that ROS generated during cerebral ischemia are markedly attenuated in Cd36 null mice and that treatment with antioxidant peptides down-regulates ischemia-induced CD36 expression (29,31). Consequently, we sought to determine whether ROS activity was implicated in the hypoxic regulation of CD36.…”

CD36 participates in a signaling pathway that regulates ROS formation in murine VSMCs

“…No function for CD36 has been identified, however, on VSMCs. Since FeCl 3 and other injuries induce thrombosis via generation of oxidant damage and since CD36 has been reported to promote ROS formation in macrophages in vitro and in a murine cerebral ischemia model in vivo (13,14), we hypothesized that CD36 on VSMCs could contribute to vascular injury by generating further oxidant stress and that part of the "thrombo-protection" seen in cd36 -/-mice is due to diminished ROS production in the vessel wall.…”

Protecting Mechanism of Puerarin on the Brain Neurocyte of Rat in Acute Local Ischemia Brain Injury and Local Cerebral Ischemia-reperfusion Injury

“…3,4) Besides, operations have some strict indications and risk. 5 7) Many pharmacological interventions such as cerebral vasodilator, 8) thrombolytics, 9) Ca 2＋ channel blocker, 10) antioxidant 11) and free radical scavenger 12) have been observed to produce acute ischemia and cerebral ischemia-reperfusion protection. Meanwhile, we still have to face that these medications present various problems such as serious side eŠects, uncertain curative eŠects, low compliance even toxicity.…”