MKEY, a Peptide Inhibitor of CXCL4‐CCL5 Heterodimer Formation, Protects Against Stroke in Mice

Abstract

Background MKEY, a synthetic cyclic peptide inhibitor of CXCL4–CCL5 heterodimer formation, has been shown to protect against atherosclerosis and aortic aneurysm formation by mediating inflammation, but whether it modulates neuroinflammation and brain injury has not been studied. We therefore studied the role of MKEY in stroke‐induced brain injury in mice.Methods and Results MKEY was injected into mice after stroke with 60 minutes of middle cerebral artery occlusion. Infarct volume and neurological deficit scores were measured. Protein levels of CCL5 and its receptor CCR5 were detected by Western blot and fluorescence‐activated cell sorting (FACS), respectively. Numbers of microglia‐derived macrophages (MiMΦs) and monocyte‐derived MΦs (MoMΦs) in the brain, and their subsets, based on the surface markers CD45, CD11b, CCR2, CX3CR1, and Ly6C, were analyzed by FACS. MΦs and neutrophil infiltration in the ischemic brain were stained with CD68 and myeloperoxidase (MPO), respectively, and assessed by immunofluorescent confocal microscopy. The results showed that expressions of CCL5 and its receptor CCR5, were increased in the ischemic brain after stroke. MKEY injection significantly reduced infarct sizes and improved neurological deficit scores measured 72 hours after stroke. In addition, MKEY injection inhibited the number of MoMΦs, but not MiMΦs, in the ischemic brain. Furthermore, MKEY inhibited protein expression levels of Ly6C,CCR2, and CX3CR1 on MoMΦs. Lastly, the confocal study also suggests that the number of CD68‐positive MΦs and MPO‐positive neutrophils was inhibited by MKEY injection.Conclusions MKEY injection protects against stroke‐induced brain injury, probably by inhibiting MoMΦ‐mediated neuroinflammation.

The dual role of platelet‐innate immune cell interactions in thrombo‐inflammation

“…Moreover, PF4 was shown to downregulate atheroprotective genes in human macrophages and to increase OxLDL uptake by macrophages, exacerbating atherosclerosis . Platelet PF4 forms heteromers with RANTES, resulting in increased monocyte adhesion to endothelial cells and disruption of this interaction inhibits atherosclerotic plaque formation in hyperlipidemic mice and in a mouse model of stroke . Moreover, platelet‐dependent monocyte recruitment and activation may increase plaque instability, partly by promoting matrix metallopeptidase 9 production by monocytes .…”

The peripheral immune response after stroke—A double edge sword for blood‐brain barrier integrity

“…According to distinct cues, the microglia/macrophages can differentiate into two subtypes—inflammatory and antiinflammatory phenotypes . In their proinflammatory phenotypes, they can aggravate the BBB injury while in their phagocytosis or antiinflammatory phenotypes they may play distinct roles toward BBB repair and regeneration . However, recent studies suggest that the terminology of microglia/macrophage polarization may be limited.…”

Advanced Functional Materials and Cell‐Based Therapies for the Treatment of Ischemic Stroke and Postischemic Stroke Effects

“…This may utilize targeting moieties that specifically target the BBB and/or the infarcted area. In view of this, several peptides have been proposed in the literature that targets the endothelial cells of the BBB (e.g., angiopep‐2), the infarcted tissue (e.g., stroke homing peptide), or cell‐penetrating peptides45d that have the ability to enhance the uptake of the bearing nanostructures.…”

“…In this section, we are going to present some of the most recent works using peptides as therapeutics, while throughout the paper we are going to present the functionalization of other nanotherapeutics with peptides that act as targeting ligands. Peptides can lead to a reduction of the infarct volume and to improved neuroprotection through several mechanisms including, modulation of neuroinflammation as well as inhibition of several apoptotic pathways44b,e,45 (e.g., caspase family). The presented peptide‐based nanotherapeutics can act as antioxidants,45c as inhibitors of specific ion channels and as inhibitors for chemokine heterodimer's formation .…”

“…Peptides can lead to a reduction of the infarct volume and to improved neuroprotection through several mechanisms including, modulation of neuroinflammation as well as inhibition of several apoptotic pathways44b,e,45 (e.g., caspase family). The presented peptide‐based nanotherapeutics can act as antioxidants,45c as inhibitors of specific ion channels and as inhibitors for chemokine heterodimer's formation . In addition, peptides can lead to functional recovery through improved circulation, enhanced angiogenesis, and finally through endogenous neural stem cells' mobilization and remyelination 44d.…”