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Apolipoprotein E (ApoE)-mimetic peptides have been demonstrated to be beneficial in secondary brain injury following experimental subarachnoid hemorrhage (SAH). However, the molecular mechanisms underlying these benefits in SAH models have not been clearly identified. This study investigated whether an ApoE-mimetic peptide affords neuroprotection in early brain injury (EBI) following SAH by attenuating BBB disruption. SAH was induced by an endovascular perforation in young, healthy, male wild-type (WT) C57BL/6J mice. Multiple techniques, including MRI with T2-weighted imaging, FDG PET-CT scanning and histological studies, were used to examine BBB integrity and neurological dysfunction in EBI following SAH. We found that SAH induced a significant increase of BBB permeability and neuron apoptosis, whereas ApoE-mimetic peptide treatment significantly reduced the degradation of tight junction proteins and endothelial cell apoptosis. These effects reduced brain edema and neuron apoptosis, increased cerebral glucose uptake, and improved neurological functions. Further investigation revealed that the ApoE-mimetic peptide inhibited the proinflammatory activators of MMP-9, including CypA, NF-κB, IL-6, TNF-α, and IL-1β, thereby ameliorating BBB disruption at the acute stage of SAH. Together, these data indicate that ApoE-mimetic peptide may be a novel and promising therapeutic strategy for EBI amelioration after SAH that are worthy of further study.

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IntroductionMalaria caused by infection with protozoan parasites of Plasmodium spp. is one of the most serious infectious diseases of humans and causes about one million deaths annually. Plasmodium infection may induce multiple disease syndromes including severe anemia, metabolic acidosis, and neurological dysfunction, e.g. cerebral malaria (CM) [1]. Sequestration of the Correspondence: Dr. Zhong Su e-mail: su_zhong@gibh.ac.cn parasitized red blood cells (pRBCs) in brain microvessels is a characteristic histopathology feature observed in human and murine CM and is believed to be the primary cause of the neurological syndrome [2,3]. Evidence from more recent studies supports the notion that CM is an immune-driven pathology. The proinflammatory cytokines and mediators produced in the "cytokine storm" during malaria induce activation and recruitment of cytotoxic CD8 + cells in brain blood vessels and upregulate the expression of adhesion receptors by brain endothelial cells, leading to leukocyte accumulation and capillary obstruction, cerebral hemorrhage, and hypoxia in brain tissues [1,[4][5][6]. Therefore, the immune regulatory cells and cytokines may be critical in counteracting the inflammatory response and prevention of malaria-associated www.eji-journal.eu 2908 Yunfeng Liu et al. Eur. J. Immunol. 2013. 43: 2907-2918 neuropathology. The levels of anti-inflammatory cytokines such as IL-10 and TGF-β have been shown to be inversely associated with the occurrence of CM in murine malaria [7,8]. However, no consensus has been reached concerning the role of regulatory T (Treg) cells in regulation of CM pathogenesis [9][10][11].B cells have been traditionally considered antibody-producing cell and APC. Many studies in recent years showed the existence of a subset of B cells that exhibit the immune regulatory functions (reviewed in [12]). An early study by Fillatreau et al.[13] reported a subset of B cells that produce IL-10 and inhibit the immune pathology in murine EAE. Further studies revealed that these regulatory B (Breg) cells play important roles in control of immunopathology in autoimmune diseases [14], cancer [15], and organ transplantation [16]. Breg cells have also been shown to modulate immune responses and immunopathology in infectious diseases. Protective immunities against Salmonella typhimurium and Brucella abortus infections were inhibited by transfer of Breg cells in mouse models [17,18]. Transfer of CD1d + CD5 hi Breg cells rendered the BALB/c mice more susceptible to Leishmania major infection [19]. Adoptive transfer of IL-10-producing B cells isolated from helminth-infected mice inhibited the allergic responses and autoimmune inflammation in recipient mice [20]. Thus, Breg cells are an important component of immunoregulatory system and plays critical roles in immune homeostasis.The immunomodulatory roles of Breg cells have been studied in autoimmune and infectious disease settings, but little is known of its role in regulation of immune response and immunopathology of malaria. In this study, we i...