Research ReportRANTES has a potential to play a neuroprotective role in an autocrine/paracrine manner after ischemic stroke
Introduction
Chemokines are a family of proteins secreted by cells that induce chemotaxis in nearby responsive cells. They are classified largely into 4 groups, i.e. C, C-C, CXC, and CX3C chemokines, based on their structure (Cyster, 1999, Murdoch and Finn, 2000, Murphy et al., 2000, Zlotnik and Yoshie, 2000). Some chemokines are considered pro-inflammatory and are induced during an immune response to recruit immunological cells, while others are involved in controlling the migration of cells during normal processes of tissue development or maintenance (Cyster, 1999, Murphy et al., 2000, Zlotnik and Yoshie, 2000). Chemokines exert their biological effects through G protein-coupled receptors (GPCR) that are selectively expressed on the surfaces of their target cells (Cyster, 1999, Murdoch and Finn, 2000, Murphy et al., 2000).
RANTES (Regulated upon Activation, Normal T-cell Expressed, and Secreted), also known as CCL5, is one of the C-C chemokines and plays an active role in recruiting leukocytes, T cells, eosinophils and basophils, into inflammatory sites, thereby functioning as a pro-inflammatory molecule (Maghazachi et al., 1996). The effects of RANTES are exerted through three different types of GPCR, i.e. CCR1, CCR3 and CCR5 (Daugherty et al., 1996, Ignatov et al., 2006, Proudfoot et al., 2001, Slimani et al., 2003, Struyf et al., 2001).
In experimental stroke models, it has been reported that infarct volume is significantly reduced in RANTES deficient mice (Terao et al., 2008). Because RANTES is a representative pro-inflammatory chemokine and inflammation is a detrimental factor of ischemic stroke, the results from RANTES deficient mice seem to be plausible. On the other hand, it has been recently reported that infarct volume is rather enlarged in mice with deletion of CCR5 (Sorce et al., 2010). Although these data highly suggest an important role of RANTES in ischemic stroke in mice, it is unclear why infarct volume is enlarged in CCR5 knockout mice and whether RANTES plays a significant role in human ischemic stroke.
In the present study, we examined the clinical significance of RANTES in human acute ischemic stroke. Plasma RANTES was elevated at day 0 after stroke onset and was highly associated with brain-derived neurotrophic factor (BDNF), epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF), major neuroprotective molecules, suggesting a neuroprotective potential of RANTES in ischemic stroke. We also examined whether RANTES was produced and could function within the brain in the acute phase of ischemic stroke, and whether the chemokine could have a neuroprotective potential using cultured neuronal cells.
Section snippets
Plasma RANTES was significantly elevated after ischemic stroke in humans and highly correlated with neurotrophic factors
In our blood biomarker study for acute ischemic stroke in humans, we found that plasma concentration of RANTES was much higher than that of other major C-C chemokines that we measured in this study by 50–100-fold at baseline and was significantly elevated at day 0 after onset when compared with healthy controls (Fig. 1A). Other major C–C chemokines, such as MCP-1 (CCL2) (Fig. 1B), MIP-1α (CCL3) (Fig. 1C) and MIP-1β (CCL4) (Fig. 1D), were not significantly altered at day 0, suggesting that the
Discussion
In the present study, we demonstrated that RANTES was elevated in plasma after ischemic stroke in humans and mice, and that it was produced in the brain, particularly from neurons in peri-infarct areas, in an experimental stroke model. Although RANTES is a well-known pro-inflammatory chemokine that recruits white blood cells into infarct areas (Montecucco et al., 2012) and thus has been believed to exaggerate brain infarction (Terao et al., 2008, Yilmaz and Granger, 2010), the present study
Blood biomarker study for ischemic stroke
Patients were recruited from the Fukuoka Stroke Registry, a multicenter observational study for acute ischemic stroke in Japan (Kamouchi et al., 2011, Kumai et al., 2012). On admission, the objectives, study design, risks, and benefits were explained in detail to each patient or surrogate family members and written informed consent was obtained. Patients who consented to the study were prospectively enrolled. Patients with ischemic stroke hospitalized within 24 h after onset and with definite
Acknowledgments
We are grateful to Naoko Kasahara and Eiko Noguchi (Kyushu University) for technical support. The work was supported in part by a Grant-in-Aid for Scientific Research (B) (21390243) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (to T.A.); the Takeda Science Foundation, Japan (to T.A.), the Innovation Center for Medical Redox Navigation (to T.A.); and a Grant-in-Aid for Scientific Research (C) (22590937) from the Ministry of Education, Culture, Sports, Science
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These authors contributed equally to this work.