C a IL and fMLP induced the expression of CD
C5a, IL-8, and fMLP induced the 9-Phenanthrol of CD11b and CD162 on the neutrophil surface and shed off CD62L, as detected by FACS (Fig. S6). HRG did not influence the basal and agonist-induced changes in adhesion molecules on the neutrophil surface except for activated form of CD11b (Fig. S6). Since HRG did not influence the expression of PSGL-1 and Mac-1 induced by IL-8, C5a, and fMLP, HRG was speculated not to inhibit the agonists-induced facilitation of neutrophil migration to the destination. This speculation was supported by the present finding that there were no differences in the total number of infiltrating neutrophils in the peritoneal cavity between HRG-treated and control CLP mice (Fig. S1F) and HRG neither stimulated nor inhibited migration to horizontal direction in chemotaxis assay (Fig. S5). Therefore, it is possible that HRG does not interfere with neutrophil activation and migration of neutrophils which are responsible for the recruitment of neutrophils into inflamed sites while playing a role in maintaining the basal state of circulating neutrophils. In contrast, HRG concentration dependently antagonized agonist-induced morphological changes and vice versa (Fig. S8).
Excess activation and even lesion of VECs represent the disorder of septic condition (Opal and van der Poll, 2015). The inhibition of expression of ICAM-1 and P-selectin on VECs induced by LPS or TNF-α in vitro by the addition of HRG (1μM) strongly suggested that physiological concentration of HRG in the circulation constantly suppresses the activation of VECs. Furthermore, HRG appeared to play a protective role against endothelial cell death induced by LPS and TNF-α. Thus, it was concluded that HRG is a crucial regulatory factor of VEC function. We should mention that HRG may exert its effects on mononuclear phagocytes in septic condition in addition to neutrophils and VECs because the binding of HRG to mononuclear phagocytes was reported (Tugues et al., 2014) and phenotype change of macrophages by HRG was observed in cancer (Rolny et al., 2011).
Taken together, the results in the present study strongly suggested that the decrease in plasma HRG constitutes the fundamental pathway for septic pathogenesis. The supplementary treatment of CLP mice with HRG may simultaneously improve complex and multiple aspects of the serious disorders found in septic conditions: the uncontrolled activation of circulating neutrophils, the activation and lesion of VECs, the immunothrombosis, cytokine overproduction, and the disorder of coagulation and fibrinolysis cascades. Supplementary therapy with HRG may provide a novel strategy for the treatment of septic patients (Ward, 2012; Opal et al., 2013; Ranieri et al., 2012; Rice et al., 2010; Russell, 2006) although there might be a therapeutic time window for the treatment.
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Conflicts of Interest
Acknowledgments This work was supported by grants from Scientific Research from the Ministry of Health, Labour, and Welfare of Japan (WA2F2547, WA2F2601), the Japan Agency for Medical Research and Development, AMED (15lk0201014h0003), the Japan Society for the Promotion of Science (JSPS No. 2567046405, 15H0468617), and Secom Science and Technology Foundation to M.N. and from the Hokuto Foundation for Bioscience to H.W. We thank M. Sato, M. Narasaki, and H. Nakamura for their technical assistance. Human fresh frozen plasma was kindly provided by the Japanese Red Cross Society.
Introduction Malaria, a mosquito-borne infectious disease caused by eukaryotic intracellular protists of the genus Plasmodium, kills close to one million people worldwide each year, predominantly children under 5years of age (Murray et al., 2012; World Health Organization, 2013). Of the five species of Plasmodium that can infect humans, infection with Plasmodium falciparum accounts for the vast majority of deaths worldwide. Plasmodium\'s complex life cycle involves invasion of hepatocytes and red blood cells (RBCs); however, the clinical symptoms arise from the invasion of RBCs by the asexual blood stage parasite. Antibodies are thought to play an important role in natural immunity as demonstrated by the reduction in parasitemia and clinical symptoms in P. falciparum-infected individuals following passive transfer of immunoglobulins from semi-immune donors (Cohen et al., 1961; McGregor, 1964a; Sabchareon et al., 1991). However, the effector mechanisms are poorly understood.