Kazunori Takenouchi

Edaravone attenuates cerebral ischemic injury by suppressing aquaporin-4

Aquaporin-4 (AQP4) plays a role in the generation of post-ischemic edema. Pharmacological modulation of AQP4 function may thus provide a novel therapeutic strategy for the treatment of stroke, tumor-associated edema, epilepsy, traumatic brain injury, and other disorders of the central nervous system (CNS) associated with altered brain water balance. Edaravone, a free radical scavenger, is used for the treatment of acute ischemic stroke (AIS) in Japan. In this study, edaravone significantly reduced the infarct area and improved the neurological deficit scores at 24h after reperfusion in a rat transient focal ischemia model. Furthermore, edaravone markedly reduced AQP4 immunoreactivity and protein levels in the cerebral infarct area. In light of observations that edaravone specifically inhibited AQP4 in a rat transient focal ischemia model, we propose that edaravone might reduce cerebral edema through the inhibition of AQP4 expression following cerebral infarction.

B Cell-Derived Vascular Endothelial Growth Factor A Promotes Lymphangiogenesis and High Endothelial Venule Expansion in Lymph Nodes

Vascular endothelial growth factor A (VEGF-A) is a prominent growth factor for both angiogenesis and lymphangiogenesis. Recent studies have shown the importance of VEGF-A in enhancing the growth of lymphatic endothelial cells in lymph nodes (LNs) and the migration of dendritic cells into LNs. VEGF-A is produced in inflamed tissues and/or in draining LNs, where B cells are a possible source of this growth factor. To study the effect of B cell-derived VEGF-A, we created transgenic mice (CD19Cre/hVEGF-Afl) that express human VEGF-A specifically in B cells. We found that the human VEGF-A produced by B cells not only induced lymphangiogenesis in LNs, but also induced the expansion of LNs and the development of high endothelial venules. Contrary to our expectation, we observed a significant decrease in the Ag-specific Ab production postimmunization with OVA and in the proinflammatory cytokine production postinoculation with LPS in these mice. Our findings suggest immunomodulatory effects of VEGF-A: B cell-derived VEGF-A promotes both lymphangiogenesis and angiogenesis within LNs, but then suppresses certain aspects of the ensuing immune responses.

C-reactive protein induces high-mobility group box-1 protein release through activation of p38MAPK in macrophage RAW264.7 cells

BACKGROUND C-reactive protein (CRP) is widely used as a sensitive biomarker for inflammation. Increasing evidence suggests that CRP plays a role in inflammation. High-mobility group box-1 (HMGB1), a primarily nuclear protein, is passively released into the extracellular milieu by necrotic or damaged cells and is actively secreted by monocytes/macrophages. Extracellular HMGB1 as a potent inflammatory mediator has stimulated immense curiosity in the field of inflammation research. However, the molecular dialogue implicated between CRP and HMGB1 in delayed inflammatory processes remains to be explored. METHODS AND RESULTS The levels of HMGB1 in culture supernatants were determined by Western blot analysis and enzyme-linked immunosorbent assay in macrophage RAW264.7 cells. Purified CRP induced the release of HMGB1 in a dose- and time-dependent fashion. Immunofluorescence analysis revealed nuclear translocation of HMGB1 in response to CRP. The binding of CRP to the Fc gamma receptor in RAW264.7 cells was confirmed by fluorescence-activated cell sorter analysis. Pretreatment of cells with IgG-Fc fragment, but not IgG-Fab fragment, efficiently blocked this binding. CRP triggered the activation of p38MAPK and ERK1/2, but not Jun N-terminal kinase. Moreover, both p38MAPK inhibitor SB203580 and small interfering RNA significantly suppressed the release of HMGB1, but not the MEK1/2 inhibitor U-0126. CONCLUSION We demonstrated for the first time that CRP, a prominent risk marker for inflammation including atherosclerosis, could induce the active release of HMGB1 by RAW264.7 cells through Fc gamma receptor/p38MAPK signaling pathways, thus implying that CRP plays a crucial role in the induction, amplification, and prolongation of inflammatory processes, including atherosclerotic lesions.

The Free Radical Scavenger Edaravone Rescues Rats from Cerebral Infarction by Attenuating the Release of High-Mobility Group Box-1 in Neuronal Cells

Edaravone, a potent free radical scavenger, is clinically used for the treatment of cerebral infarction in Japan. Here, we examined the effects of edaravone on the dynamics of high-mobility group box-1 (HMGB1), which is a key mediator of ischemic-induced brain damage, during a 48-h postischemia/reperfusion period in rats and in oxygen-glucose-deprived (OGD) PC12 cells. HMGB1 immunoreactivity was observed in both the cytoplasm and the periphery of cells in the cerebral infarction area 2 h after reperfusion. Intravenous administration of 3 and 6 mg/kg edaravone significantly inhibited nuclear translocation and HMGB1 release in the penumbra area and caused a 26.5 ± 10.4 and 43.8 ± 0.5% reduction, respectively, of the total infarct area at 24 h after reperfusion. Moreover, edaravone also decreased plasma HMGB1 levels. In vitro, edaravone dose-dependently (1–10 μM) suppressed OGD- and H2O2-induced HMGB1 release in PC12 cells. Furthermore, edaravone (3–30 μM) blocked HMGB1-triggered apoptosis in PC12 cells. Our findings suggest a novel neuroprotective mechanism for edaravone that abrogates the release of HMGB1.

Minocycline attenuates both OGD-induced HMGB1 release and HMGB1-induced cell death in ischemic neuronal injury in PC12 cells.

High mobility group box-1 (HMGB1), a non-histone DNA-binding protein, is massively released into the extracellular space from neuronal cells after ischemic insult and exacerbates brain tissue damage in rats. Minocycline is a semisynthetic second-generation tetracycline antibiotic which has recently been shown to be a promising neuroprotective agent. In this study, we found that minocycline inhibited HMGB1 release in oxygen-glucose deprivation (OGD)-treated PC12 cells and triggered the activation of p38mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinases (ERK1/2). The ERK kinase (MEK)1/2 inhibitor U-0126 and p38MAPK inhibitor SB203580 blocked HMGB1 release in response to OGD. Furthermore, HMGB1 triggered cell death in a dose-dependent fashion. Minocycline significantly rescued HMGB1-induced cell death in a dose-dependent manner. In light of recent observations as well as the good safety profile of minocycline in humans, we propose that minocycline might play a potent neuroprotective role through the inhibition of HMGB1-induced neuronal cell death in cerebral infarction.

Association between reduced ADAMTS13 and diabetic nephropathy

INTRODUCTION Deficiency of Von Willebrand factor (VWF)-cleaving protease (ADAMTS13) causes platelet thrombosis in the microcirculation. Intrarenal coagulation is thought to be associated with the development and progression of diabetic nephropathy. Our aim was to clarify the association between plasma ADAMTS13 antigen (ADAMTS13Ag) levels and diabetic nephropathy. MATERIAL AND METHODS We measured the plasma levels of VWF antigen (VWFAg) and ADAMTS13Ag, and calculated the VWF/ADAMTS13 ratio in 86 type 2 diabetic patients and 26 healthy volunteers, to investigate the relationship between these levels and renal function. With regard to diabetic macroangiopathy, the relationship between these levels and carotid intima-media thickness (IMT) was also investigated. RESULTS AND CONCLUSIONS A significant positive and negative correlation was noted between ADAMTS13Ag and the estimated glomerular filtration rate (eGFR), vWF/ADAMTS13 ratio and eGFR, respectively. The diabetic patients were divided into normoalbuminuria (n=50), microalbuminuria (n=8) and overt nephropathy (n=28) groups. Compared among these three groups and the 26 healthy volunteers, ADAMTS13Ag was significantly lower only in the overt nephropathy group. The mean carotid IMT was measured in 69 patients and was significantly negatively correlated with ADAMTS13Ag and positively correlated with VWF/ADAMTS13 ratio. When these 69 patients were divided into four groups according to eGFR and ADAMTS13 levels (ADAMTS13/eGFR; low/low: n=12; high/low: n=7; low/high: n=25; high/high: n=25), the mean carotid IMT was increased in patients with a low ADAMTS13Ag in the same eGFR group. The present study suggests that reduced ADAMTS13 might be associated with diabetic nephropathy.

Edaravone: a new therapeutic approach for the treatment of acute stroke.

Acute stroke, including acute ischemic stroke (AIS) and acute hemorrhagic stroke, (AHS) is a common medical problem with particular relevance to the demographic changes in industrialized societies. In recent years, treatments for AIS have emerged, including thrombolysis with tissue plasminogen activator (t-PA). Although t-PA is the most effective currently available therapy, it is limited by a narrow therapeutic time window and side effects, and only 3% of all AIS patients receive thrombolysis. Edaravone was originally developed as a potent free radical scavenger and, since 2001, has been widely used to treat AIS in Japan. It was shown that edaravone extended the narrow therapeutic time window of t-PA in rats. The therapeutic time window is very important for the treatment of AIS, and early edaravone treatment is more effective. Thus, more AIS patients might be rescued by administering edaravone with t-PA. Meanwhile, edaravone attenuates AHS-induced brain edema, neurologic deficits and oxidative injury in rats. Although edaravone treatment is currently only indicated for AIS, it does offer neuroprotective effects against AHS in rats. Therefore, we hypothesize that early administration of edaravone can rescue AHS patients as well as AIS patients. Taken together, our findings suggest that edaravone should be immediately administered on suspicion of acute stroke, including AIS and AHS.

Low grade inflammation inhibits VEGF induced HUVECs migration in p53 dependent manner

In the course of studying crosstalk between inflammation and angiogenesis, high doses of pro-inflammatory factors have been reported to induce apoptosis in cells. Under normal circumstances also the pro-inflammatory cytokines are being released in low doses and are actively involved in cell signaling pathways. We studied the effects of low grade inflammation in growth factor induced angiogenesis using tumor necrosis factor alfa (TNFα) and vascular endothelial growth factor A (VEGF) respectively. We found that low dose of TNFα can inhibit VEGF induced angiogenesis in human umbilical vein endothelial cells (HUVECs). Low dose of TNFα induces mild upregulation and moreover nuclear localization of tumor suppressor protein 53 (P53) which causes decrease in inhibitor of DNA binding-1 (Id1) expression and shuttling to the cytoplasm. In absence of Id1, HUVECs fail to upregulate β3-integrin and cell migration is decreased. Connecting low dose of TNFα induced p53 to β3-integrin through Id1, we present additional link in cross talk between inflammation and angiogenesis.

Upregulation of non-β cell-derived vascular endothelial growth factor A increases small clusters of insulin-producing cells in the pancreas.

Pancreatic β cell-derived vascular endothelial growth factor A (VEGF-A) contributes to normal β cell function. We therefore hypothesized that non-β cell-derived VEGF-A may affect its properties in adult mice.We generated transgenic mice expressing human VEGF-A (hVEGF-A) in a visceral smooth muscle cell (SMC)-dominant manner under the control of the transgelin (Tagln/SM22α) promoter via a tamoxifen-induced Cre/loxP recombination system (SM-CreER(T2)/hVEGF mice).SM-CreER(T2)/hVEGF mice received tamoxifen orally followed by microscopic examination of their pancreas 4 weeks after the hVEGF-A induction. The number of clusters of insulin-producing cells (IPCs) in islets, pancreatic ducts, and individual IPCs were counted.The number of small IPC clusters (100-215 μm(2)) in the pancreas increased significantly in SM-CreER(T2)/hVEGF mice compared with SM-CreER(T2)(Ki) mice (473 out of 1 992 counts vs. 199 out of 976 counts, p<0.05), although total IPC area and the number of pancreatic duct IPCs, in proportion to exocrine area, were similar between the 2 groups. Although most small IPC clusters observed in SM-CreER(T2)/hVEGF mice were not accompanied by α and/or δ cells, some were attached to a single or a few α cells. An STZ-induced diabetic state in SM-CreER(T2)/hVEGF mice was slightly ameliorated, with only one point of significance 12 weeks after STZ administration, compared with SM-CreER(T2)(Ki) mice.Upregulation of non-β cell-derived VEGF-A may alter the composition of pancreatic IPCs by increasing the number of small IPC clusters. These findings provide new information on the role of non-β cell-derived VEGF-A to IPC regeneration and insulin production.