Yuichiro Kikkawa

Impaired feedback regulation of the receptor activity and the myofilament Ca2+ sensitivity contributes to increased vascular reactiveness after subarachnoid hemorrhage.

Cerebral vasospasm determines the prognosis of subarachnoid hemorrhage (SAH). The increased vascular reactiveness has an important role in the development of cerebral vasospasm. This study analyzed the roles of the receptor-mediated signaling and the myofilament Ca2+ sensitivity in the increased vascular reactiveness in SAH, using the basilar artery of a rabbit SAH model. Endothelin-1, thrombin, and phenylephrine induced transient increases in [Ca2+]i, myosin light chain phosphorylation, and contraction in the controls. All these responses were not only enhanced but also became sustained in SAH. In the sequential stimulation of thrombin receptor or α1-adrenoceptor, the second response was substantially attenuated in the controls, whereas it was maintained in SAH. The thrombin-induced contraction in SAH irreversibly persisted even after terminating the thrombin stimulation. This contraction was completely reversed by trypsin and a Gαq inhibitor YM254890, thus suggesting the sustained receptor activity during the sustained contraction. YM254890 also inhibited the endothelin-1- and phenylephrine-induced sustained contraction. Furthermore, the GTPγS-induced transient contraction in the control α-toxin-permeabilized strips was converted to a sustained contraction in SAH. The results provide the first evidence that the feedback inactivation of the receptor activity and the myofilament Ca2+ sensitivity was impaired in SAH, thus contributing to the increased vascular reactiveness.

Preliminary Study on the Clinical Application of Augmented Reality Neuronavigation

OBJECTIVE To develop an augmented reality (AR) neuronavigation system with Web cameras and examine its clinical utility. METHODS The utility of the system was evaluated in three patients with brain tumors. One patient had a glioblastoma and two patients had convexity meningiomas. Our navigation system comprised the open-source software 3D Slicer (Brigham and Womens Hospital, Boston, Massachusetts, USA), the infrared optical tracking sensor Polaris (Northern Digital Inc., Waterloo, Canada), and Web cameras. We prepared two different types of Web cameras: a handheld type and a headband type. Optical markers were attached to each Web camera. We used this system for skin incision planning before the operation, during craniotomy, and after dural incision. RESULTS We were able to overlay these images in all cases. In Case 1, accuracy could not be evaluated because the tumor was not on the surface, though it was generally suitable for the outline of the external ear and the skin. In Cases 2 and 3, the augmented reality error was ∼2 to 3 mm. CONCLUSION AR technology was examined with Web cameras in neurosurgical operations. Our results suggest that this technology is clinically useful in neurosurgical procedures, particularly for brain tumors close to the brain surface.

Enhanced Contractile Response of the Basilar Artery to Platelet-Derived Growth Factor in Subarachnoid Hemorrhage

Background and Purpose— The level of platelet-derived growth factor (PDGF) in cerebrospinal fluid is elevated in subarachnoid hemorrhage (SAH). Therefore, the contractile effect of PDGF on the basilar artery was examined in SAH. Methods and Results— A rabbit double-hemorrhage SAH model was used. In the medial layers of the control basilar artery, PDGF had no effect on contraction up to 1 nmol/L, whereas 3 nmol/L PDGF induced slight contraction. In SAH, PDGF induced an enhanced contraction with an increase in [Ca2+]i at 1 nmol/L and higher concentrations. The levels of [Ca2+]i and tension induced by 1 nmol/L PDGF in SAH were 17% and 20%, respectively, of those obtained with 118 mmol/L K+ depolarization. The PDGF-induced elevation of [Ca2+]i and contraction seen in SAH were abolished in the absence of extracellular Ca2+. In α-toxin–permeabilized strips of SAH animals, PDGF induced no further development of tension during contraction induced by 300 nmol/L Ca2+, suggesting no direct effect on myofilament Ca2+ sensitivity. Genistein at 10 &mgr;mol/L completely inhibited the tension induced by 1 nmol/L PDGF. The level of myosin light-chain phosphorylation was significantly increased by 1 nmol/L PDGF. Conclusions— These results show that the contractile response to PDGF of the basilar artery was enhanced in SAH. The PDGF-induced contraction depended mostly on tyrosine phosphorylation and Ca2+-dependent myosin light-chain phosphorylation. The enhancement of the responsiveness to PDGF may therefore contribute to the development of cerebral vasospasm after SAH.

Mechanisms underlying potentiation of endothelin-1-induced myofilament Ca(2+) sensitization after subarachnoid hemorrhage.

Increased vascular smooth muscle contractility has an important role in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). Myofilament Ca2+ sensitivity is a major determinant of smooth muscle contractility. We investigated changes in the Ca2+-sensitizing effect of endothelin-1 (ET-1) and the mechanisms underlying ET-1-induced Ca2+ sensitization after SAH using a rabbit SAH model. After SAH, the contractile response to ET-1 was enhanced, and the ETA receptor expression was upregulated in the basilar artery. In α-toxin-permeabilized preparations, ET-1 induced enhanced and prolonged contraction after SAH, suggesting that ET-1-induced Ca2+ sensitization is potentiated after SAH. Endothelin-1-induced Ca2+ sensitization became less sensitive to inhibitors of Rho-associated coiled-coil protein kinase (ROCK) and protein kinase C (PKC) after SAH. The expression of PKCα, ROCK2, PKC-potentiated phosphatase inhibitor of 17 kDa (CPI-17) and myosin phosphatase target subunit 1 (MYPT1) was upregulated, and the level of phosphorylation of CPI-17 and MYPT1 was elevated after SAH. This study demonstrated for the first time that the Ca2+-sensitizing effect of ET-1 on myofilaments is potentiated after SAH. The increased expression and activity of PKCα, ROCK2, CPI-17, and MYPT1, as well as the upregulation of ETA receptor expression are suggested to underlie the enhanced and prolonged Ca2+ sensitization induced by ET-1.

Combined argatroban and anti-oxidative agents prevents increased vascular contractility to thrombin and other ligands after subarachnoid haemorrhage

BACKGROUND AND PURPOSE Increased vascular contractility plays a fundamental role in cerebral vasospasm in subarachnoid haemorrhage (SAH). We investigated the role of thrombin and its receptor, proteinase‐activated receptor 1 (PAR1), and other G protein‐coupled receptors in the increased contractility, and examined the preventive effects of the thrombin inhibitor, argatroban, and anti‐oxidative agents, vitamin C and tempol.

Proposed Mechanism of Cerebral Vasospasm: Our Hypothesis and Current Topics

Increased vascular contractility plays an important role in the development of cerebral vasospasm following subarachnoid hemorrhage (SAH). Increased vascular contractility can be attributed to either endothelial dysfunction or increased contractility of vascular smooth muscle. Endothelial damage and dysfunction cause impairment of endothelium-dependent vasodilation of the cerebral artery after SAH. In addition to endothelial damage and dysfunction, receptor upregulation in vascular smooth muscle contributes to the induction and enhancement of contractile responses to agonists. Our recent data revealed that feedback regulation of the activity of the G protein-coupled receptor and myofilament Ca(2+) sensitivity is impaired after SAH. This impaired feedback regulation is suggested to cause a sustained contractile response to various agonists, thereby contributing to increased vascular contractility. In addition, three current topics are reviewed: endothelin type A receptor antagonists, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors for treatment, and cortical spreading depolarization for the mechanism of cerebral vasospasm.

Executive Function and Diffusion in Frontal White Matter of Adults with Moyamoya Disease

BACKGROUND Cognitive impairment is a frequent complication of moyamoya disease (MMD) in adults. Chronic hypoperfusion in frontal lobes can lead to subtle brain injury, resulting in cognitive dysfunctions. Apparent diffusion coefficient (ADC) in normal-appearing white matter on conventional magnetic resonance imaging correlates with cerebral hemodynamics in the frontal lobe. OBJECTIVE The purpose of this study was to examine the relationship of ADC with executive function in patients with MMD. METHODS Thirty-one patients (25 women and 6 men; mean age, 32.6 ± 10.4 years) were included in this study. Executive function was evaluated by the Frontal Assessment Battery (FAB) at 21.5 ± 7.5 years after disease onset. ADC was measured in the normal-appearing frontal white matter. RESULTS ADC was statistically related to the occurrence of executive dysfunction in multivariate analysis (P = .0179). Total FAB score and ADC were negatively correlated (r(2) = .22; P = .0072; Spearman correlation coefficient, -.41; P = .024). Elevated ADC predicted executive dysfunction (area under the receiver operating characteristic curve, .73; 95% confidence interval, .55-.91; P = .029). CONCLUSIONS The association of ADC with executive function might suggest that ADC is useful in screening for executive dysfunction during follow-up in the outpatient setting.

Gene Expression Profiling and Bioinformatic Analysis of Rabbit Basilar Artery after Experimental Subarachnoid Hemorrhage

Objective: The molecular mechanisms which contribute to the development of vascular events including cerebral vasospasm after subarachnoid hemorrhage (SAH) in cerebral artery remain to be elucidated. In this study, we investigated the time course of changes in the gene expression of cerebral artery using rabbit SAH model and performed bioinformatic analysis of differentially expressed genes. Methods: Rabbit basilar arteries were harvested on days 3, 5, and 7 after initial hemorrhage. Changes in gene expression of the rabbit basilar artery were investigated by using Agilent rabbit oligo microarrays and analyzed the data by Ingenuity Pathway Analysis (IPA). Results: Among investigated 43,623 genes, 1,121 genes were differentially expressed at least 1 time point. We found that the number, magnitude of fold change, and gene expression pattern were most dynamically changed on day 3, whereas narrowing of the basilar artery became most severe on day 5. In microarray datasets analyzed by IPA revealed that 25 biological functions identified from differentially expressed genes were significantly upregulated. Conclusion: Our findings that were based on gene expression analysis followed by bioinformatic analysis may provide a simple basis to interlink the various presumed pathogenesis of vascular events including cerebral vasospasm after SAH.

Radiation-induced spinal cord glioblastoma with cerebrospinal fluid dissemination subsequent to treatment of lymphoblastic lymphoma.

Background: Radiation-induced glioma arising in the spinal cord is extremely rare. We report a case of radiation-induced spinal cord glioblastoma with cerebrospinal fluid (CSF) dissemination 10 years after radiotherapy for T-cell lymphoblastic lymphoma. Case Description: A 32-year-old male with a history of T-cell lymphoblastic lymphoma presented with progressive gait disturbance and sensory disturbance below the T4 dermatome 10 years after mediastinal irradiation. Gadolinium-enhanced magnetic resonance (MR) imaging revealed an intramedullary tumor extending from the C6 to the T6 level, corresponding to the previous radiation site, and periventricular enhanced lesions. In this case, the spinal lesion was not directly diagnosed because the patient refused any kind of spinal surgery to avoid worsening of neurological deficits. However, based on a biopsy of an intracranial disseminated lesion and repeated immmunocytochemical examination of CSF cytology, we diagnosed the spinal tumor as a radiation-induced glioblastoma. The patient was treated with radiotherapy plus concomitant and adjuvant temozolomide. Then, the spinal tumor was markedly reduced in size, and the dissemination disappeared. Conclusion: We describe our detailed diagnostic process and emphasize the diagnostic importance of immunocytochemical analysis of CSF cytology.

Upregulation of tissue inhibitor of metalloproteinase-1 contributes to restoration of the extracellular matrix in the rabbit basilar artery during cerebral vasospasm after subarachnoid hemorrhage

Vascular remodeling caused by extracellular matrix (ECM) metabolism contributes to the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). The balance between tissue inhibitor of metalloproteinases (TIMPs) and matrix metalloproteinases (MMPs) plays an important role in ECM remodeling. We investigated the mechanism of vascular remodeling following cerebral vasospasm in a rabbit double hemorrhage model. Rabbit basilar arteries were harvested on days 3, 5, and 7 after initial hemorrhage. TIMP-1, TIMP-2, MMP-2, and MMP-9 mRNA and protein expression were investigated with microarray analysis, quantitative real-time PCR, immunoblot analysis, and enzyme-linked immunosorbent assay (ELISA). The expression and localization of TIMP-1, TIMP-2, MMP-2, MMP-9, elastin, fibronectin, laminin, and collagens I, III, and IV were investigated with immuohistochemical staining. After SAH, TIMP-1 mRNA and protein expression were significantly increased on day 3 and then decreased to the control level on days 5 and 7. MMP-9 protein expression was significantly increased on day 7. TIMP-2 and MMP-2 mRNA and protein expression were significantly increased on day 7. Elastin, fibronectin, laminin, and collagens I, III, and IV protein expression was decreased on day 3 and then restored to control levels on day 7. Upregulation of TIMP-1 during the early phase of cerebral vasospasm may contribute to the recovery of the ECM during the late phase of cerebral vasospasm, resulting in a protective role of TIMP-1 from cerebral vasospasm. Moreover, the increase in arterial compliance by the decrease in ECM during the early phase of cerebral vasospasm may facilitate vasoconstriction of the cerebral artery.