Masakazu Takayasu

Interleukin-6 and Development of Vasospasm after Subarachnoid Haemorrhage

Summary The authors characterized the role of interleukins in the cerebrospinal fluid (CSF) in the development of vasospasm after subarachnoid haemorrhage (SAH), particularly interleukin-6 (IL-6). Concentrations of interleukin-1β (IL-1 β), IL-6, and interleukin-8 (IL-8) were measured serially in CSF of 24 patients and in serum of 9 patients with SAH and correlated clinically. Additionally, the effects of the same cytokines on the cerebral arteries of dogs were analyzed on angiograms after intracisternal injection. Changes in levels of eicosanoids, angiogenic factors, and soluble cell adhesion molecules were investigated in the CSF of injected dogs. CSF concentrations of IL-6 and IL-8 were elevated significantly above control levels from the acute stage of SAH until the chronic stage. Patients with symptomatic vasospasm had significantly higher levels of IL-6 as well as IL-8 in CSF on days 5 and 7. Intracisternal injection of IL-6 induced long-lasting vasoconstriction in five out of eight dogs, while IL-8 did not. The diameter of canine basilar artery after IL-6 was reduced 29±5% from pretreatment diameter at 8 hours. Prostaglandins E2 and I2 were elevated in CSF for the first 4.5 hour of this IL-6-induced vasospasm. Neither angioenic factors such as platelet-derived growth factor-AB and vascular endothelial growth factor nor soluble cell adhesion molecules were significantly elevated in CSF. IL-6, which increases to very high concentrations in CSF after SAH, may be important in inducing vasospasm, as IL-6 produced long-lasting vasoconstriction in the canine cerebral artery, which may be partly related to activation of the prostaglandin cascade.

Effects of Adrenomedullin, Calcitonin Gene-Related Peptide, and Amylin on Cerebral Circulation in Dogs

The effect of human adrenomedullin on cerebral circulation was investigated in dogs in vivo and in vitro. Bolus administration of adrenomedullin or its homologous peptides, calcitonin gene-related peptide (CGRP) and amylin, into the vertebral artery induced a dose-dependent increase in vertebral blood flow. The potencies of adrenomedullin and CGRP were similar and approximately 100 times more than that of amylin. The effects of adrenomedullin and CGRP were inhibited by CGRP8-37, an antagonist of CGRP. In contrast to substance P, adrenomedullin did not induce an increase in blood flow after prior administration of CGRP. Pretreatment with either NG-nitro-l-arginine methyl ester or indomethacin did not affect the adrenomedullin-induced increase in blood flow. Intracisternal administration of adrenomedullin induced dilation of the basilar and other major cerebral arteries in a dose-dependent manner, accompanied by an increase in the concentration of cyclic AMP in the cerebrospinal fluid. Adrenomedullin also induced relaxation of isolated basilar and middle cerebral arterial rings. These data suggest that adrenomedullin induces vasodilation of cerebral arteries and an increase in vertebral blood by acting at CGRP receptors positively coupled to adenylate cyclase, and that these effects are not dependent on nitric oxide or prostaglandin formation.

Intravenous infusion of adrenomedullin and increase in regional cerebral blood flow and prevention of ischemic brain injury after middle cerebral artery occlusion in rats.

The intravenous infusion of rat adrenomedullin, at concentrations ranging from 0.1 to 1.0 μg/kg/min, for 60 min increased the regional cerebral blood flow (rCBF) in a dose-dependent manner in rats. rCBF was measured using a laser Doppler flowmetry device placed on the surface of the parietal cortex. The increase in rCBF induced by 1.0 μg/kg/min of adrenomedullin was up to 145 ± 10.8% of controls at 60 min (n = 5, p < 0.001). These concentrations of adrenomedullin did not affect systemic blood pressure or other physiologic parameters, including pH, PaCO2, PaO2, hemoglobin, and blood glucose. Repeated infusion of 1.0 μg/kg/min of adrenomedullin at 2-h intervals caused tachyphylaxis (n = 5, p < 0.01). Rat adrenomedullin (1.0 μg/kg/min) demonstrated a more potent effect than the same dose of human adrenomedullin. The C-terminal fragment of human adrenomedullin (0.5 and 5.0 μg/kg/min), adrenomedullin22–52, which did not affect rCBF alone, inhibited the effect of rat adrenomedullin (0.5 μg/kg/min) as a receptor antagonist in a dose-dependent manner. In a model of middle cerebral artery (MCA) occlusion in spontaneously hypertensive rats, pre- and postinfusion of 1.0 μg/kg/min of adrenomedullin suppressed the reduction in rCBF following MCA occlusion (control, 29 ± 15.1%; adrenomedullin group, 45 ± 14.4%; not significant) and decreased the volume of ischemic brain injury (control, 288 ± 35 mm3; adrenomedullin group, 232 ± 35 mm3; p < 0.05). These results suggest that adrenomedullin increases rCBF and prevents ischemic brain injury, partly by increasing the collateral circulation.

Intra-Arterial Infusion of Fasudil Hydrochloride for Treating Vasospasm Following Subarachnoid Haemorrhage

Summary In this pilot study we treated cerebral vasospasm in patients with subarachnoid haemorrhage to assess intra-arterial fasudil hydrochloride. We analysed effects of intra-arterial infusion on angiographically evident cerebral vasospasm in 10 patients including 3 with symptoms of vasospasm. Over 10 to 30 min 15 to 60 mg was administered via the proximal internal carotid artery or vertebral artery following standard angiography, without superselective techniques. A total of 24 arterial territories (21 internal carotid, 3 vertebral) were treated. Angiographic improvement of vasospasm was demonstrated in 16 arterial territories (local dilation in 2, diffuse dilation in 14) in 9 patients. In 2 symptomatic patients, intra-arterial fasudil hydrochloride was associated with resolution of symptoms without sequelae. In the third symptomatic patient the benefit of fasudil hydrochloride was only temporary, and a large cerebral infarction occurred. All asymptomatic patients showed no progression of angiographic to symptomatic vasospasm after treatment with intra-arterial fasudil hydrochloride. No adverse effect was encountered.

Regional differences in the vasodilator response to vasopressin in canine cerebral arteries in vivo.

Background and Purpose The aim of this study was to investigate the regional differences in the in vivo vasodilator responses to vasopressin, which is thought to stimulate the release of nitric oxide from the endothelium, in canine cerebral arteries by angiography Methods Angiograms were performed through a catheter inserted directly into the right vertebral artery and were taken periodically after the infusion of vasopressin. The diameters of various segments of the major arteries were measured using a computerized image analysis system. Results The bolus administration of vasopressin (10 pmol to 1 nmol) into the vertebral artery produced a long-lasting, dose-dependent vasodilation in the major cerebral arteries centering around the circle of Willis. One nanomoleu of vasopressin appeared to be the optimal dose for producing maximal vasodilation. The internal diameters of the basilar, posterior communicating, and internal carotid arteries experienced the most dilation (approximately 150% that of control) 2 minutes after the infusion of 1 nmol of vasopressin, followed by those of the middle cerebral, the intracranial portion of the vertebral, and the anterior spinal arteries (approximately 130% that of control). The extracranial portion of the vertebral artery (109.8 ±4.8% that of control, n=4) was less sensitive to 1 nmol of vasopressin. Pretreatment with an intracisternal injection of 10 ¨mol of NG-monomethyl L-arginine suppressed the vasodilator effect of vasopressin and substance P, whereas it did not affect the response to vasoactive intestinal peptide. Conclusions These results suggest that the arteries composing the circle of Willis at the base of the brain are more sensitive to nitric oxide release induced by vasopressin compared with other intracranial and extracranial arteries.

Role of Nitric Oxide in the Cerebral Vasodilatory Responses to Vasopressin and Oxytocin in Dogs

We angiographically assessed the vasodilatory effects of vasopressin and oxytocin on the basilar arteries in dogs. Intracisternal bolus injections of vasopressin (100 pmol and 1 nmol) and oxytocin (1 and 10 nmol) produced dose-dependent increases in the internal diameter of the basilar arteries without affecting mean arterial blood pressure. The maximal dilatations of the basilar arteries induced by 1 nmol vasopressin and 10 nmol oxytocin were 142.3 ± 19.9 and 136.8 ± 25.5% of the baseline, respectively. When the same peptides were injected into the vertebral artery, the maximal dilatations were similar, but the duration of response was shorter. Pretreatment with intracisternal injection of 10 μmol NG-monomethyl-l-arginine (l-NMMA), which inhibits the synthesis of nitric oxide from l-arginine, suppressed the vasodilatory responses induced by intracisternal injection of vasopressin and oxytocin and by intraarterial injection of vasopressin. Calcitonin gene-related peptide also caused dilatation of the basilar artery when injected into the cisterna magna, but its effect was not blocked by l-NMMA. l-NMMA reduced the basal diameter of the basilar artery in a dose-dependent manner; l-arginine produced dose-dependent increases in diameter. The vasoconstriction induced by l-NMMA was reversed by high concentrations of l-arginine. These results suggest that vasopressin and oxytocin dilate the basilar arteries via the release of nitric oxide from both the intraluminal and the extraluminal sides and that synthesis and release of nitric oxide in the vascular wall contribute to maintenance of basal vascular tonus.

Primary Choroid Plexus Papilloma Located in the Suprasellar Region: Case Report

A 34-year-old woman with primary choroid plexus papilloma occurring in the suprasellar region is reported. No connection with the ventricular system was found during intraoperative observations. The findings of pathological examinations such as hematoxylin and eosin staining, transthyretin (prealbumin) immunoreactivity, and electron microscopy were consistent with choroid plexus papilloma. Radiologically, it was extremely difficult to differentiate from tuberculum sellae meningioma. To our knowledge, this is the first case of primary choroid plexus papilloma in this location reported in the literature.

Nitric oxide metabolites in the cisternal cerebral spinal fluid of patients with subarachnoid hemorrhage.

OBJECTIVE To investigate nitric oxide (NO) metabolism after subarachnoid hemorrhage (SAH). METHODS We measured the concentrations of the NO metabolites, nitrite and nitrate, in cerebrospinal fluid (CSF) obtained from the cisternal drainage of patients with SAH. Studies were performed for 31 patients who had undergone surgical obliteration of bleeding aneurysms within 3 days of their hemorrhage. The concentrations of nitrite and nitrate in the CSF were measured for 14 days using a nitrate/nitrite kit and samples that were obtained on a daily basis from the cisternal drainage. RESULTS Compared with the control values in the CSF (2.6 +/- 0.4 mumol/L, n = 14) obtained from patients with hemifacial spasm, trigeminal neuralgia, or nonruptured aneurysms, the concentrations of nitrite and nitrate in the CSF were significantly elevated in the acute stage of SAH and remained elevated. The concentration of NO metabolites may correlate with the amount of bleeding, inasmuch as the values in patients in Fisher Group 3 (n = 25) were higher than those in patients in Fisher Group 2 (n = 6). The concentration of nitrate was higher than that of nitrite, suggesting that NO in the subarachnoid space is mainly absorbed by hemoglobin and degraded to nitrate. No differences were demonstrated in patients treated with high doses of methylprednisolone (n = 17) compared with those treated with usual-dose steroids (n = 14). Steroids are known to prevent the formation of inducible NO synthase mediated by inflammatory cytokines. CONCLUSION NO metabolism in the brain is stimulated after SAH. Nitrate is the dominant NO metabolite in CSF after SAH. The involvement of inducible NO synthase in the pathophysiology of NO metabolism after SAH was not clearly suggested based on the present data.

Phosphorylation of neuronal nitric oxide synthase at Ser847 by CaM-KII in the hippocampus of rat brain after transient forebrain ischemia.

The authors previously demonstrated that Ca 2+/calmodulin (CaM)-dependent protein kinase IIα (CaM-KIIα) can phosphorylate neuronal nitric oxide synthase (nNOS) at Ser847 and attenuate NOS activity in neuronal cells. In the present study, they established that forebrain ischemia causes an increase in the phosphorylation of nNOS at Ser847 in the hippocampus. This nNOS phosphorylation appeared to be catalyzed by CaM-KII: (1) it correlated with the autophosphorylation of CaM-KIIα; (2) it was blocked by the CaM-KII inhibitor, KN-93; and (3) nNOS and CaM-KIIα were found to coexist in the hippocampus. Examination of the spatial relation between nNOS and CaM-KIIα in the brain revealed coexistence in the hippocampus but not in the cortex during reperfusion, with a concomitant increase in autophosphorylation of CaM-KIIα. The phosphorylation of nNOS at Ser847 probably takes place in nonpyramidal hippocampal neurons, which increased after 30 minutes of reperfusion in the hippocampus, whereas no significant increase was detected in the cortex. An intraventricular injection of KN-93 significantly decreased the phosphorylation of nNOS in the hippocampus. These results point to CaM-KII as a protein kinase, which by its colocalization may attenuate the activity of nNOS through its Ser847 phosphorylation, and may thus contribute to promotion of tolerance to postischemic damage in hippocampal neurons.

Adrenomedullin reduces ischemic brain injury after transient middle cerebral artery occlusion in rats.

Summary Background. The effect of adrenomedullin, a vasodilatory peptide on transient middle cerebral artery (MCA) occlusion was investigated in rats. Methods. Transient MCA occlusion for 2 hours was made by using the intra-arterial suture method, followed by reperfusion. Findings. An intravenous infusion of adrenomedullin (1 μ g/kg/min) from one hour before ischemia to one hour after ischemia significantly reduced the infarct size and improved neurological deficits (p<0.05), without affecting systemic blood pressure or other physiological parameters. The infarct size was reduced with adrenomedullin by 25.4±12.7%, 31.3±5.8%, 31.6±6.1% respectively at the coronal level 6, 8 and 10 mm posterior from the frontal pole. Adrenomedullin also significantly inhibited the increase in myeloperoxidase (MPO) activity in the MCA area of the ischemic hemisphere after 22-hour reperfusion (control: 0.205±0.054 unit/g wet tissue, adrenomedullin group: 0.047±0.009 unit/g wet tissue, p<0.0001). Interpretation. These data suggest that adrenomedullin reduces acute ischemic brain injury and one of is neuroprotective mechanisms may be derived from inhibition of the infiltration of neutrophils into the ischemic tissue.