Taichiro Imahori

Compensatory glutamine metabolism promotes glioblastoma resistance to mTOR inhibitor treatment

The mechanistic target of rapamycin (mTOR) is hyperactivated in many types of cancer, rendering it a compelling drug target; however, the impact of mTOR inhibition on metabolic reprogramming in cancer is incompletely understood. Here, by integrating metabolic and functional studies in glioblastoma multiforme (GBM) cell lines, preclinical models, and clinical samples, we demonstrate that the compensatory upregulation of glutamine metabolism promotes resistance to mTOR kinase inhibitors. Metabolomic studies in GBM cells revealed that glutaminase (GLS) and glutamate levels are elevated following mTOR kinase inhibitor treatment. Moreover, these mTOR inhibitor-dependent metabolic alterations were confirmed in a GBM xenograft model. Expression of GLS following mTOR inhibitor treatment promoted GBM survival in an α-ketoglutarate-dependent (αKG-dependent) manner. Combined genetic and/or pharmacological inhibition of mTOR kinase and GLS resulted in massive synergistic tumor cell death and growth inhibition in tumor-bearing mice. These results highlight a critical role for compensatory glutamine metabolism in promoting mTOR inhibitor resistance and suggest that rational combination therapy has the potential to suppress resistance.

Mechanical Thrombectomy for Acute Ischemic Stroke Patients Aged 80 Years or Older

BACKGROUND There are limited data about the prognostic factors predicting outcomes after mechanical thrombectomy with stent retrievers for the elderly. Here, we evaluated outcomes in elderly patients in a real-world setting. METHODS Between April 2015 and January 2017, 80 patients with anterior intracranial acute large vessel occlusion, who had lived independently before ictus, were treated with mechanical thrombectomy using a stent retriever at our institute. We compared outcomes between patients ≥80 years old (n = 36) and those <80 years old (n = 44), and assessed prognostic factors for favorable outcomes (modified Rankin Scale score 0-2) at 90 days in all patients. RESULTS There was no significant difference in baseline National Institutes of Health Stroke Scale score and Alberta Stroke Program Early Computed Tomography Score between the 2 groups. Successful revascularization (modified Thrombolysis in Cerebral Infarction [mTICI] scores 2b/3) (83% versus 93%, P = .286), complete recanalization (mTICI 3) (47% versus 50%, P = .826), and favorable outcomes (42% versus 57%, P = .261) were achieved more often in those <80 years old, but differences did not reach statistical significance. Multivariate regression analysis showed that baseline National Institutes of Health Stroke Scale (P = .013) and mTICI scores of 3 (P = .006) were significant predictive factors, but being ≥80 years old and baseline Alberta Stroke Program Early Computed Tomography Score were not. In those ≥80 years old, mTICI score of 3 was an influential factor for favorable outcome (P = .017). CONCLUSIONS Being aged 80 years or older was not a significant predictor for outcomes after mechanical thrombectomy, whereas complete recanalization was an influential predictor of outcome in the elderly.

Combined metabolic and transcriptional profiling identifies pentose phosphate pathway activation by HSP27 phosphorylation during cerebral ischemia

The metabolic pathophysiology underlying ischemic stroke remains poorly understood. To gain insight into these mechanisms, we performed a comparative metabolic and transcriptional analysis of the effects of cerebral ischemia on the metabolism of the cerebral cortex using middle cerebral artery occlusion (MCAO) rat model. Metabolic profiling by gas-chromatography/mass-spectrometry analysis showed clear separation between the ischemia and control group. The decreases of fructose 6-phosphate and ribulose 5-phosphate suggested enhancement of the pentose phosphate pathway (PPP) during cerebral ischemia (120-min MCAO) without reperfusion. Transcriptional profiling by microarray hybridization indicated that the Toll-like receptor and mitogen-activated protein kinase (MAPK) signaling pathways were upregulated during cerebral ischemia without reperfusion. In relation to the PPP, upregulation of heat shock protein 27 (HSP27) was observed in the MAPK signaling pathway and was confirmed through real-time polymerase chain reaction. Immunoblotting showed a slight increase in HSP27 protein expression and a marked increase in HSP27 phosphorylation at serine 85 after 60-min and 120-min MCAO without reperfusion. Corresponding upregulation of glucose 6-phosphate dehydrogenase (G6PD) activity and an increase in the NADPH/NAD+ ratio were also observed after 120-min MCAO. Furthermore, intracerebroventricular injection of ataxia telangiectasia mutated (ATM) kinase inhibitor (KU-55933) significantly reduced HSP27 phosphorylation and G6PD upregulation after MCAO, but that of protein kinase D inhibitor (CID755673) did not affect HSP27 phosphorylation. Consequently, G6PD activation via ischemia-induced HSP27 phosphorylation by ATM kinase may be part of an endogenous antioxidant defense neuroprotection mechanism during the earliest stages of ischemia. These findings have important therapeutic implications for the treatment of stroke.

Mechanical Thrombectomy Using the Trevo ProVue in 50 Consecutive Patients with Anterior Circulation Stroke: A Single-Center Experience after Approval of the Stent Retriever in Japan

Mechanical thrombectomy using the stent retriever has been proven to be effective for select patients with acute ischemic stroke. We evaluated our early experience using the device after its approval in 2014 in Japan, with a special emphasis on the occlusion site. Fifty consecutive endovascular revascularization procedures for treating anterior acute large vessel occlusion were performed using the Trevo ProVue as the first-line device at our institute between April 2015 and March 2016. Focusing on the involvement of the M1–M2 bifurcation with deployment or retrieval of the stent retriever, we regarded the middle cerebral artery M1 mid-portion as the boundary and divided the cases into proximal (n = 26) and distal (n = 24) groups. We assessed the overall clinical outcome and compared the outcome between the two groups. Among 50 patients (median age, 80 years; National Institutes of Health Stroke Scale score (NIHSS) score, 20), successful (modified Thrombolysis in Cerebral Infarction score (TICI) 2b or 3) or complete revascularization (TICI 3) was achieved in 41 patients (82%; 88% in the proximal group vs 75% in the distal group, P = 0.28) and in 27 patients (54%; 73% vs 33%, P = 0.01), respectively. Symptomatic intracranial hemorrhage occurred in three patients (6%; 4% vs 8%, P = 0.60). A good outcome (mRS score 0 to 2) was obtained in 25 patients at 90 days (50%; 54% vs 46%, P = 0.78). Mechanical thrombectomy using the Trevo ProVue was safe and effective in patients with acute cerebral artery occlusion, especially for proximal occlusions. The efficacy of the procedure for distal occlusions was somewhat inferior to those for proximal occlusions, which might be resolved by next generation devices.

Acute Ischemic Stroke Involving Both Anterior and Posterior Circulation Treated by Endovascular Revascularization for Acute Basilar Artery Occlusion via Persistent Primitive Trigeminal Artery

We report a case of acute ischemic stroke involving both the anterior and posterior circulation associated with a persistent primitive trigeminal artery (PPTA), treated by endovascular revascularization for acute basilar artery (BA) occlusion via the PPTA. An otherwise healthy 67-year-old man experienced sudden loss of consciousness and quadriplegia. Magnetic resonance imaging showed an extensive acute infarction in the right cerebral hemisphere, and magnetic resonance angiography showed occlusion of the right middle cerebral artery (MCA) and BA. Because the volume of infarction in the territory of the right MCA was extensive, we judged the use of intravenous tissue plasminogen activator to be contraindicated. Cerebral angiography revealed hypoplasia of both vertebral arteries and the presence of a PPTA from the right internal carotid artery. A microcatheter was introduced into the BA via the PPTA and revascularization was successfully performed using a Merci Retriever with adjuvant low-dose intraarterial urokinase. After treatment, his consciousness level and right motor weakness improved. Although persistent carotid-vertebrobasilar anastomoses such as a PPTA are relatively rare vascular anomalies, if the persistent primitive artery is present, it can be an access route for mechanical thrombectomy for acute ischemic stroke.

Endovascular Internal Trapping of Ruptured Occipital Artery Pseudoaneurysm Associated with Occipital–Internal Jugular Vein Fistula in Neurofibromatosis Type 1

Spontaneous cervical extradural pseudoaneurysms or arteriovenous fistulas (AVFs) are rare vascular diseases. We report a case of ruptured occipital artery (OA) pseudoaneurysm associated with occipital-internal jugular vein (IJV) fistula in neurofibromatosis type 1. Endovascular internal trapping via the OA was attempted; however, the distal entry of the OA could not be accessed because of the high shunt flow and tortuosity of the OA. The distal part of the OA was obliterated with coil via a transvenous approach through the IJV and pseudoaneurysm. The proximal entry of the OA was obliterated with coil and glue under proximal flow control with a balloon, and the fistula was successfully obliterated without placement of coils in the pseudoaneurysm. When ordinary internal trapping via a transarterial approach is not possible, the transvenous approach should be considered as an alternative for AVF associated with an aneurysmal component.

Long-Term Outcomes of Carotid Endarterectomy and Carotid Artery Stenting for Carotid Artery Stenosis: Real-World Status in Japan

BACKGROUND AND PURPOSE We investigated long-term outcomes of carotid endarterectomy (CEA) and carotid artery stenting (CAS) in our institute to evaluate the outcomes of real-world practice in Japan. METHODS Between August 2006 and July 2013, 203 consecutive carotid revascularizations with either CEA or CAS were performed in our institute. The initial treatment was regarded as the starting point in the cases of the patients who received treatment by bilateral carotid artery stenosis or retreatment. We assessed the long-term outcomes with survival analyses. RESULTS A total of 182 patients (CEA 111, CAS 71), including 86 symptomatic patients, were included in the current study with a mean follow-up period of 42.9 months. The periprocedural stroke/death/myocardial infarction (MI) rate was 3.6% for CEA and 5.6% for CAS groups (P = .71). Estimates of the 4-year event-free rate from the primary end point (the composite of any stroke, death, or MI within 30 days, and any ipsilateral stroke thereafter) using competing risk analysis were 3.6% for CEA and 7.1% for CAS (P = .156). Kaplan-Meier estimates of the 4-year event-free rate from the secondary end point (the composite of any stroke, death, or MI within 30 days, and any stroke or death thereafter) were 13.8% for CEA and 19.1% for CAS (P = .072). Age was the only significant predictor for the primary end point. Both age and CAS were significant predictors for the secondary end point. CONCLUSIONS The current study on real-world practices demonstrated perioperative and long-term outcomes that were comparable to previous major studies of large numbers of patients.

Focal hyperintensity in the dorsal brain stem of patients with cerebellopontine angle tumor: A high-resolution 3 T MRI study

Focal hyperintensity (FHI) in the dorsal brain stem on T2-weighted images of patients with cerebellopontine angle (CPA) tumor was thought to indicate degeneration of the vestibular nucleus and to be specific to vestibular schwannoma. The purpose of this study was to evaluate FHI by using high-resolution 3 Tesla magnetic resonance imaging (3 T MRI) and the relation to clinical characteristics. We retrospectively reviewed the clinical data and MRI of 45 patients with CPA tumors (34 vestibular schwannomas and 11 other tumors). FHI in the dorsal brain stem was found in 25 (55.6%) patients (20 vestibular schwannomas and 5 other tumors). For the vestibular schwannomas, the factors contributing to positive FHI were age (p = 0.025), max CPA (p =  < 0.001), hearing ability (P = 0.005), and canal paresis (p =  < 0.001) in the univariate analysis. Multivariate regression analysis showed that max CPA (p = 0.029) was a significant factor of positive FHI. In other CPA tumors, these factors were not significant predictors. With the use of 3 T MRI, FHI was observed more frequently than previously reported. Our results suggest that FHI is not a specific indicator of vestibular schwannoma and is related to not only vestibular function but also other factors.

Pentose phosphate pathway activation via HSP27 phosphorylation by ATM kinase: A putative endogenous antioxidant defense mechanism during cerebral ischemia-reperfusion

Molecular mechanism underlying ischemic stroke remains poorly understood. We previously reported glucose 6-phosphate dehydrogenase (G6PD) activity in pentose phosphate pathway (PPP) is activated via heat shock protein 27 (HSP27) phosphorylation at serine 85 (S85) by ataxia telangiectasia mutated (ATM) kinase during cerebral ischemia. This mechanism seems to be endogenous antioxidative system. To determine whether this system also works during reperfusion, we performed comparative metabolic analysis of reperfusion effect on metabolism in rat cortex using middle cerebral artery occlusion (MCAO). Metabolic profiling using gas-chromatography/mass-spectrometry analysis showed changes in metabolic state that depended on reperfusion time. Enrichment analysis showed PPP was significantly upregulated during ischemia-reperfusion. Significant increases in fructose 6-phosphate and ribulose 5-phosphate after reperfusion also suggested enhancement of PPP. In relation to PPP, ischemia-reperfusion induced an increase of up to 69-fold in HSP27 transcripts after 24-h reperfusion. Immunoblotting showed gradual increase in HSP27 protein and marked increase in HSP27 phosphorylation (S85) that were time-dependent (4.5-fold after 24-h reperfusion). G6PD activity was significantly elevated after 1-h MCAO (20%), reduced after 1-h reperfusion, increased gradually thereafter and significantly elevated after 24-h reperfusion. The NADPH/NAD+ ratio displayed similar increasing pattern. Intracerebroventricular injection of ATM kinase inhibitor (KU-55933) significantly reduced HSP27 phosphorylation and G6PD activity, significantly increased protein carbonyl, and resulted in increase in infarct size (100%) 24-h after reperfusion following 90-min MCAO. Consequently, G6PD activation via HSP27 phosphorylation by ATM kinase may be part of endogenous antioxidant defense neuroprotection mechanism that is activated during ischemia-reperfusion. These findings have important implications for treatment of stroke.

Corrigendum to “Combined metabolic and transcriptional profiling identifies pentose phosphate pathway activation by HSP27 phosphorylation during cerebral ischemia” [Neuroscience 349 (2017) 1–16]

CORRIGENDUM TO ‘‘COMBINED METABOLIC AND TRANSCRIPTIONAL PROFILING IDENTIFIES PENTOSE PHOSPHATE PATHWAY ACTIVATION BY HSP27 PHOSPHORYLATION DURING CEREBRAL ISCHEMIA” [NEUROSCIENCE 349 (2017) 1–16] TAICHIRO IMAHORI, a KOHKICHI HOSODA, * TOMOAKI NAKAI, a YUSUKE YAMAMOTO, a YASUHIRO IRINO, b MASAKAZU SHINOHARA, c,d NAOKO SATO, a TAKASHI SASAYAMA, a KAZUHIRO TANAKA, a HIROAKI NAGASHIMA, a MASAAKI KOHTA a AND EIJI KOHMURA a Department of Neurosurgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan Division of Evidence-based Laboratory Medicine, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan The Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan Division of Epidemiology, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan