Chang Hwa Choi

Role of ERK in Hydrogen Peroxide-Induced Cell Death of Human Glioma Cells

Oxidative stress is known to induce cell death in a wide variety of cell types, apparently by modulating intracellular signaling pathways. Activation of extracellular signal-regulated kinase (ERK) in oxidative stress remains controversial. In some cellular systems, the ERK activation is associated with protection against oxidative stress, while in other system, the ERK activation is involved in apoptotic cell death. The present study was undertaken to examine the role of ERK activation in H2O2-induced cell death of human glioma (A172) cells. H2O2 resulted in a time- and dose-dependent cell death, which was largely attributed to apoptosis. H2O2 treatment caused marked sustained activation of ERK. The ERK activation and cell death induced by H2O2 was prevented by catalase, the hydrogen peroxide scavenger, and U0126, an inhibitor of ERK upstream kinase MEK1/2. Transient transfection with constitutive active MEK1, an upstream activator of ERK1/2, increased H2O2-induced cell death, whereas transfection with dominant-negative mutants of MEK1 decreased the cell death. The ERK activation and cell death caused by H2O2 was inhibited by antioxidants (N-acetylcysteine and trolox), Ras inhibitor, and suramin. H2O2 produced depolarization of mitochondrial membrane potential and its effect was prevented by catalase and U0126. Taken together, these findings suggest that growth factor receptor/Ras/MEK/ERK signaling pathway plays an active role in mediating H2O2-induced apoptosis of human glioma cells and functions upstream of mitochondria-dependent pathway to initiate the apoptotic signal.

Underlying Mechanism of Quercetin-induced Cell Death in Human Glioma Cells

There has been considerable interest in recent years in the anti-tumor activities of flavonoids. Quercetin, a ubiquitous bioactive flavonoid, can inhibit proliferation and induce apoptosis in a variety of cancer cells. However, the precise molecular mechanism by which quercetin induces apoptosis in cancer cells is poorly understood. The present study was undertaken to examine the effect of quercetin on cell viability and to determine its underlying mechanism in human glioma cells. Quercetin resulted in loss of cell viability in a dose- and time-dependent manner and the decrease in cell viability was mainly attributed to cell death. Quercetin did not increase reactive oxygen species (ROS) generation and the quercetin-induced cell death was also not affected by antioxidants, suggesting that ROS generation is not involved in loss of cell viability. Western blot analysis showed that quercetin treatment caused rapid reduction in phosphorylation of extracellular signal-regulated kinase (ERK) and Akt. Transient transfection with constitutively active forms of MEK and Akt protected against the quercetin-induced loss of cell viability. Quercetin-induced depolarization of mitochondrial membrane potential. Caspase activity was stimulated by quercetin and caspase inhibitors prevented the quercetin-induced loss of cell viability. Quercetin resulted in a decrease in expression of survivin, antiapoptotic proteins. Taken together, these findings suggest that quercetin results in human glioma cell death through caspase-dependent mechanisms involving down-regulation of ERK, Akt, and survivin.

Allicin inhibits cell growth and induces apoptosis in U87MG human glioblastoma cells through an ERK-dependent pathway

Allicin, the main flavor compound in garlic, has anti-carcinogenic activities in a range of cancer cells, however, the underlying molecular mechanisms are not completely understood. This study examined the effect of allicin on the cell viability of U87MG human glioma cells along with its molecular mechanisms of induction of cell death. Apoptosis was determined by TUNEL and Hoechst 33258 staining as well as by western blot analysis. Allicin inhibited the cell viability of U87MG human glioma cells in a dose- and time-dependent manner. Allicin-induced inhibition of cell viability was due to apoptosis of cells. The mechanisms of apoptosis were found to involve the mitochondrial pathway of Bcl-2/Bax, the MAPK/ERK signaling pathway and antioxidant enzyme systems. These results suggest that allicin can serve as a novel chemotherapeutic candidate for the treatment of glioblastoma multiforme.

Silibinin Inhibits Glioma Cell Proliferation via Ca2+/ROS/MAPK-Dependent Mechanism In Vitro and Glioma Tumor Growth In Vivo

Anticancer activity of silibinin, a flavonoid, has been demonstrated in various cancer cell types. However, the underlying mechanism and in vivo efficacy in glioma were not elucidated. The present study was undertaken to determine the effect of silibinin on glioma cell proliferation in vitro and to examine whether silibinin inhibits tumor growth in vivo. Silibinin resulted in inhibition of proliferation in a dose- and time-dependent manner, which was largely attributed to cell death. Silibinin induced a transient increase in intracellular Ca2+ followed by an increase in reactive oxygen species (ROS) generation. The silibinin-induced cell death was prevented by EGTA, calpain inhibitor and antioxidants (N-acetylcysteine and Trolox). Western blot analysis showed that silibinin also induced ROS-dependent activation of extracellular signal-regulated kinase, p38 kinase, and c-Jun N-terminal kinase. Inhibitors of these kinases prevented the silibinin-induced cell death. Silibinin caused caspase activation and the silibinin-induced cell death was prevented by caspase inhibitors. Glioma cell migration was also decreased by silibinin treatment. Oral administration of silibinin in animals with subcutaneous U87MG glioma cells reduced tumor volume. Subsequent tumor tissue analysis showed a decrease in Ki-67 positive cells, an increase in TUNEL-positive cells, and caspase activation. These results indicate that silibinin induces a caspase-dependent cell death via Ca2+/ROS/MAPK-mediated pathway in vitro and inhibits glioma growth in vivo. These data suggest that silibinin may serve as a potential therapeutic agent for malignant human gliomas.

Ceramide Induces Non-Apoptotic Cell Death in Human Glioma Cells

Ceramide causes either apoptosis or non-apoptotic cell death depending on model system and experimental conditions. The present study was undertaken to examine the effect of ceramide on cell viability and its molecular events leading to cell death in A172 human glioma cells. Ceramide induced cell death in a dose-dependent manner and the cell death was dependent on generation of reactive oxygen species and lipid peroxidation. TUNEL assay, Hoechst 33258 staining, and flow cytometric analysis did not show typical apoptotic morphological features. Ceramide caused phosphorylation of extracellular signal-regulated kinase (ERK) and p38, but the cell death was not affected by inhibitors of MAPK subfamilies. Ceramide caused ATP depletion without loss of mitochondrial membrane potential. Ceramide did not induce caspase activation and ceramide-induced cell death was also not altered by inhibitors of caspase activation. Transfection of dominant inhibitory mutant of IκBα (S32A/36A) and pretreatment of pyrrolidinedithiocarbamate, an inhibitor of NF-κB, enhanced ceramide-induced cell death. These results indicate that ceramide causes non-apoptotic, caspase-independent cell death by inducing reactive oxygen species generation in A172 human glioma cells. NF-κB is involved in the regulation of ceramide-induced cell death in human glioma cells.

Ciglitazone Induces Caspase-Independent Apoptosis through Down-Regulation of XIAP and Survivin in Human Glioma Cells

Induction of apoptosis may be a promising therapeutic approach in cancer therapy. Peroxisome proliferator-activated receptor-γ (PPARγ) agonists induce apoptosis in various cancer cells. However, the molecular mechanism remains to be defined. The present study was undertaken to determine the precise mechanism of cell death induced by ciglitazone, a synthetic PPARγ agonist, in A172 human glioma cells. Ciglitazone resulted in a concentration- and time-dependent apoptotic cell death. Similar results were obtained with troglitazone, another synthetic PPARγ agonist. Ciglitazone induced reactive oxygen species (ROS) generation and ciglitazone-induced cell death was prevented by the antioxidant N-acetylcysteine, suggesting an important role of ROS generation in the ciglitazone-induced cell death. The cell death induced by ciglitazone was inhibited by the PPARγ antagonist GW9662. Although ciglitazone treatment caused a transient activation of extracellular signal-regulated kinase (ERK) and p38, the ciglitazone-induced cell death was not affected by inhibitors of these kinses. Ciglitazone caused a loss of mitochondrial membrane potential and its effect was prevented by N-acetylcysteine and GW9662. The specific inhibitor of caspases-3 DEVD-CHO and the general caspase inhibitor z-DEVD-FMK did not exert the protective effect against the ciglitazone-induced cell death and caspase-3 activity also was not altered by ciglitazone. The ciglitazone-induced cell death was accompanied by down-regulation of XIAP and Survivin, but not by release of apoptosis-inducing factor. Taken together, these findings suggest that down-regulation of XIAP and Survivin may play an active role in mediating a caspase-independent and -PPARγ-dependent cell death induced by ciglitazone in A172 human glioma cells. These data may provide a novel insight into potential therapeutic strategies for treatment of glioblastoma.

Rerupture following endovascular treatment for dissecting aneurysm of distal anterior inferior cerebellar artery with parent artery preservation: retreatment by parent artery occlusion with Guglielmi detachable coils

SummaryDistal anterior inferior cerebellar artery (AICA) aneurysms are rare and most cases have been treated surgically by clipping, wrapping or trapping. We recently treated this 20-year-old male patient by an endovascular technique. At first, he was treated by intra-aneurysmal embolisation with parent artery preservation. But he presented with rerupture 1 month after embolisation. Follow-up angiography revealed the regrowth of the aneurysm, which was considered as a dissecting aneurysm. We performed occlusion of the AICA just proximal to the aneurysm to prevent fatal rebleeding. He gradually improved and his level of consciousness fully recovered. At 2 year follow up, he had no neurological deficits. We suggest that embolisation of distal AICA aneurysm with parent artery occlusion may be safe and a simple method in the treatment of distal AICA aneurysms.

Unruptured Intracranial Aneurysms with Oculomotor Nerve Palsy : Clinical Outcome between Surgical Clipping and Coil Embolization

OBJECTIVE To evaluate the clinical outcome of coil embolization for unruptured intracranial aneurysm (UIA) with oculomotor nerve palsy (ONP) compared with surgical clipping. METHODS A total of 19 patients presented with ONP caused by UIAs between Jan 2004 and June 2008. Ten patients underwent coil embolization and nine patients surgical clipping. The following parameters were retrospectively analyzed to evaluate the differences in clinical outcome observed in both coil embolization and surgical clipping : 1) gender, 2) age, 3) location of the aneurysm, 4) duration of the symptom, and 5) degree of ONP. RESULTS Following treatment, complete symptomatic recovery or partial relief from ONP was observed in 15 patients. Seven of the ten patients were treated by coil embolization, compared to eight of the nine patients treated by surgical clipping (p = 0.582). Patients gender, age, location of the aneurysm, size of the aneurysm, duration of symptom, and degree of the ONP did not statistically correlate with recovery of symptoms between the two groups. No significant differences were observed in mean improvement time in either group (55 days in coil embolization and 60 days in surgical clipping). CONCLUSION This study indicates that no significant differences were observed in the clinical outcome between coil embolization and surgical clipping techniques in the treatment of aneurysms causing ONP. Coil embolization seems to be more feasible and safe treatment modality for the relief and recovery of oculomotor nerve palsy.

Reconstructive treatment using a stent graft for a dural arteriovenous fistula of the transverse sinus in the case of hypoplasia of the contralateral venous sinuses: technical case report.

OBJECTIVETransvenous coil embolization for transverse sinus (TS) and sigmoid sinus dural arteriovenous fistulae (DAVFs) is now recognized as one of the most effective treatment modalities. However, in the case of hypoplasia of the contralateral venous sinuses and internal jugular vein, complete occlusion of the ipsilateral sinus may cause fatal consequences. We describe a case of combined intravenous graft stent placement and transarterial coil embolization for DAVFs that involved the dominant right TS in a patient with hypoplasia of the contralateral venous sinuses. CLINICAL PRESENTATIONA 50-year-old man presented with headache, left hand tremor, and pulsatile right tinnitus. A cerebral angiogram demonstrated a right TS DAVF that was supplied by tentorial branches of both internal carotid arteries, multiple branches of the right external carotid artery, and branches of the left occipital artery. Unfortunately, left TS and sigmoid sinus hypoplasia were observed. INTERVENTIONA right TS balloon occlusion test revealed contrast stagnation of the cortical veins and of the right TS and superior sagittal sinus. In this case, the use of transvenous stent graft placement with or without transarterial embolization is safer and more effective than sacrifice of the right TS. We therefore performed balloon-expandable stent graft deployment at the right TS, and the remnant DAVF flow between the stent graft and venous sinus was treated with transarterial coil embolization. Postprocedural angiograms showed patent right TS outflow with disappearance of retrograde cortical venous drainage as well as complete eradication of the fistulous connections. CONCLUSIONIn a DAVF involving the dominant TS or sigmoid sinus in a patient with hypoplasia of the contralateral venous sinuses and an intolerable balloon occlusion test for the ipsilateral venous sinuses, the complete occlusion of the diseased venous sinus may cause hazardous consequences. In this situation, the use of a stent graft with or without transarterial embolization to preserve venous sinus flow can be an effective treatment.

Endovascular Treatment of Wide-Necked Intracranial Aneurysms Using Balloon-Assisted Technique with HyperForm Balloon

OBJECTIVE To assess the feasibility, safety, and effectiveness of the balloon-assisted technique with HyperForm balloon in the endovascular treatment of wide-necked intracranial aneurysms. METHODS A total of 34 patients with 34 wide-necked intracranial aneurysms were treated with endovascular coil embolization using balloon-assisted technique with Hyperform balloon. Twenty-nine aneurysms (85.3%) were located in the anterior circulation. The group of patients was comprised of 16 men and 18 women, aged 33 to 72 years (mean : 60.6 years). The size of aneurysms was in the range of 2.0 to 22.0 mm (mean 5.5 mm) and one of neck was 2.0 to 11.9 mm (mean 3.8 mm). The dome to neck ratio was ranged from 0.83 to 1.43 (1.15). Sixteen patients were treated for unruptured aneurysms and the remaining 18 presented with a subarachnoid hemorrhage. RESULTS In the 34 aneurysms treated by the remodeling technique with HyperForm balloon, immediate angiographic results consisted of total occlusion in 31 cases (91.2%) and partial occlusion in three cases (8.8%). There were five procedure-related complications (14.7%), including two coil protrusions and three thromboembolisms; Except one patient, all were successfully resolved without permanent neurologic deficit. No new bleeding occurred during the follow-up. Twenty patients (59%) underwent angiographic follow-up from 2 to 33 months (mean 9.2 months) after treatment. Focal recanalization with coil compaction of the neck portion was observed in 5 cases (25%). Only one case showed major recanalization and underwent stent-assisted coil embolization. CONCLUSION The balloon-assisted technique with Hyperform balloon is a feasible, safe, and effective endovascular treatment of wide-necked cerebral aneurysms.