Sains Malaysiana 39(1)(2010): 145–156

 

Comparison of the Effects of α-Tocopherol and γ-Tocotrienol against Oxidative Stress in Two Different Neuronal Cultures

(Perbandingan Kesan α-Tokoferol dan γ-Tocotrienol Terhadap Tekanan Oksidatif pada Dua Kultur Neuron yang Berlainan)

 

Then Sue-Mian*

UKM Medical Molecular Biology Institute (UMBI)

Universiti Kebangsaan Malaysia Medical Centre (UKMMC)

53000 Kuala Lumpur, Malaysia

 

Wan Zurinah Wan Ngah & Musalmah Mazlan

Department of Biochemistry, Medical Faculty

Universiti Kebangsaan Malaysia, 50300 Kuala Lumpur, Malaysia

 

Gapor Mat Top

Malaysian Palm Oil Board, Bangi, 43000 Selangor D.E., Malaysia

 

Received: 7 January 2009 / Accepted: 7 June 2009

 

 

ABSTRACT

Tocopherols and tocotrienols have been shown in previous studies to protect neurons from oxidative injuries, especially from hydrogen peroxide (H2O2) and buthionine sulfoximine (BSO) induced oxidative stress. In this study, we compared two vitamin E isomers, γ-tocotrienol (GTT) and α-tocopherol (ATF) in their neuroprotective effects against H2O2-induced apoptosis in primary rat cortical neurons and human neuroblastoma cell line SH-SY5Y. Cytotoxicity screening of H2O2, GTT and ATF was done to determine the IC50 levels. To screen for neuroprotective effects, cortical neurons and SH-SY5Y cell cultures were pre-incubated with GTT or ATF, respectively at different concentrations for 1 hour before concurrent treatment of H2O2 at IC50. Results of these treatments were compared to cells treated with H2O2 only and control cells. Cytotoxicology screening showed that IC50 of H2O2 for cortical neuron is at 50 μM while SH-SY5Y have higher IC50 of 100 μM. GTT is cytotoxic to cortical neurons at >=50 μM and SH-SY5Y at >=100 μM while ATF did not show any toxicity within the range of concentration tested (1-750 μM). Results from neuroprotection screening showed that GTT and ATF were able to protect both cortical neurons and SH-SY5Y from H2O2-induced oxidative stress at concetration of <=10 μM. Cellular uptake of GTT is higher in both cortical neurons and SH-SY5Y as compared to ATF when both cortical neuron and SH-SY5Y were incubated with 10 μM GTT or ATF, respectively for 24 hour. Although primary rat cortical neurons and human neuroblastoma SH-SY5Y were different culture system, the effects of GTT and ATF are similar in both H2O2 –induced culture which strongly suggest that both GTT and ATF act as free radical scavenger to exert their neuroprotective effects.

 

Keywords: Apoptosis; neurons; oxidative stress; tocopherol; tocotrienol

 

ABSTRAK

 

Kajian terdahulu menunjukkan bahawa kedua-dua tokoferol and tokotrienol mempunyai potensi untuk melindungi neurons daripada tekanan oksidatif, khasnya daripada apoptosis yang diaruh hidrogen peroksida (H2O2) dan buthionine sulfoximine (BSO). Dalam kajian ini, dua vitamin E isomer, iaitu γ-tokotrienol (GTT) dan α-tokoferol (ATF) dibandingkan dalam kesan neuroproteksi terhadap apoptosis yang diaruh oleh H2O2 pada sel neuron korteks tikus dan titian sel neuroblastoma manusia SH-SY5Y. Penyaringan sitotoksik terhadap H2O2, GTT dan ATF dilakukan untuk menentukan aras IC50. Untuk menyaring kesan neuroproteksi, kultur sel neuron korteks dan SH-SY5Y diberi pra-eraman GTT atau ATF masing-masing pada kepekatan berlainan selama 1 jam sebelum diperlakukan bersama H2O2 pada kepakatan IC50. Keputusan ini dibanding dengan bacaan daripada sel yang diperlakukan H2O2 sahaja dan kawalan. Penyaringan sitotoksikologi menunjukkan bahawa IC50 H2O2 untuk neuron korteks adalah 50 μM manakala SH-SY5Y mempunyai IC50 H2O2 yang lebih tinggi, iaitu 100 μM. GTT adalah sitotoksik kepada neuron korteks pada >=50 μM dan SH-SY5Y pada >=100 μM manakala ATF tidak menunjukkan ketoksikan pada jurang kepekatan yang diuji (1-750 μM). Keputusan daripada penyaringan neuroproteksi menunjukkan bahawa kedua-dua GTT dan ATF dapat melindungi neuron korteks dan SH-SY5Y daripada stress oksidatif yang diaruh oleh H2O2 pada kepekatan <=10 μM. Pengambilan GTT oleh sel adalah lebih tinggi oleh kedua-dua neuron korteks dan SH-SY5Y berbanding dengan pengambilan ATF apabila kedua-dua sel neuron korteks dan SH-SY5Y masing-masing dieram dengan 10 μM GTT atau ATF selama 24 jam. Walaupun kultur neuron korteks tikus dan titian sel neuroblastoma manusia SH-SY5Y adalah sistem kultur sel yang berbeza, kesan GTT dan ATF yang serupa terhadap kedua-dua kultur yang diaruh H2O2 mencadangkan bahawa GTT dan ATF bertindak sebagai peraih radikal bebas untuk memberikan kesan neuroproteksinya.

 

Kata kunci: Apoptosis; neurons; tekanan oksidatif; tokoferol; tokotrienol

 

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*Corresponding author; email: suemian@ppukm.ukm.my