Tài liệu Báo cáo khoa học: The role of antioxidants in the cytotoxicity of chemotherapeutic drugs

3. Molecular Basis of Disease

3.1 Oxidative Stress

S3.1-1

The role of antioxidants in the cytotoxicity of

chemotherapeutic drugs

T. Ozben, H. Akbas, I. Akan, S. Akan and M. Timur

Department of Biochemistry, Faculty of Medicine, Akdeniz

University, Antalya, Turkey. E-mail: [email protected]

A number of drugs used in cancer chemotherapy induce oxidative

stress by generation of oxygen free radicals (ROS) which might

be an alternative mechanism for their cytotoxic effect via indu￾cing apoptosis. In order to clarify the roles of antioxidants in

chemotherapy, we investigated Quercetin (3,3’,4’,5,7-pentahyd￾roxyflavone) and N-acetylcysteine (NAC) in different cell types

treated with anticancer drugs. We studied cytotoxic activity of

Topotecan alone and/or in combination with Quercetin in two

human breast cancer cell lines, MCF-7 and MDA-MB-231. We

also investigated the effect of NAC on MRP1-mediated doxoru￾bicin and vincristine cytotoxicity in Human Embryonic Kidney

(HEK293) and its MRP1 transfected (293MRP) cells. The viabil￾ity of the cells was measured using the colorimetric MTT

(3-(4,5)-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)

assay. Intracellular ROS was measured using fluorometric 2’,7’-

dichlorodihydrofluorescein diacetate (DCFH-DA) assay. Our

data indicated increased oxidative status in MCF-7 and MDA￾MB-231 cells exposed to Topotecan. Treatment with Quercetin

did not inhibit ROS generation, and enhanced cytotoxicity of

Topotecan in both cells. In contrast, NAC enhanced resistance

against doxorubicine and vincristine in MRP1 overexpressing

cells. We conclude that Quercetin and NAC may have diverse

effects in the cytotoxicity of chemotheurapeutic drugs depending

on their other pharmacological properties which may predomin￾ate their antioxidant effects.

S3.1-2

Oxidized protein degradation and repair in

ageing and oxidative stress

B. Friguet

Laboratoire de Biologie et Biochimie Cellulaire du Vieillissement,

Universite´ Denis Diderot – Paris 7, Paris, France.

E-mail: [email protected]

Cellular ageing is characterized by the accumulation of oxidatively

modified proteins and oxidized protein buildup with age may be

due to increased protein damage and/or decreased elimination of

oxidized protein. Since the proteasome is in charge of protein turn￾over and removal of oxidized protein, its fate during ageing has

received special attention, and evidence has been provided for an

age-related impairment of proteasome function. In fact, depending

on the cellular system investigated, the loss in proteasome activity

observed during ageing and upon oxidative stress appears to be

due to either or both: (i) decreased proteasome expression and con￾tent, (ii) inactivation upon modification of proteasome subunits

and (iii) formation of inhibitory proteins. However oxidized pro￾teins can be eliminated through degradation but also repair. Oxid￾ized protein repair is limited to the reversion of few modifications

such as the reduction of methionine sulfoxide by the methionine

sulfoxide reductase (Msr) system. We have previously shown that

Msr activity is impaired during ageing. To analyse the relationship

between oxidative stress, protein oxidative damage and Msr, MsrA

has been overexpressed in immortalized WI-38 human fibroblasts.

After H202-induced oxidative stress, MsrA-overexpressing cells

exhibit lower protein oxidative damage than control cells indica￾ting that MsrA may play an important role in cellular defences

against oxidative stress by limiting oxidative damage to proteins.

S3.1-3

Role of oxidative stress in progressive kidney

failure

A. Tomasi1

, S. Uggeri2

, S. Beergamini3

, L. Della Casa3

,

A. Albertazzi2

, L. Lucchi2 and A. Iannone1

1

Department Laboratory Medicine, Universita` di Modena e Reggio

Emilia, Modena, Italy, 2

Division of Nephrology, University

Hospital, Modena, Italy, 3

Department of Biomedical Sciences,

Modena, Italy. E-mail: [email protected]

The leading cause of morbidity and mortality in patients with

end stage renal disease (ESRD), who are maintained on regular

dialysis treatment, is cardiovascular disease. Increased free radical

production and oxidative stress promote the atherosclerotic pro￾cess. The association between haemodialysis and activation of

circulating monocytes, both spontaneous and endotoxin-induced

release of TNF-alpha are well known. In our research spanning

many years, as well as in many other laboratories, there has been

a massive attempt to identify reliable biomarkers of oxidative

stress. Initially our attention was drawn on direct markers of oxi￾dative stress such as malondialdehyde (MDA) and conjugated

dienes. More recently, high plasma level of homocysteine, which

is considered a putative cardiovascular risk factor by inducing

endothelial dysfunction and serum C-reactive protein (CRP),

which contributes to monocytes recruitment in the atherosclerotic

lesion have been adopted as possible markers of atherosclerotic

progression in ESRD patients. It has been postulated that ESRD

patients have also a decreased ability to withstand oxidative

stress due to a reduced antioxidant capacity, which was also

investigated as a putative biomarker. Recently, we have tried to

define novel markers of oxidative stress applying proteomic pro￾filing technologies, employing both 2-D gel electrophoresis - mass

spectrometry and high throughput SELDI technology.

Abstracts

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