Düşük dansiteli lipoproteinlerin (LDL) oksidatif modifikasyonu ve asetaminofen ile ilişkisinin araştırılması

Abstract

59 ile belirlenmiştir. Sekiz hafta süreyle %1 kolesterol içeren bir diyet ile beslenen kolesterol grubunda, plazma ve izole LDL örneklerinde TBARS düzeyleri kontrol grubuna göre anlamlı olarak yükselmiştir (p<0.05). Bu gruba ait izole LDL örneklerindeki konjuge dien düzeyleri de kontrol grubuna göre anlamlı olarak yüksek bulunmuştur (p<0.05). Bunlara ek olarak, bu grubun izole LDL örneklerinin (okside LDL), agaroz jel elektroforezinde kontrol grubu LDL örneklerine göre daha hızlı hareket ettikleri gözlenmiştir. Gavaj yoluyla günde 200 mg asetaminofen uygulanan kolesterol + asetaminofen grubunda ise, plazma ve izole LDL TBARS düzeyleri ve konjuge dienler kolesterol grubuna göre anlamlı olarak azalmıştır (p< 0.05). Bu gruptan izole edilen LDL örneklerinin agaroz jel elektroforezindeki elektroforetik hareketi kontrol grubu LDL örneklerine benzer bulunmuştur. Çalışmanın in vitro bölümünde, izole LDL örneklerinin Cu^ iyonları ile okside olduğu ve bu oksidasyonun asetaminofen varlığında azaldığı gösterilmiştir. DPPH yöntemi ile, asetaminofenin 200 uM konsantrasyonda % 50 radikal yakalama yeteneğinde olduğu gösterilmiştir. Elde ettiğimiz bulgular, asetaminofenin antioksidan özelliğinden dolayı, in vivo ve in vitro, LDL'nin oksidatif modifikasyonunu kısmen önlediğini göstermektedir. Asetaminofenin antioksidan özelliklere sahip olması, aterosklerozun gelişimi ve ilerlemesinin önlenmesinde terapötik bir önem taşıyabilir ancak bu konuda daha ileri çalışmalara gereksinim vardır. Anahtar kelimeler: LDL oksidasyonu, ateroskleroz, asetaminofen, hiperkolesterolemi, tavşanABSTRACT Atherosclerosis is a chronic inflammatory process where oxidative damage within the artery wail is implicated in the pathogenesis of the disease. Oxidative modification of low-density lipoprotein (LDL) has been suggested to play a major role in the pathogenesis of atherosclerosis. It is known that the elevated level of plasma LDL is a primary risk factor for developing atherosclerosis. Although the initiating steps involved are not fully understood, oxidative modification of LDL is thought to be an early step in atherosclerotic lesion development. Oxidized LDL particle can be efficiently endocytosed by macrophages via scavenger receptors and supports the formation of foam cells, a hallmark of early atherosclerotic lesions. Acetaminophen, a widely used analgesic and antipyretic agent, possesses significant antioxidant properties under certain experimental conditions. There are paradoxical results about the effect of acetaminophen on LDL oxidation. It was reported that in vitro oxidative modification of LDL significantly reduced by acetaminophen and suggested that acetaminophen might exert this effect by scavenging free radicals. On the other hand, it was also reported that acetaminophen could act as a catalyst in vitro oxidative modification of LDL by myeloperoxidase. The objective of this study was to investigate the in vivo effect of acetaminophen on LDL oxidation in hypercholesterolemic rabbits. The oxidative modification of LDL was identified by TBARS, conjugated dienes determinations and agarose gel electrophoresis. In the cholesterol group which rabbits were fed a

61 diet contained Ig % cholesterol for 8 weeks, the plasma and isolated LDL TBARS levels significantly increased in comparison with the control rabbits (p <0.05). In this group, conjugated diene formation also increased in the isolated LDL samples (p< 0.05). In addition, the isolated LDL samples (oxidatively modified) demonstrated faster migration on agarose gel electrophoresis than control LDL samples. In the cholesterol + acetaminophen group treated 200 mg/day acetaminophen by gavage, the plasma and isolated LDL TBARS levels and conjugated dienes were significantly lower than those of the cholesterol group (p< 0.05). The migration of isolated LDL samples from this group were similar to control LDL samples on agarose gel electrophoresis. The results from in vitro studies demonstrated that the LDL samples isolated from serum was oxidized by Cu++ ions and this oxidation reduced in the presence of acetaminophen. It was shown that acetaminophen has 50 % radical scavenger capacity at 200 uM concentration by the DPPH test. Our findings demonstrate that acetaminophen partially prevents in vivo and in vitro oxidative modification of LDL. The antioxidant properties of acetaminophen may be of therapeutic value in preventing the development and progression of atherosclerosis, but further studies are needed. Keywords: Oxidation of LDL, atherosclerosis, acetaminophen, hypercholesterolemia, rabbitsKAYNAKLAR 1. Abuja, P. M. (2002). Aggregation of LDL with chondroitin-4-sulfate makes LDL oxidizable in the presence of water-soluble antioxidants, FEBS Lett., 512: 245- 248. 2. Abuja, P. M., Albertini R. (2001). Methods for monitoring oxidative stress, lipit peroxidation and oxidation resistance of lipoproteins, Clin. Chim.Acta, 306: 1-17. 3. Ahotupa, M., Marniemi, J., Lehtimaki, T., Talvinen, K., Raitakari, O., et al. (1998). Baseline diene conjugation in LDL lipits as a direct measure of in vivo LDL oxidation, Clin. Biochem., 31 (4): 257-261. 4. Ahotupa, M., Ruutu, M., Mantyla, E. (1996). Simple methods of quantifying oxidation products and antioxidant potential of low density lipoproteins, Clin. Biochem., 29: 139-144. 5. Ahotupa, M., Vasankari,T. J. (1999). Baseline diene conjugation in LDL lipits: an indicator of circulating oxidized LDL, Free Radic. Biol. Med., 27 (11-12): 1 Mi ll 50. 6. Balkan, J., Kanbağh, Ö., hatipoğlu, A., Küçük, M., Çevikbaş, U., et al. (2004). Taurinin ateroskîerotik tavşanlarda antiaterojen ve antioxidan etkisi, Kocatepe Tıp Dergisi, (ek sayı): 37-42. T.Berliner, J. (2002). Lipit oxidation products and atherosclerosis, Vascular Pharmocol, 38: 187-191. 8. Berliner, J. A., Heinecke, J. W. (1996). The role of oxidized lipoproteins in atherogesis, Free Radic. Biol. Med. 20 (5): 707-727.