Ghosh Arnab K, Naaz Shamreen, Bhattacharjee Bharati, Ghosal Nirajan, Chattopadhyay Aindrila, Roy Souvik, Reiter Russel J, Bandyopadhyay Debasish
Department of Physiology, Oxidative Stress and Free Radical Biology Laboratory, University of Calcutta, University College of Science and Technology, 92, APC Road, Kolkata 700 009, West Bengal, India.
Department of Physiology, Oxidative Stress and Free Radical Biology Laboratory, University of Calcutta, University College of Science and Technology, 92, APC Road, Kolkata 700 009, West Bengal, India; Department of Physiology, Vidyasagar College for Women, Kolkata 700 006, India.
Life Sci. 2017 Jul 1;180:123-136. doi: 10.1016/j.lfs.2017.05.022. Epub 2017 May 18.
Involvement of oxidative stress in cardiovascular diseases is well established. Melatonin's role as an antioxidant and free radical scavenger via its receptor dependent and receptor independent pathways is well known. The aim of this study is to identify and elaborate upon a third mechanism by which melatonin is able to abrogate oxidative stress.
Oxidative stress was induced in vitro, by copper (0.2mM)-ascorbate (1mM) in isolated goat heart mitochondria, cytosol and peroxisomes and they were co-incubated with graded doses of melatonin. Similar experiments in a cell-free chemical system involving two pure antioxidant enzymes, Cu-Zn superoxide dismutase and catalase was also carried out. Biochemical changes in activity of these antioxidant enzymes were analysed. Isothermal titration calorimetric studies with pure Cu-Zn superoxide dismutase and catalase were also carried out.
Incubation with copper-ascorbate led to alteration in activity of Cu-Zn superoxide dismutase and catalase which were found to be protected upon co-incubation with melatonin (80μM for catalase and 1μM for others). Results of isothermal titration calorimetric studies with pure Cu-Zn superoxide dismutase and catalase along with different combinations of copper chloride, ascorbic acid and melatonin suggest that when melatonin is present in the reaction medium along with copper-ascorbate, it restrains the copper-ascorbate molecules by binding with them physically along with scavenging the free radicals generated by them.
The present study suggests that possibly, binding of melatonin with antioxidant enzymes masks the vulnerable sites of these antioxidant enzymes, thus preventing oxidative damage by copper-ascorbate molecules.
氧化应激参与心血管疾病已得到充分证实。褪黑素作为一种抗氧化剂和自由基清除剂，通过其受体依赖性和受体非依赖性途径发挥作用，这是众所周知的。本研究的目的是确定并阐述褪黑素能够消除氧化应激的第三种机制。
在体外，通过在分离的山羊心脏线粒体、细胞质和过氧化物酶体中加入铜（0.2mM）-抗坏血酸（1mM）诱导氧化应激，并将它们与不同剂量的褪黑素共同孵育。还在一个无细胞化学系统中进行了类似实验，该系统涉及两种纯抗氧化酶，即铜锌超氧化物歧化酶和过氧化氢酶。分析了这些抗氧化酶活性的生化变化。还对纯铜锌超氧化物歧化酶和过氧化氢酶进行了等温滴定量热研究。
与铜-抗坏血酸孵育导致铜锌超氧化物歧化酶和过氧化氢酶活性改变，而与褪黑素（过氧化氢酶为80μM，其他为1μM）共同孵育后发现这些酶的活性得到了保护。对纯铜锌超氧化物歧化酶和过氧化氢酶以及氯化铜、抗坏血酸和褪黑素的不同组合进行等温滴定量热研究的结果表明，当褪黑素与铜-抗坏血酸一起存在于反应介质中时，它通过与铜-抗坏血酸分子物理结合来限制它们，同时清除它们产生的自由基。
本研究表明，褪黑素与抗氧化酶的结合可能掩盖了这些抗氧化酶的脆弱位点，从而防止了铜-抗坏血酸分子造成的氧化损伤。
