Posts Tagged ‘Rejuvenation Research’

Day and Night Variation in Melatonin Level affects Plasma Membrane Redox System in Red Blood Cells

Author: Shilpa Chakravarty, PhD

Melatonin is a well-established antioxidant and sleep-regulating hormone. Over the past fifty years, its efficiency as a regulator of circadian rhythm and several other physiological functions has been studied extensively in different species. As a free-radical scavenger, melatonin has shown its activity in coordination with its circadian nature. One of the most important biomarkers of oxidative stress studied in red blood cells is the plasma membrane redox system (PMRS).

As a part of the research activity, PMRS activity has been summarised in this article. The experiments with PMRS and ascorbate free-radical reductase (AFR reductase) have been conducted in vitro.

The study was carried out on 61 healthy individuals of both sexes (aged 20-30) having no acute or chronic diseases (such as diabetes mellitus, asthma, or tuberculosis) or any organ dysfunction and had not taken any medication. Blood samples were collected at two different timings at 10:00AM and 10:00PM.  Red blood cell-membrane, was in retrospect a good experimental system to try to extract and isolate membrane proteins for biochemical assays. Two factors that have favoured it for experimental use are availability and simplicity. Results from its study have been replicated in every other mammalian cell type, and in some crucial points, the patterns shown by RBC
proteins have led the way to such interpretations of extensive physiological studies.

PMRS transfers electrons from extracellular substates to intracellular electron acceptors incorporating AFR reductase. An increase in PMRS activity indicates the ability of the cell to combat oxidative damage.The aging of human red cells may well be attributed to free radical induced oxidative damage. Maintenance of redox state of sulphydryl residues and reduction of lipid hydroperoxides at the expense of electron donors, such as ascorbate and NADH, is essential for normal energy metabolism in the cell. The neutralisation of oxidants also involves some membrane proteins that comprise the PMRS. The rise in PMRS activity is required to maintain a balanced NAD+/NADH ratio that is essential for normal energy metabolism. It leads to cell survival and membrane homeostasis under stress conditions and during calorie restriction in eukaryotes. The day and night variation in PMRS activity shows that the antioxidative behaviour of melatonin is also influenced by its circadian mode of action. While melatonin is an effective antioxidant against cellular toxicity, it also increases the PMRS activity in red blood cells at night. During the day, when the pineal secretion is low, the PMRS activity is also suppressed.

However, if subjected to in vitro treatment with melatonin, at such a concentration that lies close to the maximal melatonin level in the plasma (maximal secretion of melatonin occurs during the scotopic phase of the day), PMRS increases in red blood cells. This shows that the circadian nature of the hormone not only pertains to its pineal production but also to exogenous administration of the drug.


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