Plasma Protein Oxidation and Its Correlation with Antioxidant Potential During Human Aging

Abstract

Previous studies have indicated that the main molecular characteristic of aging is the progressive accumulation of oxidative damages in cellular macromolecules. Proteins are one of the main molecular targets of age-related oxidative stress, which have been observed during aging process in cellular systems. Reactive oxygen species (ROS) can lead to oxidation of amino acid side chains, formation of protein-protein cross-linkages, and oxidation of the peptide backbones. In the present study, we report the age-dependent oxidative alterations in biomarkers of plasma protein oxidation: protein carbonyls (PCO), advanced oxidation protein products (AOPPs) and plasma total thiol groups (T-SH) in the Indian population and also correlate these parameters with total plasma antioxidant potential. We show an age dependent decrease in T-SH levels and increase in PCO and AOPPs level. The alterations in the levels of these parameters correlated significantly with the total antioxidant capacity of the plasma. The levels of oxidized proteins in plasma provide an excellent biomarker of oxidative stress due to the relative long half-life of such oxidized proteins.

Age-related variations of protein carbonyls in human saliva and plasma: is saliva protein carbonyls an alternative biomarker of aging?

“…All participants were recruited on the basis of a critical inclusion and exclusion criteria: (a) having physical examination in People's Liberation Army General Hospital (PLAGH) aged between 20 and 79; (b) no taking vitamins, minerals, or drugs affecting oxidation, immunity, metabolism, or salivary secretory since latest month; (c) no smokers or alcoholic drinkers; (d) good oral health status without oral mucosal diseases; (e) females not engaged in pregnancy or lactation; (f) elderly ones free of cognitive impairment; (g) no history or sign of systematic disorders including chronic inflammation, diabetes mellitus, cryptorrhea, renal diseases, liver diseases, tumor, digestive system disease, cardiovascular disease, or neurological disease in physical examination report (elderly ones with mild chronic illness which required no treatment or intervention were also included in our study); (h) exclusive of acute infectious disease or long-term mental stress. All volunteers were given written informed consent in our study (Pandey et al 2010;Su et al 2009Su et al , 2012Zeng et al 2012). …”

“…After collection, tubes with samples were kept at 4°C while further process must be done in 1 h. The tubes were centrifuged at 4000 rpm for 20 min at 4°C (Eppendorf Co., Hamburg, Germany), and the supernatants were gathered and stored in 1-mL aliquots for less than half a month ahead of detection. Samples mixed with blood or other visible impurities were discarded immediately, and each sample should not be frozen and thawed twice or more (Pandey et al 2010;Su et al 2008Su et al , 2009Su et al , 2012Zeng et al 2012). …”

“…Plasma was stored in 1-mL aliquots for less than half a month until detection and each sample was frozen and thawed only once (Pandey et al 2010;Zeng et al 2012). …”

“…Protein carbonyl derivatives can also be generated through oxidative cleavage of proteins by either the -amidation pathway or by oxidation of glutamyl side chains, leading to formation of a peptide in which the N-terminal amino acid is blocked by an -ketoacyl derivative . For its relative early formation, chemical stability, and uncomplicated detection method, protein carbonyl content has become by far one of the most widely used markers of protein oxidation Chevion et al 2000), and elevated amount of protein carbonyls has been detected in several human aging-related diseases including Alzheimer's disease, cancer, cardiovascular diseases, diabetes, and in plasma of elderly ones (Miriana and Denisa 2013;Mannello et al 2013;Ian et al 2013;Mediha et al 2010;Pandey et al 2010). Until recently, few research about saliva protein carbonyls have emerged while most focused on plasma or tissue protein carbonyls over the past decades (Pandey et al 2010;Hensley et al 1995;Su et al 2008Su et al , 2009).…”

“…As body oxidative status is influenced by oxidants and antioxidants, it is indispensable to detect both before assessing redox homeostasis (Pandey et al 2010;Benzie and Strain 1996).…”