Differential hepatic protein tyrosine nitration of mouse due to aging - effect on mitochondrial energy metabolism, quality control machinery of the endoplasmic reticulum and metabolism of drugs.

Aging is the inevitable fate of life which leads to the gradual loss of functions of different organs and organelles of all living organisms. The liver is no exception. Oxidative damage to proteins and other macromolecules is widely believed to be the primary cause of aging. One form of oxidative damage is tyrosine nitration of proteins, resulting in the potential loss of their functions. In this study, the effect of age on the nitration of tyrosine in mouse liver proteins was examined. Liver proteins from young (19-22 weeks) and old (24 months) C57/BL6 male mice were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotted onto nitrocellulose membranes. Proteins undergoing tyrosine nitration were identified using anti-nitrotyrosine antibody. Three different protein bands were found to contain significantly increased levels of nitrotyrosine in old mice (Wilconxon rank-sum test, p<0.05). Electrospray ionization liquid chromatography tandem mass spectrometry (ESI-LC-MS/MS) was used to identify the proteins in these bands, which included aldehyde dehydrogenase 2, Aldehyde dehydrogenase family 1, subfamily A1, ATP synthase, H(+) transporting, mitochondrial F1 complex, ß subunit, selenium-binding protein 2, and protein disulfide-isomerase precursor. The possible impairment of their functions can lead to altered hepatic activity and have been discussed.