Peroxynitrite mild nitration of albumin and LDL–albumin complex naturally present in plasma and tyrosine nitration rate–albumin impairs LDL nitration

Abstract

In blood, peroxynitrite (ONOO⁻ ) and CO₂ react to form NO₂^√ and through the short-lived adduct , leading to protein-bound tyrosine nitration. ONOO⁻ -modified LDL is atherogenic. Oxidatively modified LDL generally appears in the vessel wall surrounded by antioxidants. Human serum albumin (HSA) is one of them, partly associated to LDL as a LDL–albumin complex (LAC). The purpose was to study the effect of a mild nitration on LAC and whether albumin may interfere with LDL nitration. To do so, SIN-1 was used as ONOO⁻ generator in the presence or absence of 25 mM . The human serum albumin (HSA)-bound tyrosine nitration rate was found to be 4.4 × 10^{− 3} mol/mol in the presence of . HSA decreased the LAC-tyrosine nitration rate from 2.5 × 10^{− 3} to 0.6 × 10^{− 3} mol/mol. It was concluded that HSA impaired the apoB-bound tyrosine nitration. These findings raise the question of the patho-physiological significance of these nitrations and their interactions which may potentially prevent both atheromatous plaque formation and endothelium dysfunction in particular and appear to be beneficial in terms of atherogenic risk.

• Nitration
• tyrosine
• albumin
• low-density lipoprotein
• peroxynitrite
• GC-MS

Abbreviations
DTPA	=	diethylenetriamine pentacetic acid
HSA	=	human serum albumin
LAC	=	LDL–albumin complex
MTBSTFA	=	N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide
3NT	=	3-NO2-Tyr
ox-LDL	=	oxidized LDL
SIN-1	=	3-morpholinosydnonimine hydrochloride
TFAA	=	trifluoroacetyl anhydride

Abbreviations
DTPA	=	diethylenetriamine pentacetic acid
HSA	=	human serum albumin
LAC	=	LDL–albumin complex
MTBSTFA	=	N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide
3NT	=	3-NO2-Tyr
ox-LDL	=	oxidized LDL
SIN-1	=	3-morpholinosydnonimine hydrochloride
TFAA	=	trifluoroacetyl anhydride