Is nitrotyrosine generated in human erythrocytes in circulation?

Area of Science:

• Biochemistry
• Cell Biology
• Immunology

Background:

• Nitrotyrosine is a stable biomarker for reactive nitrogen species (RNS), such as nitrogen dioxide (NO2) and peroxynitrous acid (ONOOH).
• Previous studies show inconsistent findings regarding nitrotyrosine detection in normal human plasma.
• Erythrocytes circulate for approximately 120 days and may be exposed to RNS.

Purpose of the Study:

• To investigate the presence of nitrotyrosine in membrane proteins and hemoglobin of human erythrocytes.
• To compare nitrotyrosine levels in young versus senescent erythrocytes.
• To determine if erythrocytes are a source of detectable nitrotyrosine in circulation.

Main Methods:

• Separation of young and senescent erythrocytes from healthy individuals.
• Western blot analysis using newly prepared anti-nitrotyrosine antibodies.
• In vitro nitration of erythrocyte proteins with NO2 or ONOOH for antibody validation.

Main Results:

• Anti-nitrotyrosine antibodies showed minimal binding to proteins from both young and senescent erythrocytes.
• Antibodies strongly bound to in vitro nitrated erythrocyte proteins, confirming antibody specificity.
• Nitrotyrosine was not detected in membrane proteins or hemoglobin of normal circulating human erythrocytes.

Conclusions:

• Nitrotyrosine is not significantly present in the membrane proteins or hemoglobin of normal human erythrocytes.
• The study indicates that circulating erythrocytes do not accumulate detectable levels of nitrotyrosine.
• Further research is needed to understand erythrocyte exposure to RNS despite the absence of nitrotyrosine detection.