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Nitrite ion modifies tyrosine and lysine residues of extracellular matrix proteins

Mai T Thao1, Devi Kalyan Karumanchi1, Sally M Yacout1

  • 1Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL, USA.

Nitric Oxide : Biology and Chemistry
|July 29, 2018
PubMed

Insights

Nitrite, a byproduct of inflammation, chemically modifies extracellular matrix proteins in Bruch's membrane. These modifications may initiate the degenerative changes seen in age-related macular degeneration (AMD).

Area of Science:

  • Ophthalmology
  • Biochemistry
  • Pathology

Background:

  • Age-related macular degeneration (AMD) involves degenerative changes in the retinal pigment epithelium and Bruch's membrane.
  • Inflammation is a key risk factor in AMD development and progression.
  • Elevated nitrite levels, a marker of inflammation, are found in AMD tissues.

Purpose of the Study:

  • To investigate the hypothesis that nitrite chemically modifies extracellular matrix (ECM) proteins in Bruch's membrane.
  • To understand the initial chemical alterations in ECM proteins that may lead to AMD pathogenesis.

Main Methods:

  • Used synthetic ECM peptides (fibronectin, laminin) as models for inflammation.
  • Employed liquid chromatography-mass spectrometry (LC/MS) to analyze nitration products.
  • Studied non-enzymatic nitration under controlled conditions.

Main Results:

  • Nitration predominantly occurred on tyrosine residues, forming 3-nitrotyrosine (mass shift of +45 amu).
  • Lysine residues underwent deamination, forming alkene groups (mass loss of -17 amu) or alcohol groups (mass gain of +1 amu).
  • Identified specific chemical modifications resulting from nitrite exposure.

Conclusions:

  • Nitrite-induced chemical modifications of ECM proteins, specifically nitration of tyrosine and deamination of lysine, are demonstrated.
  • These modifications are hypothesized to alter the structure and function of Bruch's membrane, potentially initiating AMD.
  • Provides a molecular mechanism linking inflammation and ECM degradation in AMD.
Keywords:
3-NitrotyrosineAMDBruch's membraneExtracellular matrixInflammationLysine deaminationNitrite

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