Proteomic characterization of nitrated cell targets after hypobaric hypoxia and reoxygenation in rat brain

This study analyzes the nitrated protein profile of the rat-brain cortex in a model of hypoxia/reoxygenation, identifying the nitrated proteins and assessing spot changes. The proteins identified were grouped into categories, according to their function: 1) metabolism: pyruvate kinase (PK), α-enolase, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), phosphoglycerate mutase 1 (PGAM1), and glutamine synthetase (GS); 2) cytoskeletal proteins: α-tubulin, β-tubulin, γ-actin, and glial fibrillary acidic protein (GFAP); 3) chaperones: heat-shock protein 71kDa (HSP71); and 4) carrier proteins: voltage-dependent anion-selective channel protein 1 (VDAC-1) and Atp6v1a. PK, α-enolase, and GS nitration rates were upregulated, increasing progressively during reoxygenation and peaking at 24h. GAPDH and PGAM1 nitration levels fell after hypoxia/reoxygenation. α-Tubulin, β-tubulin, γ-actin, and GFAP nitration rates augmented at 24h, but diminished at 5d. HSP71 suffered from nitration immediately after hypoxia, but not during reoxygenation. VDAC-1 tyrosine nitration was identified only in the control group, whereas detectable Atp6v1a nitration levels were observed only immediately after hypoxia. The data have been deposited to the ProteomeXchange with identifier PXD001049. Our findings suggest a hypothetically crucial linkage between nitration-related protein modifications and metabolic and cell-structure alterations. These changes are probably needed for the remodeling and plasticity processes activated by the hypoxic brain response.

Biological significance: For the first time the spectrum of nitrated proteins in the hypoxic brain as well as its changes during reoxygenation are described. Our findings suggest a hypothetically crucial linkage between nitration-related protein modifications and metabolic and cell-structure alterations. These changes are probably needed for the remodeling and plasticity processes activated by the hypoxic brain response. The biological relevance of these findings is linked to the important role developed by the signaling molecule NO in the hypoxic brain, and could be interpreted in two different but complementary ways: first, as a mechanism of damage due to nitration impacts over some key proteins affecting its structure and function; and second, as a regulation mechanism involved in the hypoxic response. Hence, based on the modified proteins identified and their functions, it would be possible to design new tools and therapies to prevent brain damage in low-oxygen-pressure atmospheres.