MECHANISMS AND THERAPEUTICS AGAINST GENOTOXICITY CAUSED BY NEUTROPHILIC INFLAMMATION

LOPEZ CM; FLORENCIA NAHIR CLAVELES CASAS,; BARRERAS, FS; CHACON I. DEL V; DI SCIULLO MP,; RAMÍREZ, DC.; GOMEZ MEJIBA, SANDRA;

SAN LUIS

Congreso; SBC; 2019

Neutrophilic inflammation is an important mechanism of oxidative damage to macromolecules at sites of inflammation. This process occurs when neutrophils are retained and activated at sites of acute irritation as occurs in sepsis; or at sites of chronic inflammation when macrophages are reactivated to express myeloperoxidase (MPO), such as in neurodegenerative diseases, obese adipose tissue, autoimmunity and tumors. MPO is the major protein in neutrophils and also can be synthesized by macrophages under special conditions. MPO is the only mammalian enzyme that under physiological conditions can synthesize HOCl/OCl. HOCl is a strong two- and one-electron oxidant that can oxidize macromolecules by radical or non-radical mediated mechanisms. When activated neutrophils release MPO towards the extracellular milieu as neutrophil extracellular traps (NETs). Tissue cells can take up MPO from the extracellular environment. Intracellular MPO, in the presence of physiological concentrations of chloride and H2O2, can produce HOCl and cause cell genotoxicity. There are no evidences that DNA-radicals precedes of genotoxicity at sites of inflammation. Co-incubation of lung epithelial cells with activated human neutrophils results in accumulation of MPO inside the epithelial cells?a system that resembles neutrophilic inflammation in the irritated airways. Herein we sought to test whether DNA radicalization produced by intracellularly produced HOCl can cause hypoxanthine-guanine phosporibosyltransferase (hrpt)-gene mutation in A549 airway epithelial cells and how the nitrone spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) can modulate this process. Exposure of A549 cells loaded with active MPO and exposed to a flow or bolus addition of H2O2, produced HOCl inside them. Intracellularly produced HOCl caused DNA radicalization, 8-oxo-7,8-dihydro-2´?deoxyguanosine (8-oxo-dGuo), p53 translocation within the nucleus and hrtp gene mutation. DNA radicalization precedes 8-oxo-dGuo formation and hrpt gene mutation. The DMPO trapped DNA-centered radicals, reduced 8-oxo-dGuo accumulation, and blocked hrpt gene mutation. In vivo model of acute distress respiratory syndrome showed pulmonary neutrophil accumulation and activation, DNA radicalization and 8-oxo-dGuo formation. The mechanism and therapeutics to reduce accumulation/activation of neutrophils and HOCl-mediated mutations at sites of neutrophilic inflammation will be discussed. Supported by: PICT-3435, PIP-916, PROICO-100218/023418 and PUE-013.