Cytotoxic effects of peroxynitrite, polymorphonuclear neutrophils, free-radical scavengers, inhibitors of myeloperoxidase, and inhibitors of nitric oxide synthase on bovine mammary secretory epithelial cells |
| |
| Authors: | Ledbetter T K Paape M J Douglass L W |
| |
| Institution: | Department of Animal and Avian Sciences, University of Maryland, College Park 20742, USA. |
| |
| Abstract: | OBJECTIVE: To determine cytotoxic effects of activated polymorphonuclear neutrophils (PMN) and peroxynitrite on bovine mammary secretory epithelial cells before and after addition of nitric oxide synthase inhibitors, myeloperoxidase (MPO) inhibitors, and free-radical scavengers. SAMPLE POPULATION: Polymorphonuclear neutrophils from 3 lactating cows. PROCEDURE: Cells from the bovine mammary epithelial cell line MAC-T were cultured. Monolayers were treated with activated bovine PMN, lipopolysaccharide (LPS), phorbol 12-myristate 13-acetate (PMA), 3-morpholino-sydnonimine (SIN-1), 4-amino-benzoic acid hydrazide (ABAH), NG-monomethyl-L-arginine, histidine, and superoxide dismutase (SOD). At 24 hours, activity of lactate dehydrogenase in culture medium was used as a relative index of cell death. Tyrosine nitration of proteins in MAC-T cell lysates was determined by visual examination of immunoblots. RESULTS: Lipopolysaccharide, PMA, and < or = 0.1 mM SIN-1 were not toxic to MAC-T cells. Activated PMN, > or = 6 mg of histidine/ml, and 0.5 mM SIN-1 were toxic. Together, histidine and 500,000 activated PMN/ml also were toxic. NG-monomethyl-L-arginine did not have an effect, but ABAH decreased PMN-mediated cytotoxicity. Ten and 50 U of SOD/ml protected MAC-T cells from cytotoxic effects of 0.5 mM SIN-1. Compared with control samples, nitration of MAC-T tyrosine residues decreased after addition of 500,000 PMN/ml or > or = 6 mg of histidine/ml. Superoxide dismutase increased and SIN-1 decreased tyrosine nitration of MAC-T cell proteins in a dose-responsive manner. CONCLUSIONS AND CLINICAL RELEVANCE: Peroxynitrite, MPO, and histidine are toxic to mammary secretory epithelial cells. Superoxide dismutase and inhibition of MPO activity mitigate these effects. Nitration of MAC-T cell tyrosine residues may be positively associated with viability. |
| |
| Keywords: | |
| 本文献已被 PubMed 等数据库收录！ |
|
