β-Carotene effectively scavenges toxic nitrogen oxides: nitrogen dioxide and peroxynitrous acid

Abstractβ-Carotene absorbed 2 equimolar amounts of NO2 accompanying the complete destruction of β-carotene. Electron spin resonance study using 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl revealed that no significant amounts of NO were released by the interaction. Nitrogen atoms derived from NO2 were tightly bound to the β-carotene molecules. Destruction of β-carotene was inhibited little by α-tocopherol and polyunsaturated fatty esters, and slightly by ascorbyl palmitate, indicating that β-carotene was a more effective scavenger of NO2. ONOOH/ONOO− and 3-morpholinosydononimine similarly destroyed β-carotene. The results suggest that β-carotene contributes to the prevention of cytotoxicity and genotoxicity of NO2 and ONOOH/ONOO− derived from NO.©1997 Federation of European Biochemical Societies

Involvement of calcium signaling in the fibronectin-stimulated macrophage recognition of oxidatively damaged erythrocytes

AbstractMacrophages recognize oxidatively damaged autologous erythrocytes, and cell surface fibronectin of macrophages enhances the recognition (Beppu et al., FEBS Lett. 295 (1991) 135–140). In the present study, mechanisms of enhanced macrophage recognition of oxidatively damaged erythrocytes by fibronectin were investigated. Monolayers of thioglycollate-induced mouse peritoneal macrophages with cell surface fibronectin recognized autologous erythrocytes oxidized with an iron catalyst ADP/Fe3+. The macrophage recognition of the oxidized erythrocytes was inhibited partially by pretreatment of the macrophage monolayers with a Ca2+ channel blocker (diltiazem), calmodulin inhibitors (W-7, trifluoperazine, chlorpromazine and dibucaine), an inhibitor of myosin light chain kinase (ML-9), a microfilament formation inhibitor (cytochalasin B), phospholipase A2 inhibitors (4-bromophenacyl bromide, mepacrine) and cyclooxygenase inhibitors (indomethacin and aspirin). Monolayers of macrophages depleted of fibronectin by trypsinization lost the ability of recognizing oxidized erythrocytes, but acquired the ability when stimulated with a fibronectin-coated coverslip. The recognition of fibronectin-stimulated trypsinized macrophages was also inhibited by the above inhibitors. On treatment with Ca ionophore A23187, trypsinized macrophages acquired the ability to recognize oxidized erythrocytes. The recognition of Ca ionophore-stimulated trypsinized macrophages was inhibited by the above inhibitors except the Ca2+ channel blocker. These results indicate that the Ca2+ signaling including Ca2+ influx, calmodulin activation and myosin light chain phosphorylation are involved in the fibronectin stimulation of the recognition of macrophages for oxidized erythrocytes. Involvement of microfilament formation and arachidonate cascade in the fibronectin stimulation was also suggested