Implications
(i) Chronic inflammations (rheumatoid arthritis, inflammatory skin diseases, psoriasis, Crohn’s disease, asthma, HIV), ischemia – reperfusion (infarction, stroke, organ transplantation)
Focus
(i) Production of reactive oxygen species by neutrophils and other cells of host defence
Models
(i) Screening ® demonstration of the effect in vivo (human volunteers)
Why cellular defence functions?
Generation of reactive oxygen species, hypochlorous acid and tyrosyl radical form together the basis of microbicidal action of human neutrophils. ROS production has been observed not only in neutrophils but also in macrophages, microglial cells of the brain, the Kupffer cells of the liver, monocytes, basophils, mast cells, and eosinophils. Besides the microbicidal action, reactive species generated by the oxidative burst and myeloperoxidase may cause damage to molecules and cellular components of the host organism. Prolonged overactivity of reactive species generating cell types results in sustained oxidative stress in a variety of inflammatory conditions: ischemia-reperfusion injury in myocardial infarction, stroke or transplantation, adult respiratory distress syndrome, rheumatoid arthritis, inflammatory bowel disease, HIV, psoriasis, and inflammatory conditions of the skin. Reactive species produced by the oxidative burst and myeloperoxidase activity are the ultimate damaging agents. It therefore seems logical that an effective inhibition of oxidative burst and myeloperoxidase activity would be a direct way for attenuation of the damage due to overactivity.
Effects on cellular defence functions in vitro
Tests:
(i) Superoxide anion production (”oxidative burst”)
(ii) Hypochlorite production (myeloperoxidase activity)
Aim: To find out how the test compound affects the ability of neutrophils (and other cells of the host defence) to produce reactive oxygen species in vitro.
Procedure: Studies are performed with human blood or cells isolated from human blood. Production of reactive oxygen species by stimulated neutrophils is recorded by chemiluminescence. Hypochlorite production (myeloperoxidase activity) is determined spectrophotometrically. Studies will be done with several concentrations of the test compound and repeated on separate days. The results will be presented as comparison of the potency of the test compound with that of a simultaneously tested known inhibitor of oxidative burst or myeloperoxidase activity.