OXIDATIVE STRESS AND ANTIOXIDANTS AT BIOSURFACES - PLANTS, SKIN, AND RESPIRATORY-TRACT SURFACES

Atmospheric pollutants represent an important source of oxidative and nitrosative stress to both terrestrial plants and to animals. The expo sed biosurfaces of plants and animals are directly exposed to these po llutant stresses. Not surprisingly, living organisms have developed co mplex integrated extracellular and intracellular defense systems again st stresses related to reactive oxygen and nitrogen species (ROS, RNS) , including O-3 and NO2. Plant and animal epithelial surfaces and resp iratory tract surfaces contain antioxidants that would be expected to provide defense against environmental stress caused by ambient ROS and RNS, thus ameliorating their injurious effects on more delicate under lying cellular constituents. Parallelisms among these surfaces with re gard to their antioxidant constituents and environmental oxidants are presented. The reactive substances at these biosurfaces not only repre sent an important protective system against oxidizing environments, bu t products of their reactions with ROS/RNS may also serve as biomarker s of environmental oxidative stress. Moreover, the reaction products m ay also induce injury to underlying cells or cause cell activation, re sulting in production of proinflammatory substances including cytokine s. In this review we discuss antioxidant defense systems against envir onmental toxins in plant cell wall/apoplastic fluids, dead keratinized cells/interstitial fluids of stratum corneum (the outermost skin laye r), and mucus/respiratory tract lining fluids.