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Interest in the toxicological aspects of oxidative stress has grown in recent years, and research has become increasingly focused on the mechanistic aspects of oxidative damage and cellular responses in biological systems. Toxic consequences of oxidative stress at the subcellular level include lipid peroxidation and oxidative damage to DNA and proteins. These effects are often used as end points in the study of oxidative stress. Typically, mammalian species have been used as models to study oxidative stress and to elucidate the mechanisms underlying cellular damage and response, largely because of the interest in human health issues surrounding oxidative stress. However, it is becoming apparent that oxidative stress also affects aquatic organisms exposed to environmental pollutants. Research in fish has demonstrated that mammalian and piscine systems exhibit similar toxicological and adaptive responses to oxidative stress. This suggests that piscine models, in addition to traditional mammalian models, may be useful for further understanding the mechanisms underlying the oxidative stress response.ImagesFigure 1Figure 2Figure 3

No abstract

Inflammatory cytokines have been shown to upregulate secretion of the antioxidant enzyme extracellular superoxide dismutase (EC-SOD) in dermal fibroblasts and, in other cells, to stimulate production of nitric oxide (⋅ NO). Because superoxide rapidly scavenges ⋅ NO, forming the injurious peroxynitrite anion (OONO−), we hypothesize that stimulated cells upregulate EC-SOD expression concurrently with ⋅ NO release. To test for coregulation of EC-SOD and ⋅ NO within the same cell, the timing of inducible nitric oxide synthase (iNOS) and EC-SOD transcription was measured after exposure of a rat type II pneumocyte analog, the L2 cell line, to a combination of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). Upregulation of iNOS and EC-SOD transcription occurred after 6 h of exposure, and transcription of both genes was linked by activation of the transcription factor nuclear factor-κB. Both EC-SOD and iNOS were elevated in rat lung homogenates 24 h after intratracheal instillation with IFN-γ and TNF-α. The observation that EC-SOD and iNOS are temporally coregulated after cytokine exposure suggests the possibility of a critical mechanism by which cells might protect ⋅ NO and avoid the formation of OONO− during inflammation.