In recent years it has become increasingly apparent that, in man, free radicals play a role in a variety of normal regulatory systems, the deregulation of which may play an important role in inflammation. As examples, we discuss the second messenger roles of: NO in the regulation of vascular tone, O2.- in fibroblast proliferation and H2O2 in the activation of transcription factors such as NF kappa B. Other control mechanisms, the physiological function of which may be perturbed in inflammation, include: the oxidative modification of low density lipoprotein, the oxidative inactivation of alpha-1-protease inhibitor, DNA damage/repair and heat shock protein synthesis. At sites of inflammation, increased free radical activity is associated with the activation of the neutrophil NADPH oxidase and/or the uncoupling of a variety of redox systems, including endothelial cell xanthine dehydrogenase. Although free radicals, thus produced, have the capacity to mediate tissue destruction, either alone or in concert with proteases, we argue that disturbances in the second messenger and regulatory activities of free radicals may also contribute significantly to the inflammatory process.

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Objective. To determine the relationship between hypoxia and the expression of Ets-1 and hypoxiainducible factor 1␣ (HIF-1␣) in both normal and inflamed joints. Adjuvant-induced arthritis (AIA) was used as the model system, since it mirrors many aspects of the pathology of rheumatoid arthritis.Methods. Adjuvant arthritis was induced in a group of 10 female Lewis rats. A second group of 10 uninjected female Lewis rats served as naive controls. When a maximum clinical joint score was achieved in the AIA group, all 20 rats were injected with the specific hypoxic cell marker Hypoxyprobe-1 and subsequently killed. Hypoxyprobe-1 adducts, Ets-1, and HIF-1␣ were localized in the joints of the hind feet from these groups using immunohistochemistry.Results. Compared with the joints from control rats, inflamed joints contained markedly more cells with Hypoxyprobe-1 adduct immunoreactivity, Ets-1-immunoreactive nuclei, and nuclear immunoreactivity for both Ets-1 and HIF-1␣.Conclusion. Our results demonstrate the presence of hypoxia in inflamed joints in this experimental model of arthritis. The colocalization of Ets-1 and HIF-1␣ in these hypoxic areas suggests that hypoxia may induce Ets-1 and HIF-1␣ expression during joint inflammation.

Background/Aims: We sought to determine whether hypoxia is an initiating factor in the matrix metalloproteinase-2 (MMP-2) up-regulation observed in abdominal aortic aneurysm (AAA) and whether hypoxia-inducible factor-1α (HIF-1α) or Ets-1 are mediating factors. Methods: Human AAA and normal aorta were analysed for MMP-2, HIF-1α and Ets-1 by immunohistochemistry. Human aortic smooth muscle cell (HASMC) cultures exposed to experimental hypoxia were analysed for hypoxia-induced proteins using gelatin zymography and immunoblotting. Multiplex PCR was used to detect MMP-1, membrane-type (MT)-MMP-1, MMP-2, MMP-3, MMP-7 and MMP-9. Results: AAA tissues expressed HIF-1α, MMP-2 and Ets-1 strongly within smooth muscle cells and inflammatory infiltrate of the tunica media. Up-regulated MMP-2 was detected in hypoxia-exposed HASMC (p < 0.05), with MMP-9 elevations after exposure to sequential O₂ decreases (p < 0.05). Immunoblotting confirmed HIF-1α, Ets-1, VEGF and MMP-2 are up-regulated in HASMC exposed to hypoxia (p < 0.05), while transcription for MMP-1, MT-MMP-1, MMP-9, MMP-2 and MMP-7 (p < 0.05) increased in hypoxic HASMCs. Conclusion: Hypoxia facilitates HIF-1α, Ets-1 and VEGF up-regulation in addition to driving enhanced secretion of MMP-2 and MMP-9 by HASMC. Enhanced transcription of factors relevant to aneurysmal disease in hypoxia indicates possible roles in disease progression and potential targets for therapeutic intervention.

Heat shock protein 32 (Hsp32, hemoxygenase-1) is induced by reactive oxygen metabolites (ROM) and degrades heme leading to the formation of antioxidant bilirubin. Increased mucosal generation of ROM occurs in gastritis and inflammatory bowel disease. We aimed to assess mucosal expression of Hsp32 in normal stomach and colon and to test the hypothesis that disease-related differential expression occurs in inflamed tissue. Gastric body and antral mucosal biopsies were obtained from 33 patients comprising Helicobacter pylori-negative normal controls (n = 8), H pylori-negative gastritis patients (n = 11), and H pylori-positive gastritis patients (n = 14). Forty-seven archival colonic mucosal biopsies selected comprised normal histology (n = 10), active ulcerative colitis (UC) (n = 9), inactive UC (n = 8), active Crohn's disease (CD) (n = 8), inactive CD (n = 6), and other colitides (n = 6). Hsp32 expression in formalin-fixed sections was assessed by avidin-biotin peroxidase immunohistochemistry using a polyclonal rabbit anti-Hsp32 as the primary antibody. Immunohistochemical staining identified Hsp32 in all groups. Diffuse cytoplasmic staining was seen in gastric and colonic epithelial and lamina proprial inflammatory cells. Staining scores for Hsp32 were higher in antral H pylori-positive (P = 0.002) and H pylori-negative (P = 0.02) gastritis than in controls and in body H pylori-positive gastritis than in the other 2 groups (P < 0.01). Expression of Hsp32 was increased in active UC compared with inactive disease (P = 0.03) and normal controls (P = 0.02). In conclusion, Hsp32 is expressed constitutively in normal gastric and colonic mucosa, and differential expression occurs in these tissues when they are inflamed. Upregulation of Hsp32 may be an adaptive response to protect mucosa from oxidative injury in patients with gastritis and inflammatory bowel disease.