D R Blake

HYPOXIC-REPERFUSION INJURY IN THE INFLAMED HUMAN JOINT

A series of experiments showed that, on exercise of the inflamed human knee, intra-articular pressure rises above synovial capillary perfusion pressure, causing intra-articular hypoxia; and that, on cessation of exercise, there is oxidative damage to lipids and IgG within the joint. These findings are consistent with the hypothesis that persistence of synovial inflammation can be due to exercise-induced hypoxic-reperfusion injury mediated by reactive oxygen species.

Oxidative DNA damage and cellular sensitivity to oxidative stress in human autoimmune diseases.

OBJECTIVES--To estimate the extent of genomic DNA damage and killing of lymphocytes by reactive oxygen intermediates in autoimmune diseases. METHODS--8-Oxo-7-hydrodeoxyguanosine (8-oxodG), a promutagenic DNA lesion induced by reactive oxygen intermediates, was measured by high performance liquid chromatography, coupled with electrochemical detection, in hydrolysates of DNA which had been extracted from lymphocyte and polymorphonuclear leucocyte fractions of human blood. In addition, human primary blood lymphocytes stimulated by concanavalin A were assayed for cytotoxicity induced by hydrogen peroxide on day 0, by assessing cell proliferation during seven days of culture. RESULTS--Constitutive 8-oxodG was detectable (mean (2 SEM) moles 8-oxodG/10(6) moles deoxyguanosine) in DNA isolated from normal human blood lymphocytes (68 (8), n = 26) and polymorphonuclear leucocytes (118 (24), n = 24). Lymphocyte DNA from donors with the following inflammatory autoimmune diseases contained significantly higher levels of 8-oxodG than that from healthy donors: rheumatoid arthritis (98 (16)), systemic lupus erythematosus (137 (28)), vasculitis (100 (32)), and Behçets disease (92 (19)). Lymphocyte 8-oxodG levels in non-autoimmune controls and patients with scleroderma were not significantly different from those of healthy controls. The levels of 8-oxodG were significantly higher in the DNA from normal polymorphonuclear leucocytes than in paired DNA samples from normal lymphocytes, but there were no differences between levels of 8-oxodG in polymorphonuclear leucocytes from normal subjects and the patients studied. Levels of 8-oxodG did not correlate with disease duration, disease severity, or age. Lymphocytes from patients with systemic lupus erythematosus and rheumatoid arthritis, but not those with scleroderma, also showed cellular hypersensitivity to the toxic effects of hydrogen peroxide. CONCLUSION--There was increased genomic DNA damage, and increased susceptibility to cytotoxic killing by hydrogen peroxide, in lymphocytes from patients with certain autoimmune diseases. These results might be explained by defective repair of DNA damage or by increased production of reactive oxygen intermediates in inflammation. Although more direct studies are needed, the evidence available favours the former explanation.

Raised cerebrospinal-fluid copper concentration in Parkinson's disease.

The cerebrospinal-fluid copper concentration, measured by electrothermal atomisation/atomic absorption spectrophotometry, was significantly higher in 24 patients with untreated, idiopathic Parkinsons disease than in a control population of 34 patients (p less than 0.001). The difference in the in-vitro capacity of copper to damage DNA, measured by the phenanthroline assay was even greater. The high phenanthroline-copper concentration correlated with disease severity (p = 0.02) and with the rate of progression of disease (p less than 0.05). A possible role is suggested for copper-catalysed oxidative mechanisms in the pathogenesis of Parkinsons disease.

Hypoxia and inflammatory synovitis: observations and speculation.

In recent years considerable research interest has been directed at studying the biological consequences of tissue hypoxia. As this work progresses it becomes increasingly apparent that tissue hypoxia has complex biological consequences. Much is now known about the natural defences of the body to hypoxia, including heat shock protein synthesis and angiogenesis. These systems are normally under rigid control, but this would seem not so in the rheumatoid joint. This accumulation of knowledge has prompted the belated reawakening of interest in joint hypoxia; it is now clear that an understanding of the physiological and pathological effects of joint hypoxia is of great importance to both clinical and research rheumatology. This review outlines joint hypoxia from a historical perspective and offers explanations for the phenomenon. Some of the more pertinent implications of hypoxia in the context of inflammatory synovitis are discussed.

Putative analgesic activity of repeated oral doses of vitamin E in the treatment of rheumatoid arthritis. Results of a prospective placebo controlled double blind trial

OBJECTIVE Vitamin E, the most potent naturally occurring lipid soluble antioxidant has been suggested to possess both anti-inflammatory and analgesic activity in humans. This double blind and randomised study used a broad spectrum of clinical and laboratory parameters to investigate whether there was any additional anti-inflammatory or analgesic effects, or both, of orally administered α-tocopherol in rheumatoid arthritis patients who were already receiving anti-rheumatic drugs. METHODS Forty two patients were enrolled and treated with α-tocopherol (n=20) at a dose of 600 mg twice a day (2 × 2 capsules) or with placebo (n=22) for 12 weeks. The following parameters were measured: (1) Three clinical indices of inflammation—the Ritchie articular index, the duration of morning stiffness, and the number of swollen joints; (2) three measures of pain—pain in the morning, pain in the evening, and pain after chosen activity; (3) haematological and biochemical measures of inflammatory activity; (4) assays for the oxidative modification of proteins and lipids. RESULTS All laboratory measures of inflammatory activity and oxidative modification were unchanged. Furthermore, the clinical indices of inflammation were not influenced by the treatment. However, the pain parameters were significantly decreased after vitamin E treatment when compared with placebo. CONCLUSION The results provide preliminary evidence that vitamin E may exert a small but significant analgesic activity independent of a peripheral anti-inflammatory effect, but which complements standard anti-inflammatory treatment.

The pharmacology of ebselen.

ConclusionEbselen has been demonstrated to be an effective anti-inflammatory agent in a variety of experimental modelsin vivo which differ from classical tests in that the aetiological roles of hydroperoxides and/or lipoxygenase products appear to be greater. Indeed, ebselen exhibits only weak anti-inflammatory activity in the traditional prostaglandin-dominated models, such as carrageenan paw oedema, adjuvant arthritis and yeast paw hyperalgesia [50]. The major targets of this anti-inflammatory activity appear to be plasma exudation and infiltration, possibly as a result of the inhibition of the hydroperoxide and/or leukotriene effects on leukocyte-endothelium interactions. Both reactive oxygen species [24] and LTB4 [51, 52] enhance granulocyte adhesiveness to endothelium and ebselen inhibits the generation of reactive oxygen species, catalyses the breakdown of hydroperoxides, inactivates LTB4 by isomerization and inhibits 5-lipoxygenase [9–11, 13–16, 27–29]. Consequently, any or all of these mechanisms of action, together with inhibition of hypoxic-reperfusion injury [53], could contribute to the anti-inflammatory activity of ebselen.With regard to tissue injury, the inhibitory action of ebselen on gastric mucosal injury clearly bodes well for its clinical use and offers a big advantage over current NSAIDs.In vitro findings indicate that the compound may inhibit gastric acid secretion directly [54]. As an inhibitor of hepatic pancreatic and cerebral tissue injury, ebselen also opens up new perspectives for therapy which are being actively pursued. Studies on the mechanism of action of ebselen in these experimental tissue injury models point towards inhibition of 5-lipoxygenase products, though the GSH-Px like action may also play a role. In experimental liver injury, tumor necrosis factor (TNF) has been shown to be the final mediator of endotoxin action [55] and it will be of interest to see whether ebselen is able to affect the actions of this cytokine, both in the liver and at other sites, including TNF-induced leukocyte adhesion [56]. The last word on the pharmacology of ebselen is far from being spoken or written!

Inactivation of the elastase inhibitory activity of alpha 1 antitrypsin in fresh samples of synovial fluid from patients with rheumatoid arthritis.

The proteinase inhibitory ability of alpha 1 antitrypsin was measured in 23 samples of rheumatoid arthritis synovial fluid, eight osteoarthritic synovial fluids and nine normal control serum samples. For each sample a detailed kinetic analysis was performed with porcine pancreatic elastase as the target proteinase. Samples were stored for less than 24 hours at 4 degrees C before analysis, which does not significantly alter the proportion of inactive alpha 1 antitrypsin. In rheumatoid synovial fluid the elastase inhibitory ability was disproportionately depressed relative to the immunochemically determined concentrations of alpha 1 antitrypsin.

Endothelial cell cytotoxicity in inflammatory vascular diseases--the possible role of oxidised lipoproteins.

One of the proposed mechanisms of vascular damage in connective tissue disease is the direct action of a cytotoxic serum factor inducing endothelial cell damage. The nature of this serum factor is unclear, but has been suggested to be a lipoprotein. Sera from patients with (1) systemic necrotising arteritis (polyarteritis nodosa, Wegeners granulomatosis, and necrotising arteritis associated with rheumatoid synovitis), (2) systemic or joint restricted rheumatoid disease, and (3) large vessel/giant cell arteritis have been examined for cytotoxicity to human cultured endothelial cells and azide-resistant ferroxidase-like activity (indicative of the oxidised lipoprotein content). Stored sera from patients with necrotising arteritis showed a significantly enhanced tendency to develop oxidised lipoprotein, which correlated closely with human endothelial cell cytotoxicity. Fresh sera also contained this factor, but to a lesser extent. It is argued that the cytotoxic factor detected in previous clinical studies is in part an in-vitro artefact, although its accelerated development in certain patient groups might suggest an excess of pro-oxidants that have developed in vivo.

Comparative study of intra-articular pressure dynamics in joints with acute traumatic and chronic inflammatory effusions: potential implications for hypoxic-reperfusion injury.

It has been proposed that the process of hypoxic-reperfusion injury contributes to the persistence of synovitis in the inflamed human joint. The generation of pathological, exercise induced, intra-articular pressure leading to occlusion of the synovial microcirculation is central to this mechanism. However, acute traumatic inflammatory joint effusions rarely result in chronic synovitis, suggesting that either the basic hypothesis is incorrect, or that joints with acute traumatic effusions show different intra-articular pressure dynamics. In this study the intra-articular pressure was measured at rest and during isometric exercise in five patients with acute traumatic joint effusions and in nine patients with chronic inflammatory joint effusions. The generation of intra-articular pressure in the patients with acute traumatic effusions was significantly lower at rest (mean 2.0 v 19.6 mm Hg) and during exercise (mean 13.7 v 222.5 mm Hg) than in the patients with chronic effusions. This was due to reflex muscular inhibition around the joint, which inhibited the pathological generation of intra-articular pressure. This difference in the ability to generate intra-articular pressure might mitigate against hypoxic-reperfusion injury in joints with acute traumatic effusions, thereby explaining the paradoxical clinical observation that patients with acute traumatic inflammatory joint effusions rarely develop chronic synovitis.

Thrombin receptor expression in rheumatoid and osteoarthritic synovial tissue.

OBJECTIVE: To investigate the possibility that synovial cells might respond to thrombin in the inflamed human joint, using immunohistochemical detection of thrombin receptors. METHODS: Frozen sections of synovial membrane from 20 patients with rheumatoid arthritis, 16 with osteoarthritis, and four normal controls were stained using a monoclonal antibody to the human thrombin receptor. Sections were also double stained for both receptors and non-specific esterase. RESULTS: Receptor positive cells were present in rheumatoid synovia, with some cells also staining positively for non-specific esterase. In contrast, both osteoarthritic and normal synovia contained very few cells expressing receptors. CONCLUSIONS: Thrombin may mediate important pathological changes during chronic inflammatory joint disease.