Reperfusion diseases/injuries

Improving giycaemic control may not only reduce the rate of non-enzymatic glycosyiation and monosaccharide autooxidation, but lower polyol pathway activity. In addition, it should have a beneficial effect on other haemodynamic and hormonal factors involved in the development of diabetic vascular disease. However, in studies of diabetic retinopathy, rapid control of glucose levels by intensive insulin therapy has been shown to worsen vascular disease initially and it could be postulated that a sudden improvement in retinal blood flow promotes further free-radical damage as part of a reperfusion-ischaemic injury. 

In other smdy, 20 healthy subjects were supplemented with grape juice (7 mL/kg) for 14 days. Significantly decreased platelet aggregation, increased platelet-derived NO release, and decreased superoxide production were observed. The suppressimi of platelet-mediated thrombosis represents a potential mechanism for the beneficial effects of purple grape products in cardiovascular disease [120]. Similarly, proanthocyanidin-rich extract of grape seed (50 and 100 mg/kg for 3 weeks) had cardioprotective effects against reperfusion-induced injury in isolated rat hearts [121]. A lower dose (36 g of lyophiUzed power grape/day for 4 weeks) was tested in pre- and postmenopausal women. Lipoprotein metabolism, oxidative stress, and inflammatory markers were achieved, and, therefore, CHD risk factors were reduced [122]. 

Apart from these two Vertex compounds, only one other caspase inhibitor, BDN-6556, has been used in clinical trials. This compound belongs to the class of oxamyl dipeptides and was originally developed by Idun Pharmaceuticals (taken over by Pfizer). It is the only pan-caspase inhibitor that has been evaluated in humans. BDN-6556 displays inhibitory activity against all tested human caspases. It is also an irreversible, caspase-specific inhibitor that does not inhibit other major classes of proteases, or other enzymes or receptors. The therapeutic potential of BDN-6556 was first evaluated in several animal models of liver disease because numerous publications suggested that apoptosis contributes substantially to the development of some hepatic diseases, such as alcoholic hepatitis, hepatitis B and C (HBV, HCV), non-alcoholic steato-hepatitis (NASH), and ischemia/reperfusion injury associated with liver transplant. Accordingly, BDN-6556 was tested in a phase I study. The drug was safe and... 

PI (adenosine) receptors were explored as therapeutic targets before P2 receptors. Adenosine was identified early and is in current use to treat supraventricular tachycardia. A2a receptor antagonists are being investigated for the treatment of Parkinson s disease and patents have been lodged for the application of PI receptor subtype agonists and antagonists for myocardial ischaemia and reperfusion injury, cerebral ischaemia, stroke, intermittent claudication and renal insufficiency. 

Tso and Lam suggested that astaxanthin could be useful for prevention and treatment of neuronal damage associated with age-related macular degeneration and may also be effective in treating ischemic reperfusion injury, Alzheimer s disease, Parkinson s disease, spinal cord injuries, and other types of central nervous system injuries. Astaxanthin was found to easily cross the blood-brain barrier and did not form crystals in the eye. 

As stated at the beginning of this article, the liver is the most intensively studied animal tissue in biochemistry. In the context of the role of free radicals in human diseases, the liver is not obviously at centre stage, since heart disease and cancer are more important in the industrialized world than, for example, cirrhosis. Free-radical biochemistry of the liver will remain a fertile area of work, however, not least because so many original ideas and techniques are developed there and then applied to the study of other tissues. The increasing use of liver transplantation, following the acceptance of kidney and heart transplants as almost routine, will surely increase the interest in the study of ischaemia-reperfusion injury in... 

Moreover,bioactive lipids maybe considered dual messengers they modulate cell functions as messengers and they become part of the response of the nervous tissue to injury, broadly referred to as the inflammatory response. This response occurs in ischemia-reperfusion damage associated with stroke, various forms of neurotrauma, infectious diseases and neurodegenerative diseases such as Alzheimer s disease. Inflammation in the nervous system differs from that in other tissues. If the blood-brain barrier is broken, blood-borne inflammatory cells (e.g. polymorphonuclear leukocytes, monocytes, macrophages) invade the intercellular space and glial cells are activated, particularly microglia, which play a prominent role in the inflammatory response. These responses may... 

The radical anion superoxide 02 is a product of activated leukocytes and endothelial cells and has been postulated to be a mediator of isch-emia-reperfusion injury and inflammatory and vascular diseases. Various superoxide dismutase (SOD) enzymes are known Cu,Zn-SOD in the cytoplasm of eukaryotic cells, Mn-SOD in mitochondria, and Fe-SOD and Mn-SOD in prokaryotic cells. They catalyze the conversion of 02 into H202 and 02... 

However, it is now recognised that neutrophils can contribute to host-tissue damage if they are activated to secrete reactive oxidants and granule enzymes, and if the local concentrations of anti-oxidants and protease inhibitors within the tissue are low or defective. Thus, inappropriate neutrophil activation leading to host-tissue damage has been implicated in reperfusion injury, Crohn s disease, adult respiratory distress syndrome (ARDS) and rheumatoid arthritis. In these conditions, it is envisaged that neutrophils accumulate in tissues and become inappropriately activated to secrete their cytotoxic products, which then initiate or contribute to host-tissue damage. 

In addition, there is experimental evidence showing that mitochondrial cardiolipin content markedly decreases following ischemia and reperfusion injury due to cardiolipin peroxidation (Soussi et al., 1990) and that a decrease in the mitochondrial phospholipid cardiolipin occurred in aged rat hearts (Pepe, 2000). These decreases may he attrihutahle to the hydroperoxide-formation of cardiolipin after exposure to intense or repeated oxidative stress during disease state or normal aging, respectively. 

Many pathological conditions, including ischemia/reperfusion, inflammation, and sepsis may induce tissues to simultaneously produce both superoxide and nitric oxide. For example, ischemia allows intracellular calcium to accumulate in endothelium (Fig. 20). If the tissue is reperfused, the readmission of oxygen will allow nitric oxide as well as superoxide to be produced (Beckman, 1990). For each 10-fold increase in the concentration of nitric oxide and superoxide, the rate of peroxynitrite formation will increase by 100-fold. Sepsis causes the induction of a second nitric oxide synthase in many tissues, which can produce a thousand times more nitric oxide than the normal levels of the constitutive enzyme (Moncada et al., 1991). Nitric oxide and indirectly peroxynitrite have been implicated in several important disease states. Blockade of nitric oxide synthesis with N-methyl or N-nitroarginine reduces glutamate-induced neuronal degeneration in primary cortical cultures (Dawson et al., 1991). Nitroarginine also decreases cortical infarct volume by 70% in mice subjected to middle cerebral artery occlusion (Nowicki et al., 1991). Myocardial injury from a combined hy-... 

Vascular injury resulting from ischemia-reperfusion, inflammation, xeno-biotic metabolism, hyperoxic exposure, and other diseases, causes loss of endo-... 

Figure 16.14 represents a summary of the most important studies performed in the field of free radical scavenging effects. G115 inhibits lipid peroxidation in rats. It protects the rabbit pulmonary artery from free radical injury and the rat heart from ischemia reperfusion injury. Figure 16.15 illustrates the various diseases that are due to an excessive production of free radicals, such as atheroclerosis, diabetes, rheumatoid arthritis, and aging. 

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