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Exercise Redox Signalling
Published in James N. Cobley, Gareth W. Davison, Oxidative Eustress in Exercise Physiology, 2022
Ruy A. Louzada, Jessica Bouviere, Rodrigo S. Fortunato, Denise P. Carvalho
Another important source of following contractile activity is the enzyme XO (Gomez-Cabrera et al., 2010, 2005). Xanthine oxidoreductase (XOR) is related to both XO and xanthine dehydrogenase (XDH), which are enzymes that catalyse the reduction of hypoxanthine and xanthine to uric acid. While XDH transfers electrons from the substrate to NAD+, XO transfers it to O2 and generates . The conversion of XDH to XO occurs when tissue is injured (Gomez-Cabrera et al., 2010; Ryan et al., 2011) (Figure 3.1b). XO inhibition prevents extracellular superoxide production following an isometric protocol of contraction in the gastrocnemius muscle (Gomez-Cabrera et al., 2005), pointing to XO as an important source of ROS following muscle contraction (Figure 3.1).
Cellular and Molecular Mechanisms of Ischemic Acute Renal Failure and Repair
Published in Robin S. Goldstein, Mechanisms of Injury in Renal Disease and Toxicity, 2020
Joseph V. Bonventre, Ralph Witzgall
There are a number of sources of ROS in the postischemic tissue. One source of ROS is xanthine oxidase. Tissue xanthine oxidase levels are increased due to conversion from xanthine dehydrogenase with ischemia. Under normoxic conditions xanthine dehydrogenase catalyzes the transfer of electrons to NAD as xanthine and hypoxanthine are oxidized to uric acid. This enzyme is converted to xanthine oxidase with ischemia and reperfusion by a Ca2+ dependent protease (McCord, 1985). Xanthine oxidase uses molecular oxygen as an electron acceptor and generates superoxide during the oxidation of hypoxanthine, which is increased in concentration in the postischemic tissue as discussed above. In one study, tissue hypoxanthine levels were increased approximately 300-fold after 60 min of renal ischemia (Osswald, et al., 1977). The mitochondria constitute a second source of ROS. When mitochondria are deprived of oxygen the electron transport chain intermediates become more reduced and free electrons may result in enhanced superoxide generation when oxygen delivery to the tissue is restored. A third source of ROS are the enzymes involved in the metabolism of arachidonic acid, PGH synthase, and lipoxygenase. Both of these enzymes produce superoxide in the presence of NADH or NADPH (Kukreja, et al., 1986).
The No-Reflow Phenomenon: A Misnomer?
Published in Samuel Sideman, Rafael Beyar, Analysis and Simulation of the Cardiac System — Ischemia, 2020
Lewis C. Becker, Giuseppe Ambrosio, John Manissi, Harlan F. Weisman
One of the more interesting aspects of our experiments was the nonuniform distribution of no-reflow within the risk region. Although generally confined to the subendocardium and mid-myocardium, areas of no-reflow often consisted of islands separated by myocardium with much better perfusion. In addition, the borders separating no-reflow and reflow areas were usually quite sharp. Our results suggest that the basis for this heterogeneity of noreflow was a corresponding heterogeneity of ischemia during the period of coronary artery occlusion. Areas of no-reflow, both “immediate” and “delayed”, demonstrated virtually zero flow during occlusion, while immediately adjacent areas of reflow located within the infarct zone had low but measureable levels of flow (average about 10% of baseline). An absence of flow, as opposed to a severe reduction, may have been necessary to cause ischemic damage to the microvasculature, leading, in turn, to vascular obstruction and no-reflow during arterial reperfusion. Alternatively, extremely low levels of flow may have been required to “prime” the myocardium for subsequent reperfusion injury. In the setting of very low flow, a number of processes may have occurred to precipitate a burst of oxygen radicals at the moment of reperfusion. These processes could have included a build-up of hypoxanthine and xanthine (end products of nucleotide metabolism), conversion of xanthine dehydrogenase to its oxidase form, loss of scavenging enzymes such as superoxide dismutase, and changes in the vascular endothelium to promote granulocyte adherence.
Evaluation of acute kidney injury with oxidative stress biomarkers and Renal Resistive Index after cardiac surgery
Published in Acta Chirurgica Belgica, 2021
Alper Kararmaz, Mustafa Kemal Arslantas, Ugur Aksu, Halim Ulugol, Ismail Cinel, Fevzi Toraman
In our present study, IMA levels were significantly increased in postoperative period compared to preoperative period, while AOPP levels remained unchanged. Nonetheless, this is an implication of ischemic condition [28]. Numerous researchers showed ischemic injury processes during cardiopulmonary bypass. These include cellular adenosine triphosphate depletion due to its degradation by hypoxanthine [29,30]. Under physiological conditions, xanthine dehydrogenase oxidizes hypoxanthine and this reaction produces xanthine by using nicotinamide adenine dinucleotide (NAD). However, during ischemia, xanthine dehydrogenase is converted to xanthine oxidase [30–32] and xanthine oxidase related free radicals attacks to biological macromolecules and subsequently results to necrosis and inflammation [33]. A limited number of publications have assessed the relationship between AKI and AOPPs in patients receiving CABG. Liang et al. stated that AOPPs might be associated with adverse outcomes of AKI recovery in CABG patients, but these results were not able to generalize to all cases of AKI [10]. Therefore, we believe that our patients may have had exposure to minimal and recycled oxide-inflammatory stress and none of the patients developed non-recovered AKI in our study.
Sickle cell disease as a vascular disorder
Published in Expert Review of Hematology, 2020
It is possible that vaso-occlusion may contribute to organ damage via repeated vascular damage that results in endothelial cell dysfunction; this may occur through a mechanism resembling ischemia/reperfusion injury [61–63]. Ischemia/reperfusion injury is an important concept in vascular biology. Both ischemia and the subsequent restoration of blood flow can result in vascular and tissue injury, along with injury to one or more remote organs via systemic inflammation [62,64,65]. Hypoxia/reoxygenation in mouse models of SCD activates ischemia/reperfusion pathways and is associated with vaso-occlusion, inflammation, and tissue injury [61,66,67]. Ischemia caused by vaso-occlusion can trigger the conversion of xanthine dehydrogenase to xanthine oxidase, which results in the production of ROS [67]. This is followed by a cascade of events, including nuclear factor κB (NFκB) activation, endothelial cell activation, and increased P-selectin-dependent interactions between leukocytes and endothelial cells [62,67]. P-selectin is essential in mediating the leukocyte rolling, adhesion, and extravasation that characterize vascular inflammation following hypoxia/reoxygenation in a mouse model of SCD [61]. P-selectin is also involved in enhancing the formation of platelet-neutrophil aggregates following hypoxia/reoxygenation in a mouse model of SCD [68].
Emerging medical therapies in crush syndrome – progress report from basic sciences and potential future avenues
Published in Renal Failure, 2020
Ning Li, Xinyue Wang, Pengtao Wang, Haojun Fan, Shike Hou, Yanhua Gong
Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) are interconvertible forms of the same enzyme, xanthine oxidoreductase [30,31]. This is a key enzyme in the purine decomposition pathway that catalyzes the conversion of xanthine and hypoxanthine to uric acid (UA) [32,33]. During muscle contraction, the irreversible conversion of xanthine dehydrogenase (XDH) to its xanthine oxidase (XO) [34,35] plays an important role in producing ROS in ischemic conditions [36,37]. Allopurinol is an XO inhibitor and a UA-lowering agent commonly used in the treatment of gout [38,39]. Some animal studies have reported that glycerol-induced AKI can be effectively alleviated by inhibiting oxidative stress and apoptosis [40,41]. Studies by Gois et al. [42] showed that allopurinol treatment can reduce renal dysfunction by reducing oxidative stress (systemic, kidney and muscle), inhibiting apoptosis, reducing inflammatory cell infiltration, and increasing cell proliferation in rhabdomyolysis-related AKI rat model. If clinical research obtains positive results in the future, allopurinol treatment may become a new method for preventing and treating rhabdomyolysis-related AKI.