Oxidative stress-induced signal transduction pathways in cardiac myocytes: involvement of ROS in heart diseases

Autoimmune myocarditis: cellular mediators of cardiac dysfunction

Immune mediators play a critical role in the pathogenesis and outcomes of a number of cardiac diseases. This review summarizes recent findings on the composition of the inflammatory infiltrate and the role of different types and subtypes of immune cells and their products in mediating cardiac dysfunction in experimental autoimmune myocarditis (EAM). CD4+ T cells are required for initiation of myocarditis and their numbers in the heart infiltrate correlate with systolic dysfunction during disease progression. Other immune cells, including CD8+ T cells, granulocytes, and mast cells, can directly affect cardiomyocyte function. When regulatory mechanisms fail, the local damage leads to cardiomyocyte death, replacement fibrosis and overall cardiac dysfunction. EAM provides insights into the role of the immune system in the development of dilated cardiomyopathy (DCM) and heart failure and may serve as a general paradigm for autoimmune organ-specific tissue damage.

Increased efflux of glutathione conjugate in acutely diabetic cardiomyocytes

In diabetes, cell death and resultant cardiomyopathy have been linked to oxidative stress and depletion of antioxidants like glutathione (GSH). Although the de novo synthesis and recycling of GSH have been extensively studied in the chronically diabetic heart, their contribution in modulating cardiac oxidative stress in acute diabetes has been largely ignored. Additionally, the possible contribution of cellular efflux in regulating GSH levels during diabetes is unknown. We used streptozotocin to make Wistar rats acutely diabetic and after 4 days examined the different processes that regulate cardiac GSH. Reduction in myocyte GSH in diabetic rats was accompanied by increased oxidative stress, excessive reactive oxygen species, and an elevated apoptotic cell death. The effect on GSH was not associated with any change in either synthesis or recycling, as both γ-glutamylcysteine synthetase gene expression (responsible for bio syn thesis) and glutathione reductase activity (involved with GSH recycling) remained unchanged. However, gene expression of multidrug resistance protein 1, a transporter implicated in effluxing GSH during oxidative stress, was elevated. GSH conjugate efflux mediated by multidrug resistance protein 1 also increased in diabetic cardiomyocytes, an effect that was blocked using MK-571, a specific inhibitor of this transporter. As MK-571 also decreased oxidative stress in diabetic cardiomyocytes, an important role can be proposed for this transporter in GSH and reactive oxygen species homeostasis in the acutely diabetic heart. Key words: cardiomyocytes, apoptosis, multidrug resistance protein, reactive oxygen species.

Hypoxia-regulated therapeutic gene as a preemptive treatment strategy against ischemia/reperfusion tissue injury

Ischemia and reperfusion represent major mechanisms of tissue injury and organ failure. The timing of administration and the duration of action limit current treatment approaches using pharmacological agents. In this study, we have successfully developed a preemptive strategy for tissue protection using an adenoassociated vector system containing erythropoietin hypoxia response elements for ischemia-regulated expression of the therapeutic gene human heme-oxygenase-1 (hHO-1). We demonstrate that a single administration of this vector several weeks in advance of ischemia/reperfusion injury to multiple tissues such as heart, liver, and skeletal muscle yields rapid and timely induction of hHO-1 during ischemia that resulted in dramatic reduction in tissue damage. In addition, overexpression of therapeutic transgene prevented long-term pathological tissue remodeling and normalized tissue function. Application of this regulatable system using an endogenous physiological stimulus for expression of a therapeutic gene may be a feasible strategy for protecting tissues at risk of ischemia/reperfusion injury.

Oxidative stress: a theoretical model or a biological reality?

Although oxidative stress has been extensively studied the last fifteen years, many physicians and biologists are still sceptical concerning its interest in biology and medicine. This is probably due, in part, to the fact that this subject is a matter of biophysics, and the first studies reported were written using a physical language that inspired these people used to a more concrete problematic very little. Another problem is the difficulty to detect the species mediating oxidative stress, and to determine their role in biological processes. This review is aimed at presenting oxidative stress, as well as reactive oxygen species and free radicals--the molecules that mediate it--in a clear form able to convince all researchers involved in life sciences that these short-lived intermediates are indissociable from any aerobic organism. Moreover, if reactive oxygen species and free radicals are undoubtedly involved in many pathologies, they have physiological functions too.

Bone metabolism and oxidative stress in postmenopausal rats with iron overload

Osteoporosis is associated with many etiological causes such as nutrition, cytokines, hormones, and aging. Recently, reactive oxygen species (ROS) are considered to be responsible for the aging process and osteoporosis. We investigated the relationship between ROS and bone metabolism in young female and postmenopausal rats, by using dietary iron overload and several indices including bone metabolic markers, oxidative stress and antioxidant markers, and cytokines. Postmenopausal rats exhibited significant decreases in serum alkaline phosphatase activity and the level of osteocalcin as bone formation markers compared with young female rats; however, urinary excretion of deoxypyridinoline, a bone resorption marker, did not change. On the other hand, a 5% iron lactate diet for 4 weeks in postmenopausal rats led to significantly increased excretion of urinary deoxypyridinoline and 8-hydroxy-2'-deoxyguanosine (8-OHdG) but not serum alkaline phosphatase activity. Interestingly, the diet induced significant increases of serum osteopontin and TGF-beta1, augumenting osteoclast-mediated bone resorption through the RANK/RANKL pathway [J. Clin. Invest. 112 (2003) 181]. TGF-beta1 showed a negative correlation with serum glutathione peroxidase (GPx) activity (r = -0.674, P < 0.003), but a positive correlation with the serum iron level (r = 0.836, P < 0.0001). Taken together, these results suggest for the first time that oxidative stress could be involved in the pathogenesis of metabolic bone diseases such as osteoporosis as demonstrated by analysis of the relationship between bone metabolism and oxidative stress.