Biomedical subjects

Javier Pereda

Publications and source records attributed to Javier Pereda.

8 recordsLinked to original sources

PubMed2007

Mitochondrial function in liver disease.

Oxidative stress is involved in the pathogenesis and progression of different liver diseases, such as alcoholic liver disease and biliary cirrhosis. The increased mitochondrial production of O2(-) at complexes I and III, and consequently of H2O2 and other reactive oxygen species (ROS), triggered by NADH overproduction seems the major cause of mitochondrial and cellular oxidative stress and damage in chronic alcoholism. The mitochondrial oxidative stress renders hepatocytes susceptible to ethanol- or acetaldehyde-induced mitochondrial membrane permeability transition (MMPT) and apoptosis. Nitrosative stress contributes to cell death by peroxynitrite formation. The expression of the death receptor ligand CD95 is also up-regulated by acetaldehyde metabolism. Consequently, a dual mechanism, NADH-driven MMPT and CD95-mediated apoptosis, involving in both cases acetaldehyde metabolism and ROS production, operates in ethanol-induced apoptosis. In the biliary cirrhosis induced by chronic cholestasis, liver mitochondria show increased H2O2 production and GSH depletion and oxidation. Dysfunctional hepatocytes, with a loss in mitochondrial cardiolipin and decreased mitochondrial membrane potential evolve during cholestasis to apoptosis. Ursodeoxycholic acid prevents enlargement of this population as well as mitochondrial oxidative stress. Mitochondrial oxidative stress precedes the initiation and execution of hepatocyte apoptosis in chronic alcoholism and biliary cirrhosis. We suggest that overproduction of mitochondrial NADH is the primary cause for the development of alcoholic and non-alcoholic liver disease by a situation of chronic mitochondrial oxidative stress, which should be considered the second hit that renders hepatocytes susceptible to cell injury and apoptosis.

Animals↗

PubMed2006

Interaction between cytokines and oxidative stress in acute pancreatitis.

Acute pancreatitis is an inflammation initially localized in the pancreatic gland which may lead to local and systemic complications. The development of severe acute pancreatitis is mediated by pathophysiological mechanisms involved in the systemic inflammatory response, cytokines and oxidative stress being their components of major importance. Nevertheless, it is still unknown why an episode of acute pancreatitis remains mild or progresses to a severe form. Activated leukocytes are the main source of cytokines. Interleukin 1beta and tumor necrosis factor alpha (TNF-alpha) initiate and propagate almost all the consequences of the systemic inflammatory response syndrome, leading to amplification of the inflammatory response. It is noteworthy that the systemic inflammatory response is restrained and the rate of mortality decreased in acute pancreatitis when TNF-alpha is blocked with specific antibodies or in knock-out mice deficient in its receptors. A synergy between pro-inflammatory cytokines and oxidative stress occurs in the development of the inflammatory response in acute pancreatitis. Pro-inflammatory cytokines and oxidative stress trigger common signal transduction pathways that lead to amplification of the inflammatory cascade, mainly through activation of mitogen-activated protein kinases (MAPK) and nuclear factor kappaB (NF-kappaB). Furthermore, pro-inflammatory cytokines, particularly TNF-alpha, and oxidative stress promote each other generating a vicious circle in acute pancreatitis. This cross-talk that arises between pro-inflammatory cytokines and oxidative stress greatly contributes to amplification of the uncontrolled inflammatory cascade through MAPK and NF-kappaB.

Acute Disease↗

PubMed2005

Age-associated oxidative damage leads to absence of gamma-cystathionase in over 50% of rat lenses: relevance in cataractogenesis.

Oxidative damage to lens proteins and glutathione depletion play a major role in the development of senile cataract. We previously found that a deficiency in gamma-cystathionase activity may be responsible for glutathione depletion in old lenses. The aims of this study were: (1) to investigate the mechanism that causes the age-related deficiency in gamma-cystathionase activity in the eye lens, and (2) to determine the role of gamma-cystathionase deficiency in cataractogenesis. Two populations of old rats were found, one (56%) whose lenses lacked gamma-cystathionase activity and the rest that exhibited detectable enzyme activity. gamma-Cystathionase protein was absent in lenses from old rats without gamma-cystathionase activity. Oxidative stress targeted gamma-cystathionase in the eye lens upon aging, since the enzyme contained more carbonyl groups in old lenses than in young ones. gamma-Cystathionase mRNA was also markedly reduced in old lenses, thus contributing to the age-associated deficiency in gamma-cystathionase. Inhibition of gamma-cystathionase activity caused glutathione depletion in lenses and led to cataractogenesis in vitro. In conclusion, the lack of gamma-cystathionase activity in over 50% of old lenses is due to decreased gene expression and proteolytic degradation of the oxidized enzyme. This results in a high risk for the development of senile cataract.

Aging↗

PubMed2004

RNAPol-ChIP: a novel application of chromatin immunoprecipitation to the analysis of real-time gene transcription.

We describe a procedure, RNAPol-ChIP, to measure actual transcriptional rate. It consists of the detection, by chromatin immunoprecipitation (ChIP), of RNA polymerase II within the coding region of genes. To do this, the DNA immunoprecipitated with polymerase antibodies is analysed by PCR, using an amplicon well within the coding region of the desired genes to avoid interferences with polymerase paused at the promoter. To validate RNAPol-ChIP, we compare our results to those obtained by classical methods in several genes induced during either liver regeneration or acute pancreatitis. When short half-life mRNA genes are studied (e.g. c-fos and egr1), RNAPol-ChIP gives results similar to those of other procedures. However, in genes whose mRNA is more stable (e.g. the hemopexin, hpx, gene) RNAPol-ChIP informs on real-time transcription with results comparable to those of methods such as nuclear run-on or run-off, which require the isolation of highly purified nuclei. Moreover, RNAPol-ChIP advantageously compares with methods based on the analysis of steady-state mRNA (northern blot or RT-PCR). Additional advantages of RNAPol-ChIP, such as the possibility of combining it with classical ChIP analysis to study transcription-associated changes in chromatin are discussed.

Acute Disease↗

PubMed2004

Circulating TNF-alpha and its soluble receptors during experimental acute pancreatitis.

Clinical and experimental studies have shown increased concentrations of TNF-alpha and its soluble receptors in serum of patients with acute pancreatitis. In this work, we have investigated the time-course of TNF-alpha and its soluble receptors during taurocholate-induced acute pancreatitis. In addition, since TNF-alpha itself could mediate the shedding of its receptors, we have assessed the effect of inhibiting TNF-alpha production on the release of soluble TNF-alpha receptors in experimental acute pancreatitis. Our results indicate that soluble receptors are released in the early stages of the disease and this increase is concomitant with the release of TNF-alpha, which is mainly bound to specific proteins. The increased concentrations of its receptors strongly suggest that they could be these binding proteins. Inhibition of TNF-alpha generation with pentoxifylline abrogated the shedding of sTNF-alphaR1, but had no effect on sTNF-alphaR2. This finding suggests that the shedding of sTNF-alphaR1 is induced by TNF-alpha itself, but in the case of sTNF-alphaR2, the shedding appears to be induced by another mechanism.

Acute Disease↗

PubMed2004

Ursodeoxycholic acid protects against secondary biliary cirrhosis in rats by preventing mitochondrial oxidative stress.

Ursodeoxycholic acid (UDCA) improves clinical and biochemical indices in primary biliary cirrhosis and prolongs survival free of liver transplantation. Recently, it was suggested that the cytoprotective mechanisms of UDCA may be mediated by protection against oxidative stress, which is involved in the development of cirrhosis induced by chronic cholestasis. The aims of the current study were 1) to identify the mechanisms involved in glutathione depletion, oxidative stress, and mitochondrial impairment during biliary cirrhosis induced by chronic cholestasis in rats; and 2) to determine the mechanisms associated with the protective effects of UDCA against secondary biliary cirrhosis. The findings of the current study indicate that UDCA partially prevents hepatic and mitochondrial glutathione depletion and oxidation resulting from chronic cholestasis. Impairment of biliary excretion was accompanied by decreased steady-state hepatic levels of gamma-glutamyl cysteine synthetase and gamma-cystathionase messenger RNAs. UDCA treatment led to up-regulation of gamma-glutamyl cysteine synthetase in animals with secondary biliary cirrhosis and prevented the marked increases in mitochondrial peroxide production and hydroxynonenal-protein adduct production that are observed during chronic cholestasis. A population of damaged and primarily apoptotic hepatocytes characterized by dramatic decreases in mitochondrial cardiolipin levels and membrane potential as well as phosphatidylserine exposure evolves in secondary biliary cirrhosis. UDCA treatment prevents the growth of this population along with the decreases in mitochondrial cardiolipin levels and membrane potential that are induced by chronic cholestasis. In conclusion, UDCA treatment enhances the antioxidant defense mediated by glutathione; in doing so, this treatment prevents cardiolipin depletion and cell injury in animals with secondary biliary cirrhosis.

Animals↗

PubMed2004

Effect of simultaneous inhibition of TNF-alpha production and xanthine oxidase in experimental acute pancreatitis: the role of mitogen activated protein kinases.

OBJECTIVE: To assess the effects of inhibiting both tumor necrosis factor (TNF)-alpha production and xanthine oxidase activity on the inflammatory response, mitogen-activated protein kinase (MAPK) activation and mortality in necrotizing acute pancreatitis in rats. SUMMARY BACKGROUND DATA: Pancreatic injury triggers 2 major pathways involved in the systemic effects of severe acute pancreatitis: pro-inflammatory cytokines and oxidative stress. METHODS: Pancreatitis was induced by intraductal infusion of 3.5% sodium taurocholate. We examined whether treatment with oxypurinol, a specific inhibitor of xanthine oxidase, and/or pentoxifylline, an inhibitor of TNF-alpha production, affects pancreatic damage, ascites, lung inflammation, and MAPK phosphorylation. RESULTS: Oxypurinol prevented p38 phosphorylation in the pancreas and partially avoided the rise in lung myeloperoxidase activity. Pentoxifylline prevented erk 1/2 and JNK phosphorylation in the pancreas, and it partially reduced ascites and the rise in lung myeloperoxidase activity. Combined treatment with oxypurinol and pentoxifylline almost completely abolished ascites, MAPK phosphorylation in the pancreas, and the increase in lung myeloperoxidase activity. Histology revealed a reduction in pancreatic and lung damage. These changes were associated with a significant improvement of survival. CONCLUSIONS: : Simultaneous inhibition of TNF-alpha production and xanthine oxidase activity greatly reduced local and systemic inflammatory response in acute pancreatitis and decreased mortality rate. These effects were associated with blockade of the 3 major MAPKs.

Animals↗

PubMed2002

Ginkgo biloba extract EGb 761 protects against mitochondrial aging in the brain and in the liver.

According to the free radical theory of aging, oxygen-derived free radicals causes the age-associated impairment at the cellular and tissue levels. The mitochondrial theory of aging points to mitochondria, and specially mitochondrial DNA, as the major targets of free radical attack upon aging. Thus, oxidative damage to mtDNA accumulate with age in human and rodent tissues and also is inversely related to maximum life span of mammals. Mitochondrial deficits, such as a decrease in mitochondrial membrane potential, occur upon aging due to oxidative damage. The age-related mitochondrial oxidative stress may be prevented by late onset administration of certain antioxidants, such as Ginkgo biloba extract EGb 761. These antioxidants may also delay the physiological impairment associated with aging.

Aging↗