Oxidative damage and fibrogenesis

Study on free radicals and pancreatic fibrosis--pancreatic fibrosis induced by repeated injections of superoxide dismutase inhibitor

The exact mechanisms of the development of pancreatic fibrosis are still unknown. To clarify the relationship between pancreatic fibrosis and free radicals, the effect of the administration of a superoxide dismutase (SOD) inhibitor, diethyldithiocarbamate (DDC), on pancreatic fibrosis in rats was studied. A single intraperitoneal injection of 500 mg/kg of DDC significantly reduced SOD activity and significantly increased lipid peroxidation products in the pancreas, showing no histologic changes of inflammation or necrosis. Repeated administration of 500 mg/kg DDC, twice a week, caused inter- and intralobular fibrosis with atrophy of acinar cells in the pancreas for at least 2 weeks without fibrosis of the liver and kidney. Administration of allopurinol showed preventive effects against DDC-induced pancreatic fibrosis. In conclusion, repeated administration of DDC, which caused pancreatic fibrosis, is a new experimental model of pancreatic fibrosis from the viewpoint of oxidative stress.

Interaction between 4-hydroxy-2,3-alkenals and the platelet-derived growth factor-beta receptor. Reduced tyrosine phosphorylation and downstream signaling in hepatic stellate cells

Hepatic stellate cells (HSC) undergo activation toward myofibroblast-like cells during early stages of liver injury associated with fibrogenesis. Platelet-derived growth factor (PDGF), particularly its BB isoform, has been identified as the most potent mitogen for HSC. 4-Hydroxy-2,3-nonenal and related 4-hydroxy-2, 3-alkenals (HAKs) have been suggested to modulate the process of HSC activation. In this study we investigated the relationship between HAKs and PDGF receptor activation in human HSC. By employing noncytotoxic concentrations (10(-6) m) of HAKs, we observed a significant inhibition of PDGF-BB-dependent DNA synthesis. HAKs inhibited relevant pathways of PDGF-BB-dependent mitogenic signaling, including autophosphorylation of PDGF receptor (PDGF-R) beta subunits and activation of phosphatidylinositol 3-kinase and extracellular regulated kinases 1/2. Inhibition of DNA synthesis was reversible, and recovery of PDGF-mediated mitogenic signaling occurred within 24-48 h and was associated with HAKs-induced up-regulation of PDGF-R beta gene expression. 4-Hydroxy-2,3-nonenal, used as a model HAK, inhibited the intrinsic tyrosine kinase activity associated with the PDGF-R beta subunit, whereas binding of PDGF to its receptor was unaffected. This study identifies a novel regulatory mechanism of reactive aldehydes on PDGF receptor signaling and biologic actions, which may be relevant in several pathophysiological conditions, including liver fibrosis.

Hydrogen peroxide in the human body

Hydrogen peroxide (H(2)O(2)) is widely regarded as a cytotoxic agent whose levels must be minimized by the action of antioxidant defence enzymes. In fact, H(2)O(2) is poorly reactive in the absence of transition metal ions. Exposure of certain human tissues to H(2)O(2) may be greater than is commonly supposed: substantial amounts of H(2)O(2) can be present in beverages commonly drunk (especially instant coffee), in freshly voided human urine, and in exhaled air. Levels of H(2)O(2) in the human body may be controlled not only by catabolism but also by excretion, and H(2)O(2) could play a role in the regulation of renal function and as an antibacterial agent in the urine. Urinary H(2)O(2) levels are influenced by diet, but under certain conditions might be a valuable biomarker of 'oxidative stress'.

Hypoxia promotes fibrogenesis in human renal fibroblasts

BACKGROUND

The mechanisms underlying progressive renal fibrosis are unknown, but the common association of fibrosis and microvascular loss suggests that hypoxia per se may be a fibrogenic stimulus.

METHODS

To determine whether human renal fibroblasts (HRFs), the primary matrix-producing cells in the tubulointerstitium, possess oxygen-sensitive responses relevant to fibrogenesis, cells were exposed to 1% O2 in vitro.

RESULTS

Hypoxia simultaneously stimulated extracellular matrix synthesis and suppressed turnover with increased production of collagen alpha1(I) (Coll-I), decreased expression of collagenase, and increased tissue inhibitor of metalloproteinase (TIMP)-1. These effects are time dependent, require new RNA and protein synthesis, and are specific to hypoxia. The changes in Coll-I and TIMP-1 gene expression involve a heme-protein O2 sensor and protein kinase- and tyrosine kinase-mediated signaling. Although hypoxia induced transforming growth factor-beta1 (TGF-beta1), neutralizing anti-TGF-beta1-antibody did not block hypoxia-induced Coll-I and TIMP-1 mRNA expression. Furthermore, hypoxic-cell conditioned-medium had no effect on the expression of these mRNAs in naive fibroblasts, suggesting direct effects on gene transcription. Transient transfections identified a hypoxia response element (HRE) in the TIMP-1 promoter and demonstrated HIF-1-dependent promoter activation by decreased ambient pO2.

CONCLUSIONS

These data suggest that hypoxia co-ordinately up-regulates matrix production and decreases turnover in renal fibroblasts. The results support a role for hypoxia in the pathogenesis of fibrosis and provide evidence for novel, direct hypoxic effects on the expression of genes involved in fibrogenesis.

Enhanced hepatic lipid peroxidation in patients with primary biliary cirrhosis

OBJECTIVE

The mechanisms responsible for hepatic injury have not been fully clarified in primary biliary cirrhosis (PBC). It has recently been suggested that hepatic lipid peroxidation may be involved in the pathogenesis of PBC. The aims of the current study were to determine whether patients with PBC have evidence of enhanced hepatic lipid peroxidation and to evaluate its relationship to clinicopathological features.

METHODS

Immunohistochemical detection of 4-hydroxynonenal (HNE) protein adducts was performed in the liver biopsies of 20 patients with PBC. Histological stages of PBC were evaluated. Orcein or Victoria blue staining was performed for detection of copper-associated proteins. The size of bile ducts was defined as the smallest diameter between the subepithelial basement membranes.

RESULTS

All 20 patients had immunodetectable HNE protein adducts in the cytoplasm of damaged, but also intact, biliary cells. The mean diameter of bile ducts with HNE protein adducts was smaller than those without the adducts (61.0 +/- 1.9 vs 122.5 +/- 24.4 microm, respectively, p < 0.01). Out of 20 patients, 6 (30%) also had immunodetectable HNE protein adducts in hepatocytes preferentially located around the portal tracts. Most of the patients with hepatocytic HNE protein adducts had copper-associated protein granules in hepatocytes around the portal tracts and were classified as histological stage 3, whereas all of the patients without the adducts lacked copper-associated protein granules and were classified as histological stage 1 or 2. The patients with hepatocytic HNE protein adducts had higher levels of serum total bilirubin than did those without the adducts (2.9 +/- 0.9 vs 0.7 +/- 0.1 mg/dl, respectively, p < 0.01).

CONCLUSIONS

Hepatic lipid peroxidation can occur in PBC and may be an early event in bile duct destruction. At advanced stages of PBC, hepatocellular lipid peroxidation may play a role in hepatocyte injury during cholestasis.

The flavonoid quercetin ameliorates liver damage in rats with biliary obstruction

BACKGROUND/AIMS

Our aim was to investigate whether the antioxidant quercetin might protect against liver injury in chronically biliary obstructed rats.

METHODS

Secondary biliary cirrhosis was induced by 28 days of bile duct obstruction. Animals received quercetin at 75, 150 and 300 micromol x kg body wt(-1) x day(-1) i.p. through the experimental period or at 150 micromol x kg body wt(-1) x day(-1) i.p. for the last 2 weeks.

RESULTS

Bile duct obstruction resulted in a decrease in the activities of antioxidant enzymes. Liver oxidised/reduced (GSSG/GSH) glutathione ratio, hepatic and mitochondrial thiobarbituric acid reactive substances (TBARS) and collagen content were significantly increased and a marked fibrosis and bile ductular proliferation was observed. Quercetin corrected the reduction in glutathione concentration and partially prevented the increase in collagen concentration, TBARS and GSSG/GSH ratio. Treatment resulted in a significant preservation of the activities of antioxidant enzymes, a less pronounced fibrosis and a marked inhibition of bile ductular proliferation. Maximal effects were reached with the intermediate quercetin dose given for 2 or 4 weeks.

CONCLUSIONS

Quercetin reduces liver oxidative damage, ductular proliferation and fibrosis in biliary-obstructed rats. These effects suggest that it might be a useful agent to preserve liver function in patients with biliary obstruction.

Characterization of 4-hydroxy-2-nonenal metabolism in stellate cell lines derived from normal and cirrhotic rat liver

During oxidative stress, reactive aldehydes, including trans-4-hydroxy-2-nonenal (4-HNE), are generated by peroxidation of membrane lipids and purportedly stimulate hepatic stellate cells to produce excessive extracellular matrix, including type I collagen. An important question concerning the ability of 4-HNE to modulate collagen production by stellate cells is the potential of these specialized cells to detoxify 4-HNE. The objective of the present study was to characterize the ability of stellate cell lines, derived from normal (NFSC) and cirrhotic (CFSC) rat livers, to metabolize 4-HNE by oxidative, reductive and conjugative pathways. These two stellate cell lines were noted to have differing susceptibilities to the cytotoxic effect of 4-HNE. Treatment of both stellate cell lines with a range of 4-HNE doses demonstrated that the concentration which was cytotoxic to 50% of CFSC (TD(50)) was 25% greater than that for NFSC (967.57+/-9.26 nmol/10(6) cells vs. 769.90+/-5.32 nmol/10(6) cells respectively). The capacity of these cell lines to metabolizes 4-HNE was determined by incubating them in suspension with 50 microM 4-HNE (10 nmol/10(6) cell); 4-HNE elimination and metabolite formation were quantified over a 20 min time course. Both stellate cell lines rapidly metabolized 4-HNE, with the CFSC line eliminating 4-HNE at a rate that was approx. 2-fold greater than the NFSC line. The rate of 4-HNE metabolism attributable to glutathione S-transferase (GST) was similar in both cell lines, though differential cell specific expressions of GST isoforms GSTP1-1 and GSTA4-4 were observed. The greater rate of 4-HNE elimination by CFSC was attributable to its aldehyde dehydrogenase (ALDH) activity which accounted for approx. 50% of 4-HNE metabolism in CFSC but was insignificant in NFSC. Neither cell line had detectable alcohol dehydrogenase activity or protein levels. Measurement of cellular GSH concentrations revealed that NFSC contain approx. 2-fold greater concentrations of GSH when compared to CFSC and that following 4-HNE treatment, GSH levels were rapidly depleted from both cell lines. Concomitant with 4-HNE mediated GSH depletion, a corresponding increase in the 4-HNE-glutathione adduct formation was observed with the NFSC line forming greater amounts of the glutathione adduct than did the CFSC line. Taken together, these data demonstrate that both stellate cell lines have the capacity to metabolize 4-HNE but that CFSC have a greater rate of metabolism which is attributable to their greater ALDH activity, suggesting that the stellate cells isolated from cirrhotic liver may be differentially responsive to the biologic effects of 4-HNE.

[Radiation-induced superficial fibrosis and TGF-alpha 1]

Radiation-induced fibrosis is a late sequela of both therapeutic and accidental irradiations, which has been described in various tissues, including the lung, liver, kidney and skin. This review presents different aspects of superficial radiation-induced fibrosis, such as clinical observations, histological changes, cellular and molecular regulations, and medical management. Recent evidence on the critical role played by TGF-beta 1 in the initiation, development and persistence of fibrosis are discussed, as well as the possibility that this cytokine may constitute a specific target for antifibrotic agents.

Radiomodfication of xanthine oxidoreductase system in the liver of mice by phenylmethylsulfonyl fluoride and dithiothreitol

The widely distributed xanthine oxidoreductase (XOR) system has been shown to be modulated upon exposure of animals to ionizing radiation through the conversion of xanthine dehydrogenase (XDH) into xanthine oxidase (XO). In the present work, radiomodification of the XOR system by phenylmethylsulfonyl fluoride (PMSF) and dithiothreitol (DTT) was examined using female Swiss albino mice which were irradiated with gamma rays at a dose rate 0.023 Gy s(-1). PMSF, a serine protease inhibitor, and DTT, the sulfhydryl reagent, were administered intraperitoneally prior to irradiation. The specific activities of XDH and XO as well as the XDH/XO ratio and the total activity (XDH+XO) were determined in the liver of the mice. The inhibition of XO activity, restoration of XDH activity, and increase in the XDH/XO ratio upon administration of PMSF were suggestive of irreversible conversion of XDH into XO mediated through serine proteases. The biochemical events required for the conversion were probably initiated during the early phase of irradiation, as the treatment with PMSF immediately after irradiation did not have a modulatory effect. Interestingly, DTT was not effective in modulating radiation-induced changes in the XOR system or oxidative damage in the liver of mice. The DTT treatment resulted in inhibition of the release of lactate dehydrogenase. However, the protection appears to be unrelated to the formation of TBARS. On the other hand, the presence of PMSF during irradiation inhibited radiation-induced oxidative damage and radiation-induced increases in the specific activity of lactate dehydrogenase. These findings suggest that a major effect of ionizing radiation is irreversible conversion of xanthine to xanthine oxidase.

Reactive oxygen and mechanisms of inflammatory liver injury

Reactive oxygen species (ROS) are important cytotoxic and signalling mediators in the pathophysiology of inflammatory liver diseases. They can be generated by resident and infiltrating phagocytes and/or intracellularly in every liver cell type after stimulation with cytokines. Although ROS are able to cause cell destruction by massive lipid peroxidation, in most cases, ROS are more likely to modulate signal transduction pathways by affecting redox-sensitive enzymes, organelles (e.g. mitochondria) and transcription factors. Thus, ROS can directly induce and/or regulate apoptotic and necrotic cell death. In addition, ROS can have indirect effects on the pathophysiology by supporting protease activity through inactivation of antiproteases and by modulating the formation of inflammatory mediators and adhesion molecules. Many of the effects of ROS may occur simultaneously or sequentially in the pathophysiology. Although mainly described in this review as detrimental, ROS are essential for host-defence functions of phagocytes and can modulate the formation of mediators involved in regulating sinusoidal blood flow and liver regeneration. Thus, continuous efforts are necessary to improve our understanding of the role of ROS in the pathophysiology of inflammatory liver diseases and to discover therapeutic interventions that selectively target the negative effects of reactive oxygen formation.

Evidence linking chondrocyte lipid peroxidation to cartilage matrix protein degradation. Possible role in cartilage aging and the pathogenesis of osteoarthritis

Reactive oxygen species (ROS) are implicated in both cartilage aging and the pathogenesis of osteoarthritis. We developed an in vitro model to study the role of chondrocyte-derived ROS in cartilage matrix protein degradation. Matrix proteins in cultured primary articular chondrocytes were labeled with [(3)H]proline, and the washed cell matrix was returned to a serum-free balanced salt solution. Exposure to hydrogen peroxide resulted in oxidative damage to the cell matrix as established by monitoring the release of labeled material into the medium. Calcium ionophore treatment of chondrocytes, in a dose-dependent manner, significantly enhanced the release of labeled matrix, suggesting a chondrocyte-dependent mechanism of matrix degradation. Antioxidant enzymes such as catalase or superoxide dismutase did not influence matrix release by the calcium ionophore-activated chondrocytes. However, vitamin E, at physiological concentrations, significantly diminished the release of labeled matrix by activated chondrocytes. The fact that vitamin E is a chain-breaking antioxidant indicates that the mechanism of matrix degradation and release is mediated by the lipid peroxidation process. Lipid peroxidation was measured in chondrocytes loaded with cis-parinaric acid. Both resting and activated cells showed constitutive and enhanced levels of lipid peroxidation activity, which were significantly reduced in the presence of vitamin E. In an immunoblot analysis, malondialdehyde and hydroxynonenal adducts were observed in chondrocyte-matrix extracts, and the amount of adducts increased with calcium ionophore treatment. Furthermore, vitamin E diminished aldehyde-protein adduct formation in activated extracts, which suggests that vitamin E has an antioxidant role in preventing protein oxidation. This study provides in vitro evidence linking chondrocyte lipid peroxidation to cartilage matrix protein (collagen) oxidation and degradation and suggests that vitamin E has a preventive role. These observations indicate that chondrocyte lipid peroxidation may have a role in the pathogenesis of cartilage aging and osteoarthritis.

Pathogenesis of liver fibrosis: role of oxidative stress

In the liver, the progressive accumulation of connective tissue, a complex and dynamic process termed fibrosis, represents a very frequent event following a repeated or chronic insult of sufficient intensity to trigger a "wound healing"-like reaction. The fibrotic process recognises the involvement of various cells and different factors in bringing about an excessive fibrogenesis with disruption of intercellular contacts and interactions and of extracellular matrix composition. However, Kupffer cells, together with recruited mononuclear cells, and hepatic stellate cells are by far the key-players in liver fibrosis. Their cross-talk is triggered and favoured by a series of chemical mediators, with a prominent role played by the transforming growth factor beta. Both expression and synthesis of this inflammatory and pro-fibrogenic cytokine are mainly modulated through redox-sensitive reactions. Further, involvement of reactive oxygen species and lipid peroxidation products can be clearly demonstrated in other fundamental events of hepatic fibrogenesis, like activation and effects of stellate cells, expression of metalloproteinases and of their specific inhibitors. The important outcome of such findings as regards the pathogenesis of liver fibrosis derives from the observation of a consistent and marked oxidative stress condition in many if not all chronic disease processes affecting hepatic tissue. Hence, reactive oxidant species likely contribute to both onset and progression of fibrosis as induced by alcohol, viruses, iron or copper overload, cholestasis, hepatic blood congestion.

TGF-beta1 and radiation fibrosis: a master switch and a specific therapeutic target?

Radiation fibrosis is a frequent sequel of therapeutic or accidental radiation overexposure in normal human tissues. One of the main fundamental problems yet unsolved in fibrotic tissues is the origin of the chronic activation of myofibroblasts within these tissues. It has been postulated that this chronic activation results from a continuous production of activating factors. In this context, fibrosis could be defined as a wound where continuous signals for tissue repair are emitted. Cytokines and growth factors probably play a central role in this process. Among them, transforming growth factor-beta1 (TGF-beta1) is considered as a master switch for the fibrotic program. This review discusses recent evidence on the critical role played by TGF-beta in the initiation, development, and persistence of radiation fibrosis. It summarizes the results concerning this factor after irradiation of various tissues and cells, with an emphasis on superficial fibrosis, including skin and subcutaneous tissues. Finally, recent data concerning the treatment of established fibrotic disorders of various etiology are presented, as well as the possible mechanisms involved in fibrosis regression, which show that the TGF-beta pathway may constitute a specific target for antifibrotic agents.

Lipid oxidation products in cell signaling

The recent research on the impact that oxidative changes of biolipids could have in pathophysiology serves to explain how free radical-driven reactions not only are considered as mere toxicologic events, but also modulators of cell activity and function. Oxidatively modified low-density lipoproteins are known to affect various cellular processes by modulating various molecular pathways and signaling nuclear transcription. Among the lipid oxidation products detectable in ox-LDLs, and also in the atherosclerotic plaques, 4-hydroxynonenal has been widely investigated. This aldehyde was shown to upregulate AP-1 transcription factor, signaling through the MAP kinase pathway, with eventual nuclear localization and induction of a series of genes. Further, oxidation products of cholesterol and cholesterol esters, in ox-LDL are of similar interest, especially in relation to the pathogenesis of fibrosclerotic lesions of the arterial wall.

Hemodynamic changes during aging associated with cerebral blood flow and impaired cognitive function

This study investigates the age associated changes in hemorheological properties and cerebral blood flow. Partial correlations indicate that part of the age-dependent decrease in flow velocities can be attributed to a hemorheological decrement resulting in part from enhanced oxidative stress in the aged. A possible link with Alzheimer's pathology is suggested by the augmented hemorheological impairment resulting from in vitro incubation of red cells with amyloids. These results suggest that in aging, oxidative stress as well as amyloids may influence the fluid properties of blood, resulting in a potential decrement in blood flow and oxygen delivery to the brain. Animal intervention studies further demonstrate that altered hemorheological properties of blood can actually influence cognitive function. The relationships shown to exist between hemorheology, blood flow, amyloids, oxidative stress, and cognitive function suggest that these factors may be one of the mechanisms operating in the complex etiology of Alzheimer's disease.

Inhibitory effects of angiotensin-converting enzyme (ACE) inhibitors on oxygen radicals produced by bronchoalveolar lavage cells in young and aged guinea pigs

We examined the effect of angiotensin-converting enzyme (ACE) inhibitors and age on oxygen radical formation by bronchoalveolar lavage (BAL) cells. Lung-free cells, including pulmonary alveolar macrophages, were harvested from young (4-month-old) and aged (28-month-old) male guinea pigs using BAL. The oxygen radicals produced by BAL cells were measured by a lucigenin-dependent chemiluminescence method using a photon counter. Although spontaneous oxygen radical production by BAL cells from young and aged guinea pigs did not differ, the oxygen radical generation after maximal stimulation with phorbol-myristate acetate (PMA) was greater than that produced without PMA stimulation in both young and aged animals. ACE inhibitors with and without an SH-group (alacepril and lisinopril, respectively) were tested for their effect on oxygen radical formation by BAL cells; both ACE inhibitors inhibited oxygen radical production and generation by BAL cells from both young and aged guinea pigs in a dose-dependent manner. However, the alacepril concentration giving 50% inhibition (IC50) of oxygen radical generation by BAL cells was smaller than the IC50 of lisinopril in both young and aged guinea pigs. These results indicate that ACE inhibitors, in particular those with an SH-group, effectively reduce oxygen radical production by BAL cells from young and aged guinea pigs, and suggest that treatment with ACE inhibitors may be useful for ameliorating oxidant-associated pulmonary disorders in young and aged patients.

Hyaluronate levels and markers of oxidative stress in the serum of Sudanese subjects at risk of infection with Schistosoma mansoni

We showed previously that infection by Schistosoma mansoni not only triggers the production of reactive oxygen species in mouse liver but also leads to the alteration of antioxidant defences. To determine whether such events occur in humans, we measured the serum markers of oxidative stress, i.e., lipid peroxides and protein carbonyl, as well as hyaluronate levels in subjects in the Managil area of the Sudan. Grades of fibrosis were determined by ultrasonographic examination. Two groups were used as controls, one Sudanese and the other European. We found that Sudanese subjects in the endemic area differed from the control groups, both Sudanese and European, insofar as they had higher levels of the serum metabolites measured. The latter increased with the grade of fibrosis. Moreover, protein carbonyl and hyaluronic acid levels correlated positively with lipid peroxide levels. These findings indicate that oxidative stress might contribute to S. mansoni-associated pathology in man. The serum markers considered in our study, obtained by relatively simple techniques, may provide a useful biochemical index for the identification of almost asymptomatic patients who, however, are at risk of developing severe schistosomiasis.

Pirfenidone inhibits NADPH-dependent microsomal lipid peroxidation and scavenges hydroxyl radicals

Pirfenidone (Pf), a new broad-spectrum anti-fibrotic agent, is known to offer protection against lung fibrosis in vivo in laboratory animals, and against mitogenesis and collagen formation by human lung fibroblasts in vitro. Because reactive oxygen species are thought to be involved in these events, we investigated the mechanism(s) by which Pf ameliorates oxidative stress and its effects on NADPH-dependent lipid peroxidation. Pf has been shown to cause inhibit NADPH-dependent lipid peroxidation in sheep liver microsomes in a dose-dependent manner. The concentration of Pf required to cause 50% inhibition of lipid peroxidation was approximately 6 mM. Pf was found to be ineffective as a superoxide radical scavenger. Pf was also ineffective in decomposing H2O2 and chelating iron. In deoxyribose degradation assays, Pf was a potent scavenger of hydroxyl radicals with a rate constant of 5.4 x 10(9) M(-1) sec(-1). EPR spectroscopy in combination with spin trapping techniques, using a Fenton type reaction and DMPO as a spin-trapping agent, Pf scavenged hydroxyl radicals in a dose-dependent manner. The concentration of Pf required to inhibit 50% signal height was approximately 2.5 mM. Because iron was used in the Fenton reaction, the ability of Pf in chelating iron was verified in a fluorescent competitive assay using calcein as the fluorescent probe. Pf up to 10 mM concentration was ineffective in chelating either Fe2+ or Fe3+ in this system. We propose that Pf exerts its beneficial effects, at least in part, through its ability to scavenge toxic hydroxyl radicals.

Targeting of superoxide dismutase to the liver results in anti-inflammatory effects in rats with fibrotic livers

BACKGROUND/AIMS

The rapid clearance from plasma and the limited uptake of superoxide dismutase (SOD) in the liver hampers the effectiveness of this enzyme in liver diseases. We therefore compared the pharmacokinetics and in vivo efficacy of SOD with two modified forms of this protein: SOD coupled to the copolymer DIVEMA and mannosylated-SOD.

METHODS

Reactive oxygen scavenging activity of SOD conjugates was tested in livers of bile duct ligated rats. Intrahepatic production of reactive oxygen species (ROS) and neutrophil infiltration were studied immunohistochemically and related to the organ and cellular distribution of radiolabeled SOD conjugates.

RESULTS

Native SOD was rapidly cleared from the circulation and accumulated in renal tubuli. The enzyme had no effect on the intrahepatic ROS production. Covalent attachment of SOD to DIVEMA yielded a polyanionic conjugate with a prolonged elimination half-life compared to native SOD. In contrast to native SOD, DIVEMA-SOD was taken up by the liver via scavenger receptors. Mannosylation of SOD (Man-SOD) resulted in a conjugate that was rapidly cleared from the blood. This Man-SOD was taken up by non-parenchymal liver cells. The pharmacokinetics of SOD and its derivatives were similar in normal and bile duct ligated rats. Efficacy studies with Man-SOD revealed only a slight decrease in intrahepatic ROS production. However, DIVEMA-SOD exhibited a potent inhibitory effect on ROS production in the liver. Nearly complete ROS-scavenging activity was observed in the portal areas.

CONCLUSIONS

Considering the prolonged half-life, the increased delivery of SOD to the target cells, and the concomitant increased effectiveness, application of DIVEMA-SOD seems a promising new approach to attenuate intrahepatic inflammatory processes.

Visualization of oxygen radical production in mouse liver in response to infection with Schistosoma mansoni

BACKGROUND/AIMS

The tropical parasite S. mansoni induces granulomatous inflammation in the liver, following the lodging of eggs in this organ. In vitro studies suggested that the host's response might involve the production of oxygen radicals.

METHODS

In an attempt to investigate the situation at the site of inflammation, under disease conditions, livers of infected mice were treated with dichlorodihydrofluorescein diacetate which fluoresces after oxidation.

RESULTS

Fluorescence of the oxidized tracer revealed that oxygen radicals were produced by granulomatous inflammatory cells. The phenomenon reached its highest intensity close to the eggs. The membranes of the cells were strongly labelled, probably reflecting membrane-associated NADPH oxidase activity. The cytoplasm of hepatocytes was also fluorescent but with lower intensity; hepatocyte membranes or nuclei were not labelled. Fluorescence was reduced drastically by treatment with catalase and antioxidants, indicating the occurrence of H2O2. Treatment with superoxide dismutase had no effect. Neither the livers of uninfected animals nor those of infected animals before parasite egg deposition were labelled. Eosinophil peroxidase activity was released in the areas of inflammatory cells, but was not found in hepatocytes.

CONCLUSIONS

The H2O2/peroxidase system, which is the cornerstone of the antimicrobial defense associated with inflammation, is activated in close contact with parasite eggs. The process does contribute to egg killing in vivo. Moreover, hepatocytes undergo oxidative stress in the entire organ. This finding is in agreement with the parasite-induced decrease of liver antioxidant defenses demonstrated previously.

Antioxidants in the prevention of renal disease

In view of the role of oxidative processes in inflicting damage that leads to glomerulosclerosis and renal medullary interstitial fibrosis, more attention could be paid to the use of antioxidant food constituents and the usage of drugs with recognized antioxidant potential. In any case atherosclerosis is an important component of chronic renal diseases. There is a wide choice of foods and drugs that could confer benefit. Supplementation with vitamins E and C, use of soy protein diets and drinking green tea could be sufficient to confer remarkable improvements.

Hepatic oxidative stress following prolonged sublethal microcystin LR exposure

Microcystin LR (MCLR) is a naturally occurring protein phosphatase inhibitor and potent hepatotoxin produced by strains of Microcystis aeruginosa. Although its acute toxicity has been well characterized, little is known about its chronic effects. In this study, we sought to acquire evidence that oxidative stress may play a role in the pathogenesis of prolonged sublethal MCLR toxicity. Twelve rats (3 per group) weighing on average 185 g were exposed to 1 of 3 different concentrations of MCLR (16, 32, and 48 microg/kg/day) or to saline via intraperitoneal osmotic pumps for 28 days. Histologic evidence of dose-dependent hepatic inflammation was seen, including infiltration of centrilobular regions by lymphocytes, macrophages, and neutrophils, centrilobular fibrosis, apoptosis, and steatosis. Analysis of lipid peroxidation products revealed a dose-dependent increase in malondialdehyde concentrations with an approximate 4-fold increase in the livers of the high-dose rats over those of the saline-treated controls. Livers from MCLR-exposed rats were more sensitive than those of controls to the cytotoxic effects of the organic oxidizing agent tert-butyl hydroperoxide, based on an MTT (3-[dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) viability assay. These histopathologic and biochemical findings indicate that oxidative stress may play a significant role in the pathogenesis of chronic MCLR toxicosis.

Interferon/antioxidant combination therapy for chronic hepatitis C--a controlled pilot trial

The effects of two forms of antioxidative co-therapy were analyzed in 24 interferon-alpha (IFN)-naive patients with chronic hepatitis C who were randomized to either receive IFN monotherapy (3 x 4.5 million units IFN-alpha 2a per week), (group A), or IFN and N-acetylcysteine (N-acetylcysteine (NAC) 1.800 mg/day) plus sodium selenite (400 microg/day) supplementation (group B), or treatment as in group B plus vitamin E (544 IU/day) (group C), over 24 weeks. Changes in histology, normalization of ALT, reduction of viral RNA, serum levels of glutathione, selenium, vitamin E, erythrocyte glutathione peroxidase, trolox equivalent antioxidative capacity (TEAC), thiobarbituric acid reactive substances (TBARS) and protein carbonyl groups were measured. Low baseline TEAC and elevated TBARS indicated increased oxidative stress before therapy, which was not affected by antioxidant supplementation. At the end of treatment complete responses were found in 3/8, 2/8 and 6/8 patients in groups A, B and C, respectively, but liver histology had not significantly improved. Vitamin E treated patients had a 2.4 greater chance (95% CI: 1.05-5.5) of obtaining a complete response and had significantly greater reduction in viral load (P = 0.028) than patients without vitamin E. Relapses, i.e. re-appearance of detectable hepatitis C virus (HCV) RNA and/or re-elevation of ALT-activity occurred in 7 out of the 11 responders within 6 months after termination of therapy (group A: 2/3, group B: 1/2 and group C: 4/6). Thus, no overall beneficial effect of antioxidant/IFN therapy was detected. However, the apparent trend towards a more favorable outcome with vitamin E supplementation warrants to further study this substance as an adjuvant to IFN therapy in chronic hepatitis C.

Hepatic production of apolar aldehydes in rats with carbon tetrachloride-induced cirrhosis

The aim of this study was to identify apolar aldehydes in liver homogenates from rats with CCl4-induced cirrhosis and, as a corollary, the antioxidant effect of zinc administration. The study was performed in five control rats and in ten cirrhotic rats which were further sub-divided into two groups to receive either a standard diet or one supplemented with zinc. The percentage of hepatic fibrosis, plasma malondialdehyde concentration and alanine aminotransferase activity were measured as well as the following aldehydes: hexanal, octanal, decanal, 2-hexenal, 2-octenal, 2-nonenal, 2,4-heptadienal and 2,4-decadienal. Of the 10 cirrhotic rats, 4 had elevated concentrations of the highly toxic 2,4-dialkenals which coincided with a higher percentage of fibrosis and plasma alanine aminotransferase activity. These aldehydes were not observed in the control group. Zinc administration was associated with a reduction of the hepatic malondialdehyde concentration and an amelioration on the degree of hepatic injury. In conclusion, this study demonstrates the presence of the highly toxic 2,4-dialkenals in hepatic tissue of rats whith CCl4-induced cirrhosis. Results obtained would suggest that these particular aldehydes may be related to the severity of the hepatic injury.

Chemical reactivity of the carbon-centered free radicals and ferrous iron in coals: role of bioavailable Fe2+ in coal workers pneumoconiosis

Striking differences in the prevalence of coal workers' pneumoconiosis (CWP) exist between different coal mine regions. The major factors responsible for the observed regional differences in CWP have not yet been identified. In the present study, chemical reactivity of the carbon-centered free radicals in coals and lung tissues, as well as ferrous iron in the coals, were studied by ESR techniques. The ESR spectra clearly demonstrated the presence of at least two types of carbon-centered free radical species, which might respectively attribute to the macromolecular phase and the molecular phase of coal. Grinding produced free radicals in coals. Exposure of freshly ground coal to air for 28 h induced a slight increase of free radicals for most of the coals, and a slight decrease after 4 months' exposure. The lung tissue samples of coal workers deceased of CWP showed similar ESR spectra as coal samples, and these radicals were highly stable in the lung. After incubation of coals with glutathione, hydrogen peroxide, sodium formate or oxygen, the coal sample from the Gardanne mine which has never induced CWP, and thus is the least hazardous coal, showed the most significant change in the carbon-centered free radical concentration. No significant changes were observed among other coals reported to induce CWP. On the other hand, we found that the coals released different amounts of Fe2+ in an acidic medium. Interestingly, the prevalence of CWP correlates positively with the released Fe2+ content in these coals and with the amount of oxygen radicals produced by the interaction of Fe2+ with O2 in the acidified coal filtrates. Our studies indicate that the carbon-centered free radicals may not be biologically relevant to coal dust-induced pneumoconiosis, whereas the acid soluble Fe2+, which may be dissolved in the phagolysosomes of macrophages, can then lead to Fe2+-induced oxidative stress and eventual CWP development.

Increased serum concentrations of conjugated diens and malondialdehyde in patients with pulmonary tuberculosis

During pulmonary inflammation increased amounts of reactive oxygen species (ROS) and reactive nitrogen intermediates (RNI) are produced as a consequence of phagocyte respiratory burst. One of the manifestation of these free radical-mediated processes is lipid peroxidation (LP). The aim of our study was to assess the concentration of lipid peroxidation products (LPPs), conjugated diens (CD) and malondialdehyde (MDA), in patients with active TB. Forty-two patients were enrolled into the study. Half (group I) had advanced TB and were sputum smear-positive. The remainder (group II) had only small radiographical changes and were sputum smear-negative. Serum concentrations of CD and MDA were measured at days 0, 7, 14 and 28 in group I and day 0 in group II. We found that in all patients with active TB CCD (1.0 +/- 0.05A233) and CMDA (2.01 +/- 0.16 nmol dl-1) were significantly elevated compared to healthy controls (0.67 +/- 0.03A233 and 1.36 +/- 0.08 nmol dl-1, respectively) (P < 0.001). The highest levels of LPPs were in patients with advanced TB. These concentrations were stable during the first month of anti-tuberculous therapy. Our data indicated that, as in bacterial pneumonia, LPPs were enhanced in active TB. The levels of LPPs depended on the form of the disease as they were higher in subjects with advanced disease than in those with only small radiographical changes. Further studies are needed to assess the role of antioxidants as adjuvant therapy in patients with pulmonary TB.

Development of eosinophil peroxidase activity and concomitant alteration of the antioxidant defenses in the liver of mice infected with Schistosoma mansoni

BACKGROUND/AIMS

The tropical parasite Schistosoma mansoni causes granulomatous inflammation following lodging of eggs in portal capillaries. In vitro studies indicated that the host reaction should involve reactive oxygen intermediates; however, it is not known what occurs in vivo at the site of the disease. Moreover, the ultimate pathophysiological effects of oxidative processes depend upon antioxidant factors, which are investigated in this study.

METHODS

We explored the changes in the major enzyme activities involved in liver redox metabolism during the course of infection and, for some of them, the mRNA expression. We also measured the reduced glutathione and lipid peroxide levels in the liver.

RESULTS

We found that the deposition of parasite eggs triggers the release of endogenous eosinophil peroxidase; enzyme activity developed in the immediate vicinity of the eggs and it increased dramatically with time. However, Cu,Zn-superoxide dismutase, catalase and glutathione peroxidase activities decreased drastically. In contrast, glutathione transferase was unaffected. There was no proportional decrease in mRNA levels for the H2O2 scavenging enzymes. Reduced glutathione concentrations also dropped as a result of infection. Lastly, a two-fold increase in the levels of hepatic products generated by lipid peroxidation was observed.

CONCLUSIONS

These results show that on the one hand oxidative processes occurred at the site of granulomatous inflammation and on the other hand the antioxidant capacity of the liver decreased, leading to the generation of lipid peroxides. The resulting imbalance between pro- and anti-oxidant processes may play a central role in the pathology associated with schistosomiasis.

Modulatory proteins and processes in alliance with immune cells, mediators, and extracellular proteins in renal interstitial fibrosis

A synopsis of the many aspects and factors that contribute to renal tubulo-interstitial fibrosis is presented. The role of fibrogenic cytokines and the conversion of fibroblasts to myofibroblasts are described. It is emphasized that oxygen radicals cause fibroblasts to generate collagen. The properties of those accessory modulatory proteins that affect the behavior of cells in the interstitium are considered and how matrix for ensuing fibrosis is laid down. Understanding the extracellular matrix proteins and these modulatory proteins is important because their behavior can now be modified by means of antisense oligonucleotides.

Depending on their concentration oxidized low density lipoproteins stimulate extracellular matrix synthesis or induce apoptosis in human coronary artery smooth muscle cells

Various lines of evidence indicate that oxidative stress resulting in lipid peroxidation and protein modification is involved in the pathogenesis of atherosclerosis and coronary heart disease. We have investigated the effect of modified (oxidized) low-density lipoproteins (oxLDL) on collagen and fibronectin synthesis in cultured human coronary artery smooth muscle cells (HCA-SMC). As shown by immunofluorescence microscopy and time-resolved fluorescence immunoassay, oxLDL dose-dependently stimulated collagen type I and fibronectin synthesis in cultured HCA-SMC. The effect on matrix synthesis was biphasic, with a maximum effect at concentrations between 1 and 10 microg/ml oxLDL. Higher oxLDL concentrations (>25 microg/ml) were cytotoxic. Beside oxLDL, malondialdehyde-modified LDL also stimulated extracellular matrix synthesis. In the presence of 100 microg/ml ascorbic acid, 25, 50 and 100 microg/ml oxLDL induced apoptosis within 6-8 hours (demonstrated by TUNEL-reaction, annexin-V binding and APO-2.7-expression). Apoptosis was not induced by normal (unmodified) LDL and malondialdehyde-modified LDL. The radical scavengers and antioxidants TROLOX and probucol and the hydrogen peroxide eliminator catalase significantly reduced oxLDL-induced apoptosis. Our results demonstrate that low concentrations of oxLDL are profibrogenic by stimulating extracellular matrix synthesis, whereas higher oxLDL concentrations induce oxidative stress and apoptosis in coronary artery smooth muscle cells. The profibrogenic effect might be relevant in the formation of atherosclerotic plaques, and the proapoptotic effect might contribute to an increased plaque vulnerability.

Mechanisms of progression of renal damage in lupus nephritis: pathogenesis of renal scarring

Lupus nephritis results from an acute inflammatory and immunological response to renal immune complex deposition. The acute response is characterized by activation of circulating leukocytes and renal parenchymal cells, triggering the production of pro-inflammatory cytokines and growth factors. In all too many cases, this response is followed by a chronic response, which is characterized by excessive deposition of collagen and other extracellular matrix macromolecules and the development of end-stage renal disease. Mechanisms underlying this chronic response in progressive renal disease are not adequately defined. In this overview, potential roles of reactive oxygen species (ROS) generation and transforming growth factor-beta (TGF-beta) production in the pathogenesis of lupus nephritis are considered. ROS and TGF-beta may be key elements of a pathway leading to persistent and excessive matrix deposition in progressive lupus nephritis. Further studies to define the role of this pathway in lupus nephritis may lead to the development of additional, more specific therapeutic targets to prevent progression of renal disease.

Hydrogen peroxide-induced apoptosis and necrosis in human lung fibroblasts: protective roles of glutathione

Although reactive oxygen species (ROS)-related cell damage has been implicated in pathogenesis of fibrogenetic pulmonary disorders, features of ROS-mediated cell death in human lung fibroblasts are not completely understood. We therefore examined the effects of hydrogen peroxide (H2O2) on cell growth kinetics in human lung fibroblasts (HFL-1 cells) and tested the roles of antioxidants on the H2O2-induced cell death (i.e., necrosis and apoptosis) in HFL-1 cells. We found that the relatively low concentrations of H2O2 ranging from 10 microM to 100 microM induced predominantly apoptosis, whereas higher concentration of H2O2 ranging 1 mM-10 mM induced predominantly necrosis in HFL-1 cells. Extracellular supplementation of glutathione (GSH) in culture media significantly abolished the H2O2-induced cell death, whereas GSH-depleted cells by pretreatment with buthionine sulfoxime (BSO) were likely to undergo cell death caused by a lower concentration of H2O2 than normal HFL-1 cells without BSO treatment. These results indicate that H2O2 induces both necrosis and apoptosis of human lung fibroblasts at least in part through the action of ROS and that modulation of the ROS production inside and outside of cells may influence the cell survival during oxidative insults.

Vitamin E status in patients with liver cirrhosis: normal or deficient?

The study aim was to compare the ratio of vitamin E to serum cholesterol with the serum vitamin E level alone as a measure of vitamin E status in patients with different degrees of liver dysfunction. Assessment of serum vitamin E and total serum cholesterol was performed in 85 patients with liver cirrhosis at Child's stage A (n = 26), B (n = 26), and C (n = 33) and 50 patients with noncirrhotic liver disease. As surrogate markers of liver function, 7alpha-hydroxycholesterol and prealbumin concentrations and the plasma prothrombin time were determined. Mean serum vitamin E concentrations in Child A, B, and C patients were 27.4%, 36.9%, and 37.3% lower, respectively, than in healthy controls (P<.01). Twelve of 26 Child A, 14 of 26 Child B, and 14 of 33 Child C patients had vitamin E deficiency with respect to the absolute values, i.e., serum levels less than 13.76 micromol/L (5% percentile of healthy controls). In contrast, only two of 26 Child A, five of 26 Child B, and five of 33 Child C patients (P<.01 for Child A/B and P<.05 for Child C) were vitamin E-deficient according to the serum vitamin E to cholesterol ratio, i.e., less than 2.86 micromol/mmol. Serum vitamin E was correlated significantly with prealbumin, 7alpha-hydroxycholesterol, and the plasma prothrombin time, but the vitamin E to cholesterol ratio was not. Correcting serum vitamin E for total serum cholesterol in patients with liver cirrhosis leads to the phenomenon of reduced serum vitamin E levels inadvertently shifted toward normal values. In patients with liver cirrhosis, the absolute vitamin E concentration correlates better with the typical clinical and biochemical findings of the disease than the vitamin E to cholesterol ratio. Therefore, a considerable number of patients with advanced liver cirrhosis might actually be vitamin E-deficient.

Raised concentrations of aldehyde lipid peroxidation products in premature infants with chronic lung disease

AIM

To indicate the extent of lipid peroxidation induced by oxidative stress, by measuring aldehyde end products in biological samples.

METHODS

A highly specific gas chromatography and mass spectrometry (GC/MS) method was used to measure plasma concentrations of aliphatic aldehydes within the first week of life in 13 premature infants who subsequently developed chronic lung disease (CLD) and 11 infants without CLD (non-CLD). The oxime-tert-butyldimethylsilyl derivatives of aldehydes were analysed using 2,2,6,6-d4-cyclohexanone as the internal standard.

RESULTS

All of the aldehydes measured were raised in those infants with CLD compared with non-CLD infants. Plasma concentrations of heptanal, 2-nonenal, and 4-hydroxynonenal (HNE) were significantly increased in CLD infants on the day of birth, while the differences in all aldehydes between the two groups were not significant at 4-6 days of age. Logistic regression analysis showed that the increase in these three aldehydes within the first 24 hours of life independently showed significant associations with the development of CLD. In particular, an HNE concentration of > or = 200 nM on day 0 was the best predictor for the early detection of CLD (odds ratio = 32.0), followed by a 2-nonenal concentration of > or = 150 nM (odds ratio = 16.0).

CONCLUSIONS

These findings suggest that lipid peroxidation may have a role in the pathogenesis of neonatal CLD.

4-Hydroxynonenal as a biological signal: molecular basis and pathophysiological implications

Reactive oxygen intermediates (ROI) and other pro-oxidant agents are known to elicit, in vivo and in vitro, oxidative decomposition of omega-3 and omega-6 polyunsaturated fatty acids of membrane phospholipids (i.e, lipid peroxidation). This leads to the formation of a complex mixture of aldehydic end-products, including malonyldialdehyde (MDA), 4-hydroxy-2,3-nonenal (HNE), and other 4-hydroxy-2,3-alkenals (HAKs) of different chain length. These aldehydic molecules have been considered originally as ultimate mediators of toxic effects elicited by oxidative stress occurring in biological material. Experimental and clinical evidence coming from different laboratories now suggests that HNE and HAKs can also act as bioactive molecules in either physiological and pathological conditions. These aldehydic compounds can affect and modulate, at very low and nontoxic concentrations, several cell functions, including signal transduction, gene expression, cell proliferation, and, more generally, the response of the target cell(s). In this review article, we would like to offer an up-to-date review on this particular aspect of oxidative stress--dependent modulation of cellular functions-as well as to offer comments on the related pathophysiological implications, with special reference to human conditions of disease.

Redox regulation of wound healing? NF-kappaB activation in cultured human keratinocytes upon wounding and the effect of low energy HeNe irradiation

The complex process of wound healing as well as the signaling systems orchestrating this intricate process remain incompletely defined. Using human keratinocytes in primary culture, we sought to characterize their NF-kappaB responses to wounding alone or in combination with other treatments. We initially characterized these cultured human keratinocytes responses to known NF-kappaB activators (PMA, TNF-alpha and IL-1) using two different assays, immunohistochemistry and electrophoretic mobility shift (EMSA). After eliciting the expected NF-kappaB responses, we applied these same assays to assess responses to either wounding or HeNe irradiation alone. The results obtained indicated that only a modest/sporadic activation of NF-kappaB was elicited by these which was only detectable using immunohistochemistry. When the combination of wounding and HeNe irradiation on NF-kappaB status was assessed, a marked, localized activation of NF-kappaB in keratinocytes along the wound edge was found. Treatment induced NF-kappaB activation (e.g., wounding, HeNe irradiation and combined wounding and HeNe irradiation) was abrogated by pyrrolidine dithiocarbamate (PDTC) which inhibits NF-kappaB activation through an as yet incompletely understood (antioxidant?) mechanism. These data therefore suggest that NF-kappaB and oxidation mediated changes in its activation state likely play important roles in normal cutaneous wound healing.

HNE interacts directly with JNK isoforms in human hepatic stellate cells

4-Hydroxy-2,3-nonenal (HNE) is an aldehydic end product of lipid peroxidation which has been detected in vivo in clinical and experimental conditions of chronic liver damage. HNE has been shown to stimulate procollagen type I gene expression and synthesis in human hepatic stellate cells (hHSC) which are known to play a key role in liver fibrosis. In this study we investigated the molecular mechanisms underlying HNE actions in cultured hHSC. HNE, at doses compatible with those detected in vivo, lead to an early generation of nuclear HNE-protein adducts of 46, 54, and 66 kD, respectively, as revealed by using a monoclonal antibody specific for HNE-histidine adducts. This observation is related to the lack of crucial HNE-metabolizing enzymatic activities in hHSC. Kinetics of appearance of these nuclear adducts suggested translocation of cytosolic proteins. The p46 and p54 isoforms of c-Jun amino-terminal kinase (JNKs) were identified as HNE targets and were activated by this aldehyde. A biphasic increase in AP-1 DNA binding activity, associated with increased mRNA levels of c-jun, was also observed in response to HNE. HNE did not affect the Ras/ERK pathway, c-fos expression, DNA synthesis, or NF-kappaB binding. This study identifies a novel mechanism linking oxidative stress to nuclear signaling in hHSC. This mechanism is not based on redox sensors and is stimulated by concentrations of HNE compatible with those detected in vivo, and thus may be relevant during chronic liver diseases.

Inhibitory effect of tranilast on hypertrophic collagen production in the spontaneously hypertensive rat heart

Tranilast, N-(3,4-dimethoxycinnamoyl) anthranilic acid, a widely used antiallergy drug in Japan, has been shown to inhibit transforming growth factor-beta1 release from fibroblasts and reduce collagen synthesis in keloid cells. In the present study, we have investigated the effect of this drug on cardiac hypertrophy in spontaneously hypertensive rats (SHR), with a focus on the cardiac collagen matrix, which is associated with myocardial stiffness. Twenty-four-week-old SHRs and Wistar Kyoto rats (WKYs) were administered tranilast (300 mg/kg) orally once a day for 4 weeks. This treatment significantly suppressed increases in left ventricular collagen concentration (P < 0.05) and the left ventricular weight/body weights ratios (P < 0.05) in SHRs, and tranilast was ineffective on collagen concentration and ventricular weight/body weights ratios in WKYs. Tranilast did not affect systolic or diastolic blood pressure, end-diastolic left ventricular pressure and heart rate in both SHRs and WKYs, and the agent did not change positive dp/dt or cardiac output in SHRs. The pressure-volume relationship curve was shifted to the left by the drug; the slope (k) of the logarithm of the pressure-volume relationship curve was significantly increased (P < 0.05) in SHRs. It is concluded that the suppression of increases in cardiac collagen and left ventricular mass by tranilast results in a corresponding prevention of cardiac stiffness as studied in the SHR.

Antioxidants for hypertension

Increasing evidence implicates reactive oxygen species in the pathogenesis of hypertension and its cardiovascular complications. By altering the balance in the endothelium between vasoconstrictors such as thromboxane and isoprostanes and vasodilators such as nitric oxide, reactive oxygen species contribute to endothelium-dependent contractions and increased vascular resistance. Antioxidants can restore endothelial function and decrease blood pressure in several models of hypertension and in some, but not all, studies of humans with essential hypertension. The potential of antioxidant therapy for hypertension is considerable.

Association between oxidative stress and cytokine production in nickel-treated rats

The aim of this study was to evaluate a possible relationship between lipid peroxidation, cytokine production, such as interleukin-1 (IL-1), tumor necrosis factor alpha (TNF-alpha), and transforming growth factor beta (TGF-beta), and hepatotoxicity of rats after nickel chloride (NiCl2) acute poisoning. Administration of NiCl2 significantly elevated the levels of malondialdehyde (MDA), IL-1, TNF-alpha, and TGF-beta in the serum of rats. The dose-effect relationship for the increase of serum MDA, as observed in the present study, corresponds closely to the increase of IL-1, TNF-alpha, and TGF-beta in serum. Treatment with ascorbic acid (Vit C) significantly lowered the levels of lipid peroxidation, cytokine production, and the activities of alanine transaminase and aspartate transaminase in the serum of the rats given NiCl2. The hepatic toxicity was increased in a dose-dependent manner and corresponds to the increase of serum IL-1, TNF-alpha, and TGF-beta. There was an association between lipid peroxidation and the levels of cytokines in serum of rats after NiCl2 administration. Reactive oxygen species may serve as a mediator of lipid peroxidation and production of cytokines in NiCl2 injection.

Measurement of lipid peroxidation

Lipid peroxidation results in the formation of conjugated dienes, lipid hydroperoxides and degradation products such as alkanes, aldehydes and isoprostanes. The approach to the quantitative assessment of lipid peroxidation depends on whether the samples involve complex biological material obtained in vivo, or whether the samples involve relatively simple mixtures obtained in vitro. Samples obtained in vivo contain a large number of products which themselves may undergo metabolism. The measurement of conjugated diene formation is generally applied as a dynamic quantitation e.g. during the oxidation of LDL, and is not generally applied to samples obtained in vivo. Lipid hydroperoxides readily decompose, but can be measured directly and indirectly by a variety of techniques. The measurement of MDA by the TBAR assay is non-specific, and is generally poor when applied to biological samples. More recent assays based on the measurement of MDA or HNE-lysine adducts are likely to be more applicable to biological samples, since adducts of these reactive aldehydes are relatively stable. The discovery of the isoprostanes as lipid peroxidation products which can be measured by gas chromatography mass spectrometry or immunoassay has opened a new avenue by which to quantify lipid peroxidation in vivo, and will be discussed in detail.

Can pentoxifylline prevent renal disease?

The characteristics of pentoxifylline(Trental) suggest that it is an ideal agent to be used as adjunct in the therapy of chronic proliferative glomerulonephritides. Theoretical considerations suggest that pentoxifylline should also protect against and even ameliorate tubulo-interstitial fibrosis of affected kidneys.

The pathogenesis of cutaneous fibrosis

Cutaneous fibrosis is an integral component of a variety of human disorders including keloids, hypertrophic scar, and most notably, scleroderma. Each has its own etiology and unique clinical characteristics, but all involve the dysregulation of connective tissue metabolism, in particular, the activation of dermal fibroblasts. In this review, we examine various molecular events in scleroderma that may lead to fibroblast activation, and propose a new model to explain the persistence of such activation by scleroderma fibroblasts in the apparent absence of exogenous stimuli.

Oxidative damage and transforming growth factor beta 1 expression in pretumoral and tumoral lesions of human intestine

The aim of this study was to evaluate a possible relationship between oxidative stress and transforming growth factor beta 1 (TGF beta 1) expression in human colon adenocarcinoma. Crohn's disease, an inflammatory pathology of the intestine often regarded to as precancerous, was also examined. Indices of impaired redox balance were monitored in blood and in bioptic samples from 10 adult patients with adenocarcinoma of the colon and from five patients with Crohn's disease. On tissue samples TGF beta 1 mRNA expression was also determined. Ten healthy adults provided normal reference values for plasma indices of oxidative stress, and normal tissue distant from the lesions was used for comparative analysis. Fluorescent adducts with plasma proteins of malonaldehyde (MDA) and 4-hydroxynonenal (HNE) were significantly lower than controls in the plasma from cancer patients and significantly higher in the plasma from Crohn's patients. In adenocarcinoma biopsies, susceptibility to lipid peroxidation processes and TGF beta 1 expression were below the relative control; in Crohn's disease, lipid peroxidation and cytokine expression were both above the relative control. The findings obtained suggest the existence of an association between oxidative damage and fibrogenic cytokine expression in the human intestine. Further studies are needed to conclusively prove the correlation between the two events.