Effect of pyruvate on oxidant injury to isolated and cellular DNA

Immunoglobulin Superfamily Containing Leucine-Rich Repeat (ISLR) Serves as a Redox Sensor That Modulates Antioxidant Capacity by Suppressing Pyruvate Kinase Isozyme M2 Activity

Cells defend against oxidative stress by enhancing antioxidant capacity, including stress-activated metabolic alterations, but the underlying intracellular signaling mechanisms remain unclear. This paper reports that immunoglobulin superfamily containing leucine-rich repeat (ISLR) functions as a redox sensor that responds to reactive oxygen species (ROS) stimulation and modulates the antioxidant capacity by suppressing pyruvate kinase isozyme M2 (PKM2) activity. Following oxidative stress, ISLR perceives ROS stimulation through its cysteine residue 19, and rapidly degrades in the autophagy-lysosome pathway. The downregulated ISLR enhances the antioxidant capacity by promoting the tetramerization of PKM2, and then enhancing the pyruvate kinase activity, PKM2-mediated glycolysis is crucial to the ISLR-mediated antioxidant capacity. In addition, our results demonstrated that, in triple-negative breast cancer, cisplatin treatment reduced the level of ISLR, and PKM2 inhibition sensitizes tumors to cisplatin by enhancing ROS production; and argued that PKM2 inhibition can synergize with cisplatin to limit tumor growth. Our results demonstrate a molecular mechanism by which cells respond to oxidative stress and modulate the redox balance.

Sodium Pyruvate Nasal Spray Reduces the Severity of Nasal Inflammation and Congestion in Patients with Allergic Rhinitis

Background: As an anti-inflammatory and antioxidant, sodium pyruvate significantly reduces inflammatory cytokines and oxygen radicals such as interleukin (IL) IL-6, IL-8, Monocyte Chemoattractant Protein-1, and hydrogen peroxide. Thus, sodium pyruvate holds promise as a treatment for many respiratory diseases, including allergic rhinitis (AR). Novel treatments for AR are needed as current medications, including steroids, often fail to treat severe symptoms. Methods: The data from five human clinical studies were analyzed to determine the effect of 20 mM sodium pyruvate nasal spray (N115) in patients with AR. Nasal inflammation scores were compared to a placebo control or a no-treatment baseline control. Three studies were open-labeled and two were appropriately blinded to both patients and clinicians using computer randomization of subjects. Results: The intranasal administration of sodium pyruvate significantly improved nasal inflammation scores in all five clinical trials of patients with AR (p < 0.0001 in all trials). Conclusions: These results give credence to the overall ability of sodium pyruvate, administered by nasal spray, to treat inflammation of the nasal airways.

Synergy between Non-Thermal Plasma with Radiation Therapy and Olaparib in a Panel of Breast Cancer Cell Lines

Cancer therapy has evolved to a more targeted approach and often involves drug combinations to achieve better response rates. Non-thermal plasma (NTP), a technology rapidly expanding its application in the medical field, is a near room temperature ionized gas capable of producing reactive species, and can induce cancer cell death both in vitro and in vivo. Here, we used proliferation assay to characterize the plasma sensitivity of fourteen breast cancer cell lines. These assays showed that all tested cell lines were sensitive to NTP. In addition, a good correlation was found comparing cell sensitivity to NTP and radiation therapy (RT), where cells that were sensitive to RT were also sensitive to plasma. Moreover, in some breast cancer cell lines, NTP and RT have a synergistic effect. Adding a dose of PARP-inhibitor olaparib to NTP treatment always increases the efficacy of the treatment. Olaparib also exhibits a synergistic effect with NTP, especially in triple negative breast cancer cells. Results presented here help elucidate the position of plasma use as a potential breast cancer treatment.

Ethyl Pyruvate Directly Attenuates Active Secretion of HMGB1 in Proximal Tubular Cells via Induction of Heme Oxygenase-1

Renal ischemia reperfusion (IR) is a main cause of acute kidney injury leading to high morbidity and mortality during postoperative periods. This study investigated whether ethyl pyruvate (EP) protects the kidney against renal IR injury. Male C57BL/6 mice were treated with vehicle or EP (40 mg/kg) 1 h before ischemia and the plasma creatinine (Cr) levels and tubular damage were evaluated after reperfusion. EP attenuated the IR-induced plasma Cr levels, renal inflammation and apoptotic cell death, but the effect of EP was abolished by pretreating Zinc protoporphyrin (ZnPP), a heme oxygenase (HO)-1 inhibitor. HO-1 is a stress-induced protein and protects the kidney against IR injury. EP increased significantly HO-1 expression in the proximal tubular cells in vivo and HK-2 cells in vitro. Inhibition of PI3K/Akt pathway and knockdown of Nrf2 blocked HO-1 induction by EP. High mobility group box 1 (HMGB1) secretion was assessed as an early mediator of IR injury; plasma HMGB1 were significantly elevated as early as 2 h to 24 h after reperfusion and these were attenuated by EP, but the effect of EP was abolished by ZnPP. EP also reduced HMGB1 secretion stimulated by TNF-α in HK-2 cells, and the inhibition of PI3K/Akt and knockdown of HO-1 blocked the effect of EP. Conclusively, EP inhibits the active secretion of HMGB1 from proximal tubular cells during IR injury by inducing HO-1 via activation of PI3K/Akt and Nrf2 pathway.

Stimulation of Vibrio vulnificus Pyruvate Kinase in the Presence of Glucose to Cope With H2O2 Stress Generated by Its Competitors

The bacterial phosphoenolpyruvate (PEP):carbohydrate phosphotransferase system (PTS) regulates a variety of cellular processes in addition to catalyzing the coupled transport and phosphorylation of carbohydrates. We recently reported that, in the presence of glucose, HPr of the PTS is dephosphorylated and interacts with pyruvate kinase A (PykA) catalyzing the conversion of PEP to pyruvate in Vibrio vulnificus. Here, we show that this interaction enables V. vulnificus to survive H₂O₂ stress by increasing pyruvate production. A pykA deletion mutant was more susceptible to H₂O₂ stress than wild-type V. vulnificus without any decrease in the expression level of catalase, and this sensitivity was rescued by the addition of pyruvate. The H₂O₂ sensitivity difference between wild-type and pykA mutant strains becomes more apparent in the presence of glucose. Fungi isolated from the natural habitat of V. vulnificus retarded the growth of the pykA mutant more severely than the wild-type strain in the presence of glucose by glucose oxidase-dependent generation of H₂O₂. These data suggest that V. vulnificus has evolved to resist the killing action of its fungal competitors by increasing pyruvate production in the presence of glucose.

Iron Overload Accelerates the Progression of Diabetic Retinopathy in Association with Increased Retinal Renin Expression

Diabetic retinopathy (DR) is a leading cause of blindness among working-age adults. Increased iron accumulation is associated with several degenerative diseases. However, there are no reports on the status of retinal iron or its implications in the pathogenesis of DR. In the present study, we found that retinas of type-1 and type-2 mouse models of diabetes have increased iron accumulation compared to non-diabetic retinas. We found similar iron accumulation in postmortem retinal samples from human diabetic patients. Further, we induced diabetes in HFE knockout (KO) mice model of genetic iron overload to understand the role of iron in the pathogenesis of DR. We found increased neuronal cell death, vascular alterations and loss of retinal barrier integrity in diabetic HFE KO mice compared to diabetic wildtype mice. Diabetic HFE KO mouse retinas also exhibited increased expression of inflammation and oxidative stress markers. Severity in the pathogenesis of DR in HFE KO mice was accompanied by increase in retinal renin expression mediated by G-protein-coupled succinate receptor GPR91. In light of previous reports implicating retinal renin-angiotensin system in DR pathogenesis, our results reveal a novel relationship between diabetes, iron and renin-angiotensin system, thereby unraveling new therapeutic targets for the treatment of DR.

Metabolic reprogramming and dysregulated metabolism: cause, consequence and/or enabler of environmental carcinogenesis?

Environmental contributions to cancer development are widely accepted, but only a fraction of all pertinent exposures have probably been identified. Traditional toxicological approaches to the problem have largely focused on the effects of individual agents at singular endpoints. As such, they have incompletely addressed both the pro-carcinogenic contributions of environmentally relevant low-dose chemical mixtures and the fact that exposures can influence multiple cancer-associated endpoints over varying timescales. Of these endpoints, dysregulated metabolism is one of the most common and recognizable features of cancer, but its specific roles in exposure-associated cancer development remain poorly understood. Most studies have focused on discrete aspects of cancer metabolism and have incompletely considered both its dynamic integrated nature and the complex controlling influences of substrate availability, external trophic signals and environmental conditions. Emerging high throughput approaches to environmental risk assessment also do not directly address the metabolic causes or consequences of changes in gene expression. As such, there is a compelling need to establish common or complementary frameworks for further exploration that experimentally and conceptually consider the gestalt of cancer metabolism and its causal relationships to both carcinogenesis and the development of other cancer hallmarks. A literature review to identify environmentally relevant exposures unambiguously linked to both cancer development and dysregulated metabolism suggests major gaps in our understanding of exposure-associated carcinogenesis and metabolic reprogramming. Although limited evidence exists to support primary causal roles for metabolism in carcinogenesis, the universality of altered cancer metabolism underscores its fundamental biological importance, and multiple pleiomorphic, even dichotomous, roles for metabolism in promoting, antagonizing or otherwise enabling the development and selection of cancer are suggested.

Renal cortical pyruvate as a potentially critical mediator of acute kidney injury

Pyruvate is a key intermediary in both aerobic and anaerobic energy metabolisms. In addition, a burgeoning body of experimental literature indicates that it can also dramatically impact oxidant, proinflammatory, and cytoprotective pathways. In sum, these actions can confer protection against diverse forms of tissue damage. However, the fate of pyruvate during the evolution of acute kidney injury (AKI) has remained ill defined. Recent experimental studies have indicated that following either ischemic or nephrotoxic renal injury, marked and sustained pyruvate depletion results. While multiple potential mechanisms for this pyruvate loss may be involved, experimental data suggest that a loss of lactate (a dominant pyruvate precursor) and enhanced gluconeogenesis (i.e. pyruvate utilization) are involved. The importance of pyruvate depletion for AKI pathogenesis is underscored by observations that pyruvate therapy can attenuate diverse forms of experimental AKI. This protection may stem from reductions in tissue inflammation, improved anti-inflammatory defenses, and an enhanced cellular energy metabolism. The pieces of information that give rise to these conclusions are discussed in this brief report.

Effects of sodium pyruvate on ameliorating metabolic acidosis

OBJECTIVE

To examine the effects of sodium pyruvate (SP) on metabolic acidosis.

METHODS

For the in vivo experiments, we evaluated effects of SP on an ammonium chloride (NH4Cl)-induced hyperchloremic acidosis rat model. SP was infused at overall doses of 2, 4, and 6 mmol·kg(- 1) for the SP1, SP2, and SP3 groups, respectively. Treatment with sodium bicarbonate (SB) was used as a positive control (2 mmol·kg(- 1)), and treatment with normal saline (NS) was used as a volume control (2 mL·kg(- 1)). Blood was sampled from the ophthalmic venous plexus for pH, blood gases, electrolytes, glucose, creatinine (Cr), and urea analysis after injection. For the in vitro experiment, propionate was applied to induce intracellular acidosis in human endothelial cells. Intracellular pH (pHi) was fluorimetrically measured after the addition of SP.

RESULTS

In the in vivo study, the pH of SP1 group showed no significant difference compared with that of the NS group. The SP2 and SP3 groups had a higher pH than the NS group (P < 0.01). The SP3 group had a higher pH than the SB group (P < 0.05) and SP1 group (P < 0.05). Moreover, SP treatment ameliorated the abnormality of calcium and decreased the blood potassium levels. The SP3 group had higher glucose levels than SP1 group (P < 0.05). No significant differences were observed between all the groups in the plasma Cr and urea levels. In the in vitro study, the pHi increased immediately after the addition of SP.

CONCLUSION

The data suggest that intravascular treatment with SP represents a novel therapeutic strategy to ameliorate metabolic acidosis.

Renal cortical pyruvate depletion during AKI

Pyruvate is a key intermediary in energy metabolism and can exert antioxidant and anti-inflammatory effects. However, the fate of pyruvate during AKI remains unknown. Here, we assessed renal cortical pyruvate and its major determinants (glycolysis, gluconeogenesis, pyruvate dehydrogenase [PDH], and H2O2 levels) in mice subjected to unilateral ischemia (15-60 minutes; 0-18 hours of vascular reflow) or glycerol-induced ARF. The fate of postischemic lactate, which can be converted back to pyruvate by lactate dehydrogenase, was also addressed. Ischemia and glycerol each induced persistent pyruvate depletion. During ischemia, decreasing pyruvate levels correlated with increasing lactate levels. During early reperfusion, pyruvate levels remained depressed, but lactate levels fell below control levels, likely as a result of rapid renal lactate efflux. During late reperfusion and glycerol-induced AKI, pyruvate depletion corresponded with increased gluconeogenesis (pyruvate consumption). This finding was underscored by observations that pyruvate injection increased renal cortical glucose content in AKI but not normal kidneys. AKI decreased PDH levels, potentially limiting pyruvate to acetyl CoA conversion. Notably, pyruvate therapy mitigated the severity of AKI. This renoprotection corresponded with increases in cytoprotective heme oxygenase 1 and IL-10 mRNAs, selective reductions in proinflammatory mRNAs (e.g., MCP-1 and TNF-α), and improved tissue ATP levels. Paradoxically, pyruvate increased cortical H2O2 levels. We conclude that AKI induces a profound and persistent depletion of renal cortical pyruvate, which may induce additional injury.

Pyruvate protects pathogenic spirochetes from H2O2 killing

Pathogenic spirochetes cause clinically relevant diseases in humans and animals, such as Lyme disease and leptospirosis. The causative agent of Lyme disease, Borrelia burgdorferi, and the causative agent of leptospirosis, Leptospria interrogans, encounter reactive oxygen species (ROS) during their enzootic cycles. This report demonstrated that physiologically relevant concentrations of pyruvate, a potent H2O2 scavenger, and provided passive protection to B. burgdorferi and L. interrogans against H2O2. When extracellular pyruvate was absent, both spirochetes were sensitive to a low dose of H2O2 (≈0.6 µM per h) generated by glucose oxidase (GOX). Despite encoding a functional catalase, L. interrogans was more sensitive than B. burgdorferi to H2O2 generated by GOX, which may be due to the inherent resistance of B. burgdorferi because of the virtual absence of intracellular iron. In B. burgdorferi, the nucleotide excision repair (NER) and the DNA mismatch repair (MMR) pathways were important for survival during H2O2 challenge since deletion of the uvrB or the mutS genes enhanced its sensitivity to H2O2 killing; however, the presence of pyruvate fully protected ΔuvrB and ΔmutS from H2O2 killing further demonstrating the importance of pyruvate in protection. These findings demonstrated that pyruvate, in addition to its classical role in central carbon metabolism, serves as an important H2O2 scavenger for pathogenic spirochetes. Furthermore, pyruvate reduced ROS generated by human neutrophils in response to the Toll-like receptor 2 (TLR2) agonist zymosan. In addition, pyruvate reduced neutrophil-derived ROS in response to B. burgdorferi, which also activates host expression through TLR2 signaling. Thus, pathogenic spirochetes may exploit the metabolite pyruvate, present in blood and tissues, to survive H2O2 generated by the host antibacterial response generated during infection.

Research strategies in the study of the pro-oxidant nature of polyphenol nutraceuticals

Polyphenols of phytochemicals are thought to exhibit chemopreventive effects against cancer. These plant-derived antioxidant polyphenols have a dual nature, also acting as pro-oxidants, generating reactive oxygen species (ROS), and causing oxidative stress. When studying the overall cytotoxicity of polyphenols, research strategies need to distinguish the cytotoxic component derived from the polyphenol per se from that derived from the generated ROS. Such strategies include (a) identifying hallmarks of oxidative damage, such as depletion of intracellular glutathione and lipid peroxidation, (b) classical manipulations, such as polyphenol exposures in the absence and presence of antioxidant enzymes (i.e., catalase and superoxide dismutase) and of antioxidants (e.g., glutathione and N-acetylcysteine) and cotreatments with glutathione depleters, and (c) more recent manipulations, such as divalent cobalt and pyruvate to scavenge ROS. Attention also must be directed to the influence of iron and copper ions and to the level of polyphenols, which mediate oxidative stress.

Artefacts in cell culture: α-Ketoglutarate can scavenge hydrogen peroxide generated by ascorbate and epigallocatechin gallate in cell culture media

Ascorbate and several phenolic compounds readily oxidise in cell culture media to generate hydrogen peroxide. However, addition of α-ketoglutarate, which is known to be released by several cell types, decreased the levels of H(2)O(2), and the α-ketoglutarate was depleted and converted to succinate. These observations could account for previous reports of the protective effects of α-ketoglutarate in promoting the growth of cells in culture, and may contribute to explaining some of the variability in the literature in reported rates of H(2)O(2) production from autoxidisable compounds in cell culture systems.

Measurement of mitochondrial ROS production

The significance of reactive oxygen species (ROS) as aggravating or primary factors in numerous pathologies is widely recognized, with mitochondria being considered the major intracellular source of ROS. It is not yet possible to routinely measure mitochondrial ROS in animals or cultured cells with a reasonable degree of certainty. However, at the level of isolated mitochondria, one can easily monitor and quantify the rate of ROS production, identify major sites of ROS production, and compare the rates of ROS production in mitochondria isolated from normal and diseased tissue. In this chapter, we describe in detail the most recent and reliable method to measure mitochondrial ROS as the rate of H2O2 emission. This method may be employed with minimal modifications to measure H2O2 production by mitochondria isolated from various tissues and under a wide variety of experimental conditions.

Artefacts in cell culture: pyruvate as a scavenger of hydrogen peroxide generated by ascorbate or epigallocatechin gallate in cell culture media

Ascorbate and several phenolic compounds readily oxidise in cell culture media to generate hydrogen peroxide. However, media containing pyruvate showed much less H(2)O(2) production, apparently because pyruvate can scavenge H(2)O(2) in the medium. Researchers must be aware that compounds under test can sometimes readily oxidise in cell culture media, that this might not be detected by measurement of H(2)O(2) if the media contain pyruvate, and that pyruvate can be substantially depleted in the media as a result.

Improved in vitro development of porcine embryos with different energy substrates and serum

The effect of replacing 5.5 mM glucose in North Carolina State University (NCSU)-23 medium with 0.5 mM pyruvate/5.0 mM lactate on porcine IVF embryo development was investigated in Experiment 1. Culturing embryos with pyruvate/lactate for 7 days or with pyruvate/lactate from Days 0 to 2, and then glucose from Days 2 to 7 improved cleavage rates. In Experiment 2, embryos were cultured for 7 days in pyruvate/lactate containing NCSU-23 medium supplemented with 0.05% PVA, 0.4% BSA or 10% fetal bovine serum (FBS). The BSA supplement increased the rates of cleavage, blastocyst formation, and the number of total cells in blastocysts. In Experiment 3, embryos were cultured in pyruvate/lactate containing NCSU-23 medium supplemented with 0.4% BSA for 7 days (BSA-PL), 0.4% BSA from Days 0 to 4 and then 10% FBS from Days 4 to 7 (BSA-PL-->F ) or 0.4% BSA from Days 0 to 7 with addition of 10% FBS (BSA-PL + F ) at Day 4. More blastocysts in BSA-PL--> F and hatching or hatched blastocysts in BSA-PL-->F and BSA-PL+F were obtained. Total cell number in blastocysts derived from BSA-PL-->F and BSA-PL+F were increased. Our results demonstrated that supplementing pyruvate/lactate containing NCSU-23 medium with 0.4% BSA for 4 days and replacing it with 10% FBS for another 3 days improved porcine IVF embryo development.

Improved developmental competence of cloned porcine embryos with different energy supplements and chemical activation

The present study investigated the effect of lactate/pyruvate supplement in culture medium and of chemical activation after electric stimulus on in vitro development of porcine somatic cell nuclear transfer (SCNT) embryos. In vitro matured gilt oocytes were enucleated, reconstructed with fetal fibroblasts, and simultaneously fused/activated using a single pulse of 2.0 kV/cm for 30 microsec. In Experiment 1, reconstructed embryos were cultured in North Carolina State University (NCSU)-23 medium supplemented with either 5.5 mM glucose (Group A) or lactate (5.0 mM)/pyruvate (0.5 mM) (Group B). Compared to Group A, cleavage rate (64% vs. 47%) was higher and more blastocysts developed in Group B (17% vs. 6% at Day 6, 21% vs.11% at Day 7). Experiment 2, embryos reconstructed by electric stimulus (2.0 kV/cm for 30 microsec) were subjected to three activation protocols: (1) no chemical activation (Group C), (2) 7.5 microg/ml cytochalasin B treatment at 2 hr after electric stimulus (Group D), and (3) 5 microg/ml 6-dimethylaminopurine (Group E) treatment at 2 hr after electric stimulus. The reconstructed embryos were cultured for 7 days in NCSU-23 medium supplemented with lactate (5.0 mM)/pyruvate (0.5 mM). The rates of blastocyst formation on Day 6 and Day 7 in Group C (17 and 20%, respectively) or Group D (15, 20%, respectively) were higher than in Group E (9 and 12%, respectively). The percentage of two pseudo-pronucleus (PPN) formations in Group D (88%) was significantly higher than in Group C (71%) and Group E (72%). Mean cell numbers of blastocysts in Group D (63.4 +/- 15.8) were higher than in Group C (43.9 +/- 16.5) and Group E (32.9 +/- 17.9), due to increased trophectoderm (TE) cell numbers. Our results indicate that supplementing NCSU-23 medium with lactate/pyruvate and exposure of cytochalasin B after electrical stimulus can improve in vitro developmental competence of porcine SCNT embryos.

Cytoprotection of pyruvic acid and reduced beta-nicotinamide adenine dinucleotide against hydrogen peroxide toxicity in neuroblastoma cells

Elevated production of hydrogen peroxide (H2O2) in the central nervous system has been implicated in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, ischemic reperfusion, stroke, and Alzheimer's disease. Pyruvic acid has a critical role in energy metabolism and a capability to nonenzymatically decarboxylate H2O2 into H2O. This study examined the effects of glycolytic regulation of pyruvic acid on H2O2 toxicity in murine neuroblastoma cells. Glycolytic energy substrates including D-(+)-glucose, D-(-) fructose and the adenosine transport blocker dipyridamole, were not effective in providing protection against H2O2 toxicity, negating energy as a factor. On the other hand, pyruvic acid completely prevented H2O2 toxicity, restoring the loss of ATP and cell viability. H2O2 toxicity was also attenuated by D-fructose 1,6 diphosphate (FBP), phospho (enol) pyruvate (PEP), niacinamide, beta-nicotinamide adenine dinucleotide (beta-NAD+), and reduced form (beta-NADH). Both FBP and PEP exerted positive kinetic effects on pyruvate kinase (PK) activity. Interestingly, only pyruvic acid and beta-NADH exhibited powerful stoichiometric H2O2 antioxidant properties. Further, beta-NADH may exert positive effects on PK activity. Subsequent pyruvic acid accumulation can lead to the recycling of beta-NAD+ through lactate dehydrogenase and beta-NADH through glyceraldehyde-3-phosphate dehydrogenase. It was concluded from these studies that intracellular pyruvic acid and beta-NADH appear to act in concert through glycolysis, to enhance H2O2 intracellular antioxidant capacity in neuroblastoma cells. Future research will be required to examine whether similar effects are observed in primary neuronal culture or intact tissue.

Oxidative stress and induction of heme oxygenase-1 in the kidney in sickle cell disease

Chronic nephropathy is a recognized complication of sickle cell disease. Using a transgenic sickle mouse, we examined whether oxidative stress occurs in the sickle kidney, the origins and functional significance of such oxidant stress, and the expression of the oxidant-inducible, potentially protective gene, heme oxygenase-1 (HO-1); we also examined the expression of HO-1 in the kidney and in circulating endothelial cells in sickle patients. We demonstrate that this transgenic sickle mouse exhibits renal enlargement, medullary congestion, and a reduced plasma creatinine concentration. Oxidative stress is present in the kidney as indicated by increased amounts of lipid peroxidation; heme content is markedly increased in the kidney. Exacerbation of oxidative stress by inhibiting glutathione synthesis with buthionine-sulfoximine dramatically increased red blood cell sickling in the sickle kidney: in buthionine-sulfoximine-treated sickle mice, red blood cell sickling extended from the medulla into the cortical capillaries and glomeruli. HO activity is increased in the sickle mouse kidney, and is due to induction of HO-1. In the human sickle kidney, HO-1 is induced in renal tubules, interstitial cells, and in the vasculature. Expression of HO-1 is increased in circulating endothelial cells in patients with sickle cell disease. These results provide the novel demonstration that oxidative stress occurs in the sickle kidney, and that acute exacerbation of oxidative stress in the sickle mouse precipitates acute vaso-occlusive disease. Additionally, the oxidant-inducible, heme-degrading enzyme, HO-1, is induced regionally in the murine and human sickle kidney, and systemically, in circulating endothelial cells in sickle patients.

H2O2-induced block of glycolysis as an active ADP-ribosylation reaction protecting cells from apoptosis

H2O2 treatment on U937 cells leads to the block of glycolytic flux and the inactivation of glyceraldehyde-3-phosphate-dehydrogenase by a posttranslational modification (possibly ADP-ribosylation). Glycolysis spontaneously reactivates after 2 h of recovery from oxidative stress; thereafter cells begin to undergo apoptosis. The specific ADP-ribosylation inhibitor 3-aminobenzamide inhibits the stress-induced inactivation of glyceraldehyde-3-phosphate-dehydrogenase and the block of glycolysis; concomitantly, it anticipates and increases apoptosis. Exogenous block of glycolysis (i.e., by culture in glucose-free medium or with glucose analogs or after NAD depletion), turns the transient block into a stable one: this results in protection from apoptosis, even when downstream cell metabolism is kept active by the addition of pyruvate. All this evidence indicates that the stress-induced block of glycolysis is not the result of a passive oxidative damage, but rather an active cell reaction programmed via ADP-ribosylation for cell self-defense.

Angiotensin II induces renal oxidant stress in vivo and heme oxygenase-1 in vivo and in vitro

BACKGROUND

Angiotensin II is strongly incriminated in progressive renal injury. There is recent evidence that angiotensin II induces oxidative stress in vitro. We examined the capacity of angiotensin II to induce oxidative stress in vivo and the functional significance of such stress. The capacity of angiotensin II to induce the oxidant-sensitive gene heme oxygenase (HO) in vivo and in vitro was also examined.

METHODS

Angiotensin II was administered via mini-osmotic pumps to rats maintained on standard diets. Indices of oxidative stress, including thiobarbituric acid reactive substance, carbonyl protein content, and HO activity, were determined. Indices of oxidative stress and functional markers were also determined in the DOCA salt model. The effect of angiotensin II was studied in rats maintained on antioxidant-deficient diets so as to examine the functional significance of oxidative stress induced by angiotensin II. We also explored the inductive effect of angiotensin II on HO in vivo and whether such actions occur in vitro.

RESULTS

Angiotensin II administered in vivo increased kidney content of thiobarbituric acid reactive substances protein carbonyl content, and HO activity. These indices were not present in the kidney of rats treated with DOCA salt for three weeks. Such oxidative stress was functionally significant, since the administration of angiotensin II to rats maintained on a prooxidant diet demonstrated increased proteinuria and decreased creatinine clearance. The stimulatory effect on HO activity was due to induction of HO-1 mRNA, with HO-2 mRNA remaining unchanged. Expression of HO-1 was localized to the renal proximal tubules in vivo. We also demonstrate that angiotensin II at concentrations of 10-8 and 10-7 mol/L induces expression of HO-1 mRNA in LLC-PK1 cells.

CONCLUSIONS

Angiotensin II induces oxidative stress in vivo, which contributes to renal injury. This study also demonstrates that angiotensin II induces renal HO activity caused by up-regulation of HO-1 in renal proximal tubules. Finally, angiotensin II directly induces HO-1 in renal proximal tubular epithelial cells in vitro.

Renal response to repetitive exposure to heme proteins: chronic injury induced by an acute insult

BACKGROUND

Renal diseases are conventionally classified into acute and chronic disorders. We questioned whether acute, reversible, renal insults may be induced to incite a chronic scarring process, employing as an acute insult the glycerol model of heme protein-induced renal injury.

METHODS

Rats were subjected to weekly injections of hypertonic glycerol for up to six months. Renal function was serially determined, and the effect of such insults on renal histology and renal expression of collagen and fibrogenic cytokines was assessed.

RESULTS

After the first injection of glycerol, which, expectedly, induced a prompt fall in the glomerular filtration rate (GFR), subsequent injections encountered a remarkable renal resistance in that the fall in GFR was markedly blunted. This resistance to acute decline in renal function in rats subjected to repetitive injections of glycerol was accompanied by less necrosis and apoptosis of renal tubular epithelial cells after such injections. The attenuation in the fall in GFR in response to repetitive exposure to glycerol-induced heme protein injury was maintained for up to six months. A progressive decline in GFR appeared after three months and was accompanied by histologic tubulointerstitial injury, the latter assessed at six months. These kidneys demonstrated up-regulation of collagen I, III, and IV in conjunction with increased expression of the oxidant-inducible, chemotactic cytokine, monocyte chemoattractant protein-1 (MCP-1), and the oxidant-inducible, fibrogenic cytokine, transforming growth factor-beta1 (TGF-beta1). The exposure of the kidney to a single injection of hypertonic glycerol increased the expression of both cytokines some three to five days following this exposure, while the exposure of NRK 49F cells in culture to an iron-dependent model of oxidative stress also increased expression of TGF-beta1 and collagen mRNAs.

CONCLUSIONS

We conclude that this nephrotoxic insult, repetitively administered, encounters a resistance in the kidney such that the expected fall in GFR does not occur. However, with time, such resistance is accompanied by a decrease in GFR, the latter associated with chronic tubulointerstitial disease. Thus, a long-term cost is exacted, either along with, or as a consequence of, such resistance. We suggest that chronic up-regulation of such oxidant-inducible genes such as TGF-beta1 and MCP-1 contributes to tubulointerstitial disease, and iron-mediated oxidative stress may directly induce TGF-beta1.

Pyruvate prevents peroxide-induced injury of in vitro preimplantation bovine embryos

The impact of oxidative stress on the in vitro development of bovine embryos in synthetic oviduct fluid medium (mSOF) was assessed by using H2O2 as a stress inducer. In a preliminary experiment, a chemiluminescent method was used to measure the antioxidative capacity of the mSOF culture medium. Pyruvate was the mSOF component displaying the highest H2O2 degrading ability. Essential and nonessential amino acids also significantly reduced the H2O2 concentration, whereas lactate and glutamine were ineffective. The effect on further development of a short exposure of zygotes, 9-16-cell stage embryos and blastocysts to 0 M; 10(-7) M ; 10(-6) M, and 10(-5) M H2O2 in pyruvate-free mSOF was evaluated. Developmental rates of the H2O2-treated zygotes to the 5-8-cell or blastocyst stages and survival of H2O2-treated blastocysts were reduced in a dose-dependent manner whereas the 9-16-cell embryos were unaffected by those treatments. Blastocysts treated with H2O2 also tended to have lower numbers of bisbenzimide-stained nuclei and showed increased nuclear fragmentation. Including pyruvate in the mSOF culture medium during a 10(-5) M H2O2 pulse highly reduced the H2O2 concentration as measured by chemiluminescence and improved zygote and blastocyst development, but failed to prevent blastocyst nuclei degradation. These experiments suggest that bovine embryos show developmental change in sensitivity to exogenous H2O2, the 9-16-cell embryos being more resistant than zygotes and blastocysts and that H2O2 and its toxic effects can be attenuated by including pyruvate in the medium.

Effects of calorie restriction and ω-3 dietary fat on aging in short-and long-lived rodents

Aging is accompanied by a steady increase in the incidence of spontaneous tumors and a decline in immune function. Calorie restriction (CR) or supplementation with ω-3 fats prolongs life span, suppresses tumorigenesis, and ameliorates immune function in a variety of experimental models. We suggest that decreased oxidant stress and upregulation of apoptosis mediate the effects of calorie restriction on immunity and longevity. CR prolongs life span in several animal models and our studies have examined the effects of CR on the immune system and on tumorigenesis. CR maintains naive T cells, prevents the rise in "double-negative" T cells, maintains lymphocyte responsiveness to mitogens, and preserves Dexamethasone induced apoptosis in spleen cells of MRL/Ipr mice. CR also modulates the expression of inflammatory mediators and cytokines. CR decreases the Sjögren's syndrome-like chronic inflammation of salivary glands of B/W animals while increasing expression of the immunosuppressive cytokine TGFβ1 and decreasing expression of the pro-inflammatory cytokines IL-6 and TNFα. The autoimmune disease in the B/W mouse also affects the kidneys, and we find that renal expression of platelet derived growth factor-A, (PDGF-A) and thrombin receptor are decreased in CR animals. Similarly, CR decreases the expression and localization of plasminogen activator inhibitor type 1 in glomeruli of B/W animals. CR also modulates expression and function of androgen receptors and the binding of insulin to liver nuclei. Finally, CR suppresses the development of breast tumors in the Ras oncomouse. These effects of calorie restriction are paralleled in short-lived B/W animals fed diets supplemented with ω-3 fatty acids. Omega-3 fatty acids induce the expression of hepatic antioxidant enzymes, and enhance apoptosis in lymphocytes of B/W animals.

Clusterin protects against oxidative stress in vitro through aggregative and nonaggregative properties

Perturbations of cell interactions, an early event in acute renal injury, have important pathophysiologic consequences. We hypothesized that promotion of cell interactions protects cells from injury. To test this hypothesis, a single cell suspension of LLC-PK1 cells (porcine proximal tubular cell line) treated with albumin (control) was compared to cells aggregated with fibrinogen or purified human clusterin (aggregation graded 0 to 4). Following aggregation, the cells were injured with 1.5 mM hydrogen peroxide (H2O2) for three hours. Cell aggregation induced by clusterin but not fibrinogen protected against oxidant injury by H2O2. Complete abrogation of cytotoxicity occurred at a clusterin concentration of 2.5 micrograms/ml, which resulted in an aggregation score of 1. In the absence of aggregation, clusterin at concentrations of 20 and 50 micrograms/ml, but not lower doses, partially protected against injury induced by H2O2. Cell aggregation induced by both clusterin and fibrinogen partially protected against endogenously generated oxidant stress induced by incubating LLC-PK1 cells with aminotriazole and 1-chloro-2,4-dinitrobenzene (CDNB). In conclusion, clusterin protects against models of oxidant stress in vitro, whether generated by exogenously administered hydrogen peroxide, or from endogenously produced peroxide, and such protective effects can accrue from aggregative and nonaggregative properties of clusterin.

Differential effects of glutathione and cysteine on Fe2+, Fe3+, H2O2 and myoglobin-induced proximal tubular cell attack

Glutathione (GSH) is widely advocated as a cytoprotectant for preventing oxidant forms of renal damage. However, in the case of myoglobinuric tubular injury, both beneficial and adverse effects have been noted. The purpose of this study was to help elucidate this seeming paradox by assessing the impact on thiol supplementation on normal tubules and on tubules subjected to individual components of heme protein-induced oxidant attack (Fe2+, Fe3+, and H2O2). Isolated mouse proximal tubular segments (PTS) were exposed to either GSH or cysteine under normal conditions or in the presence of exogenous Fe2+, Fe3+, or H2O2. Lethal cell injury (LDH release) and lipid peroxidation (malondialdehyde) were then assessed. GSH and cysteine exerted iron dependent, H2O2 independent, pro-oxidant effects on normal PTS. Both were also pro-oxidant in the presence of an exogenous Fe3+ challenge. In contrast, each attenuated Fe2+ cytotoxicity. The importance of iron's redox status on the expression of tubular injury was further underscored by the fact that Fe3+ partially blocked Fe2+'s cytotoxic effects. GSH mitigated H2O2 toxicity (consistent with a fueling of GSH peroxidase activity). Conversely, cysteine promoted H2O2's injurious effects. To assess the impact of thiol supplementation on a fully integrated model of heme protein toxicity, proximal tubular (HK-2) cells were cultured with myoglobin x 24 hours +/- test reactants. Exogenous GSH worsened, while GSH depletion (BSO) protected, against myoglobin toxicity (indicating a predominance of GSH's pro-oxidant effects). Conversely, cysteine (but not homocysteine) decreased myoglobin toxicity. These GSH/cysteine effects were confirmed in LLC-PK1 cells subjected to iron attack. We conclude that: (1) GSH and cysteine can exert pro- and anti-oxidant effects, depending on the nature of the oxidant challenge and iron's redox status; (2) Fe3+ can function as a cytoprotectant, partially offsetting Fe2+ toxicity; and (3) cysteine, although potentially pro-oxidant, can mitigate heme protein-induced injury. Since the kidney rapidly catabolizes GSH to cysteine, the latter may be at least partially responsible for GSH's reported cytoprotective actions against myoglobinuric acute renal failure.

Redox regulation of renal DNA synthesis, transforming growth factor-beta1 and collagen gene expression

Growth and injury represent recurrent and related themes in the study of progressive renal disease. We have previously demonstrated that a prooxidant diet, one deficient in antioxidants, selenium and vitamin E, induces renal enlargement, proteinuria, mild tubulointerstitial disease and diminished glomerular filtration rate (GFR). Our present study represents continued examination of these processes. We demonstrate that these diets increase thymidine incorporation into DNA and net DNA content in renal tissue, and induce expression of the mRNA for the proto-oncogene, c-myc, and the histone, H2b. We localize increased DNA synthesis as occurring mainly in the distal renal tubular epithelium. These deficient kidneys also exhibit interstitial expansion that parallels the pattern of DNA synthesis in that both processes are more prominent in the medulla than in the cortex. mRNAs for collagens I, III and IV in conjunction with transforming growth factor-beta1 (TGF-beta1) are up-regulated in the kidney in rats maintained on the deficient diet. In complementary in vitro studies, the exposure of rat kidney fibroblasts, NRK 49F cells, to noncytolytic doses of hydrogen peroxide, induces collagen III, collagen IV and TGF-beta1 mRNA. Induction of these genes is also observed in mesangial cells so exposed to noncytolytic doses of hydrogen peroxide. A final aspect of our study was the examination of renal generation of hydrogen peroxide and the profile of the hydrogen peroxide-degrading enzymes. Deficient kidneys exhibit increased mitochondrial generation of hydrogen peroxide independent of oxygen consumption but in conjunction with suppression of glutathione peroxidase mRNA and activity. Lipid peroxidation was increased twofold in the cortex and medulla of the deficient kidneys. Surprisingly, catalase activity, measured in the cortex and medulla, and whole kidney catalase mRNA were also reduced in rats maintained on the antioxidant deficient diet, effects that may further compromise the clearance of hydrogen peroxide. These changes in catalase represent an adverse response to this dietary deficiency, and may be relevant to decreased catalase activity described in chronic renal insufficiency. Thus, a chronic prooxidant state, with features that mimic those of clinical uremia, increases DNA synthesis of renal tubular epithelium, induces mRNA expression for collagens I, III and IV in conjunction with the mRNA for the fibrogenic cytokine, TGF-beta1. Oxidants also induce collagen III, collagen IV and TGF-beta1 mRNA in vitro.

A mixture of antioxidants and fatty acids improves the viability of cultured rat hepatocytes untreated or treated with doxorubicin

The objective of this study was to determine whether medium supplementation by antioxidants and fatty acids would improve the viability of cultured rat hepatocytes and protect them against doxorubicin toxicity. We examined the effects of three agents: vitamin E, sodium pyruvate and egg yolk (the combination of vitamin E, sodium pyruvate and fatty acids is a proprietary, patented technology of Warner Lambert called CRT) 0.3% (v/v) as a source of fatty acids, on cell viability measured by the dehydrogenase-dependent bioreduction of a tetrazolium salt (MTS). Untreated hepatocytes and hepatocytes treated with carbon tetrachloride (CCl(4), EC(50) 5.7 mm) or doxorubicin (1 and 30 mum) were exposed to different amounts of a mixture of antioxidants and fatty acids. The mixture, identified as 1X, provided a final concentration of 5 units of vitamin E, 0.1% egg yolk and 10 mm sodium pyruvate while the 3X and 5X mixtures contained proportionately higher concentrations of these components. The mixtures were added 18 hr prior to, simultaneously with or following treatment with doxorubicin and just simultaneously with CCl(4). Neither vitamin E, sodium pyruvate nor egg yolk alone improved viability. However, the viability of untreated hepatocytes improved significantly when the 3X mixture was added after 18 hr as indicated by determination of MTS reduction activity 24 hr later. The viability of doxorubicin treated cultures (1 and 30 mum) increased significantly when exposed either to the 3X or 5X mixtures simultaneously. A significant increase in viability was also seen when cells were exposed to the 3X mixture following doxorubicin (1 mum). The mixtures did not protect against toxicity caused by CCl(4), perhaps due to the overwhelming level of damage at its EC(50) concentration. It is proposed that the antioxidant properties of vitamin E and sodium pyruvate protect the cells from low levels of reactive oxygen species generated spontaneously in culture and by doxorubicin metabolism while the fatty acids help to maintain the integrity of hepatocyte membranes, resulting in greater viability of the hepatocytes.

Inhibition of human lymphocyte function by organic solvents

We studied the direct effect of reactive hydroxyl precursors and inhibitors on CD4+ T-cell function. We used hydrogen peroxide plus ferrous chloride as the hydroxyl radical-generating system and di-methyl sulphourea, di-methyl sulfoxide, pyrrolidine dithiocarbonate, methanol, and ethanol, at a noncytotoxic concentration, as inhibitors. The immune parameter studies were proliferation and interleukin-2 production by peripheral blood lymphocytes stimulated with anti-CD3 antibody, phytohemagglutinin and alloantigens; proliferation, interleukin-2 production and mRNA expression of interleukin-4 and interferon gamma by allogeneic CD4+ T-cell clones stimulated with alloantigens. The results show that lymphocytes produce significant amounts of reactive oxygen species as measured by malondialdehyde produced in cultures. The hydroxyl radical-generating system did not change any of the cellular responses studied although it doubled Malondialdehyde production. Hydroxyl radical scavengers significantly inhibited all responses at doses that didn't significantly decrease malondialdehyde production. DNA analysis failed to show evidence for apoptosis.

CONCLUSION

Hydroxyl radical scavengers inhibit lymphocyte mitogenesis by a process that is independent of scavenging hydroxyl radicals.

Lack of expression of the global regulator OxyR in Haemophilus influenzae has a profound effect on growth phenotype

A pBR322-based library of chromosomal DNA from the nontypeable Haemophilus influenzae TN106 was screened for the expression of transferrin-binding activity in Escherichia coli. A recombinant clone expressing transferrin-binding activity contained a 3.7-kb fragment of nontypeable H. influenzae DNA. Nucleotide sequence analysis of this insert revealed the presence of two complete open reading frames encoding proteins of approximately 26 and 34 kDa. Mini-Tn10kan transposon mutagenesis at different sites within the open reading frame encoding the 34-kDa protein resulted in the abolition of transferrin-binding activity in the recombinant E. coli clone. The deduced amino acid sequence of the 34-kDa protein had 70% identity with the OxyR protein of E. coli; this latter macromolecule is a member of the LysR family of transcriptional activators. When a mutated H. influenzae oxyR gene was introduced into the chromosome of the wild-type H. influenzae strain by allelic exchange, the resulting oxyR mutant still exhibited wild-type levels of transferrin-binding activity but was unable to grow on media containing the heme precursor protoporphyrin IX (PPIX) in place of heme. This mutant also exhibited reduced growth around disks impregnated with heme sources. Supplementation of the PPIX-based growth media with catalase or sodium pyruvate resulted in normal growth of the H. influenzae oxyR mutant. Provision of the wild-type H. influenzae oxyR gene in trans also permitted the growth of this mutant on a PPIX-based medium. Exogenously supplied catalase restored the growth of this mutant with heme sources to nearly wild-type levels. These results indicate that expression of a wild-type OxyR protein by H. influenzae is essential to allow this organism to protect itself against oxidative stresses in vitro.

Differential cytoprotection by glycine against oxidant damage to proximal tubule cells

Tert-butyl hydroperoxide (tBHP) injured freshly isolated proximal tubules in an Fe-dependent fashion that was ameliorated by a lipophilic antioxidant, diphenyl-p-phenylenediamine (DPPD), but was only minimally affected by glycine. Menadione-induced injury was Fe-independent and was unaffected by DPPD, but was strongly blocked by glycine. Fe was highly toxic when intracellular loading was facilitated by concomitant treatment with hydroxyquinoline (HQ). This toxicity was blocked by DPPD or chelating the Fe, but not by glycine. All of the lesions were characterized by severe depletion of glutathione and other soluble thiols. Menadione induced large increases in protein associated with the Triton-insoluble cytoskeleton and decreases in protein thiol content, consistent with extensive cross linking, but did not increase thiobarbituric acid reactive substances (TBARS). tBHP and HQ + Fe had either no effect or only moderate, delayed effects on cytoskeletal proteins, but induced substantial increases of TBARS. Glycine did not the alter changes in cytoskeletal proteins, thiols, or TBARS produced by any of the agents. Protection against tBHP toxicity by deferoxamine and DPPD was accompanied by substantial suppression of TBARS accumulation. Superimposition of hypoxia during tBHP exposure reduced TBARS accumulation and restored cytoprotective activity to glycine. Thus, in contrast to its consistently strong cytoprotection against a number of other insults, glycine is only variably cytoprotective against oxidant lesions in freshly isolated proximal tubules. Extensive oxidative crosslinking of proteins is compatible with maintenance of glycine cytoprotection against lethal membrane damage. Fe-induced injury to proximal tubules associated with lipid peroxidation as manifested by TBARS formation is a relatively glycine-insensitive insult.

Renal oxidant injury and oxidant response induced by mercury

The role of oxidative stress in mercuric chloride (HgCl2)-induced nephrotoxicity is uncertain and controversial. We demonstrate that I.L.C-PK1 cells, exposed to HgCl2, generate massive amounts of hydrogen peroxide, the latter completely quenched by the hydrogen peroxide scavenger, pyruvate. HgCl2 exerts a dose-dependent cytotoxicity which is attenuated by pyruvate and catalase. Cellular generation of hydrogen peroxide arises, at least in part, from mitochondria since mitochondrial rates of generation of hydrogen peroxide increase in response to HgCl2; HgCl2 also provokes a shift in absorbance spectra in rhodamine 123 loaded-mitochondria and stimulates mitochondrial state 4 respiration. HgCl2, applied for one hour, impairs cellular vitality as demonstrated by the MTT assay, an assay dependent in part on mitochondrial function. HgCl2 impairs function in other organelles such as lysosomes that maintain a transmembrane proton gradient; these latter effects are partially attenuated by pyruvate. We complement these in vitro findings with in vivo evidence demonstrating that HgCl2 stimulates renal generation of hydrogen peroxide. The functional significance of such generation of hydrogen peroxide was evaluated in rats deficient in selenium and vitamin E, a nutrient deficiency that impairs the scavenging of hydrogen peroxide and promotes the toxicity of this oxidant. In these rats serum creatinine values were significantly higher on sequential days following the administration of HgCl2. To probe the renal response to oxidative stress induced by HgCl2, we examined hydrogen peroxide-scavenging enzymes and redox-sensitive genes. Catalase activity was unaltered whereas glutathione peroxidase activity was decreased, effects that may contribute to the net renal generation of hydrogen peroxide. The redox sensitive enzyme, heme oxygenase, was markedly up-regulated in the kidney in response to HgCl2. HgCl2 also induced members of the bcl family, bcl2 and bclx, genes that protect against apoptosis and oxidant injury. In another model of oxidant-induced renal injury, the glycerol model, bcl2 mRNA was not induced at 6 and 24 hours after the administration of glycerol. In summary, we demonstrate that HgCl2 potently stimulates renal generation of hydrogen peroxide in vitro and in vivo and such generation of peroxide contributes to renal dysfunction in vitro and in vivo. We also demonstrate that in response to HgCl2, redox sensitive genes are expressed including heme oxygenase and members of the bcl family.

Oxidative stress induces tyrosine phosphorylation of PDGF alpha-and beta-receptors and pp60c-src in mesangial cells

Reactive oxygen species are autocrine and paracrine modulators of cell behavior. Hydrogen peroxide, a cellular oxidant, has been shown to stimulate mesangial cell proliferation. In the present study we analyzed the H2O2-induced early signaling events. Immunofluorescence analysis revealed a H2O2 induced dose-dependent increase in tyrosine phosphorylation. Short treatment (2 or 5 min) with 5 mM H2O2 induced a mitogenic response and a significant (P < 0.01) increase in the number of cells compared to non-treated controls. Proteins extracted from H2O2 (0.1 to 10 mM) treated cells were separated on SDS-PAGE and subjected to immunoblot analysis with anti-phosphotyrosine. A dose-dependent induction of tyrosine phosphorylation of 180 kDa, 120 kDa and 60 kDa proteins was observed within 1 to 10 minutes. By sequentially using immunoprecipitation and immunoblotting the 180 kDa tyrosine phosphorylated band was shown to represent both PDGF alpha- and beta-receptors. The tyrosine phosphorylated 60 kDa protein was identified as the cytoplasmic protein tyrosine kinase pp60c-src. The c-src phosphorylation was associated with an inhibition of c-src kinase activity, suggesting phosphorylation of tyrosine 527 in the c-src regulatory domain. Pretreatment with catalase completely abrogated the H2O2-induced PDGF receptor and c-src tyrosine phosphorylation. These data support the notion that the activation of a signaling pathway involving the PDGF receptors and c-src contributes to the mitogenic effects of reactive oxygen species.

The use of antioxidants in healing

BACKGROUND

Antioxidants enhance the healing of infected and noninfected wounds by reducing the damage caused by oxygen radicals.

OBJECTIVE

Studies were conducted to determine if the CTR components (vitamin E, sodium pyruvate, and specific fatty acids) could synergistically enhance healing.

METHODS

In vitro and in vivo studies were used to assess the effect of various combinations of CRT components.

RESULTS

CTR reduced oxidative damage to keratinocytes and monocytes exposed to ultraviolet light and toxic chemicals and provided protection to human subjects exposed to ultraviolet irradiation. CTR dramatically facilitated healing of infected and noninfected wounds. In herpes-infected guinea pigs, CTR reduced vaginal viral lesion development, severity, and duration, thus facilitated healing of the lesions. CTR also reversed doxorubicin cytotoxicity in monocytes and reversed doxorubicin-impaired wound healing in rats.

CONCLUSION

The CTR components worked synergistically to enhancing healing of injuries.

Heme protein-mediated renal injury: a protective role for 21-aminosteroids in vitro and in vivo

21-aminosteroids ("lazaroids") have recently excited much interest by virtue of their ability to inhibit lipid peroxidation in vitro and to protect against neural injury in vivo. We tested the effect of these compounds in models of heme protein-mediated renal injury in vitro and in vivo. We devised an in vitro model of heme protein-induced toxicity in which renal epithelial cells were exposed to heme proteins for one hour, after which they were subjected to glutathione depletion by 1-chloro-2,4-dinitrobenzene (CDNB). This model was associated with more than a threefold increase in lipid peroxidation (as measured by thiobarbituric acid reactive substances, TBARS) and a marked reduction in cellular glutathione content. In this model, 21-aminosteroids virtually prevented cytotoxicity as measured by the 51-chromium release assay, and significantly reduced TBARS in a dose-dependent manner. Catalase was partially protective in this model, thereby indicating hydrogen peroxide-dependent toxicity. While pursuing mechanisms accounting for enhanced cellular generation of hydrogen peroxide, we uncovered the first direct evidence that the heme prosthetic group per se directly stimulates cellular generation of hydrogen peroxide; complementing these findings is the remarkable efficacy of 21-aminosteroids in protecting against cytotoxicity induced by hydrogen peroxide. We also tested the capacity of 21-aminosteroids to protect against heme protein-mediated renal injury in vivo. Prior administration of 21-aminosteroids attenuated reductions in GFR and renal blood flow rates following the systemic infusion of methemoglobin in normal rats. 21-aminosteroids also attenuated renal injury observed over three successive days in the glycerol model of heme protein-mediated injury when this model was induced at a higher dose of glycerol (8 ml/kg body wt) but not at a lower dose (5 ml/kg body wt). We conclude that 21-aminosteroids protect against heme protein-mediated renal injury in vitro and in vivo. We suggest that these compounds are potentially useful in such clinical conditions as rhabdomyolysis, intravascular hemolysis and renal injury associated with hemoglobin-based red blood cell substitutes.