NF-kappa B transcription factor activation by hydrogen peroxide can be decreased by 2,3-dihydroxybenzoic acid and its ethyl ester derivative

Iron supplementation and paediatric HIV disease progression: a cohort study among children receiving routine HIV care in Dar es Salaam, Tanzania

BACKGROUND

Anaemia is common among HIV-infected children and iron supplementation is prescribed routinely for the prevention and management of anaemia among children. Limited evidence suggests iron supplementation may have adverse effects among HIV-infected populations. We aimed to estimate the effect of iron supplement use on mortality, disease progression and haematological outcomes among HIV-infected children in Dar es Salaam, Tanzania.

METHODS

A prospective cohort study was conducted among HIV-infected children (aged 0-14 years) receiving antiretroviral treatment or supportive care between October 2004 and September 2014. Clinical data were recorded on morbidity and vital status, haematological status and prescriptions at each clinical visit. Cox proportional hazards models adjusted for time-varying covariates were used to estimate the association of time-varying iron supplementation on the hazard rate of mortality, HIV disease stage progression, tuberculosis incidence and anaemia and microcytosis persistence.

RESULTS

In all, 4229 children were observed during 149 260 clinic visits for a mean follow-up of 2.9 years. After adjustment for time-varying clinical covariates, time-varying iron supplementation was associated with a 2.87 times higher hazard rate of mortality (95% CI: 1.70, 4.87) and a 1.48 times higher hazard rate of HIV disease stage progression (95% CI: 1.10, 1.98). Iron supplementation was also associated with a lower rate of anaemia persistence (HR = 0.47; 95% CI: 0.37, 0.61). No differences in the association between iron supplementation and clinical outcomes were observed by antiretroviral therapy or anaemia status.

CONCLUSIONS

Iron supplementation may increase the risk of HIV disease stage progression and mortality among HIV-infected children, while reducing the risk of anaemia.

Mechanisms underlying Nrf2 nuclear translocation by non-lethal levels of hydrogen peroxide: p38 MAPK-dependent neutral sphingomyelinase2 membrane trafficking and ceramide/PKCζ/CK2 signaling

Hydrogen peroxide is an aerobic metabolite playing a central role in redox signaling and oxidative stress. H₂O₂ could activate redox sensitive transcription factors, such as Nrf2, AP-1 and NF-κB by different manners. In some cells, treatment with non-lethal levels of H₂O₂ induces rapid activation of Nrf2, which upregulates expression of a set of genes involved in glutathione (GSH) synthesis and defenses against oxidative damage. It depends on two steps, the rapid translational activation of Nrf2 and facilitation of Nrf2 nuclear translocation. We review the molecular mechanisms by which H₂O₂ induces nuclear translocation of Nrf2 in cultured cells by highlighting the role of neutral sphingomyelinase 2 (nSMase2), a GSH sensor. H₂O₂ enters cells through aquaporin channels in the plasma membrane and is rapidly reduced to H₂O by GSH peroxidases to consume cellular GSH, resulting in nSMase2 activation to generate ceramide. H₂O₂ also activates p38 MAP kinase, which enhances transfer of nSMase2 from perinuclear regions to plasma membrane lipid rafts to accelerate ceramide generation. Low levels of ceramide activate PKCζ, which then activates casein kinase 2 (CK2). These protein kinases are able to phosphorylate Nrf2 to stabilize and activate it. Notably, Nrf2 also binds to caveolin-1 (Cav1), which protects Nrf2 from Keap1-mediated degradation and limits Nrf2 nuclear translocation. We propose that Cav1serves as a signaling hub for the control of H₂O₂-mediated phosphorylation of Nrf2 by kinases, which results in release of Nrf2 from Cav1 to facilitate nuclear translocation. In summary, H₂O₂ induces GSH depletion which is recovered by Nrf2 activation dependent on p38/nSMase2/ceramide signaling.

Plant-Derived and Dietary Hydroxybenzoic Acids-A Comprehensive Study of Structural, Anti-/Pro-Oxidant, Lipophilic, Antimicrobial, and Cytotoxic Activity in MDA-MB-231 and MCF-7 Cell Lines

Seven derivatives of plant-derived hydroxybenzoic acid (HBA)—including 2,3-dihydroxybenzoic (2,3-DHB, pyrocatechuic), 2,4-dihydroxybenzoic (2,4-DHB, β-resorcylic), 2,5-dihydroxybenzoic (2,5-DHB, gentisic), 2,6-dihydroxybenzoic (2,6-DHB, γ-resorcylic acid), 3,4-dihydroxybenzoic (3,4-DHB, protocatechuic), 3,5-dihydroxybenzoic (3,5-DHB, α-resorcylic), and 3,4,5-trihydroxybenzoic (3,4,5-THB, gallic) acids—were studied for their structural and biological properties. Anti-/pro-oxidant properties were evaluated by using DPPH^• (2,2-diphenyl-1-picrylhydrazyl), ABTS^•+ (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (ferric-reducing antioxidant power), CUPRAC (cupric-reducing antioxidant power), and Trolox oxidation assays. Lipophilicity was estimated by means of experimental (HPLC) and theoretical methods. The antimicrobial activity against Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), Salmonella enteritidis (S. enteritidis), and Candida albicans (C. albicans) was studied. The cytotoxicity of HBAs in MCF-7 and MDA-MB-231 cell lines was estimated. Moreover, the structure of HBAs was studied by means of experimental (FTIR, ¹H, and ¹³C NMR) and quantum chemical DFT methods (the NBO and CHelpG charges, electrostatic potential maps, and electronic parameters based on the energy of HOMO and LUMO orbitals). The aromaticity of HBA was studied based on the calculated geometric and magnetic aromaticity indices (HOMA, Aj, BAC, I6, NICS). The biological activity of hydroxybenzoic acids was discussed in relation to their geometry, the electronic charge distribution in their molecules, their lipophilicity, and their acidity. Principal component analysis (PCA) was used in the statistical analysis of the obtained data and the discussion of the dependency between the structure and activity (SAR: structure–activity relationship) of HBAs. This work provides valuable information on the potential application of hydroxybenzoic acids as bioactive components in dietary supplements, functional foods, or even drugs.

Hydroxybenzoic acid isomers and the cardiovascular system

Today we are beginning to understand how phytochemicals can influence metabolism, cellular signaling and gene expression. The hydroxybenzoic acids are related to salicylic acid and salicin, the first compounds isolated that have a pharmacological activity. In this review we examine how a number of hydroxyphenolics have the potential to ameliorate cardiovascular problems related to aging such as hypertension, atherosclerosis and dyslipidemia. The compounds focused upon include 2,3-dihydroxybenzoic acid (Pyrocatechuic acid), 2,5-dihydroxybenzoic acid (Gentisic acid), 3,4-dihydroxybenzoic acid (Protocatechuic acid), 3,5-dihydroxybenzoic acid (α-Resorcylic acid) and 3-monohydroxybenzoic acid. The latter two compounds activate the hydroxycarboxylic acid receptors with a consequence there is a reduction in adipocyte lipolysis with potential improvements of blood lipid profiles. Several of the other compounds can activate the Nrf2 signaling pathway that increases the expression of antioxidant enzymes, thereby decreasing oxidative stress and associated problems such as endothelial dysfunction that leads to hypertension as well as decreasing generalized inflammation that can lead to problems such as atherosclerosis. It has been known for many years that increased consumption of fruits and vegetables promotes health. We are beginning to understand how specific phytochemicals are responsible for such therapeutic effects. Hippocrates’ dictum of ‘Let food be your medicine and medicine your food’ can now be experimentally tested and the results of such experiments will enhance the ability of nutritionists to devise specific health-promoting diets.

A review of current intravaginal drug delivery approaches employed for the prophylaxis of HIV/AIDS and prevention of sexually transmitted infections

The objective of this review is to describe the current status of several intravaginal anti-HIV microbicidal delivery systems these delivery systems and microbicidal compounds in the context of their stage within clinical trials and their potential cervicovaginal defence successes. The global Human Immuno-Deficiency Virus (HIV) pandemic continues to spread at a rate of more than 15,000 new infections daily and sexually transmitted infections (STIs) can predispose people to acquiring HIV infection. Male-to-female transmission is eight times more likely to occur than female-to-male transmission due to the anatomical structure of the vagina as well as socio-economic factors and the disempowerment of women that renders them unable to refuse unsafe sexual practices in some communities. The increased incidence of HIV in women has identified the urgent need for efficacious and safe intravaginal delivery of anti-HIV agents that can be used and controlled by women. To meet this challenge, several intravaginal anti-HIV microbicidal delivery systems are in the process of been developed. The outcomes of three main categories are discussed in this review: namely, dual-function polymeric systems, non-polymeric systems and nanotechnology-based systems. These delivery systems include formulations that modify the genital environment (e.g. polyacrylic acid gels and lactobacillus gels), surfactants (e.g. sodium lauryl sulfate), polyanionic therapeutic polymers (e.g. carageenan and carbomer/lactic acid gels), proteins (e.g. cyanovirin-N, monoclonal antibodies and thromspondin-1 peptides), protease inhibitors and other molecules (e.g. dendrimer based-gels and the molecular condom). Intravaginal microbicide delivery systems are providing a new option for preventing the transmission of STIs and HIV.

Low-dose iron supplementation does not increase HIV-1 load

Observational data suggest that iron may increase HIV replication and the rate of progression of HIV infection. This is worrying, and may impede the international commitment to combat iron deficiency. However, it is crucial to clarify the role of iron in HIV infections, since iron is universally administered to anaemic patients and pregnant women, even in areas with high HIV prevalence. Based on a historical iron trial, we assessed the effect of 60 mg of elemental iron given twice weekly over four month on HIV-1 viral load. There was no effect on viral load, but effects of higher doses of iron cannot be excluded.

Ultraviolet A Radiation-Induced Immediate Iron Release Is a Key Modulator of the Activation of NF-κB in Human Skin Fibroblasts

Ultraviolet A (UVA, 320-400 nm) radiation, an oxidizing component of sunlight, leads to an immediate increase in the labile iron in human skin fibroblasts. Exposure of skin fibroblasts to UVA radiation is also known to induce nuclear factor-kappaB (NF-kappaB) DNA-binding activity, although the underlying mechanism is unclear. We report here that in skin fibroblasts, the extent of NF-kappaB activation by UVA tightly correlates with the level of "UVA-induced" labile iron release as shown by both iron chelation and iron loading treatments. Furthermore, our data indicate that the slow kinetics of induction of NF-kappaB by UVA relative to other oxidants previously studied is due to a transient increase in permeability of nuclear membrane to proteins and occurs as a result of labile iron-mediated damage to nuclear membrane. Since in addition to iron chelators, lipid peroxidation inhibitors also decrease the UVA-mediated induction of NF-kappaB, we propose that the rapid release of labile iron by UVA might act as a catalyst to exacerbate the generation of lipid secondary messengers in skin cell membranes that are responsible for induction of NF-kappaB. This novel role for iron in amplifying NF-kappaB mobilization in response to UVA-induced oxidative stress aids understanding of its involvement in UV-induced skin inflammation.

Iron, haptoglobin phenotype, and HIV-1 viral load: a cross-sectional study among pregnant Zimbabwean women

BACKGROUND

Viral load is a determinant of HIV-1 progression and transmission. Iron status and the phenotype of haptoglobin, a heme-binding acute phase reactant, may be determinants of viral load. We aimed to describe the effect of iron status, haptoglobin phenotype (Hp), and other predictors on HIV-1 viral load.

METHODS

Based on a cross-sectional study among 1669 antenatal care attenders (22-35 weeks) in Zimbabwe, 526 (31.5%) were found to be HIV infected. The role of season, age, gravidity, gestational age, malaria parasitemia, Hp, and elevated serum alpha(1)-antichymotrypsin (ACT) as well as serum ferritin, folate, retinol, and beta-carotene on HIV viral load among the 526 HIV-infected women was assessed using multiple linear regression analysis.

RESULTS

The distribution of Hp 1-1 (32%), Hp 2-1 (48%), and Hp 2-2 (20%) was not different from that of 53 uninfected women. Mean viral load was 3.85 log(10) (95% CI: 3.77-3.93) genome equivalents (geq)/mL, ranging from 3.77 (95% CI: 3.64-3.90) geq/mL in women with Hp 1-1 to 4.05 (95% CI: 3.81-4.21) geq/mL in women with Hp 2-2. With elevated serum ACT controlled for, women with Hp 2-2 had viral loads twice (95% CI: 1.4-4.0, p =.002) that of women with Hp 1-1, whereas those with serum ferritin <6 micro g/L had viral loads less than one third (95% CI: 0.13-0.53, p =.013) that of women with serum ferritin >24 micro g/L. Viral loads were also higher in women enrolled in the early rainy season compared with the dry season, in gravidae 4+ compared with gravidae 1 through 3, and in those with moderately elevated compared with low serum alpha(1)-antichymotrypsin, but neither age, gestational age, serum folate, serum retinol, nor serum beta-carotene were predictors.

CONCLUSION

Storage iron, Hp 2-2, and elevated ACT are independent positive predictors of HIV-1 viral load. The positive relationship between serum ferritin and viral load was not the result of an acute phase response or iron accumulation with advanced HIV infection. A possible detrimental role of iron in HIV infection would have serious public health implications.

The effect of hypochlorous acid on the expression of adhesion molecules and activation of NF-kappaB in cultured human endothelial cells

Exposure to oxidants can up-regulate the expression of adhesion molecules in endothelial cells with a consequent increase in neutrophil attachment. Similarly, the transcription factor nuclear factor-kappaB (NF-kappaB), which controls the expression of the intercellular adhesion molecules (ICAMs), can also be activated by oxidants in some cells. We have investigated whether hypochlorous acid (HOCl), the major strong oxidant produced by neutrophils, can affect the expression of adhesion molecules on human umbilical vein endothelial cells (HUVEC) and promote neutrophil adhesion. We found that HOCl could induce an increase in neutrophil adhesion to the endothelial cells after 60 min of treatment. Activation of NF-kappaB could be detected under similar conditions. However, the dose of HOCl required for this effect resulted in considerable longer-term toxicity to the cells. Treatment of HUVEC with sublethal doses of HOCl had no effect on NF-kappaB activation, neutrophil adhesion, or the surface expression of E-selectin, ICAM-1, or P-selectin. However, pretreatment with low concentrations of HOCl prevented phorbol myristate acetate-induced von Willebrand factor expression (a marker for P-selectin). These results show that, unlike H(2)O(2), HOCl does not significantly enhance neutrophil attachment to the endothelium. Rather it may be able to inhibit the expression of adhesion molecules with important consequences for endothelial function and inflammatory vascular disease.

Free radical mediated photoreceptor damage in uveitis

Uveitis is a major cause of blindness, with the visual loss that occurs being due primarily to retinal tissue damage. The tissue damage is mediated mainly by phagocytic inflammatory cells, such as macrophages, by the release of various proteolytic enzymes, arachidonic acid metabolites, cytokines and free radicals. The latter are found to be potent cytotoxic agents that readily cause tissue damage by peroxidation of lipid cell membranes. Recent studies of experimental uveitis indicate that other potent oxidants are generated in uveitis by macrophages. One of these is ONOO-, which is formed from *NO and O(-)2. The macrophages generate *NO preferentially in the outer retina following iNOS expression. In these phagocytes, outer retinal proteins, especially arrestin, are found to be potent iNOS inducers. Current studies of RPE show that these cells protect the retina from ONOO- mediated damage in uveitis by releasing a novel protein called retinal pigment epithelial protective protein. This protein is found to suppress O(-)2 and *NO generation by the phagocytes, in both in vitro and in vivo uveitis models. The protective protein expression is restricted to RPE, its suppressive effect is a result of the inhibition of the phosphorylation of cytosolic proteins, p47-phox, required for the assembly of NADPH and activation of NFkappaB, which are required for generation of 0(-)2 and expression of iNOS respectively. Either pharmacologically or chemically, up-regulation of RPP generation could help in preventing retinal degeneration in uveitis or other degenerative dis

Differential regulation of inducible nitric oxide synthase gene expression by ethanol in the human intestinal epithelial cell line DLD-1

We have examined the regulation of inducible nitric oxide synthase (iNOS) gene expression by ethanol in monolayers of DLD-1 cells, an epithelial cell line derived from human intestinal adenocarcinoma. Optimum induction of iNOS mRNA in these cells was obtained with IFN-gamma and IL-1beta treatment, while further addition of TNF-alpha did not have significant effect. In a set of experiments to study ethanol effects, DLD-1 monolayers were pretreated with ethanol for 24 h and were then treated with IFN-gamma + IL-1beta for an additional 24 h. Cells pretreated with ethanol showed decreased iNOS mRNA levels, indicating that ethanol may inhibit cytokine-induced iNOS transcription or affect mRNA destabilization. The suppression was ethanol-dose dependent with an IC50 of 50 mM. In another set of experiments to study ethanol effects, DLD-1 monolayers were pretreated with 66 mM ethanol for 24 h. These cells showed significant upregulation of IL-1beta mRNA and protein as detected in the supernatants. Aliquoted supernatants from these cells (i.e., conditioned media) were added to naive DLD-1 monolayers together with IFN-gamma. Conditioned medium from ethanol-treated cells increased the IFN-gamma-induced iNOS mRNA of naive cells by threefold. Two different effects of ethanol are now reported: (a) ethanol inhibits IFN-gamma + IL-1beta-induced iNOS mRNA of the same DLD-1 cells and (b) ethanol induces cellular paracrine signals by releasing IL-1beta into the medium, which in combination with IFN-gamma increases iNOS mRNA levels of the recipient naive DLD-1 cells. Because IFN-gamma and IL-1beta are produced by intestinal immune cells, these findings may have implications for differential in vivo regulation of epithelial iNOS genes by ethanol, depending on the inflammatory and immune status of the host.

Modulation of leukocyte-endothelial interactions by reactive metabolites of oxygen and nitrogen: relevance to ischemic heart disease

Ischemia and reperfusion (I/R) are thought to play an important role in the pathophysiology of ischemic diseases of the heart. It is now well appreciated that leukocyte-endothelial cell interactions are important determinants for I/R-induced microvascular injury and dysfunction. There is a growing body of experimental data to suggest that reactive metabolites of oxygen and nitrogen are important physiological modulators of leukocyte-endothelial cell interactions. A number of investigators have demonstrated that I/R enhances oxidant production within the microcirculation resulting in increases in leukocyte adhesion and transendothelial cell migration. Several other studies have shown that exogenous nitric oxide (NO) donors may attenuate leukocyte and platelet adhesion and/or aggregation in a number of different inflammatory conditions including I/R. The objective of this review is to discuss the physiological chemistry of reactive metabolites of oxygen and nitrogen with special attention given to those interactions that may modulate leukocyte-endothelial cell interactions, provide an overview of the evidence implicating reactive metabolites of oxygen and nitrogen as modulators of leukocyte-endothelial cell interactions in vivo, and discuss how these mechanisms may be involved in the pathophysiology of ischemic heart disease.

Salicylate hydroxylation as an indicator of hydroxyl radical generation in dextran sulfate-induced colitis

Reactive oxygen and nitrogen species have been implicated as mediators of mucosal injury in inflammatory bowel disease. This study investigated hydroxyl radical (.OH) generation in the inflamed colon of dextran sulfate sodium (DSS)-induced colitis by measuring the .OH-specific product of salicylate hydroxylation, 2,3-dihydroxybenzoic acid (DHB). Colitis was induced in 6-7 week old CBA/H male mice by supplementing the drinking water with 5% DSS for 7 days. On the last day of dextran exposure, mice were injected with salicylate (SAL) (100 mg/kg i.p.) 60 min before sacrifice, and mucosal homogenates were assayed for SAL and 2,3-DHB by HPLC with fluorescence and electrochemical detection. Mucosal 2,3-DHB levels in mice exposed to 5% DSS were increased by 83% (p < .005); however, SAL levels were also elevated by 182% (p < .001). This translated to a 34% decrease in the ratio 2,3-DHB:SAL in inflamed mucosa, possibly indicating greater catabolism or decreased production of 2,3-DHB. In vitro investigation of the stability of DHBs and SAL in the presence of oxidants of inflammatory lesions revealed that 2,3-DHB and 2,5-DHB were rapidly degraded by hypochlorous acid (HOCl), with initial decomposition rates of 190 and 281 nmol/min, respectively (100microM DHB with 200microM HOCl). Methionine prevented decomposition of DHBs in vitro; however, in mice with 5% DSS-induced colitis, where mucosal myeloperoxidase activity was ten-fold control levels (p < .001), administration of methionine (up to 200 mg/kg i.p.) with SAL was ineffective at increasing the ratio 2,3-DHB:SAL. SAL was also degraded in vitro by HOCl (4.7 nmol/min) resulting in the formation of new fluorescent species which may be useful as indicators of HOCl-mediated injury. Salicylate hydroxylation was unable to provide conclusive evidence supporting a role for .OH in the tissue injury of DSS-induced colitis, as metabolic disturbances in the diseased animals other than changes in .OH generation may have altered 2,3-DHB levels. This problem is relevant to any study involving the in vivo use of trapping molecules. In particular, the susceptibility of 2,3-DHB to degradation by HOCl brings into question the usefulness of salicylate hydroxylation for measurement of .OH-generation in any neutrophilic inflammatory lesion.

Activation of NF-kappaB in human neutrophils during phagocytosis of bacteria independently of oxidant generation

We have exposed human neutrophils to opsonized Staphylococcus aureus and used an electrophoretic mobility shift assay to show activation of the transcription factor NF-kappaB above basal levels. Activation was evident within 10 min and was increased with higher bacteria:neutrophil ratios. The neutrophil NADPH oxidase inhibitor diphenylene iodonium, catalase, and other oxidant scavengers did not inhibit NF-kappaB activation, and no activation was seen with added hydrogen peroxide. Oxidants produced during phagocytosis, therefore, are not involved in the activation mechanism.

Modulation of the DNA binding activity of transcription factors CREP, NFkappaB and HSF by H2O2 and TNF alpha. Differences between in vivo and in vitro effects

Human endothelial cells exposed to H2O2 showed reduced CREP DNA binding activity, enhanced HSF activation, and no induction of NFkappaB binding activity. Interestingly, H2O2 was able to induce NFkappaB subunit p65 translocation in the nucleus. In contrast, cells exposed to TNF alpha showed enhanced CREP binding activity, activation of NFkappaB and no induction of HSE-HSF complex. Addition of H2O2, diamide and iodoacetic acid to the binding reaction mixture markedly reduced the DNA binding ability of the three transcription factors. Thus free sulfhydryls were important in DNA binding activity of CREP, NFkappaB and HSF, and the lack of induction of NFkappaB by H2O2 in intact cells was likely caused by oxidation on a thiol, and not by a deficiency in the activation pathway.

Decreased expression of mitochondrial-derived H2O2 and hydroxyl radical in cytoresistant proximal tubules

Increased production of reactive oxygen metabolites (ROM) can contribute to the initiation phase of nephrotoxic and ischemic acute renal failure (ARF). However, whether altered ROM expression also exists during the maintenance phase of ARF has not been adequately assessed. Since diverse forms of tubular injury can initiate a "cytoresistant state," this study tested whether a down-regulation of ROM expression might develop in the aftermath of acute tubular damage, potentially limiting renal susceptibility to further attack. To test this hypothesis, rats were subjected to either mild myohemoglobinuria (glycerol injection) or bilateral ureteral obstruction and 24 hours later, cytoresistant proximal tubular segments (PTS) were isolated to assess ROM expression. PTS from sham operated rats were used to establish normal values. Both sets of cytoresistant PTS manifested approximately 75% reductions in H2O2 levels, as assessed by the phenol red/horseradish peroxidase technique (P < 0.01 to 0.001). A 40% reduction in hydroxyl radical (.OH) levels was also observed (salicylate trap method), thereby substantiating decreased oxidant stress in cytoresistant PTS. Catalase, glutathione peroxidase, and free iron levels were comparable in control and cytoresistant PTS, suggesting that decreased H2O2 production (such as by mitochondria) was the cause of the decreased oxidant stress. To test this latter hypothesis, H2O2 expression by control and cytoresistant PTS was assessed in the presence of respiratory chain inhibitors. Although site 1 and site 3 inhibition markedly suppressed H2O2 production in control PTS, they had no impact on H2O2 production in cytoresistant PTS, implying that production at these sites was already maximally suppressed. Correlates of the decreased mitochondrial H2O2 production were improvements in cell energetics (increased ATP/ADP ratios with Na ionophore treatment) and approximately 40 to 90% increases in PTS/renal cortical glutathione content. We conclude that: (1) proximal tubule H2O2/.OH expression can be downregulated during the maintenance phase of ARF; (2) this seemingly reflects a decrease in mitochondrial ROM generation; and (3) the associated improvements in glutathione content and/or cellular energetics could conceivably contribute to a post-injury cytoresistant state.

Antioxidant lazaroid U-74006F improves renal function and reduces the expression of cytokines, inducible nitric oxide synthase, and MHC antigens in a syngeneic renal transplant model. Partial support for the response-to-injury hypothesis

In a recent study, antioxidant therapy at the time of renal transplantation in humans was associated with fewer rejection episodes and extended graft survival. A hypothesis generated by such studies and based on the response-to-injury model is that reducing the oxidative injury during transplantation may dampen certain cellular responses to injury that are important in triggering allograft rejection. To test whether ablation of oxidative injury would limit such responses, kidneys were transplanted between Wistar-Furth rats, with and without antioxidant 21-aminosteroid. 21-Aminosteroid was administered before kidney harvest and, again, before transplant reperfusion. The recipient's left kidneys, removed to accommodate the donor kidneys, were used as normal control. The removal of the right kidneys contralateral to the transplant were delayed to day 4 to provide interim renal support. The transplanted kidneys were harvested on day 7. Administration of 21-aminosteroid was associated with better graft function and reduced lipid peroxidation. Compared with the normal control kidneys, the kidneys transplanted with vehicle had higher cytokine mRNA levels (measured by reverse transcriptase-polymerase chain reaction) for interleukin 2, interleukin 6, tumor necrosis factor-alpha, and interferon-gamma. The levels for these cytokines were reduced in kidneys transplanted with 21-aminosteroid. An increase in inducible nitric oxide synthase mRNA in the transplanted kidney was inhibited by 21-aminosteroid, as were the increase in class I and II MHC antigens. The new finding, that a reduction in transplantation-related oxidative injury in a syngeneic model is accompanied by a reduction in the expression of cytokines, MHC antigens, and inducible nitric oxide synthase, provides partial support for the response-to-injury hypothesis in the setting of renal transplantation. The data also demonstrate for the first time the efficacy of 21-aminosteroid to reduce lipid peroxidation and renal injury in kidneys transplanted after cold preservation.

Biological and biochemical inhibitors of the NF-kappa B/Rel proteins and cytokine synthesis

The NF-kappa B/Rel family of transcription factors participates in the activation of a diverse range of genes involved in inflammation, immune response, lymphoid differentiation, growth control and development. The present review provides a brief overview of NF-kappa B/Rel activation and a detailed analysis of important biological and biochemical inhibitors of the NF-kappa B/Rel pathway. Given the pleiotropic role of NF-kappa B in controlling cytokines and other immunoregulatory genes, the inhibition of NF-kappa B activation by steroid hormones, antioxidants, protease inhibitors and other compounds may provide a pharmacological basis for interfering with pathological inflammatory conditions, cancer and AIDS.

Regulation of phospholipase D by tyrosine kinases

Activation of phospholipase D (PLD) represents part of an important signalling pathway in mammalian cells. Phospholipase D catalyzed hydrolysis of phospholipids generates phosphatidic acid (PA) which is subsequently metabolized to lyso-PA (LPA) or diacylglycerol (DAG). While DAG is an endogenous activator of protein kinase C (PKC), PA and LPA have been recognized as second messengers as well. Activation of PLD in response to an external stimulus may involve PKC, Ca2+, G-proteins and/or tyrosine kinases. In this review, we will address the role of protein tyrosine phosphorylation in growth factor-, agonist- and oxidant-mediated activation of PLD. Furthermore, a possible link between PKC, Ca2+, G-proteins and tyrosine kinases is discussed to indicate the complexity involved in the regulation of PLD in mammalian cells.