Up-regulated Heme Oxygenase-1 mRNA Research Articles

Role of the Transcription Factor BTB and CNC Homology 1 in a Rat Model of Acute Liver Injury Induced by Experimental Endotoxemia.

Hepatic oxidative stress plays an important role in the pathogenesis of several acute liver diseases, and free heme is thought to contribute to endotoxemia-induced acute liver injury. The heme oxygenase 1 (HO-1) gene is upregulated and the δ-aminolevulinate synthase (ALAS1) gene is downregulated in the rat liver following lipopolysaccharide (LPS) treatment. BTB and CNC homology 1 (Bach1) is a heme-responsive transcription factor that normally represses HO-1 expression. In this study, we evaluated the changes in HO-1, ALAS1, and Bach1 expression and nuclear Bach1 expression in rat livers following intravenous LPS administration (10 mg/kg body weight). LPS significantly upregulated HO-1 mRNA and downregulated ALAS1 mRNA in the rat livers, suggesting that hepatic free heme concentrations are increased after LPS treatment. Bach1 mRNA was strongly induced after LPS injection. In contrast, nuclear Bach1 was significantly but transiently decreased after LPS treatment. Rats were also administered hemin (50 mg/kg body weight) intravenously to elevate heme concentrations, which decreased nuclear Bach1 levels. Our results suggest that elevated hepatic free heme may be associated with a decline of nuclear Bach1, and induction of Bach1 mRNA may compensate for the decreased nuclear Bach1 after LPS treatment in the rat liver.

Resveratrol Protects Against Hydroquinone-Induced Oxidative Threat in Retinal Pigment Epithelial Cells.

PurposeOxidative stress in retinal pigment epithelial (RPE) cells is associated with age-related macular degeneration (AMD). Resveratrol exerts a range of protective biologic effects, but its mechanism(s) are not well understood. The aim of this study was to investigate how resveratrol could affect biologic pathways in oxidatively stressed RPE cells.MethodsCultured human RPE cells were treated with hydroquinone (HQ) in the presence or absence of resveratrol. Cell viability was determined with WST-1 reagent and trypan blue exclusion. Mitochondrial function was measured with the XFe24 Extracellular Flux Analyzer. Expression of heme oxygenase-1 (HO-1) and glutamate cysteine ligase catalytic subunit was evaluated by qPCR. Endoplasmic reticulum stress protein expression was measured by Western blot. Potential reactions between HQ and resveratrol were investigated using high-performance liquid chromatography mass spectrometry with resveratrol and additional oxidants for comparison.ResultsRPE cells treated with the combination of resveratrol and HQ had significantly increased cell viability and improved mitochondrial function when compared with HQ-treated cells alone. Resveratrol in combination with HQ significantly upregulated HO-1 mRNA expression above that of HQ-treated cells alone. Resveratrol in combination with HQ upregulated C/EBP homologous protein and spliced X-box binding protein 1. Additionally, new compounds were formed from resveratrol and HQ coincubation.ConclusionsResveratrol can ameliorate HQ-induced toxicity in RPE cells through improved mitochondrial bioenergetics, upregulated antioxidant genes, stimulated unfolded protein response, and direct oxidant interaction. This study provides insight into pathways through which resveratrol can protect RPE cells from oxidative damage, a factor thought to contribute to AMD pathogenesis.

English

Gentamicin (GM) is an aminoglycoside that has harmful effects on the male germ cells and sperm quality. N-3 polyunsaturated fatty acids (n-3 PUFA) are natural antioxidants that influence cell signaling and inflammation. Heme-oxygenase-1 (HO-1) and heat shock proteins (HSP) aid in cellular protection against cellular insults. This study aimed to explore the potential alleviating influences of treatment with n-3 PUFA on GM-induced testicular damage. Thirty-two albino male rats were divided into four equal groups. (1) The control group received normal saline, (2) the n-3 PUFA group received 100 mg/kg body weight/day n-3 PUFA daily for 4 weeks, (3) the GM group received 100 mg/kg/day GM intraperitoneally for 10 consecutive days, and (4) the GM + n-3 PUFA group received intraperitoneal GM for ten days followed by treatment with n-3 PUFA for 4 weeks. Significant reductions in sperm motility, viability, serum testosterone, total testicular protein, and germinal epithelium height were observed in the GM-treated group, with upregulation of the oxidative stress markers, HO-1 mRNA, and HSP70, and downregulation of proliferating cell nuclear antigen (PCNA). We also observed cellular disorganization, vacuolation, tubular distortion, and a significantly higher percentage of collagen. Ultra-structurally, most of the spermatogenic cells were electron dense and degenerated with rarefied cytoplasm. Treatment with n-3 PUFA resulted in a significant increase in sperm motility, viability, serum testosterone, and in the germinal epithelium height. Upregulation of HO-1 mRNA, HSP70, and PCNA expression and a significant reduction in the oxidative stress index were also observed. The findings confirm the potential ameliorative role of and imply novel mechanisms by which n-3 PUFA protects against GM-induced testicular injury. Key words: Polyunsaturated fatty acids, gentamicin, oxidative stress, testis, male infertility. &nbsp

Anti-Inflammatory Activity of A Polyphenolic Extract from Arabidopsis thaliana in In Vitro and In Vivo Models of Alzheimer's Disease.

Alzheimer’s disease (AD) is the most common neurodegenerative disorder and the primary form of dementia in the elderly. One of the main features of AD is the increase in amyloid-beta (Aβ) peptide production and aggregation, leading to oxidative stress, neuroinflammation and neurodegeneration. Polyphenols are well known for their antioxidant, anti-inflammatory and neuroprotective effects and have been proposed as possible therapeutic agents against AD. Here, we investigated the effects of a polyphenolic extract of Arabidopsis thaliana (a plant belonging to the Brassicaceae family) on inflammatory response induced by Aβ. BV2 murine microglia cells treated with both Aβ25–35 peptide and extract showed a lower pro-inflammatory (IL-6, IL-1β, TNF-α) and a higher anti-inflammatory (IL-4, IL-10, IL-13) cytokine production compared to cells treated with Aβ only. The activation of the Nrf2-antioxidant response element signaling pathway in treated cells resulted in the upregulation of heme oxygenase-1 mRNA and in an increase of NAD(P)H:quinone oxidoreductase 1 activity. To establish whether the extract is also effective against Aβ-induced neurotoxicity in vivo, we evaluated its effect on the impaired climbing ability of AD Drosophila flies expressing human Aβ1–42. Arabidopsis extract significantly restored the locomotor activity of these flies, thus confirming its neuroprotective effects also in vivo. These results point to a protective effect of the Arabidopsis extract in AD, and prompt its use as a model in studying the impact of complex mixtures derived from plant-based food on neurodegenerative diseases.

Localization of Acrolein-Lysine Adduct in Fibrovascular Tissues of Proliferative Diabetic Retinopathy

ABSTRACTPurpose: To determine the presence of Nε-(3-formyl-3,4-dehydropiperidino) lysine adduct (FDP-Lys), unsaturated aldehyde acrolein-derived lipoxidation end-product, in fibrovascular tissues obtained from patients with proliferative diabetic retinopathy (PDR).Methods: Fibrovascular tissues were collected from 11 eyes of 11 patients with PDR and paraffin-embedded tissue sections were prepared. Tissue localization of FDP-Lys was studied by immunohistochemistry. Signal intensity was quantified by two masked evaluators and graded into three discrete categories. The relationship between FDP-Lys staining and vascular density was analyzed. In addition, subcellular localization of FDP-Lys was studied by immunofluorescent microscopy. The impact of acrolein on cell viability and proliferation was assessed and the expression level of heme oxygenase-1 (HO-1) mRNA was quantified by real-time polymerase chain reaction (PCR) in cultured retinal microvascular endothelial cells.Results: In fibrovascular tissues, FDP-Lys staining was found in vascular components containing CD34-positive cells and alpha smooth muscle actin (α-SMA)-positive cells, and clusters of rabbit anti-glial fibrillary acid protein (GFAP)-positive cells. Immunofluorescent staining depicted subcellular localization of FDP-Lys in the nucleus and cytoplasm of the cells. Morphological analysis revealed that fibrovascular tissues with FDP-Lys staining in vascular components showed high vascular density. Exposure of cultured endothelial cells to high concentration of acrolein resulted in the decrease of cell viability and proliferation, whereas lower concentration of acrolein increased cell viability and proliferation. Sublethal concentration of acrolein upregulated HO-1 mRNA expression in retinal microvascular endothelial cells.Conclusions: The current data demonstrated the presence of FDP-Lys in fibrovascular tissues and indicate its involvement in fibrovascular proliferation in PDR.

7,8-Dihydroxyflavone protects human keratinocytes against oxidative stress-induced cell damage via the ERK and PI3K/Akt-mediated Nrf2/HO-1 signaling pathways

This study investigated the effect of 7,8-dihydroxyflavone (DHF) on the expression and activity of heme oxygenase-1 (HO-1), an enzyme with potent antioxidant properties, as well as the molecular mechanisms involved. DHF markedly upregulated HO-1 mRNA and protein expression in human keratinocytes (HaCaT cells), resulting in increased HO-1 activity. DHF also increased the protein level of transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates HO-1 expression by binding to the antioxidant response element (ARE) within the HO-1 gene promoter, in a time-dependent manner. Moreover, DHF decreased the expression of Kelch-like ECH-associated protein 1, a repressor of Nrf2 activity, and induced the translocation of Nrf2 from the cytosol into the nucleus, thereby allowing its association with the ARE site. DHF activated extracellular-regulated kinase (ERK) and protein kinase B (PKB, Akt) in keratinocytes, while the ERK and Akt inhibitors attenuated DHF-enhanced Nrf2 and HO-1 expression. DHF also protected the keratinocytes against hydrogen peroxide- and ultraviolet B-induced oxidative damage, while HO-1, ERK and Akt inhibitors markedly suppressed DHF-mediated cytoprotection. Taken together, the results suggested that DHF activates ERK- and Akt-Nrf2 signaling cascades in HaCaT cells, leading to the upregulation of HO-1 and cytoprotection against oxidative stress.

Abstract 4124: The Antioxidant heme oxygenase 1 promotes proliferation and survival of Flt3-ITD-positive AML.

Abstract Acute myelogenous leukemia (AML) afflicts ∼12,330 new patients per year in the United States. Regrettably, only 25% of patients will survive five years past diagnosis. The most common mutation in AML is internal tandem duplication (ITD) of the juxtamembrane domain of the fms-like tyrosine kinase receptor-3 (Flt3), which renders it constitutively active. Flt3-ITD regulates proliferation and survival, and also increases the production of reactive oxygen species (ROS), which act as secondary messengers for oncogenic signaling. ROS can cause the induction of a number of molecules, however, one protein, heme oxygenase 1 (HO-1), a well-known antioxidant, has been connected to both proliferation and drug resistance of various cancers. We hypothesized that Flt3-ITD-dependent signaling and ROS production increase constitutive expression of HO-1, leading to the activation of antioxidant and anti-apoptotic pathways, resulting in proliferation and drug resistance in AML. Western blotting revealed a two-fold increase of HO-1 protein in Flt3-ITD+ cells as compared to Flt3-WT; a four-fold up-regulation of HO-1 mRNA was noted by quantitative real-time PCR suggesting transcriptional control. To determine if this up-regulation was due to the altered redox status of Flt3-ITD+ cells, the flavonoid inhibitor diphenylene iodonium (DPI) was used. Consistent with published results implicating the flavonoid protein complex NADPH oxidase (NOX) as a primary source of ROS in these cells, DPI reduced ROS levels as early as two hours post treatment. This ROS reduction coincided with a decrease in HO-1 protein, suggesting that NOX may be involved in HO-1 up-regulation. Our previous results in chronic myeloid leukemia suggest that a Rac1-dependent isoform of NOX controls HO-1 expression, however, in Flt3-ITD+AML, dominant negative inhibition of Rac1 was insufficient to alter HO-1 expression suggesting that either a Rac1-independent NOX isoform is involved or that another flavonoid protein modulates HO-1 expression in this leukemia subtype. Interestingly, when HO-1 expression was knocked down using RNAi, there was a 50% reduction of proliferation and 40% reduction of viability as measured by trypan blue exclusion in Flt3-ITD+AML cells. These data suggest that the function of HO-1 up-regulation is to promote survival and proliferation of Flt3-ITD+AML. Additionally, we have created a model of acquired resistance to lestaurtinib, a Flt3 kinase inhibitor, by treating with increasing doses of the drug over time. Preliminary results suggest that HO-1 is further elevated in these resistant cells as compared to parental Flt3-ITD cells; thus, we will use this model to test the functional role of HO-1 in acquired resistance. Together, our data suggest that HO-1 is a growth and survival factor in Flt3-ITD+AML; therefore, targeting HO-1 or the mechanisms that control its expression may prove therapeutically valuable. Citation Format: Mary E. Irwin, Joya Chandra. The Antioxidant heme oxygenase 1 promotes proliferation and survival of Flt3-ITD-positive AML. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4124. doi:10.1158/1538-7445.AM2013-4124

Peroxiredoxin I null mice exhibits reduced acute lung inflammation following ozone exposure

Acute ozone (O(3)) exposure causes oxidative stress leading inflammation in the lung. However, its precise mechanisms are not fully elucidated. Here, we examined the role of peroxiredoxin I (PrxI) in O(3)-induced pulmonary inflammation using PrxI null (PrxI(-/-)) and wild-type (WT) mice. PrxI is known as an antioxidant and also emerged as a potent proinflammatory factor that activates toll-like receptor 4/nuclear factor-kappa B signalling. Both mice were exposed to 2 ppm O(3) for 6 h and their responses to oxidative stress and acute inflammation in the lung were evaluated after 18 h. The O(3) inhalation activated the transcription factor nuclear factor-erythroid 2-related factor 2 and upregulated heme oxygenase-1 mRNA, the typical makers of oxidative stress, to similar extent in both lungs observed after 0 and 4 h, respectively. O(3) exposure induced significantly less pulmonary inflammation in PrxI(-/-) than in WT mice judging from the reduced infiltrations of neutrophils into the lung and the suppressed production of proinflammatory mediators, such as interleukin-6 and keratinocyte chemoattractant in the bronchoalveolar lavage fluids. Our results suggest that PrxI is not an effective protector against O(3)-induced oxidative damages reportedly caused by harmful lipid metabolites but plays a positive role in the initiation of lung inflammation following O(3) exposure.

Selective Brain Cooling in Rats Ameliorates Intracerebral Hemorrhage and Edema Caused by Penetrating Brain Injury: Possible Involvement of Heme Oxygenase-1 Expression

Brain edema formation associated with trauma-induced intracerebral hemorrhage (ICH) is a clinical complication with high mortality. Studies have shown that heme oxygenase-1 (HO-1) plays an important role in ICH-induced brain edema. In order to understand the role of HO-1 in the protective effect of selective brain cooling (SBC), we investigated the time course of HO-1 changes following penetrating ballistic-like brain injury (PBBI) in rats. Samples were collected from injured and control animals at 6, 24, 48, and 72 h, and 7 days post-injury to evaluate HO-1 expression, heme concentration, brain water content, and immunohistochemistry (IHC). Following a 10% frontal PBBI, HO-1 mRNA and protein was increased at all time points studied, reaching maximum expression levels at 24-48 h post-injury. An increase in the heme concentration and the development of brain edema coincided with the upregulation of HO-1 mRNA and protein during the 7-day post-injury period. SBC significantly decreased PBBI-induced heme concentration, attenuated HO-1 upregulation, and concomitantly reduced brain water content. These results suggest that the neuroprotective effects of SBC may be partially mediated by reducing the heme accumulation, which reduced injury-mediated upregulation of HO-1, and in turn ameliorated edema formation. Collectively, these results suggest a potential value of HO-1 as a diagnostic and/or therapeutic biomarker in hemorrhagic brain injury.

Up-regulation of heme oxygenase-1 by sevoflurane is not dependent on Kupffer cells and associates with ERK1/2 and AP-1 activation in the rat liver

Sevoflurane is a potent non-toxic inducer of the hepatoprotective enzyme heme oxygenase-1 (HO-1). So far, little is known about the underlying molecular mechanism. Therefore the aim of this study was to characterize the respective signal transduction pathway and in particular to elucidate the role of Kupffer cells in this context. Rats were treated with or without sevoflurane. The effects on hepatic HO-1 gene expression, mitogen-activated protein kinases and transcription factors were studied by Northern and Western blot analyses, immunostaining, electrophoretic mobility shift assays, and enzymatic activity assays. Kupffer cells were depleted by administration of clodronate liposomes in vivo to characterize their role in HO-1 signal transduction. In additional in vitro experiments, HO-1 mRNA expression in primary rat hepatocytes and HepG2 cells was assessed. Sevoflurane up-regulated HO-1 gene expression in pericentral hepatocytes and increased HO enzyme activity in vivo. This was associated with activation of ERK1/2 and activator protein-1. We identified c-jun/AP-1, JunD, c-fos, and Fra-1 as active subunits of the activator protein-1 complex. Administration of clodronate liposomes to rats led to depletion of Kupffer cells without affecting sevoflurane induced HO-1 expression. Moreover, sevoflurane up-regulated HO-1 mRNA in primary rat hepatocytes but not in HepG2 cells. Our results suggest that sevoflurane induced HO-1 gene expression in pericentral hepatocytes does not depend on Kupffer cells and is associated with activation of ERK1/2 and activator protein-1. Since we could recently demonstrate significant hepatoprotective effects of HO-1 induced by isoflurane, the present results may help to establish new concepts in hepatic organ protection.

Elevation of heme oxygenase‐1 by proteasome inhibition affords dopaminergic neuroprotection

Postmortem studies have shown that heme oxygenase-1 (HO-1) immunoreactivity is increased in patients with Parkinson disease. HO-1 expression is highly upregulated by a variety of stress. Since the proteasome activity is decreased in patients with Parkinson disease, we investigated whether proteasome activity regulates HO-1 content. MG-132, a proteasome inhibitor, increased the amount of HO-1 protein mainly in astrocytes of primary mesencephalic cultures. Quantitative RT-PCR analysis revealed that lactacystin upregulated HO-1 mRNA expression. Proteasome inhibition with MG132 also increased the cytomegalovirus promoter-driven expression of Flag-HO-1 protein and resulted in an accumulation of ubiquitinated Flag-HO-1 in Flag-HO-1-overexpressing PC12 cells. In addition, a cycloheximide chase assay demonstrated that the degradation of Flag-HO-1 protein was slowed by MG-132. Next, the function of HO-1 which was upregulated by proteasome inhibitors was examined. Proteasome inhibitors protected dopaminergic neurons from 6-hydroxydopamine (6-OHDA)-induced toxicity and this neuroprotection was abrogated by co-treatment with zinc protoporphyrin IX, a HO-1 inhibitor. Furthermore, 6-OHDA-induced toxicity was blocked by bilirubin and carbon monoxide, products of the HO-1-catalyzed degradation of heme. These results suggest that mesencephalic HO-1 protein level is regulated by proteasome activity and the elevation by proteasome inhibition affords neuroprotection.

Methyl gallate attenuate cadmium‐induced cytotoxicity by heme oxygenase‐1 in cultured mouse mesangial cells

The purpose of this study is to investigate the protective effect of methyl gallate (MG), a phytochemical, on cadmium (Cd)‐induced renal toxicity related by heme oxygenase‐1 (HO‐1) expression using cultured mouse mesangial cell line (MMC).By employing RT‐PCR and Western blotting techniques, we have examined the HO‐1 induction in MMCs that were treated with Cd or Methyl gallate. By employing a cell viability assay, we have also examined the cytoprotective effect of HO‐1 induction against the cytotoxicity caused by toxic dose of Cd. In MMCs exposed to Cd and methyl gallate, expression of HO‐1 (mRNA and protein) was increased in a dose‐ and time‐dependent manner. The up‐regulation of HO‐1 mRNA and protein expressions by Cd and methyl gallate was inhibited by a pre‐incubation of the cells with actinomycin D, an inhibitor of mRNA transcription. Upon the inhibition of elevated HO‐1 mRNA and protein expressions by the use of zinc protoporphyrin IX (ZnPP), an inhibitor of HO‐1 activity, the change of HO‐1 mRNA and protein expressions by ZnPP was not observed. The decreased viability of the cells by Cd was partially recovered by the treatment with methyl gallate. These cytotoxic and cytoprotective effect was dramatically decreased by the treatment with ZnPP.From these results, methyl gallate have cytoprotective effect that related with heme oxygenase‐1 activity.

Zinc mesoporphyrin induces rapid and marked degradation of the transcription factor Bach1 and up-regulates HO-1.

Heme oxygenase 1 (HO-1) is the first and rate-controlling enzyme in heme degradation. Bach1 is a mammalian transcriptional repressor of HO-1. To understand how zinc mesoporphyrin (ZnMP) induces the expression of HO-1, we investigated the effects of ZnMP on Bach1 mRNA and protein levels in human hepatoma Huh-7 cells by quantitative RT-PCR and Western blots. We found that ZnMP markedly up-regulated HO-1 mRNA and protein levels, and rapidly and significantly decreased Bach1 protein levels by increasing degradation of Bach1 protein [half life (t(1/2)) from 19 h to 45 min], whereas ZnMP did not influence Bach1 mRNA levels. The proteasome inhibitors, epoxomicin and MG132, significantly inhibited degradation of Bach1 by ZnMP in a dose-dependent fashion, indicating that the degradation of Bach1 by ZnMP is proteasome-dependent. Purified Bach1 C-terminal fragment bound heme, but there was no evidence for binding of ZnMP to the heme-binding region of Bach1. In conclusion, ZnMP produces profound post-transcriptional down-regulation of Bach1 protein levels and transcriptional up-regulation of HO-1. Our results indicate that ZnMP up-regulates HO-1 gene expression by markedly increasing Bach1 protein degradation in a proteasome-dependent manner.

흰쥐 대뇌세포의 저산소증 모델에서 황금(黃芩)에 의한 heme oxygenase-1의 표현증가

Scutellaria baicalensis GEORGI(SB) is used in oriental medicine for the treatment of incipient strokes. Although it has been reported that SB is neuroprotective in a hypoxia model, its mechanism is poorly understood. Here, we investigated the effect of SB on the modulation of heme oxygenase-1(HO-1), which has important biological roles in regulating mitochondrial heme protein turnover and in protecting against conditions such as hypoxia, neurodegenerative diseases, or sepsis. Rat cerebrocortical day In vitro(DIV)12 cells were grown in neurobasal medium. On DIV12 cells were treated with SB(<TEX>$20{\mu}g/ml$</TEX>) and given a hypoxic shock (<TEX>$2%\;O_2/5%\;CO_2,\;3\;hr$</TEX>) on DIV14. In situ hybridization results revealed that SB upregulated HO-1 mRNA in neuronal dendrites in both normoxia and hypoxia(38.5% and 59.2%, respectively). At the protein level, SB upregulated HO-1 in the neuronal soma in both normoxia and hypoxia(22.4% and 15.7%, respectively). Interestingly, most significant increase was associated with astrocytes, which increased HO-1 protein by 77.5% compared to SB-untreated culture. These results indicate that SB upregulates both neuronal and glial HO-1 expression, which contributes to the neuroprotection efficacy in hypoxia).

Involvement of JNKs and p38-MAPK/MSK1 pathways in H 2O 2-induced upregulation of heme oxygenase-1 mRNA in H9c2 cells

One of the most important challenges that cardiomyocytes experience is an increase in the levels of reactive oxygen species (ROS), i.e., during ischemia, reperfusion as well as in the failing myocardium. HOX-1 has been found to protect cells and tissues against oxidative damage; therefore, we decided to study the signalling cascades involved in its transcriptional regulation. HOX-1 mRNA levels were found to be maximally induced after 6 h of treatment with 200 μM H 2O 2 and remained elevated for at least 24 h. Inhibition of JNKs, p38-MAPK and MSK1 pathways, by pharmacological inhibitors, reduced HOX-1 mRNA levels in H 2O 2-treated H9c2 cells. In parallel, we observed that all three subfamilies of the mitogen-activated protein kinases (MAPKs) attained their maximal phosphorylation levels at 5–15 min of H 2O 2 treatment, with mitogen- and stress-activated-protein kinase 1 (MSK1) also being maximally phosphorylated at 15 min. H 2O 2-induced MSK1 phosphorylation was completely abrogated in the presence of the selective p38-MAPK inhibitor SB203580. In an effort to define possible substrates of MSK1, we found that ATF2 as well as cJun phosphorylation were equally induced after 30 min and 60 min, respectively, a response inhibited by SP600125 (JNKs inhibitor) and H89 (MSK1 inhibitor), indicating the involvement of these kinases in the observed response. This finding was further substantiated with the detection of a potential signalling complex composed of either p-MSK1 and p-cJun or p-MSK1 and p-ATF2 (co-immunoprecipitation). ATF2 and cJun are known AP1 components. Given the presence of an AP-1 site in HOX-1 promoter region, the activity of AP1 transcription factor was examined. Electrophoretic mobility shift assays performed showed a maximal upregulation of AP1 binding activity after 60 min of H 2O 2 treatment, which was significantly inhibited by SP600125 and H89. Our results show for the first time the potential role of JNKs, p38-MAPK and MSK1 in the mechanism of transducing the oxidative stress-signal to HOX-1, possibly promoting cell survival and preserving homeostasis.

Oxidized Phospholipids Induce Expression of Human Heme Oxygenase-1 Involving Activation of cAMP-responsive Element-binding Protein

Heme oxygenase-1 (HO-1) catalyzes the rate-limiting step in heme degradation, protects against oxidative stress, and shows potent anti-inflammatory effects. Oxidized phospholipids, which are generated during inflammation and apoptosis, modulate the inflammatory response by inducing the expression of several genes including HO-1. Here we investigated the signaling pathways and transcriptional events involved in the induction of HO-1 gene expression by oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC) in human umbilical vein endothelial cells. OxPAPC up-regulated HO-1 mRNA and protein in a time- and concentration-dependent manner, whereas pro-inflammatory agents like TNF-alpha and lipopolysaccharide did not significantly induce HO-1 expression in human umbilical vein endothelial cells. Signaling pathways involved in the OxPAPC-mediated HO-1 induction included protein kinases A and C, as well as the mitogen-activated protein kinases p38 and ERK. The cAMP-responsive element-binding protein (CREB) was phosphorylated via these pathways in response to OxPAPC treatment and expression of a dominant-negative mutant of CREB inhibited OxPAPC-induced activity of a human heme oxygenase-1 promoter-driven luciferase reporter construct. We identified a cAMP-responsive element and a Maf recognition element to be involved in the transcriptional activation of the HO-1 promoter by OxPAPC. In gel shift assays we observed binding of CREB to the cAMP-responsive element after OxPAPC treatment. Induction of HO-1 expression by lipid oxidation products via CREB may represent a feedback mechanism to limit inflammation and associated tissue damage.

Characterization and Biological Significance of Immunosuppressive Peptide D2702.75–84(E → V) Binding Protein: ISOLATION OF HEME OXYGENASE-1

This is the first report on peptidic inhibitors of heme oxygenase. Such peptides were originally developed from the immunomodulatory peptide 2702.75-84 which corresponds to amino acid residues 75 to 84 of the alpha1-helix of HLA-B2702 (2702.75-84) and has been shown to be immunosuppressive in vitro and in vivo. In vitro, 2702.75-84 inhibited cytotoxic T- and natural killer cell- mediated target cell lysis, and in vivo peptide therapy resulted in prolongation of heart and skin allograft survival in mice. The peptide was also shown to bind to heat shock protein 70. However, D-enantiomers of 2702.75-84 and derivatives thereof, while still being immunosuppressive, did not bind to heat shock protein 70. This study was designed to identify proteins binding to peptide D2702.75-84(E --> V) (rvnlrialry) consisting of D-amino acids. Compared with 2702.75-84 (RENLRIALRY), glutamic acid residue 76 (E) was replaced with valine (V). Affinity chromatography using immobilized D2702.75-84(E --> V) and mouse and human cell extracts, resulted in the isolation of heme oxygenase-1 (HO-1). Peptide D2702.75-84 inhibited HO activity in vitro in a dose dependent manner. Similar to what has been observed with other inhibitors of HO, administration of peptide into mice resulted in an up-regulation of HO-1 mRNA and protein, as well as enzyme activity in liver, spleen and kidney. Other peptides derived from 2702.75-84 with similar immunomodulatory activity displayed similar effects. In contrast, inactive derivatives of 2702.75-84 had no effect on HO activity. Therefore, the immunosuppressive effects of the described immunomodulatory peptides are similar to those of cobalt-protoporphyrin, a known up-regulator of HO-1. Our results suggest that HO-1 modulation may be a novel mechanism of immunomodulation.