Induction of heme oxygenase-1 expression in murine macrophages is essential for the anti-inflammatory effect of low dose 15-deoxy-Delta 12,14-prostaglandin J2

Glutathione depletion inhibits lipopolysaccharide-induced intercellular adhesion molecule 1 synthesis

Cellular redox status is known to regulate a number of biological processes, including the activation of inflammatory genes. Our previous studies demonstrated that thiol depletion using diethyl maleate (DEM) reduced neutrophil sequestration in animal models of inflammation, an effect primarily mediated by impaired upregulation of the adhesion molecule, ICAM-1. The present studies were performed to discern the mechanism whereby DEM prevents LPS-induced ICAM-1 expression in human umbilical vein endothelial cells. DEM caused a time- and concentration-dependent inhibition of ICAM-1 expression in LPS-stimulated HUVEC by blocking induction of gene transcription. Interestingly, DEM had little effect on the degradation of the inhibitory protein IkappaB-alpha, but rather appeared to prevent translocation of the transcription factor NF-kappaB into the nucleus. Readdition of glutathione following DEM treatment restored the ability of LPS to induce NF-kappaB translocation and ICAM-1 synthesis. DEM plus LPS caused synergistic induction of heme oxygenase-1 (HO-1), suggesting its role in the inhibitory effects of DEM. However, HO-1 was shown to be neither sufficient nor necessary for the anti-inflammatory effects of glutathione depletion. These studies illustrate that thiol depletion may represent a potential therapy for inflammation, exerting its effects via a distinct mechanism on cell signaling pathways.

Aging-associated changes in gene expression in the ACI rat prostate: Implications for carcinogenesis

BACKGROUND

Prostate cancer is the most frequently diagnosed neoplasm and the second leading cause of cancer-related mortality in men. Although the incidence of prostate cancer increases with age, the link between aging and prostate cancer is poorly understood.

METHODS

Affymetrix oligonucleotide microarrays were used to analyze the mRNA expression levels in the dorsolateral prostates from 6- and 18-month-old ACI rats. Real-time RT-PCR and immunohistochemistry was performed to validate microarray data in a select set of genes.

RESULTS

Microarray analysis revealed changes in gene expression associated with inflammation, oxidative stress, tissue remodeling, and energy metabolism. Most of these changes have been related to increased proliferative status of the prostate, anti-apoptosis, activated stroma, and alteration of the energy metabolism.

CONCLUSIONS

Age-associated alterations in the gene expression profile may put the aging prostate in risk for the initiation, promotion, and progression of neoplastic transformation in both our animal model and humans.

HMG-CoA reductase inhibitors upregulate heme oxygenase-1 expression in murine RAW264.7 macrophages via ERK, p38 MAPK and protein kinase G pathways

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in heme catabolism, which confers cytoprotection against oxidative injury and provides a vital function in maintaining tissue homeostasis. HMG-CoA reductase inhibitors (statins) possess several anti-inflammatory mechanisms and may be beneficial in the treatment of inflammatory diseases. Our previous study has shown that statins can inhibit iNOS gene expression in murine RAW264.7 macrophages. In this study, we showed that lovastatin, fluvastatin, atorvastatin, simvastatin, mevastatin and pravastatin are able to upregulate the mRNA expression of HO-1 gene. This effect of lovastatin was attenuated by farnesyl pyrophosphate (FPP), geranylgeranyl pyrophosphate (GGPP), a protein kinase G (PKG) inhibitor (KT5823), a soluble guanylyl cyclase inhibitor (ODQ), a p38 MAPK inhibitor (SB203580), and MEK inhibitors (U0126 and PD98059), but not by inhibitors of protein kinase C (PKC), protein kinase A (PKA), c-jun N-terminal kinase (JNK) and Rho kinase. Consistent with this notion, our previous study has reported the ability of statins to activate ERK and p38 MAPK in RAW264.7 macrophages. Here we further found the participation of cyclic guanosine monophosphate (cGMP)/PKG pathway for ERK activation in cells stimulated with statin and the ability of statin to induce AP-1 activity, which is an essential transcription factor in the regulation of HO-1 gene expression. In addition, a Ras inhibitor (manumycin A) treatment also caused a marked induction of HO-1 mRNA followed by a corresponding increase in HO-1 protein; instead, inhibition of Rho activity by toxin B only led to a transient and weak induction of HO-1. The involvement of signal pathways in manumycin A-induced HO-1 gene expression was associated with p38 MAPK, JNK and ERK activation. Taken together, these results demonstrate for the first time that statins might activate PKG to elicit activations of ERK and p38 MAPK pathways and finally induce HO-1 gene expression, which provides a novel anti-inflammatory mechanism in the therapeutic validity.

Anti-inflammatory effect of heme oxygenase 1: glycosylation and nitric oxide inhibition in macrophages

Flavonoids including the aglycones, hesperetin (HT; 5,7,3'-trihydroxy-4'-methoxy-flavanone), and naringenin (NE; 5,7,4'-trihydroxy flavanone) and glycones, hesperidin (HD; 5,7,3'-trihydroxy-4'-methoxy-flavanone 7-rhamnoglucoside) and naringin (NI; 5,7,4'-trihydroxy flavanone 7-rhamno glucoside), were used to examine the importance of rutinose at C7 on the inhibitory effects of flavonoids on lipopolysaccharide (LPS)-induced nitric oxide production in macrophages. Both HT and NE, but not their respective glycosides HD and NI, induced heme oxygenase 1 (HO-1) protein expression in the presence or absence of LPS and showed time and dose-dependent inhibition of LPS-induced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in RAW264.7, J774A.1, and thioglycolate-elicited peritoneal macrophages. Additive inhibitory effect of an HO-1 inducer hemin and NE or NI on LPS-induced NO production and iNOS expression was identified, and HO enzyme inhibitor tin protoporphyrin (SnPP) attenuated the inhibitory effects of HT, NE, and hemin on LPS-induced NO production. Both NE and HT showed no effect on iNOS mRNA and protein stability in RAW264.7 cells. Removal of rutinose at C7 of HD and NI by enzymatic digestion using hesperidinase (HDase) and naringinase (NIase) produce inhibitory activity on LPS-induced NO production, according to the production of the aglycones, HT and NE, by high-performance liquid chromatography (HPLC) analysis. Furthermore, the amount of NO produced by LPS or lipoteichoic acid (LTA) was significantly reduced in HO-1-overexpressing cells (HO-1/RAW264.7) compared to that in parental cells (RAW264.7). Results of the present study provide scientific evidence to suggest that rutinose at C7 is a negative moiety in flavonoid inhibition of LPS-induced NO production, and that HO-1 is involved in the inhibitory mechanism of flavonoids on LPS-induced iNOS and NO production.

The cyclopentenone (A2/J2) isoprostanes--unique, highly reactive products of arachidonate peroxidation

Cyclopentenone (A2/J2) isoprostanes (IsoPs) are a group of prostaglandin (PG)-like compounds generated in vivo from the free radical-induced peroxidation of arachidonic acid. Unlike other classes of IsoPs, cyclopentenone IsoPs contain highly reactive unsaturated carbonyl moieties on the prostane ring analogous to cyclooxygenase-derived PGA2 and PGJ2 that readily adduct relevant biomolecules such as thiols via Michael addition. The purpose of this review is to summarize our knowledge of the A2/J2-IsoPs. As a starting point, we will briefly discuss the formation and biological properties of PGA2 and PGJ2. Next, we will review studies definitively showing that cyclopentenone IsoPs are formed in large amounts in vivo. This is in marked contrast to cyclopentenone PGs, for which little evidence exists that they are endogenously produced. Subsequently, we will discuss studies related to the chemical syntheses of the 15-A2-IsoP series of cyclopentenone IsoPs. The successful synthesis of these compounds provides the recent impetus to explore the metabolism and biological properties of A-ring IsoPs, particularly as modulators of inflammation, and this work will be discussed. Finally, the formation of cyclopentenone IsoP-like compounds from other fatty acids such as linolenic acid and docosahexaenoic acid will be detailed.

CORM‐A1: a new pharmacologically active carbon monoxide‐releasing molecule

Carbon monoxide (CO) is emerging as an important and versatile mediator of physiological processes to the extent that treatment of animals with exogenous CO gas has beneficial effects in a range of vascular- and inflammatory-related disease models. The recent discovery that certain transition metal carbonyls function as CO-releasing molecules (CO-RMs) in biological systems highlighted the potential of exploiting this and similar classes of compounds as a stratagem to deliver CO for therapeutic purposes. Here we describe the biochemical features and pharmacological actions of a newly identified water-soluble CO releaser (CORM-A1) that, unlike the first prototypic molecule recently described (CORM-3), does not contain a transition metal and liberates CO at a much slower rate under physiological conditions. Using a myoglobin assay and an amperometric CO electrode, we demonstrated that the release of CO from CORM-A1 is both pH- and temperature-dependent with a half-life of approximately 21 min at 37 degrees C and pH 7.4. In isolated aortic rings, CORM-A1 promoted a gradual but profound concentration-dependent vasorelaxation over time, which was highly amplified by YC-1 (1 microM) and attenuated by ODQ, a stimulator and inhibitor of guanylate cyclase, respectively. Similarly, administration of CORM-A1 (30 micromol/kg i.v.) in vivo produced a mild decrease in mean arterial pressure, which was markedly potentiated by pretreatment with YC-1 (1.2 micromol/kg i.v.). Interestingly, an inactive form of CORM-A1 that is incapable of releasing CO failed to promote both vasorelaxation and hypotension, thus directly implicating CO as the mediator of the observed pharmacological effects. Our results reveal that the bioactivities exerted by CORM-A1 reflect its intrinsic biochemical behavior of a slow CO releaser, which may be advantageous in the treatment of chronic conditions that require CO to be delivered in a carefully controlled manner.

Haem oxygenase-1 in inflammation

HO-1 (haem oxygenase-1) is a stress-inducible enzyme that plays a protective role in inflammation. Pro-inflammatory mediators, including lipopolysaccharide and cytokines, induce HO-1 expression. The 5′-flanking region of the HO-1 gene contains binding sites for the transcription factors that regulate inflammation, including nuclear factor-κB and activator protein 1. However, these do not appear to mediate lipopolysaccharide-induced HO-1 gene expression. In response to haem and antioxidants, murine HO-1 is regulated by the transcription factor Nrf2 (NF-E2-related factor 2). This transcription factor may also be important in the regulation of HO-1 by pro-inflammatory stimuli.

3-Hydroxyanthranilic acid, one of metabolites of tryptophan via indoleamine 2,3-dioxygenase pathway, suppresses inducible nitric oxide synthase expression by enhancing heme oxygenase-1 expression

Inducible nitric oxide (NO) synthase (iNOS), heme oxygenase (HO)-1, and indoleamine 2,3-dioxygenase (IDO) are simultaneously expressed in murine macrophages stimulated with interferon (IFN)-gamma and lipopolysaccharide (LPS). NO produced by iNOS suppresses IDO expression and also induces HO-1 expression. The antioxidant 3-hydroxyanthranilic acid (HA), one of metabolites of tryptophan via IDO pathway, has been previously reported to suppress iNOS expression. Because HO-1 expression can suppress iNOS expression, we investigated whether HA could suppress iNOS expression by affecting HO-1 expression in murine RAW 264.7 macrophages stimulated with IFN-gamma plus LPS. Treatment with exogenous HA dose-dependently suppressed iNOS expression and coincidently enhanced HO-1 expression. This suppressive effect of HA on iNOS expression was reversed by blocking HO-1 activity, and proven to be due to carbon monoxide (CO) produced by HO-1. In addition, either blocking of iNOS activity or addition of exogenous CO further enhanced IDO expression and activity. These results show for the first time that HA is able to suppress iNOS expression by enhancing HO-1 expression, thereby resulting in further increases in IDO expression and activity.

Proteasome inhibitors up-regulate haem oxygenase-1 gene expression: requirement of p38 MAPK (mitogen-activated protein kinase) activation but not of NF-kappaB (nuclear factor kappaB) inhibition

Regulation of intracellular protein stability by the ubiquitin-dependent proteasome system plays a crucial role in cell function. HO-1 (haem oxygenase) is a stress response protein, which confers cytoprotection against oxidative injury and provides a vital function in maintaining tissue homoeostasis. In the present study, we found a novel action of proteasome inhibitors MG132 and MG262 on HO-1 induction, and characterized the underlying mechanisms. MG132 (> or =0.1 microM) treatment resulted in a marked time- and concentration-dependent induction of the steady-state level of HO-1 mRNA in RAW264.7 macrophages, followed by a corresponding increase in HO-1 protein. Actinomycin D and cycloheximide inhibited MG132-responsive HO-1 protein expression, indicating a requirement for transcription and de novo protein synthesis. The involvement of signal pathways in MG132-induced HO-1 gene expression was examined using chemical inhibitors. Antioxidant N -acetylcysteine and SB203580, an antioxidant and inhibitor of p38 MAPK (mitogen-activated protein kinase), abolished MG132-inducible HO-1 expression. Furthermore, MG132 activated the p38 MAPK pathway. The half-life of HO-1 protein was prolonged by MG132, indicating that the upregulation of HO-1 by proteasome inhibitor is partially attributable to the inhibition of protein degradation. MG132 can ablate IkappaBalpha degradation and NF-kappaB (nuclear factor kappaB) activation induced by lipopolysaccharide, similar to the effect of another NF-kappaB inhibitor pyrrolidine dithiocarbamate. We found HO-1 upregulation by MG132 and pyrrolidine dithiocarbamate is unrelated to their inhibition of NF-kappaB, since leptomycin B, another NF-kappaB inhibitor, did not elicit similar induction of HO-1. Taken together, we found a novel effect of proteasome inhibitor on induction of HO-1 expression. This action is ascribed to the activation of the p38 MAPK pathway, but is not dependent on NF-kappaB inhibition.

Carbon monoxide produced by heme oxygenase-1 suppresses T cell proliferation via inhibition of IL-2 production

Heme oxygenase-1 (HO-1) catabolizes heme into CO, biliverdin, and free iron and serves as a protective enzyme by virtue of its anti-inflammatory, antiapoptotic, and antiproliferative actions. Previously, we have demonstrated that human CD4(+) T cells express HO-1 and that HO-1-overexpressing Jurkat T cells tend to display lower proliferative response. The aim of this study is to elucidate the mechanism(s) by which HO-1 can mediate its antiproliferative effect on CD4(+) T cells. Among the three HO-1 byproducts, only CO showed suppressive effect on T cell proliferation in response to anti-CD3 plus anti-CD28 Abs, mimicking the antiproliferative action of HO-1. CO blocked the cell cycle entry of T cells, which was independent of the guanylate cyclase/cGMP pathway. CO also suppressed the secretion of IL-2, and this suppressive effect of CO on IL-2 secretion mediated the antiproliferative action of CO. CO selectively inhibited the extracellular signal-regulated kinase pathway, which could explain the suppressive effects of CO on T cell proliferation and IL-2 secretion. Based on these findings, we suggest that HO-1/CO suppresses T cell proliferation and IL-2 secretion, possibly via its inhibition of extracellular signal-regulated kinase activation.

Role of nuclear factor-kappaB and heme oxygenase-1 in the mechanism of action of an anti-inflammatory chalcone derivative in RAW 264.7 cells

The synthetic chalcone 3',4',5',3,4,5-hexamethoxy-chalcone (CH) is an anti-inflammatory compound able to reduce nitric oxide (NO) production by inhibition of inducible NO synthase protein synthesis. In this work, we have studied the mechanisms of action of this compound. CH (10-30 microm) prevents the overproduction of NO in RAW 264.7 macrophages stimulated with lipopolysaccharide (1 microg ml(-1)) due to the inhibition of nuclear factor kappaB (NF-kappaB) activation. We have shown that treatment of cells with CH results in diminished degradation of the NF-kappaB-IkappaB complex leading to inhibition of NF-kappaB translocation into the nucleus, DNA binding and transcriptional activity. We also demonstrate the ability of this compound to activate NfE2-related factor (Nrf2) and induce heme oxygenase-1 (HO-1). Our results indicate that CH determines a rapid but nontoxic increase of intracellular oxidative species, which could be responsible for Nrf2 activation and HO-1 induction by this chalcone derivative. This novel anti-inflammatory agent simultaneously induces a cytoprotective response (HO-1) and downregulates an inflammatory pathway (NF-kappaB) with a mechanism of action different from antioxidant chalcones.

Regulation of inducible nitric oxide synthase expression in advanced glycation end product-stimulated raw 264.7 cells: the role of heme oxygenase-1 and endogenous nitric oxide

Advanced glycation end products (AGEs) are closely linked to the development of diabetic atherosclerosis. The current study examines the induction of inducible nitric oxide (NO) synthase (iNOS) and heme oxygenase (HO)-1 expression by AGEs, as well as the signaling pathways involved and the interplay between these two enzymes. The stimulation of RAW 264.7 cells with 6.64 or 33.2 microg/ml AGEs leads to HO-1 protein expression, iNOS protein expression, and nitrite accumulation. AGEs lead to the phosphorylation of p42/44 and p38 mitogen-activated protein kinase (MAPK). The inhibition of p42/44 MAPK and protein kinase C prevented, whereas inhibition of p38 MAPK augmented, AGE-induced nitrite release and iNOS expression. In contrast, HO-1 expression was downregulated by inhibition of p38 MAPK. Furthermore, the expression of both proteins was prevented by coincubation with acetovanillone (NADPH oxidase inhibitor). AGE-induced iNOS expression was negatively regulated by stimulation of HO-1 expression with cadmium chloride or endogenous NO. Tin-protoporphyrin IX (HO-1 inhibitor) partially reversed the cadmium chloride-mediated downregulation of iNOS expression. The current study demonstrates that multiple signaling molecules are involved in AGE-stimulated iNOS and HO-1 expression. There also exists a downregulation of iNOS by its own product as well as the products of HO-1.

Pathogenesis of malaria and clinically similar conditions

There is now wide acceptance of the concept that the similarity between many acute infectious diseases, be they viral, bacterial, or parasitic in origin, is caused by the overproduction of inflammatory cytokines initiated when the organism interacts with the innate immune system. This is also true of certain noninfectious states, such as the tissue injury syndromes. This review discusses the historical origins of these ideas, which began with tumor necrosis factor (TNF) and spread from their origins in malaria research to other fields. As well the more established proinflammatory mediators, such as TNF, interleukin-1, and lymphotoxin, the roles of nitric oxide and carbon monoxide, which are chiefly inhibitory, are discussed. The established and potential roles of two more recently recognized contributors, overactivity of the enzyme poly(ADP-ribose) polymerase 1 (PARP-1) and the escape of high-mobility-group box 1 (HMGB1) protein from its normal location into the circulation, are also put in context. The pathogenesis of the disease caused by falciparum malaria is then considered in the light of what has been learned about the roles of these mediators in these other diseases, as well as in malaria itself.

15-Deoxy-Δ12,14-prostaglandin J2 Induces Heme Oxygenase-1 Gene Expression in a Reactive Oxygen Species-dependent Manner in Human Lymphocytes

15-Deoxy-delta(12,14)-prostaglandin J(2) (15dPGJ(2) has been recently proposed as a potent anti-inflammatory agent. However, the mechanisms by which 15dPGJ(2) mediates its therapeutic effects in vivo are unclear. We demonstrate that 15dPGJ(2) at micromolar (2.5-10 microm) concentrations induces the expression of heme oxygenase-1 (HO-1), an anti-inflammatory enzyme, at both mRNA and protein levels in human lymphocytes. In contrast, troglitazone and ciglitazone, two thiazolidinediones that mimic several effects of 15dPGJ(2) through their binding to the peroxisome proliferator-activated receptor (PPAR)-gamma, did not affect HO-1 expression, and the positive effect of 15dPGJ(2) on this process was mimicked instead by other cyclopentenone prostaglandins (PG), such as PGD(2) (the precursor of 15dPGJ(2)) and PGA(1) and PGA(2) which do not interact with PPAR-gamma. Also, 15dPGJ(2) enhanced the intracellular production of reactive oxygen species (ROS) and increased xanthine oxidase activity in vitro. Inhibition of intracellular ROS production by N-acetylcysteine, TEMPO, Me(2)SO, 1,10-phenanthroline, or allopurinol resulted in a decreased 15dPGJ(2)-dependent HO-1 expression in the cells. Furthermore, buthionine sulfoximine, an inhibitor of reduced glutathione synthesis, or Fe(2+)/Cu(2+) ions enhanced the positive effect of 15dPGJ(2) on HO-1 expression. On the other hand, the inhibition of phosphatidylinositol 3-kinase or p38 mitogen-activated protein kinase, or the blockade of transcription factor NF-kappaB activation, hindered 15dPGJ(2)-elicited HO-1 expression. Collectively, the present data suggest that 15dPGJ(2) anti-inflammatory actions at pharmacological concentrations involve the induction of HO-1 gene expression through mechanisms independent of PPAR-gamma activation and dependent on ROS produced via the xanthine/xanthine oxidase system and/or through Fenton reactions. Both phosphatidylinositol 3-kinase and p38 mitogen-activated protein kinase signaling pathways also appear implicated in modulation of HO-1 expression by 15dPGJ(2).

Stress protein activation by the cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin J2 in human mesangial cells

BACKGROUND

The cyclopentenone prostaglandin 15-deoxy-delta12,14-prostaglandin J2 (15dPGJ2) affects mesangial proliferation, survival and production of proinflammatory proteins. During a survey of the mesangial cell proteome after treatment with 15dPGJ2, heat shock protein 70 (HSP70) was found to be the most conspicuously up-regulated protein, suggesting that stress proteins are key mediators or modulators of the effects of 15dPGJ2. Because cyclopentenone prostaglandins are highly reactive toward intracellular thiols, the role of intracellular thiol modification in the stress response to 15dPGJ2 was examined.

METHODS

Human mesangial cells were treated with 15dPGJ2 and intracellular thiol status was monitored by the fluorescent thiol probe monobromobimane (MBB). Specific intracellular thiol pools were manipulated by treating the cells with buthionine sulfoximine (BSO) to deplete glutathione (GSH), or phenylarsine oxide (PAO) to modify protein vicinal dithiols. Transcription pathways were examined with reporter gene or adenoviral constructs.

RESULTS

15dPGJ2 decreased mesangial GSH and other intracellular thiols, but depletion of GSH specifically with BSO did not induce HSP70. Thiol-replenishing reagents, which can restore modified protein thiols, attenuated 15dPGJ2-induced HSP70 levels. Furthermore, PAO mimicked the effects of 15dPGJ2 on HSP70. 15dPGJ2 also activated the stress-responsive transcription factor Nrf2, which requires thiol modification of its cytoplasmic inhibitor protein for transcriptional activity, and induced the Nrf2-dependent stress protein heme oxygenase-1 (HO-1).

CONCLUSION

15dPGJ2 activates a stress response in human mesangial cells by covalent modification of protein thiols through its unique cyclopentenone ring structure. This stress response may be beneficial in preventing renal cell injury or death during kidney inflammation or ischemia.

Bifunctional role for VEGF-induced heme oxygenase-1 in vivo: induction of angiogenesis and inhibition of leukocytic infiltration

Heme-oxygenases (HOs) catalyze the conversion of heme into carbon monoxide and biliverdin. HO-1 is induced during hypoxia, ischemia/reperfusion, and inflammation, providing cytoprotection and inhibiting leukocyte migration to inflammatory sites. Although in vitro studies have suggested an additional role for HO-1 in angiogenesis, the relevance of this in vivo remains unknown. We investigated the involvement of HO-1 in angiogenesis in vitro and in vivo. Vascular endothelial growth factor (VEGF) induced prolonged HO-1 expression and activity in human endothelial cells and HO-1 inhibition abrogated VEGF-driven angiogenesis. Two murine models of angiogenesis were used: (1) angiogenesis initiated by addition of VEGF to Matrigel and (2) a lipopolysaccharide (LPS)–induced model of inflammatory angiogenesis in which angiogenesis is secondary to leukocyte invasion. Pharmacologic inhibition of HO-1 induced marked leukocytic infiltration that enhanced VEGF-induced angiogenesis. However, in the presence of an anti-CD18 monoclonal antibody (mAb) to block leukocyte migration, VEGF-induced angiogenesis was significantly inhibited by HO-1 antagonists. Furthermore, in the LPS-induced model of inflammatory angiogenesis, induction of HO-1 with cobalt protoporphyrin significantly inhibited leukocyte invasion into LPS-conditioned Matrigel and thus prevented the subsequent angiogenesis. We therefore propose that during chronic inflammation HO-1 has 2 roles: first, an anti-inflammatory action inhibiting leukocyte infiltration; and second, promotion of VEGF-driven noninflammatory angiogenesis that facilitates tissue repair.

Transcription factor Nrf2 regulates inflammation by mediating the effect of 15-deoxy-Delta(12,14)-prostaglandin j(2)

Activated macrophages express high levels of Nrf2, a transcription factor that positively regulates the gene expression of antioxidant and detoxication enzymes. In this study, we examined how Nrf2 contributes to the anti-inflammatory process. As a model system of acute inflammation, we administered carrageenan to induce pleurisy and found that in Nrf2-deficient mice, tissue invasion by neutrophils persisted during inflammation and the recruitment of macrophages was delayed. Using an antibody against 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), it was observed that macrophages from pleural lavage accumulate 15d-PGJ(2). We show that in mouse peritoneal macrophages 15d-PGJ(2) can activate Nrf2 by forming adducts with Keap1, resulting in an Nrf2-dependent induction of heme oxygenase 1 and peroxiredoxin I (PrxI) gene expression. Administration of the cyclooxygenase 2 inhibitor NS-398 to mice with carrageenan-induced pleurisy caused persistence of neutrophil recruitment and, in macrophages, attenuated the 15d-PGJ(2) accumulation and PrxI expression. Administration of 15d-PGJ(2) into the pleural space of NS-398-treated wild-type mice largely counteracted both the decrease in PrxI and persistence of neutrophil recruitment. In contrast, these changes did not occur in the Nrf2-deficient mice. These results demonstrate that Nrf2 regulates the inflammation process downstream of 15d-PGJ(2) by orchestrating the recruitment of inflammatory cells and regulating the gene expression within those cells.

Peroxisome proliferator-activated receptor gamma (PPARgamma) ligands as bifunctional regulators of cell proliferation

Peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the ligand-activated nuclear receptor superfamily, plays a key role in mediating differentiation of adipocytes and regulating fat metabolism. PPARgamma has been implicated in the pathophysiology of atherosclerosis, inflammation, obesity, diabetes, immune response, and ageing. Recently, it has been shown that activation of PPARgamma by J(2) series cyclopentenone prostaglandins (cyPGs), especially 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) or synthetic agents, such as antidiabetic thiazolidinediones, causes anti-proliferation, apoptosis, differentiation, and anti-inflammation of certain types of cancer cells. The anti-proliferative effects of PPARgamma activators are associated with de novo synthesis of proteins involved in regulating the cell cycle and cell survival/death. Anti-inflammatory effects of 15d-PGJ(2) are associated with interruption of nuclear factor-kappaB and subsequent blockade of inflammatory gene expression. Furthermore, 15d-PGJ(2) at nontoxic doses induce expression of phase II detoxification or stress-responding enzymes, which may confer cellular resistance or adaptation to oxidative stress. The presence of a reactive alpha,beta-unsaturated carbonyl moiety in the cyclopentenone ring of 15d-PGJ(2) is important for part of biological functions this cyPG has. Recently, attention has been focused on the anti-proliferative activity of nonsteroidal anti-inflammatory drugs (NSAIDs) in cancerous or transformed cells, which is mediated through interaction with PPARgamma irrespective of their ability to inhibit COX-2. Despite the fact that abnormally elevated COX-2 is associated with resistance to cell death, induction of apoptosis by certain NSAIDs is accompanied by up-regulation of COX-2 expression. This commentary focuses on dual effects of the typical PPARgamma agonist 15d-PGJ(2) on cell proliferation and growth, and its possible involvement in the NSAID-induced COX-2 expression and apoptosis.

Induction of HO-1 in tissue macrophages and monocytes in fatal falciparum malaria and sepsis

BACKGROUND: As well as being inducible by haem, haemoxygenase -1 (HO-1) is also induced by interleukin-10 and an anti-inflammatory prostaglandin, 15d PGJ2, the carbon monoxide thus produced mediating the anti-inflammatory effects of these molecules. The cellular distribution of HO-1, by immunohistochemistry, in brain, lung and liver in fatal falciparum malaria, and in sepsis, is reported. METHODS: Wax sections were stained, at a 1:1000 dilution of primary antibody, for HO-1 in tissues collected during paediatric autopsies in Blantyre, Malawi. These comprised 37 acutely ill comatose patients, 32 of whom were diagnosed clinically as cerebral malaria and the other 5 as bacterial diseases with coma. Another 3 died unexpectedly from an alert state. Other control tissues were from Australian adults. RESULTS: Apart from its presence in splenic red pulp macrophages and microhaemorrhages, staining for HO-1 was confined to intravascular monocytes and certain tissue macrophages. Of the 32 clinically diagnosed cerebral malaria cases, 11 (category A) cases had negligible histological change in the brain and absence of or scanty intravascular sequestration of parasitized erythrocytes. Of these 11 cases, eight proved at autopsy to have other pathological changes as well, and none of these eight showed HO-1 staining within the brain apart from isolated moderate staining in one case. Two of the three without another pathological diagnosis showed moderate staining of scattered monocytes in brain vessels. Six of these 11 (category A) cases exhibited strong lung staining, and the Kupffer cells of nine of them were intensely stained. Of the seven (category B) cases with no histological changes in the brain, but appreciable sequestered parasitised erythrocytes present, one was without staining, and the other six showed strongly staining, rare or scattered monocytes in cerebral vessels. All six lung sections not obscured by neutrophils showed strong staining of monocytes and alveolar macrophages, and all six available liver sections showed moderate or strong staining of Kupffer cells. Of the 14 (category C) cases, in which brains showed micro-haemorrhages and intravascular mononuclear cell accumulations, plus sequestered parasitised erythrocytes, all exhibited strong monocyte HO-1 staining in cells forming accumulations and scattered singly within cerebral blood vessels. Eleven of the available and readable 13 lung sections showed strongly staining monocytes and alveolar macrophages, and one stained moderately. All of the 14 livers had strongly stained Kupffer cells. Of five cases of comatose culture-defined bacterial infection, three showed a scattering of stained monocytes in vessels within the brain parenchyma, three had stained cells in lung sections, and all five demonstrated moderately or strongly staining Kupffer cells. Brain sections from all three African controls, lung sections from two of them, and liver from one, showed no staining for HO-1, and other control lung and liver sections showed few, palely stained cells only. Australian-origin adult brains exhibited no staining, whether the patients had died from coronary artery disease or from non-infectious, non-cerebral conditions CONCLUSIONS: Clinically diagnosed 'cerebral malaria' in children includes some cases in whom malaria is not the only diagnosis with the hindsight afforded by autopsy. In these patients there is widespread systemic inflammation, judged by HO-1 induction, at the time of death, but minimal intracerebral inflammation. In other cases with no pathological diagnosis except malaria, there is evidence of widespread inflammatory responses both in the brain and in other major organs. The relative contributions of intracerebral and systemic host inflammatory responses in the pathogenesis of coma and death in malaria deserve further investigation.

Heme oxygenase-1: unleashing the protective properties of heme

Heme oxygenase (HO)-1 catabolizes heme into three products: carbon monoxide (CO), biliverdin (which is rapidly converted to bilirubin) and free iron (which leads to the induction of ferritin, an iron-binding protein). HO-1 serves as a "protective" gene by virtue of the anti-inflammatory, anti-apoptotic and anti-proliferative actions of one or more of these three products. Administration of CO, biliverdin, bilirubin or iron-binding compounds is protective in rodent disease models of ischemia-reperfusion injury, allograft and xenograft survival, intimal hyperplasia following balloon injury or as seen in chronic graft rejection and others. We suggest that the products of HO-1 action could be valuable therapeutic agents and speculate that HO-1 functions as a "therapeutic funnel", mediating the beneficial effects attributed to other molecules, such as interleukin-10 (IL-10), inducible nitric oxide synthase (NOS2; iNOS) and prostaglandins. This Review is the third in a series on the regulation of the immune system by metabolic pathways.