Inhibition of caspase 3 abrogates lipopolysaccharide-induced nitric oxide production by preventing activation of NF-kappaB and c-Jun NH2-terminal kinase/stress-activated protein kinase in RAW 264.7 murine macrophage cells

The Role of HSP70 in the Protective Effects of NVP-AUY922 on Multiple Organ Dysfunction Syndrome in Endotoxemic Rats

Sepsis is defined as a life-threatening organ dysfunction syndrome with high morbidity and mortality caused by bacterial infection. The major characteristics of sepsis are systemic inflammatory responses accompanied with elevated oxidative stress, leading to multiple organ dysfunction syndrome (MODS), and disseminated intravascular coagulation (DIC). As a molecular chaperon to repair unfolded proteins, heat shock protein 70 (HSP70) maintains cellular homeostasis and shows protective effects on inflammatory damage. HSP 90 inhibitors were reported to exert anti-inflammatory effects via activation of the heat shock factor-1 (HSF-1), leading to induction of HSP70. We evaluated the beneficial effect of HSP 90 inhibitor NVP-AUY 922 (NVP) on multiple organ dysfunction syndrome induced by lipopolysaccharide (LPS) and further explored the underlying mechanism. NVP (5 mg/kg, i.p.) was administered 20 h prior to LPS initiation (LPS 30 mg/kg, i.v. infusion for 4 h) in male Wistar rats. Results demonstrated that pretreatment with NVP significantly increased survival rate and prevented hypotension at 6 h after LPS injection. Plasma levels of ALT, CRE and LDH as well as IL-1β and TNF-α were significantly reduced by NVP at 6 h after LPS challenge. The induction of inducible NO synthase in the liver, lung and heart and NF-κB p-p65 and caspase 3 protein expression in the heart were also attenuated by NVP. In addition, NVP markedly induced HSP70 and HO-1 proteins in the liver, lung and heart after LPS injection. These results indicated that NVP possessed the anti-inflammatory and antioxidant effects on LPS-induced acute inflammation, which might be associated with HSP70 and HO-1, leading to prevent MODS in sepsis. NVP might be considered as a novel therapeutic strategy in the prevention of sepsis-induced MODS.

Alpha-1-Antitrypsin Enhances Primary Human Macrophage Immunity Against Non-tuberculous Mycobacteria

Rationale: The association between non-tuberculous mycobacterial lung disease and alpha-1-antitrypsin (AAT) deficiency is likely due, in part, to underlying emphysema or bronchiectasis. But there is increasing evidence that AAT itself enhances host immunity against microbial pathogens and thus deficiency could compromise host protection.

Objectives: The goal of this project is to determine if AAT could augment macrophage activity against non-tuberculous mycobacteria.

Methods: We compared the ability of monocyte-derived macrophages cultured in autologous plasma that were obtained immediately before and soon after AAT infusion—given to individuals with AAT deficiency—to control an ex vivo Mycobacterium intracellulare infection.

Measurements and Main Results: We found that compared to pre-AAT infused monocyte-derived macrophages plus plasma, macrophages, and contemporaneous plasma obtained after a session of AAT infusion were significantly better able to control M. intracellulare infection; the reduced bacterial burden was linked with greater phagosome-lysosome fusion and increased autophagosome formation/maturation, the latter due to AAT inhibition of both M. intracellulare–induced nuclear factor-kappa B activation and A20 expression. While there was a modest increase in apoptosis in the M. intracellulare-infected post-AAT infused macrophages and plasma, inhibiting caspase-3 in THP-1 cells, monocyte-derived macrophages, and alveolar macrophages unexpectedly reduced the M. intracellulare burden, indicating that apoptosis impairs macrophage control of M. intracellulare and that the host protective effects of AAT occurred despite inducing apoptosis.

Conclusion: AAT augments macrophage control of M. intracellulare infection through enhancing phagosome-lysosome fusion and autophagy.

Caspases are key regulators of inflammatory and innate immune responses mediated by TLR3 in vivo

Understanding the key regulators which impact the innate immune response during initial phases of tissue injury, can advance the use of therapeutic approaches which aim at attenuating inflammation and organ damage. Recognition of microbial components by TLRs, initiates the transcription of innate immune signal pathways, that induce the expression of key inflammatory mediators: cytokines, chemokines and adhesion molecules. Beside regulating apoptotic cell death, recent studies have revealed distinct roles for caspases in the optimal production of inflammatory cytokines and host defense against injurious infections. Whether caspases can play an immune regulatory role in vivo has not been sufficiently investigated. This study aims to explore whether the pan caspase inhibitor z-VAD-fmk can control inflammation and cytokine production subsequent to challenging the innate immunity of the exocrine secretory tissues in vivo. Submandibular glands (SMGs) of the C57BL/6 mice were challenged with the TLR3 stimulant: polyinosinic-polycytidylic acid (poly (I:C)). Results obtained from the current study provide evidence that caspases can control immune responses downstream of TLR3 ligation. The present work proposes a novel mechanism that can prevent overactivation of the innate immunity, which typically leads to fatal immune disorders.

Hepatoprotective activity of Lepidium sativum seeds against D-galactosamine/lipopolysaccharide induced hepatotoxicity in animal model

BACKGROUND

Fulminant hepatic failure (FHF) is clinical syndrome with very poor prognosis and high mortality there is urgent need for the development of safe and non-toxic hepatoprotective agents for the adequate management of hepatitis. Hepatoprotective effect of the Lepidium sativum ethanolic extract (LSEE) was assessed by D-galactosamine-induced/lipopolysaccharide (400 mg/kg and 30 μg/kg) liver damage model in rats.

METHODS

Hepatoprotective activity of LSEE (150 and 300 mg/kg) and silymarin on D-GalN/LPS induced FHF in rat was assessed using several liver function enzyme parameters. Antioxidant properties as antioxidant stress enzymes were assessed in hepatic Liver as well as mRNA expression of cytokines genes such as TNF-α, IL-6, and IL-10 and stress related genes iNOS and HO-1 were determined by RT-PCR. Protein expression of apoptotic genes were evaluated through western blot. MPO and NF-κB DNA-binding activity was analyzed by ELISA. The magnitude of hepatic impairment was investigated through histopathological evaluation.

RESULTS

Marked amelioration of hepatic injuries by attenuation of serum and lipid peroxidation has been observed as comparable with silymarin (25 mg/kg p.o). D-GalN/LPS induced significant decrease in oxidative stress markers protein level, and albumin. LSEE significantly down-regulated the D-GalN/LPS induced pro-inflammatory cytokines TNFα and IL-6 mRNA expression in dose dependent fashion about 0.47 and 0.26 fold and up-regulates the IL-10 by 1.9 and 2.8 fold, respectively. While encourages hepatoprotective activity by down-regulating mRNA expression of iNOS and HO-1. MPO activity and NF-κB DNA-binding effect significantly increased and was mitigated by LSEE in a dose-dependent style as paralleled with silymarin.

CONCLUSION

Our data suggests that pretreatment of LSEE down regulates the caspase 3 and up-regulates the BCl₂ protein expression. The above findings revealed that Lepidium sativum has significant hepatoprotective activity.

The inhibitory action of quercetin on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophage cells

The effect of quercetin on lipopolysaccharide (LPS)-induced nitric oxide (NO) production was studied. Quercetin pretreatment significantly inhibited NO production in an LPS-stimulated RAW 264.7 murine macrophage cell line. Post-treatment with quercetin partially inhibited NO production. The inhibitory action of quercetin was due to neither the cytotoxic action nor altered LPS binding. The expression of inducible-type NO synthase (iNOS) was markedly down-regulated by quercetin. Quercetin suppressed the release of free nuclear factor (NF)-κB by preventing degradation of IκB-α and IκB-β. Moreover, quercetin blocked the phosphorylation of extracellular signal regulated kinase 1/2 (Erk1/2), p38, and c-Jun NH 2-terminal kinase/stress-activated protein kinase (JNK/SAPK) and, further, the activity of tyrosine kinases in LPS-stimulated RAW cells. Quercetin also inhibited interferon (IFN)-γ-induced NO production. Taken together, these results indicate that the inhibitory action of quercetin on NO production in LPS- and/or IFN-γ-stimulated macrophages might be due to abrogation of iNOS protein induction by impairment of a series of intracellular signal pathways.

Hepatoprotective effect of Commiphora myrrha against d-GalN/LPS-induced hepatic injury in a rat model through attenuation of pro inflammatory cytokines and related genes

CONTEXT

Commiphora myrrha (Burseraceae), a shrub resembling a small tree, has been used for several centuries for the treatment of various diseases.

OBJECTIVE

This study investigates the hepatoprotective activity of C. myrrha ethanol extract against d-galactosamine/lipopolysaccharide (d-GalN/LPS)-induced acute hepatic injury in an animal model.

MATERIALS AND METHODS

Rats were pretreated with ethanolic extract C. myrrha (250 and 500 mg/kg; p.o.) for 7 d prior to the induction of an acute phase response by d-GalN/LPS. Animals were sacrificed 24 h after d-GalN/LPS (800 mg/kg and 50 µg/kg i.p.) administration for the biochemical and histological analyses.

RESULTS

The administration of d-GalN/LPS increased plasma aminotransferases (174.47 ± 4.5761 and 260.96 ± 1.9839 µkat/l) and total bilirubin levels (1.012 ± 0.0288 mg/dl), which were attenuated by C. myrrha treatment. Hepatic lipid peroxidation activity and nitric oxide content also increased, while the antioxidant activity measured by GSH (0.76 nmol/g protein), SOD (81.91 U/mg protein), and CAT (15.78 U/mg protein) was reduced. Commiphora myrrha provided significant restoration of GSH (0.815 nmol/gm protein), SOD (140.57 U/mg protein), and CAT (27.02 U/mg protein) levels. Furthermore, the acute phase response elicited by d-GalN/LPS administration enhanced mRNA expressions of TNF-α, IL-6, IL-10, iNOS-2, and HO-1, which were ameliorated by C. myrrha treatment.

DISCUSSION AND CONCLUSION

These findings indicate that C. myrrha considerably reduces the oxidative stress of d-GalN/LPS-induced hepatic injury via multiple pathways including adown regulation of inflammatory mediators and cytokines. Such a property might be sufficient to combat cellular damage caused by various conditions that resemble fulminant hepatitis and could be of a potential clinical application.

Evaluation of the effectiveness of Piper cubeba extract in the amelioration of CCl4-induced liver injuries and oxidative damage in the rodent model

Background. Liver diseases still represent a major health burden worldwide. Moreover, medicinal plants have gained popularity in the treatment of several diseases including liver. Thus, the present study was to evaluate the effectiveness of Piper cubeba fruits in the amelioration of CCl₄-induced liver injuries and oxidative damage in the rodent model. Methods. Hepatoprotective activity was assessed using various biochemical parameters like SGOT, SGPT, γ-GGT, ALP, total bilirubin, LDH, and total protein. Meanwhile, in vivo antioxidant activities as LPO, NP-SH, and CAT were measured in rat liver as well as mRNA expression of cytokines such as TNFα, IL-6, and IL-10 and stress related genes iNOS and HO-1 were determined by RT-PCR. The extent of liver damage was also analyzed through histopathological observations. Results. Treatment with PCEE significantly and dose dependently prevented drug induced increase in serum levels of hepatic enzymes. Furthermore, PCEE significantly reduced the lipid peroxidation in the liver tissue and restored activities of defense antioxidant enzymes NP-SH and CAT towards normal levels. The administration of PCEE significantly downregulated the CCl₄-induced proinflammatory cytokines TNFα and IL-6 mRNA expression in dose dependent manner, while it upregulated the IL-10 and induced hepatoprotective effect by downregulating mRNA expression of iNOS and HO-1 gene.

Role of α-lipoic acid in LPS/d-GalN induced fulminant hepatic failure in mice: studies on oxidative stress, inflammation and apoptosis

This study investigated the protective effect of α-lipoic acid (LA) on lipopolysaccharide (LPS)/d-galactosamine (d-GalN)-induced fulminant hepatic failure in mice. First, we found that LA markedly reduced LPS/d-GalN-induced increases in serum ALT and AST activities, which were supplemented with histopathological examination, suggested that LA has a protective effect on this model of hepatic damage. Livers challenged with LPS/d-GalN exhibited extensive areas of vacuolization with the disappearance of nuclei and the loss of hepatic architecture. On the contrary, these pathological alterations were ameliorated by LA treatment. Next, we found that ROS and TBARS levels were increased in LPS/d-GalN treated liver homogenates, which were attenuated by LA administration. Consistently, decreases in hepatic CAT and GPx activities were observed in LPS/d-GalN group and were significantly restored by LA administration. Moreover, pretreatment with LA markedly reduced LPS/d-GalN-induced iNOS, COX-2, TNF-α, NF-κB, IL-1β and IL-6 expressions. Furthermore, our data showed that TUNEL-positive cells increased in LPS/d-GalN-treated mice liver which was counteracted by LA administration. LPS/d-GalN induced apoptosis of hepatocytes, as estimated by caspase 3, caspase 8 and caspase 9 activations. Also, the increasing of Bax and the decreasing of Bcl-2 expressions also supported LPS/d-GalN induced apoptosis. Interestingly, LA marked relieved these apoptotic features. Taking together, our results indicated that LA plays an important role on LPS/d-GalN-induced fulminant hepatic failure through its antioxidant, anti-inflammatory and anti-apoptotic activities.

Piceatannol Prevents Lipopolysaccharide (LPS)-Induced Nitric Oxide (NO) Production and Nuclear Factor (NF)-κB Activation by Inhibiting IκB Kinase (IKK)

The effect of piceatannol on lipopolysaccharide (LPS)-induced nitric oxide (NO) production was examined. Piceatannol significantly inhibited NO production in LPS-stimulated RAW 264.7 cells. The inhibition was due to the reduced expression of an inducible isoform of NO synthase (iNOS). The inhibitory effect of piceatannol was mediated by down-regulation of LPS-induced nuclear factor (NF)-kappaB activation, but not by its cytotoxic action. Piceatannol inhibited IkappaB kinase (IKK)-alpha and beta phosphorylation, and subsequently IkappaB-alpha phosphorylation in LPS-stimulated RAW 264.7 cells. On the other hand, piceatannol did not affect activation of mitogen-activated protein (MAP) kinases including extracellular signal regulated kinase 1/2 (Erk1/2), p38 and stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK). Piceatannol inhibited the phosphorylation of Akt and Raf-1 molecules, which regulated the activation of IKK-alpha and beta phosphorylation. The detailed mechanism of the inhibition of LPS-induced NO production by piceatannol is discussed.

Parvoviruses cause nuclear envelope breakdown by activating key enzymes of mitosis

Disassembly of the nuclear lamina is essential in mitosis and apoptosis requiring multiple coordinated enzymatic activities in nucleus and cytoplasm. Activation and coordination of the different activities is poorly understood and moreover complicated as some factors translocate between cytoplasm and nucleus in preparatory phases. Here we used the ability of parvoviruses to induce nuclear membrane breakdown to understand the triggers of key mitotic enzymes. Nuclear envelope disintegration was shown upon infection, microinjection but also upon their application to permeabilized cells. The latter technique also showed that nuclear envelope disintegration was independent upon soluble cytoplasmic factors. Using time-lapse microscopy, we observed that nuclear disassembly exhibited mitosis-like kinetics and occurred suddenly, implying a catastrophic event irrespective of cell- or type of parvovirus used. Analyzing the order of the processes allowed us to propose a model starting with direct binding of parvoviruses to distinct proteins of the nuclear pore causing structural rearrangement of the parvoviruses. The resulting exposure of domains comprising amphipathic helices was required for nuclear envelope disintegration, which comprised disruption of inner and outer nuclear membrane as shown by electron microscopy. Consistent with Ca⁺⁺ efflux from the lumen between inner and outer nuclear membrane we found that Ca⁺⁺ was essential for nuclear disassembly by activating PKC. PKC activation then triggered activation of cdk-2, which became further activated by caspase-3. Collectively our study shows a unique interaction of a virus with the nuclear envelope, provides evidence that a nuclear pool of executing enzymes is sufficient for nuclear disassembly in quiescent cells, and demonstrates that nuclear disassembly can be uncoupled from initial phases of mitosis.

Parvoviruses are small non-enveloped DNA viruses successfully used in gene therapy. Their nuclear replication requires transit of the nuclear envelope. Analyzing the interaction between parvoviruses and the nucleus, we showed that despite their small size, they did not traverse the nuclear pore, but attached directly to proteins of the nuclear pore complex. We observed that this binding induced structural changes of the parvoviruses and that the structural rearrangement was essential for triggering a signal cascade resulting in disintegration of the nuclear envelope. Physiologically such nuclear envelope breakdown occurs late during prophase of mitosis. Our finding that the parvovirus-mediated nuclear envelope breakdown also occurred in the absence of soluble cytosolic factors allowed us to decipher the intra nuclear pathways involved in nuclear envelope destabilization. Consistently with the physiological disintegration we found that key enzymes of mitosis were essential and we further identified Ca⁺⁺ as the initial trigger. Thus our data not only show a unique pathway of how a DNA virus interacts with the nucleus but also describes a virus-based system allowing the first time to analyze selectively the intranuclear pathways leading to nuclear envelope disintegration.

Multi-omic data integration links deleted in breast cancer 1 (DBC1) degradation to chromatin remodeling in inflammatory response

This study investigated the dynamics of ubiquitinated proteins after the inflammatory stimulation of RAW 264.7 macrophage-like cells with bacterial lipopolysaccharide. Ubiquitination is a common protein post-translational modification that regulates many key cellular functions. We demonstrated that levels of global ubiquitination and K48 and K63 polyubiquitin chains change after lipopolysaccharide stimulation. Quantitative proteomic analysis identified 1199 ubiquitinated proteins, 78 of which exhibited significant changes in ubiquitination levels following stimulation. Integrating the ubiquitinome data with global proteomic and transcriptomic results allowed us to identify a subset of 88 proteins that were targeted for degradation after lipopolysaccharide stimulation. Using cellular assays and Western blot analyses, we biochemically validated DBC1 (a histone deacetylase inhibitor) as a degradation substrate that is targeted via an orchestrated mechanism utilizing caspases and the proteasome. The degradation of DBC1 releases histone deacetylase activity, linking lipopolysaccharide activation to chromatin remodeling in caspase- and proteasome-mediated signaling.

The involvement of heme oxygenase 1 but not nitric oxide synthase 2 in a hepatoprotective action of quercetin in lipopolysaccharide-induced hepatotoxicity of D-galactosamine sensitized rats

The objective of this study was to evaluate potential hepatoprotective capabilities of quercetin in relation to its modulation of the HO-1 and NOS-2 activities in an experimental model of fulminant liver failure. Liver insult was induced by in vivo administration of D-galactosamine (d-GalN, 400 mg/kg, i.p.) and lipopolysaccharide (LPS, 10 μg/kg, i.p.). The effects of quercetin (50 mg/kg, i.p) on D-GalN toxicity was evaluated by standard biochemical, RT-PCR and Western blot methods. Administration of d-GalN/LPS combination resulted in significantly higher plasma levels of aminotransferases, as well as increased mRNA and protein expressions of both HO-1 and NOS-2 enzymes. Quercetin exhibited cytoprotective effects on the liver, as evidenced by decreased aminotransferase plasma levels. Additionally, quercetin treatment in D-GalN/LPS treated rats significantly increased HO-1 mRNA and its protein expressions. On the contrary, quercetin did not exhibit any significant effects on the levels of nitrites, and NOS-2 mRNA and protein expressions in D-GalN/LPS treated rats. Quercetin when given alone did not have any significant changes on liver enzymes nor HO-1 and NOS-2 mRNA and protein expressions. It can be concluded that the quercetin's induction of HO-1 and its byproducts, without concomitant NOS-2 activity reduction, is among mechanisms contributing to the hepatoprotective effect in D-GalN/LPS hepatotoxicity.

Inhibition of inducible nitric oxide synthase prevents graft injury after transplantation of livers from rats after cardiac death

This study investigated the roles of inducible nitric oxide synthase (iNOS) in the failure of rat liver grafts from cardiac death donors (GCDD). Livers were explanted after 30-minute aorta clamping and implanted after 4-hour storage in University of Wisconsin solution. The iNOS expression increased slightly in grafts from non-cardiac death donors (GNCDD) but markedly in GCDD. Serum nitrite and nitrate and hepatic 3-nitrotyrosine adducts, indicators of NO and peroxynitrite production, respectively, were substantially higher after transplantation of GCDD than GNCDD. Production of reactive nitrogen species (RNS) was largely blocked by 1400W (N-[1-naphthyl]ethylenediamine dihydrochloride; 5 μM), a specific iNOS inhibitor. Alanine aminotransferase release, bilirubin, necrosis, and apoptosis were 6.4-fold, 6.5-fold, 2.3-fold, and 2.7-fold higher, respectively, after transplantation of GCDD than GNCDD. The inhibitor 1400W effectively blocked these alterations and also increased survival of GCDD to 80% from 33%. Increased RNS production and failure of GCDD were associated with activation of c-Jun-N-terminal kinase (JNK), an effect that was blocked by inhibition of iNOS. Inhibition of JNK also improved the outcome after transplantation of GCDD. Together, the data indicate that iNOS increases substantially in GCDD, leading to RNS overproduction, JNK activation, and more severe graft injury. Inhibitors of iNOS are suggested as effective therapies to improve the outcome after transplantation of GCDD.

The release of microparticles by RAW 264.7 macrophage cells stimulated with TLR ligands

TLR ligands induce microparticle release by macrophages and highlight the importance of nitric oxide.

MPs are small membrane-bound particles that originate from activated and dying cells and mediate intercellular communication. Once released from cells, MPs can serve as novel signaling elements in innate immunity, with levels elevated in immune-mediated diseases. This study tested the hypothesis that TLR stimulation can induce MP release by macrophages. In these experiments, using the RAW 264.7 murine macrophage cell line as a model, LPS, a TLR4 ligand, and poly(I:C), a TLR3 ligand, induced MP release effectively, as measured by flow cytometry; in contrast, a CpG oligonucleotide, which can stimulate TLR9, induced much lower levels of particle release. To determine the role of other mediators in this response, the effects of NO were tested. Thus, MP release from RAW 264.7 cells stimulated by LPS or poly(I:C) correlated with NO production, and treatment with the iNOS inhibitor 1400W decreased particle release and NO production. Furthermore, treatment of RAW 264.7 cells with NO donors induced MP production. As TLR ligands can induce apoptosis, the effect of caspase inhibition on MP release by stimulated cells was assessed. These experiments showed that the pan-caspase inhibitor, ZVAD, although decreasing NO production, increased MP release by stimulated cells. Together, these experiments demonstrate that TLR stimulation of macrophages can lead to MP release, and NO plays a key role in this response.

Bee venom suppresses LPS-mediated NO/iNOS induction through inhibition of PKC-alpha expression

ETHNOPHARMACOLOGICAL RELEVANCE

Bee venom (BV) is a traditional Korean medicine that has been widely used with satisfactory results in the treatment of some immune-related diseases, especially rheumatoid arthritis.

AIM OF THE STUDY

The purpose of this study is to elucidate the molecular mechanism underlying the anti-inflammatory effects of BV, which is used in the treatment of various inflammatory diseases in traditional Korean medicine. We evaluated the anti-inflammatory effect of BV on NO generation and iNOS expression by LPS in rat C6 glioma cells.

MATERIAL AND METHODS

BV was obtained from the National Institute of Agricultural Science and Technology (NIAST) of Korea. Nitrite measurement, Immuno blot analysis, Reverse transcriptase-PCR and Electrophoretic mobility shift assay (EMSA) were used for assessment.

RESULTS

BV suppressed the LPS-induced NO generation and iNOS expression, and it also inhibited the expressions of LPS-induced pro-inflammatory molecules including Cox-2 and IL-1 beta in rat C6 glioma cells. Then, BV inhibited LPS-induced expression of PKC-alpha and MEK/ERK, not p38 and JNK. Moreover, inhibition of LPS-induced iNOS expression by BV was dependent on transcriptional activities of AP-1/NF-kappaB through MEK/ERK pathway.

CONCLUSION

These results indicate that BV suppresses LPS-induced iNOS activation through regulation of PKC-alpha. Accordingly, BV exerts a potent suppressive effect on pro-inflammatory responses in rat C6 glioma cells.

Dual Role of Intrauterine Immune Challenge on Neonatal and Adult Brain Vulnerability to Hypoxia-Ischemia

Epidemiologic evidence has underlined the impact of prenatal inflammation on the development of postnatal hypoxia-ischemia (HI) brain injury. To study to what extent prenatal inflammation affects CNS vulnerability later during development, C57BL/6 mice were subjected to intrauterine injection of lipopolysaccharide (LPS) at gestational day 15. At postnatal day (PND) 5, 9, and 70, the offspring were subjected to HI. It was found that, in neonatal mice, LPS-exposed brains showed markedly enhanced brain injury after HI, whereas in adult mice, LPS exposure resulted in a significant reduction in tissue loss after HI. Reduced myelin in subcortical white matter was noticed after HI in the LPS-exposed brains at PND14 and PND75. Increased activities of nuclear factor-kappaB and caspase-3 were obtained in fetal/neonatal brain after LPS administration. Conclusions were that 1) a prenatal low dose of LPS sensitized to HI-induced brain injury in neonates but confers protection in adulthood, 2) reduced myelination is seen after prenatal LPS exposure and HI in both neonatal and adult mice despite the fact that LPS reduced total tissue loss in adult mice; and 3) nuclear factor-kappaB and caspase-3 activation early after LPS exposure may play a role in the sensitization/protection (preconditioning) effects.

Insoluble matrix components of glioma cells suppress LPS-mediated iNOS/NO induction in microglia

This study examines the influence of insoluble matrix components of glioma (astrocytoma) cells on LPS-mediated inducible nitric oxide (NO)/NO synthase (iNOS) induction in microglia cells. Insoluble matrix components prepared from C6 rat glioma cells strongly suppressed iNOS induction and subsequent NO release induced by LPS. Matrices prepared from several glioma cell lines displayed similar inhibitory effects on LPS-induced NO/iNOS induction, whereas matrices from primary cultured rat astrocytes had a minimal influence. Of the various purified ECM materials examined, collagen suppressed LPS-mediated iNOS/NO induction in microglia. C6 matrices potentiated LPS-induced NF-kappaB DNA binding/transcriptional activity, suggesting that the suppression of LPS-induced iNOS by C6 matrices is NF-kappaB independent. C6 matrices inhibited LPS-mediated activation of p38 and JNK MAP kinases. This study shows that non-diffusible factors derived from astrocytoma cells in the brain are critically involved in the suppression of microglial cell activation. Our results indicate that activation of microglia can be regulated by various cellular and pathological environmental conditions, not only through cell-cell contact or soluble factors, but also via insoluble matrix components.

Angiotensin II type 2 receptor-bradykinin B2 receptor functional heterodimerization

Angiotensin II type 2 (AT2R) or bradykinin B2 (B2R) receptor activation enhances NO production. Recently, we demonstrated enhancement of NO production when AT2R and B2R are simultaneously activated in vivo. However, the mechanism involved in this enhancement is unknown. Using confocal fluorescence resonance energy transfer microscopy, we report the distance between the AT2R and B2R in PC12W cell membranes to be 50+/-5 A, providing evidence and quantification of receptor heterodimerization as the mechanism for enhancing NO production. The rate of AT2R-B2R heterodimer formation is largely a function of the degree of AT2R-B2R expression. The physical association between the dimerized receptors initiates changes in intracellular phosphoprotein signaling activities leading to phosphorylation of c-Jun terminal kinase, phosphotyrosine phosphatase, inhibitory protein kappaBalpha, and activating transcription factor 2; dephosphorylation of p38 and p42/44 mitogen-activated protein kinase and signal transducer inhibitor of transcription 3; and enhancing production of NO and cGMP. Controlling the expression of AT2R-B2R, consequently influencing their biologically active dimerization, presents a potential therapeutic target for the treatment of hypertension and other cardiovascular and renal disorders.

c-Jun N-terminal kinase inhibition and alpha-tocopherol protect midbrain dopaminergic neurons from interferon-gamma/lipopolysaccharide-induced injury without affecting nitric oxide production

Interferon-gamma (IFN-gamma)/lipopolysaccharide (LPS) induces delayed dopaminergic neuron loss in midbrain slice cultures, because of nitric oxide production resulting from p38 mitogen-activated protein kinase (p38 MAPK)-dependent induction of inducible nitric oxide synthase (iNOS). In this study, we show that inhibition of c-Jun N-terminal kinase (JNK), but not of extracellular signal-regulated kinase, protects dopaminergic neurons from IFN-gamma/LPS-induced degeneration. In contrast to a p38 MAPK inhibitor, SB203580, however, a JNK inhibitor, anthra[1,9-cd]pyrazol-6(2H)-one (SP600125), did not suppress IFN-gamma/LPS-induced iNOS expression and nitric oxide production. Involvement of NADPH oxidase-derived superoxide production in dopaminergic neurodegeneration was not obvious, in that superoxide dismutase/catalase or manganese 3-methoxy-N,N'-bis(salicylidene)ethylenediamine chloride (EUK-134), a superoxide dismutase/catalase mimetic, did not afford neuroprotection. Moreover, the NADPH oxidase inhibitors apocynin and diphenylene iodonium were protective against IFN-gamma/LPS cytotoxicity only at concentrations that suppressed nitric oxide production. Notably, alpha-tocopherol effectively prevented IFN-gamma/LPS-induced dopaminergic neuron degeneration, without affecting iNOS induction and nitric oxide production. These results underscore the neuroprotective potential of JNK inhibitor and alpha-tocopherol, in the sense that both agents could rescue dopaminergic neurons under inflammatory conditions associated with robust increases in nitric oxide production.

Caspase inhibitor Z-VAD-FMK potentiates heat shock-induced apoptosis and HSP70 synthesis in macrophages

Caspase inhibitor Z-VAD-FMK potentiated heat shock-induced apoptosis in macrophages. Z-VAD-FMK did not activate HSP70 synthesis, but significantly increased the intensity of this process during heat shock. It cannot be excluded that caspases abolish HSP70 accumulation under these conditions. The HSP70 synthesis inhibitor quercetin potentiated DNA fragmentation in macrophages cocultured with Z-VAD-FMK after heat shock. HSP70 play an important role in the protection of macrophages from caspase-independent apoptosis.

Administration of ricin induces a severe inflammatory response via nonredundant stimulation of ERK, JNK, and P38 MAPK and provides a mouse model of hemolytic uremic syndrome

Recent interest in the health consequences of ricin as a weapon of terrorism has led us to investigate the effects of ricin on cells in vitro and in mice. Our previous studies showed that depurination of the 28S rRNA by ricin results in the inhibition of translation and the coordinate activation of the stress-activated protein kinases JNK and p38 MAPK. In RAW 264.7 macrophages, ricin induced the activation of ERK, JNK, and p38 MAPK, the accumulation of mRNA encoding tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, the transcription factors c-Fos, c-Jun, and EGR1, and the appearance of TNF-alpha protein in the culture medium. Using specific inhibitors of MAPKs, we demonstrated the nonredundant roles of the individual MAPKs in mediating proinflammatory gene activation in response to ricin. Similarly, the intravenous administration of ricin to mice led to the activation of ERK, JNK, and p38 MAPK in the kidneys, and increases in plasma-borne TNF-alpha, IL-1beta, and IL-6. Ricin-injected mice developed the hallmarks of hemolytic uremic syndrome, including thrombotic microangiopathy, hemolytic anemia, thrombocytopenia, and acute renal failure. Microarray analyses demonstrated a massive proinflammatory transcriptional response in the kidneys, coincidental with the symptoms of hemolytic uremic syndrome. Therapeutic management of the inflammatory response may affect the outcome of intoxication by ricin.

Tetrahydropteridines suppress gene expression and induce apoptosis of activated RAW264.7 cells via formation of hydrogen peroxide

Tetrahydrobiopterin, a redox-active cofactor, is essential for nitric oxide (NO) biosynthesis. Previous work showed that intracellular tetrahydrobiopterin levels modulate activity of nitric oxide synthases (NOSs). The 4-amino analog of tetrahydrobiopterin is an effective inhibitor of all three purified NOS isoforms that, in intact cells, preferentially targets the inducible isoenzyme. In vivo, 4-amino-tetrahydrobiopterin prolonged allograft survival and rescued rats from septic shock. Here we investigated the effects of tetrahydrobiopterin and its 4-amino analog on RAW264.7 murine macrophages activated with lipopolysaccharide. Surprisingly, both tetrahydropteridines inhibited NO formation. This was caused by downregulation of inducible NOS expression rather than by affecting enzyme activity. In addition, expression of tumor necrosis factor-alpha was impaired, and apoptosis, as characterized by quantifying DNA content and caspase-3 activation and being associated with the formation of a 33 kDa fragment of nuclear factor-kappaB p65, was induced. The effects of tetrahydropteridines were scavenged by catalase or glutathione but not by superoxide dismutase. Like tetrahydropteridines, hydrogen peroxide at concentrations comparable to those found in tetrahydropteridine-treated cultures affected gene expression and cell survival, whereas increasing intracellular tetrahydrobiopterin levels by sepiapterin did not. Thus, extracellular tetrahydropteridines suppress gene expression and induce apoptosis in RAW264.7 cells via hydrogen peroxide formed in the culture medium during autoxidation.

The enhancing action of d-galactosamine on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophage cells

The effect of D-galactosamine (D-GalN) on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells was examined. D-GalN augmented the production of NO, but not tumor necrosis factor (TNF)-alpha in LPS-stimulated RAW 264.7 cells. Pretreatment of D-GalN augmented the NO production whereas its post-treatment did not. D-GalN augmented the NO production in RAW 264.7 cells stimulated with either TNF-alpha and interferon-gamma. The augmentation of LPS-induced NO production by D-GalN was due to enhanced expressions of an inducible type of NO synthase mRNA and proteins. Intracellular reactive oxygen species (ROS) were exclusively generated in RAW 264.7 cells stimulated with D-GalN and LPS. Scavenging of intracellular ROS abrogated the augmentation of NO production. It was therefore suggested that D-GalN might augment LPS-induced NO production through the generation of intracellular ROS.

TGF-β1 Represses Activation and Resultant Death of Microglia via Inhibition of Phosphatidylinositol 3-Kinase Activity

Overactivation of microglial cells may cause severe brain tissue damage in various neurodegenerative diseases. Therefore, the overactivation of microglia should be repressed by any means. The present study investigated the potential mechanism and signaling pathway for the repressive effect of TGF-beta1, a major anti-inflammatory cytokine, on overactivation and resultant death of microglial cells. A bacterial endotoxin LPS stimulated expression of inducible NO synthase (iNOS) and caused death in cultured microglial cells. TGF-beta1 markedly blocked these LPS effects. However, the LPS-evoked death of microglial cells was not solely attributed to excess production of NO. Because phosphatidylinositol 3-kinase (PI3K) was previously shown to play a crucial role in iNOS expression and cell survival signals, we further studied whether PI3K signaling was associated with the suppressive effect of TGF-beta1. Like TGF-beta1, the PI3K inhibitor LY294002 blocked iNOS expression and death in cultured microglial cells. Both TGF-beta1 and LY294002 decreased the activation of caspases 3 and 11 and the mRNA expression of various kinds of inflammatory molecules caused by LPS. TGF-beta1 was further found to decrease LPS-induced activation of PI3K and Akt. TGF-beta1 and LY294002 suppressed LPS-induced p38 mitogen-activated kinase and c-Jun N-terminal kinase activity. In contrast, TGF-beta1 and LY294002 enhanced LPS-induced NF-kappaB activity. Our data indicate that TGF-beta1 protect normal or damaged brain tissue by repressing overactivation of microglial cells via inhibition of PI3K and its downstream signaling molecules.

c-Jun N-terminal kinase and, to a lesser extent, p38 mitogen-activated protein kinase regulate inducible nitric oxide synthase expression in hyaluronan fragments-stimulated BV-2 microglia

Lower molecular weight of hyaluronan (HA) fragments are capable of activating macrophages to express a number of inflammatory mediators through the interaction with the HA receptor CD44. Recent evidence has demonstrated that concomitant induction of CD44 and HA synthase 2 (HAS-2) mRNA in microglia of the ischemic brain. However, the influence of HA fragments on the activation of microglia is poorly understood. In this study, we demonstrated that HA fragments induced inducible NO synthase (iNOS) expression in BV-2 microglia in a dose-dependent manner and was synergized with interferon-gamma (IFN-gamma). Moreover, HA fragments could induce the activation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK1/ERK2), and c-Jun N-terminal kinase (JNK) in a time and dose-dependent fashion. The HA fragments-induced iNOS expression was suppressed by the selective inhibitors of JNK and, to a lesser extent, p38 MAPK. These results suggest that the induction of iNOS by HA fragments is significantly dependent on JNK than on p38 MAPK signaling pathways and support the hypothesis that HA fragments may be an important regulator in the activation of microglia at sites of ischemic brain.

Gamma interferon-induced nitric oxide production in mouse CD5+ B1-like cell line and its association with apoptotic cell death

The in vitro effect of gamma interferon (IFN-gamma) on nitric oxide (NO) production in a mouse CD5+ B1-like cell line, TH2.52, was studied. The TH2.52 cell line is the hybridoma line between mouse B lymphoma line and mouse splenic B cells and expresses a series of B1 markers. IFN-gamma induced a marked NO production in TH2.52 cells through the expression of an inducible type of NO synthase (iNOS). IFN-gamma-induced NO production was triggered by the Janus tyrosine kinase (JAK)/signal transducer and activator of transcription (STAT) pathway since it was inhibited by AG490, a JAK2 inhibitor. The growth of TH2.52 cells significantly was inhibited in the presence of IFN-gamma. A significant number of cells underwent apoptotic cell death, accompanied by the DNA fragmentation, annexin V binding, and caspase 3 activation. N(G)-monomethyl-L-arginine, an iNOS inhibitor, prevented IFN-gamma-induced cell death. Therefore, IFN-gamma-induced NO production was possible in causing cell death in TH2.52 cells. Further, IFN-gamma-induced NO production and cell death significantly were prevented by interleukin-4, a representative Th2 cytokine. The immunological significance of IFN-gamma-induced NO production in a mouse B1-like cell line is discussed.

Fas (CD95) induces proinflammatory cytokine responses by human monocytes and monocyte-derived macrophages

Fas (CD95, APO-1) is regarded as the prototypical cell death receptor of the TNFR superfamily. Fas-induced apoptosis is generally considered to be a noninflammatory process, contributing to the silent resolution of immune and inflammatory responses. However, accumulating evidence indicates that Fas may also induce cellular activation signals. We hypothesized that Fas could activate proinflammatory cytokine responses by normal human monocytes and macrophages. Monocytes were isolated by negative immunoselection from the PBMC fraction of venous blood from healthy volunteers, and monocyte-derived macrophages were cultivated in vitro. Both monocytes and monocyte-derived macrophages released TNF-alpha and IL-8 following Fas ligation, and conditioned medium from Fas-activated monocytes and macrophages induced the directed migration of neutrophils in a chemotaxis assay. Fas-induced monocyte cytokine responses were associated with monocyte apoptosis, nuclear translocation of NF-kappaB, and cytokine gene expression and were blocked by caspase inhibition but not by inhibition of IL-1beta signaling. In contrast, Fas-induced macrophage cytokine responses occurred in the absence of apoptosis and were caspase independent, indicating maturation-dependent differences in the Fas signaling pathways that lead to proinflammatory cytokine induction. Rather than contributing to the resolution of inflammation, Fas ligation on circulating monocytes and tissue macrophages may induce proinflammatory cytokine responses that can initiate acute inflammatory responses and tissue injury.

Orphan nuclear receptor Nur77 is involved in caspase-independent macrophage cell death

Activation-induced cell death in macrophages has been observed, but the mechanism remains largely unknown. Activation-induced cell death in macrophages can be independent from caspases, and the death of activated macrophages can even be triggered by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD). Here, we show that this type of macrophage death can occur in the septic mouse model and that toll-like receptor (TLR)-2 or TLR4 signaling is required in this process. We conclude that Nur77 is involved in the macrophage death because Nur77 expression correlates with cell death, and cell death is reduced significantly in Nur77-deficient macrophages. The extracellular signal-regulated kinase pathway, which is downstream of TLR2 or TLR4, and myocyte-specific enhancer binding factor 2 (MEF2) transcription factor activity, which is up-regulated by zVAD, are required for Nur77 induction and macrophage death. Reporter gene analysis suggests that Nap, Ets, Rce, and Sp1 sites in the Nur77 promoter are regulated by TLR4 signaling and that MEF2 sites in the Nur77 promoter are regulated by zVAD treatment. MEF2 transcription factors are constitutively expressed and degraded in macrophages, and zVAD increases MEF2 transcription factor activity by preventing the proteolytic cleavage and degradation of MEF2 proteins. This paper delineates the dual signaling pathways that are required for Nur77 induction in macrophages and demonstrates a role of Nur77 in caspase-independent cell death.

A novel antioxidant, octyl caffeate, suppression of LPS/IFN-gamma-induced inducible nitric oxide synthase gene expression in rat aortic smooth muscle cells

In the present study, we investigated the effects and mechanisms of a novel potent antioxidant, octyl caffeate, on the induction of iNOS expression by lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) in cultured primary rat aortic smooth muscle cells (RASMCs) in vitro and LPS-induced hypotension in vivo. Octyl caffeate (0.1-1.0 microM) exerted a concentration-dependent inhibition of iron-catalyzed lipid peroxidation in rat brain homogenates. Furthermore, octyl caffeate (20, 50, and 100 microM) concentration-dependently diminished the initial rate of superoxide-induced NBT reduction and the enzymatic activity of xanthine oxidase. It also concentration-dependently (1-50 microM) inhibited the NO production, iNOS protein and messenger RNA expressions upon stimulation by LPS (100 microg/mL)/IFN-gamma (100U/mL) in RASMCs. In addition, we found that octyl caffeate did not significantly affect IkappaBalpha degradation stimulated by LPS/IFN-gamma in RASMCs. On the other hand, octyl caffeate (10 and 50 microM) significantly suppressed activation of c-Jun-N-terminal kinase and extracellular signal-regulated kinase. Moreover, octyl caffeate (10mg/kg, i.v.) significantly inhibited the fall in mean arterial pressure stimulated by LPS (7.5mg/kg) in rats. In conclusion, we demonstrate that a novel potent antioxidant, octyl caffeate, significantly ameliorates circulatory failure of endotoxemia in vivo by a mechanism involving suppression of iNOS expression through inactivation of mitogen-activated protein kinases in RASMCs.

Akt as a mediator of secretory phospholipase A2 receptor-involved inducible nitric oxide synthase expression

The induction of inducible NO synthase (iNOS) by group IIA phospholipase A(2) (PLA(2)) involves the stimulation of a novel signaling cascade. In this study, we demonstrate that group IIA PLA(2) up-regulates the expression of iNOS through a novel pathway that includes M-type secretory PLA(2) receptor (sPLA(2)R), phosphatidylinositol 3-kinase (PI3K), and Akt. Group IIA PLA(2) stimulated iNOS expression and promoted nitrite production in a dose- and time-dependent manner in Raw264.7 cells. Upon treating with group IIA PLA(2), Akt is phosphorylated in a PI3K-dependent manner. Pretreatment with LY294002, a PI3K inhibitor, strongly suppressed group IIA PLA(2)-induced iNOS expression and PI3K/Akt activation. The promoter activity of iNOS was stimulated by group IIA PLA(2), and this was suppressed by LY294002. Transfection with Akt cDNA resulted in Akt protein overexpression in Raw264.7 cells and effectively enhanced the group IIA PLA(2)-induced reporter activity of the iNOS promoter. M-type sPLA(2)R was highly expressed in Raw264.7 cells. Overexpression of M-type sPLA(2)R enhanced group IIA PLA(2)-induced promoter activity and iNOS protein expression, and these effects were abolished by LY294002. However, site-directed mutation in residue responsible for PLA(2) catalytic activity markedly reduced their ability to production of nitrites and expression of iNOS. These results suggest that group IIA PLA(2) induces nitrite production by involving of M-type sPLA(2)R, which then mediates signal transduction events that lead to PI3K/Akt activation.

Induction of in vitro reprogramming by Toll-like receptor (TLR)2 and TLR4 agonists in murine macrophages: effects of TLR "homotolerance" versus "heterotolerance" on NF-kappa B signaling pathway components

In this study, tolerance induction by preexposure of murine macrophages to Toll-like receptor (TLR)2 and TLR4 agonists was revisited, focusing on the major signaling components associated with NF-kappaB activation. Pretreatment of macrophages with a pure TLR4 agonist (protein-free Escherichia coli (Ec) LPS) or with TLR2 agonists (Porphyromonas gingivalis LPS or synthetic lipoprotein Pam3Cys) led to suppression of TNF-alpha secretion, IL-1R-associated kinase-1, and IkappaB kinase (IKK) kinase activities, c-jun N-terminal kinase, and extracellular signal-regulated kinase phosphorylation, and to suppression of NF-kappaB DNA binding and transactivation upon challenge with the same agonist (TLR4 or TLR2 "homotolerance," respectively). Despite inhibited NF-kappaB DNA binding, increased levels of nuclear NF-kappaB were detected in agonist-pretreated macrophages. For all the intermediate signaling elements, heterotolerance was weaker than TLR4 or TLR2 homotolerance with the exception of IKK kinase activity. IKK kinase activity was unperturbed in heterotolerance. TNF-alpha secretion was also suppressed in P. gingivalis LPS-pretreated, Ec LPS-challenged cells, but not vice versa, while Pam3Cys and Ec LPS did not induce a state of cross-tolerance at the level of TNF-alpha. Experiments designed to elucidate novel mechanisms of NF-kappaB inhibition in tolerized cells revealed the potential contribution of IkappaBepsilon and IkappaBxi inhibitory proteins and the necessity of TLR4 engagement for induction of tolerance to Toll receptor-IL-1R domain-containing adapter protein/MyD88-adapter-like-dependent gene expression. Collectively, these data demonstrate that induction of homotolerance affects a broader spectrum of signaling components than in heterotolerance, with selective modulation of specific elements within the NF-kappaB signaling pathway.

EDTA-induced activation of Ca-regulated proteins in the vaginal mucosa

The effects of EDTA on the expression and topologic localization of mitogen-activated protein (MAP) kinases (ERK, JNK, and p38), along with nitric oxide synthase (NOS), I-KappaB, and p53 were examined to elucidate the host response provoked by the intravaginal application of a female controlled drug delivery system (FcDDS) containing a spermicidal/microbicidal agent and EDTA. Immunohistochemical and immunoblotting studies were conducted to identify and quantitate the EDTA-inducible proteins in vaginal mucosa. The content of nitrite, which is one of the primary stable breakdown products of nitric oxide (NO), was determined to correlate the expression of NOS with NO formation in HeLa cervical carcinoma cell line. The immunohistochemical study demonstrated that the modulation of the calcium gradient by EDTA activated MAP kinases (ERK and JNK) in the rabbit vaginal mucosa. The results of Western immunoblot study demonstrated differential expression of MAP kinases (ERK and JNK) with EDTA treatment, whereas the expression of NOS and NF-KappaB was not affected by EDTA. There was no significant difference in nitrite production in the HeLa cell line upon exposure to EDTA compared with the control, which was consistent with the results of the Western blot study. The results of this work support that the regulation of MAP kinase was affected by calcium, which is controlled by chelation activity of EDTA. The specific tissue responses exerted by the loading components of a biomaterial-based system should be fully taken into consideration for its intravaginal application.

Quercetin suppresses proinflammatory cytokines production through MAP kinases andNF-kappaB pathway in lipopolysaccharide-stimulated macrophage

Quercetin is a flavonoid molecule ubiquitous in nature and functions as an anti-oxidant and anti-inflammatory agent with little toxicity in vivo and in vitro. Dose- and time-dependent effect of quercetin has been investigated on proinflammatory cytokine expression and NO production, focusing on its effects on the MAP kinases and the NF-kappaB signal transduction pathways in LPS-stimulated RAW 264.7 cells by using RT-PCR and immunoblotting. Quercetin strongly reduced activation of phosphorylated ERK kinase and p38 MAP kinase but not JNK MAP kinase by LPS treatment. In addition, quercetin treatment inhibited NF-kappaB activation through stabilization of the NF-kappaB/IkappaB complex and IkappaB degradation and proinflammatory cytokines and NO/iNOS expression. Quercetin may exert its anti-inflammatory and immunomodulatory properties in the effect molecules such as proinflammatory cytokines and NO/iNOS by suppressing the activation of ERK and p38 MAP kinase, and NF-kappaB/IkappaB signal transduction pathways.

Nitric oxide-mediated proteasome-dependent oligonucleosomal DNA fragmentation in Leishmania amazonensis amastigotes

Resistance to leishmanial infections depends on intracellular parasite killing by activated host macrophages through the L-arginine-nitric oxide (NO) metabolic pathway. Here we investigate the cell death process induced by NO for the intracellular protozoan Leishmania amazonensis. Exposure of amastigotes to moderate concentrations of NO-donating compounds (acidified sodium nitrite NaNO(2) or nitrosylated albumin) or to endogenous NO produced by lipopolysaccharide or gamma interferon treatment of infected macrophages resulted in a dramatic time-dependent cell death. The combined use of several standard DNA status analysis techniques (including electrophoresis ladder banding patterns, YOPRO-1 staining in flow cytofluorometry, and in situ recognition of DNA strand breaks by TUNEL [terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling] assay) revealed a rapid and extensive fragmentation of nuclear DNA in both axenic and intracellular NO-treated amastigotes of L. amazonensis. Despite some similarities to apoptosis, the nuclease activation responsible for characteristic DNA degradation was not under the control of caspase activity as indicated by the lack of involvement of cell-permeable inhibitors of caspases and cysteine proteases. In contrast, exposure of NO-treated amastigotes with specific proteasome inhibitors, such as lactacystin or calpain inhibitor I, markedly reduced the induction of the NO-mediated apoptosis-like process. These data strongly suggest that NO-induced oligonucleosomal DNA fragmentation in Leishmania amastigotes is, at least in part, regulated by noncaspase proteases of the proteasome. The determination of biochemical pathways leading up to cell death might ultimately allow the identification of new therapeutic targets.

Role of toll-like receptors in changes in gene expression and NF-kappa B activation in mouse hepatocytes stimulated with lipopolysaccharide

The liver is an important site of host-microbe interaction. Although hepatocytes have been reported to be responsive to lipopolysaccharide (LPS), the global gene expression changes by LPS and mechanism(s) by which LPS stimulates cultured hepatocytes remain uncertain. Cultures of primary mouse hepatocytes were incubated with LPS to assess its effects on the global gene expression, hepatic transcription factors, and mitogen-activated protein (MAP) kinase activation. DNA microarray analysis indicated that LPS modulates the selective expression of more than 80 genes and expressed sequence tags. We have shown previously that hepatocytes express CD14, which is required both for uptake and responsiveness to LPS. In other cells, responsiveness to microbial products requires expression of Toll-like receptors (TLR) and their associated accessory molecules. Hepatocytes expressed TLR1 through TLR9 as well as MyD88 and MD-2 transcripts, as shown by reverse transcriptase PCR analysis, indicating that hepatocytes express all known microbe recognition molecules. The MAP kinase extracellular signal-regulated kinase 1/2 was phosphorylated in response to LPS in mouse hepatocytes, and the levels of phosphorylation were lower in hepatocytes from TLR4-null mice. NF-kappa B activation was reduced in TLR4-mutant or -null hepatocytes compared to control hepatocytes, and this defect was partially restored by adenoviral transduction of mouse TLR4. Thus, hepatocytes respond to nanogram concentrations of LPS through a TLR4 response pathway.

Recombinant glucocorticoid induced tumor necrosis factor receptor (rGITR) induces NOS in murine macrophage

Glucocorticoid induced tumor necrosis factor receptor (GITR) is a new member of the tumor necrosis factor-nerve growth factor receptor superfamily of which the function has not been well studied. The extracellular domain of GITR was produced in Escherichia coli and purified as a single band of predicted M(r) of 18.0 kDa. GITR and GITR ligand were expressed constitutively on the surface of Raw 264.7 macrophage cell line and murine peritoneal macrophages. An extracellular domain of GITR can activate murine macrophages to express inducible nitric oxide synthase and to generate nitric oxide in a dose- and time-dependent manner.