Role of Nrf2-mediated heme oxygenase-1 upregulation in adaptive survival response to nitrosative stress. Arch Pharm Res. 2009;32:1163-1176. [PMID: 19727608 DOI: 10.1007/s12272-009-1807-8]

Fractalkine attenuates excito-neurotoxicity via microglial clearance of damaged neurons and antioxidant enzyme heme oxygenase-1 expression

Glutamate-induced excito-neurotoxicity likely contributes to non-cell autonomous neuronal death in neurodegenerative diseases. Microglial clearance of dying neurons and associated debris is essential to maintain healthy neural networks in the central nervous system. In fact, the functions of microglia are regulated by various signaling molecules that are produced as neurons degenerate. Here, we show that the soluble CX3C chemokine fractalkine (sFKN), which is secreted from neurons that have been damaged by glutamate, promotes microglial phagocytosis of neuronal debris through release of milk fat globule-EGF factor 8, a mediator of apoptotic cell clearance. In addition, sFKN induces the expression of the antioxidant enzyme heme oxygenase-1 (HO-1) in microglia in the absence of neurotoxic molecule production, including NO, TNF, and glutamate. sFKN treatment of primary neuron-microglia co-cultures significantly attenuated glutamate-induced neuronal cell death. Using several specific MAPK inhibitors, we found that sFKN-induced heme oxygenase-1 expression was primarily mediated by activation of JNK and nuclear factor erythroid 2-related factor 2. These results suggest that sFKN secreted from glutamate-damaged neurons provides both phagocytotic and neuroprotective signals.

Influence of iNOS and COX on peroxiredoxin gene expression in primary macrophages

Peroxiredoxins (Prxs) are a family of multifunctional antioxidant thiol-dependent peroxidases. This study aimed to examine the regulatory mechanisms of Prx gene expression in murine bone marrow-derived macrophages (BMMs) using standardized serum-free conditions. Stimulation with LPS and IFNγ increased mRNA levels of Prx 1, 2, 4, 5, and 6 in BMMs of both C57BL/6 and BALB/c mice, with Prx 1, 2, 4, and 6 more strongly induced in C57BL/6 BMMs. Further investigations on signaling pathways in C57BL/6 BMMs demonstrated that up-regulation of Prx 5 and 6 by LPS and IFNγ was associated with the activation of multiple protein kinases, most notably JAK2, PI3K, and p38 MAPK. Our experiments also revealed a contribution of inducible NO synthase-derived nitric oxide to the increase in Prx 1, 2, 4, and 6 mRNA expression, whereas NADPH oxidase-derived superoxide was not involved. Furthermore, we could show that LPS- and IFNγ-induced gene expression of Prx 6 was also regulated in an NO-independent manner by cyclooxygenases and prostaglandin E(2). Taken together our results indicate a possible role for Prxs in defense mechanisms of activated macrophages against oxidative stress during inflammation or infection.

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Methamphetamine preconditioning causes differential changes in striatal transcriptional responses to large doses of the drug

Methamphetamine (METH) is a toxic drug of abuse, which can cause significant decreases in the levels of monoamines in various brain regions. However, animals treated with progressively increasing doses of METH over several weeks are protected against the toxic effects of the drug. In the present study, we tested the possibility that this pattern of METH injections might be associated with transcriptional changes in the rat striatum, an area of the brain which is known to be very sensitive to METH toxicity and which is protected by METH preconditioning. We found that the presence and absence of preconditioning followed by injection of large doses of METH caused differential expression in different sets of striatal genes. Quantitative PCR confirmed METH-induced changes in some genes of interest. These include small heat shock 27 kD proteins 1 and 2 (HspB1 and HspB2), brain derived neurotrophic factor (BDNF), and heme oxygenase-1 (Hmox-1). Our observations are consistent with previous studies which have reported that ischemic or pharmacological preconditioning can cause reprogramming of gene expression after lethal ischemic insults. These studies add to the growing literature on the effects of preconditioning on the brain transcriptome.

GLP-1 receptor plays a critical role in geniposide-induced expression of heme oxygenase-1 in PC12 cells

AIM

To explore the role of activation of glucagon-like peptide 1 receptor (GLP-1R) and its relative cell signaling pathway in the cytoprotection of geniposide.

METHODS

Cell viability was determined by MTT assay. Knockdown of the Glp-1r gene was carried out with shRNA. The levels of HO-1 protein and cAMP response element binding protein (CREB) phosphorylation were measured by Western blotting.

RESULTS

Geniposide protected PC12 cells from oxidative damage induced by 3-morpholinosydnonimine hydrochloride (SIN-1) by enhancing the expression of heme oxygenase 1 (HO-1) via the cAMP-PKA-CREB signal pathway. After transfecting PC12 cells with the AB1 enhancer from the HO-1 gene, luciferase activity induced by geniposide increased in a dose-dependent manner, but not in the PC12 cells whose Glp-1r gene was disrupted. Additionally, inhibition of HO-1 activity by Sn-protoporphyrin IX (SnPP) or shRNA-mediated knockdown of Glp-1r decreased the neuroprotection of geniposide in PC12 cells.

CONCLUSION

GLP-1R plays a critical role in geniposide-induced HO-1 expression to attenuate oxidative insults in PC12 cells.

Nrf2-Keap1 signaling as a potential target for chemoprevention of inflammation-associated carcinogenesis

Persistent inflammatory tissue damage is causally associated with each stage of carcinogenesis. Inflammation-induced generation of reactive oxygen species, reactive nitrogen species, and other reactive species not only cause DNA damage and subsequently mutations, but also stimulate proliferation of initiated cells and even metastasis and angiogenesis. Induction of cellular cytoprotective enzymes (e.g., heme oxygenase-1, NAD(P)H:quinone oxidoreductase, superoxide dismutase, glutathione-S-transferase, etc.) has been shown to mitigate aforementioned events implicated in inflammation-induced carcinogenesis. A unique feature of genes encoding these cytoprotective enzymes is the presence of a cis-acting element, known as antioxidant response element (ARE) or electrophile response element (EpRE), in their promoter region. A stress-responsive transcription factor, nuclear factor erythroid-2-related factor-2 (Nrf2), initially recognized as a key transcriptional regulator of various cytoprotective enzymes, is known to play a pivotal role in cellular defense against inflammatory injuries. Activation of Nrf2 involves its release from the cytosolic repressor Kelch-like ECH-associated protein-1 (Keap1) and subsequent stabilization and nuclear localization for ARE/EpRE binding. Genetic or pharmacologic inactivation of Nrf2 has been shown to abolish cytoprotective capability and to aggravate experimentally induced inflammatory injuries. Thus, Nrf2-mediated cytoprotective gene induction is an effective strategy for the chemoprevention of inflammation-associated carcinogenesis.

Induction of peroxiredoxin I gene expression by LPS involves the Src/PI3K/JNK signalling pathway

Peroxiredoxin I (Prx I) belongs to a family of proteins with thiol-dependent peroxidase activity and is involved in the cellular protection against oxidative stress, the modulation of intracellular signalling cascades as well as the regulation of cell proliferation and apoptosis. In RAW 264.7 mouse macrophage cells Prx I was up-regulated on the mRNA and protein level by lipopolysaccharide (LPS). Treatment of cells with LPS increased the phosphorylation of c-Jun-NH(2) terminal kinase (JNK) and protein kinase B (PKB). Both SP600125, an inhibitor of JNK, and LY294002, an inhibitor of phosphoinositide 3-kinase (PI3K), dose-dependently decreased LPS-induced Prx I mRNA expression. Furthermore, up-regulation of Prx I mRNA by LPS was diminished by the Src tyrosine kinase inhibitor PP2 and the iNOS inhibitor L-NMMA. LPS-dependent induction of Prx I is likely mediated by an activator protein-1 site within the Prx I promoter region binding JunB and c-Fos. In contrast, NFkappaB was not involved in the activation of Prx I transcription. Our results suggest that the up-regulation of Prx I gene expression by LPS is part of the cellular response to stress and may protect against oxidative stress-related injury in RAW 264.7 cells.