The induction of cyclooxygenase-2 mRNA in macrophages is biphasic and requires both CCAAT enhancer-binding protein beta (C/EBP beta ) and C/EBP delta transcription factors

C/EBPδ deficiency delays infection-induced preterm birth

BACKGROUND

Parturition is an inflammation process. Exaggerated inflammatory reactions in infection lead to preterm birth. Although nuclear factor kappa B (NF-κB) has been recognized as a classical transcription factor mediating inflammatory reactions, those mediated by NF-κB per se are relatively short-lived. Therefore, there may be other transcription factors involved to sustain NF-κB-initiated inflammatory reactions in gestational tissues in infection-induced preterm birth.

METHODS

Cebpd-deficient mice were generated to investigate the role of CCAAT enhancer-binding protein δ (C/EBPδ) in lipopolysaccharide (LPS)-induced preterm birth, and the contribution of fetal and maternal C/EBPδ was further dissected by transferring Cebpd-/- or WT embryos to Cebpd-/- or WT dams. The effects of C/EBPδ pertinent to parturition were investigated in mouse and human myometrial and amnion cells. The interplay between C/EBPδ and NF-κB was examined in cultured human amnion fibroblasts.

RESULTS

The mouse study showed that LPS-induced preterm birth was delayed by Cebpd deficiency in either the fetus or the dam, with further delay being observed in conceptions where both the dam and the fetus were deficient in Cebpd. Mouse and human studies showed that the abundance of C/EBPδ was significantly increased in the myometrium and fetal membranes in infection-induced preterm birth. Furthermore, C/EBPδ participated in LPS-induced upregulation of pro-inflammatory cytokines as well as genes pertinent to myometrial contractility and fetal membrane activation in the myometrium and amnion respectively. A mechanistic study in human amnion fibroblasts showed that C/EBPδ, upon induction by NF-κB, could serve as a supplementary transcription factor to NF-κB to sustain the expression of genes pertinent to parturition.

CONCLUSIONS

C/EBPδ is a transcription factor to sustain the expression of gene initiated by NF-κB in the myometrium and fetal membranes in infection-induced preterm birth. Targeting C/EBPδ may be of therapeutic value in the treatment of infection-induced preterm birth.

FSH and ApoE4 contribute to Alzheimer's disease-like pathogenesis via C/EBPβ/δ-secretase in female mice

Alzheimer's disease (AD) is the most common dementia. It is known that women with one ApoE4 allele display greater risk and earlier onset of AD compared with men. In mice, we previously showed that follicle-stimulating hormone (FSH), a gonadotropin that rises in post-menopausal females, activates its receptor FSHR in the hippocampus, to drive AD-like pathology and cognitive impairment. Here we show in mice that ApoE4 and FSH jointly trigger AD-like pathogenesis by activating C/EBPβ/δ-secretase signaling. ApoE4 and FSH additively activate C/EBPβ/δ-secretase pathway that mediates APP and Tau proteolytic fragmentation, stimulating Aβ and neurofibrillary tangles. Ovariectomy-provoked AD-like pathologies and cognitive defects in female ApoE4-TR mice are ameliorated by anti-FSH antibody treatment. FSH administration facilitates AD-like pathologies in both young male and female ApoE4-TR mice. Furthermore, FSH stimulates AD-like pathologies and cognitive defects in ApoE4-TR mice, but not ApoE3-TR mice. Our findings suggest that in mice, augmented FSH in females with ApoE4 but not ApoE3 genotype increases vulnerability to AD-like process by activating C/EBPβ/δ-secretase signalling.

Emerging functions of C/EBPβ in breast cancer

Breast tumorigenesis relies on complex interactions between tumor cells and their surrounding microenvironment, orchestrated by tightly regulated transcriptional networks. C/EBPβ is a key transcription factor that regulates the proliferation and differentiation of multiple cell types and modulates a variety of biological processes such as tissue homeostasis and the immune response. In addition, C/EBPβ has well-established roles in mammary gland development, is overexpressed in breast cancer, and has tumor-promoting functions. In this review, we discuss context-specific roles of C/EBPβ during breast tumorigenesis, isoform-specific gene regulation, and regulation of the tumor immune response. We present challenges in C/EBPβ biology and discuss the importance of C/EBPβ isoform-specific gene regulation in devising new therapeutic strategies.

The transcription factor CCAAT/enhancer-binding protein β in spinal microglia contributes to pre-operative stress-induced prolongation of postsurgical pain

Prolongation of postsurgical pain caused by pre-operative stress is a clinically significant problem, although the mechanisms are not fully understood. Stress can promote the pro-inflammatory activation of microglia, and the transcription factor CCAAT/enhancer-binding protein (C/EBP) β regulates pro-inflammatory gene expression in microglia. Therefore, we speculated that C/EBPβ in spinal microglia may have critical roles in the development of chronic postsurgical pain. Accordingly, in this study, we used a single prolonged stress (SPS) procedure and plantar incisions to evaluate the roles of C/EBPβ in postsurgical pain. Our experiments showed that SPS exposure prolonged mechanical allodynia, increased the expression of C/EBPβ and pro-inflammatory cytokines, and potentiated the activation of spinal microglia. Subsequently, microinjection of C/EBPβ siRNA attenuated the duration of SPS-prolonged postoperative mechanical allodynia and inhibited microglial activation in the spinal cord. Conversely, mimicking this increase in C/EBPβ promoted microglial activation via pretreatment with a pre-injection of AAV5-C/EBPβ, leading to prolongation of postsurgical pain. Overall, these results suggested that spinal microglia may play key roles in prolongation of postsurgical pain induced by pre-operative stress and that C/EBPβ may be a potential target for disease treatment.

C-EBPβ mediates in cigarette/IL-17A-induced bronchial epithelial-mesenchymal transition in COPD mice

BACKGROUND

Cigarettes smoking and IL-17A contribute to chronic obstructive pulmonary disease (COPD), and have synergistical effect on bronchial epithelial cell proliferation. CCAAT/enhancer-binding protein β (C-EBPβ) could be induced by IL-17A and is up-regulated in COPD. We explored the effect of cigarettes and IL-17 on bronchial epithelial-mesenchymal transition (EMT) in COPD mice and potential mechanism involved with C-EBPβ in this study.

METHODS

COPD model was established with mice by exposing to cigarettes. E-Cadherin, Vimentin, IL-17A and C-EBPβ distributions were detected in lung tissues. Primary bronchial epithelial cells were separated from health mice and cocultured with cigarette smoke extract (CSE) or/and IL-17A. E-Cadherin, Vimentin and IL-17 receptor (IL-17R) expressions in vitro were assessed. When C-EBPβ were silenced by siRNA in cells, E-Cadherin, Vimentin and C-EBPβ expressions were detected.

RESULTS

E-Cadherin distribution was less and Vimentin distribution was more in bronchus of COPD mice than controls. IL-17A and C-EBPβ expressions were higher in lung tissues of COPD mice than controls. In vitro, C-EBPβ protein expression was highest in CSE + IL-17A group, followed by CSE and IL-17A groups. E-cadherin expression in vitro was lowest and Vimentin expression was highest in CSE + IL-17A group, followed by CSE or IL-17A group. Those could be inhibited by C-EBPβ silenced.

CONCLUSIONS

C-EBPβ mediates in cigarette/IL-17A-induced bronchial EMT in COPD mice. Our findings contribute to a better understanding on the progress from COPD to lung cancers, which will provide novel avenues in preventing tumorigenesis of airway in the context of cigarette smoking.

C/EBPδ drives key endocrine signals in the human amnion at parturition

Amnion-derived prostaglandin E2 (PGE2) and cortisol are key to labor onset. Identification of a common transcription factor driving the expression of both cyclooxygenase-2 (COX-2) and 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1), the key enzymes in their production, may hold the key to the treatment of pre-term labor. Here, we have found that the CCAAT enhancer binding protein δ (C/EBPδ) is such a transcription factor which underlies the feed-forward induction of COX-2 and 11β-HSD1 expression by their own products PGE2 and cortisol in human amnion fibroblasts so that their production would be ensured in the amnion for the onset of labor. Moreover, the abundance of C/EBPδ in the amnion increases along with COX-2 and 11β-HSD1 at term and further increases at parturition. Knockout of C/EBPδ in mice delays the onset of labor further supporting the concept. In conclusion, C/EBPδ pathway may be speculated to serve as a potential pharmaceutical target in the amnion for treatment of pre-term labor.

C/EBPβ/δ-secretase signaling mediates Parkinson's disease pathogenesis via regulating transcription and proteolytic cleavage of α-synuclein and MAOB

Parkinson's disease (PD) is characterized by dopaminergic neuronal loss and the presence of intra-neuronal Lewy body (LB) inclusions with aggregated α-synuclein (α-Syn) as the major component. MAOB, a crucial monoamine oxidase for dopamine metabolism, triggers oxidative stress in dopaminergic neurons and α-Syn aggregation. However, the key molecular mechanism that mediates PD pathogenesis remains elusive. Here we show that C/EBPβ acts as an age-dependent transcription factor for both α-Syn and MAOB, and initiates the PD pathologies by upregulating these two pivotal players, in addition to escalating δ-secretase activity to cleave α-Syn and promotes its neurotoxicity. Overexpression of C/EBPβ in human wild-type α-Syn transgenic mice facilitates PD pathologies and elicits motor disorders associated with augmentation of δ-secretase, α-Syn, and MAOB. In contrast, depletion of C/EBPβ from human α-Syn Tg mice abolishes rotenone-elicited PD pathologies and motor impairments via downregulating the expression of these key factors. Hence, our study supports that C/EBPβ/δ-secretase signaling mediates PD pathogenesis via regulating the expression and cleavage of α-Syn and MAOB.

C/EBPβ is a key transcription factor for APOE and preferentially mediates ApoE4 expression in Alzheimer's disease

The apolipoprotein E ε4 (APOE4) allele is a major genetic risk factor for Alzheimer's disease (AD), and its protein product, ApoE4, exerts its deleterious effects mainly by influencing amyloid-β (Aβ) and Tau (neurofibrillary tangles, NFTs) deposition in the brain. However, the molecular mechanism dictating its expression during ageing and in AD remains incompletely clear. Here we show that C/EBPβ acts as a pivotal transcription factor for APOE and mediates its mRNA levels in an age-dependent manner. C/EBPβ binds the promoter of APOE and escalates its expression in the brain. Knockout of C/EBPβ in AD mouse models diminishes ApoE expression and Aβ pathologies, whereas overexpression of C/EBPβ accelerates AD pathologies, which can be attenuated by anti-ApoE monoclonal antibody or deletion of ApoE via its specific shRNA. Remarkably, C/EBPβ selectively promotes more ApoE4 expression versus ApoE3 in human neurons, correlating with higher activation of C/EBPβ in human AD brains with ApoE4/4 compared to ApoE3/3. Therefore, our data support that C/EBPβ is a crucial transcription factor for temporally regulating APOE gene expression, modulating ApoE4's role in AD pathogenesis.

Production of fever mediator PGE2 in human monocytes activated with MDP adjuvant is controlled by signaling from MAPK and p300 HAT: Key role of T cell derived factor

Fever and inflammatory responses were observed in some subjects in early clinical trials of vaccines adjuvanted with muramyl dipeptide (MDP), a NOD2 agonist. Biosynthesis of Prostaglandin E2 (PGE₂) that transmits febrile signals to the brain is controlled by an inducible enzyme, Cyclooxygenase 2 (COX-2). MDP alone was not sufficient to induce expression of COX-2 and PGE₂ production in vitro. Conditioned medium prepared from Peripheral Blood Mononuclear Cells (PBMCs)-derived CD3-bead purified human T cells (TCM) dramatically increased COX2 gene transcription, COX-2 protein expression, and PGE₂ production in MDP-treated monocytes. We explored epigenetic changes at the COX2 promoter using Chromatin Immunoprecipitation assay (ChIP). Increase in COX2 transcription correlated with increased recruitment of RNA polymerase II (Pol II) and p300 histone acetyl transferase (HAT) to the COX2 promoter in monocytes activated with MDP and TCM. The role of p300 HAT was confirmed by using C646, an inhibitor of p300, that reduced binding of acetylated H3 and H4 histones at the COX2 promoter, COX2 transcription, and PGE₂ production in monocytes. Binding of p300, Nuclear Factor Kappa B (NF-κB), and Pol II to the COX2 promoter was also sensitive to inhibitors of Mitogen-Activated Protein Kinase (MAPK) pathway and to antibodies against Macrophage-1 (Mac-1) integrin in MDP/TCM-treated monocytes. Importantly, recombinant Glycoprotein Ib alfa (GPIbα), the recently identified factor in TCM, increased binding of NF-κB, p300, and of Pol II to the COX2 promoter and COX2 transcription in MDP-treated monocytes. Our findings suggest that a second signal through Mac-1 and MAPK is triggered by a T cell derived soluble GPIbα protein leading to the assembly of the transcription machinery at the COX2 promoter and production of PGE₂ in human monocytes in response to MDP/NOD2 activation.

BDNF and Netrin-1 repression by C/EBPβ in the gut triggers Parkinson's disease pathologies, associated with constipation and motor dysfunctions

Chronic constipation is one of the most prominent prodromal symptoms in Parkinson's disease (PD), and Lewy bodies, enriched with aggregated α-Synuclein (α-Syn), propagation from the gut into the brain has been proposed to play a key role in PD etiopathogenesis. BDNF (Brain-derived neurotrophic factor) and Netrin-1 promote both neuronal survival and regulate the gut functions. We hypothesize that C/EBPβ represses BDNF and Netrin-1 in peripheral nervous system and central nervous system, contributing to GI tract and brain malfunctions in PD. To test the hypothesis, we performed the studies in both human PD gut tissues and BDNF or Netrin-1 gut conditional KO mice models. Lewy bodies with α-Syn aggregation and neuro-inflammation were measured in the colon and brain samples from PD patients and healthy controls and rotenone or vehicle-treated WT and CEBPβ (+/-) mice. We show that both BDNF and Netrin-1 are strongly decreased in the brain and the gut of PD patients, and conditional KO of these trophic factors in the gut elicits dopaminergic neuronal loss, constipation and motor dysfunctions. Interestingly, the inflammation and oxidative stress-induced transcription factor C/EBPβ acts as a robust repressor for both BDNF and Netrin-1 and suppresses the expression of trophic factors, and its levels inversely correlate with BDNF and Netrin-1 in PD patients. Our findings support that gut inflammation induces C/EBPβ activation that leads to both BDNF and Netrin-1 reduction and triggers PD non-motor and motor symptoms. Possibly, C/EBPβ-mediated biological events might be early diagnostic biomarkers for PD.

Mogroside V inhibits LPS-induced COX-2 expression/ROS production and overexpression of HO-1 by blocking phosphorylation of AKT1 in RAW264.7 cells

Momordica grosvenori is a valuable edible plant with medicinal purposes, and it is widely used in medicated diets and traditional Chinese medicine in Asia. Mogroside V (MV), the main bioactive component from M. grosvenori, is commonly used as a natural sweetener. M. grosvenori extracts have been reported to exert potent anti-inflammatory property, however the underlying molecular mechanism still remains unknown. In the present study, the biological effect of MV in inflammation was investigated in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The ELISA and western blot analysis results showed that MV significantly inhibited LPS-induced prostaglandin E2 (PGE2) production and cyclooxygenase-2 (COX-2) expression. MV markedly decreased the phosphorylation of IκB-α, increased IκB-α, and reduced nuclear p-65 and C/EBPδ. Furthermore, MV attenuated LPS-induced phosphorylation of MAPKs and AKT1, and only the phosphorylation status of AKT1 was found to be consistent with the expression trend of COX-2. Moreover, MV reduced ROS level and restored overexpressed HO-1 and AP-1 to basal level, which can be markedly reversed by AKT1 inhibitor LY294002. These results revealed that AKT1 plays a key role in LPS-induced COX-2 expression, and acts as a mediator to keep the redox balance in LPS-stimulated RAW264.7 cells. MV exerts anti-inflammatory property by blocking AKT1-mediated NF-κB and C/EBPδ activation, ROS generation and AP-1/ HO-1 expression. Therefore, the present study indicated that MV has a significant chemopreventive effect on the inflammatory lesions and suggested that AKT1 is a potential specific target of MV for relieving inflammation.

Syk: a new target for attenuation of Helicobacter pylori-induced gastric mucosal inflammatory responses

The magnitude of gastric mucosal inflammatory response to H. pylori relies primarily on the extent of its key endotoxin, LPS, engagement of Toll-like receptor-4 (TLR4) and the initiation of signal transduction events converging on mitogen-activated protein kinase (MAPK) and IκB complex (IKK) cascades. These cascades, in turn, exert their control over the assembly of transcription factors, NFκB and AP1, implicated in the induction of the expression of iNOS and COX-2 proinflammatory genes. The LPS-induced TLR4 activation and the ensuing phosphorylation of its intracellular tyrosine domain by Src-family kinases not only leads to recruitment to the cytoplasmic domain of TLR4 of adaptor molecules directly involved in propagation of the signaling cascades converging on MAPK and IKK, but also provides a propitious docking site for a non-receptor tyrosine kinase, spleen tyrosine kinase (Syk), the activation of which apparently leads to upregulation in the expression of proinflammatory genes. Here, we review the pathways engaged by H. pylori in the recruitment and interaction of Syk with TLR4 in gastric mucosa, and discuss the cascades involved in Syk-mediated amplification in proinflammatory signaling. We focus, moreover, on the potential role of drugs targeting Syk and TLR4 in the treatment of H. pylori-related gastric disease.

Helicobacter pylori LPS-induced gastric mucosal spleen tyrosine kinase (Syk) recruitment to TLR4 and activation occurs with the involvement of protein kinase Cδ

Spleen tyrosine kinase (Syk) has emerged recently as a major effector of proinflammatory genes expression induced by LPS-elicited TLR4 activation, and manifested by the up-amplification in the production of inflammatory mediators, including PGE2 and NO. Here, we investigated the nature of factors involved in the recruitment and interaction of Syk with TLR4 in gastric mucosa in response to H. pylori LPS. We show that stimulation of gastric mucosal cells with the LPS leads to localization of Syk with the membrane-associated TLR4 complex and its activation through phosphorylation on Tyr. Furthermore, we reveal that the membrane translocation of Syk upon the LPS stimulation occurs with the involvement of protein kinase Cδ (PKCδ)-mediated phosphorylation of Syk on Ser. Thus, our findings demonstrate that H. pylori LPS-induced up-regulation in Syk activity proceeds through the stage of PKCδ-mediated Syk phosphorylation on Ser, required for its recruitment to the membrane-anchored TLR4, followed by the kinase activation through phosphorylation on Tyr. Hence, the phase of PKCδ-mediated Syk phosphorylation on Ser affects the extent of amplification in gastric mucosal inflammatory response to H. pylori.

Induction of cyclooxygenase-2 gene by Candida albicans through EGFR, ERK, and p38 pathways in human urinary epithelium

In the present data, we found that Candida albicans (C. albicans) caused bladder epithelial cell morphology alteration, cell damage, and inflammatory responses, including cyclooxygenase-2 (COX-2) gene and protein expression as well as prostaglandin E2 accumulation. In addition, the molecular pathway underlying C. albicans-induced urothelial COX-2 gene expression was examined. Among MAPK pathways, phosphorylation of ERK1/2, p38, and JNK each increased following C. albicans infection for 12 h. However, C. albicans-induced COX-2 protein expression was inhibited by specific inhibitors of ERK and p38 (U0126 and SB203580) but not by JNK inhibitor SP600125. Additional evidence came from the increased amount of phosphorylated RSK that is the mutual downstream molecule of ERK1/2 and p38. Furthermore, phosphorylation of RSK protein was reduced by the ERK and p38 inhibitor, suggesting that the urothelial COX-2 gene was induced majorly though the ERK/p38-RSK pathway by C. albicans infection. We also found transcription factor CREB-1 showed increased binding to the COX-2 gene promoter by chromatin immunoprecipitation assay. Next, we used receptor inhibitors including Toll-like receptor (TLR)-Myd88 inhibitor ST2825, Dectin-Syk inhibitor Syk inhibitor, and epidermal growth factor receptor (EGFR) inhibitor PD168393 to identify which one was the main target associated with C. albicans binding. The results revealed that it was EGFR, recognized by C. albicans, that mostly mediated the ERK/p38-RSK pathway activation to induce COX-2 gene expression, but this was not the case for TLRs and Dectin receptors. In summary, these results demonstrated the EGFR-ERK/p38-RSK-CREB-1 pathway was involved significantly in the C. albicans-induced COX-2 expression in human urothelium.

Role of LPS-elicited signaling in triggering gastric mucosal inflammatory responses to H. pylori: modulatory effect of ghrelin

Infection with Helicobacter pylori is a primary culprit in the etiology of gastric disease, and its cell-wall lipopolysaccharide (LPS) is recognized as a potent endotoxin responsible for triggering a pattern of the mucosal inflammatory responses. The engagement by the LPS of gastric mucosal Toll-like receptor 4 (TLR4) leads to initiation of signal transduction events characterized by the activation of mitogen-activated protein kinase (MAPK) cascade, induction of phosphoinositide-specific phospholipase C (PLC)/protein kinase C (PKC)/phosphatidylinositol 3-kinase (PI3K) pathway, and up-regulation in Src/Akt. These signaling events in turn exert their influence over H. pylori-elicited excessive generation of NO and PGE2 caused by the disturbances in nitric oxide synthase and cyclooxygenase isozyme systems, increase in epidermal growth factor receptor transactivation, and the induction in matrix metalloproteinase-9 (MMP-9) release. Interestingly, the extent of gastric mucosal inflammatory response to H. pylori is influenced by a peptide hormone, ghrelin, the action of which relays on the growth hormone secretagogue receptor type 1a (GHS-R1a)-mediated mobilization of G-protein dependent transduction pathways. Yet, the signals triggered by TLR-4 activation as well as those arising through GHS-R1a stimulation converge at MAPK and PLC/PKC/PI3K pathways that form a key integration node for proinflammatory signals generated by H. pylori LPS as well as for those involved in modulation of inflammation by ghrelin. Hence, therapeutic targeting these signals' convergence and integration node could provide a novel and attractive opportunities for developing more effective treatments of H. pylori-related gastric disease.

Leptin modulates the late fever response to LPS in diet-induced obese animals

Leptin is an important modulator of both inflammation and energy homeostasis, making it a key interface between the inflammatory response to pathogenic stimuli and the energy status of the host. In previous studies we demonstrated that sickness responses to systemic immune challenge, including fever, are significantly exacerbated in diet induced obese animals. To investigate whether this exacerbation is functionally linked to the obesity associated increase in circulating levels of leptin, a species-specific leptin antiserum (LAS) was used to neutralize endogenous leptin in diet-induced obese adult male Wistar rats treated with a single intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) (100μg/kg). LAS significantly reduced the magnitude of the later phases of the fever response, and attenuated the circulating levels of IL-6, IL-1ra and bioactivity of leptin in the obese animals. In addition, the antiserum significantly attenuated the hypothalamic expression of IL-1ß, IκBα, COX2, SOCS3 and IL-6 in both lean and obese rats 10h after the LPS injection and NF-IL6 in the hypothalamus of obese rats only. The relatively late rise in brain IL-6 suggested a role in mediating the extended fever response in obese animals and we tested this by neutralizing brain IL-6 using an IL6-AS injected intracerebroventricularly (4μl, icv). The IL6-AS significantly but transiently (between 9h and 12h post LPS) reduced the late fever response of obese rats. These results demonstrate that leptin plays an important part in modulating the late portion of the fever response to LPS, likely through the induction of hypothalamic IL-6 in obese animals.

Crosstalk between nitric oxide synthases and cyclooxygenase 2 in the adrenal cortex of rats under lipopolysaccharide treatment

The effect of lipopolysaccharide on the modulation of steroid production by adrenal cells has been recently acknowledged. The purpose of this study was to determine the in vivo effects of LPS on adrenal cyclooxygenase 2 (COX-2) expression, analyze its crosstalk with the nitric oxide synthase (NOS) system, and assess its involvement on the modulation of glucocorticoid production. Male Wistar rats were injected with LPS and with specific inhibitors for NOS and COX activities. PGE2 and corticosterone levels were determined by RIA. Protein levels were analyzed by immunoprecipitation and western blotting. Transfection assays were performed in murine adrenocortical Y1 cells. Results show that LPS treatment increases PGE2 production and COX-2 protein levels in the rat adrenal cortex. Systemic inhibition of COX-2 blunted the glucocorticoid response to ACTH, as well as the increase in NOS activity and the NOS-2 expression levels induced by LPS. Conversely, NOS inhibition prevented the LPS-dependent increase in PGE2 production, COX-2 protein levels, and the nitrotyrosine modification of COX-2 protein. Treatment of adrenocortical cells with a NO-donor significantly potentiated the LPS-dependent increase in NFκB activity and COX-2 expression levels. In conclusion, our results show a significant crosstalk between COX-2 and NOS in the adrenal cortex upon LPS stimulation, in which each activity has a positive impact on the other. In particular, as both the activities differently affect adrenal steroid production, we hypothesize that this kind of fine modulation enables the gland to adjust steroidogenesis to prevent either an excessive or an insufficient response to the endotoxin challenge.

High glucose-induced increased expression of endothelin-1 in human endothelial cells is mediated by activated CCAAT/enhancer-binding proteins

High glucose-induced endothelial dysfunction is partially mediated by the down-stream pathophysiological effects triggered by increased expression of endothelin-1 (ET-1). The molecular control mechanisms of ET-1 synthesis are yet to be discovered. Members of the CCAAT/enhancer-binding proteins (C/EBP) family are important regulators of key metabolic processes, cellular differentiation and proinflammatory genes. In this study, we aimed at elucidating the role of C/EBP in mediating the high glucose effect on ET-1 expression in human endothelial cells (EC). Human umbilical vein cells (EAhy926) and primary cultures of human aortic EC were exposed to high levels of glucose (16.5-25 mM). Real-time PCR, Western blot, enzyme-linked immunosorbent assay, ET-1 promoter-luciferase reporter analysis, and chromatin immunoprecipitation assays were employed to investigate ET-1 regulation. High glucose activated C/EBPα, C/EBPβ, and C/EBPδ in a dose-dependent manner. It also promoted significant increases in ET-1 gene and peptide expression. Chemical inhibition of JNK, p38MAPK and ERK1/2 diminished significantly the high glucose-induced nuclear translocation of C/EBP and ET-1 expression. Silencing of C/EBPα, C/EBPβ or C/EBPδ greatly reduced the high glucose-induced upregulation of ET-1 mRNA, pre-pro-ET-1, and ET-1 secretion. The expression of various C/EBP isoforms was selectively downregulated by siRNA-mediated gene silencing. In silico analysis indicated the existence of typical C/EBP elements within human ET-1 gene promoter. Transient overexpression of C/EBPα, C/EBPβ or C/EBPδ upregulated the luciferase level controlled by the ET-1 gene promoter. The direct interaction of C/EBPα, C/EBPβ or C/EBPδ proteins with the ET-1 promoter in high glucose-exposed EC was confirmed by chromatin immunoprecipitation assay. High glucose-induced ET-1 expression is mediated through multiple mechanisms. We present evidence that members of the C/EBP proinflammatory transcription factors are important regulators of ET-1 in high glucose-exposed human endothelial cells. High glucose-induced activation of C/EBP-related signaling pathways may induce excessive ET-1 synthesis, thus promoting vasoconstriction and dysfunction of the vascular wall cells in diabetes.

Highly pathogenic porcine reproductive and respiratory syndrome virus induces prostaglandin E2 production through cyclooxygenase 1, which is dependent on the ERK1/2-p-C/EBP-β pathway

Atypical porcine reproductive and respiratory syndrome (PRRS) caused by highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) is characterized by high fever and high mortality. However, the mechanism underlying the fever induction is still unknown. Prostaglandin E2 (PGE2), synthesized by cyclooxygenase type 1/2 (COX-1/2) enzymes, is essential for inducing fever. In this study, we found that PGE2, together with COX-1, was significantly elevated by HP-PRRSV. We subsequently demonstrated that extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphorylated ERK (p-ERK) were the key nodes to trigger COX-1 expression after HP-PRRSV infection. Furthermore, we proved the direct binding of p-C/EBP-β to the COX-1 promoter by luciferase reporter and chromatin immunoprecipitation assays. In addition, silencing of C/EBP-β remarkably impaired the enhancement of COX-1 production induced by HP-PRRSV infection. Taken together, our results indicate that HP-PPRSV elicits the expression of COX-1 through the ERK1/2-p-C/EBP-β signaling pathway, resulting in the increase of PGE2, which might be the cause of high fever in infected pigs. Our findings might provide new insights into the molecular mechanisms underlying the pathogenesis of HP-PRRSV infection.

IMPORTANCE

The atypical PRRS caused by HP-PRRSV was characterized by high fever, high morbidity, and high mortality in pigs of all ages, yet how HP-PRRSV induces high fever in pigs remains unknown. In the present study, we found out that HP-PRRSV infection could increase PGE2 production by upregulation of COX-1, and we subsequently characterized the underlying mechanisms about how HP-PRRSV enhances COX-1 production. PGE2 plays a critical role in inducing high temperature in hosts during pathogen infections. Thus, our findings here could help us have a better understanding of HP-PRRSV pathogenesis.

Eicosanoid modulation by the short-chain fatty acid n-butyrate in human monocytes

n-Butyrate deriving from bacterial fermentation in the mammalian intestine is a key determinant in gastrointestinal homeostasis. We examined the effects of this short-chain fatty acid and Toll-like receptor 2 (TLR) and TLR4 engagement on inflammatory/immunity-associated genes, cyclo-oxygenases (COXs), prostaglandins (PGs) and leukotrienes (LTs) in human monocytes. Before RNA isolation, freshly isolated human monocytes were co-incubated for different time-points with 1 mm n-butyrate alone or in combination with bacterial stimuli. Based on a knowledge-driven approach, a signature of 180 immunity/inflammation-associated genes was picked and real-time PCR analysis was performed. Pathway analysis was carried out using a web-based database analysing program. Based on these gene expression studies the findings were evaluated at the protein/mediator level by Western blot analysis, FACS and ELISA. Following co-incubation with n-butyrate and lipopolysaccharide, key enzymes of the eicosanoid pathway, like PTGS2 (COX-2), TXS, ALOX5, LTA4H and LTC4S, were significantly up-regulated compared with stimulation with lipopolysaccharide alone. Furthermore, release of the lipid mediators PGE(2), 15d-PGJ(2), LTB(4) and thromboxane B(2) was increased by n-butyrate. Regarding signalling, n-butyrate had no additional effect on mitogen-activated protein kinase and interfered differently with early and late phases of nuclear factor-κB signalling. Our results suggest that among many other mediators of eicosanoid signalling n-butyrate massively induces PGE(2) production by increasing the expression of PTGS2 (COX-2) in monocytes following TLR4 and TLR2 activation and induces secretion of LTB(4) and thromboxane B(2). This underscores the role of n-butyrate as a crucial mediator of gut-specific immunity.

Myeloid depletion of SOCS3 enhances LPS-induced acute lung injury through CCAAT/enhancer binding protein δ pathway

Although uncontrolled inflammatory response plays a central role in the pathogenesis of acute lung injury (ALI), the precise molecular mechanisms underlying the development of this disorder remain poorly understood. SOCS3 is an important negative regulator of IL-6-type cytokine signaling. SOCS3 is induced in lung during LPS-induced lung injury, suggesting that generation of SOCS3 may represent a regulatory product during ALI. In the current study, we created mice lacking SOCS3 expression in macrophages and neutrophils (LysM-cre SOCS3(fl/fl)). We evaluated the lung inflammatory response to LPS in both LysM-cre SOCS3(fl/fl) mice and the wild-type (WT) mice (SOCS3(fl/fl)). LysM-cre SOCS3(fl/fl) mice displayed significant increase of the lung permeability index (lung vascular leak of albumin), neutrophils, lung neutrophil accumulation (myeloperoxidase activity), and proinflammatory cytokines/chemokines in bronchial alveolar lavage fluids compared to WT mice. These phenotypes were consistent with morphological evaluation of lung, which showed enhanced inflammatory cell influx and intra-alveolar hemorrhage. We further identify the transcription factor, CCAAT/enhancer-binding protein (C/EBP) δ as a critical downstream target of SOCS3 in LPS-induced ALI. These results indicate that SOCS3 has a protective role in LPS-induced ALI by suppressing C/EBPδ activity in the lung. Elucidating the function of SOCS3 would represent prospective targets for a new generation of drugs needed to treat ALI.

Induction in gastric mucosal prostaglandin and nitric oxide by Helicobacter pylori is dependent on MAPK/ERK-mediated activation of IKK-β and cPLA2: modulatory effect of ghrelin

Among the key factors defining the extent of gastric mucosal inflammatory involvement in response to Helicobacter pylori is the excessive generation of prostaglandin (PGE2) and nitric oxide (NO), caused by the overexpression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), and triggered by the activation of mitogen-activated protein kinase (MAPK)/c-Jun N-terminal kinase, p38 and ERK, and nuclear translocation of the cognate transcription factors. In this study, we report on the role of MAPK/ERK in the regulation of H. pylori LPS-induced gastric mucosal expression of COX-2 and iNOS. We show that ERK activation by the LPS leads to phosphorylation of the inhibitory κB kinase-β (IKK-β) and cytosolic phospholipase A2 (cPLA2), and is reflected in the upsurge in NF-κB nuclear translocation, induction in COX-2 and iNOS expression, and up-regulation in cPLA2 activity. The modulatory effect of peptide hormone, ghrelin, on the LPS-induced changes, although associated with further enhancement in ERK, IKK-β, and cPLA2 phosphorylation, was reflected in the suppression of IKK-β and cPLA2 activity through S-nitrosylation. While the effect of ghrelin on S-nitrosylation was susceptible to suppression by the inhibitors of Src/Akt pathway, the inhibition of ERK activation caused the blockage in IKK-β and cPLA2 phosphorylation as well as S-nitrosylation. Taken together, our data show that H. pylori-induced ERK activation plays a critical role in up-regulation of gastric mucosal PGE2 and NO generation at the level of IKK-β and cPLA2 activation, and that ghrelin counters these proinflammatory consequences of the LPS through Src/Akt-dependent S-nitrosylation.

MSK1 and MSK2 inhibit lipopolysaccharide-induced prostaglandin production via an interleukin-10 feedback loop

Prostaglandin production is catalyzed by cyclooxygenase 2 (cox-2). We demonstrate here that MSK1 and MSK2 (MSK1/2) can exert control on the induction of cox-2 mRNA by Toll-like receptor (TLR) agonists. In the initial phase of cox-2 induction, MSK1/2 knockout macrophages confirmed a role for MSK in the positive regulation of transcription. However, at later time points both lipopolysaccharide (LPS)-induced prostaglandin and cox-2 protein levels were increased in MSK1/2 knockout. Further analysis found that while MSKs promoted cox-2 mRNA transcription, following longer LPS stimulation MSKs also promoted degradation of cox-2 mRNA. This was found to be the result of an interleukin 10 (IL-10) feedback mechanism, with endogenously produced IL-10 promoting cox-2 degradation. The ability of IL-10 to do this was dependent on the mRNA binding protein TTP through a p38/MK2-mediated mechanism. As MSKs regulate IL-10 production in response to LPS, MSK1/2 knockout results in reduced IL-10 secretion and therefore reduced feedback from IL-10 on cox-2 mRNA stability. Following LPS stimulation, this increased mRNA stability correlated to an elevated induction of both of cox-2 protein and prostaglandin secretion in MSK1/2 knockout macrophages relative to that in wild-type cells. This was not restricted to isolated macrophages, as a similar effect of MSK1/2 knockout was seen on plasma prostaglandin E2 (PGE2) levels following intraperitoneal injection of LPS.

CCAAT/enhancer-binding protein δ is a critical mediator of lipopolysaccharide-induced acute lung injury

Although inflammation plays a central role in the pathogenesis of acute lung injury, the molecular mechanisms underlying inflammatory responses in acute lung injury are poorly understood, and therapeutic options remain limited. CCAAT/enhancer-binding proteins, C/EBPβ and C/EBPδ, are expressed in the lung and have been implicated in the regulation of inflammatory mediators. However, their functions in lung pathobiological characteristics are not well characterized. Herein, we show that C/EBPβ and C/EBPδ are activated in mouse lung after intrapulmonary deposition of lipopolysaccharide (LPS). Mice carrying a targeted deletion of the C/EBPδ gene displayed significant attenuation of the lung permeability index (lung vascular leak of albumin), lung neutrophil accumulation (myeloperoxidase activity), and neutrophils in bronchial alveolar lavage fluids compared with wild-type mice. These phenotypes were consistent with morphological evaluation of lung, which showed reduced inflammatory cell influx and minimal intra-alveolar hemorrhage. Moreover, mutant mice expressed considerably less tumor necrosis factor-α, IL-6, and macrophage inflammatory protein-2 in bronchial alveolar lavage fluids in LPS-injured lung compared with wild-type mice. In contrast, C/EBPβ deficiency had no effect on LPS-induced lung injury. By using small-interfering RNA-mediated knockdown for C/EBPδ, we demonstrate, for the first time to our knowledge, that C/EBPδ plays a critical role for the tumor necrosis factor-α, IL-6, and macrophage inflammatory protein-2 production in LPS-stimulated alveolar macrophages. These findings demonstrate that C/EBPδ, but not C/EBPβ, plays an important role in LPS-induced lung inflammatory responses and injury.

Molecular Mechanisms Underlying Anti-Inflammatory Actions of 6-(Methylsulfinyl)hexyl Isothiocyanate Derived from Wasabi (Wasabia japonica)

6-(Methylsulfinyl)hexyl isothiocyanate (6-MSITC) is a major bioactive compound in wasabi (Wasabia japonica), which is a typical Japanese pungent spice. Recently, in vivo and in vitro studies demonstrated that 6-MSITC has several biological properties, including anti-inflammatory, antimicrobial, antiplatelet, and anticancer effects. We previously reported that 6-MSITC strongly suppresses cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), and cytokines, which are important factors that mediate inflammatory processes. Moreover, molecular analysis demonstrated that 6-MSITC blocks the expressions of these factors by suppressing multiple signal transduction pathways to attenuate the activation of transcriptional factors. Structure-activity relationships of 6-MSITC and its analogues containing an isothiocyanate group revealed that methylsulfinyl group and the length of alkyl chain of 6-MSITC might be related to high inhibitory potency. In this paper, we review the anti-inflammatory properties of 6-MSITC and discuss potential molecular mechanisms focusing on inflammatory responses by macrophages.

C/EBPβ regulates multiple IL-1β-induced human astrocyte inflammatory genes

Background

CCAAT enhancer-binding protein (C/EBP)β regulates gene expression in multiple organ systems and cell types, including astrocytes in the central nervous system (CNS). Inflammatory stimuli, interleukin (IL)-1β, tumor necrosis factor-α, human immunodeficiency virus (HIV)-1 and lipopolysaccharide induce astrocyte C/EBPβ expression. C/EBPβ is detectable in brains of Alzheimer’s disease (AD), Parkinson’s disease (PD) and HIV-1-associated dementia (HAD) patients, yet little is known about how C/EBPβ contributes to astrocyte gene regulation during neuroinflammation.

Methods

The expression of 92 human inflammation genes was compared between IL-1β-treated primary human astrocytes and astrocytes transfected with C/EBPβ-specific small interfering (si)RNA prior to IL-1β treatment for 12 h. Transcripts altered by > two-fold compared to control were subjected to one-way analysis of variance and Newman-Keuls post-test for multiple comparisons. Expression of two genes, cyclooxygenase-2 (COX-2) and bradykinin receptor B2 (BDKRB2) was further confirmed in additional human astrocyte donors. Astrocytes were treated with mitogen-activated protein kinase-selective inhibitors, then with IL-1β for 12 or 24 h followed by COX-2 and BDKRB2, expression analyses.

Results

IL-1β altered expression of 29 of 92 human inflammation genes by at least two-fold in primary human astrocytes in 12 h. C/EBPβ knockdown affected expression of 17 out of 29 IL-1β-regulated genes by > 25%. Two genes relevant to neuroinflammation, COX-2 and BDKRB2, were robustly decreased and increased, respectively, in response to C/EBPβ knockdown, and expression was confirmed in two additional donors. COX-2 and BDKRB2 mRNA remained altered in siRNA-transfected astrocytes at 12, 24 or 72 h. Inhibiting p38 kinase (p38K) activation blocked IL-1β-induced astrocyte COX-2 mRNA and protein expression, but not IL-1β-induced astrocyte BDKRB2 expression. Inhibiting extracellular-regulated kinase (ERK)1/2 activation blocked IL-1β-induced BDKRB2 mRNA expression while increasing COX-2 expression.

Conclusion

These data support an essential role for IL-1β in the CNS and identify new C/EBPβ functions in astrocytes. Additionally, this work suggests p38K and ERK1/2 pathways may regulate gene expression in a complementary manner to fine tune the IL-1β-mediated astrocyte inflammatory response. Delineating a role for C/EBPβ and other involved transcription factors in human astrocyte inflammatory response may lead to effective therapies for AD, PD, HAD and other neurological disorders.

Inhibition of CD200R1 expression by C/EBP β in reactive microglial cells

Background

In physiological conditions, it is postulated that neurons control microglial reactivity through a series of inhibitory mechanisms, involving either cell contact-dependent, soluble-factor-dependent or neurotransmitter-associated pathways. In the current study, we focus on CD200R1, a microglial receptor involved in one of these cell contact-dependent mechanisms. CD200R1 activation by its ligand, CD200 (mainly expressed by neurons in the central nervous system),is postulated to inhibit the pro-inflammatory phenotype of microglial cells, while alterations in CD200-CD200R1 signalling potentiate this phenotype. Little is known about the regulation of CD200R1 expression in microglia or possible alterations in the presence of pro-inflammatory stimuli.

Methods

Murine primary microglial cultures, mixed glial cultures from wild-type and CCAAT/enhancer binding protein β (C/EBPβ)-deficient mice, and the BV2 murine cell line overexpressing C/EBPβ were used to study the involvement of C/EBPβ transcription factor in the regulation of CD200R1 expression in response to a proinflammatory stimulus (lipopolysaccharide (LPS)). Binding of C/EBPβ to the CD200R1 promoter was determined by quantitative chromatin immunoprecipitation (qChIP). The involvement of histone deacetylase 1 in the control of CD200R1 expression by C/EBPβ was also determined by co-immunoprecipitation and qChIP.

Results

LPS treatment induced a decrease in CD200R1 mRNA and protein expression in microglial cells, an effect that was not observed in the absence of C/EBPβ. C/EBPβ overexpression in BV2 cells resulted in a decrease in basal CD200R1 mRNA and protein expression. In addition, C/EBPβ binding to the CD200R1 promoter was observed in LPS-treated but not in control glial cells, and also in control BV2 cells overexpressing C/EBPβ. Finally, we observed that histone deacetylase 1 co-immunoprecipitated with C/EBPβ and showed binding to a C/EBPβ consensus sequence of the CD200R1 promoter in LPS-treated glial cells. Moreover, histone deacetylase 1 inhibitors reversed the decrease in CD200R1 expression induced by LPS treatment.

Conclusions

CD200R1 expression decreases in microglial cells in the presence of a pro-inflammatory stimulus, an effect that is regulated, at least in part, by C/EBPβ. Histone deacetylase 1 may mediate C/EBPβ inhibition of CD200R1 expression, through a direct effect on C/EBPβ transcriptional activity and/or on chromatin structure.

Critical role for CCAAT/enhancer-binding protein β in immune complex-induced acute lung injury

C/EBPs, particularly C/EBPβ and C/EBPδ, are known to participate in the regulation of many genes associated with inflammation. However, very little is known regarding the activation and functions of C/EBPβ and C/EBPδ in acute lung inflammation and injury. In this study, we show that both C/EBPβ and C/EBPδ activation are triggered in lungs and in alveolar macrophages following intrapulmonary deposition of IgG immune complexes. We further show that mice carrying a targeted deletion of the C/EBPβ gene displayed significant attenuation of the permeability index (lung vascular leak of albumin), lung neutrophil accumulation (myeloperoxidase activity), total number of WBCs, and neutrophils in bronchoalveolar lavage fluids compared with wild-type mice. Moreover, the mutant mice expressed considerably less TNF-α, IL-6, and CXC/CC chemokine and soluble ICAM-1 proteins in bronchoalveolar lavage fluids, and corresponding mRNAs in the IgG immune complex-injured lung, compared with wild-type mice. These phenotypes were associated with a significant reduction in morphological lung injury. In contrast, C/EBPδ deficiency had no effect on IgG immune complex-induced lung injury. IgG immune complex-stimulated C/EBPβ-deficient alveolar macrophages released significantly less TNF-α, IL-6, MIP-2, keratinocyte cell-derived chemokine, and MIP-1α compared with wild-type cells. Similar decreases in IgG immune complex-induced inflammatory mediator production were observed following small interfering RNA ablation of C/EBPβ in a murine alveolar macrophage cell line. These findings implicate C/EBPβ as a critical regulator of IgG immune complex-induced inflammatory responses and injury in the lung.

Involvement of p38 MAPK-dependent activator protein (AP-1) activation in modulation of gastric mucosal inflammatory responses to Helicobacter pylori by ghrelin

A peptide hormone, ghrelin, plays an important role in modulation of gastric mucosal inflammatory responses to Helicobacter pylori infection by controlling the cross-talk between nitric oxide synthase (NOS) and cyclooxygenase (COX) enzyme systems. In this study, we report that H. pylori LPS-elicited induction in gastric mucosal COX-2 and inducible (i) iNOS protein expression, and the impairment in constitutive (c) cNOS phosphorylation, was associated with mitogen-activated protein kinase, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase and p38 activation, and occurred with the involvement of transcription factors, CCATT/enhancer-binding protein (C/EBP) δ, cAMP response element-binding protein, activator protein-1 (AP-1), and NF-κB. The modulatory effect of ghrelin on the LPS-induced changes was manifested in the inhibition of nuclear translocation of p65 NF-κB and C/EBPδ, and suppression in AP-1 activation, and the inhibition in phosphorylation of JNK and p38, as well as their respective downstream targets, c-Jun and ATF-2. However, only the inhibition of p38-mediated ATF-2 phosphorylation was reflected in the reduced expression of COX-2 protein. Further, the effect of ghrelin of the LPS-induced changes was reflected in the increase in Src/Akt-dependent cNOS activation through phosphorylation and the inhibition of cNOS-mediated IKK-β S-nitrosylation. Our findings indicate ghrelin counters the proinflammatory consequences of H. pylori by interfering with the p38/ATF-2-induced AP-1 activation in association with concurrent up-regulation in Src/Akt-dependent cNOS phosphorylation.

Gene expression induced by Toll-like receptors in macrophages requires the transcription factor NFAT5

NFAT5 regulates the induction of TLR-stimulated genes with constitutive binding to the Tnf promoter regardless of TLR ligation and recruitment to Nos2 and Il6 dependent on TLR activation and IKKb.

Toll-like receptors (TLRs) engage networks of transcriptional regulators to induce genes essential for antimicrobial immunity. We report that NFAT5, previously characterized as an osmostress responsive factor, regulates the expression of multiple TLR-induced genes in macrophages independently of osmotic stress. NFAT5 was essential for the induction of the key antimicrobial gene Nos2 (inducible nitric oxide synthase [iNOS]) in response to low and high doses of TLR agonists but is required for Tnf and Il6 mainly under mild stimulatory conditions, indicating that NFAT5 could regulate specific gene patterns depending on pathogen burden intensity. NFAT5 exhibited two modes of association with target genes, as it was constitutively bound to Tnf and other genes regardless of TLR stimulation, whereas its recruitment to Nos2 or Il6 required TLR activation. Further analysis revealed that TLR-induced recruitment of NFAT5 to Nos2 was dependent on inhibitor of κB kinase (IKK) β activity and de novo protein synthesis, and was sensitive to histone deacetylases. In vivo, NFAT5 was necessary for effective immunity against Leishmania major, a parasite whose clearance requires TLRs and iNOS expression in macrophages. These findings identify NFAT5 as a novel regulator of mammalian anti-pathogen responses.

Pro-inflammatory gene expression and neurotoxic effects of activated microglia are attenuated by absence of CCAAT/enhancer binding protein β

Background

Microglia and astrocytes respond to homeostatic disturbances with profound changes of gene expression. This response, known as glial activation or neuroinflammation, can be detrimental to the surrounding tissue. The transcription factor CCAAT/enhancer binding protein β (C/EBPβ) is an important regulator of gene expression in inflammation but little is known about its involvement in glial activation. To explore the functional role of C/EBPβ in glial activation we have analyzed pro-inflammatory gene expression and neurotoxicity in murine wild type and C/EBPβ-null glial cultures.

Methods

Due to fertility and mortality problems associated with the C/EBPβ-null genotype we developed a protocol to prepare mixed glial cultures from cerebral cortex of a single mouse embryo with high yield. Wild-type and C/EBPβ-null glial cultures were compared in terms of total cell density by Hoechst-33258 staining; microglial content by CD11b immunocytochemistry; astroglial content by GFAP western blot; gene expression by quantitative real-time PCR, western blot, immunocytochemistry and Griess reaction; and microglial neurotoxicity by estimating MAP2 content in neuronal/microglial cocultures. C/EBPβ DNA binding activity was evaluated by electrophoretic mobility shift assay and quantitative chromatin immunoprecipitation.

Results

C/EBPβ mRNA and protein levels, as well as DNA binding, were increased in glial cultures by treatment with lipopolysaccharide (LPS) or LPS + interferon γ (IFNγ). Quantitative chromatin immunoprecipitation showed binding of C/EBPβ to pro-inflammatory gene promoters in glial activation in a stimulus- and gene-dependent manner. In agreement with these results, LPS and LPS+IFNγ induced different transcriptional patterns between pro-inflammatory cytokines and NO synthase-2 genes. Furthermore, the expressions of IL-1β and NO synthase-2, and consequent NO production, were reduced in the absence of C/EBPβ. In addition, neurotoxicity elicited by LPS+IFNγ-treated microglia co-cultured with neurons was completely abolished by the absence of C/EBPβ in microglia.

Conclusions

These findings show involvement of C/EBPβ in the regulation of pro-inflammatory gene expression in glial activation, and demonstrate for the first time a key role for C/EBPβ in the induction of neurotoxic effects by activated microglia.

The CCAAT/enhancer binding protein (C/EBP) δ is differently regulated by fibrillar and oligomeric forms of the Alzheimer amyloid-β peptide

Background

The transcription factors CCAAT/enhancer binding proteins (C/EBP) α, β and δ have been shown to be expressed in brain and to be involved in regulation of inflammatory genes in concert with nuclear factor κB (NF-κB). In general, C/EBPα is down-regulated, whereas both C/EBPβ and δ are up-regulated in response to inflammatory stimuli. In Alzheimer's disease (AD) one of the hallmarks is chronic neuroinflammation mediated by astrocytes and microglial cells, most likely induced by the formation of amyloid-β (Aβ) deposits. The inflammatory response in AD has been ascribed both beneficial and detrimental roles. It is therefore important to delineate the inflammatory mediators and signaling pathways affected by Aβ deposits with the aim of defining new therapeutic targets.

Methods

Here we have investigated the effects of Aβ on expression of C/EBP family members with a focus on C/EBPδ in rat primary astro-microglial cultures and in a transgenic mouse model with high levels of fibrillar Aβ deposits (tg-ArcSwe) by western blot analysis. Effects on DNA binding activity were analyzed by electrophoretic mobility shift assay. Cross-talk between C/EBPδ and NF-κB was investigated by analyzing binding to a κB site using a biotin streptavidin-agarose pull-down assay.

Results

We show that exposure to fibril-enriched, but not oligomer-enriched, preparations of Aβ inhibit up-regulation of C/EBPδ expression in interleukin-1β-activated glial cultures. Furthermore, we observed that, in aged transgenic mice, C/EBPα was significantly down-regulated and C/EBPβ was significantly up-regulated. C/EBPδ, on the other hand, was selectively down-regulated in the forebrain, a part of the brain showing high levels of fibrillar Aβ deposits. In contrast, no difference in expression levels of C/EBPδ between wild type and transgenic mice was detected in the relatively spared hindbrain. Finally, we show that interleukin-1β-induced C/EBPδ DNA binding activity to both C/EBP and κB sites is abolished after exposure to Aβ.

Conclusions

These data suggest that both expression and function of C/EBPδ are dysregulated in Alzheimer's disease. C/EBPδ seems to be differently regulated in response to different conformations of Aβ. We propose that Aβ induces an imbalance between NF-κB and C/EBP transcription factors that may result in abnormal responses to inflammatory stimuli.

Noncanonical BMP signaling regulates cyclooxygenase-2 transcription

Activation of p38 MAPK has been shown to be relevant for a number of bone morphogenetic protein (BMP) physiological effects. We report here the involvement of noncanonical phosphorylated mothers against decapentaplegic (Smad) signaling in the transcriptional induction of Cox2 (Ptgs2) by BMP-2 in mesenchymal cells and organotypic calvarial cultures. We demonstrate that different regulatory elements are required for regulation of Cox2 expression by BMP-2: Runt-related transcription factor-2 and cAMP response element sites are essential, whereas a GC-rich Smad binding element is important for full responsiveness. Efficient transcriptional activation requires cooperation between transcription factors because mutation of any element results in a strong decrease of BMP-2 responsiveness. BMP-2 activation of p38 leads to increased recruitment of activating transcription factor-2, Runx2, Smad, and coactivators such as p300 at the responsive sites in the Cox2 proximal promoter. We demonstrate, by either pharmacological or genetic analysis, that maximal BMP-2 effects on Cox2 and JunB expression require the function of p38 and its downstream effector mitogen/stress-activated kinase 1. Altogether our results strongly suggest that cooperative effects between canonical and noncanonical BMP signaling allow the fine-tuning of BMP transcriptional responses on specific target genes.

Inhibition of CCAAT/enhancer binding protein δ expression by chrysin in microglial cells results in anti-inflammatory and neuroprotective effects

The control of neuroinflammation is a potential target to be considered in the treatment of neurodegenerative diseases. It is therefore important to find anti-inflammatory drugs and study new targets that inhibit neuroinflammation. We designed an experimental model of neuroinflammation in vitro to study the anti-inflammatory and neuroprotective effects of the flavonoid chrysin and the involvement of nuclear factor-κB p65 and CCAAT/enhancer binding proteins (C/EBPs) β and δ transcription factors in its mechanism of action. We used primary cultures of mouse embryonic cortical neurons and cultures of BV2 (murine microglial cell line) or mouse primary microglia. We induced neuronal death in neuronal-BV2/microglial co-cultures using lipopolysaccharide of Escherichia coli and interferon-γ. Chrysin pre-treatment inhibited nitric oxide and tumor necrosis factor-α production, as well as inducible nitric oxide synthase expression in lipopolysaccharide E. coli and interferon-γ-treated microglial cells, but did not affect cyclooxygenase-2 expression. Chrysin pre-treatment also protected neurons against the neurotoxicity induced by reactive microglial cells. These effects were associated to a decrease in C/EBPδ protein level, mRNA expression, and DNA-binding activity, with no effect on C/EBPβ and p65 nuclear protein levels or DNA-binding activity, pointing out C/EBPδ as a possible mediator of chrysin effects. Consequently, C/EBPδ is a possible target to act against neuroinflammation in neurodegenerative processes.

CCAAT/enhancer binding protein delta in microglial activation

The transcription factor CCAAT/enhancer binding protein delta (C/EBP delta) regulates transcription of genes that play important roles in glial activation. Previous studies have shown the astroglial expression of C/EBP delta but the microglial expression of C/EBP delta remains virtually unexplored, with the exception of two microarray studies. In this report, using murine primary cultures and BV2 cells we clearly demonstrate that C/EBP delta is expressed by microglia and it is upregulated in microglial activation. Lipopolysaccharide upregulates C/EBP delta both in microglia and in astrocytes. This effect is time-dependent, with a maximum effect at 3 hr at mRNA level and at 4-8 hr at protein level, and concentration-dependent, with a maximum effect at 100 ng/mL. The lipopolysaccharide-induced C/EBP delta upregulation in BV2 microglia is mimicked by agonists of the toll-like receptors 2, 3 and 9 and can be prevented by an inhibitor of extracellular signal-regulated kinase activation. C/EBP delta from activated BV2 microglia binds to the cyclooxygenase-2 promoter and forms complexes with C/EBP beta isoforms. These results point to C/EBP delta as a putative key regulator of proinflammatory gene expression in microglial activation.

Apoptosis signal-regulating kinase 1 in peptidoglycan-induced COX-2 expression in macrophages

In this study, we investigated the role of ASK1 in PGN-induced C/EBPbeta activation and COX-2 expression in RAW 264.7 macrophages. The PGN-induced COX-2 expression was attenuated by the DNs of ASK1, JNK1, JNK2, a JNK inhibitor (SP600125), and an AP-1 inhibitor (curcumin). PGN caused ASK1 dephosphorylation time-dependently at Ser967, dissociation from the ASK1-14-3-3 complex, and subsequent ASK1 activation. In addition, PGN activated PP2A and suppression of PP2A by okadaic acid markedly inhibited PGN-induced ASK1 Ser967 dephosphorylation and COX-2 expression. PGN induced the activation of the JNK-AP-1 signaling cascade downstream of ASK1. PGN-increased C/EBPbeta expression and DNA-binding activity were inhibited by the ASK1-JNK-AP-1 signaling blockade. COX-2 promoter luciferase activity induced by PGN was attenuated in cells transfected with the COX-2 reporter construct possessing the C/EBP-binding site mutation. In addition, the ASK1-JNK-AP-1-C/EBPbeta cascade was activated in human peripheral mononuclear cells exposure to PGN. The TLR2 agonist Pam(3)CSK(4) was also shown to induce ASK1 Ser967 dephosphorylation, JNK and c-jun phosphorylation, C/EBPbeta activation, and COX-2 expression in RAW 264.7 macrophages. PGN-induced COX-2 promoter luciferase activity was prevented by selective inhibition of TLR2 and c-Jun in RAW 264.7 macrophages. Our data demonstrate that PGN might activate the TLR2-mediated PP2A-ASK1-JNK-AP-1-C/EBPbeta cascade and subsequent COX-2 expression in RAW 264.7 macrophages.

Nature meets nurture: molecular genetics of gastric cancer

The immensity of genes and molecules implicated in gastric carcinogenesis is overwhelming and the relevant importance of some of these molecules is too often unclear. This review serves to bring us up-to-date with the latest findings as well as to look at the larger picture in terms of how to tackle the problem of solving this multi-piece puzzle. In this review, the environmental nurturing of intestinal cancer is discussed, beginning with epidemiology (known causative factors for inducing molecular change), an update of H. pylori research, including the role of inflammation and stem cells in premalignant lesions. The role of E-cadherin in the nature (genotype) of diffuse gastric cancer is highlighted, and finally the ever growing discipline of SNP analysis (including IL1B) is discussed.

Nature meets nurture: molecular genetics of gastric cancer

The immensity of genes and molecules implicated in gastric carcinogenesis is overwhelming and the relevant importance of some of these molecules is too often unclear. This review serves to bring us up-to-date with the latest findings as well as to look at the larger picture in terms of how to tackle the problem of solving this multi-piece puzzle. In this review, the environmental nurturing of intestinal cancer is discussed, beginning with epidemiology (known causative factors for inducing molecular change), an update of H. pylori research, including the role of inflammation and stem cells in premalignant lesions. The role of E-cadherin in the nature (genotype) of diffuse gastric cancer is highlighted, and finally the ever growing discipline of SNP analysis (including IL1B) is discussed.

Exaptation of an ancient Alu short interspersed element provides a highly conserved vitamin D-mediated innate immune response in humans and primates

BACKGROUND

About 45% of the human genome is comprised of mobile transposable elements or "junk DNA". The exaptation or co-option of these elements to provide important cellular functions is hypothesized to have played a powerful force in evolution; however, proven examples are rare. An ancient primate-specific Alu short interspersed element (SINE) put the human CAMP gene under the regulation of the vitamin D pathway by providing a perfect vitamin D receptor binding element (VDRE) in its promoter. Subsequent studies demonstrated that the vitamin D-cathelicidin pathway may be a key component of a novel innate immune response of human to infection. The lack of evolutionary conservation in non-primate mammals suggested that this is a primate-specific adaptation. Evidence for evolutionary conservation of this regulation in additional primate lineages would provide strong evidence that the TLR2/1-vitamin D-cathelicidin pathway evolved as a biologically important immune response mechanism protecting human and non-human primates against infection.

RESULTS

PCR-based amplification of the Alu SINE from human and non-human primate genomic DNA and subsequent sequence analysis, revealed perfect structural conservation of the VDRE in all primates examined. Reporter gene studies and induction of the endogenous CAMP gene in Rhesus macaque peripheral blood mononuclear cells demonstrated that the VDREs were conserved functionally. In addition, New World monkeys (NWMs) have maintained additional, functional steroid-hormone receptor binding sites in the AluSx SINE that confer retinoic acid responsiveness and provide potential thyroid hormone receptor binding sites. These sites were less well-conserved during human, ape and Old World monkey (OWM) evolution and the human CAMP gene does not respond to either retinoic acid or thyroid hormone.

CONCLUSION

We demonstrated that the VDRE in the CAMP gene originated from the exaptation of an AluSx SINE in the lineage leading to humans, apes, OWMs and NWMs and remained under purifying selection for the last 55-60 million years. We present convincing evidence of an evolutionarily fixed, Alu-mediated divergence in steroid hormone nuclear receptor gene regulation between humans/primates and other mammals. Evolutionary selection to place the primate CAMP gene under regulation of the vitamin D pathway potentiates the innate immune response and may counter the anti-inflammatory properties of vitamin D.