C/EBP beta regulation of the tumor necrosis factor alpha gene

Microglia in the hypothalamic paraventricular nucleus sense hemodynamic disturbance and promote sympathetic excitation in hypertension

Hypertension is usually accompanied by elevated sympathetic tonicity, but how sympathetic hyperactivity is triggered is not clear. Recent advances revealed that microglia-centered neuroinflammation contributes to sympathetic excitation in hypertension. In this study, we performed a temporospatial analysis of microglia at both morphological and transcriptomic levels and found that microglia in the hypothalamic paraventricular nucleus (PVN), a sympathetic center, were early responders to hypertensive challenges. Vasculature analyses revealed that the PVN was characterized by high capillary density, thin vessel diameter, and complex vascular topology relative to other brain regions. As such, the PVN was susceptible to the penetration of ATP released from the vasculature in response to hemodynamic disturbance after blood pressure increase. Mechanistically, ATP ligation to microglial P2Y12 receptor was responsible for microglial inflammatory activation and the eventual sympathetic overflow. Together, these findings identified a distinct vasculature pattern rendering vulnerability of PVN pre-sympathetic neurons to hypertension-associated microglia-mediated inflammatory insults.

Translatome analysis reveals microglia and astrocytes to be distinct regulators of inflammation in the hyperacute and acute phases after stroke

Neuroinflammation is a hallmark of ischemic stroke, which is a leading cause of death and long-term disability. Understanding the exact cellular signaling pathways that initiate and propagate neuroinflammation after stroke will be critical for developing immunomodulatory stroke therapies. In particular, the precise mechanisms of inflammatory signaling in the clinically relevant hyperacute period, hours after stroke, have not been elucidated. We used the RiboTag technique to obtain microglia and astrocyte-derived mRNA transcripts in a hyperacute (4 h) and acute (3 days) period after stroke, as these two cell types are key modulators of acute neuroinflammation. Microglia initiated a rapid response to stroke at 4 h by adopting an inflammatory profile associated with the recruitment of immune cells. The hyperacute astrocyte profile was marked by stress response genes and transcription factors, such as Fos and Jun, involved in pro-inflammatory pathways such as TNF-α. By 3 days, microglia shift to a proliferative state and astrocytes strengthen their inflammatory response. The astrocyte pro-inflammatory response at 3 days is partially driven by the upregulation of the transcription factors C/EBPβ, Spi1, and Rel, which comprise 25% of upregulated transcription factor-target interactions. Surprisingly, few sex differences across all groups were observed. Expression and log2 fold data for all sequenced genes are available on a user-friendly website for researchers to examine gene changes and generate hypotheses for stroke targets. Taken together, our data comprehensively describe the microglia and astrocyte-specific translatome response in the hyperacute and acute period after stroke and identify pathways critical for initiating neuroinflammation.

DNA damage-inducible transcript 3 deficiency promotes bone resorption in murine periodontitis models

BACKGROUND AND OBJECTIVE

Periodontitis is a multifactorial inflammatory disease that leads to the destruction of supporting structures of the teeth. DNA damage-inducible transcript 3 (DDIT3) plays crucial roles in cell survival and differentiation. DDIT3 regulates bone mass and osteoclastogenesis in femur. However, the role of DDIT3 in periodontitis has not been elucidated. This research aimed to explore the role and mechanisms of DDIT3 in periodontitis.

METHODS

DDIT3 gene knockout (KO) mice were generated using a CRISPR/Cas9 system. Experimental periodontitis models were established to explore the role of DDIT3 in periodontitis. The expression of DDIT3 in periodontal tissues was detected by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). The alveolar bone phenotypes were observed by micro-CT and stereomicroscopy. The inflammation levels and osteoclast activity were examined by histological staining, immunostaining, and qRT-PCR. Bone marrow-derived macrophages (BMMs) were isolated to confirm the effects of DDIT3 on osteoclast formation and function in vitro.

RESULTS

The increased expression of DDIT3 in murine inflamed periodontal tissues was detected. DDIT3 knockout aggravated alveolar bone loss and enhanced expression levels of inflammatory cytokines in murine periodontitis models. Increased osteoclast formation and higher expression levels of osteoclast-specific markers were observed in the inflamed periodontal tissues of KO mice. In vitro, DDIT3 deficiency promoted the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts and the bone resorption activity of mature osteoclasts.

CONCLUSIONS

Our results demonstrate that DDIT3 deletion aggravated alveolar bone loss in experimental periodontitis through enhanced inflammatory reactions and osteoclastogenesis. The anti-inflammation and the inhibition of bone loss by DDIT3 in murine periodontitis provides a potential novel therapeutic strategy for periodontitis.

Translatome analysis reveals microglia and astrocytes to be distinct regulators of inflammation in the hyperacute and acute phases after stroke

Neuroinflammation is a hallmark of ischemic stroke, which is a leading cause of death and long-term disability. Understanding the exact cellular signaling pathways that initiate and propagate neuroinflammation after stroke will be critical for developing immunomodulatory stroke therapies. In particular, the precise mechanisms of inflammatory signaling in the clinically relevant hyperacute period, hours after stroke, have not been elucidated. We used the RiboTag technique to obtain astrocyte and microglia-derived mRNA transcripts in a hyperacute (4 hours) and acute (3 days) period after stroke, as these two cell types are key modulators of acute neuroinflammation. Microglia initiated a rapid response to stroke at 4 hours by adopting an inflammatory profile associated with the recruitment of immune cells. The hyperacute astrocyte profile was marked by stress response genes and transcription factors, such as Fos and Jun , involved in pro-inflammatory pathways such as TNF-α. By 3 days, microglia shift to a proliferative state and astrocytes strengthen their inflammatory response. The astrocyte pro-inflammatory response at 3 days is partially driven by the upregulation of the transcription factors C/EBPβ, Spi1 , and Rel , which comprise 25% of upregulated transcription factor-target interactions. Surprisingly, few sex differences across all groups were observed. Expression and log ₂ fold data for all sequenced genes are available on a user-friendly website for researchers to examine gene changes and generate hypotheses for stroke targets. Taken together our data comprehensively describe the astrocyte and microglia-specific translatome response in the hyperacute and acute period after stroke and identify pathways critical for initiating neuroinflammation.

Antioxidant and Anti-Inflammatory Effects of Thyme (Thymus vulgaris L.) Essential Oils Prepared at Different Plant Phenophases on Pseudomonas aeruginosa LPS-Activated THP-1 Macrophages

Thyme (Thymus vulgaris L.) essential oil (TEO) is widely used as an alternative therapy especially for infections of the upper respiratory tract. TEO possesses antiviral, antibacterial, and antifungal properties. The emerging antibiotic resistance of bacterial strains, including Pseudomonas aeruginosa, has prompted the urge to find alternative treatments. In the present study, we examined the anti-inflammatory and antioxidant effects of thymol, the main compound of TEO, and two TEOs prepared at the beginning and at the end of the flowering period that may make these oils promising candidates as complementary or alternative therapies against P. aeruginosa infections. The activity measurements of the antioxidant enzymes peroxidase (PX), catalase (CAT), and superoxide dismutase (SOD) as well as the determination of total antioxidant capacity of P. aeruginosa-activated THP-1 cells revealed that thymol and both TEOs increased CAT and SOD activity as well as the antioxidant capacity of the THP-1 cells. The measurements of the proinflammatory cytokine mRNA expression and secreted protein level of LPS-activated THP-1 cells showed that from the two TEOs, only TEO prepared at the beginning of the flowering period acted as a potent inhibitor of the synthesis of IL-6, IL-8, IL-β, and TNF-α. Our results suggest that not only thymol, but also the synergism or the antagonistic effects of the additional compounds of the essential oils are responsible for the anti-inflammatory activity of TEOs.

From quiescence to repair: C/EBPβ as a regulator of muscle stem cell function in health and disease

CCAAT/Enhancer Binding protein beta (C/EBPβ) is a transcriptional regulator involved in numerous physiological processes. Herein, we describe a role for C/EBPβ as a regulator of skeletal muscle stem cell function. In particular, C/EBPβ is expressed in muscle stem cells in healthy muscle where it inhibits myogenic differentiation. Downregulation of C/EBPβ expression at the protein and transcriptional level allows for differentiation. Persistence of C/EBPβ promotes stem cell self-renewal and C/EBPβ expression is required for mitotic quiescence in this cell population. As a critical regulator of skeletal muscle homeostasis, C/EBPβ expression is stimulated in pathological conditions such as cancer cachexia, which perturbs muscle regeneration and promotes myofiber atrophy in the context of systemic inflammation. C/EBPβ is also an important regulator of cytokine expression and immune response genes, a mechanism by which it can influence muscle stem cell function. In this viewpoint, we describe a role for C/EBPβ in muscle stem cells and propose a functional intersection between C/EBPβ and NF-kB action in the regulation of cancer cachexia.

Three chemotypes of thyme (Thymus vulgaris L.) essential oil and their main compounds affect differently the IL-6 and TNFα cytokine secretions of BV-2 microglia by modulating the NF-κB and C/EBPβ signalling pathways

BACKGROUND

The essential oils possess both antimicrobial and anti-inflammatory effects, therefore they can provide an effective treatment against infections. Essential oils are widely used as supportive ingredients in many diseases, especially in the acute and chronic diseases of the respiratory tract. Neuroinflammation is responsible for several diseases of the central nervous system. Some plant-derived bioactive molecules have been shown to have role in attenuating neuroinflammation by regulating microglia, the immune cells of the CNS.

METHODS

In this study, the anti-inflammatory effect of three chemotypes of thyme essential oil and their main compounds (geraniol, thujanol and linalool) were examined on lipopolysaccharide-induced BV-2 microglia. Three different experimental setups were used, LPS pretreatment, essential oil pretreatment and co-treatments of LPS and essential oils in order to determine whether essential oils are able to prevent inflammation and can decrease it. The concentrations of the secreted tumour necrosis factor α (TNFα) and interleukin-6 (IL-6) proinflammatory cytokines were measured and we analysed by Western blot the activity of the cell signalling pathways, NF-κB and CCAAT-enhancer binding protein β (C/EBPβ) regulating TNFα and IL-6 proinflammatory cytokine expressions in BV-2 cells.

RESULTS

Our results showed definite alterations in the effects of essential oil chemotypes and their main compounds at the different experimental setups. Considering the changes of IL-6 and TNFα secretions the best reduction of inflammatory cytokines could be reached by the pretreatment with the essential oils. In addition, the main compounds exerted better effects than essential oil chemotypes in case of LPS pretreatment. At the essential oil pretreatment experiment, the effect of linalool and geraniol was outstanding but there was no major difference between the actions of chemotypes and standards. Main compounds could be seen to have large inhibitory effects on certain cell signalling components related to the activation of the expression of proinflammatory cytokines.

CONCLUSION

Thyme essential oils are good candidates to use in prevention of neuroinflammation and related neurodegeneration, but the exact ratio of the components has to be selected carefully.

Primary culture of the rat spinal dorsal horn: a tool to investigate the effects of inflammatory stimulation on the afferent somatosensory system

One maladaptive consequence of inflammatory stimulation of the afferent somatosensory system is the manifestation of inflammatory pain. We established and characterized a neuroglial primary culture of the rat superficial dorsal horn (SDH) of the spinal cord to test responses of this structure to neurochemical, somatosensory, or inflammatory stimulation. Primary cultures of the rat SDH consist of neurons (43%), oligodendrocytes (35%), astrocytes (13%), and microglial cells (9%). Neurons of the SDH responded to cooling (7%), heating (18%), glutamate (80%), substance P (43%), prostaglandin E₂ (8%), and KCl (100%) with transient increases in the intracellular calcium [Ca²⁺]_i. Short-term stimulation of SDH primary cultures with LPS (10 μg/ml, 2 h) caused increased expression of pro-inflammatory cytokines, inflammatory transcription factors, and inducible enzymes responsible for inflammatory prostaglandin E₂ synthesis. At the protein level, increased concentrations of tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6) were measured in the supernatants of LPS-stimulated SDH cultures and enhanced TNFα and IL-6 immunoreactivity was observed specifically in microglial cells. LPS-exposed microglial cells further showed increased nuclear immunoreactivity for the inflammatory transcription factors NFκB, NF-IL6, and pCREB, indicative of their activation. The short-term exposure to LPS further caused a reduction in the strength of substance P as opposed to glutamate-evoked Ca²⁺-signals in SDH neurons. However, long-term stimulation with a low dose of LPS (0.01 μg/ml, 24 h) resulted in a significant enhancement of glutamate-induced Ca²⁺ transients in SDH neurons, while substance P-evoked Ca²⁺ signals were not influenced. Our data suggest a critical role for microglial cells in the initiation of inflammatory processes within the SDH of the spinal cord, which are accompanied by a modulation of neuronal responses.

Troxerutin downregulates C/EBP-β gene expression via modulating the IFNγ-ERK1/2 signaling pathway to ameliorate rotenone-induced retinal neurodegeneration

Troxerutin, a natural flavonoid guards against oxidative stress and apoptosis with a high capability of passing through the blood-brain barrier. Our aim was to investigate the role of troxerutin in experimentally induced retinal neurodegeneration by modulating the interferon-gamma (IFNγ)-extracellular signal-regulated kinases 1/2 (ERK1/2)-CCAAT enhancer-binding protein β (C/EBP-β) signaling pathway. Three groups of rats (10 each group) were included. Group I (control group), group II (rotenone treated group): the rats were injected subcutaneously with a single rotenone dosage of 3 mg/kg repeated every 48 hours for 60 days to trigger retinal neurodegeneration. Group III (troxerutin-treated group): rats received troxerutin (150 mg/kg/day) by oral gavage 1 hour before rotenone administration. A real-time polymerase chain reaction technique was applied to measure messenger RNA (mRNA) levels of retinal C/EBP-β. Enzyme-linked immunosorbent assay technique was utilized to assay tumor necrosis factor-α (TNF-α), IFNγ, and ERK1/2 levels. Finally, reactive oxygen species (ROS), as well as carbonylated protein (CP) levels, were assessed spectrophotometrically. Improved retinal neurodegeneration by downregulation of C/EBP-β mRNA gene expression, also caused a significant reduction of TNF-α, IFNγ, ERK1/2 as well as ROS and CP levels compared with the diseased group. These findings could hold promise for the usage of troxerutin as a protective agent against rotenone-induced retinal neurodegeneration.

C/EBPß Isoform Specific Gene Regulation: It's a Lot more Complicated than you Think!

It has been almost 30 years since C/EBPß was discovered. Seminal studies have shown that C/EBPß is a master regulator of mammary gland development and has been shown to control and influence proliferation and differentiation through varying mechanisms. The single-exon C/EBPß mRNA yields at least three different protein isoforms which have diverse, specific, context-dependent, and often non-overlapping roles throughout development and breast cancer progression. These roles are dictated by a number of complex factors including: expression levels of other C/EBP family members and their stoichiometry relative to the isoform in question, binding site affinity, post-translational modifications, co-factor expression, and even hormone levels and lactogenic status. Here we summarize the historical work up to the latest findings in the field on C/EBPß in the mammary gland and in breast cancer. With the current emphasis on improving immunotherapy in breast cancer the role of specific C/EBPß isoforms in regulating specific chemokine and cytokine expression and the immune microenvironment will be of increasing interest.

Overexpression of the C-domain of angiotensin-converting enzyme reduces melanoma growth by stimulating M1 macrophage polarization

Angiotensin-converting enzyme (ACE) can hydrolyze many peptides and plays a central role in controlling blood pressure. Moreover, ACE overexpression in monocytes and macrophages increases resistance of mice to tumor growth. ACE is composed of two independent catalytic domains. Here, to investigate the specific role of each domain in tumor resistance, we overexpressed either WT ACE (Tg-ACE mice) or ACE lacking N- or C-domain catalytic activity (Tg-NKO and Tg-CKO mice) in the myeloid cells of mice. Tg-ACE and Tg-NKO mice exhibited strongly suppressed growth of B16-F10 melanoma because of increased ACE expression in macrophages, whereas Tg-CKO mice resisted melanoma no better than WT animals. The effect of ACE overexpression reverted to that of the WT enzyme with an ACE inhibitor but not with an angiotensin II type 1 (AT1) receptor antagonist. ACE C-domain overexpression in macrophages drove them toward a pronounced M1 phenotype upon tumor stimulation, with increased activation of NF-κB and signal transducer and activator of transcription 1 (STAT1) and decreased STAT3 and STAT6 activation. Tumor necrosis factor α (TNFα) is important for M1 activation, and TNFα blockade reverted Tg-NKO macrophages to a WT phenotype. Increased ACE C-domain expression increased the levels of reactive oxygen species (ROS) and of the transcription factor C/EBPβ in macrophages, important stimuli for TNFα expression, and decreased expression of several M2 markers, including interleukin-4Rα. Natural ACE C-domain-specific substrates are not well-described, and we propose that the peptide(s) responsible for the striking ACE-mediated enhancement of myeloid function are substrates/products of the ACE C-domain.

Constitutive and inducible in vivo protein-DNA interactions at the tumor necrosis factor-alpha promoter in primary human T lymphocytes

Tumor necrosis factor-alpha (TNF-alpha) is a key cytokine of lymphocytes with major regulatory functions in immunomodulation, chronic inflammation, and septic shock. However, only limited information on TNF promoter regulation in vivo in primary lymphocytes is available. To determine and compare protein-DNA interactions at the native TNF locus in primary lymphocytes, we analyzed the human TNF-alpha promoter by ligation-mediated polymerase chain reaction (LM-PCR) techniques. Accordingly, primary CD4+ T lymphocytes from peripheral blood were cultured in the presence of various stimuli and analyzed by LM-PCR. Inducible in vivo protein-DNA interactions at the TNF promoter were detected between -120 and -70 bp of the human TNF promoter relative to the transcriptional start site. This area includes binding sites for transcription factors such as ETS-1, NFAT, ATF-2/c-jun, SP-1/Egr-1, and NF-kappaB. In contrast, no protein-DNA interactions were observed at various binding sites with reported regulatory function in tumor cell lines such as the k2 element, the NFAT site at -160, the AP1 site at -50, and the SP1 site at -65. Additional mutagenesis and transfection studies demonstrated that NF-kappaB and CREB/AP-1 are important regulators of inducible TNF promoter activity in primary human T lymphocytes. These results provide novel insights into the complex regulation of TNF gene transcription in primary T lymphocytes in vivo by constitutive and inducible protein-DNA interactions that appear to be at least partially different compared to previously characterized tumor cell lines.

Tolerogenic bone marrow-derived dendritic cells induce neuroprotective regulatory T cells in a model of Parkinson's disease

BACKGROUND

Administration of granulocyte-macrophage colony-stimulating factor (GM-CSF) increases regulatory T cell (Treg) number and function with control of neuroinflammation and neuronal protection in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of Parkinson's disease (PD). Recently, we demonstrated in an early phase 1 clinical trial that GM-CSF also improves motor skills in PD patients. However, the mechanisms of Treg induction and its effects on neuroprotective responses remain unknown. As GM-CSF induces tolerogenic dendritic cells (DCs) that in turn convert conventional T cells to Tregs, the pathways for DC induction of Tregs were assessed.

METHODS

Following differentiation, bone marrow-derived dendritic cells (BMDCs) were cultured in media or GM-CSF with or without post-culture stimulation with nitrated α-synuclein (N-α-Syn). Expression of cell surface co-stimulatory molecules and proinflammatory cytokines, and induction of Tregs were evaluated. The neuroprotective capacity of tolerogenic BMDCs was assessed by adoptive transfer to MPTP-intoxicated mice. The extent of neuroinflammation and numbers of surviving dopaminergic neurons were assessed in relation to Treg numbers.

RESULTS

Co-culture of differentiated BMDCs with conventional T cells led to Treg induction. Stimulation of BMDCs with N-α-Syn increased expression of co-stimulatory molecules and proinflammatory cytokines, with modest increases in Treg numbers. In contrast, continued culture of BMDCs with GM-CSF modestly altered expression of co-stimulatory molecules and proinflammatory cytokines and chemokines, but decreased Treg induction. Continued culture in GM-CSF and combined stimulation with N-α-Syn reduced Treg induction to the lowest levels. Adoptive transfer of tolerogenic BMDCs to MPTP-intoxicated mice increased splenic Tregs, attenuated neuroinflammatory responses, and protected nigrostriatal dopaminergic neurons.

CONCLUSIONS

GM-CSF acts broadly to differentiate DCs and affect immune transformation from effector to regulatory immune responses. DCs skew such immune responses by increasing Treg numbers and activities that serve to attenuate proinflammatory responses and augment neuroprotection.

CCAAT/Enhancer binding protein β silencing mitigates glial activation and neurodegeneration in a rat model of Parkinson's disease

The CCAAT/Enhancer binding protein β (C/EBPβ) is a transcription factor involved in numerous physiological as well as pathological conditions in the brain. However, little is known regarding its possible role in neurodegenerative disorders. We have previously shown that C/EBPβ regulates the expression of genes involved in inflammatory processes and brain injury. Here, we have analyzed the effects of C/EBPβ interference in dopaminergic cell death and glial activation in the 6-hydroxydopamine model of Parkinson's disease. Our results showed that lentivirus-mediated C/EBPβ deprivation conferred marked in vitro and in vivo neuroprotection of dopaminergic cells concomitant with a significant attenuation of the level of the inflammatory response and glial activation. Additionally, C/EBPβ interference diminished the induction of α-synuclein in the substantia nigra pars compacta of animals injected with 6-hydroxydopamine. Taking together, these results reveal an essential function for C/EBPβ in the pathways leading to inflammatory-mediated brain damage and suggest novel roles for C/EBPβ in neurodegenerative diseases, specifically in Parkinson's disease, opening the door for new therapeutic interventions.

MCPIP1, alias Regnase-1 binds and cleaves mRNA of C/EBPβ

CCAAT/enhancer-binding protein beta (C/EBPβ) is a transcription factor controlling a broad range of genes essential for homeostasis, including genes related to immune functions, inflammation, metabolism and growth. Monocyte chemoattractant protein-1-induced protein 1 (MCPIP1) also called as Regnase-1 is an RNase and has been shown to decrease the stability of short-lived transcripts coding for inflammation-related proteins, including IL-1β, IL-6, IL-2, IL-8, IL-12b, IER-3, c-Rel. We found previously that the half-life of the C/EBPβ transcript is regulated by MCPIP. To understand the mechanism driving down-regulation of C/EBPβ by MCPIP1, we applied an in vitro cleavage assay, followed by a luciferase-reporter assay and RNA immunoprecipitation (RIP). We demonstrated that MCPIP1 recognizes regions of the 3’UTR of C/EBPβ mRNA and promotes its decay by introducing direct endonucleolytic cleavage.

Zinc Modulates Endotoxin-Induced Human Macrophage Inflammation through ZIP8 Induction and C/EBPβ Inhibition

Two vital functions of the innate immune system are to initiate inflammation and redistribute micronutrients in favor of the host. Zinc is an essential micronutrient used in host defense. The zinc importer ZIP8 is uniquely induced through stimulation of the NF-κB pathway by LPS in monocytes and functions to regulate inflammation in a zinc-dependent manner. Herein we determined the impact of zinc metabolism following LPS-induced inflammation in human macrophages. We observed that ZIP8 is constitutively expressed in resting macrophages and strikingly elevated following LPS exposure, a response that is unique compared to the 13 other known zinc import proteins. During LPS exposure, extracellular zinc concentrations within the physiological range markedly reduced IL-10 mRNA expression and protein release but increased mRNA expression of TNFα, IL-8, and IL-6. ZIP8 knockdown inhibited LPS-driven cellular accumulation of zinc and prevented zinc-dependent reduction of IL-10 release. Further, zinc supplementation reduced nuclear localization and activity of C/EBPβ, a transcription factor known to drive IL-10 expression. These studies demonstrate for the first time that zinc regulates LPS-mediated immune activation of human macrophages in a ZIP8-dependent manner, reducing IL-10. Based on these findings we predict that macrophage zinc metabolism is important in host defense against pathogens.

Complement component 3 (C3) expression in the hippocampus after excitotoxic injury: role of C/EBPβ

Background

The CCAAT/enhancer-binding protein β (C/EBPβ) is a transcription factor implicated in the control of proliferation, differentiation, and inflammatory processes mainly in adipose tissue and liver; although more recent results have revealed an important role for this transcription factor in the brain. Previous studies from our laboratory indicated that CCAAT/enhancer-binding protein β is implicated in inflammatory process and brain injury, since mice lacking this gene were less susceptible to kainic acid-induced injury. More recently, we have shown that the complement component 3 gene (C3) is a downstream target of CCAAT/enhancer-binding protein β and it could be a mediator of the proinflammatory effects of this transcription factor in neural cells.

Methods

Adult male Wistar rats (8–12 weeks old) were used throughout the study. C/EBPβ^+/+ and C/EBPβ^–/– mice were generated from heterozygous breeding pairs. Animals were injected or not with kainic acid, brains removed, and brain slices containing the hippocampus analyzed for the expression of both CCAAT/enhancer-binding protein β and C3.

Results

In the present work, we have further extended these studies and show that CCAAT/enhancer-binding protein β and C3 co-express in the CA1 and CA3 regions of the hippocampus after an excitotoxic injury. Studies using CCAAT/enhancer-binding protein β knockout mice demonstrate a marked reduction in C3 expression after kainic acid injection in these animals, suggesting that indeed this protein is regulated by C/EBPβ in the hippocampus in vivo.

Conclusions

Altogether these results suggest that CCAAT/enhancer-binding protein β could regulate brain disorders, in which excitotoxic and inflammatory processes are involved, at least in part through the direct regulation of C3.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0742-0) contains supplementary material, which is available to authorized users.

Poligalen, a new coumarin from Polygala boliviensis, reduces the release of TNF and IL-6 independent of NF-kB downregulation

An unusually substituted coumarin, named poligalen, was isolated from a chloroform extract of the aerial parts of Polygala boliviensis. This coumarin was identified by one- and two-dimensional NMR techniques, and the structure of the compound was confirmed by X-ray diffraction. Poligalen exhibits immunomodulatory effects, reducing the levels of IL-6 and TNF after LPS stimulation in peritoneal macrophages. However, poligalen potentiates NF-kB activation.

Mapping Variation in Cellular and Transcriptional Response to 1,25-Dihydroxyvitamin D3 in Peripheral Blood Mononuclear Cells

The active hormonal form of vitamin D, 1,25-dihydroxyvitamin D (1,25D) is an important modulator of the immune system, inhibiting cellular proliferation and regulating transcription of immune response genes. In order to characterize the genetic basis of variation in the immunomodulatory effects of 1,25D, we mapped quantitative traits of 1,25D response at both the cellular and the transcriptional level. We carried out a genome-wide association scan of percent inhibition of cell proliferation (Imax) induced by 1,25D treatment of peripheral blood mononuclear cells from 88 healthy African-American individuals. Two genome-wide significant variants were identified: rs1893662 in a gene desert on chromosome 18 (p = 2.32 x 10-8) and rs6451692 on chromosome 5 (p = 2.55 x 10-8), which may influence the anti-proliferative activity of 1,25D by regulating the expression of nearby genes such as the chemokine gene, CCL28, and the translation initiation gene, PAIP1. We also identified 8 expression quantitative trait loci at a FDR<0.10 for transcriptional response to 1,25D treatment, which include the transcriptional regulator ets variant 3-like (ETV3L) and EH-domain containing 4 (EHD4). In addition, we identified response eQTLs in vitamin D receptor binding sites near genes differentially expressed in response to 1,25D, such as FERM Domain Containing 6 (FRMD6), which plays a critical role in regulating both cell proliferation and apoptosis. Combining information from the GWAS of Imax and the response eQTL mapping enabled identification of putative Imax-associated candidate genes such as PAIP1 and the transcriptional repressor gene ZNF649. Overall, the variants identified in this study are strong candidates for immune traits and diseases linked to vitamin D, such as multiple sclerosis.

C/EBPβ is a transcriptional key regulator of IL-36α in murine macrophages

Interleukin (IL)-36α - one of the novel members of the IL-1 family of cytokines - is a potent regulator of dendritic and T cells and plays an important role in inflammatory processes like experimental skin inflammation in mice and in mouse models for human psoriasis. Here, we demonstrate that C/EBPβ, a transcription factor required for the selective expression of inflammatory genes, is a key activator of the Il36A gene in murine macrophages. RNAi-mediated suppression of C/EBPβ expression in macrophages (C/EBPβ(low) cells) significantly impaired Il36A gene induction following challenge with LPS. Despite the presence of five predicted C/EBP binding sites, luciferase reporter assays demonstrated that C/EBPβ confers responsiveness to LPS primarily through a half-CRE•C/EBP element in the proximal Il36A promoter. Electrophoretic mobility shift assays showed that C/EBPβ but not CREB proteins interact with this critical half-CRE•C/EBP element. In addition, overexpression of C/EBPβ in C/EBPβ(low) cells enhanced the expression of Il36A whereas CREB-1 had no effect. Finally, chromatin immunoprecipitation confirmed that C/EBPβ but neither CREB-1, ATF-2 nor ATF4 is directly recruited to the proximal promoter region of the Il36A gene. Together, these findings demonstrate an essential role of C/EBPβ in the regulation of the Il36A gene via the proximal half-CRE•C/EBP element in response to inflammatory stimuli.

Betulin protects mice from bacterial pneumonia and acute lung injury

Betulin, a naturally occurring triterpene, has shown anti-HIV activity, but details on the anti-inflammatory activity are scanty. In this study, we sought to investigate the effect of Betulin on LPS-induced activation of cell lines with relevance for lung inflammation in vitro and on lung inflammation elicited by either LPS or viable Escherichia coli (E. coli) in vivo. In vitro, Betulin inhibited LPS-induced tumor necrosis factor α (TNF-α) and (interleukin) IL-6 levels and up-regulated the level of IL-10. Also Betulin suppressed the phosphorylation of nuclear factor-κB (NF-κB) p65 protein in LPS-stimulated RAW 264.7 cells. In vivo, Betulin alleviated LPS-induced acute lung injury. Treatment with Betulin diminished pro-inflammatory cytokines, myeloperoxidase activity and bacterial loads in lung tissue during gram-negative pneumonia. Our findings demonstrated that Betulin inhibits pro-inflammatory responses induced by the gram-negative stimuli LPS and E. coli, suggesting that Betulin may represent a novel strategy for the treatment of lung inflammation.

CCAAT-enhancer binding protein-β expression and elevation in Alzheimer's disease and microglial cell cultures

CCAAT-enhancer binding proteins are transcription factors that help to regulate a wide range of inflammatory mediators, as well as several key elements of energy metabolism. Because C/EBPs are expressed by rodent astrocytes and microglia, and because they are induced by pro-inflammatory cytokines that are chronically upregulated in the Alzheimer’s disease (AD) cortex, we have investigated whether C/EBPs are expressed and upregulated in the AD cortex. Here, we demonstrate for the first time that C/EBPβ can be detected by Western blots in AD and nondemented elderly (ND) cortex, and that it is significantly increased in AD cortical samples. In situ, C/EBPβ localizes immunohistochemically to microglia. In microglia cultured from rapid autopsies of elderly patient’s brains and in the BV-2 murine microglia cell line, we have shown that C/EBPβ can be upregulated by C/EBP-inducing cytokines or lipopolysaccharide and exhibits nuclear translocation possibly indicating functional activity. Given the known co-regulatory role of C/EBPs in pivotal inflammatory mechanisms, many of which are present in AD, we propose that upregulation of C/EBPs in the AD brain could be an important orchestrator of pathogenic changes.

Curcumin: an orally bioavailable blocker of TNF and other pro-inflammatory biomarkers

TNFs are major mediators of inflammation and inflammation-related diseases, hence, the United States Food and Drug Administration (FDA) has approved the use of blockers of the cytokine, TNF-α, for the treatment of osteoarthritis, inflammatory bowel disease, psoriasis and ankylosis. These drugs include the chimeric TNF antibody (infliximab), humanized TNF-α antibody (Humira) and soluble TNF receptor-II (Enbrel) and are associated with a total cumulative market value of more than $20 billion a year. As well as being expensive ($15 000-20 000 per person per year), these drugs have to be injected and have enough adverse effects to be given a black label warning by the FDA. In the current report, we describe an alternative, curcumin (diferuloylmethane), a component of turmeric (Curcuma longa) that is very inexpensive, orally bioavailable and highly safe in humans, yet can block TNF-α action and production in in vitro models, in animal models and in humans. In addition, we provide evidence for curcumin's activities against all of the diseases for which TNF blockers are currently being used. Mechanisms by which curcumin inhibits the production and the cell signalling pathways activated by this cytokine are also discussed. With health-care costs and safety being major issues today, this golden spice may help provide the solution.

LINKED ARTICLES

This article is part of a themed section on Emerging Therapeutic Aspects in Oncology. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.169.issue-8.

Mechanisms of chronic state of inflammation as mediators that link obese adipose tissue and metabolic syndrome

The metabolic syndrome is a cluster of cardiometabolic alterations that include the presence of arterial hypertension, insulin resistance, dyslipidemia, and abdominal obesity. Obesity is associated with a chronic inflammatory response, characterized by abnormal adipokine production, and the activation of proinflammatory signalling pathways resulting in the induction of several biological markers of inflammation. Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Adiponectin can either act directly on macrophages to shift polarization and/or prime human monocytes into alternative M2-macrophages with anti-inflammatory properties. Meanwhile, the chronic inflammation in adipose tissue is regulated by a series of transcription factors, mainly PPARs and C/EBPs, that in conjunction regulate the expression of hundreds of proteins that participate in the metabolism and storage of lipids and, as such, the secretion by adipocytes. Therefore, the management of the metabolic syndrome requires the development of new therapeutic strategies aimed to alter the main genetic pathways involved in the regulation of adipose tissue metabolism.

Mechanisms of chronic state of inflammation as mediators that link obese adipose tissue and metabolic syndrome

The metabolic syndrome is a cluster of cardiometabolic alterations that include the presence of arterial hypertension, insulin resistance, dyslipidemia, and abdominal obesity. Obesity is associated with a chronic inflammatory response, characterized by abnormal adipokine production, and the activation of proinflammatory signalling pathways resulting in the induction of several biological markers of inflammation. Macrophage and lymphocyte infiltration in adipose tissue may contribute to the pathogenesis of obesity-mediated metabolic disorders. Adiponectin can either act directly on macrophages to shift polarization and/or prime human monocytes into alternative M2-macrophages with anti-inflammatory properties. Meanwhile, the chronic inflammation in adipose tissue is regulated by a series of transcription factors, mainly PPARs and C/EBPs, that in conjunction regulate the expression of hundreds of proteins that participate in the metabolism and storage of lipids and, as such, the secretion by adipocytes. Therefore, the management of the metabolic syndrome requires the development of new therapeutic strategies aimed to alter the main genetic pathways involved in the regulation of adipose tissue metabolism.

High levels of tumor necrosis factor-α downregulate antimicrobial iron transport protein, Nramp1, in chronic hemodialysis patients: a key factor for infection risk

BACKGROUND/AIMS

The susceptibility of patients on maintenance hemodialysis (MHD) to infections is a major cause of mortality and morbidity. Natural resistance-associated macrophage protein 1 (Nramp1) regulates intracellular pathogen proliferation, and its mRNA expression is highest in polymorphonuclear leukocytes (PMNLs). The purpose of this study was to determine the level of Nramp1 in PMNLs from MHD patients and the factors affecting its expression.

METHODS

Twenty MHD patients and 24 healthy volunteers (controls) were recruited. Relative quantitative PCR was used to measure Nramp1 mRNA, and protein levels were semiquantified by means of real-time PCR and Western blot analysis or immunohistochemistry. The effect of tumor necrosis factor-α (TNF-α) or interleukin-6 (IL-6) on Nramp1 expression in PMNLs from controls was also examined.

RESULTS

Nramp1 mRNA and protein levels were substantially lower in PMNLs from MHD than control subjects. Serum TNF-α levels were significantly higher in the MHD group and were inversely correlated with Nramp1 mRNA levels. The addition of TNF-α to PMNLs from control subjects decreased mRNA and protein levels of Nramp1. IL-6 did not alter Nramp1 mRNA or protein expression.

CONCLUSION

We found that Nramp1 was downregulated in the PMNLs of MHD patients, which constitute the first defense barrier against bacterial challenges. High levels of TNF-α may be associated with the downregulation of Nramp1. Our findings indicate that the susceptibility to infection observed in MHD patients could be partly due to the impairment of the intracellular handling of iron and the donation of more iron to the bacteria.

C5a-regulated CCAAT/enhancer-binding proteins β and δ are essential in Fcγ receptor-mediated inflammatory cytokine and chemokine production in macrophages

CCAAT/enhancer-binding protein β (C/EBPβ) and C/EBPδ are known to participate in the regulation of many genes associated with inflammation. However, little is known about the activation and function of C/EBPβ and -δ in inflammatory responses elicited by Fcγ receptor (FcγR) activation. Here we show that C/EBPβ and -δ activation are induced in IgG immune complex (IC)-treated macrophages. The increased expression of C/EBPβ and -δ occurred at both mRNA and protein levels. Furthermore, induction of C/EBPβ and -δ was mediated, to a large extent, by activating FcγRs. Using siRNA-mediated knockdown as well as macrophages deficient for C/EBPβ and/or -δ, we demonstrate that C/EBPβ and -δ play a critical role in the production of TNF-α, MIP-2, and MIP-1α in IgG IC-stimulated macrophages. Moreover, both ERK1/2 and p38 MAPK are involved in C/EBP induction and TNF-α, MIP-2, and MIP-1α production induced by IgG IC. We provide the evidence that C5a regulates IgG IC-induced inflammatory responses by enhancing ERK1/2 and p38 MAPK activities as well as C/EBPβ and -δ activities. Collectively, these data suggest that C/EBPβ and -δ are key regulators for FcγR-mediated induction of cytokines and chemokines in macrophages. Furthermore, C/EBPs may play an important regulatory role in IC-associated inflammatory responses.

Tumor necrosis factor-alpha and the roles it plays in homeostatic and degenerative processes within the central nervous system

Tumor Necrosis Factor-alpha (TNF-α) is a prototypic pro-inflammatory cytokine involved in the innate immune response. TNF-α ligation and downstream signaling with one of its cognate receptors, TNF-RI or TNF-RII, modulates fundamental processes in the brain including synapse formation and regulation, neurogenesis, regeneration, and general maintenance of the central nervous system (CNS). During states of chronic neuroinflammation, extensive experimental evidence implicates TNF-α as a key mediator in disease progression, gliosis, demyelination, inflammation, blood-brain-barrier deterioration, and cell death. This review explores the complex roles of TNF-α in the CNS under normal physiologic conditions and during neurodegeneration. We focus our discussion on Multiple Sclerosis, Parkinson's disease, and Alzheimer's disease, relaying the outcomes of preclinical and clinical testing of TNF-α directed therapeutic strategies, and arguing that despite the wealth of functions attributed to this central cytokine, surprisingly little is known about the cell type- and stage-specific roles of TNF-α in these debilitating disorders.

Molecular mechanisms by which saturated fatty acids modulate TNF-α expression in mouse macrophage lineage

Many macrophage functions are modulated by fatty acids (FAs), including cytokine release, such as tumor necrosis factor-α (TNF-α). TNF-α is of great interest due to its role in the inflammation process observed in several diseases such as rheumatoid arthritis, atherosclerosis, and obesity. However, the mechanisms by which FA effects occur have not been completely elucidated yet. In this study, we used a mouse monocyte lineage (J774 cells) to evaluate the effect of 50 and 100 μM of saturated (palmitic and stearic acids), monounsaturated (oleic acid) and polyunsaturated (linoleic acid) FAs on TNF-α production. Alterations in gene expression, poly(A) tail length and activation of transcription factors were evaluated. Oleic and linoleic acids, usually known as neutral or pro-inflammatory FA, inhibited LPS-induced TNF-α secretion by the cells. Saturated FAs were potent inducers of TNF-α expression and secretion under basal and inflammatory conditions (in the presence of LPS). Although the effect of the saturated FA was similar, the mechanism involved in each case seem to be distinct, as palmitic acid increased EGR-1 and CREB binding activity and stearic acid increased mRNA poly(A) tail. These results may contribute to the understanding of the molecular mechanisms by which saturated FAs modulate the inflammatory response and may lead to design of associations of dietary and pharmacological strategies to counteract the pathological effects of TNF-α.

Neutrophils activate alveolar macrophages by producing caspase-6-mediated cleavage of IL-1 receptor-associated kinase-M

Alveolar macrophages (AMs) are exposed to respirable microbial particles. Similar to phagocytes in the gastrointestinal tract, AMs can suppress inflammation after exposure to nonpathogenic organisms. IL-1R-associated kinase-M (IRAK-M) is one inhibitor of innate immunity, normally suppressing pulmonary inflammation. During pneumonia, polymorphonuclear neutrophils (PMNs) are recruited by chemotactic factors released by AMs to produce an intense inflammation. We report that intact IRAK-M is strongly expressed in resting human AMs but is cleaved in patients with pneumonia via PMN-mediated induction of caspase-6 (CASP-6) activity. PMN contact is necessary and PMN membranes are sufficient for CASP-6 induction in macrophages. PMNs fail to induce TNF-α fully in macrophages expressing CASP-6 cleavage-resistant IRAK-M. Without CASP-6 expression, PMN stimulation fails to cleave IRAK-M, degrade IκBα, or induce TNF-α. CASP-6(-/-) mice subjected to cecal ligation and puncture have impaired TNF-α production in the lung and decreased mortality. LPS did not induce or require CASP-6 activity demonstrating that TLR2/4 signaling is independent from the CASP-6 regulated pathway. These data define a central role for CASP-6 in PMN-driven macrophage activation and identify IRAK-M as an important target for CASP-6. PMNs de-repress AMs via CASP-6-mediated IRAK-M cleavage. This regulatory system will blunt lung inflammation unless PMNs infiltrate the alveolar spaces.

In vivo deficiency of both C/EBPβ and C/EBPε results in highly defective myeloid differentiation and lack of cytokine response

The CCAAT/enhancer binding proteins (C/EBPs) are transcription factors involved in hematopoietic cell development and induction of several inflammatory mediators. Here, we generated C/EBPβ and C/EBPε double-knockout (bbee) mice and compared their phenotypes to those of single deficient (bbEE and BBee) and wild-type (BBEE) mice. The bbee mice were highly susceptible to fatal infections and died within 2-3 months. Morphologically, their neutrophils were blocked at the myelocytes/metamyelocytes stage, and clonogenic assays of bone marrow cells indicated a significant decrease in the number of myeloid colonies of the bbee mice. In addition, the proportion of hematopoietic progenitor cells [Lin(-)Sca1(+)c-Kit(+)] in the bone marrow of the bbee mice was significantly increased, reflecting the defective differentiation of the myeloid compartment. Furthermore, microarray expression analysis of LPS- and IFNγ-activated bone marrow-derived macrophages from bbee compared to single knockout mice revealed decreased expression of essential immune response-related genes and networks, including some direct C/EBP-targets such as Marco and Clec4e. Overall, the phenotype of the bbee mice is distinct from either the bbEE or BBee mice, demonstrating that both transcription factors are crucial for the maturation of neutrophils and macrophages, as well as the innate immune system, and can at least in part compensate for each other in the single knockout mice.

HGF-promoted motility in primary human melanocytes depends on CD44v6 regulated via NF-kappa B, Egr-1, and C/EBP-beta

The regulation of CD44v6, a variant of the CD44 family of glycosylated adhesion molecules, through hepatocyte growth factor (HGF) has implications for motility in primary human melanocytes. We show that exposure of primary human melanocytes to HGF results in an increase of CD44v6 expression. Immunostaining of melanocytic lesions revealed low cytoplasmic positivity of CD44v6 in some nevi but high membranous expression in primary cutaneous melanomas, and cutaneous and lymph node metastases. HGF-dependent CD44v6 regulation in melanocytes is NF-kappaB dependent because BAY 11-7082, an inhibitor of NF-kappaB activation, but not interference with the mitogen-activated protein kinase or phosphatidylinositol 3-kinase cascade, antagonized HGF-induced CD44v6 expression. NF-kappaB-mediated transcriptional regulation of CD44v6 involves the transcription factors Egr-1 and CCAAT enhancer-binding protein-beta (C/EBP-beta). In gel shift assays, the initial binding of p100/p52 NF-kappaB, C/EBP-beta, and Egr-1 to the CD44 promoter experienced reshuffling toward increased affinity of C/EBP-beta after HGF stimulation. A blocking antibody to CD44v6 decreased HGF-induced c-Met phosphorylation as well as enhanced random- and site-directed migration. Our data show that HGF-induced motility in primary human melanocytes depends on c-Met-CD44v6 interaction, and that HGF-enhanced CD44v6 expression is required for motility and transcriptional upregulation of CD44v6, presumably mediated through a complex comprising NF-kappaB/C/EBP-beta and Egr-1.

Transcriptional control of the TNF gene

The cytokine TNF is a critical mediator of immune and inflammatory responses. The TNF gene is an immediate early gene, rapidly transcribed in a variety of cell types following exposure to a broad range of pathogens and signals of inflammation and stress. Regulation of TNF gene expression at the transcriptional level is cell type- and stimulus-specific, involving the recruitment of distinct sets of transcription factors to a compact and modular promoter region. In this review, we describe our current understanding of the mechanisms through which TNF transcription is specifically activated by a variety of extracellular stimuli in multiple cell types, including T cells, B cells, macrophages, mast cells, dendritic cells, and fibroblasts. We discuss the role of nuclear factor of activated T cells and other transcription factors and coactivators in enhanceosome formation, as well as the contradictory evidence for a role for nuclear factor kappaB as a classical activator of the TNF gene. We describe the impact of evolutionarily conserved cis-regulatory DNA motifs in the TNF locus upon TNF gene transcription, in contrast to the neutral effect of single nucleotide polymorphisms. We also assess the regulatory role of chromatin organization, epigenetic modifications, and long-range chromosomal interactions at the TNF locus.

Exogenous Nef is an inhibitor of Mycobacterium tuberculosis-induced tumor necrosis factor-alpha production and macrophage apoptosis

Human immunodeficiency virus-1 (HIV-1) impairs tumor necrosis factor-alpha (TNF-alpha)-mediated macrophage apoptosis induced by Mycobacterium tuberculosis (Mtb). HIV Nef protein plays an important role in the pathogenesis of AIDS. We have tested the hypothesis that exogenous Nef is a factor that inhibits TNF-alpha production/apoptosis in macrophages infected with Mtb. We demonstrate that Mtb and Nef individually trigger TNF-alpha production in macrophages. However, TNF-alpha production is dampened when the two are present simultaneously, probably through cross-regulation of the individual signaling pathways leading to activation of the TNF-alpha promoter. Mtb-induced TNF-alpha production is abrogated upon mutation of the Ets, Egr, Sp1, CRE, or AP1 binding sites on the TNF-alpha promoter, whereas Nef-mediated promoter activation depends only on the CRE and AP1 binding sites, pointing to differences in the mechanisms of activation of the promoter. Mtb-dependent promoter activation depends on the mitogen-activated kinase (MAPK) kinase kinase ASK1 and on MEK/ERK signaling. Nef inhibits ASK1/p38 MAPK-dependent Mtb-induced TNF-alpha production probably by inhibiting binding of ATF2 to the TNF-alpha promoter. It also inhibits MEK/ERK-dependent Mtb-induced binding of FosB to the promoter. Nef-driven TNF-alpha production occurs in an ASK1-independent, Rac1/PAK1/p38 MAPK-dependent, and MEK/ERK-independent manner. The signaling pathways used by Mtb and Nef to trigger TNF-alpha production are therefore distinctly different. In addition to attenuating Mtb-dependent TNF-alpha promoter activation, Nef also reduces Mtb-dependent TNF-alpha mRNA stability probably through its ability to inhibit ASK1/p38 MAPK signaling. These results provide new insight into how HIV Nef probably exacerbates tuberculosis infection by virtue of its ability to dampen Mtb-induced TNF-alpha production.

Regulation of HIV-1 transcription in cells of the monocyte-macrophage lineage

Human immunodeficiency virus type 1 (HIV-1) has been shown to replicate productively in cells of the monocyte-macrophage lineage, although replication occurs to a lesser extent than in infected T cells. As cells of the monocyte-macrophage lineage become differentiated and activated and subsequently travel to a variety of end organs, they become a source of infectious virus and secreted viral proteins and cellular products that likely initiate pathological consequences in a number of organ systems. During this process, alterations in a number of signaling pathways, including the level and functional properties of many cellular transcription factors, alter the course of HIV-1 long terminal repeat (LTR)-directed gene expression. This process ultimately results in events that contribute to the pathogenesis of HIV-1 infection. First, increased transcription leads to the upregulation of infectious virus production, and the increased production of viral proteins (gp120, Tat, Nef, and Vpr), which have additional activities as extracellular proteins. Increased viral production and the presence of toxic proteins lead to enhanced deregulation of cellular functions increasing the production of toxic cellular proteins and metabolites and the resulting organ-specific pathologic consequences such as neuroAIDS. This article reviews the structural and functional features of the cis-acting elements upstream and downstream of the transcriptional start site in the retroviral LTR. It also includes a discussion of the regulation of the retroviral LTR in the monocyte-macrophage lineage during virus infection of the bone marrow, the peripheral blood, the lymphoid tissues, and end organs such as the brain. The impact of genetic variation on LTR-directed transcription during the course of retrovirus disease is also reviewed.

C/EBPbeta regulates transcription factors critical for proliferation and survival of multiple myeloma cells

CCAAT/enhancer-binding protein beta (C/EBPbeta), also known as nuclear factor-interleukin-6 (NF-IL6), is a transcription factor that plays an important role in the regulation of growth and differentiation of myeloid and lymphoid cells. Mice deficient in C/EBPbeta show impaired generation of B lymphocytes. We show that C/EBPbeta regulates transcription factors critical for proliferation and survival in multiple myeloma. Multiple myeloma cell lines and primary multiple myeloma cells strongly expressed C/EBPbeta, whereas normal B cells and plasma cells had little or no detectable levels of C/EBPbeta. Silencing of C/EBPbeta led to down-regulation of transcription factors such as IRF4, XBP1, and BLIMP1 accompanied by a strong inhibition of proliferation. Further, silencing of C/EBPbeta led to a complete down-regulation of antiapoptotic B-cell lymphoma 2 (BCL2) expression. In chromatin immunoprecipitation assays, C/EBPbeta directly bound to the promoter region of IRF4, BLIMP1, and BCL2. Our data indicate that C/EBPbeta is involved in the regulatory network of transcription factors that are critical for plasma cell differentiation and survival. Targeting C/EBPbeta may provide a novel therapeutic strategy in the treatment of multiple myeloma.

Differential role for c-Rel and C/EBPbeta/delta in TLR-mediated induction of proinflammatory cytokines

TLR stimulation triggers a signaling pathway via MyD88 and IL-1R-associated kinase 4 that is essential for proinflammatory cytokine induction. Although NF-kappaB has been shown to be one of the key transcriptional regulators of these cytokines, evidence suggests that other factors may also be important. In this study, we showed that MyD88-deficient macrophages have defective c-Rel activation, which has been linked to IL-12p40 induction, but not IL-6 or TNF-alpha. We also investigated other transcription factors and showed that C/EBPbeta and C/EBPdelta expression was limited in MyD88- or IL-1R-associated kinase 4-deficient macrophages treated with LPS. Importantly, the absence of both C/EBPbeta and C/EBPdelta resulted in the impaired induction of proinflammatory cytokines stimulated by several TLR ligands. Our results identify c-Rel and C/EBPbeta/delta as important transcription factors in a MyD88-dependent pathway that regulate the induction of proinflammatory cytokines.

CCAAT/enhancer binding proteins alpha and beta regulate the tumor necrosis factor receptor 1 gene promoter

CCAAT/enhancer binding protein (C/EBP) transcription factors play essential roles in regulating an array of cellular processes, including differentiation, energy metabolism, and inflammation. In this report we demonstrate that both C/EBPalpha and C/EBPbeta activate the promoter driving transcription of the tumor necrosis factor receptor 1 (TNFR1). TNFR1 is the major receptor for tumor necrosis factor (TNF), a critical cytokine mediator of the inflammatory response. Although the TNFR1 protein has been shown to be regulated through post-translational modifications, very little is known about the transcriptional regulation of the TNFR1 gene. Here we have identified a specific C/EBP binding site within the TNFR1 promoter, and shown that this site is required for both C/EBPalpha and C/EBPbeta activation of the promoter in reporter gene assays. Furthermore, we show that both C/EBPalpha and C/EBPbeta are bound to the TNFR1 promoter in cells using chromatin immunoprecipitation assays. Finally, we demonstrate that reducing the level of C/EBPalpha and C/EBPbeta expression in cells using siRNA technology leads to decreased expression of the TNFR1 protein. These results suggest that the C/EBPalpha and C/EBPbeta transcription factors enhance expression of the TNFR1 protein in cells. Given that TNF and C/EBPbeta are known to activate each other's expression, C/EBPbeta may greatly amplify the initial TNF signal through a positive auto-regulatory mechanism.

CCAAT/enhancer-binding proteins and the pathogenesis of retrovirus infection

Previous studies indicate that two upstream CCAAT/enhancer-binding protein (C/EBP) sites and C/EBPbeta are required for subtype B HIV-1 gene expression in cells of the monocyte-macrophage lineage. The mechanisms of C/EBP regulation of HIV-1 transcription and replication remain unclear. This review focuses on studies concerning the role of C/EBP factors in HIV-1, human T-cell leukemia virus type 1, and SIV transcription in various cell types and tissues cultured in vitro, animal models and during human infection. The structure and function of the C/EBPbeta gene and the related protein isoforms are discussed along with the transcription factors, coactivators, viral proteins, cytokines and chemokines that affect C/EBP function.

Silencing of Abcd1 and Abcd2 genes sensitizes astrocytes for inflammation: implication for X-adrenoleukodystrophy

X-linked adrenoleukodystrophy is a metabolic disorder arising from a mutation/deletion in the ABCD1 gene, leading to a defect in the peroxisomal adrenoleukodystrophy protein (ALDP), which inhibits the oxidation of very long chain fatty acids (VLCFAs). Thus, these VLCFAs accumulate. In a cerebral form of ALD (cALD), VLCFA accumulation induces neuroinflammation that leads to loss of oligodendrocytes and myelin, which ultimately shortens the lifespan. To establish a relationship between the metabolic disease and inflammatory disease induction, we document that small interfering RNA (siRNA)-mediated silencing of Abcd1 (ALDP) and Abcd2 [adrenoleukodystrophy-related protein (ALDRP)] genes in mice primary astrocyte cultures resulted in accumulation of VLCFA and induction of an inflammatory response characteristic of human cALD. Correction of the metabolic defect using monoenoic FAs in Abcd1/Abcd2-silenced cultured astrocytes decreased inducible nitric oxide synthase and inflammatory cytokine expression, suggesting a link between VLCFA accumulation and inflammation. The inflammatory response was found to be mediated by transcription factors NF-kappaB, AP-1, and C/EBP in Abcd1/Abcd2-silenced mouse primary astrocytes. Although mechanisms of VLCFA-mediated induction of the inflammatory response have been investigated here in vitro, the in vivo mediators remain elusive. Our data represent the first study to suggest a direct link between the accumulation of VLCFA and the induction of inflammatory mediators.

St. John's Wort protein, p27SJ, regulates the MCP-1 promoter

St. John's Wort is commonly known for its antiviral, antidepressant, and cytotoxic properties, but traditionally St. John's Wort has also been used to treat inflammation. In this study, we sought to characterize the mechanisms used by St. John's Wort to treat inflammation by examining the effect of the recently isolated protein from St. John's Wort, p27SJ on the expression of MCP-1. By employing an adenovirus expression vector, we demonstrate that a low concentration of p27SJ upregulates the MCP-1 promoter through the transcription factor C/EBPbeta. In addition, we found that C/EBPbeta-homologous protein (CHOP) or siRNA-C/EBPbeta significantly reduced the ability of p27SJ to activate MCP-1 gene expression. Results from protein-protein interaction studies illustrate the existence of a physical interaction between p27SJ and C/EBPbeta in microglial cells. The use of chromatin immunoprecipitation assay (ChIP) led to the identification of a new cis-element that is responsive to C/EBPbeta within the MCP-1 promoter. Association of C/EBPbeta with MCP-1 DNA was not affected by the presence of p27SJ. The biological activity of MCP-1 produced by cultures of adenovirus-p27SJ transduced cells was increased relative to controls as measured by the transmigration of human Jurkat cells. Thus, we conclude that at high concentration, p27SJ is a potential agent that may be developed as a modulator of MCP-1 leading to the inhibition of the cytokine-mediated inflammatory responses.

Bitter gourd suppresses lipopolysaccharide-induced inflammatory responses

Bitter gourd ( Momordica charantia L.) is a popular tropical vegetable in Asian countries. Previously it was shown that bitter gourd placenta extract suppressed lipopolysaccharide (LPS)-induced TNFalpha production in RAW 264.7 macrophage-like cells. Here it is shown that the butanol-soluble fraction of bitter gourd placenta extract strongly suppresses LPS-induced TNFalpha production in RAW 264.7 cells. Gene expression analysis using a fibrous DNA microarray showed that the bitter gourd butanol fraction suppressed expression of various LPS-induced inflammatory genes, such as those for TNF, IL1alpha, IL1beta, G1p2, and Ccl5. The butanol fraction significantly suppressed NFkappaB DNA binding activity and phosphorylation of p38, JNK, and ERK MAPKs. Components in the active fraction from bitter gourd were identified as 1-alpha-linolenoyl-lysophosphatidylcholine (LPC), 2-alpha-linolenoyl-LPC, 1-lynoleoyl-LPC, and 2-linoleoyl-LPC. Purified 1-alpha-linolenoyl-LPC and 1-linoleoyl-LPC suppressed the LPS-induced TNFalpha production of RAW 264.7 cells at a concentration of 10 microg/mL.

CCAAT/enhancer binding protein beta is a major mediator of inflammation and viral replication in the gastrointestinal tract of simian immunodeficiency virus-infected rhesus macaques

The gastrointestinal tract (GIT) is a major target of infection with human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). Chronic GIT disease and inflammation are common sequelae to HIV/SIV infection. Nonetheless, the molecular mechanisms that cause and maintain GIT dysfunction remain unclear. We investigated the contribution of CCAAT/enhancer-binding protein beta (C/EBPbeta) to GIT disease and viral replication in jejunum and colon collected at necropsy from 12 SIV-infected (group 1), or 10 uninfected macaques with chronic diarrhea (group 2), and 9 uninfected control macaques (group 3). All group 1 and 2 macaques had chronic diarrhea, wasting, and colitis, but group 1 animals had more severe lesions in the jejunum. C/EBPbeta gene expression increased significantly in colon of groups 1 and 2 and in jejunum of only group 1 macaques compared with controls. In group 1 animals, CEBPbeta expression was localized predominantly to macrophages and occasionally lymphocytes. Chromatin immunoprecipitation assays confirmed the binding of C/EBPbeta and p65 to the SIV long terminal repeat region in colonic lamina propria cells, suggesting a mechanistic link between inflammation and activation of viral replication in vivo. This is the first in vivo study describing the transcriptional changes and immunophenotypic localization of C/EBPbeta in the GIT of SIV-infected macaques. More importantly, these data provide a molecular mechanism for persistent inflammation and immune activation leading to increased SIV burden and GIT pathology in SIV-infected macaques and perhaps HIV-infected individuals.