Synergism between protein-kinase C and cAMP-dependent pathways in the expression of the interleukin-1 beta gene is mediated via the activator-protein-1 (AP-1) enhancer activity

Transcriptional Regulation of Inflammasomes

Inflammasomes are multimolecular complexes with potent inflammatory activity. As such, their activity is tightly regulated at the transcriptional and post-transcriptional levels. In this review, we present the transcriptional regulation of inflammasome genes from sensors (e.g., NLRP3) to substrates (e.g., IL-1β). Lineage-determining transcription factors shape inflammasome responses in different cell types with profound consequences on the responsiveness to inflammasome-activating stimuli. Pro-inflammatory signals (sterile or microbial) have a key transcriptional impact on inflammasome genes, which is largely mediated by NF-κB and that translates into higher antimicrobial immune responses. Furthermore, diverse intrinsic (e.g., circadian clock, metabolites) or extrinsic (e.g., xenobiotics) signals are integrated by signal-dependent transcription factors and chromatin structure changes to modulate transcriptionally inflammasome responses. Finally, anti-inflammatory signals (e.g., IL-10) counterbalance inflammasome genes induction to limit deleterious inflammation. Transcriptional regulations thus appear as the first line of inflammasome regulation to raise the defense level in front of stress and infections but also to limit excessive or chronic inflammation.

Isoprenylcysteine carboxyl methyltransferase inhibitors exerts anti-inflammatory activity

Isoprenylcysteine carboxylmethyltransferase (ICMT) has been reported to regulate the inflammatory response through the Ras/MAPK/AP-1 pathway. Nevertheless, the potential of ICMT inhibitors as therapeutic agents against inflammatory diseases has not been examined. Therefore, in this study, we investigated the anti-inflammatory properties of two ICMT inhibitors, cysmethynil (CyM) and 3-methoxy-N-[2-2,2,6,6-tetramethyl-4-phenyltetrahydropyran-4-yl)ethyl]aniline (MTPA), using in vitro analyses and in vivo analyses (lipopolysaccharide (LPS)/D-GalN-triggered hepatitis and DSS-induced colitis mouse models). CyM and MTPA inhibited the production of nitric oxide (NO) and prostaglandin E (PGE)₂ and the expression of cyclooxygenase (COX)-2, tumor necrosis factor (TNF)-α and interleukin (IL)-1β in LPS-induced RAW264.7 cells and peritoneal macrophages without cytotoxicity. CyM also reduced AP-1-mediated luciferase activity in LPS-stimulated RAW264.7 cells and MyD88- and TRIF-expressing HEK293 cells. In addition, CyM and MTPA suppressed the translocation of Ras to the cell membrane and ER as well as phosphorylation of Ras-dependent AP-1 signaling molecules including Raf, MEK1/2, ERK p38, and JNK. Consistent with these results, CyM diminished the expression of inflammatory genes (COX-2, TNF-α, IL-1β, and IL-6), AP-1-Luc activity, and phosphorylation of Ras-mediated signaling enzymes in Ras-overexpressing HEK 293 cells. Moreover, CyM and MTPA ameliorated symptoms of hepatitis and colitis in mice and restrained the ICMT/Ras-dependent AP-1 pathway in inflammatory lesions of the mouse model systems. Taken together, our results indicate that CyM and MTPA alleviate the LPS-induced ICMT/Ras/AP-1 signaling pathway, thereby inhibiting the inflammatory response as promising anti-inflammatory drugs.

JAK inhibitors impair GM-CSF-mediated signaling in innate immune cells

Background

Innate immune cells play a crucial role in the pathophysiology of rheumatoid arthritis (RA) via release of cytokines. Small-molecule inhibitors of Janus kinases (JAKi) are clinically efficacious in patients with RA. However, the isoform-specific action of each JAKi is difficult to assess, since JAKs form heterodimeric complexes with cytokine receptors. We assessed the effects of several JAKi on GM-CSF-primed human innate immune cells.

Results

Treatment with JAKi (tofacitinib, baricitinib, upadacitinib) prevented GM-CSF-induced JAK2/STAT5 phosphorylation at higher concentrations (400 nM) in THP-1 cells. Whereas compared with baricitinib or upadacitinib, the inhibitory effects of tofacitinib on the GM-CSF-induced JAK2/STAT5 phosphorylation were weak at lower concentrations (≤ 100 nM). All JAKi inhibited GM-CSF-induced IL-1β production by human neutrophils. However, the inhibitory effects of baricitinib on IL-1β production were larger compared to those of tofacitinib or upadacitinib at lower concentrations (≤ 100 nM). Similarly, all JAKi inhibited GM-CSF-induced caspase-1(p20) production by human neutrophils.

Conclusion

We conclude that incubation with JAKi prevents GM-CSF-mediated JAK2/STAT5 activation in human innate immune cells. Although baricitinib and upadacitinib almost completely blocked GM-CSF-mediated JAK2/STAT5 signaling, the inhibitory effects of tofacitinib were weaker at lower concentrations suggesting that variation exists among these JAKi in the inhibition of JAK2 signaling pathways.

Benzydamine inhibits osteoclast differentiation and bone resorption via down-regulation of interleukin-1 β expression

Bone diseases such as osteoporosis and periodontitis are induced by excessive osteoclastic activity, which is closely associated with inflammation. Benzydamine (BA) has been used as a cytokine-suppressive or non-steroidal anti-inflammatory drug that inhibits the production of pro-inflammatory cytokines or prostaglandins. However, its role in osteoclast differentiation and function remains unknown. Here, we explored the role of BA in regulating osteoclast differentiation and elucidated the underlying mechanism. BA inhibited osteoclast differentiation and strongly suppressed interleukin-1β (IL-1β) production. BA inhibited osteoclast formation and bone resorption when added to bone marrow-derived macrophages and differentiated osteoclasts, and the inhibitory effect was reversed by IL-1β treatment. The reporter assay and the inhibitor study of IL-1β transcription suggested that BA inhibited nuclear factor-κB and activator protein-1 by regulating IκB kinase, extracellular signal regulated kinase and P38, resulting in the down-regulation of IL-1β expression. BA also promoted osteoblast differentiation. Furthermore, BA protected lipopolysaccharide- and ovariectomy-induced bone loss in mice, suggesting therapeutic potential against inflammation-induced bone diseases and postmenopausal osteoporosis.

Contributions of Interleukin-1 Receptor Signaling in Traumatic Brain Injury

Traumatic brain injury (TBI) in various forms affects millions in the United States annually. There are currently no FDA-approved therapies for acute injury or the chronic comorbidities associated with TBI. Acute phases of TBI are characterized by profound neuroinflammation, a process that stimulates the generation and release of proinflammatory cytokines including interleukin-1α (IL-1α) and IL-1β. Both forms of IL-1 initiate signaling by binding with IL-1 receptor type 1 (IL-1R1), a receptor with a natural, endogenous antagonist dubbed IL-1 receptor antagonist (IL-1Ra). The recombinant form of IL-1Ra has gained FDA approval for inflammatory conditions such as rheumatoid arthritis, prompting interest in repurposing these pharmacotherapies for other inflammatory diseases/injury states including TBI. This review summarizes the currently available preclinical and clinical literature regarding the therapeutic potential of inhibiting IL-1-mediated signaling in the context of TBI. Additionally, we propose specific research areas that would provide a greater understanding of the role of IL-1 signaling in TBI and how these data may be beneficial for the development of IL-1-targeted therapies, ushering in the first FDA-approved pharmacotherapy for acute TBI.

Effect of Docosahexaenoic Acid on Ca2+ Signaling Pathways in Cerulein-Treated Pancreatic Acinar Cells, Determined by RNA-Sequencing Analysis

Intracellular Ca²⁺ homeostasis is commonly disrupted in acute pancreatitis. Sustained Ca²⁺ release from internal stores in pancreatic acinar cells (PACs), mediated by inositol triphosphate receptor (IP3R) and the ryanodine receptor (RyR), plays a key role in the initiation and propagation of acute pancreatitis. Pancreatitis induced by cerulein, an analogue of cholecystokinin, causes premature activation of digestive enzymes and enhanced accumulation of cytokines and Ca²⁺ in the pancreas and, as such, it is a good model of acute pancreatitis. High concentrations of the omega-3 fatty acid docosahexaenoic acid (DHA) inhibit inflammatory signaling pathways and cytokine expression in PACs treated with cerulein. In the present study, we determined the effect of DHA on key regulators of Ca²⁺ signaling in cerulein-treated pancreatic acinar AR42 J cells. The results of RNA-Sequencing (RNA-Seq) analysis showed that cerulein up-regulates the expression of IP3R1 and RyR2 genes, and that pretreatment with DHA blocks these effects. The results of real-time PCR confirmed that DHA inhibits cerulein-induced IP3R1 and RyR2 gene expression, and demonstrated that DHA pre-treatment decreases the expression of the Relb gene, which encodes a component of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcriptional activator complex, and the c-fos gene, which encodes a component of activator protein-1 (AP-1) transcriptional activator complex. Taken together, DHA inhibits mRNA expression of IP3R1, RyR2, Relb, and c-fos, which is related to Ca²⁺ network in cerulein-stimulated PACs.

PKCδ-IRAK1 axis regulates oxidized LDL-induced IL-1β production in monocytes

This study examined the role of interleukin (IL)-1 receptor-associated kinase (IRAK) and protein kinase C (PKC) in oxidized LDL (Ox-LDL)-induced monocyte IL-1β production. In THP1 cells, Ox-LDL induced time-dependent secretory IL-1β and IRAK1 activity; IRAK4, IRAK3, and CD36 protein expression; PKCδ-JNK1 phosphorylation; and AP-1 activation. IRAK1/4 siRNA and inhibitor (INH)-attenuated Ox-LDL induced secreted IL-1β and pro-IL-1β mRNA and pro-IL-1β and mature IL-1β protein expression, respectively. Diphenyleneiodonium chloride (NADPH oxidase INH) and N-acetylcysteine (free radical scavenger) attenuated Ox-LDL-induced reactive oxygen species generation, caspase-1 activity, and pro-IL-1β and mature IL-1β expression. Ox-LDL-induced secretory IL-1β production was abrogated in the presence of JNK INH II, Tanshinone IIa, Ro-31-8220, Go6976, Rottlerin, and PKCδ siRNA. PKCδ siRNA attenuated the Ox-LDL-induced increase in IRAK1 kinase activity, JNK1 phosphorylation, and AP-1 activation. In THP1 macrophages, CD36, toll-like receptor (TLR)2, TLR4, TLR6, and PKCδ siRNA prevented Ox-LDL-induced PKCδ and IRAK1 activation and IL-1β production. Enhanced Ox-LDL and IL-1β in systemic inflammatory response syndrome (SIRS) patient plasma demonstrated positive correlation with each other and with disease severity scores. Ox-LDL-containing plasma induced PKCδ and IRAK1 phosphorylation and IL-1β production in a CD36-, TLR2-, TLR4-, and TLR6-dependent manner in primary human monocytes. Results suggest involvement of CD36, TLR2, TLR4, TLR6, and the PKCδ-IRAK1-JNK1-AP-1 axis in Ox-LDL-induced IL-1β production.

Visfatin contributes to the differentiation of monocytes into macrophages through the differential regulation of inflammatory cytokines in THP-1 cells

Visfatin is a novel multifunctional adipocytokine with inflammatory properties. Although a link between visfatin and atherosclerosis has recently been suggested, its actions in the development of atherosclerosis remain unknown. Therefore, we investigated a potential role and underlying mechanism(s) of visfatin in monocytes/macrophages differentiation, a critical early step in atherogenesis, using phorbol-12-myristate-13-acetate (PMA)-stimulated THP-1 cell models. The co-incubation of PMA with visfatin-induced CD36 expression with a concomitant increase in the phagocytosis of latex beads compared with PMA alone treatment. Moreover, visfatin markedly increased interleukin (IL)-1β secretion by enhancing IL-1β mRNA stability in a short-term incubation. Visfatin also significantly elevated the secretion of IL-6 as well as IL-1β in a longer incubation period, which was partially suppressed by nuclear factor-κB (NF-κB) inhibitor, BAY11-7082, and c-Jun-N-terminal kinase (JNK) inhibitor, SP600125. Furthermore, silencing IL-1β successfully blocked IL-6 secretion, CD36 expression, and NF-κB activation in response to visfatin. Collectively, these results suggest that visfatin enhances the IL-1β-dependent induction of IL-6 and CD36 via distinct signaling pathways mediated by JNK and NF-κB, respectively, and consequently, leading to the acceleration of monocytes/macrophages differentiation.

Cucurbitacin D is a new inflammasome activator in macrophages

We previously reported that cucurbitacin D isolated from Trichosanthes kirilowii has anti-tumor roles to leukemia cells. However, the effect of cucurbitacin D on immune cells is not fully understood although there is no toxic activity to normal cells. In this study, immunomodulating activities of cucurbitacin D were investigated in macrophages. Cucurbitacin D could increase LPS-induced interleukin (IL)-1β production in culture supernatant of THP-1 cells, peritoneal exudate cells (PECs), bone marrow derived macrophages (BMDMs), and RAW264 cells. At the transcriptional level, cucurbitacin D enhanced LPS-induced IL-1β mRNA expression through activation of ERK1/2 mitogen-activated protein kinases (MAPKs). At the posttranscriptional level, the activation of caspase-1 induced by cucurbitacin D has also been demonstrated following treatment with a caspase-1 inhibitor and siRNA. Importantly, cucurbitacin D has further been shown to induce inflammasome activation independent of ERK1/2 activation. Western blotting showed interaction of NOD-like receptor family, pyrin domain containing 3 (NALP3) and apoptosis-associated speck-like protein containing a caspase-activating and recruitment domain (ASC), suggesting activation of the inflammasome and a possible reason for activation of caspase-1. Taken together, these results suggest that cucurbitacin D could initiate immunomodulating activity in macrophages to lead to inflammasome activation as well as enhancement of LPS signaling.

Cigarette smoke condensate extracts induce IL-1-beta production from rheumatoid arthritis patient-derived synoviocytes, but not osteoarthritis patient-derived synoviocytes, through aryl hydrocarbon receptor-dependent NF-kappa-B activation and novel NF-kappa-B sites

Cigarette smoking is a major established environmental risk factor for rheumatoid arthritis (RA), and synoviocyte-derived proinflammatory cytokines are implicated in the pathogenesis of RA. We have reported that aryl hydrocarbon or cigarette smoke condensate (CSC) is able to upregulate the production of proinflammatory cytokines from an RA patient-derived synovial fibroblast cell line MH7A. In this study, we compared the effect of CSC on induction of interleukin-1β (IL-1β) from RA or osteoarthritis (OA) patient-derived synovial fibroblasts, and studied the mechanism of the effect of CSC. CSC induced IL-1β mRNA from RA patient-derived synoviocytes and MH7A, but not from OA patient-derived synoviocytes. CSC induced the mRNA and both precursor and mature forms of IL-1β, and caspase-1 activity in MH7A. The mechanism of CSC-induced IL-1β mRNA expression was investigated in MH7A. Reporter gene analyses and promoter pull-down assay indicated that 3 novel NF-κB sites at -3771 to -3762 bp, -3105 to -3096 bp, and -2787 to -2778 bp in the promoter region of the IL-1β gene, especially the far distal NF-κB site and NF-κB activation, are critical for the gene activation by CSC. CSC-induced NF-κB activation, IL-1β promoter activity, IL-1β mRNA upregulation, and CYP1A1 mRNA induction were all inhibited by an aryl hydrocarbon receptor (AhR) antagonist α-naphthoflavone. These results indicate that CSC induced IL-1β production from RA patient-derived synoviocytes, but not OA patient-derived synoviocytes, through AhR-dependent NF-κB activation and novel NF-κB sites.

Mechanisms by which licochalcone e exhibits potent anti-inflammatory properties: studies with phorbol ester-treated mouse skin and lipopolysaccharide-stimulated murine macrophages

In this study we found that licochalcone E (LicE), a recently isolated retrochalcone from Glycyrrhiza inflata, exhibits potent anti-inflammatory effects in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema and lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophage models. Topical application of LicE (0.5–2 mg) effectively inhibited TPA-induced (1) ear edema formation; (2) phosphorylation of stress-activated protein kinase/c-Jun-N-terminal kinase (SAPK/JNK), c-Jun, and extracellular signal regulated kinase 1/2; and (3) expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 proteins in mouse skin. The treatment of RAW 264.7 cells with LicE (2.5–7.5 μmol/L) induced a profound reduction in LPS-induced (1) release of NO and prostaglandin E₂; (2) mRNA expression and secretion of interleukin (IL)-6, IL-1β and tumor necrosis factor-α; (3) promoter activity of iNOS and COX-2 and expression of their corresponding mRNAs and proteins; (4) activation of AKT, p38 mitogen activated protein kinase (MAPK), SAPK/JNK and c-Jun; (5) phosphorylation of inhibitor of κB (IκB) kinase-αβ and IκBα, degradation of IκBα, translocation of p65 (RelA) to the nucleus and transcriptional activity of nuclear factor (NF)-κB; and (6) transcriptional activity of activator protein (AP)-1. These results indicate that the LicE inhibition of NF-κB and AP-1 transcriptional activity through the inhibition of AKT and MAPK activation contributes to decreases in the expression of pro-inflammatory cytokines and the inducible enzymes iNOS and COX-2.

Inhibition of transforming growth factor beta-activated kinase 1 confers neuroprotection after traumatic brain injury in rats

The transforming growth factor beta-activated kinase 1 (TAK1), a member of the Mitogen-activated protein kinase kinase kinase family, is characterized as a key regulator in inflammatory and apoptosis signaling pathways. The aim of the present study was to evaluate the role of the TAK1 pathway in experimental traumatic brain injury (TBI) in rats. Adult male Sprague-Dawley rats were subjected to TBI using a modified Feeney's weight-drop model. The time course showed that a significant increase of TAK1 and p-TAK1 expression in the cortex after TBI. Moreover, TBI induced TAK1 redistribution both in neurons and astrocytes of the lesion boundary zone. The effects of specific inhibition of the TAK1 pathway by 5Z-7-oxozeaenol (OZ, intracerebroventricular injection at 10min post-trauma) on histopathological and behavioral outcomes in rats were assessed at 24h post injury. The number of TUNEL-positive stained cells was diminished and neuronal survival and neurological function were improved with OZ treatment. Biochemically, the high dose of OZ significantly reduced the levels of TAK1 and p-TAK1, further decreased nuclear factor-κB and activator protein 1 activities and the release of inflammatory cytokines. In addition, we found that both 10min and 3h post-trauma OZ therapies could markedly improve neurological function and neuronal survival after long-term survival. These results revealed that the TAK1 pathway is activated after experimental TBI and the inhibitor OZ affords significant neuro- protection and amelioration of neurobehavioral deficits after experimental TBI, suggesting a potential rationale for manipulating this pathway in clinical practice.

TET1 is a negative transcriptional regulator of IL-1β in the THP-1 cell line

TET1 is a member of the recently identified family of epigenetic regulators, TET1-3 which catalyze the enzymatic conversion of the methyl mark on cytosine (methylcytosine, mC) to the hydroxymethyl mark (hmC). The functions of hmC are required for stem cell maintenance and for controlling differentiation and reprogramming. So far, no roles for TET proteins have been identified in cells of the immune system. Here we show that TET1 is a negative regulator of IL-1β transcription following an inflammatory stimulus and negatively modulates IL-1β secretion in THP-1 cells. In addition, TET1 expression is regulated during inflammation both in THP-1 and in primary dendritic cells. Importantly, other highly induced pro-inflammatory genes are also regulated by TET1, including cytokines, chemokines and adhesion molecules. The other member of the TET family with known roles in stem cell regulation, TET2, is also regulated in THP-1 cells following the inflammatory stimulus and may also participate in IL-1β regulation, according to our observations. Our results suggest a TET1-dependent anti-inflammatory pathway, which may include TET2. In particular, IL-1β transcriptional regulation is likely to depend on TET1-regulated chromatin domains. This work highlights the contribution of epigenetic mechanisms to the efficient organization of inflammatory responses.

IL-1R-associated kinase-1 mediates protein kinase Cδ-induced IL-1β production in monocytes

The role of IL-1R-associated kinase (IRAK)1 and its interaction with protein kinase C (PKC)δ in monocytes to regulate IL-1β production has not been reported so far. The present study thus investigates such mechanisms in the THP1 cell line and human monocytes. PMA treatment to THP1 cells induced CD11b, TLR2, TLR4, CD36, IRAK1, IRAK3, and IRAK4 expression, IRAK1 kinase activity, PKCδ and JNK phosphorylation, AP-1 and NF-κB activation, and secretory IL-1β production. Moreover, PMA-induced IL-1β production was significantly reduced in the presence of TLR2, TLR4, and CD11b Abs. Rottlerin, a PKCδ-specific inhibitor, significantly reduced PMA-induced IL-1β production as well as CD11b, TLR2 expression, and IRAK1-JNK activation. In PKCδ wild-type overexpressing THP1 cells, IRAK1 kinase activity and IL-1β production were significantly augmented, whereas recombinant inactive PKCδ and PKCδ small interfering RNA significantly inhibited basal and PMA-induced IRAK1 activation and IL-1β production. Endogenous PKCδ-IRAK1 interaction was observed in quiescent cells, and this interaction was regulated by PMA. IRAK1/4 inhibitors, their small interfering RNAs, and JNK inhibitor also attenuated PMA-induced IL-1β production. NF-κB activation inhibitor and SN50 peptide inhibitor, however, failed to affect PMA-induced IL-1β production. A similar role of IRAK1 in IL-1β production and its regulation by PKCδ was evident in the primary human monocytes, thus signifying the importance of our finding. To our knowledge, the results obtained demonstrate for the first time that IRAK1 and PKCδ functionally interact to regulate IL-1β production in monocytic cells. A novel mechanism of IL-1β production that involves TLR2, CD11b, and the PKCδ/IRAK1/JNK/AP-1 axis is thus being proposed.

Citrus flavonoid 5-demethylnobiletin suppresses scavenger receptor expression in THP-1 cells and alters lipid homeostasis in HepG2 liver cells

SCOPE

Nobiletin, a polymethoxyflavone from the peel of citrus fruits, has been reported to inhibit modified LDL uptake in macrophages and enhance hepatic LDL receptor expression and activity. We report the anti-atherogenic effect and mechanism of 5-demethylnobiletin, an auto-hydrolysis product of nobiletin.

METHODS AND RESULTS

5-Demethylnobiletin significantly attenuated phorbol 12-myristate 13-acetate-induced gene expression and activity of scavenger receptors, CD36, scavenger receptor-A and lectin-like oxidized LDL receptor-1. The inhibitory effect is partly associated with the inhibition of protein-kinase C activity and c-Jun NH(2) -terminal kinase 1/2 phosphorylation, thereby inhibiting the activation of activator protein-1 and nuclear factor-κB. 5-Demethylnobiletin treatment also led to reduction of oxidized LDL-induced CD36 mRNA expression and blockade of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanide perchlorate-modified LDL uptake in THP-1-derived macrophages. In the human hepatoma cell line HepG2, 5-demethylnobiletin significantly induced LDL receptor activity and transcription, at least in part, through steroid-response element-binding protein-2 activation. 5-Demethylnobiletin also decreased the mRNA expression of acyl CoA:diacylglycerol acyltransferase 2, the key enzyme involved in the hepatic triacylglycerol biosyntheses.

CONCLUSION

Current results suggest that 5-demethylnobiletin has diverse anti-atherogenic bioactivities. It is more potent in inhibiting monocyte-to-macrophage differentiation and foam cell formation than its permethoxylated counterpart, nobiletin. It exhibits similar hypolipidemic activity as nobiletin and both can enhance LDL receptor gene expression and activity and decreased acyl CoA:diacylglycerol acyltransferase 2 expression.

Xanthones from mangosteen prevent lipopolysaccharide-mediated inflammation and insulin resistance in primary cultures of human adipocytes

The xanthones, alpha- and gamma-mangostin (MG), are major bioactive compounds found in mangosteen and are reported to have antiinflammatory properties in several murine models. Given the association between obesity, chronic low-grade inflammation, and insulin resistance, we examined the effects of alpha- and gamma-MG on markers of inflammation and insulin resistance in primary cultures of newly differentiated human adipocytes treated with lipopolysaccharide (LPS). alpha- and gamma-MG decreased the induction by LPS of inflammatory genes, including tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-8, monocyte chemoattractant protein-1, and Toll-like receptor-2. Moreover, alpha- and gamma-MG attenuated LPS activation of the mitogen-activated protein kinases (MAPK) c-jun NH(2)-terminal kinase, extracellular signal-related kinase, and p38. alpha- and gamma-MG also attenuated LPS activation of c-Jun and activator protein (AP)-1 activity. gamma-MG was more effective than alpha-MG on an equimolar basis. Furthermore, gamma-MG but not alpha-MG attenuated LPS-mediated IkappaB-alpha degradation and nuclear factor-kappaB (NF-kappaB) activity. In addition, gamma-MG prevented the suppression by LPS of insulin-stimulated glucose uptake and PPAR-gamma and adiponectin gene expression. Taken together, these data demonstrate that MG attenuates LPS-mediated inflammation and insulin resistance in human adipocytes, possibly by inhibiting the activation of MAPK, NF-kappaB, and AP-1.

Activation of transcription factors and gene expression by oxidized low-density lipoprotein

It is well recognized that oxidized LDL (OxLDL) plays a crucial role in the initiation and progression of atherosclerosis. Many biological effects of OxLDL are mediated through signaling pathways, especially via the activation of transcription factors, which in turn stimulate the expression of genes involved in the inflammatory and oxidative stress response or in cell cycle regulation. In this review, we will discuss the various transcription factors activated by OxLDL, the studied cell types, the active compounds of the OxLDL particle, and the downstream genes when identified. Identification of the transcription factors and some of the downstream genes regulated by OxLDL has helped us understand the molecular mechanism involved in generation of the atherosclerotic plaque.

Stress and reactivation of latent herpes simplex virus: a fusion of behavioral medicine and molecular biology

Since 1978, the study of health and behavior has become a major focus of scientists in psychology, psychiatry, nursing, neuroscience, and in traditional medical science disciplines. Investigation of psychological or behavioral influences on biological systems has established that biobehavioral processes such as stress play an important role in disease processes. An excellent example of the interactions between stress and health outcomes is the reactivation of latent herpes simplex virus (HSV) leading to recurrent lesions. This article describes what is currently known about HSV latency and reactivation and considers some mechanisms by which stress-induced changes in the host's immune and nervous systems might allow for either the establishment or reactivation of latent viral infections.

Dynamic protein associations define two phases of IL-1beta transcriptional activation

IL-1beta is a key proinflammatory cytokine with roles in multiple diseases. Monocytes package the IL-1beta promoter into a "poised architecture" characterized by a histone-free transcription start site and constitutive transcription factor associations. Upon LPS stimulation, multiple proteins inducibly associate with the IL-1beta gene. To understand how the complex combination of constitutive and inducible transcription factors activate the IL-1beta gene from a poised structure, we measured temporal changes in NF-kappaB and IFN regulatory factor (IRF) association with IL-1beta regulatory elements. Association of the p65 subunit of NF-kappaB peaks 30-60 min post-monocyte stimulation, and it shortly precedes IRF-4 recruitment to the IL-1beta enhancer and maximal mRNA production. In contrast, IRF-8/enhancer association decreases poststimulation. To test the importance of delayed IRF-4/enhancer association, we introduced a mutated PU.1 protein shown to prevent PU.1-mediated IRF-4 recruitment to the enhancer sequence. Mutated PU.1 initially increased IL-1beta mRNA followed by decreased mRNA levels 2-3 h poststimulation. Taken together, these data support a dynamic model of IL-1beta transcriptional activation in which a combination of IRF-8 and p65 drives the initial phase of IL-1beta transcription, while PU.1-mediated IRF-4 recruitment to the enhancer is important for the second phase. We further demonstrate that activation of both NF-kappaB and IRF-4 depends on CK2 kinase activity. Because IRF-4/enhancer association requires CK2 but not p65 activation, we conclude that CK2 triggers the IRF-4 and p65 pathways independently to serve as a master regulator of IL-1beta transcription.

3,3'-Diindolylmethane suppresses the inflammatory response to lipopolysaccharide in murine macrophages

3,3'-Diindolylmethane (DIM), a major acid-condensation product of indole-3-carbinol, has been shown to have multiple anticancer effects in experimental models. Because recurrent or chronic inflammation has been implicated in the development of a variety of human cancers, this study examined the antiinflammatory effects of DIM and the underlying mechanisms using lipopolysaccharide (LPS)-stimulated RAW264.7 murine macrophages. DIM significantly decreased the release of nitric oxide (NO), prostaglandin (PG)E2, tumor necrosis factor alpha, interleukin (IL)-6, and IL-1beta by RAW264.7 cells treated with LPS. DIM inhibited LPS-induced increases in protein levels of inducible NO synthase (iNOS), which were accompanied by decreased iNOS mRNA levels and transcriptional activity. The mRNA levels of phospholipase A2 decreased, whereas neither cyclooxygenases-2 protein nor transcript was altered by DIM. In addition, DIM suppressed LPS-induced nuclear factor-kappaB (NF-kappaB) transcriptional activity, NF-kappaB DNA-binding activity, translocation of p65 (RelA) to the nucleus, and degradation of inhibitor of kappaB alpha. Furthermore, DIM decreased LPS-induced transcriptional activity of activator protein (AP)-1, AP-1 DNA-binding activity, and phosphorylation of stress-activated protein kinase/Jun-N-terminal kinase and c-Jun. We demonstrate that DIM inhibits LPS-induced release of proinflammatory mediators in murine macrophages. Downregulation of NF-kappaB and AP-1 signaling may be one of the mechanisms by which DIM inhibits inflammatory responses.

Aggregated ursolic acid, a natural triterpenoid, induces IL-1beta release from murine peritoneal macrophages: role of CD36

IL-1beta has been shown to play a pivotal role in the development of inflammatory disorders. We recently found that a natural triterpene, ursolic acid (UA), enhanced MIF release from nonstimulated macrophages. In this study, we examined the effects of UA on the production of several cytokines in resident murine peritoneal macrophages (pMphi). UA increased the protein release of IL-1beta, IL-6, and MIF, but not of TNF-alpha, in dose- and time-dependent manners. This triterpene also strikingly induced the activation of p38 MAPK and ERK1/2 together with that of upstream kinases. The release of UA-induced IL-1beta was significantly inhibited by the inhibitors of p38 MAPK, MEK1/2, ATP-binding cassette transporter, and caspase-1. Furthermore, UA induced intracellular ROS generation for IL-1beta production, which was suppressed by an antioxidant. Pretreatment with an anti-CD36 Ab significantly suppressed IL-1beta release, and surface plasmon resonance assay results showed that UA bound to CD36 on macrophages. In addition, the amount of IL-1beta released from UA-treated pMphi of CD36-deficient mice was markedly lower than that from those of wild-type mice. Interestingly, UA was found to aggregate in culture medium, and the aggregates were suggested to be responsible for IL-1beta production. In addition, i.p. administration of UA increased the levels of IL-1beta secretion and MPO activity in colonic mucosa of ICR mice. Taken together, our results indicate that aggregated UA is recognized, in part, by CD36 on macrophages for generating ROS, thereby activating p38 MAPK, ERK1/2, and caspase-1, as well as releasing IL-1beta protein via the ATP-binding cassette transporter.

Role of oxidative stress in thuringiensin-induced pulmonary toxicity

To understand the effect of thuringiensin on the lungs tissues, male Sprague-Dawley rats were administrated with thuringiensin by intratracheal instillation at doses 0.8, 1.6 and 3.2 mg/kg of body weight, respectively. The rats were sacrificed 4 h after treatment, and lungs were isolated and examined. Subsequently, an effective dose of 1.6 mg/kg was selected for the time course study (4, 8, 12, and 24 h). Intratracheal instillation of thuringiensin resulted in lung damage, as evidenced by increase in lung weight and decrease in alkaline phosphatase (10-54%), an enzyme localized primarily in pulmonary alveolar type II epithelial cells. Furthermore, the administration of thuringiensin caused increases in lipid peroxidation (21-105%), the indices of lung injury. In addition, the superoxide dismutase (SOD) and glutathione (GSH) activities of lung tissue extracts were measured to evaluate the effect of thuringiensin on antioxidant defense system. The SOD activity and GSH content in lung showed significant decreases in a dose-related manner with 11-21% and 15-37%, respectively. Those were further supported by the release of proinflammatory cytokines, as indicated by increases in IL-1beta (229-1017%) and TNF-alpha (234%) levels. Therefore, the results demonstrated that changes in the pulmonary oxidative-antioxidative status might play an important role in the thuringiensin-induced lung injury.

Docosahexaenoic acid-containing phosphatidylethanolamine enhances HL-60 cell differentiation by regulation of c-jun and c-myc expression

18:1/docosahexaenoic acid (DHA)-containing phosphatidylethanolamine (PE) enhanced cell differentiation and growth inhibition of HL-60 induced by dibutyryl cAMP (dbcAMP) in a dose-dependent manner. The combined treatment of 200 microM dbcAMP and 50 microM 18:1/DHA-PE increased the NBT reducing activity, which is as an indicator of cell differentiation, to more than 75% from 40% of cells treated with 200 microM dbcAMP alone. In HL-60 cells treated with 50 microM 18:1/DHA-PE and 200 microM dbcAMP for 24 h, the expression level of c-jun mRNA and c-Jun protein were remarkably elevated compared to cells treated with dbcAMP alone. In contrast, there was no difference in the expression levels of c-fos mRNA and c-Fos protein between the combination of 18:1/DHA-PE + dbcAMP or dbcAMP alone. On the other hand, the combine treatment of 18:1/DHA-PE and dbcAMP markedly reduced the expression level of c-myc oncogene during 48 h incubation. The decreases of c-myc mRNA by 18:1/DHA-PE and/or dbcAMP was correlated with growth inhibition effect. Thus, 18:1/DHA-PE might enhance dbcAMP-induced HL-60 cell differentiation and growth inhibition by regulation of c-jun and c-myc mRNA and their products.

Chlorophyllin suppresses interleukin-1 beta expression in lipopolysaccharide-activated RAW 264.7 cells

Our previous findings demonstrated that chlorophyllin (CHL) inhibits inducible nitric oxide gene expression in macrophages. In the present study, we show that CHL inhibited IL-1beta production and its mRNA expression in a lipopolysaccharide (LPS)-stimulated murine macrophage cell-line, RAW 264.7. The inhibitory effect of CHL on IL-1beta gene expression was further supported by an in vitro transfection assay using a pIL-1(870 bp)-CAT construct, where CHL inhibited the activation of the IL-1beta promoter. Furthermore, CHL attenuated the activation of NF-kappaB, NF-IL6 and AP-1, which are known to be responsible for IL-1beta gene expression, as determined by an electrophoretic mobility shift assay and an in vitro transfection assay using p(NF-kappaB)3-CAT, p(NF-IL6)3-CAT, and p(AP-1)3-CAT, respectively. However, it was evident that the inhibitory activity of CHL on IL-1beta expression in the LPS-stimulated macrophages was independent of CRE/ATF. The immunoblot experiment demonstrated that CHL also caused a substantial decrease in the phosphorylation of p38 MAP kinase in LPS-stimulated RAW 264.7. These results suggest that CHL inhibits IL-1beta production in macrophages stimulated with LPS at transcriptional level by blocking the phosphorylation of p38 and by suppressing the activation of transcription factors, NF-kappaB, NF-IL6, and AP-1.

Are transcription factors NF-κB and AP-1 involved in the ANG II-stimulated production of proinflammatory cytokines induced by LPS in dehydrated rats?

We recently reported an involvement of ANG II and the ANG II type 1 (AT1) receptor in the hepatic expression of IL-1β induced in dehydrated rats by LPS. Here, we first confirmed that ANG II and AT1 receptors contribute to the LPS-induced increase in the splenic concentration of IL-1β in dehydrated rats. We then investigated whether ANG II contributes to IL-1 production through a modulating effect on the activation of proinflammatory transcription factors (NF-κB and AP-1) that is induced in the dehydrated rat's liver and spleen by intravenous injection of LPS. Surprisingly, LPS markedly increased the hepatic activation of NF-κB, an effect that was significantly enhanced (rather than reduced) by pretreatment with an ANG-converting-enzyme (ACE) inhibitor or AT1-receptor antagonist. Furthermore, the same ACE inhibitor and AT1-receptor antagonist each increased the resting NF-κB activity in the liver and spleen, although they had no effect on the LPS-induced splenic expression of NF-κB. Both hepatic and splenic AP-1 expressions were enhanced by LPS. This response was significantly augmented by pretreatment with the AT1-receptor antagonist (but not with the ACE inhibitor) in the spleen, while in the liver, neither drug had any effect. These results suggest that the endogenous ANG II or AT1 receptor suppresses the activation of hepatic or splenic transcription factors in dehydrated rats given LPS. Our results seem not to support the idea that NF-κB and AP-1 play key roles in the ANG II-induced enhancement of the production of proinflammatory cytokines that is induced by LPS in dehydrated rats.

Time-course expression of CNS inflammatory, neurodegenerative tissue repair markers and metallothioneins during experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS). EAE and MS are characterized by CNS inflammation, demyelination and neurodegeneration. The inflammatory response occurring within the CNS leads to glial activation, dysfunction and death, as well as axonal damage and neurological deficit. Although the pathogenic mechanisms involved in EAE/MS are not well understood, accumulating data suggest that oxidative stress plays a major role in lesion development, and contributes to axonal dysfunction and degeneration. Metallothionein-I and -II are anti-inflammatory, neuroprotective, antioxidant proteins expressed during EAE and MS, in which they might play a protective role. The present study aimed to describe the expression profile of a group of inflammatory, neurodegenerative and tissue repair markers as well as metallothioneins during proteolipid protein-induced EAE, and to establish the time-relationships these molecules had during EAE. Interestingly, we found two marker expression profiles. In the first, marker expression increased as clinical signs worsened and reverted to baseline expression during recovery; in the second, marker expression increased at a later point during relapse, peaked at highest clinical score, and remained elevated throughout recovery. Of note, metallothionein expression was found to be related to the second profile, which would suggest that metallothionein proteins are implicated in the clinical recovery of EAE and perhaps these antioxidant proteins may provide therapeutic benefits in MS.

Excretory/secretory products from plerocercoids of Spirometra erinaceieuropaei suppress interleukin-1beta gene expression in murine macrophages

The present study shows that ES products from plerocercoids of Spirometra erinaceieuropaei suppressed interleukin-1beta mRNA expression in lipopolysaccharide-stimulated RAW 264.7 macrophages in the absence or presence of a cyclic AMP analogue, dibutyryl cyclic AMP. Investigation using the inhibitors of mitogen-activated protein kinase (MAPK) pathways revealed that extracellular signal-regulated protein kinase 1/2 and p38 mitogen-activated protein kinase pathways are crucial for full induction of interleukin-1beta mRNA expression. ES products additionally suppressed interleukin-1beta mRNA expression in the cells treated with p38 mitogen-activated protein kinase inhibitor (SB203580) or extracellular signal-regulated protein kinase 1/2 inhibitor (PD98059). Western blot analysis showed that dibutyryl cyclic AMP enhanced lipopolysaccharide-induced phosphorylation of extracellular signal-regulated protein kinase 1/2, p38 mitogen-activated protein kinase and cyclic AMP responsive element binding protein (CREB) and, in turn, we demonstrated that ES products reduced the lipopolysaccharide and dibutyryl cyclic AMP-induced phosphorylation of extracellular signal-regulated protein kinase 1/2 and p38 mitogen-activated protein kinase, but not cyclic AMP responsive element binding protein. These data demonstrate that ES products from the plerocercoids of S. erinaceieuropaei may evade induction of interleukin-1beta mRNA by inhibiting extracellular signal-regulated protein kinase 1/2 and p38 mitogen-activated protein kinase pathways in lipopolysaccharide and/or dibutyryl cyclic AMP-stimulated macrophages.

Costunolide inhibits interleukin-1β expression by down-regulation of AP-1 and MAPK activity in LPS-stimulated RAW 264.7 cells

Costunolide, a sesquiterpene lactone isolated from the root of Saussurea lappa Clarke, is known to have a variety of biological activities, including anti-carcinogenic and anti-fungal activities. Here, we demonstrated the inhibitory effect of costunolide on the protein and mRNA expression of interleukin-1beta (IL-1beta) in LPS-stimulated RAW 264.7 cells. We also showed that costunolide suppressed the transcriptional activity of the IL-1beta promoter. Moreover, costunolide inhibited the activity of AP-1 transcription factor, and the phosphorylation of MAPKs, including SAPK/JNK and p38 MAP kinase. The inhibitory effect of costunolide on AP-1 activity was also confirmed by an electrophoretic mobility shift assay. Additionally, specific inhibitors of SAPK/JNK and p38 MAP kinase, SP600125 and SB203580, also suppressed LPS-induced increase in IL-1beta gene expression and AP-1 DNA binding. Taken together, these results demonstrate that costunolide inhibits IL-1beta gene expression by blocking the activation of MAPKs and DNA binding of AP-1 in LPS-stimulated RAW 264.7 cells.

Protease-activated receptors 1 and 4 mediate thrombin signaling in endothelial cells

Defining the relative importance of protease-activated receptors (PARs) for thrombin signaling in mouse endothelial cells is critical for a basic understanding of thrombin signaling in these cells and for the rational use of knockout mice to probe the roles of thrombin's actions on endothelial cells in vivo. We examined thrombin- and PAR agonist-induced increases in cytoplasmic calcium, phosphoinositide hydrolysis, extracellular signal-regulated kinase (ERK) phosphorylation, and gene expression in endothelial cells from wild-type and PAR-deficient mice. PAR1 and PAR4 agonists triggered responses in wild-type but not in Par1-/- and Par4-/- endothelial cells, respectively. Calcium imaging confirmed that a substantial fraction of individual endothelial cells responded to both agonists. Compared with wild-type cells, Par1-/- endothelial cells showed markedly decreased responses to low concentrations of thrombin, and cells that lacked both PAR1 and PAR4 showed no responses to even high concentrations of thrombin. Similar results were obtained when endothelial-dependent vasorelaxation of freshly isolated mouse aorta was used as an index of signaling in native endothelial cells. Thus PAR1 is the major thrombin receptor in mouse endothelial cells, but PAR4 also contributes. These receptors serve at least partially redundant roles in endothelial cells in vitro and in vivo and together are necessary for the thrombin responses measured.

Early changes in lung gene expression due to high tidal volume

The purpose of this study was to use gene expression profiling to understand how adult rat lung responds to high tidal volume (HV) ventilation in vivo. HV ventilation for 30 minutes did not cause discernable lung injury (in terms of altered mechanics or histology) but caused obvious injury when continued for 90 minutes. However, at 30-minute ventilation, HV caused significant upregulation of 10 genes and suppression of 12 genes. Among the upregulated genes were transcription factors, stress proteins, and inflammatory mediators; the downregulated genes were exemplified by metabolic regulatory genes. On the basis of cluster analysis, we studied Egr-1, c-Jun, heat shock protein 70, and interleukin (IL)-1beta in further detail. Temporal studies demonstrated that Egr-1 and c-Jun were increased early and before heat shock protein 70 and IL-1beta. Spatial studies using in situ hybridization and laser capture microscopy revealed that all four genes were upregulated primarily in the bronchiolar airway epithelium. Furthermore, at 90 minutes of HV ventilation, a significant increase in intracellular IL-1beta protein was observed. Although there are limitations to gene array methodology, the current data suggest a global hypothesis that (1). the effects of HV are cumulative; (2). specific patterns of gene activation and suppression precede lung injury; and (3). alteration of gene expression after mechanical stretch is pathogenic.

Regulation of type II transforming-growth-factor-beta receptors by protein kinase C iota

TGF-beta (transforming growth factor-beta) is implicated in the pathogenesis of diabetic nephropathy. We previously demonstrated that up-regulation of type II TGF-beta receptor (TbetaRII) induced by high glucose might contribute to distal tubular hypertrophy [Yang, Guh, Yang, Lai, Tsai, Hung, Chang and Chuang (1998) J. Am. Soc. Nephrol. 9, 182-193]. We have elucidated the mechanism by using cultured Madin-Darby canine kidney cells. Enhancer assay and electrophoretic-mobility-shift assay were used to estimate the involvement of transcription factors. Western blotting and an in vitro kinase assay were used to evaluate the level and activity of protein kinase. We showed that glucose (100-900 mg/dl) induced an increase in mRNA level and promoter activity of TbetaRII (note: 'mg/dl' are the units commonly used in diabetes studies). The promoter region -209 to -177 appeared to contribute to positive transactivation of TbetaRII promoter by comparing five TbetaRII-promoter-CAT (chloramphenicol acetyl-transferase) plasmids. Moreover, the transcription factor AP-1 (activator protein 1) was significantly activated and specifically binds to TbetaRII promoter (-209 to -177). More importantly, we found that atypical PKC iota might be pivotal for high glucose-induced increase in both AP-1 binding and TbetaRII promoter activity. First, high glucose induced cytosolic translocation, activation and autophosphorylation of PKC iota. Secondly, antisense PKC iota expression plasmids attenuated high-glucose-induced increase in AP-1 binding and TbetaRII promoter activity; moreover, sense PKC iota expression plasmids enhanced these instead. Finally, we showed that antisense PKC iota expression plasmids might partly attenuate a high-glucose/TGF-beta1-induced increase in fibronectin. We conclude that PKC iota might mediate high-glucose-induced increase in TbetaRII promoter activity. In addition, antisense PKC iota expression plasmid effectively suppressed up-regulation of TbetaRII and fibronectin in hyperglycaemic distal-tubule cells.

Molecular interactions between glucocorticoids and long-acting beta2-agonists

beta(2)-Adrenergic receptor agonists and glucocorticoids are the two most effective treatments for asthma, and used in combination they are more effective than either alone. Glucocorticoids mediate their anti-inflammatory effects through the action of activated glucocorticoid receptors (GRs), with the level of activity being related to the number of nuclear receptors. Glucocorticoids can upregulate the synthesis of several genes in human lung cells through interaction with specific DNA binding regions (glucocorticoid response elements) within the promoter region of glucocorticoid-responsive genes. Many of the down-regulating effects of GRs on the synthesis of cytokines and other inflammatory mediators are due to repression of other transcription factors, such as activator protein-1 and nuclear factor kappaB. GR functions such as nuclear localization and gene activation can be regulated by phosphorylation status. Long-acting beta(2)-agonists may affect GR nuclear localization through modulation of GR phosphorylation and furthermore through priming of GR functions within the nucleus by modifying GR or GR-associated protein phosphorylation. Glucocorticoids in turn may regulate beta(2)-adrenergic receptor function by increasing its expression, acting through glucocorticoid response elements, and, importantly, by restoring G-protein-beta(2)-receptor coupling and inhibiting beta(2)-receptor downregulation, thereby preventing desensitization.

Decreased inducibility of TNF expression in lipid-loaded macrophages

BACKGROUND

Inflammation and immune responses are considered to be very important in the pathogenesis of atherosclerosis. Lipid accumulation in macrophages of the arterial intima is a characteristic feature of atherosclerosis which can influence the inflammatory potential of macrophages. We studied the effects of lipid loading on the regulation of TNF expression in human monocyte-derived macrophages.

RESULTS

In macrophages incubated with acetylated low density lipoprotein (ac-LDL) for 2 days, mRNA expression of TNF in cells stimulated with TNF decreased by 75%. In cell cultures stimulated over night with IL-1beta, lipid loading decreased secretion of TNF into culture medium by 48%. These results suggest that lipid accumulation in macrophages makes them less responsive to inflammatory stimuli. Decreased basal activity and inducibility of transcription factor AP-1 was observed in lipid-loaded cells, suggesting a mechanism for the suppression of cytokine expression. NF-kappaB binding activity and inducibility were only marginally affected by ac-LDL. LDL and ac-LDL did not activate PPARgamma. In contrast, oxidized LDL stimulated AP-1 and PPARgamma but inhibited NF-kappaB, indicating that the effects of lipid loading with ac-LDL were not due to oxidation of lipids.

CONCLUSIONS

Accumulation of lipid, mainly cholesterol, results in down-regulation of TNF expression in macrophages. Since monocytes are known to be activated by cell adhesion, these results suggest that foam cells in atherosclerotic plaques may contribute less potently to an inflammatory reaction than newly arrived monocytes/macrophages.

c-Fos/activator protein-1 transactivates wee1 kinase at G(1)/S to inhibit premature mitosis in antigen-specific Th1 cells

M-phase promoting factor is a complex of cdc2 and cyclin B that is regulated positively by cdc25 phosphatase and negatively by wee1 kinase. We isolated the wee1 gene promoter and found that it contains one AP-1 binding motif and is directly activated by the immediate early gene product c-Fos at cellular G(1)/S phase. In antigen-specific Th1 cells stimulated by antigen, transactivation of the c-fos and wee1 kinase genes occurred sequentially at G(1)/S, and the substrate of wee1 kinase, cdc2-Tyr15, was subsequently phosphorylated at late G(1)/S. Under prolonged expression of the c-fos gene, however, the amount of wee1 kinase was increased and its target cdc2 molecule was constitutively phosphorylated on its tyrosine residue, where Th1 cells went into aberrant mitosis. Thus, an immediate early gene product, c-Fos/AP-1, directly transactivates the wee1 kinase gene at G(1)/S. The transient increase in c-fos and wee1 kinase genes is likely to be responsible for preventing premature mitosis while the cells remain in the G(1)/S phase of the cell cycle.

Dexamethasone inhibits IL-1 beta gene expression in LPS-stimulated RAW 264.7 cells by blocking NF-kappa B/Rel and AP-1 activation

In the present study, the mechanism by which dexamethasone (DEX) inhibited IL-1beta gene expression in bacterial lipopolysaccharide (LPS)-activated RAW 264.7 cells was investigated. The decrease in LPS-induced IL-1beta mRNA expression was demonstrated by quantitative reverse transcription polymerase chain reaction (RT-PCR). Since the promoter in IL-1beta gene contains binding motifs for NF-kappaB/Rel, AP-1, NF-IL6, and CREB/ATF, which appear to be important in LPS-mediated IL-1beta induction, the effects of DEX on the activation of these transcription factors were examined. Treatment of DEX to RAW 264.7 cells induced a dose-related inhibition of NF-kappaB/Rel and AP-1 in chloramphenicol acetyltransferase activity, while neither NF-IL6 nor CREB/ATF activation was affected by DEX. Treatment of RAW 264.7 cells with DEX inhibited DNA binding of NF-kappaB/Rel and AP-1 proteins to their cognate DNA sites as measured by electrophoretic mobility shift assay (EMSA). DEX treatment caused a significant reduction in nuclear c-rel, p65, and p50 protein contents, and these decreases were paralleled by the accumulation of cytoplasmic c-rel, p65, and p50. DEX treatment of RAW 264.7 cells did not inhibit the nuclear translocation of c-jun and c-fos. We found that the inhibition of IL-1beta production by DEX is not related to p38, which is important in the IL-1beta induction. These results suggest that DEX may inhibit IL-1beta gene expression by a mechanism involving the blocking of LPS-induced NF-kappaB/Rel and AP-1 activation.

Role of transcriptional factor activation protein-1 in endogenous expression of the interleukin-1 beta gene involved in Porphyromonas gingivalis fimbria-stimulated bone resorption in the mouse calvarial system

We previously suggested that endogenous interleukin-1 beta (IL-1 beta) produced by Porphyromonas gingivalis fimbriae stimulation in calvarial bone cell cultures plays a role in bone resorption as a major cytokine. Therefore, in the present study, we initiated experiments to clarify the stimulatory mechanism of IL-1 beta gene expression in fimbria-stimulated bone resorption. Fimbria-stimulated bone resorption was dramatically inhibited by curcumin, a potent inhibitor of activation protein-1 (AP-1). In fact, the fimbriae induced markedly both the expression of c-fos and c-jun genes and their protein production in the calvarial cells. In addition, a mixture of antisense oligonucleotides against c-fos and c-jun significantly inhibited not only the fimbria-induced expression of the IL-1 beta gene but also the fimbria-induced bone resorption. Therefore, the present study demonstrates that transcriptional factor AP-1 plays a functional role in P. gingivalis fimbria-stimulated bone resorption via endogenous IL-1 beta in the mouse calvarial system.

Protein kinase c-dependent pathway is critical for the production of pro-inflammatory cytokines (TNF-alpha, IL-1beta, IL-6)

The authors hypothesized that certain PKC isoforms play an important role in the induction of pro-inflammatory cytokine (TNF-alpha, IL-1beta, IL-6) synthesis. To test this hypothesis, the cytosol-to-membrane translocation of select PKC isoforms with tested cytokine production in human monocytes cultured in vitro was correlated. It is reported that in monocytes treated with phorbol ester (PMA), translocation of PKC isoforms alpha, betaII, delta and epsilon precede cytokine synthesis. Moreover, specific inhibition of PKC translocation that occurs in the presence of Calphostin C is reflected in downstream events: lack of MAP kinases phosphorylation, loss of DNA binding ability by AP-1 transcription factor, and the reduction of pro-inflammatory cytokine synthesis. Thus, the cytosol-to-membrane translocation of PKC isoforms alpha, betaII, delta and epsilon with the subsequent activation of: (1) MAP kinases; and (2) AP-1 transcription factor, may represent critical steps in the induction of signalling cascade leading to TNF-alpha, IL-1beta, IL-6 synthesis in human monocytes.

Transcriptional modulation of the human complement factor I gene in Hep G2 cells by protein kinase C activation

This study examined the role of the protein kinase C (PKC) signalling pathway in the regulation of expression of human complement factor I (CFI) gene. The production of CFI by Hep G2 cells was enhanced in a dose- and time-dependent fashion by 12-O-tetradecanoyl-1,2-phorbol 13-acetate (TPA), a potent PKC activator. 4Alpha-phorbol didecanoate, an inactive phorbol ester, had no effect on CFI synthesis. The TPA-dependent increase in CFI secretion was correlated with an increase in CFI mRNA levels. Forskolin, a cAMP-inducing agent, augmented the TPA response. W7, an inhibitor of protein kinase A and genistein, an inhibitor of protein tyrosine kinase(s) both did not prevent the increase in CFI expression mediated by TPA. However, calphostin C, a specific inhibitor of PKC, abolished the TPA-induced increase in CFI mRNA levels. Down regulation of intracellular PKC levels by prior exposure of Hep G2 cells to a high concentration of TPA also blocked the increase in CFI mRNA levels induced by TPA suggesting that the TPA effects were mediated via activation of PKC. mRNA decay studies indicated that the half-life of CFI mRNA in TPA-induced cells was not significantly different from control. Nuclear run-on transcriptional assays on the other hand demonstrated that whereas the CFI gene is transcribed under basal conditions in Hep G2 cells, TPA induced a 3-4 fold increase in the transcription rate of CFI gene in 24 h. The transcription rate of GAPDH gene did not change, indicating that the effects were not general on gene transcription. Transient transfections of Hep G2 cells with chloramphenicol acetyltransferase reporter gene (CAT) constructs containing a series of sequential 5' deletions of the CFI promoter and CAT assays showed that the sequence between -136 and -130, containing an AP-1 consensus sequence (TGAGTCA) was required for the TPA response. This observation was substantiated by the finding that mutation of this AP-1 site to TttaTCA or TtAtcCA abolished the TPA responsiveness. The enhancement of the activity of transfected chimeric CAT constructs by TPA was abrogated by calphostin C and by pyrrolidine dithiocarbamate (an inhibitor of NF-kappaB and AP-1 transactivation). These results indicate that TPA regulation of CFI gene requires PKC signalling and is mediated by via a TPA response element (TRE) in the CFI promoter region located at -136/-130 and involves the transactivation of AP-1 and NF-kappaB transcription factors. We suggest that PKC may be one of the intracellular pathways that control CFI gene expression and that cellular processes (involving growth factors, hormones, cytokines etc.) that activate PKC may upregulate the expression of the CFI gene.

Dynamic regulation of the proinflammatory cytokine, interleukin-1beta: molecular biology for non-molecular biologists

Interleukin-1beta (IL-1beta) is a key mediator and modulator of a wide array of physiological responses important for survival. It is created by a variety of cell types, including immune cells, glia, and neurons. It is a very potent biological molecule, acting both at the periphery as well as within the central nervous system. The production and release of IL-1beta is tightly regulated by far more complex processes than previously thought. An appreciation of this complexity is necessary for proper interpretation of apparent contradictions in the literature where different aspects of IL-1beta expression are measured. Given that many researchers are not molecular biologists by training, yet need an appreciation of the controls that regulate the function of key proteins such as IL-1beta, this review is aimed at both: (a) clarifying the multiple levels at which IL-1beta production is modulated and (b) using IL-1beta regulation to explain the dynamics of gene regulation to non-molecular biologists. Three major topics will be discussed. First, regulation of IL-1beta production will be examined at every level from extracellular signals that trigger gene activation through release of active protein into the extracellular fluid. Second, regulation of IL-1beta bioavailability and bioactivity will be discussed. This section examines the fact that even after IL-1beta is released, it may or may not be able to exert a biological action due to multiple modulatory factors. Last is the introduction of the idea that IL-1beta regulation is, at times, beyond the direct control of host; that is, when IL-1beta production becomes dysregulated by pathogens.

Limited role of ceramide in lipopolysaccharide-mediated mitogen-activated protein kinase activation, transcription factor induction, and cytokine release

The involvement of ceramide in lipopolysaccharide-mediated activation of mouse macrophages was studied. Lipopolysaccharide, cell-permeable ceramide analogs, and bacterial sphingomyelinase led to phosphorylation of the extracellular signal-regulated kinases, c-Jun NH2-terminal kinases, and p38 kinase and induced AP-1 DNA binding in C3H/OuJ (Lpsn) but not in C3H/HeJ (Lpsd) macrophages. Lipopolysaccharide and ceramide mimetics showed distinct kinetics of mitogen-activated protein kinase phosphorylation and AP-1 induction and activated AP-1 complexes with different subunit compositions. Lipopolysaccharide-activated AP-1 consisted of c-Fos, Jun-B, Jun-D, and c-Jun, while C2-ceramide induced Jun-D and c-Jun only. Lipopolysaccharide and, less potently, C2-ceramide or sphingomyelinase, stimulated AP-1-dependent reporter gene transcription in RAW 264.7 cells. Unlike lipopolysaccharide, C2-ceramide failed to activate NF-kappaB and did not induce production of tumor necrosis factor or interleukin-6. The lipopolysaccharide antagonist, Rhodobacter sphae-roides diphosphoryl lipid A, inhibited lipopolysaccharide activation of NF-kappaB and AP-1 but did not block C2-ceramide-induced AP-1. Pretreatment of C3H/OuJ macrophages with C2-ceramide greatly diminished AP-1 induction following subsequent C2-ceramide stimulation. However, lipopolysaccharide-induced transcription factor activation and cytokine release were not influenced. In contrast, lipopolysaccharide pretreatment inhibited both lipopolysaccharide- and C2-ceramide-mediated responses. Thus, ceramide partially mimics lipopolysaccharide in activating the mitogen-activated protein kinases and AP-1 but not in mediating NF-kappaB induction or cytokine production, suggesting a limited role in lipopolysaccharide signaling.

Activation of protein kinase A by dibutyryl cAMP treatment of NIH 3T3 cells inhibits proliferation but fails to induce Ser-133 phosphorylation and transcriptional activation of CREB

The cAMP analogue dibutyryl cAMP (dbcAMP) is often used to activate the protein kinase A pathway and to study the expression of cAMP-responsive genes. Here we show that in NIH 3T3 cells dbcAMP is able to activate PKA, but fails to stimulate expression of the cAMP-inducible c-fos gene. Co-expression of A-kinase anchoring protein 75, previously shown to amplify cAMP signalling and to stimulate c-fos expression, could not restore cAMP responsiveness of the c-fos promoter. DbcAMP-induced activation of PKA may result in poor translocation of the catalytic sub-units of PKA to the nucleus, indicated by the lack of both Ser-133 phosphorylation of the cAMP-response element binding factor CREB and stimulation of the transcriptional activity of this factor. DbcAMP treatment, however, inhibited cell proliferation. These results suggest that cAMP-mediated inhibition of proliferation may be independent of translocation of the catalytic sub-units into the nucleus.

Interleukin-1 beta, interleukin-18, and the interleukin-1 beta converting enzyme

When injected intravenously into humans and animals, interleukin-1 beta (IL-1 beta) is perhaps the most potent of the endogenous pyrogens. However, IL-1 beta is initially synthesized as a relatively inactive precursor molecule (proIL-1 beta) which lacks a signal peptide and hence remains inside the cell. To be active as a fever-producing molecule, proIL-1 beta must first be processed to an active mature molecule and secreted. Although several enzymes associated with inflammatory tissues are capable of processing proIL-1 beta into an active molecule in the extracellular compartment, the IL-1 beta converting enzyme (ICE, also called caspase-1) cuts intracellular proIL-1 beta after the aspartic acid residue in position 116, resulting in a highly active mature IL-1 beta that is secreted into the extracellular space. IL-18 is also initially synthesized as an inactive precursor molecule (proIL-18) lacking a signal peptide. IL-18 is a member of the IL-1 family, and like IL-1 beta, proIL-18 is cleaved by ICE to yield an active molecule. However, unlike IL-1 beta, IL-18 is not an endogenous pyrogen following intraperitoneal injection into mice. Nevertheless, IL-18 may contribute to inflammation and fever because IL-18 is a potent inducer of tumor necrosis factor, chemokines, and interferon-gamma production.

Interleukin-1, interleukin-1 receptors and interleukin-1 receptor antagonist

IL-1 (IL-1 alpha or IL-1 beta) is the prototypic "multifunctional" cytokine. Unlike the lymphocyte and colony stimulating growth factors, IL-1 affects nearly every cell type, and often in concert with other cytokines or small mediator molecules. Although some lymphocyte and colony stimulating growth factors may be therapeutically useful, IL-1 is a highly inflammatory cytokine and the margin between clinical benefit and unacceptable toxicity in humans is exceedingly narrow. In contrast, agents that reduce the production and/or activity of IL-1 are likely to have an impact on clinical medicine. In support of this concept, there is growing evidence that the production and activity of IL-1, particularly IL-1 beta, are tightly regulated events as if nature has placed specific "road blocks" to reduce the response to IL-1 during disease. In addition to controlling gene expression, synthesis and secretion, this regulation extends to surface receptors, soluble receptors and a receptor antagonist. Investigators have studied how production of the different members of the IL-1 family is controlled, the various biological activities of IL-1, the distinct and various functions of the IL-1 receptor (IL-1R) family and the complexity of intracellular signaling. Mice deficient in IL-1 beta, IL-1 beta converting enzyme (ICE) and IL-1R type I have also been studied. Humans have been injected with IL-1 (either IL-1 alpha or IL-1 beta) for enhancing bone marrow recovery and for cancer treatment. The IL-1 specific receptor antagonist (IL-1Ra) has also been tested in clinical trials.

Interleukin-1

Interleukin-1 (IL-1) is the prototypic pro-inflammatory cytokine. There are two forms of IL-1, IL-1alpha and IL-1beta and in most studies, their biological activities are indistinguishable. IL-1 affects nearly every cell type, often in concert with another pro-inflammatory cytokine, tumor necrosis factor (TNF). Although IL-1 can upregulate host defenses and function as an immunoadjuvant, IL-1 is a highly inflammatory cytokine. The margin between clinical benefit and unacceptable toxicity in humans is exceedingly narrow. In contrast, agents that reduce the production and/or activity of IL-1 are likely to have an impact on clinical medicine. The synthesis, processing, secretion and activity of IL-1, particularly IL-1beta, are tightly regulated events. A unique aspect of cytokine biology is the naturally occurring IL-1 receptor antagonist (IL-1Ra). IL-1Ra is structurally similar to IL-1beta but lacking agonist activity is used in clinical trials to reduce disease severity. In addition, regulation of IL-1 activity extends to low numbers of surface receptors, circulating soluble receptors and a cell surface "decoy" receptor to down-regulate responses to IL-1beta. This review updates the current knowledge on IL-1.

TNFalpha cooperates with the protein kinase A pathway to synergistically increase HIV-1 LTR transcription via downstream TRE-like cAMP response elements

Activating protein-1 (AP-1) binding TPA responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the HIV-1 long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind both AP-1 and CREB/ATF transcription factors. Recently, we demonstrated that the DSE are also cAMP-responsive elements (CRE), since they mediated activation signals elicited by cholera toxin (Ctx), a potent activator of the cAMP-dependent protein kinase A (PKA) signal transduction pathway. In the present study, we demonstrate that the HIV-1 DSE can mediate the transcriptional synergy elicited by the combination of Ctx and TNFalpha. Ctx combined with TNFalpha or IL-1beta to produce a synergistic increase in p24 antigen production in U1 promonocytic cells. Transfection studies of LTR reporter constructs indicated that mutation of the DSE sites abrogated the LTR-mediated synergy induced by Ctx and TNFalpha, whereas the synergy induced by Ctx and IL-1beta was unaffected, suggesting TNFalpha and IL-1beta cooperate differently with the cAMP/PKA activation pathway to induce HIV-1 expression in U1 cells. Because the DSE are also TRE sites, we assessed the effect of the agonist combinations on AP-1-dependent transcription. TNFalpha as well as IL-1beta cooperated with Ctx to produce a synergistic activation of AP-1-mediated transcription. These data indicate that the TRE-like cAMP-responsive DSE sites within the 5'-untranslated leader can mediate the transcriptional cooperativity between TNFalpha and the cAMP/PKA pathway. Since the DSE and TRE sites cannot bind CREB/ATF homodimers, we propose a mechanism in which the HIV-1 DSE bind heterodimers composed of both AP-1 and CREB/ATF proteins.

U5 region of the human immunodeficiency virus type 1 long terminal repeat contains TRE-like cAMP-responsive elements that bind both AP-1 and CREB/ATF proteins

Activating protein-1 (AP-1) binding phorbol ester responsive elements (TRE) are located downstream of the transcription initiation site in the U5 region of the human immunodeficiency virus type-1 (HIV-1) long terminal repeat (LTR). These downstream sequence elements, termed DSE, can bind cFos and junD and transmit protein kinase C (PKC) activation signals to the LTR. Further studies suggested the DSE might also bind AP-1-related proteins of the CREB/ATF family. Since enhanced HIV-1 expression is associated with activation of the cAMP-dependent protein kinase A (PKA) signaling pathway, we determined whether binding of CREB/ATF proteins to the DSE mediate cAMP/PKA activation of the HIV-1 LTR. In the present study. DSE binding complexes in nuclear protein extracta from colonic epithelial cells are shown to contain ATF-1, ATF-2, and CREB and transfection of either an ATF-2 or PKA expressing plasmid transactivated the DSE. Cholera toxin (Ctx), a potent activator of the cAMP/PKA pathway. Increased HIV-1 virus production from a latently infected promonocytic cell line, U1. Ctx increased LTR promoter activity and increased the CREB content of DSE binding complexes. Transfection of U1 cells with a series of mutant LTR reporter constructs demonstrated that the Ctx response was in large part mediated by the DSE. The Ctx response was also mediated by a heterologous promoter containing multiple TRE sites. Nuclear protein extracts from a T-cell line infected by HIV-1 contained higher levels of CREB/ATF proteins and manifested increased CREB/ATF binding activity. Collectively, these results indicate the DSE are TRE-like cAMP responsive elements that bind both AP-1 and CREB/ATF permitting induction of the HIV-1 LTR by both PKC and PKA activation signals.

Copper and cell-oxidized low-density lipoprotein induces activator protein 1 in fibroblasts, endothelial and smooth muscle cells

The effect of cupric ion- or endothelial cell-oxidized low-density lipoproteins (LDL) on transcription factor AP1 activation was investigated by electrophoretic mobility shift assay. Both oxidized LDL induced AP1 activation in fibroblasts, endothelial and smooth muscle cells. This phenomenon was also observed in the presence of cycloheximide. alpha-Tocopherol, a lipophilic free radical scavenger, and N-acetylcysteine, an hydrophilic antioxidant, partially inhibited the stimulatory effect of Cu2+-oxidized LDL. LDL modified by the mixture of the oxygen radicals OH. and O2.-, which generated lipid peroxidation products, also initiated AP1 activation, whereas LDL modified by OH. alone, which did not lead to marked LDL lipid peroxidation, was ineffective. Thus, lipid peroxidation products seem at least partially involved in the activation mechanism. Since AP1 activity is essential for the regulation of genes involved in cell growth and differentiation, our study suggests that the oxidative stress induced by oxidized LDL might be related to the fibroproliferative response observed in the atherosclerotic plaque.

Characterization of human E4BP4, a phosphorylated bZIP factor

In this report we described the isolation of transcription factor E4BP4 by lambda gt11 expression cloning using a probe containing the CRE/ATF-like sequence located between -2764 bp and -2753 bp in the upstream regulatory region for the human IL-1 beta gene. DNaseI protection, gel mobility shift analysis, and cotransfection studies were performed to investigate the binding and functional properties of E4BP4 using IL-1 beta promoter sequences. By DNaseI footprinting, a protection pattern was generated over the CRE/ATF-like site and the flanking sequences by bacterially produced E4BP4. Competition experiment by gel shift assay indicated that E4BP4 bound specifically to CRE/ATF-like site, not NF kappa B-like site. In cotransfection studies, E4BP4 repressed promoter activity and this repression was mediated through the CRE/ATF-like site. Mutational analysis of E4BP4 suggested that the DNA binding as well as repression activities required leucine heptad repeat domain. Analysis of E4BP4 produced in Escherichia coli and Sf9 cells infected with recombinant baculovirus indicated that baculovirus produced protein showed enhanced binding to the CRE/ATF-like site compared to the E. coli-produced protein. Analysis of posttranslational modifications indicated that E4BP4 produced in Sf9 cells was phosphorylated and this phosphorylation was important for the DNA binding activity of E4BP4.