Transcriptional Regulation of Cyclooxygenase-2 Gene in Pancreatic β-Cells

2,3,7,8-tetrachlorodibenzo-p-dioxin induces multigenerational testicular toxicity and biosynthetic disorder of testosterone in BALB/C mice: Transcriptional, histopathological and hormonal determinants

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent environmental contaminant, is an endocrine disrupter with a proven reproductive toxicity in mammals. However, its effects on male fertility across generations are still elusive. The current work evaluates the toxicity of dioxin on male reproductive system in two separate groups of BALB/C mice; a group of pubertal males directly exposed to TCDD (referred to as DEmG), and a group of indirectly exposed males (referred to as IDEmG) comprises of F1, F2 and F3 males born from TCDD-exposed pregnant females. Both groups were exposed to 25 μg TCDD/kg body weight for a week. Our data show that males of TCDD-DEmG exhibited significant alterations in the expression of certain genes involved in the detoxification of TCDD and the biosynthesis of testosterone. This was accompanied with testicular pathological symptoms, including a sloughing in the germinal epithelium and a congestion of blood vessels in interstitial tissue with the presence of multinuclear cells into seminiferous tubule, with a 4-fold decline in the level of serum testosterone and reduced sperm count. Otherwise, the male reproductive toxicity across F1, F2 and F3 generations from TCDD-IDEmG was mainly characterized by: i) a reduce in body and testis weight. ii) a decrease in gene expression of steriodogenesis enzyme, e.g., AhR, CYP1A1, CYP11A1, COX1, COX2, LOX5 and LOX12. iii) a remarked and similar testicular histopathology that found for DEmG, iv) a serious decline in serum testosterone. v) a decreased male-to-female ratio. vi) a low sperm count with increasing abnormalities. Thus, pubertal or maternal exposure to TCDD provokes multigenerational male reproductive toxicity in mice, ultimately affecting the spermatogenesis and suggesting that the hormonal alternation and sperm abnormality are the most marked effects of the indirect exposure of mammalian male to TCDD.

Progesterone Receptor Serves the Ovary as a Trigger of Ovulation and a Terminator of Inflammation

Ovulation is triggered by the gonadotropin surge that induces the expression of two key genes, progesterone receptor (Pgr) and prostaglandin-endoperoxide synthase 2 (Ptgs2), in the granulosa cells of preovulatory follicles. Their gene products PGR and PTGS2 activate two separate pathways that are both essential for successful ovulation. Here, we show that the PGR plays an additional essential role: it attenuates ovulatory inflammation by diminishing the gonadotropin surge-induced Ptgs2 expression. PGR indirectly terminates Ptgs2 expression and PGE2 synthesis in granulosa cells by inhibiting the nuclear factor κB (NF-κB), a transcription factor required for Ptgs2 expression. When the expression of PGR is ablated in granulosa cells, the ovary undergoes a hyperinflammatory condition manifested by excessive PGE2 synthesis, immune cell infiltration, oxidative damage, and neoplastic transformation of ovarian cells. The PGR-driven termination of PTGS2 expression may protect the ovary from ovulatory inflammation.

Urolithin A augments angiogenic pathways in skeletal muscle by bolstering NAD+ and SIRT1

Urolithin A (UA) is a natural compound that is known to improve muscle function. In this work we sought to evaluate the effect of UA on muscle angiogenesis and identify the underlying molecular mechanisms. C57BL/6 mice were administered with UA (10 mg/body weight) for 12–16 weeks. ATP levels and NAD⁺ levels were measured using in vivo ³¹P NMR and HPLC, respectively. UA significantly increased ATP and NAD⁺ levels in mice skeletal muscle. Unbiased transcriptomics analysis followed by Ingenuity Pathway Analysis (IPA) revealed upregulation of angiogenic pathways upon UA supplementation in murine muscle. The expression of the differentially regulated genes were validated using quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC). Angiogenic markers such as VEGFA and CDH5 which were blunted in skeletal muscles of 28 week old mice were found to be upregulated upon UA supplementation. Such augmentation of skeletal muscle vascularization was found to be bolstered via Silent information regulator 1 (SIRT1) and peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1α) pathway. Inhibition of SIRT1 by selisistat EX527 blunted UA-induced angiogenic markers in C2C12 cells. Thus this work provides maiden evidence demonstrating that UA supplementation bolsters skeletal muscle ATP and NAD⁺ levels causing upregulated angiogenic pathways via a SIRT1-PGC-1α pathway.

Integrated Pathways of COX-2 and mTOR: Roles in Cell Sensing and Alzheimer's Disease

Cyclooxygenases (COX) are enzymes catalyzing arachidonic acid into prostanoids. COX exists in three isoforms: COX-1, 2, and 3. COX-1 and COX-2 have been widely studied in order to explore and understand their involvement in Alzheimer’s disease (AD), a progressive neuroinflammatory dementia. COX-2 was traditionally viewed to be expressed only under pathological conditions and to have detrimental effects in AD pathophysiology and neurodegeneration. However, an increasing number of reports point to much more complex roles of COX-2 in AD. Mammalian/mechanistic target of rapamycin (mTOR) has been considered as a hub which integrates multiple signaling cascades, some of which are also involved in AD progression. COX-2 and mTOR are both involved in environmental sensing, growth, and metabolic processes of the cell. They are also known to act in cooperation in many different cancers and thus, their role together in normal cellular functions as well as AD has been explored in this review. Some of the therapeutic approaches targeting COX-2 and mTOR in AD and cancer are also discussed.

Urolithin A Is a Dietary Microbiota-Derived Human Aryl Hydrocarbon Receptor Antagonist

Urolithins (e.g., UroA and B) are gut microbiota-derived metabolites of the natural polyphenol ellagic acid. Urolithins are associated with various health benefits, including attenuation of inflammatory signaling, anti-cancer effects and repression of lipid accumulation. The molecular mechanisms underlying the beneficial effects of urolithins remain unclear. We hypothesize that some of the human health benefits of urolithins are mediated through the aryl hydrocarbon receptor (AHR). Utilizing a cell-based reporter system, we tested urolithins for the capacity to modulate AHR activity. Cytochrome P450 1A1 (CYP1A1) mRNA levels were assessed by real-time quantitative polymerase chain reaction. Competitive ligand binding assays were performed to determine whether UroA is a direct ligand for the AHR. Subcellular AHR protein levels were examined utilizing immunoblotting analysis. AHR expression was repressed in Caco-2 cells by siRNA transfection to investigate AHR-dependency. UroA and B were able to antagonize 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced AHR-mediated transcriptional activity. Furthermore, UroA and B attenuated TCDD-mediated stimulation of CYP1A1 mRNA levels. In addition, competitive ligand binding assays characterized UroA as a direct AHR ligand. Consistent with other AHR antagonists, UroA failed to induce AHR retention in the nucleus. AHR is necessary for UroA-mediated attenuation of cytokine-induced interleukin 6 (IL6) and prostaglandin-endoperoxide synthase 2 (PTGS2) expression in Caco-2 cells. Here we identified UroA as the first dietary-derived human selective AHR antagonist produced by the gut microbiota through multi-step metabolism. Furthermore, previously reported anti-inflammatory activity of UroA may at least in part be mediated through AHR.

Adipose mTORC1 Suppresses Prostaglandin Signaling and Beige Adipogenesis via the CRTC2-COX-2 Pathway

Beige adipocytes are present in white adipose tissue (WAT) and have thermogenic capacity to orchestrate substantial energy metabolism and counteract obesity. However, adipocyte-derived signals that act on progenitor cells to control beige adipogenesis remain poorly defined. Here, we show that adipose-specific depletion of Raptor, a key component of mTORC1, promoted beige adipogenesis through prostaglandins (PGs) synthesized by cyclooxygenase-2 (COX-2). Moreover, Raptor-deficient mice were resistant to diet-induced obesity and COX-2 downregulation. Mechanistically, mTORC1 suppressed COX-2 by phosphorylation of CREB-regulated transcription coactivator 2 (CRTC2) and subsequent dissociation of CREB to cox-2 promoter in adipocytes. PG treatment stimulated PKA and promoted differentiation of progenitor cells to beige adipocytes in culture. Ultimately, we show that pharmacological inhibition or suppression of COX-2 attenuated mTORC1 inhibition-induced thermogenic gene expression in inguinal WAT in vivo and in vitro. Our study identifies adipocyte-derived PGs as key regulators of white adipocyte browning, which occurs through mTORC1 and CRTC2.

Ligand-mediated cytoplasmic retention of the Ah receptor inhibits macrophage-mediated acute inflammatory responses

The Ah receptor (AHR) has been shown to exhibit both inflammatory and anti-inflammatory activity in a context-specific manner. In vivo macrophage-driven acute inflammation models were utilized here to test whether the selective Ah receptor modulator 1-allyl-7-trifluoromethyl-1H-indazol-3-yl]-4-methoxyphenol (SGA360) would reduce inflammation. Exposure to SGA360 was capable of significantly inhibiting lipopolysaccharide (LPS)-mediated endotoxic shock in a mouse model, both in terms of lethality and attenuating inflammatory signaling in tissues. Topical exposure to SGA360 was also able to mitigate joint edema in a monosodium urate (MSU) crystal gout mouse model. Inhibition was dependent on the expression of the high-affinity allelic AHR variant in both acute inflammation models. Upon peritoneal MSU crystal exposure SGA360 pretreatment inhibited neutrophil and macrophage migration into the peritoneum. RNA-seq analysis revealed that SGA360 attenuated the expression of numerous inflammatory genes and genes known to be directly regulated by AHR in thioglycolate-elicited primary peritoneal macrophages treated with LPS. In addition, expression of the high-affinity allelic AHR variant in cultured macrophages was necessary for SGA360-mediated repression of inflammatory gene expression. Mechanistic studies revealed that SGA360 failed to induce nuclear translocation of the AHR and actually enhanced cytoplasmic localization. LPS treatment of macrophages enhanced the occupancy of the AHR and p65 to the Ptgs2 promoter, whereas SGA360 attenuated occupancy. AHR ligand activity was detected in peritoneal exudates isolated from MSU-treated mice, thus suggesting that the anti-inflammatory activity of SGA360 is mediated at least in part through AHR antagonism of endogenous agonist activity. These results underscore an important role of the AHR in participating in acute inflammatory signaling and warrants further investigations into possible clinical applications.

Editor's Highlight: Ah Receptor Activation Potentiates Neutrophil Chemoattractant (C-X-C Motif) Ligand 5 Expression in Keratinocytes and Skin

Chemokines are components of the skin microenvironment, which enable immune cell chemotaxis. Traditionally, transcription factors involved in inflammatory signaling (eg, NFκB) are important mediators of chemokine expression. To what extent xenobiotics and their associated receptors control chemokine expression is poorly understood. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor known to mediate physiological responses in the skin through the regulation of genes involved in xenobiotic metabolism, epidermal differentiation, and immunity. Here, we demonstrate that AHR activation within primary mouse keratinocytes regulates the expression of a neutrophil directing chemokine (C-X-C motif) ligand 5 (Cxcl5). AHR-mediated regulation of Cxcl5 is because of direct transcriptional activity upon treatment with AHR agonists such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Additionally, AHR mediates enhanced induction of Cxcl5 upon exposure to an agonist and the inflammatory cytokine interleukin 1 beta. This synergy is confined primarily to keratinocytes, as dermal fibroblasts did not achieve the same level of combinatorial induction. AHR-specific antagonists were able to reduce basal and induced levels of Cxcl5, demonstrating the potential for pharmacological intervention. Exposure of C57BL/6 J mice to ultraviolet (UV) light followed by topical treatment with the AHR agonist formylindolo(3,2-b)carbazole (FICZ) significantly induced Cxcl5 expression in skin compared with UV alone, and this response was absent in Ahr-/- mice. These results establish AHR as an important mediator of Cxcl5, with implications for the treatment of inflammatory skin diseases.

Cathelicidins positively regulate pancreatic β-cell functions

Cathelicidins are pleiotropic antimicrobial peptides largely described for innate antimicrobial defenses and, more recently, immunomodulation. They are shown to modulate a variety of immune or nonimmune host cell responses. However, how cathelicidins are expressed by β cells and modulate β-cell functions under steady-state or proinflammatory conditions are unknown. We find that cathelicidin-related antimicrobial peptide (CRAMP) is constitutively expressed by rat insulinoma β-cell clone INS-1 832/13. CRAMP expression is inducible by butyrate or phenylbutyric acid and its secretion triggered upon inflammatory challenges by IL-1β or LPS. CRAMP promotes β-cell survival in vitro via the epidermal growth factor receptor (EGFR) and by modulating expression of antiapoptotic Bcl-2 family proteins: p-Bad, Bcl-2, and Bcl-xL. Also via EGFR, CRAMP stimulates glucose-stimulated insulin secretion ex vivo by rat islets. A similar effect is observed in diabetes-prone nonobese diabetic (NOD) mice. Additional investigation under inflammatory conditions reveals that CRAMP modulates inflammatory responses and β-cell apoptosis, as measured by prostaglandin E2 production, cyclooxygenases (COXs), and caspase activation. Finally, CRAMP-deficient cnlp(-/-) mice exhibit defective insulin secretion, and administration of CRAMP to prediabetic NOD mice improves blood glucose clearance upon glucose challenge. Our finding suggests that cathelicidins positively regulate β-cell functions and may be potentially used for intervening β-cell dysfunction-associated diseases.

Interleukin-1β, cyclooxygenase-2, and hypoxia-inducible factor-1α in asthenozoospermia

Impaired male fertility may have a variety of causes, among which asthenozoospermia. In its etiology, several bioactive substances, such as cytokines may be involved. In this context, our aim was to evaluate the expression of interleukin-1β, cyclooxygenase-2, and hypoxia-inducible factor-1α, in spermatozoa isolated from normospermic fertile donors and asthenozoospermic infertile patients. We evaluated twenty-eight infertile patients affected by idiopathic asthenozoospermia and twenty-three normospermic fertile donors, age-matched. Sperm parameters were evaluated; immunohistochemical analysis and enzyme-linked immunosorbent assay were then performed in isolated spermatozoa. Spermatozoa from the asthenozoospermic group presented an increased expression of IL-1β, COX-2, and HIF-1α compared with the normospermic fertile subjects. Our results can lead us to speculate that the increased expression of these substances may influence sperm motility. Nevertheless, further studies are needed in order to assess whether these bioactive mediators have a potential relevance as targets in future therapeutic strategies for the treatment of male infertility.

Inhibitory G proteins and their receptors: emerging therapeutic targets for obesity and diabetes

The worldwide prevalence of obesity is steadily increasing, nearly doubling between 1980 and 2008. Obesity is often associated with insulin resistance, a major risk factor for type 2 diabetes mellitus (T2DM): a costly chronic disease and serious public health problem. The underlying cause of T2DM is a failure of the beta cells of the pancreas to continue to produce enough insulin to counteract insulin resistance. Most current T2DM therapeutics do not prevent continued loss of insulin secretion capacity, and those that do have the potential to preserve beta cell mass and function are not effective in all patients. Therefore, developing new methods for preventing and treating obesity and T2DM is very timely and of great significance. There is now considerable literature demonstrating a link between inhibitory guanine nucleotide-binding protein (G protein) and G protein-coupled receptor (GPCR) signaling in insulin-responsive tissues and the pathogenesis of obesity and T2DM. These studies are suggesting new and emerging therapeutic targets for these conditions. In this review, we will discuss inhibitory G proteins and GPCRs that have primary actions in the beta cell and other peripheral sites as therapeutic targets for obesity and T2DM, improving satiety, insulin resistance and/or beta cell biology.

Upregulation of COX-2/PGE2 by ET-1 mediated through Ca2+-dependent signals in mouse brain microvascular endothelial cells

Endothelin-1 (ET-1), a proinflammatory mediator, is elevated in the regions of several brain inflammatory disorders, implying that ET-1 may contribute to inflammatory responses. The deleterious effects of ET-1 on brain endothelial cells may aggravate brain inflammation mediated through the upregulation of cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) system. However, the signaling mechanisms underlying ET-1-induced COX-2 expression in mouse brain microvascular endothelial cells (bEnd.3 cells) remain unclear. Herein, we investigated the effects of Ca2+-dependent protein kinases on ET-1-induced COX-2 expression and PGE2 release in bEnd.3 cells. The data obtained with Western blotting, reverse transcription PCR, and intracellular Ca2+ analyses showed that ET-1-induced COX-2 expression was mediated through phosphatidylinositol-phospholipase C (PI-PLC) and phosphatidylcholine-phospholipase C (PC-PLC)/Ca2+-dependent activation of protein kinase C-alpha (PKC-α) and calmodulin kinase II (CaMKII) cascades. Next, we demonstrated that ET-1 stimulated intracellular Ca2+ increase, phoshorylation of PKC-α, CaMKII, and mitogen-activated protein kinases (MAPKs) (ERK1/2, p38 MAPK, and JNK1/2) and then activated the activating transcription factor 2 (ATF2)/activator protein 1 (AP-1) via Gq/i protein-coupled ETB receptors. Moreover, the data of chromatin immunoprecipitation and promoter reporter assay demonstrated that the activated ATF2/AP-1 and p300 bound to its corresponding binding sites within COX-2 promoter, thereby turning on COX-2 gene transcription. Finally, upregulation of COX-2 by ET-1 promoted PGE2 biosynthesis and release in these cells. Taken together, these results demonstrate that in bEnd.3 cells, Ca2+-dependent PKC-α and CaMKII linking to MAPKs, ATF2/AP-1, and p300 cascade is essential for ET-1-induced COX-2 upregulation. Understanding the mechanisms of COX-2/PGE2 system upregulated by ET-1 on brain microvascular endothelial cells may provide rational therapeutic interventions for brain injury and inflammatory diseases.

Up-regulation of COX-2/PGE2 by endothelin-1 via MAPK-dependent NF-κB pathway in mouse brain microvascular endothelial cells

Background

Endothelin-1 (ET-1) is a proinflammatory mediator and elevated in the regions of several brain injury and inflammatory diseases. The deleterious effects of ET-1 on endothelial cells may aggravate brain inflammation mediated through the regulation of cyclooxygenase-2 (COX-2)/prostaglandin E₂ (PGE₂) system in various cell types. However, the signaling mechanisms underlying ET-1-induced COX-2 expression in brain microvascular endothelial cells remain unclear. Herein we investigated the effects of ET-1 in COX-2 regulation in mouse brain microvascular endothelial (bEnd.3) cells.

Results

The data obtained with Western blotting, RT-PCR, and immunofluorescent staining analyses showed that ET-1-induced COX-2 expression was mediated through an ET_B-dependent transcriptional activation. Engagement of G_i- and G_q-protein-coupled ET_B receptors by ET-1 led to phosphorylation of ERK1/2, p38 MAPK, and JNK1/2 and then activated transcription factor NF-κB. Moreover, the data of chromatin immunoprecipitation (ChIP) and promoter reporter assay demonstrated that the activated NF-κB was translocated into nucleus and bound to its corresponding binding sites in COX-2 promoter, thereby turning on COX-2 gene transcription. Finally, up-regulation of COX-2 by ET-1 promoted PGE₂ release in these cells.

Conclusions

These results suggested that in mouse bEnd.3 cells, activation of NF-κB by ET_B-dependent MAPK cascades is essential for ET-1-induced up-regulation of COX-2/PGE₂ system. Understanding the mechanisms of COX-2 expression and PGE₂ release regulated by ET-1/ET_B system on brain microvascular endothelial cells may provide rationally therapeutic interventions for brain injury or inflammatory diseases.

Ahr2-dependence of PCB126 effects on the swim bladder in relation to expression of CYP1 and cox-2 genes in developing zebrafish

The teleost swim bladder is assumed a homolog of the tetrapod lung. Both swim bladder and lung are developmental targets of persistent aryl hydrocarbon receptor (AHR(2)) agonists; in zebrafish (Danio rerio) the swim bladder fails to inflate with exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB126). The mechanism for this effect is unknown, but studies have suggested roles of cytochrome P450 1 (CYP1) and cyclooxygenase 2 (Cox-2) in some Ahr-mediated developmental effects in zebrafish. We determined relationships between swim bladder inflation and CYP1 and Cox-2 mRNA expression in PCB126-exposed zebrafish embryos. We also examined effects on β-catenin dependent transcription, histological effects, and Ahr2 dependence of the effect of PCB126 on swim bladder using morpholinos targeting ahr2. One-day-old embryos were exposed to waterborne PCB126 or carrier (DMSO) for 24h and then held in clean water until day 4, a normal time for swim bladder inflation. The effects of PCB126 were concentration-dependent with EC(50) values of 1.4 to 2.0 nM for induction of the CYP1s, 3.7 and 5.1 nM (or higher) for cox-2a and cox-2b induction, and 2.5 nM for inhibition of swim bladder inflation. Histological defects included a compaction of the developing bladder. Ahr2-morpholino treatment rescued the effect of PCB126 (5 nM) on swim bladder inflation and blocked induction of CYP1A, cox-2a, and cox-2b. With 2nM PCB126 approximately 30% of eleutheroembryos(3) failed to inflate the swim bladder, but there was no difference in CYP1 or cox-2 mRNA expression between those embryos and embryos showing inflated swim bladder. Our results indicate that PCB126 blocks swim bladder inflation via an Ahr2-mediated mechanism. This mechanism seems independent of CYP1 or cox-2 mRNA induction but may involve abnormal development of swim bladder cells.

Expression of cyclooxygenase-1 (COX-1) and COX-2 in human male gametes from normal patients, and those with varicocele and diabetes: a potential molecular marker for diagnosing male infertility disorders

Rising rates of varicocele and diabetes mellitus (DM) pose a significant problem to human fertility. Recent studies have pointed out the impact of cyclooxygenase (COX) in the regulation of testicular function and male fertility. Prominent COX-2 expression has been described recently in the testes of infertile patients, but little is known about the role and identity of COX isoforms in human sperm under certain disease states such as varicocele and DM. We therefore examined the expression profile and ultrastructural localization of COX-1 and COX-2 concomitantly in semen samples from healthy donors, and patients with varicocele and DM. Using Western blotting assay, 'varicocele' and 'diabetic' sperm showed enhanced COX isoforms expression with respect to the 'healthy' sperm. Immunogold labeling revealed human sperm anatomical regions containing COX-1 and COX-2, confirming their increased expression in pathological samples. Our data demonstrate that both COX isoforms are upregulated in the spermatozoa of varicocele and diabetic patients, suggesting the harmful effect of the diseases also at the sperm molecular level, going beyond the abnormal morphology described to date. In conclusion, COX enzymes may possess a biological relevance in the pathogenesis and/or maintenance of male factor infertility associated with varicocele and DM, and may be considered additional molecular markers for the diagnosis of male infertility disorders.

c-Src-dependent EGF receptor transactivation contributes to ET-1-induced COX-2 expression in brain microvascular endothelial cells

Background

Endothelin-1 (ET-1) is elevated and participates in the regulation of several brain inflammatory disorders. The deleterious effects of ET-1 on endothelial cells may aggravate brain inflammation mediated through the upregulation of cyclooxygenase-2 (COX-2) gene expression. However, the signaling mechanisms underlying ET-1-induced COX-2 expression in brain microvascular endothelial cells remain unclear.

Objective

The goal of this study was to examine whether ET-1-induced COX-2 expression and prostaglandin E₂ (PGE₂) release were mediated through a c-Src-dependent transactivation of epidermal growth factor receptor (EGFR) pathway in brain microvascular endothelial cells (bEnd.3 cells).

Methods

The expression of COX-2 induced by ET-1 was evaluated by Western blotting and RT-PCR analysis. The COX-2 regulatory signaling pathways were investigated by pretreatment with pharmacological inhibitors, short hairpin RNA (shRNA) or small interfering RNA (siRNA) transfection, chromatin immunoprecipitation (ChIP), and promoter activity reporter assays. Finally, we determined the PGE₂ level as a marker of functional activity of COX-2 expression.

Results

First, the data showed that ET-1-induced COX-2 expression was mediated through a c-Src-dependent transactivation of EGFR/PI3K/Akt cascade. Next, we demonstrated that ET-1 stimulated activation (phosphorylation) of c-Src/EGFR/Akt/MAPKs (ERK1/2, p38 MAPK, and JNK1/2) and then activated the c-Jun/activator protein 1 (AP-1) via G_q/i protein-coupled ET_B receptors. The activated c-Jun/AP-1 bound to its corresponding binding sites within COX-2 promoter, thereby turning on COX-2 gene transcription. Ultimately, upregulation of COX-2 by ET-1 promoted PGE₂ biosynthesis and release in bEnd.3 cells.

Conclusions

These results demonstrate that in bEnd.3 cells, c-Src-dependent transactivation of EGFR/PI3K/Akt and MAPKs linking to c-Jun/AP-1 cascade is essential for ET-1-induced COX-2 upregulation. Understanding the mechanisms of COX-2 expression and PGE₂ release regulated by ET-1/ET_B system on brain microvascular endothelial cells may provide rational therapeutic interventions for brain injury and inflammatory diseases.

Expression of L1CAM, COX-2, EGFR, c-KIT and Her2/neu in anaplastic pancreatic cancer: putative therapeutic targets?

AIMS

Undifferentiated (anaplastic) pancreatic cancer and undifferentiated pancreatic carcinoma with osteoclast-like giant cells (giant cell tumour) are rare variants of pancreatic ductal adenocarcinoma. Representing biologically highly aggressive neoplasms, they are frequently diagnosed at an advanced stage. The response to established chemo- or radiochemotherapeutic treatment regimens is poor, and undifferentiated pancreatic cancer generally has a dismal prognosis. As additional therapeutic options have not yet been investigated in undifferentiated pancreatic cancer, the aim was to analyse the expression of putative therapeutic targets that have shown promising results in various other neoplasms.

METHODS AND RESULTS

Fifteen cases of undifferentiated pancreatic cancer (seven containing osteoclast-like giant cells) were investigated clinicopathologically and immunohistochemically for putative therapeutic targets. Whereas L1CAM, cyclooxygenase (COX)-2 and epidermal growth factor receptor (EGFR) were found to be significantly expressed in 80%, 93% and 87% of the investigated tumours, respectively, there was no substantial expression of c-kit (CD117) and there was no detectable expression of Her2/neu.

CONCLUSIONS

The expression of L1CAM, COX-2 and EGFR in the majority of undifferentiated pancreatic carcinomas suggests that they might represent targets for adjuvant therapy in anaplastic pancreatic cancer. On the other hand, c-kit and Her2/neu seem to have no relevance for the therapy of these tumours.

Cyclooxygenase-2 in oncogenesis

Compelling experimental and clinical evidence supports the notion that cyclooxygenase-2, the inducible isoform of cyclooxygenase, plays a crucial role in oncogenesis. Clinical and epidemiological data indicate that aberrant regulation of cyclooxygenase-2 in certain solid tumors and hematological malignancies is associated with adverse clinical outcome. Moreover, findings extrapolated from experimental studies in cultured tumor cells and animal tumor models indicate that cyclooxygenase-2 critically influences all stages of tumor development from tumor initiation to tumor progression. Cyclooxygenase-2 elicits cell-autonomous effects on tumor cells resulting in stimulation of growth, increased cell survival, enhanced tumor cell invasiveness, stimulation of neovascularization, and tumor evasion from the host immune system. Additionally, the oncogenic effects of cyclooxygenase-2 stem from its unique ability to impact tumor cell surroundings and create a proinflammatory environment conducive for tumor development, growth and progression. The initial enthusiasm generated by the availability of cyclooxygenase-2 selective inhibitors for cancer prevention and therapy has been lessened by the severe cardiovascular adverse side effects associated with their long-term use, as well as by the mixed results of recent clinical trials evaluating the efficacy of cyclooxygenase-2 inhibitors in adjuvant chemotherapy. Therefore, our ability to efficiently target the oncogenic effects of cyclooxygenase-2 for therapeutic and preventive purposes strictly depends on a better understanding of the spatial and temporal aspects of its activation in tumor cells along with a clearer elucidation of the signaling networks whereby cyclooxygenase-2 affects tumor cells and their interactions with the tumor microenvironment. This knowledge has the potential of leading to the identification of novel cyclooxygenase-2-dependent molecular and signaling networks that can be exploited to improve cancer prevention and therapy.

Identification of PARP-1 as one of the transcription factors binding to the repressor element in the promoter region of COX-2

Cyclooxygenase-2 (COX-2) plays important roles in the development of many disease conditions, including pancreatic β-cell dysfunction. Although the processes involved in the transcriptional regulation of COX-2 are well documented, some key elements, especially inhibitory elements, are still unknown. In our previous study, we identified a novel repressor element located in promoter region of mouse COX-2. In this study, we isolated several DNA-binding proteins from NIT-1 cells via DNA affinity chromatography; the most prominent among these proteins was poly (ADP-ribose) polymerase-1 (PARP-1). In this study, gel-supershift assays and chromatin immunoprecipitation assays showed that PARP-1 can bind to the inhibitory element -655/-632 in the promoter region of mouse COX-2 both in vitro and in vivo. Furthermore, overexpression of PARP-1 significantly inhibited promoter activity and decreased COX-2 expression. Conversely, repression of PARP-1 by RNAi upregulated COX-2 expression. These data suggest that PARP-1 plays an important role in the regulation of COX-2 expression via binding to the inhibitory element. Collectively, our findings provide new important information on the transcriptional regulation of COX-2 in pancreatic β-cells.

TCDD induced pericardial edema and relative COX-2 expression in medaka (Oryzias Latipes) embryos

Exposure to dioxin and other aryl hydrocarbon receptor (AhR) ligands results in multiple, specific developmental cardiovascular phenotypes including pericardial edema and circulatory failure in small aquarium fish models. Although phenotypes are well described, mechanistic underpinnings for such toxicities remain elusive. Here we suggest that AhR activation results in stimulation of inflammation and "eicosanoid" pathways, which contribute to the observed developmental, cardiovascular phenotypes. We demonstrate that medaka embryos exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (0.05-1 ppb) during early development result in a dose-related increase in the prevalence of pericardial edema and that this phenotype correlates with an increase in cyclooxygenase-2 (COX-2) gene expression. Those individuals exhibiting the edema phenotype had significantly greater COX-2 mRNA than their nonedematous cohort. Selective pharmacological inhibition of COX-2, with NS-398, and genetic knock down of COX-2 with a translation initiation morpholino significantly attenuated prevalence and severity of edema phenotype. Subsequently, exposures of medaka embryos to arachidonic acid (AA) resulted in recapitulation of the pericardial edema phenotype and significantly increased COX-2 expression only in those individuals exhibiting the edema phenotype compared with their nonedematous cohort. AA exposure does not result in significant induction of cytochrome P450 1A expression, suggesting that pericardial edema can be induced independent of AhR/aryl hydrocarbon receptor nuclear translocator/dioxin response element interactions. Results from this study demonstrate that developmental exposure to TCDD results in an induction of inflammatory mediators including COX-2, which contribute to the onset, and progression of heart dysmorphogenesis in the medaka model.

Aryl hydrocarbon receptor-mediated induction of the cytosolic phospholipase A(2)alpha gene by 2,3,7,8-tetrachlorodibenzo-p-dioxin in mouse hepatoma Hepa-1c1c7 cells

Upon binding to ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR) is activated to form a heterodimer with an aryl hydrocarbon receptor nuclear translocator (Arnt). This complex binds to DNA. It has been shown that the AhR bonds to a DNA sequence called the dioxin response element (DRE), which controls the expression of battery genes. It is reported that TCDD releases arachidonic acid from membrane phospholipids via activation of phospholipase A(2)s (PLA(2)s) in various cell types. Recently, we demonstrated that the TCDD-activated AhR binds to the second intron of the Pla2g4a gene, which encodes cytosolic phospholipase A(2)alpha (cPLA(2)alpha), in mouse hepatoma Hepa-1c1c7 cells. This result suggests that Pla2g4a appears to be a target gene of the AhR. In the present study, we investigated whether the transcriptional regulation of Pla2g4a is dependent on the AhR in Hepa-1c1c7 cells. Treatment of the cells with TCDD increased mRNA expression of Pla2g4a and enzymatic activity of PLA(2,) while this increased expression was not observed in AhR-defective c12 cells. After transient transfection of an Ahr gene-expressing plasmid into the c12 cells, expression of Pla2g4a was increased by TCDD. These results indicate that Pla2g4a may be a novel target gene of the AhR, and its transcriptional induction is mediated through binding of the AhR to the second intron of Pla2g4a, although this target site does not have a typical DRE sequence.

Upregulation of endogenous glutathione system by 3H-1,2-dithiole-3-thione in pancreatic RINm5F beta-cells as a novel strategy for protecting against oxidative beta-cell injury

This study was undertaken to investigate the inducibility of glutathione (GSH), glutathione reductase (GR) and glutathione peroxidase (GPx) by 3H-1,2-dithiole-3-thione (D3T) in beta-cells, and the resultant cytoprotection against oxidant injury. Incubation of the insulin-secreting RINm5F cells with D3T led to significant induction of GSH, GR and GPx. D3T-mediated induction of GSH was abolished by buthionine sulfoximine (BSO), suggesting a critical involvement of gamma-glutamylcysteine ligase (gammaGCL). Consistently, incubation of RINm5F cells with D3T resulted in increased expression of gammaGCL protein and mRNA. Pretreatment of RINm5F cells with D3T provided remarkable protection against oxidant-elicited cytotoxicity. On the other hand, depletion of cellular GSH by BSO sensitized RINm5F cells to oxidant injury. Furthermore, cotreatment of RINm5F cells with BSO to reverse D3T-mediated GSH induction abolished the cytoprotective effects of D3T on oxidant injury. Taken together, this study demonstrates that upregulation of glutathione system by D3T is effective for protecting against oxidative beta-cell injury.

Fascin-1 promoter activity is regulated by CREB and the aryl hydrocarbon receptor in human carcinoma cells

Background

Fascin is an actin-bundling protein that is absent from most normal epithelia yet is upregulated in multiple forms of human carcinoma, where its expression correlates clinically with a poor prognosis. How fascin-1 transcription is activated in carcinoma cells is largely unknown, although the hypothesis of regulation by β-catenin signaling has received attention. The question is important because of the clinical significance of fascin expression in human carcinomas.

Methodology/Principal Findings

Through comparative genomics we made an unbiased analysis of the DNA sequence of the fascin-1 promoter region from six mammalian species. We identified two regions in which highly conserved motifs are concentrated. Luciferase promoter reporter assays for the human fascin-1 promoter were carried out in fascin-positive and -negative human breast and colon carcinoma cells, and in human dermal fibroblasts that are constitutively fascin-positive. In all fascin-positive cells, the region −219/+114 that contains multiple highly conserved motifs had strong transcriptional activity. The region −2953/−1582 appeared to contain repressor activity. By examining the effects of single or multiple point mutations of conserved motifs within the −219/+114 region on transcriptional reporter activity, we identified for the first time that the conserved CREB and AhR binding motifs are major determinants of transcriptional activity in human colon carcinoma cells. Chromatin immunoprecipitations for CREB, AhR or β-catenin from extracts from fascin-positive or -negative human colon carcinoma cells identified that CREB and AhR specifically associate with the −219/+114 region of the FSCN1 promoter in fascin-positive colon carcinoma cells. An association of β-catenin was not specific to fascin-positive cells.

Conclusion

Upregulation of fascin-1 in aggressive human carcinomas appears to have a multi-factorial basis. The data identify novel roles for CREB and AhR as major, specific regulators of FSCN-1 transcription in human carcinoma cells but do not support the hypothesis that β-catenin signaling has a central role.

Expression pattern and functional relevance of epidermal growth factor receptor and cyclooxygenase-2: novel chemotherapeutic targets in pancreatic endocrine tumors?

OBJECTIVES

Pancreatic endocrine tumors represent morphologically and biologically heterogeneous neoplasms. Well-differentiated endocrine tumors (benign or of uncertain behavior) can be distinguished from well-differentiated and poorly differentiated endocrine carcinomas. Although many well-differentiated endocrine carcinomas show rather low rates of tumor growth, more than two-thirds of pancreatic endocrine carcinomas display distant metastases at the time of diagnosis. As the currently applied therapies beyond surgery only achieve partial or complete response rates of approximately 15%, additional chemotherapeutic targets are needed, especially in the therapy of inoperable and progressive pancreatic endocrine carcinomas.

METHODS

The expression of epidermal growth factor receptor (EGFR) and cyclooxygenase (COX)-2 were investigated in 110 clinically and pathomorphologically well-characterized pancreatic endocrine tumors, using immunohistochemistry and immunoblot analyses. Functional tests were performed using the human pancreas carcinoid cell line BON and the mouse insulinoma cell line beta-TC-3.

RESULTS

The expression of EGFR correlated significantly with the grade of malignancy, increasing from low rates of expression in benign tumors and tumors of uncertain behavior to high rates of expression in well- and poorly differentiated endocrine carcinomas. The expression of COX-2 was independent of the malignant potential, but was more frequently expressed in primary tumors than in metastases. The treatment of the human pancreas carcinoid cell line BON and the mouse insulinoma cell line beta-TC-3 with EGFR and COX-2 inhibitors (monotherapy and combined therapy) resulted in a significant, dose-dependent reduction of cell viability coupled with increased apoptosis.

CONCLUSIONS

Our results suggest that EGFR and COX-2 may represent useful additional chemotherapeutic targets in pancreatic endocrine tumors.

Role of the cyclooxygenase 2-thromboxane pathway in 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced decrease in mesencephalic vein blood flow in the zebrafish embryo

Previously, we reported that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) evoked developmental toxicity required activation of aryl hydrocarbon receptor type 2 (AHR2), using zebrafish embryos. However, the downstream molecular targets of AHR2 activation are largely unknown and are the focus of the present investigation. TCDD induces cyclooxygenase 2 (COX2), a rate-limiting enzyme for prostaglandin synthesis in certain cells. In the present study, we investigated the role of the COX2-thromboxane pathway in causing a specific endpoint of TCDD developmental toxicity in the zebrafish embryo, namely, a decrease in regional blood flow in the dorsal midbrain. It was found that the TCDD-induced reduction in mesencephalic vein blood flow was markedly inhibited by selective COX2 inhibitors, NS-398 and SC-236, and by a general COX inhibitor, indomethacin, but not by a selective COX1 inhibitor, SC-560. Gene knock-down of COX2 by two different types of morpholino antisense oligonucleotides, but not by their negative homologs, also protected the zebrafish embryos from mesencephalic vein circulation failure caused by TCDD. This inhibitory effect of TCDD on regional blood flow in the dorsal midbrain was also blocked by selective antagonists of the thromboxane receptor (TP). Treatment of control zebrafish embryos with a TP agonist also caused a reduction in mesencephalic vein blood flow and it too was blocked by a TP antagonist, without any effect on trunk circulation. Finally, gene knock-down of thromboxane A synthase 1 (TBXS) with morpholinos but not by the morpholinos' negative homologs provided significant protection against TCDD-induced mesencephalic circulation failure. Taken together, these results point to a role of the prostanoid synthesis pathway via COX2-TBXS-TP in the local circulation failure induced by TCDD in the dorsal midbrain of the zebrafish embryo.

Identification of a novel repressor element in the cyclo-oxygenase-2 promoter and its nuclear binding protein

Cyclo-oxygenase-2 (COX-2) has important functions in many diseases. Although its transcriptional regulation has been investigated in considerable detail, some important elements remain unknown. The aim of the present study was to demonstrate the existence of a novel repressor element in the mouse COX-2 promoter and characterize some of its binding proteins. In order to identify the repressor element, the activity of the mouse COX-2 promoter was investigated in the pancreatic beta-cell line RINm5F using a series of deletion and mutant constructs. The ability of nuclear proteins to bind to this repressor element was then determined by an electrophoretic mobility shift assay and the proteins binding to this repressor element were purified and identified by mass spectrometry. One of the nuclear proteins identified was overexpressed to examine its inhibitory effect on COX-2 promoter activity. We found a novel repressor element located from nucleotides -655 to -632 of the mouse COX-2 promoter region. Some proteins from RINm5F cell nuclear extracts bound to this element, one of which was identified as non-POU-domain-containing, octamer-binding protein (NonO). Overexpression of NonO significantly inhibited wild-type COX-2 promoter activity, but had no effect when the repressor element was mutated. In conclusion, we have demonstrated that a regulatory 'spot' is present in the COX-2 promoter. This provides additional data on COX-2 gene regulation and may provide an insight into the clinical treatment of diseases where COX-2 is highly expressed.

Recruitment of CREB1 and histone deacetylase 2 (HDAC2) to the mouse Ltbp-1 promoter regulates its constitutive expression in a dioxin receptor-dependent manner

Latent TGFbeta-binding protein 1 (LTBP-1) is a key regulator of TGFbeta targeting and activation in the extracellular matrix. LTBP-1 is recognized as a major docking molecule to localize, and possibly to activate, TGFbeta in the extracellular matrix. Despite this relevant function, the molecular mechanisms regulating Ltbp-1 transcription remain largely unknown. Previous results from our laboratory revealed that mouse embryonic fibroblasts (MEF) lacking dioxin receptor (AhR) had increased Ltbp-1 mRNA expression and elevated TGFbeta activity, suggesting that AhR repressed Ltbp-1 transcription. Here, we have cloned the mouse Ltbp-1 gene promoter and analysed its mechanism of transcriptional repression by AhR. Reporter gene assays, AhR over-expression and site-directed mutagenesis showed that basal Ltbp-1 transcription is AhR-dependent. Chromatin immunoprecipitation (ChIP) and RNA interference (RNAi) revealed that AhR regulates Ltbp-1 transcription by a mechanism involving recruitment of co-activators such as CREB1 and co-repressors such as HDAC2 to the Ltbp-1 promoter. In AhR-expressing (AhR+/+) MEF cells, the recruitment of HDAC1, 2 and 4 correlated with decreased K8H4 acetylation and impaired binding of pCREB(Ser133) to the Ltbp-1 promoter, likely maintaining a constitutive repressed state. AhR-/- MEF cells had the opposite pattern of HDACs and pCREB1(Ser133) binding to Ltbp-1 promoter, and therefore, over-expressed Ltbp-1 mRNA. In agreement, siRNA for HDAC2 increased Ltbp-1 expression and K8H4 acetylation in AhR+/+ but not in AhR-/- MEF cells. We suggest that HDAC2 binding keeps Ltbp-1 promoter repressed in AhR+/+ MEF cells, whereas in AhR-null MEF cells the absence of HDAC2 and the binding of pCREB(Ser133) allow Ltbp-1 transcription. Thus, epigenetics can contribute to constitutive Ltbp-1 repression by a mechanism requiring AhR activity.

Oligonol inhibits UVB-induced COX-2 expression in HR-1 hairless mouse skin--AP-1 and C/EBP as potential upstream targets

Oxidative stress and inflammatory tissue damage are two major events frequently implicated in carcinogenesis. Numerous polyphenolic compounds derived from plants possess antioxidant and anti-inflammatory activities and are hence effective in preventing cancer. Oligonol is a polyphenol formulation enriched with catechin-type oligomers. As an initial approach to assess the chemopreventive potential of oligonol, we have determined its effects on inflammatory as well as oxidative damage in mouse skin irradiated with UVB. Topical application of oligonol onto the dorsal skin of male HR-1 hairless mice 30 min prior to UVB exposure diminished epidermal hyperplasia and formation of 4-hydroxynonenal, a biochemical hallmark of lipid peroxidation. Topical application of oligonol also significantly inhibited UVB-induced cyclooxygenase (COX-2) expression in mouse skin. Oligonol diminished the DNA binding of activator protein-1 (AP-1) and CCAAT/enhancer binding protein (C/EBP), and the expression of C/EBPdelta in mouse skin exposed to UVB. Our study also revealed that oligonol attenuated UVB-induced catalytic activity as well as expression of p38 mitogen-activated protein (MAP) kinase. Moreover, UVB-induced phosphorylation of another upstream kinase Akt was attenuated by oligonol. Taken together, oligonol showed antioxidative and anti-inflammatory effects in UVB-irradiated mouse skin by inhibiting COX-2 expression via blockade of the activation of AP-1 and C/EBP, and upstream kinases including p38 MAP kinase and Akt.

Regulation of cyclooxygenase-2 expression by cyclic AMP

Prostaglandins (PG) regulate many biological processes, among others inflammatory reactions. Cyclooxygenases-1 and -2 (COX-1 and COX-2) catalyse PG synthesis. Since this step is rate limiting, the regulation of COX expression is of critical importance to PG biology. Contrary to COX-1, which is constitutively expressed, COX-2 expression is subject to regulation. For example, COX-2 levels are increased in inflammatory reactions. Many signalling pathways can regulate COX-2 expression, not least those involving receptors for COX products themselves. Analysis of the intracellular signal transducers involved reveals a crucial role for cAMP, albeit as a modulator rather than direct inducer. Indeed, the influence of cAMP on COX-2 expression is complex and dependent on the cell type and cellular environment. This review aims to summarise various topics related to cAMP-dependent COX-2 expression. Firstly, the main aspects of COX-2 regulation are briefly considered. Secondly, the molecular basis for COX-2 gene (post)-transcriptional regulation is reviewed. Lastly, a detailed overview of the effects of cAMP-dependent signalling on COX-2 mRNA and protein expression in various human and rodent cells is provided. There is a large number of marketed, clinical and preclinical concepts promoting the elevation of intracellular cAMP levels for therapeutic purposes (e.g., beta(2)-agonists, PG receptor agonists, phosphodiesterase inhibitors). In this respect, the role of cAMP in the regulation of COX-2 expression, especially the human enzyme, is of significant clinical importance.

Regulation of mouse Slo gene expression: multiple promoters, transcription start sites, and genomic action of estrogen

The large conductance, voltage- and Ca(2+)-activated K(+) channel plays key roles in diverse body functions influenced by estrogen, including smooth muscle and neural activities. In mouse (m), estrogen up-regulates the transcript levels of its pore-forming alpha-subunit (Slo, KCNMA1), yet the underlying genomic mechanism(s) is (are) unknown. We first mapped the promoters and regulatory motifs within the mSlo 5'-flanking sequence to subsequently identify genomic regions and mechanisms required for estrogen regulation. mSlo gene has at least two TATA-less promoters with distinct potencies that may direct mSlo transcription from multiple transcription start sites. These qualities mark mSlo as a prototype gene with promoter plasticity capable of generating multiple mRNAs and the potential to adapt to organismal needs. mSlo promoters contain multiple estrogen-responsive sequences, e.g. two quasi-perfect estrogen-responsive elements, ERE1 and ERE2, and Sp1 sites. Accordingly, mSlo promoter activity was highly enhanced by estrogen and blocked by estrogen antagonist ICI 182,780. When promoters are embedded in a 4.91-kb backbone, estrogen responsiveness involves a classical genomic mechanism, via ERE1 and ERE2, that may be complemented by Sp factors, particularly Sp1. Simultaneous but not individual ERE1 and ERE2 mutations caused significant loss of estrogen action. ERE2, which is closer to the proximal promoter, up-regulates this promoter via a classical genomic mechanism. ERE2 strategic position together with ERE1 and ERE2 independence and Sp contribution should ensure mSlo estrogen responsiveness. Thus, the mSlo gene seems to have uniquely evolved to warrant estrogen regulation. Estrogen-mediated mSlo genomic regulation has important implications on long term estrogenic effects affecting smooth muscle and neural functions.

Several transcription factors regulate COX-2 gene expression in pancreatic beta-cells

Cyclooxygenase-2 (COX-2) expression is associated with many aspects of physiological and pathological conditions, including pancreatic beta-cell dysfunction. Prostaglandin E2 (PGE2) production, as a consequence of COX-2 gene induction, has been reported to impair beta-cell function. The molecular mechanisms involved in the regulation of COX-2 gene expression are not fully understood. In this report, we used pancreatic beta-cells (RINm5F) to explore the potential transcription factors regulating COX-2 promoter activity. Using promoter screening method, we selected several transcription factors in our study. Through luciferase reporter studies, we found that these factors can regulate COX-2 promoter activity in RINm5F cells. Among these factors, cyclic AMP response-element binding protein (CREB), Ets family members Ets-1 and Elk-1 can positively regulate COX-2 promoter activity. On the contrary, signal transducer and activator of transcription 1 (STAT1) plays a negative role on COX-2 promoter. Our findings will be helpful for better understanding the transcriptional regulation of COX-2 in pancreatic beta-cells. Moreover, these transcriptional regulators of COX-2 expression will be potential targets for the prevention of beta-cell damage mediated by PGE2.

CRE-mediated transcription and COX-2 expression in the pilocarpine model of status epilepticus

Status epilepticus (SE) triggers neuronal death, reactive gliosis and remodeling of synaptic circuitry, thus leading to profound pathological alterations in CNS physiology. These processes are, in part, regulated by the rapid upregulation of both cytotoxic and cytoprotective genes. One pathway that may couple SE to transcriptionally dependent alterations in CNS physiology is the CREB (cAMP response element-binding protein)/CRE (cAMP response element) cascade. Here, we utilized the pilocarpine model of SE on a mouse strain transgenic for a CRE-reporter construct (beta-galactosidase) to begin to characterize how seizure activity regulates the activation state of the CREB/CRE pathway in both glia and neurons of the hippocampus. SE triggered a rapid (4-8 h post-SE) but transient increase in CRE-mediated gene expression in the neuronal sublayers. In contrast to neurons, SE induced a lasting increase (up to 20 days) in CRE-mediated transcription in both reactive astrocytes and microglia. CRE-mediated gene expression correlated with expression of the pro-inflammatory enzyme cyclooxygenase-2 (COX-2). To examine the role of CREB in SE-induced COX-2 expression, we generated a transgenic mouse strain that expresses A-CREB, a potent repressor of CREB-dependent transcription. In these animals, the capacity of SE to stimulate COX-2 expression was markedly attenuated, indicating that CREB is a key intermediate in SE-induced COX-2 expression. Collectively these data show that SE triggers two waves of CREB-mediated gene expression, a transient wave in neurons and a long-lasting wave in reactive glial cells, and that CREB couples SE to COX-2 expression.

Harpagoside suppresses lipopolysaccharide-induced iNOS and COX-2 expression through inhibition of NF-kappa B activation

Preparations of Harpagophytum procumbens, known as devil's claw, are used as an adjunctive therapy for the treatment of pain and osteoarthritis. Pharmacological evaluations have proven the effectiveness of this herbal drug as an anti-inflammatory and analgesic agent. The present study has investigated the mechanism of action of harpagoside, one of the major components of Harpagophytum procumbens, using human HepG2 hepatocarcinoma and RAW 264.7 macrophage cell lines. Harpagoside inhibited lipopolysaccharide-induced mRNA levels and protein expression of cyclooxygenase-2 and inducible nitric oxide in HepG2 cells. These inhibitions appeared to correlate with the suppression of NF-kappaB activation by harpagoside, as pre-treating cells with harpagoside blocked the translocation of NF-kappaB into the nuclear compartments and degradation of the inhibitory subunit IkappaB-alpha. Furthermore, harpagoside dose-dependently inhibited LPS-stimulated NF-kappaB promoter activity in a gene reporter assay in RAW 264.7 cells, indicating that harpagoside interfered with the activation of gene transcription. These results suggest that the inhibition of the expression of cyclooxygenase-2 and inducible nitric oxide by harpagoside involves suppression of NF-kappaB activation, thereby inhibiting downstream inflammation and subsequent pain events.

Inhibitory effects of the extracts of Sutherlandia frutescens (L.) R. Br. and Harpagophytum procumbens DC. on phorbol ester-induced COX-2 expression in mouse skin: AP-1 and CREB as potential upstream targets

Numerous anti-inflammatory agents have been shown to exert chemopreventive activity by targeting cyclooxygenase (COX)-2, a rate-limiting enzyme involved in the inflammatory process. Sutherlandia frutescens (L.) R. Br. and Harpagophytum procumbens DC., which are commonly known as Cancer bush (CB) and Devil's claw (DC), respectively, have long been used in South Africa for the management of pain and inflammation. In the present study, we investigated the effects of methanolic extracts of CB and DC on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced COX-2 expression in mouse skin. Topical application of both extracts inhibited TPA-induced COX-2 expression. As an underlying mechanism of COX-2 inhibition, these extracts diminished TPA-stimulated catalytic activity of extracellular signal-regulated protein kinase (ERK), which is known to regulate the activation of eukaryotic transcription factors mediating COX-2 induction. While TPA-induced activation of nuclear factor-(kappa)B remained unaffected by both extracts, they inhibited TPA-induced activation of activator protein-1 (AP-1) and attenuated the expression of its key component c-Fos. In another study, topical application of TPA induced DNA binding of cyclic AMP response element binding (CREB) protein in mouse skin in vivo, which was abrogated by pretreatment with either CB or DC.