Expression of cyclooxygenase-2 in rat vascular smooth muscle cells is unrelated to nuclear factor-kappaB activation

Calpain inhibitor MDL28170 improves the transplantation-mediated therapeutic effect of bone marrow-derived mesenchymal stem cells following traumatic brain injury

Background

Studies have shown that transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) protects against brain damage. However, the low survival number of transplanted BMSCs remains a pertinent challenge and can be attributed to the unfavorable microenvironment of the injured brain. It is well known that calpain activation plays a critical role in traumatic brain injury (TBI)-mediated inflammation and cell death; previous studies showed that inhibiting calpain activation is neuroprotective after TBI. Thus, we investigated whether preconditioning with the calpain inhibitor, MDL28170, could enhance the survival of BMSCs transplanted at 24 h post TBI to improve neurological function.

Methods

TBI rat model was induced by the weight-drop method, using the gravitational forces of a free falling weight to produce a focal brain injury. MDL28170 was injected intracranially at the lesion site at 30 min post TBI, and the secretion levels of neuroinflammatory factors were assessed 24 h later. BMSCs labeled with green fluorescent protein (GFP) were locally administrated into the lesion site of TBI rat brains at 24 h post TBI. Immunofluorescence and histopathology were performed to evaluate the BMSC survival and the TBI lesion volume. Modified neurological severity scores were chosen to evaluate the functional recovery. The potential mechanisms by which MDL28170 is involved in the regulation of inflammation signaling pathway and cell apoptosis were determined by western blot and immunofluorescence staining.

Results

Overall, we found that a single dose of MDL28170 at acute phase of TBI improved the microenvironment by inhibiting the inflammation, facilitated the survival of grafted GFP-BMSCs, and reduced the grafted cell apoptosis, leading to the reduction of lesion cavity. Furthermore, a significant neurological function improvement was observed when BMSCs were transplanted into a MDL28170-preconditioned TBI brains compared with the one without MDL28170-precondition group.

Conclusions

Taken together, our data suggest that MDL28170 improves BMSC transplantation microenvironment and enhances the neurological function restoration after TBI via increased survival rate of BMSCs. We suggest that the calpain inhibitor, MDL28170, could be pursued as a new combination therapeutic strategy to advance the effects of transplanted BMSCs in cell-based regenerative medicine.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1210-4) contains supplementary material, which is available to authorized users.

Increased dietary sodium induces COX2 expression by activating NFκB in renal medullary interstitial cells

High salt diet induces renal medullary cyclooxygenase 2 (COX2) expression. Selective blockade of renal medullary COX2 activity in rats causes salt-sensitive hypertension, suggesting a role for renal medullary COX2 in maintaining systemic sodium balance. The present study characterized the cellular location of COX2 induction in the kidney of mice following high salt diet and examined the role of NFκB in mediating this COX2 induction in response to increased dietary salt. High salt diet (8 % NaCl) for 3 days markedly increased renal medullary COX2 expression in C57Bl/6 J mice. Co-immunofluorescence using a COX2 antibody and antibodies against aquaporin-2, ClC-K, aquaporin-1, and CD31 showed that high salt diet-induced COX2 was selectively expressed in renal medullary interstitial cells. By using NFκB reporter transgenic mice, we observed a sevenfold increase of luciferase activity in the renal medulla of the NFκB-luciferase reporter mice following high salt diet, and a robust induction of enhanced green fluorescent protein (EGFP) expression mainly in renal medullary interstitial cells of the NFκB-EGFP reporter mice following high salt diet. Treating high salt diet-fed C57Bl/6 J mice with selective IκB kinase inhibitor IMD-0354 (8 mg/kg bw) substantially suppressed COX2 induction in renal medulla, and also significantly reduced urinary prostaglandin E2 (PGE2). These data therefore suggest that renal medullary interstitial cell NFκB plays an important role in mediating renal medullary COX2 expression and promoting renal PGE2 synthesis in response to increased dietary sodium.

The influence of COX-2 single nucleotide polymorphisms on abdominal aortic aneurysm development and the associated inflammation

INTRODUCTION

Cyclooxygenase (COX)-2 influences cardiovascular disease and serum concentration of high-sensitivity C-reactive protein (hsCRP). The study purpose was to determine the influence of single nucleotide polymorphisms (SNPs) of the COX-2 gene on abdominal aortic aneurysm (AAA) development and serum hsCRP concentrations.

PATIENTS AND METHODS

Patients with AAA and disease-free controls were recruited. High-sensitivity C-reactive protein was measured by an enzyme-linked immunosorbent assay (ELISA) test. The distributions of COX-2 SNPs were investigated (rs20417 and rs4648307). The influence of the COX-2 SNPs on the hsCRP serum concentration was assessed.

RESULTS

A total of 230 patients with AAA and 279 controls were included. No difference was found in the genotype distribution of the COX-2 SNPs rs20417 (P = .26) and rs4648307 (P = .90). They did not influence the hsCRP concentration (P = .24 and P = .61, respectively). Haplotype analysis of COX-2 SNPs revealed no difference.

CONCLUSION

These COX-2 SNPs do not play any role in AAA development and do not influence serum hsCRP. These results differentiate AAA development from atherosclerotic diseases.

Protein Never in Mitosis Gene A Interacting-1 regulates calpain activity and the degradation of cyclooxygenase-2 in endothelial cells

Background

The peptidyl-proline isomerase, Protein Never in Mitosis Gene A Interacting-1 (PIN1), regulates turnover of inducible nitric oxide synthase (iNOS) in murine aortic endothelial cells (MAEC) stimulated with E. coli endotoxin (LPS) and interferon-γ (IFN). Degradation of iNOS was reduced by a calpain inhibitor, suggesting that PIN1 may affect induction of other calpain-sensitive inflammatory proteins, such as cyclooxygenase (COX)-2, in MAEC.

Methods

MAEC, transduced with lentivirus encoding an inactive control short hairpin (sh) RNA or one targeting PIN1 that reduced PIN1 by 85%, were used. Cells were treated with LPS/IFN, calpain inhibitors (carbobenzoxy-valinyl-phenylalaninal (zVF), PD150606), cycloheximide and COX inhibitors to determine the effect of PIN1 depletion on COX-2 and calpain.

Results

LPS or IFN alone did not induce COX-2. However, treatment with 10 μg LPS plus 20 ng IFN per ml induced COX-2 protein 10-fold in Control shRNA MAEC. Induction was significantly greater (47-fold) in PIN1 shRNA cells. COX-2-dependent prostaglandin E2 production increased 3-fold in KD MAEC, but did not increase in Control cells. The additional increase in COX-2 protein due to PIN1 depletion was post-transcriptional, as induction of COX-2 mRNA by LPS/IFN was the same in cells containing or lacking PIN1. Instead, the loss of COX-2 protein, after treatment with cycloheximide to block protein synthesis, was reduced in cells lacking PIN1 in comparison with Control cells, indicating that degradation of the enzyme was reduced. zVF and PD150606 each enhanced the induction of COX-2 by LPS/IFN. zVF also slowed the loss of COX-2 after treatment with cycloheximide, and COX-2 was degraded by exogenous μ-calpain in vitro. In contrast to iNOS, physical interaction between COX-2 and PIN1 was not detected, suggesting that effects of PIN1 on calpain, rather than COX-2 itself, affect COX-2 degradation. While cathepsin activity was unaltered, depletion of PIN1 reduced calpain activity by 55% in comparison with Control shRNA cells.

Conclusion

PIN1 reduced calpain activity and slowed the degradation of COX-2 in MAEC, an effect recapitulated by an inhibitor of calpain. Given the sensitivity of COX-2 and iNOS to calpain, PIN1 may normally limit induction of these and other calpain substrates by maintaining calpain activity in endothelial cells.

Lidocaine attenuates lipopolysaccharide-induced acute lung injury through inhibiting NF-kappaB activation

BACKGROUND AND OBJECTIVES

Lidocaine has been reported to attenuate the inflammatory response in addition to its anesthetic activity, but the mechanisms are poorly understood. The objective of this study is to determine if lidocaine prior to endotoxemia diminishes pulmonary dysfunction by blocking the NF-kappaB activation.

METHODS

Rats were assigned to: (1) control (0.9% sodium chloride); (2) lipopolysaccharides (LPS); (3) LPS + lidocaine 1 mg/kg; (4) LPS + lidocaine 2 mg/kg, and (5) LPS + lidocaine 4 mg/kg. The LPS and LPS + lidocaine 4 mg/kg groups were subjected to 1-, 3-, 6- and 12-hour time points. To investigate the activation of NF-kappaB, the expression of NF-kappaB in the nuclear and I kappaB alpha in the cytosol extracts were analyzed by Western blot. The concentration of TNF-alpha and IL-6 in serum was detected by ELISA. The pathologic changes of the lung were observed using HE staining.

RESULTS

After i.p. injection of LPS, the expression of NF-kappaB in the nuclear extracts was significantly increased and I kappaB alpha in the cytosol extracts was markedly decreased. The concentration of TNF-alpha and IL-6 in serum was increased. Pathological examination showed that the normal structure of the lung was destroyed badly. However, lidocaine reversed the above results.

CONCLUSION

Lidocaine attenuates LPS-induced lung injury via mechanisms involving inhibiting NF-kappaB activation and cytokine release, which implies that lidocaine may be a potential anti-inflammatory agent in endotoxemia.

Hypertonic sodium choloride and mannitol induces COX-2 via different signaling pathways in mouse cortical collecting duct M-1 cells

The kidney cortical collecting duct is an important site for the maintenance of sodium balance. Previous studies have shown that, in renal medullary cells, hypertonic stress induces expression of cyclooxygenase-2 (COX-2) via NF-kappaB activation, but little is known about COX-2 expression in response to hypertonicity in the cortical collecting duct. Therefore, we examined the mechanism of hypertonic induction of COX-2 in M-1 cells derived from mouse cortical collecting duct. Induction of COX-2 protein was detected within 6 h of treatment with hypertonic sodium chloride. The treatment also increased COX-2 mRNA accumulation in a cycloheximide-independent manner, suggesting that ongoing protein synthesis is not required for COX-2 induction. Using reporter plasmids containing 0.2-, 0.3-, and 1.5-kb fragments of the COX-2 promoter, we found that hypertonic induction of COX-2 was due to an increase in promoter activity. The COX-2-inductive effect of hypertonicity was inhibited by SB203580, indicating that the effect is mediated by p38 MAPK. Since p38 MAPK can activate NF-kappaB, we made point mutations in the NF-kappaB binding site within the COX-2 promoter. The mutations did not block the induction of COX-2 promoter activity by hypertonic sodium chloride, and hypertonic sodium chloride failed to activate NF-kappaB binding site-driven reporter gene constructs. In contrast, hypertonic mannitol activated NF-kappaB, indicating that hypertonic mannitol and hypertonic sodium chloride activate COX-2 by different mechanisms. Thus, induction of COX-2 expression in M-1 cells by hypertonic sodium chloride does not involve activation of NF-kappaB. Furthermore, the signal transduction pathways that respond to hypertonic stress vary for different osmolytes in cortical collecting duct cells.

Role of NF-kappaB in TNF-alpha-induced COX-2 expression in synovial fibroblasts from human TMJ

In the temporomandibular joint (TMJ) synovium, cyclo-oxygenase-2 (COX-2) expression has been believed to be directly related to joint pain and synovitis. Here we investigated the role of Nuclear Factor kappaB (NF-kappaB) in the regulation of COX-2 expression in synovial fibroblasts from human TMJ induced by tumor necrosis factor-alpha (TNF-alpha). By reverse-transcriptase/polymerase chain-reaction (RT-PCR) and Western blotting analysis, TNF-alpha induced a dose- and time-dependent increase in COX-2 expression. Electrophoretic mobility shift assay (EMSA) revealed that transient NF-kappaB activation in the COX-2 promoter was triggered by TNF-alpha. In parallel with transient NF-kappaB activation, the rapid translocation of NF-kappaB, particularly the p65 subunit, from the cytoplasm into the nucleus was demonstrated. Pre-treatment with pyrolidine dithiocarbamate (PDTC), one of the NF-kappaB inhibitors, prevented binding to the COX-2 promoter and expression of COX-2 protein in response to TNF-alpha. These findings indicate that activation of NF-kappaB is responsible for TNF-alpha-induced COX-2 expression in synovial fibroblasts from the TMJ.

Toll-like receptor 2 and mitogen- and stress-activated kinase 1 are effectors of Mycobacterium avium-induced cyclooxygenase-2 expression in macrophages

Understanding how pathogenic mycobacteria subvert the protective immune response is crucial to the development of strategies aimed at controlling mycobacterial infections. Prostaglandin E(2) exerts an immunosuppressive function in the context of mycobacterial infection. Because cyclooxygenase-2 (COX-2) is a rate-limiting enzyme in prostaglandin biosynthesis, there is a need to delineate the mechanisms through which pathogenic mycobacteria regulate COX-2 expression in macrophages. Our studies demonstrate that the NF-kappaB and CRE elements of the COX-2 promoter are critical to Mycobacterium avium-induced COX-2 gene expression. M. avium-triggered signaling originates at the Toll-like receptor 2 (TLR2). Ras associates with TLR2 and activates the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK), whereas tumor necrosis factor receptor-associated factor 6 (TRAF6)/transforming growth factor beta-activated kinase 1 (TAK1)-dependent signaling activates p38 MAPK. Both ERK and p38 MAPK activation converge to regulate the activation of mitogen- and stress-activated kinase 1 (MSK1). MSK1 mediates the phosphorylation of the transcription factor CREB accounting for its stimulatory effect on CRE-dependent gene expression. M. avium-triggered cytoplasmic NF-kappaB activation following IkappaB phosphorylation is necessary but not sufficient for COX-2 promoter-driven gene expression. MSK1 activation is also essential for M. avium-triggered NF-kappaB-dependent gene expression, presumably mediating nucleosomal modifications. These studies demonstrate that the nuclear kinase MSK1 is necessary in regulating the pathogen-driven expression of a gene by controlling two transcription factors. The attenuation of MSK1 may therefore have potential benefit in restricting survival of pathogenic mycobacteria in macrophages.

The signal transduction pathway that mediates the effect of interleukin-1 beta on the Na+-K+-ATPase in LLC-PK1 cells

IL-1beta reduces the activity and protein expression of Na(+)-K(+)-ATPase in rat kidney cells. The aim of the present study was to elucidate the signalling pathway involved, using the LLC-PK(1) cell line. In these cells IL-1beta caused a time and concentration-dependent decrease in the protein expression of the Na(+)-K(+)-ATPase. Inhibition of extracellular signal-regulated kinase (ERK), nuclear factor-kappaB (NF-kappaB) and cyclooxygenase (COX), but not p38 mitogen-activated kinase (MAPK), abolished the effect of the cytokine on the pump. The activation of NF-kappaB by IL-1beta was maximal at 20 min and declined thereafter. Inhibition of the transcription factor by pyrrolidinediethyldithiocarbamate (PDTC) down-regulated the ATPase. The effects of IL-1beta on the pump and NF-kappaB were prevented by the COX inhibitor indomethacin. Exogenous PGE(2) reduced protein expression of the ATPase within 15 min, even in presence of an ERK inhibitor. It is concluded that IL-1beta stimulates the mitogen and extracellular signal regulated protein kinase kinase/extracellular signal regulated protein kinase (MEK/ERK) pathway. This activates NF-kappaB, thus leading to increased COX-2 expression and PGE(2) release. PGE(2) in turn inhibits NF-kappaB and reduces the protein expression of Na(+)-K(+)-ATPase.

MAPK regulation of gene expression in airway smooth muscle

Mitogen-activated protein kinases (MAPK) are important components of signaling modules activated by neurotransmitters, cytokines, and growth factors, as well as chemical and mechanical stressors. In the airway, these external signals produce acute responses that modify smooth muscle contraction and may also induce chronic responses that modify airway structure. Both acute and chronic events in airway remodeling result from altered expression of multiple genes encoding protein mediators of cell-cell signaling, extracellular matrix remodeling, cell cycle control and intracellular signaling pathways. This review will focus on inflammatory and growth factor mediators of cell-cell signaling regulated by the ERK and p38 MAPK pathways in airway smooth muscle (ASM). These signaling mediators affect ASM tissue mechanics, cell migration, and gene expression patterns in a paracrine and autocrine fashion, although the relative importance of each MAPK pathway varies with the stimulus. These events thereby contribute to normal airway function and participate in pathological changes in ASM that accompany symptoms of asthma.

p38 MAPK and NF-kappaB mediate COX-2 expression in human airway myocytes

We have previously demonstrated that p38 and extracellular signal-regulated protein kinase (ERK) mitogen-activated protein kinases (MAPK) are components of proinflammatory induced cytokine expression in human airway myocytes. The experiments described here further these studies by examining p38 MAPK and NF-kappaB regulation of cyclooxygenase-2 (COX-2) expression in response to a complex inflammatory stimulus consisting of 10 ng/ml interleukin (IL)-1beta, tumor necrosis factor-alpha (TNF-alpha), and interferon (IFN)-gamma. COX-2 expression was induced with this stimulus in a time-dependent manner, with maximal expression seen 12-20 h after treatment. Semiquantitative RT-PCR and immunoblotting experiments demonstrate decreased COX-2 expression following treatment with the p38 MAPK inhibitor SB-203580 (25 microM) or the proteosome inhibitor MG-132 (1 microM). SB-203580 did not affect cytokine-stimulated IkappaBalpha degradation, NF-kappaB nuclear binding activity, or NF-kappaB-dependent signaling from the COX-2 promoter, indicating that p38 MAPK and NF-kappaB may affect COX-2 expression via separate signaling pathways. SB-203580, but not MG-132, also increased the initial rate of COX-2 mRNA decay, indicating p38 MAPK, but not NF-kappaB, participates in the regulation of COX-2 mRNA stability. These findings suggest that although p38 MAPK and NF-kappaB signaling regulate steady-state levels of COX-2 expression, p38 MAPK additionally affects stability of COX-2 mRNA in cytokine-stimulated human airway myocytes.

Lipopolysaccharide and interferon gamma activate nuclear factor kappa B and induce cyclo-oxygenase-2 in equine vascular smooth muscle cells

Equine endotoxaemia is an important cause of morbidity and mortality in horses caused by the interaction of bacterial lipopolysaccharide (LPS) with cells such as macrophages and vascular smooth muscle. In this study we isolated equine vascular smooth muscle from a variety of vessels and stimulated it with LPS and human interferon (hIFN)-gamma. Using reverse transcriptase polymerase chain reaction (rt-PCR) and Western blot analysis we show that cyclooxygenase-2 (COX-2) is readily expressed in equine vascular smooth muscle. Vascular smooth muscle cells produced prostaglandin E2 in response to LPS and hIFNgamma. Using similar approaches we saw very limited expression of inducible nitric oxide synthase (iNOS) in only one vascular smooth muscle preparation. LPS and IFNgamma caused translocation of the transcription factor nuclear factor kappa B (NfkappaB) to the nucleus in equine cells suggesting the limited iNOS production seen in our cells is not due to deficits in this signal transduction pathway. These data suggest that in equine vascular smooth muscle COX-2 and NfkappaB are likely to play important roles in the pathogenesis of equine endotoxaemia.

Fluid shear-induced NFkappaB translocation in osteoblasts is mediated by intracellular calcium release

Bone formation in response to exogenous mechanical loading is dependent on prostaglandin synthesis by the inducible isoform of cyclooxygenase, COX-2. While several transcription factors target the COX-2 gene, we examined the role of nuclear factor kappa B (NFkappaB) on COX-2 upregulation in osteoblasts in response to fluid shear due to its involvement in immune and inflammatory responses in other cell types. Application of 12 dyn/cm2 laminar flow to MC3T3-E1 osteoblast-like cells resulted in translocation of NFkappaB to the nucleus within 1 h of the onset of shear, with NFkappaB returning to the cytoplasm after 2 h of continuous flow. NFkappaB translocation in response to shear was inhibited by the protease inhibitor, Nalpha-p-tosyl-L-lysine chloromethylketone hydrochloride (TLCK), or a cell-permeant peptide that blocks the nuclear localization sequence (NLS) on NFkappaB. Block of NFkappaB translocation with these inhibitors blocked the shear-induced upregulation of COX-2. We found that disruption of the actin cytoskeleton with cytochalasin D or microtubules with nocodozol did not alter NFkappaB translocation in response to shear. However, addition of the intracellular Ca2+ chelator BAPTA completely blocked NFkappaB translocation. While block of Ca2+ entry with channel blockers failed to inhibit NFkappaB translocation, inhibition of phospholipase C (PLC)-induced intracellular Ca2+ release with the PLC inhibitor U73122 completely abrogated the NFkappaB response to shear. These data indicate that NFkappaB translocation to the nucleus is essential for the fluid shear-induced increase in COX-2. Further, these studies suggest that intracellular Ca2+ release, but not the cytoskeletal architecture, is important to NFkappaB translocation.

Nitric oxide, inducible nitric oxide synthase and inflammation in veterinary medicine

Inflammation is a process consisting of a complex of cytological and chemical reactions which occur in and around affected blood vessels and adjacent tissues in response to an injury caused by a physical, chemical or biological insult. Much work has been performed in the past several years investigating inducible nitric oxide synthase (NOS, EC 1.14.13.39) and nitric oxide in inflammation. This has resulted in a rapid increase in knowledge about iNOS and nitric oxide. Nitric oxide formation from inducible NOS is regulated by numerous inflammatory mediators, often with contradictory effects, depending upon the type and duration of the inflammatory insult. Equine medicine appears to have benefited the most from the increased interest in this small, inflammatory mediator. Most of the information on nitric oxide in traditional veterinary species has been produced using models or naturally occurring inflammatory diseases of this species.

TNF-alpha, inefficient by itself, potentiates IL-1beta-induced PGHS-2 expression in human pulmonary microvascular endothelial cells: requirement of NF-kappaB and p38 MAPK pathways

1: Prostaglandin H synthase-2 (PGHS-2), is an inducible enzyme involved in various inflammatory responses. We established here that interleukin-1beta (IL-1beta) but not tumour necrosis factor-alpha (TNF-alpha) increased its expression in human pulmonary microvascular endothelial cells (HPMEC). However, associated with IL-1beta, TNF-alpha greatly potentiated this enzyme induction. 2: Although unable to induce PGHS-2 expression by itself, TNF-alpha promoted a similar transcription nuclear factor-kappaB (NF-kappaB) activation to IL-1beta. This effect was more pronounced when cells were co-exposed to both cytokines. HPMEC pre-treatment with MG-132, a proteasome inhibitor, prevented NF-kappaB activation as well as more distal signalling response, indicating that NF-kappaB activation is required but not sufficient for PGHS-2 expression. 3: Both IL-1beta and TNF-alpha failed to activate c-Jun NH2-terminal kinase (JNK). In addition, PD98059, a p42/44 mitogen-activated protein kinase (MAPK) phosphorylation inhibitor, did not decrease PGHS-2 expression. However, SB 203580, a p38 MAPK inhibitor, suppressed PGHS-2 induction by IL-1beta alone or combined with TNF-alpha, demonstrating that p38 MAPK but not p42/44 MAPK or JNK cascades are required for PGHS-2 up-regulation. 4: Finally, TNF-alpha, unlike IL-1beta, was unable to promote p38 MAPK phosphorylation, indicating that the failure of TNF-alpha to induce PGHS-2 expression is linked, at least in part, to its inability to activate p38 MAPK signalling pathway. Altogether, these data enhanced our understanding of PGHS-2 regulation in HPMEC and emphasize the heterogeneity of cellular responses to proinflammatory cytokines.

Desferrioxamine, an iron chelator, upregulates cyclooxygenase-2 expression and prostaglandin production in a human macrophage cell line

Prostaglandins (PGs) play regulatory roles in a variety of physiological and pathological processes, including the immune response, cytoprotection and inflammation. Desferrioxamine (DFX), an iron chelator, is known to reduce free radical-mediated cell injury and to upregulate certain inflammatory mediators. We investigated the effects of DFX on the production of PGs and the expression of cyclooxygenase-2 (COX-2), the rate-limiting enzyme in the synthesis of PGs, using a human macrophage cell line, U937. Our results showed that COX-2 expression and PGE(2) production are upregulated by DFX treatment and that this upregulation is dependent on both COX-2 promoter activity and alteration of mRNA stability. COX-2 promoter activity may be, at least in part, mediated by activation of the extracellular signal-regulated kinase pathway. These findings suggest that iron metabolism may regulate inflammatory processes by modulating PGs as well as other inflammatory mediators.

Critical role of C/EBPdelta and C/EBPbeta factors in the stimulation of the cyclooxygenase-2 gene transcription by interleukin-1beta in articular chondrocytes

The activity of the [-831; +103] promoter of the human cyclooxygenase-2 gene in cultured rabbit chondrocytes is stimulated 2.9 +/- 0.3-fold by interleukin-1beta and this stimulation depends on [-132; -124] C/EBP binding-and [-223; -214] NF-kappaB binding-sites. The C/EBPbeta and C/EBPdelta factors bind to the [-132; -124] sequence. The [-61; -53] sequence is also recognized by C/EBPbeta and C/EBPdelta as well as USF. Mutation of the whole [-61; -53] sequence abolished the stimulation of transcription but single mutations of the C/EBP or USF site did not alter the activity of the promoter, suggesting that the factors bound to the proximal [-61; -53] sequence interact with different members of the general transcription machinery. The [-223; -214] site binds only the p50/p50 homodimer and a non-rel-related protein, but not the transcriptionally active heterodimer p50/p65. The p50/p50 homodimer could interact with the C/EBP family members bound to the [-132; -124] sequence for full stimulation of the COX-2 transcription by interleukin-1beta in chondrocytes. By contrast, the [-448; -449] sequence binds with a low affinity both the p50/p50 homodimeric and p50/p65 heterodimeric forms of NF-kappaB but has no role in the regulation of the human COX-2 promoter in chondrocytes.

Regulation of cyclooxygenase-2 expression in human osteoblastic cells by N-acetylcysteine

Cyclooxygenase (COX) plays a pivotal role in the inflammatory process of inflammatory arthropathies. Inflammatory cytokines induce COX-2 expression in osteoblasts of inflamed joints, followed by osteoclast activation. The inhibition of COX-2 expression could help prevent prostaglandin E2 secretion, followed by osteoclast activation for bone destruction and resorption. We examined whether the antioxidant N-acetylcysteine (NAC) inhibited COX-2 expression induced in the human osteoblastic cell line MG63 by interleukin-1beta (IL-1beta). According to Western blot and reverse transcription-polymerase chain reaction (RT-PCR) test results, NAC inhibited IL-1beta-induced COX-2 expression in protein and messenger RNA. We also demonstrated immunohistochemically that NAC inhibited NFkappaB nuclear translocation. These results suggested that NAC inhibited both COX-2 expression and NFkappaB nuclear translocation in MG63, which in turn indicated that NAC could inhibit the inflammatory process involved in bone resorption by regulating COX-2 expression at the level of transcription.

Biochemistry of cyclooxygenase (COX)-2 inhibitors and molecular pathology of COX-2 in neoplasia

Several types of human tumors overexpress cyclooxygenase (COX) -2 but not COX-1, and gene knockout transfection experiments demonstrate a central role of COX-2 in experimental tumorigenesis. COX-2 produces prostaglandins that inhibit apoptosis and stimulate angiogenesis and invasiveness. Selective COX-2 inhibitors reduce prostaglandin synthesis, restore apoptosis, and inhibit cancer cell proliferation. In animal studies they limit carcinogen-induced tumorigenesis. In contrast, aspirin-like nonselective NSAIDs such as sulindac and indomethacin inhibit not only the enzymatic action of the highly inducible, proinflammatory COX-2 but the constitutively expressed, cytoprotective COX-1 as well. Consequently, nonselective NSAIDs can cause platelet dysfunction, gastrointestinal ulceration, and kidney damage. For that reason, selective inhibition of COX-2 to treat neoplastic proliferation is preferable to nonselective inhibition. Selective COX-2 inhibitors, such as meloxicam, celecoxib (SC-58635), and rofecoxib (MK-0966), are NSAIDs that have been modified chemically to preferentially inhibit COX-2 but not COX-1. For instance, meloxicam inhibits the growth of cultured colon cancer cells (HCA-7 and Moser-S) that express COX-2 but has no effect on HCT-116 tumor cells that do not express COX-2. NS-398 induces apoptosis in COX-2 expressing LNCaP prostate cancer cells and, surprisingly, in colon cancer S/KS cells that does not express COX-2. This effect may due to induction of apoptosis through uncoupling of oxidative phosphorylation and down-regulation of Bcl-2, as has been demonstrated for some nonselective NSAIDs, for instance, flurbiprofen. COX-2 mRNA and COX-2 protein is constitutively expressed in the kidney, brain, spinal cord, and ductus deferens, and in the uterus during implantation. In addition, COX-2 is constitutively and dominantly expressed in the pancreatic islet cells. These findings might somewhat limit the use of presently available selective COX-2 inhibitors in cancer prevention but will probably not deter their successful application for the treatment of human cancers.

Multiple molecular penumbras after focal cerebral ischemia

Though the ischemic penumbra has been classically described on the basis of blood flow and physiologic parameters, a variety of ischemic penumbras can be described in molecular terms. Apoptosis-related genes induced after focal ischemia may contribute to cell death in the core and the selective cell death adjacent to an infarct. The HSP70 heat shock protein is induced in glia at the edges of an infarct and in neurons often at some distance from the infarct. HSP70 proteins are induced in cells in response to denatured proteins that occur as a result of temporary energy failure. Hypoxia-inducible factor (HIF) is also induced after focal ischemia in regions that can extend beyond the HSP70 induction. The region of HIF induction is proposed to represent the areas of decreased cerebral blood flow and decreased oxygen delivery. Immediate early genes are induced in cortex, hippocampus, thalamus, and other brain regions. These distant changes in gene expression occur because of ischemia-induced spreading depression or depolarization and could contribute to plastic changes in brain after stroke.

Role of mitogen-activated protein kinase cascades in mediating lipopolysaccharide-stimulated induction of cyclooxygenase-2 and IL-1 beta in RAW264 macrophages

LPS stimulation of RAW264 macrophages triggered the activation of mitogen- and stress-activated protein kinases-1 and -2 (MSK1, MSK2) and their putative substrates, the transcription factors cyclic AMP response element-binding protein (CREB) and activating transcription factor-1 (ATF1). The activation of MSK1/MSK2 was prevented by preincubating the cells with a combination of two drugs that suppress activation of the classical mitogen-activated protein kinase cascade and stress-activated protein kinase/p38, respectively, but inhibition was only partial in the presence of either inhibitor. The LPS-stimulated activation of CREB and ATF1, the transcription of the cyclooxygenase-2 (COX-2) and IL-1 beta genes (the promoters of which contain a cyclic AMP response element), and the induction of the COX-2 protein were prevented by the same drug combination, as well as by Ro 318220 or H89, potent inhibitors of MSK1/MSK2. Two other transcription factors, C/EBP beta and NF-kappa B, have been implicated in the transcription of the COX-2 gene. However, PD 98059 and/or SB 203580 did not prevent the LPS-induced increase in the level of the transcription factor C/EBP beta, and none of the four inhibitors used in this study prevented the activation of NF-kappa B. Our results demonstrate that two different mitogen-activated protein kinase cascades are rate limiting for the LPS-induced activation of CREB/ATF1 and the transcription of the COX-2 and IL-1 beta genes. They also suggest that MSK1 and MSK2 may play a role in these processes and hence are potential targets for the development of novel antiinflammatory drugs.

Transcriptional activation of the cyclooxygenase-2 gene in endotoxin-treated RAW 264.7 macrophages

Cyclooxygenase-2 (COX-2), the enzyme primarily responsible for induced prostaglandin synthesis, is an immediate early gene induced by endotoxin in macrophages. We investigated the cis-acting elements of the COX-2 5'-flanking sequence, the transcription factors and signaling pathways responsible for transcriptional activation of the COX-2 gene in endotoxin-treated murine RAW 264.7 macrophages. Luciferase reporter constructs with alterations in presumptive cis-acting transcriptional regulatory elements demonstrate that the cyclic AMP-response element and two nuclear factor interleukin-6 (CCAAT/enhancer-binding protein (C/EBP)) sites of the COX-2 promoter are required for optimal endotoxin-dependent induction. In contrast, the E-box and NF-kappaB sites are not required for endotoxin-dependent induction. Inhibition of endotoxin-induced NF-kappaB activation by expression of an inhibitor-kappaB alpha mutant does not block endotoxin-dependent COX-2 reporter activity. Overexpression of c-Jun, C/EBPbeta, and C/EBPdelta enhances induction of the COX-2 reporter, while overexpression of cyclic AMP-response element-binding protein or "dominant negative" C/EBPbeta represses COX-2 induction. In addition, endotoxin rapidly and transiently elicits c-Jun phosphorylation in RAW 264.7 macrophages. Cotransfection of the COX-2 reporter with dominant negative expression vectors shows that endotoxin-induced COX-2 gene expression requires signaling through a Ras-independent pathway involving the adapter protein ECSIT and the signaling kinases MEKK1 and JNK. In contrast, endotoxin-induced COX-2 reporter activity is not blocked by overexpression of dominant-negative forms of Raf-1, ERK1, or ERK2.

Soluble beta-amyloid peptides mediate vasoactivity via activation of a pro-inflammatory pathway

Freshly solubilized beta-amyloid (Abeta) peptides display vasoactive properties, increasing both the magnitude and the duration of endothelin-1-induced vasoconstriction. We show that Abeta vasoactivity is mediated by the stimulation of a pro-inflammatory pathway involving activation of secretory phospholipase A(2) (PLA(2)), mitogen activated protein kinase (MAPK) kinase (MEK1/2), p38 MAPK, cytosolic PLA(2), and the release of arachidonic acid. Ultimately, arachidonic acid is metabolized into proinflammatory eicosanoids via the 5-lipoxygenase and cyclooxygenase-2 (COX-2) enzymes, both of which we show to be required for A beta vasoactivity. Accordingly, p38 MAPK activity is higher in the brains of transgenic mice that overproduce A beta, and COX-2 immunoreactivity is increased in the cerebrovasculature of these transgenic animals. Taken together, our data show that freshly solubilized A beta peptides can trigger a pro-inflammatory reaction in the vasculature that can be blocked by inhibiting specific target molecules, providing the basis for novel therapeutic intervention.

Regulation of vascular smooth muscle cell proliferation by nuclear factor-kappaB and its inhibitor, I-kappaB

Proliferation of vascular smooth muscle cells (SMC) is a crucial event in the formation of atherosclerotic tissues and is regulated by nuclear transcriptional factors including nuclear factor-kappaB (NF-kappaB). We constructed a reporter gene assay to measure NF-kappaB-dependent transcriptional activity in SMC. Thrombin receptor-activating peptide (TRAP) and basic fibroblast growth factor (bFGF) stimulated SMC proliferation and rapidly enhanced the NF-kappaB transcriptional activity in a dose-dependent manner. 4-Cyano-5,5-bis-(methoxyphenyl)4-pentenoic acid (E5510) significantly inhibited SMC proliferation and also suppressed NF-kappaB transcription stimulated by TRAP and bFGF. In contrast, although tumor necrosis factor (TNF)-alpha activated NF-kappaB transcription, E5510 had no effect on TNF-alpha-induced activation. NF-kappaB was activated after the stimulation of TRAP, bFGF, and TNF-alpha in electrophoretic mobility shift assay, and E5510 suppressed the NF-kappaB activation induced by TRAP and bFGF but not the activation by TNF-alpha. Western blot analysis of I-kappaBalpha and I-kappaBbeta, inhibitors of NF-kappaB, indicated that I-kappaBalpha degradation, rather than I-kappaBbeta degradation, was important in NF-kappaB activation after the stimulation of TRAP and bFGF. PD98059, an inhibitor of extracellular signal-regulated kinase (ERK) kinase, suppressed NF-kappaB transcriptional activity and SMC proliferation. The phosphorylation of ERK1/2 was rapidly induced by TRAP and bFGF but not by TNF-alpha. These results indicate that TRAP and bFGF induced I-kappaB degradation and NF-kappaB activation through a distinct pathway from TNF-alpha and that ERK1/2 may play an important role in NF-kappaB activation induced by TRAP and bFGF.

Transcriptional regulation of the cyclooxygenase-2 gene by diverse ligands in murine osteoblasts

Osteoblasts produce prostaglandins in response to a wide variety of stimuli. Induced prostaglandin synthesis is generally the consequence of elevated cyclooxygenase-2 (COX-2) expression. Agents as diverse as serum, bFGF, PDGF, PGE(2), or [TNFalpha + IL1beta] rapidly induce expression of COX-2 protein in murine MC3T3-E1 osteogenic cells. Transient transfection studies using reporter constructs containing either wild-type COX-2 regulatory sequences or mutated cis-acting sequences linked to a luciferase reporter gene identify a CRE site and two NF-IL6 (C/EBP) sites which play important roles in the regulation of COX-2 expression in response to all these agents in osteoblasts. Induction of wild-type COX-2 reporter gene expression in MC3T3-E1 cells by all these agents involves signaling through the MEKK/JNK pathway and activation of both c-Jun and the C/EBP family of transcription factors.