Inhibition of MAP kinase kinase (MEK) results in an anti-inflammatory response in vivo

High-Content Image-Based Screening and Deep Learning for the Detection of Anti-Inflammatory Drug Leads

We developed a high-content image-based screen that utilizes the pro-inflammatory stimulus lipopolysaccharide (LPS) and murine macrophages (RAW264.7) with the goal of enabling the identification of novel anti-inflammatory lead compounds. We screened 2,259 bioactive compounds with annotated mechanisms of action (MOA) to identify compounds that block the LPS-induced phenotype in macrophages. We utilized a set of seven fluorescence microscopy probes to generate images that were used to train and optimize a deep neural network classifier to distinguish between unstimulated and LPS-stimulated macrophages. The top hits from the deep learning classifier were validated using a linear classifier trained on individual cells and subsequently investigated in a multiplexed cytokine secretion assay. All 12 hits significantly modulated the expression of at least one cytokine upon LPS stimulation. Seven of these were allosteric inhibitors of the mitogen-activated protein kinase kinase (MEK1/2) and showed similar effects on cytokine expression. This deep learning morphological assay identified compounds that modulate the innate immune response to LPS and may aid in identifying new anti-inflammatory drug leads.

Targeting MAPK/NF-κB Pathways in Anti-Inflammatory Potential of Rutaecarpine: Impact on Src/FAK-Mediated Macrophage Migration

Studies have discovered that different extracts of Evodia rutaecarpa and its phytochemicals show a variety of biological activities associated with inflammation. Although rutaecarpine, an alkaloid isolated from the unripe fruit of E. rutaecarpa, has been exposed to have anti-inflammatory properties, the mechanism of action has not been well studied. Thus, this study investigated the molecular mechanisms of rutaecarpine (RUT) in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. RUT reserved the production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-α), and interleukin (IL)-1β in the LPS-induced macrophages. RUT showed an inhibitory effect on the mitogen-activated protein kinases (MAPKs), and it also inhibited nuclear transcription factor kappa-B (NF-κB) by hindering IκBα and NF-κB p65 phosphorylation and p65 nuclear translocation. The phospho-PI3K and Akt was concentration-dependently suppressed by RUT. However, RUT not only suggestively reduced the migratory ability of macrophages and their numbers induced by LPS but also inhibited the phospho-Src, and FAK. Taken together, these results indicate that RUT participates a vital role in the inhibition of LPS-induced inflammatory processes in RAW 264.7 macrophages and that the mechanisms involve PI3K/Akt and MAPK-mediated downregulation of NF-κB signaling pathways. Notably, reducing the migration and number of cells induced by LPS via inhibiting of Src/FAK pathway was also included to the anti-inflammatory mechanism of RUT. Therefore, RUT may have potential benefits as a therapeutic agent against chronic inflammatory diseases.

Anti-Inflammatory and Antioxidant Effects of Carpesium cernuum L. Methanolic Extract in LPS-Stimulated RAW 264.7 Macrophages

A hypernomic reaction or an abnormal inflammatory process could cause a series of diseases, such as cardiovascular disease, neurodegeneration, and cancer. Additionally, oxidative stress has been identified to induce severe tissue injury and inflammation. Carpesium cernuum L. (C. cernuum) is a Chinese folk medicine used for its anti-inflammatory, analgesic, and detoxifying properties. However, the underlying molecular mechanism of C. cernuum in inflammatory and oxidative stress conditions remains largely unknown. The aim of this study was to examine the effects of a methanolic extract of C. cernuum (CLME) on lipopolysaccharide- (LPS-) induced RAW 264.7 mouse macrophages and a sepsis mouse model. The data presented in this study indicated that CLME inhibited LPS-induced production of proinflammatory mediators such as nitric oxide (NO) and prostaglandin E₂ (PGE₂) in RAW 264.7 cells. CLME treatment also reduced reactive oxygen species (ROS) generation and enhanced the expression of heme oxygenase-1 (HO-1) protein in a dose-dependent manner in the LPS-stimulated RAW 264.7 cells. Moreover, CLME treatment abolished the nuclear translocation of nuclear factor-κB (NF-κB), enhanced the activation of nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), and reduced the expression of extracellular signal-related kinase (ERK) and ERK kinase (MEK) phosphorylation in LPS-stimulated RAW 264.7 cells. These outcomes implied that CLME could be a potential antioxidant and anti-inflammatory agent.

Bis (3-bromo-4,5-dihydroxybenzyl) ether, a novel bromophenol from the marine red alga Polysiphonia morrowii that suppresses LPS-induced inflammatory response by inhibiting ROS-mediated ERK signaling pathway in RAW 264.7 macrophages

Inflammation is a pathophysiological defense response against various factors for maintaining homeostasis in the body. However, when continued excessive inflammation becomes chronic, various chronic diseases can develop. Therefore, effective treatment before chronic inflammation development is essential. Bis (3-bromo-4,5-dihydroxybenzyl) ether (BBDE, C₁₄H₁₂Br₂O₅) is a novel bromophenol isolated from the red alga Polysiphonia morrowii. The beneficial physiological functions of various bromophenols are known, but whether BBDE has beneficial physiological functions is unknown. Therefore, we first investigated whether BBDE exerts any anti-inflammatory effect. We demonstrated that BBDE inhibits inflammation by reducing inflammatory mediators, such as nitric oxide, prostaglandin E2, iNOS, COX2, and pro-inflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), in LPS-induced macrophage cells. To examine the mechanism of action by which BBDE inhibits inflammation, we confirmed its effect on signal transduction and ROS generation. BBDE selectively inhibited ERK phosphorylation in the mitogen-activated protein kinase pathways. Moreover BBDE suppressed LPS-induced ROS generation in RAW 264.7 macrophage cells. Inhibition of LPS-induced ROS generation by BBDE also caused ERK inactivation and an inflammatory reaction. Therefore, BBDE inhibits LPS-induced inflammation by inhibiting the ROS-mediated ERK signaling pathway in RAW 264.7 macrophage cells and thus can be useful for treating inflammatory diseases.

TAK-733 inhibits inflammatory neointimal formation by suppressing proliferation, migration, and inflammation in vitro and in vivo

As a potent and selective allosteric inhibitor of MEK, TAK-733 has been shown to exert anti-cancer effects for a wide range of cancers both in vitro and in vivo. However, its effects on inhibiting growth have never been investigated in the cardiovascular system, where regulation of abnormal vascular smooth muscle cell growth in neointimal hyperplasia is an important area of focus. Angiotensin II was used to mimic inflammatory neointimal hyperplasia in an in vitro environment, and balloon catheter-induced injury with an infusion of angiotensin II was used to generate an in vivo rat restenosis model under inflammatory conditions. TAK-733 exerted anti-proliferative and anti-migratory effects on human vascular smooth muscle cells. These multiple effects of TAK-733 were evaluated using various assays, such as cell cycle analysis and wound healing. Interestingly, TAK-733 did not induce apoptosis in smooth muscle cells but only reduced the proliferation rate; additionally, it did not affect EC viability. TAK-733 also exhibited anti-inflammatory activity, as observed by attenuated monocyte adhesion to smooth muscle cells via inhibition of ICAM1 and VCAM1 overexpression. The in vivo study demonstrated that neointimal hyperplasia after balloon injury and angiotensin II stimulation was suppressed by TAK-733, and downregulation of the inflammatory signal and enhanced re-endothelialization were observed. TAK-733 may have therapeutic potential for treating neointimal hyperplasia by attenuating smooth muscle cell proliferation, migration, and inflammation. Thus, TAK-733 could be a promising drug candidate for treating patients with restenosis.

Differential Inflammatory-Response Kinetics of Human Keratinocytes upon Cytosolic RNA- and DNA-Fragment Induction

Keratinocytes are non-professional immune cells contributing actively to innate immune responses partially by reacting to a wide range of molecular patterns by activating pattern recognition receptors. Cytosolic nucleotide fragments as pathogen- or self-derived trigger factors are activating inflammasomes and inducing anti-viral signal transduction pathways as well as inducing expression of inflammatory cytokines. We aimed to compare the induced inflammatory reactions in three keratinocyte cell types—normal human epidermal keratinocytes, the HaCaT cell line and the HPV-KER cell line—upon exposure to the synthetic RNA and DNA analogues poly(I:C) and poly(dA:dT) to reveal the underlying signaling events. Both agents induced the expression of interleukin-6 and tumor necrosis factor α in all cell types; however, notable kinetic and expression level differences were found. Western blot analysis revealed rapid activation of the nuclear factor κB (NF-κB), mitogen activated protein kinase and signal transducers of activator of transcription (STAT) signal transduction pathways in keratinocytes upon poly(I:C) treatment, while poly(dA:dT) induced slower activation. Inhibition of NF-κB, p38, STAT-1 and STAT-3 signaling resulted in decreased cytokine expression, whereas inhibition of mitogen-activated protein kinase kinase 1/2 (MEK1/2) signaling showed a negative feedback role in both poly(I:C)- and poly(dA:dT)-induced cytokine expression. Based on our in vitro results nucleotide fragments are able to induce inflammatory reactions in keratinocytes, but with different rate and kinetics of cytokine expression, explained by faster activation of signaling routes by poly(I:C) than poly(dA:dT).

Knowledge-guided gene prioritization reveals new insights into the mechanisms of chemoresistance

BACKGROUND

Identification of genes whose basal mRNA expression predicts the sensitivity of tumor cells to cytotoxic treatments can play an important role in individualized cancer medicine. It enables detailed characterization of the mechanism of action of drugs. Furthermore, screening the expression of these genes in the tumor tissue may suggest the best course of chemotherapy or a combination of drugs to overcome drug resistance.

RESULTS

We developed a computational method called ProGENI to identify genes most associated with the variation of drug response across different individuals, based on gene expression data. In contrast to existing methods, ProGENI also utilizes prior knowledge of protein-protein and genetic interactions, using random walk techniques. Analysis of two relatively new and large datasets including gene expression data on hundreds of cell lines and their cytotoxic responses to a large compendium of drugs reveals a significant improvement in prediction of drug sensitivity using genes identified by ProGENI compared to other methods. Our siRNA knockdown experiments on ProGENI-identified genes confirmed the role of many new genes in sensitivity to three chemotherapy drugs: cisplatin, docetaxel, and doxorubicin. Based on such experiments and extensive literature survey, we demonstrate that about 73% of our top predicted genes modulate drug response in selected cancer cell lines. In addition, global analysis of genes associated with groups of drugs uncovered pathways of cytotoxic response shared by each group.

CONCLUSIONS

Our results suggest that knowledge-guided prioritization of genes using ProGENI gives new insight into mechanisms of drug resistance and identifies genes that may be targeted to overcome this phenomenon.

ERK activation and expression of neuronal cell cycle markers in the hippocampus after entorhinal cortex lesion

Current findings suggest that neuronal cell death is frequently associated with the aberrant expression of cell cycle-regulatory proteins in postmitotic neurons. Aberrant cell cycle reentry has been implicated in diverse neurodegenerative conditions, including Alzheimer's disease (AD). Previously we reported that the appearance of cell cycle markers in postmitotic neurons of the entorhinal cortex (EC) after excitotoxic hippocampal damage is associated with the expression of phospho-tau and amyloid precursor protein (APP). However, the question of the signaling pathway involved in this cell cycle reentry remains unresolved. Differentiated neurons use the molecular mechanisms initially acquired to direct cell proliferation, such as the Ras-extracellular signal-regulated kinase (ERK1/2) pathway, to regulate synaptic plasticity. In this work we explored whether ERK1/2-related signaling might contribute to the cell cycle reentry in hippocampal neurons after a unilateral EC lesion. We showed that, within the first 24 hr after hippocampal deafferentation, numerous neurons expressed phospho-ERK1/2, concomitantly with the gradual increases in cyclin D1 and cyclin B immunoreactivity in the dentate gyrus and hilus. Several of these immunopositive cells to phospho-ERK1/2 and cyclin B in hippocampus are postmitotic neurons, insofar as they are positive to NeuN. The intracisternal administration of U0126 (an MEK inhibitor), previous to the excitotoxic lesion, decreased the activation of ERK1/2 and the expression of cyclin D1 and cyclin B in the hippocampus. The present findings support the notion that ERK1/2 plays a role in cell cycle reactivation in mature neurons efferently connected to the lesion site.

Butyrate enhancement of inteleukin-1β production via activation of oxidative stress pathways in lipopolysaccharide-stimulated THP-1 cells

Safe and effective methods for oral bacterial disinfection have been desired, since bacteria cause many infectious diseases such as dental caries, periodontal disease, and endodontic infections. Singlet oxygen (¹O₂) is attractive, because it is toxic to prokaryotic cells, but not to eukaryotic cells. We selected irradiation of titanium dioxide (TiO₂) as a source of ¹O₂, because it has been used in sunscreens and cosmetic products without complications. In order to establish the optimal oral photodynamic therapy conditions, we measured the rate of ¹O₂ formation from the irradiated anatase or rutile forms of TiO₂ using 365 or 405 nm lamps. The rate of ¹O₂ formation decreased in the following order: anatase, 365 nm > rutile, 405 nm > rutile, 365 nm > anatase, 405 nm. Therefore, we concluded that irradiation of the rutile form of TiO₂ by a 405 nm lamp is the most favorable photodynamic therapy condition, because visible light is more desirable than UV light from the viewpoint of patient safety. We also confirmed that there was no direct HO^• formation from the irradiated TiO₂.

Blocking MAPK signaling downregulates CCL21 in lymphatic endothelial cells and impairs contact hypersensitivity responses

CCL21 expression by lymphatic endothelial cells (LECs) is essential for migration of CCR7+ immune cells from skin to regional lymph nodes (LNs). We investigated the importance of mitogen-activated protein kinase (MAPK) signaling in CCL21 expression by ECs in vitro and in vivo. Normal human dermal lymphatic microvascular ECs (HMVEC-dLy) stimulated in vitro with oncostatin M (OSM) expressed high amounts of CCL21 mRNA. CCL21 protein expression by HMVEC-dLy was also markedly increased by OSM compared with unstimulated cultures. Marked phosphorylation of MAPK 44/42 was detected in HMVEC-dLy stimulated by OSM. CCL21 expression by HMVEC-dLy was blocked by a JAK inhibitor 1, JAK3 inhibitor, and U0126 (a MAPK kinase inhibitor) in vitro, all of which blocked phosphorylation of MAPK 44/42. In addition, injection of U0126 into murine skin significantly decreased CCL21 mRNA and protein expression. Moreover, injection of U0126 before sensitization decreased migration of dendritic cells to draining LNs and decreased contact hypersensitivity responses. In summary, these results suggest that the MAPK pathway is important for CCL21 expression by LECs in vitro and in vivo. Blocking MAPK signaling within skin may offer a novel approach to treatment of inflammatory skin diseases.

CTLs respond with activation and granule secretion when serving as targets for T-cell recognition

Cytotoxic T lymphocytes (CTLs) suppress T cell responses directed against their antigens regardless of their own T cell receptor (TCR) specificity. This makes the use of CTLs promising for tolerance induction in autoimmunity and transplantation. It has been established that binding of the CTL CD8 molecule to the major histocompatibility complex (MHC) class I α3 domain of the recognizing T cell must be permitted for death of the latter cell to ensue. However, the signaling events triggered in the CTL by this molecular interaction in the absence of TCR recognition have never been clarified. Here we use single-cell imaging to study the events occurring in CTLs serving as targets for recognition by specific T cells. We demonstrate that CTLs actively respond to recognition by polarizing their cytotoxic granules to the contact area, releasing their lethal cargo, and vigorously proliferating. Using CTLs from perforin knockout (KO) mice and lymphocyte specific kinase (Lck) knockdown with specific small interfering RNA (siRNA), we show that the killing of the recognizing CD8 T cell is perforin dependent and is initiated by Lck signaling in the CTL. Collectively, these data suggest a novel mechanism in which the entire cascade generally triggered by TCR engagement is "hijacked" in CTLs serving as targets for T cell recognition without TCR ligation.

Differential modulation of keratin expression by sulforaphane occurs via Nrf2-dependent and -independent pathways in skin epithelia

Treatment with the natural chemical sulforaphane (SF) ameliorates skin blistering in keratin 14 (K14)-deficient mice, correlating with the induction of K16 and K17 in the basal layer of epidermis (Kerns et al., PNAS 104:14460, 2007). Here we address the basis for the SF-mediated K16 and K17 induction in mouse epidermis in vivo. As expected, induction of K16 partly depends on the transcription factor Nrf2, which is activated by SF exposure. Strikingly, K17 induction occurs independently of Nrf2 activity and parallels the decrease in glutathione occurring shortly after epidermal exposure to SF. Pharmacological manipulation of glutathione levels in mouse epidermis in vivo alters K17 and K16 expression in the expected manner. We present findings suggesting that select MAP kinases participate in mediating the Nrf2- and glutathione-dependent alterations in K16 and K17 levels in SF-treated epidermis. These findings advance our understanding of the effect of SF on gene expression in epidermis, point to a role for glutathione in mediating some of these effects, and establish that SF induces the expression of two contiguous and highly related genes, K16 and K17, via distinct mechanisms.

Shikonin reduces oedema induced by phorbol ester by interfering with IkappaBalpha degradation thus inhibiting translocation of NF-kappaB to the nucleus

BACKGROUND AND PURPOSE

In the present paper we studied the effect of shikonin on ear oedema induced by 12-O-tetradecanoylphorbol-13-acetate (TPA), and determined the mechanisms through which shikonin might exert its topical anti-inflammatory action.

EXPERIMENTAL APPROACH

Acute ear oedema was induced in mice by topical application of TPA. The in vitro assays used macrophages RAW 264.7 cells stimulated with lipopolysaccharide. Cyclooxygenase-2, inducible nitric oxide synthase, protein kinase Calpha, extracellular signal-regulated protein kinase (ERK), phosphorylated ERK (pERK), c-Jun N-terminal kinase (JNK), pJNK, p38, p-p38, p65, p-p65, inhibitor protein of nuclear factor-kappaB (NF-kappaB) (IkappaBalpha) and pIkappaBalpha were measured by Western blotting, activation and binding of NF-kappaB to DNA was detected by reporter gene and electrophoretic mobility shift assay, respectively, and NF-kappaB p65 localization was detected by immunocytochemistry.

KEY RESULTS

Shikonin reduced the oedema (inhibitory dose 50 = 1.0 mg per ear), the expression of cyclooxygenase-2 (70%) and of inducible nitric oxide synthase (100%) in vivo. It significantly decreased TPA-induced translocation of protein kinase Calpha, the phosphorylation and activation of ERK, the nuclear translocation of NF-kappaB and the TPA-induced NF-kappaB-DNA-binding activity in mouse skin. Moreover, in RAW 264.7 cells, shikonin significantly inhibited the binding of NF-kappaB to DNA in a dose-dependent manner and the nuclear translocation of p65.

CONCLUSIONS AND IMPLICATIONS

Shikonin exerted its topical anti-inflammatory action by interfering with the degradation of IkappaBalpha, thus inhibiting the activation of NF-kappaB.

Central role of the MEK/ERK MAP kinase pathway in a mouse model of rheumatoid arthritis: potential proinflammatory mechanisms

OBJECTIVE

To evaluate the role of the MEK/ERK MAP kinase pathway in murine collagen-induced arthritis (CIA) using the selective MEK inhibitor PD184352. We examined the effects of the inhibitor in cytokine-stimulated synovial fibroblasts and in cytokine-induced arthritis in rabbits to investigate its antiinflammatory mechanisms.

METHODS

Murine CIA was used to assess the effects of the selective MEK inhibitor on paw edema, clinical scores, weight loss, histopathologic features, and joint levels of p-ERK. Western blotting and immunohistochemistry techniques were used to assess p-ERK in human and rabbit synovial fibroblasts and synovial tissue from rheumatoid arthritis (RA) patients. Interleukin-1alpha (IL-1alpha)-stimulated stromelysin production in rabbit synovial fibroblasts was assessed by enzyme-linked immunosorbent assay. A rabbit IL-1alpha-induced arthritis model was used to assess the effects of the inhibitor on IL-1alpha-induced MEK activity, stromelysin production, and cartilage degradation.

RESULTS

In the CIA model, PD184352 inhibited paw edema and clinical arthritis scores in a dose-dependent manner. Disease-induced weight loss and histopathologic changes were also significantly improved by treatment. Inhibition of disease-induced p-ERK levels in the joints was seen with the inhibitor. Levels of p-ERK in the synovium were higher in RA patients than in normal individuals. PD184352 reduced IL-1alpha-induced p-ERK levels in human RA synovial fibroblasts. The production of p-ERK and stromelysin was also inhibited in IL-1alpha-stimulated rabbit synovial fibroblasts. We observed IL-1alpha-induced p-ERK in the synovial lining, subsynovial vasculature, and articular chondrocytes. IL-1alpha-induced stromelysin production and proteoglycan loss from the articular cartilage were reduced by PD184352.

CONCLUSION

These data demonstrate the inhibition of murine CIA by PD184352, support the hypothesis that antiinflammatory activity contributes to the mechanism of action of the inhibitor, and suggest that a selective inhibitor may effectively treat RA and other inflammatory disorders.

Intrapulmonary delivery of ricin at high dosage triggers a systemic inflammatory response and glomerular damage

In view of the possibility that ricin may be used as a bioweapon against human populations, we examined the pathological consequences that occur in mice after introduction of ricin into the pulmonary system. Intratracheal instillation of a lethal dose of ricin (20 microg/100 g body weight) resulted in a hemorrhagic inflammatory response in multiple organs, accompanied by activation of mitogen-activated protein kinases, increased synthesis of proinflammatory RNA transcripts, and increased levels of circulating cytokines and chemokines. A sublethal dose of instilled ricin (2 microg/100 g body weight) induced a similar response in lungs but did not cause detectable damage in other organs. Lungs of mice that recovered from a sublethal dose of ricin displayed evidence of fibrosis and residual damage. A lethal dose of ricin caused accumulation of proinflammatory RNA transcripts and substantial damage to 28S rRNA of multiple organs, including lung, kidney, spleen, liver, and blood, demonstrating that instilled ricin gained access to the circulation. The kidneys of mice instilled with a lethal dose of ricin showed accumulation of fibrin/fibrinogen in glomerular capillaries, increased numbers of glomerular leukocytes, and impairment of kidney function. A sublethal dose of ricin failed to induce damage to 28S rRNA in kidney or other extrapulmonary organs.

SMAD3 expression is regulated by mitogen-activated protein kinase kinase-1 in epithelial and smooth muscle cells

SMAD3 is a transcription factor that mediates TGF-beta1 signaling and is known to be important in many of the cellular processes that regulate fibrosis and inflammation. Although several studies have examined SMAD3 activation, little is known about the control of SMAD3 expression. It is well established that the mitogen-activated protein kinase (MAPK) pathway is responsive to TGF-beta1 stimulation and coordinates with SMAD signaling in many cases; therefore, the hypothesis of this study is that the MAPK pathway will be involved in the regulation of SMAD3 expression. Using a SMAD3 promoter construct, we demonstrate that inhibition of either c-Jun-N-terminal kinase (JNK) or p38 activity has little effect on SMAD3 promoter function. Inhibition of mitogen-activated protein kinase kinase-1 (MEK1) with either PD98059 or UO126, however, results in a substantial dose-dependent inhibition of SMAD3 promoter activity. Further studies confirm that promoter activity correlates with protein expression by demonstrating reduced SMAD3 protein expression in A549 cells and airway smooth muscle cells after treatment with MEK1 inhibitors. Positive regulation of SMAD3 expression is also demonstrated by expression of a constitutively active (ca)-MEK1 construct, where the presence of ca-MEK1 resulted in increased SMAD3 protein expression. These data lead to the conclusion that MEK1 is an important regulator of SMAD3 expression.

FGF19 is a target for FOXC1 regulation in ciliary body-derived cells

The forkhead C1 (FOXC1) transcription factor is involved in the development and regulation of several organs, including the eye, where FOXC1 alterations cause iris, trabecular meshwork and corneal anomalies. Using nickel agarose chromatin enrichment with human anterior segment cells, we previously identified the fibroblast growth factor 19 (FGF19) locus as a gene potentially regulated by FOXC1. Here, we demonstrate that FGF19 is a direct target of FOXC1 in the eye. FOXC1 positively regulates FGF19 expression in corneal and periocular mesenchymal cells in cell culture and in zebrafish embryos. Through the FGFR4 tyrosine kinase, FGF19 promotes MAPK phosphorylation in the developing and mature cornea. During development, loss of either FOXC1 or FGF19 results in complementary, but distinct, anterior segment dysgeneses. This study reveals an important role for FOXC1 in the direct regulation of the FGF19-FGFR4-MAPK pathway to promote both the development and maintenance of anterior segment structures within the eye.

Matrix metalloproteinase expression in vein grafts: role of inflammatory mediators and extracellular signal-regulated kinases-1 and -2

Matrix metalloproteinases (MMPs) play key roles in vascular remodeling. We characterized the role of inflammatory mediators and extracellular signal-regulated kinases (ERKs) in the control of arterialized vein graft expression of MMP-9, MMP-2, and membrane-type 1-MMP (MT1-MMP) and of the tissue inhibitor of metalloproteinases-2 (TIMP-2). For this purpose we used a canine model of jugular vein to carotid artery interposition graft and analyzed the vein grafts at various postoperative times (30 min to 28 days) using the contralateral vein as a control. To study the role of ERK-1/2, veins were incubated with the mitogen-activated protein kinase kinase (MEK-1/2) inhibitor UO126 for 30 min before being grafted. Vein graft extracts were analyzed for MMPs, TIMP-2, tumor necrosis factor-alpha (TNF-alpha), polymorphonuclear neutrophil (PMN) infiltration, myeloperoxidase (MPO), and thrombin activity, and for ERK-1/2 activation. Vein graft arterialization resulted in rapid and sustained (8 h to 28 days) upregulation of vein graft-associated MMP-9, MMP-2, MT1-MMP, thrombin activity, and TNF-alpha levels with concomitant TIMP-2 downregulation. MMP-2 activation preceded MT1-MMP upregulation. PMN infiltration and vein graft-associated MPO activity increased within hours after arterialization, indicating a prompt, local inflammatory response. In cultured smooth muscle cells, both thrombin and TNF-alpha upregulated MT1-MMP expression; however, only thrombin activated MMP-2. Inhibition of ERK-1/2 activation blocked arterialization-induced upregulation of MMP-2, MMP-9, and MT1-MMP. Thus, thrombin, inflammatory mediators, and activation of the ERK-1/2 pathway control MMP and TIMP-2 expression in arterialized vein grafts.

RAGE modulates peripheral nerve regeneration via recruitment of both inflammatory and axonal outgrowth pathways

Axotomy of peripheral nerve stimulates events in multiple cell types that initiate a limited inflammatory response to axonal degeneration and simultaneous outgrowth of neurites into the distal segments after injury. We found that pharmacological blockade of RAGE impaired peripheral nerve regeneration in mice subjected to RAGE blockade and acute crush of the sciatic nerve. As our studies revealed that RAGE was expressed in axons and in infiltrating mononuclear phagocytes upon injury, we tested the role of RAGE in these distinct cell types on nerve regeneration. Transgenic mice expressing signal transduction-deficient RAGE in mononuclear phagocytes or peripheral neurons were generated and subjected to unilateral crush injury to the sciatic nerve. Transgenic mice displayed decreased functional and morphological recovery compared with littermate controls, as assessed by motor and sensory conduction velocities; and myelinated fiber density. In double transgenic mice expressing signal transduction deficient RAGE in both mononuclear phagocytes and peripheral neurons, regeneration was even further impaired, suggesting the critical interplay between RAGE-modulated inflammation and neurite outgrowth in nerve repair. These findings suggest that RAGE signaling in inflammatory cells and peripheral neurons plays an important role in plasticity of the peripheral nervous system.

Evidence for the Involvement of the Cannabinoid CB2 Receptor and Its Endogenous Ligand 2-Arachidonoylglycerol in 12-O-Tetradecanoylphorbol-13-acetate-induced Acute Inflammation in Mouse Ear

2-Arachidonoylglycerol is an endogenous ligand for the cannabinoid receptors. Two types of cannabinoid receptors have been identified to date. The CB1 receptor is abundantly expressed in the brain, and assumed to be involved in the attenuation of neurotransmission. On the other hand, the physiological roles of the CB2 receptor, mainly expressed in several types of inflammatory cells and immunocompetent cells, have not yet been fully elucidated. In this study, we investigated possible pathophysiological roles of the CB2 receptor and 2-arachidonoylglycerol in acute inflammation in mouse ear induced by the topical application of 12-O-tetradecanoylphorbol-13-acetate. We found that the amount of 2-arachidonoylglycerol was markedly augmented in inflamed mouse ear. In contrast, the amount of anandamide, another endogenous cannabinoid receptor ligand, did not change markedly. Importantly, 12-O-tetradecanoylphorbol-13-acetate-induced ear swelling was blocked by treatment with SR144528, a CB2 receptor antagonist, suggesting that the CB2 receptor is involved in the swelling. On the other hand, the application of AM251, a CB1 receptor antagonist, exerted only a weak suppressive effect. The application of SR144528 also reduced the 12-O-tetradecanoylphorbol-13-acetate-induced production of leukotriene B(4) and the infiltration of neutrophils in the mouse ear. Interestingly, the application of 2-arachidonoylglycerol to the mouse ear evoked swelling, which was abolished by treatment with SR144528. Nitric oxide was suggested to be involved in the ear swelling induced by 2-arachidonoylglycerol. These results suggest that the CB2 receptor and 2-arachidonoylglycerol play crucial stimulative roles during the course of inflammatory reactions.

Targeting signal transduction pathways by chemopreventive agents

Cancer is a dynamic process that involves many complex factors, which may explain why a "magic bullet" cure for cancer has not been found. Death rates are still rising for many types of cancers, which possibly contributes to the increased interest in chemoprevention as an alternative approach to the control of cancer. This strategy for cancer control is based on the presumption that because cancer develops through a multi-step process, each step may be a prospective target for reversing or suppressing the process. Thus, the design and development of chemopreventive agents that act on specific and/or multiple molecular and cellular targets is gaining support as a rational approach to control cancer. Nutritional or dietary factors have attracted a great deal of interest because of their perceived ability to act as highly effective chemopreventive agents. They are professed as being generally safe and may have efficacy as chemopreventive agents by preventing or reversing premalignant lesions and/or reducing second primary tumor incidence. Many of these dietary compounds appear to act on multiple target signaling pathways. Some of the most interesting and well documented are resveratrol and components of tea, including EGCG, theaflavins and caffeine. This review will focus on recent work regarding three well-accepted cellular/molecular mechanisms that may at least partially explain the effectiveness of selected food factors, including those indicated above, as chemopreventive anti-promotion agents. These food compounds may act by: (1) inducing apoptosis in cancer cells; (2) inhibiting neoplastic transformation through the inhibition of AP-1 and/or NF-kappaB activation; and/or (3) suppressing COX-2 overexpression in cancer cells.

Beyond U0126. Dianion chemistry leading to the rapid synthesis of a series of potent MEK inhibitors

Employing phenylmalonitrile dianion chemistry, a large number of analogues of MEK inhibitor lead SH053 (IC(50)=140 nM) were rapidly synthesized leading to single digit nM inhibitors, displaying submicromolar AP-1 transcription inhibition in COS-7 cells. Compound 41, exhibiting a MEK IC(50)=12 nM showed ip activity in a TPA-induced ear edema model with an ED(50)=5 mg/kg.

Inhibition of phorbol ester-induced COX-2 expression by epigallocatechin gallate in mouse skin and cultured human mammary epithelial cells

Green tea polyphenols are reported to possess substantial antiinflammatory and chemopreventive properties. However, the molecular mechanism of chemopreventive activity of green tea polyphenols is not fully understood. An abnormally elevated level of cyclooxygenase-2 (COX-2) is implicated in the pathogenesis of carcinogenesis. In the present study, we found that pretreatment of the green tea extract enriched with catechin and epigallocatechin gallate (EGCG) by gavage inhibited COX-2 expression induced by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin. Similarly, EGCG downregulated COX-2 in TPA-stimulated human mammary epithelial cells (MCF-10A) in culture. To further elucidate the underlying mechanism of COX-2 inhibition by green tea extract and EGCG, we examined their effects on the activation of extracellular signal-regulated protein kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), which are upstream enzymes known to regulate COX-2 expression in many cell types. Pretreatment with EGCG as well as green tea extract caused a decrease in the activation of ERK. In addition, EGCG inhibited the catalytic activity of ERK and p38 MAPK, suggesting that these signal-transducing enzymes could be potential targets for previously reported antitumor promoting activity of EGCG.

Murine models of ulcerative colitis

Ulcerative colitis (UC) is an inflammatory bowel disease of unknown etiology limited to the large intestine. The disease is prevalent in industrial societies and is associated with specific ethnic populations. A number of murine models, each focused on distinct aspects of the disease process, were developed over the past 20 years to further our understanding of the pathogenesis of UC. These models have been and remain our best resource for the study of the disorder as a result of their homology to human UC and the ease in which they can be manipulated and examined. This review examines and distills what has been leamed from these models and how this information is related back to human UC.

Interferon-gamma induces C/EBP beta expression and activity through MEK/ERK and p38 in T84 colon epithelial cells

We investigated the role of IFN-gamma and MAPKs on the expression and activity of the transcription factor CCAAT/enhancer-binding protein-beta (C/EBP beta) in the T84 colon epithelial cell line. IFN-gamma induced the expression and activity of C/EBP beta and subsequently increased the secretion of IL-6 from these cells. Treatment with the p38 inhibitor SB-203580, the MEK1 and MEK2 inhibitor U-0126, or the translational inhibitor cycloheximide inhibited the induction of C/EBP beta and IL-6 by IFN-gamma, whereas the MEK1 inhibitor PD-98059 or the tyrosine kinase inhibitor genistein had no effect. These results suggest a role for MEK2 and p38 in IFN-gamma-mediated signal transduction and induction of C/EBP beta expression and activity associated with interleukin-6 (IL-6) secretion in colon epithelial cells.

Hydrocortisone and the mitogen-activated protein kinase inhibitor U0126 acutely suppress reactive oxygen species generation from circulating granulocytes after gunshot injuries in the pig

OBJECTIVE

Several external stimuli, including trauma, increase the endogenous production of reactive oxygen species that spontaneously attack vital biological molecules. In addition to their direct toxic effects, several secondary messenger systems are induced. To forestall a subsequent organ dysfunction, a short-term posttraumatic down-regulation of granulocyte function has been advocated. Corticosteroids are potent and universal anti-inflammatory agents, but they have well-known side effects. Modulation of the mitogen-activated protein kinase cascade is an alternative approach. The purpose of this study was to investigate how the posttraumatic production of reactive oxygen species can be modulated by hydrocortisone or the extracellular signal-regulated kinase inhibitor U0126.

DESIGN

Prospective randomized trial.

SETTING

Field hospital and research laboratory.

SUBJECTS

Seventeen male pigs.

INTERVENTIONS

In general anesthesia, the pigs were exposed to a standardized insult: one gunshot hitting the right femur from a distance of 25 m, and one pistol shot to the left upper abdomen from close range. Following immediate first aid treatment, the animals were transported to a nearby field hospital. According to randomization, the animals received either hydrocortisone 250 mg intravenously (group 1, n = 9) or a similar amount of saline (group 2, n = 8). The injections were given 5 mins after the last shot. Blood samples were drawn before shooting, immediately before hydrocortisone was given, and 60 mins after shooting. Circulating neutrophils were isolated, and the production of reactive oxygen species was measured fluorometrically. Neutrophils from nine randomly chosen animals (five from group 1 and four from group 2) were treated in vitro with the extracellular signal-regulated kinase inhibitor U0126.

MEASUREMENTS AND MAIN RESULTS

The injuries as evaluated by the abbreviated injury scale did not differ between the animals. All survived the first 60 mins. While the in vivo production of reactive oxygen species tended to increase in the controls, a significant reduction was measured in the hydrocortisone group. Subsequent treatment with U0126 further reduced the synthesis of reactive oxygen species by about two thirds in both groups, independently of time.

CONCLUSIONS

Early injection of hydrocortisone after trauma inhibits the synthesis of reactive oxygen species from circulating neutrophils. Inhibition of the extracellular signal-regulated kinase branch of the mitogen-activated protein kinase signaling cascade is an alternative approach. The powerful in vitro capacity of selective extracellular signal-regulated kinase inhibitors to reduce the posttraumatic reactive oxygen species generation deserves further investigations, and compelling evidence of their in vivo usefulness is still lacking.

Taming the mucosal immune response in Crohn's disease

New effective therapeutic strategies for inflammatory bowel disease are based on recent knowledge of the regulation of the immune response. Specific defects of innate immunity, such as the NOD2 mutation in a subset of patients with Crohn's disease, have been associated with inflammatory bowel disease and provide new therapeutic targets. The ultimate therapeutic goal is the complete restoration of the mucosal immune balance and healing of all intestinal lesions. This may require repair of the underlying genetic mutation, restoration of defects of apoptosis, or generation of regulatory T-lymphocytes.

Cerulein-induced acute pancreatitis in the rat is significantly ameliorated by treatment with MEK1/2 inhibitors U0126 and PD98059

INTRODUCTION

Both cerulein and cholecystokinin activate mitogen-activated protein (MAP) kinase (ERK1/2) in vivo and in isolated pancreatic acini.

AIMS AND METHODOLOGY

ERK1/2 in pancreas homogenates was activated in rats rendered pancreatitic by subcutaneous injections of cerulein (5 microg/kg per hour). To determine if blocking ERK1/2 activity might rescue cerulein-induced acute pancreatitis, the "MAP kinase kinase" (also known as MEK1/2) inhibitors PD98059 and U0126 were administered in vivo.

RESULTS

In rats pretreated with PD98059 (10 mg/kg per i.v. injection) or U0126 (5 mg/kg per i.v. injection) 30 minutes before and then together with hourly cerulein injections for 3 hours, pancreatitis was significantly attenuated on the basis of pancreatic wet weight and histology. Serum amylase concentration was significantly reduced when PD98059 was administered intraperitoneally (10 mg/kg per intraperitoneal injection). PD98059 also ameliorated pancreatitis over a 6-hour cerulein time course. The phosphorylation of pancreatic ERK1/2 was attenuated in PD98059- and U0126-treated animals at both 30 minutes and 3 hours after cerulein injection. Rats rendered neutropenic with vinblastine and pretreated with U0126 still showed attenuated manifestations of cerulein-induced acute pancreatitis, a finding suggesting that pancreatic ERK1/2 is mostly responsible for the effect, rather than infiltrating neutrophils.

CONCLUSIONS

Inhibition of pancreatic ERK1/2 in vivo affords significant protection against inflammatory sequelae following cerulein-induced acute pancreatitis.

Therapeutic modulation of inflammatory gene transcription by kinase inhibitors

Altered gene expression contributes to the aetiology of inflammatory disease by modulation of the concentration of disease-related proteins. The expression of inflammatory genes is controlled through the concerted actions of specific transcription factors. Signal transduction networks positively or negatively regulate the activity of these transcription factors. Key components of these networks are protein kinases, which phosphorylate substrates on tyrosine, threonine or serine residues. During the disease process, pro-inflammatory signalling at the cell surface leads to a cascade of kinase activation, which ultimately culminates in modulation of the activity of transcription factors. Thus, pharmacological inhibition of protein kinases is a potential therapeutic strategy to treat inflammation. There are approximately 500 protein kinases in the human genome. Targeted small molecule inhibitors of these kinases should allow for tissue- and disease-specific therapies of unprecedented selectivity. Heralding this new era in molecular medicine is imatinib (Gleevec, Norvartis) a recently marketed tyrosine kinase inhibitor. This review focuses on kinase inhibitors that are currently in development for inflammatory diseases and the transcription factors that are involved.

Anti-tumor promoting potential of selected spice ingredients with antioxidative and anti-inflammatory activities: a short review

A wide variety of phenolic substances derived from spice possess potent antimutagenic and anticarcinogenic activities. Examples are curcumin, a yellow colouring agent, contained in turmeric (Curcuma longa L., Zingiberaceae), [6]-gingerol, a pungent ingredient present in ginger (Zingiber officinale Roscoe, Zingiberaceae) and capsaicin, a principal pungent principle of hot chili pepper (Capsicum annuum L, Solanaceae). The chemopreventive effects exerted by these phytochemicals are often associated with their antioxidative and anti-inflammatory activities. Cyclo-oxygenase-2 (COX-2) has been recognized as a molecular target of many chemopreventive as well as anti-inflammatory agents. Recent studies have shown that COX-2 is regulated by the eukaryotic transcription factor NF-kappaB. This short review summarizes the molecular mechanisms underlying chemopreventive effects of the aforementioned spice ingredients in terms of their effects on intracellular signaling cascades, particularly those involving NF-kappaB and mitogen-activated protein kinases.

Evidence for a role of mitogen-activated protein kinases in proliferating and differentiating odontogenic epithelia of inflammatory and developmental cysts

OBJECTIVE

The activation of intracellular signaling cascades involving serine/threonine kinases ERK1/2 has been variably reported either to stimulate or inhibit epithelial cell differentiation in response to extracellular signals. The purpose of our study was to determine the distribution of the signaling molecule ERK1 and its activated form pERK1/2 in the epithelial components of developmental and inflammatory odontogenic cysts in relation to parameters of differentiation and proliferation.

STUDY DESIGN

Thirty samples of dental follicles, dentigerous cysts, and radicular cysts were immunostained with antibodies to ERK1, pERK1/2, and proliferating cell nuclear antigen (a marker for proliferation). The tissues were subclassified according to the pattern of histomorphological differentiation (ie, squamous differentiation) and the proliferation rate of their epithelial components. The significance of differences in the proportion of ERK1- and pERK1/2-expressing cells among the tissue groups was determined by chi-square analysis or Fisher's exact test.

RESULTS

ERK1 and pERK1/2 were found to be expressed in a significantly higher proportion of cells with differentiated and highly proliferating epithelial components, as compared with those of nondifferentiated, quiescent epithelial rests. The epithelium of radicular cysts exhibited the highest proportion of pERK1/2-positive cells. In both dentigerous and radicular cyst samples, pERK1/2 expression was significantly higher in the inflamed tissues.

CONCLUSIONS

These data demonstrate that ERK1 and its active form pERK1/2 are associated with differentiating and actively proliferating epithelia of odontogenic cysts, and are consistent with pERK1/2 involvement in the activation of odontogenic epithelia in response to inflammation.

Proteolytic inhibition of Salmonella enterica serovar typhimurium-induced activation of the mitogen-activated protein kinases ERK and JNK in cultured human intestinal cells

Bromelain, a mixture of cysteine proteases from pineapple stems, blocks signaling by the mitogen-activated protein (MAP) kinases extracellular regulated kinase 1 (ERK-1) and ERK-2, inhibits inflammation, and protects against enterotoxigenic Escherichia coli infection. In this study, we examined the effect of bromelain on Salmonella enterica serovar Typhimurium infection, since an important feature of its pathogenesis is its ability to induce activation of ERK-1 and ERK-2, which leads to internalization of bacteria and induction of inflammatory responses. Our results show that bromelain dose dependently blocks serovar Typhimurium-induced ERK-1, ERK-2, and c-Jun NH(2)-terminal kinase (JNK) activation in Caco-2 cells. Bromelain also blocked signaling induced by carbachol and anisomycin, pharmacological MAP kinase agonists. Despite bromelain inhibition of serovar Typhimurium-induced MAP kinase signaling, it did not prevent subsequent invasion of the Caco-2 cells by serovar Typhimurium or alter serovar Typhimurium -induced decreases in resistance across Caco-2 monolayers. Surprisingly, bromelain also did not block serovar Typhimurium-induced interleukin-8 (IL-8) secretion but synergized with serovar Typhimurium to enhance IL-8 production. We also found that serovar Typhimurium does not induce ERK phosphorylation in Caco-2 cells in the absence of serum but that serovar Typhimurium-induced invasion and decreases in monolayer resistance are unaffected. Collectively, these data indicate that serovar Typhimurium-induced invasion of Caco-2 cells, changes in the resistance of epithelial cell monolayers, and IL-8 production can occur independently of the ERK and JNK signaling pathways. Data also confirm that bromelain is a novel inhibitor of MAP kinase signaling pathways and suggest a novel role for proteases as inhibitors of signal transduction pathways in intestinal epithelial cells.

Molecular mechanisms underlying chemopreventive activities of anti-inflammatory phytochemicals: down-regulation of COX-2 and iNOS through suppression of NF-kappa B activation

A wide array of phenolic substances, particularly those present in edible and medicinal plants, have been reported to possess substantial anticarcinogenic and antimutagenic activities. The majority of naturally occurring phenolics retain antioxidative and anti-inflammatory properties which appear to contribute to their chemopreventive or chemoprotective activity. Cyclooxygenase-2 (COX-2) inducible and nitric oxide synthase (iNOS) are important enzymes that mediate inflammatory processes. Improper up-regulation of COX-2 and/or iNOS has been associated with pathophysiology of certain types of human cancers as well as inflammatory disorders. Since inflammation is closely linked to tumor promotion, substances with potent anti-inflammatory activities are anticipated to exert chemopreventive effects on carcinogenesis, particularly in the promotion stage. Examples are curcumin, a yellow pigment of turmeric (Curcuma longa L., Zingiberaceae), the green tea polyphenol epigallocatechin gallate (EGCG), and resveratrol from grapes (Vitis vinifera, Vitaceae) that strongly suppress tumor promotion. Recent studies have demonstrated that eukaryotic transcription factor nuclear factor-kappa B (NF-kappa B) is involved in regulation of COX-2 and iNOS expression. Several chemopreventive phytochemicals have been shown to inhibit COX-2 and iNOS expression by blocking improper NF-kappa B activation. Multiple lines of compelling evidence indicate that extracellular-regulated protein kinase and p38 mitogen-activated protein kinase are key elements of the intracellular signaling cascades responsible for NF-kappa B activation in response to a wide array of external stimuli. Curcumin, EGCG and resveratrol have been shown to suppress activation of NF-kappa B. One of the plausible mechanisms underlying inhibition of NF-kappa B activation by aforementioned phytochemicals involves repression of degradation of the inhibitory unit I kappa B alpha, which hampers subsequent nuclear translocation of the functionally active subunit of NF-kappa B.

Oscillation in the activities of MEK/ERK1/2 during cardiopulmonary bypass in pigs

BACKGROUND

Because cardiopulmonary bypass (CPB) is associated with edema and vasoreactive dysfunction and ERK1/2 pathway is involved in vascular contractility and permeability, a time course study was performed to monitor MEK/ERK1/2/Elk-1 activities during CPB.

METHODS

Pigs were subjected to normothermic CPB for 90 minutes followed by post-CPB perfusion for 180 minutes. Atrial myocardium was sampled before CPB, 5 minutes after CPB onset, 5 minutes after weaning from CPB, and at the end of post-CPB. Skeletal muscle and mesenteric vessels samples were harvested before CPB, 5 minutes after CPB institution, and every 30 minutes thereafter to the end of post-CPB. Samples were analyzed by immunoblotting and immunofluorescence microscopy with the use of specific antibodies against active (phosphorylated) forms of ERK1/2, MEK1/2, and Elk-1.

RESULTS

Pigs that were subjected to CPB showed an increase in phospho-ERK1/2 after 30 minutes of CPB, followed by a decrease after 90 minutes. Another phosphorylation peak was observed 30 to 60 minutes of post-CPB, followed by a decrease to below baseline at the end of reperfusion. MEK1/2 and Elk-1 activation profiles paralleled ERK1/2 activity peaks. Control samples showed no significant increase above basal levels.

CONCLUSIONS

Activation of MEK/ERK1/2/Elk-1 pathways closely follows major CPB surgical manipulations (institution and termination) and could be related to morbidity during and after CPB.

Dietary energy restriction inhibits ERK but not JNK or p38 activity in the epidermis of SENCAR mice

Ongoing studies in our laboratory have demonstrated that dietary energy restriction (DER) inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced AP-1 transcription factor binding to DNA in the epidermis of SENCAR mice. To dissect the specific signal transduction pathways through which DER inhibits the AP-1:DNA binding, we analyzed the activities of three major MAP kinases that lead to the induction of AP-1. The changes in ERK1 and ERK2 protein expression and phosphorylation were further characterized by western blot analysis. Female SENCAR mice were pre-fed ad libitum (AL) or 40% DER diet for 8-10 weeks. The kinase activities in mouse epidermis were determined by immune complex kinase assays at 0.5, 1, 4, or 6 h following treatment with 3.2 nmol TPA to the shaved dorsal backs. ERK activity at 1 h post-TPA treatment was nearly 5-fold (P< 0.005) above basal levels in AL mice while the increase was abolished in DER mice. The TPA-induced ERK activity in AL mice was accompanied by increased phosphorylation of ERK1 and ERK2 (P< 0.05), which was abrogated in DER mice. In addition, DER mice exhibited reduced expression of total ERK1 and ERK2 and higher proportions of ERK1 and ERK2 phosphorylation in comparison with AL mice (P<0.05). JNK activity was decreased at 1 and 6 h but increased at 4 h (P<0.05) post-TPA treatment. TPA did not change p38 kinase activity at the time points tested. Neither JNK nor p38 activity was altered by DER. Taken together, our results indicated for the first time that DER blocked the TPA stimulation of ERK activity and suggested that the inhibition of TPA-induced AP-1 activity by DER is likely through inhibition of ERK but not JNK or p38 kinase pathway.

Inactivation of the MEK/ERK pathway in the myocardium during cardiopulmonary bypass

OBJECTIVES

A general pro-inflammatory response after cardiopulmonary bypass (CPB) may involve changes in signal transduction and in part be responsible for arrhythmias and myocardial dysfunction after cardiac surgery. The MEK/ERK (mitogen-activated protein kinase kinase/extracellular regulated kinase) pathway is common to many stimuli and may play a pivotal role in morbidity associated with CPB. We investigated the changes in MEK/ERK pathway and related enzymes after CPB in pigs.

METHODS

We examined ventricular and atrial tissue from pigs before 90 minutes of normothermic CPB and after 90 minutes of post-CPB perfusion. The activities and protein levels of kinases MEK1/2, ERK1/2, a cellular tyrosine kinase (c-Src), protein kinase B (Akt), and the protein levels of mitogen-activated protein kinase phosphatase (MKP-1) were studied by immunoblotting ventricular and atrial myocardium lysates and labeling sections with antibodies that recognize the activated forms of the kinases and the phosphatase. Control pigs were subjected to sternotomy and heparinization but not CPB.

RESULTS

We found a consistent inactivation of MEK/ERK pathway in both ventricular and atrial myocardium with an increase in MKP-1, a negative regulator of ERK1/2. The activities and protein levels of c-Src and Akt were not significantly modified before or after CPB, suggesting a certain degree of specificity for the MEK/ERK pathway. Such changes were not observed in controls. The decrease of ERK1/2 and MEK1/2 phosphorylation 90 minutes after termination of CPB (as well as the increase of nuclear MKP-1 protein levels) was also apparent by confocal microscopy.

CONCLUSIONS

These results collectively reveal a prevalence of inhibitory mechanisms in the MEK/ERK signal transduction machinery in myocardium subjected to CPB.

Neuroprotection by estrogen via extracellular signal-regulated kinase against quinolinic acid-induced cell death in the rat hippocampus

Extracellular signal-regulated kinase (ERK) belongs to the family of mitogen-activated protein kinases (MAPKs), which are serine-threonine kinases activated by phosphorylation in response to a variety of mitogenic signals. We previously reported that 17 beta-estradiol rapidly activates ERK in the rat hippocampus. However, the physiological role of this rapid activation of ERK by estrogen in vivo has not yet been elucidated. This study investigated whether ERK may participate in mediating the neuroprotective effects of estrogen against quinolinic acid (QA) toxicity in the rat hippocampus in vivo. Injection of QA into the hippocampi of male rats produced a loss of Nissl-stained neurons in the CA1 after 24 h. Prior administration of 17 beta-estradiol (50 pmol/animal) to the ventricles prevented the QA-induced decrease in Nissl-stained neurons. Pretreatment with U0126, an inhibitor of MAPK/ERK kinase, inhibited the rapid activation of ERK by 17 beta-estradiol in the rat hippocampus. Moreover, the neuroprotective effects of 17beta-estradiol against QA toxicity were blocked by the pretreatment with U0126. U0126 alone did not produce a loss of neurons. These results indicate that ERK mediates estrogen neuroprotection after QA toxicity in the rat hippocampus.