MEK hyperphosphorylation coincides with cell cycle shut down of cultured smooth muscle cells

Roles of Cytokines in Pathological and Physiological Gastroesophageal Reflux Exposure

Background/Aims

Gastroesophageal reflux disease is frequently observed and has no definitive treatment. There are 2 main views on the pathogenesis of gastroesophageal reflux disease. The first is that epithelial damage starts from the mucosa by acidic-peptic damage and the inflammatory response of granulocytes. The other view is that T-lymphocytes attract chemoattractants from the basal layer to the mucosa, and granulocytes do not migrate until damage occurs. We aim to investigate the inflammatory processes occurring in the esophageal epithelium of the phenotypes at the molecular level. We also examined the effects of these changes on tissue integrity.

Methods

Patients with mild and severe erosive reflux, nonerosive reflux, reflux hypersensitivity, and functional heartburn were included. Inflammatory gene expressions (JAK/STAT Signaling and NFKappaB Primer Libraries), chemokine protein levels, and tissue integrity were examined in the esophageal biopsies.

Results

There was chronic inflammation in the severe erosion group, the acute response was also triggered. In the mild erosion group, these 2 processes worked together, but homeostatic cytokines were also secreted. In nonerosive groups, T-lymphocytes were more dominant. In addition, the inflammatory response was highly triggered in the reflux hypersensitivity and functional heartburn groups, and it was associated with physiological reflux exposure and sensitivity.

Conclusions

"Microinflammation" in physiological acid exposure groups indicates that even a mild trigger is sufficient for the initiation and progression of inflammatory activity. Additionally, the anti-inflammatory cytokines were highly increased. The results may have a potential role in the treatment of heartburn symptoms and healing of the mucosa.

The MEK-ERK-Egr-1 axis and its regulation in cardiovascular disease

Cardiovascular disease (CVD) is the primary cause of morbidity and mortality in the Western world. Multiple molecular and cellular processes underpinning the pathogenesis of CVD are regulated by the zinc finger transcription factor and product of an immediate-early gene, early growth response-1 (Egr-1). Egr-1 regulates multiple pro-inflammatory processes that underpin the manifestation of CVD. The activity of Egr-1 itself is influenced by a range of post-translational modifications including sumoylation, ubiquitination and acetylation. Egr-1 also undergoes phosphorylation by protein kinases, such as extracellular-signal regulated kinase (ERK) which is itself phosphorylated by MEK. This article reviews recent progress on the MEK-ERK-Egr-1 cascade, notably regulation in conjunction with factors and agents such as TET2, TRIB2, MIAT, SphK1, cAMP, teneligliptin, cholinergic drugs, red wine and flavonoids, wogonin, febuxostat, docosahexaenoic acid and AT1R blockade. Such insights should provide new opportunity for therapeutic intervention in CVD.

Mechanistic and Clinical Overview Cardiovascular Toxicity of BRAF and MEK Inhibitors: JACC: CardioOncology State-of-the-Art Review

Rapidly accelerated fibrosarcoma B-type (BRAF) and mitogen-activated extracellular signal-regulated kinase (MEK) inhibitors have revolutionized melanoma treatment. Approximately half of patients with melanoma harbor a BRAF gene mutation with subsequent dysregulation of the RAF-MEK-ERK signaling pathway. Targeting this pathway with BRAF and MEK blockade results in control of cell proliferation and, in most cases, disease control. These pathways also have cardioprotective effects and are necessary for normal vascular and cardiac physiology. BRAF and MEK inhibitors are associated with adverse cardiovascular effects including hypertension, left ventricular dysfunction, venous thromboembolism, atrial arrhythmia, and electrocardiographic QT interval prolongation. These effects may be underestimated in clinical trials. Baseline cardiovascular assessment and follow-up, including serial imaging and blood pressure assessment, are essential to balance optimal anti-cancer therapy while minimizing cardiovascular side effects. In this review, an overview of BRAF/MEK inhibitor-induced cardiovascular toxicity, the mechanisms underlying these, and strategies for surveillance, prevention, and treatment of these effects are provided.

Isometric exercise promotes arteriogenesis in rats after myocardial infarction

Isometric exercise (IE) is a promising intervention of noninvasive revascularization in patients with acute myocardial infarction (AMI). This study aimed to investigate the impact and mechanisms of IE training on arteriogenesis in AMI. Male Sprague-Dawley rats were randomly assigned into the sham-operation group (SO), myocardial infarction (MI) group, and 13 IE subgroups treated according to training intensity, frequency, duration, or monocyte chemoattractant protein-1 (MCP-1), or/and fibroblast growth factor-2 (FGF-2) inhibitors for eight weeks. Our results demonstrated that the IE group achieved superior improvement compared with the MI group in terms of left ventricular ejection fraction (LVEF), myocardial infarction size (MIS), arterial density (AD), monocytes (MNCs), smooth muscle cells (SMCs), endothelial cells (ECs), relative collateral blood flow (RCBF), MCP-1, and FGF-2 at the endpoint. Positive correlations between MCP-1 and MNCs, MNCs and FGF-2, FGF-2 and SMCs, SMCs and AD, as well as AD and RCBF were observed. This study demonstrated that with MI of 100% load 20 times daily for eight weeks, the arteriogenesis was improved, which may be attributed to the recruitment of MNCs and SMCs in remote ischemic myocardium caused by increases in MCP-1 and FGF-2 expression.

The MEK/ERK Module Is Reprogrammed in Remodeling Adult Cardiomyocytes

Fetal and hypertrophic remodeling are hallmarks of cardiac restructuring leading chronically to heart failure. Since the Ras/Raf/MEK/ERK cascade (MAPK) is involved in the development of heart failure, we hypothesized, first, that fetal remodeling is different from hypertrophy and, second, that remodeling of the MAPK occurs. To test our hypothesis, we analyzed models of cultured adult rat cardiomyocytes as well as investigated myocytes in the failing human myocardium by western blot and confocal microscopy. Fetal remodeling was induced through endothelial morphogens and monitored by the reexpression of Acta2, Actn1, and Actb. Serum-induced hypertrophy was determined by increased surface size and protein content of cardiomyocytes. Serum and morphogens caused reprogramming of Ras/Raf/MEK/ERK. In both models H-Ras, N-Ras, Rap2, B- and C-Raf, MEK1/2 as well as ERK1/2 increased while K-Ras was downregulated. Atrophy, MAPK-dependent ischemic resistance, loss of A-Raf, and reexpression of Rap1 and Erk3 highlighted fetal remodeling, while A-Raf accumulation marked hypertrophy. The knock-down of B-Raf by siRNA reduced MAPK activation and fetal reprogramming. In conclusion, we demonstrate that fetal and hypertrophic remodeling are independent processes and involve reprogramming of the MAPK.

Radixin Relocalization and Nonmuscle α-Actinin Expression Are Features of Remodeling Cardiomyocytes in Adult Patients with Dilated Cardiomyopathy

Background

Pediatric patients show an impressive capacity of cardiac regeneration. In contrast, severely deteriorated adult hearts do usually not recover. Since cardiac remodeling—involving the expression of fetal genes—is regarded as an adaptation to stress, we compared hearts of adult patients suffering from dilated cardiomyopathy (DCM) with remodeling of cultured neonatal (NRC) as well as adult (ARC) rat cardiomyocytes and the developing postnatal myocardium.

Methods

NRC and ARC were stimulated with serum and cardiac morphogens derived from DCM hearts. Protein synthesis (PS) as well as protein accumulation (PA) was measured, and cell survival was determined under ischemic conditions. Fetal markers were investigated by Western blot. Biomarkers of remodeling were analyzed in controls, DCM, and 2- to 6-month-old children with tetralogy of Fallot as well as in neonatal and adult rats by immunofluorescence.

Results

In NRC, serum and morphogens strongly stimulated PS and PA and the reestablishment of cell-cell contacts (CCC). In ARC, both stimulants increased PS and CCC, but PA was only elevated after serum stimulation. In contrast to serum, morphogen treatment resulted in the expression of fetal genes in ARC as determined by nonmuscle α-actinin-1 and α-actinin-4 expression (NM-actinins) and was associated with increased survival under ischemia. NM-actinins were present in cardiomyocytes of DCM in a cross-striated pattern reminiscent of sarcomeres as well as in extensions of the area of the intercalated disc (ID). NM-actinins are expressed in NRC and in the developing heart. Radixin staining revealed remodeling of the area of the ID in DCM almost identical to stimulated cultured ARC.

Conclusions

Remodeling was similar in ARC and in cardiomyocytes of DCM suggesting evolutionary conserved mechanisms of regeneration. Despite activation of fetal genes, the atrophy of ARC indicates differences in their regenerative capacity from NRC. Cardiac-derived factors induced NM-actinin expression and increased survival of ischemic ARC while circulating molecules were less effective. Identification of these cardiac-derived factors and determination of their individual capacity to heal or damage are of particular importance for a biomarker-guided therapy in adult patients.

Effects of β-adrenergic receptor drugs on embryonic ventricular cell proliferation and differentiation and their impact on donor cell transplantation

β-Adrenergic receptors (β-ARs) and catecholamines are present in rodents as early as embryonic day (E)10.5. However, it is not known whether β-AR signaling plays any role in the proliferation and differentiation of ventricular cells in the embryonic heart. Here, we characterized expression profiles of β-AR subtypes and established dose-response curves for the nonselective β-AR agonist isoproterenol (ISO) in the developing mouse ventricular cells. Furthermore, we investigated the effects of ISO on cell cycle activity and differentiation of cultured E11.5 ventricular cells. ISO treatment significantly reduced tritiated thymidine incorporation and cell proliferation rates in both cardiac progenitor cell and cardiomyocyte populations. The ISO-mediated effects on DNA synthesis could be abolished by cotreatment of E11.5 cultures with either metoprolol (a β₁-AR antagonist) or ICI-118,551 (a β₂-AR antagonist). In contrast, ISO-mediated effects on cell proliferation could be abolished only by metoprolol. Furthermore, ISO treatment significantly increased the percentage of differentiated cardiomyocytes compared with that in control cultures. Additional experiments revealed that β-AR stimulation leads to downregulation of Erk and Akt phosphorylation followed by significant decreases in cyclin D1 and cyclin-dependent kinase 4 levels in E11.5 ventricular cells. Consistent with in vitro results, we found that chronic stimulation of recipient mice with ISO after intracardiac cell transplantation significantly decreased graft size, whereas metoprolol protected grafts from the inhibitory effects of systemic catecholamines. Collectively, these results underscore the effects of β-AR signaling in cardiac development as well as graft expansion after cell transplantation.NEW & NOTEWORTHY β-Adrenergic receptor (β-AR) stimulation can decrease the proliferation of embryonic ventricular cells in vitro and reduce the graft size after intracardiac cell transplantation. In contrast, β₁-AR antagonists can abrogate the antiproliferative effects mediated by β-AR stimulation and increase graft size. These results highlight potential interactions between adrenergic drugs and cell transplantation.

The MEK1 inhibitors UO126 and PD98059 block PDGF-AB induced phosphorylation of threonine 292 in porcine smooth muscle cells

PDGF-AB and FGF-2 (GFs) induce smooth muscle cell (SMC) proliferation which is indispensible for arteriogenesis. While there is common agreement that GFs stimulate SMC proliferation through phosphorylation (P-) of MEK1/2 at Ser218/222, we previously demonstrated that the MEK inhibitors PD98059 and UO126 did not inhibit P-Ser218/222 as originally proposed but caused strong hyperphosphorylation. Here, we demonstrate that GFs increased phosphorylation of MEK1 at Thr292 while UO126 and PD98059 blocked this phosphorylation. This was again surprising since phosphorylation of Thr292 is regarded as a negative feedback loop. Our findings suggest that inhibition of Thr292 phosphorylation in combination with hyperphosphorylation of Ser218/222 serves as an "off" switch of SMC proliferation and potentially of arteriogenesis.

Mesenchymal stem cells attenuate inflammatory processes in the heart and lung via inhibition of TNF signaling

Mesenchymal stem cells (MSC) have been used to treat different clinical conditions although the mechanisms by which pathogenetic processes are affected are still poorly understood. We have previously analyzed the homing of bone marrow-derived MSC to diseased tissues characterized by a high degree of mononuclear cell infiltration and postulated that MSC might modulate inflammatory responses. Here, we demonstrate that MSC mitigate adverse tissue remodeling, improve organ function, and extend lifespan in a mouse model of inflammatory dilative cardiomyopathy (DCM). Furthermore, MSC attenuate Lipopolysaccharide-induced acute lung injury indicating a general role in the suppression of inflammatory processes. We found that MSC released sTNF-RI, which suppressed activation of the NFκBp65 pathway in cardiomyocytes during DCM in vivo. Substitution of MSC by recombinant soluble TNF-R partially recapitulated the beneficial effects of MSC while knockdown of TNF-R prevented MSC-mediated suppression of the NFκBp65 pathway and improvement of tissue pathology. We conclude that sTNF-RI is a major part of the paracrine machinery by which MSC effect local inflammatory reactions.

Cellular and pharmacological targets to induce coronary arteriogenesis

The formation of collateral vessels (arteriogenesis) to sustain perfusion in ischemic tissue is native to the body and can compensate for coronary stenosis. However, arteriogenesis is a complex process and is dependent on many different factors. Although animal studies on collateral formation and stimulation show promising data, clinical trials have failed to replicate these results. Further research to the exact mechanisms is needed in order to develop a pharmalogical stimulant. This review gives an overview of recent data in the field of arteriogenesis.

PPARγ activation inhibits cerebral arteriogenesis in the hypoperfused rat brain

AIMS

PPARγ stimulation improves cardiovascular (CV) risk factors, but without improving overall clinical outcomes. PPARγ agonists interfere with endothelial cell (EC), monocyte and smooth muscle cell (SMC) activation, function and proliferation, physiological processes critical for arterial collateral growth (arteriogenesis). We therefore assessed the effect of PPARγ stimulation on cerebral adaptive and therapeutic collateral growth.

METHODS

In a rat model of adaptive cerebral arteriogenesis (3-VO), collateral growth and function were assessed (i) in controls, (ii) after PPARγ stimulation (pioglitazone 2.8 mg kg(-1); 10 mg kg(-1) compared with metformin 62.2 mg kg(-1) or sitagliptin 6.34 mg kg(-1)) for 21 days or (iii) after adding pioglitazone to G-CSF (40 μg kg(-1) every other day) to induce therapeutic arteriogenesis for 1 week. Pioglitazone effects on endothelial and SMC morphology and proliferation, monocyte activation and migration were studied.

RESULTS

PPARγ stimulation decreased cerebrovascular collateral growth and recovery of hemodynamic reserve capacity (CVRC controls: 12 ± 7%; pio low: -2 ± 9%; pio high: 1 ± 7%; metformin: 9 ± 13%; sitagliptin: 11 ± 12%), counteracted G-CSF-induced therapeutic arteriogenesis and interfered with EC activation, SMC proliferation, monocyte activation and migration.

CONCLUSION

Pharmacologic PPARγ stimulation inhibits pro-arteriogenic EC activation, monocyte function, SMC proliferation and thus adaptive as well as G-CSF-induced cerebral arteriogenesis. Further studies should evaluate whether this effect may underlie the CV risk associated with thiazolidinedione use in patients.

Induction of Smooth Muscle Cell Migration During Arteriogenesis Is Mediated by Rap2

Objective—

Collateral artery growth or arteriogenesis is the primary means of the circulatory system to maintain blood flow in the face of major arterial occlusions. Arteriogenesis depends on activation of fibroblast growth factor (FGF) receptors, but relatively little is known about downstream mediators of FGF signaling.

Methods and Results—

We screened for signaling components that are activated in response to administration of FGF-2 to cultured vascular smooth muscle cells (VSMCs) and detected a significant increase of Rap2 but not of other Ras family members, which corresponded to a strong upregulation of Rap2 and C-Raf in growing collaterals from rabbits with femoral artery occlusion. Small interfering RNAs directed against Rap2 did not affect FGF-2 induced proliferation of VSMC but strongly inhibited their migration. Inhibition of FGF receptor-1 (FGFR1) signaling by infusion of a sulfonic acid polymer or infection with a dominant-negative FGFR1 adenovirus inhibited Rap2 upregulation and collateral vessel growth. Similarly, expression of dominant-negative Rap2 blocked arteriogenesis, whereas constitutive active Rap2 enhanced collateral vessel growth.

Conclusion—

Rap2 is part of the arteriogenic program and acts downstream of the FGFR1 to stimulate VSMC migration. Specific modulation of Rap2 might be an attractive target to manipulate VSMC migration, which plays a role in numerous pathological processes.

Characterization of kinase inhibitors using reverse phase protein arrays

Using the reverse protein array platform in combination with planar waveguide technology, which allows detection of proteins in spotted cell lysates with high sensitivity in a 96-well microtiter-plate format for growing, treating, and lysing cells was shown to be suitable for this approach and indicates the usefulness of the technology as a screening tool for characterization of large numbers of kinase inhibitors. In this study, we have used reverse protein arrays to profile kinase inhibitors in various cellular pathways in order to unravel their MoA. Multiplexing and simultaneous analysis of several phospho-proteins within the same lysate allows (1) the estimation of inhibitor concentrations needed to shut down an entire pathway, (2) the estimation of inhibitor selectivity, and (3) the comparison of inhibitors of different kinases within one assay. For example, parallel analysis of p-InsR, p-PKB, p-GSK-3, p-MEK, p-ERK, and p-S6rp in insulin treated A14 cells allows profiling for inhibitors of the InsR, PI3K, PKB, mTor, RAF, and MEK. Selective kinase inhibitors revealed different specific inhibitory pattern of the analyzed phospho-read outs. Altogether, multiplexed analysis of reverse (phase) protein arrays is a powerful tool to characterize kinase inhibitors in a semi-automated low to medium throughput assay format.

Mechanisms of action and clinical application of macrolides as immunomodulatory medications

Macrolides have diverse biological activities and an ability to modulate inflammation and immunity in eukaryotes without affecting homeostatic immunity. These properties have led to their long-term use in treating neutrophil-dominated inflammation in diffuse panbronchiolitis, bronchiectasis, rhinosinusitis, and cystic fibrosis. These immunomodulatory activities appear to be polymodal, but evidence suggests that many of these effects are due to inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and nuclear factor kappa B (NF-kappaB) activation. Macrolides accumulate within cells, suggesting that they may associate with receptors or carriers responsible for the regulation of cell cycle and immunity. A concern is that long-term use of macrolides increases the emergence of antimicrobial resistance. Nonantimicrobial macrolides are now in development as potential immunomodulatory therapies.

Activation of BAG3 by Egr-1 in response to FGF-2 in neuroblastoma cells

The co-chaperone protein, BAG3, which belongs to the BAG protein family, has an established antiapoptotic function in different tumor cell lines. Here we demonstrated that treatment of the human neuroblastoma cell line, SK-N-MC, with fibroblast growth factor-2 (FGF-2) results in induction of BAG3 expression. Induction of BAG3 protein by FGF-2 occurs at the transcriptional level; it requires the extracellular regulated kinase1/2 pathway and is dependent on the activity of Egr-1 upon the BAG3 promoter. Targeted suppression of BAG3 by small-interfering RNA results in dysregulation of cell-cycle progression most notably at S and G(2) phases, which corroborates the decreased level of cyclin B1 expression. These observations suggest a new role for BAG3 in regulation of the cell cycle.

Acute, chronic and withdrawal effects of the cannabinoid receptor agonist WIN55212-2 on the sequential activation of MAPK/Raf-MEK-ERK signaling in the rat cerebral frontal cortex: short-term regulation by intrinsic and extrinsic pathways

The cannabinoids (CB) modulate the extracellular signal-regulated kinase (ERK), leading to various forms of plasticity in the brain. Little is known, however, on the in vivo short- and long-term activation and regulation of the components of mitogen-activated protein kinase (MAPK)/ERK signaling by CB. The CB agonist WIN55212-2 (8 mg/kg) increased the immunodensities of phosphorylated c-Raf-1 (42%), MEK1/2 (63%), ERK1 (24%), and ERK2 (28%) in the rat cerebral frontal cortex. These effects were antagonized by SR141716A (rimonabant, 10 mg/kg), a selective CB(1) receptor antagonist. Repeated WIN55212-2 treatment (2-8 mg/kg for 5 days) resulted in tachyphylaxis to the acute activation of Raf-MEK-ERK signaling. Acute WIN55212-2 also induced a hypothermic effect in rats, which was reduced after repeated administration (tolerance). Treatment with SR141716A after chronic WIN55212-2 resulted in the expected cannabinoid withdrawal syndrome, without concomitant alterations in the phosphorylation state of c-Raf-1, MEK1/2, or ERK1/2. Pretreatment with SL327 (20 mg/kg, a MEK1/2 inhibitor) increased the basal phosphorylation of c-Raf-1 (40%) and MEK1/2 (74%; feedback regulation) and fully prevented the up-regulation of ERK1/2 (23-31%) induced by WIN55212-2. Pretreatment with MK801 (1 mg/kg, a NMDA receptor antagonist) effectively blocked the up-regulation c-Raf-1 (41%), MEK1/2 (57%) and ERK1/2 (25-30%) induced by the CB agonist. The main findings demonstrate that the acute stimulation of CB(1) receptors in the frontal cortex results in the sequential phosphorylation of Raf-MEK-ERK cascade, in which c-Raf-1 activation (rate-limiting process) plays a crucial role. Moreover, the in vivo stimulating effect of WIN55212-2 on Raf-MEK-ERK signaling is under the extrinsic regulation of an excitatory glutamatergic mechanism.

The range of adaptation by collateral vessels after femoral artery occlusion

Natural adaptation to femoral artery occlusion in animals by collateral artery growth restores only approximately 35% of adenosine-recruitable maximal conductance (C(max)) probably because initially elevated fluid shear stress (FSS) quickly normalizes. We tested the hypothesis whether this deficit can be mended by artificially increasing FSS or whether anatomical restraints prevent complete restitution. We chronically increased FSS by draining the collateral flow directly into the venous system by a side-to-side anastomosis between the distal stump of the occluded femoral artery and the accompanying vein. After reclosure of the shunt collateral flow was measured at maximal vasodilatation. C(max) reached 100% already at day 7 and had, after 4 weeks, surpassed (2-fold) the C(max) of the normal vasculature before occlusion. Expression profiling showed upregulation of members of the Rho-pathway (RhoA, cofilin, focal adhesion kinase, vimentin) and the Rho-antagonist Fasudil markedly inhibited arteriogenesis. The activities of Ras and ERK-1,-2 were markedly increased in collateral vessels of the shunt experiment, and infusions of L-NAME and L-NNA strongly inhibited MAPK activity as well as shunt-induced arteriogenesis. Infusions of the peroxinitrite donor Sin-1 inhibited arteriogenesis. The radical scavengers urate, ebselen, SOD, and catalase had no effect. We conclude that increased FSS can overcome the anatomical restrictions of collateral arteries and is potentially able to completely restore maximal collateral conductance. Increased FSS activates the Ras-ERK-, the Rho-, and the NO- (but not the Akt-) pathway enabling collateral artery growth.

Role of post-translational modifications in regulating c-Myc proteolysis, transcriptional activity and biological function

The Myc proteins play a central role in cellular proliferation, differentiation, apoptosis and tumorigenesis. Although it is clear that multiple molecular mechanisms mediate these functions, it is unclear how individual mechanisms contribute and if different mechanisms work in concert or separately in mediating the diverse biological functions of c-Myc. Similarly, the role of post-translational modifications in regulating c-Myc molecular and biological properties has remained uncertain, despite over 20 years of research. In particular, phosphorylation of the N-terminal transcriptional regulatory domain has been shown to have a variety of consequences ranging from dramatic effects on apoptosis, tumorigenesis and c-Myc proteolysis to negligible effects on cellular transformation and transcriptional activity. This review attempts to provide a comprehensive and critical evaluation of the accumulated evidence to address the complex and controversial issues surrounding the role of post-translational modifications in c-Myc function, focusing on phosphorylation and ubiquitination of the N-terminal transcriptional regulatory domain. An overall model emerges that suggests phosphorylation and ubiquitination play critical roles in cell cycle progression, cell growth, apoptosis and tumorigenesis that are mediated by phosphorylation-dependent transcriptional activation of distinct sets of target genes and synchronized proteolysis.