JTT-705 blocks cell proliferation and angiogenesis through p38 kinase/p27kip1 and Ras/p21waf1 pathways

MEK inhibitors: a promising targeted therapy for cardiovascular disease

Cardiovascular disease (CVD) represents the leading cause of mortality and disability all over the world. Identifying new targeted therapeutic approaches has become a priority of biomedical research to improve patient outcomes and quality of life. The RAS-RAF-MEK (mitogen-activated protein kinase kinase)-ERK (extracellular signal-regulated kinase) pathway is gaining growing interest as a potential signaling cascade implicated in the pathogenesis of CVD. This pathway is pivotal in regulating cellular processes like proliferation, growth, migration, differentiation, and survival, which are vital in maintaining cardiovascular homeostasis. In addition, ERK signaling is involved in controlling angiogenesis, vascular tone, myocardial contractility, and oxidative stress. Dysregulation of this signaling cascade has been linked to cell dysfunction and vascular and cardiac pathological remodeling, which contribute to the onset and progression of CVD. Recent and ongoing research has provided insights into potential therapeutic interventions targeting the RAS-RAF-MEK-ERK pathway to improve cardiovascular pathologies. Preclinical studies have demonstrated the efficacy of targeted therapy with MEK inhibitors (MEKI) in attenuating ERK activation and mitigating CVD progression in animal models. In this article, we first describe how ERK signaling contributes to preserving cardiovascular health. We then summarize current knowledge of the roles played by ERK in the development and progression of cardiac and vascular disorders, including atherosclerosis, myocardial infarction, cardiac hypertrophy, heart failure, and aortic aneurysm. We finally report novel therapeutic strategies for these CVDs encompassing MEKI and discuss advantages, challenges, and future developments for MEKI therapeutics.

In vivo evaluation of a pro-healing polydopamine coated stent through an in-stent restenosis rat model

Drug-eluting stents have demonstrated efficiency in in-stent restenosis (ISR) but induced a risk of late acute thrombosis by delaying strut re-endothelialization. Polydopamine (PDA), a biocompatible polymer inspired from adhesive proteins of mussels, has been reported to promote endothelial cell (EC) proliferation while limiting SMC proliferation in vitro, thus suggesting the pro-healing potential. This study aimed at evaluating in vivo the impact of the pro-healing PDA-coated stent on ISR and on the quality of the strut re-endothelialization in a rat model. PDA-coated stents demonstrated a significant reduction in ISR in vivo compared to bare metal stents (ratio neointima/media = 0.48 (±0.26) versus 0.83 (±0.42), p < 0.001). Western blot analyses identified a trend towards an increased activation of p38 MAPK phosphorylation and its anti-proliferative effects on vascular SMC that could explain the results observed in morphological analyses. This bioinspired and biocompatible polydopamine layer could intrinsically limit ISR. In addition, according to its latent reactivity, PDA offers the possibility to immobilize some relevant drugs on the PDA-functionalized stent to provide potential synergistic effects.

Actions of 1,25(OH)2-vitamin D3 on the cellular cycle depend on VDR and p38 MAPK in skeletal muscle cells

Previously, we have reported that 1,25(OH)2-vitamin D3 (1,25D) activates p38 MAPK (p38) in a vitamin D receptor (VDR)-dependent manner in proliferative C2C12 myoblast cells. It was also demonstrated that 1,25D promotes muscle cell proliferation and differentiation. However, we did not study these hormone actions in depth. In this study we have investigated whether the VDR and p38 participate in the signaling mechanism triggered by 1,25D. In C2C12 cells, the VDR was knocked down by a shRNA, and p38 was specifically inhibited using SB-203580. Results from cell cycle studies indicated that hormone stimulation prompts a peak of S-phase followed by an arrest in the G0/G1-phase, events which were dependent on VDR and p38. Moreover, 1,25D increases the expression of cyclin D3 and the cyclin-dependent kinase inhibitors, p21(Waf1/Cip1) and p27(Kip1), while cyclin D1 protein levels did not change during G0/G1 arrest. In all these events, p38 and VDR were required. At the same time, a 1,25D-dependent acute increase in myogenin expression was observed, indicating that the G0/G1 arrest of cells is a pro-differentiative event. Immunocytochemical assays revealed co-localization of VDR and cyclin D3, promoted by 1,25D in a p38-dependent manner. When cyclin D3 expression was silenced, VDR and myogenin levels were downregulated, indicating that cyclin D3 was required for 1,25D-induced VDR expression and the concomitant entrance into the differentiation process. In conclusion, the VDR and p38 are involved in control of the cellular cycle by 1,25D in skeletal muscle cells, providing key information on the mechanisms underlying hormone regulation of myogenesis.

Flow cytometry and gene expression profiling of immune cells of the carotid plaque and peripheral blood

OBJECTIVES

The relative contribution of the local vs. peripheral inflammation to the atherothrombotic processes is unknown. We compared the inflammatory status of the immune cells of the carotid plaque with similar cells in peripheral circulation of patients with advanced carotid disease (PCDs).

METHODS

Mononuclear cells (MNCs) were extracted from carotid endarterectomy (CEA) samples by enzymatic digestion and subsequent magnetic cell sorting. The cell surface antigenic expressions, and mRNA expression levels were compared between CEA MNCs and peripheral MNCs, using flow cytometry and RT-PCR techniques.

RESULTS

The percentages of resting MNCs were lower, and activated MNCs, particularly monocytes, were higher in the CEAMNCs, as compared to the peripheral MNCs. The percentages of activated T cells and B cells were higher in the peripheral MNCs of PCDs, than in healthy controls (HCs), but the percentages of activated monocytes did not differ between the two groups. The expression levels of both pro-inflammatory/pro-thrombotic (P(38), JNKB-1, Egr-1 PAI-1, MCP-1, TF, MMP-9, HMGB-1, TNF-α, mTOR) and anti-inflammatory (PPAR-γ, TGF-β) mediators were significantly higher in the CEA MNCs as compared to the peripheral MNCs. Furthermore, MMP-9 and PPAR-γ expression levels were higher in the peripheral MNCs of PCDs than HCs.

CONCLUSION

The inflammatory status is higher in the immune cells of the carotid plaque, as compared to those cells in the peripheral blood. The altered expression levels of both pro-inflammatory/pro-thrombotic and anti-inflammatory mediators in the milieu of the plaque suggest that the balance between these various mediators may play a key role in carotid disease progression.

The influence of high glucose on the Cip/Kip family expression profiles in HRECs

Neovascularization is the main characteristic of the proliferative stage of diabetic retinopathy. It has been proven that cell cycle regulation is involved in angiogenesis. The cell cycle regulators, Cip/Kip protein family, belong to the cyclin-dependent kinase inhibitors, are versatile proteins, and except for their function in cell cycle regulation, they also participate in transcription, apoptosis and migration. The expression profiles of the Cip/Kip family in human retina microvascular endothelial cells (HRECs) under normal or high glucose conditions has not been described before. This study was undertaken to determine the expression profiles of the Cip/Kip family proteins, e.g., proteins which are influenced by high glucose and in what manner. Western blot and immunofluorescence analyses were used to investigate the protein expression profiles. Only p21(cip1) and p27(kip1) were detected in HRECs, and they were located in the nucleus. P21(cip1) protein abundance was higher than p27(kip1) in HRECs. Incubation of HRECs in medium containing 30 mM D-glucose for 48 h resulted in downregulation of p21(cip1) protein expression, but had no influence on p27(kip1) protein levels or p21(cip1) mRNA abundance. These results were accompanied by cell cycle G1 phase exit and a lower cell survival rate. Our data show for the first time that high glucose changes the Cip/Kip family expression profiles in HRECs, which may be the foundation for the investigation of the role of the Cip/Kip family in the pathogenesis of diabetic retinopathy.

PYK2 signaling is required for PDGF-dependent vascular smooth muscle cell proliferation

Aberrant vascular smooth muscle cell (VSMC) growth is associated with many vascular diseases including atherosclerosis, hypertension, and restenosis. Platelet-derived growth factor-BB (PDGF) induces VSMC proliferation through control of cell cycle progression and protein and DNA synthesis. Multiple signaling cascades control VSMC growth, including members of the mitogen-activated protein kinase (MAPK) family as well as phosphatidylinositol 3-kinase (PI3K) and its downstream effector AKT/protein kinase B (PKB). Little is known about how these signals are integrated by mitogens and whether there are common receptor-proximal signaling control points that synchronize the execution of physiological growth functions. The nonreceptor proline-rich tyrosine kinase 2 (PYK2) is activated by a variety of growth factors and G protein receptor agonists in VSMC and lies upstream of both PI3K and MAPK cascades. The present study investigated the role of PYK2 in PDGF signaling in cultured rat aortic VSMC. PYK2 downregulation attenuated PDGF-dependent protein and DNA synthesis, which correlated with inhibition of AKT and extracellular signal-regulated kinases 1 and 2 (ERK1/2) but not p38 MAPK activation. Inhibition of PDGF-dependent protein kinase B (AKT) and ERK1/2 signaling by inhibitors of upstream kinases PI3K and MEK, respectively, as well as downregulation of PYK2 resulted in modulation of the G(1)/S phase of the cell cycle through inhibition of retinoblastoma protein (Rb) phosphorylation and cyclin D(1) expression, as well as p27(Kip) upregulation. Cell division kinase 2 (cdc2) phosphorylation at G(2)/M was also contingent on PDGF-dependent PI3K-AKT and ERK1/2 signaling. These data suggest that PYK2 is an important upstream mediator in PDGF-dependent signaling cascades that regulate VSMC proliferation.

Drug discovery using chemical systems biology: identification of the protein-ligand binding network to explain the side effects of CETP inhibitors

Systematic identification of protein-drug interaction networks is crucial to correlate complex modes of drug action to clinical indications. We introduce a novel computational strategy to identify protein-ligand binding profiles on a genome-wide scale and apply it to elucidating the molecular mechanisms associated with the adverse drug effects of Cholesteryl Ester Transfer Protein (CETP) inhibitors. CETP inhibitors are a new class of preventive therapies for the treatment of cardiovascular disease. However, clinical studies indicated that one CETP inhibitor, Torcetrapib, has deadly off-target effects as a result of hypertension, and hence it has been withdrawn from phase III clinical trials. We have identified a panel of off-targets for Torcetrapib and other CETP inhibitors from the human structural genome and map those targets to biological pathways via the literature. The predicted protein-ligand network is consistent with experimental results from multiple sources and reveals that the side-effect of CETP inhibitors is modulated through the combinatorial control of multiple interconnected pathways. Given that combinatorial control is a common phenomenon observed in many biological processes, our findings suggest that adverse drug effects might be minimized by fine-tuning multiple off-target interactions using single or multiple therapies. This work extends the scope of chemogenomics approaches and exemplifies the role that systems biology has in the future of drug discovery.

Both the cost to launch a new drug and the attrition rate during the late stage of the drug discovery and development process are increasing. Torcetrapib is a case in point, having been withdrawn from phase III clinical trials after 15 years of development and an estimated cost of US $800 M. Torcetrapib represents a new class of therapies for the treatment of cardiovascular disease; however, clinical studies indicated that Torcetrapib has deadly side-effects as a result of hypertension. To understand the origins of these adverse drug reactions from Torcetrapib and other related drugs undergoing clinical trials, we introduce a systematic strategy to identify off-targets in the human structural proteome and investigate the roles of these off-targets in impacting human physiology and pathology using biochemical pathway analysis. Our findings suggest that potential side-effects of a new drug can be identified at an early stage of the development cycle and be minimized by fine-tuning multiple off-target interactions. The hope is that this can reduce both the cost of drug development and the mortality rates during clinical trials.

Jun N-terminal kinase inhibitor blocks angiogenesis by blocking VEGF secretion and an MMP pathway

AIM

The excessive proliferation and migration of vascular smooth muscle cells (SMCs) and angiogenesis of endothelial cells (ECs) participate in the growth and instability of atherosclerotic plaques. It is unclear whether Jun N-terminal kinase (JNK) is pro-or anti-atherogenic.

METHODS

We examined the direct effect of JNK inhibitor (JNK-I) on the proliferation and formation of tubes by human coronary SMCs and human coronary ECs.

RESULTS

Culture medium from JNK-I-treated SMCs prevented ECs from forming tubes in an in vitro model of angiogenesis indirectly by reducing the amount of vascular endothelial growth factor (VEGF) released from SMCs. In addition, JNK-I attenuated the expression of pro-matrix metalloproteinase-2 in ECs. When added back to the medium of SMCs treated with JNK-I, VEGF blocked the inhibitory effect on the formation of tubes.

CONCLUSION

Our results indicate JNK-I to have a direct anti-atherogenic effect in SMCs and ECs.

Levels of p27kip1 determine Aplidin sensitivity

Aplidin (plitidepsin) is a novel anticancer drug isolated from the marine tunicate Aplidium albicans. Aplidin shows potent antitumor activity in preclinical models against a wide variety of human tumors. Aplidin is currently in phase II clinical trials in a variety of solid tumors and hematologic malignancies. Moreover, clinical studies of Aplidin in combination with other agents are ongoing because it generally lacks cross-resistance with other known cytotoxic drugs. The mode of action of Aplidin in tumor cells is only partially understood. Aplidin induces an early oxidative stress response, which results in a rapid and sustained activation of the epidermal growth factor receptor, the nonreceptor protein tyrosine kinase Src, and the serine threonine kinases c-Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase. Here, we show that sensitivity to Aplidin correlates inversely with the levels of expression of the cyclin-dependent kinase inhibitor p27(kip1) (p27) in a panel of low passaged human sarcoma cell lines. Aplidin induces p27 through an oxidation-dependent mechanism and the reduction of p27 levels by specific short hairpin RNA increases Aplidin sensitivity. We confirmed these results in p27 null mouse embryonic fibroblasts corroborating the specificity of the p27 role in Aplidin response because p21(waf1) null mouse embryonic fibroblasts do not show this increased sensitivity. We propose a mechanism of action of Aplidin involving p27 and support the analysis of p27 in the response to Aplidin in currently ongoing clinical trials to establish the levels of this protein as response predictor.

Pharmacogenetics and pharmacogenomics of cholesterol-lowering therapy

PURPOSE OF REVIEW

To summarize recent findings on pharmacokinetics, pharmacodynamics, drug-drug interactions and influence of lifestyle heterogeneity on adverse events in cholesterol-lowering therapy

RECENT FINDINGS

The prevention of cardiovascular disease is critically dependent on lipid-lowery therapy, including statins, cholesterol absorption inhibitors, fibrates and nicotinic acid. Statins are the most prescribed drugs in lipid lowering therapy with variability in response and almost one third of the patients do not meet their treatment goals. The severe adverse effects of treatment with cerivastatin stimulated the search for new genes and gene variations affecting pharmacokinetics, drug-drug interactions and pharmacodynamics. Moreover, instead of monotherapy, combined therapy of statins with ezetemibe and niacin was considered. This led to the identification of CD13, NPC1L1 and HM74A as new targets and CYP2C8 and glucuronidation enzymes as potential targets for drug-drug interactions. Moreover multiple polymorphic sites and pleiotrophic gene targets were reinvestigated in larger cohorts and the relevant pathogenetic factors start to evolve.

SUMMARY

Statin therapy is widely used and well tolerated by the majority of patients. To further reduce potential adverse effects and to increase efficacy, combined therapy concepts with ezetimibe or niacin are underway.

Molecular mechanism of adaphostin-mediated G1 arrest in prostate cancer (PC-3) cells: signaling events mediated by hepatocyte growth factor receptor, c-Met, and p38 MAPK pathways

Adaphostin (NSC680410), a small molecule congener of tyrphostin AG957, has been demonstrated previously to have significant anti-proliferative effects in several leukemia models. However, this effect of adaphostin in adherent cells/solid tumor models has not been examined. In this study, we investigated the anti-proliferative effects of adaphostin in the human prostate cancer cell line PC-3. Specifically, we explored the potential molecular mechanism(s) by which adaphostin elicits its anti-proliferative effect(s). We demonstrate that adaphostin inhibits the proliferation of PC-3 cells by inducing a G(1) phase cell cycle arrest. This adaphostin-induced G(1) arrest was associated with an increase in the expression of p21 and p27 and a decrease in the expression of G(1)-specific cyclins (cyclin A, D1, and D3) and cyclin-dependent kinases 4 and 6. Consequently, a dramatic decrease in the phosphorylation of retinoblastoma protein was also observed. Additionally, we found that adaphostin treatment induced a decrease in the phosphorylation of nucleophosmin, a major nuclear phosphoprotein, and that this decreased phosphorylation was a result of the p21- and p27-mediated inactivation of cyclin E-cyclin-dependent kinase 2 complex kinase activity. Furthermore, we have determined that the adaphostin-mediated cell cycle arrest of PC-3 cells is dependent upon activation of the p38 MAPK. We also demonstrate that the hepatocyte growth factor receptor-c-Met is involved in the adaphostin-mediated signaling events that regulate p38 MAPK. Taken together, these results identify for the first time a signaling cascade of adaphostin-mediated G(1) phase-specific cell cycle arrest in PC-3 cells. These findings suggest that the tyrphostin member has a broader spectrum of activity than originally predicted.