Kinase inhibitors for cardiovascular disease

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Systematic mapping of cancer cell target dependencies using high-throughput drug screening in triple-negative breast cancer

While high-throughput drug screening offers possibilities to profile phenotypic responses of hundreds of compounds, elucidation of the cell context-specific mechanisms of drug action requires additional analyses. To that end, we developed a computational target deconvolution pipeline that identifies the key target dependencies based on collective drug response patterns in each cell line separately. The pipeline combines quantitative drug-cell line responses with drug-target interaction networks among both intended on- and potent off-targets to identify pharmaceutically actionable and selective therapeutic targets. To demonstrate its performance, the target deconvolution pipeline was applied to 310 small molecules tested on 20 genetically and phenotypically heterogeneous triple-negative breast cancer (TNBC) cell lines to identify cell line-specific target mechanisms in terms of cytotoxic and cytostatic drug target vulnerabilities. The functional essentiality of each protein target was quantified with a target addiction score (TAS), as a measure of dependency of the cell line on the therapeutic target. The target dependency profiling was shown to capture inhibitory information that is complementary to that obtained from the structure or sensitivity of the drugs. Comparison of the TAS profiles and gene essentiality scores from CRISPR-Cas9 knockout screens revealed that certain proteins with low gene essentiality showed high target addictions, suggesting that they might be functioning as protein groups, and therefore be resistant to single gene knock-out. The comparative analysis discovered protein groups of potential multi-target synthetic lethal interactions, for instance, among histone deacetylases (HDACs). Our integrated approach also recovered a number of well-established TNBC cell line-specific drivers and known TNBC therapeutic targets, such as HDACs and cyclin-dependent kinases (CDKs). The present work provides novel insights into druggable vulnerabilities for TNBC, and opportunities to identify multi-target synthetic lethal interactions for further studies.

Emerging roles of the αC-β4 loop in protein kinase structure, function, evolution, and disease

The faithful propagation of cellular signals in most organisms relies on the coordinated functions of a large family of protein kinases that share a conserved catalytic domain. The catalytic domain is a dynamic scaffold that undergoes large conformational changes upon activation. Most of these conformational changes, such as movement of the regulatory αC-helix from an "out" to "in" conformation, hinge on a conserved, but understudied, loop termed the αC-β4 loop, which mediates conserved interactions to tether flexible structural elements to the kinase core. We previously showed that the αC-β4 loop is a unique feature of eukaryotic protein kinases. Here, we review the emerging roles of this loop in kinase structure, function, regulation, and diseases. Through a kinome-wide analysis, we define the boundaries of the loop for the first time and show that sequence and structural variation in the loop correlate with conformational and regulatory variation. Many recurrent disease mutations map to the αC-β4 loop and contribute to drug resistance and abnormal kinase activation by relieving key auto-inhibitory interactions associated with αC-helix and inter-lobe movement. The αC-β4 loop is a hotspot for post-translational modifications, protein-protein interaction, and Hsp90 mediated folding. Our kinome-wide analysis provides insights for hypothesis-driven characterization of understudied kinases and the development of allosteric protein kinase inhibitors.

An Update on the Association of Protein Kinases with Cardiovascular Diseases

Background:

Protein kinases are the enzymes involved in phosphorylation of different proteins which leads to functional changes in those proteins. They belong to serine-threonine kinases family and are classified into the AGC (Protein kinase A/ Protein kinase G/ Protein kinase C) families of protein and Rho-associated kinase protein (ROCK). The AGC family of kinases are involved in G-protein stimuli, muscle contraction, platelet biology and lipid signaling. On the other hand, ROCK regulates actin cytoskeleton which is involved in the development of stress fibres. Inflammation is the main signal in all ROCK-mediated disease. It triggers the cascade of a reaction involving various proinflammatory cytokine molecules.

Methods:

Two ROCK isoforms are found in mammals and invertebrates. The first isoforms are present mainly in the kidney, lung, spleen, liver, and testis. The second one is mainly distributed in the brain and heart.

Results:

ROCK proteins are ubiquitously present in all tissues and are involved in many ailments that include hypertension, stroke, atherosclerosis, pulmonary hypertension, vasospasm, ischemia-reperfusion injury and heart failure. Several ROCK inhibitors have shown positive results in the treatment of various disease including cardiovascular diseases.

Conclusion:

ROCK inhibitors, fasudil and Y27632, have been reported for significant efficiency in dropping vascular smooth muscle cell hyper-contraction, vascular inflammatory cell recruitment, cardiac remodelling and endothelial dysfunction which highlight ROCK role in cardiovascular diseases.

Research advances in kinase enzymes and inhibitors for cardiovascular disease treatment

The targeting of protein kinases has great future potential for the design of new drugs against cardiovascular diseases (CVDs). Enormous efforts have been made toward achieving this aim. Unfortunately, kinase inhibitors designed to treat CVDs have suffered from numerous limitations such as poor selectivity, bad permeability and toxicity. So, where are we now in terms of discovering effective kinase targeting drugs to treat CVDs? Various drug design techniques have been approached for this purpose since the discovery of the inhibitory activity of Staurosporine against protein kinase C in 1986. This review aims to provide context for the status of several emerging classes of direct kinase modulators to treat CVDs and discuss challenges that are preventing scientists from finding new kinase drugs to treat heart disease.

Three stories on Eph kinase inhibitors: From in silico discovery to in vivo validation

Several selective and potent EphB4 inhibitors have been discovered, optimized and biophysically characterized by our groups over the past years. On the outset of these discoveries high throughput docking techniques were applied. Herein, we review the optimization campaigns started from three of these hits (Xan-A1, Pyr-A1 and Qui-A1) with emphasis on their in depth in vitro and in vivo characterization, together with previously unpublished angiogenesis and fluorescence based assays.

KLIFS: a knowledge-based structural database to navigate kinase-ligand interaction space

Protein kinases regulate the majority of signal transduction pathways in cells and have become important targets for the development of designer drugs. We present a systematic analysis of kinase-ligand interactions in all regions of the catalytic cleft of all 1252 human kinase-ligand cocrystal structures present in the Protein Data Bank (PDB). The kinase-ligand interaction fingerprints and structure database (KLIFS) contains a consistent alignment of 85 kinase ligand binding site residues that enables the identification of family specific interaction features and classification of ligands according to their binding modes. We illustrate how systematic mining of kinase-ligand interaction space gives new insights into how conserved and selective kinase interaction hot spots can accommodate the large diversity of chemical scaffolds in kinase ligands. These analyses lead to an improved understanding of the structural requirements of kinase binding that will be useful in ligand discovery and design studies.

Targeting G protein coupled receptor-related pathways as emerging molecular therapies

G protein coupled receptors (GPCRs) represent the most important targets in modern pharmacology because of the different functions they mediate, especially within brain and peripheral nervous system, and also because of their functional and stereochemical properties. In this paper, we illustrate, via a variety of examples, novel advances about the GPCR-related molecules that have been shown to play diverse roles in GPCR pathways and in pathophysiological phenomena. We have exemplified how those GPCRs’ pathways are, or might constitute, potential targets for different drugs either to stimulate, modify, regulate or inhibit the cellular mechanisms that are hypothesized to govern some pathologic, physiologic, biologic and cellular or molecular aspects both in vivo and in vitro. Therefore, influencing such pathways will, undoubtedly, lead to different therapeutical applications based on the related pharmacological implications. Furthermore, such new properties can be applied in different fields. In addition to offering fruitful directions for future researches, we hope the reviewed data, together with the elements found within the cited references, will inspire clinicians and researchers devoted to the studies on GPCR’s properties.

Fluorescent biosensors - probing protein kinase function in cancer and drug discovery

One of the challenges of modern biology and medicine is to visualize biomolecules in their natural environment, in real-time and in a non-invasive fashion, so as to gain insight into their physiological behavior and highlight alterations in pathological settings, which will enable to devise appropriate therapeutic strategies. Fluorescent biosensors constitute a class of imaging agents which have provided major insights into the function and regulation of enzymes in their cellular context. GFP-based reporters and genetically-encoded FRET biosensors, have been successfully applied to study protein kinases in living cells with high spatial and temporal resolution. In parallel, combined efforts in fluorescence chemistry and in chemical biology have enabled the design of non-genetic, polypeptide biosensors coupled to small synthetic fluorescent probes, which have been applied to monitor protein kinase activities in vitro and in more complex biological samples, with an equally successful outcome. From a biomedical perspective, fluorescent biosensor technology is well suited to development of diagnostic approaches, for monitoring disease progression and for evaluating response to therapeutics. Moreover it constitutes an attractive technology for drug discovery programs, for high content, high throughput screening assays, to assess the potency of new hits and optimize lead compounds, whilst also serving to characterize drugs developed through rational design. This review describes the utility and versatility of fluorescence biosensor technology to probe protein kinases with a specific focus on CDK/cyclin biosensors we have developed to probe abundance, activity and conformation. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).

The Rho kinase inhibitor azaindole-1 has long-acting vasodilator activity in the pulmonary vascular bed of the intact chest rat

Responses to a selective azaindole-based Rho kinase (ROCK) inhibitor (azaindole-1) were investigated in the rat. Intravenous injections of azaindole-1 (10–300 µg/kg), produced small decreases in pulmonary arterial pressure and larger decreases in systemic arterial pressure without changing cardiac output. Responses to azaindole-1 were slow in onset and long in duration. When baseline pulmonary vascular tone was increased with U46619 or L-NAME, the decreases in pulmonary arterial pressure in response to the ROCK inhibitor were increased. The ROCK inhibitor attenuated the increase in pulmonary arterial pressure in response to ventilatory hypoxia. Azaindole-1 decreased pulmonary and systemic arterial pressures in rats with monocrotaline-induced pulmonary hypertension. These results show that azaindole-1 has significant vasodilator activity in the pulmonary and systemic vascular beds and that responses are larger, slower in onset, and longer in duration when compared with the prototypical agent fasudil. Azaindole-1 reversed hypoxic pulmonary vasoconstriction and decreased pulmonary and systemic arterial pressures in a similar manner in rats with monocrotaline-induced pulmonary hypertension. These data suggest that ROCK is involved in regulating baseline tone in the pulmonary and systemic vascular beds, and that ROCK inhibition will promote vasodilation when tone is increased by diverse stimuli including treatment with monocrotaline.

Applications of molecular imaging

Today molecular imaging technologies play a central role in clinical oncology. The use of imaging techniques in early cancer detection, treatment response, and new therapy development is steadily growing and has already significantly impacted on clinical management of cancer. In this chapter, we overview three different molecular imaging technologies used for the understanding of disease biomarkers, drug development, or monitoring therapeutic outcome. They are (1) optical imaging (bioluminescence and fluorescence imaging), (2) magnetic resonance imaging (MRI), and (3) nuclear imaging (e.g., single-photon emission computed tomography (SPECT) and positron emission tomography (PET)). We review the use of molecular reporters of biological processes (e.g., apoptosis and protein kinase activity) for high-throughput drug screening and new cancer therapies, diffusion MRI as a biomarker for early treatment response and PET and SPECT radioligands in oncology.

Novel molecular imaging platform for monitoring oncological kinases

Recent advances in oncology have lead to identification of a plethora of alterations in signaling pathways that are critical to oncogenesis and propagation of malignancy. Among the biomarkers identified, dysregulated kinases and associated changes in signaling cascade received the lion's share of scientific attention and have been under extensive investigations with goal of targeting them for anti-cancer therapy. Discovery of new drugs is immensely facilitated by molecular imaging technology which enables non-invasive, real time, dynamic imaging and quantification of kinase activity. Here, we review recent development of novel kinase reporters based on conformation dependent complementation of firefly luciferase to monitor kinase activity. Such reporter system provides unique insights into the pharmacokinetics and pharmacodynamics of drugs that modulate kinase signaling and have a huge potential in drug discovery, validation, and drug-target interactions.

MAP kinase/phosphatase pathway mediates the regulation of ACE2 by angiotensin peptides

Angiotensin-converting enzyme 2 (ACE2) catalyzes the conversion of the vasoconstrictor angiotensin II (ANG II) to the vasodilatory peptide angiotensin-(1-7) [ANG-(1-7)]. We showed that treatment of hypertensive rats with the AT(1) receptor antagonist olmesartan increased ACE2 mRNA and protein in the thoracic aorta, suggesting that endogenous ANG II tonically reduces the enzyme. We now report that ANG II downregulates ACE2 activity and mRNA in rat aortic vascular smooth muscle cells (VSMCs) to reduce the conversion of ANG II to ANG-(1-7). Although ANG-(1-7) alone had no effect on the regulation of ACE2 mRNA, the heptapeptide prevented the ANG II-mediated reduction in ACE2 mRNA, an effect blocked by the selective ANG-(1-7) receptor antagonist [d-Ala(7)]-ANG-(1-7). The reduction in ACE2 mRNA by ANG II was also prevented by the mitogen-activated protein (MAP) kinase kinase inhibitor PD98059. Treatment of VSMCs with ANG II increased ERK1/ERK2 activity, which was significantly reduced by pretreatment with ANG-(1-7). Blockade of the ANG II-mediated reduction in ACE2 mRNA and increase in MAP kinase activity by ANG-(1-7) was prevented by pretreatment with sodium vanadate, a tyrosine phosphatase inhibitor, or okadaic acid, a serine-threonine phosphatase inhibitor, suggesting that the heptapeptide activates a MAP kinase phosphatase. This study is the first to show that the MAP kinase-phosphatase pathway is a primary molecular mechanism for regulating ACE2 to maintain the balance between ANG II and ANG-(1-7). The modulatory role of ANG-(1-7) in the regulation of ACE2 by ANG II suggests a complex interplay between the two peptides that is mediated by specific receptors to activate distinct signaling pathways.

Molecular imaging of protein kinases

Protein kinases are important regulators of signal-transduction pathways. Dysregulated kinase activity is observed in a variety of human diseases such as cancer, making them targets for the development of molecular therapies. Identification of new drugs is greatly aided by molecular imaging tools which enable real time, non-invasive, dynamic and quantitative imaging of kinase activity in vivo. We have recently described a new reporter platform based on conformation dependent complementation of firefly luciferase to monitor serine/threonine kinase (Akt) activity. The reporter system provides unique insights into the pharmacokinetics and pharmacodynamics of drugs that modulate kinase activity in living subjects and also provide a platform for cell based high-throughput drug screening for modulators of kinase activity.

High-glucose-induced regulation of intracellular ANG II synthesis and nuclear redistribution in cardiac myocytes

The prevailing paradigm is that cardiac ANG II is synthesized in the extracellular space from components of the circulating and/or local renin-angiotensin system. The recent discovery of intracrine effects of ANG II led us to determine whether ANG II is synthesized intracellularly in neonatal rat ventricular myocytes (NRVM). NRVM, incubated in serum-free medium, were exposed to isoproterenol or high glucose in the absence or presence of candesartan, which was used to prevent angiotensin type 1 (AT1) receptor-mediated internalization of ANG II. ANG II was measured in cell lysates and the culture medium, which represented intra- and extracellularly synthesized ANG II, respectively. Isoproterenol increased ANG II concentration in cell lysates and medium of NRVM in the absence or presence of candesartan. High glucose markedly increased ANG II synthesis only in cell lysates in the absence and presence of candesartan. Western analysis showed increased intracellular levels of angiotensinogen, renin, and chymase in high-glucose-exposed cells. Confocal immunofluorocytometry confirmed the presence of ANG II in the cytoplasm and nucleus of high-glucose-exposed NRVM and along the actin filaments in isoproterenol-exposed cells. ANG II synthesis was dependent on renin and chymase in high-glucose-exposed cells and on renin and angiotensin-converting enzyme in isoproterenol-exposed cells. In summary, the site of ANG II synthesis, intracellular localization, and the synthetic pathway in NRVM are stimulus dependent. Significantly, NRVM synthesized and retained ANG II intracellularly, which redistributed to the nucleus under high-glucose conditions, suggesting a role for an intracrine mechanism in diabetic conditions.