Inhibition of Eph/ephrin interaction with the small molecule UniPR500 improves glucose tolerance in healthy and insulin-resistant mice

Diverse roles for axon guidance pathways in adult tissue architecture and function

Classical axon guidance ligands and their neuronal receptors were first identified due to their fundamental roles in regulating connectivity in the developing nervous system. Since their initial discovery, it has become clear that these signaling molecules play important roles in the development of a broad array of tissue and organ systems across phylogeny. In addition to these diverse developmental roles, there is a growing appreciation that guidance signaling pathways have important functions in adult organisms, including the regulation of tissue integrity and homeostasis. These roles in adult organisms include both tissue-intrinsic activities of guidance molecules, as well as systemic effects on tissue maintenance and function mediated by the nervous and vascular systems. While many of these adult functions depend on mechanisms that mirror developmental activities, such as regulating adhesion and cell motility, there are also examples of adult roles that may reflect signaling activities that are distinct from known developmental mechanisms, including the contributions of guidance signaling pathways to lineage commitment in the intestinal epithelium and bone remodeling in vertebrates. In this review, we highlight studies of guidance receptors and their ligands in adult tissues outside of the nervous system, focusing on in vivo experimental contexts. Together, these studies lay the groundwork for future investigation into the conserved and tissue-specific mechanisms of guidance receptor signaling in adult tissues.

A human-based multi-gene signature enables quantitative drug repurposing for metabolic disease

Insulin resistance (IR) contributes to the pathophysiology of diabetes, dementia, viral infection, and cardiovascular disease. Drug repurposing (DR) may identify treatments for IR; however, barriers include uncertainty whether in vitro transcriptomic assays yield quantitative pharmacological data, or how to optimise assay design to best reflect in vivo human disease. We developed a clinical-based human tissue IR signature by combining lifestyle-mediated treatment responses (>500 human adipose and muscle biopsies) with biomarkers of disease status (fasting IR from >1200 biopsies). The assay identified a chemically diverse set of >130 positively acting compounds, highly enriched in true positives, that targeted 73 proteins regulating IR pathways. Our multi-gene RNA assay score reflected the quantitative pharmacological properties of a set of epidermal growth factor receptor-related tyrosine kinase inhibitors, providing insight into drug target specificity; an observation supported by deep learning-based genome-wide predicted pharmacology. Several drugs identified are suitable for evaluation in patients, particularly those with either acute or severe chronic IR.

Cholenic acid derivative UniPR1331 impairs tumor angiogenesis via blockade of VEGF/VEGFR2 in addition to Eph/ephrin

Angiogenesis, the formation of new blood vessels from preexisting ones, is crucial for tumor growth and metastatization, and is considered a promising therapeutic target. Unfortunately, drugs directed against a specific proangiogenic growth factor or receptor turned out to be of limited benefit for oncology patients, likely due to the high biochemical redundancy of the neovascularization process. In this scenario, multitarget compounds that are able to simultaneously tackle different proangiogenic pathways are eagerly awaited. UniPR1331 is a 3β-hydroxy-Δ⁵-cholenic acid derivative, which is already known to inhibit Eph-ephrin interaction. Here, we employed an analysis pipeline consisting of molecular modeling and simulation, surface plasmon resonance spectrometry, biochemical assays, and endothelial cell models to demonstrate that UniPR1331 directly interacts with the vascular endothelial growth factor receptor 2 (VEGFR2) too. The binding of UniPR1331 to VEGFR2 prevents its interaction with the natural ligand vascular endothelial growth factor and subsequent autophosphorylation, signal transduction, and in vitro proangiogenic activation of endothelial cells. In vivo, UniPR1331 inhibits tumor cell-driven angiogenesis in zebrafish. Taken together, these data shed light on the pleiotropic pharmacological effect of UniPR1331, and point to Δ⁵-cholenic acid as a promising molecular scaffold for the development of multitarget antiangiogenic compounds.

Axon Guidance Molecules in the Islets of Langerhans

The islets of Langerhans, responsible for regulating blood glucose in vertebrates, are clusters of endocrine cells distributed throughout the exocrine pancreas. The spatial architecture of the different cell types within the islets controls cell-cell communication and impacts their ability to collectively regulate glucose. Islets rely on a range of chemotactic and adhesive cues to establish and manage intercellular relationships. Growing evidence indicates that axon guidance molecules such as Slit-Robo, Semaphorin-Neuropilin, Ephrin-Eph, and Netrins, influence endocrine progenitors' cell migration to establish correct architecture during islet morphogenesis, as well as directly regulating physical cell-cell communication in the mature islet to coordinate hormone secretion. In this mini-review, we discuss what is known and not yet known about how axon guidance molecules contribute to islet morphogenesis and function.

Intercellular Communication in the Islet of Langerhans in Health and Disease

Blood glucose homeostasis requires proper function of pancreatic islets, which secrete insulin, glucagon, and somatostatin from the β-, α-, and δ-cells, respectively. Each islet cell type is equipped with intrinsic mechanisms for glucose sensing and secretory actions, but these intrinsic mechanisms alone cannot explain the observed secretory profiles from intact islets. Regulation of secretion involves interconnected mechanisms among and between islet cell types. Islet cells lose their normal functional signatures and secretory behaviors upon dispersal as compared to intact islets and in vivo. In dispersed islet cells, the glucose response of insulin secretion is attenuated from that seen from whole islets, coordinated oscillations in membrane potential and intracellular Ca²⁺ activity, as well as the two-phase insulin secretion profile, are missing, and glucagon secretion displays higher basal secretion profile and a reverse glucose-dependent response from that of intact islets. These observations highlight the critical roles of intercellular communication within the pancreatic islet, and how these communication pathways are crucial for proper hormonal and nonhormonal secretion and glucose homeostasis. Further, misregulated secretions of islet secretory products that arise from defective intercellular islet communication are implicated in diabetes. Intercellular communication within the islet environment comprises multiple mechanisms, including electrical synapses from gap junctional coupling, paracrine interactions among neighboring cells, and direct cell-to-cell contacts in the form of juxtacrine signaling. In this article, we describe the various mechanisms that contribute to proper islet function for each islet cell type and how intercellular islet communications are coordinated among the same and different islet cell types. © 2021 American Physiological Society. Compr Physiol 11:2191-2225, 2021.

Encouraging an excitable brain state: mechanisms of brain repair in stroke

Stroke induces a plastic state in the brain. This period of enhanced plasticity leads to the sprouting of new axons, the formation of new synapses and the remapping of sensory-motor functions, and is associated with motor recovery. This is a remarkable process in the adult brain, which is normally constrained in its levels of neuronal plasticity and connectional change. Recent evidence indicates that these changes are driven by molecular systems that underlie learning and memory, such as changes in cellular excitability during memory formation. This Review examines circuit changes after stroke, the shared mechanisms between memory formation and brain repair, the changes in neuronal excitability that underlie stroke recovery, and the molecular and pharmacological interventions that follow from these findings to promote motor recovery in animal models. From these findings, a framework emerges for understanding recovery after stroke, central to which is the concept of neuronal allocation to damaged circuits. The translation of the concepts discussed here to recovery in humans is underway in clinical trials for stroke recovery drugs.

Approaches to Manipulate Ephrin-A:EphA Forward Signaling Pathway

Erythropoietin-producing hepatocellular carcinoma A (EphA) receptors and their ephrin-A ligands are key players of developmental events shaping the mature organism. Their expression is mostly restricted to stem cell niches in adults but is reactivated in pathological conditions including lesions in the heart, lung, or nervous system. They are also often misregulated in tumors. A wide range of molecular tools enabling the manipulation of the ephrin-A:EphA system are available, ranging from small molecules to peptides and genetically-encoded strategies. Their mechanism is either direct, targeting EphA receptors, or indirect through the modification of intracellular downstream pathways. Approaches enabling manipulation of ephrin-A:EphA forward signaling for the dissection of its signaling cascade, the investigation of its physiological roles or the development of therapeutic strategies are summarized here.

Harnessing the Power of Eph/ephrin Biosemiotics for Theranostic Applications

Comprehensive basic biological knowledge of the Eph/ephrin system in the physiologic setting is needed to facilitate an understanding of its role and the effects of pathological processes on its activity, thereby paving the way for development of prospective therapeutic targets. To this end, this review briefly addresses what is currently known and being investigated in order to highlight the gaps and possible avenues for further investigation to capitalize on their diverse potential.

Evaluation of the Anti-Tumor Activity of Small Molecules Targeting Eph/Ephrins in APC min/J Mice

The Eph receptors are the largest receptors tyrosine kinases (RTKs) family in humans and together with ephrin ligands constitute a complex cellular communication system often dysregulated in many tumors. The role of the Eph-ephrin system in colorectal cancer (CRC) has been investigated and different expression of Eph receptors have been associated with tumor development and progression. In light of this evidence, we investigated if a pharmacological approach aimed at inhibiting Eph/ephrin interaction through small molecules could prevent tumor growth in APC ^min/J mice. The 8-week treatment with the Eph-ephrin antagonist UniPR129 significantly reduced the number of adenomas in the ileum and decreased the diameter of adenomas in the same region. Overall our data suggested as UniPR129 could be able to slow down the tumor development in APC ^min/J mice. These results further confirm literature data about Eph kinases as a new valuable target in the intestinal cancer and for the first time showed the feasibility of the Eph-ephrin inhibition as a useful pharmacological approach against the intestinal tumorigenesis. In conclusion this work paves the way for further studies with Eph-ephrin inhibitors in order to confirm the Eph antagonism as innovative pharmacological approach with preventive benefit in the intestinal tumor development.

Ephrin or not? Six tough questions on Eph targeting

Introduction: The Eph-ephrin is a cell-cell communication system generating a forward signal in cell expressing Eph receptors and a reverse signal in ephrin-ligand expressing cells. While clearly involved in the insurgence and progression of cancer, the understanding of the molecular mechanisms regulated by this system needs development; this is a hurdle to the development of therapeutic strategies that can target the Eph receptors and/or their ephrin ligands.Areas covered: We have taken the opportunity to share some key questions on the most effective strategies to target the Eph-ephrin system. This article is based on our experience of the field and therefore is a Perspective and not comprehensive examination of the literature.Expert opinion: Targeting of the Eph-ephrin system has emerged as a potentially valuable approach for cancer therapy. Pharmacological tools have been reported in the last 15 years and these include forward signaling blockers such as kinases inhibitors and antagonists of forward and reverse signaling. Also, biologics including antibodies and recombinant proteins have been developed and some have reached early clinical stages. Data deem the Eph-ephrin system as a signaling axis that is an elusive target. A better understanding of the basic pharmacology behind the activity of available agents and a comprehensive knowledge of the ephrin biology are necessary. We are looking forward to knowing the opinion of the readers.

Targeting the Eph/Ephrin System as Anti-Inflammatory Strategy in IBD

Besides their long-known critical role in embryonic growth and in cancer development and progression, erythropoietin-producing hepatocellular carcinoma type B (EphB) receptor tyrosine kinases and their ephrin-B ligands are involved in the modulation of immune responses and in remodeling and maintaining the integrity of the intestinal epithelial layer. These processes are critically involved in the pathogenesis of inflammatory-based disorders of the gut, like inflammatory bowel diseases (IBDs). Accordingly, our aim was to investigate the role of the EphB/ephrin-B system in intestinal inflammation by assessing the local and systemic effects produced by its pharmacological manipulation in 2,4,6-trinitrobenzenesulfonic acid (TNBS)- (Th1-dependent model) and dextran sulphate sodium (DSS)- (innate response model) induced colitis in mice. To this purpose, we administered chimeric Fc-conjugated proteins, allegedly able to uni-directionally activate either forward (ephrin-B1-Fc) or reverse (EphB1-Fc) signaling, and the soluble monomeric EphB4 extracellular domain protein, that, simultaneously interfering with both signaling pathways, acts as EphB/ephrin-B antagonist.The blockade of the EphB/ephrin-B forward signaling by EphB4 and EphB1-Fc was ineffective against DSS-induced colitis while it evoked remarkable beneficial effects against TNBS colitis: it counteracted all the evaluated inflammatory responses and the changes elicited on splenic T lymphocytes subpopulations, without preventing the appearance of a splice variant of ephrin-B2 gene elicited by the haptenating agent in the colon. Interestingly, EphB4, preferentially displacing EphB4/ephrin-B2 interaction over EphB1/ephrin-B1 binding, was able to promote Tumor Necrosis Factor alpha (TNFα) release by splenic mononuclear cells in vitro. On the whole, the collected results point to a potential role of the EphB/ephrin-B system as a pharmacological target in intestinal inflammatory disorders and suggest that the therapeutic efficacy of its blockade seemingly works through the modulation of immune responses, independent of the changes at the transcriptional and translational level of EphB4 and ephrin-B2 genes.