Inhibition of EphA2 by Dasatinib Suppresses Radiation-Induced Intestinal Injury

The Eph/ephrin system symphony of gut inflammation

The extent of gut inflammation depends largely on the gut barrier's integrity and enteric neuroimmune interactions. However, the factors and molecular mechanisms that regulate inflammation-related changes in the enteric nervous system (ENS) remain largely unexplored. Eph/ephrin signaling is critical for inflammatory response, neuronal activation, and synaptic plasticity in the brain, but its presence and function in the ENS have been largely unknown to date. This review discusses the critical role of Eph/ephrin in regulating gut homeostasis, inflammation, neuroimmune interactions, and pain pathways. Targeting the Eph/ephrin system offers innovative treatments for gut inflammation disorders, offering hope for enhanced patient prognosis, pain management, and overall quality of life.

Critical Signaling Transduction Pathways and Intestinal Barrier: Implications for Pathophysiology and Therapeutics

The intestinal barrier is a sum of the functions and structures consisting of the intestinal mucosal epithelium, mucus, intestinal flora, secretory immunoglobulins, and digestive juices. It is the first-line defense mechanism that resists nonspecific infections with powerful functions that include physical, endocrine, and immune defenses. Health and physiological homeostasis are greatly dependent on the sturdiness of the intestinal barrier shield, whose dysfunction can contribute to the progression of numerous types of intestinal diseases. Disorders of internal homeostasis may also induce barrier impairment and form vicious cycles during the response to diseases. Therefore, the identification of the underlying mechanisms involved in intestinal barrier function and the development of effective drugs targeting its damage have become popular research topics. Evidence has shown that multiple signaling pathways and corresponding critical molecules are extensively involved in the regulation of the barrier pathophysiological state. Ectopic expression or activation of signaling pathways plays an essential role in the process of shield destruction. Although some drugs, such as molecular or signaling inhibitors, are currently used for the treatment of intestinal diseases, their efficacy cannot meet current medical requirements. In this review, we summarize the current achievements in research on the relationships between the intestinal barrier and signaling pathways. The limitations and future perspectives are also discussed to provide new horizons for targeted therapies for restoring intestinal barrier function that have translational potential.

The role of EphA2 in ADAM17- and ionizing radiation-enhanced lung cancer cell migration

Purpose

Ionizing radiation (IR) enhances the migratory capacity of cancer cells. Here we investigate in non-small-cell-lung-cancer (NSCLC) cells a novel link between IR-enhanced ADAM17 activity and the non-canonical pathway of EphA2 in the cellular stress response to irradiation.

Methods

Cancer cell migration in dependence of IR, EphA2, and paracrine signaling mediated by ADAM17 was determined using transwell migration assays. Changes of EphA2 pS897 and mRNA expression levels upon different ADAM17-directed treatment strategies, including the small molecular inhibitor TMI-005, the monoclonal antibody MEDI3622, and shRNAs, were mechanistically investigated. ADAM17-mediated release and cleavage of the EphA2 ligand ephrin-A1 was measured using ELISA and an acellular cleavage assay.

Results

Irradiation with 5 Gy enhanced tumor cell migration of NSCLC NCI-H358 cells in dependence of EphA2. At the same time, IR increased growth factor-induced EphA2 S897 phosphorylation via auto- and paracrine signaling. Genetic and pharmaceutical downregulation of ADAM17 activity abrogated growth factor (e.g. amphiregulin) release, which reduced MAPK pathway-mediated EphA2 S897 phosphorylation in an auto- and paracrine way (non-canonical EphA2-pathway) in NCI-H358 and A549 cells. These signaling processes were associated with reduced cell migration towards conditioned media derived from ADAM17-deficient cells. Interestingly, ADAM17 inhibition with the small molecular inhibitor TMI-005 led to the internalization and proteasomal degradation of EphA2, which was rescued by amphiregulin or MG-132 treatment. In addition, ADAM17 inhibition also abrogated ephrin-A1 cleavage and thereby interfered with the canonical EphA2-pathway.

Conclusion

We identified ADAM17 and the receptor tyrosine kinase EphA2 as two important drivers for (IR-) induced NSCLC cell migration and described a unique interrelation between ADAM17 and EphA2. We demonstrated that ADAM17 influences both, EphA2 (pS897) and its GPI-anchored ligand ephrin-A1. Using different cellular and molecular readouts, we generated a comprehensive picture of how ADAM17 and IR influence the EphA2 canonical and non-canonical pathway in NSCLC cells.

The EPH/Ephrin System in Colorectal Cancer

The EPH/ephrin system constitutes a bidirectional signaling pathway comprised of a family of tyrosine kinase receptors in tandem with their plasma membrane-bound ligand (ephrins). Its significance in a wide variety of physiologic and pathologic processes has been recognized during the past decades. In carcinogenesis, EPH/ephrins coordinate a wide spectrum of pathologic processes, such as angiogenesis, vessel infiltration, and metastasis. Despite the recent advances in colorectal cancer (CRC) diagnosis and treatment, it remains a leading cause of death globally, accounting for 9.2% of all cancer deaths. A growing body of literature has been published lately revitalizing our scientific interest towards the role of EPH/ephrins in pathogenesis and the treatment of CRC. The aim of the present review is to present the recent CRC data which might lead to clinical practice changes in the future.

Atorvastatin Inhibits Endothelial PAI-1-Mediated Monocyte Migration and Alleviates Radiation-Induced Enteropathy

Intestinal injury is observed in cancer patients after radiotherapy and in individuals exposed to radiation after a nuclear accident. Radiation disrupts normal vascular homeostasis in the gastrointestinal system by inducing endothelial damage and senescence. Despite advances in medical technology, the toxicity of radiation to healthy tissue remains an issue. To address this issue, we investigated the effect of atorvastatin, a commonly prescribed hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor of cholesterol synthesis, on radiation-induced enteropathy and inflammatory responses. We selected atorvastatin based on its pleiotropic anti-fibrotic and anti-inflammatory effects. We found that atorvastatin mitigated radiation-induced endothelial damage by regulating plasminogen activator inhibitor-1 (PAI-1) using human umbilical vein endothelial cells (HUVECs) and mouse model. PAI-1 secreted by HUVECs contributed to endothelial dysfunction and trans-endothelial monocyte migration after radiation exposure. We observed that PAI-1 production and secretion was inhibited by atorvastatin in irradiated HUVECs and radiation-induced enteropathy mouse model. More specifically, atorvastatin inhibited PAI-1 production following radiation through the JNK/c-Jun signaling pathway. Together, our findings suggest that atorvastatin alleviates radiation-induced enteropathy and supports the investigation of atorvastatin as a radio-mitigator in patients receiving radiotherapy.