The ATX-LPA Axis Regulates Vascular Permeability during Cerebral Ischemic-Reperfusion

Breast Tumor Metastasis and Its Microenvironment: It Takes Both Seed and Soil to Grow a Tumor and Target It for Treatment

Metastasis remains a major challenge in treating breast cancer. Breast tumors metastasize to organ-specific locations such as the brain, lungs, and bone, but why some organs are favored over others remains unclear. Breast tumors also show heterogeneity, plasticity, and distinct microenvironments. This contributes to treatment failure and relapse. The interaction of breast cancer cells with their metastatic microenvironment has led to the concept that primary breast cancer cells act as seeds, whereas the metastatic tissue microenvironment (TME) is the soil. Improving our understanding of this interaction could lead to better treatment strategies for metastatic breast cancer. Targeted treatments for different subtypes of breast cancers have improved overall patient survival, even with metastasis. However, these targeted treatments are based upon the biology of the primary tumor and often these patients' relapse, after therapy, with metastatic tumors. The advent of immunotherapy allowed the immune system to target metastatic tumors. Unfortunately, immunotherapy has not been as effective in metastatic breast cancer relative to other cancers with metastases, such as melanoma. This review will describe the heterogeneic nature of breast cancer cells and their microenvironments. The distinct properties of metastatic breast cancer cells and their microenvironments that allow interactions, especially in bone and brain metastasis, will also be described. Finally, we will review immunotherapy approaches to treat metastatic breast tumors and discuss future therapeutic approaches to improve treatments for metastatic breast cancer.

Network analysis-guided drug repurposing strategies targeting LPAR receptor in the interplay of COVID, Alzheimer's, and diabetes

The COVID-19 pandemic caused by the SARS-CoV-2 virus has greatly affected global health. Emerging evidence suggests a complex interplay between Alzheimer's disease (AD), diabetes (DM), and COVID-19. Given COVID-19's involvement in the increased risk of other diseases, there is an urgent need to identify novel targets and drugs to combat these interconnected health challenges. Lysophosphatidic acid receptors (LPARs), belonging to the G protein-coupled receptor family, have been implicated in various pathological conditions, including inflammation. In this regard, the study aimed to investigate the involvement of LPARs (specifically LPAR1, 3, 6) in the tri-directional relationship between AD, DM, and COVID-19 through network analysis, as well as explore the therapeutic potential of selected anti-AD, anti-DM drugs as LPAR, SPIKE antagonists. We used the Coremine Medical database to identify genes related to DM, AD, and COVID-19. Furthermore, STRING analysis was used to identify the interacting partners of LPAR1, LPAR3, and LPAR6. Additionally, a literature search revealed 78 drugs on the market or in clinical studies that were used for treating either AD or DM. We carried out docking analysis of these drugs against the LPAR1, LPAR3, and LPAR6. Furthermore, we modeled the LPAR1, LPAR3, and LPAR6 in a complex with the COVID-19 spike protein and performed a docking study of selected drugs with the LPAR-Spike complex. The analysis revealed 177 common genes implicated in AD, DM, and COVID-19. Protein-protein docking analysis demonstrated that LPAR (1,3 & 6) efficiently binds with the viral SPIKE protein, suggesting them as targets for viral infection. Furthermore, docking analysis of the anti-AD and anti-DM drugs against LPARs, SPIKE protein, and the LPARs-SPIKE complex revealed promising candidates, including lupron, neflamapimod, and nilotinib, stating the importance of drug repurposing in the drug discovery process. These drugs exhibited the ability to bind and inhibit the LPAR receptor activity and the SPIKE protein and interfere with LPAR-SPIKE protein interaction. Through a combined network and targeted-based therapeutic intervention approach, this study has identified several drugs that could be repurposed for treating COVID-19 due to their expected interference with LPAR(1, 3, and 6) and spike protein complexes. In addition, it can also be hypothesized that the co-administration of these identified drugs during COVID-19 infection may not only help mitigate the impact of the virus but also potentially contribute to the prevention or management of post-COVID complications related to AD and DM.

The Role of Autotaxin and LPA Signaling in Embryonic Development, Pathophysiology and Cancer

Autotaxin (ATX) or Ectonucleotide Pyrophosphatase/Phosphodiesterase 2 (ENPP2) is a secreted enzyme with lysophospholipase D activity, with its primary function being the extracellular hydrolysis of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), a bioactive lipid [...].

Mn(III) Porphyrin, MnTnBuOE-2-PyP5+, Commonly Known as a Mimic of Superoxide Dismutase Enzyme, Protects Cardiomyocytes from Hypoxia/Reoxygenation Induced Injury via Reducing Oxidative Stress

Myocardial ischemia-reperfusion injury (I/R) causes damage to cardiomyocytes through oxidative stress and apoptosis. We investigated the cardioprotective effects of MnTnBuOE-2-PyP5+ (BMX-001), a superoxide dismutase mimic, in an in vitro model of I/R injury in H9c2 cardiomyocytes. We found that BMX-001 protected against hypoxia/reoxygenation (H/R)-induced oxidative stress, as evident by a significant reduction in intracellular and mitochondrial superoxide levels. BMX-001 pre-treatment also reduced H/R-induced cardiomyocyte apoptosis, as marked by a reduction in TUNEL-positive cells. We further demonstrated that BMX-001 pre-treatment significantly improved mitochondrial function, particularly O2 consumption, in mouse adult cardiomyocytes subjected to H/R. BMX-001 treatment also attenuated cardiolipin peroxidation, 4-hydroxynonenal (4-HNE) level, and 4-HNE adducted proteins following H/R injury. Finally, the pre-treatment with BMX-001 improved cell viability and lactate dehydrogenase (LDH) activity in H9c2 cells following H/R injury. Our findings suggest that BMX-001 has therapeutic potential as a cardioprotective agent against oxidative stress-induced H/R damage in H9c2 cardiomyocytes.

Endothelial Specific Deletion of Autotaxin Improves Stroke Outcomes

Autotaxin (ATX) is an extracellular secretory enzyme (lysophospholipase D) that catalyzes the hydrolysis of lysophosphatidyl choline to lysophosphatidic acid (LPA). The ATX-LPA axis is a well-known pathological mediator of liver fibrosis, metastasis in cancer, pulmonary fibrosis, atherosclerosis, and neurodegenerative diseases. Additionally, it is believed that LPA may cause vascular permeability. In ischemic stroke, vascular permeability leading to hemorrhagic transformation is a major limitation for therapies and an obstacle to stroke management. Therefore, in this study, we generated an endothelial-specific ATX deletion in mice (ERT2 ATX-/-) to observe stroke outcomes in a mouse stroke model to analyze the role of endothelial ATX. The AR2 probe and Evans Blue staining were used to perform the ATX activity and vascular permeability assays, respectively. Laser speckle imaging was used to observe the cerebral blood flow following stroke. In this study, we observed that stroke outcomes were alleviated with the endothelial deletion of ATX. Permeability and infarct volume were reduced in ERT2 ATX-/- mice compared to ischemia-reperfusion (I/R)-only mice. In addition, the cerebral blood flow was retained in ERT2 ATX-/- compared to I/R mice. The outcomes in the stroke model are alleviated due to the limited LPA concentration, reduced ATX concentration, and ATX activity in ERT2 ATX-/- mice. This study suggests that endothelial-specific ATX leads to increased LPA in the brain vasculature following ischemic-reperfusion and ultimately disrupts vascular permeability, resulting in adverse stroke outcomes.

The Autotaxin-LPA Axis Emerges as a Novel Regulator of Smooth Muscle Cell Phenotypic Modulation during Intimal Hyperplasia

Neointimal hyperplasia is characterized by a loss of the contractile phenotype of vascular smooth muscle cells (VSMCs). Our group has recently shown that VSMC proliferation and migration are mediated by lysophosphatidic acid (LPA) during restenosis, but the role of autotaxin (ATX; lysophospholipase D), which produces LPA, remains unclear. Endothelial denudation of the mouse carotid artery was performed to induce neointimal hyperplasia, and the extent of damage caused by the ATX-LPA axis was assessed in VSMCs. We observed the upregulation of ATX activity (p < 0.0002) in the injured carotid artery using an AR2 probe fluorescence assay. Further, the tissue carotid LPA levels were elevated 2.7-fold in carotid vessels, augmenting neointimal hyperplasia. We used an electrical cell-substrate impedance sensor (ECIS) to measure VSMC proliferation and migration. Treatment with an ATX inhibitor (PF8380) or LPA receptor inhibitor (Ki16425) attenuated VSMC proliferation (extracellular signal-regulated kinases) activity and migration in response to recombinant ATX. Indeed, PF8380 treatment rescued the aggravated post-wire injury neointima formation of carotid arteries. The upregulation of ATX following vessel injury leads to LPA production in VSMCs, favoring restenosis. Our observations suggest that inhibition of the ATX-LPA axis could be therapeutically targeted in restenosis to minimize VSMC phenotypic modulation and inflammation after vascular injury.

ATX-LPA-Dependent Nuclear Translocation of Endonuclease G in Respiratory Epithelial Cells: A New Mode Action for DNA Damage Induced by Crystalline Silica Particles

Crystalline silica particles (CSi) are an established human carcinogen, but it is not clear how these particles cause necessary mutations. A well-established scenario includes inflammation caused by retained particles in the bronchioles, activated macrophages, and reactive oxygen species (ROS) that cause DNA damage. In previous studies, we showed that CSi in contact with the plasma membrane of human bronchial epithelium induced double strand breaks within minutes. A signaling pathway implicating the ATX-LPA axis, Rac1, NLRP3, and mitochondrial depolarization upstream of DSB formation was delineated. In this paper, we provide in vitro and in vivo evidence that this signaling pathway triggers endonuclease G (EndoG) translocation from the mitochondria to the nucleus. The DNA damage is documented as γH2AX and p53BP1 nuclear foci, strand breaks in the Comet assay, and as micronuclei. In addition, the DNA damage is induced by low doses of CSi that do not induce apoptosis. By inhibiting the ATX-LPA axis or by EndoG knockdown, we prevent EndoG translocation and DSB formation. Our data indicate that CSi in low doses induces DSBs by sub-apoptotic activation of EndoG, adding CSi to a list of carcinogens that may induce mutations via sub-apoptotic and "minority MOMP" effects. This is the first report linking the ATX-LPA axis to this type of carcinogenic effect.