Inhibitors of the Autotaxin-Lysophosphatidic Acid Axis and Their Potential in the Treatment of Interstitial Lung Disease: Current Perspectives

Pathological mechanisms and novel drug targets in fibrotic interstitial lung disease

BACKGROUND

Interstitial lung diseases (ILDs) are a diverse group of conditions characterized by inflammation and fibrosis in the lung. In some patients with ILD, a progressive fibrotic phenotype develops, which is associated with an irreversible decline in lung function and a poor prognosis.

MAIN BODY

The pathological mechanisms that underlie this process culminate in fibroblast activation, proliferation, and differentiation into myofibroblasts, which deposit extracellular matrix proteins and result in fibrosis. Upstream of fibroblast activation, epithelial cell injury and immune activation are known initiators of fibrosis progression, with multiple diverse cell types involved. Recent years have seen an increase in our understanding of the complex and interrelated processes that drive fibrosis progression in ILD, in part due to the advent of single-cell RNA sequencing technology and integrative multiomics analyses. Novel pathological mechanisms have been identified, which represent new targets for drugs currently in clinical development. These include phosphodiesterase 4 inhibitors and other molecules that act on intracellular cyclic adenosine monophosphate signaling, as well as inhibitors of the autotaxin-lysophosphatidic acid axis and  α v  integrins. Here, we review current knowledge and recent developments regarding the pathological mechanisms that underlie progressive fibrotic ILD, including potential therapeutic targets.

CONCLUSION

Knowledge of the pathological mechanisms that drive progressive fibrosis in patients with ILD has expanded, with the role of alveolar endothelial cells, the immune system, and fibroblasts better elucidated. Drugs that target novel mechanisms hold promise for expanding the future therapeutic armamentarium for progressive fibrotic ILD.

Pharmacological treatment in Idiopathic Pulmonary Fibrosis: current issues and future perspectives

Idiopathic pulmonary fibrosis (IPF) represents a fibrotic interstitial lung disease characterized by uncertain etiology and poor prognosis. Over the years, the path to effective treatments has been marked by a series of advances and setbacks. The introduction of approved antifibrotic drugs, pirfenidone and nintedanib, marked a pivotal moment in the management of IPF. However, despite these advances, these drugs are not curative, although they can slow the natural progression of the disease. The history of drug therapy for IPF goes together with the increased understanding of the pathogenic mechanisms underlying the disease. Based on that, current research efforts continue to explore new therapies, possible personalized treatment strategies, drug combinations, and potential biomarkers for diagnosis and prognosis. In this review, we outline the route that led to the discover of the first effective therapies, ongoing clinical trials, and future directions in the search for more effective treatments.

Experimental autotaxin inhibitors for the treatment of idiopathic pulmonary fibrosis

INTRODUCTION

Idiopathic Pulmonary Fibrosis (IPF) is a progressive, irreversible, and fatal lung disease with unmet medical needs. Autotaxin (ATX) is an extracellular enzyme involved in the generation of lysophosphatidic acid (LPA). Preclinical and clinical data have suggested the ATX-LPAR signaling axis plays an important role in the pathogenesis and the progression of IPF.

AREAS COVERED

The aim of this review is to provide an update on the available evidence on autotaxin inhibitors in IPF and further details on the ongoing clinical studies involving these molecules.

EXPERT OPINION

The development of autotaxin inhibitors as a potential therapy for idiopathic pulmonary fibrosis has gained attention due to evidence of their involvement in the disease. Preclinical and early-phase clinical studies have explored these inhibitors' efficacy and safety, offering a novel approach in treating this disease. Combining autotaxin inhibitors with existing anti-fibrotic agents is considered for enhanced therapeutic effects. Large phase III trials assessed Ziritaxestat but yielded disappointing results, highlighting the importance of long-term observation and clinical outcomes in clinical research. Patient stratification and personalized medicine are crucial, as pulmonary fibrosis is a heterogeneous disease. Ongoing research and collaboration are essential for this advancement.

EMT activates exocytotic Rabs to coordinate invasion and immunosuppression in lung cancer

Epithelial-to-mesenchymal transition (EMT) underlies immunosuppression, drug resistance, and metastasis in epithelial malignancies. However, the way in which EMT orchestrates disparate biological processes remains unclear. Here, we identify an EMT-activated vesicular trafficking network that coordinates promigratory focal adhesion dynamics with an immunosuppressive secretory program in lung adenocarcinoma (LUAD). The EMT-activating transcription factor ZEB1 drives exocytotic vesicular trafficking by relieving Rab6A, Rab8A, and guanine nucleotide exchange factors from miR-148a-dependent silencing, thereby facilitating MMP14-dependent focal adhesion turnover in LUAD cells and autotaxin-mediated CD8+ T cell exhaustion, indicating that cell-intrinsic and extrinsic processes are linked through a microRNA that coordinates vesicular trafficking networks. Blockade of ZEB1-dependent secretion reactivates antitumor immunity and negates resistance to PD-L1 immune checkpoint blockade, an important clinical problem in LUAD. Thus, EMT activates exocytotic Rabs to drive a secretory program that promotes invasion and immunosuppression in LUAD.

Linking medicinal cannabis to autotaxin-lysophosphatidic acid signaling

Autotaxin is primarily known for the formation of lysophosphatidic acid (LPA) from lysophosphatidylcholine. LPA is an important signaling phospholipid that can bind to six G protein-coupled receptors (LPA1-6). The ATX-LPA signaling axis is a critical component in many physiological and pathophysiological conditions. Here, we describe a potent inhibition of Δ9-trans-tetrahydrocannabinol (THC), the main psychoactive compound of medicinal cannabis and related cannabinoids, on the catalysis of two isoforms of ATX with nanomolar apparent EC50 values. Furthermore, we decipher the binding interface of ATX to THC, and its derivative 9(R)-Δ6a,10a-THC (6a10aTHC), by X-ray crystallography. Cellular experiments confirm this inhibitory effect, revealing a significant reduction of internalized LPA1 in the presence of THC with simultaneous ATX and lysophosphatidylcholine stimulation. Our results establish a functional interaction of THC with autotaxin-LPA signaling and highlight novel aspects of medicinal cannabis therapy.

Effect of BBT-877, a novel inhibitor of ATX, on a mouse model of type 1 diabetic nephropathy

Diabetic nephropathy (DN) is one of the common microvascular complications of diabetes. Autotaxin (ATX) is an enzyme with lysophospholipase D activity, producing lysophosphatidic acid (LPA). LPA signaling has been implicated in renal fibrosis, thereby inducing renal dysfunction. BBT-877 is an orally administered small molecule inhibitor of ATX. However, its effect on DN has not been studied so far. In this study, we investigated the effect of BBT-877, a novel inhibitor of ATX, on the pathogenesis of DN in a mouse model of streptozotocin (STZ)-induced diabetes. BBT-877 treatment significantly reduced albuminuria, albumin-to-creatinine ratio (ACR), neutrophil gelatinase-associated lipocalin (NGAL), and glomerular volume compared to the STZ-vehicle group. Interestingly, BBT-877 treatment attenuated hyperglycemia and dyslipidemia in STZ-induced diabetes mice. In the liver, the expression levels of β-oxidation-related genes such as PPAR α and CPT1 were significantly decreased in STZ-induced diabetic mice. However, this effect was reversed by BBT-877 treatment. BBT-877 treatment also suppressed mRNA levels of pro-inflammatory cytokines IL-6, MCP-1, and TNF-α and protein levels of fibrotic factors (TGF-β, fibronectin, CTGF, and collagen type Ι alpha Ι (COL1A1)) in the kidneys of STZ-induced diabetic mice. In conclusion, our results indicate that BBT-877 is effective in preventing the pathogenesis of DN by reducing systemic blood glucose levels and inhibiting inflammation and fibrosis in the renal tissue of diabetes mice. These novel findings suggest that inhibition of ATX may be a potential therapeutic target for DN.

Autotaxin/Lysophosphatidic Acid Axis: From Bone Biology to Bone Disorders

Lysophosphatidic acid (LPA) is a natural bioactive phospholipid with pleiotropic activities affecting multiple tissues, including bone. LPA exerts its biological functions by binding to G-protein coupled LPA receptors (LPA_1-6) to stimulate cell migration, proliferation, and survival. It is largely produced by autotaxin (ATX), a secreted enzyme with lysophospholipase D activity that converts lysophosphatidylcholine (LPC) into active LPA. Beyond its enzymatic activity, ATX serves as a docking molecule facilitating the efficient delivery of LPA to its specific cell surface receptors. Thus, LPA effects are the result of local production by ATX in a given tissue or cell type. As a consequence, the ATX/LPA axis should be considered as an entity to better understand their roles in physiology and pathophysiology and to propose novel therapeutic strategies. Herein, we provide not only an extensive overview of the relevance of the ATX/LPA axis in bone cell commitment and differentiation, skeletal development, and bone disorders, but also discuss new working hypotheses emerging from the interplay of ATX/LPA with well-established signaling pathways regulating bone mass.

A Trans-Agency Workshop on the Pathophysiology of Radiation-Induced Lung Injury

Research and development of medical countermeasures (MCMs) for radiation-induced lung injury relies on the availability of animal models with well-characterized pathophysiology, allowing effective bridging to humans. To develop useful animal models, it is important to understand the clinical condition, advantages and limitations of individual models, and how to properly apply these models to demonstrate MCM efficacy. On March 20, 2019, a meeting sponsored by the Radiation and Nuclear Countermeasures Program (RNCP) within the National Institute of Allergy and Infectious Diseases (NIAID) brought together medical, scientific and regulatory communities, including academic and industry subject matter experts, and government stakeholders from the Food and Drug Administration (FDA) and the Biomedical Advanced Research and Development Authority (BARDA), to identify critical research gaps, discuss current clinical practices for various forms of pulmonary damage, and consider available animal models for radiation-induced lung injury.

CREB-dependent LPA-induced signaling initiates a pro-fibrotic feedback loop between small airway basal cells and fibroblasts

Background

Lysophosphatidic acid (LPA), generated extracellularly by the action of autotaxin and phospholipase A2, functions through LPA receptors (LPARs) or sphingosine-1-phosphate receptors (S1PRs) to induce pro-fibrotic signaling in the lower respiratory tract of patients with idiopathic pulmonary fibrosis (IPF). We hypothesized that LPA induces changes in small airway epithelial (SAE) basal cells (BC) that create cross-talk between the BC and normal human lung fibroblasts (NHLF), enhancing myofibroblast formation.

Methods

To assess LPA-induced signaling, BC were treated with LPA for 2.5 min and cell lysates were analyzed by phosphokinase array and Western blot. To assess transcriptional changes, BC were treated with LPA for 3 h and harvested for collection and analysis of RNA by quantitative polymerase chain reaction (qPCR). To assess signaling protein production and function, BC were washed thoroughly after LPA treatment and incubated for 24 h before collection for protein analysis by ELISA or functional analysis by transfer of conditioned medium to NHLF cultures. Transcription, protein production, and proliferation of NHLF were assessed.

Results

LPA treatment induced signaling by cAMP response element-binding protein (CREB), extracellular signal-related kinases 1 and 2 (Erk1/2), and epithelial growth factor receptor (EGFR) resulting in elevated expression of connective tissue growth factor (CTGF), endothelin-1 (EDN1/ET-1 protein), and platelet derived growth factor B (PDGFB) at the mRNA and protein levels. The conditioned medium from LPA-treated BC induced NHLF proliferation and increased NHLF expression of collagen I (COL1A1), smooth muscle actin (ACTA2), and autotaxin (ENPP2) at the mRNA and protein levels. Increased autotaxin secretion from NHLF correlated with increased LPA in the NHLF culture medium. Inhibition of CREB signaling blocked LPA-induced changes in BC transcription and translation as well as the pro-fibrotic effects of the conditioned medium on NHLF.

Conclusion

Inhibition of CREB signaling may represent a novel target for alleviating the LPA-induced pro-fibrotic feedback loop between SAE BC and NHLF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01677-0.