Effect of elastin-derived peptides on the production of tissue inhibitor of metalloproteinase-1, -2, and -3 and the ratios in various endothelial cell lines

Imbalance of Pulmonary Microvascular Endothelial Cell-Expression of Metalloproteinases and Their Endogenous Inhibitors Promotes Septic Barrier Dysfunction

Sepsis is a life-threatening disease characterized by excessive inflammation leading to organ dysfunction. During sepsis, pulmonary microvascular endothelial cells (PMVEC) lose barrier function associated with inter-PMVEC junction disruption. Matrix metalloproteinases (MMP) and a disintegrin and metalloproteinases (ADAM), which are regulated by tissue inhibitors of metalloproteinases (TIMPs), can cleave cell-cell junctional proteins, suggesting a role in PMVEC barrier dysfunction. We hypothesize that septic PMVEC barrier dysfunction is due to a disruption in the balance between PMVEC-specific metalloproteinases and TIMPs leading to increased metalloproteinase activity. The effects of sepsis on TIMPs and metalloproteinases were assessed ex vivo in PMVEC from healthy (sham) and septic (cecal ligation and perforation) mice, as well as in vitro in isolated PMVEC stimulated with cytomix, lipopolysaccharide (LPS), and cytomix + LPS vs. PBS. PMVEC had high basal Timp expression and lower metalloproteinase expression, and septic stimulation shifted expression in favour of metalloproteinases. Septic stimulation increased MMP13 and ADAM17 activity associated with a loss of inter-PMVEC junctional proteins and barrier dysfunction, which was rescued by treatment with metalloproteinase inhibitors. Collectively, our studies support a role for metalloproteinase-TIMP imbalance in septic PMVEC barrier dysfunction, and suggest that inhibition of specific metalloproteinases may be a therapeutic avenue for septic patients.

Design and Discovery of Novel Cyclic Peptides as EDPs-EBP Interaction Inhibitors for the Treatment of Liver Fibrosis

Liver fibrosis is the undesirable result of excessive deposition of the extracellular matrix (ECM), and elastin is known as one of the key ECM components. Under specific pathological conditions, elastin undergoes degradation to produce elastin-derived peptides (EDPs), which bind to elastin-binding protein (EBP) to activate corresponding signal pathways, thus accelerating fibrosis progression. Herein, we describe the discovery of novel cyclic peptides that function as potent and stable inhibitors to interfere with the peptide-protein interaction between EDPs and EBP. Remarkably, C_XJ-2 exhibited potent activities to inhibit the PI3K/ERK pathway and decrease hepatic stellate cell proliferation and migration. The subsequent in vivo study demonstrated that C_XJ-2 possessed potent antifibrotic efficacy in ameliorating CCl₄-induced liver fibrosis. This work provides a successful pharmacological strategy for the development of novel inhibitors of EDPs-EBP interaction, which sheds new light on how cyclic peptides disrupt peptide-protein interaction and may also provide new structure-oriented therapeutic candidates in liver fibrosis.

Synergistic activation of AMPK by AdipoR1/2 agonist and inhibitor of EDPs-EBP interaction recover NAFLD through enhancing mitochondrial function in mice

Nonalcoholic fatty liver disease (NAFLD), especially nonalcoholic steatohepatitis (NASH), is a common hepatic manifestation of metabolic syndrome. However, there are no effective therapy to treat this devastating disease. Accumulating evidence suggests that the generation of elastin-derived peptides (EDPs) and the inhibition of adiponectin receptors (AdipoR)1/2 plays essential roles in hepatic lipid metabolism and liver fibrosis. We recently reported that the AdipoR1/2 dual agonist JT003 significantly degraded the extracellular matrix (ECM) and ameliorated liver fibrosis. However, the degradation of the ECM lead to the generation of EDPs, which could further alter liver homeostasis negatively. Thus, in this study, we successfully combined AdipoR1/2 agonist JT003 with V14, which acted as an inhibitor of EDPs-EBP interaction to overcome the defect of ECM degradation. We found that combination of JT003 and V14 possessed excellent synergistic benefits on ameliorating NASH and liver fibrosis than either alone since they compensate the shortage of each other. These effects are induced by the enhancement of the mitochondrial antioxidant capacity, mitophagy, and mitochondrial biogenesis via AMPK pathway. Furthermore, specific suppression of AMPK could block the effects of the combination of JT003 and V14 on reduced oxidative stress, increased mitophagy and mitochondrial biogenesis. These positive results suggested that this administration of combination of AdipoR1/2 dual agonist and inhibitor of EDPs-EBP interaction can be recommended alternatively for an effective and promising therapeutic strategy for the treatment of NAFLD and NASH related fibrosis.

Involvement of TIMP-1 in PECAM-1-mediated tumor dissemination

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is expressed on the vascular endothelium and has been implicated in the late progression of metastatic tumors. The activity of PECAM-1 appears to be mediated by modulation of the tumor microenvironment (TME) and promotion of tumor cell proliferation, rather than through the stimulation of tumor angiogenesis. The present study aimed to extend those initial findings by indicating that the presence of functional PECAM-1 on the endothelium promotes a proliferative tumor cell phenotype in vivo, as well as in tumor cell (B16-F10 melanoma and 4T1 breast cancer cell lines) co-culture assays with mouse endothelial cells (ECs) or a surrogate EC line (REN-MP). The pro-proliferative effects were mediated by soluble endothelial-derived factors that were dependent on PECAM-1 homophilic ligand interactions, but which were independent of PECAM-1-dependent signaling. Further analysis of the conditioned media obtained from tumor/EC and tumor/REN-MP co-cultures identified TIMP metallopeptidase inhibitor-1 (TIMP-1) as a PECAM-1-regulated factor, the targeting of which in the tumor cell/REN-MP system inhibited tumor cell proliferation. In addition, TIMP-1 expression was decreased in metastatic tumors from the lungs of PECAM-1-null mice, thus providing evidence of the in vivo significance of co-culture studies. Taken together, these studies indicated that endothelial PECAM-1, through PECAM-1-dependent homophilic binding interactions, may induce release of TIMP-1 from the endothelium into the TME, thus leading to increased tumor cell proliferation.

The Balance Between Metalloproteinases and TIMPs: Critical Regulator of Microvascular Endothelial Cell Function in Health and Disease

Endothelial cells (EC), especially the microvascular EC (MVEC), have critical functions in health and disease. For example, healthy MVEC provide a barrier between the fluid and protein found within the blood, and the surrounding tissue. Following tissue injury or infection, the microvascular barrier is often disrupted due to activation and dysfunction of the MVEC. Multiple mechanisms promote MVEC activation and dysfunction, including stimulation by cytokines, mechanical interaction with activated leukocytes, and exposure to harmful leukocyte-derived molecules, which collectively result in a loss of MVEC barrier function. However, MVEC activation is also critical to facilitate recruitment of inflammatory cells, such as neutrophils (PMNs) and monocytes, into the injured or infected tissue. Metalloproteinases, including the matrix metalloproteinases (MMPs) and the closely related, a disintegrin and metalloproteinases (ADAMs), have been implicated in regulating both MVEC barrier function, through cleavage of adherens and tight junctions proteins between adjacent MVEC and through degradation of the extracellular matrix, as well as PMN-MVEC interaction, through shedding of cell surface PMN receptors. Moreover, the tissue inhibitors of metalloproteinases (TIMPs), which collectively inhibit most MMPs and ADAMs, are critical regulators of MVEC activation and dysfunction through their ability to inhibit metalloproteinases and thereby promote MVEC stability. However, TIMPs have been also found to modulate MVEC function through metalloproteinase-independent mechanisms, such as regulation of vascular endothelial growth factor signaling. This chapter is focused on examining the role of the metalloproteinases and TIMPs in regulation of MVEC function in both health and disease.

The Elastin Receptor Complex: A Unique Matricellular Receptor with High Anti-tumoral Potential

Elastin, one of the longest-lived proteins, confers elasticity to tissues with high mechanical constraints. During aging or pathophysiological conditions such as cancer progression, this insoluble polymer of tropoelastin undergoes an important degradation leading to the release of bioactive elastin-derived peptides (EDPs), named elastokines. EDP exhibit several biological functions able to drive tumor development by regulating cell proliferation, invasion, survival, angiogenesis, and matrix metalloproteinase expression in various tumor and stromal cells. Although, several receptors have been suggested to bind elastokines (α_vβ₃ and α_vβ₅ integrins, galectin-3), their main receptor remains the elastin receptor complex (ERC). This heterotrimer comprises a peripheral subunit, named elastin binding protein (EBP), associated to the protective protein/cathepsin A (PPCA). The latter is bound to a membrane-associated protein called Neuraminidase-1 (Neu-1). The pro-tumoral effects of elastokines have been linked to their binding onto EBP. Additionally, Neu-1 sialidase activity is essential for their signal transduction. Consistently, EDP-EBP interaction and Neu-1 activity emerge as original anti-tumoral targets. Interestingly, besides its direct involvement in cancer progression, the ERC also regulates diabetes outcome and thrombosis, an important risk factor for cancer development and a vascular process highly increased in patients suffering from cancer. In this review, we will describe ERC and elastokines involvement in cancer development suggesting that this unique receptor would be a promising therapeutic target. We will also discuss the pharmacological concepts aiming at blocking its pro-tumoral activities. Finally, its emerging role in cancer-associated complications and pathologies such as diabetes and thrombotic events will be also considered.