The Ablation of VEGFR-1 Signaling Promotes Pressure Overload-Induced Cardiac Dysfunction and Sudden Death

The state of the art in secondary pharmacology and its impact on the safety of new medicines

Secondary pharmacology screening of investigational small-molecule drugs for potentially adverse off-target activities has become standard practice in pharmaceutical research and development, and regulatory agencies are increasingly requesting data on activity against targets with recognized adverse effect relationships. However, the screening strategies and target panels used by pharmaceutical companies may vary substantially. To help identify commonalities and differences, as well as to highlight opportunities for further optimization of secondary pharmacology assessment, we conducted a broad-ranging survey across 18 companies under the auspices of the DruSafe leadership group of the International Consortium for Innovation and Quality in Pharmaceutical Development. Based on our analysis of this survey and discussions and additional research within the group, we present here an overview of the current state of the art in secondary pharmacology screening. We discuss best practices, including additional safety-associated targets not covered by most current screening panels, and present approaches for interpreting and reporting off-target activities. We also provide an assessment of the safety impact of secondary pharmacology screening, and a perspective on opportunities and challenges in this rapidly developing field.

Deletion of Endothelial TRPV4 Protects Heart From Pressure Overload-Induced Hypertrophy

BACKGROUND

Left ventricular hypertrophy is a bipolar response, starting as an adaptive response to the hemodynamic challenge, but over time develops maladaptive pathology partly due to microvascular rarefaction and impaired coronary angiogenesis. Despite the profound influence on cardiac function, the mechanotransduction mechanisms that regulate coronary angiogenesis, leading to heart failure, are not well known.

METHODS

We subjected endothelial-specific knockout mice of mechanically activated ion channel, TRPV4 (transient receptor potential cation channel subfamily V member 4; TRPV4ECKO) to pressure overload via transverse aortic constriction and examined cardiac function, cardiomyocyte hypertrophy, cardiac fibrosis, and apoptosis. Further, we measured microvascular density and underlying TRPV4 mechanotransduction mechanisms using human microvascular endothelial cells, extracellular matrix gels of varying stiffness, unbiased RNA sequencing, small interfering RNA, Western blot, quantitative-PCR, and confocal immunofluorescence techniques.

RESULTS

We demonstrate that endothelial-specific deletion of TRPV4 preserved cardiac function, cardiomyocyte structure, and reduced cardiac fibrosis compared with TRPV4lox/lox mice, 28 days post-transverse aortic constriction. Interestingly, comprehensive RNA sequencing analysis revealed an upregulation of proangiogenic factors (VEGFα [vascular endothelial growth factor α], NOS3 [nitric oxide synthase 3], and FGF2 [fibroblast growth factor 2]) with concomitant increase in microvascular density in TRPV4ECKO hearts after transverse aortic constriction compared with TRPV4lox/lox. Further, an increased expression of VEGFR2 (vascular endothelial growth factor receptor 2) and activation of the YAP (yes-associated protein) pathway were observed in TRPV4ECKO hearts. Mechanistically, we found that downregulation of TRPV4 in endothelial cells induced matrix stiffness-dependent activation of YAP and VEGFR2 via the Rho/Rho kinase/large tumor suppressor kinase pathway.

CONCLUSIONS

Our results suggest that endothelial TRPV4 acts as a mechanical break for coronary angiogenesis, and uncoupling endothelial TRPV4 mechanotransduction attenuates pathological cardiac hypertrophy by enhancing coronary angiogenesis.

Therapeutic Potential of VEGF-B in Coronary Heart Disease and Heart Failure: Dream or Vision?

Coronary heart disease (CHD) is the leading cause of death around the world. Based on the roles of vascular endothelial growth factor (VEGF) family members to regulate blood and lymphatic vessels and metabolic functions, several therapeutic approaches have been attempted during the last decade. However proangiogenic therapies based on classical VEGF-A have been disappointing. Therefore, it has become important to focus on other VEGFs such as VEGF-B, which is a novel member of the VEGF family. Recent studies have shown the very promising potential of the VEGF-B to treat CHD and heart failure. The aim of this review article is to present the role of VEGF-B in endothelial biology and as a potential therapeutic agent for CHD and heart failure. In addition, key differences between the VEGF-A and VEGF-B effects on endothelial functions are demonstrated.

Novel Designed Proteolytically Resistant VEGF-B186R127S Promotes Angiogenesis in Mouse Heart by Recruiting Endothelial Progenitor Cells

Background: Previous studies have indicated that vascular endothelial growth factor B186 (VEGF-B186) supports coronary vascular growth in normal and ischemic myocardium. However, previous studies also indicated that induction of ventricular arrhythmias is a severe side effect preventing the use of VEGF-B186 in cardiac gene therapy, possibly mediated by binding to neuropilin 1 (NRP1). We have designed a novel VEGF-B186 variant, VEGF-B186R127S, which is resistant to proteolytic processing and unable to bind to NRP1. Here, we studied its effects on mouse heart to explore the mechanism of VEGF-B186-induced vascular growth along with its effects on cardiac performance.

Methods: Following the characterization of VEGF-B186R127S, we performed ultrasound-guided adenoviral VEGF-B186R127S gene transfers into the murine heart. Vascular growth and heart functions were analyzed using immunohistochemistry, RT-PCR, electrocardiogram and ultrasound examinations. Endothelial progenitor cells (EPCs) were isolated from the circulating blood and characterized. Also, in vitro experiments were carried out in cardiac endothelial cells with adenoviral vectors.

Results: The proteolytically resistant VEGF-B186R127S significantly induced vascular growth in mouse heart. Interestingly, VEGF-B186R127S gene transfer increased the number of circulating EPCs that secreted VEGF-A. Other proangiogenic factors were also present in plasma and heart tissue after the VEGF-B186R127S gene transfer. Importantly, VEGF-B186R127S gene transfer did not cause any side effects, such as arrhythmias.

Conclusion: VEGF-B186R127S induces vascular growth in mouse heart by recruiting EPCs. VEGF-B186R127S is a novel therapeutic agent for cardiac therapeutic angiogenesis to rescue myocardial tissue after an ischemic insult.