The role of neuropeptide Y in the regulation of vascular function
Objective and brief description of the project:
Neuropeptide Y (NPY) is one of the most abundant neuropeptides in the peripheral and central nervous systems in humans. It acts as a neurotransmitter regulating various autonomic and endocrine functions. Recent evidence suggests that blood vessels possess their own autocrine NPY system. NPY can be produced in vivo by sympathetic nerves and/or by the endothelium. Moreover, it may be that the main target of NPY is the regulation of vascular function locally, not of sympathetic tone at systemic level.
We have earlier reported that a rather common L7P substitution located in the signal peptide of the NPY gene. This polymorphism is associated with increased levels of serum total and LDL cholesterol levels in obese Finnish and Dutch healthy subjects, with greater increase of the intima-media thickness in longterm follow up of middle aged Finnish men and type 2 diabetics. We have also shown that L7P substitution of the NPY gene is functional and affects plasma levels of NPY in humans. Since the initial step in the development of atherosclerosis is believed to be endothelial dysfunction, these observations suggest that preproNPY sequence variation may be related to endothelial function. The crucial role of NPY in vascular function and processing is further emphasized by the observation that the carriers having P7 in the preproNPY are markedly over-represented among type 2 diabetes patients with retinopa-thy compared to type 2 diabetes patients without retinopathy and to the population control. Also results with experimental animal model of retinal neovascularization support these human association studies.
In studies on the role of NPY in the regulation of human endothelial function we are using isolated human umbilical endothelial cells (HUVECs). In previous studies with HUVECs with P7 substitution we have found out that cells can have enhanced endogenous processing of preproNPY, which can lead to increased NPY levels in the tissues expressing NPY, like sympathetic nerves and endothelium.
Although, the primary goal is to determine the role of NPY in human vascular biology, the use of NPY transgenic animal models offers a tool to study NPY mediated vascular functions in the presence of different endogenous NPY regulation. As endothelial dysfunction is a key event in atherogenesis, this project is aimed to assess the influence of NPY on endothelial function ex vivo. We have succeeded to create a transgenic mouse model with conditioned overexpression of NPY in sympathetic nervous system and vascular tissue overexpressing animals are under preparation. Studies using vessels from these different transgenic animals with different NPY regulation attempt to establish the causal role for NPY in the endothelial dysfunction and to demonstrate that altered processing of preproNPY has a preposition towards endothelial dysfunction at organ level and further on towards disease which include vascular dysfunction, like retinopathy. To identify new genes involved in the NPY pathways of sympathetic activation and vascular regulation microarray technology is used. This technology is used to study the differential expression between normal and transgenic mouse blood vessel mRNA and later on, between mRNA extracted from HUVECs of both L7L and P7L genotypes.
This project aims to accomplish the role of NPY in the vascular biology and, more detailed, in physiology and pharmacology of vascular function in humans. It may potentially lead to reconsider the role of NPY only as a sympathetic neurotransmitter and stress the importance of NPY as an endothelial paracrine factor affecting vascular endothelial function. Results can be used directly in target identification and may in future lead to development of drugs affecting through NPY-mediated systems.