Expression of Neuropeptide Y Receptors mRNA and Protein in Human Brain Vessels and Cerebromicrovascular Cells in Culture

Abstract

Neuropeptide Y (NPY) has been suggested as an important regulator of CBF. However, except for the presence of Y1 receptors in large cerebral arteries, little is known about its possible sites of action on brain vessels. In this study, we sought to identify the NPY receptors present in the human cerebrovascular bed. Specific Y1 receptor binding sites, localized on the smooth muscle of human pial vessels and potently competed by NPY, polypeptide YY (PYY), and the selective Y1 receptor antagonist BIBP 3226, were identified by quantitative radioautography of the Y1 radioligand [125I]-[Leu31, Pro34]-PYY. In contrast, no specific binding of the Y2-([125I]-PYY3-36) and Y4/Y5-(125I-human pancreatic polypeptide [hPP]) radioligands could be detected. By in situ hybridization, expression of Y1 receptor mRNA was restricted to the smooth muscle layer of pial vessels, whereas no specific signals were detected for either Y2, Y4, or Y5 receptors. Similarly, using reverse transcriptase-polymerase chain reaction (RT-PCR), mRNA for Y1 but not Y2, Y4, or Y5 receptors was consistently detected in isolated human pial vessels, intracortical microvessels, and capillaries. In human brain microvascular cells in culture, PCR products for the Y1 receptors were exclusively found in the smooth muscle cells. In cultures of human brain astrocytes, a cell type that associates intimately with brain microvessels, PCR products for Y1, Y2, and Y4 but not Y5 receptors were identified. Finally, NPY significantly inhibited the forskolin-induced cAMP production in smooth muscle but not in endothelial cell cultures. We conclude that smooth muscle Y1 receptors are the primary if not exclusive NPY receptors associated with human brain extraparenchymal and intraparenchymal blood vessels, where they most likely mediate cerebral vasoconstriction.

Cortical GABA Interneurons in Neurovascular Coupling: Relays for Subcortical Vasoactive Pathways

“…In contrast, the failure of CCK to alter microvascular tone correlated well with the lack of CCK receptor expression in microvascular smooth muscle, suggesting that this peptide is unlikely to directly couple flow to neuronal activity. We found that NPY induced contraction of intracortical microvessels consistent with contractile NPY-Y1 receptor mRNAs (Abounader et al, 1999) and proteins (Bao et al, 1997) in cortical microarterioles. Intracortical microvessels were also highly responsive to the NO donor DEA NONOate, further emphasizing the opposite vasomotor role of colocalized NO and NPY (ϮSOM) within cortical interneurons.…”

“…To assess whether or not cortical microvessels could potentially respond to perivascularly released neuropeptides from the identified GABA interneurons, we assessed, by RT-PCR, the expression of receptors for these peptides. Expression of receptors for VIP, CCK, and SOM was determined in human cerebromicrovascular endothelial (EC), smooth muscle (SMC), and fetal astroglial (AST) cell cultures generated as described previously (Abounader et al, 1999). The following primer pairs were used (receptor: GenBank accession number, primers, and length of PCR product): VPAC1: NM_004624.…”

“…To assess whether the release of neuropeptides expressed by the identified vasomotor neurons could be functionally relevant, we first studied VIP, CCK, and SOM receptor expression in different cellular compartments of resistance microvessels, as previously described for microvascular NPY Y1 receptors (Abounader et al, 1999). As illustrated in Figure 4 ( A-C, left panels), microvascular endothelial cells expressed all subtypes of VIP and CCK receptors, but only the SSTR1 and SSTR2 subtypes of SOM receptors were consistently (Ͼ50% of the preparations) expressed in these cells.…”

“…Intracortical microvessels were also highly responsive to the NO donor DEA NONOate, further emphasizing the opposite vasomotor role of colocalized NO and NPY (ϮSOM) within cortical interneurons. Likewise, astrocytes expressed various receptors for the neuropeptides found in perivascular GABA interneurons (Martin et al, 1992;Viollet et al, 1997;Abounader et al, 1999). Although they may possibly participate in the interneuron-driven vascular responses, no information is yet available on the release of vasoactive substances from astrocytes activated by VIP, NPY, or SOM.…”

Neuropeptide Y Has a Protective Role during Murine Retrovirus-Induced Neurological Disease

“…The Y1, Y2, and Y5 receptor are also expressed by macrophages, with different functions for these receptors in the macrophage response to NPY (11). Only one receptor, Y1, is expressed by capillary endothelia (1,17). Surprisingly, mRNA expression levels of Y1, Y2, and Y5 were not altered during BE infection ( Table 2).…”