Cyclic Peptides KS-133 and KS-487 Multifunctionalized Nanoparticles Enable Efficient Brain Targeting for Treating Schizophrenia.

Establishing drug delivery systems (DDSs) for transporting drugs from peripheral tissues to the brain is crucial for treating central nervous system diseases. We previously reported the interactions of (1) KS-133, a selective antagonist peptide, with vasoactive intestinal peptide receptor 2 (VIPR2), a drug target for schizophrenia, and (2) KS-487, a selective binding peptide, with the cluster IV domain of low-density lipoprotein receptor-related protein 1 (LRP1), which is involved in crossing the blood-brain barrier. We developed a novel DDS-based strategy for treating schizophrenia using KS-487 as a brain-targeting peptide and KS-133 as a drug. Dibenzocyclooctyne-KS-487 was conjugated with N3-indocyanine green (ICG) using a click reaction and administered intravenously into mice. Fluorescence was clearly observed from ICG in the brains of the mice. Nanoparticles (NPs) encapsulating ICG and displaying KS-487 were prepared and subcutaneously administered to mice, resulting in a significant accumulation of ICG in the brain. Pharmacokinetic analysis of NPs containing KS-133 and displaying KS-487 (KS-133/KS-487 NPs) revealed the time-dependent transport of KS-133 into the brain. KS-133/KS-487 NPs were subcutaneously administered to mouse models of schizophrenia, which significantly improved cognitive dysfunction. This is the first study to demonstrate the potential therapeutic efficacy of a multifunctionalized multipeptide NP in inhibiting VIPR2.

Blockade of vasoactive intestinal peptide receptor 2 (VIPR2) signaling suppresses cyclin D1-dependent cell-cycle progression in MCF-7 cells.

Vasoactive intestinal peptide (VIP) receptor 2 (VIPR2) is a G protein-coupled receptor that binds to Gαs, Gαi, and Gαq proteins to regulate various downstream signaling molecules, such as protein kinase A (PKA), phosphatidylinositol 3-kinase (PI3K), and phospholipase C. In this study, we examined the role of VIPR2 in cell cycle progression. KS-133, a newly developed VIPR2-selective antagonist peptide, attenuated VIP-induced cell proliferation in MCF-7 cells. The percentage of cells in the S-M phase was decreased in MCF-7 cells treated with KS-133. KS-133 in the presence of VIP decreased the phosphorylation of extracellular signal-regulated kinase (ERK), AKT, and glycogen synthase kinase-3ß (GSK3ß), resulting in a decrease in cyclin D1 levels. In MCF-7 cells stably-expressing VIPR2, KS-133 decreased PI3K activity and cAMP levels. Treatment with the ERK-specific kinase (MEK) inhibitor U0126 and the class I PI3K inhibitor ZSTK474 decreased the percentage of cells in the S phase. KS-133 reduced the percentage of cells in the S phase more than treatment with U0126 or ZSTK474 alone and did not affect the effect of the mixture of these inhibitors. Our findings suggest that VIPR2 signaling regulates cyclin D1 levels through the cAMP/PKA/ERK and PI3K/AKT/GSK3ß pathways, and mediates the G1/S transition to control cell proliferation.

Vasoactive intestinal peptide receptor 2 signaling promotes breast cancer cell proliferation by enhancing the ERK pathway.

Vasoactive intestinal peptide (VIP) receptor 2 (VIPR2) is a class B G protein-coupled receptor with the neuropeptide VIP as a ligand. Increased VIPR2 mRNA expression and/or VIPR2 gene copy number has been documented in several cancers including breast carcinoma. However, the pathophysiological role of increased VIPR2 in the proliferation of breast cancer cells remains largely unknown. In this study, we found that VIPR2 overexpression in MCF-7 and MDA-MB-231 cells, human breast cancer cell lines, promoted cell proliferation. Increased VIPR2 also exacerbated intraperitoneal proliferation of breast cancer MDA-MB-231 cells in a tumor nude mouse model in vivo. Treatment with KS-133, a VIPR2-selective antagonist peptide, significantly inhibited VIP-induced cell proliferation in VIPR2-overexpressing MCF-7 and MDA-MB-231 cells. Overexpressed VIPR2 caused increases in the levels of cAMP and phosphorylated extracellular signal-regulated kinase (ERK), which involves a VIPR2 signaling pathway through Gs protein. Additionally, phosphorylation of vasodilator-stimulated phosphoprotein (Ser157) and cAMP response element binding protein (Ser133) in VIPR2-overexpressing MCF-7 cells was greater than that in control cells, suggesting the increased PKA activity. Moreover, an inhibitor of mitogen-activated protein kinase kinase, U0126, attenuated tumor proliferation in exogenous VIPR2-expressing MCF-7 and MDA-MB-231 cells at the same level as observed in EGFP-expressing cells treated with U0126. Together, these findings suggest that VIPR2 controls breast tumor growth by regulating the cAMP/PKA/ERK signaling pathway, and the excessive expression of VIPR2 may lead to an exacerbation of breast carcinoma.