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Hypothalamic kisspeptin neurons are the primary modulators of gonadotropin-releasing hormone (GnRH) neurons. It has been shown that circadian rhythms driven by the suprachiasmatic nucleus (SCN) contribute to GnRH secretion. Kisspeptin neurons are potential targets of SCN neurons due to reciprocal connections with the anteroventral periventricular and rostral periventricular nuclei (AVPV/PeN) and the arcuate nucleus of the hypothalamus (ARH). Vasoactive intestinal peptide (VIP), a notable SCN neurotransmitter, modulates GnRH secretion depending on serum estradiol levels, aging or time of the day. Considering that kisspeptin neurons may act as interneurons and mediate VIP's effects on the reproductive axis, we investigated the effects of VIP on hypothalamic kisspeptin neurons in female mice during estrogen negative feedback. Our findings indicate that VIP induces a TTX-independent depolarization of approximately 30% of AVPV/PeN kisspeptin neurons in gonad-intact (diestrus) and ovariectomized (OVX) mice. In the ARH, the percentage of kisspeptin neurons that were depolarized by VIP was even higher (approximately 90%). An intracerebroventricular infusion of VIP leds to an increased percentage of kisspeptin neurons expressing the phospho Ser133 cAMP-response-element-binding protein (pCREB) in the AVPV/PeN. On the other hand, pCREB expression in ARH kisspeptin neurons was similar between saline- and VIP-injected mice. Thus, VIP can recruit different signaling pathways to modulate AVPV/PeN or ARH kisspeptin neurons, resulting in distinct cellular responses. The expression of VIP receptors (VPACR) was upregulated in the AVPV/PeN, but not in the ARH, of OVX mice compared to mice on diestrus and estradiol-primed OVX mice. Our findings indicate that VIP directly influences distinct cellular aspects of the AVPV/PeN and ARH kisspeptin neurons during estrogen negative feedback, possibly to influence pulsatile LH secretion., (Copyright © 2021 Elsevier B.V. All rights reserved.)

VIP and its receptors (VPACRs) are largely investigated in vertebrate testis, as well as their functions in the control of spermatogenesis and steroidogenesis. By contrast, a few data are available about the presence and role of VIP in the epididymis. The aim of the present paper was to investigate the localization of VIP and its receptors in the epididymis of two vertebrates: Podarcis sicula, a seasonal reproducer, and Rattus rattus, a continuous reproducer. By immunohystochemical investigation, we demonstrated for the first time that VIP and its receptors are widely represented in the epididymis of Podarcis sand Rattus; in particular in Podarcis, we showed that during the reproductive period, as well as in Rattus, VIP and its receptors are well represented in all the epithelial cells and the connective tissue of the epididymis; by contrast, during the non-reproductive period, VIP and its receptors are represented only in the connective tissue. The possible role of the VIP/VPACR system in the control of reproduction is discussed., (Copyright © 2017 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.)

Vasoactive intestinal peptide (VIP) plays important roles in many biological functions, such as, stimulation of contractility in the heart, vasodilation, promoting neuroendocrine-immune communication, lowering arterial blood pressure, and anti-inflammatory and immune-modulatory activity. Osteoarthritis (OA) is a chronic and degenerative bone disease, which is one of the most common causes of disability and most common in both sexes as people become older. Interestingly VIP can prevent chronic cartilage damage and joint remodeling. This review article provides update information on the association of VIP and OA and its treatment. Evidences suggest that VIP is down-regulated in synovial fluid of OA, and VIP down-regulation leads to increase in the production of pro-inflammatory cytokines that might contribute to the pathogenesis of OA; however contradictory reports also exist suggesting that accumulation of VIP in joints can also contribute OA. A number of studies indicated that up-regulation of VIP can counteract the action of pro-inflammatory stimuli and alleviate the pain in OA. More clinical investigations are necessary to determine the biology of VIP and its therapeutic potential in OA that might represent the future standards of care for OA.

Neuropeptides are potentially valuable tools for clinical applications as they offer many distinct advantages over other bioactive molecules like proteins and monoclonal antibodies due to their reduced side effects and simple chemical modifications. Despite such advantages, the difficulty with neuropeptides often relies on their poor metabolic stability and reduced biological activity intervals. Among the neuropeptides, VIP has been identified as a potentially bioactive agent for inflammatory, neurodegenerative, and cancer-related diseases. However, the effective translation of preclinical studies related to VIP to clinical realities faces several major challenges, most of which are commonplace for other neuropeptides. Here, we present recent studies aimed at developing nanostructured organic and inorganic systems either for the appropriate delivery of VIP or for VIP targeting. These technologies stand as an alternative starting point for chemical manipulations of the neuropeptides in order to improve potency, selectivity, or pharmacokinetic parameters., (© 2015 Elsevier Inc. All rights reserved.)

An increasing number of G protein-coupled receptors, like receptors for vasoactive intestinal peptide (VIP), are found in cell nucleus. As VIP receptors are involved in the regulation of glioma cell proliferation and migration, we investigated the expression and the nuclear localization of the VIP receptors VPAC1 and VPAC2 in this cancer. First, by applying Western blot and immunofluorescence detection in three human glioblastoma (GBM) cell lines, we observed a strong nuclear staining for the VPAC1 receptor and a weak nuclear VPAC2 receptor staining. Second, immunohistochemical staining of VPAC1 and VPAC2 on tissue microarrays (TMA) showed that the two receptors were expressed in normal brain and glioma tissues. Expression in the non-nuclear compartment of the two receptors significantly increased with the grade of the tumors. Analysis of nuclear staining revealed a significant increase of VPAC1 staining with glioma grade, with up to 50% of GBM displaying strong VPAC1 nuclear staining, whereas nuclear VPAC2 staining remained marginal. The increase in VPAC receptor expression with glioma grades and the enhanced nuclear localization of the VPAC1 receptors in GBM might be of importance for glioma progression., (Copyright © 2014 Elsevier Inc. All rights reserved.)