In vivo actions of SCTR/AT1aR heteromer in controlling Vp expression and release via cFos/cAMP/CREB pathway in magnocellular neurons of PVN.

With an increasing body of evidence regarding GPCR oligomerization and its clinical implications over the last decade, the modulation and dynamics of GPCR homo- and hetero-oligomers has more recently become an area of intense research focus. Previously, our lab showed in vitro heteromer formation between angiotensin II receptor type 1 subtype a (AT1aR) and secretin receptor (SCTR), which is involved in in vivo control of hyperosmolality-induced water drinking behavior. Because the secretin (SCT)/SCTR axis is crucial to the central actions of angiotensin II (ANGII) and both SCT and ANGII are capable of triggering vasopressin (Vp) release from hypothalamus, we investigated here the in vivo role of SCTR-AT1aR heteromer in regulating Vp release in hypothalamus using transmembrane peptides as tools. We showed that SCTR-AT1aR heteromer mediates stimulatory actions of both SCT and ANGII in hypothalamic Vp expression and release as well as neuronal activities via the immediate early gene cFos. The results from this study not only are consistent with our hypothesis that SCT and ANGII interact at the receptor level to mediate their water homeostatic activities but also provide evidence for in vivo functions of cross-class GPCR heteromers.-Mak, S. O. K., Zhang, L., Chow, B. K. C. In vivo actions of SCTR/AT1aR heteromer in controlling Vp expression and release via cFos/cAMP/CREB pathway in magnocellular neurons of PVN.

Distribution and Functional Implication of Secretin in Multiple Brain Regions.

Secretin is a polypeptide hormone initially identified for its gastrointestinal functions. However, emerging evidences show wide distribution of secretin and secretin receptor across various brain regions from cerebral cortex, hippocampus, hypothalamus to cerebellum. In this mini review, we will firstly describe the region-specific expression pattern of secretin and secretin receptor in the brain, followed by a summary of central physiological and neurological functions mediated by secretin. Using genetic manipulation and pharmaceutical approaches, one can elucidate the role of secretin in mediating various neurological functions from simple behaviors, such as water and food intake, to more complex functions including emotion, motor, and learning or memory. At last, current weakness and future perspectives of secretin in the central nervous system will be discussed, aiming to provide the potency of using secretin or its analog for treating various neurological disorders.

A novel small-molecule inhibitor of influenza A virus acts by suppressing PA endonuclease activity of the viral polymerase.

The RNA-dependent RNA polymerase of influenza A virus comprises conserved and independently-folded subdomains with defined functionalities. The N-terminal domain of the PA subunit (PA(N)) harbors the endonuclease function so that it can serve as a desired target for drug discovery. To identify a class of anti-influenza inhibitors that impedes PA(N) endonuclease activity, a screening approach that integrated the fluorescence resonance energy transfer based endonuclease inhibitory assay with the DNA gel-based endonuclease inhibitory assay was conducted, followed by the evaluation of antiviral efficacies and potential cytotoxicity of the primary hits in vitro and in vivo. A small-molecule compound ANA-0 was identified as a potent inhibitor against the replication of multiple subtypes of influenza A virus, including H1N1, H3N2, H5N1, H7N7, H7N9 and H9N2, in cell cultures. Combinational treatment of zanamivir and ANA-0 exerted synergistic anti-influenza effect in vitro. Intranasal administration of ANA-0 protected mice from lethal challenge and reduced lung viral loads in H1N1 virus infected BALB/c mice. In summary, ANA-0 shows potential to be developed to novel anti-influenza agents.

Agnathan VIP, PACAP and their receptors: ancestral origins of today's highly diversified forms.

VIP and PACAP are pleiotropic peptides belonging to the secretin superfamily of brain-gut peptides and interact specifically with three receptors (VPAC(1), PAC(1) and VPAC(2)) from the class II B G protein-coupled receptor family. There is immense interest regarding their molecular evolution which is often described closely alongside gene and/or genome duplications. Despite the wide array of information available in various vertebrates and one invertebrate the tunicate, their evolutionary origins remain unresolved. Through searches of genome databases and molecular cloning techniques, the first lamprey VIP/PACAP ligands and VPAC receptors are identified from the Japanese lamprey. In addition, two VPAC receptors (VPACa/b) are identified from inshore hagfish and ligands predicted for sea lamprey. Phylogenetic analyses group these molecules into their respective PHI/VIP, PRP/PACAP and VPAC receptor families and show they resemble ancestral forms. Japanese lamprey VIP/PACAP peptides synthesized were tested with the hagfish VPAC receptors. hfVPACa transduces signal via both adenylyl cylase and phospholipase C pathways, whilst hfVPACb was only able to transduce through the calcium pathway. In contrast to the widespread distribution of VIP/PACAP ligands and receptors in many species, the agnathan PACAP and VPAC receptors were found almost exclusively in the brain. In situ hybridisation further showed their abundance throughout the brain. The range of VIP/PACAP ligands and receptors found are highly useful, providing a glimpse into the evolutionary events both at the structural and functional levels. Though representative of ancestral forms, the VIP/PACAP ligands in particular have retained high sequence conservation indicating the importance of their functions even early in vertebrate evolution. During these nascent stages, only two VPAC receptors are likely responsible for eliciting functions before evolving later into specific subtypes post-Agnatha. We also propose VIP and PACAP's first functions to predominate in the brain, evolving alongside the central nervous system, subsequently establishing peripheral functions.

Effective melanoma immunotherapy with interleukin-2 delivered by a novel polymeric nanoparticle.

Interleukin-2 (IL-2) has been shown to possess antitumor activity in numerous preclinical and clinical studies. However, the short half-life of recombinant IL-2 protein in serum requires repeated high-dose injections, resulting in severe side effects. Although adenovirus-mediated IL-2 gene therapy has shown antitumor efficacy, the host antibody response to adenoviral particles and potential biosafety concerns still obstruct its clinical applications. Here we report a novel nanopolymer for IL-2 delivery, consisting of low molecular weight polyethylenimine (600 Da) linked by ß-cyclodextrin and conjugated with folate (named H1). H1 was mixed with IL-2 plasmid to form H1/pIL-2 polyplexes of around 100 nm in diameter. Peritumoral injection of these polyplexes suppressed the tumor growth and prolonged the survival of C57/BL6 mice bearing B16-F1 melanoma grafts. Importantly, the antitumor effects of H1/pIL-2 (50 µg DNA) were similar to those of recombinant adenoviruses expressing IL-2 (rAdv-IL-2; 2 × 10(8) pfu). Furthermore, we showed that H1/pIL-2 stimulated the activation and proliferation of CD8+, CD4+ T cell, and natural killer cells in peripheral blood and increased the infiltration of CD8+, CD4+ Tcells, and natural killer cells into the tumor environment. In conclusion, these results show that H1/pIL-2 is an effective and safe melanoma therapeutic with an efficacy comparable to that of rAdv-IL-2. This treatment represents an alternative gene therapy strategy for melanoma.

An indispensable role of secretin in mediating the osmoregulatory functions of angiotensin II.

Fluid balance is critical to life and hence is tightly controlled in the body. Angiotensin II (ANGII), one of the most important components of this regulatory system, is recognized as a dipsogenic hormone that stimulates vasopressin (VP) expression and release. However, detailed mechanisms regarding how ANGII brings about these changes are not fully understood. In the present study, we show initially that the osmoregulatory functions of secretin (SCT) in the brain are similar to those of ANGII in mice and, more important, we discovered the role of SCT as the link between ANGII and its downstream effects. This was substantiated by the use of two knockout mice, SCTR(-/-) and SCT(-/-), in which we show the absence of an intact SCT/secretin receptor (SCTR) axis resulted in an abolishment or much reduced ANGII osmoregulatory functions. By immunohistochemical staining and in situ hybridization, the proteins and transcripts of SCT and its receptor are found in the paraventricular nucleus (PVN) and lamina terminalis. We propose that SCT produced in the circumventricular organs is transported and released in the PVN to stimulate vasopressin expression and release. In summary, our findings identify SCT and SCTR as novel elements of the ANGII osmoregulatory pathway in maintaining fluid balance in the body.

Pluronic L-81 ameliorates diabetic symptoms in db/db mice through transcriptional regulation of microsomal triglyceride transfer protein.

AIM: To test whether oral L-81 treatment could improve the condition of mice with diabetes and to investigate how L-81 regulates microsomal triglyceride transfer protein (MTP) activity in the liver. METHODS: Genetically diabetic (db/db) mice were fed on chow supplemented with or without L-81 for 4 wk. The body weight, plasma glucose level, plasma lipid profile, and adipocyte volume of the db/db mice were assessed after treatment. Toxicity of L-81 was also evaluated. To understand the molecular mechanism, HepG2 cells were treated with L-81 and the effects on apolipoprotein B (apoB) secretion and mRNA level of the MTP gene were assessed. RESULTS: Treatment of db/db mice with L-81 significantly reduced and nearly normalized their body weight, hyperphagia and polydipsia. L-81 also markedly decreased the fasting plasma glucose level, improved glucose tolerance, and attenuated the elevated levels of plasma cholesterol and triglyceride. At the effective dosage, little toxicity was observed. Treatment of HepG2 cells with L-81 not only inhibited apoB secretion, but also significantly decreased the mRNA level of the MTP gene. Similar to the action of insulin, L-81 exerted its effect on the MTP promoter. CONCLUSION: L-81 represents a promising candidate in the development of a selective insulin-mimetic molecule and an anti-diabetic agent.