RET Signaling Persists in the Adult Intestine and Stimulates Motility by Limiting PYY Release From Enteroendocrine Cells.

BACKGROUND & AIMS: RET tyrosine kinase is necessary for enteric nervous system development. Loss-of-function RET mutations cause Hirschsprung disease (HSCR), in which infants are born with aganglionic bowel. Despite surgical correction, patients with HSCR often experience chronic defecatory dysfunction and enterocolitis, suggesting that RET is important after development. To test this hypothesis, we determined the location of postnatal RET and its significance in gastrointestinal (GI) motility. METHODS: RetCFP/+ mice and human transcriptional profiling data were studied to identify the enteric neuronal and epithelial cells that express RET. To determine whether RET regulates gut motility in vivo, genetic, and pharmacologic approaches were used to disrupt RET in all RET-expressing cells, a subset of enteric neurons, or intestinal epithelial cells. RESULTS: Distinct subsets of enteric neurons and enteroendocrine cells expressed RET in the adult intestine. RET disruption in the epithelium, rather than in enteric neurons, slowed GI motility selectively in male mice. RET kinase inhibition phenocopied this effect. Most RET+ epithelial cells were either enterochromaffin cells that release serotonin or L-cells that release peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), both of which can alter motility. RET kinase inhibition exaggerated PYY and GLP-1 release in a nutrient-dependent manner without altering serotonin secretion in mice and human organoids. PYY receptor blockade rescued dysmotility in mice lacking epithelial RET. CONCLUSIONS: RET signaling normally limits nutrient-dependent peptide release from L-cells and this activity is necessary for normal intestinal motility in male mice. These effects could contribute to dysmotility in HSCR, which predominantly affects males, and uncovers a mechanism that could be targeted to treat post-prandial GI dysfunction.

Autonomic Nervous System Regulation of Epicardial Adipose Tissue: Potential Roles for Regulator of G Protein Signaling-4.

The epicardial adipose tissue (EAT) or epicardial fat is a visceral fat depot in the heart that contains intrinsic adrenergic and cholinergic nerves, through which it interacts with the cardiac sympathetic (adrenergic) and parasympathetic (cholinergic) nervous systems. These EAT nerves represent a significant source of several adipokines and other bioactive molecules, including norepinephrine, epinephrine, and free fatty acids. The production of these molecules is biologically relevant for the heart, since abnormalities in EAT secretion are implicated in the development of pathological conditions, including coronary atherosclerosis, atrial fibrillation, and heart failure. Sympathetic hyperactivity and parasympathetic (cholinergic) derangement are associated with EAT dysfunction, leading to a variety of adverse cardiac conditions, such as heart failure, diastolic dysfunction, atrial fibrillation, etc.; therefore, several studies have focused on exploring the autonomic regulation of EAT as it pertains to heart disease pathogenesis and progression. In addition, Regulator of G protein Signaling (RGS)-4 is a protein with significant regulatory roles in both adrenergic and muscarinic receptor signaling in the heart. In this review, we provide an overview of the autonomic regulation of EAT, with a specific focus on cardiac RGS4 and the potential roles this protein plays in this regulation.

Efficacy of Affibody-Based Ultrasound Molecular Imaging of Vascular B7-H3 for Breast Cancer Detection.

PURPOSE: Human B7-H3 (hB7-H3) is a promising molecular imaging target differentially expressed on the neovasculature of breast cancer and has been validated for preclinical ultrasound (US) imaging with anti-B7-H3-antibody-functionalized microbubbles (MB). However, smaller ligands such as affibodies (ABY) are more suitable for the design of clinical-grade targeted MB. EXPERIMENTAL DESIGN: Binding of ABYB7-H3 was confirmed with soluble and cell-surface B7-H3 by flow cytometry. MB were functionalized with ABYB7-H3 or anti-B7-H3-antibody (AbB7-H3). Control and targeted MB were tested for binding to hB7-H3-expressing cells (MS1hB7-H3) under shear stress conditions. US imaging was performed with MBABY-B7-H3 in an orthotopic mouse model of human MDA-MB-231 coimplanted with MS1hB7-H3 or control MS1WT cells and a transgenic mouse model of breast cancer development. RESULTS: ABYB7-H3 specifically binds to MS1hB7-H3 and murine-B7-H3-expressing monocytes. MBABY-B7-H3 (8.5 ± 1.4 MB/cell) and MBAb-B7-H3 (9.8 ± 1.3 MB/cell) showed significantly higher (P < 0.0001) binding to the MS1hB7-H3 cells compared with control MBNon-targeted (0.5 ± 0.1 MB/cell) under shear stress conditions. In vivo, MBABY-B7-H3 produced significantly higher (P < 0.04) imaging signal in orthotopic tumors coengrafted with MS1hB7-H3 (8.4 ± 3.3 a.u.) compared with tumors with MS1WT cells (1.4 ± 1.0 a.u.). In the transgenic mouse tumors, MBABY-B7-H3 (9.6 ± 2.0 a.u.) produced higher (P < 0.0002) imaging signal compared with MBNon-targeted (1.3 ± 0.3 a.u.), whereas MBABY-B7-H3 signal in normal mammary glands and tumors with B7-H3 blocking significantly reduced (P < 0.02) imaging signal. CONCLUSIONS: MBABY-B7-H3 enhances B7-H3 molecular signal in breast tumors, improving cancer detection, while offering the advantages of a small size ligand and easier production for clinical imaging.