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Inflammatory process is involved in the pathogenesis of diabetic nephropathy. In this article, we show that cholecystokinin (CCK) is expressed in the kidney and exerts renoprotective effects through its anti-inflammatory actions. DNA microarray showed that CCK was upregulated in the kidney of diabetic wild-type (WT) mice but not in diabetic intracellular adhesion molecule-1 knockout mice. We induced diabetes in CCK-1 receptor (CCK-1R) and CCK-2R double-knockout (CCK-1R(-/-),-2R(-/-)) mice, and furthermore, we performed a bone marrow transplantation study using CCK-1R(-/-) mice to determine the role of CCK-1R on macrophages in the diabetic kidney. Diabetic CCK-1R(-/-),-2R(-/-) mice revealed enhanced albuminuria and inflammation in the kidney compared with diabetic WT mice. In addition, diabetic WT mice with CCK-1R(-/-) bone marrow-derived cells developed more albuminuria than diabetic CCK-1R(-/-) mice with WT bone marrow-derived cells. Administration of sulfated cholecystokinin octapeptide (CCK-8S) ameliorated albuminuria, podocyte loss, expression of proinflammatory genes, and infiltration of macrophages in the kidneys of diabetic rats. Furthermore, CCK-8S inhibited both expression of tumor necrosis factor-α and chemotaxis in cultured THP-1 cells. These results suggest that CCK suppresses the activation of macrophage and expression of proinflammatory genes in diabetic kidney. Our findings may provide a novel strategy of therapy for the early stage of diabetic nephropathy.

Afferent vagal neurons convey gut–brain signals related to the mechanical and chemical sensing of nutrients, with the latter also mediated by gut hormones secreted from enteroendocrine cells. Cell bodies of these neurons are located in the nodose ganglia (NG), with the right NG playing a key role in metabolic regulation. Notably, glucagon-like peptide-1 receptor (GLP1R) neurons primarily innervate the muscle layer of the stomach, distant from glucagon-like peptide-1 (GLP-1)-secreting gut cells. However, the co-expression of gut hormone receptors in these NG neurons remains unclear. Using RNAscope combined with immunohistochemistry, we confirmed GLP1R expression in a large population of NG neurons, with Glp1r, cholecystokinin A receptor (Cckar), and Neuropeptide Y Y2 Receptor (Npy2r) being more highly expressed in the right NG, while neurotensin receptor 1 (Ntsr), G protein-coupled receptor (Gpr65), and 5-hydroxytryptamine receptor 3A (5ht3a) showed equal expressions in the left and right NG. Co-expression analysis demonstrated the following: (i) most Glp1r, Cckar, and Npy2r neurons co-expressed all three receptors; (ii) nearly all Ntsr1- and Gpr65-positive neurons co-expressed both receptors; and (iii) 5ht3a was expressed in subpopulations of all peptide-hormone-receptor-positive neurons. Retrograde labeling demonstrated that the anterior part of the stomach was preferentially innervated by the left NG, while the right NG innervated the posterior part. The entire gastrointestinal (GI) tract, including the distal colon, was strongly innervated by NG neurons. Most importantly, dual retrograde labeling with two distinct tracers identified a population of neurons co-expressing Glp1r, Cckar, and Npy2r that innervated both the stomach and the colon. Thus, neurons co-expressing GLP-1, cholecystokinin (CCK), and peptide YY (PYY) receptors, predominantly found in the right NG, sample chemical, nutrient-induced signals along the entire GI tract and likely integrate these with mechanical signals from the stomach.

Development of optimal therapeutics for disease states that can be associated with increased membrane cholesterol requires better molecular understanding of lipid modulation of the drug target. Type 1 cholecystokinin receptor (CCK1R) agonist actions are affected by increased membrane cholesterol, enhancing ligand binding and reducing calcium signaling, while agonist actions of the closely related CCK2R are not. In this work, we identified a set of chimeric human CCK1R/CCK2R mutations that exchange the cholesterol sensitivity of these 2 receptors, providing powerful tools when expressed in CHO and HEK-293 model cell lines to explore mechanisms. Static, low energy, high-resolution structures of the mutant CCK1R constructs, stabilized in complex with G protein, were not substantially different, suggesting that alterations to receptor dynamics were key to altered function. We reveal that cholesterol-dependent dynamic changes in the conformation of the helical bundle of CCK receptors affects both ligand binding at the extracellular surface and G protein coupling at the cytosolic surface, as well as their interrelationships involved in stimulus-response coupling. This provides an ideal setting for potential allosteric modulators to correct the negative impact of membrane cholesterol on CCK1R.

Aim: Cholecystokinin (CCK) and gastrin (Gs) are a well known trophic factor for the gastrointestinal tract and their trophic effects are shown mainly toward pancreas and stomach, respectively. Though, the exact characterization of CCK and Gs receptors subtype (cholecystokinin type A receptor [CCKAR] and cholecystokinin type B receptor/gastrin receptor [CCKBR/GR]) in stomach cancer (SC) and pancreatic cancer (PC) is still controversial and necessities further validation. Subjects and Methods: CCKAR and CCKBR/GR expression was analyzed by immunohistochemistry in 55 SC, 25 benign gastric diseases (BGDs), 38 PC (including periampullary carcinoma), and 10 normal pancreatic tissue. The results were statistically correlated with the patient's clinical history to observe the prognostic significance if any. Result: CCKAR expression was detected in 18.2% of SC, 20% of BGD, 65.8% of PC, and 30.0% of normal pancreas tissue samples. The CCKBR/GR expression was detected in 58.2% of SC, 48.0% of BGD, 18.4% of PC, and 60.0% of normal pancreas tissue samples. CCKBR/GR expression was significantly high in well and moderately differentiated SC samples as compared to poorly differentiated samples. Conclusion: Our study showed significantly higher expression of CCKAR and down regulation of CCKBR in PC as compared to control while CCKBR/GR was detected in majority of SC samples. Thus, our study suggests that CCK and Gs receptors may have diagnostic and therapeutic implications. However, study need to be validated in significantly bigger sample size and need to be replicated in different cohorts.

Cholecystokinin (CCK) receptors are overexpressed in numerous human cancers, like medullary thyroid carcinomas, small cell lung cancers and stromal ovarian cancers. The specific receptor-binding property of the endogenous ligands for these receptors can be exploited by labeling peptides with a radionuclide and using these as carriers to guide the radioactivity to the tissues that express the receptors. In this way, tumors can be visualized using positron emission tomography and single photon emission computed tomography imaging. A variety of radiolabeled CCK/gastrin-related peptides has been synthesized and characterized for imaging. All peptides have the C-terminal CCK receptor-binding tetrapeptide sequence Trp-Met-Asp-Phe-NH 2 in common or derivatives thereof. This review focuses on the development and application of radiolabeled CCK/gastrin peptides for radionuclide imaging and radionuclide therapy of tumors expressing CCK receptors. We discuss both preclinical studies as well as clinical studies with CCK and gastrin peptides.

Cholecystokinin (CCK), a peptide hormone and one of the most abundant neuropeptides in vertebrate brain, mediates its actions via two G-protein coupled receptors, CCKAR and CCKBR, respectively active in peripheral organs and the central nervous system. Here, we demonstrate that the CCK receptors have a dynamic and largely reciprocal expression in embryonic and postnatal brain. Using compound homozygous mutant mice lacking the activity of both CCK receptors, we uncover their additive, functionally synergistic effects in brain development and demonstrate that CCK receptor loss leads to abnormalities of cortical development, including defects in the formation of the midline and corpus callosum, and cortical interneuron migration. Using comparative transcriptome analysis of embryonic neocortex, we define the molecular mechanisms underlying these defects. Thus we demonstrate a developmental, hitherto unappreciated, role of the two CCK receptors in mammalian neocortical development.

Background Cholecystokinin octapeptide (CCK-8), the most potent endogenous anti-opioid peptide, has been shown to regulate the processes of morphine dependence. In our previous study, we found that exogenous CCK-8 attenuated naloxone induced withdrawal symptoms. To investigate the precise effect of exogenous CCK-8 and the role of cholecystokinin (CCK) 1 and/or 2 receptors in morphine dependence, a SH-SY5Y cell model was employed, in which the μ-opioid receptor, CCK1/2 receptors, and endogenous CCK are co-expressed. Results Forty-eight hours after treating SH-SY5Y cells with morphine (10 μM), naloxone (10 μM) induced a cAMP overshoot, indicating that cellular morphine dependence had been induced. The CCK receptor and endogenous CCK were up-regulated after chronic morphine exposure. The CCK2 receptor antagonist (LY-288,513) at 1–10 μM inhibited the naloxone-precipitated cAMP overshoot, but the CCK1 receptor antagonist (L-364,718) did not. Interestingly, CCK-8 (0.1-1 μM), a strong CCK receptor agonist, dose-dependently inhibited the naloxone-precipitated cAMP overshoot in SH-SY5Y cells when co-pretreated with morphine. The L-364,718 significantly blocked the inhibitory effect of exogenous CCK-8 on the cAMP overshoot at 1–10 μM, while the LY-288,513 did not. Therefore, the CCK2 receptor appears to be necessary for low concentrations of endogenous CCK to potentiate morphine dependence in SH-SY5Y cells. An additional inhibitory effect of CCK-8 at higher concentrations appears to involve the CCK1 receptor. Conclusions This study reveals the difference between exogenous CCK-8 and endogenous CCK effects on the development of morphine dependence, and provides the first evidence for the participation of the CCK1 receptor in the inhibitory effects of exogenous CCK-8 on morphine dependence.

Cholecystokinin (CCK) is involved in gastrointestinal motor response to meals. The potential role of CCK receptor antagonists in functional gastrointestinal disorders is unclear. To evaluate the effects of dexloxiglumide, a CCK-1 receptor antagonist, on gastrointestinal transit (GIT) and symptoms in patients with constipation-predominant IBS (C-IBS); and to explore the influence of CCK-1 receptor polymorphisms on gut transit and the pharmacodynamic response to therapy. A total of 36 patients with C-IBS and normal to slow baseline colonic transit (CT) were randomized (double-blind, parallel design) to 7 days of dexloxiglumide 200 mg or placebo t.i.d. Daily bowel habits diaries and weekly relief of IBS symptoms were recorded. At the end of treatment, GIT and CT were measured. Peripheral blood DNA was examined for polymorphisms in genes controlling CCK: four related to CCK-1, one to the CCK gene promoter, and one related to CCK-2. The distributions of allelic variants and association with gastric emptying in response to dexloxiglumide and placebo were assessed. Dexloxiglumide was associated with accelerated gastric emptying t(1/2) (p= 0.004), and slower ascending colon emptying t(1/2) (p < 0.01), with no significant effect on overall CT or satisfactory relief of IBS. There was an association between CCK 779T > C polymorphism and slower rate of gastric emptying (p= 0.04). Dexloxiglumide accelerates gastric emptying and delays proximal but not overall CT in patients with C-IBS. Dexloxiglumide does not accelerate transit in C-IBS. The role of CCK-1 gene polymorphisms in delaying gastric emptying and in determining response to therapy deserves further study.

Memory is stored in neural networks via changes in synaptic strength mediated in part by NMDA receptor (NMDAR)-dependent long-term potentiation (LTP). Here we show that a cholecystokinin (CCK)-B receptor (CCKBR) antagonist blocks high-frequency stimulation-induced neocortical LTP, whereas local infusion of CCK induces LTP. CCK−/− mice lacked neocortical LTP and showed deficits in a cue–cue associative learning paradigm; and administration of CCK rescued associative learning deficits. High-frequency stimulation-induced neocortical LTP was completely blocked by either the NMDAR antagonist or the CCKBR antagonist, while application of either NMDA or CCK induced LTP after low-frequency stimulation. In the presence of CCK, LTP was still induced even after blockade of NMDARs. Local application of NMDA induced the release of CCK in the neocortex. These findings suggest that NMDARs control the release of CCK, which enables neocortical LTP and the formation of cue–cue associative memory.

Identification of sleep-active and sleep-promoting neurons in the preoptic area of the hypothalamus using neural projection tracing tools to target this population among a group of intermingled neurons, all with various functions. Sleep-promoting neurons in the preoptic area The preoptic area (POA) in the hypothalamus is an essential contributor to typical sleep regulation, but how this brain area is involved in this process has not been well-understood. Now, Yang Dan and colleagues dissect the role of sleep-active neurons in the POA using neural-projection-tracing tools to specifically target this population of neurons amongst a group of intermingled neurons with various functions. The POA sleep neurons were GABAergic and projected to the tuberomammillary nucleus and were not only active during sleep but could promote sleep when activated. Further, single-cell molecular analysis provided candidate genetic markers with which to target these neurons for future studies aiming to further dissect this sleep control circuit. In humans and other mammalian species, lesions in the preoptic area of the hypothalamus cause profound sleep impairment 1 , 2 , 3 , 4 , 5 , indicating a crucial role of the preoptic area in sleep generation. However, the underlying circuit mechanism remains poorly understood. Electrophysiological recordings and c-Fos immunohistochemistry have shown the existence of sleep-active neurons in the preoptic area, especially in the ventrolateral preoptic area and median preoptic nucleus 6 , 7 , 8 , 9 . Pharmacogenetic activation of c-Fos-labelled sleep-active neurons has been shown to induce sleep 10 . However, the sleep-active neurons are spatially intermingled with wake-active neurons 6 , 7 , making it difficult to target the sleep neurons specifically for circuit analysis. Here we identify a population of preoptic area sleep neurons on the basis of their projection target and discover their molecular markers. Using a lentivirus expressing channelrhodopsin-2 or a light-activated chloride channel for retrograde labelling, bidirectional optogenetic manipulation, and optrode recording, we show that the preoptic area GABAergic neurons projecting to the tuberomammillary nucleus are both sleep active and sleep promoting. Furthermore, translating ribosome affinity purification and single-cell RNA sequencing identify candidate markers for these neurons, and optogenetic and pharmacogenetic manipulations demonstrate that several peptide markers (cholecystokinin, corticotropin-releasing hormone, and tachykinin 1) label sleep-promoting neurons. Together, these findings provide easy genetic access to sleep-promoting preoptic area neurons and a valuable entry point for dissecting the sleep control circuit.