Expression and cell-specific localization of cholecystokinin receptors in rat lung

Exploring the Modulatory Effect of High-Fat Nutrition on Lipopolysaccharide-Induced Acute Lung Injury in Vagotomized Rats and the Role of the Vagus Nerve

During esophagectomy, the vagus nerve is transected, which may add to the development of postoperative complications. The vagus nerve has been shown to attenuate inflammation and can be activated by a high-fat nutrition via the release of acetylcholine. This binds to α7 nicotinic acetylcholine receptors (α7nAChR) and inhibits α7nAChR-expressing inflammatory cells. This study investigates the role of the vagus nerve and the effect of high-fat nutrition on lipopolysaccharide (LPS)-induced lung injury in rats. Firstly, 48 rats were randomized in 4 groups as follows: sham (sparing vagus nerve), abdominal (selective) vagotomy, cervical vagotomy and cervical vagotomy with an α7nAChR-agonist. Secondly, 24 rats were randomized in 3 groups as follows: sham, sham with an α7nAChR-antagonist and cervical vagotomy with an α7nAChR-antagonist. Finally, 24 rats were randomized in 3 groups as follows: fasting, high-fat nutrition before sham and high-fat nutrition before selective vagotomy. Abdominal (selective) vagotomy did not impact histopathological lung injury (LIS) compared with the control (sham) group (p > 0.999). There was a trend in aggravation of LIS after cervical vagotomy (p = 0.051), even after an α7nAChR-agonist (p = 0.090). Cervical vagotomy with an α7nAChR-antagonist aggravated lung injury (p = 0.004). Furthermore, cervical vagotomy increased macrophages in bronchoalveolar lavage (BAL) fluid and negatively impacted pulmonary function. Other inflammatory cells, TNF-α and IL-6, in the BALF and serum were unaffected. High-fat nutrition reduced LIS after sham (p = 0.012) and selective vagotomy (p = 0.002) compared to fasting. vagotomy. This study underlines the role of the vagus nerve in lung injury and shows that vagus nerve stimulation using high-fat nutrition is effective in reducing lung injury, even after selective vagotomy.

Antagonizing cholecystokinin A receptor in the lung attenuates obesity-induced airway hyperresponsiveness

Obesity increases asthma prevalence and severity. However, the underlying mechanisms are poorly understood, and consequently, therapeutic options for asthma patients with obesity remain limited. Here we report that cholecystokinin-a metabolic hormone best known for its role in signaling satiation and fat metabolism-is increased in the lungs of obese mice and that pharmacological blockade of cholecystokinin A receptor signaling reduces obesity-associated airway hyperresponsiveness. Activation of cholecystokinin A receptor by the hormone induces contraction of airway smooth muscle cells. In vivo, cholecystokinin level is elevated in the lungs of both genetically and diet-induced obese mice. Importantly, intranasal administration of cholecystokinin A receptor antagonists (proglumide and devazepide) suppresses the airway hyperresponsiveness in the obese mice. Together, our results reveal an unexpected role for cholecystokinin in the lung and support the repurposing of cholecystokinin A receptor antagonists as a potential therapy for asthma patients with obesity.

The hyperthermic effect of central cholecystokinin is mediated by the cyclooxygenase-2 pathway

Cholecystokinin (CCK) increases core body temperature via CCK₂ receptors when administered intracerebroventricularly (icv). The mechanisms of CCK-induced hyperthermia are unknown, and it is also unknown whether CCK contributes to the fever response to systemic inflammation. We studied the interaction between central CCK signaling and the cyclooxygenase (COX) pathway. Body temperature was measured in adult male Wistar rats pretreated with intraperitoneal infusion of the nonselective COX enzyme inhibitor metamizol (120 mg/kg) or a selective COX-2 inhibitor, meloxicam, or etoricoxib (10 mg/kg for both) and, 30 min later, treated with intracerebroventricular CCK (1.7 µg/kg). In separate experiments, CCK-induced neuronal activation (with and without COX inhibition) was studied in thermoregulation- and feeding-related nuclei with c-Fos immunohistochemistry. CCK increased body temperature by ∼0.4°C from 10 min postinfusion, which was attenuated by metamizol. CCK reduced the number of c-Fos-positive cells in the median preoptic area (by ∼70%) but increased it in the dorsal hypothalamic area and in the rostral raphe pallidus (by ∼50% in both); all these changes were completely blocked with metamizol. In contrast, CCK-induced satiety and neuronal activation in the ventromedial hypothalamus were not influenced by metamizol. CCK-induced hyperthermia was also completely blocked with both selective COX-2 inhibitors studied. Finally, the CCK₂ receptor antagonist YM022 (10 µg/kg icv) attenuated the late phases of fever induced by bacterial lipopolysaccharide (10 µg/kg; intravenously). We conclude that centrally administered CCK causes hyperthermia through changes in the activity of "classical" thermoeffector pathways and that the activation of COX-2 is required for the development of this response.NEW & NOTEWORTHY An association between central cholecystokinin signaling and the cyclooxygenase-prostaglandin E pathway has been proposed but remained poorly understood. We show that the hyperthermic response to the central administration of cholecystokinin alters the neuronal activity within efferent thermoeffector pathways and that these effects are fully blocked by the inhibition of cyclooxygenase. We also show that the activation of cyclooxygenase-2 is required for the hyperthermic effect of cholecystokinin and that cholecystokinin is a modulator of endotoxin-induced fever.

Protective effect of cholecystokinin octapeptide on angiotensin II-induced apoptosis in H9c2 cardiomyoblast cells

Cholecystokinin (CCK) and its receptors are expressed in mammalian cardiomyocytes and are involved in cardiovascular system regulation; however, the exact effect and underlying mechanism of CCK in cardiomyocyte apoptosis remain to be elucidated. We examined whether sulfated CCK octapeptide (CCK-8) protects H9c2 cardiomyoblast cells against angiotensin II (Ang II)-induced apoptosis. The H9c2 cardiomyoblasts were subjected to Ang II with or without CCK-8 and the viability and apoptotic rate were detected using a Cell Counting Kit-8 assay, Hoechst 33342 staining, terminal deoxyribonucleotide transferase-mediated nick-end labeling assays, and flow cytometry. In addition, specific antiapoptotic mechanisms of CCK-8 were investigated using specific CCK1 (Devazepide) or CCK2 (L365260) receptor antagonists, or the PI3K inhibitor LY294002. The expression of CCK, CCK1 receptor, CCK2 receptor, Akt, p-Akt, Bad, p-Bad, Bax, Bcl-2, and caspase-3 were detected by Western blot analysis and real-time polymerase chain reaction. We found that CCK and its receptor messenger RNA (mRNA) and protein are expressed in H9c2 cardiomyoblasts. Ang II-induced increased levels of CCK mRNA and protein expression and decreased levels of CCK1 receptor protein and mRNA. Pretreatment of CCK-8 attenuated Ang II-induced cell toxicity and apoptosis. In addition, pretreatment of H9c2 cells with CCK-8 markedly induced expression of p-Akt, p-bad, and Bcl-2 and decreased the expression levels of Bax and caspase-3. The protective effects of CCK-8 were partly abolished by Devazepide or LY294002. Our results suggest that CCK-8 protects H9c2 cardiomyoblasts from Ang II-induced apoptosis partly via activation of the CCK1 receptor and the phosphatidyqinositol-3 kinase/protein kinase B (PI3K/Akt) signaling pathway.

Cholecystokinin octapeptide reduces myocardial fibrosis and improves cardiac remodeling in post myocardial infarction rats

BACKGROUND/AIMS

Myocardial infarction (MI) increases myocardial fibrosis (MF) and subsequent cardiac remodeling. Cholecystokinin octapeptide (CCK-8) is expressed in cardiomyocytes and plays an important role in cardiovascular regulation. In this study, we intend to use a rat model of myocardial infarction to evaluate the effects of CCK-8 on myocardial fibrosis and cardiac remodeling.

METHODS

Male Sprague-Dawley rats were separated into 3 groups: sham operation, MI + NaCl, and MI + CCK-8. All rats were subjected to left coronary artery ligation to induce MI or sham operation and then treated with CCK-8 or saline for 28 days. After 4 weeks, echocardiography was performed to assess cardiac function and myocardial fibrosis was evaluated using H&E and Masson's Trichrome-stained sections. The levels of BNP, CCK-8 in the plasma of all rats were detected by ELISA; RNA sequencing (RNA-seq) analysis was also adapted to detect differentially expressed genes in myocardial tissues of each group. Myocardial expression of fibrosis markers was analyzed by western blotting, immunohistochemistry and qRT-PCR.

RESULTS

CCK-8 was demonstrated to improve left ventricular function and results of H&E staining, Masson's trichrome staining, immunohistochemistry and western blotting showed that CCK-8 attenuated MF. Gene expression profiles of the left ventricles were analysed by RNA-seq and validated by qRT-PCR. Cardiac fibrosis genes were downregulated by CCK-8 in the left ventricle.

SIGNIFICANCE

CCK-8 can alleviate fibrosis in the noninfarcted regions and delay the left ventricular remodeling and the progress of heart failure in a MI rat model.

Neuropeptides and breathing in health and disease

Regulatory neuropeptides control and regulate breathing in physiological and pathophysiological conditions. While they have been identified in the neurons of major respiratory areas, they can be active not only at the central level, but also at the periphery via chemoreceptors, vagal afferents, or locally within lungs and airways. Some neuropeptides, such as leptin or substance P, are respiratory stimulants; others, such as neurotensin, produce variable effects on respiration depending on the site of application. Some neuropeptides have been implicated in pathological states, such as obstructive sleep apnea or asthma. This article provides a concise review of the possible role and functions of several selected neuropeptides in the process of breathing in health and disease and in lung pathologies.

Cholecystokinin and gastrin receptors targeting in gastrointestinal cancer

Cholecystokinin and Gastrin are amongst the first gastrointestinal hormone discovered. In addition to classical actions (contraction of gallbladder, growth and secretion in the stomach and pancreas), these also act as growth stimulants for gastrointestinal malignancies and cell lines. Growth of these tumours is inhibited by antagonists of the cholecystokinin and gastrin receptors. These receptors provides most promising approach in clinical oncology and several specific radiolabelled ligands have been synthesized for specific tumour targeting and therapy of tumours overexpressing these receptors. Therefore, definition of the molecular structure of the receptor involved in the autocrine/paracrine loop may contribute to novel therapies for gastrointestinal cancer. Hence, this review tries to focus on the role and distribution of these hormones and their receptors in gastrointestinal cancer with a brief talk about the clinical trial using available agonist and antagonist in gastrointestinal cancers.

Gastrin induces leukocyte-endothelial cell interactions in vivo and contributes to the inflammation caused by Helicobacter pylori

Gastric mucosal inflammation causes hypergastrinemia, and gastrin receptors have been detected in several leukocyte types. We have analyzed whether gastrin affects the leukocyte-endothelial cell interactions in vivo by monitoring leukocyte rolling, adhesion, and emigration in rat mesenteric venules using intravital microscopy. Mesenteric superfusion with exogenous gastrin increased these processes in a concentration- and time-dependent manner, effects prevented by the cholecystokinin (CCK)-2 receptor antagonists (proglumide, L-365,260) but not by the CCK-1 receptor antagonist devazepide. A similar response was induced by exogenous CCK or endogenously released gastrin. CCK-2 receptors were localized in mesenteric macrophages and polymorphonuclear leukocytes. This effect of gastrin is not modulated by somatostatin and is independent of the endogenous release of histamine. To analyze whether hypergastrinemia elicited by Helicobacter pylori (HP) modulates the inflammation induced by the germ, rats were chronically administered with an extract of a CagA+/VacA+ strain of HP. This protocol increased gastrinemia and induced an inflammatory response in the rat mesentery. Blockade of CCK-2 receptors attenuated this response and induced a qualitative change in the leukocyte infiltrate suggestive of a receding inflammatory process. Our results reveal a new proinflammatory role of gastrin that seems to contribute to the maintenance of the inflammation elicited by HP components.

Effect of cholecystokinin octapeptide on diacylglycerol-PKC signaling pathway in rat pulmonary interstitial macrophages stimulated by lipopolysaccharide

AIM

To investigate the effect of cholecystokinin octapeptide (CCK-8) on the diacylglycerol-protein kinase C (DAG-PKC) signaling pathway in rat pulmonary interstitial macrophages (PIM) stimulated by lipopolysaccaride (LPS).

METHODS

The PIM from rat lung tissues were isolated using the collagenase digestion method combined with alveolar lavage and pulmonary vessel perfusion. DAG content and PKC activity were measured by radioenzymatic assay. The translocation of PKCzeta was determined by semi-quantitative immunoblot analysis.

RESULTS

CCK-8, at high concentrations (1 x 10(-6) - 1 x 10(-5) mol/L), decreased DAG content and inhibited PKC activity and PKCzeta translocation compared with that in rat resting PIM of a control group (P< 0.01). LPS increased DAG content, and promoted PKC activity and PKCzeta translocation (P< 0.01). CCK-8 decreased LPS-induced DAG content and inhibited LPS-induced PKC activity and PKCzeta translocation significantly at 1 x 10(-8) - 1 x 10(-5) mol/L (P< 0.01). This inhibitory effect of CCK-8 could be abrogated partly by proglumide (non-selective CCK receptor antagonist), CR-1409 (selective CCK-A receptor antagonist), and CR-2945 (selective CCK-B receptor antagonist) in a concentration-dependent manner (P< 0.01).

CONCLUSION

CCK-8 was a negative modulator of the DAG-PKC signaling pathway in rat resting PIM, which is very important for maintaining body homeostasis. It significantly inhibited LPS-induced DAG content, PKC activity and PKCzeta translocation in a concentration-dependent manner. The CCK receptor, especially the CCK-A receptor, might play a major role in this process.