Cholecystokinin and cholecystokinin-A receptor: An attractive treatment strategy for biliary dyskinesia?

Biliary dyskinesia is a relatively common gastrointestinal disease that is increasing in incidence as living standards improve. However, its underlying pathogenesis remains unclear, hindering the development of therapeutic drugs. Recently, "Expression and functional study of cholecystokinin-A receptors on the interstitial Cajal-like cells of the guinea pig common bile duct" demonstrated that cholecystokinin (CCK) regulates the contractile function of the common bile duct through interaction with the CCK-A receptor in interstitial Cajal-like cells, contributing to improving the academic understanding of biliary tract dynamics and providing emerging directions for the pathogenesis and clinical management of biliary dyskinesia. This letter provides a brief overview of the role of CCK and CCK-A receptors in biliary dyskinesia from the perspective of animal experiments and clinical studies, and discusses prospects and challenges for the clinical application of CCK and CCK-A receptors as potential therapeutic targets.

VMHvllCckar cells dynamically control female sexual behaviors over the reproductive cycle.

Sexual behavior is fundamental for the survival of mammalian species and thus supported by dedicated neural substrates. The ventrolateral part of ventromedial hypothalamus (VMHvl) is an essential locus for controlling female sexual behaviors, but recent studies revealed the molecular complexity and functional heterogeneity of VMHvl cells. Here, we identify the cholecystokinin A receptor (Cckar)-expressing cells in the lateral VMHvl (VMHvllCckar) as the key controllers of female sexual behaviors. The inactivation of VMHvllCckar cells in female mice diminishes their interest in males and sexual receptivity, whereas activating these cells has the opposite effects. Female sexual behaviors vary drastically over the reproductive cycle. In vivo recordings reveal reproductive-state-dependent changes in VMHvllCckar cell spontaneous activity and responsivity, with the highest activity occurring during estrus. These in vivo response changes coincide with robust alternation in VMHvllCckar cell excitability and synaptic inputs. Altogether, VMHvllCckar cells represent a key neural population dynamically controlling female sexual behaviors over the reproductive cycle.

Dual-agonist occupancy of orexin receptor 1 and cholecystokinin A receptor heterodimers decreases G-protein-dependent signaling and migration in the human colon cancer cell line HT-29.

The orexin (OX1R) and cholecystokinin A (CCK1R) receptors play opposing roles in the migration of the human colon cancer cell line HT-29, and may be involved in the pathogenesis and pathophysiology of cancer cell invasion and metastasis. OX1R and CCK1R belong to family A of the G-protein-coupled receptors (GPCRs), but the detailed mechanisms underlying their functions in solid tumor development remain unclear. In this study, we investigated whether these two receptors heterodimerize, and the results revealed novel signal transduction mechanisms. Bioluminescence and Förster resonance energy transfer, as well as proximity ligation assays, demonstrated that OX1R and CCK1R heterodimerize in HEK293 and HT-29 cells, and that peptides corresponding to transmembrane domain 5 of OX1R impaired heterodimer formation. Stimulation of OX1R and CCK1R heterodimers with both orexin-A and CCK decreased the activation of Gαq, Gαi2, Gα12, and Gα13 and the migration of HT-29 cells in comparison with stimulation with orexin-A or CCK alone, but did not alter GPCR interactions with ß-arrestins. These results suggest that OX1R and CCK1R heterodimerization plays an anti-migratory role in human colon cancer cells.

ATP binding cassette and cholecystokinin A receptor genetic variations in gallstone susceptibility.

AIM: It was aimed to assess the association of four polymorphisms and relative haplotypes in the ATP binding cassettes and cholecystokinin A receptor (rs6720173, rs11887534, rs4148217, rs1800857) with the risk of gallstone. BACKGROUND: Gallstone is a multifactorial disease. Besides high penetrance genes, low or moderate penetrance polymorphisms may increase susceptibility to gallstone. METHODS: 200 gallstone patients and 251 healthy controls were analyzed in a case-control association model. Genotyping was carried out by restriction fragment length polymorphism. Randomly 10% of samples underwent for direct sequencing to confirm results. RESULTS: Heterozygote variant of rs11887534 demonstrated protective effect on the risk of gallstone susceptibility in males (P=0.013; OR=0.125; CI95%=0.048-0.325). In contrast, C/C genotype associated with gallstone susceptibility in females (P=0.004; OR=5.555 CI95%=1.975-10.632). Moreover, rs1800857 showed association only in females (P=0.019; OR=0.283; CI95%=0.099-0.811). Haplotype analysis for rs1800857 showed GC, CC and CA association with gallstone. CONCLUSION: The most imperative polymorphisms of contributing genes to gallstone were analyzed in this study and rs11887534 and rs1800857 appeared to be associated with gallstone, which is expected to be further verified in a larger cohort in the future.

Effects of sphincter of Oddi motility on the formation of cholesterol gallstones.

AIM: To investigate the mechanisms and effects of sphincter of Oddi (SO) motility on cholesterol gallbladder stone formation in guinea pigs. METHODS: Thirty-four adult male Hartley guinea pigs were divided randomly into two groups, the control group (n = 10) and the cholesterol gallstone group (n = 24), which was sequentially divided into four subgroups with six guinea pigs each according to time of sacrifice. The guinea pigs in the cholesterol gallstone group were fed a cholesterol lithogenic diet and sacrificed after 3, 6, 9, and 12 wk. SO manometry and recording of myoelectric activity were obtained by a multifunctional physiograph at each stage. Cholecystokinin-A receptor (CCKAR) expression levels in SO smooth muscle were detected by quantitative real-time PCR (qRT-PCR) and serum vasoactive intestinal peptide (VIP), gastrin, and cholecystokinin octapeptide (CCK-8) were detected by enzyme-linked immunosorbent assay at each stage in the process of cholesterol gallstone formation. RESULTS: The gallstone formation rate was 0%, 0%, 16.7%, and 83.3% in the 3, 6, 9, and 12 wk groups, respectively. The frequency of myoelectric activity in the 9 wk group, the amplitude of myoelectric activity in the 9 and 12 wk groups, and the amplitude and the frequency of SO in the 9 wk group were all significantly decreased compared to the control group. The SO basal pressure and common bile duct pressure increased markedly in the 12 wk group, and the CCKAR expression levels increased in the 6 and 12 wk groups compared to the control group. Serum VIP was elevated significantly in the 9 and 12 wk groups and gastrin decreased significantly in the 3 and 9 wk groups. There was no difference in serum CCK-8 between the groups. CONCLUSION: A cholesterol gallstone-causing diet can induce SO dysfunction. The increasing tension of the SO along with its decreasing activity may play an important role in cholesterol gallstone formation. Expression changes of CCKAR in SO smooth muscle and serum VIP and CCK-8 may be important causes of SO dysfunction.

Polymorphism and Expression Profile of Cholecystokinin Type A Receptor in Relation to Gallstone Disease Susceptibility.

In the present study, we investigated expression pattern of Cholecystokinin type A receptor (CCKAR) in relation to its commonly studied polymorphism (rs1800857, T/C) in gallstone disease (GSD) patients and controls. A total of 502 subjects (272 GSD and 230 controls) were enrolled, and genotyping was performed by evaluating restriction fragments of PstI digested DNA. For analyzing expression pattern of CCKAR in relation to polymorphism, gallbladder tissue samples from 80 subjects (GSD-55; control-25) were studied. Expression of CCKAR mRNA was evaluated by reverse transcriptase-PCR and confirmed using real-time PCR. Protein expression was evaluated by enzyme-linked immunosorbent assay. We observed significantly (p < 0.0001) lower expression of CCKAR mRNA and protein in GSD tissues as compared with control. Significantly higher frequency of A1/A1 genotype (C/T transition) (p = 0.0005) was observed for GSD as compared with control. Expression of CCKAR protein was found to be significantly lower (p < 0.0001) in A1/A1 genotype as compared with other genotypes for GSD patients. Perhaps, this is the first report providing evidence of alteration in CCKAR expression in relation to its polymorphism elucidating the molecular pathway of the disease. Additional investigations with lager sample size are needed to confirm these findings.

Association of single-nucleotide polymorphism of cholecystokinin receptor A gene with schizophrenia in an Eastern Indian population.

CONTEXT: Cholecystokinin A receptor (CCK-AR) gene polymorphism is being increasingly reported in schizophrenia. It varies among different population groups but is associated with several complications of schizophrenia. AIMS: The present study was undertaken to assess whether the CCK-AR polymorphism is stabilized and is more consistently associated with schizophrenia in an Eastern Indian sub-population. SETTINGS AND DESIGN: It was carried out as a cross-sectional, observational, hospital-based study on 95 schizophrenia patients and 138 control subjects selected by the method of convenience. MATERIALS AND METHODS: Single-nucleotide polymorphisms located in the regulatory region of the CCK-AR gene were assessed by restriction fragment length polymorphism (RFLP) in the polymerase chain reaction (PCR) amplified product of CCK-AR gene in study subjects. RFLP was done by the digestion of the PCR product by the restriction enzyme Pst-1 followed by gel electrophoresis. STATISTICAL ANALYSIS: Assessment of the stability of C/T polymorphism in the study population was done by applying Hardy-Weinberg equilibrium rule. The significance of difference in the allelic distribution between case and controls was analyzed by Chi-square (χ(2)) test and odds ratio (OR) analysis. RESULT: CCK-R polymorphism was in Hardy-Weinberg equilibrium in both groups. Distribution of the C allele of this gene was significantly higher in schizophrenia patients (χ(2) = 4.35, OR = 1.51; confidence interval at 95% =1.04-2.20). CONCLUSION: C/T polymorphism of the CCK-R gene is a stable polymorphism in our study population. Moreover, the C allele is significantly more abundant in schizophrenia patients imparting them a greater risk of development of complications like auditory hallucination.

Association of caveolin-3 and cholecystokinin A receptor with cholesterol gallstone disease in mice.

AIM: To investigate the role of caveolin-3 (CAV3) and cholecystokinin A receptor (CCKAR) in cholesterol gallstone disease (CGD). METHODS: To establish a mouse model of CGD, male C57BL/6 mice were fed with a lithogenic diet containing 1.0% cholic acid, 1.25% cholesterol and 15% fat; a similar control group was given a normal diet. The fresh liver weights and liver-to-body weight ratio were compared between the two groups after one month. Serum lipid profile and bile composition were determined with an autoanalyzer. The Cav3 and Cckar mRNA and CAV3 and CCKAR protein levels in the liver and gallbladder were determined via real-time polymerase chain reaction and Western blot, respectively. RESULTS: Establishment of the mouse CGD model was verified by the presence of cholesterol gallstones in mice fed the lithogenic diet. Compared with mice maintained on a normal diet, those fed the lithogenic diet had significantly higher mean liver-to-body weight ratio (0.067 ± 0.007 vs 0.039 ± 0.007, P < 0.01), serum total cholesterol (4.22 ± 0.46 mmol/L vs 2.21 ± 0.11 mmol/L, P < 0.001), bile total cholesterol (1.33 ± 0.33 mmol/L vs 0.21 ± 0.11 mmol/L, P < 0.001), and bile phospholipid concentrations (3.55 ± 1.40 mmol/L vs 1.55 ± 0.63 mmol/L, P = 0.04), but lower total bile acid concentrations (726.48 ± 51.83 µmol/L vs 839.83 ± 23.74 µmol/L, P = 0.007). The lithogenic diet was also associated with significantly lower CAV3 in the liver and lower CAV3 and CCKAR in the gallbladder compared with the control mice (all P < 0.05). CONCLUSION: CAV3 and CCKAR may be involved in cholesterol gallstone disease.