Effects of cholecystokinin-8 induced gastric dysmotility on bile regurgitation during stress and molecular mechanisms

Gastroesophageal Mucosal Injury after Cholecystectomy: An Indication for Surveillance?

BACKGROUND

Cholecystectomy alters bile release dynamics from pulsatile meal-stimulated to continuous, and results in retrograde duodeno-gastric bile reflux (DGR). Bile is implicated in mucosal injury after gastric surgery, but whether cholecystectomy causes esophagogastric mucosal inflammation, therefore increasing the risk of metaplasia, is unclear.

STUDY DESIGN

This study examined whether cholecystectomy-induced DGR promotes chronic inflammatory mucosal changes of the stomach and/or the esophagogastric junction (EGJ). Four groups of patients were studied and compared with controls. A group of patients was studied before and 1 year after cholecystectomy; 2 further groups were studied long-term post-cholecystectomy (LTPC) at 5 to 10 years and 10 to 20 years. All underwent abdominal ultrasound and upper gastrointestinal endoscopy with gastric antral and EGJ biopsies, noting the presence of gastric bile pooling. Biopsy specimens were stained for Ki67 and p53 overexpression, and the bile reflux index (BRI) was calculated.

RESULTS

At endoscopy, bile pooling was observed in 9 of 26 (34.6%) controls, in 8 of 25 (32%) patients pre-cholecystectomy, in 15 of 25 (60%) 1 year post-cholecystectomy patients (p = 0.047), and 23 of 29 (79.3%) LTPC patients (p = 0.001). Bile reflux index positivity at the EGJ increased from 19% of controls through 41% of LTPC patients (p = 0.032). Ki67 was overexpressed at the EGJ in 19% of controls, but in 62% of LTPC patients (p = 0.044); p53 was overexpressed at the EGJ in 19% of controls compared with 66% of LTPC patients (p = 0.001).

CONCLUSIONS

Duodeno-gastric bile reflux was more common in patients with gallstones than in controls, and its incidence doubled after cholecystectomy. This was associated with inflammatory changes in the gastric antrum and the EGJ, evident in most LTPC patients. Ki67 and p53 overexpression at the EGJ suggests cellular damage attributable to chronic bile exposure post-cholecystectomy, increasing the likelihood of dysplasia. Further studies are required to determine whether DGR-mediated esophageal mucosal injury is reversible or avoidable, and whether surveillance endoscopy is indicated after cholecystectomy.

Role of calcium in activation of hyperpolarization-activated cyclic nucleotide-gated channels caused by cholecystokinin octapeptide in interstitial cells of cajal

BACKGROUND

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate pacemaker activity in some cardiac cells and neurons. Little is known about the effects of cholecystokinin octapeptide (CCK-8) on HCN channels and excitability of murine interstitial cells of Cajal (ICCs).

METHODS

In the present study, the effects and mechanisms of CCK-8 on HCN channels were investigated by measuring mechanical contraction of smooth muscle strips and ionic channels of ICCs in murine gastric antrum.

RESULTS

Sulfated CCK-8 (CCK-8S) was used, and we found that CCK-8S increased the contraction of smooth muscle strips in the gastric antrum, which could be suppressed by specific HCN channel blockers CsCl and ZD7288. Extracellular calcium could also intensify the contraction. Under the same conditions, when antral strips were exposed to calcium ion (Ca²⁺)-free solution, no significant changes could be recorded with CCK-8S or ZD7288. Isolated ICCs from the murine gastric antrum identified by specific c-Kit antibody primers were chosen for electrophysiological recordings. HCN current (I(h)) of cultured ICCs was studied by whole-cell patch clamp techniques. A spontaneous transient inward current was recorded in ICCs, which could be inhibited by addition of CsCl and ZD7288; the current proved to be I(h). CCK-8S-facilitated I(h) in cultured ICCs could be inhibited by CsCl and ZD7288. When cultured ICCs were exposed to Ca²⁺-free solution, no significant changes could be recorded by application of CCK-8S on I(h), which proved extracellular calcium might have an excitatory effect on HCN channels.

CONCLUSION

We demonstrate that HCN channels are present in ICCs in the murine gastric antrum; they might be an important regulator of ICC excitability and pacemaker activity and are strongly affected by CCK-8S. Extracellular calcium might be a trigger in the activation of HCN channels caused by CCK-8S in cultured ICCs.

Inhibitory effects of somatostatin on cholecystokinin octapeptide-mediated bile regurgitation under stress: ionic and molecular mechanisms

AIM: To investigate the ionic and molecular mechanisms underlying the effects of changes in plasma cholecystokinin octapeptide (CCK-8S) and somatostatin (SS) on stress-induced bile regurgitation in rats.

METHODS: The changes in plasma CCK-8S, SS and intragastric bile concentration under stressful condition were measured by radioimmunoassay (RIA). The contractile response of gastric antral smooth strips isolated from healthy adult rats was recorded by poly physiography. The regulatory effect of protein kinase C (PKC) on the phosphorylation of type 3 inositol 1, 4, 5-triphosphate receptor (InsP₃R3) in gastric smooth muscle cells (SMC) was determined by immunoprecipitation. The changes in intracellular calcium fluorescence intensity (FI) of SMC (presented as [Ca²⁺]i) were analyzed by laser scanning confocal microscopy. L-type voltage-dependent calcium currents (I_Ca-L) of SMC were recorded by the patch-clamp technique.

RESULTS: Both plasma CCK-8S level and gastric bile concentration significantly increased during the stress period and reached the peak at 2 h after stress, while reverse effect was observed in plasma SS level. Respective addition of CCK-8S and SS caused a rapid, sustained, concentration-dependent increase and decrease in muscle contraction of gastric antral strips, and CCK-8S-induced increase in the contractile response could be significantly blocked by administration of nifedipine or SS. Similar results were obtained for the changes in FI and I_Ca-L of SMC. Pretreatment with SS significantly increased CCK-8S-promoted phosphorylation of InsP3R3 in SMC.

CONCLUSION: Gastric mucosal damage induced by bile regurgitation under stressful condition is closely associated with gastric antral dysmotility evoked by the changes in CCK-8S and SS. CCK-8S-enhanced gastric antral contraction depends on the release of intracellular calcium stores and the influx of extracellular calcium via L-type voltage-dependent calcium channels, and can be blocked with SS, suggesting that both CCK-8S and SS play important roles in the regulation of gastric motility.

Inhibitory effects of somatostatin on cholecystokinin octapeptide induced bile regurgitation under stress: ionic and molecular mechanisms

OBJECTIVE

To investigate the possible effects and related ionic and molecular mechanisms of changes of plasma cholecystokinin octapeptide and somatostatin on stress-induced bile regurgitation in rats.

METHODS

In forty healthy adult rats, changes of plasma cholecystokinin octapeptide, somatostatin and intragastric bile concentration under stressful condition were respectively measured by specific radioimmunoassay methods. Contractile responses of gastric antral smooth strips isolated from healthy adult rats were recorded by polyphysiograph. Immunoprecipitation was used to determine the regulatory effect of protein kinase C on regulating the phosphorylation of type 3 inositol 1,4,5-triphosphate receptor (InsP3R3) in gastric smooth muscle cells. Changes of intracellular calcium fluorescence intensity of smooth muscle cells presented as intracellular calcium ([Ca2+]i) were analyzed under laser scanning confocal microscopy and L-type voltage-dependent calcium currents of smooth muscle cells were recorded by patch-clamp techniques.

RESULTS

Compared with the normal control group, plasma cholecystokinin octapeptide and gastric bile concentration of each stress group significantly increased during the stress, while adverse effect was obtained in plasma somatostatin, which decreased from the beginning of the stress and attained the minimum nearly at the same time when the plasma cholecystokinin octapeptide concentration reached the maximum. Respective addition of cholecystokinin octapeptide and somatostatin with increasing concentrations caused rapid, sustained, concentration-dependent increase and decrease in muscle contraction of gastric antral strips, and cholecystokinin octapeptide that increased the contractile response could be blocked by respective administration of nifedipine and somatostatin significantly. Similar results were obtained in the changes of calcium fluorescence intensity and calcium currents of smooth muscle cells. Pretreatment with somatostatin significantly increased cholecystokinin octapeptide-increased phosphorylation of InsP3R3 in smooth muscle cells.

CONCLUSIONS

Gastric mucosal damage induced by bile regurgitation is closely connected with gastric antral dysmotility evoked by the changes of cholecystokinin octapeptide and somatostatin under stressful condition. Cholecystokinin octapeptide-intensified contraction depends on the release of intracellular calcium stores and the influx of extracellular calcium via L-type voltage-dependent calcium channels, while this excitatory effect of cholecystokinin octapeptide could be blocked by somatostatin, suggesting that both of the two peptides play important roles in the regulation of gastric motility.