Effect of acalculous cholecystitis on gallbladder neuromuscular transmission and contractility

Enhanced expression of cystathionine β-synthase and cystathionine γ-lyase during acute cholecystitis-induced gallbladder inflammation

Background

Hydrogen sulfide (H₂S) has recently been shown to play an important role in the digestive system, but the role of endogenous H₂S produced locally in the gallbladder is unknown. The aim of this study was to investigate whether gallbladder possesses the enzymatic machinery to synthesize H₂S, and whether H₂S synthesis is changed in gallbladder inflammation during acute acalculous cholecystitis (AC).

Methods

Adult male guinea pigs underwent either a sham operation or common bile duct ligation (CBDL). One, two, or three days after CBDL, the animals were sacrificed separately. Hematoxylin and eosin-stained slides of gallbladder samples were scored for inflammation. H₂S production rate in gallbladder tissue from each group was determined; immunohistochemistry and western blotting were used to determine expression levels of the H₂S-producing enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) in gallbladder.

Results

There was a progressive inflammatory response after CBDL. Immunohistochemistry analysis showed that CBS and CSE were expressed in the gallbladder epithelium, muscular layer, and blood vessels and that the expression increased progressively with increasing inflammation following CBDL. The expression of CBS protein as well as the H₂S-production rate was significantly increased in the animals that underwent CBDL, compared to those that underwent the sham operation.

Conclusions

Both CBS and CSE are expressed in gallbladder tissues. The expression of these enzymes, as well as H₂S synthesis, was up-regulated in the context of inflammation during AC.

Disruption of gallbladder smooth muscle function is an early feature in the development of cholesterol gallstone disease

BACKGROUND; Decreased gallbladder smooth muscle (GBSM) contractility is a hallmark of cholesterol gallstone disease, but the interrelationship between lithogenicity, biliary stasis, and inflammation are poorly understood. We studied a mouse model of gallstone disease to evaluate the development of GBSM dysfunction relative to changes in bile composition and the onset of sterile cholecystitis.

METHODS

BALB/cJ mice were fed a lithogenic diet for up to 8 weeks, and tension generated by gallbladder muscle strips was measured. Smooth muscle Ca(2+) transients were imaged in intact gallbladder.

KEY RESULTS

Lipid composition of bile was altered lithogenically as early as 1 week, with increased hydrophobicity and cholesterol saturation indexes; however, inflammation was not detectable until the fourth week. Agonist-induced contractility was reduced from weeks 2 through 8. GBSM normally exhibits rhythmic synchronized Ca(2+) flashes, and their frequency is increased by carbachol (3 μm). After 1 week, lithogenic diet-fed mice exhibited disrupted Ca(2+) flash activity, manifesting as clustered flashes, asynchronous flashes, or prolonged quiescent periods. These changes could lead to a depletion of intracellular Ca(2+) stores, which are required for agonist-induced contraction, and diminished basal tone of the organ. Responsiveness of Ca(2+) transients to carbachol was reduced in mice on the lithogenic diet, particularly after 4-8 weeks, concomitant with appearance of mucosal inflammatory changes.

CONCLUSIONS & INFERENCES

These observations demonstrate that GBSM dysfunction is an early event in the progression of cholesterol gallstone disease and that it precedes mucosal inflammation.

Reduced myoelectric activity in the sphincter of Oddi in a new model of chronic cholangitis in rabbits: an in vivo and in vitro study

BACKGROUND

Chronic cholangitis caused by hepatolithiasis is a common disease in Southeast Asia. Few studies have addressed the effects of chronic cholangitis on cyclic activity of the sphincter of Oddi (SO). In this study, we investigated the changes of myoelectric activity in rabbits with chronic cholangitis in vivo and in vitro.

METHODS

Chronic cholangitis was induced in rabbits by initially introducing three pieces of 2-0 silk suture and sequentially injecting E. coli into the choledochus through the tube in ductus cysticus. In in vivo experiments, myoelectric activity of SO was recorded by a circular electrode through the jejunum stump in conscious animals. In in vitro experiments, the SO was completely isolated and the myoelectric activity was recorded by a circular electrode in a 10-mL organ bath filled with Krebs solution, with or without addition of cholecystokinin-8 (CCK-8), KCl, ionomycin or induction of capacitative calcium entry (CCE).

KEY RESULTS

In comparison with control and non-infected rabbits, the rabbits with chronic cholangitis showed higher levels of alkaline phosphatase and gamma-glutamyltransferase and significant pathological changes including increased inflammatory infiltration and collagen deposition in mucosae or muscular layer. Cyclic myoelectric activity of SO at phases 2 and 3 of migrating motor complex and the excitatory response to CCK-8 were dramatically decreased in animals with chronic cholangitis. Myoelectric activity of SO was also significantly decreased in vitro with or without agonists or with induction of CCE.

CONCLUSIONS & INFERENCES

Myoelectric activity of SO and its response to agonists are decreased in rabbits with chronic cholangitis both in vivo and in vitro.

Effects of NO/L-arginine pathway on gallbladder contractility in bile duct ligated guinea pigs

BACKGROUND

Common bile duct ligation (CBDL) produces gallbladder distension and acute inflammation similar to that seen in human acute acalculous cholecystitis. CBDL in the guinea pig affects smooth muscle contractility. The aim of this study was to determine whether the nitric oxide-L-arginine pathway plays a role in the inflammatory process and abnormal gallbladder contractility that occur after CBDL.

MATERIALS AND METHODS

Contractility of gallbladder muscle from CBDL and sham-operated guinea pigs was studied in vitro. Animals were treated with saline, aminoguanidine (AG), or an aminoguanidine + L-arginine combination (AG + L-Arg) in vivo. Potassium chloride, carbachol, and electric field stimulation (EFS) were used for contracting the gallbladder muscle strips or activating intrinsic nerves. Hematoxylin and eosin-stained slides of muscle strips were scored for inflammation.

RESULTS

Contraction responses to carbachol and EFS were decreased significantly in CBDL guinea pigs compared with those in the sham-operated group. AG partly reversed the smooth muscle contractile response to carbachol and EFS, but did not reduce the inflammation score. Treatment with AG + L-arg did not reverse either the contraction response or the inflammation score.

CONCLUSIONS

These findings suggest that AG and AG + L-Arg treatments have no beneficial effect on inflammation in guinea pigs after CBDL, although AG significantly reversed the effect on muscle contractility (P < 0.05). This improvement was independent of inflammation and may be due to a decreased level of NO and its diminished relaxant effect.

Protective effect of melatonin on Ca2+ homeostasis and contractility in acute cholecystitis

Impaired Ca2+ homeostasis and smooth muscle contractility co-exist in acute cholecystitis (AC) leading to gallbladder dysfunction. There is no pharmacological treatment for this pathological condition. Our aim was to evaluate the effects of melatonin treatment on Ca2+ signaling pathways and contractility altered by cholecystitis. [Ca2+]i was determined by epifluorescence microscopy in fura-2 loaded isolated gallbladder smooth muscle cells, and isometric tension was recorded from gallbladder muscle strips. Malondialdehyde (MDA) and reduced glutathione (GSH) contents were determined by spectrophotometry and cycloxygenase-2 (COX-2) expression was quantified by western blot. Melatonin was tested in two experimental groups, one of which underwent common bile duct ligation for 2 days and another that was later de-ligated for 2 days. Inflammation-induced impairment of Ca2+ responses to cholecystokinin and caffeine were recovered by melatonin treatment (30 mg/kg). This treatment also ameliorated the detrimental effects of AC on Ca2+ influx through both L-type and capacitative Ca2+ channels, and it was effective in preserving the pharmacological phenotype of these channels. Despite its effects on Ca2+ homeostasis, melatonin did not improve contractility. After de-ligation, Ca2+ influx and contractility were still impaired, but both were recovered by melatonin. These effects of melatonin were associated to a reduction of MDA levels, an increase in GSH content and a decrease in COX-2 expression. These findings indicate that melatonin restores Ca2+ homeostasis during AC and resolves inflammation. In addition, this indoleamine helps in the subsequent recovery of functionality.

Effects of Melatonin on Gallbladder Neuromuscular Function in Acute Cholecystitis

Gallbladder stasis is associated to experimental acute cholecystitis. Impaired contractility could be, at least in part, the result of inflammation-induced alterations in the neuromuscular function. This study was designed to determine the changes in gallbladder neurotransmission evoked by acute inflammation and to evaluate the protective and therapeutic effects of melatonin. Experimental acute cholecystitis was induced in guinea pigs by common bile duct ligation for 2 days, and then the neuromuscular function was evaluated using electrical field stimulation (EFS; 5-40 Hz). In a group of animals with the bile duct ligated for 2 days, a deligation of the duct was performed, and after 2 days, the neuromuscular function was studied. The EFS-evoked isometric gallbladder contraction was significantly lower in cholecystitic tissue. In addition, inflammation changed the pharmacological profile of these contractions that were insensitive to tetrodotoxin but sensitive to atropine and omega-conotoxin, indicating that acute cholecystitis affects action potential propagation in the intrinsic nerves. Nitric oxide (NO)-mediated neurotransmission was reduced by inflammation, which also increased the reactivity of sensitive fibers. Melatonin treatment prevented qualitative changes in gallbladder neurotransmission, but it did not improve EFS-induced contractility. The hormone recovered gallbladder neuromuscular function once the biliary obstruction was resolved, even when the treatment was started after the onset of gallbladder inflammation. These findings show for the first time the therapeutic potential of melatonin in the recovery of gallbladder neuromuscular function during acute cholecystitis.

Acute effect of smoking on gallbladder emptying and refilling in chronic smokers and nonsmokers: A sonographic study

AIM: To ultrasonographicaly evaluate the acute effects of smoking on gallbladder contraction and refilling in chronic smokers and nonsmokers.

METHODS: Fifteen chronic smokers (21-30 years old) and fifteen nonsmokers (21-35 years old) participated in this study. Chronic smokers were selected among the volunteers who had been smoking for at least 5 years and 10 cigarettes per day (mean 17.5/d). Examinations were performed in two separate days. In the first day, basal gallbladder (GB) volumes of volunteers were measured after 8-h fasting. After the examinations, participants had a meal containing at least 30-40 gram fat. Gallbladder volume was assessed at 5, 15, 30, 60, 120 and 180 min after the meal. In the second day, participants smoked 2 cigarettes after 8-h fasting. Then, they had the same meal, and gallbladder measurements were repeated at the same time points. Same procedures were applied to both groups.

RESULTS: The mean starving GB volumes were 23.3 ± 3.3 mL in the first day, 21.9 ± 3.0 mL in the second day in nonsmoker group and 18.3 ± 3.0 mL in the first day, 19.5 ± 2.8 mL in second day in smoker group. There was no significant difference between starving GB volumes. We did not find any significant difference between the GB volumes measured at 5, 15, 30, 60, 120 and 180 min in the first and second days in nonsmoker group. In smokers, post cigarette GB volume was found significantly higher at 5, 15 and 30 min which corresponded to GB contraction phase (P < 0.05). Control GB volume measurements were not significantly different between the two groups. Post-smoking GB volumes were also not significantly different between the two groups.

CONCLUSION: Smoking prolongs the maximal GB emptying time both in smokers and in nonsmokers though it is not significant. It delays GB contraction in chronic smokers and causes a significant decrease in GB emptying volume. Smoking causes no significant delay in GB refilling in both smokers and nonsmokers. These effects of smoking observed in acute phase result in bile stasis in GB. Bile stasis is the underlying cause of most GB disorders in chronic process.

Effect of Sildenafil Citrate on Postprandial Gallbladder Motility

OBJECTIVE

Sildenafil stimulates the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway through inhibition of type 5 phosphodiesterase. NO-cGMP pathway causes smooth muscle relaxation. The aim of this study is to evaluate the effects of sildenafil on gallbladder motility.

METHODS

Twenty healthy male volunteers (21-35 years old) participated in this randomized, double blind, crossover, and placebo-controlled study. Oral sildenafil (50 mg) or placebo was randomly dispensed to each volunteer on two consecutive days. After the sildenafil or placebo, a special meal with a high fat content was administered. Gallbladder volume was measured using sonography preprandially and at 5, 15, 30, 60, 120 and 180 minutes postprandially.

RESULTS

Sildenafil showed an inhibitory effect on gallbladder contraction in healthy volunteers that began at 30 minutes. Gallbladder volumes showed significant differences at 30 minutes following the test meal (approximately 50-60 min after the sildenafil intake), between placebo (15.4 +/- 5.1 mL) and the sildenafil groups (19.3 +/- 6.1 mL) (P < 0.05). In addition, gallbladder volume was significantly higher during the refilling phase in the sildenafil group (P < 0.05 at 180 min). Maximal contraction was achieved at 60 minutes in each group.

CONCLUSIONS

Sildenafil constituted a significant inhibitory effect on gallbladder discharge in healthy individuals when compared with placebo group. Because of this inhibitory effect, sildenafil consumption for long periods may potentiate risks of gallbladder disorders and gallstone formation resulting from disturbed gallbladder motility.

Changes in guinea pig gallbladder smooth muscle Ca2+ homeostasis by acute acalculous cholecystitis

Impaired smooth muscle contractility is a hallmark of acute acalculous cholecystitis. Although free cytosolic Ca2+ ([Ca2+]i) is a critical step in smooth muscle contraction, possible alterations in Ca2+ homeostasis by cholecystitis have not been elucidated. Our aim was to elucidate changes in the Ca2+ signaling pathways induced by this gallbladder dysfunction. [Ca2+]i was determined by epifluorescence microscopy in fura 2-loaded isolated gallbladder smooth muscle cells, and isometric tension was recorded from gallbladder muscle strips. F-actin content was quantified by confocal microscopy. Ca2+ responses to the inositol trisphosphate (InsP3) mobilizing agonist CCK and to caffeine, an activator of the ryanodine receptors, were impaired in cholecystitic cells. This impairment was not the result of a decrease in the size of the releasable pool. Inflammation also inhibited Ca2+ influx through L-type Ca2+ channels and capacitative Ca2+ entry induced by depletion of intracellular Ca2+ pools. In addition, the pharmacological phenotype of these channels was altered in cholecystitic cells. Inflammation impaired contractility further than Ca2+ signal attenuation, which could be related to the decrease in F-actin that was detected in cholecystitic smooth muscle cells. These findings indicate that cholecystitis decreases both Ca2+ release and Ca2+ influx in gallbladder smooth muscle, but a loss in the sensitivity of the contractile machinery to Ca2+ may also be responsible for the impairment in gallbladder contractility.

Acute acalculous cholecystitis

Acute cholecystitis can develop without gallstones in critically ill or injured patients. However, the development of acute acalculous cholecystitis is not limited to surgical or injured patients, or even to the intensive care unit. Diabetes, malignant disease, abdominal vasculitis, congestive heart failure, cholesterol embolization, and shock or cardiac arrest have been associated with acute acalculous cholecystitis. Children may also be affected, especially after a viral illness. The pathogenesis of acute acalculous cholecystitis is a paradigm of complexity. Ischemia and reperfusion injury, or the effects of eicosanoid proinflammatory mediators, appear to be the central mechanisms, but bile stasis, opioid therapy, positive-pressure ventilation, and total parenteral nutrition have all been implicated. Ultrasound of the gallbladder is the most accurate diagnostic modality in the critically ill patient, with gallbladder wall thickness of 3.5 mm or greater and pericholecystic fluid being the two most reliable criteria. The historical treatment of choice for acute acalculous cholecystitis has been cholecystectomy, but percutaneous cholecystostomy is now the mainstay of therapy, controlling the disease in about 85% of patients. Rapid improvement can be expected when the procedure is performed properly. The mortality rates (historically about 30%) for percutaneous and open cholecystostomy appear to be similar, reflecting the severity of illness, but improved resuscitation and critical care may portend a decreased risk of death. Interval cholecystectomy is usually not indicated after acute acalculous cholecystitis in survivors; if the absence of gallstones is confirmed and the precipitating disorder has been controlled, the cholecystostomy tube can be pulled out after the patient has recovered.

Effect of indomethacin on gallbladder inflammation and contractility during acute cholecystitis

OBJECTIVE

The aim of this study was to determine whether the prostaglandin synthase inhibitor indomethacin reverses the inflammation and abnormal gallbladder contractility that occur after common bile duct ligation (CBDL), a model of acute cholecystitis.

METHODS

Gallbladder muscle contractility was studied in vitro in normal, CBDL, and sham-operated guinea pigs. Animals were treated with saline or indomethacin in vivo. Acetylcholine (ACh) was used to directly contract the muscle and electric field stimulation (EFS) to activate intrinsic nerves. Hematoxylin and eosin-stained slides of muscle strips were scored for inflammation.

RESULTS

CBDL in saline-treated animals increased the inflammation score and decreased gallbladder muscle contractility to ACh and EFS. Indomethacin decreased the inflammation score and partly reversed the smooth muscle contractile response to ACh 6 and 24 h after CBDL, but not at 48 h. Indomethacin did not reverse the CBDL-induced decrease in nerve-evoked contractions.

CONCLUSION

Gallbladder inflammation and contractile dysfunction after CBDL are partly reversed with indomethacin at 6 and 24 h, but not at 48 h. This suggests that, early in the course of CBDL, the inflammation and contractile dysfunction are, in part, prostaglandin-mediated.