The effects of somatostatin and octreotide on the human sphincter of Oddi

New Insight into the Role of Nitric Oxide Pathways in Pancreas

Nitric oxide (NO) is generated by a family of enzymes termed NO synthases (NOS) that convert L-arginine to NO and citrulline. The role of NO as an important biological mediator and recognition of the pathophysiological significance of superoxides/NO interaction has led to an intensive research and development of therapies based on the interception of the NO signaling cascade in the pancreatitis course. However, the presence and localization of the NO-generating enzymes in various organs including pancreas are subject to controversy. We assumed that this controversy might reflect rather the diversity of experimental approaches and an insufficient sensitivity of the methods used. Applying tyramide signal amplification (TSA) immunohistochemical technology, we were able detect all three NOS isoforms both in exocrine and endocrine compartments and in the vasculature in the normal pancreas and in pancreatitis. This also allowed us to demonstrate that oxidative stress runs ahead of NOS up-regulation, which implies that the NO enhancement in the course of pancreatitis is likely to be an adaptive mechanism aimed at maintaining the homeostatic cellular level of the bioactive NO. The aims of this minireview are to describe normal intrapancreatic NO pathways and the role of NO in the pancreatitis course.

Sphincter of Oddi dysfunction: an evidence-based review

Sphincter of Oddi dysfunction is a painful syndrome that presents as recurrent episodes of right upper quadrant biliary pain, or recurrent idiopathic pancreatitis. It is a disease process that has been a subject of controversy, in part because its natural history, disease course and treatment outcomes have not been clearly defined in large controlled studies with long-term follow-up. This review is aimed at clarifying the state-of-the-art with an evidence-based summary of the current diagnostic and therapeutic approaches and modalities for sphincter of Oddi dysfunction.

L-arginine-NO-cGMP signalling pathway in pancreatitis

The role of nitric oxide (NO) in the human pancreas and in pancreatitis still remains controversial. Furthermore, conflicting conclusions have been reached by different laboratories about the localization of the NO-generating enzyme (NO synthase, NOS) in the pancreas. Here, we investigated the co-expression of NOS with enzymes involved in regulation of NO signalling in the normal human pancreas and in pancreatitis. We found that the whole NO signalling machinery was up-regulated in pancreatitis, especially within the exocrine compartment. Furthermore, the exocrine parenchymal cells revealed higher levels of oxidative stress markers, nitrotyrosine and 8-hydroxyguanosine, in pancreatitis, which reflects the exceptional susceptibility of the exocrine parenchyma to oxidative stress. This study provides a direct link between oxidative stress and the enzymatic control of the NO bioavailability at the cellular level and endows with further insight into fundamental mechanisms underlying pancreatic disorders associated with disruptions in the L-arginine-NO-cGMP signalling enzyme cascade.

Lanreotide autogel-induced acute pancreatitis in a patient with acromegaly

Somatostatin and somatostatin analogues are considered very useful for the treatment of hormone producing tumors and acute variceal bleeding. They have also been proposed for the treatment of acute pancreatitis and for the prevention of post-endoscopic retrograde cholangiopancreatography pancreatitis although clinical trials have failed to show any efficacy. The authors report the case of a 45-year-old man, recently diagnosed of acromegaly, which developed an acute pancreatitis shortly after his first injection of lanreotide autogel. The patient developed a severe dilatation of his hypocontractile gallbladder with distension of the intra and extrahepatic biliary ducts, the choledochus and the main pancreatic duct, without lithiasis or other abnormalities at the papilla, which resolved spontaneously in a month. We consider that lanreotide most likely induced a functional spasm of the Sphincter of Oddi, with impairment of the biliary-pancreatic outflow, leading to an acute pancreatitis, and review the literature concerning this drug related pancreatitis.

Role of neurocrine somatostatin on sphincter of Oddi contractility and intestinal ischemia reperfusion-induced acute pancreatitis in macaques

BACKGROUND

Intestinal ischemia-reperfusion (IIR) is implicated in the pathogenesis of severe acute pancreatitis (SAP). This study investigates the impact of neurocrine somatostatin (SST) on the contraction of sphincter of Oddi (SO) during IIR.

METHODS

Intestinal ischemia-reperfusion model in macaques was induced by occluding the superior mesenteric artery. Pancreatitis was confirmed by pancreatic histology and serum levels of amylase and lipase. SST and its receptors (SSTRs) in SO were visualized by immunohistochemistry. Effects of SST on the contraction of the isolated SO were recorded in vitro.

KEY RESULTS

Inflammatory scores of the pancreas and serum levels of amylase or lipase in the macaques that underwent IIR were significantly higher than those in the control group. The frequency and amplitude of phasic contraction of the circular muscle in SO was increased by SST in a concentration-dependent manner. Compared with the control group, SST innervation or SSTR2 expression in SO of macaques treated with IIR was increased 5.2 fold or 5.6 fold respectively. Prophylactic infusion of SST before IIR significantly reduced SST immunoreactive fibers in SO as compared to those in the IIR group and remarkably alleviated the pathophysiologic changes due to IIR.

CONCLUSIONS & INFERENCES

Increased SST innervation in SO during the early phase of IIR associated with the contraction of circular muscle of SO, which might be one of the promoting factors associated with the development of SAP. Prevention of IIR or intervention of SO contraction after occurrence of acute pancreatitis might be beneficial for preventing SAP.

Lethal somatostatin analog-induced acute necrotizing pancreatitis in a patient with hormone-refractory prostate cancer

We report a fatal case of acute pancreatitis which developed in a 76-year-old male with hormone-refractory prostatic carcinoma who was being treated with lanreotide, a slow-release somatostatin analog.

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Effect of native somatostatin on Sphincter of Oddi motility in patients with acute recurrent pancreatitis. A pilot study with Ultrasound-Secretin test

BACKGROUND

The effect of native somatostatin on Sphincter of Oddi motility still remains controversial. Sphincter of Oddi inhibition was demonstrated at manometry in patients in the acute phase of alcoholic pancreatitis. Other investigators showed marked somatostatin-induced impairment of bile flow by hepato-biliary scintigraphy.

AIM

Aim of the study was to determine the effects of therapeutical doses of exogenous somatostatin on Sphincter of Oddi motility.

PATIENTS AND METHODS

We studied eight patients (two men, six women, age 18-42), in the quiescent phase of idiopathic recurrent pancreatitis. We directly studied Sphincter of Oddi motility by perendoscopic manometry and, indirectly, secretin-stimulated pancreatic juice outflow by Ultrasound-Secretin test. The two tests were repeated before and after somatostatin infusion.

RESULTS

Manometry was performed in two patients. After 250 microg somatostatin bolus the sphincter showed an increase of motor activity. At Ultrasound-Secretin test mean diameters were significantly larger at 40-60 min evaluation intervals during 250 microg/h somatostatin infusion as compared to saline infusion, showing a delayed pancreatic duct emptying.

CONCLUSIONS

Acute administration of somatostatin seems to induce an excitatory effect on Sphincter of Oddi motility, with impaired pancreatic outflow in patients in the quiescent phase of recurrent pancreatitis.

Ethanol inhibits the motility of rabbit sphincter of Oddi in vitro

AIM: The role of the sphincter of Oddi (SO) in ethanol (ETOH)-induced pancreatitis is controversial. Our aim was to characterise the effect of ETOH on basal and stimulated SO motility.

METHODS: SOs removed from white rabbits were placed in an organ bath (Krebs solution, pH7.4, 37 °C). The effects of 2 mL/L, 4 mL/L, 6 mL/L and 8 mL/L of ETOH on the contractile responses of the sphincter were determined. SOs were stimulated with either 0.1 μmol/L carbachol, 1 μmol/L erythromycin or 0.1 μmol/L cholecystokinin (CCK).

RESULTS: ETOH at a dose of 4 mL/L significantly decreased the baseline contractile amplitude from 11.98 ± 0.05 mN to 11.19 ± 0.07 mN. However, no significant changes in the contractile frequency were observed. ETOH (0.6%) significantly decreased both the baseline amplitude and the frequency compared to the control group (10.50 ± 0.01 mN, 12.13 ± 0.10 mN and 3.53 ± 0.13 c/min, 5.5 ± 0.13 cycles(c)/min, respectively). Moreover, 0.8% of ETOH resulted in complete relaxation of the SO. Carbachol (0.1 μmol/L) or erythromycin (1 μmol/L) stimulated the baseline amplitudes (by 82% and 75%, respectively) and the contractile frequencies (by 150% and 106%, respectively). In the carbachol or erythromycin-stimulated groups 2-6 mL/L of ETOH significantly inhibited both the amplitude and the frequency. Interestingly, a 4-5 min administration of 6 mL/L ETOH suddenly and completely relaxed the SO. CCK (0.1 μmol/L) stimulated the baseline amplitude from 12.37 ± 0.05 mN to 27.40 ± 1.82 mN within 1.60 ± 0.24 min. After this peak, the amplitude decreased to 17.17 ± 0.22 mN and remained constant during the experiment. The frequency peaked at 12.8 ± 0.2 c/min, after which the constant frequency was 9.43 ± 0.24 c/min throughout the rest of the experiment. ETOH at a dose of 4 mL/L significantly decreased the amplitude from 16.13 ± 0.23 mN to 14.93 ± 0.19 mN. However, no significant changes in the contractile frequency were observed. ETOH at a dose of 6 mL/L inhibited both the amplitudes and the frequencies in the CCK-stimulated group, while 8 mL/L of ETOH completely relaxed the SO.

CONCLUSION: ETOH strongly inhibits the basal, carbachol, erythromycin, and CCK-stimulated rabbit SO motility. Therefore, it is possible that during alcohol-intake the relaxed SO opens the way for pancreatic fluid to flow out into the duodenum in rabbits. This relaxation of the SO may protect the pancreas against alcohol-induced damage.

Effects of octreotide on acute necrotizing pancreatitis in rabbits

AIM: To assess the role of oxygen-derived free radicals and cytokines in the pathogenesis of taurocholic acid-induced acute pancreatitis, and to evaluate the preventive effects of octreotide towards the development of acute pancreatitis.

METHODS: Acute pancreatitis was induced in male New Zealand white rabbits by retrograde injection of 0.8 mL/kg·b.m. of 50 g/L sodium taurocholate (NaTC) in the pancreatic duct. Sham-operated animals served as control. Octreotide 1 mg/kg·b.m. was administered subcutaneously before the induction of pancreatitis. Blood was taken from the jugular vein before and at 1, 3, 6, 12 and 24 h after pancreatitis induction. Serum activities of amylase, IL-6 and TNF-α and levels of malonyl dialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx), catalase and superoxide dismutase (Mn-, Cu-, and Zn-SOD) in pancreatic tissue were measured.

RESULTS: Serum TNF-α and IL-6 levels increased significantly 3 h after the onset of pancreatitis, and then returned to control level. The tissue concentration of MDA was significantly elevated at 24 h, while the GSH level and GPx, catalase, Mn-SOD, Cu-, Zn-SOD activities were all significantly decreased in animals with pancreatitis as compared to the control. Octreotide pretreatment significantly reversed the changes in cytokines and reactive oxygen metabolites. Octreotide treatment did not alter the serum amylase activity and did not have any beneficial effects on the development of histopathological changes.

CONCLUSION: Oxygen-derived free radicals and proinflammatory cytokines are generated at an early stage of NaTc-induced acute pancreatitis in rabbits. Prophylactic octreotide treatment can prevent release of cytokines and generation of reactive oxygen metabolites, but does not have any beneficial effects on the development of necrotizing pancreatitis.

Effects of bioactive agents on biliary motor function

Our understanding of biliary motility under normal and pathophysiologic conditions is still incomplete, but there have been recent advances. Of particular interest are the mechanisms involved in gallbladder filling and emptying, with a focus on understanding the processes underlying impaired gallbladder emptying leading to gallbladder dyskinesia and the formation of gallstones or cholecystitis. The sphincter of Oddi (SO) is a complex neuromuscular structure. Recent studies have attempted to unravel the specific neural or hormonal mechanisms operating under normal physiologic conditions and those that may lead to SO dysfunction. Furthermore, new research fronts are emerging, including the role of leptin in obese patients with impaired biliary motility and the action of electroacupuncture for possible treatment of SO dysfunction. This review illustrates the broad front of current research regarding the effects of bioactive agents on biliary motility, including enteric hormones, nitric oxide, opioids, inflammatory mediators, leptin, protease inhibitors, neurotransmitters, and electroacupuncture.