Effect of L-NAME on nitric oxide and gastrointestinal motility alterations in cirrhotic rats

An herbal-compound-based combination therapy that relieves cirrhotic ascites by affecting the L-arginine/nitric oxide pathway: A metabolomics-based systematic study

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine boasts a 440-year-long history of treating refractory ascites via combinations of herbal medicines, called formulae. Xiaozhang Tie (XT) is a proprietary herbal-compound-based formula that has been proven to be very effective in the treatment of cirrhosis-associated ascites in clinical practice, but the mechanism of action of XT remains unknown.

AIM OF THE STUDY

In this study, we used a metabolomics-based systematic method to elucidate the mechanism of XT in the treatment of cirrhotic ascites.

METHODS

Decompensated liver cirrhosis was induced in rats by intraperitoneal injection of Carbon tetrachloride (CCl₄). Ultra performance liquid chromatography-mass spectrometry (UPLC-MS) combined with pattern recognition approaches were used to determine differentiating metabolites relevant to XT treatment. Biomarkers were further validated by a targeted quantitative method and by the results from serum and urine analyses. Pathway analysis and correlation network construction were used to reveal the therapeutic targets associated with XT treatment, and the potential mechanisms were verified by the results from biochemical, histopathological and immunohistochemical assays.

RESULTS

XT synergistically mediated the abnormalities of amino acid metabolic pathways in cirrhotic rats. XT significantly elevated the arginine levels, reduced the serum nitric oxide (NO) levels and alleviated the gastrointestinal motility disorder of cirrhotic rats. This effect of XT has been confirmed by the inhibition of the activities of inducible NO synthase and neuronal NO synthase in the small intestine.

CONCLUSIONS

These results reveal that XT promotes gastrointestinal motility by acting on multiple targets in multiple pathways, of which the L-arginine/NO pathway is most affected.

Comparison of Oxidative Effects of Two Different Administration Form of Oxybutynin in the Potential Target Tissues

Oxybutynin is an important anticholinergic agent that prevents uncontrolled contractions in the treatment of overactive bladder (OAB). However, drugs containing oxybutynin have significant side effects such as dry eyes, dry mouth, increased heart rate, constipation, blurred vision, and confusion. In recent years, new delivery methods for this agent are being searched. One of them is vaginal delivery. In this study, we aimed to compare the effects of oxybutynin on oxidative parameters in the potential target tissues of the oral and vaginal delivery. Female New Zealand white rabbits (n=12) were divided into two groups: oral delivery and vaginal delivery. The animals were sacrificed 48 h after administration and nitric oxide (NOx), thiobarbituric acid-reactive substances (TBARs), and glutathione (GSH) levels were determined spectrophotometrically in the aorta, salivary gland, and small intestine tissue samples. Vaginal delivery significantly decreased NOx levels in all tissue samples as compared to oral delivery (p < 0.05). Moreover, it reduced TBARs levels in salivary gland and aorta tissue samples (p < 0.05). In the light on these findings, it can be said that vaginal delivery may decrease the oxidant-induced side effects of oxybutynin as compared to oral delivery.

Gastrointestinal Motility Disorders and Their Clinical Implications in Cirrhosis

Gastrointestinal motility is impaired in a substantial proportion of patients with cirrhosis. Cirrhosis-related autonomic neuropathy, increased nitric oxide production, and gut hormonal changes have been implicated. Oesophageal dysmotility has been associated with increased frequency of abnormal gastro-oesophageal reflux. Impaired gastric emptying and accommodation may result in early satiety and may have an impact on the nutritional status of these patients. Small intestinal dysmotility might be implicated in small intestinal bacterial overgrowth and increased bacterial translocation. The latter has been implicated in the pathophysiology of hepatic encephalopathy and spontaneous bacterial peritonitis. Enhanced colonic motility is usually associated with the use of lactulose. Pharmacological interventions aiming to alter gastrointestinal motility in cirrhosis could potentially have a beneficial effect reducing the risk of hepatic decompensation and improving prognosis.

The nitric oxide synthase inhibitor, Ng-nitro-L-arginine-methyl-ester, attenuates the delay in gastric emptying induced by hyperglycaemia in healthy humans

The aim of this study was to determine whether the nitric oxide (NO) synthase inhibitor, N(g)-nitro-L-arginine-methyl-ester (L-NAME), reverses the effects of acute hyperglycaemia on gastric emptying and antropyloroduodenal (APD) motility. The study had a four-way randomized crossover (hyperglycaemia vs euglycaemia; L-NAME vs placebo) design in a clinical laboratory setting. Seven healthy volunteers [four males; age 30.3 +/- 3.8 years; body mass index (BMI) 23.6 +/- 1.2 kg m(-2)] were the study subjects. After positioning a transnasal manometry catheter across the pylorus, the blood glucose concentration was maintained at either 15 or 5 mmol L(-1) using a glucose/insulin clamp. An intravenous infusion of L-NAME (180 microg kg(-1 )h(-1)) or placebo (0.9% saline) was commenced (T = -30 min) and continued for 150 min. At T = -2 min, subjects ingested a drink containing 50 g of glucose made up to 300 mL with water. Gastric emptying was measured using 3D ultrasound, and APD motility using manometry. Hyperglycaemia slowed gastric emptying (P < 0.05), and this effect was abolished by L-NAME. L-NAME had no effect on gastric emptying during euglycaemia. Hyperglycaemia suppressed fasting antral motility [motility index: 3.9 +/- 0.8 (hyperglycaemia) vs 6.5 +/- 0.6 (euglycaemia); P < 0.01]; l-NAME suppressed postprandial antral motility [motility index: 3.6 +/- 0.2 (L-NAME) vs 5.1 +/- 0.2 (placebo); P < 0.001]. Postprandial basal pyloric pressure was higher during hyperglycaemia (P < 0.001), and lower after administration of L-NAME (P < 0.001). Slowing of gastric emptying induced by hyperglycaemia is mediated by NO, and may involve the modulation of tonic pyloric activity.

Effects and mechanism of changes of local neurotransmitters in rats' pylorus and bile reflux to the stomach with stress ulcer

Stress ulcer occurs primarily in severe conditions, with a high incidence and mortality in intensive care units. However, studies on the association between stress ulcer and bile reflux to the stomach with stress ulcer are still inconclusive. Therefore, our research aimed to determine whether or not bile reflux exists during stress ulcer and then to investigate the effects and mechanism of changes of pyloric local neurotransmitters on bile reflux in such circumstances so as to provide a new pathway for clinical intervention. Cold water immersion was used to copy the stress ulcer model of rats. Sixty-five adult Sprague-Dawley rats of either sex were randomly divided into three groups: the normal control group (n = 10), the stress group (n = 30), and the antagonist group (n = 25). The gastric ulcer index, pH, and bile acid of gastric juice were measured before and after stress. Radio Immunoassay Detection Kit and Biochemic Detection Kit were used to measure local contents of CGRP (calcitonin gene-related peptide) and nitric oxide, respectively, in rats' pylorus. The local contents of nitric oxide in rats' pylorus reached a maximum at 1 hr after stress. The bile acid and pH of gastric juice peaked at 2 hr after stress and the ulcer index peaked at 4 hr after stress. But the local contents of CGRP in rats' pylorus decreased to the minimum at 4 hr after stress. The bile acid and ulcer index in the L-NAME group were significantly lower than in the antagonist control group. However, the bile acid in the hCGRP8-37 group was less than in the antagonist control group. Compared with hCGRP8-37 group, there was a significant reduction in bile acid in the L-NAME group. There was a significant reduction in the ulcer index of the hCGRP8-37 group compared with the L-NAME group and the antagonist control group. There was a certain kind of positive correlation between nitric oxide in rats' pylorus and bile acid to the stomach, for nitric oxide could loosen the pyloric sphincter and increase the bile acid to the stomach. L-NAME might reduce the local nitric oxide contents in rats' pylorus so that bile acid to the stomach might be decreased, obviously with a looser tight pyloric sphincter. Meanwhile, the CGRP in rats' pylorus was negatively associated with the ulcer index, hence CGRP might protect gastric mucosa under stress conditions.

Effects of Atractylodes macrocephalae on gastric emptying and nitrergic nerves in rats with hepatic cirrhosis

AIM: To observe the effects of atractylodes macrocephalae (AM) on gastric motility and nitrergic nerval system in rats with hepatic cirrhosis.

METHODS: Twenty-four Wister rats were randomly divided into control group, cirrhosis model group and AM treatment group. Dextran blue-2000 was used as an internal marker to assay the gastric emptying of the rats. The nitrergic nerves in the myenteric plexuses of gastric fundus, body and antrum were observed with NADPH-d histochemical staining.

RESULTS: Compared with those in control group, the gastric emptyings of rats were markedly delayed in model group (160.23±45.13 vs 100±17.78, P<0.01), and the distributions and densities of myenteric nitrergic nerves in the gastric body and antrum were significantly increased (7.35±0.95 vs 5.52±0.92, P<0.01; 6.26±0.79 vs 5.28±0.78, P<0.05). No significant changes were found in the fundus. After treatment with AM, the gastric motility of rats was markedly improved and the nitrergic nerves in antrum were significantly recovered. No significant differences were observed between the rats of AM and control group (96.12±16.25 vs 100±17.78, 5.39±0.84 vs 5.28±0.78, both P>0.05).

CONCLUSION: Atractylodes macrocephalae can improve the gastric motility and the mechanism may be related to its effect on the distributions of nitrigic nerves in the gastric body and antrum of rats with hepatic cirrhosis.

Plasma levels of motilin, cholecystokinin and somatostatin and gastric electrical activity in patients with liver cirrhosis

AIM

To investigate the mechanism of gastrointestinal dysfunction in patients with liver cirrhosis (LC) by determining the plasma levels of motilin (MTL), cholecystokinin (CCK) and somatostatin (SS) and gastric electrical activity.

METHODS

Plasma levels of MTL, CCK and SS were determined with radioimmunoassay in 38 LC patients and 30 healthy volunteers. Gastric electrical activities in all the 68 subjects were observed with the electrogastrograph (3 CPM, USA) before and after water load tests. The indexes of the gastric electrical activities included the percentage of frequency, the main frequency, the ratio of power of postprandial to preprandial, and the frequency spectrum analysis.

RESULTS

Compared with those in the control group, the levels of MTL and CCK in LC patients were increased (287±81 ng/L. 3.3±1.4 ng/L vs 131±27 ng/L. 1.1±0.5 ng/L. P<0.01, t = 11.150, n = 38; P<0.01, t = 9.146, n = 38). There was a significant difference between the levels of MTL and CCK with different liver functions (P<0.05, F = 87.570; P<0.05, F = 47.506). The levels of MTL and CCK tended to increase with the liver function from Child-Pugh A to B to C. The levels of SS in LC patients with Child-Pugh B and C liver function were increased, which showed a significant difference compared with those in the control groups (67±10 ng/L vs 28±13 ng/L.P <0.01, t =7.652, n =16; P <0.01, t =9.428, n =12). But the levels of SS in the patients with Child-Pugh A were not apparently increased. At the same time, the degree of disorder of gastric electrical activity in the patients with Child-Pugh B and C of liver function was higher than that in the control group (P<0.01, t = -8.088, n = 16; P<0.01, t = 7.697, n = 16; P<0.01, t = -10.178, n = 12; P<0.01, t = 9. 817, n = 12). The main frequency (P<0.01, t = -7.575, n = 16; P <0.01, t = -11.623, n =12) and the ratio of postprandial power to preprandial power (P<0.01. t = -3.987, n = 16; P<0.01. t = -4.330, n = 12) in patients with Child-Pugh B and C of liver function were lower than that in the control group

CONCLUSION

The percentage of disorder of gastric electrical activity in LC patients is increased compared with that in healthy volunteers. The variation of the levels of gastrointestinal hormone is one of the important causes of gastrointestinal dysfunction in patients with liver cirrhosis.

Effects of neurotrophins on gastrointestinal myoelectric activities of rats

AIM: To observe the effects of mouse nerve growth factor (NGF), rat recombinant brain derived neurotrophic factor (rm-BDNF) and recombinant human neurotrophin-3 (rh-NT-3) on the gastrointestinal motility and the migrating myoelectric complex (MMC) in rat.

METHODS: A randomized, double-blinded, placebo-controlled experiment was performed. 5-7 days after we chronically implanted four or five bipolar silver electrodes on the stomach, duodenum, jejunum and colon, 21 experimental rats were coded and divided into 3 groups and injected NGF, rm-BDNF, rh-NT-3 or placebo respectively via tail vein at a dose of 20 μg·kg^{- 1}. The gastrointestinal myoelectrical activity was recorded 2 hours before and after the test substance infusions in these consciously fasting rats.

RESULTS: The neurotrophins-induced pattern of activity was characterized by enhanced spiking activity of different amplitudes at all recording sites, especially in the colon. In the gastric antrum and intestine, only rh-NT-3 had increased effects on the demographic characteristics of electrical activities (P < 0.05), but did not affect the intervals of MMCs. In the colon, all the three kinds of neurotrophins could significantly increase the frequency, amplitude and duration levels of spike bursts, and also rh-NT-3 could prolong the intervals of MMC in the transverse colon (25 ± 11 min vs 19 ± 6 min, P < 0.05). In the distal colon rh-NT-3 could evoke phase III-like activity and disrupt the MMC pattern, which was replaced by a continuously long spike bursts (LSB) and irregular spike activity (ISA) for 48 ± 6 min.

CONCLUSION: Exogenous neurotrophic factors can stimulate gut myoelectric activities in rats.