Inhibition of nitric oxide synthase induces intestinal mucosal damage and increases mortality in rats treated by FK506

Nitric oxide protects intestinal mucosal barrier function and prevents acute graft rejection after intestinal transplantation: A mini-review

Intestinal transplantation is a complex technical procedure that provides patients suffering from end-stage intestinal failure an opportunity to enjoy improved quality of life, nutrition and survival. Compared to other types of organ transplants, it is a relatively new advancement in the field of organ transplantation. Nevertheless, great advances have been made over the past few decades to the present era, including the use of ischemic preconditioning, gene therapy, and addition of pharmacological supplements to preservation solutions. However, despite these strides, intestinal transplantation is still a challenging endeavor due to several factors. Notable among them is ischemia-reperfusion injury (IRI), which results in loss of cellular integrity and mucosal barrier function. In addition, IRI causes graft failure, delayed graft function, and decreased graft and recipient survival. This has necessitated the search for novel therapeutic avenues and improved transplantation protocols to prevent or attenuate intestinal IRI. Among the many candidate agents that are being investigated to combat IRI and its associated complications, nitric oxide (NO). NO is an endogenously produced gaseous signaling molecule with several therapeutic properties. The purpose of this mini-review is to discuss IRI and its related complications in intestinal transplantation, and NO as an emerging pharmacological tool against this challenging pathological condition. i.

Endoscopic resection of gastric neoplasm in solid-organ transplant recipients

BACKGROUND

The aim of this study was to investigate the feasibility and safety of endoscopic resection of gastric neoplasm in solid-organ transplant (SOT) recipients.

METHODS

Between January 1994 and December 2011, the results of endoscopic resection of 17 lesions in 15 consecutive patients who had previously undergone SOT at Asan Medical Center were retrospectively evaluated. We compared clinical outcomes of this group with 1:5 matched non-SOT patients treated by endoscopic resection.

RESULTS

Of the 6,491 patients who underwent SOT during the study periods, 30 patients (0.46%) with 31 lesions were diagnosed with gastric cancer, and eight patients (0.12%) with nine lesions were diagnosed with gastric adenoma. Among them, 15 patients with 17 lesions were treated by endoscopic resection, and 19 patients with 20 lesions have undergone gastrectomy. In endoscopically resected SOT group, the median duration between transplantation and endoscopic treatment was 41 months (range, 5-196 months). En bloc and complete resection were achieved in 13 (76.5%) and 15 (88.2%) lesions. Four lesions (23.5%) experienced bleeding, which was successfully managed endoscopically. When compared with post-endoscopic resection bleeding rate of non-SOT group (5.9%, [5/85]), there was no significant difference in multivariable analysis (P=0.083).

CONCLUSIONS

In endoscopic resection for gastric neoplasm of SOT recipients, only manageable complications were noted in some patients, and graft dysfunctions or perforations did not occur. To avoid surgical resection with its associated perioperative mortality and morbidity, endoscopic resection for gastric neoplasm in SOT recipients is recommended as a feasible treatment with high efficacy and safety.

Roles of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal transplantation of rats

OBJECTIVE

The study was designed to evaluate the role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in ischemia-reperfusion injury (IRI) and acute rejection (AR) in rat intestinal transplantation, by administration of nitric oxide inhibitor N(G)-nitro-L-arginine methyl ester (LNAME).

MATERIALS AND METHODS

Rats that underwent orthotopic intestinal transplantation were assigned to 2 sets of groups: (1) iso-geneic group (Lewis-Lewis), L-NAME 0 mg/kg/d group (1-1), 4 mg/kg/d (group 1-2), or 8 mg/kg/d (group 1-3) injected intraperitoneally or (2) allogeneic group (Dark Agouti-Lewis), L-NAME 0 mg/kg/d (group 2-1) or 8 mg/kg/d (group 2-2) injected intraperitoneally. We examined survival times, light microscopy as well as maltose absorption tests. The nNOS and iNOS activities were measured by immunohistochemical methods.

RESULTS

Histologic examination showed inhibited iNOS activity compared with group l-l, and Park scores decreased significantly in group 1-2 at 30 minutes after reperfusion (1.42 ± 0.38 vs 2.58 ± 0.49, P < .01). Both iNOS and nNOS activities were inhibited and Park scores increased significantly in group 1-3 from 30 minutes to day 3 after reperfusion (P < .0l). nNOS activity decreased and iNOS activity increased among group 2-1 during AR. Compared with group 2-1, iNOS activity was inhibited, progression of AR delayed, and survival significantly prolonged in group 2-2 (10.17 ± 0.98 vs 6.83 ± 0.75, P < .01).

CONCLUSION

This study suggested that decreased nNOS and increased iNOS activity both contributed to IRI and AR. More importantly, nNOS more importantly than iNOS activity was closely related to graft structure and function.

Nitrooxyethylation reverses the healing-suppressant effect of Ibuprofen

Nonsteroidal antiinflammatory drugs like ibuprofen impede tissue repair by virtue of retarding inflammation. The present study was undertaken to explore if linking of nitrooxyethyl ester to ibuprofen reverses its healing-depressant propensity. Nitrooxyethyl ester of ibuprofen (NOE-Ibu) was synthesized in our laboratory through a well-established synthetic pathway. NOE-Ibu was screened for its influence on collagenation, wound contraction and epithelialization phases of healing, and scar size of healed wound in three wound models, namely, incision, dead space, and excision wounds. Besides, its influence on the oxidative stress (levels of GSH and TBARS) was also determined in 10-day-old granulation tissue. NOE-Ibu was further screened for its antiinflammatory activity in rat paw edema model. NOE-Ibu promoted collagenation (increase in breaking strength, granulation weight, and collagen content), wound contraction and epithelialization phases of healing. NOE-Ibu also showed a significant antioxidant effect in 10-day-old granulation tissue as compared to ibuprofen. Results vindicate that the esterification of ibuprofen with nitrooxyethyl group reverses the healing-suppressant effect of ibuprofen. The compound also showed equipotent antiinflammatory activity as ibuprofen.

Wound healing activity of NOE-aspirin: a pre-clinical study

Aspirin, one of the oldest non-steroidal anti-inflammatory drugs, impedes tissue repair by virtue of retarding inflammation. The present study was undertaken to find out if linking of nitrooxyethyl ester to aspirin reverses its healing-depressant propensity. Nitrooxyethyl ester of aspirin (NOE-Asp) was synthesized in our laboratory through well-established synthetic pathway, starting from aspirin through esterification with ethylene glycol and nitration with a mixture of nitric and sulfuric acids at 0 degrees C. The effect of NOE-Asp on phases of healing such as collagenation, wound contraction and epithelialization and on scar size of healed wound was evaluated in three wound models-incision, dead space, and excision wounds. To assess its influence on the oxidative stress, the levels of glutathione (GSH) and thiobarbiturate reactive species (TBARS) were also determined in 10-day-old granulation tissue. NOE-Asp was further screened for its anti-inflammatory activity in rat paw edema model. NOE-Asp promoted collagenation (increase in breaking strength, granulation weight, and collagen content), wound contraction, and epithelialization phases of healing. NOE-Asp also showed a significant antioxidant effect in 10-day-old granulation tissue as compared to aspirin. The results vindicate our assumption that the esterification of aspirin with nirooxyethyl group reverses the healing-suppressant effect of aspirin. The compound also showed equipotent anti-inflammatory activity as aspirin.

Increased nitric oxide production in acute diarrhoea is associated with abnormal gut permeability, hypokalaemia and malnutrition in tropical Australian aboriginal children

Australian Aboriginal children hospitalized with diarrhoeal disease have severe manifestations with acidosis, hypokalaemia, osmotic diarrhoea and abnormal small bowel permeability. Nitric oxide (NO) production is increased in diarrhoeal disease, but its relationship to mucosal function and diarrhoeal complications is not known. We examined the relationship between NO production and complications of acute diarrhoea in Aboriginal and non-Aboriginal children between February 1998 and February 2000. We enrolled 318 children admitted to Royal Darwin Hospital into one of three groups: acute diarrhoea, non-diarrhoeal controls with no inflammatory illness, and non-diarrhoeal controls with inflammatory illness. Nitric oxide production was measured by urine nitrate-creatinine (NOx/Cr) excretion on a low nitrate diet. Small bowel intestinal permeability was measured by the lactulose-rhamnose (L/R) ratio on a timed blood specimen. The NOx/Cr ratios were markedly elevated in Aboriginal diarrhoeal cases (geometric mean [GM] = 1.23, 95% confidence interval [95% CI] 1.07-1.44), lowest in non-Aboriginal non-inflammatory controls (GM = 0.13, 95% CI 0.10-0.16) and intermediate in all other groups (GM = 0.35, 95% CI 0.28-0.43). Convalescent levels (day 5) in the Aboriginal diarrhoeal group (GM = 1.02, 95% CI 0.82-1.28) were slower to fall than L/R ratios. Multivariate analysis in the diarrhoeal group indicated that high NO production was associated with abnormal permeability, hypokalaemia and malnutrition, but not with the severity of diarrhoea, acidosis or osmotic diarrhoea. We concluded that increased NO production may contribute to impaired mucosal barrier function and hypokalaemia in acute gastroenteritis, which may be the cost of the known gut-protective and antimicrobial effects mediated by NO in acute intestinal inflammation.