Role of L-arginine, a substrate of nitric oxide biosynthesis, on intestinal ischemia-reperfusion in rabbits

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.

Blockage of the P2X7 Receptor Attenuates Harmful Changes Produced by Ischemia and Reperfusion in the Myenteric Plexus

INTRODUCTION

Our work analyzed the effects of a P2X7 receptor antagonist, Brilliant Blue G (BBG), on rat ileum myenteric plexus following ischemia and reperfusion (ISR) induced by 45 min of ileal artery occlusion with an atraumatic vascular clamp with 24 h (ISR 24-h group) or 14 d of reperfusion (ISR 14-d group).

MATERIAL AND METHODS

Either BBG (50 mg/kg or 100 mg/kg, BBG50 or BBG100 groups) or saline (vehicle) was administered subcutaneously 1 h after ischemia in the ISR 24-h group or once daily for the 5 d after ischemia in the ISR 14-d group (n = 5 per group). We evaluated the neuronal density and profile area by examining the number of neutrophils in the intestinal layers, protein expression levels of the P2X7 receptor, intestinal motility and immunoreactivity for the P2X7 receptor, nitric oxide synthase, neurofilament-200, and choline acetyl transferase in myenteric neurons.

RESULTS

The neuronal density and profile area were restored by BBG following ISR. The ischemic groups showed alterations in P2X7 receptor protein expression and the number of neutrophils in the intestine and decreased intestinal motility, all of which were recovered by BBG treatment.

CONCLUSION

We concluded that ISR morphologically and functionally affected the intestine and that its effects were reversed by BBG treatment, suggesting the P2X7 receptor as a therapeutic target.

Resveratrol promotes myenteric neuroprotection in the ileum of rats after ischemia-reperfusion injury

AIMS

The present study evaluated the effects of resveratrol in the myenteric plexus after intestinal ischemia-reperfusion (I/R) injury caused by occluding the superior mesenteric artery for 45min, followed by 7days of reperfusion.

MAIN METHODS

Forty-two male Wistar rats were divided into seven groups: control (C group), untreated sham surgery control (SC group), sham surgery control treated with resveratrol before surgery (STA group), sham surgery control treated with resveratrol before and after surgery (STAD group), ischemic control (IRC group), ischemic treated before I/R (IRTA group), and ischemic treated before and after I/R (IRTAD group). Resveratrol (10mg/kg) was administered for 4days and 2h prior to surgery and/or 7days later. Morphometric analyses were performed, and the density of the general neuronal population (HuC/D-immunoreactive [IR]), nitrergic subpopulation (neuronal nitric oxide synthase [nNOS]-IR), vasoactive intestinal peptide (VIP)ergic varicosities (VIP-IR), and glial cells (S100-IR) was determined.

KEY FINDINGS

Injury that was caused by I/R significantly reduced (p<0.01) the HuC/D-IR general neuronal population. Treatment with resveratrol before and after ischemia had a neuroprotective effect. Morphometric changes caused by I/R in nitrergic neurons and varicosities were also attenuated by resveratrol. Ischemia/reperfusion promoted the proliferation of enteric glial cells, and resveratrol treatment before and after I/R reversed this effect.

SIGNIFICANCE

Resveratrol had neuroprotective effects, showing promise for application in intestinal surgery and transplants.

Ischemic preconditioning and tacrolimus pretreatment as strategies to attenuate intestinal ischemia-reperfusion injury in mice

The intestine is highly sensitive to ischemia-reperfusion injury (IRI), a phenomenon occurring in different intestinal diseases. Several strategies to mitigate IRI are in experimental stages; unfortunately, no consensus has been reached about the most appropriate one. We report a protocol to study ischemic preconditioning (IPC) evaluation in mice and to combine IPC and tacrolimus (TAC) pretreatment in a warm ischemia model. Mice were divided into treated (IPC, TAC, and IPC + TAC) and untreated groups before intestinal ischemia. IPC, TAC, and IPC + TAC groups were able to decrease postreperfusion nitrites levels (P < .05). IPC-containing groups had a major beneficial effect by preserving the integrity of the intestinal histology (P < .05) and improving animal survival (P < .002) compared with TAC alone or the untreated group. The IPC + TAC group was the only one that showed significant improvement in lung histological analysis (P < .05). The TAC and IPC + TAC groups down-regulated intestinal expression of interleukin (II)-6 and IL1b more than 10-fold compared with the control group. Although IPC and TAC alone reduced intestinal IRI, the used of a combined therapy produced the most significant results in all the local and distant evaluated parameters.

Oxidative stress gene expression profile in inbred mouse after ischemia/reperfusion small bowel injury

PURPOSE

To determine the profile of gene expressions associated with oxidative stress and thereby contribute to establish parameters about the role of enzyme clusters related to the ischemia/reperfusion intestinal injury.

METHODS

Twelve male inbred mice (C57BL/6) were randomly assigned: Control Group (CG) submitted to anesthesia, laparotomy and observed by 120 min; Ischemia/reperfusion Group (IRG) submitted to anesthesia, laparotomy, 60 min of small bowel ischemia and 60 min of reperfusion. A pool of six samples was submitted to the qPCR-RT protocol (six clusters) for mouse oxidative stress and antioxidant defense pathways.

RESULTS

On the 84 genes investigated, 64 (76.2%) had statistic significant expression and 20 (23.8%) showed no statistical difference to the control group. From these 64 significantly expressed genes, 60 (93.7%) were up-regulated and 04 (6.3%) were down-regulated. From the group with no statistical significantly expression, 12 genes were up-regulated and 8 genes were down-regulated. Surprisingly, 37 (44.04%) showed a higher than threefold up-regulation and then arbitrarily the values was considered as a very significant. Thus, 37 genes (44.04%) were expressed very significantly up-regulated. The remained 47 (55.9%) genes were up-regulated less than three folds (35 genes - 41.6%) or down-regulated less than three folds (12 genes - 14.3%).

CONCLUSION

The intestinal ischemia and reperfusion promote a global hyper-expression profile of six different clusters genes related to antioxidant defense and oxidative stress.

Study of L-arginine in intestinal lesions caused by ischemia-reperfusion in rats

To examine whether treatment with L-arginine (ARG), a substrate of nitric oxide biosynthesis, attenuated intestinal dysfunction caused by ischemia (I) and reperfusion (R), we treated rats with ARG (100 mg/kg intravenously) or saline solution (SS) before 60 minutes of I produced by occlusion of the superior mesenteric artery and/or during 120 minutes of R. After I or I/R, we isolated 2-cm jejunal segments for mounting in an organ bath to study neurogenic contractions stimulated by electrical pulses or KCl with the use of a digital recording system. Thin jejunal slices were stained with hematoxylin and eosin for optical microscopy. Jejunal contractions were similar in the sham and I+ARG, but reduced in I+SS, I/R+SS, and I/R+ARG groups. Jejunal enteric nerves were damaged in I+SS, IR+SS, and IR+ARG, but not in the I+ARG group, suggesting that ARG attenuate intestinal dysfunctions due to I but not to R.

Long-term enteral arginine supplementation in rats with intestinal ischemia and reperfusion

BACKGROUND

The effects of short-term enteral arginine supplementation on intestinal ischemia-reperfusion (IR) injury have been widely studied, especially the ischemic preconditioning supplementation. The aim of this study was to investigate the effects of long-term intra-duodenal supplementation of arginine on intestinal morphology, arginine-associated amino acid metabolism, and inflammatory responses in rats with intestinal IR.

MATERIALS AND METHODS

Male Wistar rats with or without three hours of ileal ischemia underwent duodenal cannulation for continuous infusion of formula with 2% arginine or commercial protein powder for 7 d. The serological examinations, plasma amino acid and cytokine profiles, and intestinal morphology were assessed.

RESULTS

Intestinal IR injury had significant impacts on the decreases in circulating red blood cells, hemoglobin, ileum mass, and villus height and crypt depth of the distal jejunum. In addition, arginine supplementation decreased serum cholesterol and increased plasma arginine concentrations. In rats with intestinal IR injury, arginine supplementation significantly decreased serum nitric oxide, plasma citrulline and ornithine, and the mucosal protein content of the ileum.

CONCLUSIONS

These results suggest that long-term intra-duodenal arginine administration may not have observable benefits on intestinal morphology or inflammatory response in rats with intestinal ischemia and reperfusion injury. Therefore, the necessity of long-term arginine supplementation for patients with intestinal ischemia and reperfusion injury remains questionable and requires further investigation.