Effects of amrinone on bilateral renal ischemia/reperfusion injury

Cyclic nucleotide phosphodiesterase inhibition as a potential therapeutic target in renal ischemia reperfusion injury

AIMS

Ischemia/reperfusion (I/R) occurs in renal artery stenosis, partial nephrectomy and most commonly during kidney transplantation. It brings serious consequences such as DGF (Delayed Graft Function) or organ dysfunction leading to renal failure and ultimate death. There is no effective therapy to handle the consequences of Renal Ischemia/Reperfusion (I/R) injury. Cyclic nucleotides, cAMP and cGMP are the important second messengers that stimulate intracellular signal transduction for cell survival in response to growth factors and peptide hormones in normal tissues and in kidneys plays significant role that involves vascular tone regulation, inflammation and proliferation of parenchymal cells. Renal ischemia and subsequent reperfusion injury stimulate signal transduction pathways involved in oxidative stress, inflammation, alteration in renal blood flow leading to necrosis and apoptosis of renal cell.

MATERIALS AND METHODS

An extensive literature review of various search engines like PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out. To understand the functioning of Phosphodiesterases (PDEs) and its pharmacological modulation in Renal Ischemia-Reperfusion Injury.

KEY FINDINGS

Current therapeutic options may not be enough to treat renal I/R injury in group of patients and therefore, the current review has discussed the general characteristics and physiology of PDEs and preclinical-studies defining the relationship between PDEs expression in renal injury due to I/R and its outcome on renal function.

SIGNIFICANCE

The role of PDE inhibitors in renal I/R injury and the clinical status of drugs for various renal diseases have been summarized in this review.

The effects of tadalafil on renal ischemia reperfusion injury: an experimental study

Many pharmacological agents were investigated for the prevention of renal ischemic reperfusion (I/R) injury as well as the phosphodiesterase (PDE) inhibitors. The aim of the study was to examine the possible renoprotective effect of a member in this family, tadalafil (Td) on I/R injury. Thirty-six Spraque Dawley rats were allocated to six groups as; control, sham, ischemia (I), ischemia/reperfusion (I/R), Td pretreatment ischemia (Td/I) and Td pretreatment ischemia/reperfusion (Td/IR) groups. Right nephrectomy was performed in all groups. Td was dissolved in saline solution and given as a single dose (1mg/kg) through an orogastrictube 60 min before the operation in the Td pretreatment groups. In ischemia group the left renal pedicle was occluded for 45 minutes and after than underwent left nephrectomy. In I/R group left renal pedicle was occluded for 45 minutes, reperfused for 1hour and after then underwent nephrectomy. The left kidneys were evaluated after standard laboratory procedures with regard to tubular morphology, and leukocyte infiltration. The data were analyzed by using Kruskal-Wallis test to determine differences among the groups. A p value of < 0.05 was considered significant. Renal tubular damage was significant increased in the ischemia and I/R group (Groups III and IV) when compared to those in the sham group (Group II), (p = 0.004, 0.004, respectively). Tubular damage, in the Td pretreatment ischemia (Td/I) (Group V) and Td pretreatment ischemia/reperfusion (Td/IR) (Group VI) were less than that in the ischemia group (Group III) (p= 0.010, p= 0.025, respectively). Td administration prior to the renal I/R injury attenuated these morphological disarrangements, which were observed in renal I/R. Tubular necrosis, which may be considered as an important issue of the developing renal injury, was also completely prevented with Td administration.

Apart from the other members of PDE inhibitors' family, enoximone does not enhance renal ischemic reperfusion injury: the effects of enoximone on renal ischemia reperfusion

Many pharmacological agents were investigated for the prevention of renal ischemic reperfusion (IR) injury as well as the phosphodiesterase (PDE) inhibitors. The aim of the study was to examine the possible renoprotective effect of enoximone as a member of this family on IR injury. Thirty-six Wistar-Albino rats were allocated to six groups. Sham (S) and control groups (E1, E2) only received 0.09% NaCl, 5 mg/kg and 10 mg/kg enoximone via caudal caval vein, respectively. In ischemia (I) and treatment groups (IE1, IE2), the rats were subjected to bilateral renal artery occlusion and were given 0.09% NaCl, 5 mg/kg and 10 mg/kg enoximone in the same route, respectively. Bilateral kidneys were removed at the sixth hour of laparotomy for histopathological and biochemical analysis, such as superoxide dismutase, myeloperoxidase, malonyldialdehyde, and nitric oxide end products. Blood samples were taken in order to evaluate renal function tests. The data were analyzed by using one-way analysis of variance, and p < .05 was considered to be statistically significant. The worst results were achieved in ischemia group (p < .05). Treatments groups showed nearly similar findings with this group (p < .05). There was no significant difference between control and sham groups. In this study, we found that apart from the other members of the PDE inhibitors' family, enoximone did not contribute to the attenuation of IR injury of kidney.

The role of phosphodiesterase 3 in endotoxin-induced acute kidney injury

Background

Acute kidney injury frequently accompanies sepsis. Endotoxin is known to reduce tissue levels of cAMP and low levels of cAMP have been associated with renal injury. We, therefore, hypothesized that endotoxin induced renal injury by activating phosphodiesterase 3 (PDE3) which metabolizes cAMP and that amrinone an inhibitor of PDE3 would prevent the renal injury.

Methods

Animals were divided into three groups (n = 7/group): 1) Control (0.9% NaCl infusion without LPS); 2) LPS (0.9% NaCl infusion with LPS); 3) Amrinone+LPS (Amrinone infusion with LPS). Either lipopolysaccharide (LPS) or vehicle was injected via the jugular vein and the rats followed for 3 hours. We explored the expression of PDE3 isoenzymes and the concentrations of cAMP in the tissue.

Results

The PDE3B gene but not PDE3A was upregulated in the kidney of LPS group. Immunohistochemistry also showed that PDE3B was expressed in the distal tubule in the controls and LPS caused PDE3B expression in the proximal as well. However, PDE3A was not expressed in the kidney either in the control or LPS treated groups. Tissue level of cAMP was decreased after LPS and was associated with an increase in blood urea nitrogen, creatinine, ultrastructural proximal tubular changes, and expression of inducible nitric oxide synthase (iNOS) in the endotoxemic kidney. In septic animals the phosphodiesterase 3 inhibitor, amrinone, preserved the tissue cAMP level, renal structural changes, and attenuated the increased blood urea nitrogen, creatinine, and iNOS expression in the kidney.

Conclusion

These findings suggest a significant role for PDE3B as an important mediator of LPS-induced acute kidney injury.

Protective Effects of Different Antioxidants and Amrinone on Vancomycin-Induced Nephrotoxicity

We have studied the effects of three antioxidants and amrinone, an inotropic agent, against vancomycin-induced nephrotoxicity in rats by investigating renal function and morphology. Thirty adult female Sprague Dawley rats (168-234 g) were divided into six groups. A saline-treated group served as control. The other five groups were treated for 7 days with vancomycin alone or in combination with alpha-lipoic acid, Ginkgo biloba extract 761, melatonin or amrinone. On day 8, all the rats were sacrificed by decapitation, kidney tissues were excised immediately and blood and kidney samples were collected. Blood urea and creatinine, kidney tissue malondialdehyde levels, and kidney superoxide dismutase and glutathione (GSH) peroxidase activities were measured. The kidneys were also examined for histological changes. Vancomycin administration led to increased urea, creatinine and malondialdehyde levels and decreased superoxide dismutase and GSH peroxidase activities. Co-administration of alpha-lipoic acid, Ginkgo biloba extract, melatonin or amrinone with vancomycin prevented the increases in the urea, creatinine and melondialdehyde levels and also resulted in higher superoxide dismutase and GSH peroxidase activities. The antioxidants and AMR improved the renal pathology compared to rats treated with vancomycin alone (P<0.05). These results indicate that the three antioxidants and amrinone have potential protective effects against vancomycin-induced nephrotoxicity, which might in part be due to inhibition of free oxygen radical production. Amrinone was the most effective drug as judged on the basis of the pathological findings.

Effect of amrinone on mucosal permeability in experimental intestinal ischaemia/reperfusion injury

BACKGROUND

The preventive effect of amrinone on ischaemia/reperfusion (I/R) injury has been shown in the medical literature. The purpose of the present study was to investigate the preventive effect of amrinone on I/R injury of the small bowel of the rat.

METHODS

Thirty-two Wistar albino rats (140-180 g) were divided into four groups (n = 8). In all groups except the sham group the superior mesenteric artery was clamped for 30 min. At the beginning of reperfusion, 1 mL of 2405 Bq/mL 51Cr-ethylenediamine tetra-acetic acid (EDTA) was administered into the prepared ileal segment. Following 30 min of reperfusion, 1 mL of blood was obtained from the portal vein. After the rats were killed, the small intestine was removed for histopathological studies. A total of 5 mg/kg amrinone was administered to the rats in group 1 before ischaemia and in group 2 before reperfusion, whereas only saline was administered to the rats in the control group. Statistical analysis was carried out with Kruskal-Wallis and chi2 test, P < 0.01 was considered significant.

RESULTS

Both the blood 51Cr-EDTA measurements (mean +/- SD) and mucosal injury grades (MIG) were highest in the control group (3.95 +/- 0.71 c.p.m.; MIG, 3-5) followed by group 2 (0.50 +/- 0.35 c.p.m.; MIG, 1-3), group 1 (0.47 +/- 0.34 c.p.m. MIG, 0-3), and sham group (0.12 +/- 0.05 c.p.m.; MIG, 0). The difference between groups 1 and 2 and the control group were statistically significant (P < 0.01 for each comparison). The results of group 1 and 2 were similar statistically (P > 0.05).

CONCLUSIONS

Amrinone was found to be effective in preventing intestinal I/R injury.