The role of oxygen free radicals and prostaglandins in reperfusion injury to warm ischemic kidneys

Antioxidants as Renoprotective Agents for Ischemia during Partial Nephrectomy

Small renal masses have been diagnosed increasingly in recent decades, allowing surgical treatment by partial nephrectomy. This treatment option is associated with better renal function preservation, in comparison with radical nephrectomy. However, for obtaining a bloodless field during surgery, occlusion of renal artery and veins is often required, which results in transitory ischemia. The renal ischemia-reperfusion injury is associated with increased reactive oxygen species production leading to renal tissue damage. Thus, the use of antioxidants has been advocated in the partial nephrectomy perioperative period. Several antioxidants were investigated in regard to renal ischemia-reperfusion injury. The present manuscript aims to present the literature on the most commonly studied antioxidants used during partial nephrectomy. The results of experimental and clinical studies using antioxidants during partial nephrectomy are reported. Further, alimentary sources of some antioxidants are presented, stimulating future studies focusing on perioperative antioxidant-rich diets.

Alpha-tocopherol ameliorates oxidative renal insult associated with spinal cord reperfusion injury

Ischemic-reperfusion procedures targeting a specific organ often results in remote multiple organ injuries mediated possibly by heightened oxidative stress levels. As the kidney is one of the most vulnerable organs for ischemic oxidative stress, the aim of the present study was to confirm the occurrence of renal complication secondary to spinal cord ischemic-reperfusion injury (SC-IRI) induced by aortic clamping. The study also investigated the possible prophylactic effect of long-term administration of α-tocopherol (α-TOL) against high level of renal oxidative stress and inflammatory processes induced by SC-IRI. In this study, a total of 60 male Sprague-Dawley rats were randomly divided into five equal groups: C group underwent no surgery; CE group received α-TOL 600 mg/kg intramuscular twice weekly for 6 weeks; S group were subjected to laparotomy without clamping of the aorta; SE group were handled as S group and treated with α-TOL as group CE; SC-IRI group were subjected to laparotomy with clamping of the aorta just above the bifurcation of the aorta for 45 min, then the clamp was released for 48 h for reperfusion. SC-IRIE group was subjected to IRI as in group SC-IRI and was injected with α-TOL in the same dose and route as α-TOL-treated control group. SC-IRI resulted in increases in serum creatinine, blood urea nitrogen, plasma nitrite/nitrate level, serum tumor necrosis factor alpha, renal tissue homogenate level for malondialdehyde, superoxide dismutase and prostaglandin E2. Long-term prophylactic treatment with α-TOL resulted in amelioration of the renal functional disturbances and all measured parameters of oxidative stress and inflammation. Ischemic reperfusion injury of the spinal cord induced some remote renal functional disturbances although some of the observed changes may have resulted from decreased renal blood flow due to the hypotension induced during the procedure. Prophylactic long-term α-TOL administration guards against the renal function disturbances an effect that can be attributed, at least partially, to improvement of the renal pro-oxidant/antioxidant balance and inhibition of the inflammatory processes.

Interaction of eicosanoids and nitric oxide in renal reperfusion injury

BACKGROUND

Both the eicosanoids and nitric oxide are known to play an important role in the pathogenesis of postischemic injury. Recent evidence has suggested that the generation of each may affect the other via a feedback loop. This was investigated in an experimental model of renal warm ischemia reperfusion injury.

METHODS

Rats underwent bilateral renal warm ischemia (15-60 min) then reperfusion (20 or 80 min) followed by a unilateral nephrectomy to measure renal nitric oxide (as nitroxides) and eicosanoids. Renal function was measured on days 2 and 7 prior to terminal nephrectomy for tissue analysis.

RESULTS

Vasodilator eicosanoids (6-KPGF1alpha and PGE2) fell on reperfusion in line with the duration of warm ischemia with a concomitant rise in the vasoconstrictor TxA2. The ratio of vasodilator to vasoconstrictor eicosanoids fell from 8.22 (2.3) in the control to 0.82 (0.1) in the 60-min warm ischemia group (P<0.01). Renal levels of nitroxides rose on reperfusion demonstrating an inverse correlation with the eicosanoid ratio (r2=0.86). Renal function was impaired at both day 2 and day 7 and showed a positive correlation with the eicosanoid ratio (r2=0.67 and 0.62, respectively).

CONCLUSIONS

Renal warm ischemic injury is associated with a progressive fall in the ratio of vasodilator-to-vasoconstrictor eicosanoids from early in reperfusion through to day seven although nitric oxide was elevated throughout the same period. There was no evidence of coinduction of nitric oxide synthase and cyclooxygenase in this model.

The effect of methylene blue on histological damage after spermatic cord torsion in a rat model

OBJECTIVE

To investigate, in a rat model, whether methylene blue (a free-radical scavenger) is effective in alleviating the histological testicular damage caused by reperfusion after spermatic cord torsion.

MATERIALS AND METHODS

Male Wistar rats underwent a clockwise 720 degrees left spermatic cord torsion lasting 3 h; they were then randomly assigned to treatment and control groups. In the treated group, 2 mg/kg methylene blue was injected intraperitoneally 20 min before the cord was untwisted, and an additional 1 mg/kg injected into the penile vein 1--2 min beforehand. After 14 days, the left testicle was removed and assessed histologically. The control group was not treated.

RESULTS

Thirty-three rats in the treatment group and 35 untreated controls were suitable for evaluation. Treatment with methylene blue was not significantly predictive of histological damage; the colour of the testis before detorsion was not correlated with histological damage.

CONCLUSION

Anti-oxidant treatment with methylene blue had no palliative effect on the histological changes after torsion and detorsion of the spermatic cord in this rat model.

Renal handling of drugs and amino acids after impairment of kidney or liver function--influences of maturity and protective treatment

Renal tubular cells are involved both in secretion and in reabsorption processes within the kidney. Normally, most xenobiotics are secreted into the urine at the basolateral membrane of the tubular cell, whereas amino acids are reabsorbed quantitatively at the luminal side. Under different pathological or experimental circumstances, these transport steps may be changed, e.g., they may be reduced by renal impairment (reduction of kidney mass, renal ischemia, administration of nephrotoxins) or they may be enhanced after stimulation of transport carriers. Furthermore, a distinct interrelationship exists between excretory functions of the kidney and the liver. That means liver injury can influence renal transport systems also (hepato-renal syndrome). In this review, the following aspects were included: based upon general information concerning different transport pathways for xenobiotics and amino acids within kidney cells and upon a brief characterization of methods for testing impairment of kidney function, the maturation of renal transport and its stimulation are described. Similarities and differences between the postnatal development of kidney function and the increase of renal transport capacity after suitable stimulatory treatment by, for example, various hormones or xenobiotics are reviewed. Especially, renal transport in acute renal failure is described for individuals of different ages. Depending upon the maturity of kidney function, age differences in susceptibility to kidney injury occur: if energy-requiring processes are involved in the transport of the respective substance, then adults, in general, are more susceptible to renal failure than young individuals, because in immature organisms, anaerobic energy production predominates within the kidney. On the other hand, adult animals can better compensate for the loss of renal tissue (partial nephrectomy). With respect to stimulation of renal transport capacity after repeated pretreatment with suitable substances, age differences also exist: most stimulatory schedules are more effective in young, developing individuals than in mature animals. Therefore, the consequences of the stimulation of renal transport can be different in animals of different ages and are discussed in detail. Furthermore, the extent of stimulation is different for the transporters located at the basolateral and at the luminal membranes: obviously the tubular secretion at the contraluminal membrane can be stimulated more effectively than reabsorption processes at the luminal side.

Postanoxic formation of aldehydic lipid peroxidation products in human renal tubular cells

The levels of the aldehydic lipid peroxidation products 4-hydroxynonenal and malondialdehyde and the levels of adenine nucleotides were measured during anoxia/reoxygenation studies with isolated human renal tubular cells in vitro. Energy depletion of renal cells was demonstrated by the decrease of ATP level. ATP could be restored completely and rapidly during postanoxic reoxygenation. 4-Hydroxynonenal and malondialdehyde levels increased during reoxygenation. In parallel, the breakdown of physiological 4-hydroxynonenal levels was estimated. The 4-hydroxynonenal formation rate was estimated from accumulation and metabolic breakdown rates of this compound.

The effect of polyethylene glycol-superoxide dismutase administration on histological damage following spermatic cord torsion

Oxygen free radicals generated during the ischemic/reperfusion period have been suggested as a possible cause for tissue damage in different organs. In this study we address the question of whether administration of polyethylene glycol-superoxide dismutase, an oxygen free radical scavenger, can alleviate histological damage associated with testicular torsion. The study included 67 Sprague-Dawley rats. In 60 rats the left testicle was rotated 720 degrees clockwise through a scrotal incision. Torsion duration was 3 hours. Five minutes before and 5 minutes after detorsion the testicle color was evaluated and scored. The remaining 7 rats underwent a sham operation. After randomization 8,000 units per kg. polyethylene glycol-superoxide dismutase were injected intraperitoneally in the treated group 1 hour before detorsion. After 14 days histological evaluation was performed on both testicles of 58 rats (2 rats died before the evaluation). No statistically significant difference was demonstrated between the treatment (28 rats) and the control groups (30 rats). Testicular color after detorsion correlated with the histological damage.