Comparative modulating effects of captopril, diltiazem, dietary calcium and pyridoxal-5'-phosphate on gentamicin-induced nephrotoxicity in the rat

Use of 4-mg/kg/24-hour empiric aminoglycoside dosing in preoperative neonates with congenital heart disease

BACKGROUND

Empiric dosing of gentamicin has not been evaluated in critically ill neonates with unrepaired congenital heart disease (CHD). Many factors may alter gentamicin pharmacokinetics in this patient population and there are few data describing gentamicin dosing regimens in this patient population.

OBJECTIVE

To determine whether an empiric gentamicin dosing regimen for neonates achieves acceptable serum trough concentrations in neonatal patients with unrepaired CHD receiving alprostadil.

METHODS

Term neonates with unrepaired CHD who received gentamicin for empiric treatment of sepsis were identified over a 3-year period. Patients were included if they received gentamicin 4 mg/kg/dose every 24 hours, were receiving alprostadil for maintenance of a patent ductus arteriosus, and had at least one gentamicin serum trough concentration determined. Patients were evaluated to determine whether they achieved a serum trough concentration of <1 mg/L, and differences in patient characteristics were noted for those who achieved an appropriate trough concentration and those who did not.

RESULTS

Twenty-eight patients met study criteria, and 22% of patients had a trough gentamicin concentration of <1 mg/L at a mean (SD) time of 23.6 (0.3) hours after a dose. Few statistically significant differences in patient characteristics were noted for those who achieved an appropriate serum trough concentration and those who did not, and included Apgar scores at 1 minute and later day of life at admission.

CONCLUSIONS

Current empiric gentamicin dosing regimens may not be appropriate for critically ill neonates with unrepaired CHD. Routine serum concentration monitoring may be warranted in this population.

Mangafodipir protects against hepatic ischemia-reperfusion injury in mice

Introduction and Aim

Mangafodipir is a contrast agent used in magnetic resonance imaging that concentrates in the liver and displays pleiotropic antioxidant properties. Since reactive oxygen species are involved in ischemia-reperfusion damages, we hypothesized that the use of mangafodipir could prevent liver lesions in a mouse model of hepatic ischemia reperfusion injury. Mangafodipir (MnDPDP) was compared to ischemic preconditioning and intermittent inflow occlusion for the prevention of hepatic ischemia-reperfusion injury in the mouse.

Methods

Mice were subjected to 70% hepatic ischemia (continuous ischemia) for 90 min. Thirty minutes before the ischemic period, either mangafodipir (10 mg/kg) or saline was injected intraperitoneally. Those experimental groups were compared with one group of mice preconditioned by 10 minutes' ischemia followed by 15 minutes' reperfusion, and one group with intermittent inflow occlusion. Hepatic ischemia-reperfusion injury was evaluated by measurement of serum levels of aspartate aminotransferase (ASAT) activity, histologic analysis of the livers, and determination of hepatocyte apoptosis (cytochrome c release, caspase 3 activity). The effect of mangafodipir on the survival rate of mice was studied in a model of total hepatic ischemia.

Results

Mangafodipir prevented experimental hepatic ischemia-reperfusion injuries in the mouse as indicated by a reduction in serum ASAT activity (P<0.01), in liver tissue damages, in markers of apoptosis (P<0.01), and by higher rates of survival in treated than in untreated animals (P<0.001). The level of protection by mangafodipir was similar to that observed following intermittent inflow occlusion and higher than after ischemic preconditioning.

Conclusions

Mangafodipir is a potential new preventive treatment for hepatic ischemia-reperfusion injury.

Influence of Spironolactone Treatment on Gentamicin-Induced Nephrotoxicity in Rats

The effect of treatment of rats with gentamicin (80 mg/kg/day for 6 days), oral doses of spironolacatone (20 mg/kg/day for 6 days), and the combined treatment (spironolactone + gentamicin) on renal histology and reduced glutathione (GSH) concentration, and some serum constituents indicative of kidney function were studied. The serum concentrations of creatinine and urea were not significantly affected by spironolactone treatment, but were significantly elevated (P<0.05) by gentamicin administration. The antibiotic treatment also reduced GSH concentration and caused a moderate renal cortical necrosis. However, rats exposed to spironolactone + gentamicin revealed drastic increases in the serum urea and creatinine concentrations amounting to about 1.8 and 2.1 times those of rats treated with gentamicin alone, respectively. The histological examination of slides of the renal cortex of rats exposed to the combined drugs exhibited more extensive necrosis in the tubules when compared to those treated with gentamicin alone. The reduction in GSH induced by gentamicin was unaffected by the concomitant treatment of gentamicin and spironolactone. The concentration of gentamicin accumulated in the renal cortex was significantly larger (twofold) in rats treated concomitantly with spironolactone + gentamicin than in rats treated with gentamicin alone. The present results indicate that spironolactone aggravates gentamicin-induced nephrotoxicity in the rat.

Mangafodipir prevents liver injury induced by acetaminophen in the mouse

BACKGROUND/AIMS

Acute liver failure (ALF), characterized by massive hepatocyte necrosis, is often caused by drug poisoning, particularly with acetaminophen (APAP). Hepatocyte necrosis is consecutive to glutathione depletion by NAPQI, a metabolite of APAP, and to mitochondrial damages caused by reactive oxygen species (ROS) overproduction. Considering the structure of Mangafodipir, a contrast agent currently used in magnetic resonance imaging of the liver, we hypothesized that this molecule could exert an antioxidant activity and be possibly used as a treatment of APAP-induced ALF.

METHODS/RESULTS

Mangafodipir is endowed with superoxide dismutase, catalase, and glutathione reductase activities. It can inhibit ROS production by hepatocytes in culture, and protect those cells from oxidative stresses induced by exposure to xanthine oxidase, H(2)O(2), or UV light. Moreover, preventive or curative administration of Mangafodipir to mice with APAP-induced ALF significantly increases survival rates, and abrogates aspartate aminotransferase elevation and histological damage.

CONCLUSIONS

Those data point out the potential interest of Mangafodipir in the treatment of toxic ALF in humans.

The effect of calcium load and the calcium channel blocker verapamil on gentamicin nephrotoxicity in rats

Gentamicin (GM) is used against serious and life-threatening Gram negative infections. However its use is limited by the occurrence of nephrotoxicity. Reports on the interaction between GM nephrotoxicity and calcium (Ca(2+)) or Ca blockers are conflicting. Therefore, in the present work we assessed the effect of treatment of rats with graded doses of calcium carbonate, CaCO(3) (0.25, 0.5 or 1.0 g/kg) orally, or the Ca(2+) channel blocker verapamil (1.75, 3.5 or 7.0 mg/ kg) intramuscularly (i.m.), on the nephrotoxicity induced by concomitant i.m. treatment with GM (80 mg /kg/day for 6 days). Nephrotoxicity was evaluated histopathologically by light microscopy and biochemically by measuring the concentrations of urea and creatinine in plasma, reduced glutathione (GSH), lipid peroxidation and superoxide dismutase (SOD) activity in kidney cortex. The results indicated that the administration of CaCO(3) produced a dose-dependent amelioration in the biochemical indices of nephrotoxicity in plasma and renal cortex, which was significant at the two higher doses used. The histological picture of the renal proximal tubules followed a similar pattern. Treatment with verapamil induced a dose-dependent potentiation in the biochemical parameters of nephrotoxicity that was significant only at the highest dose used (7 mg/kg). This dose also exacerbated the GM-induced histological necrosis. The above interactions may be clinically relevant in patients treated concurrently with these agents.

Effect of dimethyl sulfoxide on gentamicin-induced nephrotoxicity in rats

Nephrotoxicity of gentamicin (GM) has been suggested to be mediated by the generation of reduced oxygen metabolites. The present study investigated the possible protective role of the free radical scavenger dimethyl sulfoxide (DMSO) on some indices of GM nephrotoxicity in rats. The antibiotic was injected intramuscularly (i.m.) at a dose of 100 mg/kg for six consecutive days, either with or without treatment with DMSO (12.5%, 25% or 50% in saline) at an intraperitoneal (i.p.) dose of 2 ml/kg 4 days before GM, and concomitantly with GM treatment thereafter. DMSO (25% in saline) was also given as above to rats treated with GM at i.m. doses of 25, 50 or 100 mg/kg for six consecutive days. GM caused dose-dependent significant increases in the concentrations of urea and creatinine in plasma, and in thiobarbituric acid reactive substances (TBARS) level in the kidney cortex and also caused significant decreases in the concentrations of reduced glutathione (GSH) and superoxide dismutase (SOD) activity. In GM-treated rats, DMSO dose-dependently lowered the elevated plasma urea and creatinine concentrations, and the rise in cortical TBARS. It also restored the levels of GSH and SOD activity to near normal. DMSO (25%) was effective in completely preventing the development of signs of nephrotoxicity of G (50 mg/kg). Treatment of the rats with DMSO alone, at any of the above doses, did not alter significantly any of the renal or hepatic function tests studied, and did not appear to adversely affect the kidney or liver histology. However, the efficacy and safety of DMSO require further studies. It is suggested that DMSO has potential protective effect against GM nephrotoxicity in rats.

Does captopril change oxidative stress in puromycin aminonucleoside nephropathy?

Puromycin aminonucleoside (PAN) nephropathy in rats has been induced by the intraperitoneal injections of PAN. One group of animals which received PAN has been treated simultaneously with captopril (angiotensine converting enzyme-ACE-inhibitor) with the aim to test whether continuing treatment with captopril along with PAN injections would be able to modulate the toxic effects of PAN. The third group of rats was given only captopril. Morphological changes in the kidney were evaluated by scanning electron microscopy that showed the loss of podocyte foot processes in the kidney of PAN treated animals but also in the kidney of captopril treated ones as well as in the animals treated with both drugs simultaneously. Reduced glutathione content, catalase, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), xanthine oxidase activities as well as lipid peroxides were investigated in rat blood and kidney. Captopril given alone produced a significant decrease of plasma lipid peroxides, but it did not show any significant effect on investigated antioxidative factor levels neither in blood nor in the kidney. PAN given alone produced a significant depletion of plasma lipid peroxides, kidney catalase and erythrocyte GSH-Px activity as well as a significant increase of plasma catalase and erythrocyte SOD activity. Treatment of animals with both drugs simultaneously resulted in a significant increase of erythrocyte SOD activity and a significant decrease of plasma lipid peroxides, erythrocyte GSH-Px and kidney SOD activities. Kidney xanthine oxidase activity showed a significant increase in both PAN and PAN plus captopril treated animals in comparison with the values of captopril treated rats. These data suggest that PAN changes the antioxidative factor pattern in rat blood and kidney. Contrary to our expectations that captopril may protect the toxic effects of PAN it only to a certain extent modifies these effects showing protective effect only on tissue catalase activity.

Gentamicin nephrotoxicity in humans and animals: some recent research

It would appear from the literature cited in this article, that interest in gentamicin nephrotoxicity is still thriving. Despite extensive studies, the mechanism(s) of the nephrotoxicity is uncertain. Several clinical and experimental strategies have been employed in order to ameliorate or abolish the signs of gentamicin nephrotoxicity. Most of these were unsuccessful, impractical or unsafe. Therefore there is still a need for further studies to elucidate the mechanism(s) of action of the drugs nephrotoxicity, and to discover safe, practical and effective agents to ameliorate the nephrotoxicity in patients at risk.