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

Melatonin attenuates colistin-induced nephrotoxicity in rats

Colistin-induced nephrotoxicity is a dose-limiting adverse effect when colistin is used against Gram-negative pathogens. This study examined the nephroprotective effect of melatonin against colistin in rats. Rats (n = 7 per group) were treated intravenously twice daily with saline, colistin (at increasing doses from 0.5 to 4.0 mg/kg), melatonin (5 mg/kg), or both melatonin and colistin for 7 days. The severity of renal alteration was examined both biochemically and histologically. The effect of coadministration of melatonin on colistin pharmacokinetics was investigated. Significantly lower urinary N-acetyl-β-d-glucosaminidase excretion was observed from day 1 in the colistin-melatonin group compared to the colistin group (P < 0.0001). Plasma creatinine increased significantly (P = 0.023) only in the colistin group on day 6. Significant histological abnormalities (P < 0.0001) were detected only in the kidneys of the colistin group. Melatonin altered colistin pharmacokinetics; the total body clearance in the colistin-melatonin group (1.82 ± 0.26 ml/min/kg) was lower than in the colistin group (4.28 ± 0.93 ml/min/kg). This is the first study demonstrating the protective effect of melatonin against colistin-induced nephrotoxicity, which indicates that colistin-induced nephrotoxicity is mediated through oxidative stress. It also highlights the potential of coadministering an antioxidant to widen the therapeutic window of this very important last-line antibiotic.

Biopsy-Proven Acute Tubular Necrosis due to Vancomycin Toxicity

Vancomycin (VAN) has been associated with acute kidney injury (AKI) since it has been put into clinical use in the 1950's. Early reports of AKI were likely linked to the impurities of the VAN preparation. With the advent of the more purified forms of VAN, the incidence of AKI related to VAN were limited to acute interstitial nephritis (AIN) or as a potentiating agent to other nephrotoxins such as Aminoglycosides. VAN as the sole etiologic factor for nephrotoxic acute tubular necrosis (ATN) has not been described. Here, we report a case of biopsy-proven ATN resulting from VAN.

Pharmacokinetics and pharmacodynamics: optimal antimicrobial therapy in the intensive care unit

This article reviews the principles of antimicrobial pharmacokinetics and pharmacodynamics in the context of the ICU for the most commonly used antibiotics. For therapy to truly be efficacious, the regimen must be effective against the organism, but not harmful to the patient. We review how optimization of chemotherapy requires a careful balancing of efficacy against toxicity when selecting dose and dose schedules. In addition, we discuss the importance of considering concentrations at the site of infection and how dose optimization can help suppress resistance emergence and preserve our antimicrobial armamentarium for the future. Finally, we examine combination chemotherapy and strategies for optimizing the administration of multiple agents.

Accidental and iatrogenic causes of acute kidney injury

PURPOSE OF REVIEW

Ingestions and iatrogenic administration of drugs are all too common causes of acute kidney injury. This review will discuss these preventable causes of acute kidney injury.

RECENT FINDINGS

Recent studies have examined the pathophysiology of acute kidney injury by several commonly used drugs. These studies have shown that drugs and toxins can cause acute kidney injury by altering renal hemodynamics, direct tubular injury or causing renal tubular obstruction.

SUMMARY

Knowledge of the drugs that cause acute kidney injury and how this injury is manifested can lead to improved diagnosis and treatment with the ultimate goal of prevention.

Differential efficiency of simvastatin and lipoic acid treatments on Bothrops jararaca envenomation-induced acute kidney injury in mice

Snake bite accidents by Bothrops genus is an important public health issue in Brazil and one of its most serious complications is the acute kidney injury (AKI). Here we evaluated the effects of Bothrops jararaca venom (vBj) and the treatments with lipoic acid (LA) and simvastatin (SA) on renal function, aminopeptidase (AP) activities and renal redox status. Primordial events for establishment of AKI by vBj were hyperuricemia, hypercreatinemia, urinary hyperosmolality, renal oxidative stress and reduction of hematocrit and protein content in the membrane of renal cortex and medulla and in the plasma. In the renal cortex and medulla the changes caused by vBj in soluble and membrane-bound AP activities had a similar pattern. The beneficial effects of LA and SA on envenomed mice were similar on the hyperuricemia, renal oxidative stress and reduction of hematocrit. LA mitigated the hypercreatinemia, but exacerbated the urinary urea and creatinine, whereas SA mitigated the decrease of plasma urea, urinary hyperosmolality and hypercreatinuria induced by vBj. The beneficial effects of LA and especially of SA on renal effects of vBj open a new perspective for clinical investigations of these drugs as coadjuvant agents in the serotherapy of Bothrops envenomation.

Vancomycin-associated nephrotoxicity: grave concern or death by character assassination?

Vancomycin-associated nephrotoxicity was reported in 0% to 5% of patients in the 1980s. This has been confirmed by numerous clinical trials comparing novel anti-methicillin-resistant Staphylococcus aureus agents with vancomycin at the Food and Drug Administration-approved dosage of 1 g every 12 hours. Treatment failures of vancomycin in patients with methicillin-resistant S. aureus infections have been reported despite in vitro susceptibility. These failures have led to the use of vancomycin doses higher than those approved by the Food and Drug Administration. Higher doses are being administered to achieve goal vancomycin trough concentrations of 10 to 20 microg/mL recommended by several clinical practice guidelines endorsed by the Infectious Diseases Society of America. Recent studies suggest that increased rates of nephrotoxicity are associated with aggressive vancomycin dosing. These increased rates are confounded by concomitant nephrotoxins, renal insufficiency, or changing hemodynamics. These studies also have demonstrated that vancomycin's nephrotoxicity risk is minimal in patients without risk factors for nephrotoxicity. Clinicians unwilling to dose vancomycin in accordance with clinical practice guidelines should use an alternative agent because inadequate dosing increases the likelihood of selecting heteroresistant methicillin-resistant S. aureus isolates.

Role of the poly(ADP-ribose)polymerase activity in vancomycin-induced renal injury

The aim of the present study was to investigate the role of poly(ADP-ribose)polymerase (PARP) activity in vancomycin (VCM)-induced renal injury and to determine whether 1,5-isoquinelinediol (ISO), a PARP inhibitor agent, could be offered as an alternative therapy in VCM-induced renal impairment. Rats were divided into four groups as follows: (i) control (Group 1); (ii) VCM-treated (Group 2); (iii) VCM plus ISO-treated (Group 3); and (iv) ISO-treated (Group 4). VCM (200mg/kg, i.p., twice daily) was administered to Groups 2 and 3 for 7 days. ISO (3mg/kg/day, i.p.) treatment was started 24h before the first administration of VCM and continued for 8 days. After the 14th VCM injection, the animals were placed in metabolic cages to collect urine samples. All the rats were sacrificed by decapitation, blood samples were taken in tubes and kidneys were excised immediately. Blood urea nitrogen (BUN) and plasma creatinine, and urinary N-acetyl-beta-d-glucosaminidase (NAG, a marker of renal tubular injury) were used as markers of VCM-induced renal injury in rats. Light microscopy was used to evaluate semi-quantitative analysis of the kidney sections. Poly(ADP-ribose) (PAR, the product of activated PARP) and PARP-1 expressions in renal tissues were demonstrated by immunohistochemistry and Western blot. VCM administration increased BUN levels from 8.07+/-0.75 mg/dL to 53.87+/-10.11 mg/dL. The plasma creatinine levels were 0.8+/-0.04 mg/dL and 3.38+/-0.51 mg/dL for the control and VCM-treated groups, respectively. Also, urinary excretion of NAG was increased after VCM injection. Besides, there was a significant dilatation of the renal tubules, eosinophilic casts within some tubules, desquamation and vacuolization of renal tubule epithelium, and interstitial tissue inflammation in VCM-treated rats. In VCM-treated rats, both PAR and PARP-1 expressions were increased in renal tubular cells. ISO treatment attenuated VCM-induced renal injury, as indicated by BUN and plasma creatinine levels, urinary NAG excretion, and renal histology. PARP inhibitor treatment also decreased PAR and PARP-1 protein expressions similar to that of controls. Herewith, the overactivation of the PARP pathway may have a role in VCM-induced renal impairment and pharmacological inhibition of this pathway might be an effective intervention to prevent VCM-induced acute renal injury.

Gene expression analysis reveals new possible mechanisms of vancomycin-induced nephrotoxicity and identifies gene markers candidates

Vancomycin, one of few effective treatments against methicillin-resistant Staphylococcus aureus, is nephrotoxic. The goals of this study were to (1) gain insights into molecular mechanisms of nephrotoxicity at the genomic level, (2) evaluate gene markers of vancomycin-induced kidney injury, and (3) compare gene expression responses after iv and ip administration. Groups of six female BALB/c mice were treated with seven daily iv or ip doses of vancomycin (50, 200, and 400 mg/kg) or saline, and sacrificed on day 8. Clinical chemistry and histopathology demonstrated kidney injury at 400 mg/kg only. Hierarchical clustering analysis revealed that kidney gene expression profiles of all mice treated at 400 mg/kg clustered with those of mice administered 200 mg/kg iv. Transcriptional profiling might thus be more sensitive than current clinical markers for detecting kidney damage, though the profiles can differ with the route of administration. Analysis of transcripts whose expression was changed by at least twofold compared with vehicle saline after high iv and ip doses of vancomycin suggested the possibility of oxidative stress and mitochondrial damage in vancomycin-induced toxicity. In addition, our data showed changes in expression of several transcripts from the complement and inflammatory pathways. Such expression changes were confirmed by relative real-time reverse transcription–polymerase chain reaction. Finally, our results further substantiate the use of gene markers of kidney toxicity such as KIM-1/Havcr1, as indicators of renal injury.

Novel evidence suggesting an anti-oxidant property for erythropoietin on vancomycin-induced nephrotoxicity in a rat model

1. The aim of the present study was to investigate the role of oxidative stress in renal injury and to determine whether erythropoietin (EPO) acts as an anti-oxidant in vancomycin (VCM)-induced renal impairment. 2. Twenty-four rats were divided into three groups as follows: (i) control (Group 1); (ii) VCM treated (Group 2); and (iii) VCM + EPO treated (Group 3). Vancomycin (200 mg/kg, i.p.) was administered to Groups 2 and 3 for 7 days. Erythropoietin (150 IU/kg, i.p.) treatment was started 24 h before VCM and lasted for 7 days. On Day 8, renal tissues were excised and blood samples were collected. Serum creatinine and blood urea nitrogen were measured, along with renal malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activity and tissue VCM levels. The kidneys were examined for any histopathological changes. 3. Renal MDA levels were found to be increased, whereas SOD and CAT activity was decreased, in the VCM-treated group compared with the control group. There was a marked decrease in MDA levels and an increase in SOD activity, but not CAT activity, after VCM + EPO treatment. Marked histopathological alterations, including interstitial oedema, tubular dilatation, tubular epithelial cell desquamation and vacuolization, were observed in VCM-treated rats. Histopathological changes were significantly improved after EPO administration. 4. In conclusion, the present data suggest that oxidative stress plays an important role in VCM-induced nephrotoxicity. Erythropoietin seems to act as an anti-oxidant, diminishing the toxic oxidative effects of VCM on renal tissues.

Ginkgo biloba leave extract: biological, medicinal, and toxicological effects

Ginkgo biloba leave extract is among the most widely sold herbal dietary supplements in the United States. Its purported biological effects include: scavenging free radical; lowering oxidative stress; reducing neural damages, reducing platelets aggregation; anti-inflammation; anti-tumor activities; and anti-aging. Clinically, it has been prescribed to treat CNS disorders such as Alzheimer's disease and cognitive deficits. It exerts allergy and changes in bleeding time. While its mutagenicity or carcinogenic activity has not been reported, its components, quercetin, kaempferol and rutin have been shown to be genotoxic. There are no standards or guidelines regulating the constituent components of Ginkgo biloba leave extract nor are exposure limits imposed. Safety evaluation of Ginkgo biloba leave extract is being conducted by the U.S. National Toxicology Program.

Protective effects of caffeic acid phenethyl ester, vitamin C, vitamin E and N-acetylcysteine on vancomycin-induced nephrotoxicity in rats

The objective of this study was to compare the beneficial effects of caffeic acid phenethyl ester (CAPE), vitamin C, vitamin E and N-acetylcysteine on vancomycin-induced nephrotoxicity. Thirty rats were randomly devided into six groups: (i) control; (ii) vancomycin, 200 mg/kg administrated via intraperitoneal route; (iii) vancomycin plus CAPE-vancomycin with 10 micromol/kg CAPE; (iv) vancomycin plus vitamin C-vancomycin (intraperitoneally) with 200 mg/dl vitamin C in drinking water; (v) vancomycin plus vitamin E-vancomycin with 1000 mg/kg body weight vitamin E (intramuscularly); and (vi) vancomycin plus N-acetylcysteine-vancomycin with 10 mg/kg body weight (intraperitoneally) of N-acetylcysteine. Vancomycin treatments were started 1 day after the first administrations of these agents and continued for 7 days. At the end of the experiments, catalase activity was significantly decreased by vancomycin in kidney homogenates (P < 0.05). Vitamin E, vitamin C, N-acetylcysteine and CAPE administrations decreased the blood urea nitrogen levels increased by vancomycin, although significant differences were detected only in the vitamins E and C groups (P < 0.05). Increased renal malondialdehyde and nitric oxide levels by vancomycin were significantly suppressed by agents used in the study (P < 0.05). Histopathological examination demonstrated prominent damages in the vancomycin-treated group. Vitamin E was the most beneficial agent on vancomycin-induced tubular damage, followed by vitamin C, N-acetylcysteine and CAPE treatments, respectively. The data suggest that vitamin E, as well as vitamin C, N-acetylcysteine and CAPE, could be useful for reducing the detrimental effects on vancomycin-induced toxicity in kidneys.

The effect of 2,3-dihydroxybenzoic acid and tempol in prevention of vancomycin-induced nephrotoxicity in rats

One of the major adverse effects of vancomycin (VAN) is nephrotoxicity, which the mechanism is not fully understood. However, there is some evidence that oxidative injury could be involved in its pathogenesis. In this study, we examined two antioxidants 4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol) a superoxide dismutase mimetic and 2,3-dihydroxybenzoic acid (DHB) an iron chelator in VAN-induced nephrotoxicity in rats. DHB at doses of 50 and 100 mg/kg and tempol at doses of 7.5, 15 and 30 mg/kg were administered subcutaneously to rats 30 min prior to intraperitoneal injection of 200 mg/kg VAN. Drug administrations were done every 12 h for 7 days. In animals which received only VAN, the activity of urinary gamma-glutamyl-transferase (GGT) decreased and the activity of lactate dehydrogenase (LDH) in urine increased significantly compared to controls. Serum urea and creatinine (Cr) concentrations and the weight of animals' kidneys increased and body weights were decreased significantly in this group compared to controls. DHB at both doses normalized the GGT activity, but only at the higher dose restore the LDH activity. Both doses of DHB ameliorated the rise in serum urea and Cr concentrations and improved the changes in kidney and body weights significantly. Tempol did not show any beneficial effects at all. There were marked pathologic changes in tubules of kidneys of VAN treated animals. The tissue injury was prevented by both doses of DHB and there was almost no sign of tubular injury in 100 mg/kg treated group. Tempol in any doses could not prevent the tissue injury and there were significant differences in tissue injury in all tempol treated rats with controls. It seems that VAN-induced nephrotoxicity is at least partly due to free radical formation. Hydroxyl radicals might play a major role in VAN-induced nephrotoxicity, since an iron chelator (DHB) could reverse the adverse effects. However, production of other radicals such as superoxide is also probable.