Ana I. Morales

New insights into the mechanism of aminoglycoside nephrotoxicity: an integrative point of view

Nephrotoxicity is one of the most important side effects and therapeutical limitations of aminoglycoside antibiotics, especially gentamicin. Despite rigorous patient monitoring, nephrotoxicity appears in 10-25% of therapeutic courses. Traditionally, aminoglycoside nephrotoxicity has been considered to result mainly from tubular damage. Both lethal and sub-lethal alterations in tubular cells handicap reabsorption and, in severe cases, may lead to a significant tubular obstruction. However, a reduced glomerular filtration is necessary to explain the symptoms of the disease. Reduced filtration is not solely the result of tubular obstruction and tubular malfunction, resulting in tubuloglomerular feedback activation; renal vasoconstriction and mesangial contraction are also crucial to fully explain aminoglycoside nephrotoxicity. This review critically presents an integrative view on the interactions of tubular, glomerular, and vascular effects of gentamicin, in the context of the most recent information available. Moreover, it discusses therapeutic perspectives for prevention of aminoglycoside nephrotoxicity derived from the pathophysiological knowledge.

Metformin prevents experimental gentamicin-induced nephropathy by a mitochondria-dependent pathway

The antidiabetic drug metformin can diminish apoptosis induced by oxidative stress in endothelial cells and prevent vascular dysfunction even in nondiabetic patients. Here we tested whether it has a beneficial effect in a rat model of gentamicin toxicity. Mitochondrial analysis, respiration intensity, levels of reactive oxygen species, permeability transition, and cytochrome c release were assessed 3 and 6 days after gentamicin administration. Metformin treatment fully blocked gentamicin-mediated acute renal failure. This was accompanied by a lower activity of N-acetyl-beta-D-glucosaminidase, together with a decrease of lipid peroxidation and increase of antioxidant systems. Metformin also protected the kidney from histological damage 6 days after gentamicin administration. These in vivo markers of kidney dysfunction and their correction by metformin were complemented by in vitro studies of mitochondrial function. We found that gentamicin treatment depleted respiratory components (cytochrome c, NADH), probably due to the opening of mitochondrial transition pores. These injuries, partly mediated by a rise in reactive oxygen species from the electron transfer chain, were significantly decreased by metformin. Thus, our study suggests that pleiotropic effects of metformin can lessen gentamicin nephrotoxicity and improve mitochondrial homeostasis.

An Integrative Overview on the Mechanisms Underlying the Renal Tubular Cytotoxicity of Gentamicin

Gentamicin is an aminoglycoside antibiotic widely used against infections by Gram-negative microorganisms. Nephrotoxicity is the main limitation to its therapeutic efficacy. Gentamicin nephrotoxicity occurs in 10-20% of therapeutic regimes. A central aspect of gentamicin nephrotoxicity is its tubular effect, which may range from a mere loss of the brush border in epithelial cells to an overt tubular necrosis. Tubular cytotoxicity is the consequence of many interconnected actions, triggered by drug accumulation in epithelial tubular cells. Accumulation results from the presence of the endocytic receptor complex formed by megalin and cubulin, which transports proteins and organic cations inside the cells. Gentamicin then accesses and accumulates in the endosomal compartment, the Golgi and endoplasmic reticulum (ER), causes ER stress, and unleashes the unfolded protein response. An excessive concentration of the drug over an undetermined threshold destabilizes intracellular membranes and the drug redistributes through the cytosol. It then acts on mitochondria to unleash the intrinsic pathway of apoptosis. In addition, lysosomal cathepsins lose confinement and, depending on their new cytosolic concentration, they contribute to the activation of apoptosis or produce a massive proteolysis. However, other effects of gentamicin have also been linked to cell death, such as phospholipidosis, oxidative stress, extracellular calcium-sensing receptor stimulation, and energetic catastrophe. Besides, indirect effects of gentamicin, such as reduced renal blood flow and inflammation, may also contribute or amplify its cytotoxicity. The purpose of this review was to critically integrate all these effects and discuss their relative contribution to tubular cell death.

An integrative view of the pathophysiological events leading to cisplatin nephrotoxicity.

Cisplatin is among the most effective chemotherapeutic agents against solid tumors. Nephrotoxicity is the most common side effect of cisplatin chemotherapy, which limits the clinical use of cisplatin and seriously worsens the quality of life of cancer patients resulting in dosage reduction and discontinuation of treatment. Cisplatin involves a complex multifactorial process, as it has direct toxic effect on cells of the renal tubules, vasculature and glomeruli, and causes alterations in renal blood flow and glomerular filtration rate. Indirectly, cisplatin also induces inflammation of the renal interstitium, which contributes to the acute damage and may lead to chronic interstitial fibrosis, indicative of irreversible renal damage. This review presents an integrative view of the pathophysiological effects of cisplatin on tubular, vascular, glomerular, and interstitial function and the interplay among these actions. Moreover, it reviewed human clinical trials of the last ten years in order to evaluate the incidence and severity of the renal injury induced by cisplatin at the doses and therapeutic guidelines used in the clinical practice.

Quercetin reduces cisplatin nephrotoxicity in rats without compromising its anti-tumour activity

BACKGROUND Nephrotoxicity is the major limitation for the clinical use of cisplatin as an anti-tumoural drug. Our aim was to investigate the protective effect of quercetin on cisplatin nephrotoxicity in a rat tumour model in vivo and to examine the mechanisms of renal protection. METHODS Breast adenocarcinoma (13762 Mat B-III) cells were inoculated subcutaneously in male Fischer rats and 7 days later, the rats were administered daily with quercetin [50 mg/kg/day, intraperitoneally (i.p.)] or vehicle. Four days after that, the rats were given a single dose of cisplatin (4 mg/kg, i.p.) or vehicle. Tumour growth and renal function were monitored throughout the experiment. Two or 6 days after cisplatin administration, the rats were killed and the kidneys and tumours were removed to examine renal function and toxicity markers in both tissues. RESULTS In the kidney, cisplatin treatment induced: (i) a decrease in renal blood flow and glomerular filtration rate, (ii) tubular necrosis/apoptosis, (iii) increased lipid peroxidation and decreased endogenous antioxidant systems, (iv) increased expression of inflammation markers and (v) increased activity of the apoptosis executioner caspase-3. Cisplatin effectively reduced tumour size and weight. CONCLUSIONS Co-treatment with quercetin partially prevented all the renal effects of cisplatin, whereas it did not impair its anti-tumour activity. In conclusion, in a model of tumour-bearing rats, quercetin prevents the nephrotoxic effect of cisplatin without affecting its anti-tumour activity.

Nephrotoxicity of Uranium: Pathophysiological, Diagnostic and Therapeutic Perspectives

As in the case of other heavy metals, a considerable body of evidence suggests that overexposure to uranium may cause pathological alterations to the kidneys in both humans and animals. In the present work, our aim was to analyze the available data from a critical perspective that should provide a view of the real danger of the nephrotoxicity of this metal for human beings. A further aim was to elaborate a comparative compilation of the renal pathophysiological data obtained in humans and experimental animals with a view to gaining more insight into our knowledge of the mechanisms of action and renal damage. Finally, we address the existing perspectives for the improvement of diagnostic methods and the treatment of intoxications by uranium, performing an integrated analysis of all these aspects.

Protective effect of trans-resveratrol on gentamicin-induced nephrotoxicity.

Reactive oxygen species (ROS) have been involved in glomerular filtration rate (GFR) reduction observed after gentamicin treatment. trans-Resveratrol (TR), a natural hydroxystilbene, has been identified to be a potent inhibitor of ROS production. The aim of this work has been to study whether TR has a protective effect on gentamicin-induced nephrotoxicity in vivo and the effect of TR on lipid peroxidation and the oxidative stress induced by gentamicin. Animals that received a daily intraperitoneal injection of gentamicin (100 mg/kg body weight) showed lower GFR and renal blood flow (RBF) and higher urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) than control rats. Rats receiving TR together with gentamicin showed higher GFR and RBF and lower NAG urinary excretion than rats receiving gentamicin alone. Moreover, renal lipid peroxidation increased in rats receiving gentamicin alone, and this increase was prevented by the administration of TR. The concentration in plasma of antioxidants was higher in the group that received TR with gentamicin than in the gentamicin and control groups. The activities of lactate dehydrogenase and alkaline phosphatase were higher in rats treated with gentamicin than in control rats and were reduced by the treatment with TR. This study demonstrates an improvement in renal function in response to the administration of TR in gentamicin-induced nephrotoxicity. At least a part of this effect of TR could be based on its antioxidant activity.

Novel Anti-Inflammatory Action of Edelfosine Lacking Toxicity with Protective Effect in Experimental Colitis

Edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine; ET-18-OCH3) is an antitumor alkyl-lysophospholipid analog that binds lipid rafts, altering their protein composition (J Exp Med 200:353-365). Because L-selectin locates in lipid rafts and plays a crucial role in the recruitment of leukocytes into inflamed tissues, we hypothesized that edelfosine might affect inflammation by modulating L-selectin and inflammatory cell migration. Here, we have found that edelfosine inhibited neutrophil-endothelium interaction through L-selectin shedding. Oral treatment of edelfosine diminished inflammation in two murine animal models. Edelfosine showed a higher antiinflammatory effect than the nonsteroidal anti-inflammatory drug (NSAID) indomethacin in the bentonite mouse-paw edema model. Using a rat model of experimental colitis, edelfosine oral administration ameliorated the clinical and histopathologic severity of the inflammatory colitis with a dramatic decrease in mucosal damage and neutrophil infiltration. Colon sections from edelfosine-treated rats showed a remarkable reduction in ulcer formation, edema, and inflammatory cell infiltration. Edelfosine enhanced lipopolysaccharide-induced expression of anti-inflammatory interleukin-10 in mouse macrophages. Edelfosine oral treatment in rats, at doses 8-fold higher than those displaying anti-inflammatory action, lacked toxicity. Edelfosine treatment showed no any significant cardiotoxicity, hepatotoxicity or renal toxicity. Unlike NSAIDs, edelfosine did not inhibit prostaglandin E2 synthesis in gastrointestinal mucosal biopsies, and no histologic alteration in gastrointestinal tract was detected after drug treatment. Thus, edelfosine shows a potent in vitro and in vivo anti-inflammatory activity while sparing gastric mucosa. Our data identify edelfosine as a novel anti-inflammatory drug by abating neutrophil infiltration through L-selectin shedding and may provide a new therapeutic approach for inflammatory bowel disease free from toxicity.

Cardiotrophin-1 Administration Prevents the Renal Toxicity of Iodinated Contrast Media in Rats

Although generally reversible, contrast media toxicity often induces contrast-induced nephropathy (CIN), which is associated with longer hospitalization time, the need for dialysis, and higher incidence of later cardiovascular events and higher mortality. Preventive cotreatments have been assayed at the preclinical and clinical levels, but recent meta-analysis has not demonstrated a beneficial effect, which supports the search for new nephroprotective strategies. We have assessed if the administration of cardiotrophin-1 (CT-1), an endogenous cytokine with protective properties on the heart and liver, might mitigate CIN in rats. We have developed a model of CIN induced by the administration of the contrast medium gastrographin iv (3.7mg/kg) in rats sensitized by previous administration of subnephrotoxic doses of gentamicin (50mg/kg/day, ip) for 6 days. The severity of CIN was assessed by the measurement of renal function; renal histological damage; urinary excretion of markers of tubular damage, including N-acetyl beta glucosaminidase (NAG), kidney injury molecule 1 (KIM-1), and plasminogen activator inhibitor 1; lipid peroxidation; and renal apoptosis. Treatment with CT-1 almost completely prevented the renal tissue damage, as evidenced by almost total prevention of tubular desepithelization and tubular obstruction, reduced caspase activation, and cell proliferation. Besides, CT-1 also prevented the increment in renal tissue levels of renal tissue injury markers NAG, KIM-1, and neutrophil gelatinase-associated lipocalin. Oxidative stress, a hallmark of CIN, was also prevented by CT-1. Administration of CT-1 also prevented the derangement in kidney function induced by CIN. Renal hemodynamics, also impaired by the contrast medium, was normal in rats cotreated with CT-1. CT-1 administration significantly prevents the alterations in renal function and structure observed in a rat model of CIN.

Effects of deferasirox on renal function and renal epithelial cell death.

Iron-chelating therapy results in a significant improvement in the life expectancy of patients with transfusional iron overload. However, alterations of renal function have been observed in some patients undergoing chelation therapy. In the present study we evaluated the effect of treatment with deferasirox iron chelator on the renal function in normal Wistar rats and in mouse and human cultured tubular cell lines. Results indicate that deferasirox given daily via intraperitoneal route for 7 days induced: (1) an increased urinary protein, albumin and glucose excretion, (2) tubular necrosis/apoptosis, (3) and increased tubular damage markers, in spite of normal glomerular function. Moreover, in vitro studies revealed that: (1) mouse MCT cultures resulted more susceptible to the antiproliferative/cytotoxic effect of deferasirox, mainly at 24h after treatment, than human HK-2 cultures, (2) MCT cell content of damage molecules increased after 24h of iron chelator treatment with slight changes in their excretion into the culture medium and (3) MCT cultures showed a significant evidence of apoptotic cell death through an increased expression and activation of caspase-3 and marked DNA fragmentation. In conclusion, this renal side effect of deferasirox-chelating therapy seems to be based on direct toxic effects of deferasirox on renal tubular cells.