Biochemical mechanisms of cephaloridine nephrotoxicity: time and concentration dependence of peroxidative injury

These experiments were designed to elucidate the initiating biochemical events mediating cephaloridine (CPH) nephrotoxicity. Renal cortical slices from naive male Fischer-344 rats were incubated at 37 degrees C in a phosphate- or bicarbonate-buffered medium containing 0, 1, 5, or 10 mM CPH. Slices were incubated for 15, 30, 45, 60, 90, 120, and 180 min and evaluated for accumulation of organic ions [p-aminohippurate (PAH) and tetraethylammonium (TEA)], pyruvate-stimulated gluconeogenesis, malondialdehyde (MDA) production, and reduced glutathione (GSH) content. Renal cortical slice accumulation of PAH and TEA was decreased by 5 and 10 mM CPH as early as 120 and 90 min of incubation, respectively. CPH-induced MDA production by renal cortical slices preceded the effects of CPH on organic ion accumulation. Coincubation of CPH with the antioxidants promethazine and N,N'-diphenyl-p-phenylenediamine inhibited CPH-induced lipid peroxidation and changes in organic ion accumulation. In contrast, 5 or 10 mM CPH inhibited gluconeogenic capacity at all time points examined, an effect which was not influenced by antioxidant treatment. Depletion of renal cortical GSH by 5 or 10 mM CPH was evident following 30 min of incubation and was also unaffected by antioxidant treatment. These results support the hypothesis that lipid peroxidation mediates the effects of CPH on renal organic ion transport. The early and profound inhibition of gluconeogenesis by CPH suggests that the biochemical pathways of gluconeogenesis are either proximal to or represent a primary target for CPH nephrotoxicity.     

Lead nephrotoxicity and associated disorders: biochemical mechanisms.

Lead may exert toxic effects on several organ systems, but those in the kidney are the most insidious. Acute lead nephropathy is characterized by proximal tubular dysfunction with the development of a Fanconi-type syndrome, alterations in mitochondrial structure and the development of cytosolic and nuclear inclusion bodies. Intracellular lead is associated with specific high affinity proteins and can also bind to metallothionein. Chronic lead nephropathy is irreversible and is typically accompanied by interstitial fibrosis, both hyperplasia and atrophy of the tubules, glomerulonephritis and, ultimately, renal failure. In addition, lead produces renal neoplasms in experimental animals. Chronic lead exposure is also implicated in the development of saturnine gout and hypertension. The metal interacts with renal membranes and enzymes and disrupts energy production, calcium metabolism, glucose homeostasis, ion transport processes and the renin-angiotensin system. This review summarizes the biochemical effects of lead on the kidney to understand the mechanisms of lead-induced nephropathy and other associated disorders.     

Cellular stress responses and molecular mechanisms of nephrotoxicity

Increasing our knowledge on the molecular and cellular mechanisms of acute renal tubular pathologies will lead to potential novel therapeutic strategies either to prevent the initiation of renal failure or to promote the renal regeneration after injury. Currently many genomic- and proteomic-based techniques are available to identify genes, proteins or protein modifications in relation to renal toxicity. Although we are able to identify many genes and proteins at once, the actual role of the genes and proteins with respect to cellular toxicity needs to be defined in order to better understand the molecular basis of renal cell injury and repair. This review will focus on the relationship between changes in gene and protein expression, cellular perturbations, signal transduction, and mechanisms of toxicity. A focus is on the role of stress response proteins in repair of injured renal cells.     

Potential involvement of renal transport mechanisms in nephrotoxicity

Among the various physiological factors involved in the development of a nephrotoxic insult, certain renal transport systems may be important. The movement of exogenous organic anions and cations from the blood to the tubular fluid is well recognized. The anion transport system, which has been extensively characterized for the transport of p-aminohippuric acid, may have particular relevance. The nephrotoxic effect of citrinin, certain cephalosporin antibiotics and cysteine conjugates in rats and in isolated renal cells can be blocked by probenecid, a drug known to block the organic anion transporter competitively. The reduction in toxic response is correlated with the renal and cellular content of the nephrotoxic chemical.     

Biochemical mechanisms of oxfenicine cardiotoxicity

Oxfenicine (S-4-OH-phenyl-glycine) was proposed as a compound which would stimulate carbohydrate utilization in the heart and thus reduce oxygen requirement, especially in ischemic heart disease. Oral administration to rats for several weeks gave rise to an increase in heart, liver and kidney weights. The drug damaged mitochondrial metabolism, reducing oxygen consumption and uncoupling oxidative phosphorylation in all three organs. In heart mitochondria creatine phosphate kinase was inhibited and the creatine content of the mitochondria increased. Myocyte membrane functions (Ca uptake as well as Na/K-, Mg- and Ca-ATPases) were inhibited. In all three organs lipids (phospholipids and triglycerides) as well as free fatty acids showed a transient accumulation.     

Biochemical mechanisms of cisplatin cytotoxicity

Since the discovery by Rosenberg and collaborators of the antitumor activity of cisplatin 35 years ago, three platinum antitumor drugs (cisplatin, carboplatin and oxaliplatin) have enjoyed a huge clinical and commercial hit. Ever since the initial discovery of the anticancer activity of cisplatin, major efforts have been devoted to elucidate the biochemical mechanisms of antitumor activity of cisplatin in order to be able to rationally design novel platinum based drugs with superior pharmacological profiles. In this report we attempt to provide a current picture of the known facts pertaining to the mechanism of action of the drug, including those involved in drug uptake, DNA damage signals transduction, and cell death through apoptosis or necrosis. A deep knowledge of the biochemical mechanisms, which are triggered in the tumor cell in response to cisplatin injury not only may lead to the design of more efficient platinum antitumor drugs but also may provide new therapeutic strategies based on the biochemical modulation of cisplatin activity.     

Epidemiological application of early markers of nephrotoxicity

This paper is a review of epidemiological studies in which sensitive markers of nephrotoxicity have been used to detect the early effects of chemicals on the kidney. Most of the studies are cross-sectional, and their objective was either to identify potentially nephrotoxic chemicals (organic solvents, heavy metals) in the working or general environment or to establish dose-response/effect relationships from which safe exposure levels can be defined (e.g., for cadmium and mercury vapour). A few longitudinal studies were conducted to determine the persistence of renal disturbances and to get information on their predictive value (e.g., microproteinuria in cadmium workers). Nephrotoxicity tests, which have proved to be the most useful in these epidemiological studies, rely on the determination of specific urinary proteins which, according to their size, reflect the functional integrity of the proximal tubule (e.g., retinol-binding protein or beta 2-microglobulin) or the glomerulus (e.g., albumin, immunoglobulin G). An increased urinary excretion of the lysosomal enzyme N-acetyl-beta-D-glucosaminidase has been reported in several studies (e.g., in lead-exposed workers), but the pathological significance of this finding remains to be clarified, particularly when it is not associated with changes in the urinary excretion of specific proteins. Further work is needed to assess the usefulness of tests introduced more recently such as the assay of renal antigens in urine and the use of red-blood-cell membrane negative charges as an index of the glomerular polyanion. With the exception of microproteinuria observed in chronic cadmium poisoning, no epidemiological data are available on the prognostic value of subclinical renal effects caused by nephrotoxic chemicals.     

Biochemical and histologic study of lethal cisplatin nephrotoxicity prevention by mirtazapine

BackgroundCisplatin is a platinum derivative frequently used in the chemotherapy of different solid tumors. This biochemical and histologic study investigated a possible protective effect of mirtazapine with regard to cisplatin-induced nephrotoxicity in the rat.MethodsThe animals were divided into 4 groups: 15 mg/kg mirtazapine + 10 mg/kg cisplatin, 30 mg/kg mirtazapine + 10 mg/kg cisplatin, only 10 mg/kg cisplatin and negative control (healthy) group. During 14 days, the treatment and treated control group took drugs, while the healthy animals were given distilled water on the same schedule. All animals were sacrificed by high-dose anesthesia at the end of the 14 days of treatment; their kidneys were removed and subjected to histologic and biochemical study.ResultsIn both of the doses we used, mirtazapine decreased the levels of malondialdehyde, creatinine, blood urea nitrogen and myeloperoxidase activity when compared to cisplatin group. On the other hand, it increased total glutathione level in all doses. Slight histopathological findings were determined in mirtazapine groups when compared to cisplatin control group.ConclusionIn the light of our results and literature knowledge, we can conclude that the protective effect of mirtazapine in cisplatin toxicity originates from its own antioxidant activity.     

Biochemical mechanisms in colon xenografts: Thymidylate synthase as a target for therapy

Summary Growth of human adenocarcinomas of the colon and rectum in immunoincompetent mice has allowed for a greater understanding of the interaction of 5-fluorouracil, its metabolism, and mechanism(s) of cytotoxicity under conditions of tumor growth in situ. Conversely, this agent has proven to be a useful tool in defining metabolic characteristics in human colon adenocarcinomas. Analysis of tumor sensitivity to 5-fluorouracil (FUra), 5-fluorouridine (FUrd) and 5-fluoro-2 -deoxyuridine (FdUrd) suggests that growth inhibition in vivo is related to a DNA-directed event. Resistance, de novo appears to be a consequence of relatively transient inhibition of the target enzyme thymidylate synthase (dTMP-synthase), which may be a consequence of low concentrations of 5,10-methylenetetrahydrofolate (CH₂-H₄PteGlu) or its polyglutamate forms within tumor cells in situ. In order to study the relationship between inhibition of dTMP-synthase and growth inhibition, mutant cells deficient in their ability to salvage dThd have been selected, and grown as xenografts. Data suggest that transient inhibition of dTMP-synthase and not dThd salvage is responsible for resistance de novo, and that prolonged inhibition of dTMP-synthase would be a lethal event in vivo. This would predict that a cell lacking dTMP-synthase activity would not be tumorigenic. This has been tested directly by selecting clones of GC₃ colon adenocarcinoma cells deficient in dTMP-synthase (TS^-) activity. Preliminary data indicate that each of 3 TS^- clones is tumorigenic in athymic nude mice. The importance of dTMP-synthase as a target for drug development is discussed with respect to these findings.     

Metabonomic deconvolution of embedded toxicity: application to thioacetamide hepato- and nephrotoxicity

We present here the potential of an integrated metabonomic strategy to deconvolute the biofluid metabolic signatures in experimental animals following multiple organ toxicities, using the well-known hepato- and nephrotoxin, thioacetamide. Male Han-Wistar rats were dosed with thioacetamide (150 mg/kg, n = 25), and urine, plasma, liver, and kidney samples were collected postdose for conventional NMR and magic angle spinning (MAS) NMR spectroscopy. These data were correlated with histopathology and plasma clinical chemistry collected at all time points. 1H MAS NMR data from liver and kidney were related to sequential 1H NMR measurements in urine and plasma using pattern recognition methods. One-dimensional 1H NMR spectra were data-reduced and analyzed using principal components analysis (PCA) to show the time-dependent biochemical variations induced by thioacetamide toxicity. From the eigenvector loadings of the PCA, those regions of the 1H NMR spectra, and hence the combinations of endogenous metabolites marking the main phase of the toxic episode, were identified. The thioacetamide-induced biochemical manifestations included a renal and hepatic lipidosis accompanied by hypolipidaemia; increased urinary excretion of taurine and creatine concomitant with elevated creatine in liver, kidney, and plasma; a shift in energy metabolism characterized by depleted liver glucose and glycogen; reduced urinary excretion of tricarboxylic acid cycle intermediates and raised plasma ketone bodies; increased levels of tissue and plasma amino acids leading to amino aciduria verifying necrosis-enhanced protein degradation and renal dysfunction; and elevated hepatic and urinary bile acids indicating secondary damage to the biliary system. This integrated metabonomic approach has been able to identify the tissue of origin for biomarkers present in the metabolic profiles of biofluids, following the onset and progression of a multiorgan pathology, and as such highlights its potential in the evaluation of embedded toxicity in novel drug candidates.     

Biochemical mechanisms of tumor invasion and metastasis

Cancer invasion and metastases is a complex multi-step process. In order for a tumor cell to successfully traverse all the steps of this process and initiate a metastatic colony, it must express the right combination of gene products. Such gene products may include proteins which regulate cell interaction with the basement membrane and cell motility. Tumor cells attach to the basement membrane glycoprotein laminin via the cell surface laminin receptor. The human laminin receptor was purified and molecularly cloned. The level of laminin receptor mRNA in a variety of human carcinoma cells correlated with the number of laminin receptors on the surface of these cells. Following attachment to the basement membrane, the tumor cell next secretes proteases which may degrade type IV collagen. A genetic linkage between type IV collagenase secretion and metastases was collagen. A genetic linkage between type IV collagenase secretion and metastases was studied using our new genetic system for inducing metastases by employing the ras oncogene. Following attachment and local proteolysis, the third step of invasion is tumor cell motility. We have isolated a tumor cell autocrine motility factor (AMF). This factor is secreted by the tumor cells and binds to a cell surface receptor, resulting in a profound (greater than 100 x) stimulation of cell locomotion. AMF may play a major role in the autonomous invasive behavior of tumor cells.     

代谢组学在类风湿关节炎中应用的研究进展

类风湿关节炎(rheumatoid arthritis,RA)是一种自身免疫性炎症性疾病,影响着全身多个器官和组织。随着研究新技术、新方法的出现,RA的代谢组学研究也取得了一定的进展。该文就代谢组学在RA早期生物标志物筛选、疾病发病机制等方面的应用进行综述,以期为RA的预防和诊治提供参考。     

Biochemical mechanisms for the inotropic effect of the cardiotonic drug milrinone

Milrinone is a new inotropic agent for the treatment of refractory congestive heart failure. Our understanding of the mechanisms(s) of action of this synthetic cardiotonic drug is incomplete. We examined the effects of milrinone and the parent compound amrinone on sarcoplasmic reticulum function (45Ca-uptake and Ca-ATPase); radioligand binding to adenosine, beta-adrenergic, and cholinergic muscarinic receptors; cyclic AMP accumulation; and inhibition of various forms of cyclic AMP phosphodiesterases. Comparisons were made to observe how these effects correlate with the inotropic response of heart. Milrinone was shown to be a potent phosphodiesterase inhibitor that was 40 times more potent than amrinone and 10 times more potent at inhibiting the high-affinity (Km = 0.23 microM) form (Ki = 22 microM) than the low-affinity (Km = 140 microM) form (Ki = 225 microM) of cyclic AMP phosphodiesterase in heart. The potency of milrinone as a phosphodiesterase inhibitor was the same in the presence and absence of calcium. Concentrations of milrinone that increased cyclic AMP accumulation also produced positive inotropy. A comparison of milrinone with amrinone and methylxanthines revealed the order of potency to be isobutylmethylxanthine greater than milrinone greater than theophylline greater than caffeine greater than amrinone. Milrinone and amrinone had no effect on 45Ca-uptake or Ca-ATPase activity in myocyte sarcoplasmic reticulum. However, milrinone did bind weakly to adenosine receptors (KD = 466 microM) but not to cholinergic muscarinic or beta-adrenergic receptors. Also, in combination with isoproterenol high concentrations of milrinone blocked the negative inotropic response to the adenosine agonist phenylisopropyladenosine.(ABSTRACT TRUNCATED AT 250 WORDS)