Downregulation of arginase II and renal apoptosis by inorganic mercury: overexpression of arginase II reduces its apoptosis

Inorganic mercury is a toxic metal that accumulates in the proximal tubules of the kidney, causing apoptosis. Arginase II is known to inhibit apoptosis, but its role in the renal apoptosis caused by inorganic mercury is poorly understood. In the present study, we examined the involvement of arginase II in inorganic mercury-dependent apoptosis. A single exposure to mercuric chloride (HgCl₂, 1 mg/kg) in rats resulted in a dramatic time-dependent reduction in the activity of arginase II in the kidney; for example, the activity at 48 h after exposure was 31% of the control level. The decrease in arginase II activity was due to a decrease in the protein level, not to a reduction in gene expression or to direct inhibition of the activity itself. More interestingly, diminished arginase II activity was well correlated with the induction of apoptosis as evaluated by renal DNA fragmentation (r = 0.99). Overexpression of arginase II in LLC-PK₁ cells blocked cell death during exposure to inorganic mercury. These results suggest that inorganic mercury causes a reduction in protein levels of arginase II, and that impaired arginase II activity is, at least in part, associated with the apoptotic cell damage caused by this heavy metal.     

The excretion and distribution of inorganic mercury in the rat as influenced by several chelating agents

Among 15 chelating agents tested, sodium-2,3-dimercaptopropane-1-sulfonate (DMPS), 2,3-dimercaptopropanol (BAL), sodium-mercaptoethyliminodiacetate (MEIDA), and D-penicillamine (PA) exerted an influence on the excretion of Hg and its distribution in the organs. The excretion pattern, however, is different for these compounds, and, from the practical point of view, a favourable effect is exhibited only by DMPS which enhances the urinary excretion rate and lowers the Hg-concentration in all organs.     

Metabolism and toxicity of trichloroethylene and S-(1,2-dichlorovinyl)-L-cysteine in freshly isolated human proximal tubular cells.

Trichloroethylene (Tri) caused modest cytotoxicity in freshly isolated human proximal tubular (hPT) cells, as assessed by significant decreases in lactate dehydrogenase (LDH) activity after 1 h of exposure to 500 microM Tri. Oxidative metabolism of Tri by cytochrome P-450 to form chloral hydrate (CH) was only detectable in kidney microsomes from one patient out of four tested and was not detected in hPT cells. In contrast, GSH conjugation of Tri was detected in cells from every patient tested. The kinetics of Tri metabolism to its GSH conjugate S-(1,2-dichlorovinyl)glutathione (DCVG) followed biphasic kinetics, with apparent Km and Vmax values of 0.51 and 24.9 mM and 0.10 and 1.0 nmol/min per mg protein, respectively. S-(1,2-dichlorovinyl)-L-cysteine (DCVC), the cysteine conjugate metabolite of Tri that is considered the penultimate nephrotoxic species, caused both time- and concentration-dependent increases in LDH release in freshly isolated hPT cells. Preincubation of hPT cells with 0.1 mM aminooxyacetic acid did not protect hPT cells from DCVC-induced cellular injury, suggesting that another enzyme besides the cysteine conjugate beta-lyase may be important in DCVC bioactivation. This study is the first to measure the cytotoxicity and metabolism of Tri and DCVC in freshly isolated cells from the human kidney. These data indicate that the pathway involved in the cytotoxicity and metabolism of Tri in hPT cells is the GSH conjugation pathway and that the cytochrome P-450-dependent pathway has little direct role in renal Tri metabolism in humans.     

Lack of formic acid production in rat hepatocytes and human renal proximal tubule cells exposed to chloral hydrate or trichloroacetic acid

The industrial solvent trichloroethylene (TCE) and its major metabolites have been shown to cause formic aciduria in male rats. We have examined whether chloral hydrate (CH) and trichloroacetic acid (TCA), known metabolites of TCE, produce an increase in formic acid in vitro in cultures of rat hepatocytes or human renal proximal tubule cells (HRPTC). The metabolism and cytotoxicity of CH was also examined to establish that the cells were metabolically active and not compromised by toxicity. Rat hepatocytes and HRPTC were cultured in serum-free medium and then treated with 0.3–3 mM CH for 3 days or 0.03–3 mM CH for 10 days, respectively and formic acid production, metabolism to trichloroethanol (TCE-OH) and TCA and cytotoxicity determined. No increase in formic acid production in rat hepatocytes or HRPTC exposed to CH was observed over and above that due to chemical degradation, neither was formic acid production observed in rat hepatocytes exposed to TCA. HRPTC metabolized CH to TCE-OH and TCA with a 12-fold greater capacity to form TCE-OH versus TCA. Rat hepatocytes exhibited a 1.6-fold and three-fold greater capacity than HRPTC to form TCE-OH and TCA, respectively. CH and TCA were not cytotoxic to rat hepatocytes at concentrations up to 3 mM/day for 3 days. With HRPTC, one sample showed no cytotoxicity to CH at concentrations up to 3 mM/day for 10 days, while in another cytotoxicity was seen at 1 mM/day for 3 days. In summary, increased formic acid production was not observed in rat hepatocytes or HRPTC exposed to TCE metabolites, suggesting that the in vivo response cannot be modelled in vitro. CH was toxic to HRPTC at millimolar concentrations/day over 10 days, while glutathione derived metabolites of TCE were toxic at micromolar concentrations/day over 10 days [Lock, E.A., Reed, C.J., 2006. Trichloroethylene: mechanisms of renal toxicity and renal cancer and relevance to risk assessment. Toxicol. Sci. 19, 313–331] supporting the view that glutathione derived metabolites are likely to be responsible for nephrotoxicity.     

银杏叶提取物对三氯乙烯诱导的人角质形成细胞凋亡的影响

目的研究体外培养条件下银杏叶提取物(ginkgo biloba leaf extracts,EGb)对三氯乙烯(trichloroethylene,TCE)诱导的正常人表皮角质形成细胞(normal human epidernis keratinocyte,NHEK)凋亡的影响。方法体外培养条件下,用中性红吸附试验(NRU)测定TCE对NHEK的中性红吸附减少50%的质量浓度(NR50值)和EGb的最低有效保护质量浓度。用透射电子显微镜(transmission electron microscope,TEM)观察细胞凋亡形态学改变,流式细胞仪(flow cytometer,FCM)测定细胞DNA含量并计算凋亡发生率。结果TCE对NHEK的NR50值为4.53(3.92~5.13)mmol/L;用10、50、100、150和200 mg/L EGb预孵育NHEK 2 h时,由2.0 mmol/L TCE引起的细胞活力的下降随EGb剂量的增加逐渐恢复,且150 mg/L为最低有效保护剂量。TCE可引起NHEK的超微结构呈凋亡改变,凋亡发生率呈剂量依赖式增加。与0.125、0.5和2.0 mmol/LTCE暴露组相比,150 mg/L EGb预孵育组,细胞超微结构恢复到正常对照组水平,凋亡发生率明显减少。结论体外培养条件下,EGb可以抑制TCE诱导的NHEK的细胞凋亡。     

Andrographolide sodium bisulfate-induced apoptosis and autophagy in human proximal tubular endothelial cells is a ROS-mediated pathway

Background and aimsThe nephrotoxic mechanisms of andrographolide sodium bisulfate (ASB) remain largely unknown. This study attempted to explore the mechanism of ASB-induced nephrotoxicity using human proximal tubular endothelial cells (HK-2).MethodsFor this study HK-2 cells were treated with rising concentrations of ASB. Their survival rate was detected using MTT assay and ultrastructure was observed with electron microscopy. l-Lactate dehydrogenase (LDH) assay was followed by examination of mitochondrial membrane potential (MMP). Reactive oxygen species (ROS) was detected using different methods and apoptosis/autophage related proteins were detected using immunoblotting.ResultsWe found that ASB inhibited HK-2 cell proliferation and decreased cell survival rate in a time and dose-dependent manner (P < 0.05, P < 0.01, respectively). With increasing ASB concentration, cell structure was variably damaged and evidence of apoptosis and autophagy were observed. MMP gradually decreased and ROS was induced. The expression of JNK and Beclin-1 increased and activation of the JNK signaling pathway were seen. Apoptosis was induced via the mitochondrial-dependent caspase-3 and caspase-9 pathway, and autophagy related protein Beclin-1 was enhanced by ASB.ConclusionThe data show that ASB induces high levels of ROS generation in HK-2 cells and activates JNK signaling. Furthermore, ASB induces cell apoptosis via the caspase-dependent mitochondrial pathway, and induces cellular autophagy, in part by enhancing Beclin-1 protein expression.     

Time-dependent accumulation of inorganic mercury in subcellular fractions of kidney,liver, and brain of rats exposed to methylmercury

Accumulation of inorganic mercury in subcellular fractions of the kidney, liver, and brain of rats was studied during 48 days after a single injection of 25 mg/kg of methylmercury chloride. The highest ratio of inorganic to total mercury was seen in the cytosol of kidney, 80% of the total being as inorganic mercury at day 48. The ratio in the mitochondria and microsomes of kidney attained a maximum level (about 50% of the total as inorganic) at day 26–37. In the liver, the ratio was strikingly low in the cytosol and microsomes as compared to the light and heavy mitochondria where about 40% of the total was present as inorganic maximally at day 26. The ratio in the brain, determined up to day 15, was very low as compared with the kidney and liver, showing less than 3% of the total in the mitochondria, microsomes, and cytosol, and 5.4% in the myelin fraction. The high accumulation of inorganic mercury in the cytosol of kidney was closely related to metallothionein-like component, while those in the mitochondria and microsomes of kidney and in the mitochondria of liver were exclusively bound to high molecular weight proteins even after deoxycholate treatment.This work was supported in part by a grant from the Japanese Environment Agency and by the Grant-in-Aid for Scientific Research from the Ministry of Education of Japan     

The effect of oxygen tension on the cytotoxicity of hydroquinone and selected hydroquinone metabolites to isolated rat renal proximal tubular cells

The cytotoxicity of hydroquinone (HQ) and several of its metabolites was studied using freshly isolated proximal tubular (PT) kidney cells from rats. Incubations were conducted for periods of up to 4 h at 37°C, with cytotoxicity measured either as increased leakage of lactate dehydrogenase or as a decreased energy status, as determined by decreased ratios of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). Incubation atmospheres consisted of either 95% O₂/5% CO₂, to promote cell viability in vitro, or 5% O₂/5% CO₂/90% N₂. Preliminary studies with bovine serum albumin (BSA) added to the incubation media indicated a lack of toxicity for HQ or its metabolites. For the tests discussed in this report, incubations were performed without the addition of BSA. Under 95% O₂ atmospheres, PT cells from male Fischer F344 rats were significantly more sensitive to HQ than those from male Sprague-Dawley (SD) rats, with decreases in ATP to ADP ratios seen as early as 0.5 h at a concentration of 0.5 mM. When incubations were performed under a 5% O₂ atmosphere, 2-(cysteine-S-yl)hydroquinone (Cys-HQ) and HQ toxicities were observed later (3–4 h) in the incubation period, occurred at higher concentrations, were similar in magnitude for the two strains, and were greater for Cys-HQ than for HQ. These results show that variations in oxygen tension can dramatically influence the toxicity of HQ and its metabolites. The specific compounds tested that were cytotoxic at a physiologically relevant oxygen tension (5%) were (in decreasing order of potency): Cys-HQ>2-(glutathion-S-yl)hydroquinone>HQ. These results support an association of toxicity with metabolism through the glutathione pathway, with ultimate toxicity associated with the cysteinyl conjugate. Biochemical characteristics of PT cells from these two strains suggest a significantly greater capacity of cells from the SD rat to respond to oxidative stress.     

Aldosterone induces p21‐regulated apoptosis via increased synthesis and secretion of tumour necrosis factor‐α in human proximal tubular cells

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Disposition of inhaled mercury vapor in pregnant rats: maternal toxicity and effects on developmental outcome.

The disposition and toxicity of inhaled elemental mercury (Hg0) vapor for pregnant Long-Evans rats, and potential adverse effects on reproductive outcome were investigated. Rats were exposed to 0, 1, 2, 4, or 8 mg Hg0/m(3) for 2 h/day from gestation day (GD) 6 through GD 15. Maternal toxicity occurred primarily in rats exposed to 4 and 8 mg/m(3) and was manifested as a concentration-related decrease in body weight gain and mild nephrotoxicity. Control rats gained about 13% of their initial body weight during the 10-day exposure. Rats exposed to 4 mg/m(3) Hg0 gained about 7% less than controls, and rats exposed to 8 mg/m(3) Hg0 lost about 17% of their initial body weight during the 10-day exposure period. Maternal kidney weights were significantly increased in the 4 and 8 mg/m(3) concentration groups, and urinalysis revealed increased levels of protein and alkaline phosphatase activity in urine of all Hg0-exposed rats. Dams exposed to 8 mg/m(3) were euthanized in moribund condition on postnatal day (PND) 1. There was no histopathological evidence of toxicity in maternal lung, liver, or kidney of exposed rats at GD 6, GD 15, or PND 1. The incidence of resorptions was significantly increased, litter size and PND 1 neonatal body weights were significantly decreased only in the 8-mg/m(3) group. Total Hg concentrations in maternal tissues increased with increasing number of exposure days and concentration. In general, approximately 70% of Hg was eliminated from maternal tissues during the week following the last exposure (GD 15 to PND 1). Elimination of Hg from maternal brain and kidney was slower than in other tissues, possibly due to higher levels of metallothionein. Total Hg concentrations in fetal tissues increased with increasing number of exposure days and concentration, demonstrating that a significant amount of Hg crossed the placenta. One week after the last exposure, significant amounts of Hg were still present in brain, liver, and kidney of PND 1 neonates. Metallothionein levels in neonatal tissues were not significantly increased by exposure to 4 mg/m(3) Hg0. The total amount of Hg in neonatal brain (ng/brain) continued to increase after termination of inhalation exposure, suggesting a redistribution of Hg from the dam to neonatal brain. These data demonstrate that inhaled Hg0 vapor is distributed to all maternal and fetal tissues in a dose-dependent manner. Adverse effects of Hg on developmental outcome occurred only at a concentration that caused maternal toxicity.     

Omi/HtrA2短发夹RNA在大鼠肾小管上皮细胞凋亡中的作用及机制

目的探讨Omi/HtrA2短发夹RNA(shRNA)对缺氧/复氧诱导大鼠肾小管上皮细胞(NRK-52E)凋亡的作用及机制。方法细胞分为5组:正常组(常规培养),模型组(缺氧/复氧组)、HK组(转染重组质粒Pgenesil-1/HK)、shRNA1组(转染Pgenesil-1/Omi/HtrA2shRNA1)、shRNA2组(转染Pgenesil-1/Omi/HtrA2shRNA2)。用荧光显微镜观察荧光蛋白的表达,Westernblot检测各组Omi/HtrA2、半胱氨酰天冬氨酸特异性蛋白酶(caspase)-3/-9蛋白表达,比色法测定caspase-3/-9的活性。结果在荧光显微镜下,转染组细胞均可见绿色荧光,未转染组未见绿色荧光。与模型组相比,shRNA1组和shRNA2组Omi/HtrA2、caspase-3/-9蛋白表达明显减少(P<0.01)。模型组和HK组、shRNA1组和shRNA2组之间Omi/HtrA2、caspase-3/-9蛋白表达差异无统计学意义。与正常组相比,模型组Omi/HtrA2、caspase-3/-9蛋白表达明显增强(P<0.01)。结论Pgenesil-1/Omi/HtrA2shRNA1和Pgenesil-1/Omi/HtrA2shRNA2能明显减少缺氧/复氧诱导的NRK-52E中Omi/HtrA2蛋白的表达。通过抑制procaspase-9的活化,进而减少了下游procaspase-3的激活,最终减轻了缺氧/复氧诱导的NRK-52E的凋亡程度。     

Role of mitochondrial dysfunction in cellular responses to S-(1,2-dichlorovinyl)-L-cysteine in primary cultures of human proximal tubular cells

The nephrotoxic metabolite of the environmental contaminant trichloroethylene, S-(1,2-dichlorovinyl)-l-cysteine (DCVC), is known to elicit cytotoxicity in rat and human proximal tubular (rPT and hPT, respectively) cells that involves inhibition of mitochondrial function. DCVC produces a range of cytotoxic and compensatory responses in hPT cells, depending on dose and exposure time, including necrosis, apoptosis, repair, and enhanced cell proliferation. The present study tested the hypothesis that induction of mitochondrial dysfunction is an obligatory step in the cytotoxicity caused by DCVC in primary cultures of hPT cells. DCVC-induced necrosis was primarily a high concentration (> or =50 microM) and late (> or =24h) response whereas apoptosis and increased proliferation occurred at relatively low concentrations (<50 microM) and early time points (< or =24h). Decreases in cellular DNA content, indicative of cell loss, were observed at DCVC concentrations as low as 1 microM. Involvement of mitochondrial dysfunction in DCVC-induced cytotoxicity was supported by showing that DCVC caused modest depletion of cellular ATP, inhibition of respiration, and activation of caspase-3/7. Cyclosporin A protected cells against DCVC-induced apoptosis and both cyclosporin A and ruthenium red protected cells against DCVC-induced loss of mitochondrial membrane potential. DCVC caused little or no activation of caspase-8 and did not significantly induce expression of Fas receptor, consistent with apoptosis occurring only by the mitochondrial pathway. These results support the conclusion that mitochondrial dysfunction is an early and obligatory step in DCVC-induced cytotoxicity in hPT cells.     

Assessment of the renal toxicity of novel anti-inflammatory compounds using cynomolgus monkey and human kidney cells

PF1, an anti-inflammatory drug candidate, was nephrotoxic in cynomolgus monkeys in a manner that was qualitatively comparable to that observed with the two previous exploratory drug candidates (PF2 and PF3). Based on the severity of nephrotoxicity, PF1 ranked between the other two compounds, with PF2 inducing mortality at all doses and PF3 eliciting only mild nephrotoxicity. To further characterize nephrotoxicity in monkeys and enable direct comparisons with humans, primary cultures of proximal tubular (PT) cells from monkey and human kidneys were used as in vitro tools, using lactate dehydrogenase release as the biomarker of cytotoxicity. In both human and monkey PT cells, PF2 was by far the most cytotoxic compound of the three drugs. PF1 exhibited modest cytotoxicity at the highest concentration tested in human PT cells but none in monkey kidney cells whereas PF3 exhibited the reverse pattern. Because these drugs are organic anions, mechanistic studies using human organic anion transporters 1 and 3 (hOAT1 and hOAT3) transfected cell lines were pursued to evaluate the potential of these compounds to interact with these transporters. All three drugs exhibited high affinity for hOAT3 (PF1 exhibited the lowest IC₅₀ of 6 μM) but only weakly interacted with hOAT1 (with no interaction found for PF2). PF2 was a strong hOAT3 (not hOAT1) substrate, whereas PF1 and PF3 were substrates for both hOAT1 and hOAT3. Upon pretreatment of monkeys with the OAT substrate probenecid, PF3 systemic exposure (AUC) and half-life (t_1/2) increased ∼2-fold whereas clearance (CL) and volume of distribution (Vd_ss) decreased, as compared to naïve monkeys. This indicated that PF3 competed with probenecid for hOAT1 and/or hOAT3 mediated elimination of PF3. Thus, hOAT1 and/or hOAT3 may be responsible for the uptake of this series of drugs in renal PT cells, which may directly or indirectly lead to the observed nephrotoxicity in vivo.     

Developmental toxicity of trichloroethylene,tetrachloroethylene and four of their metabolites in rat whole embryo culture

The embryotoxicity of trichloroethylene (TRI) tetrachloroethylene (PER), and of four of their oxidative metabolites i.e. trichloroacetic acid, dichloroacetic acid, chloral hydrate, and trichloroacetyl chloride, was studied in vitro, using the rat whole embryo culture system. Embryos from Sprague-Dawley rats were explanted on gestational day 10 (plug day=day 0) and cultured for 46 h in the presence of the test chemical. All of the tested chemicals produced concentration-dependent decreases in growth and differentiation and increases in the incidence of morphologically abnormal embryos. TRI and PER produced qualitatively similar patterns of abnormalities, while TRI and/or PER metabolites, each elicited clearly distinguishable dysmorphogenic profiles. The presence of hepatic microsomal fractions in the culture medium produced marked decreases in TRI- and PER-induced embryotoxic effects, including mortality, severity of malformations, and delayed growth and differentiation.     

Role of γ-glutamyltranspeptidase in renal uptake and toxicity of inorganic mercury in mice

The role of renal glutathione (GSH) metabolism as a mediating factor in the renal uptake and toxicity of inorganic mercury was investigated in mice by preadministering a γ-glutamyltranspeptidase (GGT) inhibitor, acivicin. Pretreatment with acivicin (0.25, 1.0 or 2.5 mmol/kg, i.p.) led to a dose-dependent decrease in renal mercury content and increases in mercury and GSH contents in urine measured 2 h after HgCl₂ injection (18 μmol/kg, i.v.). Acivicin pretreatment also ameliorated the renal and lethal toxicity caused by administration of inorganic mercury. Treatment of the mice with 1,2-dichloro-4-nitrobenzene (DCNB, 2.5 mmol/kg, i.p.), a specific depletor of hepatic GSH, prior to HgCl₂ injection substantially reduced renal Hg content and consequently reduced the renal damage. In addition, coadministration of GSH (36 μmol/kg, i.v.) with HgCl₂ increased the renal Hg content measured 5 min after HgCl₂ injection to 2.6 fold higher than that of mice treated with HgCl₂ alone. These results suggest that renal uptake of inorganic mercury, which is supposedly transported to the kidney as a mercury-GSH complex, is dependent on a reaction catalyzed by GGT on the outer surface of the renal brush border membrane in the same manner as the metabolism of GSH.     

Acute effects of candesartan on rat renal haemodynamics and proximal tubular reabsorption

1. The effects of the specific angiotensin II receptor type I (AT1) antagonist candesartan on renal proximal tubular sodium transport were studied using lithium clearance. The effects of candesartan on mean arterial blood pressure (MABP), renal plasma flow (RPF), glomerular filtration rate (GFR) and sodium and potassium excretion were also investigated. 2. Male Wistar rats were anaesthetized with Inactin (thiobutabarbital sodium; Sigma, St Louis, MO, USA). Clearance markers (8% polyfructosan, 1% para-aminohippuric acid and 4 mmol/l lithium chloride) were given into a jugular vein at the rate of 1.6 mL/h per 100 g bodyweight. Candesartan was given as bolus injection (0.01, 0.1, 0.2, 0.5 and 1.0 mg/kg) followed by 60 min continuous infusion at a rate of 0.5, 5, 10, 25 and 50 microg/min per kg, respectively. 3. The non-depressor dose of candesartan (0.01 mg/kg) did not alter RPF or GFR, whereas diuresis, natriuresis and kaliuresis were observed. The higher doses of candesartan reduced MABP, RPF and GFR, although diuresis, natriuresis and kaliuresis were still observed. 4. Renal tubular sodium and water reabsorption were inhibited after intravenous administration of candesartan independently of an alteration in arterial pressure. Lithium clearance data indicate that the site of inhibition was in the proximal nephron segment.     

砷致大鼠海马神经细胞凋亡对学习记忆功能的影响

目的研究长期染砷对大鼠海马细胞超微形态和学习记忆功能的影响。方法 SD大鼠随机分为高、低砷剂量组和对照组,染砷组自由饮用含砷水（高砷组10mg/（kg.d）,低砷组0.4mg/（kg.d））,对照组饮蒸馏水。连续染砷24周后,Morris水迷宫实验评估大鼠学习与记忆能力,单细胞凝胶电泳（SCGE）法检测海马神经细胞DNA损伤情况,透射电镜（TEM）观察海马神经细胞超微结构变化。结果染砷组定位航行试验平均潜伏期比对照组延长（P〈0.05）,空间探索试验在第三象限停留时间百分比均比对照组明显缩短（P〈0.05）。SCGE可见染砷组＂彗星＂拖尾和DNA断裂分级均比对照组明显增加（P〈0.05）,高砷组比低砷组增加更显著（P〈0.05）,有剂量-效应关系。TEM观察可见,对照组海马神经细胞形态和超微结构呈正常表现,低砷组可见核凹陷变形,染色质边集,线粒体肿胀,高砷组还可见线粒体和细胞器减少,胞浆＂空泡＂,部分细胞甚至呈核固缩的细胞凋亡征象。结论慢性染砷可致大鼠海马神经细胞DNA和超微结构损伤,进而引起学习记忆能力障碍。     

Neurobehavioural test results and exposure to inorganic mercury: in search of dose-response relations

The aim of the analysis was, in general, to find a way to summarise results of studies in search of exposure-response relationships and, in particular, to ask whether an exposure-response relationship can be ascertained for neurobehavioural studies on occupational mercury exposure. Eighteen studies dealing with human mercury exposure and examining 1,106 exposed and 1,105 control subjects were included in the analysis. Effect sizes were calculated for each of the single neuropsychological test results on cognitive and motor performance and were considered in relation to mean current concentrations of exposure. The total of effect sizes demonstrated a correlation to exposure in the range of r=0.50. Additional analyses showed that the influence of mercury on psychological functions was different and that results on motor performance compared with memory and attention revealed the greatest impairment in mercury-exposed workers. Implications for the reversibility of impairments could be discussed because three of the studies examined subjects whose exposure had ceased. Besides the usefulness of the approach, it became obvious that the available 18 studies are a small sample, even when non-dimensional effect-sizes are used; hence, not all psychological domains covered by tests could be analysed.     

Time-course of cadmium-induced acute hepatotoxicity in the rat liver: the role of apoptosis

Exposure to toxic metals and pollutants is a major environmental problem. Cadmium is a metal causing acute hepatic injury but the mechanism of this phenomenon is poorly understood. In the present study, we investigated the mechanism and time-course of cadmium-induced liver injury in rats, with emphasis being placed on apoptosis in parenchymal and nonparenchymal liver cells. Cadmium (3.5 mg/kg body weight) was injected intraperitoneally and the rats were killed 0, 9, 12, 16, 24, 48 and 60 h later. The extent of liver injury was evaluated for necrosis, apoptosis, peliosis, mitoses and inflammatory infiltration in hematoxylin–eosin-stained liver sections, and by assaying serum enzyme activities. The number of cells that died via apoptosis was quantified by TUNEL assay. The identification of nonparenchymal liver cells and activated Kupffer cells was performed histochemically. Liver regeneration was evaluated by assaying the activity of liver thymidine kinase and by the rate of ³H-thymidine incorporation into DNA. Both cadmium-induced necrotic cell death and parenchymal cell apoptosis showed a biphasic elevation at 12 and 48 h and peaked at 48 and 12 h, respectively. Nonparenchymal cell apoptosis peaked at 48 h. Peliosis hepatis, another characteristic form of liver injury, was first observed at 16 h and, at all time points, closely correlated with the apoptotic index of nonparenchymal liver cells, where the lesion was also maximial at 48 h. Kupffer cell activation and neutrophil infiltration were minimal for all time points examined. Based on thymidine kinase activity, liver regeneration was found to discern a classic biphasic peak pattern at 12 and 48 h. It was very interesting to observe that cadmium-induced liver injury did not involve inflammation at any time point. Apoptosis seems to be a major mechanism for the removal of damaged cells, and constitutes the major type of cell death in nonparenchymal liver cells. Apoptosis of nonparenchymal cells is the basis of the pathogenesis of peliosis hepatis. The first peaks of necrosis and parenchymal cell apoptosis seem to evolve as a result of direct cadmium effects whereas the latter ones result from ischemia.