Loss of homotypic epithelial cell adhesion by selective N-cadherin displacement in bismuth nephrotoxicity.

The nephrotoxicity of single high doses of bismuth (Bi)-containing therapeutic drugs is characterized morphologically by detachment of proximal tubular epithelial cells (PTECs) from each other, followed by cell death. We investigated whether Bi nephrotoxicity is mediated by changes in the distribution of proteins involved in intercellular adhesion. A nephrotoxic dose of colloidal bismuth subcitrate (CBS; 3.0 mmol Bi/kg) was orally administrated to 10 female Wistar rats. After 1 h, N-cadherin had disappeared from the adherence junctions of vital PTECs, whereas ZO-1, a tight junction marker, remained present at the cell-cell border until cell death occurred after 3 h. E-Cadherin, absent in PTECs, remained absent. Exposure of the renal epithelial cell lines NRK-52E and LLC-PK1 to 400 microM Bi(3+) also resulted in the disappearance of N-cadherin expression after 1 h, whereas ZO-1, E-cadherin, and Desmoplakin expression did not resolve before cell death at 24 h, thus confirming in vivo results. Our results are the first to indicate that Bi-induced death of PTECs is preceded by redistribution of N-cadherin and the disruption of homotypic cell adhesion.

Bismuth overdosing-induced reversible nephropathy in rats.

Overdosing of colloidal bismuth subcitrate (CBS), used to treat peptic ulcers and Helicobacter pylori infections, has been reported to result in serious, though reversible, nephrotoxicity in humans. However, little is known about the nature of the renal damage induced by bismuth (Bi), and no well-described experimental model exists. Single large oral CBS doses (0.75, 1.5, and 3.0 mmol Bi/kg) were administered to three groups of 20 female Wistar rats. A control group (n = 20) received only the vehicle. Standard kidney function parameters, urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG) and the Bi content were monitored in blood, urine, liver, and kidneys for 14 days. A dose of 3.0 mmol Bi/kg, 100 times the daily therapeutic dose, caused kidney damage within 6 h as detected by proteinuria, glucosuria, and elevated plasma urea and plasma creatinine levels. The kidneys of all animals, except two that died, recovered functionally within 10 days. At a dose of 1.5 mmol Bi/kg, clinical parameters changed less and normalized within 48 h, whereas a dose of 0.75 mmol Bi/kg induced no changes. Histological evaluation revealed that the S3 tubular segment necrotized first with additional necrotization of the S1/S2 segment when more Bi was absorbed. The lesions were accompanied by interstitial infiltrates of CD45+ leukocytes. In summary, we developed a rat model for Bi-induced reversible nephropathy. A large single oral overdose of CBS administered to Wistar rats led to damage to the proximal tubule, especially in the last segment.

Bismuth biokinetics and kidney histopathology after bismuth overdose in rats.

Bismuth induced nephrotoxicity has been reported to occur after acute overdoses of Bi-containing therapeutic drugs. We studied the development of bismuth induced nephropathy and bismuth biokinetics in rats. Bismuth nephropathy was induced in 33 young adult female Wistar rats weighing ca. 175 g by feeding them a single overdose of colloidal bismuth subcitrate containing 3.0 mmol Bi/kg at (t = 0). Control animals (n = 7) were fed the vehicle only. The animals were sacrificed after 1-48 h. Plasma creatinine increased from 51 +/- 6 micromol/l at t = 0 to 550 +/- 250 micromol/l after 48 h in the experimental group. The S3 segment of the proximal tubule showed epithelial cell vacuolation after 1 h and necrosis after 3 h. Cells of the S1/S2 segment demonstrated vacuolation after 6 h and necrosis after 12 h. Biokinetics of bismuth in blood could best be described with a one-compartment model characterized by an absorption half-life of 0.32 h and an elimination halflife of 16 h. The peak concentration of about 7.0 mg Bi/l was reached after 2 h. In conclusion, cells of the S3 segment of the proximal tubule necrotized first after an oral colloidal bismuth subcitrate overdose and biokinetics of Bi in blood was best described by a one-compartment model.

Comparison of enhanced elimination of bismuth in humans after treatment with meso-2,3-dimercaptosuccinic acid and D,L-2,3-dimercaptopropane-1-sulfonic acid.

Two groups of 12 human volunteers, who had been treated with colloidal bismuth subcitrate, because of Helicobacter pylori-associated gastritis, participated in the study. The patients received a single dose of meso-2,3-dimercaptosuccinic acid (DMSA) or D,L-2,3-dimercaptopropane-1-sulfonic acid (DMPS) at a dose of 30 mg kg-1 in a randomized single blind study. In contrast to DMPS, increasing concentrations of bismuth in blood were observed during the first 4 h after intake of DMSA. In urine, both chelators induced a 50-fold increase in urinary bismuth excretion compared with the control urines. The treatment was well tolerated. The results indicate that both DMSA and DMPS effectively increase the elimination of bismuth in human urine. Consequently, both chelators may be of benefit in the treatment of patients with bismuth intoxication.

Absorption of bismuth from several bismuth compounds during in vivo perfusion of rat small intestine.

Evaluation of the amount of bismuth (Bi) absorbed from the gastrointestinal tract is important for assessment of the possible risks associated with the use of Bi compounds in the treatment of gastrointestinal disorders. We compared the absorption of Bi from media containing the equivalent of 1 g of elemental Bi from either Bi subnitrate (BSN), Bi subsalicylate (BSS), colloidal Bi subcitrate (CBS), Bi chloride (BiCl3), or Bi citrate (BCit) by an in vivo perfusion system of rat small intestine. The intestinal absorption was < 1% for all compounds, but higher from BCit and CBS than from BSN, BSS, and BiCl3. The dose dependency of Bi absorption from both CBS and BiCl3 in citrate buffer showed a nonlinear relationship between the concentration of Bi in perfusate and the concentration of Bi in blood after 60 min.

Analysis for bismuth in tissue by electrothermal atomic absorption spectrometry.

We developed a simple method for the analysis of bismuth (Bi) in biological tissue, using wet digestion for sample pretreatment. Bi was determined by electrothermal atomic absorption spectrometry with platinum as a matrix modifier to decrease the volatility of Bi. The furnace program included a gas stop for sensitivity enhancement. Analytical performance was established for Bi in kidney, liver, brain, and bone. As little as 25 ng/g wet weight can be detected in the most concentrated digests. Homogenization of bone was necessary before digestion, and its matrix showed the strongest interference. In rats exposed orally to colloidal bismuth subcitrate for 14 days, the metal could be detected in liver, kidney, and spleen but not in brain and bone. In the tissues of 12 patients who died from non-Bi-related causes, no Bi were present in kidney in the other 2.

Development of a therapeutic procedure for bismuth intoxication with chelating agents.

Although bismuth poisoning is still a rare phenomenon, the increasing use of bismuth-containing drugs warrants a systematic approach to the treatment of bismuth overdose. An effective method of enhancing the elimination of toxic amounts of bismuth from the body has not been reported. Therefore we performed a study to select the best chelator to treat bismuth poisoning. Dimercaprol (BAL), meso-2,3-dimercaptosuccinic acid (DMSA), D,L-2,3-dimercapto-propane-I-sulfonic acid (DMPS), D-penicillamine (D-PEN), N-acetyl-D,L-penicillamine (Ac-PEN), thiopronine (TP), sodium-calcium edetate (EDTA) and deferoxamine (DFO) were tested with an in vitro model of equilibrium dialysis and an in vivo model of rats poisoned with bismuth. The rats (n = 6 per substance tested) were treated with the chelators in intraperitoneal doses of 250 mumol/kg.day for 3 consecutive days. Afterward, tissue and blood samples were collected. Bismuth concentrations were determined with electrothermal atomic absorption spectrometry in serum, buffer, urine, blood, brain, kidney, liver, spleen, and bone. Using in vitro results, we constructed a ranking of chelating agents; it appeared not to predict the in vivo results. The dithiol compounds (DMPS, DMSA and BAL) were effective in most organs (especially in kidney and liver) resulting in a higher elimination of bismuth in urine by DMPS and BAL. BAL was the only chelator effective in lowering brain bismuth concentrations, whereas treatment with EDTA resulted in increased brain bismuth levels. For D-PEN and DFO, no effects could be demonstrated. For clinical practice, DMSA and DMPS may well be the chelators of choice; the application of BAL should be reserved for very severe cases of poisoning because of its own toxicity.

Analysis of bismuth in serum and blood by electrothermal atomic absorption spectrometry using platinum as matrix modifier.

Bismuth-containing medicines have been used for years, but there is a lack of clinically applicable methods for measuring bismuth in body fluids. We describe a sensitive, accurate and precise method for analysis of bismuth in blood and serum, which is suitable both for monitoring purposes and for further investigations into the biokinetics and safety of bismuth. Bismuth was quantitated with electrothermal atomic absorption spectrometry with Zeeman background correction. In the furnace programme a cool-down step was introduced and platinum was used as a matrix modifier. Recovery for 40 micrograms/l is 93.7 +/- 4.6% (mean +/- SD) from serum and 92.8 +/- 5.4% from blood; within-day precision (n = 10) at 40 micrograms/l is 3.2% for serum and 4.2% for blood. Day-to-day precision at 40 micrograms/l (n = 10) was 4.5% for serum and 4.0% for blood. The detection limit is 0.7 microgram/l for serum and 1.0 microgram/l for blood. Blood samples have to be collected in glass tubes and stored at -20 degrees C.

The role of metallothionein in the reduction of cisplatin-induced nephrotoxicity by Bi3(+)-pretreatment in the rat in vivo and in vitro. Are antioxidant properties of metallothionein more relevant than platinum binding?

Nephrotoxicity induced by cisplatin (CDDP) was reported to be reduced by Bi3(+)-pretreatment, which selectively induces renal metallothionein (MT). In the present study renal MT had increased to 250% of control in rats that received bismuth subnitrate (50 mumol/kg/day, orally) for 8 days. In vitro experiments demonstrated that the reduction of CDDP-induced toxicity is a renal effect: in proximal tubular cells (PTC) isolated from Bi3(+)-treated rats the toxicity of CDDP, and also of HgCl2, CdCl2 and p-aminophenol, was reduced as compared to PTC from untreated rats. In contrast to the reduction in CDDP, Hg2+ and Cd2+ toxicity, the reduction in p-aminophenol toxicity cannot be explained by the metal-binding properties of MT. MT was reported to act as a free radical scavenger, which may explain our observation since p-aminophenol toxicity is thought to be a consequence of the generation of oxygen radicals. In vivo experiments showed that the overall renal Pt-content as well as the Pt bound to renal MT is lower in Bi3(+)-pretreated rats than in untreated rats, 24 hr after administration of CDDP (12 mg/kg), suggesting that the reduction in nephrotoxicity is not due to increased binding of Pt2+ to renal MT. Renal superoxide dismutase (SOD) activity was increased in rats that had only received CDDP. Such a rise in SOD may result from peroxidative damage caused by exposure to CDDP. The fact that SOD was not elevated in rats that received Bi3+ prior to CDDP suggests that (i) peroxidation contributes to CDDP-induced nephrotoxicity and (ii) the anti-oxidant properties of MT are responsible for the reduction of this toxicity.

Pharmacokinetics and toxicity of bismuth compounds.

Inorganic bismuth salts are poorly soluble in water: solubility is influenced by the acidity of the medium and the presence of certain compounds with (hydr)oxy or sulfhydryl groups. The analysis of bismuth in biological material is not standardised and is subject to large variation; it is difficult to compare data from different studies, and older data should be approached with caution. The normal concentration of bismuth in blood is between 1 and 15 micrograms/L, but absorption from oral preparations produces a significant rise. Distribution of bismuth in the organs is largely independent of the compound administered or the route of administration: the concentration in kidney is always highest and the substance is also retained there for a long time. It is bound to a bismuth-metal binding protein in the kidney, the synthesis of which can be induced by the metal itself. Elimination from the body takes place by the urinary and faecal routes, but the exact proportion contributed by each route is still unknown. Elimination from blood displays multicompartment pharmacokinetics, the shortest half-life described in humans being 3.5 minutes, and the longest 17 to 22 years. A number of toxic effects have been attributed to bismuth compounds in humans: nephropathy, encephalopathy, osteoarthropathy, gingivitis, stomatitis and colitis. Whether hepatitis is a side effect, however, is open to dispute. Each of these adverse effects is associated with certain bismuth compounds. Bismuth encephalopathy occurred in France as an epidemic of toxicity and was associated with the intake of inorganic salts including bismuth subnitrate, subcarbonate and subgallate. In the prodromal phase patients developed problems in walking, standing or writing, deterioration of memory, changes in behaviour, insomnia and muscle cramps, together with several psychiatric symptoms. The manifest phase started abruptly and was characterised by changes in awareness, myoclonia, astasia and/or abasia and dysarthria. Patients recovered spontaneously after discontinuation of bismuth. Intestinal lavage, forced diuresis and haemodialysis have been tried without positive effects on the clinical condition of the patient or on blood bismuth concentration, and the use of dimercaprol as an antidote has produced reports of both positive and negative findings. To confirm the diagnosis of bismuth encephalopathy, it is essential to find elevated bismuth concentrations in blood, plasma, serum or CSF. A safety level of 50 micrograms/L and an alarm level of 100 micrograms/L have been suggested in the past, but no proof is available to support the choice of these levels.(ABSTRACT TRUNCATED AT 400 WORDS)