Minoru Kasuya

Apoptosis Induced by Cadmium in Human Lymphoma U937 Cells through Ca2+-calpain and Caspase-Mitochondria- dependent Pathways

Apoptosis induced by cadmium has been shown in many tissues in vivo and in cultured cells in vitro. However, its molecular mechanism is not fully understood. When the human histiocytic lymphoma cell line U937 was treated with cadmium for 12 h, evidence of apoptotic features, including change in nuclear morphology, DNA fragmentation, formation of DNA ladder in agarose gel electrophoresis, and phosphatidylserine externalization, were obtained. Moreover, loss of the mitochondrial membrane potential (Δψm) was observed in the cadmium-treated cells and was inhibited by a broad caspase inhibitor (Z-VAD-FMK). Caspase inhibitors suppressed the DNA fragmentation in the order of Z-VAD-FMK > caspase-8 inhibitor > caspase-3 inhibitor. Expression of Bcl-xL and Bid decreased significantly in the cadmium-treated cells, although no apparent change in Bcl-2 and Bax expression was found. Tetrakis-(2-pyridylmethyl) ethylendiamine, a cell-permeable heavy metal chelator, partially reversed the increase of fluorescence of Fura-2 in the cadmium-treated cells. In addition, verapamil (70 μm), a voltage-dependent Ca2+ channel blocker, inhibited the DNA fragmentation induced by cadmium less than 100 μm and decreased the fluorescence of Fura-2. Cadmium up-regulated the expression of type 1 inositol 1,4,5-trisphosphate receptor (IP3R) but not type 2 or type 3 IP3R. Calpain inhibitors I and II partially prevented DNA fragmentation. No effects of Z-VAD-FMK on the expression of type 1 IP3R or of calpain inhibitors on the loss of Δψm were observed. These results suggest that cadmium possibly induced apoptosis in U937 cells through two independent pathways, the Ca2+-calpain-dependent pathway and the caspase-mitochondria-dependent pathway.

The effect of vitamin E on the toxicity of alkyl mercurials on nervous tissue in culture

The effects of vitamin E (DL-..cap alpha..-tocopherol acetate), a stabilizer of membranes, on the toxic effect of methylmercuric chloride (MMC) and ethyl-mercuric chloride (EMC) on nervous tissue in culture were studied. Sliced newborn rat cerebella were cultured in a medium containing the alkyl mercurials and vitamin E. Vitamin E at concentrations of 0.4, 1.0, and 2.0 x 10/sup -5/ M inhibited the toxic effect of 10/sup -5/ M MMC on the development of nerve fibers, glial cells, and fibroblasts. The same protective effect against neurotoxicity of 6 x 10/sup -6/ M EMC was observed. However, the protective effect of the vitamin decreased at higher concentrations of EMC. These results are in accord with an interaction of alkyl mercurials with membranes of nervous tissue which produces the degenerative changes in the cells. The data further suggest that the vitamin is one of the agents which modifies the neurotoxicity of alkyl mercurials. 15 references, 2 figures, 2 tables.

Effects of inorganic, aryl, alkyl and other mercury compounds on the outgrowth of cells and fibers from dorsal root ganglia in tissue culture

Abstract The purpose of this paper is to show the relationship between the structure of mercurial compounds and their toxicity on nervous tissue in culture. Dorsal root ganglia from chick embryos were cultured in a medium containing different mercurial compounds. These included mercuric chloride, methylmercuric chloride, methylmercuric iodide, ethylmercuric chloride, ethylmercuric phosphate, p -chloromercuribenzoic acid (PCMB), phenylmercuric chloride, phenylmercuric iodide, phenylmercuric acetate, phenylmercuric p -toluenesulfonanilide, p -tolylmercuric chloride and salyrganic acid. Inorganic mercury and salyrganic acid were the least toxic; phenylmercuric p -toluenesulfonanilide was the most toxic. PCMB at low concentration stimulated the outgrowth of nerve fibers. Replacement of the phenyl group of mercuric chloride and iodide by a methyl group brought about an increase in toxicity of these compounds. Phenyl- and methylmercuric chloride produced a stronger toxicity than phenyl- and methylmercuric iodide. Methylmercuric chloride (molecular size 4.343 A) was approximately as toxic as compounds having a multiple number of this value. Sphingomyelin and phosphatidyl- l -serine inhibited the toxic effect of ethylmercuric chloride, whereas l -cysteine hydrochloride, dl -β-mercaptovaline ( dl -penicillamine), 2,3-dimercaptopropanol (BAL), cholesterol, cholesterol palmitate, cephalin and lecithin did not inhibit the toxic effect of mercury compounds. From these results, it was postulated that the binding of mercury compounds of these hydrophobic and hydrophilic moieties with specific binding sites on membranes is a major factor in their toxic action.

Effect of selenium on the toxicity of methylmercury on nervous tissue in culture.

Abstract Effects of sodium selenate and selenite on the toxic effect of methylmercuric chloride (MMC) on nervous tissue in culture were studied. Sliced newborn rat cerebella were cultured in a medium containing MMC and selenate or selenite. The concentrations of sodium selenate and selenite that showed remarkable protective effect against the neurotoxicity of MMC were 0.8 and 0.2 × 10 −5 m , respectively. The protective effect of sodium selenite was additive with that of dl -α-tocopherol acetate (vitamin E). However, 4 × 10 −5 m sodium selenate and 1 × 10 −5 m sodium selenite per se showed an obvious toxic effect on the outgrowth of nerve fibers and cells from cerebellum tissue in culture. The toxicity of selenium was additive to that of MMC. These results indicate that oxidized selenium at low concentrations is able to modify the neurotoxicity of MMC and that different states of selenium produce different degrees of protection. They suggest further that the adverse effect of selenium is additive to the toxicity of alkyl mercurial at the toxic level of selenium.

Assessment of bone metabolism in cadmium-induced renal tubular dysfunction by measurements of biochemical markers

Bone metabolism related to the severity of cadmium (Cd)-induced renal tubular dysfunction (RTD) was assessed by measuring several bone biochemical markers. Fifty-three female subjects with RTD aged 65-76 years (mean 70.0+/-3.3 years) and who lived in the Cd-polluted Jinzu River basin in Toyama, Japan were studied. Bone alkaline phosphatase (bone-ALP), intact bone Gla-protein (intact-BGP) and carboxy-terminal propeptide of type I collagen (PICP) in serum as bone formation markers and pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in urine as bone resorption markers were measured. All markers of bone turnover were increased and significantly correlated with each other, suggesting that bone formation and resorption were coupled and increased in Cd-induced RTD. Fractional excretion of beta(2)-microglobulin (beta(2)-m, FE(beta 2-m)) as an index of severity of Cd-induced RTD was extremely varied ranging from 0.45 to 53%. There were no significant correlations between FE(beta 2-m) and each of the five bone biochemical markers. The bone turnover in Cd-induced RTD appeared to be determined by the glomerular filtration rate (GFR): in subjects with GFRs above 50 ml/min, the levels of bone-ALP or intact-BGP tended to be inversely related to the GFRs, whereas in subjects with GFRs below 40 ml/min, those levels tended to decrease. These results suggest that the bone turnover, in particular the bone formation, was influenced by renal tubular function as assessed by the levels of GFR in Cd-induced RTD.

Effects of air pollution on tannin biosynthesis and predation damage in Cryptomeria Japonica

Abstract Decreased levels of foliar tannin was observed with Japanese Cedars growing in the surroundings of a steam power station. Tannin content of the leaves was negatively corrrelated with the levels of foliar soluble sulphate, and a causal association was suggested between air pollution and inhibition of the shikimate pathway. Preliminary observation on predation damage of the Japanese Cedars indicates that increased feeding rate by larvae of a herbivorous moth, Dasychira abietis argentata , was associated with low foliar tannin content and the vicinity of the sampling sites to the power station. Considering the physiological function of tannins, e.g. as a defensive factor against insect predation and fungal degradation, it seems that decrease of foliar tannin levels of Japanese Cedars in the polluted areas has relevance to their high susceptibility to air pollution in field conditions.

Occupational Allergy to Adult Chironomid Midges among Environmental Researchers

A case of occupational allergy to chironomid midges in research work is described. A researcher was exposed to adult chironomid midges during his research and developed allergic rhinitis after 10 years of such exposure. Using the midge extract of adult Chironomus plumosus (CP) (Linnaeus, 1758), both immediate skin test and the ophthalmic challenge test gave positive results. IgE antibody against adult CP was also demonstrated by the radioallergosorbent test. Four of the five serum samples of the environmental researcher examined showed a positive radioallergosorbent test to at least one of the adult midges breeding around eutrophic Japanese lakes. Enzyme-linked immunosorbent assay inhibition test and immunoblot experiments indicated that the remaining hemoglobin is one of the major allergens of adult CP. These results demonstrate that the exposure to adult chironomid midges is an important occupational hazard among environmental researchers.

Urinary trehalase activity as an indicator of kidney injury due to environmental cadmium exposure

One hundred and seventy-eight subjects, patients with Itai-itai disease and their family members, aged 12–87 years living in a cadmium (Cd)-polluted area in the Jinzu River basin (Cd-exposed group) and 176 controls (control group) were examined. In the Cd-exposed group urinary trehalase increased with increasing age, urinary β2-microglobulin (β2-m) and retinol-binding protein. Although urinary cadmium was higher in the Cd-exposed group, no particular correlation was found between urinary trehalase and urinary cadmium. Seventeen men and 11 women showed raised urinary trehalase activities despite normal values of urinary β2-m (<300 μg/g.creatinine), suggesting that urinary trehalase increases earlier than urinary β2-m. In 19 patients with Itai-itai disease included in the Cd-exposed group, urinary trehalase decreased with decreasing reciprocal of serum creatinine, suggesting that urinary trehalase decreases in the most advanced cases of chronic cadmium nephropathy due to reduced tubular cell mass.

Elevation of urinary trehalase activity in patients of itai-itai disease.

The elevation of urinary trehalase activity in patients of itai-itai disease was examined. Urinary trehalase was correlated with tubular reabsorption of phosphorus (%TRP): the lower the trehelase activity, the worse was %TRP. Furthermore, this activity was inversely correlated with urinary glucose and urinary total protein. In itai-itai disease, the excretion of β2-microglobulin seems to be maximal, and urinary trehelase activity was low in the latter stages of the disease. It is inferred that itai-itai disease produces extremely severe tubular damage as well as glomerular dysfunction.

Toxicity of butylbenzyl phthalate (BBP) and other phthalate esters to nervous tissue in culture

Butylbenzyl phthalate (BBP) and n-butyl lauryl phthalate (BLP) markedly inhibited the outgrowth of nerve fibers and glial cells from cerebellar explants of newborn rat in primary culture at concentrations of 7.0 and 12.5 x 10(-4) M, respectively. The toxicity of butyl phthalyl butyl glycolate (BPBG) was not significant. From these results the order of toxicity of these three phthalate esters was determined as BBP > BLP > BPBG.