Role of tachykinins and neutral endopeptidase in toluene diisocyanate-induced bronchial hyperresponsiveness in guinea pigs.

The role of tachykinins in toluene diisocyanate (TDI)-induced non-specific bronchial hyperreactivity (NSBH) in guinea pigs was investigated, and it was determined whether or not the activity of airway neutral endopeptidase (NEP) was inhibited in conditions where a bronchial hyperreactivity to acetylcholine (ACh) was observed. Exposures to 3 ppm TDI for 1 h, or to 0.029 ppm for 8 weeks caused a significant bronchial hyperreactivity to ACh. The depletion of tachykinins by a pretreatment with capsaicin (140 mg/kg) eliminated the TDI-induced airway hyperresponsiveness in both patterns of exposure to TDI. Capsaicin treatment had no effect on the response to ACh in guinea-pigs exposed to air (controls). Bronchial NEP activity determined by histoenzymology was significantly less 4 and 24 h after the end of a 1-h exposure to 3 ppm TDI than after exposure to air. Bronchial NEP activity evaluated 24 h after the end of a 48-h exposure to 0.116 ppm TDI, or a 1-week exposure to 0.050 ppm TDI was not significantly different from those of controls exposed to air, whereas in the same conditions of exposure a NSBH is observed in guinea-pigs. These data suggest that tachykinins released from C-fibers upon acute or repeated exposures to high or low concentrations of TDI, respectively, play an essential role in the observed bronchial hyperreactivity, and that the inhibition of NEP by TDI cannot completely account for the observed airway hyperreactivity.

Relationship between IgE positive cell numbers and serum total IgE levels in mice treated with trimellitic anhydride and dinitrochlorobenzene.

Although increased total serum IgE levels have been suggested as being predictive parameters of airway hypersensitivity caused by low molecular weight chemicals, it is not yet clear what level of serum total IgE in chemically-treated animals would translate to potential risk of inducing an immediate type hypersensitivity in human beings. Quantitative determination of IgE-bearing positive cells induced by chemicals in the tissue, particularly in respiratory airway, could help to resolve this problem. In BALB/c mice, serum total IgE concentrations and tissue IgE-bearing positive cell numbers were investigated following topical exposure to the chemicals, trimellitic anhydride (TMA) and dinitrochlorobenzene (DNCB), known in human as a respiratory and dermal sensitizer, respectively. In groups of mice 8 and 10 weeks of age, there were less individual variations in 25% TMA-induced serum total IgE increase than in other groups of mice 6, 12 and 16 weeks of age. When chemical concentrations of 1, 2 and 3% DNCB and of 6.25, 12.5 and 25% TMA were studied, we observed that the increase in IgE was dose-dependent for both chemicals, r=0.96; P=0.03 for DNCB and r=0.99; P=0.002 for TMA. However, the increase in serum total IgE induced by TMA was at least twice that induced by DNCB and was associated with the numbers of IgE bearing cells in the tracheal lamina propria (r=0.67, P=0.0003). A respiratory hypersensitivity caused by TMA, but not by DNCB, may be partly due to the presence of immuno effector cells bearing IgE at their surface in airway microenvironments, and their presence might be related to the higher level of serum total IgE. The IgE bearing positive cells could, therefore, help to identify chemicals which have the potential risk of inducing an immediate type hypersensitivity in humans.

Use of Mishell-Dutton culture for the detection of the immunosuppressive effect of iron-containing compounds.

Mishell-Dutton culture, known as an in vitro model for the evaluation of the humoral immune response of mice spleen cells to sheep red blood cells (SRBC), was used to study the immunosuppressive effect of iron-containing compounds. This response was indicated by the number of antibody forming cell (AFC) per million nucleated cells. Ferrous sulfate and ferric citrate (0.1 mM), when continuously present in Mishell-Dutton culture, significantly decreased the SRBC AFC response by approximately 63% and 86% of the control values, respectively. Ferric citrate, preincubated (24 h) with spleen cells and followed by lavage, significantly decreased the SRBC AFC response by approximately 54% of the control values. Primary and iron-treated coal, in concentrations ranging from 40 micrograms.ml-1 to 120 micrograms.ml-1, significantly decreased the SRBC AFC response when continuously present in Mishell-Dutton culture. Iron-treated coal, suppressed this response, in dose-dependent amounts, to a greater extent than did the primary coal:73% versus 54% at 120 micrograms.ml-1. We concluded that Mishell-Dutton culture is suitable for studying the immunotoxicity of iron and these results may contribute to explain a decrease of host resistance against parasitic and bacterial infection in workers exposed to iron.

Nephrotoxicity mechanism of cis-platinum (II) diamine dichloride in mice.

Male Swiss OF1 mice were injected subcutaneously with 20 mg/kg of cis-platinum (II) diamine dichloride (cis-platin). Examination of cryostat kidney sections stained for alkaline phosphatase (APP) revealed damage to about 10, 20, 40 and 50% of the proximal tubules after 7, 24, 48 and 72 h, respectively. Pretreatment with the glutathione synthesis inhibitor, buthionine sulfoximine (BSO), (i.p. 3 mmol/kg) potentiated the tubule damage of cis-platin. In contrast, pretreatment with organic anion transport inhibitor probenecid (i.p. 3 x 0.75 mmol/kg) reduced the number of damaged tubules by approximately 80% at 72 h after cis-platin injection. Pretreatment with the gamma-glutamyltranspeptidase (gamma-GT) inactivator acivicin (AT-125, 50 mg/kg p.o., plus 50 mg/kg i.p.) failed to prevent cis-platin induced renal toxicity. Pretreatment with the beta-lyase inactivator aminooxyacetic acid (AOAA, 2 x 100 mg/kg p.o.) and with the renal cysteine conjugate S-oxidase inhibitor methimazole (40 mg/kg i.p.) reduced the number of damaged tubules by approximately 40% and 75%, respectively in mice treated with cis-platin. The results suggest that the platinum-sulfhydryl group complexes formed are taken up by the kidney cells through an organic anion transport mechanism which is probenecid-sensitive. In the cells these complexes are stable for several hours, depending on the intracellular glutathione (GSH) level, and gradually undergo transformation to reactive metabolite(s) by renal intracellular beta-lyase and S-oxidase.

Nephrotoxicity mechanism of 1,1-dichloroethylene in mice.

Male Swiss OF1 mice were administered orally with a single dose (200 mg/kg) of 1,1-dichloroethylene (DCE). Examination of cryostat kidney sections stained for alkaline phosphatase (APP) revealed damage to about 50% of the proximal tubules at 8 h following DCE administration. Pretreatment with the anionic transport inhibitor probenecid by i.p., (0.75 mmol/kg, 30 min prior to and 10 min and 5 h following DCE administration) and with the gamma-glutamyltranspeptidase (GGT) inactivator acivicin by gavage and i.p. (50 mg/kg, 1 h and 30 min prior to DCE administration) failed to prevent DCE-induced renal toxicity. Pretreatment with the beta-lyase inactivator amino-oxyacetic acid (AOAA) by gavage (100 mg/kg, 30 min prior to and 10 min and 5 h following DCE administration), and with the renal cysteine conjugate S-oxidase inhibitor methimazole by i.p. (40 mg/kg, 30 min prior to DCE administration) reduced the number of damaged tubules by approximately 50 and 60%, respectively in mice treated with DCE. The results suggest that the DCE undergoes biotransformation by NADPH-cytochrome P450 to several reactive species which conjugate with glutathione (GSH). After arriving in the kidneys, the resulting conjugates reach the renal cells by a mechanism which depends on neither GGT, nor on an anionic transport system which is sensitive to probenecid. Once in the cells, the presumed GSH conjugates and/or their derivatives undergo secondary modification by beta-lyase and cysteine conjugate S-oxidase to reactive metabolite(s).

TDI inhalation in guinea-pigs involves migration of dendritic cells.

Toluene diisocyanate (TDI) can cause occupational asthma, but the mechanism underlying sensitization to this chemical compound remains controversial. The present study aims to investigate whether tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) liberated in the lungs after TDI inhalation can contribute to the migration of dendritic cells from respiratory airways towards lung associated lymph nodes for presentation of TDI hapten. Exposure was studied in two modes: (1) acute exposure (experiment no. 1, 2 and 3) where animals were exposed to 2.962, 1.060, and 1.076 ppm TDI for 1, 4, and two periods of 4 h, respectively; (2) subacute exposure (experiment no. 4, 5 and 6) where animals were exposed to 0.066, 0.110, and 0.999 ppm TDI for 48 h for the two lower doses and 5 days for the highest dose. Depending on the modes of exposure, two to four post exposure times were selected. After acute exposure to 2.962 ppm TDI for 1 h, the increase in TNF-alpha and IL-6 levels in bronchoalveolar lavage (BAL) fluid was observed immediately at the end of inhalation exposure, whereas the maximum number of dendritic cells and total cells occurred at post exposure times of 48 h and 5 days, respectively. In two other acute exposures, the peak increases in TNF-alpha, IL-6 and total cell numbers were observed at 48 h post exposure time, whereas the peak increase in dendritic cells occurred at 24 h. After subacute exposure to 48 h TDI, where TDI concentrations were relatively low (0.006 or 0.110 ppm), a parallel increase in TNF-alpha and IL-6 levels, dendritic and total cell numbers were observed at 0 h post exposure time. This phenomenon was also apparent at 24 h post exposure time when the animals had been exposed to 1.999 ppm TDI for 5 days. From these results, we can conclude that dendritic cells could play a key role as antigen presenting cells in the development of TDI-induced respiratory sensitization, and that their migration toward lung-associated lymph nodes is probably conditioned by cytokine release in their micro-environment. Future work must delineate whether TNF-alpha and IL-6 are solely responsible for the migration of dendritic cells after TDI inhalation, for example by using antibodies to neutralize these cytokines.

Serum-borne factor(s) of 1,1-dichloroethylene and 1,2-dichlorobenzene-treated mice inhibited in vitro antibody forming cell response and natural killer cell activity.

1,1-Dichloroethylene and 1,2-dichlorobenzene administered to mice produced liver and/or kidney damage which was quantified in this study by a histochemical method. The in vitro effect of sera obtained from these mice on antibody forming cell (AFC) response and natural killer (NK) cell activity was investigated in parallel with the assessment of sera tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) levels. 1,1-Dichloroethylene (100, 150 and 200 mg/kg) provoked liver and kidney damage. Peak kidney damage occurred 16 h after the dose was administered and at 24 h in the case of the liver. During the peak level of liver damage, a serum-borne immunosuppressive effect was also at its highest level. With respect to sera cytokine levels, an increase of TNF-alpha and IL-6 was detected earlier, i.e. 6 h after toxic administration, followed by a decrease that tended toward a baseline level. There was a relationship between the tissue damage induced by 1,1-dichloroethylene and the immunosuppressive effect of mice sera on AFC response and NK cell activity. 1,2-Dichlorobenzene (300, 500 and 600 mg/kg) provoked only liver damage. Peak liver damage severity was observed 48 h after toxic administration, whereas the highest serum-borne immunosuppressive effect was observed almost immediately, i.e. 6 h after administration. As regards sera cytokine levels, only TNF-alpha could be detected 6 h after administering 500 and 600 mg/kg doses of 1,2 dichlorobenzene. There was a relationship between the liver damage induced by 1,2-dichlorobenzene and the immunosuppressive effect of mice sera on the AFC response. In view of the above results, this study suggests that the immunosuppressive effect in sera of mice treated with 1,1-dichloroethylene and 1,2-dichlorobenzene may result from tissue damage, and that the increased levels of TNF-alpha and IL-6 in sera may contribute to this effect. Further studies are needed to clarify the factor(s) responsible, including transforming growth factor-beta1 (TGF-beta1) causing immunosuppression.

Role of SAM-dependent thiol methylation in the renal toxicity of several solvents in mice.

The role of S-adenosylmethionine (SAM)-dependent thiol methylation in the nephrotoxicity of seven industrial solvents was studied in mice. The seven following solvents were utilized: bromobenzene (BB), styrene (STY), tetrachloroethylene (TTCE), trichloroethylene (TCE), 1,1-dichloroethylene (DCE), 1,2-dichloroethane (DCA) and hexachlorobutadiene (HCB). The experimental model comprised mice pretreated with periodate oxidized adenosine (ADOX) (100 micromol kg(-1) i.p.) 30 min before injection of solvents. In the first 4 h after ADOX treatment, the SAM levels were about fourfold higher than controls for the liver and kidney. The S-adenosylhomocysteine (SAH) levels were increased by factors of 11 and 14 and the SAM/SAH ratios were decreased by factors of 3 and 10 for the liver and kidney, respectively. These results show that ADOX treatment probably induces an inhibition of methyltransferase SAM-dependent in the liver and kidney and thus decreases the methylation capabilities. A single oral administration of BB (500 or 800 mg kg(-1)), TTCE (3500 or 4000 mg kg(-1)), TCE (3000 or 3500 mg kg(-1)) or STY (400 or 600 mg kg(-1)) did not induce renal toxicity, evaluated by the percentage of damaged tubules compared to controls. On the other hand, the three solvents DCE, HCB and DCA were nephrotoxic and the percentage of damaged tubules observed for each solvent was significantly different from the value of <1.8% for controls: 19% and 40% for DCE (130 and 200 mg kg(-1)), 50% and 46% for HCB (80 and 100 mg kg(-1)) and 5.1% and 7.6% for DCA (1000 and 1500 mg kg(-1)). The ADOX treatment in the mice did not modify the renal toxicity of the seven solvents. Thus, their renal toxicity, when it existed, was probably independent of the SAM-dependent thiolmethyltransferase activity in the mice. The results of this study are discussed from two viewpoints. The first concerns the general considerations on inhibition of thiol methyltransferase activities in mice and the second is related to the different solvents that are evoked individually.