Fumio Serita

Acute biological effects of intratracheally instilled titanium dioxide whiskers compared with nonfibrous titanium dioxide and amosite in rats.

The dimensions of man-made mineral fiber whiskers are similar to those of some kinds of asbestos. Thus these mineral fibers raise the concern for potential health hazard for workers exposed in the occupational environments. This study was designed to define acute biological effects of intratracheally administered titanium dioxide whiskers (TO1) compared with nonfibrous titanium dioxide (TOP) and UICC amosite (Ams), and their relations to acute lung inflammation in rats. The observed geometric mean length (microm) and width (microm) and geometric standard deviation are: TO1(2.1[2.0], 0.14[1. 53]); Ams (4.3[3.3], 0.31[1.9]); and TOP (50 nm, 1-2 microm aggregates). Ten-week-old Wistar-Jcl male rats received a single tracheal injection of test materials at doses between 0.05 and 1.0 mg/rat. Control animals were injected with the same volume of saline. Lung tissue and bronchoalveolar lavage (BAL) fluid were collected from rats on days 1, 3, and 7 after administration. In the group injected with TO1, total protein, cytokine-induced neutrophil chemoattractant (CINC)/growth-regulated gene product (GRO), interleukin (IL) 1beta, and tumor necrosis factor (TNF) alpha increased on day 1. Subsequently, total elastolytic activity and fucose levels in BAL increased by day 3. All parameters, except for fucose in BAL, recovered to the normal levels. Animals in the Ams group showed increased total protein and CINC/GRO and decreased total elastolytic activity in a dose-dependent manner on day 1. The fucose level increased on day 3 in the Ams group. All parameters returned to their control levels on day 7. Animals in the TOP group did not show significant changes any of parameters during the experimental period. Gene expression of TNF-alpha and monocyte chemoattractant protein (MCP) 3 in the lung increased dose-dependently in the animals treated with the three materials. The mRNAs for eotaxin and MIP-1alpha were overexpressed in the lung of animals treated with Ams and TO1, while RANTES mRNA was overexpressed dose-dependently in the lung of animals treated with Ams on day 1. Onset of inflammatory response was more rapid in the Ams group than the TO1 group. Recovery of the fucose level in BAL was slower in the TO1 group than in the Ams group, though we observed similar histopathological changes in the lung of animals with TO1 or Ams. We conclude that whisker-induced acute biological effects in the lung may be related to the shape of the whiskers and not to their chemical composition or surface crystal structure, showing biological effects similar to those of UICC amosite.

Inflammatory responses and mucus secretion in rats with acute bronchiolitis induced by nickel chloride.

The effects of inhaled particulate matter in the workplace and outdoor environment on sensitive subpopulations are not sufficiently investigated in human and animal models. Thus, animal models for pulmonary diseases are necessary for appropriate risk assessment of toxic materials. We studied biochemical characteristics of an acute inflammatory process induced by inhalation of nickel chloride aerosols in rats. Acute bronchiolitis was induced by inhalation of nickel chloride aerosols for 5 days in Wistar rats according to the method described by Kyono et al. (1999). Deterioration and recovery from inflammatory responses were evaluated by analyzing markers of inflammation in bronchoalveolar lavage (BAL) fluid. Experimental animals were sacrificed during and after the nickel aerosol exposure period. The number of neutrophils markedly increased to approximately 0.5 × 10 3 cells/µl BAL fluid during nickel aerosol exposure, accompanied by increase of total protein, soluble L-selectin, cytokine-induced neutrophil chemoattractant/growth-regulated gene products (CINC/GRO), elastolytic activity, trypsin inhibitory capacity,β -glucuronidase activity, fucose, and sialic acid in BAL fluid compared with those of the control group. There was correlation between number of leukocytes and soluble L-selectin concentration. The number of pulmonary macrophages in BAL fluid decreased to approximately 15% of those of the control group on the days of nickel aerosol exposure. The level of CINC/GRO recovered to that of the control group on day 3 after cessation of the nickel aerosol exposure. However, other inflammatory markers remained at the elevated levels. Changes in the markers of inflammation during and after the nickel aerosol exposure were consistent with previously reported morphological findings. The results indicated that this animal model is potentially useful as an acute bronchiolitis model.

Effects of surface characteristics of potassium titanate whisker samples on acute lung injury induced by a single intratracheal administration in rats.

We compared in vivo biological effects, focusing on lung inflammatory responses after a single intratracheal administration of two types of well-characterized whiskers: potassium octatitanate and potassium hexatitanate, which have similar fiber sizes and chemical compositions, except their surface morphology. The geometrical mean of length (µm), width (µm), and geometric standard deviation (GSD) are: K 2 Ti 8 O 17 (PT1), 6.0[2.0], 0.35[1.51], having rough surface; K 2 Ti 6 O 13 (PT2), 5.0[2.18], 0.31[1.63], having smooth surface. Sixty male Wistar rats (8 wk old) under anesthesia were injected intratracheally with 2 doses of fibers (0.2 mg/0.5 ml/rat, 1.0 mg/0.5 ml/rat) or the same amount of saline solution (group C). Animals were sacrificed on days 1, 3, and 7 after fiber administration, and then the lung tissue and bronchoalveolar lavage (BAL) were collected. There were no obvious differences among the three groups in the yield of BAL fluid. Total protein concentration in BAL increased significantly from day 1; BAL fucose level increased significantly from day 3 in a dose-dependent manner, which gradually recovered by day 7 in groups PT1 and PT2. BAL total protein and fucose in group PT1 increased significantly compared with those in group PT2 at a dose level of 1.0 mg. A dose-independent increase ofβ -glucuronidase activity and decrease of superoxide dismutase activity were observed in both fibers. BAL tumor necrosis factor-α (TNF-α) increased significantly in animals treated with 1.0 mg dosage of PT1 and PT2 on day 1. However, BAL IL-1β did not show any marked change during the experimental period in animals treated with both fibers. On day 1, BAL cytokine-induced neutrophil attractants (CINC)/growth-related gene product (GRO) increased significantly in the PT1 group treated with 0.2 and 1.0 mg dosage. On day 3, the group treated with 1.0 mg PT1 showed significant increase of CINC/GRO compared with the group treated with 1.0 mg PT2, which recovered to the control level on day 7. Expression of various chemokine mRNAs (MCP-3, MIP-1α, RANTES, and eotaxin) increased in rats treated with PT1 or PT2 on day 1 and/or day 3. Increase of gene expression in the PT1 group was greater than that of the PT2 group at 0.2 mg dosage level. These results suggest that differences in the surface morphology of the whisker fibers of similar length and diameter, density, and chemical composition appear to be related to the facilitation of macrophage phagocytes in the macrophage-derived biological effects in acute lung injury induced by inhaled fibers.