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Respiratory sensitisation

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Administrative data

Endpoint:
respiratory sensitisation: in vivo
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Cross-reference
Reason / purpose:
read-across: supporting information
Reference
Endpoint:
respiratory sensitisation, other
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Justification for type of information:
The read across justification document is attached in teh section 13.2.
Reason / purpose:
read-across source
Specific details on test material used for the study:
Trimellitic anhydride-chloride (TMAC)
CAS 1204-28-0
Interpretation of results:
Category 1 (respiratory sensitising) based on GHS criteria

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2002
Report Date:
2002

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
This protocol uses both sensitization and challenge by the inhalation route. The Brown Norway (BN) rat model is used in the present study to examine specific airway reactivity following sensitization by the respiratory tract route.
Respiratory sensitization (dose dependent TMA-specific IgE, pulmonary inflammatory, histopathology) and airway responses (early phase airway response (EAR) and late-phase airway response (LAR)) to repeated inhalation challenge with TMA-aerosol atmospheres were examined in the Brown Norway rat model. I

Rats were exposed to 0.04, 0.4, 4, or 40 mg/m3 TMA aerosol for 10 min, once a week, over 10 weeks.
All lower exposures were, subsequently, rechallenged to 40 mg/m3 TMA aerosol.
All rats received a sham exposure 1 week prior to the first TMA exposure.
Following the sham exposure and weekly after each TMA exposure, TMA-specific IgE and both early-phase airway response (EAR) and late-phase airway response (LAR) were measured using enhanced pause (Penh).
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Specific details on test material used for the study:
Trimellitic anhydride
CAS 552-30-7

Test animals

Species:
rat
Strain:
Brown Norway
Sex:
female
Details on test animals and environmental conditions:
- Female, inbred BN rats (150–175 g) from Charles River Laboratories (Wilmington, MA).
- Rats obtained from rooms free of ‘‘rat respiratory virus’’ and other specific pathogens.
- Animals were housed in a facility accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International
- Rats were fed Purina rat chow, and water ad libitum
- Rats kept on a standard 12:12 light:dark cycle.
- Rats were acclimated in the facility for 1 week prior to use.

Test system

Route of induction exposure:
inhalation
Route of challenge exposure:
inhalation
Vehicle:
unchanged (no vehicle)
Concentration:
40, 4, 0.4, and 0.04 mg/m3
No. of animals per dose:
4 groups: 8 animals per group for the two higher doses and 4 animals per group for the two lower doses
Details on study design:
The rats were placed in the nose-only exposure chamber at concentrations of 40, 4, 0.4, and 0.04 mg/m3, respectively, starting on day 0 and every 7 days, thereafter, for 10 weeks (exposure/challenge = 1 x per week).

All rats, except for the 40 mg/m3 TMA group, were rechallenged with 40 mg/m3 of TMA aerosol, for 10 min (in the nose-only chamber), 2 weeks after the final inhalation exposure to TMA.
Chamber concentrations were measured using a real-time, continuous dust monitor and gravimetrically using a 0.45-lm, 37-mm HAWP filter.
Rats were immediately moved to whole-body plethysmograph chambers after 10 min of TMA exposure, to monitor enhanced pause (Penh), for 12–20 h. Normal Penh values (used as control) from all rats were also recorded before the day 0 TMA inhalation exposure.
Indices were recorded every 30 s. Arithmetic means of peak values from every 30 min for the first hour and every 1 h after that were used to quantify the responses. Penh area under the curve (AUC) was also determined, as well as starting point, ending point, and duration of the LAR.
EAR (earlyphase airway response) is an increase in Penh >= 0.9 (3 SDs above the mean peak Penh value) that is apparent within 30 min of challenge and is usually resolved by 1 h.
LAR (late-phase airway response) manifests 2–4 h postchallenge as an increase in Penh > 0.9 and last for several hours.

At the end of each experiment, approximately 24 h following airway challenge, rats were euthanized and bronchoalveolar lavage fluid (BALF) obtained. BALF was used for eosinophil enumeration using a Coulter Multisizer for total cell count per milliliter and microscopic differential analysis (total cell count/ml 3 percent eosinophils).
Lungs were excised, perfused, and fixed for the preparation of stained slides.
Lung sections from the left lung lobes were histopathologically examined. The severity (intensity) and distribution (extent) of changes are each evaluated with a range of 0 (none) to 5 (greatest involvement) producing a cumulative histopathology score with a potential range of 0–10 (as described by Hubbs, Hubbs et al., 1997).
Positive control substance(s):
none
Negative control substance(s):
other: Normal Penh values from all rats were recorded before the day 0 TMA inhalation exposure and were used as control.

Results and discussion

Results:
> Specific IgE to TMA:
TMA-specific IgE was detected by day 7 in the 40 and 4 mg/m3 TMA exposure groups.
Only 1/4 rats had measurable specific IgE in the group exposed to 0.4 mg/m3 of TMA, and no specific IgE was detectable in rats from the lower exposure groups (0.04 mg/m3).

> Airway Responses after Inhalation Exposure and Final Challenge with TMA:
On day 14, 6/8 of the rats challenged with 40 mg/m3 TMA developed both EAR and LAR; however, these responses were inconsistent from week to week from each animal.
No significant respiratory changes were noted in groups before and after exposure to lower concentrations of TMA over the 10 weekly exposures.

On day 77, all the lower exposure groups were challenged with 40 mg/m3 TMA for 10 min.
All eight rats from the 4 mg/m3 TMA group and only one rat from the 0.4 mg/m3 TMA group responded with both EAR and LAR to the challenge. No airway responses were noted in
the rats from the 0.04 mg/m3 TMA group following the 40 mg/m3 TMA challenge.
The AUC of the LAR from the 4 mg/m3 TMA group challenged with 40 mg/m3 was 1120 ± 134 (the highest LAR AUC noted from each animal exposed over 10 weeks to 40 mg/m3 was 592 ± 89): the repeated high-dose exposure produced a weaker LAR than the lower dose sensitization—high-dose challenge protocol. There was no increasing or decreasing Penh AUC of the LAR with repeated exposure observed in the high dose group and, in fact, LAR Penh was inconsistently manifested following challenges in this group.
Pathologic findings: Eosinophils, but not neutrophils, were found in the lavage of animals that were sensitized with and responded to TMA challenge.
Rats exposed to 4 mg/m3 TMA (and challenged to 40 mg/m3 TMA) had significantly higher percentage of eosinophils, than that in rats exposed to 40 mg/m3 of TMA.
The total BALF eosinophils recovered was not statistically different. Lower total BALF cells in this group may be due to inflammatory changes such as activated ‘‘sticky’’ macrophages causing poor recovery of these cells.

The principal histopathologic changes in the lungs of TMA exposed rats were eosinophilic granulomatous interstitial pneumonia, eosinophil perivascular infiltrates, peribronchiolar
plasma cell infiltrates, and hyperplasia of bronchus-associated lymphoid tissue (BALT). Some rats demonstrated airway epithelial cell hypertrophy consistent with mucous metaplasia. However, the consistent and predominant histopathologic alterations in this study were not in the airways but instead were localized to the deep lung. Eosinophilic granulomatous interstitial pneumonia was characterized by interstitial infiltration by histiocytic macrophages and eosinophils. Lesser numbers of giant cells, neutrophils, and lymphocytes
contributed to the interstitial inflammation in some lungs.
Frequently, the interstitium between foci of intense inflammation was involved but to a lesser extent. At 0.4 mg/m3 TMA, two of the four rats had eosinophilic granulomatous interstitial pneumonia. All rats inhaling 4 or 40 mg/m3 had eosinophilic granulomatous interstitial pneumonia, although the severity of the response was slightly, but not significantly, reduced in rats inhaling 40 mg/m3. The pathology scores for eosinophilic granulomatous interstitial pneumonia in rats inhaling 40 mg/m3 were significantly higher than in rats inhaling 0.4 mg/m3. Perivascular eosinophils were frequently observed in TMA exposed rats and may represent vascular eosinophils migrating to the inflamed parenchyma. Peribronchiolar infiltrates of plasma cells were seen adjacent to occasional small bronchioles in all rats inhaling 40 mg/m3 and two rats inhaling 4 mg/m3. The pathology scores for these plasma cell
infiltrates were significantly greater in rats inhaling 40 mg/m3 TMA than in rats inhaling 4 or 0.4 mg/m3 TMA. These plasma cell infiltrates are unusual in the rat lung. Other evidence of antigenic stimulation seen in this study included hyperplasia of BALT. Hyperplasia of BALT was observed in all rats exposed to TMA but did not demonstrate a dose-response relationship. Eosinophilic granulomatous interstitial pneumonia, eosinophil perivascular infiltrates, peribronchiolar plasma cell infiltrates, and hyperplasia of BALT were present in TMA-exposed rats but not observed in the two controls.

Applicant's summary and conclusion

Interpretation of results:
Category 1 (respiratory sensitising) based on GHS criteria
Conclusions:
An in vivo study conducted on Brown Norway rats exposed to TMA aerosol was conducted. Inhalation exposure to TMA aerosol induces the production of measurable specific IgE following a single exposure (specific IgE noted in serum prior to second 40 mg/m3 exposure), a specific airway reactivity (Penh, EAR, and LAR), pulmonary allergic inflammatory pathology and an attenuated specific IgE response with repeated high-dose aerosol exposure.
Based on these findings, the substance is considered to induce allergic pathology by inhalation.
Executive summary:

Dosed dependent TMA-specific IgE, histopathology, and airway responses after sensitization by inhalation were examined in the Brown Norway rat. Rats were exposed to 0.04, 0.4, 4, or 40 mg/m3 TMA aerosol for 10 min, once a week, over 10 weeks.

All lower exposures were, subsequently, rechallenged to 40 mg/m3 TMA aerosol.

All rats received a sham exposure 1 week prior to the first TMA exposure. Following the sham exposure and weekly after each TMA exposure, TMA-specific IgE and both early-phase airway response (EAR) and late-phase airway response (LAR) were measured using enhanced pause (Penh).

All rats sensitized by 40 mg/m3 TMA developed specific IgE, EAR, and LAR to one or more of the challenges to 40 mg/m3 TMA. TMA of 4 mg/m3 induced a much lower, but stable, specific IgE response. EAR and LAR were observed only after a 40 mg/m3 TMA rechallenge in this group, but it was much larger than that observed in the 40 mg/m3 TMA-sensitized and challenged group. Exposure-dependent histopathological changes noted included eosinophilic granulomatous interstitial pneumonia, perivascular eosinophil infiltrates, bronchial-associated lymphoid tissue hyperplasia, and peribronchiolar plasma cell infiltrates.