Furfuryl alcohol

Respiratory sensitisation

Administrative data

Endpoint:

respiratory sensitisation: in vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: GLP status not reported. Well documented and meets good scientific principles although this is not a validated assay. Pre-publication for inclusion in peer reviewed literature. Fully adequate for assessment.

Data source

Reference

Reference Type:

publication

Title:

Evaluation of furfuryl alcohol sensitisation potential following dermal and pulmonary exposure: Enhancement of airway responsiveness

Author:

Franko J et al

Year:

2012

Bibliographic source:

Toxicol. Sci. (2012) 125 (1): 105-115

Materials and methods

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

An assessment of sensitsation potential and enhanced airway responsiveness following pulmonary exposure, and also dermal exposure prior to pulmonary exposure

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Furfuryl alcohol

EC Number:

202-626-1

EC Name:

Furfuryl alcohol

Cas Number:

98-00-0

Molecular formula:

C5H6O2

IUPAC Name:

(furan-2-yl)methanol

Details on test material:

- Name of test material (as cited in study report): Furfuryl alcohol
- Other: No further details reported

Test animals

Species:

mouse

Strain:

Balb/c

Sex:

female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Taconic Farms (German, NY)
- Age: Purchased at 6-8 weeks
- Weight at study initiation:
- Housing: 5 per cage in ventilated plastic shoebox cages with hardwood chip bedding
- Diet (e.g. ad libitum): Ad libitum, NIH-31 modified 6% irradiated
rodent diet (Harlan Teklad)
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: 5 days minimum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 22.2°C (68 to 72° F)
- Humidity (%): 36 to 57%
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light): 12 hour cycle

IN-LIFE DATES: Not detailed

Test system

Route of induction exposure:

other: Inhalation and dermal/inhalation (the latter to investigate whether prior dermal exposure to furfuryl alcohol is capable of enhancing pulmonary responses)

Route of challenge exposure:

other: pharyngeal aspiration

Vehicle:

other: phosphate buffered saline, for pulmonary exposure. The dermal applications used acetone as the vehicle

Concentration:

0.5, 1 or 2% solution for pulmonary tests. Studies with prior dermal exposure tested 25, 50 and 75% dermally.

No. of animals per dose:

5 per dose for the pulmonary assessment alone. 7 per dose for the studies investigating whether prior dermal exposure to furfuryl alcohol is capable of enhancing pulmonary responses.

Details on study design:

RANGE FINDING TESTS: Mice were lightly anesthesized with isoflurane (Abbot Laboratories, 99.9%) and exposed to furfuryl alcohol (0.5% to 10%) or vehicle (phosphate buffered saline, PBS) by pharyngeal aspiration, using the method described by Rao et al., (2003) once every fourth day for a total of 4 doses. Systemic toxicity was evaluated by clinical observation (morbidity or extensive irritation) and changes in body weight. The maximum pulmonary dose tolerated was 2%; animals exposed to higher concentrations showed lethargy, weight loss and had ruffled fur.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 8 doses
- Exposure period and frequency of applications: For studies investigating the effects of pulmonary exposure alone: mice (5 per group) mice were lightly anesthesized with isoflurane and exposed every fourth day for 3 weeks for a total of 8 doses.
For the studies investigating whether prior dermal exposure to furfuryl alcohol is capable of enhancing pulmonary responses: mice (7 per group) were sensitized on the dorsal surface of both ears with 25 µl/ear of acetone vehicle control or increasing concentrations of furfuryl alcohol (25, 50 or 75%) on days 1-4 of the experiment.
- Test groups: Group size of 5 or 7 as above
- Control group: phosphate buffered saline, PBS
- Site: Pharyngeal aspiration using the method previous described by Rao et al, 2003
- Duration: 8 doses in total
- Concentrations: 50 µl of 0.5, 1 or 2% solution for pulmonary tests. Studies with prior dermal exposure tested 25, 50 and 75%.

B. CHALLENGE EXPOSURE
- No. of exposures: A total of 4 aspirations.
- Day(s) of challenge: Days 5, 9, 13 and 17
- Exposure period: Not specified
- Concentrations: 2% furfuryl alcohol via pharyngeal aspiration
- Evaluation (hr after challenge): 24 hours after challenge an airway hyperreactivity assessment was done- airway responsiveness was assessed by measuring changes in airway function following challenge with aerosolized methacholine chloride (MCH) (using the Buxco unrestrained whole body plethysmography system). An initial 5 min baseline PenH reading was taken, then animals were challenged with aerosolized MCH (10, 25 and 50 mg/ml in PBS). At each concentration of MCH, average PenH values were collected every 30 sec for 5 min. MCH exposure occurred for the first 3 min of the 5 min period, in the final 2 minutes mice were exposed to fresh air alone. Average PenH values for each 5 min period were plotted vs. the MCH concentration and used as a measure of airway responsiveness.

OTHER: 1. Bronchial alveolar lavage-cellular infiltrate phenotyping was done 24 hours after airway challenge. 2. Ex-vivo analysis of cytokine production from lung associated draining lymph nodes was done. 3. Following the phenotypic analysis assays, total serum IGE was investigated. 4. Lungs from dermally exposed mice (test and control) and then subsequently challenged by pulmonary aspiration were insulfated with 10% formalin and collected for histopathology. Lung tissue was embedded in paraffin, sectioned at 5 microns, and stained with hematoxylin and eosin, Alcian Blue/PAS, Masons trichrome and Sirius Red. Lungs from 2 mice per sensitisation and challenge combination were evaluated for changes.

Challenge controls:

Phosphate buffered saline control group

Positive control substance(s):

none

Negative control substance(s):

none

Results and discussion

Results:

Pulmonary exposure to 8 doses pulmonary exposure to 0.5% furfuryl alcohol had little effect on airway responsiveness; however exposure to 1 and 2% furfuryl alcohol significantly enhanced airway responsiveness (AHR) to aerosolized MCH over control values.
Prior dermal exposure to furfuryl alcohol: In mice receiving prior topical treatment (50%-75%) and then subsequently challenged (2%; 4 doses) with furfuryl alcohol statistically significant enhancements of AHR was detected in comparison to the vehicle control mice, as well as in comparison to mice that received only pulmonary exposure to 2% furfuryl alcohol.

Positive control results:

No positive control group, vehicle control only.

Negative control results:

No negative control group, vehicle control only. Increasing concentrations of MCH increased AHR in the vehicle control group.

Any other information on results incl. tables

Table 1

Airway hyperreactivity following furfuryl alcohol exposure

 

Pulmonary exposure only (n=5)

 

Furfuryl alcohol concentration %	MCH concentration mg/ml
	0	10	25	50
0	0.9+0.02	1.4+0.13	2.0+0.08	3.3+0.33
0.5	1.1+0.04	1.7+0.11	2.5+0.29	4.5+0.02
1	1.1+0.03	1.8+0.20	3.1+0.34	5.9+0.72*
2	1.5+0.19	3.2+0.28*	7.2+2.36*

 * p ≤ 0.01 as compared to the vehicle control

 

Table 2

Dermal exposure followed by 2% furfuryl alcohol via pharyngeal aspiration

 

Furfuryl alcohol concentration % (pulmonary + prior dermal)	MCH concentration mg/ml
	0	10	25
0	1.1+0.05	1.6+0.04	3.0+0.49
2 + 0	1.3+0.09	2.5+0.39	5.5+1.7
2 + 25	1.5+0.09	3.6+1.0	10.8+2.8
2 + 50	1.2+0.04	5.1+0.97	12.6+3.1*^a
2 + 75	2.3+0.38	6.8+2.0*^a	13.6+2.6*^a

 

^ap ≤ 0.01) as compared to the 2% furfuryl alcohol pulmonary exposure control (2%+0%). The absolute number of eosinophils in the BAL fluid of mice exposed to 2% furfuryl alcohol was significantly enhanced in comparison to vehicle controls. A small, but not statistically significant increase in the number of eosinophils isolated from the BAL fluid was seen in the 1% exposure group. Serum IgE levels were increased (approximately 3 fold) in mice exposed to 2% furfuryl alcohol. Pulmonary exposure to furfuryl alcohol had no effect on the total number of neutrophils present in BAL fluid. No changes in organ or body weights were observed in these animals (data not reported).

Statistically significant increases in cytokine production (IL-4, IL-5 and IFN-gamma) was seen following pulmonary exposure to 2% furfuryl alcohol

compared to the vehicle control mice.

Prior dermal exposure to furfuryl alcohol: Eosinophilic infiltration in BAL fluid was also increased in mice that received furfuryl alcohol via dermal and pulmonary routes compared to the vehicle control or those that received only pulmonary exposures. Serum IgE levels were also statistically elevated in the mice exposed via dermal and pulmonary routes compared to vehicle control. Prior dermal exposure to furfuryl alcohol increased the number of neutrophils in the BAL fluid as compared to both vehicle control mice and mice exposed to 2% furfuryl alcohol alone but this was not statistically significant.

Histopathology: Aspiration with furfuryl alcohol (2%; 4 doses) produced consistent changes at the bronchioloalveolar junction of the lung. These changes include multifocal histiocytic to histiocytic and eosinophilic to eosinophilic and neutrophilic bronchointerstitial pneumonia with bronchiolar and alveolar epithelial hypertrophy and hyperplasia. Also, bronchiolar epithelial disorganization and mucous metaplasia were seen. Control mice had no bronchointerstital pneumonia or airway epithelial changes. Prior dermal exposure to furfuryl alcohol was shown to further enhance these responses. However, the authors recognise that it cannot definitively be stated that the pulmonary responses identified were not due to an irritant effect because the effect of a single pulmonary exposure to furfuryl alcohol was not investigated.

Applicant's summary and conclusion

Interpretation of results:

other: Inconclusive

Conclusions:

Furfuryl alcohol may have some potential to cause respiratory allergy in a murine model.

Executive summary:

The authors report pulmonary exposure to 2% furfuryl alcohol resulted in enhanced airway hyperreactivity, eosinophilic infiltration into the lungs, and enhanced cytokine production (IL-4, IL-5 and IFN-gamma) by ex vivo stimulated lung-associated draining lymphoid cells. Airway hyperreactivity and eosinophilic lung infiltration were augmented by prior dermal exposure to furfuryl alcohol. The authors conclude exposure to furfuryl alcohol induced sensitisation following pulmonary, or dermal then pulmonary exposure, in a murine model.

Kimber et al., 2011 proposed that topical exposure to chemical respiratory allergens, but not to contact allergens, induces in mice increases in the total serum concentration of IgE in mice. Although this is not a validated method it is believed by some to be indicative of respiratory sensitising potential.

Whilst the ability of high concentrations of furfuryl alcohol to provoke an increase in total concentrations of IgE can be viewed as suggestive of respiratory sensitising potential, these data cannot be considered conclusive, and it should be acknowledged that in an international trial of this endpoint (the Mouse IgE Test) some significant inter-laboratory variation in results was noted (Dearman et al., 1998).

Franko et al also describe airway hyperreactivity (AHR) following pulmonary exposure of mice to furfuryl alcohol, either with or without prior dermal exposure to the same chemical. The fact that AHR in response to pulmonary challenge was more pronounced following previous dermal contact is suggestive of allergic sensitisation. However, as the investigators themselves acknowledge, it is not possible to exclude the possibility that airway changes result from irritant effects rather than from allergic hypersensitivity.

Although the results of the Franko et al (2012) study are suggestive of the possibility that furfuryl alcohol may have some potential to cause respiratory allergy, the data are not conclusive. In the absence of any other evidence implicating furfuryl alcohol as a respiratory allergen it would be premature to classify this chemical as a respiratory sensitiser.