Subacute acrolein exposure to rat larynx in vivo

Abstract

Objectives/hypothesis: Inhaled pollutants can contact vocal fold tissue and induce detrimental voice changes. Acrolein is a pollutant in cigarette smoke and can also be inhaled during the combustion of fossil fuels, animal fats, and plastics in the environment. However, the vocal fold pathological changes induced by acrolein and the underlying inflammatory pathways are not well understood. These biologic data are needed to understand why voice problems may result from pollutant exposure.

Study design: In vivo prospective design with experimental and control groups.

Methods: Sprague-Dawley male rats (N = 36) were exposed to acrolein (3 ppm) or filtered air (control) through a whole-body exposure system for 5 hours/day, for 5 days/week, over 4 weeks. Histopathological changes, presence of edema, expression of proinflammatory cytokines and markers, and the phosphorylation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) were investigated.

Results: Histological evaluation and quantification demonstrated that subacute acrolein exposure induced significant vocal fold edema. Acrolein exposure also induced epithelial sloughing and cell death. Quantitative polymerase chain reaction showed a significant upregulation of genes encoding interferon regulatory factor and chitinase-3-like protein 3. Western blot revealed a 76.8% increase in phosphorylation of NF-κB P65 after subacute acrolein exposure.

Conclusions: These findings suggest that 4-week exposures to 3 ppm acrolein induce vocal fold inflammation manifested as edema, related to the activation of NF-κB signaling. The edema may underlie the voice changes reported in speakers exposed to pollutants.

Level of evidence: NA Laryngoscope, 129:E313-E317, 2019.

Keywords: Acrolein; edema; inflammation; pollutants; vocal folds; voice problems.

Figure 1.

Representative HE stained image of vocal folds in acrolein and control groups. Left: Vocal folds in acrolein exposure group showed edema. Right: Vocal folds in acrolein exposure group showed epithelial sloughing and epithelial cell death. represents epithelial sloughing and epithelial cell death.

Figure 2.

Index of staining showing the presence of edema after acrolein exposure. The lower the index, the higher the percentage of non-stained area out of total area it represents.

Figure 3.

Expression of mRNAs encoding proteins in proinflammatory reaction using quantitative PCR. Expressions of Irf-5 and Chi3l3 increased following acrolein exposure.

Figure 4.

Increased phosphorylation of NF-κB p65 following acrolein exposure assessed by Western Blot.