Protective effect of aerobic exercise on the vocal folds against cigarette smoke exposure

Histological Effect of Emodin on Acute Vocal Fold Injury in a Rat Model

OBJECTIVES

Emodin has beneficial effects on wound healing and reduces excessive fibrosis during tissue regeneration. Its positive effects on the wound-healing process were demonstrated on human fibroblasts. The aim of the present study was to evaluate the effectiveness of emodin application on acute vocal fold injury.

MATERIALS AND METHODS

Twenty-four Wistar albino rats were divided into three groups: control, sham, and emodin group. The glottis was examined using a 30°-2.7 mm diameter telescope, and vocal folds was unilaterally wounded by a microscissor through the entire layer of the lamina propria down to the vocalis muscle. While no procedure(no acute injury of the vocal fold or an injection of saline/emodin) was applied to the control group, 0.5 cc of saline was injected into the sham group and 0.5 cc of emodin in the emodin group, just lateral to the vocal folds, with 27 gauge injectors. Animals were sacrificed on the 21st day after the procedure. After excised larynx experiments, serial sections were prepared from the vocal fold. Hematoxylin eosin and immunohistochemical staining were performed and fibroblast density, lamina propria thickness, and vessel formation were graded from 0 (none) to 3 (severe reaction). Transforming growth factor-beta 1 (TGF-β1) and matrix metalloproteinase-9 (MMP-9) staining was used for immunohistochemical examinations. Four-point scoring scale for intensity being scored as 0 (no staining) to 3 (severeley stained) to quantify immonuhistochemical reaction. This scoring system was applied to vocal fold epithelium, lamina propria, vessel wall, and vocalis muscle tissues. The groups were compared with the Kruskal Wallis and Dunn tests.

RESULTS

Histologically, there was no significant difference (P > 0.05) between the sham group and the emodin group in terms of fibroblast density, vessel formation, and lamina propria thickness. These parameters were higher (P < 0.05) in both groups compared to the control group. In the lamina propria and vessel wall, MMP-9 staining was more intense in the emodin group than in the sham group. TGF-β1 staining of lamina propria, epithelial tissue, and vocalis muscle was significantly more intense in the emodin group than in the other groups.

CONCLUSION

Emodin induced MMP-9 and TGF-1 staining in the vocalis muscle and epithelium, as well as TGF-1 staining in the lamina propria. In terms of fibroblast density, new vascular creation, and LP thickness in acute vocal fold damage, there was no difference between saline administration and emodin injection. It may increase fibroblast activation in the acute phase of wound healing, but its long-term effects should be further investigated.

Polycyclic Aromatic Hydrocarbons from Fine Particulate Matter Induce Oxidative Stress and the Inflammatory Response in Human Vocal Fold Fibroblast Cells

Polycyclic aromatic hydrocarbons (PAHs) are toxicants in particulate matter (PM). The vocal fold, part of the larynx and a key structure for voicing, is always in contact with air. In recent epidemic studies, PM was shown to cause laryngitis; however, the basic mechanism has not been evaluated. In the present study, intracellular reactive oxygen species (ROS) and proinflammatory cytokine levels were analyzed after exposing human vocal fold fibroblasts (hVFFs) to PM standard reference material (SRM 2786). Expression levels of the aryl hydrocarbon receptor (AhR) and Cytochrome P450 Family 1 Subfamily A Member 1 (CYP1A1) were also evaluated. PM induced ROS formation and proinflammatory cytokines via the AhR CYP1A1 pathway and caused lipid peroxidation and DNA damage. Blocking AhR or CYP1A1 production using siRNAs significantly decreased ROS production and IL-6 and IL-9 expression in PM-exposed hVFFs, thus protecting the cells against oxidative stress. These results confirm that PAHs in PM play an important role in cell damage and inflammation, confirming a basic pathophysiologic relationship between PM exposure and laryngitis.