Erosive oral lichen planus inflicts higher cellular stress than reticular type

Abstract

Background: Lichen planus is a chronic inflammatory mucocutaneous disease which frequently involves the oral mucosa. The most common types of oral lichen planus (OLP) are reticular (asymptomatic) and erosive (ulcerative) with malignant potentiality. The aims of the present study are to assess the cellular stress level in both types of OLP lesions with respect to oxidative stress, DNA damage and inflammation.

Materials and methods: Freshly diagnosed untreated 25 OLP reticular type and 25 OLP erosive (OLP-E) type patients aged 35-55 years were enrolled in the study along with age and sex-matched 25 healthy subjects as control. Tissue antioxidant enzymes were measured biochemically, single-cell DNA damage was measured by comet assay and the molecular markers for inflammation were assessed by using semi-quantitative reverse transcriptase-polymerase chain reaction. Statistical analyses were performed using one-way ANOVA and Tukey's post hoc test.

Results: Oxidative stress was significantly greater in OLP-E type compared to the reticular. mRNA expression of cyclooxygenase-2 was significantly elevated (P < 0.0001) in erosive form, but such expression of nuclear factor kappa beta, tumor necrosis factor-alpha, Interleukin-6 and inducible nitric oxide synthase did not significantly differ between the two disease groups. Comet assay revealed a higher degree of DNA strand breakage in erosive lesions.

Conclusions: The unhandled free radicals may imbalance the homeostatic network toward pro-inflammatory, DNA damaging responses, creating a vicious cell-damaging spree resulting in stress. Molecular analyses showed that erosive lichen planus is more under stress than the reticular form.

Keywords: DNA damage; inflammation; oral lichen planus; oxidative stress.

Figure 1

Comet assay image shows DNA damage pattern of oral lichen planus lesions and healthy individuals. Comet length (μm) and tail length in OLP reticular and OLP erosive patients have been compared with healthy individuals; the standard deviation is shown for each bar graph. (C: Control)

Figure 2

Reverse transcriptase–polymerase chain reaction results shows mRNA expression of nuclear factor kappa beta, tumor necrosis factor-alpha, interlukin-6, cyclooxygenase-2 and inducible nitric oxide synthase in control, OLP reticular and OLP erosive, the standard deviation is shown for each bar diagram. (C: Control)