The Effect of Smoking on Clinical Presentation and Expression of TLR-2 and CD34 in Oral Lichen Planus Patients

Clinical and Immunohistochemical Study

Nermine Raouf Amin; Nermin Yussif; Enji Ahmed


BMC Oral Health. 2020;20(129) 

In This Article


In this work, clinical examination revealed that both groups whether smokers or non-smokers showed the classical presentation of OLP and this was confirmed by calculating the mean clinical score values which showed no significant difference between both groups. This is in accordance to Gorsky et al.[23] who showed no difference in the clinical type or symptoms of OLP between smokers and non-smokers. This can be explained by the fact that many of the patients in both groups had reticular type with low clinical score values. Moreover, Gorsky et al.[23] found no statistical association for the atrophic form of OLP with the presence and intensity of symptoms.

This study revealed an insignificant difference in pain score values between smokers and non-smokers. Some of the cases were reticular and smoking may not cause sensitivity of the oral mucosa in reticular OLP. Moreover, smoker patients with atrophic or erosive types tend to decrease the frequency of smoking to reduce irritation caused by heat and out of fear of possible malignant transformation based on previous knowledge about the relation between smoking and oral cancer.

In our results, microscopic examination of TLR-2 immunostained sections revealed positive TLR-2 reaction in normal epithelial cells of the control group. Hill and Diehl[24] declared that, in humans, TLR expression is mainly expressed in immune cells, where it drives immune responses and is less widespread in epithelial cells where it offers a barrier against pathogens.

TLR-2 was expressed in basal cells of normal epithelium. This is in accordance to Ohno et al.[8] who revealed high expression in basal keratinocytes of the normal buccal mucosa. This finding could be explained by Salem et al.[25] who pointed out that the outmost epithelial layers depend on their junctional attachments for defense not needing to express TLRs whereas the deeper basal cells use their TLRs to provide immunologic backup.

OLP patients in this study, whether smokers or non-smokers, expressed TLR − 2 in basal as well as in spinous cell layers. This is in accordance to Ohno et al.[8] who revealed high expression in basal and spinous layers in OLP patients. Salem et al.[25] revealed that the integrity of oral epithelium is disrupted in OLP thus paves the way for pathogen activated molecular patterns (PAMPs) to diffuse into deeper epithelial layers causing irritation to more superficial epithelial layers, so TLR-2 expression in OLP extended from basal to spinous layers to combat the invading allergens. This could also be attributed to the nature of TLRs which are members of PRRs that are triggered, not only by microbial structures, but also during tissue or cell damage as revealed by Takeuchi and Akira.[6] The damaged epithelial cells in OLP recruit inflammatory cells which release cytokines[3] and activate TLRs expression and enhance the inflammatory response.[7]

OLP cases, whether smokers or non-smokers, showed cytoplasmic TLR-2 immunoexpression. Uronen-Hansson et al.[26] declared that TLR-2 is highly expressed in the cytoplasm in a perinuclear region very close to Golgi complex associated with microtubules which serve as transport tracks for TLR-2 vesicles. Statistical analysis of the present results revealed that the mean area percent of TLR-2 immunoexpression in the epithelium of OLP patients whether smokers or not was significantly greater than the control group. This was previously illustrated by Ohno et al.[8] who declared that the number of TLR-2 transcripts was increased in OLP compared to normal gingival tissues as indicated by real time- polymerase chain reaction (RT-PCR) and verified their work immunohstochemically.

The previous finding is supported by Liu et al.[27] who revealed that TLR-2 expression was augmented in OLP by cytokines. These results suggest that TLR-2 may be involved in the pathogenesis of OLP.

Moreover, smoking OLP patients showed significantly greater mean area percent values for TLR-2 immunoexpression in the epithelium compared with non-smoker OLP patients. Johnson et al.[28] supported our findings and explained that tissues exposed to tobacco carcinogens responded by expressing elevated levels of cytokines as part of response to injury. Therefore, we could speculate that smoking resulted in enhanced cytokine release which led to activated TLR-2 inflammatory signaling.

Cytoplasmic CD34 immunoexpression was seen in endothelial cells lining blood vessels in the connective tissue of all groups. In the control group, blood vessels were few and small in size. In the non-smoker OLP group, more blood vessels were seen, appeared elongated and were irregularly distributed. In smoker OLP group, blood vessels were numerous, most of them were rounded and were irregularly distributed. This is in accordance with Klosek et al.[16] who observed few blood vessels in the control group and numerous elongated irregularly distributed blood vessels in the non-smoker OLP group. They also revealed that smoking in OLP increased the number of blood vessels which were small in size.

Mean area percent of CD34 immunoexpression in OLP patients whether smokers or non-smokers was greater than the control group. This was in accordance to Tao et al.[10] whose results documented an increase in the mean vascular density in OLP group compared to control group. Mittal et al.[11] found that the mean vascular density in OLP group stained by CD34 was significantly greater than the control group showing increased angiogenesis in the erosive OLP form compared to the reticular form. The previous results indicated that angiogenesis was closely correlated to OLP lesions.

Smoking in our study enhanced angiogenesis in OLP as confirmed by enhanced CD34 immunoexpression in OLP patients. Klosek et al.[16] previously noted a significant increase in blood vessel density stained by CD34 in smoking OLP patients compared to non-smoker patients. They related their results to the effect of smoking on enhancing the release of pro-inflammatory cytokines.