Regulation of immune cells in oral lichen planus

CD8+ tissue-resident memory T cells induce oral lichen planus erosion via cytokine network

CD8+ tissue-resident memory T (CD8+ Trm) cells play key roles in many immune-inflammation-related diseases. However, their characteristics in the pathological process of oral lichen planus (OLP) remains unclear. Therefore, we investigated the function of CD8+ Trm cells in the process of OLP. By using single-cell RNA sequencing profiling and spatial transcriptomics, we revealed that CD8+ Trm cells were predominantly located in the lamina propria adjacent to the basement membrane and were significantly increased in patients with erosive oral lichen planus (EOLP) compared to those with non-erosive oral lichen planus (NEOLP). Furthermore, these cells displayed enhanced cytokine production, including IFN-γ (Interferon-gamma, a pro-inflammatory signaling molecule), TNF-α (Tumor Necrosis Factor-alpha, a cytokine regulating inflammation), and IL-17 (Interleukin-17, a cytokine involved in immune response modulation), in patients with EOLP. And our clinical cohort of 1-year follow-up was also supported the above results in RNA level and protein level. In conclusion, our study provided a novel molecular mechanism for triggering OLP erosion by CD8+ Trm cells to secrete multiple cytokines, and new insight into the pathological development of OLP.

The potential roles of Th17 cells in the pathogenesis of oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is a T cell-mediated chronic autoimmune disease, whose pathogenesis and etiology are not entirely understood. OLP is characterized by subepithelial lymphocyte infiltration and elevated intra-epithelial lymphocytes. The majority of lamina propria lymphocytes are CD4⁺ T cells. CD4⁺ helper T (Th) cells play a crucial role in activating CD8⁺ cytotoxic T cells (CTLs) through interactions and cytokine production. Th1 and Th2 cells are well-accepted to be associated with OLP pathogenesis. However, OLP treatment is challenging yet, the more information we have about the pathology of OLP, the easier it will be treated. With the discovery of Th17 cells in recent years and the demonstration of their role in autoimmune disease, many researchers started to investigate the role of Th17 in the pathogenesis of OLP.

METHODS

To make up this review, studies covering the role of TH17 in different types of lichen planus were selected from major databases.

RESULTS

As we review in this article, Th17 cells and their signature cytokines play an important role in OLP pathogenesis. As well, utilizing some anti-IL-17 antibodies showed promising results in improving the disease; however, more studies are still needed to better understand and treat OLP.

Aberrant Activation of the STING-TBK1 Pathway in γδ T Cells Regulates Immune Responses in Oral Lichen Planus

Oral lichen planus (OLP) is a chronic T cell-mediated inflammatory disease. Interferon (IFN)-γ has been suggested to be vital for the OLP immune responses. A prominent innate-like lymphocyte subset, γδ T cells, span the innate-adaptive continuum and exert immune effector functions by producing a wide spectrum of cytokines, including IFN-γ. The involvement and mechanisms of γδ T cells in the pathogenesis of OLP remain obscure. The expression of γδ T cells in lesion tissues and in the peripheral blood of OLP patients was determined via flow cytometry and immunohistochemistry, respectively. Human leukocyte antigen-DR (HLA-DR), cluster of differentiation (CD) 69, Toll-like receptors (TLRs), natural killer group 2, member D (NKG2D) and IFN-γ were detected in γδ T cells of OLP patients using flow cytometry. Additionally, the involvement of stimulator of the interferon genes (STING)-TANK-binding kinase 1 (TBK1) pathway in γδ T cells was evaluated by multi-color immunofluorescence. Western blotting was employed to investigate the regulatory mechanisms of γδ T cells in OLP. γδ T cells were significantly upregulated in the lesion tissues, whereas their peripheral counterparts were downregulated in OLP patients. Meanwhile, increased frequencies of local CD69⁺ and NKG2D⁺ γδ T cells and peripheral HLA-DR⁺ and TLR4⁺ γδ T cells were detected in OLP. Furthermore, significant co-localization of STING and TBK1 was observed in the γδ T cells of OLP lesions. In addition, enhanced IFN-γ and interleukin (IL)-17A were positively associated with the activated STING-TBK1 pathway and γδ T cells in OLP. Taken together, the upregulated STING-TBK1 pathway in activated γδ T cells might participate in the regulation of immune responses in OLP.

Tobacco Use and Oral Health

This review outlines the important oral implications of tobacco use. The lining of the mouth (oral mucosa), if exposed to tobacco and its products in a susceptible individual, can develop benign, potentially malignant, and malignant tumours. Treatment and prognosis depend on tumour type, how early it is detected, its size and site in the oral cavity and whether it has spread. Advanced oral squamous cell carcinoma (OSCC) has a 20% 5-year survival rate. Tobacco use also increases the risk of periodontitis, peri-implantitis, caries, alveolar osteitis and halitosis. Although less life threatening than OSCC, these tobacco related conditions create a substantial financial and health burden for individuals and society. Dental practitioners routinely examine the oral cavity for signs of mucosal and tooth changes, are experienced in recognising variations from normal and have established management and referral pathways. They are also ideally positioned to provide brief interventions to assist their patients to quit smoking.

Interferon-γ activated T-cell IRGM-autophagy axis in oral lichen planus

Oral lichen planus (OLP) is an inflammatory immune disease featured by dense T-cell infiltrate and basal keratinocytes degeneration. Immunity related GTPase M (IRGM) is vital for the induction of autophagy. Our previous studies have demonstrated aberrant autophagy in OLP, however, the involvement of IRGM-autophagy axis in OLP has not yet been revealed. The expression of IRGM and autophagy activity were evaluated in oral mucosal tissues and peripheral T cells of OLP patients and healthy controls, respectively. We found significant upregulation of IRGM and LC3B in lesions of patients with OLP as compared with healthy donors. IRGM, LC3B and NOD2 levels were also elevated in the peripheral T cells of OLP. Then, knockdown of IRGM after electrotransfection with siRNA resulted in attenuated autophagy, growth inhibition, and apoptosis of T cells. In addition, preincubation with IFN-γ promoted the expression of IRGM mRNA and induced autophagy in T cells. Furthermore, IFN-γ decreased the proliferation and apoptosis of T cells, whereas facilitated the viability of keratinocytes in a co-culture system of activated T cells and keratinocytes. Taken together, activated IRGM-autophagy axis under IFN-γ regulation in T cells might participate in the immunoregulatory mechanism of OLP.

Expression profile of DNA repair proteins and histone H3 lys-9 acetylation in cutaneous and oral lichen planus

OBJECTIVES

To analyze the expression profile of DNA repair proteins (XRCC1 and APE1) and histone acetylation (H3K9) in oral and cutaneous lichen planus, in order to investigate potential biological markers that can clarify pathogenesis of these lesions.

DESIGN AND RESULTS

The total sample consisted of 89 lichen planus cases (66 oral and 23 cutaneous). Analysis of APE1 and XRCC1 expression was performed by immunohistochemistry in 44 oral and 20 cutaneous lichen planus, whereas the analysis of H3K9 acetylation was performed by immunofluorescence in 42 oral and 11 cutaneous lichen planus.

RESULTS

Immunoreactivity for APE1 and XRCC1 was significantly higher in cutaneous lichen planus than in oral lichen planus (P = 0.003 and P = 0.034, respectively). There was a significant and moderate positive correlation between APE1 and XRCC1 in the oral group (Rho = 0.544; P < 0.0001). In oral cases, there were no statistically significant results comparing APE1 and XRCC1 expression between reticular and erosive cases (P > 0.05). Evaluation of H9K3 histone acetylation levels did not reveal significant results comparing oral to cutaneous lichen planus, neither comparing erosive to reticular (P > 0.05).

CONCLUSIONS

Changes in the expression profile of the DNA repair proteins exerted greater influence in pathogenesis of cutaneous lichen planus than oral lichen planus, in addition, H3K9 histone acetylation is an epigenetic event found in both lesions.

Increased Serum Level and High Tissue Immunoexpression of Interleukin 17 in Cutaneous Lichen Planus: A Novel Therapeutic Target for Recalcitrant Cases?

Background

Interleukin-17 is supposed to play an important role in the pathogenesis of oral lichen planus (OLP). However, there is scarce data in the literature on its significance in the cutaneous variant of the disease.

Objectives

To determine the serum level and tissue immunoexpression of IL-17 in cutaneous lichen planus (CLP).

Methods

Fifty-two adult patients with CLP, without any significant autoimmune or inflammatory conditions, were included in the first part of the study. The control group consisted of 27 age- and sex-matched healthy volunteers. Serum concentration of IL-17 was quantified using enzyme-linked immunosorbent assay (ELISA) kit. In the second part of the study, the tissue expression of IL-17 was assessed in archival paraffin-embedded biopsy specimens from CLP (n = 14) against normal control tissues (n = 11) using immunohistochemical assays. The expression was evaluated using Zeiss Axio Imager A2 light microscope. Positively stained cells were counted in 10 fields of view for biopsy specimen at 200x magnification, and the mean value was calculated.

Results

The serum level of IL-17 was significantly elevated in patients with CLP, compared with healthy volunteers (0.218 ± 0.221 ng/ml versus 0.126 ± 0.058 ng/ml, respectively; p = 0.025). No correlation was found between the serum concentration of IL-17 and patient age, gender, disease duration, extent of skin involvement, the presence or intensity of pruritus, and coexistence of mucosal lesions. In tissue samples from CLP lesions, significantly higher numbers of cells expressing IL-17 were found when compared to a healthy skin (p < 0.001).

Conclusion

Elevated serum concentration of IL-17 and high expression in a lesional skin support the hypothesis that IL-17 is implicated in the immunopathogenesis of CLP. These findings may constitute a premise for the future use of anti-IL-17 monoclonal antibodies in the treatment of severe and recalcitrant forms of CLP.

Immunopathogenesis of canine chronic ulcerative stomatitis

Canine Chronic Ulcerative Stomatitis is a spontaneously occurring inflammatory disease of the oral mucosa. An immune-mediated pathogenesis is suspected though not yet proven. We have recently reported on the clinical and histologic features, and identification of select leukocyte cell populations within the lesion. A clinical and histologic similarity to oral lichen planus of people was proposed. In the present study, these initial observations are extended by examining lesions from 24 dogs with clinical evidence of chronic ulcerative stomatitis. Because dogs with chronic ulcerative stomatitis often have concurrent periodontal disease, we wondered if dental plaque/biofilm may be a common instigator of inflammation in both lesions. We hypothesized that dogs with chronic ulcerative stomatitis would exhibit a spectrum of pathologic changes and phenotype of infiltrating leukocytes that would inform lesion pathogenesis and that these changes would differ from inflammatory phenotypes in periodontitis. Previously we identified chronic ulcerative stomatitis lesions to be rich in FoxP3+ and IL17+ cells. As such, we suspect that these leukocytes play an important role in lesion pathogenesis. The current study confirms the presence of moderate to large numbers of FoxP3+ T cells and IL17+ cells in all ulcerative stomatitis lesions using confocal immunofluorescence. Interestingly, the majority of IL17+ cells were determined to be non-T cells and IL17+ cell frequencies were negatively correlated with severity on the clinical scoring system. Three histologic subtypes of ulcerative stomatitis were determined; lichenoid, deep stomatitis and granulomatous. Periodontitis lesions, like stomatitis lesions, were B cell and plasma cell rich, but otherwise differed from the stomatitis lesions. Direct immunofluorescence results did not support an autoantibody-mediated autoimmune disease process. This investigation contributes to the body of literature regarding leukocyte involvement in canine idiopathic inflammatory disease pathogenesis.

Relationship of infiltrating intraepithelial T lymphocytes in the diagnosis of oral lichen planus versus oral epithelial dysplasia: a pilot study

OBJECTIVE

The aim of this study was to identify the type and distribution of CD4+ and CD8+ T lymphocytes in oral mucosal specimens to potentially distinguish between underlying alterations or patterns in oral epithelial dysplasia and oral lichen planus.

STUDY DESIGN

This pilot study included 10 archived tissue samples that were received at the University of North Carolina Oral and Maxillofacial Pathology Laboratory and were diagnosed as oral lichen planus and moderate to severe epithelial dysplasia. Dual staining with CD4 and CD8 antibodies was carried out on each case. Slides were scanned in the Aperio ScanScope FL (Leica Biosystems, Wetzlar, Germany) and archived. Histomorphometric analysis was performed to detect inflammatory cells expressing CD4 and CD8 biomarkers in the epithelial and connective tissue regions.

RESULTS

No differences were found in the amount and ratio of CD4+/CD8+ lymphocytes among the 3 groups analyzed; however, the intraepithelial CD8+ lymphocyte distribution was strikingly different between lichen planus and moderate to severe epithelial dysplasia.

CONCLUSIONS

The localization of CD8+ cells can be potentially useful as an adjunctive diagnostic procedure to distinguish oral epithelial dysplasia from other inflammatory entities, such as lichen planus.

[Correlations between the T helper cell 17/regulatory T cells balance in peripheral blood of patients with oral lichen planus and clinical characteristics]

OBJECTIVE

This study aimed to investigate the ratio of T helper cell 17 (Th17) and regulatory T cells (Treg) in peripheral blood of oral lichen planus (OLP) and explore the pathogenesis of its possible role and significance.

METHODS

The peripheral blood samples were obtained from 33 patients with OLP (15 cases of reticular OLP and 18 cases of erosive OLP) and 17 healthy controls. The percentages of Th17 and Treg cells were detected by flow cytometry (FCM). Real-time fluorescence quantitative polymerase chain reaction (qPCR) technique was used to detect the expression levels of retinoid-related orphan nuclear receptor γt (RORγt) and forkhead box 3 (Foxp3).

RESULTS

The proportions of Th17, Treg cells, and their transcription factors (RORγt and Foxp3) in OLP were higher than those in the control groups (P<0.05). By contrast, in Treg cells and Foxp3, no significance was observed between erosive OLP and reticular OLP. Th17/Treg ratio increased in OLP. This ratio was significantly increased in erosive OLP compared with those in the control groups and reticular OLP (P<0.01). Nevertheless, no significance was noted between reticular OLP and control groups. Statistical analysis demonstrated positive correlations among Th17 cells, Th17/Treg, and clinical characteristics (r=0.66, P=0.00; r=0.66, P=0.00; r=0.52, P=0.00; r=0.50, P=0.00). Positive correlations also existed between Th17 and Treg cells (r=0.39, P=0.03).

CONCLUSIONS

Th17 cells, Treg cells, and their ratios all increased in the peripheral blood of OLP. Moreover, the imbalance inTh17/Treg may play a role in the pathogenesis of erosive OLP.

Using the BITOLA system to identify candidate molecules in the interaction between oral lichen planus and depression

Exacerbations of oral lichen planus (OLP) have been linked to the periods of psychological stress, anxiety and depression. The specific mechanism of the interaction is unclear. The aim of this study was to explore the candidate genes or molecules that play important roles in the interaction between OLP and depression. The BITOLA system was used to search all intermediate concepts relevant to the "Gene or Gene Product" for OLP and depression, and the gene expression data and tissue-specific gene data along with manual checking were then employed to filter the intermediate concepts. Finally, two genes (NCAM1, neural cell adhesion molecule 1; CD4, CD4 molecule) passed the follow-up inspection. By using the text mining can formulate a new hypothesis: NCAM1 and CD4 were identified as involved or potentially involved in the interaction between OLP and depression. These results offer a new clue for the experimenters and hold promise for developing innovative therapeutic strategies for these two diseases.

Increased melatonin in oral mucosal tissue of oral lichen planus (OLP) patients: A possible link between melatonin and its role in oral mucosal inflammation

OBJECTIVE

The existence of extra-pineal melatonin has been observed in various tissues. No prior studies of melatonin in human oral mucosal tissue under the condition of chronic inflammation have been reported. The aim of this study was to investigate the presence of melatonin in oral mucosal tissue of patients with oral lichen planus (OLP) which was considered as a chronic inflammatory immune-mediated disease causing oral mucosal damage and ulcerations.

MATERIALS AND METHODS

Sections from formalin-fixed and paraffin-embedded oral mucosal tissue of OLP patients (n=30), and control subjects (n=30) were used in this study. Immunohistochemical staining was performed and the semiquantitative scoring system was used to assess the levels of arylalkylamine-N-acetyltransferase (AANAT: a rate-limiting enzyme in the biosynthesis pathway of melatonin), melatonin, and melatonin receptor 1 (MT1) in oral mucosa of OLP patients and normal oral mucosa of control subjects.

RESULTS

AANAT, melatonin, and MT1were detected in oral mucosal tissue of OLP patients and control subjects. Immunostaining scores of AANAT, melatonin, and MT1 in oral mucosal tissue of OLP patients were significantly higher than those in control subjects (p=0.002, p<0.001, and p=0.031, respectively).

CONCLUSIONS

Increased levels of AANAT, melatonin, and MT1 in the inflamed oral mucosal tissue of OLP patients imply that chronic inflammation may induce the local biosynthesis of melatonin via AANAT, and may enhance the action of melatonin via MT1.

Clinical and Histopathologic Characterization of Canine Chronic Ulcerative Stomatitis

Canine chronic ulcerative stomatitis, also known as chronic ulcerative paradental stomatitis, is a painful condition of the oral cavity. The purpose of this study was to determine if there are commonalities in clinical and radiographic features among patients, whether the histopathologic evaluation might inform the pathogenesis, and whether the condition appears similar to human oral mucosal diseases. To do this, we prospectively collected clinical, radiographic, and histopathologic data from 20 dogs diagnosed with the disease. Clinical data were based on a clinical disease activity index, oral and periodontal examination parameters, and full-mouth dental radiographs. The histopathological and immunohistochemical data were based on oral mucosal samples obtained from erosive or ulcerated areas. Our findings revealed that canine chronic stomatitis is clinically characterized by painful oral mucosal ulcers of varying size, pattern, appearance, and distribution, most often associated with teeth with early periodontitis. Histologic examination revealed a subepithelial lichenoid band (interface mucositis) where B cells, T cells, and Forkhead-box protein 3 (FoxP3)- and interleukin-17-expressing cells were present. These cells might play a role in the underlying immune response and an immune-mediated pathogenesis is suspected. The clinical and histopathologic features of this chronic inflammatory mucosal disease in dogs resemble those of oral lichen planus in humans.

Distinct interferon-gamma and interleukin-9 expression in cutaneous and oral lichen planus

BACKGROUND

Cutaneous (CLP) and oral lichen planus (OLP) as the main subtypes of lichen planus (LP) present with different clinical manifestation and disease course, although their histopathologic features such as the band-like lymphocyte infiltrate and keratinocyte apoptosis are similar. So far, the underlying cellular and molecular mechanisms remain poorly understood.

OBJECTIVE

The aim of this study was to characterize and compare the in situ cellular infiltrates, cytokine expression profiles and apoptosis markers in CLP and OLP.

METHODS

Using immunofluorescence staining and laser scanning microscopy, we evaluated the cellular infiltrate (CD1a, CD3, CD4, CD8, CD21, CD57, CD123), cytokine expression (interleukin (IL)-1, IL-6, IL-9, IL-10, IL-17, IL-22, IL-23, tumour necrosis factor-α, transforming growth factor-β, interferon (IFN)-γ), and apoptosis markers (Fas, Fas ligand, cleaved caspase-3, TUNEL) of 21 anonymized biopsy specimens of LP (11 CLP, 10 OLP).

RESULTS

Among infiltrating cells mainly T cells and natural killer (NK) cells as well as plasmacytoid dendritic cells (DC) were observed. A predominance of CD8+ T cells was noted in OLP. In both CLP and OLP, T helper (Th)1, Th9, Th17, and Th22-type cytokines were expressed. The expression of IL-9, IFN-γ and IL-22 was higher in CLP compared to that of OLP (P = 0.0165; P = 0.0016; P = 0.052 respectively). Expression of Fas and Fas ligand as well as cleaved caspase-3-positive cells was observed in the epithelium of all LP samples.

CONCLUSIONS

The cell and cytokine patterns of CLP and OLP were partially distinct and generally resembled those reported for autoimmune diseases. The presence of CD8+ and NK cells as well as Fas/Fas ligand expression suggested that various pathways involved in keratinocyte apoptosis are relevant for LP. These results might help to establish targeted therapies for LP.

The many faces of interleukin-17 in inflammatory skin diseases

Interleukin (IL)-17 is an emerging target for inflammatory skin disorders. Given the remarkable success of its therapeutic inhibition in psoriasis, the pathogenic role of this cytokine is being explored in other immune-mediated diseases. Interestingly, IL-17 is linked to particular skin conditions where its activation coincides with disease flares. The leading hypothesis for its contribution to proinflammatory signalling cascades is driving inflammasome activation. However, IL-17 stimulation also releases a range of noninflammasome-related cytokines from human skin. Furthermore, a role in cytotoxic responses and an important interplay with the microbiome is hypothesized. While treatment failure would be surprising in neutrophilic dermatoses, the picture might be more complex in lymphocyte-mediated conditions. Nonetheless, increasing insights into the pathogenesis suggest that beneficial responses are also probable in the latter conditions. Study of this pathway in the skin reveals some intriguing aspects of the IL-17-related immunological network.

Phenotypically non-suppressive cells predominate among FoxP3-positive cells in oral lichen planus

BACKGROUND

Oral lichen planus (OLP) is a common T-cell-dominated oral chronic inflammatory disease occurring in periods of remission, quiescence, activity with pronounced inflammation, and acute ulceration. Cell infiltrates in OLP contain varying numbers of CD4⁺ T cells expressing the transcription factor FoxP3. FoxP3⁺ CD4⁺ T cells are, however, a heterogeneous cell population containing suppressive and non-suppressive cells, and their distribution in infiltrates from OLP is unknown.

METHODS

Biopsies were taken from normal oral mucosa (n = 8) and OLP lesions (n = 19), and a set of in situ methods for the determination of the functional phenotype of FoxP3⁺ CD4⁺ T cells was applied.

RESULTS

Numbers of FoxP3⁺ CD4⁺ T cells were highest in the atrophic form of the disease, yet low in the ulcerative form. The main FoxP3⁺ CD4⁺ T-cell population observed was FoxP3⁺ CD45RA^- CD25⁺ CD45RO⁺ and CD15s^- , a phenotype delineating a non-suppressive subset. Numbers of cells with an actively suppressing phenotype (FoxP3⁺ CD45RA^- CD25⁺ CD45RO⁺ and CD15s⁺ ) were, however, about twice as high in reticular lesions as compared with the atrophic form. Many FoxP3⁺ CD4⁺ T cells expressed T-bet, the hallmark transcription factor for IFN-γ-producing T cells, indicating that they may enhance immune and inflammatory responses rather than suppress them.

CONCLUSIONS

The absence of actively suppressing FoxP3⁺ CD4⁺ T cells may in part explain why OLP is a remarkably persisting condition, in spite of the presence of substantially high numbers of FoxP3⁺ CD4⁺ T cells. The findings emphasize that it is crucial to examine not only numbers but also functional phenotype of FoxP3⁺ CD4⁺ T cells in human tissues.

Th17 Pathway As a Target for Multipotent Stromal Cell Therapy in Dogs: Implications for Translational Research

Detrimental Th17 driven inflammatory and autoimmune disease such as Crohn’s disease, graft versus host disease and multiple sclerosis remain a significant cause of morbidity and mortality worldwide. Multipotent stromal/stem cell (MSC) inhibit Th17 polarization and activation in vitro and in rodent models. As such, MSC based therapeutic approaches are being investigated as novel therapeutic approaches to treat Th17 driven diseases in humans. The significance of naturally occurring diseases in dogs is increasingly recognized as a realistic platform to conduct pre-clinical testing of novel therapeutics. Full characterization of Th17 cells in dogs has not been completed. We have developed and validated a flow-cytometric method to detect Th17 cells in canine blood. We further demonstrate that Th17 and other IL17 producing cells are present in tissues of dogs with naturally occurring chronic inflammatory diseases. Finally, we have determined the kinetics of a canine specific Th17 polarization in vitro and demonstrate that canine MSC inhibit Th17 polarization in vitro, in a PGE₂ independent mechanism. Our findings provide fundamental research tools and suggest that naturally occurring diseases in dogs, such as inflammatory bowel disease, may be harnessed to translate novel MSC based therapeutic strategies that target the Th17 pathway.