The role of perforin-mediated apoptosis in lichen planus lesions

Increased Level of Serum Wingless-Type Mouse Mammary Tumor Virus Integration Site Family Member 5a in Patients with Cutaneous Lichen Planus

Purpose

Methods

Results

Conclusion

The possible involvement of granulysin mediated cytotoxicity in keratinocytes disruption in lichen planus

Lichen planus is a chronic mucocutanous disorder histopathologically characterized with a keratinocytes apoptosis, subsequent basal cell layer liquefaction and accumulation of the inflammatory infiltrate in papillary dermis. A formation of apoptotic bodies in basal cell layer is due to a cytotoxic lymphocyte attack to the basal keratinocytes. It has been demonstrated that the cytotoxic molecules included in this attack are perforin and granzyme B. Both molecules are found upregulated in CD8+ lymphocytes that are in close contact to keratinocytes. However, their amount is lower in lichen planus than in other skin disease characterized by liquefaction and vacuolar degeneration of the basal epidermal layer. This could speculate about other cytotoxic molecule such as granulysin that could mediate keratinocyte apoptosis. Therefore, in this article we hypothesize about the crucial role of granulysin molecule in keratinocytes killing that could contribute to a lichen planus pathogenesis.

Immunostimulatory Endogenous Nucleic Acids Perpetuate Interface Dermatitis-Translation of Pathogenic Fundamentals Into an In Vitro Model

Interface dermatitis is a histopathological pattern mirroring a distinct cytotoxic immune response shared by a number of clinically diverse inflammatory skin diseases amongst which lichen planus and cutaneous lupus erythematosus are considered prototypic. Interface dermatitis is characterized by pronounced cytotoxic immune cell infiltration and necroptotic keratinocytes at the dermoepidermal junction. The initial inflammatory reaction is established by cytotoxic immune cells that express CXC chemokine receptor 3 and lesional keratinocytes that produce corresponding ligands, CXC motif ligands 9/10/11, recruiting the effector cells to the site of inflammation. During the resulting anti-epithelial attack, endogenous immune complexes and nucleic acids are released from perishing keratinocytes, which are then perceived by the innate immune system as danger signals. Keratinocytes express a distinct signature of pattern recognition receptors and binding of endogenous nucleic acid motifs to these receptors results in interferon-mediated immune responses and further enhancement of CXC chemokine receptor 3 ligand production. In this perspective article, we will discuss the role of innate nucleic acid sensing as a common mechanism in the perpetuation of clinically heterogeneous diseases featuring interface dermatitis based on own data and a review of the literature. Furthermore, we will introduce a keratinocyte-specific in vitro model of interface dermatitis as follows: Stimulation of human keratinocytes with endogenous nucleic acids alone and in combination with interferon gamma leads to pronounced production of distinct cytokines, which are essential in the pathogenesis of interface dermatitis. This experimental approach bears the capability to investigate potential therapeutics in this group of diseases with unmet medical need.

The attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies.

IFN-γ enhances cell-mediated cytotoxicity against keratinocytes via JAK2/STAT1 in lichen planus

Lichen planus (LP) is a chronic debilitating inflammatory disease of unknown etiology affecting the skin, nails, and mucosa with no current FDA-approved treatments. It is histologically characterized by dense infiltration of T cells and epidermal keratinocyte apoptosis. Using global transcriptomic profiling of patient skin samples, we demonstrate that LP is characterized by a type II interferon (IFN) inflammatory response. The type II IFN, IFN-γ, is demonstrated to prime keratinocytes and increase their susceptibility to CD8⁺ T cell-mediated cytotoxic responses through MHC class I induction in a coculture model. We show that this process is dependent on Janus kinase 2 (JAK2) and signal transducer and activator of transcription 1 (STAT1), but not JAK1 or STAT2 signaling. Last, using drug prediction algorithms, we identify JAK inhibitors as promising therapeutic agents in LP and demonstrate that the JAK1/2 inhibitor baricitinib fully protects keratinocytes against cell-mediated cytotoxic responses in vitro. In summary, this work elucidates the role and mechanisms of IFN-γ in LP pathogenesis and provides evidence for the therapeutic use of JAK inhibitors to limit cell-mediated cytotoxicity in patients with LP.

The influence of interferon on healthy and diseased skin

Type I interferons (IFNs) are an immunomodulatory class of cytokines that serve to protect against viral and bacterial infection. In addition, mounting evidence suggests IFNs, particularly type I but also IFNγ, are important to the pathogenesis of autoimmune and inflammatory skin diseases, such as cutaneous lupus erythematosus (CLE). Understanding the role of IFNs is relevant to anti-viral responses in the skin, skin biology, and therapeutics for these IFN-related conditions. Type I IFNs (α and β) are produced by recruited inflammatory cells and by the epidermis itself (IFNκ) and have important roles in autoimmune and inflammatory skin disease. Here, we review the current literature utilizing a PubMed database search using terms [interferon/IFN/type I IFN AND lupus/ cutaneous lupus/CLE/dermatomyositis/Sjogrens/psoriasis/lichen planus/morphea/alopecia areata/vitiligo] with a focus on the role of IFNs in basic keratinocyte biology and their implications in the cutaneous autoimmune and inflammatory diseases: cutaneous lupus erythematosus, dermatomyositis, Sjogren's syndrome, psoriasis, lichen planus, alopecia areata and vitiligo. We provide information about genes and proteins induced by IFNs and how downstream mechanisms relate to clinical disease.

Bullous lichen planus - a review

Bullous lichen planus is a rare variant of lichen planus. It is characterized by vesicles or bullae, which usually develop in the context of pre-existing LP lesions. It is often misdiagnosed and should be differentiated from other subepidermal bullous diseases especially lichen planus pemphigoides. The diagnosis is based on clinical suspicion and is confirmed by histopathology and immunofluoresence. The clinical features of bullous lichen planus include typical lichen planus lesions, accompanied by the formation of bullae on the affected or perilesional skin. This is evident on histology, with alteration of the dermo-epidermal junction and intrabasal bullae as a consequence of extensive inflammation. The histologic features in conjunction with the negative immunofluoresence indicate that bullous lichen planus is a form of "hyper-reactive lichen planus" rather than a distinct entity. There is no standard treatment of bullous lichen planus. Topical and systemic corticosteroids, dapsone and acitretin have been described as effective choices.

Targeting the IFN-γ/CXCL10 pathway in lichen planus

Lichen planus is a chronic inflammatory disease of the skin, mucous membranes and nails. Management of oral involvement, particularly atrophic and erosive lesions, is challenging. Noteworthy, there is a lack of published evidence for treatment. Cell-mediated cytotoxicity is actually regarded as a major mechanism of pathogenesis. The interferon-gamma induced chemokines CXCL10 and CXCL9 are strongly expressed in serum of patients as well as in both skin and mucosal lesions. Therefore the interferon gamma/CXCL10 axis is considered a key process for both progression and maintenance of chronic cytotoxic inflammation. According to these findings, the interferon gamma/CXCL10 axis could be considered a therapeutically attractive target to reverse inflammation. Since interferon gamma signal transduction occurs through JAK 1 and 2, JAK inhibitors could lead to blockade of interferon gamma signaling and downstream CXCL10 expression.

Perforin and granzyme B involvement in oral lesions of lichen planus and chronic GVHD

BACKGROUND

Oral lesions of lichen planus and chronic graft-vs.-host disease (cGVHD) have similar clinical and histological features, but distinct etiology. Apoptosis induced by cytotoxic T lymphocyte has been proposed as a mechanism of keratinocytes death. Cytotoxicity can be mediated by granules containing granzyme B and perforin. Since common features can reflect similarities in immunological mechanisms, we studied the role of those molecules in both diseases.

METHODS

We analyzed 29 cases of oral lichen planus and 27 of oral cGVHD. The sections were studied on H&E, perforin and granzyme B staining.

RESULTS

The total means (epithelium plus connective tissue number) of the granzyme B- and perforin-positive cells were significantly higher in cGVHD than in oral lichen planus lesions (P<0.05). Also, it was found that the higher the number of perforin+ cells, the higher the number of granzyme-B+ cells in the epithelium and in the connective tissue for both groups (P < 0.05). In oral lichen planus, the number of single apoptotic bodies had a positive correlation with connective tissue granzyme immunostaining and a negative correlation with perforin (P<0.01). On the contrary, in oral cGVHD, the number of apoptotic body clusters presented a positive correlation with connective tissue perforin (P<0.01).

CONCLUSIONS

Our findings indicate that apoptosis in oral lichen planus seems to be correlated with granzyme B release, while in oral cGVHD, perforin seems to be more important. Although these diseases present clinical and histological similarities, subtle differences seem to exist in their pathogenetic mechanisms.

Increased caspase-3 and altered expression of apoptosis-associated proteins, Bcl-2 and Bax in lichen planus

BACKGROUND

Lichen planus (LP) is a chronic inflammatory disease of probable immune-based aetiology. The pathogenesis of LP is unclear, but apoptotic changes in epidermal (epithelial) cells have been reported.

OBJECTIVE

To evaluate apoptosis in LP through studying caspase-3 expression and to determine whether the apoptosis-associated proteins Bcl-2 and Bax are significantly involved in the pathogenesis of LP.

METHODS

In total, 25 lesional biopsy specimens [15 cutaneous LP (CLP) and 10 oral LP (OLP)] and 10 control specimens [5 normal skin and 5 normal oral mucosa] were studied using immunochemical methods for the expression of caspase-3, Bcl-2 and Bax proteins.

RESULTS

Compared with controls, a significant increase in caspase-3 and Bax protein expressions were found in LP lesions. Basal cell expression of caspase-3 was positive in 14 cases (56%), and 12 cases (48%) showed mild expression. Caspase-3 expression in inflammatory infiltrate was positive in 13 cases (52%). Of these, 12 cases (48%) showed mild positivity. Bax was localized mostly to the upper prickle layer. Basal cell expression of Bcl-2 was negative in 18 (72%) cases, with no significant difference between patients with LP and controls. Bcl-2 was expressed in the inflammatory infiltrate in 15 cases of LP (60%), showing mild expression in 12 cases (48%). Compared with CLP, there was a significant increase in caspase-3 expression in OLP, despite the nonsignificant difference in Bcl-2 and Bax protein expressions by the epithelial cells.

CONCLUSION

Increased caspase-3 and altered expression of Bcl-2 and Bax were found in LP, indicating the possible involvement of these proteins in the pathogenesis of the disease. The observed increase in apoptosis in OLP compared with CLP might explain the difference in clinical behaviour that distinguishes these LP variants.

Lichenoid tissue reaction/interface dermatitis: clinical and histological perspectives

A number of uncommon, clinically diverse and poorly understood inflammatory skin diseases are linked by the presence of a set of histopathological elements that have traditionally been referred to as the "lichenoid tissue reaction/interface dermatitis" (LTR/IFD). The prototypic skin disease in this category is lichen planus. However, the LTR/IFD can also be seen in skin disorders associated with systemic illnesses (lupus erythematosus, dermatomyositis), and the skin changes of potentially fatal disorders such as graft-versus-host disease, Stevens-Johnson syndrome, and toxic epidermal necrolysis. It has been traditionally felt that cytotoxic T-lymphocytes represent the final effector cell type for the epidermal basal cell layer injury pattern that is common to LTR/IFD disorders. Recent work has suggested that a number of different LTR/IFD skin disorders share a common inflammatory signaling pathway involving the actions of plasmacytoid dendritic cell-derived IFN-alpha. This signaling pathway appears to amplify cytotoxic T cell injury to the epidermal basal cell compartment. This review will summarize the work implicating this pathway as well as the other cellular and molecular mechanisms that are thought to be responsible for the prototypic LTR/IFD disorder, lichen planus. It is hoped that a better understanding of the immunological commonalities shared by various LTR/IFD disorders will lead to more effective safer treatment options for these illnesses.

Involvement of granzyme B and granulysin in the cytotoxic response in lichen planus

BACKGROUND

Lichen planus is an inflammatory dermatosis involving either skin and/or mucosal epithelial surfaces. A cell-mediated cytotoxicity response is the main suspected mechanism of this dermatosis. Granzyme B and granulysin are components of the cytoplasmic granules of cytotoxic T lymphocytes and natural killers. They are involved in cell-mediated apoptosis. This work studies the possible implication of granzyme B and granulysin in the cell-mediated cytotoxicity response in lichen planus.

METHODS

In situ expression of granzyme B and granulysin was studied by real-time reverse transcriptase polymerase chain reaction in 15 biopsies of lichen planus. The distribution and the phenotype of the inflammatory infiltrate and the expression of granzyme B were studied by immunohistochemistry in seven other biopsies of lichen planus.

RESULTS

Granzyme B and granulysin mRNA expression was one to two hundred times greater than in biopsies of normal skin. Immunohistochemical study revealed that the lymphohistiocytic infiltrate consisted mainly of CD4+ and CD8+ lymphocytes. Granzyme B+ cells were observed close to apoptotic keratinocytes.

CONCLUSION

Our results suggest a central role for cell-mediated cytotoxicity by the granule exocytosis pathway probably because of auto-cytotoxic T-cell clones in the pathogenesis of lichen planus.

Treatment of refractory erosive oral lichen planus with extracorporeal photochemotherapy: 12 cases

BACKGROUND

Case reports have suggested that extracorporeal photochemotherapy (ECP) might be beneficial for the treatment of erosive oral lichen planus (OLP) recalcitrant to conventional immunosuppressive therapies.

OBJECTIVES

To evaluate over a long-term period the clinical efficacy and toxicity of ECP in a series of patients with refractory OLP, and to monitor peripheral blood lymphocyte subset counts under treatment.

METHODS

Twelve patients with refractory OLP underwent a standardized protocol of ECP. Sessions were performed twice weekly for 3 weeks, and then the treatment schedule was adapted according to clinical benefit. The disease severity was evaluated monthly on a clinical basis. Complete remission was defined as the absence of any erosion and partial remission as a decrease of at least 50% of erosion surface. Blood cell counts with CD4+ and CD8+ lymphocyte subsets were evaluated every 3 months.

RESULTS

All patients showed a decrease of the erosive surface; nine (75%) achieved a complete remission and three (25%) a partial remission. Seven of the eight patients followed for more than 3 years had recurrences of erosions when ECP sessions became less frequent or were stopped. After resumption of an initially accelerated regimen of ECP, all again showed partial or complete remission. Blood lymphocyte counts decreased during treatment, without statistically significant changes in CD4+/CD8+ ratio, and increased during relapse.

CONCLUSIONS

ECP is an effective alternative therapy in erosive OLP showing resistance to classical treatments. The decrease in blood lymphocyte counts appears to parallel the clinical improvement under treatment.