The dysfunctional innate immune response triggered by Toll-like receptor activation is restored by TLR7/TLR8 and TLR9 ligands in cutaneous lichen planus

Distinct Variations in Gene Expression and Cell Composition across Lichen Planus Subtypes

Lichen planus (LP) is a highly prevalent inflammatory skin disease. While various clinical subtypes have been defined, detailed comparisons of these variants are lacking. This study aimed to elucidate differences in gene expression and cellular composition across LP subtypes. Lesional skin biopsies from 28 LP patients (classical, oral, genital, and lichen planopilaris) and seven non-diseased skin controls (NDC) were analyzed. Gene expression profiling of 730 inflammation-related genes was conducted using NanoString. Immune cell compositions were assessed by multiplex immunohistochemistry. Gene expression profiles revealed unique inflammatory signatures for each LP subtype. Lichen planopilaris exhibited the most divergence, with downregulated gene expression and upregulation of complement pathway genes (C5-7), along with elevated M2 macrophages. Oral and genital LP demonstrated similar profiles with strong upregulation of TNF-related and Toll-like receptor-associated genes. Oral LP showed the highest upregulation of cytotoxicity-associated genes, as well as high numbers of CD8+ IL-17A+ (Tc17) cells (8.02%). Interferon gene signatures were strongly upregulated in oral and classical LP. The study highlights distinct differences in inflammatory gene expression and cell composition across LP subtypes, emphasizing the need for tailored therapeutic approaches.

Effects of toll-like receptor agonists and SARS-CoV-2 antigens on interferon (IFN) expression by peripheral blood CD3+ T cells from COVID-19 patients

BACKGROUND

Signaling by toll-like receptors (TLRs) initiates important immune responses against viral infection. The role of TLRs in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is not well elucidated. Thus, we investigated the interaction of TLRs agonists and SARS-COV-2 antigens with immune cells in vitro.

MATERIAL & METHODS

30 coronavirus disease 2019 (COVID-19) patients (15 severe and 15 moderate) and 10 age and sex-matched healthy control (HC) were enrolled. Peripheral blood mononuclear cells (PBMCs) were isolated and activated with TLR3, 7, 8, and 9 agonists, the spike protein (SP) of SARS-CoV-2, and the receptor binding domain (RBD) of SP. Frequencies of CD3+IFN-β+ T cells, and CD3+IFN-γ+ T cells were evaluated by flow cytometry. Interferon (IFN)-β gene expression was assessed by qRT-PCR.

RESULTS

The frequency of CD3+IFN-β+ T cells was higher in PBMCs from moderate (p < 0.0001) and severe (p = 0.009) patients at baseline in comparison with HCs. The highest increase in the frequency of CD3+IFN-β+ T cells in cell from moderate patients was induced by TLR8 agonist and SP (p < 0.0001 for both) when compared to HC, while, the highest increase of the frequency of CD3+IFN-β+ T cells in sample of severe patients was seen with TLR8 and TLR7 agonists (both p = 0.002). The frequency of CD3+IFN-γ+ T cells was significantly increased upon stimulation with TLR agonists in cell from patients with moderate and severe COVID-19, compared with HC (all p < 0.01), except with TLR7 and TLR8 agonists. The TLR8 agonist did not significantly increase the frequency of CD3+IFN-γ+ T cells in PBMCs of severe patients, but did so in cells from patients with moderate disease (p = 0.01). Moreover, IFN-β gene expression was significantly upregulated in CD3+T cells from moderate (p < 0.0001) and severe (p = 0.002) COVID-19 patients, compared to HC after stimulation with the TLR8 agonist, while, stimulation of T cells with SP, significantly up-regulated IFN-β mRNA expression in cells from patients with moderate (p = 0.0003), but not severe disease.

CONCLUSION

Stimulation of PBMCs from COVID-19 patients, especially patients with moderate disease, with TLR8 agonist and SP increased the frequency of IFN-β-producing T cells and IFN-β gene expression.

Ultrasound Features of Nail Lichen Planus

OBJECTIVES

To describe the ultrasonographic features of nail lichen planus (NLP), which, so far, have not been reported in the literature.

METHODS

A retrospective single-center study of NLP patients' color Doppler ultrasound examinations was performed between March 2014 and January 2023. Inclusion criteria were patients ≥15 years with a confirmed clinical diagnosis of NLP in sequential order. Exclusion criteria included concomitant systemic or local cutaneous or nail diseases and systemic or local nail treatments before the ultrasound examination. The ultrasound protocol included the examination of all fingernails or toenails following the reported protocol for dermatologic ultrasound examinations at high and ultra-high frequencies. Patient demographics and ultrasound features of the nail bed, periungual region, nail plate, and regional vascularity were registered and analyzed statistically.

RESULTS

A total of 36 patients met the criteria. All cases presented thickened and decreased echogenicity of the nail bed. A hypoechoic halo surrounding the origin of the nail plate was present in 78% of cases. Exactly 58% of patients presented decreased echogenicity of the proximal periungual dermis, and 86% showed thickening of the periungual dermis. Hypervascularity of the nail bed was seen in 94% of cases. The mean maximum thickness of vessels, the peak systolic velocity of the arterial vessels, and other blood flow findings are provided.

CONCLUSION

Ultrasonography can support the diagnosis of NLP, which benefits the non-invasive discrimination of nail conditions and can avoid the potential permanent scars derived from nail biopsies. Furthermore, ultrasound may be a powerful tool to monitor this disease's treatment.

Review of Nail Lichen Planus: Epidemiology, Pathogenesis, Diagnosis, and Treatment

Nail lichen planus is an inflammatory disorder of the nails with potential for significant cosmetic disfigurement and functional impairment. Nail manifestations may be isolated or appear concurrently with other forms of lichen planus. Longitudinal ridging is the most common clinical finding, but progressive disease may result in irreversible scarring (dorsal pterygium) or permanent nail loss (anonychia). Data on treatment are limited to retrospective studies and case reports. The mainstays of treatment are intralesional and intramuscular corticosteroid injections and oral retinoids. There is a need for randomized controlled trials on nail lichen planus to more rigorously assess efficacy and outcomes.

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.

Lichen planus and lichenoid dermatoses: Clinical overview and molecular basis

Deriving from the Greek word λειχήν for "tree moss" and the Latin word planus for "planar," lichen planus is a relatively uncommon and heterogeneous cutaneous disorder that typically develops in middle-aged adults. Despite the significant clinical burden associated with the disorder, little well-conducted molecular research has been undertaken, possibly because of heterogeneity impeding consistent and confident phenotyping. The multiple variants of lichenoid disease bear overlapping clinical and pathologic features despite manifesting as distinct clinical disorders. The first article in this 2-part continuing medical education series provides a comprehensive overview of the clinical and pathologic characteristics of cutaneous lichenoid dermatoses and links these manifestations to recent advances in our understanding of the underlying pathobiology of such diseases.

Lichen planus: altered AIM2 and NLRP1 expression in skin lesions and defective activation in peripheral blood mononuclear cells

BACKGROUND

Lichen planus (LP) is an inflammatory skin disease with unknown aetiology. Activation by pathogen-associated molecular patterns or environmental stimuli may activate some components of inflammasomes that contribute to the inflammatory process in LP lesions.

AIM

To characterize the inflammasomes in skin lesions and peripheral blood mononuclear cells (PBMCs) of patients with LP under Toll-like receptor (TLR) activation.

METHODS

In total, 15 patients with LP and 14 healthy controls (HCs) were enrolled in the study. Inflammasome expression in skin was evaluated by real-time PCR and immunohistochemistry, while ELISA was used to assess the production of interleukin (IL)-1β by PBMCs under stimulation with TLR4 and TLR7/TLR8 agonists and adenosine triphosphate (ATP).

RESULTS

Compared with the levels in HC samples, increased expression of the inflammasome AIM2 was verified in both epidermal and dermal sections of LP skin lesions, whereas NLRP1 and IL-β expression levels were enhanced in the dermis. LP skin lesion samples exhibited higher AIM2 transcript levels, similar NLRP1 levels and lower pro-IL-1β mRNA levels compared with HC samples. We verified that, compared with PBMCs from HC subjects, PBMCs from patients with LP produced similar amounts of IL-1β after induction by TLR4 agonists but lower IL-1β levels after induction by TLR7/TLR8 agonists, regardless of the addition of ATP.

CONCLUSION

Alterations in innate immunity, such as inflammasome component expression in skin lesions and PBMCs, were observed in patients with LP. Further investigations of dysfunctional inflammasome activation and the chronic inflammatory status of LP are required.

Therapeutics for Adult Nail Psoriasis and Nail Lichen Planus: A Guide for Clinicians

Nail psoriasis (NP) and nail lichen planus (NLP) can be limiting, stigmatizing and difficult to treat. Dermatologists commonly treat psoriasis and lichen planus but when associated onychodystrophy is present or is an isolated finding, some develop apprehension. The goal of this review is to develop therapeutic ladders to be used as a guide for the management of NP and NLP in everyday clinical practice. Evidence-based therapies for NP are robust and range from topical treatments to conventional systemic therapies (i.e., methotrexate, cyclosporine), new oral agents (i.e., apremilast and tofacitinib), and biologics. The literature for treatment of NLP is severely limited, with therapy mainly consisting of topical, intralesional, or systemic corticosteroids or methotrexate.

Up-regulation of HMGB1 and TLR4 in skin lesions of lichen planus

Lichen planus (LP) is a chronic, mucocutaneous inflammatory disease of an unknown aetiology. The disease has been associated with certain viruses, and the factors such as DAMPs (damage-associated molecular patterns) and PAMPs (pathogen-associated molecular patterns) may also contribute to the inflammatory response in LP. HMGB1 (high mobility group box 1 protein) is one of the major DAMPs that induces inflammation and could trigger LP disease. The present study was aimed to examine TLR4, RAGE and HMGB1 production in epidermis or dermis by immunohistochemistry and the respective expression of these targets in the skin lesions of patients with LP. Moreover, we measured HMGB1 serum levels by ELISA. The results showed similar profile of expression by HMGB1 and TLR4, which are decreased at epidermis and up-regulated at dermis of skin lesions of LP patients that was sustained by intense cellular infiltration. RAGE expression was also increased in dermis of LP. Although there is increased RAGE protein levels, a decreased RAGE transcript levels was detected. Similar HMGB1 serum levels were detected in the LP and control groups. This study demonstrates that HMGB1 and TLR4 could contribute to the inflammatory LP process in skin.

Toll-like receptor agonists partially restore the production of pro-inflammatory cytokines and type I interferon in Sézary syndrome

Sézary syndrome (SS) carries a poor prognosis, and infections represent the most frequent cause of death in SS patients. Toll-like receptors (TLRs) are a family of innate immune receptors that induce protective immune responses against infections. We sought to evaluate the ability of TLR agonists to induce inflammatory cytokine, Th2 cytokine, and type I interferon (IFN-I) production by peripheral blood mononuclear cells (PBMC) of untreated SS patients. We detected impaired IL-6, IL-10 and IL-13 secretion by PBMC induced by the agonists for TLR5, TLR3, TLR7 and TLR9 in SS patients, while it was partially recovered by TLR2/TLR4 and TLR7/8 agonists TNF secretion was restored following stimulation with TLR2/TLR4 agonists. IFN-γ was scarcely produced upon TLR activation in SS cells, albeit TLR 7/8 (CL097) enhanced their secretion at lower levels than the control group. TLR9 agonist efficiently induced IFN-I in SS patients, although this positive regulation was not observed for other cytokines, in direct contrast to the broad activity of CL097. Among the TLR agonists, TLR4 was able to induce pro-inflammatory, IL-10 and Th2 secretion, while TLR7-8 agonist induced the inflammatory cytokines, IFN-I and IFN-γ. These findings reveal a dysfunctional cytokine response upon both extracellular and intracellular TLR activation in SS patients, which was partially restored by TLRs agonists.

Increased infiltration of CD11 c+/CD123+ dendritic cell subsets and upregulation of TLR/IFN-α signaling participate in pathogenesis of oral lichen planus

OBJECTIVE

Investigation of dendritic cell (DC) subsets and expression patterns of Toll-like receptors (TLRs) was conducted to understand the pathogenesis in oral lichen planus (OLP).

STUDY DESIGN

Blood, OLP lesion, and control samples were collected. Four DC subsets (CD11c⁺CD123^-myeloid DC1 [mDC1], CD141⁺mDC2, CD11c^-CD123⁺plasmacytoid DC [pDC], and CD1a⁺CD207⁺Langerhans cells [LC]) were investigated via flow cytometry (FCM) and immunohistochemical staining. Expression patterns of TLRs and their downstream molecules were analyzed via quantitative real-time polymerase chain reaction and immunohistochemistry in situ.

RESULTS

Thirty-two samples were collected (9 controls and 23 OLP patients). FCM results found that the percentages of LC, mDC1, mDC2, and pDC in situ were 0.0119 ± 0.0251%, 0.0064 ± 0.0134%, 0.0005 ± 0.0011%, and 0.0022 ± 0.0019% in control mucosa, respectively. The mDC1 (0.0300 ± 0.0276%) and pDC (0.0204 ± 0.0186%) subsets were significantly increased in OLP lesions (P < .01). No marked differences were evident, when comparing all 4 DC subsets from blood, between control and OLP groups. Significant upregulation of TLR7, TLR8, and TLR9 were disclosed in OLP (P < .01), along with their downstream interferon-α (IFN-α) signaling molecules (IRF7 and IFN-α, P < .01).

CONCLUSION

Our findings of increased infiltration of pDC and mDC1, along with upregulation of TLR/IFN-α signaling, provide valuable information for further understanding the immunity in OLP.

Semaphorin4D Drives CD8+ T-Cell Lesional Trafficking in Oral Lichen Planus via CXCL9/CXCL10 Upregulations in Oral Keratinocytes

Chemokine-mediated CD8⁺ T-cell recruitment is an essential but not well-established event for the persistence of oral lichen planus (OLP). Semaphorin 4D (Sema4D)/CD100 is implicated in immune dysfunction, chemokine modulation, and cell migration, which are critical aspects for OLP progression, but its implication in OLP pathogenesis has not been determined. In this study, we sought to explicate the effect of Sema4D on human oral keratinocytes and its capacity to drive CD8⁺ T-cell lesional trafficking via chemokine modulation. We found that upregulations of sSema4D in OLP tissues and blood were positively correlated with disease severity and activity. In vitro observation revealed that Sema4D induced C-X-C motif chemokine ligand 9/C-X-C motif chemokine ligand 10 production by binding to plexin-B1 via protein kinase B-NF-κB cascade in human oral keratinocytes, which elicited OLP CD8⁺ T-cell migration. We also confirmed using clinical samples that elevated C-X-C motif chemokine ligand 9/C-X-C motif chemokine ligand 10 levels were positively correlated with sSema4D levels in OLP lesions and serum. Notably, we determined matrix metalloproteinase-9 as a new proteolytic enzyme for the cleavage of sSema4D from the T-cell surface, which may contribute to the high levels of sSema4D in OLP lesions and serum. Our findings conclusively revealed an amplification feedback loop involving T cells, chemokines, and Sema4D-dependent signal that promotes OLP progression.

Chemokine, cytokine and type I interferon production induced by Toll-like receptor activation in common variable immune deficiency

Common variable immunodeficiency (CVID) is the most common symptomatic primary antibody deficiency and is associated with recurrent infections and chronic inflammatory diseases. We evaluated the ability of Toll-like receptor (TLR) ligands to induce secretion of chemokines, cytokines and type I interferons by peripheral blood mononuclear cells (PBMCs) from CVID patients. High levels of CXCL10, CCL2, CXCL9, CCL5, CXCL8, and IL-6 were detected in sera of CVID patients compared with healthy controls. Increased chemokine levels were observed in unstimulated PBMCs, but after stimulation with TLR2 and TLR4 agonists, equivalent chemokine and pro-inflammatory cytokine secretion, as in healthy controls, was observed, whereas TLR4 agonist induced a decreased secretion of CCL2 and CXCL8 and increased secretion of TNF. Decreased IFN-α secretion induced by TLR7/TLR8 activation was observed in CVID, which was recovered with TLR9 signaling. Our findings revealed that TLR9 activation has an adjuvant effect on the altered type I response in CVID.

Activation of myeloid dendritic cells, effector cells and regulatory T cells in lichen planus

Background

Lichen planus (LP) is a chronic mucocutaneous inflammatory disease. Evaluating the balance between regulatory T cells and effector T cells could be useful for monitoring the proinflammatory profile of LP. Therefore, this study aimed to assess populations of dendritic cells (DCs) and regulatory and effector T cells in peripheral blood samples collected from patients with LP to evaluate the polyfunctionality of T cells upon toll-like receptor (TLR) activation.

Methods

Peripheral blood mononuclear cells collected from 18 patients with LP and 22 healthy control subjects were stimulated with agonists of TLR4, TLR7, TLR7/TLR8 or TLR9. Frequencies of circulating IFN-α⁺ plasmacytoid DCs (pDCs); TNF-α⁺ myeloid DCs (mDCs); regulatory T cells (Tregs); and IL-17-, IL-10-, IL-22-, TNF-, and IFN-γ-secreting T cells were assessed via flow cytometry.

Results

The frequencies of regulatory CD4⁺ and CD8⁺CD25⁺Foxp3⁺CD127^low/− T cells and TNF-α⁺ mDCs were induced following activation with TLR4, TLR7 and TLR8 agonists in the LP group. Moreover, increased baseline frequencies of CD4⁺IL-10⁺ T cells and CD8⁺IL-22⁺ or IFN-γ⁺T cells were found. In the LP group, TLR4 activation induced an increased frequency of CD4⁺IFN-γ⁺ T cells, while TLR7/8 and staphylococcal enterotoxin B (SEB) activation induced an increased frequency of CD8⁺ IL-22⁺ T cells. An increased frequency of polyfunctional CD4⁺ T cells that simultaneously secreted 3 of the evaluated cytokines (not including IL-10) was verified upon TLR7/8/9 activation, while polyfunctional CD8⁺ T cells were already detectable at baseline.

Conclusions

TLR-mediated activation of the innate immune response induced the production of proinflammatory mDCs, Tregs and polyfunctional T cells in patients with LP. Therefore, TLR activation has an adjuvant role in inducing both innate and adaptive immune responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0938-1) contains supplementary material, which is available to authorized users.

Impaired CD8(+) T cell responses upon Toll-like receptor activation in common variable immunodeficiency

Background

Infections caused by bacteria or viruses are frequent in common variable immunodeficiency (CVID) patients due to antibody deficiencies, which may be associated with altered T cell function. CVID patients are frequently in contact with pathogen-associated molecular patterns (PAMPs), leading to the activation of innate immunity through Toll-like receptors (TLR) affecting T cell activation. We evaluated the effect of TLR activation on T cells in CVID patients undergoing intravenous immunoglobulin (IVIg) replacement using synthetic ligands.

Methods

Expression of exhaustion, activation and maturation markers on T cells from peripheral blood as well as regulatory T cells and follicular T cells in peripheral blood mononuclear cells (PBMCs) from CVID and healthy individuals were evaluated by flow cytometry. PBMCs cultured with TLR agonists were assessed for intracellular IFN-γ, TNF, IL-10, IL-17a or IL-22 secretion as monofunctional or polyfunctional T cells (simultaneous cytokine secretion) by flow cytometry.

Results

We found increased expression of the exhaustion marker PD-1 on effector memory CD4⁺ T cells (CD45RA⁻CCR7⁻) in the peripheral blood and increased expression of CD38 in terminally differentiated CD8⁺ T cells (CD45RA⁺CCR7⁻). Furthermore, a decreased frequency of naïve regulatory T cells (CD45RA⁺Foxp3^low), but not of activated regulatory T cells (CD45RA⁻Foxp3^high) was detected in CVID patients with splenomegaly, the non-infectious manifestation in this CVID cohort (43.7 %). Moreover, the frequency of peripheral blood follicular helper T cells (CD3⁺CD4⁺CXCR5⁺PD-1⁺ICOS⁺) was similar between the CVID and control groups. Upon in vitro TLR3 activation, a decreased frequency of CD8⁺ T cells secreting IFN-γ, IL-17a or IL-22 was detected in the CVID group compared to the control group. However, a TLR7/TLR8 agonist and staphylococcal enterotoxin B induced an increased Th22/Tc22 (IL-22⁺, IFN-γ⁻, IL-17a⁻) response in CVID patients. Both TLR2 and TLR7/8/CL097 activation induced an increased response of CD4⁺ T cells secreting three cytokines (IL-17a, IL-22 and TNF)in CVID patients, whereas CD8⁺ T cells were unresponsive to these stimuli.

Conclusion

The data show that despite the unresponsive profile of CD8⁺ T cells to TLR activation, CD4⁺ T cells and Tc22/Th22 cells are responsive, suggesting that activation of innate immunity by TLRs could be a strategy to stimulate CD4⁺ T cells in CVID.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0900-2) contains supplementary material, which is available to authorized users.

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.