Association of Pathogenic Th17 Cells with the Disease Severity and Its Potential Implication for Biological Treatment Selection in Psoriasis Patients

Utility of IL-36 immunostaining in distinguishing psoriasis from pityriasis rosea and pityriasis lichenoides

BACKGROUND

Psoriasis is an inflammatory skin disease driven by upregulation of cytokines in the Th17 pathway, including interleukin-36 (IL-36). Previous studies have highlighted the utility of IL-36 immunostaining for psoriasis compared to spongiotic dermatitis and other psoriasiform dermatoses; however, no study has examined the role of IL-36 staining in distinguishing psoriasis from pityriasis rosea (PR) and pityriasis lichenoides (PL), known histologic mimickers of psoriasis.

METHODS

We compared the immunostaining pattern of IL-36 for 21 PR cases, 22 PL cases, and 10 psoriasis cases. We graded the immunostaining as 0, negative; 1, focal weak; 2, diffuse weak; 3, focal, strong; or 4, diffuse strong. We further categorized stains as negative (0-2 score) or positive (3-4 score) and utilized Fisher's exact test to compare the immunostaining pattern of these entities.

RESULTS

All psoriasis specimens were positive for IL-36, whereas all PR specimens were negative (p = 0.00000002). Twenty PL specimens were negative (p = 0.000001). Nine of 10 pityriasis lichenoides et varioliformis acuta cases were negative (p = 0.00012), and 11 of 12 cases of pityriasis lichenoides chronica were negative (p = 0.00003).

CONCLUSIONS

Our findings highlight the potential role of IL-36 immunostaining in distinguishing psoriasis from other psoriasiform dermatoses, including PR and PL.

The role of adipokines in the pathogenesis of psoriasis - a focus on resistin, omentin-1 and vaspin

BACKGROUND

Psoriasis is a chronic immune-mediated skin condition with several types of manifestation, including psoriatic arthritis. In recent years, studies have demonstrated multiple molecules and mechanisms that play important roles in the pathophysiology of psoriasis. Studies have been conducted to determine the role of adipokines, bioactive peptides secreted by the adipose tissue, in the pathogenesis of inflammatory diseases. These studies have shown that adipokines are dysregulated in psoriasis and their abnormal expression profile could contribute to the inflammatory mechanisms observed in psoriasis.

AREAS COVERED

In this review, we discuss the immunomodulatory features of resistin, omentin-1, and vaspin, and discuss their potential involvement in the pathogenesis of psoriasis.

EXPERT OPINION

The adipokines resistin, omentin, and vaspin appear to be promising therapeutic targets in psoriasis. It is important to seek to block the action of resistin, either by blocking its receptors or by blocking its systemic effects with antibodies. In the case of omentin and vaspin, substances that are receptor mimetics of these adipokines should be sought and studies conducted of their analogues for the treatment of psoriasis. To introduce these therapies into clinical practice, multicentre clinical trials are required to confirm their efficacy and safety after initial studies in animal models.

Distinct Th17 effector cytokines differentially promote microglial and blood-brain barrier inflammatory responses during post-infectious encephalitis

Group A Streptococcus (GAS) infections can cause neuropsychiatric sequelae in children due to post-infectious encephalitis. Multiple GAS infections induce migration of Th17 lymphocytes from the nose into the brain, which are critical for microglial activation, blood-brain barrier (BBB) and neural circuit impairment in a mouse disease model. How endothelial cells (ECs) and microglia respond to GAS infections, and which Th17-derived cytokines are essential for these responses are unknown. Using single-cell RNA sequencing and spatial transcriptomics, we found that ECs downregulate BBB genes and microglia upregulate interferon-response, chemokine and antigen-presentation genes after GAS infections. Several microglial-derived chemokines were elevated in patient sera. Administration of a neutralizing antibody against interleukin-17A (IL-17A), but not ablation of granulocyte-macrophage colony-stimulating factor (GM-CSF) in T cells, partially rescued BBB dysfunction and microglial expression of chemokine genes. Thus, IL-17A is critical for neuropsychiatric sequelae of GAS infections and may be targeted to treat these disorders.

Low-Dose IL-2 Attenuated Depression-like Behaviors and Pathological Changes through Restoring the Balances between IL-6 and TGF-β and between Th17 and Treg in a Chronic Stress-Induced Mouse Model of Depression

Microglia activation, increased IL-6 and decreased TGF-β were found in depressed patients or in animal models of depression. IL-6 enhances T helper 17 cell differentiation, thereby causing an imbalance between Th17 and Treg cells, which induces neuroinflammation and neuronal dysfunction. However, whether imbalances between IL-6 and TGF-β and between Th17 and Treg occur in depression and whether depression can be improved upon restoring these imbalances are unknown. Treg promoter IL-2 (1500UI/0.1 mL/day) was used to treat a mouse model of depression induced by chronic unpredictable mild stress (CUMS). The behavior and concentrations of IL-6, TGF-β, Th17, IL-17A, IL-17Rc, Treg-related factors (helios and STAT5), astrocyte A1 phenotype S100β, microglia M1 phenotype Iba-1, indoleamine-2,3-dioxygenase (IDO) enzyme, corticosterone (CORT) and neurotransmitters were evaluated. When compared to controls, CUMS reduced sucrose preference, the number of entries into and the time spent in the open arms of the elevated plus maze and the exploration in the "open field", while it increased the immobility time in tail suspension, which was ameliorated by IL-2 treatment. RoRα, S100β, IL-17A, IL-17Rc, IL-6, Iba-1, IDO enzyme and CORT concentrations were significantly increased, and Helios, FoxP3⁺, STAT5 and TGF-β were significantly decreased by CUMS, which were significantly attenuated by IL-2 when compared to the CUMS group. The NE, DA and 5-HT contents and those of their metabolites were decreased by CUMS, which returned to control levels after IL-2 treatment. The study demonstrated that imbalances between IL-6 and TGF-β and between Th17and Treg occurred in the hippocampus of the depression model. IL-2 attenuated depression- and anxiety-like behaviors and normalized the neurotransmitter concentration and the activity of the IDO enzyme, astrocytes and microglia through restoring both balances, but it did not decrease the CORT concentration.

Ex vivo cytokine production in psoriatic disease: Towards specific signatures in cutaneous psoriasis and peripheral psoriatic arthritis

Objectives

Psoriatic arthritis (PsA) and cutaneous psoriasis (PsO) are different phenotypes of psoriatic disease (PsD), whose underlying specific mechanisms remain incompletely understood. As cytokines are key elements to induce and tune up immune responses to drive inflammatory diseases, our objective was to assess whether clinical features, disease phenotype and PsA and PsO activity were associated with a particular ex vivo cytokine production profile.

Methods

Forty-eight patients (37 PsA and 11 PsO) and 11 healthy subjects (HS) were studied. Cytokine production by peripheral blood mononuclear cells (PBMC) that were either unstimulated, or stimulated with LPS or anti-CD3/CD28 antibodies, were analysed by multiplex assay in the culture supernatants.

Results

Cytokine signature of PsD includes a high level of TNFα in supernatants of LPS-stimulated PBMC, higher levels of IL-6 and lower levels of IFN-γ and IL-17A after CD3-CD28 stimulation, as well as higher spontaneous IL-1RA and TNFα production compared to HS. High body mass index (BMI) was associated with lower levels of IL-1β, and metabolic syndrome with lower levels of IFN-γ after LPS stimulation. In PsD, dermatological activity was related with higher IL-17A level, while rheumatic activity was linked with lower levels of IFN-γ and TNFα. Comparing each PsD subtype to HS, IL-1β and IL-6 productions are higher when using LPS stimulation in PsO patients with higher levels of IL-1β and IL-1α in peripheral PsA patients after CD3/CD28 stimulation. LPS stimulation induced high levels of IL-17A in peripheral PsA compared to axial PsA. PsA patients with axial PsA share some features with PsO but shows a distinct cytokine pattern compared to peripheral PsA.

Conclusion

PsO and the different PsA subtypes exhibit distinct ex vivo cytokine production profiles and common features of the so-called PsD. Analysis of IL-1 cytokine family and IL-6 seems to be of particular interest to distinguish PsO and peripheral PsA since it depends on monocytes in PsO and T-lymphocytes in peripheral PsA. Peripheral cytokine profiles are influenced by rheumatic and dermatological activity of the disease, and also by metabolic syndrome features. Our results highlight the crucial role of immune cell interactions with different patterns of interaction depending on clinical phenotype.

The antimicrobial peptide cathelicidin drives development of experimental autoimmune encephalomyelitis in mice by affecting Th17 differentiation

Multiple sclerosis (MS) is a highly prevalent demyelinating autoimmune condition; the mechanisms regulating its severity and progression are unclear. The IL-17-producing Th17 subset of T cells has been widely implicated in MS and in the mouse model, experimental autoimmune encephalomyelitis (EAE). However, the differentiation and regulation of Th17 cells during EAE remain incompletely understood. Although evidence is mounting that the antimicrobial peptide cathelicidin profoundly affects early T cell differentiation, no studies have looked at its role in longer-term T cell responses. Now, we report that cathelicidin drives severe EAE disease. It is released from neutrophils, microglia, and endothelial cells throughout disease; its interaction with T cells potentiates Th17 differentiation in lymph nodes and Th17 to exTh17 plasticity and IFN-γ production in the spinal cord. As a consequence, mice lacking cathelicidin are protected from severe EAE. In addition, we show that cathelicidin is produced by the same cell types in the active brain lesions in human MS disease. We propose that cathelicidin exposure results in highly activated, cytokine-producing T cells, which drive autoimmunity; this is a mechanism through which neutrophils amplify inflammation in the central nervous system.

Peripheral Blood T Cells of Patients with IPAH Have a Reduced Cytokine-Producing Capacity

Pulmonary arterial hypertension (PAH) is rare disease that is categorized as idiopathic (IPAH) when no underlying cause can be identified. Lungs of most patients with IPAH contain increased numbers of T cells and dendritic cells (DCs), suggesting involvement of the immune system in its pathophysiology. However, our knowledge on circulating immune cells in IPAH is rather limited. We used flow cytometry to characterize peripheral blood DCs and T cells in treatment-naive IPAH patients, compared with connective-tissue disease-PAH (CTD-PAH) patients and healthy controls (HCs). At diagnosis, T-helper (Th) cells of IPAH patients were less capable of producing TNFα, IFNγ, IL-4 and IL-17 compared to HCs. IPAH patients showed a decreased frequency of Th2 cells and significantly enhanced expression of the CTLA4 checkpoint molecule in naive CD4⁺ T cells and both naive and memory CD8⁺ T cells. Frequencies and surface marker expression of circulating DCs and monocytes were essentially comparable between IPAH patients and HCs. Principal component analysis (PCA) separated IPAH patients—but not CTD-PAH patients—from HCs, based on T-cell cytokine profiles. At 1-year follow-up, the frequencies of IL-17⁺ production by memory CD4⁺ T cells were increased in IPAH patients and accompanied by increased proportions of Th17 and Tc17 cells, as well as decreased CTLA4 expression. Treatment-naive IPAH patients displayed a unique T-cell phenotype that was different from CTD-PAH patients and was characterized by reduced cytokine-producing capacity. These findings point to involvement of adaptive immune responses in IPAH, which may have an implication for the development of therapeutic interventions.

Minimal Physiologically-Based Pharmacokinetic (mPBPK) Metamodeling of Target Engagement in Skin Informs Anti-IL17A Drug Development in Psoriasis

The pharmacologic effect(s) of biotherapeutics directed against soluble targets are driven by the magnitude and duration of free target suppression at the tissue site(s) of action. Interleukin (IL)-17A is an inflammatory cytokine that plays a key role in the pathogenesis of psoriasis. In this work, clinical trial data from two monoclonal antibodies (mAbs) targeting IL-17A for treatment of psoriasis (secukinumab and ixekizumab) were analyzed simultaneously to quantitatively predict their target engagement (TE) profiles in psoriatic skin. First, a model-based meta-analysis (MBMA) for clinical responses was conducted separately for each drug based on dose. Next, a minimal physiologically-based pharmacokinetic (mPBPK) model was built to assess skin site IL-17A target engagement for ixekizumab and secukinumab simultaneously. The mPBPK model captured the observed drug PK, serum total IL-17A, and skin drug concentration-time profiles reasonably well across the different dosage regimens investigated. The developed mPBPK model was then used to predict the average TE (i.e., free IL-17A suppression) in skin achieved over a 12-weeks treatment period for each drug following their respective regimens and subsequently assess the TE-efficacy response relationship. It was predicted that secukinumab achieved 98.6% average TE in the skin at 300 mg q4w SC while ixekizumab achieved 99.9% average TE under 160 mg (loading) followed by 80 mg q2w SC. While direct quantification of free IL-17A levels at the site of action is technically challenging, integrated mPBPK-MBMA approaches offer quantitative predictions of free IL-17A levels at the site of action to facilitate future drug development via IL-17A suppression in psoriasis.

Proximal and Distal Regions of Pathogenic Th17 Related Chromatin Loci Are Sequentially Accessible During Pathogenicity of Th17

Pathogenic Th17, featured by their production of pro-inflammatory cytokines, are considered as a key player in most autoimmune diseases. The transcriptome of them is obviously distinct from that of conventional regulatory Th17. However, chromatin accessibility of the two Th17 groups have not been comprehensively compared yet. Here, we found that their chromatin-accessible regions(ChARs) significantly correlated with the expression of related genes, indicating that they might engage in the regulation of these genes. Indeed, pathogenic Th17 specific ChARs (patho-ChARs) exhibited a significant distribution preference in TSS-proximal region. We further filtered the patho-ChARs based on their conservation among mammalians or their concordance with the expression of their related genes. In either situation, the filtered patho-ChARs also showed a preference for TSS-proximal region. Enrichment of expression concordant patho-ChARs related genes suggested that they might involve in the pathogenicity of Th17. Thus, we also examined all ChARs of patho-ChARs related genes, and defined an opening ChAR set according to their changes in the Th17 to Th1 conversion. Interestingly, these opening ChARs displayed a sequential accessibility change from TSS-proximal region to TSS-distal region. Meanwhile, a group of patho-TFs (transcription factors) were identified based on the appearance of their binding motifs in the opening ChARs. Consistently, some of them also displayed a similar preference for binding the TSS-proximal region. Single-cell transcriptome analysis further confirmed that these patho-TFs were involved in the generation of pathogenic Th17. Therefore, our results shed light on a new regulatory mechanism underlying the generation of pathogenic Th17, which is worth to be considered for autoimmune disease therapy.

The Protective Role of pVHL in Imiquimod-Induced Psoriasis-like Skin Inflammation

Psoriasis is a chronic inflammatory disease distinguished by an excessive proliferation and abnormal differentiation of keratinocytes. Immune cells, such as T lymphocytes and neutrophils, and inflammatory cytokines, such as Tumor Necrosis Factor-α (TNF-α) and interleukin 17 (IL-17), are essential for maintaining psoriatic lesions. Additionally, a hypoxic milieu present in the skin promotes the expression of transcriptional factor hypoxia-inducible factor-1 alpha (HIF-1α). This protein regulates the expression of angiogenic and glycolytic factors, such as vascular endothelial grown factor and lactate dehydrogenase (LDH), both relevant in chronic inflammation. The von Hippel–Lindau protein (pVHL) is a negative regulator of HIF-1α. Previously, we found that pVHL was almost absent in the lesions of psoriasis patients; therefore, we investigated the impact of rescue pVHL expression in lesional skin. We used the imiquimod-induced psoriasis-like mouse model as an adenoviral vector that allowed us to express pVHL in the skin. Our data show that, in lesional skin, pVHL expression was reduced, whereas HIF-1α was increased. Remarkably, the retrieval of pVHL prevented psoriatic lesions, diminishing erythema, scale, and epidermal and vascular thickness. Furthermore, pVHL expression was capable of reducing HIF-1α, LDH, TNF-α and immune cell infiltration (mainly IL-17⁺ neutrophils). In conclusion, our results demonstrate that pVHL has a protective role to play in the pathophysiology of psoriasis.

3, 3'- diindolylmethane hinders IL-17A/IL-17RA interaction and mitigates imiquimod-induced psoriasiform in mice

Psoriasis is a highly inflammatory autoimmune-mediated skin disease. The strongest evidence has pointed to the influential role of interleukin (IL) -17A in the aberrant pathology of psoriasis. Henceforth, targeting the IL-17A cytokine is of prime importance in controlling the disease severity of psoriasis. Reportedly, 3, 3'- diindolylmethane (DIM) is a phytochemical that alleviated acute atopic dermatitis. Howbeit, the therapeutic intervention of DIM against IL-17A/IL-17RA interaction and its signaling mediated pathogenesis in psoriasis remains unexplored. In the current report, we decoded the molecular basis of DIM in psoriasis. Docking analysis has reported that DIM identified an IL-17A binding region in the functional fibronectin-III-like domain of IL-17RA and abrogated IL-17A/IL-17RA interaction. In-vitro experiments demonstrated that DIM impeded IL-17A mediated hyper-proliferative phenotype of psoriatic-like keratinocytes. Furthermore, DIM abated the catabolic effects of IL-17A stimulated expression of pathogenic mediators like HMGB-1, Cyr-61, CCL-20, and VEGF via blunted activation of JAK/STAT pathway in psoriatic like keratinocytes. Profoundly, DIM restricted the reprogramming of psoriatic-like keratinocytes to overexpress IL-17RA in concert with IL-17A stimulation. In line with in-vitro studies, DIM also ameliorated skin lesions and epidermal hyperplasia in an imiquimod-induced mice model of psoriasis. Additionally, DIM also reduced STAT-3 phosphorylation and associated expression of Cyr-61, CCL-20, and VEGF in psoriatic mice. However, if DIM has a direct effect on STAT-3 inhibition or it negatively regulates STAT-3 function via blockade of IL-17A/IL-17RA interaction needs to be investigated in the future. Conclusively, our studies demonstrated that the blockade of IL-17A/IL-17RA interaction is a novel therapeutic perspective of DIM against the progression of psoriasis disease.

Skin Barrier Dysregulation in Psoriasis

The skin barrier is broadly composed of two elements-a physical barrier mostly localised in the epidermis, and an immune barrier localised in both the dermis and epidermis. These two systems interact cooperatively to maintain skin homeostasis and overall human health. However, if dysregulated, several skin diseases may arise. Psoriasis is one of the most prevalent skin diseases associated with disrupted barrier function. It is characterised by the formation of psoriatic lesions, the aberrant differentiation and proliferation of keratinocytes, and excessive inflammation. In this review, we summarize recent discoveries in disease pathogenesis, including the contribution of keratinocytes, immune cells, genetic and environmental factors, and how they advance current and future treatments.

Th17 Cells in Periodontitis and Its Regulation by A20

Periodontitis is a prevalent chronic disease that results in loss of periodontal ligament and bone resorption. Triggered by pathogens and prolonged inflammation, periodontitis is modulated by the immune system, especially pro-inflammatory cells, such as T helper (Th) 17 cells. Originated from CD4⁺ Th cells, Th17 cells play a central role for they drive and regulate periodontal inflammation. Cytokines secreted by Th17 cells are also major players in the pathogenesis of periodontitis. Given the importance of Th17 cells, modulators of Th17 cells are of great clinical potential and worth of discussion. This review aims to provide an overview of the current understanding of the effect of Th17 cells on periodontitis, as well as a brief discussion of current and potential therapies targeting Th17 cells. Lastly, we highlight this article by summarizing the causal relationship between A20 (encoded by TNFAIP3), an anti-inflammatory molecule, and Th17 cell differentiation.

CCR6-CCL20 axis as a therapeutic target for autoimmune diseases

Chemokine receptor CCR6 is expressed on various cells such as B cells, immature dendritic cells, innate lymphoid cells (ILCs), regulatory CD4 T cells, and Th17 cells. CCL20 is the only known high-affinity ligand that binds to CCR6 and drives CCR6⁺ cells' migration in tissues. CCL20 is mainly produced by epithelial cells, and its expression is increased by several folds under inflammatory conditions. Genome-wide association studies (GWAS) in patients with inflammatory bowel disease (IBD), psoriasis (PS), rheumatoid arthritis (RA), and multiple sclerosis (MS) showed a very strong correlation between the expression of CCR6 and disease severity. It has been shown that disruption of CCR6-CCL20 interaction by using antibodies or antagonists prevents the migration of CCR6 expressing immune cells at the site of inflammation and reduces the severity of the disease. This review discussed the importance of the CCR6-CCL20 axis in IBD, PS, RA, and MS, and recent advances in targeting the CCR6-CCL20 in controlling these autoimmune diseases.