Revisiting the interleukin 17 family of cytokines in psoriasis: pathogenesis and potential targets for innovative therapies

Efficacy of Brodalumab in Patients with Psoriasis and Risk Factors for Treatment Failure: A Review of Post Hoc Analyses

Factors such as obesity, alcohol consumption, and tobacco use are associated with both increased psoriasis severity and inadequate response to systemic and biologic therapies. Obesity is linked to chronic inflammation, which can contribute to psoriasis pathogenesis. Fixed-dose therapies may have reduced efficacy in patients with a higher body mass index, while weight-based dosing can increase the burden of drug-specific side effects. Alcohol and nicotine from tobacco have also been shown to stimulate keratinocyte and immune cell proliferation and production of proinflammatory cytokines. While these risk factors are prevalent among patients with moderate-to-severe psoriasis, their influence on treatment outcomes may be overlooked when evaluating therapeutic options. Brodalumab is a fully human interleukin-17 receptor A antagonist approved for the treatment of moderate-to-severe psoriasis. In this review, we describe the lifestyle-related risk factors associated with decreased response to treatment. We further summarize the post hoc analyses of brodalumab in participant subgroups with moderate-to-severe psoriasis and a history of prior biologic failure, obesity, and alcohol or tobacco use from two phase 3 clinical trials (AMAGINE-2 and AMAGINE-3; ClinicalTrials.gov identifiers: NCT01708603 and NCT01708629, respectively). Our review of clinical trial and real-world data suggests that brodalumab is an efficacious and safe treatment option for patients with lifestyle factors that increase the likelihood of treatment failure, allowing them to achieve skin clearance and improve quality of life.

Targeting cytokine networks in neuroinflammatory diseases

In neuroinflammatory diseases, systemic (blood-borne) leukocytes invade the central nervous system (CNS) and lead to tissue damage. A causal relationship between neuroinflammatory diseases and dysregulated cytokine networks is well established across several preclinical models. Cytokine dysregulation is also observed as an inadvertent effect of cancer immunotherapy, where it often leads to neuroinflammation. Neuroinflammatory diseases can be separated into those in which a pathogen is at the centre of the immune response and those of largely unknown aetiology. Here, we discuss the pathophysiology, cytokine networks and therapeutic landscape of 'sterile' neuroinflammatory diseases such as multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), neurosarcoidosis and immune effector cell-associated neurotoxicity syndrome (ICANS) triggered by cancer immunotherapy. Despite successes in targeting cytokine networks in preclinical models of neuroinflammation, the clinical translation of targeting cytokines and their receptors has shown mixed and often paradoxical responses.

The immunologic role of IL-23 in psoriatic arthritis: a potential therapeutic target

INTRODUCTION

Psoriatic arthritis (PsA) is a debilitating chronic condition characterized by inflammation of the joints, bones, enthesis, and skin. The pivotal role of interleukin-23 (IL-23) in the pathogenesis of PsA has become increasingly evident. This proinflammatory cytokine is markedly elevated in patients with PsA, suggesting its potential as a therapeutic target. Consequently, IL-23 inhibitors have emerged as promising first-line biologic treatments for PsA.

AREAS COVERED

This review delves into the immunopathogenic mechanisms of IL-23 at the cellular and molecular levels in PsA. Furthermore, it provides the recent efficacy and safety profiles of IL-23 inhibitors. We conducted a literature search in PubMed for the following terms: 'IL-23 and psoriatic arthritis,' 'Ustekinumab,' 'Guselkumab,' 'Risankizumab,' and 'Tildrakizumab.' In addition, we retrieved clinical trials involving IL-23 inhibitors registered in ClinicalTrials.gov, EudraCT, and ICTRP.

EXPERT OPINION

Despite the promising outcomes observed with IL-23 inhibitors, several challenges persist. The long-term effects of these agents require further investigation through prospective studies, and their limited accessibility worldwide necessitates urgent attention. Additionally, ongoing research is warranted to explore other potential drug targets within the IL-23/IL-23 R axis. The development of reliable biomarkers could greatly enhance early detection, tailored management strategies, and personalized treatment approaches for patients with PsA.

IL-17 and IL-23 Inhibitors Have the Fastest Time to Meaningful Clinical Response for Plaque Psoriasis: A Network Meta-Analysis

Background/Objectives: Several treatment options with differing mechanisms exist for plaque psoriasis. The objective of this analysis was to compare the time to onset of action among the available systemic therapies for plaque psoriasis. Methods: Randomized controlled trials that investigated two or more therapeutics for the management of moderate to severe plaque psoriasis were included. A weighted average time for 50% of patients to reach PASI75 and PAI90 with each of the therapeutics was calculated. A network meta-analysis was performed to determine which therapeutics were significantly faster in time to meaningful clinical response than others. Results: IL-17 inhibitors had the shortest time to achieve PASI75 and PASI90 followed by risankizumab in the weighted mean analysis. In the meta-analysis, the fastest time to PASI75 was seen with bimekizumab, brodalumab and ixekizumab. No significant (p < 0.05) difference was seen in the time to meaningful clinical response between these drugs; however, bimekizumab was significantly faster in time to PASI75 among the remaining therapeutics. In the meta-analysis for PASI90, the fastest time was seen with ixekizumab, bimekizumab, risankizumab, secukinumab and guselkumab with no significant differences in between these therapeutics. However, bimekizumab was significantly faster than the remaining therapeutics for PASI90. Conclusions: IL-17 and IL-23 inhibitors may be considered as requiring the shortest time for meaningful clinical response in plaque psoriasis. In addition to the time to onset, the safety profile of each drug needs to be considered when deciding on a therapeutic to initiate.

New and emerging oral therapies for psoriasis

Psoriasis is a chronic inflammatory skin disease affecting 2-3% of the global population. Traditional systemic treatments, such as methotrexate, cyclosporine, acitretin and fumaric acid esters, have limited efficacy and are associated with significant adverse effects, necessitating regular monitoring and posing risks of long-term toxicity. Recent advancements have introduced biologic drugs that offer improved efficacy and safety profiles. However, their high cost and the inconvenience of parenteral administration limit their accessibility. Consequently, there is a growing interest in developing new, targeted oral therapies. Small molecules, such as phosphodiesterase 4 inhibitors (e.g. apremilast) and TYK2 inhibitor (e.g. deucravacitinib), have shown promising results with favourable safety profiles. Additionally, other novel oral agents targeting specific pathways, including IL-17, IL-23, TNF, S1PR1 and A3AR, are under investigation. These treatments aim to combine the efficacy of biologics with the convenience and accessibility of oral administration, addressing the limitations of current therapies. This narrative review synthesizes the emerging oral therapeutic agents for psoriasis, focusing on their mechanisms of action, stages of development and clinical trial results.

A Non-Coding Oligonucleotide Recruits Cutaneous CD11b+ Cells that Inhibit Thelper Responses and Promote Tregs

Skin-resident antigen-presenting cells (APC) play an important role in maintaining peripheral tolerance via immune checkpoint proteins and induction of T regulatory cells (Tregs). However, there is a lack of knowledge on how to expand or recruit immunoregulatory cutaneous cells without causing inflammation. Here, it is shown that administration of a non-coding single-stranded oligonucleotide (ssON) leads to CCR2-dependent accumulation of CD45+CD11b+Ly6C+ cells in the skin that express substantial levels of PD-L1 and ILT3. Transcriptomic analyses of skin biopsies reveal the upregulation of key immunosuppressive genes after ssON administration. Functionally, the cutaneous CD11b+ cells inhibit Th1/2/9 responses and promote the induction of CD4+FoxP3+ T-cells. In addition, ssON treatment of imiquimod-induced inflammation results in significantly reduced Th17 responses. It is also shown that induction of IL-10 production in the presence of cutaneous CD11b+ cells isolated after ssON administrations is partly PD-L1 dependent. Altogether, an immunomodulatory ssON is identified that can be used therapeutically to recruit cutaneous CD11b+ cells with the capacity to dampen Th cells.

Ameliorative effects of topical ramelteon on imiquimod-induced psoriasiform inflammation in mice

Psoriasis is a long-lasting, immune-related inflammatory skin disease that affects 2-3% of the global population. It is distinguished by erythematous, silvery, and scaly patches. Ramelteon is a type of melatonin agonist that is used to treat insomnia. It has enhanced non-classical immunomodulatory and anti-inflammatory activities. The aim of the study is to assess the ameliorative effects of topical ramelteon on imiquimod (IMQ)-aggravated psoriasiform-like dermatosis in mice. The 32 albino mouse males were placed into six groups of eight animals, all of them. With the exception of the control group, all groups gained a once-a-day regimen of topical imiquimod 5% cream at a dose of 62.5 mg for eight uninterrupted days, while mice in the control group gained vaseline-based ointment alternately. Immediately after an 8-day induction period in the imiquimod group, mice in the clobetasol and ramelteon treatment groups obtained a twice-daily regimen of topical clobetasol propionate 0.05% ointment and 0.1% ointment, respectively, for a further 8 days. This extends the total duration of the experimental study to 16 continuous days. The findings of our study found that ramelteon significantly mitigated the concentrations of inflammatory cytokines in the skin tissue, including interleukin (IL)-6, IL-17A, IL-23, tumor necrosis factor-α (TNF-α), and vascular endothelial growth factor (VEGF), as well as the scores associated with psoriatic lesions, including erythema, scaling, skin thickening, ear thickness, and overall cumulative PASI scores. Additionally, the anti-inflammatory impact of ramelteon was achieved by markedly increasing IL-10 levels in the skin tissue and correcting cutaneous histopathological alterations. Ramelteon ointment (0.1%) was comparable to that of clobetasol (0.05%) ointment in alleviating a mouse model of imiquimod-induced psoriasiform inflammation; this is probably due to its potential anti-inflammatory and immunomodulatory activities. Therefore, ramelteon could be a good additive option for therapeutic management of immune-triggered inflammatory conditions such as psoriasis.

Interleukin-38 overexpression in keratinocytes limits desquamation but does not affect the global severity of imiquimod-induced skin inflammation in mice

Psoriasis is a common chronic inflammatory skin disease that significantly impacts the patients' quality of life. Recent studies highlighted the function of the interleukin (IL)-1 family member IL-38 in skin homeostasis and suggested an anti-inflammatory role for this cytokine in psoriasis. In this study, we generated mice specifically overexpressing the IL-38 protein in epidermal keratinocytes. We confirmed IL-38 overexpression in the skin by Western blotting. We further detected the protein by ELISA in the plasma, as well as in conditioned media of skin explants isolated from IL-38 overexpressing mice, indicating that IL-38 produced in the epidermis is released from keratinocytes and can be found in the circulation. Unexpectedly, epidermal IL-38 overexpression did not impact the global severity of imiquimod (IMQ)-induced skin inflammation, Similarly, keratinocyte activation and differentiation in IMQ-treated skin were not affected by increased IL-38 expression and there was no global effect on local or systemic inflammatory responses. Nevertheless, we observed a selective inhibition of CXCL1 and IL-6 production in response to IMQ in IL-38 overexpressing skin, as well as reduced Ly6g mRNA levels, suggesting decreased neutrophil infiltration. Epidermal IL-38 overexpression also selectively affected the desquamation process during IMQ-induced psoriasis, as illustrated by reduced plaque formation. Taken together, our results validate the generation of a new mouse line allowing for tissue-specific IL-38 overexpression. Interestingly, epidermal IL-38 overexpression selectively affected specific disease-associated readouts during IMQ-induced psoriasis, suggesting a more complex role of IL-38 in the inflamed skin than previously recognized. In particular, our data highlight a potential involvement of IL-38 in the regulation of skin desquamation.

Effectiveness of Ixekizumab in Elderly Patients for the Treatment of Moderate-to-Severe Psoriasis: Results From a Multicenter, Retrospective Real-Life Study in the Lazio Region

INTRODUCTION

This was an observational, retrospective, multicenter study, enrolling elderly patients (>65 years old) treated with ixekizumab with a diagnosis of psoriasis (PsO) and/or psoriatic arthritis (PsA) during the period 2020 to 2023.

OBJECTIVES

Efficacy of ixekizumab in elderly patients in the treatment of moderate to severe psoriasis.

METHODS

We included 73 patients with psoriasis (32.9%), psoriatic arthritis (1.4%) and both of them (PsO-PsA 65.8%), attending the outpatient clinics of seven Italian referral center for psoriasis in Lazio region: Policlinico Umberto I Università Roma La Sapienza, Sant'Andrea Università di Roma La Sapienza, Polo Pontino Università Roma La Sapienza, Fondazione Policlinico Universitario A. Gemelli, Università Campus Biomedico Roma, Istituto Dermopatico dell'Immacolata - IDI and Policlinico Tor Vergata. We collected data related to the characteristics of the patients (age, sex, body mass index) and of the disease (age at onset, duration of psoriasis, previous treatments). The severity of psoriasis was measured with the Psoriasis Area and Severity Index (PASI) score at baseline and after 16, 24, 52, 104 and 156 weeks of treatment.

RESULTS

PASI90 was achieved by all the patients in week 16 and remained stable until the end of the study. PASI100 has been achieved by 55.1% of patients at weeks 16 and by 81.3% at week 104. A statistically significant difference has been showed between baseline and all the other time points (P < 0.0001) for PASI score. A similar trend was observed for Visual Analogue Scale score and Dermatology Life Quality Index score.

CONCLUSIONS

Ixekizumab was effective and with a good safety profile in psoriatic patients over 65 years. No significant adverse events were reported.

The Psoriasis Treatment Pipeline: An Overview and Update

Significant research advances in our understanding of psoriatic disease have led to the development of several highly selective, effective, and safe topical and systemic treatments. These treatments have led to unprecedented levels of disease clearance and control for most patients with psoriasis with cutaneous disease. However, there remains a need for improved treatments for those patients with recalcitrant disease, psoriatic arthritis, or nonplaque disease variants. Recently approved therapies and investigational products in ongoing clinical development programs that target IL-17A/F, IL-23, TYK2, PDE4, AhR or IL-36 cytokine signaling are improving the clinician's ability to care for a broader range of patients affected by psoriasis.

Air pollution and skin diseases: A comprehensive evaluation of the associated mechanism

Air pollutants deteriorate the survival environment and endanger human health around the world. A large number of studies have confirmed that air pollution jeopardizes multiple organs, such as the cardiovascular, respiratory, and central nervous systems. Skin is the largest organ and the first barrier that protects us from the outside world. Air pollutants such as particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs) will affect the structure and function of the skin and bring about the development of inflammatory skin diseases (atopic dermatitis (AD), psoriasis), skin accessory diseases (acne, alopecia), auto-immune skin diseases (cutaneous lupus erythematosus(CLE) scleroderma), and even skin tumors (melanoma, basal cell carcinoma (BCC), squamous-cell carcinoma (SCC)). Oxidative stress, skin barrier damage, microbiome dysbiosis, and skin inflammation are the pathogenesis of air pollution stimulation. In this review, we summarize the current evidence on the effects of air pollution on skin diseases and possible mechanisms to provide strategies for future research.

IFN-γ, IL-17A, IL-4, and IL-13: Potential Biomarkers for Prediction of the Effectiveness of Biologics in Psoriasis Patients

Biologics are widely used to treat moderate-to-severe psoriasis. However, we have unmet needs for predicting individual patient responses to biologics before starting psoriasis treatment. We investigate a reliable platform and biomarkers for predicting individual patient responses to biologics. In a cohort study between 2018 and 2023 from a referral center in Taiwan, twenty psoriasis patients with or without psoriatic arthritis who had ever experienced two or more biologics were enrolled. Peripheral blood mononuclear cells obtained from these patients were treated with Streptococcus pyogenes and different biologics. The PASI reduction rate was strongly correlated with the reduction rate in the IL-13 level (p = 0.001) and the ratios of IFN-γ to IL-13 (p < 0.001), IFN-γ to IL-4 (p = 0.019), and IL-17A to IL-13 (p = 0.001). The PASI reduction difference was strongly correlated with the difference in the IFN-γ level (p = 0.002), the difference in the ratios of IFN-γ to IL-4 (p = 0.041), the difference in the ratios of IFN-γ to IL-13 (p = 0.006), the difference in the ratios of IL-17A to IL-4 (p = 0.011), and the difference in the ratios of IL-17A to IL-13 (p = 0.029). The biomarkers IFN-γ, IL-13, IFN-γ/IL4, IFN-γ/IL13, IL-17A/IL-4, and IL-17A/IL-13 are representative of the effectiveness of psoriasis treatment.

Granzyme K+ CD8 T cells in autoimmunity

CD8 T cells expressing granzyme K are enriched in synovial tissue from patients with rheumatoid arthritis and in tissues affected by several other autoimmune diseases. The roles these cells play in autoimmune disease is under active investigation, and several recent studies have begun to shed light on this question. Putting this cell type into functional perspective is especially important given their enrichment at the sites of disease. This review summarizes available evidence for the presence of CD8 T cells and other granzyme K-expressing cells in tissues in autoimmune diseases and discusses the effects these cells may have on the pathogenesis of autoimmune conditions.

Immunotherapy in cutaneous melanoma and biologics in psoriatic disease: similarities and differences from a clinical multidisciplinary perspective

INTRODUCTION

Immunomodulating therapies harness the power of the immune system to combat disease. In advanced melanoma, immune checkpoint inhibitors have significantly improved survival outcomes by activating the immune system to recognize and eliminate cancer cells. In psoriasis, interleukin inhibitors effectively suppress inflammation and improve disease symptoms.

AREAS COVERED

We provide a meta-opinion-based consensus paper on the analogies and differences in treatment mechanisms, duration, frequency between immunotherapy for advanced melanoma and biologics for psoriasis. Combining the current scientific evidence with expert insights, we provide valuable guidance for future research and decision-making processes.

EXPERT OPINION

The development of immunological treatments in melanoma and psoriasis has revolutionized dermatology, but the quest for tailored therapies that maximize efficacy continues. Managing cutaneous exacerbations during melanoma immunotherapy in psoriatic patients remains challenging. Similarly, treating oncologic psoriasis patients resistant to traditional therapies requires individualized approaches. Research is needed to identify response predictors in both conditions and address the sustainability of healthcare systems due to the high cost of biologics. Drug delay studies for psoriasis and longer follow-up evaluations after immunotherapy discontinuation in melanoma are essential for optimizing treatment outcomes and resource allocation.

Increased neutrophil-derived IL-17A identified in generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is considered to be a distinct clinical entity from psoriasis vulgaris (PV), with different clinical and histological manifestations. The pathogenesis of GPP has not been thoroughly elucidated, especially in those patients lacking interleukin (IL)36RN. In present study, we performed RNA sequence analysis on skin lesions from 10 GPP patients (4 with and 6 without IL36RN mutation) and 10 PV patients without IL36RN mutation. Compared with PV, significantly overexpressed genes in GPP patients were enriched in IL-17 signalling pathway (MMP1, MMP3, DEFB4A and DEFB4B, etc.) and associated with neutrophil infiltration (MMP1, MMP3, ANXA and SERPINB, etc.). GPP with IL36RN mutations evidenced WNT11 upregulation and IL36RN downregulation in comparison to those GPP without IL36RN mutations. The expression of IL-17A/IL-36 in skin or serum and the origin of IL-17A in skin were also investigated. IL-17A expression in skin was significantly higher in GPP than PV patients, whereas, there were no differences in skin IL-36α/IL-36γ/IL-36RA or serum IL-17A/IL-36α/IL-36γ between GPP than PV. Besides, double immunofluorescence staining of MPO/IL-17A or CD3/IL-17A further confirmed that the majority of IL-17A in GPP skin was derived from neutrophils, but not T cells. These data emphasized the role of neutrophil-derived IL-17A in the pathogenesis of GPP with or without IL36RN mutations. Targeting neutrophil-derived IL-17A might be a promising treatment for GPP.

Emerging Oral Therapies for the Treatment of Psoriasis: A Review of Pipeline Agents

The introduction of biologic agents for the treatment of psoriasis has revolutionized the current treatment landscape, targeting cytokines in the interleukin (IL)-23/IL-17 pathway and demonstrating strong efficacy and safety profiles in clinical trials. These agents however are costly, are associated with a risk of immunogenicity, and require administration by intravenous or subcutaneous injection, limiting their use among patients. Oral therapies, specifically small molecule and microbiome therapeutics, have the potential to be more convenient and cost-effective agents for patients and have been a focus of development in recent years, with few targeted oral medications available for the disease. In this manuscript, we review pipeline oral therapies for psoriasis identified through a search of ClinicalTrials.gov (30 June 2022-1 October 2023). Available preclinical and clinical trial data on each therapeutic agent are discussed. Small molecules under development include tumor necrosis factor inhibitors, IL-23 inhibitors, IL-17 inhibitors, phosphodiesterase-4 inhibitors, Janus kinase inhibitors, A3 adenosine receptor agonists, and sphingosine-1-phosphate receptor 1 agonists, several of which are entering phase III trials. Oral microbials have also demonstrated success in early phase studies. As new oral therapies emerge for the treatment of psoriasis, real-world data and comparative trials are needed to better inform their use among patients.

Immune cells in the epithelial immune microenvironment of psoriasis: emerging therapeutic targets

Psoriasis is a chronic autoimmune inflammatory disease characterized by erroneous metabolism of keratinocytes. The development of psoriasis is closely related to abnormal activation and disorders of the immune system. Dysregulated skin protective mechanisms can activate inflammatory pathways within the epithelial immune microenvironment (EIME), leading to the development of autoimmune-related and inflammatory skin diseases. In this review, we initially emphasized the pathogenesis of psoriasis, paying particular attention to the interactions between the abnormal activation of immune cells and the production of cytokines in psoriasis. Subsequently, we delved into the significance of the interactions between EIME and immune cells in the emergence of psoriasis. A thorough understanding of these immune processes is crucial to the development of targeted therapies for psoriasis. Finally, we discussed the potential novel targeted therapies aimed at modulating the EIME in psoriasis. This comprehensive examination sheds light on the intricate underlying immune mechanisms and provides insights into potential therapeutic avenues of immune-mediated inflammatory diseases.

CD147/Basigin Is Involved in the Development of Malignant Tumors and T-Cell-Mediated Immunological Disorders via Regulation of Glycolysis

CD147/Basigin, a transmembrane glycoprotein belonging to the immunoglobulin superfamily, is a multifunctional molecule with various binding partners. CD147 binds to monocarboxylate transporters (MCTs) and supports their expression on plasma membranes. MTC-1 and MCT-4 export the lactic acid that is converted from pyruvate in glycolysis to maintain the intracellular pH level and a stable metabolic state. Under physiological conditions, cellular energy production is induced by mitochondrial oxidative phosphorylation. Glycolysis usually occurs under anaerobic conditions, whereas cancer cells depend on glycolysis under aerobic conditions. T cells also require glycolysis for differentiation, proliferation, and activation. Human malignant melanoma cells expressed higher levels of MCT-1 and MCT-4, co-localized with CD147 on the plasma membrane, and showed an increased glycolysis rate compared to normal human melanocytes. CD147 silencing by siRNA abrogated MCT-1 and MCT-4 membrane expression and disrupted glycolysis, inhibiting cancer cell activity. Furthermore, CD147 is involved in psoriasis. MCT-1 was absent on CD4+ T cells in CD147-deficient mice. The naïve CD4+ T cells from CD147-deficient mice exhibited a low capacity to differentiate into Th17 cells. Imiquimod-induced skin inflammation was significantly milder in the CD147-deficient mice than in the wild-type mice. Overall, CD147/Basigin is involved in the development of malignant tumors and T-cell-mediated immunological disorders via glycolysis regulation.

Biology of Interleukin-17 and Novel Therapies for Hidradenitis Suppurativa

Skin disorders affect ∼40% of the human population. One of the most debilitating cutaneous disorders is Hidradenitis suppurativa (HS), a noncommunicable chronic inflammatory disease with an estimated global prevalence of 0.4% to 2.5%. In January 2011, high levels of IL-17 were discovered in skin lesions of HS patients. In the following years, translational and clinical research led to a better understanding of the pathogenesis of HS. In June 2023, more than 12 years after the initial note, secukinumab, an anti-IL-17A monoclonal antibody, was approved for the treatment of moderate to severe HS. This is the next milestone in improving the treatment of these patients after the approval of the anti-TNF-α monoclonal antibody adalimumab in 2015. In this review article, we present the IL-17 pathway in HS and discuss the use of secukinumab as a therapeutic option for this disease. Our review starts with a description of the epidemiology, clinical features, etiology, and pathogenesis of HS. An overview of the IL-17/IL-17 receptor system in general and a detailed description of the known facts about the expression and action of IL-17 in HS follow. Afterward, we consider the results of clinical trials evaluating the safety and efficacy of IL-17 inhibitors in HS. Finally, a comparison is made between secukinumab and adalimumab and the characteristics of the patients that may be particularly suitable for each of these biologics are described.

Crosstalk: keratinocytes and immune cells in psoriasis

In the past, psoriasis was considered a skin disease caused only by keratinocyte disorders. However, the efficacy of immunosuppressive drugs and biologics used to treat psoriasis proves that psoriasis is an immune-mediated disease. Indeed, a variety of immune cells are involved in the pathogenesis of psoriasis, including dendritic cells, Th17 cells, and resident memory T cells. Furthermore, keratinocytes play a role in the development of psoriasis as immune cells by secreting antibacterial peptides, chemokines, tumor necrosis factor-α, interleukin (IL)-36, and IL-23. These immune cells and skin cells interact and drive the aberrant differentiation and proliferation of keratinocytes. This crosstalk between keratinocytes and immune cells critical in the pathogenesis of psoriasis forms an inflammatory loop, resulting in the persistence or exacerbation of psoriasis plaques.

Molecular consideration relevant to the mechanism of the comorbidity between psoriasis and systemic lupus erythematosus (Review)

Systemic lupus erythematosus (SLE), a common autoimmune disease with a global incidence and newly diagnosed population estimated at 5.14 (range, 1.4-15.13) per 100,000 person-years and 0.40 million people annually, respectively, affects multiple tissues and organs; for example, skin, blood system, heart and kidneys. Accumulating data has also demonstrated that psoriasis (PS) can be a systemic inflammatory disease, which can affect organs other than the skin and occur alongside other autoimmune diseases, such as inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis and SLE. The current explanations for the possible comorbidity of PS and SLE include: i) The two diseases share susceptible gene loci; ii) they share a common IL-23/T helper 17 (Th17) axis inflammatory pathway; and iii) the immunopathogenesis of the two conditions is a consequence of the interactions between IL-17 cytokines with effector Th17 cells, T regulatory cells, as well as B cells. In addition, the therapeutic efficacy of IL-17 or TNF-α inhibitors has been demonstrated in PS, and has also become evident in SLE. However, the mechanisms have not been investigated. To the best of our knowledge, there remains a lack of substantial studies on the correlation between PS and SLE. In the present review, the literature, with regards to the epidemiology, genetic predisposition, inflammatory mechanisms and treatment of the patients with both PS and SLE, has been reviewed. Further investigations into the molecular pathogenic mechanism may provide drug targets that could benefit the patients with concomitant PS and SLE.