Altered expression of intracellular Toll-like receptors in peripheral blood mononuclear cells from patients with alopecia areata

Gut microbiome, metabolome and alopecia areata

Alopecia areata (AA) is a type of dermatological disease characterized by rapid and non-scarring hair loss of the scalp or body skin that may be related to genetic, immunological and physiological factors. It is now believed that AA is associated with oxidative stress, autoimmune disease, neuropsychological factors, pathogens, immune checkpoint inhibitors and microecological imbalance under the premise of host genetic susceptibility. In recent years, studies have revealed the significant role of the gut microbiome or metabolome in many aspects of human health. Diverse studies have revealed that the gut microbiome and metabolome have an important influence on skin conditions. This review highlights the relationship between AA and the gut microbiome or metabolome to provide novel directions for the prevention, clinical diagnosis and treatment of AA.

Inhibition of T-cell activity in alopecia areata: recent developments and new directions

Alopecia areata (AA) is an autoimmune disease that has a complex underlying immunopathogenesis characterized by nonscarring hair loss ranging from small bald patches to complete loss of scalp, face, and/or body hair. Although the etiopathogenesis of AA has not yet been fully characterized, immune privilege collapse at the hair follicle (HF) followed by T-cell receptor recognition of exposed HF autoantigens by autoreactive cytotoxic CD8+ T cells is now understood to play a central role. Few treatment options are available, with the Janus kinase (JAK) 1/2 inhibitor baricitinib (2022) and the selective JAK3/tyrosine kinase expressed in hepatocellular carcinoma (TEC) inhibitor ritlecitinib (2023) being the only US Food and Drug Administration-approved systemic medications thus far for severe AA. Several other treatments are used off-label with limited efficacy and/or suboptimal safety and tolerability. With an increased understanding of the T-cell-mediated autoimmune and inflammatory pathogenesis of AA, additional therapeutic pathways beyond JAK inhibition are currently under investigation for the development of AA therapies. This narrative review presents a detailed overview about the role of T cells and T-cell-signaling pathways in the pathogenesis of AA, with a focus on those pathways targeted by drugs in clinical development for the treatment of AA. A detailed summary of new drugs targeting these pathways with expert commentary on future directions for AA drug development and the importance of targeting multiple T-cell-signaling pathways is also provided in this review.

Inheritance-Specific Dysregulation of Th1- and Th17-Associated Cytokines in Alopecia Areata

Autoimmune diseases tend to cluster in families, suggesting genetic predisposition to autoimmunity associated with familial background. We have previously reported similarities in gene expression patterns and PTPN22 polymorphisms between alopecia areata (AA) patients and their healthy relatives, but not unrelated healthy controls. However, the spectrum of disease promoting (or preventing) pathways that may be activated in blood relatives of AA patients remains to be defined. Here, we investigated the extent to which cytokines associated with the Th1 and Th17 pathway are differentially expressed in the blood of patients with AA and its clinical subtypes in comparison to both healthy relatives as well as unrelated healthy controls. A comprehensive set of Th1- and Th17-related cytokines were evaluated by ELISA. We found a significant elevation of the Th17 inducer IL-23, the Th17 product IL-17A, the Th1 hallmark cytokine IFNγ, and TNFα, a Th1 cytokine with relevance to the Th17 pathway in AA patients, regardless of disease subtype, compared to healthy individuals. On further examination, we found that healthy family members grouped together with patients in terms of elevated Th1- and Th17-pathway cytokines in an inheritance-specific manner, distinct from unrelated controls. The elevation of Th17-associated cytokines in healthy controls related to AA patients indicates that Th1 and Th17 dysregulation in AA may be genetically based. Of note, one unrelated control displayed elevated levels of IL-17A and IL-23 similar to those detected in patients. One year after initial blood draw, areas of beard hair loss consistent with the diagnosis of AA were reported by this individual, indicating that the elevation in Th17-related cytokines may have predictive value.

The Role of Serum Th1, Th2, and Th17 Cytokines in Patients with Alopecia Areata: Clinical Implications

Alopecia areata is a type of non-scarring hair loss. The dysregulation of numerous systemic Th1 (IL-2, IFN-γ, TNF, IL-12, and IL-18), Th2 (IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17E, IL-31 and IL-33) and Th17 (IL-17, IL-17F, IL-21, IL-22, IL-23 and TGF-β) cytokines was observed in patients with alopecia areata. Positive correlations between the severity of alopecia areata and an increased serum level of various cytokines including IL-2, TNF, IL-12, IL-17, and IL-17E were reported in the literature. An increased serum level of numerous cytokines, such as IL-2, IL-6, TNF, IL-12, IL-17E, and IL-22, was described as positively correlated with the duration of the disease. Moreover, it was shown that increased pre-treatment serum level of IL-12 was a positive, while increased serum levels of IL-4 and IL-13 were negative prognostic markers for the efficacy of diphenylcyclopropenone. In conclusion, alopecia areata is associated with the dysregulation of systemic Th1, Th2 and Th17 cytokines with their role in the pathogenesis, clinical manifestations and prognosis of the disease. Available data indicate the most significant role of serum IL-2, TNF, IL-12, IL-17, and IL-17E as markers of disease activity. The serum levels IL-4, IL-12 and IL-13 may be useful as potential predictors of diphenylcyclopropenone efficacy.

TLR4 gene polymorphisms in Egyptian vitiligo patients: insights into emerging association with clinical activity, family history, and response to therapy

BACKGROUND

Vitiligo is a common pigmentary disorder in which autoimmunity has been suggested to play an important role. Toll-like receptor (TLR) family are recognized different molecular structures expressed on immune cells and have been implicated in a number of autoimmune diseases (AIDs) such as vitiligo. The purpose of this study was to investigate the possible association between TLR4 gene polymorphisms: rs11536858, rs1927911, rs1927914 in Egyptian vitiligo patients and their clinical data, their response to therapy. Using PCR-RFLP for TLR4 gene polymorphisms (rs11536858, rs1927911, and rs1927914), both alleles and genotypes were determined after extraction of DNA in a case-control study of 100 vitiligo Egyptian patients and 100 matched age and sex controls.

RESULTS

The distribution of the protective CT genotype of rs1927914 was higher in the control group. After dividing both patients and controls into 2 age groups (below 18 and above 18 years), no significant associations between the genotypes of the selected TLR4 SNPs and the demographic and clinical data of the vitiligo patients in group 1 (below 18 years) were observed. For group 2 (above 18 years), also no significant associations were found except for the association between the CC genotype of rs1927914 and psychiatric trauma, from one side, and between the CT genotype of rs1927911 and alopecia, from the other side. The association between combined genotypes and the risk of vitiligo showed either higher frequency in patients (risky), or controls (protective), and some equal frequencies (non-significant). The association between haplotypes and risk of vitiligo in patients' group revealed the highest frequency for the risky ATT and the least frequency for ATC haplotypes. In control group, the protective GCT haplotype showed the highest frequency while the GTC and GCC showed the least frequency. No significant correlations of haplotypes with clinical and demographic data of selected patients' group were observed apart from that between ACC haplotype and family history of AIDs and between ATT haplotype and remission after phototherapy.

CONCLUSIONS

The significant relationship between TLR4 gene polymorphisms and vitiligo patients charcteristics clarify the role of innate immunity in pathogensis of vitiligo and its effect on the used therapies.

NLRP3 inflammasome activation contributes to development of alopecia areata in C3H/HeJ mice

Alopecia areata (AA) is an autoimmune non‐scarring hair loss disease. Recently, several reports have suggested that innate immune systems such as interferon‐α (IFN‐α)‐producing plasmacytoid dendritic cells and NOD‐like receptor family pyrin domain‐containing protein 3 (NLRP3) inflammasomes play a role in the pathogenesis of AA. However, critical studies about their involvement in the initiation of AA have not yet been reported. Therefore, we investigated the expression of innate immune cytokines in serum and skin, and examined the effect of a selective NLRP3 inhibitor, MCC950, on AA in C3H/HeJ mice, induced by transferring cultured skin‐draining lymph node cells. IFN‐α production was upregulated in lesions of AA‐affected mice, and interleukin‐1β in serum and skin was highly expressed before onset as well as postonset. Furthermore, MCC950 treatment prevented AA development and promoted hair growth in AA mouse models by reducing NLRP3 signalling and Th1/Tc1 chemokines and cytokines in the skin. These results suggest that NLRP3 inflammasome contributes to AA onset and chronicity, and NLRP3 inhibitor may be a potential therapeutic agent for AA.

Vitamin D and alopecia areata: possible roles in pathogenesis and potential implications for therapy

Alopecia areata is characterized by the loss of hair on the scalp and elsewhere on the body. It affects approximately 2% of the general population. It is believed to be an autoimmune disease. However, its pathogenesis remains incompletely understood. Recent studies have revealed a substantial link between vitamin D and alopecia areata. But the underlying mechanism still yet to be deciphered. This article reviews the current literature and discusses the possible roles of vitamin D in the pathogenesis of alopecia areata in the context of (1) loss of immune privilege in hair follicle, (2) autoreactive effector T cells and mast cells, (3) nature killer group 2 member d-positive cytotoxic T cells, (4) Janus kinase/signal transducers and activators of transcriptional signaling pathway, (5) regulatory T cells, (6) immune checkpoints, and (7) oxidative stress, which are believed to play important roles in autoimmunity in AA. This paper provides new insights into research directions to elucidate the exact mechanisms of vitamin D in the pathogenesis. Calcipotriol, a vitamin D analog, has been reported to be topically used in treating alopecia areata with promising results. Combination therapy of vitamin D analogs with corticosteroids might also be used in treating alopecia areata.

Elevated Gene Expression of Interleukin-32 Isoforms Alpha, Beta, Gamma, and Delta in the Peripheral Blood of Chronic Psoriatic Patients

Inflammatory-mediated reactions have been implicated as contributors in a number of dermatological disorders, including psoriasis. However, the potential of interleukin (IL)-32 and its isoforms to contribute to the pathogenesis of psoriasis remains unexplored. This study was undertaken to investigate the role of IL-32 and its isoforms IL-32α, IL-32β, IL-32γ, and IL-32δ in the peripheral blood of psoriatic patients. The majority of chronic plaque psoriatic patients showed elevated IL-32 mRNA levels in the peripheral blood mononuclear cells (PBMCs) as compared with the levels of IL-32 mRNA in PBMCs of healthy controls (p = 0.001). To further investigate the role of elevated levels of IL-32 in psoriatic patients, IL-32 isoforms mRNAs were determined. All tested isoforms IL-32α, IL-32β, IL-32γ, and IL-32δ were overexpressed in psoriatic patients PBMCs as compared with healthy controls’ PBMCs (p < 0.05). IL-32α mRNA expression was also significantly higher as compared with all other isoforms of IL-32 in PBMCs of psoriatic patients (p < 0.001). In short, this is the first study that shows the role of IL-32 and its isoforms in the peripheral blood of psoriatic patients. Our novel findings support an association between elevated levels of IL-32 and psoriasis. The data also suggest that a major proinflammatory response of IL-32 may derive from IL-32α isoform in psoriasis.

Functional role of human interleukin-32 and nuclear transcription factor-kB in patients with psoriasis and psoriatic arthritis

OBJECTIVE

Inflammation and its associated cell signaling events have been well documented in psoriasis and psoriatic arthritis. However, the potential for interleukin (IL)-32 and its associated signaling to provoke an inflammatory response or to contribute in the pathogenesis of psoriasis or psoriatic arthritis are still in early phase. This study determined the role of IL-32 and nuclear transcription factor (NF)-κB in patients with plaque psoriasis and psoriatic arthritis.

METHODS

Levels of IL-32 were determined in the plasma samples of patients with plaque psoriasis, psoriatic arthritis, and normal healthy subjects by human IL-32-specific Sandwich enzyme-linked immunosorbent assays. To investigate the role of a transcription factor in these patients, activated NF-κBp65 levels were determined in the peripheral blood mononuclear cells (PBMCs) by highly sensitive NF-κB transcription factor kit.

RESULTS

The levels of IL-32 in the plasma samples of plaque psoriasis or psoriatic arthritis patients were found to be significantly higher as compared with the levels of IL-32 present in the normal human plasma samples (P < 0.01). Levels of activated NF-κB were also found higher in plaque psoriasis or psoriatic arthritic patients as compared with the PBMCs of healthy humans (P < 0.05).

CONCLUSIONS

This study shows the role of IL-32 and NF-κB in plaque psoriasis and psoriatic arthritic patients. Results indicate that IL-32 and NF-κB promote inflammation in patients with psoriasis and psoriatic arthritis. Disruption of IL-32 or NF-κB signaling event might provide a novel target for the management of plaque psoriasis and psoriatic arthritis.