The role of cytokines and chemokines in the T-cell-mediated autoimmune process in alopecia areata

Phototherapy and vitamin D

The skin is the site for the photosynthesis of vitamin D and is a target tissue for the active metabolite of vitamin D. An increasing body of evidence indicates that vitamin D produced during phototherapy may be responsible for the positive effects observed during treatment of some skin diseases. Topical or oral application of vitamin D derivatives are used alone or with phototherapy. This paper reviews what is known about the use of phototherapy to enhance vitamin D levels, the use of vitamin D analogues with phototherapy, the efficacy of combination therapies, and controversies regarding some of the outcomes. Vitamin D can play a beneficial role in treating psoriasis, even though the exact role of vitamin D in the pathogenesis and severity of psoriasis remains unclear. The role of vitamin D in vitiligo, atopic dermatitis, polymorphic light eruption, and mycosis fungoides must be further investigated.

Alopecia areata: Animal models illuminate autoimmune pathogenesis and novel immunotherapeutic strategies

One of the most common human autoimmune diseases, alopecia areata (AA), is characterized by sudden, often persisting and psychologically devastating hair loss. Animal models have helped greatly to elucidate critical cellular and molecular immune pathways in AA. The two most prominent ones are inbred C3H/HeJ mice which develop an AA-like hair phenotype spontaneously or after experimental induction, and healthy human scalp skin xenotransplanted onto SCID mice, in which a phenocopy of human AA is induced by injecting IL-2-stimulated PBMCs enriched for CD56+/NKG2D+ cells intradermally. The current review critically examines the pros and cons of the available AA animal models and how they have shaped our understanding of AA pathobiology, and the development of new therapeutic strategies. AA is thought to arise when the hair follicle's (HF) natural immune privilege (IP) collapses, inducing ectopic MHC class I expression in the HF epithelium and autoantigen presentation to autoreactive CD8+ T cells. In common with other autoimmune diseases, upregulation of IFN-γ and IL-15 is critically implicated in AA pathogenesis, as are NKG2D and its ligands, MICA, and ULBP3. The C3H/HeJ mouse model was used to identify key immune cell and molecular principles in murine AA, and proof-of-principle that Janus kinase (JAK) inhibitors are suitable agents for AA management in vivo, since both IFN-γ and IL-15 signal via the JAK pathway. Instead, the humanized mouse model of AA has been used to demonstrate the previously hypothesized key role of CD8+ T cells and NKG2D+ cells in AA pathogenesis and to discover human-specific pharmacologic targets like the potassium channel Kv1.3, and to show that the PDE4 inhibitor, apremilast, inhibits AA development in human skin. As such, AA provides a model disease, in which to contemplate general challenges, opportunities, and limitations one faces when selecting appropriate animal models in preclinical research for human autoimmune diseases.

Role of nidi of infection in various skin diseases

Reviewed scientific publications that define the location of foci of chronic infections in dermatology. Indicated by the currently existing problematic issues and their solutions.

Alopecia areata profiling shows TH1, TH2, and IL-23 cytokine activation without parallel TH17/TH22 skewing

BACKGROUND

Alopecia areata (AA) is a common T cell-mediated disorder with limited therapeutics. A molecular profile of cytokine pathways in AA tissues is lacking. Although studies have focused on TH1/IFN-γ responses, several observations support a shared genetic background between AA and atopy.

OBJECTIVE

We sought to define the AA scalp transcriptome and associated biomarkers with comparisons with atopic dermatitis (AD) and psoriasis.

METHODS

We performed microarray and RT-PCR profiling of 27 lesional and 17 nonlesional scalp samples from patients with AA for comparison with normal scalp samples (n = 6). AA gene expression was also compared with samples from patients with lesional or nonlesional AD and those with psoriasis. A fold change of greater than 1.5 and a false discovery rate of less than 0.05 were used for differentially expressed genes (DEGs).

RESULTS

We established the AA transcriptomes (lesional vs nonlesional: 734 DEGs [297 upregulated and 437 downregulated]; lesional vs normal: 4230 DEGs [1980 upregulated and 2250 downregulated]), including many upregulated immune and downregulated hair keratin genes. Equally impressive as upregulation in TH1/interferon markers (IFNG and CXCL10/CXCL9) were those noted in TH2 (IL13, CCL18, CCL26, thymic stromal lymphopoietin, and periostin), TH9/IL-9, IL-23 (p40 and p19), and IL-16 mediators (all P < .05). There were no increases in TH17/TH22 markers. Hair keratin (KRT) expressions (ie, KRT86 and KRT85) were significantly suppressed in lesional skin. Greater scalp involvement (>25%) was associated with greater immune and keratin dysregulation and larger abnormalities in nonlesional scalp samples (ie, CXCL10 and KRT85).

CONCLUSIONS

Our data associate the AA signature with TH2, TH1, IL-23, and IL-9/TH9 cytokine activation, suggesting consideration of anti-TH2, anti-TH1, and anti-IL-23 targeting strategies. Similar to psoriasis and AD, clinical trials with selective antagonists are required to dissect key pathogenic pathways.