ABSTRACT
Prurigo nodularis (PN), or chronic prurigo, is a distinct disease characterized by the presence of chronic pruritus and multiple localized or generalized pruriginous lesions. While there are few epidemiologic studies describing the prevalence of PN, it is thought to be relatively rare, but is likely underdiagnosed and underrecognized. Management of PN is challenging, and there are no approved drugs that can relieve the distress as well as signs and symptoms caused by PN and its pruritus. Improved understanding of the neuroimmune pathways involved in management of PN have led to discovery and trial of emerging treatments for PN. This publication provides an overview of PN and discusses several of the most promising treatments that are undergoing evaluation.
ABSTRACT
Interactions between the epidermis and the immune system govern epidermal tissue homeostasis. These epidermis-immune interactions are altered in the inflammatory disease psoriasis; however, the pathways that underlie this aberrant immune response are not well understood. Here, we determined that Ras-related C3 botulinum toxin substrate 1 (RAC1) is a key mediator of epidermal dysfunction. RAC1 activation was consistently elevated in psoriatic epidermis and primary psoriatic human keratinocytes (PHKCs) exposed to psoriasis-related stimuli, but not in skin from patients with basal or squamous cell carcinoma. Expression of a constitutively active form of RAC1 (RACV12) in mice resulted in the development of lesions similar to those of human psoriasis that required the presence of an intact immune system. RAC1V12-expressing mice and human psoriatic skin showed similar RAC1-dependent signaling as well as transcriptional overlap of differentially expressed epidermal and immune pathways. Coculture of PHKCs with immunocytes resulted in the upregulation of RAC1-dependent proinflammatory cytokines, an effect that was reproduced by overexpressing RAC1 in normal human keratinocytes. In keratinocytes, modulating RAC1 activity altered differentiation, proliferation, and inflammatory pathways, including STAT3, NFκB, and zinc finger protein 750 (ZNF750). Finally, RAC1 inhibition in xenografts composed of human PHKCs and immunocytes abolished psoriasiform hyperplasia and inflammation in vivo. These studies implicate RAC1 as a potential therapeutic target for psoriasis and as a key orchestrator of pathologic epidermis-immune interactions.
Subject(s)
Epidermis/metabolism , Keratinocytes/cytology , Psoriasis/immunology , Psoriasis/metabolism , rac1 GTP-Binding Protein/metabolism , Animals , Cell Differentiation/drug effects , Cell Proliferation , Coculture Techniques , Cytokines/metabolism , Humans , Immune System , Inflammation , Male , Mice , Mice, Inbred NOD , Mice, SCID , Mice, Transgenic , Neoplasm Transplantation , Phenotype , Skin/pathologyABSTRACT
BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disease, for which no fundamental therapy exists. Immunostimulatory sequence CpG (ISS CpG) has potential in reducing susceptibility to allergic diseases and reversing established allergic reactions. OBJECTIVE: To investigate the effects of ISS CpG in the prevention and treatment of AD in an AD murine model. METHODS: BALB/c mice were epicutaneously exposed to ovalbumin (OVA) for 3 or 4 weeks with a 2-week resting period between each exposure week. ISS i.d. injection was given either on the 1st day of each exposure week (in the prevention experiment) or 3 days before and on the 1st, 4th and 7th day of the last exposure week (in the treatment experiment). Skin biopsy and blood were obtained at the end of the experiments. RESULTS: ISS CpG treatment increased drastically mRNA expression of proinflammatory and Th1-type cytokines and chemokines in OVA-treated skin both in the prevention and treatment experiments. The suppressing effect of ISS CpG on Th2-type cytokines and chemokines was weak and limited to IL-13 and CCL24 in the treatment experiment. No significant reduction in OVA-elicited infiltration of eosinophils and T cells in the skin was seen after ISS administration but infiltration of plasmacytoid dendritic cells was absent in ISS CpG-treated skin. In contrast, ISS injection elicited dramatic infiltration of F4/80+ and CCR5+ cells into the dermis and subcutaneous tissue. CONCLUSION: Due to unwanted side effects and minor beneficial effects in our model, administration of ISS CpG may not be suitable for the treatment of AD in humans.
