Low-dose dithranol treatment and tape stripping induce tolerance to dithranol in a mouse ear oedema model

Dithranol as novel co-adjuvant for non-invasive dermal vaccination

Transcutaneous immunization (TCI) utilizing the TLR7 agonist imiquimod (IMQ-TCI) induces T cell-driven protective immunity upon application onto intact skin. In our present work, we combine the anti-psoriatic agent dithranol with IMQ-TCI to boost vaccination efficacy (Dithranol/IMQ-based transcutaneous vaccination (DIVA)). Using ovalbumin-derived peptides as model antigens in mice, DIVA induced superior cytolytic CD8⁺ T cells and CD4⁺ T cells with a T_H1 cytokine profile in the priming as well as in the memory phase. Regarding the underlying mechanisms, dithranol induced an oxidant-dependent, monocyte-attracting inflammatory milieu in the skin boosting TLR7-dependent activation of dendritic cells and macrophages leading to superior T cell priming and protective immunity in vaccinia virus infection. In conclusion, we introduce the non-invasive vaccination method DIVA to induce strong primary and memory T cell responses upon a single local treatment. This work provides relevant insights in cutaneous vaccination approaches, paving the way for clinical development in humans.

Hyperglycemia Induces Skin Barrier Dysfunctions with Impairment of Epidermal Integrity in Non-Wounded Skin of Type 1 Diabetic Mice

Diabetes causes skin complications, including xerosis and foot ulcers. Ulcers complicated by infections exacerbate skin conditions, and in severe cases, limb/toe amputations are required to prevent the development of sepsis. Here, we hypothesize that hyperglycemia induces skin barrier dysfunction with alterations of epidermal integrity. The effects of hyperglycemia on the epidermis were examined in streptozotocin-induced diabetic mice with/without insulin therapy. The results showed that dye leakages were prominent, and transepidermal water loss after tape stripping was exacerbated in diabetic mice. These data indicate that hyperglycemia impaired skin barrier functions. Additionally, the distribution of the protein associated with the tight junction structure, tight junction protein-1 (ZO-1), was characterized by diffuse and significantly wider expression in the diabetic mice compared to that in the control mice. In turn, epidermal cell number was significantly reduced and basal cells were irregularly aligned with ultrastructural alterations in diabetic mice. In contrast, the number of corneocytes, namely, denucleated and terminally differentiated keratinocytes significantly increased, while their sensitivity to mechanical stress was enhanced in the diabetic mice. We found that cell proliferation was significantly decreased, while apoptotic cells were comparable in the skin of diabetic mice, compared to those in the control mice. In the epidermis, Keratin 5 and keratin 14 expressions were reduced, while keratin 10 and loricrin were ectopically induced in diabetic mice. These data suggest that hyperglycemia altered keratinocyte proliferation/differentiation. Finally, these phenotypes observed in diabetic mice were mitigated by insulin treatment. Reduction in basal cell number and perturbation of the proliferation/differentiation process could be the underlying mechanisms for impaired skin barrier functions in diabetic mice.

Dithranol irritation in psoriasis treatment: a study of 68 inpatients

The irritant response of perilesional skin is a serious limitation of dithranol therapy in psoriasis. No data are available on the actual prevalence and severity of irritation during 24-h dithranol treatment in an inpatient setting. Using a retrospective analysis of 68 patients with psoriasis visiting our inpatient department for dithranol treatment, the occurrence of dithranol irritation was studied. We found a relatively high frequency of dithranol irritation. Furthermore, most irritation occurs at the start of the therapy with relatively low concentrations.