Estradiol suppresses psoriatic inflammation in mice by regulating neutrophil and macrophage functions

BACKGROUND

Psoriasis is a common inflammatory skin disease resulting from dysregulation of the IL-23/T_H17 immune axis. The prevalence and severity of psoriasis is higher in men than in women, although the underlying reasons for this are unclear.

OBJECTIVE

We studied whether estradiol, a female hormone, plays protective roles in imiquimod-induced psoriatic inflammation in mice by regulating neutrophil and macrophage functions.

METHODS

Wild-type mice and conditional knockout mice were ovariectomized, supplemented with placebo or estradiol pellets, and an imiquimod-containing cream applied.

RESULTS

Mice without endogenous ovarian hormones exhibited exacerbated psoriatic inflammation including increased production of IL-17A and IL-1β, which was reversed by exogenously added estradiol. The suppressive effect of estradiol on the production of IL-1β and IL-17A was abolished in mice lacking estrogen receptors in neutrophils and macrophages (Esr1^f/fEsr2^f/fLysM-Cre+ mice). IL-1β, which is required for production of IL-17A in the psoriasis model, was mainly produced by neutrophils and inflammatory macrophages. Estradiol suppressed IL-1β production from neutrophils and macrophages in mice both in vivo and in vitro and from human neutrophils in vitro.

CONCLUSION

Our results suggest a novel mechanism for sex-dependent differences in psoriasis clinical phenotypes that may shed new light on the pathology of psoriasis.

Lymphotoxin β receptor signaling mediates the formation of high endothelial venule-like vessels in atopic dermatitis-like skin lesions in mice

High endothelial venules (HEVs) are specialized blood vessels contribute to the trafficking of lymphocytes into secondary lymphoid organs by expressing a group of L-selectin ligands called peripheral node addressins (PNAd). In lymph nodes (LNs), lymphotoxin β receptor (LTβR) signaling from dendritic cells (DCs) is essential for the formation of HEVs. On the other hand, PNAd+ HEV-like vessels are observed in the skin under certain inflammatory conditions, such as atopic dermatitis (AD). However, the characteristics and the formation mechanism of HEV-like vessels in the inflammatory skin remains unclear. To address these issues, we first identified PNAd+ HEV-like vessels in the skin using a calcipotriol-induced mouse AD model. HEV-like vessels were located in the postcapillary venules abundant in cellular organelles, which were similar to HEVs in LNs. Blockade of LTβR-signaling by administration of LTβR-Fc fusion protein markedly decreased the formation of HEV-like vessels in the AD-like skin. Analysis using published single-cell RNA-seq data of human AD skin revealed that T cells and DCs highly expressed LTB, a gene encoding LTβ. The expression of LTB was highlighted in T cells by RNAscope in both human AD lesions and mouse AD-like skin. The formation of HEV-like vessels in AD-like skin was normal in Ltbfl/flCD11cCre mice, but was partially impaired in Ltbfl/flCD4Cre mice. Collectively, HEV-like vessels in the inflammatory skin show similar characteristics to HEVs in LNs, and LTβR signaling, partly by LTβ from T cells, is responsible for their formation.

Lymphotoxin β receptor signaling and CD11c-positive dendritic cells form high endothelial venule-like vessels in the skin in murine atopic dermatitis model

High endothelial venules (HEVs), which are characterized by the expression of peripheral node addressin (PNAd), are essential routes for the trafficking of naïve T cells and central memory T cells (Tcms) into secondary lymphoid organs. In lymph nodes (LNs), lymphotoxin (LT) α1β2-LTβ receptor (LTβR) signaling from dendritic cells (DCs) is essential for the formation of HEVs. Although it has been reported that PNAd+ HEV-like vessels appear in the skin under some inflammatory condition, such as atopic dermatitis (AD), the formation mechanism of HEV-like vessels and their functions in the skin have remained unclear.

To clarify these issues, we established a system to induce PNAd+ HEV-like vessels in the skin, using a mouse AD model induced by calcipotriol. Flow cytometric (FCM) analysis revealed that around 20–30% of vessels were PNAd+ in the AD-like skin lesions. Electron microscopic analysis showed prominent formation of rough endoplasmic reticulum, Golgi apparatus and mitochondria in the HEV-like vessels similar to HEVs in LNs. These vessels were mainly detected in post-capillary venules, around which dermal DCs formed clusters. Administration of LTβR-Fc fusion protein or inhibition of the DC clusters by either pertussis toxin or depletion of DCs using CD11c diphtheria toxin receptor transgenic mice abolished the formation of HEV-like vessels in the skin. Naïve T cells and Tcms infiltration were detected in both AD patients and murine AD model skin by immunohistochemistry and FCM.

Collectively, our results suggest that LTβR signaling and CD11c+ DCs mediate the formation of HEV-like vessels in the skin, which may possess functions of HEV and regulate the transmigration of naïve T cells and Tcms.