Activation of signal transducer and activator of transcription (STAT)3 has been reported in many cancers. It is also well known that STAT3 is activated in skin lesions of psoriasis, a chronic skin disease. In this study, to ascertain whether patients with psoriasis have a predisposition to STAT3 activation, we examined phosphorylated STAT3 in cancer cells of psoriasis patients via immunohistochemistry. We selected patients with psoriasis who visited the Department of Dermatology, Jichi Medical University Hospital, from January 2000 to May 2015, and had a history of cancer. We performed immunostaining for phosphorylated STAT3 in tumor cells of five, four, and six cases of gastric, lung, and head and neck cancer, respectively. The results showed that there was no significant difference in STAT3 activation in any of the three cancer types between the psoriasis and control groups. Although this study presents limitations in its sample size and inconsistency in the histology and differentiation of the cancers, results suggest that psoriasis patients do not have a predisposition to STAT3 activation. Instead, STAT3 activation is intricately regulated by each disorder or cellular microenvironment in both cancer and psoriasis.

The role of ferroptosis in steatohepatitis development is largely unknown. We investigated (1) whether hepatocyte ferroptosis occurs in a gene-modified steatohepatitis model without modifying dietary components, (2) whether ferroptosis occurs at an early stage of steatohepatitis, and (3) whether apomorphine, recently reported as a ferroptosis inhibitor, can ameliorate steatohepatitis. Hepatocyte-specific PTEN KO mice were used. Huh 7 and primary cultured hepatocytes isolated from the mice were used in this study. The number of dead cells increased in 10-week-old PTEN KO mice. This cell death was suppressed by the administration of ferroptosis inhibitor ferrostatin-1 for 2 weeks. Apomorphine also ameliorated the severity of steatohepatitis. Treatment with ferroptosis inhibitors, including apomorphine, decreases the level of lipid peroxidase. Apomorphine suppressed cell death induced by RSL-3 (a ferroptosis inducer), which was not suppressed by apoptosis or necroptosis inhibitors. Apomorphine showed a radical trapping capacity with much more potent activity than ferrostatin-1 and Trolox, a soluble form of vitamin E. In addition, apomorphine activated nrf2 and its downstream genes, including HO-1 and xCT. In conclusion, ferroptosis occurs in steatohepatitis from an early stage in PTEN KO mice. In addition, apomorphine ameliorates the severity of steatohepatitis by inhibiting ferroptosis.

We previously reported that a pathogenic abnormality in the barrier and water-holding functions of the stratum corneum (SC) in the skin of patients with atopic dermatitis (AD) is mainly attributable to significantly decreased levels of total ceramides in the SC. That decrease is mediated by the abnormal expression of a novel ceramide-reducing enzyme, sphingomyelin/glucosylceramide deacylase (SGDase), which is the β-subunit (ASAH1b) of acid ceramidase. In this study, we determined whether mice overexpressing ASAH1b in their epidermis develop AD-like skin symptoms. We generated transgenic (TG) mice overexpressing ASAH1b, regulated by the involucrin promoter, to localize its expression in the upper epidermis. After hair removal using a depilatory cream containing glycolic acid, the TG mice without any visible skin inflammation at 8 weeks of age had increased levels of ASAH1b and decreased levels of SC ceramide, with disrupted barrier functions measured by trans-epidermal water loss compared to the wild-type (WT) mice. Interestingly, enzymatic assays revealed that SGDase activity was not detectable in the skin of the TG mice compared to WT mice. Immunological staining revealed that there was an increased expression level of IL-33 in the epidermis and an accumulation of macrophages in the dermis of TG mice compared to WT mice, which are phenotypic characteristics of AD, that were exacerbated by tape-stripping of the skin. In the skin of the TG mice, the mRNA levels of IL-5, CCL11, IL-22, CXCL10, and IFNγ were significantly upregulated compared to the WT mice, and tape-stripping significantly increased the mRNA levels of IL-4, IL-33, CXCL1, CXCL12, TLR9, and CD163 compared to WT mice. These findings strongly indicate that the skin of the depilatory cream-treated TG mice exists in an atopic dry skin condition that is highly sensitive to various environmental stimuli. The sum of our results suggests that ASAH1b itself, even in the absence of its enzymatic activity, is a major etiologic factor for atopic dry skin symptoms via an unknown mechanism.

Ceramide deficiency in the stratum corneum (SC) is a key etiological factor in atopic dermatitis (AD). To clarify the direct role of SC ceramide depletion in impairing SC barrier and water‐holding functions and in initiating AD‐like skin symptoms and disease‐specific molecular alterations, we generated Tg mice overexpressing a mutant form of acid ceramidase (aCDase) under the control of the involucrin promoter, resulting in targeted expression in the upper epidermis. By 3 weeks of age, Tg mice developed noninflammatory, scaly skin characterized by severely compromised barrier integrity and water‐holding capacity, along with significantly elevated epidermal aCDase activity and markedly reduced ceramide levels in the SC. Compared to WT controls, Tg mice also exhibited increased epidermal innervation and reduced intraepidermal semaphorin 3a protein levels. Additionally, Tg skin showed substantial changes in the expression of AD‐associated biomarkers involved in barrier impairment, pruritus, and Th2 polarization. These included increased levels of Il10 , Il17a , S100a7 , S100a8 , and S100a9 and decreased levels of Cxcl10 , Ifng, Il2 , Il13 , Il33 , Sema3a , and Tlr 9. Repeated topical application of mite antigens induced allergic responses in Tg mice, but not in WT mice. These responses were characterized by prominent eosinophil infiltration in the dermis and significantly elevated serum IgE levels. Allergen‐challenged ear skin from Tg mice also demonstrated significantly increased expression of inflammatory mediators related to AD, including Ccl17 , Ccl22 , Ccl26 , Ccl27 , Il3 , Il13 , Il22 , and Il33 . These findings establish Tg mice as a pathophysiologically relevant model of AD, presenting key features such as xerotic, pruritic skin, impaired barrier and water‐retention functions, and Th2‐dominant allergic inflammation. This model provides important insights into ceramide‐dependent mechanisms in AD pathogenesis and offers a useful platform for therapeutic development. © 2026 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.