Although rare, tuberculosis has been reported with biologic treatment against psoriasis in Japan, a tuberculosis medium-burden country. Mycobacterial infection often develops after a long incubation period and might not have been adequately identified in clinical trials or post-marketing surveillance. To determine the real-world incidence of tuberculosis in psoriatic patients treated with biologics, we conducted a retrospective, multicenter, observational study in 18 facilities in Western Japan. Psoriatic patients who visited a participating facility between 2010 and March 2017 and received biologic reagents were enrolled. Information on sex, age at first biologic treatment, results of interferon-c release assay (IGRA) for Mycobacterium tuberculosis, treatment history with isoniazid, and onset of active and/or latent tuberculosis was collected. A total of 1117 patients (830 men and 287 women) were enrolled. The mean duration of biologic treatment was 3.54 years. Sixty-five patients (5.8%) showed positive IGRA results at screening. Active tuberculosis developed in two patients after the administration of tumor necrosis factor inhibitors (both involved miliary tuberculosis). Latent tuberculosis was observed in two patients treated with anti-interleukin-12/23p40 antibody. The incidence rate of tuberculosis, including latent tuberculosis, in this survey was 0.36%. Although the incidence rate of tuberculosis was low considering the observation period of biologic treatment, active tuberculosis was found in both the screening-negative group and a screening-positive subject after isoniazid prophylaxis (both miliary tuberculosis), concluding that negative screening or isoniazid treatment does not always assure that an individual has no tuberculosis. Hence, dermatologists still need to pay careful attention to tuberculosis at every patient visit.

The serine proteases kallikrein-related peptidase (KLK) 5 and KLK7 cleave cell adhesion molecules in the epidermis. Aberrant epidermal serine protease activity is thought to play an important role in the pathogenesis of atopic dermatitis (AD). We collected the stratum corneum (SC) from healthy individuals (n = 46) and AD patients (n = 63) by tape stripping and then measuring the trypsin- and chymotrypsin-like serine protease activity. We also analyzed the p.D386N and p.E420K of SPINK5 variants and loss-of-function mutations of FLG in the AD patients. The serine protease activity in the SC was increased not only in AD lesions but also in non-lesions of AD patients. We found, generally, that there was a positive correlation between the serine protease activity in the SC and the total serum immunoglobulin E (IgE) levels, serum thymus and activation-regulated chemokine (TARC) levels, and peripheral blood eosinophil counts. Moreover, the p.D386N or p.E420K in SPINK5 and FLG mutations were not significantly associated with the SC’s serine protease activity. Epidermal serine protease activity was increased even in non-lesions of AD patients. Such activity was found to correlate with a number of biomarkers of AD. Further investigations of serine proteases might provide new treatments and prophylaxis for AD.

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Background: Serine proteases have important roles in skin barrier function and desquamation, and the aberrant expression or the dysfunction of serine proteases is associated with the pathogenesis of skin diseases. Serine protease activities are tightly regulated by serine proteases such as kallikrein-related peptidases (KLKs) and serine protease inhibitors such as lympho-epithelial Kazal-type related inhibitor (LEKTI). For a better understating of diseases' pathogenesis, the regulation mechanism of serine proteases and the inhibitors' expression in epidermal keratinocytes must be clarified. Objectives: To investigate the effects of the cytokines on the expression of LEKTI in epidermal keratinocytes. Methods: Normal human epidermal keratinocytes (NHEKs) were stimulated with panels of inflammatory cytokines. The expression of serine protease inhibitors was analyzed using quantitative real-time PCR and ELISA. LEKTI expression in normal human skin and lesions from psoriasis or atopic dermatitis (AD) were analyzed by immunohistochemically and tape-stripping. Trypsin-and chymotrypsin-like serine protease activities in culture supernatants were measured by using specific substrates. Results: TNF-α and IL-17A significantly induced the expression of LEKTI in NHEKs. The immunohistochemical and tape-stripping analysis revealed that psoriatic skin lesions had higher LEKTI expression compared to normal skin and AD lesions. Trypsin-and chymotrypsin-like protease activities in the culture media were upregulated 3-5 days later but attenuated 6-7 days later period by these cytokines. Conclusions: In epidermal keratinocytes, the Th1&Th17 cytokines TNF-α and IL-17A induce the expression of serine protease inhibitor LEKTI, and it might occur to suppress the increase in the serine protease activities under inflammation.