Cysteine-type cathepsins such as cathepsin B are involved in various steps of inflammatory processes such as antigen processing and angiogenesis. Here, we uncovered the role of cysteine-type cathepsins in the effector phase of T cell-driven cutaneous delayed-type hypersensitivity reactions (DTHR) and the implication of this role on therapeutic cathepsin B-specific inhibition. Methods: Wild-type, cathepsin B-deficient (Ctsb-/-) and cathepsin Z-deficient (Ctsz-/-) mice were sensitized with 2,4,6-trinitrochlorobenzene (TNCB) on the abdomen and challenged with TNCB on the right ear to induce acute and chronic cutaneous DTHR. The severity of cutaneous DTHR was assessed by evaluating ear swelling responses and histopathology. We performed fluorescence microscopy on tissue from inflamed ears and lymph nodes of wild-type mice, as well as on biopsies from psoriasis patients, focusing on cathepsin B expression by T cells, B cells, macrophages, dendritic cells and NK cells. Cathepsin activity was determined noninvasively by optical imaging employing protease-activated substrate-like probes. Cathepsin expression and activity were validated ex vivo by covalent active site labeling of proteases and Western blotting. Results: Noninvasive in vivo optical imaging revealed strong cysteine-type cathepsin activity in inflamed ears and draining lymph nodes in acute and chronic cutaneous DTHR. In inflamed ears and draining lymph nodes, cathepsin B was expressed by neutrophils, dendritic cells, macrophages, B, T and natural killer (NK) cells. Similar expression patterns were found in psoriatic plaques of patients. The biochemical methods confirmed active cathepsin B in tissues of mice with cutaneous DTHR. Topically applied cathepsin B inhibitors significantly reduced ear swelling in acute but not chronic DTHR. Compared with wild-type mice, Ctsb-/- mice exhibited an enhanced ear swelling response during acute DTHR despite a lack of cathepsin B expression. Cathepsin Z, a protease closely related to cathepsin B, revealed compensatory expression in inflamed ears of Ctsb-/- mice, while cathepsin B expression was reciprocally elevated in Ctsz-/- mice. Conclusion: Cathepsin B is actively involved in the effector phase of acute cutaneous DTHR. Thus, topically applied cathepsin B inhibitors might effectively limit DTHR such as contact dermatitis or psoriasis. However, the cathepsin B and Z knockout mouse experiments suggested a complementary role for these two cysteine-type proteases.

中文翻译：

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半胱氨酸型组织蛋白酶促进急性皮肤迟发型超敏反应的效应期。

半胱氨酸型组织蛋白酶，例如组织蛋白酶B，参与了炎症过程的各个步骤，例如抗原加工和血管生成。在这里，我们发现了半胱氨酸型组织蛋白酶在T细胞驱动的皮肤迟发型超敏反应（DTHR）的效应期中的作用，以及这种作用对治疗性组织蛋白酶B特异性抑制的意义。方法：对野生型，组织蛋白酶B缺陷（Ctsb-/-）和组织蛋白酶Z缺陷（Ctsz-/-）小鼠的腹部进行2,4,6-三硝基氯苯（TNCB）致敏，然后对TNCB进行攻击。右耳诱发急，慢性皮肤DTHR。通过评估耳肿胀反应和组织病理学评估皮肤DTHR的严重程度。我们对野生型小鼠发炎的耳朵和淋巴结的组织进行了荧光显微镜检查，以及牛皮癣患者的活组织检查，重点是通过T细胞，B细胞，巨噬细胞，树突状细胞和NK细胞表达组织蛋白酶B。通过使用蛋白酶激活的底物样探针的光学成像，无创测定组织蛋白酶的活性。组织蛋白酶的表达和活性通过蛋白酶的共价活性位点标记和蛋白质印迹进行了离体验证。结果：无创体内光学成像显示急性和慢性皮肤DTHR中发炎的耳朵和引流淋巴结中有很强的半胱氨酸型组织蛋白酶活性。在发炎的耳朵和引流淋巴结中，组织蛋白酶B由嗜中性粒细胞，树突状细胞，巨噬细胞，B，T和自然杀伤（NK）细胞表达。在患者的银屑病斑块中发现了相似的表达模式。生化方法证实了皮肤DTHR小鼠组织中活性组织蛋白酶B。局部应用组织蛋白酶B抑制剂可显着降低急性DTHR（而非慢性DTHR）的耳部肿胀。与野生型小鼠相比，尽管缺乏组织蛋白酶B表达，Ctsb-/-小鼠在急性DTHR期间仍表现出增强的耳部肿胀反应。组织蛋白酶Z，一种与组织蛋白酶B密切相关的蛋白酶，在Ctsb-/-小鼠发炎的耳朵中显示出补偿性表达，而在Ctsz-/-小鼠中组织蛋白酶B的表达则相互升高。结论：组织蛋白酶B积极参与急性皮肤DTHR的效应期。因此，局部应用组织蛋白酶B抑制剂可能有效地限制DTHR，例如接触性皮炎或牛皮癣。然而，