Xuehua Piao1, Ryosuke Miura2, Sanae Miyake1, Sachiko Komazawa-Sakon1, Masato Koike3, Ryodai Shindo1, Junji Takeda4, Akito Hasegawa5, Riichiro Abe5, Chiharu Nishiyama6, Tetsuo Mikami7, Hideo Yagita8, Yasuo Uchiyama9, Hiroyasu Nakano10. 1. Department of Biochemistry, Toho University School of Medicine, Tokyo, Japan. 2. Department of Biochemistry, Toho University School of Medicine, Tokyo, Japan; Laboratory of Molecular Biology and Immunology, Department of Biological Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Tokyo, Japan. 3. Department of Cell Biology and Neuroscience, Juntendo University Graduate School of Medicine, Tokyo, Japan. 4. Department of Social and Environmental Medicine, Graduate School of Medicine, Osaka University, Osaka, Japan. 5. Division of Dermatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan. 6. Laboratory of Molecular Biology and Immunology, Department of Biological Science and Technology, Faculty of Industrial Science and Technology, Tokyo University of Science, Tokyo, Japan. 7. Department of Pathology, Toho University School of Medicine, Tokyo, Japan. 8. Department of Immunology, Juntendo University Graduate School of Medicine, Tokyo, Japan. 9. Department of Cellular Molecular Neuropathology, Juntendo University Graduate School of Medicine, Tokyo, Japan. 10. Department of Biochemistry, Toho University School of Medicine, Tokyo, Japan; Host Defense Research Center, Toho University School of Medicine, Tokyo, Japan. Electronic address: hiroyasu.nakano@med.toho-u.ac.jp.
Abstract
BACKGROUND: A delicate balance between cell death and keratinocyte proliferation is crucial for normal skin development. Previous studies have reported that cellular FLICE (FADD-like ICE)-inhibitory protein plays a crucial role in prevention of keratinocytes from TNF-α-dependent apoptosis and blocking of dermatitis. However, a role for cellular FLICE-inhibitory protein in TNF-α-independent cell death remains unclear. OBJECTIVE: We investigated contribution of TNF-α-dependent and TNF-α-independent signals to the development of dermatitis in epidermis-specific Cflar-deficient (CflarE-KO) mice. METHODS: We examined the histology and expression of epidermal differentiation markers and inflammatory cytokines in the skin of CflarE-KO;Tnfrsf1a+/- and CflarE-KO;Tnfrsf1a-/- mice. Mice were treated with neutralizing antibodies against Fas ligand and TNF-related apoptosis-inducing ligand to block TNF-α-independent cell death of CflarE-KO;Tnfrsf1a-/- mice. RESULTS: CflarE-KO;Tnfrsf1a-/- mice were born but experienced severe dermatitis and succumbed soon after birth. CflarE-KO;Tnfrsf1a+/- mice exhibited embryonic lethality caused by massive keratinocyte apoptosis. Although keratinocytes from CflarE-KO;Tnfrsf1a-/- mice still died of apoptosis, neutralizing antibodies against Fas ligand and TNF-related apoptosis-inducing ligand substantially prolonged survival of CflarE-KO;Tnfrsf1a-/- mice. Expression of inflammatory cytokines, such as Il6 and Il17a was increased; conversely, expression of epidermal differentiation markers was severely downregulated in the skin of CflarE-KO;Tnfrsf1a-/- mice. Treatment of primary keratinocytes with IL-6 and, to a lesser extent, IL-17A suppressed expression of epidermal differentiation markers. CONCLUSION: TNF receptor superfamily 1 (TNFR1)-dependent or TNFR1-independent apoptosis of keratinocytes promotes inflammatory cytokine production, which subsequently blocks epidermal differentiation. Thus blockade of both TNFR1-dependent and TNFR1-independent cell death might be an alternative strategy to treat skin diseases when treatment with anti-TNF-α antibody alone is not sufficient.
BACKGROUND: A delicate balance between cell death and keratinocyte proliferation is crucial for normal skin development. Previous studies have reported that cellular FLICE (FADD-like ICE)-inhibitory protein plays a crucial role in prevention of keratinocytes from TNF-α-dependent apoptosis and blocking of dermatitis. However, a role for cellular FLICE-inhibitory protein in TNF-α-independent cell death remains unclear. OBJECTIVE: We investigated contribution of TNF-α-dependent and TNF-α-independent signals to the development of dermatitis in epidermis-specific Cflar-deficient (CflarE-KO) mice. METHODS: We examined the histology and expression of epidermal differentiation markers and inflammatory cytokines in the skin of CflarE-KO;Tnfrsf1a+/- and CflarE-KO;Tnfrsf1a-/- mice. Mice were treated with neutralizing antibodies against Fas ligand and TNF-related apoptosis-inducing ligand to block TNF-α-independent cell death of CflarE-KO;Tnfrsf1a-/- mice. RESULTS: CflarE-KO;Tnfrsf1a-/- mice were born but experienced severe dermatitis and succumbed soon after birth. CflarE-KO;Tnfrsf1a+/- mice exhibited embryonic lethality caused by massive keratinocyte apoptosis. Although keratinocytes from CflarE-KO;Tnfrsf1a-/- mice still died of apoptosis, neutralizing antibodies against Fas ligand and TNF-related apoptosis-inducing ligand substantially prolonged survival of CflarE-KO;Tnfrsf1a-/- mice. Expression of inflammatory cytokines, such as Il6 and Il17a was increased; conversely, expression of epidermal differentiation markers was severely downregulated in the skin of CflarE-KO;Tnfrsf1a-/- mice. Treatment of primary keratinocytes with IL-6 and, to a lesser extent, IL-17A suppressed expression of epidermal differentiation markers. CONCLUSION:TNF receptor superfamily 1 (TNFR1)-dependent or TNFR1-independent apoptosis of keratinocytes promotes inflammatory cytokine production, which subsequently blocks epidermal differentiation. Thus blockade of both TNFR1-dependent and TNFR1-independent cell death might be an alternative strategy to treat skin diseases when treatment with anti-TNF-α antibody alone is not sufficient.