Lupus Skin Is Primed for IL-6 Inflammatory Responses through a Keratinocyte-Mediated Autocrine Type I Interferon Loop  Jasmine N. Stannard, Tamra J. Reed, Emily Myers, Lori Lowe, Mrinal K. Sarkar, Xianying Xing, Johann E. Gudjonsson, J. Michelle Kahlenberg  Journal of Investigative Dermatology  Volume 137, Issue 1, Pages 115-122 (January 2017) DOI: 10.1016/j.jid.2016.09.008 Copyright © 2016 The Authors Terms and Conditions

Figure 1 IL-6 is increased in CLE in both the epidermis and inflammatory infiltrate. (a) Expression of IL-6 and IFN-regulated gene MX1 in discoid (n = 23) and SCLE (n = 21) biopsy samples was determined by real-time PCR and expressed as fold change over healthy control subjects. (b) Representative immunohistochemistry for IL-6 expression in healthy control (n = 3), SCLE (n = 5), and DLE (n = 5) lesions. IL-6 staining is noted in the keratinocytes and in the dermal inflammatory infiltrate. Scale bar = 50 μm. (c) Cutaneous IL-6 up-regulation via real-time PCR was significantly higher in Ro+ (n = 14) than Ro– (n = 16) patients. Data analyzed using (a) Student t test or (c) Mann-Whitney U test. ∗P < .05. CLE, cutaneous lupus erythematosus; DLE, discoid lupus erythematosus; FC, fold change; SCLE, subacute cutaneous lupus erythematosus. Journal of Investigative Dermatology 2017 137, 115-122DOI: (10.1016/j.jid.2016.09.008) Copyright © 2016 The Authors Terms and Conditions

Figure 2 Lupus keratinocytes from unaffected skin produce increased IL-6 after treatment with TLR agonists or exposure to UV radiation. Lupus and control keratinocytes were treated with (a) LPS, (b) PolyI:C, or (c) PTG at indicated concentrations, or (d) exposed to 50 mJ/cm2 UVB radiation and IL-6 production was measured via ELISA. Data represent mean ± standard error of the mean IL-6 concentration for four lupus samples, repeated in duplicate-quadruplicate. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗∗P < 0.0001 via paired t test. LPS, lipopolysaccharide; N, normal; PI, PolyI:C; PTG, peptidoglycan; SLE, systemic lupus erythematosus; TLR, toll-like receptor. Journal of Investigative Dermatology 2017 137, 115-122DOI: (10.1016/j.jid.2016.09.008) Copyright © 2016 The Authors Terms and Conditions

Figure 3 Enhanced IL-6 production by lupus keratinocytes is maintained across passages. (a) Lupus and control keratinocytes were treated with TLR 2 agonist peptidoglycan at a concentration of 10 μg/ml and IL-6 production was measured via ELISA at passages 3, 4, and 5. Data for each passage represents mean ± standard error of the mean IL-6 concentration for four lupus samples, repeated in triplicate. (b) Lupus and control keratinocytes were exposed to 50 mJ/cm2 UVB radiation and IL-6 production was measured via ELISA at passages 3, 4, and 5. Data for each passage represents mean ± standard error of the mean IL-6 concentration for four lupus samples, repeated in duplicate-quadruplicate. ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001 for comparison of SLE versus control for each passage via paired t test. SLE, systemic lupus erythematosus; TLR, toll-like receptor. Journal of Investigative Dermatology 2017 137, 115-122DOI: (10.1016/j.jid.2016.09.008) Copyright © 2016 The Authors Terms and Conditions

Figure 4 Type I IFN signaling stimulates increased production of IL-6 after TLR exposure and UV irradiation. Control keratinocytes were primed with or without (a, b) 1,000 U/ml IFN-α or (c, d) 1,000 U/ml IFN-κ for 24 hours, followed by stimulation with (a, c) PTG at described concentrations or (b, d) 50 mJ/cm2 UVB irradiation. IL-6 production was measured via ELISA. Results represent mean ± standard error of the mean for single experiment repeated in triplicate. ∗P < 0.05; ∗∗P < 0.01; ∗∗∗∗P < 0.0001, via Student paired t test. PTG, peptidoglycan; TLR, toll-like receptor. Journal of Investigative Dermatology 2017 137, 115-122DOI: (10.1016/j.jid.2016.09.008) Copyright © 2016 The Authors Terms and Conditions

Figure 5 Elevated IFN-κ production drives hyperproduction of IL-6 in lupus keratinocytes. Lupus keratinocytes were pretreated with (a) neutralizing IFNR antibody or (b) IFN-κ Ab before stimulation with TLR 2 agonist, as described, and IL-6 concentration was measured via ELISA. (c, d) Lupus and control keratinocytes were stimulated with (c) TLR 2 agonist or (d) UVB radiation, and IFN-κ concentration was measured via ELISA. Data represents mean ± standard error of the mean IL-6 for four lupus samples, repeated in triplicate. ∗P < 0.05; ∗∗P < 0.01; ∗∗∗P < 0.001 via Student paired t test. Ab, antibody; IFNR, type I IFN receptor; SLE, systemic lupus erythematosus; TLR, toll-like receptor. Journal of Investigative Dermatology 2017 137, 115-122DOI: (10.1016/j.jid.2016.09.008) Copyright © 2016 The Authors Terms and Conditions