Oxidative stress and dysfunctional NRF2 underlie pachyonychia congenita phenotypes
Michelle L. Kerns, … , Roger L. Kaspar, Pierre A. Coulombe
Michelle L. Kerns, … , Roger L. Kaspar, Pierre A. Coulombe
Published May 16, 2016
Citation Information: J Clin Invest. 2016;126(6):2356-2366. https://doi.org/10.1172/JCI84870.
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Research Article Dermatology

Oxidative stress and dysfunctional NRF2 underlie pachyonychia congenita phenotypes

Abstract

Palmoplantar keratoderma (PPK) are debilitating lesions that arise in individuals with pachyonychia congenita (PC) and feature upregulation of danger-associated molecular patterns and skin barrier regulators. The defining features of PC-associated PPK are reproduced in mice null for keratin 16 (Krt16), which is commonly mutated in PC patients. Here, we have shown that PPK onset is preceded by oxidative stress in footpad skin of Krt16–/– mice and correlates with an inability of keratinocytes to sustain nuclear factor erythroid–derived 2 related factor 2–dependent (NRF2-dependent) synthesis of the cellular antioxidant glutathione (GSH). Additionally, examination of plantar skin biopsies from individuals with PC confirmed the presence of high levels of hypophosphorylated NRF2 in lesional tissue. In Krt16–/– mice, genetic ablation of Nrf2 worsened spontaneous skin lesions and accelerated PPK development in footpad skin. Hypoactivity of NRF2 in Krt16–/– footpad skin correlated with decreased levels or activity of upstream NRF2 activators, including PKCδ, receptor for activated C kinase 1 (RACK1), and p21. Topical application of the NRF2 activator sulforaphane to the footpad of Krt16–/– mice prevented the development of PPK and normalized redox balance via regeneration of GSH from existing cellular pools. Together, these findings point to oxidative stress and dysfunctional NRF2 as contributors to PPK pathogenesis, identify K16 as a regulator of NRF2 activation, and suggest that pharmacological activation of NRF2 should be further explored for PC treatment.

Authors

Michelle L. Kerns, Jill M.C. Hakim, Rosemary G. Lu, Yajuan Guo, Andreas Berroth, Roger L. Kaspar, Pierre A. Coulombe

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Figure 5

A link between Krt16 and NRF2 activation.

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A link between Krt16 and NRF2 activation. (A) Indirect immunofluorescenc...
(A) Indirect immunofluorescence for NRF2 and p-NRF2 in 308 cells transfected with GFP-fused K14 or K16. Scale bar: 10 μm. Arrowheads mark increased nuclear immunofluorescence signal. N, nucleus. (B) Quantitation of intranuclear NRF2 and p-NRF2 immunofluorescence signal. Data represent mean ± SEM for 40 cells per group normalized for nuclear size. Student’s t test. (C) Indirect immunofluorescence for RACK1 in 308 cells transfected with GFP-fused K16. Scale bar: 10 μm; 100 μm (inset). (D) Indirect immunofluorescence for RACK1 and p21 in paw skin of 1-month-old male mice. Dotted lines mark dermoepidermal junction. Scale bar: 50 μm; 100 μm (inset). (E) Relative fold change of immunofluorescence signal for WT and Krt16–/– paw tissue stained for RACK1 and p21. Data represent mean ± SEM of 10 mice, 2 images per mouse. Student’s t test. (F) Representative Western blot for RACK1 and p-SMAD2 of 3 experiments with actin as loading control. (G) Fold change of mRNA for Rack1 and p21 in prelesional paw skin of Krt16–/– mice relative to WT. Data represent mean ± SEM of 4 biological replicates. Student’s t test. (H) Schematic of proposed regulation of NRF2 pathway in the suprabasal epidermis under normal physiological conditions and without K16. **P < 0.01.