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 6

Treatment with SF prevents hyperkeratotic front paw calluses in Krt16–/– mice.

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Treatment with SF prevents hyperkeratotic front paw calluses in Krt16–/–...
(A) Representative images of Krt16–/– mice treated with SF or vehicle (n = 10 mice per group). Insets show representative close-ups of paws. Arrowheads depict areas of skin hyperpigmentation, reflecting lesions. Quantitation of PPK index is provided at right. (B) H&E staining of SF- and jojoba oil–treated (vehicle) paw skin. Scale bar: 50 μm. (C) Indirect immunofluorescence for NRF2, p-NRF2, and HO-1. Dotted lines mark dermoepidermal junction. Scale bar: 50 μm. Original magnification, ×100. Asterisks mark areas of increased indirect immunofluorescence. (D) Representative Western blots of NRF2 and p-NRF2 with actin as loading control. (E) Fold change in GSH and GSSG and (F) GSH to GSSG ratio for Krt16–/– paw skin treated with SF or vehicle. Data represent mean ± SEM of 6 biological replicates. Student’s t test. (G and H) Relative fold change in mRNA levels of GSH synthesis enzymes (G) and GSH metabolism enzymes (H). Data represent mean ± SEM of 4 biological replicates involving 2-month-old male mice. Student’s t test. log scale. *P < 0.05; **P < 0.01.