The deubiquitinating enzyme CYLD impairs NF-κB- and STAT1-dependent macrophage intrinsic immunity to Staphylococcus aureus

In atopic dermatitis (AD), lesional skin is frequently colonized by Staphylococcus (S.) aureus, contributing to the severity and clinical symptoms of the disease. The inflammatory milieu in the skin is characterized by a type 2 inflammatory signature, including M2 macrophages, which cannot eradicate S. aureus. Since S. aureus is effectively controlled in macrophages activated by pattern recognition receptor (PRR)-induced NF-{kappa}B and interferon (IFN)-{gamma}-induced STAT1 stimulation, we hypothesized that pre-treatment with LPS as a PRR/TLR4-activating agent and IFN-{gamma} would induce effective control of S. aureus in monocyte-derived macrophages (MDMs) of AD patients. Our data show that the deubiquitinating enzyme CYLD is strongly expressed in skin macrophages and MDMs from AD patients compared to healthy controls and impairs the anti-staphylococcal activity of PRR-activated and IFN-treated MDMs. Functionally, CYLD impaired M1 macrophage polarization, as evidenced by reduced expression of CD80, TNF, and IL-6 upon LPS- and IFN-{gamma} treatment in CYLD-deficient as compared to wild-type (WT) MDM/THP1 macrophages. Mechanistically, CYLD inhibited IFN-{gamma}-induced STAT1 phosphorylation and activation by binding to STAT1 and inducing its K63 deubiquitination. CYLD also interacted with TRAF6 and NEMO/IKK{gamma} in the MYD88 signaling pathway and with RIPK2 in the NOD2 pathway, leading to impaired activation of NF-{kappa}B. Inhibition of both STAT1 by siRNA and NF-{kappa}B by IKK inhibitor treatment, respectively, independently abolished the control of S. aureus in both CYLD-deficient and WT THP1 macrophages, which harbored identical high numbers of the pathogen. The in vivo inhibitory function of CYLD on the control of S. aureus was also observed upon infection of Cyld-deficient and WT mice. Collectively, these data illustrate that the increased expression of CYLD in macrophages of AD patients is a factor contributing to the ineffective control of S. aureus, diminishes M1 macrophage polarization, and that CYLD deletion unleashes the break on effective STAT1 and NF-{kappa}B-dependent control of S. aureus.