Abstract
Keratinocytes are non-professional immune cells contributing actively to innate immune responses partially by reacting to a wide range of molecular patterns by activating pattern recognition receptors. Cytosolic nucleotide fragments as pathogen- or self-derived trigger factors are activating inflammasomes and inducing anti-viral signal transduction pathways as well as inducing expression of inflammatory cytokines. We aimed to compare the induced inflammatory reactions in three keratinocyte cell types—normal human epidermal keratinocytes, the HaCaT cell line and the HPV-KER cell line—upon exposure to the synthetic RNA and DNA analogues poly(I:C) and poly(dA:dT) to reveal the underlying signaling events. Both agents induced the expression of interleukin-6 and tumor necrosis factor α in all cell types; however, notable kinetic and expression level differences were found. Western blot analysis revealed rapid activation of the nuclear factor κB (NF-κB), mitogen activated protein kinase and signal transducers of activator of transcription (STAT) signal transduction pathways in keratinocytes upon poly(I:C) treatment, while poly(dA:dT) induced slower activation. Inhibition of NF-κB, p38, STAT-1 and STAT-3 signaling resulted in decreased cytokine expression, whereas inhibition of mitogen-activated protein kinase kinase 1/2 (MEK1/2) signaling showed a negative feedback role in both poly(I:C)- and poly(dA:dT)-induced cytokine expression. Based on our in vitro results nucleotide fragments are able to induce inflammatory reactions in keratinocytes, but with different rate and kinetics of cytokine expression, explained by faster activation of signaling routes by poly(I:C) than poly(dA:dT).
Highlights
The skin provides the primary interface between the body and the environment and forms a physical barrier against invading pathogens
Keratinocytes express a wide range of pattern recognition receptors and are responsive to various pathogen associated molecular patterns [1,2,3,4], including RNA and DNA fragments, which have been implicated in antiviral defense of keratinocytes [5,6]
Keratinocytes express deoxyribonucleases (DNases) [12]; it was recently shown that reduced keratinocyte DNase activity in psoriasis results in suppressed DNA degradation and, as a consequence, parakeratosis [13] and the presence of excess DNA fragments in the cytosol
Summary
The skin provides the primary interface between the body and the environment and forms a physical barrier against invading pathogens. Keratinocytes express a wide range of pattern recognition receptors and are responsive to various pathogen associated molecular patterns [1,2,3,4], including RNA and DNA fragments, which have been implicated in antiviral defense of keratinocytes [5,6]. Cytosolic RNA and DNA fragments are known as pathogen- as well as damage-associated molecular patterns (PAMPs and DAMPs), which induce innate immune functions of professional and non-professional immune cells. Keratinocytes express deoxyribonucleases (DNases) [12]; it was recently shown that reduced keratinocyte DNase activity in psoriasis results in suppressed DNA degradation and, as a consequence, parakeratosis [13] and the presence of excess DNA fragments in the cytosol. Disturbed ribonuclease activities were described in psoriatic skin [14,15], which might result in excess RNA fragments
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
