Effect of 1-MHz ultrasound on the proinflammatory interleukin-6 secretion in human keratinocytes

Sabrina Giantulli,Elisabetta Tortorella,Ida Silvestri,Susanna Scarpa,Gaio Paradossi,Barbara Cerroni,Angelico Bedini,Francesco Brasili,Fabio Domenici,Stefania Morrone

doi:10.1038/s41598-021-98141-2

Abstract

Keratinocytes, the main cell type of the skin, are one of the most exposed cells to environmental factors, providing a first defence barrier for the host and actively participating in immune response. In fact, keratinocytes express pattern recognition receptors that interact with pathogen associated molecular patterns and damage associated molecular patterns, leading to the production of cytokines and chemokines, including interleukin (IL)-6. Herein, we investigated whether mechanical energy transported by low intensity ultrasound (US) could generate a mechanical stress able to induce the release of inflammatory cytokine such IL-6 in the human keratinocyte cell line, HaCaT. The extensive clinical application of US in both diagnosis and therapy suggests the need to better understand the related biological effects. Our results point out that US promotes the overexpression and secretion of IL-6, associated with the activation of nuclear factor-κB (NF-κB). Furthermore, we observed a reduced cell viability dependent on exposure parameters together with alterations in membrane permeability, paving the way for further investigating the molecular mechanisms related to US exposure.

Highlights

Keratinocytes, the main cell type of the skin, are one of the most exposed cells to environmental factors, providing a first defence barrier for the host and actively participating in immune response
No statistically significant differences in IL-6 release were found after 3 and 24 h of recovery. These results suggest that 1 MHz US can induce a transient early IL-6 release, in accordance with the enhancement of IL-6 mRNA expression highlighted by real-time PCR
The topic of this work was especially addressed to IL-6, highlighting a significant transient deregulation of IL-6 expression and secretion after 1 h exposure to 1 MHz low-intensity pulsed US (LIPUS) at I spta = 65mW/cm[2]

Summary

Introduction

Keratinocytes, the main cell type of the skin, are one of the most exposed cells to environmental factors, providing a first defence barrier for the host and actively participating in immune response. According to the bilayer sonophore m odel[11], the mechanical energy transported by a low intensity US field is absorbed by the cell membranes, inducing contraction and expansion of the intermembrane space This entails a reversible, temporary enhancement of the plasma membrane permeability of the blood–brain barrier and s kin[12,13]. Regardless of its medical use, US necessarily involves the transfer of mechanical energy within skin cells, which may undergo transient micromechanical stress and wild type permeability alterations. These alterations are expected to trigger the activation of acute proinflammatory r esponses[14,15], resembling what happens when tissue cells undergo mechanical insults such as shearing and tensile straining[16,17]. A fine equilibrium among different cellular populations and microbial components allows to maintain and restore tissue uniroma2.it

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