Low‐Frequency Low‐Intensity Ultrasounds Do Not Influence the Survival and Immune Functions of Cultured Keratinocytes and Dendritic Cells

Abstract

Low-frequency ultrasounds (US) are used to enhance drug transdermal transport. Although this phenomenon has been extensively analyzed, information on US effects on the single skin cell components is limited. Here, we investigated the possible effects of low-frequency US on viability and immune functions of cultured human keratinocytes and dendritic cells (DC), skin cells involved in the regulation of many immune-mediated dermatoses. We demonstrated that US, employed at low-frequency (42 KHz) and low-intensity (0.15 W/cm2) values known to enhance drug and water transdermal transport, did not affect extracellular-signal-regulated-kinase (ERK)1/2 activation, cell viability, or expression of adhesion molecules in cultured keratinocytes. Moreover, US at these work frequency and intensity did not influence the keratinocyte expression and release of immunomodulatory molecules. Similarly, cultured DC treated with low-frequency low-intensity US were viable, and did not show an altered membrane phenotype, cytokine profile, nor antigen presentation ability. However, intensity enhancement of low-frequency US to 5 W/cm2 determined an increase of the apoptotic rate of both keratinocytes and DC as well as keratinocyte CXCL8 release and ERK1/2 activation, and DC CD40 expression. Our study sustains the employment of low-frequency and low-intensity US for treatment of those immune skin disorders, where keratinocytes and DC have a pathogenetic role.

Low-frequency sonophoresis: application to the transdermal delivery of macromolecules and hydrophilic drugs

“…In fact, LFS alone, in the absence of antigen, was found to induce activation of Langerhans cells in these studies 31. Other studies have also shown the ability of high-amplitude LFS (5–7 W/cm 2 ) to induce an increased immune response, when compared to low-amplitude LFS (0.15 W/cm 2 ) and negative controls 70. These findings demonstrate the significant potential of LFS to act as a physical adjuvant, and motivate further investigation of LFS-mediated transdermal immunization.…”

“…As stated above, the SonoPrep® has therefore been FDA approved for use in children and adults for decreasing the onset time to local anesthesia. The effect of LFS on animal models and cultured cell lines has also shown that the use of low ultrasound intensities is safe, causing no changes in skin pathology and cell viability 19, 22, 26, 70, 79. In general, for single application treatments, thermal effects caused by LFS are of most consequence to the skin if not monitored properly, causing potentially serious side effects such as burns, epidermal detachment, epidermal or dermal necrosis, and, on a cellular level, keratinocyte apoptosis 70, 79.…”

Tumor growth inhibition by sonodynamic therapy using a novel sonosensitizer

“…Although SDT is a promising approach because of its noninvasive and deeper penetration properties compared to surgery or light in PDT, the clinical application of a photosensitizer must overcome the potential problems mentioned above. Many recent reports concerning SDT have focused on apoptotic events after ultrasound irradiation with a photosensitizer in vitro [19][20][21]. However, the efficacy of SDT or whether it has any advantages over PDT has not yet been rigorously tested in vivo.…”

Skin permeabilization for transdermal drug delivery: recent advances and future prospects

“…The bubbles become unstable as a result of large local pressure gradients, and implode. This results in a jet of liquid that can penetrate the SC [25], [26]. Cavitational effects are inversely correlated with US frequency, making LFS the most efficient for permeabilization [27].…”

“…The live keratinocytes directly below the SC also serve a protective function. Upon insult, keratinocytes are able to secrete cytokines and chemokines to stimulate immune function at the site of infection [26]. This signaling can recruit patrolling dendritic cells.…”