Low-intensity pulsed ultrasound increases neurotrophic factors secretion and suppresses inflammation in in vitro models of peripheral neuropathies

Abstract

Objective: In this study, we aimed to verify the beneficial effects of low-intensity pulsed ultrasound (LIPUS) stimulation on two cell types: H2O2-treated RSC96 Schwann cells and THP-1 macrophages, used to model neuropathic inflammation. 
Approach: Using a set-up guaranteeing a fine control of the ultrasound dose at the target, different frequencies (38 kHz, 1 MHz, 5 MHz) and different intensities (20, 100, 500 mW/cm2) were screened to find the most effective experimental conditions for triggering beneficial effects on metabolic activity and release of neurotrophic cytokines (-NGF, BDNF, GDNF) of RSC96 cells. The combination of parameters resulting the optimal one was applied to evaluate anti-inflammatory effects in terms of ROS and TNF- production, also investigating a possible anti-oxidant activity and mechanotransduction pathway for the anti-inflammatory process. The same optimal combination of parameters was then applied to THP-1 cells, differentiated into M1 and M2 phenotypes, to assess the effect on the expression and release of pro-inflammatory markers (TNF-, IL-1, IL-6, IL-8) and anti-inflammatory ones (IL-10 and CD206). 
Main results: 5 MHz and 500 mW/cm2 were found as the optimal stimulation parameters on RSC96 cells Such parameters were also found to suppress ROS and TNF- in the same cell line, thus highlighting a possible anti-inflammatory effect, involving the NF-kB pathway An anti-oxidant effect induced by LIPUS was also observed. Finally, the same LIPUS parameters did not induce any differentiation towards the M1 phenotype of THP-1 cells, whereas they decreased TNF- and IL-8 gene expression, reduced IL-8 cytokine release and increased IL-10 cytokine release in M1-polarized THP-1 cells.
Significance: This study represents the first step towards the use of precisely controlled low-intensity pulsed ultrasound for the treatment of peripheral neuropathies. 

Effect of Therapeutic Ultrasound on the Recovery of the Tibialis Anterior Muscle in Remobilized Wistar Rats after a Period of Immobilization: An Analysis Using the Pathological Index

“…All the effects mentioned above are extremely important during the remobilization period, as immobilization leads to a decrease in protein synthesis and an increase in protein degradation, with consequent muscle atrophy (1,41), meaning that the anabolic stimulus of ultrasound is favorable to the trophic recovery of muscle tissue. Furthermore, since immobilization generates pro-inflammatory tissue characteristics, a reduction in angiogenic stimulus, as well as the replacement of contractile tissue by fibrous and fatty tissue (2,3,41), ultrasound may have an important action against these characteristics (37,42). Also to be taken into account is the nociceptive alteration that immobilization generates (4), which in turn can affect the dorsal root reflex and the axonal reflex, promoters of neurogenic inflammation (43,44), or be precisely caused by them.…”

Using focused ultrasound to modulate microglial structure and function

“…For instance, in vitro , Zhang et al (2019) reported an increased expression of anti-inflammatory-related genes such as arginase 1 (Arg1), peroxisome proliferator activated receptor gamma (PPAR-γ) and IL-4 involved in tissue regeneration, following 1.5 MHz ultrasound treatment of bone marrow-derived macrophages and raw264.7 cells, a murine derived macrophage-like cell line. Similarly, following ultrasound stimulation, human monocytic THP-1 macrophage-like cells treated with lipopolysaccharide (LPS) had decreased gene expression of pro-inflammatory of TNF-α and IL-8, and increased gene expression of IL-10 which promotes the resolution of inflammation, indicating that ultrasound can modulate cytokine expression in macrophages in vitro ( Fontana et al, 2023 ). LPS-stimulated macrophage-like cells, obtained from U937 monocyte-like cells, treated with 38 kHz ultrasound at 250 mW/cm 2 have been shown to significantly reduce the expression of pro-inflammatory cytokines in vitro ( Iacoponi et al, 2023 ).…”

Musculoskeletal Biomaterials: Stimulated and Synergized with Low Intensity Pulsed Ultrasound

“…LIPUS affected the proliferation and myelinating activity of Schwann cells, in a both time-and duty ratio-dependent manner. Thus, LIPUS can be used to repair peripheral nerve injury and peripheral neuropathies [126,127]. The current knowledge about the influence of LIPUS on animal and human models revealed that LIPUS may have an impact on nerve regeneration and axonal alterations in the situation of carpal tunnel syndrome, transected nerve, dementia, and neurogenic erectile dysfunction [128,129].…”