Extracorporeal Shock Wave Therapy in Inflammatory Diseases: Molecular Mechanism that Triggers Anti-Inflammatory Action

Shock waves (SW), defined as a sequence of single sonic pulses characterised by high peak pressure (100 MPa), a fast rise in pressure ( < 10 ns) and a short lifecycle (10 μs), are conveyed by an appropriate generator to a specific target area at an energy density ranging from 0.03 to 0.11 mJ/mm2. Extracorporeal SW (ESW) therapy was first used on patients in 1980 to break up kidney stones. During the last ten years, this technique has been successfully employed in orthopaedic diseases such as pseudoarthosis, tendinitis, calcarea of the shoulder, epicondylitis, plantar fasciitis and several inflammatory tendon diseases. In particular, treatment of the tendon and muscle tissues was found to induce a long-time tissue regeneration effect in addition to having a more immediate anthalgic and anti-inflammatory outcome. In keeping with this, an increase in neoangiogenesis in the tendons of dogs was observed after 4-8 weeks of ESW treatment. Furthermore, clinical observations indicate an immediate increase in blood flow around the treated area. Nevertheless, the biochemical mechanisms underlying these effects have yet to be fully elucidated. In the present review, we briefly detail the physical properties of ESW and clinical cases treated with this therapy. We then go on to describe the possible molecular mechanism that triggers the anti-inflammatory action of ESW, focusing on the possibility that ESW may modulate endogenous nitric oxide (NO) production either under normal or inflammatory conditions. Data on the rapid enhancement of endothelial NO synthase (eNOS) activity in ESW-treated cells suggest that increased NO levels and the subsequent suppression of NF-κB activation may account, at least in part, for the clinically beneficial action on tissue inflammation.