Abstract
BackgroundTherapeutic potential of low-intensity ultrasound (LIUS) has become evident in various musculoskeletal diseases. We have previously shown that LIUS has an inhibitory effect on local edema in various diseases including the arthritis and brain injury. In this study, we examined whether LIUS can attenuate paw edema formation vis-à-vis vascular permeability and inflammation in rats induced by carrageenan. LIUS with a frequency of 1 MHz and the intensities of 50, 100, or 200 mW/cm2 were exposed on rat paws for 10 min immediately after carrageenan injection.ResultsCarrageenan injection induced paw edema which was peaked at 6 h and gradually decreased nearly to the initial baseline value after 72 h. LIUS showed a significant reduction of paw edema formation at 2 and 6 h at all intensities tested. The highest reduction was observed at the intensity of 50 mW/cm2. Histological analyses confirmed that LIUS clearly decreased the carrageenan-induced swelling of interstitial space under the paw skin and infiltration of polymorphonuclear leukocytes. Moreover, Evans Blue extravasation analyses exhibited a significant decreases of vascular permeability by LIUS. Finally, immunohistochemical staining showed that expression of pro-inflammatory proteins, namely, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) induced by carrageenan injection was reduced back to the normal level after LIUS stimulation.ConclusionsThese results provide a new supporting evidence for LIUS as a therapeutic alternative for the treatment of edema in inflammatory diseases such as cellulitis.
Highlights
Therapeutic potential of low-intensity ultrasound (LIUS) has become evident in various musculoskeletal diseases
Effects of LIUS on paw edema formation To investigate whether LIUS stimulation has a therapeutic effect on inflammatory edema, we first examined the effect of LIUS on paw edema induced by carrageenan in rats
Our findings suggest that LIUS significantly inhibits paw edema formation and vascular permeability in intraplantar carrageenan-induced paw edema in rats
Summary
Therapeutic potential of low-intensity ultrasound (LIUS) has become evident in various musculoskeletal diseases. Histamine, serotonine, and prostaglandins are involved in the increased vascular leakage. Another key mediator in acute inflammation is nitric oxide (NO) which is induced in various pathological conditions by nitric oxide synthase (NOS). Diuretic or non-steroidal anti-inflammatory drugs (NSAIDs) such as indomethacin and aspirin are often used to reduce edema and inflammation [2]. These drugs have shown various side effects, such as diuretic resistance, hyponatremia, gastrointestinal irritation, and ulceration in high dosage and long-term use of them [3]. More effective and convenient therapeutic approaches with much higher safety are needed
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