Sulforaphane treatment induces phase II detoxifying enzymes and prevents acute exhaustive exercise induced muscle damage in rats.

Acute, exhaustive exercise leads to a burst of reactive oxygen species (ROS) generationthat increases the GSSG/GSH ratio in plasma, and causes structural damage to muscle cells as evidenced by an increase in plasma activity of cytosolic enzymes such as lactate dehydrogenase (LDH) and creatine kinase (CK). Acute exhaustive exercise can be considered an interesting model of oxidative stress and muscle damage. To prevent and counteract ROS generation and oxidative stress during exercise, many studies have been focused on the use of natural compounds with ROS scavenging properties acting as direct antioxidants, but the overall results are still inconclusive. In this study we have investigated the possibility to counteract exhaustive exercise induced oxidative stress and muscle damage in rats by treating animals with sulforaphane (SF). SF is a naturally occurring isothiocyanate present in the human diet and originating from the ingestion of Cruciferous vegetables. SF is known to act as a chemical inducer in many tissues, but no data on its ability to protect skeletal muscle tissues from oxidative stress induced by acute exhaustive exercise are available. MATERIALS AND METHODS. Male Wistar rats (age 4 months, weight 230±20g) were treated every 24 hours with SF (25 mg/kg bw i.p.) for three days before undergoing an acute exhaustive exercise protocol. The exercise protocol consisted in running on a treadmill at 24 m/min and 7% gradient, immediately at the end of the exercise animals were sacrified, and LDH and CK activities were determined on plasma samples. The activities and expressions of phase 2 enzymes such as NAD(P)H:quinone oxidoreductase (NQO1), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), thioredoxin reductase (TR) and the Total antioxidant activity (TAA) were evaluated in homogenates from freshly excised vastus lateralis skeletal muscle by spectrophotometric and immunoblotting techniques. RESULTS. Acute exhaustive exercise increased plasma LDH and CK activities, two well known biomarkers of tissue damage, and significantly reduced muscle tissue TAA, that provides an indication of the tissue antioxidant capacity. SF treatment significantly reduced LDH and CK release and was also able to counteract the decrease in TAA due to exhaustive exercise, evidencing a protection of muscle tissue against exhaustive induced damage. Acute exhaustive exercise induced a reduction in NQO1, an antioxidant enzyme protecting cells against the toxicity of quinones, while had no effect on GST, GR, GPx and TR expression and activity. On the other hand, SF treatment induced NQO1, GST and GR expression and activities in muscle homogenates, with no effect on GPx and TR. Our data demonstrate that SF could play a critical role in the modulation of muscle redox environment leading to the prevention of exhaustive exercise induced muscle damage. These results suggest that SF could become an interesting natural compound in the development of a dietary intervention that promotes oxidant scavenging through phase 2 protein induction, and in the development of new dietary supplements for physical active people. Supported by Fondazione del Monte di Bologna e Ravenna (Italy)