Regulation of neovascularization by S-glutathionylation via the Wnt5a/sFlt-1 pathway

S-glutathionylation occurs when reactive oxygen or nitrogen species react with protein-cysteine thiols. Glutaredoxin-1 (Glrx) is a cytosolic enzyme which enzymatically catalyses the reduction in S-glutathionylation, conferring reversible signalling function to proteins with redox-sensitive thiols. Glrx can regulate vascular hypertrophy and inflammation by regulating the activity of nuclear factor κB (NF-κB) and actin polymerization. Vascular endothelial growth factor (VEGF)-induced endothelial cell (EC) migration is inhibited by Glrx overexpression. In mice overexpressing Glrx, blood flow recovery, exercise function and capillary density were significantly attenuated after hindlimb ischaemia (HLI). Wnt5a and soluble Fms-like tyrosine kinase-1 (sFlt-1) were enhanced in the ischaemic-limb muscle and plasma respectively from Glrx transgenic (TG) mice. A Wnt5a/sFlt-1 pathway had been described in myeloid cells controlling retinal blood vessel development. Interestingly, a Wnt5a/sFlt-1 pathway was found also to play a role in EC to inhibit network formation. S-glutathionylation of NF-κB components inhibits its activation. Up-regulated Glrx stimulated the Wnt5a/sFlt-1 pathway through enhancing NF-κB signalling. These studies show a novel role for Glrx in post-ischaemic neovascularization, which could define a potential target for therapy of impaired angiogenesis in pathological conditions including diabetes.

Muscle metabolic determinants of exercise tolerance following exhaustion: relationship to the “critical power”

We tested the hypothesis that muscle high-energy phosphate compounds and metabolites related to the fatigue process would be recovered after exhaustion during recovery exercise performed below but not above critical power (CP) and that these changes would influence the capacity to continue exercise. Eight male subjects completed single-leg, knee-extension exercise to exhaustion (for ∼180 s) on three occasions, followed by a work-rate reduction to severe-intensity exercise, heavy-intensity exercise (<CP), or a 10-min passive recovery period, in random order. The muscle metabolic responses to exercise were assessed using 31P magnetic resonance spectroscopy. There was a significant difference between the sustainable exercise duration during the recovery from exhaustive exercise between the <CP and >CP conditions (at least 10 min and 39 ± 31 s, respectively; P < 0.05). During passive recovery and <CP recovery exercise, muscle phosphocreatine concentration ([PCr]) increased rapidly after the exhaustion point, reaching ∼96% and ∼76% of baseline values, respectively, after 10 min ( P < 0.05). Moreover, pH increased abruptly, reaching 7.0 ± 0.0 and 7.0 ± 0.2, respectively, after 10 min recovery ( P < 0.05). However, during >CP recovery exercise, neither muscle [PCr] nor pH recovered, reaching ∼37% of the initial baseline and 6.6 ± 0.2, respectively. These results indicate that the muscle metabolic dynamics in recovery from exhaustive >CP differ according to whether the recovery exercise is performed below or above the CP. These findings confirm the importance of the CP as an intramuscular metabolic threshold that dictates the accumulation of fatigue-related metabolites and the capacity to tolerate high-intensity exercise.