Previous experimental findings demonstrated that Cistanches Herba protected against myocardial ischemia/reperfusion (I/R) injury in rats ex vivo. The cardioprotection afforded by Cistanches Herba was found to be associated with the enhancement of mitochondrial function, as indicated by the stimulation of mitochondrial respiration and the improvement in mitochondrial glutathione redox status. Based on these findings, my thesis study aims (1) to identify the active component(s) of Cistanches Herba with respective to its effect on mitochondrial function; (2) to further investigate the effect of Cistanches Herba on mitochondrial function and the underlying biochemical mechanism(s); (3) to examine the effect of Cistanches Herba on oxidant injury in the liver and kidney of rats and (4) to exa...[ Read more ]

Previous experimental findings demonstrated that Cistanches Herba protected against myocardial ischemia/reperfusion (I/R) injury in rats ex vivo. The cardioprotection afforded by Cistanches Herba was found to be associated with the enhancement of mitochondrial function, as indicated by the stimulation of mitochondrial respiration and the improvement in mitochondrial glutathione redox status. Based on these findings, my thesis study aims (1) to identify the active component(s) of Cistanches Herba with respective to its effect on mitochondrial function; (2) to further investigate the effect of Cistanches Herba on mitochondrial function and the underlying biochemical mechanism(s); (3) to examine the effect of Cistanches Herba on oxidant injury in the liver and kidney of rats and (4) to examine the effect of Cistanches Herba on weight control in high fat diet-fed obese mice, presumably by virtue of mitochondrial uncoupling.

HCF1, a semi-purified fraction enriched with phytosterols, was isolated from Cistanches Herba by activity-directed fractionation. Chemical analysis identified campesterol (CAMP), sitostanol (SS) and β-sitosterol (BSS) are the major chemical constituent of HCF1. HCF1 and its active component, BSS (but not CAMP and SS), were found to enhance mitochondrial respiration, increase mitochondrial reactive oxygen species (ROS) production and elicit cellular antioxidant responses in H9c2 cells. HCF1/BSS also protected against hypoxia/reoxygenation-induced apoptosis in H9c2 cells and myocardial I/R injury in rats. The protective effect afforded by HCF1/BSS against oxidant injury was mediated by an up-regulation of glutathione redox cycling through the induction of mitochondrial ROS production. In addition, rat models of gentamicin nephrotoxicity and carbon tetrachloride hepatotoxicity were used to study the effect of Cistanches Herba on oxidative stress-induced injury in kidneys and livers of rats. The findings showed that HCF1/BSS protected against oxidant injury in these two organs with the action mechanism similar to that in rat hearts.

In addition to tissue protection against oxidant injury, HCF1 produced weight reduction effect against high fat diet-induced obesity in male and female mice. The HCF1-induced weight reduction was found to be mediated by a redox-dependent induction of mitochondrial uncoupling, as evidenced by the decrease in mitochondrial respiratory control ratio (RCR) and the increase in mitochondrial uncoupling protein 3 (UCP3) expression in mouse skeletal muscle. In addition, a comparative study with cholestyramine (CT), a bile acid sequestrant, indicated that the HCF1-induced weight reduction was likely mediated by the increase in energy consumption rather than the inhibition of fat absorption. To better characterize the HCF1-induced weight reduction, the effect of HCF1 on C2C12 myotubes was examined to study the molecular mechanism underlying the weight reduction effect afforded by HCF1. The measurement of mitochondrial membrane potential showed that HCF1 caused a transient increase in membrane potential immediately after drug incubation, presumably by fluidizing the mitochondrial inner membrane. The resultant increase in the mitochondrial electron transport was paralleled by an elevation in mitochondrial ROS production. Mitochondrial ROS, in turn, triggered a redox-mediated activation of UCP3 and thereby induced mitochondrial uncoupling in C2C12 myocytes. In addition, biochemical analysis in C2C12 myotubes indicated that HCF1 was capable of activating adenosine monophosphate-dependent protein kinase/peroxisome proliferator-activated receptor-γ coactivator-1 pathway and therefore increased the expression of genes, such as cytochrome c oxidase and UCP3, which are involved in cellular energy metabolism. In conclusion, Cistanches Herba, particularly the active fraction HCF1 offers a promising prospect for enhancing the energy metabolism in the body and eliciting a mitohormetic response to safeguard oxidant-induced tissue damage.