Highly purified calf hemodialysate (Actovegin®) may improve endothelial function by activation of proteasomes: A hypothesis explaining the possible mechanisms of action.

Highly purified calf hemodialysate (HPCH) known as Actovegin® or Solcoseryl® is one of the most controversial drugs currently marketed worldwide. It is not registered as drug in some countries and therefore its medical use there is illegal, while in others it is often among the top 10 of the best-selling medications. It could be also found in the list of the "most useless drugs" and was banned for short time by World Anti-Doping Agency as performance enhancer. However, the degree of its usefulness or uselessness remains unclear and there is not enough convincing data to make reliable conclusions. HPCH is claimed to have wound/muscular injuries healing, neuroprotective and antioxidant properties, to enhance glucose uptake and oxygen consumption, and possibly to improve performance of athletes. Since HPCH consists of over 200 naturally occurring substances which potentially may exert some pharmacological effects, it is extremely difficult to perform pharmacokinetic and pharmacodynamical studies. In this paper we have analyzed the available literature concerning clinical evidence, in vitro, ex vivo and in vivo effects of HPCH. Based on these data we suggest that the main target of the drug may be endothelium and improvement of endothelial function may be responsible for numerous largely nonspecific effects. We also propose the improvement of protein quality control by the means of activation of ubiquitin-proteasomal system as the most important biochemical mechanism responsible for its effects. The role of sphingolipids as potential proteasome-activators is extensively discussed. The effects of HPCH may also include direct or indirect ones on NF-kB-, Nrf2- and FOXO-mediated regulation of metabolic processes in the cells, which result in improved protein quality control, enhanced energy metabolism and increased resistance to oxidative stress.