Is it oxidative or free radical stress and why does it matter?

Abstract

Boguslaw Lipinski

Although oxidative stress is generally considered to be caused by reactive oxygen species endowed with electrophilic properties, non-oxidizing free radicals also play a role in numerous degenerative diseases. The most biologically active is hydroxyl radical known to be produced in vivo under hypoxic conditions. In addition, as shown in this paper, hydroxyl radicals can be generated in vitro in the presence of ferric ions without any additional redox agents. This free radical can convert soluble human fibrinogen into an insoluble fibrin-like aggregate. It is argued that this novel phenomenon can explain the in vivo association of iron overload with fibrin-like deposits observed in degenerative diseases. In view of the fact that hydroxyl radials are also formed under the reductive conditions, true antioxidants i.e. reducing substances, may enhance rather than diminish free radical stress. On the other hand, numerous natural substances, such as polyphenols considered to be antioxidants, can reduce free radical stress by virtue of their direct scavenging of hydroxyl radicals and/or chelation of body free iron. In conclusion, it is suggested in this overview to revise the concept of oxidative stress and introduce a more adequate term of free radical stress.