Biosynthesis, catabolism, and biological properties of HPETEs, hydroperoxide derivatives of arachidonic acid.

The oxygenation of arachidonic acid by lipoxygenases results in the formation of HPETEs (hydroperoxyeicosatetraenoic acids), the first products of the LOX pathway. These compounds are short lived and are catabolised into various families of more stable compounds of which the HETEs, hepoxilins, lipoxins and leukotrienes have been identified so far. The development of new techniques have helped to identify and understand the structures of various HPETEs and only recently the biological effects of HPETEs and their various catabolites are being unraveled. Although lipoxygenases are ubiquitous, not all tissues possess the same spectrum of lipoxygenase enzymes. Hence different HPETEs can be formed in different tissues. Recent studies have revealed that HPETEs or products derived from them possess a diversity of important biological properties including the regulation of electrolyte flux and eicosanoid and corticosterone syntheses, release of histamine, regulation of oocyte maturation and release of various reproductive hormones. HPETEs appear to be involved in some pathological conditions viz, skin psoriasis, Clarkson's disease, nerve injury and spinal cord ischemia. These novel eicosanoids are associated with the release of insulin as well as renin. Recently HPETEs have been suggested to act as second messengers in the Aplysia sensory neurons and its catabolite, hepoxilin, has been demonstrated to have effects on mammalian hippocampal neurons. The purpose of this review is to provide a brief summary of the formation of the HPETEs and the various families of compounds derived from them as well as the various types of biological activities for these products described so far.