The
leukotrienes constitute a group of
5-lipoxygenase catalyzed metabolites of
arachidonic acid, the cellular effects of which may be divided into two broad categories.
Leukotriene B4 is predominantly a leukocyte stimulant, and has recently been observed to represent the inflammatory cell component of a mutual activation mechanism between inflammatory cells and the immune system. It is thus anticipated that
LTB4 acts as an inflammatory mediator and immune regulator in a variety of immune-mediated disorders. The presence of
LTB4 in inflamed tissues from patients with
psoriasis,
rheumatoid arthritis and chronic
inflammatory bowel disease renders it probable that the novel class of
5-lipoxygenase inhibitors and
LTB4 antagonists will be capable of influencing the
clinical course of these diseases. The other main group is comprised of
leukotrienes C4, D4 and E4, collectively known as
slow reacting substance of anaphylaxis leukotrienes, and has been identified primarily in
immediate hypersensitivity conditions, e.g.
bronchial asthma in which the smooth muscle contractile and permeability increasing properties of
SRS-A appears to contribute to the early bronchoconstrictor phase.
Leukotriene D4, however, may also be involved in the late reaction mediated by inflammatory cells, since it has the ability to immobilize neutrophils attracted by
LTB4 to the inflammatory focus. The ultimate elucidation of the importance of
leukotrienes in different diseases awaits the outcome of clinical trials with the newly developed highly potent and specific
5-lipoxygenase inhibitors and
leukotriene antagonists.