Platelet-induced growth of human fibroblasts is associated with an increased expression of 5-lipoxygenase

Abstract

Proliferation of fibroblasts is vital for adequate wound healing but is probably also involved in different hyperproliferative disorders such as atherosclerosis and cancer. The regeneration of tissue usually starts with coagulation, involving release of mitogenic and inflammatory factors from activated platelets. This study focuses on the role of eicosanoids in the proliferative effects of platelets on human fibroblasts. We show that the phospholipase A (2) inhibitor 7,7-dimethyl-5,8-eicosadienoic acid (DMDA), the combined cyclooxygenase (COX) and lipoxygenase (LOX) inhibitor 5,8,11,14-eicosatetraynoic acid (ETYA) and the LOX inhibitor 5,8,11-eicosatriynoic acid (ETI) block the platelet-induced proliferation of serum starved subconfluent human fibroblasts. Anti-proliferative effects were also obtained by specific inhibition of 5-LOX with 5,6-dehydro arachidonic acid (5,6-dAA), whereas the 12-LOX inhibitor cinnamyl-3,4-dihydroxy- a -cyanocinnamate (CDC) did not affect the platelet-stimulated growth of fibroblasts. The expression of 5-LOX was analyzed by reverse-transcriptase-mediated PCR (RT-PCR), Western blotting and HPLC. 5-LOX message and protein was detected in fibroblasts but not in platelets. Incubation with platelets markedly increased, already after one hour, the expression of 5-LOX in the fibroblast culture. The increased 5-LOX activity was associated with an elevated level of the 5-LOX metabolite 5-hydroxyeicosatetraenoic acid (5-HETE) reaching its maximum after 1 - 2 hours of co-incubation of fibroblasts and platelets. The 5-HETE production was reduced by the inhibitors DMDA, ETYA and ETI. In conclusion, this study suggests that platelet-stimulated proliferation of fibroblasts is mediated by an increased 5-LOX activity, which supports recent findings indicating a crucial role for this enzyme in proliferative disorders such as atherosclerosis.

AmbLOXe—An Epidermal Lipoxygenase of the Mexican Axolotl in the Context of Amphibian Regeneration and Its Impact on Human Wound Closure In Vitro

“…The effect observed was reversible by treatment with lipoxygenase inhibitor, indicating that it might depend on AmbLOXe expression. An increased activity of 5-LOX induced by cocultivation with platelets led also led to an enhanced proliferation rate in human dermal fibroblasts, 55 indicating that skin cells are able to respond directly to LOX enzymatic activity. A full comprehension of AmbLOXe function in wound healing and regeneration, however, might only be possible after appropriate studies in vitro.…”

Platelet-vessel wall interactions in atherosclerotic disease

“…Once adherent or activated,p latelets surface-upregulate or releaseanarsenal of highlyactive substances including potent cytokines,chemokines(seeabove)ormediators of proliferation (59). Therefore it seems likely that platelets are capable of modifying progenitor cell biology.…”

Molecular characterization of a novel type of lipoxygenase (LOX) gene from common wheat (Triticum aestivum L.)

“…Linoleic and linolenic acid comprise the main part of the free lipids and are predominantly present as soluble proteins in the cytosol but are also found in membranes (Leenhardt et al 2006). Most LOX-generated metabolites from different reactions are collectively called oxylipins, and play an important role in the regulation of plant growth and development (Berg et al 2006), senescence (Seltmann et al 2010), wounding and stress response (Veronico et al 2006), and pathogen defense (Wang et al 2008). …”