The role of sex in the pathophysiology of pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterised by increased pulmonary vascular resistance and pulmonary artery remodelling as result of increased vascular tone and vascular cell proliferation, respectively. Eventually, this leads to right heart failure. Heritable PAH is caused by a mutation in the bone morphogenetic protein receptor-II (BMPR-II). Female susceptibility to PAH has been known for some time, and most recent figures show a female-to-male ratio of 4:1. Variations in the female sex hormone estrogen and estrogen metabolism modify FPAH risk, and penetrance of the disease in BMPR-II mutation carriers is increased in females. Several lines of evidence point towards estrogen being pathogenic in the pulmonary circulation, and thus increasing the risk of females developing PAH. Recent studies have also suggested that estrogen metabolism may be crucial in the development and progression of PAH with studies indicating that downstream metabolites such as 16α-hydroxyestrone are upregulated in several forms of experimental pulmonary hypertension (PH) and can cause pulmonary artery smooth muscle cell proliferation and subsequent vascular remodelling. Conversely, other estrogen metabolites such as 2-methoxyestradiol have been shown to be protective in the context of PAH. Estrogen may also upregulate the signalling pathways of other key mediators of PAH such as serotonin

Cytochrome P450-derived eicosanoids: the neglected pathway in cancer

Endogenously produced lipid autacoids are locally acting small molecule mediators that play a central role in the regulation of inflammation and tissue homeostasis. A well-studied group of autacoids are the products of arachidonic acid metabolism, among which the prostaglandins and leukotrienes are the best known. They are generated by two pathways controlled by the enzyme systems cyclooxygenase and lipoxygenase, respectively. However, arachidonic acid is also substrate for a third enzymatic pathway, the cytochrome P450 (CYP) system. This third eicosanoid pathway consists of two main branches: ω-hydroxylases convert arachidonic acid to hydroxyeicosatetraenoic acids (HETEs) and epoxygenases convert it to epoxyeicosatrienoic acids (EETs). This third CYP pathway was originally studied in conjunction with inflammatory and cardiovascular disease. Arachidonic acid and its metabolites have recently stimulated great interest in cancer biology; but, unlike prostaglandins and leukotrienes the link between cytochome P450 metabolites and cancer has received little attention. In this review, the emerging role in cancer of cytochrome P450 metabolites, notably 20-HETE and EETs, are discussed

The generation of osteoclasts from RAW 264.7 precursors in defined, serum-free conditions

Osteoclasts are the unique cell type capable of resorbing bone. The discovery of the TNF-ligand family member, RANKL, has allowed more reliable study of these important cells. The mouse monocytic cell line, RAW 264.7, has been shown to readily differentiate into osteoclasts upon exposure to recombinant RANKL. Unlike primary osteoclast precursors, there is no requirement for the addition of macrophage colony stimulating factor (M-CSF). However, to date, their differentiation has always been studied in the context of added foetal calf serum (FCS). FCS is a complex and largely undefined mixture of growth factors and matrix proteins, and varies between batches. For this reason, osteoclastogenesis would ideally be studied in the context of a defined, serum-free medium. RAW 264.7 cells were cultured in serum-replete α-MEM or serum-deprived medium (SDM) shown previously to support the growth of human osteoclasts in a co-culture with normal osteoblasts. In SDM, in the presence of recombinant RANKL, RAW 264.7 cells readily differentiated into tartrate resistant acid phosphatase (TRAP) positive multinucleated osteoclast-like cells, a process that was enhanced with the addition of 1α,25-dihydroxyvitamin D3 (1,25D). While the osteoclasts grown in SDM were smaller in size compared with those derived in serum-replete media, their resorptive capacity was significantly increased as indicated by a twofold increase in average resorption pit size. In conclusion, we describe a defined model for studying osteoclast differentiation and activity in the absence of serum, which will be ideal for studying the role of agonistic and antagonistic molecules in this process.Cristina Vincent, Masakazu Kogawa, David M. Findlay and Gerald J. Atkin