O steoblastic metastases occur in advanced cases of prostate cancer and frequently in breast cancer (1). Many factors have been proposed to cause disorganized new bone formation at sites of metastases, including insulin-like growth factors 1 and 2, transforming growth factor (TGF)-␤, prostate-specific antigen, urokinase-type plasminogen activator, fibroblast growth factors (FGF)-1 and -2, bone morphogenic proteins (BMPs), and, in particular, endothelin-1 (ET-1) (2-7).ET-1 is a potent vasoconstrictor that binds to ET A and ET B receptors with the latter functioning in ligand clearance (8,9). ET-1 is produced by and affects bone cells (10-12). It stimulates mitogenesis in osteoblasts, which express both ET A and ET B receptors (13-15). ET-1 can decrease osteoclast activity and motility (16).The prostate expresses ET-1 ligand and receptors (5-7). Primary and metastatic prostate cancers make 6,17,18), which can stimulate autocrine proliferation and potentiate effects of insulin-like growth factors, platelet-derived growth factor, epidermal growth factor, and FGF-2 (5). ET B receptor expression is decreased in prostate cancer (5). Nelson et al. (6) found that plasma ET-1 concentrations were higher in men with advanced prostate cancer with bone metastases compared with men with organ-confined disease (6). ET-1 concentrations did not correlate to tumor burden in bone. Five human prostate cancer cell lines expressed ET-1 messenger RNA, and ET-1 increased BMP-initiated bone formation (6).Breast cancers also express ET-1 and are the next most common cause of osteoblastic metastases. Breast cancer cells can convert preproET-1 to 20). Thus, substantial data implicate ET-1 in the pathogenesis of osteoblastic metastases, but a causal role for ET-1 in bone metastasis has not been directly tested. Questions remain about the importance of ET-1 on bone formation in vivo and whether ET-1 receptor blockade would decrease osteoblastic metastases.We found three human breast cancer cell lines that produce ET-1 and cause osteoblastic bone metastases. We used nude mice inoculated with ZR-75-1 cells to demonstrate a causal role for ET-1 in osteoblastic metastasis. Endothelin A receptor blockade in this model dramatically decreased metastases and tumor burden in bone. Materials and MethodsCells. ZR-75-1 and T47D were from American Type Culture Collection. C. Kent Osborne (San Antonio, TX) provided MCF-7 and MDA-MB-231. ZR-75-1 and T47D cells were grown in RPMI medium 1640; MDA-MB-231 in DMEM; MCF-7 in Iscove's modified Eagle's medium (IMEM); and BT483, BT549, MDA-MB435s, HS578T, MDA-MB-436, MDA-MB-361 PC-3, DU145, LNCaP, and TSU-Pr1 in 1:1 mixture of F12͞DMEM. All media contained 10% FCS, 1% penicillin͞streptomycin, and 1% nonessential amino acids in a 37°C atmosphere of 5% CO 2 ͞95% air. T47D and MCF-7 culture media were supplemented with insulin. At 80% confluence, 250 l of serum-free media was conditioned in 48-well plates for 48 h, and cells were counted. ET-1 and BQ-123 were from American Peptide (Sunnyvale, CA). New Bone Formation ...

Exposure to hypoxia is associated with increased pulmonary artery pressure and plasma endothelin (ET-1) levels and with selective enhancement of ET-1 peptide and messenger RNA (mRNA) and endothelin-A (ET-A) receptor mRNA in rat lung. Our study tested the hypothesis that A-127722, an orally active antagonist of the ET-A receptor, can prevent hypoxia-induced pulmonary hypertension and vascular remodeling in the rat. Pretreatment with A-127722 (3, 10, and 30 mg/kg/day in drinking water for 2 days) caused dose-dependent inhibition of the pulmonary vasoconstrictor response to short-term hypoxia (10% O2, 90 min). Long-term A-127722 treatment (10 mg/kg/day in drinking water for 2 weeks) instituted 48 h before hypoxic exposure attenuated the subsequent development of pulmonary hypertension, the associated right atrial hypertrophy, and pulmonary vascular remodeling. Institution of A-127722 treatment (10 mg/kg/day in drinking water for 4 weeks) after 2 weeks of hypoxia retarded the progression of established hypoxia-induced pulmonary hypertension and right atrial hypertrophy and reversed the pulmonary vascular remodeling despite continuing hypoxic exposure. These findings support the hypothesis that endogenous ET-1 plays a major role in hypoxic pulmonary vasoconstriction/hypertension, right heart hypertrophy, and pulmonary vascular remodeling and suggest that ET-A receptor blockers may be useful in the treatment and prevention of hypoxic pulmonary hypertension in humans.

Background/Aims: The effect of febuxostat (Fx), a non-purine and selective xanthine oxidase inhibitor, on glomerular microcirculatory changes in 5/6 nephrectomy (5/6 Nx) Wistar rats with and without oxonic acid (OA)-induced hyperuricemia was evaluated. Methods: Four groups were studied: 5/6 Nx+vehicle (V)+placebo (P) (n = 7); 5/6 Nx+V+Fx (n = 8); 5/6 Nx+OA+P (n = 6) and 5/6 Nx+OA+Fx (n = 10). OA (750 mg/kg/day, oral gavage) and Fx (3–4 mg/kg/day, drinking water) were administered for 4 weeks. Systolic blood pressure, proteinuria and plasma uric acid were measured at baseline and at the end of 4 weeks. Measurement of glomerular hemodynamics and evaluation of histology were performed at the end of 4 weeks. Results: 5/6 Nx+OA+P rats developed hyperuricemia, renal vasoconstriction and glomerular hypertension in association with further aggravation of afferent arteriolopathy compared to 5/6 Nx+V+P. Fx prevented hyperuricemia in 5/6 Nx+OA+Fx rats and ameliorated proteinuria, preserved renal function and prevented glomerular hypertension in both 5/6 Nx+V+Fx and 5/6 Nx+OA+Fx groups. Functional improvement was accompanied by preservation of afferent arteriolar morphology and reduced tubulointerstitial fibrosis. Conclusion: Fx prevented renal injury in 5/6 Nx rats with and without coexisting hyperuricemia. Because Fx helped to preserve preglomerular vessel morphology, normal glomerular pressure was maintained even in the presence of systemic hypertension.

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The purine analog xanthine oxidase (XO) inhibitors (XOIs), allopurinol and oxypurinol, have been reported to protect against heart failure secondary to myocardial infarction or rapid ventricular pacing. Since these agents might influence other aspects of purine metabolism that could influence their effect, this study examined the effect of the non-purine XOI, febuxostat, on pressure overloadinduced left ventricular (LV) hypertrophy and dysfunction. Transverse aortic constriction (TAC) in mice caused LV hypertrophy and dysfunction as well as increased myocardial nitrotyrosine at 8 days. TAC also caused increased phosphorylated Akt (p-Akt Ser473 ), p42/44 extracellular signal-regulated kinase (p-Erk Thr202/Tyr204 ) and mammalian target of rapamycin (mTOR) (p-mTOR Ser2488 ). XO inhibition with febuxostat (5mg/kg/day by gavage for 8 days) beginning ~60 minutes after TAC attenuated the TAC-induced LV hypertrophy and dysfunction. Febuxostat blunted the TAC-induced increases in nitrotyrosine (indicating reduced myocardial oxidative stress), p-Erk Thr202/Tyr204 and pmTOR Ser2488 , with no effect on total Erk or total mTOR. Febuxostat had no effect on myocardial pAkt Ser473 or total Akt. The results suggest that XO inhibition with febuxostat reduced oxidative stress in the pressure overloaded LV, thereby diminishing the activation of pathways that result in pathologic hypertrophy and contractile dysfunction.