In rat caudal artery, contraction to melatonin results primarily from activation of MT 1 melatonin receptors; however, the role of MT 2 melatonin receptors in vascular responses is controversial. We examined and compared the expression and function of MT 2 receptors with that of MT 1 receptors in male rat caudal artery. MT 1 and MT 2 melatonin receptor mRNA was amplified by reverse transcription-polymerase chain reaction from caudal arteries of three rat strains (i.e., Fisher, Sprague-Dawley, and Wistar). Antisense (but not sense) 33 P-labeled oligonucleotide probes specific for MT 1 or MT 2 receptor mRNA hybridized to smooth muscle, as well as intimal and adventitial layers, of caudal artery. In male Fisher rat caudal artery denuded of endothelium, melatonin was 10 times more potent than 6-chloromelatonin to potentiate contraction to phenylephrine, suggesting activation of smooth muscle MT 1 melatonin receptors. The MT 1 /MT 2 competitive melatonin receptor antagonist luzindole (3 M), blocked melatonin-mediated contraction (0.1-100 nM) with an affinity constant (K B value of 157 nM) similar to that for the human MT 1 receptor. However, at melatonin concentrations above 100 nM, luzindole potentiated the contractile response, suggesting blockade of MT 2 receptors mediating vasorelaxation and/or an inverse agonist effect at MT 1 constitutively active receptors. The involvement of MT 2 receptors in vasorelaxation is supported by the finding that the competitive antagonists 4-phenyl 2-acetamidotetraline and 4-phenyl-2-propionamidotetraline, at MT 2 -selective concentrations (10 nM), significantly enhanced contractile responses to all melatonin concentrations tested (0.1 nM-10 M). We conclude that MT 2 melatonin receptors expressed in vascular smooth muscle mediate vasodilation in contrast to vascular MT 1 receptors mediating vasoconstriction.Accumulating evidence indicates that the hormone melatonin regulates vascular tone; however, the nature of the response remains controversial. Both vasoconstrictor and vasodilator responses have been reported; however, data supporting the presence of melatonin receptors is found in some, but not all, vascular beds (Mahle et al., 1997). In isolated rat caudal arteries, nanomolar concentrations of melatonin potentiate contraction induced by either endogenous or exogenous vasoconstrictors (Viswanathan et al

This study investigated the receptor mechanism(s) by which the hormone melatonin directly affects ovarian function. Expression of MT 1 and MT 2 melatonin receptor mRNA was detected in the rat ovaries both by reverse transcriptase-polymerase chain reaction and in situ hybridization with digoxigenin-labeled oligoprobes. Exposure of granulosa cells in culture to 17␤-estradiol seems to alter the state of melatonin receptor coupling. Indeed, the efficacy of 4P-PDOT on forskolin-stimulated cAMP formation was reversed from an MT 2 partial agonist in vehicle-treated cells to that of an MT 1 inverse agonist in 17␤-estradiol (0.1 M)-treated granulosa cells. We conclude that MT 1 and MT 2 melatonin receptors expressed in antral follicles and corpus luteum may affect steroidogenesis through cAMPmediated signaling. These results underscore the implications of the levels of ovarian estrogen when melatonin receptor ligands are used as therapeutic agents.

Based on these results, extensive sampling of biopsy specimen with PASH and appropriate clinical and radiologic follow-up is recommended.

Triple-negative breast cancer (TNBC) demonstrates lack of expression of hormone receptors and human epidermal growth factor receptor. However, there is no targeted therapy for TNBC. The authors analyzed 29 TNBC cases for Notch-1 and Notch-4 biomarker expression and subcellular location, Ki67 proliferation rate, and relevant clinical/survival data. Results demonstrated an unfavorable Ki67 rate in 90% of cases, Notch-1 expression in tumor and endothelial cells in 100% of cases, and Notch-4 expression in tumor cells in 73% of cases and endothelial cells in 100% of cases. Additionally, subcellular localization of Notch-1 and Notch-4 was predominantly nuclear and cytoplasmic. In conclusion, (a) the majority of TNBCs are high-grade infiltrating ductal carcinomas with high Ki67 proliferation rate and (b) both Notch-1 and Notch-4 receptors are overexpressed in tumor and vascular endothelial cells with subcellular localization different from that of hormone-positive breast cancer. Targeting Notch signaling with gamma secretase inhibitors should to be explored to further improve the survival rate of TNBC patients.

Background Heart failure (HF) is associated with excessive extracellular matrix (ECM) deposition and abnormal ECM degradation leading to cardiac fibrosis. Connective Tissue Growth Factor (CTGF) modulates ECM production during inflammatory tissue injury, but available data on CTGF gene expression in failing human heart and its response to mechanical unloading are limited. Methods and Results LV tissue from patients undergoing cardiac transplantation for ischemic (ICM; n=20) and dilated (DCM; n=20) cardiomyopathies, and from nonfailing (NF; n=20) donor hearts were examined. Paired samples (n=15) from patients undergoing LV assist device (LVAD) implantation as “bridge to transplant” (34-1145 days) were also analyzed. There was more interstitial fibrosis in both ICM and DCM compared to NF hearts. Hydroxyproline concentration was also significantly increased in DCM relative to NF samples. The expression of CTGF,TGFB1, COL1-A1, COL3-A1, MMP2 and MMP9 mRNAs in ICM and DCM were also significantly elevated as compared to NF controls. Although TGFB1, CTGF, COL1-A1, and COL3-A1 mRNA levels were reduced by unloading, there was only a modest reduction in tissue fibrosis and no difference in protein-bound hydroxyproline concentration between pre- and post-LVAD tissue samples. The persistent fibrosis may be related to a concomitant reduction in MMP9 mRNA and protein levels following unloading. Conclusions CTGF may be a key regulator of fibrosis during maladaptive remodeling and progression to HF. Although mechanical unloading normalizes most genotypic and functional abnormalities, its effect on ECM remodeling during HF is incomplete.