Relaxin (RLX) is a reproductive hormone with vasodilatatory properties on several organs, including the heart. RLX-induced vasodilatation appears to depend on the stimulation of endogenous NO production. Here, we investigate whether RLX acts on rat coronary endothelial (RCE) cells in vitro by inducing changes of NO generation and, if so, to clarify the possible mechanism of action. RCE cells were treated for 24 h with vehicle (controls) or RLX, alone or in association with inhibitors of NO synthesis or dexamethasone, which inhibits transcription of NO synthase gene. In some experiments, inactivated RLX was given in the place of authentic RLX. Expression of NO synthase isozymes II and III was analyzed by immunocytochemistry, Western blot, and RT-PCR. NO production was evaluated by the Griess reaction for nitrite and the NO-sensitive fluorophore DAF-2/DA. Agonist-induced changes of intracellular Ca2+ transient were studied with the Ca2+-sensitive fluorophore Fura 2-AM. RLX was found to up regulate NOS II mRNA and protein and to stimulate intrinsic NO generation, likely through the activation of a dexamethasone-sensitive transcription factor, and to decrease agonist-induced intracellular Ca2+ transient. Conversely, RLX had negligible effects on NOS III expression. By these biological effects, RLX may afford significant protection against cardiovascular disease.

Gastrointestinal motility is reduced and the incidence of functional gastrointestinal disorders is increased in pregnancy, possibly due to hormonal influences. This study aims to clarify whether the hormone relaxin, which attains high circulating levels during pregnancy and has a nitric oxide-mediated relaxant action on vascular and uterine smooth muscle, also reduces bowel motility and, if it does, whether nitric oxide is involved. Female mice in proestrous or estrous were treated for 18 h with relaxin (1 microg s.c.) or vehicle (controls). Isolated ileal preparations from both groups were used to record contractile activity, either basal or after acute administration of relaxin (5 x 10(-8) M). Drugs inhibiting nitric oxide biosynthesis or neurotransmission were used in combination with relaxin. Expression of nitric oxide synthase isoforms by the ileum was assessed by immunocytochemistry and Western blot analysis. Relaxin caused a clear-cut decay of muscle tension and a reduction in amplitude of spontaneous contractions upon either chronic administration to mice or acute addition to isolated ileal preparations. These effects were significantly blunted by N(G)-nitro-L-arginine, but not by the neural blockers we used. Moreover, relaxin increased the expression of nitric oxide synthases II and III, but not synthase I. Relaxin markedly inhibits ileal motility in mice by exerting a direct action on smooth muscle through the activation of intrinsic nitric oxide biosynthesis.

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In this study we report on the establishment and characterization of two novel lymphoma cell lines (CRO‐AP/3 and CRO‐AP/5) which carry infection by human herpesvirus type‐8 (HHV‐8) and have derived from AIDS‐related primary effusion lymphoma (PEL). These two cell lines are representative of different virologic subtypes of PEL, i.e. HHV‐8+/EBV− PEL in the case of CRO‐AP/3 and HHV‐8+/EBV+ PEL in the case of CRO‐AP/5. Consistent with the diagnosis of PEL, both CRO‐AP/3 and CRO‐AP/5 expressed indeterminate (i.e. non‐B, non‐T) phenotypes although immunogenotypic studies documented their B‐cell origin. Both cell lines are devoid of genetic lesions of c‐MYC, BCL‐2 and p53 as well as gross rearrangements of BCL‐6. Detailed histogenetic characterization of these novel PEL cell lines suggests that PEL may derive from a post‐germinal centre B cell which has undergone pre‐terminal differentiation. The CRO‐AP/3 and CRO‐AP/5 cell lines may provide a valuable model for clarifying the pathogenesis of PEL. In particular, these cell lines may help understand the relative contribution of HHV‐8 and EBV to PEL growth and development and may facilitate the identification of recurrent cytogenetic abnormalities highlighting putative novel cancer related loci relevant to PEL.

Melatonin is endowed with a growth inhibitory effect in MCF-7 breast cancer cells whose mechanism has been related to an antiestrogenic activity exerted by inhibition of binding of the estradiol-estrogen receptor complex to its DNA responsive element. Looking for downstream gene determinants of this effect, we performed a transcriptome profiling by high-density microarrays of estrogen-treated MCF-7 cells exposed or not to melatonin. We found that cyclin D1 was one of the main downregulated genes by melatonin. Validation experiments clearly confirm that in MCF-7 cells the estrogen-induced growth inhibitory activity of melatonin is consistently associated with inhibition of estrogen-elicited cyclin D1 induction. This effect is almost purely transcriptional. Reporter gene assays indicate that the same portion of the cyclin D1 promoter which confers estrogen sensitivity, encompassing a potential cAMP responsive element binding site, is repressed by melatonin. Transcriptional downregulation of cyclin D1 is the key molecular event for melatonin's antiproliferative activity, as this activity can be completely and selectively rescued by transient cyclin D1 overexpression. Finally, we provide indirect evidence that the effect of melatonin on the cyclin D1 promoter is mediated by the c-jun and ATF-2 proteins, known to bind the minimal estrogen-sensitive cyclin D1 promoter element. These findings establish for the first time a molecular link between melatonin and its effects on the cell cycle, providing at the same time a rationale for its use in adjuvant chemotherapy.