Potent inhibition of human phosphodiesterase-5 by icariin derivatives in an enzyme assay

The pharmacological treatment of erectile dysfunction relies mostly on the use of sildenafil (Viagra\uae) and other sildenafil-type selective inhibitors of phosphodiesterase 5 (PDE5). Adverse effects and the cost of the therapy represent a stimulus to search for alternative drugs. With the aim of searching for alternative pharmacological treatments, several plant extracts traditionally used for impotence (Tribulus terrestris L., Ferula hermonis Boiss, Epimedium brevicornum Maxim, Turnera diffusa var. aphrodisiaca (G.H. Ward) Urban, Cinnamomum cassia L.) were screened against PDE5A1 activity. Human recombinant PDE5A1 was prepared by expression of the full-length cDNA into COS-7 cells [1], and the enzyme activity was determined by a radioassay [1]. Statistical analysis was performed using GraphPad Prism 4. Only E. brevicornum extract (80% inhibition at 50\ub5g/ml) and its active principle icariin (IC50 5.9\ub5M) were highly active. In order to improve the inhibitory activity, icariin was submitted to modifications directed to remove the glycosidic moieties, and to replace them with the hydroxyethyl side chain as simplification of the sugar residues, or to cyclize the prenyl group. Compound 3,7-bis (2-hydroxyethyl) icaritin (5), where both sugars were replaced with hydroxyethyl residues, potently inhibited PDE5A1 with an IC50 very close to sildenafil (IC50 75 nM vs. 74 nM). The potency of 5 was 80 fold higher than the lead compound. The improved pharmacodynamic profile, and no sign of cytotoxicity in human fibroblasts make this compound a promising candidate for further development

Potent inhibition of human phosphodiesterase-5 by icariin derivatives

Plant extracts traditionally used for male impotence (Tribulus terrestris, Ferula hermonis, Epimedium brevicornum, Cinnamomum cassia), and the individual compounds cinnamaldehyde, ferutinin, and icariin, were screened against phosphodiesterase-5A1 (PDE5A1) activity. Human recombinant PDE5A1 was used as the enzyme source. Only E. brevicornum extract (80% inhibition at 50 \u3bcg/mL) and its active principle icariin (1) (IC50 5.9 \u3bcM) were active. To improve its inhibitory activity, 1 was subjected to various structural modifications. Thus, 3,7-bis(2-hydroxyethyl)icaritin (5), where both sugars in 1 were replaced with hydroxyethyl residues, potently inhibited PDE5A1 with an IC50 very close to that of sildenafil (IC50 75 vs 74 nM). Thus, 5 was 80 times more potent than 1, and its selectivity versus phosphodiesterase-6 (PDE6) and cyclic adenosine monophosphate-phosphodiesterase (cAMP-PDE) was much higher in comparison with sildenafil. The improved pharmacodynamic profile and lack of cytotoxicity on human fibroblasts make compound 5 a promising candidate for further development

Complicações determinadas por placas de cloreto de polivinila (PVC) na estabilização da porção cervical caudal da coluna vertebral de cães Complications determined by polyvinylchloride (PVC) plates in the stabilization of caudal cervical vertebral column of dogs

Em 10 cães com peso médio de 14,6kg, as vértebras cervicais 5 e 6 foram cirurgicamente desestabilizadas através da secção do disco intervertebral e, em seguida, estabilizadas com placas ortopédicas confeccionadas com PVC de 2mm de espessura, para após 180 dias, proceder-se ao estudo histológico do tecido ósseo e conjuntivo circunvizinho. Constatou-se que o PVC causou alterações ósseas que podem ter favorecido o afrouxamento dos parafusos e a falha do implante. O material induziu ainda à formação de granuloma de corpo estranho e a reações inflamatórias locais que podem ter causado degradação do material implantado. Assim, placas de PVC, apesar de proporcionarem estabilidade e alinhamento da coluna vertebral, não satisfazem a maioria das propriedades necessárias a um biomaterial, não sendo recomendadaa a sua utilização em ortopedia veterinária.<br>In ten dogs with an average mean weight of 14,6 kg, the cervical vertebra 5 and 6 were destabilized and fixed with plates of 2mm of thickness. The purpose of this work was to verify the effect of orthopedic PVC plates on the internal stabilization of the caudal cervical spine of dogs by studying the occurrence of alterations in the bone tissue and fibrous tissue adjacent to the plate after 180 days of permanence of the material in the dogs' organism. PVC causes progressive bone alterations, which, in the long term, could promote the loosening of the screws and failure of the implant. It also induces the formation of foreign body granuloma and inflammatory reactions which could cause degradation of the implant. Thus, PVC plates do not satisfy the majority of properties required of a biomaterial, its use not being recommended in veterinary orthopedics

All Small Nuclear RNAs (snRNAs) of the [U4/U6.U5] Tri-snRNP Localize to Nucleoli; Identification of the Nucleolar Localization Element of U6 snRNA

Previously, we showed that spliceosomal U6 small nuclear RNA (snRNA) transiently passes through the nucleolus. Herein, we report that all individual snRNAs of the [U4/U6.U5] tri-snRNP localize to nucleoli, demonstrated by fluorescence microscopy of nucleolar preparations after injection of fluorescein-labeled snRNA into Xenopus oocyte nuclei. Nucleolar localization of U6 is independent from [U4/U6] snRNP formation since sites of direct interaction of U6 snRNA with U4 snRNA are not nucleolar localization elements. Among all regions in U6, the only one required for nucleolar localization is its 3′ end, which associates with the La protein and subsequently during maturation of U6 is bound by Lsm proteins. This 3′-nucleolar localization element of U6 is both essential and sufficient for nucleolar localization and also required for localization to Cajal bodies. Conversion of the 3′ hydroxyl of U6 snRNA to a 3′ phosphate prevents association with the La protein but does not affect U6 localization to nucleoli or Cajal bodies