Aging-associated prostate smooth muscle hypercontractility in rats

Abstract Benign prostatic hyperplasia (BPH) is a multifactorial disease, highly associated with aging and characterized by increased prostate smooth muscle (PSM) contractility. Animal models have been employed to explore the aging-associated PSM hypercontractility; however, studies have focused in old animals, neglecting the initial alterations in early ages. The determination of prostatic dysfunctions onset is crucial to understand the BPH pathophysiology and to propose new BPH treatments. Considering that PSM contractility in 10-month-old rats has already been explored, the aim of the present study was to characterize the PSM contractility in younger rats. Male Wistar control (3.5-month-old), 6- and 8-month-old rats were used. Concentration-response curves to phenylephrine and electrical-field stimulation (EFS) were conducted in prostate from all groups. For the first time, we showed that 6- and 8-month-old rats exhibit PSM hypercontractility. The increased prostate contractility to phenylephrine starts around at 6-month-old, worsening during the aging. The 8-month-old rats exhibited hypercontractility to phenylephrine and EFS compared to the control and 6-month-old groups. Reduced phenylephrine potency was observed in 8-month-old rats, indicating an increased age-dependent prostate sensibility to this agonist. Collectively, our findings support the use of 6- and 8-month-old aged rats as new models to explore prostate hypercontractility in BPH.

Vascular O-GlcNAcylation augments reactivity to constrictor stimuli by prolonging phosphorylated levels of the myosin light chain

O-GlcNAcylation is a modification that alters the function of numerous proteins. We hypothesized that augmented O-GlcNAcylation levels enhance myosin light chain kinase (MLCK) and reduce myosin light chain phosphatase (MLCP) activity, leading to increased vascular contractile responsiveness. The vascular responses were measured by isometric force displacement. Thoracic aorta and vascular smooth muscle cells (VSMCs) from rats were incubated with vehicle or with PugNAc, which increases O-GlcNAcylation. In addition, we determined whether proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation. PugNAc enhanced phenylephrine (PE) responses in rat aortas (maximal effect, 14.2±2 vs 7.9±1 mN for vehicle, n=7). Treatment with an MLCP inhibitor (calyculin A) augmented vascular responses to PE (13.4±2 mN) and abolished the differences in PE-response between the groups. The effect of PugNAc was not observed when vessels were preincubated with ML-9, an MLCK inhibitor (7.3±2 vs 7.5±2 mN for vehicle, n=5). Furthermore, our data showed that differences in the PE-induced contractile response between the groups were abolished by the activator of AMP-activated protein kinase (AICAR; 6.1±2 vs 7.4±2 mN for vehicle, n=5). PugNAc increased phosphorylation of myosin phosphatase target subunit 1 (MYPT-1) and protein kinase C-potentiated inhibitor protein of 17 kDa (CPI-17), which are involved in RhoA/Rho-kinase-mediated inhibition of myosin phosphatase activity. PugNAc incubation produced a time-dependent increase in vascular phosphorylation of myosin light chain and decreased phosphorylation levels of AMP-activated protein kinase, which decreased the affinity of MLCK for Ca2+/calmodulin. Our data suggest that proteins that play an important role in the regulation of MLCK and MLCP activity are directly affected by O-GlcNAcylation, favoring vascular contraction.

Mediçäo pré-anestésica com clonidina por via oral em cirurgia de catarata / Preanesthetic medication with oral clonidine in cataract surgery

Justificativa e objetivos: a clonidina é um delta2 agonista de açäo central que diminui o tônus simpático proporcionando estabilidade hemodinâmica no per-operatório. O objetivo deste estudo foi verificar a adequaçäo da medicaçäo pré-anestésica (MPA) com clonidina em pacientes submetidos a facectomia extra-capsular em regime ambulatorial, considerando as alteraçöes hemodinâmicas, poder sedativo e recuperaçäo pós-anestésica. Método: o estudo envolveu 60 pacientes com idades entre 55 e 85 anos, estado físico ASA I, II e III, distribuídos aleatoriamente entre dois grupos : grupo A, que recebeu clonidina 150µg por via oral e grupo B, que näo recebeu MPA. Foram avaliados os seguintes parâmetros: pressäo arterial; frequência cardíaca; grau de sedaçäo; eventos adversos; o tempo de alta ambulatorial. As condiçöes hemodinâmicas foram avaliadas antes e após a instalaçäo de fenilefrina a 10 po cento para dilataçäo pupilar. Resultados: os pacientes do grupo A apresentaram maior estabilidade hemodinâmica durante a dilataçäo pupilar e no per-operatório, apresentando menor incidência de picos hipertensivos quando comparados com os do grupo B. A clonidina promoveu ansiólise em 60 por cento dos pacientes e näo aumentou a incidência de eventos adversos. Um paciente que recebeu clonidina apresentou frequência cardíaca de 39 bpm, que respondeu à atropina. Näo houve diferença entre os grupos em relaçäo ao tempo de alta hospitalar. Conclusöes: a clonidina promoveu atenuaçäo da resposta hipertensiva à fenilefrina tópica, além de promover maior estabilidade hemodinâmica no per-operatório, diminuindo a incidência de eventos adversos, e mostrando-se uma droga eficaz e segura como MPA para pacientes submetidos a facectomia sob bloqueio peribulbar