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Huntington's disease (HD) is a fatal genetic disease caused by abnormal aggregation of mutant huntingtin protein (mHtt). Reduction of mHtt aggregation decreases cell death of the brain and is a promising therapeutic strategy of HD. MicroRNAs are short non-coding nucleotides which modulate various genes and dysregulated in many diseases including HD. MicroRNA miR-27a was reported to be reduced in the brain of R6/2 HD mouse model and modulate multidrug resistance protein-1 (MDR-1). Using subventricular zone-derived neuronal stem cells (NSCs), we used in vitro HD model to test the effect of miR-27a on MDR-1 and mHtt aggregation. R6/2-derived NSCs can be differentiated under condition of growth factor deprivation, and the progression of differentiation leads to a decrease of MDR-1 level and efflux function of cells. Immunocytochemistry result also confirmed that mHtt aggregation was increased with differentiation. We transfected miR-27a in the R6/2-derived differentiated NSCs, and examined phenotype of HD, mHtt aggregation. As a result, miR-27a transfection resulted in reduction of mHtt aggregation in HD cells. In addition, MDR-1, which can transport mHtt, protein level was increased by miR-27a transfection. Conversely, knock-down of MDR-1 through MDR-1 siRNA increased mHtt aggregation in vitro . Our results indicate that miR-27a could reduce mHtt level of the HD cell by augmenting MDR-1 function. [ABSTRACT FROM AUTHOR]

Abstract: Moderate hypothermia (25–31°C) may have a significant influence on vascular tone. We investigated the cellular mechanisms by which moderate hypothermia alters α-adrenoceptor-mediated contraction in rat thoracic aortae. Cyclooxygenase inhibition by indomethacin; nitric oxide (NO) synthase inhibition by l-NAME; potassium channel and endothelium-derived hyperpolarizing factor (EDHF) inhibition by glibenclamide and TEA; G protein inhibition by pertussis toxin; α2-adrenergic inhibition by yohimbine; and β-adrenergic inhibition by propranolol were assessed for their effect on the contractile response to the α1-adrenoceptor agonist phenylephrine (Phe) in combination with moderate hypothermia (25°C). Moderate hypothermia produced a shift to the right for the Phe concentration–response curves in endothelium-intact (E+) and endothelium-denuded (E−) aortic rings. The maximal response to Phe in E+ rings was significantly decreased (P <0.05) at 25°C compared to 38°C, whereas there was no significant difference in E− rings. Hypothermia-induced vasorelaxation in E+ rings was attenuated (P <0.05) following combined pretreatment with l-NAME (10−4 M) and indomethacin (10−5 M), whereas other inhibitors had no significant effect. Importantly, the addition of TEA to rings that were pretreated with l-NAME and indomethacin exhibited no further attenuation (P >0.05) of hypothermia-induced vasorelaxation. The concentrations of cGMP and cAMP, as measured by radioimmunoassay, were significantly increased (P <0.05) in E+ rings at 25°C compared to those at 38°C, whereas there were no significant differences (P >0.05) in E− rings. The present study demonstrated that rat aortic endothelium is stimulated during moderate hypothermia and that the NO–cGMP and prostacyclin (PGI2)–cAMP pathways represent endothelium-dependent mechanisms of hypothermia-induced vasorelaxation. In contrast, EDHF may not be associated with hypothermia-induced vasorelaxation. [Copyright &y& Elsevier]