Roflupram protects against rotenone-induced neurotoxicity and facilitates alpha-synuclein degradation in Parkinson's disease models

We have previously shown that roflupram (ROF) protects against MPP+-induced neuronal damage in models of Parkinson's disease (PD). Since impaired degradation of alpha-synuclein (alpha-syn) is one of the key factors that lead to PD, here we investigated whether and how ROF affects the degradation of alpha-syn in rotenone (ROT)-induced PD models in vivo and in vitro. We showed that pretreatment with ROF (10 mu M) significantly attenuated cell apoptosis and reduced the level of alpha-syn in ROT-treated SH-SY5Y cells. Furthermore, ROF significantly enhanced the lysosomal function, as evidenced by the increased levels of mature cathepsin D (CTSD) and lysosomal-associated membrane protein 1 (LAMP1) through increasing NAD(+)/NADH and the expression of sirtuin 1 (SIRT1). Pretreatment with an SIRT1 inhibitor selisistat (SELI, 10 mu M) attenuated the neuroprotection of ROF, ROF-reduced expression of alpha-syn, and ROF-increased expression levels of LAMP1 and mature CTSD. Moreover, inhibition of CTSD by pepstatin A (20 mu M) attenuated ROF-reduced expression of alpha-syn. In vivo study was conducted in mice exposed to ROT (10 mg.kg(-1).d(-1), i.g.) for 6 weeks; then, ROT-treated mice received ROF (0.5, 1, or 2 mg.kg(-1).d(-1); i.g.) for four weeks. ROF significantly ameliorated motor deficits, which was accompanied by increased expression levels of tyrosine hydroxylase, SIRT1, mature CTSD, and LAMP1, and a reduced level of alpha-syn in the substantia nigra pars compacta. Taken together, these results demonstrate that ROF exerts a neuroprotective action and reduces the alpha-syn level in PD models. The mechanisms underlying ROF neuroprotective effects appear to be associated with NAD(+)/SIRT1-dependent activation of lysosomal function.