Neuroprotection by Silencing iNOS Expression in a 6-OHDA Model of Parkinson’s Disease

Abstract

In this study, we investigated the protective role of silenced iNOS expression in neuron death in the nigrostriatal pathway in a 6-OHDA animal model of Parkinson's disease (PD). The animal model was established by intrastriatal infusion of a single dose of 6-OHDA. Silencing of iNOS expression was established by intrastriatal infusion of adenovirus-carried iNOS-targeted small interfering RNA (siRNA). Apomorphine-induced rotation behavior was measured. Expression of iNOS, OX-42, and TH; levels of DA, DOPAC, and HVA in the striatum; and the levels of p53 phosphorylation, Bax, and cleaved caspase-3 (CC3) in the substantia nigra were measured. We demonstrated that co-infusion of 6-OHDA with adenovirus expressing siRNA of iNOS blocked the activation of microglia, iNOS transcription, and p53-Bax-CC3 apoptotic cascade as well as significantly blocking 6-OHDA-induced decreases in DA, DOPAC, HVA, and TH levels and effectively decreased rotation number. Our study highlighted the role of iNOS in the neurodegeneration of nigrostriatal dopaminergic neurons in the 6-OHDA animal model of PD and suggested that the microglial activation-iNOS-p53-Bax-CC3 apoptotic pathway plays a key role in the neurodegeneration in the 6-OHDA model.

Endurance Exercise Training Attenuates the up Regulation of iNOS in the Skeletal Muscles of Chronic/Progressive Mouse Model of Parkinson’s Disease

“…The observed overexpression of iNOS PD skeletal muscles is consistent with the previous report [29] that skeletal muscle abnormalities in PD include inflammatory myopathies and myopathies associated with mitochondrial abnormalities. Upregulation of iNOS in PD skeletal muscles is also in agreement with the previous studies [43][44][45] reporting iNOS overexpression in other parkinsonian tissues including the brain, where iNOS upregulation has been suggested [46] as the cause of dopaminergic neuronal death leading to PD. Indeed, inhibition of nitric oxide synthase has been shown [45,47,48] to protect against MPTP-induced neurotoxicity in animals.…”

“…Upregulation of iNOS in PD skeletal muscles is also in agreement with the previous studies [43][44][45] reporting iNOS overexpression in other parkinsonian tissues including the brain, where iNOS upregulation has been suggested [46] as the cause of dopaminergic neuronal death leading to PD. Indeed, inhibition of nitric oxide synthase has been shown [45,47,48] to protect against MPTP-induced neurotoxicity in animals. Therefore, reducing iNOS expression either pharmacologically [49,50], genetically [48,51], or by exercise as our finding indicated can protect various tissues in the different pathological conditions including PD.…”

Inducible nitric oxide synthase is key to peroxynitrite-mediated, LPS-induced protein radical formation in murine microglial BV2 cells

“…Furthermore, iNOS inhibition by siRNA or pharmacological inhibitors decreased protein radical formation. The neuroprotection by gene- silencing of iNOS in various models of Parkinson’s disease as shown by several investigators [2, 49] is possibly due to the role of iNOS in peroxynitrite-mediated protein radical formation. Under pathological conditions nitric oxide production results from transcriptional activation of iNOS, which is barely present in the healthy brain [49].…”

“…Parkinson’s disease is the second most common neurodegenerative disease of the aging brain and manifests itself mostly as a sporadic condition [1, 2]. Microglia-mediated neuroinflammation is considered to be a priming event in onset and progression of Parkinson’s disease [3–5].…”

Hydrophilic, Potent, and Selective 7-Substituted 2-Aminoquinolines as Improved Human Neuronal Nitric Oxide Synthase Inhibitors

“…16 Nonspecific iNOS inhibition could interfere with immune defense, but its role in the brain is more complex; one study indicated that mice lacking iNOS develop enhanced Alzheimers' pathology, 17 while others indicate that iNOS inhibition could actually be neuroprotective. 18 A more recent challenge has been designing inhibitors with high potency against human nNOS (hnNOS). Historically, many structure-based design efforts have utilized rat nNOS (rnNOS), so many compounds (such as most shown in Figure 1) are selective for the rat enzyme, leading to weaker hnNOS inhibitors with low selectivity over human eNOS (heNOS).…”