NOD2 promotes dopaminergic degeneration regulated by NADPH oxidase 2 in 6-hydroxydopamine model of Parkinson’s disease

Abstract

BackgroundIn Parkinson’s disease (PD), loss of striatal dopaminergic (DA) terminals and degeneration of DA neurons in the substantia nigra (SN) are associated with inflammation. Nucleotide-binding oligomerization domain-containing protein (NOD)2, one of the first discovered NOD-like receptors, plays an important role in inflammation. However, the role of NOD2 has not been elucidated in PD.MethodsNOD2 mRNA and protein expression in the SN and the striatum of C57BL/6 mice treated with 6-hydroxydopamine (6-OHDA) was measured. We next investigated the potential contribution of the NOD2-dependent pathway to 6-OHDA-induced DA degeneration using NOD2-deficient (NOD2−/−) mice. Assays examining DA degeneration and inflammation include HPLC, Western blot, immunohistochemistry, TUNEL staining, and cytometric bead array. To further explore a possible link between NADPH oxidase 2 (NOX2) and NOD2 signaling in PD, microglia were transfected with shRNA specific to NOX2 in vitro and apocynin were given to mice subjected to 6-OHDA and muramyl dipeptide (MDP) striatal injection.ResultsThe expression of NOD2 was upregulated in an experimental PD model induced by the neurotoxin 6-OHDA. NOD2 deficiency resulted in a protective effect against 6-OHDA-induced DA degeneration and neuronal death, which was associated with the attenuated inflammatory response. Moreover, silencing of NOX2 in microglia suppressed the expression of NOD2 and the inflammatory response induced by 6-OHDA and attenuated the toxicity of conditioned medium from 6-OHDA or MDP-stimulated microglia to neuronal cells. Furthermore, apocynin treatment inhibited NOD2 upregulation and DA degeneration in the SN of WT mice induced by 6-OHDA and MDP.ConclusionThis study provides the direct evidence that NOD2 is related to 6-OHDA-induced DA degeneration through NOX2-mediated oxidative stress, indicating NOD2 is a novel innate immune signaling molecule participating in PD inflammatory response.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1289-z) contains supplementary material, which is available to authorized users.

LncRNA H19 diminishes dopaminergic neuron loss by mediating microRNA-301b-3p in Parkinson’s disease via the HPRT1-mediated Wnt/β-catenin signaling pathway

“…In our study, 6-OHDA-induced dopaminergic neuron injury in mice was used as an animal model of PD. Furthermore, substantia nigra was extracted from our PD mice to determine expression of TH, a key enzyme in the dopamine synthesis pathway, by western blot assay [22]. Relative to control mice, there was low residual TH expression in the substantia nigra tissues of 6-OHDA-induced PD mice ( Figure 1C).…”

“…The infusion was applied at a flow rate of 0.5 μl/min. The control group was similarly treated, but infused with sterile normal saline containing 0.02% ascorbic acid into the substantia nigra [22].…”

The Role of Rare Coding Variants in Parkinson's Disease GWAS Loci

“…Parkin interacts with NOD2 for regulation of stress and inflammation; Parkin knockdown in mouse dopaminergic neurons exhibited increased NOD2 expression and endoplasmic reticulum stress and cytokine release (21). NOD2 deficiency was protective against 6-OHDA-induced DA degeneration and neuronal death (22), suggesting that the identified NOD2 variants in our patients may be toxic gain of function. The average AAO within the cases of the exome dataset was mostly early onset [AAO, 35.9 years (range, 6-80)], which is significantly younger than the AAO of patients from published GWAS.…”

Tristetraprolin destabilizes NOX2 mRNA and protects dopaminergic neurons from oxidative damage in Parkinson's disease

“…Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2), the main component of NADPH oxidase, exacerbates microglial activation and dopaminergic (DA) neuronal toxicity in the inflammatory model of PD. 3,4 Also, in the 1-methyl-4-phenylpyridinium (MPP + )-treated DA neurons, NOX2 promotes reactive oxygen species (ROS) accumulation while directly damaging the cells. 5 Collective evidence points to the indispensable role of posttranscriptional mechanisms in PD.…”