BPOZ-2 Gene Delivery Ameliorates Alpha-Synucleinopathy in A53T Transgenic Mouse Model of Parkinson's Disease

BPOZ-2-deficient mice exhibit aggravated inflammation-associated tissue damage after acute dextran sodium sulfate or diethylnitrosamine exposure

An excessive inflammatory response plays an important role in pathological tissue damage associated with pathogen infection and tumorigenesis. Blood POZ-containing gene type 2 (BPOZ-2), an adaptor protein for the E3 ubiquitin ligase scaffold protein CUL3, is a negative regulator of the inflammatory response. In this study, we investigated the pathophysiological functions of BPOZ-2 in dextran sodium sulfate (DSS)-induced colon injury and diethylnitrosamine (DEN)-induced liver damage. Our results indicated that BPOZ-2 deficiency increased IL-1β induction after DSS and DEN treatment. In addition, BPOZ-2-deficient mice were more susceptible to DSS-induced colitis. Notably, BPOZ-2 deficiency aggravated DEN-induced acute liver injury. These results revealed that BPOZ-2 protected against pathological tissue damage with a dysregulated inflammatory response.

Elevated ATG13 in serum of patients with ME/CFS stimulates oxidative stress response in microglial cells via activation of receptor for advanced glycation end products (RAGE)

Myalgic Encephalomyelitis, also known as Chronic Fatigue Syndrome (ME/CFS), is a multisystem illness characterized by extreme muscle fatigue associated with pain, neurocognitive impairment, and chronic inflammation. Despite intense investigation, the molecular mechanism of this disease is still unknown. Here we demonstrate that autophagy-related protein ATG13 is strongly upregulated in the serum of ME/CFS patients, indicative of impairment in the metabolic events of autophagy. A Thioflavin T-based protein aggregation assay, array screening for autophagy-related factors, densitometric analyses, and confirmation with ELISA revealed that the level of ATG13 was strongly elevated in serum samples of ME/CFS patients compared to age-matched controls. Moreover, our microglia-based oxidative stress response experiments indicated that serum samples of ME/CFS patients evoke the production of reactive oxygen species (ROS) and nitric oxide in human HMC3 microglial cells, whereas neutralization of ATG13 strongly diminishes the production of ROS and NO, suggesting that ATG13 plays a role in the observed stress response in microglial cells. Finally, an in vitro ligand binding assay provided evidence that ATG13 employs the Receptor for Advanced Glycation End-products (RAGE) to stimulate ROS in microglial cells. Collectively, our results suggest that an impairment of autophagy following the release of ATG13 into serum could be a pathological signal in ME/CFS.

The Parkinson's disease-associated kinase LRRK2 regulates genes required for cell adhesion, polarization, and chemotaxis in activated murine macrophages

Leucine-rich repeat kinase 2 (LRRK2) encodes a complex protein that includes kinase and GTPase domains. Genome-wide association studies have identified dominant LRRK2 alleles that predispose their carriers to late-onset idiotypic Parkinson's disease (PD) and also to autoimmune disorders such as Crohn's disease. Considerable evidence indicates that PD initiation and progression involve activation of innate immune functions in microglia, which are brain-resident macrophages. Here we asked whether LRRK2 modifies inflammatory signaling and how this modification might contribute to PD and Crohn's disease. We used RNA-Seq-based high-resolution transcriptomics to compare gene expression in activated primary macrophages derived from WT and Lrrk2 knockout mice. Remarkably, expression of a single gene, Rap guanine nucleotide exchange factor 3 (Rapgef3), was strongly up-regulated in the absence of LRRK2 and down-regulated in its presence. We observed similar regulation of Rapgef3 expression in cells treated with a highly specific inhibitor of LRRK2 protein kinase activity. Rapgef3 encodes an exchange protein, activated by cAMP 1 (EPAC-1), a guanine nucleotide exchange factor that activates the small GTPase Rap-1. Rap-1 mediates cell adhesion, polarization, and directional motility, and our results indicate that LRRK2 modulates chemotaxis of microglia and macrophages. Dominant PD-associated LRRK2 alleles may suppress EPAC-1 activity, further restricting motility and preventing efficient migration of microglia to sites of neuronal damage. Functional analysis in vivo in a subclinical infection model also indicated that Lrrk2 subtly modifies the inflammatory response. These results indicate that LRRK2 modulates the expression of genes involved in murine immune cell chemotaxis.

Alpha-synuclein suppresses mitochondrial protease ClpP to trigger mitochondrial oxidative damage and neurotoxicity

Both α-Synuclein (αSyn) accumulation and mitochondrial dysfunction have been implicated in the pathology of Parkinson's disease (PD). Although studies suggest that αSyn and its missense mutant, A53T, preferentially accumulate in the mitochondria, the mechanisms by which αSyn and mitochondrial proteins regulate each other to trigger mitochondrial and neuronal toxicity are poorly understood. ATP-dependent Clp protease (ClpP), a mitochondrial matrix protease, plays an important role in regulating mitochondrial protein turnover and bioenergetics activity. Here, we show that the protein level of ClpP is selectively decreased in αSyn-expressing cell culture and neurons derived from iPS cells of PD patient carrying αSyn A53T mutant, and in dopaminergic (DA) neurons of αSyn A53T mice and PD patient postmortem brains. Deficiency in ClpP induces an overload of mitochondrial misfolded/unfolded proteins, suppresses mitochondrial respiratory activity, increases mitochondrial oxidative damage and causes cell death. Overexpression of ClpP reduces αSyn-induced mitochondrial oxidative stress through enhancing the level of Superoxide Dismutase-2 (SOD2), and suppresses the accumulation of αSyn S129 phosphorylation and promotes neuronal morphology in neurons derived from PD patient iPS cells carrying αSyn A53T mutant. Moreover, we find that αSyn WT and A53T mutant interact with ClpP and suppress its peptidase activity. The binding of αSyn to ClpP further promotes a distribution of ClpP from soluble to insoluble cellular fraction in vitro and in vivo, leading to reduced solubility of ClpP. Compensating for the loss of ClpP in the substantia nigra of αSyn A53T mice by viral expression of ClpP suppresses mitochondrial oxidative damage, and reduces αSyn pathology and behavioral deficits of mice. Our findings provide novel insights into the mechanism underlying αSyn-induced neuronal pathology, and they suggest that ClpP might be a useful therapeutic target for PD and other synucleinopathies.

Induction of Adaptive Immunity Leads to Nigrostriatal Disease Progression in MPTP Mouse Model of Parkinson's Disease

Although the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model is the most widely used animal model for Parkinson's disease (PD), it is known that nigrostriatal pathologies do not persist in the acute MPTP mouse model. This study highlights the importance of adaptive immunity in driving persistent and progressive disease in acute MPTP-intoxicated mice. Although marked infiltration of T cells into the nigra was found on 1 d of MPTP insult, T cell infiltration decreased afterward, becoming normal on 30 d of insult. Interestingly, twice-weekly supplementation of RANTES and eotaxin, chemokines that are involved in T cell trafficking, drove continuous T cell infiltration to the nigra and incessant glial inflammation. Supplementation of RANTES and eotaxin was also associated with the induction of nigral α-synuclein pathology, persistent loss of dopaminergic neurons and striatal neurotransmitters, and continuous impairment of motor functions in MPTP-intoxicated mice. In contrast, supplementation of TNF-α and IL-1β, widely studied proinflammatory cytokines, did not induce persistent disease in MPTP-insulted mice. Our results suggest that induction of adaptive immunity by RANTES and eotaxin could hold the key for driving persistent nigrostriatal pathologies in the MPTP mouse model, and that targeting these factors may halt disease progression in PD patients.