Pazopanib alleviates neuroinflammation and protects dopaminergic neurons in LPS-stimulated mouse model by inhibiting MEK4-JNK-AP-1 pathway.

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons and the accumulation of Lewy bodies (LB) in the substantia nigra (SN). Evidence shows that microglia-mediated neuroinflammation plays a key role in PD pathogenesis. Using TNF-α as an indicator for microglial activation, we established a cellular model to screen compounds that could inhibit neuroinflammation. From 2471 compounds in a small molecular compound library composed of FDA-approved drugs, we found 77 candidates with a significant anti-inflammatory effect. In this study, we further characterized pazopanib, a pan-VEGF receptor tyrosine kinase inhibitor (that was approved by the FDA for the treatment of advanced renal cell carcinoma and advanced soft tissue sarcoma). We showed that pretreatment with pazopanib (1, 5, 10 µM) dose-dependently suppressed LPS-induced BV2 cell activation evidenced by inhibiting the transcription of proinflammatory factors iNOS, COX2, Il-1ß, and Il-6 through the MEK4-JNK-AP-1 pathway. The conditioned medium from LPS-treated microglia caused mouse DA neuronal MES23.5 cell damage, which was greatly attenuated by pretreatment of the microglia with pazopanib. We established an LPS-stimulated mouse model by stereotactic injection of LPS into mouse substantia nigra. Administration of pazopanib (10 mg·kg-1·d-1, i.p., for 10 days) exerted significant anti-inflammatory and neuronal protective effects, and improved motor abilities impaired by LPS in the mice. Together, we discover a promising candidate compound for anti-neuroinflammation and provide a potential repositioning of pazopanib in the treatment of PD.

Pharmacological activation of REV-ERBα represses LPS-induced microglial activation through the NF-κB pathway.

REV-ERBα, the NR1D1 (nuclear receptor subfamily 1, group D, member 1) gene product, is a dominant transcriptional silencer that represses the expression of genes involved in numerous physiological functions, including circadian rhythm, inflammation, and metabolism, and plays a crucial role in maintaining immune functions. Microglia-mediated neuroinflammation is tightly associated with various neurodegenerative diseases and psychiatric disorders. However, the role of REV-ERBα in neuroinflammation is largely unclear. In this study, we investigated whether and how pharmacological activation of REV-ERBα affected lipopolysaccharide (LPS)-induced neuroinflammation in mouse microglia in vitro and in vivo. In BV2 cells or primary mouse cultured microglia, application of REV-ERBα agonist GSK4112 or SR9011 dose-dependently suppressed LPS-induced microglial activation through the nuclear factor kappa B (NF-κB) pathway. In BV2 cells, pretreatment with GSK4112 inhibited LPS-induced phosphorylation of the inhibitor of NF-κB alpha (IκBα) kinase (IκK), thus restraining the phosphorylation and degradation of IκBα, and blocked the nuclear translocation of p65, a NF-κB subunit, thereby suppressing the expression and secretion of the proinflammatory cytokines, such as interleukin 6 (IL-6) and tumor necrosis factor α (TNFα). Moreover, REV-ERBα agonist-induced inhibition on neuroinflammation protected neurons from microglial activation-induced damage, which were also demonstrated in mice with their ventral midbrain microinjected with GSK4112, and then stimulated with LPS. Our results reveal that enhanced REV-ERBα activity suppresses microglial activation through the NF-κB pathway in the central nervous system.

Microglial MT1 activation inhibits LPS-induced neuroinflammation via regulation of metabolic reprogramming.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Although its pathogenesis remains unclear, a number of studies indicate that microglia-mediated neuroinflammation makes a great contribution to the pathogenesis of PD. Melatonin receptor 1 (MT1) is widely expressed in glia cells and neurons in substantia nigra (SN). Neuronal MT1 is a neuroprotective factor, but it remains largely unknown whether dysfunction of microglial MT1 is involved in the PD pathogenesis. Here, we found that MT1 was reduced in microglia of SN in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model. Microglial MT1 activation dramatically inhibited lipopolysaccharide (LPS)-induced neuroinflammation, whereas loss of microglial MT1 aggravated it. Metabolic reprogramming of microglia was found to contribute to the anti-inflammatory effects of MT1 activation. LPS-induced excessive aerobic glycolysis and impaired oxidative phosphorylation (OXPHOS) could be reversed by microglial MT1 activation. MT1 positively regulated pyruvate dehydrogenase alpha 1 (PDHA1) expression to enhance OXPHOS and suppress aerobic glycolysis. Furthermore, in LPS-treated microglia, MT1 activation decreased the toxicity of conditioned media to the dopaminergic (DA) cell line MES23.5. Most importantly, the anti-inflammatory effects of MT1 activation were observed in LPS-stimulated mouse model. In general, our study demonstrates that MT1 activation inhibits LPS-induced microglial activation through regulating its metabolic reprogramming, which provides a mechanistic insight for microglial MT1 in anti-inflammation.

Silymarin protects against acrylamide-induced neurotoxicity via Nrf2 signalling in PC12 cells.

Silymarin (SM) is a well-known antioxidant, anti-inflammatory and anti-cancer compound extracted from the milk thistle. Here, we investigated the protective effect of SM against acrylamide (AA)-induced neurotoxicity, mainly caused by oxidative stress, via activation of the nuclear transcription factor E2-related factor 2 (Nrf2) signalling pathway in PC12 cells. The MTT reduction assay was used to measure cell viability in various drug-treated groups and demonstrated that SM could increase cell viability in AA-treated PC12 cells. We then measured the reactive oxygen species (ROS) levels by the peroxide-sensitive fluorescent probe DCFH-DA and intracellular glutathione (GSH) and malondialdehyde (MDA) levels by absorption spectrophotometry. Our data revealed that SM could reduce ROS and MDA levels and increase GSH levels in AA-induced PC12 cells. To identify a potential mechanism for SM-induced protection, we measured the mRNA and protein expression levels of Nrf2 and its downstream target antioxidants glutathione peroxidase (Gpx), glutamate cysteine ligase catalytic subunit (GCLC) and glutamate cysteine ligase modifier subunit (GCLM) by quantitative real-time PCR and Western blot, respectively. The results suggested that SM could activate Nrf2 signalling and increase the expression of Nrf2, Gpx, GCLC and GCLM in AA-treated PC12 cells. In conclusion, SM can effectively alleviate AA-induced neurotoxicity in PC12 cells.

Key role of peptidoglycan on acrylamide binding by lactic acid bacteria.

The primary purpose of this study was to analyze the ability of four peptidoglycan (PGN) from different lactic acid bacteria to bind acrylamide (AA) and to identify the binding mechanism. In this study, to clarify the possible binding interactions among AA and components of PGN, chemical components, surface structure, amino acids component, and functional groups of peptidoglycans were studied. It was found that PGN from Lactobacillus plantarum 1.0065 had the highest ability to bind AA with 87%. Furthermore, a significant positive relation was found between the carbohydrate content of PGN and percentage of bind AA, and the content of four specific amino acids of PGN and AA binding ability were also positive correlated. Thereinto, alanine of PGN had a significant impact on AA binding among four amino acids. Additionally, the C-O (carboxyl, polysaccharides, and arene), C=O amide, and N-H amines groups of PGN were involved in AA binding.