MALAT1 Mediates α-Synuclein Expression through miR-23b-3p to Induce Autophagic Impairment and the Inflammatory Response in Microglia to Promote Apoptosis in Dopaminergic Neuronal Cells

Abstract

Background. Parkinson’s disease (PD) is a very common neurodegenerative disease that adversely affects the physical and mental health of many patients, but there is currently no effective treatment. Objective. To this end, this study focused on investigating the potential mechanisms leading to dopaminergic neuronal apoptosis in PD. Methods. Rotenone induces damage in dopaminergic neuronal MN9D cells. Apoptosis was detected by flow cytometry, and the expression of apoptosis-related proteins was detected by western blot. RT-qPCR was used to detect the expression of MALAT1 and miR-23b-3p. The expression of α-synuclein was detected by ELISA. A dual luciferase gene reporter assay was used to determine the targeted regulatory relationship between MALAT1 and miR-23b-3p and miR-23b-3p and α-synuclein. MN9D supernatant was cocultured with BV-2 cells, or BV-2 cells were treated with exogenous α-synuclein and then treated with an autophagy inhibitor (3-MA) and autophagy activator (RAPA). The expression of α-synuclein in BV-2 cells was detected by immunofluorescence. The expression of MIP-1α, a marker of microglial activation, was detected by ELISA. The nuclear translocation of NF-κB p65 was detected by immunofluorescence. The expression of proinflammatory cytokines was detected by ELISA. Western blotting was used to detect the expression of autophagy-related proteins. Apoptosis of MN9D cells was detected after coculture of BV-2 supernatant with MN9D. Results. The expression of MALAT1 and α-synuclein was upregulated, while the expression of miR-23b-3p was downregulated in damaged MN9D cells, resulting in cell apoptosis. MALAT1 can negatively regulate the expression of miR-23b-3p, while miR-23b-3p negatively regulates the expression of α-synuclein. α-synuclein can enter BV-2 cells through cell phagocytosis. Coculture of BV-2 cells with α-synuclein or with MN9D supernatant overexpressing MALAT1 resulted in a decrease in the autophagy level of BV-2 cells and an inflammatory reaction. However, miR-23b-3p mimics and knockdown of α-synuclein reversed the effect of MALAT1 on autophagy and the inflammatory response of BV-2 cells. In addition, after coculture of BV-2 cells with α-synuclein, the level of autophagy further decreased when 3-MA was added, while the opposite result occurred when RAPA was added. After coculture of α-synuclein-treated BV-2 cell supernatant with MN9D cells, autophagy-impaired BV-2 promoted the apoptosis of MN9D cells, and 3-MA aggravated the autophagy disorder of BV-2 and further promoted the apoptosis of MN9D cells, while RAPA reversed the autophagy disorder of BV-2 and alleviated the apoptosis of MN9D cells. Conclusion. MALAT1 can promote α-synuclein expression by regulating miR-23b-3p, thereby inducing microglial autophagy disorder and an inflammatory response leading to apoptosis of dopaminergic neurons. This newly discovered molecular mechanism may provide a potential target for the treatment of PD.

The dual face of microglia (M1/M2) as a potential target in the protective effect of nutraceuticals against neurodegenerative diseases

“…PD onset and prognosis were correlated with MALAT1-relevant single nucleotide polymorphisms (SNPs), and MALAT1 contributed to increasing the neuronal inflammation of the pathogenesis of PD ( Yang, 2021 ). MALAT1 is overexpressed due to participation in activating inflammatory vesicles in microglia ( Geng et al, 2023 ). In PD models, MALAT1 induces apoptosis of dopamine neurons via sponging miRNA-124 ( Liu et al, 2017 ) and acts as a miR-23b-3p sponge that inhibits microglial autophagy and inflammatory responses to promote dopaminergic neuronal apoptosis.…”

“…As a result, microglia may exhibit impaired autophagy and inflammatory reactions. Consequently, this provides a new treatment target for PD ( Geng et al, 2023 ). Due to its effects on dopaminergic neuron apoptosis, lncRNA MALAT1 may be a new treatment target in PD.…”

“…Inhibits microglial autophagy and inflammatory responses to promote dopaminergic neuronal apoptosis by acting as miR-23b-3p sponge Parkinson's disease Geng et al (2023) miRNA-124…”

The potential of targeting microRNA-23b-3p signaling in Alzheimer’s disease: opinions on recent findings

“…These findings suggest that miR-23b-3p multimodally inhibits Aβ generation, tau phosphorylation, and neuronal apoptosis by regulating one target, namely, GSK-3β, acting upstream of several signaling pathways (Figure 1). Emerging evidence suggests additional targets for miR-23b-3p in non-cancerous diseases, such as neuropilin 1 (Xia et al, 2020), apoptotic protease activating factor-1 (Apaf-1) (Chen et al, 2014), α-synuclein (Geng et al, 2023), and phosphatase and tensin homolog (PTEN) . Among these, Apaf-1 mediates apoptosis via recruitment and activation of caspase-9 by binding with cytochrome c. Notably, PTEN is also a regulator of tau phosphorylation.…”

“…2 MiR-23b-3p plays a key role in AD MiR-23b-3p is a member of the miR-23b family. Initially described in 2012, miR-23b-3p plays important roles in carcinogenesis (Grossi et al, 2018) and non-cancerous diseases, especially nervous system diseases like ischemic stroke (Wu et al, 2017), seizure (Zhan et al, 2016), Parkinson's disease (Geng et al, 2023), peripheral nerve regeneration (Xia et al, 2020), and neuroinflammation-related diseases (Burrows et al, 2023). The first reported relationship between miR-23b-3p and AD was altered expression of miR-23b-3p in AD patients (Lugli et al, 2015).…”