Mitochondrial Disruption by Amyloid Beta 42 Identified by Proteomics and Pathway Mapping

Alzheimer’s disease (AD) is marked by chronic neurodegeneration associated with the occurrence of plaques containing amyloid β (Aβ) proteins in various parts of the human brain. An increase in several Aβ fragments is well documented in patients with AD and anti-amyloid targeting is an emerging area of therapy. Soluble Aβ can bind to various cell surface and intracellular molecules with the pathogenic Aβ42 fragment leading to neurotoxicity. Here we examined the effect of Aβ42 on network adaptations in the proteome of nerve growth factor (NGF) differentiated PC12 cells using liquid-chromatography electrospray ionization mass spectrometry (LC-ESI MS/MS) proteomics. Whole-cell peptide mass fingerprinting was coupled to bioinformatic gene set enrichment analysis (GSEA) in order to identify differentially represented proteins and related gene ontology (GO) pathways within Aβ42 treated cells. Our results underscore a role for Aβ42 in disrupting proteome responses for signaling, bioenergetics, and morphology in mitochondria. These findings highlight the specific components of the mitochondrial response during Aβ42 neurotoxicity and suggest several new biomarkers for detection and surveillance of amyloid disease.

Microtubule associated protein 4 (MAP4) phosphorylation reduces cardiac microvascular density through NLRP3-related pyroptosis

Phosphorylation of MAP4 (p-MAP4) causes cardiac remodeling, with the cardiac microvascular endothelium being considered a vital mediator of this process. In the current study, we investigated the mechanism underlying p-MAP4 influences on cardiac microvascular density. We firstly confirmed elevated MAP4 phosphorylation in the myocardium of MAP4 knock-in (KI) mice. When compared with the corresponding control group, we detected the decreased expression of CD31, CD34, VEGFA, VEGFR2, ANG2, and TIE2 in the myocardium of MAP4 KI mice, accompanied by a reduced plasma concentration of VEGF. Moreover, we observed apoptosis and mitochondrial disruption in the cardiac microvascular endothelium of MAP4 KI animals. Consistently, we noted a decreased cardiac microvascular density, measured by CD31 and lectin staining, in MAP4 KI mice. To explore the underlying mechanism, we targeted the NLRP3-related pyroptosis and found increased expression of the corresponding proteins, including NLRP3, ASC, mature IL-1β, IL-18, and GSDMD-N in the myocardium of MAP4 KI mice. Furthermore, we utilized a MAP4 (Glu) adenovirus to mimic cellular p-MAP4. After incubating HUVECs with MAP4 (Glu) adenovirus, the angiogenic ability was inhibited, and NLRP3-related pyroptosis were significantly activated. Moreover, both cytotoxicity and PI signal were upregulated by the MAP4 (Glu) adenovirus. Finally, NLRP3 inflammasome blockage alleviated the inhibited angiogenic ability induced by MAP4 (Glu) adenovirus. These results demonstrated that p-MAP4 reduced cardiac microvascular density by activating NLRP3-related pyroptosis in both young and aged mice. We thus managed to provide clues explaining MAP4 phosphorylation-induced cardiac remodeling and enriched current knowledge regarding the role of MAP4.

MiR-20a-5p Regulates MPP+-Induced Oxidative Stress and Neuroinflammation in HT22 Cells by Targeting IRF9/NF-κB Axis

Substantial evidence indicates that microRNAs (miRNAs) can be used as biological markers of Parkinson’s disease (PD) and contribute to the risk assessment, early diagnosis, and treatment. We aimed to explore the role and potential mechanism of miR-20a-5p on inflammation and oxidative stress in 1-methyl-4-phenyl pyridine ion- (MPP+-) induced HT22 cells. HT22 cells were pretreated with miR-20a-5p mimic and/or pcDNA-IRF9 for 24 h and then treated with MPP+ (0.5 mM) for 24 h. The cell viability and apoptosis were determined using the Cell Counting Kit-8 (CCK-8) and Annexin V FITC/PI staining flow cytometry assay, respectively. The expression and secretion of inflammatory factors and oxidative stress-related factors were detected by enzyme-linked immunosorbent assay (ELISA). The protein expression levels were detected using Western blot analysis. Here, we discovered that MPP+ led to mitochondrial dysfunction, inflammation, and cell damage of HT22 cells, which were alleviated by miR-20a-5p overexpression. We further clarified that interferon regulatory factor 9 (IRF9) was a target gene of miR-20a-5p. IRF9 contributed to MPP+-induced mitochondrial disruption, inflammation, and cell apoptosis. Moreover, IRF9 hindered the improvement of miR-20a-5p overexpression on MPP+-induced neurotoxicity. Furthermore, the decrease of p-P65 level induced by miR-20a-5p mimic was significantly reversed by IRF9 overexpression. These findings demonstrate that miR-20a-5p contributes to MPP+-induced mitochondrial disruption and cell damage, and miR-20a-5p might be a novel therapeutic target for PD.

Prevention of HIV-1 TAT Protein-Induced Peripheral Neuropathy and Mitochondrial Disruption by the Antimuscarinic Pirenzepine

HIV-associated distal sensory polyneuropathy (HIV-DSP) affects about one third of people with HIV and is characterized by distal degeneration of axons. The pathogenesis of HIV-DSP is not known and there is currently no FDA-approved treatment. HIV trans-activator of transcription (TAT) is associated with mitochondrial dysfunction and neurotoxicity in the brain and may play a role in the pathogenesis of HIV-DSP. In the present study, we measured indices of peripheral neuropathy in the doxycycline (DOX)-inducible HIV-TAT (iTAT) transgenic mouse and investigated the therapeutic efficacy of a selective muscarinic subtype-1 receptor (M1R) antagonist, pirenzepine (PZ). PZ was selected as we have previously shown that it prevents and/or reverses indices of peripheral neuropathy in multiple disease models. DOX alone induced weight loss, tactile allodynia and paw thermal hypoalgesia in normal C57Bl/6J mice. Conduction velocity of large motor fibers, density of small sensory nerve fibers in the cornea and expression of mitochondria-associated proteins in sciatic nerve were unaffected by DOX in normal mice, whereas these parameters were disrupted when DOX was given to iTAT mice to induce TAT expression. Daily injection of PZ (10 mg/kg s.c.) prevented all of the disorders associated with TAT expression. These studies demonstrate that TAT expression disrupts mitochondria and induces indices of sensory and motor peripheral neuropathy and that M1R antagonism may be a viable treatment for HIV-DSP. However, some indices of neuropathy in the DOX-inducible TAT transgenic mouse model can be ascribed to DOX treatment rather than TAT expression and data obtained from animal models in which gene expression is modified by DOX should be accompanied by appropriate controls and treated with due caution.

Insulin signaling mediates neurodegeneration in glioma

Cell to cell communication facilitates tissue development and physiology. Under pathological conditions, brain tumors disrupt glia-neuron communication signals that in consequence, promote tumor expansion at the expense of surrounding healthy tissue. The glioblastoma is one of the most aggressive and frequent primary brain tumors. This type of glioma expands and infiltrates into the brain, causing neuronal degeneration and neurological decay, among other symptoms. Here, we describe in a Drosophila model how glioblastoma cells produce ImpL2, an antagonist of the insulin pathway, which targets neighboring neurons and causes mitochondrial disruption as well as synapse loss, both early symptoms of neurodegeneration. Furthermore, glioblastoma progression requires insulin pathway attenuation in neurons. Restoration of neuronal insulin activity is sufficient to rescue synapse loss and to delay the premature death caused by glioma. Therefore, signals from glioblastoma to neuron emerge as a potential field of study to prevent neurodegeneration and to develop anti-tumoral strategies.

Insulin signaling mediates neurodegeneration in glioma

Cell to cell communication facilitates tissue development and physiology. Under pathological conditions, brain tumors disrupt glia-neuron communication signals that in consequence, promote tumor expansion at the expense of surrounding healthy tissue. The glioblastoma is the most aggressive and frequent brain tumor. This type of glioma expands and infiltrates into the brain, causing neuronal degeneration and neurological decay, among other symptoms. Here we describe how the glioblastoma produce ImpL2, an antagonist of the insulin pathway, which is regulated by the microRNA miR-8. ImpL2 targets neighboring neurons and causes mitochondrial disruption as well as synapse loss, both early symptoms of neurodegeneration. Furthermore, glioblastoma progression requires insulin pathway attenuation in neurons. Restoration of neuronal insulin activity is sufficient to rescue the synapse loss and to delay the premature death caused by glioma. Therefore, signals from GB to neuron emerge as a potential field of study to prevent neurodegeneration and to develop anti-tumoral strategies.Significance StatementGlioblastoma (GB) is the most aggressive type of brain tumour and currently there is no cure or effective treatment. Patients course with neurological decay and previous data in animal models indicate that GB cause a neurodegenerative process. We describe here a molecule named ImpL2 that is produced by GB cells and impact on neighbouring neurons. ImpL2 is an antagonist of the insulin pathway and signaling reduction in neurons causes mitochondrial defects and synapse loss. These mechanisms underlying GB-induced neurodegeneration plays a central role in the premature death caused by this tumour. Restoration of insulin signaling in neurons prevents tumour progression and rescues the lethality caused by GB in Drosophila models.