ChK1 activation induces reactive astrogliosis through CIP2A/PP2A/STAT3 pathway in Alzheimer's disease

Broflanilide induces zebrafish neurobehavioral defects by interfering with synaptic homeostasis

Broflanilide is a novel bisamide insecticide that is extensively used. Previous study reported that broflanilide induced neurotoxicity during zebrafish embryonic development, however, its behavior impact and the involved neural cell heterogeneous mechanism remains largely unknown. Here, we performed a series of neuro-behavior test for adult zebrafish that were exposed to 5 and 25 μg/L broflanilide for 30 days. We found that 25 μg/L broflanilide could induce abnormal locomotion and cognitive defect. These changes were accompanied by synaptic homeostasis inference (decreased number of synaptic knobs), and neuron loss. Simultaneously, a targeted metabolomic assay showed that the glutathione metabolism and GABAergic synapses in brain were significantly altered, indicating an altered synaptic transmission, which is consistent with the synaptic injury. Single-cell RNA sequencing of zebrafish brain showed changed cell composition after exposure, including a decreased ratio of neuron and oligodendrocyte, and an increased proportion of astrocytes. Meanwhile, genes involved in synaptic functional pathways were altered in neuron, astrocyte and oligodendrocytes, which partly explained the disruption of synaptic homeostasis. These findings reveal the long-term risk of broflanilide toward neural health of aquatic organisms and suggest an across-cell types transcriptional regulation in mediating the neurotoxicity.

Circular RNA Vav3 mediated ALV-J inhibition of autophagy by modulating the gga-miR-375/CIP2A axis and activating AKT

Avian leukosis virus subgroup J (ALV-J) is an immunosuppressive neoplastic virus, the growth retardation and growth performance of chickens after infection. Circular RNAs (circRNAs) play a crucial role in various types of cancer. In a previous study, we showed that circ-Vav3 was significantly elevated in the tumor livers of avian leukosis-infected chickens. Autophagy is an essential cellular process, and circRNAs have been confirmed to be key players in autophagy regulation. In this study, we demonstrated that overexpression of circ-Vav3 inhibited autophagy. Specifically, circ-Vav3 functions as a sponge for gga-miR-375, resulting in increased expression of CIP2A, which is a target gene of gga-miR-375. CIP2A, in turn, hinders the fusion of autophagosomes with lysosomes, leading to incomplete autophagic flux, consequently, the inhibition of autophagy. Further study confirmed that overexpression of gga-miR-375 inhibits CIP2A expression and promotes autophagy by downregulating p-AKT. Additionally, we treated cells with rapamycin to induce autophagy and then cotransfected them with circ-Vav3 and gga-miR-375. The results demonstrated that cotransfection of circ-Vav3 and gga-miR-375 inhibited cellular autophagy. Moreover, cells cotransfected with circ-Vav3 and gga-miR-375 exhibited further autophagy inhibition after ALV-J infection, suggesting that circ-Vav3 is involved in inhibiting autophagy caused by ALV-J infection through the regulation of gga-miR-375/CIP2A/AKT. In conclusion, our results demonstrated that circ-Vav3 inhibited autophagy through the gga-miR-375/CIP2A/AKT pathway and mediated the suppression of ALV-J-induced autophagy.

CIP2A promotes bronchiolitis obliterans by activating the NF‑κB pathway

Bronchiolitis obliterans (BO) is a destructive fibrotic lung disease, which can be partly induced by 2,3‑butanedione [also known as diacetyl (DA)]; however, the mechanism underlying the effects of DA on BO is not clear. In the present study, a bioinformatics analysis was performed using DA‑treated or untreated lung tissues of rats, and it was observed that cell proliferation regulating inhibitor of protein phosphatase 2A (CIP2A) was significantly increased in samples from the DA group. CIP2A is associated with inflammation and epithelial‑mesenchymal transition (EMT), and facilitates lung injury; however, its effect on DA‑induced BO and the underlying mechanism remain unknown. To solve these issues, DA‑treated models of BO were established in rats and cells, and ethoxysanguinarine (a CIP2A inhibitor) was administered to induce a decrease in CIP2A. The pathological changes were detected by hematoxylin and eosin, Masson and Giemsa staining. Reverse transcription‑quantitative PCR, western blotting, immunohistochemistry, immunofluorescence and enzyme‑linked immunosorbent assay were used to measure CIP2A expression and levels of pathology‑related markers. Notably, inhibition of CIP2A ameliorated the pathological features of BO, including reduced intraluminal occlusion, inflammatory infiltration and fibrosis. The expression of inflammation, fibrosis and EMT markers was also decreased in samples with CIP2A inhibition. Furthermore, CIP2A inhibition was revealed to work through the nuclear factor‑κB (NF‑κB) pathway; phosphorylation of NF‑κB inhibitor α and nuclear translocation of p65 were reduced. In summary, these results demonstrated that CIP2A may promote BO development by increasing inflammation, fibrosis and EMT through activating the NF‑κB signaling pathway. Therefore, inhibition of CIP2A may be considered a potential strategy for BO treatment.

Critical role of checkpoint kinase 1 in spinal cord injury-induced motor dysfunction in mice

Spinal cord injury (SCI) is a devastating neurotraumatic condition characterized by severe motor dysfunction and paralysis. Accumulating evidence suggests that DNA damage is involved in SCI pathology. However, the underlying mechanisms remain elusive. Although checkpoint kinase 1 (Chk1)-regulated DNA damage is involved in critical cellular processes, its role in SCI regulation remains unclear. This study aimed to explore the role and potential mechanism of Chk1 in SCI-induced motor dysfunction. Adult female C57BL/6J mice subjected to T9-T10 spinal cord contusions were used as models of SCI. Western blotting, immunoprecipitation, histomorphology, and Chk1 knockdown or overexpression achieved by adeno-associated virus were performed to explore the underlying mechanisms. Levels of p-Chk1 and γ-H2AX (a cellular DNA damage marker) were upregulated, while ferroptosis-related protein levels, including glutathione peroxidase 4 (GPX4) and x-CT were downregulated, in the spinal cord and hippocampal tissues of SCI mice. Functional experiments revealed increased Basso Mouse Scale (BMS) scores, indicating that Chk1 downregulation promoted motor function recovery after SCI, whereas Chk1 overexpression aggravated SCI-induced motor dysfunction. In addition, Chk1 downregulation reversed the SCI-increased levels of GPX4 and x-CT expression in the spinal cord and hippocampus, while immunoprecipitation assays revealed strengthened interactions between p-Chk1 and GPX4 in the spinal cord after SCI. Finally, Chk1 downregulation promoted while Chk1 overexpression inhibited NeuN cellular immunoactivity in the spinal cord after SCI, respectively. Collectively, these preliminary results imply that Chk1 is a novel regulator of SCI-induced motor dysfunction, and that interventions targeting Chk1 may represent promising therapeutic targets for neurotraumatic diseases such as SCI.

Protein Kinase C-Delta Mediates Cell Cycle Reentry and Apoptosis Induced by Amyloid-Beta Peptide in Post-Mitotic Cortical Neurons

Amyloid-beta peptide (Aβ) is a neurotoxic constituent of senile plaques in the brains of Alzheimer's disease (AD) patients. The detailed mechanisms by which protein kinase C-delta (PKCδ) contributes to Aβ toxicity is not yet entirely understood. Using fully differentiated primary rat cortical neurons, we found that inhibition of Aβ25-35-induced PKCδ increased cell viability with restoration of neuronal morphology. Using cyclin D1, proliferating cell nuclear antigen (PCNA), and histone H3 phosphorylated at Ser-10 (p-Histone H3) as the respective markers for the G1-, S-, and G2/M-phases, PKCδ inhibition mitigated cell cycle reentry (CCR) and subsequent caspase-3 cleavage induced by both Aβ25-35 and Aβ1-42 in the post-mitotic cortical neurons. Upstream of PKCδ, signal transducers and activators of transcription (STAT)-3 mediated PKCδ induction, CCR, and caspase-3 cleavage upon Aβ exposure. Downstream of PKCδ, aberrant neuronal CCR was triggered by overactivating cyclin-dependent kinase-5 (CDK5) via calpain2-dependent p35 cleavage into p25. Finally, PKCδ and CDK5 also contributed to Aβ25-35 induction of p53-upregulated modulator of apoptosis (PUMA) in cortical neurons. Together, we demonstrated that, in the post-mitotic neurons exposed to Aβs, STAT3-dependent PKCδ expression triggers calpain2-mediated p35 cleavage into p25 to overactivate CDK5, thus leading to aberrant CCR, PUMA induction, caspase-3 cleavage, and ultimately apoptosis.

Tau induces inflammasome activation and microgliosis through acetylating NLRP3

BACKGROUND

Alzheimer's disease (AD) and related Tauopathies are characterised by the pathologically hyperphosphorylated and aggregated microtubule-associated protein Tau, which is accompanied by neuroinflammation mediated by activated microglia. However, the role of Tau pathology in microglia activation or their causal relationship remains largely elusive.

METHODS

The levels of nucleotide-binding oligomerisation domain (NOD)-like receptor pyrin domain containing 3 (NLRP3) acetylation and inflammasome activation in multiple cell models with Tau proteins treatment, transgenic mice with Tauopathy, and AD patients were measured by Western blotting and enzyme-linked immunosorbent assay. In addition, the acetyltransferase activity of Tau and NLRP3 acetylation sites were confirmed using the test-tube acetylation assay, co-immunoprecipitation, immunofluorescence (IF) staining, mass spectrometry and molecular docking. The Tau-overexpressing mouse model was established by overexpression of human Tau proteins in mouse hippocampal CA1 neurons through the adeno-associated virus injection. The cognitive functions of Tau-overexpressing mice were assessed in various behavioural tests, and microglia activation was analysed by Iba-1 IF staining and [18F]-DPA-714 positron emission tomography/computed tomography imaging. A peptide that blocks the interaction between Tau and NLRP3 was synthesised to determine the in vitro and in vivo effects of Tau-NLRP3 interaction blockade on NLRP3 acetylation, inflammasome activation, microglia activation and cognitive function.

RESULTS

Excessively elevated NLRP3 acetylation and inflammasome activation were observed in 3xTg-AD mice, microtubule-associated protein Tau P301S (PS19) mice and AD patients. It was further confirmed that mimics of 'early' phosphorylated-Tau proteins which increase at the initial stage of diseases with Tauopathy, including TauT181E, TauS199E, TauT217E and TauS262E, significantly promoted Tau-K18 domain acetyltransferase activity-dependent NLRP3 acetylation and inflammasome activation in HEK293T and BV-2 microglial cells. In addition, Tau protein could directly acetylate NLRP3 at the K21, K22 and K24 sites at its PYD domain and thereby induce inflammasome activation in vitro. Overexpression of human Tau proteins in mouse hippocampal CA1 neurons resulted in impaired cognitive function, Tau transmission to microglia and microgliosis with NLRP3 acetylation and inflammasome activation. As a targeted intervention, competitive binding of a designed Tau-NLRP3-binding blocking (TNB) peptide to block the interaction of Tau protein with NLRP3 inhibited the NLRP3 acetylation and downstream inflammasome activation in microglia, thereby alleviating microglia activation and cognitive impairment in mice.

CONCLUSIONS

In conclusion, our findings provide evidence for a novel role of Tau in the regulation of microglia activation through acetylating NLRP3, which has potential implications for early intervention and personalised treatment of AD and related Tauopathies.

APOE genotype-specific methylation patterns are linked to Alzheimer disease pathology and estrogen response

The joint effects of APOE genotype and DNA methylation on Alzheimer disease (AD) risk is relatively unknown. We conducted genome-wide methylation analyses using 2,021 samples in blood (91 AD cases, 329 mild cognitive impairment, 1,391 controls) and 697 samples in brain (417 AD cases, 280 controls). We identified differentially methylated levels in AD compared to controls in an APOE genotype-specific manner at 25 cytosine-phosphate-guanine (CpG) sites in brain and 36 CpG sites in blood. Additionally, we identified seven CpG sites in the APOE region containing TOMM40, APOE, and APOC1 genes with P < 5 × 10-8 between APOE ε4 carriers and non-carriers in brain or blood. In brain, the most significant CpG site hypomethylated in ε4 carriers compared to non-carriers was from the TOMM40 in the total sample, while most of the evidence was derived from AD cases. However, the CpG site was not significantly modulating expression of these three genes in brain. Three CpG sites from the APOE were hypermethylated in APOE ε4 carriers in brain or blood compared in ε4 non-carriers and nominally significant with APOE expression in brain. Three CpG sites from the APOC1 were hypermethylated in blood, which one of the 3 CpG sites significantly lowered APOC1 expression in blood using all subjects or ε4 non-carriers. Co-methylation network analysis in blood and brain detected eight methylation networks associated with AD and APOE ε4 status. Five of the eight networks included genes containing network CpGs that were significantly enriched for estradiol perturbation, where four of the five networks were enriched for the estrogen response pathway. Our findings provide further evidence of the role of APOE genotype on methylation levels associated with AD, especially linked to estrogen response pathway.

Hydrogen sulfide ameliorates lipopolysaccharide-induced anxiety-like behavior by inhibiting checkpoint kinase 1 activation in the hippocampus of mice

Hydrogen sulfide (H2S), an endogenous gasotransmitter, exhibits the anxiolytic roles through its anti-inflammatory effects, although its underlying mechanisms remain largely elusive. Emerging evidence has documented that cell cycle checkpoint kinase 1 (Chk1)-regulated DNA damage plays an important role in the neurodegenerative diseases; however, there are few relevant reports on the research of Chk1 in neuropsychiatric diseases. Here, we aimed to investigate the regulatory role of H2S on Chk1 in lipopolysaccharide (LPS)-induced anxiety-like behavior focusing on inflammasome activation in the hippocampus. Cystathionine γ-lyase (CSE, a H2S-producing enzyme) knockout (CSE-/-) mice displayed anxiety-like behavior and activation of inflammasome-mediated inflammatory responses, manifesting by the increase levels of interleukin-1β (IL-1β), IL-6, and ionized calcium-binding adaptor molecule-1 (Iba-1, microglia marker) expression in the hippocampus. Importantly, expression of p-Chk1 and γ-H2AX (DNA damage marker) levels were also increased in the hippocampus of CSE-/- mice. LPS treatment decreased the expression of CSE and CBS while increased p-Chk1 and γ-H2AX levels and inflammasome-activated neuroinflammation in the hippocampus of mice. Moreover, p-Chk1 and γ-H2AX protein levels and cellular immunoactivity were significantly increased while CSE and CBS were markedly decreased in cultured BV2 cells followed by LPS treatment. Treatment of mice with GYY4137, a donor of H2S, inhibited LPS-induced increased in p-Chk1 and γ-H2AX levels, mitigated inflammasome activation and inflammatory responses as well as amelioration of anxiety-like behavior. Notably, SB-218078, a selective Chk1 inhibitor treatment attenuated the effect of LPS on inflammasome activation and inflammatory responses and the induction of anxiety-like behavior. Finally, STAT3 knockdown with AAV-STAT3 shRNA alleviated LPS-induced anxiety-like behavior and inhibited inflammasome activation in the hippocampus, and blockade of NLRP3 with MCC950 attenuated neuroinflammation induction and ameliorated LPS-induced anxiety-like behavior. Overall, this study indicates that downregulation of Chk1 activity by H2S activation may be considered as a valid strategy for preventing the progression of LPS-induced anxiety-like behavior.

CIP2A coordinates phosphosignaling, mitosis, and the DNA damage response

Human cancers share requirements for phosphorylation-dependent signaling, mitotic hyperactivity, and survival after DNA damage. The oncoprotein CIP2A (cancerous inhibitor of PP2A) can coordinate all these cancer cell characteristics. In addition to controlling cancer cell phosphoproteomes via inhibition of protein phosphatase PP2A, CIP2A directly interacts with the DNA damage protein TopBP1 (topoisomerase II-binding protein 1). Consequently, CIP2A allows DNA-damaged cells to enter mitosis and is essential for mitotic cells that are defective in homologous recombination (HR)-mediated DNA repair (e.g., BRCA mutants). The CIP2A-TopBP1 complex is also important for clustering fragmented chromosomes at mitosis. Clinically, CIP2A is a disease driver for basal-like triple-negative breast cancer (BL-TNBC) and a promising cancer therapy target across many cancer types.