Neurotropin alleviates Alzheimer's disease pathology by inhibiting FUS-mediated Calhm2 transcription, blocking the Calhm2/EFhd2 interaction, to improve mitochondrial dysfunction-associated microglia polarization.

Baicalein promotes the microglia M2 polarization and suppresses apoptosis by targeting HMOX1/PDE4D to alleviate Alzheimer’s disease

Berbamine targets the FKBP12-rapamycin-binding (FRB) domain of the mTOR complex to promote microglial autophagy and ameliorate neuroinflammation in Alzheimer's disease.

Neuroinflammation, triggered by aberrantly activated microglia, is widely recognized as a key contributor to the initiation and progression of Alzheimer's disease (AD). Microglial activation in the central nervous system (CNS) can be classified into two distinct phenotypes: the pro-inflammatory M1 phenotype and the anti-inflammatory M2 phenotype. In this study, we investigated the effects of a non-invasive rotating magnetic field (RMF) (0.2T, 4Hz) on cognitive and memory impairments in a sporadic AD model of female Kunming mice induced by AlCl3 and D-gal. Our findings revealed significant improvements in cognitive and memory impairments following RMF treatment. Furthermore, RMF treatment led to reduced amyloid-beta (Aβ) deposition, mitigated damage to hippocampal morphology, prevented synaptic and neuronal loss, and alleviated cell apoptosis in the hippocampus and cortex of AD mice. Notably, RMF treatment ameliorated neuroinflammation, facilitated the transition of microglial polarization from M1 to M2, and inhibited the NF-кB/MAPK pathway. Additionally, RMF treatment resulted in reduced aluminum deposition in the brains of AD mice. In cellular experiments, RMF promoted the M1-M2 polarization transition and enhanced amyloid phagocytosis in cultured BV2 cells while inhibiting the TLR4/NF-кB/MAPK pathway. Collectively, these results demonstrate that RMF improves memory and cognitive impairments in a sporadic AD model, potentially by promoting the M1 to M2 transition of microglial polarization through inhibition of the NF-кB/MAPK signaling pathway. These findings suggest the promising therapeutic applications of RMF in the clinical treatment of AD.

Cannabinoid receptor-2 stimulation suppresses neuroinflammation by regulating microglial M1/M2 polarization through the cAMP/PKA pathway in an experimental GMH rat model

Motor function deficits in the 12 month-old female 5xFAD mouse model of Alzheimer’s disease

Post-translational modifications serve as a cellular mechanism for the regulation of the activity, stability and localization of proteins. SUMOylation is a dynamic and reversible post-translational modification, which entails the attachment of a SUMO protein to a lysine residue of the target protein. SUMOylation is involved in the regulation of numerous cellular processes including transcription, nucleocytoplasmic trafficking, and DNA repair. Three or four SUMO paralogs are present in mammals – SUMO1, SUMO2, SUMO3 and SUMO4. SUMO2 and SUMO3 exhibit extremely high sequence homology and therefore cannot be distinguished by antibodies. Interestingly, SUMO2/3 conjugation has been shown to change dramatically in response to aberrant cellular conditions. The identification of endogenous SUMO substrates has long been hindered by the transient nature of SUMOylation, the lack of reliable antibodies for affinity purification, and the modification of only a small percentage of a given SUMO substrate at a given time. Thus, in a first project, analogous to a His6-HA-SUMO1 knock-in mouse model generated in our lab, we generated a Strep-Myc-SUMO3 knock-in mouse model expressing Strep-Myc-tagged SUMO3 instead of wild type SUMO3 from the endogenous SUMO3 locus. Importantly, a main advantage of this model is the possibility to distinguish specifically SU-MO3 from SUMO2. Strep-Myc-SUMO3 knock-in and wild type mice brain homogenates were used to perform anti-Myc affinity purification, which resulted in the enrichment of free SUMO3 and SUMO3 conjugates in the eluate from the knock-in mice. Thus, we proved that the newly generated mouse model can be used as a tool for the identification of SUMO3 sub-strates. However, despite the utilization of several anti-Myc and one anti-Strep antibody, we were not able to clearly localize Strep-Myc-SUMO3 in brain sections of SUMO3 knock-in mice as the antibodies showed different staining patterns. This mouse model will be further used to study SUMO3 conjugation profiles under physiological and non-physiological condi-tions. A constantly increasing number of studies have suggested a link between SUMOylation and Alzheimer's disease. Thus, in a second project, we crossbred His6-HA-SUMO1 knock-in mice with 5xFAD, a mouse model of Alzheimer's disease, in order to assess SUMO1 conjugation profile in the context of Alzheimer's disease pathology. Using mice at different stages of dis-ease progression, we intended to identify specific changes in the localization of SUMO1 and in the global SUMO1 conjugation levels. Anti-HA immunostaining of brain sections showed that in subiculum and cortical layer V SUMO1 exhibited nuclear presence in both His6-HA-SUMO1 and His6-HA-SUMO1;5xFAD mice at any of the ages examined. Furthermore, two different anti-HA antibodies produced two different types of non-nuclear anti-HA signal in His6-HA-SUMO1;5xFAD mice. While one of the antibodies produced anti-HA signal localiz-ing to amyloid plaques, the other resulted in line-shaped signals or signals with the shape of amorphous mass, with some of the line-shaped signal surrounding amyloid plaques. Im-portantly, both anti-HA antibodies produced similar signals in the 5xFAD non-knock-in mice which strongly speaks against specificity of the signal. The predominantly nuclear localiza-tion of His6-HA-SUMO1 in both 5xFAD and non-5xFAD mice was confirmed by subcellular fractionation followed by Western blot. Regarding SUMO1 conjugation levels upon Alzhei-mer's disease pathology, anti-HA Western blot did not reveal any significant differences be-tween His6-HA-SUMO1 and His6-HA-SUMO1;5xFAD mice in both cortex and hippocampus at any of the examined ages. Furthermore, a quantitative comparison of the anti-HA signal in the neuronal nuclei of His6-HA-SUMO1 and His6-HA-SUMO1;5xFAD in both subiculum and cortical layer V did not reveal substantial differences between the two genotypes. A mi-nor increase of 25.8% was observed in the pyramidal neurons of cortical layer V of 8-week-old His6-HA-SUMO1;5xFAD mice when compared to age-matched His6-HA-SUMO1 mice. In summary, we did not discover substantial changes in SUMO1 localization and SUMO1 conjugation levels in the context of increased amyloid burden. However, we cannot conclude that the SUMO1 profile is undisturbed upon Alzheimer's disease pathology as changes in the SUMOylation pattern of individual proteins may not be detected by the techniques utilized in this study. Thus, the next step will be the investigation of differentially SUMOylated sub-strates by anti-HA affinity purification of brain homogenates from His6-HA-SUMO1, His6-HA-SUMO1;5xFAD, 5xFAD and wild type mice followed by mass spectrometry analysis.

Mitochondria-targeted TPP-MoS2 with dual enzyme activity provides efficient neuroprotection through M1/M2 microglial polarization in an Alzheimer's disease model

Neuroinflammation is considered to be an important and inevitable pathological process associated with all types of damages to, and disorders of, the central nervous system. The hallmark of neuroinflammation is the microglia activation. In response to different micro-environmental disturbances, microglia could polarize into either an M1 pro-inflammatory phenotype, exacerbating neurotoxicity, or an M2 anti-inflammatory phenotype, exerting neuroprotection. Therefore, shifting the polarization of microglia toward the M2 phenotype could possess a more viable strategy for the neuroinflammatory disorders treatment. Naringenin (NAR) is naturally a grapefruit flavonoid and possesses various kinds of pharmacological activities, such as anti-inflammatory and neuroprotective activities. In the present study, we aimed to investigate the potential effects of NAR on microglial M1/M2 polarization and further reveal the underlying mechanisms of actions. First, NAR inhibited lipopolysaccharide (LPS)-induced microglial activation. Then, NAR shifted the M1 pro-inflammatory microglia phenotype to the M2 anti-inflammatory M2 microglia state as demonstrated by the decreased expression of M1 markers (i.e., inducible TNF-α and IL-1β) and the elevated expression of M2 markers (i.e., arginase 1, IL-4, and IL-10). In addition, the effects of NAR on microglial polarization were dependent on MAPK signaling, particularly JNK inactivation, as evidenced by the fact that the selective activator of JNK abolished NAR-promoted M2 polarization and further NAR-inhibited microglial activation. Together, this study demonstrated that NAR promoted microglia M1/M2 polarization, thus conferring anti-neuroinflammatory effects via the inhibition of MAPK signaling activation. These findings might provide new alternative avenues for neuroinflammation-related disorders treatment.

IL-35 promotes microglial M2 polarization in a rat model of diabetic neuropathic pain

BackgroundSwitching microglial polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype represents a novel therapeutic strategy for neuropathic pain (NP). This study aims to investigate whether botulinum toxin type A (BTX-A) regulates microglial M1/M2 polarization by inhibiting P2X7 expression in a rat model of NP.ResultsThe BTX-A administration elevated pain threshold, induced microglial polarization toward the M2 phenotype, and decreased P2X7 protein level in a rat model of NP induced by chronic compression injury (CCI). Lipopolysaccharide (LPS) was used to activate HAPI rat microglial cells as an in vitro inflammatory model and we demonstrated that BTX-A promoted microglial M2 polarization in LPS-stimulated HAPI microglial cells through suppressing P2X7.ConclusionsOur results indicate that BTX-A promotes microglial M2 polarization and suppresses CCI-induced NP through inhibiting P2X7 receptor. These findings provide new insights into the mechanism of BTX-A in relieving NP.

BackgroundMicroglia-mediated neuroinflammation is associated with epilepsy. Switching microglial polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype represents a novel therapeutic strategy for mitigating epileptogenesis. We previously found that dynorphins protected against epilepsy via activation of kappa opioid receptor (KOR). Here, this study aims to investigate the role and the mechanism of dynorphin in regulating microglial polarization.MethodsA pilocarpine-induced rat model of epilepsy was established and lipopolysaccharide (LPS)-activated BV-2 microglial cells were used as an inflammatory model to explore the mechanism of dynorphin regulating microglial polarization.ResultsOverexpression of the dynorphin precursor protein prodynorphin (PDYN) alleviated the pilocarpine-induced neuronal apoptosis, promoted microglial polarization to the M2 phenotype, and inhibited pilocarpine-induced Toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) pathway in the hippocampi of epileptic rats. Dynorphin activation of KOR promoted microglial M2 polarization via inhibiting TLR4/NF-κB pathway in LPS-stimulated BV-2 microglial cells. Moreover, dynorphin/KOR regulated microglial M2 polarization inhibited apoptosis of the primary mouse hippocampal neurons.ConclusionIn conclusion, dynorphin activation of KOR promotes microglia polarization toward M2 phenotype via inhibiting TLR4/NF-κB pathway.

Pyroglutamate-modified Aβ (AβpE3-42) peptides are gaining considerable attention as potential key players in the pathology of Alzheimer disease (AD) due to their abundance in AD brain, high aggregation propensity, stability, and cellular toxicity. Overexpressing AβpE3-42 induced a severe neuron loss and neurological phenotype in TBA2 mice. In vitro and in vivo experiments have recently proven that the enzyme glutaminyl cyclase (QC) catalyzes the formation of AβpE3-42. The aim of the present work was to analyze the role of QC in an AD mouse model with abundant AβpE3-42 formation. 5XFAD mice were crossed with transgenic mice expressing human QC (hQC) under the control of the Thy1 promoter. 5XFAD/hQC bigenic mice showed significant elevation in TBS, SDS, and formic acid-soluble AβpE3-42 peptides and aggregation in plaques. In 6-month-old 5XFAD/hQC mice, a significant motor and working memory impairment developed compared with 5XFAD. The contribution of endogenous QC was studied by generating 5XFAD/QC-KO mice (mouse QC knock-out). 5XFAD/QC-KO mice showed a significant rescue of the wild-type mice behavioral phenotype, demonstrating the important contribution of endogenous mouse QC and transgenic overexpressed QC. These data clearly demonstrate that QC is crucial for modulating AβpE3-42 levels in vivo and prove on a genetic base the concept that reduction of QC activity is a promising new therapeutic approach for AD.

Introduction: Macrophages are key mediators of the pathogenesis of acute lung injury (ALI). During ALI, lung macrophages shift into the M1 phenotype and induce severe inflammatory responses and lung tissue damage. Recently, we have shown that pan inhibition of DNA methyl transferase (DNMT) and histone deacetylase (HDAC) abrogated the inflammation and protected the mice from endotoxemia-induced ALI. Hypothesis: We hypothesize that the treatment with a combination of DNMT1-specific inhibitor, procainamide (PRO) and HDAC6-specific inhibitor, tubastatin A (TBA) attenuates lipopolysaccharide (LPS)-induced inflammation in human macrophages via polarization of macrophages towards anti-inflammatory M2 phenotype. Methods & Results: Human macrophage cell line (THP-1) was employed in this study. RNA sequencing analysis has identified a significant reduction in the mRNA expression of a panel of pro-inflammatory genes by PRO+TBA treatment in LPS-induced macrophages, and these results were validated and confirmed by qRT-PCR for the expression of TNFα and IL1β. The expression of pro-inflammatory genes IL1β, TNFα and M1 macrophage marker CD80 was significantly decreased (studied by various analysis) by PRO+TBA treatment at 24 hrs after in LPS challenged macrophages, compared to untreated or treated with either PRO alone or TBA alone (Fig. 1 and 2). On the other hand, the expression of anti-inflammatory gene TSG6 and M2 macrophage marker CD206 were significantly increased by PRO+TBA treatment at 72 hrs after LPS challenged macrophages, compared to untreated or treated with either PRO alone or TBA alone (Fig. 2). Conclusions: Our results have clearly demonstrated that the combined PRO+TBA treatment significantly reduced the expression of pro-inflammatory genes and M1 phenotype marker; and increased the expression of anti-inflammatory genes and M2 phenotype marker in human macrophages challenged with LPS.

The activated M1-like microglia induced neuroinflammation is the critical pathogenic event in Alzheimer's disease (AD). Microglial polarization from pro-inflammatory M1 toward anti-inflammatory M2 phenotype is a promising strategy. To efficiently accomplish this, amyloid-β (Aβ) aggregates as the culprit of M1 microglia activation should be uprooted. Interestingly, this study finds out that the self-reassembly of curcumin molecules into carrier-free curcumin nanoparticles (CNPs) exhibits multivalent binding with Aβ to achieve higher inhibitory effect on Aβ aggregation, compared to free curcumin with monovalent effect. Based on this, the CNPs loaded cardiolipin liposomes are developed for efficient microglial polarization. After intranasal administration, the liposomes decompose to release CNPs and cardiolipin in response to AD oxidative microenvironment. The CNPs inhibit Aβ aggregation and promote Aβ phagocytosis/clearance in microglia, removing roadblock to microglial polarization. Subsequently, CNPs are endocytosed by microglia and inhibit TLR4/NF-κB pathway for microglia polarization (M1→M2). Meanwhile, cardiolipin is identified as signaling molecule to normalize microglial dysfunction to prevent pro-inflammatory factors release. In AD transgenic mice, neuroinflammation, Aβ burden, and memory deficits are relieved after treatment. Through combined attack by extracellularly eradicating roadblock of Aβ aggregation and intracellularly inhibiting inflammation-related pathways, this nanotechnology assisted delivery system polarizes microglia efficiently, providing a reliable strategy in AD treatment.

Ischemic stroke triggers inflammatory responses that lead to neuronal damage, with microglial polarization significantly influencing post-stroke inflammation. This study explores the role of Fc gamma receptor Ia (FCGR1A) in microglial polarization and its regulatory mechanisms in ischemic stroke. Differentially expressed genes (DEGs) associated with ischemic stroke were identified using the GSE58294 dataset. Hub genes were found by analyzing protein-protein interaction (PPI) networks. BV2 microglia were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic ischemic conditions in vitro, and FCGR1A and inflammatory marker levels were assessed. Besides, BV2 cells were stimulated with lipopolysaccharide (LPS) and interferon-gamma (IFN-γ) to induce M1 polarization, and the effects of FCGR1A overexpression and knockdown on cytokine production and microglial polarization were evaluated. The function of the AMP-activated protein kinase (AMPK)-mTOR pathway in regulating microglial polarization was further investigated using the mTOR inhibitor rapamycin (RAP). From the 327 DEGs identified, FCGR1A was chosen as a hub gene. OGD/R treatment of BV2 cells produced a time-dependent rise in FCGR1A, induction of brown adipocytes 1 (Iba1), and interleukin 6 (IL-6) expression, indicating enhanced inflammation. FCGR1A overexpression induced a proinflammatory response and promoted M1 polarization, whereas FCGR1A knockdown reduced inflammation and shifted toward an anti-inflammatory M2 phenotype. Inhibition of the mTOR pathway using RAP, combined with FCGR1A knockdown, significantly enhanced AMPK activation and promoted a shift toward an anti-inflammatory M2 phenotype. FCGR1A modulates microglial polarization by affecting the AMPK-mTOR signaling pathway in ischemic conditions. Targeting FCGR1A and related pathways could offer new therapeutic strategies to lessen inflammation and facilitate the healing process after an ischemic stroke.