N-Acetylcysteine Suppresses Microglial Inflammation and Induces Mortality Dose-Dependently via Tumor Necrosis Factor-α Signaling

Oxygen Glucose Deprivation-Induced Lactylation of H3K9 Contributes to M1 Polarization and Inflammation of Microglia Through TNF Pathway

BACKGROUND

Hypoxia-induced M1 polarization of microglia and resultant inflammation take part in the damage caused by hypoxic-ischemic encephalopathy (HIE). Histone lactylation, a novel epigenetic modification where lactate is added to lysine residues, may play a role in HIE pathogenesis. This study investigates the role of histone lactylation in hypoxia-induced M1 microglial polarization and inflammation, aiming to provide insights for HIE treatment.

METHODS

In this study, we assessed the effects of hypoxia on microglial polarization using both an HIE animal model and an oxygen-glucose deprivation cell model. Histone lactylation at various lysine residues was detected by Western blotting. Microglial polarization and inflammatory cytokines were analyzed by immunofluorescence, qPCR, and Western blotting. RNA sequencing, ChIP-qPCR, and siRNA were used to elucidate mechanisms of H3K9 lactylation.

RESULTS

H3K9 lactylation increased due to cytoplasmic lactate during M1 polarization. Inhibiting P300 or reducing lactate dehydrogenase A expression decreased H3K9 lactylation, suppressing M1 polarization. Transcriptomic analysis indicated that H3K9 lactylation regulated M1 polarization via the TNF signaling pathway. ChIP-qPCR confirmed H3K9 lactylation enrichment at the TNFα locus, promoting OGD-induced M1 polarization and inflammation.

CONCLUSIONS

H3K9 lactylation promotes M1 polarization and inflammation via the TNF pathway, identifying it as a potential therapeutic target for neonatal HIE.

Lipid-polymer hybrid nanoparticles loaded with N-acetylcysteine for the modulation of neuroinflammatory biomarkers in human iPSC-derived PSEN2 (N141I) astrocytes as a model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by cognitive impairment associated with the accumulation of beta-amyloid protein (Aβ). Aβ activates glial cells in the brain, increasing the secretion of proinflammatory cytokines, which leads to neuroinflammation and neuronal death. Currently, there are no effective treatments that cure or stop its progression; therefore, AD is considered a global health priority. The main limitations are the low drug bioavailability and impermeability of the blood-brain barrier (BBB). Fortunately, nanomedicine has emerged as a promising field for the development of new nanosystems for the controlled and targeted delivery of drugs to the brain. Therefore, in this work, lipid-polymer hybrid nanoparticles (LPHNPs) conjugated with transferrin (Tf) to facilitate crossing the BBB and loaded with N-acetylcysteine (NAC) for its anti-inflammatory effect were synthesized, and their physicochemical characterization was carried out. Subsequently, an in vitro model involving human astrocytes derived from induced pluripotent stem cells (iPSC) from an AD-diagnosed patient was developed, which was brought to a reactive state by stimulation with lipopolysaccharides (LPSs). The cell culture was treated with either Tf-conjugated LPHNPs loaded with NAC (NAC-Tf-LPHNPs) at 0.25 mg mL-1, or free NAC at 5 mM. The results showed that NAC-Tf-LPHNPs favorably modulated the expression of proinflammatory genes such as interleukin-1β (IL-1β), amyloid precursor protein (APP) and glial fibrillary acidic protein (GFAP). In addition, they reduced the secretion of the proinflammatory cytokines interleukin 6 (IL-6), IL-1β and interferon-gamma (INF-γ). Results for both cases were compared to the group of cells that did not receive any treatment. In contrast, free NAC only had this effect on the expression of IL-1β and the secretion of the cytokines IL-6 and INF-γ. These results indicate the potential of NAC-Tf-LPHNPs for AD treatment.

Glial Markers of Suicidal Behavior in the Human Brain-A Systematic Review of Postmortem Studies

Suicide is a major public health priority, and its molecular mechanisms appear to be related to glial abnormalities and specific transcriptional changes. This study aimed to identify and synthesize evidence of the relationship between glial dysfunction and suicidal behavior to understand the neurobiology of suicide. As of 26 January 2024, 46 articles that met the inclusion criteria were identified by searching PubMed and ISI Web of Science. Most postmortem studies, including 30 brain regions, have determined no density or number of total Nissl-glial cell changes in suicidal patients with major psychiatric disorders. There were 17 astrocytic, 14 microglial, and 9 oligodendroglial studies using specific markers of each glial cell and further on their specific gene expression. Those studies suggest that astrocytic and oligodendroglial cells lost but activated microglia in suicides with affective disorder, bipolar disorders, major depression disorders, or schizophrenia in comparison with non-suicided patients and non-psychiatric controls. Although the data from previous studies remain complex and cannot fully explain the effects of glial cell dysfunction related to suicidal behaviors, they provide risk directions potentially leading to suicide prevention.

N-Acetylcysteine and Atherosclerosis: Promises and Challenges

Atherosclerosis remains a leading cause of cardiovascular diseases. Although the mechanism for atherosclerosis is complex and has not been fully understood, inflammation and oxidative stress play a critical role in the development and progression of atherosclerosis. N-acetylcysteine (NAC) has been used as a mucolytic agent and an antidote for acetaminophen overdose with a well-established safety profile. NAC has antioxidant and anti-inflammatory effects through multiple mechanisms, including an increase in the intracellular glutathione level and an attenuation of the nuclear factor kappa-B mediated production of inflammatory cytokines like tumor necrosis factor-alpha and interleukins. Numerous animal studies have demonstrated that NAC significantly decreases the development and progression of atherosclerosis. However, the data on the outcomes of clinical studies in patients with atherosclerosis have been limited and inconsistent. The purpose of this review is to summarize the data on the effect of NAC on atherosclerosis from both pre-clinical and clinical studies and discuss the potential mechanisms of action of NAC on atherosclerosis, as well as challenges in the field.

3',4'-Dihydroxyflavonol Attenuates Lipopolysaccharide-Induced Neuroinflammatory Responses of Microglial Cells by Suppressing AKT-mTOR and NF-κB Pathways

Microglia-related neuroinflammation contributes to the pathogenesis of a variety of neurodegenerative disorders such as Alzheimer's disease. The synthetic flavonoid, 3',4'-dihydroxyflavonol (3,3',4'-trihydroxyflavone), has been shown to protect brain or myocardial ischemia reperfusion-induced cell death and prevent the aggregation of amyloid-β protein, a process that causes progressive neurodegeneration in Alzheimer's disease. Here, we explored the anti-neuroinflammatory ability of 3',4'-dihydroxyflavonol in lipopolysaccharide (LPS)-activated MG6 microglial cells. 3',4'-Dihydroxyflavonol attenuated LPS-induced tumor necrosis factor-α and nitric oxide secretion in MG6 cells. LPS-induced phosphorylation of mammalian target of rapamycin (mTOR), nuclear factor-κB (NF-κB), and protein kinase B (AKT) (which are all associated with the neuroinflammatory response in microglia) were attenuated by 3',4'-dihydroxyflavonol treatment. Treatment with the mTOR inhibitor, rapamycin, NF-κB inhibitor, caffeic acid phenethyl ester, or AKT inhibitor, LY294002, also attenuated LPS-induced tumor necrosis factor-α and nitric oxide secretion in MG6 cells. LY294002 treatment attenuated LPS-induced phosphorylation of mTOR and NF-κB in MG6 cells. Hence, our study suggests that 3',4'-dihydroxyflavonol can attenuate the neuroinflammatory response of microglial cells by suppressing the AKT-mTOR and NF-κB pathways.