Autophagy in Neuroinflammation: A Focus on Epigenetic Regulation

The Overexpression of eIF4E Decreases Oxytocin Levels and Induces Social Cognitive Behavioral Disorders in Mice

Overexpression of the eukaryotic initiation factor 4E (eIF4E) gene has been associated with excessive stereotypic behaviors and reduced sociability, which manifest as autism-like social cognitive deficits. However, the precise mechanisms by which eIF4E overexpression insufficiently induces these autism-like behaviors and the specific brain regions implicated remain insufficiently understood. Oxytocin (OXT), a neurotransmitter known for its role in social behavior, has been proposed to modulate certain autism-related symptoms by influencing microglial function and attenuating neuroinflammation. Nonetheless, the contributions of the hippocampus and oxytocin in the content of eIF4E overexpression-induced autistic behaviors remain elucidated. To investigate this issue, researchers utilized the three-chamber social interaction test, the open-field test, and the Morris water maze to evaluate the social cognitive behaviors of the two groups of mice. Additionally, ELISA, immunofluorescence, Western blotting, and qRT-PCR were employed to quantify oxytocin levels and assess hippocampal microglial activation. The results indicate that overexpression of eIF4E in mice is associated with significant impairments in social cognition, alongside pronounced marked hyperactivation of hippocampal microglia.

A new perspective on targeting pulmonary arterial hypertension: Programmed cell death pathways (Autophagy, Pyroptosis, Ferroptosis)

Pulmonary arterial hypertension (PAH) is a severe cardiovascular disease characterized by elevated pulmonary vascular resistance, progressive increases in pulmonary artery pressures, ultimately leading to right-sided heart failure, and potentially mortality. Pulmonary vascular remodeling is pivotal in PAH onset and progression. While targeted drug therapies have notably ameliorated PAH prognosis, current medications primarily focus on vascular vasodilation, with limited ability to reverse pulmonary vascular remodeling fundamentally, resulting in suboptimal patient prognoses. Cellular death in pulmonary vasculature, once thought to be confined to apoptosis and necrosis, has evolved with the identification of pyroptosis, autophagy, and ferroptosis, revealing their association with vascular injury in PAH. These novel forms of regulated cellular death impact reactive oxygen species (ROS) generation, calcium stress, and inflammatory cascades, leading to pulmonary vascular cell loss, exacerbating vascular injury, and mediating adverse remodeling, inflammation, immune anomalies, and current emerging mechanisms (such as endothelial-mesenchymal transition, abnormal energy metabolism, and epigenetic regulation) in the pathogenesis of PAH. This review comprehensively delineates the roles of autophagy, pyroptosis, and ferroptosis in PAH, elucidating recent advances in their involvement and regulation of vascular injury. It juxtaposes their distinct functions in PAH and discusses the interplay of these programmed cell deaths in pulmonary vascular injury, highlighting the benefits of combined targeted therapies in mitigating pulmonary arterial hypertension-induced vascular injury, providing novel insights into targeted treatments for pulmonary arterial hypertension.

Docosahexaenoic acid protects against ischemic stroke in diabetic mice by inhibiting inflammatory responses and apoptosis

This study was to explore whether docosahexaenoic acid (DHA) protects against ischemic stroke in diabetic mice and its mechanisms. DHA was administered to mice and its effects on stroke outcomes in type 1 diabetes mellitus were assessed 24 h and 3 days post-reperfusion using RNA sequencing, flow cytometry, multiplex immunoassays, and western-blotting analysis. In diabetic mice, DHA administration post-ischemic stroke significantly reduced cerebral infarct size, brain edema, and neurological impairments. Flow cytometric analysis demonstrated a notable decrease in the percentage of neutrophils in the ischemic brain, suggesting a mitigated inflammatory response. Western blotting assay revealed that pro-apoptotic protein Bax was reduced whereas anti-apoptotic protein Bcl-2 was increased, indicating the attenuation of apoptosis. Additionally, RNA sequencing of brain tissue highlighted significant transcriptomic changes, with downregulation of genes for several inflammatory pathways such as NF-kappa B signaling and upregulation of genes for neuroprotective pathways such as neuroactive ligand-receptor interaction. Similar transcriptomic changes in peripheral blood mononuclear cells indicated that DHA treatment resulted the systemic anti-inflammatory and neuroprotective response. DHA treatment mitigated cerebral ischemic injuries by dampening inflammatory responses and apoptosis in diabetic mice after ischemic stroke, highlighting its therapeutic potential for clinical management of stroke in diabetic patients.

Risperidone accelerates bone loss in mice models of schizophrenia by inhibiting osteoblast autophagy

Background

Risperidone (RIS) is the first-line drug in the clinical treatment of schizophrenia, and long-term use may lead to bone loss and even osteoporosis. This study investigated whether the mechanism of RIS-induced bone loss is related to autophagy.

Methods

The schizophrenia mice were established with the administration of MK-801. Then, RIS were injected, or autophagy inducer rapamycin (RAPA) co-injected for 8 weeks. Cognitive performance was determined by the novel object recognition and Open field tests. Bone loss of schizophrenia mice were assessed using microCT, H&E staining, ALP staining, ARS staining and WB, respectively. Autophagy of schizophrenia mice were detected by immunofluorescence, transmission electron microscopy (TEM) and WB, respectively. In addition, osteogenic differentiation of MC3T3-E1 and BMSCs cells were assessed using H&E staining, ALP staining, ARS staining and WB, respectively.

Results

In the present study, we found that RIS treatment can promote bone loss in schizophrenia mice and inhibit osteogenic differentiation of MC3T3-E1 and BMSCs cells. Interesting, the number of autophagosome and autophagy-related protein expression were decreased after RIS treatment. However, the bone loss and inhibition of osteogenic differentiation induced by RIS in schizophrenia mice were reversed by autophagy inducer RAPA.

Conclusion

RIS significantly increased bone loss and inhibited osteogenic differentiation in schizophrenia mice; the underlying mechanism entails suppressing osteoblast autophagy.

Targeting selective autophagy in CNS disorders by small-molecule compounds

Autophagy functions as the primary cellular mechanism for clearing unwanted intracellular contents. Emerging evidence suggests that the selective elimination of intracellular organelles through autophagy, compared to the increased bulk autophagic flux, is crucial for the pathological progression of central nervous system (CNS) disorders. Notably, autophagic removal of mitochondria, known as mitophagy, is well-understood in an unhealthy brain. Accumulated data indicate that selective autophagy of other substrates, including protein aggregates, liposomes, and endoplasmic reticulum, plays distinctive roles in various pathological stages. Despite variations in substrates, the molecular mechanisms governing selective autophagy can be broadly categorized into two types: ubiquitin-dependent and -independent pathways, both of which can be subjected to regulation by small-molecule compounds. Notably, natural products provide the remarkable possibility for future structural optimization to regulate the highly selective autophagic clearance of diverse substrates. In this context, we emphasize the selectivity of autophagy in regulating CNS disorders and provide an overview of chemical compounds capable of modulating selective autophagy in these disorders, along with the underlying mechanisms. Further exploration of the functions of these compounds will in turn advance our understanding of autophagic contributions to brain disorders and illuminate precise therapeutic strategies for these diseases.

Thymol improves ischemic brain injury by inhibiting microglia-mediated neuroinflammation

BACKGROUND

Microglia-mediated inflammation is a critical factor in the progression of ischemic stroke. Consequently, mitigating excessive microglial activation represents a potential therapeutic strategy for ischemic injury. Thymol, a monophenol derived from plant essential oils, exhibits diverse beneficial biological activities, including anti-inflammatory and antioxidant properties, with demonstrated protective effects in various disease models. However, its specific effects on ischemic stroke and microglial inflammation remain unexplored.

METHODS

Rodent transient middle cerebral artery occlusion (tMCAO) model was established to simulate ischemic stroke. TTC staining, modified neurological function score (mNSS), and behavioral tests were used to assess the severity of neurological damage. Then immunofluorescence staining and cytoskeleton analysis were used to determine activation of microglia. Lipopolysaccharide (LPS) was utilized to induce the inflammatory response of primary microglia in vitro. Quantitative real-time polymerase chain reaction (qRT-PCR), western blot, and enzyme-linked immunosorbent assay (ELISA) were performed to exam the expression of inflammatory cytokines. And western blot was used to investigate the mechanism of the anti-inflammatory effect of thymol.

RESULTS

In this study, we found that thymol treatment could ameliorate post-stroke neurological impairment and reduce infarct volume by mitigating microglial activation and pro-inflammatory response (IL-1β, IL-6, and TNF-α). Mechanically, thymol could inhibit the phosphorylation of phosphatidylinositol-3-kinase (PI3K), sink serine/threonine kinase (Akt), and mammalian target of rapamycin (mTOR), thereby suppressing the activation of nuclear factor-κB (NF-κB).

CONCLUSIONS

Our study demonstrated that thymol could reduce the microglial inflammation by targeting PI3K/Akt/mTOR/NF-κB signaling pathway, ultimately alleviating ischemic brain injury. These findings suggest that thymol is a promising candidate as a neuroprotective agent against ischemic stroke.

Knockdown of IRF8 alleviates neuroinflammation through regulating microglial activation in Parkinson's disease

Neuroinflammation associated with microglial activation plays a role in the development of Parkinson's disease (PD). The upregulation of interferon regulatory factor 8 (IRF8) in microglia following peripheral nerve injury has been observed to induce microglial activation. This suggests the potential therapeutic significance of IRF8 in PD. This research aims to explore the effects of IRF8 on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model and lipopolysaccharide (LPS)-induced neuroinflammation, along with its underlying mechanisms. The study examines the differential expression of IRF8 and its effects on neuropathological changes using a PD mouse model and a PD model established from BV2 cells in vitro. IRF8 was found to be prominently expressed in the substantia nigra pars compacta (SNpc) region of PD mice and LPS-stimulated BV2 cells, while the expression of tyrosine hydroxylase (TH) and dopamine (DA) content in the SNpc region of PD mice was notably reduced. MPTP treatment and LPS stimulation intensified microglial activation, inflammation, and activation of the AMPK/mTOR signaling pathway in vivo and in vitro, respectively. Upon IRF8 silencing in the PD mouse and cell models, the knockdown of IRF8 ameliorated MPTP-induced behavioral deficits, increased the counts of TH and Nissl-positive neurons and DA content, reduced the number of Iba-1-positive microglia, and reduced the content of inflammatory factors, possibly by inhibiting the AMPK/mTOR signaling pathway. Similar outcomes were observed in the PD cell model. In conclusion, the suppression of IRF8 alleviates neuroinflammation through regulating microglial activation in PD models in vivo and in vitro by the AMPK/mTOR signaling pathway.

mTOR and neuroinflammation in epilepsy: implications for disease progression and treatment

Epilepsy remains a major health concern as anti-seizure medications frequently fail, and there is currently no treatment to stop or prevent epileptogenesis, the process underlying the onset and progression of epilepsy. The identification of the pathological processes underlying epileptogenesis is instrumental to the development of drugs that may prevent the generation of seizures or control pharmaco-resistant seizures, which affect about 30% of patients. mTOR signalling and neuroinflammation have been recognized as critical pathways that are activated in brain cells in epilepsy. They represent a potential node of biological convergence in structural epilepsies with either a genetic or an acquired aetiology. Interventional studies in animal models and clinical studies give strong support to the involvement of each pathway in epilepsy. In this Review, we focus on available knowledge about the pathophysiological features of mTOR signalling and the neuroinflammatory brain response, and their interactions, in epilepsy. We discuss mitigation strategies for each pathway that display therapeutic effects in experimental and clinical epilepsy. A deeper understanding of these interconnected molecular cascades could enhance our strategies for managing epilepsy. This could pave the way for new treatments to fill the gaps in the development of preventative or disease-modifying drugs, thus overcoming the limitations of current symptomatic medications.

Neuroinflammation and Neurodegenerative Diseases: How Much Do We Still Not Know?

The term "neuroinflammation" defines the typical inflammatory response of the brain closely related to the onset of many neurodegenerative diseases (NDs). Neuroinflammation is well known, but its mechanisms and pathways are not entirely comprehended. Some progresses have been achieved through many efforts and research. Consequently, new cellular and molecular mechanisms, diverse and conventional, are emerging. In listing some of those that will be the subject of our description and discussion, essential are the important roles of peripheral and infiltrated monocytes and clonotypic cells, alterations in the gut-brain axis, dysregulation of the apelinergic system, alterations in the endothelial glycocalyx of the endothelial component of neuronal vascular units, variations in expression of some genes and levels of the encoding molecules by the action of microRNAs (miRNAs), or other epigenetic factors and distinctive transcriptional factors, as well as the role of autophagy, ferroptosis, sex differences, and modifications in the circadian cycle. Such mechanisms can add significantly to understanding the complex etiological puzzle of neuroinflammation and ND. In addition, they could represent biomarkers and targets of ND, which is increasing in the elderly.