Microglia depletion as a therapeutic strategy: friend or foe in multiple sclerosis models?

Perfluoropentane-based oxygen-loaded nanodroplets reduce microglial activation through metabolic reprogramming

JOURNAL/nrgr/04.03/01300535-202504000-00032/figure1/v/2024-07-06T104127Z/r/image-tiff Microglia, the primary immune cells within the brain, have gained recognition as a promising therapeutic target for managing neurodegenerative diseases within the central nervous system, including Parkinson's disease. Nanoscale perfluorocarbon droplets have been reported to not only possess a high oxygen-carrying capacity, but also exhibit remarkable anti-inflammatory properties. However, the role of perfluoropentane in microglia-mediated central inflammatory reactions remains poorly understood. In this study, we developed perfluoropentane-based oxygen-loaded nanodroplets (PFP-OLNDs) and found that pretreatment with these droplets suppressed the lipopolysaccharide-induced activation of M1-type microglia in vitro and in vivo, and suppressed microglial activation in a mouse model of Parkinson's disease. Microglial suppression led to a reduction in the inflammatory response, oxidative stress, and cell migration capacity in vitro. Consequently, the neurotoxic effects were mitigated, which alleviated neuronal degeneration. Additionally, ultrahigh-performance liquid chromatography-tandem mass spectrometry showed that the anti-inflammatory effects of PFP-OLNDs mainly resulted from the modulation of microglial metabolic reprogramming. We further showed that PFP-OLNDs regulated microglial metabolic reprogramming through the AKT-mTOR-HIF-1α pathway. Collectively, our findings suggest that the novel PFP-OLNDs constructed in this study alleviate microglia-mediated central inflammatory reactions through metabolic reprogramming.

Microglial NLRP3 inflammasome-mediated neuroinflammation and therapeutic strategies in depression

Previous studies have demonstrated a bidirectional relationship between inflammation and depression. Activation of the nucleotide-binding oligomerization domain, leucine-rich repeat, and NLR family pyrin domain-containing 3 (NLRP3) inflammasomes is closely related to the pathogenesis of various neurological diseases. In patients with major depressive disorder, NLRP3 inflammasome levels are significantly elevated. Understanding the role that NLRP3 inflammasome-mediated neuroinflammation plays in the pathogenesis of depression may be beneficial for future therapeutic strategies. In this review, we aimed to elucidate the mechanisms that lead to the activation of the NLRP3 inflammasome in depression as well as to provide insight into therapeutic strategies that target the NLRP3 inflammasome. Moreover, we outlined various therapeutic strategies that target the NLRP3 inflammasome, including NLRP3 inflammatory pathway inhibitors, natural compounds, and other therapeutic compounds that have been shown to be effective in treating depression. Additionally, we summarized the application of NLRP3 inflammasome inhibitors in clinical trials related to depression. Currently, there is a scarcity of clinical trials dedicated to investigating the applications of NLRP3 inflammasome inhibitors in depression treatment. The modulation of NLRP3 inflammasomes in microglia holds promise for the management of depression. Further investigations are necessary to ascertain the efficacy and safety of these therapeutic approaches as potential novel antidepressant treatments.

The latest perspectives of small molecules FMS kinase inhibitors

FMS kinase is a type III tyrosine kinase receptor that plays a central role in the pathophysiology and management of several diseases, including a range of cancer types, inflammatory disorders, neurodegenerative disorders, and bone disorders among others. In this review, the pathophysiological pathways of FMS kinase in different diseases and the recent developments of its monoclonal antibodies and inhibitors during the last five years are discussed. The biological and biochemical features of these inhibitors, including binding interactions, structure-activity relationships (SAR), selectivity, and potencies are discussed. The focus of this article is on the compounds that are promising leads and undergoing advanced clinical investigations, as well as on those that received FDA approval. In this article, we attempt to classify the reviewed FMS inhibitors according to their core chemical structure including pyridine, pyrrolopyridine, pyrazolopyridine, quinoline, and pyrimidine derivatives.

Resolvin D1 Induces mTOR-independent and ATG5-dependent Autophagy in BV-2 Microglial Cells

OBJECTIVE

The activation state of microglia is known to occupy a central position in the pathophysiological process of cerebral inflammation. Autophagy is a catabolic process responsible for maintaining cellular homeostasis. In recent years, autophagy has been demonstrated to play an important role in neuroinflammation. Resolvin D1 (RvD1) is a promising therapeutic mediator that has been shown to exert substantial anti-inflammatory and proresolving activities. However, whether RvD1-mediated resolution of inflammation in microglia is related to autophagy regulation needs further investigation. The present study aimed to explore the effect of RvD1 on microglial autophagy and its corresponding pathways.

METHODS

Mouse microglial cells (BV-2) were cultured, treated with RvD1, and examined by Western blotting, confocal immunofluorescence microscopy, transmission electron microscopy, and flow cytometry.

RESULTS

RvD1 promoted autophagy in both BV-2 cells and mouse primary microglia by favoring the maturation of autophagosomes and their fusion with lysosomes. Importantly, RvD1 had no significant effect on the activation of mammalian target of rapamycin (mTOR) signaling. Furthermore, RvD1-induced mTOR-independent autophagy was confirmed by observing reduced cytoplasmic calcium levels and suppressed calcium/calmodulin-dependent protein kinase II (CaMK II) activation. Moreover, by downregulating ATG5, the increased phagocytic activity induced by RvD1 was demonstrated to be tightly controlled by ATG5-dependent autophagy.

CONCLUSION

The present work identified a previously unreported mechanism responsible for the role of RvD1 in microglial autophagy, highlighting its therapeutic potential against neuroinflammation.

Microglia in the context of multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease that commonly results in nontraumatic disability in young adults. The characteristic pathological hallmark of MS is damage to myelin, oligodendrocytes, and axons. Microglia provide continuous surveillance in the CNS microenvironment and initiate defensive mechanisms to protect CNS tissue. Additionally, microglia participate in neurogenesis, synaptic refinement, and myelin pruning through the expression and release of different signaling factors. Continuous activation of microglia has been implicated in neurodegenerative disorders. We first review the lifetime of microglia, including the origin, differentiation, development, and function of microglia. We then discuss microglia participate in the whole processes of remyelination and demyelination, microglial phenotypes in MS, and the NF-κB/PI3K-AKT signaling pathway in microglia. The damage to regulatory signaling pathways may change the homeostasis of microglia, which would accelerate the progression of MS.