Saxena, I. | Search bioRxiv

bioRxiv2024

Enhancing NADPH to Restore Redox Homeostasis and Lysosomal Function in G6PD-Deficient Microglia

Microglia, the residential immune cells in the central nervous system (CNS) exhibited in multiple states from resting to activated, play a significant role in neurogenesis, myelination, synaptic transmission, immune surveillance, and neuroinflammation. The aggravated inflammatory response by microglia triggers the generation of superoxide, which often causes the degeneration of neurons, leading to the development of Parkinsons and Alzheimers. The oxidative stress is key to many neurological disorders, often regulated by many genes. The terminal neutralization of oxidative stress is mediated by NADPH and glutathione. The cytosolic NADPH level is majorly contributed by a key enzyme called glucose-6-phosphate dehydrogenase (G6PD). The deficiency of G6PD is associated with hemolytic anemia, diabetes, cardiovascular, autoimmune, and neurological disorders. Our recent study indicated that G6PD deficiency decreases cytosolic NADPH levels and alters redox homeostasis and lysosomal function in microglia. Therefore, replenishment of NADPH is crucial for targeting G6PD deficiency-mediated microglial dysfunctions. This research promotes alternate metabolic pathways by targeting the expression and activity of enzymes such as isocitrate dehydrogenase 1 (IDH1) and malic enzyme 1 (ME1), which are responsible for cytoplasmic NADPH production. Metabolites like citric and malic acid supplementation promote NADPH production and reduce microglial oxidative stress. Additionally, using another group of small-molecule metabolites, such as dieckol and resveratrol, enhances the expression of IDH1 and ME1 enzymes to resolve potential tissue heterogeneity. Finally, combining these metabolites supplementation increased NADPH production and restored redox homeostasis and lysosomal function in G6PD deficient microglia, indicating their further use as potential therapeutics against G6PD deficiency disorders. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=101 SRC="FIGDIR/small/607918v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@5e69f2org.highwire.dtl.DTLVardef@7d9015org.highwire.dtl.DTLVardef@17e5500org.highwire.dtl.DTLVardef@fe9bc5_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2023

G6PD deficiency mediated impairment of iNOS and lysosomal acidification affecting phagocytotic clearance in microglia in response to SARS-CoV-2

The glucose-6-phosphate dehydrogenase (G6PD) deficiency is X-linked and is the most common enzymatic deficiency disorder globally. It is a crucial enzyme for the pentose phosphate pathway and produces NADPH, which plays a vital role in the regulation of oxidative stress of many cell types. The deficiency of G6PD causes hemolytic anemia, diabetes, cardiovascular and neurological disorders. Notably, the patient with G6PD deficiency was severely affected by SARS-CoV-2 and showed prolonged COVID-19 symptoms, neurological impacts, and high mortality. However, the mechanism of COVID-19 severity in G6PD deficient patients is still ambiguous. Here, using a CRISPR-edited G6PD deficient human microglia cell culture model, we observed a significant reduction in NADPH and an increase in basal reactive oxygen species (ROS) in microglia. Interestingly, the deficiency of the G6PD-NAPDH axis impairs induced nitric oxide synthase (iNOS) mediated nitric oxide (NO) production which plays a fundamental role in inhibiting viral replication. Surprisingly, we also observed that the deficiency of the G6PD-NADPH axis reduced lysosomal acidification, which further abrogates the lysosomal clearance of viral particles. Thus, impairment of NO production and lysosomal acidification as well as redox dysregulation in G6PD deficient microglia altered innate immune response, promoting the severity of SARS-CoV-2 pathogenesis.

cell biology↗