The role of ApoE-mediated microglial lipid metabolism in brain aging and disease.

Microglia are a unique population of immune cells resident in the brain that integrate complex signals and dynamically change phenotypes in response to the brain microenvironment. In recent years, single-cell sequencing analyses have revealed profound cellular heterogeneity and context-specific transcriptional plasticity of microglia during brain development, aging, and disease. Emerging evidence suggests that microglia adapt phenotypic plasticity by flexibly reprogramming cellular metabolism to fulfill distinct immune functions. The control of lipid metabolism is central to the appropriate function and homeostasis of the brain. Microglial lipid metabolism regulated by apolipoprotein E (ApoE), a crucial lipid transporter in the brain, has emerged as a critical player in regulating neuroinflammation. The ApoE gene allelic variant, ε4, is associated with a greater risk for neurodegenerative diseases. In this review, we explore novel discoveries in microglial lipid metabolism mediated by ApoE. We elaborate on the functional impact of perturbed microglial lipid metabolism on the underlying pathogenesis of brain aging and disease.

Interferon-ß modulates microglial polarization to ameliorate delayed tPA-exacerbated brain injury in ischemic stroke.

Tissue plasminogen activator (tPA) is the only FDA-approved drug for the treatment of ischemic stroke. Delayed tPA administration is associated with increased risks of blood-brain barrier (BBB) disruption and hemorrhagic transformation. Studies have shown that interferon beta (IFNß) or type I IFN receptor (IFNAR1) signaling confers protection against ischemic stroke in preclinical models. In addition, we have previously demonstrated that IFNß can be co-administered with tPA to alleviate delayed tPA-induced adverse effects in ischemic stroke. In this study, we investigated the time limit of IFNß treatment on the extension of tPA therapeutic window and assessed the effect of IFNß on modulating microglia (MG) phenotypes in ischemic stroke with delayed tPA treatment. Mice were subjected to 40 minutes transient middle cerebral artery occlusion (MCAO) followed by delayed tPA treatment in the presence or absence of IFNß at 3h, 4.5h or 6h post-reperfusion. In addition, mice with MG-specific IFNAR1 knockdown were generated to validate the effects of IFNß on modulating MG phenotypes, ameliorating brain injury, and lessening BBB disruption in delayed tPA-treated MCAO mice. Our results showed that IFNß extended tPA therapeutic window to 4.5h post-reperfusion in MCAO mice, and that was accompanied with attenuated brain injury and lessened BBB disruption. Mechanistically, our findings revealed that IFNß modulated MG polarization, leading to the suppression of inflammatory MG and the promotion of anti-inflammatory MG, in delayed tPA-treated MCAO mice. Notably, these effects were abolished in MG-specific IFNAR1 knockdown MCAO mice. Furthermore, the protective effect of IFNß on the amelioration of delayed tPA-exacerbated ischemic brain injury was also abolished in these mice. Finally, we identified that IFNß-mediated modulation of MG phenotypes played a role in maintaining BBB integrity, because the knockdown of IFNAR1 in MG partly reversed the protective effect of IFNß on lessening BBB disruption in delayed tPA-treated MCAO mice. In summary, our study reveals a novel function of IFNß in modulating MG phenotypes, and that may subsequently confer protection against delayed tPA-exacerbated brain injury in ischemic stroke.

Targeting Nrf2 with 3 H-1,2-dithiole-3-thione to moderate OXPHOS-driven oxidative stress attenuates IL-17A-induced psoriasis.

Psoriasis, a chronic autoimmune disease characterized by the hyperproliferation of keratinocytes in the epidermis and parakeratosis, significantly impacts quality of life. Interleukin (IL)- 17A dominates the pathogenesis of psoriasis and facilitates reactive oxygen species (ROS) accumulation, which exacerbates local psoriatic lesions. Biologic treatment provides remarkable clinical efficacy, but its high cost and unignorable side effects limit its applications. 3 H-1,2-Dithiole-3-thione (D3T) possesses compelling antioxidative capacities against several diseases through the nuclear factor erythroid 2-related factor 2 (Nrf2) cascade. Hence, we aimed to evaluate the effect and mechanism of D3T in psoriasis. We found that D3T attenuates skin thickening and scaling by inhibiting IL-17A-secreting γδT cells in imiquimod (IMQ)-induced psoriatic mice. Interleukin-17A markedly enhanced IL-6 and IL-8 expression, lipid peroxidation, the contents of nitric oxide and hydrogen peroxide, oxidative phosphorylation and the MAPK/NF-κB pathways in keratinocytes. IL-17A also inhibited the Nrf2-NQO1-HO-1 axis and the activities of superoxide dismutase and glutathione peroxidase. D3T significantly reversed these parameters in IL-17A-treated keratinocytes. ML-385, a Nrf2 neutralizer, failed to improve D3T-induced anti-inflammatory and antioxidative effects in IL-17A-treated keratinocytes. We conclude that targeting Nrf2 with D3T to diminish oxidative and inflammatory damage in keratinocytes may attenuate psoriasis.