Hyperbaric oxygen therapy attenuates heatstroke-induced hippocampal injury by inhibiting microglial pyroptosis.

Background: Central nervous system (CNS) injury is the most prominent feature of heatstroke and the hippocampus is prone to damage. However, the mechanisms underlying the heatstroke-induced hippocampal injury remain unclear. Hyperbaric oxygen (HBO) therapy prevents CNS injury in heatstroke mice. However, the underlying mechanisms of HBO in heatstroke-induced hippocampal injury remain unclear. This study aimed to elucidate the protective effects of HBO against hippocampal injury and its potential role in microglial pyroptosis in heatstroke rats.Methods: A rat heatstroke model and a heat stress model with a mouse microglial cell line (BV2) were, respectively, used to illustrate the effect of HBO on heat-induced microglial pyroptosis in vivo and in vitro. We used a combination of molecular and histological methods to assess microglial pyroptosis and neuroinflammation both in vivo and in vitro.Results: The results revealed that HBO improved heatstroke-induced survival outcomes, hippocampal injury, and neurological dysfunction in rats. In addition, HBO mitigates microglial pyroptosis and reduces the expression of pro-inflammatory cytokines in the hippocampus of heatstroke rats. In vitro experiments showed that HBO attenuated BV2 cell injury under heat stress. Furthermore, HBO prevented heat-induced pyroptosis of BV2 cells, and the expression of pro-inflammatory cytokines IL-18 and IL-1ß was reduced. Mechanistically, HBO alleviates heatstroke-induced neuroinflammation and hippocampal injury by preventing microglial pyroptosis. Conclusions: In conclusion, HBO attenuates heatstroke-induced neuroinflammation and hippocampal injury by inhibiting microglial pyroptosis.

INFLUENCES OF HEAT STRESS ON GLUTAMATE TRANSMISSION-DEPENDENT EXPRESSION LEVELS OF IL-1ß and IL-18 IN BV-2 MICROGLIAL CELLS.

ABSTRACT: Objective: This study aimed to explore the impact of heat stress (HS) on glutamate transmission-dependent expression levels of interleukin-1ß (IL-1ß) and IL-18 in BV-2 microglial cells. Methods: BV-2 microglial cells were cultured in vitro , with cells maintained at 37°C serving as the control. The HS group experienced incubation at 40°C for 1 h, followed by further culturing at 37°C for 6 or 12 h. The experimental group was preincubated with glutamate, the glutamate antagonist riluzole, or the mGluR5 agonist, 2-chloro-5-hydroxyphenylglycine (CHPG), before HS. Glutamate content in BV-2 culture supernatant was assessed using colorimetric assay. Moreover, mRNA expression levels of EAAT3 and/or mGluR5 in BV-2 cells were determined via quantitative polymerase chain reaction. Interleukins (IL-1ß and IL-18) in cell culture supernatant were measured using enzyme-linked immunosorbent assay. Western blot analysis was employed to assess protein levels of IL-1ß and IL-18 in BV-2 cells. Results: HS induced a significant release of glutamate and increased the expression levels of mGluR5 and EAAT3 in BV-2 cells. It also triggered the expression levels and release of proinflammatory factors, such as IL-1ß and IL-18, synergizing with the effects of glutamate treatment. Preincubation with both riluzole and CHPG significantly reduced HS-induced glutamate release and mitigated the increased expression levels and release of IL-1ß and IL-18 induced by HS. Conclusion: The findings confirmed that microglia could be involved in HS primarily through glutamate metabolisms, influencing the expression levels and release of IL-1ß and IL-18.

BV2 Membrane-Coated PEGylated-Liposomes Delivered hFGF21 to Cortical and Hippocampal Microglia for Alzheimer's Disease Therapy.

Microglia-mediated inflammation is involved in the pathogenesis of Alzheimer's disease (AD), whereas human fibroblast growth factor 21 (hFGF21) has demonstrated the ability to regulate microglia activation in Parkinson's disease, indicating a potential therapeutic role in AD. However, challenges such as aggregation, rapid inactivation, and the blood-brain barrier hinder its effectiveness in treating AD. This study develops targeted delivery of hFGF21 to activated microglia using BV2 cell membrane-coated PEGylated liposomes (hFGF21@BCM-LIP), preserving the bioactivity of hFGF21. In vitro, hFGF21@BCM-LIP specifically targets Aß1-42-induced BV2 cells, with uptake hindered by anti-VCAM-1 antibody, indicating the importance of VCAM-1 and integrin α4/ß1 interaction in targeted delivery to BV2 cells. In vivo, following subcutaneous injection near the lymph nodes of the neck, hFGF21@BCM-LIP diffuses into lymph nodes and distributes along the meningeal lymphatic vasculature and brain parenchyma in amyloid-beta (Aß1-42)-induced mice. Furthermore, the administration of hFGF21@BCM-LIP to activated microglia improves cognitive deficits caused by Aß1-42 and reduces levels of tau, p-Tau, and BACE1. It also decreases interleukin-6  (IL-6) and tumor necrosis factor-α (TNF-α) release while increasing interleukin-10 (IL-10) release both in vivo and in vitro. These results indicate that hFGF21@BCM-LIP can be a promising treatment for AD, by effectively crossing the blood-brain barrier and targeting delivery to brain microglia via the neck-meningeal lymphatic vasculature-brain parenchyma pathways.