Abstract
To explore the mechanism of TLR4/NF-κB regulation of microglia-mediated
inflammation after NSC-Exos transplantation. In this study, a right
middle cerebral artery occlusion model (MCAO) was constructed in SD
rats, NSC-Exos was injected into the lateral ventricle through brain
stereo localization. TAK-242 was given 1 day before MCAO in rats.
Histopathological changes, microglia-mediated inflammatory factor,
colocalized number of CD86/Iba1 and CD206/Iba1 cells, and TLR4/NF-κB
were detected in rats. After brain injury, the number of CD86/Iba1 cells
increased, and the expression of pro-inflammatory factors, TLR4 and
NF-κB were increased. When treatment with NSC-Exos, the number of
CD206/Iba1 cells were increased, and the expression of anti-inflammatory
factors, TLR4 and NF-κB were decreased, promoting anti-inflammatory
phenotype polarization. More importantly, TAK-242 reversed the effect of
NSC-Exos transplantation in animal model. These results suggest that
NSC-Exos can improve the microglia-mediated inflammatory response in
rats with ischemic brain injury, which may be related to the regulation
of TLR4/NF-κB pathway.
Introduction
Cerebral stroke, a fatal cerebrovascular disease, is the second most
common cause of death and disability in the world (Chidambaram et al.,
2022) . At present, one of the most commonly used treatments for
ischemic stroke is intravenous thrombolytic therapy with recombinant
tissue plasminogen activator, but thrombolytic therapy can cause brain
reperfusion injury (Herpich et al., 2020; Jolugbo et al., 2021).
Although the pathophysiological mechanisms of cerebral
ischemia-reperfusion injury have been well understood in recent decades,
there is still no effective treatment (Giuriati et al., 2021; Ran et
al., 2021). More and more evidence shows that neuroinflammation is
related to pathogenesis of cerebral ischemia-reperfusion injury, and it
is worth mentioning that microglia-mediated inflammatory response plays
a key role (Zhu et al., 2021).
Exosomes are extracellular vesicles that can cross the blood-brain
barrier as a natural carrier system with low immunogenicity (Yuan et
al., 2017), no tumorigenicity and no risk of immune rejection, so they
have been widely used as a therapeutic strategy for a variety of central
nervous system diseases (Arabpour et al., 2021; Huang et al., 2022). It
has been reported that neural stem cell-derived exosomes (NSC-Exos)
significantly improve the inflammatory response of animal stroke,
alleviating inflammation-induced neurodegeneration (Zhang et al., 2023;
Zhu et al., 2023). Other experiments have reported that activation of
Toll-like receptor 4 (TLR4) can cause activation of downstream ligand
nuclear factor NF-κB (Scalise et al., 2021), promote the activation of
microglia and further increase the release of inflammatory factors
(Scalise et al., 2021), aggravating brain injury in the early damage of
ischemia (Tian et al., 2021). So far, few studies have focused on
whether TLR4/NF-κB pathway regulates the polarization of NSC-Exos on
microglia during cerebral ischemia, and the specific mechanism of action
is unknown (Cui et al., 2022). Therefore, we speculate that TLR4/NF-κB
regulation of microglia-mediated NSC-Exos to reduce neuroinflammation
may be an effective method for the treatment of ischemic brain injury.
Therefore, this study established a rat MCAO model to observe whether
NSC-Exos therapy regulates microglial polarization through TLR4/NF-κB,
revealing the molecular mechanism of TLR4/NF-κB regulation of microglial
involvement in inflammatory response, and providing a new target for
exosomes to prevent and treat cerebral ischemia diseases.