Lipoic acid remodels neurovascular units through the AMPK/NLRP3 signaling pathway after cerebral infarction

Introduction
Ischemic stroke (IS) is a disease caused by blood circulation disorders in the brain, ischemia, and hypoxia, resulting in ischemic necrosis or softening of localized brain tissue. Lipoic acid (ALA) is effective in resisting oxidative stress and alleviating the inflammatory response. This study evaluated the mechanism and effects of ALA on neurovascular unit remodeling after cerebral infarction.

Material and methods
In male C57BL/6 mice, cerebral infarction was induced using distal middle cerebral artery occlusion (dMCAO). In an in vitro model, cells were allocated to control, model, low dose, medium dose, and high dose groups. Infarct volume analysis, Evans blue extravasation, and enzyme-linked immunosorbent assay (ELISA) kits were used to evaluate the effects of ALA on IS. Cell Counting Kit-8 (CCK-8), 5-ethynyl 2’-deoxyuridine staining (EDU) staining, Western blot and immunohistochemistry were used to evaluate the mechanism of ALA in IS.

Results
This study found that the cerebral infarct volume of the ALA treatment group was similar to dMCAO mice. Treatment with ALA reduced the area of Evans blue compared with dMCAO mice at 7 days, and promoted astrocyte and pericyte proliferation in the peri-infarct area at 28 days. Meanwhile, treatment with ALA also increased vascular endothelial growth factor (VEGF), angiopoietin (Ang)-1 and claudin-5 protein expression levels, suppressed Ang-2 and matrix metalloproteinase-9 (MMP-9) protein expression levels, reduced neuronal apoptosis inhibitory protein (NAIP), leucine-rich repeat (LRR), and PYD domain-containing protein 3 (NLRP3) expression levels, and induced phosphorylated-adenosine monophosphate-activated protein kinase (p-AMPK) protein expression levels in cerebral infarction mice (all p < 0.05). On the other hand, ALA restored cell growth and the number of EDU cells, promoted cell migration, elevated superoxide dismutase (SOD) activity, reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and inhibited inflammation levels in the in vitro model (all p < 0.05). Treatment with ALA also suppressed NLRP3 and Ang-2 protein expression, reduced MMP-9 protein expression, and induced VEGF, Ang-1, claudin-5, and p-AMPK protein expression levels in the in vitro model (all p < 0.05).

Conclusions
ALA improved neurovascular unit remodeling after cerebral infarction through anti-inflammation effects via the AMPK/NLRP3 signaling pathway.