Background Remote limb
ischemic postconditioning (RLIPoC) has been demonstrated to protect against
ischemic stroke. However, the underlying mechanisms of RLIPoC mediating cross-organ protection remain to be fully elucidated. Methods and Results
Ischemic stroke was induced by
middle cerebral artery occlusion for 60 minutes. RLIPoC was performed with 3 cycles of 10-minute
ischemia followed by 10-minute reperfusion of the bilateral femoral arteries immediately after middle cerebral artery reperfusion. The percentage of regulatory T cells (Tregs) in the spleen, blood, and brain was detected using flow cytometry, and the number of Tregs in the ischemic hemisphere was counted using transgenic mice with an
enhanced green fluorescent protein-tagged Foxp3. Furthermore, the metabolic status was monitored dynamically using a multispectral optical imaging system. The Tregs were conditionally depleted in the depletion of Treg transgenic mice after the injection of the
diphtheria toxin. The inflammatory response and neuronal apoptosis were investigated using immunofluorescent staining.
Infarct volume and neurological deficits were evaluated using magnetic resonance imaging and the modified neurological severity score, respectively. The results showed that RLIPoC substantially reduced
infarct volume, improved neurological function, and significantly increased Tregs in the spleen, blood, and ischemic hemisphere after
middle cerebral artery occlusion. RLIPoC was followed by subsequent alteration in metabolites, such as
flavin adenine dinucleotide and
nicotinamide adenine dinucleotide hydrate, both in RLIPoC-conducted local tissues and circulating blood. Furthermore,
nicotinamide adenine dinucleotide hydrate can mimic RLIPoC in increasing Tregs. Conversely, the depletion of Tregs using depletion of Treg mice compromised the
neuroprotective effects conferred by RLIPoC. Conclusions RLIPoC protects against ischemic
brain injury, at least in part by activating and maintaining the Tregs through the
nicotinamide adenine dinucleotide/
nicotinamide adenine dinucleotide hydrate pathway.