Effect of Cyclosporin H on ischemic injury and neutrophil infiltration in cerebral infarct model of rats via PET imaging

Background

Brain ischemia–reperfusion injury is a complex process, and neuroinflammation is an important secondary contributing pathological event. Neutrophils play major roles in ischemic neuroinflammation. Once activated, neutrophils express formyl peptide receptors (FPRs), which are special receptors of a class of chemoattractants and may be potential targets to regulate the activity of neutrophils and control cerebral ischemic injury. This study was aimed to explore the ameliorating effect of Cyclosporin H (CsH), a potent FPR antagonist, on brain ischemic injury by inhibiting the activation and migration of neutrophils, and improving cerebral blood flow.

Methods

We employed a middle cerebral artery occlusion (MCAO) Model on rats and performed behavioral, morphological, and microPET imaging assays to investigate the potential restoring efficacy of CsH on cerebral ischemic damages. Peptide N-cinnamoyl-F-(D)L-F-(D)L-F (cFLFLF), an antagonist to the neutrophil FPR with a high binding affinity, was used for imaging neutrophil distribution.

Results

We found that CsH had similar effect with edaravone on improving the neurobehavioral deficient symptoms after cerebral ischemia–reperfusion, and treatment with CsH also alleviated ischemic cerebral infarction. Compared with the MCAO Model group, [¹⁸F]FDG uptake ratios of the CsH and edaravone treatment groups were significantly higher. The CsH-treated groups also showed significant increases in [¹⁸F]FDG uptake at 144 h when compared with that of 24 h. This result indicates that like edaravone, treatment with both doses of CsH promoted the recovery of blood supply after cerebral ischemic event. Moreover, MCAO-induced cerebral ischemia significantly increased the radiouptake of [⁶⁸Ga]Ga-cFLFLF at 72 h after ischemia–reperfusion operation. Compared with MCAO Model group, radiouptake values of [⁶⁸Ga]-cFLFLF in both doses of CsH and edaravone groups were all decreased significantly. These results showed that both doses of CsH resulted in a similar therapeutic effect with edaravone on inhibiting neutrophil infiltration in cerebral infarction.

Conclusion

Potent FPR antagonist CsH is promisingly beneficial in attenuating neuroinflammation and improving neurobehavioral function against cerebral infarction. Therefore, FPR may become a novel target for regulating neuroinflammation and improving prognosis for ischemic cerebrovascular disorders.