Toona sinensis fruit polyphenols alleviate cerebral ischemia-reperfusion injury in rats by inhibiting MAPK signaling pathways and NLRP3 inflammasome/pyroptosis

Abstract

Ethnopharmacological relevance

Toona sinensis fruit polyphenols (TSFP) are polyphenols that have been separated and extracted from mature Toona sinensis fruits. TSFP anti-inflammatory and neuroprotective properties have demonstrated promise. However, the underlying mechanisms require more elucidation.

Study aim

The aim of this study is to investigate the mechanisms by which TSFP alleviates cerebral ischemia-reperfusion injury (CIRI) through the mitogen-activated protein kinase (MAPK) and NOD-,LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome pathways on middle cerebral artery occlusion/reperfusion (MCAO/R) rats.

Materials and methods

The TSFP neuroprotective effect was evaluated using transmission electron microscope (TEM), 2,3,5-triphenyltetrazolium chloride (TTC), neurological function, and hematoxylin-eosin (H&E) staining. An enzyme-linked immunosorbent assay (ELISA) and immunofluorescence were used to measure the TSFP influence on inflammation. In addition, a Western blot assay was performed to assess the NLRP3 inflammasome and MAPK pathway proteins expressions in the prefrontal cortex (PFC) and hippocampus, and double immunofluorescence methods were used to identify gasdermin D (GSDMD) secretion in neurons.

Results

The TSFP group in the MCAO/R model had improved levels of cerebral infarction and brain pathological damage. The TEM demonstrated that TSFP ameliorated ischemia-induced neuronal pyroptosis, and there was a significant decrease in the expressions of NLRP3, the apoptosis-associated speck-like protein containing Caspase recruitment domain (ASC), cysteine aspartate-specific protease-1 (caspase-1), and GSDMD in the TSFP groups. TSFP reduced the phosphorylation of p38 mitogen-activated protein kinase (p38) and extracellular signal-regulated kinase 1/2 (ERK1/2), promoted the phosphorylation of extracellular signal-regulated kinase 5 (ERK5), and reduced the phosphorylation of c-Jun amino terminal kinase (JNK) in the hippocampus. The results also revealed that TSFP significantly lowered the interleukin-1β (IL-1β) and interleukin-1β (IL-18) expressions and attenuated glial cell activation caused by ischemia in the PFC and hippocampus DG areas.

Conclusion

This study provided evidence for the efficacy of TSFP in the treatment of CIRI, with potential mechanisms that involved the control of the MAPK signaling pathways and NLRP3 inflammasome/pyroptosis, which highlights the potential benefits of TSFP in the treatment of CIRI.