Neuroprotective Effect of Dichloromethane Extraction From Piper nigrum L. and Piper longum L. on Permanent Focal Cerebral Ischemia Injury in Rats.

BACKGROUND: Piper nigrum L. and Piper longum L. consist a classic formula in traditional Chinese Hui medicine and are widely used in treatment of stroke. To examine the therapeutic effect of neuron injury after apoplexy, we used a permanent middle cerebral artery occlusion model in rats to investigate the effects of dichloromethane fraction (DF) of Piper nigrum L. and Piper longum L.

MATERIALS AND METHODS: After subjecting the rats to permanent middle cerebral artery occlusion, DF (100 and 200 mg/kg) were administered for 14 days. Neurological deficits and the degree of cerebral tissue injury was detected by 2,3,5-Triphenyltetrazolium Chloride Staining Hematoxylin and eosin staining and Nissl staining. Postsynaptic density protein 95 (PSD-95), synapsin-I (syn-I), and α-synuclein (α-syn) were stained by immunohistochemistry. PSD-95, Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMK II), phosphorylated CaMK II (p-CaMK II), CaM, N-methyl D-aspartate receptor subtype 2B (NR2B) expression were detected by Western blot. Meanwhile, phytochemical profile of DF was determined through ultrahigh-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS).

RESULTS: DF alleviated neurological deficits and markedly prevented ischemia-induced cellular damage. Immunohistochemical micrographs revealed that PSD-95 and syn-I proteins increased, and α-syn presented reduced expression in brain samples from the sham group. Western blot analyses revealed that the model group exhibited a noticeable reduction in PSD-95, p-CaMK II, CaM, and NR2B. The DF-treated model group exhibited increased PSD-95, p-CaMK II, CaM, and NR2B. UPLC-Q-TOF/MS analysis revealed eight main components of DF, of which piperine accounted for the largest proportion.