Procyanidin B2 inhibits lipopolysaccharide-induced apoptosis by suppressing the Bcl-2/Bax and NF-κB signalling pathways in human umbilical vein endothelial cells

Human umbilical vein endothelial cells (HUVECs) serve a critical role in maintaining normal vascular function. Lipopolysaccharide (LPS), which is released from pathogenic bacteria in the blood, induces HUVEC apoptosis and injury to cause vascular dysfunction and infectious vascular diseases. Procyanidin B2 (PB2) possesses numerous functions, including antioxidant, antitumor, anti-inflammatory and antiapoptosis effects, but the molecular mechanism is not completely understood. The present study investigated the effects of PB2 on LPS-induced cytotoxicity and apoptosis in HUVECs, as well as the underlying mechanisms. The effects of PB2 on LPS-mediated alterations to cytotoxicity, mitochondrial membrane potential, apoptosis were assessed by performing Cell Counting Kit-8, JC-1 fluorescence, Hoechst 33258 staining assays, respectively. IL-1β, IL-6 and TNF-α mRNA expression and protein levels were measured by performing reverse transcription-quantitative PCR and ELISAs, respectively. Bcl-2, Bax, cleaved caspase-3, cleaved caspase-7, cleaved caspase-9, phosphorylated (p)-IκB-α, p-IκB-β, p-NF-κB-p65 and total NF-κB p65 protein expression levels were determined via western blotting. NF-κB p65 nuclear translocation was assessed via immunofluorescence. PB2 pretreatment markedly attenuated LPS-induced cytotoxicity and apoptosis in HUVECs. PB2 also significantly downregulated the expression levels of IL-1β, IL-6, TNF-α, Bax, cleaved caspase-3, cleaved caspase-7, cleaved caspase-9 and p-NF-κB-p65, but upregulated the expression levels of Bcl-2, p-IκB-α and p-IκB-β in LPS-induced HUVECs. Moreover, PB2 markedly inhibited LPS-induced NF-κB p65 nuclear translocation in HUVECs. The results suggested that the potential molecular mechanism underlying PB2 was associated with the Bax/Bcl-2 and NF-κB signalling pathways. Therefore, PB2 may serve as a useful therapeutic for infectious vascular diseases.