Effects of TLR4 on ox-LDL induced macrophage apoptosis and its mechanism / 中华微生物学和免疫学杂志

ABSTRACT

Objective To study the effects of Toll-like receptor 4(TLR4) on oxidized low density lipoprotein ( ox-LDL) induced macrophage apoptosis and its possible mechanism .Methods THP-1 derived macrophages were divided into four groups including untreated control group , ox-LDL treated group , ox-LDL+LPS treated group and tunicamycin treated group .MTT assay and flow cytometry analysis were performed to measure cell vitality and cell apoptosis , respectively .Oil red O staining was used to observe the phagocytosis of lipids by macrophages .The persistent and intense endoplasmic reticulum ( ER) stress markers were de-tected by analyzing the expression of glucose-regulated protein 78 ( GRP78 ) and CCAAT/enhancer-binding protein homologous protein ( CHOP) at mRNA and protein levels by q-RT-PCR and Western blot .Small in-terfering RNA ( siRNA) was used to silence the expression of TLR 4 to further elucidate its possible mecha-nism.Results Flow cytomotry and MTT assay showed that the number of apoptotic cells in ox-LDL+LPS treated group were increased more significantly than that in ox-LDL treated group (P<0.01), and cell apop-tosis in both two groups were greater than that in control group (P<0.01).Compared with control group, the expression of GRP78 and CHOP at mRNA and protein levels were up-regulated in ox-LDL+LPS treated group and ox-LDL treated group (P<0.01), and the expression of GRP78 and CHOP in ox-LDL+LPS treated group was significantly higher than that in ox-LDL treated group (P<0.01).Silenced expression of TLR4 al-leviated the endoplasmic reticulum stress (P<0.05).Conclusion Increased expression of CHOP contribu-ted to cell apoptosis .TLR4 might promote ox-LDL induced macrophage apoptosis through accelerating endo-plasmic reticulum stress .