Abstract
Effects of toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway on expression of angiotensinogen and AT1a receptor were investigated, to explore the role of TLR4/NF-κB signaling pathway in cardiovascular disease. Neonatal rat left ventricular myocytes (NRVMs) were cultured and cardiomyocytes were identified by immunocytochemical staining of sarcomeric α-actin. NRVMs were treated with lipopolysaccharide (LPS) at a dose of 10, 100 and 1,000 ng/ml, and RT-PCR was performed 24 h later to detect the expression of TLR4, angiotensinogen (ATG) and AT1a at mRNA level. NRVMs were cultured and pretreated with caffeic acid phenethylester (CAPE) for 30 min. Then NRVMs were stimulated with LPS (1,000 ng/ml) for 24 h. Nuclear translocation of NF-κB p65 was detected by immunocytochemistry. Expression of TLR4, angiotensinogen and AT1a receptor after CAPE stimulation was detected by RT-PCR. TLR4 mRNA was highly expressed in in vitro cultured NRVMs, and the expression level was significantly increased by LPS (10-1,000 ng/ml) stimulation in a dose-dependent manner (P<0.05). LPS stimulation also significantly increased the expression levels of angiotensinogen and AT1a receptor in a dose-dependent manner (P<0.05). NF-κB was activated and nuclear translocation of NF-κB p65 occurred after stimulation with LPS (1,000 ng/ml) for 24 h, while CAPE (20 µg/ml) inhibited the nuclear translocation of NF-κB p65 and inhibited LPS-induced expression of angiotensinogen and AT1a receptor. With LPS stimulation, TLR4 signaling positively regulates the expression of TLR4 and upregulates the expression of angiotensinogen and AT1a receptor in NRVMs. CAPE, an inhibitor of NF-κB, inhibited NF-κB p65 activation and inhibited the upregulation of TLR4, angiotensinogen and AT1a receptors induced by LPS. These results suggest that NF-κB plays a key regulatory role in the above-mentioned effects induced by LPS. Intervention with TLR4/NF-κB signaling may become a new target for prevention and treatment of cardiovascular diseases.