Luteolin Attenuates Hypertension via Inhibiting NF-κB-Mediated Inflammation and PI3K/Akt Signaling Pathway in the Hypothalamic Paraventricular Nucleus

Background: Luteolin is widely distributed among a number of vegetal species worldwide. The pharmacological effects of luteolin are diverse and amongst antioxidant, free radical scavenging, and anti-inflammatory activities. Preliminary study showed that luteolin can ameliorate hypertension. However, the precise mechanism needs further investigation. There is no evidence that luteolin affects the paraventricular nucleus of the hypothalamus (PVN), a brain nucleus associated with a critical neural regulator of blood pressure. Our main aim was to explore the effect of luteolin on the PI3K/Akt/NF-kappa B signaling pathway within the PVN of hypertensive rats. Methods: spontaneously hypertensive rats (SHRs) and corresponding normotensive control rats, the Wistar Kyoto (WKY) rats were divided into four groups and subsequently treated for 4 weeks with bilateral PVN injections of either luteolin (20 mu g/0.11 mu L, volume: 0.11 mu L/h) or vehicle (artificial cerebrospinal fluid). Results: luteolin infusion to the PVN significantly decreased some hemodynamic parameters including the mean arterial pressure (MAP), heart rate (HR), circulating plasma norepinephrine (NE) and epinephrine (EPI). Additionally, there was a decrease in the expressions of the phosphatidylinositol 3-kinase (p-PI3K) and phosphorylated protein kinase-B (p-AKT), levels of reactive oxygen species (ROS), NAD(P)H oxidase subunit (NOX2, NOX4) in the PVN of SHRs. Meanwhile, the expression of inflammatory cytokines and the activity of nuclear factor kappa B (NF-kappa B) p65 in the PVN of SHRs were lowered. Furthermore, immunofluorescence results showed that injection of luteolin in the PVN reduced the expression of tyrosine hydroxylase (TH), and increased that of superoxide dismutase (SOD1) and the 67-kDa isoform of glutamate decarboxylase (GAD67) in the PVN of SHRs. Conclusion: Our novel findings revealed that luteolin lowered hypertension via inhibiting NF-kappa B-mediated inflammation and PI3K/Akt signaling pathway in the PVN.

Automated summary

Luteolin, widely distributed in various plants, has diverse pharmacological effects including antioxidation, free radical scavenging, and anti-inflammation. This study aims to examine the effect of luteolin on the PI3K/Akt/NF-kappa B signaling pathway in the paraventricular nucleus (PVN) of hypertensive rats. The results showed that luteolin infusion significantly reduced hemodynamic parameters, expressions of oxidative stress and inflammatory markers, and increased the expression of antioxidant enzymes in the PVN. It revealed that luteolin can lower hypertension by inhibiting inflammation and PI3K/Akt signaling in the PVN.