Vitamin K1 attenuates hypoxia-induced relaxation of rat carotid artery

Influence of vitamin K2 on lipid precursors of inflammation and fatty acids pathway activities in HepG2 cells

Vitamin K2 (VK2) is one of the two types of vitamin K present most in the human diet. VK2 seems to have a beneficial effect on inflammation related to type 2 diabetes mellitus. The aim of this study was to evaluate the influence of VK2 on lipid precursors of inflammation in lipid-overloaded human liver hepatocellular carcinoma cells. Cells were incubated with VK2 and/or palmitic acid (PA). The concentrations of lipid fractions and their fatty acid compositions were measured by gas-liquid chromatography. The expression of proteins involved in the inflammatory process was detected using western blotting. The concentration of triacylglycerols (TAGs), activities of the n-3 pathway in TAGs, and lipooxygenase 15 expression were significantly elevated in cells incubated with PA and VK2. In the same group, a marked elevation in diacylglycerol (DAG) 20:4 was observed. VK2 supplementation lowered the expression of tumour necrosis factor-alpha and interleukin-6 compared to that in the PA group. The data indicate that VK2 redirects fatty acid metabolism into the deposition of a safe TAG fraction by increasing the concentration of anti-inflammatory n-3 polyunsaturated fatty acids in this fraction. Moreover, VK2 stimulates the synthesis of anti-inflammatory factors and has anti-inflammatory effects by reducing DAG 20:4.

Mechanisms underlying the biphasic effect of vitamin K1 (phylloquinone) on arterial blood pressure

Phylloquinone (vitamin K1, VK1) is widely used therapeutically and intravenous administration of this quinone can induce hypotension. We aimed to investigate the mechanisms underlying the effects induced by VK1 on arterial blood pressure. With this purpose a catheter was inserted into the abdominal aorta of male Wistar rats for blood pressure and heart rate recording. Bolus intravenous injection of VK1 (0.5–20 mgkg−1) produced a transient increase in blood pressure followed by a fall. Both the pressor and depressor response induced by VK1 were dose-dependent. On the other hand, intravenous injection of VK1 did not alter heart rate. The nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (L-NAME, 10 and 20 mgkg−1) reduced both the increase and decrease in blood pressure induced by VK1 (5 mgkg−1). On the other hand, indometacin (10 mgkg−1), a non-selective cyclooxygenase inhibitor, did not alter the increase in mean arterial pressure (MAP) induced by VK1. However, VK1-induced fall in MAP was significantly attenuated by indometacin. We concluded that VK1 induces a dose-dependent effect on blood pressure that consists of an acute increase followed by a more sustained decrease in MAP. The hypotension induced by VK1 involves the activation of the nitric oxide (NO) pathway and the release of vasodilator prostanoid(s).

Vitamin K1 (phylloquinone) induces vascular endothelial dysfunction: Role of oxidative stress

We aimed to investigate the mechanisms underlying the vascular effects induced by phylloquinone (Vitamin K1; VK1). Vascular reactivity experiments, using standard muscle bath procedures, showed that VK1 (5 and 50 microM) enhances the contractile response of endothelium-intact, but not denuded, rat carotid rings to phenylephrine. Similarly, maximal contraction induced by phenylephrine was enhanced in the presence of the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). The combination of L-NAME and VK1 did not produce any further additional effect. Pre-incubation of intact-rings with VK1 reduced both acetylcholine- and bradykinin-induced relaxation. VK1 induced an increment in tension on carotid rings submaximally pre-contracted with phenylephrine. VK1-induced increment in tension was completely abolished by endothelial removal or incubation of intact rings with L-NAME and L-NNA. Conversely, 7-nitroindazole, 1400 W, or indomethacin did not affect VK1-induced contraction. Moreover, VK1 reduced L-arginine-induced relaxation in endothelium-intact rings. Lucigenin-amplified chemiluminescence assays showed that VK1 induced an increase in the level of superoxide anions in endothelium-intact but not denuded rings. Measurement of nitrite and nitrate generation showed that VK1 did not alter nitrate formation but strongly inhibited the generation of nitrite. Finally, the superoxide anions scavenger tiron prevented the endothelial vasomotor dysfunction caused by VK1 on phenyleprine-induced contraction and acetylcholine or bradykinin-induced relaxation. In conclusion, our data show that VK1 disrupts the vasomotor function of rat carotid. Our results suggest that VK1-induced oxidative stress through production of superoxide anion is interfering with the NO pathway, which in turn is responsible for the altered vascular reactivity induced by VK1.