Effect of trilinolein on cyclic nucleotide formation in human platelets: relationship with its antiplatelet effect and nitric oxide synthesis

Role of oxidative stress on platelet hyperreactivity during aging

Thrombotic events are common causes of morbidity and mortality in the elderly. Age-accelerated vascular injury is commonly considered to result from increased oxidative stress. There is abundant evidence that oxidative stress regulate several components of thrombotic processes, including platelet activation. Thus oxidative stress can trigger platelet hyperreactivity by decreasing nitric oxide bioavailability. Therefore oxidative stress measurement may help in the early identification of asymptomatic subjects at risk of thrombosis. In addition, oxidative stress inhibitors and platelet-derived nitric oxide may represent a novel anti-aggregation/-activation approach. In this article the relative contribution of oxidative stress and platelet activation in aging is explored.

Protective effects of (6R)-5,6,7,8-tetrahydro-l-biopterin on local ischemia/reperfusion-induced suppression of reactive hyperemia in rat gingiva

We herein investigated the regulatory mechanism in the circulation responsible for rat gingival reactive hyperemia (RH) associated with ischemia/reperfusion (I/R). RH was analyzed using a laser Doppler flowmeter. RH and I/R were elicited by gingival compression and release with a laser Doppler probe. RH increased in a time-dependent manner when the duration of compression was between 30 s and 20 min. This increase was significantly suppressed by N^ω-nitro-l-arginine-methyl-ester (l-NAME), 7-nitroindazole (7-NI), and 2,4-diamino-6-hydroxypyrimidine (DAHP). However, RH was markedly inhibited following 60 min of compression. This inhibition was significantly decreased by treatments with superoxide dismutase (SOD), (6R)-5,6,7,8-tetrahydro-l-biopterin (BH₄), and sepiapterin. The luminescent intensity of superoxide anion (O₂^•−)-induced 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo-[1,2-a] pyrazine-3-one (MCLA) was markedly decreased by SOD and BH₄, but only slightly by sepiapterin. BH₄ significantly decreased O₂^•− scavenging activity in a time-dependent manner. These results suggested that nitric oxide (NO) secreted by the nitrergic nerve played a role in regulating local circulation in rat gingiva. This NO-related regulation of local circulation was temporarily inhibited in the gingiva by the I/R treatment. The decrease observed in the production of NO, which was caused by suppression of NO synthase (NOS) activity subsequent to depletion of the NOS co-factor BH₄ by O₂^•−, played a partial role in this inhibition.

Inhibitory effects of cardiotonic pills on platelet function in dogs fed a high-fat diet

Insulin resistance and the consequent metabolic disorders are associated with a state of platelet hyperactivity. Oxidative stress is responsible for the persistent platelet activation. We sought to study the inhibitory effect of cardiotonic pills, an oral herbal component, on platelet function in a dog model with insulin resistance induced by high-fat feeding. We fed 18 dogs with a high-fat diet and six dogs with normal chow as control for 6 months. Then, six dogs were fed with a high-fat diet and received additional aspirin (250 mg/day), and another six dogs received additional cardiotonic pills (1,000 mg/day) for 4 months. Time-course changes in metabolic parameters and platelet function were detected. After high-fat feeding for 6 months, 18 dogs developed a series of metabolic disorders including obesity, dyslipidemia, oxidative stress and insulin resistance. In addition, a platelet hyperactivity state, characterized by increased agonist (arachidonic acid, ADP and collagen) induced platelet aggregation, platelet expression of adhesion molecules (P-selectin and GP IIb/IIIa), and platelet intracellular calcium concentration, was indicated. Cardiotonic pills showed a significant antioxidative activity by presenting an increase in plasma superoxide dismutase and decrease in erythrocyte glutathione, as well as a lipid-lowering effect (decrease in both plasma cholesterol and triglyceride). Either aspirin or cardiotonic pills could significantly reverse the platelet hypersensitivity and hyperfunction. Compared with aspirin, cardiotonic pills showed a more exaggerated inhibitory effect on platelet function (a significantly decreased collagen-stimulated platelet aggregation, and expression of adhesion molecules). In conclusion, cardiotonic pills inhibited platelet hyperfunction in dogs with insulin resistance. This inhibitory effect may mainly be explained by antioxidative activity and metabolic control.

Nitric oxide, human diseases and the herbal products that affect the nitric oxide signalling pathway

1. Nitric oxide (NO) is formed enzymatically from l-arginine in the presence of nitric oxide synthase (NOS). Nitric oxide is generated constitutively in endothelial cells via sheer stress and blood-borne substances. Nitric oxide is also generated constitutively in neuronal cells and serves as a neurotransmitter and neuromodulator in non-adrenergic, non-cholinergic nerve endings. Furthermore, NO can also be formed via enzyme induction in many tissues in the presence of cytokines. 2. The ubiquitous presence of NO in the living body suggests that NO plays an important role in the maintenance of health. Being a free radical with vasodilatory properties, NO exerts dual effects on tissues and cells in various biological systems. At low concentrations, NO can dilate the blood vessels and improve the circulation, but at high concentrations it can cause circulatory shock and induce cell death. Thus, diseases can arise in the presence of the extreme ends of the physiological concentrations of NO. 3. The NO signalling pathway has, in recent years, become a target for new drug development. The high level of flavonoids, catechins, tannins and other polyphenolic compounds present in vegetables, fruits, soy, tea and even red wine (from grapes) is believed to contribute to their beneficial health effects. Some of these compounds induce NO formation from the endothelial cells to improve circulation and some suppress the induction of inducible NOS in inflammation and infection. 4. Many botanical medicinal herbs and drugs derived from these herbs have been shown to have effects on the NO signalling pathway. For example, the saponins from ginseng, ginsenosides, have been shown to relax blood vessels (probably contributing to the antifatigue and blood pressure-lowering effects of ginseng) and corpus cavernosum (thus, for the treatment of men suffering from erectile dysfunction; however, the legendary aphrodisiac effect of ginseng may be an overstatement). Many plant extracts or purified drugs derived from Chinese medicinal herbs with proposed actions on NO pathways are also reviewed.

Antioxidant effects of Chinese traditional medicine: focus on trilinolein isolated from the Chinese herb sanchi (Panax pseudoginseng)

It is thought that oxygen-derived free radicals (OFR) cause lipid peroxidation, which contributes to the process of atherosclerosis, and they are also involved in the myocardial damage seen with ischemia and reperfusion. Antioxidants could potentially ameliorate such harmful effects. Many natural plant products have been shown to have antioxidant effects. Trilinolein, a triacylglycerol purified from Panax pseudoginseng, which is commonly used in Chinese traditional medicine, has been found to have pharmacological effects, including antioxidant activity that may explain the benefits in treating circulatory disorders perceived from the use of the herb over the centuries.

Trilinolein potentiates the pro-aggregating effect of phorbol-12-myristate 13-acetate in human polymorphonuclear leukocytes

Trilinolein, a triacylglycerol with linoleic acid as the only type of fatty acid residue in all three of the glycerol esterified positions, was recently reported to have an antiplatelet effect, mediated through stimulating nitric oxide and cyclic guanosine monophosphate (GMP) formation. In our study, trilinolein induced aggregation of human polymorphonuclear neutrophils (PMNs) and, pretreatment with 0.1 nM trilinolein enhanced phorbol-12-myristate 13-acetate (PMA) induced aggregation. Further investigation showed that trilinolein at concentrations ranging from 0.1 nM to 10 microM increased cyclic GMP formation after 10 min of incubation with PMNs. Pretreatment of trilinolein with 10 microM d-sphingosine, before being incubated with PMNs, attenuated the stimulatory effect of trilinolein on cyclic GMP formation, and pretreatment of 10 microM d-sphingosine also attenuated the aggregation induced by PMA and trilinolein. We conclude that trilinolein can induce the aggregation of human PMNs, and enhance the aggregation induced by PMA.

Cordyceps sinensis increases the expression of major histocompatibility complex class II antigens on human hepatoma cell line HA22T/VGH cells

Previous studies suggest that down-regulation of the major histocompatibility complex (MHC) antigens on the cell surface of certain tumors results in an escape of immune surveillance. Cordyceps sinensis is well known for its modulatory effect on host immune system. To investigate the modulatory effect of Cordyceps sinensis on MHC class II antigen expression on hepatoma cells, immunostaining with monoclonal antibody (MAb) L243, against the HLA DR region of MHC class II antigens on human hepatoma cell line HA22T/VGH was analyzed by using flow cytofluorimetry. The degree of fluorescence intensity on L243(+) cells was expressed as relative mean fluorescence intensity (RMFI). The extract of Cordyceps sinensis (VGH-CS-ME-82, 40 micrograms/ml) was found to increase the MHC class II antigen expression on HA22T/VGH cells with the percentage of L243(+) cells 40.2 +/- 2.5 and RMFI 6.6 +/- 0.4; whereas cells without treatment disclosed the percentage of L243(+) cells 17.2 +/- 1.4 and RMFI 5.4 +/- 0.3, respectively (p < 0.05). There was a dose-related increase in the degree of fluorescence intensity in terms of RMFI on VGH-CS-ME-82 induced cells. The RMFI in cells treated with IFN-gamma 0, 0.2 and 5 ng/ml were 5.4 +/- 0.3, 8.2 +/- 0.4, and 24.9 +/- 1.5, respectively; whereas the RMFI in cells co-incubated with VGH-CS-ME-82 (40 micrograms/ml) and IFN-gamma 0, 0.2 ng/ml and 5 ng/ml were 6.7 +/- 0.2 (p < 0.05), 9.2 +/- 0.9 (p < 0.1) and 29.5 +/- 1.2 (p < 0.005), respectively. We conclude that VGH-CS-ME-82, either alone or with IFN-gamma induction, increases the MHC class II antigen expression on hepatoma cell line HA22T/VGH, which will shed light into the present immunotherapy, and make the host immune surveillance more effective against tumor cells with down-regulated MHC class II antigen expression.

Trilinolein inhibits the adhesion of neutrophils to endothelial cells

1. Trilinolein is a triacylglycerol with linoleic acid as the only type of fatty acid in all three esterified positions of glycerol. It was recently reported to have a myocardial protective effect in coronary ligated rats. We now study its effect on the adhesion of human neutrophils to cultured bovine endothelial cells. 2. Pretreatment of an endothelial monolayer with trilinolein at concentrations ranging from 10(-10) to 10(-6) mol/L significantly inhibited neutrophil adhesion to endothelial cells. Trilinolein was less potent than sodium nitroprusside in inhibiting neutrophil adhesion. 3. The inhibitory effect of trilinolein was antagonized by methylene blue and N(G)-nitro-L-arginine methyl ester. The inhibitory effect of trilinolein was not mediated through linoleic acid because linoleic acid did not inhibit neutrophil adhesion. 4. Pretreatment of neutrophils with trilinolein did not reduce neutrophil adhesion. However, in neutrophils activated with N-formyl-methionyl-leucyl-phenylalanine, trilinolein inhibited the neutrophil adhesion to endothelial cells. 5. We conclude that trilinolein inhibits neutrophil adhesion to the endothelial monolayer by stimulating the nitric oxide and cyclic GMP pathways in endothelial cells. It may also inhibit neutrophil adhesion by scavenging free radicals. The inhibitory effect of trilinolein on neutrophil adhesion may play a role in its myocardial protective activity.

Myocardial protective effect of trilinolein: an antioxidant isolated from the medicinal plant Panax pseudoginseng

In a previous study we demonstrated that trilinolein, a natural plant triacylglycerol, is a novel myocardial protective agent in vivo. The mechanism probably involves an antioxidant effect. This work investigated the mechanism of myocardial protection of trilinolein to determine if inhibition of calcium influx and alteration of activity of superoxide dismutase are involved. In isolated cardiomyocytes, pretreatment with trilinolein at a low concentration of 10(-9) M effectively reduced 45Ca2+ influx stimulated by hypoxia/normoxia by 34%. In isolated perfused rat heart subjected to 60 min global hypoxemia without reperfusion, pretreatment with 10(-7) M trilinolein for 15 min reduced infarct size by 37%. Assay of superoxide dismutase-mRNA by Northern blot analysis in in vivo rat heart subjected to 30 min ischaemia and 10 min reperfusion showed pretreatment with 10(-7) M trilinolein had a synergistic action with antioxidant systems preventing the rise in superoxide dismutase-mRNA. These results reconfirm the myocardial protection of trilinolein and suggest it may be related to antioxidant activity and inhibition of 45Ca2+ influx.

The in vitro antioxidant activity of trilinolein and other lipid-related natural substances as measured by enhanced chemiluminescence

There is abundant evidence for the premise that oxygen-derived free radicals (OFR) mediate ischemia/reperfusion injury to the myocardium. OFR scavengers such as superoxide dismutase can effectively reduce damage through lipid peroxidation during ischemia/reperfusion. Enhanced chemiluminescence, which has been used to measure OFR, was used to measure the antioxidant activity of fatty acids (palmitic and linoleic acid) and triglycerides (triolein, tristearin) and natural plant antioxidants (magnolol, catechin, trilinolein). Trilinolein, which has recently been isolated from natural products, as well as the well-known water soluble analogue of vitamin E-Trolox, were used as control. During pretreatment with chemicals, at concentrations of 10(-9) to 10(-7) M, enhanced chemiluminescence of linoleic acid (C 18:2) showed a dose-responsive reduction of OFR with a maximal mean reduction of -31.9% when compared to baseline. A saturated fatty acid such as palmitic acid (C 16:0) showed only relatively weak antioxidant activity at concentrations of 10(-7) to 10(-6) M with a maximum reduction of OFR of- 15.2% only. control chemicals such as trilinolein and Trolox showed significant antioxidant activity. At concentrations between 10(-10) and 10(-6) M and trilinolein has the most potent antioxidant activity with a maximal mean reduction of OFR of -48.0%, whereas Trolox showed only -39.2%. As for the natural plant antioxidants, only catechin showed potent antioxidant activity (-40%). Polyunsaturated triglycerides such as triolein (oleic acid, C 18:1) also possess significant OFR scavenging effect (-31.9%) whilst saturated triglycerides such as tristearin (stearic acid, C 18:0) had only relatively weak antioxidant activity (-15.2%). Generally, the antioxidant activity of unsaturated compounds is stronger than saturated compounds; double-bond existence may partially explain this phenomenon.