Ginsenoside-Rp1 inhibits platelet activation and thrombus formation via impaired glycoprotein VI signalling pathway, tyrosine phosphorylation and MAPK activation

BACKGROUND AND PURPOSE

Ginsenosides are the main constituents for the pharmacological effects of Panax ginseng. Such effects of ginsenosides including cardioprotective and anti-platelet activities have shown stability and bioavailability limitations. However, information on the anti-platelet activity of ginsenoside-Rp1 (G-Rp1), a stable derivative of ginsenoside-Rg3, is scarce. We examined the ability of G-Rp1 to modulate agonist-induced platelet activation.

EXPERIMENTAL APPROACH

G-Rp1 in vitro and ex vivo effects on agonist-induced platelet-aggregation, granule-secretion, [Ca(2+) ](i) mobilization, integrin-α(IIb) β(3) activation were examined. Vasodilator-stimulated phosphoprotein (VASP) and MAPK expressions and levels of tyrosine phosphorylation of the glycoprotein VI (GPVI) signalling pathway components were also studied. G-Rp1 effects on arteriovenous shunt thrombus formation in rats or tail bleeding time and ex vivo coagulation time in mice were determined. KEY RESULT: G-Rp1 markedly inhibited platelet aggregation induced by collagen, thrombin or ADP. While G-Rp1 elevated cAMP levels, it dose-dependently suppressed collagen-induced ATP-release, thromboxane secretion, p-selectin expression, [Ca(2+) ](i) mobilization and α(IIb) β(3) activation and attenuated p38(MAPK) and ERK2 activation. Furthermore, G-Rp1 inhibited tyrosine phosphorylation of multiple components (Fyn, Lyn, Syk, LAT, PI3K and PLCγ2) of the GPVI signalling pathway. G-Rp1 inhibited in vivo thrombus formation and ex vivo platelet aggregation and ATP secretion without affecting tail bleeding time and coagulation time, respectively.

CONCLUSION AND IMPLICATIONS

G-Rp1 inhibits collagen-induced platelet activation and thrombus formation through modulation of early GPVI signalling events, and this effect involves VASP stimulation, and ERK2 and p38(-MAPK) inhibition. These data suggest that G-Rp1 may have therapeutic potential for the treatment of cardiovascular diseases involving aberrant platelet activation.

EFFECT OF PROBIOTICS AND ANTIBIOTIC SUPPLEMENTATION ON BODY WEIGHT AND HAEMATO-BIOCHEMICAL PARAMETERS IN BROILERS

The study was carried out to know the effects of probiotics (Proetxin® Boost, Novartis Bangladesh Ltd.) and antibiotic (oxytetracycline-Renamycin®, Renata Animal Health) on growth performances and haemato-biochemical parameters of "Shaver Star Bro" broiler chickens during September and October 2003. A total of 20, day old broilers were randomly selected and assigned into four equal groups n = 5) as A, B, C and D. Group A was considered as control group fed with commercial ration while groups B, C and D were fed with commercial ration with the addition of 200 mg probiotics / liter drinking water, 100 mg probiotics and 50 mg antibiotic (oxytetracycline- Renamycin®) / liter drinking water and 100 mg antibiotic (oxytetracycline- Renamycin®) / liter drinking water respectively up to 35 days of age. The results showed that the body weight gains differed significantly (p < 0.05) at the 2nd, 4th and 5th weeks of age in different treatment groups. The meat yield not differed significantly (p > 0.05). The drumstick, wing differed significantly (p < 0.01) and spleen weight differed at p < 0.05 among different groups. The mean haemato-biochemical values of Hb, ESR, PCV, heterophil, eosinophil, basophil, triglyceride, HDL, LDL, SGPT and SGOT were differed significantly (p < 0.01) in different groups. The present findings suggest that supplementation of probiotics has significant effect on growth performance and certain haemato-biochemical parameters of broiler chickens as compared to antibiotic supplementation.

Antiplatelet activity of Phellinus baummii methanol extract is mediated by cyclic AMP elevation and inhibition of collagen-activated integrin-α(IIb) β₃ and MAP kinase

Phellinus baumii is a mushroom that has been used as folk medicine against various diseases and is reported to have antidiabetic, anticancer, antioxidant, antiinflammatory and antihypertensive activities. However, information on the effects of P. baumii extract in platelet function is limited. Therefore, the aim of this study was to examine the impact of a P. baumii methanol extract (PBME) on platelet activation and to investigate the mechanism behind its antiplatelet activity. PBME effects on agonist-induced platelet aggregation, granule secretion, [Ca²⁺](i) mobilization, α(IIb) β₃ activation, cyclic AMP release and mitogen-activated protein kinase (MAPK) phosphorylations were studied using rat platelets. PBME dose-dependently inhibited collagen, thrombin and ADP-induced platelet aggregation with an IC₅₀ of 51.0 ± 2.4, 54.0 ± 2.1 and 53.0 ± 4.3 μg/mL, respectively. Likewise, thrombin-induced [Ca²⁺](i) and collagen-activated ATP secretions were suppressed in PBME treated platelets. Aggregation and ATP secretion were also markedly attenuated by PBME alone or in combination with PP2 (Src inhibitor) and U-73122 (PLC inhibitor) in collagen-stimulated platelets. Besides, PBME treatment elevated basal cyclic AMP levels and inhibited collagen-induced integrin-α(IIb) β₃ activation. Moreover, PBME attenuated extracellular-signal-regulated protein kinase 2 (ERK2) and c-Jun N-terminal kinase 1 (JNK1) phosphorylations. Further PD98059 (ERK inhibitor) and SP60025 (JNK inhibitor) reduced collagen-induced platelet aggregation and ATP secretion. In conclusion, the observed PBME antiplatelet activity may be mediated by activation of cyclic AMP and inhibition of ERK2 and JNK1 phosphorylations. Finally, these data suggest that PBME may have therapeutic potential for the treatment of cardiovascular diseases that involve aberrant platelet function.

Inhibitory effects of Bulnesia sarmienti aqueous extract on agonist-induced platelet activation and thrombus formation involves mitogen-activated protein kinases

ETHNOPHARMACOLOGICAL RELEVANCE

B. sarmienti has long been recognized in folk medicine as a medicinal plant with various medicinal uses. Traditionally, it has been appreciated for the skin-healing properties of its essence. The bark has also been employed to treat stomach and cardiovascular disorders and reported to have antitumor, antioxidant and anti-inflammatory activities. However, information on its antiplatelet activity is limited.

AIM OF THE STUDY

To examined the effects of B. sarmienti aqueous extract (BSAE) in platelet physiology.

MATERIALS AND METHODS

The anti-platelet activity of BSAE was studied using rat platelets for in vitro determination of the extract effect on agonist-induced platelet aggregation, ATP secretion, [Ca(2+)](i) mobilization and MAP kinase phosphorylation. The extract in vivo effects was also examined in arterio-venous shunt thrombus formation in rats, and tail bleeding time in mice.

RESULT

HPLC chromatographic analysis revealed that B. sarmienti extract contained (+)-catechin (C), (-)-epigallocatechin (EGC), (-)-epicatechin (EC), and (-)-epicatechin gallate (ECG). BSAE, significantly and dose dependently, inhibited collagen, thrombin, or ADP-induced platelet aggregation. The 50 percent inhibitory concentrations (IC(50)) of the extract for collagen, thrombin and ADP-induced platelet aggregation were 45.3+/-2.6, 100+/-5.6 and 110+/-4.6 microg/ml, respectively. Collagen activated ATP release and thrombin-induced intracellular Ca(2+) concentration were reduced in BSAE-treated platelets. In addition, the extract in vivo activity showed that BSAE at 100 mg/kg significantly attenuated thrombus formation in rat extracorporeal shunt model while mice tail bleeding time was not affected. Moreover, BSAE attenuated p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase 1 (JNK1) and extracellular-signal-regulated protein kinase 2 (ERK2) phosphorylations.

CONCLUSION

BSAE inhibits platelet activation, granule secretion, aggregation, and thrombus formation without affecting bleeding time, and that this effect is mediated by inhibition of P38, JNK1 and ERK2 phosphorylations. The ability of BSAE to inhibit platelet function might be relevant in cases involving aberrant platelet activation where the plant extract could be considered as a candidate to anti-platelet and antithrombotic agent.

A noble function of BAY 11-7082: Inhibition of platelet aggregation mediated by an elevated cAMP-induced VASP, and decreased ERK2/JNK1 phosphorylations

Platelets, though anucleated, possess several transcription factors, including NF-kappaB, that exert non-genomic functions regulating platelet activation. Since platelets have not only been recognized as central players of homeostasis, but also participated in pathological conditions such as thrombosis, atherosclerosis, and inflammation, we examined rat platelet NF-kappaB expression and evaluated the effects of anti-inflammatory drug BAY 11-7082, an inhibitor of NF-kappaB activation, in platelet physiology. Western blotting revealed that rat platelets express NF-kappaB. BAY 11-7082, dose dependently, inhibited collagen- or thrombin-induced-platelet aggregation. ATP release, TXB(2) formation, P-selectin expression, and intercellular Ca(2+) concentration activated by collagen were reduced in BAY 11-7082-treated platelets. BAY 11-7082 elevated intracellular levels of cAMP, but not cGMP, and its co-incubation with cAMP-activating agent (forskolin) or its hydrolyzing enzyme inhibitor (3-isobutyl-1-methylxanthine, IBMX), synergistically inhibited collagen-induced-platelet aggregation. In addition, vasodilator-stimulated-phosphoprotein (VASP) phosphorylation was enhanced in BAY 11-7082-treated platelets, which was partially inhibited by a protein kinase A (PKA) inhibitor, H-89. Moreover, while p38 mitogen-activated protein kinase (MAPK) was not affected, BAY 11-7082 attenuated c-Jun N-terminal kinase 1 (JNK1) and extracellular-signal-regulated protein kinase 2 (ERK2) phosphorylations. In conclusion, BAY 11-7082 inhibits platelet activation, granule secretion, and aggregation, and that this effect is mediated by inhibition of JNK1 and ERK2 phosphorylations, and partially by stimulation of cAMP-dependent PKA VASP phosphorylation. The ability of BAY 11-7082 to inhibit platelet function might be relevant in cases involving aberrant platelet activation where the drug is considered as anti-atherothrombosis, and anti-inflammatory therapy.

Effects of Probiotics Supplementation on Growth Performance and Certain Haemato-biochemical Parameters in Broiler Chickens

The study was carried out to know the effects of probiotics (Protexin® Boost) supplementation on growth performances and haemato-biochemical parameters of "Shaver Star Bro" broiler chickens during the period from September to October 2003. A total of 20, day-old broiler chickens were randomly assigned into four equal groups (n = 5) as A, B, C and D. Group A was considered as control fed with commercial ration while group B, C and D were fed with commercial ration with the addition of 1 g, 2 g and 3 g probiotics / 10 litres drinking water respectively up to 35 days of age. The results showed that the body weight gains corresponding to the different treatments were differed significantly (p < 0.01) at the 1st, 2nd, 3rd, 4th and 5th weeks of age. The meat yield characteristics corresponding to the different treatments did not differ significantly (p > 0.05) whereas bursa weight differed significantly (p < 0.05) among the different groups. The mean values of Hb, PCV and ESR corresponding to the different treatments were significantly (p < 0.01) differ. Triglycerides, HDL, LDL, SGPT and SGOT values corresponding to the different treatments were also differed significantly (p < 0.01). The findings suggest that supplementation of probiotics has significant effects on live weight gain and haemato-biochemical parameters of broiler chickens. Key words: Probiotics; effects; growth; haemato-biochemical parameters; broiler chickens doi: 10.3329/bjvm.v2i1.1933 Bangl. J. Vet. Med. (2004). 2 (1) : 39-43