Mechanisms involved in the antiplatelet effect of C-phycocyanin

Effects of Arthrospira platensis-derived phycocyanin on blood cells1

The cyanobacterium Arthrospira platensis (AP) is a natural source of considerable amounts of ingredients that are relevant for nutra- and pharmaceutical uses. Beyond its nutritionally valuable components, such as carbohydrates, minerals, and proteins, bioactive ingredients extracted from AP have been studied for their therapeutical values.

Evaluation of the spectral characteristics, purity and antioxidant activity of C-phycocyanin from the cyanobacteria collected in Kaunas Lagoon (Lithuania)

The physicochemical characteristics of phycocyanin extracted from cyanobacteria collected in Kaunas Lagoon were studied (spectrum characteristics, C-PC content in the dry mass and chemical purity). It was determined that the tested concentrations of C-PC in purified water should be in the range of 0.02–0.16% for measuring C-PC content in the dry mass and its spectrum characteristics. The two clear absorption maxima were detected in the spectrum of C-PC at the wavelengths of 277 and 619 nm. The content of C-PC in the dry powder form was in the range of 7.25% to 9.30% depending on its concentration in the solution and type of spectrophotometer. Furthermore, a purity factor of 1.5 was calculated, which indicated the food qualification of the obtained biomass of C-PC. Finally, the analytical procedure for studying the pro- and anti-oxidant activity of C-PC was developed and the antioxidant activity of C-PC was measured for the available markers. It was revealed that C-PC has dual properties (pro- and anti-oxidant ones) depending on its concentration, more exactly, its content in reaction mixtures with 2,2-diphenyl-1-picrylhydrazyl (DPPH). The following issues were resolved during the research: the concentration of ethanol in the DPPH solution was chosen in order to avoid precipitation of proteins in the reaction mixtures (50%); the ratio of the solution of C-PC to the DPPH solution was selected; the selected concentrations of the markers for the construction of their calibration curves were chosen for quercetin and for rutin. The antioxidant activity of the obtained C-PC sample was determined. Keywords: antioxidant activity, C-phycocyanin, cyanobacteria, DPPH, quercetin, rutin

The Therapeutic Effect and the Possible Mechanism of C-Phycocyanin in Lipopolysaccharide and Seawater-Induced Acute Lung Injury

Background

Seawater drowning-induced acute lung injury (ALI) is a severe clinical condition characterized by increased alveolar-capillary permeability, excessive inflammatory response, and refractory hypoxemia. C-phycocyanin (C-PC), a biliprotein found in blue-green algae such as spirulina platensis, is widely used in the food and dietary nutritional supplement fields due to its beneficial pharmacological effects. Previous studies have revealed that C-PC has anti-inflammatory, antioxidant, and anti-apoptotic activities.

Purpose

Therefore, this study investigated the protective effect and underlying mechanisms of C-PC on lipopolysaccharide (LPS) and seawater (SW) induced ALI (SW and LPS-induced ALI).

Methods

An SW and LPS mouse model of ALI mice was established through intratracheal administration of 5mg/kg LPS and 25% SW. Different doses of C-PC (100, 200 and 400 mg/kg) were administered by intraperitoneal injection for seven days. In addition, gap junction communication in RAW264.7 and MLE-12 cells was determined following stimulation with 25% SW and 10 μg/ml LPS after treatment with C-PC (120 μg/ml). Moreover, the arterial partial pressure of oxygen, lung wet/dry weight ratios, total protein content and MPO levels in the bronchoalveolar lavage fluid (BALF), and the histopathologic and ultrastructure staining of the lung tissues were determined. The oxidative stress index, levels of the pro-inflammatory mediators, epithelial cell viability and apoptosis, and the regulatory effect of C-PC on the NF-κB/NLRP3 axis were investigated.

Results

The results showed that C-PC significantly alleviated pathological damages, suppressed oxidative stress, inflammation and apoptosis, and enhanced the viability of epithelial cells in the lung tissues. Furthermore, C-PC was shown to inhibit activation of the NF-κB/NLRP3 pathway and the formation of the NLRP3 inflammasome complex.

Conclusions

In conclusion, C-PC shows promising therapeutic value in SW and LPS-induced ALI/ARDS, providing new insight into ALI/ARDS treatment.

C-Phycocyanin-a novel protein from Spirulina platensis- In vivo toxicity, antioxidant and immunomodulatory studies

A pigment-protein highly dominant in Spirulina is known as C-Phycocyanin. Earlier, in vitro studies has shown that C-phycocyanin is having many biological activities like antioxidant and anti-inflammatory activities, antiplatelet, hepatoprotective, and cholesterol-lowering properties. Interestingly, there are scanty in vivo experimental findings on the immunomodulatory and antioxidant effects of C-phycocyanin. This work is aimed at in vivo evaluation of the effects of C-phycocyanin on immunomodulation and antioxidant potential in Balb/c mice. Our results of in vivo toxicity, immunomodulatory and antioxidant effects of C-Phycocyanin suggests that C-phycocyanin is very safe for consumption and having substantial antioxidant potential and also possess immunomodulatory activities in Balb/c mice in a dosage dependent manner. C-phycocyanin doesn’t cause acute and subacute toxicity in the animal model (male, Balb/c mice) studied. We have reported that C-phycocyanin exhibited in vivo immunomodulation performance in this animal model.

Protective Effect of Spirulina-Derived C-Phycocyanin against Ultraviolet B-Induced Damage in HaCaT Cells

Background and objectives: Reactive oxygen species (ROS) overwhelm the antioxidant defense system, induce oxidative stress, and increase matrix metalloproteinase (MMP) expression, resulting in skin aging. Thus, preventing ultraviolet B (UVB)-induced skin damage can attenuate skin aging. Spirulina (a biomass of cyanobacteria, also called blue-green algae) is comprised of prokaryotes, whereas microalgae are eukaryotes and are rich in phycocyanin, a powerful antioxidant. Materials and Methods: Here, we investigated the photoprotective effects of spirulina-derived C-phycocyanin (C-PC) against UVB radiation using keratinocytes (HaCaT cells). Results: UVB radiation increased MMP-1 and MMP-9 expression but decreased involucrin, filaggrin, and loricrin expression. C-PC showed no toxicity at concentrations of 5–80 μg/mL in terms of HaCaT cell viability. UVB-irradiated HaCaT cells had a 50.8% survival rate, which increased to 80.3% with C-PC treatment. MMP expression increased with UVB treatment, whereas MMP-1 and MMP-9 concentrations decreased with C-PC treatment. UVB reduced involucrin, filaggrin, and loricrin expression in HaCaT cells, but 80 μg/mL C-PC increased their expression by >25%. In the UVB radiation group, dichlorofluorescin diacetate fluorescence intensity in HaCaT cells increased by 81.6% compared with that in the control group, whereas ROS production was reduced by 51.2% and 55.1% upon treatment with 40 and 80 μg/mL C-PC, respectively. Conclusions: C-PC might reduce or prevent skin aging by reducing UVB irradiation-induced skin wrinkles and free radicals.

Lactic Acid Fermentation of Arthrospira platensis (Spirulina) in a Vegetal Soybean Drink for Developing New Functional Lactose-Free Beverages

The main objective of this study was to evaluate the suitability of Arthrospira platensis F&M-C256 (spirulina) biomass in a vegetal soybean drink or in water, as substrate for lactic acid fermentation by the probiotic bacterium Lactiplantibacillus plantarum ATCC 8014 (LAB8014) and to evaluate the fermented products in terms of bacteria content and organic acids content, biochemical composition, total phenolics, and phycocyanin content, in vitro digestibility, in vitro and in vivo antioxidant activity. After 72 h of fermentation, a bacterial concentration of about 10.5 log CFU mL^–1 in the broths containing the soybean drink + spirulina + LAB8014 (SD + S + LAB8014) or water + spirulina + LAB8014 (W + S + LAB8014) was found. Lactic acid concentration reached similar values (about 1.7 g L^–1) in the two broths, while a different acetic acid concentration between SD + S + LAB8014 and W + S + LAB8014 broths was observed (7.7 and 4.1 g L^–1, respectively). A. platensis biomass was shown to be a suitable substrate for LAB8014 growth. After fermentation, both broths contained a high protein content (>50%). In both broths, total phenolics, in vitro and in vivo antioxidant activity increased after fermentation (+35, +20, and +93% on average, respectively), while phycocyanin content decreased (−40% on average). Digestibility of W + S + LAB8014 broth statistically improved after fermentation. This study highlights the potential of A. platensis F&M-C256 biomass as a substrate for the production of new functional lactose-free beverages.

Mechanisms of the antiplatelet and analgesic effects of dextromethorphan and its metabolites

Objective:

In the present study, we investigated the effects of dextromethorphan (DM) and its metabolites, including dextrorphan (LK2), 3-methoxymorphinan (LK3), and 3-hydroxymorphinan (LK4), on platelet aggregation in vitro and the inflammatory pain caused by carrageenan in rats, and their underlying mechanisms.

Materials and Methods:

Rabbit platelets were pretreated with DM or its metabolites to assess their effects on platelet aggregation and related target mediators. In addition, the analgesic activity and the underlying mechanisms of DM and LK3 were investigated in a carrageenan-evoked thermal hyperalgesia rat model.

Results:

The inhibitory potency of DM and its metabolites on platelet aggregation induced by arachidonic acid or collagen was LK3> DM > LK4>> LK2 as demonstrated by the half-maximal inhibitory concentration values. Moreover, the mechanisms of the antiplatelet effect of DM and LK3 may involve the inhibition of intracellular calcium mobilization, expression of platelet surface glycoprotein IIb/IIIa, the formation of thromboxane B₂, and elevation of platelet membrane fluidity. DM and LK3 also exhibited analgesic effects on carrageenan-evoked thermal hyperalgesia by suppressing the production of pro-inflammatory cytokines, nitric oxide, prostaglandin E₂, and neutrophil infiltration in inflammatory sites.

Conclusion:

DM and its metabolites, especially LK3, exhibit both antiplatelet and analgesic effects, and may, therefore, potentially ameliorate platelet hyperactivity and inflammatory-related diseases.

Phycocyanin Protects Against UVB-induced Apoptosis Through the PKC α/βII-Nrf-2/HO-1 Dependent Pathway in Human Primary Skin Cells

Phycocyanin (Pc) is one of the active pigment constituents of Spirulina microalgae. It has been used for its potent antioxidant and anti-inflammatory properties. However, the protective effects of Pc against ultraviolet-B (UVB)-induced primary skin cells damage are still undefined. In the present study, we investigated whether Pc prevented UVB-induced apoptotic cell death in human dermal fibroblasts (HDF) and human epidermal keratinocytes (HEK). Pc induced the transcription of heme oxygenase-1 (HO-1). Furthermore, Pc treatments resulted in a marked increase in nuclear factor erythroid-derived 2 (NF-E2)-like 2 (Nrf-2) nuclear translocation. Also, Pc protected UVB induced apoptosis and reduced the p53 and Bax levels, as well as caspase-3 activation. Pc treatment showed a significantly enhanced effect on the phosphorylation of protein kinase C (PKC) α/β II, but not that of p38 mitogen-activated protein kinase (MAPK) or Akt. Induction of HO-1 induced by Pc was suppressed by Go6976, a selective inhibitor of PKC α/β II. In addition, knockdown of HO-1 by small interfering (siRNA) caused a significant increase in poly (ADP-ribose) polymerase 1 (PARP-1) cleavage and caspase-3 activation after Pc pretreatment. Taken together, our results demonstrate that Pc-induced expression of HO-1 is mediated by the PKC α/β II-Nrf-2/HO-1 pathway, and inhibits UVB-induced apoptotic cell death in primary skin cells.

Clinical Safety of a High Dose of Phycocyanin-Enriched Aqueous Extract from Arthrospira (Spirulina) platensis: Results from a Randomized, Double-Blind, Placebo-Controlled Study with a Focus on Anticoagulant Activity and Platelet Activation

The goal for this study was to evaluate safety regarding anticoagulant activity and platelet activation during daily consumption of an aqueous cyanophyta extract (ACE), containing a high dose of phycocyanin. Using a randomized, double-blind, placebo-controlled study design, 24 men and women were enrolled after informed consent, and consumed either ACE (2.3 g/day) or placebo daily for 2 weeks. The ACE dose was equivalent to ∼1 g phycocyanin per day, chosen based on the highest dose Generally Recognized as Safe (GRAS) by the U.S. Food and Drug Administration. Consuming ACE did not alter markers for platelet activation (P-selectin expression) or serum P-selectin levels. No changes were seen for activated partial thromboplastin time, thrombin clotting time, or fibrinogen activity. Serum levels of aspartate transaminase (AST) showed a significant reduction after 2 weeks of ACE consumption (P < .001), in contrast to placebo where no changes were seen; the difference in AST levels between the two groups was significant at 2 weeks (P < .02). Reduced levels of alanine transaminase (ALT) were also seen in the group consuming ACE (P < .08). Previous studies showed reduction of chronic pain when consuming 1 g ACE per day. The higher dose of 2.3 g/day in this study was associated with significant reduction of chronic pain at rest and when physically active (P < .05). Consumption of ACE showed safety regarding markers pertaining to anticoagulant activity and platelet activation status, in conjunction with rapid and robust relief of chronic pain. Reduction in AST and ALT suggested improvement in liver function and metabolism.

Medicinal Plants with Antiplatelet Activity

Blood platelets play an essential role in the hemostasis and wound-healing processes. However, platelet hyperactivity is associated to the development and the complications of several cardiovascular diseases. In this sense, the search for potent and safer antiplatelet agents is of great interest. This article provides an overview of experimental studies performed on medicinal plants with antiplatelet activity available through literature with particular emphasis on the bioactive constituents, the parts used, and the various platelet signaling pathways modulated by medicinal plants. From this review, it was suggested that medicinal plants with antiplatelet activity mainly belong to the family of Asteraceae, Rutaceae, Fabaceae, Lamiaceae, Zygophyllaceae, Rhamnaceae, Liliaceae, and Zingiberaceae. The antiplatelet effect is attributed to the presence of bioactive compounds such as polyphenols, flavonoids, coumarins, terpenoids, and other substances which correct platelet abnormalities by interfering with different platelet signalization pathways including inhibition of the ADP pathway, suppression of TXA2 formation, reduction of intracellular Ca(2+) mobilization, and phosphoinositide breakdown, among others. The identification and/or structure modification of the plant constituents and the understanding of their action mechanisms will be helpful in the development of new antiplatelet agents based on medicinal plants which could contribute to the prevention of thromboembolic-related disorders by inhibiting platelet aggregation. Copyright © 2016 John Wiley & Sons, Ltd.

Antioxidant and anti-inflammatory properties of an aqueous cyanophyta extract derived from Arthrospira platensis: contribution to bioactivities by the non-phycocyanin aqueous fraction

The goal for this work was to characterize basic biological properties of a novel Arthrospira platensis-based aqueous cyanophyta extract (ACE), enriched in the known anti-inflammatory cyclooxygenase-2 (COX-2) inhibitor phycocyanin (PC), but also containing a high level of non-PC bioactive compounds. Antioxidant properties were tested in parallel in the Folin–Ciocalteu assay (chemical antioxidant capacity) and in the cellular antioxidant protection (CAP-e) bioassay, where both the PC and the non-PC fractions contributed to the antioxidant capacity and CAP of ACE. In contrast to the COX-2 inhibition seen in the presence of PC, the inhibition of enzymatic activity of the inflammatory mediator Lipoxygenase was associated specifically with the non-PC fraction of ACE. Inhibition of formation of reactive oxygen species (ROS) was evaluated using polymorphonuclear cells from healthy human donors. The inhibition of ROS formation was seen for both the PC and non-PC fractions, with ACE showing the most robust effect. The effects of PC, non-PC, and ACE on clotting and clot lysing was tested using a modified Euglobulin fibrinolytic assay in vitro. In the presence of PC, non-PC, and ACE, the time for clot formation and lysis was not affected; however, the clots were significantly more robust. This effect was statistically significant (p<.05) at doses between 125–500 μg/mL, and returned to baseline at lower doses. Both PC and the non-PC fraction contributed to the antioxidant properties and anti-inflammatory effects, without a negative impact on blood clotting in vitro. This suggests a potential benefit for the consumable ACE extract in assisting the reduction of inflammatory conditions.

New mechanisms of antiplatelet activity of nifedipine, an L-type calcium channel blocker

Platelet hyperactivity often occursd in hypertensive patients and is a key factor in the development of cardiovascular diseases including thrombosis and atherosclerosis. Nifedipine, an L-type calcium channel blocker, is widely used for hypertension and coronary heart disease therapy. In addition, nifedipine is known to exhibit an antiplatelet activity, but the underlying mechanisms involved remain unclear. Several transcription factors such as peroxisome proliferator-activated receptors (PPARs) and nuclear factor kappa B (NF-κB) exist in platelets and have an ability to regulate platelet aggregation through a non-genomic mechanism. The present article focuses on describing the mechanisms of the antiplatelet activity of nifedipine via PPAR activation. It has been demonstrated that nifedipine treatment increases the activity and intracellular amount of PPAR-β/-γ in activated platelets. Moreover, the antiplatelet activity of nifedipine is mediated by PPAR-β/-γ-dependent upon the up-regulation of the PI3K/AKT/NO/cyclic GMP/PKG pathway, and inhibition of protein kinase Cα (PKCα) activity via an interaction between PPAR-β/-γ and PKCα. Furthermore, suppressing NF-κB activation by nifedipine through enhanced association of PPAR-β/-γ with NF-κB has also been observed in collagen-stimulated platelets. Blocking PPAR-β/-γ activity or increasing NF-κB activation greatly reverses the antiplatelet activity and inhibition of intracellular Ca²⁺ mobilization, PKCα activity, and surface glycoprotein IIb/IIIa expression caused by nifedipine. Thus, PPAR-β/-γ- dependent suppression of NF-κB activation also contributes to the antiplatelet activity of nifedipine. Consistently, administration of nifedipine markedly reduces fluorescein sodium-induced vessel thrombus formation in mice, which is considerably inhibited when the PPAR-β/-γ antagonists are administrated simultaneously. Collectively, these results provide important information regarding the mechanism by which nifedipine inhibits platelet aggregation and thrombus formation through activation of PPAR-β/-γ- mediated signaling pathways. These findings highlight that PPARs are novel therapeutic targets for preventing and treating platelet-hyperactivity-related vascular diseases.

Relationship between Platelet PPARs, cAMP Levels, and P-Selectin Expression: Antiplatelet Activity of Natural Products

Platelets are no longer considered simply as cells participating in thrombosis. In atherosclerosis, platelets are regulators of multiple processes, with the recruitment of inflammatory cells towards the lesion sites, inflammatory mediators release, and regulation of endothelial function. The antiplatelet therapy has been used for a long time in an effort to prevent and treat cardiovascular diseases. However, limited efficacy in some patients, drug resistance, and side effects are limitations of current antiplatelet therapy. In this context, a large number of natural products (polyphenols, terpenoids, alkaloids, and fatty acids) have been reported with antiplatelet activity. In this sense, the present paper describes mechanisms of antiplatelet action of natural products on platelet P-selectin expression through cAMP levels and its role as peroxisome proliferator-activated receptors agonists.

Therapeutic effect of C-phycocyanin extracted from blue green algae in a rat model of acute lung injury induced by lipopolysaccharide

C-Phycocyanin (CPC), extracted from blue green algae, is a dietary nutritional supplement due to its several beneficial pharmacological effects. This study was conducted to evaluate whether CPC protects against lipopolysaccharide- (LPS-) induced acute lung injury (ALI) in rats. Rats were challenged with LPS (5 mg/kg body weight) intratracheally to induce ALI. After 3 h LPS instillation, rats were administrated with CPC (50 mg/kg body weight, i.p.) for another 3 h. Our results showed that posttreatment with CPC significantly inhibited LPS-induced elevation of protein concentration, nitrite/nitrate level, release of proinflammatory cytokines, the number of total polymorphonuclear cells in bronchoalveolar lavage fluid, and lung edema evidenced by decrease of lung wet/dry weight ratio accompanied by a remarkable improvement of lung histopathological alterations. Furthermore, CPC significantly attenuated LPS-induced myeloperoxidase activity, O2 (-) formation, expression of inducible nitric oxide synthase, and cyclooxygenase-2 as well as nuclear factor-kappa B (NF- κ B) activation in lungs. Additionally, CPC significantly downregulated proapoptotic proteins such as caspase-3 and Bax, but upregulated antiapoptotic proteins such as Bcl-2 and Bcl-XL in lungs exposed to LPS. These findings indicate that CPC could be potentially useful for treatment of LPS-related ALI by inhibiting inflammatory responses and apoptosis in lung tissues.

Anti-oxidative and anti-inflammatory effects of spirulina on rat model of non-alcoholic steatohepatitis

The pathogenesis of nonalcoholic steatohepatitis (NASH) remains unclear, but accumulating data suggest oxidative stress and the relationship between inflammation and immunity plays a crucial role. The aim of this study is to investigate the spirulina, which is a blue-green algae rich in proteins and other nutritional elements, and its component-phycocyanin effect on a rat model of NASH. NASH model rats were established by feeding male Wistar rats with choline-deficient high-fat diet (CDHF) and intermittent hypoxemia by sodium nitrite challenge after 5 weeks of CDHF. After experimental period of 10 weeks, blood and liver were collected to determine oxidative stress injuries and efficacies of spirulina or phycocyanin on NASH model rats. In the NASH model rats, increase in plasma liver enzymes and liver fibrosis, increases in productions of reactive oxygen species from liver mitochondria and from leukocytes, the activation of nuclear factor-kappa B, and the change in the lymphocyte surface antigen ratio (CD4(+)/CD8(+)) were observed. The spirulina and phycocyanin administration significantly abated these changes. The spirulina or phycocyanin administration to model rats of NASH might lessen the inflammatory response through anti-oxidative and anti-inflammatory mechanisms, breaking the crosstalk between oxidative stress and inflammation, and effectively inhibit NASH progression.

Antimelanogenic effect of c-phycocyanin through modulation of tyrosinase expression by upregulation of ERK and downregulation of p38 MAPK signaling pathways

Background

Pigmentation is one of the essential defense mechanisms against oxidative stress or UV irradiation; however, abnormal hyperpigmentation in human skin may pose a serious aesthetic problem. C-phycocyanin (Cpc) is a phycobiliprotein from spirulina and functions as an antioxidant and a light harvesting protein. Though it is known that spirulina has been used to reduce hyperpigmentation, little literature addresses the antimelanogenic mechanism of Cpc. Herein, we investigated the rationale for the Cpc-induced inhibitory mechanism on melanin synthesis in B16F10 melanoma cells.

Methods

Cpc-induced inhibitory effects on melanin synthesis and tyrosinase expression were evaluated. The activity of MAPK pathways-associated molecules such as MAPK/ERK and p38 MAPK, were also examined to explore Cpc-induced antimelanogenic mechanisms. Additionally, the intracellular localization of Cpc was investigated by confocal microscopic analysis to observe the migration of Cpc.

Results

Cpc significantly (P < 0.05) reduced both tyrosinase activity and melanin production in a dose-dependent manner. This phycobiliprotein elevated the abundance of intracellular cAMP leading to the promotion of downstream ERK1/2 phosphorylation and the subsequent MITF (the transcription factor of tyrosinase) degradation. Further, Cpc also suppressed the activation of p38 causing the consequent disturbed activation of CREB (the transcription factor of MITF). As a result, Cpc negatively regulated tyrosinase gene expression resulting in the suppression of melanin synthesis. Moreover, the entry of Cpc into B16F10 cells was revealed by confocal immunofluorescence localization and immunoblot analysis.

Conclusions

Cpc exerted dual antimelanogenic mechanisms by upregulation of MAPK/ERK-dependent degradation of MITF and downregulation of p38 MAPK-regulated CREB activation to modulate melanin formation. Cpc may have potential applications in biomedicine, food, and cosmetic industries.

Comparative Effects of α-, β-, and γ-Carbolines on Platelet Aggregation and Lipid Membranes

Cigarette smoking and alcohol consumption possibly affect platelet functions. To verify the hypothesis that some α-, β-, and γ-carboline components in cigarette smoke and alcoholic beverages may change platelet aggregability, their effects on human platelets were determined by aggregometry together with investigating their membrane effects by turbidimetry. Carbolines inhibited platelet aggregation induced by five agents with the potency being 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole > 3-amino-1-methyl-5H-pyrido[4,3-b]indole > 1-methyl-9H-pyrido[3,4-b]indole. The most potent 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole showed 50% aggregation-inhibitory concentrations of 6–172 μM. Both γ-carbolines interacted with phosphatidylcholine membranes to lower the lipid phase transition temperature with the potency correlating to the antiplatelet activity, suggesting that the interaction with platelet membranes to increase their fluidity underlies antiplatelet effects. Given their possible concentration and accumulation in platelets, γ- and β-carbolines would provide cigarette smokers and alcohol drinkers with reduced platelet aggregability, and they may be responsible for the occurrence of hemorrhagic diseases associated with heavy smoking and alcoholics.

Comparative effects of β-carbolines on platelet aggregation and lipid membranes

The effects of 14 β-carbolines on human platelet aggregability were comparatively studied, and the effects on lipid membranes were determined. Several β-carbolines inhibited platelet aggregation induced by collagen, epinephrine, adenosine 5'-diphosphate, platelet-activating factor and thrombin. This activity was structure-dependent. Of all the compounds examined, 1-methyl-1,2,3,4-tetrahydro-β-carboline was the most potent. Treatment with 15-177 μM 1-methyl-1,2,3,4-tetrahydro-β-carboline inhibited the aggregation responses to different stimulants by up to 50%. Its potency was comparable to or greater than that of the antiplatelet reference, aspirin. The next most effective compound was 1-methyl-3,4-dihydro-β-carboline. The structure-antiplatelet activity relationship indicated that this activity is reduced by oxidation to 1-methyl-β-carboline, by demethylation to 1,2,3,4-tetrahydro-β-carboline and by 6-hydroxylation, 7-hydroxylation and 3-carboxylation. Active 1-methyl-1,2,3,4-tetrahydro-β-carboline fluidized biomimetic membranes at 25-250 μM which corresponded to the antiaggregatory concentrations, although relatively inactive 6-hydroxy-1-methyl-1,2,3,4-tetrahydro-β-carboline showed no significant effects on the membranes. β-Carbolines are considered to be effective antiplatelet agents that inhibit human platelet aggregation by interacting with lipid membranes to modify fluidity.

Attenuation of diabetic complications by C-phycoerythrin in rats: antioxidant activity of C-phycoerythrin including copper-induced lipoprotein and serum oxidation

In the present study, the protective role of purified C-phycoerythrin (C-PE) against diabetic complications and Cu-mediated lipoprotein oxidation was evaluated. C-PE (25 and 50 mg/kg body weight per d) was administered to experimental streptozotocin-nicotinamide-induced type 2 diabetic male rats for 28 d. C-PE treatment successfully ameliorated diabetic complications by decreasing food intake, organ weights, serum concentrations of glucose, cholesterol, TAG, VLDL-cholesterol, creatinine, uric acid and thiobarbituric acid-reactive substances (TBARS), with increases in body weight, Hb, total protein, bilirubin and ferric-reducing ability of plasma values. Hepatic and renal tissues demonstrated significant decreases in TBARS, lipid hydroperoxide and conjugated diene contents, with increases in superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione, vitamin E and vitamin C levels. Furthermore, the 4-week ex vivo and in vitro administration of C-PE (0.5 and 1.0 mg/ml) indicated a decrease in Cu-mediated serum oxidation. The kinetics of the LDL oxidation profile showed significant prolongation of the lag phase with declines in oxidation rate, conjugated dienes, lipid hydroperoxide and TBARS. Results indicated the involvement of C-PE in the amelioration of diabetic complications by significant reductions in oxidative stress and oxidised LDL-triggered atherogenesis.

Strategies for antiplatelet targets and agents

Platelets play a key role in thrombosis and haemostasis, which can be either beneficial or deleterious depending on the circumstance. Antiplatelet therapy is the 'cornerstone' in the prevention and treatment of thrombotic diseases. Platelet activation is a complex process known as transmembrane signaling which then serves to activate the platelet via a cascade of biochemical interactions. Currently available strategies of antiplatelet therapy are generally based on the signaling pathway of platelet activation, which possess the characters that mono-agent, mono-target, and mainly irreversible inhibition. Therefore, both established and novel antiplatelet agents have their own pros and cons and such problems as resistance, drug-drug interaction, discontinuation and monitoring, etc. have been appeared. Due to the problems existing in current antiplatelet agents, future new strategies for antiplatelet targets, agent-developing and treatment might probably include three aspects: targeting the factors associated with platelet hyperactivity, developing novel antiplatelet agents with multiple targets, mild and reversible properties from natural products, and keeping healthy lifestyle and emphasizing prevention.

Anti-inflammatory activity of c-phycocyanin in lipopolysaccharide-stimulated RAW 264.7 macrophages

C-phycocyanin (C-PC), found in blue green algae, is often used as a dietary nutritional supplement. C-PC has been found to have an anti-inflammatory activity and exert beneficial effect in various diseases. However, little is known about its mechanism of action. Overproduction of nitric oxide (NO) derived from inducible nitric oxide synthase (iNOS) plays an important role in the pathogenesis of inflammation. The aim of this study was to determine whether C-PC inhibits production of nitrite, an index of NO, and iNOS expression in lipopolysaccharide (LPS)-treated RAW 264.7 macrophages. Our results indicated that C-PC significantly inhibited the LPS-induced nitrite production and iNOS protein expression accompanied by an attenuation of tumor necrosis factor-alpha (TNF-alpha) formation but had no effect on interleukin-10 production in macrophages. Furthermore, C-PC also suppressed the activation of nuclear factor-kappaB (NF-kappaB) through preventing degradation of cytosolic IkappaB-alpha in LPS-stimulated RAW 264.7 macrophages. Thus, the inhibitory activity of C-PC on LPS-induced NO release and iNOS expression is probably associated with suppressing TNF-alpha formation and nuclear NF-kappaB activation, which may provide an additional explanation for its anti-inflammatory activity and therapeutic effect.