Molecular Mechanisms of Leonurus Cardiaca L. Extract Activity in Prevention of Staphylococcal Endocarditis-Study on in Vitro and ex Vivo Models.

Better understanding the mechanisms of Leonurus cardiaca L. extract (LCE) activity is necessary to prepare recommendations for the use of LCE-based herbal products for preventive/supportive purposes in case of infective endocarditis (IE) and other staphylococcal invasive infections. The aim of the study was to analyze molecular mechanisms of LCE effect on Staphylococcus aureus and blood platelets in the context of their interactions playing a pivotal role in such disorders. Using atomic force microscopy, we demonstrated that adhesion forces of S. aureus were markedly reduced after exposure to LCE at subinhibitory concentrations. The effect resulted from the impact of LCE on S. aureus cell morphology and the composition of phospholipids and fatty acids in bacterial membranes (assessed by HPLC), which modulated their stabilization, hydrophobicity, and charge. Moreover, using FACS we showed also that LCE significantly reduced GP IIb/IIIa expression on blood platelets, thus the disruption of platelet-fibrinogen interactions seems to explain antiplatelet effect of LCE. The obtained results prove the usefulness of LCE in the prevention of S. aureus adhesion, platelet activation, and vegetations development, however, also pointed out the necessity of excluding the cationic antibiotics from the treatment of S. aureus-associated IE and other invasive diseases, when motherwort herb is used simultaneously as an addition to the daily diet.

New biological potential of abietane diterpenoids isolated from Salvia austriaca against microbial virulence factors.

The increasing importance of multi-resistant strains and microbial biofilms in the development of chronic infections has driven the search for more effective alternative therapy including plant-origin preparations. The present study evaluates the broadly-defined antimicrobial activity of two abietane diterpenoids isolated from Salvia austriaca transformed roots: taxodone and 15-deoxy-fuerstione. The direct biostatic/biocidal effect of these phytocompounds and their influence on Staphylococcus aureus and Candida albicans virulence factors/mechanisms (adhesion, biofilm formation, agglutination in human plasma, survival in the blood, germ tube and mycelium formation) were tested using in vitro assays. Both phytocompounds significantly inhibited microbial adhesion and biofilm formation when used at ½ and » MIC. Additionally, taxodone was able to limit staphylococcal survival in human blood, as well as C. albicans germ tube formation and hyphal growth. The tested diterpenoids express significant anti-biofilm activity against both staphylococci and yeast, and adversely affect their virulence factors/mechanisms, which are relevant in the course of the infection in vivo. Therefore, they demonstrate considerable biomedical potential as complements for classic therapy with antibiotics.

[The role of blood platelets in infections]. / Rola plytek krwi w zakazeniach.

Platelets are primarily associated with their main function, hemostasis, although it is known that these cells also exhibit biological activity in cancer progression, inflammation and infectious processes. During infection platelets, due to the expression of specific receptors - Toll-like receptors (TLRs) - which recognize molecular patterns associated with pathogens - pathogen-associated molecular patterns (PAMPs) - are activated by the presence of microorganism components and/or substances released from damaged cells/tissue. Further antimicrobial activity of platelets is based on their capacity for phagocytosis, generation of reactive oxygen species (ROS), and the synthesis, storage and release of proteins/peptides with antimicrobial activity. Another mechanism of platelet action is their immunomodulatory activity. It is based mainly on the ability to secrete chemotactic factors allowing the accumulation of professional immunocompetent cells at the site of infection, thus enhancing the effective eradication of an infectious agent. In chronic infections, platelets, due to release of numerous growth factors and various cytokines, support mechanisms of acquired immunity. They accelerate the maturation of dendritic cells, stimulate B cells to be immunoglobulin-producing plasma cells and potentiate the activity of T cells. Unfortunately, in certain situations (the existence of specific risk factors) the interaction of microorganisms with activated platelets may also be the cause of pathology within the cardiovascular system.

Saponins of Trifolium spp. aerial parts as modulators of Candida albicans virulence attributes.

The aim was to provide the insight into the biology of C. albicans influenced by undescribed yet properties of saponin-rich (80%-98%) fractions (SAPFs), isolated from extracts of Trifolium alexandrinum, T. incarnatum, T. resupinatum var. resupinatum aerial parts. Their concentrations below 0.5 mg/mL were arbitrarily considered as subMICs for C. albicans ATCC 10231 and were further used. SAPFs affected yeast enzymatic activity, lowered tolerance to the oxidative stress, to the osmotic stress and to the action of the cell wall disrupting agent. In their presence, germ tubes formation was significantly and irreversibly inhibited, as well as Candida invasive capacity. The evaluation of SAPFs interactions with anti-mycotics showed synergistic activity, mainly with azoles. Fluconazole MIC was lowered-susceptible C. albicans ATCC 10231 was more susceptible, and resistant C. glabrata (clinical strain) become more susceptible (eightfold). Moreover, the tested samples showed no hemolytic activity and at the concentrations up to 0.5 mg/mL did not reduce viability of fibroblasts L929. This study provided the original evidence that SAPFs of Trifolium spp. aerial part exhibit significant antimicrobial activity, by reduce the expression/quantity of important Candida virulence factors and have good potential for the development of novel antifungal products supporting classic drugs.

Antimicrobial/anti-biofilm activity of expired blood platelets and their released products.

INTRODUCTION: Although platelets are not part of the classical immune system, they have many features that indicate their role in the anti-infective host defense. They come into interactions with microorganisms, which results in co-aggregation and co-adhesion or destruction of the microbes due to the action of antimicrobial peptides released from platelets.The aim of this study was to evaluate the killing effect of platelets against planktonic and biofilm cultures of Staphylococcus aureus and to test their synergy with antibiotics. MATERIALS AND METHODS: S. aureus ATCC 29213; platelet rich plasma (1-3 days post shelf life). Evaluation of bactericidal activity of platelets or their lysates against planktonic cultures of S. aureus--CFU calculation after 4- and 24-hour co-incubation. Assessment of S. aureus biofilm viability under the influence of platelets--Live/Dead® BacLight™ Bacterial Viability Kit. Determination of minimum inhibitory concentrations (MICs) (oxacillin, vancomycin, linezolid) and estimation of the synergistic action of antibiotics and platelet lysates--a gradient-diffusion test strip. RESULTS: Microbicidal activity of "expired" platelets and their lysates has been shown as a significant reduction in the population of staphylococci in their planktonic cultures by 56-87% and a decrease in metabolic activity of biofilm formation by 7-38%. These activities were enhanced after activation with ADP. Platelet lysates showed a synergistic effect with ß-lactam antibiotic (oxacillin) and glycopeptide (vancomycin) but not with oxazolidinone (linezolid). CONCLUSIONS AND DISCUSSION: In summary, platelets even after the medical expiry date are still a good source of antimicrobial low molecular weight proteins (PMPs). Testing of bacterial resistance to PMPs may be advisable as a predictive indicator of susceptibility to treatment of infections such as infective endocarditis and other local infections of biofilm nature.

The immunomodulatory potential of Leonurus cardiaca extract in relation to endothelial cells and platelets.

The immunomodulatory activity of Leonurus cardiaca L. polyphenol-rich extract (LCE) was tested in vitro on HUVECs to explore its potential therapeutic usefulness in the treatment of inflammatory lesions. The phytochemical composition of LCE, its antioxidant and cytotoxic activity, and the influence of LCE on NO and platelet-activating factor (PAF) secretion by HUVECs and platelet aggregation were all assessed. Total polyphenol contents in LCE reached 137.0 ± 0.8 mg/g, with hydroxycinnamic acid derivatives as the predominant phenolic compounds. LCE expressed antioxidant capacity, which was, however, 13- to 16-fold lower than the antioxidant activity of ascorbic acid. The plant extract was not cytotoxic up to a concentration 4500 µg/ml and did not exhibit proapoptotic activity. LCE significantly increased NO production in HUVECs in a concentration-dependent manner and led to the inhibition of PAF secretion induced by staphylococcal peptidoglycan. The extract used at the concentration of 100 µg/ml significantly reduced platelet aggregation in the presence of arachidonic acid. We provide in vitro data demonstrating the immunomodulatory potential of LCE, which may be beneficial in preventing the development of difficult-to-treat inflammatory lesions within chronically infected tissues.

Is it true that plant-derived polyphenols are always beneficial for the human? In vitro study on Leonurus cardiaca extract properties in the context of the pathogenesis of Staphylococcus aureus infections.

The aim of the study was to determine whether Leonurus cardiaca L. herb extract (LCE) used at subinhibitory concentration modifies the characteristics of Staphylococcus aureus, which is important in the pathogenesis of invasive infections originating from the bloodstream, in a way favourable for the human host. Polyphenol-rich LCE, a common ingredient in pharmaceutical products used for various cardiovascular and nervous system disorders, had shown interesting antibacterial and antibiofilm properties in our previous studies. Our current findings indicate that the following S. aureus characteristics decreased, depending on the LCE concentration: (i) formation of aggregates in plasma, (ii) adherence to a fibrin-coated surface, (iii) staphylocoagulase-dependent plasma clotting, (iv) bacterial survival in whole human blood in an ex vivo model, (v) expression of cell surface protein A and (vi) synthesis of α-toxin. However, staphylococcal tolerance to exogenous hydrogen peroxide was enhanced after pre-incubation with LCE, possibly due to the increased activity of bacterial antioxidant enzymes, a possibility confirmed by the higher production of superoxide dismutase and slightly higher production of catalase. The use of LCE at sub-MIC in in vitro and ex vivo models resulted in the weakening of some important staphylococcal immunoprotective attributes but the strengthening of such virulence factors as those responsible for oxidative stress tolerance. Some of these results and the fact that LCE has direct anticoagulant properties, reflected in a reduced thrombin-dependent fibrinogen polymerization rate, suggest a risk of adverse effects, which could be important in the context of S. aureus survival in the host.

Leonurus cardiaca L. herb--a derived extract and an ursolic acid as the factors affecting the adhesion capacity of Staphylococcus aureus in the context of infective endocarditis.

The objective was an assessment of the impact of Leonurus cardiaca L. extract (LCE) and ursolic acid (UA) on the adhesive properties of Staphylococus aureus NCTC 8325 strain, expressing virulence factors important in the pathogenesis of infective endocarditis. The adhesion and biofilm formation of bacteria cultured in the presence of subinhibitory concentrations of LCE or UA on the abiotic surface or covered with fibrinogen, fibronectin or collagen, were evaluated. Inhibitory effects of LCE and UA on staphylococcal adherence to both types of surface were demonstrated. This, in the case of UA, resulted in a significant reduction of biofilm formation.

Antiadherent and antibiofilm activity of Humulus lupulus L. derived products: new pharmacological properties.

New antimicrobial properties of products derived from Humulus lupulus L. such as antiadherent and antibiofilm activities were evaluated. The growth of gram-positive but not gram-negative bacteria was inhibited to different extents by these compounds. An extract of hop cones containing 51% xanthohumol was slightly less active against S. aureus strains (MIC range 31.2-125.0 µg/mL) than pure xanthohumol (MIC range 15.6-62.5 µg/mL). The spent hop extract, free of xanthohumol, exhibited lower but still relevant activity (MIC range 1-2 mg/mL). There were positive coactions of hop cone, spent hop extracts, and xanthohumol with oxacillin against MSSA and with linezolid against MSSA and MRSA. Plant compounds in the culture medium at sub-MIC concentrations decreased the adhesion of Staphylococci to abiotic surfaces, which in turn caused inhibition of biofilm formation. The rate of mature biofilm eradication by these products was significant. The spent hop extract at MIC reduced biofilm viability by 42.8%, the hop cone extract by 74.8%, and pure xanthohumol by 86.5%. When the hop cone extract or xanthohumol concentration was increased, almost complete biofilm eradication was achieved (97-99%). This study reveals the potent antibiofilm activity of hop-derived compounds for the first time.