In vitro anti-inflammatory and anti-coagulant effects of antibiotics towards Platelet Activating Factor and thrombin.

Alexandros B Tsoupras,Nickolaos Tsogas,Constantinos A Demopoulos,George Tsekes,Maria Chini,Athina Lioni,Marios C Lazanas

doi:10.1186/1476-9255-8-17

Alexandros B Tsoupras, Nickolaos Tsogas + Show 5 more

Open Access

https://doi.org/10.1186/1476-9255-8-17

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Abstract

BackgroundSepsis is characterized as a systemic inflammatory response that results from the inability of the immune system to limit bacterial spread during an ongoing infection. In this condition the significant mediator of inflammation Platelet Activating Factor (PAF) and the coagulant factor thrombin are implicated. In animal models, treatment with PAF-antagonists or co-administration of antibiotics with recombinant-PAF-Acetylhydrolase (rPAF-AH) have exhibited promising results. In order to examine the putative anti-inflammatory and/or antithrombotic interactions between antibiotic treatment used in sepsis with PAF and/or thrombin, we studied the in vitro effects of these compounds towards PAF or/and thrombin related activities and towards PAF basic metabolic enzymes.MethodsWe assessed the inhibitory effect of these drugs against PAF or thrombin induced aggregation on washed rabbit platelets (WRPs) or rabbit Platelet Reach Plasma (rPRP) by evaluating their IC50 values. We also studied their effect on Cholinephosphotransferase of PAF (PAF-CPT)/Lyso-PAF-Acetyltransferase (Lyso-PAF-AT) of rabbit leukocytes (RLs), as well as on rabbit plasma-PAF-AH, the key enzymes of both de novo/remodelling PAF biosynthesis and PAF degradation, respectively.ResultsSeveral antibiotics inhibited PAF-induced platelet aggregation of both WRPs and rPRP in a concentration-depended manner, with clarithromycin, azithromycin and amikacin exhibiting the higher inhibitory effect, while when combined they synergistically inhibited PAF. Higher concentrations of all antibiotics tested were needed in order to inhibit PAF induced aggregation of rPRP, but also to inhibit thrombin induced aggregation of WRPs. Concentrations of these drugs similar to their IC50 values against PAF activity in WRPs, inhibited also in vitro PAF-CPT and Lyso-PAF-AT activities of rabbit leukocytes, while only clarithromycin and azithromycin increased rabbit plasma-PAF-AH activity.ConclusionsThese newly found properties of antibiotics used in sepsis suggest that apart from their general actions, these drugs may present additional beneficial anti-inflammatory and anti-coagulant effects against the onset and establishment of sepsis by inhibiting the PAF/PAF-receptor and/or the thrombin/protease-activated-receptor-1 systems, and/or by reducing PAF-levels through both PAF-biosynthesis inhibition and PAF-catabolism induction. These promising in vitro results need to be further studied and confirmed by in vivo tests, in order to optimize the efficacy of antibiotic treatment in sepsis.

Highlights

Sepsis is characterized as a systemic inflammatory response that results from the inability of the immune system to limit bacterial spread during an ongoing infection
For this reason in the present study we examined for the first time the in vitro anti-inflammatory and antithrombotic ability of a broad-spectrum of antibiotics and several of their combinations/regimens used in treatment against sepsis, based on their effect towards Platelet Activating Factor (PAF)-induced or thrombin induced platelet aggregation of Washed Rabbit Platelets (WRPs) and rabbit Platelet Reach Plasma
In the case of WRPs the antibiotics with the most prominent anti-PAF activity were clarithromycin, azithromycin, linezolid, amikacin and netilmicin, while in the case of rabbit Platelet Reach Plasma (rPRP) were amikacin, azithromycin, tigecycline and clarithromycin. These results suggest that from all antibiotics tested in both WRPs and rPRP, the same three amikacin, azithromycin and clarithromycin, belonged to the ones with the most potent anti-PAF effect, even though higher concentrations of these drugs were needed in the case of rPRP

Summary

Introduction

Sepsis is characterized as a systemic inflammatory response that results from the inability of the immune system to limit bacterial spread during an ongoing infection. In this condition the significant mediator of inflammation Platelet Activating Factor (PAF) and the coagulant factor thrombin are implicated. Platelet Activating Factor (PAF) is a phospholipid signalling molecule of inflammation and a significant mediator of the immune system [1,2]. Binding of PAF on specific membrane receptors coupled with G-proteins (PAF-receptor, PAFR) induces several intracellular signaling pathways that leads to auto/endo/para/juxta-crine cellular activation [3]. The remodeling pathway involves a structural modification of 1-O-ether-linked membrane phospholipids where the action of cytoplasmic phospholipase A2 yields lyso-PAF which is acetylated by a lyso-PAF:acetyl-CoA acetyltransferase (Lyso-PAF AT, EC 2.3.1.67) leading to the formation of PAF. Concerning PAF catabolism the most important enzyme involved is a PAFspecific acetylhydrolase (PAF-AH, EC 3.1.1.47), which cleaves the short acyl chain at the sn-2 position and forms lyso-PAF, which is biologically inactive [7]

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