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

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.

Efficacy of azithromycin in sepsis-associated acute respiratory distress syndrome: a retrospective study and propensity score analysis

“…Recently, several investigators have reported on the relationship between coagulopathy and proinflammatory events causing organ injury (Abraham 2000 ) (Coughlin 2000 ). Azithromycin has been reported to have immunomodulatory and anti-inflammatory activities, as well as anti-coagulant effects via platelet-activating factor mediated platelet aggregation (Tsoupras et al 2011 ). From the viewpoint of coagulopathy in the pathogenesis of ARDS, azithromycin might have contributed to an improvement in survival in sepsis-associated DIC.…”

Inflammation, not Cholesterol, Is a Cause of Chronic Disease

“…Apart from the effects of inflammation on plasma lipids, it is now well established that more important soluble and cellular immune factors associated with chronic inflammation can promote inflammation-related endothelial dysfunction and atherogenesis, either during dyslipidaemia or independently of dyslipidaemia [ 66 ]. Even though atherosclerosis and CVD were previously viewed as lipid storage disorders, we now recognise that inflammation drives much of endothelial dysfunction and mechanisms of clinical complications with these diseases and related comorbidities, such as sepsis [ 67 , 68 ], human immunodeficiency virus (HIV) infection [ 69 , 70 , 71 , 72 , 73 , 74 ], periodontal diseases [ 75 , 76 , 77 ], kidney disorders [ 78 , 79 , 80 , 81 ], healthy ageing, and inflammatory autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis, independently of traditional cardiovascular risk factors such as serum lipid levels [ 66 , 82 , 83 ].…”

“…The most common coexistent diseases associated with chronic infections are CVD, CNS disorders, and tumour malignancies, which are usually promoted by increased levels of PAF and PAF-related continuous and unresolved inflammation [ 57 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 85 , 208 ]. In addition, PAF seems to act in synergy with infectious agents to initiate and propagate the disease process, i.e., viral load in HIV-infected patients was positively correlated with PAF synthesis and levels, while viral products such as Tat-protein induce PAF synthesis and PAF-related HIV-induced non-AIDS comorbidities, such as CVD, Kaposi sarcoma, neurodegeneration, and dementia [ 69 , 70 , 71 , 72 , 73 , 74 ].…”

Community-Acquired Pneumonia

“…24,25 Macrolides have been documented not only to possess adjunctive anti-inflammatory, immunomodulatory activity in vitro, but also to inhibit platelet-activating factor (PAF)-mediated platelet aggregation. 26 Although these activities may underpin the benefits of these agents in the management of CAP, differentiating them from antimicrobial activity in the clinical setting is very difficult. 7…”

“… decreasing the concentrations of proatherogenic oxLDL-C 42 an inflammatory mediator which promotes platelet activation via interactions with the scavenger receptors LOX-1 and CD36, both of which are expressed on platelets, 43,44 Table 1 summarizes the documented antiplatelet activities of statins, together with those of macrolides, corticosteroids and selective platelet-targeted agents, few of which have been evaluated in CAP. 26,33,42,[45][46][47][48][49][50] We are unaware of any clinically available selective PAF receptor antagonists. Although the activation of proteinase-activated receptor 1 (PAR1, thrombin activated), TxA 2 receptors (TP) and the purinergic receptor, P2Y12 (ADP activated) is largely independent of isoprenylation, the requirement for cholesterol-rich membrane lipid rafts for optimal activity .41 is consistent with possible modulation of these receptors by statins…”