Neutrophil Cathepsin G Enhances Thrombogenicity of Mildly Injured Arteries via ADP-Mediated Platelet Sensitization

Abstract

Inhalation of particulate matter in polluted air causes direct, size-restricted passage in the circulation and pronounced lung inflammation, provoking platelet activation and (non)-fatal cardiovascular complications. To determine potency and mechanism of platelet sensitization via neutrophil enzymes, we performed in vitro aggregation studies in washed human platelets and in murine and human blood, in the presence of elastase, cathepsin G and regular platelet agonists, present in damaged arteries. The impact of both enzymes on in vivo thrombogenicity was studied in the same thrombosis mouse model, previously having demonstrated that neutrophil activation enhances peripheral thrombogenicity. At 0.05 U/mL, cathepsin G activated washed human platelets via PAR1, whereas at 0.35 U/mL, aggregation occurred via PAR4. In Swiss mouse platelet-rich plasma no aggregation occurred by cathepsin G at 0.4 U/mL. In human and murine blood, aggregations by 0.05–0.1 U/mL cathepsin G were similar and not PAR-mediated, but platelet aggregation was inhibited by ADP antagonists, advocating cathepsin G-released ADP in blood as the true agonist of sustained platelet activation. In the mouse thrombosis model, cathepsin G and elastase amplified mild thrombogenicity at blood concentrations that activated platelets in vitro. This study shows that cathepsin G and elastase secreted in the circulation during mild air pollution-induced lung inflammation lyse red blood cell membrane proteins, leading to ADP-leakage into plasma, sensitizing platelets and amplifying their contribution to cardiovascular complications of ambient particle inhalation.

Role of Immuno-Inflammatory Signals in Liver Ischemia-Reperfusion Injury

“…They furthermore showed that blocking of cathepsin G, which is contained within the NET chromatin, led to reduced expression of CD62 and phosphatidylserine and decreased aggregation. This finding was further supported by Nemmar et al who showed that neutrophil-specific elastase increased the cathepsin G-induced platelet aggregation mediated by neutrophils [ 45 ]. Similarly, NETs have also been shown to have direct thrombin inducing abilities in platelets, which was confirmed using PMA- treated neutrophils and platelet cocultures and this effect was abrogated using DNAse [ 46 ].…”

“…al. who showed that neutrophil-specific elastase increased the cathepsin G-induced platelet aggregation mediated by neutrophils [45]. Similarly, NETs have also been shown to have direct thrombin inducing abilities in platelets, which was confirmed using PMA-treated neutrophils and platelet cocultures and this effect was abrogated using DNAse [46].…”

The role of platelets in central hubs of inflammation: A literature review

“…[ 27 ] Abderrahim Nemmar found via studying platelet activation by the neutrophil-released proteases cathepsin G and elastase that it potently activated platelets via an ADP-mediated mechanism, which potently enhanced a condition accompanied by local and systemic inflammation. [ 28 ]…”

The Role of Platelets in Central Hubs of Inflammation: A literature review

“…Recep Yılmaz found that neutrophil/lymphocyte ratio but not platelet/lymphocyte ratio and mean platelet volume can be an indicator of subclinical inflammation in patients with Familial Mediterranean Fever [27]. Abderrahim Nemmar found via studying platelet activation by the neutrophil-released proteases cathepsin G and elastase that it potently activated platelets via an ADP-mediated mechanism, which potently enhanced a condition accompanied by local and systemic inflammation [28].…”