Platelet activation in experimental murine neonatal pulmonary hypertension

Abstract

Serotonin (5‐HT) contributes to the pathogenesis of experimental neonatal pulmonary hypertension (PH) associated with bronchopulmonary dysplasia (BPD). Platelets are the primary source of circulating 5‐HT and is released upon platelet activation. Platelet transfusions are associated with neonatal mortality and increased rates of BPD. As BPD is often complicated by PH, we tested the hypothesis that circulating platelets are activated and also increased in the lungs of neonatal mice with bleomycin‐induced PH associated with BPD. Newborn wild‐type mice received intraperitoneal bleomycin (3 units/kg) three times weekly for 3 weeks. Platelets from mice with experimental PH exhibited increased adhesion to collagen under flow (at 300 s−1 and 1,500 s−1) and increased expression of the αIIbβ3 integrin and phosphatidylserine, markers of platelet activation. Platelet‐derived factors 5‐HT and platelet factor 4 were increased in plasma from mice with experimental PH. Pharmacologic blockade of the 5‐HT 2A receptor (5‐HT 2A R) prevents bleomycin‐induced PH and pulmonary vascular remodeling. Here, platelets from mice with bleomycin‐induced PH demonstrate increased 5‐HT 2A R expression providing further evidence of both platelet activation and increased 5‐HT signaling in this model. In addition, bleomycin treatment increased lung platelet accumulation. In summary, platelets are activated, granule factors are released, and are increased in numbers in the lungs of mice with experimental neonatal PH. These results suggest platelet activation and release of platelet‐derived factors may increase vascular tone, promote aberrant angiogenesis, and contribute to the development of neonatal PH.

Platelet-Derived TGF (Transforming Growth Factor)-β1 Enhances the Aerobic Glycolysis of Pulmonary Arterial Smooth Muscle Cells by PKM2 (Pyruvate Kinase Muscle Isoform 2) Upregulation

“…Some reports 8 elucidate that aerobic glycolysis mediates PASMCs hyperproliferation and resistance to apoptosis causing pulmonary arterial remodeling. Although other studies have confirmed that platelet is activated in both patients with PAH and murine models, 13,[35][36][37][38][39] there has been little attention towards the platelet effect on PASMCs aerobic glycolysis. Previous studies have reported that the levels of TGF-β isoforms increase and the TGF-β-dependent signaling enhances in both familial PAH and IPAH (idiopathic pulmonary arterial hypertension) patients' lungs.…”

Serotonin‐deficient neonatal mice are not protected against the development of experimental bronchopulmonary dysplasia or pulmonary hypertension

“…Based on our prior work demonstrating both increased plasma 5‐HT and pulmonary tph1 expression, as well as accumulation of platelets, the primary source of 5‐HT within the lungs of neonatal mice with bleomycin‐induced PH, we hypothesized that circulating and pulmonary 5‐HT would be increased in neonatal mice following hypoxia exposure (Davizon‐Castillo et al, 2020 ). As the majority of circulating 5‐HT is stored within platelet dense granules, we measured both platelet and platelet poor plasma 5‐HT levels.…”

“…Our lab has also demonstrated that both lung TPH1 expression and plasma 5‐HT are increased in neonatal mice with bleomycin‐induced PH and BPD (Delaney et al, 2018 ). Additionally, we have shown increased activation and accumulation of platelets, the primary source of circulating 5‐HT, in the lungs of mice with bleomycin‐induced neonatal PH (Davizon‐Castillo et al, 2020 ).…”

EBNEO commentary: Platelet transfusions in neonates and brain development: The new frontier

“…Platelets are critical regulators of immune and inflammatory responses, and it has been hypothesised that adult (transfused) platelets are more pro-inflammatory than neonatal platelets. [5][6][7][8] In support of this hypothesis, pre-clinical studies suggest platelet transfusions trigger inflammation or dysregulated immune responses in neonates, in a context-dependent manner. 9 Whether NDI results from the direct effects of transfused platelets on the developing brain or is mediated by higher rates of IVH and BPD observed in infants randomised to the high threshold group EBNEO commentaries on manuscripts relevant to evidence-based neonatal practice are welcomed and published after a formal peer-review process.…”

“…The mechanisms underlying increased morbidity and mortality associated with platelet transfusions are likely related to non‐hemostatic effects of platelets. Platelets are critical regulators of immune and inflammatory responses, and it has been hypothesised that adult (transfused) platelets are more pro‐inflammatory than neonatal platelets 5–8 . In support of this hypothesis, pre‐clinical studies suggest platelet transfusions trigger inflammation or dysregulated immune responses in neonates, in a context‐dependent manner 9 .…”