Mechanistic insight of platelet apoptosis leading to non-surgical bleeding among heart failure patients supported by continuous-flow left ventricular assist devices

Abstract

Non-surgical bleeding (NSB) is the most common clinical complication in heart failure (HF) patients supported by continuous-flow left ventricular assist devices (CF-LVADs). In this study, oxidative stress and alteration of signal pathways leading to platelet apoptosis were investigated. Thirty-one HF patients supported by CF-LVADs were divided into bleeder (n=12) and non-bleeder (n=19) groups. Multiple blood samples were collected at pre-implant (baseline) and weekly up to one-month post-implant. A single blood sample was collected from healthy subjects (reference). Production of reactive oxygen species (ROS) in platelets, total antioxidant capacity (TAC), oxidized low density lipoproteins (oxLDL), expression of Bcl-2 and Bcl-xL, Bax and release of cytochrome c (Cyt.c), platelet mitochondrial membrane potential (Δψm), activation of caspases, gelsolin cleavage and platelet apoptosis were examined. Significantly elevated ROS, oxLDL and depleted TAC were evident in the bleeder group compared to non-bleeder group (p<0.05). Platelet pro-survival proteins (Bcl-2, Bcl-xL) were significantly reduced in the bleeder group in comparison to the non-bleeder group (p<0.05). Translocation of Bax into platelet mitochondria membrane and subsequent release of Cyt.c were more prevalent in the bleeder group. Platelet mitochondrial damage, activation of caspases, gelsolin cleavage and ultimate platelet apoptosis in the bleeder group were observed. Oxidative stress and activation of both intrinsic and extrinsic pathways of platelet apoptosis may be linked to NSB in CF-LVAD patients. Additionally, biomarkers of oxidative stress, examination of pro-survivals and pro-apoptotic proteins in platelets, mitochondrial damage, caspase activation and platelet apoptosis may be used to help identify HF patients at high risk of NSB post-implant.

Acquired coagulopathy in patients with left ventricular assist devices

“…Furthermore, a high rate of platelet damage and dysfunction has been observed in patients supported with an LVAD . Steinlechner et al ., and more recently Baghei et al ., reported that platelet aggregation is significantly reduced in the majority of patients after LVAD implantation .…”

“…Finally, in a recent publication, Mondal et al . investigated a potential mechanism of platelet apoptosis in CF‐LVAD patients who developed bleedings within 1 month post‐implantation . Higher platelet reactive oxygen (ROS) generation, a decrease in total antioxidant capacity and elevated oxidized low‐density lipoproteins were observed in the bleeding group, suggesting that the body's antioxidant capacity may not have been sufficient to combat the deleterious effects of ROS in patients who experienced a bleeding event .…”

“…investigated a potential mechanism of platelet apoptosis in CF‐LVAD patients who developed bleedings within 1 month post‐implantation . Higher platelet reactive oxygen (ROS) generation, a decrease in total antioxidant capacity and elevated oxidized low‐density lipoproteins were observed in the bleeding group, suggesting that the body's antioxidant capacity may not have been sufficient to combat the deleterious effects of ROS in patients who experienced a bleeding event . In addition, a reduction in BCl‐2 and BCl‐xL (pro‐survival) protein expression was evident in LVAD patients, whereas the translocation of Bax into the platelet mitochondria and subsequent release of cytochrome C, which leads to downstream apoptotic events, was more prevalent in the bleeding group .…”

Multidimensional Flow Cytometry for Testing Blood-Handling Medical Devices

“…The focus has been on platelet activation and platelet MPs but these have so far not shown a utility as predictors of adverse events or stratifiers. However, there are other platelet parameters, all measurable by flow cytometry, that have potential as patient risk stratifiers, or even predictors, for bleeding complications in patients with CF-VADs [18][19][20]. These include significantly greater levels of reactive oxygen species, mitochondrial damage, surface phosphatidylserine (PS) expression/apoptosis, and significantly decreased expression of α2bβ3 on the platelet surface, in bleeders compared to non-bleeders [18][19][20].…”

Mechanisms of Platelet Dysfunction in Patients with Implantable Devices

“…91,92 VADs may also be associated with changes in intracellular reactive oxygen species (ROS) in platelets and mitochondrial damage that could potentially contribute to increased nonsurgical bleeding observed in these patients. 93,94 Ligand binding to GPIb-IX-V or GPVI leads to rapid elevation of intracellular ROS, through a direct interaction of cytoplasmic sequences of GPIb and GPVI with the adaptor protein, tumor necrosis factor receptor associated factor 4 (TRAF4), which links these receptors to p47 phox of the NADPH oxidase (Nox) enzyme complex that generates ROS which is important for the propagation of Syk-dependent signals downstream of GPVI and GPIb. 95,96 Conclusions and Future Implications…”