CD40L Priming of Platelets via NF‐κB Activation is CD40‐ and TAK1‐Dependent

Abstract

Background CD40 ligand (CD40L) is a thromboinflammatory molecule that predicts cardiovascular events. CD40L is a strong activator of nuclear factor kappa B (NF‐κB) in platelets that primes and enhances platelet activation in response to thrombotic stimuli. In addition to its classical receptor CD40, CD40L binds αIIbβ3, α5β1, and αMβ2 in various cell types. However, the function of the different CD40L receptors on platelets remains unexplored. The present study aims to identify the receptors of CD40L, involved in platelet NF‐κB activation, their downstream signaling and their implication in platelet aggregation. Methods and Results We showed that platelets express CD40, αIIbβ3, and α5β1 and release CD40L in response to sCD40L stimulation. sCD40L alone dose‐dependently induced platelet NF‐κB activation; this effect was absent in CD40 −/− mouse platelets and inhibited by the CD40 blockade, but was unaffected by the αIIbβ3 or α5β1 blockade in human platelets. sCD40L/CD40 axis activates transforming growth factor‐β‐activated kinase 1 upstream of NF‐κB. In functional studies, sCD40L alone did not affect platelet aggregation but potentiated the aggregation response in the presence of suboptimal doses of thrombin; this effect was abolished by CD40, transforming growth factor‐β‐activated kinase 1, and NF‐κB inhibitors. Conclusions CD40L primes platelets via signaling pathways involving CD40/transforming growth factor‐β‐activated kinase 1/NF‐κB, which predisposes platelets to enhanced activation and aggregation in response to thrombotic stimuli.

Role of NF-κB in Platelet Function

“…Therefore, a more plausible result would necessitate the stimulation of IKK inhibitor VII-pretreated platelets with a priming/sub-optimal dose of those agonists, in order to better observe the potentiating effect of the inhibitor. In this context, our recent study demonstrated that the aggregation of platelets pretreated with BAY 11-7082 or TAK-1 inhibitors, 5Z-7-Oxozeaenol and Takinib, primed with sCD40L, and then stimulated with sub-optimal doses of thrombin was abrogated completely [95]. Our results also pinpointed the emerging importance of TAK-1 in NF-κB activation in platelets as another attractive therapeutic target in thrombotic diseases.…”

“…In platelet physiology, our laboratory showed that CD40L alone induced IκBα phosphorylation and NF-κB activation exclusively through platelet CD40 receptor [95]. We also showed that sCD40L, in the presence of sub-optimal doses of platelet agonists like collagen and thrombin, significantly increased platelet activation and aggregation through an NF-κB-independent CD40/TRAF-2/Rac-1/p38 MAPK axis [9].…”

“…This was evident in first, following the use of IKK inhibitor VII, platelet priming, and potentiation of aggregation were significantly diminished, and second, IκBα and p38 MAPK phosphorylation were found to be independent upon platelet pre-treatment with either of their inhibitors followed by sCD40L stimulation. Furthermore, our recent study dug deeper into the unique NF-κB signaling pathway, showcasing that CD40L activated NF-κB through CD40 and TAK-1 and endorsing that TAK-1 is upstream of NF-κB in CD40L signaling as its inhibition completely eliminated NF-κB activation [95]. Nevertheless, a study by Kuijpers et al [96] contradicted our results, demonstrating that CD40L enhanced collagen-induced platelet-platelet interactions by supporting integrin αIIbβ3 activation, platelet secretion, and thrombus growth via PI3Kβ but not CD40 and IKKα/NFκB.…”

“…In summary, Figure 2 resumes our previous findings that established the link between sCD40L, enhanced platelet reactivity and thrombosis involving its main receptor CD40 binding to an adaptor protein the (TNFR)-associated factor-2 (TRAF2) and downstream signaling via Rac1/p38-MAPK [9]. We have also revealed that sCD40L is a potent activator of NF-κB [100], which primes platelets through CD40 signaling via the transforming growth factor-B (TGF-B)-activated Kinase (TAK1) [95].…”

Bioinformatics Analysis and Insights for The Role of COMMD7 in Hepatocellular Carcinoma

“…The classical activation of NF-κB needs the 26 s proteasome induced ubiquitination and degradation of IKBa, NF-κB is then released from the cytoplasmic NF-κB/IkBa complex, and exposing the nuclear localization domain, forming a p50/RelA dimer, activating the transcription of tumor-related factors downstream. Additionally, NF-κB also can be activated in other ways such as nucleolar stress, tumor necrosis factor receptor (TNFR) family ligands CD40L [43], ROS [44], and angiotensin [45].Thus the inhibition of NF-κB activity is considered to be one promising strategy to manipulate the tumorigenesis and development of cancers.…”