Biology subjects

Owens, A. P.

Publications and source records attributed to Owens, A. P..

4 recordsLinked to original sources

bioRxiv2024

Platelets are Protective in Early Abdominal Aortic Aneurysm Formation

BackgroundAbdominal aortic aneurysm (AAA) is a disease associated with the pathophysiologic degradation of the tunica media resulting in aortic dilatation, systemic inflammation, and dysregulated hemostasis. Beyond role its role in initiating primary hemostasis, platelets are a source of ROS, inflammatory cytokines and growth factors necessary for angiogenesis and vascular remodeling. Although platelets contribute to the progression of established aneurysms, their role in the initiation of AAA remains undefined. MethodsLow density lipoprotein receptor deficient (Ldlr-/-) mice were examined for platelet accumulation in the angiotensin II (AngII) model of AAA utilizing in vivo labeling techniques. Two platelet antagonists (clopidogrel and aspirin), a thrombin inhibitor (dabigatran) or genetic deficiencies (protease-activated receptor 4, P2Y12, Lnk) were administered to AngII-infused mice to determine the role of platelets in initiation of AAA. The effect of platelet depletion was examined in multiple mouse strains of AngII-induced AAA and two additional aneurysm models. PheWAS and meta-analysis was analyzed in humans for platelet gene SNPs associated with AAA. ResultsWe show that platelets are recruited rapidly to the aorta after the initiation of AngII infusion. Genetic deficiency of platelet receptors had no effect on abdominal aortic diameter, but augmented rupture-induced death in littermate versus placebo controls during AngII-induced AAA. Moreover, Ldlr-/- mice receiving anti-platelet inhibitors or a thrombin inhibitor also had augmented rupture-induced death. Platelet depletion preceding aneurysm formation resulted in pervasive rupture-induced death in several mouse strains and with three different mouse models of AAA. ConclusionsInhibition of platelet function is detrimental in an early expanding aortic lumen resulting in catastrophic rupture and hemodynamic failure in murine AAA models.

pathology↗

bioRxiv2024

Attenuation of Atherosclerosis with PAR4 Deficiency: Differential Platelet Outcomes in apoE-/- vs. Ldlr-/- Mice

ObjectiveCardiovascular disease (CVD) is a significant burden globally and, despite current therapeutics, remains the leading cause of death. Platelet inhibitors are of interest in CVD treatment to reduce thrombus formation post-plaque rupture as well their contribution to inflammation throughout the progression of atherosclerosis. Protease activated receptor 4 (PAR4) is a receptor highly expressed by platelets, strongly activated by thrombin, and plays a vital role in platelet activation and aggregation. However, the role of PAR4 Approach and ResultsMice on a low-density lipoprotein receptor-deficient (Ldlr-/-) background were bred with Par4 deficient (Par4-/-) mice to create Ldlr-/-/Par4+/+ and Ldlr-/-/Par4-/- cousin lines. Mice were fed high fat (42%) and cholesterol (0.2%) Western diet for 12 weeks for all studies. Bone marrow transplant (BMT) studies were conducted by irradiating Ldlr-/-/Par4+/+ and Ldlr-/- /Par4-/- mice with 550 rads (2x, 4 hours apart) and then repopulated with Par4+/+ or Par4-/- bone marrow. To determine if the effects of thrombin were mediated solely by PAR4, the thrombin inhibitor dabigatran was added to the Western diet. Ldlr-/-/Par4-/- given dabigatran did not further decrease their atherosclerotic burden. Differences between apolipoprotein E deficient (apoE-/-) and Ldlr-/- platelets were assessed for changes in reactivity. We observed higher PAR4 abundance in arteries with atherosclerosis in human and mice versus healthy controls. PAR4 deficiency attenuated atherosclerosis in the aortic sinus and root versus proficient controls. BMT studies demonstrated this effect was due to hematopoietic cells, most likely platelets. PAR4 appeared to be acting independent of PAR1, as there werer no changes with addition of dabigatran to PAR4 deficient mice. apoE-/- platelets are hyperreactive compared to Ldlr-/- platelets. ConclusionsHematopoietic-derived PAR4, most likely platelets, plays a vital role in the development and progression of atherosclerosis. Specific targeting of PAR4 may be a potential therapeutic target for CVD. HighlightsO_LIDeficiency of protease-activated receptor 4 attenuates the development of diet-induced atherosclerosis in a Ldlr-/- mouse model. C_LIO_LIPAR4 deficiency in hematopoietic cells is atheroprotective. C_LIO_LIPAR4 deficiency accounts for the majority of thrombin-induced atherosclerosis in a Ldlr-/- mouse model. C_LIO_LIThe examination of platelet-specific proteins and platelet activation should be carefully considered before using the apoE-/- or Ldlr-/- mouse models of atherosclerosis. C_LI

pathology↗

bioRxiv2023

Glycoprotein VI is Critical for the Detection and Progression of Abdominal Aortic Aneurysms

A common feature in patients with abdominal aortic aneurysms (AAA) is the formation of a nonocclusive intraluminal thrombus (ILT) in regions of aortic dilation. Platelets are known to maintain hemostasis and propagate thrombosis through several redundant activation mechanisms, yet the role of platelet activation in the pathogenesis of AAA associated ILT is still poorly understood. Thus, we sought to investigate how platelet activation impacts the pathogenesis of AAA. Using RNA-sequencing, we identify that the platelet-associated transcripts are significantly enriched in the ILT compared to the adjacent aneurysm wall and healthy control aortas. We found that the platelet specific receptor glycoprotein VI (GPVI) is among the top enriched genes in AAA ILT and is increased on the platelet surface of AAA patients. Examination of a specific indicator of platelet activity, soluble GPVI (sGPVI), in two independent AAA patient cohorts is highly predictive of a AAA diagnosis and associates more strongly with aneurysm growth rate when compared to D-dimer in humans. Finally, intervention with the anti-GPVI antibody (J) in mice with established aneurysms blunted the progression of AAA in two independent mouse models. In conclusion, we show that levels of sGPVI in humans can predict a diagnosis of AAA and AAA growth rate, which may be critical in the identification of high-risk patients. We also identify GPVI as a novel platelet-specific AAA therapeutic target, with minimal risk of adverse bleeding complications, where none currently exist. KEY POINTSO_LISoluble glycoprotein VI, which is a platelet-derived blood biomarker, predicts a diagnosis of AAA, with high sensitivity and specificity in distinguishing patients with fast from slow-growing AAA. C_LIO_LIBlockade of glycoprotein VI in mice with established aneurysms reduces AAA progression and mortality, indicating therapeutic potential. C_LI

pathology↗

bioRxiv2023

HuR inhibition reduces post-ischemic cardiac remodeling by dampening acute inflammatory gene expression and the innate immune response

Myocardial ischemia/reperfusion (I/R) injury and the resulting cardiac remodeling is a common cause of heart failure. The RNA binding protein Human Antigen R (HuR) has been previously shown to reduce cardiac remodeling following both I/R and cardiac pressure overload, but the full extent of the HuR-dependent mechanisms within cells of the myocardium have yet to be elucidated. In this study, we applied a novel small molecule inhibitor of HuR to define the functional role of HuR in the acute response to I/R injury and gain a better understanding of the HuR-dependent mechanisms during post-ischemic myocardial remodeling. Our results show an early (two hours post-I/R) increase in HuR activity that is necessary for early inflammatory gene expression by cardiomyocytes in response to I/R. Surprisingly, despite the reductions in early inflammatory gene expression at two hours post-I/R, HuR inhibition has no effect on initial infarct size at 24-hours post-I/R. However, in agreement with previously published work, we do see a reduction in pathological remodeling and preserved cardiac function at two weeks post-I/R upon HuR inhibition. RNA-sequencing analysis of neonatal rat ventricular myocytes (NRVMs) at two hours post-LPS treatment to model damage associated molecular pattern (DAMP)-mediated activation of toll like receptors (TLRs) demonstrates a broad HuR-dependent regulation of pro-inflammatory chemokine and cytokine gene expression in cardiomyocytes. We show that conditioned media from NRVMs pre-treated with HuR inhibitor loses the ability to induce inflammatory gene expression in bone marrow derived macrophages (BMDMs) compared to NRVMs treated with LPS alone. Functionally, HuR inhibition in NRVMs also reduces their ability to induce endocrine migration of peripheral blood monocytes in vitro and reduces post-ischemic macrophage infiltration to the heart in vivo. In summary, these results suggest a HuR-dependent expression of pro-inflammatory gene expression by cardiomyocytes that leads to subsequent monocyte recruitment and macrophage activation in the post-ischemic myocardium.

molecular biology↗