Biology subjects

Alfar, H. R.

Publications and source records attributed to Alfar, H. R..

3 recordsLinked to original sources

bioRxiv2025

VAMP8 Deficiency Attenuates AngII-Induced Abdominal Aortic Aneurysm Formation via Platelet Reprogramming and Enhanced Extracellular Matrix Stability

BACKGROUNDAs vascular sentries, platelets, and their ability to release a host of bioactive molecules, are critical for vascular homeostasis as well as hemostasis. Despite data linking platelet activation to abdominal aortic aneurysms (AAA) and rupture, the underlying mechanisms remain poorly understood. This study addresses the hypothesis that VAMP8, the primary v-SNARE controlling platelet exocytosis, contributes to AAA formation. METHODS AND RESULTSIn an AngII-infused hypercholesterolemic mouse model, we observed significant platelet consumption, indicated by decreased platelet counts at both acute (5-day) and chronic (28-day) time points. Platelets accumulated at sites of elastin degradation and within false lumens of the abdominal aorta after 28 days of AngII infusion. Bulk RNA sequencing analysis of washed platelets and their releasates after 5 days of AngII infusion revealed significant transcriptomic changes, suggesting rapid reprogramming of platelet function. Parallel RNA-seq analysis of suprarenal aortic tissue highlighted changes in genes associated with extracellular matrix (ECM) organization, inflammation, and platelet signaling, linking platelets to vascular remodeling suggesting a "platelet-aorta axis". Laser speckle imaging in a FeCl injury model confirmed that VAMP8 deficiency impaired platelet function, resulting in delayed thrombosis. In vivo experiments demonstrated that VAMP8-/- mice were protected against AngII-induced AAA and aortic rupture. Aortic diameter analysis further revealed that VAMP8 deficiency significantly attenuated AngII-driven aortic pathology. RNA-seq analysis of platelets and aortic tissue suggests that loss of VAMP8 affects expression of genes controlling ECM degradation and aortic wall stability consistent with the protective effect of VAMP8 loss on AAA. CONCLUSIONShort-term AngII infusion appears to reprogram the platelet transcriptome, which may affect the aorta and contribute to AAA formation. Controlling cargo release from platelets via VAMP8 deficiency results in profound attenuation of aortic aneurysms. This introduces a novel paradigm for understanding the impact of reprogrammed platelet cargo secretion and function in aortopathies. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=139 SRC="FIGDIR/small/635525v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@22bcecorg.highwire.dtl.DTLVardef@a15207org.highwire.dtl.DTLVardef@1106fd8org.highwire.dtl.DTLVardef@1ee0ea_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPlatelet transcriptome is altered at early aneurysmal stage. C_LIO_LIVAMP8 deficiency attenuates aortic aneurysms, potentially via enhanced ECM stability. C_LIO_LIVAMP8 deficiency significantly alters various genes contributing to aortic wall structure and stability in both platelets and suprarenal aortic tissue. C_LI

physiology↗

bioRxiv2025

Platelet endocytosis and α-granule cargo packaging are essential for normal skin wound healing

The high prevalence of chronic wounds, i.e., 2.5-3% of the US population, causes a large social and financial burden. Physiological wound healing is a multi-step process that involves different cell types and growth factors. Platelet-rich plasma or platelet-derived factors have been used to accelerate wound repair, but their use has been controversial with mixed results. Thus, a detailed functional understanding of platelet functions in wound healing beyond hemostasis is needed. This study investigated the importance of platelet -granule cargo packaging and endocytosis in a dorsal full-thickness excisional skin wound model using mice with defects in -granule cargo packaging (Nbeal2-/- mice) and endocytosis (platelet-specific Arf6-/- and VAMP2/3{Delta} mice). We found that proper kinetic and morphological healing of dorsal skin wounds in mice requires both de novo as well as endocytosed platelet -granule cargo. Histological and morphometric analyses of cross-sectional wound sections illustrated that mice with defects in -granule cargo packaging or platelet endocytosis had delayed (epi)dermal regeneration in both earlier and advanced healing. This was reflected by reductions in wound collagen and muscle/keratin content, delayed scab formation and/or resolution, re-epithelialization, and cell migration and proliferation. Molecular profiling analysis of wound extracts showed that the impact of platelet function extends beyond hemostasis to the inflammation, proliferation, and tissue remodeling phases via altered expression of several bioactive molecules, including IL-1{beta}, VEGF, MMP-9, and TIMP-1. These findings provide a basis for advances in clinical wound care through a better understanding of key mechanistic processes and cellular interactions in (patho)physiological wound healing. Key pointsO_LIDe novo and endocytosed platelet -granule cargo support physiological skin wound healing C_LIO_LIPlatelet function in wound healing extends to the inflammation, proliferation, and tissue remodeling phases C_LI

cell biology↗

bioRxiv2024

Unfolded Von Willebrand Factor Binds Protein S and Reduces Anticoagulant Activity

Protein S (PS), the critical plasma cofactor for the anticoagulants tissue factor (TF) pathway inhibitor (TFPI) and activated protein C (APC), circulates in two functionally distinct pools: free (anticoagulant) or bound to complement component 4b-binding protein (C4BP) (anti-inflammatory). Acquired free PS deficiency is detected in several viral infections, but its cause is unclear. Here, we identified a shear-dependent interaction between PS and von Willebrand Factor (VWF) by mass spectrometry. Consistently, plasma PS and VWF comigrated in both native and agarose gel electrophoresis. The PS/VWF interaction was blocked by TFPI but not APC, suggesting an interaction with the C-terminal sex hormone binding globulin (SHBG) region of PS. Microfluidic systems, mimicking arterial laminar flow or disrupted turbulent flow, demonstrated that PS stably binds VWF as VWF unfolds under turbulent flow. PS/VWF complexes also localized to platelet thrombi under laminar arterial flow. In thrombin generation-based assays, shearing plasma decreased PS activity, an effect not seen in the absence of VWF. Finally, free PS deficiency in COVID-19 patients, measured using an antibody that binds near the C4BP binding site in SHBG, correlated with changes in VWF, but not C4BP, and with thrombin generation. Our data suggest that PS binds to a shear-exposed site on VWF, thus sequestering free PS and decreasing its anticoagulant activity, which would account for the increased thrombin generation potential. As many viral infections present with free PS deficiency, elevated circulating VWF, and increased vascular shear, we propose that the PS/VWF interaction reported here is a likely contributor to virus-associated thrombotic risk. Key PointsO_LIVon Willebrand Factor (VWF) binds Protein S (PS) in a shear-dependent manner, reducing the free PS pool and its anticoagulant activity. C_LIO_LIThe PS/VWF complex forms under turbulent flow conditions, is stable in whole blood, and localizes to growing platelet thrombi. C_LI

biochemistry↗