Biology subjects

Alencar, G. F.

Publications and source records attributed to Alencar, G. F..

6 recordsLinked to original sources

bioRxiv2026

Dual Lineage Tracing Identifies Cellular Mechanisms Underlying Radiation-Associated Changes in Atherosclerotic Lesion Composition

BackgroundPhenotypic plasticity of smooth muscle cells (SMCs) and endothelial cells (ECs) contributes to atherosclerotic plaque composition and stability, yet how shifts in one population influence the contribution and function of the other under conditions of vascular stress, such as irradiation, is poorly understood. A major limitation has been the inability to simultaneously fate-map both cell types within the same lesion, with most studies mapping one lineage while inferring the other using unreliable dynamically changing marker genes, risking false-positive and false-negative assignment. MethodsWe generated dual lineage-tracing Apoe-deficient mice, enabling simultaneous fate mapping of SMCs and ECs. This model was used to extend prior findings from single lineage-tracing models demonstrating irradiation-induced loss of SMC lesion investment and expansion of EC-derived cells. Dual lineage-tracing mice were subjected to irradiation and bone marrow transplantation, followed by Western diet feeding to induce atherosclerosis. Lineage tracing, immunostaining and scRNA-seq analysis were used to define coordinated SMC and EC responses and identify changes relevant to plaque instability. ResultsDual lineage tracing specifically and simultaneously labeled SMC- and EC-derived cells in healthy and atherosclerotic vessels. Irradiation induced divergent responses: SMC-derived cells failed to invest in lesions and upregulated stress-activated inflammatory genes, whereas EC-derived cells expanded and upregulated SMC-associated genes. However, EC-derived cells within lesions failed to induce extracellular matrix genes, and lesions from irradiated mice exhibited reduced collagen content and fewer ACTA2+ cells within the fibrous cap, consistent with reduced plaque stability. ConclusionsDual lineage-tracing of SMCs and ECs demonstrated that irradiation-induced loss of lesional SMC and expansion of EC-derived ACTA2+ cells are not artifacts of false lineage assignment. By resolving SMC and EC fate within the same lesion, we identify irradiation-induced cell dynamics including stress-activated inflammatory reprogramming of SMCs, EC phenotypic modulation, impaired extracellular matrix organization, and reduced ACTA2 fibrous cap cellularity that may contribute to radiotherapy-associated increased atherosclerotic cardiovascular disease risk. Clinical PerspectiveWhat Is New? O_LIWe developed a dual lineage-tracing mouse model that enables simultaneous fate mapping of smooth muscle cells and endothelial cells within the same atherosclerotic lesion. C_LIO_LIThis model reveals coordinated arterial cell wall responses to vascular injury that cannot be resolved using single lineage-tracing approaches. C_LIO_LIExtending prior observations, we show that irradiation-induced inflammatory reprogramming of smooth muscle cells and endothelial-to-mesenchymal transition of endothelial cells towards a smooth muscle cell-like state are associated with reduced total lesion collagen content and decreased overall ACTA2+ fibrous cap cellularity. C_LIO_LIThis dual lineage-tracing mouse establishes a broadly applicable model for investigating arterial wall cell dynamics across diverse vascular disease states. C_LI What Are the Clinical Implications? O_LICancer therapies involving radiotherapy are associated with increased long-term risk of atherosclerotic cardiovascular disease. C_LIO_LIOur findings identify a potential cellular mechanism underlying this risk, in which irradiation-induced smooth muscle cell loss is not functionally compensated by endothelial-to-mesenchymal transition toward a SMC-like state. C_LIO_LIThis dual lineage-tracing model provides a tool to evaluate how cancer therapies and other vascular stressors may alter arterial wall cell fate and indices of plaque stability in atherosclerosis and other vascular diseases. C_LI

physiology↗

bioRxiv2025

B cells specific for polyomavirus-derived oncoprotein are predictive of Merkel cell carcinoma progression

Merkel cell carcinomas typically arise from clonal integration of the Merkel cell polyomavirus. Immunogenic viral oncoproteins then lead to tumorigenesis. Oncoprotein-specific T cells are essential for anti-MCC immunity, but it is unclear whether B cells promote tumor control. Here, we analyzed the frequency and phenotype of viral oncoprotein-specific and total B cells in 47 blood samples and 19 unmatched tumors from MCC patients-- of which 8 out 19 progressed. The phenotype of blood B cells did not correlate with MCC patient outcomes. In contrast, all 11 patients with robust oncoprotein-specific antibody-secreting and/or germinal center B cells in tumors experienced long-term MCC control. In vitro, B cells engineered to be specific for viral oncoproteins increased the sensitivity of oncoprotein-specific CD4+ T cells by over 50-fold. Together, our findings suggest that cancer-specific B cells promote anti-tumor immunity via increased T cell responses and that cancer-specific B cell augmentation could be therapeutically relevant. Statement of SignificanceThe link between cancer-specific B cells in anti-tumor immunity and clinical outcomes remains poorly defined. Here, we show that tumor-associated B cells specific for a viral oncoprotein expressed in MCC patient tumors predict disease control with remarkable accuracy, establishing their potential as active participants in tumor immunity.

immunology↗

bioRxiv2024

Merkel cell carcinoma-derived macrophage migration inhibitory factor (MIF) may promote persistence of Chronic Lymphocytic Leukemia

While concurrent diagnoses of Merkel cell carcinoma (MCC) and other cancers, like Chronic lymphocytic leukemia (CLL), are rare, patients with MCC have a 30-fold higher incidence of CLL. While these increases have been attributed to the ability of CLL to suppress immune responses allowing for the emergence of MCC, here we found evidence that MCC could support the persistence of CLL. Using single cell sequencing approaches and computational analyses of MCC and CLL from a patient where both cancers were present in the same lymph node, we found that production of macrophage migration inhibitory factor (MIF) by MCC could promote the persistence of CLL through stimulation of CD74 and CXCR4. These results may explain why blood cell counts rapidly normalized after treatment for MCC and were maintained at normal levels despite the absence of treatment for CLL. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=144 SRC="FIGDIR/small/611517v2_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@188968forg.highwire.dtl.DTLVardef@54c084org.highwire.dtl.DTLVardef@2b3a14org.highwire.dtl.DTLVardef@1f20eba_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2023

IL-1β inhibition partially negates the beneficial effects of diet-induced lipid lowering

BackgroundThromboembolic events secondary to rupture or erosion of advanced atherosclerotic lesions are the leading cause of death in the world. The most common and effective means to reduce these major adverse cardiovascular events (MACE), including myocardial infarction (MI) and stroke, is aggressive lipid lowering via a combination of drugs and dietary modifications. However, little is known regarding the effects of reducing dietary lipids on the composition and stability of advanced atherosclerotic lesions, the mechanisms that regulate these processes, and what therapeutic approaches might augment the benefits of lipid lowering. MethodsSmooth muscle cell (SMC)-lineage tracing Apoe-/- mice were fed a Western diet (WD) for 18 weeks and then switched to a low-fat chow diet for 12 weeks. We assessed lesion size and remodeling indices, as well as the cellular composition of aortic and brachiocephalic artery (BCA) lesions, indices of plaque stability, overall plaque burden, and phenotypic transitions of SMC, and other lesion cells by SMC-lineage tracing combined with scRNA-seq, CyTOF, and immunostaining plus high resolution confocal microscopic z-stack analysis. In addition, to determine if treatment with a potent inhibitor of inflammation could augment the benefits of chow diet-induced reductions in LDL-cholesterol, SMC-lineage tracing Apoe-/- mice were fed a WD for 18 weeks and then chow diet for 12 weeks prior to treating them with an IL-1{beta} or control antibody (Ab) for 8-weeks. ResultsLipid-lowering by switching Apoe-/- mice from a WD to a chow diet reduced LDL-cholesterol levels by 70% and resulted in multiple beneficial effects including reduced overall aortic plaque burden as well as reduced intraplaque hemorrhage and necrotic core area. However, contrary to expectations, IL-1{beta} Ab treatment resulted in multiple detrimental changes including increased plaque burden, BCA lesion size, as well as increased cholesterol crystal accumulation, intra-plaque hemorrhage, necrotic core area, and senescence as compared to IgG control Ab treated mice. Furthermore, IL-1{beta} Ab treatment upregulated neutrophil degranulation pathways but down-regulated SMC extracellular matrix pathways likely important for the protective fibrous cap. ConclusionsTaken together, IL-1{beta} appears to be required for chow diet-induced reductions in plaque burden and increases in multiple indices of plaque stability. Clinical PerspectiveAlthough one must be cautious in extrapolating results of mouse studies to humans, the current and our previous studies (Gomez et al. 2018 Nature Medicine) suggest that efforts to identify anti-inflammatory therapies for treating patients with advanced atherosclerosis should consider the possibility that inhibiting a given cytokine may have a mixture of beneficial and detrimental effects that vary between individuals. What is New?In a mouse model of advanced atherosclerosis followed by diet-induced reductions in cholesterol, IL-1{beta} inhibition unexpectedly had multiple detrimental effects including increasing overall plaque burden and decreasing various indices of plaque stability, as well as markedly increasing the number of senescent cells, and cholesterol crystal accumulation in lesions as compared to IgG control Ab treated mice. What are the clinical Implications?Results suggest that some anti-inflammatory therapies may have limited efficacy for treating patients with advanced atherosclerosis because such therapies inhibit not only detrimental pro-inflammatory responses, but also evolutionarily conserved beneficial inflammatory processes, which play a critical role in resistance to pathogenic microorganisms, in tissue repair following injury, and resolution of inflammation. We propose that the latter includes clearance of senescent cells and cholesterol from advanced atherosclerotic lesions induced by dietary-induced lipid lowering.

cell biology↗

bioRxiv2023

Mouse Model of Heart Attack and Stroke Shows Improved Survival with MPO Inhibition

Thromboembolic events, including myocardial infarction (MI) or stroke, caused by the rupture or erosion of unstable atherosclerotic plaques are the leading cause of death worldwide1. Unfortunately, the lack of a mouse model that develops advanced coronary atherosclerosis and that exhibits a high incidence of spontaneous plaque rupture with MI or stroke has greatly stymied development of more effective therapeutic approaches for reducing these events beyond what has been achieved with aggressive lipid lowering. Herein, we describe a novel mouse model that develops widespread advanced atherosclerosis including in coronary, brachiocephalic, and carotid arteries. These mice show high mortality following Western Diet feeding with clear evidence of plaque rupture, MI, and stroke. To validate the utility of this model, mice were treated with the drug candidate AZM198, which inhibits myeloperoxidase, an enzyme primarily produced by activated neutrophils and predictive of rupture of human atherosclerotic lesions2-7. AZM198 treatment resulted in marked improvements in survival with a greater than 60% decrease in the incidence of plaque rupture, MI, and stroke. In summary, our work describes a novel mouse model that closely replicates late-stage clinical events of advanced human atherosclerotic disease and evidence that this model can be used to identify and test potential new therapeutic agents to prevent major adverse cardiac events.

physiology↗

bioRxiv2023

Loss of endothelial cell heterogeneity in arteries after obesogenic diet

BackgroundIt is well recognized that obesity leads to arterial endothelial dysfunction and cardiovascular disease. However, the progression to endothelial dysfunction is not clear. Endothelial cells (ECs) adapt to the unique needs of their resident tissue and respond to systemic metabolic perturbations. We sought to better understand how obesity affects EC phenotypes in different tissues specifically focusing on mitochondrial gene expression. MethodsWe performed bulk RNA sequencing (RNA-seq) and single cell RNA-seq (scRNA-seq) on mesenteric and adipose ECs isolated from normal chow (NC) and high fat diet (HFD) fed mice. Differential gene expression, gene ontology pathway, and transcription factor analyses were performed. We further investigated our hypothesis in humans using published human adipose single nuclei RNA-seq (snRNA-seq) data. ResultsBulk RNA-seq revealed higher mitochondrial gene expression in adipose ECs compared to mesenteric ECs in both NC and HFD mice. We then performed scRNA-seq and categorized EC clusters as arterial, capillary, venous, or lymphatic. HFD decreased the number of differentially expressed genes between mesenteric and adipose ECs in all subtypes, but the largest effect was seen in arterial ECs. Further analysis of arterial ECs revealed genes coding for mitochondrial oxidative phosphorylation proteins were enriched in adipose compared to mesentery under NC conditions. In HFD mice, these genes were decreased in adipose ECs becoming similar to mesenteric ECs. Transcription factor analysis revealed C/EBP and PPAR{gamma}, both known to regulate lipid handling and metabolism, had high specificity scores in the NC adipose artery ECs. These findings were recapitulated in snRNA-seq data from human adipose. ConclusionsThese data suggest mesenteric and adipose arterial ECs metabolize lipids differently and the transcriptional phenotype of these two vascular beds converge in obesity, in part, due to downregulation of PPAR{gamma} and C/EBP in adipose artery ECs. This work lays the foundation for investigating vascular bed specific adaptations to obesity.

molecular biology↗