Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease with limited treatment options. Despite endothelial cells (ECs) comprising 30% of the lung cellular composition, the role of EC dysfunction in pulmonary fibrosis (PF) remains unclear. We hypothesize that sterol regulatory element-binding protein 2 (SREBP2) plays a critical role in the pathogenesis of PF via EC phenotypic modifications. Transcriptome data demonstrate that SREBP2 overexpression in ECs led to the induction of the TGF, Wnt, and cytoskeleton remodeling gene ontology pathways and the increased expression of mesenchymal genes, such as snail family transcriptional repressor 1 (snai1), α-smooth muscle actin, vimentin, and neural cadherin. Furthermore, SREBP2 directly bound to the promoter regions and transactivated these mesenchymal genes. This transcriptomic change was associated with an epigenetic and phenotypic switch in ECs, leading to increased proliferation, stress fiber formation, and ECM deposition. Mice with endothelial-specific transgenic overexpression of SREBP2 (EC-SREBP2[N]-Tg mice) that were administered bleomycin to induce PF demonstrated exacerbated vascular remodeling and increased mesenchymal transition in the lung. SREBP2 was also found to be markedly increased in lung specimens from patients with IPF. These results suggest that SREBP2, induced by lung injury, can exacerbate PF in rodent models and in human patients with IPF.
Marcy Martin, Jiao Zhang, Yifei Miao, Ming He, Jian Kang, Hsi-Yuan Huang, Chih-Hung Chou, Tse-Shun Huang, Hsiao-Chin Hong, Shu-Han Su, Simon S. Wong, Rebecca L. Harper, Lingli Wang, Rakesh Bhattacharjee, Hsien-Da Huang, Zhen Bouman Chen, Atul Malhotra, Marlene Rabinovitch, James S. Hagood, John Y-J. Shyy
Inhibitors of the renin-angiotensin system (RAS) are widely used to treat hypertension. Using mice harboring fluorescent cell lineage tracers, single-cell RNA-seq, and long-term inhibition of RAS in both mice and humans, we found that deletion of renin or inhibition of the RAS leads to concentric thickening of the intrarenal arteries and arterioles. This severe disease is caused by the multiclonal expansion and transformation of renin cells from a classical endocrine phenotype to a matrix-secretory phenotype: the cells surround the vessel walls and induce the accumulation of adjacent smooth muscle cells and extracellular matrix, resulting in blood flow obstruction, focal ischemia, and fibrosis. Ablation of the renin cells via conditional deletion of β1integrin prevents arteriolar hypertrophy, indicating that renin cells are responsible for vascular disease. Given these findings, prospective morphological studies in humans are necessary to determine the extent of renal-vascular damage caused by the widespread use of inhibitors of RAS.
Hirofumi Watanabe, Alexandre G. Martini, Evan A. Brown, Xiuyin Liang, Silvia Medrano, Shin Goto, Ichiei Narita, Lois J. Arend, Maria Luisa S. Sequeira-Lopez, R. Ariel Gomez
Patients with diabetes with coronary microvascular disease (CMD) exhibit higher cardiac mortality than patients without CMD. However, the molecular mechanism by which diabetes promotes CMD is poorly understood. RNA-binding protein human antigen R (HuR) is a key regulator of mRNA stability and translation; therefore, we investigated the role of HuR in the development of CMD in mice with type 2 diabetes. Diabetic mice exhibited decreases in coronary flow velocity reserve (CFVR; a determinant of coronary microvascular function) and capillary density in the left ventricle. HuR levels in cardiac endothelial cells (CECs) were significantly lower in diabetic mice and patients with diabetes than the controls. Endothelial-specific HuR-KO mice also displayed significant reductions in CFVR and capillary density. By examining mRNA levels of 92 genes associated with endothelial function, we found that HuR, Cx40, and Nox4 levels were decreased in CECs from diabetic and HuR-KO mice compared with control mice. Cx40 expression and HuR binding to Cx40 mRNA were downregulated in CECs from diabetic mice. Cx40-KO mice exhibited decreased CFVR and capillary density, whereas endothelium-specific Cx40 overexpression increased capillary density and improved CFVR in diabetic mice. These data suggest that decreased HuR contributes to the development of CMD in diabetes through downregulation of gap junction protein Cx40 in CECs.
Rui Si, Jody Tori O. Cabrera, Atsumi Tsuji-Hosokawa, Rui Guo, Makiko Watanabe, Lei Gao, Yun Sok Lee, Jae-Su Moon, Brian T. Scott, Jian Wang, Anthony W. Ashton, Jaladanki N. Rao, Jian-Ying Wang, Jason X.-J. Yuan, Ayako Makino
Vascular procedures, such as stenting, angioplasty, and bypass grafting, often fail due to intimal hyperplasia (IH), wherein contractile vascular smooth muscle cells (VSMCs) dedifferentiate to synthetic VSMCs, which are highly proliferative, migratory, and fibrotic. Previous studies suggest MAPK-activated protein kinase 2 (MK2) inhibition may limit VSMC proliferation and IH, although the molecular mechanism underlying the observation remains unclear. We demonstrated here that MK2 inhibition blocked the molecular program of contractile to synthetic dedifferentiation and mitigated IH development. Molecular markers of the VSMC contractile phenotype were sustained over time in culture in rat primary VSMCs treated with potent, long-lasting MK2 inhibitory peptide nanopolyplexes (MK2i-NPs), a result supported in human saphenous vein specimens cultured ex vivo. RNA-Seq of MK2i-NP–treated primary human VSMCs revealed programmatic switching toward a contractile VSMC gene expression profile, increasing expression of antiinflammatory and contractile-associated genes while lowering expression of proinflammatory, promigratory, and synthetic phenotype–associated genes. Finally, these results were confirmed using an in vivo rabbit vein graft model where brief, intraoperative treatment with MK2i-NPs decreased IH and synthetic phenotype markers while preserving contractile proteins. These results support further development of MK2i-NPs as a therapy for blocking VSMC phenotype switch and IH associated with cardiovascular procedures.
J. William Tierney, Brian C. Evans, Joyce Cheung-Flynn, Bo Wang, Juan M. Colazo, Monica E. Polcz, Rebecca S. Cook, Colleen M. Brophy, Craig L. Duvall
We recently described a previously unknown trans-tentorial venous system (TTVS) connecting venous drainage throughout the brain in humans. Prior to this finding, it was believed that the embryologic tentorial plexus regresses, resulting in a largely avascular tentorium. Our finding contradicted this understanding and necessitated further investigation into the development of the newly described TTVS. Herein we sought to investigate mice as a model to study the development of this system. First, using vascular casting and ex vivo micro-computed tomography (micro-CT), we demonstrate that this TTVS is conserved in adult mice. Next, using high-resolution magnetic resonance imaging (MRI), we found the primitive tentorial venous plexus in murine embryo at day 14.5. We also found that, at this embryologic stage, the tentorial plexus drains the choroid plexus. Finally, using vascular casting and micro-CT, we found that the TTVS is the dominant venous drainage in the early postnatal period (P8). Herein, we demonstrate that the TTVS is conserved between mice and humans and present a longitudinal study of its development. In addition, our findings establish mice as a translational model for further study of this newly described system and its relationship to intracranial physiology.
Pashayar P. Lookian, Vikram Chandrashekhar, Anthony Cappadona, Jean-Paul Bryant, Vibhu Chandrashekhar, Jessa M. Tunacao, Danielle R. Donahue, Jeeva P. Munasinghe, James G. Smirniotopoulos, John D. Heiss, Zhengping Zhuang, Jared S. Rosenblum
Endothelial dysfunction accompanies the microvascular thrombosis commonly observed in severe COVID-19. Constitutively, the endothelial surface is anticoagulant, a property maintained at least in part via signaling through the Tie2 receptor. During inflammation, the Tie2 antagonist angiopoietin-2 (Angpt-2) is released from endothelial cells and inhibits Tie2, promoting a prothrombotic phenotypic shift. We sought to assess whether severe COVID-19 is associated with procoagulant endothelial dysfunction and alterations in the Tie2-angiopoietin axis. Primary human endothelial cells treated with plasma from patients with severe COVID-19 upregulated expression of thromboinflammatory genes, inhibited expression of antithrombotic genes, and promoted coagulation on the endothelial surface. Pharmacologic activation of Tie2 with the small molecule AKB-9778 reversed the prothrombotic state induced by COVID-19 plasma in primary endothelial cells. Lung autopsies from COVID-19 patients demonstrated a prothrombotic endothelial signature. Assessment of circulating endothelial markers in a cohort of 98 patients with mild, moderate, or severe COVID-19 revealed endothelial dysfunction indicative of a prothrombotic state. Angpt-2 concentrations rose with increasing disease severity and highest levels were associated with worse survival. These data highlight the disruption of Tie2-angiopoietin signaling and procoagulant changes in endothelial cells in severe COVID-19. Our findings provide rationale for current trials of Tie2-activating therapy with AKB-9778 in COVID-19.
Alec A. Schmaier, Gabriel M. Pajares Hurtado, Zachary J. Manickas-Hill, Kelsey D. Sack, Siyu M. Chen, Victoria Bhambhani, Juweria Quadir, Anjali K. Nath, Ai-ris Y. Collier, Debby Ngo, Dan H. Barouch, Nathan I. Shapiro, Robert E. Gerszten, Xu Yu, Kevin G. Peters, Robert Flaumenhaft, Samir M. Parikh
Autophagy has long been associated with longevity and it is well established that autophagy reverts and prevents vascular deterioration associated with aging and cardiovascular diseases. Currently, our understanding of how autophagy benefits the vasculature is centered on the premise that reduced autophagy leads to the accumulation of cellular debris resulting in inflammation and oxidative stress, which are then reversed by reconstitution or upregulation of autophagic activity. Evolutionarily, autophagy also functions to mobilize endogenous nutrients in response to starvation. Therefore, we hypothesized that the biosynthesis of the most physiologically abundant ketone body, β-hydroxybutyrate (βHB), would be autophagy dependent, and exert vasodilatory effects via its canonical receptor, Gpr109a. We have revealed for the first time that the biosynthesis of βHB can be impaired by preventing autophagy. Subsequently, βHB caused potent vasodilation via potassium-channels, but not Gpr109a. Finally, we observed that chronic consumption of a high salt diet negatively regulates both βHB biosynthesis and hepatic autophagy, and that reconstitution of βHB bioavailability prevents high salt diet-induced endothelial dysfunction. In summary, this work offers an alternative mechanism to the anti-inflammatory and anti-oxidative stress hypothesis of autophagy-dependent vasculoprotection. Furthermore, it reveals a direct mechanism, by which ketogenic interventions (e.g., intermittent fasting) improve vascular health.
Cameron G. McCarthy, Saroj Chakraborty, Gagandeep Singh, Beng San Yeoh, Zachary J. Schreckenberger, Avinash Singh, Blair Mell, Nicole R. Bearss, Tao Yang, Xi Cheng, Matam Vijay-Kumar, Camilla F. Wenceslau, Bina Joe
The mutant nuclear lamin protein (progerin) produced in Hutchinson-Gilford progeria syndrome (HGPS) results in loss of arterial smooth muscle cells (SMCs), but the mechanism has been unclear. We found that progerin induces repetitive nuclear membrane (NM) ruptures, DNA damage, and cell death in cultured SMCs. Reducing lamin B1 expression and exposing cells to mechanical stress — to mirror conditions in the aorta — triggered more frequent NM ruptures. Increasing lamin B1 protein levels had the opposite effect, reducing NM ruptures and improving cell survival. Remarkably, raising lamin B1 levels increased nuclear compliance in cells and was able to offset the increased nuclear stiffness caused by progerin. In mice, lamin B1 expression in aortic SMCs is normally very low, and in mice with a targeted HGPS mutation (LmnaG609G), levels of lamin B1 decrease further with age while progerin levels increase. Those observations suggest that NM ruptures might occur in aortic SMCs in vivo. Indeed, studies in LmnaG609G mice identified NM ruptures in aortic SMCs, along with ultrastructural abnormalities in the cell nucleus that preceded SMC loss. Our studies identify NM ruptures in SMCs as likely causes of vascular pathology in HGPS.
Paul H. Kim, Natalie Y. Chen, Patrick J. Heizer, Yiping Tu, Thomas A. Weston, Jared L.-C. Fong, Navjot Kaur Gill, Amy C. Rowat, Stephen G. Young, Loren G. Fong
The prevalence of hypertension is increasing globally, while strategies for prevention and treatment of hypertension remain limited. FG-4592 (Roxadustat) is a novel, orally active small-molecule HIF stabilizer, and is being used clinically to treat CKD anemia. In the present study, we evaluate the effects of FG-4592 on hypertension. In an Ang II hypertension model, FG-4592 abolished hypertensive responses, prevented vascular thickening, cardiac hypertrophy, and kidney injury, downregulated AGTR1 expression, and enhanced AGTR2, eNOS, and HIF1α protein levels in the aortas of mice. Additionally, the levels of thiobarbituric acid reactive substances (TBARs) in blood and urine were diminished by FG-4592 treatment. In vascular smooth muscle cells, FG-4592 treatment reduced AGTR1 and increased AGTR2 levels, while preventing Ang II-induced oxidative stress. In vascular endothelial cells, FG-4592 upregulated total and phosphorylated eNOS. Moreover, FG-4592 treatment was hypotensive in L-NAME-induced hypertension. In summary, FG-4592 treatment remarkably ameliorated hypertension and organ injury, possibly through stabilizing HIF1α and subsequently targeting eNOS, AGTR1, AGTR2, and oxidative stress. Therefore, in addition to its role in treating CKD anemia, FG-4592 could be explored as a treatment for hypertension associated with high RAS activity or eNOS defects.
Jing Yu, Shuqin Wang, Wei Shi, Wei Zhou, Yujia Niu, Songming Huang, Yue Zhang, Aihua Zhang, Zhanjun Jia
Neutrophils provide a critical line of defense in immune responses to various pathogens, but also inflict self-damage upon transition to a hyperactivated, procoagulant state. Recent work has highlighted proinflammatory neutrophil phenotypes contributing to lung injury and acute respiratory distress syndrome (ARDS) in patients suffering from COVID-19. Here, we utilize state-of-the art mass spectrometry-based proteomics, transcriptomic and correlative analyses as well as functional in vitro and in vivo studies to dissect how neutrophils contribute to the progression to severe COVID-19. We identify a reinforcing loop of both systemic and neutrophil intrinsic interleukin-8 (CXCL8/IL-8) dysregulation, which initiates and perpetuates neutrophil-driven immunopathology. This positive feedback loop of systemic and neutrophil autocrine IL-8 production leads to an activated, prothrombotic neutrophil phenotype characterized by degranulation and neutrophil extracellular trap (NET) formation. In severe COVID-19, neutrophils directly initiate the coagulation and complement cascade, highlighting a link to the immunothrombotic state observed in these patients. Targeting the IL-8-CXCR-1/-2 axis interferes with this vicious cycle and attenuates neutrophil activation, degranulation, NETosis, and IL-8 release. Finally, we show that blocking IL-8-like signaling reduces SARS-CoV-2 spike protein-induced, hACE2-dependent pulmonary microthrombosis in mice. In summary, our data provide comprehensive insights into the activation mechanisms of neutrophils in COVID-19 and uncover a self-sustaining neutrophil-IL-8-axis as promising therapeutic target in severe SARS-CoV-2 infection.
Rainer Kaiser, Alexander Leunig, Kami Pekayvaz, Oliver Popp, Markus Joppich, Vivien Polewka, Raphael Escaig, Afra Anjum, Marie-Louise Hoffknecht, Christoph Gold, Sophia Brambs, Anouk Engel, Sven Stockhausen, Viktoria Knottenberg, Anna Titova, Mohamed Haji, Clemens Scherer, Maximilian Muenchhoff, Johannes C. Hellmuth, Kathrin Saar, Benjamin Schubert, Anne Hilgendorff, Christian Schulz, Stefan Kääb, Ralf Zimmer, Norbert Hübner, Steffen Massberg, Philipp Mertins, Leo Nicolai, Konstantin Stark
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