Rapamycin regulates the expression and activity of Krüppel-like transcription factor 2 in human umbilical vein endothelial cells

Single-Cell RNA Sequencing Reveals That Adaptation of Human Aortic Endothelial Cells to Antiproliferative Therapies Is Modulated by Flow-Induced Shear Stress

BACKGROUND

Endothelial cells (ECs) are capable of quickly responding in a coordinated manner to a wide array of stresses to maintain vascular homeostasis. Loss of EC cellular adaptation may be a potential marker for cardiovascular disease and a predictor of poor response to endovascular pharmacological interventions such as drug-eluting stents. Here, we report single-cell transcriptional profiling of ECs exposed to multiple stimulus classes to evaluate EC adaptation.

METHODS

Human aortic ECs were costimulated with both pathophysiological flows mimicking shear stress levels found in the human aorta (laminar and turbulent, ranging from 2.5 to 30 dynes/cm2) and clinically relevant antiproliferative drugs, namely paclitaxel and rapamycin. EC state in response to these stimuli was defined using single-cell RNA sequencing.

RESULTS

We identified differentially expressed genes and inferred the TF (transcription factor) landscape modulated by flow shear stress using single-cell RNA sequencing. These flow-sensitive markers differentiated previously identified spatially distinct subpopulations of ECs in the murine aorta. Moreover, distinct transcriptional modules defined flow- and drug-responsive EC adaptation singly and in combination. Flow shear stress was the dominant driver of EC state, altering their response to pharmacological therapies.

CONCLUSIONS

We showed that flow shear stress modulates the cellular capacity of ECs to respond to paclitaxel and rapamycin administration, suggesting that while responding to different flow patterns, ECs experience an impairment in their transcriptional adaptation to other stimuli.

Tannic acid as a plant-derived polyphenol exerts vasoprotection via enhancing KLF2 expression in endothelial cells

The transcription factor Kruppel-like factor 2 (KLF2) is a critical anti-inflammatory and anti-atherogenic molecule in vascular endothelium. Enhancing KLF2 expression and activity improves endothelial function and prevents atherosclerosis. However, the pharmacological and molecular regulators for KLF2 are scarce. Using high-throughput luciferase reporter assay to screen for KLF2 activators, we have identified tannic acid (TA), a polyphenolic compound, as a potent KLF2 activator that attenuates endothelial inflammation. Mechanistic studies suggested that TA induced KLF2 expression in part through the ERK5/MEF2 pathway. Functionally, TA markedly decreased monocyte adhesion to ECs by reducing expression of adhesion molecule VCAM1. Using lung ECs isolated from Klf2^+/+ and Klf2^+/− mice, we showed that the anti-inflammatory effect of TA is dependent on KLF2. Collectively, our results demonstrate that TA is a potent KLF2 activator and TA attenuated endothelial inflammation through upregulation of KLF2. Our findings provide a novel mechanism for the well-established beneficial cardiovascular effects of TA and suggest that KLF2 could be a novel therapeutic target for atherosclerotic vascular disease.

Growth-promoting action and growth factor release by different platelet derivatives

Abstract Platelet derivatives are commonly used in wound healing and tissue regeneration. Different procedures of platelet preparation may differentially affect growth factor release and cell growth. Preparation of platelet-rich fibrin (PRF) is accompanied by release of growth factors, including platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and transforming growth factor β1 (TGFβ1), and several cytokines. When compared with the standard procedure for platelet-rich plasma (PRP), PRF released 2-fold less PDGF, but >15-fold and >2-fold VEGF and TGFβ1, respectively. Also, the release of several cytokines (IL-4, IL-6, IL-8, IL-10, IFNγ, MIP-1α, MIP-1β and TNFα) was significantly increased in PRF-conditioned medium (CM), compared to PRP-CM. Incubation of both human skin fibroblasts and human umbilical vein endothelial cells (HUVECs) with PRF-derived membrane (mPRF) or with PRF-CM enhanced cell proliferation by >2-fold (p<0.05). Interestingly, PRP elicited fibroblast growth at a higher extent compared to PRF. At variance, PRF effect on HUVEC growth was significantly greater than that of PRP, consistent with a higher concentration of VEGF in the PRF-CM. Thus, the procedure of PRP preparation leads to a larger release of PDGF, as a possible result of platelet degranulation, while PRF enhances the release of proangiogenic factors.