Oscillating flow promotes inflammation through the TLR2–TAK1–IKK2 signalling pathway in human umbilical vein endothelial cell (HUVECs)

Enhanced Natural Killer Cell Proliferation by Stress-Induced Feeder Cells

Natural killer (NK) cells, integral to the innate immune system, are notable in cell therapies because of their applicability in allogeneic treatments, distinguishing them from T cells typically employed in conventional cell therapies. However, their limited half-life (proliferative capability) poses a challenge for therapy. The limited half-life creates difficulties in obtaining a sufficient number of cells for in vitro adoptive therapy. Gene modification is commonly employed to address this limitation. However, due to concerns such as genetic instability and unintended gene expression, its suitability for long-term cultivation is uncertain. Consequently, safer alternatives are needed. We aimed to promote NK cell proliferation through feeder cells rather than genetic modification. These cells are designed to interact with NK cells without adverse effects, aiming to promote NK cell proliferation more safely. In our study, during the tailoring of feeder cells, we excluded genetic modification and instead applied chemical-based extracellular stress. The extracellular stress applied consisted of hypoxia and cytochalasin D. By treating the feeder cells with these stressors, we were able to inhibit feeder cell proliferation, enabling them to function more efficiently as feeder cells. Furthermore, we observed that the feeder cells subjected to extracellular stress exhibited upregulated expression of 4-1BBL, which enhances the 4-1BB/4-1BBL interaction with NK cells. The upregulated 4-1BBL binds to 4-1BB on the surface of NK cells, promoting their proliferation. Additionally, following coculture with feeder cells exposed to extracellular stress, we observed an upregulation of CD56 expression on the surface of NK cells. These CD56bright NK cells influence NK cell proliferation through enhanced cytokine release. We further validated this process under dynamic conditions where shear stress is applied, demonstrating that the feeder cell-mediated enhancement of NK cell proliferation is applicable under dynamic conditions such as those found in bioreactors.

miR-328-3p targets TLR2 to ameliorate oxygen-glucose deprivation injury and neutrophil extracellular trap formation in HUVECs via inhibition of the NF-κB signaling pathway

BACKGROUND

Endothelial cell injury is one of the important pathogenic mechanisms in thrombotic diseases, and also neutrophils are involved. MicroRNAs (miRNAs) have been demonstrated to act as essential players in endothelial cell injury, but the potential molecular processes are unknown. In this study, we used cellular tests to ascertain the protective effect of miR-328-3p on human umbilical vein endothelial cells (HUVECs) treated with oxygen-glucose deprivation (OGD).

METHODS

In our study, an OGD-induced HUVECs model was established, and we constructed lentiviral vectors to establish stable HUVECs cell lines. miR-328-3p and Toll-like receptor 2 (TLR2) interacted, as demonstrated by the dual luciferase reporter assay. We used the CCK8, LDH release, and EdU assays to evaluate the proliferative capacity of each group of cells. To investigate the expression of TLR2, p-P65 NF-κB, P65 NF-κB, NLRP3, IL-1β, and IL-18, we employed Western blot and ELISA. Following OGD, each group's cell supernatants were gathered and co-cultured with neutrophils. An immunofluorescence assay and Transwell assay have been performed to determine whether miR-328-3p/TLR2 interferes with neutrophil migration and neutrophil extracellular traps (NETs) formation.

RESULTS

In OGD-treated HUVECs, the expression of miR-328-3p is downregulated. miR-328-3p directly targets TLR2, inhibits the NF-κB signaling pathway, and reverses the proliferative capacity of OGD-treated HUVECs, while inhibiting neutrophil migration and neutrophil extracellular trap formation.

CONCLUSIONS

miR-328-3p inhibits the NF-κB signaling pathway in OGD-treated HUVECs while inhibiting neutrophil migration and NETs formation, and ameliorating endothelial cell injury, which provides new ideas for the pathogenesis of thrombotic diseases.

Quercetin protects endothelial function from inflammation induced by localized disturbed flow by inhibiting NRP2 -VEGFC complex

Atherosclerosis is a focal chronic inflammatory disease, the initial pathogenic event of which is endothelial dysfunction, and disturbed flow (DF) is the primary and vital factor underlying endothelial dysfunction. The present research aims to elucidate the mechanism underlying the regulation of Neuropilin (NRP)2 under DF in endothelial cells (ECs) in an inflammatory state. We observed that NRP2 expression was significantly upregulated in DF-stimulated human umbilical vein endothelial cells (HUVECs). Knockdown of NRP2 in HUVECs significantly ameliorated cell inflammation induced by DF. In addition, quercetin inhibited NRP2 expression as well as endothelial inflammation. Animal experiments suggested that NRP2 knockdown or intraperitoneal injection of quercetin affected the expression of inflammation-related genes. Moreover, the upstream transcription factor GATA2 was found to regulate NRP2 transcription by binding to the -1100 to +100 bp region of the NRP2 promoter. Further studies showed that quercetin inhibited NRP2-VEGFC complex formation induced by disturbed flow, although did not inhibit GATA2 expression. These findings suggest that NRP2 plays an important role in promoting inflammation. Quercetin antagonizes atherosclerosis by inhibiting NRP2 and the formation of NRP2-VEGFC complex by inhibiting the inflammatory effects induced by disordered flow.

Effects of shear stress on vascular endothelial functions in atherosclerosis and potential therapeutic approaches

Different blood flow patterns in the arteries can alter the adaptive phenotype of vascular endothelial cells (ECs), thereby affecting the functions of ECs and are directly associated with the occurrence of lesions in the early stages of atherosclerosis (AS). Atherosclerotic plaques are commonly found at curved or bifurcated arteries, where the blood flow pattern is dominated by oscillating shear stress (OSS). OSS can induce ECs to transform into pro-inflammatory phenotypes, increase cellular inflammation, oxidative stress response, mitochondrial dysfunction, metabolic abnormalities and endothelial permeability, thereby promoting the progression of AS. On the other hand, the straight artery has a stable laminar shear stress (LSS), which promotes the transformation of ECs into an anti-inflammatory phenotype, improves endothelial cell function, thereby inhibits atherosclerotic progression. ECs have the ability to actively sense, integrate, and convert mechanical stimuli by shear stress into biochemical signals that further induces intracellular changes (such as the opening and closing of ion channels, activation and transcription of signaling pathways). Here we not only outline the relationship between functions of vascular ECs and different forms of fluid shear stress in AS, but also aim to provide new solutions for potential atherosclerotic therapies targeting intracellular mechanical transductions.

The Effect of Blood Pressure Variability on Coronary Atherosclerosis Plaques

Hypertension is one of the most important risk factors for coronary heart disease (CHD). The regulation of blood pressure plays a significant role in the development and prognosis of CHD. Blood pressure variability (BPV) refers to the degree of fluctuation of blood pressure over a period of time and is an important indicator of blood pressure stability. Blood pressure fluctuations are complex physiological phenomena, being affected by physiological and pharmacological effects and regulated by behavioral, environmental, hydrodynamic, and neural factors. According to the different time periods for measuring BPV, it can be divided into very short-term, short-term, mid-term, and long-term. Multiple cardiovascular disease animal models and clinical experiments have consistently indicated that abnormal BPV is closely related to coronary events and is a risk factor for CHD independently of average blood pressure. Thrombosis secondary to plaque rupture (PR) or plaque erosion can cause varying blood flow impairment, which is the main pathological basis of CHD. Plaque morphology and composition can influence the clinical outcome, treatment, and prognosis of patients with CHD. Research has shown that PR is more easily induced by hypertension. After adjusting for the traditional factors associated with plaque development, in recent years, some new discoveries have been made on the influence of abnormal BPV on the morphology and composition of coronary plaques and related mechanisms, including inflammation and hemodynamics. This article reviews the impact of BPV on coronary plaques and their related mechanisms, with a view to prevent the occurrence and development of CHD by controlling BPV and to provide new prevention and treatment strategies for the clinical treatment of abnormal blood pressure.

NRP2 promotes atherosclerosis by upregulating PARP1 expression and enhancing low shear stress-induced endothelial cell apoptosis

Atherosclerosis-related cardiovascular diseases are leading causes of mortality worldwide, characterized by the development of endothelial cell dysfunction, increased oxidized low-density lipoprotein uptake by macrophages, and the ensuing formation of atherosclerotic plaque. Local blood flow patterns cause uneven atherosclerotic lesion distribution, and endothelial dysfunction caused by disturbed flow is an early step in the development of atherosclerosis. The present research aims to elucidate the mechanism underlying the regulation of Neuropilin 2 (NRP2) under low shear stress (LSS) in the atheroprone phenotype of endothelial cells. We observed that NRP2 expression was significantly upregulated in LSS-stimulated human umbilical vein endothelial cells (HUVECs) and in mouse aortic endothelial cells. Knockdown of NRP2 in HUVECs significantly ameliorated cell apoptosis induced by LSS. Conversely, overexpression of NRP2 had the opposite effect on HUVEC apoptosis. Animal experiments suggest that NRP2 knockdown markedly mitigated the development of atherosclerosis in Apoe^-/- mice. Mechanistically, NRP2 knockdown and overexpression regulated PARP1 protein expression in the condition of LSS, which in turn affected the expression of apoptosis-related genes. Moreover, the upstream transcription factor GATA2 was found to regulate NRP2 expression in the progression of atherosclerosis. These findings suggest that NRP2 plays an essential proatherosclerotic role through the regulation of cell apoptosis, and the results reveal that NRP2 is a promising therapeutic target for the treatment of atherosclerotic disorders.

Mechanism of cell death of endothelial cells regulated by mechanical forces

Cell death of endothelial cells (ECs) is a common devastating consequence of various vascular-related diseases. Atherosclerosis, hypertension, sepsis, diabetes, cerebral ischemia and cardiac ischemia/reperfusion injury, and chronic kidney disease remain major causes of morbidity and mortality worldwide, in which ECs are constantly subjected to a great amount of dynamic changed mechanical forces including shear stress, extracellular matrix stiffness, mechanical stretch and microgravity. A thorough understanding of the regulatory mechanisms by which the mechanical forces controlled the cell deaths including apoptosis, autophagy, and pyroptosis is crucial for the development of new therapeutic strategies. In the present review, experimental and clinical data highlight that nutrient depletion, oxidative stress, tumor necrosis factor-α, high glucose, lipopolysaccharide, and homocysteine possess cytotoxic effects in many tissues and induce apoptosis of ECs, and that sphingosine-1-phosphate protects ECs. Nevertheless, EC apoptosis in the context of those artificial microenvironments could be enhanced, reduced or even reversed along with the alteration of patterns of shear stress. An appropriate level of autophagy diminishes EC apoptosis to some extent, in addition to supporting cell survival upon microenvironment challenges. The intervention of pyroptosis showed a profound effect on atherosclerosis. Further cell and animal studies are required to ascertain whether the alterations in the levels of cell deaths and their associated regulatory mechanisms happen at local lesion sites with considerable mechanical force changes, for preventing senescence and cell deaths in the vascular-related diseases.

The Role of Toll-like Receptors in Atherothrombotic Cardiovascular Disease

Toll-like receptors (TLRs) are dominant components of the innate immune system. Activated by both pathogen-associated molecular patterns and damage-associated molecular patterns, TLRs underpin the pathology of numerous inflammation related diseases that include not only immune diseases, but also cardiovascular disease (CVD), diabetes, obesity, and cancers. Growing evidence has demonstrated that TLRs are involved in multiple cardiovascular pathophysiologies, such as atherosclerosis and hypertension. Specifically, a trial called the Canakinumab Anti-inflammatory Thrombosis Outcomes Study showed the use of an antibody that neutralizes interleukin-1β, reduces the recurrence of cardiovascular events, demonstrating inflammation as a therapeutic target and also the research value of targeting the TLR system in CVD. In this review, we provide an update of the interplay between TLR signaling, inflammatory mediators, and atherothrombosis, with an aim to identify new therapeutic targets for atherothrombotic CVD.

Pulsatile Flow in Microfluidic Systems

This review describes the current knowledge and applications of pulsatile flow in microfluidic systems. Elements of fluid dynamics at low Reynolds number are first described in the context of pulsatile flow. Then the practical applications in microfluidic processes are presented: the methods to generate a pulsatile flow, the generation of emulsion droplets through harmonic flow rate perturbation, the applications in mixing and particle separation, and the benefits of pulsatile flow for clog mitigation. The second part of the review is devoted to pulsatile flow in biological applications. Pulsatile flows can be used for mimicking physiological systems, to alter or enhance cell cultures, and for bioassay automation. Pulsatile flows offer unique advantages over a steady flow, especially in microfluidic systems, but also require some new physical insights and more rigorous investigation to fully benefit future applications.

Low shear stress damages endothelial function through STAT1 in endothelial cells (ECs)

Low shear stress (LSS) occurs in areas where atherosclerosis is prevalent. Many studies have revealed that signal transducer and activator of transcription 1 (STAT1) plays a significant role in cardiovascular disease. Nonetheless, the mechanism underlying the connection between STAT1 and LSS is not fully understood. The purpose of this study was to investigate the link between LSS and STAT1 in endothelial cells (ECs). Monolayer endothelial cells were stimulated or not stimulated by LSS. Protein expression and phosphorylation levels were determined by western blotting. Immunofluorescence was used to compare the protein expression differences in bifurcated and non-bifurcated human coronary arteries. Endothelial function was assessed by using a dihydroethidium assay, real-time PCR, western blotting and nitric oxide (NO)-sensitive fluorophore. Results showed that STAT1 played a key role in LSS-induced endothelium damage. Firstly, LSS activated STAT1, as evidenced by LSS-induced STAT1 (Tyr701) phosphorylation in ECs in vitro and the increased intimal STAT1 expression at bifurcation of human coronary arteries. Secondly, LSS-induced STAT1 phosphorylation was positively regulated by inhibitor of nuclear factor kappa-B kinase ε (IKKε). Additionally, LSS-promoted inflammatory factor expression was markedly reversed by silencing STAT1 (siSTAT1). LSS also increased reactive oxygen species (ROS) level and decreased endogenous NO release: however, siSTAT1 reversed these adverse effects through upregulating the antioxidant gene heme oxygenase-1(HO-1) and downregulating endothelial nitric oxide synthase (eNOS) Thr495 phosphorylation. According to our results, LSS-mediated EC injury may be associated with the activation of STAT1. Strategies designed to reduce STAT1 expression or inhibit STAT1 activation may be effective approaches for reducing the incidence of atherosclerosis.

Polyamine Transport Protein PotD Protects Mice against Haemophilus parasuis and Elevates the Secretion of Pro-Inflammatory Cytokines of Macrophage via JNK-MAPK and NF-κB Signal Pathways through TLR4

The potD gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system potABCD, encodes the bacterial substrate-binding subunit of the polyamine transport system. In this study, we found PotD in Haemophilus (Glaesserella) parasuis could actively stimulate both humoral immune and cellular immune responses and elevate lymphocyte proliferation, thus eliciting a Th1-type immune response in a murine immunity and infection model. Stimulation of Raw 264.7 macrophages with PotD validated that Toll-like receptor 4, rather than 2, participated in the positive transcription and expression of pro-inflammatory cytokines IL–1β, IL–6, and TNF–α using qPCR and ELISA. Blocking signal-regulated JNK–MAPK and RelA(p65) pathways significantly decreased PotD-induced pro-inflammatory cytokine production. Overall, we conclude that vaccination of PotD could induce both humoral and cellular immune responses and provide immunoprotection against H. parasuis challenge. The data also suggest that Glaesserella PotD is a novel pro-inflammatory mediator and induces TLR4-dependent pro-inflammatory activity in Raw 264.7 macrophages through JNK–MAPK and RelA(p65) pathways.

Activation of GPR81 by lactate inhibits oscillatory shear stress-induced endothelial inflammation by activating the expression of KLF2

Atherosclerosis is a common and deadly cardiovascular disease with extremely high prevalence. Areas of the vasculature exposed to oscillatory shear stress (OSS) or disturbed blood flow are particularly prone to the development of atherosclerotic lesions. In part, various mechanosensitive receptors on the surface of endothelial cells play a role in regulating the ability of the vasculature to cope with variations in blood flow patterns. However, the exact mechanisms behind flow-mediated endothelial responses remain poorly understood. Along with the development of highly specific receptor agonists, the class of G coupled-protein receptors has been receiving increasing attention as potential therapeutic targets. G coupled-protein receptor 81 (GPR81), also known as hydroxycarboxylic acid receptor 1 (HCA₁ ), is activated by lactate, its endogenous ligand. In the present study, we show for the first time that expression of GPR81 is significantly downregulated in response to OSS in endothelial cells and that activation of GPR81 using physiologically relevant doses of lactate can rescue OSS-induced reduced GPR81 expression. Importantly, our findings demonstrate that activation of GPR81 can exert valuable atheroprotective effects in endothelial cells exposed to OSS by reducing oxidative stress and significantly downregulating the expression of inflammatory cytokines including interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1, and high mobility group box 1 (HMGB1). We also show that activation of GPR81 can potentially prevent the attachment of monocytes to the endothelium by suppressing OSS-induced secretion of vascular cellular adhesion molecule (VCAM)-1 and endothelial-selectin (E-selectin). Finally, we show that activation of GPR81 can rescue OSS-induced reduced expression of the key atheroprotective transcription factor Kruppel-like factor 2 (KLF2), which is mediated through the extracellular-regulated kinase 5 (ERK5) pathway. These findings demonstrate a potential protective role of GPR81 against atherogenesis and that targeted activation of GPR81 may inhibit endothelial inflammation and dysfunction induced by OSS.