Non-Invasive Pulsatile Shear Stress Modifies Endothelial Activation; A Narrative Review

Exploring Endothelial Cell Dysfunction's Impact on the Brain-Retina Microenvironment Connection: Molecular Mechanisms and Implications

The intricate linking between the health of blood vessels and the functioning of neurons has attracted growing attention in the context of disorders that affect the neurological environment. Endothelial cells, forming the blood-brain barrier and blood-retinal barrier, play a fundamental role in maintaining the integrity of the brain-retina microenvironment connection. This review explores the molecular foundations of endothelial cell dysfunction and its implications for the brain-retina interaction. A comprehensive analysis of the complex factors contributing to endothelial dysfunction is presented, including oxidative stress, inflammation, reduced nitric oxide signaling, and disrupted vascular autoregulation. The significance of endothelial dysfunction extends to neurovascular coupling, synaptic plasticity, and trophic support. To our knowledge, there is currently no existing literature review addressing endothelial microvascular dysfunction and its interplay with the brain-retina microenvironment. The review also explains bidirectional communication between the brain and retina, highlighting how compromised endothelial function can disrupt this vital crosstalk and inhibit normal physiological processes. As neurodegenerative diseases frequently exhibit vascular involvement, a deeper comprehension of the interaction between endothelial cells and neural tissue holds promise for innovative therapeutic strategies. By targeting endothelial dysfunction, we may enhance our ability to preserve the intricate dynamics of the brain-retina microenvironment connection and ameliorate the progression of neurological disorders.

Effects of pulsatile flow on postoperative recovery in adult cardiac surgery with cardiopulmonary bypass: A systematic review and meta-analysis of randomized controlled trials

Background

The role of pulsatile versus non-pulsatile flow during cardiopulmonary bypass (CPB) is still in debate. This systematic review aimed to comprehensively assess the impact of pulsatile versus non-pulsatile flow on patients' recovery.

Methods

We searched MEDLINE, EMBASE, and Cochrane Library databases for randomized controlled trials comparing pulsatile and non-pulsatile flow in cardiac surgeries with CPB. Data were analyzed using the random-effects model. Then, sensitive analysis and meta-regression were conducted.

Findings

32 studies including 2568 patients were considered in this meta-analysis. There is no difference in in-hospital mortality between the two groups (risk ratio [RR] = 0.74, 95 % confidence interval [CI] = 0.35-1.56, p = 0.43). The ICU stay for the pulsatile group was still significantly shorter than that for the non-pulsatile group (mean difference [MD] = -0.19, 95%CI = -0.35∼-0.03, p = 0.02). Patients in the pulsatile group experienced a shorted stay in hospital (MD = -0.68, 95%CI = -0.97∼-0.39, p < 0.01) and a lower risk for acute kidney injury (AKI) compared with non-pulsatile group (RR = 0.46, 95%CI 0.35-0.60, p < 0.01). There was no significant difference of the postoperative cognitive dysfunction (POCD) between the two groups no matter the roller pump or the intra-aortic balloon pump was used (RR = 0.98, 95%CI = 0.87-1.11, p = 0.78).

Conclusions

The use of pulsatile flow during CPB in heart surgery has a protective effect on patient recovery. It can reduce the incidence of AKI, shorten the ICU and hospital stays, but its positive effect on postoperative mortality and POCD is not yet apparent.

Effects of high-frequency mechanical stimuli on flow related vascular cell biology

Mechanical forces related to blood pressure and flow patterns play a crucial role in vascular homeostasis. Perturbations in vascular stresses and strain resulting from changes in hemodynamic may occur in pathological conditions, leading to vascular dysfunction as well as in vascular prosthesis, arteriovenous shunt for hemodialysis and in mechanical circulation support. Turbulent-like blood flows can induce high-frequency vibrations of the vessel wall, and this stimulus has recently gained attention as potential contributors to vascular pathologies, such as development of intimal hyperplasia in arteriovenous fistula for hemodialysis. However, the biological response of vascular cells to this stimulus remains incompletely understood. This review provides an analysis of the existing literature concerning the impact of high-frequency stimuli on vascular cell morphology, function, and gene expression. Morphological and functional investigations reveal that vascular cells stimulated at frequencies higher than the normal heart rate exhibit alterations in cell shape, alignment, and proliferation, potentially leading to vessel remodeling. Furthermore, vibrations modulate endothelial and smooth muscle cells gene expression, affecting pathways related to inflammation, oxidative stress, and muscle hypertrophy. Understanding the effects of high-frequency vibrations on vascular cells is essential for unraveling the mechanisms underlying vascular diseases and identifying potential therapeutic targets. Nevertheless, there are still gaps in our understanding of the molecular pathways governing these cellular responses. Further research is necessary to elucidate these mechanisms and their therapeutic implications for vascular diseases.

Pulsatile flow increases METTL14-induced m 6 A modification and attenuates septic cardiomyopathy: an experimental study

INTRODUCTION

Septic cardiomyopathy is a sepsis-mediated cardiovascular complication with severe microcirculatory malperfusion. Emerging evidence has highlighted the protective effects of pulsatile flow in case of microcirculatory disturbance, yet the underlying mechanisms are still elusive. The objective of this study was to investigate the mechanisms of N 6 -methyladenosine (m 6 A) modification in the alleviation of septic cardiomyopathy associated with extracorporeal membrane oxygenation (ECMO)-generated pulsatile flow.

METHODS

Rat model with septic cardiomyopathy was established and was supported under ECMO either with pulsatile or non-pulsatile flow. Peripheral perfusion index (PPI) and cardiac function parameters were measured using ultrasonography. Dot blot assay was applied to examine the m 6 A level, while qRT-PCR, Western blot, immunofluorescence, and immunohistochemistry were used to measure the expressions of related genes. RNA immunoprecipitation assay was performed to validate the interaction between molecules.

RESULTS

The ECMO-generated pulsatile flow significantly elevates microcirculatory PPI, improves myocardial function, protects the endothelium, and prolongs survival in rat models with septic cardiomyopathy. The pulsatile flow mediates the METTL14-mediated m 6 A modification to zonula occludens-1 (ZO-1) mRNA (messenger RNA), which stabilizes the ZO-1 mRNA depending on the presence of YTHDF2. The pulsatile flow suppresses the PI3K-Akt signaling pathway, of which the downstream molecule Foxo1, a negative transcription factor of METTL14, binds to the METTL14 promoter and inhibits the METTL14-induced m 6 A modification.

CONCLUSION

The ECMO-generated pulsatile flow increases METTL14-induced m 6 A modification in ZO-1 and attenuates the progression of septic cardiomyopathy, suggesting that pulsatility might be a new therapeutic strategy in septic cardiomyopathy by alleviating microcirculatory disturbance.

Hemocompatibility and biophysical interface of left ventricular assist devices and total artificial hearts

ABSTRACT

Over the past 2 decades, there has been a significant increase in the utilization of long-term mechanical circulatory support (MCS) for the treatment of cardiac failure. Left ventricular assist devices (LVADs) and total artificial hearts (TAHs) have been developed in parallel to serve as bridge-to-transplant and destination therapy solutions. Despite the distinct hemodynamic characteristics introduced by LVADs and TAHs, a comparative evaluation of these devices regarding potential complications in supported patients, has not been undertaken. Such a study could provide valuable insights into the complications associated with these devices. Although MCS has shown substantial clinical benefits, significant complications related to hemocompatibility persist, including thrombosis, recurrent bleeding, and cerebrovascular accidents. This review focuses on the current understanding of hemostasis, specifically thrombotic and bleeding complications, and explores the influence of different shear stress regimens in long-term MCS. Furthermore, the role of endothelial cells in protecting against hemocompatibility-related complications of MCS is discussed. We also compared the diverse mechanisms contributing to the occurrence of hemocompatibility-related complications in currently used LVADs and TAHs. By applying the existing knowledge, we present, for the first time, a comprehensive comparison between long-term MCS options.

Harnessing Passive Pulsatile Shear Stress for Alzheimer's Disease Prevention and Intervention

Alzheimer's disease (AD) affects more than 40 million people worldwide and is the leading cause of dementia. This disease is a challenge for both patients and caregivers and puts a significant strain on the global healthcare system. To address this issue, the Lancet Commission recommends focusing on reducing modifiable lifestyle risk factors such as hypertension, diabetes, and physical inactivity. Passive pulsatile shear stress (PPSS) interventions, which use devices like whole-body periodic acceleration, periodic acceleration along the Z-axis (pGz), and the Jogging Device, have shown significant systemic and cellular effects in preclinical and clinical models which address these modifiable risks factors. Based on this, we propose that PPSS could be a potential non-pharmacological and non-invasive preventive or therapeutic strategy for AD. We perform a comprehensive review of the biological basis based on all publications of PPSS using these devices and demonstrate their effects on the various aspects of AD. We draw from this comprehensive analysis to support our hypothesis. We then delve into the possible application of PPSS as an innovative intervention. We discuss how PPSS holds promise in ameliorating hypertension and diabetes while mitigating physical inactivity, potentially offering a holistic approach to AD prevention and management.

Influence of enhanced external counterpulsation on endothelial function: a meta-analysis of randomized controlled trials

OBJECTIVES

Enhanced external counterpulsation (EECP) is an effective and noninvasive treatment for patients with refractory angina and chronic heart failure. However, previous studies evaluating the influence of EECP on endothelial function showed inconsistent results. This systematic review and meta-analysis was conducted to evaluate the effects of EECP on endothelial function measured by brachial artery flow-mediated dilation (FMD).

DESIGN

PubMed, Embase, Cochrane Library, CNKI, and Wanfang databases were searched for randomized controlled trials comparing the influence of EECP versus usual care on FMD in adult population. A random-effects model incorporating the potential influence of heterogeneity was used to pool the results.

RESULTS

Nineteen studies with 1647 patients were included in the meta-analysis. Compared with usual care or conventional therapy, additional treatment with EECP for 3-7 weeks was associated with a significantly improved FMD (mean difference [MD]: 1.96%, 95% confidence interval [CI]: 1.57-2.36, p < 0.001, I2 = 52%). Subgroup analysis showed consistent results in patients with coronary artery disease and in patients with other diseases (p for subgroup difference = 0.21). Results of meta-regression analysis showed that the mean baseline FMD level was positively correlated with the influence of EECP on FMD (coefficient = 0.42, p < 0.001). Results of subgroup analysis suggested that the increment of FMD following EECP was larger in patients with baseline FMD ≥ 5% (MD: 2.69, 95% CI: 2.27-3.10, p < 0.001; I2 = 15%) compared to those with baseline FMD < 5% (MD: 1.49, 95% CI: 1.13-1.85, p < 0.001; I2 = 0%; p for subgroup difference < 0.001).

CONCLUSIONS

EECP may be effective in improving endothelial function measured by FMD.

Bacterial lipopolysaccharide-induced endothelial activation and dysfunction: a new predictive and therapeutic paradigm for sepsis

BACKGROUND

Lipopolysaccharide, a highly potent endotoxin responsible for severe sepsis, is the major constituent of the outer membrane of gram-negative bacteria. Endothelial cells participate in both innate and adaptive immune responses as the first cell types to detect lipopolysaccharide or other foreign debris in the bloodstream. Endothelial cells are able to recognize the presence of LPS and recruit specific adaptor proteins to the membrane domains of TLR4, thereby initiating an intracellular signaling cascade. However, lipopolysaccharide binding to endothelial cells induces endothelial activation and even damage, manifested by the expression of proinflammatory cytokines and adhesion molecules that lead to sepsis.

MAIN FINDINGS

LPS is involved in both local and systemic inflammation, activating both innate and adaptive immunity. Translocation of lipopolysaccharide into the circulation causes endotoxemia. Endothelial dysfunction, including exaggerated inflammation, coagulopathy and vascular leakage, may play a central role in the dysregulated host response and pathogenesis of sepsis. By discussing the many strategies used to treat sepsis, this review attempts to provide an overview of how lipopolysaccharide induces the ever more complex syndrome of sepsis and the potential for the development of novel sepsis therapeutics.

CONCLUSIONS

To reduce patient morbidity and mortality, preservation of endothelial function would be central to the management of sepsis.