Intracellular ascorbate tightens the endothelial permeability barrier through Epac1 and the tubulin cytoskeleton

Vitamin C: Rationale for Its Use in Sepsis-Induced Acute Respiratory Distress Syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) is a life-threatening event that occurs in patients suffering from bacterial, fungal, or viral sepsis. Research performed over the last five decades showed that ARDS is a consequence of severe unrestrained systemic inflammation, which leads to injury of the lung's microvasculature and alveolar epithelium. ARDS leads to acute hypoxic/hypercapnic respiratory failure and death in a significant number of patients hospitalized in intensive care units worldwide. Basic and clinical research performed during the time since ARDS was first described has been unable to construct a pharmacological agent that will combat the inflammatory fire leading to ARDS. In-depth studies of the molecular pharmacology of vitamin C indicate that it can serve as a potent anti-inflammatory agent capable of attenuating the pathobiological events that lead to acute injury of the lungs and other body organs. This analysis of vitamin C's role in the treatment of ARDS includes a focused systematic review of the literature relevant to the molecular physiology of vitamin C and to the past performance of clinical trials using the agent.

How Do Minerals, Vitamins, and Intestinal Microbiota Affect the Development and Progression of Heart Disease in Adult and Pediatric Patients?

Cardiovascular diseases (CVDs) are the leading cause of death worldwide, far ahead of cancer. Epidemiological data emphasize the participation of many risk factors that increase the incidence of CVDs, including genetic factors, age, and sex, but also lifestyle, mainly nutritional irregularities and, connected with them, overweight and obesity, as well as metabolic diseases. Despite the importance of cardiovascular problems in the whole society, the principles of prevention of CVDs are not widely disseminated, especially among the youngest. As a result, nutritional neglect, growing from childhood and adolescence, translates into the occurrence of numerous disease entities, including CVDs, in adult life. This review aimed to draw attention to the role of selected minerals and vitamins in health and the development and progression of CVDs in adults and children. Particular attention was paid to the effects of deficiency and toxicity of the analyzed compounds in the context of the cardiovascular system and to the role of intestinal microorganisms, which by interacting with nutrients, may contribute to the development of cardiovascular disorders. We hope this article will draw the attention of society and the medical community to emphasize promoting healthy eating and proper eating habits in children and adults, translating into increased awareness and a reduced risk of CVD.

Association of Vitamin C, Thiamine, and Hydrocortisone Infusion With Long-term Cognitive, Psychological, and Functional Outcomes in Sepsis Survivors: A Secondary Analysis of the Vitamin C, Thiamine, and Steroids in Sepsis Randomized Clinical Trial

Importance

Sepsis is associated with long-term cognitive impairment and worse psychological and functional outcomes. Potential mechanisms include intracerebral oxidative stress and inflammation, yet little is known about the effects of early antioxidant and anti-inflammatory therapy on cognitive, psychological, and functional outcomes in sepsis survivors.

Objective

To describe observed differences in long-term cognitive, psychological, and functional outcomes of vitamin C, thiamine, and hydrocortisone between the intervention and control groups in the Vitamin C, Thiamine, and Steroids in Sepsis (VICTAS) randomized clinical trial.

Design, Setting, and Participants

This prespecified secondary analysis reports the 6-month outcomes of the multicenter, double-blind, placebo-controlled VICTAS randomized clinical trial, which was conducted between August 2018 and July 2019. Adult patients with sepsis-induced respiratory and/or cardiovascular dysfunction who survived to discharge or day 30 were recruited from 43 intensive care units in the US. Participants were randomized 1:1 to either the intervention or control group. Cognitive, psychological, and functional outcomes at 6 months after randomization were assessed via telephone through January 2020. Data analyses were conducted between February 2021 and December 2022.

Interventions

The intervention group received intravenous vitamin C (1.5 g), thiamine hydrochloride (100 mg), and hydrocortisone sodium succinate (50 mg) every 6 hours for 96 hours or until death or intensive care unit discharge. The control group received matching placebo.

Main Outcomes and Measures

Cognitive performance, risk of posttraumatic stress disorder and depression, and functional status were assessed using a battery of standardized instruments that were administered during a 1-hour telephone call 6 months after randomization.

Results

After exclusions, withdrawals, and deaths, the final sample included 213 participants (median [IQR] age, 57 [47-67] years; 112 males [52.6%]) who underwent long-term outcomes assessment and had been randomized to either the intervention group (n = 108) or control group (n = 105). The intervention group had lower immediate memory scores (adjusted OR [aOR], 0.49; 95% CI, 0.26-0.89), higher odds of posttraumatic stress disorder (aOR, 3.51; 95% CI, 1.18-10.40), and lower odds of receiving mental health care (aOR, 0.38; 95% CI, 0.16-0.89). No other statistically significant differences in cognitive, psychological, and functional outcomes were found between the 2 groups.

Conclusions and Relevance

In survivors of sepsis, treatment with vitamin C, thiamine, and hydrocortisone did not improve or had worse cognitive, psychological, and functional outcomes at 6 months compared with patients who received placebo. These findings challenge the hypothesis that antioxidant and anti-inflammatory therapy during critical illness mitigates the development of long-term cognitive, psychological, and functional impairment in sepsis survivors.

Trial Registration

ClinicalTrials.gov Identifier: NCT03509350.

Calcium-dependent cAMP mediates the mechanoresponsive behaviour of endothelial cells to high-frequency nanomechanostimulation

The endothelial junction plays a central role in regulating intravascular and interstitial tissue permeability. The ability to manipulate its integrity therefore not only facilitates an improved understanding of its underlying molecular mechanisms but also provides insight into potential therapeutic solutions. Herein, we explore the effects of short-duration nanometer-amplitude MHz-order mechanostimulation on interendothelial junction stability and hence the barrier capacity of endothelial monolayers. Following an initial transient in which the endothelial barrier is permeabilised due to Rho-ROCK-activated actin stress fibre formation and junction disruption typical of a cell's response to insults, we observe, quite uniquely, the integrity of the endothelial barrier to not only spontaneously recover but also to be enhanced considerably-without the need for additional stimuli or intervention. Central to this peculiar biphasic response, which has not been observed with other stimuli to date, is the role of second messenger calcium and cyclic adenosine monophosphate (cAMP) signalling. We show that intracellular Ca²⁺, modulated by the high frequency excitation, is responsible for activating reorganisation of the actin cytoskeleton in the barrier recovery phase, in which circumferential actin bundles are formed to stabilise the adherens junctions via a cAMP-mediated Epac1-Rap1 pathway. Despite the short-duration stimulation (8 min), the approximate 4-fold enhancement in the transendothelial electrical resistance (TEER) of endothelial cells from different tissue sources, and the corresponding reduction in paracellular permeability, was found to persist over hours. The effect can further be extended through multiple treatments without resulting in hyperpermeabilisation of the barrier, as found with prolonged use of chemical stimuli, through which only 1.1- to 1.2-fold improvement in TEER has been reported. Such an ability to regulate and enhance endothelial barrier capacity is particularly useful in the development of in vitro barrier models that more closely resemble their in vivo counterparts.

High-Dose Vitamin C Supplementation as a Legitimate Anti-SARS-CoV-2 Prophylaxis in Healthy Subjects—Yes or No?

Vitamin C has a number of acitvities that could contribute to its immune-modulating effects. The only question is whether we should provide ourselves with only the right level of it, or do we need much more during a pandemic? The possibility of reducing the incidence of viral diseases in a well-nourished population through the use of dietary supplements based on vitamin C is not supported in the literature. Despite this, the belief that an extra intake of vitamin C can increase the efficacy of the immune system is still popular and vitamin C is advertised as a remedy to prevent infectious disease. This article refers to the justification of the use of vitamin C in high doses as an anti-SARS-CoV-2 prophylaxis in healthy subjects. Does it make sense or not? As it turns out, any effects of vitamin C supplementation may be more prominent when the baseline vitamin C level is low, for example in physically active persons. People with hypovitaminosis C are more likely to respond to vitamin C administration. No studies regarding prevention of COVID-19 with high-dose vitamin C supplementation in healthy subjects were found.

Simulated Microgravity Increases the Permeability of HUVEC Monolayer through Up-Regulation of Rap1GAP and Decreased Rap2 Activation

Space microgravity condition has great physiological influence on astronauts’ health. The interaction of endothelial cells, which control vascular permeability and immune responses, is sensitive to mechanical stress. However, whether microgravity has significant effects on the physiological function of the endothelium has not been investigated. In order to address such a question, a clinostat-based culture model with a HUVEC monolayer being inside the culture vessel under the simulated microgravity (SMG) was established. The transmittance of FITC-tagged dextran was used to estimate the change of integrity of the adherens junction of the HUVEC monolayer. Firstly, we found that the permeability of the HUVEC monolayer was largely increased after SMG treatment. To elucidate the mechanism of the increased permeability of the HUVEC monolayer under SMG, the levels of total expression and activated protein levels of Rap1 and Rap2 in HUVEC cells, which regulate the adherens junction of endothelial cells, were detected by WB and GST pull-down after SMG. As the activation of both Rap1 and Rap2 was significantly decreased under SMG, the expression of Rap1GEF1 (C3G) and Rap1GAP in HUVECs, which regulate the activation of them, was further determined. The results indicate that both C3G and Rap1GAP showed a time-dependent increase with the expression of Rap1GAP being dominant at 48 h after SMG. The down-regulation of the expression of junctional proteins, VE-cadherin and β-catenin, in HUVEC cells was also confirmed by WB and immunofluorescence after SMG. To clarify whether up-regulation of Rap1GAP is necessary for the increased permeability of the HUVEC monolayer after SMG, the expression of Rap1GAP was knocked down by Rap1GAP-shRNA, and the change of permeability of the HUVEC monolayer was detected. The results indicate that knock-down of Rap1GAP reduced SMG-induced leaking of the HUVEC monolayer in a time-dependent manner. In total, our results indicate that the Rap1GAP-Rap signal axis was necessary for the increased permeability of the HUVEC monolayer along with the down-regulation of junctional molecules including VE-cadherin and β-catenin.

Conditions for maintenance of hepatocyte differentiation and function in 3D cultures

Spheroid cultures of primary human hepatocytes (PHH) are used in studies of hepatic drug metabolism and toxicity. The cultures are maintained under different conditions, with possible confounding results. We performed an in-depth analysis of the influence of various culture conditions to find the optimal conditions for the maintenance of an in vivo like phenotype. The formation, protein expression, and function of PHH spheroids were followed for three weeks in a high-throughput 384-well format. Medium composition affected spheroid histology, global proteome profile, drug metabolism and drug-induced toxicity. No epithelial-mesenchymal transition was observed. Media with fasting glucose and insulin levels gave spheroids with phenotypes closest to normal PHH. The most expensive medium resulted in PHH features most divergent from that of native PHH. Our results provide a protocol for culture of healthy PHH with maintained function - a prerequisite for studies of hepatocyte homeostasis and more reproducible hepatocyte research.

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3D spheroid cultures were established in 384-well format

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Eight different media variants were used to optimize the 3D cultures

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Optimized William's medium was as good as expensive commercial medium

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The 3D cultures were used to study drug metabolism and toxicity

The Blood-Brain Barrier, Oxidative Stress, and Insulin Resistance

The blood–brain barrier (BBB) is a network of specialized endothelial cells that regulates substrate entry into the central nervous system (CNS). Acting as the interface between the periphery and the CNS, the BBB must be equipped to defend against oxidative stress and other free radicals generated in the periphery to protect the CNS. There are unique features of brain endothelial cells that increase the susceptibility of these cells to oxidative stress. Insulin signaling can be impacted by varying levels of oxidative stress, with low levels of oxidative stress being necessary for signaling and higher levels being detrimental. Insulin must cross the BBB in order to access the CNS, levels of which are important in peripheral metabolism as well as cognition. Any alterations in BBB transport due to oxidative stress at the BBB could have downstream disease implications. In this review, we cover the interactions of oxidative stress at the BBB, how insulin signaling is related to oxidative stress, and the impact of the BBB in two diseases greatly affected by oxidative stress and insulin resistance: diabetes mellitus and Alzheimer’s disease.

Keeping a Balance During the Pandemic: a Narrative Review on the Important Role of Micronutrients in Preventing Infection and Reducing Complications of COVID-19

PURPOSE OF REVIEW

The SARS-CoV-2 (COVID-19) outbreak has manifested into a major public health concern across the globe, affecting particularly the most vulnerable population groups. Currently, there are various clinical trials being conducted to develop effective treatments. It is estimated that it could take one or more years before these drugs pass all safety tests and concrete results with regard to their effectiveness become available. In addition, despite the recent development of vaccines (licensed for use under conditional licenses) and the commencement of COVID-19 vaccination programs in several countries, there is still a need for safe and novel strategies that may reduce the symptomatology and/or prevent the severe complications associated with COVID-19. Natural compounds previously shown to have antiviral potential should be thoroughly considered and investigated for use in prophylactic treatment of COVID-19 due to their availability and safety.

RECENT FINDINGS

The current narrative review investigates whether there is evidence in the literature that supplementation with dietary minerals and vitamins may have a role in preventing infection with SARS-CoV-2 or in reducing COVID-19 symptomatology and disease progression. The current evidence from the literature supports that zinc and vitamin C have a potential in reducing the inflammatory response associated with SARS-CoV-2 while folate and vitamin D may have a role in antagonizing the entry of SARs-CoV-2 virus in host calls. Thus, further research should be conducted that could lead to the development of nutritional supplements involving natural and widely available compounds such as zinc, folate, vitamin C, and vitamin D. The latter could be an effective, safe, and inexpensive way to either prevent infection with SARS-CoV-2 and/or lessen the burden of COVID-19 disease.

Nutraceuticals in the Prevention of Viral Infections, including COVID-19, among the Pediatric Population: A Review of the Literature

In recent years, there has been a growth in scientific interest in nutraceuticals, which are those nutrients in foods that have beneficial effects on health. Nutraceuticals can be extracted, used for food supplements, or added to foods. There has long been interest in the antiviral properties of nutraceuticals, which are especially topical in the context of the ongoing COVID-19 pandemic. Therefore, the purpose of this review is to evaluate the main nutraceuticals to which antiviral roles have been attributed (either by direct action on viruses or by modulating the immune system), with a focus on the pediatric population. Furthermore, the possible applications of these substances against SARS-CoV-2 will be considered.

Paclitaxel is effective for controlling astrocyte proliferation in vitro: Implications for generating ventral mesencephalic cultures enriched with dopamine neurons

BACKGROUND

Primary embryonic ventral mesencephalic (VM) cultures are a high throughput tool for understanding and manipulating dopamine neurons, to study the mechanisms that trigger their degeneration during Parkinson's disease (PD), and to test new drugs aimed at treating the disease. Unfortunately, primary cell cultures are often quickly overwhelmed by dividing astrocytes which both obscure neuronal cells and distort the cellular composition that exists in vivo.

NEW METHOD

To develop a new in vitro system whereby astrocyte division can be readily controlled while maintaining neuronal integrity, VM cultures were treated with different doses (1.75, 3.5, 7, 14 nM) of the anti-mitotic drug paclitaxel for up to seven days in vitro. The study subsequently sought to determine the importance of astrocytes in dopamine neuron survival when challenged with an exposure to the toxin 6-hydroxydopamine (6-OHDA).

RESULTS

Optical density (O.D.) measures of GFAP expression and counts of β-III tubulin and tyrosine hydroxylase positive neurons reveals that a low dose of 3.5 nM of paclitaxel significantly reduced the density of GFAP + astrocytes in primary VM cultures, while maintaining the viability of neurons and dopamine neurons. Interestingly, a reduction of GFAP + astrocytes within primary VM cultures did not reveal any statistically significant differences in the number of dopamine neurons surviving treatment with 6-OHDA.

CONCLUSIONS

These findings detail a quick and simple method for stabilising astrocyte numbers in primary VM cultures, without affecting the viability of dopamine neurons, and suggest that astrocytes may not enhance the survival of dopamine neurons when challenged with the 6-OHDA toxin.

Vitamin C and Cardiovascular Disease: An Update

The potential beneficial effects of the antioxidant properties of vitamin C have been investigated in a number of pathological conditions. In this review, we assess both clinical and preclinical studies evaluating the role of vitamin C in cardiac and vascular disorders, including coronary heart disease, heart failure, hypertension, and cerebrovascular diseases. Pitfalls and controversies in investigations on vitamin C and cardiovascular disorders are also discussed.

Defective Neutrophil Function in Patients with Sepsis Is Mostly Restored by ex vivo Ascorbate Incubation

Background

Neutrophil function is essential for effective defence against bacterial infections but is defective in patients with sepsis. Ascorbate or vitamin C, which is low in the plasma of patients with sepsis, is stored inside human neutrophils and is essential for their normal function.

Objective

This study aimed to determine if ascorbate treatment ex vivo improved neutrophil function in patients with sepsis.

Patients and Methods

Human blood neutrophils were isolated from 20 patients with sepsis and 20 healthy age-matched controls. Neutrophils were incubated with or without ascorbate (1, 5, 10, 20 and 40 mM) for periods up to 2h. Chemotaxis was evaluated using a chemotactic chamber in response to the chemoattractant, fMLP. Phagocytosis (uptake of pHrodo red stained S. aureus) and apoptosis (annexin-V/propidium iodide staining) were measured by flow cytometry. Neutrophil extracellular trap (NET) formation was detected and quantified using DAPI, anti-myeloperoxidase and anti-neutrophil elastase immuno-fluorescence staining. Quantifluor detected the amount of dsDNA in NET supernatants, while quantitative PCR identified changes in expression of PADI4 gene.

Results

Chemotactic and phagocytic activities were decreased in patients with sepsis but increased after treatment with the high concentrations of ascorbate. Apoptosis was increased in the sepsis patients but not altered by ascorbate treatment. Spontaneous NET formation was observed in patients with sepsis. A quantity of 1mM ascorbate decreased spontaneous NETosis to that of normal, healthy neutrophils, while high concentrations of ascorbate (>10mM) further promoted NET formation.

Conclusion

Dysregulated neutrophil function was observed in patients with sepsis which could contribute to disease pathology and outcomes. Exposure to ascorbate could reverse some of these changes in function. These novel discoveries raise the possibility that ascorbate treatment could be used as an adjunctive therapy that could result in improved neutrophil function during sepsis.

Strengthening the Immune System and Reducing Inflammation and Oxidative Stress through Diet and Nutrition: Considerations during the COVID-19 Crisis

The coronavirus-disease 2019 (COVID-19) was announced as a global pandemic by the World Health Organization. Challenges arise concerning how to optimally support the immune system in the general population, especially under self-confinement. An optimal immune response depends on an adequate diet and nutrition in order to keep infection at bay. For example, sufficient protein intake is crucial for optimal antibody production. Low micronutrient status, such as of vitamin A or zinc, has been associated with increased infection risk. Frequently, poor nutrient status is associated with inflammation and oxidative stress, which in turn can impact the immune system. Dietary constituents with especially high anti-inflammatory and antioxidant capacity include vitamin C, vitamin E, and phytochemicals such as carotenoids and polyphenols. Several of these can interact with transcription factors such as NF-kB and Nrf-2, related to anti-inflammatory and antioxidant effects, respectively. Vitamin D in particular may perturb viral cellular infection via interacting with cell entry receptors (angiotensin converting enzyme 2), ACE2. Dietary fiber, fermented by the gut microbiota into short-chain fatty acids, has also been shown to produce anti-inflammatory effects. In this review, we highlight the importance of an optimal status of relevant nutrients to effectively reduce inflammation and oxidative stress, thereby strengthening the immune system during the COVID-19 crisis.

Ascorbic acid attenuates endothelial permeability triggered by cell-free hemoglobin

BACKGROUND

Increased endothelial permeability is central to shock and organ dysfunction in sepsis but therapeutics targeted to known mediators of increased endothelial permeability have been unsuccessful in patient studies. We previously reported that cell-free hemoglobin (CFH) is elevated in the majority of patients with sepsis and is associated with organ dysfunction, poor clinical outcomes and elevated markers of oxidant injury. Others have shown that Vitamin C (ascorbate) may have endothelial protective effects in sepsis. In this study, we tested the hypothesis that high levels of CFH, as seen in the circulation of patients with sepsis, disrupt endothelial barrier integrity.

METHODS

Human umbilical vein endothelial cells (HUVEC) were grown to confluence and treated with CFH with or without ascorbate. Monolayer permeability was measured by Electric Cell-substrate Impedance Sensing (ECIS) or transfer of ¹⁴C-inulin. Viability was measured by trypan blue exclusion. Intracellular ascorbate was measured by HPLC.

RESULTS

CFH increased permeability in a dose- and time-dependent manner with 1 mg/ml of CFH increasing inulin transfer by 50% without affecting cell viability. CFH (1 mg/ml) also caused a dramatic reduction in intracellular ascorbate in the same time frame (1.4 mM without CFH, 0.23 mM 18 h after 1 mg/ml CFH, p < 0.05). Pre-treatment of HUVECs with ascorbate attenuated CFH induced permeability.

CONCLUSIONS

CFH increases endothelial permeability in part through depletion of intracellular ascorbate. Supplementation of ascorbate can attenuate increases in permeability mediated by CFH suggesting a possible therapeutic approach in sepsis.

Vitamin C and Immune Function

Vitamin C is an essential micronutrient for humans, with pleiotropic functions related to its ability to donate electrons. It is a potent antioxidant and a cofactor for a family of biosynthetic and gene regulatory enzymes. Vitamin C contributes to immune defense by supporting various cellular functions of both the innate and adaptive immune system. Vitamin C supports epithelial barrier function against pathogens and promotes the oxidant scavenging activity of the skin, thereby potentially protecting against environmental oxidative stress. Vitamin C accumulates in phagocytic cells, such as neutrophils, and can enhance chemotaxis, phagocytosis, generation of reactive oxygen species, and ultimately microbial killing. It is also needed for apoptosis and clearance of the spent neutrophils from sites of infection by macrophages, thereby decreasing necrosis/NETosis and potential tissue damage. The role of vitamin C in lymphocytes is less clear, but it has been shown to enhance differentiation and proliferation of B- and T-cells, likely due to its gene regulating effects. Vitamin C deficiency results in impaired immunity and higher susceptibility to infections. In turn, infections significantly impact on vitamin C levels due to enhanced inflammation and metabolic requirements. Furthermore, supplementation with vitamin C appears to be able to both prevent and treat respiratory and systemic infections. Prophylactic prevention of infection requires dietary vitamin C intakes that provide at least adequate, if not saturating plasma levels (i.e., 100–200 mg/day), which optimize cell and tissue levels. In contrast, treatment of established infections requires significantly higher (gram) doses of the vitamin to compensate for the increased inflammatory response and metabolic demand.