Grape seed proanthocyanidin extract protects human umbilical vein endothelial cells from indoxyl sulfate-induced injury via ameliorating mitochondrial dysfunction

Proteomic analysis of endothelial cells and extracellular vesicles in response to indoxyl sulfate: Mechanisms of endothelial dysfunction in chronic kidney disease

AIMS

Cardiovascular pathology is the main cause of death in chronic kidney disease (CKD) patients. CKD is associated with the accumulation of uremic toxins in the bloodstream, and indoxyl sulfate (IS) is one of the most abundant uremic toxins found in the blood of CKD patients. We conducted an in vitro study to assess the mechanisms underlying the IS-induced endothelial dysfunction that could lead to cardiovascular diseases. We also studied their extracellular vesicles (EVs) owing to their capacity to act as messengers that transmit signals through their cargo.

MAIN METHODS

EVs were characterized by nanoparticle tracking analysis, transmission electron microscopy, flow cytometry, and tetraspanin expression. Cell lysates and isolated EVs were analyzed using liquid chromatography coupled with mass spectrometry, followed by Gene Set Enrichment Analysis to identify the altered pathways.

KEY FINDINGS

Proteomic analysis of endothelial cells revealed that IS causes an increase in proteins related to adipogenesis, inflammation, and xenobiotic metabolism and a decrease in proliferation. Extracellular matrix elements, as well as proteins associated with myogenesis, response to UV irradiation, and inflammation, were found to be downregulated in IS-treated EVs. Fatty acid metabolism was also found to be increased along with adipogenesis and inflammation observed in cells.

SIGNIFICANCE

The treatment of endothelial cells with IS increased the expression of proteins related to adipogenesis, inflammation, and xenobiotic metabolism and was less associated with proliferation. Furthermore, EVs from cells treated with IS may mediate endothelial dysfunction, since they present fewer extracellular matrix elements, myogenesis, inflammatory factors, and proteins downregulated in response to UV radiation.

The Potential Influence of Uremic Toxins on the Homeostasis of Bones and Muscles in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) often experience a high accumulation of protein-bound uremic toxins (PBUTs), specifically indoxyl sulfate (IS) and p-cresyl sulfate (pCS). In the early stages of CKD, the buildup of PBUTs inhibits bone and muscle function. As CKD progresses, elevated PBUT levels further hinder bone turnover and exacerbate muscle wasting. In the late stage of CKD, hyperparathyroidism worsens PBUT-induced muscle damage but can improve low bone turnover. PBUTs play a significant role in reducing both the quantity and quality of bone by affecting osteoblast and osteoclast lineage. IS, in particular, interferes with osteoblastogenesis by activating aryl hydrocarbon receptor (AhR) signaling, which reduces the expression of Runx2 and impedes osteoblast differentiation. High PBUT levels can also reduce calcitriol production, increase the expression of Wnt antagonists (SOST, DKK1), and decrease klotho expression, all of which contribute to low bone turnover disorders. Furthermore, PBUT accumulation leads to continuous muscle protein breakdown through the excessive production of reactive oxygen species (ROS) and inflammatory cytokines. Interactions between muscles and bones, mediated by various factors released from individual tissues, play a crucial role in the mutual modulation of bone and muscle in CKD. Exercise and nutritional therapy have the potential to yield favorable outcomes. Understanding the underlying mechanisms of bone and muscle loss in CKD can aid in developing new therapies for musculoskeletal diseases, particularly those related to bone loss and muscle wasting.

Indoxyl sulfate in atherosclerosis

Atherosclerosis (AS), a chronic vascular inflammatory disease, has become a main focus of attention worldwide for its chronic progressing disease course and serious complications in the later period. Nevertheless, explanations for the exact molecular mechanisms of AS initiation and development remain to be an unsolved problem. The classic pathogenesis theories, such as lipid percolation and deposition, endothelium injury, inflammation and immune damage, provide the foundation for discovering the new key molecules or signaling mechanisms. Recently, indoxyl sulfate (IS), one of non-free uremia toxins, has been noticeable for its multiple atherogenic effects. IS exists at high concentration in plasma for its great albumin binding rate. Patients with uremia have markedly elevated serum levels of IS due both to the deterioration of renal function and to the high binding affinity of IS to albumin. Nowadays, elevated incidence of circulatory disease among patients with renal dysfunction indicates correlation of uremic toxins with cardiovascular damage. In this review, the atherogenic effects of IS and the underlying mechanisms are summarized with emphasis on several key pathological events associated with AS developments, such as vascular endothelium dysfunction, arterial medial lesions, vascular oxidative stress, excessive inflammatory responses, calcification, thrombosis and foam cell formation. Although recent studies have proved the great correlation between IS and AS, deciphering cellular and pathophysiological signaling by confirming key factors involved in IS-mediated atherosclerosis development may enable identification of novel therapeutic targets.

Increased level of free-circulating MtDNA in maintenance hemodialysis patients: Possible role in systemic inflammation

Background

Mitochondrial DNA (MtDNA) exposed to the extracellular space due to cell death and stress has immunostimulatory properties. However, the clinical significance of circulating MtDNA in maintenance hemodialysis (MHD) patients and the precise mechanism of its emergence have yet to be investigated.

Methods

This cross‐sectional study consisted of 52 MHD patients and 32 age‐ and sex‐matched healthy controls. MHD patients were further categorized into high and low circulating cell‐free MtDNA (ccf‐MtDNA) groups based on the median value. Copy number of MtDNA was quantified using TaqMan‐based qPCR. Plasma cytokines were measured using ELISA kits. Reactive oxygen species (ROS) and mitochondrial membrane potential (Δψm) in peripheral blood mononuclear cells (PBMCs) were detected using DCFH‐DA or JC‐1 staining.

Results

The copy numbers of ccf‐MtDNA in patients with MHD were higher than those in healthy controls, and these alterations were correlated with changes of cytokines TNF‐α and IL‐6. Adjusted model in multivariate analysis showed that the presence of anuria and longer dialysis vintage were independently associated with higher levels of ccf‐MtDNA. Meanwhile, although not statistically significant, an inverse correlative trend between urinary MtDNA and ccf‐MtDNA was observed in patients with residual urine. Afterward, using PBMCs as surrogates for mitochondria‐rich cells, we found that patients in the high ccf‐MtDNA group exhibited a significantly higher ROS production and lower Δψm in cells.

Conclusions

Our data suggested that changes in ccf‐MtDNA correlate with the degree of inflammatory status in MHD patients, and that the excessive MtDNA may be caused by mitochondrial dysfunction and reduced urinary MtDNA excretion.

Effectiveness of Proanthocyanidin plus Trimetazidine in the Treatment of Non-Small-Cell Lung Cancer with Radiation Heart Injury

This study was intended to explore the effect of proanthocyanidin (PC) combined with trimetazidine in non-small-cell lung cancer (NSCLC) with radiation-induced heart damage (RIHD). It was a prospective randomized controlled study that 86 NSCLC patients with radiation treatment in Cangzhou People's Hospital from January 2019 and June 2021 were enrolled and randomized to either the control group or the study group via the random table method, 43 cases in each group. The control group received trimetazidine, and the study group additionally received PC. The incidence of RIHD-related clinical manifestation, RIHD-related ECG, and RIHD-related cardiac ultrasound change were all lower in the study group. After radiotherapy, the serum level of superoxide dismutase (SOD) was higher, and malondialdehyde (MDA) was lower in the study group when compared with the control group. After radiotherapy, the serum levels of brain natriuretic peptide (BNP), cardiac troponin (cTnT), creatine kinase (CK), and creatine kinase isoenzymes (CKMB) were all lower in the study group when compared with the control group. The efficacy of PC plus trimetazidine for NSCLC with RIHD is superior to trimetazidine alone, and it significantly mitigates radiation-induced inflammatory response and oxidative stress.

Proanthocyanidins Promote Endothelial Cell Viability and Angiogenesis

ABSTRACT

Botanic drugs are reportedly effective in treating ischemic conditions by improving vascular circulation. However, it has been very rare for biomaterial researchers to look into the possibility of using such products in the context of tissue regeneration. This work studied 4 botanic drugs to explore their effects on vascular endothelial cell growth. Human umbilical endothelial cells were cultured in the presence of different doses of astragalus powder extract, astragalus injection, puerarin injection, and proanthocyanidin (PAC). Among the 4 drugs, PAC showed a potent effect on cell viability and stimulated cell growth in a dose-dependent manner. In particular, the PAC under test was able to maintain a high level of cell viability/proliferation comparable with the cells supplemented with the endothelial cell growth medium, at both low and normal serum conditions. Blocking either endothelial cell growth factor receptors or epithelial cell growth factor receptors was ineffective in reducing the stimulatory effect. The PAC released from polyvinyl alcohol cryogels stimulated HUVECs proliferation. The chick embryo chorioallantoic membrane model was further used to test the angiogenicity of PAC, showing that this botanic drug was potent in stimulating vasculature development. This work therefore demonstrates for the first time that PAC is capable of upregulating endothelial cell activity and growth in vitro in the absence of growth factors and that PAC can be loaded and released from drug carriers and can stimulate angiogenesis. These findings suggest the application of PAC in angiogenesis and tissue regeneration.

Passage Number-Induced Replicative Senescence Modulates the Endothelial Cell Response to Protein-Bound Uremic Toxins

Endothelial aging may be induced early in pathological situations. The uremic toxins indoxyl sulfate (IS) and p-cresol (PC) accumulate in the plasma of chronic kidney disease (CKD) patients, causing accelerated endothelial aging, increased cardiovascular events and mortality. However, the mechanisms by which uremic toxins exert their deleterious effects on endothelial aging are not yet fully known. Thus, the aim of the present study is to determine the effects of IS and PC on endothelial damage and early senescence in cultured human umbilical vein endothelial cells (HUVECs). Hence, we establish an in vitro model of endothelial damage mediated by different passages of HUVECs and stimulated with different concentrations of IS and PC to evaluate functional effects on the vascular endothelium. We observe that cell passage-induced senescence is associated with apoptosis, ROS production and decreased endothelial proliferative capacity. Similarly, we observe that IS and PC cause premature aging in a dose-dependent manner, altering HUVECs' regenerative capacity, and decreasing their cell migration and potential to form vascular structures in vitro. In conclusion, IS and PC cause accelerated aging in HUVECs, thus contributing to endothelial dysfunction associated with CKD progression.

Natural Antioxidants Improve the Vulnerability of Cardiomyocytes and Vascular Endothelial Cells under Stress Conditions: A Focus on Mitochondrial Quality Control

Cardiovascular disease has become one of the main causes of human death. In addition, many cardiovascular diseases are accompanied by a series of irreversible damages that lead to organ and vascular complications. In recent years, the potential therapeutic strategy of natural antioxidants in the treatment of cardiovascular diseases through mitochondrial quality control has received extensive attention. Mitochondria are the main site of energy metabolism in eukaryotic cells, including myocardial and vascular endothelial cells. Mitochondrial quality control processes ensure normal activities of mitochondria and cells by maintaining stable mitochondrial quantity and quality, thus protecting myocardial and endothelial cells against stress. Various stresses can affect mitochondrial morphology and function. Natural antioxidants extracted from plants and natural medicines are becoming increasingly common in the clinical treatment of diseases, especially in the treatment of cardiovascular diseases. Natural antioxidants can effectively protect myocardial and endothelial cells from stress-induced injury by regulating mitochondrial quality control, and their safety and effectiveness have been preliminarily verified. This review summarises the damage mechanisms of various stresses in cardiomyocytes and vascular endothelial cells and the mechanisms of natural antioxidants in improving the vulnerability of these cell types to stress by regulating mitochondrial quality control. This review is aimed at paving the way for novel treatments for cardiovascular diseases and the development of natural antioxidant drugs.

Oxidative Storm Induced by Tryptophan Metabolites: Missing Link between Atherosclerosis and Chronic Kidney Disease

Chronic kidney disease (CKD) occurrence is rising all over the world. Its presence is associated with an increased risk of premature death from cardiovascular disease (CVD). Several explanations of this link have been put forward. It is known that in renal failure, an array of metabolites cannot be excreted, and they accumulate in the organism. Among them, some are metabolites of tryptophan (TRP), such as indoxyl sulfate and kynurenine. Scientists have become interested in them in the context of inducing vascular damage in the course of chronic kidney impairment. Experimental evidence suggests the involvement of TRP metabolites in the progression of chronic kidney disease and atherosclerosis separately and point to oxidative stress generation as one of the main mechanisms that is responsible for worsening those states. Since it is known that blood levels of those metabolites increase significantly in renal failure and that they generate reactive oxygen species (ROS), which lead to endothelial injury, it is reasonable to suspect that products of TRP metabolism are the missing link in frequently occurring atherosclerosis in CKD patients. This review focuses on reports that shed a light on TRP metabolites as contributing factors to vascular damage in the progression of impaired kidney function.

MicroRNA-214 targets COX-2 to antagonize indoxyl sulfate (IS)-induced endothelial cell apoptosis

Cardiovascular disease (CVD) serves as the major cause of mortality in chronic kidney disease (CKD) patients. The injury of endothelium associated with the long-term challenge of uremic toxins including the toxic indoxyl sulfate (IS) is one of key pathological factors leading to CVD. However, the mechanisms of uremic toxins, especially the IS, resulting in endothelial injury, remain unclear. miR-214 was reported to contribute to the pathogenesis of cardiovascular diseases, while its role in IS-induced endothelial cell apoptosis is unknown. In this study, we investigated the role of microRNA-214 (miR-214) in IS-induced endothelial cell apoptosis and the underlying mechanisms using mouse aortic endothelial cells (MAECs). Following IS treatment, miR-214 was significantly downregulated in MAECs in line with enhanced cell apoptosis. Meanwhile, COX-2 was upregulated at both mRNA and protein levels along with increased secretion of PGE₂ in medium. To define the role of miR-214 in IS-induced endothelial cell apoptosis, we modulated miR-214 level in MAECs and found that overexpression of miR-214 markedly attenuated endothelial cell apoptosis, while antagonism of miR-214 deteriorated cell death after IS challenge. Further analyses confirmed that COX-2 is a target gene of miR-214, and the inhibition of COX-2 by a specific COX-2 inhibitor NS-398 strikingly attenuated IS-induced endothelial cell apoptosis along with a significant blockade of PGE₂ secretion. In conclusion, this study demonstrated an important role of miR-214 in protecting against endothelial cell damage induced by IS possibly by direct downregulation of COX-2/PGE₂ axis.

Concentration and Duration of Indoxyl Sulfate Exposure Affects Osteoclastogenesis by Regulating NFATc1 via Aryl Hydrocarbon Receptor

Indoxyl sulfate (IS) is a chronic kidney disease (CKD)-specific renal osteodystrophy metabolite that affects the nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), a transcription factor promoting osteoclastogenesis. However, the mechanisms underlying the regulation of NFATc1 by IS remain unknown. It is intriguing that the Aryl hydrocarbon receptor (AhR) plays a key role in osteoclastogenesis, since IS is an endogenous AhR agonist. This study investigates the relationship between IS concentration and osteoclast differentiation in Raw 264.7 cells, and examines the effects of different IS concentrations on NFATc1 expression through AhR signaling. Our data suggest that both osteoclastogenesis and NFATc1 are affected by IS through AhR signaling in both dose- and time-dependent manners. Osteoclast differentiation increases with short-term, low-dose IS exposure and decreases with long-term, high-dose IS exposure. Different IS levels switch the role of AhR from that of a ligand-activated transcription factor to that of an E3 ubiquitin ligase. We found that the AhR nuclear translocator may play an important role in the regulation of these dual functions of AhR under IS treatment. Altogether, this study demonstrates that the IS/AhR/NFATc1 signaling axis plays a critical role in osteoclastogenesis, indicating a potential role of AhR in the pathology and abnormality of bone turnover in CKD patients.

Indoxyl Sulfate Contributes to Uremic Sarcopenia by Inducing Apoptosis in Myoblasts

OBJETIVE

Uremic sarcopenia is a complication of chronic kidney disease, particularly in its later stages, which leads to musculoskeletal disability. Uremic toxins have been linked to the pathogenesis of several manifestations of uremic syndrome. We sought to investigate whether indoxyl sulphate (IS), a protein-bound uremic toxin, is implicated in the development of uremic sarcopenia.

MATERIAL AND METHODS

Myoblasts were exposed to IS at normal (0.6 mg/L, IS_0.6), uremic (53 mg/L, IS₅₃) or maximum uremic (236 mg/L, IS₂₃₆) concentrations for 24, 48 and 72 h. Cell viability was evaluated by MTT assay and by 7-aminoactinomycin D staining. ROS generation and apoptosis were evaluated by flow cytometry. MyoD and myogenin mRNA expression was evaluated by qRT-PCR and myosin heavy chain expression by immunocytochemistry.

RESULTS

Myoblast viability was reduced by IS236 in a time-dependent pattern (p <0.05; 84.4, 68.0, and 63.6%). ROS production was significantly higher (p <0.05) in cells exposed to IS₅₃ and IS₂₃₆ compared to control (untreated cells). The apoptosis rate was significantly higher in cells treated with IS₅₃ and IS₂₃₆ than in control after 48h (p <0.05; 4.7 ± 0.1% and 4.6 ± 0.3% vs. 3.1 ± 0.1%, respectively) and 72h (p <0.05; 9.6 ± 1.1% and 10.4 ± 0.3% vs. 3.1 ± 0.7%, respectively). No effect was observed on MyoD, myogenin, myosin heavy chain expression, and markers of myoblast differentiation at any IS concentration tested or time-point experiment.

CONCLUSIONS

These data indicate that IS has direct toxic effects on myoblast by decreasing its viability and increasing cell apoptosis. IS may be a potential target for treating uremic sarcopenia.

Uraemic toxin-induced inflammation and oxidative stress in human endothelial cells: protective effect of polyphenol-rich extract from açaí

NEW FINDINGS

What is the central question of this study? Does a polyphenol-rich extract from açaí have a potential role in preventing uraemic toxin-induced endothelial cell dysfunction? What is the main finding and its importance? Polyphenols from açaí prevented cell death, restored migratory capacity, protected from inflammation and contributed to the restoration of the antioxidant response in endothelial cells exposed to uraemic toxins. The protective role of açaí against toxic effects exerted by uraemic toxins presents a potential new therapeutic target in endothelial cells.

ABSTRACT

In chronic kidney disease (CKD), progressive loss of kidney function results in the accumulation of protein-bound uraemic toxins such as p-cresyl sulfate (pCS) and indoxyl sulfate (IS). Among strategies to ameliorate the harmful actions of uraemic toxins, phenolic compounds have been extensively studied. The main goal of this work was to evaluate the antioxidant and anti-inflammatory actions of phenolic-rich açaí seed extract (ASE) in response to endothelial dysfunction induced by IS and pCS, in human umbilical vein endothelial cells (HUVECs). Cells were treated with ASE (10 µg ml^-1 ) in the presence or absence of IS (61 µg ml^-1 ) and pCS (40 µg ml^-1 ). Cell viability, cell death, cell migratory capacity and inflammatory biomarker expression were evaluated. Cellular antioxidant response was measured through the activity and expression of antioxidant enzymes, and oxidative damage was evaluated. IS and pCS lowered cell viability, triggered cell death and lowered the migratory capacity in endothelial cells (P < 0.05). ASE prevented cell death and restored the migratory capacity in cells exposed to IS. Both toxins up-regulated pro-inflammatory cytokine expression, and ASE was able to beneficially counteract this effect. Tumour necrosis factor-α secretion was greater in uraemic toxin-treated cells and ASE reversed this phenomenon in cells treated with both toxins concomitantly (P < 0.05). With regard to the antioxidant response, superoxide dismutase expression was strikingly lower in cells treated with both toxins, and ASE inhibited this harmful effect (P < 0.05). From the results, we conclude that ASE exerted protective effects on inflammation and oxidative stress caused by uraemic toxins (particularly by IS) in human endothelial cells.

Molecular mechanisms of protein-bound uremic toxin-mediated cardiac, renal and vascular effects: underpinning intracellular targets for cardiorenal syndrome therapy

Cardiorenal syndrome (CRS) remains a global health burden with a lack of definitive and effective treatment. Protein-bound uremic toxin (PBUT) overload has been identified as a non-traditional risk factor for cardiac, renal and vascular dysfunction due to significant albumin-binding properties, rendering these solutes non-dialyzable upon the state of irreversible kidney dysfunction. Although limited, experimental studies have investigated possible mechanisms in PBUT-mediated cardiac, renal and vascular effects. The ultimate aim is to identify relevant and efficacious targets that may translate beneficial outcomes in disease models and eventually in the clinic. This review will expand on detailed knowledge on mechanisms involved in detrimental effects of PBUT, specifically affecting the heart, kidney and vasculature, and explore potential effective intracellular targets to abolish their effects in CRS initiation and/or progression.

Inhibition of MUC1-C regulates metabolism by AKT pathway in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most common digestive tumors worldwide. The Mucin 1 (MUC1) heterodimeric protein has been confirmed that is overexpressed in ESCC and induced adverse outcomes. However, the detailed mechanism(s) remained challenging. So, we investigated the relationship between MUC1‐C and metabolism in ESCC cells. In the results, TP53‐induced glycolysis and apoptosis regulator (TIGAR) was overexpressed and correlative with MUC1‐C positively in ESCC tissue. Targeting MUC1‐C inhibits AKT–mTORC–S6K1 signaling and blocks TIGAR translation. We found that the inhibitory effect of GO‐203 on TIGAR was mediated by inhibition of AKT–mTOR–S6K1 pathway. The findings also demonstrated that the suppressive effect of GO‐203 on TIGAR is related to the decrease of glutathione level, the increase of reactive oxygen species and the loss of mitochondrial transmembrane membrane potential. In xenograft tissues, GO‐203 inhibited the growth of ESCC cells and lead to the low expression of transmembrane C‐terminal subunit (MUC1‐C) and TIGAR. This evidence supports the contention that MUC1‐C is significant for metabolism in ESCC and indicated that MUC1‐C is a potential target for the treatment of ESCC.

Impacts of Indoxyl Sulfate and p-Cresol Sulfate on Chronic Kidney Disease and Mitigating Effects of AST-120

Uremic toxins, such as indoxyl sulfate (IS) and p-cresol, or p-cresyl sulfate (PCS), are markedly accumulated in the organs of chronic kidney disease (CKD) patients. These toxins can induce inflammatory reactions and enhance oxidative stress, prompting glomerular sclerosis and interstitial fibrosis, to aggravate the decline of renal function. Consequently, uremic toxins play an important role in the worsening of renal and cardiovascular functions. Furthermore, they destroy the quantity and quality of bone. Oral sorbent AST-120 reduces serum levels of uremic toxins in CKD patients by adsorbing the precursors of IS and PCS generated by amino acid metabolism in the intestine. Accordingly, AST-120 decreases the serum IS levels and reduces the production of reactive oxygen species by endothelial cells, to impede the subsequent oxidative stress. This slows the progression of cardiovascular and renal diseases and improves bone metabolism in CKD patients. Although large-scale studies showed no obvious benefits from adding AST-120 to the standard therapy for CKD patients, subsequent sporadic studies may support its use. This article summarizes the mechanisms of the uremic toxins, IS, and PCS, and discusses the multiple effects of AST-120 in CKD patients.

Grape seed proanthocyanidin extract supplementation affects exhaustive exercise-induced fatigue in mice

Background

Grape seed proanthocyanidin extract (GSPE) has been extensively reported to possess a wide range of beneficial properties in multiple tissue damage. Previous studies have shown that exhaustive exercise-induced fatigue associates with oxidative stress injury, inflammatory response, and mitochondrial dysfunction.

Objective

The aim of this study is to investigate the anti-fatigue effects of GSPE in mice and explore its possible underlying mechanism.

Design

The mouse model of exhaustive exercise-induced fatigue was established by using the forced swimming test, and GSPE was orally treated for successive 28 days at 0, 1, 50 and 100 mg/kg/day of body weight, designated the control, GSPE-L, GSPE-M and GSPE-H groups, respectively.

Results

The presented results showed that treatment of GSPE at a dose of 50 and 100 mg/kg/day of body weight significantly relieved exhaustive exercise-induced fatigue, indicated by increasing the forced swimming time. In addition, treatment of GSPE significantly improved the creatine phosphokinase and lactic dehydrogenase, as well as lactic acid level in exhaustive swimming. For underlying mechanisms, treatment of GSPE had anti-fatigue effects by promoting antioxidant ability and resisting oxidative effect, as represented by increased total antioxidative capability levels, enhanced superoxide dismutase and catalase activities, and ameliorated malondialdehyde levels. Furthermore, treatment of GSPE significantly inhibited the activity of tumor necrosis factor-α and interleukin-1β, which suggested that its protective effects on exhaustive exercise-induced fatigue may be attributed to inhibition of inflammatory response. Last but not the least, treatment of GSPE significantly improved succinate dehydrogenase and Na+-K+-ATPase levels to enhance mitochondrial function during exhaustive swimming-induced fatigue.

Conclusions

These results proved that treatment of GSPE possessed the beneficial properties of anti-inflammatory, antioxidant, and mitochondrial protection to improve exhaustive exercise, which suggested that GSPE could be used as an effective functional food to delay fatigue.

Grape seed proanthocyanidin extract protects lymphocytes against histone-induced apoptosis

Apoptosis of lymphocytes is associated with immunosuppression and poor prognosis in sepsis. Our previous report showed that histones, nuclear proteins released from damaged or dying cells in sepsis, can mediate lymphocyte apoptosis via mitochondria damage. Grape seed proanthocyanidin extract (GSPE), a natural substance with protective properties against oxidative stress, plays a vital role in cell and mitochondria protection. We thus hypothesized that GSPE may play a protective role in histone-induced lymphocyte apoptosis through its anti-oxidative properties. In this study, we investigated the protective efficacy of GSPE on lymphocyte apoptosis induced by extracellular histones, a main contributor of death in sepsis. Human blood lymphocytes were treated with 50 μg/ml histones, 2 μg/ml GSPE, or a combination of both. A total of 100 μM N-acetylcysteine (NAC), a reactive oxygen species (ROS) inhibitor, was used as a positive control for GSPE. Apoptosis, intracellular ROS levels, mitochondrial membrane potential, Bcl-2 expression, and caspase-3 cleavage were measured. Our data clearly indicate that GSPE significantly inhibited lymphocyte apoptosis, generation of ROS, the loss of mitochondrial membrane potential, the decrease in Bcl-2 expression, and caspase-3 activation induced by extracellular histones. In conclusion, we show that GSPE has a protective effect on lymphocyte apoptosis induced by extracellular histones. This study suggests GSPE as a potential therapeutic agent that could help reduce lymphocyte apoptosis, and thus the state of immunosuppression was observed in septic patients.