Anthocyanins in Vascular Health and Disease: Mechanisms of Action and Therapeutic Potential

ABSTRACT

Unhealthy lifestyles have placed a significant burden on individuals' cardiovascular health. Anthocyanins are water-soluble flavonoid pigments found in a wide array of common foods and fruits. Anthocyanins have the potential to contribute to the prevention and treatment of cardiovascular disease by improving lipid profiles and vascular function, reducing blood glucose levels and blood pressure, and inhibiting inflammation. These actions have been demonstrated in numerous clinical and preclinical studies. At the cellular and molecular level, anthocyanins and their metabolites could protect endothelial cells from senescence, apoptosis, and inflammation by activating the phosphoinositide 3-kinase/protein kinase B/endothelial nitric oxide synthases, silent information regulator 1 (SIRT1), or nuclear factor erythroid2-related factor 2 pathways and inhibiting the nuclear factor kappa B, Bax, or P38 mitogen-activated protein kinase pathways. Furthermore, anthocyanins prevent vascular smooth muscle cell from platelet-derived growth factor -induced or tumor necrosis factor-α-induced proliferation and migration by inhibiting the focal adhesion kinase and extracellular regulated protein kinases signaling pathways. Anthocyanins could also attenuate vascular inflammation by reducing the formation of oxidized lipids, preventing leukocyte adhesion and infiltration of the vessel wall, and macrophage phagocytosis of deposited lipids through reducing the expression of cluster of differentiation 36 and increasing the expression of ATP-binding cassette subfamily A member 1 and ATP-binding cassette subfamily G member 1. At the same time, anthocyanins could lower the risk of thrombosis by inhibiting platelet activation and aggregation through down-regulating P-selectin, transforming growth factor-1, and CD40L. Thus, the development of anthocyanin-based supplements or derivative drugs could provide new therapeutic approaches to the prevention and treatment of vascular diseases.

Pelargonidin alleviates acrolein-induced inflammation in human umbilical vein endothelial cells by reducing COX-2 expression through the NF-κB pathway

Acrolein, a common environmental pollutant, is linked to the development of cardiovascular inflammatory diseases. Pelargonidin is a natural compound with anti-inflammation activity. In this study, we aimed to explore the effects of pelargonidin on inflammation induced by acrolein in human umbilical vein endothelial cells (HUVECs). MTT assay was utilized for assessing cell viability in HUVECs. LDH release in HUVECs was measured using the LDH kit. Western blot was used to detect the protein expression of p-p65, p65 and COX-2. Inflammation was evaluated through determining the levels of PGE2, IL-1β, IL-6, IL-8 and TNF-α in HUVECs after treatment. COX-2 mRNA expression and COX-2 content were examined using RT-qPCR and a human COX-2 ELISA kit, respectively. Acrolein treatment at 50 μM resulted in a 45% decrease in the viability and an increase in LDH release (2.2-fold) in HUVECs. Pelargonidin at 5, 10, 20, and 40 μM alleviated acrolein-caused inhibitory effect on cell viability (increased to 1.3-, 1.5-, 1.8-, and 1.9-fold, respectively, compared to acrolein treatment group) and promoting effect on LDH release (decreased to 82%, 75%, 62%, and 58%, respectively, compared to acrolein treatment group) in HUVECs. Moreover, pelargonidin or pyrrolidine dithiocarbamate (PDTC; an NF-κB pathway inhibitor) inhibited acrolein-induced activation of the NF-κB pathway. Acrolein elevated the levels of PGE2, IL-1β, IL-6, IL-8 and TNF-α (from 40.2, 27.3, 67.2, 29.0, 24.8 pg/mL in control group to 224.0, 167.3, 618.3, 104.6, and 275.1 pg/mL in acrolein treatment group, respectively), which were retarded after pelargonidin (decreased to 134.8, 82.3, 246.2, 70.2, and 120.8 pg/mL in acrolein + pelargonidin treatment group) or PDTC (decreased to 107.9, 80.1, 214.6, 64.0, and 96.6 pg/mL in acrolein + PDTC treatment group) treatment in HUVECs. Pelargonidin inactivated the NF-κB pathway to reduce acrolein-induced COX-2 expression. Furthermore, pelargonidin relieved acrolein-triggered inflammation through decreasing COX-2 expression by inactivating the NF-κB pathway in HUVECs. In conclusion, pelargonidin could protect against acrolein-triggered inflammation in HUVECs through attenuating COX-2 expression by inactivating the NF-κB pathway.

Update on current pharmacologic therapies for diabetic retinopathy

INTRODUCTION

Diabetic retinopathy is a major cause of visual loss worldwide. The most important clinical findings include diabetic macular edema (DME) and proliferative diabetic retinopathy (PDR).

AREAS COVERED

PubMed was used for our literature review. Articles from 1995 to 2023 were included. Pharmacologic treatment of diabetic retinopathy generally involves the use of intravitreal anti-vascular endothelial growth factor (VEGF) therapy for DME and PDR. Corticosteroids remain important second-line therapies for patients with DME. Most emerging therapies focus on newly identified inflammatory mediators and biochemical signaling pathways involved in disease pathogenesis.

EXPERT OPINION

Emerging anti-VEGF modalities, integrin antagonists, and anti-inflammatory agents have the potential to improve outcomes with reduced treatment burdens.

Pelargonidin ameliorates reserpine-induced neuronal mitochondrial dysfunction and apoptotic cascade: a comparative in vivo study

BACKGROUND

Targeting the neuronal mitochondria as a possible intervention to guard against neurodegenerative disorder progression has been investigated in the current work via the administration of pelargonidin (PEL) to rats intoxicated by the mitochondrial toxin reserpine. The main criteria for choosing PEL were its reported antioxidant, anti-apoptotic and anti-inflammatory activities.

METHODS

Male albino Wistar rats were randomized into five experimental groups; normal control, reserpinized to induce mitochondrial failure, standard PARP-1-inhibitor 1,5-isoquinolinediol (DIQ)-treated reserpinized, PEL-treated reserpinized, and GSK-3β inhibitor (AR-A 014418) -treated reserpinized.

RESULTS

PEL administration reversed the reserpine-induced abnormal behaviors marked by decreased catalepsy time. In addition, PEL restored brain glutathione with a reduction in nitric oxide content as compared to the reserpine-challenged group. Meanwhile, it improved neuronal mitochondrial function by the elevation of complex I activity associated with a low ADP/ATP ratio. Likely through its anti-inflammatory effect, PEL reduced the elevation of serum interleukin-1ß level and inhibited serum lactate dehydrogenase activity. These findings are aligned with the reduced expression of cleaved PARP and cleaved caspase-3 proteins, indicating PEL's suppressive effect on the intrinsic apoptotic pathway. Those biochemical findings were confirmed through comparable histopathological tissue examination among the experimental groups.

CONCLUSIONS

In conclusion, PEL is a promising candidate for future use in the management of mitochondria-associated neuronal complications via controlling the ongoing inflammatory and degeneration cascades.

The effects of flavonoids in experimental sepsis: A systematic review and meta-analysis

Sepsis is a host's dysregulated immune response to an infection associated with systemic inflammation and excessive oxidative stress, which can cause multiple organ failure and death. The literature suggests that flavonoids, a broad class of secondary plant metabolites, have numerous biological activities which can be valuable in the treatment of sepsis. This study aimed to review the effects of flavonoids on experimental sepsis, focusing mainly on survival rate, and also summarizing information on its mechanisms of action. We searched in the main databases up to November 2022 using relevant keywords, and data were extracted and analyzed qualitatively and quantitatively. Thirty-two articles met the study criteria for review and 29 for meta-analysis. Overall, 30 different flavonoids were used in the studies. The flavonoids were able to strongly inhibit inflammatory response by reducing the levels of important pro-inflammatory mediators, for example, tumor necrosis factor-alpha and interleukin-1β, oxidative stress, and showed antibacterial and anti-apoptotic actions. The meta-analysis found an increase of 50% in survival rate of the animals treated with flavonoids. They appear to act as multi-target drugs and may be an excellent therapeutic alternative to reduce a number of the complications caused by sepsis, and consequently, to improve survival rate.

The Key Drivers of Brain Injury by Systemic Inflammatory Responses after Sepsis: Microglia and Neuroinflammation

Sepsis is a leading cause of intensive care unit admission and death worldwide. Most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). Although accumulating studies in the past two decades focused on the pathogenesis of SAE, a systematic review of retrospective studies which exclusively focuses on the inflammatory mechanisms of SAE has been lacking yet. This review summarizes the recent advance in the field of neuroinflammation and sheds light on the activation of microglia in SAE. Activation of microglia predominates neuroinflammation. As the gene expression profile changes, microglia show heterogeneous characterizations throughout all stages of SAE. Here, we summarize the systemic inflammation following sepsis and also the relationship of microglial diversity and neuroinflammation. Moreover, a collection of neuroinflammation-related dysfunction has also been reviewed to illustrate the possible mechanisms for SAE. In addition, promising pharmacological or non-pharmacological therapeutic strategies, especially those which target neuroinflammation or microglia, are also concluded in the final part of this review. Collectively, clarification of the vital relationship between neuroinflammation and SAE-related mental disorders would significantly improve our understanding of the pathophysiological mechanisms in SAE and therefore provide potential targets for therapies of SAE aimed at inhibiting neuroinflammation.

Inflammation in diabetic retinopathy: possible roles in pathogenesis and potential implications for therapy

Diabetic retinopathy, characterized as a microangiopathy and neurodegenerative disease, is the leading cause of visual impairment in diabetic patients. Many clinical features observed in diabetic retinopathy, such as capillary occlusion, acellular capillaries and retinal non-perfusion, aggregate retinal ischemia and represent relatively late events in diabetic retinopathy. In fact, retinal microvascular injury is an early event in diabetic retinopathy involving multiple biochemical alterations, and is manifested by changes to the retinal neurovascular unit and its cellular components. Currently, intravitreal anti-vascular endothelial growth factor therapy is the first-line treatment for diabetic macular edema, and benefits the patient by decreasing the edema and improving visual acuity. However, a significant proportion of patients respond poorly to anti-vascular endothelial growth factor treatments, indicating that factors other than vascular endothelial growth factor are involved in the pathogenesis of diabetic macular edema. Accumulating evidence confirms that low-grade inflammation plays a critical role in the pathogenesis and development of diabetic retinopathy as multiple inflammatory factors, such as interleukin-1β, monocyte chemotactic protein-1 and tumor necrosis factor -α, are increased in the vitreous and retina of diabetic retinopathy patients. These inflammatory factors, together with growth factors such as vascular endothelial growth factor, contribute to blood-retinal barrier breakdown, vascular damage and neuroinflammation, as well as pathological angiogenesis in diabetic retinopathy, complicated by diabetic macular edema and proliferative diabetic retinopathy. In addition, retinal cell types including microglia, Müller glia, astrocytes, retinal pigment epithelial cells, and others are activated, to secrete inflammatory mediators, aggravating cell apoptosis and subsequent vascular leakage. New therapies, targeting these inflammatory molecules or related signaling pathways, have the potential to inhibit retinal inflammation and prevent diabetic retinopathy progression. Here, we review the relevant literature to date, summarize the inflammatory mechanisms underlying the pathogenesis of diabetic retinopathy, and propose inflammation-based treatments for diabetic retinopathy and diabetic macular edema.

Evaluating the Impact of Thermal Processing on the Anti-Inflammatory Activity of Non-Centrifugal Cane Sugar: Implications on Cytokine Secretion and TLR4 Signaling

Plant-derived products have gained considerable attention as inflammation modulators given the wide variety of anti-inflammatory phytochemicals reported to be present in plants and their limited side effects in vivo during prolonged exposure periods. Non-centrifugal cane sugar (NCS) has been identified as a promising sugarcane-derived product due to its high polyphenolic composition and antioxidant potential, but its incorporations into nutraceuticals and other relevant products of biomedical interest has been limited by the ample composition-wise variability resulting from extreme and loosely controlled processing conditions. Here, we assessed the effect of reducing thermal exposure during NCS processing on the retained polyphenolic profiles, as well as on their antioxidant and anti-inflammatory activities. Specifically, we proposed two modified NCS production methods that reduce exposure to unwanted thermal processing conditions by 1) limiting the employed temperatures through vacuum-aided dehydration and 2) by reducing exposure time through refractance window evaporation. By comparing the modified NCS products with traditional NCS, we showed that the proposed process strategies yield enhanced polyphenolic profiles, as evidenced by the results of the Folin-Ciocalteu polyphenol quantification method and the components identification by HPLC coupled to mass spectrometry. Although these compositional differences failed to impact the antioxidant profiles and cytocompatibility of the products, they showed an enhanced anti-inflammatory potential, given their superior modulation capacity of inflammatory cytokine secretion in both systemic and neuroinflammatory scenarios in vitro. Moreover, we showed that both modified NCS products interfere with TLR4 signaling in human monocytes to a significantly greater extent than traditional NCS. However, the anti-inflammatory effect of NCS produced under window refractance evaporation was slightly superior than under vacuum-aided dehydration, demonstrating that reducing exposure time to high temperatures is likely more effective than reducing the operation temperature. Overall, these findings demonstrated that limiting thermal exposure is beneficial for the development of NCS-based natural products with superior anti-inflammatory potential, which can be further exploited in the rational design of more potent nutraceuticals for potentially preventing chronic inflammatory diseases.

Human platelets release TGFBIp in acute myocardial infarction

Transforming growth factor-β-induced protein (TGFBIp) is released from activated platelets and promotes pro-thrombotic complications like pulmonary embolism. The role of TGFBIp in acute coronary syndrome, especially with a focus on platelets, has not been investigated so far. Using ELISA and immunoblotting, we demonstrate platelet TGFBIp release in patients with myocardial infarction (MI). We investigated TGFBIp-induced platelet adhesion and rolling by flow chamber and chemotactic effects of TGFBIp in transwell experiments. Immunochemistry staining of arterial vessels detected TGFBIp and the platelet-specific protein GPVI in the vessel wall.We demonstrate for the first time that platelet TGFBIp release is significantly increased in MI and correlates with the severity of acute coronary syndromes (STEMI, NSTEMI). After activation with TRAP, platelets release TGFBIp and TGFBIp itself activates platelets. Under flow, TGFBIp-mediated platelet rolling and adherence similarly to collagen. TGFBIp significantly increased platelet transmigration and we demonstrate TGFBIp deposits in the wall of human arteries. In this study, we add novel aspects to the role of TGFBIp in acute coronary syndrome by demonstrating that TGFBIp is partially released from platelets during MI and has activating, pro-adhesive and pro-migratory effects on platelets that could contribute to the disease development of coronary vascular inflammation and MI.

Inhibitory effects of aloin on TGFBIp-mediated septic responses

Aloin is the major anthraquinone glycoside obtained from the Aloe species. Transforming growth factor β-induced protein (TGFBIp) is an extracellular matrix protein and released by primary human umbilical vein endothelial cells (HUVECs) and functions as a mediator of experimental sepsis. We hypothesized that aloin could reduce TGFBIp-mediated severe inflammatory responses in HUVECs and mice. Aloin effectively inhibited lipopolysaccharide (LPS)-induced release of TGFBIp and suppressed TGFBIp-mediated septic responses. Aloin suppressed TGFBIp-induced sepsis lethality and pulmonary injury. Therefore, aloin is a potential therapeutic agent for various severe vascular inflammatory diseases, with inhibition of the TGFBIp signaling pathway as the mechanism of action. [Formula: see text].

Pelargonidin ameliorates MCAO-induced cerebral ischemia/reperfusion injury in rats by the action on the Nrf2/HO-1 pathway

BACKGROUND

Morbidity and mortality remain high for ischemic stroke victims, and at present these patients lack effective neuroprotective agents, which improve the cure rate. In recent years, studies have shown that pelargonidin has many biological actions. However, few studies are available regarding the pelargonidin treatment of cerebral ischemia.

METHODS

The rat middle cerebral artery occlusion (MCAO) model was established to investigate the neuroprotective effect of pelargonidin on cerebral ischemia/reperfusion injury. Reperfusion was performed 2 h after ischemia; magnetic resonance imaging (MRI) and 2, 3, 5-triphenyltetrazolium chloride (TTC) staining were used to measure the volume of cerebral ischemia. Both modified neurological severity scores (mNSSs) and Morris water maze test were used to assess the neurological functions. ELISA was applied to determine the levels of TNF-α, TGF-β, IL-6, IL-10, MDA, and SOD. The expression of Nuclear factor-E2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) protein in brain tissue was measured by immunofluorescence and Western blot assays.

RESULTS

The results showed that pelargonidin could effectively reduce the volume of cerebral ischemia and improve the neurological function in MCAO rats, thereby improving memory and learning ability. With the corresponding decreases in the expression of TNF-α, TGF-β, IL-6, and MDA, the level of IL-10 and SOD increased and also promoted the nuclear metastasis of Nrf2 and the expression of HO-1 in ischemic brain tissues.

CONCLUSIONS

Our data demonstrated that pelargonidin ameliorated neurological function deficits in MCAO rats, and its potential mechanism of action was associated with overexpression of the Nrf2/HO-1-signaling pathway. This study will provide a new approach to treat cerebral ischemia/reperfusion injury.

Anthocyanins and their gut metabolites attenuate monocyte adhesion and transendothelial migration through nutrigenomic mechanisms regulating endothelial cell permeability

Cardioprotective effects of dietary anthocyanins are partly attributed to their ability to maintain endothelial function. However, the underlying cellular and molecular mechanisms of action are not fully understood. This study aimed to evaluate the effect of anthocyanins and their gut metabolites, at physiologically-relevant conditions, on endothelial cell (EC) function and decipher the underlying molecular mechanisms of action using integrated omics approaches. Primary EC were treated with a mixture of 0.1 μM cyanidin-3-arabinoside, 0.1 μM cyanidin-3-galactoside, 0.1 μM cyanidin-3-glucoside, 0.1 μM delphinidin-3-glucoside, 0.1 μM peonidin-3-glucoside and 0.5 μM 4-hydroxybenzaldehyde for 3 h or a mixture of gut metabolites: 0.2 μM protocatechuic, 2 μM vanillic, 1 μM ferulic and 2 μM hippuric acids for 18 h. Also, successive exposure of EC to both mixtures was performed to mimic anthocyanin pharmacokinetics following their intake. Inflammatory stress was induced using TNFα and monocytes added to assess adhesion and transmigration. Effects of these mixtures on gene, miRNA expression and their potential interaction with cell signalling were investigated. Anthocyanins and their gut metabolites significantly reduced monocyte adhesion and transendothelial migration. Gene expression analysis, using macroarrays, showed that tested compounds modulated the expression of genes involved in cell-cell adhesion, cytoskeleton organisation or focal adhesion. Bioinformatics analyses of gene expression data identified potential transcription factors involved in the observed nutrigenomic effects and signalling proteins regulating their activity. Molecular docking revealed cell signalling proteins to which these bioactives may bind to and potentially affect their activity and the activation of downstream signalling, effects that were in agreement with the results of Western blot analyses. Microarray analysis showed that anthocyanins and their gut metabolites affected miRNA expression in EC, especially those involved in regulation of EC permeability, contributing to the observed changes in EC function. Integration of these results revealed endothelial-protective properties of anthocyanins and their gut metabolites and deciphered new underlying multi-target and multi-layered mode of action.

Antiseptic effects of dabrafenib on TGFBIp-induced septic responses

Transforming growth factor-β-induced protein (TGFBIp), an extracellular protein, is expressed on several cell types in response to TGF-β stimulation. Human umbilical vein endothelial cell (HUVEC)-derived TGFBIp functions as a mediator of sepsis. Screening of bioactive compound libraries is an effective approach for repositioning FDA-approved drugs or discovering new treatments for human diseases (drug repositioning). Dabrafenib (DAB), a B-Raf inhibitor, was initially used for treating metastatic melanoma. The present study determined whether DAB modulated TGFBIp-mediated septic responses in HUVECs and in mice. Antiseptic functions of DAB were examined by measuring permeability, leukocyte adhesion and migration, and proinflammatory protein activation in TGFBIp-stimulated HUVECs and mice. In addition, beneficial effects of DAB on survival rate were examined using a mouse model of sepsis. We found that DAB inhibited TGFBIp-induced vascular barrier disruption, cell adhesion molecule (CAM) expression, and neutrophil adhesion/transendothelial migration toward human endothelial cells. DAB also suppressed TGFBIp-induced hyperpermeability and leukocyte migration in vivo. These results suggest that DAB exerts anti-inflammatory effects by inhibiting hyperpermeability, CAM expression, and leukocyte adhesion and migration, indicating its utility for treating vascular inflammatory diseases.