A novel antioxidant Mito-Tempol inhibits ox-LDL-induced foam cell formation through restoration of autophagy flux

Single-particle rotational microrheology enables pathological staging of macrophage foaming and antiatherosclerotic studies

The formation of macrophage-derived foam cells has been recognized as the pathological hallmark of atherosclerotic diseases. However, the pathological evolution dynamics and underlying regulatory mechanisms remain largely unknown. Herein, we introduce a single-particle rotational microrheology method for pathological staging of macrophage foaming and antiatherosclerotic explorations by probing the dynamic changes of lysosomal viscous feature over the pathological evolution progression. The principle of this method involves continuous monitoring of out-of-plane rotation-caused scattering brightness fluctuations of the gold nanorod (AuNR) probe-based microrheometer and subsequent determination of rotational relaxation time to analyze the viscous feature in macrophage lysosomes. With this method, we demonstrated the lysosomal viscous feature as a robust pathological reporter and uncovered three distinct pathological stages underlying the evolution dynamics, which are highly correlated with a pathological stage-dependent activation of the NLRP3 inflammasome-involved positive feedback loop. We also validated the potential of this positive feedback loop as a promising therapeutic target and revealed the time window-dependent efficacy of NLRP3 inflammasome-targeted drugs against atherosclerotic diseases. To our knowledge, the pathological staging of macrophage foaming and the pathological stage-dependent activation of the NLRP3 inflammasome-involved positive feedback mechanism have not yet been reported. These findings provide insights into in-depth understanding of evolutionary features and regulatory mechanisms of macrophage foaming, which can benefit the analysis of effective therapeutical drugs as well as the time window of drug treatment against atherosclerotic diseases in preclinical studies.

The effect of dual antioxidant modification on oxidative stress resistance and anti-dysfunction of non-split HDL and recombinant HDL

Recombinant high-density lipoprotein (rHDL) as anti-atherosclerosis (AS) vehicle has unique advantages including multiple anti-atherogenic functions and homing features to plaques. However, rHDL may be converted into dysfunctional forms due to complex treatment during preparation. Herein, oxidation-induced dysfunction of non-split HDL and rHDL was initially investigated. It was found that although both non-split HDL and rHDL showed oxidative dysfunction behavior, non-split HDL demonstrated superior oxidation defense compared to rHDL due to its intact composition and avoidance of overprocessing such as split and recombination. Unfortunately, in vivo oxidative stress could compromise the functionality of HDL. Therefore, surface engineering of non-split HDL and rHDL with cascade antioxidant enzyme analogues Ebselen and mitochondrial-targeted TPGS-Tempo was conducted to construct a dual-line defense HDL nano system (i.e., T@E-HDLs/rHDL), aiming to restore plaque redox balance and preserving the physiological function of HDL. Results indicated that both T@E-HDLs and rHDLs performed without distinction and exhibited greater resistance to oxidative stress damage as well as better functions than unmodified HDLs in macrophage foam cells. Overall, the modification of dual antioxidants strategy bridges the gap between non-split HDL and rHDL, and provides a promising resolution for the dilemmas of oxidative stress in plaques and HDL self dysfunction.

Mito-Tempo alleviates ox-LDL-provoked foam cell formation by regulating Nrf2/NLRP3 signaling

Our previous studies have demonstrated that Mito-Tempol (also known as 4-hydroxy-Tempo), a mitochondrial reactive oxygen species scavenger, alleviates oxidized low-density lipoprotein (ox-LDL)-triggered foam cell formation. Given the effect of oxidative stress on activating the NOD-, LRR-, and pyrin domain-containing 3 (NLRP3) inflammasome, which promotes foam cell formation, we aimed to explore whether Mito-Tempo inhibits ox-LDL-triggered foam cell formation by regulating NLRP3 inflammasome. The results revealed that Mito-Tempo re-activated Nrf2 and alleviated macrophage foam cell formation induced by ox-LDL, whereas the effects were reversed by ML385 (a specific Nrf2 inhibitor). Mito-Tempo restored the expression and nuclear translocation of Nrf2 by decreasing ox-LDL-induced ubiquitination. Furthermore, Mito-Tempo suppressed ox-LDL-triggered NLRP3 inflammasome activation and subsequent pyroptosis, whereas the changes were blocked by ML385. Mito-Tempo decreased lipoprotein uptake by inhibiting CD36 expression and suppressed foam cell formation by regulating the NLRP3 inflammasome. Taken together, Mito-Tempo exhibits potent anti-atherosclerotic effects by regulating Nrf2/NLRP3 signaling.

Revitalizing Ancient Mitochondria with Nano-Strategies: Mitochondria-Remedying Nanodrugs Concentrate on Disease Control

Mitochondria, widely known as the energy factories of eukaryotic cells, have a myriad of vital functions across diverse cellular processes. Dysfunctions within mitochondria serve as catalysts for various diseases, prompting widespread cellular demise. Mounting research on remedying damaged mitochondria indicates that mitochondria constitute a valuable target for therapeutic intervention against diseases. But the less clinical practice and lower recovery rate imply the limitation of traditional drugs, which need a further breakthrough. Nanotechnology has approached favorable regiospecific biodistribution and high efficacy by capitalizing on excellent nanomaterials and targeting drug delivery. Mitochondria-remedying nanodrugs have achieved ideal therapeutic effects. This review elucidates the significance of mitochondria in various cells and organs, while also compiling mortality data for related diseases. Correspondingly, nanodrug-mediate therapeutic strategies and applicable mitochondria-remedying nanodrugs in disease are detailed, with a full understanding of the roles of mitochondria dysfunction and the advantages of nanodrugs. In addition, the future challenges and directions are widely discussed. In conclusion, this review provides comprehensive insights into the design and development of mitochondria-remedying nanodrugs, aiming to help scientists who desire to extend their research fields and engage in this interdisciplinary subject.

Effects of frog skin peptide temporin-1CEa and its analogs on ox-LDL induced macrophage-derived foam cells

Purpose: Atherosclerosis is one of the most important pathological foundations of cardiovascular and cerebrovascular diseases with high morbidity and mortality. Studies have shown that macrophages play important roles in lipid accumulation in the vascular wall and thrombosis formation in atherosclerotic plaques. This study aimed to explore the effect of frog skin antimicrobial peptides (AMPs) temporin-1CEa and its analogs on ox-LDL induced macrophage-derived foam cells.

Methods: CCK-8, ORO staining, and intracellular cholesterol measurements were used to study cellular activity, lipid droplet formation and cholesterol levels, respectively. ELISA, real-time quantitative PCR, Western blotting and flow cytometry analysis were used to study the expression of inflammatory factors, mRNA and proteins associated with ox-LDL uptake and cholesterol efflux in macrophage-derived foam cells, respectively. Furthermore, the effects of AMPs on inflammation signaling pathways were studied.

Results: Frog skin AMPs could significantly increase the cell viability of the ox-LDL-induced foaming macrophages and decrease the formation of intracellular lipid droplets and the levels of total cholesterol and cholesterol ester (CE). Frog skin AMPs inhibited foaming formation by reducing the protein expression of CD36, which regulates ox-LDL uptake but had no effect on the expression of efflux proteins ATP binding cassette subfamily A/G member 1 (ABCA1/ABCG1). Then, decreased mRNA expression of NF-κB and protein expression of p-NF-κB p65, p-IκB, p-JNK, p-ERK, p-p38 and the release of TNF-α and IL-6 occurred after exposure to the three frog skin AMPs.

Conclusion: Frog skin peptide temporin-1CEa and its analogs can improve the ox-LDL induced formation of macrophage-derived foam cells, in addition, inhibit inflammatory cytokine release through inhibiting the NF-κB and MAPK signaling pathways, thereby inhibiting inflammatory responses in atherosclerosis.

Mitochondria as novel mediators linking gut microbiota to atherosclerosis that is ameliorated by herbal medicine: A review

Atherosclerosis (AS) is the main cause of cardiovascular disease (CVD) and is characterized by endothelial damage, lipid deposition, and chronic inflammation. Gut microbiota plays an important role in the occurrence and development of AS by regulating host metabolism and immunity. As human mitochondria evolved from primordial bacteria have homologous characteristics, they are attacked by microbial pathogens as target organelles, thus contributing to energy metabolism disorders, oxidative stress, and apoptosis. Therefore, mitochondria may be a key mediator of intestinal microbiota disorders and AS aggravation. Microbial metabolites, such as short-chain fatty acids, trimethylamine, hydrogen sulfide, and bile acids, also affect mitochondrial function, including mtDNA mutation, oxidative stress, and mitophagy, promoting low-grade inflammation. This further damages cellular homeostasis and the balance of innate immunity, aggravating AS. Herbal medicines and their monomers can effectively ameliorate the intestinal flora and their metabolites, improve mitochondrial function, and inhibit atherosclerotic plaques. This review focuses on the interaction between gut microbiota and mitochondria in AS and explores a therapeutic strategy for restoring mitochondrial function and intestinal microbiota disorders using herbal medicines, aiming to provide new insights for the prevention and treatment of AS.

The Therapeutic Strategies Targeting Mitochondrial Metabolism in Cardiovascular Disease

Cardiovascular disease (CVD) is a group of systemic disorders threatening human health with complex pathogenesis, among which mitochondrial energy metabolism reprogramming has a critical role. Mitochondria are cell organelles that fuel the energy essential for biochemical reactions and maintain normal physiological functions of the body. Mitochondrial metabolic disorders are extensively involved in the progression of CVD, especially for energy-demanding organs such as the heart. Therefore, elucidating the role of mitochondrial metabolism in the progression of CVD is of great significance to further understand the pathogenesis of CVD and explore preventive and therapeutic methods. In this review, we discuss the major factors of mitochondrial metabolism and their potential roles in the prevention and treatment of CVD. The current application of mitochondria-targeted therapeutic agents in the treatment of CVD and advances in mitochondria-targeted gene therapy technologies are also overviewed.

Mitochondrial Dysfunction and Cardiovascular Disease: Pathophysiology and Emerging Therapies

Mitochondria ensure the supply of cellular energy through the production of ATP via oxidative phosphorylation. The alteration of this process, called mitochondrial dysfunction, leads to a reduction in ATP and an increase in the production of reactive oxygen species (ROS). Mitochondrial dysfunction can be caused by mitochondrial/nuclear DNA mutations, or it can be secondary to pathological conditions such as cardiovascular disease, aging, and environmental stress. The use of therapies aimed at the prevention/correction of mitochondrial dysfunction, in the context of the specific treatment of cardiovascular diseases, is a topic of growing interest. In this context, the data are conflicting since preclinical studies are numerous, but there are no large randomized studies.

MitoTEMPOL Inhibits ROS-Induced Retinal Vascularization Pattern by Modulating Autophagy and Apoptosis in Rat-Injected Streptozotocin Model

Diabetic retinopathy leads to retinal malfunction, blindness, and reduced quality of life in adult diabetes patients. The involvement of reactive oxygen species (ROS) regulation stimulated by high blood glucose levels opens the opportunity for ROS modulator agents such as MitoTEMPOL. This study aims to explore the effect of MitoTEMPOL on ROS balance that may be correlated with retinal vascularization pattern, autophagy, and apoptosis in a streptozotocin-induced rat model. Four groups of male Wistar rats (i.e., control, TEMPOL (100 mg/kg body weight [BW]), diabetic (streptozotocin, 50 mg/kg BW single dose), and diabetic + TEMPOL; n = 5 for each group) were used in the study. MitoTEMPOL was given for 5 weeks, followed by funduscopy, and gene and protein expression were explored from the rat’s retina. Streptozotocin injection decreased bodyweight and increased food and water intake, as well as fasting blood glucose. The results showed that MitoTEMPOL reduced retinal vascularization pattern and decreased superoxide dismutase gene expression and protein carbonyl, caspase 3, and caspase 9 protein levels. A modulation of autophagy in diabetes that was reversed in the diabetic + TEMPOL group was found. In conclusion, MitoTEMPOL modulation on autophagy and apoptosis contributes to its role as a potent antioxidant to prevent diabetic retinopathy by inhibiting ROS-induced retinal vascularization patterns.

Endothelial miR-199a-3p regulating cell adhesion molecules by targeting mTOR signaling during inflammation

BACKGROUND

Adherence of monocytes to endothelial cells is the initial stage for development of coronary artery disease (CAD). MiRNAs have been reported to participate in this process by regulating the expression of cell adhesion molecules. This study aimed to explore the function of miR-199a-3p in endothelial inflammation and adhesion.

METHODS

We assessed the expression of miR-199a-3p in CAD patients and ApoE^-/- mice. The relationship between miR-199a-3p level and endothelial inflammation and adhesion was examined. ELISA was used to test the level of IL-6 and IL-8. Dual luciferase reporter assay was used to evaluate the binding between miR-199a-3p and mTOR.

RESULTS

A decreased expression of miR-199a-3p was observed in the PBMCs and plasma of CAD patients, aorta of ApoE^-/- mice and inflammatory HUVECs. MiR-199a-3p significantly suppressed the expression levels of pro-inflammatory cytokine (IL-6, IL-8), endothelial adhesion molecules (ICAM-1, VCAM-1) and monocyte-endothelial cells interaction. MiR-199a-3p directly targeted and repressed mTOR, and its suppression effect on ICAM-1 and VCAM-1 was abolished by mTOR inhibitor rapamycin, and rescued by mTOR activator MHY1485. Overexpression of miR-199a-3p promoted autophagy in HUVECs and inhibiting autophagy by chloroquine attenuated the effect of miR-199a-3p on ICAM-1 and VCAM-1 expression. Inhibition of autophagy promoted endothelial adhesion molecule expression and monocyte-EC interaction.

CONCLUSIONS

Our results suggested that miR-199a-3p suppressed endothelial inflammation and adhesion by targeting mTOR signaling and increasing autophagy. Our findings point to an important role for miR-199a-3p in the early stage of cardiovascular disease.

Nanoconfined anti-oxidizing RAFT nitroxide radical polymer for reduction of low-density lipoprotein oxidation and foam cell formation

Atherosclerosis is a leading cause of death worldwide. Antioxidant therapy has been considered a promising treatment modality for atherosclerosis, since reactive oxygen species (ROS) play a major role in the pathogenesis of atherosclerosis. We developed ROS-scavenging antioxidant nanoparticles (NPs) that can serve as an effective therapy for atherosclerosis. The newly developed novel antioxidant ROS-eliminating NPs were synthesized via reversible addition-fragmentation chain-transfer (RAFT) polymerization and act as a superoxide dismutase (SOD) mimetic agent. SOD is an anti-ROS enzyme which is difficult to use for passive delivery due to its low half-life and stability. Copolymers were synthesized using different feed ratios of 2,2,6,6-tetramethyl-4-piperidyl methacrylate (PMA) and glycidyl methacrylate (GMA) monomers and an anti-ROS nitroxyl radical polymer was prepared via oxidation. The copolymer was further conjugated with a 6-aminofluorescein via a oxirane ring opening reaction for intracellular delivery in RAW 264.7 cells. The synthesized copolymers were blended to create NPs (∼150 nm size) in aqueous medium and highly stable up to three weeks. The NPs were shown to be taken up by macrophages and to be cytocompatible even at high dose levels (500 μg mL-1). Finally, the nitroxide NPs has been shown to inhibit foam cell formation in macrophages by decreasing internalization of oxidized low-density lipoproteins.

Procyanidin A1 alleviates DSS-induced ulcerative colitis via regulating AMPK/mTOR/p70S6K-mediated autophagy

Ulcerative colitis (UC) is a recurrent chronic inflammatory disease. The symptom of UC is mainly diarrhea including bloody stools. Increasing evidence has suggested that procyanidin A1 (PCA1) exerts an anti-inflammatory effect in several diseases. However, the role of PCA1 in UC is still a mystery. In our study, we explored the effect of PCA1 in dextran sulfate sodium (DSS)-induced UC mice and lipopolysaccharide (LPS)-stimulated HT-29 and IEC-6 cells. Then, cell proliferation, apoptosis, the production of proinflammatory cytokines, and autophagy-related markers were determined. Furthermore, the AMPK/mTOR/p70S6K signaling pathway was assayed by Western blot assay. In in vivo study, we found that PCA1 administration alleviated DSS-induced UC, as evidenced by reducing weight loss, clinical scores, colon weight/length ratio, histological damage, proinflammatory cytokines, and apoptosis. Moreover, we showed that the expression of Beclin-1 and LC3II/I ratio was increased, whereas the level of p62 was decreased after PCA1 treatment in vivo. Meanwhile, the reduced AMP/ATP ratio, enhanced expression of p-AMPK, and decreased p-p70S6K and p-mTOR levels indicate the activation of AMPK/mTOR/p70S6K signaling pathway. In in vitro study, PCA1 promoted cell proliferation and inhibited cell apoptosis in LPS-stimulated HT-29 and IEC-6 cells. Pro-inflammatory cytokines and autophagy-related factors exhibited the same trend as in in vivo results. Mechanically, PCA1 activated the AMPK/mTOR/p70S6K signaling pathway. The treatment with an AMPK inhibitor compound C significantly reversed the anti-inflammatory effect of PCA1 in LPS-stimulated cells. Taken together, these data indicated that PCA1 alleviated UC through induction of AMPK/mTOR/p70S6K-mediated autophagy.

Mito-targeted antioxidant prevents cardiovascular remodelling in spontaneously hypertensive rat by modulation of energy metabolism

Hypertension induced left ventricular hypertrophy (LVH) augments the risk of cardiovascular anomalies. Mitochondrial alterations result in oxidative stress, accompanied by decrease in fatty acid oxidation, leading to the activation of the hypertrophic program. Targeted antioxidants are expected to reduce mitochondrial reactive oxygen species more effectively than general antioxidants. This study was designed to assess whether the mito-targeted antioxidant, Mito-Tempol (Mito-TEMP) is more effective than the general oxidant, Tempol (TEMP) in reduction of hypertension and hypertrophy and prevention of shift in cardiac energy metabolism. Spontaneously hypertensive rats were administered either TEMP (20 mg/kg/day) or Mito-TEMP (2 mg/kg/day) intraperitoneally for 30 days. Post treatment, animals were subjected to 2D-echocardiography. Myocardial lysates were subjected to RPLC - LTQ-Orbitrap-MS analysis. Mid-ventricular sections were probed for markers of energy metabolism and fibrosis. The beneficial effect on cardiovascular structure and function was significantly higher for Mito-TEMP. Increase in mitochondrial antioxidants and stimulation of fatty acid metabolism; with significant improvement in cardiovascular function was apparent in spontaneously hypertensive rats (SHR) treated with Mito-TEMP. The study indicates that Mito-TEMP is superior to its non- targeted isoform in preventing hypertension induced LVH, and the beneficial effects on heart are possibly mediated by reversal of metabolic remodelling.

Role of macrophage autophagy in atherosclerosis: modulation by bioactive compounds

Atherosclerosis is a chronic inflammatory disease associated with lipid metabolism disorder. Autophagy is a catabolic process and contributes to maintaining cellular homeostasis. Substantial evidence suggests that defective autophagy is implicated in several diseases, including atherosclerosis, while increased autophagy mitigates atherosclerosis development. Thus, understanding the mechanisms of autophagy regulation and its association with atherosclerosis is vital to develop new therapies against atherosclerosis. Dietary bioactive compounds are non-nutrient natural compounds that include phenolics, flavonoids, and carotenoids. Importantly, these bioactive compounds possess anti-inflammatory, antioxidant, and antibacterial properties that may alleviate various chronic diseases. Recently, examining the effects of bioactive compounds on autophagy activity in atherogenesis has drawn considerable attention. The current review discusses the role of macrophage autophagy in the development and progression of atherosclerosis. We also summarize our current knowledge of the therapeutic potential of bioactive compounds on atherosclerosis and autophagy.

Rosuvastatin exerts anti-atherosclerotic effects by improving macrophage-related foam cell formation and polarization conversion via mediating autophagic activities

BACKGROUND

Atherosclerosis is a chronic vascular disease posing a great threat to public health. We investigated whether rosuvastatin (RVS) enhanced autophagic activities to inhibit lipid accumulation and polarization conversion of macrophages and then attenuate atherosclerotic lesions.

METHODS

All male Apolipoprotein E-deficient (ApoE-/-) mice were fed high-fat diet supplemented with RVS (10 mg/kg/day) or the same volume of normal saline gavage for 20 weeks. The burden of plaques in mice were determined by histopathological staining. Biochemical kits were used to examine the levels of lipid profiles and inflammatory cytokines. The potential mechanisms by which RVS mediated atherosclerosis were explored by western blot, real-time PCR assay, and immunofluorescence staining in mice and RAW264.7 macrophages.

RESULTS

Our data showed that RVS treatment reduced plaque areas in the aorta inner surface and the aortic sinus of ApoE-/- mice with high-fat diet. RVS markedly improved lipid profiles and reduced contents of inflammatory cytokines in the circulation. Then, results of Western blot showed that RVS increased the ratio LC3II/I and level of Beclin 1 and decreased the expression of p62 in aortic tissues, which might be attributed to suppression of PI3K/Akt/mTOR pathway, hinting that autophagy cascades were activated by RVS. Moreover, RVS raised the contents of ABCA1, ABCG1, Arg-1, CD206 and reduced iNOS expression of arterial wall, indicating that RVS promoted cholesterol efflux and M2 macrophage polarization. Similarly, we observed that RVS decreased lipids contents and inflammatory factors expressions in RAW264.7 cells stimulated by ox-LDL, accompanied by levels elevation of ABCA1, ABCG1, Arg-1, CD206 and content reduction of iNOS. These anti-atherosclerotic effects of RVS were abolished by 3-methyladenine intervention. Moreover, RVS could reverse the impaired autophagy flux in macrophages insulted by chloroquine. We further found that PI3K inhibitor LY294002 enhanced and agonist 740 Y-P weakened the autophagy-promoting roles of RVS, respectively.

CONCLUSIONS

Our study indicated that RVS exhibits atheroprotective effects involving regulation lipid accumulation and polarization conversion by improving autophagy initiation and development via suppressing PI3K/Akt/mTOR axis and enhancing autophagic flux in macrophages.

Mitochondria-Targeted Antioxidants: A Step towards Disease Treatment

Mitochondria are the main organelles that produce adenosine 5′-triphosphate (ATP) and reactive oxygen species (ROS) in eukaryotic cells and meanwhile susceptible to oxidative damage. The irreversible oxidative damage in mitochondria has been implicated in various human diseases. Increasing evidence indicates the therapeutic potential of mitochondria-targeted antioxidants (MTAs) for oxidative damage-associated diseases. In this article, we introduce the advantageous properties of MTAs compared with the conventional (nontargeted) ones, review different mitochondria-targeted delivery systems and antioxidants, and summarize their experimental results for various disease treatments in different animal models and clinical trials. The combined evidence demonstrates that mitochondrial redox homeostasis is a potential target for disease treatment. Meanwhile, the limitations and prospects for exploiting MTAs are discussed, which might pave ways for further trial design and drug development.

Gypenoside inhibits ox-LDL uptake and foam cell formation through enhancing Sirt1-FOXO1 mediated autophagy flux restoration

BACKGROUND

Gypenoside (GP) is the major bioactive constituent of G. pentaphyllum, a traditional Chinese medicine. It has been reported that GP can affect autophagy and lipid metabolism in cultured cells. We hypothesize that GP can inhibit foam cell formation in cultured macrophages through autophagy modulation.

METHODS

THP1 cells were cultured and treated with oxidized low-density lipoprotein (ox-LDL), followed by GP treatment at different concentrations. The autophagy flux was evaluated using western blot and confocal microscope analyses. The ox-LDL uptake and foam cell formation abilities were measured.

RESULTS

We found that ox-LDL impaired the autophagy flux in the cultured macrophages, indicated by a significant reduction of LC3-II and autophagosome puncta quantification, as well as an accumulation of p62 proteins. GP treatment, however, dose-dependently restored the autophagy flux impaired by ox-LDL and reduced the ox-LDL uptake and foam cell transformation from THP1 cells, which can be alleviated, or exacerbated, by modulation of autophagy status using autophagy enhancer or inhibitor. Coimmunoprecipitation assays showed that GP up-regulated Srit1 and FOXO1 expression and enhanced their direct interaction, and thus contributed to the regulation of autophagy.

CONCLUSION

GP inhibits ox-LDL uptake and foam cell formation through enhancing Sirt1-FOXO1 mediated autophagy flux restoration, suggesting this compound has therapeutic potential for atherosclerosis.

Mitochondrial dysfunction in cardiovascular disease: Current status of translational research/clinical and therapeutic implications

Mitochondria provide energy to the cell during aerobic respiration by supplying ~95% of the adenosine triphosphate (ATP) molecules via oxidative phosphorylation. These organelles have various other functions, all carried out by numerous proteins, with the majority of them being encoded by nuclear DNA (nDNA). Mitochondria occupy ~1/3 of the volume of myocardial cells in adults, and function at levels of high-efficiency to promptly meet the energy requirements of the myocardial contractile units. Mitochondria have their own DNA (mtDNA), which contains 37 genes and is maternally inherited. Over the last several years, a variety of functions of these organelles have been discovered and this has led to a growing interest in their involvement in various diseases, including cardiovascular (CV) diseases. Mitochondrial dysfunction relates to the status where mitochondria cannot meet the demands of a cell for ATP and there is an enhanced formation of reactive-oxygen species. This dysfunction may occur as a result of mtDNA and/or nDNA mutations, but also as a response to aging and various disease and environmental stresses, leading to the development of cardiomyopathies and other CV diseases. Designing mitochondria-targeted therapeutic strategies aiming to maintain or restore mitochondrial function has been a great challenge as a result of variable responses according to the etiology of the disorder. There have been several preclinical data on such therapies, but clinical studies are scarce. A major challenge relates to the techniques needed to eclectically deliver the therapeutic agents to cardiac tissues and to damaged mitochondria for successful clinical outcomes. All these issues and progress made over the last several years are herein reviewed.

A Novel Anticancer Therapeutic Strategy to Target Autophagy Accelerates Radiation-Associated Atherosclerosis

PURPOSE

Autophagy inhibition is a novel therapeutic strategy suggested for patients with advanced cancer, especially those who have undergone radiation therapy. In the present study, we investigated whether autophagy inhibitors accelerate the progression of radiation-associated atherosclerosis (RAA).

METHODS AND MATERIALS

Eight-week-old apolipoprotein (ApoE^-/-) mice were fed a Western diet, and their left common carotid arteries were partially ligated to induce atherogenesis. Four weeks later, local ionizing radiation (IR) at a dose of 5 or 10 Gy was used to induce RAA in the left common carotid artery. After another 4 weeks, severe plaque burden associated with increased macrophage infiltration and lipid deposition, reduced smooth muscle cells, and decreased collagen expression was observed. In addition, these changes occurred in a dose-dependent manner. Improved autophagic flux caused by IR was observed in both macrophages of the atherosclerotic plaque and peritoneal macrophages in vitro. The inhibition of autophagic flux by chloroquine (50 mg/kg/d) further accelerated the progression of RAA in the left common carotid arteries of ApoE^-/- mice. Furthermore, chloroquine treatment exacerbated IR-induced p65 nuclear translocation, IκBα degradation, and transcription of nuclear factor-κB (NF-κB) target genes in peritoneal macrophages.

CONCLUSIONS

IR promotes atherogenesis and increases autophagic flux. In addition, autophagy inhibition by chloroquine accelerates the progression of RAA lesions by stimulating NF-κB-mediated inflammatory responses in macrophages.

Inhibition of notch enhances the anti-atherosclerotic effects of LXR agonists while reducing fatty liver development in ApoE-deficient mice

Liver X receptor (LXR) activation can achieve satisfactory anti-atherosclerotic activity, but can also lead to the development of fatty liver and hypertriglyceridemia. In contrast, Notch inhibition can suppress both atherosclerosis and the hepatic accumulation of lipids. In the present study, we sought to assess whether combining LXR ligand agonists (T317) with Notch receptor inhibitors (DAPT) would lead to enhanced anti-atherosclerotic activity while overcoming the adverse events associated with LXR ligand agonist therapy. The impact of the combined T317 + DAPT therapeutic regimen on atherosclerosis, fatty liver development, and hypertriglyceridemia was assessed using ApoE deficient (ApoE^-/-) mice. The results of this analysis suggested that DAPT was able to improve the anti-atherosclerotic activity of T317 without reducing the stability of lesion plaques while simultaneously reducing blood lipids in treated ApoE^-/- mice. This combination T317 + DAPT treatment was also linked with a significant upregulation of ABCA1 and the stimulation of reverse cholesterol transport (RCT), as well as with decreases in the levels of intercellular cell adhesion molecule-1 (ICAM-1) and p-p65, and with altered M1/M2 macrophage proportions within atherosclerotic plaques. Importantly, DAPT was also able to reduce T317-mediated lipid accumulation within the liver owing to its ability to reduce SREBP-1 expression while simultaneously increasing that of Pi-AMPKα and PPARα. Together, our results suggest that administering Notch receptor inhibitors to ApoE^-/- mice may be an effective means of enhancing the anti-atherosclerotic activity of LXR ligand agonists while simultaneously limiting associated fatty liver and hypertriglyceridemia development in these animals.

MicroRNA-761 modulates foam cell formation and inflammation through autophagy in the progression of atherosclerosis

Macrophage-derived foam cells formation is the initial stage of atherosclerosis, and lipid-laden macrophage accumulation is also considered as the symbol of unstable plaque. Autophagy is a subcellular process responsible for the degradation of damaged organelles and aggregated proteins in cells (Grootaert in Oxid Med Cell Longev: 7687083, 2018). Macrophage autophagy plays an important role in atherosclerosis under various stress conditions, and microRNAs are involved in this complicated process. The present study was programmed to explore the effects of microRNA-761 on macrophage-derived foam cell formation, focusing on the role of autophagy in this pathological process. The differentiated human THP-1 macrophages were used in the study. THP-1-derived macrophages were treated with miR-761 mimics or inhibitors and cultured with oxidized low-density lipoprotein to mimic the lipid-rich environment in blood vessel. The expression of miR-761 and mRNA levels of IL-1β and IL-18 were analyzed by quantitative real-time PCR. The effect of miR-761 on autophagy was evaluated by the protein levels of Beclin1, p62/SQSTM1, microtubule-associated protein light chain 3, mammalian target of rapamycin (mTOR), and unc-51-like autophagy activating kinase 1 (ULK1), determined by immunoblot and autophagic flux detected by fluorescent staining. The secretion of IL-1β and IL-18 was tested by enzyme-linked immunosorbent reaction kit. Lipid accumulation in foam cells was detected by oil red "O" staining. We demonstrated that miR-761 was able to repress foam cell formation and reduce the production of atherogenic inflammatory cytokines IL-1β and IL-18 in an autophagy-dependent manner in atherosclerosis, possibly via mTOR-ULK1 signaling pathway. In summary, we described an athero-protective function of miR-761 in macrophages incubated with excess ox-LDL and identified an important novel modulator of mTOR signaling and autophagy in macrophage-derived foam cells. This finding may provide a potential target for the prevention and early treatment in high-risk group of atherosclerosis.

Therapeutic Potential of Quercetin as an Antiatherosclerotic Agent in Atherosclerotic Cardiovascular Disease: A Review

Atherosclerotic cardiovascular disease (ASCVD) is one of the diseases with the highest morbidity and mortality globally. It causes a huge burden on families and caregivers and high costs for medicine and surgical interventions. Given expensive surgeries and failures of most conventional treatments, medical community tries to find a more cost-effective cure. Thus, attentions have been primarily focused on food or herbs. Quercetin (Qu) extracted from food, a flavonoid component, develops potentials of alternative or complementary medicine in atherosclerosis. Due to the wide range of health benefits, researchers have considered to apply Qu as a natural compound in therapy. This review is aimed to identify the antiatherosclerosis functions of Qu in treating ASCVD such as anti-inflammatory, antioxidant properties, effects on endothelium-dependent vasodilation, and blood lipid-lowering.

Nitro-oleic acid, a ligand of CD36, reduces cholesterol accumulation by modulating oxidized-LDL uptake and cholesterol efflux in RAW264.7 macrophages

Macrophages play a pivotal role in the early stages of atherosclerosis development; they excessively accumulate cholesterol in the cytosol in response to modified Low Density Lipoprotein (mLDL). The mLDL are incorporated through scavenger receptors. CD36 is a high-affinity cell surface scavenger receptor that facilitates the binding and uptake of long-chain fatty acids and mLDL into the cell. Numerous structurally diverse ligands can initiate signaling responses through CD36 to regulate cell metabolism, migration, and angiogenesis. Nitro-fatty acids are endogenous electrophilic lipid mediators that react with and modulate the function of multiple enzymes and transcriptional regulatory proteins. These actions induce the expression of several anti-inflammatory and cytoprotective genes and limit pathologic responses in experimental models of atherosclerosis, cardiac ischemia/reperfusion, and inflammatory diseases. Pharmacological and genetic approaches were used to explore the actions of nitro-oleic acid (NO₂-OA) on macrophage lipid metabolism. Pure synthetic NO₂-OA dose-dependently increased CD36 expression in RAW264.7 macrophages and this up-regulation was abrogated in BMDM from Nrf2-KO mice. Ligand binding analysis revealed that NO₂-OA specifically interacts with CD36, thus limiting the binding and uptake of mLDL. Docking analysis shows that NO₂-OA establishes a low binding energy interaction with the alpha helix containing Lys164 in CD36. NO₂-OA also restored autophagy flux in mLDL-loaded macrophages, thus reversing cholesterol deposition within the cell. In aggregate, these results indicate that NO₂-OA reduces cholesterol uptake by binding to CD36 and increases cholesterol efflux by restoring autophagy.

Alpha7 Nicotinic Acetylcholine Receptor Alleviates Inflammatory Bowel Disease Through Induction of AMPK-mTOR-p70S6K-Mediated Autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been reported to be protective in several kinds of disorders through inflammatory suppression. Here, we investigated the role of α7nAChR in inflammatory bowel disease (IBD) on α7nAChR deficient mice (α7nAChR^-/-) and the wild-type mice (α7nAChR^+/+). Three percent dextran sulfate sodium (DSS) was used for the creation of IBD mice model and lipopolysaccharides (LPS)/DSS as an inflammatory stressor in murine bone marrow-derived macrophages (BMDMs). The severity of IBD was determined and HE staining as well as enzyme-linked immunosorbent assay (ELISA) and real-time PCR were used to detect the level of inflammatory activation. Western blot was used to determine the levels of autophagy-related proteins. Transmission electron microscopy and mRFP-GFP-LC3 plasmid were applied to determine the levels of autophagy. We demonstrated that deficiency in α7nAChR produced a detrimental effect on IBD severity and inflammatory reaction in DSS-induced colitis models. Those effects were led to via autophagy dysfunction. α7nAChR deficiency attenuated the protective and anti-inflammatory effect of autophagy inducer in IBD mice and BMDMs challenged with LPS/DSS. The alleviative effect of activating α7nAChR was attenuated through inhibiting adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-mediated signaling. In conclusion, α7nAChR contributes to alleviate IBD through the induction of AMPK-mammalian target of rapamycin rabbit (mTOR)-p70 ribosomal protein S6 kinase (p70S6K)-mediated autophagy, thus providing a novel target for the treatment of IBD.

Triphenylphosphonium (TPP)-Based Antioxidants: A New Perspective on Antioxidant Design

Mitochondrial oxidative damage and dysfunction contribute to a wide range of human diseases. Considering the limitation of conventional antioxidants and that mitochondria are the main source of reactive oxygen species (ROS) which induce oxidative damage, mitochondria-targeted antioxidants which can selectively block mitochondrial oxidative damage and prevent various types of cell death have been widely developed. As a lipophilic cation, triphenylphosphonium (TPP) has been commonly used in designing mitochondria-targeted antioxidants. Conjugated with the TPP moiety, antioxidants can achieve more than 1000-fold higher mitochondrial concentration depending on cell membrane potentials and mitochondrial membrane potentials. Herein we discuss the deficiencies of conventional antioxidants and the advantages of mitochondrial targeting, and review various types of TPP-based mitochondria-targeted antioxidants. These provide theoretical and background support for the design of new anti-oxidant.

Araloside C attenuates atherosclerosis by modulating macrophage polarization via Sirt1-mediated autophagy

Atherosclerosis-related cardiovascular disease is still the predominant cause of death worldwide. Araloside C (AsC), a natural saponin, exerts extensive anti-inflammatory properties. In this study, we explored the protective effects and mechanism of AsC on macrophage polarization in atherosclerosis in vivo and in vitro. Using a high-fat diet (HFD)-fed ApoE-/- mouse model and RAW264.7 macrophages exposed to ox-LDL, AsC was evaluated for its effects on polarization and autophagy. AsC significantly reduced the plaque area in atherosclerotic mice and lipid accumulation in ox-LDL-treated macrophages, promoted M2 phenotype macrophage polarization, increased the number of autophagosomes and modulated the expression of autophagy-related proteins. Moreover, the autophagy inhibitor 3-methyladenine and BECN1 siRNA obviously abolished the antiatherosclerotic and M2 macrophage polarization effects of AsC. Mechanistically, AsC targeted Sirt1and increased its expression, and this increase in expression was associated with increased autophagy and M2 phenotype polarization. In contrast, the effects of AsC were markedly blocked by EX527 and Sirt1 siRNA. Altogether, AsC attenuates foam cell formation and lessens atherosclerosis by modulating macrophage polarization via Sirt1-mediated autophagy.