Resveratrol as a new inhibitor of immunoproteasome prevents PTEN degradation and attenuates cardiac hypertrophy after pressure overload

Nrf2 deficiency aggravates PM2.5-induced cardiomyopathy by enhancing oxidative stress, fibrosis and inflammation via RIPK3-regulated mitochondrial disorder

PM_2.5 is a well-known air pollutant threatening public health, and long-term exposure to PM_2.5 increases the risk of cardiovascular diseases. Nrf2 plays a pivotal role in the amelioration of PM_2.5-induced lung injury. However, if Nrf2 is involved in PM_2.5-induced heart injury, and the underlying molecular mechanisms have not been explored. In this study, wild type (Nrf2^+/+) and Nrf2 knockout (Nrf2^-/-) mice were exposed to PM_2.5 for 6 months. After PM_2.5 exposure, Nrf2^-/- mice developed severe physiological changes, lung injury and cardiac dysfunction. In the PM_2.5-exposed hearts, Nrf2 deficiency caused significant collagen accumulation through promoting the expression of fibrosis-associated signals. Additionally, Nrf2^-/- mice exhibited greater oxidative stress in cardiac tissues after PM_2.5 exposure. Furthermore, PM_2.5-induced inflammation in heart samples were accelerated in Nrf2^-/- mice through promoting inhibitor of α/nuclear factor κB (IκBα/NF-κB) signaling pathways. We also found that Nrf2^-/- aggravated autophagy initiation and glucose metabolism disorder in hearts of mice with PM_2.5 challenge. Cardiac receptor-interacting protein kinase 3 (RIPK3) expression triggered by PM_2.5 was further enhanced in mice with the loss of Nrf2. Collectively, these results suggested that strategies for enhancing Nrf2 could be used to treat PM_2.5-induced cardiovascular diseases.

Pharmacological basis and new insights of resveratrol action in the cardiovascular system

Resveratrol (trans-3,4',5-trihydroxystilbene) belongs to the family of natural phytoalexins. Resveratrol first came to our attention in 1992, following reports of the cardioprotective effects of red wine. Thereafter, resveratrol was shown to exert antioxidant, anti-inflammatory, anti-proliferative, and angio-regulatory effects against atherosclerosis, ischaemia, and cardiomyopathy. This article critically reviews the current findings on the molecular basis of resveratrol-mediated cardiovascular benefits, summarizing the broad effects of resveratrol on longevity regulation, energy metabolism, stress resistance, exercise mimetics, circadian clock, and microbiota composition. In addition, this article also provides an update, both preclinically and clinically, on resveratrol-induced cardiovascular protection and discusses the adverse and inconsistent effects of resveratrol reported in both preclinical and clinical studies. Although resveratrol has been claimed as a master anti-aging agent against several age-associated diseases, further detailed mechanistic investigation is still required to thoroughly unravel the therapeutic value of resveratrol against cardiovascular diseases at different stages of disease development. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.

BRD4 blockage alleviates pathological cardiac hypertrophy through the suppression of fibrosis and inflammation via reducing ROS generation

Hypertension is an essential regulator of cardiac injury and remodeling. However, the pathogenesis that contributes to cardiac hypertrophy remains to be fully explored. BRD4, as a bromodomain and extra-terminal (BET) family member, plays an important role in critical biological processes. In the study, our results showed that BRD4 expression was up-regulated in human and mouse hypertrophied hearts, and importantly these effects were modulated by reactive oxygen species (ROS) generation. In angiotensin II (Ang II)-treated cardiomyocytes, BRD4 decrease markedly blunted the prohypertrophic effect, which was further promoted by the combinational treatment of ROS scavenger (N-acetyl-cysteine, NAC). In addition, NAC pre-treatment markedly elevated the anti-fibrotic role of BRD4 suppression in Ang II-incubated cardiomyocytes by repressing transforming growth factor β1 (TGF-β1)/SMADs signaling pathway. NAC combined with BRD4 reduction further alleviated inflammation and oxidative stress in Ang II-exposed cardiomyocytes, which was partly through inhibiting nuclear factor-κB (NF-κB) signaling and improving nuclear erythroid factor 2-related factor 2 (Nrf-2)/heme oxygenase-1 (HO-1) pathway, respectively. Furthermore, the in vivo results confirmed the protective effects of BRD4 suppression on mice against aortic banding (AB)-induced cardiac hypertrophy, as evidenced by the reduced cross sectional area and fibrotic area using H&E and Masson trichrome staining. What's more, the degree of cardiac hypertrophy (ANP and BNP), the expression of pro-fibrotic genes (TGF-β1, Collagen I, Collagen III and CTGF), the levels of inflammation and oxidative stress were all significantly attenuated by the blockage of BRD4 in AB-operated mice. Taken together, repressing BRD4 expression was found to confer a protective effect against experimental cardiac hypertrophy in mice, demonstrating its potential as an effective therapeutic target for pathological cardiac hypertrophy.

Oral flavonoid fisetin treatment protects against prolonged high-fat-diet-induced cardiac dysfunction by regulation of multicombined signaling

Excess high-fat diet (HFD) intake predisposes the occurrence of obesity-associated heart injury, but the mechanism is elusive. Fisetin (FIS), as a natural flavonoid, has potential activities to alleviate obesity-induced metabolic syndrome. However, the underlying molecular mechanisms of FIS against HFD-induced cardiac injury remain unclear. The present study was to explore the protective effects of FIS on cardiac dysfunction in HFD-fed mice. We found that FIS alleviated HFD-triggered metabolic disorder by reducing body weight, fasting blood glucose and insulin levels, and insulin resistance. Moreover, FIS supplements significantly alleviated dyslipidemia in both mouse hearts and cardiomyocytes stimulated by metabolic stress. FIS treatment abolished HFD-induced inflammatory response in heart tissues through suppressing TNF receptor-1/TNF receptor-associated factor-2 (Tnfr-1/Traf-2) signaling. Furthermore, FIS induced a strong reduction in the expression of fibrosis-related genes, contributing to the inhibition of fibrosis by inactivating transforming growth factor (Tgf)-β1/Smads/Erk1/2 signaling. Collectively, these results demonstrated that FIS could be a promising therapeutic strategy for the treatment of obesity-associated cardiac injury.

Genetic ablation and pharmacological inhibition of immunosubunit β5i attenuates cardiac remodeling in deoxycorticosterone-acetate (DOCA)-salt hypertensive mice

Hypertensive cardiac remodeling is a major cause of heart failure. The immunoproteasome is an inducible form of the proteasome and its catalytic subunit β5i (also named LMP7) is involved in angiotensin II-induced atrial fibrillation; however, its role in deoxycorticosterone-acetate (DOCA)-salt-induced cardiac remodeling remains unclear. C57BL/6 J wild-type (WT) and β5i knockout (β5i KO) mice were subjected to uninephrectomy (sham) and DOCA-salt treatment for three weeks. Cardiac function, fibrosis, and inflammation were evaluated by echocardiography and histological analysis. Protein and gene expression levels were analyzed by quantitative real-time PCR and immunoblotting. Our results showed that after 21 days of DOCA-salt treatment, β5i expression and chymotrypsin-like activity were the most significantly increased factors in the heart compared with the sham control. Moreover, DOCA-salt-induced elevation of blood pressure, adverse cardiac function, chamber and myocyte hypertrophy, interstitial fibrosis, oxidative stress, and inflammation were markedly attenuated in β5i KO mice. These findings were verified in β5i inhibitor PR-957-treated mice. Moreover, blocking of PTEN (the gene of phosphate and tensin homolog deleted on chromosome ten) markedly attenuated the inhibitory effect of β5i knockout on DOCA-salt-induced cardiac remodeling. Mechanistically, DOCA-salt stress upregulated the expression of β5i, which promoted the degradation of PTEN and the activation of downstream signals (AKT/mTOR, TGF-β1/Smad2/3, NOX, and NF-κB), which ultimately led to cardiac hypertrophic remodeling. This study provides new evidence of the critical role of β5i in DOCA-salt-induced cardiac remodeling through the regulation of PTEN stability, and indicates that the inhibition of β5i may be a promising therapeutic target for the treatment of hypertensive heart diseases.

Effects of Adiponectin on Diastolic Function in Mice Underwent Transverse Aorta Constriction

Diastolic dysfunction is common in various cardiovascular diseases, which could be affected by adiponectin (APN). Nevertheless, the effects of APN on diastolic dysfunction in pressure overload model induced by transverse aorta constriction (TAC) remain to be further elucidated. Here, we demonstrated that treatment of APN attenuated diastolic dysfunction and cardiac hypertrophy in TAC mice. Notably, APN also improved active relaxation of adult cardiomyocytes, increased N2BA/N2B ratios of titin isoform, and reduced collagen type I to type III ratio and lysyl oxidase (Lox) expressions in the myocardial tissue. Moreover, APN supplementation suppressed TAC-induced oxidative stress. In vitro, inhibition of AMPK by compound C (Cpc) abrogated the effect of APN on modulation of titin isoform shift and the anti-hypertrophic effect of APN on cardiomyocytes induced by AngII. In summary, our findings indicate that APN could attenuate diastolic dysfunction in TAC mice, which are at least partially mediated by AMPK pathway.

miR-29a promotes pathological cardiac hypertrophy by targeting the PTEN/AKT/mTOR signalling pathway and suppressing autophagy

AIM

Although miR-29 has emerged as a crucial non-coding RNA in the regulation of pathological cardiac hypertrophy, further exploration of its specific mechanisms is necessary to resolve controversy about its major role in this condition. This study therefore evaluated the role of miR-29a and whether it acts through the PTEN/AKT/mTOR pathway.

METHODS

In this study, a rat model of pressure-induced cardiac hypertrophy was established by transverse aortic constriction and verified by echocardiography, histological analysis and quantitative RT-PCR. At the cellular level, we explored the role of miR-29a in angiotensin II-stimulated hypertrophic H9c2 cardiomyoblasts by transfecting the cells with miR-29a inhibitor and mimic. The relationship between miR-29a and the signalling pathway was investigated with dual luciferase reporter assays, immunofluorescence analysis and Western blotting. We also examined whether autophagy is involved in the regulatory mechanism of miR-29a through transmission electron microscopy and detection of autophagy-associated proteins.

RESULTS

The results showed that miR-29a was upregulated both in rats 4 weeks after surgery and in 10^-6  M angiotensin II-stimulated cells. In contrast, inhibition of miR-29a partially attenuated angiotensin II-induced hypertrophy. Additionally, bioinformatics analysis revealed that PTEN was one of the target genes of miR-29a, which was also verified by luciferase assay. The results of immunofluorescence and Western blotting indicated that overexpression of miR-29a inhibited the expression of PTEN, activated the AKT/mTOR pathway and suppressed autophagy, which ultimately led to cardiac hypertrophy.

CONCLUSION

In pathological cardiac hypertrophy, miR-29a was overexpressed and promoted cardiac hypertrophy by regulating the PTEN/AKT/mTOR pathway and suppressing autophagy.

Endoplasmic reticulum stress-induced iRhom2 up-regulation promotes macrophage-regulated cardiac inflammation and lipid deposition in high fat diet (HFD)-challenged mice: Intervention of fisetin and metformin

Endoplasmic reticulum stress (ERS) has been implicated in obesity-associated cardiac remodeling and dysfunction. Inactive rhomboid protein 2 (iRhom2), also known as Rhbdf2, is an inactive member of the rhomboid intramembrane proteinase family, playing an essential role in regulating inflammation. Nevertheless, the role of ERS-meditated iRhom2 pathway in metabolic stress-induced cardiomyopathy remains unknown. In the study, we showed that 4-PBA, as an essential ERS inhibitor, significantly alleviated high fat diet (HFD)-induced metabolic disorder and cardiac dysfunction in mice. Additionally, lipid deposition in heart tissues was prevented by 4-PBA in HFD-challenged mice. Moreover, 4-PBA blunted the expression of iRhom2, TACE, TNFR2 and phosphorylated NF-κB to prevent HFD-induced expression of inflammatory factors. Further, 4-PBA restrained HFD-triggered oxidative stress by promoting Nrf-2 signaling. Importantly, 4-PBA markedly suppressed cardiac ERS in HFD mice. The anti-inflammation, anti-ERS and anti-oxidant effects of 4-PBA were verified in palmitate (PAL)-incubated macrophages and cardiomyocytes. In addition, promoting ERS could obviously enhance iRhom2 signaling in vitro. Intriguingly, our data demonstrated that PAL-induced iRhom2 up-regulation apparently promoted macrophage to generate inflammatory factors that could promote cardiomyocyte inflammation and lipid accumulation. Finally, interventions by adding fisetin or metformin significantly abrogated metabolic stress-induced cardiomyopathy through the mechanisms mentioned above. In conclusion, this study provided a novel mechanism for metabolic stress-induced cardiomyopathy pathogenesis. Therapeutic strategy to restrain ROS/ERS/iRhom2 signaling pathway could be developed to prevent myocardial inflammation and lipid deposition, consequently alleviating obesity-induced cardiomyopathy.

Ubiquitin proteasome system (UPS) activation in the cardiac hypertrophy of hyperthyroidism

Ubiquitin proteasome system (UPS) is the main proteolytic pathway in eukaryotic cells. Changes in proteasome expression and activity have been associated to cardiovascular diseases as cardiac hypertrophy. Considering that cardiac hypertrophy is commonly associated to hyperthyroidism condition, the present study aimed to investigate the contribution of UPS in cardiac hypertrophy induced by thyroid hormones. Hyperthyroidism was induced in male Wistar rats by intraperitoneal injections of triiodothyronine (T3; 7  μg/100 g of body weight) for 7 days and confirmed by raised levels of total T3 and decreased levels of total T4. In addition, systolic blood pressure and heart rate were significantly increased in hyperthyroid group. Cardiac hypertrophy was confirmed in hyperthyroid group by increased heart weight/tibia length ratio and by increased α-MHC/β-MHC relative expression. Both catalytic (20SPT) and regulatory subunits (19SPT) of the constitutive proteasome were upregulated in hyperthyroid hearts. In addition, the transcripts that encode immunoproteasome subunits were also elevated. Furthermore, ATP-dependent chymotrypsin-like activity (26SPT) was significantly increased in hyperthyroid group. Despite the upregulation and activation of UPS in hyperthyroid hearts, the content of polyubiquitinated proteins was unaltered in relation to control. Together, these results evidence the activation of cardiac proteasome by thyroid hormones, which possibly contribute to the maintenance of protein quality control and regulation of cardiac hypertrophy in response to thyroid hormones.

Cell Clearing Systems Bridging Neuro-Immunity and Synaptic Plasticity

In recent years, functional interconnections emerged between synaptic transmission, inflammatory/immune mediators, and central nervous system (CNS) (patho)-physiology. Such interconnections rose up to a level that involves synaptic plasticity, both concerning its molecular mechanisms and the clinical outcomes related to its behavioral abnormalities. Within this context, synaptic plasticity, apart from being modulated by classic CNS molecules, is strongly affected by the immune system, and vice versa. This is not surprising, given the common molecular pathways that operate at the cross-road between the CNS and immune system. When searching for a common pathway bridging neuro-immune and synaptic dysregulations, the two major cell-clearing cell clearing systems, namely the ubiquitin proteasome system (UPS) and autophagy, take center stage. In fact, just like is happening for the turnover of key proteins involved in neurotransmitter release, antigen processing within both peripheral and CNS-resident antigen presenting cells is carried out by UPS and autophagy. Recent evidence unravelling the functional cross-talk between the cell-clearing pathways challenged the traditional concept of autophagy and UPS as independent systems. In fact, autophagy and UPS are simultaneously affected in a variety of CNS disorders where synaptic and inflammatory/immune alterations concur. In this review, we discuss the role of autophagy and UPS in bridging synaptic plasticity with neuro-immunity, while posing a special emphasis on their interactions, which may be key to defining the role of immunity in synaptic plasticity in health and disease.