Irisin attenuates angiotensin II-induced cardiac fibrosis via Nrf2 mediated inhibition of ROS/ TGFβ1/Smad2/3 signaling axis

Assessment of ursolic acid effect on in vitro model of cardiac fibrosis

This study aimed to evaluate the effects of ursolic acid (UA) on Angiotensin II (Ang II)-treated neonatal rat cardiac fibroblasts (rCFs) as an in vitro model of cardiac fibrosis. The rCFs were isolated from two-day-old neonatal rats. An in vitro model of cardiac fibrosis was established using 500 nm Ang II treatment for 48 h. The cells were then treated with 5 and 10 μM of UA for 24 and 48 h. Masson's trichrome staining, hydroxyproline content assay, scratch assay, apoptosis assay, measurements of superoxide dismutase (SOD) and malondialdehyde (MDA) levels, real-time PCR, immunocytology and western blotting, were employed to assess the impact of UA. Ang II induced fibrosis in rCFs, as evidenced by the examination of various fibrotic markers. Upon treatment with 5 and 10 μM of UA, the amount of fibrosis in Ang II-treated rCFs was significantly decreased, so that the hydroxyproline concentration was reduced to 0.3 and 0.7 times, respectively. The RNA expression of the Col1a1, Col3a1, Tgfb1, Acta2 and Mmp2 genes had a decrease as well as Nrf2 and HO-1 had an increase after UA treatment. UA could lessen the harmful effects of cardiac fibrosis in a dose- and time-dependent manner, due to its antiapoptotic, antioxidant and cardioprotective properties. This suggests the potential of UA for treatment of cardiac fibrosis.

Resistance exercise upregulates Irisin expression and suppresses myocardial fibrosis following myocardial infarction via activating AMPK-Sirt1 and inactivating TGFβ1-Smad2/3

AIM

To reveal the contribution of Irisin in the beneficial effects of resistance exercise on myocardial fibrosis (MF) and cardiac function in the mice with myocardial infarction (MI).

METHODS

The MI model was built by ligating the left anterior descending coronary artery in Fndc5 knockout mice (Fndc5-/-). Resistance exercise was started one week after surgery and continued for four weeks. In addition, H2O2, AICAR, recombinant human Irisin protein (rhIRISIN), and Sirt1 shRNA lentivirus (LV-Sirt1 shRNA) were used to intervene primary isolated cardiac fibroblasts (CFs). MF was observed through Masson staining, and apoptosis was assessed using TUNEL staining. MDA and T-SOD contents were detected by biochemical kits. The expression of proteins and genes was detected by Western blotting and RT-qPCR.

RESULTS

Resistance exercise increased Fndc5 mRNA level, inhibited the activation of TGFβ1-TGFβR2-Smad2/3 pathway, activated AMPK-Sirt1 pathway, reduced the levels of oxidative stress, apoptosis, and MF in the infarcted heart, and promoted cardiac function. However, Fndc5 knockout attenuated the protective effects of resistance exercise on the MI heart. Results of the in vitro experiments showed that AICAR and rhIRISIN intervention activated the AMPK-Sirt1 pathway and inactivated the TGFβ1-Smad2/3 pathway, and promoted apoptosis in H2O2-treated CFs. Notably, these effects of rhIRISIN intervention, except for the TGFβR2 expression, were attenuated by LV-Sirt1 shRNA.

CONCLUSION

Resistance exercise upregulates Fndc5 expression, activates AMPK-Sirt1 pathway, inhibits the activation of TGFβ1-Smad2/3 pathway, attenuates MF, and promotes cardiac function after MI.

Pyruvate Kinase M2: A Potential Regulator of Cardiac Injury Through Glycolytic and Non-glycolytic Pathways

ABSTRACT

Adult animals are unable to regenerate heart cells due to postnatal cardiomyocyte cycle arrest, leading to higher mortality rates in cardiomyopathy. However, reprogramming of energy metabolism in cardiomyocytes provides a new perspective on the contribution of glycolysis to repair, regeneration, and fibrosis after cardiac injury. Pyruvate kinase (PK) is a key enzyme in the glycolysis process. This review focuses on the glycolysis function of PKM2, although PKM1 and PKM2 both play significant roles in the process after cardiac injury. PKM2 exists in both low-activity dimer and high-activity tetramer forms. PKM2 dimers promote aerobic glycolysis but have low catalytic activity, leading to the accumulation of glycolytic intermediates. These intermediates enter the pentose phosphate pathway to promote cardiomyocyte proliferation and heart regeneration. Additionally, they activate adenosine triphosphate (ATP)-sensitive K + (K ATP ) channels, protecting the heart against ischemic damage. PKM2 tetramers function similar to PKM1 in glycolysis, promoting pyruvate oxidation and subsequently ATP generation to protect the heart from ischemic damage. They also activate KDM5 through the accumulation of αKG, thereby promoting cardiomyocyte proliferation and cardiac regeneration. Apart from glycolysis, PKM2 interacts with transcription factors like Jmjd4, RAC1, β-catenin, and hypoxia-inducible factor (HIF)-1α, playing various roles in homeostasis maintenance, remodeling, survival regulation, and neovascularization promotion. However, PKM2 has also been implicated in promoting cardiac fibrosis through mechanisms like sirtuin (SIRT) 3 deletion, TG2 expression enhancement, and activation of transforming growth factor-β1 (TGF-β1)/Smad2/3 and Jak2/Stat3 signals. Overall, PKM2 shows promising potential as a therapeutic target for promoting cardiomyocyte proliferation and cardiac regeneration and addressing cardiac fibrosis after injury.

Irisin ameliorates UUO-induced renal interstitial fibrosis through TGF-β1/periostin/MMP-2 signaling pathway

Renal fibrosis is the most common pathway in progressive kidney diseases. The unilateral ureteral obstruction (UUO) model is used to induce progressive renal fibrosis. We evaluated the effects of irisin on renal interstitial fibrosis in UUO mice. The GSE121190, GSE36496, GSE42303, and GSE96101 datasets were downloaded from the Gene Expression Omnibus (GEO) database. In total, 656 differentially expressed genes (DEGs) were identified in normal and UUO mouse renal samples. Periostin and matrix metalloproteinase-2 (MMP-2) were selected to evaluate the effect of irisin on renal fibrosis in UUO mice. In UUO mice, irisin ameliorated renal function, decreased the expression of periostin and MMP-2, and attenuated epithelial-mesenchymal transition and extracellular matrix deposition in renal tissues. In HK-2 cells, irisin treatment markedly attenuated TGF-β1-induced expression of periostin and MMP-2. Irisin treatment also inhibited TGF-β1-induced epithelial-mesenchymal transition, extracellular matrix formation, and inflammatory responses. These protective effects of irisin were abolished by the overexpression of periostin and MMP-2. In summary, irisin treatment can improve UUO-induced renal interstitial fibrosis through the TGF-β1/periostin/MMP-2 signaling pathway, suggesting that irisin may be used for the treatment of renal interstitial fibrosis.

Potential role of irisin in lung diseases and advances in research

Irisin, a myokine, is secreted by the movement of skeletal muscles. It plays an important role in metabolic homeostasis, insulin resistance, anti-inflammation, oxidative stress, and bone metabolism. Several studies have reported that irisin-related signaling pathways play a critical role in the treatment of various diseases, including obesity, cardiovascular disease, diabetes, and neurodegenerative disorders. Recently, the potential role of irisin in lung diseases, including chronic obstructive pulmonary disease, acute lung injury, lung cancer, and their associated complications, has received increasing attention. This article aims to explore the role of irisin in lung diseases, primarily focusing on the underlying molecular mechanisms, which may serve as a marker for the diagnosis as well as a potential target for the treatment of lung diseases, thus providing new strategies for their treatment.

Irisin: A Potentially Fresh Insight into the Molecular Mechanisms Underlying Vascular Aging

Aging is a natural process that affects all living organisms, including humans. Aging is a complex process that involves the gradual deterioration of various biological processes and systems, including the cardiovascular system. Vascular aging refers to age-related changes in blood vessels. These changes can increase the risk of developing cardiovascular diseases, such as hypertension, atherosclerosis, and stroke. Recently, an exercise-induced muscle factor, irisin, was found to directly improve metabolism and regulate the balance of glucolipid metabolism, thereby counteracting obesity and insulin resistance. Based on a growing body of evidence, irisin modulates vascular aging. Adenosine monophosphate-activated protein kinase (AMPK) serves as a pivotal cellular energy sensor and metabolic modulator, acting as a central signaling cascade to coordinate various cellular processes necessary for maintaining vascular homeostasis. The vascular regulatory effects of irisin are closely intertwined with its interaction with the AMPK pathway. In conclusion, understanding the molecular processes used by irisin to regulate changes in vascular diseases caused by aging may inspire the development of techniques that promote healthy vascular aging. This review sought to describe the impact of irisin on the molecular mechanisms of vascular aging, including inflammation, oxidative stress, and epigenetics, from the perspective of endothelial cell function and vascular macroregulation, and summarize the multiple signaling pathways used by irisin to regulate vascular aging.

Exercise-induced irisin improves follicular dysfunction by inhibiting IRE1α-TXNIP/ROS-NLRP3 pathway in PCOS

BACKGROUND

Excessive production of androgen drives oxidative stress (OS) and inflammasome activation in ovarian granulosa cells (GCs). Therefore, the induced follicular developmental disorder is the major cause of infertility in women with polycystic ovary syndrome (PCOS). Exercise-induced upregulation of irisin is capable of regulating metabolism by reducing OS and inflammation. Exercise has been shown to alleviate a range of PCOS symptoms, including maintaining a normal menstrual cycle, in several clinical trials.

METHODS

Female Sprague-Dawley (SD) rats and primary ovarian cells were treated with two different androgens, dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT), to simulate a hyperandrogenic environment, followed by eight weeks of exercise training and irisin intervention. The levels of reactive oxygen species (ROS), tissue inflammation and fibrosis were examined using hematoxylin and eosin (H&E) staining, western blot, quantitative real-time PCR (qRT-PCR), dichlorofluorescein diacetate (DCF-DA) probe detection, immunofluorescence staining, immunohistochemistry, and Sirius red staining.

RESULTS

Exercise for eight weeks improved polycystic ovarian morphology and decreased the levels of inflammation, OS, and fibrosis in PCOS rats. Hyperandrogen increased ROS production in ovarian cells by inducing endoplasmic reticulum stress (ERS) and activating the inositol-requiring enzyme 1α (IRE1α)-thioredoxin-interacting protein (TXNIP)/ROS-NOD-like receptor family pyrin domain containing 3 (NLRP3) signaling pathway, further enhancing the levels of inflammation. Irisin suppressed the expression of IRE1α and its downstream targets, thus improving the ovarian dysfunction of PCOS rats induced by hyperandrogen.

CONCLUSION

Exercise can alleviate various phenotypes of PCOS rats induced by DHEA, and its therapeutic effect may be mediated by secreting beneficial myokines. IRE1α may be an important target of irisin for reducing OS and inflammation, thereby improving ovarian fibrosis.

Irisin inhibits neutrophil extracellular traps formation and protects against acute pancreatitis in mice

INTRODUCTION

Irisin is a newly discovered myokine which links exercise to inflammation and inflammation-related diseases through macrophage regulation. However, the effect of irisin on the activity of inflammation related immune cells (such as neutrophils) has not been clearly described.

OBJECTIVES

The objective of our study was to explore the effect of irisin on the neutrophil extracellular traps (NETs) formation.

METHODS

Phorbol-12-myristate-13-acetate (PMA) was used to construct a classic neutrophil inflammation model that was used to observe the formation of NETs in vitro. We studied the effect of irisin on NETs formation and its regulation mechanism. Subsequently, acute pancreatitis (AP) was used to verify the protective effect of irisin in vivo, which was an acute aseptic inflammatory response disease model closely related to NETs.

RESULTS

Our study found that addition of irisin significantly reduced the formation of NETs via regulation of the P38/MAPK pathway through integrin αVβ5, which might be the one of key pathways in NETs formation, and which could theoretically offset the immunoregulatory effect of irisin. Systemic treatment with irisin reduced the severity of tissue damage common in the disease and inhibited the formation of NETs in pancreatic necrotic tissue of two classical AP mouse models.

CONCLUSION

The findings confirmed for the first time that irisin could inhibit NETs formation and protect mice from pancreatic injury, which further elucidated the protective effect of exercise on acute inflammatory injury.

Effect of renal denervation on cardiac remodelling and function in rats with chronic intermittent hypoxia

Chronic intermittent hypoxia (CIH) mimicking obstructive sleep apnea elicits divergent outcomes in the cardiovascular systems. The effect of renal denervation (RDN) on the heart during CIH remains unclear. We aimed to explore the effect of RDN on cardiac remodelling in rats exposed to CIH and to discuss the underlying mechanisms. Adult Sprague Dawley rats were divided into four groups: control, control+RDN, CIH (CIH exposure for 6 weeks, nadir of 5%-7% to peak of 21% O2, 20 cycles/h, 8 h/day) and CIH+ RDN group. Echocardiography, cardiac fibrosis, left ventricle (LV) expressions of nuclear factor-E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway and inflammatory factors were tested at the end of the study. Cardiac structural remodelling and dysfunction were induced by CIH and attenuated by RDN. Myocardial fibrosis was more severe in the CIH group than in the control group and improved in the CIH + RDN group. Sympathetic activity reflected by tyrosine hydroxylase (TH) expression and noradrenaline were significantly elevated after CIH but blunted by RDN. CIH downregulated LV protein expressions of Nrf2 and HO-1, which was activated by RDN. The downstream of Nrf2/HO-1, such as NQO1 and SOD expression, elevated following RDN. RDN also decreased the mRNA expression of IL-1β and IL-6. Notably, control+RDN did not affect cardiac remodelling and Nrf2/HO-1 compared with the control. Taken together, we found that RDN exerted cardio-protective effects in a rat model of CIH involving Nrf2/HO-1 pathway and inflammation.

LncRNA MHRT Prevents Angiotensin II-Induced Myocardial Oxidative Stress and NLRP3 Inflammasome via Nrf2 Activation

The development of angiotensin II (Ang II)-induced cardiomyopathies is reportedly mediated via oxidative stress and inflammation. Nuclear factor erythroid 2-related factor (Nrf2) is an important regulator of cellular antioxidant defense, and reactive oxygen species (ROS) can activate the NLRP3 inflammasome. MHRT is a newly discovered lncRNA exhibiting cardioprotective effects, demonstrated by inhibiting myocardial hypertrophy via Brg1 and myocardial apoptosis via Nrf2 upregulation. However, the underlying mechanism of MHRT remains unclear. We explored the potential protective effects of MHRT against Ang II-induced myocardial oxidative stress and NLRP3-mediated inflammation by targeting Nrf2. Chronic Ang II administration induced NLRP3 inflammasome activation (increased NLRP3, caspase-1 and interleukin-1β expression), oxidative stress (increased 3-nitrotyrosine and 4-hydroxy-2-nonenal), cardiac dysfunction and decreased MHRT and Nrf2 expression. Lentivirus-mediated MHRT overexpression inhibited Ang II (100 nM)-induced oxidative stress and NLRP3 inflammasome activation in AC16 human cardiomyocyte cells. Mechanistically, MHRT overexpression upregulated the expression and function of Nrf2, as determined by the increased transcription of downstream genes HO-1 and CAT, subsequently decreasing intracellular ROS accumulation and inhibiting the expression of thioredoxin-interacting protein (NLRP3 activator) and its direct binding to NLRP3. Accordingly, MHRT could protect against Ang II-induced myocardial injury by decreasing oxidative stress and NLRP3 inflammasome activation via Nrf2 activation.

FNDC5/Irisin Inhibits the Inflammatory Response and Mediates the Aerobic Exercise-Induced Improvement of Liver Injury after Myocardial Infarction

Myocardial infarction (MI) causes peripheral organ injury, in addition to cardiac dysfunction, including in the liver, which is known as cardiac hepatopathy. Aerobic exercise (AE) can effectively improve liver injury, although the mechanism and targets are currently not well established. Irisin, mainly produced by cleavage of the fibronectin type III domain-containing protein 5 (FNDC5), is a responsible for the beneficial effects of exercise training. In this study, we detected the effect of AE on MI-induced liver injury and explored the role of irisin alongside the benefits of AE. Wildtype and Fndc5 knockout mice were used to establish an MI model and subjected to AE intervention. Primary mouse hepatocytes were treated with lipopolysaccharide (LPS), rhirisin, and a phosphoinositide 3-kinase (PI3K) inhibitor. The results showed that AE significantly promoted M2 polarization of macrophages and improved MI-induced inflammation, upregulated endogenous irisin protein expression and activated the PI3K/ protein kinase B (Akt) signaling pathway in the liver of MI mice, while knockout of Fndc5 attenuated the beneficial effects of AE. Exogenous rhirisin significantly inhibited the LPS-induced inflammatory response, which was attenuated by the PI3K inhibitor. These results suggest that AE could effectively activate the FNDC5/irisin-PI3K/Akt signaling pathway, promote the polarization of M2 macrophages, and inhibit the inflammatory response of the liver after MI.

Fibrosis: Types, Effects, Markers, Mechanisms for Disease Progression, and Its Relation with Oxidative Stress, Immunity, and Inflammation

Most chronic inflammatory illnesses include fibrosis as a pathogenic characteristic. Extracellular matrix (ECM) components build up in excess to cause fibrosis or scarring. The fibrotic process finally results in organ malfunction and death if it is severely progressive. Fibrosis affects nearly all tissues of the body. The fibrosis process is associated with chronic inflammation, metabolic homeostasis, and transforming growth factor-β1 (TGF-β1) signaling, where the balance between the oxidant and antioxidant systems appears to be a key modulator in managing these processes. Virtually every organ system, including the lungs, heart, kidney, and liver, can be affected by fibrosis, which is characterized as an excessive accumulation of connective tissue components. Organ malfunction is frequently caused by fibrotic tissue remodeling, which is also frequently linked to high morbidity and mortality. Up to 45% of all fatalities in the industrialized world are caused by fibrosis, which can damage any organ. Long believed to be persistently progressing and irreversible, fibrosis has now been revealed to be a very dynamic process by preclinical models and clinical studies in a variety of organ systems. The pathways from tissue damage to inflammation, fibrosis, and/or malfunction are the main topics of this review. Furthermore, the fibrosis of different organs with their effects was discussed. Finally, we highlight many of the principal mechanisms of fibrosis. These pathways could be considered as promising targets for the development of potential therapies for a variety of important human diseases.

Signaling Pathways and Potential Therapeutic Strategies in Cardiac Fibrosis

Cardiac fibrosis constitutes irreversible necrosis of the heart muscle as a consequence of different acute (myocardial infarction) or chronic (diabetes, hypertension, …) diseases but also due to genetic alterations or aging. Currently, there is no curative treatment that is able to prevent or attenuate this phenomenon that leads to progressive cardiac dysfunction and life-threatening outcomes. This review summarizes the different targets identified and the new strategies proposed to fight cardiac fibrosis. Future directions, including the use of exosomes or nanoparticles, will also be discussed.

Irisin ameliorates D-galactose-induced skeletal muscle fibrosis via the PI3K/Akt pathway

Primary sarcopenia is a multicausal skeletal muscle disease associated with muscle strength and mass loss. Skeletal muscle fibrosis is one of the significant pathological manifestations associated with the development of age-related sarcopenia. Irisin, which is cleaved by the extracellular domain of fibronectin type Ⅲ domain-containing protein 5 (FNDC5), has previously been reported to exert antifibrotic effects on the heart, liver, and pancreas, but whether it can rescue skeletal muscle fibrosis remains unknown. In this study, we examined the effects of irisin on D-galactose (D-gal)-induced skeletal muscle fibroblasts. We found that D-gal-induced senescence, fibrosis, and redox imbalance were inhibited by irisin treatment. Mechanistically, irisin or FNDC5 overexpression attenuated D-gal-induced senescence, redox imbalance, and fibrosis by regulating the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway. Overall, irisin might be a promising therapeutic candidate for age-related skeletal muscle fibrosis.

Leisure-time regular exercise and prevention of the side effects of immune system activity in middle-aged healthy subjects

Regular exercise is recommended to improve immune system function and antioxidant activity, while conversely, it may cause inflammation by increasing neutrophil-derived main enzyme, myeloperoxidase, which produces reactive oxygen species. The present study aimed to investigate changes in myeloperoxidase level, its influence on total oxidant status, and the capacity of the antioxidant defence system to counteract oxidative stress in middle-aged men participating in leisure-time regular exercise compared to untrained peer subjects. Twenty trained (age 53.58±2.94 years, body mass index (BMI) 25.47±1.6) and 17 untrained (age 54.17±2.83 years, BMI 27.83±1.12) healthy middle-aged men participated in this study [Rasht, Gilan, Iran]. Participants performed a modified Bruce treadmill test as a model of progressive exercise training. Blood samples were taken before, immediately after, and one hour after the end of the test. A mixed ANOVA and Bonferroni post hoc test was used for the analysis of variables. A significant difference was observed in myeloperoxidase levels between groups, while the trained group showed a significantly lower concentration than the untrained group (P<0.018). This result was also consistent with the lower total oxidant status in this group (P<0.001). Total antioxidant capacity changed significantly in both groups with higher concentration in the trained group (P<0.001). The leisure-time regular exercise can reduce myeloperoxidase concentration and total oxidant status in healthy middle-aged men while increasing the total antioxidant capacity, which may potentially protect them from the side effects of immune system activity induced by exercise training.

Polystyrene nanoplastics exacerbate lipopolysaccharide-induced myocardial fibrosis and autophagy in mice via ROS/TGF-β1/Smad

Polystyrene nanoplastics (PS NPs) contamination is a serious problem for human and animal health. Excessive exposure to PS NPs can affect the structure and function of the heart. And lipopolysaccharide (LPS) induces myocardial damage, leading to myocardial fibrosis (MF). To investigate whether PS NPs exacerbate LPS-induced myocardial autophagy and fibrosis, we established in vivo and in vitro models of PS NPs/LPS exposure alone and in combination. We found that PS NPs/LPS exposure disrupts myocardial structure, significantly increases reactive oxygen species (ROS), triggers oxidative stress, promotes TGF-β1/Smad pathway activation, and leads to elevated levels of fibrotic proteins and collagen. Meanwhile, activation of AMPK/mTOR/ULK1 signaling pathway induced autophagy onset, and combined exposure of PS NPs/LPS exacerbated MF and autophagy. H9C2 cells were used for in vitro experiments, and the experimental results showed that the addition of TGF-β receptor inhibitor LY2109761 to the exposed group not only inhibited the upregulation of fibrotic genes but also effectively reduced the expression of autophagic signals, indicating that combined exposure of PS NPs and LPS mediates and regulates cardiac autophagy through TGF-β1. The above results suggest that PS NPs exacerbate LPS-induced MF and autophagy in mice via ROS/TGF-β1/Smad. Our study provides some new evidence to clarify the potential mechanisms of PS NPs-induced cardiotoxicity.

Irisin, an Effective Treatment for Cardiovascular Diseases?

Irisin, as one of the myokines induced by exercise, has attracted much attention due to its important physiological functions such as white fat browning, the improvement in metabolism, and the alleviation of inflammation. Despite the positive role that irisin has been proven to play in the prevention and treatment of cardiovascular diseases, whether it can become a biomarker and potential target for predicting and treating cardiovascular diseases remains controversial, given the unreliability of its detection methods, the uncertainty of its receptors, and the species differences between animals and humans. This paper was intended to review the role of irisin in the diagnosis and treatment of cardiovascular diseases, the potential molecular mechanism, and the urgent problems to be solved in hopes of advancing our understanding of irisin as well as providing data for the development of new and promising intervention strategies by discussing the causes of contradictory results.

Novel Therapies for the Treatment of Cardiac Fibrosis Following Myocardial Infarction

Cardiac fibrosis is a common pathological consequence of most myocardial diseases. It is associated with the excessive accumulation of extracellular matrix proteins as well as fibroblast differentiation into myofibroblasts in the cardiac interstitium. This structural remodeling often results in myocardial dysfunctions such as arrhythmias and impaired systolic function in patients with heart conditions, ultimately leading to heart failure and death. An understanding of the precise mechanisms of cardiac fibrosis is still limited due to the numerous signaling pathways, cells, and mediators involved in the process. This review article will focus on the pathophysiological processes associated with the development of cardiac fibrosis. In addition, it will summarize the novel strategies for anti-fibrotic therapies such as epigenetic modifications, miRNAs, and CRISPR technologies as well as various medications in cellular and animal models.

Panaxatriol saponin ameliorates myocardial infarction-induced cardiac fibrosis by targeting Keap1/Nrf2 to regulate oxidative stress and inhibit cardiac-fibroblast activation and proliferation

Cardiac fibrosis is a common precursor of ventricular dysfunction and heart failure. We investigated the role of oxidative stress in myocardial fibrosis and the protective effect of panaxatriol saponin (PTS) against myocardial infarction (MI)-induced cardiac fibrosis and explored the underlying mechanisms. In vitro, cell viability was tested using a cell counting kit. The reactive oxygen species (ROS) levels including hydrogen peroxide (H₂O₂) and superoxide anion (O₂•^-) were determined. Antioxidant enzyme levels were determined by immunofluorescence and Western blotting. Enzyme-linked immunosorbent assays, echocardiography, histological analysis, immunofluorescence staining, and molecular analysis were performed. Nuclear factor erythroid 2-related factor 2 (Nrf2) activation was evaluated by molecular docking and immunoprecipitation. Finally, the mechanism by which PTS inhibits cardiac fibrosis was investigated using the Nrf2 activator ML334 and a small interfering RNA for Nrf2. Ang II-induced differentiation of cardiac fibroblasts was associated with oxidative stress, characterized by upregulation of α-smooth muscle actin, increased reactive oxygen species production, and inhibition of superoxide dismutase-1 and heme oxygenase expression. In addition, PTS improved cardiac function and ameliorated cardiac fibrosis in MI rats. It also reduced Ang II-induced fibroblast differentiation and proliferation, suppressed oxidative stress, and disrupted the Kelch-like ECH-associated protein 1 (Keap1)-Nrf2 interaction by directly blocking the Nrf2 binding site in Keap1. Overexpression of Nrf2 by ML334 enhanced the antifibrotic effect of PTS. However, genetic ablation of Nrf2 abrogated the antifibrotic effect of PTS in cardiac fibrosis. Taken together, our findings suggest that Nrf2 has promise as a target and PTS as a therapeutic agent for cardiac fibrosis.

Irisin Regulates Cardiac Responses to Exercise in Health and Diseases: a Narrative Review

Exercise has been recognized as an important non-pharmacological approach for the prevention, treatment, and rehabilitation of cardiovascular diseases, but the mechanisms of exercise in promoting cardiovascular health remain unclear. Exercise generates cardiac benefits via stimulating muscle to secret hundreds of myokines that directly enter circulation and target heart tissue. Therefore, inter-organ communication between skeletal muscle and heart may be one important regulating pattern, and such communication can occur through secretion of molecules, frequently known as myokines. Irisin, a newly identified myokine, is cleaved from fibronectin type III domain-containing protein 5 (FNDC5) and secreted by the stimulation of exercise. Recently, accumulating evidence focusing on the interaction between irisin and cardiac function has been reported. This review highlights the molecular signaling by which irisin regulates the benefits of exercise on cardiac function both in physiological and pathological process, and discusses the clinical potential of irisin in treating heart diseases. Exercise generates various cardiovascular benefits through stimulating skeletal muscle to secrete irisin. The exercise "hormone" irisin, both produced by exercise or recombinant form, exerts therapeutic effects in a group of cardiovascular disorders including heart failure, myocardial infarction, atherosclerosis and hypertension. However, the molecular mechanisms involved remain ambiguous.This review highlights the most up-to-date findings to bridge the gap between exercise, irisin and cardiovascular diseases, and discusses the potential clinical prospect of irisin.

The Effects of Irisin on the Interaction between Hepatic Stellate Cell and Macrophage in Liver Fibrosis

BACKGRUOUND

Hepatic stellate cells (HSCs) are the central players interacting with multiple cell types in liver fibrosis. The crosstalk between HSCs and macrophages has recently become clearer. Irisin, an exercise-responsive myokine, was known to have a potentially protective role in liver and renal fibrosis, especially in connection with stellate cells. This study investigated the effects of irisin on the interaction between HSCs and macrophages.

METHODS

Tamm-Horsfall protein-1 (THP-1) human monocytes were differentiated into macrophages, polarized into the inflammatory M1 phenotype with lipopolysaccharide. Lieming Xu-2 (LX-2) cells, human HSCs, were treated with conditioned media (CM) from M1 macrophages, with or without recombinant irisin. HSCs responses to CM from M1 macrophages were evaluated regarding activation, proliferation, wound healing, trans-well migration, contractility, and related signaling pathway.

RESULTS

CM from M1 macrophages significantly promoted HSC proliferation, wound healing, transwell migration, and contractility, but not activation of HSCs. Irisin co-treatment attenuated these responses of HSCs to CM. However, CM and irisin treatment did not induce any changes in HSC activation. Further, irisin co-treatment alleviated CM-induced increase of phopho-protein kinase B (pAKT), matrix metalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinases-1 (TIMP-1).

CONCLUSION

These findings suggested that irisin may play a protective role in the pathogenesis of liver fibrosis, especially when working in the crosstalk between HSCs and macrophages.

Association of irisin levels with cardiac magnetic resonance, inflammatory, and biochemical parameters in patients with chronic heart failure versus controls

BACKGROUND AND AIMS

Chronic heart failure (CHF) represents a significant cause of morbidity and mortality globally. Metabolic maladaptation has proven to be critical in the progression of this condition. Preclinical studies have shown that irisin, an adipomyokine involved in metabolic regulations, can induce positive cardioprotective effects by improving cardiac remodeling, cardiomyocyte viability, calcium delivery, and reducing inflammatory mediators. However, data on clinical studies identifying the associations between irisin levels and functional imaging parameters are scarce in CHF patients. The objective of this study was to determine the association of irisin levels with cardiac imaging measurements through cardiac magnetic resonance, inflammatory markers, and biochemical parameters in patients with CHF compared with control subjects.

METHODS AND RESULTS

Thirty-two subjects diagnosed with CHF and thirty-two healthy controls were evaluated in a cross-sectional study. Serum irisin levels were significantly lower in patients with CHF than in controls. This is the first study to report a significant positive correlation between irisin levels and cardiac magnetic resonance parameters such as left ventricular ejection fraction, fraction shortening, and global radial strain. A negative correlation was demonstrated between irisin levels and brain natriuretic peptide, insulin levels, and Homeostatic model assessment for insulin resistance index. We did not observe significant correlations between irisin levels and inflammatory cytokines.

CONCLUSIONS

Given the importance of fraction shortening and global radial strain as accurate markers of ventricular wall motion, these results support the hypothesis that irisin may play an essential role in maintaining an adequate myocardial wall architecture, deformation, and thickness.

Irisin is an Effector Molecule in Exercise Rehabilitation Following Myocardial Infarction (Review)

Background: Regular exercise is an effective non-pharmacological therapy for treatment and prevention of cardiovascular disease (CVD). The therapeutic benefits of exercise are mediated partly through improved vascular and increase in metabolic health. Release of exercise-responsive myokines, including irisin, is associated with beneficial effects of exercise in CVD patients.

Observations: The present review provides an overview of the role of exercise in cardiac rehabilitation of patients with myocardial infarction (MI). Further, the role of irisin as a motion-responsive molecule in improving vascular and metabolic health is explored. Possible mechanism of cardioprotective effect of irisin-mediated exercise on myocardial infarction are also summarized in this review.

Conclusion and significance of the review: Irisin is associated with reduced inflammation, antioxidant properties, and anti-apoptotic effect, implying that it is a potential key mediator of the beneficial effects of exercise on vascular and metabolic health. The findings show that irisin is a promising therapeutic target for treatment of patients with cardiovascular disease, particularly post-MI. Further research should be conducted to elucidate the potential mechanisms of cardioprotective effects of irisin and explored whether irisin induced by exercise exerts rehabilitation effects post-MI.

Roles of NRF2 in Fibrotic Diseases: From Mechanisms to Therapeutic Approaches

Fibrosis is a persistent inflammatory response that causes scarring and tissue sclerosis by stimulating myofibroblasts to create significant quantities of extracellular matrix protein deposits in the tissue. Oxidative stress has also been linked to the development of fibrosis in several studies. The nuclear erythroid 2-related factor 2 (NRF2) transcription factor controls the expression of several detoxification and antioxidant genes. By binding to antioxidant response elements, NRF2 is activated by oxidative or electrophilic stress and promotes its target genes, resulting in a protective effect on cells. NRF2 is essential for cell survival under oxidative stress conditions. This review describes Kelch-like epichlorohydrin-associated protein 1 (KEAP1)/NRF2 signaling mechanisms and presents recent research advances regarding NRF2 and its involvement in primary fibrotic lesions such as pulmonary fibrosis, hepatic fibrosis, myocardial fibrosis, and renal fibrosis. The related antioxidant substances and drugs are described, along with the mechanisms by which KEAP1/NRF2 regulation positively affects the therapeutic response. Finally, the therapeutic prospects and potential value of NRF2 in fibrosis are summarized. Further studies on NRF2 may provide novel therapeutic approaches for fibrosis.

Too hard to die: Exercise training mediates specific and immediate SARS-CoV-2 protection

Several mechanisms may explain how exercise training mechanistically confers protection against coronavirus disease 2019 (COVID-19). Here we propose two new perspectives through which cardiorespiratory fitness may protect against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Physical exercise-activated adenosine monophosphate (AMP)-activated protein kinase (AMPK) signaling induces endothelial nitric oxide (NO) synthase (eNOS), increases NO bio-availability, and inhibits palmitoylation, leading to specific and immediate SARS-CoV-2 protection. AMPK signaling also induces angiotensin 1-7 release and enhances eNOS activation thus further mediating cardio- and reno-protection. Irisin, a myokine released from skeletal muscles during aerobic exercise, also participates in the AMPK/Akt-eNOS/NO pathway, protects mitochondrial functions in endothelial cells, and antagonizes renin angiotensin system proinflammatory action leading to reductions in genes associated with severe COVID-19 outcomes. Collectively, all the above findings point to the fact that increased AMPK and irisin activity through exercise training greatly benefits molecular processes that mediate specific, immediate, and delayed SARS-CoV-2 protection. Maintaining regular physical activity levels is a safe and affordable lifestyle strategy against the current and future pandemics and may also mitigate against obesity and cardiometabolic disease syndemics. Move more because a moving target is harder to kill.

LncRNA TDRG1 aggravates TGF-β1-induced fibrogenesis and inflammatory response of cardiac fibroblasts via miR-605-3p/TNFRSF21 axis

ABSTRACT

Heart failure is mainly caused by a decline in the systolic function of the heart. LncRNAs are related to cardiac diseases. This study aimed to explore the effects of lncRNA testis development related gene 1 (TDRG1) on the fibrogenesis and inflammatory response of transforming growth factor-beta1 (TGF-β1)-stimulated human cardiac fibroblasts (HCFs). Levels of proinflammatory cytokines were evaluated by ELISA. RT-qPCR was applied to reveal the expression levels of TDRG1, miR-605-3p and TNFRSF21. Western blot analysis was prepared to detect protein levels of TNFRSF21 and fibrosis related genes. Luciferase reporter assay was conducted for confirming the interaction between miR-605-3p and TDRG1/TNFRSF21. We found that TGF-β1-stimulated HCFs showed high concentrations of proinflammatory cytokines, and increased protein levels of fibrosis related genes, suggesting the dysfunctions of TGF-β1-stimulated HCFs. In addition, TDRG1 was upregulated in TGF-β1-stimulated HCFs. We found that interfering with TDRG1 alleviated dysfunctions of TGF-β1-stimulated HCFs. Moreover, TDRG1 bound with miR-605-3p. MiR-605-3p exerted the anti-fibrogenic and anti-inflammatory effects in TGF-β1-treated HCFs. As a target gene of miR-605-3p, TNFRSF21, reversed the anti-fibrogenic and anti-inflammatory effects of TDRG1 knockdown in TGF-β1-treated HCFs. Overall, our study confirmed that TDRG1 aggravates fibrogenesis and inflammatory response in TGF-β1-treated HCFs via the miR-605-3p/TNFRSF21 axis.

PKM2 promotes angiotensin-II-induced cardiac remodelling by activating TGF-β/Smad2/3 and Jak2/Stat3 pathways through oxidative stress

Hypertensive cardiac remodelling is a common cause of heart failure. However, the molecular mechanisms regulating cardiac remodelling remain unclear. Pyruvate kinase isozyme type M2 (PKM2) is a key regulator of the processes of glycolysis and oxidative phosphorylation, but the roles in cardiac remodelling remain unknown. In the present study, we found that PKM2 was enhanced in angiotensin II (Ang II)-treated cardiac fibroblasts and hypertensive mouse hearts. Suppression of PKM2 by shikonin alleviated cardiomyocyte hypertrophy and fibrosis in Ang-II-induced cardiac remodelling in vivo. Furthermore, inhibition of PKM2 markedly attenuated the function of cardiac fibroblasts including proliferation, migration and collagen synthesis in vitro. Mechanistically, suppression of PKM2 inhibited cardiac remodelling by suppressing TGF-β/Smad2/3, Jak2/Stat3 signalling pathways and oxidative stress. Together, this study suggests that PKM2 is an aggravator in Ang-II-mediated cardiac remodelling. The negative modulation of PKM2 may provide a promising therapeutic approach for hypertensive cardiac remodelling.

NRF2 Activation and Downstream Effects: Focus on Parkinson's Disease and Brain Angiotensin

Reactive oxygen species (ROS) are signalling molecules used to regulate cellular metabolism and homeostasis. However, excessive ROS production causes oxidative stress, one of the main mechanisms associated with the origin and progression of neurodegenerative disorders such as Parkinson's disease. NRF2 (Nuclear Factor-Erythroid 2 Like 2) is a transcription factor that orchestrates the cellular response to oxidative stress. The regulation of NRF2 signalling has been shown to be a promising strategy to modulate the progression of the neurodegeneration associated to Parkinson's disease. The NRF2 pathway has been shown to be affected in patients with this disease, and activation of NRF2 has neuroprotective effects in preclinical models, demonstrating the therapeutic potential of this pathway. In this review, we highlight recent advances regarding the regulation of NRF2, including the effect of Angiotensin II as an endogenous signalling molecule able to regulate ROS production and oxidative stress in dopaminergic neurons. The genes regulated and the downstream effects of activation, with special focus on Kruppel Like Factor 9 (KLF9) transcription factor, provide clues about the mechanisms involved in the neurodegenerative process as well as future therapeutic approaches.

The Emerging Role of Irisin in Cardiovascular Diseases

Irisin, a novel hormone like polypeptide, is cleaved and secreted by an unknown protease from a membrane‐spanning protein, FNDC5 (fibronectin type III domain‐containing protein 5). The current knowledge on the biological functions of irisin includes browning white adipose tissue, regulating insulin use, and anti‐inflammatory and antioxidative properties. Dysfunction of irisin has shown to be involved in cardiovascular diseases such as hypertension, coronary artery disease, myocardial infarction, and myocardial ischemia–reperfusion injury. Moreover, irisin gene variants are also associated with cardiovascular diseases. In this review, we discuss the current knowledge on irisin‐mediated regulatory mechanisms and their roles in the pathogenesis of cardiovascular diseases.

Fibronectin type III domain-containing 5 in cardiovascular and metabolic diseases: a promising biomarker and therapeutic target

Cardiovascular and metabolic diseases are the leading causes of death and disability worldwide and impose a tremendous socioeconomic burden on individuals as well as the healthcare system. Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein that can be proteolytically cleaved and secreted as irisin to regulate glycolipid metabolism and cardiovascular homeostasis. In this review, we present the current knowledge on the predictive and therapeutic role of FNDC5 in a variety of cardiovascular and metabolic diseases, such as hypertension, atherosclerosis, ischemic heart disease, arrhythmia, metabolic cardiomyopathy, cardiac remodeling, heart failure, diabetes mellitus, and obesity.

The mechanism of myocardial fibrosis is ameliorated by myocardial infarction-associated transcript through the PI3K/Akt signaling pathway to relieve heart failure

OBJECTIVE

This study aimed to investigate the role of long noncoding RNA (LncRNA) myocardial infarction-associated transcript (MIAT) in a heart failure (HF) model in vivo and in vitro by regulating the PI3K/Akt signaling pathway.

METHODS

We established HF models in vivo and in vitro and evaluated the collagen content of these models and other factors.

RESULTS

We found that when LncRNA MIAT was silenced, vascular endothelial growth factor, phosphorylated protein kinase B (Akt), and phosphorylated phosphoinositide 3-kinase (PI3K) mRNA and protein levels were significantly downregulated, which suggested that MIAT activated the PI3K/Akt signaling pathway. Akt and PI3K expression was not significantly changed. We also found that when LncRNA MIAT was silenced, collagen expression was significantly downregulated. This finding suggested that MIAT promoted myocardial fibrosis during the development of HF. The levels of inflammatory factors were also significantly reduced with silencing of LncRNA MIAT. This finding suggested that MIAT promoted the expression of inflammatory factors in myocardial fibrosis by activating the PI3K/Akt signaling pathway.

CONCLUSION

This study indicates that silencing LncRNA MIAT may improve myocardial fibrosis and alleviate HF through the PI3K/Akt signaling pathway, which may be helpful for patients with HF to obtain a better therapeutic effect.

Exercise Training Enhances Myocardial Mitophagy and Improves Cardiac Function via Irisin/FNDC5-PINK1/Parkin Pathway in MI Mice

Myocardial infarction is the major cause of death in cardiovascular disease. In vitro and in vivo models are used to find the exercise mode which has the most significant effect on myocardial irisin/FNDC5 expression and illuminate the cardioprotective role and mechanisms of exercise-activated myocardial irisin/FNDC5-PINK1/Parkin-mediated mitophagy in myocardial infarction. The results indicated that expression of irisin/FNDC5 in myocardium could be up-regulated by different types of exercise and skeletal muscle electrical stimulation, which then promotes mitophagy and improves cardiac function and the effect of resistance exercise. Resistance exercise can improve cardiac function by activating the irisin/FNDC5-PINK1/Parkin-LC3/P62 pathway, regulating mitophagy and inhibiting oxidative stress. OPA1 may play an important role in the improvement of cardiac function and mitophagy pathway in myocardial infarction mice by irisin-mediated resistance exercise. Resistance exercise is expected to become an effective therapeutic way to promote myocardial infarction rehabilitation.

Irisin and Incretin Hormones: Similarities, Differences, and Implications in Type 2 Diabetes and Obesity

Incretins are gut hormones that potentiate glucose-stimulated insulin secretion (GSIS) after meals. Glucagon-like peptide-1 (GLP-1) is the most investigated incretin hormone, synthesized mainly by L cells in the lower gut tract. GLP-1 promotes β-cell function and survival and exerts beneficial effects in different organs and tissues. Irisin, a myokine released in response to a high-fat diet and exercise, enhances GSIS. Similar to GLP-1, irisin augments insulin biosynthesis and promotes accrual of β-cell functional mass. In addition, irisin and GLP-1 share comparable pleiotropic effects and activate similar intracellular pathways. The insulinotropic and extra-pancreatic effects of GLP-1 are reduced in type 2 diabetes (T2D) patients but preserved at pharmacological doses. GLP-1 receptor agonists (GLP-1RAs) are therefore among the most widely used antidiabetes drugs, also considered for their cardiovascular benefits and ability to promote weight loss. Irisin levels are lower in T2D patients, and in diabetic and/or obese animal models irisin administration improves glycemic control and promotes weight loss. Interestingly, recent evidence suggests that both GLP-1 and irisin are also synthesized within the pancreatic islets, in α- and β-cells, respectively. This review aims to describe the similarities between GLP-1 and irisin and to propose a new potential axis-involving the gut, muscle, and endocrine pancreas that controls energy homeostasis.

The myokine irisin: localization and effects in swine late medium and large antral ovarian follicle

Irisin is mainly synthesized by skeletal muscle tissue, where it is believed to be responsible for the benefits of exercise on metabolism and cardiovascular system. In adipose tissue, its best-known effect is the browning of white adipocytes, resulting in the increase of thermogenesis and energy expenditure. As it has been largely documented that metabolic dysfunctions can frequently be associated with reductions in fertility, the possible involvement of this molecule in the regulation of reproductive processes represents an issue to be addressed. On this basis, the first aim of this work was the evaluation of the presence of irisin in the swine ovary; then, we investigated the expression of the associated molecules FNDC5, PGC-1α, and PPAR-γ. To verify a potential modulatory role both on ovarian function and on redox status, cell growth, steroidogenesis, production of superoxide anion and nitric oxide, the nonenzymatic antioxidant scavengers, were assessed in vitro on granulosa cells treated with increasing concentrations of irisin (50, 100, and 150 ng/mL). The data collected demonstrate the presence of irisin in swine ovarian follicle. Moreover, the highest concentrations tested stimulated metabolic activity and inhibited cell proliferation (P < 0.05); the peptide exerted a biphasic effect on progesterone (P < 0.01) production and, at the highest concentrations, inhibited nitric oxide while stimulated the nonenzymatic antioxidant power (P < 0.05). Superoxide anion and estradiol 17β were unaffected. The demonstration of the local presence of irisin at the ovarian level and the highlighted effects allow us to qualify this molecule as a potential physiological regulator of follicular function.

Irisin as a Potential Biomarker Associated with Myocardial Injuries in Patients with Severe Hypothyroidism

OBJECTIVE

Irisin, a novel myokine, has recently been considered to produce a cardioprotective effect. Potential biomarkers for myocardial injuries in patients with severe hypothyroidism have yet to be identified. We aimed to investigate whether serum irisin may serve as a promising biomarker for early detecting the myocardial injuries in patients with severe hypothyroidism.

METHODS

This cross-sectional study comprised 25 newly diagnosed drug-naive patients with severe primary hypothyroidism and 17 age- and sex-matched healthy controls. Circulating irisin levels and cardiac magnetic resonance (CMR) were evaluated in each participant. Left ventricular (LV) myocardial injuries were detected by CMR-based T1 mapping technique using a modified look-locker inversion recovery (MOLLI) sequence, which is quantified as native T1 values.

RESULTS

Compared with healthy controls, the severe hypothyroidism group had significantly lower levels of serum irisin, especially those with pericardial effusion (P < 0.05). The severe hypothyroidism subjects exhibited lower peak filling rates (PFRs) and higher native myocardial T1 values than controls (P < 0.05). Additionally, the ROC analysis displayed that the sensitivity and specificity of serum irisin for diagnosing pericardial effusion in patients with severe hypothyroidism were 73.3% and 100.0%, respectively. The AUC was 0.920 (0.861-1.000) (P < 0.001). The cutoff value was 36.94 ng/mL. Moreover, the results in subgroup analysis revealed that the native T1 values of the low-irisin group were significantly higher than that of the high-irisin group (P < 0.05). According to multivariate linear regression analysis, serum irisin concentrations were negatively and independently correlated with native myocardial T1 values after adjustment for age, sex, and other conventional confounding factors (β = -1.473, P < 0.05).

CONCLUSIONS

Irisin may be a potential biomarker for predicting myocardial injuries in patients with severe hypothyroidism.

Therapeutic Effects of Specialized Pro-Resolving Lipids Mediators on Cardiac Fibrosis via NRF2 Activation

Heart disease is the number one mortality disease in the world. In particular, cardiac fibrosis is considered as a major factor causing myocardial infarction and heart failure. In particular, oxidative stress is a major cause of heart fibrosis. In order to control such oxidative stress, the importance of nuclear factor erythropoietin 2 related factor 2 (NRF2) has recently been highlighted. In this review, we will discuss the activation of NRF2 by docosahexanoic acid (DHA), eicosapentaenoic acid (EPA), and the specialized pro-resolving lipid mediators (SPMs) derived from polyunsaturated lipids, including DHA and EPA. Additionally, we will discuss their effects on cardiac fibrosis via NRF2 activation.

MicroRNA-21 Mediates a Positive Feedback on Angiotensin II-Induced Myofibroblast Transformation

Objective

Post myocardial infarction (MI) fibrosis has been identified as an important factor in the progression of heart failure. Previous studies have revealed that microRNA-21 (miR-21) plays an important role in the pathogenesis of fibrosis. The purpose of this study was to explore the role of miR-21 in post-MI cardiac fibrosis.

Material and Methods

MI was established in wild-type (WT) and miR-21 knockout (KO) mice. Primary mice cardiac fibroblasts (CFs) were isolated from WT and miR-21 KO mice and were treated with angiotensin II (Ang II) or Sprouty1 (Spry1) siRNA. Histological analysis and echocardiography were used to determine the extent of fibrosis and cardiac function.

Results

Compared with WT mice, miR-21 KO mice displayed smaller fibrotic areas and decreased expression of fibrotic markers and inflammatory cytokines. In parallel, Ang II-induced myofibroblasts transformation was partially inhibited upon miR-21 KO in primary CFs. Mechanistically, we found that the expression of Spry1, a previously reported target of miR-21, was markedly increased in miR-21 KO mice post MI, further inhibiting ERK1/2 activation. In vitro studies showed that Ang II activated ERK1/2/TGF-β/Smad2/3 pathway. Phosphorylated Smad2/3 further enhanced the expression of α-SMA and FAP and may promote the maturation of miR-21, thereby downregulating Spry1. Additionally, these effects of miR-21 KO on fibrosis were reversed by siRNA-mediated knockdown of Spry1.

Conclusion

Our findings suggest that miR-21 promotes post-MI fibrosis by targeting Spry1. Furthermore, it mediates a positive feedback on Ang II, thereby inducing the ERK/TGF-β/Smad pathway. Therefore, targeting the miR-21–Spry1 axis may be a promising therapeutic option for ameliorating post-MI cardiac fibrosis.

Implications of Oxidative Stress and Potential Role of Mitochondrial Dysfunction in COVID-19: Therapeutic Effects of Vitamin D

Due to its high degree of contagiousness and like almost no other virus, SARS-CoV-2 has put the health of the world population on alert. COVID-19 can provoke an acute inflammatory process and uncontrolled oxidative stress, which predisposes one to respiratory syndrome, and in the worst case, death. Recent evidence suggests the mechanistic role of mitochondria and vitamin D in the development of COVID-19. Indeed, mitochondrial dynamics contribute to the maintenance of cellular homeostasis, and its uncoupling involves pathological situations. SARS-CoV-2 infection is associated with altered mitochondrial dynamics with consequent oxidative stress, pro-inflammatory state, cytokine production, and cell death. Furthermore, vitamin D deficiency seems to be associated with increased COVID-19 risk. In contrast, vitamin D can normalize mitochondrial dynamics, which would improve oxidative stress, pro-inflammatory state, and cytokine production. Furthermore, vitamin D reduces renin–angiotensin–aldosterone system activation and, consequently, decreases ROS generation and improves the prognosis of SARS-CoV-2 infection. Thus, the purpose of this review is to deepen the knowledge about the role of mitochondria and vitamin D directly involved in the regulation of oxidative stress and the inflammatory state in SARS-CoV-2 infection. As future prospects, evidence suggests enhancing the vitamin D levels of the world population, especially of those individuals with additional risk factors that predispose to the lethal consequences of SARS-CoV-2 infection.

Effect of exercise training on the FNDC5/BDNF pathway in spontaneously hypertensive rats

Increased sympathetic activity contributes to the development of cardiovascular diseases such as hypertension. Exercise training lowers sympathetic activity and is beneficial for the prevention and treatment of hypertension and associated cognitive impairment. Increased BDNF expression in skeletal muscle, heart, and brain may contribute to these actions of exercise, but the mechanisms by which this occurs are unknown. We postulated that hypertension is associated with decreased hippocampal BDNF, which can be restored by exercise‐mediated upregulation of fibronectin type‐II domain‐containing 5 (FNDC5). Spontaneously hypertensive rats (SHR) and normotensive Wistar–Kyoto rats (WKY) were subjected to 5 weeks of motorized treadmill training. BDNF and FNDC5 expressions were measured in the left ventricle (LV), quadriceps, soleus muscle, and brain areas. Exercise training reduced blood pressure (BP) in both strains. BDNF and FNDC5 protein in the LV were increased in SHR, but exercise increased only BDNF protein in both strains. BDNF mRNA, but not protein, was increased in the quadriceps of SHR, and BDNF mRNA and protein were decreased by exercise in both groups. FNDC5 protein was higher in SHR in both the quadriceps and soleus muscle, whereas exercise increased FNDC5 protein only in the quadriceps in both strains. BDNF mRNA was lower in the dentate gyrus (DG) of SHR, which was normalized by exercise. BDNF mRNA expression in the DG negatively correlated with BP. No differences in FNDC5 expression were observed in the brain, suggesting that enhanced BDNF signaling may contribute to the cardiovascular and neurological benefits of exercise training, and these processes involve peripheral, but not central, FNDC5.

miR‑155 modulates high glucose‑induced cardiac fibrosis via the Nrf2/HO‑1 signaling pathway

Cardiac fibrosis is a major pathological manifestation of diabetic cardiomyopathy, which is a leading cause of mortality in patients with diabetes. MicroRNA (miR)‑155 is upregulated in cardiomyocytes in cardiac fibrosis, and the aim of the present study was to investigate if the inhibition of miR‑155 was able to ameliorate cardiac fibrosis by targeting the nuclear factor erythroid‑2‑related factor 2 (Nrf2)/heme oxygenase‑1 (HO‑1) signaling pathway. H9C2 rat cardiomyocytes were cultured with high glucose (HG; 30 mM) to establish an in vitro cardiac fibrosis model that mimicked diabetic conditions; a miR‑155 inhibitor and a miR‑155 mimic were transfected into H9C2 cells. Following HG treatment, H9C2 cells exhibited increased expression levels of miR‑155 and the fibrosis markers collagen I and α‑smooth muscle actin (α‑SMA). In addition, the expression levels of endonuclear Nrf2 and HO‑1 were decreased, but the expression level of cytoplasmic Nrf2 was increased. Moreover, oxidative stress, mitochondrial damage and cell apoptosis were significantly increased, as indicated by elevated reactive oxygen species, malonaldehyde and monomeric JC‑1 expression levels. In addition, superoxide dismutase expression was attenuated and there was an increased expression level of released cytochrome‑c following HG treatment. Furthermore, it was demonstrated that expression levels of Bcl‑2 and uncleaved Poly (ADP‑ribose) polymerase were downregulated, whereas Bax, cleaved caspase‑3 and caspase‑9 were upregulated after HG treatment. However, the miR‑155 inhibitor significantly restored Nrf2 and HO‑1 expression levels, and reduced oxidative stress levels, the extent of mitochondrial damage and the number of cells undergoing apoptosis. Additionally, the miR‑155 inhibitor significantly reversed the expression levels of collagen I and α‑SMA, thus ameliorating fibrosis. Furthermore, the knockdown of Nrf2 reversed the above effects induced by the miR‑155 inhibitor. In conclusion, the miR‑155 inhibitor may ameliorate diabetic cardiac fibrosis by reducing the accumulation of oxidative stress‑related molecules, and preventing mitochondrial damage and cardiomyocyte apoptosis by enhancing the Nrf2/HO‑1 signaling pathway. This mechanism may facilitate the development of novel targets to prevent cardiac fibrosis in patients with diabetes.

Irisin attenuates myocardial ischemia/reperfusion-induced cardiac dysfunction by regulating ER-mitochondria interaction through a mitochondrial ubiquitin ligase-dependent mechanism

BACKGROUND

Myocardial ischemia/reperfusion (MI/R) injury imposes devastating cardiovascular sequelae in particular cardiac dysfunction as a result of restored blood flow. However, the mechanism behind MI/R injury remains elusive. Mitochondrial ubiquitin ligase (MITOL/MARCH5) is localized at the mitochondria-ER contact site and may be activated in response to a variety of pathophysiological processes, such as apoptosis, mitochondrial injury, ER stress, hypoxia, and reactive oxygen species (ROS) generation. Irisin as a cleaved product of fibronectin type III domain-containing protein 5 (FNDC5) displays cardioprotection in diverse cardiac diseases.

METHODS

This study was designed to examine the role of irisin and MITOL in MI/R injury. Male C57BL/6J mice (8-10-week-old) were administered adenovirus MITOL shRNA through intracardiac injection followed by MI/R surgery through ligation and release the slipknot of cardiac left anterior descending coronary artery.

RESULTS

Our results showed that irisin improved myocardial function in the face of MI/R injury as evidenced by reduced myocardial infarct size, apoptotic rate, serum lactate dehydrogenase (LDH), ROS generation, and malondialdehyde (MDA) levels as well as lessened ER stress injury. Moreover, our results indicated that protective role of irisin was mediated by upregulation of MITOL. Irisin also protected H9c2 cells against simulated I/R through negating ER stress, apoptosis, ROS and MDA levels, as well as facilitating superoxide dismutase (SOD) by way of elevated MITOL expression.

CONCLUSIONS

To this end, our data favored that irisin pretreatment protects against MI/R injury, ER stress, ROS production, and mitochondrial homeostasis through upregulation of MITOL. These findings depicted the therapeutic potential of irisin and MITOL in the management of MI/R injury in patients with ST-segment elevation.

Role of Nrf2 and Its Activators in Cardiocerebral Vascular Disease

Cardiocerebral vascular disease (CCVD) is a common disease with high morbidity, disability, and mortality. Oxidative stress (OS) is closely related to the progression of CCVD. Abnormal redox regulation leads to OS and overproduction of reactive oxygen species (ROS), which can cause biomolecular and cellular damage. The Nrf2/antioxidant response element (ARE) signaling pathway is one of the most important defense systems against exogenous and endogenous OS injury, and Nrf2 is regarded as a vital pharmacological target. The complexity of the CCVD pathological process and the current difficulties in conducting clinical trials have hindered the development of therapeutic drugs. Furthermore, little is known about the role of the Nrf2/ARE signaling pathway in CCVD. Clarifying the role of the Nrf2/ARE signaling pathway in CCVD can provide new ideas for drug design. This review details the recent advancements in the regulation of the Nrf2/ARE system and its role and activators in common CCVD development.

Icariin Prevents Extracellular Matrix Accumulation and Ameliorates Experimental Diabetic Kidney Disease by Inhibiting Oxidative Stress via GPER Mediated p62-Dependent Keap1 Degradation and Nrf2 Activation

The present study aimed to determine whether icariin could attenuate type 1 diabetic nephropathy (T1DN) induced by streptozotocin (STZ) after 4 weeks or not. Therefore, its therapeutic effect on diabetic kidney disease was investigated in view of reactive oxygen (ROS) and extracellular matrix (ECM) generation in human glomerular mesangial cells under high glucose. To establish the participation and the key role of GPER and Nrf2 in ECM deposition, a combination of G15 (antagonist of GPER) or siGPER and siNrf2 were performed, respectively. The results showed that T1DN can be significantly inhibited by oral icariin, evidenced by improvement of 24 h urinary volume, 24 h proteinuria, microalbuminuria, and histopathological changes of kidney. Icariin decreased the levels of intracellular superoxide anion, impeded the generation of fibronectin and increased the expression and activity of antioxidant enzymes in the human glomerular mesangial cells treated with high glucose. It acted as a GPER activator, increased dissociation of Nrf2/Keap1 complexes, combination of Keap1/p62 complexes, Nrf2 translocation to nuclear, Nrf2/ARE DNA binding activity, and ARE luciferase reporter gene activity in glomerular mesangial cells. The Nrf2 inhibitor ML385 or siNrf2 obviously abolished extracellular matrix (ECM) generation inhibited by icariin. Furthermore, icariin-induced Nrf2 activation was mainly dependent on p62-mediated Keap1 degradation, which functions as an adaptor protein during autophagy. The GPER antagonist G15 and siGPER obviously abolished the above effects by icariin. Taken together, the present study demonstrated that the therapeutic effects of icariin on type 1 diabetic nephropathy in rats via GPER mediated p62-dependent Keap1 degradation and Nrf2 activation.

FOXF1 ameliorates angiotensin II-induced cardiac fibrosis in cardiac fibroblasts through inhibiting the TGF-β1/Smad3 signaling pathway

Cardiac fibrosis is a pathological feature common to a variety of heart diseases such as myocardial infarction, arrhythmias, cardiomyopathies and heart failure. The molecular mechanism underlying the cardiac fibrosis is still unclear. Forkhead box F1 (FOXF1), a member of the forkhead transcription factor superfamily, plays critical roles in the development of hepatic fibrosis. However, whether FOXF1 is involved in the pathogenesis of cardiac fibrosis remains to be elucidated. The present study aimed to investigate the role of FOXF1 and its mechanisms in regulating cardiac fibrosis. The results demonstrated that FOXF1 was downregulated in Ang II-induced CFs. Overexpression of FOXF1 inhibited angiotensin II (Ang II)-induced proliferation, migration and oxidative stress in cardiac fibroblasts (CFs). Overexpression of FOXF1 also reduced the expression of alpha-smooth muscle actin (a-SMA) in Ang II-induced CFs, suggesting that overexpression of FOXF1 prevented the differentiation of CFs to myofibroblasts. Furthermore, the production of extracellular matrix (ECM) components including type I collagen and fibronectin were reduced by overexpression of FOXF1 in Ang II-induced CFs. Furthermore, overexpression of FOXF1 prevented Ang II-induced activation of transforming growth factor beta 1 (TGF-β1)/Smad3 pathway in CFs. In conclusion, the results of the present study indicated that FOXF1 acted as a key regulator of pathological cardiac fibrosis, and overexpression of FOXF1 ameliorated cardiac fibrosis by inhabiting the TGF-β1/Smad3 signaling pathway. These results indicated that FOXF1 may be a novel target for attenuating cardiac fibrosis.

Redox Signaling in Widespread Health Benefits of Exercise

Significance: Exercise-induced reactive oxygen species (ROS) production activates multiple intracellular signaling pathways through genomic and nongenomic mechanisms that are responsible for the beneficial effects of exercise in muscle. Beyond the positive effect of exercise on skeletal muscle cells, other tissues such as white and brown adipose, liver, central nervous system, endothelial, heart, and endocrine organ tissues are also responsive to exercise. Recent Advances: Crosstalk between different cells is essential to achieve homeostasis and to promote the benefits of exercise through paracrine or endocrine signaling. This crosstalk can be mediated by different effectors that include the secretion of metabolites of muscle contraction, myokines, and exosomes. During the past 20 years, it has been demonstrated that contracting muscle cells produce and secrete different classes of myokines, which functionally link muscle with nearly all other cell types. Critical Issues: The redox signaling behind this exercise-induced crosstalk is now being decoded. Many of these widespread beneficial effects of exercise require not only a complex ROS-dependent intramuscular signaling cascade but simultaneously, an integrated network with many remote tissues. Future Directions: Strong evidence suggests that the powerful beneficial effect of regular physical activity for preventing (or treating) a large range of disorders might also rely on ROS-mediated signaling. Within a contracting muscle, ROS signaling may control exosomes and myokines secretion. In remote tissues, exercise generates regular and synchronized ROS waves, creating a transient pro-oxidative environment in many cells. These new concepts integrate exercise, ROS-mediated signaling, and the widespread health benefits of exercise.

Identification of irisin as a therapeutic agent that inhibits oxidative stress and fibrosis in a murine model of chronic pancreatitis

BACKGROUND

Abnormal activation of pancreatic stellate cells (PSCs) plays a crucial role in the pathogenesis of chronic pancreatitis (CP). Irisin, an exercise-induced hormone, has been shown to mitigate liver fibrosis by inhibiting the activation of hepatic stellate cells. However, the effect of irisin in CP has not been evaluated.

METHODS

This study aimed to determine whether irisin is protective in CP. CP was induced by 6 IP injections of cerulein (50 μg/kg/body weight). HPSCs were treated with 5 ng/ml TGF-β1 as in vitro experiment.

RESULTS

Our results showed that repeated cerulein injection induced severe pancreatic injury and fibrosis in mice and the serum irisin level in cerulein-treated mice decreased as in CP patients. Excessive oxidative and ER stress was also present in the pancreas of cerulein-treated mice. Irisin treatment significantly alleviated pancreatic injury and fibrosis, which was associated with reduced oxidative and ER stress. In cultured PSCs, irisin directly inhibited TGF-β-induced α-SMA and collagen I expression. This effect appears to be mediated through downregulation of kindlin-2 and inhibition of the SMAD2/3 pathway.

CONCLUSIONS

Irisin alleviated pancreatic injury and fibrosis, which was associated with reduced oxidative and ER stress. Thus, irisin may offer therapeutic potential for patients with CP.

Recombinant Irisin Prevents the Reduction of Osteoblast Differentiation Induced by Stimulated Microgravity through Increasing β-Catenin Expression

Background: Irisin, a novel exercise-induced myokine, was shown to mediate beneficial effects of exercise in osteoporosis. Microgravity is a major threat to bone homeostasis of astronauts during long-term spaceflight, which results in decreased bone formation. Methods: The hind-limb unloading mice model and a random position machine are respectively used to simulate microgravity in vivo and in vitro. Results: We demonstrate that not only are bone formation and osteoblast differentiation decreased, but the expression of fibronectin type III domain-containing 5 (Fdnc5; irisin precursor) is also downregulated under simulated microgravity. Moreover, a lower dose of recombinant irisin (r-irisin) (1 nM) promotes osteogenic marker gene (alkaline phosphatase (Alp), collagen type 1 alpha-1(ColIα1)) expressions, ALP activity, and calcium deposition in primary osteoblasts, with no significant effect on osteoblast proliferation. Furthermore, r-irisin could recover the decrease in osteoblast differentiation induced by simulated microgravity. We also find that r-irisin increases β-catenin expression and partly neutralizes the decrease in β-catenin expression induced by simulated microgravity. In addition, β-catenin overexpression could also in part attenuate osteoblast differentiation reduction induced by simulated microgravity. Conclusions: The present study is the first to show that r-irisin positively regulates osteoblast differentiation under simulated microgravity through increasing β-catenin expression, which may reveal a novel mechanism, and it provides a prevention strategy for bone loss and muscle atrophy induced by microgravity.