Elabela blunts doxorubicin-induced oxidative stress and ferroptosis in rat aortic adventitial fibroblasts by activating the KLF15/GPX4 signaling.

Doxorubicin (DOX) is a chemotherapeutic drug for a variety of malignancies, while its application is restricted by the cardiovascular toxic effects characterized by oxidative stress. Ferroptosis is a novel iron-dependent regulated cell death driven by lipid peroxidation. Our study aimed to investigate the role of Elabela (ELA) in DOX-induced oxidative stress and ferroptosis. In cultured rat aortic adventitial fibroblasts (AFs), stimulation with DOX dramatically induced cytotoxicity with reduced cell viability and migration ability, and enhanced lactate dehydrogenase (LDH) activity. Importantly, ELA and ferrostatin-1 (Fer-1) mitigated DOX-mediated augmentation of reactive oxygen species (ROS) in rat aortic AFs, accompanied by upregulated levels of Nrf2, SLC7A11, GPX4, and GSH. In addition, ELA reversed DOX-induced dysregulation of apoptosis- and inflammation-related factors including Bax, Bcl2, interleukin (IL)-1ß, IL6, IL-10, and CXCL1. Intriguingly, knockdown of Krüppel-like factor 15 (KLF15) by siRNA abolished ELA-mediated alleviation of ROS production and inflammatory responses. More importanly, KLF15 siRNA impeded the beneficial roles of ELA in DOX-pretreated rat aortic AFs by suppressing the Nrf2/SLC7A11/GPX4 signaling. In conclusion, ELA prevents DOX-triggered promotion of cytotoxicity, and exerts anti-oxidative and anti-ferroptotic effects in rat aortic AFs via activation of the KLF15/GPX4 signaling, indicating a promising therapeutic value of ELA in antagonizing DOX-mediated cardiovascular abnormality and disorders.

Sirtuin 7 mitigates renal ferroptosis, fibrosis and injury in hypertensive mice by facilitating the KLF15/Nrf2 signaling.

Hypertension is one of the leading causes of chronic kidney disease characterized with renal fibrosis. This study aimed to investigate roles and mechanisms of sirtuin 7 (SIRT7) in hypertensive renal injury. Mini-pumps were implanted to male C57BL/6 mice to deliver angiotensin (Ang) Ⅱ (1.5 mg/kg/d) or saline for 2 weeks. Ang Ⅱ infusion resulted in marked increases in systolic blood pressure levels, renal ferroptosis and interstitial fibrosis in hypertensive mice, concomitantly with downregulated SIRT7 and Krüppel-like factor 15 (KLF15) levels. Notably, administration of recombinant adeno-associated virus-SIRT7 or ferroptosis inhibitor ferrostatin-1 effectively mitigated Ang Ⅱ-triggered renal ferroptosis, epithelial-mesenchymal transition (EMT), interstitial fibrosis, renal functional and structural injury in hypertensive mice by blunting the KIM-1/NOX4 signaling and enforcing the KLF15/Nrf2 and xCT/GPX4 signaling, respectively. In primary cultured mouse renal tubular epithelial cells (TECs), Ang Ⅱ pretreatment led to repressed SIRT7 expression and augmented ferroptosis as well as partial EMT, which were substantially antagonized by rhSIRT7 or ferrostatin-1 administration. Additionally, both Nrf2 inhibitor ML385 and KLF15 siRNA strikingly abolished the rhSIRT7-mediated beneficial roles in mouse renal TECs in response to Ang Ⅱ with reduced expression of Nrf2, xCT and GPX4. More importantly, ML385 administration remarkably amplified Ang Ⅱ-mediated ROS generation, lipid peroxidation and ferroptosis in renal TECs, which were significantly reversed by ferrostatin-1. In conclusion, SIRT7 alleviates renal ferroptosis, lipid peroxidation, and partial EMT under hypertensive status by facilitating the KLF15/Nrf2 signaling, thereby mitigating renal fibrosis, injury and dysfunction. Targeting SIRT7 signaling serves as a promising strategy for hypertension and hypertensive renal injury.

Sirtuin 7 serves as a promising therapeutic target for cardiorenal diseases.

Cardiovascular disorders and associated renal diseases account for the main cause of morbidity and mortality worldwide, necessitating the development of novel effective approaches for the prevention and treatment of cardiorenal diseases. Mammalian sirtuins (SIRTs) function as nicotinamide adenine dinucleotide (NAD+)-dependent protein/histone deacetylases. Seven members of SIRTs share a highly invariant catalytic core domain responsible for the specific enzymatic activity. Intriguingly, the broad distribution of SIRTs and alternative isoforms implicate its distinct functions in diverse cardiac and renal cells and tissue types. Notably, SIRT7 has been shown to exert beneficial effects in cardiorenal physiology and pathophysiology via modulation of senescence, DNA damage repair, ribosomal RNA synthesis, protein biosynthesis, angiogenesis, apoptosis, superoxide generation, cardiorenal metabolism, and dysfunction. Furthermore, SIRT7 has emerged as a critical modulator of a broad range of cellular activities including oxidative stress, inflammation response, endoplasmic reticulum stress, and mitochondrial homeostasis, which are all of great significance in postponing the progression of cardiorenal diseases. More importantly, SIRT7 has been implicated in cardiorenal hypertrophy, fibrosis, remodeling, heart failure, atherosclerosis as well as renal acid-base and electrolyte homeostasis as an essential regulator. In this article, we focus on the involvement in cardiorenal physiology and pathophysiology, diverse actions and underlying mechanisms of the SIRT7 signaling, highlighting its updated research progress in heart failure, atherosclerosis, diabetic nephropathy and other cardiorenal diseases. Targeting SIRT7 signaling could be potentially exploited as a therapeutic strategy aiming to prevent and treat cardiorenal diseases.

MicroRNA-122-5p promotes renal fibrosis and injury in spontaneously hypertensive rats by targeting FOXO3.

Hypertensive renal injury is accompanied by tubular interstitial fibrosis leading to increased risk for renal failure. This study aimed to explore the influences of miR-122-5p in hypertension-mediated renal fibrosis and damage. 14-week-old male SHR and WKY rats were randomly assigned to treat with rAAV-miR-122-5p or rAAV-GFP for 8 weeks. There were marked increases in miR-122-5p and Kim-1 levels and decreases in FOXO3 and SIRT6 levels in hypertensive rats. Transfection with rAAV-miR-122-5p triggered exacerbation of renal fibrosis, apoptosis and inflammatory injury in SHR, associated with downregulated levels of FOXO3, SIRT6, ATG5 and BNIP3 as well as upregulated expression of Kim-1, NOX4, CTGF, and TGF-ß1. In cultured primary mouse renal tubular interstitial fibroblasts, exposure to angiotensin II resulted in obvious downregulation of FOXO3, SIRT6, ATG5, BNIP3 and nitric oxide levels as well as augmented cellular migration, oxidative stress, and inflammation, which were exacerbated by miR-122-5p mimic while rescued by miR-122-5p inhibitor and rhFOXO3, respectively. Notably, knockdown of FOXO3 strikingly blunted cellular protective effects of miR-122-5p inhibitor. In summary, miR-122-5p augments renal fibrosis, inflammatory and oxidant injury in hypertensive rats by suppressing the expression of FOXO3. Pharmacological inhibition of miR-122-5p has potential therapeutic significance for hypertensive renal injury and fibrosis-related kidney diseases.

Elabela prevents angiotensin II-induced apoptosis and inflammation in rat aortic adventitial fibroblasts via the activation of FGF21-ACE2 signaling.

Apoptosis, inflammation, and fibrosis contribute to vascular remodeling and injury. Elabela (ELA) serves as a crucial regulator to maintain vascular function and has been implicated in the pathogenesis of hypertensive vascular remodeling. This study aims to explore regulatory roles and underlying mechanisms of ELA in rat aortic adventitial fibroblasts (AFs) in response to angiotensin II (ATII). In cultured AFs, exposure to ATII resulted in marked decreases in mRNA and protein levels of ELA, fibroblast growth factor 21 (FGF21), and angiotensin-converting enzyme 2 (ACE2) as well as increases in apoptosis, inflammation, oxidative stress, and cellular migration, which were partially blocked by the exogenous replenishment of ELA and recombinant FGF21, respectively. Moreover, treatment with ELA strikingly reversed ATII-mediated the loss of FGF21 and ACE2 levels in rat aortic AFs. FGF21 knockdown with small interfering RNA (siRNA) significantly counterbalanced protective effects of ELA on ATII-mediated the promotion of cell migration, apoptosis, inflammatory, and oxidative injury in rat aortic AFs. More importantly, pretreatment with recombinant FGF21 strikingly inhibited ATII-mediated the loss of ACE2 and the augmentation of cell apoptosis, oxidative stress, and inflammatory injury in rat aortic AFs, which were partially prevented by the knockdown of ACE2 with siRNA. In summary, ELA exerts its anti-apoptotic, anti-inflammatory, and anti-oxidant effects in rat aortic AFs via activation of the FGF21-ACE2 signaling. ELA may represent a potential candidate to predict vascular damage and targeting the FGF21-ACE2 signaling may be a promising therapeutic intervention for vascular adventitial remodeling and related disorders.

Abnormal apelin-ACE2 and SGLT2 signaling contribute to adverse cardiorenal injury in patients with COVID-19.

BACKGROUND: Angiotensin converting enzyme 2 (ACE2) has recently been identified as the functional receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent response for novel coronavirus disease 2019 (COVID-19). This study aimed to explore the roles of ACE2, apelin and sodium-glucose cotransporter 2 (SGLT2) in SARS-CoV-2-mediated cardiorenal damage. METHODS AND RESULTS: The published RNA-sequencing datasets of cardiomyocytes infected with SARS-CoV-2 and COVID-19 patients were used. String, UMAP plots and single cell RNA sequencing data were analyzed to show the close relationship and distinct cardiorenal distribution patterns of ACE2, apelin and SGLT2. Intriguingly, there were decreases in ACE2 and apelin expression as well as marked increases in SGLT2 and endothelin-1 levels in SARS-CoV-2-infected cardiomyocytes, animal models with diabetes, acute kidney injury, heart failure and COVID-19 patients. These changes were linked with downregulated levels of interleukin (IL)-10, superoxide dismutase 2 and catalase as well as upregulated expression of profibrotic genes and pro-inflammatory cytokines/chemokines. Genetic ACE2 deletion resulted in upregulation of pro-inflammatory cytokines containing IL-1ß, IL-6, IL-17 and tumor necrosis factor α. More importantly, dapagliflozin strikingly alleviated cardiorenal fibrosis in diabetic db/db mice by suppressing SGLT2 levels and potentiating the apelin-ACE2 signaling. CONCLUSION: Downregulation of apelin and ACE2 and upregulation of SGLT2, endothelin-1 and pro-inflammatory cytokines contribute to SARS-CoV-2-mediated cardiorenal injury, indicating that the apelin-ACE2 signaling and SGLT2 inhibitors are potential therapeutic targets for COVID-19 patients.

Apelin Is a Negative Regulator of Angiotensin II-Mediated Adverse Myocardial Remodeling and Dysfunction.

The apelin pathway has emerged as a critical regulator of cardiovascular homeostasis and disease. However, the exact role of pyr1-apelin-13 in angiotensin (Ang) II-mediated heart disease remains unclear. We used apelin-deficient (APLN-/y) and apolipoprotein E knockout mice to evaluate the regulatory roles of pyr1-apelin-13. The 1-year aged APLN-/y mice developed myocardial hypertrophy and dysfunction with reduced angiotensin-converting enzyme 2 levels. Ang II infusion (1.5 mg kg-1 d-1) for 4 weeks potentiated oxidative stress, pathological hypertrophy, and myocardial fibrosis in young APLN-/y hearts resulting in exacerbation of cardiac dysfunction. Importantly, daily administration of 100 µg/kg pyr1-apelin-13 resulted in upregulated angiotensin-converting enzyme 2 levels, decreased superoxide production and expression of hypertrophy- and fibrosis-related genes leading to attenuated myocardial hypertrophy, fibrosis, and dysfunction in the Ang II-infused apolipoprotein E knockout mice. In addition, pyr1-apelin-13 treatment largely attenuated Ang II-induced apoptosis and ultrastructural injury in the apolipoprotein E knockout mice by activating Akt and endothelial nitric oxide synthase phosphorylation signaling. In cultured neonatal rat cardiomyocytes and cardiofibroblasts, exposure of Ang II decreased angiotensin-converting enzyme 2 protein and increased superoxide generation, cellular proliferation, and migration, which were rescued by pyr1-apelin-13, and Akt and endothelial nitric oxide synthase agonist stimulation. The increased superoxide generation and apoptosis in cultured cardiofibroblasts in response to Ang II were strikingly prevented by pyr1-apelin-13 which was partially reversed by cotreatment with the Akt inhibitor MK2206. In conclusion, pyr1-apelin-13 peptide pathway is a negative regulator of aging-mediated and Ang II-mediated adverse myocardial remodeling and dysfunction and represents a potential candidate to prevent and treat heart disease.

The sirtuin 6 prevents angiotensin II-mediated myocardial fibrosis and injury by targeting AMPK-ACE2 signaling.

Sirtuin 6 (SIRT6) is an important modulator of cardiovascular functions in health and diseases. However, the exact role of SIRT6 in heart disease is poorly defined. We hypothesized that SIRT6 is a negative regulator of angiotensin II (Ang II)-mediated myocardial remodeling, fibrosis and injury. The male Sprague-Dawley rats were randomized to Ang II (200 ng/kg/min) infusion with an osmotic minipump and pretreated with recombinant plasmids adeno-associated viral vector (AAV)-SIRT6 (pAAV-SIRT6) or pAAV-GFP for 4 weeks. Ang II triggered downregulated levels of SIRT6 and angiotensin-converting enzyme 2 (ACE2) and upregulated expression of connective tissue growth factor (CTGF) and proinflammatory chemokine fractalkine (FKN), contributing to enhanced cardiac fibrosis and ultrastructural injury. Reduced levels of phosphorylated pAMPK-α, increased myocardial hypertrophy and impaired heart dysfunction were observed in both Ang II-induced hypertensive rats and ACE2 knockout rats, characterized with increases in heart weight and left ventricular (LV) posterior wall thickness and decreases in LV ejection fraction and LV fractional shortening. More importantly, pAAV-SIRT6 treatment strikingly potentiated cardiac levels of pAMPKα and ACE2 as well as decreased levels of CTGF, FKN, TGFß1, collagen I and collagen III, resulting in alleviation of Ang II-induced pathological hypertrophy, myocardial fibrosis, cardiac dysfunction and ultrastructural injury in hypertensive rats. In conclusion, our findings confirmed cardioprotective effects of SIRT6 on pathological remodeling, fibrosis and myocardial injury through activation of AMPK-ACE2 signaling and suppression of CTGF-FKN pathway, indicating that SIRT6 functions as a partial agonist of ACE2 and targeting SIRT6 has potential therapeutic importance for cardiac fibrosis and heart disease.

Targeting the apelin pathway as a novel therapeutic approach for cardiovascular diseases.

The apelin/apelin receptor system is widely distributed and has a dominant role in cardiovascular homeostasis and disease. The apelin gene is X-linked and is synthesized as a 77 amino acid pre-pro-peptide that is subsequently cleaved to generate a family of apelin peptides that possess similar functions but display different tissue distribution, potency and receptor binding affinity. Loss-of-function experiments using the apelin and the apelin receptor knockout mice and gain-of-function experiments using apelin peptides have delineated a well-defined role of the apelin axis in cardiovascular physiology and diseases. Activation of the apelin receptor by its cognate peptide ligand, apelin, induces a wide range of physiological effects, including vasodilation, increased myocardial contractility, angiogenesis, and balanced energy metabolism and fluid homeostasis. The apelin/apelin receptor pathway is also implicated in atherosclerosis, hypertension, coronary artery disease, heart failure, diabetes and obesity, making it a promising therapeutic target. Hence, research is expanding to develop novel therapies that inhibit degradation of endogenous apelin peptides or their analogues. Chemical synthesis of stable apelin receptor agonists aims to more efficiently enhance the activation of the apelin system. Targeting the apelin/apelin receptor axis has emerged as a novel therapeutic approach against cardiovascular diseases and an increased understanding of cardiovascular actions of the apelin system will help to develop effective interventions.

Ascending aortic adventitial remodeling and fibrosis are ameliorated with Apelin-13 in rats after TAC via suppression of the miRNA-122 and LGR4-ß-catenin signaling.

Apelin has been proved to be a critical mediator of vascular function and homeostasis. Here, we investigated roles of Apelin in aortic remodeling and fibrosis in rats with transverse aortic constriction (TAC). Male Sprague-Dawley rats were subjected to TAC and then randomized to daily deliver Apelin-13 (50µg/kg) or angiotensin type 1 receptor (AT1) blocker Irbesartan (50mg/kg) for 4 weeks. Pressure overload resulted in myocardial hypertrophy, systolic dysfunction, aortic remodeling and adventitial fibrosis with reduced levels of Apelin in ascending aortas of rat after TAC compared with sham-operated group. These changes were associated with marked increases in levels of miRNA-122, TGFß1, CTGF, NFAT5, LGR4, and ß-catenin. More importantly, Apelin and Irbesartan treatment strikingly prevented TAC-mediated aortic remodeling and adventitial fibrosis in pressure overloaded rats by blocking AT1 receptor and miRNA-122 levels and repressing activation of the CTGF-NFAT5 and LGR4-ß-catenin signaling. In cultured primary rat adventitial fibroblasts, exposure to angiotensin II (100nmolL-1) led to significant increases in cellular migration and levels of TGFß1, CTGF, NFAT5, LGR4 and ß-catenin, which were effectively reversed by pre-treatment with Apelin (100nmolL-1) and miRNA-122 inhibitor (50nmolL-1). In conclusion, Apelin counterregulated against TAC-mediated ascending aortic remodeling and angiotensin II-induced promotion of cellular migration by blocking AT1 receptor and miRNA-122 levels and preventing activation of the TGFß1-CTGF-NFAT5 and LGR4-ß-catenin signaling, ultimately contributing to attenuation of aortic adventitial fibrosis. Our data point to Apelin as an important regulator of aortic remodeling and adventitial fibrosis and a promising target for vasoprotective therapies.

Angiotensin-converting enzyme 2 ameliorates renal fibrosis by blocking the activation of mTOR/ERK signaling in apolipoprotein E-deficient mice.

Angiotensin-converting enzyme 2 (ACE2) has been shown to prevent atherosclerotic lesions and renal inflammation. However, little was elucidated upon the effects and mechanisms of ACE2 in atherosclerotic kidney fibrosis progression. Here, we examined regulatory roles of ACE2 in renal fibrosis in the apolipoprotein E (ApoE) knockout (KO) mice. The ApoEKO mice were randomized to daily deliver either angiotensin (Ang) II (1.5mg/kg) and/or human recombinant ACE2 (rhACE2; 2mg/kg) for 2 weeks. Downregulation of ACE2 and upregulation of phosphorylated Akt, mTOR and ERK1/2 levels were observed in ApoEKO kidneys. Ang II infusion led to increased tubulointerstitial fibrosis in the ApoEKO mice with greater activation of the mTOR/ERK1/2 signaling. The Ang II-mediated renal fibrosis and structural injury were strikingly rescued by rhACE2 supplementation, associated with reduced mRNA expression of TGF-ß1 and collagen I and elevated renal Ang-(1-7) levels. In cultured mouse kidney fibroblasts, exposure with Ang II (100nmolL(-1)) resulted in obvious elevations in superoxide generation, phosphorylated levels of mTOR and ERK1/2 as well as mRNA levels of TGF-ß1, collagen I and fibronectin 1, which were dramatically prevented by rhACE2 (1mgmL(-1)) or mTOR inhibitor rapamycin (10µmolL(-1)). These protective effects of rhACE2 were eradicated by the Ang-(1-7)/Mas receptor antagonist A779 (1µmolL(-1)). Our results demonstrate the importance of ACE2 in amelioration of kidney fibrosis and renal injury in the ApoE-mutant mice via modulation of the mTOR/ERK signaling and renal Ang-(1-7)/Ang II balance, thus indicating potential therapeutic strategies by enhancing ACE2 action for preventing atherosclerosis and fibrosis-associated kidney disorders.

Deletion of angiotensin-converting enzyme 2 exacerbates renal inflammation and injury in apolipoprotein E-deficient mice through modulation of the nephrin and TNF-alpha-TNFRSF1A signaling.

BACKGROUND: The renin-angiotensin system (RAS) has been implicated in atherosclerotic lesions and progression to chronic kidney diseases. We examined regulatory roles of angiotensin-converting enzyme 2 (ACE2) in the apolipoprotein E (ApoE) knockout (KO) kidneys. METHODS: The 3-month-old wild-type, ApoEKO, ACE2KO and ApoE/ACE2 double-KO (DKO) mice in a C57BL/6 background were used. The ApoEKO mice were randomized to daily deliver either Ang II (1.5 mg/kg) and/or human recombinant ACE2 (rhACE2; 2 mg/kg) for 2 weeks. We examined changes in pro-inflammatory cytokines, renal ultrastructure, and pathological signaling in mouse kidneys. RESULTS: Downregulation of ACE2 and nephrin levels was observed in ApoEKO kidneys. Genetic ACE2 deletion resulted in modest elevations in systolic blood pressure levels and Ang II type 1 receptor expression and reduced nephrin expression in kidneys of the ApoE/ACE2 DKO mice with a decrease in renal Ang-(1-7) levels. These changes were linked with marked increases in renal superoxide generation, NADPH oxidase (NOX) 4 and proinflammatory factors levels, including interleukin (IL)-1beta, IL-6, IL-17A, RANTES, ICAM-1, Tumor necrosis factor-alpha (TNF-alpha) and TNFRSF1A. Renal dysfunction and ultrastructure injury were aggravated in the ApoE/ACE2 DKO mice and Ang II-infused ApoEKO mice with increased plasma levels of creatinine, blood urea nitrogen and enhanced levels of Ang II in plasma and kidneys. The Ang II-mediated reductions of renal ACE2 and nephrin levels in ApoEKO mice were remarkably rescued by rhACE2 supplementation, along with augmentation of renal Ang-(1-7) levels. More importantly, rhACE2 treatment significantly reversed Ang II-induced renal inflammation, superoxide generation, kidney dysfunction and adverse renal injury in ApoEKO mice with suppression of the NOX4 and TNF-alpha-TNFRSF1A signaling. However, rhACE2 had no effect on renal NOX2 and TNFRSF1B expression and circulating lipid levels. CONCLUSIONS: ACE2 deficiency exacerbates kidney inflammation, oxidative stress and adverse renal injury in the ApoE-mutant mice through modulation of the nephrin, NOX4 and TNF-alpha-TNFRSF1A signaling. While rhACE2 supplementation alleviates inflammation, renal dysfunction and glomerulus injury in the ApoE-mutant mice associated with upregulations of Ang-(1-7) levels and nephrin expression and suppression of the TNF-alpha-TNFRSF1A signaling. Strategies aimed at enhancing the ACE2/Ang-(1-7) actions may have important therapeutic potential for atherosclerotic renal injury and kidney diseases.

Loss of angiotensin-converting enzyme 2 exacerbates myocardial injury via activation of the CTGF-fractalkine signaling pathway.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2) has been implicated in human heart failure, but the mechanism remains elusive. We hypothesized that ACE2 deficiency would exacerbate angiotensin (Ang) II-mediated myocardial injury. METHODS AND RESULTS: 10-week-old ACE2 knockout (ACE2KO) and wild-type mice received by mini-osmotic pump either AngII (1.5 mg·kg(-1)·day(-1)) or saline for 2 weeks. ACE2 deficiency triggered greater increases in the expression of connective tissue growth factor (CTGF), fractalkine (FKN) and phosphorylated ERK1/2 in AngII-treated ACE2KO hearts. These changes were associated with greater activation of matrix metalloproteinase (MMP) 2, MMP9 and MT1-MMP and exacerbation of myocardial injury and dysfunction. In cultured cardiofibroblasts, exposure to AngII (100 nmol/L) for 30 min resulted in marked increases in superoxide production and expression of CTGF, FKN and phosphorylated ERK1/2, which were strikingly prevented by recombinant human ACE2 (rhACE2; 1mg/ml) and the CTGF-neutralizing antibody (5 µg/ml), but were aggravated by ACE2 inhibitor DX600 (0.5 µmol/L). These protective effects of rhACE2 were eradicated by the Ang-(1-7) antagonist A779 (1 µmol/L). More intriguingly, rhACE2 treatment significantly abolished AngII-mediated increases in MMP2, MMP9 and MT1-MMP in cardiofibroblasts. CONCLUSIONS: Loss of ACE2 exacerbates AngII-mediated inflammation, myocardial injury and dysfunction in ACE2-deficient hearts via activation of the CTGF-FKN-ERK and MMP signaling. ACE2 gene may represent a potential candidate to prevent and treat myocardial injury and heart diseases.

Cardiac protective effects of irbesartan via the PPAR-gamma signaling pathway in angiotensin-converting enzyme 2-deficient mice.

BACKGROUND: Angiotensin-converting enzyme 2 (ACE2), a monocarboxypeptidase which metabolizes angiotensin II (Ang II) to generate Ang-(1-7), has been shown to prevent cardiac hypertrophy and injury but the mechanism remains elusive. Irbesartan has the dual actions of angiotensin receptor blockade and peroxisome proliferator-activated receptor-γ (PPARγ) activation. We hypothesized that irbesartan would exert its protective effects on ACE2 deficiency-mediated myocardial fibrosis and cardiac injury via the PPARγ signaling. METHODS: 10-week-old ACE2 knockout (ACE2KO; Ace2(-/y)) mice received daily with irbesartan (50 mg/kg) or saline for 2 weeks. The wild-type mice (Ace2(+/y)) were used to the normal controls. We examined changes in myocardial ultrastructure, fibrosis-related genes and pathological signaling by real-time PCR gene array, Western blotting, Masson trichrome staining and transmission electron microscope analyses, respectively. RESULTS: Compared with the Ace2(+/y) mice, cardiac expression of PPARα and PPARγ were reduced in Ace2(-/y) mice and the myocardial collagen volume fraction (CVF) and expression of fibrosis-related genes were increased, including transforming growth factor-ß1 (TGFß1), connective tissue growth factor (CTGF), collagen I and collagen III. Moreover, ACE2 deficiency triggered cardiac hypertrophy, increased myocardial fibrosis and adverse ultrastructure injury in ACE2KO hearts with higher levels of atrial natriuretic factor (ANF) and phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), without affecting cardiac systolic function. Intriguingly, treatment with irbesartan significantly reversed ACE2 deficiency-mediated pathological hypertrophy and myocardial fibrosis in Ace2(-/y) mice linked with enhancement of plasma Ang-(1-7) level and downregulation of AT1 receptor in heart. Consistent with attenuation of myocardial fibrosis and ultrastructure injury, the myocardial CVF and levels of ANF, TGFß1, CTGF, collagen I, collagen III and phosphorylated ERK1/2 were lower, and expression of PPARγ was higher in ACE2KO mice in response to irbesartan treatment, without affecting cardiac expression of PPARα, PPARδ, ß-myosin heavy chain, TGFß2 and fibronectin. CONCLUSIONS: We conclude that irbesartan prevents ACE2 deficiency-mediated pathological hypertrophy and myocardial fibrosis in ACE2 mutant mice via activation of the PPARγ signaling and suppression of the TGFß-CTGF-ERK signaling, resulting in attenuation of myocardial injury. Drugs targeting ACE2 and PPARγ represent potential candidates to prevent and treat myocardial injury and related cardiac disorders.