Integrated miRNA-mRNA networks underlie attenuation of chronic β-adrenergic stimulation-induced cardiac remodeling by minocycline

Adverse cardiac remodeling contributes to heart failure development and progression, partly due to inappropriate sympathetic nervous system activation. Although β-adrenergic receptor (β-AR) blockade is a common heart failure therapy, not all patients respond, prompting exploration of alternative treatments. Minocycline, an FDA-approved antibiotic, has pleiotropic properties beyond antimicrobial action. Recent evidence suggests it may alter gene expression via changes in miRNA expression. Thus, we hypothesized that minocycline could prevent adverse cardiac remodeling induced by the β-AR agonist isoproterenol, involving miRNA-mRNA transcriptome alterations. Male C57BL/6J mice received isoproterenol (30 mg/kg/day sc) or vehicle via osmotic minipump for 21 days, along with daily minocycline (50 mg/kg ip) or sterile saline. Isoproterenol induced cardiac hypertrophy without altering cardiac function, which minocycline prevented. Total mRNA sequencing revealed isoproterenol altering gene networks associated with inflammation and metabolism, with fibrosis activation predicted by integrated miRNA-mRNA sequencing, involving miR-21, miR-30a, miR-34a, miR-92a, and miR-150, among others. Conversely, the cardiac miRNA-mRNA transcriptome predicted fibrosis inhibition in minocycline-treated mice, involving antifibrotic shifts in Atf3 and Itgb6 gene expression associated with miR-194 upregulation. Picrosirius red staining confirmed isoproterenol-induced cardiac fibrosis, prevented by minocycline. These results demonstrate minocycline's therapeutic potential in attenuating adverse cardiac remodeling through miRNA-mRNA-dependent mechanisms, especially in reducing cardiac fibrosis. NEW & NOTEWORTHY We demonstrate that minocycline treatment prevents cardiac hypertrophy and fibrotic remodeling induced by chronic β-adrenergic stimulation by inducing antifibrotic shifts in the cardiac miRNA-mRNA transcriptome.

Empagliflozin Reverses Oxidized LDL-Induced RECK Suppression, Cardiotrophin-1 Expression, MMP Activation, and Human Aortic Smooth Muscle Cell Proliferation and Migration

Persistent oxidative stress and inflammation contribute causally to smooth muscle cell (SMC) proliferation and migration, the characteristic features of vascular proliferative diseases. Oxidatively modified low-density lipoproteins (OxLDL) elevate oxidative stress levels, inflammatory responses, and matrix metallopeptidase (MMP) activation, resulting ultimately in SMC migration, proliferation, and phenotype change. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a membrane-anchored MMP inhibitor. Empagliflozin is an SGLT2 inhibitor and exerts pleiotropic cardiovascular protective effects, including antioxidant and anti-inflammatory effects. Here, we investigated (i) whether OxLDL regulates RECK expression, (ii) whether ectopic expression of RECK reverses OxLDL-induced SMC migration and proliferation, and (iii) whether pretreatment with empagliflozin reverses OxLDL-induced RECK suppression, MMP activation, and SMC migration, proliferation, and differentiation. Indeed, results show that OxLDL at pathophysiological concentration promotes SMC migration and proliferation via NF-κB/miR-30b-dependent RECK suppression. Moreover, OxLDL changed the SMC phenotype to a more pro-inflammatory type, and this effect is blunted by RECK overexpression. Further, treatment with empagliflozin reversed OxLDL-induced miR-30b induction, RECK suppression, MMP activation, SMC migration, proliferation, and proinflammatory phenotype changes. OxLDL-induced cardiotrophin (CT)-1 expression and CT-1 stimulated SMC proliferation and migration in part via leukemia inhibitory factor receptor (LIFR) and glycoprotein 130 (gp130). Ectopic expression of RECK inhibited these effects by physically associating with LIFR and gp130, as evidenced by immunoprecipitation/immunoblotting and double immunofluorescence. Importantly, empagliflozin inhibited CT-1-induced mitogenic and migratory effects. Together, these results suggest the therapeutic potential of sustaining RECK expression or empagliflozin in vascular diseases characterized by SMC proliferation and migration.

Cardiovascular Protective Effects of NP-6A4, a Drug with the FDA Designation for Pediatric Cardiomyopathy, in Female Rats with Obesity and Pre-Diabetes

BACKGROUND

Obese and pre-diabetic women have a higher risk for cardiovascular death than age-matched men with the same symptoms, and there are no effective treatments. We reported that obese and pre-diabetic female Zucker Diabetic Fatty (ZDF-F) rats recapitulate metabolic and cardiac pathology of young obese and pre-diabetic women and exhibit suppression of cardio-reparative AT2R. Here, we investigated whether NP-6A4, a new AT2R agonist with the FDA designation for pediatric cardiomyopathy, mitigate heart disease in ZDF-F rats by restoring AT2R expression.

METHODS

ZDF-F rats on a high-fat diet (to induce hyperglycemia) were treated with saline, NP-6A4 (10 mg/kg/day), or NP-6A4 + PD123319 (AT2R-specific antagonist, 5 mg/kg/day) for 4 weeks (n = 21). Cardiac functions, structure, and signaling were assessed by echocardiography, histology, immunohistochemistry, immunoblotting, and cardiac proteome analysis.

RESULTS

NP-6A4 treatment attenuated cardiac dysfunction, microvascular damage (-625%) and cardiomyocyte hypertrophy (-263%), and increased capillary density (200%) and AT2R expression (240%) (p < 0.05). NP-6A4 activated a new 8-protein autophagy network and increased autophagy marker LC3-II but suppressed autophagy receptor p62 and autophagy inhibitor Rubicon. Co-treatment with AT2R antagonist PD123319 suppressed NP-6A4's protective effects, confirming that NP-6A4 acts through AT2R. NP-6A4-AT2R-induced cardioprotection was independent of changes in body weight, hyperglycemia, hyperinsulinemia, or blood pressure.

CONCLUSIONS

Cardiac autophagy impairment underlies heart disease induced by obesity and pre-diabetes, and there are no drugs to re-activate autophagy. We propose that NP-6A4 can be an effective drug to reactivate cardiac autophagy and treat obesity- and pre-diabetes-induced heart disease, particularly for young and obese women.

Multi-omic analysis of the cardiac cellulome defines a vascular contribution to cardiac diastolic dysfunction in obese female mice

Coronary microvascular dysfunction (CMD) is associated with cardiac dysfunction and predictive of cardiac mortality in obesity, especially in females. Clinical data further support that CMD associates with development of heart failure with preserved ejection fraction and that mineralocorticoid receptor (MR) antagonism may be more efficacious in obese female, versus male, HFpEF patients. Accordingly, we examined the impact of smooth muscle cell (SMC)-specific MR deletion on obesity-associated coronary and cardiac diastolic dysfunction in female mice. Obesity was induced in female mice via western diet (WD) feeding alongside littermates fed standard diet. Global MR blockade with spironolactone prevented coronary and cardiac dysfunction in obese females and specific deletion of SMC-MR was sufficient to prevent obesity-associated coronary and cardiac diastolic dysfunction. Cardiac gene expression profiling suggested reduced cardiac inflammation in WD-fed mice with SMC-MR deletion independent of blood pressure, aortic stiffening, and cardiac hypertrophy. Further mechanistic studies utilizing single-cell RNA sequencing of non-cardiomyocyte cell populations revealed novel impacts of SMC-MR deletion on the cardiac cellulome in obese mice. Specifically, WD feeding induced inflammatory gene signatures in non-myocyte populations including B/T cells, macrophages, and endothelium as well as increased coronary VCAM-1 protein expression, independent of cardiac fibrosis, that was prevented by SMC-MR deletion. Further, SMC-MR deletion induced a basal reduction in cardiac mast cells and prevented WD-induced cardiac pro-inflammatory chemokine expression and leukocyte recruitment. These data reveal a central role for SMC-MR signaling in obesity-associated coronary and cardiac dysfunction, thus supporting the emerging paradigm of a vascular origin of cardiac dysfunction in obesity.

Endothelial cell-specific mineralocorticoid receptor activation promotes diastolic dysfunction in diet-induced obese male mice

Widespread consumption of diets high in fat and fructose (Western diet, WD) has led to increased prevalence of obesity and diastolic dysfunction (DD). DD is a prominent feature of heart failure with preserved ejection fraction (HFpEF). However, the underlying mechanisms of DD are poorly understood, and treatment options are still limited. We have previously shown that deletion of the cell-specific mineralocorticoid receptor in endothelial cells (ECMR) abrogates DD induced by WD feeding in female mice. However, the specific role of ECMR activation in the pathogenesis of DD in male mice has not been clarified. Therefore, we fed 4-wk-old ECMR knockout (ECMRKO) male mice and littermates (LM) with either a WD or chow diet (CD) for 16 wk. WD feeding resulted in DD characterized by increased left ventricle (LV) filling pressure (E/e') and diastolic stiffness [E/e'/LV inner diameter at end diastole (LVIDd)]. Compared with CD, WD in LM resulted in increased myocardial macrophage infiltration, oxidative stress, and increased myocardial phosphorylation of Akt, in concert with decreased phospholamban phosphorylation. WD also resulted in focal cardiomyocyte remodeling, characterized by areas of sarcomeric disorganization, loss of mitochondrial electron density, and mitochondrial fragmentation. Conversely, WD-induced DD and associated biochemical and structural abnormalities were prevented by ECMR deletion. In contrast with our previously reported observations in females, WD-fed male mice exhibited enhanced Akt signaling and a lower magnitude of cardiac injury. Collectively, our data support a critical role for ECMR in obesity-induced DD and suggest critical mechanistic differences in the genesis of DD between males and females.

Abstract P3126: Sphingomyelinase Participates Diet - Induced Increases In Aortic Stiffness And Cardiac Dysfunction

Excessive accumulation of ceramides induces mitochondria dysfunction and promotes toxicity in multiple types of cells, including endothelial cells and cardiomyocytes. Neutral sphingomyelinase (nSMase) is thought to increase ceramide levels through sphingomyelin hydrolysis, and the resultant increase in ceramides plays a role in the pathogenesis of a number of disorders, such as atherosclerosis and heart failure. While inhibition of nSMase attenuates the progression of atherosclerosis and heart failure, little is known regarding its role in correcting impaired metabolic signaling, arterial dysfunction and metabolic cardiomyopathy. Accordingly, we hypothesized that nSMase inhibition with GW4869, attenuates Western diet (WD) - induced increases in aortic stiffness and cardiac dysfunction through effects on pathways which lead to oxidative stress and inflammation. Six week-old female C57BL/6L mice were fed either a WD containing excess fat (46%) and fructose (17.5%) for 16 weeks or a standard chow diet (CD). Mice were treated with GW4869 (2.0 μg/g body weight, intraperitoneal injection every 48 hours for 12 weeks). WD consumption increased plasma nSMase activation and tissue nSMase2 expression in concert with aortic stiffening and impaired vasorelaxation as determined by pulse wave velocity (PWV) and wire myography, respectively. WD fed mice exhibited reduced EF (systolic dysfunction) and increased E/E’ and IVRT (diastolic dysfunction) determined by in vivo Doppler ultrasound. Moreover, these functional abnormalities were associated with attenuated AMP-activated protein kinase, Sirtuin 1, and endothelial nitric oxide synthase activation. These functional and metabolic abnormalities were blunted by in vivo GW4869 treatment. These findings indicate that targeting nSMase prevents diet - induced aortic stiffening and cardiac dysfunction by correction of impaired metabolic signaling.

Inhibition of sphingomyelinase attenuates diet - Induced increases in aortic stiffness

Sphingomyelinases ensure ceramide production and play an integral role in cell turnover, inward budding of vesicles and outward release of exosomes. Recent data indicate a unique role for neutral sphingomyelinase (nSMase) in the control of ceramide-dependent exosome release and inflammatory pathways. Further, while inhibition of nSMase in vascular tissue attenuates the progression of atherosclerosis, little is known regarding its role on metabolic signaling and arterial vasomotor function. Accordingly, we hypothesized that nSMase inhibition with GW4869, would attenuate Western diet (WD) - induced increases in aortic stiffness through alterations in pathways which lead to oxidative stress, inflammation and vascular remodeling. Six week-old female C57BL/6L mice were fed either a WD containing excess fat (46%) and fructose (17.5%) for 16 weeks or a standard chow diet (CD). Mice were variably treated with GW4869 (2.0 μg/g body weight, intraperitoneal injection every 48 h for 12 weeks). WD feeding increased nSMase2 expression and activation while causing aortic stiffening and impaired vasorelaxation as determined by pulse wave velocity (PWV) and wire myography, respectively. Moreover, these functional abnormalities were associated with aortic remodeling and attenuated AMP-activated protein kinase, Sirtuin 1, and endothelial nitric oxide synthase activation. GW4869 treatment prevented the WD-induced increases in nSMase activation, PWV, and impaired endothelium dependent/independent vascular relaxation. GW4869 also inhibited WD-induced aortic CD36 expression, lipid accumulation, oxidative stress, inflammatory responses, as well as aortic remodeling. These findings indicate that targeting nSMase prevents diet - induced aortic stiffening and impaired vascular relaxation by attenuating oxidative stress, inflammation and adverse vascular remodeling.

Cystamine reduces vascular stiffness in Western diet-fed female mice

Consumption of diets high in fat, sugar, and salt (Western diet, WD) is associated with accelerated arterial stiffening, a major independent risk factor for cardiovascular disease (CVD). Women with obesity are more prone to develop arterial stiffening leading to more frequent and severe CVD compared with men. As tissue transglutaminase (TG2) has been implicated in vascular stiffening, our goal herein was to determine the efficacy of cystamine, a nonspecific TG2 inhibitor, at reducing vascular stiffness in female mice chronically fed a WD. Three experimental groups of female mice were created. One was fed regular chow diet (CD) for 43 wk starting at 4 wk of age. The second was fed a WD for the same 43 wk, whereas a third cohort was fed WD, but also received cystamine (216 mg/kg/day) in the drinking water during the last 8 wk on the diet (WD + C). All vascular stiffness parameters assessed, including aortic pulse wave velocity and the incremental modulus of elasticity of isolated femoral and mesenteric arteries, were significantly increased in WD- versus CD-fed mice, and reduced in WD + C versus WD-fed mice. These changes coincided with respectively augmented and diminished vascular wall collagen and F-actin content, with no associated effect in blood pressure. In cultured human vascular smooth muscle cells, cystamine reduced TG2 activity, F-actin:G-actin ratio, collagen compaction capacity, and cellular stiffness. We conclude that cystamine treatment represents an effective approach to reduce vascular stiffness in female mice in the setting of WD consumption, likely because of its TG2 inhibitory capacity.NEW & NOTEWORTHY This study evaluates the novel role of transglutaminase 2 (TG2) inhibition to directly treat vascular stiffness. Our data demonstrate that cystamine, a nonspecific TG2 inhibitor, improves vascular stiffness induced by a diet rich in fat, fructose, and salt. This research suggests that TG2 inhibition might bear therapeutic potential to reduce the disproportionate burden of cardiovascular disease in females in conditions of chronic overnutrition.

Abstract P274: Inhibition Of Abnormal Exosome Release Prevents Excessive Aortic Stiffness And Relaxation Dysfunction In Diet-induced Obesity

Interactions between over-nutrition and abnormal exosome release impact insulin sensitivity and the development of cardiovascular disease (CVD). Recent data have shown that exosomes can be released from various cell types, including adipocytes and vascular cells, and that they exist in body fluids and tissues functioning as mediators of cell-cell communication. However, the specific role of exosomes in diet-induced excessive vascular stiffness and hypertension has not been explored. Accordingly, we hypothesized that abnormal release of exosomes contributes to western diet (WD)- induced aortic stiffening and impaired vascular diastolic relaxation. We further posited that GW4869, an antagonist of neutral sphingomyelinase 2 (nSMase2) which promotes exosome production and release, would prevent WD-induced aortic stiffening and impaired vascular relaxation. Six week-old female C57BL/6L mice were fed a mouse chow (CD) or WD containing excess fat (46%) and fructose (17.5%) for 16 weeks with or without GW4849. To this point, 200 μl of 0.3 mg/mL GW4869 in 0.9% normal saline (60 μg/mouse; 2-2.5 μg/g body weight) was injected intraperitoneally every 48 hours for 12 weeks. 16 weeks of WD induced an increase of aortic stiffness as examined by pulse wave velocity (PWV) and impaired the aortic vasodilation responses to acetylcholine (Ach) and sodium nitroprusside (SNP) (10 -9 -10 -4 mol/L). However, GW4869 treatment prevented the WD-induced excessive aortic stiffness, as well as impairment of endothelium dependent/independent vascular relaxation. There were no significant differences in blood pressure between each group examined by tail cuff blood pressure measurement. These findings support the hypothesis that abnormal release of exosomes play an important role in WD-induced excessive aortic stiffness, impaired vascular relaxation and CVD in diet-induced obesity.

Suppression of Inflammatory Cardiac Cytokine Network in Rats with Untreated Obesity and Pre-Diabetes by AT2 Receptor Agonist NP-6A4

Obesity affects over 42% of the United States population and exacerbates heart disease, the leading cause of death in men and women. Obesity also increases pro-inflammatory cytokines that cause chronic tissue damage to vital organs. The standard-of-care does not sufficiently attenuate these inflammatory sequelae. Angiotensin II receptor AT2R is an anti-inflammatory and cardiovascular protective molecule; however, AT2R agonists are not used in the clinic to treat heart disease. NP-6A4 is a new AT2R peptide agonist with an FDA orphan drug designation for pediatric cardiomyopathy. NP-6A4 increases AT2R expression (mRNA and protein) and nitric oxide generation in human cardiovascular cells. AT2R-antagonist PD123319 and AT2RSiRNA suppress NP-6A4-effects indicating that NP-6A4 acts through AT2R. To determine whether NP-6A4 would mitigate cardiac damage from chronic inflammation induced by untreated obesity, we investigated the effects of 2-weeks NP-6A4 treatment (1.8 mg/kg delivered subcutaneously) on cardiac pathology of male Zucker obese (ZO) rats that display obesity, pre-diabetes and cardiac dysfunction. NP-6A4 attenuated cardiac diastolic and systolic dysfunction, cardiac fibrosis and cardiomyocyte hypertrophy, but increased myocardial capillary density. NP-6A4 treatment suppressed tubulointerstitial injury marker urinary β-NAG, and liver injury marker alkaline phosphatase in serum. These protective effects of NP-6A4 occurred in the presence of obesity, hyperinsulinemia, hyperglycemia, and hyperlipidemia, and without modulating blood pressure. NP-6A4 increased expression of AT2R (consistent with human cells) and cardioprotective erythropoietin (EPO) and Notch1 in ZO rat heart, but suppressed nineteen inflammatory cytokines. Cardiac miRNA profiling and in silico analysis showed that NP-6A4 activated a unique miRNA network that may regulate expression of AT2R, EPO, Notch1 and inflammatory cytokines, and mitigate cardiac pathology. Seventeen pro-inflammatory and pro-fibrotic cytokines that increase during lethal cytokine storms caused by infections such as COVID-19 were among the cytokines suppressed by NP-6A4 treatment in ZO rat heart. Thus, NP-6A4 activates a novel anti-inflammatory network comprised of 21 proteins in the heart that was not reported previously. Since NP-6A4's unique mode of action suppresses pro-inflammatory cytokine network and attenuates myocardial damage, it can be an ideal adjuvant drug with other anti-glycemic, anti-hypertensive, standard-of-care drugs to protect the heart tissues from pro-inflammatory and pro-fibrotic cytokine attack induced by obesity.

Sacubitril/valsartan inhibits obesity-associated diastolic dysfunction through suppression of ventricular-vascular stiffness

OBJECTIVE

Cardiac diastolic dysfunction (DD) and arterial stiffness are early manifestations of obesity-associated prediabetes, and both serve as risk factors for the development of heart failure with preserved ejection fraction (HFpEF). Since the incidence of DD and arterial stiffness are increasing worldwide due to exponential growth in obesity, an effective treatment is urgently needed to blunt their development and progression. Here we investigated whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses DD and arterial stiffness in an animal model of prediabetes more effectively than valsartan monotherapy.

METHODS

Sixteen-week-old male Zucker Obese rats (ZO; n = 64) were assigned randomly to 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val; 68 mg•kg-1•day-1; ZOSV); Group 3: valsartan (31 mg•kg-1•day-1; ZOV) and Group 4: hydralazine, an anti-hypertensive drug (30 mg•kg-1•day-1; ZOH). Six Zucker Lean (ZL) rats that received saline only (Group 5) served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage.

RESULTS

Sac/val improved echocardiographic parameters of impaired left ventricular (LV) stiffness in untreated ZO rats, without altering the amount of food consumed or body weight gained. In addition to improving DD, sac/val decreased aortic stiffness and reversed impairment in nitric oxide-induced vascular relaxation in ZO rats. However, sac/val had no impact on LV hypertrophy. Notably, sac/val was more effective than val in ameliorating DD. Although, hydralazine was as effective as sac/val in improving these parameters, it adversely affected LV mass index. Further, cytokine array revealed distinct effects of sac/val, including marked suppression of Notch-1 by both valsartan and sac/val, suggesting that cardiovascular protection afforded by both share some common mechanisms; however, sac/val, but not val, increased IL-4, which is increasingly recognized for its cardiovascular protection, possibly contributing, in part, to more favorable effects of sac/val over val alone in improving obesity-associated DD.

CONCLUSIONS

These studies suggest that sac/val is superior to val in reversing obesity-associated DD. It is an effective drug combination to blunt progression of asymptomatic DD and vascular stiffness to HFpEF development in a preclinical model of obesity-associated prediabetes.

The SGLT2 inhibitor Empagliflozin attenuates interleukin-17A-induced human aortic smooth muscle cell proliferation and migration by targeting TRAF3IP2/ROS/NLRP3/Caspase-1-dependent IL-1β and IL-18 secretion

Chronic inflammation and persistent oxidative stress contribute to the development and progression of vascular proliferative diseases. We hypothesized that the proinflammatory cytokine interleukin (IL)-17A induces oxidative stress and amplifies inflammatory signaling in human aortic smooth muscle cells (SMC) via TRAF3IP2-mediated NLRP3/caspase-1-dependent mitogenic and migratory proinflammatory cytokines IL-1β and IL-18. Further, we hypothesized that these maladaptive changes are prevented by empagliflozin (EMPA), an SGLT2 (Sodium/Glucose Cotransporter 2) inhibitor. Supporting our hypotheses, exposure of cultured SMC to IL-17A promoted proliferation and migration via TRAF3IP2, TRAF3IP2-dependent superoxide and hydrogen peroxide production, NLRP3 expression, caspase-1 activation, and IL-1β and IL-18 secretion. Furthermore, NLRP3 knockdown, caspase-1 inhibition, and pretreatment with IL-1β and IL-18 neutralizing antibodies and IL-18BP, each attenuated IL-17A-induced SMC migration and proliferation. Importantly, SMC express SGLT2, and pre-treatment with EMPA attenuated IL-17A/TRAF3IP2-dependent oxidative stress, NLRP3 expression, caspase-1 activation, IL-1β and IL-18 secretion, and SMC proliferation and migration. Importantly, silencing SGLT2 attenuated EMPA-mediated inhibition of IL-17A-induced cytokine secretion and SMC proliferation and migration. EMPA exerted these beneficial antioxidant, anti-inflammatory, anti-mitogenic and anti-migratory effects under normal glucose conditions and without inducing cell death. These results suggest the therapeutic potential of EMPA in vascular proliferative diseases.

Endothelial sodium channel activation promotes cardiac stiffness and diastolic dysfunction in Western diet fed female mice

OBJECTIVE

Obesity is associated with myocardial fibrosis and impaired diastolic relaxation, abnormalities that are especially prevalent in women. Normal coronary vascular endothelial function is integral in mediating diastolic relaxation, and recent work suggests increased activation of the endothelial cell (EC) mineralocorticoid receptor (ECMR) is associated with impaired diastolic relaxation. As the endothelial Na⁺ channel (EnNaC) is a downstream target of the ECMR, we sought to determine whether EC-specific deletion of the critical alpha subunit, αEnNaC, would prevent diet induced-impairment of diastolic relaxation in female mice.

METHODS AND MATERIALS

Female αEnNaC KO mice and littermate controls were fed a Western diet (WD) high in fat (46%), fructose corn syrup (17.5%) and sucrose (17.5%) for 12-16 weeks. Measurements were conducted for in vivo cardiac function, in vitro cardiomyocyte stiffness and EnNaC activity in primary cultured ECs. Additional biochemical studies examined indicators of oxidative stress, including aspects of antioxidant Nrf2 signaling, in cardiac tissue.

RESULTS

Deletion of αEnNaC in female mice fed a WD significantly attenuated WD mediated impairment in diastolic relaxation. Improved cardiac relaxation was accompanied by decreased EnNaC-mediated Na⁺ currents in ECs and reduced myocardial oxidative stress. Further, deletion of αEnNaC prevented WD-mediated increases in isolated cardiomyocyte stiffness.

CONCLUSION

Collectively, these findings support the notion that WD feeding in female mice promotes activation of EnNaC in the vasculature leading to increased cardiomyocyte stiffness and diastolic dysfunction.

SAT-LB97 MiRNA-99a and mTOR2 Mediate Enhanced Endothelial Mineralocorticoid Receptor Signaling-Induced Activation of Sodium Channel and Endothelium Stiffness

In diet induced obesity enhanced endothelial cell (EC) mineralocorticoid receptor (MR) (ECMR) and downstream sodium channel (EnNaC) activity increases oxidative stress and inflammation, thereby promoting vascular stiffness and associated impaired endothelial mediated relaxation. For example, consumption of a Western diet (WD) containing excess fat (46%) and fructose (17.5%) for 16 weeks elevated plasma aldosterone levels and increased vascular MR expression in conjunction with increased endothelial and vascular stiffness in female mice. EC specific deletion of either the ECMR or EnNaC significantly attenuated this diet induced endothelial/vascular stiffness. Emerging information suggests that abnormal expression of miR-99a may be involved in these processes. To this point, we recently observed that aldosterone (10^-7 mol/L) causes a reduction in miR-99a that was prevented by the MR antagonist, spironolactone (10µM) in in vitro ECs. By using RNA sequencing, we also demonstrated that ECMR activation reduced arterial miR-99a expression in diet induced obesity. Since the mammalian target of rapamycin (mTOR2)/SGK1 signaling pathway is involved in aldosterone activation of ENaC we then explored the effects of miR-99a on mTOR2 expression. Indeed, miR-99a reduced mTOR2. We further observed that inhibition of mTOR2 with PP242 inhibited EnNaC activity as determined by patch clamping of ECs. Collectively these data suggest that consumption of a WD induced ECMR activation and increased EnNaC activity and endothelial stiffness, in part, by reducing the tonic inhibitory effects exerted by miR-99a on mTOR2 mediated EnNaC activation.

Western diet induces renal artery endothelial stiffening that is dependent on the epithelial Na+ channel

Consumption of a Western diet (WD) induces central aortic stiffening that contributes to the transmittance of pulsatile blood flow to end organs, including the kidney. Our recent work supports that endothelial epithelial Na⁺ channel (EnNaC) expression and activation enhances aortic endothelial cell stiffening through reductions in endothelial nitric oxide (NO) synthase (eNOS) and bioavailable NO that result in inflammatory and oxidant responses and perivascular fibrosis. However, the role that EnNaC activation has on endothelial responses in the renal circulation remains unknown. We hypothesized that cell-specific deletion of the α-subunit of EnNaC would prevent WD-induced central aortic stiffness and protect the kidney from endothelial dysfunction and vascular stiffening. Twenty-eight-week-old female αEnNaC knockout and wild-type mice were fed either mouse chow or WD containing excess fat (46%), sucrose, and fructose (17.5% each). WD feeding increased fat mass, indexes of vascular stiffening in the aorta and renal artery (in vivo pulse wave velocity and ultrasound), and renal endothelial cell stiffening (ex vivo atomic force microscopy). WD further impaired aortic endothelium-dependent relaxation and renal artery compliance (pressure myography) without changes in blood pressure. WD-induced renal arterial stiffening occurred in parallel to attenuated eNOS activation, increased oxidative stress, and aortic and renal perivascular fibrosis. αEnNaC deletion prevented these abnormalities and support a novel mechanism by which WD contributes to renal arterial stiffening that is endothelium and Na⁺ channel dependent. These results demonstrate that cell-specific EnNaC is important in propagating pulsatility into the renal circulation, generating oxidant stress, reduced bioavailable NO, and renal vessel wall fibrosis and stiffening.

Empagliflozin reduces high glucose-induced oxidative stress and miR-21-dependent TRAF3IP2 induction and RECK suppression, and inhibits human renal proximal tubular epithelial cell migration and epithelial-to-mesenchymal transition

Proximal tubular epithelial cells (PTEC) in the S1 segment of the kidney abundantly express sodium-glucose co-transporters (SGLT) that play a critical role in whole body glucose homeostasis. We recently reported suppression of RECK (Reversion Inducing Cysteine Rich Protein with Kazal Motifs), a membrane anchored endogenous MMP inhibitor and anti-fibrotic mediator, in the kidneys of db/db mice, a model of diabetic kidney disease (DKD), as well as in high glucose (HG) treated human kidney proximal tubule cells (HK-2). We further demonstrated that empagliflozin (EMPA), an SGLT2 inhibitor, reversed these effects. Little is known regarding the mechanisms underlying RECK suppression under hyperglycemic conditions, and its rescue by EMPA. Consistent with our previous studies, HG (25 mM) suppressed RECK expression in HK-2 cells. Further mechanistic investigations revealed that HG induced superoxide and hydrogen peroxide generation, oxidative stress-dependent TRAF3IP2 upregulation, NF-κB and p38 MAPK activation, inflammatory cytokine expression (IL-1β, IL-6, TNF-α, and MCP-1), miR-21 induction, MMP2 activation, and RECK suppression. Moreover, RECK gain-of-function inhibited HG-induced MMP2 activation and HK-2 cell migration. Similar to HG, advanced glycation end products (AGE) induced TRAF3IP2 and suppressed RECK, effects that were inhibited by EMPA. Importantly, EMPA treatment ameliorated all of these deleterious effects, and inhibited epithelial-to-mesenchymal transition (EMT) and HK-2 cell migration. Collectively, these findings indicate that hyperglycemia and associated AGE suppress RECK expression via oxidative stress/TRAF3IP2/NF-κB and p38 MAPK/miR-21 induction. Furthermore, these results suggest that interventions aimed at restoring RECK or inhibiting SGLT2 have the potential to treat kidney inflammatory response/fibrosis and nephropathy under chronic hyperglycemic conditions, such as DKD.

The combination of a neprilysin inhibitor (sacubitril) and angiotensin-II receptor blocker (valsartan) attenuates glomerular and tubular injury in the Zucker Obese rat

OBJECTIVE

Diabetic nephropathy (DN) is characterized by glomerular and tubulointerstitial injury, proteinuria and remodeling. Here we examined whether the combination of an inhibitor of neprilysin (sacubitril), a natriuretic peptide-degrading enzyme, and an angiotensin II type 1 receptor blocker (valsartan), suppresses renal injury in a pre-clinical model of early DN more effectively than valsartan monotherapy.

METHODS

Sixty-four male Zucker Obese rats (ZO) at 16 weeks of age were distributed into 4 different groups: Group 1: saline control (ZOC); Group 2: sacubitril/valsartan (sac/val) (68 mg kg^-1 day^-1; ZOSV); and Group 3: valsartan (val) (31 mg kg^-1 day^-1; ZOV). Group 4 received hydralazine, an anti-hypertensive drug (30 mg kg^-1 day^-1, ZOH). Six Zucker Lean (ZL) rats received saline (Group 5) and served as lean controls (ZLC). Drugs were administered daily for 10 weeks by oral gavage.

RESULTS

Mean arterial pressure (MAP) increased in ZOC (+ 28%), but not in ZOSV (- 4.2%), ZOV (- 3.9%) or ZOH (- 3.7%), during the 10 week-study period. ZOC were mildly hyperglycemic, hyperinsulinemic and hypercholesterolemic. ZOC exhibited proteinuria, hyperfiltration, elevated renal resistivity index (RRI), glomerular mesangial expansion and podocyte foot process flattening and effacement, reduced nephrin and podocin expression, tubulointerstitial and periarterial fibrosis, increased NOX2, NOX4 and AT₁R expression, glomerular and tubular nitroso-oxidative stress, with associated increases in urinary markers of tubular injury. None of the drugs reduced fasting glucose or HbA1c. Hypercholesterolemia was reduced in ZOSV (- 43%) and ZOV (- 34%) (p < 0.05), but not in ZOH (- 13%) (ZOSV > ZOV > ZOH). Proteinuria was ameliorated in ZOSV (- 47%; p < 0.05) and ZOV (- 30%; p > 0.05), but was exacerbated in ZOH (+ 28%; p > 0.05) (ZOSV > ZOV > ZOH). Compared to ZOC, hyperfiltration was improved in ZOSV (p < 0.05 vs ZOC), but not in ZOV or ZOH. None of the drugs improved RRI. Mesangial expansion was reduced by all 3 treatments (ZOV > ZOSV > ZOH). Importantly, sac/val was more effective in improving podocyte and tubular mitochondrial ultrastructure than val or hydralazine (ZOSV > ZOV > ZOH) and this was associated with increases in nephrin and podocin gene expression in ZOSV (p < 0.05), but not ZOV or ZOH. Periarterial and tubulointerstitial fibrosis and nitroso-oxidative stress were reduced in all 3 treatment groups to a similar extent. Of the eight urinary proximal tubule cell injury markers examined, five were elevated in ZOC (p < 0.05). Clusterin and KIM-1 were reduced in ZOSV (p < 0.05), clusterin alone was reduced in ZOV and no markers were reduced in ZOH (ZOSV > ZOV > ZOH).

CONCLUSIONS

Compared to val monotherapy, sac/val was more effective in reducing proteinuria, renal ultrastructure and tubular injury in a clinically relevant animal model of early DN. More importantly, these renoprotective effects were independent of improvements in blood pressure, glycemia and nitroso-oxidative stress. These novel findings warrant future clinical investigations designed to test whether sac/val may offer renoprotection in the setting of DN.

Empagliflozin Ameliorates Type 2 Diabetes-Induced Ultrastructural Remodeling of the Neurovascular Unit and Neuroglia in the Female db/db Mouse

Type 2 diabetes is associated with diabetic cognopathy. Anti-hyperglycemic sodium glucose transporter 2 (SGLT2) inhibitors have shown promise in reducing cognitive impairment in mice with type 2 diabetes mellitus. We recently described marked ultrastructural (US) remodeling of the neurovascular unit (NVU) in type 2 diabetic db/db female mice. Herein, we tested whether the SGLT-2 inhibitor, empagliflozin (EMPA), protects the NVU from abnormal remodeling in cortical gray and subcortical white matter. Ten-week-old female wild-type and db/db mice were divided into lean controls (CKC, n = 3), untreated db/db (DBC, n = 3), and EMPA-treated db/db (DBE, n = 3). Empagliflozin was added to mouse chow to deliver 10 mg kg⁻¹ day⁻¹ and fed for ten weeks, initiated at 10 weeks of age. Brains from 20-week-old mice were immediately immersion fixed for transmission electron microscopic study. Compared to CKC, DBC exhibited US abnormalities characterized by mural endothelial cell tight and adherens junction attenuation and/or loss, pericyte attenuation and/or loss, basement membrane thickening, glia astrocyte activation with detachment and retraction from mural cells, microglia cell activation with aberrant mitochondria, and oligodendrocyte–myelin splitting, disarray, and axonal collapse. We conclude that these abnormalities in the NVU were prevented in DBE. Empagliflozin may provide neuroprotection in the diabetic brain.

Glycemic control by the SGLT2 inhibitor empagliflozin decreases aortic stiffness, renal resistivity index and kidney injury

Background

Arterial stiffness is emerging as an independent risk factor for the development of chronic kidney disease. The sodium glucose co-transporter 2 (SGLT2) inhibitors, which lower serum glucose by inhibiting SGLT2-mediated glucose reabsorption in renal proximal tubules, have shown promise in reducing arterial stiffness and the risk of cardiovascular and kidney disease in individuals with type 2 diabetes mellitus. Since hyperglycemia contributes to arterial stiffness, we hypothesized that the SGLT2 inhibitor empagliflozin (EMPA) would improve endothelial function, reduce aortic stiffness, and attenuate kidney disease by lowering hyperglycemia in type 2 diabetic female mice (db/db).

Materials/methods

Ten-week-old female wild-type control (C57BLKS/J) and db/db (BKS.Cg-Dock7m+/+Leprdb/J) mice were divided into three groups: lean untreated controls (CkC, n = 17), untreated db/db (DbC, n = 19) and EMPA-treated db/db mice (DbE, n = 19). EMPA was mixed with normal mouse chow at a concentration to deliver 10 mg kg⁻¹ day⁻¹, and fed for 5 weeks, initiated at 11 weeks of age.

Results

Compared to CkC, DbC showed increased glucose levels, blood pressure, aortic and endothelial cell stiffness, and impaired endothelium-dependent vasorelaxation. Furthermore, DbC exhibited impaired activation of endothelial nitric oxide synthase, increased renal resistivity and pulsatility indexes, enhanced renal expression of advanced glycation end products, and periarterial and tubulointerstitial fibrosis. EMPA promoted glycosuria and blunted these vascular and renal impairments, without affecting increases in blood pressure. In addition, expression of “reversion inducing cysteine rich protein with Kazal motifs” (RECK), an anti-fibrotic mediator, was significantly suppressed in DbC kidneys and partially restored by EMPA. Confirming the in vivo data, EMPA reversed high glucose-induced RECK suppression in human proximal tubule cells.

Conclusions

Empagliflozin ameliorates kidney injury in type 2 diabetic female mice by promoting glycosuria, and possibly by reducing systemic and renal artery stiffness, and reversing RECK suppression.

The role of dipeptidylpeptidase-4 inhibitors in management of cardiovascular disease in diabetes; focus on linagliptin

Multiple population based analyses have demonstrated a high incidence of cardiovascular disease (CVD) and cardiovascular (CV) mortality in subjects with T2DM that reduces life expectancy by as much as 15 years. Importantly, the CV system is particularly sensitive to the metabolic and immune derangements present in obese pre-diabetic and diabetic individuals; consequently, CV dysfunction is often the initial CV derangement to occur and promotes the progression to end organ/tissue damage in T2DM. Specifically, diabetic CVD can manifest as microvascular complications, such as nephropathy, retinopathy, and neuropathy, as well as, macrovascular impairments, including ischemic heart disease, peripheral vascular disease, and cerebrovascular disease. Despite some progress in prevention and treatment of CVD, mainly via blood pressure and dyslipidemia control strategies, the impact of metabolic disease on CV outcomes is still a major challenge and persists in proportion to the epidemics of obesity and diabetes. There is abundant pre-clinical and clinical evidence implicating the DPP-4-incretin axis in CVD. In this regard, linagliptin is a unique DPP-4 inhibitor with both CV and renal safety profiles. Moreover, it exerts beneficial CV effects beyond glycemic control and beyond class effects. Linagliptin is protective for both macrovascular and microvascular complications of diabetes in preclinical models, as well as clinical models. Given the role of endothelial-immune cell interactions as one of the key events in the initiation and progression of CVD, linagliptin modulates these cell–cell interactions by affecting two important pathways involving stimulation of NO signaling and potent inhibition of a key immunoregulatory molecule.

Enhanced endothelium epithelial sodium channel signaling prompts left ventricular diastolic dysfunction in obese female mice

OBJECTIVE

Enhanced activation of cell specific mineralocorticoid receptors (MRs) in obesity plays a key role in the development of cardiovascular disease including cardiac diastolic dysfunction as a critical prognosticator. Our previous investigations demonstrated that selective endothelium MR activation promotes a maladaptive inflammatory response and fibrosis in cardiovascular tissue in female mice fed a western diet (WD), and this was associated with expression and activation of the epithelial sodium channel on the surface of endothelial cells (EnNaC). However, the specific role of EnNaC signaling in the development of cardiac stiffness and diastolic dysfunction has not been examined. We hypothesized that targeted inhibition of EnNaC with low dose amiloride would prevent WD-induced diastolic dysfunction by suppressing abnormal endothelial permeability, inflammation and oxidative stress, and myocardial fibrosis.

MATERIALS/METHODS

Four week-old female C57BL6/J mice were fed a WD with or without a low dose of amiloride (1mg/kg/day) for 16weeks. Left ventricular cardiac function was evaluated by magnetic resonance imaging. In addition, we examined coronary vessel and cardiac remodeling, fibrosis, macrophage infiltration using immunohistochemistry, western blot and real time PCR.

RESULTS

Amiloride, an antagonist of EnNaC, attenuated WD-induced impairment of left ventricular initial filling rate and relaxation time. Cardiac diastolic dysfunction was associated with increases in coronary endothelium remodeling and permeability that paralleled WD-induced increases in F-actin and fibronectin, decreased expression of claudin-5 and occludin, and increased macrophage recruitment, M1 polarization, cardiac oxidative stress, fibrosis and maladaptive remodeling.

CONCLUSION

Our data support the concept that EnNaC activation mediates endothelium permeability which, in turn, promotes macrophage infiltration, M1 polarization, and oxidative stress, resulting in cardiac fibrosis and diastolic dysfunction in females with diet induced obesity.

TRAF3IP2 mediates high glucose-induced endothelin-1 production as well as endothelin-1-induced inflammation in endothelial cells

Hyperglycemia-induced production of endothelin (ET)-1 is a hallmark of endothelial dysfunction in diabetes. Although the detrimental vascular effects of increased ET-1 are well known, the molecular mechanisms regulating endothelial synthesis of ET-1 in the setting of diabetes remain largely unidentified. Here, we show that adapter molecule TRAF3 interacting protein 2 (TRAF3IP2) mediates high glucose-induced ET-1 production in endothelial cells and ET-1-mediated endothelial cell inflammation. Specifically, we found that high glucose upregulated TRAF3IP2 in human aortic endothelial cells, which subsequently led to activation of JNK and IKKβ. shRNA-mediated silencing of TRAF3IP2, JNK1, or IKKβ abrogated high-glucose-induced ET-converting enzyme 1 expression and ET-1 production. Likewise, overexpression of TRAF3IP2, in the absence of high glucose, led to activation of JNK and IKKβ as well as increased ET-1 production. Furthermore, ET-1 transcriptionally upregulated TRAF3IP2, and this upregulation was prevented by pharmacological inhibition of ET-1 receptor B using BQ-788, or inhibition of NADPH oxidase-derived reactive oxygen species using gp91ds-tat and GKT137831. Notably, we found that knockdown of TRAF3IP2 abolished ET-1-induced proinflammatory and adhesion molecule (IL-1β, TNF-α, monocyte chemoattractant protein 1, ICAM-1, VCAM-1, and E-selectin) expression and monocyte adhesion to endothelial cells. Finally, we report that TRAF3IP2 is upregulated and colocalized with CD31, an endothelial marker, in the aorta of diabetic mice. Collectively, findings from the present study identify endothelial TRAF3IP2 as a potential new therapeutic target to suppress ET-1 production and associated vascular complications in diabetes. NEW & NOTEWORTHY This study provides the first evidence that the adapter molecule TRAF3 interacting protein 2 mediates high glucose-induced production of endothelin-1 by endothelial cells as well as endothelin-1-mediated endothelial cell inflammation. The findings presented herein suggest that TRAF3 interacting protein 2 may be an important therapeutic target in diabetic vasculopathy characterized by excess endothelin-1 production.