The endocytosis of oxidized LDL via the activation of the angiotensin II type 1 receptor.

Arrestin-dependent activation of a G-protein-coupled receptor (GPCR) triggers endocytotic internalization of the receptor complex. We analyzed the interaction between the pattern recognition receptor (PRR) lectin-like oxidized low-density lipoprotein (oxLDL) receptor (LOX-1) and the GPCR angiotensin II type 1 receptor (AT1) to report a hitherto unidentified mechanism whereby internalization of the GPCR mediates cellular endocytosis of the PRR ligand. Using genetically modified Chinese hamster ovary cells, we found that oxLDL activates Gαi but not the Gαq pathway of AT1 in the presence of LOX-1. Endocytosis of the oxLDL-LOX-1 complex through the AT1-ß-arrestin pathway was demonstrated by real-time imaging of the membrane dynamics of LOX-1 and visualization of endocytosis of oxLDL. Finally, this endocytotic pathway involving GPCR kinases (GRKs), ß-arrestin, and clathrin is relevant in accumulating oxLDL in human vascular endothelial cells. Together, our findings indicate that oxLDL activates selective G proteins and ß-arrestin-dependent internalization of AT1, whereby the oxLDL-LOX-1 complex undergoes endocytosis.

Effects of Low-Dose Sacubitril/Valsartan on Different Stages of Cardiac Hypertrophy in Salt-Loaded Hypertensive Rats.

BACKGROUND: Sacubitril/valsartan was shown to attenuate the development of cardiac hypertrophy with enhanced blood pressure reduction compared with valsartan alone in animal models. We investigated whether a low-dose sacubitril/valsartan has blood pressure-independent effects on cardiac hypertrophy and pulmonary edema using a rat model of hypertension and obesity. METHODS AND RESULTS: In plan 1, male SHR/NDmcr-cp rats fed normal or phase-increased high salt were treated with vehicle, 6-mg/kg sacubitril/valsartan or 3-mg/kg valsartan, for 6 months. In plan 2, after high-salt loading for 6 months, drugs were administered for 4 months. Antihypertensive effects of the 2 drugs were similar during all study periods. In plan 1 with normal salt, there were no differences between treatments in the left ventricle weight/body weight (BW), or lung weight/BW as an index of cardiac hypertrophy or pulmonary edema, respectively. These indexes were smaller in high-salt-fed rats with sacubitril/valsartan than vehicle. In plan 2, both indexes did not differ between vehicle and sacubitril/valsartan. Ventricle weight/BW was lower in valsartan than sacubitril/valsartan. In plan 2, gene markers of cardiac dysfunction were upregulated by sacubitril/valsartan compared with the other groups. CONCLUSIONS: Low-dose sacubitril/valsartan may have different effects depending on the stage of cardiac hypertrophy in rats.

Angiotensin-converting enzyme 2 deficiency accelerates and angiotensin 1-7 restores age-related muscle weakness in mice.

BACKGROUND: A pharmacologic strategy for age-related muscle weakness is desired to improve mortality and disability in the elderly. Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin II into angiotensin 1-7, a peptide known to protect against acute and chronic skeletal muscle injury in rodents. Since physiological aging induces muscle weakness via mechanisms distinct from other muscle disorders, the role of ACE2-angiotensin 1-7 in age-related muscle weakness remains undetermined. Here, we investigated whether deletion of ACE2 alters the development of muscle weakness by aging and whether angiotensin 1-7 reverses muscle weakness in older mice. METHODS: After periodic measurement of grip strength and running distance in male ACE2KO and wild-type mice until 24 months of age, we infused angiotensin 1-7 or vehicle for 4 weeks, and measured grip strength, and excised tissues. Tissues were also excised from younger (3-month-old) and middle-aged (15-month-old) mice. Microarray analysis of RNA was performed using tibialis anterior (TA) muscles from middle-aged mice, and some genes were further tested using RT-PCR. RESULTS: Grip strength of ACE2KO mice was reduced at 6 months and was persistently lower than that of wild-type mice (p < 0.01 at 6, 12, 18, and 24-month-old). Running distance of ACE2KO mice was shorter than that of wild-type mice only at 24 months of age [371 ± 26 vs. 479 ± 24 (m), p < 0.01]. Angiotensin 1-7 improved grip strength in both types of older mice, with larger effects observed in ACE2KO mice (% increase, 3.8 ± 1.5 and 13.3 ± 3.1 in wild type and ACE2KO mice, respectively). Older, but not middle-aged ACE2KO mice had higher oxygen consumption assessed by a metabolic cage than age-matched wild-type mice. Angiotensin 1-7 infusion modestly increased oxygen consumption in older mice. There was no difference in a wheel-running activity or glucose tolerance between ACE2KO and wild-type mice and between mice with vehicle and angiotensin 1-7 infusion. Analysis of TA muscles revealed that p16INK4a, a senescence-associated gene, and central nuclei of myofibers increased in middle-aged, but not younger ACE2KO mice. p16INK4a and central nuclei increased in TA muscles of older wild-type mice, but the differences between ACE2KO and wild-type mice remained significant (p < 0.01). Angiotensin 1-7 did not alter the expression of p16INK4a or central nuclei in TA muscles of both types of mice. Muscle ACE2 expression of wild-type mice was the lowest at middle age (2.6 times lower than younger age, p < 0.05). CONCLUSIONS: Deletion of ACE2 induced the early manifestation of muscle weakness with signatures of muscle senescence. Angiotensin 1-7 improved muscle function in older mice, supporting future application of the peptide or its analogues in the treatment of muscle weakness in the elderly population.

Abdominal admittance helps to predict the amount of fluid accumulation in patients with acute heart failure syndromes.

BACKGROUND: Predicting fluid volume that needs to be removed in acute heart failure syndromes (AHFS) patients remains challenging. Thoracic admittance (TA), the reciprocal of thoracic impedance measured by bioelectrical impedance, reflects the amount of fluid in the thorax. Abdominal organs play an important role in AHFS as systemic fluid reservoirs. We investigated the relationship between abdominal admittance (AA) at the time of admission for AHFS and net fluid loss (NFL) during hospitalization. METHODS: Sixty-two consecutive patients hospitalized for AHFS [age 71±10 years, left ventricular ejection fraction (LVEF) 39±17%] were studied. The admittance values, i.e. the reciprocals of the impedance values, were derived using a BioZ(®) (CardioDynamics, San Diego, CA, USA). The change in weight from admission to discharge was used as a surrogate of amount of NFL. RESULTS: At the time of admission, a significant correlation was detected between TA and AA (r=0.46, p=0.0001). TA at admission was significantly correlated with the LV structural variables (end-diastolic dimension and end-systolic dimension), and serum sodium level. AA at admission was significantly correlated with New York Heart Association (NYHA) class and plasma BNP, and also correlated with LVEF and variables related to systemic congestion [minimal inferior vena cava (IVC) diameter and tricuspid regurgitation grade]. Neither TA nor AA values were significantly correlated with weight at admission. During hospitalization, TA and AA declined from 44±8kΩ(-1) to 36±6kΩ(-1) (p<0.0001) and from 74±25kΩ(-1) to 56±17kΩ(-1) (p<0.0001), respectively. Weight fell from 60.1±10.8kg to 54.5±9.4kg (p<0.0001), while NFL was 5.8kg (range, 0.1-17.5kg). In univariate analyses, the admission NYHA class, TA, AA, weight, and IVC diameter correlated with NFL. Multivariate analysis demonstrated that only admission weight [standardized partial regression coefficient (SPRC)=0.596], AA (SPRC=0.529), and NYHA class (SPRC=0.277) were independent predictors of NFL. CONCLUSION: Abdominal admittance measurement helps to predict the amount of fluid volume to be removed in patients with AHFS.

Successful catheter ablation to accessory atrioventricular pathway as cardiac resynchronization therapy in a patient with dilated cardiomyopathy.

A 55-year-old man was admitted to our hospital for further examination of the abnormalities of chest X-ray and electrocardiogram. He was diagnosed with type B Wolff-Parkinson-White syndrome concomitant with dilated cardiomyopathy. Despite the medical therapy using enalapril and carvedilol for 20 months, his cardiac performance and brain natriuretic peptide (BNP) were not so improved. Because asynchronous septal motion caused by pre-excitation through a right-sided accessory pathway (AP) might deteriorate his cardiac performance, catheter ablation to the AP was performed. Successful procedure after 17 months improved left ventricular (LV) contraction, reduced LV volume, and decreased mitral regurgitation and BNP.