Loss of PTEN attenuates the development of pathological hypertrophy and heart failure in response to biomechanical stress.

AIMS: The maladaptive response to biomechanical stress is a fundamental response in heart disease. Loss of the 3'-lipid phosphatase, phosphatase and tensin homolog deleted on chromosome ten (PTEN), is associated with increased phosphorylation of Akt/protein kinase B and glycogen synthase kinase-beta. We hypothesize that these key changes will halt the development of pathological hypertrophy and the progression to heart failure in response to pressure overload. METHODS AND RESULTS: In mice, muscle-specific knockout of PTEN, mckCRE-PTEN(flox/flox) (PTEN KO), resulted in basal hypertrophy and mild reduction in left ventricular (LV) systolic function. Male mice were subjected to aortic banding (AB) or sham operation. In contrast to mckCRE-PTEN(+/+) control mice, pressure overload in PTEN KO mice resulted in reduced pathological hypertrophy, less interstitial fibrosis, and reduced apoptosis with a marked preservation of LV function. Western blot analysis of mitogen-activated protein kinase (MAPK) signalling showed equivalent phosphorylation of extracellular signal-regulated kinase (ERK)1 and ERK2 with markedly reduced phosphorylation of jun N-terminal kinase (JNK)1 and JNK2, and p38 in PTEN KO mice subjected to AB. Loss of PTEN was associated with increased expression of the proangiogenic factors, vascular endothelial growth factor-A and angiopoietin-2, with preservation of the myocardial capillary density in response to pressure overload. Moreover, banded PTEN KO mice maintained the expression of several key metabolic genes that are known to be dysregulated in heart failure. In contrast, a subpressor dose of the G protein-coupled receptor (GPCR) agonist angiotensin II (Ang II) leads to increased pathological hypertrophy and MAPK activation in PTEN KO mice. CONCLUSION: Loss of PTEN prevents the development of maladaptive ventricular remodelling with preservation of angiogenesis and metabolic gene expression in response to pressure overload but not in response to the GPCR agonist, Ang II. Inhibition of PTEN signalling in the heart may represent a novel approach to slow the progression of heart failure in response to pathological biomechanical stress.

Loss of angiotensin-converting enzyme-2 (Ace2) accelerates diabetic kidney injury.

Diabetic nephropathy is one of the most common causes of end-stage renal failure, but the factors responsible for the development of diabetic nephropathy have not been fully elucidated. We examined the effect of deletion of the angiotensin-convert-ing enzyme 2 (Ace2) gene on diabetic kidney injury. Ace2(-/-) mice were crossed with Akita mice (Ins2(WT/C96Y)), a model of type 1 diabetes mellitus, and four groups of mice were studied at 3 months of age: Ace2(+/y)Ins2(WT/WT), Ace2(-/y)Ins2(WT/WT), Ace2(+/y) Ins2(WT/C96Y), and Ace2(-/y)Ins2(WT/C96Y). Ace2(-/y) Ins2(WT/C96Y) mice exhibited a twofold increase in the urinary albumin excretion rate compared with Ace2(+/y)Ins2(WT/C96Y) mice despite similar blood glucose levels. Ace2(-/y)Ins2(WT/C96Y) mice were the only group to exhibit increased mesangial matrix scores and glomerular basement membrane thicknesses compared with Ace2(+/y)Ins2(WT/WT) mice, accompanied by increased fibronectin and alpha-smooth muscle actin immunostaining in the glomeruli of Ace2(-/y) Ins2(WT/C96Y) mice. There were no differences in blood pressure or heart function to account for the exacerbation of kidney injury. Although kidney levels of angiotensin (Ang) II were not increased in the diabetic mice, treatment with an Ang II receptor blocker reduced urinary albumin excretion rate in Ace2(-/y)Ins2(WT/C96Y) mice, suggesting that acceleration of kidney injury in these mice is Ang II-mediated. We conclude that ACE2 plays a protective role in the diabetic kidney, and ACE2 is an important determinant of diabetic nephropathy.