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Congestive heart failure is associated with activation of the renin-angiotensin system and skeletal muscle wasting. Angiotensin II (ANG If) has been shown to increase muscle proteolysis and decrease circulating and skeletal muscle IGF-1. We have shown previously that skeletal muscle-specific overexpression of IGF-1 prevents proteolysis and apoptosis induced by ANG II. These findings indicated that downregulation of IGF-1 signaling in skeletal muscle played an important role in the wasting effect of ANG II. However, the signaling pathways and mechanisms whereby IGF-1 prevents ANG II-induced skeletal muscle atrophy are unknown. Here we show ANG If-induced transcriptional regulation of two ubiquitin ligases atrogin-1 and muscle ring finger-1 (MuRF-1) that precedes the reduction of skeletal muscle IGF-1 expression, suggesting that activation of atrogin-1 and MuRF-1 is an initial mechanism leading to skeletal muscle atrophy in response to ANG II. IGF-1 overexpression in skeletal muscle prevented ANG II-induced skeletal muscle wasting and the expression of atrogin-1, but not MuRF-1. Dominant-negative Akt and constitutively active Foxo-1 blocked the ability of IGF-I to prevent ANG II-mediated upregulation of atrogin-1 and skeletal muscle wasting. Our findings demonstrate that the ability of IGF-1 to prevent ANG II-induced skeletal muscle wasting is mediated via an Akt-and Foxo1-dependent signaling pathway that results in inhibition of atrogin-1 but not MuRF- 1 expression. These data suggest strongly that atrogin- 1 plays a critical role in mechanisms of ANG II-induced wasting in vivo. angiotensin II; insulin-like growth factor-1 doi: 10.1152/ajpheart.00146.2010.

Am J Physiol Renal Physiol 298: F150-F157, 2010. First published October 21, 2009; doi:10.1152/ajprenal.00477.2009.--Angiotensin-converting enzyme (ACE) inhibition (ACEi) ameliorates the development of hypertension and the intrarenal ANG II augmentation in ANG II-infused mice. To determine if these effects are associated with changes in the mouse intrarenal renin-angiotensin system, the expression of angiotensinogen (AGT), renin, ACE, angiotensin type 1 receptor ([AT.sub.1]R) mRNA (by quanitative RT-PCR) and protein [by Western blot (WB) and/or immunohistochemistry (IHC)] were analyzed. C57BL/6J male mice (9-12 wk old) were distributed as controls (n = 10), ANG II infused (ANG II = 8,400 ng x [kg.sup.-1] x [min.sup.-1] for 12 days), ACEi only (ACEi = 10, lisinopril, 100 mg/1), and ANG II infused + ACEi (ANG II + ACEi = 11). When compared with controls (1.00), AGT protein (by WB) was increased by ANG II (1.29 [+ or -] 0.13, P < 0.05), and this was not prevented by ACEi (ACEi + ANG II, 1.31 [+ or -] 0.14, P < 0.05). ACE protein (by WB) was increased by ANG II (1.21 [+ or -] 0.08, P < 0.05), and it was reduced by ACEi alone (0.88 [+ or -] 0.07, P < 0.05) or in combination with ANG II (0.80 [+ or -] 0.07, P < 0.05). [AT.sub.1]R protein (by WB) was increased by ANG II (1.27 [+ or -] 0.06, P < 0.05) and ACEi (1.17 [+ or -] 0.06, P < 0.05) but not ANG II + ACEi [1.15 [+ or -] 0.06, not significant (NS)]. Tubular renin protein (semiquantified by IHC) was increased by ANG II (1.49 [+ or -] 0.23, P < 0.05) and ACEi (1.57 [+ or -] 0.15, P < 0.05), but not ANG II + ACEi (1.10 [+ or -] 0.15, NS). No significant changes were observed in AGT, ACE, or [AT.sub.1]R mRNA. In summary, reduced responses of intrarenal tubular renin, ACE, and the [AT.sub.1]R protein to the stimulatory effects of chronic ANG II infusions, in the presence of ACEi, are associated with the effects of this treatment to ameliorate augmentations in blood pressure and intrarenal ANG II content during ANG II-induced hypertension. angiotensin-converting enzyme; angiotensinogen; renin; lisinopril

There is a sex difference in hypertensive renal injury, with men experiencing greater severity and a more rapid progression of renal disease than women; however, the molecular mechanisms protecting against renal injury in women are unknown. The goal of this study was to determine whether sex hormones modulate blood pressure and the progression of albuminuria during the developmental phase of hypertension in male and female spontaneously hypertensive rats (SHR). Studies were also performed to examine how sex and sex hormones influence two major risk factors for albuminuria, overactivation of the renin-angiotensin system and oxidative stress. Blood pressure was measured by telemetry in gonad-intact and gonadectomized male and female SHR. Microalbumin excretion, measured over time, and macrophage infiltration were used to assess renal health. Male SHR had significantly higher blood pressures than female SHR, and gonadectomy decreased blood pressures in males with no effect in females. Male SHR displayed a gonad-sensitive increase in albuminuria over time, and female SHR had a gonad-sensitive suppression in macrophage infiltration. Female SHR had greater plasma ANG II levels and similar levels of renal cortical ANG II vs. levels shown in males but less ATe-receptor protein expression in the renal cortex. Female SHR also had a gonad-sensitive decrease in renal oxidative stress. Therefore, the renal protection afforded to female SHR is associated with lower blood pressure, decreased macrophage infiltration, and decreased levels of oxidative stress. gender; renin-angiotensin system; oxidative stress