Differential effects of late-life initiation of low-dose enalapril and losartan on diastolic function in senescent Fischer 344 x Brown Norway male rats.

No proven pharmacological therapies to delay or reverse age-related diastolic dysfunction exist. We hypothesized that late-life low-dose (non-blood-pressure-lowering) angiotensin-converting enzyme inhibition vs. angiotensin II receptor blockade would be equally efficacious at mitigating diastolic dysfunction in the senescent Fischer 344 × Brown Norway rat. Enalapril (10 mg/kg/day; n = 9) initiated at 24 months of age and continued for 6 months, increased myocardial relaxation (e'), reduced Doppler-derived indices of filling pressure (E/e'), favorably lowered the ratio of phospholamban-SERCA2 and reduced oxidative stress markers, Rac1 and nitrotyrosine, in aged hearts. Treatment with losartan (15 mg/kg/day; n = 9) similarly mitigated signs of cardiac oxidative stress, but impairments in diastolic function persisted when compared with untreated rats (n = 7). Our findings favor the idea that the lusitropic benefit of low-dose angiotensin-converting enzyme inhibitor initiated late in life may be related to an antioxidant-mediated modulation of SERCA2, resulting in improved relaxation rather than via overt effects on cardiac structure or blood pressure.

Transgenic overexpression of locally acting insulin-like growth factor-1 inhibits ubiquitin-mediated muscle atrophy in chronic left-ventricular dysfunction.

Metabolic abnormalities develop in various chronic diseases and lead to progressive catabolism with decrements in the skeletal musculature that result in muscle atrophy. We investigated pathways of skeletal muscle proteolysis using an experimental model of chronic left-ventricular dysfunction. Skeletal muscle atrophy developed in wild-type mice 12 weeks following myocardial infarction accompanied by an increase in total protein ubiquitination and enhanced proteasome activity, activation of Foxo transcription factors, and robust induction of the ubiquitin-protein ligase atrogin-1/MAFbx. Further studies identified skeletal muscle myosin as a specific target of ubiquitin-mediated degradation in muscle atrophy. In contrast, transgenic overexpression of a local isoform of insulin-like growth factor-1 prevented muscle atrophy and increased proteasome activity, inhibited skeletal muscle activation primarily of Foxo4, and blocked the expression of atrogin-1/MAFbx. These results suggest that skeletal muscle atrophy occurs through increased activity of the ubiquitin-proteasome pathway. The inhibition of muscle atrophy by local insulin-like growth factor-1 provides a promising therapeutic avenue for the prevention of skeletal muscle wasting in chronic heart failure and potentially other chronic diseases associated with skeletal muscle atrophy.

Biomechanically induced gene iex-1 inhibits vascular smooth muscle cell proliferation and neointima formation.

Mechanotransduction plays a prominent role in vascular pathophysiology but is incompletely understood. In this study, we report the biomechanical induction of the immediate early response gene iex-1 in vascular smooth muscle cells (SMCs). Mechanical induction of iex-1 was confirmed by Northern (30-fold induction after 2 hours) and Western (6-fold induction after 24 hours) analyses. Expression of iex-1 was regulated by mechanical activation of nuclear factor (NF)-kappaB and abolished by overexpression of IkappaB in SMCs. The function of iex-1 in SMCs was explored by gene transfer using adenoviral vectors overexpressing iex-1. After 48 hours of 4% cyclic mechanical strain, adenoviral vectors overexpressing iex-1-infected cells had lower 3[H]-thymidine incorporation compared with AdGFP-infected controls (71.3+/-8.5% versus 180.2+/-19.4% in controls; P<0.001). Overexpression of iex-1 suppressed mitogenesis induced by platelet-derived growth factor (208.1+/-108.3% versus 290.0+/-120.5% in controls; P<0.05). This was accompanied by reduced degradation of p27kip1, inhibition of Rb hyperphosphorylation, and reduced cell cycle progression. To investigate functional effects of iex-1 in vivo, we performed carotid artery mechanical injury and endothelial denudation in low-density lipoprotein receptor-deficient mice followed by intraluminal injection of adenoviral vectors (3x10(9) pfu in 50 microL) for overexpression of iex-1 or gfp (control). Vascular overexpression of iex-1 reduced neointima formation 2 weeks after injury (intima/media ratio, 0.23+/-0.04 versus 0.5+/-0.24 in controls; P<0.05). Our findings demonstrate that biomechanical strain induces iex-1 with subsequent antiproliferative effects in SMCs and that selective gene transfer of iex-1 inhibits the local vascular response after injury. These findings suggest that the induction of iex-1 represents a novel negative biomechanical feedback mechanism limiting the vascular response to injury.

Vitamin D3-upregulated protein-1 (VDUP-1) regulates redox-dependent vascular smooth muscle cell proliferation through interaction with thioredoxin.

Reactive oxygen species are important cellular signaling molecules, and thioredoxin (TRX) is a key regulator of cellular redox balance. We investigated the interaction of TRX with its endogenous inhibitor, vitamin D3-upregulated protein (VDUP)-1, in human aortic smooth muscle cells (SMCs). Adenoviral gene transfer of TRX enhanced TRX enzyme activity 2.7+/-0.4-fold (P<0.05 versus cells infected with adenoviral vector expressing green fluorescent protein [AdGFP]) and resulted in a 3.8+/-0.5-fold increase of cellular DNA synthesis as detected by methyl-[3H]thymidine incorporation (P<0.001). Platelet-derived growth factor (PDGF) also increased TRX enzyme activity 2.5+/-3.3-fold (P<0.05 versus no stimulation) and DNA synthesis 6.5+/-0.3-fold (P<0.001 versus no stimulation) without significant changes in TRX expression. PDGF and H2O2 time-dependently suppressed VDUP-1 expression (13-fold and 30-fold reduction after 1 hour, respectively; P<0.001), and this was inhibited by the cell-permeable antioxidants N-acetylcysteine and 4,5-dihydroxy-1,3-benzene-disulfonic acid (Tiron). Overexpression of VDUP-1 (AdVDUP-1) reduced TRX activity at baseline (-61+/-23% versus control cells, P<0.05) and abolished PDGF-induced TRX activity (-9+/-27% in AdVDUP-1-infected cells; P=NS versus control cells). In addition, overexpression of VDUP-1 blocked PDGF-induced DNA synthesis (1.3+/-0.4-fold increase in AdVDUP-1-infected cells versus 6.5+/-0.4-fold increase in AdGFP-infected cells, P<0.001). In conclusion, VDUP-1 has marked antiproliferative effects in SMCs through the suppression of TRX activity, suggesting that the regulation of VDUP-1 is a critical molecular switch in the transduction of pro-oxidant mitogenic signals. These data also demonstrate that activation of the reductase TRX plays a pivotal role in the redox-dependent proliferation of SMCs.