Guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) plays a critical role in the regulation of blood pressure and fluid volume homeostasis. Mice lacking functional (coding for GC-A/NPRA) exhibit hypertension and congestive heart failure. However, the underlying mechanisms remain largely less clear. The objective of the present study was to determine the physiological efficacy and impact of all--retinoic acid (ATRA) and sodium butyrate (NaBu) in ameliorating the renal fibrosis, inflammation, and hypertension in gene-disrupted haplotype (1-copy; +/-) mice (50% expression levels of NPRA). Both ATRA and NaBu, either alone or in combination, decreased the elevated levels of renal proinflammatory and profibrotic cytokines and lowered blood pressure in mice compared with untreated controls. The treatment with ATRA-NaBu facilitated the dissociation of histone deacetylase (HDAC) 1 and 2 from signal transducer and activator of transcription 1 (STAT1) and enhanced its acetylation in the kidneys of mice. The acetylated STAT1 formed a complex with nuclear factor-κB (NF-κB) p65, thereby inhibiting its DNA-binding activity and downstream proinflammatory and profibrotic signaling cascades. The present results demonstrate that the treatment of the haplotype mice with ATRA-NaBu significantly lowered blood pressure and reduced the renal inflammation and fibrosis involving the interactive roles of HDAC, NF-κB (p65), and STAT1. The current findings will help in developing the molecular therapeutic targets and new treatment strategies for hypertension and renal dysfunction in humans.

In contrast to the negative feedback of angiotensin II (ANG II) on juxtaglomerular renin, ANG II stimulates renin in the principal cells of the collecting duct (CD) in rats and mice via ANG II type 1 (AT 1R) receptor, independently of blood pressure. In vitro data indicate that CD renin is augmented by AT 1R activation through protein kinase C (PKC), but the exact mechanisms are unknown. We hypothesize that ANG II stimulates CD renin synthesis through AT 1R via PKC and the subsequent activation of cAMP/PKA/CREB pathway. In M-1 cells, ANG II increased cAMP, renin mRNA (3.5-fold), prorenin, and renin proteins, as well as renin activity in culture media (2-fold). These effects were prevented by PKC inhibition with calphostin C, PKC-␣ dominant negative, and by PKA inhibition. Forskolin-induced increases in cAMP and renin expression were prevented by calphostin C. PKC inhibition and Ca 2ϩ depletion impaired ANG II-mediated CREB phosphorylation and upregulation of renin. Adenylate cyclase 6 (AC) siRNA remarkably attenuated the ANG II-dependent upregulation of renin mRNA. Physiological activation of AC with vasopressin increased renin expression in M-1 cells. The results suggest that the ANG II-dependent upregulation of renin in the CD depends on PKC-␣, which allows the augmentation of cAMP production and activation of PKA/CREB pathway via AC6. This study defines the intracellular signaling pathway involved in the ANG II-mediated stimulation of renin in the CD. This is a novel mechanism responsible for the regulation of local renin-angiotensin system in the distal nephron.prorenin; hypertension; protein kinase; calcium; adenylyl cyclase-6; gene expression; M-1 cells IN ANGIOTENSIN II -(ANG II) dependent hypertension, the intrarenal ANG II content is greater than can be explained from the levels found in plasma (30, 31). High intrarenal ANG II levels can be partially explained by enhanced ANG II type 1 receptor (AT 1 R)-mediated uptake of ANG II (10). Augmentation of proximal tubule angiotensinogen (AGT) synthesis and secretion is responsible for increased local intratubular ANG II generation (21). The presence of AGT in the urine indicates that AGT traverses the distal nephron segments where it may then be cleaved to ANG I, if an adequate source of renin is available.In addition to the juxtaglomerular cells (JG), renin expression has been described in the proximal tubules, connecting tubules, and cortical and medullary collecting duct (CD) cells from the mouse, rat, and human kidney (39, 44). In contrast to JG cells, in the principal cells of the CD renin is upregulated by ANG II (36), via an AT 1 R-mediated mechanism (37), which is independent of blood pressure (35). In ANG II-dependent hypertensive rats with marked plasma renin activity (PRA) suppression, increased urinary levels of renin and prorenin reflect their augmented secretion by CD cells into the luminal fluid (26). In this model of experimental hypertension, intraluminal conversion of ANG I to ANG II in the CD is supported by the local presence of angiotens...

Advanced age is accompanied by aortic stiffening that is associated with decreased vascular expression of sirtuin-1 (SIRT-1). Interventions that increase SIRT-1 expression also lower age-related aortic stiffness. Therefore, we sought to determine if lifelong SIRT-1 overexpression would attenuate age-related aortic stiffening. Aortic pulse wave velocity (PWV) was assessed from 3-24 months in SIRT-1 transgenic overexpressing (SIRT TG ) and wild-type (WT) mice. To determine the role of aortic structural changes on aortic stiffening, histological assessment of aortic wall characteristics was performed. Across the age range (3-24 mo), PWV was 8-17% lower in SIRT TG vs. WT (P<0.05). Moreover, the slope of age-related aortic stiffening was lower in SIRT TG vs. WT (2.1±0.2 vs. 3.8±0.3 cm/sec/mo, respectively). Aortic elastin decreased with advancing age in WT (P<0.05 old vs. young WT), but was maintained in SIRT TG mice (P>0.05). There was an age-related increase in aortic collagen, advanced glycation end products, and calcification in WT (P<0.05 old vs. young WT). However, this did not occur in SIRT TG (P>0.05). These findings indicate that lifelong SIRT-1 overexpression attenuates age-related aortic stiffening. These functional data are complemented by histological assessment, demonstrating that the deleterious changes to the aortic wall that normally occur with advancing age are prevented in SIRT TG mice.

The present study was designed to determine the effects of gene knockout of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) on immunogenic responses affecting kidney function and blood pressure (BP) in Npr1 (coding for GC-A/NPRA)-null mutant mice. We used female Npr1 gene-disrupted ( Npr1−/−, 0 copy), heterozygous ( Npr1+/−, 1 copy), wild-type ( Npr1+/+, 2 copy), and gene-duplicated ( Npr1++/++, 4 copy) mice. Expression levels of Toll-like receptor (TLR)2/TLR4 mRNA were increased 4- to 5-fold in 1-copy mice and 6- to 10-fold in 0-copy mice; protein levels were increased 2.5- to 3-fold in 1-copy mice and 4- to 5-fold in 0-copy mice. Expression of proinflammatory cytokines and BP was significantly elevated in 1-copy and 0-copy mice compared with 2-copy and 4-copy mice. In addition, 0-copy and 1-copy mice exhibited drastic reductions in regulatory T cells (Tregs). After rapamycin treatment, Tregs were increased by 17% ( P < 0.001) in 0-copy mice and 8% ( P < 0.001) in 1-copy mice. Renal mRNA and protein levels of TLR2 and TLR4 were decreased by 70% in 0-copy mice and 50% in 1-copy mice. There were significantly higher levels of Tregs and very low levels of TLR2/TLR4 expression in 4-copy mice ( P < 0.001). These findings indicate that the disruption of Npr1 in female mice triggers renal immunogenic pathways, which transactivate the expression of proinflammatory cytokines and renal fibrosis with elevated BP in mutant animals. The data suggest that rapamycin treatment attenuates proinflammatory cytokine expression, dramatically increases anti-inflammatory cytokines, and substantially reduces BP and renal fibrosis in mutant animals.

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