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Heart failure (HF) is associated with impaired L-arginine transport. In the present study, we tested the hypothesis that augmented L-arginine transport prevents the loss of kidney function in HF. Renal function was assessed in wildtype mice (WT), transgenic mice with HF (dilated cardiomyopathy, DCM) and double transgenic mice (double transgenic mice with DCM and CAT-1 overexpression, HFCAT-1) with HF and endothelial-specific overexpression of the predominant L-arginine transporter, cationic amino acid transporter-1 (CAT-1) (n=4-8/group). Cardiac function was assessed via echocardiography and left ventricular catheterisation. Renal function was assessed via quantification of albuminuria and creatinine clearance. Plasma nitrate and nitrite levels together with renal fibrosis and inflammatory markers were also quantified at study end. Albumin/creatinine ratio was two-fold greater in DCM mice than in WT mice (P=0.002), and tubulointerstitial and glomerular fibrosis were approximately eight- and three-fold greater, respectively, in DCM mice than in WT mice (P≤0.02). Critically, urinary albumin/creatinine ratio and tubulointerstitial and glomerular fibrosis were less in HFCAT-1 mice than in DCM mice (P

Mechanisms underlying the renal pathology in cardiorenal syndrome (CRS) type 2 remain elusive. We hypothesised that renal glutathione deficiency is central to the development of CRS type 2. Glutathione precursor, N-acetylcysteine (NAC;40 mg/kg/day; 8 weeks) or saline were administered to transgenic mice with dilated cardiomyopathy (DCM) and wild-type (WT) controls. Cardiac structure, function and glutathione levels were assessed at the end of this protocol. Renal fibrosis, glutathione content, expression of inflammatory and fibrotic markers, and function were also evaluated. In both genotypes, NAC had minimal effect on cardiac glutathione, structure and function (P ≥ 0.20). In NAC treated DCM mice, loss of glomerular filtration rate (GFR), tubulointerstitial and glomerular fibrosis and renal oxidised glutathione levels were attenuated by 38%, 99%, 70% and 52% respectively, compared to saline treated DCM mice (P ≤ 0.01). Renal expression of PAI-1 was greater in saline treated DCM mice than in WT mice (P P = 0.03). Renal IL-10 expression was greater in the former cohort compared to the latter (P

Background: Dietary intake of fruit and vegetables is associated with lower incidence of hypertension, but the mechanisms involved have not been elucidated. Here, we evaluated the effect of a high-fiber diet and supplementation with the short-chain fatty acid acetate on the gut microbiota and the prevention of cardiovascular disease. Methods: Gut microbiome, cardiorenal structure/function, and blood pressure were examined in sham and mineralocorticoid excess–treated mice with a control diet, high-fiber diet, or acetate supplementation. We also determined the renal and cardiac transcriptome of mice treated with the different diets. Results: We found that high consumption of fiber modified the gut microbiota populations and increased the abundance of acetate-producing bacteria independently of mineralocorticoid excess. Both fiber and acetate decreased gut dysbiosis, measured by the ratio of Firmicutes to Bacteroidetes, and increased the prevalence of Bacteroides acidifaciens . Compared with mineralocorticoid-excess mice fed a control diet, both high-fiber diet and acetate supplementation significantly reduced systolic and diastolic blood pressures, cardiac fibrosis, and left ventricular hypertrophy. Acetate had similar effects and markedly reduced renal fibrosis. Transcriptome analyses showed that the protective effects of high fiber and acetate were accompanied by the downregulation of cardiac and renal Egr1 , a master cardiovascular regulator involved in cardiac hypertrophy, cardiorenal fibrosis, and inflammation. We also observed the upregulation of a network of genes involved in circadian rhythm in both tissues and downregulation of the renin-angiotensin system in the kidney and mitogen-activated protein kinase signaling in the heart. Conclusions: A diet high in fiber led to changes in the gut microbiota that played a protective role in the development of cardiovascular disease. The favorable effects of fiber may be explained by the generation and distribution of one of the main metabolites of the gut microbiota, the short-chain fatty acid acetate. Acetate effected several molecular changes associated with improved cardiovascular health and function.

Background— Extensive evidence implicates aldosterone excess in the development and progression of cardiovascular disease states including hypertension, metabolic syndrome, cardiac hypertrophy, heart failure, and cardiorenal fibrosis. Recent studies show that activation of inflammatory cascade may play a specific role in the sequelae of mineralocorticoid activation, although the linking mechanism remains unclear. We tested the possibility that secondary stimulation of the stromal-derived factor 1/CXC chemokine receptor 4 (SDF-1/CXCR4) pathway plays a contributory role. Methods and Results— We investigated the effect of the highly selective CXCR4 antagonist AMD3465 (6 mg/kg per day for 6 weeks through minipump) in dexoycorticosterone acetate (DOCA)-treated, uninephrectomized mice. CXCR4 antagonism significantly attenuated the induction of cardiac fibrosis, renal fibrosis, hypertension, and left ventricular hypertrophy by DOCA. Mineralocorticoid excess also stimulated the accumulation of T-lymphocytes in the heart and kidney and this was significantly blunted by CXCR4 inhibition. Conclusions— Taken together, these data strongly implicate the SDF-1/CXCR4 axis in the pathogenesis of mineralocorticoid excess induced hypertension, inflammation, and cardiorenal fibrosis. This insight provides a new potential therapeutic approach for the treatment of specific aspects of mineralocorticoid mediated cardiovascular disease.

Cardiac fibrosis contributes significantly to the phenotype of the chronically failing heart. It is not clear whether in this setting the fibrosis is contributed by native cardiac fibroblasts or alternatively by recruitment of cells arising from the bone marrow. We aimed to determine the contribution of bone marrow-derived cells to cardiac fibrosis in the failing heart and to investigate potentially contributing cytokines. Bone marrow-derived fibrocyte recruitment to the failing heart was studied in a transgenic (Mst1 mice) model of dilated cardiomyopathy. In conjunction, we examined the role of stromal-derived factor-1 (SDF-1), a key chemoattractant, by assessing myocardial expression and secretion by cardiomyocytes and in clinical samples. Bone marrow-derived cells were recruited in significantly greater numbers in Mst1 versus control mice (P < 0.001), contributing 17 ± 4% of the total fibroblast load in heart failure. Patients with heart failure had higher plasma levels of SDF-1 than healthy control subjects (P < 0.01). We found that cardiomyocytes constitutively secrete SDF-1, which is significantly up-regulated by angiotensin II. SDF-1 was shown to increases cardiac fibroblast migration by 59% (P < 0.05). Taken together, our data suggest that recruitment of bone marrow-derived cells under the influence of factors, including SDF-1, may play an important role in the pathogenesis of cardiac fibrosis in heart failure.

Enlarged early endosomes in the neurons of young Down syndrome (DS) and pre-Alzheimer's disease (AD) brains suggest that a disturbance in endocytosis is one of the earliest hallmarks of AD pathogenesis in both conditions. We identified a chromosome 21 gene, Intersectin-1 (ITSN1) that is up-regulated in DS brains and has a putative function in endocytosis and vesicle trafficking. To elucidate the function of ITSN1 and assess its contribution to endocytic defects associated with DS and AD, we generated Itsn1 null mice. In knockout mice we found alterations in a number of parameters associated with endocytic and vesicle trafficking events. We found a reduced number of exocytosis events in chromaffin cells and a slowing of endocytosis in neurons. Endosome size was increased in neurons and NGF levels were reduced in the septal region of the brain. Our data is the first indication that Itsn1 has a role in endocytosis in an in vivo mammalian model, and that a disruption in Itsn1 expression causes a disturbance in vesicle trafficking and endocytic function in the brain. These results imply a role for ITSN1 in the early endocytic anomalies reported in DS brains which may have ramifications for the onset of AD.

Heart failure (HF) is an increasingly recognized complication of diabetes. Cardiac fibrosis is an important causative mechanism of HF associated with diabetes. Recent data indicate that inflammation may be particularly important in the pathogenesis of cardiovascular fibrosis. We sought to determine the mechanism by which cardiac fibrosis develops and to specifically investigate the role of the CXCR4 axis in this process. Animals with type I diabetes (streptozotocin treated mice) or type II diabetes (Israeli Sand-rats) and controls were randomized to treatment with a CXCR4 antagonist, candesartan or vehicle control. Additional groups of mice also underwent bone marrow transplantation (GFP+ donor marrow) to investigate the potential role of bone marrow derived cell mobilization in the pathogenesis of cardiac fibrosis. Both type I and II models of diabetes were accompanied by the development of significant cardiac fibrosis. CXCR4 antagonism markedly reduced cardiac fibrosis in both models of diabetes, similar in magnitude to that seen with candesartan. In contrast to candesartan, the anti-fibrotic actions of CXCR4 antagonism occurred in a blood pressure independent manner. Whilst the induction of diabetes did not increase the overall myocardial burden of GFP+ cells, it was accompanied by an increase in GFP+ cells expressing the fibroblast marker alpha-smooth muscle actin and this was attenuated by CXCR4 antagonism. CXCR4 antagonism was also accompanied by increased levels of circulating regulatory T cells. Taken together the current data indicate that pharmacological inhibition of CXCR4 significantly reduces diabetes induced cardiac fibrosis, providing a potentially important therapeutic approach.

Background & Aims: ELF3, a member of the ETS transcription factor family, has been shown to transactivate the transforming growth factor β type II receptor (TGF-βRII) promoter. Previously we showed that Elf3-null mice have a defect in the small intestine caused by a failure of small intestinal epithelial cells to differentiate and that these cells produced significantly lower levels of Tgf-βRII. To prove that the defect observed in Elf3-null mice resulted from the lack of Elf3-dependent activation of Tgf-βRII expression, we performed a genetic rescue. Methods: We generated transgenic mice that express human TGF-βRII specifically in the intestinal epithelium under the control of the mouse A33 antigen promoter. Mice expressing the A33-TGF-βRII transgene were mated with Elf3+/− mice, and double heterozygous offspring harboring both the transgene and one mutant Elf3 allele were intercrossed. Results: The resultant A33-TGF-βRII transgenic Elf3−/− pups displayed normal small intestinal morphology, while the characteristic abnormality was retained in all Elf3−/− mice that did not express the transgene. This phenotypic rescue shows for the first time in vivo that a single gene, Elf3, is the critical upstream regulator of Tgf-βRII in mouse small intestinal epithelium. Conclusions: This has important implications for our understanding of tissue-specific gene regulation and further strengthens the potential clinical connection between ELF3 and colorectal cancer involving transforming growth factor β insensitivity.

The relationships between changes in plasma progesterone concentrations, degeneration of the luminal epithelium, the occurrence of apoptosis of endometrial cells and endometrial leucocyte populations in the bitch were determined. Mature bitches (n = 15) were euthanized and necropsied when in diestrus (Days 7-75, n = 12) or in anestrus (Days 10, 32 and 53). Degeneration of the luminal epithelium was observed in bitches in late diestrus (Days 38-75, n = 5) when plasma progesterone concentrations were decreasing and in anestrus (Days 10 and 32, n = 2) when plasma progesterone concentrations were

ROMK potassium channels are present in the cortical collecting ducts (CCDs) of the kidney and serve as the exit pathways for K+secretion in this nephron segment. Dietary K+restriction reduces the abundance of ROMK in the kidney. We have previously shown that ROMK undergoes endocytosis via clathrin-coated vesicles in Xenopus laevis oocytes and in cultured cells. Here, we examined the effect of dietary K+restriction on endocytosis of ROMK in CCDs using double-labeling immunofluorescent staining and confocal microscopic imaging in whole kidney sections as well as in individually isolated tubules. We found that ROMK abundance in kidney cortex and CCDs was reduced in rats fed a K+-restricted diet compared with rats fed the control K+diet. In the control animals, ROMK staining was preferentially localized to the apical membrane of CCDs. Compared with control tubules, ROMK staining in CCDs was markedly shifted toward intracellular locations in animals fed a K+-deficient diet for 48 h. Some of the intracellular distribution of ROMK colocalized with an early endosomal marker, early endosomal antigen-1 or with a late endosomal/lysosomal marker, lysosomal membrane glycoprotein-120. These results suggest that K+restriction reduces the abundance of ROMK in CCDs by increasing endocytosis and degradation of the channel protein. This decrease in the abundance of ROMK is likely important for maintaining K+homeostasis during K+deficiency.

The relationships between activities of matrix metalloproteinases (MMPs) in the canine uterus and the occurrence of degeneration of the luminal epithelium, cystic endometrial hyperplasia, pyometra and uterine remodelling post partum were determined. Mature bitches (n = 10) were ovariectomized, treated with hormones (oestradiol benzoate, progestagen) and investigated at stages simulating pro-oestrus (n = 2), oestrus (n = 2), dioestrus (n = 2), and mid- (n = 2) and late (n = 2) anoestrus (3 and 9 weeks, respectively, after cessation of treatment with progestagen). Untreated bitches (n = 1 per group) served as controls (Expt 1). An additional 10 ovariectomized bitches, at the end of treatment-induced simulated dioestrus, were treated each day for a further 3 weeks either with the same dose (standard dose, n = 3), a decreased dose (n = 3) or an increased dose (n = 3) of progestagen, or no treatment (withdrawal dose, n = 1). These bitches were then investigated (Expt 2). A suture was placed in the lumen of one uterine horn of another five bitches at ovariectomy. Three of these bitches were treated to induce simulated dioestrus and two bitches served as untreated controls. In the hormone-treated bitches, the suture resulted in cystic endometrial hyperplasia in one bitch and in cystic endometrial hyperplasia with pyometra in two bitches. The control bitches showed no cystic endometrial hyperplasia or pyometra (Expt 3). Four intact bitches were studied at 2 (n = 1), 3 (n = 2) and 11 (n = 1) weeks post partum. Uterine tissues were also collected from two bitches with naturally occurring cystic endometrial hyperplasia with pyometra (Expt 4). All uteri were examined histologically and the activities of MMP-2, -7 and -9 (latent and active forms) were assessed using zymography of extracts of endometrium. In Expts 1 and 2, marked degeneration of the luminal epithelium in six of 25 bitches (simulated mid-anoestrus, withdrawal dose and decreased dose groups) was not associated with changes in MMP activities. Markedly increased activities of MMP-2 (active form), -7 (latent form) and -9 (active and latent forms) were observed in the bitches with cystic endometrial hyperplasia with pyometra (but not with cystic endometrial hyperplasia alone) and in the bitches at 2 and 3 weeks post partum (but not at 11 weeks post partum). These results indicate that MMPs are not involved with degeneration of the luminal epithelium, but are involved with uterine remodelling in the postpartum bitch and with cystic endometrial hyperplasia with pyometra.

The relationship between apoptosis of endometrial cells in the bitch, and the occurrence of degeneration of the endometrial luminal epithelium and regression of the endometrial glandular epithelium was determined. Mature bitches (n = 12) were ovariectomized and treated with hormones to simulate uterine changes that occur during the oestrous cycle. All bitches were treated with oestradiol benzoate (0.6-4.8 microg x kg(-1), i. m., twice per day) for 11-12 days then with progestagen (megestrol acetate, 2 mg x kg(-1), p. o., once per day) for 35-37 days. Bitches were treated daily for a further 3 weeks with megestrol acetate at dose rates of 0.5 mg x kg(-1) (decreased-dose group (n = 3)), 2 mg x kg(-1) (standard-dose group (n = 3)), or 3 (1 wk), 4 (1 wk) and 5 (1 wk) mg x kg(-1) (increased-dose group (n = 3)), or received no treatment (withdrawal-dose group (n = 3)). These bitches were necropsied at the end of the treatment period. A further 10, ovary-intact, bitches were necropsied when in oestrus (n = 1), dioestrus (n = 5), and at 3 weeks (n = 1) and 9 weeks (n = 3) of anoestrus. Degeneration of the luminal epithelium was observed in all bitches except those in oestrus, at 9 weeks of anoestrus and one in dioestrus. Apoptosis was observed in the glandular epithelial cells, stromal cells and endothelial cells of blood capillaries in all bitches except those at oestrous and at 9 weeks of anoestrous. High average apoptotic indices were detected in the basal glandular epithelium of the dioestrous, decreased-dose, standard-dose and increased-dose groups, whereas low apoptotic indices were detected at 3 weeks of anoestrous and in the withdrawal-dose groups. These results indicate that degeneration of cells of the glandular epithelium, but not of the luminal epithelium, was due to apoptosis of these cells.