Senescence-associated phenotypes in Akita diabetic mice are enhanced by absence of bradykinin B2 receptors

We have previously reported that genetically increased angiotensin-converting enzyme levels, or absence of the bradykinin B2 receptor, increase kidney damage in diabetic mice. We demonstrate here that this is part of a more general phenomenon — diabetes and, to a lesser degree, absence of the B2 receptor, independently but also largely additively when combined, enhance senescence-associated phenotypes in multiple tissues. Thus, at 12 months of age, indicators of senescence (alopecia, skin atrophy, kyphosis, osteoporosis, testicular atrophy, lipofuscin accumulation in renal proximal tubule and testicular Leydig cells, and apoptosis in the testis and intestine) are virtually absent in WT mice, detectable in B2 receptor–null mice, clearly apparent in mice diabetic because of a dominant mutation (Akita) in the Ins2 gene, and most obvious in Akita diabetic plus B2 receptor–null mice. Renal expression of several genes that encode proteins associated with senescence and/or apoptosis (TGF-β1, connective tissue growth factor, p53, α-synuclein, and forkhead box O1) increases in the same progression. Concomitant increases occur in 8-hydroxy-2′-deoxyguanosine, point mutations and deletions in kidney mitochondrial DNA, and thiobarbituric acid–reactive substances in plasma, together with decreases in the reduced form of glutathione in erythrocytes. Thus, absence of the bradykinin B2 receptor increases the oxidative stress, mitochondrial DNA damage, and many senescence-associated phenotypes already present in untreated Akita diabetic mice

Kinin B1 Receptor Enhances the Oxidative Stress in a Rat Model of Insulin Resistance: Outcome in Hypertension, Allodynia and Metabolic Complications

BACKGROUND: Kinin B(1) receptor (B(1)R) is induced by the oxidative stress in models of diabetes mellitus. This study aims at determining whether B(1)R activation could perpetuate the oxidative stress which leads to diabetic complications. METHODS AND FINDINGS: Young Sprague-Dawley rats were fed with 10% D-Glucose or tap water (controls) for 8-12 weeks. A selective B(1)R antagonist (SSR240612) was administered acutely (3-30 mg/kg) or daily for a period of 7 days (10 mg/kg) and the impact was measured on systolic blood pressure, allodynia, protein and/or mRNA B(1)R expression, aortic superoxide anion (O(2)(*-)) production and expression of superoxide dismutase (MnSOD) and catalase. SSR240612 reduced dose-dependently (3-30 mg/kg) high blood pressure in 12-week glucose-fed rats, but had no effect in controls. Eight-week glucose-fed rats exhibited insulin resistance (HOMA index), hypertension, tactile and cold allodynia and significant increases of plasma levels of glucose and insulin. This was associated with higher aortic levels of O(2)(*-), NADPH oxidase activity, MnSOD and catalase expression. All these abnormalities including B(1)R overexpression (spinal cord, aorta, liver and gastrocnemius muscle) were normalized by the prolonged treatment with SSR240612. The production of O(2)(*-) in the aorta of glucose-fed rats was also measured in the presence and absence of inhibitors (10-100 microM) of NADPH oxidase (apocynin), xanthine oxidase (allopurinol) or nitric oxide synthase (L-NAME) with and without Sar[D-Phe(8)]des-Arg(9)-BK (20 microM; B(1)R agonist). Data show that the greater aortic O(2)(*-) production induced by the B(1)R agonist was blocked only by apocynin. CONCLUSIONS: Activation of kinin B(1)R increased O(2)(*-) through the activation of NADPH oxidase in the vasculature. Prolonged blockade of B(1)R restored cardiovascular, sensory and metabolic abnormalities by reducing oxidative stress and B(1)R gene expression in this model

The smooth muscle-selective RhoGAP GRAF3 is a critical regulator of vascular tone and hypertension

Although hypertension is a worldwide health issue, an incomplete understanding of its etiology has hindered our ability to treat this complex disease. Here we identify arhgap42 (also known as GRAF3) as a Rho-specific GAP expressed specifically in smooth muscle cells in mice and humans. We show that GRAF3-deficient mice exhibit significant hypertension and increased pressor responses to angiotensin II and endothelin-1; these effects are prevented by treatment with the Rho-kinase inhibitor, Y-27632. RhoA activity and myosin light chain phosphorylation are elevated in GRAF3-depleted smooth muscle cells in vitro and in vivo, and isolated vessel segments from GRAF3-deficient mice show increased contractility. Taken together our data indicate that GRAF3-mediated inhibition of RhoA activity in vascular smooth muscle cells is necessary for maintaining normal blood pressure homeostasis. Moreover, these findings provide a potential mechanism for a hypertensive locus recently identified within arhgap42 and provide a foundation for the future development of innovative hypertension therapies

Primary aldosteronism and impaired natriuresis in mice underexpressing TGF 1

To uncover the potential cardiovascular effects of human polymorphisms influencing transforming growth factor β1 (TGFβ1) expression, we generated mice with Tgfb1 mRNA expression graded in five steps from 10% to 300% normal. Adrenal expression of the genes for mineralocorticoid-producing enzymes ranged from 50% normal in the hypermorphs at age 12 wk to 400% normal in the hypomorphs accompanied with proportionate changes in plasma aldosterone levels, whereas plasma volumes ranged from 50% to 150% normal accompanied by marked compensatory changes in plasma angiotensin II and renin levels. The aldosterone/renin ratio ranged from 0.3 times normal in the 300% hypermorphs to six times in the 10% hypomorphs, which have elevated blood pressure. Urinary output of water and electrolytes are markedly decreased in the 10% hypomorphs without significant change in the glomerular filtration rate. Renal activities for the Na+, K+-ATPase, and epithelial sodium channel are markedly increased in the 10% hypomorphs. The hypertension in the 10% hypomorphs is corrected by spironolactone or amiloride at doses that do not change blood pressure in wild-type mice. Thus, changes in Tgfb1 expression cause marked progressive changes in multiple systems that regulate blood pressure and fluid homeostasis, with the major effects being mediated by changes in adrenocortical function

Low TGFβ1 expression prevents and high expression exacerbates diabetic nephropathy in mice

About one third of patients with type 1 diabetes mellitus develop nephropathy, which often progresses to end-stage renal diseases. The present study demonstrates that below normal transforming growth factor (TGF) β1 expression ameliorates the nephropathy and decreased glomerular filtration rate resulting from long-standing type 1 diabetes, while above normal TGFβ1 expression makes both worse. Reducing TGFβ1 expression in the glomerulus is more important in avoiding the decrease in glomerular filtration rate than altering expression in the tubule, while expression in the tubule is more important in controlling interstitial fibrosis and albuminuria. Suppressing TGFβ1 action in the kidney as a whole, or specifically in podocytes, could be a promising option for treating/preventing the progressive deterioration of renal function in diabetes

Mouse Models of Diabetic Nephropathy

Diabetic nephropathy is the major cause of end-stage renal disease worldwide. Despite its prevalence, identification of specific factors that cause or predict diabetic nephropathy has been delayed in part by lack of reliable animal models that mimic the disease in humans. The Animal Models of Diabetic Complications Consortium (AMDCC) was created 8 years ago by the National Institutes of Health to develop and characterize models of diabetic nephropathy and other complications. This interim report details the progress made toward that goal, specifically in the development and testing of murine models. Updates are provided on validation criteria for early and advanced diabetic nephropathy, phenotyping methods, the effect of background strain on nephropathy, current best models of diabetic nephropathy, negative models and views of future directions. AMDCC investigators and other investigators in the field have yet to validate a complete murine model of human diabetic kidney disease. Nonetheless, the critical analysis of existing murine models substantially enhances our understanding of this disease process

Brabykinin B1 Receptor Antagonism Is Beneficial in Renal Ischemia-Reperfusion Injury

Previously we have demonstrated that bradykinin B1 receptor deficient mice (B1KO) were protected against renal ischemia and reperfusion injury (IRI). Here, we aimed to analyze the effect of B1 antagonism on renal IRI and to study whether B1R knockout or antagonism could modulate the renal expression of pro and anti-inflammatory molecules. To this end, mice were subjected to 45 minutes ischemia and reperfused at 4, 24, 48 and 120 hours. Wild-type mice were treated intra-peritoneally with antagonists of either B1 (R-954, 200 µg/kg) or B2 receptor (HOE140, 200 µg/kg) 30 minutes prior to ischemia. Blood samples were collected to ascertain serum creatinine level, and kidneys were harvested for gene transcript analyses by real-time PCR. Herein, B1R antagonism (R-954) was able to decrease serum creatinine levels, whereas B2R antagonism had no effect. The protection seen under B1R deletion or antagonism was associated with an increased expression of GATA-3, IL-4 and IL-10 and a decreased T-bet and IL-1β transcription. Moreover, treatment with R-954 resulted in lower MCP-1, and higher HO-1 expression. Our results demonstrated that bradykinin B1R antagonism is beneficial in renal IRI

Infection of XC Cells by MLVs and Ebola Virus Is Endosome-Dependent but Acidification-Independent

Inhibitors of endosome acidification or cathepsin proteases attenuated infections mediated by envelope proteins of xenotropic murine leukemia virus-related virus (XMRV) and Ebola virus, as well as ecotropic, amphotropic, polytropic, and xenotropic murine leukemia viruses (MLVs), indicating that infections by these viruses occur through acidic endosomes and require cathepsin proteases in the susceptible cells such as TE671 cells. However, as previously shown, the endosome acidification inhibitors did not inhibit these viral infections in XC cells. It is generally accepted that the ecotropic MLV infection in XC cells occurs at the plasma membrane. Because cathepsin proteases are activated by low pH in acidic endosomes, the acidification inhibitors may inhibit the viral infections by suppressing cathepsin protease activation. The acidification inhibitors attenuated the activities of cathepsin proteases B and L in TE671 cells, but not in XC cells. Processing of cathepsin protease L was suppressed by the acidification inhibitor in NIH3T3 cells, but again not in XC cells. These results indicate that cathepsin proteases are activated without endosome acidification in XC cells. Treatment with an endocytosis inhibitor or knockdown of dynamin 2 expression by siRNAs suppressed MLV infections in all examined cells including XC cells. Furthermore, endosomal cathepsin proteases were required for these viral infections in XC cells as other susceptible cells. These results suggest that infections of XC cells by the MLVs and Ebola virus occur through endosomes and pH-independent cathepsin activation induces pH-independent infection in XC cells

Elevation of the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline: a blood pressure-independent beneficial effect of angiotensin I-converting enzyme inhibitors

Blockade of the renin-angiotensin system (RAS) is well recognized as an essential therapy in hypertensive, heart, and kidney diseases. There are several classes of drugs that block the RAS; these drugs are known to exhibit antifibrotic action. An analysis of the molecular mechanisms of action for these drugs can reveal potential differences in their antifibrotic roles. In this review, we discuss the antifibrotic action of RAS blockade with an emphasis on the potential importance of angiotensin I-converting enzyme (ACE) inhibition associated with the antifibrotic peptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP)