Role of Kinins in Hypertension and Heart Failure

The kallikrein-kinin system (KKS) is proposed to act as a counter regulatory system against the vasopressor hormonal systems such as the renin-angiotensin system (RAS), aldosterone, and catecholamines. Evidence exists that supports the idea that the KKS is not only critical to blood pressure but may also oppose target organ damage. Kinins are generated from kininogens by tissue and plasma kallikreins. The putative role of kinins in the pathogenesis of hypertension is discussed based on human mutation cases on the KKS or rats with spontaneous mutation in the kininogen gene sequence and mouse models in which the gene expressing only one of the components of the KKS has been deleted or over-expressed. Some of the effects of kinins are mediated via activation of the B(2) and/or B(1) receptor and downstream signaling such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and/or tissue plasminogen activator (T-PA). The role of kinins in blood pressure regulation at normal or under hypertension conditions remains debatable due to contradictory reports from various laboratories. Nevertheless, published reports are consistent on the protective and mediating roles of kinins against ischemia and cardiac preconditioning; reports also demonstrate the roles of kinins in the cardiovascular protective effects of the angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARBs)

Mir-21-Sox2 Axis Delineates Glioblastoma Subtypes with Prognostic Impact.

UNLABELLED: Glioblastoma (GBM) is the most aggressive human brain tumor. Although several molecular subtypes of GBM are recognized, a robust molecular prognostic marker has yet to be identified. Here, we report that the stemness regulator Sox2 is a new, clinically important target of microRNA-21 (miR-21) in GBM, with implications for prognosis. Using the MiR-21-Sox2 regulatory axis, approximately half of all GBM tumors present in the Cancer Genome Atlas (TCGA) and in-house patient databases can be mathematically classified into high miR-21/low Sox2 (Class A) or low miR-21/high Sox2 (Class B) subtypes. This classification reflects phenotypically and molecularly distinct characteristics and is not captured by existing classifications. Supporting the distinct nature of the subtypes, gene set enrichment analysis of the TCGA dataset predicted that Class A and Class B tumors were significantly involved in immune/inflammatory response and in chromosome organization and nervous system development, respectively. Patients with Class B tumors had longer overall survival than those with Class A tumors. Analysis of both databases indicated that the Class A/Class B classification is a better predictor of patient survival than currently used parameters. Further, manipulation of MiR-21-Sox2 levels in orthotopic mouse models supported the longer survival of the Class B subtype. The MiR-21-Sox2 association was also found in mouse neural stem cells and in the mouse brain at different developmental stages, suggesting a role in normal development. Therefore, this mechanism-based classification suggests the presence of two distinct populations of GBM patients with distinguishable phenotypic characteristics and clinical outcomes. SIGNIFICANCE STATEMENT: Molecular profiling-based classification of glioblastoma (GBM) into four subtypes has substantially increased our understanding of the biology of the disease and has pointed to the heterogeneous nature of GBM. However, this classification is not mechanism based and its prognostic value is limited. Here, we identify a new mechanism in GBM (the miR-21-Sox2 axis) that can classify ∼50% of patients into two subtypes with distinct molecular, radiological, and pathological characteristics. Importantly, this classification can predict patient survival better than the currently used parameters. Further, analysis of the miR-21-Sox2 relationship in mouse neural stem cells and in the mouse brain at different developmental stages indicates that miR-21 and Sox2 are predominantly expressed in mutually exclusive patterns, suggesting a role in normal neural development

A role for sweet taste receptors (T1R2/T1R3) in fructose-induced increase in nkcc2 phosphorylation in thick ascending limbs (TALs)

High fructose consumption has been implicated in hypertension, renal damage and metabolic syndrome in humans. We previously showed that a fructose-enriched diet does not increase blood pressure in rats unless it is combined with high salt intake. This effect was accompanied by a large increase in phosphorylation of the renal Na/K/2Cl cotransporter NKCC2 at threonine 96/101. The mechanisms by which fructose induces salt-sensitive hypertension are not clear. In a proteomics screen, we found that the sweet taste receptor T1R2 was present in TALs. Others reported mRNA expression of T1R2 and T1R3 in whole kidney homogenates. Both T1R2 and T1R3 are required to initiate signaling by sweet agonists such as fructose. Unlike glucose, fructose is not fully reabsorbed in the proximal tubule, thus it is possible that activation of sweet taste receptors induce signaling leading to NKCC2 phosphorylation. We hypothesize that a fructose-enriched diet (20% fructose in drinking water) stimulates NKCC2 phosphorylation in part by acting on sweet taste receptors (T1R2/T1R3). To test this, we used C57 wild-type mice (WT) and mice on the C57 background with dual deletion of T1R2 and T1R3 (T1R2/T1R3 KO). Mice were given tap water or 20% fructose in drinking water for 7-8 days. TAL suspensions from WT and T1R2/T1R3 KO mice were obtained to measure total NKCC2 expression, GAPDH (loading control) and NKCC2 phosphorylation at Thre96/101 by Western blot. In WT mice, fructose in drinking water increased phosphorylated NKCC2 by 248 ± 82% (n=5, p\u3c0.01), whereas it decreased total NKCC2 expression by 38 ± 18% (p\u3c0.05). In contrast, in TALs from T1R2/T1R3 KO mice, fructose in drinking water did not affect phosphorylated NKCC2 (PNKCC2/total NKCC2: - 16 ± 28%, p=0.88). We conclude that 1-week of a fructose-enriched diet enhances NKCC2 phosphorylation in the mouse TAL, and this effect is in part due to sweet taste receptors T1R2/T1R3. Hence, our data shows for the first time that sweet taste receptors T1R2 and T1R3 play a role in regulating renal transporters. These receptors could play a role in the deleterious effects of fructose intake in the kidney

Fructose acutely stimulates NKCC2 activity in rat thick ascending limbs by increasing surface NKCC2 expression

The thick ascending limb (TAL) reabsorbs 25% of the filtered NaCl through the Na+-K+-2Cl-cotransporter (NKCC2). NKCC2 activity is directly related to surface NKCC2 expression and phosphorylation. Higher NaCl reabsorption by TALs is linked to salt-sensitive hypertension, which is linked to consumption of fructose in the diet. However, little is known about the effects of fructose on renal NaCl reabsorption. We hypothesized that fructose, but not glucose, acutely enhances TAL-dependent NaCl reabsorption by increasing NKCC2 activity via stimulation of surface NKCC2 levels and phosphorylation at Thr96/101. We found that fructose (5 mM) increased transport-related O2 consumption in TALs by 11.1 ± 3.2% ( P \u3c 0.05). The effect of fructose on O2 consumption was blocked by furosemide. To study the effect of fructose on NKCC2 activity, we measured the initial rate of NKCC2-dependent thallium influx. We found that 20 min of treatment with fructose (5 mM) increased NKCC2 activity by 58.5 ± 16.9% ( P \u3c 0.05). We then used surface biotinylation to measure surface NKCC2 levels in rat TALs. Fructose increased surface NKCC2 expression in a concentration-dependent manner (22 ± 5,  49 ± 10, and 101 ± 59% of baseline with 1, 5, and 10 mM fructose, respectively, P \u3c 0.05), whereas glucose or a glucose metabolite did not. Fructose did not change NKCC2 phosphorylation at Thre96/101 or total NKCC2 expression. We concluded that acute fructose treatment increases NKCC2 activity by enhancing surface NKCC2 expression, rather than NKCC2 phosphorylation. Our data suggest that fructose consumption could contribute to salt-sensitive hypertension by stimulating NKCC2-dependent NaCl reabsorption in TALs

Thymosinβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin 4 (T4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for the T4 and/or its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tbeta4 by two successive enzymes meprin alpha and prolyl oligopeptidase (POP). We also discussed the possible mechanisms involved in the T4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, T4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, T4 and Ac-SDKP have anti-fibrotic and anti-inflammatory properties in the arteries, heart, lungs and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of T4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains, though promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases

Stimulation of sweet taste receptors expressed in the kidney enhance surface NKCC2 levels in thick ascending limbs (TALs)

The thick ascending limb (TAL) reabsorbs 30% of the filtered NaCl via the Na/K/2Cl cotransporter, (NKCC2). NKCC2 activity is regulated by trafficking into and out of the apical membrane. We previously found that the monosaccharide fructose, acutely (20 minutes) increases surface NKCC2 levels and NKCC2 activity in isolated TALs. In the tongue, fructose and other monosaccharides are sensed by the Gprotein coupled sweet taste receptors (T1R2/T1R3). However, the expression and function of T1R2/T1R3 in the kidney or the TAL specifically is unclear. We hypothesize that T1R2/T1R3 are expressed in TALs and their stimulation increases surface NKCC2 levels. We used surface biotinylation and Western blot to measure surface NKCC2 levels in rat or mouse TAL suspensions. By Western blot we observed a single band for T1R2 and T1R3 expression in TALs. We then used gurmarin (GUR), a selective inhibitor of T1R2/T1R3 in rodents, to inhibit fructosestimulated surface NKCC2 expression. We found that treating TALs with GUR completely blocked fructose-stimulated surface NKCC2 expression (Baseline= 100%; fructose= 132 ± 3%; GUR= 89 ± 9%; GUR + fructose= 93 ± 6% n.s.). To directly stimulate T1R2/T1R3 we used the non-caloric sweetener acesulfame-K (AceK). In TALs, 20 min treatment with AceK increased surface NKCC2 expression (Baseline= 100%; AceK 0.5 mM= 134 ± 7%, AceK 1mM= 157 ± 15%, p\u3c0.05). In GUR-treated TALs, AceK did not stimulate surface NKCC2 levels (GUR= 100%; GUR + AceK= 94 ± 5%, n.s.). To understand the role of T1R2/T1R3 in renal function we obtained knockout mice (KO) with dual deletion of the T1R2/T1R3 genes. Under baseline conditions surface NKCC2 levels was decreased in T1R2/R3 KO TALs (WT: 100, Tas1R2/3 KO: 59 ± 15%, p\u3c0.05) whereas total NKCC2 was not changed (n=4). We concluded that stimulation of sweet taste receptors T1R2/T1R3 increases surface NKCC2 expression in TALs. Our data show for the first time a renal function for stimulation of T1R2/T1R3 receptors, and suggest that some of the deleterious effect of fructose could be due to activation of renal sweet taste receptors

Moderate (20%) fructose-enriched diet stimulates salt-sensitive hypertension with increased salt retention and decreased renal nitric oxide

Previously, we reported that 20% fructose diet causes salt-sensitive hypertension. In this study, we hypothesized that a high salt diet supplemented with 20% fructose (in drinking water) stimulates salt-sensitive hypertension by increasing salt retention through decreasing renal nitric oxide. Rats in metabolic cages consumed normal rat chow for 5 days (baseline), then either: (1) normal salt for 2 weeks, (2) 20% fructose in drinking water for 2 weeks, (3) 20% fructose for 1 week, then fructose + high salt (4% NaCl) for 1 week, (4) normal chow for 1 week, then high salt for 1 week, (5) 20% glucose for 1 week, then glucose + high salt for 1 week. Blood pressure, sodium excretion, and cumulative sodium balance were measured. Systolic blood pressure was unchanged by 20% fructose or high salt diet. 20% fructose + high salt increased systolic blood pressure from 125 ± 1 to 140 ± 2 mmHg (P \u3c 0.001). Cumulative sodium balance was greater in rats consuming fructose + high salt than either high salt, or glucose + high salt (114.2 ± 4.4 vs. 103.6 ± 2.2 and 98.6 ± 5.6 mEq/Day19; P \u3c 0.05). Sodium excretion was lower in fructose + high salt group compared to high salt only: 5.33 ± 0.21 versus 7.67 ± 0.31 mmol/24 h; P \u3c 0.001). Nitric oxide excretion was 2935 ± 256 μmol/24 h in high salt-fed rats, but reduced by 40% in the 20% fructose + high salt group (2139 ± 178 μmol /24 hrs P \u3c 0.01). Our results suggest that fructose predisposes rats to salt-sensitivity and, combined with a high salt diet, leads to sodium retention, increased blood pressure, and impaired renal nitric oxide availability

Thymosinβ4-Ac-SDKP pathway: Any relevance for the cardiovascular system?

The last 20 years witnessed the emergence of the thymosin 4 (T4)-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) pathway as a new source of future therapeutic tools to treat cardiovascular and renal diseases. In this review article, we attempted to shed light on the numerous experimental findings pertaining to the many promising cardiovascular therapeutic avenues for the T4 and/or its N-terminal derivative, Ac-SDKP. Specifically, Ac-SDKP is endogenously produced from the 43-amino acid Tβ4 by two successive enzymes meprin α and prolyl oligopeptidase (POP). We also discussed the possible mechanisms involved in the T4-Ac-SDKP-associated cardiovascular biological effects. In infarcted myocardium, T4 and Ac-SDKP facilitate cardiac repair after infarction by promoting endothelial cell migration and myocyte survival. Additionally, T4 and Ac-SDKP have anti-fibrotic and anti-inflammatory properties in the arteries, heart, lungs and kidneys, and stimulate both in vitro and in vivo angiogenesis. The effects of T4 can be mediated directly through a putative receptor (Ku80) or via its enzymatically released N-terminal derivative Ac-SDKP. Despite the localization and characterization of Ac-SDKP binding sites in myocardium, more studies are needed to fully identify and clone Ac-SDKP receptors. It remains, though promising that Ac-SDKP or its degradation-resistant analogs could serve as new therapeutic tools to treat cardiac, vascular and renal injury and dysfunction to be used alone or in combination with the already established pharmacotherapy for cardiovascular diseases.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

N-acetyl-seryl-aspartyl-lysyl-proline treatment protects heart against excessive myocardial injury and heart failure in mice

Myocardial infarction (MI) in mice results in cardiac rupture at 4-7 days post-MI, whereas cardiac fibrosis and dysfunction occur later. Ac-SDKP has anti-inflammatory, anti-fibrotic, and pro-angiogenic properties. We hypothesized that Ac-SDKP reduces cardiac rupture and adverse cardiac remodeling, and improves function by promoting angiogenesis and inhibiting detrimental reactive fibrosis and inflammation after MI. C57BL/6J mice were subjected to MI and treated with Ac-SDKP (1.6 mg/kg/day) for 1 or 5 weeks. We analyzed: 1) intercellular adhesion molecule-1 (ICAM-1) expression; 2) inflammatory cell infiltration and angiogenesis; 3) gelatinolytic activity; 4) incidence of cardiac rupture; 5) p53, the endoplasmic reticulum (ER) stress marker CCAAT/enhancer binding protein homology protein (CHOP), and cardiomyocyte apoptosis; 6) sarcoplasmic reticulum Ca2+ ATPase (SERCA2) expression; 7) interstitial collagen fraction (ICF) and capillary density; and 8) cardiac remodeling and function. Acutely, Ac-SDKP reduced cardiac rupture, decreased ICAM1 expression and the number of infiltrating macrophages, decreased gelatinolytic activity, p53 expression, and myocyte apoptosis, but increased capillary density in the infarction border. Chronically, Ac-SDKP improved cardiac structures and function, reduced CHOP expression and ICF, and preserved myocardium SERCA2 expression. Thus, Ac-SDKP decreased cardiac rupture, ameliorated adverse cardiac remodeling, and improved cardiac function after MI, likely through preserved SERCA2 expression and inhibition of ER stress.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author