Tyrosine kinase receptor alteration of renal vasoconstriction in rats is sex- and age-related.

Male rat renal blood vessels undergo reduced contraction to norepinephrine with aging. There is a greater renal vascular impairment in male compared with female rats. We investigated specific tyrosine kinase receptor inhibition of renal interlobar artery responsiveness to phenylephrine in male and female rats at specifically designated ages. Vessels from young male rats contracted much less to phenylephrine when the vessels were pretreated with the tyrosine kinase inhibitors Lavendustin A, HNMPA-(AM)3, or AG1478. Vessels from adult female rats pretreated with Lavendustin A showed no difference in contraction from control, but did demonstrate a slightly reduced contraction when pretreated with AG1478. Middle-aged male rat vessels treated with Lavendustin A demonstrated no inhibition, but the insulin and epidermal growth factor receptor (EGFR) antagonists both induced a decline in contraction. Vessels from aged male rats demonstrated no effect related to the 3 pretreatments. Middle-aged and aged female rats pretreated with any inhibitor demonstrated no inhibitor-dependent alterations. We conclude that maximum contraction of interlobar arteries from adult male rats is reduced when tyrosine kinase receptor activity is reduced. Female rats demonstrated much less inhibitor-related change of contraction.

Hydrogen sulfide ameliorates hyperhomocysteinemia-associated chronic renal failure.

Elevated level of homocysteine (Hcy), known as hyperhomocysteinemia (HHcy), is associated with end-stage renal diseases. Hcy metabolizes in the body to produce hydrogen sulfide (H(2)S), and studies have demonstrated a protective role of H(2)S in end-stage organ failure. However, the role of H(2)S in HHcy-associated renal diseases is unclear. The present study was aimed to determine the role of H(2)S in HHcy-associated renal damage. Cystathionine-beta-synthase heterozygous (CBS+/-) and wild-type (WT, C57BL/6J) mice with two kidney (2-K) were used in this study and supplemented with or without NaHS (30 micromol/l, H(2)S donor) in the drinking water. To expedite the HHcy-associated glomerular damage, uninephrectomized (1-K) CBS(+/-) and 1-K WT mice were also used with or without NaHS supplementation. Plasma Hcy levels were elevated in CBS(+/-) 2-K and 1-K and WT 1-K mice along with increased proteinuria, whereas, plasma levels of H(2)S were attenuated in these groups compared with WT 2-K mice. Interestingly, H(2)S supplementation increased plasma H(2)S level and normalized the urinary protein secretion in the similar groups of animals as above. Increased activity of matrix metalloproteinase (MMP)-2 and -9 and apoptotic cells were observed in the renal cortical tissues of CBS(+/-) 2-K and 1-K and WT 1-K mice; however, H(2)S prevented apoptotic cell death and normalized increased MMP activities. Increased expression of desmin and downregulation of nephrin in the cortical tissue of CBS(+/-) 2-K and 1-K and WT 1-K mice were ameliorated with H(2)S supplementation. Additionally, in the kidney tissues of CBS(+/-) 2-K and 1-K and WT 1-K mice, increased superoxide (O(2)(*-)) production and reduced glutathione (GSH)-to-oxidized glutathione (GSSG) ratio were normalized with exogenous H(2)S supplementation. These results demonstrate that HHcy-associated renal damage is related to decreased endogenous H(2)S generation in the body. Additionally, here we demonstrate with evidence that H(2)S supplementation prevents HHcy-associated renal damage, in part, through its antioxidant properties.

Hyperhomocysteinemic diabetic cardiomyopathy: oxidative stress, remodeling, and endothelial-myocyte uncoupling.

Accumulation of oxidized-matrix (fibrosis) between the endothelium (the endothelial cells embedded among the myocytes) and cardiomyocytes is a hallmark of diabetes mellitus and causes diastolic impairment. In diabetes mellitus, elevated levels of homocysteine activate matrix metalloproteinase and disconnect the endothelium from myocytes. Extracellular matrix functionally links the endothelium to the cardiomyocyte and is important for their synchronization. However, in diabetes mellitus, a disconnection is caused by activated metalloproteinase, with subsequent accumulation of oxidized matrix between the endothelium and myocyte. This contributes to endothelial-myocyte uncoupling and leads to impaired diastolic relaxation of the heart in diabetes mellitus. Elevated levels of homocysteine in diabetes are attributed to impaired homocysteine metabolism by glucose and insulin and decreased renal clearance. Homocysteine induces oxidative stress and is inversely related to the expression of peroxisome proliferators activated receptor (PPAR). Several lines of evidence suggest that ablation of the matrix metalloproteinase (MMP-9) gene ameliorates the endothelial-myocyte uncoupling in diabetes mellitus. Homocysteine competes for, and decreases the PPARgammaactivity. In diabetes mellitus, endothelial-myocyte uncoupling is associated with matrix metalloproteinase activation and decreased PPARgamma activity. The purpose of this review is to discuss the role of endothelial-myocyte uncoupling in diabetes mellitus and increased levels of homocysteine, causing activation of latent metalloproteinases, decreased levels of thioredoxin and peroxiredoxin, and cardiac tissue inhibitor of metalloproteinase (CIMP) in response to antagonizing PPARgamma.

Decreased alpha-adrenergic constriction of renal preglomerular arteries occurs with age and is gender-specific in the rat.

Age and/or gender appear to moderate alpha-adrenergic mediated constrictor mechanisms found in the interlobar arteries of the Munich Wistar rat. We have determined the extent of constriction to alpha-adrenergic receptor stimulation using norepinephrine, phenylephrine and A61603 (α1A-adrenergic receptor agonist) as a function of age and gender. Norepinephrine produced less constriction in male-derived arteries at ages greater than eight months as compared to the younger adult male (four to six months). The arteries derived from females did not demonstrate altered constriction until greater than 15 months of age. Similarly, arteries derived from the male demonstrated weaker constrictions to phenylephrine (10(-6) to 10(-3) M) at ages greater than eight months while arteries from females showed differences at greater than 15 months. In contrast, the effective concentration of norepinephrine to cause a 50% maximal constriction (EC50) was significantly less in the four to five-month-old male rats compared to the pooled data from older groups. Interestingly, four to five month old males had A61603 EC50 values similar to the 8 to 12-month and 15+ old females. These studies conclude that an age related loss of sympathetic α-adrenergic constriction of renal interlobar arteries is present in Munich Wistar rats. Furthermore, this loss, while similar along longitudinal aspects of age, is also different as a function of gender with the loss of α-adrenergic constrictor function delayed in the female when compared to the male.

Protein kinase B, P34cdc2 kinase, and p21 ras GTP-binding in kidneys of aging rats.

Renal nephropathy present in male Wistar rats more than 13 months of age was reported as an indication that the rats were in renal failure. In this study, the renal tissue damage at 14 months of age in male Munich Wistar rats was similar to that reported for Wistar rats, indicating that Munich Wistar rats could be another model for study of kidney function in the aging rat. The usual renal response to injury involves increased cell division and/or reparative processes that involve tyrosine kinase activity (TyrK) and/or guanosine triphosphate-binding (G) protein signal trans-duction pathways. This study reveals the presence of renal tissue damage coinciding with significantly reduced activity of Ras, Akt, and p34cdc2 kinase, the signaling proteins that regulate cell division and/or growth, in renal cortical tissues of aging rats compared to young rats (P < 0.005, P < 0.005, and P< 0.001, respectively). These results suggest that proteins involved in signal transduction pathways associated with cell replication are downregulated in the aging kidney cortex at a time when renal cellular damage is also present.

Differential expression of Gs in a murine model of homocysteinemic heart failure.

High plasma homocysteine levels are a known risk factor in heart failure and sudden cardiac death. The G proteins, G(s) (stimulatory) and G(i) (inhibitory), are involved in calcium regulation; overexpression has pathological consequences. The aims of this study were to examine the differential expression of G(s) G protein and G(i) in the hearts of hyperhomocysteinemic (Hhcy) mice, and to determine if homocysteine (Hcy) acts as an agonist in cell culture to mediate the change in G protein isoforms. To create Hhcy, heterozygous cystathionine-beta-synthase (CBS) knockout (KO) mice were used. Mice were sacrificed, hearts were excised, cardiac tissue homogenates were prepared, and Western blots were performed. The results suggested that G(s) G protein was downregulated in cardiac tissue of heterozygous CBS KO mice to 46% that of control hearts. However, the intracellular G(i) G protein content remained the same in heterozygous CBS KO mice. Transformed cardiomyocyte HL-1 cells were treated with varying concentrations of homocysteine. The results suggested no detectable differential G(s) and G(i) expression. This suggested that Hcy did not act as an agonist in vitro to alter G protein content, but that Hcy produced some other in vivo effects to incur these results.

Pioglitazone mitigates renal glomerular vascular changes in high-fat, high-calorie-induced type 2 diabetes mellitus.

Our hypothesis is that impairment of peroxisome proliferator-activated receptor-gamma (PPARgamma) initiates renal dysfunction by increasing renal glomerular matrix metalloproteinase-2 (MMP-2) activity because of increased renal homocysteine (Hcy) and decreased nitric oxide (NO) levels. C57BL/6J mice were made diabetic (D) by being fed a high-fat-calorie diet, and an increase in PPARgamma activity was induced by adding pioglitazone (Pi) to the diet. Mice were grouped as follows: normal calorie diet (N), D, N+Pi, and D+Pi (n = 6/group). The glomerular filtration rate (GFR), renal artery blood flow and pressure, and plasma glucose were measured. Renal glomeruli and preglomerular arterioles were isolated. Plasma and glomerular levels of NO, Hcy, and MMP activity were measured. The contractile response to phenylephrine and the dilatation response to acetylcholine in renal arteriolar rings were measured in a tissue myobath. In N, D, N+Pi, and D+Pi groups, respectively, GFR was 9.4 +/- 1.2, 3.9 +/- 1.1, 9.2 +/- 1.6, and 8.4 +/- 1.4 microl x min(-1) x g body wt(-1). Renovascular resistance was 140 +/- 3, 367 +/- 21, 161 +/- 9, and 153 +/- 10 mmHg x ml x min(-1). Levels of Hcy were increased from 5.8 +/- 1.5 in the N to 18.0 +/- 4.0 micromol/l in the D group. Glomerular levels of MMP-2 were increased in D mice compared with N mice, and there was no change in levels of MMP-9. Treatment with Pi ameliorated glomerular levels of MMP-2 and Hcy in the D group. Renal artery ring contraction and relaxation by phenylephrine and acetylcholine, respectively, were attenuated in the D groups compared with the N groups. Results suggest that a PPARgamma agonist ameliorates preglomerular arteriole remodeling in diabetes by decreasing tissue levels of Hcy and MMP-2 activity and increasing NO.

Reduced alpha adrenergic mediated contraction of renal preglomerular blood vessels as a function of gender and aging.

As human males age, a decline in baroreflex-mediated elevation of blood pressure occurs due, at least in part, to a reduction in alpha-1 adrenergic vasoconstrictor function. Alpha adrenergic constriction is mediated by guanosine triphosphate binding Protein (G Protein) coupled signaling pathways. Alpha-1 A/C, B, and D adrenergic receptor expressions, measured by GeneChip array, are not reduced during aging in renal blood vessels of male or female rats. Alpha-1 A GeneChip expression is greater, at all ages studied, in females than in males. Prazosin binding by alpha-1 adrenergic receptors is greater in young adult female rats than in young adult male rats; however, it is reduced with aging in both male and female rats. G alpha q GeneChip expression declines while expression of adrenergic receptor kinase (GRK2) and tyrosine phosphatases (TyrP) increase with aging in male rats. The declines in alpha-1 adrenergic receptor binding and G alpha q expression and also the increases in GRK2 and TyrP expression likely relate to the age-related decline of vasoconstriction in male rats. The information that the expression of alpha-1 A adrenergic receptors is greater in female rats and (GRK2) expression does not increase during aging could relate to the gender differences in vasoconstrictor function with aging. Gene therapy to ameliorate the age-related decline in renal function could possibly reduce the need for renal dialysis. Signaling pathways such as those reviewed herein may provide an outline of the molecular pathways needed to move toward successful renal gene therapy for aging individuals.

Alpha 1 adrenergic receptor control of renal blood vessels during aging.

Aging humans and rats have a reduced renal vascular constriction response to stress, change in posture, or exercise. In this study, renal interlobar arteries from 9- (intermediate age) to 15-month-old (aging) male Wistar rats constricted less to alpha-adrenergic agonists than those of 4-month-old (young adult) rats. The reduced contraction to A61603 (alpha 1 A agonist) was similar to that to norepinephrine and phenylephrine. Therefore, it appears that the reduction in constriction is primarily related to alpha 1 A receptor stimulation. GeneChip microarray hybridization analysis of the interlobar arteries with the RAE 230A GeneChip indicated that there were no significant differences in gene expression for alpha 1 A/C, 1B, or 1D receptors between 4-month-old (young adult) and 1-year-old (aging) male Wistar rats. Competitive binding experiments (prazosin) revealed that maximal binding (Bmax, fmol/mg protein) of the alpha 1 receptors of interlobar arteries was reduced 25% by 10 months of age and 50% by 18+ months of age. Alpha 1 receptor-induced arterial constriction and prazosin binding were both down-regulated. The loss of receptor-initiated constriction likely includes down-regulation of maximum agonist binding by alpha 1 adrenergic receptors.