ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Theklothogene, originally identified by insertional mutagenesis in mice, suppresses the expression of multiple aging-associated phenotypes. This gene is predominantly expressed in the kidney. Recent studies have shown that expression of renalklothogene is regulated in animal models of metabolic diseases and in humans with chronic renal failure. However, little is known about the mechanisms and the physiological relevance of the regulation of the expression of theklothogene in the kidney in some diseased conditions. In the present study, we first investigated the role of angiotensin II in the regulation of renalklothogene expression. Long-term infusion of angiotensin II downregulated renalklothogene expression at both the mRNA and protein levels. This angiotensin II-induced renalklothodownregulation was an angiotensin type 1 receptor-dependent but pressor-independent event. Adenovirus harboring mouseklothogene (ad-klotho, 3.3×1010plaque forming units) was also intravenously administered immediately before starting angiotensin II infusion in some rats. This resulted in a robust induction of Klotho protein in the liver at day 4, which was still detectable 14 days after the gene transfer. Ad-klotho gene transfer, but not ad-lacZ gene transfer, caused an improvement of creatinine clearance, decrease in urinary protein excretion, and amelioration of histologically demonstrated tubulointerstitial damage induced by angiotensin II administration. Our data suggest that downregulation of the renalklothogene may have an aggravative role in the development of renal damage induced by angiotensin II, and that induction of theklothogene may have therapeutic possibilities in treating angiotensin II-induced end organ damage.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The mechanisms through which stress may contribute to the racial difference in the prevalence of essential hypertension and associated target organ damage remain unclear. This study examined differences in stress-induced pressure natriuresis in 69 black and 52 white normotensives age 14 to 27 years, all with a positive family history of hypertension. Urine samples for sodium excretion were collected before and after a series of tasks (video game challenge, forehead cold stimulation). The average blood pressure across the 2 tasks and the average increase in blood pressure to the 2 tasks were calculated. Blacks had higher mean systolic (131±12 versus 126±12 mm Hg,P<0.02) and diastolic (77±8 versus 72±9 mm Hg,P<0.001) blood pressure and a greater average change in systolic blood pressure (15±9 versus 11±7 mm Hg,P<0.04). This was associated with a smaller change in sodium excretion (2±6 versus 7±10 mEq/h,P<0.002). The change in sodium excretion was related to the change in systolic (r=0.31,P<0.03) and diastolic (r=0.27,P<0.05) blood pressure in whites but not in blacks. Relative wall thickness was greater in blacks (0.31±0.04 versus 0.29±0.03,P<0.002). In conclusion, impaired stress-induced pressure natriuresis in blacks may contribute to racial differences in essential hypertension and its sequelae.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

In the adult rodent kidney cortex, cyclooxygenase-2 (COX-2), NO synthase (NOS1), and renin synthesis change in parallel on alterations in distal tubular NaCl concentration, and their products in part may mutually determine synthesis and activity of these enzymes. Epithelial NO synthesis has been postulated to exert a stimulatory role on COX-2 expression. Changes in COX-2 and NOS1 may be assessed histochemically by determining changes in the number of positive cells. In rat, macula densa and adjacent cells may co-express COX-2 and NOS1, whereas cell groups of the upstream thick ascending limb (cTAL) express COX-2 alone. We have tested whether the stimulation of COX-2 expression by short- and long-term unilateral renal artery stenosis, low salt, and furosemide treatment depends on co-expression of NOS1. These conditions produced significant respective increases (40% to 351%,P<0.05) in the number of COX-2 immunoreactive cells, regardless of whether NOS1 was present or not, suggesting that co-expression of NOS1 is not necessary to produce these changes. Under high-salt conditions, analogous though inverse changes were recorded (−62% to −73%,P<0.05). In mice with genetic deletion of NOS1, low- and high-salt diets caused similar changes of COX-2 immunoreactivity (106% and −52%,P<0.05) than those seen in wild-type mice (43% and −78%,P<0.05). We conclude that alterations of distal tubular NaCl concentration and presumably NaCl transport induce changes in epithelial COX-2 expression that does not depend on presence of co-expressed NOS1. It therefore seems unlikely that NO is part of a signal transduction chain between tubular chloride sensing and the modulating effects of prostaglandins in tubulo-vascular information transfer.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Methylation of 2-hydroxyestradiol to 2-methoxyestradiol by catechol-O-methyl transferase (COMT) mediates the antimitogenic effects of 2-hydroxyestradiol on vascular smooth muscle cells. Moreover, 2-hydroxyestradiol inhibits growth of glomerular mesangial cells (GMCs). Because catecholamines are substrates for COMT, which is expressed in GMCs, we hypothesize that catecholamines may abrogate the antimitogenic effects of 2-hydroxyestradiol on GMCs by competing for COMT and inhibiting 2-methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic effects of 2-hydroxyestradiol on rat GMCs in the presence and absence of catecholamines. The capability of GMCs to methylate 2-hydroxyestradiol in the presence and absence of catecholamines was also evaluated. GMCs metabolized 2-hydoxyestradiol in a concentration-dependent manner with a Vmaxof 12.03±0.32 pmol/106cells/min and an apparent Kmof 0.23±0.04 &mgr;mol/L. Norepinephrine (10 &mgr;mol/L) and epinephrine (10 &mgr;mol/L) significantly inhibited methylation of 0.25 &mgr;mol/L 2-hydroxyestradiol. Norepinephrine concentration-dependently abrogated the ability of 2-hydroxyestradiol to inhibit3H-thymidine incorporation (index of DNA synthesis). In the presence of 5, 10, and 40 &mgr;mol/L norepinephrine, the inhibitory effect of 0.1 &mgr;mol/L 2-hydroxyestradiol on3H-thymidine incorporation was reduced from 51±0.7% to 46±0.4%, 39±0.3%, and 25±0.7%, respectively. Similar to DNA synthesis, the inhibitory effects of 2-hydroxyestradiol on cell number and3H-proline incorporation (index of collagen synthesis) on GMCs were abrogated by catecholamines. Our findings provide evidence that methylation of 2-hydroxyestradiol inhibits GMC proliferation and extracellular matrix synthesis and may in part protect against renal proliferative diseases. Moreover, catecholamines may abrogate the renoprotective effects of 2-hydroxyestradiol in the glomeruli by inhibiting COMT and 2-methoxyestradiol formation.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

An apical serine protease, channel-activating protease 1 (CAP1), augments sodium transport in A6 cells. Prostasin, a novel serine protease originally purified from seminal fluid, has been proposed to be the mammalian ortholog of CAP1. We have recently found functional evidence for a similar protease activity in the M-1 cortical collecting duct cell line. The purposes of the present studies were to determine whether prostasin (or CAP1) is present in collecting duct cells by use of mouse M-1 cells, to sequence mouse prostasin, and to further characterize the identity of the serine protease activity and additional functional features in M-1 cells. Using mouse expressed sequence tag sequences that are highly homologous to the published human prostasin sequence as templates, reverse transcription–polymerase chain reaction and RACE (rapid amplification of cDNA ends) were used to sequence mouse prostasin mRNA, which shows 99% identical to published mouse CAP1 sequence. A single 1800-bp transcript was found by Northern analysis, and this was not altered by aldosterone. Equivalent short-circuit current (Ieq), which represents sodium transport in these cells, dropped to 59±3% of control value within 1 hour of incubation with aprotinin, a serine protease inhibitor. Trypsin increased the Ieqin aprotinin-treated cells to the value of the control group within 5 minutes. Application of aprotinin not only inhibited amiloride sensitive Ieqbut also reduced transepithelial resistance (Rte) to 43±2%, an effect not expected with simple inhibition of sodium channels. Trypsin partially reversed the effect of aprotinin on Rte. Another serine protease inhibitor, soybean trypsin inhibitor (STI), decreased Ieqin M-1 cells. STI inhibited Ieqgradually over 6 hours, and the inhibition of Ieqby 2 inhibitors was additive. STI decreased transepithelial resistance much less than did aprotinin. Neither aldosterone nor dexamethasone significantly augmented protease activity or prostasin mRNA levels, and in fact, dexamethasone decreased prostasin mRNA expression. In conclusion, although prostasin is present in M-1 cells and probably augments sodium transport in these cells, serine proteases probably have other effects (eg, resistance) in the collecting duct in addition to effects on sodium channels. Steroids do not alter these effects in M-1 cells. Additional proteases are likely also present in mouse collecting duct cells.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

To elucidate potential mechanisms of enhanced type 2 matrix metalloprotease levels and activity within the thickened aged rat aorta, the present study measured its mRNA and protein levels and those of its membrane bound activator, MT1-MMP, its endogenous tissue inhibitor, TIMP-2, tissue type, and urokinase plasminogen activators and their receptors, and an inhibitor of plasminogen activation in aortae from Fisher 344X Brown Norway rats, 2 to 30 months of age. Semiquantitative immunohistochemistry, in situ hybridization, and in situ zymography of aortae detected a marked age-associated increase in gelatinolytic activity of type 2 metalloprotease within the thickened intima, internal elastic lamina, and elastic fibers in the inner part of the thickened tunica media, whereas the intimal tissue inhibitor of metalloprotease-2 mRNA and protein levels were not age related. Both activators of plasminogen and their receptors increased approximately 2-fold within the intima between 2 to 30 months. Similar, but not identical, age-associated changes in factors that regulate protease activity within the aortic media were also observed. We conclude that discordant regulation of factors that determine the activation status of type 2 matrix metalloprotease, coupled with an increase in the expression of its zymogen, occur with aging, which lead to an increase in the amount of activated protease. These factors are candidate mechanisms for age-associated vascular remodeling, a potent risk factor for vascular diseases with advancing age.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Estrogen receptors (ERs) are considered to mediate the ability of 17&bgr;-estradiol (estradiol) to reduce injury-induced proliferation of vascular smooth muscle cells (VSMCs), leading to vascular lesions. However, the finding that estradiol attenuates formation of vascular lesions in response to vascular injury in knockout mice that lack either ER-&agr; or ER-&bgr; challenges this concept. Our hypothesis is that the local metabolism of estradiol to methoxyestradiols, metabolites of estradiol with little affinity for ERs, mediates the ER-independent antimitogenic effects of estradiol on VSMCs. In human VSMCs, 2-methoxyestradiol and 2-hydroxyestradiol were more potent than was estradiol in inhibiting DNA synthesis (3[H]-thymidine incorporation), collagen synthesis (3[H]-proline incorporation), cell proliferation (cell number), and cell migration (movement of cells across a polycarbonate membrane). The inhibitory effects of estradiol on VSMCs were enhanced by cytochrome-P450 (CYP450) inducers 3-methylcholanthrene and phenobarbital. Moreover, the inhibitory effects of estradiol were blocked in the presence of the CYP450 inhibitor 1-aminobenzotriazole and the catechol-O-methyltransferase inhibitors quercetin and OR486. Both OR486 and quercetin blocked the conversion of 2-hydroxyestradiol to 2-methoxyestradiol; moreover, they blocked the antimitogenic effects of 2-hydroxyestradiol but not of 2-methoxyestradiol. The ER antagonist ICI182780 blocked the inhibitor effects of estradiol on VSMCs, but only at concentrations (>50 &mgr;mol/L) that also inhibit the metabolism of estradiol to hydroxyestradiols (precursors of methoxyestradiols). In conclusion, the inhibitory effects of locally applied estradiol on human VSMCs are mediated via a novel ER-independent mechanism involving estradiol metabolism. These findings imply that vascular estradiol metabolism may be an important determinant of the cardiovascular protective effects of estradiol and that nonfeminizing estradiol metabolites may confer cardiovascular protection regardless of gender.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID