The epidemic of cardiovascular disease in end-stage renal disease

Cardiovascular disease in children with chronic renal failure

Cardiovascular disease (CVD), including atherosclerosis, hypertension, myocardial infarction, and cerebrovascular accidents, constitutes an important cause of morbidity and mortality in adults with chronic kidney disease (CKD). However, evidence has been accumulating over the past several years that children and young adults with CKD also experience significant cardiovascular complications. Studies in the United States and Europe have shown that CVD is a leading cause of death in young adults diagnosed with CKD in childhood. Risk factors include hypertension, dyslipidemia, anemia, and abnormal calcium-phosphorus metabolism, all of which are present in many children with CKD. Although improved control of uremia and treatment of traditional and nontraditional cardiovascular risk factors have proved to be beneficial in adults with CKD, no such data exist for children. The NIH is currently conducting a large-scale, prospective observational study of children with CKD that should help to elucidate the role of CVD in the progression of CKD in children and what interventions might reduce the risk of cardiovascular complications in these young patients.

An orally active epoxide hydrolase inhibitor lowers blood pressure and provides renal protection in salt-sensitive hypertension

The present study tested the hypothesis that increasing epoxyeicosatrienoic acids by inhibition of soluble epoxide hydrolase (sEH) would lower blood pressure and ameliorate renal damage in salt-sensitive hypertension. Rats were infused with angiotensin and fed a normal-salt diet or an 8% NaCl diet for 14 days. The sEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), was given orally to angiotensin-infused animals during the 14-day period. Plasma AUDA metabolite levels were measured, and they averaged 10+/-2 ng/mL in normal-salt angiotensin hypertension and 19+/-3 ng/mL in high-salt angiotensin hypertension on day 14 in the animals administered the sEH inhibitor. Mean arterial blood pressure averaged 161+/-4 mm Hg in normal-salt and 172+/-5 mm Hg in the high-salt angiotensin hypertension groups on day 14. EH inhibitor treatment significantly lowered blood pressure to 140+/-5 mm Hg in the normal-salt angiotensin hypertension group and to 151+/-6 mm Hg in the high-salt angiotensin hypertension group on day 14. The lower arterial blood pressures in the AUDA-treated groups were associated with increased urinary epoxide-to-diol ratios. Urinary microalbumin levels were measured, and ED-1 staining was used to determine renal damage and macrophage infiltration in the groups. Two weeks of AUDA treatment decreased urinary microalbumin excretion in the normal-salt and high-salt angiotensin hypertension groups and macrophage number in the high-salt angiotensin hypertension group. These data demonstrate that sEH inhibition lowers blood pressure and ameliorates renal damage in angiotensin-dependent, salt-sensitive hypertension.

Epoxide hydrolase and epoxygenase metabolites as therapeutic targets for renal diseases

Renal epoxygenase metabolites are involved in blood flow regulation and long-term blood pressure control. One feature of renal and cardiovascular diseases is the inability of the kidney to properly increase epoxyeicosatrienoic acid (EET) levels. Others (Busse R, Edwards G, Félétou M, Fleming I, Vanhoutte PM, and Weston AH. Trends Phamacol Sci 23: 374–380, 2002; Campbell WB, Gebremedhin D, Pratt PF, and Harder DR. Circ Res 78: 415–423, 1996; Capdevila JH and Falck JR. Biochem Biophys Res Commun 285: 571–576, 2001; Roman RJ. Physiol Rev 82: 131–185, 2002; Zeldin DC. J Biol Chem 276: 36059–36062, 2001) and we (Imig JD, Falck JR, Wei S, and Capdevila JH. J Vasc Res 38: 247–255, 2001; Imig JD, Zhao X, Capdevila JH, Morisseau C, and Hammock BD. Hypertension 39: 690–694, 2002; Zhao X, Pollock DM, Inscho EW, Zeldin DC, and Imig JD. Hypertension 41: 709–714, 2003; Zhao X, Pollock DM, Zeldin DC, and Imig JD. Hypertension 42: 775–780, 2003) have provided compelling evidence that cytochrome P-450-derived EETs have antihypertensive properties and are endothelially derived hyperpolarizing factors (EDHFs) in the kidney. EETs also possess anti-inflammatory actions that could protect the kidney vasculature from injury during renal and cardiovascular diseases. A tactic that has been used to increase EET levels has been inhibition of the soluble epoxide hydrolase enzyme. Epoxide hydrolase inhibitors have been demonstrated to be antihypertensive and renal protective. Thus the renal and cardiovascular protective actions of increasing epoxygenase levels could be translated to therapies for preventing end-organ damage.

Increased vascular growth in hemodialysis patients induced by platelet-derived diadenosine polyphosphates

BACKGROUND

Enhanced vascular smooth muscle cell (VSMC) growth is one hallmark of atherosclerosis. One mechanism responsible for stimulating arterial smooth muscle cell growth is the release of growth factors from platelets aggregating at endothelial lesions. Since in end-stage renal failure (ESRF) atherogenesis is markedly accelerated, the release of VSMC growth factors on aggregation of platelets from hemodialysis patients, ESRF patients in the predialysis stage, and healthy subjects was examined.

METHODS

Platelets were activated by thrombin, and the supernatant was tested for growth stimulation in VSMCs from rat aorta. The cell proliferation rate was determined by [(3)H]-thymidine incorporation in VSMCs. The diadenosine polyphosphate (Ap(n)A with N = 3 to 6) content in the supernatant and in intact platelets was determined using a chromatographic assay established on the basis of affinity- and reversed-phase chromatographic methods.

RESULTS

The thrombin-activated platelet supernatant from hemodialysis patients (N = 15) increased the [(3)H]-thymidine incorporation rate in VSMC s in comparison to the supernatant of healthy control subjects (N = 17, counts/supernatant of 10(6) stimulated platelets +/- SEM, 604 +/- 71 vs. 364 +/- 45, P < 0.05). The addition of the selective P2-receptor blocker pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid to supernatants inhibited the stimulatory effects of Ap(n)A on the growth of vascular smooth muscle cells (219 +/- 53 vs. 156 +/- 71 counts/supernatant of 106 stimulated platelets +/- SEM). The Ap(n)A (N = 3 to 6) amount of thrombin-activated platelet supernatants from hemodialysis patients was significantly higher than in platelets from 10 healthy control subjects (Ap(3)A, 119 +/- 32 vs. 12 +/- 3; Ap(4)A, 154 +/- 59 vs. 43 +/- 20; Ap(5)A, 39 +/- 14 vs. 13 +/- 6; Ap(6)A, 42 +/- 19 vs. 2 +/- 1 fg/platelet +/- SEM, each P < 0.05, N = 10). The intracellular Ap(n)A (N = 3 to 6) amount of intact platelets from hemodialysis patients (N = 61) was significantly higher than that from healthy control subjects [N = 30, Ap(n)A amount (fg/platelet +/- SEM): Ap(3)A, 366 +/- 68 vs. 14.7 +/- 1; Ap(4)A, 336 +/- 48 vs. 19 +/- 2; Ap(5)A, 227 +/- 35 vs. 10 +/- 1; Ap(6)A, 141 +/- 45 vs. 4 +/- 1; each P < 0.01].

CONCLUSIONS

The increased amount of dinucleoside polyphosphate in platelets from hemodialysis patients may be an important additional atherogenic factor.