Mechanisms underlying renoprotection during renin-angiotensin system blockade.

Potential determinants of chronic renal disease (CRD) progression were studied in male Munich-Wistar rats subjected to 5/6 nephrectomy and treated with candesartan (Csn; n = 30) or enalapril (Ena; n = 27) from 5 wk postsurgery. Despite control of systolic blood pressure (SBP; 24 wk: Csn = 143 +/- 9; Ena = 148 +/- 8 mmHg), urinary protein excretion rates (U(pr)V) increased over 24 wk (Csn = 92 +/- 10; Ena = 99 +/- 8mg/day). Glomerulosclerosis scores (GS) at 24 wk were similar for Csn (42 +/- 7%) vs. Ena (42 +/- 4%), values close to those of untreated controls at 12 wk (43 +/- 4%). At 24 wk, SBP and UprV correlated strongly with GS, together accounting for 72% of the variance in GS. Renal cortex mRNA levels (determined by competitive RT-PCR) for transforming growth factor (TGF)-beta1 and monocyte chemoattractant protein (MCP)-1 were elevated in Csn and Ena at 12 wk and remained higher at 24 wk vs. sham. Strong correlations were evident among TGF-beta1, MCP-1, and interleukin-1beta and renal injury at 24 wk. Cns and Ena are thus equally effective renoprotective agents in this model. During renin-angiotensin system inhibition, renoprotection is dependent on control of both SBP and UprV. Incomplete suppression of renal cytokine gene expression may also contribute to CRD progression.

Adrenomedullin and its receptor complexes in remnant kidneys of rats with renal mass ablation: decreased expression of calcitonin receptor-like receptor and receptor-activity modifying protein-3.

Adrenomedullin (AM) has vasodilator and diuretic actions, similarly to natriuretic peptides. AM receptor complexes are composed of calcitonin receptor-like receptor (CRLR) and receptor-activity modifying protein-2 (RAMP2), or CRLR and RAMP3. We aimed to know whether gene expression of AM and AM receptor complexes are regulated in kidneys under pathophysiological conditions. Expression of AM, RAMP2, RAMP3 and CRLR mRNA was studied in the remnant kidney of rats with renal mass ablation using competitive quantitative RT-PCR techniques. Partial cloning was performed to determine the rat RAMP3 nucleotide sequence. In normal rat kidneys, expression levels of RAMP2, RAMP3, CRLR and AM mRNAs were 26.5 +/- 1.9 mmol/mole of GAPDH, 7.7 +/- 0.9 mmol/mole of GAPDH, 3.6 +/- 0.2 mmol/mole of GAPDH and 0.57 +/- 0.03 mmol/mole of GAPDH (mean +/- SE, n = 6), respectively. RAMP3 mRNA levels decreased significantly to about 50% and about 70% of control (sham-operated rats) 4 days and 14 days after 5/6 nephrectomy, respectively. CRLR mRNA levels also decreased significantly to about 30% and about 43% of control. Sodium intake restriction had no significant effects on the RAMP3 and CRLR gene expression. On the other hand, RAMP2 mRNA expression in the kidney was suppressed by sodium intake restriction regardless of nephrectomy, while RAMP2 levels in the remnant kidney were not significantly changed by 5/6 nephrectomy. Neither 5/6 nephrectomy or sodium intake restriction had any significant effects on the AM gene expression in the kidney. The present study showed that expression of mRNAs encoding AM, RAMP2, RAMP3 and CRLR were differentially regulated in remnant kidneys of rats with renal mass ablation.

Increased gene expression of adrenomedullin and adrenomedullin-receptor complexes, receptor-activity modifying protein (RAMP)2 and calcitonin-receptor-like receptor (CRLR) in the hearts of rats with congestive heart failure.

Adrenomedullin is a vasodilator peptide produced in various organs, including heart and kidney. A novel adrenomedullin receptor complex has recently been identified, namely the calcitonin receptor-like receptor (CRLR) and receptor-activity modifying protein (RAMP) 2. In the present study, we have examined gene expression of RAMP2, CRLR and adrenomedullin in hearts and kidneys of rats with congestive heart failure caused by coronary artery ligation. Partial cloning was performed to determine the rat RAMP2 nucleotide sequence. Messenger RNA levels were then determined using competitive, quantitative reverse transcription-PCR techniques. Significantly increased expression levels (means+/-S.E.) of RAMP2, CRLR and adrenomedullin mRNA were found in the atrium (1.8+/-0.2-fold, 1. 8+/-0.2-fold and 2.1+/-0.1-fold, respectively, compared with sham operated rats) and in the ventricle (1.4+/-0.1-fold, 1.3+/-0.03-fold and 3.0+/-0.5-fold respectively). On the other hand, expression levels of RAMP2, CRLR and adrenomedullin mRNAs were not significantly changed in the kidney. These findings suggest potential roles of locally-produced and locally-acting adrenomedullin in the failing heart.

Proinflammatory gene expression and macrophage recruitment in the rat remnant kidney.

BACKGROUND: Macrophage (Mphi) infiltration may contribute to chronic renal injury. We therefore sought to examine the expression of genes associated with Mphi recruitment in the rat remnant kidney model. METHODS: Male Munich Wistar rats underwent 5/6 nephrectomy or sham operation (SHM, N = 18) and received no treatment (VEH, N = 18), enalapril 100 mg/L (ENA, N = 18), or candesartan 70 mg/L (CSN, N = 24) in drinking water. Competitive, quantitative reverse transcription-polymerase chain reaction was used to determine renal cortex mRNA levels for cell adhesion molecules vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1), the Mphi chemoattractant monocyte chemoattractant protein-1 (MCP-1), Mphi products interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha), and the profibrotic cytokine transforming growth factor-beta1 (TGF-beta1), at intervals post-nephrectomy. RESULTS: Glomerular and interstitial Mphi infiltration in VEH rats was associated with an early (4 week) and sustained rise in MCP-1 and TGF-beta1 mRNA levels. Progressive increases in ICAM-1, VCAM-1, IL-1beta, and TNF-alpha expression followed at 8 and 12 weeks. Immunostaining in VEH rats localized TGF-beta1 to glomeruli, tubules, and interstitium; MCP-1 to tubules and interstitial cells; ICAM-1 to glomeruli; and IL-1beta and TNF-alpha to tubules and interstitial cells. At 12 weeks, both treatments normalized systolic blood pressure (ENA, 105 +/- 6; CSN, 97 +/- 3 mm Hg) and the urinary protein excretion rate (ENA, 8.4 +/- 0.9; CSN, 5.7 +/- 0.8 mg/day), prevented renal injury (focal and segmental glomerulosclerosis: ENA, 3.3 +/- 0.9; CSN, 1.3 +/- 0.4%), and suppressed Mphi infiltration and cytokine expression (with the exception of TNF-alpha) to near SHM levels. CONCLUSIONS: These findings support the hypothesis that the coordinated up-regulation of several molecules regulating Mphi recruitment and activation is a fundamental response to renal mass ablation and is dependent on an intact renin-angiotensin system. We speculate that these responses may play a role in the pathogenesis of the ensuing glomerulosclerosis and tubulointerstitial fibrosis.

Cellular and molecular mediators in common pathway mechanisms of chronic renal disease progression.

Injury mechanisms activated by the hemodynamic adaptations to nephron loss are considered to represent a final common pathway that underlies the progressive nature of chronic renal disease. In this article, we review experimental evidence that the induction of cell adhesion molecule, cytokine and profibrotic growth factor gene expression and the resultant renal infiltration by inflammatory cells, especially macrophages, are important components of these common pathway mechanisms. Interventions aimed at inhibiting these mechanisms may offer new treatments for slowing or arresting the progression of chronic renal disease.

Renal allograft protection with losartan in Fisher-->Lewis rats: hemodynamics, macrophages, and cytokines.

BACKGROUND: We sought to assess the effects of angiotensin receptor blockade on glomerular hypertension, macrophage recruitment, and cytokine expression, all of which contribute to the development of chronic graft injury in this model. METHODS: The effects of treatment with the specific angiotensin II type 1 (AT1) receptor antagonist, losartan, were assessed over 24 weeks in F344-->LEW rats (LOS, N = 9) versus vehicle-treated F344-->LEW controls (CON, N = 9). RESULTS: UprotV rose progressively in CON (from 7.0 +/- 2.9 to 41 +/- 17 mg/day at 24 wk) but remained at baseline in LOS (4.2 +/- 0.6 to 9.4 +/- 1.3 mg/day, P < 0.05 vs. CON). Glomerular capillary pressure (PGC) was increased in CON (71 +/- 1 mm Hg at week 20), but remained within the normal range in LOS rats (54 +/- 2 mm Hg, P < 0.05). Glomerulosclerosis averaged 0.3 +/- 0.2% in LOS versus 4 +/- 2% in CON rats (P < 0.05). Tubulointerstitial injury was minimal in both LOS and CON rats (+). The overexpression of renal cortical cytokine mRNA levels for the monocyte chemoattractants, monocyte chemoattractant protein-1 (MCP-1) and RANTES, as well as interleukin-1, inducible nitric oxide synthase, and transforming growth factor-beta, assessed by competitive reverse transcription-polymerase chain reaction, was suppressed in LOS versus CON rats at 20 weeks. Macrophage and T-cell numbers were decreased, and MCP-1, RANTES, and intercellular adhesion molecule-1 staining in the graft, identified by immunohistochemistry, were attenuated in LOS versus CON rats. CONCLUSIONS: The renoprotective effects of losartan in F344-->LEW rats were associated with lowered PGC, inhibition of macrophage chemoattractants and recruitment, and suppression of macrophage-associated cytokines at 20 weeks. These findings suggest that chronic allograft injury in F344-->LEW rats is, to a large extent, mediated by angiotensin II-dependent mechanisms and that these involve glomerular hemodynamics, macrophages, and macrophage-associated cytokines.

Long-term regulation of urea transporter expression by vasopressin in Brattleboro rats.

Regulation of urea concentration in the renal medullary interstitium is important for maintenance of hypertonicity and therefore the osmotic driving force for water reabsorption. Studies in Sprague-Dawley rats showed that restriction of water intake for 3 days results in upregulation of urea transporter (UT) mRNA in the inner stripe of outer medulla of the kidney (2.9-kb UT2) but not in the inner medulla (4.0-kb UT1). The present study was performed to investigate the role of vasopressin in long-term regulation of UT1 and UT2 in neurogenic diabetes insipidus (Brattleboro) rats treated with a 7-day continuous infusion of [Arg(8)]-vasopressin (AVP), [deamino-Cys(1), D-Arg(8)]-vasopressin (dDAVP) or vehicle. Northern analysis showed that water restriction alone had no effect on the level of UT2 mRNA in vehicle-treated Brattleboro rats but UT2 mRNA markedly increased and UT1 mRNA modestly decreased after treatment with dDAVP. In situ hybridization further demonstrated that the UT2 signal is upregulated and spread along the descending thin limbs of loops of Henle and that UT1 signal is downregulated in the inner medullary collecting ducts in vasopressin-treated rats, with a greater response for dDAVP compared with the AVP-treated group. Immunocytochemistry studies revealed that the UT1 and UT2 proteins are also modified in the same pattern as the transcript changes. Our studies reveal the role of vasopressin in long-term regulation of UT1 and UT2 expression during water restriction.

IHG-2, a mesangial cell gene induced by high glucose, is human gremlin. Regulation by extracellular glucose concentration, cyclic mechanical strain, and transforming growth factor-beta1.

We used cloning in silico coupled with polymerase chain reaction to demonstrate that IHG-2 is part of the 3'-untranslated region of gremlin, a member of the DAN family of secreted proteins that antagonize the bioactivities of members of the transforming growth factor (TGF)-beta superfamily. Mesangial cell gremlin mRNA levels were induced by high glucose, cyclic mechanical strain, and TGF-beta1 in vitro, and gremlin mRNA levels were elevated in the renal cortex of rats with streptozotocin-induced diabetic nephropathy in vivo. gremlin expression was observed in parallel with induction of bone morphogenetic protein-2 (BMP-2), a target for gremlin in models of cell differentiation. Together these data indicate that (a) IHG-2 is gremlin, (b) gremlin is expressed in diabetic nephropathy in vivo, (c) both glycemic and mechanical strain stimulate mesangial cell gremlin expression in vitro, (d) high glucose induces gremlin, in part, through TGFbeta-mediated pathways, and (e) Gremlin is a potential endogenous antagonist of BMPs within a diabetic glomerular milieu.

Activation of inflammatory mediators in rat renal isografts by donor brain death.

BACKGROUND: Brain death (BD) has been thought to influence the early course of transplanted organs by triggering a series of nonspecific inflammatory events that in turn may increase the kinetics and intensity of the immunological host responses. In this study early nonspecific, cellular, and molecular changes occurring in kidney isografts from BD donors are compared with those from normal anesthetized, ventilated controls. METHODS: After induction of brain death, the animals were mechanically ventilated for 6 hr before organ removal. Only rats with stable blood pressure (mean arterial pressure >80 mmHg) were included. Serum creatinines were measured daily. Representative grafts were harvested 6 hr after brain death and between 1 hr and 5 days after engraftment for morphology, immunohistology, and reverse transcriptase-polymerase chain reaction. The presence of serum cytokines was assessed by enzyme linked immunoabsorbant assay. RESULTS: Serum creatinine levels rose slightly in recipients from BD donors. Serum interleukin-1beta levels increased within 6 hr versus controls (P<0.05). mRNA levels of interleukin-1beta and macrophage inhibitory protein-1 in the kidneys were up-regulated transiently before engraftment (6 hr after BD) and 1 hr after revascularization (P<0.05). By immunohistology, numbers of infiltrating polymorphonuclear leukocytes peaked at 24 hr in parallel with intragraft induction of P- and E-selectin, complement, and other proinflammatory chemokines and cytokines. At 5 days, the isografts from BD donors were highly infiltrated by host leukocyte populations associated with intense up-regulation of their products. In contrast, those from control donors remained relatively normal through this initial follow-up period. CONCLUSIONS: The intense nonimmune inflammation produced in isografts after donor BD may represent the initial stages of a continuum between an initial nonspecific and later immune reactivity, when placed in the context of allotransplantation.

Renin-angiotensin blockade lowers MCP-1 expression in diabetic rats.

BACKGROUND: Glomerular macrophage accumulation in diabetes implicates monocyte recruitment mechanisms in the pathogenesis of diabetic nephropathy. To test the hypothesis that overexpression of monocyte chemoattractant protein-1 (MCP-1), a monocyte chemoattractant, is attenuated by renin-angiotensin system (RAS) inhibition, we assessed expression of genes regulating monocyte transmigration in the glomeruli of diabetic rats. METHODS: Competitive reverse transcription-polymerase chain reaction (RT-PCR) was used to semiquantitate mRNA expression in glomeruli harvested by sieving at serial intervals after the induction of diabetes by streptozotocin in Munich-Wistar rats. Although subject to limitations, competitive RT-PCR provides an objective measure suited to the minute quantities of RNA extractable from glomerular isolates. RESULTS: Time-dependent elevation of MCP-1 expression was dramatically suppressed by treatment with the angiotensin-converting enzyme inhibitor enalapril or the AT1 receptor antagonist candesartan, and was closely associated with effects on proteinuria and glomerular macrophage number. By contrast, no sustained suppression of the cell adhesion molecules intercellular adhesion molecule-1 or vascular cell adhesion molecule-1 or the classic MCP-1 stimulators tumor necrosis factor-alpha or interleukin-1beta followed RAS inhibition, and suppression of transforming growth factor-beta1 expression was transient. CONCLUSION: These data suggest that glomerular macrophage recruitment in experimental diabetes is largely determined by angiotensin-stimulated MCP-1 expression. We conclude that the RAS is an important regulator of local MCP-1 expression, either directly or through glomerular hemodynamic effects, and that our data strongly implicate macrophage recruitment and activation in the pathogenesis of early diabetic glomerular injury.

Angiotensin receptor blockers in chronic renal disease: the promise of a bright clinical future.

Pharmacologic interruption of the renin-angiotensin system (RAS) with angiotensin-converting enzyme inhibitors (ACEI) is considered a standard therapeutic intervention for patients with chronic renal disease, regardless of whether systemic hypertension is present. The advent of orally active angiotensin receptor blockers (ARB) increases the number of therapeutic options for inhibiting the RAS in patients with chronic renal diseases. Clinical studies of ARB that can be compared with large-scale ACEI clinical trials have yet to be completed. More than a dozen experimental studies comparing ARB with ACEI suggest that the two classes of drugs share similar renoprotective properties. Like ACEI, ARB are effective antihypertensive and antiproteinuric agents, which greatly reduce glomerular and tubulointerstitial scarring. Although both reduce stimulation of the AT1 receptor, ARB lack the kinin-potentiating effects of ACEI. ARB may exert antifibrotic actions via the AT2 receptor, through increased levels of angiotensin II resulting from AT1 receptor blockade. Despite these pharmacologic distinctions, recent studies have not detected differences in renoprotection between ARB and ACEI. In the context of RAS inhibition, the magnitude of antihypertensive and antiproteinuric effects achieved appears to be the major determinant of renoprotection, not the class of drug used. Thus, experimental data suggest that ARB will fulfill their promise as effective agents to be used as mainstays in multifaceted clinical strategies designed to slow or arrest the progression of chronic renal disease. Confirmation of this view awaits the results of clinical trials.

Renal function in high-output heart failure in rats: role of endogenous natriuretic peptides.

The physiologic and pathophysiologic importance of natriuretic peptides (NP) has been imperfectly defined. The diminished renal responses to exogenous atrial NP in heart failure have led to the perception that the endogenous NP system might be less effective and thus contribute to renal sodium retention in heart failure. This study tests the hypothesis that in experimental heart failure, the renal responses to an acute volume load are still dependent on the NP system. The specific antagonist HS-142-1 was used to block the effects of NP in a model of high-output heart failure induced by an aortocaval shunt. Plasma cGMP levels and renal cGMP excretion were significantly lower in shunted and sham-operated rats receiving HS-142-1, compared with vehicle-treated controls, indicating effective blockade of guanylate cyclase-coupled receptors. Baseline sodium excretion and urine flow rate were lower in HS-142-1-treated sham-operated rats (15.2+/-1.1 microl/min versus 27.5+/-3.1 microl/min with vehicle, P < 0.001) and in HS-142-1-treated shunted rats (8.1+/-1.3 microl/min versus 19.9+/-2.3 microl/min with vehicle, P < 0.001). After an acute volume load, the diuretic and natriuretic responses were attenuated by HS-142-1 in control and shunted rats. The renal responses were reduced by HS-142-1 to a significantly greater extent in shunted rats than in control rats. HS-142-1 did not induce any significant systemic hemodynamic changes in either group, nor did it alter renal blood flow. However, the GFR in HS-142-1-treated shunted rats was lower than that in vehicle-treated shunted rats, both at baseline (0.6+/-0.3 ml/min versus 2.1+/-0.4 ml/min with vehicle, P < 0.05) and after an acute volume load (1.2+/-0.4 ml/min versus 2.6+/-0.4 ml/min with vehicle, P = 0.01), whereas no such effect was observed in control rats. These data indicate that the maintenance of basal renal function and the responses to acute volume loading are dependent on the NP system. The NP seem to be of particular importance for the maintenance of GFR in this model of experimental heart failure. These observations provide new insights into the importance of the renal NP system in heart failure.

Suppression subtractive hybridization identifies high glucose levels as a stimulus for expression of connective tissue growth factor and other genes in human mesangial cells.

Accumulation of mesangial matrix is a pivotal event in the pathophysiology of diabetic nephropathy. The molecular triggers for matrix production are still being defined. Here, suppression subtractive hybridization identified 15 genes differentially induced when primary human mesangial cells are exposed to high glucose (30 mM versus 5 mM) in vitro. These genes included (a) known regulators of mesangial cell activation in diabetic nephropathy (fibronectin, caldesmon, thrombospondin, and plasminogen activator inhibitor-1), (b) novel genes, and (c) known genes whose induction by high glucose has not been reported. Prominent among the latter were genes encoding cytoskeleton-associated proteins and connective tissue growth factor (CTGF), a modulator of fibroblast matrix production. In parallel experiments, elevated CTGF mRNA levels were demonstrated in glomeruli of rats with streptozotocin-induced diabetic nephropathy. Mannitol provoked less mesangial cell CTGF expression in vitro than high glucose, excluding hyperosmolality as the key stimulus. The addition of recombinant CTGF to cultured mesangial cells enhanced expression of extracellular matrix proteins. High glucose stimulated expression of transforming growth factor beta1 (TGF-beta1), and addition of TGF-beta1 to mesangial cells triggered CTGF expression. CTGF expression induced by high glucose was partially suppressed by anti-TGF-beta1 antibody and by the protein kinase C inhibitor GF 109203X. Together, these data suggest that 1) high glucose stimulates mesangial CTGF expression by TGFbeta1-dependent and protein kinase C dependent pathways, and 2) CTGF may be a mediator of TGFbeta1-driven matrix production within a diabetic milieu.

Upregulation of atrial natriuretic peptide gene expression in remnant kidney of rats with reduced renal mass.

Atrial natriuretic peptide (ANP) is synthesized in the kidney but its physiologic significance there is unclear. To determine whether renal expression of the ANP gene is regulated, renal ANP mRNA expression was assessed in remnant kidneys after 5/6 nephrectomy in Munich-Wistar rats. In normal sodium intake groups, ANP mRNA expression in the remnant kidney was significantly increased by 5.0 +/- 0.8-fold (n = 7, mean +/- SEM) at 4 d when compared with sham-operated controls (n = 6, all sham-operated groups) (*P < 0.001 by Scheffe's test) and by 28.3 +/- 5.1-fold at 14 d. This latter response was markedly diminished to 7.6 +/- 2.1-fold (n = 7, versus sham) in rats maintained on a low sodium diet. At 4 d, on the other hand, no significant downregulation was observed with dietary sodium restriction. Because natriuretic peptides have previously been shown by us to play a major role in the adaptive responses of remnant nephrons to renal mass ablation, these data suggest that ANP of renal origin may contribute to the overall mechanism for enhancing sodium excretion in the face of declining nephron number.

Effects of explosive brain death on cytokine activation of peripheral organs in the rat.

BACKGROUND: The success rate of transplanted organs from brain-dead cadaver donors is consistently inferior to that of living sources. As cadaver and living unrelated donors are equally genetically disparate with a given recipient, the difference must lie within the donor himself and/or the effects of organ preservation and storage. We have hypothesized that irreversible central nervous system injury may up-regulate proinflammatory mediators and cell surface molecules in peripheral organs to be engrafted, making them more prone to host inflammatory and immunological responses. METHODS: Rats undergoing surgically induced acutely increased intracranial pressure (explosive brain death) were followed for 6 hr. Their peripheral tissues were examined by reverse transcriptase polymerase chain reaction and immunohistology, serum factors were assessed by enzyme-linked immunosorbent assay, and the influence of inflammatory molecules in the blood stream was determined by cross-circulation experiments with normal animals. RESULTS: mRNA expression of both lymphocyte- and macrophage-associated products increased dramatically in all tissues. Similar factors in serum were coincidentally increased; these were shown to be active in vivo by cross-circulation with normal animals. The organs of all control groups, including animals with important ischemic injury and with hemorrhagic shock, were negative. Up-regulation of MHC class I and II antigens and the co-stimulatory molecule B7 suggests increased immunogenicity of the peripheral organs. These changes could be inhibited by: (i) administration of a recombinant soluble P-selectin glycoprotein ligand-Ig, a P- and E-selectin antagonist; and (ii) a fusion protein, cytotoxic T lymphocyte antigen 4-Ig, which blocks B7-mediated T-cell co-stimulation. CONCLUSIONS: Activation of peripheral organs following explosive brain death may be caused by various interrelated events, including the effects of massive acute central injury, hypotension, and circulating factors. Almost complete suppression of these changes could be produced by biological agents. Such interventions, if reproducible in humans, could improve the quality of organs from "marginal" donors, broadening the criteria for donor acceptance.

Effects of combination therapy with enalapril and losartan on the rate of progression of renal injury in rats with 5/6 renal mass ablation.

Angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II receptor antagonists (AT1RA) slow the rate of progression of experimental renal disease. Although the end result of both classes of drugs is to block the renin-angiotensin system (RAS), ACEI and AT1RA act at different sites in the RAS cascade. The aim of this study was to compare the effects of an ACEI (enalapril) and AT1RA (losartan), alone or in combination, in slowing the progression of experimental renal disease in a model of reduced renal mass. Two weeks after 5/6 renal ablation, rats were divided into five groups matched for body weight, systolic BP (SBP), and urinary protein excretion rate (UprotV). The effects on SBP and UprotV of treatment with 25 and 40 mg/L enalapril (groups I and II; both n = 7), 180 mg/L losartan (group III, n = 8), or a combination of enalapril (25 mg/L) + losartan (180 mg/L) (group IV, n = 9) versus vehicle (group V, n = 9) were studied for 12 wk. Remnant kidneys were then assessed histologically for evidence of focal and segmental glomerulosclerosis and hyalinosis (FSGS), and interstitial fibrosis. There were no significant differences (NSD) in body weight among the groups at any time. Combination therapy reduced SBP (122 +/- 8 mmHg) significantly at 12 wk to levels similar to losartan (127 +/- 3 mmHg) or enalapril (40 mg/L) alone (124 +/- 5 mmHg) (P < 0.05 versus vehicle controls). With equivalent antihypertensive effects, no differences in frequency of FSGS were discerned among the treatment groups (groups II through IV; F = 1.7, NSD). Tubulointerstitial injury scores followed a similar pattern. BP was highly correlated with the extent of FSGS, both among individual rats (r = 0.68, P = 0.05) and the group means (r = 0.99, P = 0.001). We conclude that the renoprotective effects of enalapril, losartan, or combination therapy are similar in this model over the 12 wk of the study, and are closely related to the magnitude of their antihypertensive effects.

Apoptosis of endothelial cells is associated with paracrine induction of adhesion molecules: evidence for an interleukin-1beta-dependent paracrine loop.

Monocytic infiltration of the vessel wall is a hallmark of injury in a variety of vascular diseases. In the present study, we explored the relationship between endothelial apoptosis and hyperadhesiveness for monocytic cells. Apoptosis of human umbilical vein endothelial cells (HUVECs) was induced by either growth factor deprivation (GFD) for 24 hours or by incubation with mitomycin C (MMC) at 0.01 mg/ml for 24 hours and confirmed by light microscopy and DNA laddering. In parallel assessments of cell-cell adhesion, GFD and MMC induced hyperadhesiveness of HUVECs for the THP-1 monocytic cell line. Hyperadhesiveness developed in association with induction of intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 on HUVECs and was attenuated by monoclonal antibodies directed against these ligands. Culture medium conditioned by apoptotic HUVECs up-regulated the expression of adhesion molecules on normal HUVECs, suggesting that paracrine factors in the apoptotic milieu led to induction of adhesion molecules. Interleukin (IL)-1beta was implicated as a putative mediator in this setting because 1) exogenous IL-1beta up-regulates ICAM-1 and VCAM-1 with kinetics similar to those noted during endothelial cell apoptosis, 2) endothelial apoptosis was associated with increased expression of IL-1beta converting enzyme, and 3) the adhesion-promoting actions of GFD and MMC were attenuated by an anti-IL-1beta antibody.