Angiotensin II stimulates the synthesis and secretion of vascular permeability factor/vascular endothelial growth factor in human mesangial cells

Angiotensin-converting enzyme gene DD genotype neither increases susceptibility to acute pancreatitis nor influences disease severity

BACKGROUND

The renin-angiotensin system (RAS) has been implied in the pathogenesis of various diseases including acute and chronic pancreatitis. Angiotensin-converting enzyme (ACE) is the key enzyme in activating the RAS. Deletion (D)-type polymorphism in the 16th intron of the ACE gene has been associated with higher serum levels of the enzyme. Inhibition of ACE was found to ameliorate acute pancreatitis in animal models suggesting that ACE plays a role in pathogenesis and progression of acute pancreatitis. Objectives were to investigate the occurrence of the ACE insertion/deletion (I/D) polymorphism in acute pancreatitis patients and its association with the severity of the disease.

MATERIAL AND METHODS

Seventy-nine acute pancreatitis patients and 95 healthy controls were evaluated. Acute pancreatitis cases were grouped as mild or severe according to the Atlanta criteria.

MAIN OUTCOME MEASURE

The presence of the ACE I/D polymorphism.

RESULTS

ACE gene I and D allele frequency of patients (44% and 56%) were similar to controls (45% and 55%, respectively). There were no significant differences in severity of pancreatitis between patients with the ACE-insertion or ACE-insertion/deletion versus ACE-deletion genotypes.

CONCLUSIONS

The ACE gene deletion polymorphism is neither a risk factor for development of acute pancreatitis nor contributes to the severity of disease or development of complications.

Regulation of renal 12(S)-hydroxyeicosatetraenoic acid in diabetes by angiotensin AT1 and AT2 receptors

Diabetes is associated with increased production of 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE]. The mechanisms involved in this process remain unclear. We hypothesized that hyperglycemia and angiotensin II (ANG II) regulate renal 12(S)-HETE production via a balance between angiotensin AT(1) and AT(2) receptors activities. Using a microdialysis technique, renal interstitial fluid (RIF) levels of ANG II and 12(S)-HETE were monitored in normal control and streptozotocin-induced diabetic rats at baseline and then weekly thereafter for 12 wk. In a second group of normal and diabetic rats, 3 wk after development of diabetes, we monitored RIF 12(S)-HETE levels in response to acute AT(1) receptor blockade with valsartan or AT(2) receptor blockade with PD123319 individually or combined. Two weeks after induction of diabetes there was a 404% increase in ANG II (P < 0.05), a 149% increase in 12S-HETE (P < 0.05), and a 649% increase in urinary albumin excretion (P < 0.05). These levels remained elevated throughout the study. PD123319 given alone had no effect on 12(S)-HETE. Valsartan decreased 12(S)-HETE by 61.6% (P < 0.0001), a response that was abrogated when PD123319 was given with valsartan. These data demonstrate that hyperglycemia increases renal ANG II and 12(S)-HETE levels. The increase in 12(S)-HETE is mediated via AT(1) receptor. The attenuation of the effects of AT(1) receptor blockade by PD123319 suggests that AT(2) receptor contributes to the downregulation of renal 12(S)-HETE production.

AT2 receptors: functional relevance in cardiovascular disease

The renin angiotensin system (RAS) is intricately involved in normal cardiovascular homeostasis. Excessive stimulation by the octapeptide angiotensin II contributes to a range of cardiovascular pathologies and diseases via angiotensin type 1 receptor (AT₁R) activation. On the other hand, tElsevier Inc.he angiotensin type 2 receptor (AT₂R) is thought to counter-regulate AT₁R function. In this review, we describe the enhanced expression and function of AT₂R in various cardiovascular disease settings. In addition, we illustrate that the RAS consists of a family of angiotensin peptides that exert cardiovascular effects that are often distinct from those of Ang II. During cardiovascular disease, there is likely to be an increased functional importance of AT₂R, stimulated by Ang II, or even shorter angiotensin peptide fragments, to limit AT₁R-mediated overactivity and cardiovascular pathologies.

Congenic strains reveal the effect of the renin gene on skeletal muscle angiogenesis induced by electrical stimulation

Previous studies have indicated the importance of angiotensin II (ANG II) in skeletal muscle angiogenesis. The present study explored the effect of regulation of the renin gene on angiogenesis induced by electrical stimulation with the use of physiological, pharmacological, and genetic manipulations of the renin-angiotensin system (RAS). Transfer of the entire chromosome 13, containing the physiologically regulated renin gene, from the normotensive inbred Brown Norway (BN) rat into the background of an inbred substrain of the Dahl salt-sensitive (SS/Mcwi) rat restored renin levels and the angiogenic response after electrical stimulation. This restored response was significantly attenuated when SS-13BN/Mcwi consomic rats were treated with lisinopril or high-salt diet. The role of ANG II on this effect was confirmed by the complete restoration of skeletal muscle angiogenesis in SS/Mcwi rats infused with subpressor doses of ANG II. Congenic strains derived from the SS-13BN/Mcwi consomic were used to further verify the role of the renin gene in this response. Microvessel density was markedly increased after stimulation in congenic strains that contained the renin gene from the BN rat (congenic lines A and D). This angiogenic response was suppressed in control strains that carried regions of the BN genome just above (congenic line C) or just below (congenic line B) the renin gene. The present study emphasizes the importance of maintaining normal renin regulation as well as ANG II levels during the angiogenesis process with a combination of physiological, genetic, and pharmacological manipulation of the RAS.

Reactive oxygen species, PKC-beta1, and PKC-zeta mediate high-glucose-induced vascular endothelial growth factor expression in mesangial cells

Vascular endothelial growth factor (VEGF) is implicated in the development of proteinuria in diabetic nephropathy. High ambient glucose present in diabetes stimulates VEGF expression in several cell types, but the molecular mechanisms are incompletely understood. Here primary cultured rat mesangial cells served as a model to investigate the signal transduction pathways involved in high-glucose-induced VEGF expression. Exposure to high glucose (25 mM) significantly increased VEGF mRNA evaluated by real-time PCR by 3 h, VEGF cellular protein content assessed by immunoblotting or immunofluorescence within 24 h, and VEGF secretion by 24 h. High-glucose-induced VEGF expression was blocked by an antioxidant, Tempol, and antisense oligonucleotides directed against p22(phox), a NADPH oxidase subunit. Inhibition of protein kinase C (PKC)-beta(1) with the specific pharmacological inhibitor LY-333531 or inhibition of PKC-zeta with a cell permeable specific pseudosubstrate peptide also prevented enhanced VEGF expression in high glucose. Enhanced VEGF secretion in high glucose was prevented by Tempol, PKC-beta(1), or PKC-zeta inhibition. In normal glucose (5.6 mM), overexpression of p22(phox) or constitutively active PKC-zeta enhanced VEGF expression. Hypoxia inducible factor-1alpha protein was significantly increased in high glucose only by 24 h, suggesting a possible contribution to high-glucose-stimulated VEGF expression at later time points. Thus reactive oxygen species generated by NADPH oxidase, and both PKC-beta(1) and -zeta, play important roles in high-glucose-stimulated VEGF expression and secretion by mesangial cells.

Effects of Enalaprilat on Acute Necrotizing Pancreatitis in Rats

The aim of this study was to investigate the influence of enalaprilat on acute necrotizing pancreatitis (ANP) induced by glycodeoxycholic acid in rats. The induction of ANP resulted in a significant increase in the mortality rate, pancreatic necrosis, serum activity of amylase, alanine aminotransferase (ALT), and interleukin-6 (IL-6), lactate dehydrogenase (LDH) in bronchoalveolar lavage (BAL) fluid, serum concentration of urea, and tissue activity of myeloperoxidase (MPO) and maondialdehyde (MDA) in the pancreas and lung, and a significant decrease in concentrations of calcium, blood pressure, urine output and p0(2). The use of enalaprilat inhibited the changes in urine output, blood pressure, serum concentration of urea, p0(2), and tissue activity of MPO and MDA in the pancreas and lungs. It reduced the mortality and pancreatic damage. Enalaprilat demonstrated a beneficial effect on the course of ANP in rats; therefore, it may be used in the treatment of acute pancreatitis.

Vascular endothelial growth factor administration does not improve microvascular disease in the salt-dependent phase of post-angiotensin II hypertension

Renal microvascular injury and tubulointerstitial inflammation may provide a potential mechanism for the development of salt-sensitive hypertension. Therefore, we hypothesized that vascular endothelial growth factor (VEGF) administration would prevent the development of salt-sensitive hypertension induced by ANG II. Infusion of ANG II in rats for 2 wk led to an elevation in blood pressure and an increase in blood urea nitrogen. Prominent tubular injury, focal areas of peritubular capillary loss accompanied by a decrease in urinary nitrites, thickening of the afferent arteriole, and an elevation in systemic and renal VEGF protein levels also occurred. In separate studies, animals were infused with ANG II and then placed on a low-salt diet for 1 wk. At this point, the animals were paired on the basis of weight and blood pressure and treated with either VEGF121or vehicle subcutaneously for 8 wk while being fed a high-salt diet. During the treatment period, a spontaneous improvement in many parameters, including both renal function and healing of the peritubular capillaries, occurred to the same degree in both vehicle- and VEGF121-treated rats. VEGF121significantly reduced blood pressure and accelerated the recovery of tubular injury. In contrast, vehicle-treated rats demonstrated a persistent increase in afferent arteriolar media-to-lumen ratio, which was further enhanced in rats treated with VEGF121. Therefore, VEGF therapy has only limited benefits on the healing of renal lesions in the salt-dependent phase of post-ANG II-mediated hypertension.

Manipulating the angiotensin system--new approaches to the treatment of solid tumours

Angiotensin II (Ang II), a main effector peptide in the renin-angiotensin system (RAS), plays a fundamental role as a vasoconstrictor in controlling cardiovascular function and renal homeostasis. Ang II also acts as a growth promoter or angiogenic factor via type 1 angiotensin II receptors (AT1Rs) in certain tumour cell lines. Recent studies have shown the activation of the local RAS in various tumour tissues, including the abundant generation of Ang II by angiotensin-converting enzyme (ACE) and the upregulation of AT1R expression. Thus, considerable attention has been paid to the role of the RAS in cancer and its blockade as a new approach to the treatment of cancer. There is increasing evidence that the Ang II-AT1R system is involved in tumour growth, angiogenesis and metastasis in experimental models, suggesting the therapeutic potential of an ACE inhibitor and AT1R blocker, both of which have been used as antihypertensive drugs. In addition, specific Ang II-degrading enzymes are expressed in tumours and play a regulatory role in cell proliferation and invasion. This review focuses on the role of the Ang II-AT1R system in solid tumours, particularly in the progression of gynaecological cancer, and presents the clinical potential of manipulating the angiotensin system as a novel and promising strategy for cancer treatment.

Angiotensin II type 1 receptor expression in ovarian cancer and its correlation with tumour angiogenesis and patient survival

Angiotensin II, a main effector peptide in the renin–angiotensin system, acts as a growth-promoting and angiogenic factor via type 1 angiotensin II receptors (AT₁R). We have recently demonstrated that angiotensin II enhanced tumour cell invasion and vascular endothelial growth factor (VEGF) secretion via AT₁R in ovarian cancer cell lines in vitro. The aim of the present study was to determine whether AT₁R expression in ovarian cancer is correlated with clinicopathological parameters, angiogenic factors and patient survival. Immunohistochemical staining for AT₁R, VEGF, CD34 and proliferating cell nuclear antigen (PCNA) were analysed in ovarian cancer tissues (n=67). Intratumour microvessel density (MVD) was analysed by counting the CD34-positive endothelial cells. Type 1 angiotensin II receptors were expressed in 85% of the cases examined, of which 55% were strongly positive. Type 1 angiotensin II receptors expression was positively correlated with VEGF expression intensity and MVD, but not with histological subtype, grade, FIGO stage or PCNA labelling index. In patients who had positive staining for AT₁R, the overall survival and progression-free survival were significantly poor (P=0.041 and 0.017, respectively) as compared to those in patients who had negative staining for AT₁R, although VEGF, but not AT₁R, was an independent prognostic factor on multivariate analysis. These results demonstrated that AT₁R correlated with tumour angiogenesis and poor patient outcome in ovarian cancer, suggesting its clinical potential for a novel molecular target in strategies for ovarian cancer treatment.

Functional expression of the angiotensin II type 1 receptor in human ovarian carcinoma cells and its blockade therapy resulting in suppression of tumor invasion, angiogenesis, and peritoneal dissemination

PURPOSE

Angiotensin II is a bioactive peptide of the renin-angiotensin system, acting not only as a vasoconstrictor but also as a growth promoter via angiotensin II type 1 receptors (AT1R). The present study examined AT1R expression in human ovarian carcinoma and attempted to determine whether AT1R blocker could suppress the tumor progression.

EXPERIMENTAL DESIGN

Expression of AT1R, vascular endothelial growth factor (VEGF), and CD34 was immunohistochemically analyzed in ovarian tumor tissues (n=99). Effects of AT1R blocker on invasive potential and VEGF secretion in ovarian cancer cells were examined in vitro. Effects of AT1R blocker in vivo were evaluated in a mouse model of peritoneal carcinomatosis.

RESULTS

AT1R was expressed in 57 of 67 (85%) invasive ovarian adenocarcinomas and 12 of 18 (66%) borderline malignant tumors but in only 2 of 14 (14%) benign cystadenomas. In invasive carcinomas, VEGF expression intensity and intratumor microvessel density were significantly higher in cases that were strongly positive for AT1R (n = 37) compared with those in cases weakly positive (n = 20) or negative (n = 10) for AT1R. Angiotensin II significantly enhanced the invasive potential and VEGF secretion in AT1R-positive SKOV-3 ovarian cancer cells, both of which were completely inhibited by the AT1R blocker candesartan. Administration of candesartan into SKOV-3-transplanted athymic mice resulted in the reduction of peritoneal dissemination, decreased ascitic VEGF concentration, and suppression of tumor angiogenesis.

CONCLUSIONS

AT1R is functionally expressed in ovarian carcinoma and involved in tumor progression and angiogenesis. AT1R blockade therapy may become a novel and promising strategy for ovarian cancer treatment.

Temporal renal expression of angiogenic growth factors and their receptors in experimental diabetes: role of the renin-angiotensin system

OBJECTIVE

It has been postulated that vascular endothelial growth factor (VEGF) plays a role in the progression of renal injury. However, the role of other angiogenic factors and their receptors, such as the angiopoietins and Tie2, and in particular their relation to renoprotective therapies, such as agents that interrupt the renin-angiotensin system, have not been studied in the context of diabetes-related renal injury.

DESIGN AND METHODS

Renal expression of VEGF, angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and their receptors, VEGF-R2 and Tie-2, were assessed using reverse transcription-polymerase chain reaction, immunohistochemistry and Western blotting, in control and streptozotocin diabetic rats, untreated or receiving the AT1 receptor antagonist, valsartan, or the AT2 receptor antagonist, PD123319.

RESULTS

Diabetes was associated with increased gene and protein expression of VEGF, VEGF-R2, Ang-1, Ang-2 and Tie-2. AT1 receptor antagonism attenuated gene expression of these cytokines and receptors, yet PD123319, which had no effect on blood pressure, reduced VEGF-R2 and Ang-1 gene expression and decreased VEGF, Ang-1 and Ang-2 protein levels.

CONCLUSIONS

In experimental diabetes, there is significant upregulation within the kidney of various angiogenic cytokines and their receptors. Furthermore, the effects of angiotensin II receptor blockade on these parameters is consistent with the VEGF-VEGF-R2 and angiopoietin-Tie-2 axes being modulated in the kidney by haemodynamic factors in the diabetic context.

Angiotensin II stimulates alpha3(IV) collagen production in mouse podocytes via TGF-beta and VEGF signalling: implications for diabetic glomerulopathy

BACKGROUND

The podocyte is bathed in an angiotensin II (AngII)-rich ultrafiltrate, but the impact of AngII on podocyte pathobiology is not well known. Because podocytes play a direct role in the glomerular basement membrane (GBM) thickening of diabetes, the alpha3(IV) collagen chain was examined. Podocyte expression of alpha3(IV) collagen may involve the transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) systems.

METHODS

Cultured mouse podocytes were treated with various doses of AngII for selected periods of time, with or without inhibitors of TGF-beta and VEGF signalling, SB-431542 and SU5416, respectively. TGF-beta1 and VEGF were assayed by enzyme-linked immunosorbent assay (ELISA); alpha3(IV) collagen, TGF-beta type II receptor and phospho-Smad2 were assayed by immunoblotting.

RESULTS

AngII >or=10(-10) M was found to stimulate the production of alpha3(IV) collagen significantly in as short a time as 3 h. The expression of alpha3(IV) collagen was influenced by the TGF-beta system, but AngII did not increase the podocyte's production of TGF-beta1 ligand; rather, it increased the expression of the TGF-beta type II receptor and activated the TGF-beta signalling system through Smad2. Despite the TGF-beta receptor upregulation, synergy between AngII and TGF-beta1 to boost alpha3(IV) collagen production was not observed. However, blockade of TGF-beta signalling with SB-431542 prevented AngII from stimulating alpha3(IV) collagen production. Podocyte expression of alpha3(IV) collagen was also increased by the autocrine activity of VEGF. Podocytes were stimulated to secrete VEGF by 10(-10) M or higher AngII after 48 h. Blockade of the endogenous VEGF activity by SU5416 prevented AngII-stimulated alpha3(IV) collagen production.

CONCLUSIONS

AngII stimulates the podocyte to produce alpha3(IV) collagen protein via mechanisms involving TGF-beta and VEGF signalling. Alterations in alpha3(IV) collagen production may contribute to GBM thickening and perhaps proteinuria in diabetes.

Molecular and cellular mechanisms in vascular injury in hypertension: role of angiotensin II – editorial review

PURPOSE OF REVIEW

Emerging evidence indicates that hypertension is a vascular disease associated with inflammation, induced through redox-sensitive mechanisms that are regulated by angiotensin II. This review focuses on the role of inflammation, oxidative stress and angiotensin II in vascular injury and discusses implications of these processes in hypertension.

RECENT FINDINGS

The dogma that hypertension is primarily a consequence of hemodynamic alterations has changed over the recent past, with compelling evidence that high blood pressure is linked to vascular damage, oxidative stress and inflammation. Of the many factors implicated in hypertensive vascular disease, angiotensin II appears to be one of the most important. Angiotensin II, a multifunctional peptide regulating vascular contraction, growth and fibrosis, has recently been identified as proinflammatory mediator. Angiotensin II increases vascular permeability, promotes recruitment of inflammatory cells into tissues, and directly activates infiltrating immune cells, which further contribute to the inflammatory process. Moreover, angiotensin II participates in tissue repair and remodeling, by stimulating cell growth and fibrosis. Many of these processes are mediated through increased generation of reactive oxygen species (oxidative stress).

SUMMARY

Inflammation, oxidative stress and hypertension are closely interrelated. Here we discuss the (patho)physiology of vascular inflammation in hypertension, focusing specifically on the role of angiotensin II and reactive oxygen species. By understanding molecular and cellular mechanisms of hypertensive vascular disease will allow for more targeted therapy and hopefully improved management and treatment of patients with hypertension.

The role of vascular endothelial growth factor (VEGF) in renal pathophysiology

Vascular endothelial growth factor (VEGF) is an endothelial-specific growth factor that promotes endothelial cell proliferation, differentiation and survival, mediates endothelium-dependent vasodilatation, induces microvascular hyperpermeability and participates in interstitial matrix remodeling. In the kidney, VEGF expression is most prominent in glomerular podocytes and in tubular epithelial cells, while VEGF receptors are mainly found on preglomerular, glomerular, and peritubular endothelial cells. The role of VEGF in normal renal physiology is essentially unknown. The absence of prominent effects of VEGF blockade in normal experimental animals suggests a limited function during homeostasis, although a role in the formation and maintenance of glomerular capillary endothelial fenestrations has been suggested. VEGF and its receptors are up-regulated in experimental animals and humans with type 1 and type 2 diabetes. Inhibition of VEGF has beneficial effects on diabetes-induced functional and structural alterations, suggesting a deleterious role for VEGF in the pathophysiology of diabetic nephropathy. VEGF is required for glomerular and tubular hypertrophy and proliferation in response to nephron reduction, and loss of VEGF is associated with the development of glomerulosclerosis and tubulointerstitial fibrosis in the remnant kidney. No firm conclusions on the role of VEGF in minimal change or membranous glomerulonephritis can be drawn. VEGF may be an essential mediator of glomerular recovery in proliferative glomerulonephritis. Glomerular and tubulointerstitial repair in thrombotic microangiopathy and cyclosporin nephrotoxicity may also be VEGF-dependent. In conclusion, VEGF is required for growth and proliferation of glomerular and peritubular endothelial cells. While deleterious in some, it may contribute to recovery in other forms of renal diseases.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

Vascular endothelial growth factor (VEGF), prostaglandin E2(PGE2) and active renin in hypertension of adrenal origin

There are limited data regarding the role of vascular endothelial growth factor (VEGF) in arterial hypertension. The aim of the present study was to determine some markers of vascular function, including VEGF, active renin and prostaglandin E2 (PGE2) in patients with endocrine hypertension. The study comprised: 30 patients with primary aldosteronism; 32 patients with active Cushing's syndrome; 19 patients with pheochromocytoma; 22 patients with essential hypertension and 24 healthy volunteers. VEGF was significantly elevated in all groups of patients as compared to the controls. VEGF levels in patients with Cushing's syndrome were significantly higher than those in patients with essential hypertension and primary aldosteronism. We did not find significant differences in VEGF levels between patients with Conn adenomas and idiopathic aldosteronism as well as between patients with Cushing's disease and Cushing's syndrome. PGE2 levels were not significantly different among the groups. Active renin was significantly the lowest in patients with primary aldosteronism and significantly the highest in those with pheochromocytoma compared to controls. The level of active renin in patients with primary aldosteronism was significantly lower than in patients with Cushing's syndrome and pheochromocytoma. In conclusion, VEGF levels were significantly elevated in patients with endocrine hypertension due to glucocorticoid, mineralocorticoid and/or catecholamine excess. The highest VEGF levels were detected in patients with Cushing's syndrome. The latter is associated with accelerated development of atherosclerosis and increased cardiovascular risk. VEGF might contribute to the cardiovascular risk in this disease. This effect was not likely to be PGE2 mediated.

Prophylactic and therapeutic treatments with AT 1 and AT 2 receptor antagonists and their effects on changes in the severity of pancreatitis

Previous studies showed that a local pancreatic renin-angiotensin system (RAS) was upregulated in experimental acute pancreatitis. RAS inhibition could attenuate pancreatic inflammation and fibrosis, which casts a new light on the role of the pancreatic RAS in pancreatitis. The present study explores the prophylactic and therapeutic potentials, and possible molecular mechanism for the antagonism of angiotensin II receptors on the changes in the severity of pancreatic injury induced by acute pancreatitis. Experimental pancreatitis was induced by an intraperitoneal injection of supra-maximal dose of cerulein. The differential effects of angiotensin II receptors inhibitors losartan and PD123319 on the pancreatic injury were assessed by virtue of using the pancreatic water content, biochemical and histological analyses. Blockade of the AT(1) receptor by losartan at a dose of 200microg/kg could markedly ameliorate the pancreatic injury induced by cerulein, as evidenced by biochemical and histopathological studies. However, blockade of the AT(2) receptor by PD123319 appeared not to provide any beneficial role in cerulein-induced pancreatic injury. Both prophylactic and therapeutic treatments with losartan were effective against cerulein-induced pancreatic injury. The protective action of losartan was linked to an inhibition of NAD(P)H oxidase activity, thus consequential oxidative modification of pancreatic proteins in the pancreas. Inhibition of the AT(1) receptor, but not AT(2) receptor, may play a beneficial role in ameliorating the severity of acute pancreatitis. The differential effects of AT(1) and AT(2) inhibitors on cerulein-induced pancreatic injury might be due to the distinctive mechanism of the AT(1) and AT(2) receptors on the activation of NAD(P)H oxidase. Thus the protective role of AT(1) receptor antagonist, losartan, could be mediated by the inhibition of NAD(P)H oxidase-dependent generation of reactive oxygen species (ROS).

Elevated levels of vascular endothelial growth factor in serum of patients with D+ HUS

The pathogenesis of hemolytic uremic syndrome (D+ HUS) is characterized by endothelial damage of glomeruli and tubules within the kidney. In several other diseases in which glomerular endothelial damage occurs, elevated serum levels of vascular endothelial growth factor (VEGF) have been reported. VEGF is involved in angiogenesis, permeabilization of blood vessel endothelium, and wound repair. In this study we evaluated VEGF levels in the serum of 40 D+ HUS patients in the acute phase and during the course of the disease. VEGF levels were measured using a double-sandwich ELISA. Indirect immunohistochemistry was performed for the detection of VEGF in renal biopsy material of 3 HUS patients. Significantly elevated VEGF levels were found in HUS patients compared with controls in both serum ( P<0.001) and plasma ( P<0.05). A significant relationship was found between VEGF levels and severity of the disease according to the classification of Gianantonio ( P<0.05). Levels of VEGF in blood increased during the 2nd and 3rd week after HUS was diagnosed. Immunohistochemistry of renal biopsy material showed increased levels of the receptors for VEGF in the glomeruli. During the course of HUS, plasma VEGF levels increase and the increase is dependent on the severity of the disease. This is probably associated with the repair process.

Expression of vascular endothelial growth factor, hypoxia inducible factor 1alpha, and carbonic anhydrase IX in human tumours

AIMS

To measure vascular endothelial growth factor (VEGF-A) mRNA in a large, diverse cohort of tumours and to investigate whether VEGF-A expression is associated with markers of hypoxia, including hypoxia inducible factor 1alpha (HIF-1alpha) and carbonic anhydrase IX (CA9).

METHODS

The expression of VEGF-A and CA9 was assessed in 5067 fresh frozen human tissue samples and 238 cell lines by DNA microarray analysis. In addition, tissue microarrays were constructed from 388 malignancies to investigate the expression of VEGF-A and HIF-1alpha by in situ hybridisation and immunohistochemistry, respectively.

RESULTS

VEGF-A was significantly upregulated in primary malignancies of the breast, cervix, colon and rectum, oesophagus, head and neck, kidney, ovary, skin, urinary system, and white blood cells by DNA microarray analysis. However, VEGF-A expression only correlated with CA9 expression in renal tissues. In the tissue microarrays, HIF-1alpha positive cores showed a significant increase in VEGF-A expression in lung, ovary, soft tissue, and thyroid malignancies.

CONCLUSIONS

The expression of VEGF-A is upregulated in a large proportion of human malignancies, and may be associated with markers of hypoxia. VEGF-A expression can be induced in the absence of hypoxia and hypoxia does not always provoke VEGF-A upregulation in tumours.

AT1 and AT2 receptor in the kidney: role in health and disease

The renin angiotensin system plays an important role in the control of body fluid and electrolyte homeostasis and blood pressure regulation. Angiotensin II is the most effector hormone of this system and functions mainly through stimulation of its subtype receptors, namely, the AT1 and AT2 receptors. Most of the known physiological and pathologic effects of angiotensin II are mediated through stimulation of the AT1 receptor. The knowledge about the involvement of the AT2 receptor in physiological and pathologic processes is still evolving. In the kidney, both the AT1 and AT2 receptors contribute to the regulation of renal hemodynamic and tubular functions. Also, these receptors regulate renal cellular growth and matrix formation. However, AT2 receptor possesses functions that counteract the effects of the AT1 receptor. The balance between the AT1 and AT2 receptors can determine the renal status in health and disease.

Vascular endothelial growth factor induces protein synthesis in renal epithelial cells: a potential role in diabetic nephropathy

BACKGROUND

Vascular endothelial growth factor (VEGF) is an important determinant of ocular complications of diabetes. Its potential role in diabetic renal disease has not been extensively studied.

METHODS

We employed mice with streptozotocin-induced type 1 diabetes and db/db mice with type 2 diabetes to study the regulation of renal VEGF. Studies of VEGF regulation of protein synthesis were performed using proximal tubular epithelial (MCT) cells in culture.

RESULTS

A nearly three-fold increase of VEGF165 expression in the renal cortex was seen, coinciding with renal hypertrophy in mice with either type 1 or type 2 diabetes. VEGF increased de novo protein synthesis and induced significant hypertrophy in MCT cells. VEGF stimulation of protein synthesis was dependent on tyrosine phosphorylation of the type 2 VEGF receptor and phosphatidylinositol 3-kinase (PI 3-kinase) activity. Activity of Akt was increased two- to three-fold by VEGF. Expression of dominant-negative Akt showed that Akt activation was also needed for VEGF-induced protein synthesis and cell hypertrophy. As PI 3-kinase-Akt axis regulates initial events in protein translation, these events were examined in the context of VEGF regulation of protein synthesis. VEGF stimulated eukaryotic initiation factor 4E-binding protein (4E-BP1) phosphorylation, which was dependent on activation of PI 3-kinase and Akt. Stable transfection with 4E-BP1 Thr37,46-Ala37,46 mutant abolished the VEGF-induced de novo protein synthesis and cell hypertrophy.

CONCLUSION

VEGF augments protein synthesis and induces hypertrophy in MCT cells in a PI 3-kinase- and Akt-dependent manner. Phosphorylation of Thr37,46 in 4E-BP1 is required for VEGF-induced protein synthesis and hypertrophy in MCT cells. These data suggest a role for VEGF in the pathogenesis of diabetic renal disease.

An alternatively spliced variant of CXCR3 mediates the inhibition of endothelial cell growth induced by IP-10, Mig, and I-TAC, and acts as functional receptor for platelet factor 4

The chemokines CXCL9/Mig, CXCL10/IP-10, and CXCL11/I-TAC regulate lymphocyte chemotaxis, mediate vascular pericyte proliferation, and act as angiostatic agents, thus inhibiting tumor growth. These multiple activities are apparently mediated by a unique G protein-coupled receptor, termed CXCR3. The chemokine CXCL4/PF4 shares several activities with CXCL9, CXCL10, and CXCL11, including a powerful angiostatic effect, but its specific receptor is still unknown. Here, we describe a distinct, previously unrecognized receptor named CXCR3-B, derived from an alternative splicing of the CXCR3 gene that mediates the angiostatic activity of CXCR3 ligands and also acts as functional receptor for CXCL4. Human microvascular endothelial cell line-1 (HMEC-1), transfected with either the known CXCR3 (renamed CXCR3-A) or CXCR3-B, bound CXCL9, CXCL10, and CXCL11, whereas CXCL4 showed high affinity only for CXCR3-B. Overexpression of CXCR3-A induced an increase of survival, whereas overexpression of CXCR3-B dramatically reduced DNA synthesis and up-regulated apoptotic HMEC-1 death through activation of distinct signal transduction pathways. Remarkably, primary cultures of human microvascular endothelial cells, whose growth is inhibited by CXCL9, CXCL10, CXCL11, and CXCL4, expressed CXCR3-B, but not CXCR3-A. Finally, monoclonal antibodies raised to selectively recognize CXCR3-B reacted with endothelial cells from neoplastic tissues, providing evidence that CXCR3-B is also expressed in vivo and may account for the angiostatic effects of CXC chemokines.

Changes of angiotensin-converting enzyme activity in the pancreas of chronic hypoxia and acute pancreatitis

Emerging data have provided evidence for the presence of a local renin-angiotensin system (RAS) in the pancreas, which play a role in the regulation of pancreatic microcirculation, thus affecting islet hormonal secretion. The present study aimed, therefore, at elucidating the presence and changes of angiotensin-converting enzyme (ACE) using reverse transcription-polymerase chain reaction (RT-PCR) and a specific assay for ACE activity using the internally quenched fluorogenic substrate Meoc-DL-Amp-Gly-Lys(epsilon -DNP)-Gln-OH. RT-PCR clearly demonstrated the expression of ACE mRNA in the pancreas. ACE activity was markedly and significantly increased by chronic hypoxia and by acute pancreatitis when compared with that of their respective control pancreas. Addition of captopril, a specific inhibitor for ACE, completely blocked the ACE activity both in the control and experimental groups. All these data suggest that increased activity of pancreatic ACE in chronic hypoxia and acute pancreatitis could have implications for pancreatic physiology and pathophysiology.

Inflammation and angiotensin II

Angiotensin II (AngII), the major effector peptide of renin-angiotensin system (RAS), is now recognized as a growth factor that regulates cell growth and fibrosis, besides being a physiological mediator restoring circulatory integrity. In the last few years, a large number of experimental studies has further demonstrated that AngII is involved in key events of the inflammatory process. Here, we summarize the wide variety of AngII functions and discuss them in relation with the inflammatory cascade. AngII increases vascular permeability (via the release of prostaglandins and vascular endothelial cell growth factor or rearrangement of cytoskeletal proteins) that initiates the inflammatory process. AngII could contribute to the recruitment of inflammatory cells into the tissue through the regulation of adhesion molecules and chemokines by resident cells. Moreover, AngII could directly activate infiltrating immunocompetent cells, including chemotaxis, differentiation and proliferation. Recent data also suggest that RAS activation could play a certain role even in immunologically-induced inflammation. Transcriptional regulation, predominantly via nuclear factor-kappaB (NF-kappaB) and AP-1 activation, and second mediator systems, such as endothelin-1, the small G protein (Rho) and redox-pathways are shown to be involved in the molecular mechanism by which AngII exerts those functions. Finally, AngII participates in tissue repair and remodeling, through the regulation of cell growth and matrix synthesis. In summary, recent data support the hypothesis that RAS is key mediator of inflammation. Further understanding of the role of the RAS in this process may provide important opportunities for clinical research and treatment of inflammatory diseases.

Gene expression reveals vulnerability to oxidative stress and interstitial fibrosis of renal outer medulla to nonhypertensive elevations of ANG II

The present study was designed to determine whether nonhypertensive elevations of plasma ANG II would modify the expression of genes involved in renal injury that could influence oxidative stress and extracellular matrix formation in the renal medulla using microarray, Northern, and Western blot techniques. Sprague-Dawley rats were infused intravenously with either ANG II (5 ng. kg(-1). min(-1)) or vehicle for 7 days (n = 6/group). Mean arterial pressure averaged 110 +/- 0.6 mmHg during the control period and 113 +/- 0.4 mmHg after ANG II. The mRNA of 1,751 genes ( approximately 80% of all currently known rat genes) that was differentially expressed (ANG II vs. saline) in renal outer and inner medulla was determined. The results of 12 hybridizations indicated that in response to ANG II, 11 genes were upregulated and 25 were downregulated in the outer medulla, while 11 were upregulated and 13 were downregulated in the inner medulla. These differentially expressed genes, most of which were not known previously to be affected by ANG II in the renal medulla, were found to group into eight physiological pathways known to influence renal injury and kidney function. Particularly, expression of several genes would be expected to increase oxidative stress and interstitial fibrosis in the outer medulla. Western blot analyses confirmed increased expression of transforming growth factor-beta1 and collagen type IV proteins in the outer medulla. Results demonstrate that nonhypertensive elevations of plasma ANG II can significantly alter the expression of a variety of genes in the renal outer medulla and suggested the vulnerability of the renal outer medulla to the injurious effect of ANG II.

Differential effects of saralasin and ramiprilat, the inhibitors of renin-angiotensin system, on cerulein-induced acute pancreatitis

Acute pancreatitis is an inflammatory disease characterized by pancreatic tissue edema, acinar cell necrosis, hemorrhage and inflammation of the damaged gland. It is believed that acinar cell injury is initiated by the activation of digestive zymogens inside the acinar cells, leading finally to the autodigestion of the pancreas. Previous study in our laboratory demonstrated that cerulein-induced acute pancreatitis was associated with an up-regulation of local renin-angiotensin system (RAS) in rat pancreas. Therefore, the utilization of RAS inhibitors may provide a novel and alternative treatment for acute pancreatitis. By means of a rat model of cerulein-induced acute pancreatitis, results from the present study showed that an intravenous injection of saralasin, an antagonist for angiotensin II receptors, at a dose of 40 microg/kg 30 min before the induction of acute pancreatitis significantly attenuated pancreatic edema. Results from the biochemical measurements showed that pretreatment with saralasin at a dose of 20 microg/kg markedly reduced pancreatic injury, as evidenced by the decreased activities of alpha-amylase and lipase in plasma. However, the same recipe of ramiprilat, a specific inhibitor for angiotensin-converting enzyme, at a dose of 20 microg/kg did not provide any protective effect against acute pancreatitis. On the contrary, pretreatment with ramiprilat at a dose 40 microg/kg enhanced cerulein-induced pancreatic injury. Results from histopathological analysis of these RAS inhibitors further confirmed with those results as obtained from biochemical analysis. These data indicate that administration of saralasin but not ramiprilat could be protective against acute pancreatitis and that activation of pancreatic RAS in acute pancreatitis may play a role in pancreatic tissue injury.

Abnormal angiogenesis in diabetes mellitus

The adverse long-term effects of diabetes mellitus have been well described and involve many organ systems. While diabetes management has largely focused on control of hyperglycemia, the presence of abnormalities of angiogenesis may cause or contribute to many of the clinical manifestations of diabetes. When compared with non-diabetic subjects, diabetics demonstrate vascular abnormalities of the retina, kidneys, and fetus. Diabetics have impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. In each of these conditions, and possibly in diabetic neuropathy as well, abnormalities of angiogenesis can be implicated in the pathogenesis. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. In this review, the clinical features, molecular mechanisms, and potential therapeutic options of abnormal angiogenesis in diabetes will be reviewed.

Nitric oxide modulates vascular endothelial growth factor and receptors in chronic cyclosporine nephrotoxicity

BACKGROUND

Vascular endothelial growth factor (VEGF) is involved in angiogenesis, wound healing, and inflammation and exerts its effect via tyrosine kinase receptors, fms-like tyrosine kinase (Flt-1) and fetal liver kinase (Flk-1 or KDR). We have previously shown that VEGF is up-regulated in a model of chronic cyclosporine (CsA) nephrotoxicity and that l-arginine (l-Arg) improved while N-nitro-l-arginine-methyl ester (L-NAME) worsened fibrosis. We examined the role of nitric oxide modulation on VEGF in this model.

METHODS

Pair-fed salt-depleted rats were administered CsA, CsA + L-NAME, CsA +l-Arg, vehicle (VH), VH + L-NAME or VH +l-Arg and were sacrificed at 7 or 28 days. Physiologic and histologic changes were studied in addition to the mRNA expression of VEGF and its receptors Flt-1 and KDR/Flk-1 by Northern blot and the protein expression of VEGF by Western blot and immunohistochemical staining.

RESULTS

While L-NAME worsened renal function and histology, l-Arg had the opposite beneficial effect in CsA-treated rats. VEGF mRNA and protein expressions increased with CsA, further increased with L-NAME and became significantly reduced with L-Arg. Flt-1 expression was similar in all groups. On the other hand, KDR/Flk-1 mRNA expression was modulated in a fashion similar to VEGF. Also, nitric oxide modulation did not have an effect on VH-treated rats.

CONCLUSIONS

VEGF expression in chronic CsA nephrotoxicity is increased by nitric oxide blockade and decreased by nitric oxide enhancement. Moreover, VEGF probably exerted its effect via the KDR/Flk-1 receptor. The actions of VEGF in this model remain speculative, but it is probable that VEGF plays a role, either independently or through nitric oxide, in CsA-induced fibrosis.

The renin-angiotensin system influences ocular endothelial cell proliferation in diabetes: transgenic and interventional studies

Neovascularization in the retina and iris of diabetic patients is a major cause of severe visual loss. However, study of these lesions is compromised by the lack of a comparable diabetic rodent model. Because the vasoactive and angiogenic agent, angiotensin II, is involved in diabetic microvascular disease, we aimed to determine whether endothelial cell proliferation could be induced in the retinae and irides of hypertensive transgenic (mRen-2)27 rats that display an enhanced extra-renal renin-angiotensin system (RAS), including the eye. Six-week-old Ren-2, spontaneously hypertensive, and Sprague-Dawley rats received either streptozotocin or control vehicle and were studied for 36 weeks. Additional nondiabetic and diabetic Ren-2 rats were treated throughout with the angiotensin-converting enzyme inhibitor lisinopril (LIS) (10 mg/kg/day in drinking water). Endothelial cell proliferation was only observed in retinae and irides of diabetic Ren-2 rats and was reduced with LIS. In diabetic Ren-2, vascular endothelial growth factor (VEGF) and VEGFR-2 mRNA were increased in retinae and irides and reduced with LIS. Diabetes activated ocular renin in Ren-2 but not Sprague-Dawley rats. The diabetic Ren-2 rat is a model of intraocular endothelial cell proliferation that can be attenuated by RAS blockade via VEGF-dependent pathways. RAS blockade is a potential treatment for vision-threatening diabetic microvascular complications.

Regulation of glucose transporter (GLUT1) gene expression by angiotensin II in mesangial cells: involvement of HB-EGF and EGF receptor transactivation

In the development of diabetic nephropathy, angiotensin (Ang) II is thought to exert numerous actions on the glomerulus, and especially on the mesangium. However, the role(s) played by Ang II in the glucose metabolism per se in mesangial cells remains unclear. Ang II, at least via its type 1 receptor (AT1-R)-mediated effect, phosphorylates extracellular signal regulated kinase (ERK) by transactivation of epidermal growth factor receptors (EGF-Rs) via the Ca2+ or protein kinase C (PKC) pathways. Our objective in the present study was to assess the effect of Ang II on glucose transporter 1 (GLUT1) gene expression and to clarify the involvement of EGF-R in Ang II-mediated GLUT1 mRNA expression in glomerular mesangial cells. The results showed that Ang II upregulated GLUT1 mRNA accumulation in a time- and dose-dependent manner (peaking at 12 h; approximately 3.8-fold vs. control), and this upregulation was completely inhibited by the PKC inhibitor calphostin-C. The Ang Il-induced GLUT1 expression was significantly inhibited by the EGF-R inhibitor AG1478 (approximately 80% inhibition), by inactivation of ERK by PD98059, and by pretreatment with heparin and the metalloproteinase (MMP) inhibitor batimastat. On the other hand, phorbol ester markedly upregulated GLUT1 mRNA (approximately 8.6-fold). Batimostat and AG1478 significantly reduced the phorbol ester-induced GLUT1 mRNA expression (approximately 72 and approximately 69% inhibition, respectively). In conclusion, PKC-mediated heparin-binding (HB)-EGF/EGF transactivation followed by ERK activation plays a predominant role in the induction of GLUT1 expression by Ang II.

The renin-angiotensin-aldosterone system and the eye in diabetes

Diabetic retinopathy is the leading cause of blindness in the under 65s, and with the burden of disease case load expected to exceed 200 million worldwide within 10 years, much effort is being spent on prophylactic interventions. Early work focused on improving glycaemic control; however, with the publication of EURODIAB Controlled trial of Lisinopril in Insulin-dependent Diabetes (EUCLID) and United Kingdom Prospective Diabetes Study (UKPDS), the focus has recently moved to control of blood pressure and specifically the renin-angiotensin system (RAS). There is a large body of evidence for a local RAS within the eye that is activated in diabetes. This appears to be directly responsible, as well as indirectly through other mediators, for an increase in concentration of vascular endothelial growth factor (VEGF), a selective angiogenic and vasopermeability factor that is implicated in the pathogenesis of diabetic retinopathy. Inhibition of angiotensin-converting enzyme appears to reduce concentrations of VEGF, with a concurrent anti-proliferative effect independent of systemic VEGF levels or blood pressure. Angiotensin II (Ang II) Type 1 (AT(1)) receptor blockade has been shown to reduce neovascularisation independent of VEGF levels in animal models. This may be due to antagonism of activation of mitogen-activated protein kinase, which is a potent cellular proliferation stimulator, by Ang II, although this needs further evaluation.

Amelioration of long-term renal changes in obese type 2 diabetic mice by a neutralizing vascular endothelial growth factor antibody

Diabetic nephropathy in type 2 diabetic patients is a frequent complication associated with increased morbidity and mortality. Various growth factors and cytokines have been implicated in the pathogenesis of diabetic kidney disease, including vascular endothelial growth factor (VEGF). To explore a role for VEGF in renal changes in type 2 diabetes, we examined the renal effects of a neutralizing murine VEGF antibody in the diabetic db/db mouse, a model of obese type 2 diabetes. One group of db/db mice was treated for 2 months with a VEGF antibody, while another db/db group was treated for the same period with an isotype-matched irrelevant IgG. A third group consisting of nondiabetic db/+ mice was treated with the same isotype-matched IgG for 2 months. Placebo-treated db/db mice showed a pronounced increase in kidney weight, glomerular volume, basement membrane thickness (BMT), total mesangial volume, urinary albumin excretion (UAE), and creatinine clearance (CrCl) when compared with nondiabetic controls. In VEGF antibody-treated db/db mice, increases in kidney weight, glomerular volume, BMT, and UAE were attenuated, whereas the increase in CrCl was abolished. VEGF antibody administration tended to reduce expansion in total mesangial volume. These effects in diabetic animals were seen without impact on body weight, blood glucose, insulin levels, or food consumption. In conclusion, chronic inhibition of VEGF in db/db mice ameliorates the diabetic renal changes seen in type 2 diabetes.

Suppression of basic fibroblast growth factor-induced angiogenesis by a specific chymase inhibitor, BCEAB, through the chymase-angiotensin-dependent pathway in hamster sponge granulomas

1. We investigated the profound involvement of mast cell chymase, an alternative angiotensin II-generating enzyme, in angiogenesis using a specific chymase inhibitor. We also studied the functional profiles of this novel inhibitor in basic fibroblast growth factor (bFGF)-induced angiogenesis. 2. In this study, angiogenesis was induced by daily injections of bFGF (0.3 micro g site(-1) day(-1)), angiotensin I (2 nmol site(-1) day(-1)) or angiotensin II (2 nmol site(-1) day(-1)) into sponges implanted to male hamsters subcutaneously for 7 days. Angiogenesis in the granulation tissue surrounding sponges was evaluated by measuring the haemoglobin (Hb) content and local blood flow as the parameters for angiogenesis. 3. A chymase inhibitor, BCEAB (4-[1-[[bis-(4-methyl-phenyl)-methyl]-carbamoyl]-3-(2-ethoxy-benzyl)-4-oxo-azetidine-2-yloxy]-benzoic acid), was simultaneously administered into the implanted sponges (2 or 5 nmol site(-1) day(-1), for 7 days) treated with bFGF and strongly suppressed the haemoglobin contents in sponge granulomas. In the studies using a laser doppler perfusion imager, BCEAB (5 nmol site(-1) day(-1)) also attenuated the bFGF-induced increase of local blood flow around the implanted sponge granuloma. 4. In bFGF-induced angiogenesis, chymase activity in sponge granulomas was substantially increased. It was also confirmed that the chymase activity increased by bFGF was significantly and dose-dependently inhibited by BCEAB (2, 5 nmol site(-1) day(-1)). 5. BCEAB inhibited the Hb contents and the expression of vascular endothelial growth factor (VEGF) mRNA induced by angiotensin I but not by angiotensin II. 6. These results suggest that the significance of chymase in bFGF-induced angiogenesis was confirmed, and a novel inhibitor, BCEAB, strongly suppresses the bFGF-induced angiogenesis through the chymase-angiotensin II-VEGF dependent pathway.

Angiotensin II regulation of vascular endothelial growth factor and receptors Flt-1 and KDR/Flk-1 in cyclosporine nephrotoxicity

BACKGROUND

Vascular endothelial growth factor (VEGF) is involved in angiogenesis, wound healing and inflammation. VEGF exerts its effect via the tyrosine kinase receptors Flt-1 and KDR/Flk-1. We have previously shown that VEGF is up-regulated in a chronic cyclosporine (CsA) nephrotoxicity model. Our current study examined the role of angiotensin II (Ang II) blockade with enalapril (E) or losartan (L) on VEGF in this model.

METHODS

Pair-fed salt-depleted rats were administered vehicle, CsA, CsA + nilvadipine, CsA + hydralazine/hydrochlorthiazide (HCTZ), CsA + E or CsA + L, and were sacrificed at 7 or 28 days. Physiologic and histologic changes were studied in addition to the mRNA expression of VEGF and its receptors Flt-1 and KDR/Flk-1 by Northern blot, and the protein expression of VEGF by Western blot.

RESULTS

While all groups achieved similar blood pressures and creatinine clearances, the amelioration in nephrotoxicity was observed only with Ang II blockade. VEGF mRNA and protein expressions increased with CsA and became significantly reduced with Ang II blockade. Flt-1 expression was similar in all groups; it decreased early and remained low. On the other hand, KDR/Flk-1 mRNA expression was higher at seven days in all groups, except in the +E and +L groups where it was significantly lower, and then became further down-regulated at 28 days.

CONCLUSIONS

The increased VEGF expression in chronic CsA nephrotoxicity seems to be related to up-regulation of Ang II. In addition, VEGF probably exerted its effect via the KDR/Flk-1 receptor. The actions of VEGF in this model remain speculative, but may be related to its effect on macrophage infiltration or matrix deposition.

Captopril-impaired production of tumor necrosis factor-alpha-induced interleukin-1beta in human monocytes is associated with altered intracellular distribution of nuclear factor-kappaB

We evaluated the effects of the angiotensin-converting enzyme (ACE) inhibitor captopril on pathways for monocyte production of interleukin (IL)-1beta in vitro. Human monocytes were treated with captopril and stimulated with tumor necrosis factor (TNF)-alpha or lipopolysaccharide. Captopril caused a dose-dependent reduction of TNF-alpha induced IL-1beta. LPS-induced IL-1beta generation was not reduced by the ACE inhibitor. Pro-IL-1beta concentrations followed the same pattern as that for mature IL-1beta when monocytes were preincubated with captopril. Also, IL-1beta mRNA concentrations were reduced by captopril pretreatment in parallel with IL-1beta. We sought to determine whether captopril affected the nuclear factor (NF)-kappaB complex in monocytic cells. We found that the translocation of the p-65 component of NF-kappaB to the nucleus was inhibited by captopril. Thus captopril reduced TNF-alpha-induced IL-1beta and IL-1betamRNA synthesis in monocytes, in vitro, probably through interference with NF-kappaB activation of the IL-1beta gene. These results support the hypothesis that captopril has immunomodulating properties.

Inhibition of renin-angiotensin system attenuates liver enzyme-altered preneoplastic lesions and fibrosis development in rats

BACKGROUND/AIMS

It is suggested that the renin-angiotensin system (RAS) is involved in tumor development and fibrogenesis. The aim of the present study was to examine the effect of RAS inhibition on the liver enzyme-altered preneoplastic lesions and fibrosis development.

METHODS

The effects of the clinically used angiotensin-I converting enzyme inhibitor (ACE-I), perindopril (PE), on two different rat model of liver carcinogenesis models induced separately by diethylnitrosamine (DEN) and a choline-deficient L-amino acid-defined (CDAA) diet were studied. This CDAA model was also used to elucidate the effect of PE on liver fibrosis development.

RESULTS

The immunohistochemical evaluation revealed that the glutathione S-transferase placental form (GST-P), and gamma-glutamyltransferase (GGT)-positive preneoplastic foci significantly decreased in the livers of the PE-treated groups. In CDAA-induced liver fibrosis model, PE revealed a marked inhibitory effect of liver fibrosis development. The hepatic hydroxyproline, serum fibrosis markers, alpha-smooth muscle actin (alpha-SMA) immunopositive cells in number, and alpha-(III) pro-collagen mRNA expression were significantly suppressed by PE treatment. These inhibitory effects of PE were achieved even at a clinically comparable dose (2 mg/kg per day).

CONCLUSIONS

These results suggested that the RAS is involved in liver carcinogenesis and fibrosis development.

Perindopril: possible use in cancer therapy

Since angiogenesis is essential for the growth of any solid tumor, emerging efforts are being made to develop antiangiogenic therapy. To date, however, no antiangiogenic agent has become widely available for the clinical setting. Angiotensin I-converting enzyme (ACE) inhibitors are commonly used as antihypertensive agents and it has recently been suggested that they decrease the risk of cancer. Studies have found that an ACE inhibitor, perindopril, is a potent inhibitor of experimental tumor development and angiogenesis at a clinically comparable dose. The potent angiogenic factor, vascular endothelial growth factor (VEGF), is significantly suppressed by perindopril and also inhibits VEGF-induced tumor growth. In vitro studies showed that perindopril is not cytotoxic to either tumor cells or endothelial cells. Since perindopril is already in widespread clinical use without serious side effects, it may represent a potential new strategy for anticancer therapy.

Vascular endothelial growth factor enhances glomerular capillary repair and accelerates resolution of experimentally induced glomerulonephritis

Vascular endothelial growth factor (VEGF) regulates angiogenesis through endothelial cell proliferation and plays an important role in capillary repair in damaged glomeruli. We tested the hypothesis that VEGF might be beneficial in rats with severe glomerular injury in glomerulonephritis (GN) based on its angiogenic and vascular remodeling properties. Acute GN with severe glomerular destruction was induced in rats by injection of anti-Thy-1.1 antibody (day 0) and Habu-snake venom (day 1). Rats were intraperitoneally injected with recombinant human VEGF(165) (10 microg/100 g body wt/day) or vehicle from day 2 to day 9, and monitored changes in glomerular capillaries, development of glomerular inflammation, and progression to glomerular sclerosis after acute glomerular destruction in both groups. Rats that received anti-Thy-1.1 antibody and Habu-snake venom showed severe mesangiolysis and marked destruction of capillary network on day 2. VEGF was expressed on glomerular epithelial cells, proliferating mesangial cells, and some infiltrating leukocytes, and VEGF(165) protein levels increased in damaged glomeruli during day 5 to day 7. Normal, damaged, and regenerating glomerular endothelial cells expressed VEGF receptor flk-1. However, endothelial cell proliferation and capillary repair was rare in vehicle-treated rats with severe glomerular damage, which progressed to global sclerosis and chronic renal failure by week 8. In contrast, in the VEGF-treated group, VEGF(165) significantly enhanced endothelial cell proliferation and capillary repair in glomeruli by day 9 (proliferating endothelial cells: VEGF(165), 4.3 +/- 1.1; control, 2.2 +/- 0.9 cells on day 7, P < 0.001; and glomerular capillaries: VEGF(165), 24.6 +/- 4.8; control, 16.9 +/- 3.4 capillaries on day 7, P < 0.01). Thereafter, damaged glomeruli gradually recovered after development of capillary network by week 8, and significant improvement of renal function was evident in the VEGF-treated group during week 8 (creatinine: VEGF(165), 0.3 +/- 0.1; control, 2.6 +/- 0.9 mg/dl, P < 0.001; proteinuria: VEGF(165), 54 +/- 15; control, 318 +/- 60 mg/day, P < 0.001). We conclude that the beneficial effect of VEGF(165) in severe glomerular injury in GN emphasizes the importance of capillary repair in the resolution of GN, and may allow the design of new therapeutic strategies against severe GN.

Effects of different durations of pretreatment with losartan on myocardial infarct size, endothelial function, and vascular endothelial growth factor

A previous study by our group showed that 10 weeks of pretreatment with losartan reduced myocardial infarct size and arrhythmias in a rat model of ischaemia-reperfusion. However, the effect of a differing time course of pretreatment has not been investigated. 104 Sprague-Dawley rats were randomised to four groups: a control, and three treatment groups in which losartan (40 mg/kg/day) was administered in drinking water for one day, one week, and four weeks respectively. After different durations of pretreatment, the rats were subjected to 17 minutes of left coronary artery occlusion and 120 minutes of reperfusion. Haemodynamic variables were not significantly different between the four groups. Myocardial infarct size was unchanged after one day and one week of pretreatment (52+/-7, 57+/-6% vs.control 55+/-3%), but was significantly reduced by four weeks of pretreatment with losartan (38+/-6, p<0.05). Endothelial-dependent vasorelaxation was significantly increased by four weeks of pretreatment (-81+/-4 vs.-62+7%, p<0.05). As an indicator of ischaemia, vascular endothelial growth factor (VEGF) levels in ischaemic myocardium were decreased after one and four weeks of pretreatment (0.75+/-0.05, 0.58+/-0.10 vs. 1.0, p<0.05,0.01, respectively). In conclusion, losartan has time-dependent cardiovascular protective effects. Four weeks of pretreatment with losartan decreased infarct size and VEGF, and improved endothelial dysfunction.

Signal transduction by the chemokine receptor CXCR3: activation of Ras/ERK, Src, and phosphatidylinositol 3-kinase/Akt controls cell migration and proliferation in human vascular pericytes

Hepatic stellate cells (HSC) and glomerular mesangial cells (MC) are tissue-specific pericytes involved in tissue repair, a process that is regulated by members of the chemokine family. In this study, we explored the signal transduction pathways activated by the chemokine receptor CXCR3 in vascular pericytes. In HSC, interaction of CXCR3 with its ligands resulted in increased chemotaxis and activation of the Ras/ERK cascade. Activation of CXCR3 also stimulated Src phosphorylation and kinase activity and increased the activity of phosphatidylinositol 3-kinase and its downstream pathway, Akt. The increase in ERK activity was inhibited by genistein and PP1, but not by wortmannin, indicating that Src activation is necessary for the activation of the Ras/ERK pathway by CXCR3. Inhibition of ERK activation resulted in a decreased chemotactic and mitogenic effect of CXCR3 ligands. In MC, which respond to CXCR3 ligands with increased DNA synthesis, CXCR3 activation resulted in a biphasic stimulation of ERK activation, a pattern similar to the one observed in HSC exposed to platelet-derived growth factor, indicating that this type of response is related to the stimulation of cell proliferation. These data characterize CXCR3 signaling in pericytes and clarify the relevance of downstream pathways in the modulation of different biologic responses.

Renin gene transfer restores angiogenesis and vascular endothelial growth factor expression in Dahl S rats

In a previous study, we demonstrated that Dahl S rats (SS group) have low plasma renin activity, whereas transfer of a region of chromosome 13 containing the renin gene from Dahl R onto a congenic strain of Dahl SS/Jr/Hsd/MCW rats (S/ren(RR) group) restores renin secretory responses. In the present study, we compared the angiogenic responses to electrical stimulation in the SS and S/ren(RR) groups to explore the hypotheses that the renin-angiotensin system is involved in vascular endothelial growth factor (VEGF) expression and angiogenesis in skeletal muscle. Congenic SS and S/ren(RR) rats fed a 0.4% or 4% salt diet were surgically prepared by chronic implantation of an electrical stimulator. Another group of S/ren(RR) rats was treated with lisinopril 2 days before the surgery and throughout the stimulation protocol. The right tibialis anterior (TA) and extensor digitorum longus (EDL) were stimulated for 8 hours per day for 7 days. The contralateral muscles served as controls. Western blot analysis was performed to identify VEGF protein expression in these muscles. Electrical stimulation produced no change in vessel density of the SS group fed a 0.4% salt diet (change 5.50% and 8.14% for EDL and TA, respectively). Transfer of a region containing the renin gene restored the angiogenic response (change 16% and 30% for EDL and TA, respectively) despite a significantly higher blood pressure. Blockade of the renin-angiotensin system by lisinopril or high salt restored the responses observed in the SS group fed a low salt diet. In addition, increases in VEGF expression to electrical stimulation were observed only in the S/ren(RR) group fed a low salt diet. These results suggest that renin gene transfer restores angiogenesis and VEGF expression in the skeletal muscle of Dahl S rats.

Cyclic stretch and hypertension induce retinal expression of vascular endothelial growth factor and vascular endothelial growth factor receptor-2: potential mechanisms for exacerbation of diabetic retinopathy by hypertension

Systemic hypertension exacerbates diabetic retinopathy and other coexisting ocular disorders through mechanisms that remain largely unknown. Increased vascular permeability and intraocular neovascularization characterize these conditions and are complications primarily mediated by vascular endothelial growth factor (VEGF). Because systemic hypertension increases vascular stretch, we evaluated the expression of VEGF, VEGF-R2 (kinase insert domain-containing receptor [KDR]), and VEGF-R1 (fms-like tyrosine kinase [Flt]) in bovine retinal endothelial cells (BRECs) undergoing clinically relevant cyclic stretch and in spontaneously hypertensive rat (SHR) retina. A single exposure to 20% symmetric static stretch increased KDR mRNA expression 3.9 +/- 1.1-fold after 3 h (P = 0.002), with a gradual return to baseline within 9 h. In contrast, BRECs exposed to cardiac-profile cyclic stretch at 60 cpm continuously accumulated KDR mRNA in a transcriptionally mediated, time-dependent and stretch-magnitude-dependent manner. Exposure to 9% cyclic stretch increased KDR mRNA expression 8.7 +/- 2.9-fold (P = 0.011) after 9 h and KDR protein concentration 1.8 +/- 0.3-fold (P = 0.005) after 12 h. Stretched-induced VEGF responses were similar. Scatchard binding analysis demonstrated a 180 +/- 40% (P = 0.032) increase in high-affinity VEGF receptor number with no change in affinity. Cyclic stretch increased basal thymidine uptake 60 +/- 10% (P < 0.001) and VEGF-stimulated thymidine uptake by 2.6 +/- 0.2-fold (P = 0.005). VEGF-NAb reduced cyclic stretch-induced thymidine uptake by 65%. Stretched-induced KDR expression was not inhibited by AT1 receptor blockade using candesartan. Hypertension increased retinal KDR expression 67 +/- 42% (P < 0.05) in SHR rats compared with normotensive WKY control animals. When hypertension was reduced using captopril or candesartan, retinal KDR expression returned to baseline levels. VEGF reacted similarly, but Flt expression did not change. These data suggest a novel molecular mechanism that would account for the exacerbation of diabetic retinopathy by concomitant hypertension, and may partially explain the principal clinical manifestations of hypertensive retinopathy itself. Furthermore, these data imply that anti-VEGF therapies may prove therapeutically effective for hypertensive retinopathy and/or ameliorating the deleterious effects of coexistent hypertension on VEGF-associated disorders such as diabetic retinopathy.

Alternatively spliced nephrin in experimental glomerular disease of the rat

Nephrin is a novel transmembrane protein of kidney glomerular podocytes, which appears crucially important for the maintenance of the glomerular filtration barrier. According to its predicted structure, nephrin has additional roles in cell-cell adhesion and/or signal transduction. We have previously cloned the rat homologue of nephrin and described its alternatively spliced transcripts alpha and beta. In this study we examined the alterations in expression and regulation of particularly the major alternatively spliced nephrin-alpha giving rise to a variant lacking the membrane spanning domain in the puromycin nephrosis of the rat. A down-regulation of up to 78% was observed of the full length mRNA after 10 d of PAN treatment. The expression changes of nephrin-alpha followed closely the expression of the full length mRNA. Interestingly, we also found nephrin protein in urine at the peak proteinuria samples of this model. These results suggest that soluble nephrin variants may be important markers for proteinuric diseases.

Retinal neovascularization is prevented by blockade of the renin-angiotensin system

Both angiotensin II and vascular endothelial growth factor are angiogenic agents that have recently been implicated in the pathogenesis of proliferative diabetic retinopathy. In this study, retinal neovascularization was examined in a model of retinopathy of prematurity with the use of neonatal transgenic (mRen-2)27 rats, which overexpress renin in tissues, and Sprague-Dawley rats. Blockers of the renin-angiotensin system were administered during the neovascularization period. The ACE inhibitor lisinopril and the angiotensin type 1 receptor antagonist losartan both increased retinal renin levels and prevented inner retinal blood vessel growth. Quantitative in situ hybridization revealed that the expression of vascular endothelial growth factor and its type 2 receptor in the inner retina and proliferating blood vessels were increased in rats with retinopathy of prematurity. Lisinopril reduced both retinal vascular endothelial growth factor and its type 2 receptor mRNA in retinopathy of prematurity rats, whereas losartan had no effect. It is predicted that agents that interrupt the renin-angiotensin system may play an important role as retinoprotective agents in various forms of proliferative retinopathy.