Claudio Joo Turoni

Structural Changes in the Renal Vasculature in Streptozotocin-Induced Diabetic Rats without Hypertension

Background/Aim: We evaluated in diabetic-streptozotocin rats (STZR) the structural changes of glomeruli, preglomerular vessels, glomerular tuft and renal parenchyma in order to determine the degree of renal injury and the presence of remodeling in afferent arterioles developed by diabetes without overimposed hypertension. Methods: Renal mass index and histological score (glomerular number, density, tubular lesions and degree of arteriosclerosis) were estimated. In afferent arterioles the ratio of wall thickness/lumen was obtained by stereological methods. Results: STZR developed diabetes without hypertension; renal mass index increased and matched changes in glomeruli (decrease of capillary number and enlargement of mesangium and basement capillary membrane). Both glomerular number and density as well as afferent arteriole number were diminished. Degenerative changes in both proximal (glycogenic and hyaline degeneration) and distal tubules (hyaline casts) were also observed. At variance with preglomerular vessels, the efferent arterioles only presented initial arteriosclerosis. Finally, the stereological study of afferent arterioles showed a significantly lower arteriolar lumen area and arteriolar wall thickness in STZR, resulting in a remodeling without modification of wall/lumen ratio. Conclusion: Diabetes, uncomplicated by hypertension, is associated with (1) a reduction in glomerular number; (2) degeneration in parenchyma and renal tubules, and (3) a specific pattern of remodeling in preglomerular vessels different from that induced by hypertension. Although this work demonstrated that these changes are not triggered by hypertension, further investigations are required in order to determine which mediators are involved in diabetic-vascular renal dysfunction.

Arterial Stiffness and Endothelial Function in Obese Children and Adolescents and Its Relationship with Cardiovascular Risk Factors

Background: Obesity is related to an increase in the rates of cardiovascular disease. Objective: To establish the impact of obesity on vascular function (endothelial function and arterial stiffness) in children and adolescents and its relationship to cardiovascular risk factors. Methods: In obese (OB) children and adolescents, endothelial function and arterial stiffness were evaluated by a pulse plethysmography method (reactive hyperemia and index of digital volume waveforms, respectively). Data were compared with the non-obese (non-OB) group (body mass index >10th to <97th percentile). Anthropometric parameters, body fat percentage, fasting glucose, lipid profile, insulinemia, HOMA-IR and hemodynamic parameters were determined in both groups. Results: Body mass index, weight, waist circumference, body fat, insulinemia and HOMA-IR were significantly higher in the OB group. The OB group showed impaired endothelial function (15.8 ± 0.2%, n = 37) compared to the non-OB group (41.4 ± 5%, n = 20; p < 0.001) and increased arterial stiffness. Endothelial function was only negatively correlated with waist circumference and HOMA-IR in the OB group, whereas a positive correlation was found between insulinemia and HOMA-IR. Conclusions: This study shows that impaired vascular function is already present in OB children and adolescents. The fact that obesity is associated with some markers of cardiovascular risk suggests the importance of early lifestyle interventions in this population to prevent cardiovascular disease.

Inflammatory and prothrombotic activation with conserved endothelial function in patients with chronic, asymptomatic Chagas disease.

Previously, our group showed a prothrombotic state in asymptomatic patients with chronic Chagas disease. The current paper studies the inflammatory status and endothelial function in these patients. Methods: In 40 patients and 40 healthy volunteers, we evaluated prothrombotic state, blood parasitemia (molecular biology: polymerized chain reaction [PCR]-amplification), tissue factor pathway inhibitor antibodies (aTFPI), interleukin 6 (IL-6), and vascular cell adhesion molecule-1 (VCAM-1). Endothelial function was determined by reactive hyperemia (pulse plethysmography). Results: In patients, prothrombin fragment 1 + 2, d-dimer, PAI-1, and fibrinogen were higher. Amplification of 121/122 primers (Trypanosoma cruzi) was positive in 45% of the patients. Patients presented higher values of aTFPI- immunoglobulin G (IgG; P < .05), aTFPI-IgM (P < .001), IL-6 (P = .004), and VCAM-1 (P = .00001). In both groups, endothelial function was preserved. Conclusions: We found that asymptomatic patients with chronic Chagas disease presented a prothrombotic/inflammatory status. The fact that endothelial function is still preserved suggests that prothrombosis and inflammation are primarily implicated in the beginning of cardiovascular damage.

Internal mammary artery grafts reactivity in hypertensive patients : Role of stretching in extraendothelial nitric oxide

Background. The internal mammary artery (IMA) used in bypass coronary surgery remains efficient for a longer time than other grafts, such as saphenous veins; however, its biological characteristics are incompletely defined. Objective. To compare in IMA grafts from hypertensive (HT) and normotensive (NT) patients the presence of endothelium and their functionability, the response to passive stretching and basal tone, the reactivity to exogenous vasoconstrictors, the role of stretching in NO release, and the possible extraendothelial NO source. Methods and Results. IMA rings contractility, presence of endothelium, and nitrite release were studied. An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching, resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP; however, a lesser response was found in HT. Interestingly, it was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction and that stretching increased NO release. This effect was inhibited by Ca2+-free media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, the demonstration of the presence of nNOS in smooth muscle cells by immunohistochemistry supports a role of extraendothelial NO. Conclusion. We demonstrate the impact of hypertension in IMA grafts producing increased endothelial dysfunction, reduced response to passive stretching, increased basal tone, and impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO, even in the absence of the endothelium.

Nitric Oxide Modulates Reactivity to Angiotensin II in Internal Mammary Arterial Grafts in Hytertensive Patients Without Associated Risk Factors

We investigated the effects of extraendothelial nitric oxide (NO) on angiotensin II (Ang II) reactivity in internal mammary artery (IMA) rings, as well as the impact of hypertension without associated risk factors in this response. Vascular reactivity, NO levels, and resting membrane potentials were determined in hypertensive (HT) and normotensive (NT) IMA rings. Only rings with endothelial dysfunction were included. Ang II produced a dose-dependent contraction that was higher in HT rings. Response to Ang II was potentiated by Nω-nitro L-arginine methyl ester (L-NAME) in NT but not in HT rings. The antioxidant agents tempol and diphenyleneiodonium (DPI) reverted the hyperreactivity to Ang II in HT rings. Extraendothelial NO was present in both NT and HT rings. However, NT rings showed higher values. L‐NAME and S-methyl-L-thiocitrulline inhibited NO release in all cases. L-arginine reverted this inhibition. Both tempol and DPI increased NO release in both NT and HT rings. The number of vascular smooth muscle cells (VSMC) and anti-α-actin positive areas were lower in HT than in NT rings, without variations in wall thickness or wall/lumen ratio. With regard to resting membrane potential, we found in HT rings that the depolarization induced by Ang II was abolished by tempol. These findings suggest that extraendothelial NO counterregulates Ang II contractility in IMA rings; however, its action could be altered in hypertensive situations even though the patients did not have associated risk factors. We suggest two mechanisms: increased oxidative stress and a decreased ability of nNOS in VSMC to produce NO.

Antioxidant Treatment Reverts Increased Arterial Basal Tone and Oxidative Stress in Nephrectomized (5/6) Hypertensive Rats

Nonischemic 5/6 nephrectomized rat (NefR) is a model of chronic kidney disease. However, little is known about vascular dysfunction and its relation with hypertension in NefR. Aims. To evaluate possible alterations of endothelial function, NO-bioavailability, and basal tone in aorta from NefR and the role of oxidative stress. Sprague Dawley rats were divided into sham rats (SR), NefR, and NefR treated with tempol (NefR-T). Mean arterial pressure (MAP) and renal function were determined. In isolated aortic rings the following was measured: 1-endothelial function, 2-basal tone, 3-NO levels, 4-membrane potential (MP), and 5-oxidative stress. NefR increased MAP (SR: 119 ± 4 mmHg; n = 7; NefR: 169 ± 6; n = 8; P < 0.001). Tempol did not modify MAP (NefR-T: 168 ± 10; n = 6; P < 0.001). NefR showed endothelial dysfunction, increased basal tone and decreased NO levels (SR: 32 ± 2 nA; n = 7, NefR: 10 ± 2; n = 8; P < 0.001). In both in vitro and in vivo tempol improves basal tone, NO levels, and MP. Oxidative stress in NefR was reverted in NefR-T. We described, for the first time, that aorta from NefR presented increased basal tone related to endothelial dysfunction and decreased NO-bioavailability. The fact that tempol improves NO-contents and basal tone, without decrease MAP, indicates that oxidative stress could be implicated early and independently to hypertension, in the vascular alterations.

STRUCTURAL CHANGES IN THE KIDNEY INDUCED BY COARCTATION HYPERTENSION

We investigated structural alterations in renal tissue identifying the morphological and histological changes in the non-ischemic kidney (NIK) and their potential significance in aortic coarctation-hypertensive rats (HR). HRs mean arterial pressure (MAP) was higher compared with sham operated rats (SR). An oral 10 mg/kg/day losartan (LOS) dose diminished but not reverted MAP. Hypertrophy was noted in HR NIKs with significant weight increase (p< 0.01). The ratio IK/NIK in HRs decreased 22% (p<0.01). LOS proved to cause no ischemic kidney (IK) modification nor did it revert NIK hypertrophy. NIK in HRs presented glomerulosclerosis, mesangial proliferation and arteriolar thickening reverted by LOS. The stereological study of afferent NIK arterioles showed hypertrophy and an increase in the wall/lumen ratio without lumen modification. LOS diminished wall thickness. LOS-induced decrease of NIK alterations might result from arteriosclerosis regression, the media/lumen ratio, glomerulosclerosis and mesangial proliferation dependent on angiotensin II.

Vascular Function in Children with Low Birthweight and Its Relationship with Early Markers of Cardiovascular Risk

Low birthweight (LBW) increases the risk of developing cardiovascular diseases (CVD). Few studies have established its impact at early ages. Aims: To study endothelial function (EF) and arterial stiffness (AS) and their relationship to early markers of CVD risk in children with LBW. Methods: In children with LBW (4-6 years; n = 53), anthropometric, haemodynamic and laboratory parameters, including HOMA-IR, hs-CRP, adiponectin and leptin, were determined. EF and AS were evaluated by digital pulse plethysmography. Data were compared with a control group (n = 33). Results: In both groups, anthropometric parameters remained within normal limits. Insulin and HOMA-IR had normal values, but they were significantly augmented in LBW children. LBW children showed higher leptin and hs-CRP levels than the control group. The LBW group had decreased EF (37.5 ± 5.6%) compared with the control group (75.0 ± 11.9%; p < 0.01), however without differences in AS. In LBW children, EF was negatively correlated with waist circumference, leptin, hs-CRP and with a cumulative score of risk factors. Conclusions: LBW children display altered EF that is related to early changes in CVD risk factors. The differences found in the metabolic parameters might indicate a pro-inflammatory state. This hypothesis is also supported by the laboratory findings and the correlation between EF and the number of CVD risk factors, suggesting that very early lifestyle interventions may be needed.

Tempol blunts afferent arteriolar remodeling in chronic nitric oxide-deficient hypertension without normalizing blood pressure

Abstract Background/Aim: Renal preglomerular vessels play a central role in modulating renal function and injury, especially during conditions of renal hemodynamic stress such as hypertension. We evaluated whether improving the balance between nitric oxide (NO) and oxidative stress improves the morphological alterations of renal afferent arterioles that occur in NO deficiency-induced hypertension. Methods: We measured indices of NO and oxidative stress and evaluated renal morphology and afferent arteriolar remodeling in rats treated with vehicle, L-NAME or L-NAME plus tempol (a superoxide dismutase mimetic) for 6 weeks. Results: L-NAME-treated rats had hypertension, lower urinary and renal NO indices, higher renal cortical levels of TBARS, GSSG and GSSG/GSH. This was associated with significant eutrophic inward remodeling of the afferent arterioles; they had a marked decrease in arteriolar lumen area and a striking increase in arteriolar wall thickness and media to lumen ratio. Tempol did not significantly reduce blood pressure, but increased NO levels, decreased oxidative stress and partially blunted L-NAME-induced remodeling of afferent arterioles. Conclusion: L-NAME-induced remodeling of afferent arterioles is blunted by tempol. This beneficial effect on remodeling is associated with increases in NO indices, decreases in oxidative stress, without significant decreases in blood pressure. Thus, the balance between these components may contribute to the altered renal hemodynamics and function in this model.

Oxidative Stress in Hypertensive Patients Induces an Increased Contractility in Vein Grafts Independent of Endothelial Function

Objective. To evaluate the impact of oxidative stress on vascular reactivity to vasoconstrictors and on nitric oxide (NO) bioavailability in saphenous vein (SV) graft with endothelial dysfunction from hypertensive patients (HT). Methods. Endothelial function, vascular reactivity, oxidative state, nitrites and NO release were studied in isolated SV rings from HT and normotensive patients (NT). Only rings with endothelial dysfunction were used. Results. HT rings presented a hyperreactivity to vasoconstrictors that was reverted by diphenylene iodonium (DPI). In NT, no effect of DPI was obtained, but Nω-nitro-L-arginine methyl ester (L-NAME) increased the contractile response. NO was present in SV rings without endothelial function. Nitrites were higher in NT than in HT (1066.1 ± 86.3 pmol/mg; n = 11 versus 487.8 ± 51.6; n = 23; P < 0.01) and inhibited by nNOS inhibitor. L-arginine reversed this effect. Antioxidant agents increased nitrites and NO contents only in HT. The anti-nNOS-stained area by immunohistochemistry was higher in NT than HT. HT showed an elevation of oxidative state. Conclusions. Extraendothelial NO counter-regulates contractility in SV. However, this action could be altered in hypertensive situations by an increased oxidative stress or a decreased ability of nNOS to produce NO. Further studies should be performed to evaluate the implication of these results in graft patency rates.