Oxidative Stress Status in Kidney Tissue after Losartan and Atenolol Treatment in Experimental Renal Failure

Effects of losartan and enalapril on high-sensitivity C-reactive protein and total antioxidant in renal transplant recipients with Renin-Angiotensin system polymorphisms

BACKGROUND

As renin-angiotensin system (RAS) activity may affect the severity of oxidative stress and inflammatory markers, we assessed the effects of enalapril (E) and/or losartan (L) on these markers in renal transplant recipients with RAS polymorphisms.

PATIENTS AND METHODS

After determination by PCR of RAS genotypes, consisting of the angiotensin-converting enzymes (ACE I/D), angiotensinogens (AGT M235T) and angiotensin II type 1 receptors (ATR1 A1166C), 76 recipients were recruited randomly and assigned 4 groups. The first (n = 17) and second (n = 24) groups were treated with E (E(+): 10 mg/d) and L (L(+): 50 mg/d) alone, respectively. The third positive control group (n = 17) received E + L (E(+)L(+): 10 mg/d + 50 mg/d) and the fourth negative control group (n = 18) received no medication (E(-):L(-)). High-sensitivity C-reactive protein (hs-CRP) and total antioxidant (TA) inflammatory and antioxidative markers were measured after 2 months. After a 2-week washout period, the E(+) group was changed to L(+) and vice versa in a crossover design. They were followed for another 8 weeks before retesting hs-CRP and TA. A value of P < or = .05 was considered significant.

RESULTS

After 2 and 4 months of treatment with the drug regimen, hs-CRP and TA levels were significantly decreased and consequently increased among the E(+)L(+), L(+) and E(+) groups (P < .05). On analyzing the relationship between RAS polymorphisms and baseline hs-CRP or TA levels, CC genotype of ATR1 showed lower hs-CRP levels (P = .04). However, none of the RAS polymorphisms predicted the antioxidant and anti-inflammatory response rates to the drugs (P > .05).

CONCLUSION

Although hs-CRP was lower in the CC genotype patients of ATR1 polymorphisms E and/or L reduced hs-CRP and increased TA regardless of the RAS genotype.

Long-term nebivolol administration reduces renal fibrosis and prevents endothelial dysfunction in rats with hypertension induced by renal mass reduction

OBJECTIVES

D/L-Nebivolol is a lypophilic beta1-adrenergic antagonist which is devoid of intrinsic sympathomimetic activity and can increase nitric oxide (NO) bioavailability with its subsequent vasodilating properties. The purpose of the present work was to assess the effect of long-term nebivolol administration on both renal damage and endothelial dysfunction induced by renal mass reduction (RMR) in rats. Atenolol, which does not increase NO bioavailability, was included in the study as a comparative beta-adrenoceptor antagonist.

METHODS

Rats were subjected to both right nephrectomy and surgical removal of two-thirds of the left kidney in order to retain approximately one-sixth of the total renal mass. One week after ablation, rats were distributed randomly according to the following experimental groups: control group containing RMR rats without treatment; RMR rats treated daily with nebivolol for 6 months (drinking water, 8 mg/kg per day); and RMR rats treated daily with atenolol for 6 months (drinking water, 80 mg/kg per day). A group of sham-operated animals was also included.

RESULTS

Administration of either nebivolol or atenolol similarly reduced arterial pressure in comparison with RMR untreated animals; however, animals receiving nebivolol presented lower levels of collagen type I expression as well as lower glomerular and interstitial fibrosis than those receiving atenolol. Urinary excretion of oxidative stress markers were also lower in animals receiving nebivolol than in rats treated with atenolol. Furthermore, nebivolol prevented RMR-induced endothelial dysfunction more efficiently than atenolol.

CONCLUSIONS

Nebivolol protects against renal fibrosis, oxidative stress and endothelial dysfunction better than equivalent doses, in terms of arterial pressure reduction, of atenolol in a hypertensive model of renal damage induced by RMR.

Prevention of DNA damage in renal transplantation by losartan and enalapril: the role of renin-angiotensin system polymorphisms

BACKGROUND

In this study the effect of losartan and enalapril on the reduction of DNA damage was evaluated in regard to renin-angiotensin system (RAS) polymorphisms.

METHODS

After determination of genotypes of RAS polymorphism by PCR, 64 renal transplant recipients were randomly allocated to one of four groups: the first and second groups were treated with E (E+: 10 mg/day) and L (L+: 50 mg/day) alone, respectively. The third group received E+L (E+L+: 10 + 50 mg/day), and the forth group received no medication (E-L-). The subjects were followed for 8 weeks. After a 2-week washout period, the E group changed to L and vice versa as a cross-over design. They were followed for another 8 weeks. Before and after treatment, we checked 8-OHdG and malondialdehyde (MDA) as biomarkers of DNA damage and lipid peroxidation, respectively.

RESULTS

8-OHdG levels were significantly decreased after treatment in the E+L+ and L+ groups (P < 0.001, P = 0.001, respectively). Only the TT genotype of AGT had the most antioxidative role regarding the treatment (P = 0.01). We found a remarkable correlation between MDA and DNA damage levels before and after intervention (r = 0.48, P < 0.001; r = 0.35, P = 0.006).

CONCLUSION

The protective effects of L+ and E+L+ on DNA breaks are surprising regarding the RAS polymorphisms.

Effect of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension

OBJECTIVE

It has been shown that angiotensin-converting enzyme inhibition or angiotensin receptor blockade may improve endothelial dysfunction, an early manifestation of atherosclerosis, in patients with diabetes. Whether this protective effect is mediated through blood pressure-lowering effects or other specific mechanisms such as a reduction in oxidative stress is not clear. We investigated the influence of losartan, compared with atenolol, on endothelial function and oxidative stress in patients with type 2 diabetes and hypertension.

METHODS

Thirteen patients were included in this randomized, double-blind, crossover study; they received losartan 50 mg twice daily for 4 weeks followed by atenolol 50 mg twice daily or vice versa. Concomitant medication with renin-angiotensin blocking agents or beta-blockers was withdrawn, whereas other medication remained unchanged. At baseline and after each treatment period, flow-mediated dilation of the brachial artery and oxidative stress were measured in serum samples.

RESULTS

Flow-mediated dilation was increased significantly after 4 weeks' treatment with losartan (3.4 +/- 0.44%) compared with atenolol (2.58 +/- 0.42%; P = 0.01). 8-Isoprostanes, a marker of oxidative stress, were significantly reduced in the losartan group compared with baseline (0.039 +/- 0.007 versus 0.067 +/- 0.006 ng/ml; P = 0.01), but did not differ from baseline with atenolol. Glucose, hemoglobin A1c, highly sensitive C-reactive protein, lipids and systolic blood pressure remained unaltered, whereas diastolic blood pressure tended to be lower in the atenolol group.

CONCLUSIONS

This study demonstrates that losartan significantly improved endothelial function in type 2 diabetes patients with hypertension compared with atenolol. This must be independent of the blood pressure-lowering effect of losartan and is probably caused by an antioxidative effect of the angiotensin receptor blocker.

Enalapril and losartan affect lipid peroxidation in renal transplant recipients with renin–angiotensin system polymorphisms

OBJECTIVES

In this study, the effect of enalapril (E) and/or losartan (L) on lipid peroxidation (LPO) is studied in renal transplant recipients (RTRs) with regard to polymorphisms of renin-angiotensin system (RAS).

DESIGN AND METHODS

After determination of genotypes of the angiotensin-converting enzyme (ACE I/D), angiotensinogen (AGT M235T) and angiotensin II type 1 receptor (ATR1 A1166C) by PCR, sixty-four RTRs recruited to four groups randomly: first (13 patients) and second (20 patients) groups were treated with enalapril (E(+): 10 mg/day) and losartan (L(+): 50 mg/day) alone for 2 months, respectively. After 2 weeks as washout period, E group changed to L and vice versa as a cross-over design and they were treated for another 2 months. The third group (13 patients) as positive control received enalapril+losartan (E(+)L(+): 10 mg/day+50 mg/day) for 16 weeks, and the forth group (18 patients) as negative control received no medication (E(-)L(-)). Malondialdehyde (MDA) as LPO marker was measured before and after treatment. In this study, P<0.05 was considered significant.

RESULTS

After 2 months of treatment, MDA level significantly decreased in all of the groups except the E(-)L(-). MDA level in pre- vs. post-intervention for the E(+)L(+), E(+), L(+) and E(-)L(-) groups were as follows: 5.81+/-2.13 nmol/mL vs. 1.61+/-0.80 nmol/mL (P=0.001), 5.10+/-2.05 nmol/mL vs. 1.68+/-1.01 nmol/mL (P=0.003), 5.20+/-1.61 nmol/mL vs. 1.22+/-0.27 nmol/mL (P=0.000) and 5.27+/-2.12 nmol/mL vs. 5.07+/-2.03 nmol/mL (P=0.52), respectively. Also, the same results were found in the end of 16th week. Although patients with DD genotype of ACE had higher MDA (P=0.01) levels, RAS polymorphisms could not predict the antioxidative response rate to the drugs (P>0.05).

CONCLUSIONS

E and/or L reduce MDA regardless of the RAS genotypes.

Gender differences in the renin-angiotensin and nitric oxide systems: relevance in the normal and diseased kidney

Female gender is associated with better renal function and resistance to renal injury, suggesting that an oestrogen-based effect or increased androgenic effects are responsible. Studies in rodents have confirmed a biological basis for this, based on the differential effects of androgens and oestrogens on the normal and diseased kidney. Many researchers in the field believe that the pre-menopausal levels of oestrogen are key to the protection observed in females. The key pressor effects of the renin-angiotensin (RA) system are due to both direct vasoconstrictory properties and alterations in renal control of extracellular fluid volume. Additionally, the RA has been shown to promote diverse aspects of renal injury. RA activity is positively modulated by androgens and antagonized by oestrogens. Nitric oxide (NO) is a potent vasorelaxant with a key role in renal control of extracellular fluid homeostasis. NO can variously have both protective and deleterious effects on renal injury. Endogenous oestrogen has an anti-hypertensive effect as well as protective effects against cell and organ damage, many of which are mediated via increases in NO generation. We examine how the RA- and NO-generating systems may underpin key aspects of gender differences in normal renal function and renal disease.

Chronic inhibition of nuclear factor-kappaB attenuates renal injury in the 5/6 renal ablation model

Recent studies indicated that the nuclear transcription factor, NF-kappaB, activates a number of proinflammatory genes in subjects with progressive nephropathies. We investigated whether NF-kappaB inhibition limits progressive renal injury in the 5/6 renal ablation model (Nx). Adult male Munich-Wistar rats were subdivided in four groups: S (n = 16), subjected to sham operation; S+PDTC (n = 18), sham-operated rats receiving the NF-kappaB inhibitor pyrrolidine-dithiocarbamate (PDTC; 60 mg x kg(-1) x day(-1)) in drinking water; Nx (n = 16), Nx rats receiving vehicle only; and Nx+PDTC (n = 19), Nx rats given PDTC as above. Thirty days after renal ablation, Nx rats exhibited systemic and glomerular hypertension. Only the former was attenuated by PDTC treatment. Sixty days after renal ablation, Nx rats exhibited marked hypertension, albuminuria and creatinine retention, as well as glomerulosclerosis and cortical interstitial expansion/inflammation. Immunohistochemical analysis of Nx rats showed renal interstitial infiltration by macrophages and by cells staining positively for ANG II and its receptor, AT(1). Glomerular and interstitial cells expressing the p65 subunit of the NF-kappaB system were also found. PDTC treatment attenuated renal injury and inflammation, as well as the density of cells staining positively for the p65 subunit. Activation of the NF-kappaB system plays an important role in the pathogenesis of renal injury in the Nx model. Inhibition of this system may represent a new strategy to prevent the progression of chronic kidney disease.