Renal dysfunction after chronic blockade of nitric oxide synthesis

Enhanced kidney damage induced by increasing nonylphenol doses: impact on autophagy-related proteins and proinflammatory cytokines in rats

Nonylphenol (NP) is an organic pollutant and endocrine disruptor chemical that has harmful effects on the environment and living organisms. This study looked at whether kidney tissues subjected to increasing doses of nonylphenol generated alterations in histopathologic, pro-inflammatory, and autophagic markers. Fifty rats were divided into five groups of ten each: group I: healthy group, II: control (corn oil), group III: 25 μl/kg NP, group IV: 50 μl/kg NP, group V: 75 μl/kg NP. The kidney tissue samples were obtained for histopathological, immunohistochemical, and biochemical analyses. The histological deteriorations observed in all NP groups included tubular epithelial cell degeneration, inflammation areas, and hemorrhage. The immunohistochemical investigations showed that NP significantly elevated the autophagy markers (Beclin-1, LC3A/B, p62), pro-inflammatory cytokines (TNF-α, IL-6), HIF-1α, and eNOS in group III, IV and V compared with group I and II. The biochemical analysis also revealed that pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) increased in correlation with the NP doses, but only IL-1β reached statistical significance in NP treated rats kidney tissue. The biochemical findings have been confirmed by the histological studies. The damage to renal tissue caused by NP exposure may worsen it by increasing inflammatory and autophagic markers.

Effects of flavonoids in experimental models of arterial hypertension

Flavonoids are a class of substances of a vegetal origin with many interesting actions from the point of view of human disease. Interest in flavonoids in the diet has increased in recent years due to the publication of basic, clinical and epidemiological studies that have shown a whole array of salutory effects related to intake of flavonols and flavones as well as a lower morbility and mortality of cardiovascular diseases. Since arterial hypertension is the most common modifiable risk factor for cardiovascular diseases, this review will focus mainly on the effects of flavonoids on the cardiovascular system with relation to the elevation of blood pressure. Its antihypertensive effects as well as the many investigations performed in experimental models of arterial hypertension are reviewed in this mini-review.

Serum Clara-Cell Protein and β2-Microglobulin as Early Markers of Occupational Exposure to Nitric Oxides

Biochemical effects of NOx on 60 workers (both genders) of nitric acid production were studied. The control group consisted of 61 nonexposed people employed elsewhere in the plant. Although the actual threshold limit valuetime weighted averages (TLV-TWA) were not exceeded in the specific conditions of our study, the subjects were exposed to NO2 and NO during several exposure episodes with peak maximal concentrations of 140 ppm and 515 ppm, respectively. Additional cross-week evaluation of several biochemical biomarkers in 15 NOx-exposed workers from one shift was performed. The objective of the study was to evaluate the value of serum Clara-cell protein (CC16) as a marker of bronchoalveolar epithelium activity. Antioxidant status was assessed by measuring activity of enzymes: glutathione peroxidase (GSH-Px), ceruloplasmin (Cp) in plasma, or superoxide dismutase (SOD), gluthatione S-transferase (GST), and nonenzymatic alpha-tocopherol in erythrocytes and thiobarbituric acid-reactive substances (TBARS) in plasma. Serum hyaluronic acid (HA) determining the connective tissue matrix status of airways, and beta2-microglobulin in serum (beta2M-S) and urine (beta2M-U) as a marker of renal function in occupational exposure to NOx were also employed. Exposure to NOx initiates peroxidative chain depleting of lipoprotein pool (alpha-tocopherol) in blood. Serum CC16 levels in NOx-exposed workers were found to be closely connected with alpha-tocopherol content. In NOx-exposed workers, the beta2M-S level was significantly higher than in the nonexposed ones, with the exception of smokers. Results of the cross-week study confirm cumulative systemic effects of NOx on several examined biomarkers. SOD and GST were found to be depleted. A transient higher level of HA after a 5-d shift significantly inversely correlated with CC16 level. The data imply that NOx-depleted levels of CC16 are detectable already after an 8-h shift. Our results demonstrate that even low NOx human exposure can cause characteristic changes in bronchiolar epithelium cells and renal effects. Serum CC16 level, although a nonspecific marker, was lowest in NOx-exposed subjects. The most sensitive parameters in exposed workers were beta2M-S and a-tocopherol. Spirometric assessment was not useful to describe low occupational exposure to NOx. In studying the effects of NOx on biomarkers, it is essential to carefully select suitable time of sampling. Screening of CC16, beta2M-S, and a-tocopherol can be successfully employed for biological monitoring of exposure to NOx.

NO Synthase Inhibition Increases Aldosterone in Humans

To test the hypothesis that NO influences aldosterone production in humans, we examined the effect of N G -nitro- l -arginine methyl ester ( l -NAME) on aldosterone concentrations in the presence and absence of the NO precursor l -arginine (3 g TID) and the angiotensin-converting enzyme inhibitor ramipril (10 mg QD). Ten normal subjects were given l -NAME (66 μg/kg per min for 30 minutes) or vehicle in random order on separate days during placebo and after randomized, double-blind treatment with l -arginine, ramipril, or l -arginine plus ramipril. Infusion of l -NAME significantly increased systolic blood pressure (all P <0.05) and decreased heart rate (all P ≤0.02) during all 4 treatment arms. After placebo pretreatment, serum aldosterone was significantly higher during l -NAME infusion than during vehicle (6.6±1.7 versus 3.3±0.5 ng/dL; P =0.045). Combined treatment with l -arginine plus ramipril abolished this effect. There was no effect of l -NAME on plasma renin activity (PRA; P =0.297) or angiotensin II concentrations ( P =0.537). However, there was a significant interactive effect of l -NAME and time on serum potassium ( P =0.039). There was a significant linear relationship between PRA and aldosterone concentration after vehicle infusion ([aldosterone]=3.9·PRA+1.9; r 2 =0.476; P =0.027) and l -NAME infusion ([aldosterone]=7.2·PRA+3.1; r 2 =0.457; P =0.032), and the intercepts of these lines were different ( P =0.029). There was a significant linear relationship between serum potassium and aldosterone during l -NAME ([aldosterone]=8.2 · [potassium]−28.9; r 2 =0.609; P =0.008) but not during vehicle ( P =0.313). These data suggest that endogenous NO modulates aldosterone synthesis in humans.

Prolonged inhibition of nitric oxide synthesis in pregnant rats: effects on blood pressure, fetal growth and litter size

METHODS

In order to investigate the effect of chronic inhibition of nitric oxide synthesis along pregnancy, pregnant rats were given drinking water alone (control group) or drinking water containing nonselective nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME; 15 mg/day/rat equivalent to 50 mg/kg/day; treated group), from postmating days 1 to 18 of pregnancy. On days 1 to 17 of pregnancy, urinary volume, urinary sodium and potassium excretion, and urine protein concentration were measured. Systolic blood pressure (SBP) was recorded daily. On days 6, 11 and 18 of pregnancy the number of sites of implantation, number of embryos, litter size, fetal and placenta weight were determined.

RESULTS

Systolic blood pressure (mmHg) increased (p<0.001) on the 2nd day of administration of L-NAME and remained high throughout the experiment. This treatment increased urinary protein excretion and urine volume (p<0.01), with changes in the sodium and potassium excretion rate along the study. On day 6 of gestation in treated group, the number of implantation sites (0.14+/-0.10) significantly decreased (p<0.05) compared with the control group (1.45+/-0.58), but on day 11 of pregnancy the number of embryos was similar in both groups. By day 18 of pregnancy, L-NAME caused a substantial decrease (p<0.001) in litter weight (6.30+/-0.77 to 12.00+/-0.92 g), weight of placenta (3.17+/-0.22 to 4.74+/-0.21 g) (p<0.001) and litter size (7.95+/-0.59 to 11.95+/-0.45 fetus/litter; p<0.001). Also, treatment with L-NAME caused an important number of fetal resorptions (2.93+/-0.42 No./litter to 0 in control group).

CONCLUSION

Thus, treatment of pregnant rats with L-NAME, has an important effect on systolic blood pressure and on the physiology of reproduction, mainly in the third stage of pregnancy.

High concentration of glucose inhibits glomerular endothelial eNOS through a PKC mechanism

Kidney glomeruli are important targets of diabetic nephropathy. We hypothesized a high concentration of glucose could suppress glomerular endothelial nitric oxide synthase (eNOS) by a protein kinase C (PKC) mechanism, as has been found in other tissues. Mouse kidney slices (150-200 microm) were bathed in Hanks' solution with 100 microM L-arginine and exposed to either 5 or 20-30 mM D-glucose. Immunofluorescence identified only eNOS in normal mouse glomeruli. Measurements of glomerular NO concentration with NO-sensitive fluorescent dye (4,5-diaminofluorescein diacetate) using confocal microscopy and NO-sensitive microelectrodes verified that resting glomeruli had active production of NO that was inhibited by N(G)-nitro-L-arginine methyl ester. High-concentration (20-30 mM) D-glucose inhibited 60-70% of the NO production within 15-30 min; L-glucose at the same concentration did not have any effect. Inhibition of PKC-beta with 100 nM ruboxistaurin prevented eNOS suppression in high-glucose media. Activation of PKC with 100 nM phorbol ester also suppressed the glomerular NO concentration. We concluded that eNOS in the renal glomerular capillary endothelial cells is suppressed by activity of PKC at high-glucose concentrations comparable to those in diabetic animals and humans. The consequence is a rapid decline in the generation of NO in the glomerular endothelial cells in the presence of a high concentration of glucose.