A randomized trial of prophylactic acetylcysteine and theophylline compared with placebo for the prevention of renal tubular vacuolization in rats after iohexol administration

Atorvastatin attenuates experimental contrast-induced acute kidney injury: a role for TLR4/MyD88 signaling pathway

Objectives: To investigate the protective effect of different atorvastatin doses on contrast-induced acute kidney injury and the related mechanism.

Methods: Healthy male Sprague–Dawley (SD) rats were randomly divided into the blank control group, experimental control group and different-dose atorvastatin groups. A rat model of contrast-induced acute kidney injury was established. We detected changes in serum creatinine (Scr) and blood urea nitrogen (BUN) before and after model establishment, observed and scored renal tubular injury, analyzed rat renal cell apoptosis, and measure the expression of signal pathway proteins and downstream inflammatory factors.

Results: After contrast agent injection, the Scr and BUN levels of the experimental control group were significantly increased, the different doses applied in the atorvastatin group significantly reduced the Scr and BUN levels (p < .05) and ameliorated the contrast-induced acute kidney injury (p < .05) and significantly reduced Toll-like receptor 4 (TLR4), Myeloid differentiation factor 88 (Myd88), and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) protein expression and relative mRNA expression levels (p < .05) and significantly decreased expression levels of downstream inflammatory factors (p < .05).

Conclusion: Different atorvastatin doses have protective effects on contrast-induced acute renal tubular injury in rats, possibly by targeting TLR4, suppressing TLR4 expression, regulating the TLR4/Myd88 signaling pathway, and inhibiting the expression of downstream inflammatory factors.

Metabolomic Analysis of N-acetylcysteine Protection of Injury from Gadolinium-DTPA Contrast Agent in Rats with Chronic Renal Failure

Gadolinium-based contrast agents (GBCAs) are frequently used to enhance the diagnostic efficacy of magnetic resonance imaging. On the other hand, the association between GBCA administration in patients with advanced renal disease and nephrogenic systemic fibrosis (NSF) was also noted. NSF is a systemic disorder characterized by widespread tissue fibrosis that may lead to death. N-acetylcysteine (NAC) protects rats from injury induced by gadolinium-based contrast agents, but the underlying mechanisms remain unclear. In this study, a nuclear magnetic resonance-based metabolomic approach was used to systematically investigate the protective effects of NAC on Gd-DTPA-induced injury. Thirty-two male Sprague-Dawley rats were given adenine (200 mg·kg^-1 body weight) by oral gavage once a day for 3 weeks to induce chronic renal failure (CRF). NAC (600 mg/L in drinking water for 9 days) pretreatment was initiated 2 days before Gd-DTPA injection (a single tail vein injection, 2 mmol/kg body weight). Serum and liver samples were collected on day 7 after Gd-DTPA injection. By study design, the serum and hepatic metabolic changes of rats were measured in four groups of eight each: CRF, CRF-Gd, CRF-Gd-NAC, and CRF-NAC. Gd-DTPA administration to rats with CRF resulted in disturbances of several metabolic pathways, including glucose, lipid, glutamate, choline, gut microbiota, one-carbon, and purine metabolism. NAC pretreatment reversed the abundance changes of high-density lipoprotein, low-density lipoprotein, very low-density lipoprotein, glutamate, glutamine, oxidized glutathione, choline, phosphocholine, glycerophosphocholine, trimethylamine, and trimethylamine-N-oxide induced by Gd-DTPA. It is noteworthy, however, that the ameliorating effects of NAC on the disturbance of glutamate, choline, and gut microbiota metabolism may be specific to Gd-DTPA. In all, these findings could be potentially useful to decipher the underlying mechanisms of NAC protective effects from the injury induced by gadolinium-based contrast agents.

Pathophysiology of renal tissue damage by iodinated contrast media

1. The present review focuses on the cytotoxic effects of iodinated contrast media (CM) that are shared by all types of CM. 2. Although the clinical nephrotoxicity of CM has been progressively improved, all currently available CM still possess a level of cytotoxicity, which is probably caused by iodine. 3. The toxicity caused by specific CM properties, such as osmolarity, viscosity and ionic strength, can be differentiated from the cytotoxicity common to all CM in studies using cell culture, isolated blood vessels and isolated tubules. 4. The cytotoxicity induced by CM leads to apoptosis and cell death of endothelial and tubular cells and may be initiated by cell membrane damage, together with oxidative stress. 5. Cell damage may be aggravated by factors such as tissue hypoperfusion and hypoxia, properties of individual CM, such as ionic strength, high osmolarity and/or viscosity, and clinically unfavourable conditions. 6. Clinically detectable renal failure may result from the summation of all these factors.

Effects of N-acetylcysteine on radiocontrast nephropathy in rats

OBJECTIVE

N-acetylcysteine (NAC) has yielded some promising results recently in the prevention of radiocontrast nephropathy (RCN). In this study, the structural and functional effects of NAC on RCN were analyzed.

MATERIAL AND METHODS

Twenty-eight Wistar rats were randomized into four groups, as follows: Group 1, controls; Group 2, contrast; Group 3, contrast+NAC; and Group 4, NAC. All rats were deprived of water for 24 h and then contrast medium (ioxoglate; 10 ml/kg) was administered to Groups 2 and 3. NAC (50 mg/kg) was introduced enterally to Groups 3 and 4 at a dose of 50 mg/kg in 0.5 ml of distilled water, in four sequential doses 12h apart, starting after 12?h of water deprivation. After 4 days, rats were sacrificed. Creatinine clearance was calculated. The malondialdehyde (MDA) level was quantified in tissue samples. Slides stained with hematoxylin-eosin and periodic acid-Schiff were examined by means of light microscopy. Each tubular cross-section from all images was scored as either mild (preserved brush border, no necrosis), moderate (loss of brush border, no necrosis) or severe (loss of brush border accompanied by necrosis) and the frequencies of these lesion severities were compared.

RESULTS

Mean baseline serum creatinine levels and creatinine clearances were similar in all groups. Mean serum creatinine level increased significantly only in Group 2 (0.6+/-0.1 vs 0.7+/-0.2 mg/dl; p<0.05). Tissue MDA levels were similar in all groups. Moderate (13.8%+/-1.5% vs 42%+/-1.4%; p<0.05) and severe (0% vs 40%+/-2.1%; p<0.05) lesions were significantly more frequent in Group 2 compared to Group 1. The frequency of severe lesions in Group 3 was found to be halved compared to that in Group 1 (40%+/-2.1% vs 20.2%+/-0.86%; p<0.05).

CONCLUSION

NAC protects the kidneys following exposure to contrast medium as it decreased the severity of tubular lesions in rats.

Clinical and Experimental Evidence for Prevention of Acute Renal Failure Induced by Radiographic Contrast Media

Acute renal failure still occurs as a complication after radiographic examination using iodinated radiocontrast medium. The incidence rate of radiocontrast medium-induced nephropathy (radiocontrast nephropathy) is low (2 - 3%) in general. However, the rate is remarkably elevated in patients with pre-existing renal insufficiency. Radiocontrast nephropathy is associated with increased morbidity and mortality, particularly in patients with percutaneous coronary interventions. Although the reduction in renal blood flow and direct toxic action on renal tubular cells are considered to be involved, little is known about the etiology of radiocontrast nephropathy. A number of agents that improve renal circulation have been clinically tested for prevention of radiocontrast nephropathy, but none of them has succeeded. Protection of renal tubular cells against oxidative stress is another approach to avoid radiocontrast nephropathy. Prophylactic effects of antioxidants such as N-acetylcysteine and ascorbic acid have been reported by several investigators, although the effectiveness of these compounds is still a matter of debate. At present, hydration is regarded as the only effective, though incomplete, prophylactic regimen for radiocontrast nephropathy. Recently, we have shown that caspase-dependent apoptosis is an important factor in the pathogenesis of radiocontrast nephropathy and clarified cellular mechanisms underlying the radiocontrast media-induced apoptosis. This review summarizes clinical and experimental evidence for the etiology and prevention of radiocontrast nephropathy.

N-acetylcysteine in the prevention of radiocontrast-induced nephropathy: clinical trials and end points

N-acetylcysteine (NAC) has been suggested to prevent radiocontrast-induced nephropathy (RCIN) in patients with a reduced renal function. However, clinical studies have not been demonstrating this effect consistently. Also, reviews and meta-analyses dealing with the question of prevention of RCIN by NAC have been controversial. Nearly all investigators used serum creatinine as surrogate end point of their trials, and changes in serum creatinine concentrations are thought to reflect the extent of renal injury as primary outcome. In a recent study, an effect of NAC on creatinine values and estimated glomerular filtration rate without any effect on cystatin C levels has been shown in volunteers with a normal renal function. Therefore, before renal protective effects of NAC in RCIN are proposed, any direct effects of NAC on creatinine, urea, and estimated glomerular filtration rate should be addressed. In future trials, the glomerular filtration rate should preferentially be measured directly, or at least additional markers of the renal function (e.g., serum cystatin C) have to be assessed. Furthermore, additional 'hard' end points, i.e., hospital morbidity, mortality, or dialysis dependency, should be considered in the design of future studies of RCIN.