Nonionic contrast media are less nephrotoxic than ionic contrast media to rat renal cortical slices

Decomposition of Iodinated Pharmaceuticals by UV-254 nm-assisted Advanced Oxidation Processes

Iodinated pharmaceuticals, thyroxine (a thyroid hormone) and diatrizoate (an iodinated X-ray contrast medium), are among the most prescribed active pharmaceutical ingredients. Both of them have been reported to potentially disrupt thyroid homeostasis even at very low concentrations. In this study, UV-254 nm-based photolysis and photochemical processes, i.e., UV only, UV/H₂O₂, and UV/S₂O₈^2-, were evaluated for the destruction of these two pharmaceuticals. Approximately 40% of 0.5μM thyroxine or diatrizoate was degraded through direct photolysis at UV fluence of 160mJcm^-2, probably resulting from the photosensitive cleavage of C-I bonds. While the addition of H₂O₂ only accelerated the degradation efficiency to a low degree, the destruction rates of both chemicals were significantly enhanced in the UV/S₂O₈^2- system, suggesting the potential vulnerability of the iodinated chemicals toward UV/S₂O₈^2- treatment. Such efficient destruction also occurred in the presence of radical scavengers when biologically treated wastewater samples were used as reaction matrices. The effects of initial oxidant concentrations, solution pH, as well as the presence of natural organic matter (humic acid or fulvic acid) and alkalinity were also investigated in this study. These results provide insights for the removal of iodinated pharmaceuticals in water and/or wastewater using UV-based photochemical processes.

Radiocontrast-induced nephropathy is attenuated by autophagy through regulation of apoptosis and inflammation

Radiocontrast-induced nephropathy (RCN) is the third most common cause of acute renal failure among inpatients. Although the number of patients undergoing exams using radiocontrast is increasing, little progress has been made for RCN treatment. The pathophysiology of RCN is known as tubular injury due to oxidative stress. As autophagy regulates cellular damage under stressful conditions, we investigated the role of autophagy in RCN. RCN was induced in male C57BL/6 J mice by intraperitoneal injection of iohexol, and 3-methyladenine (3-MA) was used as an autophagy inhibitor. Tubular injury caused by iohexol was also examined in vitro using rat tubular cells (NRK-52E). Increased autophagy after iohexol administration was demonstrated by the increase of light chain 3-II in the damaged kidney tubules both in vivo and in vitro. Serum creatinine and tubular injury were significantly increased at 24 h after iohexol treatment, as compared to control group. Further they worsened with autophagy inhibition by 3-MA. In vitro studies also demonstrated that decreased cell viability by iohexol was aggravated with 3-MA pretreatment. Malondialdehyde measured for oxidative stress was increased by iohexol, and it was accentuated by autophagy inhibition, which resulted in increase of cytochrome c Apoptosis, increased by iohexol treatment, was augmented with autophagy inhibition. Macrophage infiltration and increase of monocyte chemotactic protein-1 in kidneys were induced by iohexol, and it was aggravated with autophagy inhibition. This study showed that autophagy was involved with the pathophysiology of RCN, and the role of autophagy in modulation of apoptosis, oxidative stress, and inflammatory cell infiltration was supposed as mechanisms mitigating RCN.

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.

Toxic effects of a high dose of non-ionic iodinated contrast media on renal glomerular and aortic endothelial cells in aged rats in vivo

Iodinated contrast media (CM) can induce apoptosis and necrosis of renal tubular cells. The injuries of endothelial cells induced by CM on the systemic condition have not been fully understood. To assess the toxic effects of non-ionic CM on the glomerular and aortic endothelial cells, iopromide and iodixanol, two kinds of representative non-ionic CM, were used for the in vivo study. Sixty aged rats were respectively received the agents or normal sodium intravascularly. No obvious apoptosis and morphological change was detected in the glomerular and aortic endothelial cells apart from renal tubules after CM administration. However, expressions of the nitric oxide synthase (eNOS) in glomerular endothelium were decreased at 12h after CM injection. Furthermore, plasma creatinine and endothelin-1 were increased and plasma nitric oxide (NO) was decreased significantly after CM administration. However, we failed to observe the significant increase of plasma von Willebrand Factor. These results suggest that non-ionic iodinated CM do not induce apoptosis and necrosis of glomerular and aortic endothelial cells in vivo. Decreased eNOS expression and increased plasma endothelin-1 may be involved in non-ionic iodinated CM-induced endothelial dysfunction and kidney injury.

Impact of renin-angiotensin-aldosterone blockade by angiotensin-converting enzyme inhibitors or AT-1 blockers on frequency of contrast medium-induced nephropathy: a post-hoc analysis from the Dialysis-versus-Diuresis (DVD) trial

BACKGROUND

After exposure to contrast medium (CM), about 10% of patients will develop contrast medium-induced nephropathy (CIN), with severe consequences for their prognosis. Although numerous studies evaluated risk factors for CIN development, it is still a matter of debate whether treatment with angiotensin-converting enzyme inhibitors (ACE-I) or AT-1 blockers increases the frequency of CIN after exposure to CM or not.

METHODS

We performed a prospective, single-centre study (January 2001-July 2004) to compare different treatments for CIN prevention. Creatinine levels within 72 h after CM application and in-hospital outcomes were documented. The impact of RAAS blockade on the frequency of CIN was assessed retrospectively.

RESULTS

Four hundred twelve patients were included (83.5% men, 29.1% diabetes mellitus, 74.6% hypertension). Of these, 269 patients (65.3%) were taking ACE-I (n = 236) or AT-1 blockers (n = 33). There were no significant differences in mean age (P = 0.075), creatinine levels (P = 0.113), gender (P = 0.281), diabetes mellitus (P = 0.172) or left ventricular ejection fraction (P = 0.09) between patients treated or not treated with RAAS blockade. Univariate analyses concerning development of CIN depending on treatment with RAAS blockade within 72 h found CIN to be significantly higher in patients treated with RAAS blockade (11.9 vs 4.2%, P = 0.006). Multivariate analyses (logistic regression) identified RAAS blockade to be an independent predictor of CIN (odds ratio 3.082, 95% confidence interval 1.234-7.698, P = 0.016).

CONCLUSION

Patients treated with RAAS blockade before exposure to CM develop significantly more often CIN within 72 h. Even after adjustment for confounding comorbidities, treatment with ACE-I or AT-1 blockers turned out to be an independent risk predictor.

Risk Factors and Therapy Strategies for Contrast-Induced Nephropathy

Contrast-induced nephropathy (CIN) is associated with increased morbidity and mortality, as well as increased costs for medical care, particularly in patients with diabetes mellitus and chronic renal failure. A key step to safer CIN is to identify patients at risk and applying proven preventive interventions. Extracellular volume expansion, minimizing the dose of contrast media, using low-osmolar non-ionic contrast media, stopping the intake of nephrotoxic drugs, and avoiding short intervals between procedures have all been shown to be effective in reducing CIN. The aim of the present review is to summarize the knowledge about the risk factors and prophylactic treatments of CIN.

Risk factors for contrast-induced nephropathy

An increasing number of diagnostic imaging and interventional procedures require the use of radiographic contrast agents which has led to a parallel increase in the incidence of contrast-induced nephropathy (CIN). CIN is a serious clinical problem associated with increased morbidity and mortality, particularly in patients with chronic renal failure (see the Case Report). A key step to minimize CIN is to identify patients at risk of CIN. The aim of the present review was to summarize the knowledge about the risk factors of CIN, including the review of ultimate clinical research and developments.

Prevention of radiocontrast nephropathy

PURPOSE OF REVIEW

The vast numbers of radiocontrast procedures performed yearly paired with the increasing prevalence of renal insufficiency in the aging population has focused recent attention on radiocontrast nephropathy. No effective treatment exists for this iatrogenic disease: therefore prevention remains the key strategy. Several clinical investigations have been published over the past 2 years that address potential prophylaxis against contrast nephropathy.

RECENT FINDINGS

Iso-osmolar non-ionic contrast media appear to have the least nephrotoxicity. Pooled data of published randomized controlled trials of pre-procedural intravenous hydration plus N-acetylcysteine versus placebo demonstrate that acute renal failure from contrast nephropathy is rare when these therapies are given several hours in advance. Strategies that employ fenoldopam and theophylline, however, do not appear to be effective. Urine alkalinization with intravenous sodium bicarbonate may be useful, especially in high-risk patients, but further investigation is needed.

SUMMARY

Available evidence indicates that several hours of intravenous pre-hydration is protective against contrast nephropathy and some studies suggest that oral N-acetylcysteine administration adds to this protection. Further research is needed, however, with agents that can be administered immediately prior to contrast administration. This is particularly important for diabetics with baseline kidney disease who require emergent contrast studies and are at high risk for acute renal failure.