Minimizing the renal toxicity of iodinated contrast

Iodinated contrast media (ICM)-induced thyroid dysfunction: a review of potential mechanisms and clinical management

Iodinated contrast media (ICM) are extensively utilized in medical imaging to enhance tissue contrast, yet their impact on thyroid function has attracted increasing attention in recent years. ICM can induce thyroid dysfunction, with reported prevalence ranging from 1 to 15% and a higher incidence observed in individuals with pre-existing thyroid conditions or other risk factors like age, gender, underlying health issues, and repeated ICM exposure. This review summarized the classification of ICM and the potential mechanisms, risk assessment, and clinical management of ICM-induced thyroid dysfunction, especially in vulnerable populations such as pregnant women and elderly patients. Despite advancements that have enriched our understanding of the pathophysiology and treatment of ICM-induced thyroid dysfunction, critical knowledge gaps remain, such as the long-term effects of ICM on thyroid function, the dose-response relationship between ICM volume and thyroid dysfunction risk, and the ecological impacts of ICM. Therefore, further exploration of the underlying mechanisms of ICM-induced thyroid dysfunction and optimization of the management strategies will be crucial for the safe and effective use of ICM in clinical practice, and collaborative efforts between clinicians and researchers are essential to ensure that the risks of thyroid dysfunction do not outweigh the benefits of imaging.

Renal impact of high-loading-dose statin pre-cardiac catheterization in patients with chronic kidney disease and long-term statin use

Previous studies have reported that short-term statin loading effectively protects statin-naive patients with mild renal insufficiency from contrast-induced acute kidney injury (CI-AKI). The aim of the present study was to determine whether patients with more advanced chronic kidney disease (CKD) and long-term statin therapy also benefit from high-loading statin pretreatment. A total of 256 consecutive patients with moderate-to-severe CKD receiving long-term statin therapy and undergoing percutaneous coronary intervention (PCI) or coronary artery angiography (CAG) were divided into the statin-loading group (n=34) and the no statin-loading group (n=222), depending on whether the respective patient received high-dose statin within 24 h prior to the intervention. The primary endpoint was the percent change in serum creatinine (SCr) levels. Additional endpoints included absolute change in SCr levels, estimated glomerular filtration rate (eGFR) at 48-72 h after contrast exposure, incidence rate of CI-AKI and composite in-hospital adverse events. The mean SCr decreased from baseline in either of the two groups, and the differences in the percent (P=0.930) and absolute change (P=0.990) in SCr levels were not significant between the two groups. Furthermore, no significant difference in the post-procedural eGFR was observed between the two groups. The incidence rates of CI-AKI (2.9 vs. 4.1%, P>0.999) and in-hospital adverse events (0.0 vs. 3.6%, P=0.602) were also similar between the two groups. Stratified analyses were then performed, which yielded results consistent with the above. Multiple linear regression indicated that the baseline eGFR value and current smoking status were independent factors affecting the post-procedural eGFR value, while high-dose statin loading was not. Therefore, statin reloading prior to intervention may not provide any further renal protection or decrease the occurrence of in-hospital adverse events in patients with moderate-to-severe CKD receiving long-term statin therapy, which warrants validation in prospective trials.

Lessons learned from the PRESERVE trial

The recently published Prevention of Serious Adverse Events Following Angiography (PRESERVE) trial is presently the largest and most comprehensive clinical trial comparing commonly applied strategies for prevention of iodinated contrast-induced acute kidney injury in high-risk patients. The fundamental conclusion of the PRESERVE trial is that oral acetylcysteine and i.v. sodium bicarbonate are not superior to simple i.v. hydration with isotonic saline for the prevention of contrast-induced renal sequelae. In this commentary, we discuss the results in the context of selected past major trials, and provide insights into the strengths and potential weaknesses of the PRESERVE trial. In the future, developing individualized preventive approaches to avoid contrast-induced acute kidney injury for different patient populations is recommended.

Targeting HO-1 by Epigallocatechin-3-Gallate Reduces Contrast-Induced Renal Injury via Anti-Oxidative Stress and Anti-Inflammation Pathways

Both oxidative stress and inflammation are involved in the pathogenesis of contrast-induced nephropathy (CIN). Epigallocatechin-3-gallate (EGCG), a purified catechin from green tea, has antioxidant and anti-inflammatory effects. However, it is unknown whether or not EGCG is effective in treating CIN. Our present study found that intravenous administration of EGCG, either before or just after the establishment of CIN, had a protective effect, determined by normalization of serum creatinine and blood urea nitrogen levels, improvement in renal histopathological scoring and alleviation of apoptosis, accompanied by decreased oxidative stress and inflammation. Because EGCG is a potent inducer of the antioxidant heme oxygenase-1 (HO-1), we studied HO-1 signaling in CIN. HO-1 levels were increased in CIN; treatment with EGCG further increased HO-1 levels, accompanied by an increase in Nrf2, a regulator of antioxidant proteins. Interestingly, blockade of HO-1 with protoporphyrin IX zinc(II) (ZnPP) prevented the protective effect of EGCG on CIN. ZnPP also blocked the ability of EGCG to increase the activity of an antioxidant (superoxide dismutase), and decrease markers of oxidative stress (myeloperoxidase and malondialdehyde) and inflammation (myeloperoxidase and IL-1β), indicating that HO-1 is the upstream molecule that regulates the EGCG-mediated protection. To determine further the role of HO-1 on the EGCG-mediated inhibition of inflammation, we studied the effect of EGCG on the NLRP3 inflammasome, an upstream signaling of IL-1β. EGCG down-regulated NLRP3 expression, which was blocked by ZnPP, indicating that HO-1 links EGCG with NLRP3. Therefore, EGCG, via up-regulation of HO-1, protects against CIN by amelioration of oxidative stress and inflammation.

Exposure to Radiocontrast Agents Induces Pancreatic Inflammation by Activation of Nuclear Factor-κB, Calcium Signaling, and Calcineurin

BACKGROUND & AIMS

Radiocontrast agents are required for radiographic procedures, but these agents can injure tissues by unknown mechanisms. We investigated whether exposure of pancreatic tissues to radiocontrast agents during endoscopic retrograde cholangiopancreatography (ERCP) causes pancreatic inflammation, and studied the effects of these agents on human cell lines and in mice.

METHODS

We exposed mouse and human acinar cells to the radiocontrast agent iohexol (Omnipaque; GE Healthcare, Princeton, NJ) and measured intracellular release of Ca(2+), calcineurin activation (using a luciferase reporter), activation of nuclear factor-κB (NF-κB, using a luciferase reporter), and cell necrosis (via propidium iodide uptake). We infused the radiocontrast agent into the pancreatic ducts of wild-type mice (C57BL/6) to create a mouse model of post-ERCP pancreatitis; some mice were given intraperitoneal injections of the calcineurin inhibitor FK506 before and after infusion of the radiocontrast agent. CnAβ(-/-) mice also were used. This experiment also was performed in mice given infusions of adeno-associated virus 6-NF-κB-luciferase, to assess activation of this transcription factor in vivo.

RESULTS

Incubation of mouse and human acinar cells, but not HEK293 or COS7 cells, with iohexol led to a peak and then plateau in Ca(2+) signaling, along with activation of the transcription factors NF-κB and nuclear factor of activated T cells. Suppressing Ca(2+) signaling or calcineurin with BAPTA, cyclosporine A, or FK506 prevented activation of NF-κB and acinar cell injury. Calcineurin Aβ-deficient mice were protected against induction of pancreatic inflammation by iohexol. The calcineurin inhibitor FK506 prevented contrast-induced activation of NF-κB in pancreata of mice, this was observed by live imaging of mice given infusions of adeno-associated virus 6-NF-κB-luciferase.

CONCLUSIONS

Radiocontrast agents cause pancreatic inflammation in mice, via activation of NF-κB, Ca(2+) signaling, and calcineurin. Calcineurin inhibitors might be developed to prevent post-ERCP pancreatitis in patients.

Meta-analysis of randomized controlled trials of preprocedural statin administration for reducing contrast-induced acute kidney injury in patients undergoing coronary catheterization

Preprocedural statin administration may reduce contrast-induced acute kidney injury (CI-AKI), but current evidence is controversial. Randomized controlled trials (RCTs) comparing preprocedural statin administration before coronary catheterization with standard strategies were searched in MEDLINE/PubMed, EMBASE, Scopus, Cochrane Library, Web of Science, and ScienceDirect databases. The outcome of interest was the incidence of postprocedural CI-AKI. Prespecified subgroup analyses were performed according to baseline glomerular filtration rate (GFR), statin type, and N-acetylcysteine use. Eight RCTs were included for a total of 4,984 patients. The incidence of CI-AKI was 3.91% in the statin group (n = 2,480) and 6.98% in the control group (n = 2,504). In the pooled analysis using a random-effects model, patients receiving statins had 46% lower relative risk (RR) of CI-AKI compared with the control group (RR 0.54, 95% confidence interval [CI] 0.38 to 0.78, p = 0.001). A moderate degree of non-significant heterogeneity was present (I(2) = 41.9%, chi-square = 12.500, p = 0.099, τ² = 0.100). In the subanalysis based on GFR, the pooled RR indicated a persistent benefit with statins in patients with GFR <60 ml/min (RR 0.67, 95% CI 0.45 to 1.00, p = 0.050) and a highly significant benefit in patients with GFR ≥60 ml/min (RR 0.40, 95% CI 0.27 to 0.61, p <0.0001). Statin type and N-acetylcysteine or hydration did not significantly influence the results. In conclusion, preprocedural statin use leads to a significant reduction in the pooled RR of CI-AKI.

Non-cardiovascular effects associated with statins

Statins form the pharmacologic cornerstone of the primary and secondary prevention of atherosclerotic cardiovascular disease. In addition to beneficial cardiovascular effects, statins seem to have multiple non-cardiovascular effects. Although early concerns about statin induced hepatotoxicity and cancer have subsided owing to reassuring evidence, two of the most common concerns that clinicians have are myopathy and diabetes. Randomized controlled trials suggest that statins are associated with a modest increase in the risk of myositis but not the risk of myalgia. Severe myopathy (rhabdomyolysis) is rare and often linked to a statin regimen that is no longer recommended (simvastatin 80 mg). Randomized controlled trials and meta-analyses suggest an increase in the risk of diabetes with statins, particularly with higher intensity regimens in people with two or more components of the metabolic syndrome. Other non-cardiovascular effects covered in this review are contrast induced nephropathy, cognition, cataracts, erectile dysfunction, and venous thromboembolism. Currently, systematic reviews and clinical practice guidelines indicate that the cardiovascular benefits of statins generally outweigh non-cardiovascular harms in patients above a certain threshold of cardiovascular risk. Literature is also accumulating on the potential non-cardiovascular benefits of statins, which could lead to novel applications of this class of drug in the future.

Pituitary adenylate cyclase-activating polypeptide prevents contrast-induced nephropathy in a novel mouse model

We determined whether pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) prevents contrast-induced nephropathy using human renal proximal tubule epithelial (HK-2) cells and homozygous endothelial nitric oxide synthase-deficient (eNOS(-/-)) mice as a novel in vivo model. Cultured HK-2 cells were pretreated with 10(-9)-10(-6) mol/L PACAP or vasoactive intestinal peptide (VIP) for 1 h, and then exposed to ionic (Urografin) or nonionic (iohexol) contrast media at 50 mg iodine/mL for 24 h. Male eNOS(-/-) mice received Urografin (1.85 g iodine/kg) intravenously after water deprivation for 24 h, and PACAP38 (10 μg) intraperitoneally 1 h before and 12 h after Urografin injection. Urografin and iohexol increased lactate dehydrogenase and kidney injury molecule 1 in the culture medium, induced apoptosis, and inhibited cell proliferation in HK-2 cell cultures. PACAP38 and VIP reduced these changes in a dose-dependent manner. PACAP38 was more potent than VIP. In eNOS(-/-) mice, Urografin raised serum creatinine and cystatin C levels, caused renal tubule damage, induced apoptosis, and promoted neutrophil influx. Urografin also increased kidney protein levels of proinflammatory cytokines, and kidney mRNA levels of proinflammatory cytokines, kidney injury biomarkers, and enzymes responsible for reactive oxygen and nitrogen species. PACAP38 significantly reduced these Urografin-induced changes in eNOS(-/-) mice. This study shows that both Urografin and iohexol are toxic to HK-2 cells, but Urografin is more toxic than iohexol. Urografin causes acute kidney injury in eNOS(-/-) mice. PACAP38 protects HK-2 cells and mouse kidneys from contrast media and is a potential therapeutic agent for contrast-induced nephropathy.

Early high-dose rosuvastatin for contrast-induced nephropathy prevention in acute coronary syndrome: Results from the PRATO-ACS Study (Protective Effect of Rosuvastatin and Antiplatelet Therapy On contrast-induced acute kidney injury and myocardial damage in patients with Acute Coronary Syndrome)

OBJECTIVES

This study sought to determine if in addition to standard preventive measures on-admission, high-dose rosuvastatin exerts a protective effect against contrast-induced acute kidney injury (CI-AKI).

BACKGROUND

Patients with acute coronary syndrome (ACS) are at high risk for CI-AKI, and the role of statin pre-treatment in preventing renal damage remains uncertain.

METHODS

Consecutive statin-naïve non-ST elevation ACS patients scheduled to undergo early invasive strategy were randomly assigned to receive rosuvastatin (40 mg on admission, followed by 20 mg/day; statin group n = 252) or no statin treatment (control group n = 252). CI-AKI was defined as an increase in creatinine concentration of ≥0.5 mg/dl or ≥25% above baseline within 72 h after contrast administration.

RESULTS

The incidence of CI-AKI was significantly lower in the statin group than in controls (6.7% vs. 15.1%; adjusted odds ratio: 0.38; 95% confidence interval [CI]: 0.20 to 0.71; p = 0.003). The benefits against CI-AKI were consistent, even applying different CI-AKI definition criteria and in all the pre-specified risk categories. The 30-day incidence of adverse cardiovascular and renal events (death, dialysis, myocardial infarction, stroke, or persistent renal damage) was significantly lower in the statin group (3.6% vs. 7.9%, respectively; p = 0.036). Moreover, statin treatment given on admission was associated with a lower rate of death or nonfatal myocardial infarction at 6 month follow-up (3.6% vs. 7.2%, respectively; p = 0.07).

CONCLUSIONS

High-dose rosuvastatin given on admission to statin-naïve patients with ACS who are scheduled for an early invasive procedure can prevent CI-AKI and improve short-term clinical outcome. (Statin Contrast Induced Nephropathy Prevention [PRATO-ACS]; NCT01185938).

Statin treatment before percutaneous cononary intervention

Treatment with 3-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) improves short-and-long term prognosis in high-risk patients with stable coronary artery disease and in those with acute coronary syndrome and their use is strongly recommended for secondary prevention. Moreover, recent data suggest that statin pre-treatment is associated with a better short- and long-term outcome in patients undergoing percutaneous coronary intervention. Current guidelines for coronary revascularization recommend the use of high-dose of statins before percutaneous coronary intervention to reduce the risk of periprocedural myocardial infarction in statin naïve patients (class IIa A) and in those on chronic statin therapy (class IIa B). However, the beneficial clinical effects elicited by statins in patients undergoing coronary angioplasty may arise not only from a cardiac protection against periprocedural myocardial injury but also from a renal protection against acute kidney injury caused by iodinated contrast media. Actually, statins exert multiple non-lipid lowering (pleiotropic) effects, including improved endothelial function, reduced inflammatory and immuno-modulatory processes, oxidative stress and platelet adhesion, that may contribute to both cardio- and nephro-protection even in the short-term.

N-acetylcysteine for Prevention of Contrast-Induced Nephropathy: A Narrative Review

Contrast-induced nephropathy (CIN) affects in-hospital, short- and long-term morbidity and mortality. It also leads to prolonged hospital stay and increased medical cost. Given the potential clinical severity of CIN, there has been considerable interest in the development of preventative strategies to reduce the risk of contrast-induced renal deterioration in at-risk populations. A number of pharmacologic and mechanical preventive measures have been attempted, but no method other than adequate periprocedural hydration has been conclusively successful. Since its introduction in 2000, N-acetylcysteine (NAC) has been widely investigated, albeit with conflicting findings for its nephroprotection capability in patients receiving contrast media procedures. However, there is still virtually no definitive evidence of effectiveness of NAC. Although the exact mechanism responsible for the protective action of NAC from renal function deterioration remains unclear, the antioxidant and vasodilatory properties of NAC have been suggested as the main mechanisms. This review summarizes the current status of NAC as a potential agent to prevent renal functional deterioration and its limitations.