Remote ischemic conditioning for the prevention of contrast-induced acute kidney injury in patients undergoing intravascular contrast administration: a meta-analysis and trial sequential analysis of 16 randomized controlled trials

Navigating nephrotoxic waters: A comprehensive overview of contrast-induced acute kidney injury prevention

Contrast-induced acute kidney injury (CI-AKI) is the third leading cause of acute kidney injury deriving from the intravascular administration of contrast media in diagnostic and therapeutic procedures and leading to longer in-hospital stay and increased short and long-term mortality. Its pathophysiology, although not well-established, revolves around medullary hypoxia paired with the direct toxicity of the substance to the kidney. Critically ill patients, as well as those with pre-existing renal disease and cardiovascular comorbidities, are more susceptible to CI-AKI. Despite the continuous research in the field of CI-AKI prevention, clinical practice is based mostly on periprocedural hydration. In this review, all the investigated methods of prevention are presented, with an emphasis on the latest evidence regarding the potential of RenalGuard and contrast removal systems for CI-AKI prevention in high-risk individuals.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Serum of limb remote ischemic postconditioning inhibits fMLP-triggered activation and reactive oxygen species releasing of rat neutrophils

Objectives

The study explores the protective role of the peripheral serum of limb remote ischemic postconditioning (LRIP) in reducing the reactive oxygen species (ROS) levels and neutrophil activation, which are responsible for the deleterious reperfusion injury.

Methods

LRIP was induced in Sprague–Dawley rats by three cycles of 5 min occlusion /5 min reperfusion on the left hind limb. The blood samples were collected before LRIP or 0 and 1 h after LRIP (named Serum_Sham, Serum_LRIP0, Serum_LRIP1, respectively). The effects of LRIP serum on ROS level and neutrophils activation were determined. The expression of MyD88-TRAF6-MAPKs and PI3K/AKT pathways in neutrophils were examined.

Results

When compared with Serum_Sham, Serum_LRIP0 and Serum_LRIP1 significantly reduced the ROS released from neutrophils activated by fMLP. Meanwhile, the mRNA expression levels of NADPH oxidase subunit p22^phox and multiple ROS-producing related key proteins, such as NADPH oxidase subunit p47^phox ser 304, ser 345. MyD88, p-ERK, p-JNK and p-P38 expression of neutrophils were downregulated by Serum_LRIP0 and Serum_LRIP1. Serum_LRIP1 also downregulated p47^phox mRNA expression and tumor necrosis factor receptor-associated factor 6 (TRAF6) protein expression.

Conclusion

LRIP serum protects against ROS level and neutrophils activation involving the MyD88-TRAF6-MAPKs. This finding provides new insight into the understanding of LRIP mechanisms.

Long Noncoding RNA PRNCR1 Reduces Renal Epithelial Cell Apoptosis in Cisplatin-Induced AKI by Regulating miR-182-5p/EZH1

BACKGROUND/AIMS

This study was designed to examine the role of long noncoding RNA PRNCR1 in cisplatin-induced acute kidney injury (AKI) in vitro and in vivo.

METHODS

The expression levels of PRNCR1 and miR-182-5p in cisplatin-induced AKI mice were examined. HK-2 cells were treated with cisplatin to induce cell damage. Then, the effects of PRNCR1 and miR-182-5p on cisplatin-stimulated HK-2 cell viability and apoptosis were detected by the CCK-8 and annexin V-FITC/PI method. Target genes of PRNCR1 and miR-182-5p were analyzed by bioinformatics analysis and luciferase.

RESULTS

The expression level of PRNCR1 was significantly reduced in cisplatin-induced AKI mice. In addition, overexpression of PRNCR1 attenuated the damage of cisplatin to HK-2. The expression level of miR-182-5p was significantly raised in cisplatin-induced AKI mice. MiR-182-5p was negatively regulated by PRNCR1 and leaded to an upregulation of EZH1 expression. Overexpression of PRNCR1 attenuated cisplatin-induced apoptosis by downregulating the miR-182-5p/EZH1 axis.

CONCLUSION

LncPRNCR1 reduced the apoptosis of renal epithelial cells induced by cisplatin by modulating miR-182-5p/EZH1.

Advances in intervention methods and brain protection mechanisms of in situ and remote ischemic postconditioning

Ischemic postconditioning (PostC) conventionally refers to a series of brief blood vessel occlusions and reperfusions, which can induce an endogenous neuroprotective effect and reduce cerebral ischemia/reperfusion (I/R) injury. Depending on the site of adaptive ischemic intervention, PostC can be classified as in situ ischemic postconditioning (ISPostC) and remote ischemic postconditioning (RIPostC). Many studies have shown that ISPostC and RIPostC can reduce cerebral IS injury through protective mechanisms that increase cerebral blood flow after reperfusion, decrease antioxidant stress and anti-neuronal apoptosis, reduce brain edema, and regulate autophagy as well as Akt, MAPK, PKC, and KATP channel cell signaling pathways. However, few studies have compared the intervention methods, protective mechanisms, and cell signaling pathways of ISPostC and RIPostC interventions. Thus, in this article, we compare the history, common intervention methods, neuroprotective mechanisms, and cell signaling pathways of ISPostC and RIPostC.

Perioperative Renoprotection: General Mechanisms and Treatment Approaches

In the perioperative setting, acute kidney injury (AKI) is a frequent complication, and AKI itself is associated with adverse outcomes such as higher risk of chronic kidney disease and mortality. Various risk factors are associated with perioperative AKI, and identifying them is crucial to early interventions addressing modifiable risk and increasing monitoring for nonmodifiable risk. Different mechanisms are involved in the development of postoperative AKI, frequently picturing a multifactorial etiology. For these reasons, no single renoprotective strategy will be effective for all surgical patients, and efforts have been attempted to prevent kidney injury in different ways. Some renoprotective strategies and treatments have proven to be useful, some are no longer recommended because they are ineffective or even harmful, and some strategies are still under investigation to identify the best timing, setting, and patients for whom they could be beneficial. With this review, we aim to provide an overview of recent findings from studies examining epidemiology, risk factors, and mechanisms of perioperative AKI, as well as different renoprotective strategies and treatments presented in the literature.

Effects of Remote Ischemic Pre-Conditioning to Prevent Contrast-Induced Nephropathy after Intravenous Contrast Medium Injection: A Randomized Controlled Trial

Objective

We aimed to assess the effects of remote ischemic pre-conditioning (RIPC) on the incidence of contrast-induced nephropathy (CIN) after an intravenous (IV) or intra-arterial injection of contrast medium (CM) in patient and control groups.

Materials and Methods

This prospective, randomized, single-blinded, controlled trial included 26 patients who were hospitalized for the evaluation of the feasibility of transcatheter aortic valve implantation and underwent investigations including contrast-enhanced computed tomography (CT), with Mehran risk scores greater than or equal to six. All the patients underwent four cycles of five minute-blood pressure cuff inflation followed by five minutes of total deflation. In the RIPC group (n = 13), the cuff was inflated to 50 mm Hg above the patient's systolic blood pressure (SBP); in the control group (n = 13), it was inflated to 10 mm Hg below the patient's SBP. The primary endpoint was the occurrence of CIN. Additionally, variation in the serum levels of cystatin C was assessed.

Results

One case of CIN was observed in the control group, whereas no cases were detected in the RIPC group (p = 0.48, analysis of 25 patients). Mean creatinine values at the baseline, 24 hours after injection of CM, and 48 hours after injection of CM were 88 ± 32 µmol/L, 91 ± 28 µmol/L and 82 ± 29 µmol/L, respectively (p = 0.73) in the RIPC group, whereas in the control group, they were 100 ± 36 µmol/L, 110 ± 36 µmol/L, and 105 ± 34 µmol/L, respectively (p = 0.78). Cystatin C values (median [Q1, Q3]) at the baseline, 24 hours after injection of CM, and 48 hours after injection of CM were 1.10 [1.08, 1.18] mg/L, 1.17 [0.97, 1.35] mg/L, and 1.12 [0.99, 1.24] mg/L, respectively (p = 0.88) in the RIPC group, whereas they were 1.11 [0.97, 1.28] mg/L, 1.13 [1.08, 1.25] mg/L, and 1.16 [1.03, 1.31] mg/L, respectively (p = 0.93), in the control group.

Conclusion

The risk of CIN after an IV injection of CM is very low in patients with Mehran risk score greater than or equal to six and even in the patients who are unable to receive preventive hyperhydration. Hence, the Mehran risk score may not be an appropriate method for the estimation of the risk of CIN after IV CM injection.

Two weeks of remote ischaemic preconditioning alters sympathovagal balance in healthy humans

NEW FINDINGS

What is the central question of this study? Delayed cardiovascular responses occur following a single bout of remote ischaemic preconditioning (RIPC). Is heart rate variability (HRV), a surrogate marker of cardiac vagal control, able to detect a delayed effect after a single bout of RIPC? Do repeated bouts of RIPC further alter HRV? What is the main finding and its importance? Indices of HRV indicated a shift in sympathovagal balance toward greater parasympathetic activity following 2 weeks of RIPC but not after a single bout of RIPC. Thus, repeated bouts of RIPC were necessary to elicit changes in autonomic function.

ABSTRACT

Remote ischaemic preconditioning (RIPC), induced by brief periods of ischaemia followed by reperfusion, protects against ischaemia-reperfusion injury and improves microvascular function. However, the effect of RIPC on autonomic function remains unclear. We hypothesized that RIPC, administered as a single bout or repeated over a 2-week period, will increase markers of cardiac vagal control measured by heart rate variability (HRV). Thirty-two young adults performed a single bout (n = 13), repeated bouts (n = 11), or served as a time control (n = 8). RIPC sessions consisted of four repetitions of 5 min unilateral brachial artery occlusion interspersed by 5 min of reperfusion. For the single bout protocol, resting lead II electrocardiogram (ECG) was collected before and 24, 48, 72 and 168 h post-RIPC. The repeated bout protocol consisted of three 4-day periods of RIPC training, each interspersed by a 1-day break. Similar to time controls, ECG was collected before and 24 h after the last RIPC bout. HRV was analysed by power spectral density and symbolic dynamics using 350-beat ECG segments. After a single bout of RIPC, no changes in HRV were observed at any time point (P > 0.05). After 2 weeks of repeated RIPC, the percentage of zero-variation fragments (baseline = 13.1 ± 1.9%, post-RIPC = 6.9 ± 1.5%, P < 0.05) and the LF/HF ratio decreased (baseline = 1.1 ± 0.2, post-RIPC = 0.7 ± 0.1, P < 0.01), whereas the percentage of two-variation fragments increased (baseline = 42.9 ± 3.6%, post-RIPC = 52.5 ± 3.0%, P < 0.01). These data indicate that repeated RIPC is necessary to elicit changes in sympathovagal balance, specifically resulting in increased vagal and decreased sympathetic activity.

Limb ischemic preconditioning ameliorates renal microcirculation through activation of PI3K/Akt/eNOS signaling pathway after acute kidney injury

Purpose

Contrast-induced acute kidney injury (CI-AKI) resulting from administration of iodinated contrast media (CM) is the third leading cause of hospital-acquired acute kidney injury and is associated with substantial morbidity and mortality. Deteriorated renal microcirculation plays an important role in CI-AKI. Limb ischemic preconditioning (LIPC), where brief and non-injurious ischemia/reperfusion is applied to a limb prior to the administration of the contrast agent, is emerging as a promising strategy for CI-AKI prevention. However, it is not known whether the renal protection of LIPC against CI-AKI is mediated by regulation of renal microcirculation and the molecular mechanisms remain largely unknown.

Methods

In this study, we examined the renal cortical and medullary blood flow in a stable CI-AKI model using 5/6-nephrectomized (NE) rat. The LIPC and sham procedures were performed prior to the injection of CM. Furthermore, we analyzed renal medulla hypoxia using in vivo labeling of hypoxyprobe. Pharmacological inhibitions and western blotting were used to determine the underlying molecular mechanisms.

Results

In this study, we found LIPC significantly ameliorated CM-induced reduction of medullary blood flow and attenuated CM-induced hypoxia. PI3K inhibitor (wortmannin) treatment blocked the regulation of medullary blood flow and the attenuation of hypoxia of LIPC. Phosphorylation of Akt/eNOS was significantly decreased via wortmannin treatment compared with LIPC. Nitric oxide synthase-inhibitor [Nω-nitro-l-arginine methyl ester (L-NAME)] treatment abolished the above effects and decreased phosphorylation of eNOS, but not Akt.

Conclusions

Collectively, the results demonstrate that LIPC ameliorates CM-induced renal vasocontraction and is mediated by activation of PI3K/Akt/eNOS signaling pathway.

The efficacy of remote ischemic conditioning in preventing contrast-induced nephropathy among patients undergoing coronary angiography or intervention: An updated systematic review and meta-analysis

Background

Numerous trials have investigated the effect of remote ischemic conditioning (RIC) in preventing contrast‐induced nephropathy (CIN) in patients receiving contrast medium (CM). This meta analysis aims to validate the role of RIC in preventing CIN.

Methods

We searched the PubMed, EMBASE, and Web of Science databases for eligible randomized controlled trials (RCTs) published before April 27, 2019. Two investigators independently extracted basic characteristics from each study. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used to examine the treatment effect.

Results

A total of 18 studies comprising 2,503 patients were included in our meta‐analysis. Compared with conventional therapy, RIC significantly reduced the risk of CIN (OR = 0.43, 95% CI: 0.33, 0.56, p < .05). Subgroup analyses showed that the protective effect of RIC was stronger in the low‐osmolar contrast media group (OR = 0.32; 95% CI: 0.23, 0.45, p < .05) and the nondiabetic group (OR = 0.39; 95% CI: 0.29, 0.53 p < .05). RIC also significantly reduced major adverse cardiovascular events within the first 6 months (OR = 0.39; p < .05), but the influence was not present after long‐term follow‐up.

Conclusions

Our meta‐analysis showed that RIC could effectively reduce CIN risk and decrease the short‐term incidence of relevant adverse events. Furthermore, the effects of CIN are more pronounced in nondiabetic patients and with the use of low‐osmolar contrast medium. This meta‐analysis of small trials suggests a possible protective effect of RIC on contrast‐induced nephropathy and favors the performance of a large randomized trial to further investigate this strategy.

Remote Ischemic Preconditioning Ameliorates Renal Fibrosis After Ischemia-Reperfusion Injury via Transforming Growth Factor beta1 (TGF-β1) Signalling Pathway in Rats

Background

The present study was conducted to explore the influence of remote ischemic preconditioning (RIPC) on the adjustment of renal fibrosis after ischemia-reperfusion injury (IRI).

Material/Methods

Male Sprague-Dawley rats were randomly assigned to 3 groups following right-side nephrectomy: the Sham group (without renal artery clamping), the IRI group (45 min left renal artery clamping), and the RIPC group (rats were treated daily with 3 cycles of 5 min of limb ischemia and 5 min of reperfusion on 3 consecutive days before left renal artery occlusion). After 3 months of reperfusion, the renal function and the extent of tubular injury and renal fibrosis were assessed. The expressions of transforming growth factor beta1 (TGF-β1), p-Smad2, Smad2, p-Smad3, and Smad3 were also evaluated.

Results

There was no significant difference in renal function and tubular damage among the 3 groups after 45 min of kidney ischemia followed by 3 months of reperfusion. However, an obvious increase of extracellular matrix components and α-SMA could be observed in the kidney tissues of the IRI group, and the changes were significantly ameliorated in rats treated with enhanced RIPC. Compared with the IRI group, the expression of TGF-β1 and the level of p-Smad2 and p-Smad3 were decreased after the intervention of enhanced RIPC.

Conclusions

Enhanced RIPC ameliorated renal fibrosis after IRI in rats, which appears to be associated with inhibition of the TGF-β1/p-Smad2/3 signalling pathway.

Very Delayed Remote Ischemic Post-conditioning Induces Sustained Neurological Recovery by Mechanisms Involving Enhanced Angioneurogenesis and Peripheral Immunosuppression Reversal

Ischemic conditioning is defined as a transient and subcritical period of ischemia integrated in an experimental paradigm that involves a stimulus of injurious ischemia, activating endogenous tissue repair mechanisms that lead to cellular protection under pathological conditions like stroke. Whereas ischemic pre-conditioning is irrelevant for stroke treatment, ischemic post-conditioning, and especially non-invasive remote ischemic post-conditioning (rPostC) is an innovative and potential strategy for stroke treatment. Although rPostC has been shown to induce neuroprotection in stroke models before, resulting in some clinical trials on the way, fundamental questions with regard to its therapeutic time frame and its underlying mechanisms remain elusive. Hence, we herein used a model of non-invasive rPostC of hind limbs after cerebral ischemia in male C57BL6 mice, studying the optimal timing for the application of rPostC and its underlying mechanisms for up to 3 months. Mice undergoing rPostC underwent three different paradigms, starting with the first cycle of rPostC 12 h, 24 h, or 5 days after stroke induction, which is a very delayed time point of rPostC that has not been studied elsewhere. rPostC as applied within 24 h post-stroke induces reduction of infarct volume on day three. On the contrary, very delayed rPostC does not yield reduction of infarct volume on day seven when first applied on day five, albeit long-term brain injury is significantly reduced. Likewise, very delayed rPostC yields sustained neurological recovery, whereas early rPostC (i.e., <24 h) results in transient neuroprotection only. The latter is mediated via heat shock protein 70 that is a well-known signaling protein involved in the pathophysiological cellular cascade of cerebral ischemia, leading to decreased proteasomal activity and decreased post-stroke inflammation. Very delayed rPostC on day five, however, induces a pleiotropic effect, among which a stimulation of angioneurogenesis, a modulation of the ischemic extracellular milieu, and a reversal of the stroke-induced immunosuppression occur. As such, very delayed rPostC appears to be an attractive tool for future adjuvant stroke treatment that deserves further preclinical attention before large clinical trials are in order, which so far have predominantly focused on early rPostC only.