Remote Ischemic Preconditioning Ameliorates Acute Kidney Injury due to Contrast Exposure in Rats through Augmented O-GlcNAcylation

O-GlcNAcylation in ischemic diseases

Protein glycosylation is an extensively studied field, with the most studied forms being oxygen or nitrogen-linked N-acetylglucosamine (O-GlcNAc or N-GlcNAc) glycosylation. Particular residues on proteins are targeted by O-GlcNAcylation, which is among the most intricate post-translational modifications. Significantly contributing to an organism's proteome, it influences numerous factors affecting protein stability, function, and subcellular localization. It also modifies the cellular function of target proteins that have crucial responsibilities in controlling pathways related to the central nervous system, cardiovascular homeostasis, and other organ functions. Under conditions of acute stress, changes in the levels of O-GlcNAcylation of these proteins may have a defensive function. Nevertheless, deviant O-GlcNAcylation nullifies this safeguard and stimulates the advancement of several ailments, the prognosis of which relies on the cellular milieu. Hence, this review provides a concise overview of the function and comprehension of O-GlcNAcylation in ischemia diseases, aiming to facilitate the discovery of new therapeutic targets for efficient treatment, particularly in patients with diabetes.

Prevention of Contrast-induced Nephropathy in Patients Undergoing Percutaneous Coronary Intervention

Contrast-induced nephropathy (CIN) or contrast-induced acute kidney injury has varying definitions, but in general, increased serum creatinine level by ≥ 0.3 mg/dL (26.5 µmol/L) or 1.5x of baseline value or urine output <0.5 mL/kg/h within 1-7 days after contrast media (CM) administration can be considered as CIN. CIN is one of the most common complications and is associated with increased mortality in patients undergoing percutaneous coronary intervention (PCI). Thus, risk stratification for CIN should be made and preventive strategies should be employed in which the intensity of the approach must be tailored to patient's risk profile. In all patients, adequate hydration is required, nephrotoxic medications should be discontinued, and pre-procedural high-intensity statin is recommended. In patients with an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2, IV hydration should be started 12 hours pre-procedure up until 12-24 hours after the procedure. Remote ischemic preconditioning may be performed pre-procedurally. Radial first approach for vascular access is recommended. During the procedure, low or iso-osmolar CM should be used and its volume should be limited to eGFR x 3.7. In patients at high risk for CIN, additional contrast-sparing strategies may be applied, such as using a contrast reduction system, 5 Fr catheter with no sideholes, CM dilution, limiting test injection, confirming placement using guidewire, use of stent enhancing imaging technology, using metallic/software roadmap to guide PCI, use of IVUS or dextran-based OCT, and coronary aspiration. A more advanced hydration technique based on central venous pressure, left ventricular end-diastolic pressure, or using furosemide-matched hydration, might be considered.

Is Renal Ischemic Preconditioning an Alternative to Ameliorate the Short- and Long-Term Consequences of Acute Kidney Injury?

Acute kidney injury (AKI) is a global health problem and has recently been recognized as a risk factor for developing chronic kidney disease (CKD). Unfortunately, there are no effective treatments to reduce or prevent AKI, which results in high morbidity and mortality rates. Ischemic preconditioning (IPC) has emerged as a promising strategy to prevent, to the extent possible, renal tissue from AKI. Several studies have used this strategy, which involves short or long cycles of ischemia/reperfusion (IR) prior to a potential fatal ischemic injury. In most of these studies, IPC was effective at reducing renal damage. Since the first study that showed renoprotection due to IPC, several studies have focused on finding the best strategy to activate correctly and efficiently reparative mechanisms, generating different modalities with promising results. In addition, the studies performing remote IPC, by inducing an ischemic process in distant tissues before a renal IR, are also addressed. Here, we review in detail existing studies on IPC strategies for AKI pathophysiology and the proposed triggering mechanisms that have a positive impact on renal function and structure in animal models of AKI and in humans, as well as the prospects and challenges for its clinical application.

O-GlcNAcylation in Renal (Patho)Physiology

Kidneys maintain internal milieu homeostasis through a well-regulated manipulation of body fluid composition. This task is performed by the correlation between structure and function in the nephron. Kidney diseases are chronic conditions impacting healthcare programs globally, and despite efforts, therapeutic options for its treatment are limited. The development of chronic degenerative diseases is associated with changes in protein O-GlcNAcylation, a post-translation modification involved in the regulation of diverse cell function. O-GlcNAcylation is regulated by the enzymatic balance between O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) which add and remove GlcNAc residues on target proteins, respectively. Furthermore, the hexosamine biosynthetic pathway provides the substrate for protein O-GlcNAcylation. Beyond its physiological role, several reports indicate the participation of protein O-GlcNAcylation in cardiovascular, neurodegenerative, and metabolic diseases. In this review, we discuss the impact of protein O-GlcNAcylation on physiological renal function, disease conditions, and possible future directions in the field.

O-GlcNAcylation: the "stress and nutrition receptor" in cell stress response

O-GlcNAcylation is an atypical, reversible, and dynamic glycosylation that plays a critical role in maintaining the normal physiological functions of cells by regulating various biological processes such as signal transduction, proteasome activity, apoptosis, autophagy, transcription, and translation. It can also respond to environmental changes and physiological signals to play the role of "stress receptor" and "nutrition sensor" in a variety of stress responses and biological processes. Even, a homeostatic disorder of O-GlcNAcylation may cause many diseases. Therefore, O-GlcNAcylation and its regulatory role in stress response are reviewed in this paper.

CaMKII as a key regulator of contrast-induced nephropathy through mPTP opening in HK-2 cells

Contrast-induced nephropathy (CIN), refers to acute kidney injury observed after administration of contrast media during angiographic or other medical procedures such as urography, and accounting for 12% of all causes of acute renal failure, but no specific prevention or treatment strategy exists for its obscure pathophysiology. The aim of our study was to explore the influence of calcium/calmodulin-dependent protein kinase II (CaMKII) in CIN by using HK-2 cells. Knockdown of CypD was achieved by lentivirus, and CaMKII overexpression by transfection with the plasmid. In this study, we have demonstrated that CypD-mediated mPTP opening triggered mitochondrial dysfunction and tubule cells apoptosis in CIN. We also found that iohexol treatment was associated with mitochondrial ROS overloading, ATP depletion and LDH release. Inhibition of CypD with the pharmacologic inhibitor or knockdown of CypD abrogated mPTP opening, oxidative stress, mitochondria damage, and cell apoptosis induced by iohexol. In addition, we found that inhibition of the CaMKII activity alleviated iohexol-induced CypD expression, whereas also decreased mPTP opening, oxidative stress, mitochondria damage, and cell apoptosis, similarly to the inhibition of CypD did. Moreover, CaMKII overexpression enhanced iohexol-induced mPTP opening, mitochondrial damage and renal tubular epithelial cells apoptosis. These findings first identified the novel role of CaMKII in iohexol-induced tubular cells apoptosis and delineated the CaMKII-CypD/mPTP pathway during contrast-induced tubular cell damage. Hence, these results could provide a new strategy for CIN protection.

The Integrated RNA Landscape of Renal Preconditioning against Ischemia-Reperfusion Injury

BACKGROUND

Although AKI lacks effective therapeutic approaches, preventive strategies using preconditioning protocols, including caloric restriction and hypoxic preconditioning, have been shown to prevent injury in animal models. A better understanding of the molecular mechanisms that underlie the enhanced resistance to AKI conferred by such approaches is needed to facilitate clinical use. We hypothesized that these preconditioning strategies use similar pathways to augment cellular stress resistance.

METHODS

To identify genes and pathways shared by caloric restriction and hypoxic preconditioning, we used RNA-sequencing transcriptome profiling to compare the transcriptional response with both modes of preconditioning in mice before and after renal ischemia-reperfusion injury.

RESULTS

The gene expression signatures induced by both preconditioning strategies involve distinct common genes and pathways that overlap significantly with the transcriptional changes observed after ischemia-reperfusion injury. These changes primarily affect oxidation-reduction processes and have a major effect on mitochondrial processes. We found that 16 of the genes differentially regulated by both modes of preconditioning were strongly correlated with clinical outcome; most of these genes had not previously been directly linked to AKI.

CONCLUSIONS

This comparative analysis of the gene expression signatures in preconditioning strategies shows overlapping patterns in caloric restriction and hypoxic preconditioning, pointing toward common molecular mechanisms. Our analysis identified a limited set of target genes not previously known to be associated with AKI; further study of their potential to provide the basis for novel preventive strategies is warranted. To allow for optimal interactive usability of the data by the kidney research community, we provide an online interface for user-defined interrogation of the gene expression datasets (http://shiny.cecad.uni-koeln.de:3838/IRaP/).

Remote Ischaemic Preconditioning Reduces Kidney Injury Biomarkers in Patients Undergoing Open Surgical Lower Limb Revascularisation: A Randomised Trial

Background and Aims

Perioperative kidney injury affects 12.7% of patients undergoing lower limb revascularisation surgery. Remote ischaemic preconditioning (RIPC) is a potentially protective procedure against organ damage and consists of short nonlethal episodes of ischaemia. The main objective of this substudy was to evaluate the effect of RIPC on kidney function, inflammation, and oxidative stress in patients undergoing open surgical lower limb revascularisation. Materials and Methods. This is a subgroup analysis of a randomised, sham-controlled, double-blinded, single-centre study. A RIPC or a sham procedure was performed noninvasively along with preparation for anaesthesia in patients undergoing open surgical lower limb revascularisation. The RIPC protocol consisted of 4 cycles of 5 minutes of ischaemia, with 5 minutes of reperfusion between every episode. Blood was collected for analysis preoperatively, 2, 8, and 24 hours after surgery, and urine was collected preoperatively and 24 hours after surgery.

Results

Data of 56 patients were included in the analysis. Serum creatinine, cystatin C, and beta-2 microglobulin increased, and eGFR decreased across all time points significantly more in the sham group than in the RIPC group (p = 0.021, p = 0.021, p = 0.021, p = 0.021, p = 0.021,

Conclusions

Our finding of reduced release of kidney injury biomarkers may indicate the renoprotective effect of RIPC in patients undergoing open surgical lower limb revascularisation. The trial is registered with ClinicalTrials.gov NCT02689414.

Remote ischemic preconditioning reduces the incidence of contrast-induced nephropathy in patients undergoing coronary angiography/intervention: Systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Contrast-induced nephropathy (CIN) is associated with increased mortality and morbidity in patients undergoing coronary angiography (CAG) and percutaneous coronary intervention (PCI). We aimed to assess the latest evidence on the effect of remote ischemic preconditioning (RIPC) on the incidence of CIN in patients undergoing CAG/PCI.

METHODS

We performed a comprehensive search on topics assessing RIPC and CIN in CAG/PCI patients from inception up until July 2019 through several electronic databases.

RESULTS

There were a total of 1,925 subjects from 14 randomized controlled trials. Remote ischemic preconditioning was associated with reduced CIN incidence in patients undergoing CAG/PCI (OR 0.41 [0.30, 0.55], p < .001; I² : 22%). The nephroprotective effect was also demonstrated in those at moderate-high risk for CIN subgroup (OR 0.41 [0.29, 0.58], p < .001; I² : 26%) and PCI-only subgroup (OR 0.41 [0.29, 0.58], p < .001; I² : 0%). Time from RIPC to CAG/PCI has similar effectiveness among ≤45, ≤60, and ≤120 min. Mortality, rehospitalization, hemodialysis, and major adverse events were lower in the RIPC group (OR 0.50 [0.33, 0.76], p = .001; I² : 0%). Grading of recommendations assessment, development and evaluation (GRADE) assessment showed that RIPC has high evidence certainty for reducing CIN in patients undergoing PCI/CAG, moderate-high risk subgroup, and PCI-only subgroup with absolute reduction of 97 per 1,000, 129 per 1,000, and 121 per 1,000, respectively. Harbord test showed no evidence for the presence of small-study effects (p = .157).

CONCLUSIONS

Remote ischemic preconditioning is an effective procedure to reduce the risk of CIN and should be considered in patients with moderate-high risk at developing CIN.