Hypoxemic reperfusion of ischemic states: an alternative approach for the attenuation of oxidative stress mediated reperfusion injury

Comprehensive Overview of Innovative Strategies in Preventing Renal Ischemia-reperfusion Injury: Insights from Bibliometric and In silico Analyses

BACKGROUND

Ischemia-reperfusion Injury (IRI) is a complex pathophysiological process with severe consequences, including irreversible loss of renal function. Various intraoperative prevention methods have been proposed to mitigate the harmful effects of warm ischemia and kidney reperfusion.

AIM

This comprehensive analysis provides an overview of pharmacological agents and intraoperative methods for preventing and treating renal IRI.

METHODS

Our analysis revealed that eplerenone exhibited the highest binding affinity to crucial targets, including Aldehyde Dehydrogenase (AD), Estrogen Receptor (ER), Klotho protein, Mineralocorticoid Receptor (MR), and Toll-like Receptor 4 (TLR4). This finding indicates eplerenone's potential as a potent preventive agent against IRI, surpassing other available therapeutics like Benzodioxole, Hydrocortisone, Indoles, Nicotinamide adenine dinucleotide, and Niacinamide. In preventing kidney IRI, our comprehensive analysis emphasizes the significance of eplerenone due to its strong binding affinity to key targets involved in the pathogenesis of IRI.

RESULTS

This finding positions eplerenone as a promising candidate for further clinical investigation and consideration for future clinical practice.

CONCLUSION

The insights provided in this analysis will assist clinicians and researchers in selecting effective preventive approaches for renal IRI in surgical settings, potentially improving patient outcomes.

Changes of antioxidant enzymes in the kidney after cardiac arrest in the rat model

Globally, cardiac arrest (CA) is a leading cause of death and disability. Asphyxial CA (ACA)-induced kidney damage is a crucial factor in reducing the survival rate. The purpose of this study was to investigate the role of antioxidant enzymes in histopathological renal damage in an ACA rat model at different time points. A total of 88 rats were divided into five groups and exposed to ACA except for the sham group. To evaluate glomerular function and oxidative stress, serum levels of blood urea nitrogen (BUN) and creatinine (Crtn) and malondialdehyde (MDA) levels in renal tissues were measured. To determine histopathological damage, hematoxylin and eosin staining, periodic acid-Schiff staining, and Masson's trichrome staining were performed. Expression levels of antioxidant enzymes including superoxide dismutase-1 (SOD-1), superoxide dismutase-2 (SOD-2), catalase (CAT), and glutathione peroxidase (GPx) were measured by immunohistochemistry (IHC). Survival rate of the experimental rats was reduced to 80% at 6 h, 55% at 12 h, 42.9% at 1 day, and 33% at 2 days after return of spontaneous circulation. Levels of BUN, Crtn, and MDA started to increase significantly in the early period of CA induction. Renal histopathological damage increased markedly from 6 h until two days post-CA. Additionally, expression levels of antioxidant enzymes were significantly decreased at 6 h, 12 h, 1 day, and 2 days after CA. CA-induced oxidative stress and decreased levels of antioxidant enzymes (SOD-1, SOD-2, CAT, GPx) from 6 h to two days could be possible mediators of severe renal tissue damage and increased mortality rate.

Retrograde reperfusion of renal grafts to reduce ischemic-reperfusion injury

Background

During transplantation, a kidney graft undergoes a cascade of pathological changes, referred to as ischemia-reperfusion injury (IRI), as it is incorporated into the bloodstream. Various studies have reported that retrograde reperfusion (RRP) leads to improved myocardial recovery and could reduce IRI in liver transplantation. This study investigated the effect of RRP in renal transplantation with a focus on reduction of kidney IRI.

Methods

Between December 2019 and July 2022, 15 consecutive kidney transplants were performed with retrograde venous reperfusion. To conduct a comparative study and to recruit a control group, 15 kidney transplants that had been performed in the same center by the same two surgeons were retrospectively analyzed. Differences between the two groups were considered statistically significant at P<0.05.

Results

The baseline characteristics of the two groups were statistically comparable (P>0.05). The surgical technique for kidney transplantation was the same in both groups. On the first postoperative day, polyuria was less pronounced in the RRP group (P<0.01). Serum creatinine and urea levels and estimated glomerular filtration rates on postoperative days 1, 4, 7, and 30 were lower in the RRP group (P<0.05).

Conclusions

Retrograde venous reperfusion of a kidney transplant, preceding antegrade arterial reperfusion, reduced the effects of renal parenchyma IRI. To validate the results of this study, it is necessary to conduct further studies on a larger cohort of patients with a longer follow-up period.

Biomolecular Pathways of Cryoinjuries in Low-Temperature Storage for Mammalian Specimens

Low-temperature preservation could effectively extend in vitro storage of biological materials due to delayed or suspended cellular metabolism and decaying as illustrated by the Arrhenius model. It is widely used as an enabling technology for a variety of biomedical applications such as cell therapeutics, assisted reproductive technologies, organ transplantation, and mRNA medicine. Although the technology to minimize cryoinjuries of mammalian specimens during preservation has been advanced substantially over past decades, mammalian specimens still suffer cryoinjuries under low-temperature conditions. Particularly, the molecular mechanisms underlying cryoinjuries are still evasive, hindering further improvement and development of preservation technologies. In this paper, we systematically recapitulate the molecular cascades of cellular injuries induced by cryopreservation, including apoptosis, necroptosis, ischemia-reperfusion injury (IRI). Therefore, this study not only summarizes the impact of low-temperature preservations on preserved cells and organs on the molecular level, but also provides a molecular basis to reduce cryoinjuries for future exploration of biopreservation methods, materials, and devices.

A computational model of cardiomyocyte metabolism predicts unique reperfusion protocols capable of reducing cell damage during ischemia/reperfusion

If a coronary blood vessel is occluded and the neighboring cardiomyocytes deprived of oxygen, subsequent reperfusion of the ischemic tissue can lead to oxidative damage due to excessive generation of reactive oxygen species. Cardiomyocytes and their mitochondria are the main energy producers and consumers of the heart, and their metabolic changes during ischemia seem to be a key driver of reperfusion injury. Here, we hypothesized that tracking changes in cardiomyocyte metabolism, such as oxygen and ATP concentrations, would help in identifying points of metabolic failure during ischemia and reperfusion. To track some of these changes continuously from the onset of ischemia through reperfusion, we developed a system of differential equations representing the chemical reactions involved in the production and consumption of 67 molecular species. This model was validated and used to identify conditions present during periods of critical transition in ischemia and reperfusion that could lead to oxidative damage. These simulations identified a range of oxygen concentrations that lead to reverse mitochondrial electron transport at complex I of the respiratory chain and a spike in mitochondrial membrane potential, which are key suspects in the generation of reactive oxygen species at the onset of reperfusion. Our model predicts that a short initial reperfusion treatment with reduced oxygen content (5% of physiological levels) could reduce the cellular damage from both of these mechanisms. This model should serve as an open-source platform to test ideas for treatment of the ischemia reperfusion process by following the temporal evolution of molecular concentrations in the cardiomyocyte.

Cox-2 Antagonizes the Protective Effect of Sevoflurane on Hypoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis through Inhibiting the Akt Pathway

Objective

To uncover the protective role of sevoflurane on hypoxia/reoxygenation-induced cardiomyocyte apoptosis through the protein kinase B (Akt) pathway.

Methods

An in vitro hypoxia/reoxygenation (H/R) model was established in cardiomyocyte cell line H9c2. Sevoflurane (SEV) was administrated in H9c2 cells during the reoxygenation period. Viability, layered double hydroxide (LDH) release, and apoptosis in H9c2 cells were determined to assess H/R-induced cell damage. Relative levels of apoptosis-associated genes were examined. Moreover, phosphorylation of Akt was determined.

Results

H/R injury declined viability and enhanced LDH release and apoptotic rate in H9c2 cells. Cyclooxygenase-2 (Cox-2) was upregulated following H/R injury, which was partially reversed by SEV treatment. In addition, SEV treatment reversed changes in viability and LDH release owing to H/R injury in H9c2 cells, which were further aggravated by overexpression of Cox-2. The Akt pathway was inhibited in H9c2 cells overexpressing Cox-2.

Conclusions

Sevoflurane protects cardiomyocyte damage following H/R via the Akt pathway, and its protective effect was abolished by overexpression of Cox-2.

Knockdown of Tripartite Motif 8 Protects H9C2 Cells Against Hypoxia/Reoxygenation-Induced Injury Through the Activation of PI3K/Akt Signaling Pathway

Tripartite motif 8 (TRIM8) is a member of the TRIM protein family that has been found to be implicated in cardiovascular disease. However, the role of TRIM8 in myocardial ischemia/reperfusion (I/R) has not been investigated. We aimed to explore the effect of TRIM8 on cardiomyocyte H9c2 cells exposed to hypoxia/reoxygenation (H/R). We found that TRIM8 expression was markedly upregulated in H9c2 cells after stimulation with H/R. Gain- and loss-of-function assays proved that TRIM8 knockdown improved cell viability of H/R-stimulated H9c2 cells. In addition, TRIM8 knockdown suppressed reactive oxygen species production and elevated the levels of superoxide dismutase and glutathione peroxidase. Knockdown of TRIM8 suppressed the caspase-3 activity, as well as caused significant increase in bcl-2 expression and decrease in bax expression. Furthermore, TRIM8 overexpression exhibited apposite effects with knockdown of TRIM8. Finally, knockdown of TRIM8 enhanced the activation of PI3K/Akt signaling pathway in H/R-stimulated H9c2 cells. Inhibition of PI3K/Akt by LY294002 reversed the effects of TRIM8 knockdown on cell viability, oxidative stress, and apoptosis of H9c2 cells. These present findings defined TRIM8 as a therapeutic target for attenuating and preventing myocardial I/R injury.

Increased inspired oxygen concentration does not adversely affect oxidative stress and the resolution of inflammation during reperfusion in patients undergoing knee replacement surgery

The level of inspired oxygen during surgery may modify free radical release, and reperfusion injury. This controlled trial examined the effect of inspired oxygen on F₂-isoprostanes (F₂-IsoPs), isofurans (IsoFs), and specialized mediators of inflammation resolution (SPM) during knee replacement surgery. Patients received either 30% O₂ (control n = 21), 50% O₂ (n = 20), or 80% O₂ (n = 19) O₂, in a parallel design. Hemoglobin (Hb) was measured throughout the surgery and F₂-IsoPs, IsoFs and SPM were analyzed by mass spectrometry. The effect of O₂ on F₂-IsoPs and IsoFs was examined during tourniquet inflation and after tourniquet release. SPM were measured at baseline and the end of surgery. There was a significant interaction between O₂ and Hb concentrations with plasma IsoFs during tourniquet inflation. An increase in plasma IsoFs over time was attenuated in the 80% O₂ group (p=.012) compared with the 30% O₂ group after adjusting for Hb concentration. After tourniquet release, plasma F₂-IsoPs were significantly lower in the 50% and 80% O₂ groups (p=.009 and p=.001, respectively) compared with the 30% O₂ group after adjustment for Hb concentration. The SPM RvD2 and RvE2 were increased with 50% and 80% O₂ (RvD2, p=.014 and p=.002, respectively; RvE2, p=.032 with 50% O₂) compared with the 30% O₂ group, in analyses that corrected for Hb concentration. We have shown for the first time that higher O₂ levels may be beneficial in reducing oxidative stress and increasing resolution of inflammation during surgery that involves reperfusion after application of a tourniquet.

Clinical impact of thrombus aspiration on in-hospital mortality in each culprit lesion in the setting of ST-segment elevation myocardial infarction

Recent randomized clinical trials have questioned the clinical benefits of thrombus aspiration (TA) in ST-segment elevation myocardial infarction (STEMI). Real-world data on TA and the efficacy of TA for various culprit lesions have not been sufficiently evaluated. This study mainly aimed to evaluate whether the clinical impact of TA depends on culprit lesions in the setting of STEMI. We surveyed the Tokyo Coronary Care Unit Network Registry, a prospective cohort study, between 2010 and 2014, which included 10,232 patients with STEMI. In-hospital deaths occurred in 538 patients (5.3%). Improved Thrombolysis in Myocardial Infarction flow was more frequently observed in patients who underwent TA than in those who did not (87 vs. 80%; p < 0.001). Univariate logistic regression analysis revealed that TA was associated with a lower in-hospital mortality rate [odds ratio (OR), 0.80; 95% confidential interval (CI), 0.66-0.96; p = 0.016]. However, the difference was not significant after multivariate logistic regression analysis (OR 0.95; 95% CI 0.71-1.17; p = 0.355). Only TA for the left circumflex (LCx) lesions was associated with a better prognosis (OR 0.38; 95% CI 0.21-0.72; p = 0.003). The effect persisted after adjustment (OR 0.50; 95% CI 0.25-0.99; p = 0.049) but was attenuated after analysis using inverse probability weighting (OR 0.97; 95% CI 0.93-0.99; p = 0.048). On the basis of the findings in a large Japanese cohort, a prognostic benefit of TA on in-hospital mortality was not observed. The effect of TA on the LCx lesions was marginally significant and limited. Therefore, TA is not recommended in Japanese patients with STEMI.

Hypothermic machine perfusion in liver transplantation

PURPOSE OF THE REVIEW

The purpose of the review is to report recent human application of hypothermic machine liver perfusion, and to discuss potential protective mechanisms.

RECENT FINDINGS

Human application of hypothermic machine liver perfusion is still very limited. Currently, three transplant centers apply this novel treatment in donation after cardiac death (DCD) or donation after brain death (DBD) liver grafts. In all cases, endischemic perfusion was performed after initial cold storage for organ transport. Perfusion conditions differ slightly in terms of oxygenation (pO2 15-60 kPa), perfusion route (dual vs. portal), perfusion time (2-4 h), and perfusate.

SUMMARY

The current data support the hypothesis that applying endischemic hypothermic machine liver perfusion protects extended criteria DBD and DCD livers from initial reperfusion injury, with better graft function and less biliary complications. Hypothermic machine perfusion may therefore offer revitalization of liver grafts before implantation by a simple and practical perfusion technique with a high impact on enlarging the donor pool. Multicentric phase III randomized control trials in DBD and DCD liver transplantation have been initiated to further test this strategy, which may establish machine liver perfusion in the clinical setting.

Adaptive homeostasis

Homeostasis is a central pillar of modern Physiology. The term homeostasis was invented by Walter Bradford Cannon in an attempt to extend and codify the principle of 'milieu intérieur,' or a constant interior bodily environment, that had previously been postulated by Claude Bernard. Clearly, 'milieu intérieur' and homeostasis have served us well for over a century. Nevertheless, research on signal transduction systems that regulate gene expression, or that cause biochemical alterations to existing enzymes, in response to external and internal stimuli, makes it clear that biological systems are continuously making short-term adaptations both to set-points, and to the range of 'normal' capacity. These transient adaptations typically occur in response to relatively mild changes in conditions, to programs of exercise training, or to sub-toxic, non-damaging levels of chemical agents; thus, the terms hormesis, heterostasis, and allostasis are not accurate descriptors. Therefore, an operational adjustment to our understanding of homeostasis suggests that the modified term, Adaptive Homeostasis, may be useful especially in studies of stress, toxicology, disease, and aging. Adaptive Homeostasis may be defined as follows: 'The transient expansion or contraction of the homeostatic range in response to exposure to sub-toxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events.'