Xenon preconditioning protects against renal ischemic-reperfusion injury via HIF-1alpha activation

Hypoxia-inducible factor-1α attenuates renal podocyte injury in male rats in a simulated high-altitude environment by upregulating Krüppel-like factor 4 expression

Previous studies have shown that podocyte injury is involved in the development of proteinuria in rats under hypobaric hypoxia conditions. Prolyl hydroxylase inhibitors (PHIs) may reduce proteinuria. This study aimed to further investigate whether the protective effects of hypoxia-inducible factor 1α (HIF1α) on podocyte injury induced by hypobaric hypoxia are related to Krüppel-like factor 4 (KLF4). Rats were housed in a low-pressure oxygen chamber to simulate a high-altitude environment (5000 m), and a PHI was intraperitoneally injected. Urinary protein electrophoresis was performed and the morphology of the podocytes was observed by electron microscopy. Rat podocytes were cultured under 1% O2, and siRNA was used to interfere with KLF4 expression. The protein expression levels of HIF1α, KLF4, CD2-associated protein (CD2AP) and nephrin were determined by western blotting. Compared with those in the experimental group, the rats in the intervention group on day 14 had lower urinary protein levels, increased protein expression levels of CD2AP and nephrin, and reduced podocyte injury. The results of in vitro experiments showed that the protein expression levels of KLF4, CD2AP and nephrin were greater in the PHI intervention group and lower in the HIF1α inhibitors group than in the low-oxygen group. The protein expression of CD2AP and nephrin in the siKLF4-transfected podocytes treated with PHI and HIF1α inhibitors did not differ significantly from that in the low-oxygen group. HIF1α may be involved in reducing progressive high-altitude proteinuria by regulating KLF4 expression and contributing to the repair of podocyte injury induced by hypobaric hypoxia.

General anaesthetics reduce acute lymphoblastic leukaemia malignancies in vitro and in vivovia CXCR4 and osteopontin mediated mechanisms

Background

Acute lymphoblastic leukaemia (ALL) is a common type of cancer in children. General anaesthetics are often used on patients undergoing painful procedures during ALL treatments but their effects on ALL malignancy remain unknown. Herein, we aim to study the effect of propofol and sevoflurane on the migration, homing and chemoresistance of ALL cells.

Methods

NALM-6 and Reh cells were treated with propofol (5 and 10 μg/ml) or sevoflurane (3.6%) in vitro for six hours. Then, cells were harvested for adhesion assay and migration assay in vitro. In in vivo experiments, GFP-NALM-6 cells were pre-treated with propofol (10 μg/ml) or sevoflurane (3.6%) for six hours. Then, cells were injected intravenously to C57BL/6 female mice followed by intravital microscopy. For chemoresistance study, cells were treated with rising concentrations of Ara-c (0.05-50 nM) plus 10μg/ml of propofol or Ara-C plus 3.6% of sevoflurane for 4 hours, followed by the assessment of cell viability via CCK-8 assay and detection of autophagy via flow cytometry.

Results

Both anaesthetics reduced in vivo migration and in vivo homing as exemplified by 1) the reduction in the number of cells entering the bone marrow and 2) the disturbance in homing location in relation to endosteal surface. Our results indicated that general anaesthetics reduced the surface CXCR4 expression and the adhesion of leukaemia cells to thrombin cleaved osteopontin (OPN) was reduced. Those changes might result in the alterations in migration and homing. In addition, both anaesthetics sensitised ALL cells to Ara-c possibly through CXCR4 mediated mechanisms. Propofol but not sevoflurane enhanced chemo-related cell death via inducing cytotoxic autophagy.

Conclusion

Together, our data suggest that both propofol and sevoflurane could reduce ALL migration, and homing in vivo and in vitro via CXCR4 and OPN mediated mechanisms. Both anaesthetics could sensitise ALL cells to chemotherapy possibly via CXCR4 mediated mechanisms.

Xenon postconditioning attenuates neuronal injury after spinal cord ischemia/reperfusion injury by targeting endoplasmic reticulum stress-associated apoptosis

The purpose of the study is to explore the underlying mechanisms of xenon (Xe) which protects against spinal cord ischemia/reperfusion injury (SCIRI). A SCIRI rat model was induced by abdominal artery occlusion for 85 min and reperfusion. Xe postconditioning (50% Xe) was administered 1 h after 1 h of reperfusion. At reperfusion time points (2, 4, 6, and 24 h), rats were treated with spinal cord scans by MRI to assess the time of peak spinal cord injury after SCIRI. Subsequently, endoplasmic reticulum (ER) stress inhibitor sodium 4-phenylbutyrate (4-PBA) was administered by daily intraperitoneal injection (50 mg/kg) for 5 days before SCIRI. At 4 h after reperfusion, motor function, immunofluorescence staining, hematoxylin and eosin (HE) staining, Nissl staining, TUNEL staining, real-time reverse transcription polymerase chain (RT-PCR) reaction, and western blot analyses were performed to investigate the protective effects of Xe against SCIRI. In the rat I/R model, spinal cord edema peaked at reperfusion 4 h. SCIRI activated ER stress, which was located in neurons. Xe postconditioning remarkably alleviated hind limb motor function, reduced neuronal apoptosis rate, increased the number of normal neurons, and inhibited the expression of ER stress-related protein in spinal cord. Furthermore, the administration of the ER stress inhibitor 4-PBA strongly decreased ER stress-induced apoptosis following SCIRI. Xe postconditioning inhibits ER stress activation, which contributes to alleviate SCIRI by suppressing neuronal apoptosis.

The cellular mechanisms associated with the anesthetic and neuroprotective properties of xenon: a systematic review of the preclinical literature

Introduction

Xenon exhibits significant neuroprotection against a wide range of neurological insults in animal models. However, clinical evidence that xenon improves outcomes in human studies of neurological injury remains elusive. Previous reviews of xenon's method of action have not been performed in a systematic manner. The aim of this review is to provide a comprehensive summary of the evidence underlying the cellular interactions responsible for two phenomena associated with xenon administration: anesthesia and neuroprotection.

Methods

A systematic review of the preclinical literature was carried out according to the PRISMA guidelines and a review protocol was registered with PROSPERO. The review included both in vitro models of the central nervous system and mammalian in vivo studies. The search was performed on 27th May 2022 in the following databases: Ovid Medline, Ovid Embase, Ovid Emcare, APA PsycInfo, and Web of Science. A risk of bias assessment was performed utilizing the Office of Health Assessment and Translation tool. Given the heterogeneity of the outcome data, a narrative synthesis was performed.

Results

The review identified 69 articles describing 638 individual experiments in which a hypothesis was tested regarding the interaction of xenon with cellular targets including: membrane bound proteins, intracellular signaling cascades and transcription factors. Xenon has both common and subtype specific interactions with ionotropic glutamate receptors. Xenon also influences the release of inhibitory neurotransmitters and influences multiple other ligand gated and non-ligand gated membrane bound proteins. The review identified several intracellular signaling pathways and gene transcription factors that are influenced by xenon administration and might contribute to anesthesia and neuroprotection.

Discussion

The nature of xenon NMDA receptor antagonism, and its range of additional cellular targets, distinguishes it from other NMDA antagonists such as ketamine and nitrous oxide. This is reflected in the distinct behavioral and electrophysiological characteristics of xenon. Xenon influences multiple overlapping cellular processes, both at the cell membrane and within the cell, that promote cell survival. It is hoped that identification of the underlying cellular targets of xenon might aid the development of potential therapeutics for neurological injury and improve the clinical utilization of xenon.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier: 336871.

Effect of xenon on brain injury, neurological outcome, and survival in patients after aneurysmal subarachnoid hemorrhage-study protocol for a randomized clinical trial

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is a neurological emergency, affecting a younger population than individuals experiencing an ischemic stroke; aSAH is associated with a high risk of mortality and permanent disability. The noble gas xenon has been shown to possess neuroprotective properties as demonstrated in numerous preclinical animal studies. In addition, a recent study demonstrated that xenon could attenuate a white matter injury after out-of-hospital cardiac arrest.

METHODS

The study is a prospective, multicenter phase II clinical drug trial. The study design is a single-blind, prospective superiority randomized two-armed parallel follow-up study. The primary objective of the study is to explore the potential neuroprotective effects of inhaled xenon, when administered within 6 h after the onset of symptoms of aSAH. The primary endpoint is the extent of the global white matter injury assessed with magnetic resonance diffusion tensor imaging of the brain.

DISCUSSION

Despite improvements in medical technology and advancements in medical science, aSAH mortality and disability rates have remained nearly unchanged for the past 10 years. Therefore, new neuroprotective strategies to attenuate the early and delayed brain injuries after aSAH are needed to reduce morbidity and mortality.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04696523. Registered on 6 January 2021. EudraCT, EudraCT Number: 2019-001542-17. Registered on 8 July 2020.

Effect of xenon and argon inhalation on erythropoiesis and steroidogenesis: A systematic review

Background

Xenon and argon inhalation were included on the WADA Prohibited List in 2014 due to the reported positive effects on erythropoiesis and steroidogenesis that occur as a result of their application. Thus, the systematic review of studies supporting these notions is of interest.

Methods

A thorough search on the effects of xenon and argon inhalation on erythropoiesis and steroidogenesis, as well as their negative effects on human health and method detection was conducted. Pubmed and Google Scholar databases and the Cochrane Library were researched, as well as the WADA research section. The search was conducted in accordance with the PRISMA guidelines. All articles written in English and published between 2000 and 2021 were analyzed, as well as reference studies meeting the search criteria.

Results

At present, there are only two publications in healthy human subjects evaluating the effects of xenon inhalation on erythropoiesis that found no conclusive evidence of a positive effect on erythropoiesis. This research was published following the inclusion of this gas on the WADA Prohibited List in 2014 and had a high risk of bias. There were no studies available on the effect of argon inhalation on erythropoiesis. Furthermore, no studies were found on the effect of xenon or argon inhalation on steroidogenesis in healthy subjects and no studies relating to the effects of xenon or argon inhalation on erythropoiesis and steroidogenesis were found on the WADA website.

Conclusion

There is still inconclusive evidence to support the administration of xenon and argon inhalations on erythropoiesis and steroidogenesis and their positive effects on health. Further research is warranted to establish the effects of these gases. Additionally, improved communication between anti-doping authorities and all key stakeholders is required to support the inclusion of various substances on recognized prohibited lists.

Immunology of the transplanted cryopreserved kidney

Transplantation has substituted dysfunctional organs with healthy organs from donors to significantly lower morbidity and mortality associated with end-stage organ disease. Since the advent of transplantation, the promise of functional replacement has attracted an exponential mismatch between organ supply and demand. Theoretical proposals to counter the increasing needs have either been to create a source through genetic engineering of porcine donors for xenotransplantation (with more potent immunosuppression protocols) or recreate one's organ in a pig using interspecies blastocyst complementation for exogenic organ transplantation (without immunosuppression). Another promising avenue has been organ banking through cryopreservation for transplantation. Although ice free preservation and acceptable early function following rewarming is critical for success in transplantation, the immunological response that predominantly defines short- and long-term graft survival has failed to captivate attention to date. It is well sorted that thermal and metabolic stress incurred at 4 °C during recovery and reperfusion of organs for clinical transplantation has varying impact on graft survival. Considering the magnitude of cellular imbalance and injury at sub-zero/ultralow temperatures in addition to the chemical toxicity of cryoprotective agents (CPA), it is essential to assess and address the immunological response associated following transplantation to maximize the success of cryopreservation.

Hypothermia combined with neuroprotective adjuvants shortens the duration of hospitalization in infants with hypoxic ischemic encephalopathy: Meta-analysis

Objective: Therapeutic hypothermia (TH) is the current standard of care for neonatal hypoxic-ischemic encephalopathy (HIE), yet morbidity and mortality remain significant. Adjuvant neuroprotective agents have been suggested to augment hypothermic-mediated neuroprotection. This analysis aims to identify the classes of drugs that have been used in combination with hypothermia in the treatment of neonatal HIE and determine whether combination therapy is more efficacious than TH alone. Methods: A systematic search of PubMed, Embase and Medline from conception through December 2022 was conducted. Randomized- and quasi-randomized controlled trials, observational studies and retrospective studies evaluating HIE infants treated with combination therapy versus TH alone were selected. Primary reviewers extracted information on mortality, neurodevelopmental impairment and length of hospitalization for meta-analyses. Effect sizes were pooled using a random-effects model and measured as odds ratio (OR) or mean difference (MD) where applicable, and 95% confidence intervals (CI) were calculated. Risk of bias was assessed using the tool from the Cochrane Handbook for Systematic Reviews of Interventions. Results: The search strategy collected 519 studies, 16 of which met analysis inclusion criteria. HIE infants totaled 1,288 infants from included studies, 646 infants received some form of combination therapy, while 642 received TH alone. GABA receptor agonists, NMDA receptor antagonists, neurogenic and angiogenic agents, stem cells, glucocorticoids and antioxidants were identified as candidate adjuvants to TH that have been evaluated in clinical settings compared to TH alone. Length of hospitalization was significantly reduced in infants treated with combination therapy (MD -4.81, 95% CI [-8.42. to -1.19], p = .009) compared to those treated with TH alone. Risk of mortality and neurodevelopmental impairment did not differ between combination therapy and TH alone groups. Conclusion: Compared to the current standard of care, administration of neuroprotective adjuvants with TH reduced the duration of hospitalization but did not impact the risk of mortality or neurodevelopmental impairment in HIE infants. Meta-analysis was limited by a moderate risk of bias among included studies and small sample sizes. This analysis highlights the need for preclinical trials to conduct drug development studies in hypothermic settings to identify relevant molecular targets that may offer additive or synergistic neuroprotection to TH, and the need for larger powered clinical trials to determine the dose and timing of administration at which maximal clinical benefits are observed for adjuvant neuroprotectants.

Medical Gas Therapy for Tissue, Organ, and CNS Protection: A Systematic Review of Effects, Mechanisms, and Challenges

Gaseous molecules have been increasingly explored for therapeutic development. Here, following an analytical background introduction, a systematic review of medical gas research is presented, focusing on tissue protections, mechanisms, data tangibility, and translational challenges. The pharmacological efficacies of carbon monoxide (CO) and xenon (Xe) are further examined with emphasis on intracellular messengers associated with cytoprotection and functional improvement for the CNS, heart, retina, liver, kidneys, lungs, etc. Overall, the outcome supports the hypothesis that readily deliverable "biological gas" (CO, H₂ , H₂ S, NO, O₂ , O₃ , and N₂ O) or "noble gas" (He, Ar, and Xe) treatment may preserve cells against common pathologies by regulating oxidative, inflammatory, apoptotic, survival, and/or repair processes. Specifically, CO, in safe dosages, elicits neurorestoration via igniting sGC/cGMP/MAPK signaling and crosstalk between HO-CO, HIF-1α/VEGF, and NOS pathways. Xe rescues neurons through NMDA antagonism and PI3K/Akt/HIF-1α/ERK activation. Primary findings also reveal that the need to utilize cutting-edge molecular and genetic tactics to validate mechanistic targets and optimize outcome consistency remains urgent; the number of neurotherapeutic investigations is limited, without published results from large in vivo models. Lastly, the broad-spectrum, concurrent multimodal homeostatic actions of medical gases may represent a novel pharmaceutical approach to treating critical organ failure and neurotrauma.

Repetitive xenon treatment improves post-stroke sensorimotor and neuropsychiatric dysfunction

Stroke is a life-changing event as stroke survivors experience changes in personality, emotions and mood. We investigated the effect of xenon gas encapsulated in liposomes on stroke-generated sensorimotor impairments, and anxiety- and depression-like phenotypes. Ischemic stroke was created by the intraluminal middle cerebral artery occlusion (MCAO) for 6 h followed by reperfusion in rats. Xenon-liposome (6 mg/kg, intravenous) treatment was given multiple times starting at 2 h post-ischemia through 6 h (5X), and once-daily for next 3 days. Rats underwent ischemic injury displayed sensorimotor deficits in the adhesive removal, vibrissae-evoked forelimb placement and rotarod tests. These animals also made lesser entries and spent less time on open arms of the elevated-plus maze and swam more in passive mode in the forced swimming test, indicating anxiety- and depression-like behaviors at 28- and 35-days post-injury, respectively. Repeated intravenous treatment with xenon-liposomes ameliorated these behavioral aberrations (p < 0.05). Gut microbiome analysis (16S ribosomal-RNA gene sequencing) showed a decrease in the Clostridium clusters XI, XIVa, XVIII and Lactobacillus bacterium, and increase of the Prevotella in the xenon-liposome group. No microbiota communities were majorly affected across the treatments. Moreover, xenon treatment group showed augmented plasma levels of IL-6 cytokines (∼5 fold) on day-35 post-ischemia, while no change was noticed in the IL-1β, IL-4, IL-10, IL-13 and MCP-1 levels. Our data highlights the safety, behavioral recovery and reversal of post-stroke brain injury following xenon-liposome treatment in an extended ischemic model. These results show the potential for this treatment strategy to be translated to patients with stroke.

Effect of Inhalation Anesthetics on Tumor Metastasis

Many factors affect the prognosis of patients undergoing tumor surgery, and anesthesia is one of the potential influencing factors. In general anesthesia, inhalation anesthesia is widely used in the clinic because of its strong curative effect and high controllability. However, the effect of inhalation anesthetics on the tumor is still controversial. More and more research has proved that inhalation anesthetics can intervene in local recurrence and distant metastasis of tumor by acting on tumor biological behavior, immune response, and gene regulation. In this paper, we reviewed the research progress of diverse inhalation anesthetics promoting or inhibiting cancer in the critical events of tumor recurrence and metastasis, and compared the effects of inhalation anesthetics on patients' prognosis in clinical studies, to provide theoretical reference for anesthesia management of patients undergoing tumor surgery.

Role of Endothelial Prolyl-4-Hydroxylase Domain Protein/Hypoxia-Inducible Factor Axis in Acute Kidney Injury

Ischemia reperfusion injury (IRI) results from a cessation or restriction of blood supply to an organ followed by reestablishment of perfusion and reoxygenation. In the kidney, IRI due to transplantation, cardiac surgery with cardiopulmonary bypass, and other major vascular surgeries contributes to acute kidney injury (AKI), a clinical condition associated with significant morbidity and mortality in hospitalized patients. In the postischemic kidney, endothelial damage promotes inflammatory responses and leads to persistent hypoxia of the renal tubular epithelium. Like other cell types, endothelial cells respond to low oxygen tension by multiple hypoxic signaling mechanisms. Key mediators of adaptation to hypoxia are hypoxia-inducible factors (HIF)-1 and -2, transcription factors whose activity is negatively regulated by prolyl-hydroxylase domain proteins 1 to 3 (PHD1 to PHD3). The PHD/HIF axis controls several processes determining injury outcome, including ATP generation, cell survival, proliferation, and angiogenesis. Here, we discuss recent advances in our understanding of the endothelial-derived PHD/HIF signaling and its effects on postischemic AKI.

Hypoxic preconditioning in renal ischaemia-reperfusion injury: a review in pre-clinical models

Ischaemia-reperfusion injury (IRI) is a major cause of acute kidney injury (AKI) and chronic kidney disease, which consists of cellular damage and renal dysfunction. AKI is a major complication that is of particular concern after cardiac surgery and to a lesser degree following organ transplantation in the immediate post-transplantation period, leading to delayed graft function. Because effective therapies are still unavailable, several recent studies have explored the potential benefit of hypoxic preconditioning (HPC) on IRI. HPC refers to the acquisition of increased organ tolerance to subsequent ischaemic or severe hypoxic injury, and experimental evidences suggest a potential benefit of HPC. There are three experimental forms of HPC, and, for better clarity, we named them as follows: physical HPC, HPC via treated-cell administration and stabilised hypoxia-inducible factor (HIF)-1α HPC, or mimicked HPC. The purpose of this review is to present the latest developments in the literature on HPC in the context of renal IRI in pre-clinical models. The data we compiled suggest that preconditional activation of hypoxia pathways protects against renal IRI, suggesting that HPC could be used in the treatment of renal IRI in transplantation.

Postoperative Natural Killer Cell Dysfunction: The Prime Suspect in the Case of Metastasis Following Curative Cancer Surgery

Surgical resection is the foundation for the curative treatment of solid tumors. However, metastatic recurrence due to the difficulty in eradicating micrometastases remain a feared outcome. Paradoxically, despite the beneficial effects of surgical removal of the primary tumor, the physiological stress resulting from surgical trauma serves to promote cancer recurrence and metastasis. The postoperative environment suppresses critical anti-tumor immune effector cells, including Natural Killer (NK) cells. The literature suggests that NK cells are critical mediators in the formation of metastases immediately following surgery. The following review will highlight the mechanisms that promote the formation of micrometastases by directly or indirectly inducing NK cell suppression following surgery. These include tissue hypoxia, neuroendocrine activation, hypercoagulation, the pro-inflammatory phase, and the anti-inflammatory phase. Perioperative therapeutic strategies designed to prevent or reverse NK cell dysfunction will also be examined for their potential to improve cancer outcomes by preventing surgery-induced metastases.

Targeting oxidative stress, a crucial challenge in renal transplantation outcome

Disorders characterized by ischemia/reperfusion (I/R) are the most common causes of debilitating diseases and death in stroke, cardiovascular ischemia, acute kidney injury or organ transplantation. In the latter example the I/R step defines both the amplitude of the damages to the graft and the functional recovery outcome. During transplantation the kidney is subjected to blood flow arrest followed by a sudden increase in oxygen supply at the time of reperfusion. This essential clinical protocol causes massive oxidative stress which is at the basis of cell death and tissue damage. The involvement of both reactive oxygen species (ROS) and nitric oxides (NO) has been shown to be a major cause of these cellular damages. In fact, in non-physiological situations, these species escape endogenous antioxidant control and dangerously accumulate in cells. In recent years, the objective has been to find clinical and pharmacological treatments to reduce or prevent the appearance of oxidative stress in ischemic pathologies. This is very relevant because, due to the increasing success of organ transplantation, clinicians are required to use limit organs, the preservation of which against oxidative stress is crucial for a better outcome. This review highlights the key actors in oxidative stress which could represent new pharmacological targets.

Pharmacological torpor prolongs rat survival in lethal normobaric hypoxia

Resistance to hypoxia is one of the most prominent features of natural hibernation and is expected to be present in the pharmacological torpor (PT) that simulates hibernation. We studied resistance to lethal hypoxia (3.5% oxygen content) in rats under PT. To initiate PT, we used the previously developed pharmacological composition (PC) which, after a single intravenous injection, can induce a daily decrease in Tb by 7 °C-8 °C at the environmental temperature of 22 °C-23 °C. Half-survival (median) time of rats in lethal hypoxia was found to increase from 5 ± 0.8 min in anesthetized control rats to 150 ± 12 min in rats injected with PC, which is a 30-fold increase. Behavioral tests after PT and hypoxia, including the traveling distance, the number of rearing and grooming episodes, revealed that animal responses are significantly restored within a week. It is assumed that the discovered unprecedented resistance of artificially torpid rats to lethal hypoxia may open up broad prospects for the therapeutic use of PT for preconditioning to various damaging factors, treatment of diseases, and extend the so-called "golden hour" for lifesaving interventions.

Xenon treatment after severe traumatic brain injury improves locomotor outcome, reduces acute neuronal loss and enhances early beneficial neuroinflammation: a randomized, blinded, controlled animal study

BACKGROUND

Traumatic brain injury (TBI) is a major cause of morbidity and mortality, but there are no clinically proven treatments that specifically target neuronal loss and secondary injury development following TBI. In this study, we evaluate the effect of xenon treatment on functional outcome, lesion volume, neuronal loss and neuroinflammation after severe TBI in rats.

METHODS

Young adult male Sprague Dawley rats were subjected to controlled cortical impact (CCI) brain trauma or sham surgery followed by treatment with either 50% xenon:25% oxygen balance nitrogen, or control gas 75% nitrogen:25% oxygen. Locomotor function was assessed using Catwalk-XT automated gait analysis at baseline and 24 h after injury. Histological outcomes were assessed following perfusion fixation at 15 min or 24 h after injury or sham procedure.

RESULTS

Xenon treatment reduced lesion volume, reduced early locomotor deficits, and attenuated neuronal loss in clinically relevant cortical and subcortical areas. Xenon treatment resulted in significant increases in Iba1-positive microglia and GFAP-positive reactive astrocytes that was associated with neuronal preservation.

CONCLUSIONS

Our findings demonstrate that xenon improves functional outcome and reduces neuronal loss after brain trauma in rats. Neuronal preservation was associated with a xenon-induced enhancement of microglial cell numbers and astrocyte activation, consistent with a role for early beneficial neuroinflammation in xenon's neuroprotective effect. These findings suggest that xenon may be a first-line clinical treatment for brain trauma.

Combination treatments with therapeutic hypothermia for hypoxic-ischemic neuroprotection

Therapeutic hypothermia is now proven to reduce death or disability in term and near-term born infants with moderate to severe hypoxic-ischemic encephalopathy. Nevertheless, many infants still survive with disability, despite treatment with hypothermia. Recent preclinical and clinical studies suggest that current protocols for therapeutic hypothermia are near-optimal. The obvious strategy, in addition to improving early initiation of therapeutic hypothermia after birth, is to combine hypothermia with other neuroprotective agents. We review evidence that the mechanisms of action of many promising agents overlap with the anti-excitotoxic, anti-apoptotic, and anti-inflammatory mechanisms of hypothermia, leading to a lack of benefit from combination treatment. Moreover, even apparently beneficial combinations have failed to translate in clinical trials. These considerations highlight the need for preclinical studies to test clinically realistic protocols of timing and duration of treatment, before committing to large randomized controlled trials.

Hypoxia-Inducible Factor and Oxygen Biology in the Kidney

Kidney tissue hypoxia is detected in various kidney diseases and is considered to play an important role in the pathophysiology of both AKI and CKD. Because of the characteristic vascular architecture and high energy demand to drive tubular solute transport, the renal medulla is especially prone to hypoxia. Injured kidneys often present capillary rarefaction, inflammation, and fibrosis, which contribute to sustained kidney hypoxia, forming a vicious cycle promoting progressive CKD. Hypoxia-inducible factor (HIF), a transcription factor responsible for cellular adaptation to hypoxia, is generally considered to protect against AKI. On the contrary, consequences of sustained HIF activation in CKD may be either protective, neutral, or detrimental. The kidney outcomes seem to be affected by various factors, such as cell types in which HIF is activated/inhibited, disease models, balance between two HIF isoforms, and time and methods of intervention. This suggests multifaceted functions of HIF and highlights the importance of understanding its role within each specific context. Prolyl-hydroxylase domain (PHD) inhibitors, which act as HIF stabilizers, have been developed to treat anemia of CKD. Although many preclinical studies demonstrated renoprotective effects of PHD inhibitors in CKD models, there may be some situations in which they lead to deleterious effects. Further studies are needed to identify patients who would gain additional benefits from PHD inhibitors and those who may need to avoid them.

Oxygen homeostasis and cardiovascular disease: A role for HIF?

Hypoxia, the decline of tissue oxygen stress, plays a role in mediating cellular processes. Cardiovascular disease, relatively widespread with increased mortality, is closely correlated with oxygen homeostasis regulation. Besides, hypoxia-inducible factor-1(HIF-1) is reported to be a crucial component in regulating systemic hypoxia-induced physiological and pathological modifications like oxidative stress, damage, angiogenesis, vascular remodeling, inflammatory reaction, and metabolic remodeling. In addition, HIF1 controls the movement, proliferation, apoptosis, differentiation and activity of numerous core cells, such as cardiomyocytes, endothelial cells (ECs), smooth muscle cells (SMCs), and macrophages. Here we review the molecular regulation of HIF-1 in cardiovascular diseases, intended to improve therapeutic approaches for clinical diagnoses. Better knowledge of the oxygen balance control and the signal mechanisms involved is important to advance the development of hypoxia-related diseases.

Xenon blunts NF-κB/NLRP3 inflammasome activation and improves acute onset of accelerated and severe lupus nephritis in mice

Xenon, an inert anesthetic gas, is increasingly recognized to possess desirable properties including cytoprotective and anti-inflammatory effects. Here we evaluated the effects of xenon on the progression of lupus nephritis (LN) in a mouse model. A two hour exposure of either 70% xenon or 70% nitrogen balanced with oxygen was administered daily for five weeks to female NZB/W F1 mice that had been induced to develop accelerated and severe LN. Xenon treatment improved kidney function and renal histology, and decreased the renal expression of neutrophil chemoattractants, thereby attenuating glomerular neutrophil infiltration. The effects of xenon were mediated primarily by deceasing serum levels of anti-double stranded DNA autoantibody, inhibiting reactive oxygen species production, NF-κB/NLRP3 inflammasome activation, ICAM-1 expression, glomerular deposition of IgG and C3 and apoptosis, in the kidney; and enhancing renal hypoxia inducible factor 1-α expression. Proteomic analysis revealed that the treatment with xenon downregulated renal NLRP3 inflammasome-mediated cellular signaling. Similarly, xenon was effective in improving renal pathology and function in a spontaneous LN model in female NZB/W F1 mice. Thus, xenon may have a therapeutic role in treating LN but further studies are warranted to determine applicability to patients.

Update of the organoprotective properties of xenon and argon: from bench to beside

The growth of the elderly population has led to an increase in patients with myocardial infarction and stroke (Wajngarten and Silva, Eur Cardiol 14: 111–115, 2019). Patients receiving treatment for ST-segment-elevation myocardial infarction (STEMI) highly profit from early reperfusion therapy under 3 h from the onset of symptoms. However, mortality from STEMI remains high due to the increase in age and comorbidities (Menees et al., N Engl J Med 369: 901–909, 2013). These factors also account for patients with acute ischaemic stroke. Reperfusion therapy has been established as the gold standard within the first 4 to 5 h after onset of symptoms (Powers et al., Stroke 49: e46-e110, 2018). Nonetheless, not all patients are eligible for reperfusion therapy. The same is true for traumatic brain injury patients. Due to the complexity of acute myocardial and central nervous injury (CNS), finding organ protective substances to improve the function of remote myocardium and the ischaemic penumbra of the brain is urgent. This narrative review focuses on the noble gases argon and xenon and their possible cardiac, renal and neuroprotectant properties in the elderly high-risk (surgical) population. The article will provide an overview of the latest experimental and clinical studies. It is beyond the scope of this review to give a detailed summary of the mechanistic understanding of organ protection by xenon and argon.

Anesthesia and brain tumor surgery: technical considerations based on current research evidence

PURPOSE OF REVIEW

Anesthetics may influence cancer recurrence and metastasis following surgery by modulating the neuroendocrine stress response or by directly affecting cancer cell biology. This review summarizes the current evidence on whether commonly used anesthetics potentially affect postoperative outcomes following solid organ cancer surgery with particular focus on neurological malignancies.

RECENT FINDINGS

Despite significant improvement in diagnostic and therapeutic technology over the past decades, mortality rates after cancer surgery (including brain tumor resection) remains high. With regards to brain tumors, interaction between microglia/macrophages and tumor cells by multiple biological factors play an important role in tumor progression and metastasis. Preclinical studies have demonstrated an association between anesthetics and brain tumor cell biology, and a potential effect on tumor progression and metastasis has been revealed. However, in the clinical setting, the current evidence is inadequate to draw firm conclusions on the optimal anesthetic technique for brain tumor surgery.

SUMMARY

Further work at both the basic science and clinical level is urgently needed to evaluate the association between perioperative factors, including anesthetics/technique, and postoperative brain tumor outcomes.

Safety, hemodynamic effects, and detection of acute xenon inhalation: rationale for banning xenon from sport

This study aimed to quantify the sedative effects, detection rates, and cardiovascular responses to xenon. On 3 occasions, participants breathed xenon (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) in a nonblinded design. Sedation was monitored by a board-certified anesthesiologist. During 70% xenon, participants were also verbally instructed to operate a manual value with time-to-task failure being recorded. Beat-by-beat hemodynamics were measured continuously by ECG, photoplethysmography, and transcranial Doppler. Over 48 h postadministration, xenon was measured in blood and urine by gas chromatography-mass spectrometry. Xenon caused variable levels of sedation and restlessness. Task failure of the self-operating value occurred at 60–90 s in most individuals. Over the first minute, 50% and 70% xenon caused a substantial reduction in total peripheral resistance ( P < 0.05). All dosages caused an increase in cardiac output ( P < 0.05). By the end of xenon inhalation, slight hypertension was observed after all three doses ( P < 0.05), with an increase in middle cerebral artery velocity ( P < 0.05). Xenon was consistently detected, albeit in trace amounts, up to 3 h after all three doses of xenon inhalation in blood and urine with variable results thereafter. Xenon inhalation caused sedation incompatible with self-operation of a breathing apparatus, thus causing a potential life-threatening condition in the absence of an anesthesiologist. Yet, xenon can only be reliably detected in blood and urine up to 3 h postacute dosing.

NEW & NOTEWORTHY Breathing xenon in dosages conceivable for doping purposes (FiXe 30% for 20 min; FiXe 50% for 5 min; FiXe 70% for 2 min) causes an initial rapid fall in total peripheral resistance with tachycardia and thereafter a mild hypertension with elevated middle cerebral artery velocity. These dose duration intervals cause sedation that is incompatible with operating a breathing apparatus and can only be detected in blood and urine samples with a high probability for up to ~3 h.

Effect of acute and chronic xenon inhalation on erythropoietin, hematological parameters, and athletic performance

This study aimed to assess the efficacy of acute subanesthetic dosages of xenon inhalation to cause erythropoiesis and determine the effect of chronic xenon dosing on hematological parameters and athletic performance. To assess the acute effects, seven subjects breathed three subanesthetic concentrations of xenon: 30% fraction of inspired xenon (FiXe) for 20 min, 50% FiXe for 5 min, and 70% FiXe for 2 min. Erythropoietin (EPO) was measured at baseline, during, and after xenon inhalation. To determine the chronic effects, eight subjects breathed 70% FiXe for 2 min on 7 consecutive days, and EPO, total blood, and plasma volume were measured. Phase II involved assessment of 12 subjects for EPO, total blood volume, maximal oxygen uptake, and 3-km time before and after random assignment to 4 wk of xenon or sham gas inhalation. FiXe 50% and 70% stimulated an increase in EPO at 6 h [+2.3 mIU/mL; 95% confidence interval (CI) 0.1–4.5; P = 0.038] and at 192 h postinhalation (+2.9 mIU/mL; 95% CI 0.6–5.1; P = 0.017), respectively. Seven consecutive days of dosing significantly elevated plasma volume (+491 mL; 95% CI 194–789; P = 0.002). Phase II showed no significant effect on EPO, hemoglobin mass, plasma volume, maximal oxygen uptake, or 3-km time. Acute exposure to subanesthetic doses of xenon caused a consistent increase in EPO, and 7 consecutive days of xenon inhalation significantly expanded plasma volume. However, this physiological response appeared to be transient, and 4 wk of xenon inhalation did not stimulate increases in plasma volume or erythropoiesis, leaving cardiorespiratory fitness and athletic performance unchanged.

NEW & NOTEWORTHY This is the first study to examine each element of the cascade by which xenon inhalation is purported to take effect, starting with measurement of the hypoxia-inducible factor effector, erythropoietin, to hemoglobin mass and blood volume and athletic performance. We found that acute exposure to xenon increased serum erythropoietin concentration, although major markers of erythropoiesis remained unchanged. While daily dosing significantly expanded plasma volume, no physiological or performance benefits were apparent following 4 wk of dosing.

Oral delivery of xenon for cardiovascular protection

Cardiac hypertrophy often causes impairment of cardiac function. Xenon (Xe), a naturally occurring noble gas, is known to provide neurological and myocardial protection without side effects. The conventional method of Xe delivery by inhalation is not feasible on a chronic basis. We have developed an orally deliverable, effective Xe formulation for long-term administration. We employed 2-hydroxypropyl)-β-cyclodextrin (HPCD), which was dissolved in water to increase the Xe concentration in solution. The beneficial effects of long-term oral administration of Xe-enriched solutions on cardiovascular function were evaluated in vivo. HPCD increased Xe solubility from 0.22 mM to 0.67 mM (3.8-fold). Aged ApoE knockout mice fed high-fat diet for 6 weeks developed hypertension, and myocardial hypertrophy with impaired cardiac function. Oral Xe prevented this ischemic damage, preserving normal blood pressure, while maintaining normal left ventricular mass and wall thickness. This novel formulation allows for gastrointestinal delivery and cardiovascular stabilization.

The Role of Heme Oxygenase-1 in Remote Ischemic and Anesthetic Organ Conditioning

The cytoprotective effects of the heme oxygenase (HO) pathway are widely acknowledged. These effects are mainly mediated by degradation of free, pro-oxidant heme and the generation of carbon monoxide (CO) and biliverdin. The underlying mechanisms of protection include anti-oxidant, anti-apoptotic, anti-inflammatory and vasodilatory properties. Upregulation of the inducible isoform HO-1 under stress conditions plays a crucial role in preventing or reducing cell damage. Therefore, modulation of the HO-1 system might provide an efficient strategy for organ protection. Pharmacological agents investigated in the context of organ conditioning include clinically used anesthetics and sedatives. A review from Hoetzel and Schmidt from 2010 nicely summarized the effects of anesthetics on HO-1 expression and their role in disease models. They concluded that HO-1 upregulation by anesthetics might prevent or at least reduce organ injury due to harmful stimuli. Due to its clinical safety, anesthetic conditioning might represent an attractive pharmacological tool for HO-1 modulation in patients. Remote ischemic conditioning (RIC), first described in 1993, represents a similar secure option to induce organ protection, especially in its non-invasive form. The efficacy of RIC has been intensively studied herein, including on patients. Studies on the role of RIC in influencing HO-1 expression to induce organ protection are emerging. In the first part of this review, recently published pre-clinical and clinical studies investigating the effects of anesthetics on HO-1 expression patterns, the underlying signaling pathways mediating modulation and its causative role in organ protection are summarized. The second part of this review sums up the effects of RIC.

Ischemia-reperfusion injury in renal transplantation: 3 key signaling pathways in tubular epithelial cells

Renal ischemia-reperfusion injury (IRI) is a significant clinical challenge faced by clinicians perioperatively in kidney transplantation. Recent work has demonstrated the key importance of transmembrane receptors in the injured tubular epithelial cell, most notably Toll-like receptors, activated by exogenous and endogenous ligands in response to external and internal stresses. Through sequential protein-protein interactions, the signal is relayed deep into the core physiological machinery of the cell, having numerous effects from upregulation of pro-inflammatory gene products through to modulating mitochondrial respiration. Inter-pathway cross talk facilitates a co-ordinated response at an individual cellular level, as well as modulating the surrounding tissue's microenvironment through close interactions with the endothelium and circulating leukocytes. Defining the underlying cellular cascades involved in IRI will assist the identification of novel interventional targets to attenuate IRI with the potential to improve transplantation outcomes. We present a focused review of 3 key cellular signalling pathways in the injured tubular epithelial cell that have been the focus of much research over the past 2 decades: toll-like receptors, sphingosine-1-phosphate receptors and hypoxia inducible factors. We provide a unique perspective on the potential clinical translations of this recent work in the transplant setting. This is particularly timely with the recent completion of phase I and ongoing phase 2 clinical trials of inhibitors targeting specific components of these signaling cascades.

Role of the Extracellular Signal-Regulated Kinase 1/2 Signaling Pathway in Ischemia-Reperfusion Injury

Extracellular signal-regulated kinase 1/2 (ERK_1/2), an important member of the mitogen-activated protein kinase family, is found in many organisms, and it participates in intracellular signal transduction. Various stimuli induce phosphorylation of ERK_1/2 in vivo and in vitro. Phosphorylated ERK_1/2 moves to the nucleus, activates many transcription factors, regulates gene expression, and controls various physiological processes, finally inducing repair processes or cell death. With the aging of the population around the world, the occurrence of ischemia-reperfusion injury (IRI), especially in the brain, heart, kidney, and other important organs, is becoming increasingly serious. Abnormal activation of the ERK_1/2 signaling pathway is closely related to the development and the metabolic mechanisms of IRI. However, the effects of this signaling pathway and the underlying mechanism differ between various models of IRI. This review summarizes the ERK_1/2 signaling pathway and the molecular mechanism underlying its role in models of IRI in the brain, heart, liver, kidneys, and other organs. This information will help to deepen the understanding of ERK_1/2 signals and deepen the exploration of IRI treatment based on the ERK_1/2 study.

Better haemodynamic stability under xenon anaesthesia than under isoflurane anaesthesia during partial nephrectomy - a secondary analysis of a randomised controlled trial

Background

Renal dysfunction following intraoperative arterial hypotension is mainly caused by an insufficient renal blood flow. It is associated with higher mortality and morbidity rates. We hypothesised that the intraoperative haemodynamics are more stable during xenon anaesthesia than during isoflurane anaesthesia in patients undergoing partial nephrectomy.

Methods

We performed a secondary analysis of the haemodynamic variables collected during the randomised, single-blinded, single-centre PaNeX study, which analysed the postoperative renal function in 46 patients who underwent partial nephrectomy. The patients received either xenon or isoflurane anaesthesia with 1:1 allocation ratio. We analysed the duration of the intraoperative systolic blood pressure decrease by > 40% from baseline values and the cumulative duration of a mean arterial blood pressure (MAP) of < 65 mmHg as primary outcomes. The secondary outcomes were related to other blood pressure thresholds, the amount of administered norepinephrine, and the analysis of confounding factors on the haemodynamic stability.

Results

The periods of an MAP of < 65 mmHg were significantly shorter in the xenon group than in the isoflurane group. The medians [interquartile range] were 0 [0–10.0] and 25.0 [10.0–47.5] minutes, for the xenon and isoflurane group, respectively (P = 0.002). However, the cumulative duration of a systolic blood pressure decrease by > 40% did not significantly differ between the groups (P = 0.51). The periods with a systolic blood pressure decrease by 20% from baseline, MAP decrease to values < 60 mmHg, and the need for norepinephrine, as well as the cumulative dose of norepinephrine were significantly shorter and lower, respectively, in the xenon group. The confounding factors, such as demographic data, surgical technique, or anaesthesia data, were similar in the two groups.

Conclusion

The patients undergoing xenon anaesthesia showed a better haemodynamic stability, which might be attributed to the xenon properties. The indirect effect of xenon anaesthesia might be of importance for the preservation of renal function during renal surgery and needs further elaboration.

Trial registration

ClinicalTrials.gov: NCT01839084. Registered 24 April 2013.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0799-2) contains supplementary material, which is available to authorized users.

Inhibition of prolyl hydroxylase domain (PHD) by JTZ-951 reduces obesity-related diseases in the liver, white adipose tissue, and kidney in mice with a high-fat diet

The epidemic of obesity and its complications is rapidly increasing worldwide. Recent drug discoveries established the utility of prolyl hydroxylase domain (PHD) inhibitors as stabilizers of hypoxia-inducible factors (HIFs) in vivo, which are currently in human clinical studies for the treatment of anemia in chronic kidney disease (CKD). These studies suggest a role for PHD inhibitors in ameliorating obesity and hyperlipidemia. We hypothesized that HIF activation using a PHD inhibitor, JTZ-951, protects from obesity-related diseases in the white adipose tissue (WAT), liver, and kidney in mice fed with high-fat diet (HFD). Eight-week-old, C57BL/6J mice were fed with HFD for 20 weeks with or without JTZ-951(0.005%; mixed in chow). Body weight and plasma non-high-density lipoprotein (HDL) cholesterol levels were significantly lower in the JTZ-951 group as compared with the vehicle group. PHD inhibition improved liver steatosis, macrophage infiltration into WAT and adipocyte fibrosis. In the kidney, PHD inhibition reduced albuminuria. Histologically, the number of F4/80- positive infiltrating macrophages and mesangial expansion were milder in the JTZ-951 group. Relative mRNA expression of adiponectin in WAT was higher in the JTZ-951-treated group and inversely correlated with hepatic steatosis score, adipocyte macrophage aggregation, and albuminuria. Activation of HIF ameliorates multiple obesity-related consequences in mice with HFD. The results of the present study offer the promising view that pharmacological PHD inhibition may be beneficial for the treatment of obesity-related diseases that can be ameliorated by weight loss.

Influence of perioperative anaesthetic and analgesic interventions on oncological outcomes: a narrative review

Surgery is an important treatment modality for the majority of solid organ cancers. Unfortunately, cancer recurrence following surgery of curative intent is common, and typically results in refractory disease and patient death. Surgery and other perioperative interventions induce a biological state conducive to the survival and growth of residual cancer cells released from the primary tumour intraoperatively, which may influence the risk of a subsequent metastatic disease. Evidence is accumulating that anaesthetic and analgesic interventions could affect many of these pathophysiological processes, influencing risk of cancer recurrence in either a beneficial or detrimental way. Much of this evidence is from experimental in vitro and in vivo models, with clinical evidence largely limited to retrospective observational studies or post hoc analysis of RCTs originally designed to evaluate non-cancer outcomes. This narrative review summarises the current state of evidence regarding the potential effect of perioperative anaesthetic and analgesic interventions on cancer biology and clinical outcomes. Proving a causal link will require data from prospective RCTs with oncological outcomes as primary endpoints, a number of which will report in the coming years. Until then, there is insufficient evidence to recommend any particular anaesthetic or analgesic technique for patients undergoing tumour resection surgery on the basis that it might alter the risk of recurrence or metastasis.

CRISPR/Cas9 Edited Induced Pluripotent Stem Cell-Based Vascular Tissues to Model Aging and Disease-Dependent Impairment

IMPACT STATEMENT

Modeling human disease as precisely as possible is of upmost importance in understanding the underlying pathology and discovering effective therapies. Therefore, disease models that are highly controlled and composed of human-origin cells that present the disease phenotype are crucial. The human induced pluripotent stem cell (hiPSC)-based tissue model we present in this study is an important example of human-origin tissue model with controlled gene expression. Through CRISPR/Cas9 editing of hypoxia inducible factor 1α in hiPSCs, we developed tissue models that show the age and disease-dependent endothelial deterioration. This model holds promise for various biomedical applications as more realistic disease phenotypes can be created using fully human-origin platforms.

Sirt1-hypoxia-inducible factor-1α interaction is a key mediator of tubulointerstitial damage in the aged kidney

Although it is known that the expression and activity of sirtuin 1 (Sirt1) decrease in the aged kidney, the role of interaction between Sirt1 and hypoxia-inducible factor (HIF)-1α is largely unknown. In this study, we investigated whether HIF-1α could be a deacetylation target of Sirt1 and the effect of their interaction on age-associated renal injury. Five-week-old (young) and 24-month-old (old) C57Bl/6J mice were assessed for their age-associated changes. Kidneys from aged mice showed increased infiltration of CD68-positive macrophages, higher expression of extracellular matrix (ECM) proteins, and more apoptosis than young controls. They also showed decreased Sirt1 expression along with increased acetylated HIF-1α. The level of Bcl-2/adenovirus E1B-interacting protein 3, carbonic anhydrase 9, Snail, and transforming growth factor-β1, which are regulated by HIF-1α, was significantly higher in aged mice suggesting that HIF-1α activity was increased. In HK-2 cells, Sirt1 inhibitor sirtinol and siRNA-mediated knockdown of Sirt1 enhanced apoptosis and ECM accumulation. During hypoxia, Sirt1 was down-regulated, which allowed the acetylation and activation of HIF-1α. Resveratrol, a Sirt1 activator, effectively prevented hypoxia-induced production of ECM proteins, mitochondrial damage, reactive oxygen species generation, and apoptosis. The inhibition of HIF-1α activity by Sirt1-induced deacetylation of HIF-1α was confirmed by Sirt1 overexpression under hypoxic conditions and by resveratrol treatment or Sirt1 overexpression in HIF-1α-transfected HK-2 cells. Finally, we confirmed that chronic activation of HIF-1α promoted apoptosis and fibrosis, using tubular cell-specific HIF-1α transgenic mice. Taken together, our data suggest that Sirt1-induced deacetylation of HIF-1α may have protective effects against tubulointerstitial damage in aged kidney.

Lasting effects of general anesthetics on the brain in the young and elderly: "mixed picture" of neurotoxicity, neuroprotection and cognitive impairment

General anesthetics are commonly used in major surgery. To achieve the depth of anesthesia for surgery, patients are being subjected to a variety of general anesthetics, alone or in combination. It has been long held an illusory concept that the general anesthesia is entirely reversible and that the central nervous system is returned to its pristine state once the anesthetic agent is eliminated from the active site. However, studies indicate that perturbation of the normal functioning of these targets may result in long-lasting desirable or undesirable effects. This review focuses on the impact of general anesthetic exposure to the brain and summarizes the molecular and cellular mechanisms by which general anesthetics may induce long-lasting undesirable effects when exposed at the developing stage of the brain. The vulnerability of aging brain to general anesthetics, specifically in the context of cognitive disorders and Alzheimer’s disease pathogeneses are also discussed. Moreover, we will review emerging evidence regarding the neuroprotective property of xenon and anesthetic adjuvant dexmedetomidine in the immature and mature brains. In conclusion, “mixed picture” effects of general anesthetics should be well acknowledged and should be implemented into daily clinical practice for better patient outcome.

Argon Mitigates Impaired Wound Healing Process and Enhances Wound Healing In Vitro and In Vivo

Diabetic foot ulcers are associated with significant morbidity and mortality, and current treatments are far from optimal. Chronic wounds in diabetes are characterised by impaired angiogenesis, leukocyte function, fibroblast proliferation, and keratinocyte migration and proliferation.

Methods: We tested the effect of exposure to argon gas on endothelial cell, fibroblast, macrophage and keratinocyte cell cultures in vitro and in vivo of a streptozotocin-induced diabetic mouse model.

Results: Exposure to normobaric argon gas promotes multiple steps of the wound healing process. Argon accelerated angiogenesis, associated with upregulation of pro-angiogenic Angiopoietin-1 and vascular endothelial growth factor (VEGF) signalling in vitro and in vivo. Treatment with argon enhanced expression of transforming growth factor (TGF)-β, early recruitment of macrophages and keratinocyte proliferation. Argon had a pro-survival effect, inducing expression of cytoprotective mediators B-cell lymphoma 2 and heme oxygenase 1. Argon was able to accelerate wound closure in a diabetic mouse model.

Conclusion: Together these findings indicate that argon gas may be a promising candidate for clinical use in treatment of diabetic ulcers.

Inhaled Gases for Neuroprotection of Neonates: A Review

Importance: Hypoxic-ischemic encephalopathy (HIE) is a significant cause of morbidity and mortality in neonates. The incidence of HIE is 1-8 per 1,000 live births in developed countries. Whole-body hypothermia reduces the risk of disability or death, but 7 infants needed to be treated to prevent death or major neurodevelopmental disability. Inhalational gases may be promising synergistic agents due to their rapid onset and easy titratability. Objective: To review current data on different inhaled gases with neuroprotective properties that may serve as adjunct therapies to hypothermia. Evidence review: Literature review was performed using the PubMed database, google scholar, and ClinicalTrials.Gov. Results focused on articles published from January 1, 2005, through December 31, 2017. Articles published earlier than 2005 were included when appropriate for historical perspective. Our review emphasized preclinical and clinical studies relevant to the use of inhaled agents for neuroprotection. Findings: Based on the relevance to our topic, 111 articles were selected pertaining to the incidence of HIE, pathophysiology of HIE, therapeutic hypothermia, and emerging therapies for hypoxic-ischemic encephalopathy in preclinical and clinical settings. Supplemental tables summarizes highly relevant 49 publications that were included in this review. The selected publications emphasize the emergence of promising inhaled gases that may improve neurologic survival and alleviate neurodevelopmental disability when combined with therapeutic hypothermia in the future. Conclusions: Many inhaled agents have neuroprotective properties and could serve as an adjunct therapy to whole-body hypothermia. Inhaled agents are ideal due to their easy administration, titrability, and rapid onset and offset.

Xenon as an adjuvant to therapeutic hypothermia in near-term and term newborns with hypoxic-ischaemic encephalopathy

BACKGROUND

Hypoxic-ischaemic encephalopathy (HIE) is a serious birth complication affecting term and late preterm newborns. Although therapeutic hypothermia (cooling) has been shown to be an effective therapy for neonatal HIE, many cooled infants have poor long-term neurodevelopmental outcomes. In animal models of neonatal encephalopathy, inhaled xenon combined with cooling has been shown to offer better neuroprotection than cooling alone.

OBJECTIVES

To determine the effects of xenon as an adjuvant to therapeutic hypothermia on mortality and neurodevelopmental morbidity, and to ascertain clinically important side effects of xenon plus therapeutic hypothermia in newborn infants with HIE. To assess early predictors of adverse outcomes and potential side effects of xenon.

SEARCH METHODS

We used the standard strategy of the Cochrane Neonatal Review Group to search the Cochrane Library (2017, Issue 8), MEDLINE (from 1966), Embase (from 1966), and PubMed (from 1966) for randomised controlled and quasi-randomised trials. We also searched conference proceedings and the reference lists of cited articles. We conducted our most recent search in August 2017.

SELECTION CRITERIA

We included all trials allocating term or late preterm encephalopathic newborns to cooling plus xenon or cooling alone, irrespective of timing (starting age and duration) and concentrations used for xenon administration.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed results of searches against predetermined criteria for inclusion, assessed risk of bias, and extracted data. We performed meta-analyses using risk ratios (RRs), risk differences (RDs), and number needed to treat for an additional beneficial outcome (NNTB) with 95% confidence intervals (CIs) for dichotomous outcomes and mean differences (MDs) for continuous data.

MAIN RESULTS

A single randomised controlled trial enrolling 92 participants was eligible for this review. Researchers have not reported long-term neurodevelopmental outcomes, including the primary outcome of this review - death or long-term major neurodevelopmental disability in infancy (18 months to three years of age). Cooling plus xenon was not associated with reduced mortality at latest follow-up, based upon low quality evidence. Investigators noted no substantial differences between groups for other secondary outcomes of this review, such as biomarkers of brain damage assessed with magnetic resonance imaging and occurrence of seizures during primary hospitalisation. Available data do not show an increased adverse event rate in the cooling plus xenon group compared with the cooling alone group.

AUTHORS' CONCLUSIONS

Current evidence from one small randomised controlled pilot trial is inadequate to show whether cooling plus xenon is safe or effective in near-term and term newborns with HIE. Further trials reporting long-term neurodevelopmental outcomes are needed.

Carnosol protects against renal ischemia-reperfusion injury in rats

Acute kidney injury, which is caused by renal ischemia-reperfusion injury (IRI), occurs in several clinical situations and causes severe renal damage. There is no effective therapeutic agent available for renal IRI at present. In this study, we performed an experiment based on an in vivo murine model of renal IRI to examine the effect of carnosol. Thirty Sprague-Dawley rats were randomized into three groups (10 rats in each group): the sham, IRI, and carnosol groups. Rats in the carnosol group were injected intravenously with 3 mg/kg of carnosol, and those in the sham and IRI groups were injected intravenously with 10% dimethyl sulfoxide 1 h before ischemia. Rats were sacrificed after 24 h of reperfusion. The blood and kidneys were harvested, renal function was assessed, and histologic evaluation was performed to analyze renal injury. A renal myeloperoxidase activity assay, in-situ apoptosis examination, enzyme-linked immunosorbent assay, immunohistochemical assay, and western blot were also performed. Carnosol pretreatment significantly reduced renal dysfunction and histologic damage induced by renal IRI. Carnosol pretreatment suppressed renal inflammatory cell infiltration and pro-inflammatory cytokine expression. In addition, carnosol markedly inhibited apoptotic tubular cell death, caspase-3 activation, and activation of the p38 pathway. Carnosol pretreatment protects rats against renal IRI by inhibiting inflammation and apoptosis. Although future investigation is needed, carnosol may be a potential therapeutic agent for preventing renal IRI.

Aged kidney: can we protect it? Autophagy, mitochondria and mechanisms of ischemic preconditioning

The anti-aging strategy is one of the main challenges of the modern biomedical science. The term "aging" covers organisms, cells, cellular organelles and their constituents. In general term, aging system admits the existence of nonfunctional structures which by some reasons have not been removed by a clearing system, e.g., through autophagy/mitophagy marking and destroying unwanted cells or mitochondria. This directly relates to the old kidney which normal functioning is critical for the viability of the organism. One of the main problems in biomedical studies is that in their majority, young organisms serve as a standard with further extrapolation on the aged system. However, some protective systems, which demonstrate their efficiency in young systems, lose their beneficial effect in aged organisms. It is true for ischemic preconditioning of the kidney, which is almost useless for an old kidney. The pharmacological intervention could correct the defects of the senile system provided that the complete understanding of all elements involved in aging will be achieved. We discuss critical elements which determine the difference between young and old phenotypes and give directions to prevent or cure lesions occurring in aged organs including kidney.

ABBREVIATIONS

AKI: acute kidney injury; I/R: ischemia/reperfusion; CR: caloric restriction; ROS: reactive oxygen species; RC: respiratory chain.

Nephropreventing effect of hypoxia-inducible factor 1α in a rat model of ischaemic/reperfusion acute kidney injury

Acute kidney injury (AKI) occurs in 5% of hospitalized patients and in 50% of sepsis patients with acute renal dysfunction. However, there have been no safe and effective therapeutic strategies. The hypoxia condition is closely related to renal injury and function under AKI. As hypoxia-inducible factor 1α (HIF-1α) is critical for the cellular response to hypoxia, we investigated the protective effect of HIF-1α in a rat AKI model. We found that HIF-1α injection improved the survival of rat with AKI, and the level of creatinine and blood urea nitrogen (BUN) was also increased. Our data showed that HIF-1α treatment significantly alleviated ischaemic/reperfusion injury to kidney tubules and nephrocytes. We also found the downstream factors, such as EPOR, VEGF, and PHD3, were also upregulated by HIF-1α. Finally, it was observed that HIF-1α treatment also increased the percentage of adult resident progenitor cells (ARPC) in vitro and in vivo. In conclusion, HIF-1α plays a protective role in the ischaemic AKI model through stimulating the proliferation of ARPC, and our study provided a potential therapeutic strategy for AKI.

Xenon Combined With Hypothermia in Perinatal Hypoxic-Ischemic Encephalopathy: A Noble Gas, a Noble Mission

Perinatal hypoxia-ischemia is a major cause of neonatal morbidity. It generates primary neuronal damage of the neonatal brain and later secondary damage when reperfusion of the ischemic brain tissue causes a surge of oxygen free radicals and inflammation. This post-hypoxic-ischemic brain damage is a leading cause of motor and intellectual disabilities in survivors. Research worldwide has focused on mitigating this injury. Mild or moderate hypothermia is the standard treatment in many centers. However, its benefit is modest and the search for combinatorial effective neuroprotectants continues. This review focuses on xenon as one such agent. The use of mild to moderate hypothermia is reviewed first. Then promising results on the use of xenon to potentiate the effect of hypothermia in in vitro and in vivo animal experiments are discussed. In the first feasibility study on human neonates, researchers found a significant benefit of using 50% xenon for 18 hours in addition to 72 hours of hypothermia. Yet, this additional benefit of xenon was lacking in a larger cohort study, potentially because xenon was used beyond six hours of birth. The future of using xenon is promising, but further clinical studies are awaited to confirm the feasibility of its routine use and its optimal timing, concentration, and duration, for human neonatal hypoxia-ischemia.