Treprostinil reduces mitochondrial injury during rat renal ischemia-reperfusion injury

Mitochondrial DNA (mtDNA) accelerates oxygen-glucose deprivation-induced injury of proximal tubule epithelia cell via inhibiting NLRC5

The high morbidity and mortality associated with acute kidney injury (AKI) are global health concerns. AKI is commonly attributed to ischemia/reperfusion injury (IRI), a condition characterized by activation of inflammatory responses and mitochondrial dysfunction. Nonetheless, mitochondrial DNA (mtDNA) has the potential to induce renal IRI. This study aimed to elucidate the mechanism and function of mtDNA in HK-2 cells that had been exposed to oxygen-glucose deprivation/reperfusion (OGD/R) and in renal IRI mice. OGD/R was discovered to induce an increase in the amount of mtDNA in HK-2 cells. Moreover, our study demonstrated that mtDNA facilitated cellular apoptosis and inflammation in vivo and in vitro. Given the potential role of inflammation in OGD/R, we investigated the effect of mtDNA on various signaling pathways associated with inflammation. Western blot analysis demonstrated that mtDNA significantly upregulated NLRC5/TAP1 signaling. Furthermore, the upregulation of NLRC5 and TAP1 expression induced by mtDNA was reversed when NLRC5 was inhibited. It is worth mentioning that the loss of NLRC5 effectively nullified the beneficial effects of mtDNA on inflammation and cell apoptosis induced by OGD/R. In addition, in renal IRI mice, mtDNA treatment also aggravated inflammation and kidney damage, and increased the NLRC5 levels in kidney tissues. These results suggested that NLRC5 acts as an intermediary between mtDNA and the pathogenicity of renal IRI. In summary, this study provides evidence that mtDNA promotes apoptosis and inflammation in OGD/R treated HK-2 cells and renal IRI mice through upregulating NLRC5 levels.

A cloud-based learning module for biomarker discovery

This manuscript describes the development of a resource module that is part of a learning platform named "NIGMS Sandbox for Cloud-based Learning" https://github.com/NIGMS/NIGMS-Sandbox. The overall genesis of the Sandbox is described in the editorial NIGMS Sandbox at the beginning of this Supplement. This module delivers learning materials on basic principles in biomarker discovery in an interactive format that uses appropriate cloud resources for data access and analyses. In collaboration with Google Cloud, Deloitte Consulting and NIGMS, the Rhode Island INBRE Molecular Informatics Core developed a cloud-based training module for biomarker discovery. The module consists of nine submodules covering various topics on biomarker discovery and assessment and is deployed on the Google Cloud Platform and available for public use through the NIGMS Sandbox. The submodules are written as a series of Jupyter Notebooks utilizing R and Bioconductor for biomarker and omics data analysis. The submodules cover the following topics: 1) introduction to biomarkers; 2) introduction to R data structures; 3) introduction to linear models; 4) introduction to exploratory analysis; 5) rat renal ischemia-reperfusion injury case study; (6) linear and logistic regression for comparison of quantitative biomarkers; 7) exploratory analysis of proteomics IRI data; 8) identification of IRI biomarkers from proteomic data; and 9) machine learning methods for biomarker discovery. Each notebook includes an in-line quiz for self-assessment on the submodule topic and an overview video is available on YouTube (https://www.youtube.com/watch?v=2-Q9Ax8EW84). This manuscript describes the development of a resource module that is part of a learning platform named ``NIGMS Sandbox for Cloud-based Learning'' https://github.com/NIGMS/NIGMS-Sandbox. The overall genesis of the Sandbox is described in the editorial NIGMS Sandbox [1] at the beginning of this Supplement. This module delivers learning materials on the analysis of bulk and single-cell ATAC-seq data in an interactive format that uses appropriate cloud resources for data access and analyses.

Quantification of treprostinil concentration in rat and human using a novel validated and rapid liquid chromatography-tandem mass spectrometry method: Experimental and clinical applications in ischemia-reperfusion injury

Treprostinil (Remodulin®) is a Food and Drug Administration (FDA) approved prostacyclin analog to treat pulmonary arterial hypertension. Recently, treprostinil has been investigated to reduce ischemia-reperfusion injury (IRI) during transplantation, which currently has no approved treatment. A validated analytical method is necessary to measure treprostinil concentrations in biological specimens. Here, a novel, sensitive, and specific method to measure treprostinil concentrations in rat serum, human serum, and human plasma has been developed using liquid chromatography with tandem mass spectrometry (LC-MS/MS). Biological samples were processed by protein precipitation before chromatography and 6-keto Prostaglandin F1α-d4 was used as an internal standard. A gradient method was established with a total run time of 4 min. The assay was linear over the range of 0.25-75.0 ng/ml with accuracy (92.97-107.87 %), intra-assay precision (1.16-3.34 %), and inter-assay precision (1.11-4.58 %) in all biological matrices, which are within FDA acceptance criteria. No significant variation in treprostinil or 6-keto Prostaglandin F1α-d4 concentrations were observed under the investigated storage conditions. This novel, sensitive, and specific LC/MS-MS method is cost-effective and suitable for measuring treprostinil concentrations in animal studies and human biological samples for clinical applications.

The protective mechanism of SIRT3 and potential therapy in acute kidney injury

Acute kidney injury (AKI) is a complex clinical syndrome with a poor short-term prognosis, which increases the risk of the development of chronic kidney diseases and end-stage kidney disease. However, the underlying mechanism of AKI remains to be fully elucidated, and effective prevention and therapeutic strategies are still lacking. Given the enormous energy requirements for filtration and absorption, the kidneys are rich in mitochondria, which are unsurprisingly involved in the onset or progression of AKI. Accumulating evidence has recently documented that Sirtuin 3 (SIRT3), one of the most prominent deacetylases highly expressed in the mitochondria, exerts a protective effect on AKI. SIRT3 protects against AKI by regulating energy metabolism, inhibiting oxidative stress, suppressing inflammation, ameliorating apoptosis, inhibiting early-stage fibrosis and maintaining mitochondrial homeostasis. Besides, a number of SIRT3 activators have exhibited renoprotective properties both in animal models and in vitro experiments, but have not yet been applied to clinical practice, indicating a promising therapeutic approach. In this review, we unravel and summarize the recent advances in SIRT3 research and the potential therapy of SIRT3 activators in AKI.

Comprehensive overview of the role of mitochondrial dysfunction in the pathogenesis of acute kidney ischemia-reperfusion injury: a narrative review

Acute kidney ischemia-reperfusion (IR) injury is a life-threatening condition that predisposes individuals to chronic kidney disease. Since the kidney is one of the most energy-demanding organs in the human body and mitochondria are the powerhouse of cells, mitochondrial dysfunction plays a central role in the pathogenesis of IR-induced acute kidney injury. Mitochondrial dysfunction causes a reduction in adenosine triphosphate production, loss of mitochondrial dynamics (represented by persistent fragmentation), and impaired mitophagy. Furthermore, the pathological accumulation of succinate resulting from fumarate reduction under oxygen deprivation (ischemia) in the reverse flux of the Krebs cycle can eventually lead to a burst of reactive oxygen species driven by reverse electron transfer during the reperfusion phase. Accumulating evidence indicates that improving mitochondrial function, biogenesis, and dynamics, and normalizing metabolic reprogramming within the mitochondria have the potential to preserve kidney function during IR injury and prevent progression to chronic kidney disease. In this review, we summarize recent advances in understanding the detrimental role of metabolic reprogramming and mitochondrial dysfunction in IR injury and explore potential therapeutic strategies for treating kidney IR injury.

Hepatic ischemia-reperfusion syndrome and its effect on the cardiovascular system: The role of treprostinil, a synthetic prostacyclin analog

Hepatic ischemia-reperfusion syndrome has been the subject of intensive study and experimentation in recent decades since it is responsible for the outcome of several clinical entities, such as major hepatic resections and liver transplantation. In addition to the organ's post reperfusion injury, this syndrome appears to play a central role in the dysfunction of distant tissues and systems. Thus, continuous research should be directed toward finding effective therapeutic options to improve the outcome and reduce the postoperative morbidity and mortality rates. Treprostinil is a synthetic analog of prostaglandin I2, and its experimental administration has shown encouraging results. It has already been approved by the Food and Drug Administration in the United States for pulmonary arterial hypertension and has been used in liver transplantation, where preliminary encouraging results showed its safety and feasibility by using continuous intravenous administration at a dose of 5 ng/kg/min. Treprostinil improves renal and hepatic function, diminishes hepatic oxidative stress and lipid peroxidation, reduces hepatictoll-like receptor 9 and inflammation, inhibits hepatic apoptosis and restores hepatic adenosine triphosphate (ATP) levels and ATP synthases, which is necessary for functional maintenance of mitochondria. Treprostinil exhibits vasodilatory properties and antiplatelet activity and regulates proinflammatory cytokines; therefore, it can potentially minimize ischemia-reperfusion injury. Additionally, it may have beneficial effects on cardiovascular parameters, and much current research interest is concentrated on this compound.

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

PRETREATMENT WITH ERYTHROPOIETIN ALLEVIATES THE RENAL DAMAGE INDUCED BY ISCHEMIA REPERFUSION VIA REPRESSION OF INFLAMMATORY RESPONSE

OBJECTIVE

The aim: This study aimed to examine the anti-inflammatory, and antiapoptotic effects of erythropoietin against kidney injury inducted by ischemia reperfusion in experimental model.

PATIENTS AND METHODS

Materials and methods: 20 male Sprague Dawley rats were randomly divided into 4 equal groups: sham (subject to median laparotomy only), control (subject to 30 minutes ischemia and 2hours reperfusion), vehicle (injected by distilled water and subjected to the same procedure of ischemia reperfusion), erythropoietin group (as in vehicle group but the rats pretreated with 1000 U/kg of erythropoietin). The left kidney and blood specimen were collected. The blood utilized to assess serum creatinine. While kidneys utilized to assessed MCP-1, TLR2, and caspase-3 in addition to histopathological evaluation.

RESULTS

Results: Control and vehicle samples showed that a significant elevation in serum creatinine, TLR2, caspase-3, and MCP-1 as compared with sham group. The histological eval¬uation showed a significant rise in kidney injury scores. Kidneys and blood samples of erythropoietin pretreated rats established histopathological and functional improvement as evidenced via reduced kidney injury scores in addition to the reduction in serum creatinine, as well as there were a significant diminished in caspase-3, MCP-1, and TLR2 levels when compared with control and vehicle groups.

CONCLUSION

Conclusions: Erythropoietin has renoprotective effect against ischemia and reperfusion, which achieved by decrease the inflammatory response as well as antiapoptotic effect.

GPX3 and GSTT1 as biomarkers related to oxidative stress during renal ischemia reperfusion injuries and their relationship with immune infiltration

Background

Renal ischemia reperfusion injuries (IRIs) are very common in clinical diagnoses and treatments, which are a common cause of impaired renal functions, worsening pathological damage, affecting disease progression and hindering recovery. Renal IRIs are an inflammatory disease mediated by the adaptive and innate immune system. There is a complex interaction between oxidative stress and immune cell infiltration. Therefore, we aimed to determine biomarkers associated with oxidative stress during renal IRIs and their relationship with immune cell infiltration.

Method

A differential gene expression analysis was made based on the GSE148420 dataset from the NCBI Gene Expression Comprehensive Database (GEO) combined with 92 oxidative-stress (OS)-related genes identified in the Molecular Signatures Database. Then we identified differentially-expressed genes (DEOSGs) associated with oxidative stress, which were used for gene ontology (GO) and a Kyoto Encyclopedia of Genomes (KEGG) enrichment analysis. At the same time, we used PPI protein interaction networks and Lasso regression analysis to identify key genes, which were verified by the validation sets GSE58438 and GSE71647, as well as Western Blot detection on rat renal IRI models. At the same time, PAS staining, HE staining and immunohistochemistry were used to detect tissue damage and expression of markers related to oxidative stress during renal ischemia-reperfusion. Single-gene enrichment analysis (GSEA) was used to further clarify the underlying biological functions of key genes. Cibersort was used to analyze the immune cell infiltration during renal IRI and the correlation of key genes with immune cells. At the same time, we constructed a network of transcription-factor (TF)-Hub genes and miRNA-Hub genes. DGIDB was used to predict drugs and molecular compounds that might interact with the Hub genes.

Results

Compared with the control group, a total of 5456 differential genes (DEGs) were measured in the renal IRI group, 2486 of which were upregulated and 2970 were down-regulated. Among them, we found 30 DEGs (DEOSGs) associated with oxidative stress. The results of GO and KEGG enrichment analysis showed that these DEOSGs were mainly enriched in glutathione metabolism, the response to oxidative stress stimulation, the regulation of T cell activation and apoptosis signaling pathways. Through a protein interaction network (PPI) and a LASSO regression analysis, a total of two Hub genes were identified, namely GPX3 and GSTT1, which were validated through external validation sets and animal experiments. Through pathological methods, we found that the pathological damage of renal tissue and the expression of oxidative stress markers increased after renal ischemia-reperfusion. The results of GSEA showed that the Hub genes were related to oxidative stress pathways, apoptosis signaling pathways and immune-response-related signaling pathways. An immunoinfiltration correlation analysis showed that genes GPX3 and GSTT1 were significantly positively correlated with plasma cells and macrophage M0, while were negatively correlated with monocytes and macrophages M1 and M2. Using the Strust, Starbase and DGIDB database, we predicted that 81 transcription factors, 49 miRNAs and 13 drug or molecular compounds might interact with the Hub genes.

Conclusion

Through a comprehensive analysis of gene expression, our findings may provide new potential biomarkers for the pathogenesis of renal IRIs and a reliable basis for its early diagnosis as well as treatment.

Roles of Mitochondrial DNA Damage in Kidney Diseases: A New Biomarker

The kidney is a mitochondria-rich organ, and kidney diseases are recognized as mitochondria-related pathologies. Intact mitochondrial DNA (mtDNA) maintains normal mitochondrial function. Mitochondrial dysfunction caused by mtDNA damage, including impaired mtDNA replication, mtDNA mutation, mtDNA leakage, and mtDNA methylation, is involved in the progression of kidney diseases. Herein, we review the roles of mtDNA damage in different setting of kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD). In a variety of kidney diseases, mtDNA damage is closely associated with loss of kidney function. The level of mtDNA in peripheral serum and urine also reflects the status of kidney injury. Alleviating mtDNA damage can promote the recovery of mitochondrial function by exogenous drug treatment and thus reduce kidney injury. In short, we conclude that mtDNA damage may serve as a novel biomarker for assessing kidney injury in different causes of renal dysfunction, which provides a new theoretical basis for mtDNA-targeted intervention as a therapeutic option for kidney diseases.

The Proximal Tubule as the Pathogenic and Therapeutic Target in Acute Kidney Injury

BACKGROUND

In 2004, the term acute kidney injury (AKI) was introduced with the intention of broadening our understanding of rapid declines in renal function and to replace the historical terms of acute renal failure and acute tubular necrosis (ATN). Despite this evolution in terminology, the mechanisms of AKI have stayed largely elusive with the pathophysiological concepts of ATN remaining the mainstay in our understanding of AKI.

SUMMARY

The proximal tubule (PT), having the highest mitochondrial content in the kidney and relying heavily on oxidative phosphorylation to generate ATP, is vulnerable to ischaemic insults and mitochondrial dysfunction. Histologically, pathological changes in the PT are more consistent than changes to the glomeruli or the loop of Henle in AKI. Physiologically, activation of tubuloglomerular feedback due to PT dysfunction leads to an increase in preglomerular afferent arteriole resistance and a reduction in glomerular filtration. Pharmacologically, frusemide - a drug commonly used in the setting of oliguric AKI - is actively secreted by the PT and its diuretic effect is compromised by its failure to be secreted into the urine and thus be delivered to its site of action at the loop of Henle in AKI. Increases in the urinary, but not plasma biomarkers, of PT injury within 1 h of shock suggest that the PT as the initiation pathogenic target of AKI.

KEY MESSAGE

Therapeutic agents targeting specifically the PT epithelial cells, in particular its mitochondria - including amino acid ergothioneine and superoxide scavenger MitoTEMPO - show great promises in ameliorating AKI.