Mitochondrial dysfunction accounts for aldosterone-induced epithelial-to-mesenchymal transition of renal proximal tubular epithelial cells

Clinical Properties and Non-Clinical Testing of Mineralocorticoid Receptor Antagonists in In Vitro Cell Models

Mineralocorticoid receptor antagonists (MRAs) are one of the renin-angiotensin-aldosterone system inhibitors widely used in clinical practice. While spironolactone and eplerenone have a long-standing profile in clinical medicine, finerenone is a novel agent within the MRA class. It has a higher specificity for mineralocorticoid receptors, eliciting less pronounced adverse effects. Although approved for clinical use in patients with chronic kidney disease and heart failure, intensive non-clinical research aims to further elucidate its mechanism of action, including dose-related selectivity. Within the field, animal models remain the gold standard for non-clinical testing of drug pharmacological and toxicological properties. Their role, however, has been challenged by recent advances in in vitro models, mainly through sophisticated analytical tools and developments in data analysis. Currently, in vitro models are gaining momentum as possible platforms for advanced pharmacological and pathophysiological studies. This article focuses on past, current, and possibly future in vitro cell models research with clinically relevant MRAs.

Revisiting airway epithelial dysfunction and mechanisms in chronic obstructive pulmonary disease: the role of mitochondrial damage

Chronic exposure to environmental hazards causes airway epithelial dysfunction, primarily impaired physical barriers, immune dysfunction, and repair or regeneration. Impairment of airway epithelial function subsequently leads to exaggerated airway inflammation and remodeling, the main features of chronic obstructive pulmonary disease (COPD). Mitochondrial damage has been identified as one of the mechanisms of airway abnormalities in COPD, which is closely related to airway inflammation and airflow limitation. In this review, we evaluate updated evidence for airway epithelial mitochondrial damage in COPD and focus on the role of mitochondrial damage in airway epithelial dysfunction. In addition, the possible mechanism of airway epithelial dysfunction mediated by mitochondrial damage is discussed in detail, and recent strategies related to airway epithelial-targeted mitochondrial therapy are summarized. Results have shown that dysregulation of mitochondrial quality and oxidative stress may lead to airway epithelial dysfunction in COPD. This may result from mitochondrial damage as a central organelle mediating abnormalities in cellular metabolism. Mitochondrial damage mediates procellular senescence effects due to mitochondrial reactive oxygen species, which effectively exacerbate different types of programmed cell death, participate in lipid metabolism abnormalities, and ultimately promote airway epithelial dysfunction and trigger COPD airway abnormalities. These can be prevented by targeting mitochondrial damage factors and mitochondrial transfer. Thus, because mitochondrial damage is involved in COPD progression as a central factor of homeostatic imbalance in airway epithelial cells, it may be a novel target for therapeutic intervention to restore airway epithelial integrity and function in COPD.

Effects of cell-free DNA on kidney disease and intervention strategies

Kidney disease has become a global public health problem. Patients with end-stage kidney disease must rely on dialysis or undergo renal transplantation, placing heavy burdens on their families and society. Therefore, it is important to develop new therapeutic targets and intervention strategies during early stages of chronic kidney disease. The widespread application of liquid biopsy has led to an increasing number of studies concerning the roles of cell-free DNA (cfDNA) in kidney disease. In this review, we summarize relevant studies concerning the roles of cfDNA in kidney disease and describe various strategies for targeted removal of cfDNA, with the goal of establishing novel therapeutic approaches for kidney disease.

Correction to: YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which has a close relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) plays an important role not only in regulating the fibrosis process but also in maintaining the mitochondrial function of pancreatic β-cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG up-regulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose-cultured HK-2 cells and 8-weeks-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF.

Blockade of the mineralocorticoid receptor improves markers of human endothelial cell dysfunction and hematological indices in a mouse model of sickle cell disease

Increased endothelin-1 (ET-1) levels in patients with sickle cell disease (SCD) and transgenic mouse models of SCD contribute to disordered hematological, vascular, and inflammatory responses. Mineralocorticoid receptor (MR) activation by aldosterone, a critical component of the Renin-Angiotensin-Aldosterone-System, modulates inflammation and vascular reactivity, partly through increased ET-1 expression. However, the role of MR in SCD remains unclear. We hypothesized that MR blockade in transgenic SCD mice would reduce ET-1 levels, improve hematological parameters, and reduce inflammation. Berkeley SCD (BERK) mice, a model of severe SCD, were randomized to either sickle standard chow or chow containing the MR antagonist (MRA), eplerenone (156 mg/Kg), for 14 days. We found that MRA treatment reduced ET-1 plasma levels (p = .04), improved red cell density gradient profile (D50 ; p < .002), and increased mean corpuscular volume in both erythrocytes (p < .02) and reticulocytes (p < .024). MRA treatment also reduced the activity of the erythroid intermediate-conductance Ca2+ -activated K+ channel - KCa 3.1 (Gardos channel, KCNN4), reduced cardiac levels of mRNAs encoding ET-1, Tumor Necrosis Factor Receptor-1, and protein disulfide isomerase (PDI) (p < .01), and decreased plasma PDI and myeloperoxidase activity. Aldosterone (10-8  M for 24 h in vitro) also increased PDI mRNA levels (p < .01) and activity (p < .003) in EA.hy926 human endothelial cells, in a manner blocked by pre-incubation with the MRA canrenoic acid (1 μM; p < .001). Our results suggest a novel role for MR activation in SCD that may exacerbate SCD pathophysiology and clinical complications.

YY1 inactivated transcription co-regulator PGC-1α to promote mitochondrial dysfunction of early diabetic nephropathy-associated tubulointerstitial fibrosis

The development of diabetic nephropathy (DN) could be promoted by the occurrence of tubulointerstitial fibrosis (TIF), which had a closely relationship with mitochondrial dysfunction of renal tubular epithelial cells (RTECs). As a key regulator of metabolic homeostasis, Yin Yang 1 (YY1) played an important role not only in regulating fibrosis process, but also in maintaining mitochondrial function of pancreatic β cells. However, it was not clear whether YY1 participated in maintaining mitochondrial function of RTECs in early DN-associated TIF. In this study, we dynamically detected mitochondrial functions and protein expression of YY1 in db/db mice and high glucose (HG)-cultured HK-2 cells. Our results showed that comparing with the occurrence of TIF, the emergence of mitochondrial dysfunction of RTECs was an earlier even, besides the up-regulated and nuclear translocated YY1. Correlation analysis showed YY1 expressions were negatively associated with PGC-1α in vitro and in vivo. Further mechanism research demonstrated the formation of mTOR-YY1 heterodimer induced by HG upregulated YY1, the nuclear translocation of which inactivated PGC-1α by binding to the PGC-1α promoter. Overexpression of YY1 induced mitochondrial dysfunctions in normal glucose cultured HK-2 cells and 8-week-old db/m mice. While, dysfunctional mitochondria induced by HG could be improved by knockdown of YY1. Finally, downregulation of YY1 could retard the progression of TIF by preventing mitochondrial functions, resulting in the improvement of epithelial-mesenchymal transition (EMT) in early DN. These findings suggested that YY1 was a novel regulator of mitochondrial function of RTECs and contributed to the occurrence of early DN-associated TIF .

The Entanglement between Mitochondrial DNA and Tumor Metastasis

Simple Summary

Mitochondrial dysfunction is one of the main features of cancer cells. As genetic material in mitochondria, mitochondrial DNA (mtDNA) variations and dysregulation of mitochondria-encoded genes have been shown to correlate with survival outcomes in cancer patients. Cancer metastasis is often a major cause of treatment failure, which is a multi-step cascade process. With the development of gene sequencing and in vivo modeling technology, the role of mtDNA in cancer metastasis has been continuously explored. Our review systematically provides a summary of the multiple roles of mtDNA in cancer metastasis and presents the broad prospects for mtDNA in cancer prediction and therapy.

Abstract

Mitochondrial DNA, the genetic material in mitochondria, encodes essential oxidative phosphorylation proteins and plays an important role in mitochondrial respiration and energy transfer. With the development of genome sequencing and the emergence of novel in vivo modeling techniques, the role of mtDNA in cancer biology is gaining more attention. Abnormalities of mtDNA result in not only mitochondrial dysfunction of the the cancer cells and malignant behaviors, but regulation of the tumor microenvironment, which becomes more aggressive. Here, we review the recent progress in the regulation of cancer metastasis using mtDNA and the underlying mechanisms, which may identify opportunities for finding novel cancer prediction and therapeutic targets.

Silent information regulator 1 suppresses epithelial-to-mesenchymal transition in lung cancer cells via its regulation of mitochondria status

AIMS

Silent information regulator 1 (SIRT1) is a NAD+-dependent protein-modifying enzyme involved in regulating gene expression, DNA damage repair, cell metabolism, and mitochondrial functions. Given that it acts as both a tumor promoter and suppressor, the complex mechanisms underlying SIRT1 signaling in cancer remain controversial. Epithelial-to-mesenchymal transition (EMT) plays a key role in the progression of carcinogenesis and tumors metastasis. Studies have shown that mitochondrial defects are critical in EMT process, and SIRT1 is found to regulate the generation and energy metabolism of mitochondria. Here, we elucidate a novel mechanism by which SIRT1 affects EMT in lung cancer cells via its regulation on mitochondria.

MAIN METHODS

SIRT1 signaling was detected in TGF-β1-induced EMT and was found to regulate mitochondria status, including mitochondrial biogenesis-related protein levels as detected by western blotting, mitochondrial structure observed by transmission electron microscopy, and respiratory functions analyzed by a respiration capacity assay. The effects of modulating SIRT1 expression on EMT and migration of lung cancer cells or normal cells were evaluated by in vitro and in vivo models.

KEY FINDINGS

We found that the regulation of SIRT1 signaling on the biogenesis or functions of mitochondria was critical to EMT. Overexpression of SIRT1 reduced EMT or metastasis potential of lung cancer cells by improving the quantity and quality of mitochondria, whereas silencing SIRT1 promote EMT in cancer cells, even in normal cells by disturbing mitochondria status.

SIGNIFICANCE

Consequently, SIRT1 is an attractive therapeutic target for reversing EMT or tumor metastasis.

Temporal characterization of mitochondrial impairment in the unilateral ureteral obstruction model in rats

Renal fibrosis is a well-known mechanism that favors chronic kidney disease (CKD) development in obstructive nephropathy, a significant pathology worldwide. Fibrosis induction involves several pathways, and although mitochondrial alterations have recently emerged as a critical factor that triggers renal damage in the obstructed kidney, the temporal mitochondrial alterations during the fibrotic induction remain unexplored. Therefore, in this work, we evaluated the time course of mitochondrial mass and bioenergetics alterations induced by a unilateral ureteral obstruction (UUO), a widely used model to study the mechanism involved in kidney fibrosis induction and progression. Our results show a marked reduction in mitochondrial oxidative phosphorylation (OXPHOS) in the obstructed kidney on days 7 to 28 of obstruction without significant mitochondrial coupling changes. Besides, we observed that mitochondrial mass was reduced, probably due to decreased biogenesis and mitophagy induction. OXPHOS impairment was associated with decreased mitochondrial biogenesis markers, the peroxisome proliferator-activated receptor γ co-activator-1alpha (PGC-1α), and nuclear respiratory factor 1 (NRF1); and also, with the induction of mitophagy in a PTEN-induced kinase 1 (PINK1) and Parkin independent way. It is concluded that the impairment of OXPHOS capacity may be explained by the reduction in mitochondrial biogenesis and the induction of mitophagy during fibrotic progression.

Longevity genes, cardiac ageing, and the pathogenesis of cardiomyopathy: implications for understanding the effects of current and future treatments for heart failure

The two primary molecular regulators of lifespan are sirtuin-1 (SIRT1) and mammalian target of rapamycin complex 1 (mTORC1). Each plays a central role in two highly interconnected pathways that modulate the balance between cellular growth and survival. The activation of SIRT1 [along with peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) and adenosine monophosphate-activated protein kinase (AMPK)] and the suppression of mTORC1 (along with its upstream regulator, Akt) act to prolong organismal longevity and retard cardiac ageing. Both activation of SIRT1/PGC-1α and inhibition of mTORC1 shifts the balance of cellular priorities so as to promote cardiomyocyte survival over growth, leading to cardioprotective effects in experimental models. These benefits may be related to direct actions to modulate oxidative stress, organellar function, proinflammatory pathways, and maladaptive hypertrophy. In addition, a primary shared benefit of both SIRT1/PGC-1α/AMPK activation and Akt/mTORC1 inhibition is the enhancement of autophagy, a lysosome-dependent degradative pathway, which clears the cytosol of dysfunctional organelles and misfolded proteins that drive the ageing process by increasing oxidative and endoplasmic reticulum stress. Autophagy underlies the ability of SIRT1/PGC-1α/AMPK activation and Akt/mTORC1 suppression to extend lifespan, mitigate cardiac ageing, alleviate cellular stress, and ameliorate the development and progression of cardiomyopathy; silencing of autophagy genes abolishes these benefits. Loss of SIRT1/PGC-1α/AMPK function or hyperactivation of Akt/mTORC1 is a consistent feature of experimental cardiomyopathy, and reversal of these abnormalities mitigates the development of heart failure. Interestingly, most treatments that have been shown to be clinically effective in the treatment of chronic heart failure with a reduced ejection fraction have been reported experimentally to exert favourable effects to activate SIRT1/PGC-1α/AMPK and/or suppress Akt/mTORC1, and thereby, to promote autophagic flux. Therefore, the impairment of autophagy resulting from derangements in longevity gene signalling is likely to represent a seminal event in the evolution and progression of cardiomyopathy.

Suppression of PGC-1α Drives Metabolic Dysfunction in TGFβ2-Induced EMT of Retinal Pigment Epithelial Cells

PGC-1α, a key orchestrator of mitochondrial metabolism, plays a crucial role in governing the energetically demanding needs of retinal pigment epithelial cells (RPE). We previously showed that silencing PGC-1α induced RPE to undergo an epithelial-mesenchymal-transition (EMT). Here, we show that induction of EMT in RPE using transforming growth factor-beta 2 (TGFβ2) suppressed PGC-1α expression. Correspondingly, TGFβ2 induced defects in mitochondrial network integrity with increased sphericity and fragmentation. TGFβ2 reduced expression of genes regulating mitochondrial dynamics, reduced citrate synthase activity and intracellular ATP content. High-resolution respirometry showed that TGFβ2 reduced mitochondrial OXPHOS levels consistent with reduced expression of NDUFB5. The reduced mitochondrial respiration was associated with a compensatory increase in glycolytic reserve, glucose uptake and gene expression of glycolytic enzymes (PFKFB3, PKM2, LDHA). Treatment with ZLN005, a selective small molecule activator of PGC-1α, blocked TGFβ2-induced upregulation of mesenchymal genes (αSMA, Snai1, CTGF, COL1A1) and TGFβ2-induced migration using the scratch wound assay. Our data show that EMT is accompanied by mitochondrial dysfunction and a metabolic shift towards reduced OXPHOS and increased glycolysis that may be driven by PGC-1α suppression. ZLN005 effectively blocks EMT in RPE and thus serves as a novel therapeutic avenue for treatment of subretinal fibrosis.

Adipocyte-Mineralocorticoid Receptor Alters Mitochondrial Quality Control Leading to Mitochondrial Dysfunction and Senescence of Visceral Adipose Tissue

Mineralocorticoid receptor (MR) expression is increased in the adipose tissue (AT) of obese patients and animals. We previously demonstrated that adipocyte-MR overexpression in mice (Adipo-MROE mice) is associated with metabolic alterations. Moreover, we showed that MR regulates mitochondrial dysfunction and cellular senescence in the visceral AT of obese db/db mice. Our hypothesis is that adipocyte-MR overactivation triggers mitochondrial dysfunction and cellular senescence, through increased mitochondrial oxidative stress (OS). Using the Adipo-MROE mice with conditional adipocyte-MR expression, we evaluated the specific effects of adipocyte-MR on global and mitochondrial OS, as well as on OS-induced damage. Mitochondrial function was assessed by high throughput respirometry. Molecular mechanisms were probed in AT focusing on mitochondrial quality control and senescence markers. Adipo-MROE mice exhibited increased mitochondrial OS and altered mitochondrial respiration, associated with reduced biogenesis and increased fission. This was associated with OS-induced DNA-damage and AT premature senescence. In conclusion, targeted adipocyte-MR overexpression leads to an imbalance in mitochondrial dynamics and regeneration, to mitochondrial dysfunction and to ageing in visceral AT. These data bring new insights into the MR-dependent AT dysfunction in obesity.

Connexin 43 prevents the progression of diabetic renal tubulointerstitial fibrosis by regulating the SIRT1-HIF-1α signaling pathway

Hyperglycemia-induced renal epithelial-to-mesenchymal transition (EMT) is a key pathological factor in diabetic renal tubulointerstitial fibrosis (RIF). Our previous studies have shown that connexin 43 (Cx43) activation attenuated the development of diabetic renal fibrosis. However, whether Cx43 regulates the EMT of renal tubular epithelial cells (TECs) and the pathological process of RIF under the diabetic conditions remains to be elucidated. In the present study, we identified that Cx43 protein expression was down-regulated in the kidney tissues of db/db mice as well as in high glucose (HG)-induced NRK-52E cells. Overexpression of Cx43 improved renal function in db/db spontaneous diabetic model mice, increased SIRT1 levels, decreased hypoxia-inducible factor (HIF)-1α expression, and reduced production of EMT markers and extracellular matrix (ECM) components. Additionally, Cx43 overexpression inhibited the EMT process and reduced the expression of ECM components such as fibronectin (FN), Collagen I, and Collagen IV in HG-induced NRK-52E cells, whereas Cx43 deficiency had the opposite effects. Mechanistically, Cx43 in a carboxyl-terminal signal transduction-dependent manner could up-regulate SIRT1 expression and enhance SIRT1-dependent deacetylation of HIF-1α to reduce HIF-1α activity, which eventually ameliorated renal EMT and diabetic RIF. Our study indicates the essential role of Cx43 in regulating renal EMT and diabetic RIF via regulating the SIRT1-HIF-1α signaling pathway and provides an experimental basis for Cx43 as a potential target for diabetic nephropathy (DN).

Mitochondrial ROS promote mitochondrial dysfunction and inflammation in ischemic acute kidney injury by disrupting TFAM-mediated mtDNA maintenance

Aims: Ischemia-reperfusion injury (IRI)-induced acute kidney injury (IRI-AKI) is characterized by elevated levels of reactive oxygen species (ROS), mitochondrial dysfunction, and inflammation, but the potential link among these features remains unclear. In this study, we aimed to investigate the specific role of mitochondrial ROS (mtROS) in initiating mitochondrial DNA (mtDNA) damage and inflammation during IRI-AKI. Methods: The changes in renal function, mitochondrial function, and inflammation in IRI-AKI mice with or without mtROS inhibition were analyzed in vivo. The impact of mtROS on TFAM (mitochondrial transcription factor A), Lon protease, mtDNA, mitochondrial respiration, and cytokine release was analyzed in renal tubular cells in vitro. The effects of TFAM knockdown on mtDNA, mitochondrial function, and cytokine release were also analyzed in vitro. Finally, changes in TFAM and mtDNA nucleoids were measured in kidney samples from IRI-AKI mice and patients. Results: Decreasing mtROS levels attenuated renal dysfunction, mitochondrial damage, and inflammation in IRI-AKI mice. Decreasing mtROS levels also reversed the decrease in TFAM levels and mtDNA copy number that occurs in HK2 cells under oxidative stress. mtROS reduced the abundance of mitochondrial TFAM in HK2 cells by suppressing its transcription and promoting Lon-mediated TFAM degradation. Silencing of TFAM abolished the Mito-Tempo (MT)-induced rescue of mitochondrial function and cytokine release in HK2 cells under oxidative stress. Loss of TFAM and mtDNA damage were found in kidneys from IRI-AKI mice and AKI patients. Conclusion: mtROS can promote renal injury by suppressing TFAM-mediated mtDNA maintenance, resulting in decreased mitochondrial energy metabolism and increased cytokine release. TFAM defects may be a promising target for renal repair after IRI-AKI.

Transcriptome Analysis of Juvenile Tilapia (Oreochromis niloticus) Blood, Fed With Different Concentrations of Resveratrol

Oreochromis niloticus (genetically improved farmed tilapia, GIFT) often bites the root of Polygonum cuspidatum when it is used as a floating bed, and resveratrol (RES) is mainly accumulated in the root of P. cuspidatum. Blood acts as a pipeline for the fish immune system. Generating blood transcriptomic resources is crucial for understanding molecular mechanisms underlying blood immune responses. In this study, we determined the effects of RES administration on blood transcriptomic response in GIFT. With increasing RES concentration, 133 (0.025 vs. 0.05 g/kg RES), 155 (0.025 vs. 0.1 g/kg RES), and 123 (0.05 vs. 0.1 g/kg RES) genes were detected as significant differentially expressed genes (DEGs). Three and ninety-five shared significant DEGs were found to be enriched among the three (except 0.1 g/kg RES) and four groups (0, 0.025, 0.05, and 0.1 g/kg RES), respectively. To determine the relationship between mitochondrial regulation and RES supplementation, the results of RNA-Seq were analyzed and nine mitochondria-related genes (ATP synthase or mitochondrial-function-related genes) were verified. The results revealed the same expression pattern: cytochrome c isoform X2 (cox2), katanin p60 ATPase-containing subunit A1 isoform X1 (katna1), plasma membrane calcium-transporting ATPase 1-like (atp2b1) and GTP-binding protein A-like (gtpbpal) showed the highest expression in the 0.1 g/kg RES group, while NADH dehydrogenase [ubiquinone] iron-sulfur protein 2 mitochondrial (nad7), ATP synthase subunit beta, mitochondrial (atpb), ATP synthase subunit alpha, mitochondrial-like (atpal), ATP synthase subunit alpha, mitochondrial (atpa) and ATP-dependent Clp protease proteolytic subunit, mitochondrial (clpp) revealed a dose-dependent expression following RES supplementation. Blood Ca²⁺-ATPase activity, and malondialdehyde, glutathione, and ATP content were significantly increased in the 0.05 (except Ca²⁺-ATPase activity), 0.1 g/kg RES group when compared with the controls. Eighty-nine shared DGEs were mainly enriched in antigen processing and presentation, cell adhesion molecules and phagosome pathways, based on the comparison between previous reported hepatic and the present blood transcriptome. Our study demonstrated that RES supplementation might improve the resistance to metabolism dysfunction via mitochondrial energy synthesis and/or the respiratory chain (e.g., ATPase).

Cellular Senescence in Kidney Fibrosis: Pathologic Significance and Therapeutic Strategies

Age-related disorders such as chronic kidney disease (CKD) are increasingly prevalent globally and pose unprecedented challenges. In many aspects, CKD can be viewed as a state of accelerated and premature aging. Aging kidney and CKD share many common characteristic features with increased cellular senescence, a conserved program characterized by an irreversible cell cycle arrest with altered transcriptome and secretome. While developmental senescence and acute senescence may positively contribute to the fine-tuning of embryogenesis and injury repair, chronic senescence, when unresolved promptly, plays a crucial role in kidney fibrogenesis and CKD progression. Senescent cells elicit their fibrogenic actions primarily by secreting an assortment of inflammatory and profibrotic factors known as the senescence-associated secretory phenotype (SASP). Increasing evidence indicates that senescent cells could be a promising new target for therapeutic intervention known as senotherapy, which includes depleting senescent cells, modulating SASP and restoration of senescence inhibitors. In this review, we discuss current understanding of the role and mechanism of cellular senescence in kidney fibrosis. We also highlight potential options of targeting senescent cells for the treatment of CKD.

Loss of Mitochondrial Control Impacts Renal Health

Disruption of mitochondrial biosynthesis or dynamics, or loss of control over mitochondrial regulation leads to a significant alteration in fuel preference and metabolic shifts that potentially affect the health of kidney cells. Mitochondria regulate metabolic networks which affect multiple cellular processes. Indeed, mitochondria have established themselves as therapeutic targets in several diseases. The importance of mitochondria in regulating the pathogenesis of several diseases has been recognized, however, there is limited understanding of mitochondrial biology in the kidney. This review provides an overview of mitochondrial dysfunction in kidney diseases. We describe the importance of mitochondria and mitochondrial sirtuins in the regulation of renal metabolic shifts in diverse cells types, and review this loss of control leads to increased cell-to-cell transdifferentiation processes and myofibroblast-metabolic shifts, which affect the pathophysiology of several kidney diseases. In addition, we examine mitochondrial-targeted therapeutic agents that offer potential leads in combating kidney diseases.

Targeting energy pathways in kidney disease: the roles of sirtuins, AMPK, and PGC1α

The kidney has extraordinary metabolic demands to sustain the active transport of solutes that is critical to renal filtration and clearance. Mitochondrial health is vital to meet those demands and maintain renal fitness. Decades of studies have linked poor mitochondrial health to kidney disease. Key regulators of mitochondrial health-adenosine monophosphate kinase, sirtuins, and peroxisome proliferator-activated receptor γ coactivator-1α-have all been shown to play significant roles in renal resilience against disease. This review will summarize the latest research into the activities of those regulators and evaluate the roles and therapeutic potential of targeting those regulators in acute kidney injury, glomerular kidney disease, and renal fibrosis.

The inhibition of eIF5A hypusination by GC7, a preconditioning protocol to prevent brain death-induced renal injuries in a preclinical porcine kidney transplantation model

The eIF5A hypusination inhibitor GC7 (N1-guanyl-1,7-diaminoheptane) was shown to protect from ischemic injuries. We hypothesized that GC7 could be useful for preconditioning kidneys from donors before transplantation. Using a preclinical porcine brain death (BD) donation model, we carried out in vivo evaluation of GC7 pretreatment (3 mg/kg iv, 5 minutes after BD) at the beginning of the 4h-donor management, after which kidneys were collected and cold-stored (18h in University of Wisconsin solution) and 1 was allotransplanted. Groups were defined as following (n = 6 per group): healthy (CTL), untreated BD (Vehicle), and GC7-treated BD (Vehicle + GC7). At the end of 4h-management, GC7 treatment decreased BD-induced markers, as radical oxygen species markers. In addition, GC7 increased expression of mitochondrial protective peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC1α) and antioxidant proteins (superoxyde-dismutase-2, heme oxygenase-1, nuclear factor [erythroid-derived 2]-like 2 [NRF2], and sirtuins). At the end of cold storage, GC7 treatment induced an increase of NRF2 and PGC1α mRNA and a better mitochondrial integrity/homeostasis with a decrease of dynamin- related protein-1 activation and increase of mitofusin-2. Moreover, GC7 treatment significantly improved kidney outcome during 90 days follow-up after transplantation (fewer creatininemia and fibrosis). Overall, GC7 treatment was shown to be protective for kidneys against BD-induced injuries during donor management and subsequently appeared to preserve antioxidant defenses and mitochondria homeostasis; these protective effects being accompanied by a better transplantation outcome.

Mitochondrial dysfunction and endoplasmic reticulum stress in the promotion of fibrosis in obstructive nephropathy induced by unilateral ureteral obstruction

Obstructive nephropathy favors the progression to chronic kidney disease (CKD), a severe health problem worldwide. The unilateral ureteral obstruction (UUO) model is used to study the development of fibrosis. Impairment of renal mitochondria plays a crucial role in several types of CKD and has been strongly related to fibrosis onset. Nevertheless, in the UUO model, the impairment of mitochondria, their relationship with endoplasmic reticulum (ER) stress induction and the participation of both to induce the fibrotic process remain unclear. In this review, we summarize the current information about mitochondrial bioenergetics, redox dynamics, mitochondrial mass, and biogenesis alterations, as well as the relationship of these mitochondrial alterations with ER stress and their participation in fibrotic processes in UUO models. Early after obstruction, there is metabolic reprogramming related to mitochondrial fatty acid β-oxidation impairment, triggering lipid deposition, oxidative stress, (calcium) Ca²⁺ dysregulation, and a reduction in mitochondrial mass and biogenesis. Mitochondria and the ER establish a pathological feedback loop that promotes the impairment of both organelles by ER stress pathways and Ca²⁺ levels dysregulation. Preserving mitochondrial and ER function can prevent or at least delay the fibrotic process and loss of renal function. However, deeper understanding is still necessary for future clinically-useful therapies.

LncRNA Mical2/miR-203a-3p sponge participates in epithelial-mesenchymal transition by targeting p66Shc in liver fibrosis

Epithelial-mesenchymal transition (EMT) is regulated by reactive oxygen species (ROS) in liver fibrosis. p66Shc is a redox enzyme, but its role of EMT is unclear in liver fibrosis. Long noncoding RNAs (lncRNAs) have been implicated as important regulators in numerous physiological and pathological processes and generally acting as a microRNA (miRNA) sponge to regulate gene expression. The aim of the current study was to evaluate the contribution of p66Shc to EMT in liver fibrosis and the regulation of p66Shc by lncRNA sponge. In vivo, p66Shc silencing prevented carbon tetrachloride (CCl₄)-induced EMT as evidenced by the upregulation of E-cadherin, downregulation of Vimentin and N-cadherin, and inhibition of oxidative stress and extracellular matrix (ECM) components. Moreover, in vitro, TGF-β1 significantly enhanced ECM components, as well as the development of the EMT phenotype. These effects were abrogated by p66Shc downregulation and aggravated by p66Shc overexpression. Mechanistically, p66Shc contributed to EMT via mediating ROS, as evidenced by p66Shc downregulation inhibiting EMT under exogenous hydrogen peroxide (H₂O₂) stimulation. Furthermore, we found that molecule interacting with CasL2 (Mical2) lncRNA functioned as an endogenous miR-203a-3p sponge to regulate p66Shc expression. Both Mical2 silencing and miR-203a-3p agomiR treatment downregulated p66Shc expression, thus suppressing EMT in vivo and in vitro. Notably, the increased p66Shc and Mical2 levels and decreased miR-203a-3p levels in murine fibrosis were consistent with those in patients with liver fibrosis. In sum, our study reveals that p66Shc is critical for liver fibrosis and that Mical2, miR-203a-3p and p66Shc compose a novel regulatory pathway in liver fibrosis.

Chronic impairment of mitochondrial bioenergetics and β-oxidation promotes experimental AKI-to-CKD transition induced by folic acid

Recent studies suggest that mitochondrial bioenergetics and oxidative stress alterations may be common mechanisms involved in the progression of renal damage. However, the evolution of the mitochondrial alterations over time and the possible effects that their prevention could have in the progression of renal damage are not clear. Folic acid (FA)-induced kidney damage is a widely used experimental model to induce acute kidney injury (AKI), which can evolve to chronic kidney disease (CKD). Therefore, it has been extensively applied to study the mechanisms involved in AKI-to-CKD transition. We previously demonstrated that one day after FA administration, N-acetyl-cysteine (NAC) pre-administration prevented the development of AKI induced by FA. Such therapeutic effect was related to mitochondrial preservation. In the present study, we characterized the temporal course of mitochondrial bioenergetics and redox state alterations along the progression of renal damage induced by FA. Mitochondrial function was studied at different time points and showed a sustained impairment in oxidative phosphorylation capacity and a decrease in β-oxidation, decoupling, mitochondrial membrane potential depolarization and a pro-oxidative state, attributed to the reduction in activity of complexes I and III and mitochondrial cristae effacement, thus favoring the transition from AKI to CKD. Furthermore, the mitochondrial protection by NAC administration before AKI prevented not only the long-term deterioration of mitochondrial function at the chronic stage, but also CKD development. Taken together, our results support the idea that the prevention of mitochondrial dysfunction during an AKI event can be a useful strategy to prevent the transition to CKD.

The impact of mitochondrial quality control by Sirtuins on the treatment of type 2 diabetes and diabetic kidney disease

The incidence of type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD) has significantly increased worldwide in recent decades, and improved treatments for T2DM and DKD are urgently needed. The pathogenesis of aging-related disorders, such as T2DM and DKD, involves multiple mechanisms, including inflammation, autophagy impairment, and oxidative stress, which are closely associated with mitochondrial dysfunction. Therefore, mitochondrial quality control may be a novel therapeutic target for T2DM and DKD. Previous reports have shown that members of the mammalian Sirtuin family, SIRT 1-7, which are recognized as antiaging molecules, play a crucial role in the regulation of mitochondrial function and quality control through the modulation of oxidative stress, inflammation and autophagy. In this review, we summarized the research published in recent years to highlight the role of Sirtuins in mitochondrial quality control as a therapeutic target for T2DM and DKD.

C-X-C motif chemokine receptor 4 aggravates renal fibrosis through activating JAK/STAT/GSK3β/β-catenin pathway

Chronic kidney disease (CKD) has a high prevalence worldwide. Renal fibrosis is the common pathological feature in various types of CKD. However, the underlying mechanisms are not determined. Here, we adopted different CKD mouse models and cultured human proximal tubular cell line (HKC-8) to examine the expression of C-X-C motif chemokine receptor 4 (CXCR4) and β-catenin signalling, as well as their relationship in renal fibrosis. In CKD mice and humans with a variety of nephropathies, CXCR4 was dramatically up-regulated in tubules, with a concomitant activation of β-catenin. CXCR4 expression level was positively correlated with the expression of β-catenin target MMP-7. AMD3100, a CXCR4 receptor blocker, and gene knockdown of CXCR4 significantly inhibited the activation of JAK/STAT and β-catenin signalling, protected against tubular injury and renal fibrosis. CXCR4-induced renal fibrosis was inhibited by treatment with ICG-001, an inhibitor of β-catenin signalling. In HKC-8 cells, overexpression of CXCR4 induced activation of β-catenin and deteriorated cell injury. These effects were inhibited by ICG-001. Stromal cell-derived factor (SDF)-1α, the ligand of CXCR4, stimulated the activation of JAK2/STAT3 and JAK3/STAT6 signalling in HKC-8 cells. Overexpression of STAT3 or STAT6 decreased the abundance of GSK3β mRNA. Silencing of STAT3 or STAT6 significantly blocked SDF-1α-induced activation of β-catenin and fibrotic lesions. These results uncover a novel mechanistic linkage between CXCR4 and β-catenin activation in renal fibrosis in association with JAK/STAT/GSK3β pathway. Our studies also suggest that targeted inhibition of CXCR4 may provide better therapeutic effects on renal fibrosis by inhibiting multiple downstream signalling cascades.

Clinical relevance of cell-free mitochondrial DNA during the early postoperative period in kidney transplant recipients

Recent studies indicate that urinary mitochondrial DNA (mtDNA) is predictive of ischemic AKI and is related to delayed graft function (DGF) in renal transplantation. Nevertheless, the clinical implications and prognostic value of urinary mtDNA in kidney transplantation remain undetermined. Here, we aimed to evaluate the associations between cell-free mtDNA and clinical parameters, including pathological findings in allograft biopsy and post-transplant renal function. A total of 85 renal transplant recipients were enrolled, and blood and urine samples were collected at a median of 17 days after transplantation. Cell-free nuclear and mtDNA levels were measured by quantitative polymerase chain reaction for LPL and ND1 genes. Urinary cell-free mtDNA levels were significantly higher in patients with DGF (P < 0.001) and cases of deceased donor transplantation (P < 0.001). The subjects with acute rejection showed higher urinary mtDNA levels than those without abnormalities (P = 0.043). In addition, allograft functions at 9- and 12-month post-transplantation were significantly different between tertile groups of mtDNA independent of the presence of DGF or acute rejection, showing significantly better graft outcome in the lowest tertile group. Urinary cell-free mtDNA levels during the early post-transplant period are significantly associated with DGF, acute rejection in graft biopsy, and short-term post-transplant renal function.

Metabolic adaptations in spontaneously immortalized PGC-1α knock-out mouse embryonic fibroblasts increase their oncogenic potential

PGC-1α controls, to a large extent, the capacity of cells to respond to changing nutritional requirements and energetic demands. The key role of metabolic reprogramming in tumor development has highlighted the potential role of PGC-1α in cancer. To investigate how loss of PGC-1α activity in primary cells impacts the oncogenic characteristics of spontaneously immortalized cells, and the mechanisms involved, we used the classic 3T3 protocol to generate spontaneously immortalized mouse embryonic fibroblasts (iMEFs) from wild-type (WT) and PGC-1α knockout (KO) mice and analyzed their oncogenic potential in vivo and in vitro. We found that PGC-1α KO iMEFs formed larger and more proliferative primary tumors than WT counterparts, and fostered the formation of lung metastasis by B16 melanoma cells. These characteristics were associated with the reduced capacity of KO iMEFs to respond to cell contact inhibition, in addition to an increased ability to form colonies in soft agar, an enhanced migratory capacity, and a reduced growth factor dependence. The mechanistic basis of this phenotype is likely associated with the observed higher levels of nuclear β-catenin and c-myc in KO iMEFs. Evaluation of the metabolic adaptations of the immortalized cell lines identified a decrease in oxidative metabolism and an increase in glycolytic flux in KO iMEFs, which were also more dependent on glutamine for their survival. Furthermore, glucose oxidation and tricarboxylic acid cycle forward flux were reduced in KO iMEF, resulting in the induction of compensatory anaplerotic pathways. Indeed, analysis of amino acid and lipid patterns supported the efficient use of tricarboxylic acid cycle intermediates to synthesize lipids and proteins to support elevated cell growth rates. All these characteristics have been observed in aggressive tumors and support a tumor suppressor role for PGC-1α, restraining metabolic adaptations in cancer.

Urinary cell-free mitochondrial and nuclear deoxyribonucleic acid correlates with the prognosis of chronic kidney diseases

Introduction

Cell-free deoxyribonucleic acid DNA (cf-DNA) in urine is promising due to the advantage of urine as an easily obtained and non-invasive sample source over tissue and blood. In clinical practice, it is important to identify non-invasive biomarkers of chronic kidney disease (CKD) in monitoring and surveillance of disease progression. Information is limited, however, regarding the relationship between urine and plasma cf-DNA and the renal outcome in CKD patients.

Methods

One hundred and thirty-one CKD patients were enrolled between January 2016 and September 2018. Baseline urine and plasma cell-free mitochondrial DNA (cf-mtDNA) and cell-free nuclear DNA (cf-nDNA) were isolated using quantitative real-time PCR. Estimated glomerular filtration rate (eGFR) measurement was performed at baseline and 6-month follow-up. Favorable renal outcome was defined as eGFR at 6 months minus baseline eGFR> = 0. Receiver operator characteristics (ROC) curve analysis was performed to assess different samples of cf-DNA to predict favorable renal outcomes at 6 months. A multivariate linear regression model was used to evaluate independent associations between possible predictors and different samples of cf-DNA.

Results

Patients with an advanced stage of CKD has significantly low plasma cf-nDNA and high plasma neutrophil gelatinase-associated lipocalin (NGAL) levels. Low urine cf-mtDNA, cf-nDNA levels and low plasma NGAL were significantly correlated with favorable renal outcomes at 6 months. The urine albumin-creatinine ratio (ACR) or urine protein-creatinine ratio (PCR) level is a robust predictor of cf-mtDNA and cf-nDNA in CKD patients. Baseline urine levels of cf-mtDNA and cf-nDNA could predict renal outcomes at 6 months.

Conclusions

Urinary cf-mtDNA and cf-nDNA may provide novel prognostic biomarkers for renal outcome in CKD patients. The levels of plasma cf-nDNA and plasma NGAL are significantly correlated with the severity of CKD.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1549-x) contains supplementary material, which is available to authorized users.

Urinary mitochondrial DNA level is an indicator of intra-renal mitochondrial depletion and renal scarring in diabetic nephropathy

Background

Mitochondrial dysfunction plays an important role in the pathogenesis and progression of diabetic nephropathy (DN). We study the relation between urinary and intra-renal mitochondrial deoxyribonucleic acid (mtDNA) levels and renal dysfunction in DN.

Methods

We recruited 92 patients with biopsy-proven DN. Urinary sediment, urinary supernatant and intra-renal mtDNA levels were measured and compared with baseline renal biopsy, kidney scarring and renal function decline in the subsequent 24 months.

Results

mtDNA could be detected in all urine supernatant, urine sediment and renal biopsy specimens. There was a modest but statistically significant inverse correlation between urinary supernatant and intra-renal mtDNA levels (r = -0.453, P = 0.012). Urinary supernatant mtDNA level had modest but statistically significant correlations, inversely with estimated glomerular filtration rate (r = -0.214, P = 0.04), and positively with interstitial fibrosis (r = 0.300, P = 0.005). Intra-renal mtDNA had significant inverse correlation with interstitial fibrosis (r = -0.537, P = 0.003). However, there was no significant relation between renal function decline and urinary supernatant, urinary sediment or intra-renal mtDNA levels.

Conclusions

mtDNA is readily detectable in urinary supernatant and kidney tissue, and their levels correlate with renal function and scarring in DN. Further studies are needed to determine the accuracy of urinary supernatant mtDNA level as a prognostic indicator of DN, as well as its role in other kidney diseases.

Adrenal βarrestin1 targeting for tobacco-associated cardiac dysfunction treatment: Aldosterone production as the mechanistic link

Tobacco kills 6 million people annually and its global health costs are continuously rising. The main addictive component of every tobacco product is nicotine. Among the mechanisms by which nicotine, and its major metabolite, cotinine, contribute to heart disease is the renin-angiotensin-aldosterone system (RAAS) activation. This increases aldosterone production from the adrenals and circulating aldosterone levels. Aldosterone is a mineralocorticoid hormone with various direct harmful effects on the myocardium, including increased reactive oxygen species (ROS) generation, which contributes significantly to cardiac mitochondrial dysfunction and cardiac aging. Aldosterone is produced in the adrenocortical zona glomerulosa (AZG) cells in response to angiotensin II (AngII), activating its type 1 receptor (AT1R). The AT1R is a G protein-coupled receptor (GPCR) that leads to aldosterone biosynthesis and secretion, via signaling from both Gq/11 proteins and the GPCR adapter protein βarrestin1, in AZG cells. Adrenal βarrestin1 is essential for AngII-dependent adrenal aldosterone production, which aggravates heart disease. Since adrenal βarrestin1 is essential for raising circulating aldosterone in the body and tobacco compounds are also known to elevate aldosterone levels in smokers, accelerating heart disease progression, our central hypothesis is that nicotine and cotinine increase aldosterone levels to induce cardiac injury by stimulating adrenal βarrestin1. In the present review, we provide an overview of the current literature of the physiology and pharmacology of adrenal aldosterone production regulation, of the effects of tobacco on this process and, finally, of the effects of tobacco and aldosterone on cardiac structure and function, with a particular focus on cardiac mitochondrial function. We conclude our literature account with a brief experimental outline, as well as with some therapeutic perspectives of our pharmacological hypothesis, that is that adrenal βarrestin1 is a novel molecular target for preventing tobacco-induced hyperaldosteronism, thereby also ameliorating tobacco-related heart disease development.

Mitochondrial dysfunction in diabetic kidney disease

Although diabetic kidney disease (DKD) is the most common cause of end-stage kidney disease worldwide, the pathogenic mechanisms are poorly understood. There is increasing evidence that mitochondrial dysfunction contributes to the development and progression of DKD. Because the kidney is the organ with the second highest oxygen consumption in our body, it is distinctly sensitive to mitochondrial dysfunction. Mitochondrial dysfunction contributes to the progression of chronic kidney disease irrespective of underlying cause. More importantly, high plasma glucose directly damages renal tubular cells, resulting in a wide range of metabolic and cellular dysfunction. Overproduction of reactive oxygen species (ROS), activation of apoptotic pathway, and defective mitophagy are interlinked mechanisms that play pivotal roles in the progression of DKD. Although renal tubular cells have the highest mitochondrial content, podocytes, mesangial cells, and glomerular endothelial cells may all be affected by diabetes-induced mitochondrial injury. Urinary mitochondrial DNA (mtDNA) is readily detectable and may serve as a marker of mitochondrial damage in DKD. Unfortunately, pharmacologic modulation of mitochondrial dysfunction for the treatment of DKD is still in its infancy. Nonetheless, understanding the pathobiology of mitochondrial dysfunction in DKD would facilitate the development of novel therapeutic strategies.

A potential role of the renin-angiotensin-aldosterone system in epithelial-to-mesenchymal transition-induced renal abnormalities: Mechanisms and therapeutic implications

Epithelial-to-mesenchymal transition (EMT) is an orchestrated event where epithelial cells progressively undergo biochemical changes and transition into mesenchymal-like cells by gradually losing their epithelial characteristics. EMT plays a crucial pathologic role in renal abnormalities, especially renal fibrosis. A number of bench studies suggest the potential involvement of renin-angiotensin-aldosterone system (RAAS) in renal EMT process and associated renal abnormalities. EMT appears to be an important pathologic mechanism for the deleterious renal effects of angiotensin II and aldosterone, the two major RAAS components. Mechanistically, the renal RAAS-TGF-β-Smad3 signalling pathway plays an important pathologic role in EMT-associated renal abnormalities. Intriguingly, the RAAS antagonists such as losartan, telmisartan, eplerenone, and spironolactone have the potential to prevent renal EMT in bench studies. This review describes the key mechanistic role of RAAS overactivation in EMT-induced renal abnormalities. Moreover, drugs interrupting the RAAS at different levels in the cascade ameliorating the EMT-associated renal abnormalities are described.

Aldosterone stimulation mediates cardiac metabolism remodeling via Sirt1/AMPK signaling in canine model

Aldosterone (Aldo), a pivotal hormone that is ubiquitously expressed in systemic tissues of mammals, is a crucial factor in the pathogenesis of cardiac disease. Accumulating evidence suggests that disturbances in cell energy metabolism are involved in increasing aldosterone levels. However, the precise mechanism underlying the impact of cardiac metabolic remodeling underlying aldosterone stimulation remains limited. In this work, we evaluated the underlying effect of aldosterone on regulating cardiac metabolism remodeling in a canine model. Fifteen beagle dogs were divided into a control group (n = 5), Aldo group (n = 5), and a group treated with spironolactone (SP), a mineralocorticoid receptor antagonist (n = 5), for 4 weeks. Blood pressure, electrocardiogram and respiratory parameters, H&E, Masson staining, ultrastructural changes, the adenosine triphosphate (ATP) and free fatty acid (FFA) levels of ventricular tissues, the level of mRNA, and the protein expression of key metabolic factors and regulators were assessed. The Sirt1/AMPK signaling pathway was significantly inhibited in the canine model of aldosterone stimulation, resulting in a reduction of the key downstream metabolic factors involved in glucose and fatty acid oxidation. The dysregulation of expression of key factors in glycogen metabolism led to glycogen deposition, an increase in FFA levels, a reduction in ATP levels, apoptosis, inflammatory cell infiltration, and mitochondrial damage in the ventricular myocardium. These effects were significantly restored by spironolactone. Aldosterone stimulation induced cardiac metabolic remodeling in ventricular cardiomyocytes possibly through the Sirt1/AMPK signaling pathway, implying that this pathway may provide a novel therapeutic target for cardiac metabolic remodeling.

PTEN-induced partial epithelial-mesenchymal transition drives diabetic kidney disease

Epithelial-mesenchymal transition (EMT) contributes significantly to interstitial matrix deposition in diabetic kidney disease (DKD). However, detection of EMT in kidney tissue is impracticable, and anti-EMT therapies have long been hindered. We reported that phosphatase and tensin homolog (PTEN) promoted transforming growth factor beta 1 (TGF-β), sonic hedgehog (SHH), connective tissue growth factor (CTGF), interleukin 6 (IL-6), and hyperglycemia-induced EMT when PTEN was modified by a MEX3C-catalyzed K27-linked polyubiquitination at lysine 80 (referred to as PTENK27-polyUb). Genetic inhibition of PTENK27-polyUb alleviated Col4a3 knockout-, folic acid-, and streptozotocin-induced (STZ-induced) kidney injury. Serum and urine PTENK27-polyUb concentrations were negatively correlated with glomerular filtration rate (GFR) for diabetic patients. Mechanistically, PTENK27-polyUb facilitated dephosphorylation and protein stabilization of TWIST, SNAI1, and YAP in renal epithelial cells, leading to enhanced EMT. We identified that a small molecule, triptolide, inhibited MEX3C-catalyzed PTENK27-polyUb and EMT of renal epithelial cells. Treatment with triptolide reduced TWIST, SNAI1, and YAP concurrently and improved kidney health in Col4a3 knockout-, folic acid-injured disease models and STZ-induced, BTBR ob/ob diabetic nephropathy models. Hence, we demonstrated the important role of PTENK27-polyUb in DKD and a promising therapeutic strategy that inhibited the progression of DKD.

p66Shc Contributes to Liver Fibrosis through the Regulation of Mitochondrial Reactive Oxygen Species

Background: p66Shc is a redox enzyme that mediates mitochondrial reactive oxygen species (ROS) generation. p66Shc inhibition confers protection against liver injury, however, its functional contribution to liver fibrosis remains unclear. The aim of this study is to explore the involvement of p66Shc in liver fibrosis and underlying mechanism of p66Shc by focusing on mitochondrial ROS. Methods: p66Shc-silenced mice were injected with carbon tetrachloride (CCl₄). Primary hepatic stellate cells (HSCs) were performed with p66Shc silencing or overexpression prior to TGF-β1 stimulation. Results: p66Shc expression was progressively elevated in mice with CCl₄-induced liver fibrosis, and p66Shc silencing in vivo significantly attenuated fibrosis development, reducing liver damage, oxidative stress and HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. Furthermore, in primary HSCs, p66Shc-mediated mitochondrial ROS production played a vital role in mitochondrial morphology and cellular metabolism. Knockdown of p66Shc significantly inhibited mitochondrial ROS production and NOD-like receptor protein 3 (NLRP3) inflammasome activation, which were closely associated with HSC activation, indicated by the decreased α-SMA, CTGF and TIMP1 levels. However, p66Shc overexpression exerted the opposite effects, which were suppressed by a specific mitochondrial ROS scavenger (mito-TEMPO). More importantly, p66Shc expression was significantly increased in human with liver fibrosis, accompanied by NLRP3 inflammasome activation. Conclusions: p66Shc is a key regulator of liver fibrosis by mediating mitochondrial ROS production, which triggers NLRP3 inflammasome activation.

SRT1720 retards renal fibrosis via inhibition of HIF1α /GLUT1 in diabetic nephropathy

Renal fibrosis is a major pathological characteristic of diabetic nephropathy (DN). Reportedly, increased SIRT1 expression played a renal protective role in animal models of DN. This study was designed to elucidate the molecular mechanisms underlying the protective effects of SRT1720, an SIRT1 activator, against diabetes-induced renal fibrosis. Type 2 diabetic mice (db/db) were treated with SRT1720 (50 mg/kg/d) by gavage for 10 weeks. Renal proximal tubular epithelial cells (HK-2 cells) were treated with high glucose (HG, 30 mM) in the presence or absence of SRT1720 (2.5 µM) for 48 h. We observed that impaired SIRT1 expression and activity were restored by SRT1720 administration in db/db mice as well as in HG-treated HK-2 cells. Moreover, SRT1720 administration improved renal function, attenuated glomerular hypertrophy, mesangial expansion, glomerulosclerosis and interstitial fibrosis, and inhibited TGFB1 and CTGF expressions and nuclear factor κB (NF-κB) activation in db/db mice. Similarly, HG-induced epithelial-to-mesenchymal transformation (EMT), and collagen IV and fibronectin expressions were inhibited in SRT1720 treated HK-2 cells. Mechanistic studies demonstrated that SRT1720 suppressed HIF1α, GLUT1 and SNAIL expressions both in vivo and in vitro. Furthermore, Hif1α or Glut1 knockdown effectively abrogated HG-induced EMT and collagen IV and fibronectin expressions in HK-2 cells. These findings suggest that SRT1720 prevented diabetes-induced renal fibrosis via the SIRT1/HIF1α/GLUT1/SNAIL pathway.

Mutation in Cytochrome B gene causes debility and adverse effects on health of sheep

Cytochrome B is the mitochondrial protein, which functions as part of the electron transport chain and is the main subunit of transmembrane cytochrome bc1 and b6f complexes affecting energy metabolism through oxidative phosphorylation. The present study was conducted to study the effect of mutation of Cytochrome B gene on the health condition of sheep, which the first report of association of mitochondrial gene with disease traits in livestock species. Non-synonymous substitutions (F33 L and D171N) and Indel mutations were observed for Cytochrome B gene, leading to a truncated protein, where anemia, malfunctioning of most of the vital organs as liver, kidney and mineral status was observed and debility with exercise intolerance and cardiomyopathy in extreme cases were depicted. These findings were confirmed by bioinformatics analysis, haematological and biochemical data analysis, and other phenotypical physiological data pertaining to different vital organs. The molecular mechanism of cytochrome B mutation was that the mutant variant interferes with the site of heme binding (iron containing) domain and calcium binding essential for electron transport chain. Mutation at amino acid site 33 is located within transmembrane helix A, a hydrophobic environment at the Qi site and close to heme binding domain, and mutation effects these domain and diseases occur. Thermodynamic stability was also observed to decrease in mutant variant. Sheep Cytochrome B being genetically more similar to the human, it may be used as a model for studying human diseases related to cytochrome B defects. Future prospect of the study includes the therapeutic application of recombinant protein, gene therapy and marker-assisted selection of disease-resistant livestock.

Role of Aldosterone in Renal Fibrosis

Aldosterone is a mineralocorticoid hormone, as its main renal effect has been considered as electrolyte and water homeostasis in the distal tubule, thus maintaining blood pressure and extracellular fluid homeostasis through the activation of mineralocorticoid receptor (MR) in epithelial cells. However, over the past decade, numerous studies have documented the significant role of aldosterone in the progression of chronic kidney disease (CKD) which has become a subject of interest. It is being studied that aldosterone can affect cardiovascular and renal system, thereby contributing to tissue inflammation, injury, glomerulosclerosis, and interstitial fibrosis. Aldosterone acts on renal vessels, renal cells (glomerular mesangial cells, podocytes, vascular smooth muscle cells, tubular epithelial cells, and interstitial fibroblasts), and infiltrating inflammatory cells, inducing reactive oxygen species (ROS) production, upregulated epithelial growth factor receptor (EGFR), and type 1 angiotensin (AT1) receptor expressions, and activating nuclear factor kappa B (NF-κB), activator protein-1 (AP-1), and EGFR to further promote cell proliferation, apoptosis, and proliferation. Phenotypic transformation of epithelial cells stimulates the expression of transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), osteopontin (OPN), and plasminogen activator inhibitor-1 (PAI-1), eventually leading to renal fibrosis. MR antagonisms are related to inhibition of aldosterone-mediated pro-inflammatory and pro-fibrotic effect. In this review, we will summarize the important role of aldosterone in the pathogenesis of renal injury and fibrosis, emphasizing on its multiple underlying mechanisms and advances in aldosterone research along with the potential therapeutics for targeting MR in a renal fibrosis.

Urinary mitochondrial DNA level as a biomarker of tissue injury in non-diabetic chronic kidney diseases

Background

Urinary mitochondrial DNA (mtDNA) fragment level has been proposed as a biomarker of chronic kidney disease (CKD). In this study, we determine the relation between urinary mtDNA level and rate of renal function deterioration in non-diabetic CKD.

Methods

We recruited 102 non-diabetic CKD patients (43 with kidney biopsy that showed non-specific nephrosclerosis). Urinary mtDNA level was measured and compared to baseline clinical and pathological parameters. The patients were followed 48.3 ± 31.8 months for renal events (need of dialysis or over 30% reduction in estimated glomerular filtration rate [eGFR]).

Results

The median urinary mtDNA level was 1519.42 (inter-quartile range 511.81–3073.03) million copy/mmol creatinine. There were significant correlations between urinary mtDNA level and baseline eGFR (r = 0.429, p < 0.001), proteinuria (r = 0.368, p < 0.001), severity of glomerulosclerosis (r = − 0.537, p < 0.001), and tubulointerstitial fibrosis (r = − 0.374, p = 0.014). The overall rate of eGFR decline was − 2.18 ± 5.94 ml/min/1.73m² per year. There was no significant correlation between the rate of eGFR decline and urinary mtDNA level. By univariate analysis, urinary mtDNA level predicts dialysis-free survival, but the result became insignificant after adjusting for clinical and histological confounding factors.

Conclusion

Urinary mtDNA levels have no significant association with the rate of renal function decline in non-diabetic CKD, although the levels correlate with baseline renal function, proteinuria, and the severity of histological damage. Urinary mtDNA level may be a surrogate marker of permanent renal damage in non-diabetic CKD.

Salvianolic Acid A Attenuates Endoplasmic Reticulum Stress and Protects Against Cholestasis-Induced Liver Fibrosis via the SIRT1/HSF1 Pathway

Background: Endoplasmic reticulum stress (ER stress) plays a critical role in the pathogenesis of liver fibrosis; thus, it can be a potential therapeutic target of fibrosis. However, the mechanism of ER stress regulation in fibrosis, particularly through sirtuin 1 (SIRT1), remains unclear. The objective of this study was to investigate the effect of SIRT1-mediated inhibition of ER stress in bile duct ligation (BDL)-induced liver fibrosis, and to explore the effect of salvianolic acid A (SalA) on BDL-induced liver fibrosis through SIRT1/heat shock factor 1 (HSF1) signaling. Materials and Methods: We explored the effects of SalA on liver fibrosis and ER stress in BDL-induced liver fibrosis in rats and the human hepatic stellate cell line LX2 cells. The LX2 cells were treated with 20 ng of platelet-derived growth factor-BB homodimer (PDGF-BB) for 24 h, and then incubated in the absence or presence of SalA (25 μM) for 24 h. Results: In vivo, SalA treatment alleviated BDL-induced liver injury and ER stress. Importantly, SalA treatment increased HSF1 expression and activity using a SIRT1-dependent mechanism. In LX2 cells, PDGF-BB induced ER stress and fibrosis were blocked by HSF1 overexpression. Furthermore, SIRT1 siRNA abrogated the SalA-mediated promotion of HSF1 deacetylation and expression, suggesting that SalA-mediated protection occurs by SIRT1 targeting HSF1 for deacetylation. Conclusion: This is the first study to identify the SIRT1/HSF1 pathway as a key therapeutic target for controlling BDL-induced liver fibrosis and to show that SalA confers protection against BDL- and PDGF-BB-induced hepatic fibrosis and ER stress through SIRT1-mediated HSF1 deacetylation.

Mitochondria-targeted antioxidant therapy for an animal model of PCOS-IR

Polycystic ovary syndrome (PCOS) is a common endocrine disorder with unknown etiology and unsatisfactory clinical treatment. Considering the ethical limitations of studies involving humans, animal models that reflect features of PCOS and insulin resistance (IR) are crucial resources in investigating this syndrome. Our previous study showed that mitochondrial dysfunction resulted from pathogenic mutations of mitochondrial DNA (mtDNA), and that oxidative stress had an active role in the phenotypic manifestation of PCOS-IR. Therefore, it was hypothesized that limiting oxidative stress and mitochondrial damage may be useful and effective for the clinical treatment of PCOS-IR. For this purpose, the present study examined the therapeutic effects of the mitochondria-targeted antioxidant MitoQ₁₀ for PCOS-IR. Furthermore, the histopathology was used to analysis the ovarian morphological changes. The endocrine and reproductive related parameters were analyzed by ELISA approach. A PCOS-IR model was successfully established by subcutaneous injection of rats with testosterone propionate and feeding a high-fat diet. The 30 female Sprague-Dawley rats were then divided into three groups, comprising a control (n=10), animal model (PCOS-IR, n=10) and MitoQ₁₀ treatment (n=10) group. It was found that MitoQ₁₀ significantly improved the IR condition and reversed the endocrine and reproductive conditions of PCOS. In addition, the impaired mitochondrial functions were improved following MitoQ₁₀ administration. Notably, western blot results suggested that this antioxidant reduced the expression levels of apoptosis-related proteins cytochrome c and B-cell lymphoma-2 (Bcl-2)-associated X protein, whereas the anti-apoptotic protein Bcl-extra large was increased following MitoQ₁₀ treatment. Taken together, the data indicated that the MitoQ₁₀ may have a beneficial favorable therapeutic effect on animals with PCOS-IR, most likely via the protection of mitochondrial functions and regulation of programmed cell death-related proteins.

PDE/cAMP/Epac/C/EBP-β Signaling Cascade Regulates Mitochondria Biogenesis of Tubular Epithelial Cells in Renal Fibrosis

AIMS

Cyclic adenosine 3'5'-monophosphate (cAMP) is a universal second messenger that plays an important role in intracellular signal transduction. cAMP is synthesized by adenylate cyclases from adenosine triphosphate and terminated by the phosphodiesterases (PDEs). In the present study, we investigated the role of the cAMP pathway in tubular epithelial cell mitochondrial biogenesis in the pathogenesis of renal fibrosis.

RESULTS

We found that the cAMP levels were decreased in fibrotic kidney tissues, and replenishing cAMP could ameliorate tubular atrophy and extracellular matrix deposition. The downregulation of cAMP was mainly attributed to the increased PDE4 expression in tubular epithelial cells. The inhibition of PDE4 by PDE4 siRNA or the specific inhibitor, rolipram, attenuated unilateral ureteral obstruction-induced renal interstitial fibrosis and transforming growth factor (TGF)-β1-stimulated primary tubular epithelial cell (PTC) damage. The Epac1/Rap1 pathway contributed to the main effect of cAMP on renal fibrosis. Rolipram could restore C/EBP-β and PGC-1α expression and protect the mitochondrial function and structure of PTCs under TGF-β1 stimulation. The antifibrotic role of rolipram in renal fibrosis relies on C/EBP-β and PGC-1α expression in tubular epithelial cells. Innovation and Conclusion: The results of the present study indicate that cAMP signaling regulates the mitochondrial biogenesis of tubular epithelial cells in renal fibrosis. Restoring cAMP by the PDE4 inhibitor rolipram may ameliorate renal fibrosis by targeting C/EBP-β/PGC1-α and mitochondrial biogenesis. Antioxid. Redox Signal. 29, 637-652.

The emerging role of aldosterone/mineralocorticoid receptors in the pathogenesis of erectile dysfunction

PURPOSE

Aldosterone is an old hormone that has been discovered for more than fifty years. The clinical application of its receptors' inhibitors, especially spirolactone, has benifited patients for decades worldwide. In this review, we briefly summarized the molecular mechanism of aldosterone/mineralocorticoid receptors (Ald-MRs) signaling in cardiovascular diseases and its emerging role in erectile dysfunction.

METHODS

We searched PubMed, Web of Science, and Scopus for manuscripts published prior to December 2017 using key words " aldosterone " AND " erectile dysfunction " OR " cardiovascular disease " OR " mineralocorticoid receptors ". Related literature and clinical perspectives were collated, summarized and discussed in this review.

RESULTS

The increase of reactive oxygen species production, inhibition of endothelial nitric oxide synthase system, and induction of inflammation are ubiquitous in vascular endothelial cells or vascular smooth muscle cells after the activation of Ald-MRs pathway. In addition, in cardiovascular diseases with over-active Ald-MRs signaling, MRs blockade could reverse the injury and improve the prognosis. Notably, multiple studies have correlated aldosterone and MRs to the pathogenesis of erectile function, while the mechanism is largely unperfectly identified.

CONCLUSION

In conclusion, we summarize the current evidence to highlight the potential role of aldosterone in erectile dysfunction and provide critical insights into the treatment of the disease.

Mitochondrial bioenergetics, redox state, dynamics and turnover alterations in renal mass reduction models of chronic kidney diseases and their possible implications in the progression of this illness

Nowadays, chronic kidney disease (CKD) is considered a worldwide public health problem. CKD is a term used to describe a set of pathologies that structurally and functionally affect the kidney, it is mostly characterized by the progressive loss of kidney function. Current therapeutic approaches are insufficient to avoid the development of this disease, which highlights the necessity of developing new strategies to reverse or at least delay CKD progression. Kidney is highly dependent on mitochondrial homeostasis and function, consequently, the idea that mitochondrial pathologies could play a pivotal role in the genesis and development of kidney diseases has risen. Although many research groups have recently published studies of mitochondrial function in acute kidney disease models, the existing information about CKD is still limited, especially in renal mass reduction (RMR) models. This paper focuses on reviewing current experimental information about the bioenergetics, dynamics (fission and fusion processes), turnover (mitophagy and biogenesis) and redox mitochondrial alterations in RMR, to discuss and integrate the mitochondrial changes triggered by nephron loss, as well as its relationship with loss of kidney function in CKD, in these models. Understanding these mechanisms would allow us to design new therapies that target these mitochondrial alterations.

Isolation, Characterization, And High Throughput Extracellular Flux Analysis of Mouse Primary Renal Tubular Epithelial Cells

Mitochondrial dysfunction in the renal tubular epithelial cells (TECs) can lead to renal fibrosis, a major cause of chronic kidney disease (CKD). Therefore, assessing mitochondrial function in primary TECs may provide valuable insight into the bioenergetic status of the cells, providing insight into the pathophysiology of CKD. While there are a number of complex protocols available for the isolation and purification of proximal tubules in different species, the field lacks a cost-effective method optimized for tubular cell isolation without the need for purification. Here, we provide an isolation protocol that allows for studies focusing on both primary mouse proximal and distal renal TECs. In addition to cost-effective reagents and minimal animal procedures required in this protocol, the isolated cells maintain high energy levels after isolation and can be sub-cultured up to four passages, allowing for continuous studies. Furthermore, using a high throughput extracellular flux analyzer, we assess the mitochondrial respiration directly in the isolated TECs in a 96-well plate for which we provide recommendations for the optimization of cell density and compound concentration. These observations suggest that this protocol can be used for renal tubular ex vivo studies with a consistent, well-standardized production of renal TECs. This protocol may have broader future applications to study mitochondrial dysfunction associated with renal disorders for drug discovery or drug characterization purposes.

Angiotensin II Stimulates the NLRP3 Inflammasome to Induce Podocyte Injury and Mitochondrial Dysfunction

Background

We previously reported that the NLRP3 inflammasome played an important role in mediating the podocyte injury induced by aldosterone. However, more studies on the role of the NLRP3 inflammasome in the pathogenesis of podocytopathy are still required. The present study was undertaken to study the role of the NLRP3 inflammasome in angiotensin II (Ang II)-induced podocyte injury, as well as the potential mechanisms.

Methods

In this study, we used an Ang II infusion model in NLRP3^-/- mice. In cultured podocytes, we used siRNA to silence NLRP3; then we treated the podocytes with Ang II.

Results

Following Ang II treatment, we found that the NLRP3 inflammasome was significantly activated in line with mitochondrial dysfunction in a dose- and time-dependent manner. Silencing NLRP3 by siRNA transfection ameliorated podocyte apoptosis, attenuated the loss of the podocyte proteins nephrin and podocin, and protected mitochondrial function. Ang II infusion activated the NLRP3 inflammasome, caused albuminuria, and induced podocyte damage, which was all blocked in the NLRP3^-/- mice. At the same time, NLRP3 deletion also ameliorated the mitochondrial dysfunction induced by Ang II infusion. However, the deletion of NLRP3 did not affect the Ang II hypertension.

Conclusion

Taken together, these results demonstrate an important role of the NLRP3 inflammasome in mediating Ang II-induced podocyte injury and mitochondrial dysfunction, suggesting that the NLRP3 inflammasome might be an effective therapeutic target against podocytopathy.

Urinary mitochondrial DNA level in non-diabetic chronic kidney diseases

BACKGROUND

Mitochondrial dysfunction plays an important role in the pathogenesis and progression of chronic kidney disease (CKD). We study the relation between urinary mitochondrial DNA (mtDNA) levels and renal dysfunction in non-diabetic CKD.

METHODS

We recruited 32 CKD patients (20 had hypertensive nephrosclerosis, 12 had IgA nephropathy). Urinary supernatant mtDNA level was measured and compared to baseline clinical and pathological parameters. The patients were followed 57.8 ± 30.5 months for renal function decline.

RESULTS

The average urinary supernatant mtDNA level was 222.0 ± 210.3 copy/μL. There was a modest but significant correlation between urinary mtDNA level and proteinuria (Spearman's r = 0.387, p = 0.035), but not any other baseline clinical or pathological parameter. Urinary mtDNA level had a significant inverse correlation with the slope of GFR decline (r = -0.402, p = 0.023). Urinary mtDNA level is a predictor of renal survival even after adjusting for baseline proteinuria with multivariate Cox analysis. In this model, every increase in urinary mtDNA by 100 copy/μL confers a 25.0% increase in risk of doubling of serum creatinine or need of dialysis (95%CI, 0.7% to 55.1%).

CONCLUSION

Mitochondrial DNA is readily detectable in the urinary supernatant of non-diabetic CKD, and its level correlates with the rate of renal function decline and predicts the risk of doubling of serum creatinine or need of dialysis. Further studies are needed to determine the value of urinary supernatant mtDNA level as a prognostic indicator of non-diabetic CKD.

Aldosterone Impairs Mitochondrial Function in Human Cardiac Fibroblasts via A-Kinase Anchor Protein 12

Aldosterone (Aldo) contributes to mitochondrial dysfunction and cardiac oxidative stress. Using a proteomic approach, A-kinase anchor protein (AKAP)-12 has been identified as a down-regulated protein by Aldo in human cardiac fibroblasts. We aim to characterize whether AKAP-12 down-regulation could be a deleterious mechanism which induces mitochondrial dysfunction and oxidative stress in cardiac cells. Aldo down-regulated AKAP-12 via its mineralocorticoid receptor, increased oxidative stress and induced mitochondrial dysfunction characterized by decreased mitochondrial-DNA and Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expressions in human cardiac fibroblasts. CRISPR/Cas9-mediated knock-down of AKAP-12 produced similar deleterious effects in human cardiac fibroblasts. CRISPR/Cas9-mediated activation of AKAP-12 blunted Aldo effects on mitochondrial dysfunction and oxidative stress in human cardiac fibroblasts. In Aldo-salt-treated rats, cardiac AKAP-12, mitochondrial-DNA and PGC-1α expressions were decreased and paralleled increased oxidative stress. In myocardial biopsies from patients with aortic stenosis (AS, n = 26), AKAP-12, mitochondrial-DNA and PGC-1α expressions were decreased as compared to Controls (n = 13). Circulating Aldo levels inversely correlated with cardiac AKAP-12. PGC-1α positively associated with AKAP-12 and with mitochondrial-DNA. Aldo decreased AKAP-12 expression, impairing mitochondrial biogenesis and increasing cardiac oxidative stress. AKAP-12 down-regulation triggered by Aldo may represent an important event in the development of mitochondrial dysfunction and cardiac oxidative stress.

Overexpressed cyclophilin B suppresses aldosterone-induced proximal tubular cell injury both in vitro and in vivo

The renin-angiotensin-aldosterone system (RAAS) is overactivated in patients with chronic kidney disease. Oxidative stress and endoplasmic reticulum stress (ERS) are two major mechanisms responsible for aldosterone-induced kidney injury. Cyclophilin (CYP) B is a chaperone protein that accelerates the rate of protein folding through its peptidyl-prolyl cis-trans isomerase (PPIase) activity. We report that overexpression of wild-type CYPB attenuated aldosterone-induced oxidative stress (evidenced by reduced production of reactive oxygen species and improved mitochondrial dysfunction), ERS (indicated by reduced expression of the ERS markers glucose-regulated protein 78 [GRP78] and C/-EBP homologous protein [CHOP]), and tubular cell apoptosis in comparison with aldosterone-induced human kidney-2 (HK-2) cells. The in vivo study also yielded similar results. Hence, CYPB performs a crucial function in protecting cells against aldosterone-induced oxidative stress, ERS, and tubular cell injury via its PPIase activity.

SIRT3 prevents angiotensin II-induced renal tubular epithelial-mesenchymal transition by ameliorating oxidative stress and mitochondrial dysfunction

Silent mating type information regulation 2 homolog 3 (SIRT3) is a major protective mediator that ameliorates oxidative stress and mitochondrial dysfunction, which are associated with the pathogenesis of epithelial-mesenchymal transition (EMT). The present study was aimed to investigate the potential role of SIRT3 in renal tubular EMT both in vitro and in vivo. Firstly, we showed that the expression of SIRT3 was repressed in angiotensin II-induced EMT. SIRT3 deficiency triggered EMT response, while over-expression of SIRT3 attenuated EMT response. In addition, over-expression of SIRT3 repressed AngⅡ-induced excessive production of mitochondrial superoxide, as well as mitochondrial dysfunction evidenced by the maintenance of mitochondrial number and morphology, and the stabilization of mitochondrial membrane potential. In conclusion, these findings identify a protective role of SIRT3 against angiotensin II-induced EMT in the kidney, and suggest SIRT3 upregulation is a potential therapeutic strategy for the treatment of renal tubulointerstitial fibrosis.

Comparison of acute kidney injury of different etiology reveals in-common mechanisms of tissue damage

Acute kidney injury (AKI) is a syndrome of reduced glomerular filtration rate and urine production caused by a number of different diseases. It is associated with renal tissue damage. This tissue damage can cause tubular atrophy and interstitial fibrosis that leads to nephron loss and progression of chronic kidney disease (CKD). This review describes the in-common mechanisms behind tissue damage in AKI caused by different underlying diseases. Comparing six high-quality microarray studies of renal gene expression after AKI in disease models (gram-negative sepsis, gram-positive sepsis, ischemia-reperfusion, malignant hypertension, rhabdomyolysis, and cisplatin toxicity) identified 5,254 differentially expressed genes in at least one of the AKI models; 66% of genes were found only in one model, showing that there are unique features to AKI depending on the underlying disease. There were in-common features in the form of four genes that were differentially expressed in all six models, 49 in at least five, and 215 were found in common between at least four models. Gene ontology enrichment analysis could be broadly categorized into the injurious processes hypoxia, oxidative stress, and inflammation, as well as the cellular outcomes of cell death and tissue remodeling in the form of epithelial-to-mesenchymal transition. Pathway analysis showed that MYC is a central connection in the network of activated genes in-common to AKI, which suggests that it may be a central regulator of renal gene expression in tissue injury during AKI. The outlining of this molecular network may be useful for understanding progression from AKI to CKD.