PGC-1α alleviates mitochondrial dysfunction via TFEB-mediated autophagy in cisplatin-induced acute kidney injury

GW1929 (an agonist of PPARγ) inhibits excessive production of reactive oxygen species in cisplatin-stimulated renal tubular epithelial cells, hampers cell apoptosis, and ameliorates renal injury

Cisplatin-induced nephrotoxicity has long been explored for development of preventative and therapeutic drugs. The current investigation focused on the renal protective effect of GW1929, an agonist for peroxisome proliferator-activated receptors gamma (PPARγ), on cisplatin-induced kidney injury. HK2 cells treated with 20 μM cisplatin and C57BL/6 mice injected with 20 mg/kg cisplatin were used as the cell model and animal model for acute kidney injury. HK2 cell viability after cisplatin or GW1929 (0-80 μM) treatment was tested using methyl thiazolyl tetrazolium assays. Flow cytometry analysis and TUNEL assays were used to measure cell apoptosis. Intracellular reactive oxygen species (ROS) level was measured through fluorescence intensities. Levels of blood urea nitrogen (BUN) and serum creatinine (SCr) were measured to evaluate the renal function of mice. For renal morphology observation and cell apoptosis assessment in vivo, hematoxylin-eosin staining and TUNEL assays were conducted. The concentrations of oxidative stress markers in renal samples were measured using colorimetric tests. It was found that GW1929 dose-dependently enhanced protein levels of PPARγ, PGC-1α and TFEB in HK2 cells. Meanwhile, intracellular ROS overproduction, the decrease in cell viability and excessive cell apoptosis mediated by cisplatin were reversed by GW1929. For in vivo experiments, GW1929 notably attenuated cisplatin-stimulated nephrotoxicity and oxidative stress while reducing BUN and Scr levels in cisplatin-challenged model mice. Moreover, GW1929 significantly dampened renal cell apoptosis in vivo. GW1929 mitigates renal tubular epithelial cell injury and renal damage by inhibiting oxidative stress and renal cell apoptosis.

From Rare Disorders of Kidney Tubules to Acute Renal Injury: Progress and Prospective

Background

Acute kidney injury (AKI) is a severe condition marked by rapid renal function deterioration and elevated mortality, with traditional biomarkers lacking sensitivity and specificity. Rare tubulointerstitial diseases encompass a spectrum of disorders, primarily including monogenic diseases, immune-related conditions, and drug-induced tubulointerstitial diseases. The clinical manifestations vary from electrolyte and acid-base imbalances to kidney function insufficiency, which is associated with AKI in up to 20% of cases. Evidence indicated that rare tubulointerstitial diseases might provide new conceptual insights and perspectives for novel biomarkers and potential therapeutic strategies for AKI.

Summary

Autosomal dominant tubulointerstitial kidney disease (ADTKD) and Fanconi syndrome (FS) are rare tubulointerstitial diseases. In ADTKD, UMOD and REN are closely related to AKI by affecting oxidative stress and tubuloglomerular feedback, which provide potential new biomarkers for AKI. Both rare tubulointerstitial diseases and AKI share etiologies and treatment responses. From the mechanism standpoint, rare tubulointerstitial diseases and AKI involve tubular transporter injury, initially manifesting as tubular dysfunction in tubulointerstitial disorder and progressing to AKI because of the programmed cell death with apoptosis, pyroptosis, or necroptosis of proximal tubule cells. Additionally, mitochondrial dysfunction has been identified as a common mechanism in both tubulointerstitial diseases and AKI induced by drugs, pSS, or monoclonal diseases. In the end, both AKI and FS patients and animal models responded well to the therapy of the primary diseases.

Key Messages

In this review, we describe an overview of ADTKD and FS to identify their associations with AKI. Mitochondrial dysfunction contributes to rare tubulointerstitial diseases and AKI, which might provide a potential therapeutic target.

Curcumin-mediated alleviation of dextran-induced leaky gut in Drosophila melanogaster

Aging is commonly characterized by a decline in the physiological functioning of the body organs, with one hallmark being the impairment of intestinal function, leading to increased intestinal permeability known as leaky gut. The aim of this study was to investigate the potential of curcumin to prevent the development of leaky gut in Drosophila melanogaster utilizing the smurf fly method. In this study, flies aged 3-5 days underwent a 10-day dextran sulfate sodium (DSS) treatment to induce intestinal permeability, followed by a smurf assay using brilliant blue dye and locomotor testing the next day. Flies displaying the smurf phenotype were divided into four groups: untreated control and curcumin-treated (10 μM, 50 μM, and 250 μM). After 21 days of treatment, flies were reassessed for the smurf phenotype and underwent locomotor testing. On day 23, flies were subjected to RT-qPCR analysis. By inducing increased intestinal permeability through the administration of DSS, a higher proportion of flies exhibiting the smurf phenotype and a reduced survival rate in the DSS-treated group were observed. Such phenotypes were reversed, decreased number of flies displaying the smurf phenotype and improved fly survival, upon the incorporation of curcumin in the fly food at concentrations of 10, 50, and 250 μM. Subsequent molecular analysis revealed upregulated expression of sod1, cat, and pepck genes, while no significant changes were observed in the expression of sod2, indy, and srl genes following treatment with curcumin at high concentration. Overall, our findings provide insight into the potential effect of curcumin to alleviate the phenotypical features associated with DSS-induced leaky gut, possibly via the selective regulation of aging-related genes.

PKM2 induces mitophagy through the AMPK-mTOR pathway promoting CSFV proliferation

Viruses exploit the host cell's energy metabolism system to support their replication. Mitochondria, known as the powerhouse of the cell, play a critical role in regulating cell survival and virus replication. Our prior research indicated that the classical swine fever virus (CSFV) alters mitochondrial dynamics and triggers glycolytic metabolic reprogramming. However, the role and mechanism of PKM2, a key regulatory enzyme of glycolytic metabolism, in CSFV replication remain unclear. In this study, we discovered that CSFV enhances PKM2 expression and utilizes PKM2 to inhibit pyruvate production. Using an affinity purification coupled mass spectrometry system, we successfully identified PKM as a novel interaction partner of the CSFV non-structural protein NS4A. Furthermore, we validated the interaction between PKM2 and both CSFV NS4A and NS5A through co-immunoprecipitation and confocal analysis. PKM2 was found to promote the expression of both NS4A and NS5A. Moreover, we observed that PKM2 induces mitophagy by activating the AMPK-mTOR signaling pathway, thereby facilitating CSFV proliferation. In summary, our data reveal a novel mechanism whereby PKM2, a metabolic enzyme, promotes CSFV proliferation by inducing mitophagy. These findings offer a new avenue for developing antiviral strategies.

IMPORTANCE

Viruses rely on the host cell's material-energy metabolic system for replication, inducing host metabolic disorders and subsequent immunosuppression-a major contributor to persistent viral infections. Classical swine fever virus (CSFV) is no exception. Classical swine fever is a severe acute infectious disease caused by CSFV, resulting in significant economic losses to the global pig industry. While the role of the metabolic enzyme PKM2 (pyruvate dehydrogenase) in the glycolytic pathway of tumor cells has been extensively studied, its involvement in viral infection remains relatively unknown. Our data unveil a new mechanism by which the metabolic enzyme PKM2 mediates CSFV infection, offering novel avenues for the development of antiviral strategies.

RTN3 deficiency exacerbates cisplatin-induced acute kidney injury through the disruption of mitochondrial stability

Reticulum 3 (RTN3) is an endoplasmic reticulum (ER) protein that has been reported to act in neurodegenerative diseases and lipid metabolism. However, the role of RTN3 in acute kidney injury (AKI) has not been explored. Here, we employed public datasets, patient data, and animal models to explore the role of RTN3 in AKI. The underlying mechanisms were studied in primary renal tubular epithelial cells and in the HK2 cell line. We found reduced expression of RTN3 in AKI patients, cisplatin-induced mice, and cisplatin-treated HK2 cells. RTN3-null mice exhibit more severe AKI symptoms and kidney fibrosis after cisplatin treatment. Mitochondrial dysfunction was also found in cells with RTN3 knockdown or knockout. A mechanistic study revealed that RTN3 can interact with HSPA9 in kidney cells. RTN3 deficiency may disrupt the RTN3-HSPA9-VDAC2 complex and affect MAMs during ER-mitochondrion contact, which further leads to mitochondrial dysfunction and exacerbates cisplatin-induced AKI. Our study indicated that RTN3 was important in the kidney and that a decrease in RTN3 in the kidney might be a risk factor for the aggravation of AKI.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

PIM1 attenuates cisplatin-induced AKI by inhibiting Drp1 activation

Cisplatin, an effective anti-cancer drug, always causes acute kidney injury (AKI) by inducing mitochondrial damage. PIM1 is a serine/threonine kinase, which has been shown to regulate mitochondrial function. However, the role and mechanisms of PIM1 in cisplatin-induced AKI remain unexplored. This study aimed to investigate the effects of PIM1 in cisplatin-induced AKI and its underlying mechanisms. To established Cisplatin-induced AKI model, mice were given a single intraperitoneal injection(20 mg/kg) and BUMPT cells were treated with cisplatin(20 μM). PIM1 inhibitor AZD1208 was used to inhibit PIM1 and PIM1-experssing adenovirus was used to overexpress PIM1. Drp1 inhibitor P110 and pcDNA3-Drp1K38A were used to inhibit the activation of Drp1 and mitochondrial fission. The indicators of renal function, renal morphology, apoptosis and mitochondrial dysfunction were assessed to evaluate cisplatin-induced nephrotoxicity. We observed that PIM1 was activated in cisplatin-induced AKI in vivo and cisplatin-induced tubular cells injury in vitro. PIM1 inhibition aggravated cisplatin-induced AKI in vivo, while PIM1 overexpression attenuated cisplatin-induced kidney injury in vivo and in vitro. Moreover, inhibiting PIM1 exacerbated mitochondrial damage in mice, but overexpressing PIM1 relieved mitochondrial damage in mice and BUMPT cells. In mice and BUMPT cells, inhibiting PIM1 deregulated the expression of p-Drp1S637, overexpressing PIM1 upregulated the ex-pression of p-Drp1S637. And inhibiting Drp1 activity alleviated cell damage in BUMPT cells with PIM1 knockdown or inhibition. This study demonstrated the protective effect of PIM1 in cisplatin-induced AKI, and regulation of Drp1 activation might be the underlying mechanism. Altogether, PIM1 may be a potential therapeutic target for cisplatin-induced AKI.

Peroxisom proliferator-activated receptor-γ coactivator-1α in neurodegenerative disorders: A promising therapeutic target

Neurodegenerative disorders (NDDs) are characterized by progressive loss of selectively vulnerable neuronal populations and myelin sheath, leading to behavioral and cognitive dysfunction that adversely affect the quality of life. Identifying novel therapies that attenuate the progression of NDDs would be of significance. Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a widely expressed transcriptional regulator, modulates the expression of genes engaged in mitochondrial biosynthesis, metabolic regulation, and oxidative stress (OS). Emerging evidences point to the strong connection between PGC-1α and NDDs, suggesting its positive impaction on the progression of NDDs. Therefore, it is urgent to gain a deeper and broader understanding between PGC-1α and NDDs. To this end, this review presents a comprehensive overview of PGC-1α, including its basic characteristics, the post-translational modulations, as well as the interacting transcription factors. Secondly, the pathogenesis of PGC-1α in various NDDs, such as Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD) is briefly discussed. Additionally, this study summarizes the underlying mechanisms that PGC-1α is neuroprotective in NDDs via regulating neuroinflammation, OS, and mitochondrial dysfunction. Finally, we briefly outline the shortcomings of current NDDs drug therapy, and summarize the functions and potential applications of currently available PGC-1α modulators (activator or inhibitors). Generally, this review updates our insight of the important role of PGC-1α on the development of NDDs, and provides a promising therapeutic target/ drug for the treatment of NDDs.

Dissecting the multifaced function of transcription factor EB (TFEB) in human diseases: From molecular mechanism to pharmacological modulation

The transcription factor EB (TFEB) is a transcription factor of the MiT/TFE family that translocations from the cytoplasm to the nucleus in response to various stimuli, including lysosomal stress and nutrient starvation. By activating genes involved in lysosomal function, autophagy, and lipid metabolism, TFEB plays a crucial role in maintaining cellular homeostasis. Dysregulation of TFEB has been implicated in various diseases, including cancer, neurodegenerative diseases, metabolic diseases, cardiovascular diseases, infectious diseases, and inflammatory diseases. Therefore, modulating TFEB activity with agonists or inhibitors may have therapeutic potential. In this review, we reviewed the recently discovered regulatory mechanisms of TFEB and their impact on human diseases. Additionally, we also summarize the existing TFEB inhibitors and agonists (targeted and non-targeted) and discuss unresolved issues and future research directions in the field. In summary, this review sheds light on the crucial role of TFEB, which may pave the way for its translation from basic research to practical applications, bringing us closer to realizing the full potential of TFEB in various fields.

Altered expression, but small contribution, of the histone demethylase KDM6A in obstructive uropathy in mice

Epigenetic processes have emerged as important modulators of kidney health and disease. Here, we studied the role of KDM6A (a histone demethylase that escapes X-chromosome inactivation) in kidney tubule epithelial cells. We initially observed an increase in tubule cell Kdm6a mRNA in male mice with unilateral ureteral obstruction (UUO). However, tubule cell knockout of KDM6A had relatively minor consequences, characterized by a small reduction in apoptosis, increase in inflammation and downregulation of the peroxisome proliferator-activated receptor (PPAR) signaling pathway. In proximal tubule lineage HK-2 cells, KDM6A knockdown decreased PPARγ coactivator-1α (PGC-1α) protein levels and mRNA levels of the encoding gene, PPARGC1A. Tubule cell Kdm6a mRNA levels were approximately 2-fold higher in female mice than in male mice, both under sham and UUO conditions. However, kidney fibrosis after UUO was similar in both sexes. The findings demonstrate Kdm6a to be a dynamically regulated gene in the kidney tubule, varying in expression levels by sex and in response to injury. Despite the context-dependent variation in Kdm6a expression, knockout of tubule cell KDM6A has subtle (albeit non-negligible) effects in the adult kidney, at least in males.

The Interplay between Immune and Metabolic Pathways in Kidney Disease

Kidney disease is a significant health problem worldwide, affecting an estimated 10% of the global population. Kidney disease encompasses a diverse group of disorders that vary in their underlying pathophysiology, clinical presentation, and outcomes. These disorders include acute kidney injury (AKI), chronic kidney disease (CKD), glomerulonephritis, nephrotic syndrome, polycystic kidney disease, diabetic kidney disease, and many others. Despite their distinct etiologies, these disorders share a common feature of immune system dysregulation and metabolic disturbances. The immune system and metabolic pathways are intimately connected and interact to modulate the pathogenesis of kidney diseases. The dysregulation of immune responses in kidney diseases includes a complex interplay between various immune cell types, including resident and infiltrating immune cells, cytokines, chemokines, and complement factors. These immune factors can trigger and perpetuate kidney inflammation, causing renal tissue injury and progressive fibrosis. In addition, metabolic pathways play critical roles in the pathogenesis of kidney diseases, including glucose and lipid metabolism, oxidative stress, mitochondrial dysfunction, and altered nutrient sensing. Dysregulation of these metabolic pathways contributes to the progression of kidney disease by inducing renal tubular injury, apoptosis, and fibrosis. Recent studies have provided insights into the intricate interplay between immune and metabolic pathways in kidney diseases, revealing novel therapeutic targets for the prevention and treatment of kidney diseases. Potential therapeutic strategies include modulating immune responses through targeting key immune factors or inhibiting pro-inflammatory signaling pathways, improving mitochondrial function, and targeting nutrient-sensing pathways, such as mTOR, AMPK, and SIRT1. This review highlights the importance of the interplay between immune and metabolic pathways in kidney diseases and the potential therapeutic implications of targeting these pathways.

Pleiotropic and multi-systemic actions of physical exercise on PGC-1α signaling during the aging process

Physical training is a potent therapeutic approach for improving mitochondrial health through peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) signaling pathways. However, comprehensive information regarding the physical training impact on PGC-1α in the different physiological systems with advancing age is not fully understood. This review sheds light on the frontier-of-knowledge data regarding the chronic effects of exercise on the PGC-1α signaling pathways in rodents and humans. We address the molecular mechanisms involved in the different tissues, clarifying the precise biological action of PGC-1α, restricted to the aged cell type. Distinct exercise protocols (short and long-term) and modalities (aerobic and resistance exercise) increase the transcriptional and translational PGC-1α levels in adipose tissue, brain, heart, liver, and skeletal muscle in animal models, suggesting that this versatile molecule induces pleiotropic responses. However, PGC-1α function in some human tissues (adipose tissue, heart, and brain) remains challenging for further investigations. PGC-1α is not a simple transcriptional coactivator but supports a biochemical environment of mitochondrial dynamics, controlling physiological processes (primary metabolism, tissue remodeling, autophagy, inflammation, and redox balance). Acting as an adaptive mechanism, the long-term effects of PGC-1α following exercise may reflect the energy demand to coordinate multiple organs and contribute to cellular longevity.

Erythropoietin promotes energy metabolism to improve LPS-induced injury in HK-2 cells via SIRT1/PGC1-α pathway

Acute kidney injury (AKI) is one of frequent complications of sepsis with high mortality. Mitochondria is the center of energy metabolism participating in the pathogenesis of sepsis-associated AKI, and SIRT1/PGC1-α signaling pathway plays a crucial role in the modulation of energy metabolism. Erythropoietin (EPO) exerts protective functions on chronic kidney disease. We aimed to assess the effects of EPO on cell damage and energy metabolism in a cell model of septic AKI. Renal tubular epithelial cells HK-2 were treated with LPS and human recombinant erythropoietin (rhEPO). Cell viability was detected by CCK-8 and mitochondrial membrane potential was determined using JC-1 fluorescent probe. Then the content of ATP, ADP and NADPH, as well as lactic acid, were measured for the assessment of energy metabolism. Oxidative stress was evaluated by detecting the levels of ROS, MDA, SOD and GSH. Pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β, were measured with ELISA. Moreover, qRT-PCR and western blot were performed to detect mRNA and protein expressions. shSIRT1 was used to knockdown SIRT1, while EX527 and SR-18292 were applied to inhibit SIRT1 and PGC1-α, respectively, to investigate the regulatory mechanism of rhEPO on inflammatory injury and energy metabolism. In LPS-exposed HK-2 cells, rhEPO attenuated cell damage, inflammation and abnormal energy metabolism, as indicated by the elevated cell viability, the inhibited oxidative stress, cell apoptosis and inflammation, as well as the increased mitochondrial membrane potential and energy metabolism. However, these protective effects induced by rhEPO were reversed after SIRT1 or PGC1-α inhibition. EPO activated SIRT1/PGC1-α pathway to alleviate LPS-induced abnormal energy metabolism and cell damage in HK-2 cells. Our study suggested that rhEPO played a renoprotective role through SIRT1/PGC1-α pathway, which supported its therapeutic potential in septic AKI.

Aldehyde dehydrogenase 2 alleviates mitochondrial dysfunction by promoting PGC-1α-mediated biogenesis in acute kidney injury

Renal tubular epithelial cells are one of the high energy-consuming cell types, which mainly depend on mitochondrial energy supply. Aldehyde dehydrogenase 2 (ALDH2) is a key enzyme that is involved in alcohol metabolism and mitochondrial oxidative ATP production; however, its function in mitochondrial homoeostasis in acute kidney injury (AKI) is unclear. Here, we found that ALDH2 expression was predominantly decreased in cisplatin or maleic acid (MA) models both in vivo and in vitro. ALDH2 knockout (KO) mice exhibited exacerbated kidney impairment and apoptosis of tubular epithelial cells after cisplatin injection. In contrast, ALDH2 activation alleviated AKI and tubular cell apoptosis in both cisplatin- and MA-induced models. RNA sequencing revealed that the oxidative phosphorylation pathway was positively enriched in the renal tissues after Alda-1 pre-treatment in MA-induced mice. ALDH2 activation restored mitochondrial structure, mitochondrial membrane potential, and respiration rate, but downregulated glycolysis in MA-induced mice and human renal proximal tubular epithelial (HK-2) cells. Mechanistically, co-immunoprecipitation assays revealed that ALDH2 interacts with peroxisomal proliferator-γ coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis, and advanced its nuclear translocation. Subsequently, PGC-1α knockdown almost abolished the improvement of ALDH2 activation on MA-induced tubular epithelial cells damage. Thus, our study revealed that ALDH2 activation alleviated mitochondrial dysfunction in AKI by enhancing PGC-1α-mediated mitochondrial biogenesis. Hence, ALDH2 may act as a potential therapeutic target to prevent AKI progression.

Macrophage-derived exosomal miR-195a-5p impairs tubular epithelial cells mitochondria in acute kidney injury mice

Macrophages (Mφ) infiltration is a common characteristic of acute kidney injury (AKI). Exosomes-mediated cell communication between tubular epithelial cells (TECs) and Mφ has been suggested to be involved in AKI. Exosomes-derived from injured TECs could regulate Mφ polarization during AKI. However, little is known regarding how activated Mφ regulates kidney injury. To explore the role of activated Mφ in the AKI process, we revealed that Mφ-derived exosomes from AKI mice (Exos^AKI ) caused mitochondria damage and induced TECs injury. Then, we detected the global miRNA expression profiles of Mφ^NC and Mφ^AKI and found that among the upregulated miRNAs, miR-195a-5p, which regulates mitochondria metabolism in cancer, was significantly increased in Mφ^AKI . Due to the enrichment of miR-195a-5p in Exos^AKI , the miR-195a-5p level in the kidney was elevated in AKI mice. More interestingly, based on the high expression of pri-miR-195a-5p in kidney-infiltrated Mφ, and the reduction of miR-195a-5p in kidney after depletion of Mφ in AKI mice, we confirmed that miR-195a-5p may be produced in infiltrated Mφ, and shuttled into TECs via Exos^Mφ . Furthermore, in vitro inhibition of miR-195a-5p alleviated the effect of Exos^AKI induced mitochondrial dysfunction and cell injury. Consistently, antagonizing miR-195a-5p with a miR-195a-5p antagomir attenuated cisplatin-induced kidney injury and mitochondrial dysfunction in mice. These findings revealed that the Mφ exosomal miR-195a-5p derived from AKI mice played a critical pathologic role in AKI progression, representing a new therapeutic target for AKI.

Cisplatin nephrotoxicity: new insights and therapeutic implications

Cisplatin is an effective chemotherapeutic agent for various solid tumours, but its use is limited by adverse effects in normal tissues. In particular, cisplatin is nephrotoxic and can cause acute kidney injury and chronic kidney disease. Preclinical studies have provided insights into the cellular and molecular mechanisms of cisplatin nephrotoxicity, which involve intracellular stresses including DNA damage, mitochondrial pathology, oxidative stress and endoplasmic reticulum stress. Stress responses, including autophagy, cell-cycle arrest, senescence, apoptosis, programmed necrosis and inflammation have key roles in the pathogenesis of cisplatin nephrotoxicity. In addition, emerging evidence suggests a contribution of epigenetic changes to cisplatin-induced acute kidney injury and chronic kidney disease. Further research is needed to determine how these pathways are integrated and to identify the cell type-specific roles of critical molecules involved in regulated necrosis, inflammation and epigenetic modifications in cisplatin nephrotoxicity. A number of potential therapeutic targets for cisplatin nephrotoxicity have been identified. However, the effects of renoprotective strategies on the efficacy of cisplatin chemotherapy needs to be thoroughly evaluated. Further research using tumour-bearing animals, multi-omics and genome-wide association studies will enable a comprehensive understanding of the complex cellular and molecular mechanisms of cisplatin nephrotoxicity and potentially lead to the identification of specific targets to protect the kidney without compromising the chemotherapeutic efficacy of cisplatin.

Role of TFEB in Diseases Associated with Lysosomal Dysfunction

Transcription factor EB (TFEB) plays a very important role in the maintenance of cellular homeostasis. TFEB is a transcription factor that regulates the expression of several genes in the Coordinated Lysosomal Expression and Regulation (CLEAR) network. The CLEAR network genes are known to regulate many processes associated with the autophagy pathway and lysosome biogenesis. Lysosomes, which are degradative organelles in the cell, are associated with several cellular mechanisms, such as autophagy and phagocytosis. Recent studies have shown that TFEB dysregulation and lysosomal dysfunction are associated with several degenerative diseases. Thus, enhancing TFEB activity and accompanied induction of lysosomal function and autophagy can have tremendous therapeutic potential for the treatment of several degenerative diseases including age-related macular degeneration (AMD). In this chapter, we briefly illustrate the expression and regulation of TFEB in response to several cellular stressors and discuss the effects of TFEB overexpression to induce cellular clearance functions.

Toosendanin Induces Hepatocyte Damage by Inhibiting Autophagic Flux via TFEB-Mediated Lysosomal Dysfunction

Toosendanin (TSN) is a triterpenoid from the fruit or bark of Melia toosendan Sieb et Zucc, which has clear antitumor and insecticidal activities, but it possesses limiting hepatotoxicity in clinical application. Autophagy is a degradation and recycling mechanism to maintain cellular homeostasis, and it also plays an essential role in TSN-induced hepatotoxicity. Nevertheless, the specific mechanism of TSN on autophagy-related hepatotoxicity is still unknown. The hepatotoxicity of TSN in vivo and in vitro was explored in this study. It was found that TSN induced the upregulation of the autophagy-marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) and P62, the accumulation of autolysosomes, and the inhibition of autophagic flux. The middle and late stages of autophagy were mainly studied. The data showed that TSN did not affect the fusion of autophagosomes and lysosomes but significantly inhibited the acidity, the degradation capacity of lysosomes, and the expression of hydrolase cathepsin B (CTSB). The activation of autophagy could alleviate TSN-induced hepatocyte damage. TSN inhibited the expression of transcription factor EB (TFEB), which is a key transcription factor for many genes of autophagy and lysosomes, such as CTSB, and overexpression of TFEB alleviated the autophagic flux blockade caused by TSN. In summary, TSN caused hepatotoxicity by inhibiting TFEB-lysosome-mediated autophagic flux and activating autophagy by rapamycin (Rapa), which could effectively alleviate TSN-induced hepatotoxicity, indicating that targeting autophagy is a new strategy to intervene in the hepatotoxicity of TSN.

Critical Reanalysis of the Mechanisms Underlying the Cardiorenal Benefits of SGLT2 Inhibitors and Reaffirmation of the Nutrient Deprivation Signaling/Autophagy Hypothesis

SGLT2 (sodium-glucose cotransporter 2) inhibitors produce a distinctive pattern of benefits on the evolution and progression of cardiomyopathy and nephropathy, which is characterized by a reduction in oxidative and endoplasmic reticulum stress, restoration of mitochondrial health and enhanced mitochondrial biogenesis, a decrease in proinflammatory and profibrotic pathways, and preservation of cellular and organ integrity and viability. A substantial body of evidence indicates that this characteristic pattern of responses can be explained by the action of SGLT2 inhibitors to promote cellular housekeeping by enhancing autophagic flux, an effect that may be related to the action of these drugs to produce simultaneous upregulation of nutrient deprivation signaling and downregulation of nutrient surplus signaling, as manifested by an increase in the expression and activity of AMPK (adenosine monophosphate-activated protein kinase), SIRT1 (sirtuin 1), SIRT3 (sirtuin 3), SIRT6 (sirtuin 6), and PGC1-α (peroxisome proliferator-activated receptor γ coactivator 1-α) and decreased activation of mTOR (mammalian target of rapamycin). The distinctive pattern of cardioprotective and renoprotective effects of SGLT2 inhibitors is abolished by specific inhibition or knockdown of autophagy, AMPK, and sirtuins. In the clinical setting, the pattern of differentially increased proteins identified in proteomics analyses of blood collected in randomized trials is consistent with these findings. Clinical studies have also shown that SGLT2 inhibitors promote gluconeogenesis, ketogenesis, and erythrocytosis and reduce uricemia, the hallmarks of nutrient deprivation signaling and the principal statistical mediators of the ability of SGLT2 inhibitors to reduce the risk of heart failure and serious renal events. The action of SGLT2 inhibitors to augment autophagic flux is seen in isolated cells and tissues that do not express SGLT2 and are not exposed to changes in environmental glucose or ketones and may be related to an ability of these drugs to bind directly to sirtuins or mTOR. Changes in renal or cardiovascular physiology or metabolism cannot explain the benefits of SGLT2 inhibitors either experimentally or clinically. The direct molecular effects of SGLT2 inhibitors in isolated cells are consistent with the concept that SGLT2 acts as a nutrient surplus sensor, and thus, its inhibition causes enhanced nutrient deprivation signaling and its attendant cytoprotective effects, which can be abolished by specific inhibition or knockdown of AMPK, sirtuins, and autophagic flux.

Neospora caninum infection induced mitochondrial dysfunction in caprine endometrial epithelial cells via downregulating SIRT1

Background

Infection of Neospora caninum, an important obligate intracellular protozoan parasite, causes reproductive dysfunctions (e.g. abortions) in ruminants (e.g. cattle, sheep and goats), leading to serious economic losses of livestock worldwide, but the pathogenic mechanisms of N. caninum are poorly understood. Mitochondrial dysfunction has been reported to be closely associated with pathogenesis of many infectious diseases. However, the effect of N. caninum infection on the mitochondrial function of hosts remains unclear.

Methods

The effects of N. caninum infection on mitochondrial dysfunction in caprine endometrial epithelial cells (EECs), including intracellular reactive oxygen species (ROS), mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) contents, mitochondrial DNA (mtDNA) copy numbers and ultrastructure of mitochondria, were studied by using JC-1, DCFH-DA, ATP assay kits, quantitative real-time polymerase chain reaction (RT-qPCR) and transmission electron microscopy, respectively, and the regulatory roles of sirtuin 1 (SIRT1) on mitochondrial dysfunction, autophagy and N. caninum propagation in caprine EECs were investigated by using two drugs, namely resveratrol (an activator of SIRT1) and Ex 527 (an inhibitor of SIRT1).

Results

The current study found that N. caninum infection induced mitochondrial dysfunction of caprine EECs, including accumulation of intracellular ROS, significant reductions of MMP, ATP contents, mtDNA copy numbers and damaged ultrastructure of mitochondria. Downregulated expression of SIRT1 was also detected in caprine EECs infected with N. caninum. Treatments using resveratrol and Ex 527 to caprine EECs showed that dysregulation of SIRT1 significantly reversed mitochondrial dysfunction of cells caused by N. caninum infection. Furthermore, using resveratrol and Ex 527, SIRT1 expression was found to be negatively associated with autophagy induced by N. caninum infection in caprine EECs, and the intracellular propagation of N. caninum tachyzoites in caprine EECs was negatively affected by SIRT1 expression.

Conclusions

These results indicated that N. caninum infection induced mitochondrial dysfunction by downregulating SIRT1, and downregulation of SIRT1 promoted cell autophagy and intracellular proliferation of N. caninum tachyzoites in caprine EECs. The findings suggested a potential role of SIRT1 as a target to develop control strategies against N. caninum infection.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05406-4.

Tubular Mitochondrial Dysfunction, Oxidative Stress, and Progression of Chronic Kidney Disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are interconnected conditions, and CKD is projected to become the fifth leading global cause of death by 2040. New therapeutic approaches are needed. Mitochondrial dysfunction and oxidative stress have emerged as drivers of kidney injury in acute and chronic settings, promoting the AKI-to-CKD transition. In this work, we review the role of mitochondrial dysfunction and oxidative stress in AKI and CKD progression and discuss novel therapeutic approaches. Specifically, evidence for mitochondrial dysfunction in diverse models of AKI (nephrotoxicity, cytokine storm, and ischemia-reperfusion injury) and CKD (diabetic kidney disease, glomerulopathies) is discussed; the clinical implications of novel information on the key role of mitochondria-related transcriptional regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha, transcription factor EB (PGC-1α, TFEB), and carnitine palmitoyl-transferase 1A (CPT1A) in kidney disease are addressed; the current status of the clinical development of therapeutic approaches targeting mitochondria are updated; and barriers to the clinical development of mitochondria-targeted interventions are discussed, including the lack of clinical diagnostic tests that allow us to categorize the baseline renal mitochondrial dysfunction/mitochondrial oxidative stress and to monitor its response to therapeutic intervention. Finally, key milestones for further research are proposed.

Mitochondrial autophagy: molecular mechanisms and implications for cardiovascular disease

Mitochondria are highly dynamic organelles that participate in ATP generation and involve calcium homeostasis, oxidative stress response, and apoptosis. Dysfunctional or damaged mitochondria could cause serious consequences even lead to cell death. Therefore, maintaining the homeostasis of mitochondria is critical for cellular functions. Mitophagy is a process of selectively degrading damaged mitochondria under mitochondrial toxicity conditions, which plays an essential role in mitochondrial quality control. The abnormal mitophagy that aggravates mitochondrial dysfunction is closely related to the pathogenesis of many diseases. As the myocardium is a highly oxidative metabolic tissue, mitochondria play a central role in maintaining optimal performance of the heart. Dysfunctional mitochondria accumulation is involved in the pathophysiology of cardiovascular diseases, such as myocardial infarction, cardiomyopathy and heart failure. This review discusses the most recent progress on mitophagy and its role in cardiovascular disease.

ZLN005 Alleviates In Vivo and In Vitro Renal Fibrosis via PGC-1α-Mediated Mitochondrial Homeostasis

Currently, chronic kidney disease (CKD) is one of the most common diseases; it is also a serious threat to human health due to its high mortality, and its treatment is still a major clinical challenge. Mitochondrial dyshomeostasis plays an important role in the development of CKD. ZLN005 is a novel peroxisome-proliferator-activated receptor-γ coactivator-1α (PGC-1α) activator from our laboratory. To explore whether ZLN005 can protect against CKD in vivo and in vitro, a unilateral ureteral obstruction (UUO) model and TGF-β1-treated renal tubular epithelial cells (TECs), respectively, were used in this study. We found that ZLN005-administrated UUO mice showed less kidney damages than control mice, as indicated by the reduced expression of fibrotic biomarkers in the kidney of UUO mice. ZLN005 treatment also alleviated the TGF-β1-induced fibrotic phenotype and lipid accumulation in TECs. Our study demonstrated ZLN005 treatment improved mitochondrial homeostasis at least partially via the activation of PGC-1α, thus maintaining mitochondria function and energy homeostasis. In summary, ZLN005 treatment ameliorates UUO-induced renal fibrosis, providing conceptional support for mitochondria-targeting therapies for chronic kidney disease.

Receptor-Interacting Protein Kinase 3 Suppresses Mitophagy Activation via the Yes-Associated Protein/Transcription Factor EB Pathways in Septic Cardiomyopathy

Mitophagy, known as the main mechanism of mitochondrial quality control, determines the pathophysiology of septic cardiomyopathy, although the precise regulatory mechanisms remain elusive. Data from the present study suggested that receptor-interacting protein kinase 3 (RIPK3) expression could be enhanced in response to lipopolysaccharide (LPS) challenge. Upregulated RIPK3 expression was accompanied by severe cardiac injury and cardiac dysfunction. Further examination revealed that elevated RIPK3 expression subsequently inhibited the Yes-associated protein (YAP) pathway, which was accompanied by reduced transcription factor EB (TFEB) expression. Inhibition of TFEB would reduce mitophagy, which ultimately induced cardiomyocyte death under LPS challenge. In contrast, loss of RIPK3 induced the YAP/TFEB/mitophagy pathway alleviated the sensitivity of cardiomyocytes to LPS-induced cytotoxicity. Collectively, the RIPK3/YAP/TFEB axis was confirmed to be responsible for the pathogenesis of septic cardiomyopathy by inhibiting mitophagy. These findings have potential significance for the progression of new approaches to the treatment of septic cardiomyopathy.

RORA alleviates LPS-induced apoptosis of renal epithelial cells by promoting PGC-1α transcription

OBJECTIVE

To explore the effect of RORA on LPS-induced renal epithelial cell apoptosis and the underlying mechanism.

METHODS

LPS-treated HK-2 cells were established as a cellular model of acute kidney injury. The expression of RORA or/and PGC-1α in LPS-induced HK-2 cells was altered by transfection. qRT-PCR and Western blotting were used to detect the expression changes of RORA and PGC-1α. ELISA was performed to detect the expression of IL-1β and IL-6 and the activity of caspase-3. Western blotting was applied for visualization of cleaved caspase-3. CCK-8 and flow cytometry were used to assess cell proliferation and apoptosis. Dual-luciferase reporter and ChIP-qPCR were utilized to verify the binding of RORA to PGC-1α promoter.

RESULTS

LPS treatment decreased the expression of RORA and PGC-1α and increased that of cleaved caspase-3 in HK-2 cells. Also, LPS treatment inhibited HK-2 cell proliferation and promoted HK-2 cell apoptosis and secretion of IL-1β and IL-6. Overexpression of RORA or PGC-1α eliminated the adverse effects of LPS treatment in HK-2 cells. RORA drove the transcription of PGC-1α by binding PGC-1α promoter. Knockdown of PGC-1α offset the reduction in HK-2 cell injury caused by overexpression of RORA.

CONCLUSION

RORA reduces LPS-induced apoptosis of renal epithelial cells by promoting PGC-1α transcription.