Stanniocalcin-1 inhibits renal ischemia/reperfusion injury via an AMP-activated protein kinase-dependent pathway

Human iPSC-derived nephron progenitor cells treat acute kidney injury and chronic kidney disease in mouse models

The number of patients requiring dialysis therapy continues to increase worldwide because of the lack of effective treatments for chronic kidney disease (CKD). Furthermore, no curative treatments for acute kidney injury (AKI) have been established. The therapeutic effects of human induced pluripotent stem cell-derived nephron progenitor cells (hiPSC-NPCs) on AKI have been reported in mice but not clinically confirmed. There are also no reports examining the therapeutic potential of hiPSC-NPCs on CKD. Although large numbers of uniform hiPSC-NPCs are required for cell therapies for AKI and CKD, effective expansion cultures remain to be developed. Here, we established a culture medium for cells that enabled more than 100-fold proliferation of hiPSC-NPCs from multiple hiPSC lines in two passages. We demonstrated that hiPSC-NPCs expanded by our medium named CFY or by their conditioned medium alone attenuated kidney injury and improved survival in cisplatin-induced AKI mice. We also observed that hiPSC-NPCs prevented kidney functional decline, interstitial fibrosis, and senescence in aristolochic acid-induced CKD mice. In addition, we found c-MET to be a specific cell surface marker for hiPSC-NPCs and confirmed that purified c-MET+ hiPSC-NPCs had therapeutic effects on AKI and CKD mice. Furthermore, we found that hiPSC-NPCs exerted their therapeutic effects in AKI and CKD mice by secreting vascular endothelial growth factor A. Expanded hiPSC-NPCs may be useful cell therapies for AKI and CKD and may open avenues for treating kidney diseases.

Sirtuins and Resveratrol in Cardiorenal Diseases: A Narrative Review of Mechanisms and Therapeutic Potential

Aging is a very complex process, and it has been linked with Sirtuins. Sirtuin enzymes are a family of deacetylases that are related to caloric restriction and aging by modulating energy metabolism, genomic stability, and stress resistance. Up to now, seven sirtuins have been recognized. This narrative review aimed to analyze the literature produced between January 2005 and March 2025 to evaluate the role of sirtuins in chronic kidney disease and, as heart and kidney diseases are strictly interrelated, to explore their role in heart diseases and cardio-renal cross-talk. A reciprocal relationship between CKD and aging seems to exist since CKD may contribute to premature biological aging of different organ systems. SIRTs are involved in the pathophysiology of renal diseases; their activation can delay the progression of several renal diseases. Notably, an increasing number of studies linked SIRTs with different CVDs. SIRTs affect the production of mitochondrial reactive oxygen species (ROS) by modulating mitochondrial function. The imbalance of SIRT levels may increase the vulnerability to CVDs. SIRTs are involved in the pathophysiological mechanisms of HFpEF (heart failure with preserved ejection fraction) through different signaling pathways. Fibrosis is the linkage mechanism between the heart and kidney in the development of cardio-renal diseases. Current studies on sirtuins, resveratrol, and cardiorenal disease highlight their potential therapeutic benefits in regulating blood pressure, kidney function, lipid profiles, and inflammation, making them a promising area of investigation for improving cardiovascular and renal health outcomes. However, significant gaps remain. The limited availability of highly selective and potent sirtuin modulators hampers their clinical translation, as most existing compounds exhibit poor bioavailability and suboptimal pharmacokinetic properties.

Stanniocalcin-1: A Novel Mediator in Diabetic Kidney Disease and Cardiovascular Disease

Diabetes mellitus represents a group of metabolic diseases characterized by hyperglycemia from defects in insulin secretion, action, or both. The prevalence of type 2 diabetes mellitus, characterized by insulin resistance, has increased over time in the UK, and is the most prevalent cause of chronic kidney disease (CKD). Cardiovascular complications are a major cause of mortality for these patients. Stanniocalcin (STC), originally identified in bony fish as a hormone regulating calcium levels, has since been found in mammals, including humans. In fish, STC functions as an antihypercalcemic factor. Mammals possess 2 STC orthologues, STC-1 and STC-2, with STC-1 demonstrating significant sequence and functional conservation across species. Unlike fish, STC-1 is not normally present in the blood of healthy humans. However, it can be detected in certain conditions such as pregnancy, cancer, and CKD. In humans, STC-1 has diverse roles, including modulation of calcium and phosphate homeostasis, and it is implicated in kidney and cardiovascular protection. It has been reported that STC-1 has antioxidant, anti-inflammatory, and antiapoptotic activities, playing a role in renoprotection in diabetic nephropathy. This review explores the molecular biology of STC-1, its physiological functions, and its emerging role in GKDs, particularly diabetic and cardiovascular diseases. We highlight its potential protective mechanisms against hypercalcemia, its antioxidant and anti-inflammatory properties, and its cardioprotective properties in ischemia-reperfusion. Further research into STC-1 could provide new insights into therapeutic strategies for managing diseases characterized by calcium imbalance and lead to new treatments for the cardiovascular morbidity associated with diabetic kidney disease.

Sirtuins in kidney homeostasis and disease: where are we now?

Sirtuins, identified as (NAD+)- dependent class III histone deacetylases, engage in a spectrum of biological functions, encompassing DNA damage repair, oxidative stress, immune modulation, mitochondrial homeostasis, apoptosis and autophagy. Sirtuins play an apoptosis role in regulating cellular operations and overall organism health. Mounting data indicate that dysregulated sirtuin expression is linked to the onset of renal diseases. Effective modulation of sirtuins expression and activity has been shown to improve renal function and attenuate the advancement of kidney diseases. In this review, we present a comprehensive overview of the biological impacts of sirtuins and their molecular targets in regulating renal diseases. Additionally, we detail advancements in elucidating sirtuin roles in the pathophysiology of both chronic and acute renal disorders. We review compounds that modulate sirtuin activity through activation or inhibition, potentially improving outcomes in renal disease. In summary, strategic manipulation of sirtuin activity represents a prospective therapeutic approach for renal diseases.

Unveiling the therapeutic potential and mechanisms of stanniocalcin-1 in retinal degeneration

Retinal degeneration (RD) is a group of ocular diseases characterized by progressive photoreceptor apoptosis and visual impairment. Mitochondrial malfunction, excessive oxidative stress, and chronic activation of neuroglia collectively contribute to the development of RD. Currently, there is a lack of efficacious therapeutic interventions for RD. Stanniocalcin-1 (STC-1) is a promising candidate molecule to decelerate photoreceptor cell death. STC-1 is a secreted calcium/phosphorus regulatory protein that exerts diverse protective effects. Accumulating evidence suggests that STC-1 protects retinal cells from ischemic injury, oxidative stress, and excessive apoptosis through enhancing the expression of uncoupling protein-2 (UCP-2). Furthermore, STC-1 exerts its antiinflammatory effects by inhibiting the activation of microglia and macrophages, as well as the synthesis and secretion of proinflammatory cytokines, such as TNF-α, IL-1, and IL-6. By employing these mechanisms, STC-1 effectively shields the retinal photoreceptors and optic nerve, thereby slowing down the progression of RD. We summarize the STC-1-mediated therapeutic effects on the degenerating retina, with a particular focus on its underlying mechanisms. These findings highlight that STC-1 may act as a versatile molecule to treat degenerative retinopathy. Further research on STC-1 is imperative to establish optimal protocols for its clinical use.

Emerging role and the signaling pathways of uncoupling protein 2 in kidney diseases

OBJECTIVES

Uncoupling protein 2 (UCP2) was involved in the pathogenesis and development of kidney diseases. Many signaling pathways and factors regulate the expression of UCP2. We aimed to investigate the precise role of UCP2 and its signaling pathways in kidney diseases.

METHODS

We summarized the available evidence to yield a more detailed conclusion of the signal transduction pathways of UCP2 and its role in the development and progression of kidney diseases.

RESULTS

UCP2 could interact with 14.3.3 family proteins, mitochondrial phospholipase iPLA2γ, NMDAR, glucokinase, PPARγ2. There existed a signaling pathway between UCP2 and NMDAR, PPARγ. UCP2 can inhibit the ROS production, inflammatory response, and apoptosis, which may protect against renal injury, particularly AKI. Meanwhile UCP2 can decrease ATP production and inhibit the secretion of insulin, which may alleviate chronic renal damages, such as diabetic nephropathy and kidney fibrosis.

CONCLUSIONS

Homeostasis of UCP2 is helpful for kidney health. UCP2 may play different roles in different kinds of renal injury.

Variants in tubule epithelial regulatory elements mediate most heritable differences in human kidney function

Kidney failure, the decrease of kidney function below a threshold necessary to support life, is a major cause of morbidity and mortality. We performed a genome-wide association study (GWAS) of 406,504 individuals in the UK Biobank, identifying 430 loci affecting kidney function in middle-aged adults. To investigate the cell types affected by these loci, we integrated the GWAS with human kidney candidate cis-regulatory elements (cCREs) identified using single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq). Overall, 56% of kidney function heritability localized to kidney tubule epithelial cCREs and an additional 7% to kidney podocyte cCREs. Thus, most heritable differences in adult kidney function are a result of altered gene expression in these two cell types. Using enhancer assays, allele-specific scATAC-seq and machine learning, we found that many kidney function variants alter tubule epithelial cCRE chromatin accessibility and function. Using CRISPRi, we determined which genes some of these cCREs regulate, implicating NDRG1, CCNB1 and STC1 in human kidney function.

Sirtuin 3 in renal diseases and aging: From mechanisms to potential therapies

The longevity protein sirtuins (SIRTs) belong to a family of nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases. In mammals, SIRTs comprise seven members (SIRT1-7) which are localized to different subcellular compartments. As the most prominent mitochondrial deacetylases, SIRT3 is known to be regulated by various mechanisms and participate in virtually all aspects of mitochondrial homeostasis and metabolism, exerting significant impact on multiple organs. Notably, the kidneys possess an abundance of mitochondria that provide substantial energy for filtration and reabsorption. A growing body of evidence now supports the involvement of SIRT3 in several renal diseases, including acute kidney injury, chronic kidney disease, and diabetic nephropathy; notably, these diseases are all associated with aging. In this review, we summarize the emerging role of SIRT3 in renal diseases and aging, and highlights the intricate mechanisms by which SIRT3 exerts its effects. In addition, we highlight the potential therapeutic significance of modulating SIRT3 and provide valuable insights into the therapeutic role of SIRT3 in renal diseases to facilitate clinical application.

Sirtuins in kidney health and disease

Sirtuins (SIRTs) are putative regulators of lifespan in model organisms. Since the initial discovery that SIRTs could promote longevity in nematodes and flies, the identification of additional properties of these proteins has led to understanding of their roles as exquisite sensors that link metabolic activity to oxidative states. SIRTs have major roles in biological processes that are important in kidney development and physiological functions, including mitochondrial metabolism, oxidative stress, autophagy, DNA repair and inflammation. Furthermore, altered SIRT activity has been implicated in the pathophysiology and progression of acute and chronic kidney diseases, including acute kidney injury, diabetic kidney disease, chronic kidney disease, polycystic kidney disease, autoimmune diseases and renal ageing. The renoprotective roles of SIRTs in these diseases make them attractive therapeutic targets. A number of SIRT-activating compounds have shown beneficial effects in kidney disease models; however, further research is needed to identify novel SIRT-targeting strategies with the potential to treat and/or prevent the progression of kidney diseases and increase the average human healthspan.

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

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

Maresin-1 Attenuates Sepsis-Associated Acute Kidney Injury via Suppressing Inflammation, Endoplasmic Reticulum Stress and Pyroptosis by Activating the AMPK/SIRT3 Pathway

Background

Sepsis-associated acute kidney injury (SA-AKI) is a common complication in patients with sepsis, triggering high morbidity and mortality. Maresin-1 (MaR1) is a pro-resolution lipid mediator that promotes the resolution of acute inflammation and protects organs from inflammation.

Methods

In this study, we established an SA-AKI model using cecal ligation and puncture (CLP) and investigated the effect and mechanism of MaR1. The blood and kidneys were harvested 24 hours after surgery. The blood biochemical/routine indicators, renal function, SA-AKI-related pathophysiological processes, and AMPK/SIRT3 signaling in septic mice were observed by histological staining, immunohistochemical staining, Western blot, qPCR, ELISA and TUNEL Assay.

Results

MaR1 treatment alleviated kidney injury in septic mice, reflected in improved pathological changes in renal structure and renal function. MaR1 treatment decreased the levels of serum creatinine (sCr) and blood urea nitrogen (BUN) and the expressions of KIM-1, NGAL and TIMP-2, which were related to kidney injury, while inhibited the expressions of inflammatory factors TNF-α, IL-1β and IL-6. The expression of endoplasmic reticulum stress-related indicators p-PERK/PERK, GRP78, p-EIF2α/EIF2α, ATF4, CHOP, and pyroptosis-related indicators Caspase-1, NLRP3, GSDMD, IL-18, and IL-1β also decreased after MaR1 treatment. The mechanism may be related to the activation of the AMPK/SIRT3 signaling pathway, and an AMPK inhibitor (compound C) partially reverses MaR1's protective effects in septic mice.

Conclusion

Taken together, these findings suggest that MaR1 may partially ameliorate SA-AKI by activating the AMPK/SIRT3 signaling pathway, providing a potential new perspective for research on SA-AKI.

Stanniocalcin 1 promotes lung metastasis of breast cancer by enhancing EGFR-ERK-S100A4 signaling

Lung metastasis is the leading cause of breast cancer-related death. The tumor microenvironment contributes to the metastatic colonization of tumor cells in the lungs. Tumor secretory factors are important mediators for the adaptation of cancer cells to foreign microenvironments. Here, we report that tumor-secreted stanniocalcin 1 (STC1) promotes the pulmonary metastasis of breast cancer by enhancing the invasiveness of tumor cells and promoting angiogenesis and lung fibroblast activation in the metastatic microenvironment. The results show that STC1 modifies the metastatic microenvironment through its autocrine action on breast cancer cells. Specifically, STC1 upregulates the expression of S100 calcium-binding protein A4 (S100A4) by facilitating the phosphorylation of EGFR and ERK signaling in breast cancer cells. S100A4 mediates the effect of STC1 on angiogenesis and lung fibroblasts. Importantly, S100A4 knockdown diminishes STC1-induced lung metastasis of breast cancer. Moreover, activated JNK signaling upregulates STC1 expression in breast cancer cells with lung-tropism. Overall, our findings reveal that STC1 plays important role in breast cancer lung metastasis.

Importance of Mitochondria in Cardiac Pathologies: Focus on Uncoupling Proteins and Monoamine Oxidases

On the one hand, reactive oxygen species (ROS) are involved in the onset and progression of a wide array of diseases. On the other hand, these are a part of signaling pathways related to cell metabolism, growth and survival. While ROS are produced at various cellular sites, in cardiomyocytes the largest amount of ROS is generated by mitochondria. Apart from the electron transport chain and various other proteins, uncoupling protein (UCP) and monoamine oxidases (MAO) have been proposed to modify mitochondrial ROS formation. Here, we review the recent information on UCP and MAO in cardiac injuries induced by ischemia-reperfusion (I/R) as well as protection from I/R and heart failure secondary to I/R injury or pressure overload. The current data in the literature suggest that I/R will preferentially upregulate UCP2 in cardiac tissue but not UCP3. Studies addressing the consequences of such induction are currently inconclusive because the precise function of UCP2 in cardiac tissue is not well understood, and tissue- and species-specific aspects complicate the situation. In general, UCP2 may reduce oxidative stress by mild uncoupling and both UCP2 and UCP3 affect substrate utilization in cardiac tissue, thereby modifying post-ischemic remodeling. MAOs are important for the physiological regulation of substrate concentrations. Upon increased expression and or activity of MAOs, however, the increased production of ROS and reactive aldehydes contribute to cardiac alterations such as hypertrophy, inflammation, irreversible cardiomyocyte injury, and failure.

Methyl eugenol protects the kidney from oxidative damage in mice by blocking the Nrf2 nuclear export signal through activation of the AMPK/GSK3β axis

Disrupted redox homeostasis contributes to renal ischemia-reperfusion (IR) injury. Abundant natural products can activate nuclear factor erythroid-2-related factor 2 (Nrf2), thereby providing therapeutic benefits. Methyl eugenol (ME), an analog of the phenolic compound eugenol, has the ability to induce Nrf2 activity. In this study, we investigated the protective effects of ME against renal oxidative damage in vivo and in vitro. An IR-induced acute kidney injury (AKI) model was established in mice. ME (20 mg·kg-1·d-1, i.p.) was administered to mice on 5 consecutive days before IR surgery. We showed that ME administration significantly attenuated renal destruction, improved the survival rate, reduced excessive oxidative stress and inhibited mitochondrial lesions in AKI mice. We further demonstrated that ME administration significantly enhanced Nrf2 activity and increased the expression of downstream antioxidative molecules. Similar results were observed in vitro in hypoxia/reoxygenation (HR)-exposed proximal tubule epithelial cells following pretreatment with ME (40 μmol·L-1). In both renal oxidative damage models, ME induced Nrf2 nuclear retention in tubular cells. Using specific inhibitors (CC and DIF-3) and molecular docking, we demonstrated that ME bound to the binding pocket of AMPK with high affinity and activated the AMPK/GSK3β axis, which in turn blocked the Nrf2 nuclear export signal. In addition, ME alleviated the development of renal fibrosis induced by nonfatal IR, which is frequently encountered in the clinic. In conclusion, we demonstrate that ME modulates the AMPK/GSK3β axis to regulate the cytoplasmic-nuclear translocation of Nrf2, resulting in Nrf2 nuclear retention and thereby enhancing antioxidant target gene transcription that protects the kidney from oxidative damage.

Responses of retinal and brain microvasculature to streptozotocin induced diabetes revealed by global expression profiling

This study aims to determine the effects of diabetes in the retinal and brain microvasculature through gene expression profiling. Twelve male Wistar rats were randomly divided into two groups: streptozotocin-induced diabetic rats and time-matched nondiabetic rats. The retinal microvessels (RMVs) and brain microvessels (BMVs) were mechanically isolated from individual rats. Differentially expressed genes (DEGs) in diabetic and nondiabetic microvessels were identified by cDNA microarrays analysis. In RMVs, we identified 43 DEGs, of which 20 were upregulated while 23 were downregulated by diabetes. In BMVs, 35 genes DEGs were identified, of which 22 were upregulated and 13 were downregulated by diabetes. Altered expression of the Nars, Gars, Mars, Iars, Yars, Bcl2, Nqo1, NR4A3, Gpd1, Stc1, Tsc22d3, Tnfrsf21 mRNA as observed in the microarray analyses, was confirmed by quantitative RT-PCR. The aminoacyl-tRNA synthetases (aaRSs) pathway in RMVs was significantly overrepresented as compared to BMVs. Our study demonstrates for the first time that in the brain microvasculature multiple compensatory mechanisms exists, serving to protect brain tissue from diabetic insults, whereas these mechanisms are not activated in the retinal microvasculature. This provides new insights as to why brain microvasculature is less susceptible to diabetes.

Identification and characterization of a membrane receptor that binds to human STC1

A study using TriCEPS-based ligand–receptor methodology and surface plasmon resonance assays identified that human stanniocalcin-1 binds to insulin-like growth factor-2 receptors in human leukemia monocytic cells with high affinity.

Stanniocalcin-1 (STC1) is a hypocalcemic hormone originally identified in bony fishes. The mammalian homolog is found to be involved in inflammation and carcinogenesis, among other physiological functions. In this study, we used the TriCEPS-based ligand–receptor methodology to identify the putative binding proteins of human STC1 (hSTC1) in the human leukemia monocytic cell line, ThP-1. LC–MS/MS analysis of peptides from shortlisted hSTC1-binding proteins detected 32 peptides that belong to IGF2/MPRI. Surface plasmon resonance assay demonstrated that hSTC1 binds to immobilized IGF2R/MPRI with high affinity (10–20 nM) and capacity (Rmax 70–100%). The receptor binding data are comparable with those of (CREG) cellular repressor of E1A-stimulated gene a known ligand of IGF2R/MPRI, with Rmax of 75–80% and affinity values of 1–2 nM. The surface plasmon resonance competitive assays showed CREG competed with hSTC1 in binding to IGF2R/MPRI. The biological effects of hSTC1 on ThP-1 cells were demonstrated via IGF2R/MPRI to significantly reduce secreted levels of IL-1β. This is the first study to reveal the high-affinity binding of hSTC1 to the membrane receptor IGF2R/MPRI.

Stanniocalcin‑1 suppresses TGF‑β‑induced mitochondrial dysfunction and cellular fibrosis in human renal proximal tubular cells

Stanniocalcin‑1 (STC1), a multifunctional glycoprotein with antioxidant and anti‑inflammatory properties, serves an important role in kidney protection. STC1 is one of the few hormones targeted to the mitochondria to regulate mitochondrial quality control by suppressing oxidative stress and mitochondrial damage. However, the mechanisms underlying the effect of STC1 remain unclear. The present study aimed to investigate the protective role of recombinant STC1 (rSTC1) in renal fibrosis and to identify the mechanisms underlying cellular fibrosis in HK2 human renal proximal tubular cells. Semi‑quantitative PCR, western blot analysis and confocal microscopy were used to detect the mRNA levels, protein levels and mitochondrial membrane potential (MMP). Mitochondrial superoxide production was evaluated using MitoSox staining. rSTC1 attenuated TGF‑β‑induced downregulation of AMP‑activated protein kinase and uncoupling protein 2 (UCP2). Treatment of HK2 cells with TGF‑β reduced the MMP and increased the production of reactive oxygen species (ROS). In addition, TGF‑β treatment upregulated fibrotic markers, such as α‑SMA and fibronectin, in HK2 cells. Treatment with rSTC1 and TGF‑β suppressed mitochondrial ROS production by recovering the MMP and reversed the upregulation of fibrotic markers in HK2 cells. The effects of rSTC1 were reversed when UCP2 expression was silenced. The present study revealed a novel role of STC1 in preventing TGF‑β induced cellular fibrosis in HK2 cells.

Correlation between coenzyme Q10 content and the nutrient sensors in AKI induced by Hemiscorpius lepturus envenomation

Introduction: Acute kidney injury (AKI) may have a negative effect on mitochondrial hemostasis and bioenergetics as well as coenzyme Q₁₀ (CoQ₁₀) content. PGC-1α, AMPK, sirtuin 1 (Sirt1), and Sirt3, as the key metabolic regulators under nutritional stress, stimulate energy production via mitochondrial biogenesis during AKI. However, no report is available on the relationship between CoQ₁₀ level and nutrient sensors in the pathophysiology of AKI caused by Hemiscorpius lepturus scorpion envenomation. Methods: Three doses of venoms (1, 5, and 10 mg/kg) were administered by subcutaneous (SC) injection to male albino mice. The animals were sacrificed 1 day or 7 days after administration of venom and their kidneys were collected to analyze gene expression involved in AKI, nutrient sensors, and apoptosis signaling activation by real-time polymerase chain reaction (PCR) and the measurement of CoQ₁₀ level using the High-performance liquid chromatography (HPLC) method. Results: The data indicated a significant decrease in CoQ₁₀ level after the administration of venom in 5 and 10 mg/kg. In addition, 1 day after the treatment, a significant over-expression of Sirt1 (5 and 10 mg/kg) was observed compared with normal mice. Overexpression of Sirt3 occurred 1 day and 7 days after treatment only at the dose of 5.0 mg/kg of venom. Furthermore, over-expression of AMPK as an important mitochondrial energetic sensor happened 1 day and 7 days after the injection of venom (5 mg/kg) (P < 0.01). The significant increase in the gene expression of caspase-9 and 3 after the injection of venom (5 and 10 mg/kg) confirmed the role of cell death signaling. Conclusion: The venom-induced energy-sensing pathways have a key role in gene expression of PGC-1α, AMPK, Sirt3, and CoQ₁₀ content after venom-induced AKI.

Interactions between leucines within the signal peptides of megalin and stanniocalcin-1 are crucial for regulation of mitochondrial metabolism

The mitochondrial intracrine Stanniocalcin 1 (STC1) activates mitochondrial anti-oxidant defenses. LRP2 (megalin) shuttles STC1 to the mitochondria through retrograde early endosome-to-Golgi- and Rab32-mediated pathway, and LRP2 KO impairs mitochondrial respiration and glycolysis. We determined STC1-LRP2 interaction domains using HA- and FLAG-tagged fragments of STC1 and LRP2, respectively, co-expressed in HEK293T cells. The trans-membrane domain of LRP2 is required for trafficking to the mitochondria. STC1-FLAG expressed in LRP2 KO cells fails to reach the mitochondria; thus, mitochondrial STC1 is extracellularly-derived via LRP2-mediated trafficking. Tri-leucines L12-14 in LRP2's signal peptide interact with STC1's signal peptide. Mutant LRP2 (L(12-14)A) does not bind STC1, while hSTC1 lacking signal peptide or Leucines L8/9/11 does not bind LRP2. STC1 fails to induce respiration or glycolysis in megalin KO mouse embryonal fibroblasts (MEF) expressing mutant LRP2, while mutant hSTC1 (L8/L9/L11 - > A8/A9/A11) fails to reach the mitochondria or induce respiration and glycolysis in WT MEF. Our data suggest direct regulation of mitochondrial metabolism by extracellular cues and reveal an important role for signal peptides' leucines in protein-protein interactions and mitochondrial biology.

Ferulic acid protects renal tubular epithelial cells against anoxia/reoxygenation injury mediated by AMPKα1

Anoxia/reoxygenation (A/R) injury causes dysfunction of rat renal tubular epithelial cells (NRK-52E), which is associated with excess reactive oxygen species (ROS) generation and eventually leads to apoptosis. Ferulic acid (FA), a phenolic acid, which is abundant in fruits and vegetables. FA possesses the properties of scavenging free radicals and cytoprotection against oxygen stress. In the study, the protective effects of FA against NRK-52E cells damage induced by A/R were explored and confirmed the role of AMP-activated protein kinaseα1 (AMPKα1). We found that after NRK-52E cells suffered A/R damage, FA pretreatment increased the cell viability and decreased LDH activity in culture medium in a concentration-dependent manner, the activities of endogenous antioxidant enzymes such as glutathione peroxidase, superoxide dismutase and catalase improved, intracellular ROS generation and malondialdehyde contents mitigated. In addition, pretreatment of 75 μM FA ameliorated mitochondrial dysfunction by A/R-injury and ultimately decreased apoptosis (25.3 ± 0.61 vs 12.1 ± 0.60), which was evidenced by preventing the release of cytochrome c from mitochondria to the cytoplasm. 75 μM FA pretreatment also significantly upregulated AMPKα1 expression (3.16 ± 0.18 folds) and phosphorylation (2.56 ± 0.13 folds). However, compound C, a specific AMPK inhibitor, significantly attenuated FA pretreatment's effects, as mentionedabove. These results firstly clarified that FA pretreatment attenuated NRK-52E cell damage induced by A/R via upregulating AMPKα1 expression and phosphorylation.

Adipose-derived stem cells alleviate liver injury induced by type 1 diabetes mellitus by inhibiting mitochondrial stress and attenuating inflammation

Background

Type 1 diabetes mellitus (T1D) is a worldwide health priority due to autoimmune destruction and is associated with an increased risk of multiorgan complications. Among these complications, effective interventions for liver injury, which can progress to liver fibrosis and hepatocellular carcinoma, are lacking. Although stem cell injection has a therapeutic effect on T1D, whether it can cure liver injury and the underlying mechanisms need further investigation.

Methods

Sprague–Dawley rats with streptozotocin (STZ)-induced T1D were treated with adipose-derived stem cell (ADSC) or PBS via the tail vein formed the ADSC group or STZ group. Body weights and blood glucose levels were examined weekly for 6 weeks. RNA-seq and PCR array were used to detect the difference in gene expression of the livers between groups.

Results

In this study, we found that ADSCs injection alleviated hepatic oxidative stress and injury and improved liver function in rats with T1D; potential mechanisms included cytokine activity, energy metabolism and immune regulation were potentially involved, as determined by RNA-seq. Moreover, ADSC treatment altered the fibroblast growth factor 21 (FGF21) and transforming growth factor β (TGF-β) levels in T1D rat livers, implying its repair capacity. Disordered intracellular energy metabolism, which is closely related to mitochondrial stress and dysfunction, was inhibited by ADSC treatment. PCR array and ingenuity pathway analyses suggested that the ADSC-induced suppression of mitochondrial stress is related to decreased necroptosis and apoptosis. Moreover, mitochondria-related alterations caused liver inflammation, resulting in liver injury involving the T lymphocyte-mediated immune response.

Conclusions

Overall, these results improve our understanding of the curative effect of ADSCs on T1D complications: ADSCs attenuate liver injury by inhibiting mitochondrial stress (apoptosis and dysfunctional energy metabolism) and alleviating inflammation (inflammasome expression and immune disorder). These results are important for early intervention in liver injury and for delaying the development of liver lesions in patients with T1D.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02760-z.

Megalin-Mediated Trafficking of Mitochondrial Intracrines: Relevance to Signaling and Metabolism

The multi-ligand binding protein megalin (LRP2) is ubiquitously expressed and facilitates cell uptake of hormones, nutrients and vitamins. We have recently shown megalin is present in the mitochondria of cultured epithelial and mesenchymal cells, as well as many organs and tissues. Mitochondrial megalin associates with stanniocalcin-1 and SIRT3; two proteins that promote anti-oxidant defenses. Megalin shuttles mitochondrial intracrines (angiotensin II, stanniocalcin-1 and TGF-β) from the cell surface to the mitochondria through the retrograde early endosome to Golgi pathway and requires Rab32. Deletion of megalin impairs mitochondrial respiration and glycolysis. This pathway overlaps molecular and vesicular trafficking defects common to Donai Barrow and Lowe syndromes, suggesting that mitochondrial intracrine signaling defects may contribute to the pathogenesis of these diseases.

Low Expression of Stanniocalcin 1 (STC-1) Protein Is Associated With Poor Clinicopathologic Features of Endometrial Cancer

Stanniocalcin-1 (STC-1) is a glycoprotein hormone involved in diverse biological processes, including regulation of calcium phosphate homeostasis, cell proliferation, apoptosis, inflammation, oxidative stress responses, and cancer development. The role of STC-1 in endometrial cancer (EC) is yet to be elucidated. In this study, we investigated the protein expression pattern of STC-1 in a tissue microarray (TMA) cohort of hysterectomy specimens from 832 patients with EC. We then evaluated the prognostic value of STC-1 expression regarding the clinicopathologic features and patients survival over a period of 140 months. Our results revealed that in EC tissue samples, STC-1 is mainly localized in the endometrial epithelium, although some expression was also observed in the stroma. Decreased STC-1 expression was associated with factors relating to a worse prognosis, such as grade 3 endometrioid tumors (p = 0.030), deep myometrial invasion (p = 0.003), lymphovascular space invasion (p = 0.050), and large tumor size (p = 0.001). Moreover, STC-1 expression was decreased in tumors obtained from obese women (p = 0.014) and in women with diabetes mellitus type 2 (DMT2; p = 0.001). Interestingly, the data also showed an association between DNA mismatch repair (MMR) deficiency and weak STC-1 expression, specifically in the endometrial epithelium (p = 0.048). No association was observed between STC-1 expression and disease-specific survival. As STC-1 expression was particularly low in cases with obesity and DMT2 in the TMA cohort, we also evaluated the correlation between metformin use and STC-1 expression in an additional EC cohort that only included women with DMT2 (n = 111). The analysis showed no difference in STC-1 expression in either the epithelium or the stroma in women undergoing metformin therapy compared to metformin non-users. Overall, our data may suggest a favorable role for STC-1 in EC behavior; however, further studies are required to elucidate the detailed mechanism and possible applications to cancer treatment.

Sirtuin-3 mediates sex differences in kidney ischemia-reperfusion injury

Studies suggest that biological sex influences susceptibility to kidney diseases with males demonstrating greater risk for developing ischemic acute kidney injury (AKI). Sex-related differences in mitochondrial function and homeostasis exist, likely contributing to sexual dimorphism in kidney injury, but the mechanisms are not well characterized. Our observations reveal lower baseline expression of Sirtuin-3 (Sirt3, a major mitochondrial acetyltransferase) in the kidneys of male mice versus females. We tested the hypothesis that differential expression of kidney Sirt3 may mediate sexual dimorphism in AKI using a bilateral kidney ischemia-reperfusion injury (IRI) model and three transgenic mouse models: (1) mice with global transgenic overexpression of Sirt3; (2) mice with inducible, kidney tubule-specific Sirt3 knockdown (iKD); and (3) mice with global Sirt3 knockout. Low mitochondrial Sirt3 (mtSirt3) in males versus females is associated with development of kidney tubular epithelium vacuoles, increased mitochondrial ROS and susceptibility to IRI. Transgenic overexpression of Sirt3 in males protects against kidney IRI and development of tubular epithelium vacuoles. In both sexes, mice with partial kidney tubular epithelium-specific Sirt3 knockdown display intermediate - while global Sirt3 knockout mice display the highest susceptibility to IRI. Female Sirt3 iKD mice demonstrate decreased survival and kidney function after IRI indistinguishable from control males, abolishing the protective effects observed in females. Mechanistically, observed differences in kidney mtSirt3 are sex hormone-dependent; estradiol increases - while testosterone decreases mtSirt3 protein. Our results demonstrate that Sirt3 is an important contributor to the observed sex-related differences in IRI susceptibility, and a potential therapeutic target in the clinical management of AKI.

Stanniocalcin-1 Protected Astrocytes from Hypoxic Damage Through the AMPK Pathway

Our previous studies revealed that the expression of stanniocalcin-1 (STC1) in astrocytes increased under hypoxic conditions. However, the role of STC1 in hypoxic astrocytes is not well understood. In this work, we first showed the increased expression of STC1 in astrocyte cell line and astrocytes in the brain tissues of mice after exposure to hypoxia. Then, we found that knockdown of STC1 inhibited cell viability and increased apoptosis. These effects were mediated by decreasing the levels of SIRT3, UCP2, and glycolytic genes and increasing the levels of ROS. Further studies suggested that STC1 silencing promoted oxidative stress and suppressed glycolysis by downregulating AMPKα1. Moreover, HIF-1α knockdown in hypoxic astrocytes led to decreased expression of STC1 and AMPKα1, indicating that the expression of STC1 was regulated by HIF-1α. In conclusion, our study showed that HIF-1α-induced STC1 could protect astrocytes from hypoxic damage by regulating glycolysis and redox homeostasis in an AMPKα1-dependent manner.

Women with polycystic ovary syndrome present with altered endometrial expression of stanniocalcin-1†

Stanniocalcin-1 (STC-1) is a pro-survival factor that protects tissues against stressors, such as hypoxia and inflammation. STC-1 is co-expressed with the endometrial receptivity markers, and recently endometrial STC-1 was reported to be dysregulated in endometriosis, a condition linked with endometrial progesterone resistance and inflammation. These features are also common in the endometrium in women with polycystic ovary syndrome (PCOS), the most common endocrine disorder in women. Given that women with PCOS present with subfertility, pregnancy complications, and increased risk for endometrial cancer, we investigated endometrial STC-1 expression in affected women. Endometrial biopsy samples were obtained from women with PCOS and controls, including samples from overweight/obese women with PCOS before and after a 3-month lifestyle intervention. A total of 98 PCOS and 85 control samples were used in immunohistochemistry, reverse-transcription polymerase chain reaction, or in vitro cell culture. STC-1 expression was analyzed at different cycle phases and in endometrial stromal cells (eSCs) after steroid hormone exposure. The eSCs were also challenged with 8-bromo-cAMP and hypoxia for STC-1 expression. The findings indicate that STC-1 expression is not steroid hormone mediated although secretory-phase STC-1 expression was blunted in PCOS. Lower expression seems to be related to attenuated STC-1 response to stressors in PCOS eSCs, shown as downregulation of protein kinase A activity. The 3-month lifestyle intervention did not restore STC-1 expression in PCOS endometrium. More studies are warranted to further elucidate the mechanisms behind the altered endometrial STC-1 expression and rescue mechanism in the PCOS endometrium.

AMPK/mTOR Signaling in Autophagy Regulation During Cisplatin-Induced Acute Kidney Injury

Autophagy is a conserved, multistep pathway that degrades and recycles dysfunctional organelles and macromolecules to maintain cellular homeostasis. Mammalian target of rapamycin (mTOR) and adenosine-monophosphate activated-protein kinase (AMPK) are major negative and positive regulators of autophagy, respectively. In cisplatin-induced acute kidney injury (AKI) or nephrotoxicity, autophagy is rapidly induced in renal tubular epithelial cells and acts as a cytoprotective mechanism for cell survival. Both mTOR and AMPK have been implicated in the regulation of autophagy in cisplatin-induced AKI. Targeting mTOR and/or AMPK may offer effective strategies for kidney protection during cisplatin-mediated chemotherapy.

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.

Tumor necrosis factor superfamily 14 is critical for the development of renal fibrosis

Objective: Tumor necrosis factor superfamily protein 14 (TNFSF14) was recently identified as a risk factor in some fibrosis diseases. However, the role of TNFSF14 in renal fibrosis pathogenesis remains unknown.

Results: It was found that TNFSF14 levels were significantly increased both in UUO-induced renal fibrotic mice and in patients with fibrotic nephropathy, compared with those in controls. Accordingly, Tnfsf14 deficiency led to a marked reduction in renal fibrosis lesions and inflammatory cytokines expression in the UUO mice. Furthermore, the levels of Sphk1, a critical molecule that causes fibrotic nephropathy, were remarkably reduced in Tnfsf14 KO mice with UUO surgery. In vitro recombinant TNFSF14 administration markedly up-regulated the expression of Sphk1 of primary mouse renal tubular epithelial cells (mTECs).

Conclusion: TNFSF14 is a novel pro-fibrotic factor of renal fibrosis, for which TNFSF14 up-regulates Sphk1 expression, which may be the underlying mechanism of TNFSF14-mediated renal fibrosis.

Methods: We investigated the effect of TNFSF14 on renal fibrosis and the relationship between TNFSF14 and pro-fibrotic factor sphingosine kinase 1 (Sphk1) by using the unilateral urethral obstruction (UUO)-induced mice renal fibrosis as a model and the specimen of patients with fibrosis nephropathy, by Masson trichrome staining, immunohistochemistry, qRT-PCR, and western blot analysis.

Plasma proteomic biomarker signature of age predicts health and life span

Older age is a strong shared risk factor for many chronic diseases, and there is increasing interest in identifying aging biomarkers. Here, a proteomic analysis of 1301 plasma proteins was conducted in 997 individuals between 21 and 102 years of age. We identified 651 proteins associated with age (506 over-represented, 145 underrepresented with age). Mediation analysis suggested a role for partial cis-epigenetic control of protein expression with age. Of the age-associated proteins, 33.5% and 45.3%, were associated with mortality and multimorbidity, respectively. There was enrichment of proteins associated with inflammation and extracellular matrix as well as senescence-associated secretory proteins. A 76-protein proteomic age signature predicted accumulation of chronic diseases and all-cause mortality. These data support the use of proteomic biomarkers to monitor aging trajectories and to identify individuals at higher risk of disease to be targeted for in depth diagnostic procedures and early interventions.

The Role of Sirtuins in Kidney Diseases

Sirtuins (SIRTs) are class III histone deacetylases (HDACs) that play important roles in aging and a wide range of cellular functions. Sirtuins are crucial to numerous biological processes, including proliferation, DNA repair, mitochondrial energy homeostasis, and antioxidant activity. Mammals have seven different sirtuins, SIRT1–7, and the diverse biological functions of each sirtuin are due to differences in subcellular localization, expression profiles, and cellular substrates. In this review, we summarize research advances into the role of sirtuins in the pathogenesis of various kidney diseases including acute kidney injury, diabetic kidney disease, renal fibrosis, and kidney aging along with the possible underlying molecular mechanisms. The available evidence indicates that sirtuins have great potential as novel therapeutic targets for the prevention and treatment of kidney diseases.

Irisin Pretreatment Protects Kidneys against Acute Kidney Injury Induced by Ischemia/Reperfusion via Upregulating the Expression of Uncoupling Protein 2

As a common disorder, acute kidney injury (AKI) is characterized by high mortality and morbidity, and current therapeutic options for AKI remain limited. Irisin, a muscle factor, plays an important role in metabolic disorders. However, the role of irisin in AKI is still unclear. To assess the effect of irisin on the course of AKI, we used an ischemia/reperfusion (I/R) C57BL/6 mouse model. Supplementation with irisin attenuated kidney injury induced by I/R, as shown by decreases in the levels of serum creatinine and blood urea nitrogen. Animal model studies also showed that irisin pretreatment upregulates the expression of uncoupling protein 2 (UCP2) and protects against the renal cell apoptosis and oxidative stress caused by I/R. In vitro, hypoxia/recovery (H/R) treatment was applied to induce tubular cell apoptosis. Irisin pretreatment ameliorated the cell apoptosis induced by H/R, while transfection of UCP2 siRNA significantly reduced the protective effect of irisin in cells after H/R. In addition, AMPK signaling may be involved in irisin-mediated upregulation of UCP2 in a renal proximal tubular epithelial cell (PTEC) model. Thus, the renoprotective effect of irisin on AKI may be mediated through increasing the expression of UCP2 in kidneys after I/R.

Ischemia-Like Stress Conditions Stimulate Trophic Activities of Adipose-Derived Stromal/Stem Cells

Adipose-derived stromal/stem cells (ASCs) have been shown to exert regenerative functions, which are mainly attributed to the secretion of trophic factors. Upon transplantation, ASCs are facing an ischemic environment characterized by oxygen and nutrient deprivation. However, current knowledge on the secretion capacity of ASCs under such conditions is limited. Thus, the present study focused on the secretory function of ASCs under glucose and oxygen deprivation as major components of ischemia. After exposure to glucose/oxygen deprivation, ASCs maintained distinct viability, but the metabolic activity was greatly reduced by glucose limitation. ASCs were able to secrete a broad panel of factors under glucose/oxygen deprivation as revealed by a cytokine antibody array. Quantification of selected factors by ELISA demonstrated that glucose deprivation in combination with hypoxia led to markedly higher secretion levels of the angiogenic and anti-apoptotic factors IL-6, VEGF, and stanniocalcin-1 as compared to the hypoxic condition alone. A conditioned medium of glucose/oxygen-deprived ASCs promoted the viability and tube formation of endothelial cells, and the proliferation and migration of fibroblasts. These findings indicate that ASCs are stimulated by ischemia-like stress conditions to secrete trophic factors and would be able to exert their beneficial function in an ischemic environment.

AdipoRon, an adiponectin receptor agonist, protects contrast-induced nephropathy by suppressing oxidative stress and inflammation via activation of the AMPK pathway

BACKGROUND

Contrast-induced nephropathy (CIN), a complication caused by using contrast medium during diagnostic and interventional procedures, occurs frequently and lacks effective treatment. AdipoRon, the agonist of adiponectin receptors, has been shown to benefit many organs including the kidney. This study aimed to investigate the role of AdipoRon in treating CIN.

METHODS

CIN model was established via infusing iopromide (1.8 g/kg) in Sprague-Dawley (SD) rats; NRK52E cells were treated with iopromide (5-50 μM). Renal function, renal histopathology, levels of lactate dehydrogenase (LDH) release, cell vitality, oxidative stress and inflammatory markers were measured to evaluate the protective effects of AdipoRon. The level of pAMPK/AMPK was determined by western blot.

RESULTS

AdipoRon (50 mg/kg) significantly reversed serum creatinine, blood urea nitrogen, creatinine clearance and urinary kidney injury molecule-1 levels induced by iopromide in SD rats. Besides, it decreased the renal injury score and apoptosis of renal cells. AdipoRon also reversed the changes of antioxidant markers, pro-oxidant and inflammatory markers induced by iopromide. Moreover, the in vitro studies showed that AdipoRon decreased LDH release and increased cell vitality in NRK52E cells treated with iopromide. Then, we demonstrated that the protection of AdipoRon was accompanied by augmented AMPK phosphorylation. Both in vivo and in vitro studies demonstrated that compound c, an AMPK inhibitor, reversed the AdipoRon-mediated improvement in the CIN model.

CONCLUSION

Our data indicate that AdipoRon protects against the CIN by suppressing oxidative stress and inflammation via activating the AMPK pathway, showing that AdipoRon might be a potential candidate for the prevention and therapy of CIN.

Poricoic acid A activates AMPK to attenuate fibroblast activation and abnormal extracellular matrix remodelling in renal fibrosis

BACKGROUND

In chronic kidney disease, although fibrosis prevention is beneficial, few interventions are available that specifically target fibrogenesis. Poricoic acid A (PAA) isolated from Poria cocos exhibits anti-fibrotic effects in the kidney, however the underlying mechanisms remain obscure.

PURPOSE

We isolated PAA and investigated its effects and the underlying mechanisms in renal fibrosis.

STUDY DESIGN

Unilateral ureteral obstruction (UUO) and 5/6 nephrectomy (Nx) animal models and TGF-β1-induced renal fibroblasts (NRK-49F) were used to investigate the anti-fibrotic activity of PAA and its underlying mechanisms.

METHODS

Western blots, qRT-PCR, immunofluorescence staining, co-immunoprecipitation and molecular docking methods were used. Knock-down and knock-in of adenosine monophosphate-activated protein kinase (AMPK) in the UUO model and cultured NRK-49F cells were employed to verify the mechanisms of action of PAA.

RESULTS

PAA improved renal function and alleviated fibrosis by stimulating AMPK and inhibiting Smad3 specifically in Nx and UUO models. Reduced AMPK activity was associated with Smad3 induction, fibroblast activation, and the accumulation and aberrant remodelling of extracellular matrix (ECM) in human renal puncture samples and cultured NRK-49F cells. PAA stimulated AMPK activity and decreased fibrosis in a dose-dependent manner, thus showing that AMPK was essential for PAA to exert its anti-fibrotic effects. AMPK deficiency reduced the anti-fibrotic effects of PAA, while AMPK overexpression enhanced its effect.

CONCLUSION

PAA activated AMPK and further inhibited Smad3 specifically to suppress fibrosis by preventing aberrant ECM accumulation and remodelling and facilitating the deactivation of fibroblasts.

Expression, function and clinical application of stanniocalcin-1 in cancer

The glycoprotein stanniocalcin-1 functions as a regulatory endocrine hormone that maintains the balance of calcium and phosphorus in bony fish and as a paracrine/autocrine factor involved in many physiological/pathological processes in humans, including carcinogenesis. In this review, we provide an overview of (a) the possible mechanisms through which STC1 affects the malignant properties of cancer, (b) transcriptional and post-transcriptional regulation pathways of STC1 and (c) the potential clinical relevance of STC1 as a cancer biomarker and even a therapeutic target in the future. Exploring the role of STC1 in cancer development may provide a better understanding of the tumorigenesis process in humans and may facilitate finding an effective therapeutic method against cancer.

The power of proteomics to monitor senescence-associated secretory phenotypes and beyond: toward clinical applications

INTRODUCTION

Cellular senescence is a rapidly growing field with potential relevance for the treatment of multiple human diseases. In the last decade, cellular senescence and the senescence-associated secretory phenotype (SASP) have emerged as central drivers of aging and many chronic diseases, including cancer, neurodegeneration, heart disease and osteoarthritis. Major efforts are underway to develop drugs that selectively eliminate senescent cells (senolytics) or alter the SASP (senomorphics) to treat age-related diseases in humans. The translation of senescence-targeting therapies into humans is still in early stages. Nonetheless, it is clear that proteomic approaches will facilitate the discovery of important SASP proteins, development of senescence- and SASP-derived biomarkers, and identification of therapeutic targets for senolytic and senomorphic drugs.

AREAS COVERED

We review recent proteomic studies of cellular senescence and their translational relevance and, particularly, characterization of the secretory phenotype and preclinical development of biomarkers (from 2008-2020, PubMed). We focus on emerging areas, such as the heterogeneity of senescent cells and the SASP, extracellular vesicles released by senescent cells, and validating biomarkers of aging in vivo.

EXPERT OPINION

Proteomic and multi-omic approaches will be important for the development of senescence-based biomarkers to facilitate and monitor future therapeutic interventions that target senescent cells.

A proteomic atlas of senescence-associated secretomes for aging biomarker development

The senescence-associated secretory phenotype (SASP) has recently emerged as a driver of and promising therapeutic target for multiple age-related conditions, ranging from neurodegeneration to cancer. The complexity of the SASP, typically assessed by a few dozen secreted proteins, has been greatly underestimated, and a small set of factors cannot explain the diverse phenotypes it produces in vivo. Here, we present the “SASP Atlas,” a comprehensive proteomic database of soluble proteins and exosomal cargo SASP factors originating from multiple senescence inducers and cell types. Each profile consists of hundreds of largely distinct proteins but also includes a subset of proteins elevated in all SASPs. Our analyses identify several candidate biomarkers of cellular senescence that overlap with aging markers in human plasma, including Growth/differentiation factor 15 (GDF15), stanniocalcin 1 (STC1), and serine protease inhibitors (SERPINs), which significantly correlated with age in plasma from a human cohort, the Baltimore Longitudinal Study of Aging (BLSA). Our findings will facilitate the identification of proteins characteristic of senescence-associated phenotypes and catalog potential senescence biomarkers to assess the burden, originating stimulus, and tissue of origin of senescent cells in vivo.

The first comprehensive proteomic characterization of senescence-associated secretory phenotypes (SASPs) to our knowledge reveals substantial heterogeneity based on senescence inducer and cell type. The SASP Atlas represents a valuable resource for the identification of further candidate biomarkers of ageing.

Effects of porcine STC-1 on cell metabolism and mitochondrial function

Stanniocalcin (STC-1), a kind of glycoprotein hormone, was first found in fish and mainly regulates calcium/phosphorus metabolism in the body. To explore the biological function of the porcine STC-1 gene, the effects of changes in stanniocalcin expression on cellular metabolism and mitochondrial function were studied. A vector overexpressing the STC-1 gene and an siRNA silencer of the STC-1 gene were transfected into porcine kidney epithelial PK15 cells. After the STC-1 gene expression level was induced to change, STC-1 protein- and mitochondrial function-related proteins such as PMP70, OPA, DRP, Mfn and STC-1-related acetylated protein were detected by Western blotting. Cell apoptosis, mitochondrial membrane potential, reactive oxygen species (ROS), and ATP were detected using flow cytometry methods. Transmission electron microscopy was used to observe the changes in mitochondrial structure and morphology. The results showed that overexpression of the STC-1 gene could significantly upregulate the levels of PMP70, OPA, DRP and Mfn. STC-1 gene expression, which could decrease the apoptosis rate and reactive oxygen species production to significantly increase the cell membrane potential and reduce the formation of intracellular ATP, which also affected the morphology and number of mitochondria. The results were reversed when the STC-1 gene expression was silenced. The results suggested that the porcine STC-1 gene is closely related to cell growth metabolism and mitochondrial function, which influence the mitochondrial function-related proteins. The present study is useful for further understanding STC-1 gene function and provides a theoretical basis for improving the production characteristics of domestic pigs.

Stanniocalcin-1 is a Modifier of Oxygen-Induced Retinopathy Severity

Purpose/Aim: Abnormal activation of signaling pathways related to angiogenesis, inflammation, and oxidative stress has been implicated in the pathophysiology of retinopathy of prematurity (ROP), a leading cause of blindness in pre-term infants. Therapies for ROP include laser and anti-vascular endothelial growth factor agents. However, these therapies have side effects, and even with adequate treatment, visual acuity can be impaired. Novel therapeutic options are needed. Stanniocalcin-1 (STC-1) is a neuroprotective protein with anti-inflammatory and anti-oxidative stress properties. Rodent models of oxygen-induced retinopathy (OIR) were selected to determine whether STC-1 plays a role in the development of OIR.Materials and methods: STC-1 gene and protein expression was first evaluated in the Sprague Dawley rat OIR model that is most similar to human ROP. OIR was then induced in wild-type and Stc-1-/- mice. Retinas were isolated and evaluated for avascular and neovascular area on retinal flat mounts. Quantification of gene expression by quantitative real-time PCR was performed. VEGF was assayed by ELISA in media obtained from induced pluripotent stem-cell-derived retinal pigment epithelial (iPS-RPE) cells following treatment with recombinant STC-1.Results: STC-1 was significantly upregulated in a rat model of OIR compared to room air controls at the gene (P < .05) and protein (P < .001) level. Stc-1-/- OIR mice showed significantly worse ROP compared to wild-type mice as assessed by avascular (20.2 ± 2.4% vs 15.2 ± 2.5%; P = .02) and neovascular area (14.3 ± 2.7% vs 8.8 ± 3.7%; P < .05). Transcript levels of vascular endothelial growth factor-A were significantly higher in Stc-1-/- OIR mice compared to wild-type controls (P = .03). STC-1 reduced VEGF production in iPS-RPE cells (P = .01).Conclusions: STC-1 plays a role in the OIR stress response and development of pathologic vascular features in rodent OIR models by regulating VEGF levels.

Sevoflurane inhibits the progression of ovarian cancer through down-regulating stanniocalcin 1 (STC1)

Background

Ovarian cancer is one of the leading causes of female death worldwide, with a poor prognosis of advanced patients. Sevoflurane, a volatile anesthetic commonly used in clinical operations, has been reported to have anti-cancer activity against some tumors. In the present study, we aimed to investigate the effects of sevoflurane on the progression of ovarian cancer and its potential mechanism.

Methods

The effects of sevoflurane on ovarian cancer cell viability, proliferation, migration, invasion, cell cycle, and apoptosis were determined by functional experiments in vitro. Gelatin zymography assay was performed to examine MMP9 activity. In vivo, sevoflurane was injected into mice of transplantation tumor with SKOV3 cells or with pcDNA-STC1 treated SKOV3 cells.

Results

We found that sevoflurane inhibited the viability of SKOV3 and OVCAR3 cells in a dose-dependent manner, and colony formation assay revealed that sevoflurane inhibited ovarian cancer cell colony-formation abilities. Additionally, sevoflurane could induce cell cycle arrest and promote cell apoptosis in SKOV3 and OVCAR3 cells. Moreover, sevoflurane reduced the migration and invasion abilities of SKOV3 and OVCAR3 cells, as well as the MMP-9 activity. Furthermore, sevoflurane down-regulated the expression of stanniocalcin 1 (STC1), and up-regulation of STC1 could reverse the inhibitory effects of sevoflurane on cell proliferation and invasion. In vivo, sevoflurane significantly inhibited the tumor growth, which was be reversed by STC1 overexpression.

Conclusion

These data reveal an anti-cancer activity of sevoflurane on the growth and invasion of ovarian cancer, which may be through down-regulating STC1. Sevoflurane may serve as a potential anti-cancer agent in ovarian cancer therapy.

Stanniocalcin-1 ameliorates cerebral ischemia by decrease oxidative stress and blood brain barrier permeability

Blood brain barrier (BBB) permeability and oxidative stress have been reported to be important mechanisms for brain damage following ischemic stroke and stanniocalcin-1 (STC-1), a neuroprotective protein, has anti-inflammatory and anti-oxidative stress properties. Herein, we report the effect of STC-1 on BBB permeability and brain oxidative stress after stroke in an animal model. Male Wistar received an intracerebroventricularly injection of human recombinant STC-1 (100 ng/kg) or saline and were subjected to sham procedure or global cerebral ischemia/reperfusion (I/R) model. Six and 24 h after I/R, neurological evaluation was performed; at 24 h brain water content was evaluated in the total brain, and BBB permeability, nitrite/nitrate (N/N) concentration, lipid peroxidation, protein carbonyls formation, superoxide dismutase (SOD) and catalase (CAT) activity were determined in the hippocampus, cortex, prefrontal cortex, striatum and cerebellum. Rats exhibited neurological deficit at 6 and 24 h after I/R and STC-1 reduction at 24 h. After I/R there were an increase of brain water content, BBB permeability in the hippocampus, cortex and pre-frontal cortex and N/N in the hippocampus, and STC-1 decreased this level only in the hippocampus. STC-1 decreased lipid peroxidation in the hippocampus, cortex and prefrontal cortex and protein oxidative damage in the hippocampus and cortex. SOD activity decreased in the hippocampus, cortex and prefrontal cortex after I/R and STC-1 reestablished these levels in the hippocampus and cortex. CAT activity decreased only in the hippocampus and cortex and STC-1 increased the CAT activity in the hippocampus. Our data provide the first experimental demonstration that STC-1 reduced brain dysfunction associated with cerebral I/R in rats, by decreasing BBB permeability and oxidative stress parameters.

Non-coding RNA-Associated ceRNA Networks in a New Contrast-Induced Acute Kidney Injury Rat Model

Contrast-induced acute kidney injury (CI-AKI) is a severe complication of intravascular applied radial contrast media, and recent progress in interventional therapy and angiography has revived interest in explaining detailed mechanisms and developing effective treatment. Recent studies have indicated a potential link between CI-AKI and microRNA (miRNA). However, the potential non-coding RNA-associated-competing endogenous RNA (ceRNA) pairs involved in CI-AKI still remain unclear. In this study, we systematically explored the circRNA or lncRNA-associated-ceRNA mechanism in a new rat model of CI-AKI through deep RNA sequencing. The results revealed that the expression of 38 circRNAs, 12 lncRNAs, 13 miRNAs and 127 mRNAs were significantly dysregulated. We performed Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses for mRNAs with significantly different expression and then constructed comprehensive circRNA or lncRNA-associated ceRNA networks in kidney of CI-AKI rats. Thereafter, two constructed ceRNA regulatory pathways in this CI-AKI rat model—novel_circ_0004153/rno-miR-144-3p/Gpnmb or Naglu and LNC_000343/rno-miR-1956-5p/KCP—were validated by real-time qPCR. This study is the first one to provide a systematic dissection of non-coding RNA-associated ceRNA profiling in kidney of CI-AKI rats. The selected non-coding RNA-associated ceRNA networks provide new insight for the underlying mechanism and may profoundly affect the diagnosis and therapy of CI-AKI.

STC-1 ameliorates renal injury in diabetic nephropathy by inhibiting the expression of BNIP3 through the AMPK/SIRT3 pathway

Diabetic kidney disease (DKD) is the leading cause of morbidity and mortality in individuals with diabetes, and it is the leading cause of end-stage renal disease (ESRD) worldwide. Stanniocalcin-1 (STC-1) is present in various tissues, and it has antioxidant and anti-apoptotic activities, which play a role in kidney protection, including diabetic nephropathy (DN). However, the mechanism that underlies these effects remains unknown. This study suggests that STC-1 ameliorates oxidative stress and cell apoptosis in the kidneys of db/db mice and high glucose (HG)-treated BUMPT cells by inhibiting Bnip3 expression through AMPK/Sirt3 pathway activation. In the clinic, DKD patients with high levels of STC-1 have a better prognosis than patients with low STC-1 levels. Thus, we concluded that STC-1 ameliorates renal injury in DN by inhibiting the expression of Bnip3 through the AMPK/SIRT3 pathway and that serum STC-1 is independently associated with DKD progression in patients with type 2 diabetes. As high STC-1 levels indicate a better prognosis, synthetic STC-1 may become a potential drug for the treatment of DKD patients.

High expression of herpes virus entry mediator is associated with poor prognosis in clear cell renal cell carcinoma

Herpes virus entry mediator (HVEM), also called tumor necrosis factor receptor superfamily 14 (TNFRSF14), is highly expressed in various tumor tissues and plays critical roles in tumor biology. However, the role of HVEM in clear cell renal cell carcinoma (ccRCC) is unknown. This study evaluated the clinical importance of HVEM in patients with ccRCC. HVEM expression was assessed in fresh and 140 archived paraffin-embedded ccRCC tissue samples by quantitative RT-PCR, western blot, and immunohistochemical staining. HVEM expression was higher in ccRCC than in paired peritumor tissue. Kaplan-Meier analysis showed that high level of HVEM expression was associated with poor overall survival (OS) and disease-free survival (DFS) in patients with ccRCC (both P < 0.001). Multivariate analysis indicated that HVEM overexpression was independently prognostic of survival in ccRCC patients. Two novel nomogram systems were constructed by integrating HVEM expression and other clinical parameters to predict OS (c-index 0.75) and DFS (c-index 0.74) in these patients, with both having better predictive accuracy than traditional TNM (c-index 0.65 for OS and 0.639 for DFS) and Fuhrman (c-index 0.612 for OS and 0.641 for DFS) systems. In addition, HVEM silencing led to an observable reduction in tumor cells growth in vitro and in vivo. Taken together, these findings indicate that high HVEM expression is a novel and independent adverse predictor of clinical outcomes in patients with ccRCC and that HVEM may be a potential therapeutic target.

Mitochondrial dysfunction in acute kidney injury and sex-specific implications

The kidney is one of the most energy-demanding organs in the human body, and the maintenance of mitochondrial homeostasis is central to kidney function. Recent advances have led to a greater appreciation of how mitochondrial dysfunction contributes to the pathogenesis of AKI, from decreased ATP production, to enhanced mitochondrial oxidative stress, cell necrosis and apoptosis. Accumulating evidence suggests sexual dimorphism in the response to AKI with males demonstrating greater risk for developing ischemia-reperfusion and sepsis-induced kidney injury. In contrast, females may be more susceptible to nephrotoxic-AKI. There are important sex-related differences in mitochondrial respiration, biogenesis and dynamics that likely contribute to the observed sexual dimorphism in AKI. Sex hormones mediate many of these differences with multiple preclinical studies demonstrating the renoprotective actions of estrogen in many rodent models of AKI. Estrogenic control of mitochondrial biogenesis, function and reactive oxygen species (ROS) generation is discussed. Furthermore, the potential role for sex chromosomes in mediating sex differences in AKI is examined. Novel animal models such as the "four core genotypes" (FCG) mouse model provide us with important tools to study sex chromosome effects in kidney health and disease. By understanding the influences of sexual dimorphism or sex hormones on mitochondrial homeostasis and disease manifestations, we may be able to identify novel therapeutic targets and improve existing treatment options for AKI.

UCP2-dependent improvement of mitochondrial dynamics protects against acute kidney injury

Acute kidney injury (AKI) is a public health concern, with high morbidity and mortality rates in hospitalized patients and because survivors have an increased risk of progression to chronic kidney disease. Mitochondrial damage is the critical driver of AKI-associated dysfunction and loss of tubular epithelial cells; however, the pathways that mediate these events are poorly defined. Here, in murine ischemia/reperfusion (I/R)-induced AKI, we determined that mitochondrial damage is associated with the level of renal uncoupling protein 2 (UCP2). In hypoxia-damaged proximal tubular cells, a disruption of mitochondrial dynamics demonstrated by mitochondrial fragmentation and disturbance between fusion and fission was clearly indicated. Ucp2-deficient mice (knockout mice) with I/R injury experienced more severe AKI and mitochondrial fragmentation than wild-type mice. Moreover, genetic or pharmacological treatment increased UCP2 expression, improved renal function, reduced tubular injury and limited mitochondrial fission. In cultured proximal tubular epithelial cells, hypoxia-induced mitochondrial fission was exacerbated in cells with UCP2 deletion, whereas an increase in UCP2 ameliorated the hypoxia-induced disturbance of the balance between mitochondrial fusion and fission. Furthermore, results following modulation of UCP2 suggested it has a role in preserving mitochondrial integrity by preventing loss of membrane potential and reducing subsequent mitophagy. Taken together, our results indicate that UCP2 is protective against AKI and suggest that enhancing UCP2 to improve mitochondrial dynamics has potential as a strategy for improving outcomes of renal injury. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Megalin mediates plasma membrane to mitochondria cross-talk and regulates mitochondrial metabolism

Mitochondrial intracrines are extracellular signaling proteins, targeted to the mitochondria. The pathway for mitochondrial targeting of mitochondrial intracrines and actions in the mitochondria remains unknown. Megalin/LRP2 mediates the uptake of vitamins and proteins, and is critical for clearance of amyloid-β protein from the brain. Megalin mutations underlie the pathogenesis of Donnai-Barrow and Lowe syndromes, characterized by brain defects and kidney dysfunction; megalin was not previously known to reside in the mitochondria. Here, we show megalin is present in the mitochondria and associates with mitochondrial anti-oxidant proteins SIRT3 and stanniocalcin-1 (STC1). Megalin shuttles extracellularly-applied STC1, angiotensin II and TGF-β to the mitochondria through the retrograde early endosome-to-Golgi transport pathway and Rab32. Megalin knockout in cultured cells impairs glycolytic and respiratory capacities. Thus, megalin is critical for mitochondrial biology; mitochondrial intracrine signaling is a continuum of the retrograde early endosome-to-Golgi-Rab32 pathway and defects in this pathway may underlie disease processes in many systems.