Cellular senescence of renal tubular epithelial cells in renal fibrosis

Klotho Protein: A Multifaceted Guardian of Healthy Aging and Its Therapeutic Potential

The Klotho protein, encoded by the KL gene, has garnered significant attention as a pivotal biomolecule in the field of aging research. Its expression levels are closely correlated with both lifespan and overall health status, exerting influence over critical physiological processes such as metabolic homeostasis, oxidative stress response, and inflammation modulation. This review aims to systematically examine the multifaceted roles of Klotho within the context of aging and its implications for various age-associated disorders. We highlight the emerging evidence suggesting that Klotho may serve as a key regulator in age-related pathologies, including cardiovascular diseases, neurodegenerative disorders, and metabolic syndromes. Furthermore, we explore the potential of Klotho as a therapeutic target, positing that interventions aimed at enhancing Klotho activity could offer novel strategies for alleviating the health burdens experienced by the aging population.

Mesenchymal Stem Cells Mediated Suppression of GREM2 Inhibits Renal Epithelial-Mesenchymal Transition and Attenuates the Progression of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide. Despite advancements in various treatments, the prevalence of DKD continues to rise, leading to a significant increase in the demand for dialysis and kidney transplantation. This study aimed to evaluate the effects of a Small cell＋Ultra Potent＋Scale UP cell (SMUP-Cell), a type of human umbilical cord blood-derived mesenchymal stem cell, on DKD in the db/db mouse model of type 2 diabetes mellitus. After administering SMUP-Cells via tail vein injection in db/db mice, the animals were monitored over a three-month period. The db/db mice exhibited an increased urine albumin-to-creatinine ratio (UACR). However, the administration of SMUP-Cells resulted in a reduction of the UACR. The expression levels of desmin, α-smooth muscle actin, and fibronectin-markers of epithelial-mesenchymal transition (EMT)-as well as kidney injury molecule 1, a sensitive marker of tubular injury, were significantly elevated in db/db mice. Treatment with SMUP-Cells ameliorated all of these changes. Notably, Gremlin isoform 2 (Grem2) exhibited the most significant difference in expression according to the transcriptome analysis. The elevated expression of Grem2 in db/db mice was significantly reduced following SMUP-Cell treatment. In vitro, treatment with high glucose and cholesterol induced Grem2 expression in renal tubular epithelial cells (RTECs), while Grem2 knockdown effectively prevented fibrosis and senescence induced by high glucose and cholesterol in RTECs. These observations suggest that SMUP-Cells inhibit the progression of DKD by inhibiting EMT through the reduction of Grem2 expression in RTECs.

G-Protein-Coupled Receptors in Chronic Kidney Disease Induced by Hypertension and Diabetes

Hypertension and diabetes are two common causes of chronic kidney disease. Hypertension can induce renal vascular injury, glomerular damage, podocyte loss, and tubular injury, leading to tubulointerstitial fibrosis. A number of factors influence the regulation of hypertension, among which G-protein-coupled receptors (GPCRs) have been studied extensively because they are desirable targets for drug development. Compared to hypertension, the regulatory effects of GPCRs on hypertensive kidney disease (HKD) are less generalized. In this review, we discussed the GPCRs involved in hypertensive kidney disease, such as angiotensin II receptors (AT1R and AT2R), Mas receptor (MasR), Mas-related G-protein-coupled receptor member D (MrgD), relaxin family receptor 1 (RXFP1), adenosine receptors (A1, A2A, A2B, and A3), purinergic P2Y receptors, and endothelin receptors (ETA and ETB). The progression of HKD is rarely reversed but can be retarded by ameliorating the hypertensive microenvironment in the kidneys. However, simply reducing blood pressure cannot stop the progression of HKD. Diabetic nephropathy (DN) is the most common cause of end-stage renal disease (ESRD), which is a major cause of morbidity and mortality in diabetes. Many GPCRs are involved in DN. Here, we select some well-studied GPCRs that are directly associated with the pathogenesis of DN to illustrate their mechanisms. The main purpose of this review is to provide an overview of the GPCRs involved in the occurrence and progression of HKD and DN and their probable pathophysiological mechanisms, which we hope will help in developing new therapeutic strategies.

Ferroptosis Activation Contributes to Kidney Aging in Mice by Promoting Tubular Cell Senescence

Kidney aging is the strongest independent risk factor for chronic kidney disease. Ferroptosis, a recently discovered form of cell death mediated by iron overload and lipid peroxidation accumulation, has an unclear role in kidney aging. To determine the pathophysiological role of ferroptosis during kidney aging, we employed immunofluorescence, Western blotting, and qRT-PCR to analyze renal cells and tissues in natural aging and accelerated aging mouse models. We investigated the activation of ferroptosis during aging and examined the effects of the ferroptosis inhibitor ferrostatin-1 and the ferroptosis inducer erastin on age-related renal interstitial fibrosis in aged model mice. We found that both naturally aged and stress-aged renal tubular cells and tissues presented extensive abnormalities in ferroptosis-related genes. This included increased expression of ACSL4 and decreased expression of GPX4. Additionally, these abnormalities were accompanied by elevated free iron concentrations; increased expression of iron import proteins, and iron storage proteins; and downregulated expression of the iron export protein Fpn. We further discovered that ferrostatin-1 inhibited, whereas erastin increased, age-related renal interstitial fibrosis in aged mouse kidneys. Finally, our study revealed that aged renal tubular cells exhibit characteristics of ferroptosis and are highly sensitive to ferroptosis, as demonstrated by the activation of ferroptosis-related genes, accumulation of lipid peroxides. Ferrostatin-1 inhibited, whereas erastin increased, D-galactose induced, renal tubular cell senescence in vitro. These findings suggest that ferroptosis exacerbates renal tubular cell senescence and age-related renal interstitial fibrosis. Managing ferroptosis may represent a novel strategy for reversing kidney aging.

Identification of potential anti aging drugs and targets in chronic kidney disease

Chronic kidney disease (CKD) is highly prevalent, incurable, and lacks effective treatments. Aging is closely linked to various kidney diseases. In this study, we combined CKD and aging using bioinformatics approaches to identify potential anti aging drugs and therapeutic targets for CKD. We analyzed datasets GSE37171 and GSE66494 from the GEO database, identifying 317 differentially expressed genes (DEGs). By intersecting these DEGs with aging related genes, we identified 23 aging associated differential genes (ARDEGs). A protein-protein interaction (PPI) network was constructed using the STRING database, and the top 10 hub ARDEGs were identified using Cytoscape software. Potential anti aging drugs, including Cinnamaldehyde, were identified through the ceRNA and transcription factor regulatory networks, as well as the DGldb database. Among the key regulatory genes identified in CKD patient samples were SOD2, FGF21, FOS, RELA, DDIT4, BMI1, DUSP6, LGALS3, CXCR2, and CEBPB. Cinnamaldehyde and other drugs were found to target aging associated pathways, suggesting their potential to delay CKD progression through modulating these pathways. Finally, we verified the low-expression of DDIT4 and DUSP6, the two targets of Cinnamaldehyde, in unilateral ureteral obstruction (UUO) animal model. Additionally, Cinnamaldehyde was shown to reduce the expression of fibrosis markers such as fibronectin (FN) and α-smooth muscle actin (α-SMA) in HK2 cells under TGF-β1 stimulation. This study provides a foundational understanding of aging related molecular targets in CKD and offers new directions for developing anti aging therapies to treat CKD.

Mechanism of Mitophagy to Protect Yak Kidney from Hypoxia-Induced Fibrosis Damage by Regulating Ferroptosis Pathway

Renal fibrosis is a critical pathological feature of various chronic kidney diseases, with hypoxia being recognized as an important factor in inducing fibrosis. Yaks have long inhabited high-altitude hypoxic environments and do not exhibit fibrotic damage under chronic hypoxia. However, the underlying protective mechanisms remain unclear. This study compared the renal tissue structure and collagen volume between low-altitude cattle and high-altitude yaks, revealing that yaks possess a significantly higher number of renal tubules than cattle, though collagen volume showed no significant difference. Under hypoxic treatment, we observed that chronic hypoxia induced renal fibrosis in cattle, but did not show a significant effect in yaks, suggesting that the hypoxia adaptation mechanisms in yaks may have an anti-fibrotic effect. Further investigation demonstrated a significant upregulation of P-AMPK/AMPK, Parkin, PINK1, LC3Ⅱ/Ⅰ, and BECN1, alongside a downregulation of P-mTOR/mTOR in yak kidneys. Additionally, hypoxia-induced renal tubular epithelial cells (RTECs) showed increased expression of mitophagy-related proteins, mitochondrial membrane depolarization, and an increased number of lysosomes, indicating that hypoxia induces mitophagy. By regulating the mitophagy pathway through drugs, we found that under chronic hypoxia, activation of mitophagy upregulated E-cadherin protein expression while downregulating the expression of Vimentin, α-SMA, Collagen I, and Fibronectin. Simultaneously, there was an increase in SLC7A11, GPX4, and GSH levels, and a decrease in ROS, MDA, and Fe2⁺ accumulation. Inhibition of mitophagy produced opposite effects on protein expression and cellular markers. Further studies identified ferroptosis as a key mechanism promoting renal fibrosis. Moreover, in renal fibrosis models, mitophagy reduced the accumulation of ROS, MDA, and Fe2⁺, thereby alleviating ferroptosis-induced renal fibrosis. These findings suggest that chronic hypoxia protects yaks from hypoxia-induced renal fibrosis by activating mitophagy to inhibit the ferroptosis pathway.

Update of cellular senescence in kidney fibrosis: from mechanism to potential interventions

Kidney fibrosis is the final common pathway of virtually all chronic kidney disease (CKD). However, despite great progress in recent years, no targeted antifibrotic therapies have been approved. Epidemiologic, clinical, and molecular evidence suggest that aging is a major contributor to the increasing incidence of CKD. Senescent renal tubular cells, fibroblasts, endothelial cells, and podocytes have been detected in the kidneys of patients with CKD and animal models. Nonetheless, although accumulated evidence supports the essential role of cellular senescence in CKD, the mechanisms that promote cell senescence and how senescent cells contribute to CKD remain largely unknown. In this review, we summarize the features of the cellular senescence of the kidney and discuss the possible functions of senescent cells in the pathogenesis of kidney fibrosis. We also address whether pharmacological approaches targeting senescent cells can be used to retard the the progression of kidney fibrosis.

Klotho alleviates oxidative stress and mitochondrial dysfunction through the Nrf2/HO-1 pathway, thereby reducing renal senescence induced by calcium oxalate crystals

Klotho is an antiaging protein that is primarily secreted by the kidneys. This study aimed to explore the protective effects of Klotho against calcium oxalate (CaOx) crystal-induced renal aging and the underlying mechanisms involved. We established a mouse model of CaOx crystal deposition via the intraperitoneal injection of glyoxylate (Gly) and constructed an in vitro model by stimulating HK2 cells with calcium oxalate monohydrate (COM). Renal aging levels were assessed through β-galactosidase (SA-β-gal) staining and the detection of senescence-associated markers. By overexpressing Klotho both in vitro and in vivo, we examined oxidative stress, mitochondrial function, and renal aging levels. We then evaluated the role of Nrf2/HO-1 signalling pathway-mediated oxidative stress in CaOx crystal-induced renal aging by applying the oxidative stress scavenger N-acetylcysteine (NAC) and overexpressing or inhibiting Nrf2 in HK2 cells. We subsequently overexpressed Klotho while inhibiting Nrf2 to confirm that Klotho exerts its protective effects through the Nrf2/HO-1 pathway. Finally, we measured the methylation levels of the Klotho promoter and assessed the degree of renal aging induced by CaOx crystals after the inhibition of Klotho DNA methylation. We found that the overexpression of Klotho alleviated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, thereby reducing renal aging. NAC mitigated CaOx crystal-induced renal aging. The overexpression of Nrf2 alleviated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, thus reducing renal aging, whereas the knockdown of Nrf2 exacerbated CaOx crystal-induced oxidative stress and mitochondrial dysfunction, leading to more severe renal aging. The combination of Klotho overexpression and Nrf2 knockdown reversed the protective effects of Klotho. CaOx crystals induced an increase in the DNA methylation levels of Klotho in the kidneys, and the inhibition of DNA methylation alleviated CaOx-induced renal aging. This study revealed that Klotho plays a crucial role in calcium oxalate crystal-induced kidney senescence by influencing kidney oxidative stress and mitochondrial function through the Nrf2/HO-1 pathway.

Cells of all trades - on the importance of spatial positioning of senescent cells in development, healing and aging

Biological processes are often spatially regulated, ensuring molecular and cellular events occur in their most strategically advantageous locations. Cellular senescence, marked by cell cycle arrest and hypersecretion, is recognized as an important part of physiological processes like development and healing, but it also contributes to aging and disease. However, the spatial distribution of senescent cells and its physiological and pathological impact remain unclear. Here we compile evidence on senescent cell localization in development, healing, and aging. We emphasize the significance of their spatial patterns and speculate on the effects of disrupted spatial positioning of senescence in relation to pathologies. To summarize the specific spatial functions of senescent cells, we propose to refer to them as 'barrier' and 'conductor' functions. The 'barrier' function of senescent cells, due to their altered morphology and apoptosis resistance, separates tissues and builds a border between two environments. The conductor function, with the secretion of signaling factors, influences the surrounding area and stimulates migration, differentiation, or proliferation, among other processes. Overall, this Review explores the spatial patterning of cellular senescence in biological processes, highlighting its dual roles as 'barrier' and 'conductor' functions, and examines the implications of senescent cell distribution in development, healing, aging, and disease.

5-aminolaevulinic acid with sodium ferrous citrate alleviated kidney injury and fibrosis in a unilateral ureteral obstruction model

PURPOSE

This study aimed to investigate the potential therapeutic effects of 5-aminolaevulinic acid (5-ALA) combined with sodium ferrous citrate (SFC) on kidney injury and fibrosis in a mouse model of unilateral ureteral obstruction (UUO)-induced chronic kidney disease (CKD).

METHODS

A murine UUO model was used to mimic human CKD. The mice received daily intragastric administration of 5-ALA/SFC for 7 and 14 consecutive days. Serum creatinine (Cr) and blood urea nitrogen (BUN) levels and histological evaluations were performed to assess the renal function parameters underlying 5-ALA/SFC treatment in the UUO model. Differentially expressed genes (DEGs) were analyzed by RNA sequencing (RNA-Seq), and the results were validated by quantitative real-time PCR (qRT-PCR). The severity of renal fibrosis was evaluated using Sirius red and Masson's trichrome (MT) staining techniques, while the expression of fibrosis-related genes was examined using western blotting and immunohistochemistry.

RESULTS

Our findings demonstrated that 5-ALA/SFC treatment improved UUO-induced renal dysfunction, attenuated tubular damage, and significantly reduced serum Cr and BUN levels as well as the mRNA expression and secretion of pro-inflammatory and programmed cell death-related cytokines in kidney tissues. Furthermore, 5-ALA/SFC suppressed renal tissue fibrosis and downregulated the mRNA and protein expression of fibrosis-related genes. Notably, treatment with 5-ALA/SFC led to the significant upregulation of protein expression levels of PPAR gamma-coactivator-1α (PGC-1α), indicating its role in inhibiting inflammation and fibrosis through the activation of the PGC-1α signaling pathway.

CONCLUSION

5-ALA/SFC exhibits renoprotective effects in UUO-induced CKD by attenuating inflammation, cell death, and suppressing renal fibrosis. These findings suggest a specific renal protective mechanism for 5-ALA/SFC, highlighting its potential as a novel therapeutic agent for human CKD treatment.

Lactobacillus paracasei Activates the KDM3A/VAMP1 Axis to Induce Autophagy in Renal Tubular Epithelial Cells in Chronic Kidney Disease

Chronic kidney disease (CKD) is anticipated to be the fifth cause of global death by 2040 due to the lack of therapeutic tools currently. Lactobacillus paracasei (L. paracasei) isolated from artisanal fermented beverages has been implicated to have health-promoting properties. This study was designed to investigate the effects of L. paracasei on the mechanisms underlying renal injury regulation during CKD. A mouse CKD model was developed by 5/6 nephrectomy, and a fibrotic cell model was induced on human kidney-2 (HK-2) cells using TGF-β1. L. paracasei alleviated renal injury in CKD mice and TGF-β1-induced inflammatory and fibrotic injury in HK-2 cells. L. paracasei exerted in vitro and in vivo benefits by inducing lysine-specific demethylase 3A (KDM3A), and the knockdown of KDM3A markedly attenuated the therapeutic benefit of L. paracasei. KDM3A activated vacuole membrane protein 1 (VMP1) by removing the H3K9me1/2 modification on its promoter. L. paracasei activated autophagy to mitigate renal damage, which was compromised by the autophagy inhibitor 3-MA, allowing renal damage to intensify. Taken together, L. paracasei activates KDM3A expression and further activates VMP1 expression by removing inhibitory H3K9me1/2 modification on the VMP1 promoter to alleviate CKD by activating autophagy in renal tubular epithelial cells.

Systemic aging and aging-related diseases

Aging is a biological process along with systemic and multiple organ dysfunction. It is more and more recognized that aging is a systemic disease instead of a single-organ functional disorder. Systemic aging plays a profound role in multiple diseases including neurodegenerative diseases, cardiovascular diseases, and malignant diseases. Aged organs communicate with other organs and accelerate aging. Skeletal muscle, heart, bone marrow, skin, and liver communicate with each other through organ-organ crosstalk. The crosstalk can be mediated by metabolites including lipids, glucose, short-chain fatty acids (SCFA), inflammatory cytokines, and exosomes. Metabolic disorders including hyperglycemia, hyperinsulinemia, and hypercholesterolemia caused by chronic diseases accelerate hallmarks of aging. Systemic aging leads to the destruction of systemic hemostasis, causes the release of inflammatory cytokines, senescence-associated secretory phenotype (SASP), and the imbalance of microbiota composition. Released inflammatory factors further aggregate senescence, which promotes the aging of multiple solid organs. Targeting senescence or delaying aging is emerging as a critical health strategy for solving age-related diseases, especially in the old population. In the current review, we will delineate the mechanisms of organ crosstalk in systemic aging and age-related diseases to provide therapeutic targets for delaying aging.

Inflammation and aging-related disease: A transdisciplinary inflammaging framework

Inflammaging, a state of chronic, progressive low-grade inflammation during aging, is associated with several adverse clinical outcomes, including frailty, disability, and death. Chronic inflammation is a hallmark of aging and is linked to the pathogenesis of many aging-related diseases. Anti-inflammatory therapies are also increasingly being studied as potential anti-aging treatments, and clinical trials have shown benefits in selected aging-related diseases. Despite promising advances, significant gaps remain in defining, measuring, treating, and integrating inflammaging into clinical geroscience research. The Clin-STAR Inflammation Research Interest Group was formed by a group of transdisciplinary clinician-scientists with the goal of advancing inflammaging-related clinical research and improving patient-centered care for older adults. Here, we integrate insights from nine medical subspecialties to illustrate the widespread impact of inflammaging on diseases linked to aging, highlighting the extensive opportunities for targeted interventions. We then propose a transdisciplinary approach to enhance understanding and treatment of inflammaging that aims to improve comprehensive care for our aging patients.

An interracial Mendelian analysis revealed a link between lipid-lowering drugs and renal failure

Lipid-lowering drugs have been used in clinics widely. It is unclear whether the drugs have an effect on renal failure. We chose high-density lipoprotein cholesterol (ieu-b-109), low-density lipoprotein cholesterol (ieu-a-300), triglyceride (ieu-b-111), and total cholesterol (ebi-a-GCST90038690) as exposures. SNPs near drug genes served as instrumental variables. Acute renal failure (ARF) and chronic renal failure (CRF) in Europeans from the GWAS catalog were selected as outcomes. Datasets on renal failure in East Asians and South Asians were used for validation. Inverse variance weighted (IVW) was the primary method for drug-targeted Mendelian randomization. In the Europeans, people who used PPARG reduced ARF risk by 69.3% (OR: 0.307, 95% CI: 0.171-0.553, p = 0.015). NPC1L1 inhibitors increased ARF risk by 2.684 times (OR: 2.684, 95% CI: 2.027-3.341, p = 0.003). APOE increased ARF risk by 1.987 times (OR: 1.987, 95% CI: 1.062-3.716, p = 0.032) but decreased CRF risk by 49.7% (OR: 0.503, 95% CI: 0.283-0.894, p = 0.019). TNFSF12 increased CRF risk by 3.866 times (OR: 3.866, 95% CI: 1.174-12.729, p = 0.026). In the East Asians, PPARG reduced CRF risk by 85.8% (OR: 0.142, 95% CI: 0.054-0.371, p < 0.001). And in the South Asians, APOE decreased ARF risk by 99.8% (OR: 0.002, 95% CI: 2.12e-05-0.179, p = 0.007). We revealed that PPARG could reduce the risk of renal failure in Europeans and Asians. APOE could cause ARF in the Europeans, but it was protective in the South Asians. Clinicians need to consider the characteristics of the local population before administering drugs to patients of different ethnicities.

Baicalin: a potential therapeutic agent for acute kidney injury and renal fibrosis

Acute kidney injury (AKI) is a common critical clinical disease that is linked to significant morbidity, recurrence, and mortality. It is characterized by a fast and prolonged loss in renal function arising from numerous etiologies and pathogenic pathways. Renal fibrosis, defined as the excessive accumulation of collagen and proliferation of fibroblasts within renal tissues, contributes to the structural damage and functional decline of the kidneys, playing a pivotal role in the advancement of Chronic Kidney Disease (CKD). Until now, while continuous renal replacement therapy (CRRT) has been utilized in the management of severe AKI, there remains a dearth of effective targeted therapies for AKI stemming from diverse etiologies. Similarly, the identification of specific biomarkers and pharmacological targets for the treatment of renal fibrosis remains a challenge. Baicalin, a naturally occurring compound classified within the flavonoid group and commonly found in the Chinese herb Scutellaria baicalensis, has shown a range of pharmacological characteristics, such as antioxidant, anti-inflammatory, antifibrotic, antitumor and antiviral effects, as evidenced by research studies. Research shows that Baicalin has potential in treating kidney diseases like AKI and renal fibrosis. This review aims to summarize Baicalin's progress in these areas, including its molecular mechanism, application in treatment, and absorption, distribution, metabolism, and excretion. Baicalin's therapeutic effects are achieved through various pathways, including antioxidant, anti-inflammatory, antifibrosis, and regulation of apoptosis and cell proliferation. Besides, we also hope this review may give some enlightenment for treating AKI and renal fibrosis in clinical practice.

Association between COPD and CKD: a systematic review and meta-analysis

Objective

Chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) are significant global health issues with a well-established association between the two. This study aims to assess the risk of developing CKD in patients with COPD through systematic review and meta-analysis, and to explore the impact of CKD on the prognosis of COPD patients.

Methods

A total of 23 studies were included in the analysis, comprising 11 studies on the risk of CKD in patients with COPD, 6 studies on the impact of CKD on the short-term all-cause mortality risk of patients with acute exacerbation of COPD (AECOPD), and 6 studies on the impact of CKD on the long-term all-cause mortality risk of COPD patients. The meta-analysis showed that the risk of developing CKD in COPD patients was significantly increased (OR 1.54, 95% CI: 1.28-1.84), and CKD significantly increased the short-term all-cause mortality risk in AECOPD patients (OR 1.53, 95% CI: 1.44-1.63) as well as the long-term all-cause mortality risk in COPD patients (OR 1.70, 95% CI: 1.35-2.15).

Results

We searched the PubMed, EMBASE, and Cochrane Library databases in accordance with the PRISMA guidelines, including studies from the inception of the databases through December 31, 2023, to identify research assessing the relationship between COPD and CKD. The quality of the studies was assessed using the Newcastle-Ottawa Scale (NOS). Data were analyzed using either a random effects model or a fixed effects model for the meta-analysis.

Conclusion

This study establishes a significant association between COPD and CKD and reveals the adverse impact of CKD on the prognosis of COPD patients, which may provide important guidance for clinical practice.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/.

MSCs-derived HGF alleviates senescence by inhibiting unopposed mitochondrial fusion-based elongation in post-acute kidney injury

BACKGROUND

The underlying mechanism of human umbilical-derived mesenchymal stem cells (hUC-MSCs) therapy for renal senescence in post-acute kidney injury (post-AKI) remains unclear. Unopposed mitochondrial fusion-based mitochondrial elongation is required for cellular senescence. This study attempted to dissect the role of hUC-MSCs therapy in modulating mitochondrial elongation-related senescence by hUC-MSCs therapy in post-AKI.

METHODS

Initially, a unilateral renal ischemia-reperfusion (uIRI) model was established in C57 mice. Subsequently, lentivirus-transfected hUC-MSCs were given by subcapsular injection. Two weeks after transplantation, histochemical staining, and transmission electron microscopy were used to assess the efficacy of hUC-MSCs in treating renal senescence, fibrosis, and mitochondrial function. To further investigate the mitochondrial regulation of hUC-MSCs secretion, hypoxic HK-2 cells were built. Finally, antibodies of HGF and its receptor were used within the hUC-MSCs supernatant.

RESULTS

Unopposed mitochondrial fusion, renal senescence, and renal interstitial fibrosis were successively identified after uIRI in mice. Then, the efficacy of hUC-MSCs after uIRI was confirmed. Subsequently, inhibiting hUC-MSCs-derived HGF significantly compromises the efficacy of hUC-MSCs and leads to ineffectively curbing mitochondrial elongation, accompanying insufficient control of elevated PKA and inhibitory phosphorylation of drp1 (Drp1pSer637). As a result, the treatment efficacy of renal senescence and fibrosis alleviation was also weakened. Furthermore, similar results were obtained with antibodies blocking HGF or cMet in hypoxic HK-2 cells treated with hUC-MSCs-condition medium for further proving. Uncurbed mitochondrial elongation induced by PKA and Drp1pSer637 was inhibited by hUC-MSCs derived HGF but reversed in the activation or overexpression of PKA.

CONCLUSIONS

The research concluded that hUC-MSCs-derived HGF can inhibit PKA-Drp1pSer637-mitochondrial elongation via its receptor cMet to alleviate renal senescence and fibrosis in post-AKI.

Complex Pathophysiology of Acute Kidney Injury (AKI) in Aging: Epigenetic Regulation, Matrix Remodeling, and the Healing Effects of H2S

The kidney is an essential excretory organ that works as a filter of toxins and metabolic by-products of the human body and maintains osmotic pressure throughout life. The kidney undergoes several physiological, morphological, and structural changes with age. As life expectancy in humans increases, cell senescence in renal aging is a growing challenge. Identifying age-related kidney disorders and their cause is one of the contemporary public health challenges. While the structural abnormalities to the extracellular matrix (ECM) occur, in part, due to changes in MMPs, EMMPRIN, and Meprin-A, a variety of epigenetic modifiers, such as DNA methylation, histone alterations, changes in small non-coding RNA, and microRNA (miRNA) expressions are proven to play pivotal roles in renal pathology. An aged kidney is vulnerable to acute injury due to ischemia-reperfusion, toxic medications, altered matrix proteins, systemic hemodynamics, etc., non-coding RNA and miRNAs play an important role in renal homeostasis, and alterations of their expressions can be considered as a good marker for AKI. Other epigenetic changes, such as histone modifications and DNA methylation, are also evident in AKI pathophysiology. The endogenous production of gaseous molecule hydrogen sulfide (H2S) was documented in the early 1980s, but its ameliorative effects, especially on kidney injury, still need further research to understand its molecular mode of action in detail. H2S donors heal fibrotic kidney tissues, attenuate oxidative stress, apoptosis, inflammation, and GFR, and also modulate the renin-angiotensin-aldosterone system (RAAS). In this review, we discuss the complex pathophysiological interplay in AKI and its available treatments along with future perspectives. The basic role of H2S in the kidney has been summarized, and recent references and knowledge gaps are also addressed. Finally, the healing effects of H2S in AKI are described with special emphasis on epigenetic regulation and matrix remodeling.

Status and role of the ubiquitin-proteasome system in renal fibrosis

The ubiquitin-proteasome system (UPS) is a basic regulatory mechanism in cells that is essential for maintaining cell homeostasis, stimulating signal transduction, and determining cell fate. These biological processes require coordinated signaling cascades across members of the UPS to achieve substrate ubiquitination and deubiquitination. The role of the UPS in fibrotic diseases has attracted widespread attention, and the aberrant expression of UPS members affects the fibrosis process. In this review, we provide an overview of the UPS and its relevance for fibrotic diseases. Moreover, for the first time, we explore in detail how the UPS promotes or inhibits renal fibrosis by regulating biological processes such as signaling pathways, inflammation, oxidative stress, and the cell cycle, emphasizing the status and role of the UPS in renal fibrosis. Further research on this system may reveal new strategies for preventing renal fibrosis.

MiRNA-133a-3p Attenuates Renal Tubular Epithelial Cell Injury via Targeting MALM1 and Suppressing the Notch Signaling Pathway in Diabetic Nephropathy

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes characterized by structural and functional changes of kidneys. Human renal tubular epithelial (HK-2) cells are important for kidney recovery post injury and usually used for establishment of DN cell models. The study explored the role of microRNA (miR)-133a-3p in DN cell model and animal model. A cell model for DN was established via high glucose (HG) stimulation to HK-2 cells. Cell viability and apoptotic rate were measured by cell counting kit 8 and flow cytometry. Polymerase chain reaction was performed to quantify levels of miR-133a-3p and targets. Luciferase reporter assay was conducted to verify the binding of miR-133a-3p and MAML1. After establishment of a mouse model of DN, levels of renal function indicators were measured by biochemical analysis. Hematoxylin-eosin and periodic acid-schiff staining of kidney samples were performed to analyze histological changes. Western blotting was conducted to quantify levels of apoptotic markers, MAML1, and factors related to Notch signaling. Results showed that HG induced HK-2 cell apoptosis and the reduction of cell viability. MiR-133a-3p was lowly expressed in HG-stimulated HK-2 cells. Overexpressed miR-133a-3p improved HK-2 cell injury by increasing cell viability and hampering apoptosis under HG condition. In addition, miR-133a-3p directly targets MAML1 3'-untranslated region. MAML1 overexpression countervailed the repressive impact of miR-133a-3p on cell apoptosis in the context of HG. Moreover, miR-133a-3p inhibited the activity of Notch pathway by downregulating MAML1. MiR-133a-3p inhibits DN progression in mice, as evidenced by reduced fasting blood glucose level, improved levels of renal function parameters, and alleviation of kidney atrophy. In conclusion, miR-133a-3p improves HG-induced HK-2 cell injury and inhibits DN progression by targeting MAML1 and inactivating Notch signaling.

Oxidative stress and senescence in aging kidneys: the protective role of SIRT1

Aging leads to a gradual decline in kidney function, making the kidneys increasingly vulnerable to various diseases. Oxidative stress, together with cellular senescence, has been established as paramount in promoting the aging process of the kidney. Oxidative stress, defined as an imbalance between ROS formation and antioxidant defense mechanisms, has been implicated in the kidney's cellular injury, inflammation, and premature senescence. Concurrently, the accumulation of SCs in the kidney also exacerbates oxidative stress via the secretion of pro-inflammatory and tissue-damaging factors as the senescence-associated secretory phenotype (SASP). Recently, SIRT1, a nicotinamide adenine dinucleotide (NAD)-dependent deacetylase, has been pivotal in combating oxidative stress and cellular senescence in the aging kidney. SIRT1 acts as a potential antioxidant molecule through myriad pathways that influence diverse transcription factors and enzymes essential in maintaining redox homeostasis. SIRT1 promotes longevity and renal health by modulating the acetylation of cell cycle and senescence pathways. This review covers the complex relationship between oxidative stress and cellular senescence in the aging kidney, emphasizing the protective role of SIRT1. See also the graphical abstract(Fig. 1).

Renal Fibrosis: SIRT1 Still of Value

Chronic kidney disease (CKD) is a major global health concern. Renal fibrosis, a prevalent outcome regardless of the initial cause, ultimately leads to end-stage renal disease. Glomerulosclerosis and renal interstitial fibrosis are the primary pathological features. Preventing and slowing renal fibrosis are considered effective strategies for delaying CKD progression. However, effective treatments are lacking. Sirtuin 1 (SIRT1), a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase belonging to class III histone deacetylases, is implicated in the physiological regulation and protection of the kidney and is susceptible to a diverse array of pathological influences, as demonstrated in previous studies. Interestingly, controversial conclusions have emerged as research has progressed. This review provides a comprehensive summary of the current understanding and advancements in the field; specifically, the biological roles and mechanisms of SIRT1 in regulating renal fibrosis progression. These include aspects such as lipid metabolism, epithelial-mesenchymal transition, oxidative stress, aging, inflammation, and autophagy. This manuscript explores the potential of SIRT1 as a therapeutic target for renal fibrosis and offers new perspectives on treatment approaches and prognostic assessments.

TGF‑β/Smad signaling in chronic kidney disease: Exploring post‑translational regulatory perspectives (Review)

The TGF‑β/Smad signaling pathway plays a pivotal role in the onset of glomerular and tubulointerstitial fibrosis in chronic kidney disease (CKD). The present review delves into the intricate post‑translational modulation of this pathway and its implications in CKD. Specifically, the impact of the TGF‑β/Smad pathway on various biological processes was investigated, encompassing not only renal tubular epithelial cell apoptosis, inflammation, myofibroblast activation and cellular aging, but also its role in autophagy. Various post‑translational modifications (PTMs), including phosphorylation and ubiquitination, play a crucial role in modulating the intensity and persistence of the TGF‑β/Smad signaling pathway. They also dictate the functionality, stability and interactions of the TGF‑β/Smad components. The present review sheds light on recent findings regarding the impact of PTMs on TGF‑β receptors and Smads within the CKD landscape. In summary, a deeper insight into the post‑translational intricacies of TGF‑β/Smad signaling offers avenues for innovative therapeutic interventions to mitigate CKD progression. Ongoing research in this domain holds the potential to unveil powerful antifibrotic treatments, aiming to preserve renal integrity and function in patients with CKD.

Macrophage-derived exosomes promote telomere fragility and senescence in tubular epithelial cells by delivering miR-155

BACKGROUND

Chronic kidney disease (CKD) is highly prevalent worldwide, and its global burden is substantial and growing. CKD displays a number of features of accelerated senescence. Tubular cell senescence is a common biological process that contributes to CKD progression. Tubulointerstitial inflammation is a driver of tubular cell senescence and a common characteristic of CKD. However, the mechanism by which the interstitial inflammation drives tubular cell senescence remains unclear. This paper aims to explore the role of exosomal miRNAs derived from macrophages in the development of tubular cell senescence.

METHODS

Among the identified inflammation-related miRNAs, miR-155 is considered to be one of the most important miRNAs involved in the inflammatory response. Macrophages, the primary immune cells that mediate inflammatory processes, contain a high abundance of miR-155 in their released exosomes. We assessed the potential role of miR-155 in tubular cell senescence and renal fibrosis. We subjected miR-155-/- mice and wild-type controls, as well as tubular epithelial cells (TECs), to angiotensin II (AngII)-induced kidney injury. We assessed kidney function and injury using standard techniques. TECs were evaluated for cell senescence and telomere dysfunction in vivo and in vitro. Telomeres were measured by the fluorescence in situ hybridization.

RESULTS

Compared with normal controls, miR-155 was up-regulated in proximal renal tubule cells in CKD patients and mouse models of CKD. Moreover, the expression of miR-155 was positively correlated with the extent of renal fibrosis, eGFR decline and p16INK4A expression. The overexpression of miR-155 exacerbated tubular senescence, evidenced by increased detection of p16INK4A/p21expression and senescence-associated β-galactosidase activity. Notably, miR-155 knockout attenuates renal fibrosis and tubule cell senescence in vivo. Interestingly, once released, macrophages-derived exosomal miR-155 was internalized by TECs, leading to telomere shortening and dysfunction through targeting TRF1. A dual-luciferase reporter assay confirmed that TRF1 was the direct target of miR-155. Thus, our study clearly demonstrates that exosomal miR-155 may mediate communication between macrophages and TECs, subsequently inducing telomere dysfunction and senescence in TECs.

CONCLUSIONS

Our work suggests a new mechanism by which macrophage exosomes are involved in the development of tubule senescence and renal fibrosis, in part by delivering miR-155 to target TRF1 to promote telomere dysfunction. Our study may provide novel strategies for the treatment of AngII-induced kidney injury.

An overview of circulating and urinary biomarkers capable of predicting the transition of acute kidney injury to chronic kidney disease

INTRODUCTION

Acute kidney injury (AKI) defined by a substantial decrease in kidney function within hours to days and is often irreversible with higher risk to chronic kidney disease (CKD) transition.

AREAS COVERED

The authors discuss the diagnostic and predictive utilities of serum and urinary biomarkers on AKI and on the risk of AKI-to-CKD progression. The authors focus on the relevant literature covering evidence of circulating and urinary biomarkers' capability to predict the transition of AKI to CKD.

EXPERT OPINION

Based on the different modalities of serum and urinary biomarkers, multiple biomarker panel seems to be potentially useful to distinguish between various types of AKI, to detect the severity and the risk of AKI progression, to predict the clinical outcome and evaluate response to the therapy. Serum/urinary neutrophil gelatinase-associated lipocalin (NGAL), serum/urinary uromodulin, serum extracellular high mobility group box-1 (HMGB-1), serum cystatin C and urinary liver-type fatty acid-binding protein (L-FABP) were the most effective in the prediction of AKI-to-CKD transition regardless of etiology and the presence of critical state in patients. The current clinical evidence on the risk assessments of AKI progression is mainly based on the utility of combination of functional, injury and stress biomarkers, mainly NGAL, L-FABP, HMGB-1 and cystatin C.

Enhanced TRPC3 transcription through AT1R/PKA/CREB signaling contributes to mitochondrial dysfunction in renal tubular epithelial cells in D-galactose-induced accelerated aging mice

Aging-associated renal dysfunction promotes the pathogenesis of chronic kidney disease. Mitochondrial dysfunction in renal tubular epithelial cells is a hallmark of senescence and leads to accelerated progression of renal disorders. Dysregulated calcium profiles in mitochondria contribute to aging-associated disorders, but the detailed mechanism of this process is not clear. In this study, modulation of the sirtuin 1/angiotensin II type 1 receptor (Sirt1/AT1R) pathway partially attenuated renal glomerular sclerosis, tubular atrophy, and interstitial fibrosis in D-galactose (D-gal)-induced accelerated aging mice. Moreover, modulation of the Sirt1/AT1R pathway improved mitochondrial dysfunction induced by D-gal treatment. Transient receptor potential channel, subtype C, member 3 (TRPC3) upregulation mediated dysregulated cellular and mitochondrial calcium homeostasis during aging. Furthermore, knockdown or knockout (KO) of Trpc3 in mice ameliorated D-gal-induced mitochondrial reactive oxygen species production, membrane potential deterioration, and energy metabolism disorder. Mechanistically, activation of the AT1R/PKA pathway promoted CREB phosphorylation and nucleation of CRE2 binding to the Trpc3 promoter (-1659 to -1648 bp) to enhance transcription. Trpc3 KO significantly improved the renal disorder and cell senescence in D-gal-induced mice. Taken together, these results indicate that TRPC3 upregulation mediates age-related renal disorder and is associated with mitochondrial calcium overload and dysfunction. TRPC3 is a promising therapeutic target for aging-associated renal disorders.

Targeting tumor suppressor p53 for organ fibrosis therapy

Fibrosis is a reparative and progressive process characterized by abnormal extracellular matrix deposition, contributing to organ dysfunction in chronic diseases. The tumor suppressor p53 (p53), known for its regulatory roles in cell proliferation, apoptosis, aging, and metabolism across diverse tissues, appears to play a pivotal role in aggravating biological processes such as epithelial-mesenchymal transition (EMT), cell apoptosis, and cell senescence. These processes are closely intertwined with the pathogenesis of fibrotic disease. In this review, we briefly introduce the background and specific mechanism of p53, investigate the pathogenesis of fibrosis, and further discuss p53's relationship and role in fibrosis affecting the kidney, liver, lung, and heart. In summary, targeting p53 represents a promising and innovative therapeutic approach for the prevention and treatment of organ fibrosis.

Secreted frizzled-related protein 5 protects against renal fibrosis by inhibiting Wnt/β-catenin pathway

Renal fibrosis (RF) is an important pathogenesis for renal function deterioration in chronic kidney disease. Secreted frizzled-related protein 5 (SFRP5) is an anti-fibrotic adipokine but its direct role on RF remains unknown. It was aimed to study the protective effect of SFRP5 against RF and interference with Wnt/β-catenin signaling pathway for the first time. First, the therapeutic efficacy of SFRP5 was evaluated by adenovirus overexpression in rats with unilateral ureteral obstruction (UUO) in vivo. Thirty-six rats were randomly divided into the sham, UUO, and SFRP5 (UUO + Ad-SFRP5) groups. Half rats in each group were selected at random for euthanasia at 7 days and the others until 14 days. Then, the transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) was established in HK-2 cells in vitro. The cells were divided into four groups: the control group, the TGF-β1 group, the TGF-β1 + SFRP5 group, and the TGF-β1 + SFRP5 + anti-SFRP5 group. The makers of EMT and Wnt/β-catenin pathway proteins were investigated. In the UUO model, expression of SFRP5 showed compensatory upregulation, and adenoviral-mediated SFRP5 over-expression remarkably attenuated RF, as demonstrated by maintenance of E-cadherin and suppression of α-smooth muscle actin (SMA). In vitro, SFRP5 was shown to inhibit TGF-β1-mediated positive regulation of α-SMA, fibronectin, collagen I but negative regulation of E-cadherin. Furthermore, SFRP5 abrogated activation of Wnt/β-catenin, which was the essential pathway in EMT and RF pathogenesis. The changes after a neutralizing antibody to SFRP5 confirmed the specificity of SFRP5 for inhibition. These findings suggest that SFRP5 can directly ameliorate EMT and protect against RF by inhibiting Wnt/β-catenin pathway.

Kangxianling formula attenuates renal fibrosis by regulating gut microbiota

BACKGROUND

Renal fibrosis (RF) produced adverse effect on kidney function. Recently, intestinal dysbiosis is a key regulator that promotes the formation of renal fibrosis. This study will focus on exploring the protective mechanism of Kangxianling Formula (KXL) on renal fibrosis from the perspective of intestinal flora.

METHODS

Unilateral Ureteral Obstruction (UUO) was used to construct rats' model with RF, and receive KXL formula intervention for 1 week. The renal function indicators were measured. Hematoxylin-eosin (HE), Masson and Sirus red staining were employed to detect the pathological changes of renal tissue in each group. The expression of α-SMA, Col-III, TGF-β, FN, ZO-1, and Occuludin was detected by immunofluorescence and immunohistochemistry. Rat feces samples were collected and analyzed for species' diversity using high-throughput sequencing 16S rRNA.

RESULTS

Rats in UUO groups displayed poor renal function as well as severe RF. The pro-fibrotic protein expression in renal tissues including α-SMA, Col-III, TGF-β and FN was increased in UUO rats, while ZO-1 and Occuludin -1 expression was downregulated in colon tissues. The above changes were attenuated by KXL treatment. 16S rRNA sequencing results revealed that compared with the sham group, the increased abundance of pathogenic bacteria including Acinetobacter, Enterobacter and Proteobacteria and the decreased abundance of beneficial bacteria including Actinobacteriota, Bifidobacteriales, Prevotellaceae, and Lactobacillus were found in UUO group. After the administration of KXL, the growth of potential pathogenic bacteria was reduced and the abundance of beneficial bacteria was enhanced.

CONCLUSION

KXL displays a therapeutical potential in protecting renal function and inhibiting RF, and its mechanism of action may be associated with regulating intestinal microbiota.

C-X-C chemokine receptor type 4 promotes tubular cell senescence and renal fibrosis through β-catenin-inhibited fatty acid oxidation

The prevalence of chronic kidney disease (CKD) is highly increasing. Renal fibrosis is a common pathological feature in various CKD. Previous studies showed tubular cell senescence is highly involved in the pathogenesis of renal fibrosis. However, the inducers of tubular senescence and the underlying mechanisms have not been fully investigated. C-X-C motif chemokine receptor 4 (CXCR4), a G-protein-coupled seven-span transmembrane receptor, increases renal fibrosis and plays an important role in tubular cell injury. Whereas, whether CXCR4 could induce tubular cell senescence and the detailed mechanisms have not studied yet. In this study, we adopted adriamycin nephropathy and 5/6 nephrectomy models, and cultured tubular cell line. Overexpression or knockdown of CXCR4 was obtained by injection of related plasmids. We identified CXCR4 increased in injury tubular cells. CXCR4 was expressed predominantly in renal tubular epithelial cells and co-localized with adipose differentiation-related protein (ADRP) as well as the senescence-related protein P16INK4A . Furthermore, we found overexpression of CXCR4 greatly induced the activation of β-catenin, while knockdown of CXCR4 inhibited it. We also found that CXCR4 inhibited fatty acid oxidation and triggered lipid deposition in tubular cells. To inhibit β-catenin by ICG-001, an inhibitor of β-catenin, could significantly block CXCR4-suppressed fatty acid oxidation. Taken together, our results indicate that CXCR4 is a key mediator in tubular cell senescence and renal fibrosis. CXCR4 promotes tubular cell senescence and renal fibrosis by inducing β-catenin and inhibiting fatty acid metabolism. Our findings provide a new theory for tubular cell injury in renal fibrosis.

Therapeutic potential of BMSC-conditioned medium in an in vitro model of renal fibrosis using the RPTEC/TERT1 cell line

We investigated the therapeutic potential of bone marrow-derived mesenchymal stem cell-conditioned medium (BMSC-CM) on immortalized renal proximal tubule epithelial cells (RPTEC/ TERT1) in a fibrotic environment. To replicate the increased stiffness characteristic of kidneys in chronic kidney disease, we utilized polyacrylamide gel platforms. A stiff matrix was shown to increase α-smooth muscle actin (α-SMA) levels, indicating fibrogenic activation in RPTEC/TERT1 cells. Interestingly, treatment with BMSC-CM resulted in significant reductions in the levels of fibrotic markers (α-SMA and vimentin) and increases in the levels of the epithelial marker E-cadherin and aquaporin 7, particularly under stiff conditions. Furthermore, BMSC-CM modified microRNA (miRNA) expression and reduced oxidative stress levels in these cells. Our findings suggest that BMSC-CM can modulate cellular morphology, miRNA expression, and oxidative stress in RPTEC/TERT1 cells, highlighting its therapeutic potential in fibrotic kidney disease. [BMB Reports 2024; 57(2): 116-121].

Klotho-derived peptide 1 inhibits cellular senescence in the fibrotic kidney by restoring Klotho expression via posttranscriptional regulation

Background: Klotho deficiency is a common feature of premature aging and chronic kidney disease (CKD). As such, restoring Klotho expression could be a logic strategy for protecting against various nephropathies. In this study, we demonstrate that KP1, a Klotho-derived peptide, inhibits cellular senescence by restoring endogenous Klotho expression. Methods: The effects of KP1 on cellular senescence and Klotho expression were assessed in mouse models of CKD. RNA-sequencing was employed to identify the microRNA involved in regulating Klotho by KP1. Gain- or loss-of-function approaches were used to assess the role of miR-223-3p and IncRNA-TUG1 in regulating Klotho and cellular senescence. Results: KP1 inhibited senescence markers p21, p16 and γ-H2AX in tubular epithelial cells of diseased kidneys, which was associated with its restoration of Klotho expression at the posttranscriptional level. Profiling of kidney microRNAs by RNA sequencing identified miR-223-3p that bound to Klotho mRNA and inhibited its protein expression. Overexpression of miR-223-3p inhibited Klotho and induced p21, p16 and γ-H2AX, which were negated by KP1. Conversely, inhibition of miR-223-3p restored Klotho expression, inhibited cellular senescence. Furthermore, miR-223-3p interacted with lncRNA-TUG1 and inhibited its expression. Knockdown of lncRNA-TUG1 increased miR-223-3p, aggravated Klotho loss and worsened cellular senescence, whereas KP1 mitigated all these changes. Conclusion: These studies demonstrate that KP1 inhibits cellular senescence and induces Klotho expression via posttranscriptional regulation mediated by miR-223-3p and lncRNA-TUG1. By restoring endogenous Klotho, KP1 elicits a broad spectrum of protective actions and could serve as a promising therapeutic agent for fibrotic kidney disorders.

Circular RNAs: An emerging precise weapon for diabetic nephropathy diagnosis and therapy

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication associated with diabetes mellitus and represents a major cause of chronic kidney disease and renal failure. Current treatment strategies for DN primarily focus on symptom alleviation, lacking effective approaches to halt or reverse DN progression. Circular RNA (circRNA), characterized by a closed-loop structure, has emerged as a novel non-coding RNA regulator of gene expression, attributed to its conservation, stability, specificity, and multifunctionality. Dysregulation of circRNA expression is closely associated with DN progression, whereby circRNA impacts kidney cell injury by modulating cell cycle, differentiation, cell death, as well as influencing the release of inflammatory factors and stromal fibronectin expression. Consequently, circRNA is considered a predictive biomarker and a potential therapeutic target for DN. This review provides an overview of the latest research progress in the classification, functions, monitoring methods, and databases related to circRNA. The paper focuses on elucidating the impact and underlying mechanisms of circRNA on kidney cells under diabetic conditions, aiming to offer novel insights into the prevention, diagnosis, and treatment of DN.

Inhibition of Indoxyl Sulfate-Induced Reactive Oxygen Species-Related Ferroptosis Alleviates Renal Cell Injury In Vitro and Chronic Kidney Disease Progression In Vivo

The accumulation of the uremic toxin indoxyl sulfate (IS) is a key pathological feature of chronic kidney disease (CKD). The effect of IS on ferroptosis and the role of IS-related ferroptosis in CKD are not well understood. We used a renal tubular cell model and an adenine-induced CKD mouse model to explore whether IS induces ferroptosis and injury and affects iron metabolism in the renal cells and the kidneys. Our results showed that exposure to IS induced several characteristics for ferroptosis, including iron accumulation, an impaired antioxidant system, elevated reactive oxygen species (ROS) levels, and lipid peroxidation. Exposure to IS triggered intracellular iron accumulation by upregulating transferrin and transferrin receptors, which are involved in cellular iron uptake. We also observed increased levels of the iron storage protein ferritin. The effects of IS-induced ROS generation, lipid peroxidation, ferroptosis, senescence, ER stress, and injury/fibrosis were effectively alleviated by treatments with an iron chelator deferoxamine (DFO) in vitro and the adsorbent charcoal AST-120 (scavenging the IS precursor) in vivo. Our findings suggest that IS triggers intracellular iron accumulation and ROS generation, leading to the induction of ferroptosis, senescence, ER stress, and injury/fibrosis in CKD kidneys. AST-120 administration may serve as a potential therapeutic strategy.

Mitigation of Cardiovascular Disease and Toxicity through NRF2 Signalling

Cardiovascular toxicity and diseases are phenomena that have a vastly detrimental impact on morbidity and mortality. The pathophysiology driving the development of these conditions is multifactorial but commonly includes the perturbance of reactive oxygen species (ROS) signalling, iron homeostasis and mitochondrial bioenergetics. The transcription factor nuclear factor erythroid 2 (NFE2)-related factor 2 (NRF2), a master regulator of cytoprotective responses, drives the expression of genes that provide resistance to oxidative, electrophilic and xenobiotic stresses. Recent research has suggested that stimulation of the NRF2 signalling pathway can alleviate cardiotoxicity and hallmarks of cardiovascular disease progression. However, dysregulation of NRF2 dynamic responses can be severely impacted by ageing processes and off-target toxicity from clinical medicines including anthracycline chemotherapeutics, rendering cells of the cardiovascular system susceptible to toxicity and subsequent tissue dysfunction. This review addresses the current understanding of NRF2 mechanisms under homeostatic and cardiovascular pathophysiological conditions within the context of wider implications for this diverse transcription factor.