Search Results (14)

Acute kidney injury (AKI) causes damage to the renal epithelium, initiating a reparative process intended to restore renal function. Although effective repair can result in the complete recovery of kidney function, this process is frequently incomplete. In instances where repair is unsuccessful, the kidney experiences maladaptive alterations that may progressively result in chronic kidney disease (CKD), a phenomenon referred to as failed repair. This condition is precipitated by hypotensive, septic, or toxic insults, which initiate a series of pathophysiological processes, including microcirculatory dysfunction, the activation of inflammatory responses, and the death of tubular epithelial cells. These events collectively compromise renal function and trigger a complex repair response. This review provides a comprehensive examination of the multifactorial mechanisms underlying the initiation and progression of AKI, the regenerative pathways facilitating structural recovery in severely damaged kidneys, and the critical transition from adaptive repair to maladaptive remodeling. Central to this transition are mechanisms such as epigenetic reprogramming, G2/M cell-cycle arrest, cellular senescence, mitochondrial dysfunction, metabolism reprogramming, and cell death, which collectively drive the progression of CKD. These mechanistic insights offer a robust foundation for the development of targeted therapeutic strategies aimed at enhancing adaptive renal repair. Full article

Cellular communication network factor 2 (CCN2, also known as CTGF) is a complex protein that regulates numerous cellular functions. This biomolecule exhibits dual functions, depending on the context, and can act as a matricellular protein or as a growth factor. CCN2 is an established marker of fibrosis and a well-known mediator of kidney damage, involved in the regulation of inflammation, extracellular matrix remodeling, cell death, and activation of tubular epithelial cell (TECs) senescence. In response to kidney damage, cellular senescence mechanisms are activated, linked to regeneration failure and progression to fibrosis. Our preclinical studies using a total conditional CCN2 knockout mouse demonstrate that CCN2 plays a significant role in the development of a senescence phenotype after exposure to a nephrotoxic agent. CCN2 induces cell growth arrest in TECs, both in the early phase and in the chronic phase of folic acid nephropathy (FAN), associated with cell-death/necroinflammation and fibrosis, respectively. Renal CCN2 overexpression was found to be linked to excessive collagen accumulation in tubulointerstitial areas, microvascular rarefaction, and a decline in renal function, which were observed three weeks following the initial injury. All these findings were markedly diminished in conditional CCN2 knockout mice. In the FAN model, injured senescent TECs are associated with microvascular rarefaction, and both were modulated by CCN2. In primary cultured endothelial cells, as previously described in TECs, CCN2 directly induced senescence. The findings collectively demonstrate the complexity of CCN2, highlight the pivotal role of cellular senescence as an important mechanism in renal injury, and underscore the critical function of this biomolecule in kidney damage progression. Full article

Background: Ionizing radiation (IR) is a well-known inducer of cellular senescence and the senescence-associated secretory phenotype (SASP). SASP factors play dual roles in cancer, either promoting or inhibiting its development. This study investigates IR-induced SASP factors specifically secreted by renal cortical epithelial (RCE) cells and their role in promoting renal cell carcinoma (RCC) progression. Methods: Proteomic data from the SASP Atlas were analyzed to identify IR-induced factors unique to RCE cells, with subsequent evaluations performed at both the gene and protein levels. Thirty-seven proteins were identified as exclusively upregulated and secreted by senescent RCE cells. Gene expression analysis of these RCE-specific SASP factors was conducted using the Gene Expression database of Normal and Tumor tissues (GENT2) and The Cancer Genome Atlas (TCGA). To assess their prognostic relevance in RCC, the corresponding proteins were further analyzed using the Human Protein Atlas (HPA), emphasizing the relationship between SASP factor expression and RCC progression. Results: ALDH18A1 and ASPH emerged as key RCE-specific SASP factors with significant upregulation at both the gene and protein levels (Log2 ratio > 1.15, p < 0.05). These proteins are implicated in pro-cancer activities and are strongly associated with poor prognostic outcomes in RCC. Their critical roles in RCC progression underscore their potential as promising therapeutic targets for the prevention and treatment of the disease. Conclusions: This study provides novel insights into the role of IR-induced SASP in renal carcinogenesis, marking the first identification of ALDH18A1 and ASPH as specific secreted proteins associated with tumor progression in RCC. This study suggests that ALDH18A1 and ASPH hold promise as early biomarkers for RCC and as therapeutic targets for disease prevention and treatment. Full article

Chronic kidney disease (CKD) is a major public health issue around the world. A significant number of CKD patients originates from acute kidney injury (AKI) patients, namely “AKI–CKD”. CKD is significantly related to the consequences of AKI. Damaged renal proximal tubular (PT) cell repair has been widely confirmed to indicate the renal prognosis of AKI. Oxidative stress is a key damage-associated factor and plays a significant role throughout the development of AKI and CKD. However, the relationships between AKI–CKD progression and oxidative stress are not totally clear and the underlying mechanisms in “AKI–CKD” remain indistinct. In this research, we constructed unilateral ischemia–reperfusion injury (UIRI)-model mice and performed single-nucleus RNA sequencing (snRNA-seq) of the kidney samples from UIRI and sham mice. We obtained our snRNA-seq data and validated the findings based on the joint analysis of public databases, as well as a series of fundamental experiments. Proximal tubular cells associated with failed repair express more complete senescence and oxidative stress characteristics compared to other subgroups. Furthermore, oxidative stress-related transcription factors, including Stat3 and Dnmt3a, are significantly more active under the circumstance of failed repair. What is more, we identified abnormally active intercellular communication between PT cells associated with failed repair and macrophages through the APP–CD74 pathway. More notably, we observed that the significantly increased expression of CD74 in hypoxia-treated TECs (tubular epithelial cells) was dependent on adjacently infiltrated macrophages, which was essential for the further deterioration of failed repair in PT cells. This research provides a novel understanding of the process of AKI to CKD progression, and the oxidative stress-related characteristics that we identified might represent a potentially novel therapeutic strategy against AKI. Full article

Besides being a marker of kidney disease severity, albuminuria exerts a toxic effect on renal proximal tubular epithelial cells (RPTECs). We evaluated whether an unfolded protein response (UPR) or DNA damage response (DDR) is elicited in RPTECs exposed to high albumin concentration. The deleterious outcomes of the above pathways, apoptosis, senescence, or epithelial-to-mesenchymal transition (EMT) were evaluated. Albumin caused reactive oxygen species (ROS) overproduction and protein modification, and a UPR assessed the level of crucial molecules involved in this pathway. ROS also induced a DDR evaluated by critical molecules involved in this pathway. Apoptosis ensued through the extrinsic pathway. Senescence also occurred, and the RPTECs acquired a senescence-associated secretory phenotype since they overproduced IL-1β and TGF-β1. The latter may contribute to the observed EMT. Agents against endoplasmic reticulum stress (ERS) only partially alleviated the above changes, while the inhibition of ROS upregulation prevented both UPR and DDR and all the subsequent harmful effects. Briefly, albumin overload causes cellular apoptosis, senescence, and EMT in RPTECs by triggering UPR and DDR. Promising anti-ERS factors are beneficial but cannot eliminate the albumin-induced deleterious effects because DDR also occurs. Factors that suppress ROS overproduction may be more effective since they could halt UPR and DDR. Full article

The mechanisms of acute kidney injury and chronic kidney disease remain incompletely revealed, and drug development is a pressing clinical challenge. Oxidative stress-induced cellular senescence and mitochondrial damage are important biological events in a variety of kidney diseases. As a type of carotenoid, β-Cryptoxanthin (BCX) has various biological functions, which means it is a potential therapeutic candidate for the treatment of kidney disease. However, the role of BCX in the kidney is unclear, and the effect of BCX on oxidative stress and cellular senescence in renal cells is also unknown. Therefore, we conducted a series of studies on human renal tubular epithelial (HK-2) cells in vitro. In the present study, we investigated the effect of BCX pretreatment on H₂O₂-induced oxidative stress and cellular senescence and explored the potential mechanism of BCX action. The results showed that BCX attenuated H₂O₂-induced oxidative stress and cellular senescence in HK-2 cells. Moreover, BCX promoted NRF2 nuclear expression, maintained mitochondrial function, and reduced mitochondrial damage in HK-2 cells. In addition, silencing NRF2 altered the protective effect of BCX on mitochondria and significantly reversed the anti-oxidative stress and anti-senescence effects of BCX in HK-2 cells. We concluded that BCX maintained mitochondrial function by promoting NRF2 nuclear translocation to inhibit oxidative stress-induced senescence in HK-2 cells. In light of these findings, the application of BCX might be a promising strategy for the prevention and treatment of kidney diseases. Full article

Gliflozins are a new class of antidiabetic drugs with renoprotective properties. In cultures of primary human renal tubular epithelial cells (RPTECs) subjected to high-glucose conditions in the presence or absence of dapagliflozin, we evaluated cellular senescence pathways. High glucose increased sodium–glucose cotransporter-2 (SGLT-2) expression and glucose consumption, enhancing reactive oxygen species production. The latter induced DNA damage, ataxia telangiectasia mutated kinase (ATM), and p53 phosphorylation. Stabilized p53 increased the cell cycle inhibitor p21, resulting in cell cycle arrest and increasing the cellular senescence marker beta-galactosidase (GLB-1). RPTECs under high glucose acquired a senescence-associated secretory phenotype, which was detected by the production of IL-1β, IL-8, and TGF-β1. By decreasing SGLT-2 expression and glucose consumption, dapagliflozin inhibited the above pathway and prevented RPTEC senescence. In addition, dapagliflozin reduced the cell cycle inhibitor p16 independently of the glucose conditions. Neither glucose concentration nor dapagliflozin affected the epithelial-to-mesenchymal transition when assessed with α-smooth muscle actin (α-SMA). Thus, high glucose induces p21-dependent RPTEC senescence, whereas dapagliflozin prevents it. Since cellular senescence contributes to the pathogenesis of diabetic nephropathy, delineating the related molecular mechanisms and the effects of the widely used gliflozins on them is of particular interest and may lead to novel therapeutic approaches. Full article

Ischemia-reperfusion injury is the leading cause of acute kidney injury. Reactive oxygen species (ROS) production causes cell death or senescence. In cultures of primary human renal tubular epithelial cells (RPTECs) subjected to anoxia-reoxygenation, inhibition of the Krebs cycle at the level of malate dehydrogenase-2 (MDH-2) decreases hypoxia-inducible factor-1α and oxidative stress and protects from apoptotic or ferroptotic cell death. Inhibition of MDH-2 decreased reoxygenation-induced upregulation of p53 and p21, restored the levels of the proliferation marker Ki-67, and prevented the upregulation of the senescence marker beta-galactosidase and interleukin-1β production. MDH-2 inhibition reduced the reoxygenation-induced upregulation of ATP, but the alterations of critical cell metabolism enzymes allowed enough ATP production to prevent cell energy collapse. Thus, inhibition of the Krebs cycle at the level of MDH-2 protects RPTECs from anoxia-reoxygenation-induced death or senescence. MDH-2 may be a promising pharmaceutical target against ischemia-reperfusion injury. Full article

Chronic kidney disease (CKD) will become the fifth global cause of death by 2040, thus emphasizing the need to better understand the molecular mechanisms of damage and regeneration in the kidney. CKD predisposes to acute kidney injury (AKI) which, in turn, promotes CKD progression. This implies that CKD or the AKI-to-CKD transition are associated with dysfunctional kidney repair mechanisms. Current therapeutic options slow CKD progression but fail to treat or accelerate recovery from AKI and are unable to promote kidney regeneration. Unraveling the cellular and molecular mechanisms involved in kidney injury and repair, including the failure of this process, may provide novel biomarkers and therapeutic tools. We now review the contribution of different molecular and cellular events to the AKI-to-CKD transition, focusing on the role of macrophages in kidney injury, the different forms of regulated cell death and necroinflammation, cellular senescence and the senescence-associated secretory phenotype (SAPS), polyploidization, and podocyte injury and activation of parietal epithelial cells. Next, we discuss key contributors to repair of kidney injury and opportunities for their therapeutic manipulation, with a focus on resident renal progenitor cells, stem cells and their reparative secretome, certain macrophage subphenotypes within the M2 phenotype and senescent cell clearance. Full article

AKI, due to the fact of altered oxygen supply after kidney transplantation, is characterized by renal ischemia–reperfusion injury (IRI). Recent data suggest that AKI to CKD progression may be driven by cellular senescence evolving from prolonged DNA damage response (DDR) following oxidative stress. Cellular communication factor 2 (CCN2, formerly called CTGF) is a major contributor to CKD development and was found to aggravate DNA damage and the subsequent DDR–cellular senescence–fibrosis sequence following renal IRI. We therefore investigated the impact of CCN2 inhibition on oxidative stress and DDR in vivo and in vitro. Four hours after reperfusion, full transcriptome RNA sequencing of mouse IRI kidneys revealed CCN2-dependent enrichment of several signaling pathways, reflecting a different immediate stress response to IRI. Furthermore, decreased staining for γH2AX and p-p53 indicated reduced DNA damage and DDR in tubular epithelial cells of CCN2 knockout (KO) mice. Three days after IRI, DNA damage and DDR were still reduced in CCN2 KO, and this was associated with reduced oxidative stress, marked by lower lipid peroxidation, protein nitrosylation, and kidney expression levels of Nrf2 target genes (i.e., HMOX1 and NQO1). Finally, silencing of CCN2 alleviated DDR and lipid peroxidation induced by anoxia-reoxygenation injury in cultured PTECs. Together, our observations suggest that CCN2 inhibition might mitigate AKI by reducing oxidative stress-induced DNA damage and the subsequent DDR. Thus, targeting CCN2 might help to limit post-IRI AKI. Full article

Cellular senescence of renal tubular cells is associated with chronic diseases and age-related kidney disorders. Therapies to antagonize senescence are, therefore, explored as novel approaches in nephropathy. Exosomes derived from human mesenchymal stroma-/stem-like cells (MSC) entail the transfer of multiple bioactive molecules, exhibiting profound regenerative potential in various tissues, including therapeutic effects in kidney diseases. Here, we first demonstrate that exosomes promote proliferation and reduce senescence in aged MSC cultures. For potential therapeutic perspectives in organ rejuvenation, we used MSC-derived exosomes to antagonize senescence in murine kidney primary tubular epithelial cells (PTEC). Exosome treatment efficiently reduced senescence while diminishing the transcription of senescence markers and senescence-associated secretory phenotype (SASP) factors. Concomitantly, we observed less DNA damage foci and more proliferating cells. These data provide new information regarding the therapeutic property of MSC exosomes in the development of renal senescence, suggesting a contribution to a new chapter of regenerative vehicles in senotherapy. Full article

Ischemia-reperfusion injury is the commonest form of acute kidney injury (AKI). Tubular epithelial cell senescence contributes to incomplete recovery from AKI and predisposes to subsequent chronic kidney disease. In cultures of primary proximal renal tubular epithelial cells (RPTECs) subjected to anoxia or reoxygenation, we evaluated the role of indoleamine 2,3-dioxygenase 1 (IDO) in cellular senescence. Proteins of interest were assessed with Western blotting or enzyme-linked immunosorbent assay or histochemically. Under anoxia or reoxygenation, IDO expression and activity were increased. Moreover, the two IDO-derived pathways, the general control nonderepressible 2 kinase (GCN2K) pathway and the aryl-hydrocarbon receptor (AhR) pathway, were also activated. A DNA damage response (DDR) took place and led to increased levels of the cell-cycle inhibitors p21 and p16, and senescence-associated β-galactosidase (SA-β-Gal) activity. Cell proliferation was inhibited, and more IL-6 was produced. The IDO inhibitor 1-DL-methyl-tryptophan ameliorated the DDR; decreased p21, p16, and SA-β-Gal activity; restored cell proliferation; and decreased IL-6 production. The AhR inhibitor CH223191 did not affect the above parameters. In conclusion, anoxia and the subsequent reoxygenation upregulate IDO. IDO depletes tryptophan and activates GCN2K. The latter enhances the anoxia- or reoxygenation-induced DDR, resulting in increased p21 and p16 expression and eventually leading to RPTEC senescence. Since cellular senescence affects AKI outcome, the role of IDO in cellular senescence and the possible therapeutic role of IDO inhibitors deserve further investigation. Full article

The increasing load of senescent cells is a source of aging, and chronic inflammation plays a pivotal role in cellular senescence. In addition, senescent renal tubular epithelial cells are closely associated with renal aging. Lysophosphatidic acid (LPA) is a bioactive lipid mainly produced by the catalytic action of autotaxin (ATX), and its ligation to LPA receptor-1 (LPAR1) is associated with chronic inflammation and renal fibrosis; however, its role in renal aging is unclear. Male 2-, 12-, and 24-month-old C57BL/6 mice and Human renal proximal tubular epithelial cells (HRPTEpiC) were used in the present study. DNA damage and oxidative stress-induced senescence were simulated using doxorubicin (DOXO) and H₂O₂, respectively. The aged kidney showed decreased renal function, increased fractional mesangial area, and tubulointerstitial fibrosis. Both aged kidney and senescent cells showed increased levels of LPAR1, Nuclear factor κB (NF-κB), and inflammatory cytokines. In addition, LPAR1-knockdown reduced NF-κB and subsequent inflammatory cytokine induction, and NF-κB-knockdown resulted in decreased LPAR1 expression. Our study revealed a positive feedback loop between LPAR1 and NF-κB, which reinforces the role of inflammatory response, suggesting that blocking of aberrantly activated LPAR1 may reduce excessive inflammation, thereby providing a new possible therapeutic strategy to attenuate renal aging. Full article

Diabetic nephropathy (DN) is the major cause of end stage renal disease. Proximal tubular epithelial cell (PTEC) injury occurs early in diabetic kidney, and it is correlated with consequent renal failure. Cellular senescence participates in the pathophysiology of DN, but its role remains unclear. We conducted a cross-disciplinary study, including human, in vivo, and in vitro studies, to explore the novel molecular mechanisms of PTEC senescence in DN. We found that HG induced cell senescence in PTECs, supported by enhanced β-galactosidase staining, p53 and p27 expression, and reduced cyclin E levels. Transcriptome analysis of PTECs from a type 2 diabetic patient and a normal individual using next generation sequencing (NGS) and systematic bioinformatics analyses indicated that miR-378i and its downstream target S-phase kinase protein 2 (Skp2) contribute to HG-induced senescence in PTECs. High glucose (HG) elevated miR-378i expression in PTECs, and miR-378i transfection reduced Skp2 expression. Urinary miR-378i levels were elevated in both db/db mice and type 2 diabetic patients, whereas decreased Skp2 levels were shown in proximal tubule of db/db mice and human DN. Moreover, urinary miR-378i levels were positively correlated with urinary senescence-associated secretory phenotype cytokines and renal function in in vivo and human study. This study demonstrates that the interaction between miR-378i and Skp2 regulates PTEC senescence of DN. miR-378i has the potential to predict renal injury in DN. These findings suggest future applications in both therapy and in predicting renal dysfunction of DN. Full article