PTEN-induced kinase 1 is associated with renal aging, via the cGAS-STING pathway

Mitochondrial dysfunction-associated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury

An earlier study found that respiratory cadmium chloride (CdCl2) exposure caused COPD-like lung injury. This study aimed to explore whether mitochondrial dysfunction-mediated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury. Adult C57BL/6 mice were exposed to CdCl2 (10 mg/L) aerosol for six months. Beta-galactosidase-positive cells, p21 and p16 were increased in CdCl2-exposed mouse lungs. The in vitro experiments showed that γ-H2AX was elevated in CdCl2-exposed alveolar epithelial cells. The cGAS-STING pathway was activated in CdCl2-exposed alveolar epithelial cells and mouse lungs. Cxcl1, Cxcl9, Il-10, Il-1β and Mmp2, several senescence-associated secretory phenotypes (SASP), were upregulated in CdCl2-exposed alveolar epithelial cells. Mechanistically, CdCl2 exposure caused SIRT3 reduction and mitochondrial dysfunction in mouse lungs and alveolar epithelial cells. The in vitro experiment found that Sirt3 overexpression attenuated CdCl2-induced alveolar epithelial senescence and SASP. The in vivo experiments showed that Sirt3 gene knockout exacerbated CdCl2-induced alveolar epithelial senescence, alveolar structure damage, airway inflammation and pulmonary function decline. NMN, an NAD+ precursor, attenuated CdCl2-induced alveolar epithelial senescence and SASP in mouse lungs. Moreover, NMN supplementation prevented CdCl2-induced COPD-like alveolar structure damage, epithelial-mesenchymal transition and pulmonary function decline. These results suggest that mitochondrial dysfunction-associated alveolar epithelial senescence is involved in CdCl2-induced COPD-like lung injury.

Kidney Aging and Chronic Kidney Disease

The process of aging inevitably leads to an increase in age-related comorbidities, including chronic kidney disease (CKD). In many aspects, CKD can be considered a state of accelerated and premature aging. Aging kidney and CKD have numerous common characteristic features, ranging from pathological presentation and clinical manifestation to underlying mechanisms. The shared mechanisms underlying the process of kidney aging and the development of CKD include the increase in cellular senescence, the decrease in autophagy, mitochondrial dysfunction, and the alterations of epigenetic regulation, suggesting the existence of potential therapeutic targets that are applicable to both conditions. In this review, we provide a comprehensive overview of the common characteristics between aging kidney and CKD, encompassing morphological changes, functional alterations, and recent advancements in understanding the underlying mechanisms. Moreover, we discuss potential therapeutic strategies for targeting senescent cells in both the aging process and CKD.

A p21-ATD mouse model for monitoring and eliminating senescent cells and its application in liver regeneration post injury

Cellular senescence associates with pathological aging and tissue dysfunctions. Studies utilizing mouse models for cell lineage tracings have emphasized the importance of senescence heterogeneity in different organs and cell types. Here, we constructed a p21- (Akaluc - tdTomato - Diphtheria Toxin Receptor [DTR]) (ATD) mouse model to specifically study the undefined mechanism for p21-expressing senescent cells in the aged and liver injury animals. The successful expressions of these genes enabled in vitro flow cytometric sorting, in vivo tracing, and elimination of p21-expressing senescent cells. During the natural aging process, p21-expressing cells were found in various tissues of p21-ATD mice. Eliminating p21-expressing cells in the aged p21-ATD mice recovered their multiple biological functions. p21-ATD/Fah-/- mice, bred from p21-ATD mice and fumarylacetoacetate hydrolase (Fah)-/- mice of liver injury, showed that the majority of their senescent hepatocytes were the phenotype of p21+ rather than p16+. Furthermore, eliminating the p21-expressing hepatocytes significantly promoted the engraftment of grafted hepatocytes and facilitated liver repopulation, resulting in significant recovery from liver injury. Our p21-ATD mouse model serves as an optimal model for studying the pattern and function of p21-expressing senescent cells under the physical and pathological conditions during aging.

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.

Molecular Mechanisms Associated with Aging Kidneys and Future Perspectives

The rapid growth of the elderly population is making the need for extensive and advanced information about age-related organ dysfunction a crucial research area. The kidney is one of the organs most affected by aging. Aged kidneys undergo functional decline, characterized by a reduction in kidney size, decreased glomerular filtration rate, alterations in renal blood flow, and increased inflammation and fibrosis. This review offers a foundation for understanding the functional and molecular mechanisms of aging kidneys and for selecting identifying appropriate targets for future treatments of age-related kidney issues.

GLIS1 alleviates cell senescence and renal fibrosis through PGC1-α mediated mitochondrial quality control in kidney aging

Mitochondrial dysfunction is implied as a crucial factor in age-related chronic kidney disease. It is confirmed that Gli-like transcription factor 1 (GLIS1) is involved in age-related renal fibrosis, however, the correlation between mitochondrial disturbances and GLIS1-driven kidney aging are not clearly clarified. Thus, we investigated the regulatory mechanism of GLIS1 in the homeostasis of mitochondrial quality control both in vivo and in vitro. The lower expression of GLIS1 was identified in natural and accelerated kidney aged models, accompanied by the dysfunctions of mitochondrial quality control, including enhanced mitochondrial fission, reduced mitochondrial biogenesis and mitophagy, whereas, GLIS1 could maintain mitochondrial stability by interacting with peroxisome proliferator-activated receptor γ coactivator-1α (PGC1-α). Additionally, the over-expressed GLIS1 inhibited extracellular matrix accumulation and alleviated renal fibrosis while siGLIS1 inhibited PGC1-α transcription, as well as affecting its mitochondria-protective functions. Collectively, we demonstrated that GLIS1 mediated mitochondrial quality control through targeting PGC1-α in kidney aging, which might be a promising therapeutic target for attenuating cell senescence and age-related renal fibrosis.

Fibroblast-derived CXCL14 aggravates crystalline silica-induced pulmonary fibrosis by mediating polarization and recruitment of interstitial macrophages

Exposure to crystalline silica (CS) particles in worksites and dwellings can lead to silicosis due to excessive fibroblast activation. Considering their immuno-regulatory activities, the contribution of pulmonary fibroblasts in the progression of silicosis has not been thoroughly characterized. Here, we demonstrate that exposure of the lung to CS particles leads to the upregulation of fibroblast-derived C-X-C motif chemokine ligand 14 (CXCL14). By employing an in vitro co-culture system, we demonstrated activated fibroblasts recruited bone marrow-derived macrophages (BMDMs) and favored alternative macrophage polarization (M2) mediated by CXCL14. Furthermore, in vivo studies echoed that systemic CXCL14 neutralizing or fibroblast-specific Cxcl14 knockout proved CXCL14 was indispensable for the recruitment and phenotype alteration of lung macrophages, especially interstitial macrophages (IMs), under stimulation by CS particles. Mechanistically, we showed that GLI2 and p21-mediated cellular senescence were mediators of CXCL14 production following CS exposure. Accordingly, GLI2 blockage and countering cellular senescence by reviving PINK1-mediated mitophagy may be efficient strategies to reduce CXCL14 expression in activated fibroblasts during silicosis. Our findings emphasize the immuno-regulatory function of fibroblasts in silicosis via CXCL14, providing intervention targets for CS-induced pulmonary fibrosis.