Inhibition of transglutaminase 2 inhibits ionizing radiation-induced cellular senescence in skin keratinocytes in vitro.

Senescent cells are typically characterized by a stable proliferation arrested in dividing cells accompanied with a senescence-associated secretory phenotype (SASP). Skin cellular senescence is the primary cause of skin aging, whereas the lack of identified skin senescence markers limits our understanding of the mechanisms involved in skin aging. Recent studies have revealed that intracellular calcium signaling has emerged as a key player in regulating cellular senescence and aging. However, the implication and roles of calcium signaling in skin keratinocyte senescence remain only partially understood. In this study, we developed a model for skin keratinocyte senescence using ionizing radiation (I/R) stimulation and found that the calcium-associated gene transglutaminase 2 (TGM2) was significantly induced compared with normal control. Interestingly, inhibition of TGM2 was found to delay skin keratinocyte senescence by suppressing I/R-promoted intracellular calcium signaling, accumulation of reactive oxygen species (ROS), DNA damage, as well as NF-κB-mediated SASP secretion. Taken together, our findings demonstrate that inhibition of TGM2 contributes to bypassing I/R-induced skin keratinocyte senescence and sheds light on novel strategies against skin stresses caused by I/R.

Zinc finger protein ZBTB17 controls cellular senescence via interacting with nuclear receptor RXRA and its downstream calcium signaling.

Cellular senescence is broadly known as a stable cell cycle arrest accompanied by a senescence-associated secretory phenotype (SASP). In the past decades, calcium signaling has emerged as a key mediator of cellular senescence. However, the transcriptional regulation of calcium signaling during cellular senescence remains partially understood. We have previously identified the nuclear receptor RXRA as a key senescence repressor through inhibiting the endoplasmic reticulum (ER) calcium release channel inositol 1,4,5-trisphosphate receptor, type 2 (ITPR2) mediated intracellular calcium signaling. Nevertheless, as a transcriptional recruiter, the mechanism by which RXRA inhibits ITPR2 during cellular senescence remains unclear. Here we identified the zinc finger protein ZBTB17 can interact with RXRA. Interestingly, knockdown of ZBTB17 induces a cascade of RXRA-dependent intracellular calcium signaling, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) accumulation, DNA damages, and ultimately cellular senescence. Moreover, the signaling and senescence phenotype induced by knocking down of ZBTB17 can also be abolished after silencing ITPR2. Altogether, our work provides a new mechanism controlling intracellular calcium signaling and cellular senescence and unveils novel insight toward the role of zinc finger proteins.

Troxerutin Delays Skin Keratinocyte Senescence Induced by Ionizing Radiation Both In Vitro and In Vivo.

BACKGROUNDS: With the increasing demand for beauty and a healthy lifespan, studies regarding anti-skin aging have drawn much more attention than ever before. Skin cellular senescence, the primary cause of skin aging, is characterized by a cell cycle arrest in proliferating cells along with a senescence-associated secretory phenotype (SASP), which can be triggered by various internal or external stimuli. AIMS: Recent studies have made significant progress in the fields of anti-senescence and anti-aging. However, little is known about the roles and functions of natural compounds, particularly flavonoids, in skin cellular senescence studies. METHODS: In this study, using strategies including ionizing radiation (IR), senescence-associated ß galactosidase assay (SA-ß-Gal), immunofluorescence (IF), flow cytometry, PCR array, as well as in vivo experiments, we investigated the effects and roles of troxerutin (Trx), a natural flavonoid, in skin keratinocyte senescence. RESULTS: We found that Trx delays skin keratinocyte senescence induced by IR. Mechanistically, Trx protects the skin keratinocyte cells from senescence by alleviating reactive oxygen species (ROS) accumulation, mitochondrial dysfunction, and DNA damage caused by IR. In addition, Trx was also proved to relieve skin senescence and SASP secretion in vivo induced by IR stimulation. CONCLUSIONS: Altogether, our findings pointed to a new function of Trx in delaying stress-induced skin keratinocyte senescence, and should thus provide theoretical foundations for exploring novel strategies against skin aging.

Targeted apoptosis of senescent cells by valproic acid alleviates therapy-induced cellular senescence and lung aging.

BACKGROUND: Accumulation of senescent cells in tissues and their downstream effect programs have emerged as key drivers of aging and age-associated pathologies. Recent progresses in senotherapeutics indicated that either selectively killing senescent cells with senolytics or suppressing the senescence-associated secretory phenotype (SASP) secretion using senomorphics contributes to extending of the healthy lifespan and alleviating numerous age-related disorders in mice. PURPOSE: However, the potential side-effects and long-term cytotoxicity of the above novel compounds have not yet been determined. Therefore, it seems to be more efficient to explore new senotherapeutical functions from approved drugs. METHODS: The effects of valproic acid (VPA), a derivative of valine, in cellular senescence were evaluated by senescence-associated ß galactosidase (SA-ß-Gal) staining, flow cytometry and western blot (WB). The cell viability was tested using CCK-8 kits. Cell apoptosis was detected by Annexin V-EGFP/PI apoptosis detection kit. Cell autophagy was checked using GFP-RFP-LC3 ratiometric plasmid. The roles of VPA in lung aging were investigated by in vivo experiments using H&E and Masson staining, WB, as well as electronic microscope strategies. RESULTS: Here we identified VPA was able to induce an over-accumulation of reactive oxygen species (ROS) (>1.5 times increasing) and apoptosis (>2 times increasing) of senescent cells. Mechanistically, VPA activated the phospholipid modifying enzyme membrane-bound O-acyltransferase domain-containing protein 1 (MBOAT1), which was repressed during senescence, then promoted mitochondrial autophagy and apoptosis. In addition, VPA was also found to alleviate therapy induced abnormal mitochondria and lung aging phenotype (>1.5 times decreasing of lung fibrosis markers and >2.5 times increasing of naïve/memory CD4+ or CD8+ T cells) in vivo. CONCLUSION: Taken together, our study demonstrated that VPA was able to selectively kill senescent cells both in vitro and in vivo, and thus shedding light on new functions and novel potential application of VPA in anti-aging and anti-age-associated diseases.

Calcium transferring from ER to mitochondria via miR-129/ITPR2 axis controls cellular senescence in vitro and in vivo.

Senescent cells are known to be accumulated in aged organisms. Although the two main characteristics, cell cycle arrest (for dividing cells) and secretion of senescence-associated secretory phenotype (SASP) factors, have been well described, the lack of sufficient senescent markers and incomplete understanding of mechanisms have limited the progress of the anti-senescence field. Calcium transferred from the endoplasmic reticulum (ER) via inositol 1, 4, 5-trisphosphate receptor type 2 (ITPR2) to mitochondria has emerged as a key player during cellular senescence and aging. However, the internal regulatory mechanisms, particularly those of endogenous molecules, remain only partially understood. Here we identified miRNA-129 (miR-129) as a direct repressor of ITPR2. Interestingly, miR-129 controlled a cascade of intracellular calcium signaling, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), DNA damage, and consequently cellular senescence through ITPR2 and mitochondrial calcium uniporter (MCU). In addition, miR-129 was repressed in different senescence models and delayed bleomycin-induced cellular senescence. Importantly, intraperitoneal injection of miR-129 partly postponed bleomycin-accelerated lung aging and natural aging markers as well as reduced immunosenescence markers in mice. Altogether, these findings demonstrated that miR-129 regulated cellular senescence and aging markers via intracellular calcium signaling by directly targeting ITPR2.

Identification of novel key markers that are induced during traumatic brain injury in mice.

Background: Traumatic brain injury (TBI) has emerged as an increasing public health problem but has not been well studied, particularly the mechanisms of brain cellular behaviors during TBI. Methods: In this study, we established an ischemia/reperfusion (I/R) brain injury mice model using transient middle cerebral artery occlusion (tMCAO) strategy. After then, RNA-sequencing of frontal lobes was performed to screen key inducers during TBI. To further verify the selected genes, we collected peripheral blood mononuclear cells (PBMCs) from TBI patients within 24 h who attended intensive care unit (ICU) in the Affiliated Hospital of Yangzhou University and analyzed the genes expression using RT-qPCR. Finally, the receiver operator characteristic (ROC) curves and co-expression with cellular senescence markers were applied to evaluate the predictive value of the genes. Results: A total of six genes were screened out from the RNA-sequencing based on their novelty in TBI and implications in apoptosis and cellular senescence signaling. RT-qPCR analysis of PBMCs from patients showed the six genes were all up-regulated during TBI after comparing with healthy volunteers who attended the hospital for physical examination. The area under ROC (AUC) curves were all >0.7, and the co-expression scores of the six genes with senescence markers were all significantly positive. We thus identified TGM1, TGM2, ATF3, RCN3, ORAI1 and ITPR3 as novel key markers that are induced during TBI, and these markers may also serve as potential predictors for the progression of TBI.