Pb induced mitochondrial fission of fibroblast cells via ATM activation

Mitochondrial iron deficiency mediated inhibition of ecdysone synthesis underlies lead (Pb) induced developmental toxicity in Drosophila melanogaster

Lead (Pb) is a pervasive heavy metal possessing developmental toxicity, at least in part, by disrupting iron homeostasis. In this study, we aimed to elucidate the underlying mechanism of iron deficiency mediated developmental defects in Pb exposed Drosophila melanogaster, mainly focusing on iron-dependent synthesis of ecdysone signaling, which plays a key role in the development of insects. Herein, we found Pb exposure resulted in iron deficiency in mitochondria by inhibiting expression of mitoferrin (evidenced by qPCR assay), the mitochondrial iron importer. Further study demonstrated that biosynthesis of ecdysone, a hormone synthesized with the help of iron-containing cytochrome P450s in mitochondria, was inhibited following Pb exposure. Ecdysone supplementation, to some extent, rescued Pb induced developmental delay and reproductive defects in Drosophila melanogaster. Furthermore, we found that disruption of mitoferrin and ecdysone synthesis was restored by NAC (N-Acetylcysteine, a well-known ROS scavenger), suggesting that oxidative stress plays a key role in Pb mediated mitochondrial iron dys-homeostasis and developmental toxicity. This study therefore revealed that mitochondrial iron deficiency mediated inhibition of ecdysone synthesis is a key event associated with iron dys-homeostasis mediated developmental defects caused by Pb exposure. Meanwhile, our study indicated that mitochondria may act as an important target of Pb, thus providing potential protective strategies against Pb toxicity.

Overexpression Bcl-2 alleviated ferroptosis induced by molybdenum and cadmium co-exposure through inhibiting mitochondrial ROS in duck kidneys

Excessive molybdenum (Mo) and cadmium (Cd) are environmental pollutants with serious nephrotoxicity. B-cell lymphoma 2 (Bcl-2) plays a critical role in modulating mitochondrial ROS (Mito-ROS). Ferroptosis is a form of cell death dependent on lipid peroxidation. However, the impacts of Mo and Cd co-exposure on ferroptosis in duck kidneys and the function of Bcl-2 in the process are still unclear. Ducks and duck primary renal tubular epithelial cells exposed to different doses of Mo and/or Cd were used as the research target. Our work suggested that Mo and/or Cd significantly decreased Bcl-2 protein level and induced ferroptosis with the increase of ferrous ion, lipid peroxidation, TF protein level and the decrease of GPX4, FT protein levels. The Bcl-2 inhibitor HA14-1 exacerbated the changes of these indexes, but Bcl-2 overexpression had the opposite effect. Mito-ROS inhibitor ROS-IN-1 alleviated ferroptosis induced by Mo and Cd. Besides, Bcl-2 was involved in mitochondrial dysfunction induced by Mo and Cd, accompanied by disturbing Mito-ROS, ATP level, mitochondrial complex IV activity, Bcl-2 and COX-2 co-localization, lipid peroxidation, mitochondrial membrane potential (MMP) and mitochondrial structure. These findings substantiated that overexpression Bcl-2 alleviated ferroptosis co-induced by Mo and Cd through reducing Mito-ROS level in duck kidneys.

Enhancing bone regeneration and immunomodulation via gelatin methacryloyl hydrogel-encapsulated exosomes from osteogenic pre-differentiated mesenchymal stem cells

Mesenchymal stem cell-derived exosomes (MSC-Exos) have emerged as promising candidates for cell-free therapy in tissue regeneration. However, the native osteogenic and angiogenic capacities of MSC-Exos are often insufficient to repair critical-sized bone defects, and the underlying immune mechanisms remain elusive. Furthermore, achieving sustained delivery and stable activity of MSC-Exos at the defect site is essential for optimal therapeutic outcomes. Here, we extracted exosomes from osteogenically pre-differentiated human bone marrow mesenchymal stem cells (hBMSCs) by ultracentrifugation and encapsulated them in gelatin methacryloyl (GelMA) hydrogel to construct a composite scaffold. The resulting exosome-encapsulated hydrogel exhibited excellent mechanical properties and biocompatibility, facilitating sustained delivery of MSC-Exos. Osteogenic pre-differentiation significantly enhanced the osteogenic and angiogenic properties of MSC-Exos, promoting osteogenic differentiation of hBMSCs and angiogenesis of human umbilical vein endothelial cells (HUVECs). Furthermore, MSC-Exos induced polarization of Raw264.7 cells from a pro-inflammatory phenotype to an anti-inflammatory phenotype under simulated inflammatory conditions, thereby creating an immune microenvironment conducive to osteogenesis. RNA sequencing and bioinformatics analysis revealed that MSC-Exos activate the p53 pathway through targeted delivery of internal microRNAs and regulate macrophage polarization by reducing DNA oxidative damage. Our study highlights the potential of osteogenic exosome-encapsulated composite hydrogels for the development of cell-free scaffolds in bone tissue engineering.

Sensitivity of triple negative breast cancer cells to ATM-dependent ferroptosis induced by sodium selenite

Targeting ferroptosis, a type of cell death elicited by Fe2+ and lipid reactive oxygen species (L-ROS), provides a novel strategy for cancer therapy. Selenium has the potential to treat cancers by acting as a pro-oxidative agent, thus leading to cancer cell death. Here, we found that the triple negative breast cancer (TNBC) MDA-MB-231 cells were more sensitive to ferroptosis induced by sodium selenite (Na2SeO3) than that of non-TNBC MCF-7 cells. Na2SeO3 significantly elevated the level of L-ROS, MDA and Fe2+, decreased the content of GSH and the enzyme activity of GPx, disrupted the expression of ferroptosis related proteins such as GPx4 and FTH1, as well as compromised mitochondrial morphology in MDA-MB-231 cells. Moreover, ATM was activated by Na2SeO3 in MDA-MB-231 cells. Notably, Na2SeO3-induced ferroptosis was inhibited by ATM kinase inhibitor KU55933 or siATM, suggesting that Na2SeO3-induced ferroptosis was mediated by ATM protein in MDA-MB-231 cells. Our findings suggest a therapeutic strategy by ferroptosis against TNBC and deepened our understanding of ATM function.

Tl(I) and Tl(III)-induce genotoxicity, reticulum stress and autophagy in PC12 Adh cells

Thallium (Tl) and its two cationic species, Tl(I) and Tl(III), are toxic for most living beings. In this work, we investigated the effects of Tl (10-100 µM) on the viability and proliferation capacity of the adherent variant of PC12 cells (PC12 Adh cells). While both Tl(I) and Tl(III) halted cell proliferation from 24 h of incubation, their viability was ~ 90% even after 72 h of treatment. At 24 h, increased levels of γH2AX indicated the presence of DNA double-strand breaks. Simultaneously, increased expression of p53 and its phosphorylation at Ser15 were observed, which were associated with decreased levels of p-AKTSer473 and p-mTORSer2448. At 72 h, the presence of large cytoplasmic vacuoles together with increased autophagy predictor values suggested that Tl may induce autophagy in these cells. This hypothesis was corroborated by images obtained by transmission electron microscopy (TEM) and from the decreased expression at 72 h of incubation of SQSTM-1 and increased LC3β-II to LC3β-I ratio. TEM images also showed enlarged ER that, together with the increased expression of IRE1-α from 48 h of incubation, indicated that Tl-induced ER stress preceded autophagy. The inhibition of autophagy flux with chloroquine increased cell mortality, suggesting that autophagy played a cytoprotective role in Tl toxicity in these cells. Together, results indicate that Tl(I) or Tl(III) are genotoxic to PC12 Adh cells which respond to the cations inducing ER stress and cytoprotective autophagy.

Nickel induces hepatotoxicity by mitochondrial biogenesis, mitochondrial dynamics, and mitophagy dysfunction

Nickel (Ni) is an important and widely hazardous chemical industrial waste. Excessive Ni exposure could cause multi-organs toxicity in human and animals. Liver is the major target organ of Ni accumulation and toxicity, however, the precise mechanism is still unclear. In this study, nickel chloride (NiCl₂ )-treatment induced hepatic histopathological changes in the mice, and, transmission electron microscopy results showed mitochondrial swollen and deformed of hepatocyte. Next, the mitochondrial damages including mitochondrial biogenesis, mitochondrial dynamics, and mitophagy were measured after NiCl₂ administration. The results showed that NiCl₂ suppressed mitochondrial biogenesis by decreasing PGC-1α, TFAM, and NRF1 protein and mRNA expression levels. Meanwhile, the proteins involved in mitochondrial fusion were reduced by NiCl₂ , such as Mfn1 and Mfn2, however, mitochondrial fission proteins Drip1 and Fis1 were significantly increased. The up-regulation of mitochondrial p62 and LC3II expression indicated that NiCl₂ increased mitophagy in the liver. Moreover, the receptor-mediated mitophagy and ubiquitin (Ub)-dependent mitophagy were detected. NiCl₂ promoted PINK1 accumulation and Parkin recruitment on mitochondria. And, the receptor proteins of mitophagy Bnip3 and FUNDC1 were increased in the NiCl₂ -treated mice liver. Overall, these results show that NiCl₂ could induce mitochondria damage in the liver of mice, and, dysfunction of mitochondrial biogenesis, mitochondrial dynamics and mitophagy involved in the molecular mechanism of NiCl₂ -induced hepatotoxicity.