bims-mitdyn 2025-01-05 papers

Int J Biol Sci. 2025 ;21(1): 400-414

Nuclear receptor 4A1 Regulates Mitochondrial Homeostasis in Cardiac Post-Ischemic Injury by Controlling Mitochondrial Fission 1 Protein-Mediated Fragmentation and Parkin-Dependent Mitophagy.

Haoran Ye, Jialong Lin, Hui Zhang, Jing Wang, Yuan Fu, Zhaopei Zeng, Junmeng Zheng, Jun Tao, Junxiong Qiu.

The close interaction of mitochondrial fission and mitophagy, two crucial mechanisms, is key in the progression of myocardial ischemia-reperfusion (IR) injury. However, the upstream regulatory mechanisms governing these processes remain poorly understood. Here, we demonstrate a marked elevation in Nr4a1 expression following myocardial IR injury, which is associated with impaired cardiac function, heightened cardiomyocyte apoptosis, exacerbated inflammatory responses, and endothelial dysfunction. Notably, Nr4a1-knockout mice exhibited remarkable resistance to acute myocardial IR injury, characterized by preserved mitochondrial integrity relative to their wild-type counterparts. Functional analyses revealed that elevated Nr4a1 expression after IR injury promotes Fis1-mediated mitochondrial fission while suppressing Parkin-driven mitophagy. Importantly, interventions that inhibit mitochondrial fission or enhance mitophagy effectively ameliorated IR-induced cardiomyocyte and endothelial dysfunction. Collectively, these results highlight that the absence of Nr4a1 provides a shield against cardiac post-ischemic damage by reinstating balance within the mitochondria through inhibiting Fis1-induced fission and promoting Parkin-triggered mitophagy. Furthermore, therapeutic strategies targeting the Nr4a1/mitochondria axis may offer promising avenues for improving cardiac outcomes under myocardial IR stress.

Keywords: Cardiac post-ischemic damage; Fis1; Mitochondrial fission and Mitophagy; Nr4a1; Parkin

DOI: https://doi.org/10.7150/ijbs.104680

PLoS One. 2024 ;19(12): e0306243

Loss of Mfn1 but not Mfn2 enhances adipogenesis.

Jake P Mann, Luis Carlos Tábara, Satish Patel, Pushpa Pushpa, Anna Alvarez-Guaita, Liang Dong, Afreen Haider, Koini Lim, Panna Tandon, Fabio Scurria, James E N Minchin, Stephen O'Rahilly S, Daniel J Fazakerley, Julien Prudent, Robert K Semple, David B Savage.

OBJECTIVE: A biallelic missense mutation in mitofusin 2 (MFN2) causes multiple symmetric lipomatosis and partial lipodystrophy, implicating disruption of mitochondrial fusion or interaction with other organelles in adipocyte differentiation, growth and/or survival. In this study, we aimed to document the impact of loss of mitofusin 1 (Mfn1) or 2 (Mfn2) on adipogenesis in cultured cells.
METHODS: We characterised adipocyte differentiation of wildtype (WT), Mfn1-/- and Mfn2-/- mouse embryonic fibroblasts (MEFs) and 3T3-L1 preadipocytes in which Mfn1 or 2 levels were reduced using siRNA.
RESULTS: Mfn1-/- MEFs displayed striking fragmentation of the mitochondrial network, with surprisingly enhanced propensity to differentiate into adipocytes, as assessed by lipid accumulation, expression of adipocyte markers (Plin1, Fabp4, Glut4, Adipoq), and insulin-stimulated glucose uptake. RNA sequencing revealed a corresponding pro-adipogenic transcriptional profile including Pparg upregulation. Mfn2-/- MEFs also had a disrupted mitochondrial morphology, but in contrast to Mfn1-/- MEFs they showed reduced expression of adipocyte markers. Mfn1 and Mfn2 siRNA mediated knockdown studies in 3T3-L1 adipocytes generally replicated these findings.
CONCLUSIONS: Loss of Mfn1 but not Mfn2 in cultured pre-adipocyte models is pro-adipogenic. This suggests distinct, non-redundant roles for the two mitofusin orthologues in adipocyte differentiation.

DOI: https://doi.org/10.1371/journal.pone.0306243

Nat Commun. 2024 Dec 30. 15(1): 10806

DLK-dependent axonal mitochondrial fission drives degeneration after axotomy.

Jorge Gómez-Deza, Matthew Nebiyou, Mor R Alkaslasi, Francisco M Nadal-Nicolás, Preethi Somasundaram, Anastasia L Slavutsky, Wei Li, Michael E Ward, Trent A Watkins, Claire E Le Pichon.

Currently there are no effective treatments for an array of neurodegenerative disorders to a large part because cell-based models fail to recapitulate disease. Here we develop a reproducible human iPSC-based model where laser axotomy causes retrograde axon degeneration leading to neuronal cell death. Time-lapse confocal imaging revealed that damage triggers an apoptotic wave of mitochondrial fission proceeding from the site of injury to the soma. We demonstrate that this apoptotic wave is locally initiated in the axon by dual leucine zipper kinase (DLK). We find that mitochondrial fission and resultant cell death are entirely dependent on phosphorylation of dynamin related protein 1 (DRP1) downstream of DLK, revealing a mechanism by which DLK can drive apoptosis. Importantly, we show that CRISPR mediated Drp1 depletion protects mouse retinal ganglion neurons from degeneration after optic nerve crush. Our results provide a platform for studying degeneration of human neurons, pinpoint key early events in damage related neural death and provide potential focus for therapeutic intervention.

DOI: https://doi.org/10.1038/s41467-024-54982-9

Free Radic Biol Med. 2024 Dec 27. pii: S0891-5849(24)01158-4. [Epub ahead of print]

Lipotoxicity-induced upregulation of FIS1 exacerbates mitochondrial fragmentation and promotes NLRP3-dependent pyroptosis in diabetic cardiomyopathy.

Libo Luo, Qingrui Wu, Qingyu Xiao, Yuqiong Chen, Zhanxiang Deng, Chunren Cen, Jijin Lin.

BACKGROUND: Lipotoxicity is a significant factor in the pathogenesis of diabetic cardiomyopathy (DbCM), a condition characterized by mitochondrial fragmentation and pyroptosis. Mitochondrial fission protein 1 (FIS1) plays a role in mitochondrial fission by anchoring dynamin-related protein 1 (DRP1). However, the specific contribution of FIS1 to DbCM remains unclear. This study aims to clarify how lipotoxicity-induced upregulation of FIS1 affects mitochondrial fragmentation and the mechanisms linking this fragmentation to NLRP3-dependent pyroptosis in DbCM.
METHODS: To model lipotoxicity in DbCM, we used db/db mice and primary neonatal rat cardiomyocytes (NRCMs) treated with palmitic acid (PA) and conducted a series of in vivo and in vitro experiments. Gain- and loss-of-function studies on NRCMs were performed using pharmacological inhibitors and small interfering RNA (siRNA) transfection, and we assessed the expression and function of FIS1, mitochondrial dynamics, mitochondrial reactive oxygen species (mitoROS) production, NLRP3-dependent pyroptosis, and their interrelationships.
RESULTS: Our results show that in the myocardium of db/db mice, NLRP3-dependent pyroptosis is associated with upregulation of FIS1, mitochondrial fragmentation, and increased oxidative stress. In NRCMs subjected to PA, the application of VX-765 and MCC950 to inhibit caspase-1 and NLRP3, respectively, significantly reduced pyroptosis. Additionally, pretreatment with Mito-TEMPO (MT) demonstrated that mitoROS are critical initiators for NLRP3 inflammasome activation and subsequent pyroptosis. Furthermore, PA-induced upregulation of FIS1 exacerbates mitochondrial fragmentation. Downregulation of FIS1 or inhibition of FIS1/DRP1 interaction reversed mitochondrial fragmentation, reduced mitoROS levels, and mitigated pyroptosis.
CONCLUSIONS: Lipotoxicity-induced FIS1 upregulation exacerbates mitochondrial fragmentation through its interaction with DRP1, leading to increased mitoROS production and the initiation of NLRP3-dependent pyroptosis in DbCM. Therefore, targeting FIS1 emerges as a potential therapeutic approach for managing DbCM.

Keywords: Diabetic cardiomyopathy; FIS1; Inflammation; Lipotoxicity; Mitochondrial fragmentation; Pyroptosis; mitoROS

DOI: https://doi.org/10.1016/j.freeradbiomed.2024.12.049

Exp Hematol Oncol. 2024 Dec 28. 13(1): 123

AOH1996 targets mitochondrial dynamics and metabolism in leukemic stem cells via mitochondrial PCNA inhibition.

HyunJun Kang, Melissa Valerio, Jia Feng, Long Gu, Dinh Hoa Hoang, Amanda Blackmon, Shawn Sharkas, Khyatiben Pathak, Jennifer Jossart, Zhuo Li, Hongyu Zhang, Bin Zhang, Patrick Pirrotte, J Jefferson P Perry, Robert J Hickey, Linda Malkas, Guido Marcucci, Le Xuan Truong Nguyen.

Cytoplasmic proliferating cell nuclear antigen (PCNA) is highly expressed in acute myeloid leukemia (AML) cells, supporting oxidative metabolism and leukemia stem cell (LSC) growth. We report on AOH1996 (AOH), an oral compound targeting cancer-associated PCNA, which shows significant antileukemic activity. AOH inhibited growth in AML cell lines and primary CD34 + CD38 - blasts (LSC-enriched) in vitro while sparing normal hematopoietic stem cells (HSCs). In vivo, AOH-treated mice demonstrated prolonged survival compared to controls (50 vs. 35 days; p < 0.0001) with reduced LSC burden, as shown in secondary transplants (42 vs. 30 days, p < 0.0001). Mechanistically, AOH disrupted mitochondrial PCNA's binding to the OPA1 protein, enhancing OPA1's interaction with its E3 ligase, MARCH5, which led to OPA1 degradation. This process reduced mitochondrial length, fatty acid oxidation (FAO), and oxidative phosphorylation (OXPHOS), thereby inhibiting LSC expansion. The addition of venetoclax (VEN), an FDA-approved Bcl-2 inhibitor, further enhanced AOH's effects, reducing mitochondrial length, FAO, and OXPHOS while improving survival in AML models. While VEN is approved for AML, AOH is under clinical investigation for solid tumors, and our findings support its broader therapeutic potential.

Keywords: AML; AOH1996; Leukemic stem cells; Mitochondrial metabolism; PCNA inhibitor

DOI: https://doi.org/10.1186/s40164-024-00586-4