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Iron homeostasis and ferroptosis in muscle diseases and disorders: mechanisms and therapeutic prospects

The muscular system plays a critical role in the human body by governing skeletal movement, cardiovascular function, and the activities of digestive organs. Additionally, muscle tissues serve an endocrine function by secreting myogenic cytokines, thereby regulating metabolism throughout the entire body. Maintaining muscle function requires iron homeostasis. Recent studies suggest that disruptions in iron metabolism and ferroptosis, a form of iron-dependent cell death, are essential contributors to the progression of a wide range of muscle diseases and disorders, including sarcopenia, cardiomyopathy, and amyotrophic lateral sclerosis. Thus, a comprehensive overview of the mechanisms regulating iron metabolism and ferroptosis in these conditions is crucial for identifying potential therapeutic targets and developing new strategies for disease treatment and/or prevention. This review aims to summarize recent advances in understanding the molecular mechanisms underlying ferroptosis in the context of muscle injury, as well as associated muscle diseases and disorders. Moreover, we discuss potential targets within the ferroptosis pathway and possible strategies for managing muscle disorders. Finally, we shed new light on current limitations and future prospects for therapeutic interventions targeting ferroptosis.

Melanoma bone metastasis-induced osteocyte ferroptosis via the HIF1α-HMOX1 axis

Osteocytes are the main cells in mineralized bone tissue. Elevated osteocyte apoptosis has been observed in lytic bone lesions of patients with multiple myeloma. However, their precise contribution to bone metastasis remains unclear. Here, we investigated the pathogenic mechanisms driving melanoma-induced osteocyte death. Both in vivo models and in vitro assays were combined with untargeted RNA sequencing approaches to explore the pathways governing melanoma-induced osteocyte death. We could show that ferroptosis is the primary mechanism behind osteocyte death in the context of melanoma bone metastasis. HMOX1 was identified as a crucial regulatory factor in this process, directly involved in inducing ferroptosis and affecting osteocyte viability. We uncover a non-canonical pathway that involves excessive autophagy-mediated ferritin degradation, highlighting the complex relationship between autophagy and ferroptosis in melanoma-induced osteocyte death. In addition, HIF1α pathway was shown as an upstream regulator, providing a potential target for modulating HMOX1 expression and influencing autophagy-dependent ferroptosis. In conclusion, our study provides insight into the pathogenic mechanisms of osteocyte death induced by melanoma bone metastasis, with a specific focus on ferroptosis and its regulation. This would enhance our comprehension of melanoma-induced osteocyte death.

Insights on the crosstalk among different cell death mechanisms

The phenomenon of cell death has garnered significant scientific attention in recent years, emerging as a pivotal area of research. Recently, novel modalities of cellular death and the intricate interplay between them have been unveiled, offering insights into the pathogenesis of various diseases. This comprehensive review delves into the intricate molecular mechanisms, inducers, and inhibitors of the underlying prevalent forms of cell death, including apoptosis, autophagy, ferroptosis, necroptosis, mitophagy, and pyroptosis. Moreover, it elucidates the crosstalk and interconnection among the key pathways or molecular entities associated with these pathways, thereby paving the way for the identification of novel therapeutic targets, disease management strategies, and drug repurposing.

Targeting macrophage polarization by inhibiting Pim2 alleviates inflammatory arthritis via metabolic reprogramming

Macrophage polarization and energy metabolic reprogramming play pivotal roles in the onset and progression of inflammatory arthritis. Moreover, although previous studies have reported that the proviral integration of Moloney virus 2 (Pim2) kinase is involved in various cancers through the mediation of aerobic glycolysis in cancer cells, its role in inflammatory arthritis remains unclear. In this study, we demonstrated that multiple metabolic enzymes are activated upon Pim2 upregulation during M1 macrophage polarization. Specifically, Pim2 directly phosphorylates PGK1-S203, PDHA1-S300, and PFKFB2-S466, thereby promoting glycolytic reprogramming. Pim2 expression was elevated in macrophages from patients with inflammatory arthritis and collagen-induced arthritis (CIA) model mice. Conditional knockout of Pim2 in macrophages or administration of the Pim2 inhibitor HJ-PI01 attenuated arthritis development by inhibiting M1 macrophage polarization. Through molecular docking and dynamic simulation, bexarotene was identified as an inhibitor of Pim2 that inhibits glycolysis and downstream M1 macrophage polarization, thereby mitigating the progression of inflammatory arthritis. For targeted treatment, neutrophil membrane-coated bexarotene (Bex)-loaded PLGA-based nanoparticles (NM@NP-Bex) were developed to slow the progression of inflammatory arthritis by suppressing the polarization of M1 macrophages, and these nanoparticles (NPs) exhibited superior therapeutic effects with fewer side effects. Taken together, the results of our study demonstrated that targeting Pim2 inhibition could effectively alleviate inflammatory arthritis via glycolysis inhibition and reversal of the M1/M2 macrophage imbalance. NM@NPs loaded with bexarotene could represent a promising targeted strategy for the treatment of inflammatory arthritis.

Acyl-CoA thioesterase 8 induces gemcitabine resistance via regulation of lipid metabolism and antiferroptotic activity in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) comprises a group of highly malignant tumors of the pancreas. Metabolic reprogramming in tumors plays a pivotal role in promoting cancer progression. However, little is known about the metabolic alterations in tumors that drive cancer drug resistance in patients with PDAC. Here, we identified acyl-CoA thioesterase 8 (ACOT8) as a key player in driving PDAC gemcitabine (GEM) resistance. The expression of ACOT8 is significantly upregulated in GEM-resistant PDAC tissues and is closely associated with poor survival in patients with PDAC. Gain- and loss-of-function studies have shown that ACOT8 drives PDAC GEM resistance both in vitro and in vivo. Mechanistically, ACOT8 regulates cellular cholesterol ester (CE) levels, decreases the levels of phosphatidylethanolamines (PEs) that bind to polyunsaturated fatty acids and promote peroxisome activation. The knockdown of ACOT8 promotes ferroptosis and increases the chemosensitivity of tumors to GEM by inducing ferroptosis-associated pathway activation in PDAC cell lines. The combination of orlistat, an ACOT8 inhibitor, and GEM significantly inhibited tumor growth in PDAC organoid and mouse models. This study reveals the biological importance of ACOT8 and provides a potential combination therapy for treating patients with advanced GEM-resistant PDAC.

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