Accurate measurement of cysteine and related thiol-containing metabolites is essential for understanding cellular redox regulation. However, the intrinsic reactivity and instability of cysteine present substantial analytical challenges. This review summarizes the biochemical context of cysteine and glutathione metabolism, emphasizing their dynamic redox equilibria and physiological relevance. We critically examine existing analytical approaches, including mass spectrometry-based, enzyme-coupled, and colorimetric methods, and discuss their respective strengths and limitations. Particular attention is given to sample preparation, derivatization strategies, and reagent selection, as these steps are crucial for preserving native thiol-disulfide status. Among various alkylating agents, N-ethylmaleimide is identified as the most reliable for thiol stabilization in liquid chromatography–mass spectrometry (LC-MS) workflows, while specific reagents such as monobromobimane or β-(4-hydroxyphenyl)ethyl iodoacetamide (HPE-IAM) are required for persulfide and polysulfide detection. The review also highlights the pitfalls of using indirect surrogates—such as glutathione or cystathionine levels—to infer cysteine availability, which can lead to significant misinterpretation of metabolic states. We conclude that direct LC-MS-based quantification of cysteine and glutathione, combined with careful derivatization and sample handling, remains the most reliable and accurate approach currently available for the assessment of thiol metabolism and redox homeostasis.

Ferroptosis, a regulated form of cell death driven by iron-dependent lipid peroxidation, has emerged as a crucial tumor suppressive mechanism and a promising therapeutic target in oncology. This review synthesizes the current understanding of its core molecular machinery, encompassing lipid metabolism, iron homeostasis, and multi-layered cellular defense systems. We highlight the unique metabolic and genetic vulnerabilities that render specific cancer cell types intrinsically susceptible to ferroptosis. Furthermore, we discuss the dynamic propagation of ferroptotic signals within the tumor microenvironment and their complex immunomodulatory effects. Central to this review is a strategic framework for targeting ferroptosis, synthesizing recent advances in the development of specific ferroptosis inducers and evaluating their synergistic potential when combined with chemotherapy, radiotherapy, targeted therapy, and immunotherapy. By integrating mechanistic insight with translational perspectives, this work provides a systematic guide for rationally exploiting ferroptosis in cancer treatment.

Neurons exist at the intersection of two essential yet hazardous metabolic demands: iron-driven bioenergetics and lipid-dependent membrane remodeling. Their reliance on mitochondrial iron for adenosine triphosphate (ATP) generation, combined with the requirement for polyunsaturated fatty acids to sustain synaptic plasticity, creates a biochemical environment primed for ferroptosis. This Perspective examines how the interplay between iron and lipid metabolism defines neuronal vulnerability in neurodegenerative diseases, focusing on apolipoprotein E (ApoE) as a metabolic gatekeeper coordinating those pathways. Beyond its canonical function in lipid transport, ApoE acts as a potent anti-ferroptotic factor by inhibiting ferritinophagy and restraining the release of labile iron, thereby coupling lipid trafficking with iron homeostasis. Dysregulation of this axis in Alzheimer’s disease amplifies lipid peroxidation and compromises antioxidant defenses. Parallel mechanisms are observed in Neurodegeneration with Brain Iron Accumulation disorders, where mutations in lipid-metabolic genes paradoxically lead to brain iron accumulation, underscoring the genetic entanglement of these pathways. Collectively, these findings support a unifying model in which neuronal ferroptosis arises not from isolated iron overload or lipid imbalance, but from the breakdown of a coordinated iron-lipid defense network. We propose that restoring this equilibrium through modulation of ApoE function, preservation of mitochondrial iron utilization, and suppression of lipid peroxidation represents a promising avenue for therapeutic intervention in neurodegenerative disease.