Neurons Die Not by One Hit, but by Signaling Convergence

There is an emerging understanding of neurodegenerative diseases as complex diseases with a combination of multiple interrelated signaling pathways as opposed to one causative factor. This review examines the idea that neurons do not die in a single event, but through convergence of signals, which outlines the different pathological events such as oxidative stress, mitochondrial dysfunction, excitotoxicity, calcium imbalance, impaired proteostasis and neuroinflammation that interact to determine the fate of neurons. The processes are closely connected by molecular nodes like ROS, NF-κB, and MAPK signaling pathways, Nrf2/Keap1 antioxidant axis, and dysregulated autophagy and endoplasmic reticulum stress responses. The review also discusses the contribution of neuron glia interactions and the impact of microglial activation, astrocyte malfunction and cytokine networks in enhancing neuronal damage in a feedback mechanism. Mechanisms that have been mentioned as the oxidative stress inflammation cycle, mitochondrial damage, ROS feedback, and protein aggregation cellular stress loop are cited to be the major contributors to disease progression. Also, the review mentions new biomarkers, multi-omics methods, and sophisticated research instruments, such as artificial intelligence and organoid models, which can contribute to our knowledge of disease pathogenesis and help diagnose it earlier. On the whole, this review presents a complete paradigm on how to perceive neurodegeneration as a systems-level phenomenon. It combines molecular, cellular, and clinical perspectives and offers the rationale for the need to consider the therapeutic approach to neurodegenerative diseases in a holistic and multi-dimensional manner.