Neurodegenerative diseases are significant health concerns that have a profound impact on the quality and duration of life for millions of individuals. These diseases are characterized by pathological changes in various brain regions, specific genetic mutations associated with the disease, deposits of abnormal proteins, and the degeneration of neurological cells. As neurodegenerative disorders vary in their epidemiological characteristics and vulnerability of neurons, treatment of these diseases is usually aimed at slowing disease progression. The heterogeneity of genetic and environmental factors involved in the process of neurodegeneration makes current treatment methods inadequate. However, the existence of common molecular mechanisms in the pathogenesis of these diseases may allow the development of new targeted therapeutic strategies. Oxidative and nitrosative stress damages membrane components by accumulating ROS and RNS and disrupting redox balance. This process results in the induction of apoptosis, which is important in the pathogenesis of neurodegenerative diseases through oxidative stress. Studies conducted using postmortem human samples, animal models, and cell cultures have demonstrated that oxidative stress, nitrosative stress, and apoptosis are crucial factors in the development of diseases such as Alzheimer's, Parkinson's, Multiple Sclerosis, amyotrophic lateral sclerosis, and Huntington's disease. The excessive production of reactive oxygen and nitrogen species, elevated levels of free radicals, heightened mitochondrial stress, disturbances in energy metabolism, and the oxidation and nitrosylation of cellular macromolecules are recognized as triggers for neuronal cell death. Challenges in managing and treating neurodegenerative diseases require a better understanding of this field at the molecular level. Therefore, this review elaborates on the molecular mechanisms by which oxidative and nitrosative stress are involved in neuronal apoptosis.

Background/Objectives: The G protein-coupled estrogen receptor (GPER) is known to interact with cellular stress responses and DNA damage pathways. Therefore, exposure to ionizing radiation may modulate the biological consequences of single-nucleotide polymorphisms in the GPR30 gene. This study aims to evaluate the association between GPER polymorphisms and radiation sensitivity. Methods: The study included 50 healthcare workers exposed to ionizing radiation and 36 healthy individuals with no known occupational exposure to radiation. Genomic DNA was isolated and PCR products were purified using GeneAll kits. Genomic regions encompassing three GPER single-nucleotide polymorphisms (rs3808350, rs3808351, and rs11544331) were amplified by polymerase chain reaction (PCR), followed by DNA sequencing analysis using the BigDye Cycle Sequencing Kit. In addition, an in silico functional and clinical annotation of rs11544331 was performed using Ensembl VEP, SIFT, PolyPhen-2, AlphaMissense, CADD, UniProt, and ClinVar. Results: Genotypic, dominant, and allelic analyses revealed no significant association between radiation exposure and the rs3808350 or rs3808351 polymorphisms. In contrast, a statistically significant association was observed for rs11544331. The frequency of individuals carrying the CT and TT genotypes (CT + TT) was significantly higher in the ionizing radiation-exposed group compared with the control group (OR = 2.981; 95% CI: 1.106–7.904; p = 0.0241). In allelic analysis, the T allele was more prevalent in the exposed group and was significantly associated with radiation exposure (OR = 2.959; 95% CI: 1.282–6.606; p = 0.0110). In silico analysis confirmed that rs11544331 corresponds to the p.Pro16Leu substitution in GPER1; however, SIFT, PolyPhen-2, AlphaMissense, CADD, and ClinVar consistently indicated a tolerated, benign, likely benign, or low-deleteriousness profile. Conclusions: GPER-mediated stress responses and genetic polymorphisms may play a potential role in determining genetic susceptibility following exposure to ionizing radiation.

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) are considered promising biological carriers for biomolecule and drug delivery because of their inherent biological activities, biocompatibility, and capacity to carry a variety of therapeutic cargoes. However, the limited cargo-loading capacity of native EVs, their inefficient delivery to target cells, intracellular trafficking barriers, and limitations in the functional release of their cargo restrict their therapeutic applications. EV engineering encompasses a range of approaches to overcome these limitations, including donor cell modification, endogenous cargo loading and active sorting mechanisms, post-isolation loading methods, surface engineering, and EV–lipid-based hybrid systems. In this review, engineered MSC-EVs are evaluated in terms of cargo loading, targeting, cellular uptake, intracellular trafficking, and functional cargo delivery. We also compare the loading strategies used for nucleic acids, proteins, enzymes, and small molecules, in terms of their advantages, their limitations, and their effect on EV biological activity. The therapeutic applications of MSC-EV-based systems in cardiovascular diseases, wound healing, neurological and musculoskeletal disorders, inflammatory diseases, and cancer are evaluated. The central conclusion of this review is that the therapeutic efficacy of MSC-EVs depends not only on the amount of cargo delivered but also on its delivery to the appropriate target cells, intracellular targeting, and preservation of its biological activity. Accordingly, future EV engineering strategies should aim to simultaneously improve cargo loading, disease-specific targeting, local retention, and cargo stability. Progress on these four fronts is what would make MSC-EVs predictable enough for clinical use.