A Systematic Review of the Vascular and Neuronal Role of L-Carnosine: Mechanistic and Pharmacological Perspectives.

<h4>Introduction</h4>L-carnosine is a powerful natural antioxidant found in the brain, muscles, and digestive systems of all vertebrates, including humans, that helps fight Reactive Oxygen Species (ROS) and other harmful byproducts of oxidative stress. L-carnosine has antioxidant properties as well as the ability to bind with metal ions and prevent glycation, a process that can damage cells. This review article highlights the protective effects of L-carnosine against a variety of pathological conditions, such as Alzheimer's Disease (AD), Parkinson's Disease (PD), ischemia‒reperfusion injury, Huntington's disease, stroke, depression, traumatic brain injury, cancer, diabetes, ageing, etc. Among these conditions, mitochondrial dysfunction(definition) and increased oxidative stress are common. Moreover, methylglyoxal (MG), another metabolic product, and Advanced Glycation End products (AGEs) damage cells through interactions with proteins. Through receptor-mediated endocytosis, macrophages absorb them and release proinflammatory chemicals that induce severe inflammation and lead to cell death.<h4>Methods</h4>Search engines, including PubMed, ScienceDirect, ProQuest, Scopus, ResearchGate, MDPI, journals, websites, and databases such as Google Scholar, were thoroughly searched and reviewed. The search strategy for articles published between 2000 and 2025 used various combinations of key Medical Subject Headings (MeSH) terms and phrases, including L-carnosine, alanine, histidine, Randomized Controlled Trial (RCT), aging, cancer, cardiovascular disease, diabetes, and neurodegenerative disorders, and various non-MeSH terms.<h4>Results</h4>L-carnosine exhibits protective effects on models of neurological, ischemic, metabolic, and malignant diseases because of its antioxidant, anti-inflammatory, and neuroprotective properties. In Alzheimer's disease, carnosine specifically increases the production of heat shock proteins (Hsps). In Parkinson's disease, it increases dopamine levels and stops alpha-synuclein protein accumulation. In ischemia‒reperfusion injury, L-carnosine inhibits the release of inflammatory mediators such as cytokines and TNF-alpha. In cancer, it inhibits the Mitogen-Activated Protein Kinase (MAPK)/ Extracellular Signal-Related Kinase (ERK) signaling pathway. It mitigates aging-related damage to proteins. Additionally, L-carnosine inhibits the formation of MG and AGEs, suggesting its potential therapeutic efficacy in a range of diseases.<h4>Discussion</h4>L-carnosine shows multitarget therapeutic potential through antioxidant, anti-inflammatory, and antiglycation actions, as well as mitochondrial protection. It influences key pathways involved in neurodegeneration, including protein aggregation and oxidative stress. Evidence from preclinical and early clinical studies suggests benefits in neurological and metabolic disorders. Despite promising outcomes, challenges such as rapid degradation and limited bioavailability affect clinical translation. Further studies are needed to define the optimal dosing and therapeutic use.<h4>Conclusion</h4>L-carnosine acts as a cytoprotective molecule in multiple ways, including mitigating oxidative stress, protein glycation, mitochondrial dysfunction, and inflammation, thereby modulating pathways characteristic of chronic illnesses. By altering these interconnected pathways, L-carnosine has the potential for several therapeutic applications as an adjuvant for a range of neurological, metabolic, ischemic, cancer, and aging-related illnesses.