Estrogen as a Neuroprotective Agent: Mechanisms and Clinical Implications for Neuroinflammatory Disorders

Abstract

Neuroinflammatory disorders, including Alzheimer’s disease (AD), Multiple Sclerosis (MS), and Parkinson’s disease (PD), are characterized by chronic glial activation and the subsequent release of neurotoxic cytokines. Emerging evidence identifies Estrogen (17 β-estradiol) as a multifaceted neuroprotective agent capable of modulating the central nervous system's (CNS) immune response. This review synthesizes current understanding of the molecular mechanisms through which estrogen exerts its effects, primarily via Estrogen Receptors alpha (ERα), beta (ER β), and the G protein-coupled estrogen receptor (GPER). We evaluate estrogen’s role in inhibiting microglial polarization toward the pro-inflammatory M1 phenotype, promoting mitochondrial bioenergetics, and enhancing synaptic plasticity. Furthermore, the review discusses the "timing hypothesis," which suggests that the efficacy of estrogen therapy is contingent upon the window of administration relative to menopause or disease onset. We also explore the clinical implications of Selective Estrogen Receptor Modulators (SERMs) and the challenges of translating neuroprotective effects into clinical practice without systemic side effects. By bridging the gap between molecular signaling and clinical trials, this paper outlines future directions for estrogen-based therapies as potential disease-modifying interventions for neuroinflammatory and neurodegenerative conditions.