Betaine alleviates scleral remodeling in experimental myopia by regulating the TLR4/TAK1/NF-κB signaling pathway

Myopia progression is closely associated with scleral remodeling, in which oxidative stress, inflammation, and disruption of extracellular matrix (ECM) homeostasis may play important roles. Betaine has antioxidant and anti-inflammatory properties, but its effects on myopic scleral remodeling remain unclear. Public transcriptomic data, network pharmacology, and molecular docking were used as exploratory approaches to identify potentially relevant molecules and pathways. The in vivo and in vitro effects of betaine were subsequently evaluated in lens-induced myopia (LIM) guinea pigs and in lipopolysaccharide (LPS)-stimulated primary guinea pig scleral fibroblasts, respectively. As a result, LIM induced axial elongation, a myopic refractive shift, scleral structural alterations, reactive oxygen species (ROS) accumulation, inflammation, and disruption of ECM homeostasis. These changes were accompanied by activation of the toll-like receptor 4 (TLR4)/transforming growth factor-β-activated kinase 1 (TAK1)/nuclear factor-κB (NF-κB) pathway and increased tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) levels. Betaine attenuated these changes, reduced matrix metalloproteinase-2 (MMP2) expression, and partially restored tissue inhibitor of metalloproteinases-2 (TIMP2), Collagen I, and α-smooth muscle actin (α-SMA) levels. In vitro, betaine partially restored cell viability, reduced ROS and inflammatory cytokine levels, suppressed TLR4/TAK1/NF-κB pathway activation, and ameliorated alterations in ECM-related proteins. Exploratory computational analyses suggested possible associations with inflammation-, oxidative stress-, and ECM-related pathways. Collectively, betaine attenuated LIM-induced myopia progression and scleral remodeling, potentially by reducing oxidative stress and inflammation, suppressing TLR4/TAK1/NF-κB signaling, and improving ECM homeostasis.