Laminaria japonica Polysaccharide Alleviates Radiation-Induced Salivary Gland Injury by Promoting DNA Damage Repair

This study aimed to assess the protective effects of a polysaccharide extracted from Laminaria japonica polysaccharide (LJP) on radiation-induced injury of the salivary gland (SG), focusing especially on mechanisms related to DNA damage repair.

A murine model of radiation-induced SG injury was established using a linear electron accelerator after a 7-day course of daily intraperitoneal LJP injections. The effectiveness of model establishment and LJP intervention was evaluated by assessing body weight, salivary flow, glandular morphology and histopathology. Cellular senescence, apoptosis, DNA damage and DNA repair capacity were examined using β-galactosidase staining, immunohistochemistry and immunofluorescence.

Ionizing radiation significantly reduced salivary flow, induced histopathological injury and increased markers of senescence (SA-β-gal), and apoptosis (Bax/Bcl-2), along with elevated DNA double-strand breaks (γ-H2AX) and downregulation of key DNA repair proteins (DNA-PKcs, Mre11, Rad51).LJP pretreatment preserved SG function, reduced tissue injury and fibrosis, attenuated senescence and apoptosis, decreased γ-H2AX expression and enhanced the expression of DNA-PKcs, Mre11 and Rad51.

LJP may exert radioprotective effects on SG by mitigating cellular senescence and apoptosis, potentially through modulation of pathway involved in the repair of DNA damage. These preclinical findings provide a theoretical basis for further investigation of LJP as a potential protective agent against radiation-induced xerostomia.