Acute radiation-induced changes in the submandibular salivary gland and possible radioprotective role of silver nanoparticles: a histological, immunohistochemical, and ultrastructural study

Gamma radiation is widely used in the treatment of head and neck malignancies, it can cause irreversible damage to the submandibular salivary glands, leading to xerostomia and oral infections. This study evaluated the acute radiation-induced changes in the submandibular gland and the prophylactic and therapeutic effects of silver nanoparticles (AgNPs) in adult male albino rats. Forty-five adult male albino rats (150-200 g) were divided into five groups. Twenty rats served as normal and sham controls, while 25 rats received a single 15 Gy dose of gamma radiation and were assigned to irradiated (n=10), prophylactic AgNPs (n=10), and therapeutic AgNPs (n=5) groups. Right submandibular glands were processed for histological and immunohistochemical analyses, and left glands for ultrastructural examination. Irradiated glands showed acinar atrophy, cytoplasmic vacuolation, pyknotic nuclei, ductal dilatation, reduced PAS optical density, and significantly increased CD3 and BAX immunoreactivity compared with controls. Ultrastructural examination revealed clumped chromatin, swollen mitochondria, and disrupted rough endoplasmic reticulum. Prophylactic AgNP administration largely preserved glandular architecture, maintained acinar area and duct diameter, reduced CD3 and BAX expression, and restored normal ultrastructural features. In contrast, therapeutic AgNP administration produced only minimal improvement, with persistent structural abnormalities. Prophylactic AgNP administration effectively attenuated acute gamma radiation-induced submandibular gland injury, whereas post-irradiation treatment provided only limited therapeutic benefit.