Pulmonary and Systemic Toxicity in a Rat Model of Pulmonary Alveolar Proteinosis Induced by Indium-Tin Oxide Nanoparticles

PURPOSE: The main objective of this study was to clarify the biodistribution and in vivo toxicological effects of indium-tin oxide nanoparticles (Nano-ITO) in male rats. METHODS: Dose-response (three divided doses) and time-course studies (six exposure durations) were performed to examine Nano‑ITO-induced pulmonary and systemic toxicity. At the end of the experiment, hematology and serum biochemical parameters were determined, and cytokines levels and oxidative stress were analyzed in the bronchoalveolar lavage fluid. In addition, indium biodistribution following Nano‑ITO exposure was determined using inductively coupled plasma mass spectrometer to measure indium concentration in the lung, spleen, brain, liver, kidney, and testis. Rat lung tissues were also harvested for staining with hematoxylin and eosin, periodic acid Schiff stain, Masson’s trichrome, and Sirius red. RESULTS: Relative lung weights were significantly increased in all Nano-ITO-exposed groups. All organs exhibited a statistically significant difference in indium levels. Rat exposure to Nano‑ITO resulted in a dose-response increase in acute systemic inflammation and injury. BALF analysis revealed significantly elevated levels of lung oxidative stress, pulmonary injury, and inflammatory markers across most groups. Serum biochemistry results showed that Nano-ITO could affect the liver and renal functions of rats when exposed for 3 days. Compared with the control group, significant inflammatory responses or pathological changes were observed in the liver, kidney, and testis of rats at different sampling times and three doses examined. Histopathologically, foci of slight-to-severe pulmonary inflammatory response along with acute inflammatory, pulmonary fibrosis and alveolar proteinosis were detected, and the severity of these lesions worsened in a dose- and time-dependent manner. DISCUSSION: These findings provide novel evidence that enhanced progressive massive pulmonary fibrosis, diffuse interstitial fibrosis, and collagen accumulation play a role in the development of pulmonary alveolar proteinosis following Nano-ITO exposure.