Immunomodulation and oxidative stress in denim sandblasting workers: changes caused by silica exposure

Workers in denim sandblasting are at a high risk of developing silicosis, an occupational lung disease caused by inhaling crystalline silica dust. The development and progress of silicosis is associated with the activation of the immune system and oxidative stress. In the former, interferon-gamma induces both neopterin release and the enzyme indoleamine [2, 3]-dioxygenase (IDO) in various cells. The determination of the kynurenine-to-tryptophan ratio and neopterin concentration has proven to be an efficient method to monitor the activation status of IDO and cellular immunity. The present study aimed to investigate whether occupational silica exposure leads to any alterations in neopterin levels, tryptophan degradation, and activities of superoxide dismutase (SOD) and catalase (CAT), agents in the antioxidant defense system. Fifty-five male denim sandblasting workers and twenty-two healthy men as controls were included. Mean neopterin and kynurenine levels, kynurenine-to-tryptophan ratio, and SOD activity were higher in subjects with silicosis compared to non-exposed controls (all, p<0.05). Neopterin levels and kynurenine-totryptophan ratios were positively correlated (p<0.05); however, no correlation was observed between length of employment and the measured parameters. Some of the measured parameters were significantly affected by the severity of the pathology. Our results suggest that silica exposure activates the cellular immune response. The increased neopterin levels and tryptophan degradation confirm the possibility of their use as an indicator of cellular immune response.