Background: Alveolar macrophages (AMs) are the primary targets of silicosis. Blockade of autophagy may aggravate the apoptosis of AMs. Trehalose (Tre), a transcription factor EB (TFEB) activator, may impact the autophagy-lysosomal system in AMs during silicosis. However, the mechanism by which Tre acts upon AMs in silicosis is unknown.
Methods: We collected AMs from twenty male workers exposed to silica and divided them into observer and silicosis patient groups. AMs from the two groups were then exposed to Tre. Western blot was used to measure the expression of autophagy-associated proteins. Lysosomal-associated membrane protein 1 (LAMP1) expression was observed using immunofluorescence and western blot. Apoptosis of the AMs was detected by TUNEL assay and western blot.
Results: Tre induced localization of TFEB to the nucleus in the AMs of both groups. After Tre exposure, LAMP1 levels increased and LC3 levels decreased in the AMs of both groups, suggesting that Tre may increase the function of the autophagy-lysosomal system. The LC3-II/I ratio in the Tre-exposed AMs was lower than in the AMs not exposed to Tre. The LC3-II/I ratio in AMs subjected to Tre plus Bafilomycin (Baf) was higher than the ratio in cells exposed to Tre or Baf individually. Additionally, p62 levels decreased after Tre stimulation in the AMs of both groups. This indicates that Tre may accelerate the process of autophagic degradation. We also found decreased levels of cleaved caspase-3 after Tre treatment in the AMs of both groups. However, p-mTOR (Ser2448) and p-mTOR (Ser2481) levels did not change significantly after Tre treatment, suggesting that the mTOR signaling pathway was not affected by Tre treatment.
Conclusion: Our findings suggest that the restoration of autophagy-lysosomal function by Tre may be a potential protective strategy against silicosis.
Keywords: Alveolar macrophages; Apoptosis; Autophagic degradation; Autophagy; Silicosis; Trehalose.
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