Silicosis is a disease that affects coal miners when they inhale silica particle

Question

Silicosis is a disease that affects coal miners when they inhale silica particles which are ingested by macrophages in the lungs. Ultimately, the particles are found in the lysosomes of fibroblasts and stimulate the cell to produce and secrete excess collagen, which reduces lung capacity and leads to death. Consider the process of endocytosis and answer each of the following questions.

a. How does silica get into the macrophages? What type of coat do you expect on the vesicles? How will they be carried and recognize their target (the lysosome)?

b. What do you expect happens to the silica (small particles of glass or sand) when the cell dies? Explain how this can lead to on-going symptoms of silicosis, even when the patient is no longer working in a coal mine.

Explanation / Answer

Silicosis develops when silica interact with pulmonary alveolar macrophages leading to impairment of lung tissue. Silica enter the macrophages of lungs through endocytosis mediated by clathrin coated vescicles.Silica particles enter lysosome through caveolae-mediated endocytosis and interact with phagolysosomal membranes, allowing the translocation of lysosomal enzymes to the cytosol and leading cell death.

The ingestion of silica particles by macrophages of lungs enter lumphatic system and then to the lymph nodes.When a cell containing silica macrophages with silica particles die, macrophages release proteolytic enzymes , cytokines, inflammatory cells The cytokines and other inflammatory cells collectively produce superoxide anions and hydroxyl radicals leading to injury to lung tissues and produce tumour necrosis factor causing fibrosis. The fibroblast produce excess collagen leading to death.

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