Mixed-dust pneumoconiosis

Pathogenesis
The reaction of the lung to mineral dusts depends on many variables, including size, shape, solubility, and reactivity of the particles. For example, particles greater than 5 to 10 μm are unlikely to reach distal airways, whereas particles smaller than 0.5 μm move into and out of alveoli, often without substantial deposition and injury. Particles that are 1 to 5 μm in diameter are the most dangerous, because they get lodged at the bifurcation of the distal airways. Coal dust is relatively inert, and large amounts must be deposited in the lungs before lung disease is clinically detectable. Silica, asbestos, and beryllium are more reactive than coal dust, resulting in fibrotic reactions at lower concentrations. Most inhaled dust is entrapped in the mucus blanket and rapidly removed from the lung by ciliary movement. However, some of the particles become impacted at alveolar duct bifurcations, where macrophages accumulate and engulf the trapped particulates. The pulmonary alveolar macrophage is a key cellular element in the initiation and perpetuation of lung injury and fibrosis. Many particles activate the inflammasome and induce IL-1 production. The more reactive particles trigger the macrophages to release a number of products that mediate an inflammatory response and initiate fibroblast proliferation and collagen deposition. Some of the inhaled particles may reach the lymphatics either by direct drainage or within migrating macrophages and thereby initiate an immune response to components of the particulates and/or to self-proteins that are modified by the particles. This then leads to an amplification and extension of the local reaction.
However, higher doses of dexamethasone override the export capacity of P-glycoprotein and enter the brain to produce central activation of GRs. In conjunction with the suppression of endogenous corticosteroids by dexamethasone, this results in skewed ratios of activation of peripheral versus central GRs as well as skewed ratios of activation of GRs versus MRs when compared to non-synthetic corticosteroids. These differences can have significant clinical relevance. Chemistry
Dexamethasone is a synthetic pregnane corticosteroid and derivative of cortisol (hydrocortisone) and is also known as 1-dehydro-9α-fluoro-16α-methylhydrocortisone or as 9α-fluoro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione. The molecular and crystal structure of dexamethasone has been determined by X-ray crystallography. It is a stereoisomer of betamethasone, the two compounds differing only in the spatial configuration of the methyl group at position 16 (see steroid nomenclature). Synthesis
To synthesize dexamethasone, 16β-methylprednisolone acetate is dehydrated to the 9,11-dehydro derivative. This is then reacted with a source of hypobromite, such as basic N-bromosuccinimide, to form the 9α-bromo-11β-hydrin derivative, which is then ring-closed to an epoxide. A ring-opening reaction with hydrogen fluoride in tetrahydrofuran gives dexamethasone. History
Dexamethasone was first synthesized by Philip Showalter Hench in 1957. It was introduced for medical use in 1958.On 16 June 2020, the RECOVERY Trial announced preliminary results stating that dexamethasone improves survival rates of hospitalized patients with COVID-19 receiving oxygen or on a ventilator. Benefits were only observed in patients requiring respiratory support; those who did not require breathing support saw a worse survival rate than the control group, although the difference may have been due to chance.