Pyrrolidine Dithiocarbamate and Dexamethasone Are Novel Treatments of Acute Exogenous Lipoid Pneumonia

Background: Acute exogenous lipoid pneumonia (AELP) is characterized by pulmonary inflammation. This mainly occur in children who have ingested sewing machine oil or other mineral oils accidentally. Despite emerging evidences revealing that inhibiting inflammation improves acute exogenous lipoid pneumonia, the actual process of inhibiting inflammation remains unknown. This study aimed to evaluate the effects of PDTC and dexamethasone on AELP to gain insight into the mechanism of AELP.

Methods: The experimental rats were randomly divided into 10 groups: NS control group (NS3 group, NS5 group), Oil inhalation group (AE3 group, AE5 group), PDTC intervention group (PDTC3 group, PDTC5 group), DXM intervention group (DXM3 group, DXM5 group), PDTC + DXM combined intervention group (PDTC + DXM3 group, PDTC + DXM 5 group). Enzyme-linked immunosorbent assay (ELISA) was used to determine concentrations of macrophage migration inhibitory factor (MIF), interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα) in bronchoalveolar lavage fluid (BALF) and serum samples. On the other hand, western blotting was used to measure the expression levels of nuclear factor-κB p65 (NF-κB p65) and b-cell leukemia 2 (Bcl-2) in the lungs. Hematoxylin and Eosin (H&E) staining was performed to evaluate changes in the lung tissue. The wet-to-dry lung weight ratio was subsequently used to determine the pulmonary edema of the lungs.

Results: There were increased MIF levels in both serum and BALF samples of the AE group. Pyrrolidine dithiocarbamate (PDTC) and dexamethasone (DXM) independently and in combination reduced pulmonary inflammation induced by the sewing machine oil by regulating MIF expression. TNF-α and IL-6 levels in serum and BALF samples of the AE group were higher than those of the NS control animals. However, their levels decreased after treatment with either PDTC, DXM or PDTC + DXM. Similarly, NF-κBp65 expression increased after oil inhalation but decreased after treatment with either PDTC, DXM or PDTC + DXM. PDTC, DXM and PDTC + DXM treatment significantly reduced pulmonary inflammation and pulmonary edema of the lung tissue following induction of acute exogenous lipoid pneumonia.

Conclusions: Individual or combined use of PDTC and DXM can ameliorate pulmonary inflammation induced by inhalation of sewing machine oil by inhibiting the NF-κB pathway in young rats. These findings provide novel insights that will greatly contribute in treatment of AELP.

Keywords: Acute exogenous lipoid pneumonia; NF-κB; Pulmonary inflammation; Sewing machine oil.