Intratracheal Candida administration induced lung dysbiosis, activated neutrophils, and worsened lung hemorrhage in pristane-induced lupus mice.

Because the innate immunity might and fungi in the lungs might enhance the severity of lupus-induced diffuse alveolar hemorrhage (DAH), intraperitoneal pristane injection was performed in C57BL6 mice with intratracheal administration by Candida albicans or phosphate buffer solution (PBS). Despite the similar pristane-induced lupus (proteinuria, serum creatinine, and serum anti-dsDNA) at 5 weeks of the model, Candida administration worsened several characteristics, including mortality, body weight, serum cytokines (TNF-α and IL-6), and lung hemorrhage score, and cytokines in the lung tissue (TNF-α, IL-6, and IL-10), but not gut permeability (FITC-dextran assay), serum IL-10, immune cells in the spleens (flow cytometry analysis), and activities of peritoneal macrophages (polymerase-chain reaction). Although Candida administration reduced proteobacterial abundance and altered alpha and beta diversity compared with PBS control, lung microbiota was not different between Candida administration in pristane- and non-pristane-administered mice. Because of the prominent Gram-negative bacteria in lung microbiota and the role of neutrophils in DAH, lipopolysaccharide (LPS) with and without heat-killed Candida preparation was tested. Indeed, Candida preparation with LPS induced more severe pro-inflammatory neutrophils than LPS stimulation alone as indicated by the expression of several genes (TNF-α, IL-6, IL-1β, IL-10, Dectin-1, and NF-κB). In conclusion, the intratracheal Candida worsened pristane-induced lung hemorrhage partly through the enhanced neutrophil responses against bacteria and fungi. More studies on Candida colonization in sputum from patients with lupus-induced DAH are interesting.