Mouse pulmonary pathological characteristics induced by Asian-mineral dust transported with Coniothyrium fuckelii at a high altitude of 2,000 meters

Abstract

Asian sand dust (ASD) events are known to transport not only mineral particles but also bioaerosols such as fungi across East Asia, posing complex respiratory health risks. Previously, we isolated Coniothyrium fuckelii (Strain Con-15H316)--a dematiaceous phytopathogenic fungus--from the ASD samples collected at an altitude of 2000 m over the Noto Peninsula, Japan. While Con-15H316 elicited potent immunological responses in our earlier cytokine-focused studies, its histopathological impact on mammalian lungs remained uncharacterized. Here, we re-evaluated formalin-fixed murine lung tissues from mice intratracheally administered heat-treated ASD (H-ASD: only mineral particles), Con-15H316, and Con-15H316 in combination with H-ASD. H-ASD alone induced macrophage-dominant alveolar granulomas, and Con-15H316 alone triggered peribronchiolitis with eosinophilic infiltration. Strikingly, co-exposure resulted in a qualitatively distinct and synergistically worsened phenotype, featuring neutrophil-rich suppurative alveolar pneumonia, granulomas, and peribronchiolitis. Bronchoalveolar lavage fluid (BALF) analysis revealed marked co-elevation of lactate dehydrogenase (LDH) and CCL2 (C-C motif chemokine 2, also known as monocyte chemoattractant protein-1, MCP-1), suggesting concurrent tissue injury and monocyte-driven immune activation. To elucidate the cellular origin of the CCL2 protein, we reanalyzed two publicly available single-cell RNA-seq datasets, identifying monocytes and interstitial macrophages as the dominant Ccl2-expressing populations in microbially injured lungs. Although C. fuckelii has been recognized generally as a plant pathogen, this study exhibited the first histological evidence of the potential of this fungus to induce or exacerbate mammalian lung injury, especially in combination with mineral dust. Our findings uncover a novel, non-allergic alveolar injury phenotype associated with microbial-particulate co-exposure, expanding current toxicological paradigms beyond pathologies associated with excessive immune reactions to inhaled particulates and bioaerosols.