(T1530-03-19) Respiratory and Genomic Effects Induced by Phosphine Gas Exposure: Insights from Mouse Model to Identify Therapeutic Targets

Purpose: Phosphine (PH₃) is a highly toxic gas; it is one of the most popularly used fumigants because of its efficacy against a wide range of pest species of agricultural products. It is also used in the semiconductor industry, as a polymerization initiator, and as an intermediate for preparation of some flame retardants. Human exposure to PH₃ occurs by inhalation of accidentally released gas or when phosphide-containing pesticides are ingested or comes in contact with water or moisture when gas is generated. It is also a concern as a potential chemical threat agent due to its high toxicity and availability. The mechanism of PH₃ toxicity is not fully understood. However, previous research suggests that PH₃ induces oxidative stress by generating reactive oxygen species (ROS) and disrupts mitochondrial function leading to cell death. There is no effective antidote available due to the absence of reliable therapeutic targets. The aim of this study is to investigate pulmonary effects of acute PH₃ exposure and to explore which biological pathways are affected in the lungs and heart in an effort to understand key toxic events and design treatment strategies.

Methods: Female mice (C57Bl/6J) were exposed to different doses of PH₃ in a dynamic whole-body exposure chamber. Their respiratory functions were measured by a whole-body plethysmography at several time points post exposure. Bronchoalveolar lavage fluid (BALF) was collected to evaluate lung cellularity and total protein levels, and lungs were fixed in formalin for histopathology evaluation. Lungs were stored in RNAlater buffer until RNA extraction. RNA sequencing, including sample, library, and data quality controls, was performed by Novogene. Differently expressed genes (DEGs) were analyzed with iPathwayGuide (Advaita Bioinformatics) to identify biological pathways affected by PH₃ inhalation.

Results: Immediately after exposure, mice exposed to PH₃ showed a decrease in respiratory rate, minute volume, and an increase in enhanced pause (Penh). Mice exposed to PH₃ had a significant increase of total protein and number of total cells in BAL fluid. The histopathological evaluation of the lung showed regions of hypercellularity near vessels that were mononuclear and neutrophils in nearby perivascular and alveolar space. RNA sequencing analysis identified 338 DEGs in the lungs of exposed groups (average) compared to controls. The most significantly impacted pathways were those associated with lipid and atherosclerosis, MAPK (mitogen-activated protein kinase) and TNF signaling pathway. Furthermore, genes involved in key biological processes were significantly impacted, including those related to cellular responses to chemical stimuli, apoptotic signaling pathways, and the regulation of programmed cell death. RNA sequencing analysis of the heart tissues of exposed mice identified 309 DEGs compared to controls. The most significantly affected biological pathways in the heart were those related to IL-17 signaling, TNF signaling, cytokine-cytokine interaction, MAPK signaling pathway and cell cycle, which were supported by hallmark signatures such as: TNFα signaling, hypoxia, apoptosis, G2 M cell cycle, inflammatory response and P53 pathway.

Conclusion: There was apparent hypercellularity observed in female mice exposed to PH₃, with functional changes in respiratory parameters. Gene expression analyses revealed that biological pathways related to inflammatory responses, cellular stress and apoptotic processes were affected in lungs. These findings highlight potential therapeutic targets and will inform our selection and development of treatment strategies for PH₃-induced toxicity.

References: 1. Shabani M, Khezri S, Salimi A. Mitotherapy with fresh isolated cardiac mitochondria via injection into blood reduces aluminum phosphide-induced mortality and protects cardiac tissue against oxidative stress and mitochondrial damages. Cardiovascular Toxicology. 2024 Sep;24(9):929-41.
2. De Santi O, Orellana MJ, Di Niro CA, Lashin HI, Greco V. The adjuvant effect of oil-based gastric lavage on the outcome of acute Aluminum phosphide poisoning: a systematic review and meta-analysis. Toxicology Research. 2024 Apr 1;13(2):tfae029.
3. Abdo N, Mohamed S, Luyckx V, Mohammad A, Rahman SA, Christine K, Alexander J, Khaled HN, Lina M, Oussama RA, Alasfar S. Metal phosphide poisoning in a disaster‐stricken area. Can early hemodialysis improve outcomes?. Hemodialysis international. 2024 Jul;28(3):351-7.


Figure 1: Respiratory function parameters (Frequency of respiration (A) and enhanced pause (B)) measured by whole-body plethysmography at several time points post exposure. Values represent mean ± SEM.


Figure 2: Histopathological sections of lungs of unexposed control group (A), and group exposed to 22,500ppm x min (B).


Figure 3: Chord diagrams of enriched Gene ontology top pathways (A) and biological processes (B) and their most important genes in lungs of PH3-exposed (both exposure groups averaged) necropsied within 4 or 24 h compared to controls.