Molecular Mechanism of Perfluorooctane Sulfonate-Induced Lung Injury Mediated by the Ras/Rap Signaling Pathway in Mice

Abstract

Perfluorooctane sulfonate (PFOS), a persistent organic pollutant, has raised significant public health concerns because of its widespread environmental presence and potential toxicity. Epidemiological studies have linked PFOS exposure to respiratory diseases, but the underlying molecular mechanisms remain poorly understood. Male C57 BL/6J mice were divided into a control group receiving Milli-Q water, a low-dose PFOS group (0.2 mg/kg/day), and a high-dose PFOS group (1 mg/kg/day) administered via intranasal instillation for 28 days. Lung tissue transcriptome sequencing revealed significantly enriched differentially expressed genes in the Ras and Rap signaling pathways. Key genes including Rap1b, Kras, and BRaf as well as downstream genes, such as MAPK1 and MAP2K1, exhibited dose-dependent upregulation in the high-dose PFOS exposure group. Concurrently, the downstream effector proteins MEK, ERK, ICAM-1, and VEGFa were significantly elevated in bronchoalveolar lavage fluid (BALF). These alterations are mechanistically associated with increased oxidative stress, inflammatory cytokine release, and pulmonary tissue damage. The results indicated that PFOS-induced lung injury is likely predominantly mediated through the activation of the Rap1b- and Kras-dependent BRaf-MEK-ERK axis. These findings highlight the critical role of Ras/Rap signaling pathways in PFOS-associated respiratory toxicity and underscore the need to develop therapeutic interventions targeting these pathways to mitigate associated health risks.

Keywords: Rap; Ras; mitogen-activated protein kinase; perfluorooctane sulfonate; signaling pathway; vascular endothelial growth factor.

Figure 1

Enzyme-linked Immunosorbent Assay (ELISA). (A) The protein expression level of IL-1β in BALF. (B) The protein expression level of TNF-α in BALF. (C) The protein expression level of in IL-6 BALF. (D) The protein expression level of IL-8 in BALF. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 1

Enzyme-linked Immunosorbent Assay (ELISA). (A) The protein expression level of IL-1β in BALF. (B) The protein expression level of TNF-α in BALF. (C) The protein expression level of in IL-6 BALF. (D) The protein expression level of IL-8 in BALF. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 2

Top Significantly Enriched KEGG Pathways. (A) KEGG pathway enrichment in low-dose PFOS exposure group. (B) KEGG pathway enrichment in high-dose PFOS exposure group.

Figure 2

Top Significantly Enriched KEGG Pathways. (A) KEGG pathway enrichment in low-dose PFOS exposure group. (B) KEGG pathway enrichment in high-dose PFOS exposure group.

Figure 3

Quantitative real-time polymerase chain reaction (q-PCR). (A) The gene expression level of Kras in lung tissues. (B) The gene expression level of Rap1b in lung tissues. (C) The gene expression level of BRaf in lung tissues. (D) The gene expression level of VEGFa in lung tissues. (E) The gene expression level of MAPK1 in lung tissues. (F) The influence on the gene expression level of MAP2K1 in lung tissues. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 3

Quantitative real-time polymerase chain reaction (q-PCR). (A) The gene expression level of Kras in lung tissues. (B) The gene expression level of Rap1b in lung tissues. (C) The gene expression level of BRaf in lung tissues. (D) The gene expression level of VEGFa in lung tissues. (E) The gene expression level of MAPK1 in lung tissues. (F) The influence on the gene expression level of MAP2K1 in lung tissues. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 4

Enzyme-linked Immunosorbent Assay (ELISA). (A) The protein expression level of MEK in BALF. (B) The protein expression level of ERK in BALF. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).

Figure 5

Enzyme-linked Immunosorbent Assay (ELISA). (A) The protein expression level of ICAM-1 in BALF. (B) The protein expression level of VEGFa in BALF. All data are presented as mean ± SEM. (N = 5, * p < 0.05, ** p < 0.01, *** p < 0.001).