Nasal exposure to PM2.5 induces testicular injury and activation of pyroptosis-related signaling in rats: Inhibitor intervention and public transcriptomic analysis
TL;DR
Exposure to PM2.5 significantly elevated the levels of several testicular proteins, including NLRP3, ASC, cleaved caspase-1, cleaved caspase-1, cleaved caspase-3, GSDMD-N, total caspase-1, and full-length GSDMD, whereas cleaved caspase-3 did not differ significantly.
Abstract
Objective This study aimed to investigate the testicular injury induced by PM2.5 and the associated enhancement of NLRP3/caspase-1/GSDMD-related pyroptotic signaling in rats by integrating animal experiments with public transcriptomic analysis. Methods Thirty-two male Sprague-Dawley rats were randomly assigned to four groups (n = 8 per group): a control group (saline), a caspase-1 inhibitor group (Z-YVAD-FMK, 5 mg/kg), a PM2.5 exposure group (10 mg/kg), and a combination group (PM2.5 plus Z-YVAD-FMK). The animals were treated for 4 weeks. The particle-size distribution of the prepared PM2.5 exposure suspension was characterized. Testicular histopathology was evaluated using hematoxylin and eosin (H&E) staining, and sperm count and morphology were assessed. Western blotting was employed to determine the expression levels of NLRP3, ASC, cleaved caspase-1, cleaved caspase-3, GSDMD-N, total caspase-1, and full-length GSDMD. Concurrently, the public GEO dataset GSE189187 (PM2.5-treated versus control GC-2spd cells; n = 3 per group) was analyzed for differential gene expression, functional enrichment, and protein-protein interaction (PPI) networks. Core modules and hub genes were identified using MCODE and cytoHubba in Cytoscape. Finally, the mRNA expression of Hmox1, Stat1, Irf9, and Usp18 in rat testicular tissue was measured using quantitative reverse-transcription PCR (qRT-PCR) to assess whether the candidate signals from the public transcriptomic dataset exhibited concordant changes in vivo. Results Western blotting analysis revealed that exposure to PM2.5 significantly elevated the levels of several testicular proteins, including NLRP3, ASC, cleaved caspase-1, cleaved caspase-3, GSDMD-N, total caspase-1, and full-length GSDMD. Compared with PM2.5 alone, Z-YVAD-FMK co-treatment reduced ASC, GSDMD-N, cleaved caspase-1, total caspase-1, full-length GSDMD, and NLRP3, whereas cleaved caspase-3 did not differ significantly. These findings are consistent with partial attenuation of caspase-1/GSDMD-related signaling. The d(0.1), d(0.5), and d(0.9) values of the final exposure suspension were measured at 0.32 ± 0.04 μm, 1.15 ± 0.08 μm, and 2.38 ± 0.15 μm, respectively. In comparison to the control group, sperm counts decreased from 41.62 ± 3.38 × 10^6/mL to 11.48 ± 4.46 × 10^6/mL in the PM2.5 group, while the sperm abnormality rate increased from 6.31 ± 0.81% to 13.66 ± 1.87%. Following Z-YVAD-FMK treatment, sperm counts rose to 27.21 ± 3.34 × 10^6/mL, and the sperm abnormality rate decreased to 9.78 ± 0.72%. Public transcriptomic analysis identified a total of 217 differentially expressed genes (DEGs), comprising 91 upregulated and 126 downregulated genes. Functional enrichment and protein-protein interaction (PPI) network analyses suggested that PM2.5 treatment was linked to transcriptional alterations associated with interferon-mediated immune responses, inflammation, and cellular stress and injury, identifying Hmox1 and Stat1 as DEGs related to pyroptosis. Additionally, network topology analysis pinpointed STAT1, IRF9, members of the GBP family, IRGM1, and USP18 as potential hub nodes. Quantitative reverse transcription PCR (qRT-PCR) demonstrated increased Hmox1 mRNA expression alongside decreased Stat1, Irf9, and Usp18 mRNA expression in the testes of PM2.5-exposed rats. These alterations were partially reversed by Z-YVAD-FMK; because the public dataset and animal experiment differed in species and sample type, this comparison was interpreted as exploratory rather than as direct validation. Conclusion PM2.5 exposure induced histopathological injury in rat testes and was accompanied by enhanced NLRP3/caspase-1/GSDMD-related signaling. Z-YVAD-FMK partially alleviated tissue injury and reduced several pyroptosis-related proteins, whereas cleaved caspase-3 did not differ significantly between the PM2.5 and PM2.5 plus Z-YVAD-FMK groups. The rat-tissue qRT-PCR findings provided a cross-system comparison for selected candidate signals identified in the public transcriptomic dataset, rather than direct mechanistic validation. The transcriptomic analysis further suggested immune-inflammatory and stress-related remodeling in GC-2spd cells; the resulting STAT/IRF-GBP-IRGM-USP18/PARP network should be interpreted as exploratory.