Potential mechanistic insights into PM10-induced cytotoxicity and cardiovascular defects involving WNT, FGF, and inflammatory signaling

Particulate matter (PM) air pollution in Saudi Arabia (KSA) is a real health concern. KSA has exceeded the WHO-recommended limits for PM concentrations. Airborne PM collected from Jeddah city was reported to be associated with pulmonary inflammation and morbidity, thrombosis, hypertension, hyperglycemia, and increased cancer risk. The developmental and molecular health impacts of PM
10
exposure remain not fully understood. Here, we evaluated its effects using a multidisciplinary approach integrating
in vivo
chick embryo assays,
in vitro
analyses of human endothelial cells (HUVECs), and
in silico
pathway enrichment tools to investigate the biological effects of the PM
10
. 


PM
10
was collected from Jeddah, KSA. Chick embryos at early and late stages of development and human umbilical cord vein endothelial cell (HUVEC) cultures were treated with varying concentrations of PM
10
. Morphological, histological, and cellular impacts of PM
10
were carried out. The gene and protein expression of targeted key factors were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and immunostaining to unravel possible associations of PM
10
-induced phenotypes with key signaling pathways. Gene set enrichment analysis (WebGestalt tool) was carried out to unravel the associated biological processes and disease functions of the differentially regulated genes.


PM
10
-treated chick embryos showed developmental retardation and cardiovascular defects, including abnormal heart structure, impaired, vascular network development, and severe hemorrhage. These were, in addition, associated with head and brain structural malformations. HUVEC cultures treated with PM
10
demonstrated cell shrinkage, inhibition of proliferation, and cell death in a concentration-dependent manner. The expression of inflammation-associated genes of 
IL6
(interleukin-6)
, VEGF
(vascular endothelial growth factor)
, and MMP1
(matrix metallopeptidase 1)
 
was upregulated, and the anti-apoptotic B-cell leukemia/lymphoma 2 protein (BCL2)
 
gene was downregulated. Protein expression of β-catenin, frizzled receptor 8 (FZD8), NF-KB (Nuclear Factor Kappa-light-chain-enhancer of activated B cells), and Sprouty receptor tyrosine kinase (RTK) signaling antagonist 2 (SPRY2
),
was elevated. Changes in the expression of these key markers indicate that PM
10
effects may be potentially associated with WNT (wingless/integrated), inflammation, and FGF (fibroblast growth factor) signaling pathways and may contribute to the induction of the detected defects. Gene set enrichment analysis using differentially regulated molecules revealed positively associated biological processes and disease functions, including cardiovascular disease. 


PM
10
 induced developmental delay, cardiovascular defects, proliferation inhibition, and impacted the WNT, FGF, and inflammation signaling pathways. Future studies employing pathway inhibition or rescue experiments will be necessary to establish direct causality between the observed phenotypes and the impacted signaling pathways.