Chronic Inhaled Benzene Exposure Exacerbates Atherosclerosis in LDL Receptor-Null Mice.

Background: Benzene is a ubiquitous environmental pollutant generated by a variety of natural and anthropological sources. It is a known carcinogen and hematopoietic toxin; however, little is known about benzene's potential atherogenicity.

Hypothesis: Inhaled benzene induces atherogenesis by increasing vascular inflammation in LDL receptor Knockout (LDLR-KO) mice.

Methods: Male LDLR-KO mice were exposed to HEPA-filtered air or benzene (1 ppm, 6h/day, 5days/week) for 24 weeks. For the last 12 weeks of exposure, the mice were maintained on a western diet. The single nuclei RNA sequencing (snRNAseq) of aortae was performed at Novogene. For experiments, splenic naïve T cells were exposed to 1 μM of hydroquinone (HQ) for 24 hours, and intracellular ROR-gamma levels were measured by flow cytometry.

Results: Benzene inhalation increased the aortic valve lesion area by more than 25% (P<0.05) in LDLR-KO mice. Using snRNAseq, eleven major cell types were detected, including T cells and vascular smooth muscle cells (VSMC). Benzene increased the number of T cells by 2.5-fold, proliferating T-cells by 5.8-fold, and VSMC by 1.6-fold, suggesting increased cellularity and reduced plaque stability. In addition, benzene upregulated Th17 polarization marker and negative regulators of apoptosis and while significantly attenuating the expression of proliferation inhibitor in T cells. In VSMC, benzene downregulated extracellular matrix organization genes and upregulated platelet degranulation pathways. Polarization of T cells into Th17 was confirmed by HQ-dependent upregulation of ROR-gamma .

Conclusion: Our data suggest that inhaled benzene exposure compromises plaque cellularity and stability by facilitating T-cell proliferation and polarization, which coincides with the degradation of smooth muscle extracellular matrix and platelet activation.