Exposure to Nanomaterials Results in Alterations of Inflammatory and Atherosclerotic Signaling Pathways in the Coronary Vasculature of Wildtype Rodents
Authors:   , Davis Griffith M. 
Published: February 2025

Cardiovascular disease (CVD) is the leading cause of death for people of most ethnicities on a global scale, and countless research efforts on the pathology of CVD has been well-characterized over the years. However, advancement in modern technologies, such as nanotechnology, has generated environmental and occupational health concerns within the scientific community. Current investigation of nanotoxicity calls into question the negative effects nanomaterials may invoke from their environmental, commercial, and therapeutic usage. As a result, further research is needed to investigate and characterize the toxicological implications associated with nanomaterial-exposure and CVD. We investigated the toxicity of multi-walled carbon nanotubes (MWCNT) and titanium dioxide (TiO2), which are two prominently used nanomaterials that have been previously linked to upregulation of inflammatory and atherogenic factors. However, the mechanistic pathways involved in these nanomaterials mediating detrimental effects on the heart and/or coronary vasculature have not yet been fully determined. Thus, we utilized two different routes of exposure in rodent models to assess alterations in proinflammatory and proatherogenic signaling pathways, which are represented in contrast throughout the dissertation. In our MWCNT study, we used C57Bl/6 mice exposed to MWCNTs (1 mg/m3) or filtered air (FA-Controls), via inhalation, for 6 hr/d for 14d. Conversely, intravenous TiO2 was administered to F344 male fisher rats, following 24h and 28d post-exposure to a single injection of TiO2-NPs (1 mg/kg), compared to control animals. MWCNT-exposed endpoints investigated the alterations in cholesterol transport, such as lectin-like oxidized low-density lipoprotein receptor (LOX)-1 and ATP-binding cassette transporter (ABCA)-1, inflammatory markers [tumor necrosis factor (TNF)-α], interleukin (IL)-1β/IL-6, nuclear-factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signaling factors involved in activation of the pathway, as well as intracellular/vascular adhesion molecule(s) (VCAM-1, ICAM-1), and miRNAs (miR-221/-21/-1), associated with CVD, were analyzed in cardiac tissue and coronary vasculature. Cardiac fibrotic deposition, matrix-metalloproteinases (MMP)-2/9, and reactive oxygen species (ROS) were also assessed. TiO2-exposure endpoints also involved alterations on cholesterol transport proteins via LOX-1 and ABCA-1, factors of inflammation, namely intracellular macrophages and interleukin (IL)-1β, MMP-2/9 activity and protein expression, fibrotic deposition, and ROS generation were analyzed via quantitative detection or histologically in both cardiac tissue and coronary vasculature. Results from both studies found alterations in fibrotic deposition, upregulation in LOX-1 expression and MMP-2/9 activity, and ROS generation; with a concurrent decrease in ABCA-1 expression in cardiac tissue and coronary vasculature. Individually, MWCNT-exposed endpoints had shown induction of cardiac TNF-α, MMP-9, IκB Kinase (IKK)-α/β, and miR-221 mRNAs; as well as increased coronary expression of TNF-α and VCAM-1. TiO2 studies found increases in IL-1β and MMP-9 protein expression, as well as intracellular macrophage induction. Both studies also found, through pre-treatment of NADPH oxidase inhibitor, apocynin, resulted in attenuation of nanomaterial-exposure mediated ROS production; with nitric oxide synthase inhibitor, L-NNA, also showing attenuation, but only in our MWCNT-exposed inhalation study. The results from both studies have demonstrated, through different routes of administration, exposures, and rodent models; that exposure to nanomaterials can mediate signaling pathways involved in initiation and/or progression of CVD.