Small nucleolar RNA expression and NADPH oxidase-mediated ROS production in THP-1 macrophages treated with VLDL hydrolysis products

Tijani, Mariam Olanrewaju (2025) Small nucleolar RNA expression and NADPH oxidase-mediated ROS production in THP-1 macrophages treated with VLDL hydrolysis products. Masters thesis, Memorial University of Newfoundland.

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Abstract

One of the fundamental pathogenetic processes of atherosclerosis, oxidative stress, is defined by an increase in reactive oxygen species (ROS) generation. An increase in ROS production and oxidative stress have been linked to the expression of some specific kinds of snoRNAs. NADPH oxidase (NOX) appears to play a role in regulating snoRNA expression and snoRNA accumulation in the cell cytosol. Our laboratory previously reported an upregulation of 63 snoRNA transcripts in macrophages incubated with lipoprotein (Lp) lipid hydrolysis products (HPs) generated by lipoprotein lipase (LPL). I hypothesized that Lp HPs produced by LPL lead to NOX-mediated oxidative stress within THP-1 macrophages that can be inhibited using the NADPH oxidase inhibitors (NOXi) apocynin or GKT136901. I further hypothesized that snoRNA expression would increase due to NOX activity in macrophages incubated with Lp hydrolysis products by LPL. My results show significant NOX-induced ROS production, using cellular ROS detection assay, in differentiated THP-1 macrophages treated with very low-density lipoprotein (VLDL) HPs by LPL. The NOX-induced ROS production was inhibited by 20 μM of GKT136901, while 100 μM of apocynin had no inhibitory effect. The NOX-induced ROS did not induce lipid peroxidation in the macrophages. RNA integrity numbers (RIN) were analyzed using an RNA bioanalyzer, with no significant alteration in the RIN of the total RNA isolated from the THP-1 macrophages treated with 0.25 mM VLDL HPs. The NOX-induced ROS also did not alter the expression of SNORA56, SNORA60, and SNORA80E in the VLDL HP-treated macrophages. Overall, NOX-induced ROS production seems not to mediate the overexpression of SNORA56, SNORA60, and SNORA80E in PMA-differentiated THP-1 macrophages treated with 0.25 mM VLDL HPs by LPL.

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