(002) OCTANAL ACTIVATES AIM2 AND CASPASE-1 IN ENDOTHELIAL CELLS
Authors: Wilczynski S , Rodrigues Dos Passos Jr. R , Priviero F , Webb RC 
Published: December 2024

Abstract

Introduction
Octanal is an aldehyde derived from oleic acid, a main product of lipid peroxidation. As a volatile organic aldehyde, octanal has been shown to induce an inflammatory response in epithelial cells and has also been contraindicated in the development of atherosclerosis due to its role in lipid metabolism. A recent study showed that the receptor for octanal, olfactory receptor 2 (olfr2) is present in vascular macrophages. Upon binding with olfr2, octanal caused an increase in reactive oxygen species (ROS) which activates the AIM2 inflammasomes. Highly inflammatory conditions may have increased circulating mtDNA from cell death and damage. mtDNA is known to activate Toll-like receptors (TLRs), which are important in the innate immune response. Excessive inflammation can contribute to sexual dysfunction through endothelial activation and dysfunction. Conditions such as obesity and diabetes often present with marked systemic inflammation and dyslipidemia and tissue dysfunction surpasses macrophage activation.

Objective
The object of this study is to determine the physiological role of octanal and how it may impact sexual function via the endothelial and cavernosal smooth muscle. With a significant portion of the population being exposed to octanal, via lipid dysfunction or artificial fragrances, it is critical to understand the effect of this volatile organic compound. We hypothesize that octanal increases ROS production and in turn, TLR9 activation and AIM2 inflammasome recruitment, leading to endothelial dysfunction and vasogenic erectile dysfunction.

Methods
Primary murine endothelial cells were isolated and cultured. Endothelial cells underwent incubation with vehicle or octanal (10 uM) for 24 hours (n = 2). Treated cells were analyzed for AIM2 and Caspase-1 protein expression. Murine endothelial cells also underwent flow cytometry after incubation with mtDNA (4 ug/mL, 24 hours) to determine the phenotype of the endothelial cells using CD80 and MHCII as markers for activated endothelial cells. Cells treated with mtDNA also received ODN2088 (3 uM), a TLR9 inhibitor.

Results
The endothelial cells treated with octanal (10 uM) showed an increase in AIM2 expression compared to the vehicle. Expression of caspase-1 was significantly increased after treatment with octanal [p = 0.038, Mean: 0.778 +/-SEM 0.1]. Analysis via flow cytometry revealed that incubation with mtDNA (3 ug/mL) showed a significant increase in activated endothelial cells [p = 0.0010, Mean: 45482 +/-SEM 796.5], and the inflammatory response to mtDNA was rescued after treatment with the TLR9 inhibitor, ODN2088 [p = 0.0044, Mean: 60179 +/- SEM 1522]. MHCII presenting endothelial cells were also increased after 24 incubation with mtDNA [p = 0.0003, Mean: 0.203 +/- SEM 0.003].

Conclusions
Octanal increases the activity of caspase-1, which is responsible for the release of Il-□ and IL-18 after inflammasome recruitment and activation. Additionally, the endothelial cells switch to an activated state when treated with mtDNA, endothelial cells becoming MHCII and CD80 antigen presenting cells. Octanal and the downstream mtDNA play a much more critical role in the innate immune response than previously thought. The effect of physiological stress on endothelial cells may help to explore these treatments in the cavernosum and analyze the impact of the endothelial phenotypic change in sexual dysfunction.

Disclosure
No.