Abstract
Purpose :
The eye is one of the most sensitive organs to toxic chemical exposures. Ocular chemical injuries cause corneal damage and the loss of viable corneal epithelial cells, leaving patients with few effective treatment options. Nitrogen mustard (NM), a structural analog of warfare agent sulfur mustard, is a vesicating agent. Chloropicrin (CP), is a broad-spectrum pesticide that is used in agriculture, and is also a warfare agent. NM and CP can have severe toxic effects to the eye including irritation, corneal edema, and long-term ocular injuries but there are no effective therapies available. Our previous studies indicate that eye toxicity from NM and CP exposure can cause activation of signaling pathways related to DNA damage, oxidative stress, and inflammation. Triterpenoids are activators of the nuclear factor-erythroid factor 2-related factor 2 (Nrf2) pathway, which transcriptionally activates genes related to anti-inflammatory responses and cytoprotective effects reducing oxidative stress. Thus, activating Nrf2 pathway can be a targeted approach for the treatment of chemical induced corneal toxicity.
Methods :
Human corneal epithelial (HCE) cells were exposed to 60 μM NM for 6 or 24 hours. mRNA was isolated and qPCR analyses were carried out for Nrf2 pathway related genes, inflammatory markers, and cytokines.
Results :
NM exposure led to a decrease in Nrf2 mRNA expression at 24h post exposure. Changes in phase II antioxidant enzymes of the Nrf2 pathway NAD(P)H quinone dehydrogenase-1 (NQO-1) and heme oxygenase-1 (HO-1) were observed. NQO-1 mRNA expression decreased at both 6 and 24h post NM-exposure, while HO-1 expression increased at 6h (6.5-fold increase) followed by a decrease at 24 h. NM exposure caused a decrease in the mRNA expression of antioxidant enzymes catalase and glutathione peroxidase-1 at both the time points. An increase in TNF-α mRNA expression (1.8-fold) was observed at 24h post NM exposure.
Conclusions :
NM exposure in HCE cells causes increased expression of inflammation, and oxidative stress related markers and decreases the expression of Nrf2 pathway genes. Since CP has similar effects to the vesicating agent NM, we are investigating the involvement of the Nrf2 pathway in CP-induced corneal injury in HCE cells. Based on these studies, we will further evaluate the effect of activating Nrf2 pathway by triterpenoids for the treatment of NM and CP-induced corneal toxicity.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.