Abstract
Purpose :
The inhibitory effect of some anti-inflammatory agents on corneal inflammation has been associated with an activation of autophagy. However, those agents non-specifically activate autophagy. Such non-specificity can have a variety of side effects. Unlike non-selective autophagy that degrades random cellular contents, selective autophagy can regulate specific signaling pathways because it degrades the key components (cargos) of these pathways via recruitment of cargos to selective adaptors (such as NDP52). However, the role of selective autophagy in corneal inflammation remains unclear.
Methods :
A Beclin1 het and a LysM-Cre; Atg7flox/flox (Atg7 M-cKO) mice were used as a model of global inhibition of autophagy and compromised autophagy specifically in myeloid cells, respectively. To induce inflammation, mouse corneas were exposed to 1M NaOH solution for 30s. Histology, expression of cytokines and chemokines, and infiltration of immune cells were determined by H&E staining, RT-qPCR, and flow cytometry. A THP-1 dual NF-kB reporter cell line was used to monitor NF-kB activity.
Results :
Compared with the WT, the Beclin1 het and Atg7 M-cKO mouse corneas displayed a dramatic infiltration of inflammatory cells as well as increased expression of pro-inflammatory genes (e.g., Ifn gamma, Il6, Mmp9). This indicates that the corneal inflammatory response is augmented by general global attenuation of autophagy and specific inhibition of autophagy in monocytes and mature macrophages. Knockdown of Beclin1, Atg5 and NDP52 in THP-1 reporter cells markedly increased NF-kB activity. Knockdown of Atg5 and NPD52, which inhibits selective autophagy in primary human corneal epithelial cells, significantly increased the expression of pro-inflammatory genes. This suggests that NDP52-mediated selective autophagy in myeloid macrophages and corneal epithelium has an anti-inflammatory effect. Finally, knockdown of Atg5 and NDP52 markedly increased TRAF2 proteins, a positive regulator of NF-kB signaling and a cargo for NDP52-mediated selective autophagy.
Conclusions :
Our observations suggest that in the context of corneal inflammation, the NDP52-mediated selective autophagy/TRAF2 pathway regulates the inflammatory response in corneal epithelial cells and macrophages. This knowledge provides a rational to develop a novel therapy targeting this selective autophagy pathway to alleviate inflammation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.