Targeting the self-amplifying loop between ATF6 and SNAI1 to inhibit epithelial‒mesenchymal transition in fibrotic lesions.

Background

The epithelial‒mesenchymal transition (EMT) decisively contributes to human diseases such as organ fibrosis and tumors. However, the molecular mechanism triggering EMT remains unclear.

Methods

We elucidated a novel self-amplifying feedback loop involving activating transcription factor 6 (ATF6) and Snail family transcriptional repressor 1 (SNAI1) and assessed its significant role in unfolded protein response (UPR)-dependent EMT. Multiple in vivo and in vitro models were applied, including mouse models of trauma and laser-induced lens injury and human lens epithelial explants from patients with senile cataracts. RNA sequencing was performed to comprehensively analyze the molecular mechanisms underlying UPR-dependent EMT, and heterozygous Atf6 knockout mice provided insights into the UPR-EMT crosstalk. The direct interaction between ATF6 and SNAI1 was verified via dual-luciferase assays. ATF6 expression was inhibited using AAV-shATF6 and melatonin (MLT) treatment in rodent models and cell cultures, respectively. Slit-lamp imaging, immunostaining, and western blotting were performed to assess EMT inhibition.

Results

ATF6 expression was markedly upregulated in fibrotic cataracts, and ATF6 overexpression was sufficient to induce EMT-like changes both in vivo and in vitro. Similarly, compared with wild-type control mice, heterozygous Atf6 knockout mice presented ameliorated injury-induced EMT. Dual-luciferase assays combined with functional studies revealed a self-amplifying loop between ATF6 and SNAI1 that drives the uncontrollable progression of UPR-dependent EMT. Notably, MLT emerged as an effective inhibitor of UPR-dependent EMT and mitigated EMT-like alterations in parallel with Atf6 knockdown, suggesting that MLT could be leveraged to target the ATF6-SNAI1 self-amplifying loop and inhibit EMT in human diseases.

Conclusions

Collectively, the results of this work demonstrate that the ATF6-SNAI1 self-amplifying loop acts as an important mediator of EMT and that MLT could be leveraged to target this loop and inhibit EMT in lens fibrosis.