# Triptolide alleviates hyperosmotic stress-induced human corneal epithelial cell damage by inhibiting NLRP3 inflammasome-mediated pyroptosis via the TLR4/NF-κB pathway

## TL;DR

Triptolide helps protect human corneal cells from damage caused by high osmolarity by reducing inflammation and cell death through a specific molecular pathway.

## Contribution

This study demonstrates that triptolide alleviates hyperosmotic stress in corneal cells by inhibiting the TLR4/NF-κB/NLRP3 pathway.

## Key findings

- Triptolide reduced pyroptosis and increased cell viability in hyperosmotic-stressed corneal cells.
- Triptolide suppressed the release of inflammatory cytokines IL-1β and IL-8.
- Triptolide downregulated NLRP3 and NF-κB expression and inhibited NF-κB p65 nuclear translocation.

## Abstract

To verify that Triptolide alleviates hyperosmotic stress-induced damage to human corneal epithelial cells (HCECs) by suppressing pyroptosis via the Toll-like receptor 4/nuclear factor-κB/NOD-like receptor family, pyrin domain-containing 3 (TLR4/NF-κB/NLRP3) axis.

HCECs were divided into six groups: control (CG), hyperosmotic model (MG, 500 mOsm for 12 h), hyperosmotic model with LPS (MG + LPS), triptolide intervention (THSG, 30 nM in 500 mOsm medium), triptolide with LPS (THSG + LPS), and triptolide-only (TOG, 30 nM in standard medium). Cell viability was detected using Cell Counting Kit-8 (CCK-8). The pyroptosis rate was measured by flow cytometry, and lactate dehydrogenase (LDH) release was quantified to assess cytotoxicity. Inflammatory cytokines interleukin-1β (IL-1β) and interleukin-8 (IL-8) were measured by enzyme-linked immunosorbent assay (ELISA). The mRNA and protein expression levels of NLRP3 and NF-κB were analyzed by quantitative real-time polymerase chain reaction (qPCR) and Western blot, respectively. NF-κB p65 nuclear translocation was detected by immunofluorescence.

Compared to the CG (100.00 ± 0.00)%, MG significantly reduced HCECs proliferation to (54.47 ± 3.10)% and increased the pyroptosis rate to (40.28 ± 3.74)%. LPS further exacerbated these effects in the MG + LPS. The levels of inflammatory cytokines IL-1β and IL-8 were markedly elevated under hyperosmotic conditions, and further increased with LPS stimulation. THSG significantly ameliorated hyperosmotic-induced injury: cell proliferation increased to (86.47 ± 5.51)%, the pyroptosis rate decreased to (17.01 ± 2.33)%, and the release of IL-1β and IL-8 was substantially reduced. Triptolide also downregulated mRNA and protein expression of NLRP3 and NF-κB, and inhibited NF-κB p65 nuclear translocation. In the THSG + LPS group, triptolide partially reversed the LPS-enhanced inflammatory and pyroptotic responses, though its protective effect was attenuated compared to THSG without LPS. Notably, TOG showed no adverse effects on normal HCECs, with proliferation, pyroptosis rate, and inflammatory cytokine levels comparable to those of the CG.

Triptolide alleviates hyperosmotic stress-induced pyroptosis and inflammatory injury in HCECs, likely through inhibiting the TLR4/NF-κB/NLRP3 pathway. This study suggests the potential of triptolide in treating hyperosmolarity-related ocular surface diseases.