TLR3 Overexpression Attenuates D-GalN/LPS-Induced Acute Liver Injury and Is Associated With AMPK Phosphorylation, Autophagy-Related Changes, and IRF3 Upregulation
TL;DR
TLR3 overexpression significantly alleviated acute liver injury and apoptosis in GalN/LPS-induced acute liver injury models, and was associated with increased AMPK phosphorylation and elevated IRF3 expression in both in vivo and in vitro experiments.
Abstract
Background: Toll-like receptor 3 (TLR3) has been implicated in innate immune regulation, but its role in acute liver injury is unknown. The aim of this study was to investigate the functional significance of TLR3 and its underlying mechanisms in D-GalN/lipopolysaccharide (LPS)-induced acute liver injury.Methods: Acute liver injury models were established in rats; Kupffer cells were used to investigate the underlying cellular and molecular mechanisms. Liver function indicators, including alanine transaminase (ALT), aspartate transaminase (AST), lactate dehydrogenase (LDH), and histopathological changes in liver tissues were evaluated in rats. The expression levels of the inflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18) in Kupffer cells were measured. In addition, apoptosis was assessed in both models. To investigate the underlying molecular mechanisms, the expression of apoptosis-related proteins (B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax)), autophagy-related markers (microtubule-associated protein 1 light chain 3 (LC3I/II), sequestosome 1 (P62)), and signaling proteins involved in the adenosine monophosphate-activated protein kinase (AMPK) and interferon regulatory factor 3 (IRF3) pathways were assessed by western blotting in both models. TLR3-overexpressing lentivirus was used to examine the functional role of TLR3. Compound C and 3-methyladenine (3-MA) were applied to inhibit AMPK signaling and autophagy, respectively. Furthermore, in Kupffer cells, the mRNA levels of IL-1β and IL-6 were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR), and autophagy was evaluated by immunofluorescence.Results: TLR3 overexpression significantly alleviated acute liver injury and apoptosis in GalN/LPS-induced acute liver injury models. It modulated apoptosis-related proteins, enhanced autophagy markers, and was associated with increased AMPK phosphorylation and elevated IRF3 expression in both in vivo and in vitro experiments. TLR3 also lowered inflammatory cytokine expression. Notably, the protective effects of TLR3 were markedly reversed by Compound C or 3-methyladenine treatment.Conclusion: TLR3 overexpression correlates with protection against acute liver injury, accompanied by enhanced AMPK-associated autophagy and IRF3 upregulation. These findings suggest that TLR3 links innate immune sensing with metabolic and autophagic pathways, providing a mechanistic basis for its potential protective role in acute liver injury.