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TLR4 regulates insulin-resistant proteins to increase apoptosis in the mouse retina
Li Liu1, Youde Jiang1, Elizabeth Curtiss1
1Department of Anatomy and Cell Biology, Wayne State University School of Medicine, 9314 Scott Hall, Detroit, MI, 48202, USA.
Objective And Design:
Work in multiple organs has suggested that toll-like receptor 4 (TLR4) may play a role in insulin resistance. Additional studies have shown a negative role for TLR4 on retinal health. We have previously reported that β-adrenergic receptors can regulate both TLR4 signal transduction, as well as insulin signaling in the retina and in retinal endothelial cells. Thus, we hypothesized that TLR4 would regulate retinal insulin signaling.
Materials And Methods:
We used endothelial cell-specific TLR4 knockout mice, as well as TLR4-overexpressing mice for these studies.
Methods:
Western blotting and ELISA analyses were done for investigations of insulin receptor, insulin receptor substrate 1 (IRS-1) serine 307, and Akt phosphorylation, as well as cleaved caspase 3 levels in the mouse retina.
Results:
We found that loss of TLR4 led to increased insulin receptor and Akt phosphorylation, as well as decreased IRS-1Ser307 levels. In support of these results, TLR4 overexpression decreased insulin signaling and the cleavage of caspase 3.
Conclusions:
Therefore, these results suggest that TLR4 plays a key role in insulin signaling in the retina. Reduction of TLR4 levels may be protective to the retina.
Insights
Toll-like receptor 4 (TLR4) significantly impacts retinal insulin signaling. Reducing TLR4 levels may protect the retina from insulin resistance and related damage.
Area of Science:
- Ophthalmology
- Endocrinology
- Immunology
Background:
- Toll-like receptor 4 (TLR4) is implicated in insulin resistance across various organs.
- TLR4 negatively affects retinal health.
- β-adrenergic receptors modulate TLR4 and insulin signaling in retinal cells.
Purpose of the Study:
- To investigate the role of TLR4 in regulating insulin signaling within the retina.
- To determine if TLR4 influences key components of the retinal insulin pathway.
Main Methods:
- Utilized endothelial cell-specific TLR4 knockout and TLR4-overexpressing mouse models.
- Performed Western blotting and ELISA to analyze insulin receptor, IRS-1, Akt phosphorylation, and cleaved caspase 3 levels in retinal tissues.
Main Results:
- Loss of TLR4 enhanced insulin receptor and Akt phosphorylation while reducing IRS-1 (Ser307) phosphorylation.
- TLR4 overexpression diminished insulin signaling and decreased caspase 3 cleavage.
- These findings indicate TLR4's critical role in modulating retinal insulin pathway activity.
Conclusions:
- TLR4 plays a pivotal role in regulating insulin signaling in the retina.
- Decreasing TLR4 expression may offer a protective strategy against retinal pathologies associated with insulin resistance.
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