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Jong-Jer Lee, Pei-Wen Wang, I-Hui Yang, Hsiu-Mei Huang, Chia-Shiang Chang, Chia-Lin Wu, Jiin-Haur Chuang; High-Fat Diet Induces Toll-Like Receptor 4-Dependent Macrophage/Microglial Cell Activation and Retinal Impairment. Invest. Ophthalmol. Vis. Sci. 2015;56(5):3041-3050. doi: https://doi.org/10.1167/iovs.15-16504.
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© ARVO (1962-2015); The Authors (2016-present)
The toll-like receptor 4 (TLR4) signaling pathway is involved in chronic inflammation and insulin resistance, which are associated with obesity and diabetes mellitus. In the present study, a model of high-fat diet (HFD) feeding of mice was used to investigate the role of TLR4 in overnutrition- and obesity-associated inflammation and infiltration of macrophages and microglia in the retina.
Wild-type C57BL/6 and TLR4 knockout (TLR4KO; B6.B10ScN-Tlr4lps-del/JthJ) mice were fed a HFD or control chow diet (CD) for 6 months. The TLR4 expression, the relative increase in macrophages/microglia (CD11b+ and CD45+ cells), the presence of markers of oxidative stress (gp91phox and malondialdehyde; MDA), and DNA damage (phosphorylated histone H2AX; γH2AX) were assessed by real-time PCR and immunofluorescence studies.
The HFD for 6 months showed increased obesity, glucose intolerance, and insulin resistance in mice. Toll-like receptor 4 expression was found in vascular pericytes at the inner retina. Increased CD11b+ and CD45+ cells, phosphorylated NF-κB, interleukin-6, gp91phox, MDA, and γH2AX were observed in the retina of mice fed a HFD compared to CD counterparts. TLR4KO mice did not show the adverse effects of HFD.
Our results indicate that HFD-induced macrophage/microglial cell activation and retinal impairment were reduced in the absence of TLR4. The findings suggest that TLR4 is implicated in the pathogenesis of retinal diseases caused by metabolic disorders.
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