Jong-Jer Lee1, Pei-Wen Wang2, I-Hui Yang3, Hsiu-Mei Huang3, Chia-Shiang Chang3, Chia-Lin Wu4, Jiin-Haur Chuang5. 1. Department of Ophthalmology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan 2The Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan. 2. Department of Internal Medicine and Nuclear Medicine, Division of Endocrinology and Metabolism, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. 3. Department of Ophthalmology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. 4. Department of Surgery, Division of Pediatric Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan. 5. The Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan 4Department of Surgery, Division of Pediatric Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Ka.
Abstract
PURPOSE: 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. METHODS: Wild-type C57BL/6 and TLR4 knockout (TLR4KO; B6.B10ScN-Tlr4(lps-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. RESULTS: 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. CONCLUSIONS: 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.
PURPOSE: 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. METHODS: Wild-type C57BL/6 and TLR4 knockout (TLR4KO; B6.B10ScN-Tlr4(lps-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. RESULTS: 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. CONCLUSIONS: 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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