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Knockout of toll-like receptor-4 attenuates the pro-inflammatory state of diabetes
Sridevi Devaraj1, Peter Tobias, Ishwarlal Jialal
1Laboratory for Atherosclerosis and Metabolic Research, University of California, Davis, Medical Center, Sacramento CA, USA.
Abstract:
Type 1 diabetes (T1DM) is associated with increased vascular complications and is a pro-inflammatory state. Recent findings have shown increased TLR2 and 4 expression, signaling, ligands, and functional activation in T1DM subjects compared to controls and further accentuated in T1DM with microvascular complications. Thus, the aim of this study was to examine if genetic deficiency of TLR4 attenuates the increased inflammation associated with T1DM using the streptozotocin-induced diabetic mouse model. C57BL/6 and TLR4(-/-) mice were obtained and studied in the native state and following induction of diabetes using streptozotocin. Diabetic (WT+STZ) mice had increased expression of both TLR2 and TLR4, while TLR4(-/-) STZ mice had increased expression only of TLR2, but not TLR4 compared to the non-diabetic mice TLR2 expression was significantly increased with STZ-induced diabetes and was unaffected by knockout of TLR4. Also, levels of MyD88, IRAK-1 protein phosphorylation, Trif, IRF3, and NF-κB activity were significantly reduced in TLR4(-/-) +STZ mice compared to the WT+STZ mice. WT+STZ mice exhibited significantly increased levels of serum and macrophage IL-1β, IL-6, KC/IL-8, IP-10, MCP-1, IFN beta and TNF-α compared to WT mice and this was significantly attenuated in TLR4(-/-) +STZ mice (P<0.01). Thus, TLR4 contributes to the pro-inflammatory state and TLR4KO attenuates inflammation in diabetes.
Insights
Toll-like receptor 4 (TLR4) contributes to inflammation in type 1 diabetes (T1DM). Genetic deficiency of TLR4 significantly reduces inflammatory markers in a mouse model of T1DM, suggesting TLR4 plays a key role in diabetes-related inflammation.
Area of Science:
- Immunology
- Endocrinology
- Pathophysiology
Background:
- Type 1 diabetes (T1DM) is characterized by a pro-inflammatory state and increased vascular complications.
- Elevated Toll-like receptor 2 (TLR2) and Toll-like receptor 4 (TLR4) expression and activation are observed in T1DM, particularly with microvascular complications.
Purpose of the Study:
- To investigate whether genetic deficiency of TLR4 (TLR4 knockout) attenuates the heightened inflammation associated with T1DM.
- To utilize the streptozotocin-induced diabetic mouse model to assess the role of TLR4 in T1DM-related inflammation.
Main Methods:
- Comparison of wild-type (WT) and TLR4 knockout (TLR4(-/-)) mice in both native and streptozotocin-induced diabetic states.
- Measurement of TLR2 and TLR4 expression, inflammatory signaling pathway components (MyD88, IRAK-1, Trif, IRF3, NF-κB), and cytokine levels (IL-1β, IL-6, KC/IL-8, IP-10, MCP-1, IFN-β, TNF-α).
Main Results:
- Diabetic WT mice showed increased TLR2 and TLR4 expression, while diabetic TLR4(-/-) mice showed increased TLR2 but not TLR4.
- Key inflammatory signaling pathway components and NF-κB activity were significantly reduced in diabetic TLR4(-/-) mice compared to diabetic WT mice.
- Pro-inflammatory cytokine levels were significantly elevated in diabetic WT mice and markedly attenuated in diabetic TLR4(-/-) mice.
Conclusions:
- TLR4 plays a significant role in mediating the pro-inflammatory state observed in type 1 diabetes.
- Genetic deficiency of TLR4 effectively attenuates inflammation in the context of T1DM, highlighting TLR4 as a potential therapeutic target.
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