Toll-Like Receptor 3 Is Critical for Coxsackievirus B4-Induced Type 1 Diabetes in Female NOD Mice

Abstract

Group B coxsackieviruses (CVBs) are involved in triggering some cases of type 1 diabetes mellitus (T1DM). However, the molecular mechanism(s) responsible for this remain elusive. Toll-like receptor 3 (TLR3), a receptor that recognizes viral double-stranded RNA, is hypothesized to play a role in virus-induced T1DM, although this hypothesis is yet to be substantiated. The objective of this study was to directly investigate the role of TLR3 in CVB-triggered T1DM in nonobese diabetic (NOD) mice, a mouse model of human T1DM that is widely used to study both spontaneous autoimmune and viral-induced T1DM. As such, we infected female wild-type (TLR3(+/+)) and TLR3 knockout (TLR3(-/-)) NOD mice with CVB4 and compared the incidence of diabetes in CVB4-infected mice with that of uninfected counterparts. We also evaluated the islets of uninfected and CVB4-infected wild-type and TLR3 knockout NOD mice by immunohistochemistry and insulitis scoring. TLR3 knockout mice were markedly protected from CVB4-induced diabetes compared with CVB4-infected wild-type mice. CVB4-induced T-lymphocyte-mediated insulitis was also significantly less severe in TLR3 knockout mice compared with wild-type mice. No differences in insulitis were observed between uninfected animals, either wild-type or TLR3 knockout mice. These data demonstrate for the first time that TLR3 is 1) critical for CVB4-induced T1DM, and 2) modulates CVB4-induced insulitis in genetically prone NOD mice.

Laser Capture Microdissection Tailored to Type 1 Diabetes Mellitus Research

“…There was not diffrence between the genotypes either in the baseline Log 10 (C q ) level at 5 weeks ( P > 0.2) or in the rate of change over time ( P > 0.2), indicating no effect of genotype on average CXCL10 expression. These results were as predicted, based on our previous research that has shown no difference in the incidence of diabetes in uninfected TLR3 / vs TLR3 +/+ NOD mice (10). Observations were plotted, with model best-fit regression line in blue, with the gray shading representing the 95% confidence interval (Supplementary Figure S3).…”

“…Therefore, we wanted to investigate if there was a difference in expression of CXCL10 between wild-type (TLR3 +/+ ) and TLR3-deficient (TLR3 / ) NOD mice in the pre-diabetic stage. We predicted that CXCL10 levels should be similar in both sets of animals that have not been exposed to virus since the insulitis scores of both sets of animals were the same in our previous study (10), as was the rate of development of spontaneous diabetes (9, 10). …”

“…We are particularly interested in characterizing early (weaning to 10 weeks of age) molecular differences between wild-type NOD mice and toll-like receptor 3 (TLR3)deficient mice (9, 10), as we have recently shown that TLR3 is critical for virus-mediated acceleration of TIDM (10). RNA extraction for gene expression studies from pancreatic islets of juvenile mice is complicated by the small size of the immature pancreas and a dearth of islets.…”

The importance of the Non Obese Diabetic (NOD) mouse model in autoimmune diabetes

“…It is interesting that TLR3−/− had no influence on spontaneous diabetes development in NOD mice [97] whereas TLR3 was indispensable for virus-induced diabetes in NOD [118, 119] or BALB/c mice [120] and in BB rats [121, 122]. Therefore, changing how these innate immune receptors interact with the environment is important for altering susceptibility to or protection from diabetes.…”

Activation of Toll-like receptor 3 increases mouse aortic vascular smooth muscle cell contractility through ERK1/2 pathway

“…However, further examination of the role of TLR3 signaling in glucose metabolism and diabetes merits consideration. In fact, the association between TLR3 and glucose metabolism has been recently proposed [50,31]. Moreover, reports show that polymorphisms in the TLR3 gene are associated with risk for type 1 diabetes [36,5].…”