We have shown that type 2 diabetic Goto-Kakizaki (GK) rats develop cerebrovascular endothelial dysfunction, impaired cerebral blood flow (CBF) and mild cognitive deficits. It is increasingly recognized that vascular cognitive impairment may be a new complication of the disease in both type 1 and type 2 diabetes. Toll-like receptor-2 (TLR2) plays a role in cardiovascular complications of diabetes but its involvement in diabetic cerebrovascular disease is unknown. Since brain function heavily depends on constant perfusion, and decreased CBF precedes development of inflammation and cognitive deficits, we hypothesized that enhanced TLR2 signaling in both type 1 and 2 diabetes would contribute to cerebrovascular dysfunction and decreased CBF. Endothelium-dependent relaxation was assessed by measuring acetylcholine (ACh, 10-9 -10-4 M) induced dilatory response in basilar arteries from GK rats in the presence and absence of an anti-TLR2 (1μg) antibody. Vascular contractility to serotonin (10-9 -10-5 M) stimulation was also assessed. Area under the curve (AUC) and maximal effective concentration (Emax as % of max KCl response) were calculated as indices of total relaxation and total contraction, respectively. Basilar artery relaxation was significantly improved in the vessels preincubated (30’) with antiTLR2 (184.8± 24.0 vs. 87.7± 4, p =0.007). The EMax in response to serotonin stimulation in the anti-TLR2 treated vessels was not significantly different than the vessels from the untreated diabetic GK rats (110.6± 4.9% vs 99.4.±4.5%). To further assess the in vivo functional effects of TLR2 signaling, CBF (relative intensity) was measured using laser speckle imaging in wild type and TLR2-knockout (KO) mice using an STZ induced diabetes model. Six weeks after induction of diabetes, wild-type diabetic mice exhibited a significant decrease in CBF vs. control (210±22.5 vs. 300.3±18.4, p<0.05). This decrease in cerebral perfusion was attenuated in the TLR2-KO diabetic mice compared to TLR2 KO control (322.6±10.1 vs. 344. 5±11. 04). These findings suggest that TLR2 signaling leads to vascular dysfunction through decreased endothelium dependent relaxation, and could contribute to decreased CBF in diabetes predisposing to vascular cognitive impairment.
Toll-like receptor 2 type 1 and type 2 polymorphisms in different chicken breeds
