Activation of AGEs-RAGE signal at macrophage (Mφ) aggravates local inflammation in diabetic polyneuropathy (DPN). Mφ skewing toward pro-inflammatory phenotype (M1) is implicated in insulin resistance (IR) in fatty tissue, suggesting activation of RAGE at Mφ may similarly trigger IR in DPN. Generally, IR leads to axonal transport deficit in peripheral nerves. The aim of this study is to clarify the role of RAGE in the inflammation of DPN and its relationship to IR and axonal transport. Male C57BL/6 mice (W) and RAGE null mice (R) were recruited and rendered diabetic with streprozotocin (STZ) (D). DPN was confirmed by delay of nerve conduction velocities (NCVs) 8 weeks later of STZ injection. Polarization of Mφ in the sciatic nerve (SN) was determined by immunofluorescence (IF) and qPCR. IR of SN was evaluated by phospho (p)-AKT expression with stimulation of 5 unit insulin. Cell size of the dorsal root ganglia (DRG) neuron was morphometrically measured. For the retrograde axonal transport, DRG was quantitatively evaluated by IF for Fluoro-Gold (FG) 7 days after subcutaneous injection of FG into the hindlimb footpad. WD showed significant delay of NCVs (p<0.01, vs. W), while those were maintained in RD. Significant increase in the infiltration M1 in SN of WD (p<0.05, vs. W), whereas robust infiltration of anti-inflammatory Mφ (M2) was seen in RD (p<0.01, vs. R and WD). Increased nuclear translocation of NF-κB p65 and decreased pAKT expression were seen in SN of WD, but not in RD. The cell size in DRG neuron was significantly decreased in WD (p<0.05, vs. W), but that was similar in R and RD. The frequency of transported FG in DRG were significantly decreased in WD (p<0.05, vs. W), while maintained in RD. Taken together, our results suggest that RAGE induces inflammation in SN with skewing toward M1, which associates with IR and attenuation of the retrograde axonal transport in STZ DPN model. Those changes may contribute to the atrophic change of neuronal body in DRG of DPN.
S. Osonoi: None. H. Mizukami: None. K. Takahashi: None. K. Kudo: None. K. Sango: None. S. Yagihashi: None.
Japan Society for the Promotion of Science