Figure 6. Expression, function, and phenotypic reflection of voltage-gated soium channel 1.7 in α-galactosidase A deficient mice.
(A) Boxplots show the results of voltage-gated sodium channel 1.7 (Nav1.7) gene expression in dorsal root ganglia (DRG) of young (3 months) and old (≥12 months) wildtype (WT) and α-galactosidase A deficient (GLA KO) mice. No intergroup difference was found. (B) Nav1.7 protein levels, as investigated by enzyme-linked immunosorbent assay, did not differ between genotypes and age-groups. (C) Graphs display exemplified sodium currents of old GLA KO and WT mice at −40 mV. Comparing young GLA KO mice with young and old WT mice, there no difference was found in current densities of sodium currents (D), while sodium currents of old GLA KO mice were markedly reduced compared to young GLA KO (p<0.001) and old WT mice (p<0.001). At baseline (E, black trace) sodium currents showed fast inactivation kinetics. After adding 100 nM tetrodotoxin (TTX) to the bath solution, sodium currents were completely blocked (E, red trace). Sodium currents recovered completely after washout with bath solution (E, grey trace). Line charts show thermal withdrawal latencies (F) and mechanical withdrawal thresholds (G) of young and old GLA KO and WT mice before and after intraplantar injection of complete Freund`s adjuvant (CFA). While young and old WT mice showed thermal and mechanical hypersensitivity already one hour after CFA injection lasting up to day seven, old GLA KO mice were spared from heat hypersensitivity (p<0.001). GLA KO: young (3 months; gene expression: n = 2 male, n = 4 female; protein expression: n = 3 male, n = 1 female), old (≥12 months; gene expression: n = 4 male, n = 2 female; protein expression: n = 2 male, n = 2 female). WT: young (3 months; gene expression: n = 2 male, n = 4 female; protein expression: n = 2 male, n = 2 female), old (≥12 months; gene expression: n = 3 male, n = 3 female; protein expression: n = 2 male, n = 2 female). Sodium currents: At least nine cells per genotype and age-group from at least three different mice each were analyzed. GLA KO young (3 months; n = 4 male, n = 5 female), old (≥12 months; n = 3 male, n = 7 female). WT young (3 months; n = 3 male, n = 6 female), old (≥12 months; n = 4 male, n = 6 female). CFA: GLA KO: young (3 months; n = 4 male, n = 2 female), old (≥12 months; Baseline: n = 33; CFA: n = 6 male, n = 6 female). WT: young (3 months; n = 4 male, n = 2 female), old (≥12 months; Baseline 32; CFA: n = 6 male, n = 6 female). Scale bar: 50 µm. The non-parametric Mann-Whitney U test for group comparisons was applied. Behavioral data were analyzed using a two-way ANOVA followed by Tukey’s post-hoc test. *p<0.05;***p<0.001.