Figure 3
Inducible nitric oxide synthase expression in microglia of amyotrophic lateral sclerosis-linked mutant human superoxide dismutase transgene (SOD1 G93A ) and wild-type (WT) lumbar spinal cord ventral horn. The majority of tomato lectin (TL)-positive microglia (red) in the ventral horn did not express inducible nitric oxide synthase (iNOS) (arrows, A,B) at 6 weeks of age in either WT (A) or SOD1G93A (B) mice. A subset of microglia were iNOS-positive (green) (arrows, C,D). The numbers of iNOS-positive and iNOS-negative microglia stayed relatively constant over time in WT mice (E). The number of iNOS-positive microglia increased with disease progression in SOD1G93A mice; the number of iNOS-negative microglia increased at 22 and 25 weeks of age in SOD1G93A mice (F). The combined data from Figure 2F and 3F show that the number of both arginase1 (Arg1)-positive and iNOS-positive microglia increased with disease progression (G); the percentage of microglia expressing Arg1 and expressing iNOS also increased with time (H). Scale bar 50 μm in A-D. * P < 0.05, ** P < 0.01, *** P < 0.001. NY, Nuclear yellow; EP, endpoint.