Bmi1 Is Down-Regulated in the Aging Brain and Displays Antioxidant and Protective Activities in Neurons
Figure 1
Bmi1 is down-regulated in the aging mouse brain.
A) Coronal sections from the cerebral cortex were analyzed by IHC using Bmi1 and NeuN (top panels), or Bmi1 and GFAP (lower panels) antibodies. Bmi1 (brown) is highly expressed in NeuN+ (pink) neurons and its expression decreases with age, while it remains unchanged in GFAP+ (Pink) astrocytes. Note that in aged neurons, Bmi1 labeling was not uniform, with some neurons expressing Bmi1 at moderate levels (blue arrowheads), while others showing nearly undetectable level (red arrowheads). Scale bars; 20 µm. (B) The relative expression of Bmi1 in cortices from young and old brains was analyzed by Q-PCR. Each point represents a comparison between one old and one young mouse cortex. The blue line represents the mean, and the red line represents the standard deviation (n = 15; **P<1.022E−24). (C)Young (40–55 days old) and old (21–26 months old) mice brain samples were analyzed by Western blot for Bmi1 expression. Protein loading was normalized using β-actin and α-tubulin. Data in brackets are levels of Bmi1 and are expressed as Mean ± s.d. (n = 4 brains per group; *P<0.05). (D)Thenumbers of neurons (NeuN+ cells) and non-neuronal cells (NeuN- cells) were counted in young and old mice brain slices. (left panel) Data were presented as absolute neuron number per cortical field. (right panel) Data were expressed as the percentage of neurons versus all cortical cells (neurons + non-neuronal cells). Results are Mean +/− s.d. (n = 3 brains per age, and counts were made on 4 to 9 slices per brain; P = 0.18).