SMAD2 and Alzheimer disease: In the RV, the protein expression of pSmad2/3 and the ratio of pSmad2/3 to Smad2/3 were significantly upregulated in the AV group compared to the S group (both P < 0.01) and significantly downregulated in the AD group compared to the AV group (P < 0.05 and P < 0.01, respectively).