Fig. 4

Methylglyoxal (MGO) induced neuronal cell loss upon tryptophan depletion. (A, B) Immunofluorescent staining of primary hippocampal neurons. The cells were treated with MGO (500 µM) and Trp-(-) or Trp (+) medium for 24 h. Dendritic spine density was counted from neuronal dendritic segments. Scale bar: 100 μm (20× magnification). (C) The cell viability of primary hippocampal neurons. (D) The levels of Trp in cell culture medium and cell extracts by using HPLC system. (E) The neurite length images of N2a cells by treating MGO (500 µM) and Trp-(-) or Trp (+) medium for 24 h. Quantitative analyses of neurite outgrowth were conducted by calculating the number of neurite lengths from randomly selected fields per well. Scale bar: 200 μm (10× magnification). (F, G) The mRNA expression levels of TPH1, and TPH-2 in N2a cells. All data presented as mean ± SEM (n = 3). ^#p < 0.05, ^##p < 0.01, and ^###p < 0.001 vs. Trp (+) medium treatment