Fig 2: DAO activity in human enterocytes Caco-2 treated with the psychostimulant drugs methylphenidate and lisdexamfetamine. Doses: Methylphenidate (0.5 µg/mL); lisdexamfetamine (0.3 µM), aminoguanidine (10 mg/mL). Data are expressed as mean ± SEM (n = 3). The results are expressed relative to the vehicle group and relative to the amount of protein added in the assay. A one-way ANOVA revealed that there was a statistically significant difference in mean exam score between at least two groups (F(3, 8) = [12.77], p = 0.020). Dunnett’s multiple comparisons test found that the mean value of exam score was significantly different between cells treated with vehicle and cells treated with aminoguanidine (p = 0.017, 95% C.I. = [0.1779, 1.558]). There were no statistically significant differences between cells treated with vehicle and cells treated with methylphenidate (p = 0.0903) or between cells treated with vehicle and cells treated with lisdexamfetamine (p = 0.9857). * p < 0.05 vs. vehicle.

Fig 3: mRNA expression of DAO in human enterocytes Caco-2 treated with the psychostimulant drugs methylphenidate and lisdexamfetamine. Doses: methylphenidate (0.5 µg/mL); lisdexamfetamine (0.3 µM), aminoguanidine (10 mg/mL). Data are expressed as mean ± SEM (n = 3). The results are expressed relative to the vehicle group. One-way Anova test followed by Dunnett post hoc test, ** p < 0.01 vs. vehicle.

Fig 4: Protein expression DAO in human enterocytes Caco-2 treated with the psychostimulant drugs methylphenidate and lisdexamfetamine. (a) Densitometry analysis of relative DAO protein concentration after the indicated treatments. (b) A representative Western blot analysis of human DAO and housekeeping ß-actin levels. Doses: methylphenidate (0.5 µg/mL); lisdexamfetamine (0.3 µM), aminoguanidine (10 mg/mL). The results are expressed relative to the vehicle group. Data are expressed as mean ± SEM (n = 3).

Fig 5: DAO activity was not affected by the presence of methylphenidate (1 µM) or lisdexamfetamine (1 µM) previously incubated with microsomes. In contrast, aminoguanidine produced an important reduction of DAO activity. Data are expressed as mean ± SEM. The results are expressed relative to the vehicle group. One-way Anova test followed by Dunnett post hoc test, **** p < 0.0001 vs. vehicle.