Pharmacometabolomics reveals that serotonin is implicated in aspirin response variability

Abstract

While aspirin is generally effective for prevention of cardiovascular disease, considerable variation in drug response exists, resulting in some individuals displaying high on-treatment platelet reactivity. We used pharmacometabolomics to define pathways implicated in variation of response to treatment. We profiled serum samples from healthy subjects pre- and postaspirin (14 days, 81 mg/day) using mass spectrometry. We established a strong signature of aspirin exposure independent of response (15/34 metabolites changed). In our discovery (N = 80) and replication (N = 125) cohorts, higher serotonin levels pre- and postaspirin correlated with high, postaspirin, collagen-induced platelet aggregation. In a third cohort, platelets from subjects with the highest levels of serotonin preaspirin retained higher reactivity after incubation with aspirin than platelets from subjects with the lowest serotonin levels preaspirin (72 ± 8 vs. 61 ± 11%, P = 0.02, N = 20). Finally, ex vivo, serotonin strongly increased platelet reactivity after platelet incubation with aspirin (+20%, P = 4.9 × 10(-4), N = 12). These results suggest that serotonin is implicated in aspirin response variability.

Figure 1

Serotonin in the two extreme quartiles of aspirin response. Data represent means and 95% confidence intervals of serotonin levels before (blue) and after (red) aspirin exposure in the discovery cohort (a: first quartile n = 42, fourth quartile n = 38) and in the replication cohort (b, first quartile n = 19, fourth quartile n = 19). *P < 0.05, ***P < 0.001.

Figure 2

Correlation between serotonin and ex vivo agonist-induced platelet aggregation in the replication cohort (N = 125). (a–c) Platelet aggregation after stimulation with collagen (2 µg/ml). (d–f) Platelet aggregation after stimulation with arachidonic acid (0.5 mmol/l).

Figure 3

Ex vivo functional studies of serotonin. Thirty-eight healthy subjects (functional cohort 1) independent from the Heredity and Phenotype Intervention study were selected to participate in functional studies. (a,b) Serotonin was measured at fasting in platelet-rich plasma (PRP), serum, and platelet-poor plasma (PPP). (c,d) Subjects were separated into four quartiles of PRP serotonin levels. Arachidonic acid–stimulated (c) and collagen-stimulated (d) platelet aggregation were measured before (blue) and after (red) incubation of PRP with aspirin in subjects with low (N = 10) vs. high (N = 10) baseline serotonin level. (e) Platelets from 12 additional healthy subjects (functional cohort 2) were exposed ex vivo to serotonin (1 µmol/l) alone or to serotonin plus aspirin. Data represent means and 95% confidence intervals of collagen-stimulated platelet aggregation. *P < 0.05, ***P < 0.001.