Fig 2: Methylation status of the TPH1/2 genes in rats(A) Methylation-specific polymerase chain reaction (MSP) was used to assess the methylation status of the TPH1/2 genes in the brain, liver, and kidney of healthy, depressive model and treated rats; GAPDH was used as an internal control. Relativequantity of TPH1 (from the images shown in A) (B) and TPH2 (from the images shown in A) (C) Un-MSP: un-methylated-specificPCR, MSP: methylated-specificPCR. **P<0.01 vs healthy and treated groups, ##P<0.01 vs healthy groups. The images are representative of six independent experiments.

Fig 3: Herpes simplex virus upregulation of TPH-1 and TPH-2 expression is associated with a corresponding increase in serotonin production. Cells were mock or HSV-1 infected and at 24 h post infection, expression of TPH-2 (top and middle series of panels, aTPH2; red), TPH-1, (bottom series of panels, aTPH1; red), serotonin (middle and bottom series of panels, aSerotonin; green), or HSV-viral proteins (top series of panels, aHSV; green) was visualized by confocal immunofluorescent analysis. Cell nuclei were counterstained with DRAQ5, pseudocolored blue and channels merged.

Fig 4: Expression and localization of TPH1/2 in rat tissuesThe expression and localization of TPH1 (A) and TPH2 (B) were analyzed by immunohistochemistry in the rat brain, liver, and kidney of the healthy, depressive model, and treated groups. The images are representative of six independent experiments.

Fig 5: Serotonin enhanced HSV replication is suppressed by pharmacological inhibition of TPH-1/2. (A) ELISA determination of total intra- and extra-cellular serotonin concentrations from mock- or HSV-infected cells. (B) HSV-1 viral yield (left panel) and fold increase in viral yield (right panel) were determined for infected cells either mock treated or treated with 50 µM serotonin. (C) ELISA determination of extracellular serotonin concentration from supernatants of HSV-1 infected or mock-infected cells that had been mock treated or treated with 500 nM of the TPH inhibitor LX1031. (D) HSV-1 infected A549 cells were mock treated (Mock Tx), treated with 50 µM serotonin (Serotonin) and 500 nM LX1031 (LX1031), or cotreated with 500 nM LX1031 and 50 µM serotonin (LX1031 + Serotonin). Viral titers were determined using a limiting dilution plaque formation assay and were expressed as a percentage of Viral Yield Relative to Mock Treatment. Data are graphed as mean ± SEM. (*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001, and NS: not significant).