Interferon (IFN)-α upregulates serotonin (5-HT) uptake and serotonin transporter (5-HTT) messenger ribonucleic acid (mRNA) expression in immune cells, which implies the mechanism underlying IFN-α-induced depression. However, the signal transduction of this effect remains unclear. We investigated whether the effects of IFN-α on the functions of 5-HTT were related to mitogen-activated protein kinase (MAPK). By performing Western blotting, real-time reverse transcriptase—polymerase chain reaction and [³H]5-HT labelling, we examined MAPK phosphorylation, 5-HTT mRNA expression and 5-HT uptake in Jurkat T cells. The cells had been cultured for different time periods (1) with IFN-α alone and (2) preincubated with either MAPK inhibitors or with the selective serotonin reuptake inhibitor, fluoxetine, and subsequently cultured along with IFN-α. The levels of MAPK phosphorylation, 5-HTT mRNA expression and 5-HT uptake all increased in the IFN-α-treated cells but were blocked in those that were pretreated with MAPK inhibitors and fluoxetine. These results appear to clarify the association of depression with IFN-α-induced 5-HT uptake that reduces the 5-HT levels and IFN-α-regulated transcription of 5-HTT; further, the results suggest the involvement of MAPK in this process.

Context: Metformin is widely used for treatment of type 2 diabetes and has a potential application on the treatment of inflammation and cancer. Phosphatase and tensin homolog (PTEN) plays a critical role in cancer cell growth and inflammation; however, precise mechanisms remain unclear. Objective: We aimed to investigate the possible mechanisms of how PTEN regulates metformin against cell growth and inflammation. Materials and methods: We established PTEN knockdown in RAW264.7 murine macrophages (shPTEN cells) to detect inflammatory mediators using commercial kits, production of reactive oxygen species (ROS) by flow cytometry, cell growth by MTT assay and phosphorylated levels of signal molecules by western blot. Results: The shPTEN cells had a significant large amount of inflammatory mediators, such as inducible nitric oxide synthase (iNOS)/nitric oxide (NO) and cyclooxygenase-2 (COX-2)/prostaglandin E₂ (PGE₂); and also elevated the production of ROS and increased cell proliferation. These effects were accompanied with the activation of Akt and p38 mitogen-activated protein kinase (MAPK), and the inactivation of an AMP-activated protein kinase (AMPK) activator and extracellular signal-regulated kinase 1/2. Pretreatment with metformin not only blocked these inflammatory mediators, but also caused growth inhibition induced by significant apoptosis. Furthermore, inactivation of Akt, blockade of ROS generation and independence of activations of AMPK and MAPK by metformin were also observed. Conclusion: Macrophages with PTEN deficiency developed a continuous inflammatory microenvironment, which further aggravated tumor cell growth. Moreover, metformin affected PTEN-deficient cells dependent of inhibition of ROS production and Akt activation against enlarged inflammatory mediators and/or cell growth in shPTEN cells.

Peroxisome proliferator-activated receptor gamma (PPARγ) agonist has anti-inflammatory and anticancer properties. However, the mechanisms by which PPARγagonist rosiglitazone interferes with inflammation and cancer via phosphatase and tensin homolog-(PTEN)-dependent pathway remain unclear. We found that lower doses (<25 μM) of rosiglitazone significantly inhibited lipopolysaccharide-(LPS)-induced nitric oxide (NO) release (via inducible nitric oxide synthase, iNOS), prostaglandin E2 (PGE₂) production (via cyclooxygenase-2, COX-2), and activation of Akt in RAW 264.7 murine macrophages. However, rosiglitazone did not inhibit the production of reactive oxygen species (ROS). In PTEN knockdown (shPTEN) cells exposed to LPS, rosiglitazone did not inhibit NO release, PGE₂production, and activation of Akt. These cells had elevated basal levels of iNOS, COX-2, and ROS. However, higher doses (25–100 μM) of rosiglitazone, without LPS stimulation, did not block NO release and PGE₂productions, but they inhibited p38 MAPK phosphorylation and blocked ROS generation in shPTEN cells. In addition, rosiglitazone caused G1 arrest and reduced the number of cells in S + G2/M phase, leading to growth inhibition. These results indicate that the anti-inflammatory property of rosiglitazone is related to regulation of PTEN independent of inhibition on ROS production. However, rosiglitazone affected the dependence of PTEN-deficient cell growth on ROS.

Vitamin D has been identified as an innate anti-hepatitis C virus (HCV) agent but the possible mechanisms for this issue remain unclear. Here, we clarified the mechanisms of calcitriol-mediated inhibition of HCV infection. Calcitriol partially inhibited HCV infection, nitric oxide (NO) release and lipid accumulation in Huh7.5 human hepatoma cells via the activation of vitamin D receptor (VDR). When cells were pretreated with the activators of peroxisome proliferator-activated receptor (PPAR)-α (Wy14643) and -γ (Ly171883), the calcitriol-mediated HCV suppression was reversed. Otherwise, three individual stimulators of PPAR-α/β/γ blocked the activation of VDR. PPAR-β (linoleic acid) reversed the inhibition of NO release, whereas PPAR-γ (Ly171883) reversed the inhibitions of NO release and lipid accumulation in the presence of calcitriol. The calcitriol-mediated viral suppression, inhibition of NO release and activation of VDR were partially blocked by an inhibitor of endoplasmic reticulum-associated degradation (ERAD), kifunensine. Furthermore, calcitriol blocked the HCV-induced expressions of apolipoprotein J and 78 kDa glucose-regulated protein, which was restored by pretreatment of kifunensine. These results indicated that the calcitriol-mediated HCV suppression was associated with the activation of VDR, interference with ERAD process, as well as blockades of PPAR, lipid accumulation and nitrative stress.

Clinical reports document that depression as a side effect is more prevalent in hepatic patients given interferon (IFN)‐α therapy than in those given lamivudine. The mechanisms, however, are poorly understood. Serotonin transporter (5‐HTT), via uptake of serotonin (5‐HT) into presynaptic serotoninergic neurons, is an initial action site for antidepressants. Real‐time polymerase chain reaction (PCR) was used to quantify 5‐HTT mRNA expression in immune cells in order to evaluate whether 5‐HTT acted as an indicator of depression. Results showed that the 5‐HTT mRNA expression was much higher in T‐cell and B‐cell lines than that in a monocytic cell line. Treatment with either lamivudine or ribavirin reduced the 5‐HTT mRNA expression, protein level and 5‐HT uptake in T‐cell line. Treatment with IFN‐α, however, increased those levels in the same group. A similar effect was observed in peripheral blood mononuclear cells (PBMC). Mimicking clinical use by treating PBMC with a combination of IFN‐α and ribavirin increased the 5‐HTT mRNA expression level. Our study indicates that these therapeutic drugs regulate 5‐HTT expression, which implies that 5‐HTT might be a trait marker in IFN‐α‐induced depression after hepatic therapy.