Induction of indoleamine 2,3-dioxygenase in vivo by IFN-con1

Inflammation-induced depression: Its pathophysiology and therapeutic implications

Inflammation is not the only cause of depression and cannot explain its entire pathophysiology, but it is an important pathogenic factor that explains one possible mechanism of depression, with the kynurenine (KYN) pathway of tryptophan at its center. In particular, greater impairment seems to exist in the KYN pathway in inflammation-induced depression related to immunotherapy, autoimmune disease, and infection. In patients with these conditions, immunopharmacology is likely to be an important therapy. To develop this therapy, clear evidence of the immune-KYN pathway must be established via multiple types of experiments. This paper reviews the body of evidence, not only for the action of tryptophan (TRY) and consequent serotonin depletion, but also for the detrimental effects of TRY catabolites and the key enzymes in the KYN pathway that play important roles in the pathophysiology of inflammation-induced depression. In addition, this paper explores a potential treatment strategy for inflammation-induced depression using KYN metabolism.

REFINEMENT: A search framework for the identification of interferon-responsive elements in DNA sequences – a case study with ISRE and GAS

Interferons (IFN) are a family of pleiotropic secreted proteins that play a key role in mediating antiviral and apoptotic responses, and in immune modulation. Interferons induce a large number of genes through activating the janus tyrosine kinase (JAK)-signal transducers and activators of transcription proteins (STAT) pathway, and the binding of transcription factors to upstream regions of the inducible genes (interferon-stimulated gene, ISG) at specific DNA regulatory elements known as interferon-stimulated response element (ISRE) and gamma-activated sequence (GAS). We have previously performed DNA micro-arrays on peripheral blood mononuclear cells (PBMC) treated with interferon-alpha in culture and showed that approximately 700 genes are significantly modulated (P < or = 0.001). In order to search for ISRE and GAS we have developed a framework called regulatory element finding with iteration and effective model refinement (REFINEMENT) using an existing program (HMMER) and a standard discriminating scoring technique. Although REFINEMENT uses existing programs, our framework itself is novel as it effectively discriminates occurrences using an iterative model refinement technique. REFINEMENT has detected either ISRE or GAS sequence in all of the genes shown to be induced at a P-value < or = 0.001. There were far more functional occurrences in ISRE than in GAS, suggesting that ISRE plays a greater role in response to interferon-alpha than GAS sequences. This method can be used to identify such sequences in any set of genes. REFINEMENT is non-commercial and is accessible at .

5-Hydroxytryptophan plus SSRIs for interferon-induced depression: Synergistic mechanisms for normalizing synaptic serotonin

Interferon-alpha (IFN) is widely used in the treatment of certain cancers and viral infections, including hepatitis C (HCV). Unfortunately, depression is a common side effect of IFN therapy, affecting approximately a third of HCV patients receiving IFN therapy. Studies have shown that selective serotonin reuptake inhibitors (SSRIs) can effectively treat IFN-induced depression in only 63-75% of cases. For the remaining percentage, depression often necessitates dose reduction of or discontinuation from IFN therapy. Emerging evidence indicates that IFN may cause depression by affecting brain serotonin. IFN has been shown to increase serotonin reuptake and to decrease serotonin synthesis. We hypothesize that SSRIs are not fully effective because they affect only serotonin reuptake, not serotonin synthesis, and that effective treatment must address both uptake and synthesis. 5-Hydroxytryptophan (5-HTP) effectively increases central nervous system synthesis of serotonin. It is the immediate precursor of serotonin and is widely available as a dietary supplement, which is well absorbed after an oral dose. Several double-blind studies have shown 5-HTP to be effective in the treatment of nondrug-induced depression. We hypothesize that patients who become depressed on IFN will respond to the synergistic combination of SSRIs plus 5-HTP.