Proposed Pathway Linking Respiratory Infections with Depression
Zeinab Karimi 1, Maryam Chenari 1, Farhad Rezaie 1, Shima Karimi 2, Najmeh Parhizgari 1, Talat Mokhtari-Azad 1*
1Department of Virology, School of Public Health, Tehran University of Medical Science, 2Ilam University of Medical Sciences
Received: May 10, 2021; Revised: July 15, 2021; Accepted: July 15, 2021; Published online: July 15, 2021.
© The Korean College of Neuropsychopharmacology. All rights reserved.

Depression is one of the most important causes of disability and loss of useful life of people around the world. Acute respiratory infection caused a large number of severe illnesses and deaths of the world and most of these due to viral infections, which is estimated more than 80% of respiratory infections. Detection of viruses by immune pathogen recognition receptors activates the intracellular signaling cascade and eventually cause produces interferons.
Inflammatory process begins with secretion of interferons and the expression of ISG genes. One of the most important of these genes is IDO, which plays a major role in tryptophan catabolism. IDO is an intracellular monomeric enzyme that is also responsible for breaking down and consuming tryptophan in the Kynurenine pathway. Increased inflammation has been linked to decrease tryptophan concentrations and increase kynurenine levels. we tried to explain the role of inflammation by viral respiratory infections in causing depression.
Keywords: Depression, Viral Respiratory Infection, Inflammation, IDO(Indoleamine 2,3-dioxygenase), kynurenine