Recent studies suggest that some cases of prenatal depression may be associated with reactivation of latent infections of the herpesvirus family. The possible relationships among stress, prenatal depression, and herpes viral reactivation in pregnancy are understudied and the molecular pathways such as the neuroimmune biogenic amine pathway are unidentified. Chronic stress shifts the T helper-1 cell (Th1) cytokine profile to a Th2 profile, which favors virus induced pathogenesis and survival. Pregnancy is also associated with a similar Th2 dominance. In non-pregnant individuals, exposure to psychological or physical stress may be associated with latent herpes viral reactivation and could result in behavioral deficits and depression. Normally, type-1 cytokines such as Interferon-gamma (IFN -gamma) and inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) induce indoleamine-2, 3-dioxygenase (IDO) activation which inhibits herpes virus replication and reactivation, decreases tryptophan production, and alters phenylalanine /tyrosine metabolism. Thus it is possible that prenatal depression may occur from tryptophan stealing through the IDO pathway which results in decreased serotonin as well as increased risk for latent herpes viral reactivation.
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