Serotonin exerts important functions in several liver pathophysiological processes. In this study, we investigated the role of
serotonin in
concanavalin A (Con A)-induced
liver fibrosis (LF) in mice and the underlying mechanisms. To establish the mouse model of LF, mice of wild-type (WT) and
tryptophan hydroxylase 1 (Tph1) knockout (
serotonin depletion) received Con A for 8 successive weeks. Degree of
fibrosis was assessed by Sirius red staining, as well as the measurements of alpha smooth muscle actin (α- SMA),
hydroxyproline (Hyp) and
type I collagen in liver tissues. To elucidate the potential mechanisms, we assessed the effect of
serotonin depletion on inflammatory, oxidative stress as well as TGF-β1/Smads signaling pathway. We found that
serotonin depletion significantly inhibited
collagen deposition as evaluated by less collagenous fiber in Sirus Red staining and reduced contents of Hyp and
type I collagen. In addition, the absence of
serotonin significantly inhibited the release of several inflammatory
cytokines, including
interleukin-6 (IL-6),
interferon-gamma (IFN-γ),
tumor necrosis-alpha (TNF-α), and
transforming growth factor β1 (TGF-β1). Oxidative stress was also largely mitigated in LF mice with
serotonin deficiency as manifested by the decreases of oxidative stress markers (
malonaldehyde (MDA) and
myeloperoxidase (MPO)), as well as the increases of
antioxidant stress indicators (
glutathione (GSH), and GSH-px,
catalase (CAT),
superoxide dismutase (SOD)) in liver tissues. Moreover, the lack of
serotonin may provide an antifibrotic role by inhibiting the intrahepatic expressions of TGF-β1, phosphorylated-smad2 (p-smad2), and phosphorylated-smad3 (p-smad3). These results indicated that,
serotonin depletion attenuates Con A-induced LF through the regulation of inflammatory response, oxidative stress injury, and TGF-β1/Smads signaling pathway.