Diabetic hepatic
fibrosis (DHF) is a progressive
liver disease and a chronic complication of
diabetes mellitus. The main cause of DHF is the activation of quiescent hepatic stellate cells (HSCs) by high
glucose stimulation.
Dopamine receptor D2 (DRD2)-mediated
dopamine signalling can be involved in the regulation of diabetic
liver disease, but the exact role of DRD2 in DHF is still poorly understood. This study aimed to investigate the protective effect of DRD2 inhibition on diabetic
liver fibrosis and the potential mechanism. We established both
streptozotocin (STZ)-induced
type 1 diabetes (T1D, fed for 20 weeks) rat model and high
glucose (HG, 40 mmol/L)-stimulated HSCs model. The results from both the rats with STZ and the HSCs treated with HG showed increased expression of DRD2, NOX-5,
inflammation-related
proteins (IL-6 and TNFα) and
fibrosis-related
proteins (TGF-β1, CO-Ⅰ/Ⅲ/ IV,
MMP-2/9 and
fibronectin). In vivo, the serum
aspartate aminotransferase (AST),
alanine aminotransferase (ALT) and total
antioxidant capacity (T-AOC) levels were significantly increased, and
hematoxylin-
eosin (HE) staining, Masson staining, and electron microscopy revealed liver lesions and hepatocyte injury. In addition, HG-treated HSCs exhibited altered oxidative stress - related indexes, including
superoxide dismutase (SOD),
malondialdehyde (MDA) and
reactive oxygen species (ROS), changed and abnormally proliferated in vitro. TGF-β1, the phosphorylated Smad2, nuclear NFκB-p65, phosphorylated NFκB-p65 and phosphorylated IκBα were also increased. Interestingly,
haloperidol (DRD2 inhibitor) and
n-acetyl-L-cysteine (NAC, an
active oxygen scavenger) reduced the above-mentioned changes. In conclusion, DRD2 inhibition can reduce diabetic HSCs oxidative damage and fibrotic proliferation partly via the TGF-β1/Smads and NFκB pathways.