Objective        To investigate the effect of ursolic acid(UA) on leptin induced JAK2-STAT3 activation

ROS generation and mRNA expression of matrix metalloproteinase inhibition factor-1 (TIMP-1) and matrix metalloproteinase 1 (MMP-1) in hepatic stellate cells (HSC).      Methods       HSC-T6 cells were treated with recombinant rat leptin (100 ng/ml). Intervention groups were pretreated with several inhibitors respectively - UA (50 μmol/L)

N-acetyl-L-cysteine (NAC

10 mmol/L)

two phenylene iodine chloride OM (DPI

20 mmol/L）and JAK inhibitor AG490 for 30 min. The normal control group was not treated with any medication. Immunocytochemical staining assay was applied to evaluate phosphorylation of Janus kinase2 (JAK2) and protein expression of signal transducers and activators of transcription 3 (STAT3). Intracellular ROS level was measured by flow cytometry and mRNA expression of TIMP-1 and MMP-1 was evaluated by RT-PCR.       Results       Cytoplasmic p-JAK2 expression and nucleic p-STAT3 expression in HSC-T6 cells 2 hours after leptin induction were significantly increased as compared with that in the normal control group (P0.01). p-JAK2 and p-STAT3 expressions of the UA intervention group were significantly lower than that of the leptin-induced group (85.50±3.78 vs 96.67±3.01

26.50±3.66 vs 86.67±10.87

all P0.01). ROS levels of the intervention groups pretreated with UA

NAC

DPI and AG490 were lower than that of the leptin-induced group (43.62±5.58

55.56±6.43

36.54±3.21

48.12±6.63 vs 90.86±3.86

P0.01). Therefore

UA

NAC

DPI and AG490 blocked leptin-stimulated ROS production. However

ROS level of the UA intervention group was lower than that of the NAC intervention group (P0.01). Compared with leptin-induced group

TIMP-1 mRNA in UA intervention group was significantly down-regulated at 12 and 24 hours after the pretreatment (0.28±0.03 vs 0.37±0.01

0.29±0.04 vs 0.41±0.03

P0.01)

while MMP-1 mRNA expression was significantly increased (0.33±0.02 vs 0.26±0.02

0.37±0.04 vs 0.22±0.04

P0.01).      Conclusions       UA inhibits JAK2-STAT3 signal transduction and ROS production

down-regulates TIMP-1 expression and up-regulates MMP-1 exression in HSC induced by leptin.