Effects Of TACI-Ig On MRL/lpr Mice And Activation Of JAK1-STAT1 Signaling Pathway In Lupus Nephritis

AIMTo observe the general signs, damage index and weight of MRL/lpr mice after TACI-Ig injected subcutaneously. The change of renal tissue, renal function and the levels of cytokines in serum were detected after TACI-Ig treatment. To study the effects of TACI-Ig on MRL/lpr mice and activation of JAK1-STAT1 signaling pathway in lupus nephritis.METHODSMRL/lpr mice were randomly divided into 6 groups, mice in group 1 were given normal saline as model group, mice in the other five groups were given TACI-Ig (3.75, 7.5, 15 mg·kg^-1), IgG-Fc (7.5 mg·kg^-1, negative control), prednisone (5 mg·kg^-1, positive control) respectively, continuously for 8 weeks. Normal control (BALB/c) group was given normal saline. All groups were treated subcutaneously once every other day except prednisone group (intragastrically once a day). The general signs, damage index and weight of MRL/lpr mice were observed after TACI-Ig treatment. Proteinuria of mice was detected by the demi-quantitate albustix. The sections of kidney tissues for pathological analysis were stained with HE. The serum levels of BUN, Cre and BLyS, IL-10, IFN-γwere determined by automatic biochemistry analyzer and ELISA kits, respectively. The expression of phosphorylated JAK1 and STAT1 in renal tissue was detected by immunohistochemical techniques.RESULTS1. Effects of TACI-Ig treatment on the general signs and damage index in MRL/lpr mice.MRL/lpr mice were treated subcutaneously once every other day. TACI-Ig (7.5, 15 mg·kg^-1) could improve the pelage gloss, hair loose and hair loss of MRL/lpr mice after 8 weeks. The levels of proteinuria and damage index were reduced remarkably.2. Effects of TACI-Ig treatment on weight of MRL/lpr mice.The results of animal weight showed that the weight of MRL/lpr mice gained slowly compared with normal control (BALB/c) group after 3 to 4 weeks. The average weight of animals in treatment group had no significant difference compared with model group.3. Effects of TACI–Ig treatment on renal histology in MRL/lpr mice.Renal histopathological results showed that the outline of glomerular was clear and mesangial cells without proliferation in normal control mice. There were obvious features of interstitial nephritis in model control mice, such as: mesangial cell proliferation, increased mesangial matrix, glomerular fibrosis, neutrophil local infiltration, crescent body formation. TACI-Ig (3.75mg·kg^-1) could not effectively reduce the proliferation of mesangial cells, TACI-Ig (7.5, 15 mg·kg^-1) could effectively alleviate mesangial cell proliferation, inflammatory state and glomerular fibrosis. Pre (5mg·kg^-1) had similar improvement effect. But IgG-Fc treatment had no obvious effect on pathological changes of animals.4. Effects of TACI-Ig treatment on renal function in MRL/lpr mice. The levels of Cre and BUN in MRL/lpr mice were significantly increased than normal control (BALB/c) mice. TACI-Ig (7.5, 15 mg·kg^-1) administration could remarkably reduce the levels of Cre and BUN in MRL/lpr mice. Pre had the same effect as TACI-Ig. There were no significant difference between IgG-Fc group and model group on the levels of Cre and BUN.5. Effects of TACI-Ig treatment on the serum levels of BLyS,IL-10 and IFN-γin MRL/lpr mice.The serum level of BLyS was significantly increased in MRL/lpr mice, subcutaneous injection of TACI-Ig (3.75,7.5,15 mg·kg^-1) could remarkably reduce the level of BlyS. Moreover, the levels of IFN-γand IL-10 were decreased by TACI-Ig (7.5,15 mg·kg^-1). Pre could also significantly reduce the level of BLyS, but it had no effect on the levels of IL-10 and IFN-γ. There were no significant differences between IgG-Fc group and model group on the levels of BLyS,IL-10 and IFN-γ.6. Effects of TACI-Ig treatment on the expression of p-JAK1 and p-STAT1 in renal tissue of MRL/lpr mice.Immunohistochemical results showed that the protein expression of p-JAK1, p-STAT1 in glomerular and interstitial of renal tissue was weakly positive or negative in normal BALB/c mice. The expression of p-JAK1, p-STAT1 was obviously increased in MRL/lpr model mice, especially in glomerular and renal interstitium, which was strongly positive, while it decreased with varying degrees compared with model group by TACI-Ig (3.75, 7.5 mg·kg^-1) treatment. The most obvious decreasing of the expression of p-JAK1, p-STAT1 protein was TACI-Ig 15 mg·kg^-1 treatment, which was weakly positive or negative in glomerular and interstitial. Pre had the same effect as TACI-Ig 15 mg·kg^-1. However, the expression of glomerular and interstitial was strongly positive in IgG-Fc group.CONCLUSIONS1. TACI-Ig (7.5, 15mg/kg) could significantly reduce the levels of proteinuria and damage index.2. There was no obvious effect to the weight of MRL/lpr mice by TACI-Ig treatment.3. Mesangial cell hyperplasia, glomerular fibrosis and inflammatory cell infiltration were alleviated effectively by TACI-Ig (7.5, 15mg/kg) treatment.4. The serum levels of BUN and Cre of MRL/lpr mice were remarkably decreased by TACI-Ig (7.5, 15mg/kg) treatment.5. The serum levels of BLyS, IL-10 and IFN-γwere obviously decreased by TACI-Ig (7.5, 15mg/kg) treatment.6. TACI-Ig treatment could decrease the protein expression of phosphorylated JAK1 and STAT1 in renal tissue.