Effects Of Methylprednisolone On Expression Of Monocyte Chemoattractant Protein-1 In Kidneys Of BXSB Mice

Objective(1) To investigate whether there is expression of monocyte chemoattractant protein-1 (MCP-1) in kidneys of BXSB mice.(2) To investigate whether methylprednisolone(MPS) ameliorate LN in BXSB mice via inhibiting MCP-1 expression and the following infiltration of monocytes in kidneys of BXSB mice.MethodsTwelve 18-week-old male BXSB mice displaying clinical symptoms of glomerulonephritis were randomly grouped into two, i.e. BXSB treatment group (MPS group) and BXSB control group,with 6 mice in each group. Mice in group BXSB treatment group were treated(i.p.) with MPS (25mg/kg.d) dissolved in N.S.for three weeks. Mice in BXSB control group were given N.S. alone. 6 age- and sex- matched BALB/c mice were used as normal mice(non-LN) controls that were treated in the same way as the BXSB controls. 24h total volume urines of all mice were collected at the end of every week's treatment, with dimethylbenzene as preservative. After three weeks'treatment, all mice were killed. Mice's kidneys were removed and put into liguid nitrogen as soon as possible. MCP-1 expression was investigated by means of RT-PCR,hematoxylin-eosin staining and immunohistochemistry staining. Urinary protein was also measured. Medical imaging analysis system was performed to detect the relationship between MCP-1 expression and proteinuria .Results(1) Compared with BXSB control mice, 24h total amount of urinary protein of mice in BXSB treatment group significantly decreased after three weeks'treatment(p<0.01).(2) Semi-quantative RT-PCR demonstrates that MCP-1 was strongly expressed in kidneys of all BXSB mice, while no signals of expression were found in kidneys of BALB/c mice. MCP-1 expression in kidneys of mice in BXSB treatment group dramatically reduced in comparison with that of BXSB model mice(p<0.01).(3) Hematoxylin-eosin staining showed that there was no obvious pathological alterations in kidneys of BALB/c mice,and kidneys of BXSB mice presented various pathological alterations similar to human LN, such as mesangial cells proliferation , endothelial cells proliferation, interstitial inflammation, cellular crescent formation, etc.,and the infiltration of inflammation cells decreased in kidneys of BXSB treatment group.(4) Immunohistochemistry staining showed that there was no expression signal of MCP-1 in kidneys of BALB/c mice.in kidneys of BXSB control mice, stronger MCP-1 staining was found in cytoplasm of tubular epithelial cells than glomerular. Weaker MCP-1 staining was found inkidneys of mice in BXSB treatment group in the same location as the BXSB control mice. Although the number of infiltrating inflammation cells in the renal interstitium and glomeruli reduces.(5) Medical imaging analysis system showed that MCP-1 expression in tubular cells in BXSB control group was closely correlated with proteinuria.Significent down-regulation of MCP-1 expression was observed in BXSB treatment group,and MCP-1 expression in tubular cells was also closely correlated with proteinuria.Conclusion(1) There is no expression of MCP-1 in kidneys of BALB/c mice.In kidneys of BXSB control mice, stronger MCP-1 staining is found in cytoplasm of tubular epithelial cells than glomerular. MCP-1 expression in tubular cells in BXSB control group is closely correlated with proteinuria. so,MCP-1 may mediate LN in BXSB mice.(2) MPS can reduce urinary protein and ameliorate LN of BXSB mice, partly via inhibiting MCP-1 expression in kidney and thus decreasing monocytes infiltrating in the renal interstitium and glomeruli.