ABSTRACT
<p><b>AIM</b>To investigate the significance of the calcineurin (CaN) activation in active lupus nephritis patient.</p><p><b>METHODS</b>Peripheral blood mononuclear cells (PBMCs) were separated from twenty-one active LN patients and 12 healthy controls. Phosphatase activity of CaN was determined using the CaN assay kit by measuring the content of released PO4. Reverse transcription-PCR was used to detect the expression of CD40L mRNA. Flow cytometry analysis was used to detect the expression of CD40L in LN PBMC.</p><p><b>RESULTS</b>(1) Increased activation of CaN in spontaneous cultured PBMC in active LN group was found as compared with control group (46.08 +/- 5.58 vs 8.81 +/- 3.61, P < 0.01). In stimulated by PMA/Ionomycin , activity of CaN in active LN group was also higher than that of control (69.34 +/- 12.59 vs 37.12 +/- 11.57, P < 0.01). (2) Relative content of CD40L in PBMC in active LN groups increased significantly as compared with the control groups under spontaneous and PMA/Ionomycin-induced culture, respectively (P < 0.01). (3) FK506 reduced significantly production of CD40L in spontaneous and PMA/Ionomycin-induced PBMC of LN.</p><p><b>CONCLUSION</b>Elevated activation of CaN in active LN may participate in regulation overexpression of CD40L in PBMC of LN. Through inhibiting CaN activity, FK506 may prevent abnormal activation of CD40-CD40L costimulatory pathway in lupus nephritis.</p>