| Objective: To inverstigate whether Interferon-γinduce lipid deposition in mesangial cell by activating JAK / STAT signaling pathway, and whether HMGB1, SREBP-1 and FAS are involved in this process.Lupus nephritis (LN) is an inflammatory lesion of kidney caused by Autoimmune disease - systemic lupus erythematosus (SLE). LN can be associated with different pathological types of immunologic renal injury and different clinical presentations caused by renal damage,which involve hypertension, high glucose, high lipids. they can increase the severrity and mortality of SLE by interacting with each other. Currently the pathogenesis of systemic lupus erythematosus is still not clear, but dysfunction of immune cells and cytokines imbalance are the core of SLE pathogenesis. interferon-γ(IFN-γ) is an important cytokine in the pathogenesis of SLE, with the function of promoting disease, and playing the dual role in the disease and IFN-γis closely related with kidney damage. Both clinical and experimental studies have shown that: patients with SLE are associated with abnormal lipid metabolism and renal injury, and lipid metabolism can increase the renal lesions, the renal injury aggravate the abnormal of lipid metabolis. Our previous experimental study had been shown that there were abnormal of lipid metabolism and overexpression of high mobility group protein 1 (HMGB1) in the pathogenesis of lupus nephritis. A large number of studies have shown that HMGB1 with sterol regulatory element binding protein -1 (SREBP-1) interacted with each other, and then increased fatty acid synthase (FAS), which both involved in lipid metabolism. However, whether INF-γcaused lipid deposition by up-regulating of HMGB1, SREBP-1 expression, and whether JAK / STAT signaling pathway was involved in this process is not clear.Therefore, the mouse mesangial cell(MMC) were used in this study based on the prior experiments, and observed the effect of IFN-γon the JAK1, p-JAK1, JAK2, p-JAK2, STAT1, p-STAT1, HMGB1, SREBP-1, FAS expression, and then analyzed the relationship between those expression and lipid deposition in the MC cells; To investigate whether JAK inhibitor AG490 could reduce the lipid deposition in the IFN-γgroup in order to clarify the role of IFN-γin pathogenesis of lupus nephritis. There results would play an important role in clarifying the molecular mechanism of abnormal lipid metabolism in lupus nephritis pathogenesis and providing impotant experimental basis for seraching an effective clinical treatment options.Methods: Mouse mesangial cells (MMC) were randomly divided into normal control group, IFN-γ(500 IU / ml) stimulation group and INF-γ+ AG490 (INF-γ500 IU / ml + AG490 200μmol/ml) group after being cultured in serum-free medium for 12h to synchronization, then the cells were collected to extract total RNA and protein at 0,2,4,6,8,12 h.1 p-JAK1, JAK1, p-JAK2, JAK2, p-STAT1, STAT1 protein expression were detected at 0,2,4,6,8,12 h by Western blot.2 HMGB1, SREBP-1, FAS protein and mRNA expression were detected at 0,2,4,8,12h by Western blot and RT-PCR.3 Lipid deposition in MC cells were detected by oil red O staining.Results:1 IFN-γpromoted JAK, STAT1 phosphorylation and STAT1 transfer into nucleus in mouse mesangial cells.In IFN-γgroup, p-JAK1, p-JAK2, p-STAT1 protein expression were higher than that in cells of normal culture group at 0,2,4,6,8,12h (P <0.05), and grandually increased with progress of time (from 0h to 2,4,6,8,12h); There were no significant difference of non-phosphorylated JAK1, JAK2, and STAT1 protein expressions at different time point in IFN-γgroup. Meanwhile, in IFN-γgroup, STAT1 nucleoprotein expression grandually increased at 0,2,4,6,8,12h. (P <0.05).Specific JAK inhibitor AG490 could reduce IFN-γmediated JAK1, JAK2, STAT1 activation. Compared with IFN-γgroup, p-JAK1, p-JAK2 , P-STAT1 protein expresson in IFN-γ+AG490 group significantly decreased at 0,2,4,6,8,12 h. At the same time, in IFN-γ+ AG490 group, STAT1 nucleoprotein expression was significantly lower than that in IFN-γgroup in time-dependent manner.2 Compared with normal control group, HMGB1, SREBP-1 and FAS mRNA and protein expression were grandually higher at 0,2,4,6,8,12h in IFN-γgroup than that in control group (P <0.05). However, pre-treatment of AG490 could decreased the expression of HMGB1, SREBP-1 and FAS mRNA and protein induced by IFN-γin time-dependent fashion.3 In vitro, IFN-γinduced lipid deposition of MMC at 6,8,12h with no significant difference. But in IFN-γ+AG490 group lipid accumulation were not detected.Conclusion:In vitro, IFN-γcould activate JAK/STAT signaling pathway in mouse mesangial cells and mediate lipid deposition. Meanwhile, up-regulation of HMGB1, SREBP-1 and FAS induced by JAK/STAT1 signal pathway might be involved in this process .
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