Background: Endothelial expression of membrane-bound fractalkine/CX3CL1 (Fkn) reportedly acts as a strong mediator of inflammation. Toll-like receptor 3 (TLR3) axes are thought to play some roles in the development of chronic glomerulonephritis (CGN) including lupus nephritis (LN). However, detailed mechanism of TLR3-mediated Fkn expression in glomerular endothelial cells (GECs) remains to be elucidated. Methods: We examined the effect of polyinosinic-polycytidylic acid (poly IC) on Fkn expression in cultured human GECs. Fkn mRNA and protein levels were quantified by real-time PCR and enzyme-linked immunosorbent assay, respectively. To further elucidate the effects of poly IC on this signaling pathway, we used small interfering RNA (siRNA) to knockdown expression of TLR3, nuclear factor (NF)-κB p65, interferon (IFN)-β, and IFN regulatory factor 3 (IRF3). We then analyzed whether pretreatment of chloroquine or dexamethasone inhibits poly IC-induced Fkn expression. Results: We found that poly IC-induced Fkn expression in GECs, and that this involved NF-κB, IFN-β, and IRF3. Pretreating cells with chloroquine, but not dexamethasone attenuated poly IC-induced Fkn expression in GECs. Conclusion: Since the activation of TLR3/NF-κB/IFN-β/Fkn and TLR3/IRF3/Fkn axes is involved in inflammatory reactions in GECs, intervention of glomerular TLR3 signaling may be a suitable therapeutic strategy for treating CGN especially LN.

Recently, we found a strict bone association between Fibroblast growth factor 23 (FGF23) and Fetuin-A, both involved in cardiovascular and mineral bone disorders. In this study, an uninvestigated bone marrow positivity for both was found. Though the role of exogenous FGF23 on mesenchymal cells (MSCs) was reported, no information is as yet available on the possible production of this hormone by MSCs. To further analyze these uninvestigated aspects, we studied human primary cells and mouse and human cell lines by means of immunostaining, qRT-PCR, enzyme linked immunosorbent assays, chromatin immunoprecipitation, transfection, and a streamlined approach for the FGF23–Fetuin-A interaction called Duolink proximity ligation assay. Mesenchymal cells produce but do not secrete FGF23 and its expression increases during osteo-differentiation. Fibroblast growth factor 23 is also involved in the regulation of Fetuin-A by binding directly to the Fetuin-A promoter and then activating its transcription. Both FGF23 overexpression and addition induced an upregulation of Fetuin-A in the absence of osteo-inducer factors. Fibroblast growth factor 23 and Fetuin-A promoter were increased by osteo-inducer factors with this effect being abolished after FGF23 silencing. In conclusion, both FGF23 and Fetuin-A are present and strictly linked to each other in MSCs with FGF23 driving Fetuin-A production. This mechanism suggests a role for these two proteins in the osteoblast differentiation.

We report here the case of a 9-year-old Japanese boy with nephrotic syndrome caused by focal segmental glomerulosclerosis, which was refractory to treatment. Although aggressive immunosuppressive therapy consisting of methylprednisolone pulse therapy combined with cyclosporine A (CsA) and intermittent low density lipoprotein apheresis was effective in overcoming his steroid-resistant state, the child became persistently steroid-dependent, that is, more than 0.75 mg/kg per day of prednisolone combined with CsA was required to maintain a negative test for proteinuria. Since adverse effects of prednisolone, such as short stature, obesity, osteoporosis and cataract, were noted, CsA in his treatment regimen was replaced with tacrolimus at the dose of 0.1 mg/kg per day, with the trough blood level of the drug maintained at around 10 ng/ml. Within 4 months of the inclusion of tacrolimus in the treatment regimen, complete remission was achieved, with no recurrence of the proteinuria, while the prednisolone dose could be tapered to 0.3 mg/kg per day. No adverse effects of tacrolimus were observed. These clinical results suggest that tacrolimus may be the drug of choice in selected patients with refractory nephrotic syndrome, even if pediatric-onset cases, at least those in whom the steroid-sparing effects of CsA is unsatisfactory.