Calcineurin deficiency decreases inflammatory lesions in transforming growth factor beta1-deficient mice

Loss of the Protein Cystathionine β-Synthase During Kidney Injury Promotes Renal Tubulointerstitial Fibrosis

BACKGROUND/AIMS

Renal tubulointerstitial fibrosis (TIF) is the common pathway of progressive chronic kidney disease. Inflammation has been widely accepted as the major driving force of TIF. Cystathionine β-synthase (CBS) is the first and rate-limiting enzyme in the transsulfuration pathway. CBS is considered to play protective role in liver and pulmonary fibrosis, but its role in TIF remains unknown. The purpose of this study was to investigate the potential role and mechanism of CBS in renal inflammation and TIF.

METHODS

Renal function, tubulointerstitium damage index score, extracellular matrix (ECM) deposition, and the expressions of collagen I, collagen III, fibronectin, CD3, CD68, IL-1β, TNF-α were measured in sham operation and unilateral ureteral obstruction (UUO) rats. Proteomics and gene array analysis were performed to screen differentially expressed molecules in the development of renal inflammation and TIF in UUO rats. The expression of CBS was detected in patients with obstructive nephropathy and UUO rats. We confirmed the expression of CBS using western blot and real-time PCR in HK-2 cells. Overexpression plasmid and siRNA were transfected specifically to study the possible function of CBS in HK-2 cells.

RESULTS

Abundant expression of CBS, localized in renal tubular epithelial cells, was revealed in human and rat renal tissue, which correlated negatively with the progression of fibrotic disease. Expression of CBS was dramatically decreased in the obstructed kidney from UUO rats as compared with the sham group (SHM). In addition, knocking down CBS exacerbated extracellular matrix (ECM) deposition, whereas CBS overexpression attenuated TGF-β1-induced ECM deposition in vitro. Inflammatory and chemotactic factors were also increased in CBS knockdown HK-2 cells stimulated by IL-1β.

CONCLUSIONS

These findings establish CBS as a novel inhibitor in renal fibrosis and as a new therapeutic target in patients with chronic kidney disease.

Human Parthenogenetic Embryonic Stem Cell-Derived Neural Stem Cells Express HLA-G and Show Unique Resistance to NK Cell-Mediated Killing

Parent-of-origin imprints have been implicated in the regulation of neural differentiation and brain development. Previously we have shown that, despite the lack of a paternal genome, human parthenogenetic (PG) embryonic stem cells (hESCs) can form proliferating neural stem cells (NSCs) that are capable of differentiation into physiologically functional neurons while maintaining allele-specific expression of imprinted genes. Since biparental ("normal") hESC-derived NSCs (N NSCs) are targeted by immune cells, we characterized the immunogenicity of PG NSCs. Flow cytometry and immunocytochemistry revealed that both N NSCs and PG NSCs exhibited surface expression of human leukocyte antigen (HLA) class I but not HLA-DR molecules. Functional analyses using an in vitro mixed lymphocyte reaction assay resulted in less proliferation of peripheral blood mononuclear cells (PBMC) with PG compared with N NSCs. In addition, natural killer (NK) cells cytolyzed PG less than N NSCs. At a molecular level, expression analyses of immune regulatory factors revealed higher HLA-G levels in PG compared with N NSCs. In line with this finding, MIR152, which represses HLA-G expression, is less transcribed in PG compared with N cells. Blockage of HLA-G receptors ILT2 and KIR2DL4 on natural killer cell leukemia (NKL) cells increased cytolysis of PG NSCs. Together this indicates that PG NSCs have unique immunological properties due to elevated HLA-G expression.

Human neural stem/progenitor cells derived from embryonic stem cells and fetal nervous system present differences in immunogenicity and immunomodulatory potentials in vitro

To develop cell therapies for damaged nervous tissue with human neural stem/progenitor cells (hNPCs), the risk of an immune response and graft rejection must be considered. There are conflicting results and lack of knowledge concerning the immunocompetence of hNPCs of different origin. Here, we studied the immunogenicity and immunomodulatory potentials of hNPCs cultured under equivalent conditions after derivation from human embryonic stem cells (hESC-NPCs) or human fetal spinal cord tissue (hfNPCs). The expression patterns of human leukocyte antigen, co-stimulatory and adhesion molecules in hESC-NPCs and hfNPCs were relatively similar and mostly not affected by inflammatory cytokines. Unstimulated hfNPCs secreted more transforming growth factor-β1 (TGF-β1) and β2 but similar level of interleukin (IL)-10 compared to hESC-NPCs. In contrast to hfNPCs, hESC-NPCs displayed 4-6 fold increases in TGF-β1, TGF-β2 and IL-10 under inflammatory conditions. Both hNPCs reduced the alloreaction between allogeneic peripheral blood mononuclear cells (PBMCs) and up-regulated CD4(+)CD25(+)forkhead box P3 (FOXP3)(+) T cells. However, hESC-NPCs but not hfNPCs dose-dependently triggered PBMC proliferation, which at least partly may be due to TGF-β signaling. To conclude, hESC-NPCs and hfNPCs displayed similarities but also significant differences in their immunocompetence and interaction with allogeneic PBMCs, differences may be crucial for the outcome of cell therapy.

Calcineurin stimulates the expression of inflammatory factors in RAW 264.7 cells by interacting with proteasome subunit alpha type 6

Calcineurin is the only Ca(2+)-dependent serine/threonine-specific protein phosphatase and is considered a potential regulator of many intracellular signaling events. In this study we identified a novel interaction between calcineurin and the 20S proteasome subunit PSMA6 that increased intracellular proteasomal activity. Using RAW 264.7 macrophage cells, we demonstrated that expression of inflammatory factors was induced by calcineurin, and suppressed by the calcineurin inhibitor FK506. We also found that these calcineurin-activated processes result from activation of NF-κB, and that the interaction of calcineurin with PSMA6 stimulates transcription by NF-κB via degradation of IκB by the ubiquitin-proteasome pathway. These findings indicate that calcineurin is required for expression of inflammatory factors, and reveal a novel process of calcineurin-mediated activation of NF-κB.

Divergent effects of calcineurin Aβ on regulatory and conventional T-cell homeostasis

Calcineurin (CN) is a phosphatase that activates nuclear factor of activated T cells (NFAT). While the CN inhibitors cyclosporine A (CsA) and tacrolimus (FK506) can prevent graft rejection, they also cause inflammatory diseases. We investigated the role of calcineurin using mice deficient in the CN catalytic subunit Aβ (CNAβ). Cnab(-/-) mice exhibit defective thymocyte maturation, splenomegaly and hepatomegaly. Further, as Cnab(-/-) mice age, they exhibit spontaneous T-cell activation and enhanced production of proinflammatory cytokines (IL-4, IL-6, and IFNγ). FOXP3(+) T(reg) cells were significantly decreased in Cnab(-/-) mice likely contributing to increased T-cell activation. Interestingly, we found that CNAβ is critical for promotion of BCL-2 expression in FOXP3(+) T(reg) and for permitting TGFβ signaling, as TGFβ induces FOXP3 in control but not in Cnab(-/-) T-cells. Together, these data suggest that CNAβ is important for the production and maintenance of T(reg) cells and to ensure mature T-cell quiescence.