Hui-Chun Yu

Anti–citrullinated protein antibodies bind surface-expressed citrullinated Grp78 on monocyte/macrophages and stimulate tumor necrosis factor α production

OBJECTIVE Anti-citrullinated protein antibodies (ACPAs), which are the most specific autoantibody marker in patients with rheumatoid arthritis (RA), correlate with disease activity; however, the role of ACPAs in RA pathogenesis has not been elucidated. We hypothesized that ACPAs may directly stimulate mononuclear cells to produce inflammatory cytokines. Thus, we identified cognate antigens of ACPAs on monocyte/macrophages and examined their immunopathologic roles in the pathogenesis of RA. METHODS ACPAs were purified from pooled ACPA-positive RA sera by cyclic citrullinated peptide-conjugated affinity column. After coculture of U937 cells with ACPAs, the tumor necrosis factor alpha (TNFalpha) production and NF-kappaB DNA binding activity of the cells were measured by enzyme-linked immunosorbent assay. The cognate antigens of ACPAs on the U937 cell surface were probed by ACPAs, and the reactive bands were examined via proteomic analysis. RESULTS ACPAs specifically enhanced TNFalpha production and increased the DNA-binding activity of NF-kappaB in U937 cells. Proteomic analysis revealed that Grp78 protein (72 kd) was one of the cognate antigens of ACPAs. The truncated form of cell surface-expressed Grp78 (55 kd) on U937 cells contained citrulline capable of binding with ACPAs. After citrullination, glutathione S-transferase-tagged recombinant Grp78 (97.52 kd) became a 72-kd fragment and bound with ACPAs. ACPAs also bound to human monocytes and lymphocytes to promote TNFalpha production. CONCLUSION We clearly demonstrated that ACPAs enhance NF-kappaB activity and TNFalpha production in monocyte/macrophages via binding to surface-expressed citrullinated Grp78.

Decreased microRNA(miR)-145 and increased miR-224 expression in T cells from patients with systemic lupus erythematosus involved in lupus immunopathogenesis

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with abnormal T cell immune responses. We hypothesized that aberrant expression of microRNAs (miRNAs) in T cells may contribute to the pathogenesis of SLE. First, we analysed the expression profiles of 270 human miRNAs in T cells from five SLE patients and five healthy controls and then validated those potentially aberrant‐expressed miRNAs using real‐time polymerase chain reaction (PCR). Then, the expression of mRNAs regulated by these aberrant‐expressed miRNAs was detected using real‐time PCR. Finally, miRNA transfection into Jurkat T cells was conducted for confirming further the biological functions of these miRNAs. The initial analysis indicated that seven miRNAs, including miR‐145, miR‐224, miR‐513‐5p, miR‐150, miR‐516a‐5p, miR‐483‐5p and miR‐629, were found to be potentially abnormally expressed in SLE T cells. After validation, under‐expressed miR‐145 and over‐expressed miR‐224 were noted. We further found that STAT1 mRNA targeted by miR‐145 was over‐expressed and apoptosis inhibitory protein 5 (API5) mRNA targeted by miR‐224 was under‐expressed in SLE T cells. Transfection of Jurkat cells with miR‐145 suppressed STAT1 and miR‐224 transfection suppressed API5 protein expression. Over‐expression of miR‐224 facilitates activation‐induced cell death in Jurkat cells. In the clinical setting, the increased transcript levels of STAT1 were associated significantly with lupus nephritis. In conclusion, we first demonstrated that miR‐145 and miR‐224 were expressed aberrantly in SLE T cells that modulated the protein expression of their target genes, STAT1 and API5, respectively. These miRNA aberrations accelerated T cell activation‐induced cell death by suppressing API5 expression and associated with lupus nephritis by enhancing signal transducer and activator of transcription‐1 (STAT)‐1 expression in patients with SLE.

Increased miR-223 expression in T cells from patients with rheumatoid arthritis leads to decreased insulin-like growth factor-1-mediated interleukin-10 production

We hypothesized that the aberrant expression of microRNAs (miRNAs) in rheumatoid arthritis (RA) T cells was involved in the pathogenesis of RA. The expression profile of 270 human miRNAs in T cells from the first five RA patients and five controls were analysed by real‐time polymerase chain reaction. Twelve miRNAs exhibited potentially aberrant expression in RA T cells compared to normal T cells. After validation with another 22 RA patients and 19 controls, miR‐223 and miR‐34b were over‐expressed in RA T cells. The expression levels of miR‐223 were correlated positively with the titre of rheumatoid factor (RF) in RA patients. Transfection of Jurkat cells with miR‐223 mimic suppressed insulin‐like growth factor‐1 receptor (IGF‐1R) and transfection with miR‐34b mimic suppressed cAMP response element binding protein (CREB) protein expression by Western blotting. The protein expression of IGF‐1R but not CREB was decreased in RA T cells. The addition of recombinant IGF‐1‐stimulated interleukin (IL)‐10 production by activated normal T cells, but not RA T cells. The transfection of miR‐223 mimic impaired IGF‐1‐mediated IL‐10 production in activated normal T cells. The expression levels of SCD5, targeted by miR‐34b, were decreased in RA T cells after microarray analysis. In conclusion, both miR‐223 and miR‐34b were over‐expressed in RA T cells, but only the miR‐223 expression levels were correlated positively with RF titre in RA patients. Functionally, the increased miR‐223 expression could impair the IGF‐1‐mediated IL‐10 production in activated RA T cells in vivo, which might contribute to the imbalance between proinflammatory and anti‐inflammatory cytokines.

Aberrant expression of microRNAs in T cells from patients with ankylosing spondylitis contributes to the immunopathogenesis

Ankylosing spondylitis (AS) is a chronic inflammatory disorder characterized by dysregulated T cells. We hypothesized that the aberrant expression of microRNAs (miRNAs) in AS T cells involved in the pathogenesis of AS. The expression profile of 270 miRNAs in T cells from five AS patients and five healthy controls were analysed by real‐time polymerase chain reaction (PCR). Thirteen miRNAs were found potentially differential expression. After validation, we confirmed that miR‐16, miR‐221 and let‐7i were over‐expressed in AS T cells and the expression of miR‐221 and let‐7i were correlated positively with the Bath Ankylosing Spondylitis Radiology Index (BASRI) of lumbar spine in AS patients. The protein molecules regulated by miR‐16, miR‐221 and let‐7i were measured by Western blotting. We found that the protein levels of Toll‐like receptor‐4 (TLR‐4), a target of let‐7i, in T cells from AS patients were decreased. In addition, the mRNA expression of interferon (IFN)‐γ was elevated in AS T cells. Lipopolysaccharide (LPS), a TLR‐4 agonist, inhibited IFN‐γ secretion by anti‐CD3+anti‐CD28 antibodies‐stimulated normal T cells but not AS T cells. In the transfection studies, we found the increased expression of let‐7i enhanced IFN‐γ production by anti‐CD3+anti‐CD28+ lipopolysaccharide (LPS)‐stimulated normal T cells. In contrast, the decreased expression of let‐7i suppressed IFN‐γ production by anti‐CD3+anti‐CD28+ LPS‐stimulated AS T cells. In conclusion, we found that miR‐16, miR‐221 and let‐7i were over‐expressed in AS T cells, but only miR‐221 and let‐7i were associated with BASRI of lumbar spine. In the functional studies, the increased let‐7i expression facilitated the T helper type 1 (IFN‐γ) immune response in T cells.

Higher LPS-stimulated TNF-α mRNA levels in peripheral blood mononuclear cells from Chinese ankylosing spondylitis patients with −308G/A polymorphism in promoter region of tumor necrosis factor: association with distinct A33/B58/Cw10 haplotypes

To investigate the effects of TNF-α −308, −238 promoter polymorphisms on TNF-α transcription in B27 positive Chinese patients with ankylosing spondylitis (AS). The possible relationship between polymorphisms, MHC antigens, and quantitative TNF-α mRNA expression were evaluated. Single nucleotide polymorphisms (SNPS) of TNF-α −308 and −238 were performed by PCR-amplification refractory mutation system method (PCR-ARMS) in sixty-seven B27-positive AS patients and 60 HLA-B27 positive healthy controls in Chinese. Quantitative measurement of TNF-α mRNA in peripheral blood mononuclear cells was performed with real time RT-PCR. The polymorphisms were correlated to quantitative TNF-α mRNA, and MHC antigens (determined by SSP method) in AS patients. The prevalence rate of both −308G/A and −238G/A TNF-α promoter polymorphisms in patients were not significantly different from those in normal subjects. However, a significant high LPS-stimulated TNF-α mRNA expression was found in peripheral blood mononuclear cells from patients with promoter −308G/A polymorphism (TNF2) as compared to those in −308G/G genotype (TNF1). Furthermore, −308G/A polymorphism in patients was found to be tightly associated with distinct haplotypes of A33/B58/Cw10 [12 out of 14 –308G/A patients (85.7%) versus none in 53 –308G/G patients], independent of B27 antigen. HLA-A33-B58-Cw10 haplotypes associated TNF-α promoter −308G/A polymorphism might play an important role in disease pathogenesis of AS in Chinese population, partially related to a driving force of a higher TNF-α production. It confirms once again the importance and complexity of MHC related molecules in disease pathogenesis of AS.

Increased expression of long noncoding RNAs LOC100652951 and LOC100506036 in T cells from patients with rheumatoid arthritis facilitates the inflammatory responses.

The aim of this study was to evaluate whether the presence of aberrantly expressed lncRNAs could promote T cell inflammatory responses in patients with RA. The expression levels of 10 potential aberrantly expressed lncRNAs were evaluated in T cells from 39 patients with RA and 17 controls using real-time reverse transcription polymerase chain reaction. The aberrantly expressed lncRNAs were measured in Jurkat cells co-cultured with or without ionomycin and phorbol 12-myristate 13-acetate. Transfection studies using small interfering RNA (siRNA) were conducted for biological functions, and microarray analysis was performed to search for target genes of specific lncRNAs. We confirmed that the expression levels of LOC100652951 and LOC100506036 were higher in RA T cells compared with controls. RA patients treated with biologic agents had lower expression levels of LOC100652951, and female RA patients had lower LOC100506036 expression levels after multivariate analysis. After activation, the expression levels of LOC100506036, but not LOC100652951, increased in Jurkat cells. Transfection of siRNA targeting LOC100506036 inhibited interferon gamma production and the expression of nuclear factor of activated T cells in activated Jurkat cells. After the microarray analysis with validation, inhibition of LOC100506036 expression by siRNA leaded to the decreased expression of sphingomyelin phosphodiesterase 1 (SMPD1). In conclusion, the expression levels of LOC100652951 and LOC100506036 were increased in RA T cells. Treatment with biologic agents could lower the expression of LOC100652951 in RA T cells. LOC100506036 could regulate the expression of SMPD1 and NFAT1 and could contribute to the inflammatory responses in RA.

Anti-citrullinated protein antibodies activated ERK1/2 and JNK mitogen-activated protein kinases via binding to surface-expressed citrullinated GRP78 on mononuclear cells.

In a previous study, we found that anti-citrullinated protein antibodies (ACPAs) enhance nuclear factor (NF)-κB activity and tumor necrosis factor (TNF)-α production by normal human peripheral blood mononuclear cells (PBMCs) and U937 cells via binding to surface-expressed citrullinated glucose-regulated protein 78 (cit-GRP78). However, the downstream signaling pathways remain unclear after binding. In the present study, we firstly measured the effects of different kinase inhibitors on ACPA-mediated TNF-α production from normal PBMCs and monocytes. Then, the native and phosphorylated mitogen-activated protein kinases (MAPKs) were detected in ACPA-activated U937 cells by Western blotting. We also explored the role of the phosphoinositide 3-kinase (PI3K)-Akt pathway in activating IκB kinase alpha (IKK-α) in ACPA-stimulated U937 cells. Finally, we measured the amount of cit-GRP78 from PBMC membrane extracts in RA patients and controls. We found that MAPK and Akt inhibitors, but not PI3K inhibitor, remarkably suppressed ACPA-mediated TNF-α production. Interestingly, ACPAs selectively activated extracellular signal-regulated kinase 1/2 (ERK1/2) and c-jun N-terminal kinase (JNK), but not p38 MAPK, in U937 cells. This activation was suppressed by cit-GRP78, but not GRP78. The JNK activation further enhanced the phosphorylation of Akt and IKK-α. The expression of cit-GRP78 on cell membrane was higher in RA than normal PBMCs. Taken together; these results suggest that through binding to surface, over-expressed cit-GRP78 on RA PBMCs, ACPAs selectively activate ERK1/2 and JNK signaling pathways to enhance IKK-α phosphorylation, which leads to the activation of NF-κB and the production of TNF-α .

Nifedipine suppresses Th1/Th2 cytokine production and increased apoptosis of anti-CD3 + anti-CD28-activated mononuclear cells from patients with systemic lupus erythematosus via calcineurin pathway

Increased Ca(2+) influx is found in mononuclear cells (MNC) of patients with systemic lupus erythematosus (SLE). The role of calcineurin and potential implication of calcium channel blocker to suppress the abnormal Ca(2+) influx in SLE remain to be determined. In the present study, we found that the expression and phosphatase activity of calcineurin, but not calcineurin inhibitor in SLE-MNC were greater than normal MNC. Functionally, 1 microM nifedipine could suppress SLE-MNC IFN-gamma secretion but 10 microM nifedipine was required for suppressing that of normal MNC. IL-10 secretion by both SLE-MNC and normal MNC was suppressed by 1 microM nifedipine. However, high dose of nifedipine (50 microM) suppressed NFATc1 activation in SLE-MNC and enhanced apoptosis of anti-CD3 + anti-CD28-activated SLE-MNC irrelevant to expression of Fas ligand. These data suggest that SLE-MNC overexpressed calcineurin and hyper-responded to L-type Ca(2+) channel blocker-mediated apoptosis and cytokine suppression. We proposed that L-type Ca(2+) channel blocker maybe a potential medication for controlling SLE.

Aberrant T cell expression of Ca2+ influx-regulated miRNAs in patients with systemic lupus erythematosus promotes lupus pathogenesis

OBJECTIVE The aim of this study was to investigate the pathogenic role of calcium (Ca(2+)) influx-regulated microRNAs (miRNAs) in T cells from patients with SLE. METHODS Expression profiles of 270 human miRNAs in Jurkat cells co-cultured with or without ionomycin were analysed by real-time PCR. Differential expression of miRNAs in T cell samples from 28 patients with SLE (SLE T cells) and 20 healthy controls were investigated using western blot analysis of proteins expressed by respective miRNA target transcripts. Transfection studies were conducted to investigate miRNA-specific biological functions. RESULTS Initial analysis revealed differential expression of nine miRNAs in Jurkat cells after co-culture with ionomycin. Of these, miR-524-5p and miR-449b were overexpressed in SLE T cells. Levels of expressed miR-524-5p showed a significant direct correlation with the SLEDAI. Transfection of Jurkat cells with miR-524-5p mimic suppressed Jagged-1 and Hes-1 protein expression. Likewise, expression of both Jagged-1 and Hes-1 proteins were diminished in SLE T cells. Upon activation of Jurkat cells transfected with miR-524-5p mimic, production of IFN-γ increased but the apoptotic rate was unaffected. CONCLUSION In SLE T cells, miR-524-5p and miR-449b (both regulated by Ca(2+) influx) were overexpressed. Moreover, increased miR-524-5p expression, as shown by patients with SLE, directly paralleled disease activity (SLEDAI). Transfection of miR-524-5p also enhanced IFN-γ production in activated Jurkat cells.

Anti-citrullinated protein antibodies suppress let-7a expression in monocytes from patients with rheumatoid arthritis and facilitate the inflammatory responses in rheumatoid arthritis.

We hypothesized that anti-citrullinated protein antibodies (ACPAs) could affect the expression of miRNAs in monocytes and contribute to the inflammatory responses in rheumatoid arthritis (RA). The expression profiles of 270 human miRNAs, co-cultured with ACPAs or human immunoglobulin G (IgG), were analyzed using real-time polymerase chain reaction. Ten miRNAs exhibited differential expression in U937 cells after co-cultured with ACPAs compared with human IgG. The expression levels of these miRNAs were investigated in monocytes from 21 ACPA-positive RA patients and 13 controls. Among these miRNAs, the expression levels of let-7a was decreased in monocytes from ACPA-positive RA patients. The expression levels of let-7a showed a negative correlation with positivity of rheumatoid factor in patients sampled. We found that transfection of U937 cells with let-7a mimic suppressed K-Ras protein expression. In the ACPA-mediated signaling pathway, transfection of U937 cells with let-7a mimic suppressed the ACPA-enhanced phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2 (ERK1/2), and the expression and secretion of interleukin (IL)-1β. In conclusion, ACPA-mediated decreased let-7a expression in monocytes from ACPA-positive RA patients. Decreased let-7a expression was associated with the positivity of RF in ACPA-positive RA patients. The decreased expression of let-7a could facilitate the inflammatory pathway via enhanced ACPA-mediated phosphorylation of ERK1/2 and JNK and increased expression of IL-1β through an increase in the expression of Ras proteins.