LIGHT deficiency attenuates acute kidney disease development in an in vivo experimental renal ischemia and reperfusion injury model.

Ischemia-reperfusion (I/R), a leading risk factor of acute kidney injury (AKI), is associated with high mortality and risk of progression to chronic kidney disease. However, the molecular mechanism of I/R-AKI remains not fully understood, which hinders its efficient clinical treatment. In this study, we observed that LIGHT deficiency remarkably attenuated I/R-AKI, as evidenced by rescued renal function, ameliorated tubular cell apoptosis, and alleviated inflammatory responses. Consistently, blocking LIGHT signaling with its soluble receptor fusion proteins (HVEM-IgG-Fc or LTßR-IgG-Fc) improved I/R renal dysfunction. RNA-sequencing and corresponding results indicated that LIGHT promoted oxidative stress and inflammation triggered by ischemic injury. Moreover, LIGHT signaling augmented ischemic stress-induced mitochondrial dysfunction characterized by an imbalance in mitochondrial fission and fusion, decreased mtDNA copies, impaired mitophagy, and increased mitochondrial membrane potential (ΔΨm). Mechanistically, LIGHT promoted mitochondrial fission by enhancing Drp1 phosphorylation (Ser616) and its translocation to the mitochondria. In conclusion, these results suggest that LIGHT-HVEM/LTßR signaling is critical for the I/R-AKI pathogenesis and it is further confirmed to be related to the increase in I/R-induced oxidative stress and mitochondria dysfunction, which may be the underlying mechanism of LIGHT signaling-mediated I/R-AKI.

Bone Marrow Mesenchymal Stem Cells Exert Protective Effects After Ischemic Stroke Through Upregulation of Glutathione.

Bone marrow mesenchymal stem cells (BMSCs) have been shown to promote stroke recovery, however, the underlying mechanisms are not well understood. In this study naïve rats were intravenously injected with syngeneic BMSCs to screen for potential differences in brain metabolite spectrum versus vehicle-treated controls by capillary electrophoresis-mass spectrometry. A total of 65 metabolites were significantly changed after BMSC treatment. Among them, 5-oxoproline, an intermediate in the biosynthesis of the endogenous glutathione (GSH), was increased. To confirm the obtained results and investigate the metabolic pathways, BMSCs were injected into rats 24 h after middle cerebral artery occlusion (MCAO). Rats receiving vehicle solution and sham-operated animals served as controls. High performance liquid chromatography, reverse transcription-quantitative polymerase chain reaction, and Western blotting revealed that intravenous BMSC application increased the levels of 5-oxoproline and GSH in MCAO rats, as well as the expression of key enzymes involved in GSH synthesis including, gamma-glutamylcyclotransferase and gamma-glutamylcysteine ligase. Subsequent clinical investigation confirmed that acute ischemic stroke patients had higher plasma 5-oxoproline and GSH levels than age- and sex-matched non-stroke controls. The optimal cutoff value for 5-oxoproline diagnosing acute ischemic stroke (≤ 7d) was 3.127 µg/mL (sensitivity, 63.4 %; specificity, 81.2 %) determined by receiver characteristic operator curve. The area under the curve was 0.782 (95 % confidence interval: 0.718-0.845). Our findings indicate that BMSCs play a protective role in ischemic stroke through upregulation of GSH and 5-oxoproline is a potential biomarker for acute ischemic stroke. Ischemic stroke causes oxidative stress and induction of endogenous, glutathione-dependent anti-oxidative mechanisms. 5-oxoproline, an important metabolite in glutathione biosynthesis, could serve as a biomarker of acute ischemic stroke. Moreover, intravenous bone marrow mesenchymal stem cell (BMSC) treatment after experimental stroke upregulates the expression of key enzymes involved in glutathione synthesis, which results in better antioxidative defense and improved stroke outcome.

Tumor necrosis factor superfamily 14 is critical for the development of renal fibrosis.

OBJECTIVE: Tumor necrosis factor superfamily protein 14 (TNFSF14) was recently identified as a risk factor in some fibrosis diseases. However, the role of TNFSF14 in renal fibrosis pathogenesis remains unknown. RESULTS: It was found that TNFSF14 levels were significantly increased both in UUO-induced renal fibrotic mice and in patients with fibrotic nephropathy, compared with those in controls. Accordingly, Tnfsf14 deficiency led to a marked reduction in renal fibrosis lesions and inflammatory cytokines expression in the UUO mice. Furthermore, the levels of Sphk1, a critical molecule that causes fibrotic nephropathy, were remarkably reduced in Tnfsf14 KO mice with UUO surgery. In vitro recombinant TNFSF14 administration markedly up-regulated the expression of Sphk1 of primary mouse renal tubular epithelial cells (mTECs). CONCLUSION: TNFSF14 is a novel pro-fibrotic factor of renal fibrosis, for which TNFSF14 up-regulates Sphk1 expression, which may be the underlying mechanism of TNFSF14-mediated renal fibrosis. METHODS: We investigated the effect of TNFSF14 on renal fibrosis and the relationship between TNFSF14 and pro-fibrotic factor sphingosine kinase 1 (Sphk1) by using the unilateral urethral obstruction (UUO)-induced mice renal fibrosis as a model and the specimen of patients with fibrosis nephropathy, by Masson trichrome staining, immunohistochemistry, qRT-PCR, and western blot analysis.

LIGHT deficiency aggravates cisplatin-induced acute kidney injury by upregulating mitochondrial apoptosis.

Cisplatin is widely used as a chemotherapeutic agent for treating patients with solid tumors. The most common side effect of cisplatin treatment is nephrotoxicity. Recent studies have shown that mitochondrial apoptotic pathways are involved in cisplatin-induced acute kidney injury (Cis-AKI). LIGHT, the 14th member of the tumor necrosis factor superfamily (TNFSF14), was found to induce apoptosis of certain types of tumor cells. So far, a link between LIGHT and Cis-AKI has not been reported. In this study, we observed that expression of LIGHT and its receptors HVEM and LTßR was increased in kidney tissues of mice after cisplatin treatment. LIGHT deficiency aggravated kidney injury, as evidenced by more severe tubular injury; remarkably increased levels of serum creatinine (Scr), blood urea nitrogen (BUN), and both kidney injury molecule-1 (KIM-1) and inflammatory cytokine mRNAs in renal tissues. Moreover, in the renal tissues of LIGHT KO mice, cisplatin-induced mitochondrion injury and the levels of the pro-apoptotic molecules Bax, Cytochrome C (Cyt C), cleaved caspase-3, and cleaved caspase-9 were dramatically increased; in contrast, the expression of anti-apoptotic molecule Bcl-2 was markedly reduced, compared to those in WT mice, suggesting that LIGHT deficiency accelerated cisplatin-induced mitochondrial apoptosis of renal tubular cells in these mice. Accordingly, treatment with recombinant human LIGHT (rLIGHT) was shown to alleviate cisplatin-induced kidney injury in vivo. Similar results were observed after the human renal tubular epithelial cell line HK-2 cells exposure to rLIGHT stimulation, evidenced by the reduction in the mitochondrion dysfunction (as confirmed by the significant reduced oxidative stress and membrane potential changes) and in the percentage of cells apoptosis. While blocking LIGHT with the soluble fusion protein LTßR-Ig or HVEM-Ig accelerated the HK-2 cells apoptosis. In conclusion, LIGHT deficiency aggravates Cis-AKI by promoting mitochondrial apoptosis pathways.

LIGHT aggravates sepsis-associated acute kidney injury via TLR4-MyD88-NF-κB pathway.

Sepsis-associated acute kidney injury (SA-AKI) is a common clinical critical care syndrome. It has received increasing attention due to its high morbidity and mortality; however, its pathophysiological mechanisms remain elusive. LIGHT, the 14th member of the tumour necrosis factor (TNF) superfamily and a bidirectional immunoregulatory molecule that regulates inflammation, plays a pivotal role in disease pathogenesis. In this study, mice with an intraperitoneal injection of LPS and HK-2 cells challenged with LPS were employed as a model of SA-AKI in vivo and in vitro, respectively. LIGHT deficiency notably attenuated kidney injury in pathological damage and renal function and markedly mitigated the inflammatory reaction by decreasing inflammatory mediator production and inflammatory cell infiltration in vivo. The TLR4-Myd88-NF-κB signalling pathway in the kidney of LIGHT knockout mice was dramatically down-regulated compared to the controls. Recombinant human LIGHT aggravated LPS-treated HK-2 cell injury by up-regulating the expression of the TLR4-Myd88-NF-κB signalling pathway and inflammation levels. TAK 242 (a selective TLR4 inhibitor) reduced this trend to some extent. In addition, blocking LIGHT with soluble receptor fusion proteins HVEM-Fc or LTßR-Fc in mice attenuated renal dysfunction and pathological damage in SA-AKI. Our findings indicate that LIGHT aggravates inflammation and promotes kidney damage in LPS-induced SA-AKI via the TLR4-Myd88-NF-κB signalling pathway, which provide potential strategies for the treatment of SA-AKI.

Fibrinogen-like protein 2 deficiency aggravates renal fibrosis by facilitating macrophage polarization.

Renal fibrosis has no effective target for its prevention or reversal. Fibinogen-like protein 2 (Fgl2) is a novel prothrombinase exhibiting coagulation activity and immunomodulatory effects. Although Fgl2 is known to play a vital role in the development of liver and interstitial fibrosis, its function in renal fibrosis remains unclear. In this study, Fgl2 expression was found to be markedly increased in kidney tissues from mice with unilateral ureteral obstruction (UUO)-induced renal fibrosis and patients with chronic kidney disease. However, Fgl2 deficiency aggravated UUO-induced renal fibrosis, as evidenced by the significantly increasing collagen I, fibronectin, and α-SMA expression, extracellular matrix deposition, and profibrotic factor (TGF-ß1) secretion. Administration of rmFgl2 (recombinant mouse Fgl2) significantly alleviated UUO-induced renal fibrosis in mice, suggesting that the increased fibrosis can be reversed by supplementing rmFgl2. Although there was no difference in the percentages of total macrophages between Fgl2+/+ and Fgl2-/- mice, Fgl2 deficiency remarkably facilitated M2 macrophage polarization and accelerated M1 macrophage polarization to a low degree, during UUO-induced renal fibrosis development in mice. Similar results were observed when Fgl2+/+ and Fgl2-/- mice bone marrow-derived macrophages were treated for M1 or M2 polarization. Moreover, Fgl2 deficiency significantly increased the phosphorylation of STAT6, a critical mediator of M2 polarization, in both UUO-induced fibrotic kidney tissues and bone marrow-derived M2 macrophages. In conclusion, the aggravation of renal fibrosis by Fgl2 deficiency is facilitated by the p-STAT6-dependent upregulation of macrophage polarization, especially of M2.

C5aR deficiency attenuates the breast cancer development via the p38/p21 axis.

Emerging evidence has shown activation of the complement component C5 to C5a in cancer tissues and C5aR expression in breast cancer cells relates to the tumor development and poor prognosis, suggesting the involvement of complement C5a/C5aR pathway in the breast cancer pathogenesis. In this study, we found that as compared to the non-tumoral tissues, both C5aR and MAPK/p38 showed an elevated expression, but p21/p-p21 showed lower expression, in the tumoral tissues of breast cancer patients. Mice deficient in C5aR or mice treated with the C5aR antagonist exhibited attenuation of breast cancer growth and reduction in the p38/p-p38 expression, but increase in p21/p-p21 expression, in the tumor tissues. Pre-treatment of the breast cancer cells with recombinant C5a resulted in reduced p21 expression, and MAPK/p38 inhibitors prevented C5a-induced reduction in p21 expression, suggesting the involvement of the MAPK/p38 signaling pathway in the C5a/C5aR-mediated suppression of p21/p-p21 expression. These results provide evidence that breast cancer development may rely on C5a/C5aR interaction, for which MAPK/p38 pathway participate in down-regulating the p21 expression. Inhibition of C5a/C5aR pathway is expected to be helpful for the treatment of patients with breast cancer.

C5a/C5aR1 mediates IMQ-induced psoriasiform skin inflammation by promoting IL-17A production from γδ-T cells.

Psoriasis is a chronic relapsing inflammatory skin disease, affecting up to 3% of the global population. Accumulating evidence suggests that the complement system is involved in its pathogenesis. Our previous study revealed that the C5a/C5aR1 pathway is crucial for disease development. However, the underlying mechanisms remain largely unknown. To explore potential mechanisms, psoriatic skin lesions and histological changes were assessed following imiquimod (IMQ) cream treatment. Inflammatory cytokine expression was tested by real-time RT-PCR. Immunohistochemistry and flow cytometry were used to identify inflammatory cell infiltration and interleukin (IL-17A) IL-17A expression. A C5aR1 antagonist (C5aR1a) and PI3K inhibitor (wortmannin) were used for blocking experiments (both in vivo and in vitro) to explore the mechanism. C5a/C5aR1-pathway inhibition significantly attenuated psoriasis-like skin lesions with decreased epidermal hyperplasia, downregulated type 17-related inflammatory gene expression, and reduced IL-17A-producing γδ-T cell responses. Mechanistically, C5a/C5aR1 promoted the latter phenotype via PI3K-Akt signaling. Consistently, C5aR1 deficiency clearly ameliorated IMQ-induced chronic psoriasiform dermatitis, with a significant decrease in IL-17A expression. Finally, blocking C5aR1 signaling further decreased psoriasiform skin inflammation in IL-17-deficient mice. Results suggest that C5a/C5aR1 mediates experimental psoriasis and skin inflammation by upregulating IL-17A expression from γδ-T cells. Blocking C5a/C5aR1/IL-17A axis is expected to be a promising strategy for psoriasis treatment.

Complement component 3 prevents imiquimod-induced psoriatic skin inflammation by inhibiting apoptosis in mice.

Complement component 3 (C3), a pivotal molecule in the complement system, is an essential immune mediator in various diseases, including psoriasis. However, the mechanistic role of C3 in psoriasis pathology and development remains elusive. Here, we showed that C3 deficiency dramatically augmented imiquimod-induced psoriasis-like skin inflammation, characterized by greater epidermal hyperplasia, inflammatory cell infiltration, and inflammatory gene expression than those in wild-type counterparts. In addition, C3 deficiency promoted imiquimod-induced skin cell apoptosis and supported greater proportions of IFN-γ+ T cells in the inflamed tissues. Accordingly, C3 supplement in the C3 deficient mice reduced skin inflammation and cells apoptosis. Moreover, blocking apoptosis with Z-VAD-FMK, a broad caspase inhibitor, markedly attenuated imiquimod-induced psoriasis-like skin inflammation and IFN-γ+ T cell responses in C3-deficient mice. Collectively, our results suggest that C3 prevents imiquimod-induced psoriasis-like skin inflammation by inhibiting apoptosis.

C5a/C5aR1 Pathway Is Critical for the Pathogenesis of Psoriasis.

Psoriasis is one of the most common chronic inflammatory skin diseases, affecting ~2% of the population. The lack of characterization of the pathogenesis of psoriasis has hindered efficient clinical treatment of the disease. In our study, we observed that expression of complement component 5a receptor 1(C5aR1) was significantly increased in skin lesions of both imiquimod (IMQ) and IL23-induced psoriatic mice and patients with psoriasis. C5aR1 deficiency or treatment with C5a receptor 1 antagonist (C5aR1a) in mice significantly attenuated psoriasis-like skin lesions and expression of inflammatory cytokines and chemokines. Moreover, C5aR1 deficiency significantly decreased IMQ-induced infiltration of plasmacytoid dendritic cells (pDCs), monocytes and neutrophils in psoriatic skin lesions and functions of pDCs, evidenced by the remarkable reduction in the IMQ-induced production of interferon-α (IFN-α) and tumor necrosis factor α (TNF-α), and FMS-like tyrosine kinase 3 ligand (FLT3L)-dependent pDCs differentiation. Accordingly, in vitro treatment with recombinant C5a accelerated pDCs migration and the differentiation of bone marrow cells into pDCs. Furthermore, biopsies of psoriatic patients showed a dramatic increase of C5aR1+ pDCs infiltration in psoriatic skin lesions, compared to healthy subjects. Our results provide direct evidence that C5a/C5aR1 signaling plays a critical role in the pathogenesis of psoriasis. Inhibition of C5a/C5aR1 pathway is expected to be beneficial in the treatment of patients with psoriasis.

High expression of herpes virus entry mediator is associated with poor prognosis in clear cell renal cell carcinoma.

Herpes virus entry mediator (HVEM), also called tumor necrosis factor receptor superfamily 14 (TNFRSF14), is highly expressed in various tumor tissues and plays critical roles in tumor biology. However, the role of HVEM in clear cell renal cell carcinoma (ccRCC) is unknown. This study evaluated the clinical importance of HVEM in patients with ccRCC. HVEM expression was assessed in fresh and 140 archived paraffin-embedded ccRCC tissue samples by quantitative RT-PCR, western blot, and immunohistochemical staining. HVEM expression was higher in ccRCC than in paired peritumor tissue. Kaplan-Meier analysis showed that high level of HVEM expression was associated with poor overall survival (OS) and disease-free survival (DFS) in patients with ccRCC (both P < 0.001). Multivariate analysis indicated that HVEM overexpression was independently prognostic of survival in ccRCC patients. Two novel nomogram systems were constructed by integrating HVEM expression and other clinical parameters to predict OS (c-index 0.75) and DFS (c-index 0.74) in these patients, with both having better predictive accuracy than traditional TNM (c-index 0.65 for OS and 0.639 for DFS) and Fuhrman (c-index 0.612 for OS and 0.641 for DFS) systems. In addition, HVEM silencing led to an observable reduction in tumor cells growth in vitro and in vivo. Taken together, these findings indicate that high HVEM expression is a novel and independent adverse predictor of clinical outcomes in patients with ccRCC and that HVEM may be a potential therapeutic target.

Celastrol alleviates renal fibrosis by upregulating cannabinoid receptor 2 expression.

Renal fibrosis is the final manifestation of various chronic kidney diseases, and no effective therapy is available to prevent or reverse it. Celastrol, a triterpene that derived from traditional Chinese medicine, is a known potent anti-fibrotic agent. However, the underlying mechanisms of action of celastrol on renal fibrosis remain unknown. In this study, we found that celastrol treatment remarkably attenuated unilateral ureteral obstruction (UUO)-induced mouse renal fibrosis. This was evidenced by the significant reduction in tubular injury; collagen deposition; accumulation of fibronectin, collagen I, and α-smooth muscle actin; and the expression levels of pro-fibrotic factors Vim, Cola1, and TGF-ß1 mRNA, as well as inflammatory responses. Celastrol showed similar effects in a folic acid-induced mouse renal fibrosis model. Furthermore, celastrol potentiated the expression of the anti-fibrotic factor cannabinoid receptor 2 (CB2R) in established mouse fibrotic kidney tissues and transforming growth factor ß1 (TGF-ß1)-stimulated human kidney 2 (HK-2) cells. In addition, the CB2R antagonist (SR144528) abolished celastrol-mediated beneficial effects on renal fibrosis. Moreover, UUO- or TGF-ß1-induced activation of the pro-fibrotic factor SMAD family member 3 (Smad3) was markedly inhibited by celastrol. Inhibition of Smad3 activation by an inhibitor (SIS3) markedly reduced TGF-ß1-induced downregulation of CB2R expression. In conclusion, our study provides the first direct evidence that celastrol significantly alleviated renal fibrosis, by contributing to the upregulation of CB2R expression through inhibiting Smad3 signaling pathway activation. Therefore, celastrol could be a potential drug for treating patients with renal fibrosis.

Complement C5a/C5aR pathway potentiates the pathogenesis of gastric cancer by down-regulating p21 expression.

Although the complement C5a/C5aR pathway is suggested to play a critical role in tumor pathogenesis, the underlying mechanism has yet to be fully elucidated. In the present study, we found that in patients with gastric cancer in different clinical stages (from stageⅠto stage Ⅳ), both C5aR and p-PI3K/AKT levels were significantly higher in tumoral tissues than in adjacent non-tumoral tissues. In contrast, p21/p-p21 levels were significantly lower in tumoral tissues than in adjacent non-tumoral tissues. In vitro recombinant C5a administration remarkably promoted p-PI3K/p-AKT expression, but inhibited p21/p-p21 expression. Blockage of C5a/C5aR signaling with a C5aR antagonist reversed the C5a-induced inhibitory effect on p21/p-p21 expression. C5a administration to cells pre-treated with a PI3K inhibitor also prevented this inhibitory effect, suggesting the involvement of the PI3K/AKT signaling pathway in C5a/C5aR-mediated suppression of p21/p-p21 expression. In vivo C5aR antagonist treatment caused significant reduction in tumor growth in mice, accompanied by a remarkable elevation in p21/p-p21 expression and reduction in p-PI3K/AKT activation. These results indicate that the C5a/C5aR pathway promotes gastric cancer pathogenesis by suppressing p21/p-p21 expression via activation of PI3K/AKT signaling.

C5a/C5aR pathway accelerates renal ischemia-reperfusion injury by downregulating PGRN expression.

Recent reports indicate that the complement C5a/C5aR pathway and progranulin (PGRN) deficiency both contribute to ischemia-reperfusion (IR)-induced acute kidney injury. However, the underlying relationship between the C5a/C5aR signaling pathway and PGRN expression during acute kidney injury is poorly understood. In this study, we showed that C5aR expression was significantly upregulated after renal IR, and that C5aR deficiency led to a marked increase in PGRN expression and a significant reduction in tubular damage and production of inflammatory cytokines. In accordance with these results, recombinant C5a caused downregulation of PGRN protein and mRNA levels in renal tubular epithelial cells (HK-2 cells), which could be negated by disruption of C5a/C5aR signaling by the C5aR antagonist, as confirmed by immunofluorescence, western blotting, and quantitative real-time PCR. Moreover, C5aR deficiency resulted in attenuated NF-κB expression 24h after IR, and recombinant C5a potentiated TNFα-induced NF-κB activation in HK-2 cells. Inhibition of NF-κB activation reversed C5a-induced downregulation of PGRN expression. Our results show for the first time that the complement C5a/C5aR pathway aggravates IR-induced acute kidney injury by suppressing PGRN expression and confirm that suppression of PGRN expression is associated with increased NF-κB activation induced by C5a.

Increased expression of Fibrinogen-Like Protein 2 is associated with poor prognosis in patients with clear cell renal cell carcinoma.

Fibrinogen-like protein 2 (FGL2) is highly expressed in various tumour tissues and plays a vital role in tumour initiation and progression. This study evaluated the clinical significance of FGL2 in patients with clear cell renal cell carcinoma (ccRCC). FGL2 expression in fresh and 170 archived paraffin-embedded ccRCC tissues was measured by quantitative RT-PCR, western blotting, and immunohistochemitry. FGL2 expression was significantly upregulated in ccRCC. Statistical analyses by using Kaplan-Meier method showed that high FGL2 expression was associated with poor overall survival (OS) and recurrence-free survival (RFS) of patients with ccRCC. Multivariate analyses indicated that FGL2 was as an independent prognostic factor of survivaland that tumoural FGL2 levels could significantly predict the prognosis of patients with early-stage ccRCC. Nomogram systems, which integrated FGL2 expression and other clinical parameters, were established and were found to be better than TNM staging in predicting the OS and RFS of patients with ccRCC. FGL2 silencing led to a significant reduction in cells viability and increase in cells apoptosis, accompanied with a reduced ERK1/2 and p38 MAPK activation, in ccRCC cells. Thus, our results suggest that high FGL2 expression is a novel, independent, and an adverse prognostic factor of clinical outcomes in patients with ccRCC.

Complement component 3 deficiency prolongs MHC-II disparate skin allograft survival by increasing the CD4(+) CD25(+) regulatory T cells population.

Recent reports suggest that complement system contributes to allograft rejection. However, its underlying mechanism is poorly understood. Herein, we investigate the role of complement component 3 (C3) in a single MHC-II molecule mismatched murine model of allograft rejection using C3 deficient mice (C3(-/-)) as skin graft donors or recipients. Compared with C3(+/+) B6 allografts, C3(-/-) B6 grafts dramatically prolonged survival in MHC-II molecule mismatched H-2(bm12) B6 recipients, indicating that C3 plays a critical role in allograft rejection. Compared with C3(+/+) allografts, both Th17 cell infiltration and Th1/Th17 associated cytokine mRNA levels were clearly reduced in C3(-/-) allografts. Moreover, C3(-/-) allografts caused attenuated Th1/Th17 responses, but increased CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cell expression markedly in local intragraft and H-2(bm12) recipients. Depletion of Treg cells by anti-CD25 monoclonal antibody (mAb) negated the survival advantages conferred by C3 deficiency. Our results indicate for the first time that C3 deficiency can prolong MHC-II molecule mismatched skin allograft survival, which is further confirmed to be associated with increased CD4(+) CD25(+) Treg cell population expansion and attenuated Th1/Th17 response.

LIGHT/IFN-γ triggers ß cells apoptosis via NF-κB/Bcl2-dependent mitochondrial pathway.

LIGHT recruits and activates naive T cells in the islets at the onset of diabetes. IFN-γ secreted by activated T lymphocytes is involved in beta cell apoptosis. However, whether LIGHT sensitizes IFNγ-induced beta cells destruction remains unclear. In this study, we used the murine beta cell line MIN6 and primary islet cells as models for investigating the underlying cellular mechanisms involved in LIGHT/IFNγ - induced pancreatic beta cell destruction. LIGHT and IFN-γ synergistically reduced MIN6 and primary islet cells viability; decreased cell viability was due to apoptosis, as demonstrated by a significant increase in Annexin V(+) cell percentage, detected by flow cytometry. In addition to marked increases in cytochrome c release and NF-κB activation, the combination of LIGHT and IFN-γ caused an obvious decrease in expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, but an increase in expression of the pro-apoptotic proteins Bak and Bax in MIN6 cells. Accordingly, LIGHT deficiency led to a decrease in NF-κB activation and Bak expression, and peri-insulitis in non-obese diabetes mice. Inhibition of NF-κB activation with the specific NF-κB inhibitor, PDTC (pyrrolidine dithiocarbamate), reversed Bcl-xL down-regulation and Bax up-regulation, and led to a significant increase in LIGHT- and IFN-γ-treated cell viability. Moreover, cleaved caspase-9, -3, and PARP (poly (ADP-ribose) polymerase) were observed after LIGHT and IFN-γ treatment. Pretreatment with caspase inhibitors remarkably attenuated LIGHT- and IFNγ-induced cell apoptosis. Taken together, our results indicate that LIGHT signalling pathway combined with IFN-γ induces beta cells apoptosis via an NF-κB/Bcl2-dependent mitochondrial pathway.

STAT1-mediated down-regulation of Bcl-2 expression is involved in IFN-γ/TNF-α-induced apoptosis in NIT-1 cells.

Tumor necrosis factor (TNF)-α and interferon (IFN)-γ are the major pro-inflammatory cytokines involved in beta-cell destruction. The fate of islet beta-cells in the cytokine-induced intrinsic mitochondrial apoptotic pathway is determined by the interaction between members of the Bcl-2 family. However, the mechanism through which beta-cell apoptosis is regulated remains unclear. In this study, we treated the murine beta-cell line NIT-1 with TNF-α and IFN-γ and then investigated the regulation of signal transducer and activator of transcription-1 (STAT-1) and expression of the members of the Bcl-2 family in this apoptotic pathway. Results showed that TNF-α and IFN-γ synergistically reduced NIT-1 cell viability. In addition, the decrease in cell growth was due to apoptosis as shown by apoptotic body formation, detected by confocal laser microscope, and a significant increase in Annexin-Vup(+) cell percentage, detected by flow cytometry. Combination treatment with TNF-α and IFN-γ caused a remarkable increase in the release of cytochrome c, and in the activation of caspase-9 and caspase-3, as well as, an obvious enhancement in STAT-1 phosphorylation; the treatment, however, resulted in the down-regulation in Bcl-2 expression. The enhancement in STAT-1 activity and a down-regulation in Bcl-2 expression was also observed in MIN6 cells, another murine beta-cell derived line, after cells exposure to the combination of TNF-α and IFN-γ treatment. Knockdown of STAT-1 gene expression by siRNA or inhibition of STAT-1 activation with fludarabine reversed Bcl-2 down-expression and led to a significant decrease in apoptosis in TNF-α- and IFN-γ-treated NIT-1 cells. Taken together, our results suggest that STAT1-mediated down-regulation of Bcl-2 is involved in NIT-1 cell apoptosis induced by combination treatment with TNF-α and IFN-γ.

C5a/C5aR pathway is essential for the pathogenesis of murine viral fulminant hepatitis by way of potentiating Fgl2/fibroleukin expression.

UNLABELLED: Viral fulminant hepatitis (FH) remains a serious clinical problem with very high mortality. Lacking understanding of FH pathogenesis has in essence hindered efficient clinical treatment. Inferring from a correlation observed between the genetic differences in the complement component 5 (C5) and the susceptibility of mouse strains to murine hepatitis virus strain-3 (MHV-3) infections, we propose that excessive complement activation plays a critical role in the development of FH. We show that MHV-3 infection causes massive complement activation, along with a rapid increase in serum C5a levels and quick development of FH in susceptible strains. Mice deficient in the C5a receptor (C5aR) or the susceptible strains treated with C5aR antagonists (C5aRa) exhibit significant attenuation of the disease, accompanied by a remarkable reduction of hepatic fibrinogen-like protein 2 (Fgl2), a hallmark protein that causes necrosis of infected livers. In accordance, biopsy of FH patients shows a dramatic increase of Fgl2 expression, which correlates with C5aR up-regulation in the liver. In vitro C5a administration accelerates MHV-3-induced Fgl2 secretion by macrophages. Furthermore, inhibiting ERK1/2 and p38 efficiently blocks C5a-mediated Fgl2 production during viral infections. CONCLUSION: These data provide evidence that mouse susceptibility to MHV-3-induced FH may rely on C5a/C5aR interactions, for which ERK1/2 and p38 pathways participate in up-regulating Fgl2 expression. Inhibition of C5a/C5aR interactions is expected to be beneficial in the clinical treatment of FH patients.

Caspase-3 is involved in IFN-γ- and TNF-α-mediated MIN6 cells apoptosis via NF-κB/Bcl-2 pathway.

TNF-α and IFN-γ are the major pro-inflammatory cytokines in the ß-cell destruction. However, the underlying mechanism remains unclear. The present study used a murine insulinoma cell line MIN6 for further investigation of the effect of Caspase-3 on the cytokines-induced pancreatic ß-cell apoptosis and analyzed the mechanisms involved in the activation of Caspase-3. It was showed that the combination of IFN-γ and TNF-α significantly reduced the viability of MIN6 cells and the observed cells growth inhibition was due to cell apoptosis as judged by the morphological changes under a confocal laser scanning microscopy and FACS assay of Annexin-V/7-AAD double staining. Accompanying with NF-κB activation and Bcl-2 downregulation, both the cleaved Caspase-3 and PARP, a known substrate of Caspase-3 in vivo, were observed at 24 and 12 h, respectively, after cells exposure to IFN-γ and TNF-α treatment. Pretreatment of Caspase-3 inhibitors remarkably attenuated IFN-γ- and TNF-α-induced cells apoptosis. Inhibition of NF-κB activation led to the increase in Bcl-2 expression, a significant attenuation in Caspase-3 activity, and an obvious amelioration in cells viability in IFN-γ- and TNF-α-treated MIN6 cells. Taken together, our results indicate that Caspase-3 is critical for the induction of MIN6 cells apoptosis and it's activation is further confirmed to be related to the NF-κB-mediated Bcl-2 downregulation, which may be the underlying mechanism of IFN-γ- and TNF-α-mediated MIN6 cells apoptosis.