Yuanyuan Zhang

MicroRNA-92a negatively regulates Toll-like receptor (TLR)-triggered inflammatory response in macrophages by targeting MKK4 kinase.

Background: microRNAs (miRNAs) participate in innate immune responses. Results: miR-92a decreases rapidly in macrophages once stimulated with TLR ligands, and miR-92a controls inflammatory response by targeting MKK4/JNK/c-Jun pathway. Conclusion: TLR-mediated miR-92a reduction feedback enhances TLR-triggered inflammatory response. Significance: Our findings reveal a novel positive feedback loop in which TLR-reduced miR-92a expression functions to regulate the innate inflammatory responses. Toll-like receptors (TLRs) play a critical role in the initiation of immune responses against invading pathogens. MicroRNAs have been shown to be important regulators of TLR signaling. In this study, we have found that the stimulation of multiple TLRs rapidly reduced the levels of microRNA-92a (miRNA-92a) and some other members of the miRNA-92a family in macrophages. miR-92a mimics significantly decreased, whereas miR-92a knockdown increased, the activation of the JNK/c-Jun pathway and the production of inflammatory cytokines in macrophages when stimulated with ligands for TLR4. Furthermore, mitogen-activated protein kinase kinase 4 (MKK4), a kinase that activates JNK/stress-activated protein kinase, was found to be directly targeted by miR-92a. Similar to the effects of the miR-92a mimics, knockdown of MKK4 inhibited the activation of JNK/c-Jun signaling and the production of TNF-α and IL-6. In conclusion, we have demonstrated that TLR-mediated miR-92a reduction feedback enhances TLR-triggered production of inflammatory cytokines in macrophages, thus outlining new mechanisms for fine-tuning the TLR-triggered inflammatory response.

hPEBP4 resists TRAIL-induced apoptosis of human prostate cancer cells by activating Akt and deactivating ERK1/2 pathways.

The treatment options available for prostate cancer are limited because of its resistance to therapeutic agents. Thus, a better understanding of the underlying mechanisms of the resistance of prostate cancer will facilitate the discovery of more efficient treatment protocols. Human phosphatidylethanolamine-binding protein 4 (hPEBP4) is recently identified by us as an anti-apoptotic molecule and a potential candidate target for breast cancer treatment. Here we found the expression levels of hPEBP4 were positively correlated with the severity of clinical prostate cancer. Furthermore, hPEBP4 was not expressed in TRAIL-sensitive DU145 prostate cancer cells, but was highly expressed in TRAIL-resistant LNCaP cells, which show highly activated Akt. Interestingly, hPEBP4 overexpression in TRAIL-sensitive DU145 cells promoted Akt activation but inhibited ERK1/2 activation. The hPEBP4-overexpressing DU145 cells became resistant to TRAIL-induced apoptosis consequently, which could be reversed by PI3K inhibitors. In contrast, silencing of hPEBP4 in TRAIL-resistant LNCaP cells inhibited Akt activation but increased ERK1/2 activation, resulting in their sensitivity to TRAIL-induced apoptosis that was restored by the MEK1 inhibitor. Therefore, hPEBP4 expression in prostate cancer can activate Akt and deactivate ERK1/2 signaling, leading to TRAIL resistance. We also demonstrated that hPEBP4-mediated resistance to TRAIL-induced apoptosis occurred downstream of caspase-8 and at the level of BID cleavage via the regulation of Akt and ERK pathways, and that hPEBP4-regulated ERK deactivation was upstream of Akt activation in prostate cancer cells. Considering that hPEBP4 confers cellular resistance to TRAIL-induced apoptosis and is abundantly expressed in poorly differentiated prostate cancer, silencing of hPEBP4 suggests a promising approach for prostate cancer treatment.

IPP5, a Novel Protein Inhibitor of Protein Phosphatase 1, Promotes G1/S Progression in a Thr-40-dependent Manner

Abstract Protein phosphatase 1 (PP1) is a major serine/threonine phosphatase that controls gene expression and cell cycle progression. Here we describe the characterization of a novel inhibitory molecule for PP1, human inhibitor-5 of protein phosphatase 1 (IPP5). We find that IPP5, containing the PP1 inhibitory subunits, specifically interacts with the PP1 catalytic subunit and inhibits PP1 phosphatase activity. Furthermore, the mutation of Thr-40 within the inhibitory subunit of IPP5 into Ala eliminates the phosphorylation of IPP5 by protein kinase A and its inhibitor activity to PP1, whereas the mutation of Thr-40 within a truncated form of IPP5 into Asp can serve as a dominant active form of IPP5 in inhibiting PP1 activity. In IPP5-negative SW480 and IPP5-highly positive SW620 human colon cancer cells, we find that overexpression of IPP5 promotes the growth and accelerates the G1-S transition of SW480 cells in a Thr-40-dependent manner, which could be reversed by downregulation of the PP1 expression. Moreover, silencing of IPP5 inhibits the growth of SW620 cells both in vitro and in nude mice possibly by inducing G0/G1 arrest but not by promoting apoptosis. According to its role in the promotion of cell cycle progression and cell growth, IPP5 up-regulates the expression of cyclin E and the phosphorylated form of retinoblastoma protein. Our findings suggest that IPP5, by acting as an inhibitory molecule for PP1, can promote tumor cell growth and cell cycle progression, and may be a promising target in cancer therapeutics in IPP5-highly expressing tumor cells.

Cytokines as the good predictors of refractory Mycoplasma pneumoniae pneumonia in school-aged children

Excessive immune response against pathogens may play an important role in refracory Mycoplasma pneumoniae pneumonia (RMPP). The aim of this study was to elucidate the associations between cytokines and the prediction of RMPP in school-aged patients. Retrospective analysis was performed on school-aged children with Mycoplasma pneumoniae pneumonia (MPP) hospitalized in our hospital between January 1, 2011 and December 31, 2015. The clinical charcteristics, including the cytokines in serum between the RMPP group and the general Mycoplasma pneumoniae pneumonia (GMPP) group were compared and the predictive values of RMPP were explored. Of total 180 patients, 115 patients were in the GMPP group, 65 were in the RMPP group. We found the levels of cytokines, including nterleukin (IL)-6, IL-10, interferon gamma (IFN-γ) in RMPP group were significantly higher than those in GMPP group (P < 0.01). In ROC curve analysis, IL-10 and IFN-γ were useful for differentiating patients with RMPP from those with GMPP. Logistic regression analysis showed that the IL-10 ≥ 3.65 pg/ml and IFN-γ ≥ 29.05 pg/ml were significant predictors regarding to RMPP. Additionally, a positive correlation between serum IL-10 and IFN-γ concentrations was observed. Conclusions: IL-10 and IFN-γ could be used as the good predictors of RMPP in school-aged children.

E3 ligase FBXW7 is critical for RIG-I stabilization during antiviral responses

Viruses can escape from host recognition by degradation of RIG-I or interference with the RIG-I signalling to establish persistent infections. However, the mechanisms by which host cells stabilize RIG-I protein for avoiding its degradation are largely unknown. We report here that, upon virus infection, the E3 ubiquitin ligase FBXW7 translocates from the nucleus into the cytoplasm and stabilizes RIG-I. FBXW7 interacts with SHP2 and mediates the degradation and ubiquitination of SHP2, thus disrupting the SHP2/c-Cbl complex, which mediates RIG-I degradation. When infected with VSV or influenza A virus, FBXW7 conditional knockout mice (Lysm+FBXW7f/f) show impaired antiviral immunity. FBXW7-deficient macrophages have decreased RIG-I protein levels and type-I interferon signalling. Furthermore, PBMCs from RSV-infected children have reduced FBXW7 mRNA levels. Our results identify FBXW7 as an important interacting partner for RIG-I. These findings provide insights into the function of FBXW7 in antiviral immunity and its related clinical significance.

Amelioration of experimental autoimmune encephalomyelitis through transplantation of placental derived mesenchymal stem cells

Placental derived mesenchymal stem cells (PMSCs) have been suggested as a possible source of cells to treat multiple sclerosis (MS) due to their immunomodulatory functions, lack of ethical concerns, and potential to differentiate into neurons and oligodendrocytes. To investigate whether PMSCs share similar characteristics with embryonic mesenchymal stem cells (EMSCs), and if transplanted PMSCs have the ability to integrate and replace degenerated neural cells, we transplanted rat PMSCs and EMSCs into the central nervous system (CNS) of Lewis rats with experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Our findings demonstrated that transplanted PMSCs, similar to EMSCs, were effective in decreasing infiltrating inflammatory cells, preserving axons, and ameliorating demyelination, thereby improving the neurological functions of animals. Moreover, both PMSCs and EMSCs had the ability to migrate into inflamed tissues and express neural–glial lineage markers. These findings suggest that PMSCs may replace EMSCs as a source of cells in MS stem cell therapy.

TIPE2 negatively regulates mycoplasma pneumonia -triggered immune response via MAPK signaling pathway

Excessive immune responses played an important role in pathophysiology of mycoplasma pneumonia (MP) infection. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2) is a negative regulator of immune response. This study investigated the expression change of TIPE2 and its role in immune defense against MP infection, as well as the underlying mechanisms. Expressions of TIPE2 both in patients and in macrophages in vitro after MP infection were measured. We further studied cytokine production and mitogen-activated protein kinase (MAPK) signaling function in macrophages with interfered expression of TIPE2 upon MP infection. A significant decrease of TIPE2 mRNA expression was observed in peripheral blood mononuclear cells (PBMCs) from MP patients, which was correlated with the severity of infection. Accordingly we found down-regulation of TIPE2 expression in macrophages after MP infection. In vitro study further suggested that TIPE2 jeopardized inflammatory cytokine production trigged by MP infection via inhibiting MAPK signaling pathway. These findings provided evidences of the novel function of TIPE2 in anti-MP immunity and its possible clinical utility related clinical significance.

Intravenous C16 and angiopoietin-1 improve the efficacy of placenta-derived mesenchymal stem cell therapy for EAE

The placenta has emerged as an attractive source of mesenchymal stem cells (MSCs) because of the absence of ethical issues, non-invasive access, and abundant yield. However, inflammatory cell invasion into grafts negatively impacts the survival and efficacy of transplanted cells. Previous studies have shown that synthetic C16 peptide can competitively block the transmigration of leukocytes into the central nerve system, while angiopoietin-1 (Ang-1) can inhibit inflammation-induced blood vessel leakage and inflammatory cell infiltration in rats with experimental allergic encephalomyelitis (EAE). In this study, we investigated the effects of intravenous administration of C16 and Ang-1 on the efficacy of placenta-derived MSC (PMSC) transplantation in a rat model of EAE. We found that, compared with PMSCs alone, treatment with PMSCs along with intravenously administered C16 and Ang-1 was more effective at ameliorating demyelination/neuronal loss and neurological dysfunction, reducing inflammatory cell infiltration, perivascular edema, and reactive astrogliosis (p < 0.05). Mechanistic studies revealed that intravenous C16 and Ang-1 increased PMSC engraftment in the central nervous system and promoted expression of the neurotropic proteins brain-derived neurotrophic factor, growth-associated protein 43, and p75 neurotrophin receptor as well as the neuronal-glial lineage markers neurofilament protein 200 and myelin basic protein in the engrafted PMSCs.

MicroRNA-92a inhibits macrophage antiviral response by targeting retinoic acid inducible gene-I: MiR-92a inhibits antiviral immunity

MicroRNAs are short, non‐coding RNAs that have been shown to regulate a wide range of biological processes, including host antiviral immune responses. In the present study, microRNA‐92a (miR‐92a) was identified as a negative regulator in macrophage‐mediated antiviral responses. Overexpression of miR‐92a decreases vesicular stomatitis virus (VSV)‐induced production of type‐I IFNs and facilitates viral replication in macrophages. The mechanism is that miR‐92a directly targets RIG‐I and reduces its expression, thereby attenuating VSV‐triggered activation of TBK‐binding kinase 1 and IRF3, both of which are crucial for initiating transcription of type‐I IFN genes. Our results demonstrate for the first time the novel role of miR‐92a in suppressing antiviral innate immunity.