Renjin Chen

The Regulatory Mechanism of Neurogenesis by IGF-1 in Adult Mice

Growth factors like insulin-like growth factor 1 (IGF-1) is reported to mediate neurogenesis in the subgranular zone (SGZ) and the subventricular zone (SVZ) of the adult mammalian brain, but its regulatory mechanism remains unclear. We generated transgenic mice overexpressing IGF-1 specifically in neural stem cells (NSCs) and assessed the effect of IGF-1 on neurogenesis in adult mice NSCs. Overexpression of IGF-1 could stimulate the expression of phospho-Akt and phospho-ERK1/2 while inducing proliferation and differentiation of NSCs in the SGZ and SVZ. The MEK/ERK inhibitor U0126 could inhibit ERK1/2 phosphorylation, further inhibiting the proliferation of NSCs in the SGZ and SVZ but had no effect on the phosphorylation of Akt. By contrast, The PI3K/Akt inhibitor LY294002 inhibited phosphorylation of Akt and differentiation of NSCs in the SGZ and SVZ, resulting in no change in the proliferation of NSCs and ERK1/2 phosphorylation. These results demonstrate that IGF-1 upregulates the proliferation of NSCs by triggering MEK/ERK pathway signaling in the adult mice SGZ and SVZ. Meanwhile, IGF-1 also induces differentiation of NSCs via the PI3K/Akt pathway in adult mice. However, we found no evidence of crosstalk between the PI3K/Akt and MEK/ERK pathways in adult mice NSCs. Our work provides new experimental evidence of the involvement of the PI3K/Akt and MEK/ERK pathways in the proliferation and differentiation of the NSCs of adult mice.

Heme Oxygenase-2 Suppress TNF-α and IL6 Expression via TLR4/MyD88-Dependent Signaling Pathway in Mouse Cerebral Vascular Endothelial Cells

Heme oxygenase (HO) represents an intrinsic antiinflammatory system based on its ability to inhibit expression of proinflammatory cytokines. The constitutive isoform heme oxygenase-2 (HO-2) has high expression and activity in cerebral microvascular endothelial cells (CMVEC). This study was undertaken to evaluate the role of HO-2 in regulation of TLR4/MyD88-dependent signaling and to study the effect of HO-2 on the expression and secretion of the proinflammatory cytokines tumor necrosis factor α (TNF-α) and Interleukin-6 (IL6) in CMVEC. HO-2 short hairpin RNA (shRNA) and HO-2 overexpression plasmids were used to observe the effect of HO-2 on proinflammatory cytokines in CMVEC in vitro, and the results showed that the messenger RNA (mRNA) and protein levels of TNF-α and IL6 were increased and decreased, respectively, compared with control groups. LPS-stimulated TNF-α and IL6 mRNA and protein were also reduced in CMVEC treated with an inhibitor of TLR4 signaling, CLI-095, or HO-2 overexpression. CLI-095 and HO-2 overexpression both reduced TLR4 expression in CMVEC, and HO-2 shRNA blocked these effects of CLI-095. CLI-095 and HO-2 overexpression potently suppressed TLR4/MyD88-dependent proinflammatory cytokine expression in CMVEC. These results suggest that HO-2 plays an important role in protecting CMVEC against cytokine-mediated inflammation.

The immunosuppression mechanism of hypodermin A on complement

Hypodermin A (HA), a serine protease secreted by first-instar larvae of Hypoderma lineatum (Diptera: Oestridae) is associated with inflammatory and the specific immune responses in cattle hosts. In the present study, the cDNA sequence of HA was synthesized, and found to have fifteen amino acids which differed from the sequence available in GenBank. We then examined the association between recombinant HA and guinea-pig complement component 3 (C3) through a co-immunoprecipitation assay. Cos7 cells stably expressing HA were generated, and were found to be more resistant to lysis by guinea-pig C3 than the controls. HA was also able to degrade the C6 and C5b-9 of guinea-pig C3. The presumed DNA binding site of HA with guinea-pig C3 was detected by an electrophoretic mobility shift assay (EMSA). In contrast, after stable transfection, mHA was unable to reduce the amount of C3 or to inhibit its cytotoxicity, while HA could degrade guinea-pig C3 and inhibit the complement pathway. The findings suggest that recombinant HA could serve as an immunosuppressive agent against organ rejection after xenotransplantation.

The effect of constitutive over-expression of insulin-like growth factor 1 on the cognitive function in aged mice.

The neurotrophic factor insulin-like growth factor (IGF)-1 promotes neurogenesis in the mammalian brain and provides protection against brain injury. However, studies regarding the effects of IGF-1 on cognitive function in aged mice remain limited. We investigated the effects of overexpression of IGF-1 specifically in neural stem cells of the hippocampal dentate gyrus on the recognitive function in 18-month-old transgenic mice. Immunohistocytochemistry and Nissl staining revealed the increased population of BrdU-positive cells as well as the upregulated expression of Nestin and neuronal nuclei (NeuN), respective markers for neural progenitors and neurons, in the hippocampus of the aged IGF-1 transgenic mice versus the wild-type, suggesting that IGF-1 overexpression promotes neurogenesis. In addition, the IGF-1 receptor (IGF-1R), the phosphorylation of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinase (ERK) were enhanced in the transgenic mice than in the wild-type. Transgenic mice also showed superior performance in the Morris water maze and step-down memory tests to their wild-type counterparts. Moreover, the learning and memory abilities of transgenic mice were significantly undermined with the blockage of CaMKII and ERK signaling pathway. Accordingly, our findings indicated that IGF-1 may mitigate the aged-associated cognitive decline via promoting neurogenesis in the hippocampus and activating CaMKII and ERK signaling by binding with IGF-1R.

Immunosuppressive Effect of Hypodermin C on Complement Component 3 In Vitro.

Hypodermins A (HA), B (HB) and C (HC) are the major proteases secreted by first-instar larvae of Hypoderma lineatum (Diptera: Oestridae). These proteases are involved in the larval migration in the tissue, and prevent the activation of the host immune response. We previously showed that the recombinant HA functions as an immunosuppressive agent which could inhibit the rejection of xenotransplants. In the current study, we cloned the cDNA sequence of HC, which was transfected in Cos7 cells using the pEF1α-IRES-AcGFP expression vector. The Cos7 cells stably expressed HC, and were more resistant to lysis by guinea pig C3 than the control cells. The HC protease degraded the guinea pig C3, and inhibited the complement pathway in vitro. The DNA binding sites of HC were identified using an electrophoretic mobility shift assay. Our findings suggest that the recombinant HC might be useful as an immunosuppressive agent for the inhibition of the xenotransplant rejection.

Hypodermin A, a potential agent for prevention of allogeneic acute rejection.

Immunosuppressive agents play an important role in the success of organ transplantation, however the chronic toxicity of these agents is a major issue over the long-term. Hypodermin A (HA) is an enzyme secreted by the larvae of Hypoderma lineatum (Diptera: Oestridae), and has been implicated in immunosuppression in cattle. Malassagne et al. have demonstrated that HA can degrade the C3 protein, and could be used to prevent hyperacute xenogeneic rejection. We found that overexpression of HA in RAW264.7 cells induced significant secretion of prostaglandin E2 (PGE2), which mediates a variety of innate and adaptive immune responses through four E-type prostanoid (EP) receptor subtypes (EP1-4). PGE2 is useful in the management of allogeneic acute rejection. In addition, we found that induction of PGE2 expression downregulates the expression of interferon (IFN)-γ and interleukin (IL)-2, and promotes the secretion of IL-10 in vitro through the EP4 receptor. It was previously shown that activation of IL-2 and IFN-γ is involved in allograft acute rejection. IL-10 is known to prevent inflammation, and can improve allograft survival rates. We concluded that besides preventing hyperacute xenogeneic rejection, HA might also be a potential therapeutic candidate for ameliorating acute rejection during allotransplantation.

Association of IL8 -105G/A with mastitis somatic cell score in Chinese Holstein dairy cows.

The single nucleotide polymorphisms (SNPs) in the 5′ upstream of bovine IL8 gene were investigated in 810 Chinese Holstein cows from 35 bull families in a dairy farm in Shanghai using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) technique. The Real-time PCR and Western blot were used to detect the mRNA and protein levels of genotype Chinese Holstein dairy cows. The results showed that one SNP -105G>A was detected, designating three genotypes (GG, GA and AA) with respective frequencies of 0.38, 0.46, and 0.16. The significant association of the SNP -105G>A with somatic cell score (SCS) was identified. Genotype GG had a significantly lower SCS than genotype GA or AA (P < 0.01), and the relative mRNA expression and protein level of GG was found to be the highest. These results suggest that the genotype GG may be a useful genetic marker for mastitis resistance selection and breeding in Chinese Holstein dairy cows.

Heme oxygenase-2 suppresses acute inflammation and improves the survival of skin allografts

&NA; The heme oxygenase (HO) system is an important regulatory arm of the intrinsic cytoprotective and anti‐inflammatory system. HO‐2 plays an important role in regulating inflammation following injury. The aim of this study was to evaluate the effect of HO‐2 overexpression on inflammatory responses. A skin transplantation model, involving the application of skin grafts from wild‐type or HO‐2 overexpressing mice to BALB/c mice, was used for investigation. HO‐2 overexpression suppressed the production of pro‐inflammatory cytokines (IL‐1&bgr;, TNF‐&agr;, and IL‐6) in macrophages compared to that in macrophages obtained from control mice. HO‐2 overexpression also significantly prolonged the survival of allografted skin. Our findings suggest that HO‐2 attenuates inflammatory responses and effectively prolongs skin graft survival. HighlightsHO‐2 overexpression suppressed pro‐inflammatory cytokine production in macrophages.Expression of the pro‐inflammatory cytokines was suppressed in HO‐2 overexpression skin allografts compared with controls.HO‐2 prolonged allograft skin survival.

Research Progress on the Relationship between Atherosclerosis and Inflammation

Atherosclerosis is a chronic inflammatory disease; unstable atherosclerotic plaque rupture, vascular stenosis, or occlusion caused by platelet aggregation and thrombosis lead to acute cardiovascular disease. Atherosclerosis-related inflammation is mediated by proinflammatory cytokines, inflammatory signaling pathways, bioactive lipids, and adhesion molecules. This review discusses the effects of inflammation and the systemic inflammatory signaling pathway on atherosclerosis, the role of related signaling pathways in inflammation, the formation of atherosclerosis plaques, and the prospects of treating atherosclerosis by inhibiting inflammation.

A novel SNP of Lysozyme Gene and Its Association with Mastitis Trait in Chinese Holstein

Abstract. Mastitis is the most frequent and important disease in the dairy industry worldwide, which leads to great economic losses in the dairy industry (Nash et al. 2003). Direct selection for resistance to clinical mastitis may be very difficult and indirect selection has been practiced widely. The recommended measure is to record herd milk somatic cell scores (SCS) based on the positive correlation between clinical mastitis and milk SCS (Rupp et al. 1999).