Cong-Yi Wang

Loss of methyl-CpG-binding domain protein 2 enhances endothelial angiogenesis and protects mice against hind-limb ischemic injury.

Background— Despite intensive investigation, how DNA methylation influences endothelial function remains poorly understood. We used methyl-CpG–binding domain protein 2 (MBD2), an interpreter for DNA methylome–encoded information, to dissect the impact of DNA methylation on endothelial function in both physiological and pathophysiological states. Methods and Results— Human umbilical vein endothelial cells under normal conditions express moderate levels of MBD2, but knockdown of MBD2 by siRNA significantly enhanced angiogenesis and provided protection against H2O2-induced apoptosis. Remarkably, Mbd2−/− mice were protected against hind-limb ischemia evidenced by the significant improvement in perfusion recovery, along with increased capillary and arteriole formation. Loss of MBD2 activated endothelial survival and proangiogenic signals downstream of vascular endothelial growth factor signaling characterized by an increase in endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor receptor 2 expression, along with enhanced extracellular signal-regulated kinase 1/2 activation and BCL-2 expression. Mechanistic studies confirmed the methylation of CpG elements in the eNOS and vascular endothelial growth factor receptor 2 promoter. MBD2 binds to these methylated CpG elements and suppresses eNOS promoter activity. On ischemic insult, key endothelial genes such as eNOS and vascular endothelial growth factor receptor 2 undergo a DNA methylation turnover, and MBD2 interprets the changes of DNA methylation to suppress their expressions. Moreover, MBD2 modulation of eNOS expression is likely confined to endothelial cells because nonendothelial cells such as splenocytes fail to express eNOS after loss of MBD2. Conclusions— We provided direct evidence supporting that DNA methylation regulates endothelial function, which forms the molecular basis for understanding how environmental insults (epigenetic factor) affect the genome to modify disease susceptibility. Because MBD2 itself does not affect the methylation of DNA and is dispensable for normal physiology in mice, it could be a viable epigenetic target for modulating endothelial function in disease states.

High-mobility group box 1 promotes early acute allograft rejection by enhancing IL-6-dependent Th17 alloreactive response

Previously, we reported that extracellular high-mobility group box 1 (HMGB1) functions as an innate alarmin implicated in cardiac allograft acute rejection. We now present evidence suggesting that HMGB1 is pivotal in inducing interleukin-17 (IL-17)-producing alloreactive T cells by stimulating dendritic cells secretion of IL-6. Those IL-17+ T cells are likely to be the major effector cells responsible for the early stage of cardiac allograft rejection through mediating an influx of neutrophils into allografts, and therefore, blockade of IL-17A significantly prolonged murine cardiac allograft survival. In contrast to the classical model for a dominant role of IFN-γ+-Th1 cells have in acute allograft rejection, our data suggest that IFN-γ+-Th1 cells are responsible for the late stage of graft destruction by inducing monocyte infiltration when IL-17+ T-cell response recedes. Blockade of HMGB1 significantly decreased splenic alloreactive Th17 cells and IFN-γ-producing CD8+ T cells in the recipients, leading to less infiltration of neutrophils along with lower IL-6 and IL-17 expression levels in the grafts as well as prolongation of cardiac allograft survival. Together, these data support a novel model in which HMGB1 induces IL-17-producing alloreactive T cells to mediate early stage of allograft rejection, whereas IFN-γ-producing alloreactive Th1 cells provoke graft destruction after Th17 response recedes.

SUMO1 Negatively Regulates Reactive Oxygen Species Production From NADPH Oxidases

Objective—Increased protein SUMOylation (small ubiquitin-related modifier [SUMO]) provides protection from cellular stress, including oxidative stress, but the mechanisms involved are incompletely understood. The NADPH oxidases (Nox) are a primary source of reactive oxygen species (ROS) and oxidative stress, and thus our goal was to determine whether SUMO regulates NADPH oxidase activity. Methods and Results—Increased expression of SUMO1 potently inhibited the activity of Nox1 to Nox5. In contrast, inhibition of endogenous SUMOylation with small interfering RNA to SUMO1 or ubiquitin conjugating enzyme 9 or with the inhibitor anacardic acid increased ROS production from human embryonic kidney-Nox5 cells, human vascular smooth muscle cells, and neutrophils. The suppression of ROS production was unique to SUMO1, and it required a C-terminal diglycine and the SUMO-specific conjugating enzyme ubiquitin conjugating enzyme 9. SUMO1 did not modify intracellular calcium or Nox5 phosphorylation but reduced ROS output in an isolated enzyme assay, suggesting direct effects of SUMOylation on enzyme activity. However, we could not detect the presence of SUMO1 conjugation on Nox5 using a variety of approaches. Moreover, the mutation of more than 17 predicted and conserved lysine residues on Nox5 did not alter the inhibitory actions of SUMO1. Conclusion—Together, these results suggest that SUMO is an important regulatory mechanism that indirectly represses the production of ROS to ameliorate cellular stress.

MBD2 regulates TH17 differentiation and experimental autoimmune encephalomyelitis by controlling the homeostasis of T-bet/Hlx axis.

Unlike genetic alterations, epigenetic modifications are reversible and amenable to pharmacological interventions, which make them appealing targets for clinical therapy. However, little is known about epigenetic regulation in experimental autoimmune encephalomyelitis (EAE). Here we demonstrated that methyl-CpG-binding domain protein 2 (MBD2), an epigenetic regulator, controls autoimmunity and EAE through T-bet/Hlx. Tbx21 and Hlx underwent a DNA methylation turnover upon polarizations and a unique methylation pattern was essential for TH17 development. Loss of Mbd2 resulted in a defect for reading the information encoded by this methylation turnover, which disrupted the homeostasis of T-bet/Hlx axis and suppressed TH17 differentiation. DNA demethylation induced similar effect on helper T cell differentiation. Therefore, Mbd2(-/-) mice were completely protected from EAE. Pathogenic splenocytes isolated from wild-type mice challenged with MOG35-55 could adoptively transfer disease to Mbd2(-/-) mice. In addition, Mbd2(-/-) mice reconstituted with unstimulated wild-type splenocytes developed EAE as wild-type mice did. These data would provide novel insights into epigenetic regulation of EAE.

Chop Deficiency Protects Mice Against Bleomycin-induced Pulmonary Fibrosis by Attenuating M2 Macrophage Production

C/EBP homologous protein (Chop) has been shown to have altered expression in patients with idiopathic pulmonary fibrosis (IPF), but its exact role in IPF pathoaetiology has not been fully addressed. Studies conducted in patients with IPF and Chop(-/-) mice have dissected the role of Chop and endoplasmic reticulum (ER) stress in pulmonary fibrosis pathogenesis. The effect of Chop deficiency on macrophage polarization and related signalling pathways were investigated to identify the underlying mechanisms. Patients with IPF and mice with bleomycin (BLM)-induced pulmonary fibrosis were affected by the altered Chop expression and ER stress. In particular, Chop deficiency protected mice against BLM-induced lung injury and fibrosis. Loss of Chop significantly attenuated transforming growth factor β (TGF-β) production and reduced M2 macrophage infiltration in the lung following BLM induction. Mechanistic studies showed that Chop deficiency repressed the M2 program in macrophages, which then attenuated TGF-β secretion. Specifically, loss of Chop promoted the expression of suppressors of cytokine signaling 1 and suppressors of cytokine signaling 3, and through which Chop deficiency repressed signal transducer and activator of transcription 6/peroxisome proliferator-activated receptor gamma signaling, the essential pathway for the M2 program in macrophages. Together, our data support the idea that Chop and ER stress are implicated in IPF pathoaetiology, involving at least the induction and differentiation of M2 macrophages.

Characterization of a negative feedback network between SUMO4 expression and NFκB transcriptional activity

Previously, we have demonstrated evidence suggesting that SUMO4 negatively regulates NFkappaB transcriptional activity, probably through sumoylation of IkappaBalpha. Here, we present data indicating that SUMO4 possesses the capacity to conjugate to IkappaBalpha. Luciferase reporter assays in 3T3 cells deficient for IkappaBalpha further demonstrated that SUMO4 regulates NFkappaB signaling dependent on its sumoylation of IkappaBalpha. More importantly, a putative NFkappaB binding motif has been characterized within the SUMO4 promoter. Subsequent promoter reporter assays revealed that SUMO4 promoter with disrupted NFkappaB binding motif failed to response to NFkappaB specific IL-1beta stimulation. ChIP assays showed that NFkappaB binds to SUMO4 promoter and activates its transcription. Together, our data suggest that SUMO4 may act as a negative feedback regulator to prevent excessive activation of NFkappaB. Given the importance of NFkappaB signaling in immune response, SUMO4 could play a role to tightly control the potency of immune response to prevent autoimmunity.

High-mobility group box 1 exacerbates CCl4-induced acute liver injury in mice

High-mobility group box 1 (HMGB1) is a nuclear factor that can also serve as an imflammatory mediator once released into extracellular milieu. Therefore, HMGB1 has been recognized to play a pivotal role in inflammatory diseases such as sepsis, acute lung injury, ischemia reperfusion injury and type 1 diabetes. Nevertheless, its impact on carbon tetrachloride (CCl4)-induced hepatic injury is yet to be elucidated. In the present report, we demonstrated evidence indicating that high levels of HMGB1 were not only present in the necrotic area of liver but also in the serum after CCl4 challenge. In line with these observations, administration of exogenous recombinant HMGB1 exacerbated CCl4-induced hepatic injury, while HMGB1 blocking antibody provided protection for mice against CCl4-induced acute liver injury as evidenced by the decrease of serum transaminase and reduction of hepatic tissues necrosis. Mechanistic studies revealed that blockade of HMGB1 attenuated CCl4-induced MDA accumulation along with improved SOD and GSH activity. Treatment of mice with HMGB1 neutralizing antibody also significantly inhibited the production of proinflammatory mediators TNF-α and IL-6 along with attenuated HMGB1 expression and its extracellular release. Together, our data suggest an essential role for HMGB1 in CCl4-induced acute liver injury, while HMGB1 neutralizing antibody could be served as an effective regimen for preventing CCl4-induced acute liver injury.

Assessment of type 2 diabetes risk conferred by SNPs rs2241766 and rs1501299 in the ADIPOQ gene, a case/control study combined with meta-analyses

We conducted a case/control study to assess the impact of two SNPs, rs2241766 and rs1501299 within the ADIPOQ gene, on type 2 diabetes (T2D) susceptibility in a Chinese Han dataset (741 cases and 902 controls). SNP rs2241766 was found significantly associated with T2D risk in the additive model, dominant model and recessive model. A marginal association was detected for SNP rs1501299 in the additive model and recessive model after Bonferroni correction, and haplotype analysis provided additional evidence supporting the association between these two SNPs and T2D risk. A meta-analysis including 29 published datasets along with current dataset was next carried out to further confirm the association. In consistent with our case/control results, rs2241766 showed a significant association with T2D in the dominant model and additive model, and the association between rs1501299 and T2D was also characterized in the homozygote model, dominant model, recessive model, and additive model. Of note, the association became much stronger in East Asians after exclusion of ethnic stratification. Together, our data support that the rs2241766 and rs1501299 polymorphisms within the ADIPOQ gene confer genetic susceptibility for type 2 diabetes, especially in the Chinese Han population.

Comparative analysis of the alveolar macrophage proteome in ALI/ARDS patients between the exudative phase and recovery phase

BackgroundDespite decades of extensive studies, the morbidity and mortality for acute lung injury/acute respiratory distress syndrome (ALI/ARDS) remained high. Particularly, biomarkers essential for its early diagnosis and prognosis are lacking.MethodsRecent studies suggest that alveolar macrophages (AMs) at the exudative phase of ALI/ARDS initiate, amplify and perpetuate inflammatory responses, while they resolve inflammation in the recovery phase to prevent further tissue injury and perpetuated inflammation in the lung. Therefore, proteins relevant to this functional switch could be valuable biomarkers for ALI/ARDS diagnosis and prognosis. We thus conducted comparative analysis of the AM proteome to assess its dynamic proteomic changes during ALI/ARDS progression and recovery.Results135 proteins were characterized to be differentially expressed between AMs at the exudative and recovery phase. MALDI-TOF-MS and peptide mass fingerprint (PMF) analysis characterized 27 informative proteins, in which 17 proteins were found with a marked increase at the recovery phase, while the rest of 10 proteins were manifested by the significantly higher levels of expression at the exudative phase.ConclusionsGiven the role of above identified proteins played in the regulation of inflammatory responses, cell skeleton organization, oxidative stress, apoptosis and metabolism, they have the potential to serve as biomarkers for early diagnosis and prognosis in the setting of patients with ALI/ARDS.

Loss of Mbd2 Protects Mice Against High-Fat Diet-Induced Obesity and Insulin Resistance by Regulating the Homeostasis of Energy Storage and Expenditure.

Previous studies including ours demonstrated that methyl-CpG–binding domain 2 (MBD2) acts as a reader to decipher DNA methylome-encoded information. We thus in the current study used Mbd2−/− mice as a model to dissect the impact of high-fat diet (HFD) on DNA methylome relevant to the pathoetiology of obesity. It was interestingly noted that mice deficient in Mbd2 were protected from HFD-induced obesity and insulin resistance. Mechanistic study revealed that HFD rendered epididymal adipose tissues to undergo a DNA methylation turnover as evidenced by the changes of methylation levels and patterns. Specifically, HFD was noted with higher potency to induce DNA hypomethylation in genes relevant to energy storage than that in genes associated with energy expenditure. As a result, arrays of genes were subjected to expression changes, which led to an altered homeostasis for energy storage and expenditure in favor of obesity development. Loss of Mbd2 resulted in impaired implementation of above DNA methylation changes associated with altered energy homeostasis, which then protected mice from HFD-induced obesity and insulin resistance. Those data would provide novel insight into the understanding of the pathoetiology underlying obesity with potential for developing effective therapies against obesity in clinical settings.