Complement regulator CD59 protects against angiotensin II-induced abdominal aortic aneurysms in mice

Emerging role of complement in COVID-19 and other respiratory virus diseases

The complement system, a key component of innate immunity, provides the first line of defense against bacterial infection; however, the COVID-19 pandemic has revealed that it may also engender severe complications in the context of viral respiratory disease. Here, we review the mechanisms of complement activation and regulation and explore their roles in both protecting against infection and exacerbating disease. We discuss emerging evidence related to complement-targeted therapeutics in COVID-19 and compare the role of the complement in other respiratory viral diseases like influenza and respiratory syncytial virus. We review recent mechanistic studies and animal models that can be used for further investigation. Novel knockout studies are proposed to better understand the nuances of the activation of the complement system in respiratory viral diseases.

Deficiency of Caspase-1 Attenuates HIV-1-Associated Atherogenesis in Mice

Within arterial plaque, HIV infection creates a state of inflammation and immune activation, triggering NLRP3/caspase-1 inflammasome, tissue damage, and monocyte/macrophage infiltration. Previously, we documented that caspase-1 activation in myeloid cells was linked with HIV-associated atherosclerosis in mice and people with HIV. Here, we mechanistically examined the direct effect of caspase-1 on HIV-associated atherosclerosis. Caspase-1-deficient (Casp-1-/-) mice were crossed with HIV-1 transgenic (Tg26+/-) mice with an atherogenic ApoE-deficient (ApoE-/-) background to create global caspase-1-deficient mice (Tg26+/-/ApoE-/-/Casp-1-/-). Caspase-1-sufficient (Tg26+/-/ApoE-/-/Casp-1+/+) mice served as the controls. Next, we created chimeric hematopoietic cell-deficient mice by reconstituting irradiated ApoE-/- mice with bone marrow cells transplanted from Tg26+/-/ApoE-/-/Casp-1-/- (BMT Casp-1-/-) or Tg26+/-/ApoE-/-/Casp-1+/+ (BMT Casp-1+/+) mice. Global caspase-1 knockout in mice suppressed plaque deposition in the thoracic aorta, serum IL-18 levels, and ex vivo foam cell formation. The deficiency of caspase-1 in hematopoietic cells resulted in reduced atherosclerotic plaque burden in the whole aorta and aortic root, which was associated with reduced macrophage infiltration. Transcriptomic analyses of peripheral mononuclear cells and splenocytes indicated that caspase-1 deficiency inhibited caspase-1 pathway-related genes. These results document the critical atherogenic role of caspase-1 in chronic HIV infection and highlight the implication of this pathway and peripheral immune activation in HIV-associated atherosclerosis.

Hepatocyte-specific disruption of soluble epoxide hydrolase attenuates abdominal aortic aneurysm formation: novel role of the liver in aneurysm pathogenesis

Introduction

Inflammation is a key pathogenic feature of abdominal aortic aneurysm (AAA). Soluble epoxide hydrolase (sEH) is a pro-inflammatory enzyme that converts cytochrome P450-derived epoxides of fatty acids to the corresponding diols, and pharmacological inhibition of sEH prevented AAA formation. Both cytochrome P450 enzymes and sEH are highly expressed in the liver. Here, we investigated the role of hepatic sEH in AAA using a selective pharmacological inhibitor of sEH and hepatocyte-specific Ephx2 (which encodes sEH gene) knockout (KO) mice in two models of AAA [angiotensin II (AngII) infusion and calcium chloride (CaCl 2 ) application].

Methods and results

sEH expression and activity were strikingly higher in mouse liver compared with aorta and further increased the context of AAA, in conjunction with elevated expression of the transcription factor Sp1 and the epigenetic regulator Jarid1b, which have been reported to positively regulate sEH expression. Pharmacological sEH inhibition, or liver-specific sEH disruption, achieved by crossing sEH floxed mice with albumin-cre mice, prevented AAA formation in both models, concomitant with reduced expression of hepatic sEH as well as complement factor 3 (C3) and serum amyloid A (SAA), liver-derived factors linked to AAA formation. Moreover, sEH antagonism markedly reduced C3 and SAA protein accumulation in the aortic wall. Co-incubation of liver ex vivo with aneurysm-prone aorta resulted in induction of sEH in the liver, concomitant with upregulation of Sp1, Jarid1b, C3 and SAA gene expression, suggesting that the aneurysm-prone aorta secretes factors that activate sEH and downstream inflammatory signaling in the liver. Using an unbiased proteomic approach, we identified a number of dysregulated proteins [ e.g., plastin-2, galectin-3 (gal-3), cathepsin S] released by aneurysm-prone aorta as potential candidate mediators of hepatic sEH induction.

Conclusion

We provide the first direct evidence of the liver's role in orchestrating AAA via the enzyme sEH. These findings not only provide novel insight into AAA pathogenesis, but they have potentially important implications with regard to developing effective medical therapies for AAA.

Dexmedetomidine protects cells from Angiotensin II-induced smooth muscle cell phenotype switch and endothelial cell dysfunction

Abdominal aortic aneurysm (AAA) is a vascular disorder greatly threatening life of the elderly population. Dexmedetomidine (DEX), an α2-adrenergic receptor agonist, has been shown to suppress AAA development. Nevertheless, the signaling pathways that might be mediated by DEX in AAA has not been clarified. Vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) were treated with Angiotensin II (Ang II) to mimic AAA in vitro. BrdU, wound healing, and Transwell assays were utilized for measuring VSMC proliferation and migration. Western blotting was used for evaluating protein levels of contractile VSMC markers, collagens and matrix metalloproteinases (MMPs) in VSMCs as well as apoptosis- and HMGB1/TLR4/NF-κB signaling-related markers in ECs. Cell adhesion molecule expression and monocyte-endothelial adhesion were assessed by immunofluorescence staining and adhesion assays. Flow cytometry was implemented for analyzing EC apoptosis. Hematoxylin-eosin staining and ELISA were used to detect the effect of DEX in vivo. In this study, DEX inhibited Ang II-evoked VSMC phenotype switch and extracellular matrix degradation. DEX suppressed the inflammatory response and apoptosis of ECs induced by Ang II. DEX inhibited HMGB1/TLR4/NF-κB signaling pathway in Ang II-treated ECs. DEX attenuated Ang II-induced AAA and inflammation in mice. Overall, DEX ameliorates Ang II-induced VSMC phenotype switch, and inactivates HMGB1/TLR4/NF-κB signaling pathway to alleviate Ang II-induced EC dysfunction.

Common molecular mechanism and immune infiltration patterns of thoracic and abdominal aortic aneurysms

BACKGROUND

Aortic disease (aortic aneurysm (AA), dissection (AD)) is a serious threat to patient lives. Little is currently known about the molecular mechanisms and immune infiltration patterns underlying the development and progression of thoracic and abdominal aortic aneurysms (TAA and AAA), warranting further research.

METHODS

We downloaded AA (includes TAA and AAA) datasets from the GEO database. The potential biomarkers in TAA and AAA were identified using differential expression analysis and two machine-learning algorithms. The discrimination power of the potential biomarkers and their diagnostic accuracy was assessed in validation datasets using ROC curve analysis. Then, GSEA, KEGG, GO and DO analyses were conducted. Furthermore, two immuno-infiltration analysis algorithms were utilized to analyze the common immune infiltration patterns in TAA and AAA. Finally, a retrospective clinical study was performed on 78 patients with AD, and the serum from 6 patients was used for whole exome sequencing (WES).

RESULTS

The intersection of TAA and AAA datasets yielded 82 differentially expressed genes (DEGs). Subsequently, the biomarkers (CX3CR1 and HBB) were acquired by screening using two machine-learning algorithms and ROC curve analysis. The functional analysis of DEGs showed significant enrichment in inflammation and regulation of angiogenic pathways. Immune cell infiltration analysis revealed that adaptive and innate immune responses were closely linked to AA progression. However, neither CX3CR1 nor HBB was associated with B cell-mediated humoral immunity. CX3CR1 expression was correlated with macrophages and HBB with eosinophils. Finally, our retrospective clinical study revealed a hyperinflammatory environment in aortic disease. The WES study identified disease biomarkers and gene variants, some of which may be druggable.

CONCLUSION

The genes CX3CR1 and HBB can be used as common biomarkers in TAA and AAA. Large numbers of innate and adaptive immune cells are infiltrated in AA and are closely linked to the development and progression of AA. Moreover, CX3CR1 and HBB are highly correlated with the infiltration of immune cells and may be potential targets of immunotherapeutic drugs. Gene mutation research is a promising direction for the treatment of aortic disease.

Identification of a biomarker and immune infiltration in perivascular adipose tissue of abdominal aortic aneurysm

Objective: Abdominal aortic aneurysm (AAA) refers to unusual permanent dilation of the abdominal aorta, and gradual AAA expansion can lead to fatal rupture. However, we lack clear understanding of the pathogenesis of this disease. The effect of perivascular adipose tissue (PVAT) on vascular functional status has attracted increasing attention. Here, we try to identify the potential mechanisms linking AAA and PVAT.

Methods: We downloaded dataset GSE119717, including 30 dilated AAA PVAT samples and 30 non-dilated aorta PVAT samples from AAA cases, from Gene Expression Omnibus to identify differentially expressed genes (DEGs). We performed pathway enrichment analysis by Metascape, ClueGo and DAVID to annotate PVAT functional status according to the DEGs. A protein-protein interaction network, the support vector machine (SVM)-recursive feature elimination and the least absolute shrinkage and selection operator regression model were constructed to identify feature genes. Immune infiltration analysis was explored by CIBERSORT. And the correlation between feature gene and immune cells was also calculated. Finally, we used the angiotensin II (Ang II)-ApoE−/− mouse model of AAA to verify the effect of feature gene expression by confirming protein expression using immunohistochemistry and western blot.

Results: We identified 22 DEGs, including 21 upregulated genes and 1 downregulated gene. The DEGs were mainly enriched in neutrophil chemotaxis and IL-17 signaling pathway. FOS was identified as a good diagnostic feature gene (AUC = 0.964). Immune infiltration analysis showed a higher level of T cells follicular helper, activated NK cells, Monocytes, activated Mast cells in AAA group. And FOS was correlated with immune cells. Immunohistochemistry and western blot confirmed higher FOS expression in PVAT of the AAA mouse model compared to control group.

Conclusion: The differentially expressed genes and pathways identified in this study provide further understanding of how PVAT affects AAA development. FOS was identified as the diagnostic gene. There was an obvious difference in immune cells infiltration between normal and AAA groups.

FOS gene associated immune infiltration signature in perivascular adipose tissues of abdominal aortic aneurysm

Abdominal aortic aneurysms (AAA) are pathological dilations in local aortic wall. The inflammatory infiltrates of the perivascular adipose tissue (PAT) surrounding AAAs were associated with AAAs and have been shown to contribute vascular pathology. However, the mechanism by which PAT inflammation contributes to vascular pathology in AAA remains to be clarified. This study aimed to explore the association between immune cell infiltration and key gene expression profile in PAT of AAA. For that, a gene expression dataset of human dilated perivascular adipose tissue (dPAT), non-dilated perivascular adipose tissue (ndPAT), subcutaneous abdominal fat (SAF) and omental-visceral fat (OVF) samples, as well as another microarray dataset of the abdominal perivascular adipose tissue in peripheral artery disease patients were downloaded from GEO database for analysis in this study. The CIBERSORT algorithm, weighted gene co-expression network analysis (WGCNA) and LASSO algorithm were used for the identification of immune infiltration, immune-related genes and the development of diagnostic signature. Our data discovered a significant higher proportion of activated mast cells and follicular helper T (Tfh) cells in dPAT than ndPAT, OVT and SAF samples. Moreover, AP-1 family members (FOS, FOSB, ATF3, JUN and JUNB) were found to compose the hub genes of purple module in WGCNA. Among them, FOS gene acts as a higher efficient marker to discriminate dPAT from ndPAT, OVT and SAF in AAA. Meanwhile, the expression profiles of the AP-1 family members are all significantly positive correlated with activated mast cell, plasma cell and Tfh cell infiltration in dPAT of AAA. Therefore, in the PAT surrounding AAA, the signature of inflammatory infiltration might be represented by a FOS-dominated cell network consist of activated mast cell, plasma cell and Tfh cell. Given the complicated etiology of AAA, our results are likely to shed new light on the pathophysiologic mechanism of AAA influenced by the local dPAT.

Statin therapy protects against abdominal aortic aneurysms by inducing the accumulation of regulatory T cells in ApoE-/- mice

CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to protect against abdominal aortic aneurysm (AAA) progression. Statins have immunomodulatory properties, and their effect on AAA partly depends on immune-related mechanisms. In this study, we aimed to explore whether there is an association between statins and Tregs in AAA progression. Sixty ApoE^-/- mice were randomly divided into four groups (n = 15 per group): A, saline group; B, control group; C, simvastatin group (intragastric administration of simvastatin); and D, PC61 group (simvastatin combined with an intraperitoneal injection of 100 μg CD25-depleting antibody PC61). After 2 weeks of simvastatin treatment, the mice received a continuous subcutaneous infusion of angiotensin II (Ang II; B, C, and D groups) or saline (A group) for 28 days. Simvastatin therapy for 6 weeks significantly decreased the incidence and severity of AAA and inhibited the apoptosis of smooth muscle cells and generation of reactive oxygen species, which was partly abolished after the injection of PC61 antibody. Importantly, simvastatin increased the number of Tregs and the levels of Treg-associated cytokines (TGF-β and IL-10) and decreased the level of IL-17 both in aortic tissues and serum. Interestingly, simvastatin attenuated Ang II-induced gut microbial dysbiosis, which might be associated with the accumulation of Tregs. In conclusion, simvastatin therapy prevented the development of AAA induced by Ang II in ApoE^-/- mice, which might be partly due to the induction of Treg accumulation. In addition, simvastatin regulated gut microbial dysbiosis, which might also be associated with Treg generation.

Ageing- and AAA-associated differentially expressed proteins identified by proteomic analysis in mice

Background

Abdominal aortic aneurysm (AAA) is a disease of high prevalence in old age, and its incidence gradually increases with increasing age. There were few studies about differences in the circulatory system in the incidence of AAA, mainly because younger patients with AAA are fewer and more comorbid nonatherosclerotic factors.

Method

We induced AAA in ApoE^-/- male mice of different ages (10 or 24 weeks) and obtained plasma samples. After the top 14 most abundant proteins were detected, the plasma was analyzed by a proteomic study using the data-dependent acquisition (DDA) technique. The proteomic results were compared between different groups to identify age-related differentially expressed proteins (DEPs) in the circulation that contribute to AAA formation. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) network analyses were performed by R software. The top 10 proteins were determined with the MCC method of Cytoscape, and transcription factor (TF) prediction of the DEPs was performed with iRegulon (Cytoscape).

Results

The aortic diameter fold increase was higher in the aged group than in the youth group (p < 0.01). Overall, 92 DEPs related to age and involved in AAA formation were identified. GO analysis of the DEPs showed enrichment of the terms wounding healing, response to oxidative stress, regulation of body fluid levels, ribose phosphate metabolic process, and blood coagulation. The KEGG pathway analysis showed enrichment of the terms platelet activation, complement and coagulation cascades, glycolysis/gluconeogenesis, carbon metabolism, biosynthesis of amino acids, and ECM-receptor interaction. The top 10 proteins were Tpi1, Eno1, Prdx1, Ppia, Prdx6, Vwf, Prdx2, Fga, Fgg, and Fgb, and the predicted TFs of these proteins were Nfe2, Srf, Epas1, Tbp, and Hoxc8.

Conclusion

The identified proteins related to age and involved in AAA formation were associated with the response to oxidative stress, coagulation and platelet activation, and complement and inflammation pathways, and the TFs of these proteins might be potential targets for AAA treatments. Further experimental and biological studies are needed to elucidate the role of these age-associated and AAA-related proteins in the progression of AAA.

HIST1H2BN induced cell proliferation and EMT phenotype in prostate cancer via NF-κB signal pathway

BACKGROUND

The potential role of HIST1H2BN in prostate cancer remains unclear.

OBJECTIVE

To evaluate the carcinogenic role of HIST1H2BN in prostate cancer.

METHODS

The expression of HIST1H2BN in prostate cancer was analyzed using TCGA database and clinical samples. The roles and mechanisms of HIST1H2BN were investigated in DU145 and PC3 cells.

RESULTS

HIST1H2BN was significantly upregulated in prostate cancer. HIST1H2BN knockdown inhibited cell proliferation, migration and EMT phenotype in prostate cancer cells. Downregulating HIST1H2BN diminished the expression and binding activity of NF-κB p65, then influenced the expression of MMP2 and MMP9. CONCLUSION : This is the first study to elaborate a HIST1H2BN-NF-κB-EMT regulatory axis in oncogenesis, indicating that HIST1H2BN might be potential therapeutic target for prostate cancer.

Endothelial cell infection and dysfunction, immune activation in severe COVID-19

Rationale: Pulmonary vascular endotheliitis, perivascular inflammation, and immune activation are observed in COVID-19 patients. While the initial SARS-CoV-2 infection mainly infects lung epithelial cells, whether it also infects endothelial cells (ECs) and to what extent SARS-CoV-2-mediated pulmonary vascular endotheliitis is associated with immune activation remain to be determined. Methods: To address these questions, we studied SARS-CoV-2-infected K18-hACE2 (K18) mice, a severe COVID-19 mouse model, as well as lung samples from SARS-CoV-2-infected nonhuman primates (NHP) and patient deceased from COVID-19. We used immunostaining, RNAscope, and electron microscopy to analyze the organs collected from animals and patient. We conducted bulk and single cell (sc) RNA-seq analyses, and cytokine profiling of lungs or serum of the severe COVID-19 mice. Results: We show that SARS-CoV-2-infected K18 mice develop severe COVID-19, including progressive body weight loss and fatality at 7 days, severe lung interstitial inflammation, edema, hemorrhage, perivascular inflammation, systemic lymphocytopenia, and eosinopenia. Body weight loss in K18 mice correlated with the severity of pneumonia, but not with brain infection. We also observed endothelial activation and dysfunction in pulmonary vessels evidenced by the up-regulation of VCAM1 and ICAM1 and the downregulation of VE-cadherin. We detected SARS-CoV-2 in capillary ECs, activation and adhesion of platelets and immune cells to the vascular wall of the alveolar septa, and increased complement deposition in the lungs, in both COVID-19-murine and NHP models. We also revealed that pathways of coagulation, complement, K-ras signaling, and genes of ICAM1 and VCAM1 related to EC dysfunction and injury were upregulated, and were associated with massive immune activation in the lung and circulation. Conclusion: Together, our results indicate that SARS-CoV-2 causes endotheliitis via both infection and infection-mediated immune activation, which may contribute to the pathogenesis of severe COVID-19 disease.

Involvement of Myeloid Cells and Noncoding RNA in Abdominal Aortic Aneurysm Disease

Significance: Abdominal aortic aneurysm (AAA) is a potentially fatal condition, featuring the possibility of high-mortality rupture. To date, prophylactic surgery by means of open surgical repair or endovascular aortic repair at specific thresholds is considered standard therapy. Both surgical options hold different risk profiles of short- and long-term morbidity and mortality. Targeting early stages of AAA development to decelerate disease progression is desirable. Recent Advances: Understanding the pathomechanisms that initiate formation, maintain growth, and promote rupture of AAA is crucial to developing new medical therapeutic options. Inflammatory cells, in particular macrophages, have been investigated for their contribution to AAA disease for decades, whereas evidence on lymphocytes, mast cells, and neutrophils is sparse. Recently, there has been increasing interest in noncoding RNAs (ncRNAs) and their involvement in disease development, including AAA. Critical Issues: The current evidence on myeloid cells and ncRNAs in AAA largely originates from small animal models, making clinical extrapolation difficult. Although it is feasible to collect surgical human AAA samples, these tissues reflect end-stage disease, preventing examination of critical mechanisms behind early AAA formation. Future Directions: Gaining more insight into how myeloid cells and ncRNAs contribute to AAA disease, particularly in early stages, might suggest nonsurgical AAA treatment options. The utilization of large animal models might be helpful in this context to help bridge translational results to humans.

Potential of mesenchymal stem cells for bioengineered blood vessels in comparison with other eligible cell sources

Application of stem cells in tissue engineering has proved to be effective in many cases due to great proliferation and differentiation potentials as well as possible paracrine effects of these cells. Human mesenchymal stem cells (MSCs) are recognized as a valuable source for vascular tissue engineering, which requires endothelial and perivascular cells. The goal of this review is to survey the potential of MSCs for engineering functional blood vessels in comparison with other cell types including bone marrow mononuclear cells, endothelial precursor cells, differentiated adult autologous smooth muscle cells, autologous endothelial cells, embryonic stem cells, and induced pluripotent stem cells. In conclusion, MSCs represent a preference in making autologous tissue-engineered vascular grafts (TEVGs) as well as off-the-shelf TEVGs for emergency vascular surgery cases.

Versatile cell ablation tools and their applications to study loss of cell functions

Targeted cell ablation is a powerful approach for studying the role of specific cell populations in a variety of organotypic functions, including cell differentiation, and organ generation and regeneration. Emerging tools for permanently or conditionally ablating targeted cell populations and transiently inhibiting neuronal activities exhibit a diversity of application and utility. Each tool has distinct features, and none can be universally applied to study different cell types in various tissue compartments. Although these tools have been developed for over 30 years, they require additional improvement. Currently, there is no consensus on how to select the tools to answer the specific scientific questions of interest. Selecting the appropriate cell ablation technique to study the function of a targeted cell population is less straightforward than selecting the method to study a gene's functions. In this review, we discuss the features of the various tools for targeted cell ablation and provide recommendations for optimal application of specific approaches.

Role of complement system in pathological remodeling of the vascular wall

Cardiovascular diseases (CVD) remain the major cause of morbidity and mortality in Europe. The clinical complications associated to arterial wall rupture involve intimal cap rupture in complicated atherosclerotic plaques and medial rupture in abdominal aortic aneurysm (AAA). The mechanisms underlying pathological vascular remodeling include lipid accumulation, cell proliferation, redox imbalance, proteolysis, leukocyte infiltration, cell death, and eventually, thrombosis. The complement system could participate in vascular remodeling by several mechanisms, from an initial protective response that aims in the clearing of cell debris to a potential deleterious role participating in leukocyte chemotaxis and cell activation and bridging innate and adaptive immunity. We have reviewed the presence and distribution of complement components, as well as the triggers of complement activation in atherosclerotic plaques and AAA, to later assess the functional consequences of complement modulation in experimental models of pathological vascular remodeling and the potential role of complement components as potential circulating biomarkers of CVD. On the whole, complement system is a key mechanism involved in vascular remodelling, which could be useful in the diagnostic/prognostic setting, as well as a potential therapeutic target, of CVD.

Regulatory T cells protected against abdominal aortic aneurysm by suppression of the COX-2 expression

CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to protect against the development of abdominal aortic aneurysm (AAA). Cyclooxygenase‐2 (COX‐2), a pro‐inflammatory protein, can convert arachidonic acid into prostaglandins (PGs). The present study was aimed to investigate the effect of Tregs on COX‐2 expression in angiotension II (Ang II)‐induced AAA in ApoE^−/− mice. Tregs were injected via tail vein in every 2 weeks. Ang II was continuously infused by a micropump for 28 days to induce AAA. In vivo, compared with the control group, adoptive transfer of Tregs significantly reduced the incidence of AAA, maximal diameter, and the mRNA and protein expression of COX‐2 in mice. Immunofluorescence showed that Tregs treatment reduced COX‐2 expression both in smooth muscle cells (SMCs) and macrophages in AAA. In vitro, the Western blot analysis showed that Tregs reduced Ang II‐induced COX‐2 expression in macrophages and SMCs. Meanwhile, ELISA showed that Tregs reduced Ang II‐induced prostaglandin E₂ (PGE₂) secretion. Moreover, Tregs increased SMC viability and induced transition of macrophages phenotype from M1 to M2. In conclusion, Tregs treatment dramatically decreased the expression of COX‐2 in vivo and in vitro, suggesting that Tregs could protect against AAA through inhibition of COX‐2. The study may shed light on the immune treatment of AAA.

Intracerebral matrix metalloproteinase 9 in fatal diabetic ketoacidosis

There is increasing awareness that in addition to the metabolic crisis of diabetic ketoacidosis (DKA) caused by severe insulin deficiency, the immune inflammatory response is likely an active multicomponent participant in both the acute and chronic insults of this medical crisis, with strong evidence of activation for both the cytokine and complement system. Recent studies report that the matrix metalloproteinase enzymes and their inhibitors are systemically activated in young Type 1 diabetes mellitus (T1D) patients during DKA and speculate on their involvement in blood-brain barrier (BBB) disruption. Based on our previous studies, we address the question if matrix metalloproteinase 9 (MMP9) is expressed in the brain in the fatal brain edema (BE) of DKA. Our data show significant expression of MMP9 on the cells present in brain intravascular areas. The presence of MMP9 in intravascular cells and that of MMP+ cells seen passing the BBB indicates a possible role in tight junction protein disruption of the BBB, possibly leading to neurological complications including BE. We have also shown that MMP9 is expressed on neurons in the hippocampal areas of both BE/DKA cases investigated, while expression of tissue inhibitor of metalloproteinases 1 (TIMP1) was reduced in the same areas. We can speculate that intraneuronal MMP9 can be a sign of neurodegeneration. Further studies are necessary to determine the role of MMP9 in the pathogenesis of the neurologic catastrophe of the brain edema of DKA. Inhibition of MMP9 expression might be helpful in preserving neuronal function and BBB integrity during DKA.

Complement regulatory protein CD59a plays a protective role in immune liver injury of trichloroethylene-sensitized BALB/c mice

Trichloroethylene (TCE) is a major occupational and environmental chemical compound which causes occupational dermatitis medicamentosa-like of TCE with severe liver damage. Our previous studies showed that complement activation was a newly recognized mechanism for TCE-induced liver damage. The objective of this study was to explore the role of the key complement regulatory protein, CD59a, in TCE-induced immune liver injury. We firstly evaluated the changes of CD59a expression in liver tissue and then investigated if the changes were associated with membrane attack complex (MAC) formation, nuclear factor kappa B (NF-κB) activation and liver damage in BALB/c mice model of TCE-induced skin sensitization in the absence or presence of soluble recombinant rat CD59-Cys. The results showed that low expression of CD59a accompanied by MAC deposition in the liver of TCE-sensitized BALB/c mice, which was consistent in time. In addition, activation of NF-κB pathway, upregulation of inflammatory cytokine and liver damage also occured. Additional experiment showed that recombinant rat sCD59-Cys alleviated inflammation and liver damage in TCE-sensitized BALB/c mice. Moreover, recombinant rat sCD59-Cys reduced MAC formation and inhibited NF-κB activation measured by P-IκBα and nuclear NF-κB p65 in the liver of TCE-sensitized BALB/c mice. In conclusion, recombinant rat sCD59-Cys plays a protective role in immune liver injury of TCE-sensitized BALB/c mice.

PARP-1 (Poly[ADP-Ribose] Polymerase 1) Inhibition Protects From Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysm in Mice

Abdominal aortic aneurysm (AAA) is a common vascular degenerative disease. PARP-1 (poly[ADP-ribose] polymerase 1) is a nuclear enzyme, which plays a critical role in vascular diseases. We hypothesized that PARP-1 inhibition might have protective effects on AAA. In vivo, Ang II (angiotensin II) was continuously infused by a micropump for 28 days to induce AAA in mice. In vitro, aortic endothelial cells and smooth muscle cells were stimulated by Ang II for 24 hours. Ang II infusion increased PARP-1 expression and activity and successfully induced AAA formation partly with a hemorrhage in ApoE^-/- mice. Genetic deletion of PARP-1 markedly reduced the AAA incidence, abdominal aortic diameter, macrophage infiltration, ICAM-1 (intercellular adhesion molecule 1) and VCAM-1 (vascular adhesion molecule 1) expression, and MMP (matrix metalloproteinase) expression, as well as MMP activity; but increased smooth muscle cells content and collagens expression in AAA. PARP-1 inhibition by PJ-34 also exerted a protective effect on AAA in mice. In aortic endothelial cells, Ang II-induced oxidative stress and DNA damage, resulting in increased PARP-1 expression and activity. Compared with the control, Ang II increased TNF-α (tumor necrosis factor α) and IL-6 (interleukin-6) secretions, ICAM-1 expression and THP-1 (human acute monocytic leukemia cell line) cells adhesion, while PARP-1 inhibition by siRNA reduced the inflammatory response probably through inhibition of the phosphorylation of ERK (extracellular signal-regulated kinase), NF-κB (nuclear factor-κB), and Akt signaling pathways. In smooth muscle cells, Ang II promoted cell migration, proliferation, and apoptosis, reduced collagens expression, but increased MMPs expression, while PARP-1 deletion alleviated these effects partly by reducing NF-κB-targeted MMP-9 expression. PARP-1 inhibition might be a feasible strategy for the treatment of AAA.

Silencing of Non-POU-domain-containing octamer-binding protein stabilizes atherosclerotic plaque in apolipoprotein E-knockout mice via NF-κB signaling pathway

BACKGROUND

It remains unknown whether Non-POU-domain-containing octamer-binding protein (NonO) plays a causative role in plaque destabilization. We hypothesized that NonO gene silencing may stabilize atherosclerotic plaque by increasing P4Hα1 expression and inhibiting the inflammation.

METHODS AND RESULTS

Vulnerable atherosclerotic plaques were induced in ApoE-/- mice by high fat diet, perivascular collar placement and mental stress. Compared with normal carotid arteries, those contained vulnerable plaques had high NonO expression. In another in vivo experiment, mice contained vulnerable plaques were randomly divided into 5 groups to receive physiological saline, si-N.C-lentivirus (LV), si-NonO-LV, pGC-GFP-LV and NonO-LV, respectively. NonO overexpression increased while NonO silencing decreased the incidence of carotid plaque disruption. NonO overexpression enhanced macrophage infiltration and lipid deposition but reduced the content of vascular smooth muscle cells and collagen in plaques, leading to an increased plaque vulnerability index, whereas NonO silencing exhibited the opposite effect. In addition, NonO overexpression increased the expression of proinflammatory cytokines and matrix metalloproteinases and decreased the expression of P4Hα1 both in vivo and in vitro, whereas NonO silencing showed the contrary effect. NonO co-immunoprecipitated with NF-κB p65, and promoted its nuclear translocation and phosphorylation, and these effects were reversed by NonO silencing.

CONCLUSION

NonO may promote plaque destabilization and increase the incidence of plaque disruption in ApoE-/- mice by inducing the expression of inflammatory cytokines and matrix metalloproteinases and suppressing that of P4Hα1. The mechanism may involve the interaction of NonO with NF-κB leading to enhanced NF-κB nuclear translocation and phosphorylation.

Complement activation in the arteries of patients with severe atherosclerosis

BACKGROUND

Excessive complement activation plays an important role in the pathogenesis of atherosclerosis (AS). We therefore wanted to investigate whether complement is activated in areas of AS by detecting the deposition of C3b/iC3b and membrane attack complex (MAC). We also analyzed the relationships between C3b/iC3b and MAC levels and the clinicopathological features of patients with AS.

METHODS

The sample comprised 79 patients who had been diagnosed with AS. Their levels of C3b/iC3b and MAC deposition were evaluated by immunohistochemistry (IHC). The results were translated into scores, and the patients' clinical features were recorded.

RESULTS

Compared with normal arteries, significantly greater deposits of C3b/iC3b and MAC were found in AS arteries. In the group with more C3b/iC3b deposition, the ratio of patients with hypertension was higher. Moreover, in the group with more MAC deposition, the ratio of patients with hypertriglyceridemia was higher.

CONCLUSIONS

The finding of C3b/iC3b and MAC deposition in atherosclerotic arteries points to the activation of complement. Greater amounts of C3b/iC3b and MAC deposition imply excessive complement activation, which can lead to the development of AS. Hypertension and hypertriglyceridemia may, respectively, contribute to the activation of complement C3 or the formation of MAC.

Deletion of resistin-like molecule-beta attenuates angiotensin II-induced abdominal aortic aneurysm

In the present study, we want to test whether deletion of resistin-like molecule-beta (RELMβ) attenuates angiotensin II (Ang II)-induced formation of abdominal aortic aneurysm (AAA). RELMβ gene expression was inhibited by siRNA both in vivo and in vitro. Apolipoprotein E-knockout (ApoE^−/−) mice were randomly divided into saline, Ang II, siRNA negative control (si-NC) and siRNA RELMβ (si-RELMβ) groups (n=15 each), and mice in the last three groups underwent Ang II infusion for 4 weeks to induce AAA. RELMβ gene deficiency significantly decreased AAA incidence and severity, which was associated with reduced macrophage accumulation and decreased expression of proinflammatory cytokines (monocyte chemoattractant protein 1 and interleukin 6), matrix metalloproteinase 2 (MMP-2) and MMP-9 in the aortic wall. In cultured macrophages, RELMβ deficiency blunted the response of macrophages to Ang II and downregulated the levels of proinflammatory cytokines, MMP-2 and MMP-9. Recombinant RELMβ promoted the secretion of proinflammatory cytokines, MMP-2 and MMP-9 in macrophages and activated extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) signaling, which was reversed with pretreatment with inhibitors of ERK1/2 and JNK. Deletion of RELMβ attenuated Ang II-induced AAA formation in ApoE^−/− mice. The inherent mechanism may involve the reduced expression of proinflammatory cytokines, MMP-2 and MMP-9, which was mediated by ERK1/2 and JNK activation. Therefore, inhibiting RELMβ secretion may be a novel approach for anti-aneurysm treatment.

Weighted Gene Co-expression Network Analysis Identifies FKBP11 as a Key Regulator in Acute Aortic Dissection through a NF-kB Dependent Pathway

Acute aortic dissection (AAD) is a life-threatening disease. Despite the higher risk of mortality, currently there are no effective therapies that can ameliorate AAD development or progression. Identification of meaningful clusters of co-expressed genes or representative biomarkers for AAD may help to identify new pathomechanisms and foster development of new therapies. To this end, we performed a weighted gene co-expression network analysis (WGCNA) and calculated module-trait correlations based on a public microarray dataset (GSE 52093) and discovered 9 modules were found to be related to AAD. The module which has the strongest positive correlation with AAD was further analyzed and the top 10 hub genes SLC20A1, GINS2, CNN1, FAM198B, MAD2L2, UBE2T, FKBP11, SLMAP, CCDC34, and GALK1 were identified. Furthermore, we validated the data by qRT-PCR in an independent sample set originated from our study center. Overall, the qRT-PCR results were consistent with the results of the microarray analysis. Intriguingly, the highest change was found for FKBP11, a protein belongs to the FKBP family of peptidyl-prolyl cis/trans isomerases, which catalyze the folding of proline-containing polypeptides. In congruent with the gene expression analysis, FKBP11 expression was induced in cultured endothelial cells by angiotensin II treatment and endothelium of the dissected aorta. More importantly we show that FKBP11 provokes inflammation in endothelial cells by interacting with NF-kB p65 subunit, resulting in pro-inflammatory cytokines production. Accordingly, siRNA mediated knockdown of FKBP11 in cultured endothelial cells suppressed angiotensin II induced monocyte transmigration through the endothelial monolayer. Based on these data, we hypothesize that pro-inflammatory cytokines elicited by FKBP11 overexpression in the endothelium under AAD condition could facilitate transendothelial migration of the circulating monocytes into the aorta, where they differentiate into active macrophages and secrete MMPs and other extracellular matrix (ECM) degrading proteins, contributing to sustained inflammation and AAD. Taken together, our data identify important role of FKBP11 which can serve as biomarker and/or therapeutic target for AAD.

Target deletion of complement component 9 attenuates antibody-mediated hemolysis and lipopolysaccharide (LPS)-induced acute shock in mice

Terminal complement membrane attack complex (MAC) formation is induced initially by C5b, followed by the sequential condensation of the C6, C7, C8. Polymerization of C9 to the C5b-8 complex forms the C5b-9 (or MAC). The C5b-9 forms lytic or non lytic pores in the cell membrane destroys membrane integrity. The biological functionalities of MAC has been previously investigated by using either the mice deficient in C5 and C6, or MAC’s regulator CD59. However, there is no available C9 deficient mice (mC9^−/−) for directly dissecting the role of C5b-9 in the pathogenesis of human diseases. Further, since C5b-7 and C5b-8 complexes form non lytic pore, it may also plays biological functionality. To better understand the role of terminal complement cascades, here we report a successful generation of mC9^−/−. We demonstrated that lack of C9 attenuates anti-erythrocyte antibody-mediated hemolysis or LPS-induced acute shock. Further, the rescuing effect on the acute shock correlates with the less release of IL-1β in mC9^−/−, which is associated with suppression of MAC-mediated inflammasome activation in mC9^−/−. Taken together, these results not only confirm the critical role of C5b-9 in complement-mediated hemolysis and but also highlight the critical role of C5b-9 in inflammasome activation.

B lymphocytes in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a progressive inflammatory disease of the artery walls. Immune cells, including B lymphocytes, are implicated in the pathogenesis of AAA through interconnected mechanisms. Many studies have shown that compared with normal abdominal aortic tissue, the amount of B lymphocytes that infiltrate the adventitia of AAAs was significantly higher. Activated B lymphocytes promote AAA by producing immunoglobulins, cytokines, and matrix metalloproteinases (MMPs), resulting in the activation of macrophages, mast cells (MCs) and complement pathways. Finally, all of these factors lead to the degradation of collagen and matrix proteins and to aortic wall remodeling, which are hallmarks of AAA. However, few studies focus on the relative function of B cells, and their precise mechanisms in AAA remain unclear. Thus, we summarize the current knowledge on the role of B cells in AAA and offer recommendations for further investigation of preventing the progression of AAA.

Transcriptional (ChIP-Chip) Analysis of ELF1, ETS2, RUNX1 and STAT5 in Human Abdominal Aortic Aneurysm

We investigated transcriptional control of gene expression in human abdominal aortic aneurysm (AAA). We previously identified 3274 differentially expressed genes in human AAA tissue compared to non-aneurysmal controls. Four expressed transcription factors (ELF1, ETS2, STAT5 and RUNX1) were selected for genome-wide chromatin immunoprecipitation. Transcription factor binding was enriched in 4760 distinct genes (FDR < 0.05), of which 713 were differentially expressed in AAA. Functional classification using Gene Ontology (GO), KEGG, and Network Analysis revealed enrichment in several biological processes including “leukocyte migration” (FDR = 3.09 × 10⁻⁰⁵) and “intracellular protein kinase cascade” (FDR = 6.48 × 10⁻⁰⁵). In the control aorta, the most significant GO categories differed from those in the AAA samples and included “cytoskeleton organization” (FDR = 1.24 × 10⁻⁰⁶) and “small GTPase mediated signal transduction” (FDR = 1.24 × 10⁻⁰⁶). Genes up-regulated in AAA tissue showed a highly significant enrichment for GO categories “leukocyte migration” (FDR = 1.62 × 10⁻¹¹), “activation of immune response” (FDR = 8.44 × 10⁻¹¹), “T cell activation” (FDR = 4.14 × 10⁻¹⁰) and “regulation of lymphocyte activation” (FDR = 2.45 × 10⁻⁰⁹), whereas the down-regulated genes were enriched in GO categories “cytoskeleton organization” (FDR = 7.84 × 10⁻⁰⁵), “muscle cell development” (FDR = 1.00 × 10⁻⁰⁴), and “organ morphogenesis” (FDR = 3.00 × 10⁻⁰⁴). Quantitative PCR assays confirmed a sub-set of the transcription factor binding sites including those in MTMR11, DUSP10, ITGAM, MARCH1, HDAC8, MMP14, MAGI1, THBD and SPOCK1.

Pivotal Role of Serum- and Glucocorticoid-Inducible Kinase 1 in Vascular Inflammation and Atherogenesis

Objective—

Atherosclerosis, an inflammatory disease of arterial vessel walls, requires migration and matrix metalloproteinase (MMP)-9–dependent invasion of monocytes/macrophages into the vascular wall. MMP-9 expression is stimulated by transcription factor nuclear factor-κB, which is regulated by inhibitor κB (IκB) and thus IκB kinase. Regulators of nuclear factor-κB include serum- and glucocorticoid-inducible kinase 1 (SGK1). The present study explored involvement of SGK1 in vascular inflammation and atherogenesis.

Approach and Results—

Gene-targeted apolipoprotein E (ApoE)–deficient mice without ( apoe −/− sgk1 +/+ ) or with ( apoe −/− sgk1 −/− ) additional SGK1 knockout received 16-week cholesterol-rich diet. According to immunohistochemistry atherosclerotic lesions in aorta and carotid artery, vascular CD45 + leukocyte infiltration, Mac-3 + macrophage infiltration, vascular smooth muscle cell content, MMP-2, and MMP-9 positive areas in atherosclerotic tissue were significantly less in apoe −/− sgk1 −/− mice than in apoe −/− sgk1 +/+ mice. As determined by Boyden chamber, thioglycollate-induced peritonitis and air pouch model, migration of SGK1-deficient CD11b + F4/80 + macrophages was significantly diminished in vitro and in vivo. Zymographic MMP-2 and MMP-9 production, MMP-9 activity and invasion through matrigel in vitro were significantly less in sgk1 −/− than in sgk1 +/+ macrophages and in control plasmid–transfected or inactive K127N SGK1-transfected than in constitutively active S422D SGK1-transfected THP-1 cells. Confocal microscopy revealed reduced macrophage number and macrophage MMP-9 content in plaques of apoe −/− sgk1 −/− mice. In THP-1 cells, MMP-inhibitor GM6001 (25 μmol/L) abrogated S422D SGK1-induced MMP-9 production and invasion. According to reverse transcription polymerase chain reaction, MMP-9 transcript levels were significantly reduced in sgk1 −/− macrophages and strongly upregulated in S422D SGK1-transfected THP-1 cells compared with control plasmid–transfected or K127N SGK1-transfected THP-1 cells. According to immunoblotting and confocal microscopy, phosphorylation of IκB kinase and inhibitor κB and nuclear translocation of p50 were significantly lower in sgk1 −/− macrophages than in sgk1 +/+ macrophages and significantly higher in S422D SGK1-transfected THP-1 cells than in control plasmid–transfected or K127N SGK1-transfected THP-1 cells. Treatment of S422D SGK1-transfected THP-1 cells with IκB kinase-inhibitor BMS-345541 (10 μmol/L) abolished S422D SGK1-induced increase of MMP-9 transcription and gelatinase activity.

Conclusions—

SGK1 plays a pivotal role in vascular inflammation during atherogenesis. SGK1 participates in the regulation of monocyte/macrophage migration and MMP-9 transcription via regulation of nuclear factor-κB.

Regulatory T cells prevent angiotensin II-induced abdominal aortic aneurysm in apolipoprotein E knockout mice

To test the hypothesis that adoptive transfer of regulatory T cells (Tregs) may dose-dependently inhibit the formation of angiotensin II-induced abdominal aortic aneurysm in apolipoprotein E knockout mice, we established an animal model of abdominal aortic aneurysm by angiotensin II infusion in apolipoprotein E knockout mice. Then mice received different treatment with PBS, low-dose Tregs, high-dose Tregs, or CD25-depleting PC61 antibody. Histopathologic analysis showed that the incidence of abdominal aortic aneurysm was 80%, 76%, 27%, and 71% in the PBS, low-dose Tregs, high-dose Tregs, and PC61 groups, respectively. Tregs treatment markedly decreased macrophage and CD4+ T-cell infiltration and preserved the medial smooth muscle cells. Furthermore, Tregs decreased the levels of proinflammatory cytokines, matrix metalloproteinase-2 (MMP-2) and MMP-9, increased the expression of anti-inflammatory interleukin-10 and transforming growth factor-β, and suppressed apoptosis and oxidative stress. In vitro, Tregs inhibited the response of human aortic smooth muscle cells to angiotensin II and reduced the expression of proinflammatory cytokines, MMP-2 and MMP-9, possibly by inhibiting the activation of nuclear factor-κB and extracellular signal-regulate kinase 1/2. In addition, Tregs downregulated macrophage type 1-related genes and upregulated macrophage type 2-related genes. However, Tregs-mediated effects were largely reversed by disrupting cell-cell contact or using neutralizing antibodies against interleukin-10 and transforming growth factor-β. Adoptive transfer of Tregs dose-dependently prevents angiotensin II-induced abdominal aortic aneurysm in apolipoprotein E knockout mice. The mechanisms may involve declined proinflammatory cytokine expression and MMP-2 and MMP-9 levels and enhanced anti-inflammatory cytokine expression, which is mediated by direct cell-cell contact and soluble mediators.

Complement and HIV-I infection/HIV-associated neurocognitive disorders

The various neurological complications associated with HIV-1 infection, specifically HIV-associated neurocognitive disorders (HAND) persist as a major public health burden worldwide. Despite the widespread use of anti-retroviral therapy, the prevalence of HAND is significantly high. HAND results from the direct effects of an HIV-1 infection as well as secondary effects of HIV-1-induced immune reaction and inflammatory response. Complement, a critical mediator of innate and acquired immunity, plays important roles in defeating many viral infections by the formation of a lytic pore or indirectly by opsonization and recruitment of phagocytes. While the role of complement in the pathogenesis of HIV-1 infection and HAND has been previously recognized for over 15 years, it has been largely underestimated thus far. Complement can be activated through HIV-1 envelope proteins, mannose-binding lectins (MBL), and anti-HIV-1 antibodies. Complement not only fights against HIV-1 infection but also enhances HIV-1 infection. In addition, HIV-1 can hijack complement regulators such as CD59 and CD55 and can utilize these regulators and factor H to escape from complement attack. Normally, complement levels in brain are much lower than plasma levels and there is no or little complement deposition in brain cells. Interestingly, local production and deposition of complement are dramatically increased in HIV-1-infected brain, indicating that complement may contribute to the pathogenesis of HAND. Here, we review the current understanding of the role of complement in HIV-1 infection and HAND, as well as potential therapeutic approaches targeting the complement system for the treatment and eradications of HIV-1 infection.

Targeted mouse complement inhibitor CR2-Crry protects against the development of atherosclerosis in mice

OBJECTIVE

Atherosclerosis is a chronic inflammatory and immune vascular disease, and clinical and experimental evidence has indicated an important role of complement activation products, including the terminal membrane attack complex (MAC), in atherogenesis. Here, we investigated whether complement inhibition represents a potential therapeutic strategy to treat/prevent atherogenesis using CR2-Crry, a recently described complement inhibitor that specifically targets to sites of C3 activation.

METHODS AND RESULTS

Previous studies demonstrated that loss of CD59 (a membrane inhibitor of MAC formation) accelerated atherogenesis in Apoe deficient (Apoe(-/-)) mice. Here, both CD59 sufficient and CD59 deficient mice in an Apoe deficient background (namely, mCd59 ab(+/+)/Apoe(-/-) and mCd59 ab(-/-)/Apoe(-/-)) were treated with CR2-Crry for 4 and 2 months respectively, while maintained on a high fat diet. Compared to control treatment, CR2-Crry treatment resulted in significantly fewer atherosclerotic lesions in the aorta and aortic root, and inhibited the accelerated atherogenesis seen in mCd59 ab(+/+)/Apoe(-/-) and mCd59 ab(-/-)/Apoe(-/-) mice. CR2-Crry treatment also resulted in significantly reduced C3 and MAC deposition in the vasculature of both mice, as well as a significant reduction in the number of infiltrating macrophages and T cells.

CONCLUSION

The data demonstrate the therapeutic potential of targeted complement inhibition.

Gelatinase B/MMP-9 in Tumour Pathogenesis and Progression

Since its original identification as a leukocyte gelatinase/type V collagenase and tumour type IV collagenase, gelatinase B/matrix metalloproteinase (MMP)-9 is now recognised as playing a central role in many aspects of tumour progression. In this review, we relate current concepts concerning the many ways in which gelatinase B/MMP-9 influences tumour biology. Following a brief outline of the gelatinase B/MMP-9 gene and protein, we analyse the role(s) of gelatinase B/MMP-9 in different phases of the tumorigenic process, and compare the importance of gelatinase B/MMP-9 source in the carcinogenic process. What becomes apparent is the importance of inflammatory cell-derived gelatinase B/MMP-9 in tumour promotion, early progression and triggering of the "angiogenic switch", the integral relationship between inflammatory, stromal and tumour components with respect to gelatinase B/MMP-9 production and activation, and the fundamental role for gelatinase B/MMP-9 in the formation and maintenance of tumour stem cell and metastatic niches. It is also apparent that gelatinase B/MMP-9 plays important tumour suppressing functions, producing endogenous angiogenesis inhibitors, promoting inflammatory anti-tumour activity, and inducing apoptosis. The fundamental roles of gelatinase B/MMP-9 in cancer biology underpins the need for specific therapeutic inhibitors of gelatinase B/MMP-9 function, the use of which must take into account and substitute for tumour-suppressing gelatinase B/MMP-9 activity and also limit inhibition of physiological gelatinase B/MMP-9 function.

Novel mechanisms of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAAs) are a common but asymptomatic disease that has high susceptibility to rupture. Current therapeutic options are limited to surgical procedures because no pharmacological approaches have been proven to decrease either expansion or rupture of human AAAs. The current dearth of effective medical treatment is attributed to insufficient understanding of the mechanisms underlying the initiation, propagation and rupture of AAAs. This review will emphasize recent advances in mechanistic studies that may provide insights into potential pharmacological treatments for this disease. While we primarily focus on recent salient findings, we also discuss mechanisms that continue to be controversial depending on models under study. Despite the progress on exploring mechanisms of experimental AAAs, ultimate validation of mechanisms will require completion of prospective double-blinded clinical trials. In addition, we advocate increased emphasis of collaborative studies using animal models and human tissues for determination of mechanisms that explore expansion and rupture of existing AAAs.

Involvement of the renin-angiotensin system in abdominal and thoracic aortic aneurysms

Aortic aneurysms are relatively common maladies that may lead to the devastating consequence of aortic rupture. AAAs (abdominal aortic aneurysms) and TAAs (thoracic aortic aneurysms) are two common forms of aneurysmal diseases in humans that appear to have distinct pathologies and mechanisms. Despite this divergence, there are numerous and consistent demonstrations that overactivation of the RAS (renin-angiotensin system) promotes both AAAs and TAAs in animal models. For example, in mice, both AAAs and TAAs are formed during infusion of AngII (angiotensin II), the major bioactive peptide in the RAS. There are many proposed mechanisms by which the RAS initiates and perpetuates aortic aneurysms, including effects of AngII on a diverse array of cell types and mediators. These experimental findings are complemented in humans by genetic association studies and retrospective analyses of clinical data that generally support a role of the RAS in both AAAs and TAAs. Given the lack of a validated pharmacological therapy for any form of aortic aneurysm, there is a pressing need to determine whether the consistent findings on the role of the RAS in animal models are translatable to humans afflicted with these diseases. The present review compiles the recent literature that has shown the RAS as a critical component in the pathogenesis of aortic aneurysms.

DAF/CD55 and Protectin/CD59 modulate adaptive immunity and disease outcome in experimental autoimmune myasthenia gravis

The role of regulators of complement activity (RCA) involving CD55 and CD59 in the pathogenesis of experimental autoimmune myasthenia gravis (EAMG) remains unclear. CD55 and CD59 restrict complement activation by inhibiting C3/C5 convertases' activities and membrane attack complex formation, respectively. Actively immunized EAMG mice deficient in either CD55 or CD59 showed significant differences in adaptive immune responses and worsened disease outcome associated with increased levels of serum cytokines, modified production of acetylcholine receptor antibodies, and more complement deposition at the neuromuscular junction. We conclude that modulation of complement activity by RCA represents an alternative in controlling of autoimmune processes in EAMG.

The protective role of CD59 and pathogenic role of complement in hepatic ischemia and reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) is a major factor influencing graft outcome in liver transplantation, but its mechanism is not well defined. Although complement, including the membrane attack complex (MAC), a terminal product of complement activation, is thought to be involved in the multiple reactions subsequent to the ischemia-reperfusion (IR) process, the role of MAC in the pathogenesis of hepatic IRI requires further investigation. We used a warm ischemia-reperfusion injury model in mice and a syngeneic orthotopic liver transplantation model in rats to define the role of complement, including MAC, in hepatic IR. CD59-deficient mice had more severe liver dysfunction, evidenced by increased aspartate aminotransferase levels and increased injury of liver parenchymal and nonparenchymal cells than did CD59-sufficient mice during warm hepatic IR. Furthermore, complement depletion in CD59-deficient mice by pretreatment with cobra venom factor (CVF) or the genetic introduction of C3 deficiency partially protected against development of the severe liver dysfunction that occurred in CD59-deficient mice. Severity of liver dysfunction correlated with MAC deposition, apoptotic cells, and increased inflammatory mediators such as tumor necrosis factor α. Moreover, depletion of complement with CVF in orthotopic liver transplantation recipient rats attenuated IRI of the donor livers. Taken together, these results highlight the protective role of CD59 and pathogenic role of complement, including MAC, in the pathogenesis of hepatic IRI.

Heme oxygenase-1 in inflammation and cardiovascular disease

Cardiovascular disease accounts for 1 of every 2.9 deaths in the United States, thus the burden of the disease remains high. Given the high mortality and escalating healthcare cost for the disease, it is of urgent need to treat cardiovascular disease effectively. Heme oxygenase-1 (HO-1) catalyzes the oxidation of heme to generate carbon monoxide, biliverdin, and iron. These reaction products of HO-1 have potent anti-inflammatory and anti-oxidative functions. Although HO-1 is expressed at low levels in most tissues under normal basal conditions, it is highly inducible in response to various pathophysiological stresses. Numerous studies have indicated that HO-1 induction is an adaptive defense mechanism to protect cells and tissues against injury in many disease settings. This review highlights the role of HO-1 in inflammation and several cardiovascular diseases-atherosclerosis, myocardial infarction, graft survival after heart transplantation, and abdominal aortic aneurysm. Given that inflammation and oxidative stress are associated with development of cardiovascular disease and that HO-1 has anti-inflammatory and anti-oxidative properties, HO-1 is emerging as a great potential therapeutic target for treating cardiovascular disease.

Role of complement cascade in abdominal aortic aneurysms

OBJECTIVE

The goal of this study was to investigate the role of complement cascade genes in the pathobiology of human abdominal aortic aneurysms (AAAs).

METHODS AND RESULTS

Results of a genome-wide microarray expression profiling revealed 3274 differentially expressed genes between aneurysmal and control aortic tissue. Interestingly, 13 genes in the complement cascade were significantly differentially expressed between AAA and the controls. In silico analysis of the promoters of the 13 complement cascade genes showed enrichment for transcription factor binding sites for signal transducer and activator of transcription (STAT)5A. Chromatin-immunoprecipitation experiments demonstrated binding of transcription factor STAT5A to the promoters of the majority of the complement cascade genes. Immunohistochemical analysis showed strong staining for C2 in AAA tissues.

CONCLUSIONS

These results provide strong evidence that the complement cascade plays a role in human AAA. Based on our microarray studies, the pathway is activated in AAA, particularly via the lectin and classical pathways. The overrepresented binding sites of transcription factor STAT5A in the complement cascade gene promoters suggest a role for STAT5A in the coordinated regulation of complement cascade gene expression.

The critical roles of platelet activation and reduced NO bioavailability in fatal pulmonary arterial hypertension in a murine hemolysis model

Pulmonary arterial hypertension (PAH) is suspected to be a strong mortality determinant of hemolytic disorders. However, direct contribution of acute intravascular hemolysis to fatal PAH has not been investigated. The roles of nitric oxide (NO) insufficiency and platelet activation in hemolysis-associated fatal PAH have been suspected but not been experimentally studied. We recently generated a unique intravascular hemolysis mouse model in which the membrane toxin, intermedilysin (ILY), exclusively lyses the erythrocytes of transgenically expressing human CD59 mice (ThCD59(RBC)), thereby inducing ILY-dose-dependent massive hemolysis. Using this murine hemolysis model, we found that the acute increase in pulmonary arterial pressure leading to right ventricle failure caused sudden death. Reduced NO bioavailability and massive platelet activation/aggregation leading to the formation of massive thrombosis specifically in the pulmonary microvasculature played the critical roles in pathogenesis of acute hemolysis-associated fatal PAH. Therapeutic interventions enhancing NO bioactivity or inhibiting platelet activation prevented sudden death or prolonged survival time via the suppression of the acute increase in pulmonary arterial pressure and improvement of right ventricle function. These findings further highlight the importance of the inhibition of platelet activation and the enhancement of NO bioavailability for the treatment and prevention of hemolysis-associated (fatal) PAH.