Combining SARS-CoV-2 interferon-gamma release assay with humoral response assessment to define immune memory profiles.

OBJECTIVES: In the post-SARS-CoV-2 pandemic era, "breakthrough infections" are still documented, due to variants of concerns (VoCs) emergence and waning humoral immunity. Despite widespread utilization, the definition of the anti-Spike (S) immunoglobulin-G (IgG) threshold to define protection has unveiled several limitations. Here, we explore the advantages of incorporating T-cell response assessment to enhance the definition of immune memory profile. METHODS: SARS-CoV-2 interferon-gamma release assay test (IGRA) was performed on samples collected longitudinally from immunocompetent healthcare workers throughout their immunization by infection and/or vaccination, anti-receptor-binding domain IgG levels were assessed in parallel. The risk of symptomatic infection according to cellular/humoral immune capacities during Omicron BA.1 wave was then estimated. RESULTS: Close to 40% of our samples were exclusively IGRA-positive, largely due to time elapsed since their last immunization. This suggests that individuals have sustained long-lasting cellular immunity, while they would have been classified as lacking protective immunity based solely on IgG threshold. Moreover, the Cox regression model highlighted that Omicron BA.1 circulation raises the risk of symptomatic infection while increased anti-receptor-binding domain IgG and IGRA levels tended to reduce it. CONCLUSION: The discrepancy between humoral and cellular responses highlights the significance of assessing the overall adaptive immune response. This integrated approach allows the identification of vulnerable subjects and can be of interest to guide antiviral prophylaxis at an individual level.

Fully automated interferon-γ release assay to monitor antigen-independent T cell functionality: A proof of concept study in septic shock.

In sepsis, personalized immunotherapy is being evaluated as a means of restoring immune function in the most severely affected patients. Biomarkers play a crucial role in this process, as there are no clear clinical indicators of immune dysfunction. Functional testing is considered a gold standard for assessing immune function, but this approach faces analytical challenges in terms of clinical implementation. The use of technician-dependent, time-consuming, home-made protocols often leads to poor standardization. This study represents the first beta testing of a fully automated interferon-γ release assay (IGRA) for monitoring the functionality of antigen-independent T lymphocytes. We observed a significant decrease in IFN-γ release capacity, which was associated with typical alterations in immunological cellular parameters (such as low mHLA-DR expression and decreased CD8 T lymphocyte count), in 22 patients with septic shock. Since the test is performed using whole blood and requires no technician intervention, with results available within 4 h, it may offer new possibilities for monitoring patients with immune alterations in routine clinical conditions. Further investigations in larger cohorts of patients are now needed to validate its clinical potential.

Impact of SARS-CoV-2 RBD Mutations on the Production of a Recombinant RBD Fusion Protein in Mammalian Cells.

SARS-CoV-2 receptor-binding domain (RBD) is a major target for the development of diagnostics, vaccines and therapeutics directed against COVID-19. Important efforts have been dedicated to the rapid and efficient production of recombinant RBD proteins for clinical and diagnostic applications. One of the main challenges is the ongoing emergence of SARS-CoV-2 variants that carry mutations within the RBD, resulting in the constant need to design and optimise the production of new recombinant protein variants. We describe here the impact of naturally occurring RBD mutations on the secretion of a recombinant Fc-tagged RBD protein expressed in HEK 293 cells. We show that mutation E484K of the B.1.351 variant interferes with the proper disulphide bond formation and folding of the recombinant protein, resulting in its retention into the endoplasmic reticulum (ER) and reduced protein secretion. Accumulation of the recombinant B.1.351 RBD-Fc fusion protein in the ER correlated with the upregulation of endogenous ER chaperones, suggestive of the unfolded protein response (UPR). Overexpression of the chaperone and protein disulphide isomerase PDIA2 further impaired protein secretion by altering disulphide bond formation and increasing ER retention. This work contributes to a better understanding of the challenges faced in producing mutant RBD proteins and can assist in the design of optimisation protocols.

Specific detection of memory T-cells in COVID-19 patients using standardized whole-blood Interferon gammarelease assay.

Antigen-specific T-cells are essential for protective immunity against SARS-CoV-2. We set up a semi-automated whole-blood Interferon-gamma release assay (WB IGRA) to monitor the T-cell response after stimulation with SARS-CoV-2 peptide pools. We report that the WB IGRA is complementary to serological assays to assess SARS-CoV-2 immunity.

A20/TNFAIP3 Increases ENOS Expression in an ERK5/KLF2-Dependent Manner to Support Endothelial Cell Health in the Face of Inflammation.

Rationale: Decreased expression and activity of endothelial nitric oxide synthase (eNOS) in response to inflammatory and metabolic insults is the hallmark of endothelial cell (EC) dysfunction that preludes the development of atherosclerosis and hypertension. We previously reported the atheroprotective properties of the ubiquitin-editing and anti-inflammatory protein A20, also known as TNFAIP3, in part through interrupting nuclear factor-kappa B (NF-κB) and interferon signaling in EC and protecting these cells from apoptosis. However, A20's effect on eNOS expression and function remains unknown. In this study, we evaluated the impact of A20 overexpression or knockdown on eNOS expression in EC, at baseline and after tumor necrosis factor (TNF) treatment, used to mimic inflammation. Methods and Results: A20 overexpression in human coronary artery EC (HCAEC) significantly increased basal eNOS mRNA (qPCR) and protein (western blot) levels and prevented their downregulation by TNF. Conversely, siRNA-induced A20 knockdown decreased eNOS mRNA levels, identifying A20 as a physiologic regulator of eNOS expression. By reporter assays, using deletion and point mutants of the human eNOS promoter, and knockdown of eNOS transcriptional regulators, we demonstrated that A20-mediated increase of eNOS was transcriptional and relied on increased expression of the transcription factor Krüppel-like factor (KLF2), and upstream of KLF2, on activation of extracellular signal-regulated kinase 5 (ERK5). Accordingly, ERK5 knockdown or inhibition significantly abrogated A20's ability to increase KLF2 and eNOS expression. In addition, A20 overexpression in HCAEC increased eNOS phosphorylation at Ser-1177, which is key for the function of this enzyme. Conclusions: This is the first report demonstrating that overexpression of A20 in EC increases eNOS transcription in an ERK5/KLF2-dependent manner and promotes eNOS activating phosphorylation. This effect withstands eNOS downregulation by TNF, preventing EC dysfunction in the face of inflammation. This novel function of A20 further qualifies its therapeutic promise to prevent/treat atherosclerosis.

Performance Characteristics of the Vidas SARS-CoV-2 IgM and IgG Serological Assays.

The COVID-19 pandemic, caused by the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread worldwide. Serological testing for SARS-CoV-2-specific antibodies plays an important role in understanding and controlling the pandemic, notably through epidemiological surveillance. Well-validated and highly specific SARS-CoV-2 serological assays are urgently needed. We describe here the analytical and clinical performance of Vidas SARS-CoV-2 IgM and Vidas SARS-CoV-2 IgG, two CE-marked, emergency use authorization (EUA)-authorized, automated, qualitative assays for the detection of SARS-CoV-2-specific IgM and IgG, respectively. Both assays showed high within-run and within-laboratory precision (coefficients of variation < 11.0%) and very low cross-reactivity toward sera of patients with a past common coronavirus or respiratory virus infection. Clinical specificity determined on up to 989 prepandemic healthy donors was ≥99% with a narrow 95% confidence interval for both IgM and IgG assays. Clinical sensitivity was determined on up to 232 samples from 130 reverse transcriptase PCR (RT-PCR)-confirmed SARS-CoV-2 patients. The positive percent agreement (PPA) with SARS-CoV-2 PCR reached 100% at ≥16 days (Vidas SARS-CoV-2 IgM) and ≥32 days (Vidas SARS-CoV-2 IgG) of symptom onset. Combined IgM/IgG test results improved the PPA compared to each test alone. SARS-CoV-2 IgG seroconversion followed closely that of SARS-CoV-2 IgM and remained stable over time, while SARS-CoV-2 IgM levels rapidly declined. Interestingly, SARS-CoV-2-specific IgM and IgG responses were significantly higher in COVID-19 hospitalized versus nonhospitalized patients. Altogether, the Vidas SARS-CoV-2 IgM and IgG assays are highly specific and sensitive serological tests suitable for the reliable detection of past acute SARS-CoV-2 infections.

Performance characteristics of the VIDAS® ANTI-HEV IgM and IgG assays.

BACKGROUND: Several unautomated anti-HEV diagnostic tests are presently available. OBJECTIVE: We have evaluated the performance of the new automated VIDAS® ANTI-HEV IgM and IgG assays. STUDY DESIGN: We assessed the reproducibility and cross-reactivity of both VIDAS assays and the analytical sensitivity and linearity of the VIDAS IgG assay. We also tested the VIDAS and comparator assays Wantai IgG and IgM on immunocompetent and immunocompromised patients. Data were analysed according to the infectious profile, with samples from viremic phase (HEV RNA/IgM positive) and post-viremic phase (HEV RNA negative, IgM positive) infections, and uninfected patients (HEV RNA/IgM negative). RESULTS: Within-run reproducibility was <10% and between-run reproducibility was <12% for both assays. We found no cross-reactivity, except for the VIDAS IgG assay in some patients with HBV (1/10) or malaria (3/23) infections and for the VIDAS IgM assay in some HIV-infected patients (1/10). The VIDAS IgG assay was linear over 0.10-10.0 U/mL. Analytical sensitivity of the IgG assay was 0.71 IU/ml (probit analysis). The clinical sensitivity of the VIDAS IgM assay was 97.65% for viremic samples (83/85) and 59.15% (42/71) for post-viremic samples from immunocompetent patients. It was 78.95% (45/57) for acute phase samples and 77.78% (28/36) for post-viremic samples from immunocompromised patients. Specificity was excellent (>99%) in both populations. CONCLUSION: The analytical and clinical performance of the new VIDAS® ANTI-HEV assays was excellent. These rapid, automated assays for detecting HEV antibodies will strengthen the arsenal for diagnosing HEV infections.

Expression, refolding and bio-structural analysis of a tetravalent recombinant dengue envelope domain III protein for serological diagnosis.

Dengue is a mosquito-borne disease caused by four genetically and serologically related viruses that affect several millions of people. Envelope domain III (EDIII) of the viral envelope protein contains dengue virus (DENV) type-specific and DENV complex-reactive antigenic sites. Here, we describe the expression in Escherichia coli, the refolding and bio-structural analysis of envelope domain III of the four dengue serotypes as a tetravalent dengue protein (EDIIIT2), generating an attractive diagnostic candidate. In vitro refolding of denatured EDIIIT2 was performed by successive dialysis with decreasing concentrations of chaotropic reagent and in the presence of oxidized glutathione. The efficiency of refolding was demonstrated by protein mobility shifting and fluorescent visualization of labeled cysteine in non-reducing SDS-PAGE. The identity and the fully oxidized state of the protein were verified by mass spectrometry. Analysis of the structure by fluorescence, differential scanning calorimetry and circular dichroism showed a well-formed structural conformation mainly composed of ß-strands. A label-free immunoassay based on biolayer interferometry technology was subsequently used to evaluate antigenic properties of folded EDIIIT2 protein using a panel of dengue IgM positive and negative human sera. Our data collectively support the use of an oxidatively refolded EDIIIT2 recombinant chimeric protein as a promising antigen in the serological diagnosis of dengue virus infections.

A20-mediated modulation of inflammatory and immune responses in aortic allografts and development of transplant arteriosclerosis.

BACKGROUND: Transplant arteriosclerosis (TA) is the pathognomonic feature of chronic rejection, the primary cause of allograft failure. We have shown that the NF-κB inhibitory protein A20 exerts vasculoprotective effects in endothelial and smooth muscle cells (SMC), and hence is a candidate to prevent TA. We sought direct proof for this hypothesis. METHODS: Fully mismatched, C57BL/6 (H2) into BALB/c (H2), aorta to carotid allografts were preperfused with saline, recombinant A20 adenovirus (rAd.A20) or rAd.ß-galactosidase (ß-gal), implanted, harvested 4 weeks after transplantation, and analyzed by histology, immunohistochemistry, and immunofluorescence staining. We measured indoleamine 2,3-dioxygenase, interleukin-6, and transforming growth factor-ß mRNA and protein levels in nontransduced, and rAd.A20 or rAd.ß-gal-transduced human SMC cultures after cytokine treatment. RESULTS: Vascular overexpression of A20 significantly reduced TA lesions. This correlated with decreased graft inflammation and increased apoptosis of neointimal SMC. Paradoxically, T-cell infiltrates increased in A20-expressing allografts, including the immunoprivileged media, which related to A20 preventing indoleamine 2,3-dioxygenase upregulation in SMC. However, infiltrating T cells were predominantly T-regulatory cells (CD25+/Forkhead Box P3 [FoxP3+]). This agrees with A20 inhibiting interleukin-6 and promoting transforming growth factor-ß production by medial SMC and in SMC cultures exposed to cytokines, which favors differentiation of regulatory over pathogenic T cells. CONCLUSIONS: In summary, A20 prevents immune-mediated remodeling of vascular allografts, therefore reduces TA lesions by affecting apoptotic and inflammatory signals and modifying the local cytokine milieu to promote an immunoregulatory response within the vessel wall. This highlights a novel function for A20 in local immunosurveillance, which added to its vasculoprotective effects, supports its therapeutic promise in TA.

Hepatocyte growth factor preferentially activates the anti-inflammatory arm of NF-κB signaling to induce A20 and protect renal proximal tubular epithelial cells from inflammation.

Inflammation induces the NF-κB dependent protein A20 in human renal proximal tubular epithelial cells (RPTEC), which secondarily contains inflammation by shutting down NF-κB activation. We surmised that inducing A20 without engaging the pro-inflammatory arm of NF-κB could improve outcomes in kidney disease. We showed that hepatocyte growth factor (HGF) increases A20 mRNA and protein levels in RPTEC without causing inflammation. Upregulation of A20 by HGF was NF-κB/RelA dependent as it was abolished by overexpressing IκBα or silencing p65/RelA. Unlike TNFα, HGF caused minimal IκBα and p65/RelA phosphorylation, with moderate IκBα degradation. Upstream, HGF led to robust and sustained AKT activation, which was required for p65 phosphorylation and A20 upregulation. While HGF treatment of RPTEC significantly increased A20 mRNA, it failed to induce NF-κB dependent, pro-inflammatory MCP-1, VCAM-1, and ICAM-1 mRNA. This indicates that HGF preferentially upregulates protective (A20) over pro-inflammatory NF-κB dependent genes. Upregulation of A20 supported the anti-inflammatory effects of HGF in RPTEC. HGF pretreatment significantly attenuated TNFα-mediated increase of ICAM-1, a finding partially reversed by silencing A20. In conclusion, this is the first demonstration that HGF activates an AKT-p65/RelA pathway to preferentially induce A20 but not inflammatory molecules. This could be highly desirable in acute and chronic renal injury where A20-based anti-inflammatory therapies are beneficial.

A20 inhibits post-angioplasty restenosis by blocking macrophage trafficking and decreasing adventitial neovascularization.

OBJECTIVE: Neointimal hyperplasia is an inflammatory and proliferative process that occurs as a result of injury to the vessel wall. We have shown that the homeostatic protein A20 prevents neointimal hyperplasia by affecting endothelial cell (EC) and smooth muscle cell (SMC) responses to injury. In this work, we questioned whether A20 impacts other pathogenic effectors of neointimal hyperplasia including homing of monocyte/macrophages and EC/SMC precursors to the site of vascular injury, vascular endothelial growth factor (VEGF) secretion, and adventitial neovascularization. METHODS AND RESULTS: Carotid balloon angioplasty was performed on rat recipients of a bone marrow transplant from green fluorescent rats. Adenoviral delivery of A20 prevented neointimal hyperplasia and decreased macrophage infiltration. This was associated with decreased ICAM-1 and MCP-1 expression in vitro. Additionally, A20 reduced neovascularization in the adventitia of balloon injured carotid arteries, which correlated with fewer VEGF positive cells. CONCLUSIONS: A20 downregulates adhesion markers, chemokine production, and adventitial angiogenesis, all of which are required for macrophage trafficking to sites of vascular injury. This, in turn, diminishes the inflammatory milieu to prevent neointimal hyperplasia.

A20 protects mice from lethal liver ischemia/reperfusion injury by increasing peroxisome proliferator-activated receptor-alpha expression.

The nuclear factor-kappaB inhibitory protein A20 demonstrates hepatoprotective abilities through combined antiapoptotic, anti-inflammatory, and pro-proliferative functions. Accordingly, overexpression of A20 in the liver protects mice from toxic hepatitis and lethal radical hepatectomy, whereas A20 knockout mice die prematurely from unfettered liver inflammation. The effect of A20 on oxidative liver damage, as seen in ischemia/reperfusion injury (IRI), is unknown. In this work, we evaluated the effects of A20 upon IRI using a mouse model of total hepatic ischemia. Hepatic overexpression of A20 was achieved by recombinant adenovirus (rAd.)-mediated gene transfer. Although only 10%-25% of control mice injected with saline or the control rAd.beta galactosidase survived IRI, the survival rate reached 67% in mice treated with rAd.A20. This significant survival advantage in rAd.A20-treated mice was associated with improved liver function, pathology, and repair potential. A20-treated mice had significantly lower bilirubin and aminotransferase levels, decreased hemorrhagic necrosis and steatosis, and increased hepatocyte proliferation. A20 protected against liver IRI by increasing hepatic expression of peroxisome proliferator-activated receptor alpha (PPARalpha), a regulator of lipid homeostasis and of oxidative damage. A20-mediated protection of hepatocytes from hypoxia/reoxygenation and H(2)O(2)-mediated necrosis was reverted by pretreatment with the PPARalpha inhibitor MK886. In conclusion, we demonstrate that PPARalpha is a novel target for A20 in hepatocytes, underscoring its novel protective effect against oxidative necrosis. By combining hepatocyte protection from necrosis and promotion of proliferation, A20-based therapies are well-poised to protect livers from IRI, especially in the context of small-for-size and steatotic liver grafts. Liver Transpl 15:1613-1621, 2009. (c) 2009 AASLD.

Neutrophils and B lymphocytes in ANCA-associated vasculitis.

The pathogenesis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is unknown but is most consistent with a primary role for neutrophils in the acute injury. Thus, neutrophils are cardinal cells in the pathophysiological process in AAV because they are both effector cells responsible for endothelial damage and targets of autoimmunity. In addition, because of their capacity to synthesize a wide variety of cytokines and chemokines, neutrophils can be considered as important modulators of the inflammatory and potentially of the autoimmune process. ANCA directed against two main autoantigens, namely proteinase 3 and myeloperoxidase, are likely to play a modulatory role in the inflammatory process. Interestingly, neutrophils are an important source of lymphocyte stimulator (BLy), a cytokine that plays a fundamental role in B-cell physiology, including differentiation, proliferation and immunoglobulin production. The issue of B-cell activation and/or dysregulation in vasculitis will be discussed.

Coronin-1 is associated with neutrophil survival and is cleaved during apoptosis: potential implication in neutrophils from cystic fibrosis patients.

Because neutrophil apoptosis plays a key role in resolving inflammation, identification of proteins regulating neutrophil survival should provide new strategies to modulate inflammation. Using a proteomic approach, coronin-1 was identified as a cytosolic protein cleaved during neutrophil apoptosis. Coronin-1 is an actin-binding protein that can associate with phagosomes and NADPH oxidase, but its involvement in apoptosis was currently unknown. In coronin-1-transfected PLB985 cells, coronin-1 overexpression did not modify the kinetics of granulocyte differentiation as assessed by CD11b labeling. Concerning apoptosis, increased coronin-1 expression in dimethylformamide-differentiated PLB985 significantly decreased gliotoxin-induced mitochondrial depolarization as compared with controls. Likewise, coronin-1 significantly decreased TRAIL-induced apoptosis with less mitochondrial depolarization, caspase-3 and caspase-9 activities, but not caspase-8 or Bid truncation suggesting that coronin-1 interfered with mitochondria-related events. To validate the prosurvival role of coronin-1 in a pathophysiological condition involving neutrophil-dominated inflammation, neutrophils from cystic fibrosis (CF) patients were studied. Circulating neutrophils from CF patients had more coronin-1 expression assessed by immunoblotting or proteomic analysis of cytosolic proteins. This was associated with a lower apoptosis rate than those from controls evidenced by delayed phosphatidylserine externalization and mitochondria depolarization. In addition, inflammatory neutrophils from CF patients lungs showed an intense coronin-1 immunolabeling. We concluded that coronin-1 could constitute a potential target in resolving inflammation.

TNFalpha-induced macrophage death via caspase-dependent and independent pathways.

Macrophages are the principal source of TNFalpha, yet they are highly resistant to TNFalpha-mediated cell death. Previously, employing in vitro differentiated human macrophages, we showed that following the inhibition of NF-kappaB, TNFalpha-induced caspase-8 activation contributes to DNA fragmentation but is not necessary for the loss of the inner mitochondrial transmembrane potential (DeltaPsim) or cell death. We here extend these observations to demonstrate that, when NF-kappaB is inhibited in macrophages, TNFalpha alters lysosomal membrane permeability (LMP). This results in the release of cathepsin B with subsequent loss of DeltaPsim and caspase-8 independent cell death. Interestingly, the cytoprotective, NF-kappaB-dependent protein A20 was rapidly induced in macrophages treated with TNFalpha. Ectopic expression of A20 in macrophages preserves LMP following treatment with TNFalpha, and as a result, mitochondrial integrity is safeguarded and macrophages are protected from cell death. These observations demonstrate that TNFalpha triggers both caspase 8-dependent and -independent cell death pathways in macrophages and identify a novel mechanism by which A20 protects these cells against both pathways.

A novel function for cadherin 11/osteoblast-cadherin in vascular smooth muscle cells: modulation of cell migration and proliferation.

OBJECTIVE: Intimal hyperplasia is a common cause of vein graft failure in cardiovascular surgery. The molecular basis for intimal hyperplasia remains poorly defined. We have previously identified, by gene chip analysis of vein grafts, increased messenger (mRNA) for the adhesion molecule cadherin 11/osteoblast-cadherin (CDH11). The function of CDH11 in vascular cells is unknown. The aim of the present study is to confirm CDH11 expression in vein grafts and characterize its role in vascular remodeling. METHODS: Cephalic vein interposition grafts were implanted in a canine model and harvested at predetermined time points. CDH11 protein expression was determined by immunohistochemistry. Early passage human coronary artery smooth muscle cells (SMCs) were used for in vitro studies. Real-time polymerase chain reaction was used to assess cellular CDH11 mRNA levels. CDH11 signaling was inhibited by either transfection with silencing RNA targeting CDH11 or with a blocking antibody to CDH11. Cellular migration was evaluated and cellular proliferation was assessed. RESULTS: Expression of CDH11 was increased in medial SMCs of vein grafts recovered at 7, 14, and 30 days after surgery compared with control veins from the same animals. In vitro CDH11 mRNA was up-regulated 1.8 +/- 0.2-fold (P = .003) in SMCs after treatment with tumor necrosis factor-alpha. Cellular migration was attenuated by inhibition of CDH11 both with a blocking antibody (0.67 +/- 0.09; P = .063) and gene knockdown mediated by small interfering RNA (0.67 +/- 0.14; P = .036). SMC proliferation decreased by 3.1-fold (P = .006) in the presence of CDH11-blocking antibody. Knockdown of CDH11 mediated by small interfering RNA resulted in a 1.3-fold (P = .018) decrease in proliferation. CONCLUSIONS: CDH11 is up-regulated in SMC in vivo and in vitro as part of the response to injury. Inhibition of CDH11 decreases SMC migration and proliferation, two pathogenic effectors of intimal hyperplasia.

Comparison of gene silencing in human vascular cells using small interfering RNAs.

BACKGROUND: Gene silencing achieved through small interfering RNA (siRNA) transfection represents a promising approach to vascular gene therapy. Here we characterize the behavior of RNA interference (RNAi) in vascular biology by comparing the RNAi response to single- and multigene siRNA transfections in vitro in human vascular cells. STUDY DESIGN: The strength and specificity of multigene silencing in cultured human coronary artery smooth muscle and human coronary artery endothelial cells (HCASMC/HCAEC) were assessed by quantitative reverse transcription-polymerase chain reaction (QRT-PCR) and Western blot after transfection singly or simultaneously with siRNAs targeting glyceraldehyde-3-phosphate dehydrogenase, the myristoylated alanine-rich C kinase substrate, and cadherin 11. RNAi response to low-dose (0.25 to 10 nM) siRNA transfection was characterized between the two cell types by QRT-PCR and fluorescence-activated cell sorter analysis. RESULTS: Powerful and specific silencing of all targets was observed in both cell types after multigene siRNA transfections, but with a reduction in effect compared with single-gene siRNA transfections. Multigene messenger RNA (mRNA) reductions in HCAECs exceeded those achieved in HCASMCs, and superior mRNA silencing and siRNA delivery were observed in HCAECs after low-dose siRNA transfections. CONCLUSIONS: Multigene silencing by siRNA stands as a promising nonviral approach for manipulating gene expression in human vascular cells. Under our in vitro conditions, endothelial cells were more susceptible to siRNA transfection and gene silencing than vascular smooth muscle cells. RNAi technology could potentially find use in the development of siRNA cocktails for application to vein bypass grafts or for modulating endothelial cell function in other forms of vascular disease.

A20, a modulator of smooth muscle cell proliferation and apoptosis, prevents and induces regression of neointimal hyperplasia.

A20 is a NF-kappaB-dependent gene that has dual anti-inflammatory and antiapoptotic functions in endothelial cells (EC). The function of A20 in smooth muscle cells (SMC) is unknown. We demonstrate that A20 is induced in SMC in response to inflammatory stimuli and serves an anti-inflammatory function via blockade of NF-kappaB and NF-kappaB-dependent proteins ICAM-1 and MCP-1. A20 inhibits SMC proliferation via increased expression of cyclin-dependent kinase inhibitors p21waf1 and p27kip1. Surprisingly, A20 sensitizes SMC to cytokine- and Fas-mediated apoptosis through a novel NO-dependent mechanism. In vivo, adenoviral delivery of A20 to medial rat carotid artery SMC after balloon angioplasty prevents neointimal hyperplasia by blocking SMC proliferation and accelerating re-endothelialization, without causing apoptosis. However, expression of A20 in established neointimal lesions leads to their regression through increased apoptosis. This is the first demonstration that A20 exerts two levels of control of vascular remodeling and healing. A20 prevents neointimal hyperplasia through combined anti-inflammatory and antiproliferative functions in medial SMC. If SMC evade this first barrier and neointima is formed, A20 has a therapeutic potential by uniquely sensitizing neointimal SMC to apoptosis. A20-based therapies hold promise for the prevention and treatment of neointimal disease.

Combined expression of A1 and A20 achieves optimal protection of renal proximal tubular epithelial cells.

BACKGROUND: Apoptotic death of renal proximal tubular epithelial cells (RPTECs) is a feature of acute and chronic renal failure. RPTECs are directly damaged by ischemia, inflammatory, and cytotoxic mediators but also contribute to their own demise by up-regulating proinflammatory nuclear factor-kappaB (NF-kappaB)-dependent proteins. In endothelial cells, the Bcl family member A1 and the zinc finger protein A20 have redundant and dual antiapoptotic and anti-inflammatory effects. We studied the function(s) of A1 and A20 in human RPTECs in vitro. METHODS: Expression of A1 [reverse transcription-polymerase chain reaction (RT-PCR) and A20 (Northern and Western blot analysis)] in RPTECs was evaluated. A1 and A20 were overexpressed in RPTECs by recombinant adenoviral-mediated gene transfer. Their effect upon inhibitor of NFkappaB alpha (IkappaBalpha) degradation (Western blot), NF-kappaB nuclear translocation [electrophoretic mobility shift assay (EMSA)], up-regulation of intercellular adhesion molecule-1 (ICAM-1) [fluorescence-activated cell sorter (FACS)] and monocyte chemoattractant protein-1 (MCP-1) (Northern blot) and apoptosis [terminal deoxynucleotiddyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL)] and FACS analysis of DNA content) was determined. RESULTS: A1 and A20 were induced in RPTECs as part of the physiologic response to tumor necrosis factor (TNF). A20, but not A1, inhibited TNF-induced NF-kappaB activation by preventing IkappaBalpha degradation, hence subsequent up-regulation of the proinflammatory molecules ICAM-1 and MCP-1. Unexpectedly, A20 did not protect RPTECs from TNF and Fas-mediated apoptosis while A1 protected against both stimuli. Coexpression of A1 and A20 in RPTECs achieved additive anti-inflammatory and antiapoptotic cytoprotection. CONCLUSION: A1 and A20 exert differential cytoprotective effects in RPTECs. A1 is antiapoptotic. A20 is anti-inflammatory via blockade of NF-kappaB. We propose that A1 and A20 are both required for optimal protection of RPTECs from apoptosis (A1) and inflammation (A20) in conditions leading to renal damage.

A20 protects mice from lethal radical hepatectomy by promoting hepatocyte proliferation via a p21waf1-dependent mechanism.

The liver has a remarkable regenerative capacity, allowing recovery following injury. Regeneration after injury is contingent on maintenance of healthy residual liver mass, otherwise fulminant hepatic failure (FHF) may arise. Understanding the protective mechanisms safeguarding hepatocytes and promoting their proliferation is critical for devising therapeutic strategies for FHF. We demonstrate that A20 is part of the physiological response of hepatocytes to injury. In particular, A20 is significantly upregulated in the liver following partial hepatectomy. A20 protects hepatocytes from apoptosis and ongoing inflammation by inhibiting NF-kappaB. Hepatic expression of A20 in BALB/c mice dramatically improves survival following extended and radical lethal hepatectomy. A20 expression in the liver limits hepatocellular damage hence maintains bilirubin clearance and the liver synthetic function. In addition, A20 confers a proliferative advantage to hepatocytes via decreased expression of the cyclin-dependent kinase inhibitor p21(waf1). In conclusion, A20 provides a proliferative advantage to hepatocytes. By combining anti-inflammatory, antiapoptotic and pro-proliferative functions, A20-based therapies could be beneficial in prevention and treatment of FHF.