Functional coupling of TRPM2 and extrasynaptic NMDARs exacerbates excitotoxicity in ischemic brain injury.

Excitotoxicity induced by NMDA receptor (NMDAR) activation is a major cause of neuronal death in ischemic stroke. However, past efforts of directly targeting NMDARs have unfortunately failed in clinical trials. Here, we reveal an unexpected mechanism underlying NMDAR-mediated neurotoxicity, which leads to the identification of a novel target and development of an effective therapeutic peptide for ischemic stroke. We show that NMDAR-induced excitotoxicity is enhanced by physical and functional coupling of NMDAR to an ion channel TRPM2 upon ischemic insults. TRPM2-NMDAR association promotes the surface expression of extrasynaptic NMDARs, leading to enhanced NMDAR activity and increased neuronal death. We identified a specific NMDAR-interacting motif on TRPM2 and designed a membrane-permeable peptide to uncouple the TRPM2-NMDAR interaction. This disrupting peptide protects neurons against ischemic injury in vitro and protects mice against ischemic stroke in vivo. These findings provide an unconventional strategy to mitigate excitotoxic neuronal death without directly targeting NMDARs.

The voltage-gated proton channel Hv1 promotes microglia-astrocyte communication and neuropathic pain after peripheral nerve injury.

Activation of spinal cord microglia contributes to the development of peripheral nerve injury-induced neuropathic pain. However, the molecular mechanisms underlying microglial function in neuropathic pain are not fully understood. We identified that the voltage-gated proton channel Hv1, which is functionally expressed in spinal microglia, was significantly increased after spinal nerve transection (SNT). Hv1 mediated voltage-gated proton currents in spinal microglia and mice lacking Hv1 (Hv1 KO) display attenuated pain hypersensitivities after SNT compared with wildtype (WT) mice. In addition, microglial production of reactive oxygen species (ROS) and subsequent astrocyte activation in the spinal cord was reduced in Hv1 KO mice after SNT. Cytokine screening and immunostaining further revealed that IFN-γ expression was compromised in spinal astrocytes in Hv1 KO mice. These results demonstrate that Hv1 proton channel contributes to microglial ROS production, astrocyte activation, IFN-γ upregulation, and subsequent pain hypersensitivities after SNT. This study suggests Hv1-dependent microglia-astrocyte communication in pain hypersensitivities and identifies Hv1 as a novel therapeutic target for alleviating neuropathic pain.

The voltage-gated proton channel Hv1 contributes to neuronal injury and motor deficits in a mouse model of spinal cord injury.

Traumatic injury to the spinal cord initiates a series of pathological cellular processes that exacerbate tissue damage at and beyond the original site of injury. This secondary damage includes oxidative stress and inflammatory cascades that can lead to further neuronal loss and motor deficits. Microglial activation is an essential component of these secondary signaling cascades. The voltage-gated proton channel, Hv1, functionally expressed in microglia has been implicated in microglia polarization and oxidative stress in ischemic stroke. Here, we investigate whether Hv1 mediates microglial/macrophage activation and aggravates secondary damage following spinal cord injury (SCI). Following contusion SCI, wild-type (WT) mice showed significant tissue damage, white matter damage and impaired motor recovery. However, mice lacking Hv1 (Hv1-/-) showed significant white matter sparing and improved motor recovery. The improved motor recovery in Hv1-/- mice was associated with decreased interleukin-1ß, reactive oxygen/ nitrogen species production and reduced neuronal loss. Further, deficiency of Hv1 directly influenced microglia activation as noted by decrease in microglia numbers, soma size and reduced outward rectifier K+ current density in Hv1-/- mice compared to WT mice at 7 d following SCI. Our results therefore implicate that Hv1 may be a promising potential therapeutic target to alleviate secondary damage following SCI caused by microglia/macrophage activation.

RNAseq analysis of hippocampal microglia after kainic acid-induced seizures.

Microglia have been shown to be of critical importance to the progression of temporal lobe epilepsy. However, the broad transcriptional changes that these cells undergo following seizure induction is not well understood. As such, we utilized RNAseq analysis upon microglia isolated from the hippocampus to determine expression pattern alterations following kainic acid induced seizure. We determined that microglia undergo dramatic changes to their expression patterns, particularly with regard to mitochondrial activity and metabolism. We also observed that microglia initiate immunological activity, specifically increasing interferon beta responsiveness. Our results provide novel insights into microglia transcriptional regulation following acute seizures and suggest potential therapeutic targets specifically in microglia for the treatment of seizures and epilepsy.

Niche astrocytes promote the survival, proliferation and neuronal differentiation of co-transplanted neural stem cells following ischemic stroke in rats.

Niche astrocytes have been reported to promote neuronal differentiation through juxtacrine signaling. However, the effects of astrocytes on neuronal differentiation following ischemic stroke are not fully understood. In the present study, transplanted astrocytes and neural stem cells (NSCs) were transplanted into the ischemic striatum of transient middle cerebral artery occlusion (MCAO) model rats 48 h following surgery. It was observed that the co-transplantation of astrocytes and NSCs resulted in a higher ratio of survival and proliferation of the transplanted NSCs, and neuronal differentiation, in MCAO rats compared with NSC transplantation alone. These results demonstrate that the co-administration of astrocytes promotes the survival and neuronal differentiation of NSCs in the ischemic brain. These results suggest that the co-transplantation of astrocytes and NSCs is more effective than NSCs alone in the production of neurons following ischemic stroke in rats.

The Dose of Intravenously Transplanted Bone Marrow Stromal Cells Determines the Therapeutic Effect on Vascular Remodeling in a Rat Model of Ischemic Stroke.

The therapeutic benefits of bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation for ischemic stroke have been extensively demonstrated. However, studies on the optimal cell dose for intravenous administration are still limited. This study aimed to determine an appropriate cell dose for BM-MSC intravenous transplantation and to investigate the effect of cell dose on vascular remodeling in a rat model of ischemic stroke. BM-MSCs at doses of 5104 (low-dose group), 5105 (medium-dose group), and 2106 (high-dose group) were intravenously injected into rats at 72 h after ischemia. The therapeutic efficacy of BM-MSCs was evaluated by measuring infarct volume, vascular diameters, capillary area in the peri-infarct zone, level of basic fibroblast growth factor (bFGF) in the peri-infarct zone, and serum vascular endothelial growth factor (VEGF) level at 7 days after ischemia. Compared with the low-dose and control groups, medium-dose and high-dose BM-MSC transplantation significantly reduced the volume of the infarct area, enlarged the diameters of pial vessels and the basilar artery, and increased the capillary area in the peri-infarct zone of the cerebral cortex. Furthermore, transplanted BM-MSCs elevated the expressions of bFGF in the peri-infarct zone and the serum VEGF level. Administration of 5105 BM-MSCs is an appropriate cell dose for ischemic stroke therapy in rats. These findings may be helpful for designing future clinical trials.

Heat shock protein inhibitor, quercetin, as a novel adjuvant agent to improve radiofrequency ablation-induced tumor destruction and its molecular mechanism.

BACKGROUND: We investigated the effect of a small molecular inhibitor of heat shock protein (HSP), quercetin, on tumor radiofrequency (RF) ablation, and explored the underlying molecular mechanisms. METHODS: In in vivo study, rats with R3230 breast adenocarcinoma were sacrificed 24 h post-treatment and gross coagulation areas were compared, and next, randomized into four treatment arms (control, quercetin alone, RF alone, and combination) for Kaplan-Meier analysis of defined endpoint survival. Then the distribution and expression levels of heat shock protein 70 (HSP70), cleaved caspase-3 and heat shock factor 1 (HSF1) were analyzed after different treatments. In in vitro study, we used quercetin to promote SK-HEP-1 (hepatic) and MCF-7 (breast) cancer cell apoptosis in heat shock cell model, and siRNA was used to block c-Jun and to explore the role of activating protein-1 (AP-1) signaling pathways. RESULTS: We found the effects of quercetin plus RFA resulted in increase on the tumor destruction/endpoint survival (26.5±3.4 d) in vivo, compared with RF alone (17.6±2.5 d) and quercetin alone (15.7±3.1 d). Most importantly, quercetin-induced cancer cell death required the presence of HSF1 in animal model. Furthermore, quercetin directly down-regulated expression of HSF1 in vitro, which our findings have revealed, required the activation of AP-1 signaling pathways by loss-of-function analysis using siRNA mediated targeting of c-Jun. CONCLUSIONS: These results indicated a protective role of quercetin in tumor ablation and highlighted a novel mechanism involving HSP70 with HSF1 pathway in thermal ablation of solid tumors.

Allergic lung inflammation promotes atherosclerosis in apolipoprotein E-deficient mice.

Inflammation drives asthma and atherosclerosis. Clinical studies suggest that asthmatic patients have a high risk of atherosclerosis. Yet this hypothesis remains uncertain, given that Th2 imbalance causes asthma whereas Th1 immunity promotes atherosclerosis. In this study, chronic allergic lung inflammation (ALI) was induced in mice by ovalbumin sensitization and challenge. Acute ALI was induced in mice by ovalbumin and aluminum sensitization and ovalbumin challenge. Atherosclerosis was produced in apolipoprotein E-deficient (Apoe(-/-)) mice with a Western diet. When chronic ALI and atherosclerosis were produced simultaneously, ALI increased atherosclerotic lesion size, lesion inflammatory cell content, elastin fragmentation, smooth muscle cell (SMC) loss, lesion cell proliferation, and apoptosis. Production of acute ALI before atherogenesis did not affect lesion size, but increased atherosclerotic lesion CD4(+) T cells, lesion SMC loss, angiogenesis, and apoptosis. Production of acute ALI after atherogenesis also did not change atherosclerotic lesion area, but increased lesion elastin fragmentation, cell proliferation, and apoptosis. In mice with chronic ALI and diet-induced atherosclerosis, daily inhalation of a mast cell inhibitor or corticosteroid significantly reduced atherosclerotic lesion T-cell and mast cell contents, SMC loss, angiogenesis, and cell proliferation and apoptosis, although these drugs did not affect lesion area, compared with those that received vehicle treatment. In conclusion, both chronic and acute ALI promote atherogenesis or aortic lesion pathology, regardless whether ALI occurred before, after, or at the same time as atherogenesis. Antiasthmatic medication can efficiently mitigate atherosclerotic lesion pathology.

The matricellular protein CCN1 regulates TNF-α induced vascular endothelial cell apoptosis.

Due to the epidemic obesity and associated diabetes, the incidence of atherosclerosis is increasing worldwide. Atherosclerosis is a chronic inflammatory disease characterized by the hardening and narrowing of arteries with plaques that consist of inflammatory cells, dead endothelial cells, lipids, and often hyper proliferated vascular smooth muscle cells. During the development of atherosclerosis, vascular endothelial cell (EC) apoptosis induced by the adipokine tumor necrosis factor alpha (TNF-α), is an early event in the plaque formation. However, TNF-α alone is not sufficient to induce apoptosis of endothelial cells. Recent studies suggested that the matricellular protein CCN family member 1 (CCN1) involves in endothelial cell dysfunction besides its well-known angiogenic function during tissue repair by promoting vascular smooth muscle cells proliferation and migration. Herein, we explored the possibility and mechanism of CCN1 in TNF-α induced endothelial cells apoptosis. Both mRNA and protein levels of CCN1 are found up-regulated in endothelial cells after TNF-α treatment. In addition, overexpression of CCN1 promoted endothelial cell apoptosis in the presence of TNF-α. Furthermore, CCN1 directly up-regulated the expression of TNF-α-target genes, and this up-regulation required the activation of P53 and NF-κB both in vivo and in vitro. Taken together, CNN1 regulates TNF-α induced endothelial cells apoptosis that may underlie poor response to TNF-α therapy and hence may be a better therapeutic target for preventing vascular dysfunction in obesity.

Preserved DNA Damage Checkpoint Pathway Protects against Complications in Long-Standing Type 1 Diabetes.

The mechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D (disease duration ≥ 50 years) with severe (Medalist +C) or absent to mild complications (Medalist -C) revealed impaired growth, reprogramming, and differentiation in Medalist +C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist -C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated in Medalist +C serum. Notably, neurons differentiated from Medalist +C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalist +C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage. We propose miR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.

Heat shock protein 27 promotes cell proliferation through activator protein-1 in lung cancer.

Heat shock protein 27 (HSP27) is an important regulator involved in the development of lung cancer. However, limited evidence exists concerning the underlying molecular mechanisms of its action. The results of the present study revealed that HSP27 was highly expressed in the lung cancer tissues of mice. In an in vitro model, the overexpression of HSP27 promoted cell proliferation, while HSP27 knockdown inhibited cell proliferation. HSP27 promoted cell proliferation in vitro by directly upregulating the expression of HSP27 target genes, which required the activation of the activator protein-1 (AP-1) signaling pathway. This was evaluated by the phosphorylation status of an important pathway component, c-Jun in lung cancer tissue and cells. These results suggested that HSP27 has a promotional role in lung cancer, and therefore indicated a novel mechanism involving lung cancer cell proliferation, which may underlie poor responses to therapy. Therefore, HSP27 may be a suitable therapeutic target for the treatment of lung cancer.

Radiofrequency ablation of hepatocellular carcinoma in difficult locations: Strategies and long-term outcomes.

AIM: To investigate the treatment strategies and long-term outcomes of radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) in difficult locations and to compare the results with non-difficult HCC. METHODS: From 2004 to 2012, a total of 470 HCC patients underwent ultrasound-guided percutaneous RFA. Among these HCC patients, 382 with tumors located ≤ 5 mm from a major vessel/bile duct (n = 87), from peripheral important structures (n = 232) or from the liver capsule (n = 63) were regarded as difficult cases. There were 331 male patients and 51 female patients, with an average age of 55.3 ± 10.1 years old. A total of 235 and 147 patients had Child-Pugh class A and class B liver function, respectively. The average tumor size was 3.4 ± 1.2 cm. Individual treatment strategies were developed to treat these difficult cases. During the same period, 88 HCC patients with tumors that were not in difficult locations served as the control group. In the control group, 74 patients were male, and 14 patients were female, with an average age of 57.4 ± 11.8 years old. Of these, 62 patients and 26 patients had Child-Pugh class A and class B liver function, respectively. Regular follow-up after RFA was performed to assess treatment efficacy. Survival results were generated from Kaplan-Meier estimates, and multivariate analysis was performed using the Cox regression model. RESULTS: Early tumor necrosis rate in the difficult group was similar to that in the control group (97.6% vs 94.3%, P = 0.080). The complication rate in the difficult group was significantly higher than that in the control group (4.9% vs 0.8%, P = 0.041). The follow-up period ranged from 6 to 116 mo, with an average of 28 ± 22.4 mo. Local progression rate in the difficult group was significantly higher than that in the control group (12.7% vs 7.1%, P = 0.046). However, the 1-, 3-, 5-, and 7-year overall survival rates in the difficult group were not significantly different from those in the control group (84.3%, 54.4%, 41.2%, and 29.9% vs 92.5%, 60.3%, 43.2%, and 32.8%, respectively, P = 0.371). Additionally, a multivariate analysis revealed that tumor location was not a significant risk factor for survival. CONCLUSION: There was no significant difference in long-term overall survival between the two groups even though the local progression rate was higher in the difficult group.

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.

From the Cover: Neutralization of terminal differentiation in gliomagenesis.

An immature state of cellular differentiation--characterized by stem cell-like tendencies and impaired differentiation--is a hallmark of cancer. Using glioblastoma multiforme (GBM) as a model system, we sought to determine whether molecular determinants that drive cells toward terminal differentiation are also genetically targeted in carcinogenesis and whether neutralizing such genes also plays an active role to reinforce the impaired differentiation state and promote malignancy. To that end, we screened 71 genes with known roles in promoting nervous system development that also sustain copy number loss in GBM through antineoplastic assay and identified A2BP1 (ataxin 2 binding protein 1, Rbfox1), an RNA-binding and splicing regulator that is deleted in 10% of GBM cases. Integrated in silico analysis of GBM profiles to elucidate the A2BP1 pathway and its role in glioma identified myelin transcription factor 1-like (Myt1L) as a direct transcriptional regulator of A2BP1. Reintroduction of A2BP1 or Myt1L in GBM cell lines and glioma stem cells profoundly inhibited tumorigenesis in multiple assays, and conversely, shRNA-mediated knockdown of A2BP1 or Myt1L in premalignant neural stem cells compromised neuronal lineage differentiation and promoted orthotopic tumor formation. On the mechanistic level, with the top-represented downstream target TPM1 as an illustrative example, we demonstrated that, among its multiple functions, A2BP1 serves to regulate TPM1's alternative splicing to promote cytoskeletal organization and terminal differentiation and suppress malignancy. Thus, in addition to the activation of self-renewal pathways, the neutralization of genetic programs that drive cells toward terminal differentiation may also promote immature and highly plastic developmental states that contribute to the aggressive malignant properties of GBM.

A synthetic steroid 5α-androst-3ß,5,6ß-triol blocks hypoxia/reoxygenation-induced neuronal injuries via protection of mitochondrial function.

Ischemic stroke is a leading cause of death worldwide, yet therapies are limited. During periods of ischemia following reperfusion in ischemic stroke, not only loss of energy supply, but a few other factors including mitochondrial dysfunction and oxidative stress also make vital contribution to neuronal injury. Here we synthesized a steroid compound 5α-androst-3ß,5,6ß-triol by 3 steps starting from dehydroepiandrosterone and examined its effect on mitochondrial function and oxidative stress in primary cultured cortical neurons exposed to hypoxia followed by reoxygenation. 5α-Androst-3ß,5,6ß-triol dose-dependently protected cortical neurons from hypoxia/reoxygenation exposure. Rates of reduction in neuronal viability, loss of mitochondrial membrane potential, disruption of ATP production and oxidative stress were ameliorated in 5α-androst-3ß,5,6ß-triol pretreated cultures. In summary, these results suggest that 5α-androst-3ß,5,6ß-triol is neuroprotective against hypoxia/reoxygenation induced neuronal injuries through mediation of mitochondrial function and oxidative stress.

The voltage-gated proton channel Hv1 enhances brain damage from ischemic stroke.

Phagocytic cell NADPH oxidase (NOX) generates reactive oxygen species (ROS) as part of innate immunity. Unfortunately, ischemia can also induce this pathway and inflict damage on native cells. The voltage-gated proton channel Hv1 enables NOX function by compensating cellular loss of electrons with protons. Accordingly, we investigated whether NOX-mediated brain damage in stroke can be inhibited by suppression of Hv1. We found that mouse and human brain microglia, but not neurons or astrocytes, expressed large Hv1-mediated currents. Hv1 was required for NOX-dependent ROS generation in brain microglia in situ and in vivo. Mice lacking Hv1 were protected from NOX-mediated neuronal death and brain damage 24 h after stroke. These results indicate that Hv1-dependent ROS production is responsible for a substantial fraction of brain damage at early time points after ischemic stroke and provide a rationale for Hv1 as a therapeutic target for the treatment of ischemic stroke.

Neuronal and microglial mechanisms of neuropathic pain.

Neuropathic pain is generally defined as a chronic pain state resulting from peripheral and/or central nerve injury. Effective treatment for neuropathic pain is still lacking, due in part to poor understanding of pathological mechanisms at the molecular level. Neuronal mechanisms of neuropathic pain, especially synaptic plasticity, are the major focus of many investigators. N-methyl-D-aspartate (NMDA) receptor dependent synaptic plasticity at the spinal and cortical levels is believed to contribute to enhanced sensory responses after injury. Glial cells, including astrocytes and microglia, have recently been implicated in neuropathic pain. These glial cells form close interactions with neurons and thus may modulate nociceptive transmission under pathological conditions. In this review, we present recent progress in the study of neuronal and microglial mechanisms underlying neuropathic pain. We propose that activity-dependent neuronal plasticity is a key target for treatment in neuropathic pain.

Human CD59 inhibitor sensitizes rituximab-resistant lymphoma cells to complement-mediated cytolysis.

Rituximab efficacy in cancer therapy depends in part on induction of complement-dependent cytotoxicity (CDC). Human CD59 (hCD59) is a key complement regulatory protein that restricts the formation of the membrane attack complex, thereby inhibiting induction of CDC. hCD59 is highly expressed in B-cell non-Hodgkin's lymphoma (NHL), and upregulation of hCD59 is an important determinant of the sensitivity of NHL cells to rituximab treatment. Here, we report that the potent hCD59 inhibitor rILYd4 enhances CDC in vitro and in vivo, thereby sensitizing rituximab-resistant lymphoma cells and primary chronic lymphocytic leukemia cells (CLL) to rituximab treatment. By defining pharmcokinetic/pharmacodynamic profiles of rILYd4 in mice, we showed that by itself rILYd4 does not adversely mediate in vivo hemolysis of hCD59-expressing erythrocytes. Increasing expression levels of the complement regulators CD59 and CD55 in rituximab-resistant cells occur due to selection of preexisting clones rather than de novo induction of these proteins. Moreover, lymphoma cells overexpressing CD59 were directly responsible for the resistance to rituximab-mediated CDC therapy. Our results rationalize the use of rILYd4 as a therapeutic adjuvant for rituximab treatment of rituximab-resistant lymphoma and CLL. Furthermore, they suggest that preemptive elimination of CD59-overexpressing subpopulations along with rituximab treatment may be a useful approach to ablate or conquer rituximab resistance.

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

BACKGROUND: Complement system, an innate immunity, has been well documented to play a critical role in many inflammatory diseases. However, the role of complement in the pathogenesis of abdominal aortic aneurysm, which is considered an immune and inflammatory disease, remains obscure. METHODS AND RESULTS: Here, we evaluated the pathogenic roles of complement membrane attack complex and CD59, a key regulator that inhibits the membrane attack complex, in the development of abdominal aortic aneurysm. We demonstrated that in the angiotensin II-induced abdominal aortic aneurysm model, deficiency of the membrane attack complex regulator CD59 in ApoE-null mice (mCd59ab(-/-)/ApoE(-/-)) accelerated the disease development, whereas transgenic overexpression of human CD59 (hCD59(ICAM-2+/-)/ApoE(-/-)) in this model attenuated the progression of abdominal aortic aneurysm. The severity of aneurysm among these 3 groups positively correlates with C9 deposition, and/or the activities of MMP2 and MMP9, and/or the levels of phosphorylated c-Jun, c-Fos, IKK-alpha/beta, and p65. Furthermore, we demonstrated that the membrane attack complex directly induced gene expression of matrix metalloproteinase-2 and -9 in vitro, which required activation of the activator protein-1 and nuclear factor-kappaB signaling pathways. CONCLUSIONS: Together, these results defined the protective role of CD59 and shed light on the important pathogenic role of the membrane attack complex in abdominal aortic aneurysm.