Statin-induced expression of CD59 on vascular endothelium in hypoxia: a potential mechanism for the anti-inflammatory actions of statins in rheumatoid arthritis

Canonical and non-canonical roles of complement in atherosclerosis

Cardiovascular diseases are the leading cause of death globally, and atherosclerosis is the major contributor to the development and progression of cardiovascular diseases. Immune responses have a central role in the pathogenesis of atherosclerosis, with the complement system being an acknowledged contributor. Chronic activation of liver-derived and serum-circulating canonical complement sustains endothelial inflammation and innate immune cell activation, and deposition of complement activation fragments on inflamed endothelial cells is a hallmark of atherosclerotic plaques. However, increasing evidence indicates that liver-independent, cell-autonomous and non-canonical complement activities are underappreciated contributors to atherosclerosis. Furthermore, complement activation can also have atheroprotective properties. These specific detrimental or beneficial contributions of the complement system to the pathogenesis of atherosclerosis are dictated by the location of complement activation and engagement of its canonical versus non-canonical functions in a temporal fashion during atherosclerosis progression. In this Review, we summarize the classical and the emerging non-classical roles of the complement system in the pathogenesis of atherosclerosis and discuss potential strategies for therapeutic modulation of complement for the prevention and treatment of atherosclerotic cardiovascular disease.

Statins Restore Endothelial Protection against Complement Activity in Obstructive Sleep Apnea: A Randomized Clinical Trial

Rationale: Increased cardiovascular risk in obstructive sleep apnea (OSA) persists after continuous positive airway pressure (CPAP) and alternative therapies are needed. Impaired endothelial protection against complement is a cholesterol-dependent process that initiates endothelial inflammation in OSA, which increases cardiovascular risk. Objectives: To investigate directly whether lowering cholesterol improves endothelial protection against complement and its proinflammatory effects in OSA. Methods: Newly diagnosed patients with OSA (n = 87) and OSA-free controls (n = 32) participated. Endothelial cells and blood were collected at baseline, after 4 weeks of CPAP therapy, and again after 4 weeks of 10 mg atorvastatin versus placebo using a randomized, double-blind, parallel-group design. Primary outcome was the proportion of a complement inhibitor, CD59, on the endothelial cell plasma membrane in OSA patients after 4 weeks of statins versus placebo. Secondary outcomes were complement deposition on endothelial cells and circulating levels of its downstream proinflammatory factor, angiopoietin-2, after statins versus placebo. Results: Baseline expression of CD59 was lower, whereas complement deposition on endothelial cells and levels of angiopoietin-2 were greater, in patients with OSA compared with controls. CPAP did not affect expression of CD59 or complement deposition on endothelial cells in patients with OSA, regardless of adherence. Compared with placebo, statins increased expression of endothelial complement protector CD59 and lowered complement deposition in patients with OSA. Good CPAP adherence was associated with increased angiopoietin-2 levels, which was reversed by statins. Conclusions: Statins restore endothelial protection against complement and reduce its downstream proinflammatory effects, suggesting a potential approach to reduce residual cardiovascular risk after CPAP in patients with OSA. Clinical trial registered with www.clinicaltrials.gov (NCT03122639).

Association of Blood Group Antigen CD59 with Disease

In 2014, the membrane-bound protein CD59 became a blood group antigen. CD59 has been known for decades as an inhibitor of the complement system, located on erythrocytes and on many other cell types. In paroxysmal nocturnal haemoglobinuria (PNH), a stem cell clone with acquired deficiency to express GPI-anchored molecules, including the complement inhibitor CD59, causes severe and life-threatening disease. The lack of CD59, which is the only membrane-bound inhibitor of the membrane attack complex, contributes a major part of the intravascular haemolysis observed in PNH patients. This crucial effect of CD59 in PNH disease prompted studies to investigate its role in other diseases. In this review, the role of CD59 in inflammation, rheumatic disease, and age-related macular degeneration is investigated. Further, the pivotal role of CD59 in PNH and congenital CD59 deficiency is reviewed.

Targeting the complement system in neuromyelitis optica spectrum disorder

INTRODUCTION

Neuromyelitis optica spectrum disorder (NMOSD) is characterized by central nervous system inflammation and demyelination. In AQP4-IgG seropositive NMOSD, circulating immunoglobulin G (IgG) autoantibodies against astrocyte water channel aquaporin-4 (AQP4) cause tissue injury. Compelling evidence supports a pathogenic role for complement activation following AQP4-IgG binding to AQP4. Clinical studies supported the approval of eculizumab, an inhibitor of C5 cleavage, in AQP4-IgG seropositive NMOSD.

AREAS COVERED

This review covers in vitro, animal models, and human evidence for complement-dependent and complement-independent tissue injury in AQP4-IgG seropositive NMOSD. Complement targets are discussed, including complement proteins, regulators and anaphylatoxin receptors, and corresponding drug candidates.

EXPERT OPINION

Though preclinical data support a central pathogenic role of complement activation in AQP4-IgG seropositive NMOSD, they do not resolve the relative contributions of complement-dependent vs. complement-independent disease mechanisms such as antibody-dependent cellular cytotoxicity, T cell effector mechanisms, and direct AQP4-IgG-induced cellular injury. The best evidence that complement-dependent mechanisms predominate in AQP4-IgG seropositive NMOSD comes from eculizumab clinical data. Various drug candidates targeting distinct complement effector mechanisms may offer improved safety and efficacy. However, notwithstanding the demonstrated efficacy of complement inhibition in AQP4-IgG seropositive NMOSD, the ultimate niche for complement inhibition is not clear given multiple drug options with alternative mechanisms of action.Abbreviations: AAV2, Adeno-associated virus 2; ADCC, antibody-dependent cellular cytotoxicity; ANCA, antineutrophilic cytoplasmic autoantibody; AQP4, aquaporin-4; AQP4-IgG, AQP4-immunoglobulin G; C1-INH, C1-esterase inhibitor; C3aR, C3a receptor; C4BP, C4 binding protein; C5aR, C5a receptor; CDC, complement-dependent cytotoxicity; CFHR1, complement factor H related 1; CNS, central nervous system; EAE, experimental autoimmune encephalomyelitis; EndoS, endoglycosidase S; FHL-1, factor-H-like protein 1; GFAP, glial fibrillary acidic protein; Iba-1, ionized calcium-binding adaptor protein-1; IgG, immunoglobulin G; IVIG, intravenous human immunoglobulin G; MAC, membrane attack complex; MBL, maltose-binding lectin; MBP, myelin basic protein; MOG, myelin oligodendrocyte glycoprotein; NK cell, natural killer cell; NMOSD, neuromyelitis optica spectrum disorder; OAP, orthogonal arrays of particles; PNH, paroxysmal nocturnal hemoglobinuria.

The complement system in primary Sjögren's syndrome: the expression of certain cascade and regulatory proteins in labial salivary glands - observational study

Introduction

The complement cascade and regulatory proteins are involved in the pathogenesis of the Sjögren's syndrome and other autoimmune diseases. The complement activation via the alternative pathway was recognized as a major pathogenic mechanism in autoimmune conditions. The aim of this study was to assess expression of complement cascade components and regulatory proteins in minor salivary glands in patients with primary Sjögren's syndrome (pSS).

Materials and methods

The expression of C1q and C5b-9 - membrane attack complex and regulatory proteins such as: membrane cofactor protein (MCP), decay-accelerating factor (DAF) and protectin were examined using immunochemistry method in specimens from biopsy of minor salivary glands in pSS patients. The biopsy material was obtained from 20 pSS patients, 5 patients with non-specific sialadenitis and from 5 patients with suspicion of dryness syndrome without sialadenitis confirmation.

Results

None of the examined samples showed the expression of C1q or the effector C5b-9. Membrane cofactor protein expression was lower in pSS group than in both non-specific sialadenitis and noninflamed salivary glands. The inflammatory cells in pSS samples partially expressed MCP. There were differences in the sites and intensity of membrane protectin expression exclusively on the luminal surfaces in pSS; on the luminal and, partially, antiluminal surface in non-specific inflammation, and on the entire cell surface in unaffected salivary glands. There were no DAF expression in salivary gland tissue in biopsy specimens in all studied subjects.

Conclusions

The study demonstrated the absence of complement-cascade proteins (C1q, MAC) in the salivary glands of pSS patients, which may indicated a lack of local complement activation via the classical pathway and the observed gland tissue damage being due to a mechanism other than MAC-induced cytolysis. The differences in the expression of complement regulatory proteins between pSS, non-specific sialadenitis, and normal salivary glands may indicate that alternative functions of these regulatory proteins may be of greater significance in pSS. Low MCP expression in pSS in comparison with non-specific sialadenitis and normal salivary glands, may suggest altered modulation of cell-mediated immunity in pSS. The differences in the location and intensity of protectin (CD59) expression indicates a possibility of reducing the proinflammatory effect of protectin in pSS.

Exosomes derived from synovial fibroblasts under hypoxia aggravate rheumatoid arthritis by regulating Treg/Th17 balance

IMPACT STATEMENT

A comparative study of osteoarthritis (OA) and RA mice was implemented to suggest that miR-424 expression was increased in RA, and exosome-miR-424 derived from synovial fibroblasts (SFs-exo) could significantly induce T cells differentiation in which Th17 cells increased and Treg cells decreased via targeting FOXP3. And thus, miR-424 may be a potential therapeutic target for RA.

Hypoxia-induced complement dysregulation is associated with microvascular impairments in mouse tracheal transplants

BACKGROUND

Complement Regulatory Proteins (CRPs), especially CD55 primarily negate complement factor 3-mediated injuries and maintain tissue homeostasis during complement cascade activation. Complement activation and regulation during alloimmune inflammation contribute to allograft injury and therefore we proposed to investigate a crucial pathological link between vascular expression of CD55, active-C3, T cell immunity and associated microvascular tissue injuries during allograft rejection.

METHODS

Balb/c→C57BL/6 allografts were examined for microvascular deposition of CD55, C3d, T cells, and associated tissue microvascular impairments during rejection in mouse orthotopic tracheal transplantation.

RESULTS

Our findings demonstrated that hypoxia-induced early activation of HIF-1α favors a cell-mediated inflammation (CD4⁺, CD8⁺, and associated proinflammatory cytokines, IL-2 and TNF-α), which proportionally triggers the downregulation of CRP-CD55, and thereby augments the uncontrolled release of active-C3, and Caspase-3 deposition on CD31⁺ graft vascular endothelial cells. These molecular changes are pathologically associated with microvascular deterioration (low tissue O₂ and Blood flow) and subsequent airway epithelial injuries of rejecting allografts as compared to non-rejecting syngrafts.

CONCLUSION

Together, these findings establish a pathological correlation between complement dysregulation, T cell immunity, and microvascular associated injuries during alloimmune inflammation in transplantation.

Altered Expression of Complement Regulatory Proteins CD35, CD46, CD55, and CD59 on Leukocyte Subsets in Individuals Suffering From Coronary Artery Disease

Studies conducted in animal models have suggested that membrane complement regulatory proteins play an important role in the pathophysiology of coronary artery disease (CAD). In this study, a total of 100 individuals, with stable CAD and 100 healthy controls, both groups predominantly male, were recruited. We evaluated the plasma levels of complement regulatory proteins (Cregs) CD35, CD46, CD55, and CD59 and their surface expression on granulocytes, lymphocytes, and monocytes by flow cytometry. The mRNA expression of these Cregs in total leukocytes was determined by quantitative PCR. The soluble forms of Cregs, C3c, Mannose binding protein-associated serine protease 2 (MASP-2), Platelet activating factor-acetyl hydrolase (PAF-AH), and inflammatory cytokines were quantified by ELISA. High plasma levels of C3c, indicative of complement activation, in addition to significantly low levels of Cregs, were observed in CAD patients. A significantly lower expression of CD46 and CD55 on the surface of lymphocytes, monocytes, and granulocytes and higher surface expression of CD35 and CD59 on granulocytes (p < 0.0001) was seen in CAD patients as compared to healthy donors. The high expression of CD59 on granulocytes positively correlated with the severity of disease and may serve as a potential marker of disease progression in CAD.

CD55 upregulation in astrocytes by statins as potential therapy for AQP4-IgG seropositive neuromyelitis optica

Background

Neuromyelitis optica spectrum disorder (herein called NMO) is an inflammatory demyelinating disease that can be initiated by binding of immunoglobulin G autoantibodies (AQP4-IgG) to aquaporin-4 on astrocytes, causing complement-dependent cytotoxicity (CDC) and downstream inflammation. The increased NMO pathology in rodents deficient in complement regulator protein CD59 following passive transfer of AQP4-IgG has suggested the potential therapeutic utility of increasing the expression of complement regulator proteins.

Methods

A cell-based ELISA was developed to screen for pharmacological upregulators of endogenous CD55 and CD59 in a human astrocyte cell line. A statin identified from the screen was characterized in cell culture models and rodents for its action on complement regulator protein expression and its efficacy in models of seropositive NMO.

Results

Screening of ~ 11,500 approved and investigational drugs and nutraceuticals identified transcriptional upregulators of CD55 but not of CD59. Several statins, including atorvastatin, simvastatin, lovastatin, and fluvastatin, increased CD55 protein expression in astrocytes, including primary cultures, by three- to four-fold at 24 h, conferring significant protection against AQP4-IgG-induced CDC. Mechanistic studies revealed that CD55 upregulation involves inhibition of the geranylgeranyl transferase pathway rather than inhibition of cholesterol biosynthesis. Oral atorvastatin at 10–20 mg/kg/day for 3 days strongly increased CD55 immunofluorescence in mouse brain and spinal cord and reduced NMO pathology following intracerebral AQP4-IgG injection.

Conclusion

Atorvastatin or other statins may thus have therapeutic benefit in AQP4-IgG seropositive NMO by increasing CD55 expression, in addition to their previously described anti-inflammatory and immunomodulatory actions.

Membrane complement regulatory protein reduces the damage of transplanting autologous bone marrow mesenchymal stem cells by suppressing the activation of complement

There are few studies on the interaction of transplanting autologous bone marrow mesenchymal stem cells (BMSCs) and complement. In order to further explore the effect of complement on BMSCs, BMSCs were obtained from bone marrow of 20 cases clinical patients, and then experimented in vitro. The cytotoxicity of complement on the mesenchymal stem cells in autologous human serum (AHS) was measured by Europium cytotoxicity assay. The complement membrane attack complex (MAC) deposited on the membrane surface was detected by flow cytometry. Finally, the cytotoxicity on BMSCs was measured after mCRPs overexpression or knockdown. We found that more than 90% of cells derived from bone marrow were identified to be mesenchymal stem cells through detection of cell membrane surface markers by flow cytometry. BMSCs harvested from the 20 patients all had cytotoxicity after incubated with AHS, and the cytotoxicity was significant higher than that incubated with complement inactivated autologous human serum (iAHS). Complement attack complex (MAC) could be detected on the BMSCs incubated with AHS, which implied the complement activation. We also found that mCRPs CD55 and CD59 overexpressions can resist the cytotoxicity induced by complement activation, while mCRPs CD55 and CD59 knockdown can enhance the cytotoxicity. Thus, the results indicated that mCRPs could effectively protect BMSCs from attacking by complement by suppressing the activation of complement.

Evaluation of the Anti-inflammatory Effects of Atorvastatin on Patients with Rheumatoid Arthritis: A Randomized Clinical Trial

Background

Rheumatoid arthritis (RA) is a chronic inflammatory joint disorder with unknown etiology. Atorvastatin is a lipid-lowering agent that affects the inflammatory processes.

Objective

This study aimed to determine the anti-inflammatory effects of atorvastatin on the Disease Activity Index and high-density lipoprotein (HDL) concentrations in RA patients.

Methods

This clinical trial was performed on 38 RA patients, who were referred to the Imam Reza and Ghaem Medical Centers of Mashhad, Iran between 2013 and 2014. Patients were divided into two groups: 1) the intervention group, which received 40 mg of atorvastatin, and 2) the control group. Response to treatment and the clinical status of patients were evaluated using the Disease Activity Score (DAS-28) and Visual Analogue Scale (VAS) at weeks zero, four, eight, and twelve, based on the 2010 ACR/EULAR Criteria by two rheumatologists. Disease activity and laboratory parameters, including erythrocyte sedimentation rate (ESR), high-sensitivity C-reactive protein (hs-CRP), DAS-ESR, DAS- hs-CRP, high-density lipoprotein (HDL), low-density lipoprotein (LDL), and liver function test (LFT) were measured in both groups.

Results

There was a significant difference in the mean number of swollen joints (p<0.011), ESR (p <0.005), DAS-ESR (P<0.043), LDL (0.036), and HDL (0.016) between the two groups. The changes in trend showed no significant difference in the mean number of tender joints (p =0.38), VAS (p =0.715), CRP (p =0.07), DAS-hs-CRP (p=0.431), total cholesterol (p=0.285), or TG (p =0.331) between the two groups. However, the Disease Activity Index decreased by 48.4% in the intervention group, compared to 35.5% in the control group.

Conclusion

As the results indicated, atorvastatin has a positive effect on the course of RA. In fact, atorvastatin, as an anti-inflammatory agent, could significantly influence inflammation in RA patients. Therefore, adding a lipid-lowering agent to standard medications in RA may be warranted and could decrease disease activity.

Clinical trial registration

The trial was registered at the Iranian Registry of Clinical Trials (Website: http://www.irct.ir, Irct ID: IRCT2015122425648N2).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Cytoprotective pathways in the vascular endothelium. Do they represent a viable therapeutic target?

The vascular endothelium is a critical interface, which separates the organs from the blood and its contents. The endothelium has a wide variety of functions and maintenance of endothelial homeostasis is a multi-dimensional active process, disruption of which has potentially deleterious consequences if not reversed. Vascular injury predisposes to endothelial apoptosis, dysfunction and development of atherosclerosis. Endothelial dysfunction is an end-point, a central feature of which is increased ROS generation, a reduction in endothelial nitric oxide synthase and increased nitric oxide consumption. A dysfunctional endothelium is a common feature of diseases including rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus and chronic renal impairment. The endothelium is endowed with a variety of constitutive and inducible mechanisms that act to minimise injury and facilitate repair. Endothelial cytoprotection can be enhanced by exogenous factors such as vascular endothelial growth factor, prostacyclin and laminar shear stress. Target genes include endothelial nitric oxide synthase, heme oxygenase-1, A20 and anti-apoptotic members of the B cell lymphoma protein-2 family. In light of the importance of endothelial function, and the link between its disruption and the risk of atherothrombosis, interest has focused on therapeutic conditioning and reversal of endothelial dysfunction. A detailed understanding of cytoprotective signalling pathways, their regulation and target genes is now required to identify novel therapeutic targets. The ultimate aim is to add vasculoprotection to current therapeutic strategies for systemic inflammatory diseases, in an attempt to reduce vascular injury and prevent or retard atherogenesis.

Peripheral tolerance can be modified by altering KLF2-regulated Treg migration

Tregs are essential for maintaining peripheral tolerance, and thus targeting these cells may aid in the treatment of autoimmunity and cancer by enhancing or reducing suppressive functions, respectively. Before these cells can be harnessed for therapeutic purposes, it is necessary to understand how they maintain tolerance under physiologically relevant conditions. We now report that transcription factor Kruppel-like factor 2 (KLF2) controls naive Treg migration patterns via regulation of homeostatic and inflammatory homing receptors, and that in its absence KLF2-deficient Tregs are unable to migrate efficiently to secondary lymphoid organs (SLOs). Diminished Treg trafficking to SLOs is sufficient to initiate autoimmunity, indicating that SLOs are a primary site for maintaining peripheral tolerance under homeostatic conditions. Disease severity correlates with impaired Treg recruitment to SLOs and, conversely, promotion of Tregs into these tissues can ameliorate autoimmunity. Moreover, stabilizing KLF2 expression within the Treg compartment enhances peripheral tolerance by diverting these suppressive cells from tertiary tissues into SLOs. Taken together, these results demonstrate that peripheral tolerance is enhanced or diminished through modulation of Treg trafficking to SLOs, a process that can be controlled by adjusting KLF2 protein levels.

Increased internalization of complement inhibitor CD59 may contribute to endothelial inflammation in obstructive sleep apnea

Obstructive sleep apnea (OSA), characterized by intermittent hypoxia (IH) during transient cessation of breathing, triples the risk for cardiovascular diseases. We used a phage display peptide library as an unbiased approach to investigate whether IH, which is specific to OSA, activates endothelial cells (ECs) in a distinctive manner. The target of a differentially bound peptide on ECs collected from OSA patients was identified as CD59, a major complement inhibitor that protects ECs from the membrane attack complex (MAC). A decreased proportion of CD59 is located on the EC surface in OSA patients compared with controls, suggesting reduced protection against complement attack. In vitro, IH promoted endothelial inflammation predominantly via augmented internalization of CD59 and consequent MAC deposition. Increased internalization of endothelial CD59 in IH appeared to be cholesterol-dependent and was reversed by statins in a CD59-dependent manner. These studies suggest that reduced complement inhibition may mediate endothelial inflammation and increase vascular risk in OSA patients.

Hepatic ischemia/reperfusion injury is diminished by atorvastatin in Wistar rats

BACKGROUND AND AIMS

Temporal occlusion of the hepatoduodenal ligament (HDL) is often used during liver surgeries in order to reduce blood loss, resulting in ischemia/reperfusion injury (I/R). The aim of the study was to investigate the effects of atorvastatin (ATOR) on hepatic I/R injury and on serum levels of tumor necrosis factor-alpha (TNF-α), endothelin-1 (ET-1), antithrombin III (ATIII) and intracellular adhesion molecule-1 (ICAM-1).

METHODS

Liver ischemia was induced in Wistar rats by clamping the HDL for 60 min, followed by either 60 or 180 min reperfusion. Rats received either vehicle or 10 mg/kg ATOR before hepatic I/R. Control group received sham surgery. Livers were examined for histological damage and serum AST, ALT, TNF-α, ET-1, ATIII and ICAM-1 concentrations were measured.

RESULTS

After I/R, AST and ALT were significantly elevated, ATIII levels were significantly depleted, both TNF-α and ICAM-1 levels increased and ET-1 was significantly elevated (at 180 min). ATOR pretreatment attenuated these alterations and diminished histological injury scores.

CONCLUSIONS

Our results show that ATOR protects the liver from I/R injury.

Cytoprotective signaling and gene expression in endothelial cells and macrophages-lessons for atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the medium and large arteries driven in large part by the accumulation of oxidized low-density lipoproteins and other debris at sites rendered susceptible because of the geometry of the arterial tree. As lesions develop, they acquire a pathologic microcirculation that perpetuates lesion progression, both by providing a means for further monocyte and T-lymphocyte recruitment into the arterial wall and by the physical and chemical stresses caused by micro-hemorrhage. This review summarizes work performed in our department investigating the roles of signaling pathways, alone and in combination, that lead to specific programs of gene expression in the atherosclerotic environment. Focusing particularly on cytoprotective responses that might be enhanced therapeutically, the work has encompassed the anti-inflammatory effects of arterial laminar shear stress, mechanisms of induction of membrane inhibitors that prevent complement-mediated injury, homeostatic macrophage responses to hemorrhage, and the transcriptional mechanisms that control the stability, survival, and quiescence of endothelial monolayers. Lastly, while the field has been dominated by investigation into the mechanisms of DNA transcription, we consider the importance of parallel post-transcriptional regulatory mechanisms for fine-tuning functional gene expression repertoires.

Shiga toxin 2 reduces complement inhibitor CD59 expression on human renal tubular epithelial and glomerular endothelial cells

Infections with enterohemorrhagic Escherichia coli (EHEC) are a primary cause of hemolytic-uremic syndrome (HUS). Recently, Shiga toxin 2 (Stx2), the major virulence factor of EHEC, was reported to interact with complement, implying that the latter is involved in the pathogenesis of EHEC-induced HUS. The aim of the present study was to investigate the effect of Stx2 on the expression of membrane-bound complement regulators CD46, CD55, and CD59 on proximal tubular epithelial (HK-2) and glomerular endothelial (GEnC) cells derived from human kidney cells that are involved in HUS. Incubation with Stx2 did not influence the amount of CD46 or CD55 on the surface of HK-2 and GEnC cells, as determined by fluorescence-activated cell sorter analysis. In contrast, CD59 was significantly reduced by half on GEnC cells, but the reduction on HK-2 cells was less pronounced. With increasing amounts of Stx2, reduction of CD59 also reached significance in HK-2 cells. Enzyme-linked immunosorbent assay analyses showed that CD59 was not present in the supernatant of Stx2-treated cells, implying that CD59 reduction was not caused by cleavage from the cell surface. In fact, reverse transcription-quantitative PCR analyses showed downregulation of CD59 mRNA as the likely reason for CD59 cell surface reduction. In addition, a significant increase in terminal complement complex deposition on HK-2 cells was observed after treatment with Stx2, as a possible consequence of CD59 downregulation. In summary, Stx2 downregulates CD59 mRNA and protein levels on tubular epithelial and glomerular endothelial cells, and this downregulation likely contributes to complement activation and kidney destruction in EHEC-associated HUS.

Mesenchymal stem cells are injured by complement after their contact with serum

Despite the potent immunosuppressive activity that mesenchymal stem cells (MSCs) display in vitro, recent clinical trial results are disappointing, suggesting that MSC viability and/or function are greatly reduced after infusion. In this report, we demonstrated that human MSCs activated complement of the innate immunity after their contact with serum. Although all 3 known intrinsic cell-surface complement regulators were present on MSCs, activated complement overwhelmed the protection of these regulators and resulted in MSCs cytotoxicity and dysfunction. In addition, autologous MSCs suffered less cellular injury than allogeneic MSCs after contacting serum. All 3 complement activation pathways were involved in generating the membrane attack complex to directly injure MSCs. Supplementing an exogenous complement inhibitor, or up-regulating MSC expression levels of CD55, one of the cell-surface complement regulators, helped to reduce the serum-induced MSC cytotoxicity. Finally, adoptively transferred MSCs in complement deficient mice or complement-depleted mice showed reduced cellular injury in vivo compared with those in wild type mice. These results indicate that complement is integrally involved in recognizing and injuring MSCs after their infusion, suggesting that autologous MSCs may have ad-vantages over allogeneic MSCs, and that inhibiting complement activation could be a novel strategy to improve existing MSC-based therapies.

The pleiotropic effects of the hydroxy-methyl-glutaryl-CoA reductase inhibitors in rheumatologic disorders: a comprehensive review

The hydroxy-methyl-glutaryl-CoA reductase inhibitors (statins) are used extensively in the treatment for hyperlipidemia. They have also demonstrated a benefit in a variety of other disease processes, including a wide range of rheumatologic disorders. These secondary actions are known as pleiotropic effects. Our paper serves as a focused and updated discussion on the pleiotropic effects of statins in rheumatologic disorders and emphasizes the importance of randomized, placebo-controlled trials to further elucidate this interesting phenomenon.

Geranylgeranylacetone, a non-toxic inducer of heat shock protein, induces cell death in fibroblast-like synoviocytes from patients with rheumatoid arthritis

Fluvastatin (Fluv) is reported to induce apoptosis in rheumatoid arthritis (RA) synoviocytes through the blocking of protein geranylgeranylation. We report here our investigation of whether geranylgeranylacetone (GGA) induces cell death in RA synoviocytes. Synovial tissues were obtained from patients with RA at the time of total knee arthroplasty. Fibroblast-like synoviocytes (FLS) cultured in three passages were used for the experiments. The FLS were then cultured for 48 h in 48-well flat-bottomed plates containing various concentrations of GGA (0.1-4.0 microg/ml) and either 0.1 or 0.5 microM Fluv. We also examined the effect of GGA and Fluv in human fibroblasts from normal skin (CCD-25SK) and FLS from patients with osteoarthritis (OA). Cells demonstrating cell death were counted following trypan blue staining. In the absence of GGA, there was no apparent cell death, as evidence by trypan blue staining. Concentrations of GGA between 0.1 and 4.0 microg/ml induced cell death in RA FLS, but not in skin fibroblasts (CCD-25SK) nor OA FLS. The number of synoviocytes demonstrating cell death induced by 0.1 or 0.5 microM Fluv was significantly higher than that by the medium alone. In summary, we found that GGA induced cell death in RA FLS, suggesting that GGA may be a potential new therapeutic agent for RA as well as osteoporosis.

Statins impair antitumor effects of rituximab by inducing conformational changes of CD20

BACKGROUND

Rituximab is used in the treatment of CD20+ B cell lymphomas and other B cell lymphoproliferative disorders. Its clinical efficacy might be further improved by combinations with other drugs such as statins that inhibit cholesterol synthesis and show promising antilymphoma effects. The objective of this study was to evaluate the influence of statins on rituximab-induced killing of B cell lymphomas.

METHODS AND FINDINGS

Complement-dependent cytotoxicity (CDC) was assessed by MTT and Alamar blue assays as well as trypan blue staining, and antibody-dependent cellular cytotoxicity (ADCC) was assessed by a 51Cr release assay. Statins were found to significantly decrease rituximab-mediated CDC and ADCC of B cell lymphoma cells. Incubation of B cell lymphoma cells with statins decreased CD20 immunostaining in flow cytometry studies but did not affect total cellular levels of CD20 as measured with RT-PCR and Western blotting. Similar effects are exerted by other cholesterol-depleting agents (methyl-beta-cyclodextrin and berberine), but not filipin III, indicating that the presence of plasma membrane cholesterol and not lipid rafts is required for rituximab-mediated CDC. Immunofluorescence microscopy using double staining with monoclonal antibodies (mAbs) directed against a conformational epitope and a linear cytoplasmic epitope revealed that CD20 is present in the plasma membrane in comparable amounts in control and statin-treated cells. Atomic force microscopy and limited proteolysis indicated that statins, through cholesterol depletion, induce conformational changes in CD20 that result in impaired binding of anti-CD20 mAb. An in vivo reduction of cholesterol induced by short-term treatment of five patients with hypercholesterolemia with atorvastatin resulted in reduced anti-CD20 binding to freshly isolated B cells.

CONCLUSIONS

Statins were shown to interfere with both detection of CD20 and antilymphoma activity of rituximab. These studies have significant clinical implications, as impaired binding of mAbs to conformational epitopes of CD20 elicited by statins could delay diagnosis, postpone effective treatment, or impair anti-lymphoma activity of rituximab.

KLF2-dependent, shear stress-induced expression of CD59: a novel cytoprotective mechanism against complement-mediated injury in the vasculature

Complement activation may predispose to vascular injury and atherogenesis. The atheroprotective actions of unidirectional laminar shear stress led us to explore its influence on endothelial cell expression of complement inhibitory proteins CD59 and decay-accelerating factor. Human umbilical vein and aortic endothelial cells were exposed to laminar shear stress (12 dynes/cm(2)) or disturbed flow (+/- 5 dynes/cm(2) at 1Hz) in a parallel plate flow chamber. Laminar shear induced a flow rate-dependent increase in steady-state CD59 mRNA, reaching 4-fold at 12 dynes/cm(2). Following 24-48 h of laminar shear stress, cell surface expression of CD59 was up-regulated by 100%, whereas decay-accelerating factor expression was unchanged. The increase in CD59 following laminar shear was functionally significant, reducing C9 deposition and complement-mediated lysis of flow-conditioned endothelial cells by 50%. Although CD59 induction was independent of PI3-K, ERK1/2 and nitric oxide, an RNA interference approach demonstrated dependence upon an ERK5/KLF2 signaling pathway. In contrast to laminar shear stress, disturbed flow failed to induce endothelial cell CD59 protein expression. Likewise, CD59 expression on vascular endothelium was significantly higher in atheroresistant regions of the murine aorta exposed to unidirectional laminar shear stress, when compared with atheroprone areas exposed to disturbed flow. We propose that up-regulation of CD59 via ERK5/KLF2 activation leads to endothelial resistance to complement-mediated injury and protects from atherogenesis in regions of laminar shear stress.

Protective effects of atorvastatin on chronic allograft nephropathy in rats

OBJECTIVE

Chronic allograft nephropathy (CAN) is the leading cause of late kidney allograft loss. Recent studies have suggested that atorvastatin (ATO) may interact with the acute inflammatory process in the renal interstitium and suppress the proliferation of mesangial cells. We hypothesized that ATO could also inhibit the chronic inflammatory process and prevent the progression of CAN.

MATERIALS AND METHODS

Fisher (F344) kidneys were orthotopically transplanted into Lewis rat recipients. Lewis-to-Lewis rat kidney transplantation was served as the syngeneic control (Syn group). Allograft recipients were randomized and treated with cyclosporine A alone (Allo group) or in combination with ATO (15 or 30 mg/kg/d intrgastric, respectively, the low dose treatment group/high dose treatment group [LT/HT] groups). Renal function and the urine protein excretion were analyzed. Animals were sacrificed 20 weeks posttransplantation for histological and immunohistochemical studies, as well as analysis of mRNA levels of cytokines and chemokines.

RESULTS

Renal function progressively deteriorated and substantial proteinuria developed in the Allo group compared with the Syn group. ATO-treated rats had significantly higher creatinine clearance rate and less amount of proteinuria. Histological examination revealed obvious features of CAN in the Allo group, whereas LT/HT groups demonstrated minimal glomerulosclerosis, interstitial fibrosis, intimal thickening, and tubular atrophy. The numbers of infiltrating mononuclear cells (ED1+, CD8+, and CD68+) decreased markedly, and the intragraft expression of transforming growth factor beta1 (TGF-beta1) and collagen III were also significantly attenuated in the LT/HT groups, as compared with the Allo group. The mRNA levels of proinflammatory cytokines (interleukin-2, interferon-gamma, interleukin-10), chemokines (RANTES, MCP-1), and profibrotic genes (TGF-beta1, collagen III) were significantly down-regulated in ATO-treated rats.

CONCLUSION

Atorvastatin showed excellent favorable effects on blocking renal inflammation and fibrosis, and thus, efficiently inhibited the development and progression of CAN, which might improve the long-term survival rate of renal allografts.

Cardioprotective effect of rosuvastatin in vivo is dependent on inhibition of geranylgeranyl pyrophosphate and altered RhoA membrane translocation

Hydroxymethyl glutaryl (HMG)-coenzyme A (CoA) reductase inhibitors (statins) protect the myocardium against ischemia-reperfusion injury via a mechanism unrelated to cholesterol lowering. Statins may inhibit isoprenylation and thereby prevent activation of proteins such as RhoA. We hypothesized that statins protect the myocardium against ischemia-reperfusion injury via a mechanism involving inhibition of geranylgeranyl pyrophosphate synthesis and translocation of RhoA to the plasma membrane. Sprague-Dawley rats were given either the HMG-CoA reductase inhibitor rosuvastatin, geranylgeranyl pyrophosphate dissolved in methanol, the combination of rosuvastatin and geranylgeranyl pyrophosphate, rosuvastatin and methanol, or distilled water (control) by intraperitoneal injection for 48 h before ischemia-reperfusion. Animals were anesthetized and either subjected to 30 min of coronary artery occlusion followed by 2 h of reperfusion where at infarct size was determined, or the expression of RhoA protein was determined in cytosolic and membrane fractions of nonischemic myocardium. There were no significant differences in hemodynamics between the control group and the other groups before ischemia or during ischemia and reperfusion. The infarct size was 80 +/- 3% of the area at risk in the control group. Rosuvastatin reduced infarct size to 64 +/- 2% (P<0.001 vs. control). Addition of geranylgeranyl pyrophosphate (77 +/- 2%, P<0.01 vs. rosuvastatin) but not methanol (65 +/- 2%, not significant vs. rosuvastatin) abolished the cardioprotective effect of rosuvastatin. Geranylgeranyl pyrophosphate alone did not affect infarct size per se (84 +/- 2%). Rosuvastatin increased the cytosol-to-membrane ratio of RhoA protein in the myocardium (P<0.05 vs. control). These changes were abolished by addition of geranylgeranyl pyrophosphate. We conclude that the cardioprotection and the increase of the RhoA cytosol-to-membrane ratio induced by rosuvastatin in vivo are blocked by geranylgeranyl pyrophosphate. The inhibition of geranylgeranyl pyrophosphate formation and subsequent modulation of cytosol/membrane-bound RhoA are of importance for the protective effect of statins against myocardial ischemia-reperfusion injury.

Statins and the vascular endothelial inflammatory response

Statins reduce cholesterol synthesis and are widely used for the treatment of hyperlipidaemia and ischaemic heart disease. Besides their cholesterol-lowering effects, statins also possess broad immunomodulatory and anti-inflammatory properties. Vascular endothelial cells have a crucial role in the pathogenesis of inflammatory disease, and, alongside leukocytes and antigen-presenting cells, represent a key cellular target for statin therapy. Recent studies investigating how these drugs modify endothelial cell function demonstrate that the therapeutic effect of statins can be attributed, in part, to their action on the endothelium. Accordingly, statins attenuate endothelial MHC class II expression, increase endothelial nitric oxide synthase and fibrinolytic activity, decrease leukocyte adhesion and transmigration, and enhance resistance to local injurious stimuli. Many of these effects are brought about by the modulation of small GTPase function and the downregulation of proinflammatory gene expression.