Neutralizing interferon-α blocks inflammation-mediated vascular injury via PI3K and AMPK in systemic lupus erythematosus.

Plasmacytoid dendritic cells (pDCs) play a key role in the initiation and amplification of systemic lupus erythematosus (SLE)-associated vascular injury. In this study, we found that dsDNA induced dose- and time-dependent increase in IFN-α and Toll-like receptor 7 (TLR7), TLR9 and IRF7 expression in pDCs. Co-cultured circulating endothelial cells (ECs) with activated pDCs significantly decreased proliferation, tube formation and migration in ECs. The elevated level of cellular IFN-α increased cell adhesion, promoted cell apoptosis, induced cell senescence and arrested cells at G0/G1 phase of endothelial progenitor cells (EPCs). Additionally, the co-culture system activated MAPK and inactivated PI3K. Pristane was used to establish a in vivo SLE-like mouse model. Importantly, we showed that INF-α-neutralizing antibody (IFN-α-NA) rescued all the changes induced by IFN-α in vitro and prevented vascular injury in pristane-induced SLE model in vivo. In conclusion, we confirmed that activated pDCs promoted vascular damage and the dysfunction of ECs/EPCs via IFN-α production. IFN-α-neutralizing antibody may be a clinical implication for preventing vascular injury. PI3K signalling and AMPK signalling were associated with SLE-associated vascular functions.

Examining the controllability of sepsis using genetic algorithms on an agent-based model of systemic inflammation.

Sepsis, a manifestation of the body's inflammatory response to injury and infection, has a mortality rate of between 28%-50% and affects approximately 1 million patients annually in the United States. Currently, there are no therapies targeting the cellular/molecular processes driving sepsis that have demonstrated the ability to control this disease process in the clinical setting. We propose that this is in great part due to the considerable heterogeneity of the clinical trajectories that constitute clinical "sepsis," and that determining how this system can be controlled back into a state of health requires the application of concepts drawn from the field of dynamical systems. In this work, we consider the human immune system to be a random dynamical system, and investigate its potential controllability using an agent-based model of the innate immune response (the Innate Immune Response ABM or IIRABM) as a surrogate, proxy system. Simulation experiments with the IIRABM provide an explanation as to why single/limited cytokine perturbations at a single, or small number of, time points is unlikely to significantly improve the mortality rate of sepsis. We then use genetic algorithms (GA) to explore and characterize multi-targeted control strategies for the random dynamical immune system that guide it from a persistent, non-recovering inflammatory state (functionally equivalent to the clinical states of systemic inflammatory response syndrome (SIRS) or sepsis) to a state of health. We train the GA on a single parameter set with multiple stochastic replicates, and show that while the calculated results show good generalizability, more advanced strategies are needed to achieve the goal of adaptive personalized medicine. This work evaluating the extent of interventions needed to control a simplified surrogate model of sepsis provides insight into the scope of the clinical challenge, and can serve as a guide on the path towards true "precision control" of sepsis.

Involvement of CD8+ T cell subsets in early response to vascular injury in patients with peripheral artery disease in vivo.

AIMS: Adaptive immunity is critical in vascular remodelling following arterial injury. We hypothesized that acute changes in T cells at a percutaneous transluminal angioplasty (PTA) site could serve as an index of their potential interaction with the injured vascular wall. METHODS AND RESULTS: T cell subsets were characterised in 45 patients with Rutherford 3-4 peripheral artery disease (PAD) undergoing PTA. Direct angioplasty catheter blood sampling was performed before and immediately after the procedure. PTA was associated with an acute reduction of α/ß-TcR CD8+ T cells. Further characterisation revealed significant reduction in pro-atherosclerotic CD28nullCD57+ T cells, effector (CD45RA+CCR7-) and effector memory (CD45RA-CCR7-) cells, in addition to cells bearing activation (CD69, CD38) and tissue homing/adhesion markers (CD38, CCR5). CONCLUSIONS: The acute reduction observed here is likely due to the adhesion of cells to the injured vascular wall, suggesting that immunosenescent, activated effector CD8+ cells have a role in the early vascular injury immune response following PTA in PAD patients.

Role of Natural Killer T (NKT) Cells in Type II Diabetes-Induced Vascular Injuries.

BACKGROUND This study investigated the distribution and features of natural killer T (NKT) cells in the peripheral blood of diabetic patients, and their regulatory roles on vascular endothelial cells. MATERIAL AND METHODS Peripheral lymphocytes were isolated from diabetic patients. NKT cell distribution, proportion, and surface and intracellular markers were detected with flow cytometry. Peripheral blood-derived NKT cells were isolated and co-cultured with human umbilical vein endothelial cells (HUVECs). Proliferation and migration of HUVECs were assessed with the CCK-8 assay and the Transwell chamber assay. RESULTS The ratios of CD3-CD56+ NK and CD3+CD56+ NKT cells in the peripheral blood of patients with type II diabetes were significantly elevated. The expression levels of NKp30, NKG2D, and NKp44 on the surface were increased in the CD3+CD56+ NKT cells, while the expression levels of NKG2A and 158b were significantly downregulated. The expression level of granzymes in the peripheral blood-derived NKT cells were not changed in patients with type II diabetes, but the expression levels of IFNg and IL-4 were significantly increased. However, after co-culture with NKT cells derived from the peripheral blood of diabetic patients, the proliferation and migration of HUVECs were significantly inhibited, and was restored by treatment with IL-4 antibody. In addition, the IL-4 stimulus inhibited the proliferation and migration of HUVECs. ls were not changed in patients with type II diabetes, while the expression levels of IFNγ and IL-4 were significantly increased. However, after co-cultured with NKT cells derived from the peripheral blood of diabetic patients, the proliferation and migration of HUVECs were significantly inhibited, which could significantly restored by the treatment of IL-4 antibody. In addition, the IL-4 stimulus could down-regulate the proliferation and migration of HUVECs.  CONCLUSIONS Peripheral blood NKT cells are increased and activated in diabetes. NKT cells inhibit the proliferation and migration of HUVECs by secreting IL-4, thereby inducing vascular injuries.

A depleting antibody toward sca-1 mitigates a surge of CD34(+)/c-kit(+) progenitors and reduces vascular restenosis in a murine vascular injury model.

OBJECTIVE: Vascular restenosis remains a major obstacle to long-term success after vascular intervention. Circulating progenitor cells have been implicated in restenosis, and yet it has remained unclear if these cells, particularly nonendothelial progenitors, have an active role in this pathologic process. We hypothesized that circulating CD34(+)/c-kit(+) progenitors would increase after vascular injury, mirrored by changes in the injury signal, stromal cell-derived factor 1α (sdf1α). We further postulated that an antibody-based depletion would mitigate progenitor surge and, in turn, reduce restenosis in a murine model. METHODS: C57BL6 mice underwent wire injury of the femoral artery and were compared with mice with sham surgery and vessel ligation by flow cytometry as well as by sdf1α enzyme-linked immunosorbent assay of peripheral blood. Next, injured C57BL6 mice treated with a depleting antibody toward the progenitor marker sca-1 or with an isotype control were compared in terms of sdf1α as well as enumeration of progenitors. At 28 days, restenosis was quantified between sca-1- and isotype-treated animals. RESULTS: Wire injury generated an increase in sdf1α as well as a surge of CD34(+)/c-kit(+) progenitors relative to nonsurgical controls (P = .005). Treatment with sca-1 antibody ablated the peripheral surge compared with isotype-treated, injured animals (P = .02), and sca progenitor depletion reduced the 28-day intima to media ratio in a statistically significant fashion compared with either nontreated (P = .04) or isotype-treated (P = .036) animals. CONCLUSIONS: Our study has demonstrated that sca-1 antibody reduces both progenitor surge and vascular restenosis after endoluminal vascular injury in a murine model. This suggests that circulating progenitors play an active role in restenotic disease.

Myeloid cell 5-lipoxygenase activating protein modulates the response to vascular injury.

RATIONALE: Human genetics have implicated the 5-lipoxygenase enzyme in the pathogenesis of cardiovascular disease, and an inhibitor of the 5-lipoxygenase activating protein (FLAP) is in clinical development for asthma. OBJECTIVE: Here we determined whether FLAP deletion modifies the response to vascular injury. METHODS AND RESULTS: Vascular remodeling was characterized 4 weeks after femoral arterial injury in FLAP knockout mice and wild-type controls. Both neointimal hyperplasia and the intima/media ratio of the injured artery were significantly reduced in the FLAP knockouts, whereas endothelial integrity was preserved. Lesional myeloid cells were depleted and vascular smooth muscle cell (VSMC) proliferation, as reflected by bromodeoxyuridine incorporation, was markedly attenuated by FLAP deletion. Inflammatory cytokine release from FLAP knockout macrophages was depressed, and their restricted ability to induce VSMC migration ex vivo was rescued with leukotriene B(4). FLAP deletion restrained injury and attenuated upregulation of the extracellular matrix protein, tenascin C, which affords a scaffold for VSMC migration. Correspondingly, the phenotypic modulation of VSMC to a more synthetic phenotype, reflected by morphological change, loss of α-smooth muscle cell actin, and upregulation of vascular cell adhesion molecule-1 was also suppressed in FLAP knockout mice. Transplantation of FLAP-replete myeloid cells rescued the proliferative response to vascular injury. CONCLUSIONS: Expression of lesional FLAP in myeloid cells promotes leukotriene B(4)-dependent VSMC phenotypic modulation, intimal migration, and proliferation.

Proinflammatory stimuli engage Brahma related gene 1 and Brahma in endothelial injury.

RATIONALE: Endothelial dysfunction inflicted by inflammation is found in a host of cardiovascular pathologies. One hallmark event in this process is the aggregation and adhesion of leukocyte to the vessel wall mediated by the upregulation of adhesion molecules (CAM) in endothelial cells at the transcriptional level. The epigenetic modulator(s) of CAM transactivation and its underlying pathophysiological relevance remain poorly defined. OBJECTIVE: Our goal was to determine the involvement of Brahma related gene 1 (Brg1) and Brahma (Brm) in CAM transactivation and its relevance in the pathogenesis of atherosclerosis. METHODS AND RESULTS: In the present study, we report that proinflammatory stimuli augmented the expression of Brg1 and Brm in vitro in cultured endothelial cells and in vivo in arteries isolated from rodents. Overexpression of Brg1 and Brm promoted while knockdown of Brg1 and Brm abrogated transactivation of adhesion molecules and leukocyte adhesion induced by inflammatory signals. Brg1 and Brm interacted with and were recruited to the CAM promoters by nuclear factor κB/p65. Conversely, depletion of Brg1 and Brm disrupted the kinetics of p65 binding on CAM promoters and crippled CAM activation. Silencing of Brg1 and Brm also altered key epigenetic changes associated with CAM transactivation. Of intrigue, 17ß-estradiol antagonized both the expression and activity of Brg1/Brm. Most importantly, endothelial-targeted elimination of Brg1/Brm conferred atheroprotective effects to Apoe(-/-) mice on a Western diet. CONCLUSIONS: Our data suggest that Brg1 and Brm integrate various proinflammatory cues into CAM transactivation and endothelial malfunction and, as such, may serve as potential therapeutic targets in treating inflammation-related cardiovascular diseases.

Macrophage-derived IL-18 and increased fibrinogen deposition are age-related inflammatory signatures of vascular remodeling.

Aging has been associated with pathological vascular remodeling and increased neointimal hyperplasia. The understanding of how aging exacerbates this process is fundamental to prevent cardiovascular complications in the elderly. This study proposes a mechanism by which aging sustains leukocyte adhesion, vascular inflammation, and increased neointimal thickness after injury. The effect of aging on vascular remodeling was assessed in the rat balloon injury model using microarray analysis, immunohistochemistry, and LINCOplex assays. The injured arteries in aging rats developed thicker neointimas than those in younger animals, and this significantly correlated with a higher number of tissue macrophages and increased vascular IL-18. Indeed, IL-18 was 23-fold more abundant in the injured vasculature of aged animals compared with young rats, while circulating levels were similar in both groups of animals. The depletion of macrophages in aged rats with clodronate liposomes ameliorated vascular accumulation of IL-18 and significantly decreased neointimal formation. IL-18 was found to inhibit apoptosis of vascular smooth muscle cells (VSMC) and macrophages, thus favoring both the formation and inflammation of the neointima. In addition, injured arteries of aged rats accumulated 18-fold more fibrinogen-γ than those of young animals. Incubation of rat peritoneal macrophages with immobilized IL-18 increased leukocyte adhesion to fibrinogen and suggested a proinflammatory positive feedback loop among macrophages, VSMC, and the deposition of fibrinogen during neointimal hyperplasia. In conclusion, our data reveal that concentration changes in vascular cytokine and fibrinogen following injury in aging rats contribute to local inflammation and postinjury neointima formation.

The interferon stimulated gene 12 inactivates vasculoprotective functions of NR4A nuclear receptors.

RATIONALE: Innate and adaptive immune responses alter numerous homeostatic processes that are controlled by nuclear hormone receptors. NR4A1 is a nuclear receptor that is induced in vascular pathologies, where it mediates protection. OBJECTIVE: The underlying mechanisms that regulate the activity of NR4A1 during vascular injury are not clear. We therefore searched for modulators of NR4A1 function that are present during vascular inflammation. METHODS AND RESULTS: We report that the protein encoded by interferon stimulated gene 12 (ISG12), is a novel interaction partner of NR4A1 that inhibits the transcriptional activities of NR4A1 by mediating its Crm1-dependent nuclear export. Using 2 models of vascular injury, we show that ISG12-deficient mice are protected from neointima formation. This effect is dependent on the presence of NR4A1, as mice deficient for both ISG12 and NR4A1 exhibit neointima formation similar to wild-type mice. CONCLUSIONS: These findings identify a previously unrecognized feedback loop activated by interferons that inhibits the vasculoprotective functions of NR4A nuclear receptors, providing a potential new therapeutic target for interferon-driven pathologies.

Novel role of copper transport protein antioxidant-1 in neointimal formation after vascular injury.

OBJECTIVE: Vascular smooth muscle cell (VSMC) migration is critically important for neointimal formation after vascular injury and atherosclerosis lesion formation. Copper (Cu) chelator inhibits neointimal formation, and we previously demonstrated that Cu transport protein antioxidant-1 (Atox1) is involved in Cu-induced cell growth. However, role of Atox1 in VSMC migration and neointimal formation after vascular injury is unknown. APPROACH AND RESULTS: Here, we show that Atox1 expression is upregulated in injured vessel, and it is colocalized with the Cu transporter ATP7A, one of the downstream targets of Atox1, mainly in neointimal VSMCs at day 14 after wire injury. Atox1(-/-) mice show inhibition of neointimal formation and extracellular matrix expansion, which is associated with a decreased VSMCs accumulation within neointima and lysyl oxidase activity. Mechanistically, in cultured VSMC, Atox1 depletion with siRNA inhibits platelet-derived growth factor-induced Cu-dependent VSMC migration by preventing translocation of ATP7A and small G protein Rac1 to the leading edge, as well as Cu- and Rac1-dependent lamellipodia formation. Furthermore, Atox1(-/-) mice show decreased perivascular macrophage infiltration in wire-injured vessels, as well as thioglycollate-induced peritoneal macrophage recruitment. CONCLUSIONS: Atox1 is involved in neointimal formation after vascular injury through promoting VSMC migration and inflammatory cell recruitment in injured vessels. Thus, Atox1 is a potential therapeutic target for VSMC migration and inflammation-related vascular diseases.

Toll-like receptor 2/6 agonist macrophage-activating lipopeptide-2 promotes reendothelialization and inhibits neointima formation after vascular injury.

OBJECTIVE: Reendothelialization after vascular injury (ie, balloon angioplasty or stent implantation) is clinically extremely relevant to promote vascular healing. We here investigated the therapeutic potential of the toll-like receptor 2/6 agonist macrophage-activating lipopeptide (MALP)-2 on reendothelialization and neointima formation in a murine model of vascular injury. APPROACH AND RESULTS: The left common carotid artery was electrically injured, and reendothelialization was quantified by Evans blue staining after 3 days. A single injection of MALP-2 (1 or 10 µg, IV) after vascular injury accelerated reendothelialization (P<0.001). Proliferation of endothelial cells at the wound margins determined by 5-ethynyl-2'-deoxyuridine incorporation was significantly higher in MALP-2-treated animals (P<0.05). Furthermore, wire injury-induced neointima formation of the left common carotid artery was completely prevented by a single injection of MALP-2 (10 µg, IV). In vitro, MALP-2 induced proliferation (BrdU incorporation) and closure of an artificial wound of endothelial cells (P<0.05) but not of smooth muscle cells. Protein array and ELISA analysis of isolated primary endothelial cells and ex vivo stimulated carotid segments revealed that MALP-2 stimulated the release of multiple growth factors and cytokines predominantly from endothelial cells. MALP-2 induced a strong activation of the mitogen-activated protein kinase cascade in endothelial cells, which was attenuated in smooth muscle cells. Furthermore, MALP-2 significantly enhanced circulating monocytes and hematopoietic progenitor cells. CONCLUSIONS: The toll-like receptor 2/6 agonist MALP-2 promotes reendothelialization and inhibits neointima formation after experimental vascular injury via enhanced proliferation and migration of endothelial cells. Thus, MALP-2 represents a novel therapeutic option to accelerate reendothelialization after vascular injury.

Porphyromonas gingivalis promotes neointimal formation after arterial injury through toll-like receptor 2 signaling.

We previously demonstrated that Porphyromonas gingivalis infection induces neointimal hyperplasia with an increase in monocyte chemoattractant protein (MCP)-1 after arterial injury in wild-type mice. Toll-like receptor (TLR) 2 is a key receptor for the virulence factors of P. gingivalis. The aim of this study was to assess whether TLR2 plays a role in periodontopathic bacteria-induced neointimal formation after an arterial injury. Wild-type and TLR2-deficient mice were used in this study. The femoral arteries were injured, and P. gingivalis or vehicle was injected subcutaneously once per week. Fourteen days after arterial injury, the murine femoral arteries were obtained for histopathologic and immunohistochemical analyses. The immunoglobulin-G levels of the P. gingivalis-infected groups were significantly increased in comparison with the level in the corresponding noninfected groups in both wild-type and TLR2-deficient mice. TLR2 deficiency negated the P. gingivalis-induced neointimal formation in comparison with the wild-type mice, and reduced the number of positive monocyte chemoattractant protein-1 cells in the neointimal area. These findings demonstrate that P. gingivalis infection can promote neointimal formation after an arterial injury through TLR2 signaling.

Regulatory T cells limit vascular endothelial injury and prevent pulmonary hypertension.

RATIONALE: Pulmonary arterial hypertension (PAH) is an incurable disease associated with viral infections and connective tissue diseases. The relationship between inflammation and disease pathogenesis in these disorders remains poorly understood. OBJECTIVE: To determine whether immune dysregulation due to absent T-cell populations directly contributes to the development of PAH. METHODS AND RESULTS: Vascular endothelial growth factor receptor 2 (VEGFR2) blockade induced significant pulmonary endothelial apoptosis in T-cell-deficient rats but not in immune-reconstituted (IR) rats. T cell-lymphopenia in association with VEGFR2 blockade resulted in periarteriolar inflammation with macrophages, and B cells even prior to vascular remodeling and elevated pulmonary pressures. IR prevented early inflammation and attenuated PAH development. IR with either CD8 T cells alone or with CD4-depleted spleen cells was ineffective in preventing PAH, whereas CD4-depleting immunocompetent euthymic animals increased PAH susceptibility. IR with either CD4(+)CD25(hi) or CD4(+)CD25(-) T cell subsets prior to vascular injury attenuated the development of PAH. IR limited perivascular inflammation and endothelial apoptosis in rat lungs in association with increased FoxP3(+), IL-10- and TGF-ß-expressing CD4 cells, and upregulation of pulmonary bone morphogenetic protein receptor type 2 (BMPR2)-expressing cells, a receptor that activates endothelial cell survival pathways. CONCLUSIONS: PAH may arise when regulatory T-cell (Treg) activity fails to control endothelial injury. These studies suggest that regulatory T cells normally function to limit vascular injury and may protect against the development of PAH.

Macrophage-derived tumor necrosis factor-alpha is an early component of the molecular cascade leading to angiogenesis in response to aortic injury.

OBJECTIVE: The goal of this study was to define the role of tumor necrosis factor-α (TNFα) in the cascade of gene activation that regulates aortic angiogenesis in response to injury. METHODS AND RESULTS: Angiogenesis was studied by culturing rat or mouse aortic rings in collagen gels. Gene expression was evaluated by quantitative reverse transcription-polymerase chain reaction, microarray analysis, immunocytochemistry, and ELISA. TNFα gene disruption and recombinant TNFα or blocking antibodies against vascular endothelial growth factor (VEGF) or TNF receptors were used to investigate TNFα-mediated angiogenic mechanisms. Resident aortic macrophages were depleted with liposomal clodronate. Angiogenesis was preceded by overexpression of TNFα and TNFα-inducible genes. Studies with isolated cells showed that macrophages were the main source of TNFα. Angiogenesis, VEGF production, and macrophage outgrowth were impaired by TNFα gene disruption and promoted by exogenous TNFα. Antibody-mediated inhibition of TNF receptor 1 significantly inhibited angiogenesis. The proangiogenic effect of TNFα was suppressed by blocking VEGF or by ablating aortic macrophages. Exogenous TNFα, however, maintained a limited proangiogenic capacity in the absence of macrophages and macrophage-mediated VEGF production. CONCLUSIONS: Overexpression of TNFα is required for optimal VEGF production and angiogenesis in response to injury. This TNFα/VEGF-mediated angiogenic pathway requires macrophages. The residual capacity of TNFα to stimulate angiogenesis in macrophage-depleted aortic cultures implies the existence of a VEGF-independent alternate pathway of TNFα-induced angiogenesis.

Low molecular weight (LMW) heparin inhibits injury-induced femoral artery remodeling in mouse via upregulating CD44 expression.

OBJECTIVE: The mechanism of postangioplasty restenosis remains poorly understood. Low molecular weight (LMW) heparin has been shown to inhibit the proliferation of vascular smooth muscle cells (VSMCs), which is the principal characteristic of restenosis. Studies have shown that LMW heparin could bind to CD44. We hypothesized that LMW heparin might modulate CD44 expression thereby decreasing vascular remodeling. METHODS: Vascular remodeling was induced in CD44(+/+) and CD44(-/-) mice and treated with LMW heparin. The arteries were harvested for histologic assessment and determination of CD44 expression. Bone marrow transplantation was introduced to further explore the role and functional sites of CD44. Effects of LMW heparin on growth capacity, CD44 expression were further studied using the cultured mouse VSMCs. RESULTS: Transluminal injury induced remarkable remodeling in mouse femoral artery (sham wall thickness percentage [WT%]: 3.4 ± 1.2% vs injury WT%: 31.8 ± 4.7%; P < .001). LMW heparin reduced the remodeling significantly (WT%: 17.8 ± 3.5%, P < .005). CD44(-/-) mice demonstrated considerably thicker arterial wall remodeling (WT%: 46.2 ± 7.6%, P = .0035), and CD44-chimeric mice exhibited equal contributions of the local and circulating CD44 signal to the neointima formation. LMW heparin markedly upregulated CD44 expression in the injured femoral arteries. In vitro, LMW heparin decreased mouse VSMC growth capacity and upregulated its CD44 expression simultaneously in a dose-dependent and time-dependent manner, which could be partially blocked by CD44 inhibitor. CONCLUSIONS: LMW heparin inhibits injury-induced femoral artery remodeling, at least partially, by upregulating CD44 expression.

Immune responses regulating the response to vascular injury.

PURPOSE OF REVIEW: Immune modulation of neointimal formation after vascular injury has been investigated for several decades but the complexities involved continue to obscure a clearer understanding of the process. The rapidly changing field of immunology makes this knowledge imperative. RECENT FINDINGS: The review discusses immune factors involved in the response to vascular injury. Although innate immune responses play a predominantly detrimental role, the adaptive immune response is more complex. Mechanisms of T-cell activation, recruitment, as well as possible regulation are highlighted. SUMMARY: Progress in understanding the role of the immune system in the response to arterial injury has been impressive. However, recent findings underscore the need to unravel the intricacies involved such as the kinetics and specific pathways of activation, specificity of immune cell involvement, and identification of targets for therapy. This is relevant in light of the increasing reports of immune factors involved in vascular disease and intervention in the clinical setting.

The Role of Regulatory T Cells in Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) is a chronic, incurable condition characterized by pulmonary vascular remodeling, perivascular inflammation, and right heart failure. Regulatory T cells (Tregs) stave off autoimmunity, and there is increasing evidence for their compromised activity in the inflammatory milieu of PAH. Abnormal Treg function is strongly correlated with a predisposition to PAH in animals and patients. Athymic Treg-depleted rats treated with SU5416, an agent causing pulmonary vascular injury, develop PAH, which is prevented by infusing missing CD4+CD25highFOXP3+ Tregs. Abnormal Treg activity may also explain why PAH disproportionately affects women more than men. This mini review focuses on the role of Tregs in PAH with a special view to sexual dimorphism and the future promise of Treg therapy.

Identification of key signaling pathways induced by SARS-CoV2 that underlie thrombosis and vascular injury in COVID-19 patients.

The SARS-CoV-2 pandemic has led to hundreds of thousands of deaths and billions of dollars in economic damage. The immune response elicited from this virus is poorly understood. An alarming number of cases have arisen where COVID-19 patients develop complications on top of the symptoms already associated with SARS, such as thrombosis, injuries of vascular system, kidney, and liver, as well as Kawasaki disease. In this review, a bioinformatics approach was used to elucidate the immune response triggered by SARS-CoV-2 infection in primary human lung epithelial and transformed human lung alveolar. Additionally, examined the potential mechanism behind several complications that have been associated with COVID-19 and determined that a specific cytokine storm is leading to excessive neutrophil recruitment. These neutrophils are directly leading to thrombosis, organ damage, and complement activation via neutrophil extracellular trap release.

Complement fragments are biomarkers of antibody-mediated endothelial injury.

Antibody-mediated rejection (AbMR) adversely affects long-term graft survival in kidney transplantation. Currently, the diagnosis of AbMR requires a kidney biopsy, and detection of complement C4d deposition in the allograft is one of the diagnostic criteria. Complement activation also generates several soluble fragments which could potentially provide non-invasive biomarkers of the process. Furthermore, microvesicles released into the plasma from injured cells can serve as biomarkers of vascular injury. To explore whether soluble complement fragments or complement fragments bound to endothelial microvesicles can be used to non-invasively detect AbMR, we developed an in vitro model in which human endothelial cells were exposed to anti-HLA antibodies and complement sufficient serum. We found that complement fragments C4a and sC5b-9 were increased in the supernatants of cells exposed to complement-sufficient serum compared to cells treated complement-deficient serum. Furthermore, complement activation on the cell surface was associated with the release of microvesicles bearing C4 and C3 fragments. We next measured these analytes in plasma from kidney transplant recipients with biopsy-proven acute AbMR (n = 9) and compared the results with those from transplant recipients who also had impaired allograft function but who did not have AbMR (n = 30). Consistent with the in vitro results, complement fragments C4a and Ba were increased in plasma from patients with AbMR compared to control subjects (P < 0.001 and P < 0.01, respectively). Endothelial microvesicle counts were not increased in patients with AbMR, however, and the number of microvesicles with C4 and C3 bound to the surface was actually lower compared to control subjects (both P < 0.05). Our results suggest that plasma complement activation fragments may be useful as non-invasive biomarkers of antibody-mediated complement activation within the allograft. Complement-opsonized endothelial microvesicles are decreased in patients with AbMR, possibly due to enhanced clearance of microvesicles opsonized with C3 and C4 fragments.

NK cell recruitment limits tissue damage during an enteric helminth infection.

Parasitic helminths cause significant damage as they migrate through host tissues to complete their life cycle. While chronic helminth infections are characterized by a well-described Type 2 immune response, the early, tissue-invasive stages are not well understood. Here we investigate the immune pathways activated during the early stages of Heligmosomoides polygyrus bakeri (Hpb), a natural parasitic roundworm of mice. In contrast to the Type 2 immune response present at later stages of infection, a robust Type 1 immune signature including IFNg production was dominant at the time of parasite invasion and granuloma formation. This early response was associated with an accumulation of activated Natural Killer (NK) cells, with no increase of other innate lymphoid cell populations. Parabiosis and confocal microscopy studies indicated that NK cells were recruited from circulation to the small intestine, where they surrounded parasitic larvae. NK cell recruitment required IFNγ receptor signaling, but was independent of CXCR3 expression. The depletion of tissue-infiltrating NK cells altered neither worm burden nor parasite fitness, but increased vascular injury, suggesting a role for NK cells in mediating tissue protection. Together, these data identify an unexpected role for NK cells in promoting disease tolerance during the invasive stage of an enteric helminth infection.