Interleukin 6 promotes vasculogenesis of murine brain microvessel endothelial cells

Interleukin-6 in Traumatic Brain Injury: A Janus-Faced Player in Damage and Repair

Traumatic brain injury (TBI) is a common and often devastating illness, with wide-ranging public health implications. In addition to the primary injury, victims of TBI are at risk for secondary neurological injury by numerous mechanisms. Current treatments are limited and do not target the profound immune response associated with injury. This immune response reflects a convergence of peripheral and central nervous system-resident immune cells whose interaction is mediated in part by a disruption in the blood-brain barrier (BBB). The diverse family of cytokines helps to govern this communication and among these, Interleukin (IL)-6 is a notable player in the immune response to acute neurological injury. It is also a well-established pharmacological target in a variety of other disease contexts. In TBI, elevated IL-6 levels are associated with worse outcomes, but the role of IL-6 in response to injury is double-edged. IL-6 promotes neurogenesis and wound healing in animal models of TBI, but it may also contribute to disruptions in the BBB and the progression of cerebral edema. Here, we review IL-6 biology in the context of TBI, with an eye to clarifying its controversial role and understanding its potential as a target for modulating the immune response in this disease.

Cytological and Biochemical Analyses of Lymphatic Fluid from Patients with Lymphatic Malformations

Background: Intracystic hemorrhage from lymphangiomas is a common phenomenon in lymphatic malformations (LMs); however, little is known about the associated compositional changes in the lymphatic fluid. Materials and Methods: We prospectively collected lymphatic fluid from children with LMs. Lymphatic fluid was divided depending on the bleeding status into the bleeding and nonbleeding groups. The fluid was subjected to cytological and biochemical analyses to determine protein and cytokine levels. The Mann-Whitney U test was used to compare the two groups. Results: There were significant differences in the levels of interleukin (IL)-6, IL-10, and glucose, and the percentage of white blood cells between the bleeding and nonbleeding groups. There was no significant difference in chlorine and protein content; white blood cell count; and IL-2, IL-4, tumor necrosis factor α, and interferon γ levels between the two groups. Conclusion: Lymphatic fluid is less stable in bleeding LMs than in non-bleeding LMs and is prone to inflammatory reactions. The inflammatory reaction in lymphatic fluid does not stimulate the cytokine storm in blood. The inflammatory reaction due to LMs does not affect the contents of protein and chlorine in lymphatic cyst fluid.

Mitogen-activated protein kinase inhibitor PD98059 improves neuroimmune dysfunction in experimental autoimmune encephalomyelitis in SJL/J mice through the inhibition of nuclear factor-kappa B signaling in B cells

Multiple sclerosis (MS) is a severe autoimmune disease leading to demyelination, followed by consequent axonal degeneration, causing sensory, motor, cognitive, and visual symptoms. Experimental autoimmune encephalomyelitis (EAE) is the most well-studied animal model of MS. Most current MS treatments are not completely effective, and severe side effects remain a great challenge. In this study, we report the therapeutic efficacy of PD98059, a potent mitogen-activated protein kinase inhibitor, on proteolipid protein (PLP)_139-151-induced EAE in SJL/J mice. Following the induction of EAE, mice were intraperitoneally treated with PD98059 (5 mg/kg for 14 days) daily from day 14 to day 28. This study investigated the effects of PD98059 on C-C motif chemokine receptor 6 (CCR6), CD14, NF-κB p65, IκBα, GM-CSF, iNOS, IL-6, TNF-α in CD45R⁺ B lymphocytes using flow cytometry. Furthermore, we analyzed the effect of PD98059 on CCR6, CD14, NF-κB p65, GM-CSF, iNOS, IL-6, and TNF-α mRNA and protein expression levels using qRT-PCR analysis in brain tissues. Mechanistic investigations revealed that PD98059-treated in mice with EAE had reduced CD45R⁺CCR6⁺, CD45R⁺CD14⁺, CD45R⁺NF-κB p65⁺, CD45R⁺GM-CSF⁺, CD45R⁺iNOS⁺, CD45R⁺IL-6⁺, and CD45R⁺TNF-α⁺ cells and increased CD45R⁺IκBα⁺ cells compared with vehicle-treated control mice in the spleen. Moreover, downregulation of CCR6, CD14, NF-κB p65, GM-CSF, iNOS, IL-6, and TNF-α mRNA expression level was observed in PD98059-treated mice with EAE compared with vehicle-treated control mice in the brain tissue. The results of this study demonstrate that PD98059 modulates inflammatory mediators through multiple cellular mechanisms. The results of this study suggest that PD98059 may be pursued as a therapeutic agent for the treatment of MS.

Biomaterials-Based Regenerative Strategies for Skin Tissue Wound Healing

Skin tissue wound healing proceeds through four major stages, including hematoma formation, inflammation, and neo-tissue formation, and culminates with tissue remodeling. These four steps significantly overlap with each other and are aided by various factors such as cells, cytokines (both anti- and pro-inflammatory), and growth factors that aid in the neo-tissue formation. In all these stages, advanced biomaterials provide several functional advantages, such as removing wound exudates, providing cover, transporting oxygen to the wound site, and preventing infection from microbes. In addition, advanced biomaterials serve as vehicles to carry proteins/drug molecules/growth factors and/or antimicrobial agents to the target wound site. In this review, we report recent advancements in biomaterials-based regenerative strategies that augment the skin tissue wound healing process. In conjunction with other medical sciences, designing nanoengineered biomaterials is gaining significant attention for providing numerous functionalities to trigger wound repair. In this regard, we highlight the advent of nanomaterial-based constructs for wound healing, especially those that are being evaluated in clinical settings. Herein, we also emphasize the competence and versatility of the three-dimensional (3D) bioprinting technique for advanced wound management. Finally, we discuss the challenges and clinical perspective of various biomaterial-based wound dressings, along with prospective future directions. With regenerative strategies that utilize a cocktail of cell sources, antimicrobial agents, drugs, and/or growth factors, it is expected that significant patient-specific strategies will be developed in the near future, resulting in complete wound healing with no scar tissue formation.

Peptide nanogels as a scaffold for fabricating dermal grafts and 3D vascularized skin models

Millions of people worldwide suffer from skin injuries, which create significant problems in their lives and are costly to cure. Tissue engineering is a promising approach that aims to fabricate functional organs using biocompatible scaffolds. We designed ultrashort tetrameric peptides with promising properties required for skin tissue engineering. Our work aimed to test the efficacy of these scaffolds for the fabrication of dermal grafts and 3D vascularized skin tissue models. We found that the direct contact of keratinocytes and fibroblasts enhanced the proliferation of the keratinocytes. Moreover, the expression levels of TGF-β1, b-FGF, IL-6, and IL-1α is correlated with the growth of the fibroblasts and keratinocytes in the co-culture. Furthermore, we successfully produced a 3D vascularized skin co-culture model using these peptide scaffolds. We believe that the described results represent an advancement in the fabrication of skin tissue equivalent, thereby providing the opportunity to rebuild missing, failing, or damaged parts.

Pluripotent stem cell-derived mesenchymal stromal cells improve cardiac function and vascularity after myocardial infarction

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs) have been shown to improve cardiac function after injury and are the subject of ongoing clinical trials. In this study, the authors tested the cardiac regenerative potential of an induced pluripotent stem cell-derived MSC (iPSC-MSC) population (Cymerus MSCs) in a rat model of myocardial ischemia-reperfusion (I/R). Furthermore, the authors compared this efficacy with bone marrow-derived MSCs (BM-MSCs), which are the predominant cell type in clinical trials.

METHODS

Four days after myocardial I/R injury, rats were randomly assigned to (i) a Cymerus MSC group (n = 15), (ii) a BM-MSC group (n = 15) or (iii) a vehicle control group (n = 14). For cell-treated animals, a total of 5 × 10⁶ cells were injected at three sites within the infarcted left ventricular (LV) wall.

RESULTS

One month after cell transplantation, Cymerus MSCs improved LV function (assessed by echocardiography) compared with vehicle and BM-MSCs. Interestingly, Cymerus MSCs enhanced angiogenesis without sustained engraftment or significant impact on infarct scar size. Suggesting safety, Cymerus MSCs had no effect on inducible tachycardia or the ventricular scar heterogeneity that provides a substrate for cardiac re-entrant circuits.

CONCLUSIONS

The authors here demonstrate that intra-myocardial administration of iPSC-MSCs (Cymerus MSCs) provide better therapeutic effects compared with conventional BM-MSCs in a rodent model of myocardial I/R. Because of its manufacturing scalability, iPSC-MSC therapy offers an exciting opportunity for an "off-the-shelf" stem cell therapy for cardiac repair.

Neuroprotection in early stages of Alzheimer's disease is promoted by transthyretin angiogenic properties

Background

While still controversial, it has been demonstrated that vascular defects can precede the onset of other AD hallmarks features, making it an important therapeutic target. Given that the protein transthyretin (TTR) has been established as neuroprotective in AD, here we investigated the influence of TTR in the vasculature.

Methods

We evaluated the thickness of the basement membrane and the length of brain microvessels, by immunohistochemistry, in AβPPswe/PS1A246E (AD) transgenic mice and non-transgenic mice (NT) bearing one (TTR+/−) or two (TTR+/+) copies of the TTR gene. The angiogenic potential of TTR was evaluated in vitro using the tube formation assay, and in vivo using the chick chorioallantoic membrane (CAM) assay.

Results

AD transgenic mice with TTR genetic reduction, AD/TTR+/−, exhibited a thicker BM in brain microvessels and decreased vessel length than animals with normal TTR levels, AD/TTR+/+. Further in vivo investigation, using the CAM assay, revealed that TTR is a pro-angiogenic molecule, and the neovessels formed are functional. Also, TTR increased the expression of key angiogenic molecules such as proteins interleukins 6 and 8, angiopoietin 2, and vascular endothelial growth factor, by endothelial cells, in vitro, under tube formation conditions. We showed that while TTR reduction also leads to a thicker BM in NT mice, this effect is more pronounced in AD mice than in NT animals, strengthening the idea that TTR is a neuroprotective protein. We also studied the effect of TTR tetrameric stabilization on BM thickness, showing that AD mice treated with the TTR tetrameric stabilizer iododiflunisal (IDIF) displayed a significant reduction of BM thickness and increased vessel length, when compared to non-treated littermates.

Conclusion

Our in vivo results demonstrate the involvement of TTR in angiogenesis, particularly as a modulator of vascular alterations occurring in AD. Since TTR is decreased early in AD, its tetrameric stabilization can represent a therapeutic avenue for the early treatment of AD through the maintenance of the vascular structure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13195-021-00883-8.

Alpha and beta adrenoceptors activate interleukin-6 transcription through different pathways in cultured astrocytes from rat spinal cord

In brain astrocytes, noradrenaline (NA) has been shown to up-regulate IL-6 production via β-adrenoceptors (ARs). However, the underlying intracellular mechanisms for this regulation are not clear, and it remains unknown whether α-ARs are involved. In this study, we investigated the AR-mediated regulation of IL-6 mRNA levels in the cultured astrocytes from rat spinal cord. NA, the α1-agonist phenylephrine, and the β-agonist isoproterenol increased IL-6 mRNA levels. The phenylephrine-induced IL-6 increase was accompanied by an increase in ERK phosphorylation, and these effects were blocked by inhibitors of PKC and ERK. The isoproterenol-induced IL-6 increase was accompanied by an increase in CREB phosphorylation, and these effects were blocked by a PKA inhibitor. Our results indicate that IL-6 increases by α1- and β-ARs are mediated via the PKC/ERK and cAMP/PKA/CREB pathways, respectively. Moreover, conditioned medium collected from astrocytes treated with the α2-AR agonist dexmedetomidine, increased IL-6 mRNA in other astrocytes. In this study, we elucidate that α1- and α2-ARs, in addition to β-ARs, promote IL-6 transcription through different pathways in spinal cord astrocytes.

Enhanced Biological Activity of a Novel Preparation of Lavandula angustifolia Essential Oil

Lavandula angustifolia, one of the most popular medicinal plants, is the source of a bioactive essential oil characterized by a wide spectrum of biological activity, e.g., antiseptic, analgesic, and anticancer effects. In dermatology, the oil helps to relieve skin inflammation and exhibit wound healing potential. However, the mechanism of action of the lavender oil depends on its composition, which in turn is dependent on the origin and growing conditions. Our study aimed to compare the composition and proregenerative properties of the commercially-available narrow-leaved lavender oil produced in Provence, France, with the oil obtained from the narrow-leaved lavender cultivated locally in Poland. GC/MS analysis showed that self-manufactured essential oil had lower linalool content than commercial oil (23.2 vs. 40.2%), comparable linalyl acetate content (40.6 vs. 44%), while the proportion of lavandulyl acetate was significantly higher (23.2 vs. 5.5%). To determine the influence of lavender oil on the production of proinflammatory cytokines and proregenerative growth factors, gene expression of the selected signaling molecules by HaCaT cells was investigated using real-time PCR. Results showed a concentration-dependent effect of lavender oils on the production of IL-6, IL-8, and VEGF by the keratinocyte cell line. Finally, the potential of the lavender oil to increase the production of VEGF, the most important angiogenic factor, with the in-house preparation performing significantly better in the in vitro cell models was identified.

Notch1 signaling determines the plasticity and function of fibroblasts in diabetic wounds

Fibroblasts play a pivotal role in wound healing. However, the molecular mechanisms determining the reparative response of fibroblasts remain unknown. Here, we identify Notch1 signaling as a molecular determinant controlling the plasticity and function of fibroblasts in modulating wound healing and angiogenesis. The Notch pathway is activated in fibroblasts of diabetic wounds but not in normal skin and non-diabetic wounds. Consistently, wound healing in the FSP-1 ^+/- ;ROSA ^LSL-N1IC+/+ mouse, in which Notch1 is activated in fibroblasts, is delayed. Increased Notch1 activity in fibroblasts suppressed their growth, migration, and differentiation into myofibroblasts. Accordingly, significantly fewer myofibroblasts and less collagen were present in granulation tissues of the FSP-1 ^+/- ;ROSA ^LSL-N1IC+/+ mice, demonstrating that high Notch1 activity inhibits fibroblast differentiation. High Notch1 activity in fibroblasts diminished their role in modulating the angiogenic response. We also identified that IL-6 is a functional Notch1 target and involved in regulating angiogenesis. These findings suggest that Notch1 signaling determines the plasticity and function of fibroblasts in wound healing and angiogenesis, unveiling intracellular Notch1 signaling in fibroblasts as potential target for therapeutic intervention in diabetic wound healing.

Metabolic Flexibility Assists Reprograming of Central and Peripheral Innate Immunity During Neurodevelopment

Central innate immunity assists time-dependent neurodevelopment by recruiting and interacting with peripheral immune cells. Microglia are the major player of central innate immunity integrating peripheral signals arising from the circumventricular regions lacking the blood-brain barrier (BBB), via neural afferent pathways such as the vagal nerve and also by choroid plexus into the brain ventricles. Defective and/or unrestrained activation of central and peripheral immunity during embryonic development might set an aberrant connectome establishment and brain function, leading to major psychiatric disorders in postnatal stages. Molecular candidates leading to central and peripheral innate immune overactivation identified metabolic substrates and lipid species as major contributors of immunological priming, supporting the role of a metabolic flexibility node during trained immunity. Mechanistically, trained immunity is established by an epigenetic program including DNA methylation and histone acetylation, as the major molecular epigenetic signatures to set immune phenotypes. By definition, immunological training sets reprogramming of innate immune cells, enhancing or repressing immune responses towards a second challenge which potentially might contribute to neurodevelopment disorders. Notably, the innate immune training might be set during pregnancy by maternal immune activation stimuli. In this review, we integrate the most valuable scientific evidence supporting the role of metabolic cues assisting metabolic flexibility, leading to innate immune training during development and its effects on aberrant neurological phenotypes in the offspring. We also add reports supporting the role of methylation and histone acetylation signatures as a major epigenetic mechanism regulating immune training.

The Role of IL-6 in Skin Fibrosis and Cutaneous Wound Healing

The timely resolution of wound healing is critical for restoring the skin as a protective barrier. The switch from a proinflammatory to a reparative microenvironment must be tightly regulated. Interleukin (IL)-6 is a key modulator of the inflammatory and reparative process: it is involved in the differentiation, activation, and proliferation of leukocytes, endothelial cells, keratinocytes, and fibroblasts. This review examines the role of IL-6 in the healing of cutaneous wounds, and how dysregulation of IL-6 signaling can lead to either fibrosis or a failure to heal. The role of an IL-6/TGF-β feedback loop is discussed in the context of fibrogenesis, while IL-6 expression and responses in advanced age, diabetes, and obesity is outlined regarding the development of chronic wounds. Current research on therapies that modulate IL-6 is explored. Here, we consider IL-6′s diverse impact on cutaneous wound healing.

Cellular senescence links aging and diabetes in cardiovascular disease

Aging is a powerful independent risk factor for cardiovascular diseases such as atherosclerosis and heart failure. Concomitant diabetes mellitus strongly reinforces this effect of aging on cardiovascular disease. Cellular senescence is a fundamental mechanism of aging and appears to play a crucial role in the onset and prognosis of cardiovascular disease in the context of both aging and diabetes. Senescent cells are in a state of cell cycle arrest but remain metabolically active by secreting inflammatory factors. This senescence-associated secretory phenotype is a trigger of chronic inflammation, oxidative stress, and decreased nitric oxide bioavailability. A complex interplay between these three mechanisms results in age- and diabetes-associated cardiovascular damage. In this review, we summarize current knowledge on cellular senescence and its secretory phenotype, which might be the missing link between aging and diabetes contributing to cardiovascular disease.

TNF-α-sensitive brain pericytes activate microglia by releasing IL-6 through cooperation between IκB-NFκB and JAK-STAT3 pathways

Interleukin (IL)-6 is an important mediator of neurovascular dysfunction, neurodegeneration and/or neuroinflammation. We previously reported that brain pericytes released higher levels of IL-6 than did glial cells (astrocytes and microglia) in response to tumor necrosis factor (TNF)-α. Moreover, pericytes stimulated with TNF-α enhanced activation of BV-2 microglia. In this study, we investigated the mechanisms of TNF-α mediated induction of IL-6 release from brain pericytes and astrocytes and whether pericyte-derived IL-6 would facilitate activation of BV-2 microglia. Using rat brain pericyte and astrocyte primary cultures and pharmacological inhibitors, we found that, TNF-α induced the highest levels of IL-6 release from pericytes by activating the inhibitor kappa B (IκB)-nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) and Janus family of tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT)3 pathways. STAT3 contributed to TNF-α induced nuclear translocation of phospho-NFκB in pericytes. TNF-α-induced IL-6 release in astrocytes was mediated by NFκB but not by STAT3. The presence of pericytes amplified TNF-α-induced iNOS mRNA expression in BV-2 microglia. This effect was blocked by a neutralizing antibody for IL-6. These findings indicated that crosstalk between the IκB-NFκB and JAK-STAT3 pathways is a pericyte specific mechanism, not occurring in astrocytes, for TNF-α-induced IL-6 release. IL-6 derived from pericytes enhanced microglial activation. Our findings increase understanding of the role of pericyte-microglia crosstalk in the brain under neuroinflammatory conditions and suggest a potentially attractive therapeutic target for brain inflammation.

Innate immunity and cellular senescence: The good and the bad in the developmental and aged brain

Ongoing studies evidence cellular senescence in undifferentiated and specialized cells from tissues of all ages. Although it is believed that senescence plays a wider role in several stress responses in the mature age, its participation in certain physiological and pathological processes throughout life is coming to light. The "senescence machinery" has been observed in all brain cell populations, including components of innate immunity (e.g., microglia and astrocytes). As the beneficial versus detrimental implications of senescence is an open question, we aimed to analyze the contribution of immune responses in regulatory mechanisms governing its distinct functions in healthy (development, organogenesis, danger patrolling events) and diseased brain (glioma, neuroinflammation, neurodeneration), and the putative connection between cellular and molecular events governing the 2 states. Particularly this review offers new insights into the complex roles of senescence both as a chronological event as age advances, and as a molecular mechanism of brain homeostasis through the important contribution of innate immune responses and their crosstalk with neighboring cells in brain parenchyma. We also highlight the impact of the recently described glymphatic system and brain lymphatic vasculature in the interplay between peripheral and central immune surveillance and its potential implication during aging. This will open new ways to understand brain development, its deterioration during aging, and the occurrence of several oncological and neurodegenerative diseases.

Biology of Microglia in the Developing Brain

Microglia exist in different morphological forms in the developing brain. They show a small cell body with scanty cytoplasm with many branching processes in the grey matter of the developing brain. However, in the white matter such as the corpus callosum where the unmyelinated axons are loosely organized, they appear in an amoeboid form having a round cell body endowed with copious cytoplasm rich in organelles. The amoeboid cells eventually transform into ramified microglia in the second postnatal week when the tissue becomes more compact with the onset of myelination. Microglia serve as immunocompetent macrophages that act as neuropathology sensors to detect and respond swiftly to subtle changes in the brain tissues in pathological conditions. Microglial functions are broadly considered as protective in the normal brain development as they phagocytose dead cells and sculpt neuronal connections by pruning excess axons and synapses. They also secrete a number of trophic factors such as insulin-like growth factor-1 and transforming growth factor-β among many others that are involved in neuronal and oligodendrocyte survival. On the other hand, microglial cells when activated produce a plethora of molecules such as proinflammatory cytokines, chemokines, reactive oxygen species, and nitric oxide that are implicated in the pathogenesis of many pathological conditions such as epilepsy, cerebral palsy, autism, and perinatal hypoxic-ischemic brain injury. Although many studies have investigated the origin and functions of the microglia in the developing brain, in-depth in vivo studies along with analysis of their transcriptome and epigenetic changes need to be undertaken to elucidate their full potential be it protective or neurotoxic. This would lead to a better understanding of their roles in the healthy and diseased developing brain and advancement of therapeutic strategies to target microglia-mediated neurotoxicity.

The roles of signal transducer and activator of transcription factor 3 in tumor angiogenesis

Angiogenesis is the development of new blood vessels, which is required for tumor growth and metastasis. Signal transducer and activator of transcription factor 3 (STAT3) is a transcription factor that regulates a variety of cellular events including proliferation, differentiation and apoptosis. Previous studies revealed that activation of STAT3 promotes tumor angiogenesis. In this review, we described the activities of STAT3 signaling in different cell types involved in angiogenesis. Particularly, we elucidated the molecular mechanisms of STAT3-mediated gene regulation in angiogenic endothelial cells in response to external stimulations such as hypoxia and inflammation. The potential for STAT3 as a therapeutic target was also discussed. Overall, this review provides mechanistic insights for the roles of STAT3 signaling in tumor angiogenesis.

Cytokines in Endocrine Dysfunction of Plasma Cell Disorders

Monoclonal gammopathies (MG) are classically associated with lytic bone lesions, hypercalcemia, anemia, and renal insufficiency. However, in some cases, symptoms of endocrine dysfunction are more prominent than these classical signs and misdiagnosis can thus be possible. This concerns especially the situation where the presence of M-protein is limited and the serum protein electrophoresis (sPEP) appears normal. To understand the origin of the endocrine symptoms associated with MG, we overview here the current knowledge on the complexity of interactions between cytokines and the endocrine system in MG and discuss the perspectives for both the diagnosis and treatments for this class of diseases. We also illustrate the role of major cytokines and growth factors such as IL-6, IL-1β, TNF-α, and VEGF in the endocrine system, as these tumor-relevant signaling molecules not only help the clonal expansion and invasion of the tumor cells but also influence cellular metabolism through autocrine, paracrine, and endocrine mechanisms. We further discuss the broader impact of these tumor environment-derived molecules and proinflammatory state on systemic hormone signaling. The diagnostic challenges and clinical work-up are illustrated from the point of view of an endocrinologist.

Interleukin-6 trans-signalling induces vascular endothelial growth factor synthesis partly via Janus kinases-STAT3 pathway in human mesothelial cells

AIMS

Interleukin-6 (IL-6) is a vital inflammatory factor in the peritoneal cavity of peritoneal dialysis (PD) patients. Because intraperitoneal inflammation is closely associated with angiogenesis, we sought to explore the effect of IL-6 on vascular endothelial growth factor (VEGF) synthesis and its transduction pathway in mesothelial cells.

METHODS

Human mesothelial cells (Met-5A) were incubated with different concentrations of glucose and mannitol, and the effect of glucose and mannitol on the expression of IL-6 was determined. Then, the cells were stimulated by IL-6 with or without two soluble receptors of IL-6 (sIL-6R or sgp130), and VEGF synthesis was detected. Finally, the cells were incubated with IL-6/sIL-6R combined with or without the inhibitor of Janus kinases (JAK) AG490. The phosphorylation of the signal transducer and activator of transcription 3 (STAT3) and its intracellular translocation were examined.

RESULTS

1. High glucose and mannitol could upregulate IL-6 mRNA expression and IL-6 secretion in mesothelial cells significantly, and there was no difference of its effect between high glucose and mannitol. 2. Met-5A was a cell line with a single IL-6 receptor. The IL-6/sIL-6R complex induced VEGF synthesis of mesothelial cells, which was alleviated by sgp130 or AG490. IL-6 trans-signalling could induce the phosphorylation of STAT3, which is recruited to the cellular nucleus of Met-5A cells.

CONCLUSION

The present study might provide evidence that high glucose upregulates IL-6 synthesis in Met-5A cells, to some extent, depending on its osmolality and that IL-6 trans-signalling could induce VEGF synthesis partly dependent on the JAK/STAT3 pathway.

Astrocytic IL-6 Influences the Clinical Symptoms of EAE in Mice

Interleukin-6 (IL-6) is a multifunctional cytokine that not only plays major roles in the immune system, but also serves as a coordinator between the nervous and endocrine systems. IL-6 is produced in multiple cell types in the CNS, and in turn, many cells respond to it. It is therefore important to ascertain which cell type is the key responder to IL-6 during both physiological and pathological conditions. In order to test the role of astrocytic IL-6 in neuroinflammation, we studied an extensively-used animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), in mice with an IL-6 deficiency in astrocytes (Ast-IL-6 KO). Results indicate that lack of astrocytic IL-6 did not cause major changes in EAE symptomatology. However, a delay in the onset of clinical signs was observed in Ast-IL-6 KO females, with fewer inflammatory infiltrates and decreased demyelination and some alterations in gliosis and vasogenesis, compared to floxed mice. These results suggest that astrocyte-secreted IL-6 has some roles in EAE pathogenesis, at least in females.

Malignant T cells express lymphotoxin α and drive endothelial activation in cutaneous T cell lymphoma

Lymphotoxin α (LTα) plays a key role in the formation of lymphatic vasculature and secondary lymphoid structures. Cutaneous T cell lymphoma (CTCL) is the most common primary lymphoma of the skin and in advanced stages, malignant T cells spreads through the lymphatic to regional lymph nodes to internal organs and blood. Yet, little is known about the mechanism of the CTCL dissemination. Here, we show that CTCL cells express LTα in situ and that LTα expression is driven by aberrantly activated JAK3/STAT5 pathway. Importantly, via TNF receptor 2, LTα functions as an autocrine factor by stimulating expression of IL-6 in the malignant cells. LTα and IL-6, together with VEGF promote angiogenesis by inducing endothelial cell sprouting and tube formation. Thus, we propose that LTα plays a role in malignant angiogenesis and disease progression in CTCL and may serve as a therapeutic target in this disease.

Distinct Contributions of Astrocytes and Pericytes to Neuroinflammation Identified in a 3D Human Blood-Brain Barrier on a Chip

Neurovascular inflammation is a major contributor to many neurological disorders, but modeling these processes in vitro has proven to be difficult. Here, we microengineered a three-dimensional (3D) model of the human blood-brain barrier (BBB) within a microfluidic chip by creating a cylindrical collagen gel containing a central hollow lumen inside a microchannel, culturing primary human brain microvascular endothelial cells on the gel’s inner surface, and flowing medium through the lumen. Studies were carried out with the engineered microvessel containing endothelium in the presence or absence of either primary human brain pericytes beneath the endothelium or primary human brain astrocytes within the surrounding collagen gel to explore the ability of this simplified model to identify distinct contributions of these supporting cells to the neuroinflammatory response. This human 3D BBB-on-a-chip exhibited barrier permeability similar to that observed in other in vitro BBB models created with non-human cells, and when stimulated with the inflammatory trigger, tumor necrosis factor-alpha (TNF-α), different secretion profiles for granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6) were observed depending on the presence of astrocytes or pericytes. Importantly, the levels of these responses detected in the 3D BBB chip were significantly greater than when the same cells were co-cultured in static Transwell plates. Thus, as G-CSF and IL-6 have been reported to play important roles in neuroprotection and neuroactivation in vivo, this 3D BBB chip potentially offers a new method to study human neurovascular function and inflammation in vitro, and to identify physiological contributions of individual cell types.

IL-1alpha induces angiogenesis in brain endothelial cells in vitro: implications for brain angiogenesis after acute injury

Inflammation is a major contributor to neuronal injury and is associated with poor outcome after acute brain injury such as stroke. The pro-inflammatory cytokine interleukin (IL)-1 is a critical regulator of cerebrovascular inflammation after ischemic injury, mainly through action of both of its isoforms, IL-1α and IL-1β, at the brain endothelium. In contrast, the differential action of these ligands on endothelial activation and post-stroke angiogenesis is largely unknown. Here, we demonstrate that IL-1α is chronically elevated in the brain after experimental stroke suggesting that it is present during post-stroke angiogenic periods. Furthermore, we demonstrate that IL-1α is a potent mediator of endothelial activation and inducer of angiogenic markers in endothelial cells in vitro. Using brain endothelial cell lines, we found that IL-1α was significantly more potent than IL-1β at inducing endothelial cell activation, as measured by expression of the pro-angiogenic chemokine CXCL-1. IL-1α also induced strong expression of the angiogenic mediator IL-6 in a concentration-dependent manner. Furthermore, IL-1α induced significant proliferation and migration of endothelial cells, and promoted formation of tube-like structures that are established key hallmarks of angiogenesis in vitro. Finally, all of those responses were blocked by the IL-1 receptor antagonist (IL-1RA). In conclusion, our data highlights a potential new role for IL-1 in brain repair mechanisms and identifies IL-1α as a potential new therapy to promote post-stroke angiogenesis. Inflammation is a major contributor to neuronal injury and is associated with poor outcome after neurotrauma. We demonstrate that cytokine IL-1α is chronically elevated in the brain after experimental stroke suggesting that it is present chronically post-stroke. We demonstrate that IL-1α is a potent mediator of endothelial activation and inducer of angiogenic markers in endothelial cells. Our data highlights a new role for IL-1 in brain repair mechanisms and identifies IL-1α as a potential therapy to promote post-stroke angiogenesis.

Engineering macrophages to control the inflammatory response and angiogenesis

Macrophage (MΦ) dysregulation is increasingly becoming recognized as a risk factor for a number of inflammatory complications including atherosclerosis, cancer, and the host response elicited by biomedical devices. It is still unclear what roles the pro-inflammatory (M1) MΦ and pro-healing (M2) MΦ phenotypes play during the healing process. However, it has been shown that a local overabundance of M1 MΦs can potentially lead to a chronically inflamed state of the tissue; while a local over-exuberant M2 MΦ response can lead to tissue fibrosis and even promote tumorigenesis. These notions strengthen the argument that the tight temporal regulation of this phenotype balance is necessary to promote inflammatory resolution that leads to tissue homeostasis. In this study, we have engineered pro-inflammatory MΦs, MΦ-cTLR4 cells, which can be activated to a M1-like MΦ phenotype with a small molecule, the chemical inducer of dimerization (CID) drug. The MΦ-cTLR4 cells when activated with the CID drug, express increased levels of TNFα, IL-6, and iNOS. Activated MΦ-cTLR4 cells stay stimulated for at least 48h; once the CID drug is withdrawn, the MΦ-cTLR4 cells return to baseline state within 18h. Further, in vitro CID-activated MΦ-cTLR4 cells induce upregulation of VCAM-1 and ICAM-1 on endothelial cells (EC) in a TNFα-dependent manner. With the ability to specifically modulate the MФ-cTLR4 cells with the presence or absence of a small molecule, we now have the tool necessary to observe a primarily M1 MФ response during inflammation. By isolating this phase of the wound healing response, it may be possible to determine conditions for ideal healing.

Endogenous repair signaling after brain injury and complementary bioengineering approaches to enhance neural regeneration

Traumatic brain injury (TBI) affects 5.3 million Americans annually. Despite the many long-term deficits associated with TBI, there currently are no clinically available therapies that directly address the underlying pathologies contributing to these deficits. Preclinical studies have investigated various therapeutic approaches for TBI: two such approaches are stem cell transplantation and delivery of bioactive factors to mitigate the biochemical insult affiliated with TBI. However, success with either of these approaches has been limited largely due to the complexity of the injury microenvironment. As such, this review outlines the many factors of the injury microenvironment that mediate endogenous neural regeneration after TBI and the corresponding bioengineering approaches that harness these inherent signaling mechanisms to further amplify regenerative efforts.

Circadian rhythmicity, variability and correlation of interleukin-6 levels in plasma and cerebrospinal fluid of healthy men

BACKGROUND

Interleukin-6 (IL-6) is a cytokine with pleiotropic actions in both the periphery of the body and the central nervous system (CNS). Altered IL-6 secretion has been associated with inflammatory dysregulation and several adverse health consequences. However, little is known about the physiological circadian characteristics and dynamic inter-correlation between circulating and CNS IL-6 levels in humans, or their significance.

METHODS

Simultaneous assessment of plasma and cerebrospinal fluid (CSF) IL-6 levels was performed hourly in 11 healthy male volunteers over 24h, to characterize physiological IL-6 secretion levels in both compartments.

RESULTS

IL-6 levels showed considerable within- and between-subject variability in both plasma and CSF, with plasma/CSF ratios revealing consistently higher levels in the CSF. Both CSF and plasma IL-6 levels showed a distinctive circadian variation, with CSF IL-6 levels exhibiting a main 24h, and plasma a biphasic 12h, circadian component. Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was at around 7 p.m. There was no correlation between coincident CSF and plasma IL-6 values, but evidence for significant correlations at a negative 7-8h time lag.

CONCLUSIONS

This study provides evidence in humans for a circadian IL-6 rhythm in CSF and confirms prior observations reporting a plasma biphasic circadian pattern. Our results indicate differential IL-6 regulation across the two compartments and are consistent with local production of IL-6 in the CNS. Possible physiological significance is discussed and implications for further research are highlighted.

Intraperitoneal interleukin-6 levels predict peritoneal solute transport rate: a prospective cohort study

BACKGROUND

To evaluate the association of dialysate interleukin-6 (IL-6), a marker of ongoing peritoneal inflammation, with the alteration of peritoneal solute transport rate (PSTR) in continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS

Stable CAPD patients were enrolled in the present study. A total of 128 patients were analyzed in this prospective study. IL-6 concentration in the overnight effluent was determined and expressed as the IL-6 appearance rate (IL-6AR). Mass transfer area coefficients of creatinine (MTACcr) were measured at enrollment and 12 months later. Logistic regression was used to examine the association between IL-6AR and change in MTACcr.

RESULTS

Multivariable linear regression showed that historical glucose exposure was significantly associated with dialysate IL-6AR level [β = 0.008 (0.001-0.015), p = 0.021]. After 12 months, MTACcr was significantly increased [6.40 (4.70-8.75) vs. 7.14 (5.69-8.73) ml/min, p = 0.004], while ultrafiltration capacity decreased [4 h UF 340 (220-400) vs. 280 (180-380) ml, p = 0.006]. Compared to the patients with stable PSTR, the dialysate IL-6AR in patients with increasing PSTR was significantly higher [277.08 (247.45-349.53) vs. 263.18 (69.94-286.72) pg/min, p = 0.015]. Patients with increasing PSTR had lower residual renal function [0.79 (0-2.12) vs. 1.70 (0.39-3.38) ml/min, p = 0.006] and less urine output [225 (0-600) vs. 500 (125-900) ml/24 h, p = 0.014]. Logistic analysis showed that both high dialysate IL-6AR [OR 1.333 and 95% CI (1.024-1.735), p = 0.033] and low RRF [OR 0.831 and 95% CI (0.699-0.988), p = 0.036] were independent risk factors for increasing PSTR.

CONCLUSIONS

This prospective study suggests that intraperitoneal IL-6 is a predictor of increasing PSTR in peritoneal dialysis patients.

Trans-signaling is a dominant mechanism for the pathogenic actions of interleukin-6 in the brain

IL-6 is implicated in the pathogenesis of various neuroinflammatory and neurodegenerative disorders of the CNS. IL-6 signals via binding to either the membrane bound IL-6Rα (classic signaling) or soluble (s)IL-6Ra (trans-signaling) that then form a complex with gp130 to activate the JAK/STAT signaling pathway. The importance of classic versus trans-signaling in mediating IL-6 actions in the living CNS is relatively unknown and was the focus of this investigation. Bigenic mice (termed GFAP-IL6/sgp130 mice) were generated with CNS-restricted, astrocyte-targeted production of IL-6 and coproduction of the specific inhibitor of IL-6 trans-signaling, human sgp130-Fc. Transgene-encoded IL-6 mRNA levels were similar in the brain of GFAP-IL6 and GFAP-IL6/sgp130 mice. However, GFAP-IL6/sgp130 mice had decreased pY(705)-STAT3 in the brain due to a reduction in the total number of pY(705)-STAT3-positive cells and a marked loss of pY(705)-STAT3 in specific cell types. Blockade of trans-signaling in the brain of the GFAP-IL6 mice significantly attenuated Serpina3n but not SOCS3 gene expression, whereas vascular changes including angiogenesis and blood-brain barrier leakage as well as gliosis were also reduced significantly. Hippocampal neurogenesis which was impaired in GFAP-IL6 mice was rescued in young GFAP-IL6 mice with cerebral sgp130 production. Finally, degenerative changes in the cerebellum characteristic of GFAP-IL6 mice were absent in GFAP-IL6/sgp130 mice. The findings indicate that in the CNS: (1) sgp130 is able to block IL-6 trans-signaling, (2) trans-signaling is important for IL-6 cellular communication with selective cellular and molecular targets, and (3) blocking of trans-signaling alleviates many of the detrimental effects of IL-6.

Fetal alcohol spectrum disorders and neuroimmune changes

The behavioral consequences of fetal alcohol spectrum disorders (FASD) are serious and persist throughout life. The causative mechanisms underlying FASD are poorly understood. However, much has been learned about FASD from human structural and functional studies as well as from animal models, which have provided a greater understanding of the mechanisms underlying FASD. Using animal models of FASD, it has been recently discovered that ethanol induces neuroimmune activation in the developing brain. The resulting microglial activation, production of proinflammatory molecules, and alteration in expression of developmental genes are postulated to alter neuron survival and function and lead to long-term neuropathological and cognitive defects. It has also been discovered that microglial loss occurs, reducing microglia's ability to protect neurons and contribute to neuronal development. This is important, because emerging evidence demonstrates that microglial depletion during brain development leads to long-term neuropathological and cognitive defects. Interestingly, the behavioral consequences of microglial depletion and neuroimmune activation in the fetal brain are particularly relevant to FASD. This chapter reviews the neuropathological and behavioral abnormalities of FASD and delineates correlates in animal models. This serves as a foundation to discuss the role of the neuroimmune system in normal brain development, the consequences of microglial depletion and neuroinflammation, the evidence of ethanol induction of neuroinflammatory processes in animal models of FASD, and the development of anti-inflammatory therapies as a new strategy for prevention or treatment of FASD. Together, this knowledge provides a framework for discussion and further investigation of the role of neuroimmune processes in FASD.

The immune system and developmental programming of brain and behavior

The brain, endocrine, and immune systems are inextricably linked. Immune molecules have a powerful impact on neuroendocrine function, including hormone-behavior interactions, during health as well as sickness. Similarly, alterations in hormones, such as during stress, can powerfully impact immune function or reactivity. These functional shifts are evolved, adaptive responses that organize changes in behavior and mobilize immune resources, but can also lead to pathology or exacerbate disease if prolonged or exaggerated. The developing brain in particular is exquisitely sensitive to both endogenous and exogenous signals, and increasing evidence suggests the immune system has a critical role in brain development and associated behavioral outcomes for the life of the individual. Indeed, there are associations between many neuropsychiatric disorders and immune dysfunction, with a distinct etiology in neurodevelopment. The goal of this review is to describe the important role of the immune system during brain development, and to discuss some of the many ways in which immune activation during early brain development can affect the later-life outcomes of neural function, immune function, mood and cognition.

Neural transmembrane protease and endothelial Gs protein activation in cell contact-dependent signaling between neural stem/progenitor cells and brain endothelial cells

Vasculature is an important component of the neural stem cell niche in brain. It regulates neural stem/progenitor (NS/P) cell self-renewal, differentiation, and migration. In the neurogenic niches of adult brain, NS/P cells lie close to blood vessels, and proliferating NS/P cells frequently contact the vasculature. In the present study we showed that NS/P cells in co-culture with brain endothelial (bEND) cells activated endothelial G proteins and p38 mitogen-activated protein kinase (p38 MAPK) and stimulated cytokine/chemokine expression. These NS/P cell-induced endothelial responses took place during NS/P cell and bEND cell direct contact and were critically dependent on the expression of the type II transmembrane serine protease matriptase (MTP) by NS/P cells, because knocking down of MTP in NS/P cells impaired and re-expression of MTP restored their ability to induce endothelial cytokine/chemokine expression, p38 MAPK, or G protein activation. Cholera toxin blocked NS/P cell-induced endothelial responses, suggesting that the endothelial G protein activated by NS/P MTP is in the G(s) subfamily. The addition of p38 MAPK inhibitor impaired NS/P cell-induced endothelial cytokine/chemokine expression. The known G protein-coupled receptor substrate of MTP, protease-activated receptor 2, was not involved in this system. These results revealed a novel signaling pathway in neural stem cell vascular niches that is mediated by neural MTP and endothelial G(s) protein signaling at the cell-cell interface. This is the first report of direct cell-cell signaling between NS/P and bEND cells.

A lifespan approach to neuroinflammatory and cognitive disorders: a critical role for glia

Cognitive decline is a common problem of aging. Whereas multiple neural and glial mechanisms may account for these declines, microglial sensitization and/or dystrophy has emerged as a leading culprit in brain aging and dysfunction. However, glial activation is consistently observed in normal brain aging as well, independent of frank neuroinflammation or functional impairment. Such variability suggests the existence of additional vulnerability factors that can impact neuronal-glial interactions and thus overall brain and cognitive health. The goal of this review is to elucidate our working hypothesis that an individual's risk or resilience to neuroinflammatory disorders and poor cognitive aging may critically depend on their early life experience, which can change immune reactivity within the brain for the remainder of the lifespan. For instance, early-life infection in rats can profoundly disrupt memory function in young adulthood, as well as accelerate age-related cognitive decline, both of which are linked to enduring changes in glial function that occur in response to the initial infection. We discuss these findings within the context of the growing literature on the role of immune molecules and neuroimmune crosstalk in normal brain development. We highlight the intrinsic factors (e.g., chemokines, hormones) that regulate microglial development and their colonization of the embryonic and postnatal brain, and the capacity for disruption or "re-programming" of this crucial process by external events (e.g., stress, infection). An impact on glia, which in turn alters neural development, has the capacity to profoundly impact cognitive and mental health function at all stages of life.

Effect of tocopherol supplementation during last trimester of pregnancy on mRNA abundances of interleukins and angiogenesis in ovine placenta and uterus

BACKGROUND

Interleukins (IL) play an important role in angiogenesis. Tocopherol possesses immunomodulating effect in addition to antioxidant property. The objective of this study was to determine whether gamma tocopherol's (gT) angiogenic activity in placental network is enhanced via promoting interleukins.

METHODS

Pregnant ewes (N=18) were supplemented, orally, with 500 mg of alpha tocopherol (aT; N=6) or 1,000 mg of gT (N=7) or placebo (CON; N=5) once daily from 107 to 137 days post breeding. Uterine and placental tissue samples were obtained at the end of supplementation to evaluate relative mRNA expressions of IL-1b, IL-6, IL-8, Tumor Necrosis Factor (TNF) alpha, Vascular Endothelial Growth Factor (VEGF), kinase insert domain receptor (KDR; VGFR2; a type III receptor tyrosine kinase), and soluble fms-like tyrosine kniase-1 (sFlt1 or sVEGFR1) in uterus, caruncle and cotyledon.

RESULTS

Oral supplementation of gT increased IL-6, IL-8, KDR and VEGF mRNA abundances whereas sFlt1 mRNA abundance was suppressed in uterus, caruncle and cotyledon, compared to aT and placebo treated ewes (P<0.05). The TNF alpha and IL-1b mRNA abundances were suppressed in uterus, caruncle and cotyledon but TNF alpha is higher in gT group compared to aT group (P<0.05), whereas IL-1b was similar between treatment groups (P>0.1).

CONCLUSIONS

Gamma tocopherol supplementation increased IL-6, IL-8, and KDR mRNA abundances and suppressed sFlt1 and TNFalpha mRNA abundances thereby increased VEGF mRNA expression and angiogenesis in placental vascular network during late gestation. It is plausible that the angiogenic effect of gamma tocopherol in placental vascular network is exerted via an alternate path by enhancing IL-6 and IL-8.

Regulation of soluble VEGFR-2 secreted by microvascular endothelial cells derived from human BPH

BACKGROUND

Recently, it was reported that the soluble vascular endothelial growth factor receptor-2 (sVEGFR-2) is secreted by microvascular endothelial cells from human BPH (HPECs). The purpose of this study was to investigate the modulation of sVEGFR-2 by common endothelial cell stimulators. In addition, the physiological role of sVEGFR-2 with regard to the VEGF-stimulated proliferation of HPEC was investigated.

METHODS

HPECs were isolated and cultured from fresh BPH tissue. After the incubation of HPECs either with adenosine triphosphate (ATP), interleukin (IL)-6, IL-8 or IL-12, the secretion of sVEGFR-2 was measured by enzyme-linked immunosorbent assay. For measurement of HPEC proliferation influenced by sVEGFR-2, VEGF-stimulated HPEC was cultured with/without sVEGFR-2. Cell proliferation was assessed with the Alamar Blue method.

RESULTS

The sVEGFR-2 secretion was increased by ATP and decreased by IL-12 and IL-8, respectively. IL-6 did not show any significant effect on sVEGFR-2 secretion of HPECs. HPEC proliferation was significantly inhibited by sVEGFR-2.

CONCLUSIONS

In this study, our data suggest that the secretion of sVEGFR-2 by microvascular endothelial cells from prostate origin is influenced by multiple endothelial cell stimulators. Furthermore, our data suggest that sVEGFR-2 acts as an antiangiogenic factor.

CREB-binding protein silencing inhibits thrombin-induced endothelial progenitor cells angiogenesis

Endothelial progenitor cells (EPCs) are known to promote neovascularization in ischemic diseases. Recent evidence from our group suggested that CREB-binding protein (CBP) plays an important role in thrombin-induced EPCs migration. However, whether CBP could regulate EPCs angiogenic properties is unknown. In the present study, we investigated whether CBP silencing could inhibit thrombin-induced EPCs angiogenesis. EPCs isolated from the bone marrow of Sprague-Dawley rats were cultured and identified, and then were treated by thrombin alone or combined with CBP-shRNA lentivirus. The effect of CBP silencing on EPCs proliferation was assessed using BrdU incorporation assay. Cell adhesion and tube formation were detected to evaluate the angiogenic functions. Finally, mRNA and protein expression of relevant angiogenic genes were examined by real-time PCR, western-blot, and enzyme-linked immunoassay respectively. Luciferase reporter gene assay was performed to evaluate NF-κB activity. Administration of thrombin significantly promoted EPCs proliferation and adhesion. Thrombin also increased the tube formation in Matrigel assay. However, these effects of thrombin were abolished by CBP gene silencing. CBP silencing also abrogated thrombin-induced increases of integrin β2 expression. In thrombin-induced EPCs, CBP silencing significantly decreased the secretion of VEGF, IL-6 and suppressed NF-κB activity. In conclusion, thrombin-induced EPCs proliferation, adhesion, and tube formation were inhibited by CBP silencing, indicating that CBP plays an important role in thrombin-induced EPCs neovascularization.

Adrenomedullin augments the angiogenic potential of late outgrowth endothelial progenitor cells

The therapeutic utility of endothelial progenitor cells (EPCs) in cardiovascular disease is potentially hampered by their low numbers in the circulation, impaired functional activity, and inhibitory factors in the recipient. These obstacles can possibly be circumvented by the use of proangiogenic cytokines and peptides. We sought to examine the effect of the endogenous vasoactive peptide adrenomedullin (AM) on the angiogenic potential of late outgrowth EPCs and their release of proangiogenic and proinflammatory cytokines/chemokines. Human peripheral blood mononuclear cells were cultured until the appearance of typical late outgrowth EPC colonies. The effect of AM on EPC proliferation was assessed using a colorimetric MTS proliferation assay while differentiation and formation of tubular structures in an EPC/fibroblast coculture or matrigel assay was used to assess the angiogenic potential of the cells. Finally, the release and mRNA transcripts of cytokines/chemokines were quantified in stimulated vs. nonstimulated EPCs using real-time PCR and a bead-based multiplex assay. The cultured EPCs possessed an endothelial phenotype and expressed the AM receptor (calcitonin receptor-like receptor/receptor activity modifying protein-2). AM stimulation induced proliferation of EPCs compared with controls ( P < 0.05). Furthermore, AM produced a 36% and 80% increase in the formation of tubular networks in the EPC/fibroblast coculture and matrigel assay, respectively ( P < 0.05). These effects seemed to be mediated through the phosphatidylinositol 3-kinase/Akt signaling pathway. AM did not seem to significantly influence the release or production of IL-6, IL-8, VEGF, stromal cell-derived factor 1, or the expression of CXCR-4 or VEGF receptor 2. In conclusion, adrenomedullin augmented the growth and angiogenic properties of late outgrowth EPCs, but did not influence their paracrine properties.

Osteocyte apoptosis is mechanically regulated and induces angiogenesis in vitro

Osteocyte apoptosis, associated with reduced interstitial fluid flow, precedes osteoclast precursor recruitment and may aid in the delivery of osteoclast precursors to the remodeling site by promoting angiogenesis. To test the association between fluid flow and osteocyte apoptosis, osteocyte-like MLO-Y4 cells were subjected to either oscillatory fluid flow (10 dynes/cm², 1 Hz) or no flow conditions with or without TNF-α treatment to induce osteocyte apoptosis chemically. Flow protected osteocytes from apoptosis regardless of whether they were treated with TNF-α (p < 0.001) or not (p < 0.05). TNF-α-induced apoptotic and nonapoptotic osteocyte conditioned media were used to study the effect of osteocyte apoptosis on angiogenesis. Apoptotic osteocyte conditioned media caused more endothelial cell proliferation (p < 0.05) and migration (p < 0.05), and tubule networks with longer (p < 0.01) and more (p < 0.001) branches than nonapoptotic osteocyte conditioned media. Apoptotic osteocyte conditioned media contained more vascular endothelial growth factor (VEGF) than nonapoptotic osteocyte conditioned media (p < 0.05). VEGF concentrations found in apoptotic osteocyte conditioned media formed endothelial tubule networks with longer (p < 0.05) and more (p < 0.02) branches than VEGF concentrations in nonapoptotic osteocyte conditioned media. Blocking VEGF in apoptotic osteocyte conditioned media abolished tubule formation effects (p < 0.001). Our results suggest that osteocyte apoptosis is flow-regulated and promotes angiogenesis in a VEGF-mediated manner.

Hypoxic/normoxic preconditioning increases endothelial differentiation potential of human bone marrow CD133+ cells

CD133+ cells are hemangioblasts that have capacity to generate into both hematopoietic and endothelial cells (ECs). Hypoxia/normoxia has shown to be the regulator of the balance between stemness and differentiation. In this study we performed Agilent's whole human genome oligo microarray analysis and examined the differentiation potential of the bone-marrow-derived CD133+ cells after hypoxic/normoxic preconditioning of CD133+ cells. Results showed that there was no significant increase in erythroid colony forming unit (CFU-E) and CFU-granulocyte, erythrocyte, monocyte, and megakaryocyte formation with cells treated under hypoxia/normoxia. However, a significant increment of EC forming unit at 24 h (143.2 +/- 8.0%) compared to 0 h (100 +/- 11.4%) was observed in CFU-EC analysis. Reverse transcription-polymerase chain reaction and immunostaining analysis showed that the differentiated cells diminished hematopoietic stem cell surface markers and acquired the gene markers and functional phenotype of ECs. The transcriptome profile revealed a cluster of 232 downregulated and 498 upregulated genes in cells treated for 24 h under hypoxia. The upregulated genes include angiogenic genes, angiogenic growth factor genes, angiogenic cytokine and chemokine genes, as well as angiogenic-positive regulatory genes, including FGFBP1, PDGFB, CCL15, CXCL12, CXCL6, IL-6, PTN, EREG, ERBB2, EDG5, FGF3, FHF2, GDF15, JUN, L1CAM, NRG1, NGFR, and PDGFB. On the other hand, angiogenesis inhibitors and related genes, including IL12A, MLLT7, STAB1, and TIMP2, are downregulated. Taken together, hypoxic/normoxic preconditioning may lead to the differentiation of CD133+ cells toward endothelial lineage, which may improve the current clinical trial studies.

Directed evolution of a three-finger neurotoxin by using cDNA display yields antagonists as well as agonists of interleukin-6 receptor signaling

Background

Directed evolution of biomolecules such as DNA, RNA and proteins containing high diversity has emerged as an effective method to obtain molecules for various purposes. In the recent past, proteins from non-immunoglobulins have attracted attention as they mimic antibodies with respect to binding potential and provide further potential advantages. In this regard, we have attempted to explore a three-finger neurotoxin protein (3F). 3F proteins are small (~7 kDa), structurally well defined, thermally stable and resistant to proteolysis that presents them as promising candidates for directed evolution.

Results

We have engineered a snake α-neurotoxin that belongs to the 3F family by randomizing the residues in the loops involved in binding with acetylcholine receptors and employing cDNA display to obtain modulators of interleukin-6 receptor (IL-6R). Selected candidates were highly specific for IL-6R with dissociation constants and IC50s in the nanomolar range. Antagonists as well as agonists were identified in an IL-6 dependent cell proliferation assay. Size minimization yielded peptides of about one-third the molecular mass of the original proteins, without significant loss of activities and, additionally, lead to the identification of the loops responsible for function.

Conclusions

This study shows 3F protein is amenable to introduce amino acid changes in the loops that enable preparation of a high diversity library that can be utilized to obtain ligands against macromolecules. We believe this is the first report of protein engineering to convert a neurotoxin to receptor ligands other than the parent receptor, the identification of an agonist from non-immunoglobulin proteins, the construction of peptide mimic of IL-6, and the successful size reduction of a single-chain protein.

Lipocalin-7 is a matricellular regulator of angiogenesis

BACKGROUND

Matricellular proteins are extracellular regulators of cellular adhesion, signaling and performing a variety of physiological behaviors such as proliferation, migration and differentiation. Within vascular microenvironments, matricellular proteins exert both positive and negative regulatory cues to vascular endothelium. The relative balance of these matricellular cues is believed to be critical for vascular homeostasis, angiogenesis activation or angiogenesis resolution. However, our knowledge of matricellular proteins within vascular microenvironments and the mechanisms by which these proteins impact vascular function remain largely undefined. The matricellular protein lipocalin-7 (LCN7) is found throughout vascular microenvironments, and circumstantial evidence suggests that LCN7 may be an important regulator of angiogenesis. Therefore, we hypothesized that LCN7 may be an important regulator of vascular function.

METHODOLOGY AND PRINCIPAL FINDINGS

To test this hypothesis, we examined the effect of LCN7 overexpression, recombinant protein and gene knockdown in a series of in vitro and in vivo models of angiogenesis. We found that overexpression of LCN7 in MB114 and SVEC murine endothelial cell lines or administration of highly purified recombinant LCN7 protein increased endothelial cell invasion. Similarly, LCN7 increased angiogenic sprouting from quiescent endothelial cell monolayers and ex vivo aortic rings. Moreover, LCN7 increased endothelial cell sensitivity to TGF-β but did not affect sensitivity to other pro-angiogenic growth factors including bFGF and VEGF. Finally, morpholino based knockdown of LCN7 in zebrafish embryos specifically inhibited angiogenic sprouting but did not affect vasculogenesis within injected embryos.

CONCLUSIONS AND SIGNIFICANCE

No functional analysis has previously been performed to elucidate the function of LCN7 in vascular or other cellular processes. Collectively, our results show for the first time that LCN7 is an important pro-angiogenic matricellular protein of vascular microenvironments.

IL-6 in human cytomegalovirus secretome promotes angiogenesis and survival of endothelial cells through the stimulation of survivin

Human cytomegalovirus (HCMV) is linked to the acceleration of vascular diseases such as atherosclerosis and transplant vasculopathy. One of the hallmarks of these diseases is angiogenesis (AG) and neovessel formation. Endothelial cells (ECs) are an integral part of AG and are sites of HCMV persistence. AG requires multiple synchronous processes that include EC proliferation, migration, and vessel stabilization. Virus-free supernatant (secretome) from HCMV-infected ECs induces AG. To identify factor(s) involved in this process, we performed a human cytokine array. Several cytokines were significantly induced in the HCMV secretomes including interleukin-6 (IL-6), granulocyte macrophage colony-stimulating factor, and IL-8/CXCL8. Using in vitro AG assays, neutralization of IL-6 significantly reduced neovessel formation. Addition of the HCMV secretome to preformed vessels extended neovessel survival, but this effect was blocked by neutralization of IL-6. In these cells, IL-6 prevented apoptosis by blocking caspase-3 and -7 activation through the induction of survivin. Neutralization of IL-6 receptor on ECs abolished the ability of HCMV secretome to increase survivin expression and activated effector caspases. Moreover, survivin shRNA expression induced rapid regression of tubule capillary networks in ECs stimulated with HCMV secretome and activated effector caspases. These observations may explain how CMV accelerates vascular disease despite limited infection in tissues.

Mediators of neovascularization and the hypoxic cornea

The maintenance of corneal avascularity is essential to vision. The mechanisms by which the cornea becomes vascularized in response to inflammation or hypoxic stress are beginning to be elucidated. A detailed understanding of the molecular responses of the cornea to hypoxia is critical for prevention and development of novel treatments for neovascularization in a range of disease states. Here, we have examined the current literature on the major mediators of angiogenesis, which have previously been reported during hypoxia in the cornea in order to better understand the mechanisms by which corneal angiogenesis occurs in circumstances where the available oxygen is reduced. The normal cornea produces angiogenic factors that are regulated by the production of anti-angiogenic molecules. The various cell types of the cornea respond differentially to inflammatory and hypoxic stimuli. An understanding of the factors that may predispose patients to development of corneal blood vessels may provide an opportunity to develop novel prophylactic strategies. The difficulties with extrapolating data from other cell types and animal models to the cornea are also examined.

STAT3: a critical transcription activator in angiogenesis

Angiogenesis, the formation of new blood vessels from the pre-existing vasculature, is a complex multistage process regulated by a number of signal transduction pathways. Accumulating evidence suggests that signal transducer and activator of transcription (STATs), mainly STAT3, play an important role in angiogenesis under both physiological and pathological conditions in addition to cell survival, proliferation, differentiation, and oncogenesis. STAT3, as a critical multifunctional mediator, regulates many aspects of angiogenesis at the transcriptional level. This review will highlight the pivotal role of STAT3 in well-studied tumorous angiogenesis and cardiac angiogenesis, and summarize various potential mechanisms utilized by STAT3 to regulate the transcriptional activation of VEGF.

Interleukin-6 stimulates circulating blood-derived endothelial progenitor cell angiogenesis in vitro

Circulating blood endothelial progenitor cells (EPCs) contribute to postnatal vasculogenesis, providing a novel therapeutic target for vascular diseases. However, the molecular mechanism of EPC-induced vasculogenesis is unknown. Interleukin-6 plays multiple functions in angiogenesis and vascular remodeling. Our previous study demonstrated that the polymorphism (174G>C) in IL-6 gene promoter was associated with brain vascular disease. In this study, we investigated if IL-6 receptor is expressed in human EPCs derived from circulating mononuclear cells, and if interleukin-6 (IL-6) stimulates EPC angiogenesis in vitro. First, we isolated and cultured mononuclear cells from adult human circulating blood. We obtained EPC clones that were further cultured and expended for the angiogenesis study. We found that the EPCs possessed human mature endothelial cell phenotypes; however, they proliferated much faster than mature endothelial cells (P<0.05). We then found that IL-6 receptor (gp-80) was expressed in the EPCs, and that administration of IL-6 could activate receptor gp80/gp130 signaling pathways including downstream extracellular signal-regulated kinase 1/2 and STAT3 phosphorylation in EPCs. Furthermore, IL-6 stimulated EPC proliferation, migration, and matrigel tube formation in a dose-dependent manner (P<0.05); anti-IL-6 antibodies or IL-6 receptor could abolish these effects (P<0.05). These results suggest that IL-6 plays a crucial role in the biologic behavior of blood-derived EPCs, which may help clarify the mechanism of IL-6 inflammatory-related diseases.