Modulation of endothelial function by interleukin-1. A novel target for pharmacological intervention?

Therapeutic Moderate Hypothermia for Severe Traumatic Brain Injury

Use of therapeutic hypothermia to treat patients with severe traumatic brain injury was described more than 50 years ago. Unexpected improvement in some of these patients was attributed to hypothermia, but none of the early studies systematically evaluated the efficacy of hypothermia, and many patients were thought to have been harmed by the treatment, particularly when cooled below 30°C or when cooled for longer than 48 hours. Recent investigations have found that therapeutic moderate hypothermia (32–34°C) for relatively brief durations can improve histological and behavioral outcome following experimental brain injury. Cooling to this degree and duration has not been implicated as a cause for the cardiac arrhythmias, coagulation abnormalities, or infections attributed to hypothermia in the earlier studies. These laboratory investigations also defined several neurochemical mechanisms through which hypothermia may limit secondary brain injury and brain swelling. Four clinical trials of therapeutic moderate hypothermia were completed during the past three years; each detected a beneficial effect from cooling patients with severe traumatic brain injury to 32 to 34°C for up to 48 hours. In the largest of these studies, therapeutic moderate hypothermia was shown to cause a significant improvement in neurological outcomes 3, 6, and 12 months after injury for those patients with an initial Glasgow Coma Scale score of 5 to 7. The improvement in outcome for these patients was associated with a hypothermia-induced reduction of intracranial pressure and cerebrospinal fluid levels of interleukln-1β and glutamate.

The role of endothelium in the pathogenesis of diabetic microangiopathy

Damage caused to the vessel wall by diverse mechanisms may lead to diabetic microangiopathy. Consequently, research work is more and more focusing on the pathophysiology of vascular cells, with particular emphasis on endothelium. This paper reviews the present knowledge on the alterations of small vessel endothelium in diabetes. The most important risk factors for diabetic microangiopathy are the duration of disease and the degree of metabolic control maintained throughout the years. However, genetic factors may also contribute. These are examined first, followed by the presumed roles played by increased protein glycation and the production of Advanced Glycosylation End Products, the "polyol pathway" and free radical generation. Endothelium is a widespread, extremely active organ which regulates complex physiologic functions and its structure and function are discussed in the second section of this review. The third part deals with how diabetes can affect endothelium and describes observations on endothelial metabolism in vitro as well as morphologic and functional alterations in the patients. Unfortunately, the mechanisms leading to progressive degeneration of the microcirculation and organ damage in diabetic patients remain largely unaccounted for.

Effects of intracellular ions on interleukin-1 beta production by lipopolysaccharide-activated human monocytes

Following the observation that interleukin 1 beta (IL-1 beta) production in lipopolysaccharide (LPS)activated monocytes increases in concert with a rise in intracellular pH (pHi), the role of ion transport in IL-1 beta production was investigated. The amiloride analogue 5-(N-ethyl-N-isopropyl)amiloride (EIPA), an inhibitor of the Na(+)-H+ antiporter, inhibited extracellular IL-1 beta. The replacement of Na+ in the culture medium with sucrose or choline chloride also prevented monocyte activation. The sodium ionophore monensin, in doses from 100 pM to 1 microM, potentiated LPS-stimulated extracellular IL-1 beta when compared with LPS alone. In the absence of LPS activation, monensin by itself at 10 nM stimulated IL-1 beta production to 63%. EIPA at 10 microM inhibited the Na+ influx, the rise in pHi, and intra- and extracellular IL-1 beta production in activated monocytes; this inhibition was reversed by 10 nM monensin. In the absence of bicarbonate, or in the presence of 10 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, the pHi of activated monocytes and the total protein synthesis did not change, but the production of IL-1 beta was inhibited. The data suggest that the stimulated influx of Na+ via the Na(+)-H+ antiporter regulates both pHi and IL-1 beta production in LPS-activated monocytes. The requirement for bicarbonate indicates an additional mechanism(s), separate from the modulation of pHi and intracellular Na+.

Intracellular signal transduction for interleukin-1 beta-induced endothelin production in human umbilical vein endothelial cells

The authors investigated the intracellular signal transduction for interleukin (IL)-1 beta-induced endothelin (ET) production by endothelial cells from cultured human umbilical vein (HUVEC). Cultured HUVEC released immunoreactive (iR)-ET into the media in a time-dependent manner and a significant increase of iR-ET production was observed by the addition of IL-1 beta. The stimulating effect of IL-1 beta on iR-ET production was respectively inhibited by protein kinase C (C kinase) inhibitor (H-7), Ca-calmodulin inhibitor (W-7), cyclic AMP-dependent protein kinase (A kinase) inhibitor (H-8) and tyrosine kinase inhibitor (genistain) in a dose-dependent fashion. The data suggested that intracellular signal transduction for IL-1 beta-induced iR-ET production were via such pathways as C kinase, A kinase, Ca-calmodulin and tyrosine kinase in combination or independently, though possible mediation by other pathways cannot be ruled out.

Polymorphonuclear leukocytes and monocytes/macrophages in the pathogenesis of cerebral ischemia and stroke

BACKGROUND

The extent to which polymorphonuclear leukocytes and monocytes/macrophages contribute to the pathobiology of cerebral ischemia and stroke is an issue of long-standing contradiction and controversy. Recent developments in the ability to selectively modify leukocyte adhesion with antiadhesion antibodies and the potential clinical application of this therapeutic approach have spurred a resurgence of experimental studies examining the role of leukocytes in cerebral ischemia and stroke.

SUMMARY OF REVIEW

We review studies examining leukocyte accumulation, initiation of thrombosis, and exacerbation of ischemic brain injury in stroke, and we examine other proposed contributions of leukocytes to cerebrovascular pathophysiology.

CONCLUSIONS

The importance of specific characteristics of a given ischemia model and of underlying stroke risk factors in determining the degree of leukocyte involvement and effectiveness of therapies directed against these cells is discussed.

Actions and interactions of mediator systems and mediators in the pathogenesis of ARDS and multiorgan failure

A great variety of mediators and mediator systems are involved in the disturbance of the microcirculation and vascular permeability following polytrauma and sepsis. The locally accentuated, organ related activation and the cooperation of several of these mediators and mediator systems over a longer period of time seem to be responsible for the development of an acute organ failure in terms of ARDS and MOF. Cytokines from macrophages seem to be the determining factors converting a primarily functional and reversible systemic vascular reaction into organ related morphological lesions. This pathogenetic complexity has to be considered in future concepts for therapy and prophylaxis with regard to the hierarchical rank of the mediators involved.

Immunoregulators in the nervous system

The nervous system, through the production of neuroregulators (neurotransmitters, neuromodulators and neuropeptides) can regulate specific immune system functions, while the immune system, through the production of immunoregulators (immunomodulators and immunopeptides) can regulate specific nervous system functions. This indicates a reciprocal communication between the nervous and immune systems. The presence of immunoregulators in the brain and cerebrospinal fluid is the result of local synthesis--by intrinsic and blood-derived macrophages, activated T-lymphocytes that cross the blood-brain barrier, endothelial cells of the cerebrovasculature, microglia, astrocytes, and neuronal components--and/or uptake from the peripheral blood through the blood-brain barrier (in specific cases) and circumventricular organs. Acute and chronic pathological processes (infection, inflammation, immunological reactions, malignancy, necrosis) stimulate the synthesis and release of immunoregulators in various cell systems. These immunoregulators have pivotal roles in the coordination of the host defense mechanisms and repair, and induce a series of immunological, endocrinological, metabolical and neurological responses. This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulators--in the nervous system. It also describes the monitoring of immunoregulators by the central nervous system (CNS) as part of the regulatory factors that induce neurological manifestations (e.g., fever, somnolence, appetite suppression, neuroendocrine alterations) frequently accompanying acute and chronic pathological processes.

IL-1 beta-induced expression of PDGF-AA isoform in rabbit articular chondrocytes is modulated by TGF-beta 1

Interleukin 1 beta (IL-1 beta) and platelet-derived growth factor (PDGF) induced proliferation in many cell types. Both peptides are released by activated macrophages and other cells in response to injury and are thought to play a crucial role in a number of pathological processes. We found that IL-1 beta stimulates proliferation of rabbit articular chondrocytes and induces synthesis and release of PDGF into their culture medium. This effect, which is time- and dose-dependent (0.05-5 ng/ml), is restricted to PDGF-AA, one of the three PDGF isoforms; IL-1 beta effect on PDGF is inhibited by actinomycin D and alpha-amanitin, suggesting a transcriptional regulation of PDGF-A chain. IL-1 beta stimulates PDGF-AA synthesis also in the presence of indomethacin, a prostaglandin synthesis inhibitor. Transforming growth factor beta 1 (TGF-beta 1), a dimeric polypeptide which displays multiple biological activities, inhibits in a dose-dependent manner (1-10 ng/ml) PDGF-AA production induced by IL-1 beta. In a binding assay, TGF-beta 1 induces 45% decrease in specific binding sites for 125I-IL-1 beta, with no change in affinity.

Interleukin-1 beta increases the biosynthesis of the heat shock protein hsp70 and selectively decreases the biosynthesis of five proteins in rat pancreatic islets

Prolonged exposure to high concentrations of human recombinant interleukin-1 beta (rIL-1 beta) has been reported to exert both suppressive and cytotoxic effects on pancreatic beta-cells during culture in vitro. In order to investigate the molecular mechanism(s) underlying the actions of rIL-1 beta on the beta-cell, we have exposed isolated rat pancreatic islets for 3 or for 24 h to 25 U/ml of rIL-1 beta. Subsequently the biosynthesis of heat shock proteins, as assessed by western blot analysis, and total protein biosynthesis patterns were studied, using one and two-dimensional gel electrophoresis of [35S]methionine labelled islet proteins from different subcellular compartments. It was found that rIL-1 beta exerted no specific effects on protein synthesis when added during a 3 h incubation period. However, after a 24 h incubation period, the synthesis of a group of acidic proteins with the approximate molecular weight of 35 kD was specifically inhibited in the rIL-1 beta treated islets. This alteration was predominantly associated with the endoplasmic reticulum fraction. The cytokine also inhibited the synthesis of four cytosolic proteins with the molecular weights 75, 85, 95 and 120 kD. In contrast, rIL-1 beta increased the expression of the heat shock protein hsp70 both in the microsomal and cytosolic fractions, in contrast to the islet nuclei in which no increase was found. These results show that exposure of pancreatic islets to rIL-1 beta is accompanied by specific alterations in the protein synthesis of the islet cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin 1 increases the production of endothelin-1 by cultured endothelial cells

We examined the effect of human recombinant interleukin 1 (IL-1) on the production of endothelin-1 by cultured porcine endothelial cells. The induction of endothelin-1 mRNA began within 1 hr of exposure to IL-1, showed twin peaks at 4 and 24 hr, and declined thereafter. Enzyme-linked immunosorbent assay revealed that the amount of endothelin-1 peptide in conditioned media was also increased by IL-1 in a dose- and time-dependent manner. Our results suggested that IL-1, a macrophage-derived cytokine, may affect the contraction and proliferation of vascular smooth muscle cells by stimulating the production of endothelin by endothelial cells.

Immunomodulators and feeding regulation: a humoral link between the immune and nervous systems

Cells of the nervous and immune systems have specific receptors for humoral substances that originate in both systems. These elements establish a bidirectional information exchange network between the nervous and immune systems. In particular, neuroregulators (neurotransmitters and neuromodulators) can modulate specific immune system function(s) and immunoregulators (immunomodulators) can modulate specific nervous system function(s). Modulation of immune functions by neuroregulators has been receiving considerable attention; however, modulation of nervous system functions by immunomodulators has been little studied. The presence of immunomodulators in the brain and cerebrospinal fluid may represent local synthesis by astrocytes, microglia, endothelial cells, intrinsic macrophages and blood-derived lymphocytes which cross the blood-brain barrier, or the concentration of substances derived from the peripheral blood. Acute and chronic inflammatory processes, malignancy, and immunological reactions stimulate the synthesis and release of immunomodulators in various cell systems. These immunomodulators have pivotal roles in the coordination of the host defense mechanisms and repair and induce a series of endocrine, metabolic, and neurologic responses. This paper focuses on the effects of immunomodulators (interleukins, tumor necrosis factor, tuftsin, platelet activating factor, and others) on the central nervous system (CNS), in particular, on feeding regulation. It is proposed that an immunomodulatory system regulates food intake by a direct action in the CNS through a specific neuro-immuno interaction. This regulatory system may be operative during acute and chronic disease.

Granulocyte- and granulocyte-macrophage-colony stimulating factors induce human endothelial cells to migrate and proliferate

Granulocyte-colony stimulating factor (G-CSF) and granulocyte-macrophage-colony stimulating factor (GM-CSF) belong to a family of glycoprotidic growth factors required for the survival, growth and differentiation of haematopoietic precursors and which affect the function of circulating mature cells. They are produced by resting or stimulated stromal cells of the haematopoietic microenvironment (fibroblasts and endothelium) and by immunocompetent cells (T cells and monocytes/macrophages). The action of these CSF molecules was thought to be restricted to cells of haematopoietic origin. Here, we report that G-CSF and GM-CSF influence the migration and proliferation of human endothelial cells suggesting that these molecules may act as regulatory signals outside the haematopoietic system.

Interleukin-1 and tumor necrosis factor production in acute non-lymphoid leukemia

We have investigated interleukin-1 (IL-1) and tumor necrosis factor (TNF) release in 20 patients with acute non-lymphoid leukemia (ANLL) after culture with bacterial lipopolysaccharide (LPS) or in the absence of deliberate stimulation. IL-1 and TNF were identified by appropriate bioassays inhibitable by specific antibodies. The capacity to produce IL-1 was expressed by most ANLL cases investigated irrespective of the FAB (French, American, British) subtype. However, the M4 and M5 cases tended to be better producers of IL-1 than M1-M3 cases. In contrast, TNF release was only restricted to M5 leukemias (3 out of 4 cases examined). Cytokine production may therefore provide additional criteria for a functional classification of ANLL. A considerable proportion of ANLL cases (7/18 bone marrow samples and 12/20 blood samples) released appreciable quantities of IL-1 in culture in the absence of deliberate stimulation. "Spontaneous" TNF production was also detected in 1 out of 3 M5 cases. Cells were cultured under LPS-negative conditions and polymixin B did not affect spontaneous cytokine release. Moreover, Northern blot analysis showed that freshly isolated, non-cultured ANLL cells expressed IL-1 beta transcripts. Inasmuch as IL-1 is responsible for hemopoietin-1 activity and IL-1 induces colony stimulating factor production in various cell types, the observation of IL-1 production in ANLL suggests that this mediator may be involved in regulatory amplifying circuits of leukemic cell proliferation.

Interleukin-1 enhances pain reflexes. Mediation through increased prostaglandin E2 levels

Interleukin-1 (IL-1) has been shown to induce inflammatory reactions in part through increased prostaglandin production. Prostaglandins of the E- and I-type sensitize nociceptors in peripheral tissues. We have therefore investigated the effect of IL-1 perfusion in the isolated rabbit ear, a model which allows the assessment of peripheral pain. Natural IL-1 from human monocytes, IL-1 from glioblastoma cells as well as recombinant IL-1 alpha or beta, increased the pain reflex induced by acetylcholine in a concentration dependent manner. The PGE2 levels were measured in the perfusate and were found to be enhanced more than 10-fold after the infusion of IL-1 alpha or IL-1 beta. This effect was paralleled by the enhanced pain reflexes and persisted for at least one hour after cessation of the IL-1 perfusion. Both the increased pain reflexes as well as the enhanced PGE2 levels were abolished by addition of the cyclooxygenase inhibitor diclofenac-Na (Voltaren) to the perfusion fluid. These results show that besides the numerous known physiological functions of IL-1, it may also play a role in peripheral pain sensations.

Tumor necrosis factor and interleukin-1 beta: suppression of food intake by direct action in the central nervous system

Intracerebroventricular microinfusion of recombinant human tumor necrosis factor (rhTNF) and recombinant human interleukin-1 beta (rhIL-1 beta) suppressed food intake in rats. Central infusion of heat-inactivated rhTNF and rhIL-1 beta, bovine serum albumin, heparin or transforming growth factor-beta had no such effect. Central infusion of rhIL-1 beta did not affect the dipsogenic response to central administration of angiotensin II. Peripheral administration of rhTNF and rhIL-1 beta in doses equivalent to or higher than those administered centrally had no effect. Electrophoretically applied rhTNF and rhIL-1 beta specifically suppressed the activity of glucose-sensitive neurons in the lateral hypothalamic area. Glucose-insensitive neurons were little affected. The results suggest that TNF and IL-1 beta act directly in the central nervous system to suppress feeding, and this effect may be operative during acute and chronic disease.

Augmentation of procoagulant activity in monokine stimulated human endothelial cells by calmodulin/protein kinase C inhibitors

The incubation of human umbilical cord endothelial cell cultures with inflammatory mediators results in the induction of procoagulant activity. As many of these mediators activate protein kinase C, the effect of calmodulin and protein kinase C inhibitors on IL-1, TNF, phorbol ester and LPS stimulated procoagulant activity was determined. Incubation of endothelial cell cultures with these inflammatory agents in the presence of phenothiazine derivatives or other classes of calmodulin and protein kinase C antagonists resulted in a 2-4 fold increase in procoagulant activity compared to parallel stimulated cultures in the absence of antagonists. The augmented response of IL-1 stimulated endothelial cells to these antagonists was actinomycin D sensitive.

The recruitment of leukocytes and their interaction with the vessel wall: the role of interleukin-1 and tumor necrosis factor

The vascular endothelium has long been considered to have very little or no active function in inflammatory reactions and hemostasis. However, it has been recently discovered that endothelial cells can dramatically change their functional competence in response to the mononuclear phagocyte products interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 induces synthesis of prostacyclin, platelet activating factor, thromboplastin and plasminogen activator inhibitor. Both IL-1 and TNF cause leukocyte adhesion to the endothelium. On the other hand endothelial cells can themselves initiate the immune response through synthesis and release of IL-1. TNF, released in tissues may act as a chemoattractant and further promote interaction of leukocytes with the vascular lining. IL-1 and TNF can therefore act as a communications signal between circulating cells and the vessel wall and play an important role in the inflammatory and coagulation disorders.