The effect of glucocorticosteroids on the kinetics of mononuclear phagocytes

Hepatocyte-specific glucose-6-phosphatase deficiency disturbs platelet aggregation and decreases blood monocytes upon fasting-induced hypoglycemia

OBJECTIVE

Glycogen storage disease type 1a (GSD Ia) is a rare inherited metabolic disorder caused by mutations in the glucose-6-phosphatase (G6PC1) gene. When untreated, GSD Ia leads to severe fasting-induced hypoglycemia. Although current intensive dietary management aims to prevent hypoglycemia, patients still experience hypoglycemic events. Poor glycemic control in GSD Ia is associated with hypertriglyceridemia, hepatocellular adenoma and carcinoma, and also with an increased bleeding tendency of unknown origin.

METHODS

To evaluate the effect of glycemic control on leukocyte levels and coagulation in GSD Ia, we employed hepatocyte-specific G6pc1 deficient (L-G6pc-/-) mice under fed or fasted conditions, to match good or poor glycemic control in GSD Ia, respectively.

RESULTS

We found that fasting-induced hypoglycemia in L-G6pc-/- mice decreased blood leukocytes, specifically proinflammatory Ly6Chi monocytes, compared to controls. Refeeding reversed this decrease. The decrease in Ly6Chi monocytes was accompanied by an increase in plasma corticosterone levels and was prevented by the glucocorticoid receptor antagonist mifepristone. Further, fasting-induced hypoglycemia in L-G6pc-/- mice prolonged bleeding time in the tail vein bleeding assay, with reversal by refeeding. This could not be explained by changes in coagulation factors V, VII, or VIII, or von Willebrand factor. While the prothrombin and activated partial thromboplastin time as well as total platelet counts were not affected by fasting-induced hypoglycemia in L-G6pc-/- mice, ADP-induced platelet aggregation was disturbed.

CONCLUSIONS

These studies reveal a relationship between fasting-induced hypoglycemia, decreased blood monocytes, and disturbed platelet aggregation in L-G6pc-/- mice. While disturbed platelet aggregation likely accounts for the bleeding phenotype in GSD Ia, elevated plasma corticosterone decreases the levels of proinflammatory monocytes. These studies highlight the necessity of maintaining good glycemic control in GSD Ia.

More Than Suppression: Glucocorticoid Action on Monocytes and Macrophages

Uncontrolled inflammation is a leading cause of many clinically relevant diseases. Current therapeutic strategies focus mainly on immunosuppression rather than on the mechanisms of inflammatory resolution. Glucocorticoids (GCs) are still the most widely used anti-inflammatory drugs. GCs affect most immune cells but there is growing evidence for cell type specific mechanisms. Different subtypes of monocytes and macrophages play a pivotal role both in generation as well as resolution of inflammation. Activation of these cells by microbial products or endogenous danger signals results in production of pro-inflammatory mediators and initiation of an inflammatory response. GCs efficiently inhibit these processes by down-regulating pro-inflammatory mediators from macrophages and monocytes. On the other hand, GCs act on “naïve” monocytes and macrophages and induce anti-inflammatory mediators and differentiation of anti-inflammatory phenotypes. GC-induced anti-inflammatory monocytes have an increased ability to migrate toward inflammatory stimuli. They remove endo- and exogenous danger signals by an increased phagocytic capacity, produce anti-inflammatory mediators and limit T-cell activation. Thus, GCs limit amplification of inflammation by repressing pro-inflammatory macrophage activation and additionally induce anti-inflammatory monocyte and macrophage populations actively promoting resolution of inflammation. Further investigation of these mechanisms should lead to the development of novel therapeutic strategies to modulate undesirable inflammation with fewer side effects via induction of inflammatory resolution rather than non-specific immunosuppression.

Recruited alveolar macrophages, in response to airway epithelial-derived monocyte chemoattractant protein 1/CCl2, regulate airway inflammation and remodeling in allergic asthma

Although alveolar macrophages (AMs) from patients with asthma are known to be functionally different from those of healthy individuals, the mechanism by which this transformation occurs has not been fully elucidated in asthma. The goal of this study was to define the mechanisms that control AM phenotypic and functional transformation in response to acute allergic airway inflammation. The phenotype and functional characteristics of AMs obtained from human subjects with asthma after subsegmental bronchoprovocation with allergen was studied. Using macrophage-depleted mice, the role and trafficking of AM populations was determined using an acute allergic lung inflammation model. We observed that depletion of AMs in a mouse allergic asthma model attenuates Th2-type allergic lung inflammation and its consequent airway remodeling. In both human and mouse, endobronchial challenge with allergen induced a marked increase in monocyte chemotactic proteins (MCPs) in bronchoalveolar fluid, concomitant with the rapid appearance of a monocyte-derived population of AMs. Furthermore, airway allergen challenge of allergic subjects with mild asthma skewed the pattern of AM gene expression toward high levels of the receptor for MCP1 (CCR2/MCP1R) and expression of M2 phenotypic proteins, whereas most proinflammatory genes were highly suppressed. CCL2/MCP-1 gene expression was prominent in bronchial epithelial cells in a mouse allergic asthma model, and in vitro studies indicate that bronchial epithelial cells produced abundant MCP-1 in response to house dust mite allergen. Thus, our study indicates that bronchial allergen challenge induces the recruitment of blood monocytes along a chemotactic gradient generated by allergen-exposed bronchial epithelial cells.

Beyond stem cells: self-renewal of differentiated macrophages

In many mammalian tissues, mature differentiated cells are replaced by self-renewing stem cells, either continuously during homeostasis or in response to challenge and injury. For example, hematopoietic stem cells generate all mature blood cells, including monocytes, which have long been thought to be the major source of tissue macrophages. Recently, however, major macrophage populations were found to be derived from embryonic progenitors and to renew independently of hematopoietic stem cells. This process may not require progenitors, as mature macrophages can proliferate in response to specific stimuli indefinitely and without transformation or loss of functional differentiation. These findings suggest that macrophages are mature differentiated cells that may have a self-renewal potential similar to that of stem cells.

Proinflammatory CD14+CD16+ monocytes are associated with subclinical atherosclerosis in renal transplant patients

Atherosclerotic cardiovascular disease is a major cause of death in renal transplant (TX) recipients. Atherosclerotic lesions are characterized by monocytic infiltration. Circulating monocytes can be divided into functionally distinct subpopulations, among which CD14++CD16+ and CD14+CD16+ monocytes (summarized as CD16+ monocytes) are proinflammatory cells. We hypothesized that the frequency of circulating CD16+ monocytes is associated with subclinical atherosclerosis in TX patients. Monocyte subpopulations were quantified in 95 TX and 31 hemodialysis patients (HD). In TX patients, subclinical atherosclerosis was determined by carotid intima media thickness (IMT) measurement. TX patients had lower frequencies of CD16+ monocytes than HD patients. When stratifying by immunosuppressive treatment, patients on methylprednisolone (MP) therapy had fewer CD14+CD16+ monocytes than patients not receiving MP. CD14+CD16+ monocytes decrease very shortly after transplantation. CD14+CD16+ monocyte frequency correlated with IMT in TX recipients (r = 0.34, p < 0.001). This correlation was most pronounced among patients without MP treatment (r = 0.55, p = 0.02). In a multivariate regression analysis, the association of CD14+CD16+ monocytes with IMT was independent from traditional cardiovascular risk factors. The frequency of proinflammatory CD14+CD16+ monocytes is independently associated with subclinical atherosclerosis in transplant recipients. Further studies on the association between circulating leukocytes and atherosclerosis should take monocyte heterogeneity into account.

Induction immunosuppression

Induction immunosuppression is intense, prophylactic therapy used at the time of transplantation based on the empiric observation that more powerful immunosuppression is required to prevent acute rejection early. In the past decade, there has been a growing trend towards the use of specialized agents such as antibody therapies for induction. In general, these agents have been shown to reduce the rate of acute rejection. However, their use has not been clearly shown to improve long-term transplant outcomes. This overview will review the biological basis for induction immunosuppression and the mechanisms of action of those specialized induction agents currently in clinical use. Clinical trials investigating induction regimens will be evaluated, and an individualized approach to the use of induction immunosuppressants will be presented.

New and established topical corticosteroids in dermatology: clinical pharmacology and therapeutic use

Currently, topical glucocorticosteroids are the most frequently used drugs in dermatologic practice. Over the years, research has focused on strategies to optimize potency and, in particular, the anti-inflammatory and immunosuppressive capacity of these drugs, while minimizing adverse effects. However, 'ideal' topical corticosteroids have not yet been synthesized. They should be able to permeate the stratum corneum and reach adequate concentrations in the skin without reaching high serum concentrations. Such characteristics can be obtained by increasing the natural lipophilicity of corticosteroids, e.g. by esterification. In the past, many structural modifications have been made to improve the efficacy of topical corticosteroids to produce drugs with greater potency, although this has often been associated with a higher likelihood of adverse effects. Betamethasone dipropionate and clobetasol propionate, known as fifth-generation corticosteroids, are a typical example of potent molecules that can control specific dermatoses very rapidly, but which are associated with a high risk of topical and systemic adverse effects. Recently, steroid components have been synthesized that aim to have adequate anti-inflammatory effects and minimal adverse effects. The newest topical corticosteroids used for the treatment of different dermatoses and allergic reactions of the respiratory tract (in particular asthma) are budesonide, mometasone furoate, prednicarbate, the di-esters 17,21-hydrocortisone aceponate and hydrocortisone-17-butyrate-21-propionate, methylprednisolone aceponate, alclometasone dipropionate, and carbothioates such as fluticasone propionate. These new topical corticosteroids are evaluated in the current review, which compares the risk/benefit ratio of each molecule with established agents. The new molecules, compared with the well known and established corticosteroids, generally have a higher anti-inflammatory effect, good compliance among patients (only a once-daily application is needed), rarely induce cross-sensitivity reactions and have weak atrophogenicity.

Phagocytosis by macrophages mediated by receptors for denatured proteins - dependence on tyrosine protein kinases

Previous studies have demonstrated that some components of the leukocyte cell membrane, CR3 (Mac-1, CD11b/CD18) and p150/95, are able to bind to denatured proteins. Thus, it is of interest to know which effector functions of these cells can be triggered by these receptors when they interact with particles or surfaces covered with denatured proteins. In the present study we analyzed their possible role as mediators of phagocytosis of red cells covered with denatured bovine serum albumin (BSA) by mouse peritoneal macrophages. We observed that a) macrophages are able to recognize (bind to) these red cells, b) this interaction can be inhibited by denatured BSA in the fluid phase, c) there is no phagocytosis of these particles by normal macrophages, d) phagocytosis mediated by denatured BSA can be, however, effectively triggered in inflammatory macrophages induced by glycogen or in macrophages activated in vivo with LPS, and e) this phagocytic capacity is strongly dependent on the activity of tyrosine protein kinases in its signal transduction pathway, as demonstrated by using three kinds of enzyme inhibitors (genistein, quercetin and herbimycin A).

Effect of steroids on lipopolysaccharide/interleukin 2-induced interleukin 18 production in peripheral blood mononuclear cells

Interleukin (IL) 18, a powerful inducer of the immunoregulatory cytokine interferon-gamma (IFN-gamma), presents upstream of the cytokine activation cascade in the inflammatory response. The anti-inflammatory properties of steroids permit their use in various conditions, although effects are transient and pathological states are not fully relieved by short-term steroidal use. We examined the effect of lipopolysaccharide (LPS)/IL-2 on the cytokine cascade in human peripheral blood mononuclear cells (PBMCs). We also examined the effect of steroids on LPS/IL-2-induced cytokine production in human PBMCs taken from healthy volunteers. Cell-free supernatant fractions were assayed for IL-18, IL-12, IL-2, IFN-gamma and IL-10 protein, using enzyme-linked immunosorbent assays, and synergy between LPS and IL-2 in enhanced production of IL-18 was observed. Steroids suppressed the production of IL-18 and other secondary cytokines in LPS/IL-2-stimulated PBMCs, in a concentration- and time-dependent manner, although inhibition was incomplete even at high concentrations. Effects of steroid treatment on expression of membrane-bound LPS receptor antigen (mCD14) and intercellular adhesion molecule-1 (ICAM-1) in PBMCs were studied by flow cytometric analysis. Steroid treatment up-regulated mCD14 expression in a concentration-dependent manner, with no effect on ICAM-1 expression. These results suggest that the incomplete counteraction of steroids in the LPS/IL-2-initiating cytokine cascade is due, at least partly, to the up-regulation of mCD14 by steroid preparations, which increases susceptibility to bacterial endotoxins.

Role of the CD95/CD95 ligand system in glucocorticoid-induced monocyte apoptosis

Glucocorticoids (GC) act as potent anti-inflammatory and immunosuppressive agents on a variety of immune cells. However, the exact mechanisms of their action are still unknown. Recently, we demonstrated that GC induce apoptosis in human peripheral blood monocytes. In the present study, we examined the signaling pathway in GC-induced apoptosis. Monocyte apoptosis was demonstrated by annexin V staining, DNA laddering, and electron microscopy. Apoptosis required the activation of caspases, as different caspase inhibitors prevented GC-induced cell death. In addition, the proteolytic activation of caspase-8 and caspase-3 was observed. In additional experiments, we determined the role of the death receptor CD95 in GC-induced apoptosis. CD95 and CD95 ligand (CD95L) were up-regulated in a dose- and time-dependent manner on the cell membrane and also released after treatment with GC. Costimulation with the GC receptor antagonist mifepristone diminished monocyte apoptosis as well as CD95/CD95L expression and subsequent caspase-8 and caspase-3 activation. In contrast, the caspase inhibitor N:-acetyl-Asp-Glu-Val-Asp-aldehyde suppressed caspase-3 activation and apoptosis, but did not down-regulate caspase-8 activation and expression of CD95 and CD95L. Importantly, GC-induced monocyte apoptosis was strongly abolished by a neutralizing CD95L mAb. Therefore, our data suggest that GC-induced monocyte apoptosis is at least partially mediated by an autocrine or paracrine pathway involving the CD95/CD95L system.

Review of 49 neonates with acquired fungal sepsis: further characterization

BACKGROUND

Neonatal acquired fungal sepsis (AFS) is a risky condition that warrants every effort for early diagnosis and management.

METHODS

We retrospectively reviewed the medical charts of all 4445 neonatal intensive care unit (NICU) admissions in the past 10 years and detected 49 neonates with AFS. We then compared their data with those of 49 matched control neonates who did not have AFS. The following details were collected: gestational, perinatal and neonatal courses; bacterial sepsis; antibacterial therapy; laboratory and imaging investigations; and antifungal therapy and its complications.

RESULTS

The incidence of AFS was.4 to 2 cases per 1000 live-births and 3.8% to 12.9% of very low birth weight (VLBW) infants. Compared with 1989 through 1992, between 1993 and 1995 the rate of AFS in VLBW neonates significantly increased (3. 8%-5.6% --> 9.6%-12.9%), along with a significant increase of NICU admission rate (369-410 --> 496-510 admissions/year). Compared with controls, AFS neonates had significantly longer hospitalizations, higher rates of mechanical ventilation, umbilical vein catheterization, and previous treatment with broad-spectrum antibacterial agents (amikacin, vancomycin, ceftazidime, or imipenem). At the onset of AFS, 42.8% of patients had hyperthermia and 40.9% had normal white blood cell count. Causative fungi were as follows: Candida albicans-42.8% of cases, Candida parapsilosis-26.5%, and Candida tropicalis-20.4%. Fungal dissemination was rare, complications of antifungal therapy were infrequent, and no deaths occurred.

CONCLUSIONS

First, non-albicans Candida have become more frequent in neonatal AFS. Second, mechanical ventilation and antibacterial agents are significant risk factors for AFS. Third, hyperthermia is a frequent presenting sign of AFS. Fourth, a normal white blood cell count does not rule out AFS. Fifth, meningeal involvement in neonatal AFS should be ruled out before initiation of antifungal therapy. Sixth, the policy of empiric antifungal therapy for AFS should be considered on an individual NICU basis.newborn infant, fungal sepsis, clinical signs, risk factors.

Glucocorticoids Induce Apoptosis in Human Monocytes: Potential Role of IL-1β

Glucocorticoids (GC) are potent anti-inflammatory and immunosuppressive agents that act on a variety of immune cells, including monocytes and macrophages. However, the exact cellular mechanisms underlying this anti-inflammatory capacity are still unknown. In our study, we determined the induction of apoptosis by GC in human monocytes. Peripheral blood monocytes were isolated by density centrifugation methods with a purity of &gt;90% and were cultured in RPMI 1640 medium. Monocyte apoptosis was determined by four independent methods, including annexin-V staining, TUNEL, DNA-laddering, and typical morphology by means of transmission electron microscopy. TNF-α and IL-1β were measured by ELISA. GC receptor was blocked with mifepristone. Caspase 3 was inhibited with caspase-3 inhibitor (DEVD-CHO). Stimulation with different GC at therapeutic concentrations resulted in monocyte apoptosis in a time- and dose-dependent manner. Necrosis was excluded by propidium iodide staining. Proinflammatory cytokines such as IL-1β and TNF-α were down-regulated by GC treatment. Continuous treatment of monocytes with IL-1β, but not with TNF-α, could almost completely prevent GC-induced cell death. The addition of mifepristone or caspase-3 inhibitor could partially abrogate GC-induced apoptosis as well as GC-induced inhibition of IL-1β. This is the first study to demonstrate induction of apoptosis by GC in human monocytes. GC-induced monocyte apoptosis may be partially mediated through effects on IL-1β production. It is conceivable that GC exert their anti-inflammatory capacity in various diseases, at least in part, by the induction of apoptosis in monocytes.

Altered leucocyte trafficking and suppressed tumour necrosis factor alpha release from peripheral blood monocytes after intra-articular glucocorticoid treatment

OBJECTIVES

A generalised transient improvement may follow intra-articular administration of glucocorticoids to patients with inflammatory arthropathy. This may represent a systemic anti-inflammatory effect of glucocorticoid released from the joint, mediated through processes such as altered leucocyte trafficking or suppressed release of pro-inflammatory cytokines. Patients, who had received intra-articular injections of glucocorticoids were therefore studied for evidence of these two systemic effects.

METHODS

Patients with rheumatoid arthritis were studied. Peripheral blood leucocyte counts, tumour necrosis factor alpha (TNF alpha) release by peripheral blood monocytes, blood cortisol concentrations, and blood methylprednisolone concentration were measured for 96 hours after intra-articular injection of methylprednisolone acetate.

RESULTS

Measurable concentrations of methylprednisolone were present in blood for up to 96 hours after injection. Significant suppression of the hypothalamic-pituitary-adrenal axis persisted throughout this time. Altered monocyte and lymphocyte trafficking, as evidenced by peripheral blood monocytopenia and lymphopenia, was apparent by four hours after injection and resolved in concordance with the elimination of methylprednisolone. Granulocytosis was observed at 24 and 48 hours. Release of TNF alpha by endotoxin stimulated peripheral blood monocytes was suppressed at four hours and thereafter. Suppression was maximal at eight hours and was largely reversed by the glucocorticoid antagonist, mifepristone.

CONCLUSIONS

After intra-articular injection of methylprednisolone, blood concentrations of glucocorticoid are sufficient to suppress monocyte TNF alpha release for at least four days and to transiently alter leucocyte trafficking. These effects help to explain the transient systemic response to intra-articular glucocorticoids. Suppression of TNF alpha is principally a direct glucocorticoid effect, rather than a consequence of other methylprednisolone induced changes to blood composition.

Steroid therapy in obstructive airway diseases

Asthma and chronic obstructive pulmonary disease (COPD) are two common illnesses that cause significant morbidity and mortality. Steroids are widely used in both conditions. They act through steroid or glucocorticoid receptors (GR) causing up or down regulation of protein synthesis resulting in an increase in lipocortin 1 and beta 2 adrenergic receptors, and decreased levels and activities of cytokines or cytokine receptors, which reduces the inflammatory process in the airways and decreases bronchial hyperreactivity. Consequently symptoms of airway obstruction are alleviated and lung function is improved. In asthma, steroids have been convincingly shown to be effective in the treatment of both acute exacerbations and chronic condition. In COPD, however, only a subset of patients seem to respond favourably to steroid therapy. Therapeutic trials are therefore recommended before committing to a long-term treatment in order to determine this subset of patients, as no markers of steroid responsiveness can be identified. The inhaled steroids currently available have a good safety profile with significant side effects occurring only occasionally. Such side effects are usually confined to the oropharynx, causing local irritation, candidiasis and dysphonia, which can be easily overcome. Biochemical abnormalities involving bone, adrenal, carbohydrate and lipid profiles have been noted with high doses of inhaled steroids; however, these have no significant clinical effects.

Changes in blood and spleen lymphocyte populations following antigen challenge in immature male chickens

1. The effects of antigen (Ag) injection on the distribution of lymphocyte populations of Cornell K-strain male chickens were studied. 2. Two experiments were conducted. In the first, chickens were injected with Brucella abortus (BA), a purported T-independent antigen. In the second, chickens were injected with sheep red blood cells (SRBC), a T-dependent antigen. Peripheral blood lymphocytes (PBL) and spleen lymphocytes isolated at 0, 3, 6, 9, 12 and 24 h following Ag injection were stained with monoclonal antibodies (mAb) detecting B-lymphocytes, CD4+ and CD8+ cells. 3. B-lymphocytes in the blood or spleen showed no significant changes following either BA or SRBC injection. In contrast, CD4+ cells were decreased in the blood and increased in the spleen following BA and SRBC injections. CD8+ cells were decreased in both blood and spleen following BA injection but were unchanged in either blood or the spleen following SRBC injection. 4. These results indicate that there is a change in both spleen and circulating lymphocyte populations, especially T-helper cells, following Ag injection. T-helper cells are apparently the primary population involved in the initiation of humoral immunity.

S. typhi vaccine strain Ty21a can cause a generalized infection in whole body-irradiated but not in hydrocortisone-treated mice

Various mutations including galE- in the S.typhi vaccine strain Ty21a are thought to prevent proliferation of these micro-organisms in the host, and elimination of Ty21a would occur independent of the immune system of the host. To investigate this issue, we determined whether Ty21a can proliferate in immunosuppressed mice, and assessed the role of phagocytes in the eradication of Ty21a from tissues. Mice were rendered lymphocytopenic and monocytopenic by hydrocortisone s.c., or were made leucocytopenic by whole body irradiation. Bacteria were injected into a tail vene to evaluate eradication from the blood, liver and spleen, and into thigh muscle, i.e. a tissue that lacks resident macrophages. Ty21a were grown overnight in glucose [glu], or galactose and glucose [gal.glu]; only the Ty21a [gal.glu] expressed somatic O-antigens. After i.v. injection of 10(4) to 10(6) micro-organisms, Ty21a were rapidly eliminated from the liver and spleen of normal and immunosuppressed mice, i.e. within 1 day a 95% reduction of bacterial counts was observed. After i.m. injection of 10(4) to 10(6) bacteria, the number of viable Ty21a decreased in normal and hydrocortisone-treated mice, but in irradiated mice the micro-organisms proliferated and caused generalized infection. In all cases, Ty21a [glu] was eliminated more rapidly than Ty21a [gal.glu], confirming reports that killing of bacteria that lack O-antigens is more rapid than that of smooth bacteria of the same species. These results indicate that elimination of the vaccine strain against typhoid fever, Ty21a, from host tissues is not due to an intrinsic property of the micro-organisms that prevents proliferation but instead depends on the action of resident macrophages and exudate monocytes and granulocytes.

Topical application of a corticosteroid destabilizes the host-parasite relationship in an experimental model of the oral carrier state of Candida albicans

Using an experimental model in the mouse we have shown that both local and central lines of defense, involving CD4+ T cells, participate in a dynamic interaction to maintain a long-term carrier state of Candida albicans in the oral cavity. We have tested the impact of a predisposing factor to oral candidiasis in the form of a topical application of a corticosteroid (Topsyn gel) to the oral mucosa for 75 mice twice a day for a 20-day period. Very rapidly after the treatment was initiated, i.e. on day 4, the residual population of Candida increased up to 40-fold and by day 21, the population was 400-fold that of the carrier state. The resident population of intraepithelial CD4+ T cells in the oral mucosa virtually disappeared during the treatment. A topical corticosteroid application also resulted in a massive depletion of T cells in the lymph nodes and in the transient abrogation of the DTH reaction to Candida antigens. On cessation of treatment, normal levels of both Candida and intraepithelial CD4+ T cells were also quickly restored. These results suggest that resistance to superficial invasion by Candida is linked to the presence of an oral mucosal line of defense and that topical application of corticosteroids may dramatically shift the host-parasite relationship in favor of Candida.

The role of macrophage colony-stimulating factor in hepatic glucan-induced granuloma formation in the osteopetrosis mutant mouse defective in the production of macrophage colony-stimulating factor

To elucidate the effects of macrophage colony-stimulating factor (M-CSF) on Kupffer cells and monocyte/macrophages in hepatic granuloma formation, we examined granulomas produced by glucan injection in the liver of osteopetrotic mice and littermates with or without M-CSF administration. In the osteopetrotic mice, monocytes were deficient in peripheral blood, and their number did not increase after glucan injection. Hepatic granulomas were formed in the osteopetrotic mice by glucan injection without a supply of blood monocytes. During this process, M-CSF-independent Kupffer cells proliferated, particularly before the granuloma formation, clustered in the hepatic sinusoid, and transformed into epithelioid cells and multinuclear giant cells. In the M-CSF-treated osteopetrotic mice, glucan injection induced an increase in the number of blood monocytes and formed hepatic granulomas at a nearly similar degree to that of littermate mice. Thus, it is concluded that neither monocytes nor M-CSF are necessary for granuloma formation. In contrast, Kupffer cells play a crucial role as granulomas develop in M-CSF-uninjected osteopetrotic mice.

The two-edged sword of large-dose steroids for spinal cord trauma

OBJECTIVE

In 1990, large-dose steroid administration was advocated in spine-injured patients to lessen neurologic deficits. The authors undertook both prospective and retrospective studies to evaluate the response of such profound pharmacologic intervention.

SUMMARY BACKGROUND DATA

Of all sources of nonfatal injury, spinal cord trauma remains the most devastating in both cost and impact on the quality of the patient's life. One study found that routine large-dose steroid administration after injury lessened the extent of neurologic injury. After uncommonly prompt and broad lay press publicity, this practice was widely accepted. Biased by knowledge of the known immunosuppressive effects of steroids, the authors suspected that pneumonia was both more frequent and severe in steroid-treated patients.

METHODS

Thirty-two patients with cervical or upper thoracic spinal injuries (C3-6, 20 patients; C6-7, 6 patients; and T1-6, 6 patients) were studied at an urban level I trauma center from January 1987 to February 1993. Complete spinal cord injury was present in 22 of 32 patients; 14 patients received steroids postinjury. There was no difference in mean age, cord level, age-adjusted injury severity score, or the percent of injury severity score caused by the spinal injury.

RESULTS

The length of hospital stay was longer in steroid-treated patients (S) than in nonsteroid (NS) patients, that is, 44.4 days versus 27.7 days, respectively (p = 0.065). Seventy-nine per cent of S patients had pneumonia compared with 50% of NS patients (p = 0.614). There was no statistical difference in the episodes of pneumonia per patient between the two groups (p > 0.05). Prospectively, the authors evaluated sequentially several parameters known to be important in human immune responses to bacterial challenges in nine S and five NS patients. In S patients, both the per cent and density of monocyte class II antigen expression and T-helper/suppressor cell ratios were lower than in NS patients. However, S patients did have an initially higher, earlier boost in some host defense parameters that rapidly declined, and their subsequent response was both blunted and delayed. These differences became even clearer when stratified according to cord level and incomplete versus complete cord status. Not surprisingly, infected patients, whether S or NS, had lower levels of monocyte antigen expression, CR3, and helper/suppressor ratios.

CONCLUSIONS

These data do not permit a judgment to be made whether neurologic status was improved by S administration. It is known that vital immune responses were adversely affected, that pneumonia was somewhat more prevalent, and that hospitalization was prolonged and costs therefore increased by an average of $51,504 per admission. Further clinical studies will be needed to determine to what extent these observations offset the putative benefits of large-dose steroids in the treatment of spinal trauma.

Comparison of the antibacterial efficacies of ampicillin and ciprofloxacin against experimental infections with Listeria monocytogenes in hydrocortisone-treated mice

The efficacies of ciprofloxacin and ampicillin against Listeria monocytogenes in an immunosuppressed mouse model of listeriosis were compared. Immunosuppression was achieved by administration of 2.5 mg of hydrocortisone acetate daily. Both ciprofloxacin and ampicillin were effective in reducing the number of viable L. monocytogenes cells in the liver and spleen. After treatment with 100 mg of ampicillin per kg of body weight every 6 h for 3 days, virtually no L. monocytogenes could be recovered from the livers and spleens of the mice. In contrast, after treatment with 100 mg of ciprofloxacin per kg every 6 h for 3 days, a geometric mean of 5 x 10(4) CFU of L. monocytogenes was recovered from the spleens and 1 x 10(5) CFU was recovered from the livers of the mice. Results of the study show that the antibacterial efficacy of ampicillin is far superior to that of ciprofloxacin in our animal model of listeriosis.

Hydrocortisone treatment of BCG-infected mice impairs the activation and enhancement of antimicrobial activity of peritoneal macrophages

The present study concerns the effect of hydrocortisone (HC) on the effector functions of Bacillus Calmette Guerin-purified protein derivative (BCG-PPD)-activated macrophages. Such activated macrophages release greater amounts of H2O2 and NO2-, inhibit the intracellular proliferation of T. gondii and kill L. monocytogenes more efficiently than resident macrophages. This activation was not fully expressed by macrophages from BCG-activated mice that had received a subcutaneous injection of HC 2 days before intraperitoneal injection of PPD, since the inhibition of the intracellular proliferation of T. gondii, the release of NO2- and the rate of intracellular killing of L. monocytogenes were lower than in macrophages from BCG-PPD-activated mice. However, treatment with HC did not impair the release of H2O2 by BCG-PPD-activated macrophages. The results show that the treatment of infected mice with HC inhibits their ability to develop adequate intracellular microbicidal mechanisms.

In vivo clearance by the mononuclear phagocyte system in humans: an overview of methods and their interpretation

The mononuclear phagocyte system (MPS) is responsible for the elimination of foreign material, effete autologous material and immune complexes. To study the relationship between MPS function and human disease, several test substances have been developed, and used to determine the clearance capacity of the MPS in human subjects in vivo. These test substances and the multitude of factors that influence the elimination of these substances (and complicate the interpretation of the test results) are discussed. Use of these probes has provided important new insights, that may lead to the development of treatment modalities by which MPS function is modified in order to influence disease processes more effectively.

The influence of corticosteroids on host defense mechanisms

Glucocorticosteroid hormones affect virtually every tissue type in the body, including tissues of host-defense systems. There is an enormous body of literature concerning specific effects of corticosteroids on host defenses. This literature review examines the affects of corticosteroids on leukocyte kinetics, phagocytic immunity, cell-mediated immunity, and humoral immunity in steroid-resistant species.

Bronchoalveolar lavage in an immunosuppressed rabbit model of invasive pulmonary aspergillosis

A rabbit model of invasive aspergillosis has been used to investigate the pathogenesis of Aspergillus infection in the immunosuppressed host. The animals received hydrocortisone daily and a single dose of cyclophosphamide 2 days prior to intratracheal instillation of conidia from Aspergillus fumigatus. Bronchoalveolar lavage (BAL) was performed in 3 infected and 2 control saline treated animals sacrificed on days 1, 2, 4, 7 and 10 following inoculation. Infective load within the lung was quantified using an assay for chitin which is an important component of fungal cell walls (in particular the hyphal cell wall) and is not present in vertebrate tissue. The total BAL white cell count did not discriminate between infected and saline treated animals and Aspergillus was cultured from one lavage specimen only. Infected animals developed a marked neutrophil alveolitis by day 2 in contrast to a near total absence of neutrophils in the lavages of the control animals. Phagocytosis of conidia by alveolar macrophages was prominent but did not prevent progressive infection as confirmed by measurement of lung chitin. This pattern of cellular response within the alveolar airspace reflects the complex nature of the response to Aspergillus infection in the immunosuppressed host.

Effect of irradiation, cyclophosphamide, and etoposide (VP-16) on number of peripheral blood and peritoneal leukocytes in mice under normal conditions and during acute inflammatory reaction

In order to develop a suitable model for studying the role of granulocytes and monocytes in resistance against pathogenic microorganisms, we investigated the effect of irradiation and cytostatic treatment (cyclophosphamide and VP-16) on the number of both peripheral blood and peritoneal leukocytes in male Swiss mice. Irradiation and cyclophosphamide treatment severely decreased the number of both granulocytes and monocytes in peripheral blood, whereas VP-16 only lowered the number of blood monocytes to a significant degree and had little effect on the number of blood granulocytes or lymphocytes. When normal mice were injected intraperitoneally with newborn calf serum (NBCS) the number of peritoneal granulocytes rose about 100-fold within 6 h. In irradiated and cyclophosphamide-treated mice, this influx of granulocytes into the peritoneal cavity was virtually eliminated, as was the concomitant increase in the number of blood granulocytes; in VP-16-treated mice, on the other hand, the number of peripheral blood and peritoneal granulocytes increased to the same degree as in normal mice. An increase in the number of peripheral blood monocytes and peritoneal macrophages occurred 24-48 h after injection of NBCS in normal mice. This increase was significantly impaired by irradiation as well as by treatment with cyclophosphamide or VP-16.

The leucocytosis of exercise. A review and model

Exercise is known to induce an immediate leucocytosis, the magnitude of which is related, in most instances, to the intensity and duration of the work. On finishing exercise, however, the leucocyte count may change in any one of several different ways. The pattern of postexercise changes in the leucocyte count is determined mainly by the time which has elapsed since beginning exercise, rather than the work intensity or the total work done, if, for example, exercise has been intermittent. Consideration of, firstly, the circumstances under which the plasma concentrations of catecholamines and cortisol have been found separately to correlate with the leucocyte count at the finish of exercise, and, secondly, the effects on the leucocyte count of exogenous administration of these substances has led us to develop a model which can satisfactorily account for all of the principal changes in the leucocyte count that have been noted during and after exercise. It is proposed that catecholamines produced during exercise act to increase the ratio of circulating to non-circulating leucocytes, while cortisol acts, by a mechanism which involves a time lag, to increase the total number of leucocytes in the vascular compartment. Examination of previously published reports shows that many contain results which support this model. Using the model as a basis, some predictions are made that can be tested experimentally, and some experiments are suggested which should help elucidate the mode of action of catecholamines and cortisol.

Locally dividing macrophages in normal and inflamed mammary glands

Goat mammary macrophage division in vivo was assessed by detection of mitotic figures, by autoradiographic measurement of the uptake of 3H thymidine, and by a 96-well proliferation assay. Autoradiography revealed that 3.74 +/- 0.77% of nonstimulated mammary macrophages were actively synthesizing DNA. Eight days of sterile inflammation, induced by lipopolysaccharide or thioglycollate, increased mammary macrophage division (10.9 +/- 2.1%). The division increased within 2 h after inducing inflammation with thioglycollate. After 1 day, the rate of division decreased, and another increase occurred 3-4 days later. The high rate of division was maintained for greater than 60 days after the induction of sterile inflammation. Division was further shown to occur by injecting 3H-thymidine directly into the mammary gland, harvesting the macrophages 1.5 h later, and determining incorporation by autoradiography. The results of all assays of division were in agreement, suggesting they reflected the same event. The dividing cells were nonspecific esterase-positive, adherent, motile, phagocytic, and had morphological characteristics of macrophages.

Comparative studies of inflammatory responses in susceptible and resistant mice infected with Giardia muris

A comparative assessment of in-vivo and in-vitro inflammatory responses in mice which are susceptible (A/J) and resistant (B10.A) to Giardia muris was made. B10.A mice which have the ability to eliminate the parasites exhibited a greater capacity to recruit cells into the peritoneal cavity after thioglycollate injection, when compared to A/J mice. The recruitment of inflammatory cells into the peritoneal cavity by B10.A mice was higher on day 15 (acute phase) and on day 60 (elimination phase) of the infection. Quantitative differences in inflammatory responses of A/J and B10.A mice in vivo were related to the functional differences in macrophage phagocytosis and chemotaxis in vitro. Macrophages from the resistant B10.A mice were more phagocytically active and were more chemotactically responsive during both acute and elimination phases of the infection, compared to those from the susceptible A/J mice. There was a relationship between the capacity of A/J and B10.A mice to mount inflammatory responses and the ability of these strains of mice to control the infection with G. muris.

The effect of glucocorticosteroids on bone marrow mononuclear phagocytes in culture

The effect of hydrocortisone and dexamethasone both in vivo and in vitro was studied in mouse bone marrow cultures in methylcellulose and in two liquid culture systems, one using Leighton tubes with a flying coverslip to grow adherent colonies and the other using Teflon culture bags to obtain suspension cultures. Although the total number of nucleated bone marrow cells was not greatly influenced by glucocorticosteroid treatment of the mice, a marked decrease in the number of colony-forming units and of mononuclear phagocytes was observed. Inhibition of colony growth in methylcellulose and of growth of mononuclear phagocytes in Teflon culture bags also occurred when glucocorticosteroids were added to in vitro cultures. Both drugs caused an almost complete inhibition of the growth of adherent colonies, and 3H-thymidine labeling of the cells was correspondingly low. When the glucocorticosteroids were added to cultures pre-incubated for 5 days in the presence of conditioned medium, the 3H-thymidine labeling of macrophages and promonocytes was markedly reduced, whereas there was no change in the labeling of monoblasts.

The effect of corticosteroids or nitrogen mustard on aqueous humor chemotactic activity induced by intravitreal endotoxin

In rabbits intravitreal injection of endotoxin induces potent chemotactic activity for monocytes in aqueous humor. We have assessed the effect of methylprednisolone (30 mg/kg intramuscularly) or nitrogen mustard (1.75 mg/kg intravenously) on the generation of this chemotactic activity. Histologic changes, anterior chamber protein extravasation, and aqueous humor cellular infiltration were reduced by corticosteroids to a variable degree. However, even in animals with a marked reduction in protein extravasation or histologic change, chemotactic activity was substantially preserved. Similarly, nitrogen mustard induced a leukopenia without affecting the ability of endotoxin to generate chemotactic activity in aqueous humor. In contrast, corticosteroids reduced both protein extravasation and the generation of chemotactic activity induced by intravenously injected endotoxin. The results suggest that the chemotactic activity induced in the eye by intravitreal endotoxin may be locally synthesized and may be present without a substantial leukocytic infiltrate.

Genetic control of macrophage responses

A short review of current concepts concerning the origin and kinetics of monocytes and macrophages is given, and the humoral regulation of monocyte production by FIM, a factor synthesized and secreted by macrophages, is discussed. Genetic control of the responsiveness of monocyte precursors to FIM and that of the phagocytosis and intracellular killing of bacteria is dealt with.

Effects of dexamethasone and chlorpromazine treatment on X-Y dissociation and multinucleated giant cell formation in hyperthermic mice

The effects of anti-stress drugs on X-Y dissociation and multinucleated giant cell formation in the testes of hyperthermic mice were determined for the possible use of such drugs in animal production. Mice were injected with dexamethasone 1 mg/kg or 2 mg/kg, chlorpromazine 1 mg/kg or 4 mg/kg, or 0.85% saline, and heat stressed for 4 d at 35 +/- 1 C and 65 +/- 1 % relative humidity. Mice were killed 5 d after stress, and the testes processed for observation of meiotic chromosomes and testicular histology. Heat stress caused a significant increase in X-Y bivalent dissociation in diakinesis-metaphase I spermatocytes and a significant increase in formation of multinucleated giant cells. Drug treatment increased X-Y dissociation but had no significant effect on giant cell formation.

Evaluation of anti-inflammatory agents using a model of granuloma formation evoked by divinyl copolymer beads in the mouse lung

We have developed and quantitated a reproducible standardized granulomatous inflammatory reaction using divinyl copolymer beads. Approximately 10000 gas sterilized beads (43-53 micron in diameter) are injected into the tail veins of mice and embolize to the lungs where they evoke granuloma formation which is maximal at 48 h. The anti-inflammatory effects of both steroidal and nonsteroidal agents, namely, bacterial levan, hydrocortisone acetate, polyanetholsulfonate, indomethacin, acetylsalicylic acid, ellagic acid, and aminophylline were determined by comparing granuloma size in treated animals with those in untreated controls. Granulomas in paraffin sections were traced on the ground glass screen of a light microscope and the area of each granuloma measured with a digitizer-computer programmed to prepare histograms and merge data from replicate experiments. Of the agents tested, the greatest reductions in granuloma size occurred after treatment with bacterial levan (71%), hydrocortisone (70%), polyanetholsulfonate (58%), and indomethacin (55%).

Distribution of blood monocytes between a marginating and a circulating pool

Studies on the blood volume of SPF Swiss mice in the steady state led to reevaluation of the distribution of monocytes in the blood compartment. It was concluded from the results of our calculations that monocytes entering the circulation are distributed over a circulating and a marginating pool. The circulating pool accounts for approximately 40%, and the marginating pool or approximately 60% of the population of peripheral blood monocytes.

The characterization, origin, and kinetics of skin macrophages during inflammation

This report deals with the characterization, origin, and kinetics of exudate skin macrophages. The inflammatory stimulus used was a subcutaneously inserted glass coverslip. The macrophages adhering to the glass surface have many characteristics in common with circulating monocytes. During this kind of inflammation there is little differentiation into a more mature or activated type of mononuclear phagocyte. The kinetic studies with [3H]thymidine as cell marker and calculation of local production at the site of inflammation as well as the influx of cells to that site led to the conclusion that greater than or equal to 99% of the exudate skin macrophages were monocyte derived and less than or equal to 1% originated by local division of macrophages.

Failure of intraperitoneal adjuncts to improve the outcome of pelvic operations in young women

An examination was made of the possibility that 100 to 200 ml of intraperitoneal 32% dextran 70 and/or 0.5% hydrocortisone sodium succinate (randomized independently with similar volumes of Ringer's lactate solution) might help to lessen the postoperative formation of adhesions among patients undergoing surgical procedures for peritubal adhesions (n = 76), endometriosis (n = 27), or midtubal occlusion (n = 61). Patients in the first two groups who were given intraperitoneal corticosteroids were also given systemic steroids. Nonparametric comparison of median adhesion scores at operation and at subsequent laparoscopy showed that there was a poorer outcome with dextran than when dextran was not used in every subgroup except one (repeat salpingolysis after previous operation for adhesions), including first operations for adnexal adhesions (Mann-Whitney U = 200, m = 23, n = 26; p less than 0.05). The probability was small (p beta less than 0.002) that an important beneficial effect of dextran was overlooked. Systemic corticosteroids were associated with a consistent trend toward improved outcome, especially in patients who initially had few or no adhesions, such as those operated on for endometriosis (U = 2, m = 7, n = 4; p less than 0.025), but among patients with tubal resections and anastomoses with adnexal adhesions the use of intraperitoneal hydrocortisone alone was associated with a worse outcome (U = 15, m = 12, n = 8; p less than 0.02). Life-table analysis of the accumulating probability of pregnancy showed that no significant difference resulted from adjunct use in any group. The conclusion is that no empiric basis supports the use of intraperitoneal 32% dextran 70 or 0.5% hydrocortisone in the attempt to prevent peritoneal adhesions, but further investigations on the systemic administration of corticosteroids to decrease the formation of adhesions would be useful.

Septic complications of corticosteroid administration after central nervous system trauma

The records of 197 consecutive multiple trauma patients were reviewed to define the infectious complications of corticosteroids used to treat brain and spinal cord injury. An injury severity score (ISS) and a central nervous system (CNS) injury score were determined for each patient. Patients with an ISS less than 20 did well with or without steroids and were excluded from further study. All deaths that occurred 5 or more days after injury were caused by sepsis, and all occurred in steroid recipients. Twenty-nine of 61 steroid-treated early survivors developed infectious complications, compared to eight of 55 patients who did not receive steroids (47.5% vs. 14.5%, p less than 0.001). There was no correlation between severity of CNS trauma and infectious complication rate. Steroid-treated patients frequently developed multiple pathogen primary infections and multiple, simultaneous septic foci. Patients treated with steroids more often developed infections caused by Staphylococcus aureus, assorted gram negative rods, anerobic bacteria, or fungi. The study strongly suggests a significant increase in both the incidence and severity of infectious complications occurring in patients treated with corticosteroids for CNS trauma.

Morphologic and physiologic response of lungs to steroid and cigarette smoke: an animal model

The combined effects of cigarette smoke inhalation and hydrocortisone acetate (HCA) treatment induce prominent abnormalities in lungs of C57BL/6 male mice. These abnormalities include (1) a marked reduction of pulmonary macrophage population which is normally elevated by smoke inhalation, (2) an accumulation of surfactant and flocculent material in alveoli, (3) a decrease in alveolar space surrounded by normal septal tissue, and (4) an increase in hypertrophied alveolar parenchyma. Concomitant with altered lung morphology, lung volume and gas diffusing capacity were significantly compromised in animals subjected to smoke exposure and steroid treatment. It was found that smoke inhalation or HCA administration alone had no ill effects on the animals. The data presented indicate that manifestation of pathologic conditions resembling pulmonary fibrosis and pulmonary alveolar proteinosis is a result of cigarette smoke-drug interaction. The information reported provides a basis for an animal model which might be applicable to assessment of factors related to smoke inhalation and development of pulmonary disorders.

A new method of eliciting delayed hypersensitivity in the mouse abdominal cavity

A new method of determining delayed hypersensitivity quantitatively was investigated in mice. Mice were sensitized with 150 micrograms of ferritin and, 3 weeks later, antigen challenge was performed by implanting a sponge containing antigen in the abdominal cavity. Cells accumulated in the sponge markedly increased in number for 24-72 h after the challenge; mononuclear cells predominated by 48 h. When sensitized lymphocytes were transferred passively to a normal recipient, marked cell accumulation in the sponge was found 48 h after the challenge. Immunological specificity was confirmed in animals sensitized to antigen and receiving passive transfer of sensitized cells. Strain differences in this reaction were observed. Cortisone (20 mg/kg for 6 days before challenge) significantly decreased cell accumulation. Delayed hypersensitivity was also elicited in the ear of sensitized animals. Extracts of sponges removed from antigen-challenged mice had macrophage chemotactic activity.