[Sarcoid uveitis: Ophthalmologist's and internist's viewpoints]. / Uvéites sarcoïdosiques : regards croisés de l'ophtalmologiste et de l'interniste.

Sarcoidosis is one of the leading causes of inflammatory eye disease. All ocular structures can be affected, but uveitis is the main manifestation responsible for vision loss in ocular sarcoidosis. Typical sarcoid anterior uveitis presents with mutton-fat keratic precipitates, iris nodules, and posterior synechiae. Posterior involvement includes vitritis, vasculitis, and choroidal lesions. Cystoid macular edema is the most important and sight-threatening consequence of sarcoid uveitis. Patients with clinically isolated uveitis at diagnosis rarely develop other organ involvement. Even though, ocular sarcoidosis can have a severe impact on visual prognosis, early diagnosis and a wider range of available therapies (including intravitreal implants) have lessened the functional impact of the disease, particularly in the last decade. Corticosteroids are the cornerstone of treatment for sarcoidosis, but up to 30% of patients achieve remission with requiring high-dose systemic steroids. In these cases, the use of steroid-sparing immunosuppressive therapy (such as methotrexate) is unavoidable. Among these immunosuppressive treatments, anti TNF-α drugs have been a revolution in the management of non-infectious uveitis.

[Parvovirus B19 infections in adults]. / Infection de l'adulte à Parvovirus.

Acute Parvovirus B19 (PVB19) infection is responsible for erythema infectiosum in children and non-specific polyarthralgias in immunocompetent adults associated with skin lesions and rarer manifestations (hepatic, neurological, cardiac or nephrological). In immunocompromised patients, cytopenias are more frequent and in some cases, viremia persists and is responsible for PVB19 chronic infection. PVB19 is responsible for pure red cell aplasia during chronic hemolytic diseases. Acute PVB19 infection is a differential diagnosis of some autoimmune diseases and has been suspected to be a trigger for some autoimmune diseases because of its ability to promote the emergence of autoimmune markers. Mechanisms of molecular mimicry, induction of apoptosis and activation of enzymes have been demonstrated, explaining in part the production of autoantibodies during infection. However, the demonstration of a causal relationship in the triggering of autoimmune disease remains to be done. This review provides a synthesis of the PVB19 infection clinical data in adults with a particular focus on these links with autoimmunity.

Murine typhus complicated by sHLH mimicking adult-onset Still's disease.

INTRODUCTION: Adult-onset Still's disease (AOSD) is a rare multisystemic disorder and a diagnostic challenge for physicians because of the wide range of differential diagnoses. Common features of AOSD and secondary hemophagocytic lymphohistiocytosis (sHLH) could favour diagnostic uncertainty, in particular in case of infection-related sHLH. OBSERVATION: A 61-year-old man was admitted to our internal medicine department for suspected AOSD. He reported a 2-week history of sudden onset fever, headaches, myalgia, sore throat, diarrhoea, and an erythematous macular rash of the trunk as well as petechial purpuric lesions on both legs on return from Reunion Island. Laboratory tests found cytopenia, hepatic cytolysis, hypertriglyceridaemia, and hyperferritinaemia. Hemophagocytosis was diagnosed on bone marrow aspiration in favour of the diagnosis of secondary hemophagocytic lymphohistiocytosis (sHLH). Subcutaneous anakinra (100mg) was initiated to treat sHLH with favourable course. Oral doxycycline was added 3days later because of atypical features for AOSD diagnosis such as diarrhoea, hypergammaglobulinaemia, and doubtful serologies for Rickettsia and Coxiella. Three weeks later, Rickettsia typhi serology was checked again and revealed an increase in IgG titer>4 times that confirmed the diagnosis of murine typhus. A diagnosis of murine typhus complicated by sHLH was retained, successfully treated by anakinra and doxycycline. CONCLUSION: Our observation shows that AOSD diagnosis has to be stringent due to the many differential diagnoses, particularly infection complicated by sHLH, which may be rare. It is important to consider murine typhus in patients returning from endemic areas, such as La Reunion or other tropical areas, when they present fever of unknown origin with non-specific clinical features. Moreover, this case illustrates the effectiveness of IL-1 blockers as a treatment for symptomatic sHLH without severity criteria, regardless of the aetiology.

Glucose uptake by rat erythroid cells: the effects of erythropoietin and dexamethasone.

Erythropoietin (Ep) stimulated glucose uptake by erythroid progenitor cells in the liver of fetal rats, as measured by [3H]2-deoxy-D-glucose uptake. This dose-dependent stimulation was maximal at 0.2 U/ml Ep and decreased during cell differentiation. Dexamethasone (DEX) inhibited glucose uptake by erythroid progenitors; this dose-dependent effect was maximal at 10(-7) M DEX. Ep partly counteracted the inhibitory effect of DEX. This antagonism may contribute to the overall antagonism between Ep and glucocorticoids in the development of erythroid tissue in vivo and in vitro.

Induction of erythropoietin receptors during aclacinomycin-mediated erythroid differentiation of K562 leukemia cells.

Human K562 leukemia cells have been induced to differentiate along the erythroid lineage by aclacinomycin (ACM), an anthracyclic antitumor drug. During differentiation over 3 days in culture, the expression and the nature of erythropoietin (EPO) receptors have been analyzed using 125I-labeled bioactive recombinant human EPO. Aclacinomycin at 20 nM, the concentration inducing optimum differentiation, progressively increased EPO-specific binding. On day 3, EPO binding was nine-fold higher than that of the controls (1031 +/- 101 cpm/5 x 10(6) cells versus 112 +/- 15 cpm); with various concentrations of ACM, the increase in EPO binding appeared to parallel the recruitment of hemoglobin-producing cells. However, at 95% of growth inhibition, EPO binding remained constant while the percentage of differentiated cells decreased. Specific binding was reversible, saturable, and proportional to cell number; bound EPO was displaced by unlabeled EPO. Scatchard analysis of the equilibrium binding data suggested the existence of a single class of EPO receptors with an apparent Kd of 867 +/- 458 pM, corresponding to 400 +/- 142 receptors per cell. Affinity cross-linking of 125I-EPO using disuccinimidyl suberate followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions demonstrated that EPO was preferentially cross-linked to a protein of approximately 116 kD. Taken together, these results demonstrate that, in addition to cytostatic properties, antitumor drugs such as ACM can modulate the expression of differentiation factor receptors on the surface of leukemic cells.

Differentiating activity of adriamycin in human erythroleukemic cells: effect on globin and heme synthesis.

The human leukemic cell line K 562 can be induced to differentiate along the erythroid lineage by various chemical compounds and particularly by the anthracyclic antitumor drug, adriamycin (ADR). In this study, we show that, in the presence of a subtoxic concentration of ADR (30 nM), the appearance of hemoglobin-producing K 562 cells is associated with a specific increase in globin mRNA accumulation corresponding to epsilon-, zeta-, gamma-, alpha-globin chains. At the translational level, bulk protein synthesis is strongly decreased following ADR treatment, whereas globin chain synthesis is specifically enhanced. Globin chains represent about 20% of total proteins in ADR-treated cells, versus about 3.5% in controls on day 3. Similarly, on day 3, heme synthesis (55Fe incorporation) is about 10-times higher in ADR-treated cells than in control cells (20,888 dpm/10(5) cells versus 1693 dpm/10(5) cells) which confirms the increase in heme content (420 pM/10(6) treated cells versus 100 pM/10(6) control cells). In the presence of succinylacetone, a heme synthesis inhibitor which prevented the differentiating effects of ADR, the globin mRNA accumulation was not affected. This suggests that heme did not play a regulatory role in globin mRNA transcription, a result at variance with observations published by others. Such results strongly support the notion that in addition to cytostatic properties, ADR stimulates specifically globin and heme synthesis.

In vivo effects of glucocorticoid excess on the contents of the rat fetal liver in erythroid progenitors.

Following a laparotomy of the pregnant rat at 12 days of gestation, erythroid cell suspensions prepared from the fetal livers at 14 days contained an increased proportion of progenitor cells forming colonies after 2 or 7 days of culture. When laparotomy was performed at 14 days and the fetal livers were sampled at 16 days, the opposite effects were observed. Injection of 0.25 mg/kg dexamethasone to the 12 days pregnant rat increased the proportion of erythroid progenitors in suspensions from 14 days fetal livers; injection of 10 mg/kg (a long-acting dose) produced the opposite effects. Both the composition of the erythroid cell line and its environment change between 12 and 14 days, and these modifications might explain the inversion of glucocorticoid effects between these two stages.

The erythropoietin receptor of rat erythroid progenitor lens. Characterization and affinity cross-linkage.

Commercially available 125I-labeled erythropoietin, obtained by genetic engineering from a human gene, was used to characterize receptors for this hormone on the cell surface of rat erythroid progenitor cells. A low number of high affinity binding sites (487 +/- 32 sites/cell, Kd = 167 +/- 14 pm) were found. Nonerythroid cells and erythrocytes did not exhibit specific binding. The high affinity binding was reversible and displaced by unlabeled erythropoietin, but not by other hormones and growth factors. After incubation at 37 degrees C, nearly 35% of the specifically bound erythropoietin seemed to be internalized, as judged by resistance to acidic buffer treatment. Thus, binding showed characteristics of a hormone-receptor association. 125I-Erythropoietin-labeled cells were treated with the bifunctional reagent dissucinimidyl suberate. Analysis of the cellular extracts by polyacrylamide gel electrophoresis under denaturing and reducing conditions revealed that erythropoietin can be cross-linked to two molecules of 94 and 78 kDa, respectively. Both labeled bands disappeared when the cells were labeled in the presence of an excess of unlabeled erythropoietin. Under nonreducing conditions, a cross-linked band of 230-255 kDa was observed. The relationships between these bands are discussed.

Murine erythroleukaemia cells (Friend cells) possess high-affinity binding sites for erythropoietin.

Murine erythroleukaemia cells represent erythroid precursors blocked near the CFU-E or proerythroblast stage. In contrast to their non-leukaemic equivalents, neither their proliferation nor their differentiation seems to be affected by erythropoietin. However, we show in this paper that both uncommitted and committed, benzidine-positive, cells bind iodinated erythropoietin. The binding is of high affinity (Kd = 490 +/- 160 pM) and reversible with a half-life of the complex of 77 +/- 19 min. The number of binding sites is low (300-600 per cell). In contrast the haematopoietic non-erythroid cell lines HL 60 and L 1210 and the myeloid-erythroid human cell line K 562 do not exhibit specific binding. If these binding sites represent true hormone receptors, their presence on a permanent cell line should facilitate erythropoietin receptor purification.

Induction by hemin of proliferation and of differentiation of progenitor erythroid cells responsible for erythropoietin.

Erythroid progenitor cells were obtained from rat fetal liver by immunolysis of the whole erythroid population with an antiserum directed against adult rat erythrocytes, followed by separation on a density gradient. Immediately after their isolation, these cells contained only minute amounts of globin mRNAs and their heme synthesis was negligible. In the absence of erythropoietin (Epo), they did not proliferate or differentiate. In the presence of Epo, they proliferated, synthetized heme and globins actively, accumulated large amounts of globin mRNAs, and developed hemoglobinized colonies in methylcellulose. Hemin, in concentrations of 5-100 microM, induced, in the absence of Epo, the proliferation and differentiation of these cells (e.g., accumulation of globin mRNAs, synthesis of heme and globins, and increased density of membrane antigens characteristic of the erythrocyte). Nevertheless, Epo and hemin actions were not superimposable: in methylcellulose, Epo induced the appearance of large (greater than or equal to 32 cells) hemoglobinized colonies in 48 h, whereas hemin induced smaller and fewer colonies in only 24 h. Succinylacetone (SA, inhibitor of heme synthesis) mostly prevented the effects of Epo on cell proliferation and differentiation; SA inhibition was relieved by hemin. Thus, hemin seems to intervene in erythroid differentiation as a factor of both proliferation and maturation.

Mode of action of erythropoietin and glucocorticoids on the hepatic erythroid precursor cells: role of prostaglandins.

The hypothesis that prostaglandins, and especially PGE2, are the second messengers of erythropoietin (Ep) and that glucocorticoids inhibit Ep action by inhibiting PG synthesis was tested on the erythroid cell line from fetal rat liver. The optimal (10(-9) M) stimulatory concentration of PGE2 did not reproduce, by far, the maximal effect of Ep on the growth of CFUE erythroid colonies. Ep did not increase PGE2 release in liquid culture media of cell suspensions made of the whole erythroid line or enriched (over 85%) in precursor cells. Ep did not modify the turnover rate of arachidonate. Nevertheless, indomethacin partially inhibited Ep effect on CFUE development, and this inhibition was abolished by PGE2. These results suggest that PGE2 potentiates Ep action but is not its second messenger. Spontaneous PGE2 release in liquid culture media brought about concentrations of the order of 10(-9) M, and 10(-7) M dexamethasone completely inhibited this release. Part of (but not all) the anti-Ep effects of glucocorticoids might thus be mediated this way. Dexamethasone effects required previous protein synthesis.

Effect of the antiglucocorticoid agent RU 38486 on the dexamethasone inhibition of Friend cell differentiation.

Glucocorticoid hormones are known to inhibit the erythroid differentiation of Friend cells. The mechanism of action of these hormones has been questioned, and results suggesting an action not involving the nuclear binding of the receptors have been published. We have used the antiglucocorticoid RU 38486 to block the inhibitory effect of dexamethasone on the induced differentiation of Friend cells. Our results strongly suggest a glucocorticoid action involving the binding of classical receptors to the cell nucleus.

Effect of thyroid hormones on postnatal fibrinogen levels in the rat.

From normal adult values of about 2.4 g/l at birth, rat plasma fibrinogen levels decrease to a minimum between 10 and 30 days of age and increase again at the end of weaning. The values of fibrinogenemia measured with different methods (heat precipitation at 56 degrees C versus clotting time) disagree. These results are discussed in connection with the development of the hypothalamic-pituitary-thyroid axis.

Kinetics of dexamethasone binding to the glucocorticoid receptor of intact erythroid cells from rat fetal liver.

The erythroid cells from the rat fetal liver have been shown to possess a receptor for glucocorticoids. In the present work, the characteristics of [3H]dexamethasone binding have been studied on intact cells, in order to minimize receptor degradation, and at 4 degrees C, in order to prevent the activation of the hormone-receptor complex. Dissociation kinetics were those of a first-order reaction and the value of the rate constant of dissociation was similar to the values available in the literature. When studied at low concentrations of the ligand and using short-term incubations, association kinetics were apparently those of a simple bimolecular reaction. But at high ligand concentrations and/or using long-term incubations, association kinetics indicated a more complex reaction. Our results were compatible with the model proposed by Pratt W.B., Kaine J.L. and Pratt V.D. (J. Biol. Chem. 250 (1975) 4584-4591) for cytosolic preparations. This model implies the rapid formation of a transient unstable form of the complex, further converted into a stable form with slower kinetics. Equilibrium dissociation constant of the first (rapid) reaction was 80 microM and the rate constant of 'stabilization' was of the order of 70 X 10(-3) min-1. These values agree with the results of Pratt et al. relative to a cytosolic preparation from rat thymocytes.

In vitro and in vivo regulation of hepatic erythropoiesis by erythropoietin and glucocorticoids in the rat fetus.

Glucocorticoids affect evolution of rat fetal liver erythropoietic tissue, where their receptors have been characterized. This paper describes erythropoietin (Ep) and dexamethasone (Dex) effects on the number of CFUE and BFUE grown from erythroid cells isolated from 14 day fetal livers. CFUE number showed a linear log dose-response towards Ep. In absence of exogenous Ep, it was increased by 10(-10) - 10(-9) mol/L Dex. At Ep concentrations less than or equal to 0.025 U/ml, it was increased by Dex concentrations less than or equal to 10(-9) mol/L, higher Dex concentrations being inhibitory. At Ep concentrations greater than 0.025 U/ml, only a linear log dose inhibitory effect of Dex was observed, related to receptor occupancy. BFUE number was not affected by Dex. Ep activity of fetal serum, measured by CFUE induction, was high at 15-16 days of gestation and much lower thereafter. Proliferation of erythropoietic tissue in rat fetal liver before 16 days probably results from high Ep and low corticosterone levels; the regression of proliferation after 16 days probably results from the reverse hormonal status.

Early erythropoiesis in foetal rat bone marrow: evidence for a liver-to-bone marrow relay.

Erythropoietic activity of foetal rat femoral marrow was examined during the last four days of intra-uterine life. Insignificant at day 18, it develops slowly thereafter until birth. In the non-suckled neonate (not older than two hours), it appears notably enhanced. In order to test the potential of the foetal marrow to develop precocious or increased erythropoiesis, the activity of the erythropoietic organ predominant at this time, the liver, was altered by modifying the level of circulating corticosteroids, which govern its function. Maturation and involution of the hepatic erythron wee prevented by corticosteroid deprivation of the foetus (maternal adrenalectomy and foetal hypophysectomy). Precocious maturation and exhaustion of the hepatic erythron was induced by submitting foetuses to corticosteroids excess from day 14. Both corticosteroid deprivation and excess increase the erythropoietic activity of the femoral marrow. This activity can reach and even exceed by day 20 of intrauterine life that in neonatal marrow. Foetal hepatic erythron misfunction can therefore initiate and stimulate bone marrow erythropoiesis. The study of circulating red blood cells demonstrates that : (1) anaemia initiates medullary erythropoietic activity; (2) this anaemia is largely corrected by the bone marrow. The regulatory mechanism is presumably erythropoietin mediated.

Binding of glucocorticosteroids to hepatic erythropoietic cells of the rat fetus.

A role for glucocorticosteroids in the evolution of the fetal liver erythron in vivo has been proposed. If direct, such an intervention implies the presence of receptor sites in the cells of the erythroid cell lines. To test this hypothesis cell suspensions were prepared from liver haematopoietic tissue obtained from rat fetuses aged 13, 14, 17 and 20 days. Their composition was determined by light microscopy. The populations consisted essentially of cells of the erythroid line: juvenile cell types (progenitor and basophilic cells) predominated in tissue collected at 13 and 14 days of gestation, more mature types (polychromatic and acidophilic cells) became more abundant at 17 and 20 days of gestation. Suppressible binding of glucocorticosteroid at 4 degrees C was studied on these suspensions, using [3H]dexamethasone. Binding sites were found at all stages of gestation studied. The mean number per cell (for the entire erythroid population) was roughly 3600, 3500, 2300 and 1700 at 13, 14, 17 and 20 days of gestation respectively, without any change in the apparent equilibrium dissociation constant (Kd:5.5 X 10(-9) to 6.5 X 10(-9) mol/l). Suspensions containing essentially progenitor cells were prepared from erythropoietic cells from livers obtained at 14 and 16 days of gestation, using a rabbit immune serum against rat erythrocytes in the presence of an excess of complement. These cells had 1800 and 1600 receptor sites per cell respectively (same Kd as above). No receptors were found on circulating adult or fetal erythrocytes. The results strongly suggest that there is an uneven distribution of the number of the glucocorticosteroid binding sites per cell amongst the different cell types of the erythroid line. These sites were present in progenitors, increased in number in the basophilic cells and then progressively disappeared as the cells matured.

Evidence for fibrinogen synthesis and secretion by rat foetal hepatocytes.

Fibrinogen concentration in rat foetal plasma is very low at 18 days of gestation but increases rapidly thereafter. The present study provides evidence that this increase is due to synthesis by the foetus itself. (1) 125I-labelled human fibrinogen, injected intravenously into the pregnant adult, did not reach the foetal circulation; (2) turpentine administration to the adult induced an increased maternal plasma fibrinogen concentration without affecting the foetal one; (3) conversely, in utero administration of turpentine to foetuses increased their plasmas fibrinogen concentration without affecting the maternal one; (4) using sheep anti-rat fibrinogen antibodies labelled with peroxidase, in electron microscopy, fibrinogen was located in foetal hepatocytes within the organelles known to be responsible for the synthesis and the ultimate secretion of the protein.