Frank Buttgereit

Rapid glucocorticoid effects on immune cells.

Apart from their classic genomic effects, it is well known that glucocorticoids also have rapid, nongenomically mediated effects. Three different mechanisms are currently under discussion as being responsible for these effects: (1) specific interaction with the cytosolic glucocorticoid receptor (cGCR), (2) nonspecific interactions with cellular membranes and (3) specific interactions with membrane-bound glucocorticoid receptors (mGCR). With regard to the first mechanism, there is evidence that although the binding of glucocorticoids to the cGCR-associated multi-protein complex induces the further processes of the classic path, it also leads to a rapid intracellular signalling through other components of the complex (e.g. Src). For the second mechanism, a nonspecific interactive effect with cellular membranes through the intercalation of glucocorticoid molecules is being discussed, which primarily alters cellular functions by influencing cation transport via the plasma membrane and by increasing the proton leak of the mitochondria. With regard to the third, mGCR-mediated mechanism, the first evidence has now been found to suggest a physiological expression of membrane-bound glucocorticoid receptors on human cells, whereas in humans this had previously only been demonstrated on lymphoma cells. The clinical importance and therapeutic relevance of these rapid glucocorticoid effects remains unclear at present, although effects on intracellular signalling, interferences with bioenergetically relevant cell functions and the induction of apoptosis via the mGCR are being discussed. This article gives a detailed presentation of the data available at present concerning rapid glucocorticoid effects on immune cells.

Molecular mechanisms of glucocorticoid-induced osteoporosis.

Bone loss resulting from long-term glucocorticoid therapy is common and clinically relevant. A number of different glucocorticoid-mediated effects are responsible for the reduction in bone density: (i) glucocorticoid-induced direct impairment of osteoblast, osteocyte, and osteoclast function leads to reduced bone remodeling and diminished repair of microdamage in bone; (ii) the effects of parathyroid hormone (PTH) might be more pronounced in the presence of glucocorticoids, whereas vitamin D plays a lesser role in the pathogenesis of steroid-induced osteoporosis; (iii) glucocorticoids antagonize gonadal function and inhibit the osteoanabolic action of sex steroids; and (iv) increased renal elimination and reduced intestinal absorption of calcium lead to a negative calcium balance that has been suggested to promote secondary hyperparathyroidism. From a mechanistic point of view, all of the aforementioned effects have long been considered to be mediated at the molecular level exclusively by genomic actions. However, there is now increasing evidence for the existence of rapid glucocorticoid effects that are incompatible with this classical mode of action. These rapid effects, termed nongenomic effects, are mediated by glucocorticoid interactions with biological membranes, either through binding to membrane receptors or by physicochemical interactions. It is possible, but has yet to be shown, that these effects play a role in the pathogenesis of glucocorticoid-induced osteoporosis.

Equivalent Doses and Relative Drug Potencies for Non-genomic Glucocorticoid Effects: A Novel Glucocorticoid Hierarchy

Glucocorticoids have three distinct therapeutically relevant effects (genomic, specific nongenomic, and unspecific non-genomic), raising the hypothesis that the relative potencies of non-genomic and genomic effects of glucocorticoids may differ. Therefore, we measured the unspecific non-genomic potencies of five clinically important glucocorticoids and compared them with the classical (genomic) potencies. We studied the immediate glucocorticoid effects on respiration, on protein synthesis, and on Na+-K+-ATPase and Ca2+-ATPase in concanavalin A-stimulated rat thymocytes. We titrated the respiration of the cells with methylprednisolone, prednylidene, dexamethasone, prednisolone or betamethasone, and then interpolated the glucocorticoid concentrations needed to inhibit concanavalin A-stimulated respiration back to normal. These equivalent doses produced equal inhibition of respiration, of specific energy-consuming pathways, and of the concanavalin A effect on quiescent cells. The relative drug potencies were calculated as the inverse of the equivalent doses normalized to methylprednisolone and were: prednylidene (3.0) > dexamethasone (1.2) > methylprednisolone (1.0) > prednisolone (0.4) > betamethasone (0.2). This hierarchy is completely different from that for the classical effects. These new data are of crucial relevance for in vitro experiments and clinical use, especially in glucocorticoid high-dose therapy. Examples are the choice between methylprednisolone and prednisolone in pulse therapy, and the completely different clinical usage of dexamethasone and betamethasone, despite their similar affinities for nuclear receptors.

Mechanism of action of glucocorticosteroid hormones: possible implications for therapy of neuroimmunological disorders.

Glucocorticosteroids are the most potent immunosuppressive and antiinflammatory drugs. Over the six decades that have passed since their discovery, a variety of genomic effector mechanisms of steroid hormones has been described which are mediated by the cytosolic steroid receptor. Recent evidence supports a direct effect of glucocorticosteroids on cellular membranes that occurs at higher hormone concentrations, termed nongenomic effects. These imply a qualitatively distinct mode of steroid action leading to cellular apoptosis. In this review, we discuss in vitro and in vivo data on nongenomic effects of glucocorticosteroids and their possible implications for the therapy of human neuroimmunological diseases.

The influence of obesity on perioperative morbidity and mortality in revision total hip arthroplasty.

Abstract The significance of obesity as a risk factor for postoperative complications was determined in a consecutive series of 229 cases of revision total hip replacement. The body mass index (BMI) was used as an objective measure to classify the patients. The group-wise analysis of data included all medical and procedure-related complications, the number of fatal cases, operative time, requirement for analgesics, the number of transfusions and perioperative haemoglobin levels. The results of our study demonstrate a clear association between obesity and operative time, whereas no statistically significant relationships were observed between obesity and the other parameters. We conclude that obesity does not have any significant influence on perioperative morbidity and mortality but is clearly related to operation time and, therefore, to higher costs per operation.

Tumoral calcinosis revisited: pathophysiology and treatment

In two renal failure patients, tumoral calcinoses were observed as a result of secondary hyperparathyroidism. The primary conservative therapy conducted with dietetic measures and phosphate-binding medication could not prevent the progression of the massive polytopic foci. Therefore, a subtotal parathyroidectomy was performed in one case, after which a rapid complete regression of the tumours was observed, with the exception of one location where the finding remained progressive. The second patient declined surgical intervention on the parathyroid gland. Therefore, the foci were only resected, whereby local recurrences were observed. Renal failure patients with tumoral calcinosis should undergo subtotal parathyroidectomy after initial conservative therapy. In view of the high risk of recurrence, local excision is a treatment procedure to be considered in exceptional cases only.

Bioenergetics of immune cells to assess rheumatic disease activity and efficacy of glucocorticoid treatment.

Objective: To investigate whether activity and glucocorticoid treatment of rheumatic diseases are reflected by selected parameters of cellular energy metabolism of peripheral blood mononuclear cells (PBMC). Methods: PBMC were obtained from 30 healthy volunteers, 28 patients (16 inactive; 12 active) with rheumatoid arthritis, systemic lupus erythematosus, vasculitis, or other autoimmune diseases, and five patients with infectious diseases. Patients with active rheumatic diseases were examined before and 4–5 days after starting, restarting, or increasing the dose of glucocorticoids. Cellular oxygen consumption (as a measure of ATP production), bioenergetic ability to be stimulated, and major ATP consuming processes were measured amperometrically with a Clark electrode. Results: A normal value for oxygen consumption of 3.84 (SEM 0.1) (all data in nmol O2/min/107 cells) independent of sex was found. In patients with inactive disease the respiration rate was slightly higher, but was significantly increased in active patients to 4.82 (SEM 0.33) (p<0.001). PBMC from active patients showed a significantly lower bioenergetic response to a mitogenic stimulus than controls (p<0.05). In stimulated cells from active patients there was a significant reduction in cation transport and protein synthesis. All parameters above were almost normalised within 4–5 days upon optimised treatment with glucocorticoids. For comparison, PBMC from patients with active infectious diseases also showed an increased respiration rate; their response to mitogenic stimulation was even higher. Conclusions: This study shows for the first time that parameters describing the cellular function of PBMC in bioenergetic terms are suitable for (a) describing semiquantitatively the activity of a rheumatic disease and (b) assessing the therapeutic effect on the disease.

Therapeutically targeting lymphocyte energy metabolism by high-dose glucocorticoids

Lymphocytes use a considerable amount of energy, mainly in the form of ATP, especially when they become stimulated following activation by antibodies or mitogens. Cellular respiration is the major energy source, and in quiescent cells the ATP produced is used to drive protein synthesis and sodium transport. In stimulated cells there is significantly higher ATP production to balance the higher ATP demand of specific processes resulting from activation. The major ATP-consuming processes under these conditions are protein synthesis and Na(+),K(+)-ATPase (about 20% each), while Ca(2+)-ATPase and RNA/DNA syntheses contribute about 10% each. There is a wealth of available information about glucocorticoid effects on lymphocytes, but here we focus on the extent to which this lymphocyte bioenergetic machinery is targeted by glucocorticoids when they are used therapeutically at high doses. High-dose glucocorticoids have been shown recently to interfere with processes that are essential for the activation and maintenance of lymphocytes, such as sodium and potassium transport. Therefore, in this article we describe the bioenergetics of lymphocytes in resting, activated, and glucocorticoid-treated states and present a concept for discussion to describe the relationship among these states in fundamental and clinical terms.

Oxygen consumption and mitochondrial membrane potential indicate developmental adaptation in energy metabolism of rat cortical neurons

Neuronal energy needs are mainly covered via mitochondrial oxidative phosphorylation. Even if the energy supply appears identical in immature and adult brain, nevertheless quantitative differences exist. The present study focuses on the adaptations in cellular energy metabolism caused by the neuronal maturation. As main parameters of oxidative phosphorylation, cellular oxygen consumption and mitochondrial membrane potential were measured in isolated rat cortical cells using a Clark‐type oxygen electrode and microfluorometric techniques. In four age groups (E18–P2, P8–P12, P16–P20, ≥u200aP28), unstimulated neurons showed a significant age‐dependent increase in basal oxygen consumption (6.1 up to 10.2u2003nm/min/107u2003cells). The excitatory neurotransmitter glutamate induced a further, but age‐ and concentration‐independent, elevation of oxygen consumption to a plateau ≥u200a14u2003nm/min/107u2003cells and a complete depolarization of mitochondrial membrane in neurons ≥u200aP8. Stimulation using K+ (5–50u2003mm) effected a concentration‐ and age‐dependent increase in oxygen consumption, but a similar nearby complete depolarization of mitochondrial membrane in all tested age groups. Furthermore, uncoupling mitochondrial membrane function followed by a complete depolarization of mitochondrial membrane showed a maximal oxygen consumption (14–15u2003nm/min/107u2003cells) only in neurons ≥u200aP8. These data suggest that developing and adult cortical neurons cover their increased need of energy following stimulation by an efficiency improvement of mitochondrial oxidative phosphorylation. The age‐independent limited capacity of mitochondrial oxidative phosphorylation, however, causes a reduction in cellular energy disposal in mature neurons and therefore may play a critical role in the increased sensitivity of adult neurons against excitotoxicity and ischaemia.

Coincidence of asymptomatic avascular necrosis and fracture of the femoral neck: a rare combination of glucocorticoid induced side effects

Glucocorticoids have profound anti-inflammatory and immunosuppressive actions when used therapeutically. Unfortunately, these drugs have adverse effects—for example, on bone metabolism. Osteoporosis is well known to be a common side effect, whereas a glucocorticoid associated avascular osteonecrosis is rarely diagnosed. However, as far as we know, the coincidence of manifest osteoporosis with fracture and avascular osteonecrosis in the same area is unique.nnWe present the case of a 47 year old postmenopausal woman who had had mixed connective tissue disease (MCTD) for more than 20 years. The MCTD was complicated by progressive vasculitis, and had required immunosuppressive treatment with prednisolone (maximum dose 500 mg/day (pulse therapy; average dose 15 mg/day) for 20 years and azathioprine (75 mg/day). In 1995, she complained for the first time of severe back pain and noticed a height loss of 10 cm within two years. There was no history of previous fractures.nnGlucocorticoid induced osteoporosis was suspected. Indeed, bone densitometry (DXA-LUNAR) showed decreased bone mineral density (BMD) of the lumbar spine (L2–4) …