Cellular uptake and transport of methylprednisolone at the blood-brain barrier

Glucocorticoid effects in the regenerating fin reflect tissue homeostasis disturbances in zebrafish by affecting Wnt signaling

As a treatment for various immune-mediated diseases, the use of glucocorticoids as anti-inflammatory and immunosuppressive agents is common practice. However, their use is severely hampered by the risk of the development of adverse effects such as secondary osteoporosis, skin atrophy, and peptic ulcer formation. The exact molecular and cellular mechanisms underlying those adverse effects, which involve most major organ systems, are not yet fully understood. Therefore, their investigation is of great importance to improve treatment regimens for patients. Here, we investigated the effects of the glucocorticoid prednisolone on cell proliferation and Wnt signaling in homeostatic skin and intestinal tissue and compared them to the anti-regenerative effects in zebrafish fin regeneration. We also investigated a potential recovery from the glucocorticoid treatment and the impact of short-term treatment with prednisolone. We identified a dampening effect of prednisolone on Wnt signaling and proliferation in highly proliferative tissues, namely the skin and intestine, as well as reduced fin regenerate length and Wnt reporter activity in the fin. The presence of the Wnt inhibitor Dickkopf1 was enhanced in prednisolone treated skin tissue. A decreased number of mucous producing goblet cells was observed in the intestine of prednisolone treated zebrafish. Unexpectedly, proliferation in bone forming osteoblasts of the skull, homeostatic scales, as well as the brain was not decreased, opposite to the observed effects in the skin, fin, and intestine. Short-term treatment with prednisolone for a few days did not significantly alter fin regenerate length, skin cell proliferation, intestinal leukocyte number and proliferation of intestinal crypt cells. However, it affected the number of mucous-producing goblet cells in the gut. Likewise, discontinuation of prednisolone treatment for a few days saved the skin and intestine from a significant reduction of skin and intestinal cell proliferation, intestinal leukocyte number and regenerate length, but did not rescue goblet cell number. The suppressive effects of glucocorticoids in highly proliferative tissues may be relevant in the context of their therapeutic applications in patients with inflammatory diseases.

Enduring glucocorticoid-evoked exacerbation of synaptic plasticity disruption in male rats modelling early Alzheimer's disease amyloidosis

Synaptic dysfunction is a likely proximate cause of subtle cognitive impairment in early Alzheimer's disease. Soluble oligomers are the most synaptotoxic forms of amyloid ß-protein (Aß) and mediate synaptic plasticity disruption in Alzheimer's disease amyloidosis. Because the presence and extent of cortisol excess in prodromal Alzheimer's disease predicts the onset of cognitive symptoms we hypothesised that corticosteroids would exacerbate the inhibition of hippocampal synaptic long-term potentiation in a rat model of Alzheimer's disease amyloidosis. In a longitudinal experimental design using freely behaving pre-plaque McGill-R-Thy1-APP male rats, three injections of corticosterone or the glucocorticoid methylprednisolone profoundly disrupted long-term potentiation induced by strong conditioning stimulation for at least 2 months. The same treatments had a transient or no detectible detrimental effect on synaptic plasticity in wild-type littermates. Moreover, corticosterone-mediated cognitive dysfunction, as assessed in a novel object recognition test, was more persistent in the transgenic animals. Evidence for the involvement of pro-inflammatory mechanisms was provided by the ability of the selective the NOD-leucine rich repeat and pyrin containing protein 3 (NLRP3) inflammasome inhibitor Mcc950 to reverse the synaptic plasticity deficit in corticosterone-treated transgenic animals. The marked prolongation of the synaptic plasticity disrupting effects of brief corticosteroid excess substantiates a causal role for hypothalamic-pituitary-adrenal axis dysregulation in early Alzheimer's disease.

Intranasal Methylprednisolone Effectively Reduces Neuroinflammation in Mice With Experimental Autoimmune Encephalitis

Relapsing-remitting multiple sclerosis, the most common form, is characterized by acute neuroinflammatory episodes. In addition to continuous disease-modifying therapy, these relapses require treatment to prevent lesion accumulation and progression of disability. Intravenous methylprednisolone (1-2 g for 3-5 days) is the standard treatment for relapses. However, this treatment is invasive, requires hospitalization, leads to substantial systemic exposure of glucocorticoids, and can only reach modest concentrations in the central nervous system (CNS). Intranasal delivery may represent an alternative to deliver relapse treatment directly to the CNS with higher concentrations and reducing side effects. Histopathological analysis revealed that intranasal administration of methylprednisolone to mice with experimental autoimmune encephalomyelitis (EAE) suppressed the neuroinflammatory peak, and reduced immune cell infiltration and demyelination in the CNS similarly to intravenous administration. Treatment also downregulated Iba1 and GFAP expression. A similar significant reduction of IL-1β, IL-6, IL-17, IFN-γ, and TNF-α levels in the spinal cord was attained in both intranasal and intravenously treated mice. No damage in the nasal cavity was found after intranasal administration. This study demonstrates that intranasal delivery of methylprednisolone is as efficient as the intravenous route to treat neuroinflammation in EAE.

Improving the prediction of the brain disposition for orally administered drugs using BDDCS

In modeling blood-brain barrier (BBB) passage, in silico models have yielded ~80% prediction accuracy, and are currently used in early drug discovery. Being derived from molecular structural information only, these models do not take into account the biological factors responsible for the in vivo outcome. Passive permeability and P-glycoprotein (Pgp, ABCB1) efflux have been successfully recognized to impact xenobiotic extrusion from the brain, as Pgp is known to play a role in limiting the BBB penetration of oral drugs in humans. However, these two properties alone fail to explain the BBB penetration for a significant number of marketed central nervous system (CNS) agents. The Biopharmaceutics Drug Disposition Classification System (BDDCS) has proved useful in predicting drug disposition in the human body, particularly in the liver and intestine. Here we discuss the value of using BDDCS to improve BBB predictions of oral drugs. BDDCS class membership was integrated with in vitro Pgp efflux and in silico permeability data to create a simple 3-step classification tree that accurately predicted CNS disposition for more than 90% of 153 drugs in our data set. About 98% of BDDCS class 1 drugs were found to markedly distribute throughout the brain; this includes a number of BDDCS class 1 drugs shown to be Pgp substrates. This new perspective provides a further interpretation of how Pgp influences the sedative effects of H1-histamine receptor antagonists.

Pharmaceutical drug transport: the issues and the implications that it is essentially carrier-mediated only

All cells necessarily contain tens, if not hundreds, of carriers for nutrients and intermediary metabolites, and the human genome codes for more than 1000 carriers of various kinds. Here, we illustrate using a typical literature example the widespread but erroneous nature of the assumption that the 'background' or 'passive' permeability to drugs occurs in the absence of carriers. Comparison of the rate of drug transport in natural versus artificial membranes shows discrepancies in absolute magnitudes of 100-fold or more, with the carrier-containing cells showing the greater permeability. Expression profiling data show exactly which carriers are expressed in which tissues. The recognition that drugs necessarily require carriers for uptake into cells provides many opportunities for improving the effectiveness of the drug discovery process.

ACTH-dependent ultradian rhythm of corticosterone secretion

The activity of the hypothalamic-pituitary-adrenal axis is characterized by an ultradian pulsatile pattern of glucocorticoid secretion. Despite increasing evidence for the importance of pulsatility in regulating glucocorticoid-responsive gene transcription, little is known about the mechanism underlying the pulsatility of glucocorticoid synthesis and release. We tested the hypothesis that pulsatile ACTH release is critical for optimal adrenocortical function. Hypothalamic-pituitary-adrenal activity was suppressed by oral methylprednisolone, and ACTH (4 ng/h) was infused for 24h either as a constant infusion or in 5-min pulses at hourly intervals. Control methylprednisolone-treated rats had very low plasma corticosterone (CORT) levels with undetectable pulses and also had steroidogenic acute regulatory protein (StAR) and cytochrome P450 side-chain cleavage (P450scc) heteronuclear RNA levels reduced to approximately 50% of that seen in untreated animals. Pulsatile but not constant ACTH infusion restored pulsatile CORT secretion, and this was accompanied by parallel rises in StAR and P450scc heteronuclear RNA levels during the rising phase of the CORT pulse, which then fell during the falling phase. The pulsatile pattern of StAR and P450scc was paralleled by pulsatile transcription of the melanocortin 2 receptor accessory protein. Pulsatile ACTH activation of the adrenal cortex not only is critical for the secretion of CORT but also induces episodic transcription of the rate-limiting enzymes necessary for physiological steroidogenic responses. Because constant infusion of identical amounts of ACTH did not activate CORT secretion, pulsatility of ACTH provides a more effective signaling system for the activation of adrenocortical activity.

Glucocorticoid protection of oligodendrocytes against excitotoxin involving hypoxia-inducible factor-1alpha in a cell-type-specific manner

Glucocorticoids are commonly used in treating diseases with white matter lesions, including demyelinating diseases and spinal cord injury (SCI). However, glucocorticoids are ineffective in gray matter injuries, such as head injury and stroke. The differential glucocorticoid effects in white and gray matter injuries are unclear. We report here a novel mechanism of methylprednisolone (MP), a synthetic glucocorticoid widely used for treating multiple sclerosis and SCI, in protecting oligodendrocytes (OLGs) against AMPA-induced excitotoxicity, which has been implicated in the white matter injuries and diseases. The cytoprotective action of MP in OLGs is causally related to its upregulation of a neuroprotective cytokine erythropoietin (Epo). MP transactivation of Epo expression involves dual transcription factors: glucocorticoid receptor (GR) and hypoxia-inducible factor-1alpha (HIF-1alpha). Coimmunoprecipitation, chromatin immunoprecipitation analysis, yeast two-hybrid analysis, and structure modeling of three-dimensional protein-protein interactions confirm that MP induces interaction between GR DNA binding domain and HIF-1alpha PAS domain, with subsequent recruitment of HIF-1beta to transactivate Epo expression in OLGs. In contrast, MP activates GR but does not induce GR-HIF-1alpha interaction, HIF-1alpha binding to Epo enhancer/promoter, or Epo expression in cultured cortical neurons. The OLG-specific GR-HIF-1alpha transactivation of Epo provides novel insights into the development of more effective therapies for diseases affecting the white matter.

Influence of methylprednisolone on magnetic resonance and histological measures during cuprizone-induced demyelination

MRI is widely used for routine assessment of the progression of white matter injury while patients receive therapeutic agents, such as the glucocorticoid agonist methylprednisolone (MP). Given this, it is important to determine whether MRI parameters are altered by MP treatment in the absence of changes in cellular and myelin pathology. In this study, we compared magnetic resonance and histological measures during myelin injury in mice with and without short duration MP administration. Mice were scanned with a 4.7T MRI scanner before and after MP or vehicle injections using T2WI and DTI sequences and histology was performed on the brains following the second scan. Comparison of post-injection to pre-injection MRI showed a reduced T2WI intensity in the CC and an attenuated response in ADC|| and ADC perpendicular in the MP group in comparison with the vehicle group. However, quantitative analyses of myelin staining, neurofilament intensity and oligodendrocyte and microglial density were not different between the MP and the vehicle groups, indicating that the short duration MP treatment did not alter cellular and myelin pathology. These data suggest that MP could confound the validity of paraclinical measures such as ADC|| and ADC perpendicular that are otherwise being touted as markers of either axonal integrity or myelin repair.

A glucocorticoid sensitive biphasic rhythm of testosterone secretion

Studies of the hypothalamic-pituitary-adrenal (HPA) axis and the hypothalamic-pituitary-testicular (HPT) axis have revealed a reciprocal relationship between these two endocrine pathways. In rats, for example, disruption of the HPT axis alters the circadian secretion of corticosterone. Stress, on the other hand, can have varying effects on testosterone secretion in both rats and humans. Furthermore, in contrast to humans, where several pulses of testosterone secretion can be detected across the 24-h period with the largest in the morning, rats appear to exhibit a diurnal rhythm of testosterone secretion. In the present study, we used an automated blood sampling system to investigate the true circadian pattern of testosterone secretion under basal conditions and investigated how this responds to changes in levels of circulating corticosteroids. Analysis of plasma testosterone revealed the expected bimodal pattern of basal testosterone secretion. The two secretory episodes were 12.59 h +/- 41 min apart and 4.04 h +/- 16 min long, with one in the light phase and the other in the dark phase of the cycle. Interestingly, when both testosterone and corticosterone diurnal profile were compared, we found that the circadian rise in plasma corticosterone levels falls neatly between the two testosterone secretory episodes. Treatment of rats with the synthetic glucocorticoid methylprednisolone in their drinking water abolished the normal bimodal profile of testosterone secretion. These rats show transient pulses of testosterone throughout the 24 h, but no circadian pattern. By contrast, adrenalectomised rats maintain their bimodal circadian pattern, suggesting that an intact HPA axis is not necessary for generation of the endogenous HPT rhythm. Thus, although the circadian rhythm of testosterone does not depend on normal HPA function, increased levels of glucocorticoids can abolish normal HPT rhythmicity.

The mechanism of action of methylprednisolone in the treatment of multiple sclerosis

Methylprednisolone plays an important role in the current treatment of multiple sclerosis (MS), particularly in the acute phase of relapse. It acts in various ways to decrease the inflammatory cycle including: dampening the inflammatory cytokine cascade, inhibiting the activation of T cells, decreasing the extravasation of immune cells into the central nervous system, facilitating the apoptosis of activated immune cells, and indirectly decreasing the cytotoxic effects of nitric oxide and tumor necrosis factor alpha. This paper reviews the most recent observations on these mechanisms both to understand the disease mechanism and its treatment. As more becomes known about these mechanisms, it may become possible to design treatment regimes that are more specific towards both the individual and the disease state.

Oral Administration of Prednisone to Control Refractory Vertigo in Ménière's Disease: A Pilot Study

OBJECTIVE

To establish whether the oral administration of moderate doses of prednisone reduces refractory vertigo in Ménière's disease.

STUDY DESIGN

Blinded, randomized, controlled trial.

SETTING

Tertiary referral center.

PATIENTS

Patients with Ménière's disease with limited vertigo control (Class C) and severe disability (Scale 3).

INTERVENTIONS

Two groups (n = 8 per group) were treated orally with either diphenidol (25 mg/d) plus acetazolamide (250 mg/48 h) (control group), or the same treatment plus prednisone (0.35 mg/kg) daily for 18 weeks (prednisone group).

MAIN OUTCOME MEASURES

The variables evaluated were the frequency and duration of vertigo, tinnitus, aural fullness, and audiographic parameters. The clinical surveillance was performed for 12 months after prednisone withdrawal.

RESULTS

The frequency and duration of vertigo episodes were reduced by 50% and 30%, respectively, by prednisone treatment. Prednisone-treated patients manifested a significant reduction in tinnitus. No changes were observed in aural fullness or hearing. No metabolic or infectious disorders were observed.

CONCLUSION

Oral prednisone helps to control refractory vertigo in Ménière's disease. These preliminary data suggest that prednisone can be a good noninvasive antivertigo management regimen for these patients.

Glucocorticoid receptor antagonists: new tools to investigate disorders characterized by cortisol hypersecretion

Increased cortisol levels have been observed in patients suffering from a number of metabolic and psychiatric disorders. In some of these disorders a causal relationship has been suggested between the increased cortisol secretion and the observed clinical phenomena. Glucocorticoid receptor antagonists which block cortisol effects might have a benefit in both the diagnosis and treatment of these disorders. Selective glucocorticoid receptor antagonists with in vivo potency have not been described thus far, partly due to the similarity between the glucocorticoid and progesterone receptors. In the present studies, we report on three different chemical classes derived from the glucocorticoid/progestagen antagonist RU486. Selected compounds from the classes 11-monoaryl steroids, 11,21-bisaryl steroids and 11-aryl, 16-hydroxy steroids proved to be selective glucocorticoid receptor binders with in vivo antagonistic activity. Most compounds were able to pass the blood-brain barrier. These compounds offer the opportunity to investigate and possibly treat patients with a disturbed hypothalamus-pituitary-adrenal axis without side effects caused by an antiprogestagenic action.

Proinflammatory cytokines in cerebrospinal fluid in repair of thoracoabdominal aorta

BACKGROUND

Little is known about alterations of cytokine levels in cerebrospinal fluid (CSF) during thoracoabdominal aortic surgery. We measured perioperative CSF cytokine levels to determine their clinical significances.

METHODS

Perioperative serum and CSF levels of cytokine were measured in 15 adult patients undergoing repair of the descending thoracic aorta (n = 4) or thoracoabdominal aorta (n = 11). All patients underwent prosthetic replacement and perioperative CSF drainage. Serum and CSF levels of tumor necrosis factor-alpha, Interleukin- (IL-) 1beta, IL-6, IL-8, IL-10, and IL-12 were measured before operation and at 0, 6, 12, 18, 24, 48, and 72 hours postoperatively using enzyme-linked immunosorbent assays.

RESULTS

There were no hospital deaths, but 1 patient suffered paraplegia. Cerebrospinal fluid IL-8 levels peaked at immediately after operation (751.7 +/- 42.1 pg/mL versus preoperative levels, 54.9 +/- 24.6 pg/mL; p < 0.001), and the higher levels persisted for 72 hours. In contrast, serum IL-8 levels did not change and remained lower than CSF levels. The patient with paraplegia had the highest CSF IL-8 levels throughout the study period. Serum and CSF levels of tumor necrosis factor-alpha, IL-1beta, IL-6, and IL-12 did not significantly change. Serum and CSF levels of IL-10 were significantly elevated after operation compared with preoperative levels. In contrast to IL-8, serum IL-10 levels surpassed CSF levels.

CONCLUSIONS

Cerebrospinal fluid IL-8 levels are significantly elevated in thoracoabdominal aortic operation, and may be the most sensitive to the inflammatory response in the ischemic spinal cord injury. Persistent elevation of CSF IL-8 levels may be predictive of further development of neurologic deficits, and a reduction of proinflammatory cytokine levels may be a beneficial effect of CSF drainage, but this requires further investigation.

Neuronal cell death in the ischemic spinal cord: the effect of methylprednisolone

BACKGROUND

Cell death occurs by either necrosis or apoptosis. The role of apoptosis in the neuronal degeneration after ischemia remains to be defined. We studied (1) the nature of neuronal death and (2) the neuroprotective action of methylprednisolone in a rat model of spinal cord ischemia.

METHODS

Spinal cord ischemia was induced in adult Long-Evans rats by occluding the aortic arch for 14 minutes and simultaneously equilibrating the femoral artery pressure to the atmospheric pressure. Twenty rats were subjected to ischemia without treatment and another twenty to ischemia after treatment with methylprednisolone (30 mg/kg, 4 hours before ischemia). The animals were sacrificed and the lumbar spinal cords were examined on postoperative days 1 and 2.

RESULTS

On day 1, neurons with morphology indicative of apoptosis were present in the gray matter. Their numbers increased from the ventral to the dorsal location. There were significantly fewer apoptotic neurons in the dorsal horn of the methylprednisolone-treated animals. DNA obtained from the spinal cord of untreated rats on days 1 and 2 showed laddering after electrophoresis, a feature of apoptosis. Pretreatment with methylprednisolone inhibited the development of DNA laddering. Methylprednisolone treatment was not associated with significantly improved neurologic function in the postoperative period.

CONCLUSIONS

Apoptotic neuronal death occurs in the rat spinal cord after transient ischemia and is attenuated by pretreatment with methylprednisolone.

Neuroprotective therapy for argon-laser induced retinal injury

Laser photocoagulation treatment of the central retina is often complicated by an immediate side effect of visual impairment, caused by the unavoidable laser-induced destruction of the normal tissue lying adjacent to the lesion and not affected directly by the laser beam. Furthermore, accidental laser injuries are at present untreatable. A neuroprotective therapy for salvaging the normal tissue might enhance the benefit obtained from treatment and allow safe perifoveal photocoagulation. We have developed a rat model for studying the efficacy of putative neuroprotective compounds in ameliorating laser-induced retinal damage. Four compounds were evaluated: the corticosteroid methylprednisolone, the glutamate-receptor blocker MK-801, the anti-oxidant enzyme superoxide dismutase, and the calcium-overload antagonist flunarizine. The study was carried out in two steps: in the first, the histopathological development of retinal laser injuries was studied. Argon laser lesions were inflicted in the retinas of 18 pigmented rats. The animals were killed after 3, 20 or 60 days and their retinal lesions were evaluated under the light microscope. The laser injury mainly involved the outer layers of the retina, where it destroyed significant numbers of photoreceptor cells. Over time, evidence of two major histopathological processes was observed: traction of adjacent normal retinal cells into the central area of the lesion forming an internal retinal bulging, and a retinal pigmented epithelial proliferative reaction associated with subretinal neovascularization and invasion of the retinal lesion site by phagocytes. The neuroprotective effects of each of the four compounds were verified in a second step of the study. For each drug tested, 12 rats were irradiated with argon laser inflictions: six of them received the tested agent while the other six were treated with the corresponding vehicle. Twenty days after laser exposure, the rats were killed and their lesions were subjected to image-analysis morphometry. The extent of retinal destruction was assessed by measuring the lesion diameter and the amount of photoreceptor cell loss in the outer nuclear layer. Methylprednisolone and MK-801 were shown to ameliorate laser-induced retinal damage, whereas both superoxide dismutase and flunarizine were ineffective. Furthermore, MK-801 diminished the proliferative reaction of the retinal pigment epithelial cells. On the basis of our results we suggest that the pigmented rat model is suitable for studying and screening various compounds for their neuroprotective efficacy in treating retinal laser injury. We further suggest that glutamate might play a key role in mediating retinal injury induced by laser irradiation.