The need for mathematical modelling of spatial drug distribution within the brain.

The blood brain barrier (BBB) is the main barrier that separates the blood from the brain. Because of the BBB, the drug concentration-time profile in the brain may be substantially different from that in the blood. Within the brain, the drug is subject to distributional and elimination processes: diffusion, bulk flow of the brain extracellular fluid (ECF), extra-intracellular exchange, bulk flow of the cerebrospinal fluid (CSF), binding and metabolism. Drug effects are driven by the concentration of a drug at the site of its target and by drug-target interactions. Therefore, a quantitative understanding is needed of the distribution of a drug within the brain in order to predict its effect. Mathematical models can help in the understanding of drug distribution within the brain. The aim of this review is to provide a comprehensive overview of system-specific and drug-specific properties that affect the local distribution of drugs in the brain and of currently existing mathematical models that describe local drug distribution within the brain. Furthermore, we provide an overview on which processes have been addressed in these models and which have not. Altogether, we conclude that there is a need for a more comprehensive and integrated model that fills the current gaps in predicting the local drug distribution within the brain.

Comparison among ACR1997, SLICC and the new EULAR/ACR classification criteria in childhood-onset systemic lupus erythematosus

Abstract Background: To date there are no specific classification criteria for childhood-onset systemic lupus erythematosus (cSLE). This study aims to compare the performance among the American College of Rheumatology (ACR) 1997, the Systemic Lupus International Collaborating Clinics criteria (SLICC) and the new European League Against Rheumatism (EULAR)/ACR criteria, in a cSLE cohort. Methods: We conducted a medical chart review study of cSLE cases and controls with defined rheumatic diseases, both ANA positive, to establish each ACR1997, SLICC and EULAR/ACR criterion fulfilled, at first visit and 1-year-follow-up. Results: Study population included 122 cSLE cases and 89 controls. At first visit, SLICC criteria had higher sensitivity than ACR 1997 (89.3% versus 70.5%, p < 0.001), but similar specificity (80.9% versus 83.2%, p = 0.791), however performance was not statistically different at 1-year-follow-up. SLICC better scored in specificity compared to EULAR/ACR score ≥ 10 at first visit (80.9% versus 67.4%, p = 0.008) and at 1-year (76.4% versus 58.4%, p = 0.001), although sensitivities were similar. EULAR/ACR criteria score ≥ 10 exhibited higher sensitivity than ACR 1997 (87.7% versus 70.5%, p < 0.001) at first visit, but comparable at 1-year, whereas specificity was lower at first visit (67.4% versus 83.2%, p = 0.004) and 1-year (58.4% versus 76.4%, p = 0.002). A EULAR/ACR score ≥ 13 against a score ≥ 10, resulted in higher specificity, positive predictive value, and cut-off point accuracy. Compared to SLICC, a EULAR/ACR score ≥ 13 resulted in lower sensitivity at first visit (76.2% versus 89.3%, p < 0.001) and 1-year (91% versus 97.5%, p = 0.008), but similar specificities at both assessments. When compared to ACR 1997, a EULAR/ACR total score ≥ 13, resulted in no differences in sensitivity and specificity at both observation periods. Conclusions: In this cSLE population, SLICC criteria better scored at first visit and 1-year-follow-up. The adoption of a EULAR/ACR total score ≥ 13 in this study, against the initially proposed ≥10 score, was most appropriate to classify cSLE. Further studies are necessary to address if SLICC criteria might allow fulfillment of cSLE classification earlier in disease course and may be more inclusive of cSLE subjects for clinical studies.

Cell growth of immortalized arachnoid cells in the presence of fibroblasts and blood products.

OBJECT: The pathophysiology of non-obstructive hydrocephalus involves alteration in cerebrospinal fluid (CSF) pathways. The exact mechanism is unknown, but as arachnoid CSF egress is a major route of CSF removal, damage or alteration to the growth of arachnoid cells may influence the rate of CSF absorption. We investigated the effect of soluble factors secreted by fibroblasts and the presence of blood products on arachnoid cell growth. METHODS: An immortalized arachnoid cell line was developed and cells were grown on semipermeable membranes in a culture chamber. Arachnoid cells were plated in Transwells®, with fibroblasts separated from the arachnoid cells. Cell phenotype was analyzed and cell growth rates were determined by manual counts. Similar experiments were conducted with biliverdin, bilirubin, as well as fibroblast challenge. DNA content in the cell cultures was then determined as corroborative data. Cell counts for the additional arachnoid cell lines were calculated at each day and represented the controls. RESULTS: Cell counts increased with each time point. Arachnoid cells in the three experimental conditions showed a statistically significant decrease in cell counts for each day when compared to the control group. Post hoc analysis showed differences between the control and experimental conditions but no significant difference between groups. The DNA content for each experimental condition was reduced at all time points when compared to the control arachnoid cells, but only became statistically significant at day 7. CONCLUSION: Inflammation and hemorrhage are two common conditions associated with the development of hydrocephalus. The arachnoid membrane is exposed to fibroblasts and blood products (bilirubin, biliverdin) in these conditions, and their effect on arachnoid cell growth was studied. We have shown that arachnoid cell growth decreases in the presence of fibroblasts, bilirubin, and biliverdin. Given its intimate relationship with CSF, it is possible that the decreased growth of arachnoid cells may affect absorption and thus contribute to the development of hydrocephalus.

Temozolomide or bevacizumab for spinal cord high-grade gliomas.

High-grade gliomas of the spinal cord are rare tumors, traditionally managed with surgery and radiotherapy. Once patients fail standard treatment, many receive some chemotherapy, although the data supporting such is limited. We reviewed our experience treating high-grade gliomas of the spinal cord with standard intracranial regimens including temozolomide and bevacizumab. Outcomes investigated include radiographic response, clinical response, progression-free survival, and overall survival. We identified eight patients who were treated with temozolomide and six who were treated with bevacizumab. Temozolomide was administered to three patients at initial diagnosis and five patients at recurrence after failing prior radiotherapy. For the recurrent patients, the median time-to-progression was 6.6 months (range 1-40 months) and the median overall survival from initiation of temozolomide was 16.6 months (range 1.2-64.5 months). We identified six patients who received bevacizumab at the time of recurrence. MRI demonstrated a partial response in five patients which also correlated with clinical improvement. The median time to progression was 20.7 months (range 3.3-29.9 months) and median overall survival was 22.8 months (range 3.3-31.8 months). This retrospective review suggests that temozolomide and bevacizumab may be beneficial in spinal cord high-grade gliomas. The compact architecture of the spinal cord makes bevacizumab a particularly appealing agent due to the drug's effect on peritumoral edema and mass effect.

Permeability of the arachnoid and pia mater. The role of ion channels in the leptomeningeal physiology.

PURPOSE: The purpose of this paper is to study the ionic permeability of the leptomeninges related to the effect of ouabain (sodium-potassium-ATPase inhibitor) and amiloride (epithelial sodium channel (ENaC) inhibitor) on the tissue, as well as identify the presence of ion channels. METHODS: Cranial leptomeningeal samples from 26 adult sheep were isolated. Electrophysiological measurements were performed with Ussing system and transmembrane resistance values (R(TM) in Ω*cm(2)) obtained over time. Experiments were conducted with the application of ouabain 10(-3) M or amiloride 10(-5) M at the arachnoidal and pial sides. Immunohistochemical studies of leptomeningeal tissue were prepared with alpha-1 sodium-potassium-ATPase (ATP1A1), beta-ENaC, and delta-ENaC subunit antibodies. RESULTS: The application of ouabain at the arachnoidal side raised the transmembrane resistance statistically significantly and thus decreased its ionic permeability. The addition of ouabain at the pial side led also to a significant but less profound increment in transmembrane resistance. The addition of amiloride at the arachnoidal or pial side did not produce any statistical significant change in the R(TM) from controls (p > 0.05). Immunohistochemistry confirmed the presence of the ATP1A1 and beta- and delta-ENaC subunits at the leptomeninges. CONCLUSIONS: In summary, leptomeningeal tissue possesses sodium-potassium-ATPase and ENaC ion channels. The application of ouabain alters the ionic permeability of the leptomeninges thus reflecting the role of sodium-potassium-ATPase. Amiloride application did not alter the ionic permeability of leptomeninges possibly due to localization of ENaC channels towards the subarachnoid space, away from the experimental application sites. The above properties of the tissue could potentially be related to cerebrospinal fluid turnover at this interface.

Evaluation of tenoxicam on prevention of arachnoiditis in rat laminectomy model.

Post laminectomy arachnoiditis has been shown by experiments with rats and post operative radiological imaging in humans. The purpose of this experimental study was to determine the efficacy of tenoxicam in preventing arachnoiditis in rats. Twenty-four Wistar rats were divided into two groups, and L3 laminectomy was performed. In the tenoxicam group, 0.5 mg/kg tenoxicam was applied intraperitoneally. Normal saline was applied intraperitoneally in the control group. Later, the rats were killed at weeks 3 and 6, and the laminectomy sites were evaluated pathologically for arachnoiditis. The results showed that 6 weeks after surgery, the tenoxicam group showed lowest arachnoiditis grades. However, statistically significant difference was not found in arachnoiditis between the control group and the tenoxicam group. Based on these findings it is concluded that application of the tenoxicam after lumbar laminectomy did not effectively reduce arachnoiditis. Performing the most effective surgical technique without damage around tissue in a small surgical wound and having meticulous hemostasis in surgery seem to be the key for preventing arachnoiditis effectively.

Arachnoid cells on culture plates and collagen scaffolds: phenotype and transport properties.

INTRODUCTION: The arachnoid tissue is a critical component of cerebrospinal fluid removal. Failure of that function results in hydrocephalus, a serious medical condition. The purpose of this study was to characterize arachnoid cell transport in culture and on three-dimensional collagen scaffold. METHODS: Arachnoid cells were harvested from rat brainstems and cultured onto bilayered bovine collagen scaffolds. Cell growth and phenotype (protein expression and morphometry) were determined. Permeability and hydraulic conductivity were quantified. RESULTS: Cells harvested from the anterior brainstem surface exhibited arachnoid cell phenotype (positive for vimentin, desmoplakin, and cytokeratin), readily penetrated the collagen scaffold, and doubled approximately every 2-3 days. The transepithelial electrical resistance value for a monolayer of cells was 160 Ω cm(2) and the permeability of indigo carmine was 6.7×10(-6)±1.1×10(-6) cm/s. Hydraulic conductivity of the collagen construct was 6.39 mL/min/mmHg/cm(2). CONCLUSION: Cells isolated from the anterior brain stem exhibited the same phenotype as those found in the native tissue and exhibited aspects of barrier function found in vivo. These studies suggest that an ex vivo model for the arachnoid granulation can be developed.

NF2/merlin is a novel negative regulator of mTOR complex 1, and activation of mTORC1 is associated with meningioma and schwannoma growth.

Inactivating mutations of the neurofibromatosis 2 (NF2) gene, NF2, result predominantly in benign neurological tumors, schwannomas and meningiomas, in humans; however, mutations in murine Nf2 lead to a broad spectrum of cancerous tumors. The tumor-suppressive function of the NF2 protein, merlin, a membrane-cytoskeleton linker, remains unclear. Here, we identify the mammalian target of rapamycin complex 1 (mTORC1) as a novel mediator of merlin's tumor suppressor activity. Merlin-deficient human meningioma cells and merlin knockdown arachnoidal cells, the nonneoplastic cell counterparts of meningiomas, exhibit rapamycin-sensitive constitutive mTORC1 activation and increased growth. NF2 patient tumors and Nf2-deficient mouse embryonic fibroblasts demonstrate elevated mTORC1 signaling. Conversely, the exogenous expression of wild-type merlin isoforms, but not a patient-derived L64P mutant, suppresses mTORC1 signaling. Merlin does not regulate mTORC1 via the established mechanism of phosphoinositide 3-kinase-Akt or mitogen-activated protein kinase/extracellular signal-regulated kinase-mediated TSC2 inactivation and may instead regulate TSC/mTOR signaling in a novel fashion. In conclusion, the deregulation of mTORC1 activation underlies the aberrant growth and proliferation of NF2-associated tumors and may restrain the growth of these lesions through negative feedback mechanisms, suggesting that rapamycin in combination with phosphoinositide 3-kinase inhibitors may be therapeutic for NF2.

Incidence of central nervous system involvement in chronic lymphocytic leukemia and outcome to treatment.

Leptomeningeal involvement in patients with CLL is relatively rare and the prognosis is usually considered to be poor. The authors reviewed all CLL patients treated in a tertiary referral center to assess the incidence and outcome of leptomeningeal involvement (LI) in CLL. They found an incidence of 1-2% of LI. Most of the patients with LI had a longterm survival, despite failure to clear the cerebrospinal fluid from tumor cells.

Modeling NF2 with human arachnoidal and meningioma cell culture systems: NF2 silencing reflects the benign character of tumor growth.

Meningiomas, common tumors arising from arachnoidal cells of the meninges, may occur sporadically, or in association with the inherited disorder, neurofibromatosis 2 (NF2). Most sporadic meningiomas result from NF2 inactivation, resulting in loss of tumor suppressor merlin, implicated in regulating membrane-cytoskeletal organization. To investigate merlin function in an authentic target cell type for NF2 tumor formation, we established primary cultures from genetically-matched meningioma and normal arachnoidal tissues. Our studies revealed novel and distinct cell biological and biochemical properties unique to merlin-deficient meningioma cells compared to merlin-expressing arachnoidal and meningioma cells, and other NF2-deficient cell types. Merlin-deficient meningioma cells displayed cytoskeletal and cell contact defects, altered cell morphology and growth properties, most notably cell senescence, implicating the activation of senescence pathways in limiting benign meningioma growth. Merlin suppression by RNAi in arachnoidal cells replicated merlin-deficient meningioma features, thus establishing these cell systems as disease-relevant models for studying NF2 tumorigenesis.

Serum and CSF vitamin A concentrations in idiopathic intracranial hypertension.

BACKGROUND: Elevated serum retinol, CSF retinol, and serum retinol binding protein (RBP) levels have been found in some patients with idiopathic intracranial hypertension (IIH), but serum and CSF retinol levels have not been studied in matched serum and CSF samples in patients with IIH. OBJECTIVE: To determine whether serum and CSF vitamin A concentrations are associated with IIH. METHODS: The serum and CSF retinol concentrations were prospectively assessed in 20 patients with IIH and 20 control subjects. RESULTS: CSF retinol concentration was higher in the patient group (median 575.91 nM) vs the control group (median 63.35 nM) (p < 0.05). There was no difference in serum retinol levels between control subjects (median 896.51 nM) and patients (median 1,002.62 nM) (p = 0.10). There was an association between higher vitamin A levels (> 250 nM) and IIH (p = 0.039). There was a correlation between CSF and serum retinol levels in patients (r = 0.82) and control subjects (r = 0.66). CONCLUSION: Elevated CSF retinol concentration is associated with idiopathic intracranial hypertension (IIH), but serum retinol level is not associated with IIH.

Spatial learning transiently disturbed by intraventricular administration of ouabain.

The presence of sodium-potassium-adenosine triphosphatase (Na+,K+-ATPase) on the surface of arachnoid cells indicates that active transport of electrolytes and water occurs there. Previously, we accidentally found that intraventricular administration of TGF-beta1 impaired rat spatial learning. Levels of Na+,K+ -ATPase were decreased in arachnoid cells with fibrosis. To characterize the role of the Na+,K+ -ATPase, Wistar rats were intraventricularly administered a total of 200 microl of ouabain, at concentrations of 10(-5), 10(-4) and 10(-3) M, for one week with an osmotic pump, and were examined with a Morris water maze. Latency for reaching the platform did not significantly differ between ouabain-administered rats and controls. Spatial learning was impaired in a dose-dependent manner. Na+,K+ -ATPase activity of arachnoid cells ceased during ouabain administration, and recovered completely three weeks after the end of ouabain administration. The present results suggest that the Na+,K+ -ATPase on the surface of arachnoid cells contributes to maintenance of rat spatial learning.

Release of substance P, calcitonin gene-related peptide and prostaglandin E2 from rat dura mater encephali following electrical and chemical stimulation in vitro.

Neurogenic inflammation of the dura, expressed in plasma extravasation and vasodilatation, putatively contributes to different types of headache. A novel in vitro preparation of the fluid-filled skull cavities was developed to measure mediator release from dura mater encephali upon antidromic electrical stimulation of the trigeminal ganglion and after application of a mixture of inflammatory mediators (serotonin, histamine and bradykinin, 10(-5) M each, pH 6.1) to the arachnoid side of rat dura. The release of calcitonin gene-related peptide, substance P and prostaglandin E2 from dura mater was measured in 5-min samples of superfusates using enzyme immunoassays. Orthodromic chemical and antidromic electrical stimulation of dural afferents caused significant release of calcitonin gene-related peptide (2.8- and 4.5-fold of baseline). The neuropeptide was found to be increased during the 5-min stimulation period and returned to baseline (20.9 +/- 12 pg/ml) in the sampling period after stimulation. In contrast, release of substance P remained at baseline levels (19.3 +/- 11 pg/ml) throughout the experiment. Prostaglandin E2 release was elevated during chemical and significantly also after antidromic electrical stimulation (6- and 4.2-fold of baseline, which was 305 +/- 250 pg/ml). Prostaglandin E2 release outlasted the stimulation period for at least another 5 min. The data support the hypothesis of neurogenic inflammation being involved in headaches and provide new evidence for prostaglandin E2 possibly facilitating meningeal nociceptor excitation and, hence, pain.

Distribution and induction of cytochrome P450 1A1 and 1A2 in rat brain.

Cytochromes P450 1A1 and 1A2 are involved in the oxidation of a wide spectrum of endogenous compounds and xenobiotics. Although their presence has been repeatedly confirmed in brain tissue, reports regarding their distribution in the brain are often contradictory. In the present study the possibility was examined that CYP1A1 and CYP1A2 are localized and inducible in the brain-CSF barrier and regions with a leaky blood brain barrier, where they may serve as a protective metabolic barrier. CYP1A1 and CYP1A2 levels were determined in subcellular fractions of multiple brain regions, as well as tissue homogenates of circumventricular organs, and the meninges by Western blotting and catalytic activity in control male rats and rats treated with the inducer beta-naphthoflavone (BNF). In control animals CYP1A1 immunoreactive protein was undetectable in regional brain microsomes or whole tissue homogenates of the arachnoid, dura mater, choroid plexus, pineal gland, median eminence, and pituitary. However, low levels of ethoxyresorufin O-deethylase (EROD) activity were observed in homogenates of the arachnoid, dura mater, choroid plexus, pineal gland, and pituitary. Western blotting revealed only low levels of CYP1A2 immunoreactive protein in brain microsomes from the cortex, cerebellum, brainstem, thalamus, hippocampus, and striatum from control animals. Following BNF treatment, EROD activity was induced 12-42-fold in the arachnoid, choroid plexus, dura mater, pineal gland, pituitary, and median eminence. Western blot analysis revealed CYP1A1 to be induced in the arachnoid, dura mater, choroid plexus, pineal gland, and pituitary, while CYP1A2 was undetectable. No induction of CYP1A1 or CYP1A2 protein was observed in brain microsomes from the olfactory bulb, cortex, striatum, hippocampus, cerebellum, or brainstem following BNF treatment, providing that the arachnoid membranes and choroid plexus had been carefully removed prior to brain dissection. Neither CYP1A1, 1A2 protein, nor EROD activity were detected in purified brain mitochondria, regardless of treatment or region. In conclusion, catalytically active CYP1A1 is located in the meninges as well as certain circumventricular organs, is inducible by BNF, and appears to be absent or expressed constitutively at very low levels in the majority of the brain parenchyma. The localization of CYP1A1 in the blood-CSF barrier and circumventricular tissues likely plays a role in protecting the brain from xenobiotics.

Effect of neurotropin on cerebral edema, calcium and other elements in mice subarachnoidally injected with carrageenan.

Neurotropin, an inhibitor of the kallikrein-kinin system, was therapeutically i.p. administered to mice with brain inflammation induced by subarachnoidal injection of carrageenan. Brain water content was determined by the wet/dry weight ratio. The concentrations of cerebral Ca, K, Mn, Fe, Cu, Zn, Se, Rb, and Sr were measured by particle-induced X-ray emission. It was found that neurotropin dose dependently reduced brain water content. The mean concentration of cerebral calcium was significantly lower in the neurotropin-treated group than that in the non-treated group, suggesting less cell damage. Since it has been reported that dexamethasone and some prostaglandin inhibitors have no effect on brain swelling in this model and that, in contrast to these drugs, neurotropin has only a weak inhibiting activity on carrageenan-induced paw swelling, it is hypothesized that the kallikrein-kinin system is differently implicated in cerebral and peripheral inflammation.

[Morphogenesis of experimental neuroleukemia]. / Morfogenez éksperimental'nogo neiroleikoza.

22 mice with L-1210 leukemia treated with quinoline dibromide were studied histologically. Two ways of the development of leptomeningeal infiltrates in the brain are established. The first is due to the growth of uninhibited by treatment bone-marrow leukemic infiltrates (LI) of the skull, while the second-when the above infiltrates are suppressed-due to the proliferation of leukemic cells penetrating from the dura mater to the leptomeninges protected by the hematoencephalic barrier from the effect of anticancer drugs. when the recurrence of leukemia occurs the growth of bone-marrow LI continues resulting in the additional migration of leukemic cells to the leptomeninges. These ways of the leptomeninx LI formation should be taken into consideration in the leukemia treatment.

A pilot investigation of poloxamer 407 for the prevention of leptomeningeal adhesions in the rabbit.

Leptomeningeal adhesion formation frequently complicates operations and diseases of the central nervous system. Chronic adhesive arachnoiditis may follow intraspinal surgery for disc, tumor, and closure of myelomeningocele, eventually producing pain and declining neurological status of the patient. Reoperation for scar removal is seldom successful as the arachnoidal adhesions reform. Poloxamer 407 (P407) has been shown to reduce postoperative peritoneal adhesion formation in rats and golden hamsters. In a rabbit model, we investigated the potential of P407 to prevent the production of arachnoidal adhesions and nerve root scarring following laminectomy and surgical meningeal injury. The lumbar spinal roots of 8 New Zealand white rabbits were surgically isolated under magnification. One root sleeve axilla was opened and immediately closed with 10-0 suture (control site) and a second root sleeve axilla was opened, P407 injected, and closed with 10-0 suture (treatment site). Five of 7 rabbits treated with P407 and followed for 7-42 days showed no arachnoidal adhesions at the level of the nerve root. Four New Zealand white rabbits had the lamina removed, and the dura over the spinal cord was opened at two sites separated by one to two lumbar segments. At one site P407 was inserted beneath the dura following durotomy, and the other site was opened in a similar fashion and immediately closed without the insertion of P407. There was a 50% reduction in leptomeningeal adhesion formation with the use of P407. P407 may be useful in neurosurgery for the prevention of arachnoidal adhesions.

The etiology of focal spinal arachnoiditis. An experimental study.

Focal arachnoiditis and back pain have been attributed to potentially irritating substances leaking into the spinal canal from the lumbar intervertebral disc or facet joints. Through experimentation this hypothesis was tested: the nucleus pulposus (escaping from the intervertebral disc), lactic acid (from anaerobic glycolysis in the disc), chondroitin sulfate (a component of glycosaminoglycans in the disc), or synovial fluid (from degenerating facet joints) causes inflammation in the meninges if it contacts the dura mater. The test and control substances were injected into the epidural space of monkeys. Twelve weeks later the animals were killed; the dural sac was exposed by total lumbar laminectomy, grossly inspected, and then removed, fixed, sectioned, stained, and examined microscopically. Nucleus pulposus produced significant fibrosus in the arachnoid and epidural spaces; the other substances did not cause fibrosus or inflammation. The study suggests that leakage of nucleus pulposus into the epidural space causes an inflammatory response in the arachnoid and epidural spaces.

Effect of lidocaine on the meninges in an experimental animal model.

Arachnoiditis has been reported in patients who had received previous epidural injections of anesthetic agents. The purpose of this study was to determine if epidural injections of lidocaine are sufficient to cause arachnoiditis. Four monkeys that received a single epidural injection of lidocaine hydrochloride 1% were compared to four controls that had epidural injections of 0.9% saline. Four dogs that had multiple epidural injections of lidocaine hydrochloride 1% were compared to four controls that had multiple injections of saline. All animals were killed on the eighty-fourth day of the experiment. The dural sac, containing nerve roots and spinal cord, was removed intact from the lumbar spinal canal, fixed, sectioned, stained, and examined microscopically for evidence of arachnoid inflammation and fibrosis. No significant changes were found in the treated animals. Lidocaine hydrochloride 1% injected singly or repeatedly in the epidural space does not appear to be a cause of significant chronic meningeal reaction.