Reduction of astrogliosis and microgliosis by cerebrospinal fluid shunting in experimental hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Reactive gliosis has the potential to alter biomechanical properties of the brain, impede neuronal regeneration and affect plasticity. Determining the onset and progression of reactive astrogliosis and microgliosis due to hydrocephalus is important for designing better clinical treatments.</p> <p>Methods</p> <p>Reactive astrogliosis and microgliosis were evaluated as the severity of hydrocephalus increased with age in hydrocephalic H-Tx rats and control littermates. Previous studies have suggested that gliosis may persist after short-term drainage (shunt treatment) of the cerebrospinal fluid. Therefore shunts were placed in 15d hydrocephalic rats that were sacrificed after 6d (21d of age) or after 21d (36d of age). Tissue was processed for Western blot procedures and immunohistochemistry, and probed for the astrocytic protein, Glial Fibrillary Acidic Protein (GFAP) and for microglial protein, Isolectin B4 (ILB4).</p> <p>Results</p> <p>In the parietal cortex of untreated hydrocephalic animals, GFAP levels increased significantly at 5d and at 12d compared to age-matched control rats. There was a continued increase in GFAP levels over control at 21d and at 36d. Shunting prevented some of the increase in GFAP levels in the parietal cortex. In the occipital cortex of untreated hydrocephalic animals, there was a significant increase over control in levels of GFAP at 5d. This trend continued in the 12d animals, although not significantly. Significant increases in GFAP levels were present in 21d and in 36d animals. Shunting significantly reduced GFAP levels in the 36d shunted group. Quantitative grading of immuno-stained sections showed similar changes in GFAP stained astrocytes.</p> <p>Immuno-stained microglia were altered in shape in hydrocephalic animals. At 5d and 12d, they appeared to be developmentally delayed with a lack of processes. Older 21d and 36d hydrocephalic animals exhibited the characteristics of activated microglia, with thicker processes and enlarged cell bodies. Following shunting, fewer activated microglia were present.</p> <p>Histologic examination of the periventricular area and the periaqueductal area showed similar findings with the 21d and 36d animals having increased populations of both astrocytes and microglia which were reduced following shunting with a more dramatic reduction in the long term shunted animals.</p> <p>Conclusion</p> <p>Overall, these results suggest that reactive astrocytosis and microgliosis are associated with progressive untreated ventriculomegaly, but that shunt treatment can reduce the gliosis occurring with hydrocephalus.</p

Low levels of amyloid-beta and its transporters in neonatal rats with and without hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Previous studies in aging animals have shown that amyloid-beta protein (Aβ) accumulates and its transporters, low-density lipoprotein receptor-related protein-1 (LRP-1) and the receptor for advanced glycation end products (RAGE) are impaired during hydrocephalus. Furthermore, correlations between astrocytes and Aβ have been found in human cases of normal pressure hydrocephalus (NPH) and Alzheimer's disease (AD). Because hydrocephalus occurs frequently in children, we evaluated the expression of Aβ and its transporters and reactive astrocytosis in animals with neonatal hydrocephalus.</p> <p>Methods</p> <p>Hydrocephalus was induced in neonatal rats by intracisternal kaolin injections on post-natal day one, and severe ventriculomegaly developed over a three week period. MRI was performed on post-kaolin days 10 and 21 to document ventriculomegaly. Animals were sacrificed on post-kaolin day 21. For an age-related comparison, tissue was used from previous studies when hydrocephalus was induced in a group of adult animals at either 6 months or 12 months of age. Tissue was processed for immunohistochemistry to visualize LRP-1, RAGE, Aβ, and glial fibrillary acidic protein (GFAP) and with quantitative real time reverse transcriptase polymerase chain reaction (qRT-PCR) to quantify expression of LRP-1, RAGE, and GFAP.</p> <p>Results</p> <p>When 21-day post-kaolin neonatal hydrocephalic animals were compared to adult (6–12 month old) hydrocephalic animals, immunohistochemistry demonstrated levels of Aβ, RAGE, and LRP-1 that were substantially lower in the younger animals; in contrast, GFAP levels were elevated in both young and old hydrocephalic animals. When the neonatal hydrocephalic animals were compared to age-matched controls, qRT-PCR demonstrated no significant changes in Aβ, LRP-1 and RAGE. However, immunohistochemistry showed very small increases or decreases in individual proteins. Furthermore, qRT-PCR indicated statistically significant increases in GFAP.</p> <p>Conclusion</p> <p>Neonatal rats with and without hydrocephalus had low expression of Aβ and its transporters when compared to adult rats with hydrocephalus. No statistical differences were observed in Aβ and its transporters between the control and hydrocephalic neonatal animals.</p

Minocycline inhibits glial proliferation in the H-Tx rat model of congenital hydrocephalus

<p>Abstract</p> <p>Background</p> <p>Reactive astrocytosis and microgliosis are important features of the pathophysiology of hydrocephalus, and persistent glial "scars" that form could exacerbate neuroinflammation, impair cerebral perfusion, impede neuronal regeneration, and alter biomechanical properties. The purpose of this study was to determine the efficacy of minocycline, an antibiotic known for its anti-inflammatory properties, to reduce gliosis in the H-Tx rat model of congenital hydrocephalus.</p> <p>Methods</p> <p>Minocycline (45 mg/kg/day i.p. in 5% sucrose at a concentration of 5-10 mg/ml) was administered to hydrocephalic H-Tx rats from postnatal day 15 to day 21, when ventriculomegaly had reached moderate to severe stages. Treated animals were compared to age-matched non-hydrocephalic and untreated hydrocephalic littermates. The cerebral cortex (both gray matter laminae and white matter) was processed for immunohistochemistry (glial fibrillary acidic protein, GFAP, for astrocytes and ionized calcium binding adaptor molecule, Iba-1, for microglia) and analyzed by qualitative and quantitative light microscopy.</p> <p>Results</p> <p>The mean number of GFAP-immunoreactive astrocytes was significantly higher in untreated hydrocephalic animals compared to both types of controls (<it>p </it>< 0.001). Minocycline treatment of hydrocephalic animals reduced the number of GFAP immunoreactive cells significantly (<it>p </it>< 0.001). Likewise, the mean number of Iba-1 immunoreactive microglia was significantly higher in untreated hydrocephalic animals compared to both types of controls (<it>p </it>< 0.001). Furthermore, no differences in the numbers of GFAP-positive astrocytes or Iba-1-positive microglia were noted between control animals receiving no minocycline and control animals receiving minocycline, suggesting that minocycline does not produce an effect under non-injury conditions. Additionally, in six out of nine regions sampled, hydrocephalic animals that received minocycline injections had significantly thicker cortices when compared to their untreated hydrocephalic littermates.</p> <p>Conclusions</p> <p>Overall, these data suggest that minocycline treatment is effective in reducing the gliosis that accompanies hydrocephalus, and thus may provide an added benefit when used as a supplement to ventricular shunting.</p

Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordThere is another record in ORE for this publication: http://hdl.handle.net/10871/33419The choroid plexus epithelium (CPE) secretes higher volumes of fluid (cerebrospinal fluid, CSF) than any other epithelium and simultaneously functions as the blood-CSF barrier to gate immune cell entry into the central nervous system. Posthemorrhagic hydrocephalus (PHH), an expansion of the cerebral ventricles due to CSF accumulation following intraventricular hemorrhage (IVH), is a common disease usually treated by suboptimal CSF shunting techniques. PHH is classically attributed to primary impairments in CSF reabsorption, but little experimental evidence supports this concept. In contrast, the potential contribution of CSF secretion to PHH has received little attention. In a rat model of PHH, we demonstrate that IVH causes a Toll-like receptor 4 (TLR4)- and NF-κB-dependent inflammatory response in the CPE that is associated with a ∼3-fold increase in bumetanide-sensitive CSF secretion. IVH-induced hypersecretion of CSF is mediated by TLR4-dependent activation of the Ste20-type stress kinase SPAK, which binds, phosphorylates, and stimulates the NKCC1 co-transporter at the CPE apical membrane. Genetic depletion of TLR4 or SPAK normalizes hyperactive CSF secretion rates and reduces PHH symptoms, as does treatment with drugs that antagonize TLR4-NF-κB signaling or the SPAK-NKCC1 co-transporter complex. These data uncover a previously unrecognized contribution of CSF hypersecretion to the pathogenesis of PHH, demonstrate a new role for TLRs in regulation of the internal brain milieu, and identify a kinase-regulated mechanism of CSF secretion that could be targeted by repurposed US Food and Drug Administration (FDA)-approved drugs to treat hydrocephalus.We thank D.R. Alessi (Dundee) and R.P. Lifton (Rockefeller) for their support. K.T.K. is supported by the March of Dimes Basil O'Connor Award, a Simons Foundation SFARI Grant, the Hydrocephalus Association Innovator Award, and the NIH (4K12NS080223-05). J.M.S. is supported by the National Institute of Neurological Disorders and Stroke (NINDS) (NS060801; NS061808) and the US Department of Veterans Affairs (1BX002889); R.M. is supported by the Howard Hughes Medical Institute

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Roadmap on dynamics of molecules and clusters in the gas phase

This roadmap article highlights recent advances, challenges and future prospects in studies of the dynamics of molecules and clusters in the gas phase. It comprises nineteen contributions by scientists with leading expertise in complementary experimental and theoretical techniques to probe the dynamics on timescales spanning twenty order of magnitudes, from attoseconds to minutes and beyond, and for systems ranging in complexity from the smallest (diatomic) molecules to clusters and nanoparticles. Combining some of these techniques opens up new avenues to unravel hitherto unexplored reaction pathways and mechanisms, and to establish their significance in, e.g. radiotherapy and radiation damage on the nanoscale, astrophysics, astrochemistry and atmospheric science

Effects of congenital hydrocephalus on the hypothalamic gonadotrophin-releasing hormone system

Object Despite the investigations that have linked hydrocephalus to reproductive system abnormalities, no researchers have attempted to identify the pathophysiological mechanism of this relationship. Because the role of the hypothalamic gonadotrophin-releasing hormone (GnRH) system in the regulation of reproductive functions is well established, the authors used immunohistochemical and radioimmunoassay (RIA) techniques to determine the morphological and biochemical effects of hydrocephalus on the hypothalamic GnRH system. Methods Hypothalamic GnRH levels, fiber density, and cell types were studied in 21- and 50-day-old control and congenitally hydrocephalic Texas rats. Results of RIA indicated a significant (8.4%) increase in GnRH in 21-day-old hydrocephalic rats (9.17 ± 0.64 pg/ng total protein) compared with that in controls (0.97 ± 0.74 pg/ng total protein). In addition, the 50-day-old hydrocephalic animals had a significantly higher level of GnRH compared with age-matched controls (20.4 pg/ng compared with 1.88 ± 2.1 pg/ng total protein). This increase was accompanied by changes in the fiber appearance and a shift from low GnRH producing cells to high GnRH producing cells in the hydrocephalic animals; however, there was no significant difference in the fiber density between the control and hydrocephalic animals at 21 days. In addition, poor neurological scores correlated with the severity of hydrocephalus. Conclusions These results demonstrated that hypothalamic GnRH levels are significantly affected by fetal-onset hydrocephalus and that the mechanisms responsible for these effects may take place at the cellular rather than the gross structural level. Furthermore, they suggest that impairments in the GnRH system may be protracted in neonates and infants with hydrocephalus, and thus may be overcome by relatively early treatment with ventricular diversion. However, the clinical implications of GnRH perturbations in shunt-dependent patients must await a forthcoming study in shunted animals