Circadian-Related Sleep Disorders and Sleep Medication Use in the New Zealand Blind Population: An Observational Prevalence Survey

STUDY OBJECTIVES: To determine the prevalence of self-reported circadian-related sleep disorders, sleep medication and melatonin use in the New Zealand blind population. DESIGN: A telephone survey incorporating 62 questions on sleep habits and medication together with validated questionnaires on sleep quality, chronotype and seasonality. PARTICIPANTS: PARTICIPANTS WERE GROUPED INTO: (i) 157 with reduced conscious perception of light (RLP); (ii) 156 visually impaired with no reduction in light perception (LP) matched for age, sex and socioeconomic status, and (iii) 156 matched fully-sighted controls (FS). SLEEP HABITS AND DISTURBANCES: The incidence of sleep disorders, daytime somnolence, insomnia and sleep timing problems was significantly higher in RLP and LP compared to the FS controls (p<0.001). The RLP group had the highest incidence (55%) of sleep timing problems, and 26% showed drifting sleep patterns (vs. 4% FS). Odds ratios for unconventional sleep timing were 2.41 (RLP) and 1.63 (LP) compared to FS controls. For drifting sleep patterns, they were 7.3 (RLP) and 6.0 (LP). MEDICATION USE: Zopiclone was the most frequently prescribed sleep medication. Melatonin was used by only 4% in the RLP group and 2% in the LP group. CONCLUSIONS: Extrapolations from the current study suggest that 3,000 blind and visually impaired New Zealanders may suffer from circadian-related sleep problems, and that of these, fewer than 15% have been prescribed melatonin. This may represent a therapeutic gap in the treatment of circadian-related sleep disorders in New Zealand, findings that may generalize to other countries

Dysregulation of locus coeruleus development in congenital central hypoventilation syndrome.

Human congenital central hypoventilation syndrome (CCHS), resulting from mutations in transcription factor PHOX2B, manifests with impaired responses to hypoxemia and hypercapnia especially during sleep. To identify brainstem structures developmentally affected in CCHS, we analyzed two postmortem neonatal-lethal cases with confirmed polyalanine repeat expansion (PARM) or Non-PARM (PHOX2B∆8) mutation of PHOX2B. Both human cases showed neuronal losses within the locus coeruleus (LC), which is important for central noradrenergic signaling. Using a conditionally active transgenic mouse model of the PHOX2B∆8 mutation, we found that early embryonic expression (<E10.5) caused failure of LC neuronal specification and perinatal respiratory lethality. In contrast, later onset (E11.5) of PHOX2B∆8 expression was not deleterious to LC development and perinatal respiratory lethality was rescued, despite failure of chemosensor retrotrapezoid nucleus formation. Our findings indicate that early-onset mutant PHOX2B expression inhibits LC neuronal development in CCHS. They further suggest that such mutations result in dysregulation of central noradrenergic signaling, and therefore, potential for early pharmacologic intervention in humans with CCHS

Microtubules coordinate VEGFR2 signaling and sorting.

VEGF signaling is a key regulator of vessel formation and function. In vascular endothelial cells, this signaling is mediated through its cognate receptor VEGFR2, which is dynamically sorted in response to ligand. Little is known about the underlying mechanism of this intracellular sorting. Here we examined the role of different components of the cytoskeleton in this process. We found that VEGFR2 mainly associates with microtubule fibers and to a lesser extent with intermediate filaments and actin. Microtubule disruption leads to accumulation of VEGFR2 protein in the membrane and cytoplasm leading to defects in VEGF signaling. In contrast, inhibition of actin filaments results in no accumulation of VEGFR2 total protein or apparent changes in microtubule association. Instead, actin inhibition leads to a more global signaling disruption of the ERK1/2 pathway. This is the first report demonstrating that VEGFR2 associates closely with microtubules in modulating the subcellular sorting and signaling of VEGFR2

Microtubules Coordinate VEGFR2 Signaling and Sorting

<div><p>VEGF signaling is a key regulator of vessel formation and function. In vascular endothelial cells, this signaling is mediated through its cognate receptor VEGFR2, which is dynamically sorted in response to ligand. Little is known about the underlying mechanism of this intracellular sorting. Here we examined the role of different components of the cytoskeleton in this process. We found that VEGFR2 mainly associates with microtubule fibers and to a lesser extent with intermediate filaments and actin. Microtubule disruption leads to accumulation of VEGFR2 protein in the membrane and cytoplasm leading to defects in VEGF signaling. In contrast, inhibition of actin filaments results in no accumulation of VEGFR2 total protein or apparent changes in microtubule association. Instead, actin inhibition leads to a more global signaling disruption of the ERK1/2 pathway. This is the first report demonstrating that VEGFR2 associates closely with microtubules in modulating the subcellular sorting and signaling of VEGFR2. </p> </div

Distinct VEGFR2 pools are present in endothelial cells.

<p>(A) Endothelial cells stained for alpha tubulin (red) and total VEGFR2 (green). (B) Inset from panel A shows cell in more detail. Two insets (B1) and (B2) from panel B separate channels in red and green to more clearly show the distinct pools of VEGFR2 present in endothelial cells. This includes a pool of VEGFR2 on the cell surface (arrowhead), a granular cytoplasmic VEGFR2 pool (black arrow) and a pool of VEGFR2 arranged in fibrous arrays (white arrow). (C) Endothelial cells stained for microfilament beta actin (red) and total VEGFR2 (green). (D) Inset from panel C shows cell in more detail. The insets (D1) and (D2) from panel D separate channels into red and green to demonstrate more clearly distinct pools of VEGFR2 present in endothelial cells. This includes a pool of VEGFR2 on the cell surface (arrowhead, green), a granular cytoplasmic VEGFR2 pool (black arrow) and a pool of VEGFR2 arranged in fibrous arrays (white arrow). (E) Cell stained for intermediate filament Vimentin (red) and total VEGFR2 (green). (F) Inset from panel E shows cell in more detail. Insets (F1) and (F2) taken from panel F separate channels in green and red to show more clearly the distinct pools of VEGFR2 present in endothelial cells. This includes a granular cytoplasmic VEGFR2 pool (black arrow) and a pool of VEGFR2 arranged in fibrous arrays (white arrow). All displayed images are single focal planes.</p

Cytoskeletal disruption leads to a delay in the VEGFR2 response.

<p>(A) Endothelial cells treated with cytoskeletal inhibitors Nocodazole or CCD show a loss of immediate ERK1/2 phosphorylation (pERK1/2) after 5 minutes of VEGF stimulation compared to controls while total ERK1/2 levels remain constant. (B) Endothelial cells treated with cytoskeletal inhibitors, similar to controls, undergo a decrease in the total VEGFR2 levels after 60 minutes of VEGF stimulation. Panels (C) and (D) are data derived from 2 independent experiments and show the mean densitometry of these bands normalized to untreated control levels. Significant differences (denoted by asterisks) determined using paired student’s T-Test. Threshold of significance (alpha) was set to p<0.01. *p= 0.00014, **p= 0.00049.</p

Proposed Model of Microtubule Role in VEGFR2 Signaling.

<p>This model is based on the findings presented in this study. VEGFR2 exists in an equilibrium concentration on endothelial cell membranes due to its constant internalization and recycling. (A) The disruption of microtubules causes this equilibrium membrane concentration to increase indicating that it is either interfering with uptake or recycling of the receptor to the membrane. In response to VEGF, VEGFR2 becomes phosphorylated, internalizes and activates second messenger molecules such as ERK1/2. (B) We propose that VEGFR2 is trafficked along microtubules after VEGF activation thus increasing the likelihood that it will come in contact with MAP Kinases such as ERK1/2 that are known to associate with the microtubule cytoskeleton. In the absence of microtubules, the immediate phosphorylation of ERK1/2 is much less efficient. Finally, the total VEGFR2 amounts in the cell are dictated by the rate of degradation of the receptor. (C) Since actin and microtubule disruption changes total levels of VEGFR2, it is likely that the cytoskeleton also plays a function in increasing the efficiency of receptor degradation in response to VEGF.</p

Upregulation of glial clusterin in brains of patients with AIDs

Since clusterin (CLU) production in reactive astrocytes may be neuroprotective, we examined its distribution in AIDS brains where brain injury and reactive astrocytosis are common. The relative area and number of CLU-positive astrocytes, as well as their percent total of all white matter glia, significantly increased in AIDS brains with and without HIV encephalitis ( P<0.05). Proliferation markers were absent. In contrast, the relative area and number of GFAP-positive astrocytes and their percent of all white matter glia, increased in some cases but the mean increases were not significant. Clusterin is sensitive marker of glial reactivity in AIDS brains and its enhanced expression was not dependent on increases in GFAP

Chronic systemic administration of tumor necrosis factor alpha and HIV gp120: Effects on adult rodent brain and blood-brain barrier

Since tumor necrosis factor alpha (TNF-α) and HIV gp120 glycoprotein are both neurotoxic, the possibility that systemic sources of these two agents mediate AIDS-associated blood-brain barrier (BBB) breakdown and brain damage was tested in two murine models: (1) intramuscular implantation of a TNF-α-transfected tumor in nu/nu mice and (2) daily subcutaneous injections of HIV gp120 in BALB/c mice. The BBB remained intact; brain damage was not found, and apoptotic cell numbers did not increase. These results show that normal adult brain and BBB is unaffected by exposure to TNF-α or HIV gp120 and suggest that severity of brain disease is not directly affected by systemic levels of these compounds