Rationale: An increased cancer aggressiveness and mortality have been recently reported among patients with obstructive sleep apnea (OSA). Intermittent hypoxia (IH), a hallmark of OSA, enhances melanoma growth and metastasis in mice.Objectives: To assess whether OSA-related adverse cancer outcomes occur via IH-induced changes in host immune responses, namely tumor-associated macrophages (TAMs).Measurements and Main Results: Lung epithelial TC1 cell tumors were 84% greater in mice subjected to IH for 28 days compared with room air (RA). In addition, TAMs in IH-exposed tumors exhibited reductions in M1 polarity with a shift toward M2 protumoral phenotype. Although TAMs from tumors harvested from RA-exposed mice increased TC1 migration and extravasation, TAMs from IHexposed mice markedly enhanced such effects and also promoted proliferative rates and invasiveness of TC1 cells. Proliferative rates of melanoma (B16F10) and TC1 cells exposed to IH either in single culture or in coculture with macrophages (RAW 264.7) increased only when RAW 264.7 macrophages were concurrently present.Conclusions: Our findings support the notion that IH-induced alterations in TAMs participate in the adverse cancer outcomes reported in OSA.

Rationale: Sleep fragmentation (SF) is one of the major characteristics of sleep apnea, and has been implicated in its morbid consequences, which encompass excessive daytime sleepiness and neurocognitive impairments. We hypothesized that absence of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity is neuroprotective in SF-induced cognitive impairments. Objectives: To examine whether increased NADPH oxidase activity may play a role in SF-induced central nervous system dysfunction. Methods: The effect of chronic SF during the sleep-predominant period on sleep architecture, sleep latency, spatial memory, and oxidative stress parameters was assessed in mice lacking NADPH oxidase activity (gp91phox-/Y ) and wild-type littermates. Measurements and Main Results: SF for 15 days was not associated with differences in sleep duration, sleep state distribution, or sleep latency in both gp91phox-/Y and control mice. However, on a standard place training task, gp91phox-/Y mice displayed normal learning and were protected from the spatial learning deficits observed in wildtype littermates exposed to SF. Moreover, anxiety levels were increased in wild-type mice exposed to SF, whereas no changes emerged in gp91phox-/Y mice. Additionally, wild-type mice, but not gp91phox-/Y mice, had significantly elevated NADPH oxidase gene expression and activity, and in malondialdehyde and 8-oxo-29-deoxyguanosine levels in cortical and hippocampal lysates after SF exposures. Conclusions: This work substantiates an important role for NADPH oxidase in hippocampal memory impairments induced by SF, modeling sleep apnea. Targeting NADPH oxidase, therefore, is expected to minimize hippocampal impairments from both intermittent hypoxia and SF associated with the disease. Keywords: NADPH oxidase; sleep fragmentation; neurocognitive impairmentsThe manifestations of obstructive sleep apnea (OSA) reflect the interactions of intermittent hypoxia (IH), intermittent hypercapnia, increased intrathoracic pressure swings, and sleep fragmentation (SF) as elicited by the episodic changes in upper airway resistance during sleep. SF is a common phenomenon among several clinical disorders, and can lead to impaired cognitive function via mechanisms that remain poorly understood (1). Indeed, uninterrupted sleep for a minimum length of time is required for optimal daytime vigilance and neurocognitive function (1-3). Preliminary studies in rodents using short-term SF paradigms have also confirmed the adverse effects of SF on learning and seem to be independent of adenosine-mediated synaptic inhibition (4-7).In clinical populations with severe SF (e.g., in OSA) total sleep time typically diminishes only slightly (8). The effects of experimentally induced SF on sleep patterns have not been critically characterized in rodents. It is likely that OSA-induced sleep perturbations are accompanied by obvious cognitive deficits because of increased levels of systemic markers of oxidative stress and inflammation, the latter leading to gray matter loss in neural...

Fragmented sleep (SF) is a highly prevalent condition and a hallmark of sleep apnea, a condition that has been associated with increased cancer incidence and mortality. In this study, we examined the hypothesis that SF promotes tumor growth and progression through pro-inflammatory TLR4 signaling. In the design, we compared mice that were exposed to SF one week before engraftment of syngeneic TC1 or LL3 tumor cells and tumor analysis three weeks later. We also compared host contributions through the use of mice genetically deficient in TLR4 or its effector molecules MYD88 or TRIF. We found that SF enhanced tumor size and weight compared to control mice. Increased invasiveness was apparent in SF tumors, which penetrated the tumor capsule into surrounding tissues including adjacent muscle. Tumor-associated macrophages (TAM) were more numerous in SF tumors where they were distributed in a relatively closer proximity to the tumor capsule, compared to control mice. Although tumors were generally smaller in both MYD88−/− and TRIF−/− hosts, the more aggressive features produced by SF persisted. In contrast, these more aggressive features produced by SF were abolished completely in TLR4−/− mice. Our findings offer mechanistic insights into how sleep perturbations can accelerate tumor growth and invasiveness through TAM recruitment and TLR4 signaling pathways.

BackgroundSleepiness and cognitive dysfunction are recognized as prominent consequences of sleep deprivation. Experimentally induced short-term sleep fragmentation, even in the absence of any reductions in total sleep duration, will lead to the emergence of excessive daytime sleepiness and cognitive impairments in humans. Tumor necrosis factor (TNF)-α has important regulatory effects on sleep, and seems to play a role in the occurrence of excessive daytime sleepiness in children who have disrupted sleep as a result of obstructive sleep apnea, a condition associated with prominent sleep fragmentation. The aim of this study was to examine role of the TNF-α pathway after long-term sleep fragmentation in mice.MethodsThe effect of chronic sleep fragmentation during the sleep-predominant period on sleep architecture, sleep latency, cognitive function, behavior, and inflammatory markers was assessed in C57BL/6 J and in mice lacking the TNF-α receptor (double knockout mice). In addition, we also assessed the above parameters in C57BL/6 J mice after injection of a TNF-α neutralizing antibody.ResultsMice subjected to chronic sleep fragmentation had preserved sleep duration, sleep state distribution, and cumulative delta frequency power, but also exhibited excessive sleepiness, altered cognitive abilities and mood correlates, reduced cyclic AMP response element-binding protein phosphorylation and transcriptional activity, and increased phosphodiesterase-4 expression, in the absence of AMP kinase-α phosphorylation and ATP changes. Selective increases in cortical expression of TNF-α primarily circumscribed to neurons emerged. Consequently, sleepiness and cognitive dysfunction were absent in TNF-α double receptor knockout mice subjected to sleep fragmentation, and similarly, treatment with a TNF-α neutralizing antibody abrogated sleep fragmentation-induced learning deficits and increases in sleep propensity.ConclusionsTaken together, our findings show that recurrent arousals during sleep, as happens during sleep apnea, induce excessive sleepiness via activation of inflammatory mechanisms, and more specifically TNF-α-dependent pathways, despite preserved sleep duration.