Brain region-specific alterations in gene expression trajectories in the offspring born from influenza A virus infected mice.

Influenza A virus (IAV) infection during pregnancy can increase the risk for neurodevelopmental disorders in the offspring, however, the underlying neurobiological mechanisms are largely unknown. To recapitulate viral infection, preclinical studies have traditionally focused on using synthetic viral mimetics, rather than live IAV, to examine consequences of maternal immune activation (MIA)-dependent processes on offspring. In contrast, few studies have used live IAV to assess effects on global gene expression, and none to date have addressed whether moderate IAV, mimicking seasonal influenza disease, alters normal gene expression trajectories in different brain regions across different stages of development. Herein, we show that moderate IAV infection during pregnancy, which causes mild maternal disease and no overt foetal complications in utero, induces lasting effects on the offspring into adulthood. We observed behavioural changes in adult offspring, including disrupted prepulse inhibition, dopaminergic hyper-responsiveness, and spatial recognition memory deficits. Gene profiling in the offspring brain from neonate to adolescence revealed persistent alterations to normal gene expression trajectories in the prefronal cortex, hippocampus, hypothalamus and cerebellum. Alterations were found in genes involved in inflammation and neurogenesis, which were predominately dysregulated in neonatal and early adolescent offspring. Notably, late adolescent offspring born from IAV infected mice displayed altered microglial morphology in the hippocampus. In conclusion, we show that moderate IAV during pregnancy perturbs neurodevelopmental trajectories in the offspring, including alterations in the neuroinflammatory gene expression profile and microglial number and morphology in the hippocampus, resulting in behavioural changes in adult offspring. Such early perturbations may underlie the vulnerability in human offspring for the later development of neurodevelopmental disorders, including schizophrenia. Our work highlights the importance of using live IAV in developing novel preclinical models that better recapitulate the real-world impact of inflammatory insults during pregnancy on offspring neurodevelopmental trajectories and disease susceptibility later in life.

Ginsenosides enhance P2X7-dependent cytokine secretion from LPS-primed rodent macrophages.

The activation of P2X7 is a well-known stimulus for the NLRP3-caspase 1 inflammasome and subsequent rapid IL-1ß secretion from monocytes and macrophages. Here we show that positive allosteric modulators of P2X7, ginsenosides, can enhance the release of three important cytokines, IL-1ß, IL-6 and TNF-α from LPS-primed rodent macrophages using the J774 mouse macrophage cell line and primary rat peritoneal macrophages. We compared the immediate P2X7 responses in un-primed and LPS-primed macrophages and found no difference in calcium response amplitude or kinetics. These results suggest that under inflammatory conditions positive allosteric modulators are capable of increasing cytokine secretion at lower concentrations of ATP, thus boosting the initial pro-inflammatory signal. This may be important in the control of intracellular infections.

Cigarette smoke-induced pulmonary impairment is associated with social recognition memory impairments and alterations in microglial profiles within the suprachiasmatic nucleus of the hypothalamus.

Chronic obstructive pulmonary disease (COPD) is a major, incurable respiratory condition that is primarily caused by cigarette smoking (CS). Neurocognitive disorders including cognitive dysfunction, anxiety and depression are highly prevalent in people with COPD. It is understood that increased lung inflammation and oxidative stress from CS exposure may 'spill over' into the systemic circulation to promote the onset of these extra-pulmonary comorbidities, and thus impacts the quality of life of people with COPD. The precise role of the 'spill-over' of inflammation and oxidative stress in the onset of COPD-related neurocognitive disorders are unclear. The present study investigated the impact of chronic CS exposure on anxiety-like behaviors and social recognition memory, with a particular focus on the role of the 'spill-over' of inflammation and oxidative stress from the lungs. Adult male BALB/c mice were exposed to either room air (sham) or CS (9 cigarettes per day, 5 days a week) for 24 weeks and were either daily co-administered with the NOX2 inhibitor, apocynin (5 mg/kg, in 0.01 % DMSO diluted in saline, i.p.) or vehicle (0.01 % DMSO in saline) one hour before the initial CS exposure of the day. After 23 weeks, mice underwent behavioral testing and physiological diurnal rhythms were assessed by monitoring diurnal regulation profiles. Lungs were collected and assessed for hallmark features of COPD. Consistent with its anti-inflammatory and oxidative stress properties, apocynin treatment partially lessened lung inflammation and lung function decline in CS mice. CS-exposed mice displayed marked anxiety-like behavior and impairments in social recognition memory compared to sham mice, which was prevented by apocynin treatment. Apocynin was unable to restore the decreased Bmal1-positive cells, key in cells in diurnal regulation, in the suprachiasmatic nucleus of the hypothalamus to that of sham levels. CS-exposed mice treated with apocynin was associated with a restoration of microglial area per cell and basal serum corticosterone. This data suggests that we were able to model the CS-induced social recognition memory impairments seen in humans with COPD. The preventative effects of apocynin on memory impairments may be via a microglial dependent mechanism.

Ebselen prevents cigarette smoke-induced cognitive dysfunction in mice by preserving hippocampal synaptophysin expression.

BACKGROUND: Cigarette smoking (CS) is the leading cause of chronic obstructive pulmonary disease (COPD). The "spill-over" of pulmonary inflammation into the systemic circulation may damage the brain, leading to cognitive dysfunction. Cessation of CS can improve pulmonary and neurocognitive outcomes, however, its benefit on the neuroinflammatory profile remains uncertain. Here, we investigate how CS exposure impairs neurocognition and whether this can be reversed with CS cessation or an antioxidant treatment. METHODS: Male BALB/c mice were exposed to CS (9 cigarettes/day for 8 weeks) followed by 4 weeks of CS cessation. Another cohort of CS-exposed mice were co-administrated with a glutathione peroxidase mimetic, ebselen (10 mg/kg) or vehicle (5% CM-cellulose). We assessed pulmonary inflammation, spatial and working memory, and the hippocampal microglial, oxidative and synaptic profiles. RESULTS: CS exposure increased lung inflammation which was reduced following CS cessation. CS caused spatial and working memory impairments which were attributed to hippocampal microglial activation and suppression of synaptophysin. CS cessation did not improve memory deficits or alter microglial activation. Ebselen completely prevented the CS-induced working and spatial memory impairments, which was associated with restored synaptophysin expression without altering microglial activation. CONCLUSION: We were able to model the CS-induced memory impairment and microglial activation seen in human COPD. The preventative effects of ebselen on memory impairment is likely to be dependent on a preserved synaptogenic profile. Cessation alone also appears to be insufficient in correcting the memory impairment, suggesting the importance of incorporating antioxidant therapy to help maximising the benefit of cessation.

Ebselen abolishes vascular dysfunction in influenza A virus-induced exacerbations of cigarette smoke-induced lung inflammation in mice.

People with chronic obstructive pulmonary disease (COPD) are susceptible to respiratory infections which exacerbate pulmonary and/or cardiovascular complications, increasing their likelihood of death. The mechanisms driving these complications remain unknown but increased oxidative stress has been implicated. Here we investigated whether influenza A virus (IAV) infection, following chronic cigarette smoke (CS) exposure, worsens vascular function and if so, whether the antioxidant ebselen alleviates this vascular dysfunction. Male BALB/c mice were exposed to either room air or CS for 8 weeks followed by inoculation with IAV (Mem71, 1 × 104.5 pfu). Mice were treated with ebselen (10 mg/kg) or vehicle (5% w/v CM-cellulose in water) daily. Mice were culled 3- and 10-days post-infection, and their lungs lavaged to assess inflammation. The thoracic aorta was excised to investigate endothelial and smooth muscle dilator responses, expression of key vasodilatory and oxidative stress modulators, infiltrating immune cells and vascular remodelling. CS increased lung inflammation and caused significant vascular endothelial dysfunction, which was worsened by IAV infection. CS-driven increases in vascular oxidative stress, aortic wall remodelling and suppression of endothelial nitric oxide synthase (eNOS) were not affected by IAV infection. CS and IAV infection significantly enhanced T cell recruitment into the aortic wall. Ebselen abolished the exaggerated lung inflammation, vascular dysfunction and increased T cell infiltration in CS and IAV-infected mice. Our findings showed that ebselen treatment abolished vascular dysfunction in IAV-induced exacerbations of CS-induced lung inflammation indicating it may have potential for the treatment of cardiovascular comorbidities seen in acute exacerbations of COPD (AECOPD).

Microglial ablation in rats disrupts the circadian system.

Microglia, the key neuroimmune cells of the central nervous system, are best known for their function in defending an individual from pathogens and injury. Recent findings, including our own, suggest microglia also have several immune-independent roles, including in regulating satiety, promoting memory, and modifying pain responses. Many of these microglia-associated functions are affected by circadian rhythmicity, thus, varying substantially depending upon the time of day. To gain further insight into this link, we used a Cx3cr1-Dtr transgenic Wistar rat model to acutely deplete microglia and examined if this could lead to a disruption in diurnal temperature, metabolism, and activity measures. We also examined if differences in the physiological rhythms corresponded with changes in the expression of key circadian rhythm-regulating genes and proteins. Our data show that in the absence of microglia there is a pronounced disruption of diurnal rhythms in several domains consistent with a shift toward the inactive phase, in conjunction with changes in circadian rhythm-regulating genes and proteins. These data suggest microglia are involved in the regulation of circadian rhythms and indicate an exciting potential to manipulate these cells to improve disrupted circadian rhythms such as with shift-work or jet-lag.

Ovarian follicles are resistant to monocyte perturbations-implications for ovarian health with immune disruption†.

Monocytes and macrophages are the most abundant immune cell populations in the adult ovary, with well-known roles in ovulation and corpus luteum formation and regression. They are activated and proliferate in response to immune challenge and are suppressed by anti-inflammatory treatments. It is also likely they have a functional role in the healthy ovary in supporting the maturing follicle from the primordial through to the later stages; however, this role has been unexplored until now. Here, we utilized a Cx3cr1-Dtr transgenic Wistar rat model that allows a conditional depletion of circulating monocytes, to investigate their role in ovarian follicle health. Our findings show that circulating monocyte depletion leads to a significant depletion of ovarian monocytes and monocyte-derived macrophages. Depletion of monocytes was associated with a transient reduction in circulating anti-Müllerian hormone (AMH) at 5 days postdepletion. However, the 50-60% ovarian monocyte/macrophage depletion had no effect on ovarian follicle numbers, follicle atresia, or apoptosis, within 5-21 days postdepletion. These data reveal that the healthy adult ovary is remarkably resistant to perturbations of circulating and ovarian monocytes despite acute changes in AMH. These data suggest that short-term anti-inflammatory therapies that transiently impact on circulating monocytes are unlikely to disrupt ovarian follicle health, findings that have significant implications for fertility planning relative to the experience of an immune challenge or immunosuppression.

Glial remodeling enhances short-term memory performance in Wistar rats.

BACKGROUND: Microglia play a key role in neuronal circuit and synaptic maturation in the developing brain. In the healthy adult, however, their role is less clear: microglial hyperactivation in adults can be detrimental to memory due to excessive synaptic pruning, yet learning and memory can also be impaired in the absence of these cells. In this study, we therefore aimed to determine how microglia contribute to short-term memory in healthy adults. METHODS: To this end, we developed a Cx3cr1-Dtr transgenic Wistar rat with a diphtheria toxin receptor (Dtr) gene inserted into the fractalkine receptor (Cx3cr1) promoter, expressed on microglia and monocytes. This model allows acute microglial and monocyte ablation upon application of diphtheria toxin, enabling us to directly assess microglia's role in memory. RESULTS: Here, we show that short-term memory in the novel object and place recognition tasks is entirely unaffected by acute microglial ablation. However, when microglia repopulate the brain after depletion, learning and memory performance in these tasks is improved. This transitory memory enhancement is associated with an ameboid morphology in the newly repopulated microglial cells and increased astrocyte density that are linked with a higher density of mature hippocampal synaptic spines and differences in pre- and post-synaptic markers. CONCLUSIONS: These data indicate that glia play a complex role in the healthy adult animal in supporting appropriate learning and memory and that subtle changes to the function of these cells may strategically enhance memory.

Ebselen prevents cigarette smoke-induced gastrointestinal dysfunction in mice.

Gastrointestinal (GI) dysfunction is a common comorbidity of chronic obstructive pulmonary disease (COPD) for which a major cause is cigarette smoking (CS). The underlying mechanisms and precise effects of CS on gut contractility, however, are not fully characterised. Therefore, the aim of the present study was to investigate whether CS impacts GI function and structure in a mouse model of CS-induced COPD. We also aimed to investigate GI function in the presence of ebselen, an antioxidant that has shown beneficial effects on lung inflammation resulting from CS exposure. Mice were exposed to CS for 2 or 6 months. GI structure was analysed by histology and immunofluorescence. After 2 months of CS exposure, ex vivo gut motility was analysed using video-imaging techniques to examine changes in colonic migrating motor complexes (CMMCs). CS decreased colon length in mice. Mice exposed to CS for 2 months had a higher frequency of CMMCs and a reduced resting colonic diameter but no change in enteric neuron numbers. Ten days cessation after 2 months CS reversed CMMC frequency changes but not the reduced colonic diameter phenotype. Ebselen treatment reversed the CS-induced reduction in colonic diameter. After 6 months CS, the number of myenteric nitric-oxide producing neurons was significantly reduced. This is the first evidence of colonic dysmotility in a mouse model of CS-induced COPD. Dysmotility after 2 months CS is not due to altered neuron numbers; however, prolonged CS-exposure significantly reduced enteric neuron numbers in mice. Further research is needed to assess potential therapeutic applications of ebselen in GI dysfunction in COPD.

The role of microglia in the second and third postnatal weeks of life in rat hippocampal development and memory.

Microglia are resident immune cells of the central nervous system (CNS). In adulthood they are involved in surveillance and responses to pathogens and injury and prenatally they play a role in brain development. However, the role of microglia during the early postnatal period and how they impact development long-term remains poorly understood. Here, to investigate the specific role of microglia in postnatal development, we used a Cx3cr1-Dtr transgenic Wistar rat model to acutely ablate microglia from either postnatal day (P) 7 or 14. We specifically assessed how transient microglial ablation affected astrocytes and neurons acutely, during the juvenile period, and in adulthood. Hippocampal microglial numbers remained low at P21 in the P7-ablated animals and complexity remained reduced after P14-ablation. This protracted effect on these key immune cells led to a small but significant increase in CA1 mature neuron numbers and a significant increase in astrocyte density in the subgranular dentate gyrus in adults that had their microglia ablated at P14. However, these histological differences were small, and spatial and recognition memory in novel objection and place recognition tests were not affected. Overall, our data reveal for the first time that the transient depletion of microglia during the neonatal period impacts briefly on the brain but that the long-lasting effects are minimal. Neonatal microglia may be dispensable in the establishment of hippocampal brain function. These data also imply that novel therapeutic anti-inflammatories that cross the blood-brain barrier to inhibit microglia are unlikely to have long-term negative consequences if administered in the neonatal period.

Conditional microglial depletion in rats leads to reversible anorexia and weight loss by disrupting gustatory circuitry.

Microglia are highly sensitive to dietary influence, becoming activated acutely and long-term by high fat diet. However, their role in regulating satiety and feeding in healthy individuals remains unclear. Here we show that microglia are essential for the normal regulation of satiety and metabolism in rats. Short-term microglial depletion in a Cx3cr1-Dtr rat led to a dramatic weight loss that was largely accounted for by an acute reduction in food intake. This weight loss and anorexia were not likely due to a sickness response since the rats did not display peripheral or central inflammation, withdrawal, anxiety-like behavior, or nausea-associated pica. Hormonal and hypothalamic anatomical changes were largely compensatory to the suppressed food intake, which occurred in association with disruption of the gustatory circuitry at the paraventricular nucleus of the thalamus. Thus, microglia are important in supporting normal feeding behaviors and weight, and regulating preference for palatable food. Inhibiting this circuitry is able to over-ride strong compensatory drives to eat, providing a potential target for satiety control.

Acylated ghrelin suppresses the cytokine response to lipopolysaccharide and does so independently of the hypothalamic-pituitary-adrenal axis.

Ghrelin, one of the major metabolic hormones involved in controlling energy balance, has recently been shown to have other properties including regulating the hypothalamic-pituitary-adrenal (HPA) axis response to psychological stress and being a potent anti-inflammatory agent. Ghrelin's HPA axis and anti-inflammatory actions have previously been identified as principally due to the acylated form (AG). However, our recent work has also suggested a role for des-acylated ghrelin (DAG) in these functions. Here we hypothesized ghrelin's anti-inflammatory activity is mediated by the HPA axis and this effect is differentially executed by AG and DAG. We gave adult male Wistar rats a concomitant injection of AG or DAG and lipopolysaccharide (LPS) and measured their effects on circulating cytokines, stress hormones and neuronal activation of the paraventricular nucleus of the hypothalamus (PVN). AG, but not DAG significantly suppressed the pro- and anti-inflammatory cytokine response induced by LPS in vivo. DAG also had no effects on any components of the HPA axis. AG, despite stimulating neuronal activation in the PVN in vivo and stimulating ACTH release from the pituitary in vitro, did not affect the HPA axis response to LPS. These findings suggest AG's anti-inflammatory effects are independent of its actions on the HPA axis and have implications for the potential use of this peptide for treatment of inflammatory conditions without compromising HPA axis activity.

Effects of exercise on adolescent and adult hypothalamic and hippocampal neuroinflammation.

Adolescence is a period of significant brain plasticity that can be affected by environmental factors, including the degree of physical activity. Here we hypothesized that adolescent rats would be more sensitive to the beneficial metabolic and anti-inflammatory effects of voluntary exercise than adult rats, whose more mature brains have less capacity for plasticity. We tested this by giving adolescent and adult Wistar rats four weeks' voluntary access to running wheels. At the end of this period we assessed metabolic effects, including weight and circulating leptin and ghrelin, as well as performance in a novel object recognition test of memory and central changes in neuronal proliferation, survival, synaptic density, and inflammatory markers in hippocampus. We found exercise reduced fat mass and circulating leptin levels in both adults and adolescents but suppressed total weight gain and lean mass in adults only. Exercise stimulated neuronal proliferation in the suprapyramidal blade of the dentate gyrus in both adults and adolescents without altering the number of mature neurons during this time frame. Exercise also increased dentate microglial numbers in adolescents alone and microglial numbers in this region were inversely correlated with performance in the novel object recognition test. Together these data suggest that adolescent hippocampal microglia are more sensitive to the effects of exercise than those of adults, but this leads to no apparent improvement in recognition memory. © 2016 Wiley Periodicals, Inc.

Early life overfeeding impairs spatial memory performance by reducing microglial sensitivity to learning.

BACKGROUND: Obesity can lead to cognitive dysfunction including poor performance in memory tasks. However, poor memory is not seen in all obese humans and takes several months to develop in animal models, indicating the adult brain is relatively resistant to obesity's cognitive effects. We have seen that, in the rat, overfeeding for as little as 3 weeks in early life leads to lasting obesity and microglial priming in the hypothalamus. Here we hypothesized that microglial hyper-sensitivity in the neonatally overfed rats extends beyond the hypothalamus into memory-associated brain regions, resulting in cognitive deficits. METHODS: We tested this idea by manipulating Wistar rat litter sizes to suckle pups in litters of 4 (overfed) or 12 (control). RESULTS: Neonatally overfed rats had microgliosis in the hippocampus after only 14 days overfeeding, and this persisted into adulthood. These changes were coupled with poor performance in radial arm maze and novel object recognition tests relative to controls. In controls, the experience of the radial arm maze reduced cell proliferation in the dentate gyrus and neuron numbers in the CA3. The learning task also suppressed microglial number and density in hippocampus and retrosplenial cortex. Neonatally overfed brains had impaired sensitivity to learning, with no neuronal or cell proliferative effects and less effective microglial suppression. CONCLUSIONS: Thus, early life overfeeding contributes to a long-term impairment in learning and memory with a likely role for microglia. These data may partially explain why some obese individuals display cognitive dysfunction and some do not, i.e. the early life dietary environment is likely to have a vital long-term contribution.

Targeting accelerated pulmonary ageing to treat chronic obstructive pulmonary disease-induced neuropathological comorbidities.

Chronic obstructive pulmonary disease (COPD) is a major incurable health burden, ranking as the third leading cause of death worldwide, mainly driven by cigarette smoking. COPD is characterised by persistent airway inflammation, lung function decline and premature ageing with the presence of pulmonary senescent cells. This review proposes that cellular senescence, a state of stable cell cycle arrest linked to ageing, induced by inflammation and oxidative stress in COPD, extends beyond the lungs and affects the systemic circulation. This pulmonary senescent profile will reach other organs via extracellular vesicles contributing to brain inflammation and damage, and increasing the risk of neurological comorbidities, such as stroke, cerebral small vessel disease and Alzheimer's disease. The review explores the role of cellular senescence in COPD-associated brain conditions and investigates the relationship between cellular senescence and circadian rhythm in COPD. Additionally, it discusses potential therapies, including senomorphic and senolytic treatments, as novel strategies to halt or improve the progression of COPD.

Inhibition of oxidative stress by apocynin attenuated chronic obstructive pulmonary disease progression and vascular injury by cigarette smoke exposure.

BACKGROUND AND PURPOSE: Cardiovascular disease affects up to half of the patients with chronic obstructive pulmonary disease (COPD), exerting deleterious impact on health outcomes and survivability. Vascular endothelial dysfunction marks the onset of cardiovascular disease. The present study examined the effect of a potent NADPH Oxidase (NOX) inhibitor and free-radical scavenger, apocynin, on COPD-related cardiovascular disease. EXPERIMENTAL APPROACH: Male BALB/c mice were exposed to either room air (Sham) or cigarette smoke (CS) generated from 9 cigarettes·day-1 , 5 days a week for up to 24 weeks with or without apocynin treatment (5 mg·kg-1 ·day-1 , intraperitoneal injection). KEY RESULTS: Eight-weeks of apocynin treatment reduced airway neutrophil infiltration (by 42%) and completely preserved endothelial function and endothelial nitric oxide synthase (eNOS) availability against the oxidative insults of cigarette smoke exposure. These preservative effects were maintained up until the 24-week time point. 24-week of apocynin treatment markedly reduced airway inflammation (reduced infiltration of macrophage, neutrophil and lymphocyte), lung function decline (hyperinflation) and prevented airway collagen deposition by cigarette smoke exposure. CONCLUSION AND IMPLICATIONS: Limiting NOX activity may slow COPD progression and lower cardiovascular disease risk, particularly when signs of oxidative stress become evident.

Influenza A Virus-Driven Airway Inflammation may be Dissociated From Limb Muscle Atrophy in Cigarette Smoke-Exposed Mice.

Limb muscle dysfunction is a hallmark of Chronic Obstructive Pulmonary Disease (COPD) which is further worsened following a viral-induced acute exacerbation of COPD (AECOPD). An amplified airway inflammation underlies the aggravated respiratory symptoms seen during AECOPD, however, its contributory role to limb muscle dysfunction is unclear. The present study examined the impact of influenza A virus (IAV)-induced exacerbation on hind limb muscle parameters. Airway inflammation was established in male BALB/c mice by exposure to cigarette smoke (CS) for 8 weeks. Exacerbation was then induced via inoculation with IAV, and various lung and muscle parameters were assessed on day 3 (peak of airway inflammation) and day 10 (resolution phase) post-infection. IAV infection exacerbated CS-induced airway inflammation as evidenced by further increases in immune cell counts within bronchoalveolar lavage fluid. Despite no significant impact on muscle mass, IAV exacerbation worsened the force-generating capacity of the tibialis anterior (TA) muscle. Protein oxidation and myogenic disruption was observed in the TA following CS exposure, however, IAV exacerbation did not augment these detrimental processes. To further explore the contributory role of airway inflammation on myogenic signaling, cultured myotubes were exposed to conditioned medium (CM) derived from bronchial epithelial cells stimulated with polyinosinic:polycytidylic acid and cigarette smoke extract (CSE). Despite an amplified inflammatory response in the lung epithelial cells, the CM derived from these cells did not potentiate myogenic disruption in the C2C12 myotubes. In conclusion, our data suggest that certain parameters of limb muscle dysfunction seen during viral-induced AECOPD may be independent of airway inflammation.

Novel pharmacological strategies to treat cognitive dysfunction in chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and currently the 3rd largest cause of death in the world, with approximately 3.23 million deaths per year. Globally, the financial burden of COPD is approximately €82 billion per year and causes substantial morbidity and mortality. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities and viral and bacterial-induced acute exacerbations (AECOPD). Recent clinical studies have shown that cognitive dysfunction is present in up to 60% of people with COPD, with impairments in executive function, memory, and attention, impacting on important outcomes such as quality of life, hospitalisation and survival. The high prevalence of cognitive dysfunction in COPD may also help explain the insufficient adherence to therapeutic plans and strategies, thus worsening disease progression in people with COPD. However, the mechanisms underlying the impaired neuropathology and cognition in COPD remain largely unknown. In this review, we propose that the observed pulmonary oxidative burden and inflammatory response of people with COPD 'spills over' into the systemic circulation, resulting in damage to the brain and leading to cognitive dysfunction. As such, drugs targeting the lungs and comorbidities concurrently represent an exciting and unique therapeutic opportunity to treat COPD and cognitive impairments, which may lead to the production of novel targets to prevent and reverse the debilitating and life-threatening effects of cognitive dysfunction in COPD.

Cigarette Smoke Exposure Induces Neurocognitive Impairments and Neuropathological Changes in the Hippocampus.

Background and Objective: Neurocognitive dysfunction is present in up to ∼61% of people with chronic obstructive pulmonary disease (COPD), with symptoms including learning and memory deficiencies, negatively impacting the quality of life of these individuals. As the mechanisms responsible for neurocognitive deficits in COPD remain unknown, we explored whether chronic cigarette smoke (CS) exposure causes neurocognitive dysfunction in mice and whether this is associated with neuroinflammation and an altered neuropathology. Methods: Male BALB/c mice were exposed to room air (sham) or CS (9 cigarettes/day, 5 days/week) for 24 weeks. After 23 weeks, mice underwent neurocognitive tests to assess working and spatial memory retention. At 24 weeks, mice were culled and lungs were collected and assessed for hallmark features of COPD. Serum was assessed for systemic inflammation and the hippocampus was collected for neuroinflammatory and structural analysis. Results: Chronic CS exposure impaired lung function as well as driving pulmonary inflammation, emphysema, and systemic inflammation. CS exposure impaired working memory retention, which was associated with a suppression in hippocampal microglial number, however, these microglia displayed a more activated morphology. CS-exposed mice showed changes in astrocyte density as well as a reduction in synaptophysin and dendritic spines in the hippocampus. Conclusion: We have developed an experimental model of COPD in mice that recapitulates the hallmark features of the human disease. The altered microglial/astrocytic profiles and alterations in the neuropathology within the hippocampus may explain the neurocognitive dysfunction observed during COPD.

Apocynin prevents cigarette smoking-induced loss of skeletal muscle mass and function in mice by preserving proteostatic signalling.

BACKGROUND AND PURPOSE: Skeletal muscle dysfunction is a major comorbidity of chronic obstructive pulmonary disease (COPD). This type of muscle dysfunction may be a direct consequence of oxidative insults evoked by cigarette smoke (CS) exposure. The present study examined the effects of a potent Nox inhibitor and reactive oxygen species (ROS) scavenger, apocynin, on CS-induced muscle dysfunction. EXPERIMENTAL APPROACH: Male BALB/c mice were exposed to either room air (sham) or CS generated from nine cigarettes per day, 5 days a week for 8 weeks, with or without the coadministration of apocynin (5 mg·kg-1 , i.p.). C2C12 myotubes exposed to either hydrogen peroxide (H2 O2 ) or water-soluble cigarette smoke extract (CSE) with or without apocynin (500 nM) were used as an experimental model in vitro. KEY RESULTS: Eight weeks of CS exposure caused muscle dysfunction in mice, reflected by 10% loss of muscle mass and 54% loss of strength of tibialis anterior which were prevented by apocynin administration. In C2C12 myotubes, direct exposure to H2 O2 or CSE caused myofibre wasting, accompanied by ~50% loss of muscle-derived insulin-like growth factor (IGF)-1 and two-fold induction of Cybb, independent of cellular inflammation. Expression of myostatin and MAFbx, negative regulators of muscle mass, were up-regulated under H2 O2 but not CSE conditions. Apocynin treatment abolished CSE-induced Cybb expression, preserving muscle-derived IGF-1 expression and signalling pathway downstream of mammalian target of rapamycin (mTOR), thereby preventing myofibre wasting. CONCLUSION AND IMPLICATIONS: Targeted pharmacological inhibition of Nox-derived ROS may alleviate the lung and systemic manifestations in smokers with COPD.