Interdependent feedback regulation of breathing by the carotid bodies and the retrotrapezoid nucleus.
J Physiol. 2017 Nov 22;:
Authors: Guyenet PG, Bayliss DA, Stornetta RL, Kanbar R, Shi Y, Holloway BB, Souza GMPR, Basting TM, Abbott SBG, Wenker IC
The retrotrapezoid nucleus, RTN, regulates breathing in a CO2 and state-dependent manner. RTN neurons are glutamatergic and innervate principally the respiratory pattern generator; they regulate multiple aspects of breathing, including active expiration, and maintain breathing automaticity during non-REM sleep. RTN neurons encode arterial PCO2 /pH via cell-autonomous and paracrine mechanisms, and via input from other CO2 -responsive neurons. In short, RTN neurons are a pivotal structure for breathing automaticity and arterial PCO2 homeostasis. The carotid bodies stimulate the respiratory pattern generator directly and, indirectly, by activating RTN via a neuronal projection originating within the solitary tract nucleus. The indirect pathway operates under normo- or hypercapnic conditions; under respiratory alkalosis (e.g. hypoxia) RTN neurons are silent and the excitatory input from the carotid bodies is suppressed. Also, silencing RTN neurons optogenetically quickly triggers a compensatory increase in carotid body activity. Thus, in conscious mammals, breathing is subject to a dual and interdependent feedback regulation by chemoreceptors. Depending on the circumstance, the activity of the carotid bodies and that of RTN vary in the same or the opposite direction, producing additive or countervailing effects on breathing. These interactions are mediated either via changes in blood gases or by brainstem neuronal connections but their ultimate effect is invariably to minimize arterial PCO2 fluctuations. We discuss the potential relevance of this dual chemoreceptor feedback to cardiorespiratory abnormalities present in diseases in which the carotid bodies are hyperactive at rest, e.g. essential hypertension, obstructive sleep apnea and heart failure. This article is protected by copyright. All rights reserved.
PMID: 29168167 [PubMed - as supplied by publisher]
Silencing of NAC1 Expression Induces Cancer Cells Oxidative Stress in Hypoxia and Potentiates the Therapeutic Activity of Elesclomol.
Front Pharmacol. 2017;8:804
Authors: Ren YJ, Wang XH, Ji C, Guan YD, Lu XJ, Liu XR, Zhang HH, Guo LC, Xu QH, Zhu WD, Ming ZJ, Yang JM, Cheng Y, Zhang Y
In order to survive under conditions of low oxygen, cancer cells can undergo a metabolic switch to glycolysis and suppress mitochondrial respiration in order to reduce oxygen consumption and prevent excessive amounts of reactive oxygen species (ROS) production. Nucleus accumbens-1 (NAC1), a nuclear protein of the BTB/POZ gene family, has pivotal roles in cancer development. Here, we identified that NAC1-PDK3 axis as necessary for suppression of mitochondrial function, oxygen consumption, and more harmful ROS generation and protects cancer cells from apoptosis in hypoxia. We show that NAC1 mediates suppression of mitochondrial function in hypoxia through inducing expression of pyruvate dehydrogenase kinase 3 (PDK3) by HIF-1α at the transcriptional level, thereby inactivating pyruvate dehydrogenase and attenuating mitochondrial respiration. Re-expression of PDK3 in NAC1 absent cells rescued cells from hypoxia-induced metabolic stress and restored the activity of glycolysis in a xenograft mouse model, and demonstrated that silencing of NAC1 expression can enhance the antitumor efficacy of elesclomol, a pro-oxidative agent. Our findings reveal a novel mechanism by which NAC1 facilitates oxidative stress resistance during cancer progression, and chemo-resistance in cancer therapy.
PMID: 29163184 [PubMed]
Sleep-disordered breathing in heart failure: The state of the art after the SERVE-HF trial.
Rev Port Cardiol. 2017 Nov 18;:
Authors: Carmo J, Araújo I, Marques F, Fonseca C
Heart failure (HF) is one of the most prevalent conditions worldwide and despite therapeutic advances, its prognosis remains poor. Among the multiple comorbidities in HF, sleep-disordered breathing (SDB) is frequent and worsens the prognosis. Preliminary observational studies suggested that treatment of SDB could modify the prognosis of HF, and the issue has gained importance in recent years. The diagnosis of SDB is expensive, slow and suboptimal, and there is thus a need for screening devices that are easier to use and validated in this population. The first-line treatment involves optimization of medical therapy for heart failure. Continuous positive airway pressure (CPAP) is used in patients who mainly suffer from obstructive sleep apnea. In patients with predominantly central sleep apnea, CPAP is not sufficient and adaptive servo-ventilation (ASV), despite promising results in observational studies, showed no benefit in patients with symptomatic HF and reduced ejection fraction in the SERVE-HF randomized trial; on the contrary, there was unexpectedly increased mortality in the ASV group compared to controls, and so ASV is contraindicated in these patients, calling into question the definition and pathogenesis of SDB and risk stratification in these patients. There are many gaps in the evidence, and so further research is needed to better understand this issue: definitions, simple screening methods, and whether and how to treat SDB in patients with HF.
PMID: 29162360 [PubMed - as supplied by publisher]
Motion compensation with skin contact control for high intensity focused ultrasound surgery in moving organs.
Phys Med Biol. 2017 Nov 21;:
Authors: Diodato A, Cafarelli A, Schiappacasse A, Tognarelli S, Ciuti GC, Menciassi A
High Intensity Focused Ultrasound (HIFU) is an emerging therapeutic solution that enables non-invasive treatment of several pathologies, mainly in oncology. On the other hand, accurate targeting of moving abdominal organs (e.g., liver, kidney, pancreas) is still an open challenge. This paper proposes a novel method to compensate the physiological respiratory motion of organs during HIFU procedures, by exploiting a robotic platform for ultrasound-guided HIFU surgery provided with a therapeutic annular phased array transducer. The proposed method enables to keep the same contact point between the transducer and the patient's skin during the whole procedure, thus minimizing the modification of the acoustic window during the breathing phases. The motion of the target point is compensated through the rotation of the transducer around a virtual pivot point, while the focal depth is continuously adjusted thanks to the axial electronically steering capabilities of the HIFU transducer. The feasibility of the angular motion compensation strategy has been demonstrated in a simulated respiratory-induced organ motion environment. Based on the experimental results, the proposed method appears to be significantly accurate (i.e., the maximum compensation error is always under 1 mm), thus paving the way for the potential use of this technique for in-vivo treatment of moving organs, and therefore enabling a wide use of HIFU in clinics.
PMID: 29160777 [PubMed - as supplied by publisher]
An orphan cbb3-type cytochrome oxidase subunit supports Pseudomonas aeruginosa biofilm growth and virulence.
Elife. 2017 Nov 21;6:
Authors: Jo J, Cortez KL, Cornell WC, Price-Whelan A, Dietrich LE
Hypoxia is a common challenge faced by bacteria during associations with hosts due in part to the formation of densely packed communities (biofilms). cbb3-type cytochrome c oxidases, which catalyze the terminal step in respiration and have a high affinity for oxygen, have been linked to bacterial pathogenesis. The pseudomonads are unusual in that they often contain multiple full and partial (i.e. 'orphan') operons for cbb3-type oxidases and oxidase subunits. Here, we describe a unique role for the orphan catalytic subunit CcoN4 in colony biofilm development and respiration in the opportunistic pathogen Pseudomonas aeruginosa PA14. We also show that CcoN4 contributes to the reduction of phenazines, antibiotics that support redox balancing for cells in biofilms, and to virulence in a Caenorhabditis elegans model of infection. These results highlight the relevance of the colony biofilm model to pathogenicity and underscore the potential of cbb3-type oxidases as therapeutic targets.
PMID: 29160206 [PubMed - in process]
Pulmonary Rehabilitation With Balance Training for Fall Reduction in Chronic Obstructive Pulmonary Disease: Protocol for a Randomized Controlled Trial.
JMIR Res Protoc. 2017 Nov 20;6(11):e228
Authors: Beauchamp MK, Brooks D, Ellerton C, Lee A, Alison J, Camp PG, Dechman G, Haines K, Harrison SL, Holland AE, Marques A, Moineddin R, Skinner EH, Spencer L, Stickland MK, Xie F, Goldstein RS
BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality worldwide. A growing body of evidence shows that individuals with COPD have important deficits in balance control that may be associated with an increased risk of falls. Pulmonary rehabilitation (PR) is a key therapeutic intervention for individuals with COPD; however, current international guidelines do not include balance training and fall prevention strategies.
OBJECTIVE: The primary aim of this trial is to determine the effects of PR with balance training compared to PR with no balance training on the 12-month rate of falls in individuals with COPD. Secondary aims are to determine the effects of the intervention on balance, balance confidence, and functional lower body strength, and to estimate the cost-effectiveness of the program.
METHODS: A total of 400 individuals from nine PR centers across Canada, Europe, and Australia will be recruited to participate in a randomized controlled trial. Individuals with COPD who have a self-reported decline in balance, a fall in the last 2 years, or recent near fall will be randomly assigned to an intervention or control group. The intervention group will undergo tailored balance training in addition to PR and will receive a personalized home-based balance program. The control group will receive usual PR and a home program that does not include balance training. All participants will receive monthly phone calls to provide support and collect health care utilization and loss of productivity data. Both groups will receive home visits at 3, 6, and 9 months to ensure proper technique and progression of home exercise programs. The primary outcome will be incidence of falls at 12-month follow-up. Falls will be measured using a standardized definition and recorded using monthly self-report fall diary calendars. Participants will be asked to record falls and time spent performing their home exercise program on the fall diary calendars. Completed calendars will be returned to the research centers in prepaid envelopes each month. Secondary measures collected by a blinded assessor at baseline (pre-PR), post-PR, and 12-month follow-up will include clinical measures of balance, balance confidence, functional lower body strength, and health status. The cost-effectiveness of the intervention group compared with the control group will be evaluated using the incremental cost per number of falls averted and the incremental cost per quality-adjusted life years gained.
RESULTS: Recruitment for the study began in January 2017 and is anticipated to be complete by December 2019. Results are expected to be available in 2020.
CONCLUSIONS: Findings from this study will improve our understanding of the effectiveness and resource uses of tailored balance training for reducing falls in individuals with COPD. If effective, the intervention represents an opportunity to inform international guidelines and health policy for PR in individuals with COPD who are at risk of falling.
TRIAL REGISTRATION: ClinicalTrials.gov NCT02995681; https://clinicaltrials.gov/ct2/show/NCT02995681 (Archived by WebCite at http://www.webcitation.org/6ukhxgAsg).
PMID: 29158206 [PubMed]