Midbrain control of breathing and blood pressure: The role of periaqueductal gray matter and mesencephalic collicular neuronal microcircuit oscillators

Whole-brain monosynaptic inputs and outputs of leptin receptor b neurons of the nucleus tractus solitarii in mice

The nucleus tractus solitarii (NTS) is the primary central station that integrates visceral afferent information and regulates respiratory, gastrointestinal, cardiovascular, and other physiological functions. Leptin receptor b (LepRb)-expressing neurons of the NTS (NTSLepRb neurons) are implicated in central respiration regulation, respiratory facilitation, and respiratory drive enhancement. Furthermore, LepRb dysfunction is involved in obesity, insulin resistance, and sleep-disordered breathing. However, the monosynaptic inputs and outputs of NTSLepRb neurons in whole-brain mapping remain to be elucidated. Therefore, the exploration of its whole-brain connection system may provide strong support for comprehensively understanding the physiological and pathological functions of NTSLepRb neurons. In the present study, we used a cell type-specific, modified rabies virus and adeno-associated virus with the Cre-loxp system to map monosynaptic inputs and outputs of NTSLepRb neurons in LepRb-Cre mice. The results showed that NTSLepRb neurons received inputs from 48 nuclei in the whole brain from five brain regions, including especially the medulla. We found that NTSLepRb neurons received inputs from nuclei associated with respiration, such as the pre-Bötzinger complex, ambiguus nucleus, and parabrachial nucleus. Interestingly, some brain areas related to cardiovascular regulation-i.e., the ventrolateral periaqueductal gray and locus coeruleus-also sent a small number of inputs to NTSLepRb neurons. In addition, anterograde tracing results demonstrated that NTSLepRb neurons sent efferent projections to 15 nuclei, including the dorsomedial hypothalamic nucleus and arcuate hypothalamic nucleus, which are involved in regulation of energy metabolism and feeding behaviors. Quantitative statistical analysis revealed that the inputs of the whole brain to NTSLepRb neurons were significantly greater than the outputs. Our study comprehensively revealed neuronal connections of NTSLepRb neurons in the whole brain and provided a neuroanatomical basis for further research on physiological and pathological functions of NTSLepRb neurons.

A First Look at Childhood Abuse in Women with Obstructive Sleep Apnea

Study objectives. Women who experienced childhood sexual abuse have higher rates of obesity, a risk factor for obstructive sleep apnea (OSA). We assessed if prior childhood sexual abuse was more common in women with OSA vs. control, with possible mediation by obesity. Methods . We studied 21 women with OSA (age mean±s.d. 59±12 years, body mass index (BMI) 33±8 kg/m 2 , respiratory event index [REI] 25±16 events/hour, Epworth Sleepiness Scale [ESS] 8±5) and 21 women without OSA (age 53±9 years, BMI 25±5 kg/m 2 , REI (in 7/21 women) 1±1 events/hour, ESS 5±3). We evaluated four categories of trauma (general trauma, physical, emotional, and sexual abuse) with the early trauma inventory self-report-short form (ETISR-SF). We assessed group differences in trauma scores with independent samples t-tests and multiple regressions. Parametric Sobel tests were used to model BMI as a mediator for individual trauma scores predicting OSA in women. Results. Early childhood sexual abuse reported on the ETISR-SF was 2.4 times more common in women with vs. without OSA ( p =0.02 for group difference). Other trauma scores were not significantly different between women with and without OSA. However, BMI was a significant mediator ( p =0.02) in predicting OSA in women who experienced childhood physical abuse. Conclusions. Childhood sexual abuse was more common in a group of women with OSA than those without OSA. Additionally, BMI was a mediator for OSA of childhood physical but not sexual abuse. There may be physiological impacts of childhood trauma in women that predispose them to OSA.

Baroreflex sensitivity during rest and pressor challenges in obstructive sleep apnea patients with and without CPAP

INTRODUCTION

Obstructive sleep apnea (OSA) increases sympathetic vasoconstrictor drive and reduces baroreflex sensitivity (BRS), the degree to which blood pressure changes modify cardiac output. Whether nighttime continuous positive airway pressure (CPAP) corrects BRS in the awake state in OSA remains unclear. We assessed spontaneous BRS using non-invasive continuous BP and ECG recordings at rest and during handgrip and Valsalva challenges, maneuvers that increase vasoconstrictor drive with progressively higher BP, in untreated OSA (unOSA), CPAP-treated OSA (cpOSA) and healthy (CON) participants.

METHODS

In a cross-sectional study of 104 participants, 34 unOSA (age mean±std, 50.6±14.1years; Respiratory Event Index [REI] 21.0±15.3 events/hour; 22male), 31 cpOSA (49.6±14.5years; REI 23.0±14.2 events/hour; 22male; self-report 4+hours/night,5+days/week,6months), and 39 CON (42.2±15.0years; 17male), we calculated BRS at rest and during handgrip and Valsalva. Additionally, we correlated BP variability (BPV) with BRS during these protocols.

RESULTS

BRS in unOSA, cpOSA and CON was, respectively (mean±sdv in ms/mmHg), at rest: 14.8±11.8, 15.8±17.0, 16.1±11.3; during handgrip 13.3±7.6, 12.7±8.4, 16.4±8.7; and during Valsalva 12.7±8.0, 11.5±6.6, 15.1±8.9. BRS was lower in cpOSA than CON for handgrip (p=0.04) and Valsalva (p=0.03). BRS was negatively correlated with BPV in unOSA during Valsalva and handgrip for cpOSA, both R=-0.4 (p=0.02). BRS was negatively correlated with OSA severity (levels: none, mild, moderate, severe) at R=-0.2 (p=0.04,n=104).

CONCLUSIONS

As expected, BRS was lower and BPV higher in OSA during the pressor challenges, and disease severity negatively correlated with BRS. In this cross-sectional study, both CPAP-treated (self-reported) and untreated OSA showed reduced BRS, leaving open whether within-person CPAP improves BRS.

Freezing revisited: coordinated autonomic and central optimization of threat coping

Animals have sophisticated mechanisms for coping with danger. Freezing is a unique state that, upon threat detection, allows evidence to be gathered, response possibilities to be previsioned and preparations to be made for worst-case fight or flight. We propose that - rather than reflecting a passive fear state - the particular somatic and cognitive characteristics of freezing help to conceal overt responses, while optimizing sensory processing and action preparation. Critical for these functions are the neurotransmitters noradrenaline and acetylcholine, which modulate neural information processing and also control the sympathetic and parasympathetic branches of the autonomic nervous system. However, the interactions between autonomic systems and the brain during freezing, and the way in which they jointly coordinate responses, remain incompletely explored. We review the joint actions of these systems and offer a novel computational framework to describe their temporally harmonized integration. This reconceptualization of freezing has implications for its role in decision-making under threat and for psychopathology.

The Mesencephalic Periaqueductal Gray, a Further Structure Involved in Breathing Failure Underlying Sudden Infant Death Syndrome

The aim of this study was to investigate the involvement of the periaqueductal gray (PAG), an area of gray matter surrounding the cerebral aqueduct of Sylvius, in the pathogenetic mechanism of SIDS, a syndrome frequently ascribed to arousal failure from sleep. We reconsidered the same samples of brainstem, more precisely midbrain specimens, taken from a large series of sudden infant deaths, namely 46 cases aged from 1 to about 7 months, among which 26 SIDS and 20 controls, in which we already highlighted significant developmental alterations of the substantia nigra, another mesencephalic structure with a critical role in breath and awakening regulation. Specific histological and immunohistochemical methods were applied to examine the PAG cytoarchitecture and the expression of the tyrosine hydroxylase, a marker of catecholaminergic neurons. Hypoplasia of the PAG subnucleus medialis was observed in 65% of SIDS but never in controls; tyrosine hydroxylase expression was significantly higher in controls than in SIDS. A significant correlation was found between these findings and those related to the substantia nigra, demonstrating a link between these neuronal centers and the brainstem respiratory network and a common involvement in the sleep-arousal phase failure leading to SIDS.

Synergistic efficacy of curcumin and anti-programmed cell death-1 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) ranks near the top in the global list of malignancies causing cancer-related death. Recently, combination therapy has gained popularity in treating this cancer. We tried to investigate the efficacy of combined treatment with curcumin and anti-programmed cell death-1 (anti-PD-1) in HCC. Hep3B cells were treated with different concentrations of curcumin, followed by determination of Hep3B cell proliferation and programmed cell death ligand-1 (PD-L1) expression. Then, Hep3B cells were co-cultured with peripheral blood mononuclear cells (PBMCs), after which the Hep3B cell growth and immune activity were detected following treatment with curcumin and/or anti-PD-1. Besides, we investigated the effect of transforming growth factor beta 1 (TGF-β1) on lymphocyte activation and the interaction between E1A binding protein P300 (P300), histone acetylation, TGF-β1, and thrombin. Additionally, the synergistic role of curcumin and anti-PD-1 in mouse models of HCC was studied. Curcumin retarded Hep3B cell growth and reduced surface PD-L1 expression in Hep3B cells. After co-culture of Hep3B cells and PBMCs, curcumin had a synergistic effect with anti-PD-1 to slow Hep3B cell proliferation, activate lymphocytes, inhibit immune evasion, and down-regulate TGF-β1 expression. Functionally, curcumin inhibited thrombin to reduce P300-induced histone acetylation in the TGF-β1 promoter region, and anti-PD-1 suppressed binding of PD-1 and PD-L1 to promote immune activity; the combination of the two showed better in vitro anti-cancer effects. In vivo, curcumin combined with anti-PD-1 also lowered HCC growth rate and improved the tumor microenvironment. In conclusion, the combination of curcumin and anti-PD-1 is synergistically effective in the treatment of HCC treatment.

Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus)

Previous reports suggested the existence of direct somatic motor control over heart rate (f H) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2 storage management, but would also allow ventilation-perfusion matching for selective gas exchange, where O2 and CO2 can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid diving related gas bubble formation during repeated dives, and how stress could interrupt this mechanism and cause excessive N2 exchange. To investigate the conditioned response, we measured the f H-response before and during static breath-holds in three bottlenose dolphins (Tursiops truncatus) when shown a visual symbol to perform either a long (LONG) or short (SHORT) breath-hold, or during a spontaneous breath-hold without a symbol (NS). The average f H (if Hstart), and the rate of change in f H (dif H/dt) during the first 20 s of the breath-hold differed between breath-hold types. In addition, the minimum instantaneous f H (if Hmin), and the average instantaneous f H during the last 10 s (if Hend) also differed between breath-hold types. The dif H/dt was greater, and the if Hstart, if Hmin, and if Hend were lower during a LONG as compared with either a SHORT, or an NS breath-hold (P < 0.05). Even though the NS breath-hold dives were longer in duration as compared with SHORT breath-hold dives, the dif H/dt was greater and the if Hstart, if Hmin, and if Hend were lower during the latter (P < 0.05). In addition, when the dolphin determined the breath-hold duration (NS), the f H was more variable within and between individuals and trials, suggesting a conditioned capacity to adjust the f H-response. These results suggest that dolphins have the capacity to selectively alter the f H-response during diving and provide evidence for significant cardiovascular plasticity in dolphins.