Benefits of intratracheal and extrathoracic high-frequency percussive ventilation in a model of capnoperitoneum.

Abdominal inflation with CO2 is used to facilitate laparoscopic surgeries, however, providing adequate mechanical ventilation in this scenario is of major importance during anesthesia management. We characterized high-frequency percussive ventilation (HFPV) in protecting from the gas exchange and respiratory mechanical impairments during capnoperitoneum. In addition, we aimed to assess the difference between conventional pressure-controlled mechanical ventilation (CMV) and HFPV modalities generating the high-frequency signal intratracheally (HFPVi) or extrathoracally (HFPVe). Anesthetized rabbits (n = 16) were mechanically ventilated by random sequences of CMV, HFPVi, and HFPVe. The ventilator superimposed the conventional waveform with two high-frequency signals (5 Hz and 10 Hz) during intratracheal HFPV (HFPVi) and HFPV with extrathoracic application of oscillatory signals through a sealed chest cuirass (HFPVe). Lung oxygenation index ([Formula: see text]/[Formula: see text]), arterial partial pressure of carbon dioxide ([Formula: see text]), intrapulmonary shunt (Qs/Qt), and respiratory mechanics were assessed before abdominal inflation, during capnoperitoneum, and after abdominal deflation. Compared with CMV, HFPVi with additional 5-Hz oscillations during capnoperitoneum resulted in higher [Formula: see text]/[Formula: see text], lower [Formula: see text], and decreased Qs/Qt. These improvements were smaller but remained significant during HFPVi with 10 Hz and HFPVe with either 5 or 10 Hz. The ventilation modes did not protect against capnoperitoneum-induced deteriorations in respiratory tissue mechanics. These findings suggest that high-frequency oscillations combined with conventional pressure-controlled ventilation improved lung oxygenation and CO2 removal in a model of capnoperitoneum. Compared with extrathoracic pressure oscillations, intratracheal generation of oscillatory pressure bursts appeared more effective. These findings may contribute to the optimization of mechanical ventilation during laparoscopic surgery.NEW & NOTEWORTHY The present study examines an alternative and innovative mechanical ventilation modality in improving oxygen delivery, CO2 clearance, and respiratory mechanical abnormalities in a clinically relevant experimental model of capnoperitoneum. Our data reveal that high-frequency oscillations combined with conventional ventilation improve gas exchange, with intratracheal oscillations being more effective than extrathoracic oscillations in this clinically relevant translational model.

Lipid Droplet Proteins in Acne Skin: A Sound Target for the Maintenance of Low Comedogenic Sebum and Acne-Prone Skin Health.

In adipocytes and sebocytes, lipid droplet proteins control the storage of lipids in organized droplets and their release on demand. The contribution of lipid droplet proteins to the pathogenesis of acne is plausible because they control the levels of comedogenic free fatty acids. The expression of two lipid droplet proteins, CIDEA and PLIN2, was analyzed in the skin of patients with acne by immunohistochemistry and western blotting. The design of clinical protocols allowed correlating the expression of CIDEA and PLIN2 with both comedogenesis and the release of free fatty acids. Both proteins were detected by immunohistochemistry in the sebaceous glands of patients with acne, with a disturbed expression pattern of PLIN2 compared with that in the controls. Higher levels of PLIN2 and CIDEA, as detected by western blotting in the infundibulum, significantly correlated with lower ongoing comedogenesis over 48 weeks of Silybum marianum fruit extract application. Accordingly, free fatty acid release from sebum triglycerides was significantly decreased, as shown with two distinct methods. The data are consistent with the expected role of PLIN2 and CIDEA in the prevention of comedogenic free fatty acid release. Modulation of PLIN2 and CIDEA expression appears as a sound target for the maintenance of low comedogenic sebum and acne-prone skin health.

From the Cover: High Susceptibility of Lrig1 Sebaceous Stem Cells to TCDD in Mice.

We have previously shown that cytochrome P450 1A1 (CYP1A1) was highly induced for a long period of time in a patient who had been poisoned by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a compound known to activate the aryl hydrocarbon receptor (AhR). During that period of time, no sebaceous glands could be observed in the skin of this patient. In this study, starting from observations in the patient exposed to TCDD, we analyzed the seboatrophy induced by dioxins in mice. We observed a very different pattern of AhR and CYP1A1 immunostaining in skin biopsies of the patient. When applying TCDD and beta-naphthoflavone, another AhR agonist, on the ears of C57BL/6J mice, we reproduced (1) an atrophy of sebaceous glands, (2) a strong induction of CYP1A1 within the glands, and (3) a dramatic repression of the genes encoding the sebogenic enzymes AWAT1, ELOVL3, and SCD1. These effects were reversible. Leucine-rich repeats and immunoglobulin-like domains protein 1 (LRIG1) expressing progenitor cells, found in the vicinity of sebaceous glands, were shown to be the initial skin cellular targets of AhR agonists. These cells retained the DNA label BrdU and colocalized with the CYP1A1 protein for at least 30 days. A downregulation of LRIG1 by siRNA in cultured sebocytes significantly decreased the CYP1A1 response to TCDD, indicating that LRIG1 contributes to a higher susceptibility of AhR agonists. In conclusion, these observations provide for the first time a strong experimental support to the concept that dioxin-induced skin pathology may be driven by a molecular switch in progenitor cells involved in the physiological turnover of sebaceous glands.

Aryl Hydrocarbon Receptor Activation in Acne Vulgaris Skin: A Case Series from the Region of Naples, Italy.

BACKGROUND: Dioxins are persistent organic pollutants present in the environment. They exert their biological effects by binding to an intracellular receptor, the aryl hydrocarbon receptor (AhR). Activation of AhR leads to the induction of cytochrome p450 1A1 (CYP1A1). Expression of CYP1A1 in human skin is a key marker for AhR activation, and it may induce comedogenesis resulting in acne-like lesions known as chloracne/metabolising acquired dioxin-induced skin hamartomas (MADISH). The contribution of this pathway in patients seen in a busy acne clinic is unknown. MATERIALS AND METHODS: We explored the expression of CYP1A1 by immunohistochemistry in the acne lesions of 16 patients living in the region of Naples, Italy, where epidemiological studies have suggested a possibly increased exposure to environmental dioxins. A composite score to outline potential components of the chloracne/MADISH histological pattern was used. RESULTS: CYP1A1 expression was observed in 11 lesions (69%) and was distributed in sebaceous glands, follicular epithelium, cystic wall and endothelial cells. The histological score for chloracne/MADISH was 'likely' in 3 cases and 'possible' in 11 cases. Compared to current data on CYP1A1 expression in the skin of 67 patients with proven exposure to AhR agonists, these data indicate a high incidence of AhR activation in this series. CONCLUSION: This is the first study analysing AhR activation in skin in a series of patients from a hospital-based acne clinic. It provides information for future controlled prospective studies. The significance of CYP1A1 expression in terms of AhR ligand exposure is discussed.

The cutaneous lesions of dioxin exposure: lessons from the poisoning of Victor Yushchenko.

Several million people are exposed to dioxin and dioxin-like compounds, primarily through food consumption. Skin lesions historically called "chloracne" are the most specific sign of abnormal dioxin exposure and classically used as a key marker in humans. We followed for 5 years a man who had been exposed to the most toxic dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), at a single oral dose of 5 million-fold more than the accepted daily exposure in the general population. We adopted a molecular medicine approach, aimed at identifying appropriate therapy. Skin lesions, which progressively covered up to 40% of the body surface, were found to be hamartomas, which developed parallel to a complete and sustained involution of sebaceous glands, with concurrent transcriptomic alterations pointing to the inhibition of lipid metabolism and the involvement of bone morphogenetic proteins signaling. Hamartomas created a new compartment that concentrated TCDD up to 10-fold compared with serum and strongly expressed the TCDD-metabolizing enzyme cytochrome P450 1A1, thus representing a potentially significant source of enzymatic activity, which may add to the xenobiotic metabolism potential of the classical organs such as the liver. This historical case provides a unique set of data on the human tissue response to dioxin for the identification of new markers of exposure in human populations. The herein discovered adaptive cutaneous response to TCDD also points to the potential role of the skin in the metabolism of food xenobiotics.

Sevoflurane and desflurane protect cholinergic-induced bronchoconstriction of hyperreactive airways in rabbits.

PURPOSE: The potential of desflurane to alter respiratory mechanics in the presence of bronchial hyperresponsiveness (BHR) is still a subject of debate. Accordingly, we evaluated the bronchoprotective potential of desflurane compared with sevoflurane following cholinergic lung constriction in rabbits with normal and hyperreactive airways. METHODS: The input impedance of the respiratory system (Zrs) was measured during midazolam-based anesthesia before and during intravenous infusions of increasing doses of methacholine (MCh). The rabbits in the control group (Group C) were then randomized to receive either sevoflurane 1 MAC followed by desflurane 1 MAC or vice versa, whereas ovalbumin-sensitized rabbits received sevoflurane followed by desflurane (Group S-SD) or vice versa (Group S-DS). Baseline Zrs measurements and the MCh provocations were repeated under the maintenance of each volatile agent. Airway resistance (Raw), tissue damping (G), and elastance data were obtained from Zrs by model fitting. RESULTS: Similar bronchoprotective effects of sevoflurane and desflurane against MCh-induced bronchoconstriction were observed independently of the severity of the bronchospasm and the presence of BHR. With sevoflurane, the decreases in Raw ranged from 22 (8.8)% to 44 (12)%, and with desflurane, they ranged from 22 (8.7)% to 50 (12)%. The increases in G reflecting the enhanced ventilation heterogeneities in the lung periphery were not affected by the volatile agents. CONCLUSIONS: If the contractile stimulus is cholinergic in origin, sevoflurane and desflurane exert similar bronchoprotective potentials to act against lung constriction independent of the presence of BHR. These volatile anesthetics otherwise lack a potential to improve the enhanced ventilation heterogeneities that develop particularly in the presence of BHR.

Prevention of bronchial hyperreactivity in a rat model of precapillary pulmonary hypertension.

BACKGROUND: The development of bronchial hyperreactivity (BHR) subsequent to precapillary pulmonary hypertension (PHT) was prevented by acting on the major signalling pathways (endothelin, nitric oxide, vasoactive intestine peptide (VIP) and prostacyclin) involved in the control of the pulmonary vascular and bronchial tones. METHODS: Five groups of rats underwent surgery to prepare an aorta-caval shunt (ACS) to induce sustained precapillary PHT for 4 weeks. During this period, no treatment was applied in one group (ACS controls), while the other groups were pretreated with VIP, iloprost, tezosentan via an intraperitoneally implemented osmotic pump, or by orally administered sildenafil. An additional group underwent sham surgery. Four weeks later, the lung responsiveness to increasing doses of an intravenous infusion of methacholine (2, 4, 8 12 and 24 µg/kg/min) was determined by using the forced oscillation technique to assess the airway resistance (Raw). RESULTS: BHR developed in the untreated rats, as reflected by a significant decrease in ED50, the equivalent dose of methacholine required to cause a 50% increase in Raw. All drugs tested prevented the development of BHR, iloprost being the most effective in reducing both the systolic pulmonary arterial pressure (Ppa; 28%, p = 0.035) and BHR (ED50 = 9.9 ± 1.7 vs. 43 ± 11 µg/kg in ACS control and iloprost-treated rats, respectively, p = 0.008). Significant correlations were found between the levels of Ppa and ED50 (R = -0.59, p = 0.016), indicating that mechanical interdependence is primarily responsible for the development of BHR. CONCLUSIONS: The efficiency of such treatment demonstrates that re-establishment of the balance of constrictor/dilator mediators via various signalling pathways involved in PHT is of potential benefit for the avoidance of the development of BHR.

Precapillary pulmonary hypertension leads to reversible bronchial hyperreactivity in rats.

Congenital heart disease with left-to-right shunt may lead to precapillary pulmonary hypertension (PREPHT) with potential lung function impairment. The authors investigated the effects of PREPHT on lung responsiveness in a rat model of PREPHT by creating and repairing an abdominal aortocaval shunt (ACS). Rats were studied 4 weeks after the induction of ACS, and 4 weeks after its surgical repair. Control rats underwent sham surgery. To assess bronchial hyperreactivity, airway resistance (Raw) was measured at baseline and after increasing doses of methacholine. Raw was estimated by model fitting of the mechanical impedance of the respiratory system generated by forced oscillation technique. Lung morphological changes were assessed by histology. The prolonged presence of the ACS led to only minor changes in the basal respiratory mechanics, whereas it induced marked bronchial hyperreactivity, the methacholine-induced elevations in Raw being 49% +/- 5% before and 232% +/- 32% (P <.001) after ACS. These alterations were not associated with any changes in lung histology and were completely reversible on closure of the shunt. These results suggest that the induction of chronic increases in pulmonary blood flow and pressure causes reversible bronchial hyperreactivity. This may be consequent to the altered mechanical interdependence between the pulmonary vasculature and the respiratory tract.

Mechanisms for lung function impairment and airway hyperresponsiveness following chronic hypoxia in rats.

Although chronic normobaric hypoxia (CH) alters lung function, its potential to induce bronchial hyperreactivity (BHR) is still controversial. Thus the effects of CH on airway and tissue mechanics separately and changes in lung responsiveness to methacholine (MCh) were investigated. To clarify the mechanisms, mechanical changes were related to end-expiratory lung volume (EELV), in vivo results were compared with those in vitro, and lung histology was assessed. EELV was measured plethysmographically in two groups of rats exposed to 21 days of CH (11% O(2)) or to normoxia. Total respiratory impedance was measured under baseline conditions and following intravenous MCh challenges (2-18 microg x kg(-1) x min(-1)). The lungs were then excised and perfused, and the pulmonary input impedance was measured, while MCh provocations were repeated under a pulmonary capillary pressure of 5, 10, and 15 mmHg. Airway resistance, tissue damping, and elastance were extracted from the respiratory impedance and pulmonary input impedance spectra. The increases in EELV following CH were associated with decreases in airway resistance, whereas tissue damping and elastance remained unaffected. CH led to the development of severe BHR to MCh (206 +/- 30 vs. 95 +/- 24%, P < 0.001), which was not detectable when the same lungs were studied in vitro at any pulmonary capillary pressure levels maintained. Histology revealed pulmonary arterial vascular remodeling with overexpression of alpha-smooth muscle actin antibody in the bronchial wall. These findings suggest that, despite the counterbalancing effect of the increased EELV, BHR develops following CH, only in the presence of intact autonomous nervous system. Thus neural control plays a major role in the changes in the basal lung mechanics and responsiveness following CH.

Impact of elevated pulmonary blood flow and capillary pressure on lung responsiveness.

Since alterations in pulmonary hemodynamics may lead to airway hyperreactivity, the consequences of individual changes in pulmonary blood flow (Qp) and capillary pressure (Pc) on lung responsiveness were investigated. During maintenance of a steady-state Pc of 5, 10, or 15 mmHg (groups 1-3), acute increases of Qp were generated in isolated, perfused rat lungs by simultaneous pulmonary arterial pressure elevation and venous pressure lowering. Conversely, at constant low (groups 4 and 5) or high Qp (groups 6 and 7), Pc was lowered or elevated by changing, in parallel, the pulmonary arterial and venous pressures. Pulmonary input impedance was measured under baseline conditions and during methacholine provocation (2-18 microg*kg(-1)*min(-1)), whereas the pulmonary hemodynamics were altered in accordance with the group allocation. The airway resistance and constant-phase parenchymal model parameters were identified from the pulmonary input impedance spectra. Increases of Qp at constant Pc had no effect on the basal lung mechanics, whereas they enhanced the lung reactivity to methacholine, particularly when high Pc was maintained [peak airway resistance increases of 299 +/- 99% (SE) vs. 609 +/- 217% at Qp levels of 5 and 10 ml/min, respectively, P < 0.05]. In contrast, the change of Pc at constant Qp slightly deteriorated the basal parenchymal mechanics without affecting the lung responsiveness. These findings suggest that increases in Qp per se may lead to the development of airway hyperreactivity. This phenomenon may contribute to the airway susceptibility under conditions associated with simultaneous elevations in pulmonary vascular pressures and Qp, such as exercise-induced asthma and the situation in children with congenital heart diseases.

Lung mechanical and vascular changes during positive- and negative-pressure lung inflations: importance of reference pressures in the pulmonary vasculature.

The continuous changes in lung mechanics were related to those in pulmonary vascular resistance (Rv) during lung inflations to clarify the mechanical changes in the bronchoalveolar system and the pulmonary vasculature. Rv and low-frequency lung impedance data (Zl) were measured continuously in isolated, perfused rat lungs during 2-min inflation-deflation maneuvers between transpulmonary pressures of 2.5 and 22 cmH(2)O, both by applying positive pressure at the trachea and by generating negative pressure around the lungs in a closed box. ZL was averaged and evaluated for 2-s time windows; airway resistance (Raw), parenchymal damping and elastance (H) were determined in each window. Lung inflation with positive and negative pressures led to very similar changes in lung mechanics, with maximum decreases in Raw [-68 +/- 4 (SE) vs. -64 +/- 18%] and maximum increases in H (379 +/- 36 vs. 348 +/- 37%). Rv, however, increased with positive inflation pressure (15 +/- 1%), whereas it exhibited mild decreases during negative-pressure expansions (-3 +/- 0.3%). These results demonstrate that pulmonary mechanical changes are not affected by the opposing modes of lung inflations and confirm the importance of relating the pulmonary vascular pressures in interpreting changes in Rv.

Mechanisms of airway hyper-responsiveness after coronary ischemia.

We explored the consequences of myocardial ischemia (MI) on the lung responsiveness and identified the pathophysiological mechanisms involved. Airway resistance (R(aw)) was identified from the respiratory system input impedance (Z(rs)) in rats. Z(rs) was determined under baseline conditions, and following iv boluses of 20 and 30 microg/kg serotonin. MI was then induced in the animals in Group I by ligating the left-interventricular coronary artery, while rats in Group C underwent sham surgery. Four weeks later, baseline Z(rs) and its changes following serotonin administration were reassessed. Lung morphological changes were assessed by histology, and alpha smooth muscle actin cells (alpha-SMA) were identified. MI induced no changes in baseline R(aw) but led to bronchial hyper-reactivity (BHR) with 2.7+/-0.5-times (p<0.05) greater responses in R(aw) to 30 microg/kg serotonin. Perivascular edema and alpha-SMA cell proliferation were observed after MI. The development of BHR following MI is a consequence of the expression of alpha-SMA, while the geometrical alterations caused by the pulmonary vascular engorgement have smaller impact.

Differential roles of endothelin-1 ETA and ETB receptors and vasoactive intestinal polypeptide in regulation of the airways and the pulmonary vasculature in isolated rat lung.

The available treatment strategies against pulmonary hypertension include the administration of endothelin-1 (ET-1) receptor subtype blockers (ET(A) and ET(B) antagonists); vasoactive intestinal polypeptide (VIP) has recently been suggested as a potential new therapeutic agent. We set out to investigate the ability of these agents to protect against the vasoconstriction and impairment of lung function commonly observed in patients with pulmonary hypertension. An ET(A) blocker (BQ123), ET(B) blocker (BQ788), a combination of these selective blockers (ET(A) + ET(B) blockers) or VIP (V6130) was administered into the pulmonary circulation in four groups of perfused normal rat lungs. Pulmonary vascular resistance (PVR) and forced oscillatory lung input impedance (Z(L)) were measured in all groups under baseline conditions and at 1 min intervals following ET-1 administrations. The airway resistance, inertance, tissue damping and elastance were extracted from the Z(L) spectra. While VIP, ET(A) blocker and combined ET(A) and ET(B) blockers significantly prevented the pulmonary vasoconstriction induced by ET-1, ET(B) blockade enhanced the ET-1-induced increases in PVR. In contrast, the ET(A) and ET(B) blockers markedly elevated the ET-1-induced increases in airway resistance, while VIP blunted this constrictor response. Our results suggest that VIP potently acts against the airway and pulmonary vascular constriction mediated by endothelin-1, while the ET(A) and ET(B) blockers exert a differential effect between airway resistance and PVR.

The contribution of the pulmonary microvascular pressure in the maintenance of an open lung during mechanical ventilation.

Changes in pulmonary hemodynamics modify the mechanical properties of the lungs. The effects of alterations in pulmonary capillary pressure (Pc) were investigated on the airway and lung tissue mechanics during positive-pressure ventilation and following lung recruitment maneuvers. Isolated, mechanically normoventilated (PEEP 2.5 cmH(2)O) rat lungs were perfused with Pc set to 0 (unperfused), 5, 10 or 15 mmHg, in random sequence. The pulmonary input impedance (ZL) was measured at end-expiration before and after a 10-min long ventilation. After inflation of the lung to 30 cmH(2)O during P-V curve recordings, another set of ZL was measured to evaluate the degree of recruitment. The PEEP was then decreased to 0.5 cmH(2)O and the sequence was repeated. Airway resistance and parenchymal damping and elastance (H) were estimated from ZL by model fitting. From the P-V curves, elastance (E) and hysteresis indices were determined. Mechanical ventilation at both PEEP levels resulted primarily in elevations in the tissue parameters, with the greatest increases at the 0 Pc level (H changes of 27.8+/-4.2 and 61.3+/-3.7% at 2.5 and 0.5 cmH(2)O PEEP, respectively). The maintenance of physiological Pc (10 mmHg) led to a significantly lower elevation in H (11.6+/-1.5% versus 31.4+/-3.6%). The changes in the oscillatory mechanics were also reflected in E and the hysteresis of the P-V curves. These findings indicate that pulmonary hypoperfusion during mechanical ventilation forecasts a parenchymal mechanical deterioration. Physiological pressure in the pulmonary capillaries is therefore an important mechanical factor promoting maintenance of the stability of the alveolar architecture during positive-pressure mechanical ventilation.