Circulating endogenous opioids and ventilatory response to CO2 and hypoxia

The role of endogenous opioids in the control of breathing is not yet well defined. Radioimmunoassays that measure beta-endorphin (BE) and met-enkephalin (MET) having recently become available, we decided to evaluate the possible relation between the blood levels of these two opioids and different hypercapnic and hypoxic ventilatory responses observed in a group of normal subjects. Ventilatory response to hypercapnia (n = 9) and to hypoxia (n = 7) were determined by classical rebreathing methods. A voluntary isocapnic normoxic hyperventilation test was used as a control. Basal levels of BE and MET did not correlate with the magnitude of the ventilatory response to either hypercapnia or hypoxia. Moreover, BE and MET levels measured repeatedly up to 30 min after each test did not change significantly. We conclude that circulating endogenous opioids do not play a role in the control of breathing in normal humans. These results do not rule out a possible role for these substances as locally released mediators.

Effects of LTB4 and Ca++ ionophore A23187 on the release by human alveolar macrophages of factors controlling fibroblast functions

Cultured human alveolar macrophages from smokers with lung cancer produced spontaneously variable amounts of factors stimulating fibroblast proliferation and production of prostaglandin E2 and collagenase by fibroblasts. These biological activities belong to molecules similar or identical to interleukin 1. Exogenous leukotriene B4 added to alveolar macrophage cultures increased the production of these factors. The Ca++ ionophore A23187 was found to have similar effects. By the control of monokine production, leukotriene B4 locally released by inflammatory cells may modulate lung fibroblast functions.

Cultured human alveolar macrophages from smokers with lung cancer: resolution of factors that stimulate fibroblast proliferation, production of collagenase, or prostaglandin E2

Marked connective tissue remodelling involves both destruction and repair in inflammatory lung diseases. Throughout the remodelling event, it was reasoned that alveolar macrophages may release substances similar to those produced by blood monocyte-macrophages that affect fibroblast functions, ie, the interleukin 1 family of monokines (or cytokines). We have examined human alveolar macrophage cultures obtained after bronchoalveolar lavage of freshly excised lungs from heavy smokers with bronchial carcinoma. Crude culture media contained fibroblast proliferative activity and collagenase- and PGE2- production-stimulating activity. The main peak of these biological activities was located around approximately 18 kilodaltons (kD) on gel filtration chromatography. Resolution of this peak by high performance liquid chromatography showed the presence of three distinct peaks, with quantitative and qualitative differences in biological activities. This suggests the presence of heterogeneous factors.

Simultaneous measurement of serotonin and propranolol pulmonary extraction in patients after extracorporeal circulation and surgery

To evaluate the use of markers of pulmonary endothelial cell function in humans, we simultaneously measured the pulmonary extraction of serotonin (SER) and propranolol (PROP) in patients before and after extracorporeal circulation (ECC) for coronary bypass surgery. No change was seen in SER extraction ratio after anesthesia, ECC, and surgery. Twenty-four hours after ECC and surgery, PROP extraction ratio was decreased by 11%. It remained low for as long as 5 days thereafter. A similar drop in PROP extraction was found in 6 patients 24 h after ilioaortic bypass surgery, without ECC (from 81 to 66%, p less than 0.01). Treatment of 11 other patients with a 30-min period of continuous positive airway pressure (CPAP), 24 to 48 h after ECC, resulted in a significant increase in PROP extraction ratio from 61 to 67% (p less than 0.01). Measurement of PROP extraction appears to be more sensitive than that of SER to lung changes related to postoperative atelectasis.

Direct toxic effects of paraquat and oxygen on cultured endothelial cells

Paraquat (PQ) is a herbicide known to generate O2 radicals and to injure lung epithelial cells, leading eventually to pulmonary fibrosis. To test for the possible existence of a direct cytotoxic action of PQ on endothelial cells, we have studied, for up to 5 days, the action of 10(-6) to 10(-4) M PQ on primary cultures of pig aortic endothelial cells and compared these effects to those obtained with exposure to 95% O2-5% CO2. The decrease in DNA and protein content of Petri dishes and the increase in lactate dehydrogenase release were found to depend on PQ concentration and the duration of exposure to PQ. The toxic effects of hyperoxia were intermediate, ranging between those obtained with 10(-5) and 10(-4) M PQ. Hyperoxia and 10(-4) M PQ produced a similar marked inhibition of DNA synthesis after a 1-day period of exposure. Combined exposure to both PQ and hyperoxia resulted in changes comparable to those obtained with hyperoxia alone (decrease in protein and DNA content) or PQ alone (lactate dehydrogenase release). Additive effects were seen only for the inhibition of DNA synthesis. The selenomethionine-related increase in glutathione peroxidase activity had a protective effect against hyperoxia-induced lactate dehydrogenase release but not against PQ induced cytolysis. Finally, shorter exposures to O2 and PQ revealed the existence of a trend toward recovery only for cells exposed to hyperoxia. The prolonged toxic action of PQ could not be related to PQ accumulation and storage by endothelial cells. These studies indicate that PQ can exert a direct, dose-dependent, and prolonged cytotoxic effect on cultured endothelial cells.

[Respiratory problems during sleep]

Continuous recording of numerous physiological variables during the night has led to the discovery of various respiratory disorders occurring during sleep. The most important are: 1. central apneas, defined by excessive frequency of respiratory arrests of excessive duration, 2. obstructive apneas, characterized by marked obstruction at the level of the oropharynx with persistence of respiratory movements, 3. episodes of marked nocturnal hypoxemia, without apnea, in certain patients with chronic obstructive lung disease. The pathophysiology, clinical picture and possible therapeutic resources are analyzed for each of the respiratory disorders occurring during sleep.

Ventilatory response to bronchospasm induced by methylcholine and histamine in man

In 9 normal subjects, we compared mouth occlusion pressure (P0.1) and breathing pattern in bronchospasm of the same magnitude induced by inhalation of acetyl-beta-methylcholine (M) and histamine phosphate (H). The measurements were performed on two different days, in a single blind randomized crossover design, under basal conditions first, then after control inhalation of isotonic buffered saline and finally after inhalation of M or H. For a same mean decrease in FEV1 (+/- SD) by 22.2% (+/- 7.2) after M and 22.3% (+/- 9.4) after H (P less than 0.001), the increases in P0.1 were similar (P less than 0.01 for both drugs) and were correlated to the magnitude of the bronchospasm (r = 0.775, P less than 0.01 for M; r = 0.692, P less than 0.05 for H). However, the minute ventilation and breathing pattern parameters did not differ from each other and from basal or control conditions. Thus, although we can assume that both drugs have different effects on vagal airway receptors, they induce the same respiratory response. We conclude that only receptors indirectly stimulated via airway smooth muscle contraction contribute to the mediation of drive and breathing pattern in drug induced bronchospasm in humans.

A comparison of adenine and some derivatives on pig isolated tracheal muscle

We studied the muscle relaxation induced by adenine and several adenine derivatives in strips of tracheal smooth muscle from pigs; in addition their metabolism by the tissue was examined. Adenine relaxed tissue which was contracted by carbachol, histamine, or KCl. Adenine's potency was similar to that of adenosine and ATP (threshold about 4 X 10(-5)M). In tissues with carbachol-induced tone, the adenine effect differed from adenosine and ATP by being slower in onset and in 'washout' time. Furthermore, neither dipyridamole nor theophylline modified the response to adenine. The relationship was examined between pharmacological effects and the metabolism of [3H]-adenosine and [3H]-adenine. Both substrates were taken up by the tissue and converted to nucleotides, but relaxation correlated with nucleotide accumulation only in the case of [3H]-adenine. We conclude that the site and mechanism of adenine-induced relaxation is different from that of adenosine and ATP in porcine tracheal muscle.

Oxygen toxicity in cultured aortic endothelium: selenium-induced partial protective effect

The time course of biochemical changes related to cell loss and damage during exposure to 95% O2 [DNA and protein content of dishes, lactate dehydrogenase (LDH) release] was studied in postconfluent endothelial cells isolated from pig aorta, cultured in standard medium and in medium supplemented with 2 X 10(-7) M selenomethionine (Se-Met). A fourfold increase in glutathione peroxidase (G-Px) was the only major enzymatic Se-related effect under both normoxic and hyperoxic conditions, the other antioxidant enzymes being little or not at all affected by this treatment. The addition of Se-Met had a clearcut protective action against the cytotoxic effect of O2 as shown by measurements of DNA and protein content of Petri dishes and of LDH release. On the other hand, the most sensitive O2-related effect, namely the decrease in [3H]thymidine incorporation into DNA, was not affected by Se-Met addition. These experiments suggest that some of the O2-related toxic effects (but not the inhibition of DNA synthesis) could be mediated by lipid peroxides, since they were, at least partly, prevented by a Se-Met-induced increase in G-Px activity.

Effects of hyperoxia on biochemical indexes of pig aortic endothelial function

To determine what biochemical indexes might be useful in measuring the endothelial response to hyperoxia in vitro we exposed endothelial cell monolayers (ECM) from pig aortas to either hyperoxic (95% O2:5% CO2, 1 atm) or control conditions (95% air:5% CO2) and made the following measurements: (a) DNA and protein contents remaining in the ECM; (b) lactate dehydrogenase (LDH) activity in the medium; (c) the net uptake of rubidium (Rb+), adenine, and adenosine; and (d) cellular ATP and medium lactate. Twelve hours of hyperoxic exposure did not cause significant changes. After 24 or 48 h of hyperoxia, DNA and protein contents were decreased; LDH activity and the protein-to-DNA ratio were increased; adenosine uptake was decreased per ECM but was unchanged when corrected for culture DNA and protein contents. Adenine uptake was unaltered as were cellular ATP content and medium lactate concentration. The net Rb+ uptake-to-DNA ratio was increased after 24 h but not after 48 h of hyperoxia. The extent of the DNA and LDH changes indicated that the cellular disturbance caused by hyperoxia was progressive from 12 to 48 h. Presence of superoxide dismutase (250 U/ml) prevented both the increase of LDH activity and the decrease of protein after 48 h but did not affect the decrease of DNA. These results suggest that the cells remaining in the ECM after hyperoxia have normal biochemical function and may represent a subpopulation of cells more resistant to oxygen toxicity than the damaged cells.

Ventilatory dysfunction resulting from bilateral anterolateral high cervical cordotomy. Dual beneficial effect of aminophylline

Because of metastatic pain resistant to medical treatment after left pneumonectomy for squamous cell carcinoma, a 46-year-old patient underwent a bilateral cervical cordotomy at the C1-C2 anterolateral level, in two phases. The second intervention was followed by severe ventilatory problems requiring mechanical ventilation, and at a later stage, the implantation of a phrenic pacemaker on the right side. Analysis of the ventilatory pattern during spontaneous breathing and during phrenic pacing and measurement of the transdiaphragmatic pressure during phrenic nerve stimulation revealed the existence of a beneficial effect of aminophylline on both the regulation of ventilation and diaphragmatic contractility.

Effects of culture conditions and hyperoxia on antioxidant enzymes in pig pulmonary artery and aortic endothelium

Because hyperoxia induces early injury to lung endothelial cells and since tolerance to hyperoxia is correlated with increased lung antioxidant enzyme activity, we measured superoxide dismutase, catalase and glutathione peroxidase in both fresh isolates and primary cultures of endothelial cells from pig pulmonary artery and aorta. Cultured endothelial cells were studied at confluency and up to 5 days thereafter under control or hyperoxic conditions. In both types of confluent cell, total and cyanide-insensitive superoxide dismutase increased when compared to fresh cells. The most conspicuous postconfluency change in both types of endothelial cell was a marked decrease in glutathione peroxidase, which could be prevented by the addition of selenomethionine to culture media. A 5-day exposure to hyperoxia resulted in a 2-fold increase in cyanide-insensitive superoxide dismutase in both aortic and pulmonary artery endothelial cells. In view of a similar decrease in DNA in both types of cells despite some differences in enzyme levels, oxygen cytotoxicity could not be related to a particular antioxidant enzyme profile.

[Physiopathology of chronic respiratory insufficiency]

The use by West et al. of gases with different solubilities and of appropriate models has indicated that impairment of gas exchange in patients with chronic obstructive pulmonary disease and respiratory failure resulted essentially from altered ventilation/perfusion ratios. To understand why some patients do not appear to be capable of compensating this impairment and become hypercapnic, it is necessary to examine the other components of the respiratory system (control of ventilation, respiratory muscles) and their interactions. The measurement of occlusion pressure and of average inspiratory flow, and analysis of the timing of the respiratory cycle provides interesting information on the output of the control system and the efficiency of respiratory muscles. Electromyography of respiratory muscles also affords useful information on the degree of fatigue of these muscles. The use of this data should help to clarify the problem that has remained unanswered for many years: is the patient with hypercapnia someone who does not want to, or cannot, increase his ventilation? Other studies in the same group of patients during sleep have supplied evidence for the presence of numerous episodes of arterial oxygen desaturation with marked effects on the cardiovascular system. Pathophysiology should also consider this aspect of respiratory failure which occurs in the third of our lifetime devoted to sleep.

Time course of lung function changes in atypical pneumonia

We measured pulmonary function in each of 21 patients suffering from "atypical", non-bacterial pneumonia during the acute illness and during convalescence (two to 18 months) to study the course and the nature of functional impairment at different stages of the disease. In six patients, no aetiological agent was found. An aetiological agent was identified in 15 of the patients: Mycoplasma pneumoniae (seven patients), influenza A (three patients), parainfluenza 3 (one patient), varicella (two patients), Q fever (one patient), coxsackie B3 (one patient). At the time of admission we observed a restrictive pattern in 52%, an obstructive pattern (decreased FEV1/FVC ratio) in 52% abnormalities in distribution of ventilation (abnormal slope of phase 3) in 63%, and abnormalities in gas exchange (increased AaDO2) in 75% of the patients. The frequency of abnormalities in these pulmonary function tests decreased dramatically after two to four weeks and nearly disappeared in most patients during convalescence. The only major residual abnormality was a decreased FEV1/FVC ratio in five subjects, four of whom were smokers. However, when MMEF and V75 were measured at this stage, their average value for all the groups of patients with the exclusion of the Mycoplasma pneumoniae group, was markedly reduced. These data suggest that small airways involvement can be demonstrated during the convalescence of patients recovering from various types of atypical pneumonia other than those caused by Mycoplasma pneumoniae.

PGA1 and PGF2 alpha metabolism by pig pulmonary endothelium, smooth muscle, and fibroblasts

To determine the cellular site for uptake and degradation of circulating prostaglandins (PGs) by the lung, the metabolism of PGA1 and PGF2 alpha was studied in pig lung slices, smooth muscle preparations, and pulmonary valves, as well as in isolated and cultured endothelial cells and cultured fibroblasts. Formation of 15-keto metabolites of both PGA1 and PGF2 alpha by lung slices was confirmed. No evidence of PGF2 alpha degradation could be found in any of the remaining preparations. For PGA1, however, 15-hydroxyprostaglandin dehydrogenase activity was detected in the three smooth muscle preparations studied (trachea, aorta, pulmonary artery) and found to be similar to that measured in lung slices. But the inhibitory effect of diphloretin phosphate and bromcresol green was much more marked in smooth muscle tissues than in lung slices, which suggested that PGA1 metabolism by the lung was not due to smooth muscle cells. Endothelial cells, freshly isolated and cultured, originating from the pulmonary artery and from the aorta, formed a PGA1-glutathione adduct, poorly extractable in ethyl acetate. This reaction, also present in cultured fibroblasts, was inhibited by ethacrynic acid. The cellular site responsible for the pulmonary degradation of circulating PGs remains undetermined.

[Endogenous factors in the development of emphysema]

The relationship between the development of pulmonary emphysema and the presence of proteolytic enzymes with elastolytic properties released by polymorphonuclear leukocytes or by alveolar macrophages is briefly reviewed. The possible role of various antiproteolytic substances present in the lung is also described. The pathogenesis of pulmonary emphysema is discussed in the light of hypotheses recently put forward implicating an excess of proteolytic factors and/or a relative or absolute lack of protection substances.

Amine uptake and metabolism by endothelium of pig pulmonary artery and aorta

The uptake and metabolism of 5-hydroxytryptamine (5HT) and l-norepinephrine (NE) were measured in endothelial cells of pig pulmonary artery and aorta, as well as in lung slices. Evidence for oxidative deamination and for a saturable uptake mechanism, sensitive to cold, imipramine, and NA+-free medium was obtained for 5HT in lung slices and in the pulmonary as well as in the aortic endothelium, separated from the lumen by absorption to Millipore filters or by exposure to collagenase. For NE, however, a similar type of uptake could be deomonstrated in lung slices only. In the aortic and pulmonary endothelium, NE was metabolized, but its uptake was not influenced by imipramine, Na+-free medium, and high substrate concentration. The aortic and pulmonary endothelium have, therefore, similar properties and exhibit for 5HT, but not for NE, a type of uptake similar to that existing in lung capillaries.