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Benedetti F, Dogue S. Different Placebos, Different Mechanisms, Different Outcomes: Lessons for Clinical Trials. PLoS One 2015; 10:e0140967. [PMID: 26536471 PMCID: PMC4633056 DOI: 10.1371/journal.pone.0140967] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Accepted: 10/03/2015] [Indexed: 11/17/2022] Open
Abstract
Clinical trials use placebos with the assumption that they are inert, thus all placebos are considered to be equal. Here we show that this assumption is wrong and that different placebo procedures are associated to different therapeutic rituals which, in turn, trigger different mechanisms and produce different therapeutic outcomes. We studied high altitude, or hypobaric hypoxia, headache, in which two different placebos were administered. The first was placebo oxygen inhaled through a mask, whereas the second was placebo aspirin swallowed with a pill. Both placebos were given after a conditioning procedure, whereby either real oxygen or real aspirin was administered for three consecutive sessions to reduce headache pain. We found that after real oxygen conditioning, placebo oxygen induced pain relief along with a reduction in ventilation, blood alkalosis and salivary prostaglandin (PG)E2, yet without any increase in blood oxygen saturation (SO2). By contrast, after real aspirin conditioning, placebo aspirin induced pain relief through the inhibition of all the products of cyclooxygenase, that is, PGD2, PGE2, PGF2, PGI2, thromboxane (TX)A2, without affecting ventilation and blood alkalosis. Therefore, two different placebos, associated to two different therapeutic rituals, used two different pathways to reduce headache pain. The analgesic effect following placebo oxygen was superior to placebo aspirin. These findings show that different placebos may use different mechanisms to reduce high altitude headache, depending on the therapeutic ritual and the route of administration. In clinical trials, placebos and outcome measures should be selected very carefully in order not to incur in wrong interpretations.
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Affiliation(s)
- Fabrizio Benedetti
- University of Turin Medical School, Neuroscience Department, Turin, Italy.,Plateau Rosa Labs, Breuil-Cervinia, Italy, Zermatt, Switzerland
| | - Sara Dogue
- Plateau Rosa Labs, Breuil-Cervinia, Italy, Zermatt, Switzerland
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Hançerlioğullari O, Cakmak M, Soyer T, Aktuna Z. In vitro sensitivity of rat esophagus to agonists in different alkaline mediums. J Pediatr Surg 2012; 47:1848-52. [PMID: 23084196 DOI: 10.1016/j.jpedsurg.2012.04.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2012] [Revised: 03/23/2012] [Accepted: 04/14/2012] [Indexed: 11/19/2022]
Abstract
AIM An in vitro study was performed to determine the in vitro sensitivity of rat esophagi to contracting and relaxing agonists in different alkaline mediums. MATERIALS AND METHODS Twenty-four Wistar rats weighing 200 to 250 g were included in the study. After inducing anesthesia with thiopental sodium (50 mg/kg), the rats were killed, and the distal esophagus (DE) and gastroesophageal junction (GEJ) were removed. Excised tissues were suspended under 0.6 g of resting tension in a tissue bath containing 10 mL of Tyrode solution at 37°C. The esophageal segments were divided into 4 groups, each with a different pH medium: 7.4, 7.6, 7.8, and 8. To evaluate the smooth muscle activity of the rat esophagus in different alkaline mediums, cholinergic agonist carbachol (a cholinergic agonosit) and KCl (which acts on calcium channels) were added to the organ baths to obtain concentration-dependent contraction responses. Relaxation responses were obtained using an adrenergic agonist, isoproterenole. Data obtained from different pH mediums were analyzed using Kruskal-Wallis nonparametric analysis of variance and post hoc Dunn's test. RESULTS The pH of the medium has no effect on the concentration-dependent contracting responses to carbachol in the DE, but responses obtained in pH 8 medium were significantly lower in the GEJ (P < .05). In pH 8 medium, concentration-dependent relaxation responses to isoproterenole were also significantly lower (P < .05). When contractile responses to KCl were evaluated, the groups with pH 7.6 and 7.8 medium were found to have higher responses in the DE segments than other groups (P < .05). However, the GEJ segments had lower contractile responses to KCl in pH 8 medium (P < .05). CONCLUSION Although different alkaline mediums caused no alteration in esophageal smooth muscle responses to cholinergic stimulation, GEJ responses were lower in pH 8 medium. Relaxation responses, owing to increased adrenergic activity, decreased when the pH of the medium was increased to 8. Calcium-dependent contractions caused by KCl decreased in both segments in pH 8 medium but increased in the DE in pH 7.6 medium.
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Affiliation(s)
- Oymen Hançerlioğullari
- Department of Pediatric Surgery, Kirikkale, Kirikkale University, School of Medicine, Turkey
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Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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Affiliation(s)
- J. T. Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Larissa A. Shimoda
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Philip I. Aaronson
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Jeremy P. T. Ward
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
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Celotto AC, Capellini VK, Restini CBA, Baldo CF, Bendhack LM, Evora PRB. Extracellular alkalinization induces endothelium-derived nitric oxide dependent relaxation in rat thoracic aorta. Nitric Oxide 2010; 23:269-74. [PMID: 20682356 DOI: 10.1016/j.niox.2010.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 07/10/2010] [Accepted: 07/29/2010] [Indexed: 10/19/2022]
Abstract
AIM To investigate the mechanism through which the extracellular alkalinization promotes relaxation in rat thoracic aorta. METHODS The relaxation response to NaOH-induced extracellular alkalinization (7.4-8.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M). The vascular reactivity experiments were performed in endothelium-intact and -denuded rings, in the presence or and absence of indomethacin (10(-5) M), NG-nitro-l-arginine methyl ester (L-NAME, 10(-4) M), N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide/HCl (W-7, 10(-7) M), 2,5-dimethylbenzimidazole (DMB, 2×10(-5) M) and methyl-β-cyclodextrin (10(-2) M). In addition, the effects of NaOH-induced extracellular alkalinization (pH 8.0 and 8.5) on the intracellular nitric oxide (NO) concentration was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5 μM), in the presence and absence of DMB (2×10(-5) M). RESULTS The extracellular alkalinization failed to induce any change in vascular tone in aortic rings pre-contracted with KCl. In rings pre-contracted with Phe, the extracellular alkalinization caused relaxation in the endothelium-intact rings only, and this relaxation was maintained after cyclooxygenase inhibition; completely abolished by the inhibition of nitric oxide synthase (NOS), Ca(2+)/calmodulin and Na(+)/Ca(2+) exchanger (NCX), and partially blunted by the caveolae disassembly. CONCLUSIONS These results suggest that, in rat thoracic aorta, that extracellular alkalinization with NaOH activates the NCX reverse mode of endothelial cells in rat thoracic aorta, thereby the intracellular Ca(2+) concentration and activating the Ca(2+)/calmodulin-dependent NOS. In turn, NO is released promoting relaxation.
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Affiliation(s)
- A C Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
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Hirenallur-S DK, Haworth ST, Leming JT, Chang J, Hernandez G, Gordon JB, Rusch NJ. Upregulation of vascular calcium channels in neonatal piglets with hypoxia-induced pulmonary hypertension. Am J Physiol Lung Cell Mol Physiol 2008; 295:L915-24. [PMID: 18776054 DOI: 10.1152/ajplung.90286.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Inhibition of voltage-gated, L-type Ca(2+) (Ca(L)) channels by clinical calcium channel blockers provides symptomatic improvement to some pediatric patients with pulmonary arterial hypertension (PAH). The present study investigated whether abnormalities of vascular Ca(L) channels contribute to the pathogenesis of neonatal PAH using a newborn piglet model of hypoxia-induced PAH. Neonatal piglets exposed to chronic hypoxia (CH) developed PAH by 21 days, which was evident as a 2.1-fold increase in pulmonary vascular resistance in vivo compared with piglets raised in normoxia (N). Transpulmonary pressures (DeltaPtp) in the corresponding isolated perfused lungs were 20.5 +/- 2.1 mmHg (CH) and 11.6 +/- 0.8 mmHg (N). Nifedipine reduced the elevated DeltaPtp in isolated lungs of CH piglets by 6.4 +/- 1.3 mmHg but only reduced DeltaPtp in lungs of N piglets by 1.9 +/- 0.2 mmHg. Small pulmonary arteries from CH piglets also demonstrated accentuated Ca(2+)-dependent contraction, and Ca(2+) channel current was 3.94-fold higher in the resident vascular muscle cells. Finally, although the level of mRNA encoding the pore-forming alpha(1C)-subunit of the Ca(L) channel was similar between small pulmonary arteries from N and CH piglets, a profound and persistent upregulation of the vascular alpha(1C) protein was detected by 10 days in CH piglets at a time when pulmonary vascular resistance was only mildly elevated. Thus chronic hypoxia in the neonate is associated with the anomalous upregulation of Ca(L) channels in small pulmonary arteries in vivo and the resulting abnormal Ca(2+)-dependent resistance may contribute to the pathogenesis of PAH.
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Affiliation(s)
- Dinesh K Hirenallur-S
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, 4301 West Markham St., Little Rock, AR 72205, USA
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Celotto A, Capellini V, Baldo C, Dalio M, Rodrigues A, Evora P. Effects of acid-base imbalance on vascular reactivity. Braz J Med Biol Res 2008; 41:439-45. [DOI: 10.1590/s0100-879x2008005000026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 05/29/2008] [Indexed: 11/22/2022] Open
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Nagy S, Harris MB, Ju H, Bhatia J, Venema RC. pH and nitric oxide synthase activity and expression in bovine aortic endothelial cells. Acta Paediatr 2006; 95:814-7. [PMID: 16801177 DOI: 10.1080/08035250500462083] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
AIM Nitric oxide (NO) plays an important role in the transition from intrauterine to extrauterine life. If this transition fails, a condition called persistent pulmonary hypertension of the neonate (PPHN) may develop. The current treatment modalities for this disease include induction of alkalosis by hyperventilation or alkali infusion, inhaled nitric oxide (iNO) and extracorporeal membrane oxygenation. There is evidence from animal studies that the elevated pH, not the low pCO2 is responsible for the resultant pulmonary vasodilatation. In this study, we examined the effect of pH on the activity and expression of endothelial nitric oxide synthase (eNOS) in cultured bovine aortic endothelial cells (BAEC) as a possible explanation for the pH dependent drop in pulmonary vascular resistance. METHODS BAEC were exposed to a pH gradient of 7.1-7.6 for 4 h (short-term) and 16 h (long-term). Standard Western blotting technique was used to detect expression of eNOS. Activity was measured by an indirect assay using bovine aortic smooth muscle cells (BASM) as reporter cells and measuring cGMP levels as a marker of NO production. The cells were exposed to the pH gradient for a total of 4 h and measurement were made at 30, 60 and 90 min, and 2, 3 and 4 hours. RESULTS eNOS activity and expression remained unchanged during the four and sixteen hours of exposure. CONCLUSION In this in vitro experiment, we could not demonstrate an alkalosis-induced increase in eNOS activity and expression. The clinically observed pH dependent vasodilatation does not appear to be directly mediated through the induction of eNOS.
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Affiliation(s)
- Sandor Nagy
- Section of Neonatology, Medical College of Georgia, Augusta, Georgia 30912-3740, USA
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Myrianthefs PM, Briva A, Lecuona E, Dumasius V, Rutschman DH, Ridge KM, Baltopoulos GJ, Sznajder JI. Hypocapnic but not metabolic alkalosis impairs alveolar fluid reabsorption. Am J Respir Crit Care Med 2005; 171:1267-71. [PMID: 15764729 PMCID: PMC2718461 DOI: 10.1164/rccm.200408-998oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Acid-base disturbances, such as metabolic or respiratory alkalosis, are relatively common in critically ill patients. We examined the effects of alkalosis (hypocapnic or metabolic alkalosis) on alveolar fluid reabsorption in the isolated and continuously perfused rat lung model. We found that alveolar fluid reabsorption after 1 hour was impaired by low levels of CO2 partial pressure (PCO2; 10 and 20 mm Hg) independent of pH levels (7.7 or 7.4). In addition, PCO2 higher than 30 mm Hg or metabolic alkalosis did not have an effect on this process. The hypocapnia-mediated decrease of alveolar fluid reabsorption was associated with decreased Na,K-ATPase activity and protein abundance at the basolateral membranes of distal airspaces. The effect of low PCO2 on alveolar fluid reabsorption was reversible because clearance normalized after correcting the PCO2 back to normal levels. These data suggest that hypocapnic but not metabolic alkalosis impairs alveolar fluid reabsorption. Conceivably, correction of hypocapnic alkalosis in critically ill patients may contribute to the normalization of lung ability to clear edema.
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Affiliation(s)
- Pavlos M Myrianthefs
- Division of Pulmonary and Critical Care Medicine, 240 East Huron, McGaw 2-2300, Northwestern University, Chicago, IL 60611, USA
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