Publications by authors named "Pekka O Kaapa"

9 Publications

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Meconium aspiration syndrome (MAS) - Where do we go? Research perspectives.

Authors:
Pekka O Kääpä

Early Hum Dev 2009 Oct 12;85(10):627-9. Epub 2009 Oct 12.

Department of Pediatrics and Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Kiinamyllynkatu 10, FIN-20520 Turku, Finland.

The pathogenetic cascade of meconium aspiration syndrome (MAS) in newborn infants is complex and still incompletely studied. The variable clinical presentation of MAS is basically connected with variation of the amount and consistency of aspirated meconium and also its distribution within the affected lungs. The contributing role of other factors, like intrauterine fetal compromises, lung maturity at the time of insult as well as direct and indirect effects of meconium and its components on the lung alveolar and vascular integrity and development, remains to be studied in further detail. Better understanding of the lung injury processes in MAS, specifically inflammatory injury and non-inflammatory apoptosis and their interplay, may offer new possibilities to treat the severely affected infants, and needs therefore to be explored. Systemic dispersion of intrapulmonary meconium and its components may further induce inflammatory circulatory changes and injurious effects in distant organs, but the mechanisms and clinical significance of these systemic complications are still poorly known. It is thus evident that lung injury processes and potent long-term consequences in various extrapulmonary organs, specifically the brain, as well as development of new approaches to their treatment and prevention form great challenges for future research of MAS.
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http://dx.doi.org/10.1016/j.earlhumdev.2009.09.014DOI Listing
October 2009

Inhaled nitric oxide treatment inhibits neuronal injury after meconium aspiration in piglets.

Early Hum Dev 2007 Feb 21;83(2):77-85. Epub 2006 Jun 21.

Research Centre of Applied and Preventive Cardiovascular Medicine (CAPC), University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland.

Background: Meconium aspiration-induced hypertensive lung injury is frequently associated with neuronal damage. Inhaled nitric oxide (iNO) is widely used in the treatment of pulmonary hypertension, but its effects on the brain are poorly known.

Aims: The aim of this study was to determine the effects of iNO treatment on the neuronal tissue after meconium aspiration.

Study Design: 71 anesthetized, catheterized and ventilated newborn piglets were studied for 6 h. Thirty-five piglets were instilled with a bolus of human meconium intratracheally and 36 piglets with saline instillation served as controls. Nineteen meconium piglets and 17 control piglets were continuously treated with 20 ppm of iNO, started at 30 min after the insult. The extent of neuronal injury was analysed histologically, and the levels of brain tissue lipid peroxidation products, reduced glutathione (GSH), myeloperoxidase activity and oxidized DNA were analysed as indicators of oxidative stress.

Results: iNO treatment diminished the pulmonary hypertensive response caused by meconium aspiration, but did not change systemic or carotid hemodynamics. NO administration was associated with reduced neuronal injury and diminished amount of oxidized DNA in the hippocampus of the meconium piglets. Further, iNO treatment was associated with decreased level of GSH in the cortex, but no change in lipid peroxidation production or myeloperoxidase activity was detected in any of the studied brain areas.

Conclusions: Our results suggest that iNO treatment may inhibit DNA oxidation and neuronal injury in the hippocampus, associated with newborn meconium aspiration.
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http://dx.doi.org/10.1016/j.earlhumdev.2006.05.003DOI Listing
February 2007

Meconium aspiration induces neuronal injury in piglets.

Acta Paediatr 2005 Oct;94(10):1468-75

Research Centre of Applied and Preventive Cardiovascular Medicine (CAPC), University Hospital of Turku, Turku, Finland.

Aim: Meconium aspiration-induced hypertensive lung injury, especially when connected with perinatal asphyxia, has been associated with brain damage. We aimed to determine the neuronal injury induced by pulmonary meconium contamination alone and with concurrent asphyxia.

Methods: 36 anaesthetized and ventilated newborn piglets were haemodynamically monitored for 6 h. Seven piglets without concurrent asphyxia and seven piglets with asphyxia were instilled with a bolus of human meconium intratracheally. Seven piglets had only asphyxia and 15 piglets served as controls. The brains were studied histologically.

Results: Meconium aspiration did not change systemic haemodynamics acutely, while its combination with asphyxia diminished the abrupt postasphyxic systemic hypertensive peak and resulted in a transient increase in carotid artery flow, not seen after isolated asphyxia. Systemic pressure declined after 4 h in all insulted groups, but only isolated asphyxia was associated with a sustained decrease in carotid artery flow. Arterial oxygenation remained normal, except during the acute insults. Brain examination after meconium instillation indicated neuronal injury, especially in the CA3 region of the hippocampus. Asphyxia resulted in neuronal injury in the cortical, cerebellar and hippocampal hilus regions.

Conclusion: Severe meconium aspiration itself may result in hippocampal neuronal injury.
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http://dx.doi.org/10.1111/j.1651-2227.2005.tb01822.xDOI Listing
October 2005

Meconium aspiration induces oxidative injury in the hippocampus of newborn piglets.

Early Hum Dev 2005 May;81(5):439-47

Research Centre of Applied and Preventive Cardiovascular Medicine (CAPC), University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland.

Background: Meconium aspiration-induced hypertensive lung injury has been associated with neuronal damage in the newborn, but the mechanisms of the injury are poorly known.

Aims: The aim of the study was to determine the contribution of oxidative stress to the brain damage after pulmonary meconium contamination.

Study Design: Sixteen anesthetized and ventilated newborn piglets were studied for 6 h. Eight piglets were instilled with a bolus of human meconium intratracheally and eight piglets with saline instillation served as controls. Brain tissue lipid peroxidation products (TBARS), reduced glutathione (GSH), myeloperoxidase activity and oxidized DNA were analyzed as indicators of oxidative stress.

Results: Meconium aspiration did not change the systemic or carotid hemodynamics, but caused a well-established pulmonary hypertensive response. Sustained increase in additional oxygen demand was also observed after meconium insult, but no actual hypoxemia or hypercarbia was evident during the whole study period. Myeloperoxidase activity was elevated in the cerebellum after pulmonary meconium instillation, whereas concentrations of peroxidation products and glutathione were similar in the cortical, cerebellar and hippocampal regions of the two groups. Still, the amount of oxidized DNA was increased in the hippocampus of the meconium-aspirated piglets when compared to controls.

Conclusions: Our data thus suggest that oxidative injury associated with pulmonary, but not systemic, hemodynamic disturbances may contribute to hippocampal damage after meconium aspiration in newborns.
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http://dx.doi.org/10.1016/j.earlhumdev.2005.03.011DOI Listing
May 2005

Angiotensin II receptor inhibition prevents pneumocyte apoptosis in surfactant-depleted rat lungs.

Pediatr Pulmonol 2005 Apr;39(4):349-58

Research Center of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland.

Pneumocyte apoptosis is implicated in the pathophysiology of acute inflammatory lung injuries in newborns and adults. Pulmonary angiotensin (ANG) II contributes to lung epithelial apoptosis in vitro, but its role in acute lung injury in vivo is unclear. We therefore studied the effects of ANG II receptor action on the pulmonary inflammatory and apoptotic changes in surfactant-depleted lungs in rats. Lung injury was induced by repeated lung lavage with saline, and the rats were then ventilated with 60% oxygen for 1, 3, or 5 hr. Separate groups of rats were pretreated with a nonspecific ANG II receptor inhibitor saralasin, the specific ANG II type 1 receptor antagonist losartan, or ANG II type 2 receptor inhibitor PD123319, and were similarly studied. Lungs were studied histologically for tissue injury, and with terminal deoxynucleodityl transferase-mediated dUTP nick end-labeling (TUNEL) and cleaved caspase 3 antibody staining, and by electron microscopy for apoptotic cell death. Surfactant-depleted lungs showed an increased number of TUNEL-positive epithelial cells throughout the study, and intrapulmonary leukocyte migration and histological tissue injury scores were similarly elevated, compared to controls, from 1-5 hr of ventilation. Pretreatment with saralasin or losartan significantly prevented the increase of TUNEL positivity in pneumocytes, but had no effect on the amount of neutrophil influx or total injury score in lavaged lungs. In contrast, administration of PD123319 did not affect the number of TUNEL-positive epithelial cells or histological injury . The results suggest that increased epithelial apoptosis in surfactant-deficient lungs is mediated by ANG II receptor (specifically, subtype 1) action.
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http://dx.doi.org/10.1002/ppul.20187DOI Listing
April 2005

Meconium induces only localized inflammatory lung injury in piglets.

Pediatr Res 2003 Aug 7;54(2):192-7. Epub 2003 May 7.

Research Centre of Applied and Preventive Cardiovascular Medicine (CAPC), Kiinamyllynkatu 10, FIN-20520 Turku, Finland.

Neonatal meconium aspiration often produces severe respiratory distress due to an inflammatory pulmonary injury, but the extension of this damaging reaction to the noncontaminated lung regions is still uncertain. To investigate the presence of generalized pulmonary inflammatory response, 31 anesthetized and ventilated neonatal piglets (1-3 d) were studied. Meconium (n = 16) or saline (n = 15) was instilled unilaterally into the right lung, and analysis of the lung tissue or bronchoalveolar lavage (BAL) fluid from both lungs was performed after 12 h. Meconium increased the wet/dry weight ratio, histologic tissue injury score and tissue myeloperoxidase activity as well as BAL fluid total cell count in the contaminated lung. Tumor necrosis factor-alfa concentrations in BAL fluid did not however differ significantly. Furthermore, in the meconium-instilled lungs the tissue and lavage fluid catalytic activity of phospholipase A2 (PLA2) and tissue PLA2 group-I and group-II concentrations were significantly elevated. Although BAL fluid catalytic activity of PLA2 was moderately increased also in the meconium noninstilled lung, significant inflammatory injury in this lung was absent. The results thus indicate that meconium aspiration induces severe local inflammation and lung injury, but significant generalized pulmonary inflammatory damage in the pathogenesis of meconium aspiration syndrome is unlikely.
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http://dx.doi.org/10.1203/01.PDR.0000072784.55140.1EDOI Listing
August 2003

Asphyxia aggravates systemic hypotension but not pulmonary hypertension in piglets with meconium aspiration.

Pediatr Res 2003 Mar;53(3):473-8

Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland.

Meconium aspiration and birth asphyxia are both separately connected to significant pulmonary and systemic hemodynamic changes in newborns, but, although these insults frequently coexist, their combined effects on the neonatal circulation are still controversial. To determine the pulmonary and systemic circulatory changes induced by pulmonary meconium contamination with concurrent asphyxia, 41 anesthetized and ventilated newborn piglets (10-12 d) were studied for 6 h. Eleven piglets were instilled with a bolus of human meconium intratracheally, and 10 piglets had meconium instillation with immediate induction of an asphyxic insult. Eight piglets had only asphyxia and 12 ventilated piglets served as controls. Meconium instillation (with and without asphyxia) resulted in a sustained decrease in the oxygenation, which remained, however, on the control level in the asphyxic group. Although meconium insufflation (with and without asphyxia) increased pulmonary artery pressure and vascular resistance progressively during the study period, the meconium-induced hypertensive effect was actually diminished by additional asphyxia. Asphyxia alone did not have any effect on these pulmonary hemodynamic parameters. On the other hand, whereas systemic arterial pressure and vascular resistance remained on the control level after meconium instillation alone, asphyxia (with and without pulmonary meconium insult) resulted in a sustained fall in systemic pressure already by 4 h. Our data thus indicate that although the coexisting asphyxia seems to moderate the meconium aspiration-induced pulmonary hypertensive response, this additional asphyxic insult does not affect the associated hypoxemia, but rather significantly exacerbates systemic hypotension.
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http://dx.doi.org/10.1203/01.PDR.0000049514.02607.03DOI Listing
March 2003

Lung epithelial cells undergo apoptosis in neonatal respiratory distress syndrome.

Pediatr Res 2003 Feb;53(2):254-9

Research Centre of Applied and Preventive Cardiovascular Medicine, University of Turku, Turku, Finland.

For studying the presence of programmed cell death in the lungs of infants with fatal respiratory distress syndrome (RDS) and the possible contribution of postnatal glucocorticoid administration on this cell destruction, lung tissue samples from autopsies of 16 premature infants with fatal RDS were studied. The infants had neither been exposed to antenatal steroids nor received surfactant therapy, but seven of these infants had been subjected to postnatal dexamethasone treatment. Lung autopsy samples of seven term and two preterm neonates without any obvious lung disease served as controls. Lungs were studied histologically, and apoptotic cell death was identified using DNA nick end-labeling assay and caspase-related M30 antibody staining (CytoDeath). Lung tissue from the RDS infants showed elevated leukocyte infiltration, histologic injury score, and number of apoptotic cells, located mainly in the respiratory epithelium, when compared with controls. In contrast, lungs from infants who had RDS and received dexamethasone demonstrated markedly reduced tissue leukocyte accumulation and injury score and lower rates of epithelial apoptosis than the lungs of infants who had RDS and did not receive dexamethasone. These results suggest that significant epithelial apoptosis is present in the lungs of newborn infants with fatal RDS and that this apoptosis may be attenuated by steroid administration.
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http://dx.doi.org/10.1203/01.PDR.0000047522.71355.08DOI Listing
February 2003

Meconium stimulates neutrophil oxidative burst.

Am J Perinatol 2002 Jul;19(5):279-84

Research Centre of Applied and Preventive Cardiovascular Medicine and Department of Pediatrics, University of Turku, Finland.

Acute lung injury induced by meconium aspiration is characterized by rapidly developing pulmonary inflammation with influx of activated polymorphonuclear cells. To evaluate the role of meconium in the activation of these invading cells, we described the oxidative capacity of circulating neutrophils after intratracheal administration of thick human meconium in pigs. We also examined the direct effects of varying meconium concentrations on the oxidative burst of human neutrophils in vitro. In neutrophils isolated from meconium-insufflated pigs, phorbol myristate acetate stimulation led to an average 11.7-fold increase in production of reactive oxygen species, measured by chemiluminescence, whereas the increase in control cells from saline-instilled pigs was only 3.1-fold, p =.012 between the groups. Activation of unstimulated human leukocytes by meconium resulted in a dose-dependent response. The lowest meconium concentration (0.2 mg/mL) had an inhibitory effect on neutrophil activation, whereas higher concentrations of meconium (1 and 2 mg/mL) increased neutrophil oxygen radical production progressively. These results thus indicate that moderate and high concentrations of aspirated meconium rapidly activate circulating neutrophils with a resulting oxidative burst contributing to pulmonary tissue injury, whereas low contamination of the aspirated material may in fact suppress the development of oxidative lung injury.
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http://dx.doi.org/10.1055/s-2002-33089DOI Listing
July 2002
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