Resuscitation of Hypoxic Piglets with 100% O2 Increases Pulmonary Metalloproteinases and IL-8

Abstract

We hypothesized that resuscitation with 100% O 2 compared with 21% O 2 is detrimental to pulmonary tissue. The pulmonary injury was assessed by matrix metalloproteinase (MMP) activity, oxidative stress, IL-8, and histology 2.5 h after resuscitation from a hypoxic state. In pulmonary tissue extracts, MMP activity was analyzed by broad matrix-degrading capacity (total MMP) and zymography. MMP-2 mRNA expression was evaluated by quantitative real-time PCR. Total endogenous antioxidant capacity was measured by the oxygen radical absorbance capacity (ORAC) assay, and IL-8 was analyzed by ELISA technique. In bronchoalveolar lavage (BAL) fluid, MMPs were analyzed by zymography. In pulmonary tissue, pro-and active MMP-2 levels were increased in piglets that were resuscitated with 100% O 2 compared with 21% O 2 . Pro-MMP-9, total MMP activity, and MMP-2 mRNA levels were significantly increased in resuscitated piglets compared with baseline. Net gelatinolytic activity increased in submucosa and blood vessels after 100% O 2 and only in the blood vessels after 21% O 2 . Compared with baseline, ORAC values were considerably lowered in the resuscitated piglets and significantly reduced in the 100% O 2 versus 21% O 2 group. In BAL fluid, both pro-MMP-9 and pro-MMP-2 increased 2-fold in the 100% O 2 group compared with 21% O 2 . Moreover, IL-8 concentration increased significantly in piglets that were resuscitated with 100% O 2 compared with 21% O 2 , suggesting a marked proinflammatory response in the pulmonary tissue. Altogether, these data strongly suggest that caution must be taken when applying pure O 2 to the newborn infant. Traditionally, asphyxiated newborn infants have been resuscitated with 100% O 2 . This recommendation is based mainly on precedent rather than sound evidence. Hyperoxia leads to generation of O 2 free radicals, which have a role in reperfusion injury after asphyxia (1). Naturally, the lung is exposed directly to the highest partial pressure of inspired O 2 , and pulmonary damage, as a result of O 2 exposure, is a serious clinical complication in infants who require high levels of O 2 as treatment (2). It is important not only to provide adequate O 2 consumption in organs but also to prevent further tissue damage during resuscitation caused by reoxygenation injury or O 2 toxicity. This might be achieved by lowering the O 2 concentration during resuscitation. There is therefore an ongoing debate whether to use 21% or 100% O 2 in neonatal resuscitation (3).Matrix metalloproteinases (MMPs) are involved in the pathogenesis of tissue inflammation and wound healing in lung injury (4,5). The role of oxidative stress and its toxic effects on lipids, as well as on disruption of extracellular matrix through up-regulation of MMPs, is well established (6,7). Reduced Received November 19, 2004; accepted February 1, 2005

Brain inflammation induced by severe asphyxia in newborn pigs and the impact of alternative resuscitation strategies on the newborn central nervous system

“…We did not include sham animals in this study in which the intention was to compare different resuscitation variations represented by seven groups of 94 animals described in Table 1. Previous experimental series in our lab have clearly demonstrated brain inflammatory responses after asphyxia followed by reoxygenation and resuscitation (13,26), and we argue that this also applies when pigs are more severely asphyxiated.…”

“…The choice of brain inflammation markers is somewhat limited but includes cytokines that rise within few hours after an inflammatory event (TNF-α and IL-6) (7-10); S100 (11,12), indicative of poor neurological outcome; ICAM-1 (15-17); the apoptosis pathway gene (caspase 3) (14); and MMPs (13,14), known to rise in pigs after hypoxia and reoxygenation. In group 3 (90 s), the CSF markers S100, IL-6, and TNF-α were elevated as compared with the reference group, and in the hippocampus tissue, MMP-9 and ICAM-1 genes appeared significantly differently expressed.…”

“…Alternatives to today's ventilation and chest compression guidelines may be easier to perform and teach and should be considered if the brain inflammatory response is of similar intensity. We chose to study a spectrum of inflammation markers in cerebrospinal fluid (CSF) and brain tissue by quantification of cytokines, interleukin-6 (IL-6) (7-9) and tumor necrosis factor-α (TNF-α) (10) and S100 (11,12) in CSF, and gene expression of matrix metalloproteinases (MMPs) (13,14), intercellular adhesion molecule 1 (ICAM-1) (15)(16)(17), the apoptosis-related cysteine peptidase caspase 3 (14), and cytokines IL-6 and TNF-α in the hippocampus and frontal cortex tissue. On the basis of our previous papers on return of spontaneous circulation (ROSC) (18)(19)(20)(21), we aimed to find out if initial ventilation periods longer than 30 s, compression-to-ventilation (C:V) ratios other than the 3:1, or air instead of pure oxygen may induce less brain injury and inflammation in extremely sick pigs.…”

Transcriptome profiling of the newborn mouse lung after hypoxia and reoxygenation: hyperoxic reoxygenation affects mTOR signaling pathway, DNA repair, and JNK-pathway regulation

“…Gene expression changes after both brief (12) and prolonged hyperoxia (13) in the newborn lung. In the experimental bronchopulmonary dysplasia model, transcription of several genes involved in inflammation, cell cycle, and signal transduction is described (13).…”

“…The mitogen-activated protein kinase signaling pathway may play an important role in hyperoxia-induced cell death (14), whereas the subfamily member c-jun N-terminal kinase (JNK1/2) appears to be involved in reactive oxygen species -induced cell death (15). The mechanisms behind the detrimental effects of hypoxia-reoxygenation injury in the lungs are not completely understood, but experimental evidence indicates a worsening of hypoxic injury by reoxygenation with high FiO 2 (12,16).…”