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01.12.2015 | Research article | Ausgabe 1/2015 Open Access

BMC Physiology 1/2015

Hypoxia mediated pulmonary edema: potential influence of oxidative stress, sympathetic activation and cerebral blood flow

Zeitschrift:
BMC Physiology > Ausgabe 1/2015
Autoren:
Shadi Khademi, Melinda A. Frye, Kimberly M. Jeckel, Thies Schroeder, Eric Monnet, Dave C. Irwin, Patricia A. Cole, Christopher Bell, Benjamin F. Miller, Karyn L. Hamilton
Wichtige Hinweise

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

KLH, DCI, and TS designed the project and acquired funding; EM, DCI, MAF, SK, KMJ and PAC carried out experimental protocols; SK, MAF, KLH, CB and BFM analyzed data; KLH, SK, BFM and CB, MAF, DCI, EM and TS participated in manuscript preparation and revision. All authors read and approved the final manuscript.

Abstract

Background

Neurogenic pulmonary edema (NPE) is a non-cardiogenic form of pulmonary edema that can occur consequent to central neurologic insults including stroke, traumatic brain injury, and seizure. NPE is a public health concern due to high morbidity and mortality, yet the mechanism(s) are unknown. We hypothesized that NPE, evoked by cerebral hypoxia in the presence of systemic normoxia, would be accompanied by sympathetic activation, oxidative stress, and compensatory antioxidant mechanisms.

Methods

Thirteen Walker hounds were assigned to cerebral hypoxia (SaO2 ~ 55 %) with systemic normoxia (SaO2 ~ 90 %) (CH; n = 6), cerebral and systemic (global) hypoxia (SaO2 ~ 60 %) (GH; n = 4), or cerebral and systemic normoxia (SaO2 ~ 90 %) (CON; n = 3). Femoral venous (CH and CON) perfusate was delivered via cardiopulmonary bypass to the brain and GH was induced by FiO2 = 10 % to maintain the SaO2 at ~60 %. Lung wet to lung dry weight ratios (LWW/LDW) were assessed as an index of pulmonary edema in addition to hemodynamic measurements. Plasma catecholamines were measured as markers of sympathetic nervous system (SNS) activity. Total glutathione, protein carbonyls, and malondialdehyde were assessed as indicators of oxidative stress. Brain and lung compensatory antioxidants were measured with immunoblotting.

Results

Compared to CON, LWW/LDW and pulmonary artery pressure were greater in CH and GH. Expression of hemeoxygenase-1 in brain was higher in CH compared to GH and CON, despite no group differences in oxidative damage in any tissue. Catecholamines tended to be higher in CH and GH.

Conclusion

Cerebral hypoxia, with systemic normoxia, is not systematically associated with an increase in oxidative stress and compensatory antioxidant enzymes in lung, suggesting oxidative stress did not contribute to NPE in lung. However, increased SNS activity may play a role in the induction of NPE during hypoxia.
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