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Zhang L, Patel S, Soulakova JN, Caldwell CC, St Pierre Schneider B. Mild hypobaric hypoxia influences splenic proliferation during the later phase of stress erythropoiesis. Exp Biol Med (Maywood) 2021; 247:509-518. [PMID: 34904451 DOI: 10.1177/15353702211060775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Tissue trauma and hemorrhagic shock are common battlefield injuries that can induce hypoxia, inflammation, and/or anemia. Inflammation and hypoxia can initiate adaptive mechanisms, such as stress erythropoiesis in the spleen, to produce red blood cells and restore the oxygen supply. In a military context, mild hypobaric hypoxia-part of the environmental milieu during aeromedical evacuation or en route care-may influence adaptive mechanisms, such as stress erythropoiesis, and host defense. In the present study, healthy (control), muscle trauma, and polytrauma (muscle trauma and hemorrhagic shock) mice were exposed to normobaric normoxia or hypobaric hypoxia for ∼17.5 h to test the hypothesis that hypobaric hypoxia exposure influences splenic erythropoiesis and splenic inflammation after polytrauma. This hypothesis was partially supported. The polytrauma + hypobaric hypoxia group exhibited more splenic neutrophils, fewer total spleen cells, and fewer splenic proliferating cells than the polytrauma+normobaric normoxia group; however, no splenic erythroid cell differences were detected between the two polytrauma groups. We also compared splenic erythropoiesis and myeloid cell numbers among control, muscle trauma, and polytrauma groups. More reticulocytes at 1.7 days (40 h) post-trauma (dpt) and neutrophils at 4 dpt were produced in the muscle trauma mice than corresponding control mice. In contrast to muscle trauma, polytrauma led to a reduced red blood cell count and elevated serum erythropoietin levels at 1.7 dpt. There were more erythroid subsets and apoptotic reticulocytes in the polytrauma mice than muscle trauma mice at 4 and 8 dpt. At 14 dpt, the red blood cell count of the polytrauma + normobaric normoxia mice was 12% lower than that of the control + normobaric normoxia mice; however, no difference was observed between polytrauma + hypobaric hypoxia and control + hypobaric hypoxia mice. Our findings suggest muscle trauma alone induces stress erythropoiesis; in a polytrauma model, hypobaric hypoxia exposure may result in the dysregulation of splenic cells, requiring a treatment plan to ensure adequate immune functioning.
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Affiliation(s)
- Liyuan Zhang
- School of Nursing, University of Nevada, Las Vegas, NV 89154, USA
| | - Shailey Patel
- School of Nursing, University of Nevada, Las Vegas, NV 89154, USA
| | - Julia N Soulakova
- Department of Population Health Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Charles C Caldwell
- College of Medicine, University of Cincinnati, Cincinnati, OH 45267, USA
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Lopez K, Suen A, Yang Y, Wang S, Williams B, Zhu J, Hu J, Fiskum G, Cross A, Kozar R, Miller C, Zou L, Chao W. Hypobaria Exposure Worsens Cardiac Function and Endothelial Injury in AN Animal Model of Polytrauma: Implications for Aeromedical Evacuation. Shock 2021; 56:601-610. [PMID: 33394971 PMCID: PMC8522996 DOI: 10.1097/shk.0000000000001716] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Aeromedical evacuation can expose traumatically injured patients to low pressure (hypobaria) and hypoxia. Here, we sought to assess the impact of hypobaria on inflammation, organ injury, and mortality in a mouse model of polytrauma. METHODS Eight to 12-week-old male C57BL/6J mice were subjected to sham or polytrauma consisting of bowel ischemia by superior mesenteric artery occlusion, hindlimb muscle crush, and tibia fracture. Two hours after injury, animals were randomized to undergo either 6 h of hypobaria or sea-level, room air conditions. At 8 or 24 h after injury, transthoracic echocardiography was performed. Acute kidney injury (AKI) biomarkers were measured by qRT-PCR. Plasma cytokine and endothelial injury markers were determined by enzyme-linked immunosorbent assay. RESULTS Eight hours after traumatic injury, mice exhibited a marked increase in plasma IL-6 (57 pg/mL vs. 1,216 pg/mL), AKI with increased Ngal and Kim-1, and endothelial injury as evidenced by significantly increased plasma hyaluronic acid (96 ng/mL vs.199 ng/mL), thrombomodulin (23.2 ng/mL vs. 58.9 ng/mL), syndecan-1 (0.99 ng/mL vs. 4.34 ng/mL), and E-selectin (38.6 ng/mL vs. 62.7 ng/mL). The trauma mice also developed cardiac dysfunction with decreased cardiac output and stroke volume at 8 h postinjury. Hypobaric exposure after polytrauma led to decreased ejection fraction (81.0% vs. 74.2%, P < 0.01) and increased plasma hyaluronic acid (199 ng/mL vs. 260 ng/mL, P < 0.05), thrombomodulin (58.9 ng/mL vs. 75.4 ng/mL, P < 0.05), and syndecan-1 (4.34 ng/mL vs. 8.33 ng/mL, P < 0.001) at 8 h postinjury. CONCLUSIONS Hypobaria exposure appeared to worsen cardiac dysfunction and endothelial injury following polytrauma and thus may represent a physiological "second hit" following traumatic injury.
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Affiliation(s)
- Kerri Lopez
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Surgery, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Andrew Suen
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Anesthesia, Pain Management & Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
| | - Yang Yang
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Ultrasound, The 2 Teaching Hospital, Xiangya School of Medicine, Central South University, Changsha, China
| | - Sheng Wang
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Brittney Williams
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Jing Zhu
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Jiang Hu
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
- Department of Anesthesiology, Xiangya Hospital, Central South University, Changsha, China
| | - Gary Fiskum
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Alan Cross
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Rosemary Kozar
- Program in Trauma & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Catriona Miller
- Enroute Care Division, Department of Aeromedical Research, USAF School of Aerospace Medicine, Wright Patterson AFB, Dayton OH, USA
| | - Lin Zou
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Wei Chao
- Translational Research Program, Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD, USA
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