![Sample our Medicine, Dentistry, Nursing & Allied Health journals, sign in here to start your FREE access for 14 days]({"type":"image" , "src" : "/sda/5944/TOC-Subject-Sample-2021-Medicine-Dentistry-Nursing-Allied-Health.jpg"})
ABSTRACT
Introduction: Sepsis is characterized by dysregulated systemic inflammation and cytokine storm. Angiopoietin-2 (Ang-2) is known to closely correlate with severity of sepsis-related acute lung injury and mortality. The aim of this study was to clarify the mechanisms involved in Ang-2 secretion to better understand the pathophysiology of sepsis. Materials and Methods: The concentration of Ang-2 was assessed in culture medium of pulmonary microvascular endothelial cells in the presence or absence of Gram-positive bacteria cell wall components [lipoteichoic acid (LTA) and peptidoglycan (PGN)] stimulation at different time points ranging from 15 minutes to 24 hours. Constitutive and LTA-PGN-stimulated Ang-2 level changes were also assessed after cells were pretreated with different pathway inhibitors for 1 hour. Results: Two distinctive mechanisms of Ang-2 secretion, constitutive and stimulated secretion, were identified. Constitutive secretion resulted in slow but continuous increase in Ang-2 in culture medium over time. It was regulated by 3'5'-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-Ca2+ and nitric oxide (NO)-3′5′-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG)-Ca2+ pathways and partially regulated by N-ethyl-maleimide-sensitive factor-Ca2+ pathways. LTA-PGN stimulation caused rapid and potent increase followed by gradual decrease of Ang-2. It was partially regulated by both Ral A-phospholipase D and NSF-Ca2+ pathways. Conclusions: We demonstrated characteristics and involved pathways for two distinctive secretory mechanisms, constitutive and stimulated, of Ang-2 in pulmonary microvascular endothelial cells. Considering the close correlation of Ang-2 with sepsis outcomes, our findings provide a better understanding of an important mechanism associated with sepsis pathophysiology and identify possible therapeutic targets to improve outcomes in the potentially lethal disease.
Abbreviations
| Ang-2 | = | angiopoietin-2 |
| LTA | = | lipoteichoic acid |
| PGN | = | peptidoglycan |
| PKA | = | protein kinase A |
| NO | = | nitric oxide |
| PKG | = | protein kinase G |
| NSF | = | N-ethyl-maleimide-sensitive factor |
| PLD | = | phospholipase D |
| Tie | = | tyrosine kinase with immunoglobulin-like and EGF-like domains |
| ALI | = | acute lung injury |
| HPMEC | = | human pulmonary microvascular endothelial cell line |
| EGTA | = | ethylene glycol tetraacetic acid |
| FIPI | = | 5-fluoro-2-indolyl des-chlorohalopemide |
| H-89 | = | N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide 2HCl |
| IBMX | = | 3-isobutyl-1-methylxanthine |
| L-NAME | = | Nω-nitro-l-arginine methyl ester hydrochloride |
| 3-AT | = | 3-amino-1,2,4-triazole |
| SNARE | = | SNAP (soluble NSF attachment protein) receptor |
| VWF | = | von Willebrand's factor |
| WPB | = | Weibel Palade bodies |
| PDE | = | phosphodiesterase |
| ET-1 | = | endothelin-1 |
Acknowledgments
We thank C. James Kirkpatrick at the Johannes-Gutenberg University, Germany, for kindly providing HPMEC-ST1.6R cells. The first author thanks Dr. Brian Fouty, Dr. Karen Fagan, Dr. Johnson Haynes and Dr. Troy Stevens at the University of South Alabama for their advice and support on writing.
Declaration of interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the article.
Funding
Supported by funds from The Elmezzi Graduate School of Molecular Medicine and The Feinstein Institute for Medical Research.