title: Protective effect of Growth Hormone-Releasing Hormone agonist in bacterial toxin-induced pulmonary barrier dysfunction.
abstract: BACKGROUND
  Antibiotic treatment of patients infected with G(-) or G(+) bacteria promotes release of the toxins lipopolysaccharide (LPS) and pneumolysin (PLY) in their lungs. Growth Hormone-releasing Hormone (GHRH) agonist JI-34 protects human lung microvascular endothelial cells (HL-MVEC), expressing splice variant 1 (SV-1) of the receptor, from PLY-induced barrier dysfunction. We investigated whether JI-34 also blunts LPS-induced hyperpermeability. Since GHRH receptor (GHRH-R) signaling can potentially stimulate both cAMP-dependent barrier-protective pathways as well as barrier-disruptive protein kinase C pathways, we studied their interaction in GHRH agonist-treated HL-MVEC, in the presence of PLY, by means of siRNA-mediated protein kinase A (PKA) depletion.
  
  
  METHODS
  Barrier function measurements were done in HL-MVEC monolayers using Electrical Cell substrate Impedance Sensing (ECIS) and VE-cadherin expression by Western blotting. Capillary leak was assessed by Evans Blue dye (EBD) incorporation. Cytokine generation in broncho-alveolar lavage fluid (BALF) was measured by multiplex analysis. PKA and PKC-α activity were assessed by Western blotting.
  
  
  RESULTS
  GHRH agonist JI-34 significantly blunts LPS-induced barrier dysfunction, at least in part by preserving VE-cadherin expression, while not affecting inflammation. In addition to activating PKA, GHRH agonist also increases PKC-α activity in PLY-treated HL-MVEC. Treatment with PLY significantly decreases resistance in control siRNA-treated HL-MVEC, but does so even more in PKA-depleted monolayers. Pretreatment with GHRH agonist blunts PLY-induced permeability in control siRNA-treated HL-MVEC, but fails to improve barrier function in PKA-depleted PLY-treated monolayers.
  
  
  CONCLUSIONS
  GHRH signaling in HL-MVEC protects from both LPS and PLY-mediated endothelial barrier dysfunction and concurrently induces a barrier-protective PKA-mediated and a barrier-disruptive PKC-α-induced pathway in the presence of PLY, the former of which dominates the latter.
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Istvan
authors: I
authors: Czikora
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Supriya
authors: S
authors: Sridhar
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Boris
authors: B
authors: Gorshkov
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA ; Department of Electron Microscopy, A.N. Belozorksy Institute, Moscow State University Moscow, Russia.
authors: Irina B
authors: IB
authors: Alieva
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Anita
authors: A
authors: Kasa
authors: Department of Medicine, Division of Pulmonary Medicine, Medical College of Georgia, Georgia Regents University Augusta, GA, USA.
authors: Joyce
authors: J
authors: Gonzales
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Olena
authors: O
authors: Potapenko
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Nagavedi S
authors: NS
authors: Umapathy
authors: Department of Medicine, Institute of Medical Microbiology, Justus-Liebig University Giessen Giessen, Germany.
authors: Helena
authors: H
authors: Pillich
authors: Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center Miami, FL, USA ; Department of Urology, Herbert Wertheim College of Medicine, Florida International University Miami, FL, USA.
authors: Ferenc G
authors: FG
authors: Rick
authors: Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center Miami, FL, USA ; Department of Pathology, Miller School of Medicine, University of Miami Miami, FL, USA ; Department of Medicine, Miller School of Medicine, University of Miami Miami, FL, USA ; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami Miami, FL, USA.
authors: Norman L
authors: NL
authors: Block
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA.
authors: Alexander D
authors: AD
authors: Verin
authors: Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center Miami, FL, USA.
authors: Trinad
authors: T
authors: Chakraborty
authors: Department of Medicine and Anesthesia, Cardiovascular Research Institute, University of California San Francisco San Francisco, CA, USA.
authors: Michael A
authors: MA
authors: Matthay
authors: Endocrine, Polypeptide and Cancer Institute, Veterans Affairs Medical Center Miami, FL, USA ; Department of Pathology, Miller School of Medicine, University of Miami Miami, FL, USA ; Department of Medicine, Miller School of Medicine, University of Miami Miami, FL, USA ; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami Miami, FL, USA.
authors: Andrew V
authors: AV
authors: Schally
authors: Department of Pharmacology and Toxicology, Vascular Biology Center, Georgia Regents University Augusta, GA, USA ; Department of Medicine, Division of Pulmonary Medicine, Medical College of Georgia, Georgia Regents University Augusta, GA, USA ; Department of Pharmacology and Toxicology, Medical College of Georgia, Georgia Regents University Augusta, GA, USA.
authors: Rudolf
authors: R
authors: Lucas
keywords: capillary leak; growth hormone-releasing hormone; lipopolysaccharide; pneumolysin; protein kinase A; protein kinase C