Protective effect of Growth Hormone-Releasing Hormone agonist in bacterial toxin-induced pulmonary barrier dysfunction

Istvan Czikora, Supriya Sridhar, Boris A Gorshkov, Irina B. Alieva, Anita Kasa, Joyce N Gonzales, Olena Potapenko, Umapathy N Siddaramappa, Helena Pillich, Ferenc G. Rick, Norman L. Block, Alexander Dmitriyevich Verin, Trinad Chakraborty, Michael A. Matthay, Andrew V. Schally, Rudolf Lucas

Research output: Contribution to journalArticle

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Abstract

Rationale: 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-a 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-a-induced pathway in the presence of PLY, the former of which dominates the latter.

Original languageEnglish (US)
Article number00259
JournalFrontiers in Physiology
Volume5 JUL
DOIs
Publication statusPublished - Jan 1 2014

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Keywords

  • Capillary leak
  • Growth hormone-releasing hormone
  • Lipopolysaccharide
  • Pneumolysin
  • Protein kinase A
  • Protein kinase C

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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