title: Baclofen, a GABABR agonist, ameliorates immune-complex mediated acute lung injury by modulating pro-inflammatory mediators.
abstract: Immune-complexes play an important role in the inflammatory diseases of the lung. Neutrophil activation mediates immune-complex (IC) deposition-induced acute lung injury (ALI). Components of gamma amino butyric acid (GABA) signaling, including GABA B receptor 2 (GABABR2), GAD65/67 and the GABA transporter, are present in the lungs and in the neutrophils. However, the role of pulmonary GABABR activation in the context of neutrophil-mediated ALI has not been determined. Thus, the objective of the current study was to determine whether administration of a GABABR agonist, baclofen would ameliorate or exacerbate ALI. We hypothesized that baclofen would regulate IC-induced ALI by preserving pulmonary GABABR expression. Rats were subjected to sham injury or IC-induced ALI and two hours later rats were treated intratracheally with saline or 1 mg/kg baclofen for 2 additional hours and sacrificed. ALI was assessed by vascular leakage, histology, TUNEL, and lung caspase-3 cleavage. ALI increased total protein, tumor necrosis factor α (TNF-α and interleukin-1 receptor associated protein (IL-1R AcP), in the bronchoalveolar lavage fluid (BALF). Moreover, ALI decreased lung GABABR2 expression, increased phospho-p38 MAPK, promoted IκB degradation and increased neutrophil influx in the lung. Administration of baclofen, after initiation of ALI, restored GABABR expression, which was inhibited in the presence of a GABABR antagonist, CGP52432. Baclofen administration activated pulmonary phospho-ERK and inhibited p38 MAPK phosphorylation and IκB degradation. Additionally, baclofen significantly inhibited pro-inflammatory TNF-α and IL-1βAcP release and promoted BAL neutrophil apoptosis. Protective effects of baclofen treatment on ALI were possibly mediated by inhibition of TNF-α- and IL-1β-mediated inflammatory signaling. Interestingly, GABABR2 expression was regulated in the type II pneumocytes in lung tissue sections from lung injured patients, further suggesting a physiological role for GABABR2 in the repair process of lung damage. GABABR2 agonists may play a potential therapeutic role in ALI.
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Shunying
authors.initials: S
authors.lastname: Jin
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Merchant
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Ritzenthaler
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America; Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: McLeish
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America; Department of Physiology, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Eleanor D
authors.initials: ED
authors.lastname: Lederer
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Edilson
authors.initials: E
authors.lastname: Torres-Gonzalez
authors.affiliation: Department of Pathology, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Fraig
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Michelle T
authors.initials: MT
authors.lastname: Barati
authors.affiliation: Department of Surgery, University of Cincinnati, Cincinnati, OH, United States of America.
authors.forename: Alex B
authors.initials: AB
authors.lastname: Lentsch
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America.
authors.forename: Jesse
authors.initials: J
authors.lastname: Roman
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America; Robley Rex VA Medical Center, Zorn Avenue, Louisville, Kentucky, United States of America.
authors.forename: Jon B
authors.initials: JB
authors.lastname: Klein
authors.affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America; Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, Kentucky, United States of America.
authors.forename: Madhavi J
authors.initials: MJ
authors.lastname: Rane
mesh_terms: D055371:Acute Lung Injury / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D000818:Animals; D000936:Antigen-Antibody Complex / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001418:Baclofen / Q000494:pharmacology*; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D058786:GABA-B Receptor Agonists / Q000494:pharmacology*; D007124:Immunoenzyme Techniques; D018836:Inflammation Mediators / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D018080:Receptors, GABA-B / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000936:Antigen-Antibody Complex; D058786:GABA-B Receptor Agonists; D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D018080:Receptors, GABA-B; D001418:Baclofen
references.citation: Am J Physiol Lung Cell Mol Physiol. 2008 Jun;294(6):L1206-16
references.pmid: 18408071
references.citation: Arch Immunol Ther Exp (Warsz). 2000;48(2):59-63
references.pmid: 10807044
references.citation: J Neurochem. 2001 Jan;76(1):1-10
references.pmid: 11145972
references.citation: Brain Res. 2001 Jan 19;889(1-2):118-30
references.pmid: 11166695
references.citation: Respir Physiol. 2001 Oct;128(1):17-22
references.pmid: 11535258
references.citation: Prog Neuropsychopharmacol Biol Psychiatry. 2002 Feb;26(2):393-6
references.pmid: 11817519
references.citation: J Biol Chem. 2002 Mar 15;277(11):9049-53
references.pmid: 11782465
references.citation: Disabil Rehabil. 2002 May 20;24(8):443-53
references.pmid: 12033999
references.citation: Free Radic Biol Med. 2002 Aug 1;33(3):303-10
references.pmid: 12126752
references.citation: Mol Cell Biochem. 2002 May-Jun;234-235(1-2):225-8
references.pmid: 12162438
references.citation: Eur J Neurosci. 2003 Oct;18(8):2213-26
references.pmid: 14622182
references.citation: J Clin Invest. 1974 Aug;54(2):349-57
references.pmid: 4277008
references.citation: Am J Pathol. 1979 Oct;97(1):85-92
references.pmid: 158982
references.citation: Trends Pharmacol Sci. 1993 Jan;14(1):26-9
references.pmid: 8382886
references.citation: Chest. 1994 Sep;106(3):758-61
references.pmid: 8082355
references.citation: Exp Dermatol. 2010 Jul 1;19(7):661-6
references.pmid: 20201957
references.citation: Acta Pharmacol Sin. 2010 Aug;31(8):889-99
references.pmid: 20644551
references.citation: Proteomics Clin Appl. 2010 Jan;4(1):84-96
references.pmid: 21137018
references.citation: PLoS One. 2010;5(11):e14171
references.pmid: 21152393
references.citation: Neurosci Lett. 2011 Feb 25;490(2):112-5
references.pmid: 21184807
references.citation: Am J Respir Cell Mol Biol. 2011 Feb;44(2):222-9
references.pmid: 20448051
references.citation: J Lab Clin Med. 1997 Apr;129(4):400-4
references.pmid: 9104882
references.citation: Am J Pathol. 1998 May;152(5):1327-36
references.pmid: 9588901
references.citation: J Immunol. 1998 Jul 15;161(2):957-62
references.pmid: 9670975
references.citation: Am J Pathol. 1998 Oct;153(4):1113-22
references.pmid: 9777942
references.citation: J Immunol. 1998 Nov 15;161(10):5614-20
references.pmid: 9820540
references.citation: J Immunol. 1999 Jan 15;162(2):1071-6
references.pmid: 9916735
references.citation: Clin Chem Lab Med. 1999 Mar;37(3):205-8
references.pmid: 10353462
references.citation: J Biol Chem. 2005 Sep 30;280(39):33566-72
references.pmid: 16081421
references.citation: N Engl J Med. 2005 Oct 20;353(16):1685-93
references.pmid: 16236739
references.citation: J Immunol. 2006 Jul 1;177(1):612-20
references.pmid: 16785559
references.citation: Intensive Care Med. 2006 Aug;32(8):1115-24
references.pmid: 16783553
references.citation: Am J Physiol Lung Cell Mol Physiol. 2006 Nov;291(5):L923-31
references.pmid: 16829628
references.citation: J Leukoc Biol. 2006 Dec;80(6):1512-21
references.pmid: 17138860
references.citation: Chest. 2007 Feb;131(2):554-62
references.pmid: 17296661
references.citation: Neurobiol Dis. 2007 Mar;25(3):631-41
references.pmid: 17207629
references.citation: Biol Pharm Bull. 2007 Apr;30(4):687-91
references.pmid: 17409503
references.citation: Pharm Res. 2007 Jul;24(7):1309-24
references.pmid: 17404814
references.citation: Cell Signal. 2007 Sep;19(9):1996-2002
references.pmid: 17582742
references.citation: Eur J Pharmacol. 2008 Apr 14;584(1):159-65
references.pmid: 18328478
references.citation: J Immunol. 2008 Apr 15;180(8):5575-81
references.pmid: 18390742
references.citation: Proc Assoc Am Physicians. 1996 May;108(3):198-208
references.pmid: 8774053
references.citation: Can J Physiol Pharmacol. 1965 May;43:405-10
references.pmid: 14324243
references.citation: J Immunol. 2005 Jun 1;174(11):7242-9
references.pmid: 15905570
references.citation: Am J Physiol Lung Cell Mol Physiol. 2008 Sep;295(3):L379-99
references.pmid: 18621912
references.citation: Clin Exp Allergy. 2009 Jul;39(7):956-61
references.pmid: 19400904
references.citation: Proc Natl Acad Sci U S A. 2010 Feb 9;107(6):2580-5
references.pmid: 20133656
references.citation: Mol Cell Proteomics. 2011 Mar;10(3):M110.001552
references.pmid: 21097543
references.citation: Neuroimmunomodulation. 2011;18(3):150-5
references.pmid: 21242699
references.citation: Autoimmunity. 2011 Sep;44(6):465-70
references.pmid: 21604972
references.citation: Pharmacol Ther. 2011 Nov;132(2):170-9
references.pmid: 21718720
references.citation: Curr Drug Targets. 2012 Jan;13(1):129-44
references.pmid: 22023408
references.citation: Neurosci Lett. 2012 Mar 28;513(1):89-94
references.pmid: 22366257
references.citation: EMBO J. 2012 Aug 1;31(15):3239-51
references.pmid: 22692127
references.citation: Intensive Care Med. 2012 Sep;38(9):1548-55
references.pmid: 22711173
references.citation: J Psychosoc Nurs Ment Health Serv. 2012 Oct;50(10):11-4
references.pmid: 22998536
references.citation: Crit Care. 2012;16(2):R55
references.pmid: 22480160
references.citation: Shock. 2013 Mar;39(3):286-92
references.pmid: 23364427
references.citation: Int Immunopharmacol. 2013 Feb;15(2):240-5
references.pmid: 23246979
references.citation: Inflammation. 2013 Apr;36(2):501-11
references.pmid: 23180366
references.citation: Anesthesiology. 2013 May;118(5):1065-75
references.pmid: 23485993
references.citation: Dig Dis Sci. 2013 Jul;58(7):1909-15
references.pmid: 23508979
references.citation: Mol Med Rep. 2013 Aug;8(2):565-70
references.pmid: 23784034
references.citation: Biochem Pharmacol. 2013 Dec 1;86(11):1525-30
references.pmid: 24084431
references.citation: J Biol Chem. 2013 Nov 29;288(48):34897-905
references.pmid: 24114844