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Baclofen, a GABABR agonist, ameliorates immune-complex mediated acute lung injury by modulating pro-inflammatory mediators.

Jin S, Merchant ML, Ritzenthaler JD, McLeish KR, Lederer ED, Torres-Gonzalez E, Fraig M, Barati MT, Lentsch AB, Roman J, Klein JB, Rane MJ - PLoS ONE (2015)

Bottom Line: 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).Protective effects of baclofen treatment on ALI were possibly mediated by inhibition of TNF-α- and IL-1β-mediated inflammatory signaling.GABABR2 agonists may play a potential therapeutic role in ALI.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.

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.

No MeSH data available.


Related in: MedlinePlus

Baclofen reverses altered expression of GABABRs in the lung tissue from rats subjected to IC induced ALI.(A) Lung tissue homogenates from three animal groups: control (lane 1), lung injury (LI) (lanes 2 and 3), or LI followed by baclofen administration (LI+B) (lanes 4, 5, and 6), were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (B) GABABR2 and GAPDH immunoblots from above three animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group). (C) Lung tissue homogenates from five animal groups: control, lung injury (LI), or LI followed by baclofen administration (LI+B), CGP52432 pretreatment followed by lung injury (CGP+LI), and CGP52432 pretreatment followed by lung injury and baclofen administration (CGP+LI+B) were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (D) GABABR2 and GAPDH immunoblots from above five animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group).
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pone.0121637.g005: Baclofen reverses altered expression of GABABRs in the lung tissue from rats subjected to IC induced ALI.(A) Lung tissue homogenates from three animal groups: control (lane 1), lung injury (LI) (lanes 2 and 3), or LI followed by baclofen administration (LI+B) (lanes 4, 5, and 6), were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (B) GABABR2 and GAPDH immunoblots from above three animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group). (C) Lung tissue homogenates from five animal groups: control, lung injury (LI), or LI followed by baclofen administration (LI+B), CGP52432 pretreatment followed by lung injury (CGP+LI), and CGP52432 pretreatment followed by lung injury and baclofen administration (CGP+LI+B) were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (D) GABABR2 and GAPDH immunoblots from above five animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group).

Mentions: While GABABRs are expressed in the lung cells any changes in its expression after IC induced ALI are unclear [15–17]. According to previous reports we demonstrate expression of GABABR2 in the lung tissue of control animals. Interestingly, we demonstrate for the first time significant decrease in pulmonary GABABR2 expression in animals subjected to ALI compared to control (Fig 5A and 5B). Baclofen significantly restored pulmonary GABABR2 expression in animals subjected to ALI (Fig 5A and 5B). Three animals were used in each of the 3 groups tested. To examine whether baclofen exerted its effects by binding specifically to GABABRs two additional groups were examined. These two groups included animals that were pretreated intratracheally with 1 mg/kg CGP52432 (GABABR antagonist) and subjected to ALI with or without baclofen treatment 2 h after initiation of ALI. CGP52432 pretreatment significantly blocked baclofen-induced preservation of GABABR2 expression after ALI (Fig 5C and 5D). CGP52432 pretreatment followed by ALI decreased GABABR2 expression to the same extent as ALI alone (Fig 5D). Three animals were used in each of the 3 groups tested. These results indicate that baclofen preserves GABABR2 expression after ALI by binding GABABRs.


Baclofen, a GABABR agonist, ameliorates immune-complex mediated acute lung injury by modulating pro-inflammatory mediators.

Jin S, Merchant ML, Ritzenthaler JD, McLeish KR, Lederer ED, Torres-Gonzalez E, Fraig M, Barati MT, Lentsch AB, Roman J, Klein JB, Rane MJ - PLoS ONE (2015)

Baclofen reverses altered expression of GABABRs in the lung tissue from rats subjected to IC induced ALI.(A) Lung tissue homogenates from three animal groups: control (lane 1), lung injury (LI) (lanes 2 and 3), or LI followed by baclofen administration (LI+B) (lanes 4, 5, and 6), were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (B) GABABR2 and GAPDH immunoblots from above three animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group). (C) Lung tissue homogenates from five animal groups: control, lung injury (LI), or LI followed by baclofen administration (LI+B), CGP52432 pretreatment followed by lung injury (CGP+LI), and CGP52432 pretreatment followed by lung injury and baclofen administration (CGP+LI+B) were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (D) GABABR2 and GAPDH immunoblots from above five animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4388838&req=5

pone.0121637.g005: Baclofen reverses altered expression of GABABRs in the lung tissue from rats subjected to IC induced ALI.(A) Lung tissue homogenates from three animal groups: control (lane 1), lung injury (LI) (lanes 2 and 3), or LI followed by baclofen administration (LI+B) (lanes 4, 5, and 6), were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (B) GABABR2 and GAPDH immunoblots from above three animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group). (C) Lung tissue homogenates from five animal groups: control, lung injury (LI), or LI followed by baclofen administration (LI+B), CGP52432 pretreatment followed by lung injury (CGP+LI), and CGP52432 pretreatment followed by lung injury and baclofen administration (CGP+LI+B) were subjected to immunoblot analysis with anti-GABABR2 and anti-GAPDH antisera. (D) GABABR2 and GAPDH immunoblots from above five animal groups were scanned and band densities were quantified using ImageJ software GABABR2 band density is normalized to its respective GAPDH band intensity. Data is expressed as mean ± SEM (n = 3 animals per group).
Mentions: While GABABRs are expressed in the lung cells any changes in its expression after IC induced ALI are unclear [15–17]. According to previous reports we demonstrate expression of GABABR2 in the lung tissue of control animals. Interestingly, we demonstrate for the first time significant decrease in pulmonary GABABR2 expression in animals subjected to ALI compared to control (Fig 5A and 5B). Baclofen significantly restored pulmonary GABABR2 expression in animals subjected to ALI (Fig 5A and 5B). Three animals were used in each of the 3 groups tested. To examine whether baclofen exerted its effects by binding specifically to GABABRs two additional groups were examined. These two groups included animals that were pretreated intratracheally with 1 mg/kg CGP52432 (GABABR antagonist) and subjected to ALI with or without baclofen treatment 2 h after initiation of ALI. CGP52432 pretreatment significantly blocked baclofen-induced preservation of GABABR2 expression after ALI (Fig 5C and 5D). CGP52432 pretreatment followed by ALI decreased GABABR2 expression to the same extent as ALI alone (Fig 5D). Three animals were used in each of the 3 groups tested. These results indicate that baclofen preserves GABABR2 expression after ALI by binding GABABRs.

Bottom Line: 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).Protective effects of baclofen treatment on ALI were possibly mediated by inhibition of TNF-α- and IL-1β-mediated inflammatory signaling.GABABR2 agonists may play a potential therapeutic role in ALI.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, University of Louisville, Louisville, Kentucky, United States of America.

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.

No MeSH data available.


Related in: MedlinePlus