(S)-Albuterol activates pro-constrictory and pro-inflammatory pathways in human bronchial smooth muscle cells.
BACKGROUND
Pro-constrictory and proinflammatory properties of (S)-albuterol have been widely reported both under in vivo and in vitro conditions. However, underlying mechanisms are unclear.


OBJECTIVE
We examined and compared the cellular effects of albuterol enantiomers on key intracellular molecules involved in constrictory and inflammatory pathways in human bronchial smooth muscle cells (hBSMCs).


METHODS
Primary hBSMCs were grown in culture and treated with various concentrations of albuterol enantiomers for various periods. Methacholine was used to stimulate cells. The expression and activity of Gs and Gi proteins, the intracellular free calcium concentration ([Ca2+]i), the activity of phosphatidylinositol 3'-OH-kinase (PI3) kinase, and the transcriptional nuclear factor kappaB (NF-kappaB) level were examined.


RESULTS
There was a significant increase in the expression and activity of Gialpha-1 protein and a decrease in the expression of Gs protein in hBSMCs after 8 hours of treatment with (S)-albuterol. These effects of (S)-albuterol were observed in a dose-dependent manner. Nonreceptor-mediated activation of adenylate cyclase by forskolin was attenuated with (S)-albuterol. Treatment of the cells for 24 hours with (S)-albuterol significantly increased [Ca2+]i on stimulation with methacholine. Interestingly, the effect of (R)-albuterol was opposite to that of (S)-albuterol. The effect of the racemic albuterol in some cases was similar to that of (S)-albuterol. (S)-Albuterol significantly activated both PI3 kinase and NF-kappaB in hBSMCs.


CONCLUSIONS
These studies demonstrated an (S)-albuterol-induced increase in the expression and activity of pro-constrictory pathways involving Gialpha-1 protein and [Ca2+]i and a decrease in the activity of the bronchodilatory pathway involving Gs proteins in hBSNMCs. Additionally, (S)-albuterol activated proinflammatory pathways involving PI3 kinase and NF-kappaB. Because (S)-albuterol metabolizes at least 10-fold slower than (R)-albuterol and has a longer elimination half-life, these cellular effects of (S)-albuterol might explain the detrimental effect seen with chronic administration of racemic albuterol in the treatment of airway diseases, such as bronchial asthma.
Center for Allergy, Asthma and Immunology, Creighton University School of Medicine, Omaha, NE 68178, USA.
Devendra K
DK
Agrawal
Krishan
K
Ariyarathna
Peter W
PW
Kelbe
D000262:Adenylyl Cyclases / Q000096:biosynthesis; D000318:Adrenergic beta-Agonists / Q000737:chemistry / Q000633:toxicity; D000420:Albuterol / Q000737:chemistry / Q000633:toxicity*; D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000139:chemically induced; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D013237:Stereoisomerism
D000318:Adrenergic beta-Agonists; D044385:GTP-Binding Protein alpha Subunits; D016328:NF-kappa B; D005576:Colforsin; D019869:Phosphatidylinositol 3-Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; D000420:Albuterol; D002118:Calcium