Nitric oxide inhibits surfactant protein B gene expression in lung epithelial cells.
Surfactant protein B (SP-B) is an essential constituent of pulmonary surfactant. In a number of inflammatory diseases of the lung, elevated nitric oxide (NO) levels are associated with decreased SP-B levels, suggesting that reduced SP-B levels contribute to lung injury. In this study, we investigated the effects of NO on SP-B gene expression in H441 and MLE-12 cells, cell lines with characteristics of bronchiolar (Clara) and alveolar type II epithelial cells, respectively. Results show that NO donors decreased SP-B mRNA levels in a concentration- and time-dependent manner in H441 and MLE-12 cells. The NO donors also antagonized dexamethasone induction of SP-B mRNA in H441 cells. NO donor inhibition of SP-B mRNA was blocked by the transcriptional inhibitor 5,6-dichloro-1-beta-D-ribofuranozyl-benzimidazole. NO donors decreased luciferase expression from a reporter plasmid containing -911/+41 bp of human SP-B 5'-flanking DNA in H441 and MLE-12 cells, indicating inhibitory effects on SP-B promoter activity. NO inhibition of SP-B mRNA levels was not blocked by LY-83583 and KT-5823, inhibitors of soluble guanylate cyclase and protein kinase G, respectively. Furthermore, cell-permeable cGMP analog 8-bromo-cGMP had no effect on SP-B mRNA levels. These data indicate that elevated NO levels negatively regulate SP-B gene expression by inhibiting gene transcription and that NO inhibits SP-B gene expression independently of cGMP levels. These data imply that reduced SP-B expression due to elevated NO levels can contribute to lung injury.
Salinas
Darrell
D
Department of Molecular Biology, University of Texas Health Center at Tyler, Tyler, Texas 75708-3154, USA.
Sparkman
Loretta
L
Berhane
Kiflu
K
Boggaram
Vijayakumar
V
D000230:Adenocarcinoma; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000502:physiology*; D008175:Lung Neoplasms; D051379:Mice; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D037701:Pulmonary Surfactant-Associated Protein B / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D020545:Respiratory Mucosa / Q000502:physiology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D020030:Nitric Oxide Donors; D037701:Pulmonary Surfactant-Associated Protein B; D012333:RNA, Messenger; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D003907:Dexamethasone