Alpha-defensins increase lung fibroblast proliferation and collagen synthesis via the beta-catenin signaling pathway.
Alpha-defensins are released from granules of leukocytes and are implicated in inflammatory and fibrotic lung diseases. In the present study, the effects of alpha-defensins on the proliferation and collagen synthesis of lung fibroblasts were examined. We found that alpha-defensin-1 and alpha-defensin-2 induced dose-dependent increases in the incorporation of 5-bromo-2'-deoxy-uridine into newly synthesized DNA in two lines of human lung fibroblasts (HFL-1 and LL-86), suggesting that alpha-defensin-1 and alpha-defensin-2 stimulate the proliferation of lung fibroblasts. alpha-defensin-1 and alpha-defensin-2 also increased collagen-I mRNA (COL1A1) levels and protein contents of collagen-I and active/dephosphorylated beta-catenin without changes in total beta-catenin protein content in lung fibroblasts (HFL-1 and LL-86). Inhibition of the beta-catenin signaling pathway using quercetin prevented increases in cell proliferation and the protein content of collagen-I and active/dephosphorylated beta-catenin in lung fibroblasts, and in COL1A1 mRNA levels and collagen release into culture medium induced by alpha-defensin-1 and alpha-defensin-2. Knocking-down beta-catenin using small interfering RNA technology also prevented alpha-defensin-induced increases in cell proliferation and the protein content of collagen-I and active/dephosphorylated beta-catenin in lung fibroblasts, and in COL1A1 mRNA levels. Moreover, increases in the phosphorylation of glycogen synthase kinase 3beta, accumulation/activation of beta-catenin, and collagen synthesis induced by alpha-defensin-1 and alpha-defensin-2 were prevented by p38 mitogen-activated protein kinase inhibitor SB203580 and phosphoinositide 3-kinase inhibitor LY294002. These results indicate that alpha-defensin-1 and alpha-defensin-2 stimulate proliferation and collagen synthesis of lung fibroblasts. The beta-catenin signaling pathway mediates alpha-defensin-induced increases in cell proliferation and collagen synthesis of lung fibroblasts. alpha-defensin-induced activation of beta-catenin in lung fibroblasts might be caused by phosphorylation/inactivation of glycogen synthase kinase 3beta as a result of the activation of the p38 mitogen-activated protein kinase and phosphoinositide 3-kinase/Akt pathways.
Han
Weihong
W
Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912, USA.
Wang
Wei
W
Mohammed
Kamal A
KA
Su
Yunchao
Y
D000890:Anti-Infective Agents / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D003094:Collagen / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects*; D006801:Humans; D015151:Immunoblotting; D008168:Lung / Q000166:cytology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D023084:alpha-Defensins / Q000494:pharmacology*; D051176:beta Catenin / Q000235:genetics / Q000502:physiology*
D000890:Anti-Infective Agents; D034741:RNA, Small Interfering; D023084:alpha-Defensins; D051176:beta Catenin; D003094:Collagen