Dissimilar effects of LY 294002 and PD 098059 in IGF-I-mediated inhibition of TGF-beta1 expression and apoptosis in bovine mammary epithelial cells.
In mammary epithelial cells (MEC) TGF-beta(1) is the auto-/paracrine growth inhibitor and inducer of apoptosis and therefore is considered as an important local regulator of mammary tissue involution. However, the mechanisms of controlled TGF-beta(1) expression in the course of bovine mammary gland remodelling are still unclear. Recent study performed in this laboratory support the evidence that TGF-beta(1) expression in bovine MEC is regulated by hormones of somatotropic axis (GH, IGF-I and somatostatin). Present study was focused on the contribution of IGF-I-induced signaling pathways in anti-TGF-beta(1) and anti-apoptotic effects of IGF-I. Laser scanning cytometry was applied for the measurement of TGF-beta(1) content and apoptotic cell number in bovine BME-UV1 MEC. Involution of the bovine mammary gland in vitro was modeled by decreasing the availability of FBS for bovine MEC. Reducing FBS content in the medium from 10% to 0.5% evoked highly significant increase of TGF-beta(1) expression and increase of apoptotic cell number. IGF-I (50 ng/ml) completely abrogated FBS deficiency-induced TGF-beta(1) expression and apoptosis in bovine MEC. In order to establish which of the IGF-I signaling pathways contributed to anti-TGF-beta(1) and anti-apoptotic effects, the inhibitors of PI3-kinase - (LY 294002) and MEK- (MAPKK for ERK) (PD 098059) mediated signaling pathways were applied to our model. The results clearly showed that inhibition of PI3-K reverses the ability of IGF-I to suppress TGF-beta(1) expression and apoptosis. An inhibition of ERK1/2 pathway even potentiated inhibitory effect of IGF-I on TGF-beta(1) expression, but partially abrogated anti-apoptotic effect of IGF-I. In conclusion, the results of the study indicate that PI3-K/Akt pathway contributed significantly to the inhibition of TGF-beta(1) expression by IGF-I, whereas both PI3-K/Akt and ERK1/2 pathways are involved in the anti-apoptotic effect of IGF-I in bovine MEC.
Zarzyńska
J
J
Department of Physiological Sciences, Faculty of Veterinary Medicine, Warsaw Agricultural University, Warsaw, Poland.
Motyl
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T
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002417:Cattle; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004847:Epithelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D005419:Flavonoids / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D047569:Laser Scanning Cytometry; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D009025:Morpholines / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
D002867:Chromones; D048049:Extracellular Signal-Regulated MAP Kinases; D005419:Flavonoids; D007334:Insulin-Like Growth Factor I; D020930:MAP Kinase Kinase Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D053773:Transforming Growth Factor beta1; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one