Insulin Causes a Transient Induction of Proliferation via Activation of the PI3-Kinase Pathway in Airway Smooth Muscle Cells

Abstract

Insulin regulates glucose metabolism and activates cell growth. As the respiratory system is an alternative route for insulin administration in patients with diabetes mellitus, we studied the effect of insulin on rabbit tracheal airway smooth muscle (ASM) cell proliferation. We show that treatment of quiescent ASM cells with insulin for 24 h increased cell number compared to control cells. This increase was similar to the increase caused by the addition of fetal bovine serum (FBS). Moreover, in contrast to cells treated with FBS, exposure of ASM cells with insulin for longer periods (48 and 72 h) did not have any further influence on cell proliferation. In ASM cells, insulin activated the phosphatidylinositol 3-kinase (PI3 K) pathway, while FBS activated both PI3 K and the mitogen-activated protein kinase (MAPK) pathway. The PI3K pathway inhibitors LY294002 and wortmannin abolished the stimulation of cell proliferation by insulin, indicating a role for this pathway in the cellular response to insulin. These results show that while insulin has a mitogenic effect on ASM cells, prolonged insulin treatment does not lead to excessive ASM cell proliferation and suggest that the use of aerosolized insulin does not represent a potential hazard for airway remodeling.

Key words

signal transduction - diabetes - protein kinases

References

• 1 Ammit AJ, Panettieri Jr RA. Signal transduction in smooth muscle: invited review: the circle of life: cell cycle regulation in airway smooth muscle.  J Appl Physiol. 2001;  91 1431-1437
• 2 Avena R, Mitchell ME, Neville RF, Sidawy AN. The additive effects of glucose and insulin on the proliferation of infragenicular vascular smooth muscle cells.  J Vasc Surg. 1998;  28 1033-1038
• 3 Begum N, Song Y, Rienzie J, Ragolia L. Vascular smooth muscle cell growth and insulin regulation of mitogen-activated protein kinase in hypertension.  Am J Physiol Cell Physiol. 1998;  275 C42-C49
• 4 Berridge MV, Tan AS. Characterization of the cellular reduction of 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT): subcellular localization, substrate dependence, and involvement of mitochondrial electron transport in MTT reduction.  Archives of Biochemistry and Biophysics. 1993;  303 474-482
• 5 Black JL, Johnson PR. Factors controlling smooth muscle proliferation and airway remodelling.  Curr Opin Allergy Clin Immunol. 2002;  2 47-51
• 6 Cefalu WT. Concept, strategies, and feasibility of noninvasive insulin delivery.  Diabetes Care. 2004;  27 239-246
• 7 Chachami G, Simos G, Hatziefthimiou A, Bonanou S, Molyvdas P-A, Paraskeva E. Cobalt induces hypoxia-inducible factor-1{alpha} expression in airw.  Am J Respir Cell Mol Biol. 2004;  31 544-551
• 8 Cherrington AD, Neal DW, Edgerton DS, Glass D, Bowen L, Hobbs CH, Leach C, Rosskamp R, Strack TR. Inhalation of insulin in dogs: assessment of insulin levels and comparison to subcutaneous injection.  Diabetes. 2004;  53 877-881
• 9 Chiappara G, Gagliardo R, Siena A, Bonsignore MR, Bousquet J, Bon-signore G, Vignola AM. Airway remodelling in the pathogenesis of asthma.  Curr Opin Allergy Clin Immunol. 2001;  1 85-93
• 10 Colthorpe P, Farr SJ, Taylor G, Smith IJ, Wyatt D. The pharmacokinetics of pulmonary-delivered insulin: a comparison of intratracheal and aerosol administration to the rabbit.  Pharmaceutical Research. 1992;  9 764-768
• 11 Cory AH, Owen TC, Barltrop JA, Cory JG. Use of an aqueous soluble tet-razolium/formazan assay for cell growth assays in culture.  Cancer Commun. 1991;  3 207-212
• 12 Gosens R, Nelemans SA, Hiemstra M, Grootte Bromhaar MM, Meurs H, Zaagsma J. Insulin induces a hypercontractile airway smooth muscle phenotype.  Eur J Pharmacol. 2003;  481 125-131
• 13 Halayko AJ, Kartha S, Stelmack GL, McConville J, Tam J, Camoretti-Mercado B, Forsythe SM, Hershenson MB, Solway J. Phophatidylinosi-tol-3 kinase/mammalian target of rapamycin/p 70S6Kregulates contractile protein accumulation in airway myocyte differentiation.  Am J Respir Cell Mol Biol. 2004;  31 266-275
• 14 Halayko AJ, Rector E, Stephens NL. Airway smooth muscle cell proliferation: characterization of subpopulations by sensitivity to heparin inhibition.  Am J Physiol Lung Cell Mol Physiol. 1998;  274 L17-L25
• 15 Halayko AJ, Solway J. Plasticity in skeletal, cardiac, and smooth muscle: invited review: molecular mechanisms of phenotypic plasticity in smooth muscle cells.  J Appl Physiol. 2001;  90 358-368
• 16 Hilsted J, Madsbad S, Hvidberg A, Rasmussen MH, Krarup T, Ipsen H, Hansen B, Pedersen M, Djurup R, Oxenboll B. Intranasal insulin therapy: the clinical realities.  Diabetologia. 1995;  38 680-684
• 17 Jendle JH, Karlberg BE. Effects of intrapulmonary insulin in patients with non-insulin-dependent diabetes.  Scand J Clin Lab Invest. 1996;  56 555-561
• 18 Jung F, Haendeler J, Goebel C, Zeiher AM, Dimmeler S. Growth factor-induced phosphoinositide 3-OH kinase/Akt phosphorylation in smooth muscle cells: induction of cell proliferation and inhibition of cell death.  Cardiovasc Res. 2000;  48 148-157
• 19 Karpova AY, Abe MK, Li J, Liu PT, Rhee JM, Kuo WL, Hershenson MB. MEK1 is required for PDGF-induced ERK activation and DNA synthesis in tracheal myocytes.  Am J Physiol. 1997;  272 L558-L565
• 20 Kobayashi Y, Naruse K, Hamada Y, Nakashima E, Kato K, Akiyama N, Kamiya H, Watarai A, Nakae M, Oiso Y, Nakamura J. Human proinsulin C-peptide prevents proliferation of rat aortic smooth muscle cells cultured in high-glucose conditions.  Diabetologia. 2005;  48 2396-2401
• 21 Laube B, Benedict G, Dobs A. The lung as an alternative route of delivery for insulin in controlling postprandial glucose levels in patients with diabetes.  Chest. 1998;  114 1734-1739
• 22 Ma X, Wang Y, Stephens NL. Serum deprivation induces a unique hypercontractile phenotype of cultured smooth muscle cells.  Am J Physiol Cell Physiol. 1998;  274 C1206-C1214
• 23 Mandal TK. Inhaled insulin for diabetes mellitus.  Am J Health Syst Pharm. 2005;  62 1359-1364
• 24 Noveral JP, Grunstein MM. Tachykinin regulation of airway smooth muscle cell proliferation.  Am J Physiol. 1995;  269 L339-L343
• 25 Papayianni M, Gourgoulianis KI, Molyvdas PA. Insulin NO-dependent action on airways smooth muscles.  Nitric Oxide. 2001;  5 72-76
• 26 Rave K, Bott S, Heinemann L, Sha S, Becker RHA, Willavize SA, Heise T. Time-action profile of inhaled insulin in comparison with subcutaneously injected insulin lispro and regular human insulin.  Diabetes Care. 2005;  28 1077-1082
• 27 Saltiel AR, Kahn CR. Insulin signalling and the regulation of glucose and lipid metabolism.  Nature. 2001;  414 799-806
• 28 Skalli O, Ropraz P, Trzeciak A, Benzonana G, Gillessen D, Gabbiani G. A monoclonal antibody against alpha-smooth muscle actin: a new probe for smooth muscle differentiation.  J Cell Biol. 1986;  103 2787-2796
• 29 Wang CC, Gurevich I, Draznin B. Insulin affects vascular smooth muscle cell phenotype and migration via distinct signaling pathways.  Diabetes. 2003;  52 2562-2569
• 30 White MF. Insulin signaling in health and disease.  Science. 2003;  302 1710-1711
• 31 Zhou L, Hershenson MB. Mitogenic signaling pathways in airway smooth muscle.  Respiratory Physiology & Neurobiology. 2003;  137 295-308

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