Regulation of glomerular mesangial cell proliferation in culture by adrenomedullin.
Adrenomedullin is a recently discovered vasodilatory peptide that has been shown to be a potent activator of adenylate cyclase in a variety of cell systems, including rat mesangial cells. The major aim of the present study was to determine the regulation of rat mesangial cell proliferation (using [3H]thymidine incorporation as an index), apoptosis (using nucleosome-associated cytoplasmic DNA fragmentation as an index) and mitogen-activated protein kinase (MAPK) cascade, specifically extracellular signal-regulated kinase (ERK), jun-amino terminal kinase (JNK) and P38 mitogen-activated protein kinase (P38 MAPK) activities, by adrenomedullin-stimulated cyclic AMP-protein kinase-A pathway. Adrenomedullin increased cAMP levels significantly above basal and the response was inhibited by the adrenomedullin receptor antagonist, adrenomedullin-(22-52). Adrenomedullin also decreased [3H]thymidine incorporation and increased nucleosome-associated cytoplasmic DNA fragmentation, in a concentration-dependent fashion. Both these responses were receptor mediated as, adrenomedullin-(22-52) inhibited these effects. The decrease in proliferation and increase in apoptosis were both mimicked by forskolin, a direct adenylate cyclase activator. Adrenomedullin-mediated decrease in proliferation and increase in apoptosis were inhibited by H89 [[N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, hydrochloride]], a potent protein kinase-A inhibitor. Associated with the changes in proliferation and apoptosis, adrenomedullin decreased ERK2 activity, and increased JNK1 and P38 MAPK activities. All these kinase activities, except the increase in JNK1 activity could be simulated using forskolin. In addition, only adrenomedullin-mediated changes in ERK2 and P38 MAPK activities were inhibited by H89 while, adrenomedullin-stimulated JNK1 was not consistently inhibited by the protein kinase-A inhibitor. These results suggest that adrenomedullin might play an important role in mesangial cell turnover and that although adrenomedullin-mediated responses are primarily cAMP-dependent, it does not preclude the involvement of cAMP-independent pathways.
Parameswaran
N
N
Department of Physiology, Michigan State University, East Lansing 48824, USA.
Nambi
P
P
Brooks
D P
DP
Spielman
W S
WS
D053607:Adrenomedullin; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D048031:JNK Mitogen-Activated Protein Kinases; D008565:Membrane Proteins / Q000037:antagonists & inhibitors; D020928:Mitogen-Activated Protein Kinases; D009707:Nucleosomes / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D058265:Receptors, Adrenomedullin; D018000:Receptors, Peptide; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014665:Vasodilator Agents / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases
D008565:Membrane Proteins; D009707:Nucleosomes; D010446:Peptide Fragments; D010455:Peptides; D058265:Receptors, Adrenomedullin; D018000:Receptors, Peptide; D014665:Vasodilator Agents; C104782:adrenomedullin (22-52); D014316:Tritium; D053607:Adrenomedullin; D005576:Colforsin; D000242:Cyclic AMP; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D013936:Thymidine