title: Chronic hypoxia induces proliferation of cultured mesangial cells: role of calcium and protein kinase C.
abstract: The effect of hypoxia on the proliferation of cultured rat mesangial cells was examined. To evaluate the underlying signaling mechanisms, the roles of intracellular calcium ([Ca2+]i) and protein kinase C (PKC) were determined. Quiescent cultures were exposed to hypoxia (3% O2) or normoxia (18% O2), and [3H]thymidine incorporation, cell number, [Ca2+]i, and PKC were assessed. Mesangial cells exposed to 28 h of hypoxia exhibited a significant increase in [3H]thymidine incorporation followed by a significant increase in cell number at 72 h in comparison with respective normoxic controls. Hypoxia induced a biphasic activation of PKC, reflected by translocation of the enzyme activity from cytosol to membrane at 1 h, a return to baseline at 4 and 8 h, with subsequent reactivation from 16 to 48 h. In addition, hypoxia-induced proliferation was prevented by a PKC inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). Cells exposed to hypoxia produced progressive increases in resting [Ca2+]i from 15 to 60 min which remain sustained up to 24 h of examination. Verapamil significantly prevented the hypoxia-induced proliferation, and both verapamil treatment and incubations in a calcium-free medium for 1 h blocked the hypoxia-induced stimulation of [Ca2+]i as well as PKC. These results provide the first in vitro evidence that chronic hypoxia induces proliferation of cultured glomerular mesangial cells, which is mediated by the stimulation of [Ca2+]i and the subsequent activation of PKC.
authors.affiliation: Division of Renal Diseases and Hypertension, University of Colorado Health Sciences Center, Denver 80262, USA.
authors.forename: A
authors.initials: A
authors.lastname: Sahai
authors.forename: C
authors.initials: C
authors.lastname: Mei
authors.forename: T A
authors.initials: TA
authors.lastname: Pattison
authors.forename: R L
authors.initials: RL
authors.lastname: Tannen
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002455:Cell Division; D015687:Cell Hypoxia / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000502:physiology*; D007700:Kinetics; D008297:Male; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013936:Thymidine / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D002118:Calcium; D013936:Thymidine