Inhibition of mitogenesis and c-fos induction in mesangial cells by heparin and heparan sulfates.
When rat renal mesangial cells (RMC) or vascular smooth muscle cells are released from quiescence by serum stimulation they express c-fos mRNA transiently at 30 to 60 minutes and progress in synchrony to S phase. Heparin causes significant suppression of [3H]-thymidine incorporation into DNA in S phase and a decrease and delay of entry of cells into S/G2. Added at the time of serum stimulation, heparin (1 microgram/ml or less) causes a decrease in the subsequent expression of c-fos mRNA in RMC, and a similar effect is observed with heparan sulfate chains isolated from RMC-cultures themselves. Although these cells internalize and degrade heparin, the timing of the maximal effect indicates an extracellular action of heparin. In keeping with this idea, 125I-heparin binds specifically to a single class of high affinity sites on the cell surface. The effect of heparin on c-fos induction may be independent of interaction with cytokines or cytokine receptors; its magnitude is not diminished when heparin-binding substances are removed from serum by heparin-Sepharose. Furthermore, direct activation of protein kinase C (PKC) with a phorbol ester in the absence of serum likewise induces c-fos and 1 microgram/ml heparin inhibits this response by 65%. Phorbol ester caused an increase in the proportion of histone H1-active PKC associated with the cell membrane fraction, from approximately 25% to 70% of total activity. Heparin affected neither the total activity of the kinase nor the proportion associated with the membrane. When PKC was inhibited with staurosporine, only very low levels of c-fos were induced by serum. We conclude that low concentrations of heparin and heparan sulfate suppress the mitogenic response of mesangial cells to serum and inhibit c-fos mRNA induction through an effect of cell surface-bound glycosaminoglycan on a signalling pathway downstream of PKC.
Wang
A
A
Department of Clinical Biochemistry, University of Toronto, Ontario, Canada.
Templeton
D M
DM
D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D017781:Genes, Immediate-Early / Q000187:drug effects; D005920:Glomerular Mesangium / Q000187:drug effects / Q000378:metabolism*; D006131:Growth Inhibitors; D006493:Heparin / Q000378:metabolism / Q000494:pharmacology*; D006497:Heparan Sulfate / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D008297:Male; D008934:Mitogens / Q000037:antagonists & inhibitors*; D010703:Phorbol Esters / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D006131:Growth Inhibitors; D006493:Heparin; D006497:Heparan Sulfate; D007457:Iodine Radioisotopes; D008934:Mitogens; D010703:Phorbol Esters; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger