Decreased susceptibility of cultured smooth muscle cells from SHR rats to growth inhibition by heparin

Abstract

Smooth muscle cell proliferation is regulated through the coordinated action of growth inhibitors and growth factors/mitogens; a specific heparin-epidermal growth factor (EGF) complementation has been proposed (Reilly et al., 1987, J. Cell. Physiol., 131:149-157). In culture, vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) proliferate more rapidly than VSMC from control Wistar Kyoto rats (WKY). We observed that, compared with WKY-derived VSMC, cells from SHR were markedly less susceptible to growth inhibition both by heparin and its homopolysaccharide analogue pentosan polysulphate (PPS). SHR-derived VSMC exhibited a reduced capacity for binding of [3H]heparin to specific extracellular surface receptors, whereas affinities for heparin were comparable between both VSMC isolates. The early (0-2 hr at 37 degrees C) kinetics of internalization did not differ between SHR- and WKY-derived VSMC, but both internalized equivalent proportions (approximately 10%) of initially surface-bound heparin. VSMC from SHR exhibited a greater capacity, without a changed affinity, for [I125]EGF binding than VSMC from WKY. Pre-exposure of VSMC to heparin or PPS decreased, in a time-dependent manner, the EGF binding capacity for both SHR and WKY (by 40-50% after 72 hr). However, in absolute terms, the EGF-binding capacity of VSMC from SHR exposed to heparinoids was similar to that of nonexposed VSMC from WKY.

Trans-repressor activity of nuclear glycosaminoglycans on Fos and Jun/AP-1 oncoprotein-mediated transcription.

“…Castellot et al (1986) reported the inhibition of SMC proliferation by GAG required the presence of a 3-0-sulfated pentasaccharide. Similarly, Resink et al (1989) found that pentosan polysulfate and heparin were competitive for the same cellular binding site and that both were inhibitory to vascular SMC proliferation . That pentosan polysulfate blocked the The Joumal of Cell Biology, Volume 116, 1992 induction ofTHE/TK-CAT expression while chondroitin sulfate A and C did not, shows a specificity for GAG structure which may be related to the degree and/or pattern of sulfation.…”

“…The many steps involved in the regulation and accumulation of nuclear GAGs include : selective synthesis (Fritze et al, 1985 ;Bassols and Massqué, 1988;Carey and Evans, 1989) and secretion of both free (Piepkorn et al ., 1989) and attached chains to cell surface and cell matrix proteoglycans (Ishihara et al ., 1987;Jalkanen et al ., 19887;Carey and Evans, 1989) ; cellular secretion of heparitinases, proteinases, and phospholipases (Castellot et al, 1982;Jalkanen et al, 1987;Ishihara et al, 1987;Nakajima et al, 1987Nakajima et al, , 1988 required for release and uptake of GAGs; specific binding and internalization ofGAGs by cell surface receptors (Hoover et al ., 1980 ;Castellot et al, 19ß5b;Resink et al, 1989) ; and transport and metabolism in the cytosol and translocation into the nucleus (Castellot et al, 19ß5b;Fedarko and Conrad, 1986;Ishihara et al, 1986;Herbert and Maffrand, 1989) . Regulation at any or all of these steps may precede regulation of transcription factor activities by selective nuclear interactions with GAG.…”

“…Glycosaminoglycans have been shown to enter the cell through high affinity receptor-mediated processes (Castellot etal., 1985b ;Resink et al ., 1989), and in the case ofprimary hepatocytes, specific GAG subfractions have been shown to concentrate in the nucleus Ishihara et al, 1986Ishihara et al, , 1987 . To determine whether the attenuated promoter function observed in the previous experiments was because of the presence of an inhibitory nuclear GAG, the relative level of TPA-inducible TRE-binding activity in HeLa cell nuclear lysates was examined by polyacrylamide gel DNAbinding assays.…”

“…Inhibition of cell growth was not due to the sequestration of serum nutrients, mitogens, and growth factors (Reilly et al, 1986;Benitz et al, 1986) but rather involved the high affinity binding of heparin to specific cell surface receptors (Castellot et al ., 1985;Resink et al ., 1989) and internalization of the GAGs characterized by a ti/2 of 15-20 min in primary cell cultures . Inhibition of cell migration and proliferation in vivo after heparin perfusion has also been reported (Clowes and Karnovsky, 1977;Guyton et al, 1980) .…”

Allograft-induced arterial wall injury and response in normotensive and spontaneously hypertensive rats.

“…13 Qowes and Clowes 35 and Krupski et al 36 have reported greater intimal proliferation in SHRs than in WKYs after balloon-induced arterial wall injury. Nevertheless, blood pressure could also play a role in this hyperresponsiveness.…”