Heparin Responses in Vascular Smooth Muscle Cells Involve cGMP‐Dependent Protein Kinase (PKG)

Abstract

Published data provide strong evidence that heparin treatment of proliferating vascular smooth muscle cells results in decreased signaling through the ERK pathway and decreases in cell proliferation. In addition, these changes have been shown to be mimicked by antibodies that block heparin binding to the cell surface. Here we provide evidence that the activity of protein kinase G is required for these heparin effects. Specifically, a chemical inhibitor of protein kinase G, Rp-8-pCPT-cGMS, eliminates heparin and anti-heparin receptor antibody effects on bromodeoxyuridine incorporation into growth factor stimulated cells. In addition, protein kinase G inhibitors decrease heparin effects on ERK activity, phosphorylation of the transcription factor ELK-1, and heparin induced MKP-1 synthesis. Although transient, the levels of cGMP increase in heparin treated cells. Finally, knock down of protein kinase G also significantly decreases heparin effects in growth factor activated vascular smooth muscle cells. Together, these data indicate that heparin effects on vascular smooth muscle cell proliferation depend, at least in part, on signaling through protein kinase G.

Heparin Decreases in Tumor Necrosis Factor α (TNFα)-induced Endothelial Stress Responses Require Transmembrane Protein 184A and Induction of Dual Specificity Phosphatase 1

“…The heparin effects in ECs are mimicked by HRmAbs that bind to a heparin receptor. The observations that pretreatment with antibodies to a putative heparin receptor decreases TNF␣-induced JNK and p38 activation and decreases stress fiber formation are consistent with previous reports showing that these antibodies mimic the effects of heparin in VSMCs (19,22,24). Here we provide functional evidence that the anti-inflammatory effects of heparin in ECs are mediated through the heparin receptor TMEM184A, as seen in VSMCs (28).…”

“…This causes ECs to become vasoconstrictive and, eventually, dysfunctional (38,57). Recent studies have shown that the effects of heparin in VSMCs involve cGMP-dependent protein kinase (22). We hypothesize that the effects of heparin in ECs might also be dependent on cGMP-dependent protein kinase and that the heparin-induced increased cGMP prior to exposure to TNF␣ could prevent the effects resulting from changes in NO production.…”

“…In support of this idea, DUSP1 induction by anti-inflammatory glucocorticoid hormones does increase DUSP1 expression (25,26), and low molecular weight heparin has been reported to decrease peroxide-induced JNK and p38 activity (27). Heparin uptake and many heparin functions likely depend on a heparin/HS receptor.Monoclonal antibodies that block heparin binding to endothelial cells (HRmAbs) are able to mimic heparin responses in VSMCs (10,19,22,24), providing evidence that the protein to which they bind functions as a heparin receptor. The accompanying report identifies TMEM184A as the heparin-interacting protein to which the HRmAbs bind (28).…”

“…Numerous reports have identified VSMC responses to heparin. These responses include decreases in cell proliferation (18,19), ERK pathway activity (19 -21), and activation of specific transcription factors (21)(22)(23). Heparin binding results in increased levels of DUSP1 protein that are required for decreases in ERK activity (24).…”

“…Monoclonal antibodies that block heparin binding to endothelial cells (HRmAbs) are able to mimic heparin responses in VSMCs (10,19,22,24), providing evidence that the protein to which they bind functions as a heparin receptor. The accompanying report identifies TMEM184A as the heparin-interacting protein to which the HRmAbs bind (28).…”