Small heat shock proteins and vasospasm in human umbilical artery smooth muscle

Human umbilical artery smooth muscle is uniquely refractory to cyclic nucleotide-dependent vasorelaxation. Small heat shock proteins (HSPs) have been implicated as contractile regulatory proteins. Thus, we hypothesized that alterations in the phosphorylation of small HSPs may contribute to human umbilical artery smooth muscle vasospasm. Physiologic contractile responses were determined in a muscle bath and compared with phosphorylation events determined with whole-cell phosphorylation and 2-dimensional gel electrophoresis. Precontraction of bovine carotid artery smooth muscle with serotonin followed by relaxation with forskolin was associated with increases in the phosphorylation of HSP27 and HSP20. Precontraction of umbilical artery with serotonin followed by forskolin treatment led to increases in the phosphorylation of HSP27. However, the umbilical artery smooth muscle did not relax, nor was there an increase in the phosphorylation of HSP20 with forskolin treatment. These data suggest that impaired cyclic nucleotide-dependent relaxation of umbilical artery smooth muscle is associated with a lack of phosphorylation of HSP20.