Stress causes decrease in vascular relaxation linked with altered phosphorylation of heat shock proteins

Cyclic nucleotide-dependent vascular relaxation is associated with increase s in the phosphorylation of a small heat shock protein (HSP), HSP20. An inc rease in phosphorylation of another small HSP, HSP27, is associated with im paired cyclic nucleotide-dependent vascular relaxation. Expression of HSPs is altered by exposure to several types of cellular stress in vitro. To det ermine if behavioral stress in vivo alters vascular expression and phosphor ylation of the small HSPs and cyclic nucleotide-dependent vascular relaxati on, borderline hypertensive rats were stressed by restraint and exposure to air-jet stress 2 h/day for 10 days or remained in their home cage. Stress impaired relaxation of aorta to forskolin, which activates adenylyl cyclase , and sodium nitroprusside, which activates guanylyl cyclase. This was asso ciated with an increase in the aortic expression and phosphorylation of HSP 27, which was localized to the vascular smooth muscle, but a decrease in th e amount of phosphorylated (P)-HSP20. To determine if P-HSP27 inhibits phos phorylation of HSP20, P-HSP27 was added to a reaction mixture containing re combinant HSP20 and the catalytic subunit of cAMP-dependent protein kinase. P-HSP27 inhibited phosphorylation of HSP20 in a concentration-dependent ma nner. These data demonstrate that P-HSP27 can inhibit phosphorylation of HS P20. The increase in P-HSP27 and decrease in P-HSP20 were associated with r educed cyclic nucleotide-dependent vascular smooth muscle relaxation in res ponse to behavioral stress in vivo, an effect similar to that observed prev iously in response to cellular stress in vitro.