Ca2+/calmodulin-dependent protein kinase II-γ (CaMKIIγ) negatively regulates vascular smooth muscle cell proliferation and vascular remodeling.

Vascular smooth muscle (VSM) expresses calcium/calmodulin-dependent protein kinase II (CaMKII)-δ and -γ isoforms. CaMKIIδ promotes VSM proliferation and vascular remodeling. We tested CaMKIIγ function in vascular remodeling after injury. CaMKIIγ protein decreased 90% 14 d after balloon injury in rat carotid artery. Intraluminal transduction of adenovirus encoding CaMKIIγC rescued expression to 35% of uninjured controls, inhibited neointima formation (>70%), inhibited VSM proliferation (>60%), and increased expression of the cell-cycle inhibitor p21 (>2-fold). Comparable doses of CaMKIIδ2 adenovirus had no effect. Similar dynamics in CaMKIIγ mRNA and protein expression were observed in ligated mouse carotid arteries, correlating closely with expression of VSM differentiation markers. Targeted deletion of CaMKIIγ in smooth muscle resulted in a 20-fold increase in neointimal area, with a 3-fold increase in the cell proliferation index, no change in apoptosis, and a 60% decrease in p21 expression. In cultured VSM, CaMKIIγ overexpression induced p53 mRNA (1.7 fold) and protein (1.8-fold) expression; induced the p53 target gene p21 (3-fold); decreased VSM cell proliferation (>50%); and had no effect on expression of apoptosis markers. We conclude that regulated CaMKII isoform composition is an important determinant of the injury-induced vasculoproliferative response and that CaMKIIγ and -δ isoforms have nonequivalent, opposing functions.

Functional and molecular evidence for impairment of calcium-activated potassium channels in type-1 diabetic cerebral artery smooth muscle cells.

Cerebral vascular dysfunction and associated diseases often occur in type-1 diabetes, but the underlying mechanisms are largely unknown. In this study, we sought to determine whether big-conductance, Ca(2+)-activated K(+) (BK) channels were impaired in vascular (cerebral artery) smooth muscle cells (CASMCs) from streptozotocin-induced type-1 diabetic mice using patch clamp, molecular biologic, and genetic approaches. Our data indicate that the frequency and amplitude of spontaneous transient outward currents (STOCs) are significantly decreased, whereas the activity of spontaneous Ca(2+) sparks is increased, in diabetic CASMCs. The sensitivity of BK channels to voltage, Ca(2+), and the specific inhibitor iberiotoxin are all reduced in diabetic myocytes. Diabetic mice show increased myogenic tone and decreased contraction in response to iberiotoxin in cerebral arteries and elevated blood pressure. The expression of the BK channel beta1, but not alpha-subunit protein, is markedly decreased in diabetic cerebral arteries. Diabetic impairment of BK channel activity is lost in CASMCs from BK channel beta1-subunit gene deletion mice. In conclusion, the BK channel beta1-subunit is impaired in type-1 diabetic vascular SMCs, resulting in increased vasoconstriction and elevated blood pressure, thereby contributing to vascular diseases in type-1 diabetes.

MicroRNA-30 inhibits neointimal hyperplasia by targeting Ca(2+)/calmodulin-dependent protein kinase IIδ (CaMKIIδ).

The multifunctional Ca(2+)/calmodulin-dependent protein kinase II δ-isoform (CaMKIIδ) promotes vascular smooth muscle (VSM) proliferation, migration, and injury-induced vascular wall neointima formation. The objective of this study was to test if microRNA-30 (miR-30) family members are endogenous regulators of CaMKIIδ expression following vascular injury and whether ectopic expression of miR-30 can inhibit CaMKIIδ-dependent VSM cell function and neointimal VSM hyperplasia induced by vascular injury. The CaMKIIδ 3'UTR contains a consensus miR-30 binding sequence that is highly conserved across species. A significant decrease in miR-30 family members and increase in CaMKIIδ2 protein expression, with no change in CaMKIIδ mRNA expression, was observed in medial layers of VSM 7 days post-injury. In vitro, overexpression of miR-30c or miR-30e inhibited CaMKIIδ2 protein expression by ~50% in cultured rat aortic VSM cells, and inhibited VSM cell proliferation and migration. In vivo, lenti-viral delivery of miR-30c into injured rat carotid arteries prevented the injury-induced increase in CaMKIIδ2. Furthermore, neointima formation was dramatically inhibited by lenti-viral delivery of miR-30c in the injured medial smooth muscle. These studies define a novel mechanism for regulating CaMKIIδ expression in VSM and provide a new potential therapeutic strategy to reduce progression of vascular proliferative diseases, including atherosclerosis and restenosis.

Oxidative and calcium stress regulate DSCR1 (Adapt78/MCIP1) protein.

DSCR1 (adapt78) is a stress-inducible gene and cytoprotectant. Its protein product, DSCR1 (Adapt78), also referred to as MCIP1, inhibits intracellular calcineurin, a phosphatase that mediates many cellular responses to calcium. Exposure of human U251 and HeLa cells to hydrogen peroxide led to a rapid hyperphosphorylation of DSCR1 (Adapt78). Inhibitor and agonist studies revealed that a broad range of kinases were not responsible for DSCR1 (Adapt78) hyperphosphorylation, including ERK1/2, although parallel activation of the latter was observed. Phosphorylation of both DSCR1 (Adapt78) and ERK1/2 was attenuated by inhibitors of tyrosine phosphatase, suggesting the common upstream involvement of tyrosine dephosphorylation. The hyperphosphorylation electrophoretic shift in DSCR1 (Adapt78) mobility was also observed with other oxidizing agents (peroxynitrite and menadione) but not nonoxidants. Calcium ionophores strongly induced the levels of both hypo- and hyper-phosphorylated DSCR1 (Adapt78) but did not alter phosphorylation status. Calcium-dependent growth factor- and angiotensin II-stimulation also induced both DSCR1 (Adapt78) species. Phosphorylation of either or both serines in a 13-amino acid peptide made to a calcineurin-interacting conserved region of DSCR1 (Adapt78) attenuated inhibition of calcineurin. These data indicate that DSCR1 (Adapt78) protein is a novel, early stage oxidative stress-activated phosphorylation target and newly identified calcium-inducible protein, and suggest that these response mechanisms may contribute to the known cytoprotective and calcineurin-inhibitory activities of DSCR1 (Adapt78).

Gender-dependent modulation of alpha 1-adrenergic responses in rat mesenteric arteries.

The purpose of this study was to test the hypothesis that pathways modulating vasoconstriction in rat mesenteric resistance arteries are gender dependent. Net contractile responses to phenylephrine were significantly increased by endothelium disruption in arteries from males but not females. This gender-dependent effect was stimulus specific, because disruption of endothelium increased reactivity to serotonin comparably in arteries from both genders. Ovariectomy unmasked an increase in net alpha(1)-adrenergic contractile responsiveness after endothelium disruption, suggesting alpha(1)-adrenergic-stimulated production of endothelial vasodilators is suppressed in control females by gonadal sex steroids. Production of modulatory endothelium-derived vasodilators in males is balanced by production of vasoconstricting arachidonic acid metabolites. This was revealed by decreased alpha(1)-adrenergic contractile responses in arteries from males after pretreatment with indomethacin or the cyclooxygenase-1 selective inhibitor SC-560. The indomethacin-induced effect persisted after endothelium disruption, indicating smooth muscle as the source of cyclooxygenase-1-derived vasoconstrictors and was attenuated after orchiectomy. This study indicates gender differences in the expression of two pathways modulating alpha(1)-adrenergic sensitivity in mesenteric arteries: an endothelium-dependent vasodilator pathway and a balancing smooth muscle cyclooxygenase-1-dependent vasoconstrictor pathway. One consequence of these differences is that endothelial damage produces a selective increase in alpha(1)-adrenergic agonist reactivity in arteries from males.