Rescue of cGMP Kinase I knockout mice by smooth muscle specific expression of either isozyme

Weber S, Bernhard D, Lukowski R, et al. Rescue of cGMP Kinase I Knockout Mice by Smooth Muscle–Specific Expression of Either Isozyme. Circulation Research. 2007;101(11):1096-1103.Smooth muscle expresses the Iα and the Iβ isoforms of cGMP-dependent protein kinase I (cGKI). Inactivation of the murine cGKI geneprkg1leads to multiple phenotypes and premature death at ≈6 weeks. We reconstituted mice with the cGKIα or -Iβ isozyme to test which isozyme was needed to support basic smooth muscle functions. Mice were generated by gene targeting. The cGKIα or the -Iβ coding sequences were placed under the control of the SM22α promoter to express either isoform selectively in smooth muscle cells (SM-Iα or SM-Iβ transgene). To generate smooth muscle–specific cGKIα or cGKIβ rescue mice, the SM-Iα or SM-Iβ transgenes were crossed on a cGKI−/−genetic background. The levels of cGKIα or -Iβ expression were comparable to endogenous cGKI expression in wild-type aortic and intestinal smooth muscles. In cGKIα or -Iβ rescue mice, expression of the isozymes was not detectable in non–smooth muscle tissues and cells. Median survival time of the Iα and Iβ rescue mice was 52 weeks. Both isozymes mediated the 8-bromo-cGMP–induced relaxation of precontracted jejunum and aorta muscle strips. Activation of both isozymes reduced hormone- or K+-induced [Ca2+]ilevels. The cGKIα and cGKIβ rescue mice did not show a significant difference in intestinal passage time of BaSO4in comparison with wild-type animals. Telemetric blood pressure measurements in conscious freely moving animals did not show differences between rescues and control mice in basal blood pressure and its regulation by DETA-NO, sodium nitroprusside, carbachol, or Y-27632. These results show that cGKI in smooth muscle is essential and that either cGKI isozyme alone can rescue basic vascular and intestinal smooth muscle functions

Role of smooth muscle cGMP/cGKI signaling in murine vascular restenosis

Background-Nitric oxide (NO) is of crucial importance for smooth muscle cell (SMC) function and exerts numerous, and sometimes opposing, effects on vascular restenosis. Although cGMP-dependent protein kinase type I (cGKI) is a principal effector of NO, the molecular pathway of vascular NO signaling in restenosis is unclear. The purpose of this study was to examine the functional role of the smooth muscle cGMP/cGKI signaling cascade in restenosis of vessels. METHODS AND RESULTS: Tissue-specific mouse mutants were generated in which the cGKI protein was ablated in SMCs. We investigated whether the absence of cGKI in SMCs would affect vascular remodeling after carotid ligation or removal of the endothelium. No differences were detected between the tissue-specific cGKI mutants and control mice at different time points after vascular injury on a normolipidemic or apoE-deficient background. In line with these results, chronic drug treatment of injured control mice with the phosphodiesterase-5 inhibitor sildenafil elevated cGMP levels but had no influence on the ligation-induced remodeling. CONCLUSIONS: The genetic and pharmacological manipulation of the cGMP/cGKI signaling indicates that this pathway is not involved in the protective effects of NO, suggesting that NO affects vascular remodeling during restenosis via alternative mechanisms