Medial vascular calcification, associated with enhanced mortality in chronic kidney disease (CKD), is fostered by osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). Here, we describe that serum- and glucocorticoid-inducible kinase 1 (SGK1) was upregulated in VSMCs under calcifying conditions. In primary human aortic VSMCs, overexpression of constitutively active SGK1^S422D, but not inactive SGK1^K127N, upregulated osteo-/chondrogenic marker expression and activity, effects pointing to increased osteo-/chondrogenic transdifferentiation. SGK1^S422D induced nuclear translocation and increased transcriptional activity of NF-κB. Silencing or pharmacological inhibition of IKK abrogated the osteoinductive effects of SGK1^S422D. Genetic deficiency, silencing, and pharmacological inhibition of SGK1 dissipated phosphate-induced calcification and osteo-/chondrogenic transdifferentiation of VSMCs. Aortic calcification, stiffness, and osteo-/chondrogenic transdifferentiation in mice following cholecalciferol overload were strongly reduced by genetic knockout or pharmacological inhibition of Sgk1 by EMD638683. Similarly, Sgk1 deficiency blunted vascular calcification in apolipoprotein E–deficient mice after subtotal nephrectomy. Treatment of human aortic smooth muscle cells with serum from uremic patients induced osteo-/chondrogenic transdifferentiation, effects ameliorated by EMD638683. These observations identified SGK1 as a key regulator of vascular calcification. SGK1 promoted vascular calcification, at least partly, via NF-κB activation. Inhibition of SGK1 may, thus, reduce the burden of vascular calcification in CKD.

Background Perivascular adipose tissue secretes an adipocyte-derived relaxing factor (ADRF) that opens voltage-dependent K⁺ (K_v) channels in peripheral arteries. We studied the role of KCNQ-type K_v channels and tested the hypothesis that hydrogen sulfide (H₂S) could be an ADRF. Methods We performed isometric contraction studies on systemic arteries of rats and mice. Results In mesenteric arteries and aortas without perivascular adipose tissue, the KCNQ channel openers retigabine, VRX0530727, VRX0621238, and VRX0621688 produced concentration-dependent vasorelaxation; VRX0621688 was the most potent vasodilator. The KCNQ inhibitor XE991 (30 μmol/l) blocked the effects of both the drugs and ADRF. Inhibitors of cystathionine gamma lyase (CSE) β-cyano-L-alanine (BCA, 5 mmol/l) and 4-propargyl glycine (PPG, 10 mmol/l) also blocked the relaxations. CSE is expressed in perivascular adipose tissue and endogenously generates H₂S. The H₂S donor NaHS produced concentration-dependent vasorelaxation, which was also blocked by XE991. The vasodilatory capacities of retigabine, VRX0530727, VRX0621238, and VRX0621688 were preserved following inhibition of H₂S generation in perivascular fat. Conclusion We suggest that KCNQ channel opening is a powerful mechanism to produce vasorelaxation of systemic arteries in rats and mice. Furthermore, KCNQ channels play a major role in the paracrine control of vascular tone by perivascular adipose tissue, which is at least in part mediated or modulated by H₂S. In conditions of reduced H₂S release from perivascular adipose tissue, these paracrine effects can be mimicked by synthetic KCNQ channel openers.

Objective— Epoxyeicosatrienoic acids (EETs) serve as endothelial-derived hyperpolarizing factors (EDHF), but may also affect vascular function by other mechanisms. We identified a novel interaction between EETs and endothelial NO release using soluble epoxide hydrolase (sEH) −/− and +/+ mice. Methods and Results— EDHF responses to acetylcholine in pressurized isolated mesenteric arteries were neither affected by the sEH inhibitor, N-adamantyl-N′-dodecylurea (ADU), nor by sEH gene deletion. However, the EDHF responses were abolished by catalase and by apamin/charybdotoxin (ChTx), but not by iberiotoxin, nor by the cytochrome P450 inhibitor PPOH. All four EETs (order of potency: 8,9-EET >14,15-EET≈5,6-EET >11,12-EET) and all 4 dihydroxy derivatives (14,15-DHET≈8,9-DHET≈11,12-DHET >5,6-DHET) produced dose-dependent vasodilation. Endothelial removal or L-NAME blocked 8,9-EET and 14,15-DHET-dependent dilations. The effects of apamin/ChTx were minimal. 8,9-EET and 14,15-DHET induced NO production in endothelial cells. ADU (100 μg/mL in drinking water) lowered blood pressure in angiotensin II–infused hypertension, but not in L-NAME–induced hypertension. Blood pressure and EDHF responses were similar in L-NAME–treated sEH +/+ and −/− mice. Conclusions— Our data indicate that the EDHF response in mice is caused by hydrogen peroxide, but not by P450 eicosanoids. Moreover, P450 eicosanoids are vasodilatory, largely through their ability to activate endothelial NO synthase (eNOS) and NO release.

Rationale: Vascular wall stretch is the major stimulus for the myogenic response of small arteries to pressure. The molecular mechanisms are elusive, but recent findings suggest that G protein–coupled receptors can elicit a stretch response.Objective: To determine whether angiotensin II type 1 receptors (AT₁R) in vascular smooth muscle cells exert mechanosensitivity and identify the downstream ion channel mediators of myogenic vasoconstriction.Methods and Results: We used mice deficient in AT₁R signaling molecules and putative ion channel targets, namely AT₁R, angiotensinogen, transient receptor potential channel 6 (TRPC6) channels, or several subtypes of the voltage-gated K⁺(K_v7) gene family (KCNQ3, 4, or 5). We identified a mechanosensing mechanism in isolated mesenteric arteries and in the renal circulation that relies on coupling of the AT₁R subtype a to a G_q/11protein as a critical event to accomplish the myogenic response. Arterial mechanoactivation occurs after pharmacological block of AT₁R and in the absence of angiotensinogen or TRPC6 channels. Activation of AT₁R subtype a by osmotically induced membrane stretch suppresses an XE991-sensitive K_vchannel current in patch-clamped vascular smooth muscle cells, and similar concentrations of XE991 enhance mesenteric and renal myogenic tone. Although XE991-sensitive KCNQ3, 4, and 5 channels are expressed in vascular smooth muscle cells, XE991-sensitive K⁺current and myogenic contractions persist in arteries deficient in these channels.Conclusions: Our results provide definitive evidence that myogenic responses of mouse mesenteric and renal arteries rely on ligand-independent, mechanoactivation of AT₁R subtype a. The AT₁R subtype a signal relies on an ion channel distinct from TRPC6 or KCNQ3, 4, or 5 to enact vascular smooth muscle cell activation and elevated vascular resistance.

Hydrogen sulfide (H₂S) is a potent vasodilator. However, the complex mechanisms of vasoregulation by H₂S are not fully understood. We tested the hypotheses that (1) H₂S exerts vasodilatory effects by opening KCNQ-type voltage-dependent (K_v) K⁺ channels and (2) that H₂S-producing cystathionine-γ-lyase (CSE) in perivascular adipose tissue plays a major role in this pathway. Wire myography of rat and mouse aortas was used. NaHS and 5-(4-hydroxyphenyl)-3H-1,2-dithiole-3-thione (ADTOH) were used as H₂S donors. KCNQ-type K_v channels were blocked by XE991. 4-Propargylglycine (PPG) and ß-cyano-l-alanine (BCA), or 2-(aminooxy)-acetic acid (AOAA) were used as inhibitors of CSE or cystathionine-ß-synthase (CBS), respectively. NaHS and ADTOH produced strong vasorelaxation in rat and mouse aortas, which were abolished by KCNQ channel inhibition with XE991. Perivascular adipose tissue (PVAT) exerted an anticontractile effect in these arteries. CSE inhibition by PPG and BCA reduced this effect in aortas from rats but not from mice. CBS inhibition with AOAA did not inhibit the anticontractile effects of PVAT. XE991, however, almost completely suppressed the anticontractile effects of PVAT in both species. Exogenous l-cysteine, substrate for the endogenous production of H₂S, induced vasorelaxation only at concentrations >5 mmol/l, an effect unchanged by CSE inhibition. Our results demonstrate potent vasorelaxant effects of H₂S donors in large arteries of both rats and mice, in which XE991-sensitive KCNQ-type channel opening play a pivotal role. CSE-H₂S seems to modulate the effect of adipocyte-derived relaxing factor in rat but not in mouse aorta. The present study provides novel insight into the interaction of CSE-H₂S and perivascular adipose tissue. Furthermore, with additional technical advances, a future clinical approach targeting vascular H₂S/KCNQ pathways to influence states of vascular dysfunction may be possible.