Anna Cantalupo

cGMP-dependent protein kinase contributes to hydrogen sulfide-stimulated vasorelaxation.

A growing body of evidence suggests that hydrogen sulfide (H2S) is a signaling molecule in mammalian cells. In the cardiovascular system, H2S enhances vasodilation and angiogenesis. H2S-induced vasodilation is hypothesized to occur through ATP-sensitive potassium channels (KATP); however, we recently demonstrated that it also increases cGMP levels in tissues. Herein, we studied the involvement of cGMP-dependent protein kinase-I in H2S-induced vasorelaxation. The effect of H2S on vessel tone was studied in phenylephrine-contracted aortic rings with or without endothelium. cGMP levels were determined in cultured cells or isolated vessel by enzyme immunoassay. Pretreatment of aortic rings with sildenafil attenuated NaHS-induced relaxation, confirming previous findings that H2S is a phosphodiesterase inhibitor. In addition, vascular tissue levels of cGMP in cystathionine gamma lyase knockouts were lower than those in wild-type control mice. Treatment of aortic rings with NaHS, a fast releasing H2S donor, enhanced phosphorylation of vasodilator-stimulated phosphoprotein in a time-dependent manner, suggesting that cGMP-dependent protein kinase (PKG) is activated after exposure to H2S. Incubation of aortic rings with a PKG-I inhibitor (DT-2) attenuated NaHS-stimulated relaxation. Interestingly, vasodilatory responses to a slowly releasing H2S donor (GYY 4137) were unaffected by DT-2, suggesting that this donor dilates mouse aorta through PKG-independent pathways. Dilatory responses to NaHS and L-cysteine (a substrate for H2S production) were reduced in vessels of PKG-I knockout mice (PKG-I−/−). Moreover, glibenclamide inhibited NaHS-induced vasorelaxation in vessels from wild-type animals, but not PKG-I−/−, suggesting that there is a cross-talk between KATP and PKG. Our results confirm the role of cGMP in the vascular responses to NaHS and demonstrate that genetic deletion of PKG-I attenuates NaHS and L-cysteine-stimulated vasodilation.

Nogo-B regulates endothelial sphingolipid homeostasis to control vascular function and blood pressure

Endothelial dysfunction is a critical factor in many cardiovascular diseases, including hypertension. Although lipid signaling has been implicated in endothelial dysfunction and cardiovascular disease, specific molecular mechanisms are poorly understood. Here we report that Nogo-B, a membrane protein of the endoplasmic reticulum, regulates endothelial sphingolipid biosynthesis with direct effects on vascular function and blood pressure. Nogo-B inhibits serine palmitoyltransferase, the rate-limiting enzyme of the de novo sphingolipid biosynthetic pathway, thereby controlling production of endothelial sphingosine 1-phosphate and autocrine, G protein–coupled receptor–dependent signaling by this metabolite. Mice lacking Nogo-B either systemically or specifically in endothelial cells are hypotensive, resistant to angiotensin II–induced hypertension and have preserved endothelial function and nitric oxide release. In mice that lack Nogo-B, pharmacological inhibition of serine palmitoyltransferase with myriocin reinstates endothelial dysfunction and angiotensin II–induced hypertension. Our study identifies Nogo-B as a key inhibitor of local sphingolipid synthesis and shows that autocrine sphingolipid signaling within the endothelium is critical for vascular function and blood pressure homeostasis.

Hypoxia-Inducible Factor-1α in Vascular Smooth Muscle Regulates Blood Pressure Homeostasis Through a Peroxisome Proliferator–Activated Receptor-γ–Angiotensin II Receptor Type 1 Axis

Hypertension is a major worldwide health issue for which only a small proportion of cases have a known mechanistic pathogenesis. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here, we reported a previously undescribed role for smooth muscle hypoxia-inducible factor-1&agr; (HIF-1&agr;) in controlling blood pressure homeostasis. The lack of HIF-1&agr; in smooth muscle caused hypertension in vivo and hyperresponsiveness of resistance vessels to angiotensin II stimulation ex vivo. These data correlated with an increased expression of angiotensin II receptor type I in the vasculature. Specifically, we show that HIF-1&agr;, through peroxisome proliferator–activated receptor-&ggr;, reciprocally defined angiotensin II receptor type I levels in the vessel wall. Indeed, pharmacological blockade of angiotensin II receptor type I by telmisartan abolished the hypertensive phenotype in smooth muscle cell-HIF-1&agr;-KO mice. These data revealed a determinant role of a smooth muscle HIF-1&agr;/peroxisome proliferator–activated receptor-&ggr;/angiotensin II receptor type I axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.Hypertension (HTN) is a major worldwide health issue for which only a small proportion of cases have a known mechanistic etiology. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here we reported a previously undescribed role for smooth muscle hypoxia inducible factor 1α (HIF-1α) in controlling blood pressure homeostasis. The lack of HIF-1α in smooth muscle caused hypertension in vivo and hyper-responsiveness of resistance vessels to angiotensin II (AngII) stimulation ex-vivo. These data correlated with an increased expression of angiotensin II receptor type I (ATR1) in the vasculature. Specifically, we show that HIF-1α, through peroxisome proliferator-activated receptor-γ (PPARγ), reciprocally defined ATR1 levels in the vessel wall. Indeed, pharmacological blockade of ATR1 by telmisartan abolished the hypertensive phenotype in SMC-HIF1α-KO mice. These data revealed a determinant role of a smooth muscle HIF1α/PPARγ/ATR1 axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.

S1PR1 (Sphingosine-1-Phosphate Receptor 1) Signaling Regulates Blood Flow and Pressure

Nitric oxide is one of the major endothelial-derived vasoactive factors that regulate blood pressure (BP), and the bioactive lipid mediator S1P (sphingosine-1-phosphate) is a potent activator of endothelial nitric oxide synthase through G protein–coupled receptors. Endothelial-derived S1P and the autocrine/paracrine activation of S1PR (S1P receptors) play an important role in preserving vascular functions and BP homeostasis. Furthermore, FTY720 (fingolimod), binding to 4 out of 5 S1PRs recently approved by the Food and Drug Administration to treat autoimmune conditions, induces a modest and transient decrease in heart rate in both animals and humans, suggesting that drugs targeting sphingolipid signaling affect cardiovascular functions in vivo. However, the role of specific S1P receptors in BP homeostasis remains unknown. The aim of this study is to determine the role of the key vascular S1P receptors, namely, S1PR1 and S1PR3, in BP regulation in physiological and hypertensive conditions. The specific loss of endothelial S1PR1 decreases basal and stimulated endothelial-derived nitric oxide and resets BP to a higher-than-normal value. Interestingly, we identified a novel and important role for S1PR1 signaling in flow-mediated mechanotransduction. FTY720, acting as functional antagonist of S1PR1, markedly decreases endothelial S1PR1, increases BP in control mice, and exacerbates hypertension in angiotensin II mouse model, underlining the antihypertensive functions of S1PR1 signaling. Our study identifies S1P–S1PR1–nitric oxide signaling as a new regulatory pathway in vivo of vascular relaxation to flow and BP homeostasis, providing a novel therapeutic target for the treatment of hypertension.Nitric oxide is one of the major endothelial-derived vasoactive factors that regulate blood pressure and the bioactive lipid mediator S1P is a potent activator of endothelial nitric oxide synthase through G-protein coupled receptors. Endothelial-derived S1P and the autocrine/paracrine activation of S1P receptors play an important role in preserving vascular functions and blood pressure homeostasis. Furthermore, FTY720, binding to four out of five S1PRs recently approved by the FDA to treat autoimmune conditions, induces a modest and transient decrease in heart rate in both animals and humans, suggesting that drugs targeting sphingolipid signaling affect cardiovascular functions in vivo. However, the role of specific S1P receptors in BP homeostasis remains unknown. The aim of this study is to determine the role of the key vascular S1P receptors, namely, S1PR1 and S1PR3 in BP regulation in physiological and hypertensive conditions. The specific loss of endothelial S1PR1 decreases basal and stimulated endothelial-derived NO, and re-sets blood pressure to a higher-than-normal value. Interestingly, we identified a novel and important role for S1PR1 signaling in flow-mediated mechanotransduction. FTY720 (fingolimod), acting as functional antagonist of S1PR1, markedly decreases endothelial S1PR1, increases blood pressure in control mice and exacerbates hypertension in Ang-II mouse model, underlining the anti-hypertensive functions of S1PR1 signaling. Our study identifies S1P-S1PR1-NO signaling as a new regulatory pathway in vivo of vascular relaxation to flow and blood pressure homeostasis, providing a novel therapeutic target for the treatment of hypertension.

An engineered S1P chaperone attenuates hypertension and ischemic injury.

Cardiovascular diseases could be treated by chaperones that deliver the lipid mediator S1P that promotes endothelial function. Targeting S1P1 on endothelial cells The lipid mediator sphingosine 1-phosphate (S1P) is ferried in the blood by different chaperone proteins, the identity of which determines the specific signaling pathway triggered by S1P binding to its receptor S1P1. When bound to the lipoprotein ApoM+HDL, S1P suppresses endothelial cell inflammation and atherosclerosis. However, globally increasing HDL abundance does not confer these benefits, and ApoM is unstable when not bound to HDL. Swendeman et al. generated a stable form of ApoM (ApoM-Fc) that bound to S1P and activated S1P1 receptors in a sustained manner in endothelial cells. ApoM-Fc–S1P treatment of mice reduced hypertension induced by angiotensin II and improved outcomes after experimentally induced myocardial infarction or stroke, without inducing the lymphopenia characteristic of S1P1 agonists. These results provide proof-of-concept evidence that developing a chaperone that targets S1P to S1P1 selectively on endothelial cells could be used to treat cardiovascular diseases. Endothelial dysfunction, a hallmark of vascular disease, is restored by plasma high-density lipoprotein (HDL). However, a generalized increase in HDL abundance is not beneficial, suggesting that specific HDL species mediate protective effects. Apolipoprotein M–containing HDL (ApoM+HDL), which carries the bioactive lipid sphingosine 1-phosphate (S1P), promotes endothelial function by activating G protein–coupled S1P receptors. Moreover, HDL-bound S1P is limiting in several inflammatory, metabolic, and vascular diseases. We report the development of a soluble carrier for S1P, ApoM-Fc, which activated S1P receptors in a sustained manner and promoted endothelial function. In contrast, ApoM-Fc did not modulate circulating lymphocyte numbers, suggesting that it specifically activated endothelial S1P receptors. ApoM-Fc administration reduced blood pressure in hypertensive mice, attenuated myocardial damage after ischemia/reperfusion injury, and reduced brain infarct volume in the middle cerebral artery occlusion model of stroke. Our proof-of-concept study suggests that selective and sustained targeting of endothelial S1P receptors by ApoM-Fc could be a viable therapeutic strategy in vascular diseases.

Perthamide C inhibits eNOS and iNOS expression and has immunomodulating activity in vivo.

Here we have characterized perthamide C, a cyclopeptide from a Solomon Lithistid sponge Theonella swinhoei, which displays an anti-inflammatory/immunomodulatory activity. The study has been performed using the carragenan-induced mouse paw edema that displays an early (0–6 h) and a late phase (24–96 h). Perthamide C significantly inhibits neutrophils infiltration in tissue both in the early and late phases. This effect was coupled to a reduced expression of the endothelial nitric oxide synthase (eNOS) in the early phase while cyclooxygenase-1 and 2 (COX-1, COX-2), and inducible NOS (iNOS) expression were unaffected. In the late phase perthamide C reduced expression of both NOS isoforms without affecting COXs expression. This peculiar selectivity toward the two enzymes deputed to produce NO lead us to investigate on a possible action of perthamide C on lymphocytes infiltration and activation. We found that perthamide C inhibited the proliferation of peripheral lymphocytes, and that this effect was secondary to its metabolic activation in vivo. Indeed, in vitro perthamide C did not inhibit proliferation as opposite to its metabolite perthamide H. In conclusion, perthamide C selectively interferes with NO generation triggered by either eNOS or iNOS without affecting either COX-1 or COX-2. This in turn leads to modulation of the inflammatory response through a reduction of vascular permeability, neutrophil infiltration as well as lymphocyte proliferation.

S1P Signaling and De Novo Biosynthesis in Blood Pressure Homeostasis.

Initially discovered as abundant components of eukaryotic cell membranes, sphingolipids are now recognized as important bioactive signaling molecules that modulate a variety of cellular functions, including those relevant to cancer and immunologic, inflammatory, and cardiovascular disorders. In this review, we discuss recent advances in our understanding of the role of sphingosine-1-phosphate (S1P) receptors in the regulation of vascular function, and focus on how de novo biosynthesized sphingolipids play a role in blood pressure homeostasis. The therapeutic potential of new drugs that target S1P signaling is also discussed.

HIF-1α in vascular smooth muscle regulates blood pressure homeostasis through a PPARγ-angiotensin II receptor type 1 (ATR1) axis

Hypertension is a major worldwide health issue for which only a small proportion of cases have a known mechanistic pathogenesis. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here, we reported a previously undescribed role for smooth muscle hypoxia-inducible factor-1&agr; (HIF-1&agr;) in controlling blood pressure homeostasis. The lack of HIF-1&agr; in smooth muscle caused hypertension in vivo and hyperresponsiveness of resistance vessels to angiotensin II stimulation ex vivo. These data correlated with an increased expression of angiotensin II receptor type I in the vasculature. Specifically, we show that HIF-1&agr;, through peroxisome proliferator–activated receptor-&ggr;, reciprocally defined angiotensin II receptor type I levels in the vessel wall. Indeed, pharmacological blockade of angiotensin II receptor type I by telmisartan abolished the hypertensive phenotype in smooth muscle cell-HIF-1&agr;-KO mice. These data revealed a determinant role of a smooth muscle HIF-1&agr;/peroxisome proliferator–activated receptor-&ggr;/angiotensin II receptor type I axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.Hypertension (HTN) is a major worldwide health issue for which only a small proportion of cases have a known mechanistic etiology. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here we reported a previously undescribed role for smooth muscle hypoxia inducible factor 1α (HIF-1α) in controlling blood pressure homeostasis. The lack of HIF-1α in smooth muscle caused hypertension in vivo and hyper-responsiveness of resistance vessels to angiotensin II (AngII) stimulation ex-vivo. These data correlated with an increased expression of angiotensin II receptor type I (ATR1) in the vasculature. Specifically, we show that HIF-1α, through peroxisome proliferator-activated receptor-γ (PPARγ), reciprocally defined ATR1 levels in the vessel wall. Indeed, pharmacological blockade of ATR1 by telmisartan abolished the hypertensive phenotype in SMC-HIF1α-KO mice. These data revealed a determinant role of a smooth muscle HIF1α/PPARγ/ATR1 axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.

Hypoxia-Inducible Factor-1α in Vascular Smooth Muscle Regulates Blood Pressure Homeostasis Through a Peroxisome Proliferator–Activated Receptor-γ–Angiotensin II Receptor Type 1 AxisNovelty and Significance

Hypertension is a major worldwide health issue for which only a small proportion of cases have a known mechanistic pathogenesis. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here, we reported a previously undescribed role for smooth muscle hypoxia-inducible factor-1&agr; (HIF-1&agr;) in controlling blood pressure homeostasis. The lack of HIF-1&agr; in smooth muscle caused hypertension in vivo and hyperresponsiveness of resistance vessels to angiotensin II stimulation ex vivo. These data correlated with an increased expression of angiotensin II receptor type I in the vasculature. Specifically, we show that HIF-1&agr;, through peroxisome proliferator–activated receptor-&ggr;, reciprocally defined angiotensin II receptor type I levels in the vessel wall. Indeed, pharmacological blockade of angiotensin II receptor type I by telmisartan abolished the hypertensive phenotype in smooth muscle cell-HIF-1&agr;-KO mice. These data revealed a determinant role of a smooth muscle HIF-1&agr;/peroxisome proliferator–activated receptor-&ggr;/angiotensin II receptor type I axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.Hypertension (HTN) is a major worldwide health issue for which only a small proportion of cases have a known mechanistic etiology. Of the defined causes, none have been directly linked to heightened vasoconstrictor responsiveness, despite the fact that vasomotor tone in resistance vessels is a fundamental determinant of blood pressure. Here we reported a previously undescribed role for smooth muscle hypoxia inducible factor 1α (HIF-1α) in controlling blood pressure homeostasis. The lack of HIF-1α in smooth muscle caused hypertension in vivo and hyper-responsiveness of resistance vessels to angiotensin II (AngII) stimulation ex-vivo. These data correlated with an increased expression of angiotensin II receptor type I (ATR1) in the vasculature. Specifically, we show that HIF-1α, through peroxisome proliferator-activated receptor-γ (PPARγ), reciprocally defined ATR1 levels in the vessel wall. Indeed, pharmacological blockade of ATR1 by telmisartan abolished the hypertensive phenotype in SMC-HIF1α-KO mice. These data revealed a determinant role of a smooth muscle HIF1α/PPARγ/ATR1 axis in controlling vasomotor responsiveness and highlighted an important pathway, the alterations of which may be critical in a variety of hypertensive-based clinical settings.