Src is an important mediator of extracellular signal-regulated kinase 1/2-dependent growth signaling by angiotensin II in smooth muscle cells from resistance arteries of hypertensive patients

3-phosphoinositide-dependent protein kinase 1 (PDK1) mediates crosstalk between Src and Akt pathways in MET receptor signaling

The high-affinity tyrosine kinase receptor MET plays a pivotal role in several facets of cell regulation. Although its mitogenic effect is well documented, some aspects of connection patterns between signaling pathways involved in cell cycle progression remain to be deciphered. We have used a tractable heterologous expression system, the Xenopus oocyte, to detect connections between distinct MET signaling cascades involved in G2/M progression. Our results reveal that Src acts as an adapter via its SH2 domain to recruit 3-phosphoinositide-dependent protein kinase 1 (PDK1) to the MET signaling complex leading to Akt phosphorylation. These data define an original crosstalk between Src and Akt signaling pathways that contributes to MET-induced entry into the M phase, and deserves further investigation in pathologies harboring deregulation of this receptor.

Inhibition of Maternal c-Src Ameliorates the Male Offspring Hypertension by Suppressing Inflammation and Neurotransmitters in the Paraventricular Nucleus

Long-term maternal salt intake induces the hypertension in offspring. Numerous studies have also indicated that high-salt diet causes the inflammation and an imbalance in neurotransmitters in the paraventricular nucleus (PVN) which increases the blood pressure and sympathetic activity. This study aimed to explore whether maternal salt intake induces hypertension in their male offspring by increasing the inflammation and changing the neurotransmitters balance in the paraventricular nucleus of offspring. This study includes two parts: Part I to explore the effect of high-salt diet on pregnant rats and the changes in inflammation and neurotransmitters in their male offspring PVN; Part II to reveal the influence on their offspring of bilateral PVN infusion of c-Src inhibitor dasatinib (DAS) in pregnant rats fed a high-salt diet. Maternal high-salt diet intake during copulation, pregnancy, and lactation impacted the offspring mean arterial pressure (MAP) and elevated the offspring PVN levels of p-Src, proinflammatory cytokines, and excitatory neurotransmitters. Bilateral PVN infusion of a c-Src inhibitor combined with maternal high-salt diets decreased MAP in the offspring. The infusion was also shown to suppress the Src-induced MAPK/NF-κB signaling pathway (p38 MAPK, JNK, Erk1/2), which attenuates inflammatory reactions. Finally, bilateral PVN infusion of the Src inhibitor in pregnant rat with high-salt diets improved the levels of inhibitory neurotransmitters in offspring PVN, which restored the excitatory-inhibitory neurotransmitter balance in male offspring. High-salt diets increase sympathetic activity and blood pressure in adult offspring, probably by activating the c-Src/MAPKs/NF-κB signaling pathway-induced inflammation. Moreover, NF-κB disrupts the downstream excitatory-inhibitory neurotransmitter balance in the PVN of male offspring.

Blockade of c-Src Within the Paraventricular Nucleus Attenuates Inflammatory Cytokines and Oxidative Stress in the Mechanism of the TLR4 Signal Pathway in Salt-Induced Hypertension

Toll-like receptor 4 (TLR4) and cellular Src (c-Src) are closely associated with inflammatory cytokines and oxidative stress in hypertension, so we designed this study to explore the exact role of c-Src in the mechanism of action of the TLR4 signaling pathway in salt-induced hypertension. Salt-sensitive rats were given a high salt diet for 10 weeks to induce hypertension. This resulted in higher levels of TLR4, activated c-Src, pro-inflammatory cytokines, oxidative stress, and arterial pressure. Infusion of a TLR4 blocker into the hypothalamic paraventricular nucleus (PVN) decreased the activated c-Src, while microinjection of a c-Src inhibitor attenuated the PVN levels of nuclear factor-kappa B, pro-inflammatory cytokines, and oxidative stress. Our findings suggest that a long-term high-salt diet increases TLR4 expression in the PVN and this promotes the activation of c-Src, which upregulates the expression of pro-inflammatory cytokines and results in the overproduction of reactive oxygen species. Therefore, inhibiting central c-Src activity may be a new target for treating hypertension.

G-Protein-Coupled Receptors in Heart Disease

GPCRs (G-protein [guanine nucleotide-binding protein]-coupled receptors) play a central physiological role in the regulation of cardiac function in both health and disease and thus represent one of the largest class of surface receptors targeted by drugs. Several antagonists of GPCRs, such as βARs (β-adrenergic receptors) and Ang II (angiotensin II) receptors, are now considered standard of therapy for a wide range of cardiovascular disease, such as hypertension, coronary artery disease, and heart failure. Although the mechanism of action for GPCRs was thought to be largely worked out in the 80s and 90s, recent discoveries have brought to the fore new and previously unappreciated mechanisms for GPCR activation and subsequent downstream signaling. In this review, we focus on GPCRs most relevant to the cardiovascular system and discuss traditional components of GPCR signaling and highlight evolving concepts in the field, such as ligand bias, β-arrestin-mediated signaling, and conformational heterogeneity.

Gene-gene interactions and associations of six hypertension related single nucleotide polymorphisms with obesity risk in a Chinese children population

Obesity is a major risk for hypertension. However, the associations between hypertension susceptibility loci and the risk of obesity as well as the effects of gene-gene interactions are unclear, especially in the Chinese children population. Six single nucleotide polymorphisms (SNPs) (ATP2B1 rs17249754, CSK rs1378942, MTHFR rs1801133, CYP17A1 rs1004467, STK39 rs3754777, FGF5 rs16998073) were genotyped for 3503 Chinese children, aged 6-18 years. Of them, 758 obese cases and 2745 controls were identified based on the International Obesity Task Force age- and sex-specific BMI references. Among the six SNPs, three were associated with obesity risk (CSK rs1378942: odds ratio (OR) = 1.20, 95% confidence interval (CI) 1.01-1.43, P = 0.042; MTHFR rs1801133: OR = 1.19, 95% CI 1.05-1.34, P = 0.006; FGF5 rs16998073: OR = 1.14, 95% CI 1.00-1.29, P = 0.047). The genetic risk score (GRS), based on these three SNPs (CSK rs1378942, MTHFR rs1801133, FGF5 rs16998073), showed a positive association with risk of obesity (OR = 1.18, 95% CI 1.09-1.28, P = 7.60 × 10-5). The same association signals were also detected in the subgroups of puberty and inactivity. In addition, interaction analyses among these loci implied a potential gene-gene interaction between MTHFR and FGF5. These findings show a significant association of hypertension susceptibility loci in Chinese children, suggesting a likely influence of genetic and environmental factors on the risk of obesity.

α-Isocubebene modulates vascular tone by inhibiting myosin light chain phosphorylation in murine thoracic aorta

α-Iso-cubebene (ICB) is a dibenzocyclooctadiene lignin contained in Schisandra chinensis (SC), a well-known medicinal herb that ameliorates cardiovascular symptoms, but the mechanism responsible for this activity has not been determined. To determine the role played by ICB on the regulation of vascular tone, we investigated the inhibitory effects of ICB on vascular contractile responses by adrenergic α-receptor agonists. In addition, we investigated the role on myosin light chain (MLC) phosphorylation and cytosolic calcium concentration in vascular smooth muscle cells (VSMC). In aortic rings isolated from C57BL/6J mice, ICB significantly attenuated the contraction induced by phenylephrine (PE) and norepinephrine (NE), whereas ICB had no effects on KCl (60 mM)-induced contraction. In vasculatures precontracted with PE, ICB caused marked relaxation of aortic rings with or without endothelium, suggesting a direct effect on VSMC. In cultured rat VSMC, PE or NE increased MLC phosphorylation and increased cytosolic calcium levels. Both of these effects were significantly suppressed by ICB. In conclusion, our results showed that ICB regulated vascular tone by inhibiting MLC phosphorylation and calcium flux into VSMC, and suggest that ICB has anti-hypertensive properties and therapeutic potential for cardiovascular disorders related to vascular hypertension.

The PPI network analysis of mRNA expression profile of uterus from primary dysmenorrheal rats

To elucidate the mechanisms of molecular regulations underlying primary dysmenorrhea (PD), we used our previously published mRNA expression profile of uterus from PD syndrome rats to construct protein-protein interactions (PPI) network via STRING Interactome. Consequently, 34 subnetworks, including a "continent" (Subnetwork 1) and 33 "islands" (Subnetwork 2-34) were generated. The nodes, with relative expression ratios, were visualized in the PPI networks and their connections were identified. Through path and module exploring in the network, the bridges were found from pathways of cellular response to calcium ion, SMAD protein signal transduction, regulation of transcription from RNA polymerase II promoter in response to stress and muscle stretch that were significantly enriched by the up-regulated mRNAs, to the cascades of cAMP metabolic processes and positive regulation of cyclase activities by the down-regulated ones. This link is mainly dependent on Fos/Jun - Vip connection. Our data, for the first time, report the PPI network analysis of differentially expressed mRNAs in the uterus of PD syndrome rats, to give insight into screening drugs and find new therapeutic strategies to relieve PD.

Interaction between Single Nucleotide Polymorphism and Urinary Sodium, Potassium, and Sodium-Potassium Ratio on the Risk of Hypertension in Korean Adults

Hypertension is a complex disease explained with diverse factors including environmental factors and genetic factors. The objectives of this study were to determine the interaction effects between gene variants and 24 h estimated urinary sodium and potassium excretion and sodium-potassium excretion ratios on the risk of hypertension. A total of 8839 participants were included in the genome-wide association study (GWAS) to find genetic factors associated with hypertension. Tanaka and Kawasaki formulas were applied to estimate 24 h urinary sodium and potassium excretion. A total of 4414 participants were included in interaction analyses to identify the interaction effects of gene variants according to 24 h estimated urinary factors on the risk of hypertension. CSK rs1378942 and CSK-MIR4513 rs3784789 were significantly modified by urinary sodium-potassium excretion ratio. In addition, MKLN rs1643270 with urinary potassium excretion, LOC101929750 rs7554672 with urinary sodium and potassium excretion, and TENM4 rs10466739 with urinary sodium-potassium excretion ratio showed significant interaction effects. The present study results indicated that the mutant alleles of CSK rs1378942 and CSK-MIR4513 rs3784789 had the strongest protective effects against hypertension in the middle group of 24 h estimated urinary sodium-potassium excretion ratio. Further studies are needed to replicate these analyses in other populations.

c-Src, ERK1/2 and Rho kinase mediate hydrogen peroxide-induced vascular contraction in hypertension: role of TXA2, NAD(P)H oxidase and mitochondria

AIM

: The aim of this study was to analyse the signalling pathways involved in H2O2 vascular responses in hypertension.

METHODS

Vascular function, thromboxane A2 (TXA2) production, oxidative stress and protein expression were determined in mesenteric resistance arteries (MRAs) from hypertensive (spontaneously hypertensive rats, SHR) and normotensive Wistar Kyoto (WKY) rats.

RESULTS

H2O2 and the TP agonist U46619 induced greater contractile responses in MRA from SHR than WKY. Moreover, H2O2 increased TXA2 production more in SHR than in WKY. The c-Src inhibitor PP1 reduced H2O2 and U46619-induced contraction and TXA2 release in both strains. The ERK1/2 inhibitor PD98059 reduced H2O2 but not U46619-induced contraction only in SHR arteries. The Rho kinase inhibitor Y26372 reduced H2O2 and U46619-induced contractions only in SHR arteries. Basal c-Src, ERK1/2 and Rho kinase expression were greater in MRA from SHR than WKY. In SHR, the combination of PD98059 with the TP antagonist SQ29548 but not with Y27632 inhibited the H2O2 contraction more than each inhibitor alone. H2O2 and U46619 increased NAD(P)H oxidase activity and O2 production and decreased mitochondrial membrane potential in vessels from SHR. The effects induced by H2O2 were abolished by inhibitors of TXA2 synthase, ERK1/2 and c-Src. The mitochondrial antioxidant mitoTEMPO reduced H2O2-induced contraction and NAD(P)H oxidase activation.

CONCLUSION

In arteries from WKY, c-Src mediates H2O2 contractile responses by modulating TXA2 release and TXA2 effect. In SHR, H2O2 induces c-Src dependent TXA2 release that provokes vascular contractile responses through Rho kinase, c-Src and O2 from NAD(P)H Oxidase and mitochondria. Moreover, ERK1/2 activation contributes to H2O2 contraction in SHR through effects on mitochondria/NAD(P)H Oxidase.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]

The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.

Vasodilatory effect of a novel Rho-kinase inhibitor, DL0805-2, on the rat mesenteric artery and its potential mechanisms

PURPOSE

In the present study, we investigated the vasodilatory effect of a novel scaffold Rho-kinase inhibitor, DL0805-2, on isolated rat arterial rings including mesenteric, ventral tail, and renal arteries. We also examined the potential mechanisms of its vasodilatory action using mesenteric artery rings.

METHODS

A DMT multiwire myograph system was used to test the tension of isolated small arteries. Several drugs were employed to verify the underlying mechanisms.

RESULTS

DL0805-2 (10(-7)-10(-4) M) inhibited KCl (60 mM)-induced vasoconstriction in three types of small artery rings (pEC50: 5.84 ± 0.03, 5.39 ± 0.03, and 5.67 ± 0.02 for mesenteric, renal, and ventral tail artery rings, respectively). Pre-incubation with DL0805-2 (1, 3, or 10 μM) attenuated KCl (10-60 mM) and angiotensin II (AngII; 10(-6) M)-induced vasoconstriction in mesenteric artery rings. The relaxant effect on the rat mesenteric artery was partially endothelium-dependent (pEC50: 6.02 ± 0.05 for endothelium-intact and 5.72 ± 0.06 for endothelium-denuded). The influx and release of Ca(2+) were inhibited by DL0805-2. In addition, the increased phosphorylation levels of myosin light chain (MLC) and myosin-binding subunit of myosin phosphatase (MYPT1) induced by AngII were blocked by DL0805-2. However, DL0805-2 had little effect on K(+) channels.

CONCLUSIONS

The present results demonstrate that DL0805-2 has a vasorelaxant effect on isolated rat small arteries and may exert its action through the endothelium, Ca(2+) channels, and the Rho/ROCK pathway.

Circulating mitochondrial DNA and Toll-like receptor 9 are associated with vascular dysfunction in spontaneously hypertensive rats

AIMS

Immune system activation is a common feature of hypertension pathogenesis. However, the mechanisms that initiate this activation are not well understood. Innate immune system recognition and response to danger are becoming apparent in many cardiovascular diseases. Danger signals can arise from not only pathogens, but also damage-associated molecular patterns (DAMPs). Our first hypothesis was that the DAMP, mitochondrial DNA (mtDNA), which is recognized by Toll-like receptor 9 (TLR9), is elevated in the circulation of spontaneously hypertensive rats (SHR), and that the deoxyribonuclease enzymes responsible for its degradation have decreased activity in SHR. Based on these novel SHR phenotypes, we further hypothesized that (i) treatment of SHR with an inhibitory oligodinucleotide for TLR9 (ODN2088) would lower blood pressure and that (ii) treatment of normotensive rats with a TLR9-specific CpG oligonucleotide (ODN2395) would cause endothelial dysfunction and increase blood pressure.

METHODS AND RESULTS

We observed that SHR have elevated circulating mtDNA and diminished deoxyribonuclease I and II activity. Additionally, treatment of SHR with ODN2088 lowered systolic blood pressure. On the other hand, treatment of normotensive rats with ODN2395 increased systolic blood pressure and rendered their arteries less sensitive to acetylcholine-induced relaxation and more sensitive to norepinephrine-induced contraction. This dysfunctional vasoreactivity was due to increased cyclooxygenase and p38 mitogen-activated protein kinase activation, increased reactive oxygen species generation, and reduced nitric oxide bioavailability.

CONCLUSION

Circulating mtDNA and impaired deoxyribonuclease activity may lead to the activation of the innate immune system, via TLR9, and contribute to elevated arterial pressure and vascular dysfunction in SHR.

Angiotensin II and vascular injury

Vascular injury, characterized by endothelial dysfunction, structural remodelling, inflammation and fibrosis, plays an important role in cardiovascular diseases. Cellular processes underlying this include altered vascular smooth muscle cell (VSMC) growth/apoptosis, fibrosis, increased contractility and vascular calcification. Associated with these events is VSMC differentiation and phenotypic switching from a contractile to a proliferative/secretory phenotype. Inflammation, associated with macrophage infiltration and increased expression of redox-sensitive pro-inflammatory genes, also contributes to vascular remodelling. Among the many factors involved in vascular injury is Ang II. Ang II, previously thought to be the sole biologically active downstream peptide of the renin-angiotensin system (RAS), is converted to smaller peptides, [Ang III, Ang IV, Ang-(1-7)], that are functional and that modulate vascular tone and structure. The actions of Ang II are mediated via signalling pathways activated upon binding to AT1R and AT2R. AT1R activation induces effects through PLC-IP3-DAG, MAP kinases, tyrosine kinases, tyrosine phosphatases and RhoA/Rho kinase. Ang II elicits many of its (patho)physiological actions by stimulating reactive oxygen species (ROS) generation through activation of vascular NAD(P)H oxidase (Nox). ROS in turn influence redox-sensitive signalling molecules. Here we discuss the role of Ang II in vascular injury, focusing on molecular mechanisms and cellular processes. Implications in vascular remodelling, inflammation, calcification and atherosclerosis are highlighted.

Upregulation of ERK1/2-eNOS via AT2 receptors decreases the contractile response to angiotensin II in resistance mesenteric arteries from obese rats

It has been clearly established that mitogen-activated protein kinases (MAPKS) are important mediators of angiotensin II (Ang II) signaling via AT1 receptors in the vasculature. However, evidence for a role of these kinases in changes of Ang II-induced vasoconstriction in obesity is still lacking. Here we sought to determine whether vascular MAPKs are differentially activated by Ang II in obese animals. The role of AT2 receptors was also evaluated. Male monosodium glutamate-induced obese (obese) and non-obese Wistar rats (control) were used. The circulating concentrations of Ang I and Ang II, determined by HPLC, were increased in obese rats. Ang II-induced isometric contraction was decreased in endothelium-intact resistance mesenteric arteries from obese compared with control rats and exhibited a retarded AT1 receptor antagonist response. Blocking of AT2 receptors and inhibition of either endothelial nitric oxide synthase (eNOS) or extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) restored Ang II-induced contraction in obese rats. Western blot analysis revealed increased protein expression of AT2 receptors in arteries from obese rats. Basal and Ang II-induced ERK1/2 phosphorylation was also increased in obese rats. Blockade of either AT1 or AT2 receptors corrected the increased ERK1/2 phosphorylation in arteries from obese rats to levels observed in control preparations. Phosphorylation of eNOS was increased in obese rats. Incubation with the ERK1/2 inhibitor before Ang II stimulation did not affect eNOS phosphorylation in control rats; however, it corrected the increased phosphorylation of eNOS in obese rats. These results clearly demonstrate that enhanced AT2 receptor and ERK1/2-induced, NO-mediated vasodilation reduces Ang II-induced contraction in an endothelium-dependent manner in obese rats.

Serum starvation regulates E-cadherin upregulation via activation of c-Src in non-small-cell lung cancer A549 cells

E-cadherin is essential for the integrity of adherens junctions between lung epithelial cells, and the loss of E-cadherin allows cell motility and is thought to promote lung cancer metastasis. While the downregulation of E-cadherin expression has been well characterized and is seen with transforming growth factor-β1 (TGF-β1) exposure, few studies have focused on E-cadherin upregulation. Here, we show that serum starvation causes increased E-cadherin expression via the activation of c-Src kinase in non-small-cell lung cancer A549 cells. Serum starvation increased E-cadherin protein levels in a time- and dose-dependent manner. E-cadherin mRNA transcripts were unchanged with starvation, while protein translation inhibition with cycloheximide attenuated E-cadherin protein induction by starvation, suggesting that E-cadherin is regulated at the translational level by serum starvation. c-Src is a nonreceptor tyrosine kinase known to regulate protein translation machinery; serum starvation caused early and sustained activation of c-Src in A549 cells followed by E-cadherin upregulation. Furthermore, overexpression of a dominant negative c-Src attenuated the induction of E-cadherin by serum deprivation. Finally, we observed that TGF-β1 treatment attenuated the serum activation of c-Src as well as E-cadherin expression when cells were deprived of serum. In conclusion, our data demonstrate that the c-Src kinase is activated by serum starvation to increase E-cadherin expression in A549 cells, and these phenomena are antagonized by TGF-β1. These novel observations implicate the c-Src kinase as an upstream inducer of E-cadherin protein translation with serum starvation and TGF-β1 diametrically regulating c-Src kinase activity and thus E-cadherin abundance in A549 cells.

Interaction between a CSK gene variant and fish oil intake influences blood pressure in healthy adults

Blood pressure is a heritable determinant of cardiovascular disease (CVD) risk. Recent genome-wide association studies have identified several single-nucleotide polymorphisms (SNPs) associated with blood pressure, including rs1378942 in the c-Src tyrosine kinase (CSK) gene. Fish oil supplementation provides inconsistent protection from CVD, which may reflect genetic variation. We investigated the effect of rs1378942 genotype interaction with fish oil dosage on blood pressure measurements in the MARINA (Modulation of Atherosclerosis Risk by Increasing doses of N-3 fatty Acids) study, a parallel, double-blind, controlled trial in 367 participants randomly assigned to receive treatment with 0.45, 0.9, and 1.8 g/d eicosapentaenoic acid [EPA (20:5n-3)] and docosahexaenoic acid [DHA (22:6n-3)] (1.51:1) or an olive oil placebo for 12 mo. A total of 310 participants were genotyped. There were no significant associations with blood pressure measures at baseline; however, the interaction between genotype and treatment was a significant determinant of systolic blood pressure (SBP) (P = 0.010), diastolic blood pressure (DBP) (P = 0.037), and mean arterial blood pressure (MABP) (P = 0.014). After the 1.8 g/d dose, noncarriers of the rs1378942 variant allele showed significantly lower SBP (P = 0.010), DBP (P = 0.016), and MABP (P = 0.032) at follow-up, adjusted for baseline values, than did carriers. We found no evidence of SNP genotype association with endothelial function (brachial artery diameter and flow-mediated dilatation), arterial stiffness (carotid-femoral pulse wave velocity and digital volume pulse), and resting heart rate. A high intake of EPA and DHA could help protect noncarriers but not carriers of the risk allele. Dietary recommendations to reduce blood pressure in the general population may not necessarily benefit those most at risk. This trial was registered at controlled-trials.com as ISRCTN66664610.

Toll-like receptors and damage-associated molecular patterns: novel links between inflammation and hypertension

Low-grade systemic inflammation is a common manifestation of hypertension; however, the exact mechanisms that initiate this pathophysiological response, thereby contributing to further increases in blood pressure, are not well understood. Aberrant vascular inflammation and reactivity via activation of the innate immune system may be the first step in the pathogenesis of hypertension. One of the functions of the innate immune system is to recognize and respond to danger. Danger signals can arise from not only pathogenic stimuli but also endogenous molecules released following cell injury and/or death [damage-associated molecular patterns (DAMPs)]. In the short-term, activation of the innate immune system is beneficial in the vasculature by providing cytoprotective mechanisms and facilitating tissue repair following injury or infection. However, sustained or excessive immune system activation, such as in autoimmune diseases, may be deleterious and can lead to maladaptive, irreversible changes to vascular structure and function. An initial source of DAMPs that enter the circulation to activate the innate immune system could arise from modest elevations in peripheral vascular resistance. These stimuli could subsequently lead to ischemic- or pressure-induced events aggravating further cell injury and/or death, providing more DAMPs for innate immune system activation. This review will address and critically evaluate the current literature on the role of the innate immune system in hypertension pathogenesis. The role of Toll-like receptor activation on somatic cells of the vasculature in response to the release of DAMPs and the consequences of this activation on inflammation, vasoreactivity, and vascular remodeling will be specifically discussed.

Influence of obesity on association between genetic variants identified by genome-wide association studies and hypertension risk in Chinese children

BACKGROUND

Childhood hypertension is a complex disease influenced by both genetic and environmental factors. We aimed to examine how obesity status influences the association of 6 single nucleotide polymorphisms (SNPs) identified by genome-wide association studies (GWASs) with systolic/diastolic blood pressure (SBP/DBP) and hypertension in Chinese children.

METHODS

We recruited 619 hypertensive case subjects and 2,458 individuals with normal blood pressure from the Beijing Child and Adolescent Metabolic Syndrome study, a population-based case-control study. We selected 6 SNPs from earlier GWASs of hypertension and genotyped them using TaqMan assay.

RESULTS

In the normal weight group, we did not observe any significant association of 6 SNPs and the genetic risk score (GRS) with SBP/DBP and hypertension (all P > 0.05). Only STK39 rs3754777 was significantly associated with higher DBP (P = 0.02) in the overweight subjects. In the obese group, 3 SNPs and the GRS were significantly associated with higher SBP (ATP2B1 rs17249754: P = 0.02; CSK rs1378942: P = 0.003; CYP17A1 rs1004467: P = 0.04; GRS: P = 0.0002). We also observed a significant association of 4 SNPs and the GRS with hypertension (ATP2B1 rs17249754: P = 0.02; CSK rs1378942: P = 0.02; CYP17A1 rs1004467: P = 0.02; MTHFR rs1801133: P = 0.03; GRS: P = 0.0004). Correction for multiple testing had no influence on the statistical significance of the association of GRS with SBP/hypertension.

CONCLUSIONS

This study shows a significant association of hypertension susceptibility loci only in obese Chinese children, suggesting a likely influence of childhood obesity on the risk of hypertension.

Cross-talk between angiotensin II and IGF-1-induced connexin 43 expression in human saphenous vein smooth muscle cells

Vascular restenosis following coronary artery bypass graft can cause major clinical complications due to intimal hyperplasia in venous conduits. However, the precise underlying mechanisms of intimal hyperplasia are still unclear. We have recently reported that increased expression of connexin43 (Cx43) is involved in the proliferation of vascular smooth muscle cells (SMCs) in human saphenous vein (SV). In this study, we investigated the signalling transduction pathway involved in Cx43 expression and SV SMC proliferation. Angiotensin-II (AT-II, 100 ng/ml) increased AT-II receptor 1 (AT-1R) protein expression and insulin-like growth factor-1 (IGF-1) (100 ng/ml) up-regulated IGF-1 receptor (IGF-1R) protein expression in SV SMCs. Interestingly, AT-1R expression was also increased by IGF-1 treatment, and IGF-1R expression was increased by AT-II treatment, which was blocked by siRNA-IGF-1R and siRNA-AT-1R, respectively. Furthermore, the effect of AT-II and IGF-1 signal cross-talk i nducing up-regulation of their reciprocal receptors was blocked by siRNA against extracellular signal-regulated kinases 1/2 (Erk 1/2) in SMCs of SV. Moreover, AT-II and IGF-1-induced Cx43 expression via phosphorylation of Erk 1/2 and activation of transcription factor activator protein 1 (AP-1) through their reciprocal receptors in SV SMCs. These data demonstrate a cross-talk between IGF-1R and AT-1R in AT-II and IGF-1-induced Cx43 expression in SV SMCs involving Erk 1/2 and downstream activation of the AP-1 transcription factor.

Hck is a key regulator of gene expression in alternatively activated human monocytes

IL-13 is a Th2 cytokine that promotes alternative activation (M2 polarization) in primary human monocytes. Our studies have characterized the functional IL-13 receptor complex and the downstream signaling events in response to IL-13 stimulation in alternatively activated monocytes/macrophages. In this report, we present evidence that IL-13 induces the activation of a Src family tyrosine kinase, which is required for IL-13 induction of M2 gene expression, including 15-lipoxygenase (15-LO). Our data show that Src kinase activity regulates IL-13-induced p38 MAPK tyrosine phosphorylation via the upstream kinases MKK3 or MKK6. Our findings also reveal that the IL-13 receptor-associated tyrosine kinase Jak2 is required for the activation of both Src kinase as well as p38 MAPK. Further, we found that Src tyrosine kinase-mediated activation of p38 MAPK is required for Stat1 and Stat3 serine 727 phosphorylation in alternatively activated monocytes/macrophages. Additional studies identify Hck as the specific Src family member, stimulated by IL-13 and involved in regulating both p38 MAPK activation and p38 MAPK-mediated 15-LO expression. Finally we show that the Hck regulates the expression of other alternative state (M2)-specific genes (Mannose receptor, MAO-A, and CD36) and therefore conclude that Hck acts as a key regulator controlling gene expression in alternatively activated monocytes/macrophages.

Garlic components inhibit angiotensin II-induced cell-cycle progression and migration: Involvement of cell-cycle inhibitor p27(Kip1) and mitogen-activated protein kinase

Garlic has been used for prevention and treatment of hypertension; however, the molecular mechanisms of garlic's effects remain to be elucidated. In this study, the mechanisms of the in vitro effect of organosulphur compounds derived from garlic on growth and migration of cultured aortic smooth muscle cells isolated from spontaneously hypertensive rats were investigated. We demonstrated that allyl methyl sulphide (AMS) and diallyl sulphide (DAS) inhibited aortic smooth muscle cell angiotensin II-stimulated cell-cycle progression and migration. Neither cell viability nor annexin-V-binding analysis revealed cytotoxic effects of both organosulphur compounds at the used concentrations. Instead, their inhibitory effects were associated to the prevention of the cell-cycle inhibitor p27(Kip1) (p27) downregulation and the reduction of extracellular signal-regulated kinase 1/2 phosphorylation. When we assessed the antioxidant activity of AMS and DAS, we found that both organosulphur compounds inhibited angiotensin II-reactive oxygen species generation. Our findings show that AMS and DAS, compounds derivate from garlic, could be effective antioxidants targeted at the arterial remodelling seen in hypertension.

Olmesartan inhibits angiotensin II-Induced migration of vascular smooth muscle cells through Src and mitogen-activated protein kinase pathways

Clinical studies have shown that angiotensin-receptor blockers (ARBs) reduce the risk of cardiovascular diseases in hypertensive patients. It is assumed that the reduction of the risk by ARBs may be attributed in part to the inhibition of angiotensin II (AII)-induced vascular smooth muscle cell (VSMC) migration associated with atherosclerosis. However, the effect of ARBs on AII-induced changes in intracellular signaling and resultant cell migration has not been well established. Here, we investigated the effect of olmesartan, an ARB, on AII-induced extracellular signal-regulated kinases 1/2 (ERK1/2) and c-Jun N-terminal kinase (JNK) activation and rat aortic smooth muscle cell (RASMC) migration. Olmesartan inhibited AII-induced ERK1/2 and JNK activation at lower concentrations (10 nM). On the other hand, PP2, a Src tyrosine kinase inhibitor, also inhibited AII-induced ERK1/2 and JNK activation, but its effect on ERK1/2 was less pronounced than that of olmesartan. Olmesartan, U0126 (an ERK1/2 inhibitor), SP600125 (a JNK inhibitor), and PP2 potently inhibited AII-induced RASMC migration. From these findings, it was inferred that angiotensin-receptor blockade by olmesartan results in the inhibition of AII-induced activation of Src, ERK1/2, and JNK in RASMC. Olmesartan may be a potent inhibitor of AII-induced VSMC migration, which may be involved in the progression of atherosclerosis.

Angiotensin II-induced migration of vascular smooth muscle cells is mediated by p38 mitogen-activated protein kinase-activated c-Src through spleen tyrosine kinase and epidermal growth factor receptor transactivation

Angiotensin II (Ang II) stimulates protein synthesis by activating spleen tyrosine kinase (Syk) and DNA synthesis through epidermal growth factor receptor (EGFR) transactivation in vascular smooth muscle cells (VSMCs). This study was conducted to determine whether Syk mediates Ang II-induced migration of aortic VSMCs using a scratch wound approach. Treatment with Ang II (200 nM) for 24 h increased VSMC migration by 1.56 +/- 0.14-fold. Ang II-induced VSMC migration and Syk phosphorylation as determined by Western blot analysis were minimized by the Syk inhibitor piceatannol (10 microM) and by transfecting VSMCs with dominant-negative but not wild-type Syk plasmid. Ang II-induced VSMC migration and Syk phosphorylation were attenuated by inhibitors of c-Src [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP2)], p38 mitogen-activated protein kinase (MAPK) [4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole (SB202190)], and extracellular signal-regulated kinase (ERK) 1/2 [1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio) butadiene (U0126)]. SB202190 attenuated p38 MAPK and c-Src but not ERK1/2 phosphorylation, indicating that p38 MAPK acts upstream of c-Src and Syk. The c-Src inhibitor PP2 attenuated Syk and ERK1/2 phosphorylation, suggesting that c-Src acts upstream of Syk and ERK1/2. Ang II- and epidermal growth factor (EGF)-induced VSMC migration and EGFR phosphorylation were inhibited by the EGFR blocker 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) (2 microM). Neither the Syk inhibitor piceatannol nor the dominant-negative Syk mutant altered EGF-induced cell migration or Ang II- and EGF-induced EGFR phosphorylation. The c-Src inhibitor PP2 diminished EGF-induced VSMC migration and EGFR, ERK1/2, and p38 MAPK phosphorylation. The ERK1/2 inhibitor U0126 (10 microM) attenuated EGF-induced cell migration and ERK1/2 but not EGFR phosphorylation. These data suggest that Ang II stimulates VSMC migration via p38 MAPK-activated c-Src through Syk and via EGFR transactivation through ERK1/2 and partly through p38 MAPK.

Genetic variations in ATP2B1, CSK, ARSG and CSMD1 loci are related to blood pressure and/or hypertension in two Korean cohorts

Blood pressure, one of the important vital signs, is affected by multiple genetic and environmental factors. Recently, several genome-wide association (GWA) studies have successfully identified genetic factors that influence blood pressure and hypertension risk. In this study, we report results of the Korean Association REsource (KARE, 8842 subjects) GWA study on blood pressure and hypertension risk. In all, 10 single-nucleotide polymorphisms (SNPs) that showed significant association with hypertension were further analysed for replication associations in the Health2 project (7861 subjects). Among these 10 SNPs, 3 were replicated in the Health2 cohort for an association with systolic or diastolic blood pressure. The most significant SNP (rs17249754 located in ATPase, Ca(++) transporting, plasma membrane 1 (ATP2B1)) has been previously reported, and the other two SNPs are rs1378942 in the c-src tyrosine kinase (CSK) gene and rs12945290 in the arylsulphatase G (ARSG) gene. An additional hypertension case-control study confirmed that rs17249754 (in ATP2B1) increases hypertension risk in both the KARE and Health2 (meta-analysis, P-value=4.25 x 10(-9)) cohorts. One more SNP, rs995322, located in the CUB and Sushi multiple domains 1 (CSMD1), is also associated with increased risk of hypertension (meta-analysis, P-value=1.00 x 10(-4)). Despite the difficulty of obtaining replication results for a complex trait genetic association between blood pressure and hypertension, we were able to identify consistent genetic factors in both the Korean cohorts in ATP2B1, CSK, ARSG and CSMD1 genes.

Substance P receptor in U373 MG human astrocytoma cells activates mitogen-activated protein kinases ERK1/2 through Src

Substance P (SP) acting through substance P receptor (SPR) increases the proliferation of glioblastoma cells. At the molecular level, stimulation of SPR in human U373 MG glioblastoma cells results in phosphorylation of mitogen-activated protein kinases ERK1/2. Examination of the underlying mechanism reveals that SPR mediates ERK1/2 phosphorylation in a calcium-dependent manner. Surprisingly, blockade of epidermal growth factor receptor (EGFR), which is transactivated by SPR, has a minimal effect on SPR-mediated ERK1/2 phosphorylation. However, SPR-mediated ERK1/2 phosphorylation is significantly reduced by the Src kinase inhibitor PP2. Interestingly, ERK1/2 in U373 MG cells is also activated by several other mitogenic G protein-coupled receptors (GPCRs) including alpha(1B)-adrenergic, M(3)-muscarinic, and H(1)-histaminergic in an Src-dependent manner. We conclude that c-Src is a mediator of SP-stimulated ERK1/2 phosphorylation in human U373 MG glioblastoma cells.

Isoproterenol inhibits angiotensin II-stimulated proliferation and reactive oxygen species production in vascular smooth muscle cells through heme oxygenase-1

Heme oxygenase (HO)-1 is a well-known cytoprotectant against oxidative stress and exhibits an antiproliferative effect in vascular smooth muscle cells (VSMCs). The purpose of the present study was to test whether isoproterenol, one of the synthetic catecholamines having beta-adrenergic activity, affected angiotensin II (Ang II)-induced cell proliferation and reactive oxygen species (ROS) production. Also, the presumptive underlying signaling pathways in VSMCs were studied. Aortic VSMCs from 11-week-old male Sprague-Dawley rats were used. Isoproterenol dose-dependently increased HO-1 expression through beta(2)-adrenoceptor (AR) and protein kinase A (PKA) pathway, and isoproterenol concentration-dependently increased beta(2)-AR mRNA expression. Isoproterenol attenuated Ang II-induced cell proliferation, as evidenced by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. This effect of isoproterenol was inhibited by pretreatment of the cells with beta(2)-AR antagonist butoxamine, PKA inhibitor H-89 and HO inhibitor Tin Protoporphyrin IX (SnPP IX), respectively. Isoproterenol inhibited phosphorylation level of Ang II-induced extracellular signal-regulated kinase (ERK1/2). Isoproterenol significantly inhibited Ang II-induced ROS production through the ERK1/2 pathway. These findings suggest that isoproterenol, via induction of HO-1, inhibits Ang II-stimulated proliferation and ROS production in cultured VSMCs.

The Src tyrosine kinase pathway regulates thecal CYP17 expression and androstenedione secretion

In order to evaluate the role of Src tyrosine kinase in thecal cell steroidogenesis, a pharmacological approach was utilized by treating enriched populations of mouse ovarian theca-interstitial cells in vitro with a direct Src kinase inhibitor, PP2. Inhibition of Src with PP2 increased both basal and forskolin-stimulated androstenedione secretion, and increased cytochrome P450 17-alpha hydroxylase-lyase (CYP17) promoter activity and steady state mRNA. PP2 did not change thecal levels of StAR mRNA. Inhibition of mitogen-activated protein kinase kinase, a downstream regulator of Src activity, using PD98059 also increased forskolin-stimulated secretion of androstenedione above forskolin alone, but had no effect on basal secretion of androstenedione. Src inhibition increased mitogen-activated protein kinase phosphatase-1 protein and decreased phosphorylation of SF-1, which correlated with increased CYP17 promoter activity and mRNA levels. These results implicate Src tyrosine kinase in the regulation of CYP17 and thecal androgen secretion.

Superoxide anion mediates angiotensin II-induced potentiation of contractile response to sympathetic stimulation

Angiotensin II is known to potentiate vasoconstriction induced by electrical field stimulation (EFS), but the underlying mechanisms for this potentiation are not fully understood. This study was designed to investigate the role of superoxide anion in the potentiation effects of angiotensin II. Contraction of rat mesenteric arterial segments was induced by perivascular nerve stimulation with EFS, and superoxide production was measured with lucigenin-enhanced chemiluminescence. Extracellular signal-regulated kinase (ERK) phosphorylation was determined in cultured smooth muscle cells with Western blot. Angiotensin II concentration dependently potentiated the contraction of rat mesenteric arteries to EFS, which is frequency-dependent. This potentiation was blunted by an angiotensin AT(1) receptor antagonist (2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylic acid, CV-11974), NAD(P)H oxidase inhibitor (apocynin), superoxide dismutase (SOD) and its mimetic tiron, but not affected by angiotensin AT(2) receptor antagonist and inhibitors of xanthine oxidase, cytochrome P450, and cyclooxygenase. Angiotensin II increased superoxide production by mesenteric arteries, which was blunted by angiotensin AT(1) receptor antagonist CV-11974, and NAD(P)H oxidase inhibitor apocynin. Superoxide generating compound pyrogallol mimicked the effects of angiotensin II. Tyrosine kinase inhibitor (tyrphostin A25) and mitogen-activated protein kinase (MAPK)/ERK inhibitors (1,4-diamino-2,3-dicyano-1,4-bis [2-aminophenylthio]butadiene (U 0126)) inhibited angiotensin II- and pyrogallol-induced potentiation of EFS-induced contraction, while inactive forms of these inhibitors did not show any inhibitory effects. In cultured smooth muscle cells from mesenteric arteries, angiotensin II and superoxide similarly induced ERK phosphorylation. These results showed that superoxide mediated angiotensin II-induced potentiation of contractile response to EFS and tyrosine kinase-MAPK/ERK activation was involved.

Arsenic alters vascular smooth muscle cell focal adhesion complexes leading to activation of FAK-src mediated pathways

Chronic exposure to arsenic has been linked to tumorigenesis, cardiovascular disease, hypertension, atherosclerosis, and peripheral vascular disease; however, the molecular mechanisms underlying its pathological effects remain elusive. In this study, we investigated arsenic-induced alteration of focal adhesion protein complexes in normal, primary vascular smooth muscle cells. We demonstrate that exposure to environmentally relevant concentrations of arsenic (50 ppb As(3+)) can alter focal adhesion protein co-association leading to activation of downstream pathways. Co-associated proteins were identified and quantitated via co-immunoprecipitation, SDS-PAGE, and Western blot analysis followed by scanning densitometry. Activation of MAPK pathways in total cell lysates was evaluated using phosphor-specific antibodies. In our model, arsenic treatment caused a sustained increase in FAK-src association and activation, and induced the formation of unique signaling complexes (beginning after 3-hour As(3+) exposure and continuing throughout the 12-hour time course studied). The effects of these alterations were manifested as chronic stimulation of downstream PAK, ERK and JNK pathways. Past studies have demonstrated that these pathways are involved in cellular survival, growth, proliferation, and migration in VSMCs.

Involvement of connexin 43 in angiotensin II-induced migration and proliferation of saphenous vein smooth muscle cells via the MAPK-AP-1 signaling pathway

Proliferation and migration of vascular smooth muscle cells (VSMCs) lead to intimal thickening and influence the long-term patency of venous graft post coronary arterial bypass graft. There is increasing evidence that connexins are involved in the development of intimal hyperplasia and restenosis. We assessed connexin 43 (Cx43) expression and its role in angiotensin II-induced proliferation and migration of smooth muscle cells and the signal pathways involved in human saphenous vein bypass conduits. Angiotensin II significantly increased gap junctional intercellular communication and induced the expression of Cx43 in human saphenous vein SMCs in a dose- and time-dependent manner through angiotensin II type 1 receptor. The effect of angiotensin II was blocked by siRNA of ERK 1/2, p38 MAPK and JNK, respectively. Overexpression of Cx43 markedly increased the proliferation of saphenous vein SMCs. However, siRNA for Cx43 inhibited angiotensin II-induced proliferation, cyclin E expression and migration of human saphenous vein SMCs. In dual-luciferase reporter assay, angiotensin II markedly activated AP-1 transcription factor, which was significantly attenuated by a dominant-negative AP-1 (A-Fos) with subsequent inhibition of angiotensin II-induced transcriptional expression of Cx43. These data demonstrate the role of Cx43 in the proliferation and migration of human saphenous vein SMCs and angiotensin II-induced Cx43 expression via mitogen-activated protein kinases (MAPK)-AP-1 signaling pathway.

Hypertension and microvascular remodelling

In the present review, microvascular remodelling refers to alterations in the structure of resistance vessels contributing to elevated systemic vascular resistance in hypertension. We start with some historical aspects, underscoring the importance of Folkow's contribution made half a century ago. We then move to some basic concepts on the biomechanics of blood vessels, and explicit the definitions proposed by Mulvany for specific forms of remodelling, especially inward eutrophic and inward hypertrophic. The available evidence for the existence of remodelled resistance vessels in hypertension comes next, with relatively more weight given to human, in comparison with animal data. Mechanisms are discussed. The impact of antihypertensive drug treatment on remodelling is described, again with emphasis on human data. Some details are given on the three studies to date which point to remodelling of subcutaneous resistance arteries as an independent predictor of cardiovascular risk in hypertensive patients. We terminate by considering the potential role of remodelling in the pathogenesis of end-organ damage and in the perpetuation of hypertension.

Transactivation of epidermal growth factor receptor in vascular and renal systems in rats with experimental hyperleptinemia: role in leptin-induced hypertension

We examined the role of epidermal growth factor (EGF) receptor in the pathogenesis of leptin-induced hypertension in the rat. Leptin, administered in increasing doses (0.1-0.5 mg/kg/day) for 10 days, increased phosphorylation levels of non-receptor tyrosine kinase, c-Src, EGF receptor and extracellular signal-regulated kinases (ERK) in aorta and kidney, which was accompanied by the increase in plasma concentration and urinary excretion of isoprostanes and H2O2. Blood pressure and renal Na+,K+-ATPase activity were higher, whereas urinary sodium excretion was lower in animals receiving leptin. The effects of leptin on renal Na+,K+-ATPase, natriuresis and blood pressure were abolished by NADPH oxidase inhibitor, apocynin, Src kinase inhibitor, PP2, EGF receptor inhibitor, AG1478, protein farnesyltransferase inhibitor, manumycin A, and ERK inhibitor, PD98059. In contrast, inhibitors of insulin-like growth factor-1 and platelet-derived growth factor receptors, AG1024 and AG1295, respectively, only slightly reduced ERK phosphorylation and had no effect on blood pressure in rats receiving leptin. These data indicate that: (1) experimental hyperleptinemia is associated with oxidative stress and c-Src-dependent transactivation of the EGF receptor, which stimulates ERK in vascular wall and the kidney, (2) overactivity of EGF receptor-ERK pathway contributes to leptin-induced hypertension by stimulating renal Na+,K+-ATPase and reducing sodium excretion, (3) inhibitors of c-Src, EGF receptor and ERK may be considered as a novel therapy for hypertension associated with hyperleptinemia, e.g. in patients with obesity and metabolic syndrome.

Angiotensin II activates extracellular signal-regulated kinase independently of receptor tyrosine kinases in renal smooth muscle cells: implications for blood pressure regulation

Angiotensin II can cause hypertension through enhanced vasoconstriction of renal vasculature. One proposed mechanism for reduction of angiotensin II-induced hypertension is through inhibition of the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase cascade. MEK/ERK has been shown to phosphorylate the regulatory subunit of myosin light chain at identical positions as myosin light chain kinase. There are multiple mechanisms proposed regarding angiotensin II-mediated ERK activation. We hypothesized that renal microvascular smooth muscle cells (RmuVSMCs) signal through a unique pathway compared with thoracic aorta smooth muscle cells (TASMCs), which is involved in blood pressure regulation. Use of epidermal growth factor (EGF) and platelet derived growth factor (PDGF) receptor-specific inhibitors 4-(3-chloroanilino)-6,7-dimethoxyquinazoline (AG1478) and 6,7-dimethoxy-3-phenylquinoxaline (AG1296), respectively, demonstrates that angiotensin II activates ERK in TASMCs, but not RmuVSMCs, through transactivation of EGF and PDGF receptors. In addition, inhibition of Src with its specific inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo[3,4-d]pyrimidine (PP2) abolishes angiotensin II-, but not EGF-or PDGF-, mediated phosphorylation of ERK in RmuVSMCs, yet it has no effect in TASMCs. The physiological significance of transactivation was examined in vivo using anesthetized Wistar-Kyoto rats with 15 mg/kg 2'-amino-3'-methoxyflavone (PD98059), an MEK inhibitor, as well as 20 mg/kg AG1478 and 1.5 mg/kg AG1296 in an acute model of angiotensin II-mediated increase in blood pressure. None of the inhibitors had an effect on basal blood pressure, and only PD98059 reduced angiotensin II-mediated increase in blood pressure. Moreover, in RmuVSMCs, but not TASMCs, angiotensin II localizes phosphorylated ERK to actin filaments. In conclusion, angiotensin II signals through a unique mechanism in the renal vascular bed that may contribute to hypertension.

Src and Pyk2 mediate angiotensin II effects in cultured rat astrocytes

Angiotensin II (Ang II)-induced proliferation of rat astrocytes is mediated by multiple signaling pathways. In the present study, we investigated the role of non-receptor tyrosine kinases on Ang II-signaling and proliferation of astrocytes cultured from neonatal rat pups. Ang II stimulated astrocyte growth, ERK1/2 phosphorylation and the phosphorylation of Src and proline-rich tyrosine kinase-2 (Pyk2), in astrocytes obtained from brainstem and cerebellum. Pretreatment with 10 microM PP2, a selective Src inhibitor, inhibited Ang II stimulated ERK1/2 phosphorylation by 59% to 91% both in brainstem and cerebellum astrocytes. PP2 also inhibited Ang II induction of brainstem (76% inhibition) and cerebellar (64% inhibition) astrocyte growth. Similarly, pretreatment with 25 microM dantrolene, the Pyk2 inhibitor, attenuated ERK1/2 activity in brainstem (62% inhibition) and in cerebellum astrocytes (44% inhibition). Interestingly, inhibition of Pyk2 inhibited Ang II-induced Src activation suggesting that these two non-receptor tyrosine kinases may be acting in concert to mediate Ang II effects in astrocytes. In summary, we found that Ang II stimulates the non-receptor tyrosine kinases Src and Pyk2 which mediate Ang II-induced ERK1/2 activation leading to stimulation of astrocyte growth. In addition, these two tyrosine kinases may be interacting to regulate effects of the peptide in these cells.

Regulation of c-fos, c-jun and c-myc Gene Expression by Angiotensin II in Primary Cultured Rat Astrocytes: Role of ERK1/2 MAP Kinases

We have previously shown that angiotensin II (Ang II) stimulates astrocyte growth through activation of ERK1/2 mitogen activated protein (MAP) kinases. In the current study, we determined whether Ang II stimulates the expression of c-fos, c-jun and c-myc in brainstem astrocyte cultures. Reverse transcriptase-PCR analysis showed c-fos, c-jun, and c-myc mRNAs were induced by Ang II. The EC50 values for Ang II stimulation of c-fos, c-jun and c-myc were 1.3, 1.68 and 1.4 nM, respectively. Ang II (100 nM) induced peak stimulation for all genes by 45 min followed by a gradual decline. Inhibition of ERK1/2 by PD98059 attenuated Ang II-induced c-fos and c-myc mRNA expression (by 75% and 100%, respectively) but was ineffective in preventing Ang II induction of c-jun. These studies show for the first time in brainstem astrocytes that Ang II induces the expression of c-fos, c-myc and c-jun, and showed that ERK1/2 mediate Ang II stimulation of c-fos and c-myc. These data implicate the ERK1/2 MAP kinase pathway as a divergent point in controlling Ang II stimulation of immediate early response genes in the central nervous system.

Interleukin 1-beta (IL-1beta) enhances contractile responses in endothelium-denuded aorta from hypertensive, but not normotensive, rats

BACKGROUND

The chronic effects of interleukin 1-beta (IL-beta) on vascular reactivity include augmentation of contraction and relaxation. Few studies have assessed the acute effects of IL-1beta in vessels from hypertensive and normotensive rats. We hypothesized that IL-1beta would enhance constriction in aorta from stroke prone spontaneously hypertensive rats (SHRSP).

METHODS

Endothelium denuded aortic rings from 12 week-old SHRSP and Wistar Kyoto (WKY) rats were mounted in a myograph and incubated with IL-1beta (20 ng/ml) for 1 h before construction of a phenylephrine dose response curve. Indomethacin (1 microM) and PP-2 (1 microM) were utilized to inhibit cyclooxygenase (COX) and Src-kinase respectively.

RESULTS

In aorta from SHRSP, IL-1beta caused a significant increase in the force generated over the hour incubation; inhibition of COX or Src-kinase prevented this. The maximum phenylephrine-induced contraction was greater in aorta from SHRSP incubated with IL-1beta than control. COX or Src-kinase inhibition prevented this. IL-1beta had no effect on the vessels from WKY rats.

CONCLUSIONS

These novel data suggest that IL-1beta has rapid effects on vascular smooth muscle from hypertensive rats to produce constriction and to enhance phenylephrine-induced constriction. The COX and Src-kinase pathways appear to be involved in this response.

Angiotensin II inhibits insulin-induced actin stress fiber formation and glucose uptake via ERK1/2

There is crosstalk in intracellular signaling between Angiotensin II (Ang II) and insulin. We hypothesized that the underlying mechanism might be related to changes in cytoskeleton. In the presence of 100 nM of Ang II, insulin-induced glucose uptake was decreased and insulin-induced actin filament organization was inhibited. PKC inhibitors, including GF109203x and p38MAPK inhibitor (SB203580) neither improved insulin-induced actin reorganization nor glucose uptake. In contrast, the Ang II-induced inhibition of glucose uptake and actin filament disorganization was reversed by 10 micromol ERK 1/2 MAPK inhibitor (PD98059). Pretreatment of Ang II increased ERK1/2 phosphorylation and inhibited insulin-induced Akt phosphorylation. The effect of Ang II on ERK1/2 phosphorylation was blocked by Ang II type 1 receptor antagonists, RNH6270 and PD98059 but not by SB203580 or Guanosine-5'-O-(2-ThioDiphosphate), a G-protein inhibitor. We next tested the effect of broad-spectrum matrix metalloproteinase (MMP) inhibitor (GM6001) on Ang II-inhibition of insulin signaling pathway. GM6001 did not improve Ang II-induced actin filament disorganization and did not inhibit ERK1/2 phosphorylation. From these data in L6 myotube, we conclude that Ang II negatively regulates the insulin signal not through MMP signaling pathway but specifically through MMP-independent ERK1/2 activation pathway, providing an alternative molecular mechanism for angiotensin-induced insulin resistance.

Vascular signaling through cholesterol-rich domains: implications in hypertension

PURPOSE OF REVIEW

Lipid rafts are emerging as key players in the integration of cellular responses. Alterations in these highly regulated signaling cascades are important in structural, mechanical and functional abnormalities that underlie vascular pathological processes. The present review focuses on recent advances in signal transduction through caveolae/lipid rafts, implicated in hypertensive processes.

RECENT FINDINGS

Caveolae/lipid rafts function as sites of dynamic regulatory events in receptor-induced signal transduction. Mediators of vascular function, including G-protein coupled receptors, Src family tyrosine kinases, receptor tyrosine kinases, protein phosphatases and nitric oxide synthase, are concentrated within these microdomains. The assembly of functionally active nicotinamide adenine dinucleotide phosphate oxidase and subsequent reactive oxygen species production are also dependent on interactions within the caveolae/lipid rafts. Recent findings have also demonstrated the importance of actin-cytoskeleton and focal adhesion sites for protein interactions with caveolae/lipid raft.

SUMMARY

Many vascular signaling processes are altered in hypertension. Whether these events involve lipid rafts/caveolae remains unclear. A better understanding of how signaling molecules compartmentalize in lipid rafts/caveolae will provide further insights into molecular mechanisms underlying vascular damage in cardiovascular disease.

ERK1/2 regulates ANG II-dependent cell proliferation via cytoplasmic activation of RSK2 and nuclear activation of elk1

In a concurrently submitted article, we show that ANG II-induced ERK1/2 activation is mediated by both c-Src/Yes/Fyn and heterotrimeric G protein/PKCζ-dependent signaling. Furthermore, we show that heterotrimeric G protein/PKCζ-activated ERK1/2 is destined for the nucleus while ERK1/2 activated by c-Src/Yes/Fyn-dependent signaling remains in the cytoplasm. Interestingly, both mechanisms of activation are required for maximum ANG II-induced cell proliferation. In this study, we sought to determine the mechanisms by which ERK1/2 facilitate cell proliferation via these distinct nuclear and cytoplasmic events, using cells that were lacking either c-Src/Yes/Fyn or heterotrimeric G protein/PKCζ-dependent ERK1/2 activation. A loss of c-Src/Yes/Fyn blocked ANG II-dependent RSK2 activation, RSK2 nuclear translocation, serum-response factor (SRF) phosphorylation, a portion of c-fos transcriptional activity and c-Fos phosphorylation. Blocking ANG II-induced heterotrimeric G protein/PKCζ activity resulted in a loss of ERK1/2 nuclear translocation, elk1 phosphorylation, and the remaining portion of c-fos transcriptional activity not dependent on c-Src/Yes/Fyn. Inhibition of RSK with the potent and selective inhibitor, SL0101, attenuated ANG II-induced cell proliferation, and, in combination with a PKCζ pseudosubstrate, completely attenuated cell proliferation. Thus we conclude that ERK1/2 mediate ANG II-dependent cell proliferation via distinct cytoplasmic and nuclear signaling events, which are in turn governed by c-Src/Yes/Fyn and heterotrimeric G protein/PKCζ-dependent signaling, respectively.

ANG II-induced cell proliferation is dually mediated by c-Src/Yes/Fyn-regulated ERK1/2 activation in the cytoplasm and PKCζ-controlled ERK1/2 activity within the nucleus

High-affinity binding of angiotensin II (ANG II) to the ANG II type 1 receptor (AT1R) results in the activation of ERK1/2 mitogen-activated protein kinases (MAPK). However, the precise mechanism of ANG II-induced ERK1/2 activation has not been fully characterized. Here, we investigated the signaling events leading to ANG II-induced ERK1/2 activation using a c-Src/Yes/Fyn tyrosine kinase-deficient mouse embryonic fibroblast (MEF) cell line stably transfected with the AT1R (SYF/AT1). ERK1/2 activation was reduced by ∼50% within these cells compared with wild-type controls (WT/AT1). The remaining ∼50% of intracellular ERK1/2 activation was dependent upon heterotrimeric G protein and protein kinase C zeta (PKCζ) activation. Therefore, ANG II-induced ERK1/2 activation occurs via two independent mechanisms. We next investigated whether a loss of either c-Src/Yes/Fyn or PKCζ signaling affected ERK1/2 nuclear translocation and cell proliferation in response to ANG II. ANG II-induced cell proliferation was markedly reduced in SYF/AT1cells compared with WT/AT1cells ( P < 0.01), but interestingly, ERK2 nuclear translocation was normal. ANG II-induced nuclear translocation of ERK2 was blocked via pretreatment of WT/AT1cells with a PKCζ pseudosubstrate. ANG II-induced cell proliferation was significantly reduced in PKCζ pseudosubstrate-treated WT/AT1cells ( P < 0.01) and was completely blocked in SYF/AT1cells treated with this same compound. Thus ANG II-induced cell proliferation appears to be regulated by both ERK1/2-driven nuclear and cytoplasmic events. In response to ANG II, the ability of ERK1/2 to remain within the cytoplasm or translocate into the nucleus is controlled by c-Src/Yes/Fyn or heterotrimeric G protein/PKCζ signaling, respectively.