Mitochondrial DNA integrity and function are critical for endothelium-dependent vasodilation in rats with metabolic syndrome.

Endothelial dysfunction in diabetes is generally attributed to oxidative stress, but this view is challenged by observations showing antioxidants do not eliminate diabetic vasculopathy. As an alternative to oxidative stress-induced dysfunction, we interrogated if impaired mitochondrial function in endothelial cells is central to endothelial dysfunction in the metabolic syndrome. We observed reduced coronary arteriolar vasodilation to the endothelium-dependent dilator, acetylcholine (Ach), in Zucker Obese Fatty rats (ZOF, 34 ± 15% [mean ± standard deviation] 10-3 M) compared to Zucker Lean rats (ZLN, 98 ± 11%). This reduction in dilation occurred concomitantly with mitochondrial DNA (mtDNA) strand lesions and reduced mitochondrial complex activities in the endothelium of ZOF versus ZLN. To demonstrate endothelial dysfunction is linked to impaired mitochondrial function, administration of a cell-permeable, mitochondria-directed endonuclease (mt-tat-EndoIII), to repair oxidatively modified DNA in ZOF, restored mitochondrial function and vasodilation to Ach (94 ± 13%). Conversely, administration of a cell-permeable, mitochondria-directed exonuclease (mt-tat-ExoIII) produced mtDNA strand breaks in ZLN, reduced mitochondrial complex activities and vasodilation to Ach in ZLN (42 ± 16%). To demonstrate that mitochondrial function is central to endothelium-dependent vasodilation, we introduced (via electroporation) liver mitochondria (from ZLN) into the endothelium of a mesenteric vessel from ZOF and restored endothelium-dependent dilation to vasoactive intestinal peptide (VIP at 10-5 M, 4 ± 3% vasodilation before mitochondrial transfer and 48 ± 36% after transfer). Finally, to demonstrate mitochondrial function is key to endothelium-dependent dilation, we administered oligomycin (mitochondrial ATP synthase inhibitor) and observed a reduction in endothelium-dependent dilation. We conclude that mitochondrial function is critical for endothelium-dependent vasodilation.

Left Ventricular Outflow Tract Gradient Is Associated With Coronary Artery Obstruction in Children With Williams-Beuren Syndrome.

OBJECTIVES: Patients with Williams-Beuren syndrome are associated with a high risk of hemodynamic collapse during sedation and/or anesthesia, presumably due to occult coronary obstruction. The objective of this study was to determine the association between transthoracic echocardiogram findings and the presence of coronary obstruction to examine if coronary obstruction can be predicted by transthoracic echocardiogram before anesthesia. DESIGN: Retrospective data analysis of patients with Williams-Beuren syndrome who underwent transthoracic echocardiogram, cardiac catheterization, and/or surgical interventions to determine the correlation between echocardiogram findings and the presence of coronary obstruction determined by cardiac catheterization and/or surgery. SETTING: Single-center university teaching hospital. PARTICIPANTS: The study included 49 patients with Williams-Beuren syndrome who underwent transthoracic echocardiogram, cardiac catheterization, and/or surgical interventions. MEASUREMENTS AND MAIN RESULTS: The only variable associated with coronary artery obstruction was the maximum instantaneous gradient (MIG) across the left ventricular outflow tract (LVOT) on a transthoracic echocardiogram. LVOT MIG ≥ 75 mmHg as the optimal cutoff value was associated with coronary artery obstruction (area under the curve 0.659, odds ratio 6.71, 95% CI 1.31-34.35, p = 0.022). CONCLUSION: LVOT gradient can serve as a good predictor of the presence of coronary obstruction in patients with Williams-Beuren syndrome.

High-content screen using zebrafish (Danio rerio) embryos identifies a novel kinase activator and inhibitor.

In this report we utilized zebrafish (Danio rerio) embryos in a phenotypical high-content screen (HCS) to identify novel leads in a cancer drug discovery program. We initially validated our HCS model using the flavin adenosine dinucleotide (FAD) containing endoplasmic reticulum (ER) enzyme, endoplasmic reticulum oxidoreductase (ERO1) inhibitor EN460. EN460 showed a dose response effect on the embryos with a dose of 10µM being significantly lethal during early embryonic development. The HCS campaign which employed a small library identified a promising lead compound, a naphthyl-benzoic acid derivative coined compound 1 which had significant dosage and temporally dependent effects on notochord and muscle development in zebrafish embryos. Screening a 369 kinase member panel we show that compound 1 is a PIM3 kinase inhibitor (IC50=4.078µM) and surprisingly a DAPK1 kinase agonist/activator (EC50=39.525µM). To our knowledge this is the first example of a small molecule activating DAPK1 kinase. We provide a putative model for increased phosphate transfer in the ATP binding domain when compound 1 is virtually docked with DAPK1. Our data indicate that observable phenotypical changes can be used in future zebrafish screens to identify compounds acting via similar molecular signaling pathways.

Exploring Adenosine Receptor Ligands: Potential Role in the Treatment of Cardiovascular Diseases.

Cardiovascular diseases remain the number one diseases affecting patients' morbidity and mortality. The adenosine receptors are G-protein coupled receptors which have been of interest for drugs target for the treatment of multiple diseases ranging from cardiovascular to neurological. Adenosine receptors have been connected to several biological pathways affecting the physiology and pathology of the cardiovascular system. In this review, we will cover the different adenosine receptor ligands that have been identified to interact with adenosine receptors and affect the vascular system. These ligands will be evaluated from clinical as well as medicinal chemistry perspectives with more emphasis on how structural changes in structure translate into ligand potency and efficacy. Adenosine receptors represent a novel therapeutic target for development of treatment options treating a wide variety of diseases, including vascular disease and obesity.

Stimulation of coronary collateral growth by granulocyte stimulating factor: role of reactive oxygen species.

OBJECTIVE: The purpose of this study was to determine whether G-CSF promotes coronary collateral growth (CCG) and decipher the mechanism for this stimulation. METHODS AND RESULTS: In a rat model of repetitive episodic myocardial ischemia (RI, 40 seconds LAD occlusion every 20 minutes for 2 hours and 20 minutes, 3 times/d for 5 days) CCG was deduced from collateral-dependent flow (flow to LAD region during occlusion). After RI, G-CSF (100 microg/kg/d) increased CCG (P<0.01) (0.47+/-0.15) versus vehicle (0.14+/-0.06). Surprisingly, G-CSF treatment without RI increased CCG (0.57+/-0.18) equal to G-CSF+RI. We evaluated ROS by dihydroethidine (DHE) fluorescence (LV injection, 60 microg/kg, during two episodes of ischemia). DHE fluorescence was double in G-CSF+RI versus vehicle+RI (P<0.01), and even higher in G-CSF without RI (P<0.01). Interestingly, the DHE signal did not colocalize with myeloperoxidase (immunostaining, neutrophil marker) but appeared in cardiac myocytes. The study of isolated cardiac myocytes revealed the cytokine stimulates ROS which elicit production of angiogenic factors. Apocynin inhibited G-CSF effects both in vivo and in vitro. CONCLUSIONS: G-CSF stimulates ROS production directly in cardiomyocytes, which plays a pivotal role in triggering adaptations of the heart to ischemia including growth of the coronary collaterals.

Publisher Correction: The Extended Polydimensional Immunome Characterization (EPIC) web-based reference and discovery tool for cytometry data.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Vitamin B(12) and redox homeostasis: cob(II)alamin reacts with superoxide at rates approaching superoxide dismutase (SOD).

We report a kinetic study of the reaction between superoxide and an important intracellular form of vitamin B(12), cob(II)alamin. Superoxide is implicated in the pathophysiology of many inflammatory diseases, whereas vitamin B(12) derivatives are often beneficial in their treatment. We found that cob(II)alamin reacts with superoxide at rates approaching those of superoxide dismutase itself, suggesting a probable mechanism by which vitamin B(12) protects against chronic inflammation and modulates redox homeostasis.

Gene expression profiling of alpha(1b)-adrenergic receptor-induced cardiac hypertrophy by oligonucleotide arrays.

OBJECTIVE: Cardiac hypertrophy is closely associated with the development of cardiomyopathies that lead to heart failure. The alpha(1B) adrenergic receptor (alpha(1)-AR) is an important regulator of the hypertrophic process. Cardiac hypertrophy induced by systemic overexpression of the alpha(1b)-AR in a mouse model does not progress to heart failure. We wanted to explore potential gene expression differences that characterize this type of hypertrophy that may identify genes that prevent progression to heart failure. METHODS: Transgenic and normal mice (B6CBA) representing two time points were compared; one at 2-3 months of age before disease manifests and the other at 12 months when the hypertrophy is significant. Age-matched hearts were removed, cRNA prepared and biotinylated. Aliquots of the cRNA was subjected to hybridization with Affymetrix chips representing 12,656 murine genes. Gene expression profiles were compared with normal age-matched controls as the baseline and confirmed by Northern and Western analysis. RESULTS: The non-EST genes could be grouped into five functional classifications: embryonic, proliferative, inflammatory, cardiac-related, and apoptotic. Growth response genes involved primarily Src-related receptors and signaling pathways. Transgenic hearts also had a 60% higher Src protein content. There was an inflammatory response that was verified by an increase in IgG and kappa-chained immunoglobulins by western analysis. Apoptosis may be regulated by cell cycle arrest through a p53-dependent mechanism. Cardiac gene expression was decreased for common hypertrophy-inducing proteins such as actin, collagen and GP130 pathways. CONCLUSIONS: Our results suggest a profile of gene expression in a case of atypical cardiac hypertrophy that does not progress to heart failure. Since many of these altered gene expressions have not been linked to heart failure models, our findings may provide a novel insight into the particular role that the alpha(1B)AR plays in its overall progression or regression.

The alpha(1B)-adrenergic receptor decreases the inotropic response in the mouse Langendorff heart model.

OBJECTIVE: alpha(1)-Adrenergic receptors (ARs) are known mediators of a positive inotropy in the heart, which may play even more important roles in heart disease. Due to a lack of sufficiently selective ligands, the contribution of each of the three alpha(1)-AR subtypes (alpha(1A), alpha(1B) and alpha(1D)) to cardiac function is not clearly defined. In this study, we used a systemically expressing mouse model that overexpresses the alpha(1B)-AR to define the role of this subtype in cardiac function. METHODS: We used the mouse Langendorff heart model to assess changes in contractility under basal and phenylephrine-induced conditions. RESULTS: We find that a 50% increase of the alpha(1B)-AR in the heart does not change basal cardiac parameters compared to age-matched normals (heart rate, +/-dP/dT and coronary flow). However, the inotropic response to phenylephrine is blunted. The same results were obtained in isolated adult myocytes. The difference in inotropy could be blocked by the selective alpha(1A)-AR antagonist, 5-methylurapidil, which correlated with decreases in alpha(1A)-AR density, suggesting that the alpha(1B)-AR had caused a compensatory downregulation of the alpha(1A)-AR. CONCLUSIONS: These results suggest that the alpha(1B)-AR does not have a major role in the positive inotropic response in the mouse myocardium but may negatively modulate the response of the alpha(1A)-AR.

An unusual route taken by a central venous catheter resulting in inadvertent subclavian artery cannulation: a case report.

Ultrasound-guided cannulation of a central venous catheter into the internal jugular vein (IJV) was performed in the intensive care unit for a critically ill patient. The catheter was inserted into the subclavian artery distally, despite prior ultrasound confirmation of the guidewire position using both the in-plane and out-of-plane views. The catheter was removed successfully by the interventional radiologist with a closure device. To our knowledge, there have been previous case reports of subclavian artery injury during IJV cannulation with ultrasound guidance, but rarely in the setting whereby the guidewire was visualized before dilatation and railroading of the catheter. This case demonstrates that the confirmation of the guidewire in the proximal segment of the vein is insufficient to exclude arterial cannulation.

Differential regulation of the cell cycle by alpha1-adrenergic receptor subtypes.

Alpha(1)-Adrenergic receptors have been implicated in growth-promoting pathways. A microarray study of individual alpha(1)-adrenergic receptor subtypes (alpha(1A), alpha(1B), and alpha(1D)) expressed in Rat-1 fibroblasts revealed that epinephrine altered the transcription of several cell cycle regulatory genes in a direction consistent with the alpha(1A)- and alpha(1D)-adrenergic receptors mediating G(1)-S cell cycle arrest and the alpha(1B-)mediating cell-cycle progression. A time course indicated that in alpha(1A) cells, epinephrine stimulated a G(1)-S arrest, which began after 8 h of stimulation and maximized at 16 h, at which point was completely blocked with cycloheximide. The alpha(1B)-adrenergic receptor profile also showed unchecked cell cycle progression, even under low serum conditions and induced foci formation. The G(1)-S arrest induced by alpha(1A)- and alpha(1D)-adrenergic receptors was associated with decreased cyclin-dependent kinase-6 and cyclin E-associated kinase activities and increased expression of the cyclin-dependent kinase inhibitor p27(Kip1), all of which were blocked by prazosin. There were no differences in kinase activities and/or expression of p27(Kip1) in epinephrine alpha(1B)-AR fibroblasts, although the microarray did indicate differences in p27(Kip1) RNA levels. Cell counts proved the antimitotic effect of epinephrine in alpha(1A) and alpha(1D) cells and indicated that alpha(1B)-adrenergic receptor subtype expression was sufficient to cause proliferation of Rat-1 fibroblasts independent of agonist stimulation. Analysis in transfected PC12 cells also confirmed the alpha(1A)- and alpha(1B)-adrenergic receptor effect. The alpha(1B)-subtype native to DDT1-MF2 cells, a smooth muscle cell line, caused progression of the cell cycle. These results indicate that the alpha(1A)- and alpha(1D)-adrenergic receptors mediate G(1)-S cell-cycle arrest, whereas alpha(1B)-adrenergic receptor expression causes a cell cycle progression and may induce transformation in sensitive cell lines.

Vitamin B12 protects against superoxide-induced cell injury in human aortic endothelial cells.

Superoxide (O(2)(•-)) is implicated in inflammatory states including arteriosclerosis and ischemia-reperfusion injury. Cobalamin (Cbl) supplementation is beneficial for treating many inflammatory diseases and also provides protection in oxidative-stress-associated pathologies. Reduced Cbl reacts with O(2)(•-) at rates approaching that of superoxide dismutase (SOD), suggesting a plausible mechanism for its anti-inflammatory properties. Elevated homocysteine (Hcy) is an independent risk factor for cardiovascular disease and endothelial dysfunction. Hcy increases O(2)(•-) levels in human aortic endothelial cells (HAEC). Here, we explore the protective effects of Cbl in HAEC exposed to various O(2)(•-) sources, including increased Hcy levels. Hcy increased O(2)(•-) levels (1.6-fold) in HAEC, concomitant with a 20% reduction in cell viability and a 1.5-fold increase in apoptotic death. Pretreatment of HAEC with physiologically relevant concentrations of cyanocobalamin (CNCbl) (10-50nM) prevented Hcy-induced increases in O(2)(•-) and cell death. CNCbl inhibited both Hcy and rotenone-induced mitochondrial O(2)(•-) production. Similarly, HAEC challenged with paraquat showed a 1.5-fold increase in O(2)(•-) levels and a 30% decrease in cell viability, both of which were prevented with CNCbl pretreatment. CNCbl also attenuated elevated O(2)(•-) levels after exposure of cells to a Cu/Zn-SOD inhibitor. Our data suggest that Cbl acts as an efficient intracellular O(2)(•-) scavenger.

Design and use of peptide-based antibodies decreasing superoxide production by mitochondrial complex I and complex II.

Mitochondria are the major source of reactive oxygen species. Both complex I and complex II mediate O2*- production in mitochondria and host reactive protein thiols. To explore the functions of the specific domains involved in the redox modifications of complexes I and II, various peptide-based antibodies were generated against these complexes, and their inhibitory effects were subsequently measured. The redox domains involved in S-glutathionylation and nitration, as well as the binding 2011. motif of the iron-sulfur cluster (N1a) of the complexes I and II were utilized to design B-cell epitopes for generating antibodies. The effect of antibody binding on enzyme-mediated O2*- generation was measured by EPR spin trapping. Binding of either antibody AbGSCA206 or AbGSCB367 against glutathione (GS)-binding domain to complex I inhibit its O2*- generation, but does not affect electron transfer efficiency. Binding of antibody (Ab24N1a) against the binding motif of N1a to complex I modestly suppresses both O2*- generation and electron transfer efficiency. Binding of either antibody Ab75 or Ab24 against nonredox domain decreases electron leakage production. In complex II, binding of antibody AbGSC90 against GS-binding domain to complex II marginally decreases both O2*- generation and electron transfer activity. Binding of antibody AbY142 to complex II against the nitrated domain modestly inhibits electron leakage, but does not affect the electron transfer activity of complex II. In conclusion, mediation of O2*- generation by complexes I and II can be regulated by specific redox and nonredox domains.

Redox-dependent mechanisms in coronary collateral growth: the "redox window" hypothesis.

This review addresses the complexity of coronary collateral growth from the aspect of redox signaling and introduces the concept of a "redox window" in the context of collateral growth. In essence, the redox window constitutes a range in the redox state of cells, which not only is permissive for the actions of growth factors but also amplifies their actions. The interactions of redox-dependent signaling with growth factors are well established through the actions of many redox-dependent kinases (e.g., Akt and p38 mitogen-activated protein kinase). The initial changes in cellular redox can be induced by a variety of events, from the oxidative burst during reperfusion after ischemia, to recruitment of various types of inflammatory cells capable of producing reactive oxygen species. Any event that "upsets" the normal redox equilibrium is capable of amplifying growth. However, extremes of the redox window, oxidative and reductive stresses, are associated with diminished growth-factor signaling and reduced activation of redox-dependent kinases. This concept of a redox window helps to explain why the clinical trials aimed at stimulating coronary collateral growth, the "therapeutic angiogenesis trials," failed. However, understanding of redox signaling in the context of coronary collateral growth could provide new paradigms for stimulating collateral growth in patients.

A noninflammatory interleukin-1beta fragment stimulates fetal lung fluid absorption in guinea pigs.

We have previously demonstrated that full-length interleukin (IL)-1beta can induce and stimulate lung fluid absorption in near-term guinea pig fetuses via stimulation of fetal cortisol synthesis and release. To develop a potentially clinically useful drug, we tested the hypothesis that maternal administration of a noninflammatory IL-1beta-fragment (IL-1beta(Fr)) induced cortisol synthesis and stimulated lung fluid absorption in preterm fetuses. IL-1beta(Fr) was administered s.c. daily to timed-pregnant guinea pigs for 3 days with and without simultaneous cortisol synthesis inhibition by metyrapone. Fetuses were obtained by abdominal hysterotomy at 61 and 68 days gestation and instilled with isosmolar 5% albumin into the lungs, and lung fluid absorption was measured over 1 h by mass balance. Lung fluid absorption was induced at 61 days and stimulated at 68 days gestation by IL-1beta(Fr), which both were attenuated by cortisol synthesis inhibition. Moreover, induction of labor by oxytocin stimulated lung fluid absorption at 61 days but had no stimulatory effect at 68 days gestation when given with the IL-1beta(Fr). Plasma adrenocorticotropin and cortisol concentrations were increased by IL-1beta(Fr) at 61 days gestation and remained high but unstimulated by IL-1beta(Fr) at 68 days gestation, and metyrapone always reduced cortisol concentrations. Prenatal lung fluid absorption, when present as well as IL-1beta(Fr)-induced, was always propranolol- and amiloride-sensitive, suggesting that beta-adrenoceptor stimulation and the epithelial Na(+) channel (ENaC) were critical for the induced/stimulated lung fluid absorption. ENaC expression was increased by IL-1beta(Fr) and attenuated by cortisol synthesis inhibition. Thus, our results suggest a potential clinical use of IL-1beta(Fr) therapeutically to induce lung fluid absorption in fetuses at risk of preterm delivery.

Activation of metabotropic glutamate receptor 1 dimers requires glutamate binding in both subunits.

Group I metabotropic glutamate receptors (mGluRs) form stable, disulfide-linked homodimers. Lack of a verifiably monomeric mGluR1 mutant has led to difficulty in assessing the role of dimerization in the molecular mechanism of mGluR1 activation. The related GABA(B) receptor exhibits striking intradimer cross talk (ligand binding at one subunit effectively produces G protein activation at the other), but it is unclear whether group I mGluRs exhibit analogous cross talk. Signaling of heterologously expressed mGluR1 was examined in isolated rat sympathetic neurons by measuring glutamate-mediated inhibition of native calcium currents. To examine mGluR1 activity when only one dimer subunit has access to glutamate ligand, wildtype mGluR1 was coexpressed with mGluR1 Y74A, a mutant with impaired glutamate binding, and the activity of the heterodimer (mutant/wild type) was examined. The mGluR1 Y74A mutant alone had a dose-response curve that was shifted by about 2 orders of magnitude. The half-maximal dose of glutamate shifted from 1.3 (wild-type mGluR1) to about 450 (mGluR1 Y74A) microM. However, the maximal effect was similar. Wild-type mGluR1 was expressed with excess Y74A mGluR1 to generate a receptor population consisting largely of mutant homodimers and mutant/wild-type heterodimers but without detectable wild-type homodimers. Under these conditions, no glutamate-mediated calcium current inhibition was observed below approximately 300 microM glutamate, although wild-type mGluR1 protein was detectable with immunofluorescence. These data suggest that mutant/wild-type heterodimeric receptors are inactive at ligand concentrations favoring glutamate association with receptor dimers at only one subunit.

Aminoglycoside-mediated rescue of a disease-causing nonsense mutation in the V2 vasopressin receptor gene in vitro and in vivo.

Many human diseases are caused by inactivating mutations in specific G-protein-coupled receptors (GPCRs). In about 10% of these cases, a premature stop codon leads to the generation of a truncated, functionally inactive receptor protein. In this study, we tested the hypothesis that such GPCR mutations can be functionally rescued in vitro and in vivo by treatment with aminoglycoside antibiotics, which are known for their ability to suppress premature termination codons. As a model system, we studied a mutant V2 vasopressin receptor (AVPR2) containing the inactivating E242X nonsense mutation which mimics human X-linked nephrogenic diabetes insipidus (XNDI) when introduced into mice via gene targeting techniques. Studies with cultured mammalian cells expressing the E242X mutant receptor showed that G418 (geneticin) was by far the most potent aminoglycoside antibiotic capable of suppressing the E242X nonsense codon. Strikingly, G418 treatment increased AVP-mediated cAMP responses in cultured kidney collecting duct cells prepared from E242X mutant mice in vitro, and significantly improved the urine-concentrating ability of E242X mutant mice in vivo. This is the first study demonstrating that G418 (aminoglycosides) can ameliorate the clinical symptoms of a disease-causing premature stop codon in a member of the GPCR superfamily.

Mice expressing the alpha(1B)-adrenergic receptor induces a synucleinopathy with excessive tyrosine nitration but decreased phosphorylation.

We had previously reported that systemic overexpression of the alpha(1B)-adrenergic receptor (AR) in a transgenic mouse induced a neurodegenerative disease that resembled the parkinsonian-like syndrome called multiple system atrophy (MSA). We now report that our mouse model has cytoplasmic inclusion bodies that colocalize with oligodendrocytes and neurons, are positive for alpha-synuclein and ubiquitin, and therefore may be classified as a synucleinopathy. Alpha-synuclein monomers as well as multimers were present in brain extracts from both normal and transgenic mice. However, similar to human MSA and other synucleinopathies, transgenic mice showed an increase in abnormal aggregated forms of alpha-synuclein, which also increased its nitrated content with age. However, the same extracts displayed decreased phosphorylation of alpha-synuclein. Other traits particular to MSA such as Purkinje cell loss in the cerebellum and degeneration of the intermediolateral cell columns of the spinal cord also exist in our mouse model but differences still exist between them. Interestingly, long-term therapy with the alpha(1)-AR antagonist, terazosin, resulted in protection against the symptomatic as well as the neurodegeneration and alpha-synuclein inclusion body formation, suggesting that signaling of the alpha(1B)-AR is the cause of the pathology. We conclude that overexpression of the alpha(1B)-AR can cause a synucleinopathy similar to other parkinsonian syndromes.

Genetic profiling of alpha 1-adrenergic receptor subtypes by oligonucleotide microarrays: coupling to interleukin-6 secretion but differences in STAT3 phosphorylation and gp-130.

Alpha(1)-adrenoceptor subtypes (alpha(1A)-, alpha(1B)-, alpha(1D)-) are known to couple to similar signaling pathways, although differences among the subtypes do exist. As a more sensitive assay, we used oligonucleotide microarrays to identify gene expression changes in Rat-1 fibroblasts stably expressing each individual subtype. We report the gene expressions that change by at least a factor of 2 or more. Gene expression profiles significantly changed equally among all three subtypes, despite the unequal efficacy of the inositol phosphate response. Gene expressions were clustered into cytokines/growth factors, transcription factors, enzymes, and extracellular matrix proteins. There were also a number of individual subtype-specific changes in gene expression, suggesting a link to independent pathways. In addition, all three alpha(1)-AR subtypes robustly stimulated the transcription of the prohypertrophic cytokine interleukin (IL)-6, but differentially altered members of the IL-6 signaling pathway (gp-130 and STAT3). This was confirmed by measurement of secreted IL-6, activated STAT3, and gp-130 levels. Activation of STAT3 Tyr705 phosphorylation by the alpha(1)-ARs was not through IL-6 activation but was synergistic with IL-6, suggesting direct effects. Interestingly, alpha(1B)-AR stimulation caused the dimerization-dependent phosphorylation of Tyr705 on STAT3 but did not activate the transcriptional-dependent phosphorylation of Ser727. The alpha(1B)-AR also constitutively down-regulated the protein levels of gp-130. These results suggest that the alpha(1B)-AR has differential effects on the phosphorylation status of the STAT3 pathway and may not be as prohypertrophic as the other two subtypes.