George P Sorescu

Publications of George P Sorescu

• Speckle-tracking strain echocardiography for detecting cardiac dyssynchrony in a canine model of dyssynchrony and heart failure.

  Authors: Takeshi Arita, George P Sorescu, Brian T Schuler, Laura S Schmarkey, John D Merlino, Jakob Vinten-Johansen, Angel R Leon, Randolph P Martin, Dan Sorescu

  American journal of physiology. Heart and circulatory physiology. 08/2007; 293(1):H735-42.

  Multiple echocardiographic criteria have been proposed to diagnose mechanical dyssynchrony in patients with heart failure without being validated against a model of cardiac dyssynchrony with heartMultiple echocardiographic criteria have been proposed to diagnose mechanical dyssynchrony in patients with heart failure without being validated against a model of cardiac dyssynchrony with heart failure. This study examines which of these methods can detect dyssynchrony in a canine model. Adult mongrel dogs underwent His-bundle ablation and right-ventricular pacing for 4 wk at either 110 bpm to induce dyssynchrony without heart failure (D group, n = 12) or 170 bpm to induce dyssynchrony with heart failure (DHF group, n = 9). To induce heart failure with narrow QRS, atria were paced at 190 bpm for 4 wk (HF group, n = 8). Tissue Doppler imaging (TDI) and two-dimensional echocardiography were performed at baseline and at end of study. Standard deviation of time to peak systolic velocity (color-coded TDI), time to peak S wave on pulse-wave TDI, time to peak radial and circumferential strain by speckle-tracking analysis (E(rr) and E(cc), respectively), and septal-to-posterior wall motion delay on M mode were obtained. In D group, only E(rr) and E(cc) were increased by dyssynchrony. In contrast, all the echocardiographic parameters of dyssynchrony appeared significantly augmented in the DHF group. Receiver-operator curve analysis showed good sensitivity of E(rr) (90%) and E(cc) (100%) to detected dyssynchrony without heart failure and excellent sensitivity and specificity of E(rr) and E(cc) to detect dyssynchrony with heart failure. Radial strain by speckle tracking is more accurate than TDI velocity to detect cardiac dyssynchrony in a canine model of dyssynchrony with or without heart failure.

• Nox4 is required for maintenance of the differentiated vascular smooth muscle cell phenotype.

  Authors: Roza E Clempus, Dan Sorescu, Anna E Dikalova, Lily Pounkova, Patricia Jo, George P Sorescu, Harald H H Schmidt, Bernard Lassègue, Kathy K Griendling

  Arteriosclerosis, thrombosis, and vascular biology. 02/2007; 27(1):42-8.

  OBJECTIVE: The mechanisms responsible for maintaining the differentiated phenotype of adult vascular smooth muscle cells (VSMCs) are incompletely understood. Reactive oxygen species (ROS) have beenOBJECTIVE: The mechanisms responsible for maintaining the differentiated phenotype of adult vascular smooth muscle cells (VSMCs) are incompletely understood. Reactive oxygen species (ROS) have been implicated in VSMC differentiation, but the responsible sources are unknown. In this study, we investigated the role of Nox1 and Nox4-derived ROS in this process. METHODS AND RESULTS: Primary VSMCs were used to study the relationship between Nox homologues and differentiation markers such as smooth muscle alpha-actin (SM alpha-actin), smooth muscle myosin heavy chain (SM-MHC), heavy caldesmon, and calponin. We found that Nox4 and differentiation marker genes were downregulated from passage 1 to passage 6 to 12, whereas Nox1 was gradually upregulated. Nox4 co-localized with SM alpha-actin-based stress fibers in differentiated VSMC, and moved into focal adhesions in de-differentiated cells. siRNA against nox4 reduced NADPH-driven superoxide production in serum-deprived VSMCs and downregulated SM-alpha actin, SM-MHC, and calponin, as well as SM-alpha actin stress fibers. Nox1 depletion did not decrease these parameters. CONCLUSIONS: Nox4-derived ROS are critical to the maintenance of the differentiated phenotype of VSMCs. These findings highlight the importance of identifying the specific source of ROS involved in particular cellular functions when designing therapeutic interventions.

• Simulated microgravity using the Random Positioning Machine inhibits differentiation and alters gene expression profiles of 2T3 preosteoblasts.

  Authors: Steven J Pardo, Mamta J Patel, Michelle C Sykes, Manu O Platt, Nolan L Boyd, George P Sorescu, Min Xu, Jack J W A van Loon, May D Wang, Hanjoong Jo

  American journal of physiology. Cell physiology. 07/2005; 288(6):C1211-21.

  Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, weExposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity compared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcription factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only microgravity-induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis.

• Bone morphogenic protein 4 produced in endothelial cells by oscillatory shear stress induces monocyte adhesion by stimulating reactive oxygen species production from a nox1-based NADPH oxidase.

  Authors: George P Sorescu, Hannah Song, Sarah L Tressel, Jinah Hwang, Sergey Dikalov, Debra A Smith, Nolan L Boyd, Manu O Platt, Bernard Lassègue, Kathy K Griendling, Hanjoong Jo

  Circulation research. 11/2004; 95(8):773-9.

  Atherosclerosis is an inflammatory disease occurring preferentially in arterial regions exposed to disturbed flow conditions including oscillatory shear stress (OS). OS exposure induces endothelialAtherosclerosis is an inflammatory disease occurring preferentially in arterial regions exposed to disturbed flow conditions including oscillatory shear stress (OS). OS exposure induces endothelial expression of bone morphogenic protein 4 (BMP4), which in turn may activate intercellular adhesion molecule-1 (ICAM-1) expression and monocyte adhesion. OS is also known to induce monocyte adhesion by producing reactive oxygen species (ROS) from reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, raising the possibility that BMP4 may stimulate the inflammatory response by ROS-dependent mechanisms. Here we show that ROS scavengers blocked ICAM-1 expression and monocyte adhesion induced by BMP4 or OS in endothelial cells (ECs). Similar to OS, BMP4 stimulated H2O2 and O2- production in ECs. Next, we used ECs obtained from p47phox-/- mice (MAE-p47-/-), which do not produce ROS in response to OS, to determine the role of NADPH oxidases. Similar to OS, BMP4 failed to induce monocyte adhesion in MAE-p47-/-, but it was restored when the cells were transfected with p47phox plasmid. Moreover, OS-induced O2- production was blocked by noggin (a BMP antagonist), suggesting a role for BMP. Furthermore, OS increased gp91phox (nox2) and nox1 mRNA levels while decreasing nox4. In contrast, BMP4 induced nox1 mRNA expression, whereas nox2 and nox4 were decreased or not affected, respectively. Also, OS-induced monocyte adhesion was blocked by knocking down nox1 with the small interfering RNA (siRNA). Finally, BMP4 siRNA inhibited OS-induced ROS production and monocyte adhesion. Together, these results suggest that BMP4 produced in ECs by OS stimulates ROS release from the nox1-dependent NADPH oxidase leading to inflammation, a critical early atherogenic step.

• Oscillatory shear stress stimulates endothelial production of O2- from p47phox-dependent NAD(P)H oxidases, leading to monocyte adhesion.

  Authors: Jinah Hwang, Aniket Saha, Yong Chool Boo, George P Sorescu, J Scott McNally, Steven M Holland, Sergei Dikalov, Don P Giddens, Kathy K Griendling, David G Harrison, Hanjoong Jo

  The Journal of biological chemistry. 12/2003; 278(47):47291-8.

  Arterial regions exposed to oscillatory shear (OS) in branched arteries are lesion-prone sites of atherosclerosis, whereas those of laminar shear (LS) are relatively well protected. Here, we examinedArterial regions exposed to oscillatory shear (OS) in branched arteries are lesion-prone sites of atherosclerosis, whereas those of laminar shear (LS) are relatively well protected. Here, we examined the hypothesis that OS and LS differentially regulate production of O2- from the endothelial NAD(P)H oxidase, which, in turn, is responsible for their opposite effects on a critical atherogenic event, monocyte adhesion. We used aortic endothelial cells obtained from C57BL/6 (MAE-C57) and p47phox-/- (MAE-p47-/-) mice, which lack a component of NAD(P)H oxidase. O2- production was determined by dihydroethidium staining and an electron spin resonance using an electron spin trap methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine. Chronic exposure (18 h) to an arterial level of OS (+/- 5 dynes/cm2) increased O2- (2-fold) and monocyte adhesion (3-fold) in MAE-C57 cells, whereas chronic LS (15 dynes/cm2, 18 h) significantly decreased both monocyte adhesion and O2- compared with static conditions. In contrast, neither LS nor OS were able to induce O2- production and monocyte adhesion to MAE-p47-/-. Treating MAE-C57 with a cell-permeable superoxide dismutase compound, polyethylene glycol-superoxide dismutase, also inhibited OS-induced monocyte adhesion. In addition, over-expressing p47phox in MAE-p47-/- restored OS-induced O2- production and monocyte adhesion. These results suggest that chronic exposure of endothelial cells to OS stimulates O2- and/or its derivatives produced from p47phox-dependent NAD(P)H oxidase, which, in turn, leads to monocyte adhesion, an early and critical atherogenic event.

• High glucose induced NF-kappaB DNA-binding activity in HAEC is maintained under low shear stress but inhibited under high shear stress: role of nitric oxide.

  Authors: Sumathy Mohan, Masao Hamuro, Koichi Koyoma, George P Sorescu, Hanjoong Jo, Mohan Natarajan

  Atherosclerosis. 12/2003; 171(2):225-34.

  In the present study, we investigated whether low shear (LS, 2 dyn/cm2) favors high glucose (HG, 30 mM) induced nuclear factor kappa B (NF-kappaB) activity by regulating NO release in human aorticIn the present study, we investigated whether low shear (LS, 2 dyn/cm2) favors high glucose (HG, 30 mM) induced nuclear factor kappa B (NF-kappaB) activity by regulating NO release in human aortic endothelial cells (HAEC). The results show that (i) under LS, the NF-kappaB activity of HAEC exposed to HG was significantly higher than HAEC in normal glucose (NG, 5.5mM) (P < 0.05). In contrast, under HS, the activation of NF-kappaB in HAEC exposed to HG showed no significant difference compared to that of NG. (ii) The NF-kappaB activity induced by HG is suppressed by high shear (HS) in the absence of a NO synthase inhibitor, Nomega-nitro-L-arginine methyl ester (L-NAME) but restored in its presence, while LS + HG induced NF-kappaB activity remains the same in the presence or absence of L-NAME. (iii) Endothelial nitric oxide synthase (eNOS) protein expression and quantitative detection of NO indicated that high shear stress significantly induced higher eNOS expression and NO production compared to low shear stress condition. Collectively, these data suggest that HS exerts a protective effect on HG induced NF-kappaB activity through NO mediated signaling. LS, on the other hand, may down-regulate eNOS expression resulting in reduced NO release, and thereby maintain high glucose induced NF-kappaB DNA-binding activity. These observations explain, in part, the mechanism by means of which hyperglycemia accelerates the focal development of atherosclerotic lesions in low shear (lesion prone) areas of the arterial tree.

• Endothelial NO synthase phosphorylated at SER635 produces NO without requiring intracellular calcium increase.

  Authors: Yong Chool Boo, George P Sorescu, Philip M Bauer, David Fulton, Bruce E Kemp, David G Harrison, William C Sessa, Hanjoong Jo

  Free radical biology & medicine. 11/2003; 35(7):729-41.

  Shear stress stimulates NO production involving the Ca2+-independent mechanisms in endothelial cells. We have shown that exposure of bovine aortic endothelial cells (BAEC) to shear stress stimulatesShear stress stimulates NO production involving the Ca2+-independent mechanisms in endothelial cells. We have shown that exposure of bovine aortic endothelial cells (BAEC) to shear stress stimulates phosphorylation of eNOS at S635 and S1179 by the protein kinase A- (PKA-) dependent mechanisms. We examined whether phosphorylation of S635 of eNOS induced by PKA stimulates NO production in a calcium-independent manner. Expression of a constitutively active catalytic subunit of PKA (Cqr) in BAEC induced phosphorylation of S635 and S1179 residues and dephosphorylation of T497. Additionally, Cqr expression stimulated NO production, which could not be prevented by treating cells with the intracellular calcium chelator BAPTA-AM. To determine the role of each eNOS phosphorylation site in NO production, HEK-293 cells transfected with eNOS point mutants whereby S116, T497, S635, and S1179 were mutated to either A or D. Maximum NO production from S635D-expressing cells was significantly higher than that of either wild type or S635A in both basal and elevated [Ca2+]i conditions. More interestingly, S635D cells produced NO even when [Ca2+]i was nearly depleted by BAPTA-AM. We confirmed these results obtained in HEK-293 cells in BAEC transfected with S635D, S635A, or wild-type eNOS vector. These findings suggest that, once phosphorylated at S635 residue, eNOS produces NO without requiring any changes in [Ca2+]i. PKA-dependent phosphorylation of eNOS S635 and subsequent basal NO production in a Ca2+-independent manner may play an important role in regulating vascular biology and pathophysiology.

• Chronic shear induces caveolae formation and alters ERK and Akt responses in endothelial cells.

  Authors: Nolan L Boyd, Heonyong Park, Hong Yi, Yong Chool Boo, George P Sorescu, Michelle Sykes, Hanjoong Jo

  American journal of physiology. Heart and circulatory physiology. 10/2003; 285(3):H1113-22.

  Caveolae are plasmalemmal domains enriched with cholesterol, caveolins, and signaling molecules. Endothelial cells in vivo are continuously exposed to shear conditions, and their caveolae density andCaveolae are plasmalemmal domains enriched with cholesterol, caveolins, and signaling molecules. Endothelial cells in vivo are continuously exposed to shear conditions, and their caveolae density and location may be different from that of static cultured cells. Here, we show that chronic shear exposure regulates formation and localization of caveolae and caveolin-1 in bovine aortic endothelial cells (BAEC). Chronic exposure (1 or 3 days) of BAEC to laminar shear increased the total number of caveolae by 45-48% above static control. This increase was due to a rise in the luminal caveolae density without changing abluminal caveolae numbers or increasing caveolin-1 mRNA and protein levels. Whereas some caveolin-1 was found in the plasma membrane in static-cultured cells, it was predominantly localized in the Golgi. In contrast, chronic shear-exposed cells showed intense caveolin-1 staining in the luminal plasma membrane with minimum Golgi association. The preferential luminal localization of caveolae may play an important role in endothelial mechanosensing. Indeed, we found that chronic shear exposure (preconditioning) altered activation patterns of two well-known shear-sensitive signaling molecules (ERK and Akt) in response to a step increase in shear stress. ERK activation was blunted in shear preconditioned cells, whereas the Akt response was accelerated. These results suggest that chronic shear stimulates caveolae formation by translocating caveolin-1 from the Golgi to the luminal plasma membrane and alters cell signaling responses.

• Bone morphogenic protein 4 produced in endothelial cells by oscillatory shear stress stimulates an inflammatory response.

  Authors: George P Sorescu, Michelle Sykes, Daiana Weiss, Manu O Platt, Aniket Saha, Jinah Hwang, Nolan Boyd, Yong C Boo, J David Vega, W Robert Taylor, Hanjoong Jo

  The Journal of biological chemistry. 09/2003; 278(33):31128-35.

  Atherosclerosis is now viewed as an inflammatory disease occurring preferentially in arterial regions exposed to disturbed flow conditions, including oscillatory shear stress (OS), in branchedAtherosclerosis is now viewed as an inflammatory disease occurring preferentially in arterial regions exposed to disturbed flow conditions, including oscillatory shear stress (OS), in branched arteries. In contrast, the arterial regions exposed to laminar shear (LS) are relatively lesion-free. The mechanisms underlying the opposite effects of OS and LS on the inflammatory and atherogenic processes are not clearly understood. Here, through DNA microarrays, protein expression, and functional studies, we identify bone morphogenic protein 4 (BMP4) as a mechanosensitive and pro-inflammatory gene product. Exposing endothelial cells to OS increased BMP4 protein expression, whereas LS decreased it. In addition, we found BMP4 expression only in the selective patches of endothelial cells overlying foam cell lesions in human coronary arteries. The same endothelial patches also expressed higher levels of intercellular cell adhesion molecule-1 (ICAM-1) protein compared with those of non-diseased areas. Functionally, we show that OS and BMP4 induced ICAM-1 expression and monocyte adhesion by a NFkappaB-dependent mechanism. We suggest that BMP4 is a mechanosensitive, inflammatory factor playing a critical role in early steps of atherogenesis in the lesion-prone areas.

• Mechanisms of VE-cadherin processing and degradation in microvascular endothelial cells.

  Authors: Kanyan Xiao, David F Allison, Margaret D Kottke, Susan Summers, George P Sorescu, Victor Faundez, Andrew P Kowalczyk

  The Journal of biological chemistry. 06/2003; 278(21):19199-208.

  VE-cadherin is an endothelial-specific cadherin that plays important roles in vascular morphogenesis and growth control. To investigate the mechanisms by which endothelial cells regulate cadherinVE-cadherin is an endothelial-specific cadherin that plays important roles in vascular morphogenesis and growth control. To investigate the mechanisms by which endothelial cells regulate cadherin cell surface levels, a VE-cadherin mutant containing the non-adhesive interleukin-2 (IL-2) receptor extracellular domain and the VE-cadherin cytoplasmic tail (IL-2R-VE-cadcyto) was expressed in microvascular endothelial cells. Expression of the IL-2R-VE-cadcyto mutant resulted in the internalization of endogenous VE-cadherin and in a dramatic decrease in endogenous VE-cadherin levels. The internalized VE-cadherin co-localized with early endosomes, and the lysosomal inhibitor chloroquine dramatically inhibited the down-regulation of VE-cadherin in cells expressing the IL-2R-VE-cadcyto mutant. Chloroquine treatment also resulted in the accumulation of a VE-cadherin fragment lacking the beta-catenin binding domain of the VE-cadherin cytoplasmic tail. The formation of the VE-cadherin fragment could be prevented by treating endothelial cells with proteasome inhibitors. Furthermore, inhibition of the proteasome prevented VE-cadherin internalization and inhibited the disruption of endothelial intercellular junctions by the IL-2RVE-cadcyto mutant. These results provide new insights into the mechanisms of VE-cadherin processing and degradation in microvascular endothelial cells.

• IkappaBalpha-dependent regulation of low-shear flow-induced NF-kappa B activity: role of nitric oxide.

  Authors: Sumathy Mohan, Masao Hamuro, George P Sorescu, Koichi Koyoma, Eugene A Sprague, Hanjoong Jo, Anthony J Valente, Thomas J Prihoda, Mohan Natarajan

  American journal of physiology. Cell physiology. 05/2003; 284(4):C1039-47.

  We have investigated the role of inhibitor kappaBalpha (IkappaBalpha) in the activation of nuclear factor kappaB (NF-kappaB) observed in human aortic endothelial cells (HAEC) undergoing a low shearWe have investigated the role of inhibitor kappaBalpha (IkappaBalpha) in the activation of nuclear factor kappaB (NF-kappaB) observed in human aortic endothelial cells (HAEC) undergoing a low shear stress of 2 dynes/cm(2). Low shear for 6 h resulted in a reduction of IkappaBalpha levels, an activation of NF-kappaB, and an increase in kappaB-dependent vascular cell adhesion molecule 1 (VCAM-1) mRNA expression and endothelial-monocyte adhesion. Overexpression of IkappaBalpha in HAEC attenuated all of these shear-induced responses. These results suggest that downregulation of IkappaBalpha is the major factor in the low shear-induced activation of NF-kappaB in HAEC. We then investigated the role of nitric oxide (NO) in the regulation of IkappaBalpha/NF-kappaB. Overexpression of endothelial nitric oxide synthase (eNOS) inhibited NF-kappaB activation in HAEC exposed to 6 h of low shear stress. Addition of the structurally unrelated NO donors S-nitrosoglutathione (300 microM) or sodium nitroprusside (1 mM) before low shear stress significantly increased cytoplasmic IkappaBalpha and concomitantly reduced NF-kappaB binding activity and kappaB-dependent VCAM-1 promoter activity. Together, these data suggest that NO may play a major role in the regulation of IkappaBalpha levels in HAEC and that the application of low shear flow increases NF-kappaB activity by attenuating NO generation and thus IkappaBalpha levels.

• Compensatory phosphorylation and protein-protein interactions revealed by loss of function and gain of function mutants of multiple serine phosphorylation sites in endothelial nitric-oxide synthase.

  Authors: Philip M Bauer, David Fulton, Yong Chool Boo, George P Sorescu, Bruce E Kemp, Hanjoong Jo, William C Sessa

  The Journal of biological chemistry. 05/2003; 278(17):14841-9.

  We examined the influence of individual serine phosphorylation sites in endothelial nitric-oxide synthase (eNOS) on basal and stimulated NO release, cooperative phosphorylation, and co-associationWe examined the influence of individual serine phosphorylation sites in endothelial nitric-oxide synthase (eNOS) on basal and stimulated NO release, cooperative phosphorylation, and co-association with hsp90 and Akt. Mutation of the serine phosphorylation sites 116, 617, and 1179 to alanines affected the phospho-state of at least one other site, demonstrating cooperation between multiple phosphorylation events, whereas mutation of serine 635 to alanine did not cause compensation. Mutation of serines 116 and 617 to alanine promoted a greater protein-protein interaction with hsp90 and Akt and greater phosphorylation on serine 1179, the major site for Akt phosphorylation. More importantly, using alanine substitutions, Ser-116 is important for agonist, but not basal NO release, Ser-635 is important for basal, but not stimulated, Ser-617 negatively regulates basal and stimulated NO release, and Ser-1179 phosphorylation is stimulatory for both basal and agonist-mediated NO release. Using putative "gain of function" mutants (serine to aspartate) serines 635 and 1179 are important positive regulators of basal and stimulated NO release. S635D eNOS is the most efficacious, yielding 5-fold increases in basal and 2-fold increases in stimulated NO release from cells. However, S617A and S617D eNOS both increased NO release with opposite actions in NOS activity assays. Thus, multiple serine phosphorylation events regulate basal and stimulate NO release with Ser-635 and Ser-1179 being important positive regulatory sites and Ser-116 as a negative regulatory. Ser-617 may not be important for directly regulating NO release but is important as a modulator of phosphorylation at other sites and protein-protein interactions.

• Superoxide production and expression of nox family proteins in human atherosclerosis.

  Authors: Dan Sorescu, Daiana Weiss, Bernard Lassègue, Roza E Clempus, Katalin Szöcs, George P Sorescu, Liisa Valppu, Mark T Quinn, J David Lambeth, J David Vega, W Robert Taylor, Kathy K Griendling

  Circulation. 04/2002; 105(12):1429-35.

  BACKGROUND: NAD(P)H oxidases are important sources of superoxide in the vasculature, the activity of which is associated with risk factors for human atherosclerosis. This study was designed toBACKGROUND: NAD(P)H oxidases are important sources of superoxide in the vasculature, the activity of which is associated with risk factors for human atherosclerosis. This study was designed to investigate the localization of superoxide production and the expression of the Nox family of NAD(P)H oxidase proteins (gp91phox, Nox1, and Nox4) in nonatherosclerotic and atherosclerotic human coronary arteries. METHODS AND RESULTS: In coronary artery segments from explanted human hearts, we examined intracellular superoxide production with dihydroethidium. In nonatherosclerotic coronary arteries, superoxide was present homogenously throughout the intima, media, and adventitia. In atherosclerotic arteries, there was an additional intense area of superoxide in the plaque shoulder, which is rich in macrophages and alpha-actin-positive cells. p22phox colocalized with gp91phox mainly in macrophages, whereas Nox4 was found only in nonphagocytic vascular cells. Expression of gp91phox and p22phox mRNA was associated with the severity of atherosclerosis. gp91phox correlated with the plaque macrophage content, whereas Nox4 correlated with the content of alpha-actin-positive cells. Nox1 expression was low both in human coronary arteries and isolated vascular cells. CONCLUSIONS: Several Nox proteins, including gp91phox and Nox4, may contribute to increased intracellular oxidative stress in human coronary atherosclerosis in a cell-specific manner and thus may be involved in the genesis and progression of human coronary atherosclerotic disease.

• Endothelial NO synthase phosphorylated at SER635 produces NO without requiring intracellular calcium increase

  Authors: Yong Chool Boo, George P Sorescu, Philip M Bauer, David Fulton, Bruce E Kemp, David G Harrison, William C Sessa, Hanjoong Jo

  Free Radical Biology and Medicine.

  Shear stress stimulates NO production involving the Ca2+-independent mechanisms in endothelial cells. We have shown that exposure of bovine aortic endothelial cells (BAEC) to shear stress stimulatesShear stress stimulates NO production involving the Ca2+-independent mechanisms in endothelial cells. We have shown that exposure of bovine aortic endothelial cells (BAEC) to shear stress stimulates phosphorylation of eNOS at S635 and S1179 by the protein kinase A- (PKA-) dependent mechanisms. We examined whether phosphorylation of S635 of eNOS induced by PKA stimulates NO production in a calcium-independent manner. Expression of a constitutively active catalytic subunit of PKA (Cqr) in BAEC induced phosphorylation of S635 and S1179 residues and dephosphorylation of T497. Additionally, Cqr expression stimulated NO production, which could not be prevented by treating cells with the intracellular calcium chelator BAPTA-AM. To determine the role of each eNOS phosphorylation site in NO production, HEK-293 cells transfected with eNOS point mutants whereby S116, T497, S635, and S1179 were mutated to either A or D. Maximum NO production from S635D-expressing cells was significantly higher than that of either wild type or S635A in both basal and elevated [Ca2+]i conditions. More interestingly, S635D cells produced NO even when [Ca2+]i was nearly depleted by BAPTA-AM. We confirmed these results obtained in HEK-293 cells in BAEC transfected with S635D, S635A, or wild-type eNOS vector. These findings suggest that, once phosphorylated at S635 residue, eNOS produces NO without requiring any changes in [Ca2+]i. PKA-dependent phosphorylation of eNOS S635 and subsequent basal NO production in a Ca2+-independent manner may play an important role in regulating vascular biology and pathophysiology.