In vitro biological responses of plasma nanocoatings for coronary stent applications

In-stent restenosis and thrombosis remain to be long-term challenges in coronary stenting procedures. The objective of this study was to evaluate the in vitro biological responses of trimethylsilane (TMS) plasma nanocoatings modified with NH3 /O2 (2:1 molar ratio) plasma post-treatment (TMS + NH3 /O2 nanocoatings) on cobalt chromium (CoCr) alloy L605 coupons, L605 stents, and 316L stainless steel (SS) stents. Surface properties of the plasma nanocoatings with up to 2-year aging time were characterized by wettability assessment and x-ray photoelectron spectroscopy (XPS). It was found that TMS + NH3 /O2 nanocoatings had a surface composition of 41.21 ± 1.06 at% oxygen, 31.90 ± 1.08 at% silicon, and 24.12 ± 1.7 at% carbon, and very small but essential amount of 2.77 ± 0.18 at% nitrogen. Surface chemical stability of the plasma coatings was noted with persistent O/Si atomic ratio of 1.292-1.413 and N/Si atomic ratio of ~0.087 through 2 years. The in vitro biological responses of plasma nanocoatings were studied by evaluating the cell proliferation and migration of porcine coronary artery endothelial cells (PCAECs) and smooth muscle cells (PCASMCs). 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay results revealed that, after 7-day incubation, TMS + NH3 /O2 nanocoatings maintained a similar level of PCAEC proliferation while showing a decrease in the viability of PCASMCs by 73 ± 19% as compared with uncoated L605 surfaces. Cell co-culture of PCAECs and PCASMCs results showed that, the cell ratio of PCAEC/PCASMC on TMS + NH3 /O2 nanocoating surfaces was 1.5-fold higher than that on uncoated L605 surfaces, indicating enhanced selectivity for promoting PCAEC growth. Migration test showed comparable PCAEC migration distance for uncoated L605 and TMS + NH3 /O2 nanocoatings. In contrast, PCASMC migration distance was reduced nearly 8.5-fold on TMS + NH3 /O2 nanocoating surfaces as compared to the uncoated L605 surfaces. Platelet adhesion test using porcine whole blood showed lower adhered platelets distribution (by 70 ± 16%), reduced clotting attachment (by 54 ± 12%), and less platelet activation on TMS + NH3 /O2 nanocoating surfaces as compared with the uncoated L605 controls. It was further found that, under shear stress conditions of simulated blood flow, TMS + NH3 /O2 nanocoating significantly inhibited platelet adhesion compared to the uncoated 316L SS stents and TMS nanocoated 316L SS stents. These results indicate that TMS + NH3 /O2 nanocoatings are very promising in preventing both restenosis and thrombosis for coronary stent applications.

A novel approach to expedite wound healing with plasma brush of cold flame

Excessive or persistent infection is a major contributing factor in impeding chronic wound healing. Wound bed preparations using antiseptics do not necessarily target the entire bacterial spectrum, and the highly proliferating granulation tissue may be sensitive to the cytotoxic effects, impairing tissue repair. Non-thermal gas atmospheric pressure plasmas are partially ionized gases that contain highly reactive particles while the gas phase remains near room temperature, thus having the capability of accessing small irregular cavities and fissures and killing bacteria because of the diffusive nature of gas phase plasma species that are chemically reactive, providing an ideal approach to topical wound disinfection. A non-thermal plasma brush device of novel design has been developed that is suitable for clinical application in the disinfection of oral and wound bacteria. In vivo studies have indicated that the plasma brush treatment rendered no harmful effect on healthy skin or tissues, while it could improve wound healing in Pseudomonas aeruginosa biofilm infected wounds exposed to an optimized treatment with argon plus 1% nitrogen (Ar + N2) plasma.

The novel pyridazine pyrazolecarboxamide insecticide dimpropyridaz inhibits chordotonal organ function upstream of TRPV channels

BACKGROUND

Pyridazine pyrazolecarboxamides (PPCs) are a novel insecticide class discovered and optimized at BASF. Dimpropyridaz is the first PPC to be submitted for registration and controls many aphid species as well as whiteflies and other piercing-sucking insects.

RESULTS

Dimpropyridaz and other tertiary amide PPCs are proinsecticides that are converted in vivo into secondary amide active forms by N-dealkylation. Active secondary amide metabolites of PPCs potently inhibit the function of insect chordotonal neurons. Unlike Group 9 and 29 insecticides, which hyperactivate chordotonal neurons and increase Ca²⁺ levels, active metabolites of PPCs silence chordotonal neurons and decrease intracellular Ca²⁺ levels. Whereas the effects of Group 9 and 29 insecticides require TRPV (Transient Receptor Potential Vanilloid) channels, PPCs act in a TRPV-independent fashion, without compromising cellular responses to Group 9 and 29 insecticides, placing the molecular PPC target upstream of TRPVs.

CONCLUSIONS

PPCs are a new class of chordotonal organ modulator insecticide for control of piercing-sucking pests. Dimpropyridaz is a PPC proinsecticide that is activated in target insects to secondary amide forms that inhibit the firing of chordotonal organs. The inhibition occurs at a site upstream of TRPVs and is TRPV-independent, providing a novel mode of action for resistance management. © 2023 BASF Corporation. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A Biocompatibility Study of Plasma Nanocoatings onto Cobalt Chromium L605 Alloy for Cardiovascular Stent Applications

The objective of this study was to evaluate the biocompatibility of trimethylsilane (TMS) plasma nanocoatings modified with NH₃/O₂ (2:1 molar ratio) plasma post-treatment onto cobalt chromium (CoCr) L605 alloy coupons and stents for cardiovascular stent applications. Biocompatibility of plasma nanocoatings was evaluated by coating adhesion, corrosion behavior, ion releasing, cytotoxicity, and cell proliferation. Surface chemistry and wettability were studied to understand effects of surface properties on biocompatibility. Results show that NH₃/O₂ post-treated TMS plasma nanocoatings are hydrophilic with water contact angle of 48.5° and have a typical surface composition of O (39.39 at.%), Si (31.92 at.%), C (24.12 at.%), and N (2.77 at.%). The plasma nanocoatings were conformal to substrate surface topography and had excellent adhesion to the alloy substrates, as assessed by tape test (ASTM D3359), and showed no cracking or peeling off L605 stent surfaces after dilation. The plasma nanocoatings also improve the corrosion resistance of CoCr L605 alloy by increasing corrosion potential and decreasing corrosion rates with no pitting corrosion and no mineral adsorption layer. Ion releasing test revealed that Co, Cr, and Ni ion concentrations were reduced by 64-79%, 67-69%, and 57-72%, respectively, in the plasma-nanocoated L605 samples as compared to uncoated L605 control samples. The plasma nanocoatings showed no sign of cytotoxicity from the test results according to ISO 10993-05 and 10993-12. Seven-day cell culture demonstrated that, in comparison with the uncoated L605 control surfaces, the plasma nanocoating surfaces showed 62 ± 7.3% decrease in porcine coronary artery smooth muscle cells (PCASMCs) density and had comparable density of porcine coronary artery endothelial cells (PCAECs). These results suggest that TMS plasma nanocoatings with NH₃/O₂ plasma post-treatment possess the desired biocompatibility for stent applications and support the hypothesis that nanocoated stents could be very effective for in-stent restenosis prevention.

Sorting nexin 1 loss results in increased oxidative stress and hypertension

Acute renal depletion of sorting nexin 1 (SNX1) in mice results in blunted natriuretic response and hypertension due to impaired dopamine D₅ receptor (D₅ R) activity. We elucidated the molecular mechanisms for these phenotypes in Snx1^-/- mice. These mice had increased renal expressions of angiotensin II type 1 receptor (AT₁ R), NADPH oxidase (NOX) subunits, D₅ R, and NaCl cotransporter. Basal reactive oxygen species (ROS), NOX activity, and blood pressure (BP) were also higher in Snx1^-/- mice, which were normalized by apocynin, a drug that prevents NOX assembly. Renal proximal tubule (RPT) cells from hypertensive (HT) Euro-American males had deficient SNX1 activity, impaired D₅ R endocytosis, and increased ROS compared with cells from normotensive (NT) Euro-American males. siRNA-mediated depletion of SNX1 in RPT cells from NT subjects led to a blunting of D₅ R agonist-induced increase in cAMP production and decrease in Na⁺ transport, effects that were normalized by over-expression of SNX1. Among HT African-Americans, three of the 12 single nucleotide polymorphisms interrogated for the SNX1 gene were associated with a decrease in systolic BP in response to hydrochlorothiazide (HCTZ). The results illustrate a new paradigm for the development of hypertension and imply that the trafficking protein SNX1 may be a crucial determinant for hypertension and response to antihypertensive therapy.

Designing a therapeutic hepatitis B vaccine to circumvent immune tolerance

An effective prophylactic hepatitis B virus (HBV) vaccine has long been available but is ineffective for chronic infection. The primary cause of chronic hepatitis B (CHB) and greatest impediment for a therapeutic vaccine is the direct and indirect effects of immune tolerance to HBV antigens. The resulting defective CD4⁺/CD8⁺ T cell response, poor cytokine production, insufficient neutralizing antibody (nAb) and poor response to HBsAg vaccination characterize CHB infection. The objective of this study was to develop virus-like-particles (VLPs) that elicit nAb to prevent viral spread and prime CD4⁺/CD8⁺ T cells to eradicate intracellular HBV. Eight neutralizing B cell epitopes from the envelope PreS1 region were consolidated onto a species-variant of the HBV core protein, the woodchuck hepatitis core antigen (WHcAg). PreS1-specific B cell epitopes were chosen because of preferential expression on HBV virions. Because WHcAg and HBcAg are not crossreactive at the B cell level and only partially cross-reactive at the CD4⁺/CD8⁺ T cell level, CD4⁺ T cells specific for WHcAg-unique T cell sites can provide cognate T-B cell help for anti-PreS1 Ab production that is not curtailed by immune tolerance. Immunization of immune tolerant HBV transgenic (Tg) mice with PreS1-WHc VLPs elicited levels of high titer anti-PreS1 nAbs equivalent to wildtype mice. Passive transfer of PreS1 nAbs into human-liver chimeric mice prevented acute infection and cleared serum HBV from mice previously infected with HBV in a model of CHB. At the T cell level, PreS1-WHc VLPs and hybrid WHcAg/HBcAg DNA immunogens elicited HBcAg-specific CD4⁺ Th and CD8⁺ CTL responses.

Language function in childhood idiopathic epilepsy syndromes

PURPOSE

To examine the impact of diverse syndromes of focal and generalized epilepsy on language function in children with new and recent onset epilepsy. Of special interest was the degree of shared language abnormality across epilepsy syndromes and the unique effects associated with specific epilepsy syndromes.

METHODS

Participants were 136 youth with new or recent-onset (diagnosis within past 12 months) epilepsy and 107 healthy first-degree cousin controls. The participants with epilepsy included 20 with Temporal Lobe Epilepsy (TLE; M age = 12.99  years, SD = 3.11), 41 with Benign Epilepsy with Centrotemporal Spikes (BECTS; M age = 10.32, SD = 1.67), 42 with Juvenile Myoclonic Epilepsy (JME; M age = 14.85, SD = 2.75) and 33 with absence epilepsy (M age = 10.55, SD = 2.76). All children were administered a comprehensive test battery which included multiple measures of language and language-dependent abilities (i.e., verbal intelligence, vocabulary, verbal reasoning, object naming, reception word recognition, word reading, spelling, lexical and semantic fluency, verbal list learning and delayed verbal memory). Test scores were adjusted for age and gender and analyzed via MANCOVA.

RESULTS

Language abnormalities were found in all epilepsy patient groups. The most broadly affected children were those with TLE and absence epilepsy, whose performance differed significantly from controls on 8 of 11 and 9 of 11 tests respectively. Although children with JME and BECTS were less affected, significant differences from controls were found on 4 of 11 tests each. While each group had a unique profile of language deficits, commonalities were apparent across both idiopathic generalized and localization-related diagnostic categories.

DISCUSSION

The localization related and generalized idiopathic childhood epilepsies examined here were associated with impact on diverse language abilities early in the course of the disorder.

A modular route to boron doped PAHs by combining borylative cyclisation and electrophilic C-H borylation

Starting from simple alkynes, sequential borylative cyclisation/electrophilic C–H borylation represents a simple modular route to novel B-doped PAHs.

Heteroatom doping into polyaromatic hydrocarbons (PAHs) is a powerful approach for modifying key physical properties, however, there are extremely few modular routes that enable facile formation of B-, B₂- and B,N-(specifically not containing direct B–N bonds) doped PAHs despite the growing importance of these materials. Sequential, one pot borylative cyclisation/intramolecular electrophilic C–H borylation of naphthyl-alkynes provides a simple new route to access novel B-, B,N- and B₂-doped (PAHs). The initial products, dihydronaphthalene/dihydroquinoline B-mesityl PAHs, were reacted with [Ph₃C][BF₄]/pyridyl base to form the oxidised B-, and B,N-doped PAHs. However, for B-triisopropylphenyl (Trip) PAH congeners oxidation has to be performed prior to Trip installation due to preferential oxidation of an isopropylaryl moiety to the styrene. This alternative sequence enables access to Trip-B-PAHs and to structurally constrained B and B₂-PAHs. Analysis of the solid state structures and optoelectronic properties of these PAHs confirm that frontier orbital energies, extended packing structures, Stokes shift and quantum yields all can be rationally modified using this methodology. The simplicity of this synthetic approach makes it a powerful tool for rapidly generating novel bench stable boron doped PAHs, which is important for facilitating further structure–property relationship studies and the wider utilisation of these materials in optoelectronic applications.

Structural and Functional Characterization of Programmed Ribosomal Frameshift Signals in West Nile Virus Strains Reveals High Structural Plasticity Among cis-Acting RNA Elements

West Nile virus (WNV) is a prototypical emerging virus for which no effective therapeutics currently exist. WNV uses programmed -1 ribosomal frameshifting (-1 PRF) to synthesize the NS1' protein, a C terminally extended version of its non-structural protein 1, the expression of which enhances neuro-invasiveness and viral RNA abundance. Here, the NS1' frameshift signals derived from four WNV strains were investigated to better understand -1 PRF in this quasispecies. Sequences previously predicted to promote -1 PRF strongly promote this activity, but frameshifting was significantly more efficient upon inclusion of additional 3' sequence information. The observation of different rates of -1 PRF, and by inference differences in the expression of NS1', may account for the greater degrees of pathogenesis associated with specific WNV strains. Chemical modification and mutational analyses of the longer and shorter forms of the -1 PRF signals suggests dynamic structural rearrangements between tandem stem-loop and mRNA pseudoknot structures in two of the strains. A model is suggested in which this is employed as a molecular switch to fine tune the relative expression of structural to non-structural proteins during different phases of the viral replication cycle.

Human GRK4γ142V Variant Promotes Angiotensin II Type I Receptor-Mediated Hypertension via Renal Histone Deacetylase Type 1 Inhibition

The influence of a single gene on the pathogenesis of essential hypertension may be difficult to ascertain, unless the gene interacts with other genes that are germane to blood pressure regulation. G-protein-coupled receptor kinase type 4 (GRK4) is one such gene. We have reported that the expression of its variant hGRK4γ(142V) in mice results in hypertension because of impaired dopamine D1 receptor. Signaling through dopamine D1 receptor and angiotensin II type I receptor (AT1R) reciprocally modulates renal sodium excretion and blood pressure. Here, we demonstrate the ability of the hGRK4γ(142V) to increase the expression and activity of the AT1R. We show that hGRK4γ(142V) phosphorylates histone deacetylase type 1 and promotes its nuclear export to the cytoplasm, resulting in increased AT1R expression and greater pressor response to angiotensin II. AT1R blockade and the deletion of the Agtr1a gene normalize the hypertension in hGRK4γ(142V) mice. These findings illustrate the unique role of GRK4 by targeting receptors with opposite physiological activity for the same goal of maintaining blood pressure homeostasis, and thus making the GRK4 a relevant therapeutic target to control blood pressure.

Abstract P180: Dopamine D2 Receptors Regulate Wnt Signaling and Apoptosis in Human Renal Proximal Tubule Cells

Previous work from our laboratory indicates that the dopamine D2 receptor (D2R) in the kidney has a direct role in regulating renal inflammation and injury and blood pressure. Some common single nucleotide polymorphisms (D2R SNPs; rs 6276, 6277, and 1800497) in the human DRD2 gene are associated with decreased D2R expression and function. Immortalized renal proximal tubule cells (RPTCs) from subjects carrying D2R SNPs (RPTC-D2R SNPs) express less D2Rs than RPTCs carrying no D2R SNPs (RPTC-D2R WT) (62±4 vs 100±6%; P<0.04) and a pro-inflammatory and pro-fibrotic phenotype with markers of epithelial mesenchymal transition. RPTC-D2R SNPs showed increased apoptosis compared with RPTC-D2R WT (11± 0.8 vs 2.3±0.4% TUNEL positive cells, P<0.01, n=5/group). We hypothesized that the D2R regulates renal cell survival through effects on Wnt signaling. We found that Wnt3 expression was increased in RPTC-D2R SNPs compared with RPTC-D2R WT (mRNA: 2.6±0.35 vs 1±0.11 fold; P<0.05; protein: 133±4 vs 100±5%; P<0.05). RPTC-D2R SNPs showed activated Wnt3/β-catenin signaling pathway demonstrated by decreased β-catenin phosphorylation (64±4 vs 100±8%; P<0.05) and increased expression of downstream pro-apoptotic factors Bax (136±4.6 vs 100±5%, P<0.05) and FasL (128±5.6 vs 100±6.5%, P<0.05). Silencing D2R in RPTC-D2R WT (siRNA; 0.30±0.02 vs 1±0.07 fold, P<0.05) increased Wnt 3 expression, decreased β-catenin phosphorylation, and increased expression of Bax and FasL. By contrast, treatment of RPTC-D2R WT with a D2R agonist (quinpirole,1μM, 24h) or transfection of RPTC-D2R SNPs with a DRD2 which restored D2R expression decreased Wnt3 expression, increased β-catenin phosphorylation, and decreased Bax and FasL expression. Moreover, Wnt3 silencing (siRNA) in RPTC-D2R SNPs increased β-catenin phosphorylation (132±5 vs100±9%, P<0.05), decreased Bax and FasL expression, and reduced the number of apoptotic cells (6±1.0 vs12± 0.9 % TUNEL positive cells, P<0.01). Our results indicate that D 2 R function is important in the regulation of the Wnt pathway and that the alterations in D 2 R function result in modifications in the pathway potentially leading to fibrosis, cell death, and hypertension. These results may have clinical relevance for subjects bearing D2R SNPs.

Regulation of blood pressure, oxidative stress and AT1R by high salt diet in mutant human dopamine D5 receptor transgenic mice

Humans have dopamine D5 receptors (hD5R) with single-nucleotide polymorphisms and a diminished function. We generated hD5(F173L) cDNA that has a decreased response to D5R agonist-mediated increase in cAMP production and increased production of reactive oxygen species, relative to wild-type hD5R (hD5(WT)) cDNA expressed in Chinese hamster ovary cells. To investigate the role of hD5(F173L) in the pathogenesis of salt-sensitive hypertension, we generated transgenic mice overexpressing hD5(F173L) or hD5(WT) and fed them normal (0.8% NaCl) or high (4% NaCl) salt diet. On normal salt diet, the blood pressure, and renal NADPH oxidase activity and angiotensin type 1 receptor (AT1R) expression were higher in hD5(F173L) than hD5(WT) transgenic mice. After 2 weeks on high salt diet, the blood pressure and renal NADPH oxidase activity, but not AT1R expression, were increased in hD5(F173L) but not in hD5(WT) transgenic mice. Candesartan, an AT1R antagonist, decreased the blood pressure and NADPH oxidase activity in hD5(F173L) but not in hD5(WT) transgenic mice. We suggest that the ability of the hD5R to negatively regulate the renal NADPH oxidase activity and AT1R function may have important implications in the pathogenesis of salt-sensitive blood pressure. However, the mechanisms involved in regulating the balance of renal D5R and AT1R function in the oxidative stress-mediated salt-sensitive blood pressure remain to be determined.

A systematic review of outcome reporting in colorectal cancer surgery

AIM

Evaluation of surgery for colorectal cancer (CRC) is necessary to inform clinical decision-making and healthcare policy. The standards of outcome reporting after CRC surgery have not previously been considered.

METHOD

Systematic literature searches identified randomized and nonrandomized prospective studies reporting clinical outcomes of CRC surgery. Outcomes were listed verbatim, categorized into broad groups (outcome domains) and examined for a definition (an appropriate textual explanation or a supporting citation). Outcome reporting was considered inconsistent if results of the outcome specified in the methods were not reported. Outcome reporting was compared between randomized and nonrandomized studies.

RESULTS

Of 5644 abstracts, 194 articles (34 randomized and 160 nonrandomized studies) were included reporting 766 different clinical outcomes, categorized into seven domains. A mean of 14 ± 8 individual outcomes were reported per study. 'Anastomotic leak', 'overall survival' and 'wound infection' were the three most frequently reported outcomes in 72, 60 and 44 (37.1%, 30.9% and 22.7%) studies, respectively, and no single outcome was reported in every publication. Outcome definitions were significantly more often provided in randomized studies than in nonrandomized studies (19.0% vs 14.9%, P = 0.015). One-hundred and twenty-seven (65.5%) papers reported results of all outcomes specified in the methods (randomized studies, n = 21, 61.5%; nonrandomized studies, n = 106, 66.2%; P = 0.617).

CONCLUSION

Outcome reporting in CRC surgery lacks consistency and method. Improved standards of outcome measurement are recommended to permit data synthesis and transparent cross-study comparisons.

Abstract 296: Sorting Nexin 19: A Novel Regulator of Renal Dopamine D 1 Receptor

The D 1 dopamine receptor (D 1 R) plays a pivotal role in blood pressure regulation. The present study aimed to demonstrate the role of sorting nexin 19 (SNX19) in the regulation of renal D 1 R trafficking and signaling. We tested the dynamic interaction between these proteins and showed that SNX19 coimmunoprecipitated with the D 1 R, as well as with GRK4 and β-arrestin--proteins that are required for D 1 R homologous desensitization, in human renal proximal tubule cells (hPRTCs) and mouse kidney homogenates. These proteins colocalized basally at the cell membrane in hRPTCs, while treatment with the D 1 R/D 5 R agonist fenoldopam (Fen) promoted their endocytosis to the juxtanuclear area, indicating that SNX19 is involved in the agonist-activated D 1 R trafficking. SNX19 silencing in hPRTCs reduced the D 1 R abundance (non-silencing “mock” siRNA=1.0±0.05 vs . Snx19 -specific siRNA=0.45±0.06, P <0.05, n=3/group), although D 1 R depletion did not affect SNX19 expression. SNX19 depletion also blunted the cAMP response after Fen treatment (1μM, 15min) (mock: basal=12.4±4.5 pmol/mg protein vs . mock+Fen=147.8±3.4; Snx19 siRNA: basal=6.8±3.4 vs . siRNA+Fen=63.1±5.4, P <0.05, n=4). Moreover, SNX19 depletion impaired the sodium transport in response to Fen treatment (1μM, 15min) (mock: Δ intracellular Na + from basal= + 15.4±3.2%, vs . Snx19 siRNA: Δ Na + = + 3.3±7.5%, P <0.05, n=3). SNX19 and D 1 R colocalized at the brush border in mouse and human renal proximal tubules at the basal state. Stimulation D 1 -like receptors in mouse kidneys with the intravenous infusion of Fen (2 μg/kg/hr, 15 min) promoted D 1 R internalization with SNX19 and enhanced their colocalization at the cytoplasm. Relative to control mice, the renal selective silencing of Snx19 in C57Bl/6J mice increased the systolic blood pressure (before injection: mock=100±5 mmHg vs . Snx19 siRNA=102±2; after injection: mock=101±6 vs . Snx19 siRNA=118±5, P <0.05, n=5), and decreased renal D 1 R expression (mock=1.0±0.09 vs . Snx19 siRNA=0.57±0.17, P <0.05, n=5). Our results indicate that SNX19 is crucial to normal D 1 R function and that loss of renal SNX19 results in renal D 1 R deficiency and dysfunction. Our data suggest that the absence of SNX19 may be a novel mechanism for the pathogenesis of essential hypertension.

Abstract 257: miR-217 Mediates the Protective Effects of the Dopamine D2 Receptor on Renal Inflammation and Fibrosis

Some common single nucleotide polymorphisms (SNPs; rs 6276, 6277, and 1800497) in the human dopamine D2 receptor (DRD2) gene are associated with decreased receptor expression and function, as well as high blood pressure. We have reported that human renal proximal tubule cells (hRPTCs) from subjects carrying D2R SNPs had decreased D2R expression and function and increased expression of the pro-fibrotic factor TGFβ1 and its signaling targets Smad3 and Snail1. These cells also showed induction of epithelial mesenchymal transition and production of extracellular matrix proteins fibronectin-1 (FN-1), Collagen 1a (Col 1a), and vimentin. To determine the mechanisms underlying the effects of the D2R SNPs, we studied the expression of several microRNAs (miRs) that are associated with the regulation of chemokines, anti-fibrosis, extracellular matrix remodeling, and cell adhesion through post-transcriptional repression of their target mRNAs. The expression of 4 miRs (miR-217, miR-224, miR-335, miR-1265) was downregulated (-10.3 to -6.0 fold) and that of one miRNA (miR-1290; 5.3 fold) was upregulated in hRPTCs with D2R SNPs. The expression of miR-217 and miR-224 is regulated by the D2R; the expression is decreased by D2R downregulation in cells not carrying D2R SNPs (WT) and normalized by treating cells carrying D2R SNPs with a Drd2 plasmid. Treatment of WT cells with a miR-217 mimic significantly decreased the mRNA expression of TGFβ1 (43±2%), MMP3 (65±4%), and FN-1 (30±4%) while treatment with a miR-217 inhibitor increased TGFβ1 (94± 9%), MMP3 (96±5%), and FN-1 (212±30%). miR-217 mimic treatment of D2R SNPs cells also significantly decreased the expression of TGFβ1, MMP3, and FN-1. However, treatment of these cells with a miR-217 inhibitor had non-significant effects probably because miR-217 level was already reduced. In contrast treatment of either WT or D2R SNPs cells with miR-224 mimic or inhibitor had no significant effects on the expression of TGFβ1, MMP3, or FN-1. These results indicate that the protective effects of D2R on inflammation and fibrosis are at least, in part, mediated by regulation of miR-217 expression. Dysregulation of miR-217 expression may be responsible for the profibrotic phenotype of hRPTCs in individuals with these D2R SNPs.

Abstract 573: Uncovering the Molecular Mechanisms Underlying the Hypertension in Snx1 Knockout Mice

We have reported that sorting nexin 1 (SNX1) is crucial for renal dopamine D 5 receptor (D 5 R) trafficking, signal transduction, and function in human renal epithelial cells and in C57Bl/6J and BALB/cJ mice, as shown by the development of hypertension and impaired natriuretic response to agonist stimulation after an acute SNX1 depletion in the kidney. Thus, we elucidated the renal molecular mechanisms for these phenotypes in Snx1 -/- mice, which have congenital absence of SNX1. These mice have increased expression of glycosylated AT 1 R (123.8±2.1 vs . 100±2.0% in wild-type littermates, P<0.05, Student’s t -test, n=5/group), a receptor with pro-oxidant and hypertensinogenic effects. We next determined the expression profiles of the components of the NADPH oxidase (NOX), an enzyme complex that is a major source of reactive oxygen species (ROS). We found an increased expression of renal NOX1 (153.4±12.2% vs . 100±4.1%, P<0.05), NOX2 or gp91 phox (129.9±5.5% vs . 100±7.7%, P<0.05), and p47 phox (118.2±2.7% vs . 100±5.0%, P<0.05), suggesting increased oxidative stress in these mice. Interestingly, the Snx1 null mice have elevated renal D 5 R (142.9±4.7% vs . 100±6.8%, P<0.05) and D 3 R (134.3±5.3% vs . 100 ± 1.6%, P<0.05), receptors with anti-oxidant activity, as well as the antioxidant paraoxonase 2, perhaps as compensatory mechanisms; the loss of SNX1 impairs the function of D 5 R. To corroborate our findings, we treated the Snx1 -/- mice and controls with a 10-day renal infusion of apocynin, a drug that blocks NOX assembly by preventing p47 phox translocation to NOX2. Apocynin treatment resulted in the amelioration of systolic blood pressure (SBP) in Snx1 -/- mice (131.3±4.8 mm Hg to 105.7±1 mm Hg, P<0.05). There was no difference in the SBP with vehicle treatment in both strains, or with apocynin in control mice. Basal NOX activity was higher in Snx1 -/- mice (169±12.8 units/mg protein/min vs . 100±13.3 in controls, P<0.05), which was normalized by apocynin (99.4±16.5), while basal ROS levels were 2-fold higher in the Snx1 -/- mice (218.6±7.7 units/mg protein vs . 100±17.9, P<0.05), which was also normalized by apocynin (125.8±20.4). Our data indicate that the hypertension in Snx1 -/- mice is due to impaired D 5 R activity, higher NOX expression and activity, and increased AT 1 R.

D1-like dopamine receptors downregulate Na+-K+-ATPase activity and increase cAMP production in the posterior gills of the blue crab Callinectes sapidus

Dopamine-mediated regulation of Na(+)-K(+)-ATPase activity in the posterior gills of some crustaceans has been reported to be involved in osmoregulation. The dopamine receptors of invertebrates are classified into three groups based on their structure and pharmacology: D1- and D2-like receptors and a distinct invertebrate receptor subtype (INDR). We tested the hypothesis that a D1-like receptor is expressed in the blue crab Callinectes sapidus and regulates Na(+)-K(+)-ATPase activity. RT-PCR, using degenerate primers, showed the presence of D1βR mRNA in the posterior gill. The blue crab posterior gills showed positive immunostaining for a dopamine D5 receptor (D5R or D1βR) antibody in the basolateral membrane and cytoplasm. Confocal microscopy showed colocalization of Na(+)-K(+)-ATPase and D1βR in the basolateral membrane. To determine the effect of D1-like receptor stimulation on Na(+)-K(+)-ATPase activity, intact crabs acclimated to low salinity for 6 days were given an intracardiac infusion of the D1-like receptor agonist fenoldopam, with or without the D1-like receptor antagonist SCH23390. Fenoldopam increased cAMP production twofold and decreased Na(+)-K(+)-ATPase activity by 50% in the posterior gills. This effect was blocked by coinfusion with SCH23390, which had no effect on Na(+)-K(+)-ATPase activity by itself. Fenoldopam minimally decreased D1βR protein expression (10%) but did not affect Na(+)-K(+)-ATPase α-subunit protein expression. This study shows the presence of functional D1βR in the posterior gills of euryhaline crabs chronically exposed to low salinity and highlights the evolutionarily conserved function of the dopamine receptors on sodium homeostasis.

Abstract 200: Development and Proof of Concept Testing of an Ex Vivo Perfusion Chamber for Studying Platelet Adhesion to Coronary Stents Under Physiological Conditions

Background: Current-generation drug-eluting stents unblock atherosclerotic arteries, inhibit restenosis, but also render the artery prone to thrombosis by inhibiting endothelial cell function. Hence, there is strong clinical interest in developing stents that inhibit restenosis, yet are less thrombogenic. Goals of this study were to 1) develop an ex vivo method to measure platelet adhesion and aggregation on coronary stents under clinically-relevant conditions, and 2) test the hypothesis that treating metal stents with trimethylsilane (TMS) through a novel glow discharge process that coats stents with a nanoscale layer of hydrophobic plasma coating, with or without additional post-deposition glow discharge treatment with NH 3 and O 2 gas, generating elemental nitrogen and oxygen on the stent surface, inhibits platelet adhesion to stents.

Methods: Bare-metal stents (BMS) made of 316L stainless steel was deployed in Masterflex tubing by inflating an over-the-wire coronary balloon within the stent. Tubing containing stents was filled with porcine indium-labeled platelets in anticoagulated whole blood and the ends were connected to create a closed circuit, which was connected to a peristaltic pump to generate unidirectional flow with shear stress of 67 s -1 , similar to that present in human coronary arteries. After 30 min of continuous flow at 37°C the tubing was disconnected and extensively rinsed to remove blood. Platelet adhesion to stents was measured with a gamma counter and by scanning electron microscopy (SEM).

Results: Platelet adhesion to metal stents treated with TMS followed by NH 3 and O 2 (DC-TMS+NH 3 /O 2 ) was 56±8.2% reduced compared to BMS (n=12; P=0.003), whereas TMS treatment alone did not significantly inhibit platelet adhesion. SEM confirmed significantly decreased platelet deposition on DC-TMS+ NH 3 /O 2 stents vs. BMS.

Conclusions: A novel glow discharge surface modification involving TMS, NH 3 , and O 2 gas generates stents with a bioactive surface that resists platelet adhesion under physiological conditions. Our ex vivo perfusion circuit facilitates rapid and precise comparison of stent thrombogenicity under physiological conditions, which should prove useful to other investigators developing coronary stents for clinical use.

Single-nucleotide polymorphisms of the dopamine D2 receptor increase inflammation and fibrosis in human renal proximal tubule cells

The dopamine D2 receptor (D2R) negatively regulates inflammation in mouse renal proximal tubule cells (RPTCs), and lack or downregulation of the receptor in mice increases the vulnerability to renal inflammation independent of blood pressure. Some common single-nucleotide polymorphisms (SNPs; rs6276, rs6277, and rs1800497) in the human DRD2 gene are associated with decreased D2R expression and function, as well as high blood pressure. We tested the hypothesis that human RPTCs (hRPTCs) expressing these SNPs have increased expression of inflammatory and injury markers. We studied immortalized hRPTCs carrying D2R SNPs and compared them with cells carrying no D2R SNPs. RPTCs with D2R SNPs had decreased D2R expression and function. The expressions of the proinflammatory tumor necrosis factor-α and the profibrotic transforming growth factor-β1 and its signaling targets Smad3 and Snail1 were increased in hRPTC with D2R SNPs. These cells also showed induction of epithelial mesenchymal transition and production of extracellular matrix proteins, assessed by increased vimentin, fibronectin 1, and collagen I a1. To test the specificity of these D2R SNP effects, hRPTC with D2R SNPs were transfected with a plasmid encoding wild-type DRD2. The expression of D2R was increased and that of transforming growth factor-β1, Smad3, Snail1, vimentin, fibronectin 1, and collagen I a1 was decreased in hRPTC with D2R SNPs transfected with wild-type DRD2 compared with hRPTC-D2R SNP transfected with empty vector. These data support the hypothesis that D2R function has protective effects in hRPTCs and suggest that carriers of these SNPs may be prone to chronic renal disease and high blood pressure.

Dopamine D3 receptor inhibits the ubiquitin-specific peptidase 48 to promote NHE3 degradation

The dopamine D3 receptor (D3R) is crucial in the regulation of blood pressure and sodium balance, in that Drd3 gene ablation in mice results in hypertension and failure to excrete a dietary salt load. The mechanism responsible for the renal sodium retention in these mice is largely unknown. We now offer and describe a novel mechanism by which D3R decreases sodium transport in the long term by inhibiting the deubiquitinylating activity of ubiquitin-specific peptidase 48 (USP48), thereby promoting Na(+)-H(+) exchanger (NHE)-3 degradation. We found that stimulation with the D3R-specific agonist PD128907 (1 μM, 30 min) promoted the interaction and colocalization among D3R, NHE3, and USP48; inhibited USP48 activity (-35±6%, vs. vehicle), resulting in increased ubiquitinylated NHE3 (+140±10%); and decreased NHE3 expression (-50±9%) in human renal proximal tubule cells (hRPTCs). USP48 silencing decreased NHE3's half-life (USP48 siRNA t1/2=6.1 h vs. vehicle t1/2=12.9 h), whereas overexpression of USP48 increased NHE3 half-life (t1/2=21.8 h), indicating that USP48 protects NHE3 from degradation via deubiquitinylation. USP48 accounted for ∼30% of the total deubiquitinylating activity in these cells. Extending our studies in vivo, we found that pharmacologic blockade of D3R via the D3R-specific antagonist GR103691 (1 μg/kg/min, 4 d) in C57Bl/6J mice increased renal NHE3 expression (+310±15%, vs. vehicle), whereas an innovative kidney-restricted Usp48 silencing via siRNA (3 μg/d, 7 d) increased ubiquitinylated NHE3 (+250±30%, vs. controls), decreased total NHE3 (-23±2%), and lowered blood pressure (-24±2 mm Hg), compared with that in control mice that received either the vehicle or nonsilencing siRNA. Our data demonstrate a crucial role for the dynamic interaction between D3R and USP48 in the regulation of NHE3 expression and function.

Abstract 468: The Dopamine D 1 -like Receptors Negatively Regulate the Expression and Function of the a 1 A Adrenergic Receptor

The homeostatic control of blood pressure hinges upon the delicate balance between pro-hypertensinogenic (e.g., sympathetic nervous system) and anti-hypertensinogenic systems (e.g., dopamine system). The D 1 -like dopamine receptors (D 1 R and D 5 R) and the α 1A adrenergic receptor (ARα 1A ) are endogenously expressed in the renal proximal tubules and engender opposing effects on sodium transport, i.e., natriuresis (D 1 R and D 5 R) or anti-natriuresis (ARα 1A ). We tested the hypothesis that the D 1 R and D 5 R interact with and regulate the ARα 1A in human renal proximal tubule cells (hRPTCs) and in mice. We found that the D 1 R and D 5 R colocalized with the ARα 1A in hRPTCs and in proximal tubules in human kidney sections. Both receptors immunoprecipitated, pulled-down, and co-fractionated with ARα 1A in lipid rafts. Short-term co-treatment with fenoldopam (1 μM, 15 min) reversed the ARα 1 agonist phenylephrine (10 μM, 15 min)-induced Na + ,K + -ATPase (NKA) translocation from the cytosol to the plasma membrane in hRPTCs (plasma membrane NKA: vehicle=100±5% vs. fenoldopam=65±3% vs. phenylephrine=177±5% vs. co-treatment=115±7%; P<0.05, n=3-4). Long-term fenoldopam (1 μM, 24 hr) treatment resulted in decreased D 1 R (70.0±5.9%, P<0.05, n=3) and D 5 R (50.1±10.7%, P<0.05, n=3), consistent with D 1 -like receptor desensitization, but increased ARα 1A abundance (142.6±4.3%, P<0.05, n=3) in hRPTCs. RNAi silencing of ARα 1A (48 hr) increased the expression of D 1 R and D 5 R. To determine the extent of regulation of each D 1 -like receptor on ARα 1A , we used the subclass-selective ARα 1 agonist phenylephrine (5 μg/kg body weight, i.p.) and the receptor-specific ARα 1A agonist A610603 (25 ng/kg body weight, i.p.) to inhibit Na + excretion in three mouse strains. Phenylephrine treatment resulted in 59.6%, 84.2%, 99.3%, and 99.5% reduction from basal level of 24-hr Na + excretion_while A61603 treatment resulted in 42.4%, 67.1%, 99.9%, and 100% reduction_in wild-type controls, D 1 R -/- , and D 5 R -/- knockout mice, and D 1 R/D 5 R -/- double knockout mice, respectively, suggesting a stronger regulatory effect of D 5 R on ARα 1A . Elucidating the intricacies of the interaction among these receptors is crucial for a better understanding of the crosstalk between anti- and pro-hypertensive systems.

Upregulation of renal D5 dopamine receptor ameliorates the hypertension in D3 dopamine receptor-deficient mice

D3 dopamine receptor (D3R)-deficient mice have renin-dependent hypertension associated with sodium retention, but the hypertension is mild. To determine whether any compensatory mechanisms in the kidney are involved in the regulation of blood pressure with disruption of Drd3, we measured the renal protein expression of all dopamine receptor subtypes (D1R, D2R, D4R, and D5R) in D3R homozygous (D3(-/-)) and heterozygous (D3(+/-)) knockout mice and their wild-type (D3(+/+)) littermates. The renal immunohistochemistry and protein expression of D5R were increased (n=5/group) in D3(-/-) mice; renal D4R protein expression was decreased, whereas renal protein expressions of D1R and D2R were similar in both groups. Renal D5R protein expression was also increased in D3(+/-) (n=5/group) relative to D3(+/+) mice, whereas D1R, D2R, and D4R protein expressions were similar in D3(+/-) and D3(+/+) mice. The increase in renal D5R protein expression was abolished when D3(-/-) mice were fed a high-salt diet. Treatment with the D1-like receptor antagonist, SCH23390, increased the blood pressure in anesthetized D3(-/-) but not D3(+/+) mice (n=4/group), suggesting that the renal upregulation of D5R may have minimized the hypertension in D3(-/-) mice. The renal D5R protein upregulation was not caused by increased transcription because renal mRNA expression of D5R was similar in D3(-/-) and D3(+/+) mice. Our findings suggest that the renal upregulation of D5R may have minimized the hypertension that developed in D3(-/-) mice.

Reduced hind limb ischemia-reperfusion injury in Toll-like receptor-4 mutant mice is associated with decreased neutrophil extracellular traps

OBJECTIVE

Ischemia-reperfusion (IR) injury is a significant problem in the management of patients with acute limb ischemia. Despite rapid restoration of blood flow after technically successful open and endovascular revascularization, complications secondary to IR injury continue to occur and limit clinical success. Our aim was to create a murine model of hind limb IR injury to examine the role of Toll-like receptor-4 (TLR4) and to determine whether inactive TLR4 led to a decrease in the detection of neutrophil extracellular traps (NETs), which are known to be highly thrombogenic and may mediate microvascular injury.

METHODS

A calibrated tension tourniquet was applied to unilateral hind limb of wild-type (WT) and TLR4 receptor mutant (TLR4m) mice for 1.5 hours to induce ischemia and then removed to initiate reperfusion. At the end of 48 hours of reperfusion, mice were euthanized and hind limb tissue and serum specimens were collected for analysis. Hematoxylin and eosin-stained sections of hind limb skeletal muscle tissue were examined for fiber injury. For immunohistochemistry, mouse monoclonal antihistone H2A/H2B/DNA complex antibody to detect NETs and rabbit polyclonal antimyeloperoxidase antibody were used to identify infiltrating cells containing myeloperoxidase. Muscle adenosine triphosphate levels, nuclear factor (NF)-κB activity, the α-subunit of inhibitor of NF-κB light polypeptide gene enhancer, poly (adenosine diphosphate-ribose) polymerase activity, and inducible nitric oxide synthase expression were measured. Systemic levels of keratinocyte-derived chemokine, monocyte chemotactic protein-1, and vascular endothelial growth factor in the serum samples were also examined.

RESULTS

IR injury in the hind limb of WT mice demonstrated significant levels of muscle fiber injury, decreased energy substrates, increased NF-κB activation, decreased levels of α-subunit of inhibitor of NF-κB light polypeptide gene enhancer, increased inducible nitric oxide synthase expression, and increased poly (adenosine diphosphate-ribose) polymerase activity levels compared with the TLR4m samples. Additionally, there was marked decrease in the level of neutrophil and monocyte infiltration in the TLR4m mice, which corresponded to similar levels of decreased NET detection in the interstitial space and in microvascular thrombi. In situ nuclease treatment of WT tissue sections significantly diminished the level of NET immunostaining, demonstrating the specificity of the antibody to detect NETs and suggesting a potential role for nuclease treatment in IR injury.

CONCLUSIONS

These results suggest a pivotal role for TLR4 in mediating hind limb IR injury and suggest that NETs may contribute to muscle fiber injury.

The neuropsychological and academic substrate of new/recent-onset epilepsies

OBJECTIVE

To characterize neuropsychological and academic status in children, ages 8-18 years, with new-/recent-onset idiopathic generalized epilepsy (IGE) and idiopathic localization-related epilepsy (ILRE) compared with healthy controls.

STUDY DESIGN

Participants underwent neuropsychological assessment, and parents were interviewed regarding their child's academic history. Cognitive scores for children with epilepsy were age- and sex-adjusted and compared with controls across both broad-band (IGE n = 41 and ILRE n = 53) and narrow-band (childhood/juvenile absence, juvenile myoclonic, benign epilepsy with centro-temporal spikes, and focal [temporal/frontal/not otherwise specified]) syndromes. Academic histories were examined, including problems antecedent to epilepsy onset and diagnosis.

RESULTS

Children with new/recent-onset epilepsies exhibit considerable cognitive abnormality at baseline, including patterns of shared abnormalities across syndromes (eg, psychomotor slowing) as well as unique syndrome-specific cognitive effects (eg, executive function in IGE and language/verbal memory in ILRE) that are observed and sometimes exacerbated in specific IGE and ILRE syndromes. Academic difficulties are evident in approximately 50% of the children with epilepsy, affecting all syndrome groups to an equal degree.

DISCUSSION

Patterns of shared and syndrome-specific cognitive abnormalities and academic problems are present early in the course of virtually all epilepsy syndromes examined here, including syndromes classically viewed as benign. This is the base upon which the effects of recurrent seizures, treatment, and psychosocial effects will be added over time.

Novel role of sorting nexin 5 in renal D(1) dopamine receptor trafficking and function: implications for hypertension

The D1 dopamine receptor (D1R) is widely expressed in the kidney and plays a crucial role in blood pressure regulation. Although much is known about D1R desensitization, especially through G-protein-coupled receptor kinase 4 (GRK4), comparatively little is known about other aspects of D1R trafficking and the proteins involved in the process. We now report the discovery of a dynamic interaction between sorting nexin 5 (SNX5), a component of the mammalian retromer, and D1R in human renal epithelial cells. We show that internalization of agonist-activated D1R is regulated by both SNX5 and GRK4, and that SNX5 is critical to the recycling of the receptor to the plasma membrane. SNX5 depletion increases agonist-activated D1R phosphorylation (>50% at basal condition), prevents D1R internalization and cAMP response, and delays receptor recycling compared to mock siRNA-transfected controls. Moreover, renal restricted subcapsular infusion of Snx5-specific siRNA (vs. mock siRNA) decreases sodium excretion (Δ=-0.2±0.005 mEq/mg creatinine) and further elevates the systolic blood pressure (Δ=48±5 mm Hg) in spontaneously hypertensive rats, indicating that SNX5 depletion impairs renal D1R function. These studies demonstrate an essential role for SNX5 in regulating D1R function, which may have important diagnostic, prognostic, and therapeutic implications in the management of essential hypertension.

Inhibition of Staphylococcus epidermidis biofilm by trimethylsilane plasma coating

Biofilm formation on implantable medical devices is a major impediment to the treatment of nosocomial infections and promotes local progressive tissue destruction. Staphylococcus epidermidis infections are the leading cause of biofilm formation on indwelling devices. Bacteria in biofilms are highly resistant to antibiotic treatment, which in combination with the increasing prevalence of antibiotic resistance among human pathogens further complicates treatment of biofilm-related device infections. We have developed a novel plasma coating technology. Trimethylsilane (TMS) was used as a monomer to coat the surfaces of 316L stainless steel and grade 5 titanium alloy, which are widely used in implantable medical devices. The results of biofilm assays demonstrated that this TMS coating markedly decreased S. epidermidis biofilm formation by inhibiting the attachment of bacterial cells to the TMS-coated surfaces during the early phase of biofilm development. We also discovered that bacterial cells on the TMS-coated surfaces were more susceptible to antibiotic treatment than their counterparts in biofilms on uncoated surfaces. These findings suggested that TMS coating could result in a surface that is resistant to biofilm development and also in a bacterial community that is more sensitive to antibiotic therapy than typical biofilms.

Salt sensitivity of blood pressure is associated with polymorphisms in the sodium-bicarbonate cotransporter

Previous studies have demonstrated that single nucleotide polymorphisms (SNPs) of the sodium-bicarbonate co-transporter gene (SLC4A5) are associated with hypertension. We tested the hypothesis that SNPs in SLC4A5 are associated with salt sensitivity of blood pressure in 185 whites consuming an isocaloric constant diet with a randomized order of 7 days of low Na(+) (10 mmol/d) and 7 days of high Na(+) (300 mmol/d) intake. Salt sensitivity was defined as a ≥ 7-mm Hg increase in mean arterial pressure during a randomized transition between high and low Na(+) diet. A total of 35 polymorphisms in 17 candidate genes were assayed, 25 of which were tested for association. Association analyses with salt sensitivity revealed 3 variants that associated with salt sensitivity, 2 in SLC4A5 (P<0.001) and 1 in GRK4 (P=0.020). Of these, 2 SNPs in SLC4A5 (rs7571842 and rs10177833) demonstrated highly significant results and large effects sizes, using logistic regression. These 2 SNPs had P values of 1.0 × 10(-4) and 3.1 × 10(-4) with odds ratios of 0.221 and 0.221 in unadjusted regression models, respectively, with the G allele at both sites conferring protection. These SNPs remained significant after adjusting for body mass index and age (P=8.9 × 10(-5) and 2.6 × 10(-4) and odds ratios 0.210 and 0.286, respectively). Furthermore, the association of these SNPs with salt sensitivity was replicated in a second hypertensive population. Meta-analysis demonstrated significant associations of both SNPs with salt sensitivity (rs7571842 [P=1.2 × 10(-5)]; rs1017783 [P=1.1 × 10(-4)]). In conclusion, SLC4A5 variants are strongly associated with salt sensitivity of blood pressure in 2 separate white populations.

Abstract 479: A novel Interaction Between G protein-Coupled Receptor Kinase 4 and Sorting Nexin 5 in the Regulation of Dopamine D1 Receptor Phosphorylation

A dysfunction of the renal dopaminergic system is implicated in the pathogenesis of essential hypertension. Independent of renal nerves, the kidney synthesizes dopamine to regulate salt and water homeostasis by inhibiting ion transport in the nephron. The dopamine D 1 receptor (D 1 R) plays a pivotal role in regulating salt metabolism and blood pressure. The regulatory mechanisms or proteins involved in D 1 R trafficking are not completely understood, although our group has reported how G protein-coupled receptor kinase 4 (GRK4) promotes agonist-activated D 1 R desensitization and plasma membrane localization. We have recently identified the sorting nexin 5 (SNX5)_a protein involved in protein trafficking and a member of the mammalian retromer_as a novel binding partner of D 1 R using a yeast two-hybrid screen and have endeavored to elucidate how GRK4 and SNX5 cooperatively interact and regulate the D 1 R. Using a series of biological, biophysical and immunological approaches, we showed that GRK4 and SNX5 colocalize with the D 1 R and that these proteins co-segregate in lipid rafts in human renal proximal tubule cells (hRPTCs). Moreover, endogenous SNX5 co-immunoprecipitated with GRK4, but not with the β-arrestins, another class of proteins involved in D 1 R desensitization; treatment with the D1-like dopamine receptor agonist fenoldopam (1 uM, 15 min) enhanced this process 3-fold (n=3/group). We next determined the functional relevance of this interaction by silencing SNX5 and then evaluating the extent of agonist-activated D 1 R phosphorylation. In control cells that were transfected with non-silencing siRNA, fenoldopam increased D 1 R phosphorylation at 10, 20, and 30 min (137%, 140%, and 148%, respectively, compared to basal; P<0.5 vs. 0 min, n=3/group). Interestingly, SNX5 depletion resulted in 160% increase in phosphorylated D 1 R at the basal state and 145%, 170%, 178% and 200% increase after 5, 10, 20 and 30 min of agonist treatment (P<0.5 vs. 0 min, n=3/group). These indicate that SNX5 restricts the GRK4 from phosphorylating the receptor and may help explain why GRK4 is not involved in early phase of D 1 R desensitization. These data highlight the importance of SNX5 and its interaction with GRK4 in regulating D 1 R function in the control of blood pressure.

Abstract 370: Upregulation of Renal D5 Dopamine Receptor Ameliorates Hypertension in D3 Deficient Mice

D 3 dopamine receptor (D 3 R) deficient mice have renin-dependent hypertension but the hypertension is mild and is not associated with oxidative stress. In order to determine if any compensatory mechanism in the kidney is involved in the regulation of blood pressure with disruption of D 3 R, we measured the renal protein expression of dopamine receptors in D 3 R homozygous (D 3 -/-) and heterozygous (D 3 +/-) knockout mice and their wild type (D 3 +/+) littermates. D 5 dopamine receptor (D 5 R) (169±23%, reported as % of D 3 +/+, n=5/group) expression was increased but D 4 dopamine receptors protein expression (59±8%) was decreased, while no significant changes were found with D 1 and D 2 dopamine receptors. Immunocytochemistry showed a stronger renal staining of D 5 R but without a change in renal tubule cell distribution in D 3 -/- relative to D 3 +/+ mice. D 5 R abundance was also increased in D 3 +/- (205±30%, n=5/group) relative to D 3 +/+ mice, while D 1 R abundance was similar between D 3 +/- and D 3 +/+ mice. The increase in D 5 R expression was abolished while blood pressure was increased further in D 3 -/- mice fed a high salt diet. Treatment of the D 1 -like (including D 1 and D 5 receptors) antagonist, SCH23390 , increased the blood pressure to a greater extent in anesthetized D 3 -/- mice than in D 3 +/+ mice (n=4/group), suggesting that the upregulation of D 5 R may modulate the hypertension in mice caused by the disruption of D 3 R. Since dopamine inhibits the NADPH oxidase-induced production of reactive oxygen species (ROS) via the D 5 R, we also measured the protein expression of NOXs in the kidney and isoprostane in the urine. No NADPH oxidase subunit was increased in D 3 -/- and D 3 +/- mice relative to D 3 +/+ mice fed a normal or salt high salt diet, and urinary isoprostane excretion was also similar in D 3 -/- and D 3 +/+ mice. Our findings suggest that the upregulation of D 5 R may minimize the hypertension and prevent oxidative stress in D 3 -/- mice.

Deficient dopamine D2 receptor function causes renal inflammation independently of high blood pressure

Renal dopamine receptors participate in the regulation of blood pressure. Genetic factors, including polymorphisms of the dopamine D(2) receptor gene (DRD2) are associated with essential hypertension, but the mechanisms of their contribution are incompletely understood. Mice lacking Drd2 (D(2)-/-) have elevated blood pressure, increased renal expression of inflammatory factors, and renal injury. We tested the hypothesis that decreased dopamine D(2) receptor (D(2)R) function increases vulnerability to renal inflammation independently of blood pressure, is an immediate cause of renal injury, and contributes to the subsequent development of hypertension. In D(2)-/- mice, treatment with apocynin normalized blood pressure and decreased oxidative stress, but did not affect the expression of inflammatory factors. In mouse RPTCs Drd2 silencing increased the expression of TNFα and MCP-1, while treatment with a D(2)R agonist abolished the angiotensin II-induced increase in TNF-α and MCP-1. In uni-nephrectomized wild-type mice, selective Drd2 silencing by subcapsular infusion of Drd2 siRNA into the remaining kidney produced the same increase in renal cytokines/chemokines that occurs after Drd2 deletion, increased the expression of markers of renal injury, and increased blood pressure. Moreover, in mice with two intact kidneys, short-term Drd2 silencing in one kidney, leaving the other kidney undisturbed, induced inflammatory factors and markers of renal injury in the treated kidney without increasing blood pressure. Our results demonstrate that the impact of decreased D(2)R function on renal inflammation is a primary effect, not necessarily associated with enhanced oxidant activity, or blood pressure; renal damage is the cause, not the result, of hypertension. Deficient renal D(2)R function may be of clinical relevance since common polymorphisms of the human DRD2 gene result in decreased D(2)R expression and function.

Role of renal DJ-1 in the pathogenesis of hypertension associated with increased reactive oxygen species production

The D(2) dopamine receptor (D(2)R) is important in the pathogenesis of essential hypertension. We have already reported that systemic deletion of the D(2)R gene in mice results in reactive oxygen species (ROS)-dependent hypertension, suggesting that the D(2)R has antioxidant effects. However, the mechanism of this effect is unknown. DJ-1 is a protein that has antioxidant properties. D(2)R and DJ-1 are expressed in the mouse kidney and colocalize and coimunoprecipitate in mouse renal proximal tubule cells. We hypothesized that D(2)Rs regulate renal ROS production in the kidney through regulation of DJ-1 expression or function. Heterozygous D(2)(+/-) mice have increased blood pressure, urinary 8-isoprostanes, and renal Nox 4 expression, but decreased renal DJ-1 expression. Silencing D(2)R expression in mouse renal proximal tubule cells increases ROS production and decreases the expression of DJ-1. Conversely, treatment of these cells with a D(2)R agonist increases DJ-1 expression and decreases Nox 4 expression and NADPH oxidase activity, effects that are partially blocked by a D(2)R antagonist. Silencing DJ-1 expression in mouse renal proximal tubule cells increases ROS production and Nox 4 expression. Selective renal DJ-1 silencing by the subcapsular infusion of DJ-1 siRNA in mice increases blood pressure, renal Nox4 expression, and NADPH oxidase activity. These results suggest that the inhibitory effects of D(2)R on renal ROS production are at least, in part, mediated by a positive regulation of DJ-1 expression/function and that DJ-1 may have a role in the prevention of hypertension associated with increased ROS production.

Genetics of salt-sensitive hypertension

The assessment of salt sensitivity of blood pressure is difficult because of the lack of universal consensus on definition. Regardless of the variability in the definition of salt sensitivity, increased salt intake, independent of the actual level of blood pressure, is also a risk factor for cardiovascular morbidity and mortality and kidney disease. A modest reduction in salt intake results in an immediate decrease in blood pressure, with long-term beneficial consequences. However, some have suggested that dietary sodium restriction may not be beneficial to everyone. Thus, there is a need to distinguish salt-sensitive from salt-resistant individuals, but it has been difficult to do so with phenotypic studies. Therefore, there is a need to determine the genes that are involved in salt sensitivity. This review focuses on genes associated with salt sensitivity, with emphasis on the variants associated with salt sensitivity in humans that are not due to monogenic causes. Special emphasis is given to gene variants associated with salt sensitivity whose protein products interfere with cell function and increase blood pressure in transgenic mice.

Lack of renal dopamine D5 receptors promotes hypertension

Disruption of the dopamine D(5) receptor gene in mice increases BP and causes salt sensitivity. To determine the role of renal versus extrarenal D(5) receptors in BP regulation, we performed cross-renal transplantation experiments. BP was similar between wild-type mice and wild-type mice transplanted with wild-type kidneys, indicating that the transplantation procedure did not affect BP. BP was lower among D(5)(-/-) mice transplanted with wild-type kidneys than D(5)(-/-) kidneys, demonstrating that the renal D(5) receptors are important in BP control. BP was higher in wild-type mice transplanted with D(5)(-/-) kidneys than wild-type kidneys but not significantly different from syngenic transplanted D(5)(-/-) mice, indicating the importance of the kidney in the development of hypertension. On a high-salt diet, all mice with D(5)(-/-) kidneys excreted less sodium than mice with wild-type kidneys. Transplantation of a wild-type kidney into a D(5)(-/-) mouse decreased the renal expression of AT(1) receptors and Nox-2. Conversely, transplantation of a D(5)(-/-) kidney into a wild-type mouse increased the expression of both, suggesting that both renal and extrarenal factors are important in the regulation of AT(1) receptor and Nox-2 expression. These results highlight the role of renal D(5) receptors in BP homeostasis and the pathogenesis of hypertension.

HK-2 human renal proximal tubule cells as a model for G protein-coupled receptor kinase type 4-mediated dopamine 1 receptor uncoupling

HK-2 human renal proximal tubule cells (RPTC) are commonly used in the in vitro study of "normal" RPTCs. We discovered recently that HK-2 cells are uncoupled from dopamine 1 receptor (D(1)R) adenylyl cyclase (AC) stimulation. We hypothesized that G protein-coupled receptor kinase type 4 (GRK4) single nucleotide polymorphisms may be responsible for the D(1)R/AC uncoupling in HK-2. This hypothesis was tested by genotyping GRK4 single nucleotide polymorphisms, measuring D(1)-like receptor agonist (fenoldopam)-stimulated cAMP accumulation, quantifying D(1)R inhibition of sodium transport, and testing the ability of GRK4 small interfering RNA to reverse the D(1)R/AC uncoupling. We compared HK-2 with 2 normally coupled human RPTC cell lines and 2 uncoupled RPTC cell lines. The HK-2 cell line was found to have 4 of 6 potential GRK4 single nucleotide polymorphisms known to uncouple the D(1)R from AC (namely, R65L, A142V, and A486V). AC response to fenoldopam stimulation was increased in the 2 normally coupled human RPTC cell lines (FEN: 2.02+/-0.05-fold and 2.33+/-0.19-fold over control; P<0.001; n=4) but not in the 2 uncoupled or HK-2 cell lines. GRK4 small interfering RNA rescued the fenoldopam-mediated AC stimulation in the uncoupled cells, including HK-2. The expected fenoldopam-mediated inhibition of sodium hydrogen exchanger type 3 was absent in HK-2 (n=6) and uncoupled RPTC cell lines (n=6) but was observed in the 2 normally coupled human RPTC cell lines (-25.41+/-4.7% and -27.36+/-2.70%; P<0.001; n=6), which express wild-type GRK4. Despite the fact that HK-2 cells retain many functional characteristics of RPTCs, they are not normal from the perspective of dopaminergic function.

Upregulation of renal sodium transporters in D5 dopamine receptor-deficient mice

D(5) dopamine receptor (D(5)R)-deficient (D(5)(-/-)) mice have hypertension that is aggravated by an increase in sodium intake. The present experiments were designed to test the hypothesis that a dysregulation of renal sodium transporters is related to the salt sensitivity in D(5)(-/-) mice. D(5)R was expressed in the renal proximal tubule, thick ascending limb, distal convoluted tubule, and cortical and outer medullary collecting ducts in D(5)(+/+) mice. On a control Na(+) diet, renal protein expressions of NKCC2 (sodium-potassium-2 chloride cotransporter), sodium chloride cotransporter, and alpha and gamma subunits of the epithelial sodium channel were greater in D(5)(-/-) than in D(5)(+/+) mice. Renal renin abundance and urine aldosterone levels were similar but renal angiotensin II type 1 receptor (AT(1)R) protein expression was increased in D(5)(-/-) mice. An elevated Na(+) diet increased further the elevated blood pressure of D(5)(-/-) mice but did not affect the normal blood pressure of D(5)(+/+) mice. The increased levels of NKCC2, sodium chloride cotransporter, and alpha and gamma subunits of the epithelial sodium channel persisted with the elevated Na(+) diet and unaffected by chronic AT(1)R blockade (losartan) in D(5)(-/-) mice. The expressions of proximal sodium transporters NHE3 (sodium hydrogen exchanger type 3) and NaPi2 (sodium phosphate cotransporter type 2) were increased by the elevated Na(+) diet in D(5)(-/-) mice; the increased expression of NHE3 but not NaPi2 was abolished by AT(1)R blockade. Our findings suggest that the increased protein expression of sodium transporters/channels in distal nephron segments may be the direct consequence of the disruption of D(5)R, independent of the renin-angiotensin aldosterone system.

Development of Faecalibacterium 16S rRNA gene marker for identification of human faeces

AIMS

The focus of this study was to identify a bacterial 16S rRNA gene sequence, unique to microbiota in the human gut, for use in development of a dependable PCR assay to detect human faecal pollution in water.

METHODS AND RESULTS

Suppression subtractive hybridization (SSH) and bioinformatics were used to identify a genetic marker, within the 16S rRNA gene of Faecalibacterium, for the detection of human faeces. DNA sequencing analysis demonstrated that a majority (16) of 74 clones of the SSH library contained insertion sequences identified as Faecalibacterium 16S rRNA genes. Human faeces-specific sequences were derived and six PCR primer sets designed and tested against faecal DNA samples from human and nonhuman sources. One PCR primer set, HFB-F3 and HFB-R5, was exclusively associated with human faeces. These primers generated a human faeces-specific amplicon of 399 bp from 60.2% of human faecal samples and 100% of sewage samples.

CONCLUSIONS

The subject Faecalibacterium marker is specific for sewage.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study represents the initial report of a Faecalibacterium marker for human faeces, which may prove useful for microbial source tracking.

Use of a Bacteroides thetaiotaomicron-specific alpha-1-6, mannanase quantitative PCR to detect human faecal pollution in water

AIMS

The aims of this work were to develop a quantitative test, based on Bacteroides thetaiotaomicron, for human faecal pollution in water and to evaluate test performance.

METHODS AND RESULTS

qPCR primers, based on the complete genomic sequence of B. thetaiotaomicron VPI 5482, were designed and tested. The single-copy putative mannanase homologue, alpha-1-6 mannanase, was selected as the particular target and sequences within this gene chosen as the qPCR primers by Blast search for specificity to B. thetaiotaomicron. The average concentration of B. thetaiotaomicron in human faeces was 1.39 x 10(8) cells per gram faeces and the detection limit was 9.3 B. thetaiotaomicron copies per qPCR procedure. Comparison of B. thetaiotaomicron content in sewage vs pooled nonhuman faecal samples indicated that the current assay is specific for sewage.

CONCLUSION

The subject assay is potentially useful for quantification of sewage pollution in water.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bacteroides-associated markers, proposed for faecal source tracking, have exclusively been based on gene sequences related to generally classified and uncultured bacteria. However, genes associated with host-microbe interaction have been suggested as more specific markers. The present assay targets such a gene of B. thetaiotaomicron which is considered to be a symbiont in the human gut.

Postischemic poly (ADP-ribose) polymerase (PARP) inhibition reduces ischemia reperfusion injury in a hind-limb ischemia model

BACKGROUND

Several experiments were designed to determine whether the systemic, postischemic administration of PJ34,which is a poly-adenosine diphosphate (ADP)-ribose polymerase inhibitor, decreased tissue injury and inflammation after hind-limb ischemia reperfusion (I/R).

METHODS

C57BL6 mouse limbs were subjected to 1.5 h ischemia followed by 24-h reperfusion. The treatment group (PJ) received intraperitoneal PJ34 (30 mg/kg) immediately before reperfusion, as well as 15 min and 2 h into reperfusion. The control group (CG) received lactated Ringer's alone at the same time intervals as PJ34 administration. The skeletal muscle levels of adenosine triphosphate (ATP), macrophage inflammatory protein-2 (MIP-2), keratinocyte derived chemokine (KC), and myeloperoxidase (MPO) were measured. Quantitative measurement of skeletal muscle tissue injury was assessed by microscopic analysis of fiber injury.

RESULTS

ATP levels were higher in limbs of PJ versus CG mice (absolute ATP: 4.7 +/- 0.35 vs 2.3 +/- 0.15-ng/mg tissue, P = .002). The levels of MIP-2, KC, and MPO were lower in PJ versus CG mice (MIP-2: 1.4 +/- 0.34 vs 3.67 +/- 0.67-pg/mg protein, P = .014; KC: 4.97 +/- 0.97 vs 12.65 +/- 3.05-pg/mg protein, P = .037; MPO: 46.27 +/- 10.53 vs 107.34 +/- 13.58-ng/mg protein, P = .008). Muscle fiber injury was markedly reduced in PJ versus CG mice (4.25 +/- 1.9% vs 22.68 +/- 3.0% total fibers, P = .0004).

CONCLUSION

Systemic postischemic administration of PJ34 preserved skeletal muscle energy levels, decreased inflammatory markers, and preserved tissue viability post-I/R. These results support PARP inhibition as a viable treatment for skeletal muscle I/R in a clinically relevant post hoc scenario.

G protein-coupled receptor kinase 4 (GRK4) regulates the phosphorylation and function of the dopamine D3 receptor

During conditions of moderate sodium excess, the dopaminergic system regulates blood pressure and water and electrolyte balance by engendering natriuresis. Dopamine exerts its effects on dopamine receptors, including the dopamine D(3) receptor. G protein-coupled receptor kinase 4 (GRK4), whose gene locus (4p16.3) is linked to essential hypertension, desensitizes the D(1) receptor, another dopamine receptor. This study evaluated the role of GRK4 on D(3) receptor function in human proximal tubule cells. D(3) receptor co-segregated in lipid rafts and co-immunoprecipitated and co-localized in human proximal tubule cells and in proximal and distal tubules and glomeruli of kidneys of Wistar Kyoto rats. Bimolecular fluorescence complementation and confocal microscopy revealed that agonist activation of the receptor initiated the interaction between D(3) receptor and GRK4 at the cell membrane and promoted it intracellularly, presumably en route to endosomal trafficking. Of the four GRK4 splice variants, GRK4-gamma and GRK4-alpha mediated a 3- and 2-fold increase in the phosphorylation of agonist-activated D(3) receptor, respectively. Inhibition of GRK activity with heparin or knockdown of GRK4 expression via RNA interference completely abolished p44/42 phosphorylation and mitogenesis induced by D(3) receptor stimulation. These data demonstrate that GRK4, specifically the GRK4-gamma and GRK4-alpha isoforms, phosphorylates the D(3) receptor and is crucial for its signaling in human proximal tubule cells.