Adolescents' exposure to and evaluation of food promotions on social media: a multi-method approach.

BACKGROUND: Traditional food marketing, mostly involving advertisement of nutrient poor and energy dense foods, has the effect of enhancing attitudes, preferences, and increasing intake of marketed foods in adolescents, with detrimental consequences for health. While the use of social media applications in adolescents has proliferated, little is known about the content of food promotions within these applications. The aim of this study was to investigate adolescents' exposure to and evaluation of social media food promotions (SMFPs). METHODS: Australian adolescents aged 13-16 years joined one-on-one Zoom meetings with the researcher on the device they normally used for social media. Participants shared their screen and visited up to three of their favourite social media platforms for 10 min each, during which the researcher pointed out examples of SMFPs to participants. Next, participants answered questions about their awareness and appreciation of SMFPs. Screenshots of SMFPs were de-identified and analysed. RESULTS: The study included 35 adolescents aged 14.4 (± 1.2) years (boys: n = 18; girls: n = 17). Instagram, Snapchat and YouTube were the most favoured social media platforms. During a total of 1000 min of viewing time, 1801 unbranded (n = 1221) and branded (n = 580) SMFPs were identified. Participants viewed a median rate (IQR) of 12.0 (6.3-20) SMFPs per 10 min, with a median rate of 6.0 (3-11) non-core SMFPs per 10 min. A majority of SMFPs (62%) were embedded into celebrity influencer or entertaining content (e.g., vlogs, cooking videos, streamed TV content). In total, 60% of the participants said they had sometimes, rarely or never noticed the SMFPs pointed out by the researcher themselves. Participants largely remembered non-core foods or brands (77%). Almost half (49%) of participants liked SMFPs, while only 6% disliked them. CONCLUSIONS: This study contributes to a relatively unexplored research area. The outcomes show adolescents' SMFP exposure mostly concerns unhealthy foods, shown in advertisements and other food-related posts, which are integrated into a wide variety of entertainment that is appreciated by adolescents. The results emphasise the need for more research on SMFPs, with particular focus on the impact on adolescent dietary behaviours, and clearer definitions and stricter regulations regarding adolescent-targeted social media food marketing.

Factors influencing SARS-CoV-2 infection rate in Belgian nursing home residents during the first wave of COVID-19 pandemic.

In April 2020, Belgium experienced high numbers of fatal COVID-19 cases among nursing home (NH) residents. In response, a mass testing campaign was organised testing all NH residents and staff. We analysed the data of Flemish NHs to identify institutional factors associated with increased SARS-CoV-2 infection rates among NH residents. Cross-sectional study was conducted between 8 April and 15 May 2020. Data collected included demographics, group category (i.e. staff or resident), symptom status and test result. We retrieved additional data: number of beds and staff, type of beds (level of dependency of residents) and ownership (public, private for profit/non-profit institutions). Risk factor analysis was performed using negative binomial regression. In total, 695 NHs were included, 282 (41%) had at least one resident tested positive. Higher infection rate among residents was associated with a higher fraction of RVT beds, generally occupied by more dependent residents (incidence rate ratio (IRR) 1.97; 95% CI 1.00-3.86) and higher staff infection rate (IRR 1.89; 95% CI 1.68-2.12). No relationship was found between other investigated NH characteristics and infection rate among residents. Staff-resident interactions are key in SARS-CoV-2 transmission dynamics. Vaccination, regular staff testing, assessment of infection prevention and control strategies in all NHs are needed to face future SARS-CoV-2 epidemics in these settings.

Seasonality of urinary tract infections in the United Kingdom in different age groups: longitudinal analysis of The Health Improvement Network (THIN).

Evidence regarding the seasonality of urinary tract infection (UTI) consultations in primary care is conflicting and methodologically poor. To our knowledge, this is the first study to determine whether this seasonality exists in the UK, identify the peak months and describe seasonality by age. The monthly number of UTI consultations (N = 992 803) and nitrofurantoin and trimethoprim prescriptions (N = 1 719 416) during 2008-2015 was extracted from The Health Improvement Network (THIN), a large nationally representative UK dataset of electronic patient records. Negative binomial regression models were fitted to these data to investigate seasonal fluctuations by age group (14-17, 18-24, 25-45, 46-69, 70-84, 85+) and by sex, accounting for a change in the rate of UTI over the study period. A September to November peak in UTI consultation incidence was observed for ages 14-69. This seasonality progressively faded in older age groups and no seasonality was found in individuals aged 85+, in whom UTIs were most common. UTIs were rare in males but followed a similar seasonal pattern than in females. We show strong evidence of an autumnal seasonality for UTIs in individuals under 70 years of age and a lack of seasonality in the very old. These findings should provide helpful information when interpreting surveillance reports and the results of interventions against UTI.

Does appropriate empiric antibiotic therapy modify intensive care unit-acquired Enterobacteriaceae bacteraemia mortality and discharge?

BACKGROUND: Conflicting results have been found regarding outcomes of intensive care unit (ICU)-acquired Enterobacteriaceae bacteraemia and the potentially modifying effect of appropriate empiric antibiotic therapy. AIM: To evaluate these associations while adjusting for potential time-varying confounding using methods from the causal inference literature. METHODS: Patients who stayed more than two days in two general ICUs in England between 2002 and 2006 were included in this cohort study. Marginal structural models with inverse probability weighting were used to estimate the mortality and discharge associated with Enterobacteriaceae bacteraemia and the impact of appropriate empiric antibiotic therapy on these outcomes. FINDINGS: Among 3411 ICU admissions, 195 (5.7%) ICU-acquired Enterobacteriaceae bacteraemia cases occurred. Enterobacteriaceae bacteraemia was associated with an increased daily risk of ICU death [cause-specific hazard ratio (HR): 1.48; 95% confidence interval (CI): 1.10-1.99] and a reduced daily risk of ICU discharge (HR: 0.66; 95% CI: 0.54-0.80). Appropriate empiric antibiotic therapy did not significantly modify ICU mortality (HR: 1.08; 95% CI: 0.59-1.97) or discharge (HR: 0.91; 95% CI: 0.63-1.32). CONCLUSION: ICU-acquired Enterobacteriaceae bacteraemia was associated with an increased daily risk of ICU mortality. Furthermore, the daily discharge rate was also lower after acquiring infection, even when adjusting for time-varying confounding using appropriate methodology. No evidence was found for a beneficial modifying effect of appropriate empiric antibiotic therapy on ICU mortality and discharge.

Seasonal changes in the incidence of Escherichia coli bloodstream infection: variation with region and place of onset.

Previous research has shown that Escherichia coli infection rates peak in the summer; however, to date there has been no investigation as to whether this is seen in both hospital and community-onset cases, and how this differs across regions. We investigated and quantified E. coli bloodstream infection (BSI) seasonality. A generalized additive Poisson model was fitted to mandatory E. coli BSI surveillance data reported in England. There was no impact of seasonality in hospital-onset cases; however, for the community-onset cases, there was statistically significant seasonal variation over time nationally. When examined regionally, seasonality was significant in the North of England only. This variation resulted in an absolute increase of 0.06 (95% CI 0.02-0.1) cases above the mean (3.25) in each hospital trust for each week of the peak summer season, and a decrease of (-) 0.07 (95% CI -0.1 to -0.03) in the autumn. We estimate that fewer than one hospital bed-day per week per hospital is lost because of seasonal increases during the summer. Our findings highlight the need to understand the distinct community and hospital dynamics of E. coli BSI, and to explore the regional differences driving the variation in incidence, in order to design and implement effective control measures.

Reduction in Clostridium difficile environmental contamination by hospitalized patients treated with fidaxomicin.

Fidaxomicin is sporicidal and may be associated with a reduced time to resolution of diarrhoea when used to treat patients with Clostridium difficile infection (CDI). This study investigated whether fidaxomicin for treatment of all patients with CDI reduced C. difficile environmental contamination. Surfaces in the rooms of 66 hospitalized patients treated with metronidazole and/or vancomycin and 68 hospitalized patients treated with fidaxomicin were sampled. Patients treated with fidaxomicin were less likely to contaminate their environment (25/68, 36.8%) than patients treated with metronidazole and/or vancomycin (38/66 57.6%) (P = 0.02). Treatment with fidaxomicin was associated with reduced environmental contamination with C. difficile.

Excess length of stay and mortality due to Clostridium difficile infection: a multi-state modelling approach.

BACKGROUND: The burden of healthcare-associated infections, such as healthcare-acquired Clostridium difficile (HA-CDI), can be expressed in terms of additional length of stay (LOS) and mortality. However, previous estimates have varied widely. Although some have considered time of infection onset (time-dependent bias), none considered the impact of severity of HA-CDI; this was the primary aim of this study. METHODS: The daily risk of in-hospital death or discharge was modelled using a Cox proportional hazards model, fitted to data on patients discharged in 2012 from a large English teaching hospital. We treated HA-CDI status as a time-dependent variable and adjusted for confounders. In addition, a multi-state model was developed to provide a clinically intuitive metric of delayed discharge associated with non-severe and severe HA-CDI respectively. FINDINGS: Data comprised 157 (including 48 severe) HA-CDI cases among 42,618 patients. HA-CDI reduced the daily discharge rate by nearly one-quarter [hazard ratio (HR): 0.72; 95% confidence interval (CI): 0.61-0.84] and increased the in-hospital death rate by 75% compared with non-HA-CDI patients (HR: 1.75; 95% CI: 1.16-2.62). Whereas overall HA-CDI resulted in a mean excess LOS of about seven days (95% CI: 3.5-10.9), severe cases had an average excess LOS which was twice (∼11.6 days; 95% CI: 3.6-19.6) that of the non-severe cases (about five days; 95% CI: 1.1-9.5). CONCLUSION: HA-CDI contributes to patients' expected LOS and risk of mortality. However, when quantifying the health and economic burden of hospital-onset of HA-CDI, the heterogeneity in the impact of HA-CDI should be accounted for.

Successful development of satiety enhancing food products: towards a multidisciplinary agenda of research challenges.

In the context of increasing prevalence of overweight and obesity in societies worldwide, enhancing the satiating capacity of foods may help people control their energy intake and weight. This requires an integrated approach between various food-related disciplines. By structuring this approach around the new product development process, this paper aims to present the contours of such an integrative approach by going through the current state of the art around satiety enhancing foods. It portrays actual food choice as the end result of a complex interaction between internal satiety signals, other food benefits, and environmental cues. Three interrelated routes to satiating enhancement are to change the food composition to develop stronger physiological satiation and satiety signals, anticipate and build on smart external stimuli at the moment of purchase and consumption, and improve palatability and acceptance of satiety enhanced foods. Key research challenges in achieving these routes in the field of nutrition, food technology, consumer, marketing, and communication are outlined.

Consumer evaluations of food risk management quality in Europe.

In developing and implementing appropriate food risk management strategies, it is important to understand how consumers evaluate the quality of food risk management practices. The aim of this study is to model the underlying psychological factors influencing consumer evaluations of food risk management quality using structural equation modeling techniques (SEM), and to examine the extent to which the influence of these factors is country-specific (comparing respondents from Denmark, Germany, Greece, Slovenia, and the United Kingdom). A survey was developed to model the factors that drive consumer evaluations of food risk management practices and their relative importance (n= 2,533 total respondents). The measurement scales included in the structural model were configurally and metrically invariant across countries. Results show that some factors appear to drive perceptions of effective food risk management in all the countries studied, such as proactive consumer protection, which was positively related to consumers' evaluation of food risk management quality, while opaque and reactive risk management was negatively related to perceived food risk management quality. Other factors appeared to apply only in certain countries. For example, skepticism in risk assessment and communication practices was negatively related to food risk management quality, particularly so in the UK. Expertise of food risk managers appeared to be a key factor in consumers' evaluation of food risk management quality in some countries. However, trust in the honesty of food risk managers did not have a significant effect on food risk management quality. From the results, policy implications for food risk management are discussed and important directions for future research are identified.

Radiation-induced glomerular thrombus formation and nephropathy are not prevented by the ADP receptor antagonist clopidogrel.

PURPOSE: To assess the effects of kidney irradiation on glomerular adenosine diphosphatase (ADPase) activity and intraglomerular microthrombus formation, and their correlation to the development of renal functional impairment. METHODS AND MATERIALS: C3H/HenAf-nu(+) mice were given single-dose or fractionated kidney irradiations. Glomerular ADPase activity was measured using a cerium-based histochemical method. Microthrombus formation within the glomeruli was assessed by a semiquantitative immunohistochemical analysis of fibrinogen/fibrin deposits. Renal function was assessed by the [(51)Cr]EDTA retention assay. RESULTS: The ADPase activity was significantly reduced, to approximately 50% of pretreatment value, 4--40 weeks after 10--16 Gy single-dose irradiation and at 44 weeks after 20 x 2 Gy. No dose--effect relationship was found. An approximately fourfold increase in glomerular fibrinogen/fibrin staining was observed at 1 year after irradiation. This increase was not influenced by treating the mice with daily, oral clopidogrel, a platelet ADP receptor antagonist, which reduced platelet aggregation by more than 75%. Radiation-induced impairment of glomerular filtration was also not affected by the clopidogrel treatment. CONCLUSION: These data indicate that irradiation significantly reduced glomerular ADPase activity, which correlated with an increased glomerular fibrinogen/fibrin deposition. We were not able to reduce these prothrombotic changes, nor to protect against radiation nephropathy, by pharmacological intervention with an ADP-receptor antagonist.

Radiation nephropathy--the link between functional damage and vascular mediated inflammatory and thrombotic changes.

The extent of radiation-induced nephropathy, which develops progressively over periods of months to years after treatment, is strongly influenced by both total dose and dose per fraction. In this study we examined the relationship between the early expression of various thrombotic and inflammatory markers of endothelial cell (EC) damage in irradiated mouse kidneys and the subsequent development of nephropathy. Decreased levels of glomerular ADPase and increased levels of glomerular Vwf were seen from 4 or 20 weeks after irradiation, respectively. These pro-thrombotic changes were associated with increased fibrin/fibrinogen deposits, indicative of microthrombus formation, at later times. These events were, however, not sensitive to changes in total dose or dose per fraction, therefore they cannot be quantitatively linked to the development of radiation nephropathy. Increased leucocyte invasion of the renal cortex was also seen after irradiation; this was quantitatively dependent on both total dose and dose per fraction. Linear quadratic analysis of the leucocyte dose-response curves yielded an alpha/beta ratio of 7.7 Gy, which is significantly greater than the alpha/beta ratio or 2.7 Gy determined for nephropathy, indicating less fractionation sensitivity for the inflammatory response. We conclude that inflammatory changes contribute to, but do not entirely explain, radiation nephropathy. The role of thrombotic changes is less clear.

Influence of acetylsalicylic acid on development of radiation-induced nephropathy.

PURPOSE: Previous studies have demonstrated that long-term treatment with acetylsalicylic acid (ASA) can significantly reduce the renal functional impairment that develops after high doses of irradiation. The effect is hypothesized to be mediated by selective inhibition of thromboxane A2 synthesis and inhibition of platelet aggregation. The present study was undertaken to investigate this phenomenon further using more clinically relevant fractionated and re-irradiation schedules. METHODS AND MATERIALS: Groups of mice were given bilateral renal irradiation with a series of four or 20 daily fractions of X-rays, or 10 daily fractions with a single dose of re-irradiation (0-10 Gy) after 27 weeks. Half the mice received ASA in drinking water (2.4 g x l(-1)) from 1 week before the start of irradiation and continuously throughout the follow-up period. Renal function was assessed by clearance of [51Cr]EDTA, about every 4 weeks for up to 80 weeks after the start of treatment. Histological damage in representative groups of mice was also assessed. RESULTS: Oral administration of ASA caused inhibition of thromboxane A2 synthesis (to < 36% of controls) and a strong inhibition of platelet aggregation in whole mouse blood (ex vivo). Prolonged treatment with ASA also resulted in a small, non-significant reduction of radiation-induced renal functional damage. No reduction in histological damage was seen in the ASA treated mice. CONCLUSION: Long-term oral administration of ASA gave only a modest, non-significant reduction of renal radiation injury after clinically relevant fractionated irradiation schedules.

In vitro and in vivo expression of endothelial von Willebrand factor and leukocyte accumulation after fractionated irradiation.

Previous investigations have demonstrated an increased release of von Willebrand factor (VWF; also known as vWF) in endothelial cells after high single-dose irradiation in vitro. We have also found increased levels of Vwf protein in mouse glomeruli after a high single dose of renal irradiation in vivo. In addition, increased numbers of leukocytes were observed in the renal cortex after irradiation in vivo. The aim of the present study was to investigate and quantify these biological processes after clinically relevant fractionated irradiation and to relate them to changes in renal function. A significantly greater increase in release of VWF was observed in cultured human umbilical vein endothelial cells (HUVECs) after fractionated irradiation (20 x 1.0 Gy) than after a single dose of 20 Gy (147% compared to 115% of control, respectively, P < 0.0005). In contrast with the in vitro observations, glomerular Vwf staining was lower after fractionated irradiation in vivo (20 x 2.0 Gy or 10 x 1.6 Gy +/- re-irradiation) than after a single dose of 16 Gy. The number of leukocytes accumulating in the renal cortex was also lower after fractionated in vivo irradiation than after a single radiation dose. The onset of these events preceded renal functional and histopathological changes by approximately 10 weeks. These data indicate that radiation-induced changes in endothelial VWF expression after in vivo irradiation may be distinct from the in vitro observations. Increased VWF expression may reflect pivotal processes in the pathogenesis of late radiation nephropathy and provide a clue to appropriate timing of pharmacological intervention.

Long-term effects of total-body irradiation on the kidney of Rhesus monkeys.

PURPOSE: To investigate the long-term effects of total-body irradiation (TBI) on kidneys in non-human primates. METHODS AND MATERIALS: The kidneys of Rhesus monkeys were histologically examined at 6-8 years after TBI with low single doses of 4.5-8.5Gy or two fractions of 5.4Gy. The kidneys of age-matched non-irradiated monkeys served as controls. Irradiation was performed on adult monkeys aged about 3 years; 6-8 years later animals were sacrificed and the kidneys removed and processed for histology. A semi-quantitative scoring system was used to evaluate overall histological damage. Glomerular changes were also morphometrically analysed according to previously published criteria. In selected dose groups (pro)thrombotic and inflammatory changes were investigated by immunostaining cryosections with antibodies against von Willebrand factor (vWF), leukocytes and macrophages. RESULTS: Histological changes were generally mild and only seen in kidneys irradiated with doses higher than 7 Gy. Glomerular changes were characterized by increased mesangial matrix and capillary dilatation. Tubulo-interstitial changes included hypercellularity, fibrosis and mild tubular atrophy. The mean glomerular area expressing vWF protein in the irradiated kidneys was not different from that in the age-matched controls. Numbers of infiltrating leukocytes were not significantly different between irradiated kidneys and controls. However, slightly increased numbers of macrophages were present in the renal cortex after irradiation. CONCLUSIONS: Renal damage after TBI of Rhesus monkeys with single doses of 4.5-8.5 Gy or two fractions of 5.4 Gy was mild, even after follow-up times of 6-8 years.

Increased expression of glomerular von Willebrand factor after irradiation of the mouse kidney.

Ionizing irradiation has been shown to induce an increased release of von Willebrand factor (vWF) in human endothelial cells in vitro. The present study was undertaken to investigate whether an increase in expression of vWF also occurs in glomerular endothelial cells in vivo after irradiation of the kidney. Increased expression of vWF may initiate prothrombotic changes, and the resultant vascular damage could cause renal failure. The amount of adherent leukocytes in the renal cortex after irradiation was also quantified, since this may contribute to the histological changes that occur after irradiation. Changes in expression of glomerular vWF and in the amount of leukocytes were related to the development of impairment of renal function, as assessed with the [51Cr]EDTA retention assay. Mice were given bilateral irradiation (single dose of 16 Gy) or were sham-irradiated and were sacrificed at intervals of 1 day to 40 weeks after irradiation. Immunohistochemical analysis of kidney cryosections was performed using a polyclonal vWF antibody or monoclonal CD45 antibody (leukocyte common antigen). The amount of glomerular vWF staining and CD45 staining in the renal cortex (percentage surface coverage) was quantified using a computerized image analyzer. The mean glomerular vWF staining in the nonirradiated kidneys was 34.4 +/- 6.2% (mean +/- SEM, 10 weeks after sham treatment). After irradiation, the expression of glomerular vWF increased gradually from 10 weeks to 53.4 +/- 3.6% at 40 weeks. The total number of leukocytes in the renal cortex of nonirradiated mice at 10 weeks after sham treatment was low, with a mean area of 1.0 +/- 0.09%, whereas in the irradiated kidneys the relative tissue area covered by leukocytes increased to 7.6 +/- 2.1% at 40 weeks. These alterations preceded impairment of renal function. The extent to which these changes are causally related to impairment of function will be the subject of future study using specific antithrombotic and anti-inflammatory agents.

Effects of chemical sympathectomy on angiotensin II-induced neointimal growth in the balloon-injured rat carotid artery.

To investigate the role of the sympathetic nervous system in angiotensin II (AngII)-stimulated medial and neointimal smooth muscle cell (SMC) replication, we sympathectomized rats with 6-hydroxydopamine (6-OHDA) in which the left carotid artery was injured by a balloon catheter. Balloon injury is associated with a loss of specific [3H]-prazosin binding. AngII (250 ng/kg/min), infused 2 weeks after balloon injury of the rat left carotid artery, increased systolic blood pressure by approximately 70 mm Hg. There was no effect of 6-OHDA on this pressor response. AngII increased the cumulative 5-bromo-2'-deoxyuridine (BrdU) labeling fraction (LF) in the uninjured right carotid media and the injured left carotid neointima as compared to controls (5.7+/-1.6% vs. 0.4+/-0.1%, p<0.05; 10.6+/-0.9% vs. 5.0+/-0.8%, p<0.05, respectively). 6-OHDA decreased the AngII-induced increase in LF in the media of the uninjured right carotid artery (AngII/6-OHDA 0.9+/-0.2% vs. AngII 5.7+/-1.6%, p < 0.05). 6-OHDA did not decrease the AngII-induced increase in LF in both the injured left carotid media and neointima at 4 weeks after balloon injury. The effects of chemical sympathectomy were comparable with those obtained 12 weeks after balloon injury. Thus, the data show that the sympathetic nervous system mediates the AngII-induced increase in SMC DNA synthesis, but only in the uninjured carotid media. This indicates a differential regulation of AngII-induced SMC replication in injured and uninjured vessels.

Neointimal smooth muscle cell phenotype is important in its susceptibility to cytomegalovirus (CMV) infection: a study in rat.

OBJECTIVE: Recently, we have found that rat CMV (RCMV) infected smooth muscle cells (SMCs) in rat carotid arteries when administered 14 days after balloon injury. In the present study we investigated (1) the long term effects of CMV infection on neointimal cross-sectional area, and (2) whether the phenotype of the intimal SMCs influences their susceptibility to active CMV infection. METHODS: In the first part of the study, rats received RCMV intravenously, two weeks after balloon catheterisation of the left carotid artery and were sacrificed twenty weeks after catheterisation. Continuous BrdU infusion was performed by subcutaneously implanted osmotic pumps during the last two weeks of life. In the second part RCMV was administered eight weeks after catheterisation and rats were sacrificed two weeks later. Immunohistochemistry was used to detect viral antigens, to determine BrdU incorporation as well as the contents of alpha-actin, desmin and vimentin in the carotid arteries. Intima and media cross-sectional areas were determined using computerized morphometry. RESULTS AND CONCLUSIONS: RCMV infection did not induce any differences in intima or media cross-sectional areas of the injured carotid artery, nor in the extent of SMC proliferation as shown by BrdU incorporation, 20 weeks after balloon catheterisation. Eight weeks after balloon catheterisation, RCMV no longer infected neointimal SMCs. This non-responsiveness to RCMV was associated with "re-differentiation" of the eight weeks old neointima, compared with two weeks after catheterization, as shown by the contents of alpha-actin, desmin and vimentin. Our data suggest that intimal SMC phenotype determines its susceptibility to active RCMV infection in vivo. Since de-differentiation of neointimal SMCs is associated with enhanced proliferation of these cells it is stated that de-differentiation or proliferation is prerequisite for infection.

Chronic alpha 1-adrenoreceptor stimulation increases DNA synthesis in rat arterial wall. Modulation of responsiveness after vascular injury.

Despite indirect evidence from studies using adrenergic antagonists or sympathectomy, catecholamines have never been shown directly to stimulate vascular smooth muscle cell (SMC) DNA replication in vivo. We studied whether a chronic infusion of catecholamine stimulates SMC replication in vivo in both uninjured arteries and arteries with a neointima formed after vascular injury. Animals were killed after 2 weeks of continuous infusion of bromodeoxyuridine (to label replicating DNA) and either phenylephrine, norepinephrine, or vehicle solution, starting early (third week) or late (ninth week) after balloon injury to the left common carotid artery. In catecholamine-infused animals, the uninjured carotid artery or thoracic aorta showed a marked increase in cross-sectional area (> 25%) and frequency of cells undergoing DNA synthesis among medial SMCs (4- to 10-fold) and endothelial cells (13-fold). With catecholamine infusion at 9 to 10 weeks after injury, the media or neointima of the injured carotid artery showed a smaller increase in SMC DNA replication (< or = 4-fold) than did the normal arterial media. In contrast, catecholamine infusion at 3 to 4 weeks did not cause significant SMC growth in the injured vessel. Catecholamine infusion caused labile elevations of systolic blood pressure. Taken together with our previous observation that alpha 1-blockers suppress arterial SMC replication without preventing severe hypertension in the rat, the present data strongly suggest that alpha 1-adrenoreceptors stimulate SMC DNA synthesis in vivo in arteries with or without intimal thickening, although not during the first weeks after balloon injury. The stimulation of DNA synthesis in vascular cells via the alpha 1-adrenoreceptor pathway may contribute to the vascular remodeling that occurs in hypertension and atherosclerosis.

Angiotensin II-induced progression of neointimal thickening in the balloon-injured rat carotid artery is AT1 receptor mediated.

To investigate the relative importance of AT1 and AT2 receptors in angiotensin II (Ang II)-induced restimulation of neointimal smooth muscle cell (SMC) DNA synthesis and increased neointimal cross-sectional area (CSA), male Wistar rats were subcutaneously infused for 2 weeks with Ang II and losartan, an AT1 receptor antagonist, or Ang II and PD123319, an AT2 receptor antagonist, during the third and fourth week after balloon injury of the left common carotid artery. Concomitantly, all rats received 5-bromo-2'-deoxyuridine to label DNA-synthesizing SMCs. Neointimal CSAs and SMC DNA synthesis were compared with control groups that received Ang II, 0.9% NaCl, losartan, or PD123319. Systolic blood pressure (SBP) was measured at different times during the infusion. Ang II induced an increase in SBP that was significantly different from the SBP in the NaCl group. Infusion of Ang II together with losartan reduced the Ang II-induced increase in SBP to levels comparable with those obtained in the NaCl group. Infusion of Ang II+PD123319 caused an increase in SBP that was comparable with the increase in SBP of the Ang II group and significantly different from the SBP of the NaCl group. Infusion of losartan or PD123319 alone did not affect SBP. Ang II significantly enhanced neointimal CSA (47%, P < .05) compared with the control group infused with NaCl. Losartan significantly reduced Ang II-induced neointimal thickening (neointimal CSA, -37%, P < .05). Infusion of PD123319 together with Ang II did not affect Ang II-induced neointimal thickening. Losartan or PD123319 alone did not reduce neointimal thickening, since the neointimal CSAs in these groups did not differ from the neointimal CSA of the NaCl group. Comparable effects were found for SMC DNA synthesis in the neointima. Ang II infusion increased neointimal SMC DNA synthesis. Addition of losartan reduced the fraction of DNA-synthesizing neointimal SMCs from 23.7 +/- 2.1% in the Ang II group to 12.8 +/- 1.8% in the Ang II+losartan group, whereas the labeling fraction in the neointima remained 26.6 +/- 3.1% in the Ang II+PD123319 group. The labeling fractions in the neointimas of the groups that received losartan or PD123319 alone did not differ from the labeling fraction in the NaCl group. These data indicate that AT1 but not AT2 receptors mediate the progression of neointimal thickening induced by delayed application of Ang II in the injured left carotid artery in the rat. Furthermore, these data suggest that AT1 and AT2 receptors are not involved in the regulation of normal growth of a neointima in the third and fourth week after balloon injury.

Doxazosin blocks the angiotensin II-induced smooth muscle cell DNA synthesis in the media, but not in the neointima of the rat carotid artery after balloon injury.

OBJECTIVE: Infusion of angiotensin II (AngII) during the third and fourth week after balloon injury of the left common carotid artery of the rat induces smooth muscle cell (SMC) DNA synthesis. In this study we wanted to investigate whether alpha 1-adrenoreceptors are involved in AngII-induced SMC DNA synthesis in the neointima. METHODS: Adult male Wistar Kyoto rats were subcutaneously infused for 2 weeks with AngII and the alpha 1-adrenoreceptor antagonist doxazosin during the 3rd and the 4th week after balloon injury of the left common carotid artery. Control groups received AngII, 0.9% NaCl, AngII + 50% dimethylsulfoxide (DMSO, the solvent of doxazosin), doxazosin or 50% dimethylsulfoxide. Each rat received 5-bromo-2'-deoxyuridine in a separate osmotic minipump to label DNA-synthesizing SMC. Systolic blood pressures were measured in all groups. RESULTS: Angiotensin II caused an increase in systolic blood pressure, whereas addition of doxazosin did not affect the increase in SBP caused by AngII. In the media of the non-injured carotid artery, AngII increased SMC DNA synthesis, as the BrdUrd labeling fraction increased from 0.2 +/- 0.1% (mean +/- s.e.m.) in the NaCl group towards 3.4 +/- 0.6% in the AngII group. Coinfusion with doxazosin reduced the AngII-induced increase in BrdUrd labeling fraction from 3.2 +/- 0.8% in the AngII + DMSO group towards 0.6 +/- 0.2% in the AngII+doxazosin group. A similar effect of doxazosin was found in the media of the injured left carotid artery, in which coinfusion with doxazosin also reduced the BrdUrd labeling fraction from 2.6 +/- 0.8% in the AngII+DMSO group towards 0.3 +/- 0.1% in the AngII+doxazosin group. In the neointima of the injured left carotid artery, AngII increased the BrdUrd labeling fraction from 11.7 +/- 1.6% in the NaCl group towards 28.0 +/- 3.4% in the AngII group. Coinfusion with doxazosin did not influence the AngII-induced SMC DNA synthesis, since the BrdUrd labeling fraction in the neointima of the AngII+doxazosin group was 22.5 +/- 2.9%, whereas the neointimal BrdUrd labeling fraction in the AngII+DMSO group was 22.9 +/- 2.3%. Little effect was found on the medial cross-sectional area. The neointimal cross-sectional area was increased as a result of infusion of AngII (0.12 +/- 0.01 mm2 vs. 0.18 +/- 0.01 mm2), and coinfusion of doxazosin did not reduce the AngII-induced increase in neointimal cross-sectional area (0.18 +/- 0.03 mm2). CONCLUSIONS: These data suggest that alpha 1-adrenoreceptors are not involved in AngII-induced neointimal SMC DNA synthesis and cross-sectional area, but only play a role in the media of the carotid artery.