Multifunctional cytokine production marks influenza A virus-specific CD4 T cells with high expression of survival molecules.

Cytokine production by memory T cells is a key mechanism of T cell mediated protection. However, we have limited understanding of the persistence of cytokine producing T cells during memory cell maintenance and secondary responses. We interrogated antigen-specific CD4 T cells using a mouse influenza A virus infection model. Although CD4 T cells detected using MHCII tetramers declined in lymphoid and non-lymphoid organs, we found similar numbers of cytokine+ CD4 T cells at days 9 and 30 in the lymphoid organs. CD4 T cells with the capacity to produce cytokines expressed higher levels of pro-survival molecules, CD127 and Bcl2, than non-cytokine+ cells. Transcriptomic analysis revealed a heterogeneous population of memory CD4 T cells with three clusters of cytokine+ cells. These clusters match flow cytometry data and reveal an enhanced survival signature in cells capable of producing multiple cytokines. Following re-infection, multifunctional T cells expressed low levels of the proliferation marker, Ki67, whereas cells that only produce the anti-viral cytokine, interferon-γ, were more likely to be Ki67+ . Despite this, multifunctional memory T cells formed a substantial fraction of the secondary memory pool. Together these data indicate that survival rather than proliferation may dictate which populations persist within the memory pool.

Peripheral Ophthalmic Artery Aneurysm Associated with Multifocal Intracranial and Extracranial Aneurysms: Case Report and Literature Review.

Peripheral ophthalmic artery aneurysm is a rare disease entity. We review the relevant literature and report a case of fusiform aneurysm involving the entire intraorbital ophthalmic artery in association with multiple intracranial and extracranial aneurysms, diagnosed on digital subtraction angiography. The patient suffered irreversible blindness secondary to compressive optic neuropathy which did not improve after a 3-day trial of intravenous methylprednisolone. Autoimmune screen was normal. The underlying cause is unknown.

Quantitative proteomic landscape of unstable atherosclerosis identifies molecular signatures and therapeutic targets for plaque stabilization.

Atherosclerotic plaque rupture leading to myocardial infarction is a major global health burden. Applying the tandem stenosis (TS) mouse model, which distinctively exhibits the characteristics of human plaque instability/rupture, we use quantitative proteomics to understand and directly compare unstable and stable atherosclerosis. Our data highlight the disparate natures and define unique protein signatures of unstable and stable atherosclerosis. Key proteins and pathway networks are identified such as the innate immune system, and neutrophil degranulation. The latter includes calprotectin S100A8/A9, which we validate in mouse and human unstable plaques, and we demonstrate the plaque-stabilizing effects of its inhibition. Overall, we provide critical insights into the unique proteomic landscape of unstable atherosclerosis (as distinct from stable atherosclerosis and vascular tissue). We further establish the TS model as a reliable preclinical tool for the discovery and testing of plaque-stabilizing drugs. Finally, we provide a knowledge resource defining unstable atherosclerosis that will facilitate the identification and validation of long-sought-after therapeutic targets and drugs for plaque stabilization.

The tandem stenosis mouse model: Towards understanding, imaging, and preventing atherosclerotic plaque instability and rupture.

The rupture of unstable atherosclerotic plaques is the major cause of cardiovascular mortality and morbidity. Despite significant limitations in our understanding and ability to identify unstable plaque pathology and prevent plaque rupture, most atherosclerosis research utilises preclinical animal models exhibiting stable atherosclerosis. Here, we introduce the tandem stenosis (TS) mouse model that reflects plaque instability and rupture, as seen in patients. The TS model involves dual ligation of the right carotid artery, leading to locally predefined unstable atherosclerosis in hypercholesterolaemic mice. It exhibits key characteristics of human unstable plaques, including plaque rupture, luminal thrombosis, intraplaque haemorrhage, large necrotic cores, thin or ruptured fibrous caps and extensive immune cell accumulation. Altogether, the TS model represents an ideal preclinical tool for improving our understanding of human plaque instability and rupture, for the development of imaging technologies to identify unstable plaques, and for the development and testing of plaque-stabilising treatments for the prevention of atherosclerotic plaque rupture. LINKED ARTICLES: This article is part of a themed issue on Preclinical Models for Cardiovascular disease research (BJP 75th Anniversary). To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v179.5/issuetoc.

Pharmacological Inhibition of Factor XIIa Attenuates Abdominal Aortic Aneurysm, Reduces Atherosclerosis, and Stabilizes Atherosclerotic Plaques.

BACKGROUND: 3F7 is a monoclonal antibody targeting the enzymatic pocket of activated factor XII (FXIIa), thereby inhibiting its catalytic activity. Given the emerging role of FXIIa in promoting thromboinflammation, along with its apparent redundancy for hemostasis, the selective inhibition of FXIIa represents a novel and highly attractive approach targeting pathogenic processes that cause thromboinflammation-driven cardiovascular diseases. METHODS: The effects of FXIIa inhibition were investigated using three distinct mouse models of cardiovascular disease-angiotensin II-induced abdominal aortic aneurysm (AAA), an ApoE-/- model of atherosclerosis, and a tandem stenosis model of atherosclerotic plaque instability. 3F7 or its isotype control, BM4, was administered to mice (10 mg/kg) on alternate days for 4 to 8 weeks, depending on the experimental model. Mice were examined for the development and size of AAAs, or the burden and instability of atherosclerosis and associated markers of inflammation. RESULTS: Inhibition of FXIIa resulted in a reduced incidence of larger AAAs, with less acute aortic ruptures and an associated fibro-protective phenotype. FXIIa inhibition also decreased stable atherosclerotic plaque burden and achieved plaque stabilization associated with increased deposition of fibrous structures, a >2-fold thicker fibrous cap, increased cap-to-core ratio, and reduction in localized and systemic inflammatory markers. CONCLUSION: Inhibition of FXIIa attenuates disease severity across three mouse models of thromboinflammation-driven cardiovascular diseases. Specifically, the FXIIa-inhibiting monoclonal antibody 3F7 reduces AAA severity, inhibits the development of atherosclerosis, and stabilizes vulnerable plaques. Ultimately, clinical trials in patients with cardiovascular diseases such as AAA and atherosclerosis are warranted to demonstrate the therapeutic potential of FXIIa inhibition.

Early Endothelial Activation in a Mouse Model of Graft vs Host Disease Following Chemotherapy.

Allogenic hematopoietic stem cell transplant (allo-HSCT) can lead to sinusoidal obstruction syndrome (SOS) and graft-versus-host disease (GvHD) in some individuals. GvHD is characterised by an immune triggered response that arises due to donor T cells recognizing the recipient tissue as "foreign". SOS results in impaired liver function due to microvascular thrombosis and consequent obstruction of liver sinusoids. Endothelial damage occurs following chemotherapy and allo-HSCT and is strongly associated with GvHD onset as well as hepatic SOS. Animal models of GvHD are rarely clinically relevant, and endothelial dysfunction remains uncharacterised. Here we established and characterised a clinically relevant model of GvHD wherein Balb/C mice were subjected to myeloablative chemotherapy followed by transplantation of bone marrow (BM) cells± splenic T-cells from C57Bl6 mice, resulting in a mismatch of major histocompatibility complexes (MHC). Onset of disease indicated by weight loss and apoptosis in the liver and intestine was discovered at day 6 post-transplant in mice receiving BM+T-cells, with established GvHD detectable by histology of the liver within 3 weeks. Together with significant increases in pro-inflammatory cytokine gene expression in the liver and intestine, histopathological signs of GvHD and a significant increase in CD4+ and CD8+ effector and memory T-cells were seen. Endothelial activation including upregulation of vascular cell adhesion molecule (VCAM)- 1 and downregulation of endothelial nitric oxide synthase (eNOS) as well as thrombosis in the liver indicated concomitant hepatic SOS. Our findings confirm that endothelial activation is an early sign of acute GvHD and SOS in a clinically relevant mouse model of GvHD based on myeloablative chemotherapy. Preventing endothelial activation may be a viable therapeutic strategy to prevent GvHD.

Effects of lignocaine vs. opioids on antiplatelet activity of ticagrelor: the LOCAL trial.

AIMS: We assessed the impact of intravenous fentanyl and lignocaine on the pharmacokinetics and pharmacodynamics of ticagrelor in patients with unstable angina and non-ST-elevation myocardial infarction and their procedural analgesic efficacy and safety. METHODS AND RESULTS: Seventy patients undergoing coronary angiography with ticagrelor loading were included in the pharmacokinetic and pharmacodynamic analyses of this randomized trial. Plasma ticagrelor levels 2 h post-loading dose were significantly lower in the fentanyl arm than in the lignocaine treatment arm (598 vs. 1008 ng/mL, P = 0.014). The area under the plasma-time curves for ticagrelor (1228 vs. 2753 ng h/mL, P < 0.001) and its active metabolite (201 vs. 447 ng h/mL, P = 0.001) were both significantly lower in the fentanyl arm. Expression of activated platelet glycoprotein IIb/IIIa receptor (2829 vs. 1426 mean fluorescence intensity, P = 0.006) and P-selectin (439 vs. 211 mean fluorescence intensity, P = 0.001) was significantly higher at 60 min in the fentanyl arm. A higher proportion of patients had high on-treatment platelet reactivity in the fentanyl arm at 60 min using the Multiplate Analyzer (41% vs. 9%, P = 0.002) and 120 min using the VerifyNow (30% vs. 3%, P = 0.003) and VASP (37% vs. 6%, P = 0.002) assays. Both drugs were well tolerated with a high level of patient satisfaction. CONCLUSIONS: Unlike fentanyl, lignocaine does not impair the bioavailability or delay the antiplatelet effect of ticagrelor. Both drugs were well tolerated and effective with a high level of patient satisfaction for procedural analgesia. Routine procedural analgesia during percutaneous coronary intervention should be reconsidered and if performed, lignocaine is a beneficial alternative to fentanyl.

Molecular imaging of cardiovascular inflammation.

Cardiovascular diseases (CVDs), including atherosclerosis, are chronic inflammatory diseases characterised by a complex and evolving tissue micro-environment. Molecular heterogeneity of inflammatory responses translates into clinical outcomes. However, current medical imaging modalities are unable to reveal the cellular and molecular events at a level of detail that would allow more accurate and timely diagnosis and treatment. This is an inherent limitation of the current imaging tools, which are restricted to anatomical or functional data. Molecular imaging-the visualisation and quantification of molecules in the body-is already established in the clinic in the form of PET, yet the use of PET in CVD is limited. In this visual review, we will guide you through the current state of molecular imaging research, assessing the respective strengths and weaknesses of molecular imaging modalities, including those already being used in the clinic such as PET and MRI and emerging technologies at preclinical stage, such as photoacoustic imaging. We discuss the basic principles of each technology and provide key examples of their application in imaging inflammation in CVD and the added value into the diagnostic decision-making process. Finally, we discuss the barriers to the rapid successful clinical translation of these novel diagnostic modalities. LINKED ARTICLES: This article is part of a themed issue on Molecular imaging - visual themed issue. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.21/issuetoc.

Higher mortality of COVID-19 in males: sex differences in immune response and cardiovascular comorbidities.

The high mortality rate of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection is a critical concern of the coronavirus disease 2019 (COVID-19) pandemic. Strikingly, men account for the majority of COVID-19 deaths, with current figures ranging from 59% to 75% of total mortality. However, despite clear implications in relation to COVID-19 mortality, most research has not considered sex as a critical factor in data analysis. Here, we highlight fundamental biological differences that exist between males and females, and how these may make significant contributions to the male-biased COVID-19 mortality. We present preclinical evidence identifying the influence of biological sex on the expression and regulation of angiotensin-converting enzyme 2 (ACE2), which is the main receptor used by SARS-CoV-2 to enter cells. However, we note that there is a lack of reports showing that sexual dimorphism of ACE2 expression exists and is of functional relevance in humans. In contrast, there is strong evidence, especially in the context of viral infections, that sexual dimorphism plays a central role in the genetic and hormonal regulation of immune responses, both of the innate and the adaptive immune system. We review evidence supporting that ineffective anti-SARS-CoV-2 responses, coupled with a predisposition for inappropriate hyperinflammatory responses, could provide a biological explanation for the male bias in COVID-19 mortality. A prominent finding in COVID-19 is the increased risk of death with pre-existing cardiovascular comorbidities, such as hypertension, obesity, and age. We contextualize how important features of sexual dimorphism and inflammation in COVID-19 may exhibit a reciprocal relationship with comorbidities, and explain their increased mortality risk. Ultimately, we demonstrate that biological sex is a fundamental variable of critical relevance to our mechanistic understanding of SARS-CoV-2 infection and the pursuit of effective COVID-19 preventative and therapeutic strategies.

The aorta can act as a site of naïve CD4+ T-cell priming.

AIMS: Aortic adaptive immunity plays a role in atherosclerosis; however, the precise mechanisms leading to T-cell activation in the arterial wall remain poorly understood. METHODS AND RESULTS: Here, we have identified naïve T cells in the aorta of wild-type and T-cell receptor transgenic mice and we demonstrate that naïve T cells can be primed directly in the vessel wall with both kinetics and frequency of T-cell activation found to be similar to splenic and lymphoid T cells. Aortic homing of naïve T cells is regulated at least in part by the P-selectin glycosylated ligand-1 receptor. In experimental atherosclerosis the aorta supports CD4+ T-cell activation selectively driving Th1 polarization. By contrast, secondary lymphoid organs display Treg expansion. CONCLUSION: Our results demonstrate that the aorta can support T-cell priming and that naïve T cells traffic between the circulation and vessel wall. These data underpin the paradigm that local priming of T cells specific for plaque antigens contributes to atherosclerosis progression.

A Novel Triple-Cell Two-Dimensional Model to Study Immune-Vascular Interplay in Atherosclerosis.

Atherosclerosis is a complex inflammatory pathology underpinning cardiovascular diseases (CVD), which are the leading cause of death worldwide. The interplay between vascular stromal cells and immune cells is fundamental to the progression and outcome of atherosclerotic disease, however, the majority of in vitro studies do not consider the implications of these interactions and predominantly use mono-culture approaches. Here we present a simple and robust methodology involving the co-culture of vascular endothelial (ECs) and smooth muscle cells (SMCs) alongside an inflammatory compartment, in our study containing THP-1 macrophages, for studying these complex interactions. Using this approach, we demonstrate that the interaction between vascular stromal and immune cells produces unique cellular phenotypes and soluble mediator profiles not observed in double-cell 2D cultures. Our results highlight the importance of cellular communication and support the growing idea that in vitro research must evolve from mono-culture systems to provide data more representative of the multi-cellular environment found in vivo. The methodology presented, in comparison with established approaches, has the advantage of being technically simple whilst enabling the isolation of pure populations of ECs, SMCs and immune cells directly from the co-culture without cell sorting. The approach described within would be applicable to those studying mechanisms of vascular inflammation, particularly in relation to understanding the impact cellular interaction has on the cumulative immune-vascular response to atherogenic or inflammatory stimuli.

Hypertension and increased endothelial mechanical stretch promote monocyte differentiation and activation: roles of STAT3, interleukin 6 and hydrogen peroxide.

Aims: Monocytes play an important role in hypertension. Circulating monocytes in humans exist as classical, intermediate, and non-classical forms. Monocyte differentiation can be influenced by the endothelium, which in turn is activated in hypertension by mechanical stretch. We sought to examine the role of increased endothelial stretch and hypertension on monocyte phenotype and function. Methods and results: Human monocytes were cultured with confluent human aortic endothelial cells undergoing either 5% or 10% cyclical stretch. We also characterized circulating monocytes in normotensive and hypertensive humans. In addition, we quantified accumulation of activated monocytes and monocyte-derived cells in aortas and kidneys of mice with Angiotensin II-induced hypertension. Increased endothelial stretch enhanced monocyte conversion to CD14++CD16+ intermediate monocytes and monocytes bearing the CD209 marker and markedly stimulated monocyte mRNA expression of interleukin (IL)-6, IL-1ß, IL-23, chemokine (C-C motif) ligand 4, and tumour necrosis factor α. STAT3 in monocytes was activated by increased endothelial stretch. Inhibition of STAT3, neutralization of IL-6 and scavenging of hydrogen peroxide prevented formation of intermediate monocytes in response to increased endothelial stretch. We also found evidence that nitric oxide (NO) inhibits formation of intermediate monocytes and STAT3 activation. In vivo studies demonstrated that humans with hypertension have increased intermediate and non-classical monocytes and that intermediate monocytes demonstrate evidence of STAT3 activation. Mice with experimental hypertension exhibit increased aortic and renal infiltration of monocytes, dendritic cells, and macrophages with activated STAT3. Conclusions: These findings provide insight into how monocytes are activated by the vascular endothelium during hypertension. This is likely in part due to a loss of NO signalling and increased release of IL-6 and hydrogen peroxide by the dysfunctional endothelium and a parallel increase in STAT activation in adjacent monocytes. Interventions to enhance bioavailable NO, reduce IL-6 or hydrogen peroxide production or to inhibit STAT3 may have anti-inflammatory roles in hypertension and related conditions.

In vivo multiplex molecular imaging of vascular inflammation using surface-enhanced Raman spectroscopy.

Vascular immune-inflammatory responses play a crucial role in the progression and outcome of atherosclerosis. The ability to assess localized inflammation through detection of specific vascular inflammatory biomarkers would significantly improve cardiovascular risk assessment and management; however, no multi-parameter molecular imaging technologies have been established to date. Here, we report the targeted in vivo imaging of multiple vascular biomarkers using antibody-functionalized nanoparticles and surface-enhanced Raman scattering (SERS). Methods: A series of antibody-functionalized gold nanoprobes (BFNP) were designed containing unique Raman signals in order to detect intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and P-selectin using SERS. Results: SERS and BFNP were utilized to detect, discriminate and quantify ICAM-1, VCAM-1 and P-selectin in vitro on human endothelial cells and ex vivo in human coronary arteries. Ultimately, non-invasive multiplex imaging of adhesion molecules in a humanized mouse model was demonstrated in vivo following intravenous injection of the nanoprobes. Conclusion: This study demonstrates that multiplexed SERS-based molecular imaging can indicate the status of vascular inflammation in vivo and gives promise for SERS as a clinical imaging technique for cardiovascular disease in the future.

Molecular imaging of atherosclerosis: spotlight on Raman spectroscopy and surface-enhanced Raman scattering.

To accurately predict atherosclerotic plaque progression, a detailed phenotype of the lesion at the molecular level is required. Here, we assess the respective merits and limitations of molecular imaging tools. Clinical imaging includes contrast-enhanced ultrasound, an inexpensive and non-toxic technique but with poor sensitivity. CT benefits from high spatial resolution but poor sensitivity coupled with an increasing radiation burden that limits multiplexing. Despite high sensitivity, positron emission tomography and single-photon emission tomography have disadvantages when applied to multiplex molecular imaging due to poor spatial resolution, signal cross talk and increasing radiation dose. In contrast, MRI is non-toxic, displays good spatial resolution but poor sensitivity. Preclinical techniques include near-infrared fluorescence (NIRF), which provides good spatial resolution and sensitivity; however, multiplexing with NIRF is limited, due to photobleaching and spectral overlap. Fourier transform infrared spectroscopy and Raman spectroscopy are label-free techniques that detect molecules based on the vibrations of chemical bonds. Both techniques offer fast acquisition times with Raman showing superior spatial resolution. Raman signals are inherently weak; however, leading to the development of surface-enhanced Raman spectroscopy (SERS) that offers greatly increased sensitivity due to using metallic nanoparticles that can be functionalised with biomolecules targeted against plaque ligands while offering high multiplexing potential. This asset combined with high spatial resolution makes SERS an exciting prospect as a diagnostic tool. The ongoing refinements of SERS technologies such as deep tissue imaging and portable systems making SERS a realistic prospect for translation to the clinic.

Differential Association of Generalized and Abdominal Obesity With Diabetic Retinopathy in Asian Patients With Type 2 Diabetes.

IMPORTANCE: The association between obesity and diabetic retinopathy (DR) is equivocal, possibly owing to the strong interrelation between generalized and abdominal obesity leading to a mutually confounding effect. To our knowledge, no study in Asia has investigated the independent associations of these 2 parameters with DR to date. OBJECTIVE: To investigate the associations of generalized (defined by body mass index [BMI], calculated as weight in kilograms divided by height in meters squared) and abdominal obesity (assessed by waist to hip ratio [WHR]) with DR in a clinical sample of Asian patients with type 2 diabetes mellitus. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional clinic-based study was conducted at the Singapore National Eye Centre, a tertiary eye care institution in Singapore, from December 2010 to September 2013. We recruited 498 patients with diabetes. After exclusion of participants with ungradable retinal images and type 1 diabetes, 420 patients (mean [SD] age, 57.8 [7.5] years; 32.1% women) were included in the analyses. EXPOSURES: Body mass index and WHR as waist/hip circumference (in centimeters). MAIN OUTCOMES AND MEASURES: The presence and severity of DR were graded from retinal images using the modified Airlie House Classification into none (n = 189), mild-moderate (Early Treatment Diabetic Retinopathy Study scale score, 20-41; n = 125), and severe DR (Early Treatment Diabetic Retinopathy Study scale score ≥53; n = 118). The associations of BMI and WHR with DR were assessed using multinomial logistic regression models adjusting for age, sex, traditional risk factors, and mutually for BMI and WHR. RESULTS: Among the total of 420 patients, the median (interquartile range) for BMI and WHR were 25.7 (5.7) and 0.94 (0.08), respectively. In multivariable models, BMI was inversely associated with mild-moderate and severe DR (odds ratio [OR], 0.90 [95% CI, 0.84-0.97] and OR, 0.92 [95% CI, 0.85-0.99] per 1-unit increase, respectively), while WHR was positively associated with mild-moderate and severe DR (OR, 3.49 [95% CI, 1.50-8.10] and OR, 2.68 [95% CI, 1.28-5.62] per 0.1-unit increase, respectively) in women (P for interaction = .006). No sex-specific associations were found between BMI and DR (P for interaction >.10). CONCLUSIONS AND RELEVANCE: In Asian patients with type 2 diabetes, a higher BMI appeared to confer a protective effect on DR, while higher WHR was associated with the presence and severity of DR in women. Our results may inform future clinical trials to determine whether WHR is a more clinically relevant risk marker than BMI for individuals with type 2 diabetes.

Neuronal activity-dependent regulation of retinal blood flow.

Blood flow in the retina is intrinsically regulated to meet the metabolic demands of its constituent cells. Flickering light or stationary contrast reversals induce an increase in blood flow within seconds of the stimulus onset. This phenomenon is thought to compensate for an increase in ganglion cell activity and energy consumption. Ganglion cell activity is in turn dependent on signals from photoreceptors, bipolar cells, horizontal cells and amacrine cells. The physiological properties of these neurons determine how each type is affected by a particular light characteristic. Neuronal activity then triggers the release of signalling molecules that dilate local blood vessels and increase blood flow. Nitric oxide has been implicated as an important mediator, but metabolites of arachidonic acid may also be involved. Detailed elucidation of these mechanisms, together with advances in imaging technology, may facilitate the use of neurovascular tests to improve the detection of retinal damage in pathological conditions.

Associations of retinal oximetry in persons with diabetes.

BACKGROUND: There are limited data available on the variables that might affect retinal vessel oxygen saturation (SO2) in diabetes. Therefore, the aim of this study is to assess factors associated with retinal oximetry values in persons with diabetes. DESIGN: Clinic-based cross-sectional study. PARTICIPANTS: Fifty-eight persons with diabetes aged 18+ years, recruited from the University of Melbourne, the Royal Victorian Eye and Ear Hospital, and St. Vincent's Hospital (Melbourne), Australia. METHODS: Retinal oximetry was performed using the oximetry module of the Vesselmap system (Imedos UG, Jena, Germany) in 92 diabetic eyes. Generalized estimating equation models were used to estimate the associations between candidate variables (age; gender; retinal capillary flow; duration of diabetes; hypertension; smoking status; presence of diabetic retinopathy [DR]; glycated haemoglobin; triglyceride; total cholesterol; finger SO2 and ocular perfusion pressure) with retinal oximetry measures. MAIN OUTCOME MEASURE: Arteriolar SO2, venular SO2 and the arterio-venous (A-V) difference. RESULTS: Of the candidate factors assessed, only the presence of DR was significantly associated with increased venular SO2 and decreased A-V difference in unadjusted analyses. In models adjusting for age and gender and significant variables from unadjusted analyses, compared with no DR, the presence of DR was significantly associated with greater retinal venular SO2 values (ß = 3.65%, 95% confidence interval: 0.67-6.63%) and decreased A-V difference (ß = -2.00%, 95% confidence interval: -3.46 to -0.53%). CONCLUSION: In patients with diabetes, eyes with DR were associated with increased venular SO2 and decreased A-V difference compared with eyes without DR, suggesting an altered metabolic state in DR.

Flicker light-induced retinal vasodilation is unaffected by inhibition of epoxyeicosatrienoic acids and prostaglandins in humans.

PURPOSE: To investigate the role of epoxyeicosatrienoic acids (EETs) and prostaglandins (PGs) in retinal blood vessel calibers and vasodilation during flicker light stimulation in humans. METHODS: Twelve healthy nonsmokers participated in a balanced crossover study. Oral fluconazole 400 mg and dispersible aspirin 600 mg were used to inhibit production of EETs and PGs, respectively. Retinal imaging was performed 1 hour after drug ingestion with the Dynamic Vessel Analyzer. Resting calibers of selected vessel segments were recorded in measurement units (MU). Maximum percentage dilations during flicker stimulation were calculated from baseline calibers. We then studied six participants each after fluconazole and aspirin ingestions at 30-minute intervals for 2 hours. Within-subject differences were assessed by ANOVA and Dunnett-adjusted pairwise comparisons with significance taken at P < 0.05. RESULTS: In crossover study participants, mean (SD) arteriole and venule dilations without drug administration were 4.4% (2.0%) and 4.6% (1.7%), respectively. Neither drug affected vasodilation during flicker stimulation. Mean (SD) resting arteriole and venule calibers on no-drug visits were 119.6 (10.6) MU and 145.7 (17.0) MU, respectively. Fluconazole reduced mean (±95% CI) resting venule calibers by 5.1 (4.3) MU. In repeated measures participants, neither drug affected vasodilations, but fluconazole reduced resting venule calibers over 2 hours (P < 0.001). CONCLUSIONS: Epoxyeicosatrienoic acids and prostaglandins are unlikely to be primary mediators of flicker light-induced retinal vasodilation in humans. However, EETs may play a role in the regulation of retinal vascular tone and blood flow under resting physiological conditions.