Predictors of damage accrual and its impact on health-related quality of life of thrombotic antiphospholipid syndrome: Independent validation of the damage index for antiphospholipid syndrome (DIAPS).

OBJECTIVES: We aim to independently assess the validity of the damage index for antiphospholipid syndrome (DIAPS) in thrombotic antiphospholipid syndrome (APS) patients by exploring the prevalence and risk factors of organ damage and evaluating its impact on health-related quality of life (HR-QoL). METHODS: Cross-sectional study including all thrombotic APS patients (Sydney criteria) attending a Portuguese tertiary centre. Damage was assessed using the DIAPS, and HR-QoL using the 3- and 5-level EuroQol HR-QoL (EQ-D5-3L and 5L), and Visual Analogue Scale (VAS) applied via a phone questionnaire. Spearman's correlation between DIAPS and the HR-QoL scales was performed. Risk factors for damage accrual and HR-QoL impairment were explored using univariate and multivariate logistic regression. RESULTS: Among the 108 patients (female, 65.7%; white, 90.7%; primary APS, 75.9%; median disease duration, 6 years), damage (DIAPS≥1) developed in 48.2% of patients (mean ± SD DIAPS, 3.08 ± 1.83). DIAPS's neuropsychiatric domain was the most affected (24.2%), followed by the peripheral vascular domain (20.3%). No clinical, demographic nor laboratory parameters were significantly associated with damage. Regarding HR-QoL, pain/discomfort, anxiety/depression and usual activities domains were the most frequently impaired in both scales. DIAPS's domains correlated similarly with the EQ-5D-3L and 5L scales' individual domains. Female sex, medical disorders, secondary APS and type of presenting thrombosis (arterial) increased the risk of HR-QoL impairment. Total DIAPS was associated with higher odds of mobility, self-care and pain/discomfort impairment in both EQ-5D-3L and 5L scales but lost its independent risk in multivariable analysis. CONCLUSION: This external validation of DIAPS reinforces the ability of the score to correlate with HR-QoL while also highlighting risk factors for HR-QoL impairment other than damage accrual.

Early-Onset Dystonia and Visual Impairment Preceding Epileptic Encephalopathy Associated with PIGA Gene Mutation.

The association between dystonia and early-onset epileptic encephalopathy (EOEE) may have a genetic basis. Phosphatidylinositol glycan biosynthesis class A protein (PIGA) germline mutations have been described in the last decade and associated with refractory EOEEs. Dysmorphisms and visceral abnormalities have also been reported. Here, we present the case of a now 8-month-old child who was evaluated for dystonia, visual impairment, and developmental delay at 2 months of age, followed by refractory focal seizures when he was 4 months old. The remaining examination was normal, besides an accelerated linear growth. His brain magnetic resonance and an extensive metabolic investigation failed to show any abnormalities. At 7 months of age, the exome sequencing found a hemizygous PIGA pathogenic variant-c.1352T > C (p.(Ile451Thr). Seizures improved after the association of carbamazepine with levetiracetam and the beginning of the ketogenic diet. To our knowledge, this is the first time the phenotype associated with this specific mutation is described. Our patient had the singularity of manifesting with remarkable dystonia, over 2 months before the onset of seizures. We also point to the utility of the gene sequencing approach in the diagnosis of patients with dystonia and EOEEs, since identification of the genetic cause may help in patient's management and families' empowerment.

How do people in prison access palliative care? A scoping review of models of palliative care delivery for people in prison in high-income countries.

BACKGROUND: An ageing prison population with complex health needs combined with punitive sentencing practices means palliative care for incarcerated individuals is increasingly important. However, there is limited evidence regarding the models of care delivery in high-income countries, and their associated challenges and benefits. AIM: To develop a typology of models of palliative care provision for incarcerated individuals, synthesise evidence of their outcomes and describe facilitators of and challenges in delivering different models of palliative and end-of-life care in prisons. DESIGN: Scoping review following Arksey and O'Malley, with narrative synthesis. The protocol was registered prospectively (reviewregistry1260). DATA SOURCES: MEDLINE, EMBASE, CINAHL, PsycINFO, the Social Sciences Citation Index and grey literature were searched on 15th March 2023. The Mixed Methods Appraisal Tool (MMAT) was used for quality appraisal. RESULTS: A total of 16,865 records were screened; 22 peer-reviewed articles and 18 grey literature sources met the inclusion criteria. Three models were identified: Embedded Hospice, Outsourcing Care and Community Collaboration. The Embedded Hospice model shows potential benefits for patients and prisons. Outsourcing Care may miss opportunities for comprehensive care. Collaborative Care relies on proactive prison-community relationships that could be formalised for improvement. Psychosocial and bereavement needs of those dying in prison and their caregivers lack sufficient documentation. CONCLUSION: Further research is needed to evaluate prison hospice costs and examine how prison hospices impact compassionate release usage. Beyond the USA, policies might formalise care pathways and recognise best practices. Further investigation to address psychosocial needs of people in prison with life-limiting illnesses and post-death bereavement support is required.

Correlation Between Pedal Acceleration Time and Transcutaneous Oxygen Pressures - A Prognostic Tool for Wound Healing in the Diabetic Foot Population.

BACKGROUND: Pedal arch interrogation by ultrasound through systolic acceleration time measurement (Pedal Acceleration Time [PAT]) is a recently described technique that offers valuable insights into foot hemodynamics. Previous studies have demonstrated a correlation between PAT and the ankle-brachial index and PAT has been proposed as a prognostic tool for wound healing in patients with peripheral artery disease. This study aims to assess the correlation between PAT and Transcutaneous Pressure of Oxygen (TcPO2) in the diabetic foot population. METHODS: In this single-center cross-sectional study PAT and TcPO2 were measured in diabetic patients with ischemic foot ulcers. The assessment of wound status was performed between the 12th and 16th week after the first evaluation. The primary outcome was to assess the correlation between the values obtained for PAT and TcPO2. The secondary outcome was to establish a cut-off value for wound healing. RESULTS: Sixty limbs with ischemic foot ulcers were evaluated. The results showed a correlation between PAT and TcPO2 [F (1.52) = 16.928; R2 = 0.246; P < 0.001]. The receiver operating characteristics curve analysis showed an optimal cut-off value at PAT >186 ms for predicting a nonhealing ulcer with a 96% specificity (area under the curve = 0.774; confidence interval 0.648-0.872; P < 0.001). CONCLUSIONS: PAT showed a significant correlation with TcPO2 with high specificity to identify nonhealing foot ulcers due to insufficient foot perfusion with a potential prognostic value in the diabetic foot population.

Photoswitchable Calixarene Activators for Controlled Peptide Transport across Lipid Membranes.

Supramolecular synthetic transporters are crucial to understand and activate the passage across lipid membranes of hydrophilic effector molecules. Herein, we introduce photoswitchable calixarenes for the light-controlled transport activation of cationic peptide cargos across model lipid bilayers and inside living cells. Our approach was based on rationally designed p-sulfonatocalix[4]arene receptors equipped with a hydrophobic azobenzene arm, which recognize cationic peptide sequences at the nM range. Activation of membrane peptide transport is confirmed, in synthetic vesicles and living cells, for calixarene activators featuring the azobenzene arm in the E configuration. Therefore, this method allows the modulation of the transmembrane transport of peptide cargos upon Z-E photoisomerization of functionalized calixarenes using 500 nm visible light. These results showcase the potential of photoswitchable counterion activators for the light-triggered delivery of hydrophilic biomolecules and pave the way for potential applications in remotely controlled membrane transport and photopharmacology applications of hydrophilic functional biomolecules.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition).

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

OMIP-084: 28-color full spectrum flow cytometry panel for the comprehensive analysis of human γδ T cells.

Using full spectrum flow cytometry, we designed a 28-color panel for the analysis of markers known to be associated with the γδ T cell immune response. This panel allows the classification of γδ T cell subsets via specific V gene usage (Vγ9, Vδ1, Vδ2, and Vδ3) of their T cell receptor (TCR) and according to their functional differentiation. Phenotypical surface receptors to distinguish different stages of cell maturation included CD45RA, CD27, CD28, CD127, CD57, and CD16; chemokine receptors CXCR6, CCR5, CCR6, and CX3CR1; NK-associated markers NKG2A, NKG2D, CD56, and CD161, checkpoint-inhibitor PD-1, and activating receptors CD38 and CD25. T cell lineage markers for the analysis of αß T cells (CD4 and CD8) and MAIT cells (Vα7.2) were also included. This optimized multicolor panel allows a comprehensive immune-profiling of all main human γδ T cell subsets and is suitable for longitudinal or exploratory analysis of γδ T cell development and γδ T cell dynamics in clinical cohorts.

Mutual interplay between IL-17-producing γδT cells and microbiota orchestrates oral mucosal homeostasis.

γδT cells are a major component of epithelial tissues and play a role in tissue homeostasis and host defense. γδT cells also reside in the gingiva, an oral tissue covered with specialized epithelium that continuously monitors the challenging dental biofilm. Whereas most research on intraepithelial γδT cells focuses on the skin and intestine epithelia, our knowledge on these cells in the gingiva is still incomplete. In this study, we demonstrate that even though the gingiva develops after birth, the majority of gingival γδT cells are fetal thymus-derived Vγ6+ cells, and to a lesser extent Vγ1+ and Vγ4+ cells. Furthermore, we show that γδT cells are motile and locate preferentially in the epithelium adjacent to the biofilm. Vγ6+ cells represent the major source of IL-17-producing cells in the gingiva. Chimeric mice and parabiosis experiments indicated that the main fraction of gingival γδT cells is radioresistant and tissue-resident, persisting locally independent of circulating γδT cells. Notably, gingival γδT cell homeostasis is regulated by the microbiota as the ratio of Vγ6+ and Vγ4+ cells was reversed in germ-free mice, and their activation state was decreased. As a consequence, conditional ablation of γδT cells results in elevated gingival inflammation and subsequent alterations of oral microbial diversity. Taken together, these findings suggest that oral mucosal homeostasis is shaped by reciprocal interplays between γδT cells and local microbiota.

Changes in NAD and Lipid Metabolism Drive Acidosis-Induced Acute Kidney Injury.

BACKGROUND: The kidney plays an important role in maintaining normal blood pH. Metabolic acidosis (MA) upregulates the pathway that mitochondria in the proximal tubule (PT) use to produce ammonia and bicarbonate from glutamine, and is associated with AKI. However, the extent to which MA causes AKI, and thus whether treating MA would be beneficial, is unclear. METHODS: Gavage with ammonium chloride induced acute MA. Multiphoton imaging of mitochondria (NADH/membrane potential) and transport function (dextran/albumin uptake), oxygen consumption rate (OCR) measurements in isolated tubules, histologic analysis, and electron microscopy in fixed tissue, and urinary biomarkers (KIM-1/clara cell 16) assessed tubular cell structure and function in mouse kidney cortex. RESULTS: MA induces an acute change in NAD redox state (toward oxidation) in PT mitochondria, without changing the mitochondrial energization state. This change is associated with a switch toward complex I activity and decreased maximal OCR, and a major alteration in normal lipid metabolism, resulting in marked lipid accumulation in PTs and the formation of large multilamellar bodies. These changes, in turn, lead to acute tubular damage and a severe defect in solute uptake. Increasing blood pH with intravenous bicarbonate substantially improves tubular function, whereas preinjection with the NAD precursor nicotinamide (NAM) is highly protective. CONCLUSIONS: MA induces AKI via changes in PT NAD and lipid metabolism, which can be reversed or prevented by treatment strategies that are viable in humans. These findings might also help to explain why MA accelerates decline in function in CKD.

Valorization of Amaranth (Amaranthus cruentus) Grain Extracts for the Development of Alginate-Based Active Films.

This research work investigates the development of alginate-based films incorporating phenolic compounds extracted from Amaranthus cruentus grain using different solvents. Alginate, glycerol, and amaranth grain phenolic compounds at various concentrations were used to produce the films. An experimental Central Composite Rotatable Design (CCRD) was used to evaluate the effect of these variables on different film's properties, i.e., water vapor permeability, hydrophobicity, moisture content, solubility, thermal, mechanical, and optical properties. This study demonstrated that high phenolic compound content and antioxidant capacity were obtained from amaranth grain using ethanol as the extraction solvent. Alginate films incorporating amaranth phenolic compounds were successfully manufactured, and this study can be used to tailor the formulation of alginate films containing amaranth phenolic compounds, depending on their final food application. For example, less flexible but more resistant and water-soluble films can be produced by increasing the alginate concentration, which was confirmed by a Principal Component Analysis (PCA) and Partial Least Squares (PLS) analysis. This study showed that active alginate films with amaranth phenolic compounds can be tailored to be used as food packaging material with potential antioxidant activity.

Intravital kidney microscopy: entering a new era.

The development of intravital imaging with multiphoton microscopy has had a major impact on kidney research. It provides the unique opportunity to visualize dynamic behavior of cells and organelles in their native environment and to relate this to the complex 3-dimensional structure of the organ. Moreover, changes in cell/organelle function can be followed in real time in response to physiological interventions or disease-causing insults. However, realizing the enormous potential of this exciting approach has necessitated overcoming several substantial practical hurdles. In this article, we outline the nature of these challenges and how a variety of technical advances have provided effective solutions. In particular, improvements in laser/microscope technology, fluorescent probes, transgenic animals, and abdominal windows are collectively making previously opaque processes visible. Meanwhile, the rise of machine learning-based image analysis is facilitating the rapid generation of large amounts of quantitative data, amenable to deeper statistical interrogation. Taken together, the increased capabilities of multiphoton imaging are opening up huge new possibilities to study structure-function relationships in the kidney in unprecedented detail. In addition, they are yielding important new insights into cellular mechanisms of tissue damage, repair, and adaptive remodeling during disease states. Thus, intravital microscopy is truly entering an exciting new era in translational kidney research.

Nonlinear plant-plant interactions modulate impact of extreme drought and recovery on a Mediterranean ecosystem.

Interaction effects of different stressors, such as extreme drought and plant invasion, can have detrimental effects on ecosystem functioning and recovery after drought. With ongoing climate change and increasing plant invasion, there is an urgent need to predict the short- and long-term interaction impacts of these stressors on ecosystems. We established a combined precipitation exclusion and shrub invasion (Cistus ladanifer) experiment in a Mediterranean cork oak (Quercus suber) ecosystem with four treatments: (1) Q. suber control; (2) Q. suber with rain exclusion; (3) Q. suber invaded by shrubs; and (4) Q. suber with rain exclusion and shrub invasion. As key parameter, we continuously measured ecosystem water fluxes. In an average precipitation year, the interaction effects of both stressors were neutral. However, the combination of imposed drought and shrub invasion led to amplifying interaction effects during an extreme drought by strongly reducing tree transpiration. Contrarily, the imposed drought reduced the competitiveness of the shrubs in the following recovery period, which buffered the negative effects of shrub invasion on Q. suber. Our results demonstrate the highly dynamic and nonlinear effects of interacting stressors on ecosystems and urges for further investigations on biotic interactions in a context of climate change pressures.

Multiparametric imaging reveals that mitochondria-rich intercalated cells in the kidney collecting duct have a very high glycolytic capacity.

Alpha intercalated cells (αICs) in the kidney collecting duct (CD) belong to a family of mitochondria rich cells (MRCs) and have a crucial role in acidifying the urine via apical V-ATPase pumps. The nature of metabolism in αICs and its relationship to transport was not well-understood. Here, using multiphoton live cell imaging in mouse kidney tissue, FIB-SEM, and other complementary techniques, we provide new insights into mitochondrial structure and function in αICs. We show that αIC mitochondria have a rounded structure and are not located in close proximity to V-ATPase containing vesicles. They display a bright NAD(P)H fluorescence signal and low uptake of voltage-dependent dyes, but are energized by a pH gradient. However, expression of complex V (ATP synthase) is relatively low in αICs, even when stimulated by metabolic acidosis. In contrast, anaerobic glycolytic capacity is surprisingly high, and sufficient to maintain intracellular calcium homeostasis in the presence of complete aerobic inhibition. Moreover, glycolysis is essential for V-ATPase-mediated proton pumping. Key findings were replicated in narrow/clear cells in the epididymis, also part of the MRC family. In summary, using a range of cutting-edge techniques to investigate αIC metabolism in situ, we have discovered that these mitochondria dense cells have a high glycolytic capacity.

Nationwide Study of Drug Resistance Mutations in HIV-1 Infected Individuals under Antiretroviral Therapy in Brazil.

The success of antiretroviral treatment (ART) is threatened by the emergence of drug resistance mutations (DRM). Since Brazil presents the largest number of people living with HIV (PLWH) in South America we aimed at understanding the dynamics of DRM in this country. We analyzed a total of 20,226 HIV-1 sequences collected from PLWH undergoing ART between 2008-2017. Results show a mild decline of DRM over the years but an increase of the K65R reverse transcriptase mutation from 2.23% to 12.11%. This increase gradually occurred following alterations in the ART regimens replacing zidovudine (AZT) with tenofovir (TDF). PLWH harboring the K65R had significantly higher viral loads than those without this mutation (p < 0.001). Among the two most prevalent HIV-1 subtypes (B and C) there was a significant (p < 0.001) association of K65R with subtype C (11.26%) when compared with subtype B (9.27%). Nonetheless, evidence for K65R transmission in Brazil was found both for C and B subtypes. Additionally, artificial neural network-based immunoinformatic predictions suggest that K65R could enhance viral recognition by HLA-B27 that has relatively low prevalence in the Brazilian population. Overall, the results suggest that tenofovir-based regimens need to be carefully monitored particularly in settings with subtype C and specific HLA profiles.

Quantitative intravital Ca2+ imaging maps single cell behavior to kidney tubular structure.

Ca2+ is an important second messenger that translates extracellular stimuli into intracellular responses. Although there has been significant progress in understanding Ca2+ dynamics in organs such as the brain, the nature of Ca2+ signals in the kidney is still poorly understood. Here, we show that by using a genetically expressed highly sensitive reporter (GCaMP6s), it is possible to perform imaging of Ca2+ signals at high resolution in the mouse kidney in vivo. Moreover, by applying machine learning-based automated analysis using a Ca2+-independent signal, quantitative data can be extracted in an unbiased manner. By projecting the resulting data onto the structure of the kidney, we show that different tubular segments display highly distinct spatiotemporal patterns of Ca2+ signals. Furthermore, we provide evidence that Ca2+ activity in the proximal tubule decreases with increasing distance from the glomerulus. Finally, we demonstrate that substantial changes in intracellular Ca2+ can be detected in proximal tubules in a cisplatin model of acute kidney injury, which can be linked to alterations in cell structure and transport function. In summary, we describe a powerful new tool to investigate how single cell behavior is integrated with whole organ structure and function and how it is altered in disease states relevant to humans.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition).

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Efficacy and safety of sirolimus in the treatment of vascular anomalies: A systematic review.

OBJECTIVE: The management of vascular anomalies is complex and requires a multidisciplinary team with a combination of medical, surgical, and intervention treatments. Medical treatment is limited and has conflicting results. Off-label use of mammalian target of rapamycin inhibitors shows promising results. The objective of this study was to systematically evaluate the literature published about the efficacy and safety of sirolimus in the treatment of vascular anomalies. METHODS: A systematic review of the published literature was conducted using the PubMed database and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. RESULTS: There were 73 articles included: 2 randomized controlled studies, 2 nonrandomized prospective studies, and 69 retrospective case reports and case series. In total, 373 patients were included. Sirolimus was administered topically to 56 patients and orally to 317 patients. Sirolimus was highly effective in the treatment of vascular tumors associated with Kasabach-Merritt phenomenon (95.5% of the patients clinically improved and 93% had normalization of coagulopathy), venous malformations (size reduction was observed in 88.9% of patients), and lymphatic malformations (clinical improvement in 94.9% of patients). Topical sirolimus results were conflicting. Arteriovenous malformations were not improved by sirolimus. CONCLUSIONS: Low-level evidence suggests that sirolimus can improve the prognosis of vascular anomalies, most notably vascular tumors associated with life-threatening coagulopathy and venous and lymphatic malformations. Further research is needed to establish the benefits of sirolimus in the management of vascular anomalies.

Protein Phosphatase 1 Inhibitor-1 Mediates the cAMP-Dependent Stimulation of the Renal NaCl Cotransporter.

BACKGROUND: A number of cAMP-elevating hormones stimulate phosphorylation (and hence activity) of the NaCl cotransporter (NCC) in the distal convoluted tubule (DCT). Evidence suggests that protein phosphatase 1 (PP1) and other protein phosphatases modulate NCC phosphorylation, but little is known about PP1's role and the mechanism regulating its function in the DCT. METHODS: We used ex vivo mouse kidney preparations to test whether a DCT-enriched inhibitor of PP1, protein phosphatase 1 inhibitor-1 (I1), mediates cAMP's effects on NCC, and conducted yeast two-hybrid and coimmunoprecipitation experiments in NCC-expressing MDCK cells to explore protein interactions. RESULTS: Treating isolated DCTs with forskolin and IBMX increased NCC phosphorylation via a protein kinase A (PKA)-dependent pathway. Ex vivo incubation of mouse kidney slices with isoproterenol, norepinephrine, and parathyroid hormone similarly increased NCC phosphorylation. The cAMP-induced stimulation of NCC phosphorylation strongly correlated with the phosphorylation of I1 at its PKA consensus phosphorylation site (a threonine residue in position 35). We also found an interaction between NCC and the I1-target PP1. Moreover, PP1 dephosphorylated NCC in vitro, and the PP1 inhibitor calyculin A increased NCC phosphorylation. Studies in kidney slices and isolated perfused kidneys of control and I1-KO mice demonstrated that I1 participates in the cAMP-induced stimulation of NCC. CONCLUSIONS: Our data suggest a complete signal transduction pathway by which cAMP increases NCC phosphorylation via a PKA-dependent phosphorylation of I1 and subsequent inhibition of PP1. This pathway might be relevant for the physiologic regulation of renal sodium handling by cAMP-elevating hormones, and may contribute to salt-sensitive hypertension in patients with endocrine disorders or sympathetic hyperactivity.

Selective Recognition of Amino Acids and Peptides by Small Supramolecular Receptors.

To this day, the recognition and high affinity binding of biomolecules in water by synthetic receptors remains challenging, while the necessity for systems for their sensing, transport and modulation persists. This problematic is prevalent for the recognition of peptides, which not only have key roles in many biochemical pathways, as well as having pharmacological and biotechnological applications, but also frequently serve as models for the study of proteins. Taking inspiration in nature and on the interactions that occur between several receptors and peptide sequences, many researchers have developed and applied a variety of different synthetic receptors, as is the case of macrocyclic compounds, molecular imprinted polymers, organometallic cages, among others, to bind amino acids, small peptides and proteins. In this critical review, we present and discuss selected examples of synthetic receptors for amino acids and peptides, with a greater focus on supramolecular receptors, which show great promise for the selective recognition of these biomolecules in physiological conditions. We decided to focus preferentially on small synthetic receptors (leaving out of this review high molecular weight polymeric systems) for which more detailed and accurate molecular level information regarding the main structural and thermodynamic features of the receptor biomolecule assemblies is available.

Systemic ß adrenergic stimulation/ sympathetic nerve system stimulation influences intraocular RAS through cAMP in the RPE.

Several lines of evidence support the existence of a renin-angiotensin system (RAS) in the retina that is separated from the blood stream by the retinal pigment epithelium (RPE). Under physiological conditions, increased activity of intraretinal RAS regulates neuronal activity of the retina but patho-physiologically participates in retinal degeneration such as hypertensive or diabetic retinopathy. Interestingly, the RPE appears to be a modulator of intraretinal RAS in response to changes in systemic RAS. As increased systemic RAS activity is associated with increased sympathetic tonus, we investigated whether systemic ß-adrenergic stimulation of the RPE also modulates renin expression in the RPE. In vivo, the mouse RPE expresses the ß-adrenergic receptor subtypes 1 and 2. Staining of retina sagittal sections showed tyrosine hydroxylase positive nerve endings in the choroid indicating adrenaline/noradrenaline production sites in close proximity to the RPE. Systemic infusion of isoproterenol increased renin expression in the RPE but not in the retina. This increase was sensitive to concomitant systemic application of the angiotensin-2 receptor-type-1 blocker losartan. In vitro analysis of renin gene expression using polarized porcine RPE showed that the activity of the renin promoter can be increased by cAMP stimulation (IBMX/forskolin) but was not influenced by angiotensin-2. Thus, with the identification of the ß-adrenergic system we added a new regulator of the retinal RAS with relevance for retinal function and pathology. Furthermore, it appears that the RPE is not only a close interaction partner of the photoreceptors but also a regulator or retinal activity in general.