Background: Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. Upregulation of COX2 (cyclooxygenase 2) and prostaglandin E2 (PGE2) was linked to podocyte damage in GH. We explored the potential renoprotective effects of either separate or combined pharmacological blockade of EP2 (PGE2 receptor type 2) and EP4 (PGE2 receptor type 4) in GH. Methods: We conducted in vivo studies in a transgenic zebrafish model (Tg[fabp10a:gc-EGFP]) suitable for analysis of glomerular filtration barrier function and a genetic rat model with GH, albuminuria, and upregulation of PGE2. Similar pharmacological interventions and primary outcome analysis on albuminuria phenotype development were conducted in both model systems. Results: Stimulation of zebrafish embryos with PGE2 induced an albuminuria-like phenotype, thus mimicking the suggested PGE2 effects on glomerular filtration barrier dysfunction. Both separate and combined blockade of EP2 and EP4 reduced albuminuria phenotypes in zebrafish and rat models. A significant correlation between albuminuria and podocyte damage in electron microscopy imaging was identified in the rat model. Dual blockade of both receptors showed a pronounced synergistic suppression of albuminuria. Importantly, this occurred without changes in arterial blood pressure, glomerular filtration rate, or tissue oxygenation in magnetic resonance imaging, while RNA sequencing analysis implicated a potential role of circadian clock genes. Conclusions: Our findings confirm a role of PGE2 in the development of albuminuria in GH and support the renoprotective potential of combined pharmacological blockade of EP2 and EP4 receptors. These data support further translational research to explore this therapeutic option and a possible role of circadian clock genes.

Background: Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. The Munich Wistar Frömter (MWF) rat is a non-diabetic model of chronic kidney disease (CKD) with GH due to inherited low nephron number resulting in spontaneous albuminuria and podocyte injury. In MWF rats, we identified prostaglandin (PG) E2 (PGE2) signaling as a potential causative mechanism of albuminuria in GH.Method: For evaluation of the renal PGE2 metabolic pathway, time-course lipidomic analysis of PGE2 and its downstream metabolites 15-keto-PGE2 and 13-14-dihydro-15-keto-PGE2 was conducted in urine, plasma and kidney tissues of MWF rats and albuminuria-resistant spontaneously hypertensive rats (SHR) by liquid chromatography electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS).Results: Lipidomic analysis revealed no dysregulation of plasma PGs over the time course of albuminuria development, while glomerular levels of PGE2 and 15-keto-PGE2 were significantly elevated in MWF compared to albuminuria-resistant SHR. Overall, averaged PGE2 levels in glomeruli were up to ×150 higher than the corresponding 15-keto-PGE2 levels. Glomerular metabolic ratios of 15-hydroxyprostaglandin dehydrogenase (15-PGDH) were significantly lower, while metabolic ratios of prostaglandin reductases (PTGRs) were significantly higher in MWF rats with manifested albuminuria compared to SHR, respectively.Conclusion: Our data reveal glomerular dysregulation of the PGE2 metabolism in the development of albuminuria in GH, resulting at least partly from reduced PGE2 degradation. This study provides first insights into dynamic changes of the PGE2 pathway that support a role of glomerular PGE2 metabolism and signaling for early albuminuria manifestation in GH.

Objective: Apart from the respiratory system, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can potentially infect multiple other organs including podocytes in the kidney. The latter play a crucial role in glomerular filtration. Podocytes can be damaged by increased fluid flow shear stress (FFSS) of the ultrafiltrate in Bowman's space in the setting of glomerular hyperfiltration that occurs in disease states such as hypertension, diabetes or in several forms of chronic kidney disease. These conditions are associated with an increased risk of a more severe course of coronavirus disease 2019 (COVID-19) and mortality. Design and method: To assess the susceptibility of human podocytes (hPC) for SARS-CoV-2 infection in the context of hyperfiltration in vitro, we used a recently established model system (Streamer® Shear Stress Device)) to mimic hyperfiltration by exposing hPC to increased FFSS of 1 dyne/cm2 for 2 h. In this setting we nalysed the effects of FFSS on mRNA expression of angiotensin I-converting enzyme 2 (ACE2) as the pivotal entry receptor for SARS-CoV-2 infection in hPC. Moreover, other potential critical host cell factors including transmembrane serine protease 2 (TMPRSS2), furin (FURIN), and neuropilin 1 (NRP1) were also assessed in parallel with changes of the F-actin fiber structure, i.e. an important cytoskeletal marker in hPC. Results: Under control conditions, hPC displayed long, parallel F-actin fibers crossing the entire cell body. After FFSS, an enrichment of cells that express F-actin in a cortically condensed pattern near the cell membrane was observed. FFSS induced a significant upregulation of ACE2 expression (about twofold) and of all other nalysed SARS-CoV-2 entry factors in hPC (p < 0.05, respectively compared to control conditions, Figure 1 with data plotted as log2fold change [FC]). Conclusions: Our data support a potential link between glomerular hyperfiltration, podocyte damage and renal tropism of SARS-CoV-2 that may contribute to kidney damage including albuminuria development in COVID-19 patients.

Objective: Glomerular hyperfiltration (GH) is an important mechanism in the development of albuminuria in hypertension. Recent in vitro data indicated an activation of an autocrine/paracrine cyclooxygenase 2 (COX2)/prostaglandin E2 (PGE2) pathway resulting in podocyte injury in GH by using fluid flow shear stress exposure. This was mediated by concerted ignalling via both prostaglandin E2 receptors (EP), EP2 and EP4. Here, we explored the role to target this pathway in vivo by using a rat model with GH and albuminuria. Design and method: We used the Munich Wistar Frömter (MWF) rat model with an inherited nephron deficit as a model of GH and albuminuria. Because analysis of PGE2 levels in vivo is limited by conventional methods, we developed a modified liquid chromatography tandem mass spectrometry (LC/ESI-MS/MS) protocol to quantify PGE2 levels in glomerular tissue. We then assessed glomerular PGE2 during the onset of albuminuria in young MWF at 4 to 8 weeks of age. Furthermore, the renoprotective effects of either separate or combined pharmacological blockade of EP2 (by PF-04418948) and EP4 (by ONO-AE3-208) in MWF was explored. Treatment started at the onset of albuminuria at 4 weeks and was continued for 8 weeks. Results: During the onset of albuminuria, PGE2 levels were significantly elevated in isolated glomeruli of MWF at both 4 and 8 weeks of age (p < 0.01, respectively) as compared to albuminuria resistant spontaneously hypertensive rats (SHR). At 12 weeks of age, untreated MWF developed pronounced albuminuria, which was significantly, although modestly, reduced by separate EP2 or EP4 blockade. Remarkably, combined EP2 and EP4 blockade resulted in a significant suppression (-71%) of albuminuria in MWF at 12 weeks. Importantly, this pharmacological treatment did not affect systolic blood pressure and creatinine clearance (Figure 1). Conclusions: We demonstrated the activation of glomerular PGE2 in vivo in the setting of hyperfiltration and albuminuria in the MWF rat model. Dual EP2 and EP4 receptor blockade exhibited a marked suppression of albuminuria without affecting systemic blood pressure and glomerular filtration rate. These data support further translational research to explore this therapeutic option for renoprotection.

Our results support a role of augmented PGE2/EP2/EP4 signaling in the setting of glomerular hyperfiltration and albuminuria.

Aims: Prostaglandins are important signaling lipids with prostaglandin E2 (PGE2) known to be the most abundant prostaglandin across tissues. In kidney, PGE2 plays an important role in the regulation of kidney homeostasis through its EP receptor signaling. Catabolism of PGE2 yields the metabolic products that are widely considered biologically inactive. Although recent in vitro evidence suggested the ability of 15-keto-PGE2 (a downstream metabolite of PGE2) to activate EP receptors, the question whether 15-keto-PGE2 exhibits physiological roles remains unresolved.Materials and methods: Pharmacological treatment was performed in transgenic zebrafish embryos using 500 mu M 15-keto-PGE2 and 20 mu M EP receptors antagonists' solutions during zebrafish embryonic development. After the exposure period, the embryos were fixed for confocal microscopy imaging and glomerular morphology analysis.Key findings: Here, we show that 15-keto-PGE2 can bind and stabilize EP2 and EP4 receptors on the plasma membrane in the yeast model. Using lipidomic analysis, we demonstrate both PGE2 and 15-keto-PGE2 are present at considerable levels in zebrafish embryos. Our high-resolution image analysis reveals the exogenous treatment with 15-keto-PGE2 perturbs glomerular vascularization during zebrafish development. Specifically, we show that the increased levels of 15-keto-PGE2 cause intercalation defects between podocytes and endothelial cells of glomerular capillaries effectively reducing the surface area of glomerular filtration barrier. Importantly, 15-keto-PGE2-dependent defects can be fully reversed by combined blockade of the EP2 and EP4 receptors.Significance: Altogether, our results reveal 15-keto-PGE2 to be a biologically active metabolite that modulates the EP receptor signaling in vivo, thus playing a potential role in kidney biology.

β-Blockers are important drugs in the treatment of cardiovascular diseases. They are suspected of inducing various psychiatric adverse events (PAEs), particularly depression, affecting cardiovascular morbidity and mortality. We performed a systematic search for double-blind, randomized controlled trials investigating β-blockers to analyze the risk of PAEs or withdrawal of therapy due to PAEs. We extracted the frequencies of PAEs and rates of withdrawals and reviewed them to the number of exposed patients. For β-blockers versus placebo or other active treatment, we calculated odds ratios for individual PAEs and withdrawal rates. We retrieved overall 285 eligible studies encompassing 53 533 patients. The risk of bias was judged to be high in 79% of the studies. Despite being the most frequently reported PAE with a total of 1600 cases, depression did not occur more commonly during β-blockers than during placebo (odds ratio, 1.02 [95% CI, 0.83–1.25]). β-Blocker use was also not associated with withdrawal for depression (odds ratio, 0.97 [95% CI, 0.51–1.84]). Similar results were obtained for comparisons against active agents. Among other PAEs, only unusual dreams, insomnia, and sleep disorder were possibly related to β-blocker therapy. In conclusion, this analysis of large-scale data from double-blind, randomized controlled trials does not support an association between β-blocker therapy and depression. Similarly, no effect for β-blockers was found for other PAEs, with the possible exceptions of sleep-related disorders. Consequently, concerns about β-blockers’ impact on psychological health should not affect their use in clinical practice.

Abstract Background and Aims We recently identified prostaglandin reductase 2 (Ptgr2) and the prostaglandin E2 (PGE2) pathway as potential causative mechanism in the Munich Wistar Frömter (MWF) non-diabetic rat model of chronic kidney disease. MWF is characterized by early onset of spontaneous albuminuria during a critical time window between 4 and 8 weeks of age, that associates with hyperfiltration, due to low nephron number, and podocyte injury. Ptgr2 plays an important role in the prostaglandin metabolism, in which PGE2 is metabolized by 15-prostaglandin dehydrogenase (15-PGDH) to 15-keto-PGE2. The latter is terminally degraded by prostaglandin reductases (PTGRs) 1, 2, and 3 to 13,14-dihydro-15-keto-PGE2. Recently, we detected elevated glomerular levels of PGE2 and 15-keto-PGE2 in MWF compared to spontaneously hypertensive rats (SHR) with no albuminuria. The aim of the present study was to characterize in detail the renal PGE2 metabolic pathway in MWF by lipidomic analysis during the time window of albuminuria onset. Method Male MWF and SHR rats were studied at week 4 and 8, respectively; 24 h-urine was collected in metabolic cages. In addition, plasma and kidney tissues including kidney cortex and isolated glomeruli were obtained from anesthetized rats. Lipidomic analysis was done by liquid chromatography electrospray ionization tandem mass spectrometry. Statistical analysis was performed by unpaired, two-tailed Student’s t-test, or otherwise the Mann-Whitney test. Results Urinary PGE2 was significantly lower (p<0.01), while urinary 15-keto-PGE2 and 13,14-dihydro-15-keto PGE2 levels were significantly increased in MWF compared to SHR at week 4 (p<0.01, respectively). All three analytes were significantly decreased in urine of MWF with increased albuminuria at week 8 (p<0.05 vs. SHR). The urinary metabolic ratio of 15-keto-PGE2/13,14-dihydro-15-keto-PGE2 as a surrogate for PTGRs activities was significantly increased at week 4 (p<0.01), whereas it was significantly decreased in MWF vs. SHR at week 8 (p<0.05). Plasma levels of PGE2 and 13,14-dihydro-15-keto-PGE2 did not differ between strains at both time points, while 15-keto-PGE2 was below the detection limit. Glomerular levels of PGE2 and 15-keto-PGE2 were increased in MWF at week 4 and 8 (p<0.01, respectively). In contrast, 13,14-dihydro-15-keto-PGE2 was only significantly higher at week 4 compared to SHR (p<0.01). In isolated glomeruli, the metabolic ratios of PTGRs were similar between the strains at week 4, but significantly increased in MWF compared to SHR at week 8 (p<0.01, respectively). In kidney cortex, 15-keto-PGE2 and 13,14-dihydro-15-keto-PGE2 were increased in MWF at week 4 (p<0.05 and p<0.01, respectively), whereas PGE2 levels were comparable to SHR. No difference for cortical levels of PGE2 and its metabolites was observed at week 8. Conclusion This study provides the first insights into age-dependent dynamic changes in the PGE2 pathway that support potential causality for the onset of albuminuria in the setting of non-diabetic hyperfiltration due to low nephron number. Notably, the increased glomerular levels of PGE2 and its downstream metabolites in 4-week-old MWF point towards an early activation of this pathway, i.e. before albuminuria occurs. This finding corroborates the hypothesis that glomerular PGE2 signaling is relevant in the early stages of hyperfiltration and suggests this pathway as a target for future therapeutics to modify the manifestation and progression of renal disease.

Glomerular hyperfiltration is an important mechanism in the development of albuminuria. During hyperfiltration, podocytes are exposed to increased fluid flow shear stress (FFSS) in Bowman’s space. Elevated Prostaglandin E2 (PGE2) synthesis and upregulated cyclooxygenase 2 (Cox2) are associated with podocyte injury by FFSS. We aimed to elucidate a PGE2 autocrine/paracrine pathway in human podocytes (hPC). We developed a modified liquid chromatography tandem mass spectrometry (LC/ESI-MS/MS) protocol to quantify cellular PGE2, 15-keto-PGE2, and 13,14-dihydro-15-keto-PGE2 levels. hPC were treated with PGE2 with or without separate or combined blockade of prostaglandin E receptors (EP), EP2, and EP4. Furthermore, the effect of FFSS on COX2, PTGER2, and PTGER4 expression in hPC was quantified. In hPC, stimulation with PGE2 led to an EP2- and EP4-dependent increase in cyclic adenosine monophosphate (cAMP) and COX2, and induced cellular PGE2. PTGER4 was downregulated after PGE2 stimulation in hPC. In the corresponding LC/ESI-MS/MS in vivo analysis at the tissue level, increased PGE2 and 15-keto-PGE2 levels were observed in isolated glomeruli obtained from a well-established rat model with glomerular hyperfiltration, the Munich Wistar Frömter rat. COX2 and PTGER2 were upregulated by FFSS. Our data thus support an autocrine/paracrine COX2/PGE2 pathway in hPC linked to concerted EP2 and EP4 signaling.