Serum Calcification Propensity Is Increased in Myocardial Infarction and Hints at a Pathophysiological Role Independent of Classical Cardiovascular Risk Factors.

BACKGROUND: Vascular calcification is associated with increased mortality in patients with cardiovascular disease. Secondary calciprotein particles are believed to play a causal role in the pathophysiology of vascular calcification. The maturation time (T50) of calciprotein particles provides a measure of serum calcification propensity. We compared T50 between patients with ST-segment-elevated myocardial infarction and control subjects and studied the association of T50 with cardiovascular risk factors and outcome. METHODS: T50 was measured by nephelometry in 347 patients from the GIPS-III trial and in 254 matched general population controls from PREVEND (Prevention of Renal and Vascular End-Stage Disease). We also assessed the association between T50 and left ventricular ejection fraction, as well as infarct size, the incidence of ischemia-driven reintervention during 5 years of follow-up, and serum nitrite as a marker of endothelial dysfunction. RESULTS: Patients with ST-segment-elevated myocardial infarction had a significantly lower T50 (ie, higher serum calcification propensity) compared with controls (T50: 289±63 versus 338±56 minutes; P<0.001). In patients with ST-segment-elevated myocardial infarction, lower T50 was associated with female sex, lower systolic blood pressure, lower total cholesterol, lower LDL (low-density lipoprotein) cholesterol, lower triglycerides, and higher HDL (high-density lipoprotein) cholesterol but not with circulating nitrite or nitrate. Ischemia-driven reintervention was associated with higher LDL (P=0.03) and had a significant interaction term for T50 and sex (P=0.005), indicating a correlation between ischemia-driven reintervention and T50 above the median in men and below the median in women, between 150 days and 5 years of follow-up. CONCLUSIONS: Serum calcification propensity is increased in patients with ST-segment-elevated myocardial infarction compared with the general population, and its contribution is more pronounced in women than in men. Its lack of/inverse association with nitrite and blood pressure confirms T50 to be orthogonal to traditional cardiovascular disease risk factors. Lower T50 was associated with a more favorable serum lipid profile, suggesting the involvement of divergent pathways of calcification stress and lipid stress in the pathophysiology of myocardial infarction.

The role of neutrophil extracellular trap formation in kidney transplantation: Implications from donors to the recipient.

Kidney transplantation remains the gold standard for patients with end-stage renal disease, but severe donor organ shortage has led to long waiting lists. The utilization of expanded criteria donor kidneys within the category of deceased donors has enlarged the pool of available kidneys for transplantation; however, these grafts often have an increased risk for delayed graft function or reduced graft survival following transplantation. During brain or circulatory death, neutrophils are recruited to the vascular beds of kidneys where a proinflammatory microenvironment might prime the formation of neutrophil extracellular traps (NETs), web-like structures, containing proteolytic enzymes, DNA, and histones. NETs are known to cause tissue damage and specifically endothelial damage while activating other systems such as coagulation and complement, contributing to tissue injury and an unfavorable prognosis in various diseases. In lung transplantation and kidney transplantation studies, NETs have also been associated with primary graft dysfunction or rejection. In this review, the role that NETs might play across the different phases of transplantation, already initiated in the donor, during preservation, and in the recipient, will be discussed. Based on current knowledge, NETs might be a promising therapeutic target to improve graft outcomes.

Serum T50 predicts cardiovascular mortality in individuals with type 2 diabetes: A prospective cohort study.

BACKGROUND AND AIMS: Individuals with type 2 diabetes (T2D) have a higher risk of cardiovascular disease, compared with those without T2D. The serum T50 test captures the transformation time of calciprotein particles in serum. We aimed to assess whether serum T50 predicts cardiovascular mortality in T2D patients, independent of traditional risk factors. METHODS: We analyzed 621 individuals with T2D in this prospective cohort study. Cox regression models were performed to test the association between serum T50 and cardiovascular and all-cause mortality. Causes of death were categorized according to ICD-10 codes. Risk prediction improvement was assessed by comparing Harrell's C for models without and with T50. RESULTS: The mean age was 64.2 ± 9.8 years, and 61% were male. The average serum T50 time was 323 ± 63 min. Higher age, alcohol use, high-sensitive C-reactive protein, and plasma phosphate were associated with lower serum T50 levels. Higher plasma triglycerides, venous bicarbonate, sodium, magnesium, and alanine aminotransferase were associated with higher serum T50 levels. After a follow-up of 7.5[5.4-10.7] years, each 60 min decrease in serum T50 was associated with an increased risk of cardiovascular (fully adjusted HR 1.32, 95% CI 1.08-1.50, and p = 0.01) and all-cause mortality (HR 1.15, 95%CI 1.00-1.38, and p = 0.04). Results were consistent in sensitivity analyses after exclusion of individuals with estimated glomerular filtration rate <45 or <60 mL/min/1.73 m2 and higher plasma phosphate levels. CONCLUSIONS: Serum T50 improves prediction of cardiovascular and all-cause mortality risk in individuals with T2D. Serum T50 may be useful for risk stratification and to guide therapeutic strategies aiming to reduce cardiovascular mortality in T2D.

Calciprotein Particles Induce Endothelial Dysfunction by Impairing Endothelial Nitric Oxide Metabolism.

BACKGROUND: Calciprotein particles (CPPs) are associated with the development of vascular calcifications in chronic kidney disease. The role of endothelial cells (ECs) in this process is unknown. Here, we investigated the interaction of CPPs and ECs, thereby focusing on endothelial nitric oxide metabolism and oxidative stress. METHODS: CPPs were generated in calcium- and phosphate-enriched medium. Human umbilical vein endothelial cells were exposed to different concentrations of CPPs (0-100 µg/mL) for 24 or 72 hours. Ex vivo porcine coronary artery rings were used to measure endothelial cell-dependent vascular smooth muscle cell relaxation after CPP exposure. Serum samples from an early chronic kidney disease cohort (n=245) were analyzed for calcification propensity (measure for CPP formation) and nitrate and nitrite levels (NOx). RESULTS: CPP exposure for 24 hours reduced eNOS (endothelial nitric oxide synthase) mRNA expression and decreased nitrite production, indicating reduced nitric oxide bioavailability. Also, 24-hour CPP exposure caused increased mitochondria-derived superoxide generation, together with nitrotyrosine protein residue formation. Long-term (72 hours) exposure of human umbilical vein endothelial cells to CPPs induced eNOS uncoupling and decreased eNOS protein expression, indicating further impairment of the nitric oxide pathway. The ex vivo porcine coronary artery model showed a significant reduction in endothelial-dependent vascular smooth muscle cell relaxation after CPP exposure. A negative association was observed between NOx levels and calcification propensity (r=-0.136; P=0.049) in sera of (early) chronic kidney disease patients. CONCLUSIONS: CPPs cause endothelial cell dysfunction by impairing nitric oxide metabolism and generating oxidative stress. Our findings provide new evidence for direct effects of CPPs on ECs and pathways involved.

Validation of an ex vivo Flow Model Including Magnetic Resonance Imaging to Study the Effects of Endovascular Treatments on the Arterial Wall.

Endovascular revascularization is the preferred treatment for peripheral arterial disease. Restenosis often occurs as a response to procedure-induced arterial damage. Reducing vascular injury during endovascular revascularization may improve its success rate. This study developed and validated an ex vivo flow model using porcine iliac arteries, obtained from a local abattoir. Twenty arteries (of 10 pigs) were equally allocated to two groups: a mock-treated control group and an endovascular intervention group. Arteries of both groups were perfused with porcine blood for 9 min, including 3 min of balloon angioplasty in the intervention group. Vessel injury was assessed by calculating the presence of endothelial cell denudation, vasomotor function, and histopathological analysis. MR imaging displayed balloon positioning and inflation. Endothelial cell staining showed 76% of denudation after ballooning compared to 6% in the control group (p < 0.001). This was confirmed by histopathological analysis, showing a significantly reduced endothelial nuclei count after ballooning compared to the controls (median: 22 vs. 37 nuclei/mm, p = 0.022). In the intervention group, vasoconstriction and endothelium-dependent relaxation were significantly reduced (p < 0.05).We present an ex vivo flow model to test the effects of endovascular therapy on the vessel's wall morphology, endothelial denudation, and endothelial-dependent vasomotor function under physiological conditions. Additionally, it allows the future testing of human arterial tissue.

Calciprotein Particles: Balancing Mineral Homeostasis and Vascular Pathology.

[Figure: see text].

COVID-19: immunopathology, pathophysiological mechanisms, and treatment options.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread globally despite the worldwide implementation of preventive measures to combat the disease. Although most COVID-19 cases are characterised by a mild, self-limiting disease course, a considerable subset of patients develop a more severe condition, varying from pneumonia and acute respiratory distress syndrome (ARDS) to multi-organ failure (MOF). Progression of COVID-19 is thought to occur as a result of a complex interplay between multiple pathophysiological mechanisms, all of which may orchestrate SARS-CoV-2 infection and contribute to organ-specific tissue damage. In this respect, dissecting currently available knowledge of COVID-19 immunopathogenesis is crucially important, not only to improve our understanding of its pathophysiology but also to fuel the rationale of both novel and repurposed treatment modalities. Various immune-mediated pathways during SARS-CoV-2 infection are relevant in this context, which relate to innate immunity, adaptive immunity, and autoimmunity. Pathological findings in tissue specimens of patients with COVID-19 provide valuable information with regard to our understanding of pathophysiology as well as the development of evidence-based treatment regimens. This review provides an updated overview of the main pathological changes observed in COVID-19 within the most commonly affected organ systems, with special emphasis on immunopathology. Current management strategies for COVID-19 include supportive care and the use of repurposed or symptomatic drugs, such as dexamethasone, remdesivir, and anticoagulants. Ultimately, prevention is key to combat COVID-19, and this requires appropriate measures to attenuate its spread and, above all, the development and implementation of effective vaccines. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

The Disease-Modifying Role of Taurine and Its Therapeutic Potential in Coronavirus Disease 2019 (COVID-19).

Taurine is an amino sulfonic acid that is implicated in numerous physiological functions, including the regulation of oxidative stress, which plays an important role in coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), together with other pathophysiological processes. The recent finding of decreased serum taurine levels in SARS-CoV-2-infected patients, in tandem with its potential modulatory role in COVID-19 due to its antiviral, antioxidant, anti-inflammatory, and vascular-related effects, provides a rationale for considering taurine as a beneficial supplement in patients suffering from COVID-19. Here, we reviewed the potential disease-modifying effects of taurine and combined these with the current knowledge on COVID-19 to clarify the potential role of taurine in this respiratory disease.

Serum Calcification Propensity and the Risk of Cardiovascular and All-Cause Mortality in the General Population: The PREVEND Study.

OBJECTIVE: Vascular calcification contributes to the cause of cardiovascular disease. The calciprotein particle maturation time (T50) in serum, a measure of calcification propensity, has been linked with adverse outcomes in patients with chronic kidney disease, but its role in the general population is unclear. We investigated whether serum T50 is associated with cardiovascular mortality in a large general population-based cohort. Approach and Results: The relationship between serum T50 and cardiovascular mortality was studied in 6231 participants of the PREVEND (Prevention of Renal and Vascular End-Stage Disease) cohort. All-cause mortality was the secondary outcome. Mean (±SD) age was 53±12 years, 50% were male, and mean serum T50 was 329±58 minutes. A shorter serum T50 is indicative of a higher calcification propensity. Serum T50 was inversely associated with circulating phosphate, age, estimated glomerular filtration rate, and alcohol consumption, whereas plasma magnesium was positively associated with serum T50 (P<0.001, total multivariable model R2=0.281). During median (interquartile range) follow-up for 8.3 (7.8-8.9) years, 364 patients died (5.8%), of whom 95 (26.1%) died from a cardiovascular cause. In multivariable Cox proportional hazard models, each 60 minutes decrease in serum T50 was independently associated with a higher risk of cardiovascular mortality (fully adjusted hazard ratio [95% CI], 1.22 [1.04-1.36], P=0.021). This association was modified by diabetes mellitus; stratified analysis indicated a more pronounced association in individuals with diabetes mellitus. CONCLUSIONS: Serum T50 is independently associated with an increased risk of cardiovascular mortality in the general population and thus may be an early and potentially modifiable risk marker for cardiovascular mortality.

Angiotensin-converting enzyme 2 (ACE2), SARS-CoV-2 and the pathophysiology of coronavirus disease 2019 (COVID-19).

Angiotensin-converting enzyme 2 (ACE2) has been established as the functional host receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the current devastating worldwide pandemic of coronavirus disease 2019 (COVID-19). ACE2 is abundantly expressed in a variety of cells residing in many different human organs. In human physiology, ACE2 is a pivotal counter-regulatory enzyme to ACE by the breakdown of angiotensin II, the central player in the renin-angiotensin-aldosterone system (RAAS) and the main substrate of ACE2. Many factors have been associated with both altered ACE2 expression and COVID-19 severity and progression, including age, sex, ethnicity, medication, and several co-morbidities, such as cardiovascular disease and metabolic syndrome. Although ACE2 is widely distributed in various human tissues and many of its determinants have been well recognised, ACE2-expressing organs do not equally participate in COVID-19 pathophysiology, implying that other mechanisms are involved in orchestrating cellular infection resulting in tissue damage. Reports of pathologic findings in tissue specimens of COVID-19 patients are rapidly emerging and confirm the established role of ACE2 expression and activity in disease pathogenesis. Identifying pathologic changes caused by SARS-CoV-2 infection is crucially important as it has major implications for understanding COVID-19 pathophysiology and the development of evidence-based treatment strategies. Currently, many interventional strategies are being explored in ongoing clinical trials, encompassing many drug classes and strategies, including antiviral drugs, biological response modifiers, and RAAS inhibitors. Ultimately, prevention is key to combat COVID-19 and appropriate measures are being taken accordingly, including development of effective vaccines. In this review, we describe the role of ACE2 in COVID-19 pathophysiology, including factors influencing ACE2 expression and activity in relation to COVID-19 severity. In addition, we discuss the relevant pathological changes resulting from SARS-CoV-2 infection. Finally, we highlight a selection of potential treatment modalities for COVID-19. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Magnetic resonance imaging assessment of renal flow distribution patterns during ex vivo normothermic machine perfusion in porcine and human kidneys.

Acceptance criteria of deceased donor organs have gradually been extended toward suboptimal quality, posing an urgent need for more objective pre-transplant organ assessment. Ex vivo normothermic machine perfusion (NMP) combined with magnetic resonance imaging (MRI) could assist clinicians in deciding whether a donor kidney is suitable for transplantation. Aim of this study was to characterize the regional distribution of perfusate flow during NMP, to better understand how ex vivo kidney assessment protocols should eventually be designed. Nine porcine and 4 human discarded kidneys underwent 3 h of NMP in an MRI-compatible perfusion setup. Arterial spin labeling scans were performed every 15 min, resulting in perfusion-weighted images that visualize intrarenal flow distribution. At the start of NMP, all kidneys were mainly centrally perfused and it took time for the outer cortex to reach its physiological dominant perfusion state. Calculated corticomedullary ratios based on the perfusion maps reached a physiological range comparable to in vivo observations, but only after 1 to 2 h after the start of NMP. Before that, the functionally important renal cortex appeared severely underperfused. Our findings suggest that early functional NMP quality assessment markers may not reflect actual physiology and should therefore be interpreted with caution.

Klotho Deficiency Induces Arteriolar Hyalinosis in a Trade-Off with Vascular Calcification.

Hyalinosis is a vascular lesion affecting the renal vasculature and contributing to aging-related renal function decline. We assessed whether arteriolar hyalinosis is caused by Klotho deficiency, a state known to induce both renal and vascular phenotypes associated with aging. Histochemistry was used to assess hyalinosis in Klotho-/- kidneys, compared with Klotho+/- and wild-type littermates. Immunohistochemistry was used to investigate vascular lesion composition and the different layers of the vascular wall. Finally, spironolactone was used to inhibit calcification in kl/kl mice, and vascular lesions were characterized in the kidney. Arteriolar hyalinosis was detected in Klotho-/- mice, which was present up to the afferent arterioles. Hyalinosis was accompanied by loss of α-smooth muscle actin expression, whereas the endothelial lining was mostly intact. Hyalinous lesions were positive for IgM and iC3b/c/d, indicating subendothelial leakage of plasma proteins. The presence of extracellular matrix proteins suggested increased production by smooth muscle cells (SMCs). Finally, in Klotho-/- mice with marked vascular calcification, treatment with spironolactone allowed for replacement of calcification by hyalinosis. Klotho deficiency potentiates both endothelial hyperpermeability and SMC dedifferentiation. In the absence of a calcification-inducing stimulus, SMCs assume a synthetic phenotype in response to subendothelial leakage of plasma proteins. In the kidney, this results in arteriolar hyalinosis, which contributes to the decline in renal function. Klotho may play a role in preventing aging-related arteriolar hyalinosis.

Effects of Sodium-Glucose Co-transporter 2 Inhibition with Empaglifozin on Renal Structure and Function in Non-diabetic Rats with Left Ventricular Dysfunction After Myocardial Infarction.

BACKGROUND: The use of sodium-glucose co-transporter 2 inhibitors (SGLT2i) is currently expanding to cardiovascular risk reduction in non-diabetic subjects, but renal (side-)effects are less well studied in this setting. METHODS: Male non-diabetic Sprague Dawley rats underwent permanent coronary artery ligation to induce MI, or sham surgery. Rats received chow containing empagliflozin (EMPA) (30 mg/kg/day) or control chow. Renal function and electrolyte balance were measured in metabolic cages. Histological and molecular markers of kidney injury, parameters of phosphate homeostasis and bone resorption were also assessed. RESULTS: EMPA resulted in a twofold increase in diuresis, without evidence for plasma volume contraction or impediments in renal function in both sham and MI animals. EMPA increased plasma magnesium levels, while the levels of glucose and other major electrolytes were comparable among the groups. Urinary protein excretion was similar in all treatment groups and no histomorphological alterations were identified in the kidney. Accordingly, molecular markers for cellular injury, fibrosis, inflammation and oxidative stress in renal tissue were comparable between groups. EMPA resulted in a slight increase in circulating phosphate and PTH levels without activating FGF23-Klotho axis in the kidney and bone mineral resorption, measured with CTX-1, was not increased. CONCLUSIONS: EMPA exerts profound diuretic effects without compromising renal structure and function or causing significant electrolyte imbalance in a non-diabetic setting. The slight increase in circulating phosphate and PTH after EMPA treatment was not associated with evidence for increased bone mineral resorption suggesting that EMPA does not affect bone health.

Tubular maximum phosphate reabsorption capacity in living kidney donors is independently associated with one-year recipient GFR.

The donor glomerular filtration rate (GFR) measured before kidney donation is a strong determinant of recipient graft outcome. No tubular function markers have been identified that can similarly be used in donors to predict recipient outcomes. In the present study we investigated whether the pre-donation tubular maximum reabsorption capacity of phosphate (TmP-GFR), which may be considered a functional tubular marker in healthy kidney donors, is associated with recipient GFR at 1 yr after transplantation, a key determinant of long-term outcome. We calculated the pre-donation TmP-GFR from serum and 24-h urine phosphate and creatinine levels in 165 kidney donors, and recipient 125I-iothalamate GFR and eGFR (CKD-EPI) at 12 mo after transplantation. Kidney donors were 51 ± 10 yr old, 47% were men, and mean GFR was 118 ± 26 ml/min. The donor TmP-GFR was associated with recipient GFR 12 mo after transplantation (GFR 6.0 ml/min lower per 1 mg/dl decrement of TmP-GFR), which persisted after multivariable adjustment for donor age, sex, pre-donation GFR, and blood pressure and other potential confounders. Results were highly similar when eGFR at 12 mo was taken as the outcome. Tubular damage markers kidney injury molecule-1 and neutrophil gelatinase-associated lipocalin were low and not associated with recipient GFR. A lower donor TmP-GFR before donation, which may be considered to represent a functional measure of tubular phosphate reabsorption capacity, is independently associated with a lower recipient GFR 1 yr after transplantation. These data are the first to link donor tubular phosphate reabsorption with recipient GFR post-transplantation.

Renal Klotho is Reduced in Septic Patients and Pretreatment With Recombinant Klotho Attenuates Organ Injury in Lipopolysaccharide-Challenged Mice.

OBJECTIVES: To determine the applicability of recombinant Klotho to prevent inflammation and organ injury in sepsis in man and mice. DESIGN: Prospective, clinical laboratory study using "warm" human postmortem sepsis-acute kidney injury biopsies. Laboratory study using a mouse model of endotoxemia. SETTING: Research laboratory at a university teaching hospital. SUBJECTS: Adult patients who died of sepsis in the ICU and control patients undergoing total nephrectomy secondary to renal cancer; male C57BL/6 and Klotho haploinsufficient mice. INTERVENTIONS: Lipopolysaccharide (0.05 mg/kg) injection and kill after 4, 8, and 24 hours. Mice received recombinant Klotho (0.05 mg/kg) 30 minutes prior to lipopolysaccharide (1 mg/kg) injection. Mice treated with saline were included as controls. MEASUREMENTS AND MAIN RESULTS: Quantitative reverse transcription polymerase chain reaction and immunohistochemical staining were used to quantify Klotho messenger RNA and protein expression in the kidney of sepsis-acute kidney injury patients and the kidney and brain of mice. The messenger RNA and protein expression of damage markers, inflammatory cytokine, chemokines, and endothelial adhesion molecules were also determined in mice. Renal neutrophil influx was quantified. We found significantly lower renal Klotho messenger RNA and protein levels in sepsis-acute kidney injury biopsies than in control subjects. These findings were recapitulated in the kidney and brain of lipopolysaccharide-challenged mice. Decreased Klotho expression paralleled an increase in kidney damage markers neutrophil gelatinase-associated lipocalin and kidney injury molecule-1. Administration of recombinant Klotho prior to lipopolysaccharide injection attenuated organ damage, inflammation and endothelial activation in the kidney and brain of mice. Furthermore, less neutrophils infiltrated into the kidneys of recombinant Klotho mice compared with lipopolysaccharide only treated mice. CONCLUSIONS: Renal Klotho expression in human sepsis-acute kidney injury and in mouse models of sepsis was significantly decreased and correlated with renal damage. Recombinant Klotho intervention diminished organ damage, inflammation, and endothelial activation in the kidney and brain of lipopolysaccharide-challenged mice. Systemic Klotho replacement may potentially be an organ-protective therapy for septic patients to halt acute, inflammatory organ injury.

Critical role for complement receptor C5aR2 in the pathogenesis of renal ischemia-reperfusion injury.

The complement system, and specifically C5a, is involved in renal ischemia-reperfusion (IR) injury. The 2 receptors for complement anaphylatoxin C5a (C5aR1 and C5aR2) are expressed on leukocytes as well as on renal epithelium. Extensive evidence shows that C5aR1 inhibition protects kidneys from IR injury; however, the role of C5aR2 in IR injury is less clear as initial studies proposed the hypothesis that C5aR2 functions as a decoy receptor. By Using wild-type, C5aR1-/-, and C5aR2-/- mice in a model of renal IR injury, we found that a deficiency of either of these receptors protected mice from renal IR injury. Surprisingly, C5aR2-/- mice were most protected and had lower creatinine levels and reduced acute tubular necrosis. Next, an in vivo migration study demonstrated that leukocyte chemotaxis was unaffected in C5aR2-/- mice, whereas neutrophil activation was reduced by C5aR2 deficiency. To further investigate the contribution of renal cell-expressed C5aR2 vs leukocyte-expressed C5aR2 to renal IR injury, bone marrow chimeras were created. Our data show that both renal cell-expressed C5aR2 and leukocyte-expressed C5aR2 mediate IR-induced renal dysfunction. These studies reveal the importance of C5aR2 in renal IR injury. They further show that C5aR2 is a functional receptor, rather than a decoy receptor, and may provide a new target for intervention.-Poppelaars, F., van Werkhoven, M. B., Kotimaa, J., Veldhuis, Z. J., Ausema, A., Broeren, S. G. M., Damman, J., Hempel, J. C., Leuvenink, H. G. D., Daha, M. R., van Son, W. J., van Kooten, C., van Os, R. P., Hillebrands, J.-L., Seelen, M. A. Critical role for complement receptor C5aR2 in the pathogenesis of renal ischemia-reperfusion injury.

Fibroblast growth factor 23 modifies the pharmacological effects of angiotensin receptor blockade in experimental renal fibrosis.

Background: Blockade of the renin-angiotensin-aldosterone system (RAAS) retards progression of chronic kidney disease. Yet, in many patients, the renoprotective effect is incomplete. A high circulating level of the phosphaturic hormone fibroblast growth factor 23 is associated with an impaired response to RAAS blockade-based therapy in clinical studies. Therefore, we addressed whether administration of recombinant fibroblast growth factor 23 (FGF23) interferes with the efficacy of angiotensin receptor blocker (ARB) treatment in a mouse model of renal fibrosis [unilateral ureteral obstruction (UUO)]. Methods: UUO mice were treated with losartan (100 mg/L in drinking water), recombinant FGF23 (160 ng/kg i.p. twice daily), their combination or vehicle ( n = 10 per group). Seven days after the UUO procedure, kidney tissue was analyzed for markers of RAAS activity, inflammation and fibrosis using real-time PCR and immunohistochemistry. Results: In the contralateral (non-affected) kidneys of ARB-treated UUO mice, administration of FGF23 reversed the induction of renin, ACE, ACE2 and AT1 receptor mRNA expression, suggesting interference with the physiological response to RAAS blockade by FGF23. Furthermore, recombinant FGF23 infusion prevented ARB-induced klotho upregulation in contralateral kidneys. In the UUO kidneys, klotho was majorly reduced in all groups. Pro-inflammatory gene expression (MCP-1, TNF-α) induced in UUO kidneys was reduced by ARB treatment; this anti-inflammatory effect was reversed by FGF23. In contrast, ARB-induced reduction of (pre-)fibrotic gene expression was not reversed by FGF23. Conclusions: Our findings show pharmacological interaction between exogenous FGF23 and losartan, thus serving as a proof of principle for crosstalk between the FGF23-klotho axis and RAAS.

The bipartite rac1 Guanine nucleotide exchange factor engulfment and cell motility 1/dedicator of cytokinesis 180 (elmo1/dock180) protects endothelial cells from apoptosis in blood vessel development.

Engulfment and cell motility 1/dedicator of cytokinesis 180 (Elmo1/Dock180) is a bipartite guanine nucleotide exchange factor for the monomeric GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1). Elmo1/Dock180 regulates Rac1 activity in a specific spatiotemporal manner in endothelial cells (ECs) during zebrafish development and acts downstream of the Netrin-1/Unc5-homolog B (Unc5B) signaling cascade. However, mechanistic details on the pathways by which Elmo1/Dock180 regulates endothelial function and vascular development remained elusive. In this study, we aimed to analyze the vascular function of Elmo1 and Dock180 in human ECs and during vascular development in zebrafish embryos. In vitro overexpression of Elmo1 and Dock180 in ECs reduced caspase-3/7 activity and annexin V-positive cell number upon induction of apoptosis. This protective effect of Elmo1 and Dock180 is mediated by activation of Rac1, p21-activated kinase (PAK) and AKT/protein kinase B (AKT) signaling. In zebrafish, Elmo1 and Dock180 overexpression reduced the total apoptotic cell and apoptotic EC number and promoted the formation of blood vessels during embryogenesis. In conclusion, Elmo1 and Dock180 protect ECs from apoptosis by the activation of the Rac1/PAK/AKT signaling cascade in vitro and in vivo. Thus, Elmo1 and Dock180 facilitate blood vessel formation by stabilization of the endothelium during angiogenesis.

Hydrogen sulfide in hypertension.

PURPOSE OF REVIEW: Hypertension is an important determinant of cardiovascular disease, and strict blood pressure regulation is beneficially associated with the risk for cardiovascular events or all-cause mortality. However, intensive antihypertensive treatment is not always sufficient to reach normotension. Hydrogen sulfide (H2S) is a gaseous signalling molecule with antihypertensive properties. It is endogenously produced, but can also be exogenously administrated. The current review provides an overview on H2S research performed in the context of hypertension and cardiovascular disease. RECENT FINDINGS: H2S has been increasingly found to contribute to different (patho-)physiological processes such as blood pressure regulation and scavenging of reactive oxygen species. A deficiency of H2S-producing enzymes results in hypertension, and administration of H2S donors lowers blood pressure and protects against organ damage in the experimental setting. Thiosulfate, a H2S metabolite, can act as a H2S donor, and is already clinically used for the treatment of calciphylaxis in patients with end-stage renal disease. Treatment of hypertensive rats with thiosulfate results in lower blood pressure and reduces organ damage. SUMMARY: Although human data on H2S and hypertension are scarce, experimental data indicate that elevation of H2S levels using dietary sulfate or exogenous H2S (donors) could be a promising therapeutic strategy in the setting of hypertension.

Selective delivery of IFN-γ to renal interstitial myofibroblasts: a novel strategy for the treatment of renal fibrosis.

Renal fibrosis leads to end-stage renal disease demanding renal replacement therapy because no adequate treatment exists. IFN-γ is an antifibrotic cytokine that may attenuate renal fibrosis. Systemically administered IFN-γ causes side effects that may be prevented by specific drug targeting. Interstitial myofibroblasts are the effector cells in renal fibrogenesis. Here, we tested the hypothesis that cell-specific delivery of IFN-γ to platelet-derived growth factor receptor ß (PDGFRß)-expressing myofibroblasts attenuates fibrosis in an obstructive nephropathy [unilateral ureteral obstruction (UUO)] mouse model. PEGylated IFN-γ conjugated to PDGFRß-recognizing peptide [(PPB)-polyethylene glycol (PEG)-IFN-γ] was tested in vitro and in vivo for antifibrotic properties and compared with free IFN-γ. PDGFRß expression was >3-fold increased (P < 0.05) in mouse fibrotic UUO kidneys and colocalized with α-smooth muscle actin-positive (SMA(+)) myofibroblasts. In vitro, PPB-PEG-IFN-γ significantly inhibited col1a1, col1a2, and α-SMA mRNA expression in TGF-ß-activated NIH3T3 fibroblasts (P < 0.05). In vivo, PPB-PEG-IFN-γ specifically accumulated in PDGFRß-positive myofibroblasts. PPB-PEG-IFN-γ treatment significantly reduced renal collagen I, fibronectin, and α-SMA mRNA and protein expression. Compared with vehicle treatment, PPB-PEG-IFN-γ preserved tubular morphology, reduced interstitial T-cell infiltration, and attenuated lymphangiogenesis (all P < 0.05) without affecting peritubular capillary density. PPB-PEG-IFN-γ reduced IFN-γ-related side effects as manifested by reduced major histocompatibility complex class II expression in brain tissue (P < 0.05 vs. free IFN-γ). Our findings demonstrate that specific targeting of IFN-γ to PDGFRß-expressing myofibroblasts attenuates renal fibrosis and reduces systemic adverse effects.