Reduced COVID-19 morbidity and mortality in hemodialysis patients across the various Omicron sublineages-A retrospective analysis.

Introduction: Hemodialysis (HD) patients are a COVID-19 high risk population due to comorbidities and impaired immune response. Vaccines, advent of effective treatment and the emergence of novel variants have fundamentally changed the pandemic. We aimed to assess temporal changes of COVID-19 in HD patients of our catchment area, and risk factors for severe and fatal course. Methods and materials: We retrospectively collected data from 274 patients admitted to the Medical University Graz, Austria for HD between 1st of May 2020 and 31st of August 2022. We analyzed clinical and demographic data between different COVID-19 waves and assessed factors associated with hospitalization, ICU admission and mortality by logistic regression. To further evaluate the dialysis at-risk population, we collected demographic and vaccination data between August 2021 and August 2022. Results: Time of infection and SARS-CoV-2 sequencing data allowed for distinction of five separate waves of infection with different impact on the dialysis population: While in the initial four waves frequencies of hospitalization, necessity of critical care and mortality were around 60%, 10% and 20%, respectively. These events became rare during the large fifth wave, when Omicron had become the dominant variant. Although only 16.9% had to be hospitalized, this resulted in 29 hospital admissions, due to the high prevalence of COVID-19 during the Omicron era. Furthermore, we observed similar clinical outcomes with BA.4/5 as with BA.1/BA.2 Omicron sublineages. The proportion of previously infected increased simultaneously with the number of vaccination doses in our dialysis population. Vaccination at time of positivity and infection with an Omicron variant conferred protection against hospitalization and mortality in univariate analysis, but only infection with an Omicron variant remained a robust predictor for these outcomes in multivariable analysis. Discussion: While a fourth of our at-risk population became infected during the Omicron wave, mortality was almost non-existent. Several concomitant factors have contributed to the decrease of COVID-19 severity in HD patients. This trend appears to be continued with BA.4/5, which was equally mild as BA.1 and BA.2 in our well vaccinated dialysis population.

Low-Dose rIL-15 Protects from Nephrotoxic Serum Nephritis via CD8+ T Cells.

Rapid progressive glomerulonephritis (GN) often leads to end-stage kidney disease, driving the need for renal replacement therapy and posing a global health burden. Low-dose cytokine-based immunotherapies provide a new strategy to treat GN. IL-15 is a strong candidate for the therapy of immune-mediated kidney disease since it has proven to be tubular-protective before. Therefore, we set out to test the potential of low-dose rIL-15 treatment in a mouse model of nephrotoxic serum nephritis (NTS), mimicking immune complex-driven GN in humans. A single low-dose treatment with rIL-15 ameliorated NTS, reflected by reduced albuminuria, less tissue scarring, fewer myeloid cells in the kidney, and improved tubular epithelial cell survival. In addition, CD8+ T cells, a primary target of IL-15, showed altered gene expression and function corresponding with less cytotoxicity mediated by rIL-15. With the use of transgenic knock-out mice, antibody depletion, and adoptive cell transfer studies, we here show that the beneficial effects of rIL-15 treatment in NTS depended on CD8+ T cells, suggesting a pivotal role for them in the underlying mechanism. Our findings add to existing evidence of the association of IL-15 with kidney health and imply a potential for low-dose rIL-15 immunotherapies in GN.

Blockade of tumor necrosis factor superfamily members CD30 and OX40 abrogates disease activity in murine immune-mediated glomerulonephritis.

Co-stimulation is a prerequisite for pathogenic activity in T cell-mediated diseases and has been demonstrated to achieve tolerance in organ-specific autoimmunity as a therapeutic target. Here, we evaluated the involvement of the tumor necrosis factor family members CD30 and OX40 in immune-complex mediated kidney disease. In vitro stimulation and proliferation studies were performed with CD4+ cells from wild type and CD30/OX40 double knock-out (CD30OX40-/-) mice. In vivo studies were performed by induction of nephrotoxic serum nephritis in wild type, CD30OX40- /- , CD30-/-, OX40-/-, reconstituted Rag1-/- and C57Bl/6J mice treated with αCD30L αOX40L antibodies. CD30, OX40 and their ligands were upregulated on various leukocytes in nephrotoxic serum nephritis. CD30OX40-/- mice, but not CD30-/- or OX40-/- mice were protected from nephrotoxic serum nephritis. Similar protection was found in Rag1-/- mice injected with CD4+ T cells from CD30OX40-/- mice compared to Rag1-/- mice injected with CD4+ T cells from wild type mice. Furthermore, CD4+ T cells deficient in CD30OX40-/- displayed decreased expression of CCR6 in vivo. CD30OX40-/- cells were fully capable of differentiating into disease mediating T helper cell subsets, but showed significantly decreased levels of proliferation in vivo and in vitro compared to wild type cells. Blocking antibodies against CD30L and OX40L ameliorated nephrotoxic serum nephritis without affecting pan-effector or memory T cell populations. Thus, our results indicate disease promotion via CD30 and OX40 signaling due to facilitation of exaggerated T cell proliferation and migration of T helper 17 cells in nephrotoxic serum nephritis. Hence, co-stimulation blockade targeting the CD30 and OX40 signaling pathways may provide a novel therapeutic strategy in autoimmune kidney disease.

Agonism of Prostaglandin E2 Receptor 4 Ameliorates Tubulointerstitial Injury in Nephrotoxic Serum Nephritis in Mice.

Selectively targeting the E-type prostanoid receptor 4 (EP4) might be a new therapeutic option in the treatment of glomerulonephritis (GN), since the EP4 receptor is expressed on different immune cells, resident kidney cells, and endothelial cells, which are all involved in the pathogenesis of immune-complex GN. This study aimed to evaluate the therapeutic potential and to understand the mode of action of EP4 agonist in immune-complex GN using the murine model of nephrotoxic serum nephritis (NTS). In vivo, NTS mice were treated two times daily with two different doses of an EP4 agonist ONO AE1-329 or vehicle for 14 days total. The effect of PGE2 and EP4 agonism and antagonism was tested on murine distal convoluted tubular epithelial cells (DCT) in vitro. In vivo, the higher dose of the EP4 agonist led to an improved NTS phenotype, including a reduced tubular injury score and reduced neutrophil gelatinase-associated lipocalin (NGAL) and blood urea nitrogen (BUN) levels. EP4 agonist treatment caused decreased CD4+ T cell infiltration into the kidney and increased proliferative capacity of tubular cells. Injection of the EP4 agonist resulted in dose-dependent vasodilation and hypotensive episodes. The low-dose EP4 agonist treatment resulted in less pronounced episodes of hypotension. In vitro, EP4 agonism resulted in cAMP production and increased distal convoluted tubular (DCT) proliferation. Taken together, EP4 agonism improved the NTS phenotype by various mechanisms, including reduced blood pressure, decreased CD4+ T cell infiltration, and a direct effect on tubular cells leading to increased proliferation probably by increasing cAMP levels.

Glucagon-Like Peptide-1 Receptor Agonism Improves Nephrotoxic Serum Nephritis by Inhibiting T-Cell Proliferation.

Glucagon-like peptide (GLP)-1 analogs such as liraglutide improved albuminuria in patients with type 2 diabetes in large randomized controlled trials. One of the suspected mechanisms is the anti-inflammatory potential of GLP-1 receptor (Glp1r) agonism. Thus, the anti-inflammatory action of Glp1r agonism was tested in a nondiabetic, T-cell-mediated murine model of nephrotoxic serum nephritis (NTS). The role of Glp1r in NTS was evaluated by using Glp1r-/- mice or C57BL/6 mice treated with liraglutide. In vitro, murine T cells were stimulated in the presence of liraglutide or vehicle. Glp1r-/- mice displayed increased renal infiltration of neutrophils and T cells after induction of NTS. Splenocyte proliferation and TH1 cytokine transcription were increased in spleen and lymph nodes of Glp1r-/- mice. Liraglutide treatment significantly improved the renal outcome of NTS in C57BL/6 mice by decreasing renal infiltration and proliferation of T cells, which resulted in decreased macrophage infiltration. In vitro, T cells stimulated in the presence of liraglutide showed decreased proliferation of TH1 and TH17 cells. Liraglutide blocked glycolysis in T cells and decreased their Glut1 mRNA expression. Together, Glp1r agonism protects mice from a T-cell-dependent glomerulonephritis model by inhibition of T-cell proliferation, possibly by interacting with their metabolic program. This mechanism may explain in part the renoprotective effects of Glp1r agonism in diabetic nephropathy.

Blockade of prostaglandin E2 receptor 4 ameliorates nephrotoxic serum nephritis.

Prostaglandin E2 (PGE2) signaling is known to modulate inflammation and vascular resistance. Receptors of PGE2 [E-type prostanoid receptors (EP)] might be an attractive pharmacological target in immune-mediated diseases such as glomerulonephritis. We hypothesized that selective EP4 antagonism improves nephrotoxic serum nephritis (NTS) by its anti-inflammatory properties. Mice were subjected to NTS and treated with the EP4 antagonist ONO AE3-208 (10 mg·kg body wt-1·day-1] or vehicle starting from disease initiation. In one set of experiments, treatment was started 4 days after NTS induction. Tubular epithelial cells were evaluated in vitro under starving conditions. EP4 antagonist treatment significantly improved the NTS phenotype without affecting blood pressure levels. Remarkably, the improved NTS phenotype was also observed when treatment was started 4 days after NTS induction. EP4 antagonism decreased tubular chemokine (C-X-C motif) ligand ( Cxcl) 1 and Cxcl-5 expression and thereby subsequently reduced interstitial neutrophil infiltration into the kidney. In vitro, tubular epithelial cells increasingly expressed Cxcl-5 mRNA and Cxcl-5 protein when treated with PGE2 or an EP4 agonist under starving conditions, which was blunted by EP4 antagonist treatment. Together, EP4 antagonism improves the NTS phenotype, probably by decreasing mainly Cxcl-5 production in tubular cells, thereby reducing renal neutrophil infiltration.

Autophagy Protects From Uremic Vascular Media Calcification.

Chronic kidney disease and diabetes mellitus are associated with extensive media calcification, which leads to increased cardiovascular morbidity and mortality. Here, we investigated the role of autophagy in the pathogenesis of uremic vascular media calcification. DBA/2 mice were fed with high-phosphate diet (HPD) in order to cause vascular calcification. DBA/2 mice on standard chow diet were used as control. In parallel, autophagy and its response to rapamycin, 3-methyladenine (3-MA), and bafilomycin were studied in an in vitro model using mouse vascular smooth muscle cells (MOVAS). DBA/2 mice on HPD developed severe vascular media calcification, which is mirrored in vitro by culturing MOVAS under calcifying conditions. Both, in vitro and in vivo, autophagy significantly increased in MOVAS under calcifying conditions and in aortas of HPD mice, respectively. Histologically, autophagy was located to the aortic Tunica media, but also vascular endothelial cells, and was found to continuously increase during HPD treatment. 3-MA as well as bafilomycin blocked autophagy in MOVAS and increased calcification. Vice versa, rapamycin treatment further increased autophagy and resulted in a significant decrease of vascular calcification in vitro and in vivo. Rapamycin reduced Runx2 transcription levels in aortas and MOVAS to control levels, whereas it increased α-smooth muscle actin and Sm22α transcription in MOVAS to control levels. Furthermore, rapamycin-treated HPD mice survived significantly longer compared to HPD controls. These findings indicate that autophagy is an endogenous response of vascular smooth muscle cells (VSMC) to protect from calcification in uremia. Induction of autophagy by rapamycin protects cells and mice from uremic media calcification possibly by inhibiting osteogenic transdifferentiation of VSMC.

A New Murine Model of Chronic Kidney Disease-Mineral and Bone Disorder.

Chronic kidney disease (CKD) is associated with mineral and bone disorder (MBD), which is the main cause of the extensively increased cardiovascular mortality in the CKD population. We now aimed to establish a new murine experimental CKD-MBD model. Dilute brown non-Agouti (DBA/2) mice were fed with high-phosphate diet for 4 (HPD4) or 7 (HPD7) days, then with standard chow diet (SCD) and subsequently followed until day 84. They were compared to DBA/2 mice maintained on SCD during the whole study period. Both 4 and 7 days HPD-fed mice developed phosphate nephropathy with tubular atrophy, interstitial fibrosis, decreased glomerular filtration rate, and increased serum urea levels. The abdominal aorta of HPD-treated mice showed signs of media calcification. Histomorphometric analysis of HPD-treated mice showed decreased bone volume/tissue volume, low mineral apposition rate, and low bone formation rate as compared to SCD-fed mice, despite increased parathyroid hormone levels. Overall, the observed phenotype was more pronounced in the HPD7 group. In summary, we established a new, noninvasive, and therefore easy to perform reproducible CKD-MBD model, which showed media calcification, secondary hyperparathyroidism, and low-turnover bone disease.

The Spleen Plays No Role in Nephrotoxic Serum Nephritis, but Constitutes a Place of Compensatory Haematopoiesis.

BACKGROUND: The spleen has been implicated in the pathogenesis of immune-complex glomerulonephritis by initiating and resolving adaptive immune responses. Thus, we aimed to evaluate the role of the spleen in experimental nephrotoxic serum nephritis (NTS). METHODS: In order to accelerate the disease, animals were subjected to NTS by preimmunizing male C57BL/6J mice with rabbit IgG three days before injecting the rabbit anti-glomerular basement antiserum, or were immunized only. A group underwent splenectomy before NTS induction. RESULTS: We observed enlargement of the spleen with a maximum at 14 days after NTS induction or immunization only. Splenectomized mice were found to develop albuminuria and renal histological changes comparable to sham-operated controls. Nevertheless, anaemia was aggravated in mice after splenectomy. During the course of NTS, we detected CD41+ megakaryocytes and Ter119+ erythroid precursor cells in the spleen of mice with NTS and of immunized mice. Ter119+Cxcr4+ cells and the binding partner Cxcl12 increased in the spleen, and decreased in the bone marrow. This was accompanied by a significant systemic increase of interferon-gamma in the serum. CONCLUSIONS: In summary, splenectomy does not influence the course of NTS per se, but is involved in concomitant anaemia. Extramedullary haematopoiesis in the spleen is probably facilitated through the migration of Cxcr4+ erythroid precursor cells from the bone marrow to the spleen via a Cxcl12 gradient and likely arises from the suppressive capacity of chronic inflammation on the bone marrow.

Heterogeneous susceptibility for uraemic media calcification and concomitant inflammation within the arterial tree.

BACKGROUND: End-stage renal disease (ESRD) is strongly associated with arterial calcification of the tunica media, decreased vascular compliance and sudden cardiac death. Here, we analysed the distribution pattern of uraemic media calcification and concomitant inflammation in mice and men. METHODS: Uraemia was induced in DBA/2 mice with high-phosphate diet. Subsequently, we analysed arterial medial calcification using histology, mass spectrometry, and wire myography. Gene expression was quantified using a whole transcriptome array and quantitative PCR. In a cohort of 36 consecutive patients with CKD stage 4-5, we measured the calcium score of the coronary arteries, the ascending thoracic aorta and the infrarenal abdominal aorta using computed tomography scans. RESULTS: Uraemic DBA/2 mice showed only minor calcifications in thoracic aortas, whereas there was overt media calcification in abdominal aortas. The transcriptional profile and immunohistochemistry revealed induction of Vcam1 expression by vascular smooth muscle cells in uraemic abdominal aortas. Macrophages infiltrated the tunica media of the abdominal aorta. Anti-inflammatory treatment did not improve uraemic media calcification in our animal model. Arterial calcifications in ESRD patients showed a similar distribution pattern in computed tomography scans, with higher calcium scores of the abdominal aorta when compared with the thoracic aorta. CONCLUSION: Taken together, there was a similar heterogeneous pattern of calcification in both mice and humans, where the abdominal aorta was more prone to media calcification when compared with the thoracic aorta. In uraemia, smooth muscle cells of the abdominal aorta showed a phenotypic switch to an inflammatory and osteoblastic phenotype.