Neutrophils and NADPH Oxidases Are Major Contributors to Mild but Not Severe Ischemic Acute Kidney Injury in Mice.

Upregulation of free radical-generating NADPH oxidases (NOX), xanthine oxidoreductase (XOR), and neutrophil infiltration-induced, NOX2-mediated respiratory burst contribute to renal ischemia-reperfusion injury (IRI), but their roles may depend on the severity of IRI. We investigated the role of NOX, XOR, and neutrophils in developing IRI of various severities. C57BL/6 and Mcl-1ΔMyelo neutrophil-deficient mice were used. Oxidases were silenced by RNA interference (RNAi) or pharmacologically inhibited. Kidney function, morphology, immunohistochemistry and mRNA expression were assessed. After reperfusion, the expression of NOX enzymes and XOR increased until 6 h and from 15 h, respectively, while neutrophil infiltration was prominent from 3 h. NOX4 and XOR silencing or pharmacological XOR inhibition did not protect the kidney from IRI. Attenuation of NOX enzyme-induced oxidative stress by apocynin and neutrophil deficiency improved kidney function and ameliorated morphological damage after mild but not moderate/severe IRI. The IR-induced postischemic renal functional impairment (BUN, Lcn-2), tubular necrosis score, inflammation (TNF-α, F4/80), and decreases in the antioxidant enzyme (GPx3) mRNA expression were attenuated by both apocynin and neutrophil deficiency. Inhibition of NOX enzyme-induced oxidative stress or the lack of infiltration by NOX2-expressing neutrophils can attenuate reperfusion injury after mild but not moderate/severe renal IR.

mRNA-LNP COVID-19 Vaccine Lipids Induce Complement Activation and Production of Proinflammatory Cytokines: Mechanisms, Effects of Complement Inhibitors, and Relevance to Adverse Reactions.

A small fraction of people vaccinated with mRNA-lipid nanoparticle (mRNA-LNP)-based COVID-19 vaccines display acute or subacute inflammatory symptoms whose mechanism has not been clarified to date. To better understand the molecular mechanism of these adverse events (AEs), here, we analyzed in vitro the vaccine-induced induction and interrelations of the following two major inflammatory processes: complement (C) activation and release of proinflammatory cytokines. Incubation of Pfizer-BioNTech's Comirnaty and Moderna's Spikevax with 75% human serum led to significant increases in C5a, sC5b-9, and Bb but not C4d, indicating C activation mainly via the alternative pathway. Control PEGylated liposomes (Doxebo) also induced C activation, but, on a weight basis, it was ~5 times less effective than that of Comirnaty. Viral or synthetic naked mRNAs had no C-activating effects. In peripheral blood mononuclear cell (PBMC) cultures supplemented with 20% autologous serum, besides C activation, Comirnaty induced the secretion of proinflammatory cytokines in the following order: IL-1α < IFN-γ < IL-1ß < TNF-α < IL-6 < IL-8. Heat-inactivation of C in serum prevented a rise in IL-1α, IL-1ß, and TNF-α, suggesting C-dependence of these cytokines' induction, although the C5 blocker Soliris and C1 inhibitor Berinert, which effectively inhibited C activation in both systems, did not suppress the release of any cytokines. These findings suggest that the inflammatory AEs of mRNA-LNP vaccines are due, at least in part, to stimulation of both arms of the innate immune system, whereupon C activation may be causally involved in the induction of some, but not all, inflammatory cytokines. Thus, the pharmacological attenuation of inflammatory AEs may not be achieved via monotherapy with the tested C inhibitors; efficacy may require combination therapy with different C inhibitors and/or other anti-inflammatory agents.

Modulated Electro-Hyperthermia Accelerates Tumor Delivery and Improves Anticancer Activity of Doxorubicin Encapsulated in Lyso-Thermosensitive Liposomes in 4T1-Tumor-Bearing Mice.

Modulated electro-hyperthermia (mEHT) is an adjuvant cancer therapy that enables tumor-selective heating (+2.5 °C). In this study, we investigated whether mEHT accelerates the tumor-specific delivery of doxorubicin (DOX) from lyso-thermosensitive liposomal doxorubicin (LTLD) and improves its anticancer efficacy in mice bearing a triple-negative breast cancer cell line (4T1). The 4T1 cells were orthotopically injected into Balb/C mice, and mEHT was performed on days 9, 12, and 15 after the implantation. DOX, LTLD, or PEGylated liposomal DOX (PLD) were administered for comparison. The tumor size and DOX accumulation in the tumor were measured. The cleaved caspase-3 (cC3) and cell proliferation were evaluated by cC3 or Ki67 immunohistochemistry and Western blot. The LTLD+mEHT combination was more effective at inhibiting tumor growth than the free DOX and PLD, demonstrated by reductions in both the tumor volume and tumor weight. LTLD+mEHT resulted in the highest DOX accumulation in the tumor one hour after treatment. Tumor cell damage was associated with cC3 in the damaged area, and with a reduction in Ki67 in the living area. These changes were significantly the strongest in the LTLD+mEHT-treated tumors. The body weight loss was similar in all mice treated with any DOX formulation, suggesting no difference in toxicity. In conclusion, LTLD combined with mEHT represents a novel approach for DOX delivery into cancer tissue.

The Application of a New, Modified Algorithm for the Differentiation of Regular Ventricular and Pre-Excited Tachycardias.

BACKGROUND: The three-step Brugada group algorithm is the only published electrocardiographical (ECG) algorithm for differentiating ventricular tachycardia (VT) from pre-excited tachycardia (PXT) as a cause of regular wide QRS complex tachycardia (WCT). This study aimed to improve the diagnostic accuracy of the Brugada group algorithm. METHODS: This study modified the Brugada group algorithm by adding a new aVR lead criterion (initial positive deflection in lead aVR and the QRS complex area above the baseline is greater than the area below the baseline). The Brugada group algorithm and the new, modified four-step algorithm in 300 WCT ECGs (241 VTs, 59 PXTs) was applied. If any of the criteria were fulfilled, VT was diagnosed; if none were fulfilled, a diagnosis of PXT was established. RESULTS: The test accuracy, VT diagnosis sensitivity, and negative predictive value (NPV) of the new, modified algorithm were significantly greater than that of the Brugada group algorithm: test accuracy 220 of 300 (73%) vs 182 of 300 (61%); sensitivity 73% vs 55% (p<0.001 for both); NPV 40% vs 31% (p=0.0205). The VT diagnosis specificity of the Brugada group algorithm was greater than that of the new, modified algorithm (83% vs 75%; p=0.019). There was no significant difference between the new, modified and Brugada group algorithms in the positive predictive values (92% vs 93%, respectively) for a VT diagnosis, and positive and negative likelihood ratio values (2.87 vs 3.26; 0.36 vs 0.54, respectively). CONCLUSIONS: The new, modified algorithm proved to be more sensitive for the differentiation of VT from PXT than the Brugada group algorithm.

Complement-mediated hypersensitivity reactions to an amphotericin B-containing lipid complex (Abelcet) in pediatric patients and anesthetized rats: Benefits of slow infusion.

Intravenous administration of lipid-based nanodrugs can cause hypersensitivity, also known as infusion reactions (IRs), that can be attenuated by slow infusion in adult patients. We studied the role of infusion rate and complement (C) activation in IRs in pediatric patients treated with Abelcet, and also in anesthetized rats. IRs were observed in 6 out of 10 (60%) patients who received Abelcet infusion in 4 h or less, while no patients who received the infusion in 6 h showed C activation or IRs. The rat model indicated an inverse relationship between infusion speed and Abelcet-induced hypotension, taken as an experimental endpoint of IRs, while the rise of C3a in blood, an index of C activation, directly correlated with hypotension. The results suggest that pediatric patients are more prone to produce IRs, and that the optimal infusion time of Abelcet may be much longer than the presently recommended 2 h.

A porcine model of hemodialyzer reactions: roles of complement activation and rinsing back of extracorporeal blood.

Hemodialysis reactions (HDRs) resemble complement-activation-related pseudoallergy (CARPA) to certain i.v. drugs, for which pigs provide a sensitive model. On this basis, to better understand the mechanism of human HDRs, we subjected pigs to hemodialysis using polysulfone (FX CorDiax 40, Fresenius) or cellulose triacetate (SureFlux-15UX, Nipro) dialyzers, or Dialysis exchange-set without membranes, as control. Experimental endpoints included typical biomarkers of porcine CARPA; pulmonary arterial pressure (PAP), blood cell counts, plasma sC5b-9 and thromboxane-B2 levels. Hemodialysis (60 min) was followed by reinfusion of extracorporeal blood into the circulation, and finally, an intravenous bolus injection of the complement activator zymosan. The data indicated low-extent steady rise of sC5b-9 along with transient leukopenia, secondary leukocytosis and thrombocytopenia in the two dialyzer groups, consistent with moderate complement activation. Surprisingly, small changes in baseline PAP and plasma thromboxane-B2 levels during hemodialysis switched into 30%-70% sharp rises in all three groups resulting in synchronous spikes within minutes after blood reinfusion. These observations suggest limited complement activation by dialyzer membranes, on which a membrane-independent second immune stimulus was superimposed, and caused pathophysiological changes also characteristic of HDRs. Thus, the porcine CARPA model raises the hypothesis that a second "hit" on anaphylatoxin-sensitized immune cells may be a key contributor to HDRs.

Purinergic-Glycinergic Interaction in Neurodegenerative and Neuroinflammatory Disorders of the Retina.

Neurodegenerative-neuroinflammatory disorders of the retina seriously hamper human vision. In searching for key factors that contribute to the development of these pathologies, we considered potential interactions among purinergic neuromodulation, glycinergic neurotransmission, and microglia activity in the retina. Energy deprivation at cellular levels is mainly due to impaired blood circulation leading to increased release of ATP and adenosine as well as glutamate and glycine. Interactions between these modulators and neurotransmitters are manifold. First, P2Y purinoceptor agonists facilitate reuptake of glycine by glycine transporter 1, while its inhibitors reduce reverse-mode operation; these events may lower extracellular glycine levels. The consequential changes in extracellular glycine concentration can lead to parallel changes in the activity of NR1/NR2B type NMDA receptors of which glycine is a mandatory agonist, and thereby may reduce neurodegenerative events in the retina. Second, P2Y purinoceptor agonists and glycine transporter 1 inhibitors may indirectly inhibit microglia activity by decreasing neuronal or glial glycine release in energy-compromised retina. These inhibitions may have a role in microglia activation, which is present during development and progression of neurodegenerative disorders such as glaucomatous and diabetic retinopathies and age-related macular degeneration or loss of retinal neurons caused by thromboembolic events. We have hypothesized that glycine transporter 1 inhibitors and P2Y purinoceptor agonists may have therapeutic importance in neurodegenerative-neuroinflammatory disorders of the retina by decreasing NR1/NR2B NMDA receptor activity and production and release of a series of proinflammatory cytokines from microglial cells.

Time-Dependent miRNA Profile during Septic Acute Kidney Injury in Mice.

(1) Background: Lipopolysaccharide (LPS)-induced systemic inflammation is associated with septic acute kidney injury (AKI). We investigated the time-dependent miRNA expression changes in the kidney caused by LPS. (2) Methods: Male outbred NMRI mice were injected with LPS and sacrificed at 1.5 and 6 h (40 mg/kg i.p., early phase, EP) or at 24 and 48 h (10 mg/kg i.p., late phase, LP). The miRNA profile was established using miRCURY LNA™ microarray and confirmed with qPCR. Total renal proteome was analyzed by LC-MS/MS (ProteomeXchange: PXD014664). (3) Results: Septic AKI was confirmed by increases in plasma urea concentration and in renal TNF-α and IL-6 mRNA expression. Most miRNAs were altered at 6 and 24 h and declined by 48 h. In EP miR-762 was newly identified and validated and was the most elevated miRNA. The predicted target of miR-762, Ras related GTPase 1B (Sar1b) was downregulated. In LP miR-21a-5p was the most influenced miRNA followed by miR-451a, miR-144-3p, and miR-146a-5p. Among the potential protein targets of the most influenced miRNAs, only aquaporin-1, a target of miR-144-3p was downregulated at 24 h. (4) Conclusion: Besides already known miRNAs, septic AKI upregulated miR-762, which may regulate GTP signaling, and miR-144-3p and downregulated its target, aquaporin-1.

Post-Ischemic Renal Fibrosis Progression Is Halted by Delayed Contralateral Nephrectomy: The Involvement of Macrophage Activation.

(1) Background: Successful treatment of acute kidney injury (AKI)-induced chronic kidney disease (CKD) is unresolved. We aimed to characterize the time-course of changes after contralateral nephrectomy (Nx) in a model of unilateral ischemic AKI-induced CKD with good translational utility. (2) Methods: Severe (30 min) left renal ischemia-reperfusion injury (IRI) or sham operation (S) was performed in male Naval Medical Research Institute (NMRI) mice followed by Nx or S one week later. Expression of proinflammatory, oxidative stress, injury and fibrotic markers was evaluated by RT-qPCR. (3) Results: Upon Nx, the injured kidney hardly functioned for three days, but it gradually regained function until day 14 to 21, as demonstrated by the plasma urea. Functional recovery led to a drastic reduction in inflammatory infiltration by macrophages and by decreases in macrophage chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) mRNA and most injury markers. However, without Nx, a marked upregulation of proinflammatory (TNF-α, IL-6, MCP-1 and complement-3 (C3)); oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2) and fibrosis (collagen-1a1 (Col1a1) and fibronectin-1 (FN1)) genes perpetuated, and the injured kidney became completely fibrotic. Contralateral Nx delayed the development of renal failure up to 20 weeks. (4) Conclusion: Our results suggest that macrophage activation is involved in postischemic renal fibrosis, and it is drastically suppressed by contralateral nephrectomy ameliorating progression.

ECM Characterization Reveals a Massive Activation of Acute Phase Response during FSGS.

The glomerular basement membrane (GBM) and extra-cellular matrix (ECM) are essential to maintain a functional interaction between the glomerular podocytes and the fenestrated endothelial cells in the formation of the slit diaphragm for the filtration of blood. Dysregulation of ECM homeostasis can cause Focal segmental glomerulosclerosis (FSGS). Despite this central role, alterations in ECM composition during FSGS have not been analyzed in detail yet. Here, we characterized the ECM proteome changes in miR-193a-overexpressing mice, which suffer from FSGS due to suppression of Wilms' tumor 1 (WT1). By mass spectrometry we identified a massive activation of the acute phase response, especially the complement and fibrinogen pathways. Several protease inhibitors (ITIH1, SERPINA1, SERPINA3) were also strongly increased. Complementary analysis of RNA expression data from both miR-193a mice and human FSGS patients identified additional candidate genes also mainly involved in the acute phase response. In total, we identified more than 60 dysregulated, ECM-associated genes with potential relevance for FSGS progression. Our comprehensive analysis of a murine FSGS model and translational comparison with human data offers novel targets for FSGS therapy.

The Acute Phase Response Is a Prominent Renal Proteome Change in Sepsis in Mice.

(1) Background: Sepsis-induced acute kidney injury (AKI) is the most common form of acute kidney injury (AKI). We studied the temporal profile of the sepsis-induced renal proteome changes. (2) Methods: Male mice were injected intraperitoneally with bacterial lipopolysaccharide (LPS) or saline (control). Renal proteome was studied by LC-MS/MS (ProteomeXchange: PXD014664) at the early phase (EP, 1.5 and 6 h after 40 mg/kg LPS) and the late phase (LP, 24 and 48 h after 10 mg/kg LPS) of LPS-induced AKI. Renal mRNA expression of acute phase proteins (APP) was assessed by qPCR. (3) Results: Renal proteome change was milder in EP vs. LP. APPs dominated the proteome in LP (proteins upregulated at least 4-fold (APPs/all): EP, 1.5 h: 0/10, 6 h: 1/10; LP, 24 h: 22/47, 48 h: 17/44). Lipocalin-2, complement C3, fibrinogen, haptoglobin and hemopexin were the most upregulated APPs. Renal mRNA expression preceded the APP changes with peak effects at 24 h, and indicated renal production of the majority of APPs. (4) Conclusions: Gene expression analysis revealed local production of APPs that commenced a few hours post injection and peaked at 24 h. This is the first demonstration of a massive, complex and coordinated acute phase response of the kidney involving several proteins not identified previously.

Glomerular Collagen Deposition and Lipocalin-2 Expression Are Early Signs of Renal Injury in Prediabetic Obese Rats.

Feeding rats with high-fat diet (HFD) with a single streptozotocin (STZ) injection induced obesity, slightly elevated fasting blood glucose and impaired glucose and insulin tolerance, and caused cardiac hypertrophy and mild diastolic dysfunction as published before by Koncsos et al. in 2016. Here we aimed to explore the renal consequences in the same groups of rats. Male Long-Evans rats were fed normal chow (CON; n = 9) or HFD containing 40% lard and were administered STZ at 20 mg/kg (i.p.) at week four (prediabetic rats, PRED, n = 9). At week 21 blood and urine samples were taken and kidney and liver samples were collected for histology, immunohistochemistry and for analysis of gene expression. HFD and STZ increased body weight and visceral adiposity and plasma leptin concentration. Despite hyperleptinemia, plasma C-reactive protein concentration decreased in PRED rats. Immunohistochemistry revealed elevated collagen IV protein expression in the glomeruli, and Lcn2 mRNA expression increased, while Il-1ß mRNA expression decreased in both the renal cortex and medulla in PRED vs. CON rats. Kidney histology, urinary protein excretion, plasma creatinine, glomerular Feret diameter, desmin protein expression, and cortical and medullary mRNA expression of TGF-ß1, Nrf2, and PPARγ were similar in CON and PRED rats. Reduced AMPKα phosphorylation of the autophagy regulator Akt was the first sign of liver damage, while plasma lipid and liver enzyme concentrations were similar. In conclusion, glomerular collagen deposition and increased lipocalin-2 expression were the early signs of kidney injury, while most biomarkers of inflammation, oxidative stress and fibrosis were negative in the kidneys of obese, prediabetic rats with mild heart and liver injury.

Complement Activation-Related Pathophysiological Changes in Anesthetized Rats: Activator-Dependent Variations of Symptoms and Mediators of Pseudoallergy.

Complement (C) activation can underlie the infusion reactions to liposomes and other nanoparticle-based medicines, a hypersensitivity syndrome that can be partially reproduced in animal models. However, the sensitivities and manifestations substantially differ in different species, and C activation may not be the only cause of pathophysiological changes. In order to map the species variation of C-dependent and -independent pseudoallergy (CARPA/CIPA), here we used known C activators and C activator liposomes to compare their acute hemodynamic, hematological, and biochemical effects in rats. These C activators were cobra venom factor (CVF), zymosan, AmBisome (at 2 doses), its amphotericin B-free vehicle (AmBisombo), and a PEGylated cholesterol-containing liposome (PEG-2000-chol), all having different powers to activate C in rat blood. The pathophysiological endpoints measured were blood pressure, leukocyte and platelet counts, and plasma thromboxane B2, while C activation was assessed by C3 consumption using the Pan-Specific C3 assay. The results showed strong linear correlation between C activation and systemic hypotension, pointing to a causal role of C activation in the hemodynamic changes. The observed thrombocytopenia and leukopenia followed by leukocytosis also correlated with C3 conversion in case of C activators, but not necessarily with C activation by liposomes. These findings are consistent with the double hit hypothesis of hypersensitivity reactions (HSRs), inasmuch as strong C activation can fully account for all symptoms of HSRs, but in case of no-, or weak C activators, the pathophysiological response, if any, is likely to involve other activation pathways.

Novel electrocardiographic dyssynchrony criteria improve patient selection for cardiac resynchronization therapy.

Aims: We hypothesized that the greater the intra- or interventricular dyssynchrony (intraD, interD), the more effective cardiac resynchronization therapy (CRT) is. We sought to improve patient selection for CRT by using novel ECG dyssynchrony criteria. Methods and results: Left ventricular (LV) intraD was estimated by the absolute time difference between the intrinsicoid deflections (ID) in leads aVL and aVF divided by the QRS duration (QRSd): [aVLID - aVFID]/QRSd (%). InterD was estimated from the formula: [V5ID - V1ID]/QRSd (%). Their >25% value indicated electrical dyssynchrony present (ED+) and ≤25% value electrical dyssynchrony absent (ED-) diagnoses. Using the intraD + interD criteria (intra + interDC) together, if at least one of them indicated ED+ diagnosis, a final ED+ diagnosis, if both indicated ED- diagnosis, a final ED- diagnosis was made. Two authors, blinded to CRT response, retrospectively analysed pre-CRT ECGs of 124 patients with known CRT outcome. CRT response was defined as improvement of ≥ 1 NYHA class, being alive and having no hospitalizations for heart failure during 6 months of follow-up. 35/124 (28%) patients were non-responders (NRs), using the traditional criteria (TC) correct diagnosis was made in the remaining 89/124 (72%) responder (R) cases. The test accuracy (TA) of intra + interDC + TC [100/124 (81%), P < 0.001] was superior to that of TC [89/124 (72%)] due to its superior TA [36/43 (84%) vs. 29/43 (67%), respectively, P = 0.0156] in the non-specific intra-ventricular conduction disturbance (NICD) subgroup [43/124 (35%)]. In the left bundle branch block subgroup [70/124 (56%)] there was no between-criteria difference in TA. Conclusion: The intra + interDC + TC predicts clinical response after CRT more accurately than TC alone, due to greater TA in the NICD subgroup.

Therapeutic miR-21 Silencing Ameliorates Diabetic Kidney Disease in Mice.

Diabetic nephropathy is the main cause of end-stage renal disease. MicroRNAs are powerful regulators of the genome, and global expression profiling revealed miR-21 to be among the most highly regulated microRNAs in kidneys of mice with diabetic nephropathy. In kidney biopsies of diabetic patients, miR-21 correlated with tubulointerstitial injury. In situ PCR analysis showed a specific enrichment of miR-21 in glomerular cells. We identified cell division cycle 25a (Cdc25a) and cyclin-dependent kinase 6 (Cdk6) as novel miR-21 targets in mesangial cells. miR-21-mediated repression of Cdc25a and Cdk6 resulted in impaired cell cycle progression and subsequent mesangial cell hypertrophy. miR-21 increased podocyte motility by regulating phosphatase and tensin homolog (Pten). miR-21 antagonism in vitro and in vivo in streptozotocin-induced diabetic mice decreased mesangial expansion, interstitial fibrosis, macrophage infiltration, podocyte loss, albuminuria, and fibrotic- and inflammatory gene expression. In conclusion, miR-21 antagonism rescued various functional and structural parameters in mice with diabetic nephropathy and, thus, might be a viable option in the treatment of patients with diabetic kidney disease.

The Effect of Combined Treatment with the (Pro)Renin Receptor Blocker HRP and Quinapril in Type 1 Diabetic Rats.

BACKGROUND/AIMS: Diabetic nephropathy remains a major clinical problem. The effects of prorenin might be adverse, but the literature data are controversial. We compared the renal effects of the (pro)renin receptor ((P)RR) blockade and angiotensin converting enzyme (ACE) inhibition on the progression of diabetic nephropathy in rats. METHODS: Diabetes (DM) was induced by ip. streptozotocin administration in adult male Sprague-Dawley rats, followed by eight weeks of treatment with the (P)RR blocker "handle region" decoy peptide (HRP, 0,1 mg/kg/day) or with the ACE inhibitor Quinapril (Q, 50 mg/kg/day) and grouped as follows: 1. Control (n=10); 2. DM (n=8); 3. DM+HRP (n=6); 4. DM+Q (n=10); 5. DM+Q+HRP (n=10). Renal functional parameters, histology and gene expressions were evaluated. RESULTS: HRP reduced glomerulosclerosis and podocyte desmin expression, but did not affect proteinuria and tubular ERK(1/2) phosphorylation. Both Q and Q+HRP treatment reduced proteinuria, glomerular and tubular damage, tubular TGF-ß1 expression and ERK(1/2) phosphorylation to the same extent. CONCLUSION: The effects of HRP were partially beneficial on diabetic kidney lesions as HRP reduced damage but did not improve tubular damage and failed to reduce ERK(1/2) phosphorylation in rats. The combination of HRP with Quinapril had no additive effects over Quinapril monotherapy on the progression of diabetic nephropathy.

Some Operational Characteristics of Glycine Release in Rat Retina: The Role of Reverse Mode Operation of Glycine Transporter Type-1 (GlyT-1) in Ischemic Conditions.

Rat posterior eyecups containing the retina were prepared, loaded with [(3)H]glycine and superfused in order to determine its release originated from glycinergic amacrine cells and/or glial cells. Deprivation of oxygen and glucose from the Krebs-bicarbonate buffer used for superfusion evoked a marked increase of [(3)H]glycine release, an effect that was found to be external Ca(2+)-independent. Whereas oxygen and glucose deprivation increased [(3)H]glycine release, its uptake was reduced suggesting that energy deficiency shifts glycine transporter type-1 operation from normal to reverse mode. The increased release of [(3)H]glycine evoked by oxygen and glucose deprivation was suspended by addition of the non-competitive glycine transporter type-1 inhibitor NFPS and the competitive inhibitor ACPPB further suggesting the involvement of this transporter in the mediation of [(3)H]glycine release. Oxygen and glucose deprivation also evoked [(3)H]glutamate release from rat retina and the concomitantly occurring release of the NMDA receptor agonist glutamate and the coagonist glycine makes NMDA receptor pathological overstimulation possible in hypoxic conditions. [(3)H]Glutamate release was suspended by addition of the excitatory amino acid transporter inhibitor TBOA. Sarcosine, a substrate inhibitor of glycine transporter type-1, also increased [(3)H]glycine release probably by heteroexchange shifting transporter operation into reverse mode. This effect of sarcosine was also external Ca(2+)-independent and could be suspended by NFPS. Energy deficiency in retina induced by ouabain, an inhibitor of the Na(+)-K(+)-dependent ATPase, and by rotenone, a mitochondrial complex I inhibitor added with the glycolytic inhibitor 2-deoxy-D-glucose, led to increase of retinal [(3)H]glycine efflux. These effects of ouabain and rotenone/2-deoxy-D-glucose could also be blocked by NFPS pointed to the preferential reverse mode operation of glycine transporter type-1 as a consequence of impaired cellular energy homeostasis. Immunohistochemical studies revealed that glycine transporter type-1, of which reverse mode operation assures [(3)H]glycine release, is expressed in amacrine cells in the inner nuclear and plexiform layers of the retina and also in Müller macroglia cells. We conclude that disruption of the balanced normal/reverse mode operation of glycine transporter type-1 is likely a significant factor contributing to neurotoxic processes of the retina. The possibility to inhibit glycine transporter type-1 mediated glycine efflux by drugs more potently than glycine uptake might offer some therapeutic potential for the treatment of various neurodegenerative disorders of the retina.

Novel electrocardiographic criteria may render possible the more accurate recognition of cardiac amyloidosis.

AIMS: The early diagnosis of cardiac amyloidosis (CA) is paramount, since there are effective therapies that improve patient survival. The diagnostic accuracy of classical electrocardiographic (ECG) signs, such as low voltage, pseudoinfarct pattern, and conduction disturbances in the diagnosis of CA, is inferior to that of the echocardiographic myocardial deformation criteria; therefore, our aim was to find more accurate novel ECG criteria for this purpose. METHODS: We tested the diagnostic value of five novel ECG criteria, two of them devised by us, in 34 patients with confirmed CA (20 transthyretin amyloidosis and 14 AL amyloidosis) and 45 control patients with left ventricular hypertrophy on echocardiography due to hypertension, valvular aortic stenosis and hypertrophic cardiomyopathy. The following novel ECG criteria, that suggested CA, were tested: QRS amplitude in lead I < 0.55 mV (I < 0.55); QRS amplitude in lead aVR < 0.5 mV (aVR < 0.5); average QRS amplitude of leads I + aVR < 0.575 mV [(I + aVR) < 0.575]; average QRS amplitude of leads I + aVR/average QRS amplitude of leads V1-4 < 0.375 [(I + aVR)/(V1-4) < 0.375]; average QRS amplitude of leads I + aVR/longest intrinsicoid deflection in leads I,aVL,V1-6 < 0.0115 [(I + aVR)/I,aVL,V1-6ID < 0.0115]. RESULTS: The I < 0.55, aVR < 0.5, (I + aVR) < 0.575, (I + aVR)/(V1-4) < 0.375, (I + aVR)/I,aVL,V1-6ID < 0.0115 test accuracy (TA) were 81%, 84.8%, 82.3%, 84.8%, and 83.3%, respectively; the sensitivity (SE): 76.5%, 82.4%, 85.3%, 82.4%, and 76.9%; specificity (SP): 84.4%, 86.7%, 80%, 86.7%, and 87.5%; positive predictive values (PPV): 78.8%, 82.4%, 76.3%, 82.4%, and 80%; negative predictive values (NPV): 82.6%, 86.7%, 87.8%, 86.7%, and 85.4%; area under curve (AUC) values: 0.8922, 0.8794, 09016, 0.8824, and 0.8462 were respectively. These parameters of the novel ECG criteria were at least as good as those reported by other authors in the literature of the qualitative (TA: 67%, SE: 80%, SP: 34%, PPV: 75%, NPV: 42%, AUC: 0.57) and quantitative apical sparing (TA: 64-80%, SE: 66-81.3%, SP: 55-78.3%, PPV: 33-83.9%, NPV: 41-75%, AUC: 0.62-0.68) and left ventricular ejection fraction/global longitudinal strain >4.1 (TA: 77%, SE: 93%, SP: 38%, PPV: 79%, NPV: 69%, AUC: 0.65) echocardiographic criteria. Among the classical criteria, the low voltage in limb leads criterion was present most frequently (in 73.5%) in patients with CA, with slightly worse diagnostic value than the novel ECG criteria (TA: 78.5%, SE: 73.5%, SP: 82.2%, PPV: 75.8%, NPV: 80.4%). CONCLUSIONS: The novel ECG criteria [mostly the aVR < 0.5, (I + aVR)/(V1-4) < 0.375] seem at least as reliable in the diagnosis of CA as the best echocardiographic myocardial deformation criteria and might be used either together with the echocardiographic criteria or as stand-alone criteria to diagnose CA in the future.

Myocardial postconditioning is lost in vascular nitrate tolerance.

Organic nitrates play an important role in the therapy of ischemic heart disease; however, their clinical application is limited by the development of vascular nitrate tolerance. We have previously shown attenuation of the cardioprotective effect of preconditioning in vascular nitrate tolerance. Here, we studied whether the development of vascular nitrate tolerance affects the infarct size, limiting effect of ischemic postconditioning (IPost) in the myocardium, and whether the activation of survival kinases plays a role in the molecular mechanism of postconditioning in the presence or absence of vascular nitrate tolerance. Male Wistar rats were treated with nitroglycerin/vehicle for 3 days to induce vascular nitrate tolerance. On the fourth day, isolated hearts were subjected to 30-minute coronary occlusion followed by 120-minute reperfusion with or without IPost. In nontolerant hearts, postconditioning significantly decreased infarct size as compared with ischemia/reperfusion; however, postconditioning failed to decrease infarct size in hearts of nitrate tolerant rats. Phosphorylation of ERK 1/2, Akt, or endothelial nitric oxide synthetase showed no significant differences between the groups at the 10th minute of reperfusion. Vascular nitrate tolerance interferes with the infarct size limiting effect of IPost. Activation of survival kinases is not crucial in the molecular mechanism of postconditioning, which remains unaffected in nitrate tolerance.

Eculizumab suppresses zymosan-induced release of inflammatory cytokines IL-1α, IL-1ß, IFN-γ and IL-2 in autologous serum-substituted PBMC cultures: Relevance to cytokine storm in Covid-19.

BACKGROUND AND OBJECTIVE: Cytokine storm (CS) is a major contributor to the fatal outcome of severe infectious diseases, including Covid-19. Treatment with the complement (C) C5 inhibitor eculizumab was beneficial in end-stage Covid-19, however, the mechanism of this effect is unknown. To clarify this, we analyzed the relationship between C activation and production of pro-inflammatory cytokines in a PBMC model. METHODS: Human PBMC with or without 20 % autologous serum was incubated with C3a, C5a, zymosan or zymosan-pre-activated serum (ZAS) for 24 h with or without eculizumab or the C5a receptor antagonist, DF2593A. C activation (sC5b-9) and 9 inflammatory cytokines were measured by ELISA. RESULTS: In serum-free unstimulated PBMC only IL-8 release could be measured during incubation. Addition of C5a increased IL-8 secretion only, ZAS induced both IL-2 and IL-8, while zymosan led to significant production of all cytokines, most abundantly IL-8. In the presence of serum the above effects were greatly enhanced, and the zymosan-induced rises of IL-1α, IL-1ß IFN-γ and IL-2 were significantly attenuated by eculizumab but not by DF2593a. CONCLUSIONS: These data highlight the complexity of interrelationships between C activation and cytokine secretion under different experimental conditions. The clinically relevant findings include the abundant formation of the chemokine IL-8, which was stimulated by C5a, and the suppression of numerous inflammatory cytokines by eculizumab, which explains its therapeutic efficacy in severe Covid-19. These data strengthen the clinical relevance of the applied PBMC model for drug screening against CS, enabling the separation of complex innate immune cross-talks.