Effect of Ovocystatin on Amyloid ß 1-42 Aggregation-In Vitro Studies.

Amyloid ß peptides (Aß) aggregating in the brain have a potential neurotoxic effect and are believed to be a major cause of Alzheimer's disease (AD) development. Thus, inhibiting amyloid polypeptide aggregation seems to be a promising approach to the therapy and prevention of this neurodegenerative disease. The research presented here is directed at the determination of the inhibitory activity of ovocystatin, the cysteine protease inhibitor isolated from egg white, on Aß42 fibril genesis in vitro. Thioflavin-T (ThT) assays, which determine the degree of aggregation of amyloid peptides based on fluorescence measurement, circular dichroism spectroscopy (CD), and transmission electron microscopy (TEM) have been used to assess the inhibition of amyloid fibril formation by ovocystatin. Amyloid beta 42 oligomer toxicity was measured using the MTT test. The results have shown that ovocystatin possesses Aß42 anti-aggregation activity and inhibits Aß42 oligomer toxicity in PC12 cells. The results of this work may help in the development of potential substances able to prevent or delay the process of beta-amyloid aggregation-one of the main reasons for Alzheimer's disease.

Renal Handling of Albumin-From Early Findings to Current Concepts.

Albumin is the main protein of blood plasma, lymph, cerebrospinal and interstitial fluid. The protein participates in a variety of important biological functions, such as maintenance of proper colloidal osmotic pressure, transport of important metabolites and antioxidant action. Synthesis of albumin takes place mainly in the liver, and its catabolism occurs mostly in vascular endothelium of muscle, skin and liver, as well as in the kidney tubular epithelium. Long-lasting investigation in this area has delineated the principal route of its catabolism involving glomerular filtration, tubular endocytic uptake via the multiligand scavenger receptor tandem-megalin and cubilin-amnionless complex, as well as lysosomal degradation to amino acids. However, the research of the last few decades indicates that also additional mechanisms may operate in this process to some extent. Direct uptake of albumin in glomerular podocytes via receptor for crystallizable region of immunoglobulins (neonatal FC receptor) was demonstrated. Additionally, luminal recycling of short peptides into the bloodstream and/or back into tubular lumen or transcytosis of whole molecules was suggested. The article discusses the molecular aspects of these processes and presents the major findings and controversies arising in the light of the research concerning the last decade. Their better characterization is essential for further research into pathophysiology of proteinuric renal failure and development of effective therapeutic strategies.

[Clathrin-independent endocytosis - role in disease processes and pharmaceutical aspects]. / Endocytoza niezalezna od klatryny-rola w patomechanizmie chorób i aspekty farmaceutyczne.

Clathrin-independent endocytosis (CIE) is the process of cellular uptake of various particles, including pathogens, without the coat protein clathrin. It occurs commonly in mammalian cells and is regulated by protein-lipid composition of the cell membranes. Understanding of different routes of CIE allowed the identification of novel molecular mechanisms involved in uptake of molecules and cell signaling and explained their role in pathological processes. In this paper we characterize diseases associated with genetic defects of proteins involved in CIE and the relationship between expression of these proteins and pathology of atherosclerosis, hypercholesterolemia, diabetes and neoplasia. The role of CIE in bacterial, viral, fungal, and protozoal infections is also presented. In the second part we describe the plausible use of clathrin-independent endocytosis in increasing drug absorption, their penetration through biological membranes, and the design of specific nanocarriers for selective cell uptake.

History of Heart Failure in Patients Hospitalized Due to COVID-19: Relevant Factor of In-Hospital Complications and All-Cause Mortality up to Six Months.

BACKGROUND: Patients with heart failure (HF) are at high risk of unfavorable courses of COVID-19. The aim of this study was to evaluate characteristics and outcomes of COVID-19 patients with HF. METHODS: Data of patients hospitalized in a tertiary hospital in Poland between March 2020 and May 2021 with laboratory-confirmed COVID-19 were analyzed. The study population was divided into a HF group (patients with a history of HF) and a non-HF group. RESULTS: Out of 2184 patients (65 ± 13 years old, 50% male), 12% had a history of HF. Patients from the HF group were older, more often males, had more comorbidities, more often dyspnea, pulmonary and peripheral congestion, inflammation, and end-organ damage biomarkers. HF patients had longer and more complicated hospital stay, with more frequent acute HF development as compared with non-HF. They had significantly higher mortality assessed in hospital (35% vs. 12%) at three (53% vs. 22%) and six months (72% vs. 47%). Of 76 (4%) patients who developed acute HF, 71% died during hospitalization, 79% at three, and 87% at six months. CONCLUSIONS: The history of HF identifies patients with COVID-19 who are at high risk of in-hospital complications and mortality up to six months of follow-up.

Anticoagulation Prior to COVID-19 Infection Has No Impact on 6 Months Mortality: A Propensity Score-Matched Cohort Study.

The coronavirus disease 2019 (COVID-19) shows high incidence of thromboembolic events in humans. In the present study, we aimed to evaluate if anticoagulation prior to COVID-19 infection may impact clinical profile, as well as mortality rate among patients hospitalized with COVID-19. The study was based on retrospective analysis of medical records of patients with laboratory confirmed SARS-CoV-2 infection. After propensity score matching (PSM), a group of 236 patients receiving any anticoagulant treatment prior to COVID-19 infection (AT group) was compared to 236 patients without previous anticoagulation (no AT group). In 180 days, the observation we noted comparable mortality rate in AT and no AT groups (38.5% vs. 41.1%, p = 0.51). Similarly, we did not observe any statistically significant differences in admission in the intensive care unit (14.1% vs. 9.6%, p = 0.20), intubation and mechanical ventilation (15.0% vs. 11.6%, p = 0.38), catecholamines usage (14.3% vs. 13.8%, p = 0.86), and bleeding rate (6.3% vs. 8.9%, p = 0.37) in both groups. Our results suggest that antithrombotic treatment prior to COVID-19 infection is unlikely to be protective for morbidity and mortality in patients hospitalized with COVID-19.

Characterization of chicken cystatin binding to rat renal brush-border membranes.

Chicken cystatin, a homologue of human cystatin C, like other low-molecular-weight proteins is metabolized by renal proximal tubule cells. However, the precise mechanism(s) of this process has not been elucidated yet. To characterize chicken cystatin binding to renal brush-border membranes, the incubation of fluorescein labelled protein with rat cortical homogenate was performed. Saturation-dependent and reversible binding with low affinity (K(d)=3.67-4.07 microM) and high capacity (B(max)=2.32-2.79 nmol/mg) was observed. Bovine albumin was the most potent competitor (K(i)=0.7 microM) among other megalin/cubilin ligands tested. The presence of Ca(+2) ions was necessary to effective cystatin binding by brush-border membranes. Obtained data strongly support the hypothesis that chicken cystatin is a novel ligand for megalin/cubilin receptors tandem on proximal tubular cells.

[Molecular aspects of aminoglycoside nephrotoxicity]. / Molekularne aspekty nefrotoksycznosci antybiotyków aminoglikozydowych.

Aminoglycosides are potent bactericidal antibiotics particularly active against aerobic Gram-negative bacteria. This review focuses on the recent concept of a molecular understanding of aminoglycoside-induced nephrotoxicity. As receptor-mediated endocytosis plays an important role in the accumulation of aminoglycosides in renal proximal tubules, the biochemical properties of the two main receptors, megalin and cubilin, involved in this process are described. Literature data on megalin and acidic phospholipids as potential targets for preventing aminoglycoside-induced nephrotoxicity are also presented.

Binding of glycated ovocystatin to rat renal brush border membranes.

Glycated proteins are considered as one of the factors involved in the pathogenesis of diabetic complications, including nephropathy. These proteins are formed endogenously under conditions of hyperglycemia, as well as being provided with food containing sugars, which was subjected to high temperature. Examples are egg products. One of the proteins found in eggs in a relatively high concentration is chicken cystatin (ovocystatin). It is now believed that some proteins can passage the intestinal epithelium by transcytosis directly into the bloodstream. Thus, glycated protein present in food can be an additional source of glycotoxins. The aim of this study was to compare the affinity of native and glycated cystatin to the brush border membranes of rat kidney. Kinetic analysis was performed with surface plasmon resonance technique using sensor chip L1. Dissociation constants for native and glycated cystatin (Kd ) were 2.76 µmol/L and 3.82 µmol/L, respectively. The results of our study indicate that glycation only slightly affects binding of cystatin to brush border membranes. This suggests that glycated cystatin and other glycated proteins may also be efficiently taken up in the kidney proximal tubule. The observation may be important for understanding the mechanisms involved in the development of diabetic nephropathy.

Influence of aminoglycoside antibiotics on chicken cystatin binding to renal brush-border membranes.

OBJECTIVES: Drug-induced kidney injury is a serious adverse event which needs to be monitored during aminoglycoside therapy. Urine cystatin C is considered an early and sensitive marker of nephrotoxicity. Cystatin C, a low-molecular-weight serum protein, and basic drugs have a common transport system expressed in the apical membrane of renal proximal tubular cells. The aim of this study was to investigate whether aminoglycoside antibiotics influenced cystatin C binding to the renal brush-border membrane. METHODS: The binding study was performed using a rapid filtration technique and affinity column displacement method. KEY FINDINGS: Concentration-dependent inhibition of chicken cystatin binding to brush-border membranes by gentamicin was observed. The gentamicin interaction with brush-border membranes was of relatively low affinity (Ki = 32 µm) in comparison with the chicken cystatin affinity to the binding sites (Kd = 3.6 µm). Amikacin and gentamicin were only able to displace chicken cystatin from the chromatographic affinity column in concentrations several times higher than normally found in the tubular fluid during standard aminoglycoside therapy. CONCLUSION: Cystatin reabsorption in the proximal tubule cannot be significantly affected by aminoglycoside antibiotics because of their relatively low affinity to common binding sites on the brush-border membrane.