Uremia-related oxidative stress in leukocytes is not triggered by β2-microglobulin

Antimicrobial and Immunomodulatory Effect of Gum Arabic on Human and Bovine Granulocytes Against Staphylococcus aureus and Escherichia coli

Gum arabic (GA) is a traditional herbal medicine from Acacia Senegal (L.) Willdenow trees, which consist of a complex mixture of polysaccharides and glycoproteins. It is used in daily applications for several diseases and is considered to protect against bacterial infections. The detailed mechanisms behind these observations are still unclear. In this study, we investigated the direct antibacterial activity of GA water and ethanol extracts against Staphylococcus (S.) aureus or Escherichia (E.) coli and the immunomodulating properties of those extracts on granulocytes as a first line of defense against bacteria. Firstly, the direct antimicrobial effect of GA was tested on three different S. aureus strains and two E. coli strains. The growth of bacteria was analyzed in the presence of different GA concentrations over time. GA water as well as ethanol extracts showed a significant growth inhibition in a concentration-dependent manner in the case of S. aureus Newman, S. aureus Rd5, and E. coli 25922, but not in the case of S. aureus USA300 and E. coli K1. Transmission electron microscopic analysis confirmed an antibacterial effect of GA on the bacteria. Secondly, the immunomodulatory effect of GA on the antimicrobial activity of bovine or human blood-derived granulocytes was evaluated. Interestingly, water and ethanol extracts enhanced antimicrobial activity of granulocytes by the induction of intracellular ROS production. In line with these data, GA increased the phagocytosis rate of E. coli. No effect was seen on neutrophil extracellular trap (NET) formation that mediates killing of extracellular bacteria such as S. aureus. In conclusion, we show that GA exhibits a direct antibacterial effect against some S. aureus and E. coli strains. Furthermore, GA boosts the antimicrobial activities of granulocytes and increases intracellular ROS production, which may lead to more phagocytosis and intracellular killing. These data might explain the described putative antimicrobial activity of GA used in traditional medicine.

Biochemical and Clinical Impact of Organic Uremic Retention Solutes: A Comprehensive Update

In this narrative review, the biological/biochemical impact (toxicity) of a large array of known individual uremic retention solutes and groups of solutes is summarized. We classified these compounds along their physico-chemical characteristics as small water-soluble compounds or groups, protein bound compounds and middle molecules. All but one solute (glomerulopressin) affected at least one mechanism with the potential to contribute to the uremic syndrome. In general, several mechanisms were influenced for each individual solute or group of solutes, with some impacting up to 7 different biological systems of the 11 considered. The inflammatory, cardio-vascular and fibrogenic systems were those most frequently affected and they are one by one major actors in the high morbidity and mortality of CKD but also the mechanisms that have most frequently been studied. A scoring system was built with the intention to classify the reviewed compounds according to the experimental evidence of their toxicity (number of systems affected) and overall experimental and clinical evidence. Among the highest globally scoring solutes were 3 small water-soluble compounds [asymmetric dimethylarginine (ADMA); trimethylamine-N-oxide (TMAO); uric acid], 6 protein bound compounds or groups of protein bound compounds [advanced glycation end products (AGEs); p-cresyl sulfate; indoxyl sulfate; indole acetic acid; the kynurenines; phenyl acetic acid;] and 3 middle molecules [β₂-microglobulin; ghrelin; parathyroid hormone). In general, more experimental data were provided for the protein bound molecules but for almost half of them clinical evidence was missing in spite of robust experimental data. The picture emanating is one of a complex disorder, where multiple factors contribute to a multisystem complication profile, so that it seems of not much use to pursue a decrease of concentration of a single compound.

Efficacy of Fenugreek-based bionanocomposite on renal dysfunction and endogenous intoxication in high-calorie diet-induced obesity rat model-comparative study

BACKGROUND

Worldwide obesity spread is a global health problem and needs to be further studied. Co-morbidities of obesity include insulin resistance, diabetes mellitus type 2, and dyslipidemia, which are the most frequent contributing factors for metabolic syndrome (MetS), as well as non-alcoholic fatty liver disease and chronic kidney disease. The aim was to study renal function and endogenous intoxication panel on high-calorie diet-induced obesity rat model and perform comparative study of the treatment efficacy of Fenugreek-based bionanocomposite vs antiobesogenic drugs (Orlistat).

MATERIALS

We included 60 male rats and equally divided them to 6 groups of 10 animals in each group: the experimental groups were firstly assigned as controls and high caloric diet (HCD)-fed groups, and each group further was subdivided to remain untreated, Fenugreek bionanocomposite (BNC)-treated, and Orlistat-treated. Normal control rats (groups 1, 2, 3) were fed by a standard chow, while the others (groups 4, 5, 6) were fed with HCD ad libitum during 98 days. From days 77 to 98, groups 2 and 5 were treated with BNC based on Fenugreek (150 mg/kg body weight, orally) and groups 3 and 6 were treated with antiobesogenic drug Orlistat (10 mg/kg body weight, orally). Food and water consumptions were measured daily and body weights were measured once a week. On day 99, blood was collected; the creatinine, urea, and uric acid were estimated in serum according to the standard protocols. Levels of low and middle molecules (MMs) were measured; the quantity of oligopeptides was estimated by Bradford method. We performed the liver and kidney ultrasonography in rats.

RESULTS

We revealed an increase in the levels of endogenous intoxication syndrome markers (MM and oligopeptides) in all animals with experimental obesity. Ultrasound data showed injury of the liver and kidneys in obese rats. We observed significant decreasing of MM levels after Orlistat treatment vs controls (p < 0.05). However, this effect was more pronounced in Fenugreek BNC-treated group vs both Orlistat-treated and controls (p < 0.05). Orlistat treatment evoked rising of serum creatinine and oligopeptides in control animals and failed to normalize these markers in experimental group. Fenugreek-based BNC treatment did not evoke signs of kidney failure and changes in the studied indices in control group. We noticed normalization levels of uric acid and urea in the blood under the use of BNC and Orlistat.

CONCLUSION

High-calorie diet-induced obesity evokes endogenous intoxication syndrome and kidney dysfunction in rats. Application of Orlistat- and Fenugreek-based BNC decreases MM content to the normal level. Orlistat induces increasing levels of oligopeptides in both groups, likely due to adverse side effects on renal function and its pro-oxidant activity.

Role of β2-microglobulin in uremic patients may be greater than originally suspected

The role of beta2-microglobulin (β₂M) in dialysis-related amyloidosis as a specific amyloid precursor was defined in the 1980s. Studies in those years were largely related to β₂M amyloidosis. In 2005, for what was probably the first time in the available literature, we provided data about the association between β₂M and early-onset atherosclerosis in hemodialysis patients without co-morbidities. In recent years, the role of uremic toxins in uremic atherosclerosis and the interest in β₂M as a marker of cardiovascular (CV) and/or mortality risk have grown. In the current literature, clinical studies suggest that β₂M is an independent, significant predictor of mortality, not only in dialysis patients, but also in predialysis patients and in the high-risk portion of the general population, and it seems to be a factor strongly linked to the presence and severity of CV disease. It is still unknown whether β₂M is only a uremic toxin marker or if it also has an active role in vascular damage, but data support that it may reflect an increased burden of systemic atherosclerosis in a setting of underlying chronic kidney disease. Thus, although there have been some inconsistencies among the various analyses relating to β₂M, it promises to be a novel risk marker of kidney function in the awareness and detection of high-risk patients. However, more research is required to establish the pathophysiological relationships between retained uremic toxins and further biochemical modifications in the uremic milieu to get answers to the questions of why and how. In this review, the recent literature about the changing role of β₂M in uremic patients will be examined.

The peptidic middle molecules: is molecular weight doing the trick?

Chronic kidney disease (CKD) is characterized by a gradual endogenous intoxication caused by the progressive accumulation of bioactive compounds that in normal conditions would be excreted and/or metabolized by the kidney. Uremic toxicity now is understood as one of the potential causes for the excess of cardiovascular disease and mortality observed in CKD. An important family of uremic toxins is that of the peptidic middle molecules, with a molecular weight ranging between 500 and 60,000 Da, which makes them, as a consequence, difficult to remove in the process of dialysis unless the dialyzer pore size is large enough. This review provides an overview of the main and best-characterized peptidic middle molecules and their role as potential culprits of the cardiometabolic complications inherent to CKD patients.