Effects of spermidine and p-cresol on polymorphonuclear cell apoptosis and function

COVID-19 Vaccination in Kidney Transplant Candidates and Recipients

Kidney transplant candidates and kidney transplant recipients (KTRs) are at particular risk of severe complications of COVID-19 disease. In Western countries, mortality in affected hospitalized KTRs ranges between 19% and 50%. COVID-19 vaccination remains the most important measure to prevent the severity of infection in candidates and recipients of kidney transplant. However, the uraemic condition may affect the vaccine-induced immunity in patients with advanced chronic kidney disease (CKD) and in KTRs. Retention of uraemic toxins, dysbiosis, dysmetabolism, and dialysis can diminish the normal response to vaccination, leading to dysfunction of inflammatory and immune cells. In KTRs the efficacy of vaccines may be reduced by the immunosuppressive medications, and more than half of kidney transplant recipients are unable to build an immune response even after four administrations of anti-COVID-19 vaccines. The lack of antibody response leaves these patients at high risk for SARS-CoV-2 infection and severe COVID-19 disease. The aim of the present review is to focus on the main reasons for the impaired immunological response among candidates and kidney transplant recipients and to highlight some of the present options available to solve the problem.

Tauroursodeoxycholic Acid Protects against the Effects of P-Cresol-Induced Reactive Oxygen Species via the Expression of Cellular Prion Protein

Mesenchymal stem cells (MSCs) could be a promising solution in the treatment of various diseases including chronic kidney disease (CKD). However, endoplasmic reticulum (ER) stress induced by ischemia in the area of application limits the integration and survival of MSCs in patients. In our study, we generated ER stress-induced conditions in MSCs using P-cresol. As P-cresol is a toxic compound accumulated in the body of CKD patients and induces apoptosis and inflammation through reactive oxygen species (ROS), we observed ER stress-induced MSC apoptosis activated by oxidative stress, which in turn resulted from ROS generation. To overcome stress-induced apoptosis, we investigated the protective effects of tauroursodeoxycholic acid (TUDCA), a bile acid, on ER stress in MSCs. In ER stress, TUDCA treatment of MSCs reduced ER stress-associated protein activation, including GRP78, PERK, eIF2α, ATF4, IRE1α, and CHOP. Next, to explore the protective mechanism adopted by TUDCA, TUDCA-mediated cellular prion protein (PrP^C) activation was assessed. We confirmed that PrP^C expression significantly increased ROS, which was eliminated by superoxide dismutase and catalase in MSCs. These findings suggest that TUDCA protects from inflammation and apoptosis in ER stress via PrP^C expression. Our study demonstrates that TUDCA protects MSCs against inflammation and apoptosis in ER stress by PrP^C expression in response to P-cresol exposure.

p-Cresol affects reactive oxygen species generation, cell cycle arrest, cytotoxicity and inflammation/atherosclerosis-related modulators production in endothelial cells and mononuclear cells

Aims

Cresols are present in antiseptics, coal tar, some resins, pesticides, and industrial solvents. Cresol intoxication leads to hepatic injury due to coagulopathy as well as disturbance of hepatic circulation in fatal cases. Patients with uremia suffer from cardiovascular complications, such as atherosclerosis, thrombosis, hemolysis, and bleeding, which may be partly due to p-cresol toxicity and its effects on vascular endothelial and mononuclear cells. Given the role of reactive oxygen species (ROS) and inflammation in vascular thrombosis, the objective of this study was to evaluate the effect of p-cresol on endothelial and mononuclear cells.

Methods

EA.hy926 (EAHY) endothelial cells and U937 cells were exposed to different concentrations of p-cresol. Cytotoxicity was evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5 -diphenyltetrazolium bromide (MTT) assay and trypan blue dye exclusion technique, respectively. Cell cycle distribution was analyzed by propidium iodide flow cytometry. Endothelial cell migration was studied by wound closure assay. ROS level was measured by 2′,7′-dichlorofluorescein diacetate (DCF) fluorescence flow cytometry. Prostaglandin F_2α (PGF_2α), plasminogen activator inhibitor-1 (PAI-1), soluble urokinase plasminogen activator receptor (suPAR), and uPA production were determined by Enzyme-linked immunosorbant assay (ELISA).

Results

Exposure to 100–500 µM p-cresol decreased EAHY cell number by 30–61%. P-cresol also decreased the viability of U937 mononuclear cells. The inhibition of EAHY and U937 cell growth by p-cresol was related to induction of S-phase cell cycle arrest. Closure of endothelial wounds was inhibited by p-cresol (>100 µM). P-cresol (>50 µM) also stimulated ROS production in U937 cells and EAHY cells but to a lesser extent. Moreover, p-cresol markedly stimulated PAI-1 and suPAR, but not PGF_2α, and uPA production in EAHY cells.

Conclusions

p-Cresol may contribute to atherosclerosis and thrombosis in patients with uremia and cresol intoxication possibly due to induction of ROS, endothelial/mononuclear cell damage and production of inflammation/atherosclerosis-related molecules.