Indoxyl Sulfate Induces Apoptosis Through Oxidative Stress and Mitogen-Activated Protein Kinase Signaling Pathway Inhibition in Human Astrocytes.

Yi-Ting Lin,Yi-Chun Tsai,Ya-Ling Hsu,Mei-Chuan Kuo,Shang-Jyh Hwang,Han Ying Wang,Ping-Hsun Wu,Po-Lin Kuo

doi:10.3390/jcm8020191

Abstract

Uremic toxins accumulated in chronic kidney disease (CKD) increases the risk of cognitive impairment. Indoxyl sulfate (IS) is a well-known protein-bound uremic toxin that is correlated with several systemic diseases, but no studies on human brain cells are available. We investigated the effect of IS on primary human astrocytes through next-generation sequencing and cell experiment confirmation to explore the mechanism of IS-associated brain damage. Total RNAs extracted from IS-treated and control astrocytes were evaluated by performing functional and pathway enrichment analysis. The toxicities of IS in the astrocytes were investigated in terms of cell viability through flow cytometry; the signal pathway was then investigated through immunoblotting. IS stimulated the release of reactive oxygen species, increased nuclear factor (erythroid-derived 2)-like 2 levels, and reduced mitochondrial membrane potential. IS triggered astrocyte apoptosis by inhibiting the mitogen-activated protein kinase (MAPK) pathway, including extracellular-signal-regulated kinase (ERK), MAPK/ERK kinase, c-Jun N-terminal kinase, and p38. The decreased ERK phosphorylation was mediated by the upregulated dual-specificity phosphatase 1, 5, 8, and 16. In conclusion, IS can induce neurotoxicity in patients with CKD and the pathogenesis involves cell apoptosis through oxidative stress induction and MAPK pathway inhibition in human astrocytes.

Highlights

Patients with chronic kidney disease (CKD) exhibit higher rates of cognitive impairment and dementia than does the general population [1]
Further flow cytometry analy6soifs19 showed that apoptosis of the indoxyl sulfate (IS)-treated astrocytes increased dramatically at 48 h in contrast to (Figuthreat2Bo,fCt)h
Based on the results of NGS with bioinformatics analysis and that of an experimental study on human astrocytes, we found that IS induced activation of reactive oxygen species (ROS) and downregulated cell-protective factors such as nuclear factor (erythroid-derived 2)-like 2 (NRF2)

Summary

Introduction

Patients with chronic kidney disease (CKD) exhibit higher rates of cognitive impairment and dementia than does the general population [1]. The major causes of cognitive impairment in patients with CKD include cerebrovascular disease, anemia, secondary hyperparathyroidism, dialysis disequilibrium, and uremic toxins [4,5]. IS accumulation within brain structures may be linked to the expression of OAT3 efflux transporter [12,13] in the BBB and the blood–cerebrospinal fluid barrier (BCSFB). Both in vivo and in vitro studies have suggested that infiltration of uremic toxins within brain structures may have deleterious impacts on brain resident cells, such as microglia, astrocytes, and neurons

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Conclusion