Korean J Intern Med.  2019 Jan;34(1):146-155. 10.3904/kjim.2016.298.

Paricalcitol attenuates indoxyl sulfate-induced apoptosis through the inhibition of MAPK, Akt, and NF-κB activation in HK-2 cells

Affiliations
  • 1Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea. skimw@chonnam.ac.kr

Abstract

BACKGROUND/AIMS
Indoxyl sulfate (IS) is a uremic toxin and an important causative factor in the progression of chronic kidney disease. Recently, paricalcitol (19-nor-1,25-dihydroxyvitamin D2) was shown to exhibit protective effects in kidney injury. Here, we investigated the effects of paricalcitol treatment on IS-induced renal tubular injury.
METHODS
The fluorescent dye 2ʹ,7ʹ-dichlorofluorescein diacetate was used to measure intracellular reactive oxygen species (ROS) following IS administration in human renal proximal tubular epithelial (HK-2) cells. The effects of IS on cell viability were determined using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays and levels of apoptosis-related proteins (Bcl-2-associated protein X [Bax] and B-cell lymphoma 2 [Bcl-2]), nuclear factor-κB (NF-κB) p65, and phosphorylation of mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) were determined by semiquantitative immunoblotting. The promoter activity of NF-κB was measured by luciferase assays and apoptosis was determined by f low cytometry of cells stained with f luorescein isothiocyanate-conjugated Annexin V protein.
RESULTS
IS treatment increased ROS production, decreased cell viability and induced apoptosis in HK-2 cells. IS treatment increased the expression of apoptosis-related protein Bax, decreased Bcl-2 expression, and activated phosphorylation of MAPK, NF-κB p65, and Akt. In contrast, paricalcitol treatment decreased Bax expression, increased Bcl-2 expression, and inhibited phosphorylation of MAPK, NF-κB p65, and Akt in HK-2 cells. NF-κB promoter activity was increased following IS, administration and was counteracted by pretreatment with paricalcitol. Additionally, flow cytometry analysis revealed that IS-induced apoptosis was attenuated by paricalcitol treatment, which resulted in decreased numbers of fluorescein isothiocyanate-conjugated Annexin V positive cells.
CONCLUSIONS
Treatment with paricalcitol inhibited IS-induced apoptosis by regulating MAPK, NF-κB, and Akt signaling pathway in HK-2 cells.

Keyword

Apoptosis; Proximal tubular epithelial cell; Indican; Paricalcitol; Signal transduction

MeSH Terms

Annexin A5
Apoptosis*
Cell Survival
Flow Cytometry
Fluorescein
Humans
Immunoblotting
Indican
Kidney
Luciferases
Lymphoma, B-Cell
Phosphorylation
Protein Kinases
Proto-Oncogene Proteins c-akt
Reactive Oxygen Species
Renal Insufficiency, Chronic
Signal Transduction
Annexin A5
Fluorescein
Indican
Luciferases
Protein Kinases
Proto-Oncogene Proteins c-akt
Reactive Oxygen Species
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