• The Korean Journal of Physiology and Pharmacology
• /
• v.17 no.5
• /
• pp.435-440
• /
• 2013

While the anti-apoptotic effect of paricalcitol has been demonstrated in various animal models, it is not yet clear whether paricalcitol attenuates the apoptosis in gentamicin (GM)-induced kidney injury. We investigated the effect of paricalcitol on apoptotic pathways in rat kidneys damaged by GM. Rats were randomly divided into three groups: 1) Control group (n=8), where only vehicle was delivered, 2) GM group (n=10), where rats were treated with GM (150 mg/kg/day) for 7 days, 3) PARI group (n=10), where rats were co-treated with paricalcitol (0.2 ${\mu}g/kg/day$) and GM for 7 days. Paricalcitol attenuated renal dysfunction by GM administration in biochemical profiles. In terminal deoxynucleotidyl transferase dUTP nick end labeling staining, increased apoptosis was observed in GM group, which was reversed by paricalcitol co-treatment. Immunoblotting using protein samples from rat cortex/outer stripe of outer medulla showed increased Bax/Bcl-2 ratio and cleaved form of caspase-3 in GM group, both of which were reversed by paricalcitol. The phosphorylated Jun-N-terminal kinase (JNK) expression was increase in GM, which was counteracted by paricalcitol. The protein expression of p-Akt and nitro-tyrosine was also enhanced in GM-treated rats compared with control rats, which was reversed by paricalcitol co-treatment. Paricalcitol protects GM-induced renal injury by antiapoptotic mechanisms, including inhibition of intrinsic apoptosis pathway and JNK.

• The Korean journal of internal medicine
• /
• v.34 no.1
• /
• pp.146-155
• /
• 2019

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 2',7'-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 $factor-{\kappa}B$ ($NF-{\kappa}B$) p65, and phosphorylation of mitogen-activated protein kinase (MAPK) and protein kinase B (Akt) were determined by semiquantitative immunoblotting. The promoter activity of $NF-{\kappa}B$ 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, $NF-{\kappa}B$ p65, and Akt. In contrast, paricalcitol treatment decreased Bax expression, increased Bcl-2 expression, and inhibited phosphorylation of MAPK, $NF-{\kappa}B$ p65, and Akt in HK-2 cells. $NF-{\kappa}B$ 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, $NF-{\kappa}B$, and Akt signaling pathway in HK-2 cells.

• Kidney Research and Clinical Practice
• /
• v.36 no.2
• /
• pp.145-157
• /
• 2017

Background: Vitamin D is considered to exert a protective effect on various renal diseases but its underlying molecular mechanism remains poorly understood. This study aimed to determine whether paricalcitol attenuates inflammation and apoptosis during lipopolysaccharide (LPS)-induced renal proximal tubular cell injury through the prostaglandin $E_2$ ($PGE_2$) receptor EP4. Methods: Human renal tubular epithelial (HK-2) cells were pretreated with paricalcitol (2 ng/mL) for 1 hour and exposed to LPS ($1{\mu}g/mL$). The effects of paricalcitol pretreatment in relation to an EP4 blockade using AH-23848 or EP4 small interfering RNA (siRNA) were investigated. Results: The expression of cyclooxygenase-2, $PGE_2$, and EP4 were significantly increased in LPS-exposed HK-2 cells treated with paricalcitol compared with cells exposed to LPS only. Paricalcitol prevented cell death induced by LPS exposure, and the cotreatment of AH-23848 or EP4 siRNA offset these cell-protective effects. The phosphorylation and nuclear translocation of p65 nuclear factor-kappaB ($NF-{\kappa}B$) were decreased and the phosphorylation of Akt was increased in LPS-exposed cells with paricalcitol treatment. AH-23848 or EP4 siRNA inhibited the suppressive effects of paricalcitol on p65 $NF-{\kappa}B$ nuclear translocation and the activation of Akt. The production of proinflammatory cytokines and the number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were attenuated by paricalcitol in LPS exposed HK-2 cells. The cotreatment with an EP4 antagonist abolished these anti-inflammatory and antiapoptotic effects. Conclusion: EP4 plays a pivotal role in anti-inflammatory and antiapoptotic effects through Akt and $NF-{\kappa}B$ signaling after paricalcitol pretreatment in LPS-induced renal proximal tubule cell injury.