Pioglitazone modulates immune activation and ameliorates inflammation induced by injured renal tubular epithelial cells via PPARγ/miRNA‑124/STAT3 signaling

Abstract

Acute kidney injury (AKI) is commonly a result of renal ischemia reperfusion injury (IRI), which produces clinical complications characterized by the rapid deterioration of renal function, leading to chronic kidney disease and increases the risk of morbidity and mortality. Currently, only supportive treatment is available. AKI, which is accompanied by immune activation and inflammation, is caused by proximal tubular injury. The present study investigated the role of tubular epithelial cells as drivers of inflammation in renal IRI and their potential function as antigen-presenting cells, as well as the molecular mechanisms by which peroxisome proliferator-activated receptor-γ (PPARγ) agonists [such as pioglitazone (Pio)] exert reno-protective action in renal IRI. A total of 50 Wistar male albino rats were divided into five groups: Sham + DMSO, Sham + Pio, IRI + DMSO, IRI + prophylactic preoperative (pre) Pio and IRI + postoperative Pio. The histopathological changes in renal tissue samples and the renal epithelial cell expression of CD86, miRNA-124, STAT3, pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and Arginase-II were analyzed by immunohistochemistry, reverse transcription-quantitative PCR, western blotting and ELISA respectively. IRI was a potent inducer for CD86 immunoexpression. An ameliorative action of Pio was demonstrated via decreased CD86 immunoexpression, upregulation of miRNA-124, decreased STAT3 expression and beneficial anti-inflammatory effects. The tubular epithelium served a notable role in the inflammatory response in renal IRI. Pio exerted its anti-inflammatory effects via PPARγ/miRNA-124/STAT3 signaling.

Keywords: STAT3; microRNA-124; peroxisome proliferator-activated receptor-γ; pioglitazone; renal ischemia reperfusion injury.

Figure 1

Effect of Pioglitazone on the serum levels of creatinine and BUN. Serum (A) creatinine and (B) BUN at 24 h after renal IRI. ^*P<0.05 vs. Sham + DMSO group, ^**P<0.05 vs.Sham + Pio group, ^#P<0.05 vs. IRI + DMSO, ^$P<0.05 vs. IRI + prophylactic preoperative (pre) Pio. Data shown are means ± SD. BUN, blood urea nitrogen; IRI, ischemia reperfusion injury; Pio, pioglitazone; pre, preoperative; post, postoperative.

Figure 2

Photomicrographs of hematoxylin and eosin-stained renal tissue sections. (A) Sham + DMSO shows normal histological features of cortical and medullary components of renal parenchyma with apparently intact renal corpuscles and tubular segments with almost intact tubular epithelium as well as intact vasculature. (B) Sham + Pio shows almost the same records as Sham + DMSO without abnormal histological changes. (C) IRI + DMSO shows severe degenerative changes of tubular epithelium with moderate dilatation in different segments, occasional focal records of tubular necrosis with intraluminal casts, severe congested glomerular tufts, congested interstitial BVs and mild inflammatory cell infiltrate. (D) IRI + Pio pre shows almost the same records as IRI group without notable protective efficacy and mild focal improvement of renal tissue architecture. (E) IRI + Pio post shows more organized renal parenchyma with notable protective efficacy on renal tubular epithelium, mild focal records of degenerated tubular epithelial cells, occasional nuclear pyknosis and mild congested interstitial BVs and glomerular tufts. Magnification, x400. IRI, ischemia reperfusion injury; Pio, pioglitazone; pre, preoperative; post, postoperative; BVs, blood vessels.

Figure 3

Immunohistochemical detection of CD86 in renal tissue. (A) Sham + DMSO. (B) Sham + Pio. (C) IRI + DMSO (D) IRI + prophylactic preoperative (pre) Pio (E) IRI + postoperative (post) Pio. Magnification, x400. (F) Mean area % of CD86 immunoexpression. Data are expressed as the mean ± SD (n=6). ^*P<0.05 vs. Sham + DMSO; ^**P<0.05 vs. Sham + Pio; ^#P<0.05 vs. IRI + DMSO; ^$P<0.05 vs. IRI + prophylactic preoperative (pre) Pio. IRI, ischemia reperfusion injury; Pio, pioglitazone; pre, preoperative; post, postoperative.

Figure 4

Detection of STAT3 expression. (A) Western blotting for detection of STAT3 protein expression. (B) STAT3/β-actin ratio. ^*P<0.05 vs. Sham + DMSO; ^**P<0.05 vs. Sham + Pio; ^#P<0.05 vs. IRI + DMSO. Data are presented as the mean ± SD. IRI, ischemia reperfusion injury; Pio, pioglitazone; pre, preoperative; post, postoperative.

Figure 5

miRNA-124 expression in renal tissue (n=10/group). ^*P<0.05 vs. Sham + DMSO; ^**P<0.05 vs. Sham + Pio; ^#P<0.05 vs. IRI + DMSO; ^$P<0.05 vs. IRI + prophylactic preoperative (pre) Pio. Data are presented as the mean ± SD. IRI, ischemia reperfusion injury; Pio, pioglitazone; pre, preoperative; post, postoperative; miRNA, microRNA.