Association of PAX2 with cell apoptosis in unilateral ureteral obstruction rats

Cyclin-dependent kinase 4-related tubular epithelial cell proliferation is regulated by Paired box gene 2 in kidney ischemia-reperfusion injury

Paired box 2 (Pax2) is a transcription factor essential for kidney development and is reactivated in proximal tubular epithelial cells (PTECs) during recovery from kidney injury. However, the role of Pax2 in this process is still unknown. Here the role of Pax2 reactivation during injury was examined in the proliferation of PTECs using an ischemia-reperfusion injury (IRI) mouse model. Kidney proximal tubule-specific Pax2 conditional knockout mice were generated by mating kidney androgen-regulated protein-Cre and Pax2 flox mice. The degree of cell proliferation and fibrosis was assessed and a Pax2 inhibitor (EG1) was used to evaluate the role of Pax2 in the hypoxic condition of cultured PTECs (O₂ 5%, 24 hours). The number of Pax2-positive cells and Pax2 mRNA increased after IRI. Sirius red staining indicated that the area of interstitial fibrosis was significantly larger in knockout mice 14 days after IRI. The number of Ki-67-positive cells (an index of proliferation) was significantly lower in knockout than in wild-type mice after IRI, whereas the number of TUNEL-positive cells (an index of apoptotic cells) was significantly higher in knockout mice four days after IRI. Expression analyses of cell cycle-related genes showed that cyclin-dependent kinase 4 (CDK4) was significantly less expressed in the Pax2 knockout mice. In vitro data showed that the increase in CDK4 mRNA and protein expression induced by hypoxia was attenuated by EG1. Thus, Pax2 reactivation may be involved in PTEC proliferation by activating CDK4, thereby limiting kidney fibrosis.

Effects of exercise training on urinary tract function after spinal cord injury

Spinal cord injury (SCI) causes dramatic changes in the quality of life, including coping with bladder dysfunction which requires repeated daily and nightly catheterizations. Our laboratory has recently demonstrated in a rat SCI model that repetitive sensory information generated through task-specific stepping and/or loading can improve nonlocomotor functions, including bladder function (Ward PJ, Herrity AN, Smith RR, Willhite A, Harrison BJ, Petruska JC, Harkema SJ, Hubscher CH. J Neurotrauma 31: 819-833, 2014). To target potential underlying mechanisms, the current study included a forelimb-only exercise group to ascertain whether improvements may be attributed to general activity effects that impact target organ-neural interactions or to plasticity of the lumbosacral circuitry that receives convergent somatovisceral inputs. Male Wistar rats received a T9 contusion injury and were randomly assigned to three groups 2 wk postinjury: quadrupedal locomotion, forelimb exercise, or a nontrained group. Throughout the study (including preinjury), all animals were placed in metabolic cages once a week for 24 h to monitor water intake and urine output. Following the 10-wk period of daily 1-h treadmill training, awake cystometry data were collected and bladder and kidney tissue harvested for analysis. Metabolic cage frequency-volume measurements of voiding and cystometry reveal an impact of exercise training on multiple SCI-induced impairments related to various aspects of urinary tract function. Improvements in both the quadrupedal and forelimb-trained groups implicate underlying mechanisms beyond repetitive sensory information from the hindlimbs driving spinal network excitability of the lumbosacral urogenital neural circuitry. Furthermore, the impact of exercise training on the upper urinary tract (kidney) underscores the health benefit of activity-based training on the entire urinary system within the SCI population.

Potential signal pathway of all-trans retinoic acid for MMP-2 and MMP-9 expression in injury podocyte induced by adriamycin

All-trans-retinoic acid (ATRA) can regulate some specific genes expression in various tissue and cells via nuclear retinoic acid receptors (RARs), including three subtypes: retinoic acid receptor-alpha (RAR-α), retinoic acid receptor-beta (RAR-β) and retinoic acid receptor-gamma (RAR-γ). Podocyte injury plays a pivotal role in the progression of glomerulosclerosis (GS). This study was performed to study the potential signal pathway of ATRA in the expression of matrix metalloproteinases-2 (MMP-2) and matrix metalloproteinases-9 (MMP-9) in injury podocyte. Cells were divided into three groups: group of negative control (NC), group of injury podocyte induced by adriamycin (ADR) (AI) and group of ADR inducing podocyte injury model treated with ATRA (AA). The cells morphology changes were detected using microscope and scanning electron microscopy. MMP-2 and MMP-9 enzymic activity was detected using the gelatin zymography method. Protein and mRNA expressions of MMP-2, MMP-9, RAR-α, RAR-β and RAR-γ were measured by western-blot and real-time RT-PCR. Enzymatic activity of MMP-2 and MMP-9 in group AA was significantly enhanced compared to AI group after ATRA-treated 24 h (p < 0.05). The protein and mRNA expressions of MMP-2/MMP-9 in group AA were significantly increased than those in group AI at both 12 and 24 h time points (p < 0.05). Compared to group AI, RAR-α and RAR-γ protein/mRNA expressions of group AA were significantly increased at both 12 and 24 h time points (p < 0.05). There was no difference for the expression of RAR-β between group AI and group AA (p > 0.05). RAR-α protein level was positively correlated with MMP-2 or MMP-9 protein expression (p < 0.05), and RAR-γ protein level was also positively correlated with MMP-2 or MMP-9 protein expression (p < 0.05). In conclusion, ATRA may increase expression of MMP-2 and MMP-9 by the potential signal pathway of RAR-α and RAR-γ in injury podocyte induced by adriamycin, but not RAR-β.

Hydrogen-rich saline ameliorates renal injury induced by unilateral ureteral obstruction in rats

Hydrogen has been demonstrated to have effective protection against tissue injuries caused by oxidative stress, inflammation, and apoptosis. This study investigated the efficacy of hydrogen-rich saline (HS) on the prevention of renal injury induced by unilateral ureteric obstruction (UUO) in rats. Male Sprague-Dawley rats were divided randomly into 4 groups: sham group, UUO group, UUO+saline group, and UUO+HS group. UUO was induced by ligation of the left ureter. 5ml/kg HRSS or saline was administered beginning 1day after UUO and for 10days thereafter. Rats were killed at 10days after UUO. Left kidneys were excised immediately for the tissue histologic examinations and biochemical assays. Renal injury scores in the UUO group and the UUO+saline group were significantly higher compared with those in the sham group. However, administration of HS significantly reduced the injury score. Apoptosis index was significantly increased in UUO group and the UUO+saline group. HS treatment also reduced the apoptosis index. Interstitial fibrosis and macrophage infiltration were obvious in UUO kidneys. However, HS treatment significantly reduced the fibrosis and infiltration of macrophage in UUO kidneys. Significant increase in the MDA level and decrease in the SOD activity were observed in UUO group and the UUO+saline group. MDA level of UUO+HS group was significantly reduced. In addition, SOD activity of was significantly improved after treatment of HS. The data provide a biochemical and histologic basis for HS acting as a novel therapeutic strategy for preventing the renal injury induced by UUO.

Association of retinoic acid receptors with extracellular matrix accumulation in rats with renal interstitial fibrosis disease

The nuclear retinoic acid receptors (RARs) function as ligand-dependent transcriptional regulators and include three subtypes (RARα, RARβ and RARγ), which control the expression of specific gene subsets subsequent to ligand binding and to strictly controlled phosphorylation processes. Extracellular matrix (ECM) accumulation is the most important characteristic of renal interstitial fibrosis (RIF). This study was performed to investigate whether RARs were associated with ECM accumulation in the progression of RIF in rats. Eighty Wistar male rats were divided into a sham operation group (SHO) and a model group subjected to unilateral ureteral obstruction (GU) at random; n = 40, respectively. The RIF disease in GU group was established by left ureteral ligation. The renal tissues were collected at two weeks and four weeks after surgery. Protein expressions of RARα, RARβ, RARγ, transforming growth factor-βl (TGF-β1), collagen-IV (Col-IV) and fibronectin (FN) were detected using immunohistochemical analysis, and mRNA expressions of RARα, RARβ, RARγ and TGF-β1 in renal tissue were detected by real time reverse transcription polymerase chain reaction. RIF index in renal interstitium was also calculated. When compared with those in SHO group, expressions of RARα and RARβ (protein and mRNA) were markedly reduced in the GU group (each p < 0.01). There was no marked difference for the expression of RARγ (protein and mRNA) between the SHO group and the GU group. The expressions of TGF-β1, Col-IV, FN and the RIF index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of RARα/RARβ was negatively correlated with protein expression of TGF-β1, Col-IV or FN and the RIF index (all p < 0.01). In conclusion, the low expression of RARα/RARβ is associated with ECM accumulation in the progression of RIF in rats, suggesting that RARα/RARβ is a potentially therapeutic target for prevention of RIF.

Less expression of prohibitin is associated with increased paired box 2 (PAX2) in renal interstitial fibrosis rats

Prohibitin (PHB) and paired box 2 (PAX2) are associated with the development of renal interstitial fibrosis (RIF). This study was performed to investigate whether or not the PHB could regulate the PAX2 gene expression in unilateral ureteral obstruction (UUO) in rats. Eighty Wistar male rats were randomly divided into two groups: sham operation group (SHO) and model group subjected to unilateral ureteral obstruction (GU), n = 40, respectively. The model was established by left ureteral ligation. Renal tissues were collected at 14-day and 28-day after surgery. RIF index, protein expression of PHB, PAX2, transforming growth factor-βl (TGF-β1), α-smooth muscle actin (α-SMA), collagen-IV (Col-IV), fibronectin (FN) or cleaved Caspase-3, and cell apoptosis index in renal interstitium, and mRNA expressions of PHB, PAX2 and TGF-β1 in renal tissue were detected. When compared with those in SHO group, expression of PHB (mRNA and protein) was significantly reduced, and expressions of PAX2 and TGF-β1 (protein and mRNA) were markedly increased in the GU group (each p < 0.01). Protein expressions of α-SMA, Col-IV, FN and cleaved Caspase-3, and RIF index or cell apoptosis index in the GU group were markedly increased when compared with those in the SHO group (each p < 0.01). The protein expression of PHB was negatively correlated with protein expression of PAX2, TGF-β1, α-SMA, Col-IV, FN or cleaved Caspase-3, and RIF index or cell apoptosis index (all p < 0.01). In conclusion, less expression of PHB is associated with increased PAX2 gene expression and RIF index in UUO rats, suggesting that increasing the PHB expression is a potential therapeutic target for prevention of RIF.

All-trans retinoic acid treatment is associated with prohibitin expression in renal interstitial fibrosis rats

This study was performed to investigate the association of prohibitin with renal interstitial fibrosis (RIF) lesion and to explore the association of all-trans retinoic acid (ATRA) treatment with prohibitin expression in RIF rats. Rats were divided into three groups: the sham operation group (SHO), the model group subjected to unilateral ureteral obstruction (UUO), and the model group treated with ATRA (GA). Renal tissues were collected at 14 and 28 days after surgery, and the relevant indicators were detected. In comparison with the SHO group, the RIF index in the UUO group was markedly elevated (p < 0.01), and the RIF index in the GA group was alleviated compared with that in the UUO group (p < 0.01). Compared with the SHO group, the expression of prohibitin (protein or mRNA) in the UUO group was significantly reduced (each p < 0.01). Prohibitin expression in the GA group was markedly increased when compared with that in the UUO (p < 0.01). The expression of TGF-β1 (protein and mRNA), protein expressions of Col-IV, fibronectin, α-SMA and cleaved Caspase-3, ROS generation and cell apoptosis index in the UUO group were markedly higher than those in the SHO group (all p < 0.01), and their expressions in the GA group were markedly down-regulated compared to those in the UUO group (all p < 0.01, respectively). The protein expression of prohibitin was negatively correlated with the RIF index, protein expression of TGF-β1, Col-IV, fibronectin, α-SMA or cleaved Caspase-3, ROS generation and the cell apoptosis index (each p < 0.01). In conclusion, lower expression of prohibitin is associated with the RIF, and ATRA treatment is associated with increased prohibitin, which can prevent the progression of RIF.