Expression of the Integrin-Linked Kinase in a Rat Kidney Model of Chronic Allograft Nephropathy

Decreased expression of sirtuin 3 protein correlates with early stage chronic renal allograft dysfunction in a rat kidney model

Chronic renal allograft dysfunction (CRAD) is the primary factor affecting the long-term survival of patients who have undergone renal transplantation. Oxidative stress and inflammation serve an important role in the pathological damage caused by CRAD in the early post-transplantation phase. Previous studies have demonstrated that sirtuin 3 (sirt3) protects cells from oxidative stress and inflammation. A model of renal orthotopic transplantation was established in the current study and kidney samples were harvested from the rats 12 weeks following surgery. Compared with the control groups, there were significantly increased levels of serum creatinine, blood urea nitrogen and 24 h urinary protein in the allograft group (P<0.05). Pathological examinations indicated mononuclear cell infiltration and intimal proliferation in the allograft group, which had a higher Banff score compared with the control groups. There were increased levels of malondialdehyde, decreased sirt3 protein expression and decreased superoxide dismutase enzyme activity in the allograft group compared with the control groups (P<0.05). In addition, there was a negative correlation between the expression of sirt3 and 24 h urinary protein excretion, serum creatinine levels, tubulointerstitial mononuclear cell infiltration, smooth muscle cell migration in the vascular wall and Banff scores. Thus, sirt3 may serve an important protective role in the early stage of CRAD.

Correlation between PKB/Akt, GSK-3β expression and tubular epithelial-mesenchymal transition in renal allografts with chronic active antibody-mediated rejection

Chronic antibody-mediated rejection (ABMR) is a major cause of the transplant renal interstitial fibrosis and transplanted kidney epithelial cell transdifferentiation is one of the main mechanisms. The transforming growth factor (TGF)-β1/integrin-linked kinase (ILK) signaling pathway has a significant role in the epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells; however, the molecular mechanisms of this process have remained elusive. The present study confirmed that Akt and glycogen synthase kinase (GSK)-3β, as TGF-β1 downstream signaling factors, are involved in fibrotic processes caused by kidney disease, which, however, has been rarely reported in the kidney transplant field. Based on the Banff 2009 standard, transplanted kidney specimens were classified according to the fibrosis level. The results showed that with the reduction of the interstitial fibrosis level, E-cadherin expression was gradually reduced, while α-smooth muscle actin expression progressively increased. The expression of Akt and GSK-3β in normal human kidney tissue was not obvious but showed a marked increase with the aggravation of the interstitial fibrosis level, which confirmed the occurrence of EMT during the fibrosis process, and that phosphorylated (p)-Akt and GSK-3β have an important role in the EMT process in the transplanted kidney. A correlation analysis of p-Akt, GSK-3β, TGF-β1 and ILK suggested that overexpression of p-Akt and GSK-3β may induce and mediate the transdifferentiation of renal tubular epithelial cells to myofibroblasts and that this proceeds via TGFβ1/ILK signaling pathways.

Advanced glycation end products accelerate arteriosclerosis after renal transplantation through the AGE/RAGE/ILK pathway

BACKGROUND

The effects of advanced glycation end products (AGEs) on arteriosclerosis (AS) after kidney transplantation and the molecular mechanisms involved remain unclear.

METHODS

Samples were collected from 30 healthy volunteers and 30 renal transplant recipients (RTRs) to determine the levels of AGEs and to observe both histological changes and α-smooth muscle actin (α-SMA) and osteopontin (OPN) expression. Furthermore, we analyzed α-SMA, OPN and integrin-linked kinase (ILK) in rat vascular smooth muscle cells (VSMCs) that were treated with AGEs and in ILK plasmid transfected rat VSMCs treated with AGEs. Finally, we measured the expression of ILK and the receptor for advanced glycation end (RAGE) products in rat VSMCs treated with AGEs and an anti-RAGE antibody.

RESULTS

Significant differences in the histological changes, serum AGEs, and expression of α-SMA and OPN in arterial walls were noted between healthy volunteers and RTRs. Significant OPN and ILK overexpression and reduced α-SMA expression were detected in a time-dependent manner in rat VSMCs after treatment with AGEs. Similar outcomes were observed regarding the overexpression of ILK, and these results could be prevented via RAGE inhibition.

CONCLUSIONS

AGEs may play a critical role in the formation and progression of AS after renal transplantation by inducing VSMCs-to-osteoblast trans-differentiation through the AGE/RAGE/ILK pathway.