The association between activation of the ERK1/2-NF-κB signaling pathway by TIMP2 expression and chronic renal allograft dysfunction in the CRAD rat model

PURPOSE

The tissue inhibitor of metalloproteinase 2 (TIMP2), a natural inhibitor of matrix metalloproteinase (MMP), regulates inflammation, fibrosis, and cell proliferation. Chronic renal allograft dysfunction (CRAD) is a primary factor affecting the long-term survival of renal allografts. We assessed whether up-regulation of TIMP2 expression may affect the ERK1/2-NF-κB signaling pathway and CRAD development.

METHODS

Lewis rats received orthotopic F344 kidney allografts to establish the classical CRAD model. The treatment group was injected with a lentivirus encoding a TIMP2-targeting small hairpin (sh)RNA (LTS) at 5 × 108 TU/ml monthly after kidney transplantation. A second CRAD group was injected with a lentivirus TIMP2-control vector (LTC). After 12 weeks, blood, urine, and kidney tissue were harvested to evaluate renal function and pathological examinations. Hematoxylin and eosin staining, Masson staining, and Periodic acid-Schiff staining were performed for renal histopathological evaluation according to the Banff criteria. TIMP2, phospho (p)-ERK1/2, p-p65 (NF-κB) expression levels were measured via immunohistochemical and Western blot analyses.

RESULTS

Compared to the F344 and Lewis control groups, the expression of TIMP2, p-ERK1/2, and p-p65 were significantly higher in the CRAD and CRAD+LTC renal tissues (p < 0.05). There were also increased levels of serum creatinine, nitrogen, and 24 h urinary protein in these two groups (p < 0.05). Typical histopathological changes of CRAD were observed in the CRAD and CRAD+LTC groups. Administration of LTS effectively decreased the expression of TIMP2, p-ERK1/2, and p-P65, and reduced interstitial fibrosis and macrophage infiltration in the treatment group (p < 0.05). Additionally, MCP1 and ICAM-1, which are downstream cytokines of the NF-κB pathway, were also inhibited in the renal rat kidney from the LTS group (p < 0.05). Furthermore, renal function was well preserved in the LTS group compared to the CRAD group and CRAD+LTC group.

CONCLUSION

A decrease of TIMP2 can alleviate the progression of inflammation in CRAD via inhibition of the ERK1/2-NF-κB signaling pathway.

Renoprotective effects of pirfenidone on chronic renal allograft dysfunction by reducing renal interstitial fibrosis in a rat model

AIM

Pirfenidone (PFD) has been used as medication for idiopathic pulmonary fibrosis due to its ability in reducing lung fibrosis. However, the underlying mode of action in renal fibrosis during chronic renal allograft dysfunction (CRAD) requires further investigation. Therefore, the present study was conducted to explore the effects of PFD on renal injury induced by CRAD.

MAIN METHODS

Initially, the CRAD rat model was established, followed by the intragastric administration of PFD to the rats. Urine and blood samples were collected and tested against indicators of renal functions. The renal tissues were microscopically observed to determine the changes in pathological morphology. The anti-inflammatory, anti-fibrotic and anti-oxidant properties of PFD were explored in the setting of CRAD.

KEY FINDINGS

The success rate of model establishment was 92.31%, which was reflected by weight loss, appetite loss, faded fur, and retarded reaction, with the symptoms found to exacerbate with time. PFD treatment could improve renal function, ameliorate inflammation and renal fibrosis as well as promote the anti-oxidant ability of renal allograft, indicating its potential role as an effective therapeutic agent for CRAD.

SIGNIFICANCE

In conclusion, PFD was found to have renoprotective effects on renal injury induced by CRAD, which resulted in the alleviation of inflammation and renal fibrosis, providing novelty for CRAD clinical treatment.

Increased circulating Tfh to Tfr ratio in chronic renal allograft dysfunction: a pilot study

BACKGROUND

T follicular helper (Tfh) cells play a control role in contribution of B cell differentiation and antibody production. T follicular regulatory (Tfr) cells inhibit Tfh-B cell interaction.

METHODS

To identify whether circulating Tfh (cTfh) and Tfr (cTfr) cells contribute to chronic renal allograft dysfunction (CAD), 67 kidney transplant recipients (34 recipients with CAD, 33 recipients with stable function) were enrolled. The frequency of cTfh and cTfr cells, the level of serum CXCL13 were measured.

RESULTS

The frequency of cTfr cells in CAD group was significantly lower than that in stable group (0.31% vs 0.68%, P = 0.002). The cTfh to cTfr ratio in CAD group was significantly higher than that in stable group (55.4 vs 25.3, P = 0.013). Serum CXCL13 in CAD group was significantly higher than stable group (30.4 vs 21.9 ng/ml, P = 0.025). After linear regression analysis, the cTfh to cTfr ratio was an independent risk factor for estimated glomerular filtration rate (eGFR) in recipients (standardized coefficient = - 0.420, P = 0.012). After logistic regression analysis, the cTfh to cTfr ratio was an independent risk factor for CAD (OR = 1.043, 95%CI = 1.004-1.085, P = 0.031).

CONCLUSION

The imbalance between cTfh and cTfr cells contribute to the development of CAD.

Protective effect of rosiglitazone on chronic renal allograft dysfunction in rats

BACKGROUND

Chronic renal allograft dysfunction (CRAD) is the main condition affecting the long-term survival of renal allografts. Rosiglitazone, which is a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, has been shown to exert antifibrotic and anti-inflammatory effects on some renal diseases. The present paper investigates the effect of rosiglitazone on CRAD using a murine model.

METHODS

The CRAD group received classical orthotopic F344-Lewis kidney transplantation. The treatment group was treated with rosiglitazone for 12 weeks following renal transplantation. The control subjects were uninephrectomized F344 and Lewis rats. Twelve weeks after the operation, the rats were harvested for renal function, histological, immunohistochemical and molecular biological analyses.

RESULTS

Rosiglitazone treatment effectively decreased urine protein excretion and preserved renal function in the CRAD rats. Administration of rosiglitazone also inhibited interstitial fibrosis and macrophage infiltration in the CRAD rat kidneys. Furthermore, rosiglitazone treatment inhibited TGF-β and NF-κB pathway activation, decreased collagen I, collagen IV, α-SMA, MCP-1, ICAM-1, TNF-α, and IL-1β expression, and increased E-cadherin expression in renal allograft tissues from the CRAD rats.

CONCLUSIONS

Rosiglitazone successfully attenuates the development of CRAD via inhibition of TGF-β signaling, the renal tubular epithelial-to-mesenchymal transition (EMT), and inflammation.