[Show abstract][Hide abstract] ABSTRACT: Epithelial-mesenchymal transition (EMT) is an underlying mechanism of tissue fibrosis, generating myofibroblasts, which serve as the primary source of extracellular matrix production from tissue epithelial cells. Recently, EMT has been implicated in immunosuppressive cyclosporin A (CsA)-induced renal fibrosis. In this study, the potential role of NRF2, which is the master regulator of genes associated with the cellular antioxidant defense system, in CsA-induced EMT renal fibrosis has been investigated. Pretreatment of rat tubular epithelial NRK-52E cells with sulforaphane, an activator of NRF2, could prevent EMT gene changes such as the loss of E-cadherin and the increase in alpha-smooth muscle actin (alpha-SMA) expression. Conversely, genetic inhibition of NRF2 in these cells aggravated changes in CsA-induced EMT markers. These in vitro observations could be confirmed in vivo: CsA treatment resulted in severe renal damage and fibrosis with increased expression of alpha-SMA in NRF2-deficient mice compared to wild-type mice. NRF2-mediated amelioration of CsA-caused EMT changes could be accounted for in part by the regulation of heme oxygenase-1 (HO-1). CsA treatment increased HO-1 expression in an NRF2-dependent manner in NRK cells as well as in murine fibroblasts. Induction of HO-1 by CsA seems to be advantageous in that it counteracts EMT gene changes: specific increase in HO-1 expression caused by cobalt protoporphyrin prevented CsA-mediated alpha-SMA induction, whereas genetic inhibition of HO-1 by siRNA substantially enhanced alpha-SMA induction compared to control cells. Collectively, our results suggest that the NRF2-HO-1 system plays a protective role against CsA-induced renal fibrosis by modulating EMT gene changes.
Preview · Article · Apr 2010 · Free Radical Biology and Medicine
[Show abstract][Hide abstract] ABSTRACT: The 26S proteasome plays a major role in degradation of abnormal proteins within the cell. The indirect antioxidant including sulforaphane (SFN) protects cells from oxidative damage by increasing the expression of Nrf2-target genes. It has been observed that the expression of multiple subunits of the proteasome was up-regulated by indirect antioxidants through the Nrf2 pathway. In the current study, the role of SFN in amyloid beta(1-42) (Abeta(1-42))-induced cytotoxicity has been investigated in murine neuroblastoma cells. Treatment with SFN protected cells from Abeta(1-42)-mediated cell death in Neuro2A and N1E 115 cells. Inhibition of proteasome activities by MG132 could abolish the protective effect of SFN against Abeta(1-42). Neuro2A cells, which were stably overexpressing the catalytic subunit of the proteasome PSMB5, showed an elevated resistance toward Abeta(1-42) toxicity compared to control cells. Furthermore, the in vitro assay demonstrated that the Abeta(1-42) peptide is degraded by the proteasome fraction. These results suggest that proteasome-inducing indirect antioxidants may facilitate the removal of the Abeta(1-42) peptide and lead to the amelioration of abnormal protein-associated etiologies.
No preview · Article · Feb 2009 · Archives of Pharmacal Research
[Show abstract][Hide abstract] ABSTRACT: Cisplatin is commonly used for the treatment of several solid tumors. However, its clinical use is often limited by renal toxicity. The indirect antioxidant 3H-1,2-dithiole-3-thione (D3T) has been known to protect cells from oxidative damage by up-regulating the expression of antioxidative genes through the transcription factor NF-E2-related factor 2 (Nrf2) pathway. We hypothesized that D3T treatment may be protective against cisplatin-induced nephrotoxicity by enhancing the antioxidative capacity of renal cells. In cultured murine tubular epithelial cells, D3T facilitates the nuclear accumulation of Nrf2 and the subsequent expression of its target genes such as glutamate cysteine ligase (GCL). Increased GSH pool in D3T-treated renal cells appears to be associated with amelioration of cisplatin-mediated cell death. Protective effects of D3T were also observed in mice. Oral administration of D3T (0.25mmol/kg) increased the expression of GCL in mouse kidney, which resulted in suppression of cisplatin-mediated increases in blood urea nitrogen and serum creatinine. Histopathological changes representing cisplatin-induced acute renal failure were also effectively ameliorated by D3T treatment. Collectively, these results indicate that pharmacological activation of the Nrf2 pathway might have a beneficial effect on reducing chemotherapy-associated cytotoxic adverse effects.
No preview · Article · Sep 2008 · Biochemical pharmacology
[Show abstract][Hide abstract] ABSTRACT: The treatment of alkylating cytotoxic drug cisplatin is often limited by high incidence rate of resistance. In the present study, the potential involvement of the transcription factor Nrf2 in determination of cisplatin cytotoxicity has been investigated. Nrf2-deficient murine embryonic fibroblasts showed increased cell death, cytotoxicity, and apoptosis in response to cisplatin treatment compared to wild-type cells. Cisplatin-resistant human ovarian cancer SK-OV cells, which are retaining 25-fold higher levels of GSH than murine fibroblasts, could be sensitized by inhibition of Nrf2. Transfection with Nrf2 siRNA into SK-OV cells resulted in severe degree of GSH depletion and exacerbated cytotoxicity following cisplatin treatment compared to scrambled RNA control. In conclusion, we propose that the Nrf2 pathway, which plays a protective role in normal cells, can be a potential target to control cancer cell resistance to oxidants, cytotoxic chemicals, and radiation.