Abstract
Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis- Menten constant (K(m)) and a reduction in maximum uptake (V(max)) (50, 33, and 16.6 fmol/μg protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.
| Original language | English |
|---|---|
| Pages (from-to) | 464-470 |
| Number of pages | 7 |
| Journal | Hepatology |
| Volume | 29 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 1999 |
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ASJC Scopus subject areas
- Hepatology
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Nitric oxide reduces nontransferrin-bound iron transport in HepG2 cells. / Barisani, Donatella; Cairo, Gaetano; Ginelli, Enrico; Marozzi, Anna; Conte, Dario.
In: Hepatology, Vol. 29, No. 2, 1999, p. 464-470.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Nitric oxide reduces nontransferrin-bound iron transport in HepG2 cells
AU - Barisani, Donatella
AU - Cairo, Gaetano
AU - Ginelli, Enrico
AU - Marozzi, Anna
AU - Conte, Dario
PY - 1999
Y1 - 1999
N2 - Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis- Menten constant (K(m)) and a reduction in maximum uptake (V(max)) (50, 33, and 16.6 fmol/μg protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.
AB - Nitric oxide (NO) donors S-nitroso-N-acetylpenicillamine (SNAP) and sodium nitroprusside (SNP) modulate iron regulatory protein (IRP) activity and may, therefore, affect iron uptake through transferrin receptor expression. However, iron also enters the cell as nontransferrin-bound iron (NTBI), and the aim of this study was to evaluate the effects of NO donors on NTBI transport in HepG2 cells, a model of liver physiology. Incubation with SNP and SNAP led to a time- and concentration-dependent reduction in Fe3+ and Fe2+ uptake, thus indicating an effect on the transporter rather than on the reductase. In terms of Fe2+ uptake, no variations in the Michaelis- Menten constant (K(m)) and a reduction in maximum uptake (V(max)) (50, 33, and 16.6 fmol/μg protein/min in control, SNP-, and SNAP-treated cells, respectively) were detected, which suggested a decrease in the number of putative NTBI transport protein(s). Gel shift assays showed that IRP activity was reduced by SNP and slightly increased by SNAP. Northern blot analysis of transferrin receptor messenger RNA (mRNA) levels showed variations similar to those observed for IRPs, but both NO donors increased L-ferritin mRNA levels and had no effect on the stimulator of Fe transport (SFT) mRNA. In conclusion, NO donors significantly reduce NTBI transport in HepG2 cells, an effect that seems to be IRP and SFT independent. Moreover, the reduction in NTBI uptake after NO treatment suggests that this form of iron may play a minor role in the increased hepatic iron stores observed in inflammation or that other liver cells are more involved in this pathological condition.
UR - http://www.scopus.com/inward/record.url?scp=0033024496&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033024496&partnerID=8YFLogxK
U2 - 10.1002/hep.510290205
DO - 10.1002/hep.510290205
M3 - Article
C2 - 9918923
AN - SCOPUS:0033024496
VL - 29
SP - 464
EP - 470
JO - Hepatology
JF - Hepatology
SN - 0270-9139
IS - 2
ER -