Radio frequency magnetic field effects on molecular dynamics and iron uptake in cage proteins.

The protein ferritin has a natural ferrihydrite nanoparticle that is superparamagnetic at room temperature. For native horse spleen ferritin, we measure the low field magnetic susceptibility of the nanoparticle as 2.2 x 10(-6) m(3) kg(-1) and its Néel relaxation time at about 10(-10) s. Superparamagnetic nanoparticles increase their internal energy when exposed to radio frequency magnetic fields due to the lag between magnetization and applied field. The energy is dissipated to the surrounding peptidic cage, altering the molecular dynamics and functioning of the protein. This leads to an increased population of low energy vibrational states under a magnetic field of 30 microT at 1 MHz, as measured via Raman spectroscopy. After 2 h of exposure, the proteins have a reduced iron intake rate of about 20%. Our results open a new path for the study of non-thermal bioeffects of radio frequency magnetic fields at the molecular scale.

Influence of glucose and inflammatory cytokines on TGF-beta1 and CTGF mRNA expressions in human peritoneal mesothelial cells.

Peritoneal fibrosis is a major complication of long-term continuous ambulatory peritoneal dialysis (CAPD) treatment. Transforming growth factor-beta (TGF-beta) has been reported to play an important role in the fibrosis of various tissues by stimulating connective tissue growth factor (CTGF) expression. In order to elucidate the mechanism of CAPD-related peritoneal fibrosis, we studied the influence of high glucose concentrations and inflammatory cytokines on mRNA expressions of TGF-beta and CTGF in cultured human peritoneal mesothelial cells (HPMC). HPMC were isolated from normal omentum and cultured with 0.5 or 1.0% glucose or mannitol for 7 days. TGF-beta1 and CTGF mRNA were quantified by one step real-time reverse transcription-polymerase chain reaction (real-time RT-PCR). TGF-beta1 and CTGF mRNA expression levels were significantly increased (p<0.05) by glucose in a dose-dependent manner, but not by mannitol. The expression levels were correlated between TGF-beta1 and CTGF. Effects of inflammatory cytokines were also examined by adding tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1) or interleukin-6 (IL-6) to the medium at 0.1 ng/ml for 2 days. TGF-beta1 expression tended to be increased by TNF-alpha and IL-6. On the other hand, CTGF expression was significantly decreased (p<0.01) by IL-1 but not changed by TNF-alpha or IL-6. These results suggest that high glucose concentration may play a central role in peritoneal fibrosis. Responses of TGF-beta1 and CTGF to inflammatory cytokines were not necessarily identical, suggesting that CTGF may be a better therapeutic target for peritoneal fibrosis than TGF-beta1.

Decreased sulfotransferase SULT1C2 gene expression in DPT-induced polycystic kidney.

BACKGROUND: The pathogenesis of polycystic kidney disease (PKD) remains unclear despite the identification of the genes responsible for hereditary PKD. In this study, we investigated the alteration of gene expressions in an acquired PKD model induced by 2-amino-4,5-diphenylthiazole (DPT) using the differential display method. METHODS: Kidney mRNA from a Sprague-Dawley rat fed with 1% DPT for 4 days and from a control rat was compared by the RT-PCR differential display method. Differentially expressed bands were re-amplified and subcloned. Using these subclones as probes, the changes in gene expressions were confirmed by Northern blot analysis. Subsequently, mouse kidney cDNA library was screened. RESULTS: The isolated 1.5-kb cDNA contained an open reading frame encoding 296 amino acids, which shared 94.3% identity with rat SULT1C2 sulfotransferase, and was considered to be its mouse ortholog (GenBank Accession No. AY005469). Mouse SULT1C2 mRNA was abundant in the kidney and stomach among normal mouse tissues. The expression of SULT1C2 mRNA was decreased in the rat kidney after DPT feeding but not in the stomach. Mouse SULT1C2 was expressed successfully using pET plasmid vector and E. coli. The recombinant 34-kD protein was capable of catalyzing the sulfation of p-nitrophenol at a Km of 3.1 mmol/L, by utilizing 3'-phosphoadenosine 5'-phosphosulfate (PAPS) as the sulfate donor. CONCLUSIONS: Although the physiological substrate and function of SULT1C2 have yet to be elucidated, its down-regulation could be involved in the cystic changes of tubules by decreasing the sulfation of the tubular basement membrane components.