Publications by authors named "Kishor Raja"

14 Publications

  • Page 1 of 1

Gadolinium Concentrations in Biological Matrices From Patients Exposed to Gadolinium-Based Contrast Agents.

Invest Radiol 2021 Jul;56(7):458-464

Viapath Analytics, King's College Hospital NHS Foundation Trust.

Objectives: There is increasing evidence that Gd may be retained within the skin, bones, and solid organs in patients with normal renal function after exposure to Gd-based contrast agents (GBCAs). Here we present clinical data from 19 patients who requested referral to our clinical toxicology service for assessment of potential "Gd toxicity."

Materials And Methods: Patients had undergone a median of 2 (interquartile range [IQR], 1-5) exposures to GBCAs and were reviewed at a median of 5 months (IQR, 2-8 months) after the last GBCA exposure. Patients had a clinical assessment by a clinical toxicologist, and biological samples were taken in 17 patients (89.5%). Gd concentrations were measured in these samples using inductively coupled plasma mass spectrometry.

Results: All patients had significant comorbidities, and after an extensive clinical review, none of the reported symptoms were considered likely to be related to "Gd toxicity." Whole blood, plasma, and urine samples had detectable Gd concentrations in 69.2%, 78.6%, and 95.2% of samples, respectively. Median (IQR) concentrations of Gd were as follows: whole blood, 0.013 ng/mL (IQR, limit of detection [LOD]-0.884 ng/mL); plasma, 0.012 ng/mL (IQR, LOD-0.046 ng/mL); and spot urine, 0.304 μg/g creatinine (IQR, 0.070-3.702 μg/g creatinine). There were positive correlations between whole blood and plasma (P = 0.0024, r = 0.84), whole blood and urine (P = 0.0018, r = 0.82), and plasma and urine (P = 0.0001, r = 0.89) Gd concentrations. There was a negative correlation between Gd concentrations and the period after exposure for whole blood (P = 0.0028, r = -0.80), plasma (P = 0.0004, r = -0.86), and urine (P < 0.0001, r = -0.91).

Conclusions: We identified detectable Gd concentrations in biological matrices from all patients reporting exposure to GBCAs who were reviewed in our clinical toxicology outpatient clinic with concerns regarding potential "Gd toxicity"; however, there were no clinical features of toxicity present in this cohort. Further research is required to explore the pharmacokinetics and pharmacodynamics of GBCAs in patients with normal renal function and to determine the clinical significance of these detectable Gd concentrations.
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http://dx.doi.org/10.1097/RLI.0000000000000762DOI Listing
July 2021

Establishing Reference Intervals for Gadolinium Concentrations in Blood, Plasma, and Urine in Individuals Not Previously Exposed to Gadolinium-Based Contrast Agents.

Invest Radiol 2020 07;55(7):405-411

Viapath Analytics, King's College Hospital NHS Foundation Trust, London, United Kingdom.

Objectives: Over the recent years, there have been increasing concerns that exposure to gadolinium-based contrast agents (GBCAs) may be associated with retention of Gd within the skin, bones, and solid organs in patients with normal renal function, although the clinical implications of this deposition remain to be established. There are no published data available to guide the development of reference intervals for Gd concentrations in biological samples from healthy people. The aims of this study were to (1) determine whether healthy individuals who have not received GBCAs have detectable concentrations of Gd in their blood and urine, and (2) to develop a reference range for Gd concentrations in blood and spot urine samples for healthy individuals.

Materials And Methods: Whole blood, plasma, and spot urine samples were taken from 120 healthy volunteers with estimated glomerular filtration rate 70 mL/min per 1.73 m or greater. Gd concentrations were measured in these samples using inductively coupled plasma mass-spectrometry. The reference intervals for Gd concentrations in whole blood, plasma, and urine were estimated as the 2.5th percentile and the upper reference limit as the 97.5th percentile.

Results: Ten (8.33%) of the 120 subjects had detectable concentrations of Gd in their whole blood (n = 5) or spot urine (n = 5) samples; no subjects had detectable concentrations of Gd in their plasma samples. Our proposed reference intervals for Gd are as follows: whole blood, <0.008 ng/mL or <0.050 nmol/L; plasma, <0.009 ng/mL or <0.057 nmol/L; spot urine, <0.036 μg/g or <0.0250 nmol/mmol.

Conclusions: The results of this study provide reference intervals for whole blood, plasma, and urine Gd concentrations in healthy subjects who have not previously received GBCAs and will assist clinicians in assessing patients who have concerns regarding potential Gd retention postexposure and help guide further clinical studies to explore the pharmacokinetics of GBCAs in patients with normal renal function.
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http://dx.doi.org/10.1097/RLI.0000000000000657DOI Listing
July 2020

Clinical relevance of trace element measurement in patients on initiation of parenteral nutrition.

Ann Clin Biochem 2016 Nov 28;53(6):680-685. Epub 2016 Sep 28.

2 Department of Clinical Biochemistry, King's College Hospital NHS Foundation Trust, Denmark Hill, London, UK.

Background and Aims Serum zinc, copper and selenium are measured in patients prior to commencing on parenteral nutrition; however, their interpretation can be difficult due to acute phase reactions. We assessed (i) the relationship of raised C-reactive protein with trace elements and albumin (ii) benefits of measuring trace elements when C-reactive protein is raised in patients requiring short-term parenteral nutrition. Methods Samples were collected for zinc, copper, selenium and albumin at baseline and then every two weeks and correlated with C-reactive protein results in patients on parenteral nutrition. Results were categorized into four groups based on the C-reactive protein concentrations: (i) <20 mg/L, (ii) 20-39 mg/L, (iii) 40-79 mg/L and (iv) ≥80 mg/L. Results In 166 patients, zinc, selenium and albumin correlated (Spearman's) negatively with C-reactive protein; r = -0.26, P < 0.001 (95% CI -0.40 to -0.11), r = -0.44, P < 0.001 (-0.56 to -0.29) and r = -0.22 P = 0.005 (-0.36 to -0.07), respectively. Copper did not correlate with C-reactive protein (r = 0.09, P = 0.25 [-0.07 to 0.25]). Comparison of trace elements between the four groups showed no difference in zinc and copper (both P > 0.05), whereas selenium and albumin were lower in the group with C-reactive protein > 40 mg/L ( P < 0.05). Conclusion In patients on short-term parenteral nutrition, measurement of C-reactive protein is essential when interpreting zinc and selenium but not copper results. Routine measurement of trace elements prior to commencing parenteral nutrition has to be considered on an individual basis in patients with inflammation.
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http://dx.doi.org/10.1177/0004563216633489DOI Listing
November 2016

A healthy volunteer study to investigate trace element contamination of blood samples by stainless steel venepuncture needles.

Clin Toxicol (Phila) 2012 Feb;50(2):99-107

King's College London, UK.

Context: The trace elements cobalt (Co), chromium (Cr), manganese (Mn) and nickel (Ni) are normally present at low concentrations in blood. There has been a concern that stainless steel venepuncture needles typically used for collection of blood samples may contaminate these samples, leading to the masking of deficiency states or causing potential clinical confusion as to whether an individual has a "toxic" concentration.

Objective: To determine whether there is any difference between the concentrations of the trace elements obtained by different methods of blood sampling.

Methods: We took blood samples using a standard venepuncture needle, a "butterfly" winged infusion needle (three consecutive samples) and a plastic intravenous cannula (three consecutive samples) from 10 healthy volunteers. We measured the concentrations of Co, Cr, Mn and Ni in the samples using Inductively Coupled Plasma Mass Spectrometry, and used analysis of variance (ANOVA) to investigate if there was any difference between the methods of blood sampling.

Results: The mean ± standard deviation blood metal concentrations were: Co 0.33 ± 0.2 μg/l, Cr 2.43 ± 1.55 μg/l, Mn 8.07 ± 7.74 μg/l and Ni 10.4 ± 4.69 μg/l. There was considerable variation between blood metal concentrations of individual subjects and a few sporadic high values. By ANOVA, there was no significant difference between the metal concentrations measured using different methods of blood collection.

Conclusions: It is not necessary to routinely use a plastic cannula for blood sampling for trace element analysis. However, it is possible that sporadic contamination due to stainless steel needles may occur, so we would recommend that unexpected high concentrations are verified by taking a second sample taken through a plastic cannula.
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http://dx.doi.org/10.3109/15563650.2011.654146DOI Listing
February 2012

Fetal iron levels are regulated by maternal and fetal Hfe genotype and dietary iron.

Haematologica 2012 May 16;97(5):661-9. Epub 2011 Dec 16.

Department of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK.

Background: Iron metabolism during pregnancy maintains fetal iron levels at the expense of the mother. The mechanism behind this regulation is still not clear despite recent advances. Here we examine the role of maternal and fetal Hfe, its downstream signaling molecule, hepcidin and dietary iron in the regulation of placental iron transfer.

Design And Methods: Hfe wild-type, knockout and heterozygote dams were fed iron deficient (12.5 ppm), adequate (50 ppm) and replete (150 ppm) iron diets and mated with heterozygote males to produce pups of all genotypes. Dams and pups were sacrificed at Day 18 of gestation; serum, placenta, body and liver iron parameters were measured. Protein and mRNA levels of various iron transporter genes were determined in duodenum, liver and placenta by Western blotting and real time PCR.

Results: Maternal liver iron levels were dependent on both dietary iron intake and Hfe genotype. Increasing iron levels in the maternal diet resulted in increased total iron in the fetus, primarily in the liver. However, fetuses of Hfe-knockout mothers showed further elevation of liver iron levels, concomitant with elevated expression of Tfr1, Dmt1 and Fpn in the placenta. Hfe-knockout fetuses that express low levels of liver hepcidin accumulated more iron in their liver than wild-type fetuses due to increased ferroportin levels in the placenta.

Conclusions: Maternal and fetal status, as well as dietary iron, is important in regulating iron transfer across placenta. Maternal Hfe regulates iron transfer by altering gene expression in the placenta. Fetal Hfe is important in regulating placental iron transfer by modulating fetal liver hepcidin expression.
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http://dx.doi.org/10.3324/haematol.2011.055046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3342966PMC
May 2012

Use of a clinically approved iron oxide MRI contrast agent to label human hepatocytes.

Cell Transplant 2011 19;20(6):963-75. Epub 2010 Nov 19.

Institute of Liver Studies, King's College London School of Medicine at King's College Hospital, London, UK.

Reliable noninvasive methods are needed to monitor cell engraftment and graft survival after hepatocyte transplantation. Superparamagnetic iron oxide nanoparticles (SPIOs) have been shown to accumulate in various types of cells, and are currently the labeling agent of choice for cellular magnetic resonance imaging (MRI). However, for successful clinical translation to hepatocyte transplantation, it is important that hepatocytes maintain their viability and synthetic function after labeling. In this study, primary human hepatocytes were incubated with increasing concentrations of clinical grade SPIOs for different time intervals. SPIOs uptake was confirmed by light and fluorescence microscopy, and intracellular iron content quantified by a colorimetric ferrozine-based assay. Studies were performed to determine if labeling affected cell viability and function. Intracellular iron concentrations increased in a time- and dose-dependent manner after incubation with SPIOs. Labeling had minimal short-term effects on cell attachment and mitochondrial function. However, exposure of hepatocytes to SPIOs resulted in a dose- and time-dependent reduction in protein synthesis. Cell labeling for 16 h had no significant effect on hepatocyte-specific function, but longer periods of incubation resulted in a dose-dependent decrease in albumin production. Hepatocytes incorporated SPIOs at sufficient levels for in vitro detection on a 7-T MRI imaging system, with a minimum of 2,000 SPIO-labeled cells/μl detected by a decreased T2 relaxivity compared to controls. Intrasplenic transplantation of human hepatocytes labeled with 50 μg Fe/ml of SPIOs was performed in nonobese diabetic/severe combined immune deficiency (NOD-Scid) mice. Recipient livers showed a clear decrease in signal intensity on T2*-weighted MR images when compared to controls, allowing detection of hepatocytes. With further experiments to optimize the conditions for labeling human hepatocytes, it should be possible to apply this technique to track hepatocyte transplantation in patients with liver disease.
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http://dx.doi.org/10.3727/096368910X543367DOI Listing
December 2011

Factitiously elevated blood chromium.

Clin Toxicol (Phila) 2010 May;48(4):388-9

Guy's and St. Thomas' NHS Foundation Trust and King's Health Partners, London, UK.

Context: Chromium toxicity is rare in individuals who do not have a history of occupational or deliberate exposure to chromium or chromium-containing compounds.

Case Report: A 39-year-old female with confirmed bile acid malabsorption had an elevated whole blood chromium concentration of 76.3 nmol/L (normal < 40 nmol/L). There was no history of chromium exposure and no clinical signs of chromium toxicity. Two repeat samples drawn through a butterfly needle, after discarding of an initial blood draw, also revealed an elevated blood chromium concentration (60.1, 122.7 nmol/L). A subsequent sample collected through a plastic intravenous cannula revealed a normal whole blood chromium concentration of 35 nmol/L.

Discussion: The elevated chromium concentrations were likely because of exogenous contamination from chromium within the venepuncture and butterfly needles. An appropriate sampling technique involving plastic cannula should be used when measuring blood chromium concentrations.
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http://dx.doi.org/10.3109/15563651003733674DOI Listing
May 2010

Identification of a Steap3 endosomal targeting motif essential for normal iron metabolism.

Blood 2009 Feb 27;113(8):1805-8. Epub 2008 Oct 27.

Henry Wellcome Building for Molecular Physiology, Oxford University, Oxford, United Kingdom.

Hereditary forms of iron-deficiency anemia, including animal models, have taught us much about the normal physiologic control of iron metabolism. However, the discovery of new informative mutants is limited by the natural mutation frequency. To address this limitation, we have developed a screen for heritable abnormalities of red blood cell morphology in mice with single-nucleotide changes induced by the chemical mutagen ethylnitrosourea (ENU). We now describe the first strain, fragile-red, with hypochromic microcytic anemia resulting from a Y228H substitution in the ferrireductase Steap3 (Steap3(Y288H)). Analysis of the Steap3(Y288H) mutant identifies a conserved motif required for targeting Steap3 to internal compartments and highlights how phenotypic screens linked to mutagenesis can identify new functional variants in erythropoiesis and ascribe function to previously unidentified motifs.
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http://dx.doi.org/10.1182/blood-2007-11-120402DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947353PMC
February 2009

Iron and cadmium uptake by duodenum of hypotransferrinaemic mice.

Biometals 2006 Oct;19(5):547-53

Department of Clinical Biochemistry, King's College London, London, UK.

Absorption from food is an important route for entry of the toxic metal, cadmium, into the body. Both cadmium and iron are believed to be taken up by duodenal enterocytes via the iron regulated, proton-coupled transporter, DMT1. This means that cadmium uptake could be enhanced in conditions where iron absorption is increased. We measured pH dependent uptake of (109)Cd and (59)Fe by duodenum from mice with an in vitro method. Mice with experimental (hypoxia, iron deficiency) or hereditary (hypotransferrinaemia) increased iron absorption were studied. All three groups of mice showed increased (59)Fe uptake (p<0.05) compared to their respective controls. Hypotransferrinaemic and iron deficient mice exhibited an increase in (109)Cd uptake (p<0.05). Cadmium uptake was not, however, increased by lowering the medium pH from 7.4 to 6. In contrast, (59)Fe uptake (from (59)FeNTA(2)) and ferric reductase activity was increased by lowering medium pH in control and iron deficient mice (p<0.05). The data show that duodenal cadmium uptake can be increased by hereditary iron overload conditions. The uptake is not, however, altered by lowering medium pH suggesting that DMT1-independent uptake pathways may operate.
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http://dx.doi.org/10.1007/s10534-005-5919-4DOI Listing
October 2006

Effect of areca nut on salivary copper concentration in chronic chewers.

Biometals 2007 Feb 11;20(1):43-7. Epub 2006 May 11.

Department of Clinical Biochemistry, Guy's, King's and St. Thomas' School of Medicine, Denmark Hill Campus, London, SE5 9RS, UK.

The chewing of areca nut is associated with the development of oral submucous fibrosis (OSF), a condition predominantly encountered in Asians indulging in the habit. The pathogenesis of this condition is however, unclear, though several mechanisms have been proposed. Copper has previously been implicated as a possible aetiological factor. In this study, total copper concentration was measured via atomic absorption spectrophotometry in whole mouth saliva of 15 volunteers who were regular chewers, before and after their habitual chew. An aliquot of the latter was also analysed for copper. Six non-chewing volunteers acted as controls. Salivary copper concentrations were corrected for protein content. Over 50% of the subjects had basal salivary copper concentration higher than the range seen in normal controls. All but two subjects demonstrated an increase in the salivary [Cu] following their habitual chew. Marked changes were seen in those with low basal salivary concentrations. These data indicate that soluble copper found in areca nut is released into the oral environment of habitual chewers. Its buccal absorption may contribute to the oral fibrosis in Asians who regularly chew this nut.
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http://dx.doi.org/10.1007/s10534-006-9013-3DOI Listing
February 2007

Role of interleukin-6 in hypoxic regulation of intestinal iron absorption.

Br J Haematol 2005 Dec;131(5):656-62

Department of Clinical Biochemistry, King's College Hospital, London, UK.

The regulation of intestinal iron absorption is not fully understood. Hepcidin, a liver-produced peptide, has recently been identified as a negative regulator of iron absorption in various conditions associated with altered iron metabolism (e.g. inflammation, anaemia, hypoxia). It is not clear whether these perturbants share a common signalling pathway. In this study, the importance of the cytokine interleukin-6 (IL-6) was investigated in the hypoxic mouse model. Hypoxia was associated with increased levels of circulating IL-6, decreased liver hepcidin mRNA and increased iron absorption (especially MT). A significant positive correlation existed between the total iron uptake and IL-6 levels in circulation. IL-6 per se, though inducing hepcidin mRNA, failed to affect basal iron absorption. The adaptive response to absorption following the hypoxic exposure was, however, more prominent if mice had been treated concurrently with IL-6. This enhancement in absorption occurred even though hepcidin mRNA was not significantly changed. Similar prominent responses were seen with both human and mouse IL-6. Anti-IL-6 antiserum normalised iron absorption in mice exposed to hypoxia, because of a reduction in the MT. These data indicate that IL-6 can influence iron absorption (especially MT) during the hypoxic exposure, but via a mechanism independent of hepcidin.
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http://dx.doi.org/10.1111/j.1365-2141.2005.05814.xDOI Listing
December 2005

The effects of inhibition of haem biosynthesis by griseofulvin on intestinal iron absorption.

Basic Clin Pharmacol Toxicol 2004 Apr;94(4):161-8

Department of Clinical Biochemistry, GKT School of Medicine and Dentistry, Bessemer Rd, London SE5 9PJ, UK.

The relationship between haem biosynthesis and intestinal iron absorption in mice was investigated by ascertaining the effect of the haem synthesis inhibitor, griseofulvin, on duodenal iron absorption using both in vivo and in vitro measurements. Urinary 5-aminolaevulinic acid levels were increased within 24 hr of feeding mice with griseofulvin diet (2.5% w/w), with more marked increases seen after 3-7 days. Urinary porphobilinogen levels also showed a similar trend. In vivo intestinal iron absorption was significantly reduced (P<0.05) in experimental mice, mainly due to reduction in the transfer of 59Fe from the enterocytes to the portal circulation. In vitro studies using isolated duodenal fragments also exhibited marked decreases in both iron uptake and Fe (III) reduction. Changes in mucosal Divalent Metal Transporter 1 (DMT-1), Dcytb and Ireg1 (iron regulated protein 1) mRNA levels paralleled the changes in iron absorption. The reduction in iron absorption after griseofulvin treatment was normalised when mice were simultaneously injected with haem-arginate. These data support the hypothesis that intermediates in haem biosynthesis, particularly 5-aminolaevulinic acid, regulate intestinal iron absorption.
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http://dx.doi.org/10.1111/j.1742-7843.2004.pto940402.xDOI Listing
April 2004

Effect of Tin-mesoporphyrin, an inhibitor of haem catabolism, on intestinal iron absorption.

Br J Haematol 2003 Jul;122(2):298-304

Department of Clinical Biochemistry, GKT School of Medicine and Dentistry Department of Life Sciences, King's College London, London, UK.

Haem biosynthesis is the most important destination for absorbed iron, hence it can be hypothesized that iron absorption regulation should be integrated with haem metabolism. As an initial step to test this hypothesis, the effect on iron absorption of Tin-mesoporphyrin (SnMP), inhibitor of haem oxygenase, altering haem and its biosynthetic intermediates, was studied. Mice injected with SnMP (5-25 micro mol/kg daily for up to 3 d) showed dose-dependent increases in intestinal iron absorption measured in vivo and in vitro. In order to investigate the effects of SnMP, enzymes and intermediates of haem metabolism were measured. Hepatic 5-amino-laevulinate (ALA) synthase activity (pmol/min/mg protein) was significantly reduced in SnMP-treated mice (10 and 25 micro mol/kg daily for 3 d) (mean +/- standard deviation, control 11.2 +/- 2.6; treated 6.3 +/- 1.7; P < 0.01). Hepatic ALA dehydratase activity (pmol porphobilinogen/mg protein/min) showed significant reductions following SnMP treatment (control 180 +/- 60, treated 130 +/- 50; P < 0.05). The effect of SnMP on iron absorption was reversible, with absorption returning to normal after 3 d. Furthermore, the effect of SnMP on duodenal iron absorption was abolished by the simultaneous injection of ALA (6 micro mol/l). ALA alone had no effect on iron absorption. In-vitro studies using duodenal fragments isolated from mice treated with SnMP (10 micro mol/kg daily for 3 d), showed significant increases (P < 0.05) in both mucosal iron uptake and Fe(III) reducing activity. We conclude that intermediates in haem metabolism, in particular levels of ALA, may play a role in duodenal iron absorption.
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http://dx.doi.org/10.1046/j.1365-2141.2003.04376.xDOI Listing
July 2003

Iron absorption: biochemical and molecular insights into the importance of iron species for intestinal uptake.

Pharmacol Toxicol 2002 Sep;91(3):97-102

Italfarmaco Research Center, v. Dei Lavoratori 64 Cinisello B. Milano, Italy.

Recent advances in cloning of proteins involved in intestinal iron absorption can inform design and understanding of therapeutic iron preparations. Redox chemistry of iron is particularly important in iron metabolism, both as a potential source of toxic intermediates and as an essential requirement for efficient iron transport. The initial step in iron absorption (uptake from lumen to mucosa) is particularly important and several pathways involving Fe(III) reduction or transport and Fe(II) transport have been identified. Novel genes associated with iron uptake include Dcytb, a putative iron-regulated reductase and DMT1, a Fe(II) carrier in the brush border membrane. Other mechanisms may also operate, however. We review the recent findings and apply this to understanding the absorption of Fe(III) pharmaceuticals.
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http://dx.doi.org/10.1034/j.1600-0773.2002.910301.xDOI Listing
September 2002
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