Ascorbic acid ameliorates renal injury in a murine model of contrast-induced nephropathy.
Contrast induced nephropathy (CIN) is the commonest cause of iatrogenic renal injury and its incidence has increased with the advent of complex endovascular procedures. Evidence suggests that ascorbic acid (AA) has a nephroprotective effect in percutaneous coronary interventions when contrast media are used. A variety of biomarkers (NGAL, NGAL:creatinine, mononuclear cell infiltration, apoptosis and RBP-4) in both the urine and kidney were assayed using a mouse model of CIN in order to determine whether AA can reduce the incidence and/or severity of renal injury.



Twenty-four BALB/c mice were divided into 4 groups. Three groups were exposed to high doses of contrast media (omnipaque) in a well-established model of CIN, and then treated with low or high dose AA or placebo (saline). CIN severity was determined by measurement of urinary neutrophil gelatinase-associated lipocalin (NGAL):creatinine at specific time intervals. Histological analysis was performed to determine the level of mononuclear inflammatory infiltration as well as immunohistochemistry to determine apoptosis in the glomeruli by staining for activated caspase-3 and DNA nicking (TUNEL assays). Reverse transcriptase PCR (rtPCR) of mRNA transcripts prepared from mRNA extracted from mouse kidneys was also performed for both lipocalin-2 (Lcn2) encoding NGAL and retinol binding protein-6 (RBP4) genes. NGAL protein expression was also confirmed by ELISA analysis of kidney lysates.



Urinary NGAL:creatinine ratio was significantly lower at 48 h with a 44% and 62% (204.3μg/mmol versus 533.6μg/mmol, p = 0.049) reduction in the low and high dose AA groups, respectively. The reduced urinary NGAL:creatinine ratio remained low throughout the time period assessed (up to 96 h) in the high dose AA group. In support of the urinary analysis ELISA analysis of NGAL in kidney lysates also showed a 57% reduction (12,576 ng/ml versus 29,393 ng/ml) reduction in the low dose AA group. Immunohistochemistry for apoptosis demonstrated decreased TUNEL and caspase-3 expression in both low and high dose AA groups.



Ascorbic acid reduced the frequency and severity of renal injury in this murine model of CIN. Further work is required to establish whether AA can reduce the incidence of CIN in humans undergoing endovascular procedures.
National Institute for Health Research Nottingham Digestive Diseases Biomedical Research Unit, Nottingham University Hospitals NHS Trust, Queen's Medical Centre, Nottingham, UK.
K
K
Rollins
Cambridge Vascular Unit, Addenbrookes Hospital, Cambridge, UK.
A
A
Noorani
Antitope Ltd, Babraham Research Campus, Cambridge, UK.
L
L
Janeckova
Antitope Ltd, Babraham Research Campus, Cambridge, UK.
T
T
Jones
Department of Histopathology, Addenbrookes Hospital, Cambridge, UK.
M
M
Griffiths
Antitope Ltd, Babraham Research Campus, Cambridge, UK.
M P
MP
Baker
Cambridge Vascular Unit, Addenbrookes Hospital, Cambridge, UK. jonathan.boyle@addenbrookes.nhs.uk.
J R
JR
Boyle
D058186:Acute Kidney Injury / Q000139:chemically induced* / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001205:Ascorbic Acid / Q000494:pharmacology*; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D003287:Contrast Media / Q000633:toxicity*; D003404:Creatinine / Q000652:urine; D004195:Disease Models, Animal; D057510:Endovascular Procedures; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007472:Iohexol / Q000633:toxicity*; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000071068:Lipocalin-2 / Q000187:drug effects / Q000378:metabolism / Q000652:urine; D051379:Mice; D008807:Mice, Inbred BALB C; D054839:Retinol-Binding Proteins, Plasma / Q000187:drug effects / Q000378:metabolism
D000975:Antioxidants; D003287:Contrast Media; D000071068:Lipocalin-2; C502487:Rbp4 protein, mouse; D054839:Retinol-Binding Proteins, Plasma; C071332:Lcn2 protein, mouse; D007472:Iohexol; D003404:Creatinine; C505409:Casp3 protein, mouse; D053148:Caspase 3; D001205:Ascorbic Acid
Ascorbic acid; Contrast-induced nephropathy; Endovascular procedures; Histopathology; Immunohistochemistry; Nephroprotection