Time evolution of methotrexate‐induced kidney injury: A comparative study between different biomarkers of renal damage in rats

Abstract

Methotrexate (MTX) is commonly used in the treatment of malignant diseases and autoimmune and chronic inflammatory disorders. Along with its effective therapeutic power, MTX has adverse effects on the kidneys. Discovery of new biomarkers is required to improve the early detection of renal damage and optimize the effectiveness of treatments. The aim of this study was to evaluate the time course of MTX‐induced nephrotoxicity and to compare the urinary excretion of the organic anion transporter 5 (uOat5) with alterations in other markers of renal function, and to elucidate the possible molecular mechanisms involved in uOat5. Animals were exposed to a unique dose of MTX (80 mg/kg body weight, intraperitoneal). Experiments were carried out at days 2, 4, 8 or 14 after MTX administration. Markers of renal damage, such as creatinine and urea plasma levels, urinary activity of alkaline phosphatase, microalbuminuria, urinary excretion of neutrophil gelatinase‐associated lipocalin (uNGAL) and histopathology, were evaluated. Renal organic anion transporter 5 (Oat5) expression and its presence in different urine fraction were assessed by western blotting. uOat5 was significantly increased 2 days after MTX treatment, before than any alteration in other parameters of kidney injury or renal morphology occurred. uNGAL showed an inverted pattern of urinary excretion compared to uOat5. Exosomal pathway is involved in the urinary excretion of Oat5 and depends on the degree of damage induced by MTX. These experimental data allow proposing uOat5 as a potential non‐invasive biomarker for early detection of MTX‐induced nephrotoxicity.

Utility of urinary organic anion transporter 5 as an early biomarker of obstructive nephropathy

“…Oat5 in urine was first detected by our research group 12 . In addition, Oat5 u has been proposed as a biomarker of prerenal damage induced by ischaemia or by vascular calcification 12,25 and of intrarenal damage induced by different nephrotoxic agents 13‐18 . In this study, the aim was to determine if Oat5 u could be considered as a biomarker of postrenal damage as well, and to compare it with plasma levels of urea and creatinine, creatinine clearance, some urinary parameters (total proteins, glucose, alkaline phosphatase activity) and with a more recently described marker of renal injury, urinary NGAL.…”

“…Total proteins, glucose, alkaline phosphatase activity, Oat5 and NGAL in urine were related to urinary creatinine concentration to correct for variations in urine production as previously described 12‐18,21 …”

“…Protein abundances of Oat5, Oat1 and NGAL in BUO groups were calculated as percentages of the mean Sham value for that gel. Proteins urinary levels were normalized to urinary creatinine values as reported previously 12‐18,21,29 …”

“…Our group was pioneering in the urinary detection of Oat5 in rat 12 . Moreover, it has been proposed the Oat5 urinary excretion (Oat5 u ) as an early noninvasive biomarker of prerenal damage (ischaemia–reperfusion) and of nephrotoxicity induced by mercury, cisplatin, and methotrexate 12‐18 …”

Carbon monoxide: An emerging therapy for acute kidney injury

“…Beyond transplantation, the kidney remains a key target organ where CO has been shown to be protective with unique opportunities in areas such as chemotherapy-mediated injury as observed with CP or methotrexate. 193,194 With the advent of new agents entering the marketplace, especially within the areas of neurologic and cardiovascular disorders as well as various antivirals and antimicrobials, the incidence of AKI can only increase and this does not include the vast unknown of what occurs in individuals prescribed multidrug therapeutics where drug-drug interactions have not been comprehensively studied. Given the lack of metabolism of CO, it offers a unique ability to protect the kidney against drug toxicities without the likelihood of interactions with other agents.…”