MO443: Accumulation of REG-1Α in Proximal Tubules of a Rat Model of Chronic Kidney Disease: A New Biomarker at the Interface Between Renal Impairment and Neurodegenerative Diseases

• Published in: Nephrology, dialysis, transplantation Vol. 37; no. Supplement_3
• Main Authors: Cortijo, Irene, Muyor, Karen, Laget, Jonas, Jover, Bernard, Reynaud, Fabrice, Duranton, Flore, Fontès, Pascaline, Trousse, Françoise, Marcilhac, Anne, Mestre-Francés, Nadine, Argiles Ciscart, Angel, Gayrard, Nathalie
• Format: Journal Article
• Language: English
• Published: 03.05.2022
• ISSN: 0931-0509; 1460-2385
• DOI: 10.1093/ndt/gfac070.057

Abstract BACKGROUND AND AIMS Chronic kidney disease (CKD) increases the risk of developing cognitive dysfunction and it has been identified as a modifiable risk factor for Alzheimer's disease (AD) [1]. Regenerating family member 1 alpha (Reg-1α) protein, originally identified as a 16 kDa polypeptide in the pancreas, is increased in cerebrospinal fluid (CSF) and in neurons of AD patients [2, 3]. Reg-1α is also elevated in blood in inflammatory conditions and chronic illnesses such as diabetes and interestingly, in patients with renal function impairment [4, 5]. It is not known whether Reg-1α is synthesized in the kidney or the modifications observed in CKD are merely due to a decline in the glomerular filtration rate. The aim of our study was to localize and quantify the Reg-1α protein in the kidneys of normal rats or CKD rats (5/6 nephrectomized rats) and determine, in a second time, if serum Reg-1α level is a suitable marker for assessment of renal function. As Reg-1a is able to cross the altered blood-brain barrier, it might be a new interesting biomarker at the interface between renal impairment and neurodegenerative diseases. METHOD A total of 16 3-month-old rats were randomly allocated to 5/6 nephrectomy (Nx) or Sham operation. Three months after surgery, serum creatinine and urea, systolic blood pressure (SBP) were measured and renal fibrosis (Sirius Red) was quantified. The expression of Reg-1α was evaluated by double-immunofluorescence using anti-Reg-1α and anti-Aquaporin-1 (Aqp-1) (as a proximal tubule marker) antibodies to determine the localization of Reg-1α in the kidney. RESULTS 5/6Nx rats showed increased serum creatinine levels (97.3 ± 17.6 versus Sham 26.3 ± 0.8 µmol/L; P < 0.05) and serum urea levels (23.9 ± 8.9 versus Sham 4.7 ± 0.1 mmol/L). They also had a higher SBP (158 ± 12 versus Sham 133 ± 5 mmHg) and renal fibrosis increased in the 5/6Nx group (8.1 ± 1.5 versus Sham 2.7 ± 0.2% staining). The double-immunofluorescence revealed an increased expression of Reg-1α of 5/6Nx rats compared with the Sham group. This expression seemed to be specific to the cytoplasm of the proximal tubules, with a ring-shaped distribution (preliminary results, Figure 1). CONCLUSION Our data show, for the first time, a proximal tubule-specific accumulation in Reg-1α in CKD suggesting an influence of impaired renal function on Reg-1α accumulation. Further assessment of Reg-1a in the blood, the blood-brain barrier and neuroinflammation status in this model is needed to better understand the potential effect of kidney accumulation of Reg-1α on brain dysfunction. Should this effect be confirmed, Reg-1α would be a new actor involved in the kidney-brain dialogue.