P0020
THE NEPHRO-PROTECTIVE ROUTE OF CGMP DOES NOT COMPENSATE NPRHOGENIC DIABETES INSIPIDUS, BOTH CONDITIONS MEDIATED BY RENAL INTEGRIN LINKED KINASE (ILK)

Renal ILK transgenic deletion on mice (cKD-ILK) address basal polyuria compatible with nephrogenic diabetes insipidus (NDI), due to disrupted tubular water channel aquaporin 2 (AQP2) AQP2 expression and vesicular trafficking to the apical membrane [Cano-Peñalver JL et al. FASEB J. 2014; Mamuya FA et al. Am J Physiol Renal Physiol. 2016]. An early symptom of chronic renal diseases (CKD) is NDI. ILK depletion also have a nephron-protective effect in renal damage in mice due to the increase in cGMP [Cano-Peñalver JL et al. Mol Med. 2016; de Frutos S et al. Biochim Biophys Acta Mol Basis Dis. 2019], the latter an alternative anti-NDI mediator. Here we demonstrate that ILK-mediated regulation of AQP2, under basal or CKD contexts, does not depend on cGMP.

cKD-ILK and controls (WT) were treated orally with a NO donor, as precursor of cGMP formation (IDN, 300mg / Kg / day) for 24 hours. Urine volume was determined as a measure of tubular functionality. Fresh kidneys from non-treated mice were cultured ex vivo with precursors of cGMP (NO donor SNP, 1 µM or cGMP analogue 8Br-cGMP, 0.2 mM) for 30 minutes. AQP2 in the apical membrane of the tubules was quantified by immunohistochemistry. More cKD-ILK and WT were subjected for 6 weeks to a diet supplemented with 0.2% adenine (A) as CKD inducer or baseline standard diet. Urine volume and total ranal AQP2 levels were determined.

Compared to WT, cGMP axis activation in vivo did not compensate the basal NDI present in cKD-ILK and the activation ex vivo did not improve the apical presence of AQP2 in cKD-ILK. Both WT and cKD-ILK subjected to CKD showed exacerbated polyuria and decreased levels of renal AQP2, but no differences were observed between groups.

ILK regulates AQP2, both in a basal and pathological context (CKD) independent of cGMP which otherwise is nephron-protective. Our results probably explain the co-existence of cGMP increase together with AQP2 decrease observed in the cKD-ILK kidneys.