P MEHTA 1, T SLATTER 1, R WALKER 1
1University of Otago, Dunedin, New Zealand
Aim: To explore pathways through which amiloride reduces lithium-induced interstitial fibrosis.
Background: Lithium therapy is associated with the development of nephrogenic diabetes insipidus (NDI), interstitial fibrosis and dilated microcystic distal tubules. We have previously demonstrated that co-administration with amiloride reverses NDI and slows the rate of development of lithium-induced interstitial fibrosis associated with reduced collagen deposition and myofibroblast formation. The pathways of how amiloride down-regulates lithium-induced interstitial fibrosis has not been elucidated.
Methods: RNA sequencing of kidney from rat model of long (6 months, n =10) and short-term (14 days and 28 days, n=17 each) lithium-induced chronic kidney disease without or with amiloride was performed. Transcripts from lithium alone, lithium/amiloride and control treated rat kidneys were mapped to rat genome. As fibrosis is driven by persistent injury to tubular epithelial cells leading to inflammation, we were interested in validating inflammatory and immune response candidates. These included p21, pAKT, p53, ki67, Notch1, PDGFrβ, CD3 T-lymphocytes and p65/NFκB investigated using immunohistochemistry, immunofluorescence and RNAscope® on tissue sections.
Results: Lithium increased tubular expression of p65/NFκB, Ki67 and pAKT at all time points. Lithium/amiloride increased tubular expression of p53 and p21 compared to lithium alone (P<0.05, ANOVA) at all time points. In the interstitium, lithium increased expression of PDGFrβ positive pericytes, p65/NFκB, Notch1 and CD3 expression, around the dilated cystic tubules, but was decreased in lithium/amiloride tissue
Conclusion: Amiloride induced up-regulation of cell cycle regulatory genes p53 and p21 with down-regulation of immune and inflammatory genes compared to lithium alone, leading to reduction in interstitial fibrosis. This suggests amiloride has anti-inflammatory properties unrelated to its action as a competitive antagonist of ENaC.
I am a final year PhD student at the University of Otago in the Department of Pathology and I work in the renal lab on a project related to fibrosis.