#2170 BET inhibitor nanotherapy reduces chronic kidney disease progression after ischemia-reperfusion injury
Authors: Alvarez Maria Laura Saiz , Diaz-Bulnes Paula , Chamizo Laura Lozano , Florez Aida Bernardo , Marciello Marzia , Iglesias Viviana Corte , Bernet Cristian Ruiz , Martin Cristina Martin , Filice Marco , Suarez-Alvarez Beatriz , Lopez-Larrea Carlos 
Published: May 2024

Abstract

Background and Aims
Targeting epigenetic mechanisms offer a potential breakthrough in addressing kidney diseases. Thus, inhibition of the bromodomain and extra-terminal (BET) domain proteins using the small molecule inhibitor JQ1, has shown promise in preclinical models of acute kidney injury (AKI) and chronic kidney disease (CKD). However, clinical translation faces hurdles like poor pharmacokinetics and side effects. To tackle this, we engineered liposomes loaded with JQ1 to enhance kidney drug delivery and minimize side effects. By optimizing the encapsulation of JQ1, our aim was to improve its efficacy compared to freely delivered JQ1 and reduce its cytotoxicity. Moreover, the therapeutic potential of this new nanoformulation to halt the acute renal ischemic injury and its transition to CKD will be explored.

Method
JQ1 was encapsulated in different types of lipid nanoparticles (NPs), and its effect was analyzed in vitro on the HK2 tubular epithelial line. Additionally, in vivo administration was carried out 1 hour after the induction of 45 minutes bilateral renal ischemia, and its effect was further analyzed at 24 h in the AKI setting or at 21 days for CKD. Non-encapsulated JQ1 was used as a control, and in vivo biodistribution studies were conducted using IVIS and fluorescent Cy5.5-labelled NPs. Damage markers, inflammatory burden and fibrosis development were analyzed through conventional techniques (Western blot, RT-PCR, IHC, flow cytometry), and functional parameters (BUN, Creatinine) were assessed through colorimetric assays.

Results
Three types of liposomal NPs were assayed to optimize JQ1 encapsulation, being the combined encapsulation of JQ1 in both the core and lipid layer the ones proving the best effectiveness. With an average hydrodynamic diameter of 78 nm, these NPs effectively reached the kidneys as assayed by in vivo biodistribution assays. In vitro assays performed on the HK2 cell line reveal their potential to inhibit TNF-α-induced inflammation. Importantly, in vivo dose-dependent studies determined that a 40 mg/kg dose was effective in post-ischemic acute kidney injury, showing a reduction in inflammatory (Il6, Csf2, Ccl2, Ccl5) and renal damage markers (Ngal), as well as reduced immune cell infiltration into the renal tissue of monocytes (CD45+CD11b+Ly6G−Ly6ChiF4/80low) and neutrophils (CD45+CD11b+Ly6GhiLy6Clow) quantified by flow cytometry. In accordance, decreased levels of serum BUN and Creatinine were detected in the group of mice treated with NPs-JQ1, indicating a better renal function. Of note, none of these effects were observed when the same dose of the unencapsulated inhibitor was used, demonstrating no effectiveness whatsoever. In the long term, by establishing an AKI to CKD transition model analysing fibrosis at 21 days post-ischemia induction, mice receiving a single dose of NPs-JQ1 early after damage displayed reduced fibrosis markers expression (α-SMA and Fibronectin), decreased collagen deposits quantified by Masson's Trichrome tissue staining and a partial recovery of the renal function.

Conclusion
The encapsulation of JQ1 in lipid nanoparticles is an effective strategy that allows for a decrease in the minimum effective dose of the drug. Due to its higher concentration and stability in the kidney, this therapy could be relevant in the treatment of renal pathologies and represents a significant step forward in the development of an innovative therapy for AKI-to-CKD transition. Our pioneering liposomal formulation not only expands the therapeutic potential of JQ1 but also addresses a significant barrier to its clinical translation in the nephrology field.