Kidney Week

Abstract: FR-PO385

Mesangial Matrix Expansion Attenuated by All-Trans Retinoic Acid Through Direct Suppression of Bone Morphogenetic Protein 4 in Mouse Diabetic Nephropathy

Session Information

• Diabetic Kidney Disease: Basic - II
  October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Diabetic Kidney Disease

• 601 Diabetic Kidney Disease: Basic

Authors

• Tamaki, Masanori, Department of Nephrology, Tokushima University, Tokushima, Japan

Masanori Tamaki,

• Tominaga, Tatsuya, Department of Nephrology, Tokushima University, Tokushima, Japan

Tatsuya Tominaga,

• Fujita, Yui, Department of Nephrology, Tokushima University, Tokushima, Japan

Yui Fujita,

• Kishi, Seiji, Department of Nephrology, Tokushima University, Tokushima, Japan

Seiji Kishi,

• Murakami, Taichi, Department of Nephrology, Tokushima University, Tokushima, Japan

Taichi Murakami,

• Nagai, Kojiro, Department of Nephrology, Tokushima University, Tokushima, Japan

Kojiro Nagai,

• Abe, Hideharu, Department of Nephrology, Tokushima University, Tokushima, Japan

Hideharu Abe,

• Doi, Toshio, Department of Nephrology, Tokushima University, Tokushima, Japan

Toshio Doi,

Background

Diabetic nephropathy (DN) leads to mesangial matrix expansion, resulting in glomerulosclerosis and renal failure. Collagen IV (COL4), a major component of the mesangial matrix, is positively regulated by bone morphogenetic protein 4 (BMP4)/suppressor of mothers against decapentaplegic (Smad1) signaling. All-trans retinoic acid (atRA) treatment has a beneficial effect on several kidney disease models, although the effect on mesangial matrix expansion in DN remains unclear. AtRA is a representative ligand for retinoic acid receptor (RAR), which heterodimerizes with retinoid X receptor (RXR). Because RAR/RXR heterodimer binds to RA response element (RARE) and regulates various gene transcriptions, the therapeutic effect of atRA on DN through BMP4 regulation by RAR/RXR–RARE was investigated in the present study.

Methods

Streptozotocin was given to male ICR mice at 12 weeks old for diabetes induction. Both control mice and diabetic mice were given all-trans retinoic acid (atRA, 15 µg/gBW) intraperitoneally thrice weekly from 16 weeks old to 24 weeks old. Animal kidneys were harvested at 24 weeks. AtRA or specific agonists for each subtype of RAR were added to cultured mouse mesangial cells for 24 h (from 1 nM to 1 µM). The RAR binding capacity to RARE, suggested by genome analysis, was confirmed by ChIP analysis. The functional role of the putative RARE was confirmed by a reporter assay.

Results

Mesangial matrix expansion worsened in diabetic mice and was associated with increased BMP4, phosphorylated Smad1, and COL4. These levels were attenuated after atRA administration. In cultured mesangial cells, BMP4 and COL4 expression levels were significantly decreased by atRA or low concentrations (1 nM) of RARα agonist but not by 1 nM of RARβ or γ agonists. Two putative regions with significant homology to RARE were identified around the mouse Bmp4 gene. ChIP analysis and subsequent reporter assays indicated the binding of one putative RARE of the Bmp4 gene to RARα and RXR, resulting in suppression of BMP4 expression.

Conclusion

AtRA directly suppressed BMP4 via RARα/RXR heterodimer binding to a unique RARE, resulting in amelioration of mesangial matrix expansion in diabetic mice. These findings provide a novel regulatory mechanism for treatment of DN.

Funding

• Government Support - Non-U.S.