Figure 3.

In transfused ^-thalassemia mice, mitapivat reduces kidney iron accumulation and downregulates profibrotic kidney miRNA let-7 expression. (A) Upper panels: iron staining (Perl’s Prussian blue is a semi-quantitative method to assess organ iron accumulation) in kidney from wild-type (WT) and Hbb^th3/+ mice treated with either vehicle or transfusion (Tr.) or transfusion plus mitapivat. One representative image from 3-6 with similar results. Lower panels: quantification of iron staining in kidney. Data are mean ± standard error of the mean (SEM) (n=3-6). *P<0.05 compared with vehicle Hbb^th3/+ mice and ^#P<0.05 compared with vehicle-treated transfused (Tr.) Hbb^th3/+ mice. (B) Relative expression of miRNA let-7b and -7d in kidneys from WT or Hbb^th3/+ mice exposed to either vehicle or mitapivat or to chronic transfusion with and without mitapivat treatment. Small RNA was isolated from frozen kidneys using a silica spin column-based Quick-RNA kit (Zymo Research), quantified with a UV NanoPhotometer (Implen), and reverse transcribed with the qScript microRNA cDNA Synthesis for RT-PCR (QuantaBio). For real time polymerase chain reaction (RT-PCR) analysis of let-7b and let-7d miRNA, 3 ng of cDNA were used as a template in reaction mixtures (10 mL final volume) including a PowerUp SYBR Green Master Mix (5 mL, Applied Biosystems), miRNA-specific forward and universal reverse primers (1 mL each, miRCURY assays, Qiagen), and PCR-grade water. The expression of the indicated mRNA was quantitated by the comparative ΔCt method. RNU6-1 was used as control for normalization. Data are mean ± SEM (n=3-4). *P<0.05. **P<0.01. ***P<0.001. (C ) Phospho-tyrosine immunoprecipitation of kidneys from WT or Hbb^th3/+ mice exposed to either vehicle or mitapivat or to chronic transfusion with and without mitapivat treatment, using anti-phospho-tyrosine specific antibodies (IP: PY, clone PY99 from SCBT, Santa Cruz, CA and clone 4G10 from Merck KGaA, Darmstadt, Germany), revealed with anti-TGF-β receptor (Rec) specific antibody. GAPDH in whole-cell lysate (WCL) is used as loading control. One representative gel from 4 others with similar results is presented. Blots were developed using the Luminata Forte Chemiluminescent HRP Substrate from Merck Millipore (Armstadt, Germany), and images were acquired with the Alliance Q9 Advanced imaging system (Uvitec, UK). Densitometric analysis of immunoblots is shown on the right. Data are mean ± SEM (n=4). °P<0.05 compared to WT; *P<0.05 compared with vehicle Hbb^th3/+ mice, ^#P<0.05 compared with vehicle-treated transfused Hbb^th3/+ mice. RBC: red blood cells.