RESUMO
<p><b>OBJECTIVE</b>To observe the effects of paired box gene 8 (Pax-8) silencing by RNA interference on mitochondrial function and cardiomyocytes apoptosis.</p><p><b>METHODS</b>The cultured H9C2 (2-1) myocytes were divided into 3 groups: short interference RNA targeting Pax-8 (Pax-8 siRNA) group, non-specific siRNA group as the negative control (NC siRNA), and blank control group (BC siRNA). Fluorescence spectrophotometry was used to detect the activity of caspase-3. RT-PCR was performed to detect mRNA expression of Bcl2 and Bax. The protein expression of Bcl2, Bax and cytoplasm of Cytochrome was examined by Western blot. Changes of ΔΨm were detected by flow cytometry.ΔΨm with JC-1 monomer/polymer ratio was calculated for measuring mitochondrial depolarization proportion.</p><p><b>RESULTS</b>Compared to NC siRNA and BC siRNA group (0.075 ± 0.021, 0.072 ± 0.019), the activity of caspase-3 in Pax-8 siRNA group (0.167 ± 0.012) was significantly increased (P < 0.05); Bcl2 mRNA and protein expression in Pax-8 siRNA group (0.61 ± 0.06, 0.94 ± 0.11) were significantly downregulated compared with NC siRNA group (0.90 ± 0.070, 1.39 ± 0.15) and BC siRNA group (0.94 ± 0.087, 1.49 ± 0.20) (P < 0.05); Bax mRNA and protein expression in Pax-8 siRNA group (1.05 ± 0.10, 1.25 ± 0.12) were markedly upregulated compared with NC siRNA group (0.72 ± 0.03, 0.99 ± 0.12) and BC siRNA group (0.64 ± 0.03, 0.92 ± 0.06), P < 0.05; cytosolic cytochrome expression in Pax-8 siRNA group (0.75 ± 0.14) was significantly upregulated compared with NC siRNA group (0.51 ± 0.06) and BC siRNA group (0.48 ± 0.07) (P < 0.05); JC-1 monomer/polymer ratio in Pax-8 siRNA group (0.163 ± 0.011) was significantly increased compared with NC siRNA group (0.092 ± 0.015) and BC siRNA group (0.072 ± 0.025) (P < 0.05) indicating mitochondrial membrane potential was significantly reduced in Pax-8 siRNA group. Above parameters were similar between NC siRNA group and BC siRNA group (P > 0.05).</p><p><b>CONCLUSION</b>Inhibiting Pax-8 results in enhanced cardiomyocytes apoptosis through the mitochondrial pathway.</p>