Department of Cardiovascular Medicine, Xiangya Hospital, Central South University, Changsha, Hunan, China.
Department of the Geriatrics, The Third Xiangya Hospital, Central South University, Changsha, Hunan, China.
Cell Death Dis. 2021 Apr 26;12(5):418. doi: 10.1038/s41419-021-03699-4.
Autophagy, a well-observed intracellular lysosomal degradation process, is particularly important to the cell viability in diabetic cardiomyopathy (DCM). Peroxidasin (PXDN) is a heme-containing peroxidase that augments oxidative stress and plays an essential role in cardiovascular diseases, while whether PXDN contributes to the pathogenesis of DCM remains unknown. Here we reported the suppression of cell viability and autophagic flux, as shown by autophagosomes accumulation and increased expression level of LC3-II and p62 in cultured H9C2 and human AC16 cells that treated with 400 μM palmitate acid (PA) for 24 h. Simultaneously, PXDN protein level increased. Moreover, cell death, autophagosomes accumulation as well as increased p62 expression were suppressed by PXDN silence. In addition, knockdown of PXDN reversed PA-induced downregulated forkhead box-1 (FoxO1) and reduced FoxO1 phosphorylation, whereas did not affect AKT phosphorylation. Not consistent with the effects of si-PXDN, double-silence of PXDN and FoxO1 significantly increased cell death, suppressed autophagic flux and declined the level of FoxO1 and PXDN, while the expression of LC3-II was unchanged under PA stimulation. Furthermore, inhibition of FoxO1 in PA-untreated cells induced cell death, inhibited autophagic flux, and inhibited FoxO1 and PXDN expression. Thus, we come to conclusion that PXDN plays a key role in PA-induced cell death by impairing autophagic flux through inhibiting FoxO1, and FoxO1 may also affect the expression of PXDN. These findings may develop better understanding of potential mechanisms regarding autophagy in insulin-resistant cardiomyocytes.
自噬是一种观察到的细胞内溶酶体降解过程，对糖尿病心肌病（DCM）中的细胞活力尤为重要。过氧化物酶（PXDN）是一种含有血红素的过氧化物酶，可增强氧化应激，在心血管疾病中发挥重要作用，而 PXDN 是否有助于 DCM 的发病机制尚不清楚。在这里，我们报道了细胞活力和自噬流的抑制，表现为自噬体积累和 LC3-II 和 p62 的表达水平增加在培养的 H9C2 和人 AC16 细胞中，用 400 μM 棕榈酸（PA）处理 24 小时。同时，PXDN 蛋白水平增加。此外，沉默 PXDN 可抑制细胞死亡、自噬体积累以及 p62 表达增加。此外，PA 诱导的叉头框蛋白 1（FoxO1）下调和 FoxO1 磷酸化减少被 PXDN 敲低所逆转，而 AKT 磷酸化不受影响。与 si-PXDN 的作用不一致，沉默 PXDN 和 FoxO1 后显著增加细胞死亡，抑制自噬流，降低 FoxO1 和 PXDN 的水平，而在 PA 刺激下 LC3-II 的表达不变。此外，在未经 PA 处理的细胞中抑制 FoxO1 可诱导细胞死亡，抑制自噬流，并抑制 FoxO1 和 PXDN 的表达。因此，我们得出结论，PXDN 通过抑制 FoxO1 损害自噬流在 PA 诱导的细胞死亡中起关键作用，FoxO1 也可能影响 PXDN 的表达。这些发现可能有助于更好地了解胰岛素抵抗心肌细胞中自噬的潜在机制。
