Inhibition of MALAT1 facilitates ROS accumulation via the Keap1/HO-1 pathway to enhance photodynamic therapy in secondary hyperparathyroidism.

The prevalence of secondary hyperparathyroidism (SHPT) in advanced chronic kidney disease (CKD) exceeds 80 %. Our previous study indicated that photodynamic therapy (PDT) has potential for treating SHPT. Long noncoding RNA (lncRNA) is involved in various oxidative stress and apoptotic processes, but the molecular mechanism remains unreported. In this study, we found that PDT induced apoptosis in SHPT through reactive oxygen species (ROS) accumulation. The expression of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and heme oxygenase 1 (HO-1) within SHPT was upregulated after PDT. Inhibition of MALAT1 increased PDT-induced ROS, which promoted the apoptosis. Pearson correlation analysis confirmed that there was a positive correlation between MALAT1 and HO-1, and MALAT1 inhibition down-regulated HO-1, whereas concomitant overexpression of HO-1 was able to eliminate the PDT-induced ROS and inhibit apoptosis. The direct binding of MALAT1 to Kelch-like ECH-associated protein 1 (Keap1) protein was confirmed by high-throughput sequencing, RNA pulldown, silver staining and western blotting assays. Si-Keap1 was able to rescue the down-regulation of HO-1 caused by MALAT1 inhibition, restoring the elimination of ROS by HO-1 and attenuating the effect of PDT. In addition, PDT effectively reduced parathyroid hormone (PTH) secretion in SHPT rats, and this effect was further enhanced in combination with MALAT1 inhibitors. Overall, MALAT1 activates downstream HO-1 expression by binding to Keap1, thereby reducing ROS and inhibiting apoptosis, which in turn mediates PDT resistance in SHPT. Inhibition of MALAT1 significantly enhanced the efficacy of PDT, suggesting a potential therapeutic target for improving PDT for SHPT outcomes.