Calcitriol potentially alters HeLa cell viability via inhibition of autophagy

Objective: This study was conducted to evaluate the effect of Calcitriol on cellular death in HeLa cells via autophagy and turn over due to mitochondria homeostasis. Methods: HeLa cell lines were grown in 24-well plates and treated with Calcitriol at varying doses (0.013 mu M-0.325 mu M) for varying time periods (2, 6, 12, and 18 h). Cell proteins were extracted with scrapers and lysed using RIPA buffer. Western blots were performed for proteins involved with autophagy (Lc3, p62), signaling (mTOR, PI3K, HIF1 alpha), mitochondria (PGC1 alpha, COX4, and Tom 20), and apoptosis (Caspase 3, Caspase 9, and PARP). Protein carbonyl levels were determined by measuring the indirect ROS level. An inhibition study using L-mimosine was performed to analyze the significance of HIF1 alpha. Results: Calcitriol treatment induced cytotoxicity in a dose- and time-dependent manner and caused growth arrest in HeLa cells. The PI3K-AKT-mTOR pathway was activated, leading to inhibition of autophagy and alterations in mitochondria biogenesis homeostasis. Treatment with Calcitriol produced protein carbonyl levels similar to those in the cisplatin-treated and control groups. Increased ROS levels may cause toxicity and induce cell death specifically in cancer cells but not in normal cells. The inhibition of HIF1 alpha partially rescued the HeLa cells from the toxic effects of Calcitriol treatment. Conclusion: We suggest that Calcitriol may shut down mitochondrial homeostasis in HeLa cells by inducing the PI3K-AKT-mTOR pathway and inhibiting autophagy, which leads to cell death.

Automated summary

This study evaluated the effect of Calcitriol on autophagy and mitochondria homeostasis in HeLa cells and found that Calcitriol can induce cell death by activating the PI3K-AKT-mTOR pathway and inhibiting autophagy.