A ruthenium(II) complex containing a p-cresol group induces apoptosis in human cervical carcinoma cells through endoplasmic reticulum stress and reactive oxygen species production

doi:10.1016/j.jinorgbio.2018.11.015

Journal of Inorganic Biochemistry

Volume 191, February 2019, Pages 126-134

https://doi.org/10.1016/j.jinorgbio.2018.11.015 Get rights and content

Highlights

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HIPMP is 2-(1H-imidazo-[4,5-f] [1,10] phenanthrolin-2-yl)-4-methylphenol.
•
Complex Ru2 is [Ru(phen)₂(HIPMP)](ClO₄)₂ (phen = 1,10-phenanthroline).
•
Ru2 induced endoplasmic reticulum stress-mediated apoptosis.
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Ru2 induced reactive oxygen species generation and mitochondrial membrane potential depolarization.
•
The protein expression induced by Ru2 was assayed by the western blot.

Abstract

The chemical structures of Ru (II) complexes are known to affect their cellular behavior and toxicity. In this study, three new luminescent Ru (II) complexes, [Ru(bpy)₂(HIPMP)](ClO₄)₂ (Ru1, bpy = 2,2′-bipyridine, HIPMP = 2-(1H-imidazo-[4,5-f] [1,10] phenanthrolin-2-yl)-4-methylphenol), [Ru(phen)₂(HIPMP)](ClO₄)₂ (Ru2, phen = 1,10-phenanthroline), [Ru(dmb)₂(HIPMP)](ClO₄)₂ (Ru3, dmb = 4,4′-dimethyl-2,2′-bipyridine), were synthesized, and their anticancer activities were examined. All three complexes displayed anticancer activities against various cancer cells, with Ru2 exhibiting the highest cytotoxic activities. Ru2 was shown to accumulate specifically in the endoplasmic reticulum (ER) and induce ER stress-mediated apoptosis. In addition, Ru2 could generate reactive oxygen species (ROS) and trigger mitochondrial membrane potential depolarization. These results demonstrated that Ru2 induced apoptosis in HeLa cells through ER stress and ROS production.

Graphical abstract

Introduction

Based on their unique and versatile biochemical properties, ruthenium-based complexes have been regarded as promising anticancer agents for alternative drugs to cisplatin and its derivatives [1]. The first two approved Ru(III) complexes, namely, NAMI-A(H₂Im)[trans-RuCl₄(DMSO)(HIm)], where HIm = 1H-imidazole and DMSO = dimethylsulfoxide) [2] and KP1019 (H₂Ind)[trans-RuCl₄(HInd)₂], where Hind = 1H-indazole) [3], have successfully been used in clinical studies. Recently, many ruthenium (II) complexes with potent therapeutic properties have been designed and developed as anticancer drugs, including inorganic Ru (II), organometallic Ru (II) and nanomaterial Ru (II) complexes [[4], [5], [6], [7]]. Furthermore, several mechanisms have been applied to elucidate the anticancer activities of Ru (II) complexes depending on their intracellular targets, which include nucleic acids [8], proteins [9,10], and cell organelles [11,12]. A different pathway of cell apoptosis involving endoplasmic reticulum (ER) stress induced by metal complexes, such as ruthenium- [13,14], iridium- [[15], [16], [17]], platinum- [18,19] and lanthanide-based complexes [20] has been reported.

The ER is a cytoplasmic organelle for the folding and trafficking of secretory and membrane proteins [21] as well as intracellular calcium storage, making it very important in cellular signal-transducing [22] and extremely sensitive to alterations in homeostasis and to a number of biochemical and physiological stimuli. The perturbation of ER functions leads to ER stress, such as the accumulation of unfolded or misfolded proteins [23] and the failure of the ER to cope with an excessive protein load. ER stress causes an imbalance between ER protein folding load and capacity. Severe ER stress can activate intrinsic apoptosis, resulting in cell death. Certain cancer cells, including multiple myelomacells, possessing high ER activity are especially sensitive to ER stress-mediated cell death [24]. Thus, the development of anticancer drugs that affect ER stress-mediated apoptosis pathways could be an effective therapeutic strategy [25].

ROS are thought to play important roles in the induction of apoptosis by Ru (II) complexes in cancer cells [[26], [27], [28]]. ROS have been proven to cause cellular damage, such as damaging lipids, proteins and DNA in early stages of apoptosis [29]. Additionally, ROS trigger the depolarization of the mitochondrial membrane and induce mitochondrial dysfunction [30].

In this study, we synthesized and characterized three new Ru(II) complexes [Ru(N single bond N)₂(HIPMP)](ClO₄)₂ (N-N = 2,2′-bipyridine (bpy, Ru1), 1,10-phenanthroline (phen, Ru2), and 4,4′-dimethyl-2,2′-bipyridine (dmb, Ru3). Ru2 showed higher cytotoxicity than Ru1 and Ru3. Further investigations indicated that Ru2 can induce ER stress and ROS-mediated mitochondrial dysfunction in the apoptotic signaling pathway, indicating that Ru2 has the potential to serve as an emerging chemotherapeutic agent for cancer therapy.

Section snippets

Materials

All reagents and solvents were purchased commercially and used without further purification unless specifically noted. Cisplatin, propidium iodide (PI), 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT), dimethyl sulfoxide(DMSO), RuCl₃·xH₂O, 2,2′-bipyridine (bpy), 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine and 2-hydroxy-5-methylbenzaldehyde were obtained from Sigma Aldrich. Lyso Tracker Green DND-26 (LTG), MitoTracker Green FM (MTG), ER-Tracker™ Green, and

Synthesis and characterization

The structures of Ru1, Ru2 and Ru3 are illustrated in Scheme 1. The ligand HIPMP was obtained in good yield by reacting 1,10-phenanthroline-5,6-dione with 2-hydroxy-5-methylbenzaldehyde by refluxing glacial acetic acid containing ammonium acetate at a molar ratio of 1:1. HIPMP was used as the starting material in a reaction with the appropriate molar ratios of the precursor complexes in ethanol, resulting in relatively high yields for Ru1–Ru3. The desired Ru(II) complexes were purified using

Conclusions

Three new Ru(II) complexes containing a p-cresol group were synthesized and characterized. An in vitro cytotoxicity assay indicated that these ruthenium (II) complexes exhibited potent cancer inhibitory effects against selected cancer cell lines. Interestingly, Ru2 showed higher anticancer activity than Ru1 and Ru3. Subcellular distribution studies showed that Ru2 localized preferentially in the endoplasmic reticulum. The results of the western blot analysis demonstrated that CHOP was activated

Acknowledgements

This work was supported by the National Science Foundation of China (No. 21301034, 21771042) and the National Science Foundation of Guangdong Province (No. S2013040014083, 2016A030310298).

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Citation Excerpt :
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A ruthenium(II) complex containing a p-cresol group induces apoptosis in human cervical carcinoma cells through endoplasmic reticulum stress and reactive oxygen species production

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Synthesis and characterization

Conclusions

Acknowledgements

Coord. Chem. Rev.

Pharmacol. Res.

Chem

Chem. Sci.

Cancer Lett.

Cell Calcium

Eur. J. Pharmacol.

J. Pharm. Sci.

J. Immunol. Methods

Eur. J. Med. Chem.

J. Immunol. Methods

J. Biol. Chem.

J. Pharm. Sci.

Free Radic. Biol. Med.

The development of anticancer ruthenium(II) complexes: from single molecule compounds to nanomaterials

Chem. Soc. Rev.

Ruthenium complexes can target determinants of tumour malignancy

Dalton Trans.

KP1019, a new redox-active anticancer agent-preclinical development and results of a clinical phase I study in tumor patients

Chem. Biodivers.

A macrocyclic ruthenium(III) complex inhibits angiogenesis with down-regulation of vascular endothelial growth factor receptor-2 and suppresses tumor growth in vivo

Angew. Chem.

A ruthenium polypyridyl intercalator stalls DNA replication forks, radiosensitizes human cancer cells and is enhanced by Chk1 inhibition

Sci. Rep.

Structurally sophisticated octahedral metal complexes as highly selective protein kinase inhibitors

J. Am. Chem. Soc.

Nuclear permeable ruthenium(II) β-carboline complexes induce autophagy to antagonize mitochondrial-mediated apoptosis

J. Med. Chem.