Effect of the nature of the chelated metal on the photodynamic activity of metalloporphyrins.
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2023-11
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Coordination of metal ions by the tetrapyrrole ring of porphyrin-based photosensitizers (PSs) affects their photophysical properties and consequently, their photodynamic activity. Diamagnetic metals increase the singlet oxygen quantum yield while paramagnetic metals have the opposite effect. Since singlet oxygen is considered the main cell-damaging species in photodynamic therapy (PDT), the nature of the chelated cation would directly affect PDT efficacy. This expectation, however, is not always supported by experimental results and numerous exceptions have been reported. Understanding the effect of the chelated metal is hindered because different chelators were used. The aim of this work was to investigate the effect of the nature of chelated cation on the photophysical and photodynamic properties of metalloporphyrins, using the same tetrapyrrole core as a chelator of Ag(II), Cu(II), Fe(III), In(III), Mn(III), or Zn(II). Results demonstrated that with the exception of Ag(II), all paramagnetic metalloporphyrins were inefficient as generators of singlet oxygen and did not act as PSs. In contrast, the coordination of diamagnetic ions produced highly efficient PSs. The unexpected photodynamic activity of the Ag(II)-containing porphyrin was attributed to reduction of the chelated Ag(II) to Ag(I) or to demetallation of the complex caused by cellular reductants and/or by exposure to light. Our results indicate that in biological systems, where PSs localize to various organelles and are subjected to the action of enzymes, reactive metabolites, and reducing or oxidizing agents, their physicochemical and photosensitizing properties change. Consequently, the photophysical properties alone cannot predict the anticancer efficacy of a PS.
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Abbas, Ghadeer, Fatemah Alibrahim, Rawan Kankouni, Sara Al-Belushi, Dalal A Al-Mutairi, Artak Tovmasyan, Ines Batinic-Haberle, Ludmil Benov, et al. (2023). Effect of the nature of the chelated metal on the photodynamic activity of metalloporphyrins. Free radical research. pp. 1–18. 10.1080/10715762.2023.2288997 Retrieved from https://hdl.handle.net/10161/29600.
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Scholars@Duke
Ines Batinic-Haberle
A major interest of mine has been in the design and synthesis of Mn porphyrin(MnP)-based powerful catalytic antioxidants which helped establish structure-activity relationship (SAR). It relates the redox property of metalloporphyrins to their ability to remove superoxide. SAR has facilitated the design of redox-active therapeutics and served as a tool for mechanistic considerations. Importantly SAR parallels the magnitude of the therapeutic potential of SOD mimics and is valid for all classes of redox-active compounds. Two lead Mn porphyrins are already in five Phase II clinical trials (reviewed in Batinic-Haberle et al, Oxid Med Cell Longevity 2021). Recent research suggests immense potential of MnPs in cardiac diseases. MnTE-2-PyP (AEOL10113, BMX-010) prevents and treats cardiac arrhythmia, while MnTnBuOE-2-PyP (BMX-001) fully suppressed the development of aortic sclerosis in mice. The latter result is relevant to the cancer patients undergoing chemotherapy. In addition to breast cancer, in collaboration with Angeles Alvarez Secord, MD, MHSc, we have recently shown the anticancer effects of Mn porphyrin/ascorbate in cellular and mouse models of ovarian cancer.
In parallel with synthetic efforts, I have also been interested in the mechanistic aspects of differential actions of Mn porphyrins in normal vs tumor tissue. In-depth studies of chemistry and biology of the reactions of MnPs with redox-active agents relevant to cancer therapy – ascorbate, chemotherapy and radiation – set ground for understanding the role of thermodynamics and kinetics in the mechanism of action of Mn porphyrins. Mechanistic studies have been revealed in Batinic-Haberle et al, Antioxidant Redox Signal 2018, Batinic-Haberle and Tome, Redox Biology 2019 and Batinic-Haberle et al Oxidative Medicine and Cellular Longevity 2021. My research has resulted in over 230 publications, 18 268 citations and an h-index of 64. For my achievements, I have been awarded the 2021 Discovery Award from the Society for Redox Biology and Medicine, SfRBM.
Additional Training
- Postdoctoral fellowship with Professor Alvin Crumbliss in the field of Bioinorganic Chemistry, Department of Chemistry, Duke University
- Postdoctoral fellowship with Professor Irwin Fridovich in the field of Redox Biology, Department of Biochemistry, Duke University School of Medicine
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