Protoporphyrin IX-induced structural and functional changes in human red blood cells, haemoglobin and myoglobin.
TL;DR: Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes, which may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.
Abstract: Protoporphyrin IX and its derivatives are used as photosensitizers in the photodynamic therapy of cancer. Protoporphyrin IX penetrates into human red blood cells and releases oxygen from them. This leads to a change in the morphology of the cells. Spectrophotometric studies reveal that protoporphyrin IX interacts with haemoglobin and myoglobin forming ground state complexes. For both proteins, the binding affinity constant decreases, while the possible number of binding sites increases, as the aggregation state of the porphyrin is increased. The interactions lead to conformational changes of both haemoglobin and myoglobin as observed in circular dichroism studies. Upon binding with the proteins, protoporphyrin IX releases the heme-bound oxygen from the oxyproteins, which is dependent on the stoichiometric ratios of the porphyrin : protein. The peroxidase activities of haemoglobin and myoglobin are potentiated by the protein-porphyrin complexation. Possible mechanisms underlying the relation between the porphyrin-induced structural modifications of the heme proteins and alterations in their functional properties have been discussed. The findings may have a role in establishing efficacy of therapeutic uses of porphyrins as well as in elucidating their mechanisms of action as therapeutic agents.
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TL;DR: Targeting “free heme” may be used as a therapeutic intervention against diseases related to oxidative stress and immune-mediated inflammatory conditions.
Abstract: Heme, iron (Fe) protoporphyrin IX, functions as a prosthetic group in a range of hemoproteins essential to support life under aerobic conditions. The Fe contained within the prosthetic heme groups of these hemoproteins can catalyze the production of reactive oxygen species. Presumably for this reason, heme must be sequestered within those hemoproteins, thereby shielding the reactivity of its Fe-heme. However, under pathologic conditions associated with oxidative stress, some hemoproteins can release their prosthetic heme groups. While this heme is not necessarily damaging per se, it becomes highly cytotoxic in the presence of a range of inflammatory mediators such as tumor necrosis factor. This can lead to tissue damage and, as such, exacerbate the pathologic outcome of several immune-mediated inflammatory conditions. Presumably, targeting “free heme” may be used as a therapeutic intervention against these diseases.
94 citations
Cites background from "Protoporphyrin IX-induced structura..."
...A number of factors can contribute to this (Kempe et al., 2007; Lang et al., 2008), including deregulated plasma osmolarity, acidosis, bacterial hemolysins (particularly Clostridium perfringens; Gutierrez et al., 1995), or free heme itself (Sil et al., 2004)....
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TL;DR: It is shown by co-purification and electron microscopy that mycobacteria via Mt-Enc can encapsulate Mt-DyP, Mt-BfrB, and Mt-FolB, which may aid in detoxification of the local environment to ensure long term survival.
82 citations
Cites methods from "Protoporphyrin IX-induced structura..."
...Heme (23) and PPIX (24) solutions were freshly prepared prior to each experiment....
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...JUNE 27, 2014 • VOLUME 289 • NUMBER 26 JOURNAL OF BIOLOGICAL CHEMISTRY 18283 Although Mt-DyP has heme-dependent peroxidase activity, Mt-DyP deferrochelatase activity was also tested because we have shown that Mt-DyP can bind PPIX (Fig....
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...Crystals of PPIX were dissolved in 150 mM NaCl, vortexed periodically over 20 min, and centrifuged....
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...Heme and PPIX solutions were protected from light and used within 12 h. Micromolar increments of either heme or PPIX were titrated into either 5 or 2.5 M purified apo-Mt-DyP, respectively, in 50 mM Tris-HCl (pH 7.4) and 150 mM NaCl....
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...Finally, Mt-DyP 18282 JOURNAL OF BIOLOGICAL CHEMISTRY VOLUME 289 • NUMBER 26 • JUNE 27, 2014 bound both heme and PPIX (Fig....
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TL;DR: It is shown that the Pseudomonas proteases and the neutrophil proteases (neutrophil elastase (NE) and proteinase-3) are capable of almost complete degradation of hemoglobin in vitro but that NE is the predominant protease that cleaves hemoglobinIn vivo in CF bronchoalveolar lavage fluid.
63 citations
TL;DR: Enhanced delivery systems for ALA in the skin will play an important role in ALA-PDT, and several enhancement techniques for increasing ALA permeation through the skin are introduced.
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TL;DR: Scatchard analysis indicates that all four ligands are true agonists of the receptor exhibiting positive cooperative binding with the existence of more than one class of binding site.
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29 citations
TL;DR: Experimental evidence suggests that these observations should be ascribed to the formation of a porphyrin anion radical in the horseradish peroxidase/NADPH system.
Abstract: Uroporphyrin I, haematoporphyrin and haematoporphyrin derivative had no effect on O2-. generation during oxidation of hypoxanthine by xanthine oxidase and on the formation of hydroxyl radicals (OH.) in the hypoxanthine/xanthine oxidase/Fe3+-EDTA/deoxyribose system. On the other hand, these porphyrins strongly inhibited O2-. formation in a horseradish peroxidase/H2O2/NADPH mixture, whereas they augmented OH. generation in this system after addition of Fe3+-EDTA. Experimental evidence suggests that these observations should be ascribed to the formation of a porphyrin anion radical in the horseradish peroxidase/NADPH system. The formation of this anion radical was confirmed by e.s.r. spectroscopy. This radical is apparently unable to reduce cytochrome c, but it can replace O2-. in the OH.-generating Haber-Weiss reaction.
29 citations
"Protoporphyrin IX-induced structura..." refers background in this paper
...…generated in HRP/H2O2/NAD(P)H system (Takayama and Nakano 1977) and these radicals may inhibit the peroxidase activity of HRP (Fridovich 1986). van Steveninck et al (1987, 1988) have postulated that superoxide radical generation is prevented by the porphyrin hematoporphyrin derivative leading to…...
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...This view is also supported by porphyrininduced potentiation of horseradish peroxidase (HRP)catalysed oxidation of NAD(P)H (van Steveninck et al 1987, 1988; Sil and Chakraborti 1997)....
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TL;DR: Spectrophotometric and spectrofluorimetric studies reveal that an interaction occurs between hemoglobin and hematoporphyrin, a photosensitizing drug used in photodynamic therapy, and appears to be predominantly electrostatic and enthalpy-driven in the lower range of porphyrIn concentration.
Abstract: Spectrophotometric and spectrofluorimetric studies reveal that an interaction occurs between hemoglobin and hematoporphyrin, a photosensitizing drug used in photodynamic therapy. Two concentration ranges of hematoporphyrin, 0.4–0.9 μM and 1.8–3.6 μM, representing significantly monomeric and aggregated (dimeric) state, respectively, have been used in the binding studies. The binding affinity constant ( K ) decreases, while the possible number of binding sites ( p ) increases as the concentration range of the porphyrin is increased. The nature of interaction has been studied by fluorescence quenching titration method under different ionic strengths and temperature conditions. It appears to be predominantly electrostatic and enthalpy-driven in the lower range of porphyrin concentration. However, the interaction follows mostly hydrophobic and entropy-driven modality in the higher concentration range of the ligand. The porphyrin-hemoglobin interaction results in release of oxygen from the protein. The extent of oxygen release depends on the stoichiometric ratio of hematoporphyrin: hemoglobin.
26 citations
"Protoporphyrin IX-induced structura..." refers background in this paper
...Several reports have been published on Hb-porphyrin interactions (Sil and Chakraborti 1996; Sil et al 1997, 2000; Chakraborti 2003; Hirsch et al 1993)....
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TL;DR: The effect of porphyrins on heme proteins should be given due consideration in elucidating the details of the mechanism of p Morphyrin actions in therapy.
Abstract: Two important porphyrins, protoporphyrin IX and hematoporphyrin IX, derivatives of which form the basis of photosensitization in the photodynamic therapy of cancer treatment, interact with two physiologically important heme proteins hemoglobin and myoglobin. The extent and modality of these interactions vary with the state of aggregation of the two porphyrins. Upon binding with these proteins, both the drugs change the protein conformations and release the heme-bound oxygen from the oxyproteins. At the same time, the peroxidase activities of these proteins are potentiated due to the protein-porphyrin complexation, as is found in case of horseradish peroxidase also. The effect of porphyrins on heme proteins should be given due consideration in elucidating the details of the mechanism of porphyrin actions in therapy.
25 citations