Hemolysis of Human Red Blood Cells by Riboflavin-Cu(II) System: Enhancement by Azide

Ali, Iyad; Sakhnini, Nina; Naseem, Imrana

doi:10.1007/s10541-005-0217-x

Cited by 6 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…. Ali et al 58 reported that the hemolysis of human red blood cells by a photoactivated (cool fluorescent light) riboflavin–Cu(II) system was enhanced by addition of 150 µM azide. They attributed their observation to inhibition of the photodegradation of riboflavin, but commented that “as the riboflavin–Cu(II) system has been shown to produce HO .…”

Section: Discussionmentioning

confidence: 99%

Type I and Type II mechanisms of antimicrobial photodynamic therapy: An in vitro study on gram‐negative and gram‐positive bacteria

et al. 2012

View full text Add to dashboard Cite

Background and Objectives Antimicrobial photodynamic therapy (APDT) employs a nontoxic photosensitizer (PS) and visible light, which in the presence of oxygen produce reactive oxygen species (ROS), such as singlet oxygen (1O2, produced via Type II mechanism) and hydroxyl radical (HO•, produced via Type I mechanism). This study examined the relative contributions of 1O2 and HO• to APDT killing of Gram-positive and Gram-negative bacteria. Study Design/Materials and Methods Fluorescence probes, 3'-(p-hydroxyphenyl)-fluorescein (HPF) and singlet oxygen sensor green reagent (SOSG) were used to determine HO• and 1O2 produced by illumination of two PS: tris-cationic-buckminsterfullerene (BB6) and a conjugate between polyethylenimine and chlorin(e6) (PEI–ce6). Dimethylthiourea is a HO• scavenger, while sodium azide (NaN3) is a quencher of 1O2. Both APDT and killing by Fenton reaction (chemical generation of HO•) were carried out on Gram-positive bacteria (Staphylococcus aureus and Enteroccoccus fecalis) and Gram-negative bacteria (Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa. Results Conjugate PEI-ce6 mainly produced 1O2 (quenched by NaN3), while BB6 produced HO• in addition to 1O2 when NaN3 potentiated probe activation. NaN3 also potentiated HPF activation by Fenton reagent. All bacteria were killed by Fenton reagent but Gram-positive bacteria needed a higher concentration than Gram-negatives. NaN3 potentiated Fenton-mediated killing of all bacteria. The ratio of APDT killing between Gram-positive and Gram-negative bacteria was 2 or 4:1 for BB6 and 25:1 for conjugate PEI-ce6. There was a NaN3 dose dependent inhibition of APDT killing using both PEI-ce6 and BB6 against Gram-negative bacteria while NaN3 almost failed to inhibit killing of Gram-positive bacteria. Conclusion Azidyl radicals may be formed from NaN3 and HO•. It may be that Gram-negative bacteria are more susceptible to HO• while Gram-positive bacteria are more susceptible to 1O2. The differences in NaN3 inhibition may reflect differences in the extent of PS binding to bacteria (microenvironment) or differences in penetration of NaN3 into cell walls of bacteria.

show abstract

Section: Discussionmentioning

confidence: 99%

Type I and Type II mechanisms of antimicrobial photodynamic therapy: An in vitro study on gram‐negative and gram‐positive bacteria

et al. 2012

View full text Add to dashboard Cite

show abstract

“…Land and Prutz [62] found that addition of 10 mM azide potentiated the inactivation of enzymes by pulse radiolysis and attributed the finding to production of

N_{3}^{•}

from HO • . Ali et al [63] reported that the hemolysis of human red blood cells by a photoactivated (cool fluorescent light) riboflavin–Cu(II) system was enhanced by addition of 150 μM azide. They attributed their observation to inhibition of the photodegradation of riboflavin, but commented that “as the riboflavin–Cu(II) system has been shown to produce HO • the intermediacy of N3 • could not be ruled out.”…”

Section: Discussionmentioning

confidence: 99%

Paradoxical potentiation of methylene blue-mediated antimicrobial photodynamic inactivation by sodium azide: Role of ambient oxygen and azide radicals

Huang

Denis

et al. 2012

Free Radical Biology and Medicine

109

110

View full text Add to dashboard Cite

Sodium azide (NaN3) is widely employed to quench singlet oxygen during photodynamic therapy (PDT), especially when PDT is used to kill bacteria in suspension. We observed that addition of NaN3 (100 μM or 10 mM) to gram-positive Staphylococcus aureus and gram-negative Escherichia coli incubated with methylene blue (MB) and illuminated with red light gave significantly increased bacterial killing (1–3 logs), rather than the expected protection from killing. A different antibacterial photosensitizer, the conjugate between polyethylenimine and chlorin(e6) (PEI-ce6), showed reduced PDT killing (1–2 logs) after addition of 10 mM NaN3. Azide (0.5 mM) potentiated bacterial killing by Fenton reagent (hydrogen peroxide and ferrous sulfate) by up to 3 logs, but protected against killing mediated by sodium hypochlorite and hydrogen peroxide (considered to be a chemical source of singlet oxygen). The intermediacy of N3• was confirmed by spin-trapping and electron spin resonance studies in both MB-photosensitized reactions and Fenton reagent with addition of NaN3. We found that N3• was formed and bacteria were killed even in the absence of oxygen, suggesting the direct one-electron oxidation of azide anion by photoexcited MB. This observation suggests a possible mechanism to carry out oxygen-independent PDT.

show abstract

“…Nonetheless, the mechanism through which riboflavin biosynthesis boosts hemolysis is not clear. Riboflavin has been shown to direct light-mediated rat and human erythrocytes hemolysis but only in the presence of other factors such as serum, oxygen, copper, azide, and aminophylline ( Suzuki et al, 1982 ; Ali and Naseem, 2002 ; Ali et al, 2005 ). Moreover, riboflavin alone does not directly promote hemolysis in agar plates were H. pylori experiments were conducted ( Bereswill et al, 1998 ).…”

Section: Riboflavin Production As a Mean To Increase Iron Availabilitmentioning

confidence: 99%

Overview on the Bacterial Iron-Riboflavin Metabolic Axis

2018

View full text Add to dashboard Cite

Redox reactions are ubiquitous in biological processes. Enzymes involved in redox metabolism often use cofactors in order to facilitate electron-transfer reactions. Common redox cofactors include micronutrients such as vitamins and metals. By far, while iron is the main metal cofactor, riboflavin is the most important organic cofactor. Notably, the metabolism of iron and riboflavin seem to be intrinsically related across life kingdoms. In bacteria, iron availability influences expression of riboflavin biosynthetic genes. There is documented evidence for riboflavin involvement in surpassing iron-restrictive conditions in some species. This is probably achieved through increase in iron bioavailability by reduction of extracellular iron, improvement of iron uptake pathways and boosting hemolytic activity. In some cases, riboflavin may also work as replacement of iron as enzyme cofactor. In addition, riboflavin is involved in dissimilatory iron reduction during extracellular respiration by some species. The main direct metabolic relationships between riboflavin and iron in bacterial physiology are reviewed here.

show abstract

Hemolysis of Human Red Blood Cells by Riboflavin-Cu(II) System: Enhancement by Azide

Cited by 6 publications

References 29 publications

Type I and Type II mechanisms of antimicrobial photodynamic therapy: An in vitro study on gram‐negative and gram‐positive bacteria

Type I and Type II mechanisms of antimicrobial photodynamic therapy: An in vitro study on gram‐negative and gram‐positive bacteria

Paradoxical potentiation of methylene blue-mediated antimicrobial photodynamic inactivation by sodium azide: Role of ambient oxygen and azide radicals

Overview on the Bacterial Iron-Riboflavin Metabolic Axis

Contact Info

Product

Resources

About