Further characterization of the subunits of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) by SDS-PAGE electrophoresis and MALDI-TOF-MS

A Novel Molecular Approach for Enhancing the Safety of Ozone in Autohemotherapy and Insights into Heme Pocket Autoxidation of Hemoglobin

Major ozone autohemotherapy (MAH) is a popular clinical practice for treating a variety of pathological conditions due to the mild and controlled oxidative stress produced by the reaction of ozone gas with other biological components. Previous studies have shown that blood ozonation leads to structural changes in hemoglobin (Hb); therefore, in the present study, the molecular effects of ozonation on Hb of a healthy individual were assessed by ozonating whole blood samples with single doses of ozone at 40, 60, and 80 μg/mL or double doses of ozone at 20 + 20, 30 + 30, and 40 + 40 μg/mL ozone to investigate whether ozonating once versus twice (but with the same final ozone concentration) would have varying effects on Hb. Additionally, our study aimed to verify whether using a very high ozone concentration (80 + 80 μg/mL), despite mixing it with blood in two steps, would result in Hb autoxidation. The pH, oxygen partial pressure, and saturation percentage of the whole blood samples were measured through a venous blood gas test, and the purified Hb samples were analyzed using several techniques including intrinsic fluorescence, circular dichroism and UV-vis absorption spectroscopies, SDS-polyacrylamide gel electrophoresis, dynamic light scattering, and a zeta potential analyzer. Structural and sequence analyses were also used to study the Hb heme pocket autoxidation sites and the residues involved. The results showed that the oligomerization and instability of Hb can be reduced if the ozone concentration to be used in MAH is divided into two doses. Indeed, our study demonstrated that two-step ozonation with 20, 30, and 40 μg/mL of ozone instead of single-dose ozonation with 40, 60, and 80 μg/mL of ozone reduced the potential adverse effects of ozone on Hb including protein instability and oligomerization. Moreover, it was found that for certain residues, their orientation or displacement leads to the entry of excess water molecules into the heme moiety, which can contribute to Hb autoxidation. Additionally, the autoxidation rate was found to be higher in alpha globins compared to beta globins.

Structural characterization and stability analysis of phosphorylated nitrosohemoglobin

Phosphorylation modification by sodium tripolyphosphate (STP) on nitrosohemoglobin (NO-Hb) and its effect on the protein structure and stability were studied. Phosphate groups were found to bridge to NO-Hb via C-O-P bonds through serine and tyrosine residues. Hydrothermal treatment with STP maintained the α-helix stability of NO-Hb, and this change in secondary structure improved the proteins stability. Compared to NO-Hb, phosphorylated NO-Hb (P-NO-Hb) was more stable with respect to light (outdoor light, indoor light, and dark conditions), oxidant (hydrogen peroxide), high temperature, and non-neutral pH. The absorbance of P-NO-Hb was nearly twice those of Hb and NO-Hb (P < 0.05), and the absorbance of P-NO-Hb decreased more slowly over time than those of Hb and NO-Hb. The results confirm that the presence of phosphate groups can increase the stability of Hb through structural changes.

Highlighting the Importance of Water Alkalinity Using Phosphate Buffer Diluted With Deionized, Double Distilled and Tap Water, in Lowering Oxidation Effects on Human Hemoglobin Ozonated at High Ozone Concentrations in vitro

In autohemotherapy, it is important to find a way to lower the effects of oxidation, especially at high concentrations of ozone. One of the parameters, other than ozone concentration, which can have a significant effect on the stability and rate of decomposition of ozone at high concentrations, is the presence of ions in water. A number of spectroscopic techniques including intrinsic fluorescence, circular dichroism and UV–VIS were used as well as SDS-PAGE, Native-PAGE dynamic light scattering and water ion analysis, in order to investigate the effects of two relatively high concentrations of ozone on purified human hemoglobin (Hb) in phosphate buffer and diluted versions with deionized, double distilled and tap water in vitro. Purified human Hb and not whole blood human Hb was used in this study, since the addition of water to the whole blood would have caused the RBCs to lyse, affecting the purification of Hb for further analysis. Therefore, using purified Hb, it was possible to investigate the effects of dilution of 50 mM phosphate buffer to 10 mM phosphate buffer with different water types including non-ion containing deionized and double distilled water as well as ion-containing tap water, when ozonated at 55 and 80 μg/ml ozone. The fundamental changes in the secondary and tertiary structures of Hb were seen to be related to non-ozonated Hb samples diluted with deionized and double distilled waters, respectively. Generally, Hb oligomerization was more likely to occur at the higher concentration of ozone (80 μg/ml) and in samples where phosphate buffer was diluted with non-ion containing deionized and double distilled waters and not the ion-containing tap water. This could be explained by the presence of water alkalinity or bicarbonate ions in tap water, which can scavenge free radicals and reduce Hb oxidation/oligomerization. Therefore, it was concluded that Hb could best withstand high concentrations of ozone in the presence of the undiluted 50 mM phosphate buffer followed by phosphate buffer diluted with tap water, containing bicarbonate ions.

Initial biophysical characterization of Amynthas gracilis giant extracellular hemoglobin (HbAg)

The aim of the present work was the biophysical characterization of the Amynthas gracilis hemoglobin (HbAg). The oxy-HbAg optical absorption data, with Soret and Q bands centered at 415, 540 and 575 nm, were stable and unchanged at pH 7.0. An increase in pH promotes decrease in the intensity in the optical absorption bands, suggesting an oligomeric dissociation and partial oxidation. Identical stability at pH 7.0 was observed in DLS results that presented a hydrodynamic diameter of 28 nm, characteristic of the whole oligomer. DLS shows that HbAg undergoes oligomeric dissociation and an aggregation/denaturation process that corroborates spectroscopic data. Our results showed that the monomer d presents four isoforms with molecular mass (MM) ranging from 16,244 to 16,855 Da; the trimer subunit presents two isoforms, (abc)₁ and (abc)₂, with MM of 51,415 ± 20 Da and 51,610 ± 14 Da, respectively, and a less intense species, at 67,793 Da, assigned to the tetramer abcd. Monomeric chains a, obtained from reduction of the disulfide-bonded trimer abc, present four isoforms with MM 17,015 Da, 17,061 Da, 17,138 Da and 17,259 Da. DLS and LSI revealed an isoeletric point (pI) of oxy-HbAg of 6.0 ± 0.3 and 5.5, respectively. Data analysis by IEF-SDS-PAGE revealed that the pI of oxy-HbAg is 6.11, correlating with DLS and LSI data. These studies indicate that oxy-HbAg is very stable, at pH 7.0, and has differing properties from orthologous giant hemoglobins.

Characterization of the apo-form of extracellular hemoglobin of Glossoscolex paulistus (HbGp) and its stability in the presence of urea

The structural study of small heme-containing proteins, such as myoglobin, in the apo-form lacking heme has been extensively described, but the characterization and stability of the giant Glossoscolex paulistus hemoglobin (HbGp), in the absence of heme groups, has not been studied. Spectroscopic data show efficient extraction of the heme groups from the hemoglobin, with relatively small secondary and tertiary structural changes in apo-HbGp noticed compared to oxy-HbGp. Electrophoresis shows a partial precipitation of the trimer abc (significantly lower intensity of the corresponding band in the gel), due to extraction of heme groups, and the predominance of the intense monomeric d band, as well as of two linker bands. AUC and DLS data agree with SDS-PAGE in showing that the apo-HbGp undergoes dissociation into the d and abc subunits. Subunits d and abc are characterized by sedimentation coefficients and percentage contributions of 2.0 and 3.0 S and 76 and 24%, respectively. DLS data suggest that the apo-HbGp is unstable, and two populations are present in solution: one with a diameter around 6.0 nm, identified with the dissociated species, and a second one with diameter 100-180 nm, due to aggregated protein. Finally, the presence of urea promotes the exposure of the fluorescent probes, extrinsic ANS and intrinsic protein tryptophans to the aqueous solvent due to the unfolding process. An understanding of the effect of heme extraction on the stability of hemoproteins is important for biotechnological approaches such as the introduction of non-native prosthetic groups and development of artificial enzymes with designed properties.

Personalizing the safe, appropriate and effective concentration(s) of ozone for a non-diabetic individual and four type II diabetic patients in autohemotherapy through blood hemoglobin analysis

Background

Diabetes is a chronic disease associated with many problems and high costs. In recent decades, a lot of research has been carried out in order to improve methods of treatment of diabetic patients. One of the currently used complementary therapies for diabetes is ozone therapy or autohemotherapy. The beneficial effects of ozone has been proven in many diseases such as diabetes, but the critical issue is the determination of the safe and effective concentration of ozone reacting with blood and in particular hemoglobin.

Methods

A number of spectroscopic techniques including intrinsic fluorescence, circular dichroism and UV–VIS spectroscopies were used as well as SDS-PAGE, Native-PAGE and dynamic light scattering to analyze the effect of ozonation on hemoglobin of a non-diabetic individual and four diabetic patients in order to find the appropriate concentration(s) of ozone for personalized autohemotherapy.

Results

In this study, we determined the personalized concentration(s) for a safe and effective ozonation of a non-diabetic individual and four diabetic type II patients, based on blood hemoglobin analysis.

Conclusions

A number of techniques were used to determine the personalized ozone concentration(s) for a safe and effective autohemotherapy based on blood hemoglobin analysis. SDS-PAGE and dynamic light scattering were identified as the two main techniques needed for personalizing the ozone concentration(s) for each individual as otherwise hemoglobin in blood can oligomerise and cause serious damage if the inappropriate ozone concentration is used.

Oligomeric stability of Glossoscolex paulistus hemoglobin as a function of the storage time

Glossoscolex paulistus hemoglobin structure is composed of 144 globin chains and 36 polypeptide chains lacking the heme group, with a total molecular mass of 3600 kDa. The current study focuses on the oxy-HbGp oligomeric stability, as a function of the storage time, at pH 7.0, using dynamic light scattering, analytical ultracentrifugation (AUC), optical absorption and size exclusion chromatography (SEC). HbGp stored in Tris-HCl buffer, pH 7.0, at 4 °C, for two years remains in the native form, while 4-6 years HbGp stocks present typical hemichrome species absorption spectra. AUC and SEC analyses show that the contribution of HbGp-subunits, such as, dodecamer (abcd)₃, tetramer abcd, trimer abc and monomer d, increases with the protein aging due to the lower stability of the HbGp with the time. The dissociation and the oxidation of the iron noted for the older protein solutions indicate that HbGp storage for periods of time longer than two years changes its ability to carry oxygen. Despite the reduction of HbGp stability and oxygen carrying capacity with aging, the protein stability is still larger as compared to mammalian hemoglobins. Thus, the extracellular hemoglobins are quite stable and resistant to the auto-oxidation process, making them of interest for biotechnological applications.

Molecular insights into the effect of ozone on human hemoglobin in autohemotherapy: Highlighting the importance of the presence of blood antioxidants during ozonation

Ozone has been known for several decades, with its antiseptic and therapeutic effects determined by the hormesis theory. It is shown that the therapeutic efficacy of ozone therapy may be partly due to the controlled and moderate oxidative stress produced by the reaction of ozone with several biological components. In this study, the effect of ozone on healthy human hemoglobin (Hb) in the whole blood environment (in the presence of antioxidants) and in the purified form (in the absence of antioxidants) is investigated using a number of different techniques including intrinsic fluorescence, circular dichroism and UV-VIS absorption spectroscopy as well as SDS- and Native-PAGE and dynamic light scattering. The results show that the presence of antioxidants prevents damage to Hb while its absence means that as the exposure to ozone is increased, Hb is increasingly damaged. These results highlight the importance for the use of appropriate doses of ozone, for patients with different diseases and hence antioxidant levels, in autohemotherapy.

Interaction of Glossoscolex paulistus extracellular hemoglobin with hydrogen peroxide: Formation and decay of ferryl-HbGp

The giant extracellular hemoglobin from earthworm Glossoscolex paulistus (HbGp) reacts with hydrogen peroxide, displaying peroxidase activity in the presence of guaiacol. The formation of ferryl-HbGp (compound II) from the peroxidase cycle was studied in the present work. The hypervalent ferryl-HbGp species was formed directly by the reaction of oxy-HbGp and hydrogen peroxide. The oxy-HbGp heme groups (144) under different excess of H₂O₂, relative to heme, showed an influence in the total amount of ferryl-HbGp at the end of the reaction. The ferryl-HbGp was formed with second order rate constant of 27.1±0.5M^-1s^-1, at pH7.0 and 25°C. The increase of the pH value to 8.0 induces both faster formation and decay of ferryl-HbGp, together with oligomeric dissociation induced by the presence of H₂O₂, as observed by DLS. This effect of dissociation increases the heme exposure and decreases the ferryl-HbGp stability, affecting the rate constant as a parallel reaction. At pH7.0, high excess of H₂O₂, above 1:5 oxy-HbGp heme: H₂O₂, produces the aggregation of the protein. Our results show for the first time, for an extracellular giant hemoglobin, the possible effects of oxidative stress induced by hydrogen peroxide.

The structure of the giant haemoglobin from Glossoscolex paulistus

The sequences of all seven polypeptide chains from the giant haemoglobin of the free-living earthworm Glossoscolex paulistus (HbGp) are reported together with the three-dimensional structure of the 3.6 MDa complex which they form. The refinement of the full particle, which has been solved at 3.2 Å resolution, the highest resolution reported to date for a hexagonal bilayer haemoglobin composed of 12 protomers, is reported. This has allowed a more detailed description of the contacts between subunits which are essential for particle stability. Interpretation of features in the electron-density maps suggests the presence of metal-binding sites (probably Zn(2+) and Ca(2+)) and glycosylation sites, some of which have not been reported previously. The former appear to be important for the integrity of the particle. The crystal structure of the isolated d chain (d-HbGp) at 2.1 Å resolution shows different interchain contacts between d monomers compared with those observed in the full particle. Instead of forming trimers, as seen in the complex, the isolated d chains associate to form dimers across a crystallographic twofold axis. These observations eliminate the possibility that trimers form spontaneously in solution as intermediates during the formation of the dodecameric globin cap and contribute to understanding of the possible ways in which the particle self-assembles.

Guanidine hydrochloride and urea effects upon thermal stability of Glossoscolex paulistus hemoglobin (HbGp)

Glossoscolex paulistus hemoglobin (HbGp) has a molecular mass of 3600kDa. It belongs to the hexagonal bilayer hemoglobin class, which consists of highly cooperative respiratory macromolecules found in mollusks and annelids. The present work focusses on oxy-HbGp thermal stability, in the presence of urea and guanidine hydrochloride (GuHCl), monitored by several techniques. Initially, dynamic light scattering data show that the presence of GuHCl induces the protein oligomeric dissociation, followed by a significant 11-fold increase in the hydrodynamic diameter (DH) values, due to the formation of protein aggregates in solution. In contrast, urea promotes the HbGp oligomeric dissociation, followed by unfolding process at high temperatures, without aggregation. Circular dichroism data show that unfolding critical temperature (Tc) of oxy-HbGp decreases from 57°C, at 0.0 mol/L of the denaturant, to 45°C, in the presence of 3.5 mol/L of urea, suggesting the reduction of HbGp oligomeric stability. Moreover, differential scanning calorimetry results show that at lower GuHCl concentrations, some thermal stabilization of the hemoglobin is observed, whereas at higher concentrations, the reduction of stability takes place. Besides, HbGp is more stable in the presence of urea when compared with the guanidine effect, as deduced from the differences in the concentration range of denaturants.