https://aasldpubs.onlinelibrary.wiley.com/doi/epdf/10.1053/jhep.2002.36780

Risk factors for hepatocellular carcinoma: Synergism of alcohol with viral hepatitis and diabetes mellitus

Transferrin: structure, function and potential therapeutic actions

A major function of haptoglobin (Hp) is to bind hemoglobin (Hb) to form a stable Hp-Hb complex and thereby prevent Hb-induced oxidative tissue damage. Clearance of the Hp-Hb complex can be mediated by the monocyte/macrophage scavenger receptor CD163. We recently demonstrated that diabetic individuals homozygous for the Hp 2 allele (Hp 2-2) were at 500% greater risk of cardiovascular disease (CVD) compared with diabetic individuals homozygous for the Hp 1 allele (Hp 1-1). No differences in risk by Hp type were seen in individuals without diabetes. To understand the relationship between the Hp polymorphism and diabetic CVD, we sought to identify differences in antioxidant and scavenging functions between the Hp types and to determine how these functions were modified in diabetes. The scavenging function of Hp was assessed using rhodamine-tagged and 125I-Hp in cell lines stably transfected with CD163 and in macrophages expressing endogenous CD163. We found that the rate of clearance of Hp 1-1-Hb by CD163 is markedly greater than that of Hp 2-2-Hb. Diabetes is associated with an increase in the nonenzymatic glycosylation of serum proteins, including Hb. The antioxidant function of Hp was assessed with glycosylated and nonglycosylated Hb. We identified a severe impairment in the ability of Hp to prevent oxidation mediated by glycosylated Hb. We propose that the specific interaction between diabetes, CVD, and Hp genotype is the result of the heightened urgency of rapidly clearing glycosylated Hb-Hp complexes from the subendothelial space before they can oxidatively modify low-density lipoprotein to atherogenic oxidized low-density lipoprotein.

Genetically Determined Heterogeneity in Hemoglobin Scavenging and Susceptibility to Diabetic Cardiovascular Disease

Mucormycosis is a fungal infection of the sinuses, brain, or lungs that causes a mortality rate of at least 50% despite first-line therapy. Because angioinvasion is a hallmark of mucormycosis infections, we sought to define the endothelial cell receptor(s) for fungi of the order Mucorales (the fungi that cause mucormycosis). Furthermore, since patients with elevated available serum iron, including those with diabetic ketoacidosis (DKA), are uniquely susceptible to mucormycosis, we sought to define the role of iron and glucose in regulating the expression of such a receptor. Here, we have identified glucose-regulated protein 78 (GRP78) as what we believe to be a novel host receptor that mediates invasion and damage of human endothelial cells by Rhizopus oryzae, the most common etiologic species of Mucorales, but not Candida albicans or Aspergillus fumigatus. Elevated concentrations of glucose and iron, consistent with those seen during DKA, enhanced GRP78 expression and the resulting R. oryzae invasion and damage of endothelial cells in a receptor-dependent manner. Mice with DKA, which have enhanced susceptibility to mucormycosis, exhibited increased expression of GRP78 in sinus, lungs, and brain compared with normal mice. Finally, GRP78-specific immune serum protected mice with DKA from mucormycosis. These results suggest a unique susceptibility of patients with DKA to mucormycosis and provide a foundation for the development of new therapeutic interventions for these deadly infections.

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The endothelial cell receptor GRP78 is required for mucormycosis pathogenesis in diabetic mice

Spectroscopic studies on the interaction between human hemoglobin and CdS quantum dots.

Effect of nonenzymatic glycation on functional and structural properties of hemoglobin.

Increased blood glucose in diabetes mellitus stimulates nonenzymatic glycosylation of several proteins, including haemoglobin. Although iron is tightly bound to haemoglobin, it is liberated under specific circumstances yielding free reactive iron. Studies with purified haemoglobin from normal individuals and diabetic patients revealed that concentration of free iron was significantly higher in the latter cases and increased progressively with extent of the disease. In vitro glycosylation of haemoglobin also led to increase in release of iron from protein. This increase in free iron, acting as a Fenton reagent, might produce free radicals, which, in turn might be causing oxidative stress in diabetes.

/pdf/release-of-iron-from-haemoglobin-a-possible-source-of-free-4bp14ydkth.pdf

Release of iron from haemoglobin--a possible source of free radicals in diabetes mellitus.

Trifluoperazine (TFZ), a phenothiazine drug, penetrates into human erythrocytes and releases oxygen by interaction with hemoglobin. TFZ-induced oxygen release from hyperglycemic erythrocytes isolated from diabetic patients is considerably less compared to that from the cells of normoglycemic individuals. In diabetes mellitus, hemoglobin is significantly glycated by glucose. Non-glycated hemoglobin, HbA0 and its major glycated analog, HbA1c have been separated from the blood samples of diabetic patients. TFZ releases considerable amount of oxygen from HbA0, but very little from HbA1c. Spectrofluorimetric studies reveal that TFZ forms excited state complexes with both HbA0 and HbA1c. Titration of HbA0 with TFZ in a spectrophotometric study exhibits two isosbestic points. Similar experiment with HbA1c causes gradual loss of the Soret peak without appearance of any isosbestic point indicating a possibility of heme loss during interaction, which is also supported by gel filtration experiment and SDS-PAGE experiment followed by heme staining. The results suggest that drug action on hemoglobin is influenced by glycation-induced structural modification of the protein.

Effect of Glycation of Hemoglobin on its Interaction with Trifluoperazine

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.

Studies on the interaction of hematoporphyrin with hemoglobin.

The effect of haematoporphyrin, a component of some of the widely used anticancer drugs, on the peroxidase activity of haemoglobin has been studied. Haematoporphyrin increases the haemoglobin-catalysed hydrogen peroxide-mediated oxidation of o-dianisidine or NADH. Spectrophotometric study reveals that an interaction occurs between haemoglobin and haematoporphyrin which leads to a conformational change of the protein. The extent of enhanced peroxidase activity as well as conformational change of the protein vary in a positive manner with the stoichiometric ratio of haematoporphyrin/haemoglobin. An increase in the peroxidase activity of haemoglobin was also observed in the presence of superoxide dismutase, which catalysed the removal of superoxide anion generated during autoxidation of haemoglobin. Possible mechanisms underlying the relation between the conformational change of haemoglobin due to its interaction with haematoporphyrin and the enhanced peroxidase activity are discussed.

Manoj Kar

Papers

Effect of nonenzymatic glycation on functional and structural properties of hemoglobin.

Release of iron from haemoglobin--a possible source of free radicals in diabetes mellitus.

Effect of Glycation of Hemoglobin on its Interaction with Trifluoperazine

Studies on the interaction of hematoporphyrin with hemoglobin.

Haematoporphyrin enhances the peroxidase activity of haemoglobin