Adenosine-5'-triphosphate-adenosine-glutathione cross-linked hemoglobin as erythropoiesis-stimulating agent

(-)-Epicatechin, a Natural Flavonoid Compound, Protects Astrocytes Against Hemoglobin Toxicity via Nrf2 and AP-1 Signaling Pathways

(-)-Epicatechin is a brain-permeable, natural product found at high concentrations in green tea and cocoa. Our previous research has shown that (-)-epicatechin treatment reduces hemorrhagic stroke injury via nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in vivo. However, the mechanism of action of this compound in modulation of oxidant stress and in protection against hemoglobin-induced astrocyte injury is unclear. Therefore, we explored the cellular and molecular mechanisms that underlie these protective effects in vitro. Mouse primary astrocytes isolated from wild-type mice and Nrf2 knockout (KO) mice were preconditioned with hemoglobin to simulate intracerebral hemorrhage (ICH) in vitro. Effects of (-)-epicatechin were measured by Western blotting, immunostaining, MTT assay, and reactive oxidant stress (ROS) assay. (-)-Epicatechin increased Nrf2 nuclear accumulation and cytoplasmic levels of superoxide dismutase 1 (SOD1) in wild-type astrocytes but did not increase SOD1 expression in Nrf2 knockout (KO) astrocytes. Furthermore, (-)-epicatechin treatment did not alter heme oxygenase 1 (HO1) expression in wild-type astrocytes after hemoglobin exposure, but it did decrease HO1 expression in similarly treated Nrf2 KO astrocytes. In both wild-type and Nrf2 KO astrocytes, (-)-epicatechin suppressed phosphorylated JNK and nuclear expression of JNK, c-jun, and c-fos, indicating that inhibition of activator protein-1 (AP-1) activity by (-)-epicatechin is Nrf2-independent. These novel findings indicate that (-)-epicatechin protects astrocytes against hemoglobin toxicity through upregulation of Nrf2 and inhibition of AP-1 activity. These cellular and molecular effects may partially explain the cerebroprotection as we previously observed for (-)-epicatechin in animal models of ICH.

Artificial oxygen carrier with pharmacologic actions of adenosine-5'-triphosphate, adenosine, and reduced glutathione formulated to treat an array of medical conditions

Effective artificial oxygen carriers may offer a solution to tackling current transfusion medicine challenges such as blood shortages, red blood cell storage lesions, and transmission of emerging pathogens. These products, could provide additional therapeutic benefits besides oxygen delivery for an array of medical conditions. To meet these needs, we developed a hemoglobin (Hb)-based oxygen carrier, HemoTech, which utilizes the concept of pharmacologic cross-linking. It consists of purified bovine Hb cross-linked intramolecularly with open ring adenosine-5'-triphosphate (ATP) and intermolecularly with open ring adenosine, and conjugated with reduced glutathione (GSH). In this composition, ATP prevents Hb dimerization, and adenosine promotes formation of Hb polymers as well as counteracts the vasoconstrictive and pro-inflammatory properties of Hb via stimulation of adenosine receptors. ATP also serves as a regulator of vascular tone through activation of purinergic receptors. GSH blocks Hb's extravasation and glomerular filtration by lowering the isoelectric point, as well as shields heme from nitric oxide and reactive oxygen species. HemoTech and its manufacturing technology have been broadly tested, including viral and prion clearance validation studies and various nonclinical pharmacology, toxicology, genotoxicity, and efficacy tests. The clinical proof-of-concept was carried out in sickle cell anemia subjects. The preclinical and clinical studies indicate that HemoTech works as a physiologic oxygen carrier and has efficacy in treating: (i) acute blood loss anemia by providing a temporary oxygen bridge while stimulating an endogenous erythropoietic response; (ii) sickle cell disease by counteracting vaso-occlusive/inflammatory episodes and anemia; and (iii) ischemic vascular diseases particularly thrombotic and restenotic events. The pharmacologic cross-linking of Hb with ATP, adenosine, and GSH showed usefulness in designing an artificial oxygen carrier for multiple therapeutic indications.

Effects of liposome-encapsulated hemoglobin on gastric wound healing in the rat

Liposome-encapsulated hemoglobin (LEH) may improve microcirculation and oxygen (O2 ) metabolism at a surgical wound to accelerate its healing. Ten mL/kg of LEH with high (h-LEH) or low O2 -affinity (l-LEH), homologous red blood cells (RBC), empty liposome or saline as a control was infused before a 10-mm incision and interrupted suture closure of the gastric wall in a total of 110 rats. Two and 4 days later, the stomach was excised for bursting pressure determination and histological sampling. The dose-response relationship was examined in 70 additional rats receiving progressively reduced doses of h-LEH. Hypoxia-inducible factor-1α (HIF-1α) was stained immunohistochemically in 54 other rats to examine its accumulation at the anastomotic sites. Bursting pressure of the surgical wound was significantly higher 2 days after surgery only in the h-LEH-treated rats (P < 0.05), but not at 4 days after surgery, when other rats showed increased bursting pressure to a nonsignificant level. Histological examination revealed less granulocyte infiltration, better granulation, and more macrophage infiltration in h-LEH-treated rats at 2 days, but no longer at 4 days postsurgery. Dose-response study revealed that 0.4 mL/kg of h-LEH (hemoglobin 24 mg/kg) was effective for elevating bursting pressure at 2 days. h-LEH-treated rats had significantly suppressed HIF-1α accumulation in the wound 6, 24, and 48 h after surgery as compared with control animals treated with homologous RBC or saline. In conclusion, the results suggest that h-LEH, but not l-LEH or homologous transfusion, may accelerate wound healing early after gastric incision and anastomosis in the rat. The mechanism(s) appears to be related to improved O2 supply, aerobic metabolism, and suppressed inflammation in the wound.