High impact information on HO2

• The similarity of NOS and HO-2 localizations and functions in blood vessels and the autonomic nervous system implies complementary and possibly coordinated physiologic roles for these two mediators [1].
• Heme oxygenase 2 (HO-2), which synthesizes carbon monoxide (CO), has been localized by immunohistochemistry to endothelial cells and adventitial nerves of blood vessels [1].
• HO-2 is also localized to neurons in autonomic ganglia, including the petrosal, superior cervical, and nodose ganglia, as well as ganglia in the myenteric plexus of the intestine [1].
• At high [O2], direct dissociation of the neutral superoxide radical (HO2) from oxymyoglobin dominates, and this process is accelerated by decreasing pH [2].
• The neutral side chain of the distal histidine (His64) inhibits autooxidation by hydrogen bonding to bound oxygen, preventing both HO2 dissociation and the oxidative bimolecular reaction with deoxymyoglobin [2].

Biological context of HO2

• Using cerebral vascular endothelial cells from newborn pigs and HO-2-knockout mice, we addressed the hypotheses that 1) glutamate induces oxidative stress-related endothelial death by apoptosis, and 2) HO-1 and HO-2 are protective against glutamate cytotoxicity [3].
• HO-2 catalytic activity is stimulated by tyrosine phosphorylation [4].

Anatomical context of HO2

• The present study revealed by means of immunohistochemistry the presence of BVR and HO-2 in mucosal epithelial cells and in the endothelium of intramural vessels of both human and porcine gastric fundus [5].
• Piglet cerebral microvessels and endothelial and smooth muscle cells grown on microcarrier beads were used to address the hypothesis that glutamate increases endothelial CO production by increasing HO-2 catalytic activity [6].
• Furthermore, the vascular endothelium of the intramural vessels of the urethra, bladder and OGJ, and the extramural vessels of the bladder, displayed HO-2 immunoreactivity [7].
• 2. HO-2 immunoreactivity was observed in coarse nerve trunks within the smooth muscle of the urethra and OGJ, and in nerve cell bodies of the enteric plexuses of the OGJ [7].
• The similarities between heme oxygenase-2 (HO-2) and nitric oxide synthase (nNOS) and the transient expression of nNOS during development led us to investigate whether both systems are similarly affected by changes that occur during development and by regional differences along the small intestine [8].

Associations of HO2 with chemical compounds

• 0. The rate constants for the oxidation of the LDH-NADH by HO2 and O2 determined at 23 degrees are 1.2 times 10-6 M(-1) s(-1) and 3.6 times 10-4 M(-1) s(-1), respectively [9].
• Kinetic study by pulse radiolysis of the lactate dehydrogenase-catalyzed chain oxidation of nicotinamide adenine dinucleotide by HO2 and O2-RADICALS [9].
• 0. The rate constant for the oxidation of the glyceraldehyde-3-phosphate dehydrogenase.NADH complex by HO2 was estimated to be 2 X 10(7) M-1 S-1 at ambient temperatures (23-24 degrees C) [10].
• These data suggest that glutamate may activate NOS producing NO that leads to CO synthesis via a cGMP-dependent elevation of HO-2 catalytic activity [11].
• Inhibition of protein tyrosine phosphatases increased HO-2 catalytic activity [4].

Analytical, diagnostic and therapeutic context of HO2

• The lactate dehydrogenase-catalyzed chain oxidation of NADH (LDH-NADH) by the superoxide radicals, HO2 and O2, has been studied with pulse radiolysis in the pH range between 4.5 and 9 [9].

References