Disease relevance of SOD1

• Alterations in pH that shift the HCO3-/CO2 equilibrium as occur in disease processes such as ischemia, sepsis, or shock would modulate the peroxidase function of SOD1 [1].
• This new and different perspective on HCO(3)(-)-mediated oxidative reactions of SOD1 may help us understand the free radical mechanism of SOD1 and related mutants linked to amyotrophic lateral sclerosis [2].
• Recombinant ExoU (rExoU) was activated in a dose-dependent manner by either bovine liver SOD1 or the yeast ortholog, Sod1p, but not by either Fe or Mn-containing SODs from E. coli or small molecule SOD mimetics [3].
• Survival of the dopaminergic cells exposed to 6-OHDA was 50% higher among the SOD1-producing cells than the cells infected with control adenoviruses [4].
• The effect of chronic hyperglycemia on endothelial NO-synthase (eNOS) activity and expression, glycogen synthase (GS) activity, extracellular-signal-regulated kinase (ERK 1,2), p38, Akt expression, and Cu/Zn superoxide-dismutse (SOD-1) activity and expression were determined [5].

High impact information on SOD1

• We postulate that HCO(3)(-) enhances SOD1 peroxidase activity via formation of a putative carbonate radical anion [2].
• The effect of bicarbonate anion (HCO(3)(-)) on the peroxidase activity of copper, zinc superoxide dismutase (SOD1) was investigated using three structurally different probes: 5, 5'-dimethyl-1-pyrroline N-oxide (DMPO), tyrosine, and 2, 2'-azino-bis-[3-ethylbenzothiazoline]-6-sulfonic acid (ABTS) [2].
• Thus, the amplification of peroxidase activity of SOD1/H(2)O(2) by bicarbonate is attributed to the intermediary role of the diffusible oxidant, the carbonate radical anion [6].
• We examined the effect of bicarbonate on the peroxidase activity of copper-zinc superoxide dismutase (SOD1), using the nitrite anion as a peroxidase probe [6].
• However, bicarbonate enhanced SOD1/H(2)O(2)-dependent oxidation of tocopherols in the presence and absence of nitrite and dramatically enhanced SOD1/H(2)O(2)-mediated oxidation of unsaturated lipid in the presence of nitrite [6].

Biological context of SOD1

• These species produced immuno-spin trapping-detectable SOD1-centered radicals associated with H2O2-induced active site ( approximately 5 and approximately 10 kDa fragments) and non-active site (smearing between 3 and 16 kDa) copper-dependent backbone oxidations and subsequent fragmentation of SOD1 [7].
• Cu, Zn superoxide dismutase (SOD1) forms a crucial component of the cellular defence against oxidative stress [8].
• On the basis of these rate constants, we conclude that the thiol oxidase activity of SOD1 stimulates carbonate anion radical (CO3*-) formation in the presence of HCO3- and that the CO3*- formed in the SOD1/Cys/ HCO3- system is responsible for oxidation and hydroxylation reactions [9].
• Fc-receptor-mediated intracellular delivery of Cu/Zn-superoxide dismutase (SOD1) protects against redox-induced apoptosis through a nitric oxide dependent mechanism [10].
• CONCLUSIONS: To define the pharmacologic mechanism of action of bovine SOD1, we attempted to identify the second messengers that are induced by SOD1 IC [10].

Anatomical context of SOD1

• RESULTS: We demonstrated that SOD1 IC induced a Fcgamma receptor (FcgammaR)-dependent intracellular delivery of the antioxidant enzyme in IFN-gamma activated murine macrophages (the J774 AI cell line) [10].

Associations of SOD1 with chemical compounds

• Second, in the presence of DTPA, which inhibits H2O2-induced SOD1 non-active site fragmentation, (bi)carbonate scavenged the enzyme-bound oxidant at the SOD1 active site to produce the carbonate radical anion, CO3*-, thus protecting against active site SOD1 fragmentation [7].
• These radicals are involved in H2O2-induced structural and functional damage to SOD1, and their mechanism of generation depends on copper and/or (bi)carbonate (i.e., CO2, CO3(-2), or HCO3-) [7].
• First, in the absence of DTPA and (bi)carbonate, Cu(II) was partially released and rebound at His, Cys, and Tyr residues in SOD1 with the generation of protein-copper-bound oxidants outside the SOD1 active site by reaction with excess H2O2 [7].
• We used a combined biochemical and proteomic approach to identify Cu(2+), Zn(2+)-superoxide dismutase (SOD1) as a cofactor that activates the phospholipase activity of ExoU [3].
• The addition of HCO3- to aerobic incubations containing SOD1, Cys, and DTPA in phosphate buffer enhanced the peroxidase activity of SOD1, as measured by hydroxylation of cyclic nitrone spin traps, dichlorodihydrofluorescein oxidation to dichlorofluorescein, and oxidation of tyrosine to dityrosine [9].

Analytical, diagnostic and therapeutic context of SOD1

• Western blot analysis revealed a 40-60% decrease in ERK 1,2 and p38 protein levels, small modification of phosphorylated Akt expression, and a 30% increase in SOD-1 protein expression in HG cells [5].

References