H<sub>2</sub>O<sub>2</sub>Determination in Rat Lens: Chemiluminescent versus Radioisotopic Methods

Devamanoharan, P.S.; Varma, Shambhu D.

doi:10.1159/000267837

Cited by 8 publications

(2 citation statements)

References 9 publications

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“…One hundred to 300 mM H 2 O 2 was detected in the lens (Devamanoharan, Ramachandran and Varma, 1991;Devamanoharan and Varma, 1995) and 30±80 mM H 2 O 2 were detected in the aqueous humor which surrounds the lens (Spector and Garner, 1981;Giblin et al, 1984;Ramachandran et al, 1991). The lens also has an active UPP (Huang, Jahngen-Hodge and Taylor, 1993;Shang and Taylor 1995;Shang et al, 1997a,b).…”

Section: Introductionmentioning

confidence: 99%

Removal of Oxidatively Damaged Proteins from Lens Cells by the Ubiquitin-Proteasome Pathway

Shang

Nowell

Taylor

2001

Experimental Eye Research

105

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Section: Introductionmentioning

confidence: 99%

Removal of Oxidatively Damaged Proteins from Lens Cells by the Ubiquitin-Proteasome Pathway

Shang

Nowell

Taylor

2001

Experimental Eye Research

105

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“…Oxidation is a major stress to the lens due to its constant exposure to light and oxidants (1)(2)(3)(4). H 2 O 2 in the lens (100 -300 M) has been detected using different methods (5,6). In addition, H 2 O 2 was detected in the aqueous humor (the fluid from which the lens receives its nutriture) of normal (0.03 mM) or cataract patients (0.08 -0.19 mM) by various laboratories (7)(8)(9).…”

mentioning

confidence: 99%

Activity of Ubiquitin-dependent Pathway in Response to Oxidative Stress

Shang

Gong

Taylor

1997

Journal of Biological Chemistry

215

135

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Relations between the ubiquitin pathway and cellular stress have been noted, but data regarding responses of the ubiquitin pathway to oxidative stress are scanty. This paper documents the response of this pathway to oxidative stress in lens cells. A brief exposure of lens epithelial cells to physiologically relevant levels of H 2 O 2 induces a transient increase in activity of the ubiquitindependent pathway. Ubiquitin conjugation activity was maximal and increased 3.5-9.2-fold over the activity noted in untreated cells by 4 h after removal of H 2 O 2 . By 24 h after removal of H 2 O 2 , ubiquitin conjugation activity returned to the level noted in untreated cells. In parallel to the changes in ubiquitin conjugation activity, the activity of ubiquitin-activating enzyme (E1), as determined by thiol ester formation, increased 2-6.7-fold during recovery from oxidation. Addition of exogenous E1 resulted in an increase in ubiquitin conjugation activity and in the levels of ubiquitin carrier protein (E2)-ubiquitin thiol esters in both the untreated cells and the H 2 O 2 -treated cells. These data suggest that E1 is the rate-limiting enzyme in the ubiquitin conjugation process and that the increases in ubiquitin conjugation activity which are induced upon recovery from oxidation are primarily due to increased E1 activity. The oxidation-and recovery-induced up-regulation of E1 activity is primarily due to post-synthetic events. Substrate availability and up-regulation of E2 activities also appear to be related to the enhancement in ubiquitinylation upon recovery from oxidative stress. The oxidationinduced increases in ubiquitin conjugation activity were associated with an increase in intracellular proteolysis, suggesting that the transient increase in ubiquitinylation noted upon recovery from oxidative stress may play a role in removal of damaged proteins from the cells.

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