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Differential Effects of Buffer pH, CaCl 2 , and Superoxide Dismutase on Ca 2+ ‐Induced H 2 O 2 Release from Mitochondrial Complexes I and III
Author(s) -
Lubbe Ryan,
Lindsay Daniel,
Aldakkak Mohammed,
Camara Amadou,
Stowe David
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.979.1
Subject(s) - antimycin a , chemistry , superoxide dismutase , mitochondrion , substrate (aquarium) , reactive oxygen species , mitochondrial matrix , egta , superoxide , biochemistry , nuclear chemistry , biophysics , calcium , enzyme , cytosol , biology , organic chemistry , ecology
Mitochondrial dysfunction underlies many aspects of cardiovascular disease, but the role mitochondria play in cardiac ischemia/reperfusion (IR) injury is uncertain. During IR injury, electron transport chain complexes I and III are considered primary sources of reactive oxygen species (ROS). Increased extra‐matrix Ca 2+ , decreased extra‐matrix pH, and substrate utilization change contribute to enhancing ROS emission during ischemia. Studies in isolated mitochondria show ROS emission is modulated by buffer pH or extra‐matrix [CaCl 2 ] with complex I substrate pyruvate (P) or complex II substrate succinate (S). We tested the combined effects of these factors on mitochondrial H 2 O 2 release. Guinea pig heart mitochondria were suspended in buffer of varied pH (7.15, 6.9, or 6.5), ± exogenous superoxide dismutase (SOD), and ± 150 µM CaCl 2 (+40 µM EGTA). Mitochondria were energized with P and rotenone (R, complex I blocker) or S and antimycin A (AA, complex III blocker). H 2 O 2 release rate was compared for P+R and S+AA. For P+R, there were no significant differences in H 2 O 2 release at all pHs with added SOD and no added CaCl 2 . However, H 2 O 2 release increased at pH 7.15 and 6.9 ± SOD after adding CaCl 2 . In contrast, with S+AA there were no significant differences in H 2 O 2 release at all pHs when exogenous SOD was added to the experimental buffer and incubated ± added CaCl 2 ; however, at 150 µM CaCl 2 H 2 O 2 release increased at each pH. These results suggest a higher extra‐matrix pH (7.15, 6.9), coupled with a large increase in extra‐matrix [CaCl 2 ], may play a role in enhancing SOD activity to dismutate O 2 •‐ generated at complexes I and III to H 2 O 2 . In contrast, at an acidic pH (6.5) a rise in [Ca 2+ ] may have little effect on SOD activity.