Abstract
Background Superoxide anions (O2
−) have multiple effects on pulmonary parenchyma altering cell proliferation, cellular
metabolism, and airway smooth muscle (ASM) contraction. Intracellular calcium ([Ca2+]i) concentration plays a significant role in the regulation of ASM contraction, relaxation,
proliferation, and gene expression.
Objective We investigated the effects of O2
− on agonist-stimulated changes in [Ca2+]i in ASM cells.
Design/Methods Fura-2 AM-loaded, freshly isolated porcine ASM (PASM) cells were used to examine
[Ca2+]i release in response to acetylcholine (ACh), histamine, endothelin, caffeine, and
thapsigargin (TPG) in the presence or absence of extracellular Ca2+.
Results Exposure of PASM cells to xanthine and xanthine oxidase (X + XO) resulted in a time-dependent
generation of O2
−, inhibited by superoxide dismutase (SOD). Preincubating PASM cells with X + XO for
15- or 45-minute inhibited net [Ca2+]i responses to ACh, histamine, caffeine, and TPG compared with control cells. Pretreating
PASM cells with SOD for 30 minutes mitigated the inhibitory effect of X + XO treatment
on ACh-induced Ca2+ elevation suggesting role of O2
−. X + XO treatment also inhibited caffeine- and TPG-induced Ca2+ elevation suggesting effect of O2
− on [Ca2+]i release and reuptake mechanisms.
Conclusion Superoxide attenuates [Ca2+]i release, reuptake, and may interfere with physiological functions of ASM cells.
Keywords
superoxide - airway smooth muscle cell - intracellular calcium - superoxide dismutase
- oxidative - lung illnesses
