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Myotonic dystrophy: defective oxidative burst of polymorphonuclear leukocytes
Abstract:
Because myotonic dystrophy (MD) is an autosomal dominant multisystemic disorder affecting plasma membrane, we have studied the oxidative burst of PMNs. The PMA and fMet-Leu-Phe-stimulated superoxide generation is defective in the patient group as compared to controls: the response is both delayed and low. The kinetic parameters of the NADPH oxidase complex are not affected. We have not found any abnormalities in the membrane potential changes. In addition, the cytosolic protein kinase C (PKC) activity of resting PMNs is similar in MD patients and controls, and the translocation of protein kinase C in response to PMA is not impaired. The decrease of the oxidative response of PMNs from MD patients may be related to an abnormality of the environment of the NADPH oxidase.
Insights
Myotonic dystrophy patients exhibit a defective oxidative burst in neutrophils (PMNs), characterized by delayed and reduced superoxide generation. This impairment may stem from alterations in the NADPH oxidase environment, not the enzyme itself.
Area of Science:
- Biochemistry
- Immunology
- Genetics
Background:
- Myotonic dystrophy (MD) is an autosomal dominant disorder impacting multiple systems, notably the plasma membrane.
- Neutrophils (PMNs) play a crucial role in the immune response through oxidative burst mechanisms.
Purpose of the Study:
- To investigate the oxidative burst function of PMNs in patients with myotonic dystrophy.
- To identify potential defects in superoxide generation and related cellular processes in MD.
Main Methods:
- Stimulation of PMNs with phorbol 12-myristate 13-acetate (PMA) and fMet-Leu-Phe.
- Measurement of superoxide generation kinetics.
- Assessment of NADPH oxidase complex kinetics, membrane potential, and protein kinase C (PKC) activity and translocation.
Main Results:
- PMNs from MD patients showed a delayed and diminished superoxide generation response compared to controls.
- No significant abnormalities were found in NADPH oxidase kinetics, membrane potential, or PKC activity/translocation.
- The defect appears localized to the environment surrounding the NADPH oxidase complex.
Conclusions:
- Myotonic dystrophy is associated with impaired neutrophil oxidative burst function.
- The defect is not due to alterations in the core NADPH oxidase complex or PKC signaling.
- An abnormality in the PMN environment affecting NADPH oxidase function is suggested in MD patients.