ABSTRACT
We describe a 16-year old boy with glycogen storage disease type Ib, homozygous for the common 1211-1212delCT mutation, who never experienced neutropenia, and did not suffer from frequent infections or inflammatory bowel disease. In addition, neutrophil function tests showed no abnormalities.
Subject(s)
Glycogen Storage Disease Type I/genetics , Mutation , Neutropenia/diagnosis , Neutropenia/genetics , Neutrophils/pathology , Adolescent , Antiporters/genetics , Homozygote , Humans , Liver/enzymology , Male , Monosaccharide Transport Proteins/genetics , Neutrophils/metabolism , PhenotypeABSTRACT
Regulation of the neutrophil life span by apoptosis provides a fine balance between their function as effector cells of host defense and a safe turnover of these potentially harmful cells. Alterations of neutrophil apoptosis are associated with a number of diseases. As do other cell types, neutrophils possess components of both extrinsic and intrinsic apoptotic routes. The intrinsic pathway of apoptosis seems to be of major importance in neutrophils since they are programmed for a rapid spontaneous cell death. However, in neutrophils this mechanism of apoptosis has special features, probably due to peculiarities of neutrophil mitochondria, which are believed to be a core regulator of intrinsic cell death. A better understanding of mechanisms underlying neutrophil cell death would help to understand neutrophil physiology and contribute to the search of new approaches for handling of pathology related to disturbances in neutrophil apoptosis and also increase our knowledge of inflammation in general.
Subject(s)
Apoptosis/immunology , Neutrophils/cytology , Neutrophils/physiology , Humans , Mitochondria/physiologyABSTRACT
Mitochondria are known to combine life-supporting functions with participation in apoptosis by controlling caspase activity. Here, we report that in human blood neutrophils the mitochondria are different, because they preserve mainly death-mediating abilities. Neutrophil mitochondria hardly participate in ATP synthesis, and have a very low activity of the tested marker enzymes. The presence of mitochondria in neutrophils was confirmed by quantification of mitochondrial DNA copy number, by detection of mitochondrial porin, and by JC-1 measurement of Deltapsi(m). During neutrophilic differentiation, HL-60 cells demonstrated a profound cytochrome c depletion and mitochondrial shape change reminiscent of neutrophils. However, blood neutrophils containing extremely low amounts of cytochrome c displayed strong caspase-9 activation during apoptosis, which was also observed in apoptotic neutrophil-derived cytoplasts lacking any detectable cytochrome c. We suggest that other proapoptotic factors such as Smac/DIABLO and HtrA2/Omi, which are massively released from the mitochondria, have an important role in neutrophil apoptosis.
