Neutrophils in Barth syndrome (BTHS) avidly bind annexin-V in the absence of apoptosis.
Barth syndrome (BTHS) is a rare X-linked disease characterized by a triad of dilated cardiomyopathy, skeletal myopathy, and neutropenia. The disease is associated with mutations of the TAZ gene, resulting in defective cardiolipin (CL), an important inner mitochondrial membrane component. Untreated boys die in infancy or early childhood from septicemia or cardiac failure. To date, neutrophil function has never been studied. Directed motility and killing activity of neutrophils was investigated in 7 BTHS patients and found normal in those tested. The circulating neutrophils and eosinophils (but not monocytes or lymphocytes) showed annexin-V binding, suggesting phosphatidylserine (PS) exposure due to apoptosis. However, caspase activity was absent in fresh BTHS cells. Unexpectedly, the near absence of CL impacted neither the mitochondrial mass and shape in fresh BTHS neutrophils nor mitochondrial clustering and Bax translocation upon apoptosis. Annexin-V binding to BTHS neutrophils was not caused by phospholipid scrambling. Moreover, freshly purified BTHS neutrophils were not phagocytosed by macrophages. In sum, a massive number of circulating annexin-V-binding neutrophils in the absence of apoptosis can be demonstrated in BTHS. These neutrophils expose an alternative substrate for annexin-V different from PS and not recognized by macrophages, excluding early clearance as an explanation for the neutropenia.
Kuijpers
Taco W
TW
Emma Children's Hospital, Academic Medical Centre, University of Amsterdam, the Netherlands. t.w.kuijpers@amc.uva.nl
Maianski
Nikolai A
NA
Tool
Anton T J
AT
Becker
Kolja
K
Plecko
Barbara
B
Valianpour
Fredoen
F
Wanders
Ron J A
RJ
Pereira
Rob
R
Van Hove
Johan
J
Verhoeven
Arthur J
AJ
Roos
Dirk
D
Baas
Frank
F
Barth
Peter G
PG
D000293:Adolescent; D000328:Adult; D017304:Annexin A5 / Q000378:metabolism*; D017209:Apoptosis; D002308:Cardiolipins / Q000032:analysis; D002311:Cardiomyopathy, Dilated; D002648:Child; D002675:Child, Preschool; D004804:Eosinophils / Q000378:metabolism / Q000473:pathology; D040181:Genetic Diseases, X-Linked / Q000097:blood / Q000473:pathology*; D006801:Humans; D007223:Infant; D008264:Macrophages / Q000502:physiology; D008928:Mitochondria / Q000737:chemistry / Q000473:pathology; D009135:Muscular Diseases; D009503:Neutropenia / Q000097:blood / Q000209:etiology*; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology*; D010587:Phagocytosis; D011485:Protein Binding; D013577:Syndrome
D017304:Annexin A5; D002308:Cardiolipins